Use these links to rapidly review the document
Table of Contents
TABLE OF CONTENTS

Table of Contents

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT
SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the
Securities Exchange Act of 1934
(Amendment No.    )

Table of Contents

July 24, 2020

Dear Stockholders of Advanced Disposal:

You are cordially invited to attend a Special Meeting (which we refer to as the "Special Meeting") of the stockholders of Advanced Disposal Services, Inc. (which we refer to as "Advanced Disposal," "we," "us," "our," and the "Company"). The Special Meeting will be held virtually via the Internet on August 25, 2020 beginning at 10:00 a.m. Eastern Time. As part of our precautions regarding the COVID-19 (coronavirus) pandemic, we are sensitive to the public health and travel concerns that our stockholders may have, as well as any quarantines or other protocols that governments may impose. As a result, the Special Meeting will be held in a virtual meeting format only via live webcast. There will not be a physical meeting location. You will be able to attend the Special Meeting online and vote your shares electronically by visiting www.virtualshareholdermeeting.com/ADSW2020SM (which we refer to as the "Special Meeting website").

At the Special Meeting, you will be asked to consider and vote upon a proposal to adopt the Agreement and Plan of Merger, dated as of April 14, 2019 (which we refer to as the "original merger agreement"), as amended by Amendment No. 1 thereto, dated June 24, 2020 (which we refer to as the "merger agreement amendment"), as may be further amended from time to time, by and among Advanced Disposal, Waste Management, Inc. (which we refer to as "Waste Management") and Everglades Merger Sub Inc. (which we refer to as "Merger Sub"), which is an indirect, wholly-owned subsidiary of Waste Management. We refer to the original merger agreement, as amended by the merger agreement amendment, and as it may be further amended from time to time, as the "amended merger agreement". Pursuant to the merger agreement amendment, among other things, we and Waste Management agreed that Waste Management is required to use its "best efforts" to take all actions to consummate the transactions by the end date, including using its "best efforts" to obtain antitrust approval, to eliminate the limitations on the divestiture obligation of Waste Management as provided in the original merger agreement applicable to any divestiture required by the U.S. Department of Justice (which we refer to as the "DOJ") to obtain antitrust approval of the merger, and that if the merger is completed, the price per share of Advanced Disposal common stock would be reduced from $33.15 in cash to $30.30 in cash. Pursuant to the terms of the amended merger agreement, Merger Sub will merge with and into Advanced Disposal (which we refer to as the "merger"), and Advanced Disposal will continue as the surviving company and an indirect, wholly-owned subsidiary of Waste Management. You will also be asked to consider and vote upon a non-binding advisory proposal to approve specified compensation that may be paid or become payable to Advanced Disposal's named executive officers in connection with the merger and contemplated by the amended merger agreement (which we refer to as the "compensation advisory proposal") and a proposal to approve one or more adjournments of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to approve the proposal to adopt the amended merger agreement (which we refer to as the "adjournment proposal").

If the merger is completed, you will be entitled to receive $30.30 in cash, without interest and less applicable withholding taxes, for each share of Advanced Disposal common stock, par value $0.01 per share (which we refer to as "Advanced Disposal common stock") you own (unless you have properly exercised your appraisal rights with respect to such shares).

The Advanced Disposal Board of Directors (which we refer to as the "Board") unanimously determined that the amended merger agreement and the transactions contemplated by the amended merger agreement are

Table of Contents

fair to, and in the best interests of, Advanced Disposal and its stockholders, approved and declared advisable the amended merger agreement and the transactions contemplated by the amended merger agreement, including the merger, and approved the execution and delivery by Advanced Disposal of the amended merger agreement and performance by Advanced Disposal of the amended merger agreement and the consummation of the transactions, including the merger, contemplated by the amended merger agreement. The Board unanimously recommends that you vote (1) "FOR" the proposal to adopt the amended merger agreement, (2) "FOR" the compensation advisory proposal and (3) "FOR" the adjournment proposal.

Advanced Disposal agreed to reduce the purchase price from the original merger agreement and make other changes to the original merger agreement because, among other things, (1) the parties believed they would be unable to obtain clearance from the DOJ under the divestiture threshold outlined in the original merger agreement by July 13, 2020, the "end date" in the original merger agreement, and (2) the Board believed, for the reasons described in the proxy statement, including the increased closing certainty as a result of the elimination of the divestiture threshold, that it was in the best interests of Advanced Disposal stockholders to agree to a reduced price and other amended terms, rather than risk termination of the original merger agreement and continuing as a standalone company. The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger agreement in connection with the June 28, 2019 special meeting of Advanced Disposal stockholders (which we refer to as the "Original Special Meeting"), Advanced Disposal is asking for your vote again.

All Advanced Disposal stockholders of record at the close of business on July 23, 2020, the record date for the Special Meeting, are welcome to attend the Special Meeting via the Special Meeting website. Every stockholder's vote is important to us, so it is important that your shares are represented at the Special Meeting whether or not you plan to attend via the Special Meeting website. To ensure that you will be represented, please promptly vote by submitting the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone. You will also be able to attend the Special Meeting online and vote your shares electronically by visiting the Special Meeting website. If you plan to attend the Special Meeting, you will need the 16-digit control number included on your proxy card or voting instruction form that is accompanied by your proxy materials. If you attend the Special Meeting and vote via the Special Meeting website, your vote will revoke any proxy that you have previously submitted. If you hold your shares in street name, you should instruct your broker, bank or other nominee how to vote in accordance with the voting instruction form you will receive from your broker, bank or other nominee.

The enclosed proxy statement provides detailed information about the Special Meeting, the amended merger agreement, the changes to the original merger agreement set forth in the merger agreement amendment, and the merger. A copy of the original merger agreement is attached as Annex A to the proxy statement and a copy of the merger agreement amendment is attached as Annex B to the proxy statement. The proxy statement also describes the actions and determinations of the Board in connection with its evaluation of the amended merger agreement and the merger. We encourage you to read the proxy statement and its annexes, including the original merger agreement and the merger agreement amendment, carefully and in their entirety. You may also obtain more information about Advanced Disposal from documents we file with the U.S. Securities and Exchange Commission (which we refer to as the "SEC") from time to time.

Your vote is very important, regardless of the number of shares that you own. We cannot consummate the merger unless the proposal to adopt the amended merger agreement is approved by the affirmative vote of the holders of a majority of the shares of Advanced Disposal common stock issued and outstanding and entitled to vote thereon. The failure of any stockholder to vote by ballot via the Special Meeting website, to submit a signed proxy card or to grant a proxy electronically over the Internet or by telephone or an abstention from voting will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. If you hold your shares in street name, the failure to instruct your broker, bank or other nominee on how to vote your shares will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement.

Table of Contents

If you have any questions or need assistance voting your shares of Advanced Disposal common stock, please contact Innisfree M&A Incorporated, our proxy solicitor, by calling the toll-free number at +1 (877) 687-1866.

On behalf of the Board, management and employees of Advanced Disposal, thank you for your continued support of Advanced Disposal and we appreciate your consideration of this matter.

Sincerely,

Richard Burke
Chairman and Chief Executive Officer

Neither the SEC nor any state securities regulatory agency has approved or disapproved of the transactions described in this document, including the merger, or determined if the information contained in this document is accurate or adequate. Any representation to the contrary is a criminal offense.

The accompanying proxy statement is dated July 24, 2020 and, together with the enclosed form of proxy card, is first being mailed to stockholders of record of Advanced Disposal on or about July 27, 2020.

Table of Contents

Advanced Disposal Services, Inc.

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

NOTICE IS HEREBY GIVEN that a Special Meeting (which we refer to as the "Special Meeting") of the stockholders of Advanced Disposal Services, Inc. (which we refer to as "Advanced Disposal," "we," "us," "our," and the "Company"), is to be held virtually via the Internet on August 25, 2020 beginning at 10:00 a.m. Eastern Time. As part of our precautions regarding the COVID-19 (coronavirus) pandemic, we are sensitive to the public health and travel concerns that our stockholders may have, as well as any quarantines or other protocols that governments may impose. As a result, the Special Meeting will be held in a virtual meeting format only, via live webcast. There will not be a physical meeting location. You will be able to attend the Special Meeting online and vote your shares electronically by visiting www.virtualshareholdermeeting.com/ADSW2020SM (which we refer to as the "Special Meeting website"). The Special Meeting will be held for Advanced Disposal stockholders to consider and vote upon the following proposals:

1.

to adopt the Agreement and Plan of Merger, dated as of April 14, 2019 (which we refer to as the "original merger agreement"), as amended by Amendment No. 1 thereto, dated as of June 24, 2020 (which we refer to as the "merger agreement amendment"), by and among Advanced Disposal, Waste Management, Inc. (which we refer to as "Waste Management") and Everglades Merger Sub Inc. (which we refer to as "Merger Sub"), as it may be amended from time to time (a copy of the original merger agreement is attached as Annex A to the proxy statement and a copy of the merger agreement amendment is attached as Annex B to the proxy statement; we refer to the original merger agreement, as amended by the merger agreement amendment and as it may be further amended from time to time, as the "amended merger agreement"). Pursuant to the amended merger agreement, Merger Sub will merge with and into Advanced Disposal (which we refer to as the "merger"), and Advanced Disposal will continue as the surviving company and an indirect, wholly-owned subsidiary of Waste Management;



2.

to approve, on a non-binding advisory basis, specified compensation that may be paid or become payable to Advanced Disposal's named executive officers in connection with the merger and contemplated by the amended merger agreement (which we refer to as the "compensation advisory proposal"); and



3.

to approve one or more adjournments of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to approve the proposal to adopt the amended merger agreement (which we refer to as the "adjournment proposal").

Your vote is very important, regardless of the number of shares that you own.    We cannot consummate the merger unless the proposal to adopt the amended merger agreement is approved by the affirmative vote of the holders of a majority of the shares of Advanced Disposal common stock, par value $0.01 per share (which we refer to as the "Advanced Disposal common stock") issued and outstanding at the close of business on the record date and entitled to vote thereon. The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger

Table of Contents

agreement in connection with the June 28, 2019 special meeting of Advanced Disposal stockholders (which we refer to as the "Original Special Meeting"), Advanced Disposal is asking for your vote again.

Even if you plan to attend the Special Meeting via the Special Meeting website, we request that you complete, sign, date and return, as promptly as possible, the enclosed proxy card in the accompanying prepaid reply envelope or submit your proxy or voting instructions by telephone or the Internet prior to the Special Meeting to ensure that your shares of Advanced Disposal common stock will be represented and voted at the Special Meeting if you are unable to attend via the Special Meeting website.

For Advanced Disposal to consummate the merger, stockholders holding a majority of the shares of Advanced Disposal common stock issued and outstanding at the close of business on the record date and entitled to vote thereon must vote "FOR" the proposal to adopt the amended merger agreement. Failure to submit a signed proxy card, grant a proxy by phone or the Internet or to vote by ballot via the Special Meeting website or an abstention from voting will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise and will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement.

The approval, on a non-binding advisory basis, of the compensation advisory proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Advanced Disposal common stock that are present at the Special Meeting via the Special Meeting website or represented by proxy at the Special Meeting and entitled to vote thereon, so long as a quorum is present, to vote "FOR" the compensation advisory proposal. An abstention from voting will have the same effect as a vote "AGAINST" the compensation advisory proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the compensation advisory proposal, so long as a quorum is otherwise present.

The affirmative vote of the holders of a majority of the issued and outstanding shares of Advanced Disposal common stock that are present at the Special Meeting via the Special Meeting website or represented by proxy at the Special Meeting and entitled to vote thereon, whether or not a quorum is present, is required to approve the adjournment proposal. An abstention from voting will have the same effect as a vote "AGAINST" the adjournment proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the adjournment proposal.

Only stockholders of record as of the close of business on July 23, 2020, the record date for the Special Meeting, are entitled to notice of the Special Meeting and to vote at the Special Meeting or at any adjournment or postponement thereof. As required by our amended and restated bylaws, a list of stockholders entitled to vote at the Special Meeting will be available in our corporate offices located at 90 Fort Wade Road, Ponte Vedra, FL 32081 during regular business hours for a period of at least ten (10) days before the Special Meeting and available online during the Special Meeting. If our headquarters are closed for health and safety reasons related to the COVID-19 (coronavirus) pandemic during such period, the list of stockholders will be made available for inspection upon request via email to investorrelations@advanceddisposal.com, subject to our satisfactory verification of stockholder status, and will also be made available online during the Special Meeting via the Special Meeting website.

The enclosed proxy statement provides detailed information about the Special Meeting, the amended merger agreement, including the original merger agreement and the merger agreement amendment, and the merger. A copy of the original merger agreement is attached as Annex A to the proxy statement and a copy of the merger agreement amendment is attached as Annex B to the proxy statement. The proxy statement also describes the actions and determinations of the Board in connection with its evaluation of the amended merger agreement and the merger. We encourage you to read the proxy statement and its annexes, including the original merger agreement and the merger agreement amendment, carefully and in their entirety. You may also obtain more information about Advanced Disposal from documents we file with the U.S. Securities and Exchange Commission from time to time. If you have any questions concerning the merger, the Special Meeting or this proxy statement, would like additional copies of this

Table of Contents

proxy statement or need help voting your shares of Advanced Disposal common stock, please contact our proxy solicitor:

Innisfree M&A Incorporated
501 Madison Avenue, 20th Floor
New York, NY 10022
Stockholders may call toll-free: +1 (877) 687-1866
Banks and brokers may call collect: +1 (212) 750-5833

Stockholders who do not vote "FOR" the proposal to adopt the amended merger agreement will have the right to seek appraisal for the fair value of their shares of Advanced Disposal common stock if they deliver a demand for appraisal before the vote is taken on the amended merger agreement and comply with all applicable requirements under Delaware law, which are summarized herein and reproduced in their entirety in Annex E to the proxy statement.

The Advanced Disposal Board of Directors unanimously recommends that you vote (1) "FOR" the proposal to adopt the amended merger agreement, (2) "FOR" the compensation advisory proposal and (3) "FOR" the adjournment proposal.

By Order of the Board of Directors,

Michael K. Slattery
Corporate Secretary
Ponte Vedra, Florida
July 24, 2020

Table of Contents

YOUR VOTE IS IMPORTANT

WHETHER OR NOT YOU EXPECT TO ATTEND THE SPECIAL MEETING VIA THE SPECIAL MEETING WEBSITE, WE ENCOURAGE YOU TO SUBMIT YOUR PROXY AS PROMPTLY AS POSSIBLE (1) BY TELEPHONE, (2) THROUGH THE INTERNET OR (3) BY MARKING, SIGNING AND DATING THE ENCLOSED PROXY CARD AND RETURNING IT IN THE POSTAGE-PAID ENVELOPE PROVIDED. You may revoke your proxy or change your vote at any time before the Special Meeting. If your shares are held in the name of a broker, bank or other nominee, please follow the instructions on the voting instruction card furnished to you by such broker, bank or other nominee, which is considered the stockholder of record, in order to vote. As a beneficial owner, you have the right to direct your broker, bank or other nominee on how to vote the shares in your account. Your broker, bank or other nominee cannot vote on any of the proposals, including the proposal to adopt the amended merger agreement, without your instructions.

If you fail to return your proxy card, to grant your proxy electronically over the Internet or by telephone, or to vote by ballot via the Special Meeting website, your shares will not be counted for purposes of determining whether a quorum is present at the Special Meeting. If you are a stockholder of record, voting by ballot via the Special Meeting website will revoke any proxy that you previously submitted. If you hold your shares through a broker, bank or other nominee, you must obtain from the record holder a valid proxy issued in your name in order to vote via the Special Meeting website.

The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger agreement in connection with the Original Special Meeting, Advanced Disposal is asking for your vote again.

Table of Contents

Table of Contents

i

Table of Contents

Annexes

ii

Table of Contents

1

Table of Contents

2

Table of Contents

3

Table of Contents

4

Table of Contents

5

Table of Contents

6

Table of Contents

7

Table of Contents

8

Table of Contents

9

Table of Contents

10

Table of Contents

11

Table of Contents

12

Table of Contents

13

Table of Contents

14

Table of Contents

QUESTIONS AND ANSWERS

The following questions and answers are intended to address briefly some commonly asked questions regarding the Special Meeting, the amended merger agreement and the transactions. These questions and answers may not address all questions that may be important to you as an Advanced Disposal stockholder. Please refer to the section entitled "Summary" preceding this section and the more detailed information contained elsewhere in this proxy statement, the annexes to this proxy statement, including the original merger agreement and the merger agreement amendment, and the documents referred to in this proxy statement, all of which you should read carefully. The original merger agreement is attached as Annex A to the proxy statement and the merger agreement amendment is attached as Annex B to the proxy statement.

Q:

Why am I receiving this proxy statement?

A:    On June 24, 2020, Advanced Disposal entered into the merger agreement amendment, which modified the original merger agreement. The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger agreement in connection with the Original Special Meeting, Advanced Disposal is asking for your vote again. The amended merger agreement provides for the merger of Merger Sub with and into Advanced Disposal, with Advanced Disposal surviving the merger as an indirect, wholly-owned subsidiary of Waste Management. You are receiving this proxy statement in connection with the solicitation of proxies by the Board "FOR" the proposal to adopt the amended merger agreement and to approve the other proposals to be voted on at the Special Meeting.

Q:

What is a proxy?

A:    A proxy is your legal designation of another person, referred to as a "proxy," to vote your shares of Advanced Disposal common stock. The written document describing the matters to be considered and voted on at the Special Meeting is called a "proxy statement." The document used to designate a proxy to vote your shares of Advanced Disposal common stock is called a "form of proxy" or "proxy card." The Board has designated each of Richard Burke, Chairman and Chief Executive Officer, and Michael K. Slattery, Corporate Secretary, with full power of substitution, as proxy for the Special Meeting.

Q:

What is the proposed transaction?

A:    The proposed transaction is the acquisition of Advanced Disposal by Waste Management through the merger of Merger Sub with and into Advanced Disposal pursuant to the amended merger agreement. Following the effective time, Advanced Disposal will be privately held as an indirect, wholly-owned subsidiary of Waste Management, and you will no longer own shares of Advanced Disposal common stock and instead will have only the right to receive the merger consideration. Following the consummation of the merger, Advanced Disposal common stock will be de-listed from NYSE and de-registered under the Exchange Act; thus, Advanced Disposal will no longer be a public company.

Q:

What will I receive in the merger?

A:    If the merger is consummated, you will be entitled to receive $30.30 in cash for each share of Advanced Disposal common stock you own, without interest and less applicable withholding taxes. For example, if you own 100 shares of Advanced Disposal common stock, you will be entitled to receive $3,030.00 in cash, without interest and less applicable withholding taxes. After the effective time, you will no longer have any rights as an Advanced Disposal stockholder, other than the right to receive the merger consideration.

15

Table of Contents

Q:

Why is there a second special meeting relating to the merger?

A:    In connection with agreeing to certain changes to the terms of the transactions and increased closing certainty, Advanced Disposal agreed to reduce the purchase price from the original merger agreement and make the other changes to the original merger agreement, and the Board believed, for the reasons described in this proxy statement, that it was in the best interests of Advanced Disposal to agree to a reduced price and other amended terms, rather than terminate the original merger agreement and continue as a standalone company. The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger agreement in connection with the Original Special Meeting, Advanced Disposal is asking for your vote again.

Q:

What changes were made to the original merger agreement pursuant to the merger agreement amendment?

A:    In exchange for agreeing to reduce the per share merger consideration, Advanced Disposal and Waste Management agreed to amend the terms of the original merger agreement to provide increased closing certainty to the Advanced Disposal stockholders, including by: (i) extending the end date from July 13, 2020 to September 30, 2020, which will be further extended automatically to November 30, 2020 if, subject to certain conditions, Advanced Disposal stockholder approval or antitrust approval has not been obtained by September 30, 2020; (ii) providing for a Waste Management termination fee of $250,000,000 (increased from $150,000,000); (iii) providing that Waste Management must use "best efforts" to take all actions to consummate the transactions by the end date, including using its "best efforts" to obtain antitrust approval, is required to sell or divest assets (belonging to Waste Management or Advanced Disposal or any of its subsidiaries) in order to obtain antitrust approval and to eliminate the $200,000,000 revenue threshold on the divestiture obligation of Waste Management as provided in the original merger agreement and (iv) providing that each party has certified to the other that such party's closing conditions with respect to the accuracy of its representations and performance of its covenants, and, with respect to Waste Management, the absence of a material adverse effect on Advanced Disposal, would be satisfied as of the date of the merger agreement amendment as if the closing were to occur on such date (and that Waste Management and Merger Sub will not assert that any of such conditions are not satisfied at the closing as a result of what such parties had knowledge of as of the date of the merger agreement amendment). In addition, the original merger agreement was amended to eliminate the obligation of Advanced Disposal to reimburse Waste Management's expenses of up to $15,000,000 if the amended merger agreement is terminated by either Advanced Disposal or Waste Management as a result of a failure to obtain the Advanced Disposal stockholder approval as provided in the original merger agreement.

Q:

Why was the original merger agreement amended to, among other things, reduce the per share merger consideration?

A:    Under the original merger agreement, subject to certain conditions, Waste Management and Advanced Disposal each had the right to terminate the original merger agreement after July 13, 2020 if the closing had not occurred by such date. In addition, the original merger agreement contained limitations on Waste Management's divestiture obligation, which the parties sought to eliminate. The parties did not expect to receive antitrust approval by such date on terms acceptable to the parties. The Board considered Advanced Disposal's options and the proposed terms of the merger agreement amendment, and unanimously determined that the amended merger agreement and the transactions contemplated by the amended merger agreement, including the merger, are advisable, fair to, and in the best interests of Advanced Disposal and its stockholders, and approved, adopted and declared advisable the amended merger agreement and the transactions contemplated thereby. A more complete description of the background of the negotiations relating to the merger agreement amendment is provided under "The

16

Table of Contents

Merger (Proposal 1)—Background of the Merger" beginning on page 40 of this proxy statement and a more complete description of the factors that the Board considered and reasons for the merger is provided under "The Merger (Proposal 1)—Recommendation of the Board and Reasons for Recommendation" beginning on page 54 of this proxy statement.

Q:

What is included in these materials?

