Primoris Services (PRIM) 424B5Prospectus supplement for primary offering

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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-248535

The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus do not constitute an offer to sell these securities and we are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated March 16, 2021

PROSPECTUS SUPPLEMENT
(To Prospectus dated September 1, 2020)

4,500,000 Shares

Primoris Services Corporation

Common Stock

          We are offering 4,500,000 shares of our common stock, $0.0001 par value per share. Our common stock is listed on the Nasdaq Global Market ("Nasdaq") under the symbol "PRIM." The last reported sale price of our common stock on Nasdaq on March 15, 2021, was $40.43 per share.

          Investing in our common stock involves risks. See "Risk factors" beginning on page S-11 of this prospectus supplement and in the documents incorporated by reference or deemed to be incorporated by reference into this prospectus supplement and the accompanying prospectus.

          Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

          We have granted the underwriters an option for a period of 30 days to purchase up to an additional 675,000 shares of our common stock from us at the price to the public less underwriting discounts and commissions.

          Delivery of the shares of our common stock is expected to be made on or about                          , 2021.

Book-Running Managers

Prospectus Supplement dated                           , 2021.

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PROSPECTUS SUPPLEMENT

PROSPECTUS

          We have not, and the underwriters have not, authorized anyone to provide you with any information other than the information contained in this prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, and in any free writing prospectus that we have authorized for use in connection with this offering. We take no responsibility for, and can provide no assurances as to the reliability of, any information that is in addition to or different from that contained or incorporated by reference in this prospectus supplement and the accompanying prospectus. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this

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prospectus supplement and the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision.

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ABOUT THIS PROSPECTUS SUPPLEMENT

          This prospectus supplement and the accompanying prospectus form part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or the "SEC," using a "shelf" registration process. This document contains two parts. The first part consists of this prospectus supplement, which provides you with specific information about this offering. The second part, the accompanying prospectus, provides more general information, some of which may not apply to this offering. Generally, when we refer only to the "prospectus," we are referring to both parts combined. This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent that any statement we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents dated prior to the date of this prospectus supplement and incorporated by reference herein or therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference herein and therein.

          Unless the context otherwise indicates, references in this prospectus to "Primoris," the "Company," "we," "our" and "us" refer, collectively, to Primoris Services Corporation, a Delaware corporation, and its consolidated subsidiaries. References to our "common stock" refer to the common stock, par value $0.0001 per share, of Primoris Services Corporation.

          All references in this prospectus supplement to our financial statements include, unless the context indicates otherwise, the related notes.

          The industry and market data and other statistical information contained in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference herein and therein are based on management's own estimates, independent publications, government publications, reports by market research firms or other published independent sources, and, in each case, are believed by management to be reasonable estimates. Although we believe these sources are reliable, we have not independently verified the information.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

          This prospectus supplement and the accompanying prospectus contain or incorporate by reference forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or the "Securities Act," and Section 21E of the Securities Exchange Act of 1934, as amended, or the "Exchange Act," and we intend that such forward-looking statements be subject to the safe harbors contained in the Private Securities Litigation Reform Act of 1995. Forward-looking statements include information concerning our possible or assumed future results of operations, business strategies, financing plans, competitive position, industry environment, growth opportunities, the effects of regulation and the economy, generally. Forward-looking statements include all statements that are not historical facts and usually can be identified by terms such as "anticipates," "believes," "could," "estimates," "expects," "intends," "may," "plans," "potential," "predicts," "projects," "should," "will," "would" or similar expressions.

          Forward-looking statements include information concerning our possible or assumed future results of operations, business strategies, financing plans, competitive position, industry environment, potential growth opportunities, the effects of regulation and the economy, generally. Forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. Actual results may differ materially as a result of a number of factors, including, among other things, customer timing, project duration, weather, and general economic conditions; changes in our mix of customers, projects, contracts and business; regional or national and/or general economic conditions and demand for our services; price, volatility, and expectations of future prices of oil, natural gas, and natural gas liquids; variations and changes in the margins of projects performed during any particular quarter; increases in the costs to perform services caused by changing conditions; the termination, or expiration of existing agreements or contracts; the budgetary spending patterns of customers; increases in construction costs that we may be unable to pass through to our customers; cost or schedule overruns on fixed-price contracts; availability of qualified labor for specific projects; changes in bonding requirements and bonding availability for existing and new agreements; the need and availability of letters of credit; costs we incur to support growth, whether organic or through acquisitions; the timing and volume of work under contract; losses experienced in our operations; the results of the review of prior period accounting on certain projects; developments in governmental investigations and/or inquiries; intense competition in the industries in which we operate; failure to obtain favorable results in existing or future litigation or regulatory proceedings, dispute resolution proceedings or claims, including claims for additional costs; failure of our partners, suppliers or subcontractors to perform their obligations; cyber-security breaches; failure to maintain safe worksites; risks or uncertainties associated with events outside of our control, including severe weather conditions, public health crises and pandemics (such as COVID-19), political crises or other catastrophic events; client delays or defaults in making payments; the availability of credit and restrictions imposed by credit facilities; failure to implement strategic and operational initiatives; risks or uncertainties associated with acquisitions, dispositions and investments; possible information technology interruptions or inability to protect intellectual property; the Company's failure, or the failure of our agents or partners, to comply with laws; the Company's ability to secure appropriate insurance; new or changing legal requirements, including those relating to environmental, health and safety matters; the loss of one or a few clients that account for a significant portion of the Company's revenues; asset impairments; and risks arising from the inability to successfully integrate acquired businesses. Given these uncertainties, you should not place undue reliance on forward-looking statements.

          See the section titled "Risk Factors" in this prospectus supplement and the risk factors included in our periodic reports filed with the SEC under the Exchange Act for a further discussion

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regarding reasons that actual results may differ materially from the results, developments and business decisions contemplated by our forward-looking statements. We do not undertake any obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws. We assume no obligation to update forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in any forward-looking statements, even if new information becomes available.

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RISK FACTORS

          In addition to the risks described below, you should also carefully read all of the other information included in this prospectus supplement, the accompanying prospectus and the documents we have incorporated by reference into this prospectus supplement in evaluating an investment in our common stock. See "Where You Can Find More Information." If any of the described risks actually were to occur, our business, financial condition, results of operations and cash flows could be materially adversely affected. In that event, the trading price of our common stock could decline, and you may lose all or part of your investment in our common stock.

          The risks described below and incorporated by reference herein are not the only ones facing the Company. Additional risks not presently known to us or that we currently deem immaterial individually or in the aggregate may also impair our business operations.

          This prospectus supplement and documents incorporated by reference herein also contain forward-looking statements that involve risks and uncertainties, some of which are described in the documents incorporated by reference in this prospectus supplement and the accompanying prospectus. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of various factors, including the risks and uncertainties faced by us described below or incorporated by reference in this prospectus supplement and the accompanying prospectus. See "Special Note Regarding Forward-Looking Statements."

Risks Related to this Offering and Ownership of our Common Stock

We will have broad discretion as to the use of the proceeds from this offering, and we may not use the proceeds that we receive effectively.

          Although we intend to use the proceeds from this offering for general corporate purposes, including to repay a portion of the borrowings outstanding under the Amended Credit Agreement as described in the section entitled "Use of Proceeds," we will retain broad discretion as to the application of the net proceeds and could use them for purposes other than those contemplated at the time of this offering. Our stockholders may not agree with the manner in which we choose to allocate and spend the net proceeds. Moreover, we may use the net proceeds for corporate purposes that may not increase our profitability or our market value.

You may experience dilution as a result of this offering.

          This offering may have a dilutive effect on our earnings per share after giving effect to the issuance of our common shares in this offering and the receipt of the expected net proceeds. The actual amount of dilution from this offering or from any future offering of our common shares will be based on numerous factors, particularly the number of our common shares issued, the use of proceeds and the return generated by any investments made with the net proceeds, and cannot be determined at this time.

