UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant  ☒                             Filed by a Party other than the Registrant  ☐

Check the appropriate box:

Willbros Group, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):

Willbros Group, Inc.

4400 Post Oak Parkway
Suite 1000
Houston, Texas 77027
Tel 713-403-8000
Fax 713-403-8066

May 2, 2018

Dear Fellow Stockholder:

The Board of Directors (the “Board”) of Willbros Group, Inc. (“Willbros”) has unanimously approved a merger agreement (as it may be amended from time to time, the “merger agreement”) providing for Willbros to be acquired by Primoris Services Corporation (“Primoris”). You are cordially invited to attend a special meeting of Willbros stockholders to be held at 9:00 a.m., local time, on May 31, 2018, at the Conference Center at Post Oak, 4400 Post Oak Parkway, Suite 240, Houston, Texas 77027.

At the special meeting, you will be asked to consider and vote on:

If the merger contemplated by the merger agreement is completed, the holders of Willbros common stock (“common stock”), other than (i) shares owned by Willbros (as treasury stock or otherwise) or any of its respective direct or indirect wholly-owned subsidiaries and (ii) any shares held by a holder who does not vote in favor of the merger and who is entitled to demand and properly demands appraisal for such shares pursuant to the applicable provisions of the General Corporation Law of the State of Delaware (the shares in clauses (i) and (ii) collectively being referred to as “excluded shares”), will receive $0.60 in cash, without interest and less applicable withholding tax, for each share of Willbros common stock that they own immediately prior to the effective time of the merger.

After careful consideration, the Board unanimously approved the merger agreement, the merger and the other transactions contemplated by the merger agreement, and unanimously declared that the merger agreement, the merger and the other transactions contemplated by the merger agreement are advisable, fair to and in the best interests of the stockholders of Willbros. THE BOARD OF WILLBROS UNANIMOUSLY RECOMMENDS THAT YOU VOTE:

The accompanying proxy statement provides you with information about the proposed merger, the transactions contemplated by the merger agreement, and the special meeting of Willbros’ stockholders. Willbros encourages you to read the entire proxy statement carefully, including the annexes and documents incorporated by reference. You may also obtain more information about Willbros from documents Willbros has filed with the Securities and Exchange Commission.

Your vote is important. The adoption of the merger agreement and the transactions contemplated by the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of Willbros common stock. The failure of any stockholder to vote will have the same effect as a vote against adopting the merger agreement and the transactions contemplated by the merger agreement. Accordingly, whether or not you plan to attend the special meeting, you are requested to promptly vote your shares by completing, signing and dating the enclosed proxy card and returning it in the envelope provided, or by voting over the telephone or over the Internet as instructed in these materials. If you sign, date and mail your proxy card without indicating how you wish to vote, your vote will be counted as a vote “FOR” adoption of the merger agreement and the transactions contemplated by the merger agreement, “FOR” adjourning or postponing (subject to the terms of the merger agreement) the special meeting, if necessary or appropriate, to solicit additional proxies and “FOR” approving the compensation that will or may become payable to Willbros’ named executive officers in connection with the merger.

Voting by proxy will not prevent you from voting your shares in person if you subsequently choose to attend the special meeting.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the proposal to adopt the merger agreement and transactions contemplated by the merger agreement, without your instructions.

If you have any questions or need assistance voting your shares, please contact Willbros’ proxy solicitor:

Alliance Advisors, LLC

200 Broadacres Drive, 3^rd Floor

Bloomfield, NJ 07003

Stockholders Call Toll Free: 855-835-8313

Banks and Brokers Call Toll Free: 973-873-7700

Thank you for your support and your consideration of this matter.

Respectfully submitted,

S. Miller Williams

Chairman of the Board of Directors

The merger agreement and the transactions contemplated by the merger agreement have not been approved or disapproved by the Securities and Exchange Commission or any state securities commission. Neither the Securities and Exchange Commission nor any state securities commission has passed upon the merits or fairness of the merger agreement or the transactions contemplated by the merger agreement or upon the adequacy or accuracy of the information contained in this document or the accompanying proxy statement. Any representation to the contrary is a criminal offense.

The proxy statement is dated May 2, 2018 and is first being mailed

to stockholders of Willbros Group, Inc. on or about May 2, 2018.

		WILLBROS GROUP, INC. Five Post Oak Park 4400 Post Oak Parkway Suite 1000 Houston, Texas 77027

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

TO BE HELD May 31, 2018

To the Stockholders of Willbros Group, Inc.:

A special meeting of stockholders of Willbros Group, Inc., a Delaware corporation (“Willbros,” the “Company,” “we,” “our,” or “us”), will be held at 9:00 a.m., local time, on May 31, 2018, at the Conference Center at Post Oak, 4400 Post Oak Parkway, Suite 240, Houston, Texas 77027 for the following purposes:

1.    Adoption of the Merger Agreement and the Transactions Contemplated by the Merger Agreement. To consider and vote on a proposal to adopt the Agreement and Plan of Merger, dated as of March 27, 2018, among Willbros, Primoris Services Corporation (“Primoris”), and Waco Acquisition Vehicle, Inc. (“merger sub”) (as it may be amended from time to time, the “merger agreement”), and the transactions contemplated thereby, pursuant to which merger sub will be merged with and into Willbros, with Willbros surviving the merger as a wholly-owned subsidiary of Primoris;

2.    Adjournment or Postponement of the Special Meeting. To approve the adjournment or postponement (subject to the terms of the merger agreement) of the special meeting, if necessary or appropriate, to solicit additional proxies in the event that there are not sufficient votes at the time of the special meeting to adopt the merger agreement and the transactions contemplated by the merger agreement; and

3.    Compensation Proposal. To consider and vote on a proposal, on an advisory (non-binding) basis, to approve the compensation that may be paid or become payable to Willbros’ named executive officers in connection with the merger, and the agreements and understandings pursuant to which such compensation may be paid or become payable, as described in the section entitled “The Merger — Interests of the Company’s Directors and Executive Officers in the Merger — Compensation Proposal.”

Only stockholders of record at the close of business on May 1, 2018 are entitled to notice of and to vote at the special meeting and at any adjournment or postponement of the special meeting. All stockholders of record as of such date are cordially invited to attend the special meeting in person. To ensure your representation at the meeting in case you cannot attend, you are urged to vote your shares by completing, signing, dating and returning the enclosed proxy card as promptly as possible in the postage prepaid envelope enclosed for that purpose or submitting your proxy by telephone or through the Internet. Any stockholder attending the special meeting may vote in person even if he or she has returned or otherwise submitted a proxy card.

Stockholders of Willbros who do not vote in favor of adopting the merger agreement and the transactions contemplated by the merger agreement will have the right to seek appraisal of the fair value of their shares if the merger is completed, but only if they submit a written demand for appraisal to Willbros prior to the time the vote is taken on the merger agreement and the transactions contemplated by the merger agreement and comply with all other requirements of the General Corporation Law of the State of Delaware (“DGCL”). A copy of the applicable DGCL statutory provisions is included as Annex E to the accompanying proxy statement, and a summary of these provisions can be found under the section entitled “Appraisal Rights” in the accompanying proxy statement.

Even if you plan to attend the special meeting in person, please complete, sign, date and return the enclosed proxy or vote over the telephone or the Internet as instructed in these materials as promptly as possible to ensure that your shares will be represented at the special meeting if you are unable to attend. The failure to vote on the first proposal will have the same effect as a vote “AGAINST” the adoption of the merger agreement and the transactions contemplated by the merger agreement (but will not affect the adjournment proposal or the non-binding advisory vote on merger-related compensation). If you do attend the special meeting and wish to vote in person, you may withdraw your proxy and vote in person. If you sign, date and mail your proxy card without indicating how you wish to vote, your vote will be counted as a vote:

If you fail to return your proxy card, the effect will be that your shares will not be counted for purposes of determining whether a quorum is present at the special meeting and if a quorum is present will have the same effect as a vote “AGAINST” the adoption of the merger agreement and the transactions contemplated by the merger agreement, but will not affect the adjournment proposal or the non-binding advisory vote on merger-related compensation.

YOUR VOTE IS IMPORTANT

WHETHER OR NOT YOU PLAN TO ATTEND THE SPECIAL MEETING IN PERSON, WILLBROS ENCOURAGES YOU TO SUBMIT YOUR PROXY AS PROMPTLY AS POSSIBLE:

You may revoke your proxy or change your vote at any time before it is voted at the special meeting.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the proposal to adopt the merger agreement and the transactions contemplated by the merger agreement, without your instructions.

If you are a stockholder of record, voting in person by ballot at the special meeting will revoke any proxy that you previously submitted. If you hold your shares through a bank, broker or other nominee, you must obtain a “legal proxy” in order to vote in person at the special meeting.

If you fail to (1) return your proxy card, (2) grant your proxy electronically over the Internet or by telephone or (3) attend the special meeting in person, your shares will not be counted for purposes of determining whether a quorum is present at the special meeting and, if a quorum is present, will have the same effect as a vote “AGAINST” the proposal to adopt the merger agreement and the transactions contemplated by the merger agreement, but will have no effect on the other two proposals.

The accompanying proxy statement provides a detailed description of the merger and the merger agreement and other matters to be considered at the special meeting. We urge you to read the accompanying proxy statement and its annexes, including all documents incorporated by reference into the accompanying proxy statement, carefully and in their entirety. If you have any questions concerning the merger agreement or the transactions contemplated by the merger agreement, the special meeting or the accompanying proxy statement, would like additional copies of the accompanying proxy statement or need help voting your shares of common stock, please contact Willbros’ proxy solicitor:

Alliance Advisors, LLC

200 Broadacres Drive, 3^rd Floor

Bloomfield, NJ 07003

Stockholders Call Toll Free: 855-835-8313

Banks and Brokers Call Toll Free: 973-873-7700

TABLE OF CONTENTS

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QUESTIONS AND ANSWERS

Below are brief answers to some of the key questions that we anticipate you might have. These questions do not address all of the material topics covered by this proxy statement, nor do the answers include all of the material information provided by this proxy statement. Please refer to the complete proxy statement for additional information and before you vote.

Q:    Why am I receiving this document?

A:    On March 27, 2018, Willbros entered into a definitive agreement providing for Willbros to be acquired by way of a merger and become a wholly-owned subsidiary of Primoris. You are receiving this document in connection with the solicitation of proxies by the Board for you to vote in favor of the proposal to adopt the merger agreement, which we refer to as the merger proposal, and related proposals to be voted on at the special meeting.

Q:    What is a proxy?

A:    It is your designation of another person to vote stock you own. That other person is called a proxy. If you designate someone as your proxy in a written document, that document also is called a proxy or a proxy card. When you designate a proxy, you also may direct the proxy how to vote your shares. We refer to this as your “proxy vote.” Three executive officers, Michael J. Fournier, Jeffrey B. Kappel and Linnie A. Freeman, have been designated as the proxies for our special meeting of stockholders.

Q:    What will the Company’s stockholders receive in the merger?

A:    If the merger contemplated by the merger agreement is completed, the holders of our common stock, other than (i) shares held by Willbros (as treasury stock or otherwise) or any of its respective direct or indirect wholly owned subsidiaries and (ii) any shares held by a holder who does not vote in favor of the merger and who is entitled to demand and properly demands appraisal for such shares (the shares in clauses (i) and (ii) collectively being referred to as “excluded shares”), will receive $0.60 in cash, without interest and less applicable withholding tax (the “merger consideration”), for each share of common stock that they own immediately prior to the actual time of effectiveness of the merger (the “effective time”).

Q:    Where and when is the special meeting?

A:    The special meeting will take place at 9:00 a.m., local time, on May 31, 2018, at the Conference Center at Post Oak, 4400 Post Oak Parkway, Suite 240, Houston, Texas 77027.

Q:    Who is eligible to vote?

A:    Holders of our common stock as of the close of business on May 1, 2018, the record date for the special meeting, are eligible to vote.

Q:    What happens if I sell or otherwise transfer my shares after the record date but before the special meeting?

A:    The record date for the special meeting is earlier than the date of the special meeting and the date the merger is expected to be completed. If you sell or transfer your shares after the record date, but before the special meeting, unless special arrangements (such as provision of a proxy) are made between you and the person to whom you sell or otherwise transfer your shares and each of you notifies the Company in writing of such special arrangements, you will transfer the right to receive the per-share merger consideration, if the merger is completed, to the person to whom you sell or transfer your shares, but you will retain your right to vote these

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shares at the special meeting. Even if you sell or otherwise transfer your shares after the record date, we encourage you to complete, date, sign and return the enclosed proxy card, or by voting over the telephone or over the Internet.