A:    These materials include:

•

this proxy statement for the Special Meeting;

•

a proxy card or voting instruction form (enclosed with this proxy statement);

•

a copy of the original merger agreement (attached as Annex A to this proxy statement);

•

a copy of the merger agreement amendment (attached as Annex B to this proxy statement);

•

a copy of the amended and restated voting agreement (attached as Annex C to this proxy statement);

•

the written opinion of UBS (attached as Annex D to this proxy statement); and

•

the full text of Section 262 of the DGCL (attached as Annex E to this proxy statement).

Q:

Where and when is the Special Meeting?

A:    The Special Meeting will be held virtually via the Internet on August 25, 2020 beginning at 10:00 a.m. Eastern Time. As part of our precautions regarding the COVID-19 (coronavirus) pandemic, we are sensitive to the public health and travel concerns that our stockholders may have, as well as any quarantines or other protocols that governments may impose. As a result, the Special Meeting will be held in a virtual meeting format only, via live webcast. There will not be a physical meeting location. You will be able to attend the Special Meeting online and vote your shares electronically by visiting www.virtualshareholdermeeting.com/ADSW2020SM (which we refer to as the "Special Meeting website"). If you plan to attend the Special Meeting, you will need the 16-digit control number included on your proxy card or voting instruction form that is accompanied by your proxy materials.

To ensure that you will be represented, we encourage you to promptly vote by submitting the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone. In certain circumstances, the Special Meeting could be adjourned to another time or place. All references in our proxy materials to Special Meeting include any adjournment or postponement of the Special Meeting.

Q:

How do I attend the Special Meeting?

A:    You will be able to attend the Special Meeting online and vote your shares electronically by visiting the Special Meeting website. If you plan to attend the Special Meeting, you will need the 16-digit control number included on your proxy card or voting instruction form that is accompanied by your proxy materials. During the Special Meeting, Advanced Disposal stockholders will be able to vote their shares. Shares previously voted at the Special Meeting do not need to be voted again unless you intend to change or revoke your prior vote.

If you are a beneficial owner of shares held in street name and wish to vote via the Special Meeting website, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions. If you are not a holder of record as of the close of business on the record date, you will be permitted to vote at the Special Meeting only if you have a valid legal proxy from a holder of record as of the close of business on the record date.

17

Table of Contents

Q:

What proposals will be voted on at the Special Meeting?

A:    There are three (3) proposals scheduled to be voted on at the Special Meeting:

•

to adopt the amended merger agreement;

•

to approve, on a non-binding advisory basis, specified compensation that may be paid or become payable to Advanced Disposal's named executive officers in connection with the merger and contemplated by the amended merger agreement (which we refer to as the "compensation advisory proposal"); and

•

to approve one or more adjournments of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to approve the proposal to adopt the amended merger agreement (which we refer to as the "adjournment proposal").

Q:

What is the Board's voting recommendation?

A:    Upon consideration, the Board unanimously recommends that you vote your shares:

•

"FOR" the proposal to adopt the amended merger agreement;

•

"FOR" the compensation advisory proposal; and

•

"FOR" the adjournment proposal.

For a discussion of the factors that the Board considered in determining to approve the execution and delivery of the amended merger agreement by Advanced Disposal and to recommend the adoption of the amended merger agreement, please see the section entitled "The Merger (Proposal 1)—Recommendation of the Board and Reasons for Recommendation" beginning on page 54 of this proxy statement. In addition, in considering the recommendation of the Board with respect to the amended merger agreement, you should be aware that some of our directors and executive officers have interests that may be different from, or in addition to, the interests of Advanced Disposal stockholders generally. For a discussion of these interests, please see the section entitled "The Merger (Proposal 1)—Interests of Advanced Disposal Directors and Executive Officers in the Merger" beginning on page 71 of this proxy statement.

Q:

Who is entitled to vote at the Special Meeting?

A:    All shares of Advanced Disposal common stock owned by you as of the record date, which is the close of business on July 23, 2020, may be voted by you. You may cast one vote per share of Advanced Disposal common stock that you held on the record date. These shares include shares that are:

•

held directly in your name as the stockholder of record; and

•

held through a broker, bank or other nominee for you as the beneficial owner, including those shares over which a broker, bank or other nominees has provided you with a specific control number and further instructions allowing you to vote those shares via the Special Meeting website.

As of the close of business on the record date, there were 90,758,187 shares of Advanced Disposal common stock issued and outstanding, and entitled to vote at the Special Meeting. Each share of Advanced Disposal common stock issued and outstanding as of the close of business on the record date will be entitled to one vote on each matter submitted to a vote at the Special Meeting.

18

Table of Contents

Q:

What is the difference between holding shares as a "stockholder of record" and as a "beneficial owner"?

A:    Our stockholders may hold their shares through a broker, bank or other nominee rather than directly in their own name. As summarized below, there are some differences between shares held of record and those owned beneficially.

•

Stockholder of Record.  If your shares of Advanced Disposal common stock are registered directly in your name with Advanced Disposal's transfer agent, EQ Shareowner Services, you are considered, with respect to those shares, the stockholder of record, and this proxy statement was sent directly to you by Advanced Disposal. As the stockholder of record, you have the right to vote via the Special Meeting website, grant your voting proxy directly to certain officers of Advanced Disposal or to appoint a representative of your choosing to attend the Special Meeting and vote on your behalf by granting such person a "legal proxy."

•

Beneficial Owner.  If your shares of Advanced Disposal common stock are held in an account at a broker, bank or other nominee, you are considered the beneficial owner of shares held in street name, and this proxy statement was forwarded to you by your broker, bank or other nominee, who is considered, with respect to those shares, to be the "stockholder of record." As the beneficial owner, you have the right to direct your broker, bank or other nominee how to vote your shares on your behalf at the Special Meeting, or you may contact your broker, bank or other nominee to obtain your specific control number and further instructions. Because you are not the "stockholder of record," you may not vote your shares via the Special Meeting website, unless you request and obtain your specific control number from your broker, bank or other nominee.

Q:

What must I do if I want to attend the Special Meeting?

A:    Only individuals who were Advanced Disposal stockholders as of the close of business on the record date and their authorized representatives may attend the Special Meeting. If you plan to attend the Special Meeting, you will need the 16-digit control number included on your proxy card or voting instruction form that is accompanied by your proxy materials. During the Special Meeting, Advanced Disposal stockholders will be able to vote their shares. If you are a beneficial owner of shares held in street name and wish to vote at the Special Meeting, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions. To ensure that you will be represented, even if you plan to attend the Special Meeting via the Special Meeting website, we encourage you to promptly vote by submitting the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone. If you attend the Special Meeting and vote by ballot via the Special Meeting website, your vote will revoke any proxy that you have previously submitted. Please contact your broker, bank or other nominee for instructions regarding obtaining your specific control number and further instructions.

Q:

If I am a stockholder of record of shares of Advanced Disposal common stock, how do I vote?

A:    If you are a stockholder of record, there are four (4) ways you can vote:

•

via the Special Meeting website;

•

via the Internet, at the Internet address provided on the proxy card;

•

by telephone, by using the toll-free number listed on the proxy card; or

•

by mail, by completing, signing and dating the proxy card and returning it in the enclosed postage-paid envelope.

19

Table of Contents

Q:

If I am a beneficial owner of shares of Advanced Disposal common stock held in street name, how do I vote?

A:    If you are a beneficial owner of shares of Advanced Disposal common stock held in street name, you will receive instructions from your broker, bank or other nominee as to how to vote your shares. You must follow the instructions of your broker, bank or other nominee in order for your shares to be voted. Telephone and Internet voting also will be offered to stockholders owning shares through certain brokers, banks and other nominees. If your shares are not registered in your own name but are held through your broker, bank or other nominee and you plan to vote your shares via the Special Meeting website, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions. Please note that if you hold your shares through a broker, bank or other nominee, such nominee cannot vote your shares unless you have given your nominee specific instructions as to how to vote. In order for your vote to be counted, please make sure that you submit your vote to your broker, bank or other nominee.

Q:

Will my shares of Advanced Disposal common stock held in street name or another form of record ownership be combined for voting purposes with shares I hold of record?

A:    No. Because any shares of Advanced Disposal common stock you may hold in street name will be deemed to be held by a different stockholder of record than any shares of Advanced Disposal common stock you hold of record, any shares of Advanced Disposal common stock held in street name will not be combined for voting purposes with shares of Advanced Disposal common stock you hold of record.

Similarly, if you own shares of Advanced Disposal common stock in various registered forms, such as jointly with your spouse, as trustee of a trust or as custodian for a minor, you will receive, and will need to sign and return, a separate proxy card or vote separately by telephone or Internet with respect to those shares of Advanced Disposal common stock because they are held in a different form of record ownership. Shares of Advanced Disposal common stock held by a corporation or business entity must be voted by an authorized officer of the entity. Shares of Advanced Disposal common stock held in an individual retirement account must be voted under the rules governing such account.

Q:

What is the quorum requirement for the Special Meeting?

A:    A quorum is necessary to hold a valid meeting of the Advanced Disposal stockholders. The holders of record of a majority of the shares entitled to vote, present at the Special Meeting via the Special Meeting website or represented by proxy, at the close of business on the record date will constitute a quorum at the Special Meeting. If a quorum is not present at the Special Meeting, the Special Meeting may be adjourned or postponed from time to time until a quorum is obtained. Pursuant to the amended and restated voting agreement, CPPIB has agreed to cause its shares of Advanced Disposal common stock to be counted at the Special Meeting for purposes of determining whether a quorum has been obtained.

If you submit a proxy but fail to provide voting instructions or abstain on any of the proposals listed on the proxy card, your shares will be counted for the purpose of determining whether a quorum is present at the Special Meeting.

If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, these shares will not be counted for purposes of determining whether a quorum is present for the transaction of business at the Special Meeting.

In the event that a quorum is not present at the Special Meeting, we expect to adjourn or postpone the Special Meeting until we solicit enough proxies to obtain a quorum.

20

Table of Contents

Q:

What happens if I do not give specific voting instructions?

A:    Stockholder of Record.    If you are a stockholder of record and you submit a signed proxy card or submit your proxy by telephone or the Internet, but do not specify how you want to vote your shares on a particular proposal, then the proxy holders will vote your shares in accordance with the recommendations of the Board on all matters presented in this proxy statement. Thus, your shares of Advanced Disposal common stock will be voted:

•

"FOR" the proposal to adopt the amended merger agreement;

•

"FOR" the compensation advisory proposal; and

•

"FOR" the adjournment proposal.

Beneficial Owner.    If you are a beneficial owner of shares held in street name, under applicable stock exchange rules the broker, bank or other nominee that holds your shares may generally vote on routine proposals but cannot vote without instructions on non-routine matters unless they have discretionary authority. None of the proposals to be voted on at the Special Meeting are considered routine proposals. As a result, if the broker, bank or other nominee that holds your shares does not receive instructions from you on how to vote your shares, a "broker non-vote" will occur. Therefore, we urge you to give voting instructions to your broker. Shares represented by such "broker non-votes" will not be counted as present at the Special Meeting or represented by proxy in determining whether there is a quorum. A "broker non-vote" will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. Your abstention will have no effect on the compensation advisory proposal or the adjournment proposal.

Q:

What is the voting requirement to approve the proposal to adopt the amended merger agreement?

A:    Adoption of the amended merger agreement requires stockholders holding a majority of the shares of Advanced Disposal common stock issued and outstanding at the close of business on the record date and entitled to vote thereon to vote "FOR" the proposal to adopt the amended merger agreement. A failure to vote your shares of Advanced Disposal common stock or an abstention from voting on this proposal will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise and will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement.

Q:

What is the voting requirement to approve the compensation advisory proposal?

A:    The approval of the compensation advisory proposal requires stockholders holding a majority of the issued and outstanding shares of Advanced Disposal common stock which are present at the Special Meeting via the Special Meeting website or represented by proxy at the Special Meeting and entitled to vote thereon, so long as a quorum is present, to vote "FOR" the compensation advisory proposal. An abstention from voting on the compensation advisory proposal will have the same effect as a vote "AGAINST" the compensation advisory proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but, so long as a quorum is otherwise present at the Special Meeting, will have no effect on the compensation advisory proposal. Because the vote to approve the compensation advisory proposal is only advisory in nature, it will not be binding on Advanced Disposal, Waste Management or the surviving company. Accordingly, if the amended merger agreement is adopted by Advanced Disposal stockholders and the merger is completed, the merger-related compensation may be paid to Advanced Disposal's named executive officers even if stockholders fail to approve the compensation advisory proposal, so long as quorum is otherwise present.

21

Table of Contents

Q:

What is the voting requirement to approve the adjournment proposal?

A:    The approval of the adjournment proposal requires stockholders holding a majority of the issued and outstanding shares of Advanced Disposal common stock, present at the Special Meeting via the Special Meeting website or represented by proxy at the Special Meeting and entitled to vote thereon, whether or not a quorum is present, to vote "FOR" the adjournment proposal. An abstention from voting on the adjournment proposal will have the same effect as a vote "AGAINST" the adjournment proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the adjournment proposal.

Q:

How do Advanced Disposal directors and executive officers intend to vote?

A:    We currently expect that Advanced Disposal directors and executive officers will vote their shares of Advanced Disposal common stock "FOR" the proposal to adopt the amended merger agreement and the other proposals to be considered at the Special Meeting, although they have no obligation to do so.

The directors and executive officers of Advanced Disposal have interests in the merger that may be different from, or in addition to, the interests of Advanced Disposal stockholders generally. These interests are described in more detail in the section entitled "The Merger (Proposal 1)—Interests of Advanced Disposal Directors and Executive Officers in the Merger" beginning on page 71 of this proxy statement.

Q:

Have any stockholders already agreed to vote "FOR" the adoption of the amended merger agreement?

A:    Yes. CPPIB, which beneficially owned approximately 18.3% of the issued and outstanding shares of Advanced Disposal common stock as of the close of business on the record date, entered into the amended and restated voting agreement with Waste Management to vote the Advanced Disposal common stock beneficially owned by it as of the close of business on the record date for the adoption of the amended merger agreement, subject to the terms and conditions of the amended and restated voting agreement. The amended and restated voting agreement is described in more detail in the section entitled "The Amended and Restated Voting Agreement" beginning on page 109 of this proxy statement.

Q:

What effects will the merger have on Advanced Disposal and the Advanced Disposal common stock?

A:    Advanced Disposal common stock is currently registered under the Exchange Act, and is listed on NYSE under the symbol "ADSW." At the effective time, Merger Sub will merge with and into Advanced Disposal, with Advanced Disposal continuing as the surviving company and as an indirect, wholly-owned subsidiary of Waste Management. As a result of the merger, Advanced Disposal will cease to be a publicly traded company. Following the consummation of the merger, Advanced Disposal common stock will be de-listed from NYSE and de-registered under the Exchange Act.

Q:

What effects will the merger have on Advanced Disposal equity awards?

A:    At the effective time, each Advanced Disposal stock option that is outstanding immediately prior to the effective time and that has an exercise price per share that is less than $30.30, whether or not vested, will become fully vested and will be cancelled and thereafter entitle the holder to receive, promptly after the effective time, a cash payment (without interest and subject to all applicable tax withholding requirements) equal to the product of (i) the excess of $30.30 over the per-share exercise price of such Advanced Disposal stock option and (ii) the number of shares issuable upon exercise of such Advanced Disposal stock option. Each Advanced Disposal stock option with an exercise price equal to or greater than $30.30 will be cancelled as of the effective time without payment of any consideration and will have no further force or effect.

22

Table of Contents

At the effective time, each performance share unit award that is outstanding immediately prior to the effective time will become fully vested and will be cancelled and thereafter entitle the holder to receive, promptly after the effective time, a cash payment (without interest and subject to all applicable tax withholding requirements) equal to the product of (i) the number of shares equal to the greater of (x) the target number of shares with respect to such performance share unit award and (y) the number of shares that would be considered earned under the terms of such performance share unit award based on the most recent fiscal year-end results multiplied by (ii) $30.30.

At the effective time, each restricted share unit award that is outstanding immediately prior to the effective time will become fully vested and will be cancelled and thereafter entitle the holder to receive, promptly after the effective time, a cash payment (without interest and subject to all applicable tax withholding requirements) equal to the product of (i) the number of shares subject to such restricted share unit award and (ii) $30.30.

Further, at the effective time, each restricted share award that is outstanding immediately prior to the effective time will become fully vested and will be cancelled and thereafter entitle the holder to receive, promptly after the effective time, a cash payment (without interest and subject to all applicable tax withholding requirements) equal to the product of (i) the number of shares subject to such restricted share award and (ii) $30.30.

No Advanced Disposal equity awards have been granted to any director, executive officer or employee of Advanced Disposal between the date of the original merger agreement and the date of this proxy statement.

Q:

When is the merger expected to be completed?

A:    Together with Waste Management, we are working toward completing the merger as quickly as possible after the date of the Special Meeting, and currently expect to consummate the merger by the end of the third quarter of 2020. We cannot be certain when or if the conditions to the merger will be satisfied (or, to the extent permitted, waived). The merger cannot be completed until the conditions to closing are satisfied (or, to the extent permitted, waived), including, among other things, the adoption of the amended merger agreement by Advanced Disposal stockholders.

Q:

What happens if the merger is not completed?

A:    If the amended merger agreement is not adopted by Advanced Disposal stockholders, or if the merger is not completed for any other reason, the Advanced Disposal stockholders will not receive any payment for their shares of Advanced Disposal common stock in connection with the merger. Except in certain circumstances where Advanced Disposal has entered into an alternative transaction to the merger, Advanced Disposal would remain a public company, and shares of Advanced Disposal common stock would continue to be registered under the Exchange Act, as well as listed and traded on NYSE. In the event that the amended merger agreement is terminated, in certain specified circumstances, the Company termination fee (or potentially an amount of up to $15,000,000 in expenses) will be due and payable by Advanced Disposal to Waste Management, and in certain other specified circumstances, the Waste Management termination fee will be due and payable by Waste Management to Advanced Disposal. See the sections entitled "The Amended Merger Agreement—Termination; Effect of Termination" beginning on page 105 of this proxy statement and "The Amended Merger Agreement—Company Termination Fee; Waste Management Termination Fee" beginning on page 106 of this proxy statement.

23

Table of Contents

Q:

What will happen if stockholders do not approve the compensation advisory proposal?

A:    The inclusion of this proposal is required by the SEC rules. However, the approval of the compensation advisory proposal is not a condition to the completion of the merger and the vote on the compensation advisory proposal is an advisory vote and will not be binding on Advanced Disposal, Waste Management or the surviving company. If the amended merger agreement is adopted by Advanced Disposal stockholders and the merger is completed, the merger-related compensation may be paid to Advanced Disposal's named executive officers even if stockholders fail to approve the compensation advisory proposal.

Q:

Is it possible for stockholders to reject the amended merger agreement and return to the terms of the original merger agreement?

A:    No. Approval of the amended merger agreement (for the avoidance of doubt, as it has been amended by the merger agreement amendment) is a condition to closing the merger. If the amended merger agreement is not adopted by Advanced Disposal stockholders or if the merger is not completed for any other reason, Advanced Disposal stockholders will not receive any payment for their shares of common stock. Instead, Advanced Disposal will remain an independent public company, your common stock will continue to be listed and traded on the NYSE and registered under the Exchange Act and Advanced Disposal will continue to file periodic reports with the SEC. In addition, if the amended merger agreement is not adopted by Advanced Disposal stockholders, Advanced Disposal would not be entitled under any circumstance to the Waste Management termination fee.

Q:

Am I also voting on the GFL divestiture agreement? Why did Advanced Disposal execute the GFL divestiture agreement?

Advanced Disposal stockholders are not voting on the GFL divestiture agreement. In connection with entering into the merger agreement amendment, on June 24, 2020, Advanced Disposal entered into the GFL divestiture agreement at the request of Waste Management in furtherance of the merger. Waste Management and Advanced Disposal executed the GFL divestiture agreement in order to address substantially all of the divestitures anticipated to be required by the DOJ to obtain approval under the HSR Act. Closing of the GFL divestiture agreement is subject to customary closing conditions, including, among others, the closing of the merger and the absence of a material adverse effect on the equity interests and assets of each of Advanced Disposal (as owned by Waste Management after the closing (which we refer to as the "ADS businesses")) and Waste Management (which we refer to as the "WM businesses") to be acquired by GFL, taken as a whole. The transactions contemplated by the GFL divestiture agreement also remain subject to antitrust approval. For a more detailed description of why Advanced Disposal entered into the GFL divestiture agreement, see "The Merger (Proposal 1)—Background of the Merger" beginning on page 40 of this proxy statement.

Q:

Can I revoke my proxy or change my vote?

A:    Yes. If you are a stockholder of record, you may revoke your proxy at any time before the vote is taken at the Special Meeting by:

•

voting over the Internet or by telephone as instructed on the proxy card. Only your latest Internet or telephone vote will be counted. You may not change your vote over the Internet or by telephone after 11:59 p.m. Eastern Time on August 24, 2020;

•

providing a written notice of revocation that is received before the Special Meeting by the Corporate Secretary at Advanced Disposal Services, Inc., 90 Fort Wade Road, Ponte Vedra, Florida 32081, Attention: Michael K. Slattery, Corporate Secretary;

24

Table of Contents

•

completing, signing, dating and returning a new proxy card by mail to Advanced Disposal before the Special Meeting (received by or with our last mail delivery before the Special Meeting); or

•

attending the Special Meeting and requesting that your proxy be revoked and/or voting via the Special Meeting website as instructed above.

Please note, however, that only your last-dated proxy will count. Attending the Special Meeting without taking one of the actions described above will not in itself revoke your proxy. Please note that if you want to revoke your proxy by mailing a new proxy card or by sending a written notice of revocation to Advanced Disposal, you should ensure that you send your new proxy card or written notice of revocation in sufficient time for it to be received by Advanced Disposal before the Special Meeting (such new proxy cards or written notices of revocation received by or with our last mail delivery before the Special Meeting begins will be counted).

If you hold your shares in street name through a broker, bank or other nominee, you will need to follow the instructions provided to you by your broker, bank or other nominee in order to revoke your proxy or submit new voting instructions. You may also revoke your proxy by obtaining your specific control number and further instructions from your broker, bank or other nominee that holds the shares of record and voting your shares via the Special Meeting website.

Q:

What happens if I do not vote or if I abstain from voting on the proposals?

