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* Onterris 2026 Earnings : 2Q Results August 5 , 2026 For Planet & Progress
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© Onterris • 2Q26 Earnings • Our team applies data-driven rigor and specialized expertise to deliver outcomes that help protect the planet while enabling progress. With continued partnership, we will extend our reach, accelerate innovation and help shape a more sustainable future. Please contact ir@onterris.com to discuss our vision for the opportunities ahead. • We remain committed to achieving our long-term goals and are continuing to execute against the priorities within our control, including serving our clients, maintaining cost discipline and converting a greater share of our revenue into earnings and cash flow. That work is strengthening Onterris and supporting our objective of enhancing value for stockholders. 2Q26 Results Vijay Manthripragada President & Chief Executive Officer 2
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© Onterris • 2Q26 Earnings • Statements contained herein and in the accompanying oral presentation contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements may be identified by the use of words such as “intend,” “expect” and “may” and other similar expressions that predict or indicate future events or that are not statements of historical matters. Forward-looking statements are based on current information available at the time the statements are made and on management’s reasonable belief or expectations with respect to future events and are subject to risks and uncertainties, many of which are beyond Onterris, Inc.’s (“Onterris,” “we,” “us” and “our”) control, that could cause actual performance or results to differ materially from the belief or expectations expressed in or suggested by the forward-looking statements. Additional factors or events that could cause actual results to differ may also emerge from time to time and it is not possible for us to predict all of them. These factors and events include (i) general global economic, business and other conditions, including inflationary and interest rate pressures and tariffs and other trade tensions, the cyclical nature of our industry and the significant fluctuations in events that impact our business; (ii) the parts of our business that depend on difficult to predict natural or manmade events and the fluctuations in our revenue and customer concentration as a result thereof; (iii) our ability to adapt to changing technology, industry standards or regulatory requirements, including emerging environmental, social and governance requirements; (iv) the highly competitive nature of our business; (v) significant environmental governmental regulation or de-regulation; (vi) our ability to execute on our acquisition strategy and successfully integrate and realize benefits from our acquisitions; (vii) our ability to maintain and expand our client base; (viii) our ability to attract and retain qualified managerial and skilled technical personnel; (ix) safety-related issues; (x) any failure in or breach of our networks and systems or other forms of cyber-attack; (xi) our ability to promote and develop our new brand; (xii) our ability to maintain necessary accreditations and other authorizations in varying jurisdictions; (xiii) allegations regarding compliance with professional standards, duties and statutory obligations and our ability to provide accurate results; (xiv) the lack of formal long-term agreements with many of our clients; (xv) government clients and contracts; (xvi) our ability to maintain our prices and manage costs; (xvii) our ability to protect our intellectual property or claims that we infringe on the intellectual property rights of others; (xviii) laws and regulations regarding handling of confidential information; (xix) our international operations; (xx) product related risks; (xxi) whether the objectives of the strategic review process will be achieved; (xxii) the terms, structure, benefits and costs of any strategic transaction; the timing of any transaction and whether any transaction will be consummated at all; (xxiii) the risk that the board review and its announcement could have an adverse effect on the our ability to retain and hire key personnel and maintain relationships with partners, suppliers, employees, shareholders and other business relationships and on its operating results and business generally; (xxiv) the risk the board review could divert the attention and time of our management; (xxv) the risk of any unexpected costs or expenses resulting from the review; and (xxvi) the risk of any litigation relating to the review. Disclosures 3