          In addition, as part of our acquisition strategy, we have issued shares of common stock and used shares of common stock as a part of contingent earn-out consideration, which have resulted in dilution to our stockholders. Our Certificate of Incorporation permits us to issue up to 90.0 million shares of common stock of which approximately 48.1 million were outstanding at December 31, 2020. We are also permitted under our Certificate of Incorporation to issue shares of preferred stock which could cause further dilution to our common stockholders, resulting in reduced net income and cash flow available to common stockholders.

          In 2013, our stockholders adopted our 2013 Equity Incentive Plan ("Equity Plan"). The Equity Plan replaced a previous plan. The Equity Plan authorized the Board of Directors to issue equity awards totaling 2,526,275 shares of our common stock. Our current director compensation plan,

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our bonus incentive plan, and our management long-term incentive plan and any additional equity awards made will have the effect of diluting our earnings per share and stockholders' percentage of ownership.

Cash available for distribution may not be sufficient to maintain dividends to our shareholders at current levels, or at all.

          Holders of our common stock are entitled to receive dividends, if any, as may be declared from time to time by our board of directors. The payment of dividends is contingent upon our revenue and earnings, capital requirements, and general financial condition, as well as contractual restrictions and other considerations deemed to be relevant by our board of directors. While our board of directors has declared quarterly cash dividends for each of the years ended December 31, 2020, 2019 and 2018, the board may eliminate or otherwise reduce the amount of such dividend. No assurance can be given that we will be able to continue making quarterly distributions at the current rate or at all.

Delaware law and our charter documents may impede or discourage a takeover or change in control.

          As a Delaware corporation, anti-takeover provisions may impose an impediment to the ability of others to acquire control of us, even if a change of control would be of benefit to our stockholders. In addition, certain provisions of our Certificate of Incorporation and Bylaws also may impose an impediment, or discourage others from a takeover. These provisions include:

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Stockholders may not act by written consent;



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There are restrictions on the ability of a stockholder to call a special meeting, or nominate a director for election; and



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Our Board of Directors can authorize the issuance of preferred shares.

          These types of provisions may limit the ability of stockholders to obtain a premium for their shares.

Risks Related Primarily to Operating our Business

Our financial and operating results may vary significantly from quarter-to-quarter and year-to-year.

          Our business is subject to seasonal and annual fluctuations. Some of the quarterly variation is the result of weather, particularly rain, ice, snow, and named storms, which create difficult operating conditions. Similarly, demand for routine repair and maintenance services for gas utilities is lower during their peak customer needs in the winter, and demand for routine repair and maintenance services for electric utilities is lower during their peak customer needs in the summer. Some of the annual variation is the result of construction projects which fluctuate based on customer timing, project duration, weather, and general economic conditions. Annual and quarterly results may also be adversely affected by:

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Changes in our mix of customers, projects, contracts and business;



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Regional or national and/or general economic conditions and demand for our services;



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Variations and changes in the margins of projects performed during any particular quarter;



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Increases in the costs to perform services caused by changing conditions;



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The termination, or expiration of existing agreements or contracts;

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The budgetary spending patterns of customers;



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Increases in construction costs that we may be unable to pass through to our customers;



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Cost or schedule overruns on fixed-price contracts;



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Availability of qualified labor for specific projects;



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Changes in bonding requirements and bonding availability for existing and new agreements;



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The need and availability of letters of credit;



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Costs we incur to support growth, whether organic or through acquisitions;



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The timing and volume of work under contract; and



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Losses experienced in our operations.

          As a result, our operating results in any particular quarter may not be indicative of the operating results expected for any other quarter, or for an entire year.

Demand for our services may decrease during economic recessions or volatile economic cycles, and a reduction in demand in end markets may adversely affect our business.

          A substantial portion of our revenue and profit is generated from construction projects, the awarding of which we do not directly control. The engineering and construction industry historically has experienced cyclical fluctuations in financial results due to economic recessions, downturns in business cycles of our customers, material shortages, price increases by subcontractors, interest rate fluctuations and other economic factors beyond our control. When the general level of economic activity deteriorates, our customers may delay, or cancel upgrades, expansions, and/or maintenance and repairs to their systems. Many factors, including the financial condition of the industry, could adversely affect our customers and their willingness to fund capital expenditures in the future.

          Economic, regulatory and market conditions affecting our specific end markets may adversely impact the demand for our services, resulting in the delay, reduction or cancellation of certain projects and these conditions may continue to adversely affect us in the future. For example, much of the work that we perform in the highway markets involves funding by federal, state and local governments. This funding is subject to fluctuation based on the budgets and operating priorities of the various government agencies.

          We are also dependent on the amount of work our customers outsource. In a slower economy, our customers may decide to outsource less infrastructure services, reducing demand for our services. In addition, consolidation, competition or capital constraints in the industries we serve may result in reduced spending by our customers.

Industry trends and government regulations could reduce demand for our pipeline construction services.

          The demand for our pipeline construction services is dependent on the level of operating and capital project spending by midstream companies in the oil and gas industry. This level of spending is subject to large fluctuations depending primarily on the current price, volatility, and expectations of future prices of oil, natural gas, and natural gas liquids. The price is a function of many factors, including levels of supply and demand, government policies and regulations, oil industry refining capacity and the potential development of alternative fuels.

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          Specific government decisions could affect demand for our construction services. For example, a limitation on the use of "fracking" technology, or creation of significant regulatory issues for the construction of underground pipelines, could significantly reduce our underground work.

          Conversely, government regulations may increase the demand for our pipeline services. The anticipation by utilities that coal-fueled power plants may become uneconomical to operate because of potential environmental regulations or low natural gas prices could increase demand for gas pipeline construction for utility customers.

Many of our customers are regulated by federal and state government agencies and the addition of new regulations or changes to existing regulations may adversely impact demand for our services and the profitability of those services.

          Many of our energy customers are regulated by the Federal Energy Regulatory Commission ("FERC"), and our utility customers are regulated by state public utility commissions. These agencies could change the way in which they interpret current regulations and may impose additional regulations. These changes could have an adverse effect on our customers and the profitability of the services they provide, which could reduce demand for our services or delay our ability to complete projects.

Our business may be materially adversely impacted by regional, national and/or global requirements related to climate change and the impact of greenhouse gas emissions in the future.

          Greenhouse gases that result from human activities, including burning of fossil fuels, are the focus of increased scientific and political scrutiny and may be subject to changing legal requirements. International agreements, federal laws, state laws and various regulatory schemes limit or otherwise regulate emissions of greenhouse gases, and additional restrictions are under consideration by different governmental entities. We derive a significant amount of revenue and contract profit from engineering and construction services to clients that own and/or operate a wide range of process plants and own and/or operate electric power generating plants that generate electricity from burning natural gas or various types of solid fuels. These plants may emit greenhouse gases as part of the process to generate electricity or other products. Compliance with existing greenhouse gas regulation may prove costly or difficult. It is possible that owners and operators of existing or future process plants and electric generating plants could be subject to new or changed environmental regulations that result in significantly limiting, or reducing the amounts of greenhouse gas emissions, increasing the cost of emitting such gases or requiring emissions allowances. The costs of controlling such emissions or obtaining required emissions allowances could be significant. It also is possible that necessary controls or allowances may not be available. Such regulations could negatively impact client investments in capital projects in our markets, which could negatively impact the market for our products and/or services. This could materially adversely affect our business.

          The establishment of additional rules limiting greenhouse gas emissions could also impact our ability to perform construction services, or to perform these services with current levels of profitability. New regulations may require us to acquire different equipment or change processes. The new equipment may not be available, or it may not be purchased or rented in a cost effective manner. Project deferrals, delays or cancellations resulting from the potential regulations could adversely impact our business.

          In addition, we could be held liable for significant penalties and damages under certain environmental laws and regulations and also could be subject to a revocation of our licenses or permits. Our contracts with our customers may also impose liabilities on us regarding

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environmental issues that arise through the performance of our services. From time to time, we may incur costs and obligations for correcting environmental noncompliance matters and for remediation at or relating to certain of our job sites or properties. We believe that we are in substantial compliance with our environmental obligations.