Q:    How many votes do the Company’s stockholders have?

A:     Holders of our common stock have one vote for each share of our common stock owned at the close of business on May 1, 2018, the record date for the special meeting.

Q:    What vote of the Company’s stockholders is required to adopt the merger agreement and the transactions contemplated by the merger agreement?

A:    In order to complete the merger and the transactions contemplated by the merger agreement, the holders of a majority of the outstanding shares of Willbros common stock (the “Willbros stockholder approval”) must vote “FOR” the adoption of the merger agreement and the transactions contemplated by the merger agreement (the “merger agreement proposal”). Willbros is also soliciting proxies from its stockholders with respect to two additional proposals; however, completion of the merger and approval of the merger agreement proposal is not conditioned upon receipt of these approvals:

For each of the adjournment proposal and the compensation proposal to be approved, a quorum must be present and each proposal must receive the affirmative vote of a majority of the shares of our common stock represented in person or by proxy at the special meeting and entitled to vote thereon.

Q:    How does the Company’s Board recommend that I vote?

A:    Willbros’ Board, by unanimous vote, has determined that it is advisable and in the best interests of Willbros and its stockholders to enter into the merger agreement and to consummate the merger and the other transactions contemplated by the merger agreement, and unanimously recommends that stockholders vote:

You should read the section entitled “The Merger — The Recommendation of Willbros’ Board and Willbros’ Reasons for the Merger” for a discussion of the factors that the Board considered in deciding to recommend voting FOR the merger agreement proposal.

You should be aware that some of Willbros’ directors and executive officers are subject to plans or arrangements that may provide them with interests in the merger that are different from, or are in addition to, the interests of

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Willbros’ stockholders generally. These interests relate to certain change in control severance provisions under management severance plans and retention arrangements covering Willbros’ executive officers and indemnification of Willbros’ directors and officers by the surviving corporation following the merger. See the section entitled “The Merger — Interests of the Company’s Directors and Executive Officers in the Merger.”

Q:    Have any stockholders already agreed to vote “FOR” approval of the merger agreement?

A:    Yes. The KKR Stockholders and the D&O Stockholders, who collectively beneficially own approximately 17% of Willbros’ outstanding shares as of March 22, 2018, have each entered into an agreement with Primoris to vote the shares beneficially owned by such stockholder as of the record date in favor of the merger agreement proposal and the transactions contemplated thereby, subject to the terms and conditions of the voting agreement. See “Form of Voting Agreement — KKR Stockholders” and “Form of Voting Agreement — D&O Stockholders” attached as Annexes B and C, respectively.

Q:    What happens if the merger is not completed?

A:    If the merger agreement is not adopted by the Company’s stockholders or if the merger is not completed for any other reason, the Company’s stockholders will not receive the merger consideration for their shares. If the merger is not completed, we would likely be forced to seek immediate protection under U.S. bankruptcy laws and the Company’s stockholders could receive little or no value for their investment in the Company.

Q:    Why am I being asked to cast a non-binding, advisory vote regarding certain compensation that will or may become payable by the Company to its named executive officers in connection with the merger?

A:    SEC rules require the Company to seek a non-binding, advisory vote regarding certain compensation that will or may become payable by the Company to its named executive officers in connection with the merger.

Q:    What will happen if, at the special meeting, stockholders do not approve the compensation that will or may become payable by the Company to its named executive officers in connection with the merger?

A:    Approval of the compensation that will or may become payable by the Company to its named executive officers in connection with the merger is not a condition to completion of the merger. The vote with respect to the compensation that will or may become payable by the Company to its named executive officers in connection with the merger is an advisory vote and will not be binding on the Company or Primoris. If the merger is completed, the compensation that will or may become payable by the Company to its named executive officers in connection with the merger may be paid to the Company’s named executive officers even if stockholders fail to approve the payment of that compensation.

Q:    What do I need to do now?

A:    Please read this proxy statement carefully, including its annexes, to consider how the merger affects you. After you read this proxy statement, you should complete, sign and date your proxy card and mail it in the enclosed return envelope or submit your proxy over the telephone or over the Internet as soon as possible so that your shares can be voted at the special meeting of the Company’s stockholders. If you sign, date and mail your proxy card without indicating how you wish to vote, your shares will be voted in accordance with the recommendations of the Board, as applicable, with respect to each proposal.

Q:    What happens if I do not return a proxy card or otherwise vote?

A:    The failure to return your proxy card or to otherwise vote will have the same effect as voting against the merger agreement proposal, but assuming a quorum is present, will have no effect on the adjournment proposal or on the compensation proposal. A vote to abstain will also have the same effect as voting against the merger agreement proposal, and, if a quorum is present, against the adjournment proposal or the compensation proposal.

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Q:    What is a quorum?

A:     For purposes of transacting business at the special meeting, a majority of the outstanding shares of common stock represented in person or by proxy will constitute a quorum.

Q:    How do I vote?

A:    If you are a stockholder of record, you may vote in person at the special meeting, vote by proxy using the enclosed proxy card, vote by proxy over the telephone or vote by proxy on the Internet. If you vote by proxy, your shares will be voted as you specify on the proxy card, over the telephone or on the Internet. Whether or not you plan to attend the meeting, the Company urges you to vote by proxy to ensure your vote is counted. You may still attend the special meeting and vote in person if you have already voted by proxy.

If your shares of common stock are held in “street name” by your broker, bank or other nominee, you should have received a proxy card and voting instructions with these proxy materials from that organization rather than from the Company. Your broker, bank or other nominee will vote your shares only if you provide instructions to your broker, bank or other nominee on how to vote. You should instruct your broker to vote your shares following the procedures provided by your broker. Without such instructions, your shares will not be voted, which will have the same effect as voting against the merger agreement proposal. See the section entitled “The Special Meeting of the Company’s Stockholders — Voting by Proxy.”

The Company provides Internet proxy voting to allow you to vote your shares online, with procedures designed to ensure the authenticity and correctness of your proxy vote instructions. However, please be aware that you must bear any costs associated with your Internet access, such as usage charges from Internet access providers and telephone companies.

Q:    What does it mean if I receive more than one set of materials?

A:     This means you own shares of our common stock that are registered under different names. For example, you may own some shares directly as a stockholder of record and other shares through a broker or you may own shares through more than one broker. In these situations, you will receive multiple sets of proxy materials. You must complete, sign, date and return each of the proxy cards that you receive, or vote all of your shares over the telephone or over the Internet in accordance with the instructions above, in order to vote all of the shares you own. Each proxy card you receive comes with its own prepaid return envelope and control number(s); if you vote by mail, make sure you return each proxy card in the return envelope that accompanies that proxy card, and if you vote by telephone or via the Internet, use the control number(s) on each proxy card.

Q:    May I vote in person?

A:    If you are the stockholder of record of shares of our common stock, you have the right to vote in person at the special meeting with respect to those shares.

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If you are the beneficial owner of shares of our common stock, you are invited to attend the special meeting. However, if you are not the stockholder of record, you may not vote these shares in person at the special meeting, unless you obtain a legal proxy from your broker, bank or nominee giving you the right to vote the shares at the special meeting.

Even if you plan to attend the special meeting as a stockholder of record, we recommend that you also submit your proxy card or voting instructions as described in the above Q&A entitled “How do I vote?” so that your vote will be counted if you later decide not to attend the special meeting.

Q:    Am I entitled to appraisal rights?

A:    Under Section 262 of the General Corporation Law of the State of Delaware (“DGCL”), our stockholders will be entitled to dissent and to seek appraisal for their shares only if certain criteria are satisfied. See the section entitled “Appraisal Rights” and Annex E of this proxy statement.

Q:    Is the merger expected to be taxable to owners of our common stock?

A:    Yes, in general, your receipt of the cash consideration for each of your shares of Willbros common stock pursuant to the merger will be a taxable transaction for U.S. federal income tax purposes and may be a taxable transaction under state, local or non-U.S. income or other tax laws. You should read the section entitled “The Merger — Material U.S. Federal Income Tax Consequences of the Merger” for a more complete discussion of the U.S. federal income tax consequences of the merger. You should also consult your tax advisor on the tax consequences of the merger in light of your particular circumstances.

Q:    When do you expect the merger to be completed?

A:    Willbros and Primoris are working to complete the merger as quickly as possible after the special meeting. Willbros currently anticipates that the merger will be completed in the second quarter of 2018. In order to complete the merger, we must obtain the required Willbros stockholder approval, and a number of other closing conditions under the merger agreement must be satisfied or waived. See the section entitled “The Merger Agreement — Conditions to the Closing of the Merger.”

Q:    Should I send in my stock certificates now?

A:    No. At or about the date of completion of the merger, if you hold certificated shares, you will receive a letter of transmittal with instructions informing you how to send in your stock certificates to Primoris’ paying agent in order to receive the merger consideration. You should use the letter of transmittal to exchange stock certificates for the merger consideration to which you are entitled as a result of the merger. DO NOT SEND ANY STOCK CERTIFICATES WITH YOUR PROXY.

If you own shares of our common stock that 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 how to surrender your “street name” shares and receive cash for those shares following the completion of the merger.

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Q:    Who can help answer my questions?

A:    The information provided above in the question-and-answer format is for your convenience only and is merely a summary of some of the information in this proxy statement. You should carefully read the entire proxy statement, including its annexes. If you would like additional copies of this proxy statement, without charge, or if you have questions about the merger or the transactions contemplated by the merger agreement, including the procedures for voting your shares, you should contact the Company’s proxy solicitation agent:

Alliance Advisors, LLC

200 Broadacres Drive, 3^rd Floor

Bloomfield, NJ 07003

Stockholders Call Toll Free: 855-835-8313

Banks and Brokers Call Toll Free: 973-873-7700

You may also wish to consult your legal, tax and/or financial advisors with respect to any aspect of the merger, the merger agreement or other matters discussed in this proxy statement.

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CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING INFORMATION

This proxy statement contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements involve a number of risks and uncertainties. We caution readers that any forward-looking statement is not a guarantee of future performance and that actual results could differ materially from those contained in the forward-looking statement. All statements, other than historical facts, included in this proxy statement that address activities, events or developments which we expect or anticipate will or may occur in the future, including such things as management’s expectations related to our pending acquisition by Primoris, financial projections of our Company, our ability to continue as a going concern, our business and growth strategies, future capital expenditures, demand for our services, anticipated trends in our business, the outcome of legal proceedings and other such matters are forward-looking statements. These forward-looking statements are based on assumptions and analysis we made in light of information available to us and the current beliefs and expectations of our management and are subject to significant risks and uncertainties. If underlying assumptions prove inaccurate or unknown risks or uncertainties materialize, actual results may differ materially from current expectations and projections. The following factors, among others, could cause actual results to differ from those set forth in the forward-looking statements:

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All subsequent written or oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. We do not undertake any obligation to release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this document or to reflect the occurrence of unanticipated events, except as may be required under applicable U.S. securities laws. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

We refer you to our filings with the Securities and Exchange Commission (“SEC”), and specifically to Item 1A-Risk Factors, of our latest Annual Report on Form 10-K, for a discussion of certain risks that could affect our business, financial results and results of operations. See the section entitled “Where You Can Find More Information.” These risk factors could cause our actual results and conditions to differ materially from our historical performance or those projected in our forward-looking statements. The risks highlighted therein are not the only ones that we face. There may be additional risks that are not presently material or known. If any of the risks actually occur, our business, financial condition or results of operations could be negatively affected.

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THE PARTIES TO THE MERGER

Willbros is a specialty energy infrastructure contractor serving the power and oil and gas industries with offerings that primarily include construction, maintenance and facilities development services. Willbros provides its services through operating subsidiaries. The Willbros corporate structure is designed to comply with jurisdictional and registration requirements and to minimize worldwide taxes. Subsidiaries may be formed in specific work locations where such subsidiaries are necessary or useful to comply with local laws or tax objectives.

Willbros’ executive offices are located at 4400 Post Oak Parkway, Suite 1000, Houston, TX 77027, and its telephone number is 713-403-8000.