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© Onterris • 2Q26 Earnings • Forward-looking statements speak only as of the date on which they are made and we undertake no obligation to update any forward-looking statement to reflect future events, developments or otherwise, except as may be required by applicable law. Investors are referred to the Onterris filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the year ended December 31, 2025, as supplemented by its Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, for additional information regarding the risks and uncertainties that may cause actual results to differ materially from those expressed in any forward-looking statement. Included in this presentation and the accompanying oral presentation are certain financial measures that are not calculated in accordance with U.S. generally accepted accounting principles ("GAAP") designed to supplement and not substitute, the Onterris financial information presented in accordance with GAAP. The non-GAAP measures as defined by Onterris may not be comparable to similar non-GAAP measures presented by other companies. The presentation of such measures, which may include adjustments to exclude unusual or non-recurring items, should not be construed as an inference that future results, cash flows or leverage of Onterris will be unaffected by other unusual or nonrecurring items. Please see the Appendix to this presentation for how we define these non-GAAP measures, a discussion of why we believe they are useful to investors and certain limitations thereof, reconciliations for historical periods thereof to the most directly comparable GAAP measures and certain matters related to forward-looking non-GAAP information. The data included in this presentation regarding markets and the industry in which we operate, including the size of certain markets, are based on publicly available information, reports of government agencies and published industry sources such as Environmental Business International, Inc. (“EBI”). In presenting this information, we have also made certain estimates and assumptions that we believe to be reasonable based on the information referred to above and similar sources, as well as our internal research, calculations and assumptions based on our analysis of such information and our knowledge of and our experience to date in, our industries and markets. Market share data is subject to change and may be limited by the availability of raw data, the voluntary nature of the data gathering process and other limitations inherent in any statistical survey of market share data. In addition, customer preferences are subject to change. Accordingly, you are cautioned not to place undue reliance on such market share data or any other such estimates. While we believe such information is reliable, we cannot guarantee its accuracy or completeness. We have not independently verified third-party information, nor has any independent source verified data derived from our internal research. Disclosures 4
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© Onterris • 2Q26 Earnings • 5 Key Updates
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© Onterris • 2Q26 Earnings • Financial 2Q26 Highlights (comparisons to 2Q25) • 2Q26 revenue of $186.7M, a decrease of $47.9M, primarily due to historically low environmental emergency response and related recovery services • Consolidated Adjusted EBITDA1 as a percentage of revenue of 17.1% (Consolidated Adjusted EBITDA1 of $31.9 million), compared to 16.9% (Consolidated Adjusted EBITDA1 of $39.6 million) o Continued expansion of Consolidated Adjusted EBITDA1 as a % of revenue primarily due to successful ongoing cost optimization Capital Allocation & Balance Sheet • Repurchased 1.6M shares of common stock for $30.0M through 1H26 • Leverage of 3.2x as of June 30, 2026 2Q26 Financial Summary Despite Lower Revenue, Margin Improved 61) Non-GAAP Measure. See the Appendix to this presentation for a discussion of these non-GAAP measures and reconciliations, including certain matters with respect to guidance.