A:    The requisite number of shares to approve the proposal to adopt the amended merger agreement is based on the total number of shares of Advanced Disposal common stock issued and outstanding, not just the shares that are voted. Failure to submit a signed proxy card, grant a proxy by phone or the Internet or to vote via the Special Meeting website by ballot at the Special Meeting will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise and will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. For more information concerning the Special Meeting, the amended merger agreement and the merger, please review this proxy statement and the copy of (i) the original merger agreement attached as Annex A and (ii) the merger agreement amendment attached as Annex B thereto.

The requisite number of shares to approve the compensation advisory proposal is a majority of the shares of Advanced Disposal common stock issued and outstanding and that are present or represented by proxy at the Special Meeting and entitled to vote thereon. A quorum is a majority of the shares of Advanced Disposal common stock issued and outstanding. An abstention from voting will have the same effect as a vote "AGAINST" the compensation advisory proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the compensation advisory proposal, so long as a quorum is otherwise present.

The requisite number of shares to approve the adjournment proposal is a majority of shares of Advanced Disposal common stock issued and outstanding and that are present or represented by proxy at the Special Meeting and entitled to vote thereon, whether or not a quorum is present. An abstention from voting will have the same effect as a vote "AGAINST" the adjournment proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the adjournment proposal.

Only shares of Advanced Disposal common stock that are issued and outstanding as of the close of business on the record date are eligible to be voted on each of the three (3) proposals and will be counted for purposes of determining whether a quorum is present at the Special Meeting.

25

Table of Contents

If the amended merger agreement is not adopted by Advanced Disposal stockholders, the merger cannot close and Advanced Disposal would not be entitled under any circumstance to the Waste Management termination fee.

Q:

If the merger is consummated, how will I receive the cash for my shares of Advanced Disposal common stock?

A:    If the merger is consummated and your shares of Advanced Disposal common stock are held in book-entry or in the name of a broker, bank or other custodian, the cash proceeds will be deposited into your bank or brokerage account without any further action on your part. If you hold your shares of Advanced Disposal common stock in certificate form, you will receive a letter of transmittal with instructions on how to send your shares of Advanced Disposal common stock to the paying agent in connection with the merger. The paying agent will issue and deliver to you a check for your shares of Advanced Disposal common stock after you comply with such instructions. Employees of Advanced Disposal who hold outstanding Advanced Disposal equity awards at the effective time will receive consideration for those awards through payroll.

Q:

What happens if the market price of shares of Advanced Disposal common stock significantly changes before the closing?

A:    Waste Management is not obligated to change the merger consideration of $30.30 per share of Advanced Disposal common stock as a result of a change in the market price of Advanced Disposal common stock.

Q:

What happens if I sell my shares of Advanced Disposal common stock before completion of the merger?

A:    In order to receive the merger consideration, you must hold your shares of Advanced Disposal common stock through completion of the merger. Consequently, if you transfer your shares of Advanced Disposal common stock before completion of the merger, you will have transferred your right to receive the merger consideration in the merger.

The record date for stockholders entitled to vote at the Special Meeting is July 23, 2020. If you transfer your shares of Advanced Disposal common stock after the record date but before the closing, unless you have granted a "legal proxy" to the purchaser as part of the transfer, you will have the right to vote at the Special Meeting, although you will have transferred your right to receive the merger consideration in the merger.

Q:

Should I send in my evidence of ownership now?

A:    No. After the merger is completed, you will receive a letter of transmittal, if applicable, and related materials from the paying agent for the merger with detailed written instructions for exchanging your shares of Advanced Disposal common stock evidenced by stock certificates for the merger consideration. If your shares of Advanced Disposal common stock are held in street name by your broker, bank or other nominee, you will receive instructions from your broker, bank or other nominee as to what action, if any, you need to take in order to effect the surrender of your street name shares in exchange for the merger consideration. Please do not send in any documentation of evidence of ownership now.

26

Table of Contents

Q:

Am I entitled to exercise dissenters' or appraisal rights instead of receiving the merger consideration for my shares of Advanced Disposal common stock?

A:    Yes. Under Section 262 of the DGCL, stockholders who do not vote for the adoption of the amended merger agreement have the right to seek appraisal of the fair value of their shares as determined by the Delaware Court of Chancery, but only if they fully comply with all applicable requirements of the DGCL, which are summarized in this proxy statement. Any appraisal amount determined by the court could be more than, the same as, or less than the merger consideration. Any stockholder intending to exercise appraisal rights must, among other things, submit a written demand for appraisal to Advanced Disposal before the vote on the proposal to adopt the amended merger agreement and such stockholder must not vote or otherwise submit a proxy in favor of the adoption of the amended merger agreement. Failure to comply exactly with the procedures and requirements specified under the DGCL will result in the loss of appraisal rights. The discussion of appraisal rights contained in this proxy statement is not a full summary of the law pertaining to appraisal rights under the DGCL and is qualified in its entirety by the full text of Section 262 of the DGCL that is attached as Annex E to this proxy statement. For additional information, see the section entitled "Appraisal Rights" beginning on page 88 of this proxy statement. Because of the complexity of the DGCL relating to appraisal rights, if you are considering exercising your appraisal rights, we encourage you to seek the advice of your own legal counsel.

Q:

Will I be subject to U.S. federal income tax upon the exchange of Advanced Disposal common stock for the merger consideration pursuant to the merger?

A:    Generally, yes, if you are a U.S. stockholder. The exchange of shares of Advanced Disposal common stock for the merger consideration pursuant to the merger will be a taxable transaction for U.S. federal income tax purposes. Accordingly, an Advanced Disposal stockholder that is a "U.S. holder" (as defined in the section entitled "The Merger (Proposal 1)—Material U.S. Federal Income Tax Consequences of the Merger" beginning on page 78 of this proxy statement) will recognize taxable gain or loss in an amount equal to the difference, if any, between (i) the amount of cash received by such U.S. holder in the merger plus the amount used to satisfy any applicable withholding taxes and (ii) such U.S. holder's adjusted tax basis in the shares of Advanced Disposal common stock exchanged therefor. With respect to an Advanced Disposal stockholder that is a "non-U.S. holder" (as defined in the section entitled "The Merger (Proposal 1)—Material U.S. Federal Income Tax Consequences of the Merger" beginning on page 78 of this proxy statement), the exchange of shares of Advanced Disposal common stock for the merger consideration pursuant to the merger generally will not result in tax to such non-U.S. holder under U.S. federal income tax laws unless such non-U.S. holder has certain connections with the United States. Backup withholding may apply to the cash payment made pursuant to the merger unless the Advanced Disposal stockholder or other payee provides a valid taxpayer identification number and complies with certain certification procedures (generally, by providing a properly completed and executed IRS Form W-9 or IRS Form W-8 or applicable successor form).

Each Advanced Disposal stockholder is urged to read the discussion in the section entitled "The Merger (Proposal 1)—Material U.S. Federal Income Tax Consequences of the Merger" beginning on page 78 of this proxy statement and to consult its tax advisor to determine the particular U.S. federal, state or local or non-U.S. income or other tax consequences to it of the merger.

Because particular circumstances may differ, we recommend that you consult your own tax advisor to determine the U.S. federal income tax consequences relating to the merger in light of your own particular circumstances and any consequences arising under any state, local or non-U.S. tax laws or tax treaties.

27

Table of Contents

Q:

What does it mean if I get more than one proxy card?

A:    If your shares of Advanced Disposal common stock are registered differently or are held in more than one account, you will receive more than one proxy or voting instruction form. Please complete and return all of the proxy cards or voting instructions forms you receive (or submit each of your proxies or voting instructions forms by telephone or the Internet, if available to you) to ensure that all of your shares of Advanced Disposal common stock are voted.

Q:

How many copies should I receive if I share an address with another stockholder?

A:    Some banks, brokers and other nominees may participate in the practice of "householding" proxy statements, annual reports and notices of Internet availability of proxy materials. This means that a single set of our proxy materials, containing a single copy of this proxy statement but multiple proxy cards or voting instruction forms, may have been sent to multiple stockholders in your household. We will promptly deliver a separate copy of our proxy materials to you if you contact Broadridge Householding Department, in writing at Broadridge Householding Department, 51 Mercedes Way, Edgewood, NY 11717, or by phone at +1 (866) 540-7095. In addition, stockholders who share a single address, but receive multiple copies of the proxy statement, may request that in the future they receive a single copy by contacting (i) Advanced Disposal at Advanced Disposal Services, Inc., 90 Fort Wade Road, Ponte Vedra, FL 32081, Attention: Michael K. Slattery, Corporate Secretary or by calling +1 (904) 737-7900 (if your shares are registered in your own name) or (ii) your broker, bank or other nominee (if your shares are registered in their name).

Q:

Who will count the votes?

A:    The votes will be counted by one or more inspectors of election appointed for the Special Meeting.

Q:

Who will solicit and bear the cost of soliciting votes for the Special Meeting?

A:    Advanced Disposal will pay the entire cost of preparing, assembling, printing, mailing and distributing these proxy materials. In addition to the mailing of these proxy materials, the solicitation of proxies or votes may be made by telephone or by electronic and facsimile transmission by our directors, officers and employees, who will not receive any additional compensation for such solicitation activities. Advanced Disposal has engaged Innisfree M&A Incorporated (which we refer to as "Innisfree") as proxy advisor to assist in the solicitation of proxies for the Advanced Disposal Special Meeting. Advanced Disposal estimates that it will pay the proxy advisor a fee of approximately $20,000, plus reimbursement of certain expenses. In addition, Advanced Disposal may reimburse its transfer agent, brokerage firms and other persons representing beneficial owners of shares of Advanced Disposal common stock for their expenses in forwarding solicitation material to such beneficial owners.

Q:

Are there any other risks to me from the merger that I should consider?

A:    Yes. There are risks associated with all business combinations, including the merger. See the section entitled "Forward-Looking Statements" beginning on page 30 of this proxy statement.

Q:

Where can I find the voting results of the Special Meeting?

A:    Advanced Disposal will announce preliminary voting results at the Special Meeting via the Special Meeting website and publish preliminary, or final results if available, in a current report on Form 8-K filed with the SEC within four (4) business days after the Special Meeting.

28

Table of Contents

Q:

What do I need to do now?

A:    We urge you to carefully read this entire document, the appendices, including the original merger agreement and the merger agreement amendment, and the documents incorporated by reference, and to consider how the merger affects you. Your vote is important, regardless of the number of shares of Advanced Disposal common stock you own. Please see the above questions "If I am a stockholder of record of Advanced Disposal shares, how do I vote?" and "If I am a beneficial owner of shares held in street name, how do I vote?" for a summary of instructions on how to vote.

Q:

Where can I find more information about Advanced Disposal?

A:    You can find more information about us from various sources described in the section entitled "Where You Can Find Additional Information" beginning on page 124 of this proxy statement.

Q:

Who can help answer my other questions?

A:    If you have more questions about the merger, or require assistance in submitting your proxy or voting your shares or need additional copies of the proxy statement or the enclosed proxy card, please contact Innisfree, which is acting as the proxy solicitor and information agent for Advanced Disposal in connection with the merger:

Innisfree M&A Incorporated
501 Madison Avenue, 20th Floor
New York, NY 10022
Stockholders may call toll-free: +1 (877) 687-1866
Banks and brokers may call collect: +1 (212) 750-5833

If your broker, bank or other nominee holds your shares, you should also call your broker, bank or other nominee for additional information.

29

Table of Contents

FORWARD-LOOKING STATEMENTS

This proxy statement contains "forward-looking statements" within the meaning of the U.S. federal securities laws. Such statements include statements concerning anticipated future events and expectations that are not historical facts. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Forward-looking statements are typically identified by words such as "believe," "expect," "anticipate," "intend," "target," "estimate," "continue," "positions," "plan," "predict," "project," "forecast," "guidance," "goal," "objective," "prospects," "possible" or "potential," by future conditional verbs such as "assume," "will," "would," "should," "could" or "may," or by variations of such words or by similar expressions or the negative thereof. All forward-looking statements included in this proxy statement are based upon information available to us as of the filing date of this proxy statement, and, except to the extent required by applicable law, we undertake no obligation to update any of these forward-looking statements for any reason. You should not place undue reliance on forward-looking statements. The forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance, or achievements to differ materially from those expressed or implied by these statements. Important factors that could cause actual results to differ materially from those contained in any forward-looking statement include the factors identified in Advanced Disposal annual report on Form 10-K for the year ended December 31, 2019, under the heading "Risk Factors," as updated from time to time by Advanced Disposal quarterly reports on Form 10-Q, including Advanced Disposal Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2020, and other documents of Advanced Disposal on file with the SEC or in this proxy statement filed with the SEC by Advanced Disposal, and the following factors:

•

risks related to the consummation of the merger, including the risks that (i) the merger may not be consummated within the anticipated time period, or at all, (ii) the parties may fail to obtain stockholder approval of the amended merger agreement, (iii) the parties may fail to secure the termination or expiration of any waiting period applicable under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, despite entering into the merger agreement amendment and the GFL divestiture agreement, (iv) the risk that the parties to the GFL divestiture agreement may not receive regulatory approval or the GFL divestiture agreement is otherwise terminated prior to the effective time, and (v) other conditions to the consummation of the merger under the amended merger agreement may not be satisfied;

•

the effects that any termination of the amended merger agreement may have on Advanced Disposal or its business, including the risks that (i) Advanced Disposal's stock price may decline significantly if the merger is not completed, (ii) the amended merger agreement may be terminated in circumstances requiring Advanced Disposal to pay to Waste Management the Company termination fee or reimburse certain of Waste Management's expenses, or (iii) the circumstances of the termination, including the possible imposition of a 12-month tail period during which the termination fee could be payable upon the occurrence of, or entry into a definitive agreement for, certain subsequent transactions, which may have a chilling effect on alternatives to the merger;

•

the effects that the announcement or pendency of the merger may have on Advanced Disposal and its business, including the risks that as a result (i) Advanced Disposal's business, operating results or stock price may suffer, (ii) Advanced Disposal's current plans and operations may be disrupted, (iii) Advanced Disposal's ability to retain or recruit key employees may be adversely affected, (iv) Advanced Disposal's business relationships (including customers and suppliers) may be adversely affected, or (v) Advanced Disposal's management's or employees' attention may be diverted from other important matters;

•

the effect of limitations that the amended merger agreement places on Advanced Disposal's ability to operate its business, return capital to stockholders or engage in alternative transactions;

30

Table of Contents

•

the nature, cost and outcome of pending and future litigation and other legal proceedings, including any such proceedings related to the merger and instituted against Advanced Disposal and others;

•

the risk that the merger and related transactions may involve unexpected costs, liabilities or delays;

•

the scope and duration of the COVID-19 (coronavirus) pandemic and actions taken by governmental authorities to contain the spread of the virus; and

•

other economic, business, competitive, legal, regulatory, and/or tax factors.

Consequently, all of the forward-looking statements we make in this proxy statement are qualified by the information contained or incorporated by reference herein, including, but not limited to, (i) the information contained under this heading and (ii) the information contained under the heading "Risk Factors" and information in our consolidated financial statements and notes thereto included in our most recent filing on Form 10-K and subsequent periodic and interim report filings (see "Where You Can Find Additional Information" beginning on page 124 of this proxy statement). No assurance can be given that these are all of the factors that could cause actual results to vary materially from the forward-looking statements.

31

Table of Contents

PARTIES INVOLVED IN THE MERGER

Advanced Disposal Services, Inc.
90 Fort Wade Road
Ponte Vedra, FL 32081
Telephone: (904) 737-7900

Advanced Disposal is a leading integrated provider of nonhazardous solid waste collection, transfer, recycling and disposal services operating primarily in secondary markets or under exclusive arrangements. We have a presence in 16 states across the Midwest, South and East regions of the United States as well as in the Commonwealth of the Bahamas, serving approximately 2.7 million residential customers and over 200,000 commercial and industrial customers through our extensive network of 95 collection operations, 73 transfer stations, 3 material recycling facilities, 19 locations where we receive and bale recyclable material and 41 owned or operated active landfills. Our principal executive offices are located at 90 Fort Wade Road, Ponte Vedra, FL 32081 and our telephone number is (904) 737-7900.

Advanced Disposal is a Delaware corporation and Advanced Disposal common stock trades on NYSE under the symbol "ADSW."

Additional information about Advanced Disposal is contained in our public filings, which are incorporated by reference herein. See "Where You Can Find Additional Information" beginning on page 124 of this proxy statement.

Waste Management, Inc.
1001 Fannin Street
Houston, Texas 77002
Telephone: (713) 512-6200

Waste Management, a Delaware corporation, is North America's leading provider of comprehensive waste management environmental services that partners with residential, commercial, industrial and municipal customers and the communities it serves to manage and reduce waste at each stage from collection to disposal, while recovering valuable resources and creating clean, renewable energy. Waste Management's "Solid Waste" business is operated and managed locally by its subsidiaries that focus on distinct geographic areas and provides collection, transfer, disposal, and recycling and resource recovery services. Through its subsidiaries, Waste Management is also a leading developer, operator and owner of landfill gas-to-energy facilities in the United States. Waste Management's stock is traded on NYSE under the symbol "WM." Its principal executive offices are located at 1001 Fannin Street, Houston, Texas 77002 and its telephone number is (713) 512-6200.

Everglades Merger Sub Inc.
1001 Fannin Street
Houston, Texas 77002
Telephone: (713) 512-6200

Merger Sub is a Delaware corporation formed for the purpose of entering into the amended merger agreement and completing the merger with Advanced Disposal. Merger Sub is an indirect, wholly-owned subsidiary of Waste Management. Merger Sub has not engaged in any business to date except for activities incidental to its incorporation and activities undertaken in furtherance of the transactions. Upon completion of the merger, Merger Sub will merge with and into Advanced Disposal and will cease to exist. Merger Sub's principal executive offices are located at 1001 Fannin Street, Houston, Texas 77002 and its telephone number is (713) 512-6200.

32

Table of Contents

THE SPECIAL MEETING

We are furnishing this proxy statement to Advanced Disposal stockholders as part of the solicitation of proxies by the Board for use at the Special Meeting or any adjournment or postponement thereof. This proxy statement provides Advanced Disposal stockholders with the information they need to know to be able to vote or instruct their vote to be cast at the Special Meeting or any adjournment or postponement thereof.

Date, Time and Place of the Special Meeting

This proxy statement is being furnished to our stockholders as part of the solicitation of proxies by the Board for use at the Special Meeting to be held virtually via the Internet on August 25, 2020 beginning at 10:00 a.m. Eastern Time or at any adjournment or postponement thereof. Advanced Disposal has chosen to hold the Special Meeting solely by means of remote location (via the Internet) and not in a physical location given the current public health impacts of COVID-19 (coronavirus) and our desire to promote the health and safety of Advanced Disposal stockholders, as well as Advanced Disposal directors, officers, employees and other constituents.

Only individuals who were Advanced Disposal stockholders as of the close of business on the record date and their authorized representatives may attend the Special Meeting. If you plan to attend the Special Meeting, you will need the 16-digit control number included on your proxy card or voting instruction form that is accompanied by your proxy materials. If you are a beneficial owner of shares held in street name and wish to vote in person at the Special Meeting, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions. To ensure that you will be represented, even if you plan to attend the Special Meeting via the Special Meeting website, we encourage you to promptly vote by submitting the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone. If you attend the Special Meeting and vote by ballot via the Special Meeting website, your vote will revoke any proxy that you have previously submitted. Please contact your broker, bank or other nominee for instructions regarding obtaining your specific control number and further instructions.

This proxy statement and the enclosed form of proxy are first being mailed to our stockholders of record on or about July 27, 2020.

Purposes of the Special Meeting

The primary purpose of the Special Meeting is for our stockholders to consider and vote upon the proposal to adopt the amended merger agreement. Our stockholders holding a majority of the shares of Advanced Disposal common stock issued and outstanding at the close of business on the record date and entitled to vote thereon must adopt the amended merger agreement in order for the merger to occur. If the amended merger agreement is not adopted by Advanced Disposal stockholders, the merger cannot close and Advanced Disposal would not be entitled under any circumstance to receive the Waste Management termination fee. A copy of (i) the original merger agreement is attached as Annex A to this proxy statement and (ii) the merger agreement amendment is attached as Annex B to this proxy statement, and the material provisions of the amended merger agreement are summarized in the section of this proxy statement entitled "The Amended Merger Agreement" beginning on page 85 of this proxy statement. The entry into the merger agreement amendment necessitates a new vote with respect to the merger, so despite the fact that you may have voted on the original merger agreement in connection with the Original Special Meeting, Advanced Disposal is asking for your vote again.

In addition, our stockholders are being asked to approve the compensation advisory proposal, which is the approval, on a non-binding advisory basis, of specified compensation that may be paid or become payable to Advanced Disposal's named executive officers in connection with the merger and contemplated by the

33

Table of Contents

amended merger agreement, the value of which is disclosed in the table entitled "Golden Parachute Compensation" and the notes accompanying that table in the section entitled "Advisory Vote on Specified Compensation (Proposal 2)" beginning on page 110 of this proxy statement.

Our stockholders are also being asked to approve the adjournment proposal, which is one or more adjournments of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to approve the proposal to adopt the amended merger agreement.

Record Date and Quorum

The holders of record of Advanced Disposal common stock as of the close of business on July 23, 2020, the record date for the Special Meeting, are entitled to receive notice of and to vote at the Special Meeting. As of the close of business on the record date, 90,758,187 shares of Advanced Disposal common stock were issued and outstanding.

The presence at the Special Meeting of the holders of record of a majority of the shares of Advanced Disposal common stock entitled to vote, present via the Special Meeting website or represented by proxy, at the close of business on the record date will constitute a quorum. Once a share is represented at the Special Meeting, it will be counted for the purpose of determining a quorum at the Special Meeting. However, if a new record date is set for an adjourned Special Meeting, then a new quorum will have to be established. Proxies received but marked as abstentions will be included in the calculation of the number of shares considered to be present for the purpose of determining a quorum at the Special Meeting. "Broker non-votes," described below under the section entitled "The Special Meeting—Attendance; Voting; Proxies; Revocation—Providing Voting Instructions by Proxy—Shares of Advanced Disposal Common Stock Held in Street Name" beginning on page 36 of this proxy statement, will not be included in the calculation of the number of shares considered to be present for the purpose of determining a quorum at the Special Meeting.

Pursuant to the amended and restated voting agreement, CPPIB has agreed to cause its shares of Advanced Disposal common stock to be counted at the Special Meeting for quorum purposes pursuant to this proxy statement.