Primoris Services Corporation (referred to in this proxy statement as “Primoris”) is a Delaware corporation founded in 1960. Primoris is a holding company of various subsidiaries which form one of the larger publicly traded specialty contractors and infrastructure companies in the United States. Serving diverse end-markets, Primoris provides a wide range of construction, fabrication, maintenance, replacement, water and wastewater, and engineering services to major public utilities, petrochemical companies, energy companies, municipalities, state departments of transportation and other customers. Primoris installs, replaces, repairs and rehabilitates natural gas, refined product, water and wastewater pipeline systems; large diameter gas and liquid pipeline facilities; and heavy civil projects, earthwork and site development. It also constructs mechanical facilities and other structures, including power plants, petrochemical facilities, refineries, water and wastewater treatment facilities and parking structures. Finally, it also provides specialized process and product engineering services.

Primoris’ executive offices are located at 2100 McKinney Avenue, Suite 1500, Dallas, Texas 75201, and its telephone number is (214) 740-5600.

Waco Acquisition Vehicle, Inc. (referred to in this proxy statement as “merger sub”) is a wholly-owned subsidiary of Primoris, whose principal executive offices are located at 2100 McKinney Avenue, Suite 1500, Dallas, Texas 75201, and its telephone number is (214) 740-5600. Merger sub was formed solely for the purpose of facilitating Primoris’ acquisition of Willbros.

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THE SPECIAL MEETING OF THE COMPANY’S STOCKHOLDERS

Time, Place and Purpose of the Special Meeting

The special meeting will be held at 9:00 a.m., local time on May 31, 2018, at the Conference Center at Post Oak, 4400 Post Oak Parkway, Suite 240, Houston, Texas 77027. The purpose of the special meeting is to consider and vote on the proposal to adopt the merger agreement and the transactions contemplated by the merger agreement, and the other proposals described in this proxy statement.

The Board, by unanimous vote, has determined that it is advisable and in the best interests of Willbros and its stockholders to enter into the merger agreement and to consummate the merger and the other transactions contemplated by the merger agreement, and unanimously recommends that stockholders vote:

Who Can Vote at the Special Meeting

Only holders of record of Willbros common stock, as of the close of business on May 1, 2018, which is the record date for the special meeting, are entitled to receive notice of and to vote at the special meeting. If you own shares that are registered in the name of someone else, such as a broker, you need to direct that person to vote those shares or obtain an authorization from them and vote the shares yourself at the meeting. On the record date, there were 63,219,047 shares of common stock outstanding.

Quorum; Vote Required

For purposes of transacting business at the special meeting, a majority of the outstanding shares of common stock represented in person or by proxy will constitute a quorum. Once a share is represented at the special meeting, it will be counted for the purpose of determining a quorum and any adjournment of the special meeting, unless the holder is present solely to object to the special meeting. Votes “FOR” and “AGAINST” and abstentions will be counted for purposes of determining the presence of a quorum.

Under applicable Delaware law, the adoption of the merger agreement and the transactions contemplated by the merger agreement by the Willbros stockholders is required to effect the merger. The Willbros stockholder approval requires the affirmative vote of a majority of the outstanding shares of common stock. Because the required votes of Willbros’ stockholders are based on the number of outstanding shares of common stock with respect to the Willbros stockholder approval, and not based on the number of shares represented in person or by proxy at the special meeting, failure to submit a proxy or to vote in person will have the same effect as a vote “AGAINST” the merger agreement proposal, but, assuming a quorum is present, will have no effect on the adjournment proposal or on the compensation proposal. A vote to abstain will have the same effect as voting “AGAINST” the merger agreement proposal and “AGAINST” the adjournment proposal or the compensation proposal. A broker non-vote will have the same effect as voting “AGAINST” the merger agreement proposal, but will have no effect on the adjournment proposal or the compensation proposal.

Approval of the adjournment proposal and the compensation proposal will each require the affirmative vote of holders of a majority of the shares of our common stock represented in person or by proxy at the special meeting and entitled to vote thereon.

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If your shares of common stock are held in “street name” by your broker, bank, or other nominee, you should instruct your broker, bank or other nominee how to vote your shares using the instructions provided by your broker, bank or other nominee. Under applicable regulations, brokers, banks or other nominees who hold shares in “street name” for customers may not exercise their voting discretion with respect to non-routine matters such as the approval of the merger agreement proposal. As a result, if you do not instruct your broker, bank, or other nominee to vote your shares of common stock, your shares will not be voted, which will have the same effect as voting against the merger agreement proposal.

Voting by Proxy

This proxy statement is being sent to you on behalf of the Board for the purpose of requesting that you allow your shares of our common stock to be represented at the special meeting by the persons named in the enclosed proxy card. All shares of our common stock represented at the special meeting by properly executed proxy cards, voted over the telephone or voted over the Internet will be voted in accordance with the instructions indicated on those proxies. If you sign and return a proxy card without giving voting instructions, your shares will be voted as recommended by the Board. The Board recommends a vote:

You may revoke your proxy at any time before the vote is taken at the special meeting. To revoke your proxy, you must either advise Willbros’ Corporate Secretary in writing, deliver a proxy dated after the date of the proxy you wish to revoke or attend the special meeting and vote your shares in person. Attendance at the special meeting will not by itself constitute revocation of a proxy. If you have instructed your broker, bank, or other nominee to vote your shares, you must follow the directions provided by your broker, bank or other nominee to change those instructions.

Householding

The SEC has adopted rules that permit companies and intermediaries such as brokers to satisfy delivery requirements for proxy statements with respect to two or more stockholders sharing the same address by delivering a single proxy statement addressed to those stockholders. This process, which is commonly referred to as “householding,” potentially provides extra convenience for stockholders and cost savings for companies. Although we do not household for our registered stockholders, some brokers household Willbros proxy materials, delivering a single proxy statement to multiple stockholders sharing an address unless contrary instructions have been received from the affected stockholders. Once you have received notice from your broker that they will be householding materials to your address, householding will continue until you are notified otherwise or until you revoke your consent. If, at any time, you no longer wish to participate in householding and would prefer to receive a separate proxy statement, or if you are receiving multiple copies and wish to receive only one, please notify your broker. We will deliver promptly upon written or oral request a separate copy of our annual report to a stockholder at a shared address to which a single copy was delivered. For copies of the proxy statement, stockholders should write to Willbros Group, Inc., 4400 Post Oak Parkway, Suite 1000, Houston, Texas 77027, Attention: Investor Relations, or call (713) 403-8000.

Solicitation of Proxies

Willbros will pay all of the costs of this proxy solicitation. In addition to soliciting proxies by mail, directors, officers and employees of Willbros may solicit proxies personally and by telephone, email or otherwise. None of

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these persons will receive additional or special compensation for soliciting proxies. Willbros will, upon request, reimburse brokers, banks and other nominees for their expenses in sending proxy materials to their customers who are beneficial owners and obtaining their voting instructions.

Willbros has engaged Alliance Advisors, LLC (“Alliance”) to assist in the solicitation of proxies for the special meeting and will pay Alliance a fee of approximately $20,000, plus reimbursement of out-of-pocket expenses. The address of Alliance is 200 Broadacres Drive, 3^rd Floor, Bloomfield, NJ 07003. For any questions, stockholders can call Alliance toll-free at 855-835-8313, and Banks and Brokers can call Alliance at 973-873-7700.

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THE MERGER

The discussion of the merger in this proxy statement is qualified by reference to the merger agreement, which is attached to this proxy statement as Annex A. You should read the merger agreement carefully in its entirety.

Background of the Merger

As part of its ongoing strategic planning process, the Board regularly reviews and assesses Willbros’ strategic goals and opportunities, industry trends, competitive environment, and short- and long-term performance with the goal of maximizing stockholder value. In connection with these activities, the Board regularly met in the ordinary course of business to consider and evaluate potential strategic alternatives, including business combinations, acquisitions, dispositions, internal restructurings and other transactions. During some of these meetings, the Board also discussed Willbros’ stock price and stockholder returns, both on an absolute basis and relative to the Company’s peers, and potential risks that Willbros faced in executing its strategy, including challenging economic conditions in the power and oil and gas industries, the Company’s high level of indebtedness, burdensome debt service requirements and difficulty renewing, extending or recapitalizing its indebtedness in light of an extended period of poor operating results.

From time to time during 2014 through 2017, the Board consulted with Greenhill, as the Company’s financial advisor, to review and assess various strategic alternatives, including a potential sale of the Company or one or more Company segments or non-core business units. In order to address the challenges specified above and identified by management and the Board, and with the assistance of multiple financial advisors, Willbros engaged in a series of dispositions, large and small, including the sale of the CTS business in April 2014, the UTILX and Premier units in March 2015, Downstream Professional Services in June 2015, its Bemis subsidiary in October 2015, the remainder of the Professional Services (engineering) segment in November 2015 and, most recently, the sale of its tank services and mainline pipeline construction businesses in January 2018.

Largely as a result of these and other dispositions, Willbros achieved a reduction in its total debt from $289.0 million at December 31, 2014, to $133.3 million at December 31, 2017. Nonetheless, Willbros continued to experience difficulty servicing its debt burden and complying with the financial covenants included in its 2014 term credit agreement. Due primarily to challenging industry conditions in its Oil & Gas and Canada segments and to a lesser extent in its Utility Transmission and Distribution (“UT&D”) segment, Willbros experienced a sustained period of poor operating performance. As a result, Willbros sought and received repeated waivers under its term credit agreement with respect to certain financial covenants over a covenant suspension period that was ultimately extended from the quarterly period ended December 31, 2014 through the quarterly period ended December 31, 2017.

Beginning in May 2017, Willbros’ management team initiated discussions with Bank of America, N.A. (“BAML”), serving as administrative agent under the Company’s 2013 ABL credit facility for a renewal, extension or refinancing of the existing facility, which expires on August 7, 2018. In October 2017, BAML indicated that it would defer any decision to extend the ABL credit facility until after it reviewed the Company’s fourth quarter results.

Willbros’ operating performance deteriorated in the second half of 2017. In November 2017, the Company reported an operating loss of $27.8 million for the quarter ended September 30, 2017, nearly double the total operating loss it reported for the first two quarters of the 2017 fiscal year. The increased operating loss was driven primarily by losses on three projects in the mainline pipeline business within the Oil & Gas segment, due to difficult terrain conditions compounded by the impacts of challenging weather conditions. In addition, the Company reported an operating loss in its UT&D segment, primarily driven by an unexpected increase in the volume discount that was provided under an alliance agreement with a major customer, and by losses on two projects. Willbros also reported $22.6 million of negative operating cash flow for the quarter ended September 30, 2017. In September 2017, the Company borrowed $12.0 million under its ABL credit facility.

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Pursuant to the sixth amendment to the term credit agreement entered into on November 6, 2017 among Willbros, certain subsidiary guarantors, KKR Credit Advisors (US) LLC, as arranger, and various affiliated lenders (collectively, the “term loan lender”), Willbros secured an additional $15.0 million term loan and an extension of the covenant suspension period through December 31, 2017. In addition, on November 6, 2017, Willbros borrowed an additional $17.0 million under its ABL credit facility.

In light of its weak operating results, continuing heavy debt burden and deteriorating liquidity position, in late November 2017, the Willbros Board retained Greenhill as its financial advisor in connection with the Board’s review of strategic alternatives, including consideration of either a sale of all or a part the Company or a recapitalization transaction, if warranted. With input from Company counsel, Conner & Winters, LLP (“Conner & Winters”), and prior to engaging Greenhill, the Board evaluated any potential conflicts of interest that Greenhill might have, and discussed the terms of the Greenhill engagement letter and fee structure, as well as the role the Board desired for Greenhill. The Board determined to engage Greenhill due to its familiarity with the Company, its expertise in the industry and its experience in advising on strategic alternatives.

In a Board meeting held on November 27, 2017, Greenhill, the Company’s management and the Board reviewed and discussed the Company’s difficult operating environment, financial and operational underperformance and its existing capital structure. Greenhill and the Board discussed the sixth amendment to the term credit agreement and noted that, while it provided a short-term liquidity solution, the fee structure of the term loan created a strong incentive for the Company to refinance its term loan indebtedness prior to August 2018. Moreover, Greenhill and the Board discussed the August 2018 expiration date for the ABL credit facility and that the potential need for further covenant relief under the two credit facilities raised the risk that Willbros’ audited financial statements for 2017, scheduled to be filed with the SEC in March 2018, would be accompanied by a “going concern” qualification or explanation, which would have a further negative impact on the Company.