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© Onterris • 2Q26 Earnings • • Pass-through revenue (revenue generated on subcontractor and non-labor direct costs, PTR) in FY26 expected significantly below historical levels o FY26 expect lower PTR of $35M to $55M • Emergency response activity in FY26 remains significantly below historical levels o FY26 expect environmental emergency response revenue to be lower by $35M to $45M • Other impacts, such as temporary regulatory waivers for federal and state air permitting rules that remain promulgated o FY26 expect lower revenue by $15M to $25M • 3Q26: Expected revenue of $190M to $210M Updated FY26 Revenue Guidance $740M – $790M 7 Original Revenue Guidance Lower Pass Through Revenue Lower Emergency Response Revenue Other Revenue Impacts Revised Revenue Guidance FY26 Revenue Guidance* $740 to $790 $840 to $900 ($35) to ($55) ($35) to ($45) ($15) to ($25) ($ in millions)
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© Onterris • 2Q26 Earnings • Original Consol. Adj. EBITDA Guidance Impact of Lower Pass Through Revenue Impact of Lower Emergency Response Revenue Net of Other Revenue Impacts & Benefits of Cost Optimization Revised Consol. Adj. EBITDA Guidance FY26 Consol. Adj. EBITDA1 Guidance* • Expect 4th consecutive year of margin expansion o Expect Consol. Adj. EBITDA1 as a % of FY26 revenue of ~15.5% – 300+ bps increase since 2022 • Strong Operating & Free Cash Flow Outlook Largely Unchanged o Continue to expect FY26 OCF as a % of Consolidated Adjusted EBITDA¹ of ~60% – Above the long-term annual target of 50%+ • 3Q26: Expect 17% to 18% Consol. Adj. EBITDA1 as a % of 3Q26 revenue guidance midpoint FY26 Consol. Adj. EBITDA1 & Margin Expected to Exceed FY25 $117M - $120M 8 $117 to $120 $125 to $130 1) Non-GAAP Measure. See the Appendix to this presentation for a discussion of these non-GAAP measures and reconciliations, including certain matters with respect to guidance. *Changes in Consol. Adj. EBITDA approximated at the mid-point of the revenue ranges on the prior slide. Pass Through Revenue equals revenue generated from subcontractors and non-labor direct costs. ($ in millions) ($4.5) ($10.0) $5.5
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© Onterris • 2Q26 Earnings • Maintain Balance Sheet Strength • Expect to generate $70M to $80M in operating cash flow in 2H26 • Expect to end FY26 with leverage ~2.5x without acquisitions • Balanced approach to growth investments and shareholder returns Organic Investments • Prioritize high-return investments in proprietary technology, patents and R&D to expand applications and strengthen competitive advantages • Growth capital expenditures including geographic and capacity expansion to support growth 9 Capital Framework Share Repurchase Program • Repurchased 1.6 million shares of common stock for approximately $30.0M 1H26 Portfolio Optimization • Evaluating smaller, bolt-on and highly accretive acquisitions over the course of 2026, subject to valuation and leverage • Continue margin optimization
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© Onterris • 2Q26 Earnings • 10 Investment Highlights Large TAM and secular tailwinds backed by regulatory and corporate initiatives Patent protected technology provides significant competitive advantages in a highly fragmented industry International reach and diverse customer base support recurring revenue and cross-selling upside Strong organic growth coupled with opportunistic accretive acquisitions Strong balance sheet, demonstrated cash flow generation & path to margin enhancement Experienced management team & client-centric culture Consistent financial performance across political and economic cycles Uniquely integrated across environmental services consulting, testing and treatment
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2Q26 and 1H26 Segment Results
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© Onterris • 2Q26 Earnings • 12 Consulting & Treatment Segment 2Q26 Performance $171.7 $125.6 Revenue 2Q26 2Q25 Growth in Consulting Services offset by Historically Low Environmental Emergency Response Revenue • 2Q26 Revenue of $125.6M compared to $171.7M in 2Q25 o Consulting growth of $3.5M, was more than offset by: o Lower emergency response revenue ($37.7M), lower recovery services associated with environmental events ($11.2M), and operations exited or wound down by the end of FY25 ($1.9M) (Compared to 2Q25) Segment Adjusted EBITDA Lower, Margins Stable • 2Q26 Segment Adj. EBITDA of $27.9M and margin of 22.2%, compared to $37.6M and 21.9%. • Margin expansion due to project mix & improved operational efficiency 2Q Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) $37.6 $27.9 Segment Adjusted EBITDA 2Q26 2Q25 21.9% 22.2% Note: For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 19 to our consolidated financial statements included in our Form 10-Q for the periods ended June 30, 2026, and March 31, 2026. Prior period amounts have been recast to reflect resegmentation.