          The potential physical impact of climate change on our operations is highly uncertain. Climate change may result in, among other things, changes in rainfall patterns, storm patterns and intensities and temperature levels. Our operating results are significantly influenced by weather, and major changes in historical weather patterns could significantly impact our future operating results. For example, if climate change results in significantly more adverse weather conditions in a given period, we could experience reduced productivity, which could negatively impact our revenue and gross margins.

          Climate change could also affect our customers and the types of projects that they award. Demand for power projects, underground pipelines or highway projects could be affected by significant changes in weather, or climate conditions, or by regulatory changes relating to climate change, which could in turn reduce demand for our services.

Our results could be adversely affected by natural disasters, public health crises, political crises, or other catastrophic events.

          Natural disasters, such as hurricanes, tornadoes, floods, earthquakes, and other adverse weather and climate conditions; unforeseen public health crises, such as pandemics and epidemics; political crises, such as terrorist attacks, war, labor unrest, and other political instability; or other catastrophic events could disrupt our operations, or the operations of one or more of our vendors or customers, and could adversely affect our financial results. In particular, these types of events could impact our product supply chain from or to the impacted region and could cause our customers to delay or cancel projects, which could impact our ability to operate. In addition, these types of events could lead to general inefficiencies from having to start and stop work, re-sequencing work, requiring on-site health screenings before entering a job site, and following proper social distancing practices.

          In December 2019, a novel strain of coronavirus 2019 ("COVID-19") emerged and has since extensively impacted global health and the economic environment. In an effort to contain COVID-19 or slow its spread, governments around the world have also enacted various measures, including orders to close all businesses not deemed "essential", isolate residents to their homes or places of residence, and practice social distancing when engaging in essential activities. While our services have generally been deemed to be essential services, we have experienced project interruptions and restrictions that have delayed project timelines from those originally planned. In some cases, we have experienced temporary work stoppages, which has led to general inefficiencies from having to start and stop work, re-sequence work, require on-site health screenings before entering a job site, and follow proper social distancing practices. We have also been restricted from completing work or have been prevented from starting work on certain projects. There are no comparable recent events that can provide guidance as to the effect of the COVID-19 global pandemic, and, as a result, the ultimate impact of COVID-19 or a similar health pandemic or epidemic is highly uncertain. We will continue to actively monitor the situation and may take further actions to alter our business operations that we determine are in the best interests of our employees, customers, suppliers, and stakeholders, or as required by federal, state, or local authorities. We will also continue to monitor our customers and their industries to assess the effect that changes in economic, market and regulatory conditions may have on them. Due to uncertainties regarding the duration and impact of the current COVID-19 pandemic, we are unable to predict the extent to which the COVID-19 pandemic may have a material adverse effect on our business, financial condition or results of operations.

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Changes to renewable portfolio standards and decreased demand for renewable energy projects could negatively impact our future results of operations, cash flows and liquidity.

          A significant portion of our future business may be focused on providing construction and/or installation services to owners and operators of solar power and other renewable energy facilities. Currently, the development of solar and other renewable energy facilities is dependent on the existence of renewable portfolio standards and other state incentives and requirements. Renewable portfolio standards are state-specific statutory provisions requiring that electric utilities generate a certain amount of electricity from renewable energy sources. These standards have initiated significant growth in the renewable energy industry and a potential demand for renewable energy infrastructure construction services. Elimination of, or changes to, existing renewable portfolio standards, tax credits or similar environmental policies may negatively affect future demand for our services.

We may lose business to competitors through the competitive bidding processes.

          We are engaged in highly competitive businesses in which most customer contracts are awarded through bidding processes based on price and the acceptance of certain risks. We compete with other general and specialty contractors, both regional and national, as well as small local contractors. The strong competition in our markets requires maintaining skilled personnel and investing in technology, and also puts pressure on profit margins. We do not obtain contracts from all of our bids and our inability to win bids at acceptable profit margins would adversely affect our business.

We may be unsuccessful at generating internal growth which may affect our ability to expand our operations, or grow our business.

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Hire and retain qualified personnel;



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Secure appropriate levels of construction equipment;



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Successfully bid for new projects; and



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Adapt the range of services we offer to address our customers' evolving construction needs.

          In addition, our customers may reduce the number or size of projects available to us due to their inability to obtain capital. Our customers may also reduce projects in response to economic conditions.

          Many of the factors affecting our ability to generate internal growth may be beyond our control, and we cannot be certain that our strategies will be successful or that we will be able to generate cash flow sufficient to fund our operations and to support internal growth. If we are unsuccessful, we may not be able to achieve internal growth, expand our operations or grow our business.

The timing of new contracts may result in unpredictable fluctuations in our business.

          Substantial portions of our revenue are derived from project-based work that is awarded through a competitive bid process. The portion of revenue generated from the competitive bid process for 2020, 2019 and 2018 was approximately 51.7%, 44.3%, and 48.6%, respectively. It is generally very difficult to predict the timing and geographic distribution of the projects that we will

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be awarded. The selection of, timing of or failure to obtain projects, delays in award of projects, the re-bidding or termination of projects due to budget overruns, cancellations of projects or delays in completion of contracts could result in the under-utilization of our assets and reduce our cash flows. Even if we are awarded contracts, we face additional risks that could affect whether, or when work will begin. For example, some of our contracts are subject to financing, permitting and other contingencies that may delay or result in termination of projects. We may have difficulty in matching workforce size and equipment location with contract needs. In some cases, we may be required to bear the cost of a ready workforce and equipment that is larger than necessary, resulting in unpredictability in our cash flow, expenses and profitability. If any expected contract award, or the related work release is delayed or not received, we could incur substantial costs without receipt of any corresponding revenue. Finally, the winding down or completion of work on significant projects will reduce our revenue and earnings if these projects have not been replaced.

We derive a significant portion of our revenue from a few customers, and the loss of one or more of these customers could have significant effects on our revenue, resulting in adverse effects on our financial condition, results of operations and cash flows.

          Our customer base is reasonably concentrated, with our top ten customers accounting for approximately 47.0% of our revenue in 2020, 47.2% of our revenue in 2019 and 52.2% of our revenue in 2018. However, the customers included in our top ten customer list generally vary from year to year. Our revenue is dependent both on performance of larger construction projects and relatively smaller projects under MSAs. For the large construction projects, the completion of the project does not necessarily represent the permanent loss of a customer; however, the future revenue generated from work for that customer may fluctuate significantly.

          We also generate ongoing revenue from our MSA customers, which are generally comprised of regulated gas and electric utilities. If we were to lose one of these customers, our revenue could significantly decline. Reduced demand for our services by larger construction customers or a loss of a significant MSA customer could have an adverse effect on our business.

Our international operations expose us to legal, political and economic risks in different countries as well as currency exchange rate fluctuations that could harm our business and financial results. We could be adversely affected by our failure to comply with laws applicable to our foreign activities, such as the U.S. Foreign Corrupt Practices Act.

          During 2020, 2019 and 2018, revenue attributable to our services outside of the United States, principally in Canada, was 3.5%, 5.8% and 2.9% of our total revenue, respectively. There are risks inherent in doing business internationally, including:

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Imposition of governmental controls and changes in laws, regulations, policies, practices, tariffs and taxes;



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Political and economic instability;



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Changes in United States and other national government trade policies affecting the market for our services;



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Potential non-compliance with a wide variety of laws and regulations, including the United States Foreign Corrupt Practices Act ("FCPA") and similar non-United States laws and regulations;



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Currency exchange rate fluctuations, devaluations and other conversion restrictions;



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Restrictions on repatriating foreign profit back to the United States; and



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Difficulties in staffing and managing international operations.