During that meeting, Greenhill and the Board identified two potential strategic alternatives for the Company to address the Company’s situation: a stand-alone recapitalization of its existing debt structure or a potential sale transaction. The Board reviewed the Company’s liquidity needs and determined that other strategic alternatives presented practical and timing limitations and were unlikely to be successful given the Company’s financial condition. Additionally, the Board considered a stand-alone sale of the Company’s UT&D segment, but was concerned that the remaining segments without the UT&D segment would not generate additional value for stockholders. In this context, the Board also discussed that the Company had received inbound inquiries from two privately-held infrastructure construction companies (Parties A and B) in September 2017 and October 2017 indicating their interest in pursuing a potential transaction. The Board directed Greenhill to pursue a parallel recapitalization and sale process and also to further explore a potential transaction with Party A or Party B. Recognizing the financial position of the Company, the Board determined it appropriate to authorize Greenhill to conduct a broad search of both strategic and financial buyers with respect to a potential sale transaction in an effort to achieve the best transaction for the Company and its stockholders.

Over the next several weeks following the November 27, 2017 Board meeting, at the direction of the Board, Greenhill initiated exploratory discussions with approximately 57 potential acquirers and stand-alone recapitalization investors, including 15 strategic parties and 42 financial parties. In addition, at the direction of the Board, Greenhill contacted eight potential ABL lenders. Of this group, approximately 31 parties signed non-disclosure agreements (“NDAs”), including 23 potential acquirers and all eight potential ABL lenders. A total of 19 potential acquirers performed due diligence.

From November 28, 2017 to March 27, 2018 (the date of the signing of the merger agreement with Primoris), the Board held eight meetings and another nine informal conference calls. Representatives from Greenhill attended each of the meetings. In addition, during this period, Greenhill provided the Company’s President and CEO, Mike Fournier with regular updates on the status of discussions with potential acquirers and potential ABL lenders, and Mr. Fournier forwarded these updates to the remainder of the Board. At these meetings and through these weekly updates, the Board and its advisors (i) reviewed, analyzed and discussed the outreach and

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discussions regarding potential strategic transactions, the terms of the specific proposals for potential strategic transactions, and the status of continuing negotiations with respect to each of these proposals and (ii) conducted a review of Willbros and its strategic alternatives and reviewed and discussed the financial forecasts and projections, and the Company’s financial condition and operating results, including the Company’s liquidity position. In addition, Conner & Winters reviewed and discussed with the members of the Board their applicable fiduciary duties under Delaware law.

During the first week of December 2017, Willbros management and Greenhill participated in a series of ongoing discussions and exchanges of information with Party A, which had earlier signed an NDA. Party A submitted an initial non-binding indication of interest, in which it proposed an all-stock merger between Willbros and Party A through which the stockholders of Willbros would own 20% of the combined company, which would continue to be publicly traded. In its proposal, Party A assumed that the term loan lender would agree to a 75% discount on the make-whole and prepayment fees that were payable in connection with a partial or final repayment under the term credit agreement. In addition, Party A requested a 60-day period of exclusive negotiations during which it proposed to complete its remaining confirmatory due diligence, negotiate a definitive agreement, and announce the transaction.

Also during the first week of December 2017, following execution of an NDA, Willbros management held an introductory meeting with members of Party B’s management team. Party B outlined its proposal for a potential all-stock merger transaction in which Willbros’ stockholders would own 33.8% of the combined company, which would continue to be publicly traded. Greenhill also provided its first weekly update to Mr. Fournier in which it reported on its preliminary contacts with numerous potential buyers and capital providers and potential ABL lenders.

Greenhill contacted Primoris on December 4, 2017 to explore Primoris’ interest in a potential acquisition of Willbros. Primoris signed an NDA on December 4, 2017. During the period between December 11, 2017 and December 22, 2017, Greenhill shared preliminary materials and held initial discussions with the Primoris senior management team, including its President and CEO, David King. In addition, Willbros management worked with Greenhill to prepare a profile of the Company and financial model for potential buyers and to populate a virtual data room to facilitate the due diligence process. On December 14, 2017, the Company also retained Streusand, Landon & Ozburn, LLP (“Streusand”), to provide counsel regarding refinancing and liquidity issues.

During the final week of December, Greenhill held a conference call with Houlihan Lokey, Primoris’ financial advisors (“Houlihan”), to respond to various financial questions. An additional three potential lenders and investors signed NDAs during that week in connection with evaluating a potential recapitalization. In addition, Willbros retained Alvarez & Marsal (“Alvarez”) to assist with reviewing its current forecast, liquidity situation and potential recapitalization solutions.

On December 28, 2017, Primoris submitted a proposal to acquire Willbros in a merger transaction for an enterprise value of between $120.0 million and $145.0 million in cash. Primoris’ proposal also indicated that it would also be willing to include a stock component as consideration if the Company deemed that preferable. However, Primoris indicated that it was only willing to move forward if the Company entered into a 45-day period of exclusive negotiations. The Board authorized Greenhill to engage in due diligence discussions with the Primoris management team and its financial advisor, but declined to authorize an exclusive negotiation period with Primoris at this time.

In early January 2018, at the direction of the Board, Greenhill held telephonic meetings with several potential investors and ABL lenders and scheduled in-person meetings in New York City for mid-January between Mr. Fournier, and various potential investors and financial sponsors.

On January 10, 2018, Willbros’ management team and Greenhill conducted in-depth discussions with Party A’s management team, including its President and CEO. On January 12, 2018, Mr. Fournier met in New York with

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several potential financial sponsors, including Party C, a private equity firm specializing in buyouts, corporate carveouts and turnarounds. During that week, Parties A and B and Primoris were provided access to the virtual data room, including the Company’s latest forecasts. Data room access was also provided to other parties starting on January 12, 2018.

On January 16, 2018, at the direction of the Board, Greenhill advised Primoris that it would need to increase its offer price and discussed with Primoris Willbros’ financial results. Furthermore, Greenhill advised Primoris that Willbros was not prepared to proceed on an exclusive basis with Primoris at this stage of the process. In light of that information, Primoris withdrew its proposal to acquire Willbros.

On January 19, 2018, Party C submitted an indication of interest to acquire the Company’s UT&D segment only at a purchase price ranging from $150.0 million to $175.0 million in cash. Party C confirmed it was not interested in acquiring all of Willbros and further indicated that its offer was contingent upon its ability to secure financing for the proposed transaction.

Also on January 19, 2018, the Company requested that Streusand provide additional counseling regarding restructuring and reorganization planning and directed Streusand and Alvarez to assist the Company in preparing for a possible bankruptcy filing.

On January 22, 2018, Party B submitted an indication of interest to acquire all of Willbros for an enterprise value of $120.0 million. Party B further indicated that it was also prepared to acquire only the Company’s UT&D segment, as an alternative. Party B verbally indicated that, based on a number of assumptions, it valued the Company’s UT&D segment at $145.0 million.

During an informal Board call held on January 24, 2018, Greenhill and the Board discussed the parallel process to sell or recapitalize the Company and the status of the various transaction proposals from Parties B and C. The Board expressed concern over potential delays in light of the fact that Party B’s and Party C’s offers were each contingent on negotiating a rollover of the term loan and that Party C needed to secure third party financing in order to complete a transaction. The Board also discussed the merits of a sale of all of Willbros as compared to a carveout of the Company’s UT&D segment. The Board believed that a carveout of the Company’s UT&D segment would raise significant concerns regarding the viability of the remainder of the Company as a public company and as to certain contingent liabilities that would remain with the Company. Nonetheless, the Board expressed interest in continuing to explore a potential transaction with Party C and also with Primoris, if a purchase of only the Company’s UT&D segment represented a more appealing alternative to these parties and might lead to an offer that was more attractive to Willbros and its stockholders than an offer for all of Willbros.

During this call, the Company’s management informed the Board and Greenhill that the Company’s fourth quarter operating losses were likely to exceed the losses realized in the third quarter, and that the Company’s negative operating cash flow and liquidity would show further serious deterioration. Greenhill and the Board discussed the timing of the proposals received from Parties A and B and Primoris, and noted that they had been provided without knowledge of the Company’s worse than expected fourth quarter results. Greenhill and the Board discussed exploring contingency plans with the Company’s existing lenders for securing additional short-term liquidity and to restructure its existing indebtedness.

On January 24, 2018, after Greenhill updated Party A on Willbros’ financial results, Party A submitted a revised proposal to acquire Willbros for an enterprise value of $90.0 to $110.0 million. Party A’s offer was predicated on the term loan lender’s willingness to roll over the term loan to the combined company on terms that were substantially more favorable to the borrower than under the existing term loan credit agreement. After further due diligence, on January 31, 2018, Party A revised its proposal to acquire Willbros for an enterprise value of $100.0 million.

On January 26, 2018, at the direction of the Board, Greenhill contacted Houlihan and advised Houlihan that Willbros and the Board were still analyzing various strategic alternatives. Greenhill indicated that the Company

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was exploring a possible sale of the Company’s UT&D segment. Greenhill further indicated that the Board continued to be concerned that a carve out transaction of the Company’s UT&D segment presented various strategic and practical problems, but now believed such a transaction could generate stockholder value at the right purchase price. Greenhill queried whether Primoris would be interested in such a transaction. Greenhill and Houlihan also agreed that Mr. Fournier and Mr. King should discuss the idea directly.

On January 26, 2018, Primoris verbally expressed continuing interest in a potential acquisition of all of Willbros or only the Company’s UT&D segment notwithstanding having withdrawn its previous offer, but only in the event that the Company was willing to negotiate exclusively with Primoris and compensate Primoris in the event that the Company did not enter into an agreement with Primoris. Greenhill also received verbal expressions of interest from one potential investor in a convertible note recapitalization transaction, two potential term loan lenders and two potential ABL lenders. Another possible ABL lender withdrew from the process in light of Willbros’ difficult financial prospects.

Following a conference call on February 1, 2018 to discuss the status of the process, the Board agreed that Greenhill should invite Party B, Party C and Primoris to continue with the sale process. However, in light of its significantly lower offer, Party A was not invited to continue with the sale process.

On February 2, 2018, Party B held discussions with representatives of the term loan lender. Party B emphasized its view that, in light of the need for transaction speed and certainty, there was insufficient time for Willbros to secure third party financing. Party B stressed that the combined company would need an appropriate capital structure following the transaction. Party B added that, after the transaction was completed, it intended to divest Willbros’ Oil & Gas and Canada segments and that the combined company would need adequate time in order to complete the divestitures and stabilize the remaining business.

On February 5, 2018, Mr. Fournier spoke with Mr. King. During their conversation, Mr. Fournier queried on what terms Primoris would be willing to re-engage. Mr. King indicated that, based on the diligence to date, he believed Primoris would be willing to purchase Willbros at a transaction value ranging from Primoris’ original indication of $120.0 million to $145.0 million, subject to confirmatory diligence. Mr. King reiterated, however, that Primoris’ willingness to pursue a potential transaction was conditioned on, among other items, Willbros entering into exclusive negotiations with Primoris (with a potential exception for continued negotiations with Party B and Party C) and Willbros’ agreement to pay a $5.0 million fee to Primoris in the event that Primoris proposed an acquisition proposal above $135.0 million and Willbros did not accept the offer. Mr. King then indicated that he believed that Primoris and Willbros could negotiate a definitive agreement within three weeks.

On February 6, 2018, BAML advised the Company that it would not pursue a renewal, extension or refinancing of the ABL credit facility.

Mr. Fournier reported to the Board on his conversation with Mr. King in a conference call on February 6, 2018. The Board discussed the merits of re-engaging with Primoris and authorized the Company and its advisors to negotiate the parameters of an exclusivity agreement and fee payable to Primoris in the event that Willbros chose not to accept a Primoris offer, but only with exclusivity exceptions that would allow the Company to continue to explore potential transactions with Party B and Party C and potential stand-alone recapitalization transactions.

On February 7, 2018, Party A reaffirmed its interest in pursuing a potential transaction with Willbros. However, Party A indicated that its view of the value of the transaction had not changed and that it was unwilling to raise its offer. Party A expressed interest in reengaging in negotiations if other transaction alternatives did not lead to a definitive agreement.

