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November 5, 2026 2026 Earnings: 3Q Results
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© Onterris • 3Q26 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. • Our third-quarter results demonstrate meaningful progress against our commitments. We delivered higher Adjusted EBITDA1, a record quarterly Consolidated Adjusted EBITDA1 margin, and stronger cash generation despite lower reported revenue. Growth in core consulting and treatment, improved project execution and cost discipline are strengthening the underlying earnings power of Onterris. 3Q26 Results Vijay Manthripragada President & Chief Executive Officer 21) 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 • 3Q26 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) whether the objectives of the strategic review process will be achieved; (xxi) the terms, structure, benefits and costs of any strategic transaction; the timing of any transaction and whether any transaction will be consummated at all; (xxii) the risk that the board review and its announcement could have an adverse effect on 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; (xxiii) the risk the board review could divert the attention and time of our management; (xxiv) the risk of any unexpected costs or expenses resulting from the review; and (xxv) the risk of any litigation relating to the review. Disclosures 3
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© Onterris • 3Q26 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. 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 • 3Q26 Earnings • 5 Key Updates
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© Onterris • 3Q26 Earnings • Core Business Momentum Revenue growth in core consulting & treatment, together with higher environmental emergency response activity, were partially offset by lower recovery services revenue associated with a prior-year large-scale emergency response Improved Operating Performance Improved project execution, favorable business mix and cost discipline strengthen profitability Delivering Against Commitments 3Q26 results were consistent with financial expectations communicated in August 2026. Reiterated FY26 guidance midpoints represent at least 150 bps of margin expansion compared with 2025. 3Q26: Record Quarterly Margin and Strong Cash Generation Higher profitability and disciplined execution despite lower reported revenue 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. Revenue $203.0M, -9.7% Net Service Revenue1 $162.5M, +1.2% Consolidated Adj. EBITDA1 $35.9M, +6.7% Consolidated Adj. EBITDA1 as a % of: (a) Revenue 17.7%, +270 bps (b) Net Service Revenue1 22.1%, +110 bps Operating Cash Flow $40.9M, +46% Consolidated Financial Highlights 3Q26 vs 3Q25
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© Onterris • 3Q26 Earnings • Balance Sheet Strength Supports Disciplined Capital Allocation Lower leverage and strong liquidity provide flexibility to pursue targeted acquisitions 7 Leverage Ratio2.9x Ambient Air Monitoring Expansion Expanded presence in Colorado, creating cross- selling opportunities with existing clients Balance Sheet Strength (as of 9/30/26) 3 Strategic Tuck-In Transactions in 2H26 EcOz Environmental Consultants Established presence in Australia’s Northern Territory & expanded consulting capabilities Permian Basin Environmental Lab Strengthened analytical capabilities in Midland, Texas, complementing our newly constructed Houston Lab Total Available Liquidity$192.0M From 3.2x at 6/30/26 $20.1M Cash $171.9M Revolver availability Expect ~2.5x at FYE26, inclusive of recent acquisitions
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© Onterris • 3Q26 Earnings • 8 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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3Q26 and YTD26 Segment Results
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© Onterris • 3Q26 Earnings • 10 Consulting & Treatment Segment 3Q26 Performance Revenue Comparison Reflects Prior-Year Event • 3Q26 Revenue of $142.0M compared to $161.9M in 3Q25 o Prior-year quarter included $45.4M of revenue associated with a single environmental emergency response o Core consulting revenue increased $5.9M, environmental emergency response revenue increased $5.5M, and treatment revenue increased $3.8M, partially offsetting lower recovery services associated with the prior-year event (Compared to 3Q25) Segment Adjusted EBITDA Higher, Margins Expand • 3Q26 Segment Adj. EBITDA of $30.8M and margin of 21.7%, compared to $29.8M and 18.4% o 330 bps of margin expansion driven by operating efficiencies, favorable project mix including higher consulting and water treatment margins, and the absence of losses from the exited renewables business 3Q Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) 18.4% 21.7% 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 period ended September 30, 2026. Prior period amounts have been recast to reflect resegmentation. 275 $161.9 $142.0 Revenue 3Q26 3Q25 Normalize 40 $29.8 $30.8 Segment Adjusted EBITDA 3Q26 3Q25 18.4% 21.7%
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© Onterris • 3Q26 Earnings • 11 Consulting & Treatment Segment YTD 2026 Performance 275 $452.5 $382.2 Revenue YTD 2026 YTD 2025 Normalize Revenue Comparison Reflects Prior-Year Event, Partially Offset by Core Consulting Growth • YTD 2026 Revenue of $382.2M compared to $452.5M o Prior-year period included $99.0M of revenue from a single environmental event, comprising $53.2M of emergency response revenue and $45.8M of recovery services revenue o Excluding the prior-year single event, core consulting revenue increased $10.6M, driven by growth in the U.S. and Australia (Compared to YTD 2025) Segment Adjusted EBITDA Lower, Margins Stronger • YTD 2026 Segment Adj. EBITDA of $78.9M and margin of 20.6%, compared to $83.9M and 18.5% • 210 bps margin expansion reflected higher consulting and water treatment margins, driven by project mix, improved operational efficiency and the absence of prior-year renewables losses YTD Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) 40 $83.9 $78.9 Segment Adjusted EBITDA YTD 2026 YTD 2025 18.5% 20.6% 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 period ended September 30, 2026. Prior period amounts have been recast to reflect resegmentation.