Required Vote

Holders of Advanced Disposal common stock are entitled to one vote on each proposal submitted to a vote at the Special Meeting for each share of Advanced Disposal common stock they own at the close of business on the record date. As of the close of business on the record date, there were 90,758,187 shares of Advanced Disposal common stock issued and outstanding.

For Advanced Disposal to complete the merger, stockholders holding a majority of the shares of Advanced Disposal common stock issued and outstanding at the close of business on the record date and entitled to vote thereon must vote "FOR" the proposal to adopt the amended merger agreement. A failure to vote your shares of Advanced Disposal common stock or an abstention from voting will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise and will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement.

The approval, on a non-binding advisory basis, of the compensation advisory proposal requires the affirmative vote of stockholders holding a majority of the issued and outstanding shares of Advanced Disposal common stock which are present via the Special Meeting website or represented by proxy and entitled to vote thereon, so long as a quorum is present, to vote "FOR" the proposal. An abstention from

34

Table of Contents

voting will have the same effect as a vote "AGAINST" the compensation advisory proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the compensation advisory proposal, so long as a quorum is otherwise present.

The affirmative vote of stockholders holding a majority of the issued and outstanding shares of Advanced Disposal common stock which are present via the Special Meeting website or represented by proxy and entitled to vote thereon, whether or not a quorum is present, is required to approve the adjournment proposal. An abstention from voting will have the same effect as a vote "AGAINST" the adjournment proposal. If your shares are held in street name by your broker, bank or other nominee and you do not instruct the nominee how to vote your shares, a "broker non-vote" will arise but will have no effect on the adjournment proposal.

Voting by CPPIB

Concurrently with the execution of the merger agreement amendment, on June 24, 2020, CPPIB entered into the amended and restated voting agreement with Waste Management, pursuant to which, among other things, and subject to the terms and conditions set forth therein, CPPIB agreed to vote its shares of Advanced Disposal common stock at the Special Meeting for the adoption of the amended merger agreement and against any alternative proposal (unless the Board withdraws or changes the Board recommendation or until the amended and restated voting agreement has terminated in accordance with its terms). The amended and restated voting agreement automatically terminates upon the earliest to occur of: (i) the merger contemplated by the amended merger agreement becoming effective, (ii) the amended merger agreement being validly terminated in accordance with the terms thereof, or (iii) CPPIB's election to terminate in its sole discretion promptly following any amendment to the amended merger agreement that reduces or changes the form of consideration payable. In addition, CPPIB waived its appraisal rights. The amended and restated voting agreement is described in more detail in the section entitled "The Amended and Restated Voting Agreement" beginning on page 109 of this proxy statement. CPPIB owned, as of the close of business on the record date, approximately 18.3% of the outstanding Advanced Disposal common stock.

Voting by Advanced Disposal Directors and Executive Officers

At the close of business on the record date, directors and executive officers of Advanced Disposal were entitled to vote 414,858 shares of Advanced Disposal common stock, or approximately 0.5% of the shares of Advanced Disposal common stock issued and outstanding on that date. We currently expect that Advanced Disposal directors and executive officers will vote their shares "FOR" the proposal to adopt the amended merger agreement and "FOR" the other proposals to be considered at the Special Meeting, although they have no obligation to do so.

The directors and executive officers of Advanced Disposal have interests in the merger that may be different from, or in addition to, the interests of Advanced Disposal stockholders generally. These interests are described in more detail in the section entitled "The Merger (Proposal 1)—Interests of Advanced Disposal Directors and Executive Officers in the Merger" beginning on page 71 of this proxy statement.

Attendance; Voting; Proxies; Revocation

Attendance

All holders of shares of Advanced Disposal common stock as of the close of business on the record date, including stockholders of record and beneficial owners of Advanced Disposal common stock registered in the street name of a broker, bank or other nominee, are invited to attend the Special Meeting via the

35

Table of Contents

Special Meeting website. During the Special Meeting, Advanced Disposal stockholders will be able to vote their shares. If you are a beneficial owner of shares held in street name and wish to vote via the Special Meeting website, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions.

Voting Via Virtual Meeting

Stockholders of record who have registered in advance to attend the Special Meeting will be able to vote at the Special Meeting via the Special Meeting website. If you are a beneficial owner of shares held in street name and wish to vote at the Special Meeting via the Special Meeting website, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions.

Providing Voting Instructions by Proxy

To ensure that your shares of Advanced Disposal common stock are voted at the Special Meeting, we recommend that you provide voting instructions promptly by proxy, even if you plan to attend the Special Meeting via the Special Meeting website.

Shares of Advanced Disposal Common Stock Held by Record Holder

If you are a stockholder of record, you may provide voting instructions by proxy using one of the following methods:

•

via the Internet, at the Internet address provided on the proxy card;

•

by telephone, by using the toll-free number listed on the proxy card; or

•

by mail, by completing, signing and dating the proxy card and returning it in the enclosed postage-paid envelope.

If you submit a signed proxy card or submit your proxy by telephone or the Internet, but do not specify how you want to vote your shares on a particular proposal, then the proxy holders will vote your shares in accordance with the recommendations of the Board on all matters presented in this proxy statement. If you fail to return your proxy card and you are a holder of record as of the close of business on the record date, unless you attend the Special Meeting and vote via the Special Meeting website, the effect will be that your shares of Advanced Disposal common stock will not be considered present at the Special Meeting for purposes of determining whether a quorum is present at the Special Meeting, will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement, will have no effect on the vote regarding the compensation advisory proposal, so long as a quorum is otherwise present, and will have no effect on the vote regarding the adjournment proposal.

Shares of Advanced Disposal Common Stock Held in Street Name

If your shares of Advanced Disposal common stock are held in the name of a bank, broker or other nominee, you will receive instructions from your bank, broker or other nominee as to how to vote your shares. You must follow the instructions of your bank, broker or other nominee in order for your shares of Advanced Disposal common stock to be voted. Telephone and Internet voting also will be offered to stockholders owning shares through certain banks, brokers and other nominees. If your shares of Advanced Disposal common stock are not registered in your own name but are held through your bank, broker or other nominee and you plan to vote your shares at the Special Meeting via the Special Meeting website, you should contact your broker, bank or other nominee to obtain your specific control number and further instructions.

In accordance with the rules of NYSE, brokers, banks and other nominees that hold shares of Advanced Disposal common stock in street name for their customers do not have discretionary authority to vote the

36

Table of Contents

shares with respect to the proposal to adopt the amended merger agreement, the compensation advisory proposal or the adjournment proposal. Accordingly, if brokers, banks or other nominees do not receive specific voting instructions from the beneficial owner of such shares, they may not vote such shares with respect to these proposals. Under such circumstance, a "broker non-vote" would arise. "Broker non-votes," if any, will not be considered present at the Special Meeting for purposes of determining whether a quorum is present at the Special Meeting, will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement and will have no effect (x) so long as a quorum is otherwise present, on the compensation advisory proposal or (y) on the adjournment proposal. Thus, for shares of Advanced Disposal common stock held in street name, only shares of Advanced Disposal common stock affirmatively voted "FOR" the proposal to adopt the amended merger agreement will be counted as a vote "FOR "such proposal.

Revocation of Proxies

Any person giving a proxy pursuant to this solicitation has the power to revoke and change it at any time before it is voted. If you are a stockholder of record, you may revoke your proxy at any time before the vote is taken at the Special Meeting by:

•

voting over the Internet or by telephone as instructed on the proxy card. Only your latest Internet or telephone vote will be counted. You may not change your vote over the Internet or by telephone after 11:59 p.m. Eastern Time on August 24, 2020;

•

providing a written notice of revocation that is received before the Special Meeting by the Corporate Secretary at Advanced Disposal Services, Inc., 90 Fort Wade Road, Ponte Vedra, FL 32081, Attention: Michael K. Slattery, Corporate Secretary;

•

completing, signing, dating and returning a new proxy card by mail to Advanced Disposal before the Special Meeting (received by or with our last mail delivery before the Special Meeting); or

•

attending the Special Meeting and request that your proxy be revoked and/or voting via the Special Meeting website as instructed above.

Please note, however, that only your last-dated proxy will count. Attending the Special Meeting without taking one of the actions described above will not in itself revoke your proxy. If you want to revoke your proxy by mailing a new proxy card or by sending a written notice of revocation to Advanced Disposal, you should ensure that you send your new proxy card or written notice of revocation in sufficient time for it to be received by Advanced Disposal before the Special Meeting (such new proxy cards or written notices of revocation received by or with our last mail delivery before the Special Meeting will be counted).

If you hold your shares in street name through a broker, bank or other nominee, you will need to follow the instructions provided to you by your broker, bank or other nominee in order to revoke your proxy or submit new voting instructions. You may also revoke your proxy by obtaining your specific control number and further instructions from your broker, bank or other nominee and voting your shares at the Special Meeting via the Special Meeting website.

Abstentions

An abstention occurs when a stockholder attends a meeting, either virtually or by proxy, but abstains from voting. Abstentions will be included as shares of Advanced Disposal common stock present or represented at the Special Meeting for purposes of determining whether a quorum has been achieved. Abstaining from voting will have the same effect as a vote "AGAINST" the proposal to adopt the amended merger agreement, the compensation advisory proposal and the adjournment proposal.

37

Table of Contents

Adjournments or Postponements

Although it is not currently expected, the Special Meeting may be adjourned or postponed if necessary or appropriate, including for the purpose of soliciting a sufficient number of proxies "FOR" the proposal to adopt the amended merger agreement. In the event that a sufficient number of shares of Advanced Disposal common stock is present at the Special Meeting via the Special Meeting website or represented by proxy, and voted "FOR" the proposal to adopt the amended merger agreement at the Special Meeting such that the Advanced Disposal stockholder approval will have been obtained, Advanced Disposal does not anticipate that it will adjourn or postpone the Special Meeting.

The Special Meeting may be adjourned by the affirmative vote of the holders of a majority of the shares of Advanced Disposal common stock that are present at the Special Meeting via the Special Meeting website or represented by proxy at the Special Meeting and entitled to vote at the Special Meeting or as otherwise permitted by law, whether or not a quorum is present. Any adjournment or postponement of the Special Meeting will allow Advanced Disposal stockholders who have already sent in their proxies to revoke them at any time before their use at the Special Meeting that was adjourned or postponed.

Solicitation of Proxies

We are paying the cost for the preparation, printing and distribution of the proxy materials. We may use the services of our directors, officers and employees, without additional compensation, to solicit proxies. We will reimburse any holder of record for its reasonable expenses incurred in completing the mailing of stockholder requested proxy materials to the beneficial owners of our common stock. Advanced Disposal has engaged Innisfree to assist in the solicitation of proxies for the Special Meeting. Advanced Disposal estimates that it will pay Innisfree a fee of approximately $20,000, plus reimbursement of certain expenses. In addition, Advanced Disposal may reimburse its transfer agent, brokerage firms and other persons representing beneficial owners of shares of Advanced Disposal common stock for their expenses in forwarding solicitation material to such beneficial owners.

Householding

We are permitted to send a single set of proxy materials to stockholders who share the same last name and address. This procedure is called "householding" and is designed to reduce our printing and postage costs. This means that we may send a single set of our proxy materials, containing a single copy of this proxy statement but separate proxy cards or voting instruction forms for each stockholder in your household. We will promptly deliver a separate copy of our proxy materials to you if you contact Broadridge Householding Department, in writing at Broadridge Householding Department, 51 Mercedes Way, Edgewood, NY 11717, or by phone at +1 (866) 540-7095. Such requests by street name holders should be made through their broker, bank or other nominee.

In addition, stockholders who share a single address, but receive multiple copies of the proxy statement, may request that in the future they receive a single copy by contacting (i) Advanced Disposal at Advanced Disposal Services, Inc., 90 Fort Wade Road, Ponte Vedra, FL 32081, Attention: Corporate Secretary or by calling +1 (904) 737-7900 (if your shares are registered in your own name) or (ii) your broker, bank or other nominee (if your shares are registered in their name).

Other Information

You should not return any evidence of your shares of Advanced Disposal common stock or send documents representing Advanced Disposal common stock with the proxy card. If the merger is completed, the paying agent for the merger will send to you a letter of transmittal, if applicable, and related materials and instructions for exchanging your shares of Advanced Disposal common stock.

38

Table of Contents

THE MERGER (PROPOSAL 1)

The description of the merger in this section and elsewhere in this proxy statement is qualified in its entirety by reference to the complete text of the original merger agreement and the merger agreement amendment, copies of which are attached as Annex A and Annex B, respectively, to this proxy statement and are incorporated by reference herein. This summary does not purport to be complete and may not contain all of the information about the merger that is important to you. You are encouraged to read the original merger agreement and the merger agreement amendment carefully and in their entirety.

Certain Effects of the Merger; Merger Consideration

If the amended merger agreement is adopted by Advanced Disposal stockholders and the other conditions to the closing are either satisfied or waived, Merger Sub will merge with and into Advanced Disposal, the separate corporate existence of Merger Sub will cease, and Advanced Disposal will continue as the surviving company in the merger as an indirect, wholly-owned subsidiary of Waste Management.

Upon the consummation of the merger, each share of Advanced Disposal common stock issued and outstanding immediately prior to the effective time, other than shares of Advanced Disposal common stock (i) owned by Waste Management, Merger Sub or Advanced Disposal, including shares held in treasury by Advanced Disposal, (ii) held by stockholders who will have neither voted for the merger nor consented thereto in writing and who will have demanded properly in writing appraisal for such shares in accordance with Section 262 of the DGCL, and (iii) owned by any direct or indirect, wholly-owned subsidiary of Advanced Disposal or Waste Management (which we refer to as the "excluded shares"), will be cancelled and converted into the right to receive $30.30 in cash, without interest and less applicable withholding taxes. At the effective time of the merger, Advanced Disposal stockholders will cease to have ownership interests in Advanced Disposal or rights as stockholders of Advanced Disposal, except as provided in the amended merger agreement or by law.

Advanced Disposal common stock is currently registered under the Exchange Act and is listed on NYSE under the symbol "ADSW." As a result of the merger, Advanced Disposal will cease to be a publicly traded company and will be an indirect, wholly-owned subsidiary of Waste Management. Following the consummation of the merger, Advanced Disposal common stock will be de-listed from NYSE and de-registered under the Exchange Act, in each case in accordance with applicable law, rules and regulations.

If the amended merger agreement is not adopted by Advanced Disposal stockholders, or if the merger is not completed for any other reason, the Advanced Disposal stockholders will not receive any payment for their shares of Advanced Disposal common stock in connection with the merger. Except in certain circumstances where Advanced Disposal has entered into an alternative transaction to the merger, Advanced Disposal will remain a public company, and shares of Advanced Disposal common stock will continue to be registered under the Exchange Act, as well as listed and traded on NYSE.

Changes to the Original Merger Agreement Pursuant to the Merger Agreement Amendment

In exchange for agreeing to reduce the per share merger consideration, Advanced Disposal and Waste Management agreed to amend the terms of the original merger agreement to provide increased closing certainty to the Advanced Disposal stockholders, including by: (i) extending the end date from July 13, 2020 to September 30, 2020, which will be further extended automatically to November 30, 2020 if, subject to certain conditions, Advanced Disposal stockholder approval or antitrust approval has not been obtained by September 30, 2020; (ii) providing for a Waste Management termination fee of $250,000,000 (increased from $150,000,000); (iii) providing that Waste Management must use "best efforts" to take all actions to consummate the transactions by the end date, including using its "best efforts" to obtain regulatory

39

Table of Contents

approval, is required to sell or divest assets (belonging to Waste Management or Advanced Disposal or any of its subsidiaries) in order to obtain antitrust approval and to eliminate the $200,000,000 revenue threshold on the divestiture obligation of Waste Management as provided in the original merger agreement; and (iv) providing that each party has certified to the other that such party's closing conditions with respect to the accuracy of its representations and performance of its covenants, and, with respect to Waste Management, the absence of a material adverse effect on Advanced Disposal, would be satisfied as of the date of the merger agreement amendment if the closing were to occur on such date (and that Waste Management and Merger Sub will not assert that any of such conditions are not satisfied at the closing as a result of what such parties had knowledge of as of the date of the merger agreement amendment). In addition, the original merger agreement was amended to eliminate the obligation of Advanced Disposal to reimburse Waste Management's expenses of up to $15,000,000 if the amended merger agreement is terminated by either Advanced Disposal or Waste Management as a result of a failure to obtain the Advanced Disposal stockholder approval as provided in the original merger agreement.

Background of the Merger

Note that the portion of this "Background of the Merger" covering the period beginning in 2018 and ending on April 14, 2019 (the date of the original merger agreement with Waste Management) is substantively the same as the disclosure provided in the definitive proxy statement filed on May 23, 2019 relating to the original merger agreement as supplemented in a proxy supplement filed on June 21, 2019.

The Board and Advanced Disposal's senior management regularly review and assess Advanced Disposal's business strategies and objectives, and the Board regularly discusses Advanced Disposal's performance, risks and opportunities, all with the goal of enhancing stockholder value. As part of these ongoing efforts, the Board and Advanced Disposal's senior management evaluate from time to time various strategic alternatives, taking into account current and potential economic and other market conditions and developments and trends in the solid waste industry. These strategic alternatives include the continued operation of Advanced Disposal as an independent, standalone company, acquiring new businesses to complement or expand existing businesses, divesting one or more of its businesses, reducing its outstanding debt and entering into strategic partnerships or other investments with respect to one or more of Advanced Disposal's businesses. In addition, Advanced Disposal and its representatives have been approached periodically by other companies and their representatives regarding potential interest in a material transaction involving Advanced Disposal.

During the second quarter of 2018, a substantial industry participant (which we refer to as "Company A") approached Mr. Richard Burke, Chairman and Chief Executive Officer of Advanced Disposal, regarding its potential interest in a material transaction involving Advanced Disposal. Separately, a financial sponsor with significant industry experience (which we refer to as "Company B") also contacted Mr. Burke with respect to its potential interest in a material transaction involving Advanced Disposal. In June 2018, Advanced Disposal entered into confidentiality agreements with each of Company A and Company B to facilitate ongoing discussions. Both confidentiality agreements contained a standstill provision and a covenant restricting the counterparty from requesting that Advanced Disposal amend or waive the agreed-upon standstill during the applicable standstill period, with both such provisions terminating automatically upon Advanced Disposal's entry into the original merger agreement.

On July 9, 2018, senior management of Advanced Disposal, including Mr. Burke, participated in a meeting with Company A to discuss an overview of Advanced Disposal's business.

On July 31, 2018, the Board convened a regular meeting, during which the Board discussed the status of preliminary discussions with each of Company A and Company B. A representative of Shearman & Sterling LLP (which we refer to as "Shearman & Sterling"), Advanced Disposal's legal advisor, presented on the fiduciary duties and confidentiality obligations of the directors under Delaware law, as well as considerations in the context of discussions with potential counterparties. The Board authorized Advanced

40

Table of Contents

Disposal's senior management to continue preliminary discussions with Company A and Company B and requested updates as such discussions progressed.

Following the July 9, 2018 meeting with Company A, representatives of Advanced Disposal held calls and meetings with representatives of Company A pursuant to which Company A conducted preliminary diligence on Advanced Disposal. By early September 2018, representatives of Company A informed Mr. Burke that Company A could not offer a price that, in Company A's opinion, would be considered an attractive premium to the trading price of Advanced Disposal common stock around such time. Company A did not engage in further discussions with Advanced Disposal with respect to a potential transaction following early September 2018.

Also in the summer of 2018, representatives of Advanced Disposal had preliminary discussions with Company B, including an in-person meeting in June 2018 among representatives of Company B and senior management of Advanced Disposal, including Mr. Burke, to discuss an overview of Advanced Disposal's business, and provided Company B with preliminary diligence materials. By the end of August 2018, representatives of Company B informed Advanced Disposal that Company B was not prepared to proceed with a material transaction involving Advanced Disposal at a price that, in Company B's opinion, would be acceptable to the Board.

On October 11, 2018, Mr. Burke received a call from Mr. James C. Fish, Jr., President and Chief Executive Officer of Waste Management, to request a meeting. At a meeting in Dallas, Texas on November 9, 2018, Mr. Fish expressed to Mr. Burke Waste Management's potential interest in pursuing an acquisition of Advanced Disposal.

On November 23, 2018, Waste Management and Advanced Disposal executed a mutual confidentiality agreement, which was followed by the execution of a joint defense agreement on December 7, 2018 for the purpose of sharing confidential information in connection with regulatory matters without waiving legal privileges or protections. Pursuant to the joint defense agreement, Advanced Disposal and Waste Management, along with their respective antitrust counsel, agreed that the parties shared a common interest in resolving antitrust, competition and other related legal issues regarding a potential acquisition of Advanced Disposal by Waste Management, and such agreement generally outlined the scope of confidential information and the manner by which the parties could share such confidential information without waiving attorney-client privilege, the work product privilege, or any other applicable privilege or protections.

On December 10, 2018, the Board held a meeting with Advanced Disposal's senior management and representatives of UBS in attendance. The representatives of UBS provided an update on recent developments in the solid waste industry and activities being undertaken by other industry participants, discussed its preliminary financial analyses of Advanced Disposal and certain valuation considerations, and reviewed with the Board various strategic alternatives potentially available to Advanced Disposal, including the future prospects and risks and uncertainties associated with such alternatives. The Board discussed various options, including (i) continuing as an independent, standalone company, (ii) engaging in a material acquisition, (iii) merging with or engaging in a strategic transaction with another strategic company, (iv) a sale to an industry participant (including a discussion of potential counterparties), (v) a sale to a financial sponsor (including a discussion of potential counterparties) and (vi) taking measures to reduce its outstanding debt.

On December 21, 2018, senior management of Advanced Disposal, including Mr. Burke, participated in a meeting in Charleston, South Carolina with senior management of Waste Management, including Mr. John J. Morris Jr., Executive Vice President and Chief Operating Officer of Waste Management, to discuss, among other things, an overview of Advanced Disposal's business, as well as the possible synergies that could result from an acquisition of Advanced Disposal by Waste Management.

41

Table of Contents

On January 23, 2019, Mr. Morris telephoned Mr. Burke and submitted a verbal expression of interest on behalf of Waste Management to purchase all of the outstanding shares of Advanced Disposal for a price of $32.00 per share in cash. The closing price of Advanced Disposal common stock was $24.35 per share on January 23, 2019.