On February 8, 2018, representatives of Party C met with UT&D’s management team and with representatives of Oncor, UT&D’s key customer in Fort Worth, Texas. Additionally, Party C’s management team held a due diligence meeting with UT&D’s management team on February 8 and 9, 2018, in which several topics were

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discussed, including the segment forecast, UT&D’s growth opportunities, UT&D’s relationship with Oncor, and the status of certain UT&D loss projects. Party C indicated that it had retained certain advisors to assist with its evaluation of a potential transaction. Party C requested that Willbros provide Party C with a draft of a purchase agreement for the sale of the UT&D segment. Following receipt of the draft purchase agreement, Party C was to provide Willbros with an updated offer including an updated valuation and proposed transaction structure.

At the Board’s direction, during the week of February 12, 2018, Greenhill contacted a total of approximately 13 lenders and investors, including seven parties that had previously been contacted, to determine their interest in a potential refinancing transaction. Greenhill emphasized the need for interested parties to address Willbros’ short-term liquidity needs and requested that the potential parties consider a range of options, including a stand-alone recapitalization, a partial sale of the Company as well as “debtor in possession” financing in the event of a filing under Chapter 11 of the U.S. Bankruptcy Code.

On February 12, 2018, Primoris submitted a “Proposal Outline” for the acquisition of all of Willbros at a transaction value ranging from $120.0 million to $135.0 million in cash. Primoris indicated that it was prepared to offer cash or Primoris stock. Primoris’ proposal continued to be conditioned on the Company negotiating with only one other party for a sale of the Company. Primoris also proposed a revised break fee ranging from $1.0 million to $5.0 million, depending on the ultimate transaction value of Primoris’ offer. Later that week, the Company provided a draft merger agreement to Primoris.

During a Board conference call with the Company’s management team and its legal and financial advisors on February 13, 2018, the Board further discussed with its advisors the request by Primoris for modified exclusivity in light of the Company’s operating performance, liquidity and strategic alternatives, and the risks and benefits of granting exclusivity, and considered potential limited time periods for an exclusivity period should the Board ultimately agree to one. The Board and its legal and financial advisors also discussed a financial analysis of Primoris’ then-current offer and the then-current offers of Parties B and C. Following that discussion, the Board determined that, if Primoris was willing to allow Willbros to continue with discussions with Party B and Party C (for an acquisition of the whole Company and UT&D only, respectively) while also continuing to explore a potential recapitalization of the Company, Willbros should enter into an appropriate exclusivity agreement with Primoris for a limited period of time, not to exceed one month. The Board subsequently approved the entry into an exclusivity agreement with Primoris on this basis.

On February 15, 2018, Party B met with Willbros’ corporate and UT&D’s management teams in Houston, Texas to discuss UT&D’s business plan and various financial due diligence items. Party B requested a meeting with the administrative agent for the ABL credit facility to explore potential solutions to Willbros’ short-term liquidity needs. Additional on-site due diligence meetings with the Willbros management team in Houston were scheduled for February 20 and 21, 2018. During that week, Willbros provided Party B with the Company’s draft of a merger agreement.

On February 22, 2018, Party C submitted a revised indication of interest for the purchase of the Company’s UT&D segment at a transaction value of $150.0 million. Party C also offered to assume all operating liabilities of the UT&D business, but indicated that it would require Willbros to cash collateralize the approximately $26.0 million of outstanding letters of credit associated with the UT&D segment. Party C’s proposal also required (i) the term loan lender to provide a commitment for either a new long-term credit agreement or an 18-month bridge loan on terms that were acceptable both to the term loan lender and Party C, (ii) a five year extension of the Company’s alliance agreement with Oncor that would otherwise expire on December 31, 2018 and (iii) that Willbros reimburse Party C for its transaction expenses in an amount not to exceed $750,000 in the event that Party C was unsuccessful in acquiring UT&D.

On February 22, 2018, representatives of Willbros held meetings with representatives of Primoris at Willbros’ UT&D offices in Fort Worth, Texas, to allow Primoris to meet Willbros’ UT&D, Oil & Gas and Canadian management teams and continue Primoris’ due diligence efforts.

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On February 23, 2018, at the direction of the Board, Greenhill provided the term loan lender with a preliminary stand-alone recapitalization proposal that was prepared by Greenhill with input from the Willbros management team. The proposal was designed to create a stable and sustainable capital structure for Willbros. The plan called for the exchange of $85.0 million of existing term loan indebtedness into Willbros common stock so that the term loan lender would become the majority stockholder in Willbros. The proposal further provided for the rollover of the remaining $25.0 million under the existing term loan and a new term loan in the amount of $60.0 million. A portion of the new capital provided by the term loan lender would be used to pay down the ABL loan.

On February 28, 2018, Willbros and Primoris entered into an exclusivity agreement pursuant to which Willbros agreed to negotiate exclusively with Primoris for a period ending March 31, 2018. The terms of the exclusivity agreement authorized Willbros to continue pursuing any of the following: (1) a potential transaction with Parties B and C, (2) a refinancing of any of the Company’s indebtedness and (3) a potential sale of the Company’s Canada segment or its Lineal business. In addition, the exclusivity agreement provided that in the event that Primoris delivered to Willbros a written proposal to acquire all of Willbros for a transaction value of at least $120.0 million and within 12 months thereafter Willbros entered into a “definitive alternate transaction” with a party other than Primoris, Willbros would be required to pay Primoris a fee ranging from $5.0 million to $1.0 million, depending on the transaction value proposed by Primoris.

Following the execution of the exclusivity agreement, Primoris and its legal and financial advisors continued the due diligence process through a series of meetings and calls. Primoris held management, financial and human resources due diligence meetings at Willbros’ headquarters office in Houston, Texas on February 28, 2018.

On March 1, 2018, Party B submitted a significantly modified proposal. Party B indicated that it was no longer interested in a purchase of all of Willbros. Instead, Party B indicated that it was only interested in the acquisition of UT&D and solely through a “stalking horse” auction process under Section 363 of the U.S. Bankruptcy Code for a price of $60.0 million. Party B also indicated that its proposal would require the term loan lender to roll over $30.0 million of existing term loan indebtedness in the reorganized company while Party B would contribute the remaining $30.0 million to complete the acquisition. In light of this substantially reduced proposal, Willbros focused on its other acquisition proposals and continued discussions with its existing and potential lenders.

During the final week of February and the first full week of March, Primoris continued to perform due diligence, including several in-person meetings with representatives of the Willbros management team and a meeting with Oncor on March 1, 2018.

On March 6, 2018, the term loan lender informed Greenhill that it was not interested in proceeding with the recapitalization plan involving an investment of $60.0 million of new capital but engaged with the Company and its advisors in discussions regarding a potential restructuring involving a smaller, new investment that could be implemented through the bankruptcy reorganization process.

Party C continued its due diligence investigation during the first half of March 2018. Party C and its advisors met with the Houston operational team on March 8, 2018 and the UT&D operational team in Fort Worth, Texas on March 12, 2018 and March 13, 2018. Party C’s accounting advisors met in Houston with Willbros’ outside auditor on March 14, 2018 and with the Willbros management team on March 15, 2018.

During the first half of March 2018, at the direction of the Board, Greenhill continued to reach out to prospective lenders. In particular, Greenhill sent detailed debtor-in-possession financing (“DIP”) forecasts that were prepared with input and review from Company management and Alvarez to four lenders to prepare such lenders to share a DIP proposal. Willbros did not receive any term sheets or formal proposals for DIP financing.

On March 13, 2018, Primoris submitted an updated proposal to acquire Willbros for $120.0 million in cash. Primoris’ proposal was conditioned on the ABL and term loan lender’s willingness to enter into forbearance

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agreements, in which the lender would agree not to pursue any of their remedies against Willbros or the other loan parties in exchange for a final payoff for an unspecified principal amount upon closing of the acquisition. Primoris’ proposal was further conditioned on the term loan lender’s willingness to agree to a limited amount of cash at closing with the balance of what it would be owed payable subsequent to closing following a net working capital “true up” arrangement in which the final payoff to the term loan lender would be reduced by the amount of any net working capital deficit at closing.

On March 13, 2018, Conner & Winters furnished a draft merger agreement to Weil, Gotshal & Manges LLP (“Weil”), M&A counsel to Primoris, together with earlier drafts that were previously exchanged, discussed and negotiated among Conner & Winters and Primoris’ corporate counsel.

On March 16, 2018, Greenhill and Willbros shared with Primoris a financial model that reflected the estimated payments to Willbros stockholders and lenders based on Primoris’ March 13, 2018 proposed offer. Later that day, representatives of Primoris, Houlihan and Weil discussed the model with representatives of Willbros and Greenhill. Additionally, throughout the day, Mr. King and Mr. Fournier separately discussed issues related to the term loan lender and Primoris’s updated proposal. During these calls, Mr. Fournier proposed that Primoris consider providing Willbros with approximately $10.0 million of bridge financing in order for Willbros to meet its liquidity needs prior to consummation of a transaction between Primoris and Willbros. Mr. King advised Mr. Fournier that Primoris was unwilling to provide bridge financing and suggested that Willbros seek bridge financing from other sources, including its current lenders. Mr. Fournier further advised Mr. King that the Company intended to file a Form 12b-25 on March 19, 2018.

Later that day, Conner & Winters and Weil discussed certain aspects of the draft merger agreement, as well as various structuring alternatives to effect a potential transaction between Primoris and the Company.

On March 17, 2018, after the term loan lender rejected Primoris’ proposal for a working capital true up, Primoris submitted a revised proposal to acquire Willbros for all cash at a 20% premium to the closing market share price on March 20, 2018, subject to a cap of $0.75 per share. The revised proposal contemplated a one-step structure in which the merger and merger agreement would be subject to the approval of Willbros’ stockholders at a special meeting of the stockholders called for such purpose. Although the revised proposal eliminated a working capital true up arrangement with the term loan lender, it was conditioned on the term loan lender agreeing: (i) to forbear from pursuing any of their rights and remedies under the term loan agreement against Willbros and the other loan parties prior to closing, (ii) to accept $100.0 million at closing in full satisfaction of any amounts owing to the term loan lender, including principal, interest and any make-whole or other repayment fees to which they would otherwise be entitled and (iii) not to require any payments under the existing term loan agreement prior to closing. The revised proposal was further conditioned on the ABL lenders agreeing to forbear from pursuing any of their rights and remedies under the ABL loan agreement against Willbros and the other loan parties prior to closing. The revised proposal was also conditioned on certain to-be-identified Willbros stockholders entering into voting and support agreements prior to the signing of a merger agreement. The revised proposal also indicated that Primoris would consider providing bridge financing on a secured basis, but was subject to approval and discussion with Primoris’ board.

On the evening of March 17, 2018, the Company reviewed Primoris’ latest proposal with the term loan lender, including payment to the term loan lender at closing of $100.0 million in full satisfaction of any amounts owing to the term loan lender and the possibility that Primoris would be willing to provide Willbros with some level of bridge financing through the closing of the merger.

On March 18, 2018, following discussion with Greenhill, Primoris verbally submitted a revised proposal substantially similar to the March 17, 2018 proposal but including a floor share price of $0.60 per share.

On March 19, 2018, Weil and Conner & Winters discussed by telephone conference the terms of the definitive merger agreement.

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On the afternoon of March 19, 2018, Willbros filed a Form 12b-25 Notification of Late Filing with the SEC. The Form 12b-25 disclosed that Willbros was unable to timely file, without unreasonable effort and expense, its Annual Report on Form 10-K for the year ended December 31, 2017. The Form 12b-25 also indicated that Willbros expected to report an operating loss in the range of $85.0 to $95.0 million for the year ended December 31, 2017, that it did not expect to be in compliance with its financial covenants for the period ending March 31, 2018 and that it was working towards completing a strategic alternative. The Form 12b-25 filing further disclosed that there was no assurance that a strategic transaction would be completed and that this uncertainty, coupled with Willbros’ expected future non-compliance with its financial covenants and need for additional liquidity raised substantial doubt about the Company’s ability to continue as a going concern. On the day prior to filing the Form 12b-25, Willbros’ stock price closed at $0.84 per share. On the following day, March 20, 2018, Willbros stock price closed at $0.19 per share and on March 21, 2018, the closing price for Willbros common stock was $0.24 per share.