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          The FCPA and similar anti-bribery laws in other jurisdictions prohibit U.S.-based companies and their intermediaries from making improper payments to non-U.S. officials for the purpose of obtaining or retaining business. We pursue opportunities in certain parts of the world that experience government corruption, and in certain circumstances, compliance with anti-bribery laws may conflict with local customs and practices. Our internal policies mandate compliance with all applicable anti-bribery laws. We require our partners, subcontractors, agents and others who work for us or on our behalf to comply with the FCPA and other anti-bribery laws. There is no assurance that our policies or procedures will protect us against liability under the FCPA or other laws for actions taken by our agents, employees and intermediaries. If we are found to be liable for FCPA violations (either due to our own acts or our inadvertence, or due to the acts or inadvertence of others), we could suffer from severe criminal or civil penalties or other sanctions, which could have a material adverse effect on our reputation and business. In addition, detecting, investigating and resolving actual or alleged FCPA violations is expensive and could consume significant time and attention of our senior management.

Backlog may not be realized or may not result in revenue or profit.

          Backlog is measured and defined differently by companies within our industry. We refer to "backlog" as our anticipated revenue from the uncompleted portions of existing contracts where scope is adequately defined, and therefore we can reasonably estimate total contract value, and the estimated revenue on MSA work for the next four quarters. Backlog is not a comprehensive indicator of future revenue. Most contracts may be terminated by our customers on short notice. Reductions in backlog due to cancellation by a customer, or for other reasons, could significantly reduce the revenue that we actually receive from contracts in backlog. In the event of a project cancellation, we are typically reimbursed for all of our costs through a specific date, as well as all reasonable costs associated with demobilizing from the jobsite, but we typically have no contractual right to the total revenue reflected in our backlog. Projects may remain in backlog for extended periods of time. While backlog includes estimated MSA revenue, customers are not contractually obligated to purchase a certain amount of services under the MSA.

          Given these factors, our backlog at any point in time may not accurately represent the revenue that we expect to realize during any period, and our backlog as of the end of a fiscal year may not be indicative of the revenue we expect to earn in the following fiscal year. Inability to realize revenue from our backlog could have an adverse effect on our business.

          While backlog may not be indicative of the revenue we expect to earn the following fiscal year, it is a potential indicator of future revenue; however, recognition of revenue from backlog does not necessarily ensure that the projects will be profitable. Poor project execution could impact profit from contracts included in backlog. For projects for which a loss is expected, future revenue will be recorded with no margin, which may reduce the overall margin percentage for work performed.

Our actual cost may be greater than expected in performing our contracts where scope is adequately defined, causing us to realize significantly lower profit or losses on our projects.

          We currently generate, and expect to continue to generate, a portion of our revenue and profit under contracts where scope is adequately defined. The approximate portion of revenue generated in 2020 from contracts where scope is adequately defined was 66.8%. In general, we must estimate the costs of completing a specific project to bid these types of contracts. The actual cost of labor and materials may vary from the costs we originally estimated, and we may not be successful in recouping additional costs from our customers. These variations may cause gross profit for a

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project to differ from those we originally estimated. Reduced profitability or losses on projects could occur due to changes in a variety of factors such as:

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Failure to properly estimate costs of engineering, materials, equipment or labor;



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Unanticipated technical problems with the structures, materials or services being supplied by us, which may require that we spend our own money to remedy the problem;



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Project modifications not reimbursed by the client creating unanticipated costs;



•

Changes in the costs of equipment, materials, labor or subcontractors;



•

Our suppliers or subcontractors failure to perform;



•

Changes in local laws and regulations, and;



•

Delays caused by weather conditions.

          As projects grow in size and complexity, multiple factors may contribute to reduced profit or losses, and depending on the size of the particular project, variations from the estimated contract costs could have a material adverse effect on our business.

Weather can significantly affect our revenue and profitability.

          Our ability to perform work and meet customer schedules can be affected by weather conditions such as snow, ice, rain, and named storms. Weather may affect our ability to work efficiently and can cause project delays and additional costs. Our ability to negotiate change orders for the impact of weather on a project could impact our profitability. In addition, the impact of weather can cause significant variability in our quarterly revenue and profitability.

We require subcontractors and suppliers to assist us in providing certain services, and we may be unable to retain the necessary subcontractors or obtain supplies to complete certain projects adversely affecting our business.

          We use subcontractors to perform portions of our contracts and to manage workflow, particularly for design, engineering, procurement and some foundation work. While we are not dependent on any single subcontractor, general market conditions may limit the availability of subcontractors to perform portions of our contracts causing delays and increases in our costs.

          Although significant materials are often supplied by the customer, we use suppliers to provide some materials and equipment used for projects. If a supplier fails to provide supplies and equipment at the estimated price, fails to provide adequate amounts of supplies and equipment, fails to provide supplies or equipment that meet the project requirements, or fails to provide supplies when scheduled, we may be required to source the supplies or equipment at a higher price or may be required to delay performance of the project. The additional cost or project delays could negatively impact project profitability.

          Failure of a subcontractor or supplier to comply with laws, rules or regulations could negatively affect our reputation and our business.

We periodically enter into joint ventures which require satisfactory performance by our venture partners of their obligations. The failure of our joint venture partners to perform their joint venture obligations could impose additional financial and performance obligations on us that could result in reduced profit or losses for us with respect to the joint venture.

          We periodically enter into various joint ventures and teaming arrangements where control may be shared with unaffiliated third parties. At times, we also participate in joint ventures where we are

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not a controlling party. In such instances, we may have limited control over joint venture decisions and actions, including internal controls and financial reporting which may have an impact on our business. If our joint venture partners fail to satisfactorily perform their joint venture obligations, the joint venture may be unable to adequately perform or deliver its contracted services. Under these circumstances, we may be required to make additional investments or provide additional services to ensure the adequate performance and delivery of the contracted services. These additional obligations could result in reduced profit and may impact our reputation in the industry.

We may experience delays and defaults in client payments and we may pay our suppliers and subcontractors before receiving payment from our customers for the related services, which could result in an adverse effect on our financial condition, results of operations and cash flows.

          We use subcontractors and material suppliers for portions of certain work, and our customers pay us for those related services. If we pay our suppliers and subcontractors for materials purchased and work performed for customers who fail to pay us, or such customers delay paying us for the related work or materials, we could experience a material adverse effect on our business. In addition, if customers fail to pay us for work we perform, we could experience a material adverse effect on our business.

Our inability to recover on contract modifications against project owners or subcontractors for payment or performance could negatively affect our business.

          We occasionally present contract modifications to our clients and subcontractors for changes in contract specifications or requirements. We consider unapproved change orders to be contract modifications for which customers have not agreed to both scope and price. We consider claims to be contract modifications for which we seek, or will seek, to collect from customers, or others, for customer-caused changes in contract specifications or design, or other customer-related causes of unanticipated additional contract costs on which there is no agreement with customers. Claims can also be caused by non-customer-caused changes, such as rain or other weather delays. In some cases, settlement of contract modifications may not occur until after completion of work under the contract. A failure to promptly document and negotiate a recovery for contract modifications could have a negative impact on our cash flows, and an overall ability to recover contract modifications could have a negative impact on our financial condition, results of operations and cash flows.

For some projects we may guarantee a timely completion or provide a performance guarantee which could result in additional costs, such as liquidated damages, to cover our obligations.

          In our fixed-price and unit-price contracts we may provide a project completion date, and in some of our projects we may commit that the project will achieve specific performance standards. Failure to complete the project as scheduled or at the contracted performance standards could result in additional costs or penalties, including liquidated damages, and such amounts could exceed expected project profit.

A significant portion of our business depends on our ability to provide surety bonds, and we may be unable to compete for or work on certain projects if we are not able to obtain the necessary surety bonds.

          Our contracts frequently require that we provide payment and performance bonds to our customers. Under standard terms in the surety market, sureties issue or continue bonds on a project-by-project basis and can decline to issue bonds at any time, or require the posting of additional collateral as a condition to issuing, or renewing bonds.