On January 25, 2019, the Board convened a special telephonic meeting to discuss Waste Management's verbal expression of interest. During such meeting, a representative of Shearman & Sterling discussed with the Board certain corporate governance matters and reviewed the fiduciary duties and confidentiality obligations of the directors under Delaware law generally and in the context of inquiries of this type. In light of the earlier discussions with Company A and Company B, the Board noted the low probability that another industry participant or financial sponsor would be in a position to propose a transaction more favorable to the stockholders of Advanced Disposal than the transaction proposed by Waste Management. The Board, Advanced Disposal's senior management and Shearman & Sterling also discussed the considerations of conducting a broader market check, including the risk of a leak. Following such discussion, the Board concluded that it would not be in the best interests of stockholders to solicit any other alternatives to Waste Management's proposal at that time. After deliberations, the Board authorized Mr. Burke to inform Mr. Morris that prior to further engagement by Advanced Disposal, Waste Management should submit its indication of interest in writing. Mr. Burke conveyed the Board's message to Mr. Morris on the same date.

On February 5, 2019, Waste Management submitted a written, non-binding indication of interest that stated Waste Management would be prepared to acquire all of the Advanced Disposal common stock for a price of $32.00 per share in cash. In addition, Waste Management requested a 45-day exclusivity period during which Advanced Disposal would not be permitted to discuss a potential material transaction with another counterparty.

On February 6, 2019, the Board convened a special telephonic meeting, attended by representatives of UBS and Shearman & Sterling, to discuss Waste Management's written, non-binding indication of interest. A representative of Shearman & Sterling reminded the Board of its fiduciary duties and confidentiality obligations under Delaware law. The Board discussed the terms of Waste Management's written, non-binding indication of interest, including the price, approach on regulatory matters, and the request for a 45-day exclusivity period. At the conclusion of such discussion, the Board authorized Advanced Disposal's senior management to continue to have preliminary discussions with Waste Management but to convey that Advanced Disposal would not agree to Waste Management's request for exclusivity and that Advanced Disposal would not respond to Waste Management's proposed price without first getting a clearer understanding of Waste Management's regulatory analysis of the potential transaction. Following the February 6, 2019 Board meeting, Mr. Burke contacted Mr. Morris to communicate the Board's position and schedule an in-person meeting.

On February 12, 2019, UBS provided the Board with certain disclosures relating to its relationships with Advanced Disposal and Waste Management. The Company and UBS entered into an engagement letter, dated February 14, 2019, pursuant to which UBS would provide certain services, including, if requested, rendering an opinion as to the fairness, from a financial point of view, to the holders of the Company's common stock (other than the excluded shares), of the consideration to be received in a proposed transaction.

On February 15, 2019, senior management of Advanced Disposal, including Mr. Burke, met with senior management of Waste Management, including Mr. Morris, in Roanoke, Virginia, and the participants further discussed operational and regulatory matters.

On February 20, 2019, the Board convened a regular meeting, attended by representatives of UBS and Shearman & Sterling, during which Mr. Burke updated the Board on discussions with Waste Management since the previous Board meeting. A representative of Shearman & Sterling then reviewed certain legal considerations in the context of these discussions. Following such discussion, at the direction of the Board,

42

Table of Contents

representatives of UBS reviewed with the Board the strategic alternatives potentially available to Advanced Disposal and financial analyses of Advanced Disposal, including some of those that were previously discussed with the Board at the December 10, 2018 meeting. The Board discussed the prospects of Advanced Disposal continuing on a standalone basis and other alternatives. The Board also noted the low probability that another industry participant or financial sponsor would be in a position to propose a transaction more favorable to the stockholders of Advanced Disposal than the transaction proposed by Waste Management.

The Board held a special telephonic meeting on February 25, 2019 to discuss the current status of discussions with Waste Management. After discussion, the Board instructed representatives of UBS to make a counterproposal to representatives of Centerview Partners LLC (which we refer to as "Centerview"), the financial advisor of Waste Management, that included a price of $34.50 per share in cash, no exclusivity, 30 days to complete any remaining due diligence and a requirement that a meeting be scheduled between the legal advisors of Advanced Disposal and Waste Management to discuss regulatory matters (which we refer to as the "February 25 proposal").

On February 26, 2019, at the direction of the Board, representatives of UBS met with representatives of Centerview to discuss the February 25 proposal, valuation and feasibility of a transaction between Advanced Disposal and Waste Management. After representatives of UBS raised the February 25 proposal, representatives of Centerview reiterated that the board of directors and senior management of Waste Management considered the $32.00 per share in cash pursuant to Waste Management's original proposal as an appropriate valuation based on the diligence information provided by Advanced Disposal as of such date, which information representatives of UBS relayed to senior management of Advanced Disposal.

On March 1, 2019, representatives of Centerview contacted representatives of UBS to indicate that Waste Management had discussed the February 25 proposal and that Waste Management needed access to additional information in order to properly evaluate the February 25 proposal. Representatives of Centerview indicated that thereafter, Waste Management would be in a position to respond to the February 25 proposal. Representatives of Centerview stated that Waste Management agreed that, while other diligence was occurring, a meeting should be scheduled between the legal advisors of Advanced Disposal and Waste Management to discuss regulatory matters. Representatives of UBS relayed the response from representatives of Centerview to senior management of Advanced Disposal.

On March 7, 2019, at the direction of the Board, senior management of Advanced Disposal, including Mr. Burke, met with senior management of Waste Management, including Mr. Morris and Ms. Devina A. Rankin, Senior Vice President and Chief Financial Officer of Waste Management, along with representatives of UBS and Centerview, in New York City, New York, during which meeting the senior management of Advanced Disposal presented a business overview of Advanced Disposal, including the pre-announcement projections (as described in the section entitled "The Merger (Proposal 1)—Projected Financial Information" beginning on page 67 of this proxy statement). On the same day, Advanced Disposal made available an online data room with due diligence materials regarding Advanced Disposal to representatives of Waste Management. Over the course of the following several weeks, Advanced Disposal and its representatives facilitated Waste Management's and its representatives' due diligence investigations of Advanced Disposal and its business, including participation in a March 20, 2019 meeting among representatives of Advanced Disposal, Waste Management, Mayer Brown LLP (which we refer to as "Mayer Brown"), regulatory counsel for Advanced Disposal, Vedder Price P.C., regulatory counsel for Waste Management, and Simpson Thacher & Bartlett LLP (which we refer to as "Simpson Thacher"), legal counsel to Waste Management, in Washington, DC to discuss regulatory matters.

On March 26, 2019, the Board convened a special telephonic meeting to discuss the status of discussions between representatives of Advanced Disposal and Waste Management.

43

Table of Contents

Later on March 26, 2019, Waste Management submitted an updated non-binding indication of interest, which outlined Waste Management's proposal to acquire all of the Advanced Disposal common stock for a price of $32.75 per share in cash. The letter also contemplated other material terms, including the level of potential divestitures that might be required in the potential transaction, as well as the amount of any termination fees payable by and to Advanced Disposal in certain circumstances. Representatives of Waste Management also circulated an initial draft of the original merger agreement on the same date. The draft original merger agreement contemplated a voting agreement to be executed by CPPIB, which was a condition of Waste Management's proposal. The closing price of Advanced Disposal common stock was $28.00 per share on March 26, 2019.

The Board convened a special telephonic meeting on March 28, 2019, attended by representatives of UBS and Shearman & Sterling, to discuss Waste Management's updated non-binding indication of interest. Representatives of UBS reviewed with the Board its preliminary financial analyses of the proposed transaction and discussed with the Board the prior written indication of interest submitted by Waste Management. The Board, with the assistance of its legal and financial advisors, then discussed potential responses to the indication of interest. A representative of Shearman & Sterling then discussed certain corporate governance matters with the Board and reviewed the fiduciary duties and confidentiality obligations of the directors under Delaware law. The Board then discussed Advanced Disposal's strategic plan as an independent, standalone company, including the timing and achievability of such plan, as compared to the transaction contemplated by Waste Management's updated indication of interest. The Board determined to continue to explore a potential transaction with Waste Management and authorized Advanced Disposal's senior management and representatives of Advanced Disposal to counter Waste Management's proposal with a counterproposal of $33.50 per share in cash (which we refer to as the "March 28 proposal"). The Board also authorized Mr. Burke to negotiate other material terms within certain specified parameters.

On March 29, 2019, Mr. Burke sent a letter to Mr. Morris indicating that the Board authorized Advanced Disposal's senior management to proceed with negotiations with Waste Management, subject to Waste Management's acceptance of the March 28 proposal.

On April 1, 2019, Mr. Morris telephoned Mr. Burke and informed him that Waste Management would be willing to acquire Advanced Disposal at a price of $33.15 per share in cash in what was described as the "best and final" price. Mr. Morris also stated that the reverse termination fee payable by Waste Management should be equal to the termination fee payable by Advanced Disposal. As directed by the Board, representatives of UBS contacted representatives of Centerview and proposed a price of $33.25 per share in cash. Later on April 1, 2019, representatives of Centerview reiterated to representatives of UBS that $33.15 was Waste Management's "best and final" price, but, after discussing with Waste Management, Waste Management would be willing to consider a lower termination fee payable by Advanced Disposal and a higher reverse termination fee payable by Waste Management than had been previously discussed (which we refer to as the "April 1 proposal").

On April 2, 2019, the Board convened a special telephonic meeting, attended by representatives of UBS and Shearman & Sterling, and Mr. Burke relayed the conversation he had the previous day with Mr. Morris and the subsequent conversations between UBS and Centerview, held at the direction of the Board. A representative of Shearman & Sterling then discussed with the Board the legal obligations of the directors in the context of a sale of Advanced Disposal. During this meeting, the Board, Advanced Disposal's senior management and representatives of UBS and Shearman & Sterling discussed and considered the risks and benefits of performing a further "market check" to assess whether a transaction that offered greater immediate value to Advanced Disposal stockholders was reasonably available as compared to the transaction proposed by Waste Management, in terms of price, timing, likelihood of consummation, regulatory and other considerations, and the effect such "market check" would have on Waste Management's engagement and interest. The participants also noted that any "market check" could result in public leaks of a potential sale process, which could also have an adverse impact on employees,

44

Table of Contents

customers and external partners. The participants further discussed parties that could potentially be interested in acquiring Advanced Disposal, including whether Company A or Company B might re-engage in discussions regarding a potential transaction, and whether any such parties could have the financial capacity and interest to make such acquisition. Mr. Burke reviewed the history of prior discussions with Company A and Company B with the Board. Following this discussion, the Board concluded that it was unlikely that any other party would be able to match or exceed the terms of the transaction proposed by Waste Management. The Board also unanimously authorized Advanced Disposal's senior management to proceed with negotiations on the original merger agreement based on the price and material terms of the April 1 proposal, as described by Mr. Burke.

On April 5, 2019, Simpson Thacher circulated an initial draft of the original voting agreement to Shearman & Sterling, which Shearman & Sterling shared with CPPIB's legal counsel, Debevoise & Plimpton LLP on April 7, 2019.

Between April 6, 2019 and April 8, 2019, Advanced Disposal, Waste Management and their respective legal counsel (Shearman & Sterling and Mayer Brown, on behalf of Advanced Disposal, and Simpson Thacher, on behalf of Waste Management), engaged in various negotiations regarding the terms of the original merger agreement and exchanged drafts. During this time, Waste Management, CPPIB and their respective legal counsel engaged in various negotiations regarding the terms of the original voting agreement and exchanged drafts.

On April 10, 2019, the Board convened a special telephonic meeting, during which the Board discussed the status of negotiations between Advanced Disposal and Waste Management, including with respect to employment matters. The Board also discussed the materials provided to the Board, including Advanced Disposal's pre-announcement projections (as defined in the section entitled "The Merger (Proposal 1)—Projected Financial Information" beginning on page 67 of this proxy statement), which were the same as provided to Waste Management on March 7, 2019, and Advanced Disposal's strategic plan as an independent, standalone company. Senior management of Advanced Disposal explained how the materials differed from materials previously distributed to the Board, including to update the strategic plan to take into account fiscal year 2018 actual results and among other things, changes to the fuel and commodities prices and volume growth used in developing Advanced Disposal's projected results. Later on April 10, 2019, Shearman & Sterling provided Simpson Thacher with a revised draft of the original merger agreement.

From April 11, 2019 through April 13, 2019, Advanced Disposal, Waste Management and their respective legal counsel continued to engage in negotiations regarding, and exchange drafts of, the original merger agreement. Waste Management and CPPIB and their respective legal counsel also continued to negotiate, and exchange drafts of, the original voting agreement.

On April 14, 2019, Mr. Burke reported to the Board that negotiations with Waste Management on the transaction documents had substantially concluded and that the language of the original merger agreement was being finalized and would reflect the April 1 proposal. In the late afternoon of April 14, 2019, the Board convened a special telephonic meeting, attended by representatives of UBS, Mayer Brown and Shearman & Sterling.

During the meeting, a representative of Mayer Brown discussed the process of obtaining regulatory approvals with respect to the original merger agreement, and a representative of Shearman & Sterling summarized the regulatory covenants and commitments in the original merger agreement, including each party's obligations in connection with obtaining the applicable regulatory approvals, the risks that approval would not be obtained and the circumstances under which the reverse termination fee would be payable by Waste Management in the event regulatory approvals are not obtained, as well as the amount payable under such circumstances.

45

Table of Contents

Representatives of UBS reviewed with the Board UBS's financial analysis of the proposed transaction with Waste Management. Representatives of UBS also provided certain disclosures relating to UBS's relationships with Advanced Disposal, CPPIB, and Waste Management, including the fee UBS would receive from Advanced Disposal in connection with the proposed transaction with Waste Management, which disclosures were updated relative to those that UBS provided to the Board on February 12, 2019, as described above. At the conclusion of such discussions, a representative of UBS delivered to the Board an oral opinion (which oral opinion was subsequently confirmed by delivery of a written opinion, dated April 14, 2019), to the effect that, as of that date and based on and subject to various procedures, assumptions and matters considered and the qualifications and limitations described in its opinion, the original merger consideration to be received by the holders of Advanced Disposal common stock (other than the holders of excluded shares) in the merger was fair, from a financial point of view, to such holders. Following this discussion, representatives of UBS left the meeting.

A representative of Shearman & Sterling then presented certain corporate governance matters and the fiduciary duties of the directors under Delaware law. Such representative of Shearman & Sterling then provided the Board with an overview of the proposed transaction, including the principal terms of the transaction documents that would be executed in connection with the proposed transaction. The Board and the remaining participants again discussed the merits and considerations of a "market check" process, both prior to and after entering into a merger agreement (taking into account the terms and conditions of the original merger agreement and the original voting agreement), and the Board concluded not to pursue a further "market check."

After deliberation and consideration of the factors described in the section entitled "The Merger (Proposal 1)—Recommendation of the Board and Reasons for Recommendation—Reasons for Recommendation" beginning on page 55 of this proxy statement as they relate to the original merger agreement and the transactions contemplated therein, the Board unanimously (i) determined that the original merger agreement and the transactions were fair to, and in the best interests of, Advanced Disposal and its stockholders, (ii) approved and declared advisable the original merger agreement and the transactions, including the merger, (iii) approved the execution, delivery and performance by Advanced Disposal of the original merger agreement and the consummation of the transactions, including the merger, upon the terms and subject to the conditions of the original merger agreement, (iv) recommended the approval of the adoption of the original merger agreement by the stockholders of Advanced Disposal, and (v) directed that the adoption of the original merger agreement be submitted to a vote of the holders of Advanced Disposal common stock.

Following the conclusion of the Board meeting, Advanced Disposal, Waste Management, and their respective legal counsel finalized negotiations of the original merger agreement on terms consistent with the terms approved by the Board and the April 1 proposal, and all relevant parties executed and exchanged the definitive documentation on April 14, 2019.

Prior to the opening of U.S. stock markets on April 15, 2019, Advanced Disposal and Waste Management issued a joint press release publicly announcing their entry into the original merger agreement.

Following the date of the execution of the original merger agreement, Advanced Disposal generally was prohibited from soliciting acquisition proposals or engaging in negotiations or discussions with third parties concerning acquisition proposals under the terms of the original merger agreement (as more fully described in the section entitled "The Amended Merger Agreement—Other Covenants and Agreements—No Solicitation; Acquisition Proposals" beginning on page 95 of this proxy statement). Up until the time that stockholder approval was obtained to adopt the original merger agreement, Advanced Disposal would have been permitted to furnish certain information and engage in discussions or negotiations with a third party regarding an acquisition proposal that could have been superior to the merger with Waste Management, in certain circumstances, subject to certain exceptions described in more detail in the original merger agreement. However, this right was not exercised because no acquisition proposals were

46

Table of Contents

received from the date of the execution of the original merger agreement until the date of the special meeting of stockholders on June 28, 2019. In addition, no acquisition proposal has been received from the date of such special meeting of stockholders until the date of this proxy statement.

Advanced Disposal, Waste Management and their respective antitrust counsel began working with the staff of the DOJ shortly after the announcement of the original merger agreement, and have continued to work with the DOJ staff to try to resolve the DOJ staff's questions about the proposed transaction.

On May 9, 2019, each of Advanced Disposal and Waste Management filed its respective premerger notification and report with the DOJ and the U.S. Federal Trade Commission under the HSR Act. In order to provide the DOJ with additional time for review, Advanced Disposal and Waste Management voluntarily withdrew the premerger notification and report on June 10, 2019 and then refiled the premerger notification and report on June 12, 2019.

On June 28, 2019, Advanced Disposal held a special meeting of stockholders and approximately 85.9% of the total outstanding shares of Advanced Disposal common stock as of the May 22, 2019 record date for such meeting voted in favor of the adoption of the original merger agreement, which constituted a majority of the outstanding shares of Advanced Disposal common stock entitled to vote at the special meeting, as required to adopt the original merger agreement under the DGCL.

On July 12, 2019, as expected, Advanced Disposal and Waste Management each received a Second Request from the DOJ in connection with the DOJ's review of the merger. The effect of the Second Request was to extend the waiting period imposed under the HSR Act until the 30th day after substantial compliance by Advanced Disposal and Waste Management with the Second Request, unless the waiting period is terminated earlier by the DOJ.

Following the signing of the original merger agreement, both before and after the receipt of the Second Request, Advanced Disposal, Waste Management and their respective antitrust counsel have had extensive discussions with the DOJ staff, either telephonically or in person, on a range of topics, including the merits of the transaction, the proposed synergies, potential remedies, and divestitures, as well as each company's respective data systems, document collections, and document retention policies. Advanced Disposal and Waste Management have provided data and documents on a continuous basis to the DOJ in response to the Second Request and various other requests from the DOJ staff.

On October 25, 2019, Advanced Disposal, Waste Management and the DOJ entered into a timing agreement pursuant to which the parties agreed to a settlement period of a minimum of 70 days, which can terminate with notice by either party or the DOJ, to attempt to reach an agreement on receiving DOJ approval for the merger during such period. As of the date of this proxy statement, neither party nor the DOJ has terminated the settlement period.

Between October 2019 and February 2020, Advanced Disposal, Waste Management and their respective advisors negotiated confidentiality agreements with potential divestiture buyers relating to the assets of Advanced Disposal and Waste Management to potentially be divested based on discussions with the DOJ. Waste Management advised Advanced Disposal that it received inbound interest from more than 50 parties regarding interest in a potential acquisition of some or all of the assets to potentially be divested and conducted management presentations and business diligence with multiple selected parties. Advanced Disposal and Waste Management also prepared drafts of purchase agreements and ancillary documents in anticipation of the divestiture process.

Over the course of the next several months, Advanced Disposal, Waste Management and their respective antitrust counsel continued to respond to the DOJ staff, and Waste Management worked to establish a divestiture framework that it believed would potentially satisfy the DOJ staff's questions about the transaction. As in all mergers that require a remedy, the DOJ staff typically analyzes whether the proposed transaction will have anticompetitive effects in specific product and geographic markets in violation of Section 7 of the Clayton Act. Once the DOJ staff determines that anticompetitive effects are likely, it will

47

Table of Contents

discuss with the parties its findings. Typically, the parties then propose an acceptable remedy that will maintain or restore competition in the markets in which the DOJ has expressed competition concerns. In this case, Waste Management proposed the divestiture of certain landfills, transfer stations, other facilities and hauling routes of both Waste Management and Advanced Disposal as a cure to maintain or restore competition in certain areas. Pursuant to the terms of the original merger agreement, Waste Management was entitled to control the strategy for obtaining DOJ approval. While Waste Management was specifically required to sell or divest assets (belonging to Waste Management or Advanced Disposal or any of their respective subsidiaries) if required in order to obtain antitrust approval, it was not, however, required to sell assets that would, individually or in the aggregate, result in a reduction of revenue (without duplication and net of any intercompany revenues) in excess of $200,000,000 (for any rolling 12-month period ending the last full month prior to any date between the date of the original merger agreement and the closing date) to Waste Management, Advanced Disposal and their respective subsidiaries (taken as a whole after giving effect to the merger) if such actions had been taken at the beginning of any such rolling 12-month period (which we refer to as the "Antitrust Revenue Threshold").

On March 11, 2020, the World Health Organization designated the COVID-19 (coronavirus) outbreak as a global pandemic. The COVID-19 (coronavirus) pandemic continues to cause significant and unprecedented disruption in the global economy including in the solid waste collection, transfer, recycling and disposal services industry. Such disruption, along with the effect of governmental regulations imposed in response to the COVID-19 (coronavirus) pandemic, has resulted in volume declines in all of our lines of business except residential, as outlined in Advanced Disposal's Quarterly Report on Form 10-Q filed on May 7, 2020.

On March 19, 2020, Advanced Disposal filed a Current Report on Form 8-K to update prior timing expectations on the closing. Advanced Disposal, based on a Current Report on Form 8-K filed by Waste Management the day before, informed the public that as a result of, and subject to any further effects from, the COVID-19 (coronavirus) pandemic, and subject to obtaining final regulatory approval from the DOJ (which was then-anticipated in the second quarter of 2020), Advanced Disposal anticipated closing the merger mid to late second quarter 2020.

On April 13, 2020, a day before the initial end date under the original merger agreement, representatives of Simpson Thacher and representatives of Shearman & Sterling confirmed with each other that the initial end date would be automatically extended for an additional 90 days pursuant to the original merger agreement, i.e., until July 13, 2020 (which we refer to as the "July 13 end date").

