TETRA TECH INC

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Stockholders of Tetra Tech, Inc.

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated balance sheets of Tetra Tech, Inc. and its subsidiaries (the "Company") as of September 28, 2025 and September 29, 2024, and the related consolidated statements of income, of comprehensive income, of equity and of cash flows for each of the three years in the period ended September 28, 2025, including the related notes and financial statement schedule listed in the accompanying index (collectively referred to as the "consolidated financial statements"). We also have audited the Company's internal control over financial reporting as of September 28, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of September 28, 2025 and September 29, 2024, and the results of its operations and its cash flows for each of the three years in the period ended September 28, 2025 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of September 28, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO.

Basis for Opinions

The Company's management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in Management’s Report on Internal Control over Financial Reporting appearing under Item 9A. Our responsibility is to express opinions on the Company’s consolidated financial statements and on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the consolidated financial statements included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

As described in Management’s Report on Internal Control over Financial Reporting, management has excluded SAGE Group Holdings ("SAGE") from its assessment of internal control over financial reporting as of September 28, 2025 because it was acquired by the Company in a purchase business combination during 2025. We have also excluded SAGE from our audit of internal control over financial reporting. SAGE is a wholly-owned subsidiary whose total assets and total revenues excluded from management’s assessment and our audit of internal control over financial reporting represent 1.2% and 0.8%, respectively, of the related consolidated financial statement amounts as of and for the year ended September 28, 2025.

Definition and Limitations of Internal Control over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matters

The critical audit matter communicated below is a matter arising from the current period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that (i) relates to accounts or disclosures that are material to the consolidated financial statements and (ii) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Revenue Recognition – Certain fixed-price, time-and-materials and cost-plus contracts

As described in Note 3 to the consolidated financial statements, the Company recognized revenue of $5,443 million for the year ended September 28, 2025, of which a majority relates to revenue recognized for certain fixed-price, time-and-materials and cost-plus contracts. The Company recognizes revenue over time as the related performance obligation is satisfied by transferring control of a promised good or service to the Company’s customers. Progress toward complete satisfaction of the performance obligation is primarily measured using a cost-to-cost measure of progress method. The cost input is based primarily on contract cost incurred to date compared to total estimated contract cost. This measure includes forecasts based on the best information available and reflects management's judgment to depict the value of the services transferred to the customer. For those performance obligations for which revenue is recognized using a cost-to-cost measure of progress method, changes in total estimated costs, and related progress towards complete satisfaction of the performance obligation, are recognized on a cumulative catch-up basis in the period in which the revisions to the estimates are made. For certain on-call engineering or consulting and similar contracts, the Company recognizes revenue in the amount which they have the right to invoice the customer if that amount corresponds directly with the value of the performance completed to date. Due to uncertainties inherent in the estimation process, it is possible that estimates of costs to complete a performance obligation will be revised in the near-term.

The principal consideration for our determination that performing procedures relating to revenue recognition for certain fixed-price, time-and-materials and cost-plus contracts is a critical audit matter is a high degree of audit effort in performing procedures related to the Company’s revenue recognition.

Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to the revenue recognition process. These procedures also included, among others, (i) evaluating management’s significant accounting policies related to revenue recognition; (ii) for certain fixed-price contracts, testing management’s process for developing the estimate of total contract cost for a sample of contracts with cumulative catch-up adjustments and anticipated losses or claims, and evaluating the contract terms and other documents that support the changes in total estimated contract costs; (iii) assessing, for a sample of fixed-price contracts, estimated total contract costs by performing a comparison of the total estimated contract cost as compared with prior period estimates and evaluating the timely identification of circumstances that may warrant a modification to the total estimated contract cost; (iv) evaluating, for certain contracts, management’s methodologies and assessing the consistency of management’s methodology over the life of the contract; (v) re-calculating revenue recognized based on the contract value, year-to-date costs, and total estimated costs to complete; (vi) testing the existence and accuracy of total contract revenue recorded, on a sample basis, by obtaining and inspecting source documents such as contracts and purchase orders; (vii) for certain on-call engineering or consulting contacts where revenue is recognized using the practical expedient right to invoice, testing the accuracy of revenue recognized, on a sample basis by obtaining and inspecting source documents, such as contracts and purchase orders; and (viii) for certain contracts, testing the completeness and accuracy of costs incurred to date, on a sample basis, by obtaining and inspecting source documents, such as invoices and timecards.

/s/PricewaterhouseCoopers LLP

Los Angeles, California

November 20, 2025

We have served as the Company’s auditor since 2004.