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© Onterris • 2Q26 Earnings • 13 Consulting & Treatment Segment 1H26 Performance 275 $290.6 $240.2 Revenue 1H26 1H25 Growth in Consulting Services offset by Historically Low Environmental Emergency Response Revenue • 1H26 Revenue of $240.2M compared to $290.6M o Consulting growth of $4.6M, was more than offset by o Decline driven by lower environmental response revenues ($43.5M), reduced recovery services revenue ($6.1M), and impact of operations exited or wound down by the end of FY25 ($3.5M) (Compared to 1H25) Segment Adjusted EBITDA Lower, Margins Stronger • 1H26 Segment Adj. EBITDA of $48.0M and margin of 20.0%, compared to $54.1M and 18.6% • 140 basis-point margin expansion was driven by significantly higher margins in consulting and water treatment 1H Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) 40 $54.1 $48.0 Segment Adjusted EBITDA 1H26 1H25 18.6% 20.0% Note: For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 19 to our consolidated financial statements included in our Form 10-Q for the periods ended June 30, 2026, and March 31, 2026. Prior period amounts have been recast to reflect resegmentation.
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© Onterris • 2Q26 Earnings • 14 Measurement & Analysis Segment 2Q26 Performance 100 $62.8 $61.1 Revenue 2Q26 2Q25 Normalize 2Q Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) Lab Testing Growth offset by Field Service Decline • 2Q26 Revenue of $61.1M compared to $62.8M, primarily due to o Lab testing increase was offset by decline in field services (Compared to 2Q25) 40 $18.3 $16.0 Segment Adjusted EBITDA 2Q26 2Q25 Normalize 29.1% 26.2% Strong Margin Continues • 2Q26 Segment Adj. EBITDA of $16.0M and margin of 26.2%, compared to $18.3M and 29.1% o Margin normalization was expected and margin remains strong o Margin change reflects project mix and lower operating leverage resulting from lower 2Q26 revenue Note: For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 19 to our consolidated financial statements included in our Form 10-Q for the periods ended June 30, 2026, and March 31, 2026. Prior period amounts have been recast to reflect resegmentation.
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© Onterris • 2Q26 Earnings • 15 Measurement & Analysis Segment 1H26 Performance Note: For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 19 to our consolidated financial statements included in our Form 10-Q for the periods ended June 30, 2026, and March 31, 2026. Prior period amounts have been recast to reflect resegmentation. $121.8 $115.0 Revenue 1H26 1H25 Normalize 1H Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) Revenue Reflects 1Q26 Weather Impact • 1H26 Revenue of $115.0M compared to $121.8M, primarily due to o Decrease in field services revenue of $7.7M, which included impact of 1Q26 adverse weather conditions ($3.5M) (Compared to 1H25) 40 $32.1 $25.9 Segment Adjusted EBITDA 1H26 1H25 Normalize 26.3% 22.5% Margin Remains Healthy on Lower Revenue • 1H26 Segment Adj. EBITDA of $25.9M and margin of 22.5%, compared to $32.1M and 26.3% o Margin normalization was expected and margin remains strong o Margin change reflects project mix and lower operating leverage resulting from reduced 1H26 revenue
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Appendix
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© Onterris • 2Q26 Earnings • Brand and Resegmentation: On April 17, 2026, Montrose Environmental Group, Inc. rebranded to Onterris, Inc. Beginning in the first quarter of 2026, the Company realigned its reportable segments to reflect updates made to the organizational structure and operating model. The Company's rebranding is intended to strengthen cross-functional collaboration, improve cross-selling opportunities, and optimize labor utilization. As a result of the reporting segment realignment, the Company's Assessment, Permitting and Response and Remediation and Reuse segments were aggregated into a newly created Consulting and Treatment segment. The Company's Measurement and Analysis and corporate segments were not affected by the realignment. In addition to our results under GAAP, in this presentation we also present certain other supplemental financial measures of financial performance that are not required by, or presented in accordance with, GAAP, including, Consolidated Adjusted EBITDA, Consolidated Adjusted EBITDA margin, Adjusted Net Income, Diluted Adjusted Net Income per Share and Free cash flow. We calculate Consolidated Adjusted EBITDA as net income (loss) before interest expense, income