Since the outbreak of COVID-19 (coronavirus), senior management of Advanced Disposal and Waste Management discussed the financial outlook of Advanced Disposal in light of COVID-19 (coronavirus) and the steps that Advanced Disposal implemented, or was planning to implement, to mitigate the impact. On April 29, 2020 and May 6, 2020, in response to a request made by Waste Management (and as further discussed between representatives of Centerview and representatives of UBS on May 4, 2020) pursuant to the original merger agreement and to facilitate Waste Management's continued consideration of agreeing to divestitures in excess of the Antitrust Revenue Threshold at the request of the DOJ, Advanced Disposal provided updated financial forecasts to Waste Management (as described in the section entitled "The Merger (Proposal 1)—Projected Financial Information" beginning on page 67 of this proxy statement).

On May 6, 2020, Waste Management filed a Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2020, which included an update of prior timing expectations on the closing, informing the public that despite the general business disruption caused by COVID-19 (coronavirus), Waste Management continued to make progress and that the then-current expectation was that Waste Management would be in a position to receive final antitrust regulatory approval and proceed toward closing by the end of the second quarter of 2020.

On May 13, 2020, Mr. Burke received a call from Mr. Fish, who stated that, in light of the impact of COVID-19 (coronavirus) on the solid waste industry generally and on Advanced Disposal and the fact the

48

Table of Contents

DOJ indicated it was not likely to approve the merger prior to the July 13 end date without divestitures in excess of the Antitrust Revenue Threshold, after a series of general discussions with the board of directors of Waste Management, Waste Management proposed a reduction in the original merger consideration to $28.00 per share in cash (which we refer to as the "May 13 proposal"). Mr. Fish also informed Advanced Disposal that they would engage actively with one of the divestiture bidders, GFL, on purchase agreement documentation, and discuss with the DOJ staff GFL's ability to purchase the divested assets being discussed. Later that day, representatives of Centerview reiterated the May 13 proposal to representatives of UBS.

That same day, the Board convened a special telephonic meeting, and Mr. Burke updated the Board on his conversation with Mr. Fish. Representatives of UBS and Shearman & Sterling each then discussed with the Board considerations related to various options, including whether to engage with Waste Management in discussions regarding a reduced price, decline to discuss while continuing to work toward a closing prior to the July 13 end date, or a variation of one or more of such options. Further discussion followed by the members of the Board, including with respect to the objectives of Advanced Disposal and whether and how to communicate with Waste Management.

On May 15, 2020, the Board convened another special telephonic meeting to further discuss the May 13 proposal. Representatives of UBS presented materials to the Board regarding the current performance of Advanced Disposal, the current state of the solid waste industry, and an overview of a comparison of the pre-announcement projections and the updated financial forecasts. Representatives of UBS then left the meeting. Representatives of Shearman & Sterling then presented key considerations of the Board when evaluating the May 13 proposal and outlined various options available to Advanced Disposal at that point. Representatives of Shearman & Sterling then discussed with the Board the terms of the original merger agreement related to termination and the payment of the original Waste Management termination fee, the circumstances under which such fee would be available and the potential for disputes relating to the payment of such fee. Discussion followed by the members of the Board, including with respect to the objectives of Advanced Disposal, assessment of the likelihood of obtaining approval of the merger by stockholders of Advanced Disposal at a decreased merger consideration, the need to couple any potential decrease in the per share merger consideration with changes to an amended merger agreement designed to enhance closing certainty, the ability of Advanced Disposal to execute on a standalone plan in the event the original merger agreement with Waste Management was terminated, and the potential for litigation. The members of the Board also discussed that, based on information communicated by Waste Management, it was the understanding of Advanced Disposal management that the revenues associated with the assets that the DOJ staff would require to be divested in order to grant approval would exceed the Antitrust Revenue Threshold, resulting in the right for Waste Management to terminate the original merger agreement in accordance with its terms. The Board then authorized Mr. Burke to inform Waste Management that Advanced Disposal was not prepared at this time to entertain any changes to the existing terms of the original merger agreement and for Advanced Disposal and Waste Management to continue to work towards a closing on the terms and conditions agreed in the existing original merger agreement between Waste Management and Advanced Disposal.

On May 19, 2020, Messrs. Fish and Morris telephoned Mr. Burke and other senior management of Advanced Disposal and reiterated Waste Management's desire to reduce the original merger consideration in light of the impact of COVID-19 (coronavirus) on the solid waste industry generally and on Advanced Disposal and the fact that the DOJ staff was requiring assets to be divested in order to grant approval of the merger that would result in a reduction of revenue in excess of the Antitrust Revenue Threshold, such that Waste Management would not be obligated to close the merger. In response, Mr. Burke reiterated Advanced Disposal's position as authorized by the Board on May 15, 2020.

On May 21, 2020, the Board convened a special telephonic meeting. Mr. Burke updated the Board on the May 19, 2020 conversation with Messrs. Fish and Morris. Mr. Burke noted that Waste Management and Advanced Disposal were continuing to work towards obtaining antitrust approval of the merger to permit a

49

Table of Contents

closing, but the Board should continue to assess its options. Mr. Burke informed the Board that UBS and management of Advanced Disposal were continuing to review financial metrics of the Company, including the standalone plan, as well as conducting an analysis of the stockholder base of Advanced Disposal and the likelihood of approval of a transaction on revised terms. The Board then discussed the various options previously discussed at prior meetings in light of the most recent conversation with Messrs. Fish and Morris. The Board agreed that, at this time, Advanced Disposal should continue to work with Waste Management to obtain antitrust approval to permit a closing as promptly as practicable.

On May 22, 2020, a representative of Centerview telephoned a representative of UBS and requested that Advanced Disposal propose potential terms of the merger agreement amendment, which such representative of UBS promptly relayed to senior management of Advanced Disposal and members of the Board.

On May 26, 2020, the Board convened a special telephonic meeting to review the current state of discussions with Waste Management and recent industry publications with respect to the merger. Representatives of UBS provided an overview of a comparison of the pre-announcement projections and the updated financial forecasts, an update on recent trading statistics in the solid waste industry, and an analysis of potential impacts to stock prices in various alternatives. A representative of Shearman & Sterling summarized the existing terms of the original merger agreement and the governing principles for the Board to consider when evaluating a potential merger agreement amendment, including the need to consider Advanced Disposal's standalone plan in the event it remained a public company. The Board then discussed that, given the divestitures then being required by the DOJ to approve the merger and Waste Management's obligation to pay the original Waste Management termination fee of $150,000,000 in certain circumstances if such approval is not obtained, changes to the terms designed to enhance closing certainty would be critical for a potential merger agreement amendment. The Board then discussed terms to propose to Waste Management, including, among others, (i) imposing a "hell or high water" obligation on Waste Management to obtain the requisite regulatory approval by July 13, 2020 without limitations on its divestiture obligations, i.e., without any threshold like the Antitrust Revenue Threshold, (ii) an increase to the original Waste Management termination fee from $150,000,000 to $300,000,000, (iii) confirmation that Advanced Disposal had not suffered a material adverse effect or had breached the original merger agreement giving rise to a termination right of Waste Management from the signing date of the original merger agreement until the date of the merger agreement amendment, and (iv) by requiring Waste Management to pay a fee of $150,000,000 and not be reimbursed for its expenses in the event that Advanced Disposal stockholders do not approve the transaction with the revised terms (which we collectively refer to as the "May 26 proposed terms"). In addition, the Board discussed potential timing and structural considerations associated with the May 26 proposed terms. The Board then authorized representatives of UBS to convey the May 26 proposed terms and a price of $31.45 per share in cash to representatives of Centerview, which representatives of UBS conveyed on May 27, 2020.

On May 29, 2020, the Board convened a special telephonic meeting to discuss the conversation between the representatives of UBS and representatives of Centerview. Representatives of UBS relayed to the Board that Waste Management was willing to increase their offer price from $28.00 per share in cash to $29.50 per share in cash and understood that Waste Management would be required to agree to enhanced closing certainty in any amendment, but noted that Waste Management would not consider under any circumstances paying Advanced Disposal a fee of $150,000,000 in the event Advanced Disposal stockholders did not approve any amended terms. Representatives of UBS then presented recent trading statistics in the solid waste industry and an analysis of potential impacts to stock prices in various alternatives. The Board then discussed various options and whether to continue to engage with Waste Management regarding revised terms. The Board noted that during these preliminary discussions on revised terms, Advanced Disposal and Waste Management were continuing to work towards obtaining antitrust approval on the terms and conditions agreed in the existing original merger agreement between

50

Table of Contents

Waste Management and Advanced Disposal, including with respect to advancing documentation with GFL and another bidder of divested assets.

On June 1, 2020, all of the independent members of the Board (other than Tanuja Dehne) convened a special telephonic meeting to discuss the status of discussions between Waste Management and Advanced Disposal. Representatives of Shearman & Sterling, who were present at the invitation of the independent directors, recounted the proposals made to date and the various options available to the Board, including considerations regarding the achievability of Advanced Disposal's standalone plan. The Board also discussed the likelihood of obtaining approval of Advanced Disposal stockholders in the event it agreed to reduce the per share merger consideration in light of the composition of Advanced Disposal's stockholders base.

Later that afternoon, the Board convened a special telephonic meeting, attended by representatives of UBS and Shearman & Sterling, to continue to discuss whether to continue to engage with Waste Management on revised terms, and if so, the terms of any response. After discussion, the Board determined to provide Waste Management with a counterproposal on price of $31.15 per share in cash and to provide a draft merger agreement amendment consistent with the May 26 proposed terms. Additionally, representatives of Shearman & Sterling advised Advanced Disposal that the merger agreement amendment would re-open the "fiduciary out" provisions that would allow Advanced Disposal to respond to unsolicited acquisition proposals and potentially enter into a superior proposal between the date of the merger agreement amendment and the date of the second stockholders meeting, because Advanced Disposal's stockholders would be required to vote again to adopt the amended merger agreement. Advanced Disposal, representatives of Shearman & Sterling and representatives of UBS had previously discussed these "fiduciary out" provisions, and representatives of UBS had indicated that they believed it was unlikely that another buyer would make a superior offer to acquire Advanced Disposal at that time, taking into consideration, among other things, the fact that no proposal for an alternative transaction had been made after signing the original merger agreement. Nonetheless, Advanced Disposal and its advisors believed that it was important as part of the amendment to allow third parties to make a superior proposal to acquire Advanced Disposal before another stockholders meeting in order to maximize value for Advanced Disposal's stockholders. On June 2, 2020, Shearman & Sterling circulated an initial draft of the merger agreement amendment to Simpson Thacher that reflected such "fiduciary out" mechanics and the May 26 proposed terms.

On June 3, 2020, representatives of Simpson Thacher and Shearman & Sterling had a telephone call to discuss the terms of the May 26 proposed terms and Waste Management's response to such proposal. Thereafter, from time to time following June 3, 2020 until the announcement of the merger agreement amendment on June 24, 2020, representatives of Simpson Thacher and Shearman & Sterling had discussions regarding the terms of the merger agreement amendment and the GFL divestiture agreement.

On June 5, 2020, Mr. Morris telephoned Mr. Burke to state that a price of $31.15 per share in cash and the May 26 proposed terms were not acceptable to Waste Management. Mr. Morris reiterated that the assets that the DOJ staff may require to be divested prior to providing approval would result in a reduction of revenue in excess of the Antitrust Revenue Threshold. In such case, Waste Management would not be required to close the merger pursuant to the original merger agreement.

The Board convened a special telephonic meeting the same day, which was attended by representatives of UBS and Shearman & Sterling, and again on June 7, 2020, to assess their options, including whether to reach the July 13 end date expecting to terminate the original merger agreement and the likelihood that Waste Management would promptly pay the original Waste Management termination fee to which the Board believed Advanced Disposal would be entitled.

On June 11, 2020, Mr. Morris telephoned Mr. Burke to offer a revised price of $30.30 per share in cash as a "best and final" offer that had been authorized by the Waste Management board of directors the prior day. In addition, Mr. Morris informed Mr. Burke that Waste Management (which we collectively refer to

51

Table of Contents

as the "June 11 proposed terms"): (i) rejected a "hell or high water" standard for the regulatory efforts covenant, such that Waste Management must undertake its "best efforts" to receive requisite regulatory approval without limitations, and instead replaced it with a new capped divestiture obligation, (ii) proposed a change to the original Waste Management termination fee to $200,000,000, (iii) qualified with knowledge the acknowledgement that Advanced Disposal has not had a material adverse effect or terminable breach from the signing date until the date of the merger agreement amendment, as well as requesting certification from Advanced Disposal regarding the same, (iv) rejected the proposed fee payable by Waste Management in the event that Advanced Disposal stockholders do not approve the transaction with the revised terms, and (v) proposed an end date of September 30, 2020 with an ability for an automatic 90-day extension if either antitrust or stockholder approval has not been obtained. Later that day, Simpson Thacher circulated to Shearman & Sterling a revised draft of the merger agreement amendment on behalf of Waste Management in line with the June 11 proposed terms.

On June 15, 2020, the Board convened a special telephonic meeting, attended by representatives of UBS, Mayer Brown and Shearman & Sterling, to discuss the June 11 proposed terms and potential responses if the Board determined to continue to engage with Waste Management regarding an amendment. A representative of Mayer Brown provided an update on the antitrust process and confirmed to the Board that the DOJ staff was requiring assets to be divested prior to providing approval that would result in a reduction of revenue in excess of the Antitrust Revenue Threshold, and the DOJ staff indicated that antitrust approval would likely not be obtained by the July 13 end date. A representative of Shearman & Sterling discussed again with the Board the applicable existing terms of the original merger agreement and the factors for the Board to consider when evaluating whether to enter into a potential merger agreement amendment. The Board noted that if Advanced Disposal agreed to an amendment to the original merger agreement, closing certainty and protection of Advanced Disposal's ability to receive the Waste Management termination fee of an amount higher than the original Waste Management termination fee would be of key importance; therefore, Waste Management's proposal of a new capped divestiture obligation instead of a "hell or high water" standard would not be acceptable. The Board determined that they would continue to engage with Waste Management on a potential amendment to the original merger agreement and attempt to finalize terms of such amendment before responding on price.

On June 16, 2020, at the request of the Board, Shearman & Sterling circulated to Simpson Thacher a revised draft of the merger agreement amendment reflecting, among other things, the following terms: (i) reinsertion of a "hell or high water" standard for the regulatory efforts covenant such that Waste Management must undertake its "best efforts" to receive requisite regulatory approval without limitations by the proposed end date, (ii) a change to the original Waste Management termination fee to $275,000,000, (iii) eliminating the requirement in the original merger agreement that required Advanced Disposal to enter into a divestiture agreement in advance of a closing of the merger, and (iv) a proposed end date of September 30, 2020 with an ability for an automatic extension to October 31, 2020 if either antitrust or stockholder approval has not been obtained.

On June 18, 2020, representatives of Simpson Thacher relayed to representatives of Shearman & Sterling that Waste Management was willing to agree to the "hell or high water" standard proposed by Advanced Disposal only in the event that a divestiture agreement with GFL was executed by Waste Management, Advanced Disposal and GFL concurrently with the merger agreement amendment. In addition, Waste Management proposed, among other things, a $225,000,000 Waste Management termination fee and an extended end date of November 30, 2020. Representatives of Shearman & Sterling promptly relayed the proposed terms to the Board and representatives of UBS. On June 19, 2020, Simpson Thacher circulated a draft merger agreement amendment to Shearman & Sterling reflecting the conversation on June 18, 2020, and an initial draft of the amended and restated voting agreement, which Shearman & Sterling shared with CPPIB's legal counsel.

On June 20, 2020, as authorized by the Board, Mr. Burke telephoned Mr. Morris to convey Advanced Disposal's position with respect to the latest proposal from Waste Management. In particular, Mr. Burke

52

Table of Contents

conveyed that Advanced Disposal would be willing to accept: (i) a price of $30.60 per share in cash, (ii) a change to the original Waste Management termination fee to $250,000,000, (iii) agreement to execute a divestiture agreement that is conditioned on the closing of the merger with Waste Management but with a statement in the amended merger agreement that breach under such divestiture agreement would not constitute a breach under the amended merger agreement, and (iv) an end date of September 30, 2020 with an ability for an automatic extension to October 31, 2020 (not November 30, 2020) if either antitrust or stockholder approval has not been obtained. Over the course of the following days, Waste Management, Advanced Disposal, GFL, and their respective advisors also continued to negotiate the GFL divestiture transaction.

On June 21 and 22, 2020, representatives of Simpson Thacher and Centerview informed representatives of Shearman & Sterling and UBS, respectively, that Waste Management: (i) was not willing to negotiate its "best and final" offer of $30.30 per share in cash, (ii) was willing to agree to a $250,000,000 Waste Management termination fee, (iii) was willing to agree to a "hell or high water" standard for the regulatory efforts covenant such that Waste Management must undertake its "best efforts" to receive requisite regulatory approval only in the event that a divestiture agreement with GFL was executed in the next day or two concurrently with the merger agreement amendment, and (iv) would agree to limit the circumstances in which a breach by Advanced Disposal of its obligations in the GFL divestiture agreement would prevent Advanced Disposal from receiving the Waste Management termination fee. Mr. Morris telephoned Mr. Burke to reiterate the same as well as the importance, from Waste Management's perspective, of finalizing the terms of the merger agreement amendment and GFL divestiture agreement in the coming days. On the same date, Simpson Thacher circulated a revised merger agreement amendment to Shearman & Sterling.

On June 22, 2020, the Board convened a special telephonic meeting. Mr. Burke relayed the status of discussions with Waste Management and a representative of Shearman & Sterling reviewed for the Board the most recent proposals made by the parties. The Board then discussed the applicable termination provisions of the original merger agreement and the prospect for receiving the original Waste Management termination fee of $150,000,000. The Board and representatives of UBS again discussed Advanced Disposal's potential prospects if it were to operate as a standalone company, including the potential that Advanced Disposal's stock price could decrease significantly if the original merger agreement were terminated given that the trading price of Advanced Disposal common stock likely reflected the potential consummation of the pending transaction with Waste Management on the terms of the original merger agreement rather than necessarily Advanced Disposal's underlying financial and business performance. The Board then authorized Mr. Burke to accept Waste Management's proposal of $30.30 per share in cash, subject to management reaching agreement on the remaining terms of the merger agreement amendment consistent with those discussed with the Board.

That same date, Shearman & Sterling and Simpson Thacher exchanged drafts of the merger agreement amendment. Advanced Disposal, Waste Management, GFL and their respective advisors also continued to negotiate the GFL divestiture agreement.

On June 23, 2020, the Board convened a special telephonic meeting. Mr. Burke reported to the Board that negotiations with Waste Management on the merger agreement amendment documents and the GFL divestiture agreement had substantially concluded if the Board were to determine to proceed with the amendment at a price of $30.30 per share in cash and on the terms as presented to the Board in materials circulated prior to the meeting.

Representatives of UBS then reviewed with the Board UBS's financial analysis of the reduced merger consideration. Representatives of UBS also provided certain disclosures relating to UBS's relationships with Advanced Disposal, CPPIB, and Waste Management, including the fee UBS would receive from Advanced Disposal in connection with the proposed transaction with Waste Management as amended, which disclosures were updated relative to those that UBS provided to the Board on April 14, 2019 first on

53

Table of Contents

June 4, 2020 and again on June 22, 2020, along with the agreed amendment to their previous engagement letter to reflect fees for an additional opinion and updates to the fees payable to UBS due to the potential change in merger consideration. At the conclusion of such discussions, a representative of UBS delivered to the Board an oral opinion (which oral opinion was subsequently confirmed by delivery of a written opinion, dated June 23, 2020), to the effect that, as of that date and based on and subject to various procedures, assumptions and matters considered and the qualifications and limitations described in its opinion, the revised merger consideration to be received by the holders of Advanced Disposal common stock (other than the holders of excluded shares) in the merger was fair, from a financial point of view, to such holders. A copy of the written opinion of UBS is attached to this proxy statement as Annex D. Representatives of Shearman & Sterling then discussed certain corporate governance matters and the fiduciary duties of the directors under Delaware law. Such representatives of Shearman & Sterling then provided the Board with an overview of the merger agreement amendment and the GFL divestiture transaction, including the principal terms of the documents that would be executed in connection with the proposed transactions.

After deliberation and consideration of the factors described in the section entitled "The Merger (Proposal 1)—Recommendation of the Board and Reasons for Recommendation—Reasons for Recommendation" beginning on page 54 of this proxy statement, the Board unanimously (i) determined that the amended merger agreement and the transactions were fair to, and in the best interests of, Advanced Disposal and its stockholders, (ii) approved and declared advisable the amended merger agreement and the transactions, including the merger, (iii) approved the execution, delivery and performance by Advanced Disposal of the merger agreement amendment and the consummation of the transactions under the amended merger agreement, including the merger, upon the terms and subject to the conditions of the amended merger agreement, (iv) recommended the approval of the adoption of the amended merger agreement by the stockholders of Advanced Disposal, and (v) directed that the adoption of the amended merger agreement be submitted to a vote of the holders of Advanced Disposal common stock. The Board also unanimously approved the GFL divestiture agreement.

Following the conclusion of the Board meeting, Advanced Disposal, Waste Management, GFL and their respective legal counsel finalized negotiations of the GFL divestiture agreement on terms consistent with the terms approved by the Board, and all relevant parties executed the merger agreement amendment, the amended and restated voting agreement and the GFL divestiture agreement on the morning of June 24, 2020.

Prior to the opening of U.S. stock markets on June 24, 2020, Advanced Disposal and Waste Management issued a joint press release publicly announcing their entry into the merger agreement amendment and the GFL divestiture agreement.

Recommendation of the Board and Reasons for Recommendation

Recommendation of the Board

After considering the various factors described below, on June 23, 2020, the Board unanimously (i) determined that the amended merger agreement and the transactions were fair to, and in the best interests of, Advanced Disposal and its stockholders, (ii) approved and declared advisable to enter into the merger agreement amendment and the transactions, (iii) approved the execution and delivery by Advanced Disposal of the amended merger agreement and performance by Advanced Disposal of the amended merger agreement and the consummation of the transactions, including the merger, contemplated by the amended merger agreement, (iv) recommended the adoption of the amended merger agreement by Advanced Disposal stockholders, and (v) directed that the amended merger agreement be submitted to a vote of Advanced Disposal stockholders.

The Board unanimously recommends that you vote (1) "FOR" the proposal to adopt the amended merger agreement (2) "FOR" the compensation advisory proposal and (3) "FOR" the adjournment proposal.