Beginning on March 20, 2018 through the signing of the merger agreement on March 27, 2018, Weil and Conner & Winters negotiated and exchanged multiple drafts of a merger agreement, disclosure schedule and form of voting and support agreement to be entered into by certain to-be-identified stockholders of the Company.

On March 22, 2018, Primoris verbally submitted a final proposal to acquire Willbros for $0.60 per share in cash, subject to the same conditions outlined in its letter of March 17, 2018.

Beginning on March 22, 2018 and through March 27, 2018, Cravath, Swaine & Moore LLP (“Cravath”), legal advisors to Willbros with respect to its credit agreements, exchanged multiple drafts of a term loan forbearance agreement, ABL forbearance agreement and seventh amendment to the term credit agreement with Paul, Weiss Rifkind, Wharton & Garrison LLP (“Paul Weiss”), counsel to the term loan lender and Vinson & Elkins, counsel to the ABL lenders, allowing Primoris to provide up to $20.0 million of bridge financing to Willbros prior to closing of the merger agreement.

On March 22, 2018, Weil provided a bridge loan term sheet to Willbros and Greenhill, which Greenhill subsequently forwarded to the term loan lender. Later the same day, Paul Weiss provided comments to the bridge loan term sheet.

On March 22, 2018, Cravath circulated a draft of the seventh amendment to the term credit agreement to Paul Weiss, Weil and Willbros and advised Conner & Winters that Paul Weiss was preparing a term loan forbearance agreement.

From March 22, 2018 through March 26, 2018, Vinson & Elkins and Paul Weiss exchanged drafts of the ABL forbearance agreement and term loan forbearance agreement with Cravath and Weil.

On March 24, 2018, Weil advised Conner & Winters of the identity of the Company stockholders from which it expected to enter into voting agreements. Later that day, Conner & Winters delivered the draft form voting agreement to Paul Weiss, counsel to the term loan lender and to certain directors and officers of the Company. From March 25, 2018 until March 27, 2018, Weil and Paul Weiss negotiated the terms of the voting agreement to be entered into by the term loan lender.

From March 24, 2018 to March 27, 2018, successive drafts of the seventh amendment to the term credit agreement were exchanged among the parties.

On March 26, 2018, counsel to Party C, provided Conner & Winters with a mark-up of a Membership Interest Purchase Agreement (the “MIPA”), for the purchase of the Company’s UT&D segment. The MIPA provided for the purchase of the Company’s UT&D segment for an aggregate purchase price of $150.0 million minus Willbros’ transaction expenses and any indebtedness of UT&D and was subject to a post-closing net working capital adjustment.

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Also on March 26, 2018, the Board convened a meeting with its legal and financial advisors to discuss the final terms of the transaction with Primoris and the status of discussions with Party C. At the meeting, Alvarez provided an update on the Company’s liquidity and financial position. Alvarez advised that Willbros’ current liquidity position was very constricted notwithstanding various actions which the Company had taken to extend its liquidity for a sufficient time to conduct a strategic sale process. Alvarez further reported that, in the absence of an infusion of bridge financing, the Company’s liquidity was expected to be negative beginning with the following week. Alvarez then presented the Company’s financial position showing the positive impact of up to $20.0 million of bridge financing, the deferral of approximately $3.5 million of term loan interest payments and the reduction of cash dominion under the ABL credit agreement from $15.0 million of availability to $10.0 million of availability, as contemplated by the terms of the proposed transaction with Primoris.

Also at the meeting, the Board and the Company’s financial and legal advisors discussed Party C’s offer to purchase the Company’s UT&D segment and concluded that, in light of various factors affecting the Company, the sale of UT&D only was not an attractive alternative. The Board concluded that, in its business judgment, Party C’s offer to purchase UT&D did not fully address the issues the Company was facing, including that the proposal did not include any bridge financing to address Willbros’ short-term liquidity issues, which Alvarez had noted was critical for the Company to avoid a bankruptcy filing. The Board further concluded that in the event of a bankruptcy filing, the Company’s stockholders would likely receive nothing in light of the fact that substantially all of the Company’s assets were pledged to secure its ABL and term loan indebtedness. In addition, the Board and its financial and legal advisors noted that the MIPA was yet to be negotiated and raised multiple complexities and potential costs of unknown size, including the cost and duration of disposing of or unwinding the remaining public company and providing transition services to Party C, the risks of stranded liabilities, including general liabilities and workers compensation claims that would not be transferred with UT&D, various lease expenses associated with Willbros’ headquarters operations and potential multi-employer pension plan liabilities. Accordingly, the Board concluded that pursuing Party C’s offer was not in the best interest of the Company and its stockholders in light of the Primoris transaction currently before the Board.

Also at the meeting, representatives of Conner & Winters provided a presentation regarding the Board’s fiduciary duties under Delaware law in connection with the proposed transaction and a summary of the key terms of the merger agreement and related documentation with respect to the Primoris transaction based on materials circulated to the Board in advance of the meeting.

Also at the meeting, Greenhill presented certain financial analyses to the Board based on materials circulated to the Board in advance of the meeting. Greenhill rendered to the Board its oral opinion, which was subsequently confirmed by delivery of a written opinion dated as of the same date, that, as of March 26, 2018, and based upon and subject to the factors, procedures, assumptions, qualifications, limitations and other matters set forth in its written opinion, the merger consideration to be received by the holders of Willbros common stock entitled to receive such merger consideration was fair, from a financial point of view, to such holders of Willbros common stock. The financial analysis and written opinion of Greenhill & Co., LLC are described below under “—Opinion of Willbros’ Financial Advisor” beginning on page 43.

The Board then unanimously (i) determined that the merger agreement and the transactions contemplated thereby and the merger are advisable and fair to and in the best interests of the Company and its stockholders; (ii) authorized and approved the execution, delivery and performance by the Company of the merger agreement and the consummation of the transactions contemplated thereby and the merger; (iii) resolved to recommend that the Company’s stockholders vote in favor of the adoption of the merger agreement; and (iv) directed that the adoption of the merger agreement and the approval of the merger be submitted to the Company’s stockholders. In connection therewith, the Board also approved an amendment to the Company’s Bylaws providing for the Delaware Court of Chancery as the exclusive forum for certain legal proceedings.

Also on March 26, 2018, the board of directors of Primoris (the “Primoris Board”) convened a meeting with its legal and financial advisors. The Primoris Board resolved to establish a transaction committee that would be

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responsible for finalizing negotiations with respect to the merger agreement and approving Primoris’ entry into the merger agreement once all approvals by the ABL lenders were received. In the evening on March 27, 2017, the final consents of the ABL lenders were received by the Company, and the transaction committee of the Primoris Board approved the merger agreement.

Following the meeting of the transaction committee during the evening of March 27, 2017, the parties executed the merger agreement and related agreements.

The parties issued press releases announcing the transaction the morning of March 28, 2018, prior to market opening.

Willbros Without the Merger

Our stockholders will not receive any payment for their shares of our common stock if the merger agreement is not adopted by our stockholders or if the merger is not consummated for any other reason. Instead, Willbros will remain a public company, its common stock will continue to be registered under the Exchange Act and continue to be traded on the over-the-counter market. If the merger is not completed, we would likely be forced to seek immediate protection under U.S. bankruptcy laws. If the merger is not completed, the forbearance agreements with the respective lenders under our term loan facility and ABL credit facility will each terminate. We do not expect to be in compliance with our maximum total leverage ratio and minimum interest coverage ratio under our term loan facility beginning with the quarterly period ended March 31, 2018, and would be required to successfully negotiate covenant relief under the term loan facility and the extension, modification or refinancing of the ABL credit facility which expires on August 7, 2018. There is no assurance that we will be able to obtain covenant relief under the term loan facility or extend, modify, or negotiate acceptable refinancing terms prior to the expiration of the ABL credit facility.

Without covenant relief under the term loan facility and an extension, modification or refinancing of the ABL credit facility, all of our debt obligations would become due under the default provisions of such facilities. If our debt obligations are accelerated, we would not have sufficient liquidity to retire our existing debt obligations, which raises substantial doubt about our ability to continue as a going concern. Failure to comply with loan covenants, failure to make payments when due and failure to deliver audited financial statements without a going concern or like qualification or explanation are considered events of default under both the term loan facility and ABL credit facility. Accordingly, if the merger is not completed, stockholders of the Company could receive little or no value for their investment in the Company.

If the merger agreement is terminated under specified circumstances, we may be required to pay Primoris a termination fee, as described under the section entitled “The Merger Agreement — Termination of the Merger Agreement — Termination Fees; Expense Reimbursement.”

The Recommendation of Willbros’ Board and Willbros’ Reasons for the Merger

The Board, by unanimous vote, has determined that it is advisable and in the best interests of Willbros and its stockholders to consummate the merger and the other transactions contemplated by the merger agreement, and unanimously recommends that the Company’s stockholders vote “FOR” the proposal to adopt the merger agreement and the transactions contemplated by the merger agreement. When you consider the Board’s recommendation, you should be aware that Willbros’ directors may have interests in the merger that may be different from, or in addition to, your interests. These interests are described in “The Merger — Interests of the Company’s Directors and Executive Officers in the Merger” on page 37.

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In determining that the merger and the other transactions contemplated by the merger agreement are advisable and in the best interests of Willbros and its stockholders, the Board consulted with management and its financial and legal advisors and considered a number of factors, including the following:

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The Board also identified and considered a number of countervailing factors and risks to Willbros and its stockholders relating to the merger and the merger agreement, including the following:

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The foregoing discussion of the information and factors considered by the Board is not intended to be exhaustive but includes the material factors considered by the Board. In view of the complexity and wide variety of factors considered, the Board did not find it useful to and did not attempt to quantify, rank or otherwise assign weights to these factors. In addition, the Board did not undertake to make any specific determination as to whether any particular factor, or any aspect of any particular factor, was favorable or unfavorable to its ultimate determination, but rather the Board conducted an overall analysis of the factors described above, including discussions with Willbros’ management and its financial and legal advisors. In considering the factors described above, individual members of the Board may have given different weights to different factors.

Interests of the Company’s Directors and Executive Officers in the Merger

Stockholders should be aware that Willbros’ executive officers and directors are subject to plans or arrangements that may provide them with interests that differ from, or are in addition to, those of stockholders generally. In particular, as further described below, Willbros’ executive officers are entitled to certain benefits if they are involuntarily terminated not for cause or resign for good reason within 12 months following the consummation of the merger.

The Board was aware of these plans and arrangements during its deliberations of the merits of the merger agreement and in determining the recommendation set forth herein.

Executive Officers and Directors

Willbros’ executive officers and directors as of the date hereof are:

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For purposes of determining Golden Parachute Compensation, our “named executive officers” are:

Consideration Payable for Shares Held Pursuant to the Merger Agreement

The executive officers and directors of Willbros who hold shares at the closing of the merger will be eligible to receive the same merger consideration as the other Willbros stockholders with respect to each outstanding share held. As of April 16, 2018, the executive officers and directors of Willbros held, in the aggregate, 732,113 shares of Willbros common stock (or approximately 1.2% of all outstanding shares), excluding outstanding unvested time-based restricted stock awards of Willbros.

The table below sets forth the number of shares held by the executive officers and directors of Willbros, excluding outstanding unvested time-based restricted stock awards of Willbros, as of April 16, 2018, and the value (at $0.60 per share) they would receive for those shares upon consummation of the merger.

The above table does not reflect acquisitions and dispositions of shares by executive officers or directors subsequent to April 16, 2018.

Consideration Payable for Equity Awards Pursuant to the Merger Agreement

As described below under the section entitled “The Merger Agreement — Merger Consideration; Conversion of Shares,” the merger agreement provides that:

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The table below sets forth the estimated amounts that each executive officer and director would be eligible to receive (without subtraction of applicable withholding taxes) with regard to any unvested time-based restricted stock and restricted stock unit awards (assuming Primoris elects a cash settlement of such restricted stock and restricted stock units in lieu of substituting Primoris restricted stock awards) and unvested performance-based restricted stock unit awards held by the executive officer and director as of April 16, 2018.

Retention Awards

Messrs. Priest and Kinch have each been granted a retention award. Under the retention award, each of them is entitled to receive a cash retention bonus in a single lump sum if he remains continuously employed through the earliest to occur of (i) September 14, 2018, or such later date as the Company’s President may determine, (ii) the completion of a “sale transaction” or (iii) the date of his death, disability or termination of his employment in an employer-initiated termination for reasons other than cause. Mr. Priest is entitled to receive a retention bonus in an amount equal to his annual base salary of $430,000 and Mr. Kinch is entitled to receive a retention bonus in an amount equal to 75% of his annual base salary, or $218,244.