tax expense (benefit) and depreciation and amortization, adjusted for the impact of certain other items, including stock-based compensation expense and acquisition-related costs, as set forth in greater detail in this Appendix. We calculate Consolidated Adjusted EBITDA margin as Consolidated Adjusted EBITDA divided by revenue. We calculate Adjusted Net Income as net income (loss) before amortization of intangible assets, stock-based compensation expense, fair value changes to financial instruments and contingent earnouts and other gain or losses, as set forth in greater detail in this Appendix. Diluted Adjusted Net Income per share represents Adjusted Net Income attributable to stockholders divided by the fully diluted number of shares of common stock outstanding during the applicable period. Free cash flow is defined as net cash provided by (used in) operating activities plus net cash used in investing activities, adjusted for the impact of certain other items, including contingent consideration and other purchase price true ups, minority investments and cash paid for acquisitions, net of cash acquired; and, dividend payments to the Series A-2 holders. Consolidated Adjusted EBITDA is one of the primary metrics used by management to evaluate our financial performance and compare it to that of our peers, evaluate the effectiveness of our business strategies, make budgeting and capital allocation decisions and in connection with our executive incentive compensation. Adjusted Net Income and Diluted Adjusted Net Income per Share are useful metrics to evaluate ongoing business performance after interest and tax. These measures are also frequently used by analysts, investors and other interested parties to evaluate companies in our industry. Further, we believe they are helpful in highlighting trends in our operating results because they allow for more consistent comparisons of financial performance between periods by excluding gains and losses that are non-operational in nature or outside the control of management and, in the case of Consolidated Adjusted EBITDA, by excluding items that may differ significantly depending on long-term strategic decisions regarding capital structure, the tax jurisdictions in which we operate and capital investments. Free cash flow is used by management as one of the means by which it assesses cash generation in excess of ongoing capital needs of the business. These non-GAAP measures do, however, have certain limitations and should not be considered as an alternative to net income (loss), earnings (loss) per share or any other performance measure derived in accordance with GAAP. Our presentation of Consolidated Adjusted EBITDA, Adjusted Net Income and Diluted Adjusted Net Income per Share should not be construed as an inference that our future results will be unaffected by unusual or non-recurring items for which we may make adjustments. In addition, Consolidated Adjusted EBITDA, Adjusted Net Income and Diluted Adjusted Net Income per Share may not be comparable to similarly titled measures used by other companies in our industry or across different industries and other companies may not present these or similar measures. Non-GAAP Financial Information 17
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© Onterris • 2Q26 Earnings • Management compensates for these limitations by using these measures as supplemental financial metrics and in conjunction with our results prepared in accordance with GAAP. We encourage investors and others to review our financial information in its entirety, not to rely on any single measure and to view Consolidated Adjusted EBITDA, Adjusted Net Income and Diluted Adjusted Net Income per Share in conjunction with the related GAAP measures. Free cash flow has certain limitations and should not be considered as an alternative to or in isolation from net cash provided by (used in) operating activities or any other liquidity measure calculated in accordance with GAAP. In evaluating Free cash flow, you should be aware that Free cash flow does not represent residual cash flow available for discretionary expenditures. Additionally, we have provided estimates regarding Consolidated Adjusted EBITDA for 2026. These projections account for estimates of revenue, operating margins and corporate and other costs. However, we cannot reconcile our projection of Consolidated Adjusted EBITDA to net income (loss), the most directly comparable GAAP measure, without unreasonable efforts because of the unpredictable or unknown nature of certain significant items excluded from Consolidated Adjusted EBITDA