54

Table of Contents

Reasons for Recommendation

In evaluating the amended merger agreement and the merger, the Board consulted with Advanced Disposal's senior management and its outside legal and financial advisors and, in reaching its determination to recommend that the Advanced Disposal stockholders adopt the amended merger agreement, the Board relied upon and considered numerous factors, including the factors set forth below (the order in which the following factors appear is not intended to reflect any relative significance):

Financial Terms; Certainty of Value

•

The belief of the Board that the merger consideration of $30.30 per share in cash of Advanced Disposal common stock represents fair value for shares of Advanced Disposal common stock, taking into account Advanced Disposal's current and historical financial condition, results of operations, business, competitive position and prospects, as well as Advanced Disposal's near-term and long-term standalone plan in the event Advanced Disposal were to remain an independent public company, and the future prospects and risks associated with remaining an independent public company and the risks and uncertainties associated with the execution of the standalone plan, including the scope and duration of the COVID-19 (coronavirus) pandemic and actions taken by governmental authorities to contain the spread of the virus and the impact of COVID-19 (coronavirus) and such actions on Advanced Disposal and our business and prospects.

•

The opportunity for Advanced Disposal's stockholders to realize substantial value based on the receipt of the merger consideration representing a premium of 11.6% to the closing share price of April 12, 2019, the last trading day prior to the announcement of the merger, a premium of approximately 10.5% to the 30-day volume weighted average price of April 12, 2019, and a premium of approximately 8.1% to the all-time highest closing share price prior to April 12, 2019.

•

The fact that the merger consideration consists solely of cash, which provides certainty of value and liquidity to the stockholders of Advanced Disposal and does not expose them to any future risks related to the business or the financial markets generally, as compared to a transaction in which stockholders receive equity or other securities, or as compared to remaining an independent, standalone company.

•

The oral opinion of UBS (which oral opinion was subsequently confirmed by delivery of a written opinion, dated as of June 23, 2020), provided to the Board, to the effect that, as of that date and based on and subject to various procedures, assumptions and matters considered and the qualifications and limitations described in its opinion, the merger consideration to be received by the holders of Advanced Disposal common stock (other than the holders of excluded shares) in the merger was fair, from a financial point of view, to such holders. A copy of the written opinion of UBS is attached to this proxy statement as Annex D.

•

The fact that appraisal rights will be available to the holders of Advanced Disposal common stock who properly exercise their rights under the DGCL, which would give these stockholders the ability to seek and be paid a judicially determined appraisal of the "fair value" of their shares of Advanced Disposal common stock if they do not wish to accept the merger consideration.

•

The fact that the merger consideration Waste Management agreed to pay to the holders of Advanced Disposal common stock was increased from $28.00 to $30.30 per share as a result of extensive negotiations following the initial indication by Waste Management that it was considering terminating the original merger agreement following the July 13, 2020 end date in the event it had not, by that time, received antitrust approval on terms it was required to accept under the terms of the original merger agreement, as described in the section above entitled "The Merger (Proposal 1)—Background of the Merger" beginning on page 40 of this proxy statement.

55

Table of Contents

•

The fact that the parties have agreed that all vested and unvested equity awards of Advanced Disposal will automatically accelerate and settle in cash based on the value of the merger consideration, rather than be assumed by, and converted into equity awards of, Waste Management, which provides certainty of value and liquidity to holders of Advanced Disposal equity awards and does not expose them to the risk of lost value based on Waste Management's performance or future risks related to the financial markets generally.

Prospects of Advanced Disposal

•

Advanced Disposal's current and historical business, financial condition, results of operations, competitive position, strategic options and prospects, as well as Advanced Disposal's near-term and long-term standalone plan in the event Advanced Disposal were to remain an independent public company, the risks and challenges associated with remaining an independent public company, and the risks and uncertainties associated with the execution of the standalone plan, and the potential impact of those factors on the future trading price of Advanced Disposal common stock, including risks related to:

–

the general business environment for the solid waste industry, including industry trends, increased labor, transportation and fuel costs, high level of capital expenditures, and substantial governmental regulation and involvement;



–

the costs, risks and uncertainties relating to the execution by Advanced Disposal of its near-term and long-term standalone plan in the event Advanced Disposal were to remain an independent public company;



–

the additional costs and burdens involved with being a public company;



–

the U.S. and global economy and general stock market conditions and volatility;



–

the challenges and potential impacts of the COVID-19 (coronavirus) pandemic, including volume declines in lines of business due to deteriorating macroeconomic conditions and stay-at-home orders resulting from the COVID-19 (coronavirus) pandemic;



–

the challenges of, after having operated since April 14, 2019 in accordance with the restrictions on the conduct of Advanced Disposal's business included in the original merger agreement, identifying and capitalizing on opportunities to grow the Advanced Disposal business and execute on the standalone plan;



–

the other risks and uncertainties identified in Advanced Disposal's filings with the SEC, including in its Annual Report on Form 10-K for the year ended December 31, 2019 and its Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2020; and



–

the Board's belief, after consideration of the factors described in this section, that the consummation of the transactions represent Advanced Disposal's best reasonably available alternative for maximizing stockholder value.

Process and Consideration of Alternatives

•

The Board's belief, at the time of the original merger agreement and the merger agreement amendment, based on the fact that no potential parties approached Advanced Disposal with a credible offer since the date of the announcement of the original merger agreement and a review of the possible alternatives to a sale of Advanced Disposal, including the prospects of continuing to operate in accordance with the near-term and long-term strategic plan, the potential value to Advanced Disposal stockholders of such alternatives and the timing and likelihood of actually achieving additional value for such stockholders from these alternatives, that none of these options,

56

Table of Contents

on a risk- and time-adjusted basis, was reasonably likely to create value for Advanced Disposal stockholders greater than the merger consideration.

•

The fact that Advanced Disposal had preliminary discussions with respect to a potential material transaction involving Advanced Disposal with at least two other potential strategic or financial counterparties in 2018, none of which provided any indication that it was interested in proceeding with a transaction on terms competitive with the terms of the amended merger agreement, as described in "The Merger (Proposal 1)—Background of the Merger," beginning on page 40 of this proxy statement.

•

The determination by the Board, after discussion with Advanced Disposal's senior management, that Waste Management was and continues to be one of the most logical acquirers of Advanced Disposal and, in light of Waste Management's complementary businesses, as well as the projected synergies that would result from the combination, together with Waste Management's strong balance sheet and financial position, that Waste Management would be the potential transaction partner most likely to offer the best combination of value and closing certainty to Advanced Disposal's stockholders, particularly in light of the terms included in the merger agreement amendment.

•

The Board's belief that, at the time of the original merger agreement, there were no other credible potential parties that might have an interest in engaging in a strategic transaction with Advanced Disposal at a value higher than $33.15 per share; the potential regulatory, commercial and financing issues that might arise in connection with pursuing such an alternative transaction; and the belief that Waste Management would withdraw from consideration of a potential transaction if Advanced Disposal were to pursue discussions with other potential counterparties.

•

The Board's belief that, at the time of the merger agreement amendment, there were no other credible potential parties that might have an interest in engaging in a strategic transaction with Advanced Disposal at a value higher than $30.30 per share; the potential regulatory, commercial and financing issues that might arise in connection with pursuing such an alternative transaction; and that no potential parties approached Advanced Disposal with a credible offer since the date of the announcement of the original merger agreement.

Likelihood of Consummation

•

The Board's belief of the likelihood that, without a reduction in merger consideration and execution of the merger agreement amendment, Waste Management would terminate the original merger agreement after July 13, 2020.

•

The fact that the terms of the merger agreement amendment substantially increased the closing certainty for Advanced Disposal's stockholders, including by, among other things: (i) extending the end date from July 13, 2020 to September 30, 2020, which will be further extended automatically to November 30, 2020 if, subject to certain conditions, Advanced Disposal stockholder approval or antitrust approval has not been obtained by September 30, 2020; (ii) providing for a Waste Management termination fee of $250,000,000 (increased from $150,000,000); (iii) providing that Waste Management must use "best efforts" to take all actions to consummate the transactions by the end date, including using its "best efforts" to obtain antitrust approval, is required to sell or divest assets (belonging to Waste Management or Advanced Disposal or any of its subsidiaries) in order to obtain antitrust approval and to eliminate the $200 million revenue threshold on the divestiture obligation of Waste Management as provided in the original merger agreement; and (iv) providing that each party has certified to the other that such party's closing conditions with respect to the accuracy of its representations and performance of its covenants, and, with respect to Waste Management, the absence of a material adverse effect on Advanced Disposal, would be satisfied as of the date of the merger agreement amendment if the closing were to occur on such date (and that Waste Management and Merger Sub will not assert that any of such conditions are not satisfied at the

57

Table of Contents

closing as a result of what such parties had knowledge of as of the date of the merger agreement amendment), as more fully described in the section entitled "The Amended Merger Agreement" beginning on page 85 of this proxy statement.

•

The fact that concurrently with the execution of the merger agreement amendment, on June 24, 2020, Waste Management, Advanced Disposal and GFL entered into the GFL divestiture agreement in order to the address substantially all of the divestitures anticipated to be required by the DOJ to obtain antitrust approval for the merger, as more fully described in the section entitled "The Merger (Proposal 1)—Regulatory Clearances—GFL Divestiture Agreement" beginning on page 82 of this proxy statement.

•

The business reputation and capabilities of Waste Management and its management.

•

The fact that Waste Management's obligation to complete the transactions is not conditioned on Waste Management or Merger Sub obtaining financing, and the Board's knowledge of Waste Management's financial condition and ability to fund the aggregate per share merger consideration and all other payments required in connection with the transactions, including associated fees and expenses.

•

The fact that concurrently with the execution of the merger agreement amendment, on June 24, 2020, Advanced Disposal's largest stockholder, CPPIB, entered into the amended and restated voting agreement with Waste Management, pursuant to which, among other things, and subject to the terms and conditions set forth therein, CPPIB agreed to vote its shares of Advanced Disposal common stock for the adoption of the amended merger agreement and against any alternative proposal, as more fully described in the section entitled "The Amended and Restated Voting Agreement" beginning on page 85 of this proxy statement.

•

The fact that the merger is not subject to approval by Waste Management's stockholders.

Terms of the Amended Merger Agreement

•

The Board considered, after discussions with Advanced Disposal's legal advisors, all of the terms and conditions of the amended merger agreement, including the representations, warranties, covenants and agreements of the parties, the conditions to closing, the form of the merger consideration and the termination rights, including:

–

that the terms of the amended merger agreement were the products of arms'-length negotiations among sophisticated parties and their respective legal and financial advisors, as more fully described in "The Merger (Proposal 1)—Background of the Merger" beginning on page 40 of this proxy statement;



–

that the "fiduciary out" provisions, subject to Advanced Disposal's compliance with the terms and conditions of the amended merger agreement, give the Board the ability to furnish information to, and engage in negotiations with, third parties that have made a bona fide unsolicited proposal that is a superior proposal or could reasonably be expected to lead to a superior proposal, and, upon payment of the Company termination fee and compliance with the other terms and conditions of the amended merger agreement, terminate the amended merger agreement in order to enter into an agreement with respect to a superior proposal (as more fully described in the section entitled "The Amended Merger Agreement—Other Covenants and Agreements—No Solicitation; Acquisition Proposals" beginning on page 95 of this proxy statement);



–

that the Board has the ability in certain circumstances, and subject to certain conditions, to change, qualify, withdraw or modify its recommendation that the Advanced Disposal stockholders vote to adopt the amended merger agreement (as more fully described in the

58

Table of Contents

section entitled "The Amended Merger Agreement—Other Covenants and Agreements—The Advanced Disposal Board Recommendation; Change of Recommendation; Fiduciary Exception" beginning on page 96 of this proxy statement;

–

the availability of appraisal rights for the holders of Advanced Disposal common stock who do not vote in favor of the merger and otherwise properly exercise their appraisal rights under the DGCL;



–

the fact that, if the amended merger agreement is terminated by Advanced Disposal due to a nonappealable court order or legal restraint has been issued prohibiting the merger due to antitrust reasons or the failure of the merger to be consummated by the end date, and at such time, antitrust approval under the HSR Act has not been obtained, Waste Management will be required to pay Advanced Disposal the Waste Management termination fee if certain specified conditions are met;



–

the fact that, subject to certain customary limitations, Advanced Disposal will have sufficient operating flexibility for it to conduct its business in the ordinary course consistent with past practice during the pre-closing period;



–

the fact that the conditions to the closing are specific and limited in scope;



–

the fact that a vote of Advanced Disposal stockholders is required under the DGCL to adopt the amended merger agreement;



–

that the remedies of specific performance and monetary damages are available to Advanced Disposal under the amended merger agreement as more fully described in the section entitled "The Amended Merger Agreement—Limitations on Remedies; Specific Performance" beginning on page 107 of this proxy statement; and



–

the fact that the original merger agreement was amended to, in addition to the terms designed to increase the closing certainty to Advanced Disposal's stockholders, eliminate Advanced Disposal's obligation to reimburse Waste Management's expenses in the event Advanced Disposal does not obtain the Advanced Disposal stockholder approval.

In addition to the factors above, the Board identified and considered a variety of risks and potentially negative factors concerning the merger, including:

•

the reduced per share merger consideration;

•

the possibility that the merger might not be consummated, and the risks and costs to Advanced Disposal in such event, including the diversion of management and employee attention and the potential disruptive effect on business and customer relationships, vendor relationships, stock price and ability to attract and retain key management personnel and employees;

•

the possibility that completion of the merger might be delayed or subject to adverse conditions that may be imposed by governmental authorities that are not within Advanced Disposal's control, that the required governmental approvals, including antitrust approval by the DOJ, may not be obtained at all, and the period of time Advanced Disposal may be subject to the amended merger agreement without assurance that the merger will be completed;

•

the fact that upon termination of the amended merger agreement under specified circumstances, Advanced Disposal may be required to pay Waste Management the Company termination fee or reimburse Waste Management's expenses of up to $15,000,000 and that these payments may discourage other parties that may otherwise have an interest in a business combination with, or an acquisition of, Advanced Disposal;

59

Table of Contents

•

the fact that Advanced Disposal could have terminated the original merger agreement after July 13, 2020 and the Board belief's that Advanced Disposal had the right to collect a termination fee of $150,000,000 payable by Waste Management to Advanced Disposal, and the fact that if the amended merger agreement is later terminated, there are no assurances that the Waste Management termination fee will be payable;

•

the significant costs involved in connection with completing the merger, the substantial management time and effort required to complete the merger and the GFL divestiture transaction, and the related disruption to Advanced Disposal's operations;

•

the limitations imposed on the solicitation or consideration by Advanced Disposal of alternative transactions prior to the completion of the Special Meeting and the other terms and conditions of the amended merger agreement;

•

that the Board is required to submit the merger to the vote of the Advanced Disposal stockholders at the Special Meeting even if the Board has made a change of recommendation, unless the amended merger agreement is terminated;

•

the interests that certain Advanced Disposal executive officers and directors may have with respect to the merger in addition to their interests as Advanced Disposal stockholders as described in "The Merger (Proposal 1)—Interests of Advanced Disposal Directors and Executive Officers in the Merger" beginning on page 71 of this proxy statement; and

•

that the gain likely to be realized by Advanced Disposal stockholders as a result of the merger generally will be taxable to such stockholders for U.S. federal income tax purposes if they are not otherwise exempt from the payment of such taxes (as more fully described in "The Merger (Proposal 1)—Material U.S. Federal Income Tax Consequences of the Merger" beginning on page 78 of this proxy statement.

The foregoing discussion of the information and factors considered by the Board is not intended to be exhaustive, but rather includes the principal material information, factors and analyses considered by the Board in reaching its conclusions and recommendation in relation to the amended merger agreement and the transactions. The Board evaluated the various factors listed above in light of its knowledge of the business, financial condition and prospects of Advanced Disposal, in consultation with Advanced Disposal's senior management and outside legal and financial advisors. The Board did not provide a specific assessment of, quantify or otherwise assign any relative weights to, the factors considered in determining its recommendation. Instead, the Board conducted an overall analysis of the factors and reasons described above and determined in its business judgment that, in the aggregate, the potential benefits of the merger to the stockholders of Advanced Disposal outweighed the risks or potential negative consequences. Individual members of the Board may have given different weight to different factors. In addition, in arriving at its recommendation, the directors of Advanced Disposal were aware of the interests of certain officers and directors of Advanced Disposal as described in "The Merger (Proposal 1)—Interests of Advanced Disposal Directors and Executive Officers in the Merger" beginning on page 71 of this proxy statement.

Opinion of Financial Advisor

UBS was retained as financial advisor to the Board in connection with the merger. As part of that engagement, UBS had rendered an opinion, as to the fairness, from a financial point of view, to the Advanced Disposal stockholders (other than holders of excluded shares) of the original merger consideration to be received by such stockholders in the merger. The execution of the original merger agreement was publicly announced on April 15, 2019. In connection with the merger agreement amendment, the Board requested that UBS render an opinion, as to the fairness, from a financial point of view, to the Advanced Disposal stockholders (other than holders of excluded shares) of the merger

60

Table of Contents

consideration of $30.30 per share in cash to be received by such stockholders in the merger. On June 23, 2020, at a meeting of the Board held to evaluate the proposed merger, UBS delivered to the Board an oral opinion, confirmed by delivery of a written opinion, dated June 23, 2020, to the effect that, as of that date and based on and subject to various procedures, assumptions and matters considered and the qualifications and limitations described in its opinion, the merger consideration to be received by the Advanced Disposal stockholders (other than the holders of excluded shares) in the merger was fair, from a financial point of view, to such stockholders.

The full text of UBS's opinion describes the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by UBS. UBS's opinion is attached as Annex D to this proxy statement and is incorporated by reference herein. UBS's opinion was provided for the benefit of the Board (in its capacity as such) in connection with, and for the purpose of, its evaluation of the fairness, from a financial point of view, of the merger consideration to be received by the Advanced Disposal stockholders (other than the holders of excluded shares) in the merger, and does not address any other aspect of the merger or any related transaction. UBS's opinion does not address the relative merits of the merger or any related transaction as compared to other business strategies or transactions that might be available to Advanced Disposal or Advanced Disposal's underlying business decision to effect the merger or any related transaction. UBS's opinion does not constitute a recommendation to any Advanced Disposal stockholder as to how such stockholder should vote or act with respect to the merger or any related transaction. The following summary of UBS's opinion is qualified in its entirety by reference to the full text of UBS's opinion.

In arriving at its opinion, UBS, among other things:

•

reviewed certain publicly available business and financial information relating to Advanced Disposal and Waste Management;

•

reviewed certain internal financial information and other data relating to the business and financial prospects of Advanced Disposal that were not publicly available, including the updated financial forecasts (as defined in the section entitled "The Merger (Proposal 1)—Projected Financial Information" beginning on page 67 of this proxy statement) that the Board directed UBS to utilize for purposes of its analysis;

•

conducted discussions with members of the senior management of Advanced Disposal concerning the businesses and financial prospects of Advanced Disposal;

•

performed a discounted cash flow analysis of Advanced Disposal in which UBS analyzed the future cash flows of Advanced Disposal using the updated financial forecasts;

•

reviewed publicly available financial and stock market data with respect to certain other companies UBS believed to be generally relevant;

•

compared the financial terms of the merger with the publicly available financial terms of certain other transactions that UBS believed to be generally relevant;

•

reviewed current and historical market prices of Advanced Disposal common stock;

•

reviewed the amended merger agreement, including a draft of the merger agreement amendment, delivered to UBS on June 23, 2020; and

•

conducted such other financial studies, analyses and investigations, and considered such other information, as UBS deemed necessary or appropriate.

In connection with its review, with the consent of the Board, UBS assumed and relied upon, without independent verification, the accuracy and completeness in all material respects of the information provided to or reviewed by UBS for the purpose of its opinion. In addition, with the consent of the Board, UBS did not make any independent evaluation or appraisal of any of the assets or liabilities (contingent or

61

Table of Contents

otherwise) of Advanced Disposal, nor was UBS furnished with any such evaluation or appraisal. With respect to the updated financial forecasts that UBS utilized for its analysis, UBS assumed at the direction of the Board, that they were reasonably prepared on a basis reflecting the best currently available estimates and judgements of the management of Advanced Disposal as to the future financial performance of Advanced Disposal. In addition, UBS assumed with the approval of the Board that the financial forecasts and estimates referred to above would be achieved at the times and in the amounts projected. UBS's opinion is necessarily based on economic, monetary, market and other conditions as in effect on, and the information available to UBS as of, the date of its opinion.

UBS's opinion does not address the relative merits of the merger or any related transaction as compared to other business strategies or transactions that might be available to Advanced Disposal or Advanced Disposal's underlying business decision to effect the merger or any related transaction. UBS's opinion does not constitute a recommendation to any Advanced Disposal stockholder as to how such stockholder should vote or act with respect to the merger or any related transaction. At the direction of the Board, UBS was not asked to, nor did it, offer any opinion as to the terms, other than the merger consideration to the extent expressly specified in its opinion, of the amended merger agreement or any related documents or the form of the merger or any related transaction. In addition, UBS expressed no opinion as to the fairness of the amount or nature of any compensation to be received by any officers, directors or employees of any parties to the merger, or any class of such persons, relative to the merger consideration. UBS expressed no opinion as to the price at which Advanced Disposal common stock will trade at any time. In rendering its opinion, UBS assumed, with the consent of the Board, that (i) the final executed form of the merger agreement amendment would not differ in any material respect from the draft UBS reviewed dated June 23, 2020, (ii) the parties to the amended merger agreement would comply with all material terms of the amended merger agreement and (iii) the merger would be consummated in accordance with the terms of the amended merger agreement and in accordance with all applicable laws and other relevant documents or requirements without any adverse waiver or amendment of any material term or condition thereof. UBS also assumed that all governmental, regulatory or other consents and approvals necessary for the consummation of the merger would be obtained without any adverse effect on Advanced Disposal, Waste Management or the merger. The issuance of UBS's opinion was approved by an authorized committee of UBS.

In connection with rendering its opinion to the Board, UBS performed a variety of financial and comparative analyses, which are summarized below. The following summary is not a complete description of all analyses performed and factors considered by UBS in connection with its opinion. The preparation of a fairness opinion is a complex process involving subjective judgments and is not necessarily susceptible to partial analysis or summary description. With respect to the selected public companies analysis and the selected transactions analysis summarized below, no company or transaction used as a comparison was identical to Advanced Disposal, Waste Management or the merger. These analyses necessarily involve complex considerations and judgments concerning financial and operating characteristics and other factors that could affect the public trading or acquisition values of the companies concerned.