Any retention bonus which is paid to Mr. Priest or Mr. Kinch under the retention award will be applied to reduce any payments to which he may otherwise become entitled as a participant in the Willbros management severance plans. In addition, any amounts which are paid to Mr. Priest or Mr. Kinch under the retention award will not be considered an annual cash bonus or, also in the case of Mr. Priest, a payment under an “incentive plan” as that term is defined under the management severance plans and, therefore, will not result in the payment of any

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additional severance compensation to Mr. Priest or Mr. Kinch in the event he becomes entitled to severance benefits in the future.

Change in Control Severance Benefits for Executive Officers

Pursuant to certain provisions in Willbros’ management severance plans, the executive officers of Willbros will receive severance benefits upon qualified terminations of employment within 12 months following a change in control of Willbros, such as the consummation of the proposed merger. Accordingly, if a Willbros executive officer is terminated not for “cause,” or resigns for “good reason,” within 12 months following the merger, the executive officer will be entitled to the following benefits:

If such executive officer’s employment is terminated for any other reason, he or she will be entitled to receive severance or other benefits only to the extent he or she would be entitled to receive under Willbros’ then-existing severance or benefit plans or pursuant to any other written agreement. Willbros’ U.S. management severance plans provide that if any amount or benefit to be paid otherwise under the plan would constitute an “excess parachute payment” under the Internal Revenue Code, then the payment to be paid or provided will be “cut back”

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to the minimum extent necessary so that no portion of the amounts received by a participant will be subject to the excise tax imposed under Section 4999 of the Internal Revenue Code.

As defined in Willbros’ management severance plans, “cause” generally means:

With respect to the above definition of cause, no act or conduct by an executive will constitute cause if the executive acted: (i) in accordance with the instructions or advice of counsel representing Willbros or, if there was a conflict such that the executive could not consult with counsel representing Willbros, other qualified counsel, or (ii) as required by legal process.

As defined in Willbros’ management severance plans, “good reason” generally means:

Willbros’ management severance plans contain one-year non-compete and non-solicitation restrictive provisions, a non-disparagement covenant and a covenant not to disclose Willbros’ confidential and proprietary information following the termination of an executive officer’s employment. In conjunction with Mr. Fournier’s appointment as Chief Executive Officer, Willbros waived his compliance with the non-compete provision in the event that he voluntarily leaves Willbros on or after December 31, 2018. In addition, Willbros shall not have any obligation to make any payment under any management severance plan unless and until the executive officer delivers to Willbros a required waiver and release.

Compensation Proposal

The following table sets forth the golden parachute compensation potentially payable to or realizable by the named executive officers in connection with the merger based on compensation and benefits in effect as of April 16, 2018, assuming the completion of the merger occurred on April 16, 2018, and each named executive officer experiences a simultaneous qualifying termination of employment.

Golden Parachute Compensation

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Willbros Board of Directors Following the Merger

Following the merger, and pursuant to the terms of the merger agreement, the members of the Board will be replaced by the board of directors of merger sub.

Indemnification and Insurance

The merger agreement provides that from and after the effective time of the merger, Primoris will cause Willbros, as the surviving corporation, to indemnify and hold harmless each present and former officer and director of Willbros against any costs or expenses (including reasonable attorneys’ fees), judgments, fines, losses, claims, damages or liabilities, whether civil, criminal administrative or investigative, arising out of matters existing or occurring at or prior to the effective time of the merger, to the fullest extent Willbros would have been permitted to do so under Delaware law and its certificate of incorporation or bylaws or pursuant to other agreements in effect as of the date of the merger agreement to indemnify such individuals (and Primoris shall

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also advance expenses as incurred to the fullest extent permitted under applicable law, provided the individual to whom expenses are advanced provides an undertaking to repay such advances if it is ultimately determined that such individual is not entitled to indemnification).

The merger agreement further provides that Willbros, as the surviving corporation, shall maintain its existing officers’ and directors’ liability insurance for a period of six years after the effective time of the merger so long as the annual premium therefor (on an annualized basis) is not in excess of 3.0 times the last annual premium paid prior to the date of the merger agreement (the “current premium”); provided, however, that if the existing officers’ and directors’ liability insurance expires, is terminated or cancelled during such six-year period, Willbros, as the surviving corporation, will use reasonable efforts to obtain as much officers’ and directors’ liability insurance as can be obtained for the remainder of such period for a premium not in excess (on an annualized basis) of 2.0 times the current premium. In lieu of maintaining such officers’ and directors’ liability insurance, prior to the effective time, Willbros (and its subsidiaries) may, at its option and expense (following reasonable consultation with Primoris), purchase prepaid “tail” insurance for Willbros (and its subsidiaries) and their current and former officers, directors and employees who are covered by policies of officers’ and directors’ liability insurance and fiduciary liability insurance currently maintained by or for the benefit of Willbros (and its subsidiaries) as of the date of the merger agreement for a period of six years after the effective time of the merger, which tail insurance to provide coverage in an amount substantially equivalent to the existing coverage.

Opinion of Willbros’ Financial Advisor

The Company retained Greenhill to, among other things, act as its financial advisor in connection with the merger. At the March 26, 2018, meeting of the Board held to evaluate the merger, Greenhill rendered an oral opinion, confirmed by delivery of a written opinion dated March 26, 2018, to the effect that, as of such date and subject to and based on the various assumptions made, procedures followed, matters considered and qualifications and limitations of the review set forth therein, the merger consideration was fair, from a financial point of view, to the Company’s stockholders.

The full text of Greenhill’s written opinion, dated March 26, 2018, which discusses, among other things, the assumptions made, procedures followed, matters considered, and qualifications and limitations of the review undertaken by Greenhill in rendering its opinion, is attached as Annex D to this proxy statement and is incorporated herein by reference. The summary of Greenhill’s opinion in this proxy statement is qualified in its entirety by reference to the full text of the opinion. You are urged to read Greenhill’s opinion carefully and in its entirety. Greenhill’s opinion is solely for the information of the Board, in its capacity as such, and addresses only the fairness of the merger consideration, from a financial point of view, to the Company’s stockholders, as of the date of the opinion. Greenhill was not requested to opine as to, and its opinion does not in any manner address, the underlying business decision to proceed with or effect the merger or any related transactions, or the relative merits of the merger as compared to other potential strategies or transactions that may be available to the Company. Greenhill’s opinion is not intended to and does not address the amount or nature of any compensation or bonuses to any officers, directors or employees of any party to the merger or related transactions, or any class of such persons, relative to the merger consideration or otherwise or with respect to the fairness of any such compensation or consideration. Furthermore, Greenhill expressed no view or opinion regarding matters that require legal, regulatory, accounting, insurance, tax, environmental, executive compensation or other similar professional advice and Greenhill assumes that opinions, counsel and interpretations regarding such matters have been or would be obtained from appropriate professional sources. Greenhill’s opinion was approved by its Fairness Committee. Greenhill’s opinion is not intended to be and does not constitute a recommendation to the members of the Board as to whether they should approve the merger or the merger agreement or take any other action in connection therewith, nor does it constitute a recommendation as to how any stockholder of the Company should vote on any matter or otherwise act with respect to the merger.

In arriving at its opinion, Greenhill, among other things, has:

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For purposes of its opinion, Greenhill assumed and relied upon, without independent verification or expressing any views with respect to, the following facts relating to the Company’s liquidity and strategic options as of the close of business on March 26, 2018, based on Greenhill’s discussions with the Company’s management and other advisors, including Alvarez, Conner & Winters, and Streusand, Landon & Ozburn, LLP (the “Liquidity and Strategic Option Assumptions”):

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In arriving at its opinion, Greenhill assumed and relied upon, without independent verification, the accuracy and completeness of the information and data publicly available, supplied or otherwise made available to, or reviewed by or discussed with Greenhill. Greenhill further relied upon the assurances of the representatives and management of the Company that they were not aware of any facts or circumstances that would make any such information inaccurate, incomplete or misleading. With respect to the Forecasts, Greenhill assumed that such Forecasts, including the underlying assumptions, were reasonably prepared on a basis reflecting the best currently available estimates and good faith judgments of the management of the Company or Alvarez, as applicable, and Greenhill relied upon the Forecasts in arriving at its opinion. With respect to the Liquidity and Strategic Option Assumptions, Greenhill assumed that such Liquidity and Strategic Option Assumptions reflected the best currently available information and good faith judgments of the management of the Company and the Company’s other advisors, and Greenhill relied upon the Liquidity and Strategic Option Assumptions in arriving at its opinion. Greenhill expressed no opinion with respect to the Forecasts, the Liquidity and Strategic Option Assumptions or the assumptions upon which either of them were based. Greenhill made no independent evaluation or appraisal of the assets or liabilities (contingent or otherwise) of the Company or any other entity, nor was Greenhill furnished with any such evaluation or appraisal. In addition, Greenhill did not evaluate the solvency of any party to the merger agreement under any state or federal laws relating to bankruptcy, insolvency or similar matters. With the Company’s consent, Greenhill did not perform certain analyses that it would customarily prepare for the Company in connection with a fairness opinion because such analyses were not meaningful as a result of the extraordinary circumstances of the Company described herein. Greenhill assumed that the merger will be consummated in accordance with the terms set forth in the final, executed merger agreement, which Greenhill further assumed was identical in all material respects to the latest draft thereof it reviewed, and without waiver or amendment of any material terms or conditions set forth in the merger agreement. Greenhill further assumed that all governmental, regulatory and other consents and approvals necessary for the consummation of the merger will be obtained without any adverse effect on the Company, the merger or the contemplated benefits of the merger in any way meaningful to Greenhill’s analysis. Greenhill is not legal, regulatory, accounting or tax experts and has relied on the assessments made by the Company and its advisors with respect to such issues. Greenhill’s opinion is necessarily based on financial, economic, market and other conditions as in effect on, and the information made available to Greenhill as of, the date of the written opinion. It should be understood that subsequent developments may affect Greenhill’s opinion, and Greenhill does not have any obligation to update, revise or reaffirm its opinion.

Summary of Greenhill’s Financial Analysis

The following is a summary of the material financial and comparative analyses contained in the presentation that was made by Greenhill to the Board in connection with rendering its opinion described above. The following summary, however, does not purport to be a complete description of the analyses performed by Greenhill, nor does the order of analyses described represent relative importance or weight given to those analyses by Greenhill. Some of the summaries of the financial analyses include information presented in tabular format. In order to fully understand the financial analyses performed by Greenhill, the tables must be read together with the full text of each summary and are not alone a complete description of Greenhill’s financial analyses. Considering the data set forth in the tables below without considering the narrative description of the financial analyses, including the methodologies and assumptions underlying such analyses, could create a misleading or incomplete view of Greenhill’s financial analysis.

Selected Comparable Company Analysis

Greenhill performed a comparable company analysis which compared selected financial information and multiples for the Company to corresponding data for publicly traded companies selected by Greenhill.

Greenhill’s analysis included the following publicly-traded companies (“Selected Companies”):

UT&D Peers (as defined below):

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Oil & Gas Peers (as defined below):

The Selected Companies were divided into two subsets, utility transmission & distribution sector business peers (“UT&D Peers”) and oil & gas services business peers (“Oil & Gas Peers”). Although none of the Selected Companies is directly comparable to the Company, Greenhill selected each of the above-listed companies because, among other reasons, they are publicly-traded companies with operations or businesses in related sectors or for purposes of analysis may be considered similar or reasonably similar to the operations of the Company. However, because of the inherent differences between the business, operations and prospects of the Company and those of the Selected Companies, Greenhill believed that it was inappropriate to, and therefore did not, rely solely on the numerical results of the Selected Company analysis. Accordingly, Greenhill also made qualitative judgments concerning differences between the business, financial and operating characteristics and prospects of the Company and the Selected Companies that could affect the public trading values of each in order to provide a context in which to consider the results of the quantitative analysis. These qualitative judgments related primarily to the scale of the company relative to the industry, margin profile, issues related to customer concentration and relative contribution of oil and gas earnings to the company’s total business. Greenhill’s analysis was based on publicly available data and information for the Selected Companies, including information published by FactSet Research Systems Inc. (“FactSet”) and public filings, and the Forecasts, as of March 23, 2018.