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          Current or future market conditions, as well as changes in our surety providers' assessments of our operating and financial risk, could cause our surety providers to decline to issue or renew, or to substantially reduce, the availability of bonds for our work and could increase our bonding costs. These actions could be taken on short notice. If our surety providers were to limit or eliminate our access to bonding, our alternatives would include seeking bonding capacity from other sureties, finding more business that does not require bonds and posting other forms of collateral for project performance, such as letters of credit or cash. We may be unable to secure these alternatives in a timely manner, on acceptable terms, or at all. Accordingly, if we were to experience an interruption or reduction in the availability of bonding capacity, we may be unable to compete for, or work on certain projects.

Our bonding requirements may limit our ability to incur indebtedness, which would limit our ability to refinance our existing credit facilities or to execute our business plan.

          Our ability to obtain surety bonds depends upon various factors including our capitalization, working capital, tangible net worth and amount of our indebtedness. In order to obtain required bonds, we may be limited in our ability to incur additional indebtedness that may be needed to refinance our existing credit facilities upon maturity, to complete acquisitions, and to otherwise execute our business plans.

We may be unable to win some new contracts if we cannot provide clients with letters of credit.

          For many of our clients surety bonds provide an adequate form of security, but for some clients additional security in the form of a letter of credit may be required. While we have capacity for letters of credit under our credit facility, the amount required by a client may be in excess of our credit limit. Any such amount would be issued at the sole discretion of our lenders. Failure to provide a letter of credit when required by a client may result in our inability to compete for, win, or retain a project.

During the ordinary course of our business, we may become subject to material lawsuits or indemnity claims.

          We have in the past been, and may in the future be, named as a defendant in lawsuits, claims and other legal proceedings during the ordinary course of our business. These actions may seek, among other things, compensation for alleged personal injury, workers' compensation, employment discrimination, breach of contract, property damage, punitive damages, and civil penalties, or other losses or injunctive or declaratory relief. In addition, we generally indemnify our customers for claims related to the services we provide and actions we take under our contracts with them, and, in some instances, we may be allocated risk through our contract terms for actions by our customers, or other third parties. Because our services in certain instances may be integral to the operation and performance of our customers' infrastructure, we may become subject to lawsuits or claims for any failure of the systems on which we work, even if our services are not the cause of such failures, and we could be subject to civil and criminal liabilities to the extent that our services contributed to any property damage, personal injury or system failure. The outcome of any of these lawsuits, claims or legal proceedings could result in significant costs and diversion of management's attention from the business. Payments of significant amounts, even if reserved, could adversely affect our reputation, our cash flows, and our business.

We are self-insured against potential liabilities.

          Although we maintain insurance policies with respect to employer's liability, general liability, auto and workers compensation claims, those policies are subject to deductibles or self-insured

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retention amounts of up to $500,000 per occurrence. We are primarily self-insured for all claims that do not exceed the amount of the applicable deductible/self-insured retention. In addition, for our employees not part of a collective bargaining agreement, we provide employee health care benefit plans. Our primary health insurance plan is subject to a deductible of $400,000 per individual claim per year.

          Our insurance policies include various coverage requirements, including the requirement to give appropriate notice. If we fail to comply with these requirements, our coverage could be denied.

          Losses under our insurance programs are accrued based upon our estimates of the ultimate liability for claims reported and an estimate of claims incurred but not reported, with assistance from third-party actuaries. Insurance liabilities are difficult to assess and estimate due to unknown factors, including the severity of an injury, the extent of damage, the determination of our liability in proportion to other parties and the number of incidents not reported. The accruals are based upon known facts and historical trends.

Our business is labor intensive. If we are unable to attract and retain qualified managers and skilled employees, our operating costs may increase.

          Our business is labor intensive and our ability to maintain our productivity and profitability may be limited by our ability to employ, train and retain skilled personnel necessary to meet our requirements. We may not be able to maintain an adequately skilled labor force necessary to operate efficiently and to support our growth strategy. We have from time-to-time experienced, and may in the future experience, shortages of certain types of qualified personnel. For example, periodically there are shortages of engineers, project managers, field supervisors, and other skilled workers capable of working on and supervising the construction of underground, heavy civil and industrial facilities, as well as providing engineering services. The supply of experienced engineers, project managers, field supervisors and other skilled workers may not be sufficient to meet current or expected demand. The beginning of new, large-scale infrastructure projects, or increased competition for workers currently available to us, could affect our business, even if we are not awarded such projects. Labor shortages, or increased labor costs could impair our ability to maintain our business or grow our revenue. If we are unable to hire employees with the requisite skills, we may also be forced to incur significant training expenses.

Our unionized workforce may commence work stoppages or impact our ability to complete certain acquisitions, which could adversely affect our operations.

          As of December 31, 2020, approximately 31.6% of our hourly employees, primarily consisting of field laborers, were covered by collective bargaining agreements. Of the 81 collective bargaining agreements to which we are a party, 30 expire during 2021 and require renegotiation. Although the majority of these agreements prohibit strikes and work stoppages, we cannot be certain that strikes or work stoppages will not occur in the future. Strikes or work stoppages would adversely impact our relationships with our customers and could have an adverse effect on our business.

          Our ability to complete future acquisitions could be adversely affected because of our union status for a variety of reasons. For instance, in certain geographic areas, our union agreements may be incompatible with the union agreements of a business we want to acquire and some businesses may not want to become affiliated with a union company.

Withdrawal from multiemployer pension plans associated with our unionized workforce could adversely affect our financial condition and results of operations.

          Our collective bargaining agreements generally require that we participate with other companies in multiemployer pension plans. To the extent those plans are underfunded, the

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Employee Retirement Income Security Act of 1974 ("ERISA"), as amended by the Multiemployer Pension Plan Amendments Act of 1980 ("MEPA"), may subject us to substantial liabilities under those plans if we withdraw from them, or if they are terminated. In addition, the Pension Protection Act of 2006 added new funding rules for multiemployer plans that are classified as endangered, seriously endangered or critical status. For a plan in critical status, additional required contributions and benefit reductions may apply if a plan is determined to be underfunded, which could adversely affect our financial condition or results of operations. For plans in critical status, we may be required to make additional contributions, generally in the form of surcharges on contributions otherwise required. Participation in those plans with high funding levels could adversely affect our results of operations, financial condition or cash flows if we are not able to adequately mitigate these costs.

          The amount of the withdrawal liability legislated by ERISA and MEPA varies for every pension plan to which we contribute. For each plan, our liability is the total unfunded vested benefits of the plan multiplied by a fraction: the numerator of the fraction is the sum of our contributions to the plan for the past ten years and the denominator is the sum of all contributions made by all employers for the past ten years. For some pension plans to which we contribute, the total unfunded vested benefits are in the billions of dollars. If we cannot reduce the liability through exemptions or negotiations, the withdrawal from a plan could have a material adverse impact on our business.

We depend on key personnel and we may not be able to operate and grow our business effectively if we lose the services of any of our key persons or are unable to attract qualified and skilled personnel in the future.

          We are dependent upon the efforts of our key personnel, and our ability to retain them and hire other qualified employees. The loss of our executive officers, or other key personnel could affect our ability to run our business effectively. Competition for senior management is intense, and we may not be able to retain our personnel. The loss of any key person requires the remaining key personnel to divert immediate and substantial attention to seeking a replacement, as well as to performing the departed person's responsibilities until a replacement is found. In addition, as some of our key persons approach retirement age, we need to provide for smooth transitions. If we fail to find a suitable replacement for any departing executive or senior officer on a timely basis, such departure could adversely affect our ability to operate and grow our business.

If we fail to integrate acquisitions successfully, we may experience operational challenges and risks which may have an adverse effect on our business.