and the resulting difficulty in quantifying the amounts thereof that are necessary to estimate net income (loss). Specifically, we are unable to estimate for the future impact of certain items, including income tax (expense) benefit, stock- based compensation expense and fair value changes. We expect the variability of these items could have a significant impact on our reported GAAP financial results. In this presentation we also reference our organic growth. We define organic growth as the change in revenues excluding revenues from i) our environmental emergency response business, ii) acquisitions for the first twelve months following the date of acquisition and iii) businesses held for sale, disposed of or discontinued. Management uses organic growth as one of the means by which it assesses our results of operations. Organic growth is not, however, a measure of revenue growth calculated in accordance with U.S. generally accepted accounting principles, or GAAP and should be considered in conjunction with revenue growth calculated in accordance with GAAP. We have grown organically over the long term and expect to continue to do so. In a given reporting period, when we refer to revenue changes driven by acquisitions, we are referring to the revenue contribution from any acquisition from its closing date through the first 12 months of that acquisition, at which point any subsequent contribution therefrom would be organic. Client recurring revenue defined as the percentage of revenue from clients in a given year that recurred in the next year, excluding environmental emergency response revenue and revenue from acquisitions in either year. Emergency environmental response revenue is excluded from the calculation in light of episodic nature of emergency response work. Cross-selling activity defined as the percentage of total revenue from customers purchasing two or more Onterris services within the same fiscal year. Cross-selling excludes acquisition revenue in the first-year post closing. Net Service Revenue represents revenue from our labor services and is calculated as revenues less subconsultants and non-labor direct costs. Non-GAAP Financial Information (Continued) 18
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© Onterris • 2Q26 Earnings • 1) Represents non-cash stock-based compensation expenses related to option awards issued to employees and restricted stock grants issued to directors and selected employees. 2) Includes financial and tax diligence, consulting, legal, valuation, accounting and travel costs and acquisition-related incentives related to our acquisition activity, including direct costs of integration. 3) Amounts for the three and six months ended June 30, 2026 relate to the change in fair value of the interest rate swap instruments. Amounts for the three and six months ended June 30, 2025 relate to the change in fair value of the interest rate swap instruments and the embedded derivative attached to the Series A-2 preferred stock. 4) Amounts reflect the difference between the expected settlement value of acquisition related earn-out payments at the beginning of the relevant period and the expected (or actual) value of earn-outs at the end of the relevant period. 5) Amounts for the three and six months ended June 30, 2026 consist primarily of severance costs related to organizational restructuring of business lines within the Company's former Assessment, Permitting and Response and Remediation and Reuse segments and IT migration costs. Amounts for the three and six months ended June 30, 2025 consist primarily of non-recurring costs incurred to restructure the Company's renewable energy business, third party expenses associated with the independent review and analysis of assertions in a short seller report regarding the Company, and costs to centralize certain back-office functions. 6) The Company applied the estimated effective tax rate on portions of the adjustments related to our significant foreign entities, and determined the US portion of the adjustments do not have any tax impact since we are in a full deferred tax asset valuation allowance as of June 30, 2026. 7) Represents Adjusted Net Income attributable to stockholders divided by the weighted average number of shares of common stock outstanding. 