UBS believes that its analyses and the summary below must be considered as a whole and that selecting portions of its analyses and factors or focusing on information presented in tabular format, without considering all analyses and factors or the narrative description of the analyses, creates a misleading or incomplete view of the processes underlying UBS's analyses and opinion. UBS did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis for purposes of its opinion, but rather arrived at its ultimate opinion based on the results of analyses undertaken by it and assessed as a whole.

The updated financial forecasts in or underlying UBS's analyses are not necessarily indicative of actual future results or values, which may be significantly more or less favorable than those estimates. In performing these analyses, UBS considered industry performance, general business and economic conditions and other matters, many of which were beyond Advanced Disposal's control. Estimates of the

62

Table of Contents

financial value of companies do not purport to be appraisals or necessarily reflect the prices at which businesses or securities actually may be sold or acquired.

The merger consideration was determined through negotiations between Advanced Disposal and Waste Management and their respective representatives and the decision by the Board to recommend that Advanced Disposal enter into the merger was solely that of the Board, and the decision by Advanced Disposal to enter into the merger was solely that of the Board. UBS's opinion and financial analyses were only one of many factors considered by the Board in its evaluation of the merger and should not be viewed as determinative of the views of the Board or the management of Advanced Disposal with respect to the merger or the merger consideration to be received by the Advanced Disposal stockholders (other than the holders of excluded shares) in the merger.

The following is a brief summary of the material financial analyses performed by UBS and reviewed with the Board on June 23, 2020 in connection with its opinion. The financial analyses summarized below include information presented in tabular format. In order for UBS's financial analyses to be fully understood, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. Considering the data below without considering the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of UBS's financial analyses.

Trading Statistics for Selected Public Companies Analysis

UBS compared selected financial and stock market data of Advanced Disposal with corresponding data of certain publicly traded companies whose primary business is municipal solid waste collection and disposal in the United States and Canada (collectively referred to as the selected companies):

•

Waste Management;

•

Republic Services, Inc. (which we refer to as "Republic");

•

Waste Connections, Inc. (which we refer to as "Waste Connections");

•

GFL; and

•

Casella Waste Systems, Inc. (which we refer to as "Casella").

Although none of the selected companies is directly comparable to Advanced Disposal, the companies included were chosen because they are publicly traded companies with operations that, for purposes of analysis, may be considered generally relevant to certain operations of Advanced Disposal. UBS included GFL as a selected company after GFL completed an initial public offering in March 2020.

UBS reviewed, among other things:

•

the enterprise values of each of the selected companies, calculated as equity market value based on closing stock prices on June 23, 2020, the last trading date prior to the delivery of UBS's oral opinion, plus debt at book value, less cash and cash equivalents, plus minority interest at book value of each of the selected companies, as a multiple of earnings before taxes, interest and depreciation (after stock-based compensation and before landfill retirement accretion and certain non-recurring items based on prevalent treatment by selected public companies, where available) (which we refer to as "Market Adjusted EBITDA") as projected and estimated with respect to calendar year 2021 (which we refer to as "2021E Market Adjusted EBITDA") for such selected company (which we refer to as "EV/2021E Market Adjusted EBITDA"); and

•

the equity market value calculated based on closing stock prices on June 23, 2020, the last trading price date prior to the delivery of UBS's oral opinion, of each of the selected companies as a multiple of projected, estimated calendar year 2021 free cash flow (which we refer to as "2021E FCF"),

63

Table of Contents

defined as cash flow from operations minus capital expenditures, of such selected company (which we refer to as "P/2021E FCF").

Financial data for the selected companies were based on FactSet data, public filings and other publicly available information, as well as analyst research. Financial data for Advanced Disposal was based on public filings and the financial forecasts and estimates prepared by the management of Advanced Disposal that the Board directed UBS to utilize for purposes of its analyses. This analysis indicated the following implied multiples for the selected companies, as compared to corresponding multiples implied for Advanced Disposal.

The following table presents the results of this analysis of the selected companies:

Using its experience and professional judgment, UBS made qualitative judgments concerning differences between the business, financial and operating characteristics and prospects of Advanced Disposal and the selected companies and selected a reference range for EV/2021E Market Adjusted EBITDA of 10.0x – 11.5x and for P/2021E FCF of 16.0x – 20.5x and applied such ranges to Advanced Disposal's 2021E Market Adjusted EBITDA of $425 million, as provided by the management of Advanced Disposal, and Advanced Disposal's 2021E Adjusted FCF of $141 million, as described under the section entitled "The Merger (Proposal 1)—Projected Financial Information—Updated financial forecasts" beginning on page 70 of this proxy statement, to derive a range of implied consideration per share for Advanced Disposal, rounded to the nearest $0.05, of $26.45 to $33.20 and $24.80 to $31.50, respectively, as compared to the $30.30 offer price.

Precedent Transactions Analysis

UBS also analyzed certain publicly available information related to United States and Canadian publicly disclosed transactions with enterprise values over $250 million since 2008 with municipal solid waste collection and disposal being the target's primary line of business.

With respect to this group of transactions, which is listed below, UBS calculated and compared the target company's enterprise value (which we refer to as "EV"), based on public disclosure related to the transaction, as a multiple of last twelve months Market Adjusted EBITDA (which we refer to as "LTM Market Adjusted EBITDA").

64

Table of Contents

The following table presents the results of this analysis of the precedent transactions:

Precedent Transactions

None of the precedent transactions or companies that participated in the precedent transactions are directly comparable to the merger, Advanced Disposal or Waste Management. Each of the target companies in the precedent transactions was involved in the municipal solid waste collection and disposal industry and the selected transactions are all of the transactions since 2008 that, in UBS's professional judgment, involved target companies with operations that, for the purposes of UBS's analyses, may be considered generally relevant to certain operating characteristics of Advanced Disposal.

With respect to the precedent transactions and based on the results of the foregoing calculations and UBS's analyses of the various transactions and its professional judgment, UBS applied a reference range of enterprise value to Market Adjusted EBITDA multiples of 9.5x – 12.0x to Advanced Disposal's actual LTM Market Adjusted EBITDA for the quarter ending March 31, 2020 of $414 million, as provided by Advanced Disposal's public filings, to derive a range of implied per share consideration for Advanced Disposal, rounded to the nearest $0.05, of $23.05 to $33.95, as compared to the $30.30 offer price.

Discounted Cash Flow Analysis

UBS performed discounted cash flow analyses utilizing financial forecasts and estimates prepared by the management of Advanced Disposal (as more fully described in the section entitled "The Merger (Proposal 1)—Projected Financial Information" beginning on page 67 of this proxy statement). UBS calculated ranges of implied present values (as of July 1, 2020) of the standalone, unlevered, free cash flows that Advanced Disposal was forecasted to generate from the second half of 2020 through December 31, 2024 and of terminal values for Advanced Disposal. UBS calculated the unlevered, free cash flows as Adjusted EBITDA less (a) (i) stock-based compensation, (ii) taxes, (iii) changes in working capital, and (iv) capital expenditures, plus (b) (i) other operating cash flows and (ii) in the second half of 2020, a net cash flow of $125 million calculated as the original Waste Management termination fee of $150 million less expenses of $25 million as provided by Advanced Disposal's senior management. Based on the foregoing calculations, UBS calculated unlevered, free cash flows for each fiscal year during the period from the second half of 2020 through December 31, 2024 of $216 million, $160 million, $173 million, $191 million, and $203 million, respectively. Implied terminal values were derived by applying

65

Table of Contents

to the projection of Advanced Disposal's 2024 estimated Market Adjusted EBITDA a range of estimated terminal last twelve months Market Adjusted EBITDA multiples of 9.5x to 11.5x, which range was selected based upon UBS's experience and professional judgment, taking into account current and historical trading Market Adjusted EBITDA multiples of Advanced Disposal and certain of the selected companies. Implied present values of cash flows and terminal values were calculated using discount rates ranging from 7.5% to 8.5%, reflecting estimates of Advanced Disposal's weighted average cost of capital (derived by utilizing the capital asset pricing model, and taking into account macroeconomic assumptions and estimates of risk, the expected cost of debt, expected returns and other appropriate factors). UBS then divided the implied equity value by the number of fully-diluted outstanding shares of Advanced Disposal common stock (determined using the treasury stock method and taking into account outstanding in-the-money options, restricted stock units and performance stock units) based on latest public filings. The discounted cash flow analyses resulted in a range of implied equity values per share for Advanced Disposal, rounded to the nearest $0.05, of $26.05 to $35.35, as compared to the $30.30 offer price.

Trading History Analysis

UBS also reviewed the 52-week unaffected trading range of Advanced Disposal common stock and determined that over the 52 weeks ended April 12, 2019, the last trading date prior to the announcement of the original merger agreement, Advanced Disposal common stock traded within a range, rounded to the nearest $0.05, of $22.05 to $28.00 per share, as compared to the $30.30 offer price.

Miscellaneous

Under the terms of UBS's engagement, Advanced Disposal agreed to pay UBS an aggregate fee of $23.25 million for its financial advisory services in connection with the merger, of which $2.5 million was paid upon the delivery by UBS of the opinion dated April 14, 2019 (which amount is required to be deducted from any fee paid in connection with the consummation of the merger), $2.25 million was paid upon the delivery by UBS of the opinion dated June 23, 2020 and the remaining $18.5 million is payable contingent upon consummation of the merger. If the merger is terminated and Advanced Disposal receives from Waste Management a termination fee, UBS is entitled to a fee of up to 10% of such termination fee, not to exceed $5.25 million. In addition, Advanced Disposal agreed to reimburse UBS for its reasonable expenses, including fees, disbursements and other charges of counsel, and indemnify UBS and related parties against liabilities, including liabilities under federal securities laws, relating to, or arising out of, its engagement. In the past, UBS and its affiliates have provided investment banking, commercial banking and other financial services to Advanced Disposal and CPPIB unrelated to the merger, for which UBS and its affiliates have received or will receive compensation, including in the past four years having acted as (a) co-underwriter to Advanced Disposal in connection with an underwritten secondary offering of Advanced Disposal common stock in May 2018 and (b) co-lead joint book-running manager to Advanced Disposal in connection with a secondary public offering of Advanced Disposal common stock in May 2017. In the past four years, UBS received (i) less than $11.5 million in fees from Advanced Disposal and (ii) no fees from Waste Management. In the ordinary course of business, UBS, its affiliates and its and their respective employees may hold or trade, for their own accounts and the accounts of their customers loans, debt and/or equity securities of Advanced Disposal and Waste Management, and accordingly, may at any time hold a long or short position in such securities.

The Board selected UBS as its financial advisor in connection with the merger because UBS is an internationally recognized investment-banking firm with substantial experience in similar transactions. UBS is regularly engaged in the valuation of businesses and their securities in connection with mergers and acquisitions, leveraged buyouts, negotiated underwritings, competitive bids, secondary distributions of listed and unlisted securities and private placements.

66

Table of Contents

Projected Financial Information

Advanced Disposal does not, on a routine basis, publicly disclose long-term projections as to future financial performance due to, among other reasons, the unpredictability of the underlying assumptions and estimates, though Advanced Disposal has in the past provided investors with full-fiscal year financial guidance on certain financial metrics, including total revenue, adjusted EBITDA and adjusted free cash flow, which are updated when necessary during the relevant fiscal year. However, in connection with the evaluation of the proposed merger pursuant to the original merger agreement, Advanced Disposal's senior management shared certain non-public, unaudited prospective financial information prepared by it for strategic planning purposes with the Board, Waste Management and UBS, for the fiscal year ending December 31, 2019 and the four (4) following fiscal years ending December 31, 2023 (which we refer to as the "pre-announcement projections"). In addition, Advanced Disposal's senior management shared certain non-public, unaudited prospective financial information prepared by it for strategic planning purposes with the Board and UBS, for the fiscal year ending December 31, 2020 and the four (4) following fiscal years ending December 31, 2024 (which we refer to as the "updated financial forecasts"; we refer to the pre-announcement projections and the updated financial forecasts collectively as the "projections"). A sub-set of the updated financial forecasts for the fiscal year ending December 31, 2020 and the two (2) following fiscal years ending December 31, 2022 was also shared with Waste Management at Waste Management's request pursuant to Waste Management's rights under the original merger agreement and as further detailed in the section entitled "The Merger (Proposal 1)—Background of the Merger" beginning on page 40 of this proxy statement.

The projections were not prepared with a view to public disclosure and are included in this proxy statement only because such information was made available to the Board, Waste Management and UBS as described above. The projections were not prepared with a view to compliance with generally accepted accounting principles as applied in the United States (which we refer to as "GAAP"), the published guidelines of the SEC regarding projections and forward-looking statements or the guidelines established by the American Institute of Certified Public Accountants for preparation and presentation of prospective financial information. The prospective financial information included in this proxy statement has been prepared by, and is the responsibility of, Advanced Disposal's senior management, and is subjective in many respects. The projections were, in the view of Advanced Disposal's senior management, prepared on a reasonable basis, reflected the best available estimates and judgments at the time of preparation, and presented as of the time of preparation, to the best of senior management's knowledge and belief, the expected course of action and the expected future financial performance of Advanced Disposal on a standalone basis, subject to the assumptions and limitations described in this section. Furthermore, neither Advanced Disposal's independent auditors nor any other independent accountants have audited, reviewed, examined, compiled or applied agreed-upon procedures with respect to the accompanying prospective financial information and, accordingly, assume no responsibility for, and express no opinion or other form of assurance on, such information or its achievability.

The projections are forward-looking statements. Although summaries of the projections are presented with numerical specificity, the projections reflect numerous assumptions and estimates as to future events made by Advanced Disposal's senior management, which it believes were reasonable at the time the projections were prepared, taking into account the relevant information available to management at such time. However, this information is not fact and should not be relied upon as being necessarily predictive of actual future results. Important factors may affect actual results and cause the forecasts not to be achieved. These factors include general economic conditions, accuracy of certain accounting assumptions, timing of business investments by Advanced Disposal, changes in actual or projected cash flows, competitive pressures, changes in tax or other laws or regulations, and the other factors described in the section entitled "Forward-Looking Statements" beginning on page 30 of this proxy statement, the "Risk Factors" section in our 2019 Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q, and the information referenced in the section entitled "Where You Can Find Additional Information"

67

Table of Contents

beginning on page 124 of this proxy statement. Generally, the further out the period to which the projections relate, the less predictable and more unreliable the information becomes. In addition, the projections do not take into account any circumstances or events occurring after the date that the projections were prepared. Furthermore, the projections were prepared on a standalone basis without giving effect to the merger, including the impact of negotiating or executing the merger agreement, the expenses that may be incurred in connection with consummating the merger, including the expenses payable pursuant to the merger agreement, the potential synergies that may be achieved as a result of the merger, the effect of any business or strategic decision or action that has been or will be taken as a result of the merger agreement, or payment of any termination fee. As a result, there can be no assurance that the projections will be realized, and actual results may be materially better or worse than those contained in the projections. The inclusion of this information in the proxy statement should not be regarded as an indication that Advanced Disposal's senior management, the Board, UBS, Waste Management or any other recipient of this information considered, or now considers, the projections to be material information of Advanced Disposal, or necessarily predictive of actual future results, nor should it be construed as financial guidance, and it should not be relied upon as such. The summary of the projections is not included in this proxy statement in order to induce any stockholder to vote for the proposal to adopt the merger agreement or any of the other proposals to be voted on at the Special Meeting or to influence any stockholder to make any investment decision with respect to the merger, including whether or not to seek appraisal rights with respect to the shares of Advanced Disposal common stock.

The projections should be evaluated, if at all, in conjunction with the historical financial statements and other information regarding Advanced Disposal contained in Advanced Disposal's public filings with the SEC. The projections were reviewed by Advanced Disposal's senior management with, and considered by, the Board in connection with its evaluation and approval of the merger and were relied upon by UBS for purposes of its financial analyses and opinion, as described more fully in the sections entitled "The Merger (Proposal 1)—Recommendation of the Board and Reasons for Recommendation" beginning on page 54 of this proxy statement and "The Merger (Proposal 1)—Opinion of Financial Advisor" beginning on page 60 of this proxy statement.

Except to the extent required by applicable federal securities laws, we do not intend, and expressly disclaim any responsibility to update or otherwise revise the forecasts to reflect circumstances existing after the date when we prepared the projections or to reflect the occurrence of future events or changes in general economic or industry conditions, even in the event that any of the assumptions underlying the projections are shown to be in error. We can give no assurance that, had our projections been prepared either as of the date of the merger agreement or as of the date of this proxy statement, similar estimates and assumptions would be used. Neither Advanced Disposal nor any of its affiliates, directors, officers, advisors or other representatives has made or makes any representation to any of our stockholders or any other person regarding the ultimate performance of Advanced Disposal compared to the information contained in our projections or that our projections will be achieved.

In light of the foregoing factors and the uncertainties inherent in the projections and considering that the Special Meeting will be held several months after the projections were prepared, stockholders are cautioned not to rely on the projections included in this proxy statement.

Certain of the measures included in the projections may be considered non-GAAP financial measures, as noted below. These non-GAAP financial measures are useful to investors and management in understanding current profitability levels and liquidity that may serve as a basis for evaluating future performance and facilitating comparability of results. Non-GAAP financial measures should not be considered in isolation from, or as a substitute for, financial information presented in compliance with GAAP, and non-GAAP financial measures as used by Advanced Disposal may not be comparable to similarly titled amounts used by other companies. The non-GAAP financial measures used in the forecasts were relied upon by UBS for purposes of its respective financial analyses and opinion and by the Board in connection with its consideration of the merger. Financial measures provided to a financial advisor are

68

Table of Contents

excluded from the definition of non-GAAP financial measures and, therefore, are not subject to SEC rules regarding disclosures of non-GAAP financial measures, which would otherwise require a reconciliation of a non-GAAP financial measure to a GAAP financial measure.

Summary of the Projections

Pre-announcement projections

The following is a summary of the pre-announcement projections prepared by senior management of Advanced Disposal and provided to its Board, UBS and Waste Management prior to the execution of the original merger agreement:

Reconciliation of Non-GAAP Projections to GAAP

The following table reflects the calculation of Adjusted EBITDA by Advanced Disposal for purposes of the pre-announcement projections:

69

Table of Contents

The following table reflects the calculation of Cash Flow from Operations less Adjusted Capital Expenditures by Advanced Disposal for purposes of the pre-announcement projections:

Updated financial forecasts

The following is a summary of the updated financial forecasts prepared by senior management of Advanced Disposal and provided to its Board and UBS (and with respect to the fiscal year ending December 31, 2020 and the two (2) following fiscal years ending December 31, 2022, to Waste Management) prior to the execution of the merger agreement amendment as described above:

Reconciliation of Non-GAAP Projections to GAAP

The following table reflects the calculation of Adjusted EBITDA by Advanced Disposal for purposes of the updated financial forecasts:

70

Table of Contents

The following table reflects the calculation of Adjusted Free Cash Flow by Advanced Disposal for purposes of the updated financial forecasts:

Interests of Advanced Disposal Directors and Executive Officers in the Merger

In considering the recommendation by the Board that Advanced Disposal stockholders vote to adopt the amended merger agreement, stockholders should be aware that the directors and executive officers of Advanced Disposal have certain interests in the transactions that may be different from, or in addition to, the interests of Advanced Disposal stockholders generally. The members of the Board were aware of these interests in evaluating the amended merger agreement and the transactions and in recommending that Advanced Disposal stockholders adopt the amended merger agreement. These interests may present such directors and executive officers with actual or potential conflicts of interest and these interests are described in this section and the section entitled "Advisory Vote on Specified Compensation (Proposal 2)—Golden Parachute Compensation" beginning on page 110 of this proxy statement.

Michael Koen is a nonemployee director nominated by CPPIB. To Advanced Disposal's knowledge, Mr. Koen does not hold shares of Advanced Disposal common stock or Advanced Disposal equity awards and is not entitled to payments in connection with the transactions contemplated by the amended merger agreement. The interests of the other persons who are or have been since January 1, 2019, directors or executive officers of Advanced Disposal are discussed below.

For the numerical disclosure in this section of the proxy statement, we have assumed a closing date of August 31, 2020. August 31, 2020 is an illustrative date used solely for purposes of this specified disclosure and is not intended to indicate that the closing will or will not occur on such date. This description and the tables below assume that Advanced Disposal grants no new Advanced Disposal equity awards prior to the closing to Advanced Disposal's directors or executive officers.

Treatment of Advanced Disposal Equity Awards

This section sets forth the treatment of Advanced Disposal equity awards pursuant to the amended merger agreement. No Advanced Disposal equity awards have been granted to any director, executive officer or employee of Advanced Disposal between the date of the original merger agreement and the date of this proxy statement.

Treatment of Advanced Disposal Stock Options

The amended merger agreement provides that at the effective time, each Advanced Disposal stock option that is outstanding immediately prior to the effective time and that has an exercise price per share that is less than $30.30, whether or not vested, will become fully vested and will be cancelled and thereafter entitle the holder to receive, promptly after the effective time, a cash payment (without interest and subject to all applicable tax withholding requirements) equal to the product of (i) the excess of $30.30 over the per-share exercise price of such Advanced Disposal stock option and (ii) the number of shares issuable upon exercise of such Advanced Disposal stock option. Each Advanced Disposal stock option with an exercise price equal to or greater than $30.30 will be cancelled as of the effective time without payment of any consideration and will have no further force or effect.

71

Table of Contents

The following table shows, with respect to each individual who served as a director or an executive officer of Advanced Disposal at any point in time on or following January 1, 2019 and who, as of the close of business on June 24, 2020, held Advanced Disposal stock options with a per-share exercise price less than $30.30, (i) the number of shares of Advanced Disposal common stock underlying each Advanced Disposal stock option that is held as of June 24, 2020 and is scheduled to be vested as of August 31, 2020, (ii) the expected value of such Advanced Disposal stock options as of the effective time, (iii) the number of shares of Advanced Disposal common stock underlying each Advanced Disposal stock option that is held as of June 24, 2020 and is scheduled to be unvested as of August 31, 2020, (iv) the expected value of such Advanced Disposal stock options as of the effective time and (v) the total expected value of outstanding Advanced Disposal stock options as of the effective time.