          As part of our growth strategy, we intend to acquire companies that expand, complement or diversify our business. Acquisitions may expose us to operational challenges and risks, including, among others:

•

The diversion of management's attention from the day-to-day operations of the combined company;



•

Managing a significantly larger company than before completion of an acquisition;



•

The assimilation of new employees and the integration of business cultures;



•

Training and facilitating our internal control processes within the acquired organization;



•

Retaining key personnel;



•

The integration of information, accounting, finance, sales, billing, payroll and regulatory compliance systems;

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•

Challenges in keeping existing customers and obtaining new customers;



•

Challenges in combining service offerings and sales and marketing activities;



•

The assumption of unknown liabilities of the acquired business for which there are inadequate reserves;



•

The potential impairment of acquired goodwill and intangible assets; and



•

The inability to enforce covenants not to compete.

          Failure to effectively manage the integration process could adversely impact our business, financial condition, results of operations, and cash flows.

We may incur higher costs to lease, acquire and maintain equipment necessary for our operations.

          A significant portion of our contracts is built utilizing our own construction equipment rather than leased or rented equipment. To the extent that we are unable to buy or build equipment necessary for a project, either due to a lack of available funding, or equipment shortages in the marketplace, we may be forced to rent equipment on a short-term basis, or to find alternative ways to perform the work without the benefit of equipment ideally suited for the job, which could increase the costs of completing the project. We often bid for work knowing that we will have to rent equipment on a short-term basis, and we include the equipment rental rates in our bid. If market rates for rental equipment increase between the time of bid submission and project execution, our margins for the project may be reduced. In addition, our equipment requires continuous maintenance, which we generally provide through our own repair facilities. If we are unable to continue to maintain the equipment in our fleet, we may be forced to obtain additional third-party repair services at a higher cost or be unable to bid on contracts.

Our business may be affected by difficult work sites and environments which may adversely affect our ability to procure materials and labor.

          We perform our work under a variety of conditions, including, but not limited to, difficult and hard to reach terrain, difficult site conditions, and busy urban centers, where delivery of materials and availability of labor may be impacted. Performing work under these conditions can slow our progress, potentially causing us to incur contractual liability to our customers. These difficult conditions may also cause us to incur additional, unanticipated costs that we might not be able to pass on to our customers.

We may incur liabilities or suffer negative financial or reputational impacts relating to health and safety matters.

          Our operations are subject to extensive laws and regulations relating to the maintenance of safe conditions in the workplace. While we have invested, and will continue to invest, substantial resources in our environmental, health and safety programs, our industry involves a high degree of operational risk and there can be no assurance that we will avoid significant liability exposure. Although we have taken what we believe are appropriate precautions, we have suffered fatalities in the past and may suffer additional fatalities in the future. Serious accidents, including fatalities, may subject us to substantial penalties, civil litigation or criminal prosecution. Claims for damages to persons, including claims for bodily injury or loss of life, could result in substantial costs and liabilities, which could materially and adversely affect our financial condition, results of operations or cash flows. In addition, if our safety record were to substantially deteriorate over time or we were to suffer substantial penalties or criminal prosecution for violation of health and safety regulations, our customers could cancel our contracts and not award us future business.

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Interruptions in our operational systems or successful cyber security attacks on any of our systems could adversely impact our operations, our ability to report financial results and our business.

          We rely on computer, information and communication technology and related systems to operate our business and to protect sensitive company information. Any cyber security attack that affects our facilities, our systems, our customers or any of our financial data could have a material adverse effect on our business. Our computer and communications systems, and consequently our operations, could be damaged or interrupted by cyber-attacks and physical security risks, such as natural disasters, loss of power, telecommunications failures, acts of war, acts of terrorism, computer viruses, physical or electronic break-ins and actions by hackers and cyber-terrorists. Any of these, or similar, events could cause system disruptions, delays and loss of critical information, delays in processing transactions and delays in the reporting of financial information.

          We have experienced cyber security threats, such as viruses and attacks targeting our systems, and expect the frequency and sophistication of such incidents to continue to grow. Such prior events have not had a material impact on our financial condition, results of operations or liquidity. However, future threats or existing threats of which we are not yet aware could cause harm to our business and our reputation, disrupt our operations, expose us to potential liability, regulatory actions and loss of business, and impact our results of operations materially. Our insurance coverage may not be adequate to cover all the costs related to cyber security attacks or disruptions resulting from such events.

          While we have taken steps to mitigate persistent and continuously evolving cyber security threats by implementing network security and internal control measures, implementing policies and procedures for managing risk to our information systems, periodically testing our information technology systems, and conducting employee training on cyber security, there can be no assurance that a system or network failure or data security breach would not adversely affect our business. Furthermore, the continuing and evolving threat of cyber-attacks has resulted in increased regulatory focus on prevention. To the extent we face increased regulatory requirements, we may be required to expend significant additional resources to meet such requirements.

We may need additional capital in the future for working capital, capital expenditures or acquisitions, and we may not be able to access capital on favorable terms, or at all, which would impair our ability to operate our business or achieve our growth objectives.

          Our ability to generate cash is essential for the funding of our operations and the servicing of our debt. If existing cash balances together with the borrowing capacity under our credit facilities were not sufficient to make future investments, make acquisitions or provide needed working capital, we may require financing from other sources. Our ability to obtain such additional financing in the future will depend on a number of factors including prevailing capital market conditions, conditions in our industry, and our operating results. These factors may affect our ability to arrange additional financing on terms that are acceptable to us. If additional funds were not available on acceptable terms, we may not be able to make future investments, take advantage of acquisitions or pursue other opportunities.

Risks Related Primarily to the Financial Accounting of our Business

Our financial results are based upon estimates and assumptions that may differ from actual results.

          In preparing our consolidated annual and quarterly financial statements in conformity with generally accepted accounting principles, many estimates and assumptions are used in determining the reported revenue, costs and expenses recognized during the periods presented, and

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disclosures of contingent assets and liabilities known to exist as of the date of the financial statements. These estimates and assumptions must be made because certain information that is used in the preparation of our financial statements cannot be calculated with a high degree of precision from data available, is dependent on future events, or is not capable of being readily calculated based on generally accepted methodologies. Often times, these estimates are particularly difficult to determine, and we must exercise significant judgment. Estimates may be used in our assessments of the allowance for doubtful accounts, useful lives of property and equipment, fair value assumptions in analyzing goodwill and long-lived asset impairments, self-insured claims liabilities, accounting for revenue recognized over time, and provisions for income taxes. Actual results could differ materially from the estimates and assumptions that we used.

Our accounting for revenue recognized over time could result in a reduction or elimination of previously reported revenue and profit.

          For contracts where scope is adequately defined, and therefore we can reasonably estimate total contract value, we recognize revenue over time as work is completed because of the continuous transfer of control to the customer (typically using an input measure such as costs incurred to date relative to total estimated costs at completion to measure progress). Accounting for long-term contracts involves the use of various techniques to estimate total transaction price and costs. For long-term contracts, transaction price, estimated cost at completion and total costs incurred to date are used to calculate revenue earned. Unforeseen events and circumstances can alter the estimate of the costs and potential profit associated with a particular contract. Total estimated costs, and thus contract revenue and income, can be impacted by changes in productivity, scheduling, the unit cost of labor, subcontracts, materials and equipment. Additionally, external factors such as weather, client needs, client delays in providing permits and approvals, labor availability, governmental regulation, politics and any prevailing impacts from the COVID-19 pandemic may affect the progress of a project's completion, and thus the timing of revenue recognition. Actual results could differ from estimated amounts and could result in a reduction or elimination of previously recognized earnings. In certain circumstances, it is possible that such adjustments could be significant and could have an adverse effect on our business.

Our reported results of operations could be adversely affected as a result of impairments of goodwill, other identifiable intangible assets or investments.