8) Represents Adjusted Net Income attributable to stockholders divided by fully diluted number of shares of common stock. Onterris, Inc. Reconciliation of Net Income (Loss) to Adjusted Net Income 19 Three Months Ended June 30, Six Months Ended June 30, 2026 2025 2026 2025 Net income (loss) $ 1,366 $ 18,356 $ (11,324) $ (1,003) Amortization of intangible assets 6,662 7,326 13,336 15,716 Stock-based compensation(1) 9,618 10,834 18,691 24,557 Acquisition costs(2) 137 325 218 1,036 Fair value changes in financial instruments(3) (532) (9,256) (1,242) (8,040) Fair value changes in business acquisition contingencies(4) 141 354 (697) 831 Rebranding expenses 1,422 — 2,523 — Other losses and expenses(5) 1,207 453 2,615 1,485 Tax effect of adjustments(6) (460) (1,018) 1,354 (1,873) Adjusted Net Income $ 19,561 $ 27,374 $ 25,475 $ 32,709 Preferred dividends Series A-2 — (1,400) — (4,150) Adjusted Net Income attributable to stockholders $ 19,561 $ 25,974 $ 25,474 $ 28,559 Net Income (Loss) per share attributable to stockholders $ 0.04 $ 0.48 $ (0.32) $ (0.15) Basic Adjusted Net Income per share(7) $ 0.55 $ 0.74 $ 0.71 $ 0.82 Diluted Adjusted Net Income per share(8) $ 0.51 $ 0.60 $ 0.65 $ 0.64 Weighted average common shares outstanding 35,806 35,206 35,926 34,855 Fully diluted shares 38,714 43,455 38,984 44,664
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© Onterris • 2Q26 Earnings • Onterris, Inc. Reconciliation of Net Income (Loss) to Consolidated Adjusted EBITDA 1) Represents non-cash stock-based compensation expenses related to option awards issued to employees and restricted stock grants issued to directors and selected employees. 2) Includes financial and tax diligence, consulting, legal, valuation, accounting and travel costs and acquisition-related incentives related to our acquisition activity, including direct costs of integration. 3) Amounts for the three and six months ended June 30, 2026 relate to the change in fair value of the interest rate swap instruments. Amounts for the three and six months ended June 30, 2025 relate to the change in fair value of the interest rate swap instruments and the embedded derivative attached to the Series A-2 preferred stock. 4) Reflects the difference between the expected settlement value of acquisition related earn-out payments at the beginning of the relevant period and the expected (or actual) value of earn-outs at the end of the relevant period. 5) Amounts for the three and six months ended June 30, 2026 consist primarily of severance costs related to organizational restructuring of business lines within the Company's former Assessment, Permitting and Response and Remediation and Reuse segments and IT migration costs. Amounts for the three and six months ended June 30, 2025 consist primarily of non-recurring costs incurred to restructure the Company's renewable energy business, third-party expenses associated with the independent review and analysis of assertions in a short seller report regarding the Company, and costs to centralize certain back-office functions. 20 Three Months Ended June 30, Six Months Ended June 30, 2026 2025 2026 2025 Net income (loss) $ 1,366 $ 18,356 $ (11,324) $ (1,003) Interest expense 5,471 4,768 10,937 9,833 Income tax expense 346 988 2,649 3,859 Depreciation and amortization 12,704 12,763 25,333 26,057 EBITDA $ 19,887 $ 36,875 $ 27,595 $ 38,746 Stock-based compensation(1) 9,618 10,834 18,691 24,557 Acquisition costs(2) 137 325 218 1,036 Fair value changes in financial instruments(3) (532) (9,256) (1,242) (8,040) Fair value changes in business acquisition contingencies(4) 141 354 (697) 831 Rebranding expenses 1,422 — 2,523 — Other losses and expenses(5) 1,207 453 2,615 1,485 Consolidated Adjusted EBITDA $ 31,880 $ 39,585 $ 49,703 $ 58,615
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© Onterris • 2Q26 Earnings • Onterris, Inc. Reconciliation of Revenue to Net Service Revenue 21 For the Three Months Ended June 30, For the Six Months Ended June 30, 2026 2025 2026 2025 Revenue $ 186,661 $ 234,543 $ 355,179 $ 412,377 Subconsultants and non-labor direct costs (36,178) (63,007) (66,831) (101,605) Net Service Revenue $ 150,483 $ 171,536 $ 288,348 $ 310,772
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© Onterris • 2Q26 Earnings • Adrianne D. Griffin Senior Vice President, Investor Relations & Treasury ir@onterris.com • Book a meeting +1 949.988.3383 Our innovative solutions and integrated expertise deliver stronger environmental compliance and performance, generating new value for stakeholders and securing a better future for clients, communities and the ecosystems we all depend on. Thank you for supporting our mission. For more information, visit ir.onterris.com . Connect with our dedicated Investor Relations specialist to turn opportunity into action. Investing for Planet & Progress 22
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© Onterris • 2Q26 Earnings • Thank You 23