For each of the Selected Companies, Greenhill reviewed the ratio of enterprise value (which we refer to in this section of the proxy statement as “EV”) which was calculated for each Selected Company by multiplying the number of fully diluted outstanding shares of that company as reported in its most recent public filings by the company’s common stock closing share price on March 23, 2018, plus the book value of debt, plus minority interest, less cash and cash equivalents, less investments in unconsolidated affiliates, as a multiple of earnings from operations before interest expense, income taxes and depreciation and amortization (which we refer to in this section of the proxy statement as “EBITDA”) for 2017 and 2018. The multiple ranges resulting from this analysis is summarized below:

The average multiples exclude the Company. The aggregate average of the Selected Companies is weighted such that UT&D Peers are given 80% of the weight and Oil & Gas Peers are given 20% of the weight. For purposes of these analyses, (i) EV of the Company is based on the Company’s fully diluted share count as of March 21, 2018, and includes total debt-related items owed to the term loan lender equal to $136 million, under the ABL credit

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facility equal to $23 million, incremental debt to fund operating losses equal to $15 million and restricted cash equal to $40 million, (ii) “Unadjusted EBITDA” means the Company’s estimated earnings from operations before interest expense, income taxes and depreciation and amortization and (iii) “Pro Forma Adjusted EBITDA” means Unadjusted EBITDA, as adjusted by management of the Company for non-recurring items, asset sales, discontinued operations, problem projects and certain other items. From this analysis, based on its professional judgment and experience, Greenhill selected the following ranges of multiples it deemed most meaningful for its analysis:

Greenhill applied such ranges of multiples to the corresponding financial information for the Company and, as a result, arrived at high and low implied Share prices for the Company. The results of this analysis are summarized below:

Greenhill noted that the Company’s Unadjusted EBITDA and Pro Forma Adjusted EBITDA for 2017 were both negative. Therefore, Greenhill’s analysis of the 2017 multiples implied by the Selected Companies resulted in negative implied per Share value ranges for the Company. Greenhill compared these ranges to the merger consideration, taking into account the Liquidity and Strategic Option Assumptions.

Precedent Transactions Analysis

Greenhill performed an analysis of selected recent change of control transactions (the “Precedent Transactions”), which compared selected transactions since 2013 in the utility and transmission and distribution sector (“UT&D Precedent Transactions”) and the oil and gas services sector (“Oil & Gas Precedent Transactions”), that in Greenhill’s judgment were relevant for its analysis. This analysis was based on publicly available information, the FactSet and Capital IQ databases, earnings transcripts, Mergermarket reports, equity research, industry sources and the Company Forecasts. None of these Precedent Transactions or associated companies is identical to the merger or the Company. Accordingly, Greenhill’s analysis of the Precedent Transactions necessarily involved complex considerations and judgments that would necessarily affect the implied value of the Company versus the values of the companies in the Precedent Transactions. In evaluating the Precedent Transactions, Greenhill considered the size, business mix and margin profile of the companies party to the Precedent Transactions.

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The following table identifies the Precedent Transactions reviewed by Greenhill in this analysis:

Greenhill reviewed the total transaction value for each of the Precedent Transactions and analyzed the EV implied by such total transaction value as a multiple of last 12-month EBITDA (for the 12-month period prior to the fiscal quarter in which the applicable transaction was announced). Using the above results, Greenhill derived reference ranges of multiples paid in the Precedent Transactions, as summarized below:

Greenhill analyzed the Company’s Unadjusted EBITDA and Pro Forma Adjusted EBITDA, in each case for the 12-month period ended December 31, 2017, and for the forecasted period ended June 30, 2018 (the estimated date of Closing, which forecast was based on the Company Forecasts). Greenhill noted that its analysis of the multiples implied by the Precedent Transactions, based on Unadjusted EBITDA and Pro Forma Adjusted EBITDA for each of these two periods (after taking into account total debt-related items owed to the term loan lender equal to $136 million, under the ABL credit facility equal to $23 million, incremental debt to fund operating losses equal to $15 million and restricted cash equal to $40 million, and based on the Company’s fully diluted share count as of March 21, 2018), resulted in negative implied per Share value ranges for the Company.

General

The summary set forth above does not purport to be a complete description of the analyses performed by Greenhill, but simply describes, in summary form, the material analyses that Greenhill conducted in connection with rendering its opinion. The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. In arriving at its opinion, Greenhill did not attribute any

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particular weight to any analyses or factors considered by it and did not form an opinion as to whether any individual analysis or factor, considered in isolation, supported or failed to support its opinion. Rather, Greenhill considered the totality of the factors and analyses performed in determining its opinion. Accordingly, Greenhill believes that the summary set forth above and its analyses must be considered as a whole and that selecting portions thereof, without considering all of its analyses, could create an incomplete view of the processes underlying its analyses and opinion. Greenhill based its analyses on assumptions that it deemed reasonable, including assumptions concerning general business and economic conditions and industry-specific factors. Analyses based on forecasts or projections of future results are inherently uncertain, as they are subject to numerous factors or events beyond the control of the parties or their advisors. Accordingly, Greenhill’s analyses are not necessarily indicative of actual values or actual future results that might be achieved, which values may be higher or lower than those indicated or implied. Moreover, Greenhill’s analyses are not and do not purport to be appraisals or otherwise reflective of the prices at which businesses actually could be bought or sold. In addition, no company or transaction used in Greenhill’s analysis as a comparison is directly comparable to the Company or the merger. Because these analyses are inherently subject to uncertainty, being based on numerous factors or events beyond the control of the parties or their respective advisors, none of the Company or Greenhill or any other person assumes responsibility if future results are materially different from those forecasts or projections.

The merger consideration payable pursuant to the merger agreement was determined through arms’ length negotiations between the Company and Primoris and was approved by the Board. Greenhill provided advice to the Company during these negotiations. Greenhill did not, however, recommend any specific amount of consideration to the Company or the Board or that any specific amount of consideration constituted the only appropriate consideration for the merger. Greenhill’s opinion did not in any manner address the underlying business decision to proceed with or effect the merger.

Greenhill has acted as financial advisor to the Company in connection with the merger. During the three years preceding the date of its opinion, Greenhill had not been engaged by, performed any services for or received any compensation from the Company or any other parties to the merger or their respective affiliates (other than any amounts that were paid to Greenhill under the letter agreement pursuant to which Greenhill was retained as a financial advisor to the Company in connection with the merger and $2,500,000 that was paid to Greenhill in the aggregate under other letter agreements pursuant to which Greenhill was retained as a financial advisor to the Company in connection with certain other matters). Under the terms of Greenhill’s engagement with the Company, the Company has agreed to pay Greenhill a fee for rendering its opinion equal to $1,000,000 and for other services rendered in connection with the merger totaling $4,625,000, which includes the $1,000,000 opinion fee, the principal portion of which is contingent on the consummation of the merger. In addition, the Company agreed to indemnify Greenhill for certain liabilities arising out of its engagement.

Greenhill is an internationally recognized investment banking firm regularly engaged in providing financial advisory services in connection with mergers and acquisitions. The Company selected Greenhill as its financial advisor in connection with the merger on the basis of Greenhill’s experience in similar transactions, its reputation in the investment community and its familiarity with the engineering and construction business.

Greenhill’s opinion was one of the 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 with respect to the merger.

Company Financial Projections

Although Willbros periodically may issue limited financial guidance, it does not, as a matter of course, develop or publicly disclose long-term projections or internal projections of its future financial performance, revenues, earnings, financial condition or other results due to, among other reasons, the uncertainty of the underlying assumptions and estimates. However, in connection with the evaluation of the merger by the Board, the Board considered certain non-public unaudited prospective financial information provided by our management relating

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to Willbros for the fourth quarter of 2017 and the year ended 2018 and with respect to cash flow information through June 1, 2018. These projections were also provided to Greenhill for its use and reliance in connection with its financial analyses and opinion summarized under the section entitled “The Merger — Opinion of Willbros’ Financial Advisor.”

The projections were not prepared with a view to public disclosure, but are included in this proxy statement because such information was made available to the Board and Greenhill, and were used in the evaluation process leading to the execution of the merger agreement. 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 and the use of non-GAAP measures 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 document has been prepared by, and is the responsibility of, the Company’s management. PricewaterhouseCoopers LLP has not audited, reviewed, examined, compiled nor applied agreed-upon procedures with respect to the accompanying prospective financial information and, accordingly, PricewaterhouseCoopers LLP does not express an opinion or any other form of assurance with respect thereto. The PricewaterhouseCoopers LLP report incorporated by reference in this document relates to the Company’s previously issued financial statements. It does not extend to the prospective financial information and should not be read to do so.

The projections were developed by Willbros management and considered various material assumptions, including, but not limited to, the following:

The projections include certain non-GAAP financial measures. 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 Willbros may not be comparable to similarly titled amounts used by other companies.

Although a summary of our projections is presented with numerical specificity, this information is not fact and should not be relied upon as being necessarily predictive of actual future results. These projections are forward-looking statements. Important factors that may affect actual results and cause our projections not to be achieved include general economic conditions, accuracy of certain financial assumptions, our ability to continue as a going concern, the inability to comply with the financial and other covenants in, or to obtain waivers under, our credit facilities, changes in the demand for energy, changes in our future financial performance (including actual or projected cash flows and actual or projected expenses), competitive pressures, changes in tax laws, and the other factors described under the section entitled “Cautionary Statement Concerning Forward-Looking Information.” In addition, the projections do not take into account any circumstances or events occurring after the date that they were prepared, which was January 10, 2018 with respect to the year ended 2018, February 22, 2018 with respect to the fourth quarter of 2017 information and March 23, 2018 with respect to the cash flow information through

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June 1, 2018. 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. The projections also do not give effect to the transactions contemplated by the merger agreement, including the merger or the post-closing operations of Willbros and its subsidiaries. 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 our projections. The inclusion of this information should not be regarded as an indication that the Board, the Board’s financial advisor or any other recipient of this information considered, or now considers, our projections to be material information of Willbros 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 our projections is not included in this proxy statement in order to induce any stockholder to vote in favor of the merger proposal or 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 dissenters’ rights with respect to shares of our common stock.

These projections should be evaluated, if at all, in conjunction with the historical financial statements and other information regarding Willbros contained in our public filings with the SEC. The projections were reviewed by Willbros’ management with, and considered by, the Board in connection with its evaluation of the merger.

Except to the extent required by applicable federal securities laws, we do not intend, and expressly disclaim any responsibility, to update or otherwise revise our projections to reflect circumstances existing after the date when we prepared our 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 our projections are shown to be in error. Neither Willbros nor any of its affiliates, directors, officers, advisors or other representatives has made or makes any representation to any of our stockholders regarding the ultimate performance of Willbros compared to the information contained in these projections or that these projections will be achieved.

In light of the foregoing factors and the uncertainties inherent in our projections and considering that the special meeting may be held several months after these projections were prepared, stockholders are cautioned not to place undue, if any, reliance on these projections.

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The following tables set forth certain summarized historical, historical pro forma and prospective financial information for Willbros for the periods presented, which were prepared by Willbros management. The historical and prospective financial information below includes the identification of subsequently disposed businesses, certain loss projects, restructuring charges and other adjustments. For additional information regarding these items, see the section entitled “The Merger — Background of the Merger.” Willbros believed the exclusion of these items provided more comparable and useful financial information in evaluating its operational trends and performance. In addition, Willbros believed the exclusion of these items are more indicative of the future operating prospects of the Company as a whole. At the time this information was prepared, Willbros had not yet filed its Annual Report on Form 10-K for the fiscal year ended December 31, 2017, and thus the information for the fourth quarter 2017 and for the year ended December 31, 2017 were estimates. Willbros filed such Annual Report on Form 10-K with the SEC on March 30, 2018. See the section entitled “Where You Can Find More Information.” For purposes of the following tables, “A” means actual and “E” means estimate.

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The following table sets forth certain summarized prospective cash flow information for Willbros through June 1, 2018, which was prepared by management with the assistance of Alvarez. The cash forecast below does not include Primoris’ bridge loan; any acceleration payment of the term loan or ABL resulting from default provisions under the agreements; includes interest payment to the term loan lender which will be waived as part of the merger; and does not reflect reduction in minimum ABL borrowing base availability from $15.0 million to $10.0 million under the ABL forbearance agreement.