          When we acquire a business, we record an asset called "goodwill" for the excess amount we pay for the business over the net fair value of the tangible and identifiable intangible assets of the business we acquire. At December 31, 2020, our balance sheet included goodwill of $215.1 million and intangible assets of $61.0 million resulting from previous acquisitions, and we expect these amounts to increase based on the FIH acquisition that was completed in January 2021. Fair value is determined using a combination of the discounted cash flow, market multiple and market capitalization valuation approaches. Under current accounting rules, goodwill and other identifiable intangible assets that have indefinite useful lives cannot be amortized, but instead must be tested at least annually for impairment, while identifiable intangible assets that have finite useful lives are amortized over their useful lives. Significant judgment is required in completing these tests, as described in "Management's Discussion and Analysis of Financial Condition and Results of Operations — Critical Accounting Policies and Estimates — Goodwill and Indefinite — Lived Intangible Assets" included elsewhere in this prospectus supplement. Any impairment of the goodwill, or identifiable intangible assets recorded in connection with the various acquisitions, or for any future acquisitions, would negatively impact our results of operations.

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          In addition, we may enter into various types of investment arrangements, such as an equity interest we hold in a business entity. Our equity method investments are carried at original cost and are included in other assets in our Consolidated Balance Sheet and are adjusted for our proportionate share of the investees' income, losses and distributions. Equity investments are reviewed for impairment by assessing whether any decline in the fair value of the investment below its carrying value is other than temporary. In making this determination, factors such as the ability to recover the carrying amount of the investment and the inability of the investee to sustain future earnings capacity are evaluated in determining whether an impairment should be recognized.

Compliance with and changes in tax laws could adversely affect our performance.

          We are subject to extensive tax liabilities imposed by multiple jurisdictions, including federal, state, local and international jurisdictions. The Tax Cuts and Jobs Act (the "Tax Act") that was signed into law on December 22, 2017 made significant changes to the U.S. Internal Revenue Code and requires complex computations not previously provided in U.S. tax law. New tax laws and regulations and changes in existing tax laws and regulations are continuously being enacted or proposed, and could result in a different tax rate on our earnings, which could have a material impact on our earnings and cash flow from operations. In addition, significant judgment is required in determining our provision for income taxes, as described in "Management's Discussion and Analysis of Financial Condition and Results of Operations — Critical Accounting Policies and Estimates — Income Taxes" included elsewhere in this prospectus supplement. In the ordinary course of our business, there are many transactions and calculations where the ultimate tax determination is uncertain. We are regularly subject to audits by tax authorities, and our tax estimates and tax positions could be materially affected by many factors including the final outcome of tax audits and related litigation, the introduction of new tax accounting standards, legislation, regulations and related interpretations, our mix of earnings, the realizability of deferred tax assets and changes in uncertain tax positions. A significant increase in our tax rate could have a material adverse effect on our profitability and liquidity.

We may not be successful in continuing to meet the internal control requirements of the Sarbanes-Oxley Act of 2002.

          The Sarbanes-Oxley Act of 2002 has many requirements applicable to us regarding corporate governance and financial reporting, including the requirements for management to report on internal controls over financial reporting and for our independent registered public accounting firm to express an opinion over the operating effectiveness of our internal control over financial reporting. At December 31, 2020, our internal control over financial reporting was effective using the internal control framework issued by the Committee of Sponsoring Organizations ("COSO") of the Treadway Commission: Internal control — Integrated Framework (2013).

          There can be no assurance that our internal control over financial reporting will be effective in future years. Failure to maintain effective internal controls, or the identification of material internal control deficiencies in acquisitions already made, or made in the future could result in a decrease in the market value of our common stock, the reduced ability to obtain financing, the loss of customers, penalties and additional expenditures to meet the requirements in the future.

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USE OF PROCEEDS

          We estimate that the net proceeds from this offering will be approximately $             (or approximately $             if the underwriters exercise in full their option to purchase additional shares) after deducting underwriting discounts and commissions and estimated offering expenses. We intend to use the net proceeds from this offering for general corporate purposes, including to repay a portion of the borrowings outstanding under the Amended Credit Agreement. Please see "Summary — Recent Developments — Second Amended and Restated Credit Agreement."

          The Amended Credit Agreement provides for a $592.5 million New Term Loan and a $200.0 million revolving credit facility, and the lenders agreed to make loans on a revolving basis from time to time and to issue letters of credit for up to the $200.0 million committed amount. The Amended Credit Agreement also contains an accordion feature that would allow us to increase the New Term Loan or the borrowing capacity under the revolving credit facility by up to $75.0 million. The proceeds from the New Term Loan were used to finance the acquisition of FIH and for general corporate purposes.

          At February 28, 2021, we had (i) $592.5 million borrowings outstanding under the New Term Loan, (ii) $100.0 million borrowings outstanding under the revolving credit facility and (iii) $51.2 million commercial letters of credit outstanding. The principal amount of all loans under the Amended Credit Agreement will bear interest at either: (i) LIBOR plus an applicable margin as specified in the Amended Credit Agreement (based on our senior debt to EBITDA ratio as defined in the Amended Credit Agreement), or (ii) the Base Rate (which is the greater of (a) the Federal Funds Rate plus 0.5% or (b) the prime rate as announced by the Administrative Agent) plus an applicable margin as specified in the Amended Credit Agreement. Quarterly non-use fees, letter of credit fees and administrative agent fees are payable at rates specified in the Amended Credit Agreement. The Amended Credit Agreement matures on January 15, 2026.

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CAPITALIZATION

          The following table sets forth our cash and cash equivalents and our capitalization as of December 31, 2021:

•

on a historical basis;



•

on a pro forma basis, reflecting the effect of the Merger as if it occurred on December 31, 2020;



•

on a pro forma basis, as adjusted to give effect to this offering and the application of the net proceeds of this offering as described under "Use of Proceeds."

          You should read the information below in conjunction with the sections titled "Summary Historical and Unaudited Pro Forma Financial Data," "Use of proceeds," and "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the audited historical consolidated financial statements and unaudited pro forma condensed combined financial statements and accompanying notes included elsewhere in this prospectus supplement.

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UNAUDITED PRO FORMA CONSOLIDATED COMBINED FINANCIAL STATEMENTS

Introduction

          On January 15, 2021, we completed our previously announced acquisition of FIH. Pursuant to the terms of that Agreement and Plan of Merger (the "Merger Agreement") dated as of December 14, 2020 and Amendment No. 1 to the Merger Agreement (the "Amendment") dated January 11, 2021, Primoris Merger Sub, LLC, a Delaware limited liability company and wholly owned subsidiary of Primoris ("Merger Sub"), merged with and into FIH (the "Merger"), with FIH surviving the Merger as a wholly-owned subsidiary of Primoris.

          The aggregate amount of consideration paid was approximately $611.2 million, net of cash acquired, which was funded through a combination of existing cash balances, borrowings under our term loan facility, and borrowings under our revolving credit facility.

          The foregoing descriptions of the Merger Agreement and the Amendment are qualified in their entirety by reference to the full text of the Merger Agreement and the Amendment, which are attached as Exhibit 2.2 and Exhibit 2.3, respectively, to our Annual Report on Form 10-K, which is incorporated by reference in this prospectus supplement.

          The following unaudited pro forma consolidated combined financial statements are based on the historical financial statements of Primoris and FIH after giving effect to the acquisition, and the assumptions, reclassifications and adjustments described in the accompanying notes to the unaudited pro forma consolidated combined financial statements, as prescribed by the Securities and Exchange Commission guidelines. On October 30, 2020, FIH acquired Pridemore Case Holdings, Inc ("Pride"), which expanded FIH's operations. Therefore, we have included Pride's results of operations for the ten-month period ended October 30, 2020 in the unaudited pro forma consolidated combined statement of income for the year ended December 31, 2020.

          The following unaudited pro forma consolidated combined balance sheet as of December 31, 2020 is presented as if the Merger had occurred on December 31, 2020. The unaudited pro forma consolidated combined statement of income for the year ended December 31, 2020, is presented as if the Merger had occurred on January 1, 2020 with acquisition-related adjustments reflected assuming the transaction occurred at the beginning of the fiscal year presented and had a continuing impact through the period presented and described in the accompanying notes.

          The historical consolidated financial information has been adjusted in the unaudited pro forma consolidated combined financial data to illustrate the Transaction Accounting Adjustments related to the Merger.

          The following unaudited pro forma consolidated combined financial statements are prepared for illustrative purposes only and are not necessarily indicative of or intended to represent the results that would have been achieved had the acquisition been consummated as of the dates indicated or that may be achieved in the future. The unaudited pro forma consolidated combined financial statements do not reflect the realization of any expected operating efficiencies or other synergies that may result from the Merger as a result of planned initiatives with respect to the combined companies.

          The unaudited pro forma consolidated combined financial statements should be read in conjunction with the accompanying notes to the unaudited pro forma consolidated combined financial statements. In addition, the unaudited pro forma consolidated combined financial statements should be read in conjunction with (i) our audited consolidated financial statements and accompanying notes included elsewhere in this prospectus supplement, and (ii) FIH's audited consolidated financial statements and accompanying notes for the year ended December 31, 2020, which are attached as Exhibit 99.1 to our Current Report on Form 8-K/A, as filed with the SEC on March 9, 2021, which is incorporated by reference in this prospectus supplement.

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PRIMORIS SERVICES CORPORATION
UNAUDITED PRO FORMA CONSOLIDATED COMBINED BALANCE SHEET
December 31, 2020
(In thousands)

See accompanying notes to the unaudited pro forma consolidated combined financial statements

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PRIMORIS SERVICES CORPORATION
UNAUDITED PRO FORMA CONSOLIDATED COMBINED STATEMENT OF INCOME
For the year ended December 31, 2020
(In thousands, except per share amounts)

See accompanying notes to the unaudited pro forma consolidated combined financial statements

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PRIMORIS SERVICES CORPORATION
NOTES TO THE UNAUDITED PRO FORMA CONSOLIDATED COMBINED FINANCIAL STATEMENTS

Note 1 — Basis of Presentation

          The unaudited pro forma consolidated combined balance sheet as of December 31, 2020 is presented as if the acquisition of FIH had occurred on December 31, 2020. The unaudited pro forma consolidated combined statement of income for the year ended December 31, 2020, is presented as if the acquisition of FIH had occurred on January 1, 2020. On October 30, 2020, FIH acquired Pride, which expanded FIH's operations. Therefore, we have included Pride's results of operations for the period ended October 30, 2020 in the unaudited pro forma consolidated combined statement of income for the year ended December 31, 2020.

          The unaudited pro forma consolidated combined financial statements are not necessarily indicative of what our consolidated statements of income or consolidated balance sheet would have been had the Merger been completed as of the dates indicated or will be for any future periods. The unaudited pro forma consolidated combined financial statements do not purport to project our future financial position or results of income following the Merger. The unaudited pro forma consolidated combined financial statements reflect transaction related adjustments that management believes are necessary to present fairly our pro forma consolidated combined results of income assuming the Merger had been consummated as of January 1, 2020. The transaction related adjustments are based on currently available information and assumptions management believes are, under the circumstances and given the information available at this time, reasonable, and reflective of adjustments necessary to report our financial condition and results of income as a result of the closing of the Merger. The unaudited pro forma consolidated combined financial statements do not reflect the realization of any expected operating efficiencies or other synergies that may result from the Merger as a result of planned initiatives with respect to the combined companies.

Note 2 — Conforming Accounting Policies

          The accounting policies used in the preparation of this unaudited pro forma consolidated combined financial information are those set out in our audited consolidated financial statements as of and for the year ended December 31, 2020. We have conducted a review of the accounting policies of FIH to determine if differences in accounting policies potentially required recasting to conform to our accounting policies and determined that certain adjustments are necessary to conform FIH's Pre-Merger financial statements to our accounting policies, specifically with regard to Accounting Standards Codification ("ASC") 842, Leases. Since FIH was a privately held company, they were not required to adopt ASC 842 until January 1, 2022, and we adopted ASC 842 on January 1, 2019. Therefore, the unaudited pro forma consolidated combined financial statements have been adjusted to properly reflect the adoption of ASC 842 by FIH.

Note 3 — Reclassification Adjustments

          Certain reclassification adjustments have been made to the unaudited pro forma consolidated combined financial statements to conform FIH's consolidated balance sheet as of December 31, 2020 and statement of income for the year ended December 31, 2020, to Primoris' presentation, as follows:

(A)

We recognize retainage amounts as a contract asset, while FIH recognized these amounts as accounts receivable. Retainage is the portion of the contract price earned by us for work performed, but held for payment by the customer as a form of security until

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we reach certain construction milestones. Therefore, we reclassified $4.8 million from Accounts receivable, net to Contract assets.

(B)

We recognize accrued state taxes in Accrued liabilities, while FIH recognized these amounts as a separate component of Total current liabilities. Therefore, we reclassified $0.5 million from Accrued state taxes to Accrued liabilities.



(C)

We recognize certain administrative costs as Selling, general, and administrative ("SG&A") expenses, while FIH recognized these amounts as Cost of revenue. Therefore, we reclassified $1.8 million from Cost of revenue to SG&A expenses.



(D)

We recognize gains on sale of assets as a reduction in Cost of revenue, while FIH recognized these amounts as SG&A expenses. Therefore, we reclassified gains of $0.4 million from SG&A expenses to Cost of revenue.

Note 4 — Preliminary Acquisition Accounting

          The table below represents the purchase consideration and the preliminary estimated fair values of the assets acquired and liabilities assumed as of the acquisition date. The preliminary estimated fair values have been used to prepare pro forma Transaction Accounting Adjustments in the pro forma consolidated combined financial statements. The final determination of fair value for certain assets and liabilities will be completed as soon as the information necessary to complete the analysis is obtained. The final purchase consideration allocation is expected to be completed within the measurement period, as defined in ASC 805, following the close of the Merger and may differ materially from the preliminary estimates used in the pro forma adjustments described below. The primary areas of the preliminary estimates that are not yet finalized relate to property, plant and equipment, identifiable intangible assets, contract assets and liabilities, and the fair value of certain contractual obligations.

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Note 5 — Pro Forma Adjustments

          The pro forma adjustments are based on our preliminary estimates and assumptions that are subject to change. The following adjustments have been reflected in the unaudited pro forma consolidated combined financial statements:

(a)

To record approximately $621.7 million of cash consideration paid for the FIH acquisition.



(b)

The below table reflects the net increase to debt for $500.0 million of new debt incurred to finance the FIH acquisition, less the effects of extinguishing FIH's outstanding debt of $178.4 million upon consummation of the acquisition (in thousands):

          The adjustment also reflects the reduction in accrued interest of $0.1 million due to the extinguishment of FIH debt.

(c)

To eliminate prepaid insurance of approximately $2.0 million.



(d)

To record the difference between the historical net book value of FIH's fixed assets and our preliminary estimate of fair value and the related impact to depreciation expense. On a preliminary basis, we increased the book value of FIH's fixed assets by $2.3 million. The resulting adjustment to depreciation expense, including finance lease depreciation expense, was an increase of approximately $0.3 million for the pro forma year ended December 31, 2020.



(e)

To eliminate FIH capital lease assets and liabilities recorded under ASC 840 of approximately $6.6 million and record the fair value of FIH finance lease assets and liabilities under ASC 842 of approximately $6.7 million. The difference of $0.1 million was due to our incremental borrowing rate used to calculate the fair value of the finance lease assets and liabilities under ASC 842.



(f)

To record FIH operating lease assets and liabilities under ASC 842 of approximately $12.5 million.



(g)

Reflects the elimination of FIH's pre-existing intangible assets and recognition of the estimated preliminary fair value of identifiable intangible assets acquired. To determine the estimated fair value of intangibles acquired, we engaged a third party valuation specialist to assist management. Our valuation estimates are preliminary and subject to

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change. The estimated preliminary fair value of identifiable intangible assets acquired is comprised of the following (in thousands):