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© Onterris • 3Q26 Earnings • 12 Measurement & Analysis Segment 3Q26 Performance 100 $63.0 $61.1 Revenue 3Q26 3Q25 Normalize 3Q Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) Revenue Decline of $1.9M, or 3.0% • 3Q26 Revenue decline primarily due to lower field services more than offsetting the increase in lab services revenue (Compared to 3Q25) 40 $17.3 $16.0 Segment Adjusted EBITDA 3Q26 3Q25 27.5% 26.1% Lower Revenue and Project Mix Impact Margins • 3Q26 Segment Adj. EBITDA of $16.0M, or 26.1% margin, compared to $17.3M, or 27.5% o Modestly lower profitability reflected 3Q26 project mix o 3Q26 margin of 26.1% remains among industry leading 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 period ended September 30, 2026 Prior period amounts have been recast to reflect resegmentation.
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© Onterris • 3Q26 Earnings • 13 Measurement & Analysis Segment YTD 2026 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 period ended September 30, 2026 Prior period amounts have been recast to reflect resegmentation. $184.8 $176.1 Revenue YTD 2026 YTD 2025 YTD Revenue and Segment Adj. EBITDA ($ in millions, % as a percent of segment revenue) Revenue Decline Driven by Lower Field Services Revenue • YTD 2026 Revenue of $176.1M compared to $184.8M o Decline primarily reflected a $9.6M decrease in field testing revenue, including the impact of 1Q26 adverse weather conditions, and certain federal and temporary regulatory waivers affecting parts of the air testing business (Compared to YTD 2025) 40 $49.4 $41.9 Segment Adjusted EBITDA YTD 2026 YTD 2025 26.7% 23.8% Lower Revenue and Project Mix Impact Margins • YTD 2026 Segment Adj. EBITDA of $41.9M and margin of 23.8%, compared to $49.4M and 26.7% o Lower profitability reflected project mix o Margin of 23.8% remains among industry leading
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Appendix
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© Onterris • 3Q26 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, and Diluted Adjusted Net Income per Share. 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. 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. 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 15
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© Onterris • 3Q26 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. 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) 16
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© Onterris • 3Q26 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 nine months ended September 30, 2026 relate to the change in fair value of the interest rate swap instruments. Amounts for the three and nine months ended September 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) Proceeds from a representations and warranties insurance settlement related to a previously completed acquisition. 6) Amount for the three months ended September 30, 2026 consists primarily of third- party costs associated with a global IT migration and expenses associated with the Board-led strategic review. Amount for the nine months ended September 30, 2026 consists 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, third-party costs associated with a global IT migration, and expenses associated with the Board-led strategic review. Amount for the three months ended September 30, 2025 consists primarily of severance costs. Amount for the nine months ended September 30, 2025 consists primarily of the aforementioned severance costs, 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. 7) 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 September 30, 2026. 8) Represents Adjusted Net Income attributable to stockholders divided by the weighted average number of shares of common stock outstanding. 9) 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 17 Three Months Ended September 30, Nine Months Ended September 30, 2026 2025 2026 2025 Net income (loss) $ 8,986 $ 8,378 $ (2,338) $ 7,375 Amortization of intangible assets 6,331 7,275 19,667 22,991 Stock-based compensation(1) 9,733 9,220 28,424 33,777 Acquisition costs(2) 151 754 369 1,790 Fair value changes in financial instruments(3) (1,031) (10,354) (2,273) (18,394) Fair value changes in business acquisition contingencies(4) — 13 (697) 844 Rebranding expenses 587 — 3,110 — Proceeds from insurance settlement related to business combination(5) (3,700) — (3,700) — Other losses and expenses(6) 741 372 3,356 1,857 Tax effect of adjustments(7) (456) (1,446) (12,749) (5,255) Adjusted Net Income $ 21,342 $ 14,212 $ 33,169 $ 44,985 Preferred dividends Series A-2 — — — (4,150) Adjusted Net Income attributable to stockholders $ 21,342 $ 14,212 $ 33,169 $ 40,835 Net Income (Loss) per share attributable to stockholders $ 0.26 $ 0.24 $ (0.07) $ 0.09 Basic Adjusted Net Income per share(8) $ 0.61 $ 0.40 $ 0.93 $ 1.17 Diluted Adjusted Net Income per share(9) $ 0.56 $ 0.36 $ 0.86 $ 1.03 Weighted average common shares outstanding 35,132 35,300 35,661 35,003 Fully diluted shares 38,033 39,935 38,673 39,547
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© Onterris • 3Q26 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 nine months ended September 30, 2026 relate to the change in fair value of the interest rate swap instruments. Amounts for the three and nine months ended September 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) Proceeds from a representations and warranties insurance settlement related to a previously completed acquisition. 6) Amount for the three months ended September 30, 2026 consists primarily of third-party costs associated with a global IT migration and expenses associated with the Board-led strategic review. Amount for the nine months ended September 30, 2026 consists 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, third-party costs associated with a global IT migration, and expenses associated with the Board-led strategic review. Amount for the three months ended September 30, 2025 consists primarily of severance costs. Amount for the nine months ended September 30, 2025 consists primarily of the aforementioned severance costs, 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. 18 Three Months Ended September 30, Nine Months Ended September 30, 2026 2025 2026 2025 Net income (loss) $ 8,986 $ 8,378 $ (2,338) $ 7,375 Interest expense 5,564 5,039 16,501 14,872 Income tax expense 2,273 7,281 4,922 11,140 Depreciation and amortization 12,599 12,958 37,932 39,015 EBITDA $ 29,422 $ 33,656 $ 57,017 $ 72,402 Stock-based compensation(1) 9,733 9,220 28,424 33,777 Acquisition costs(2) 151 754 369 1,790 Fair value changes in financial instruments(3) (1,031) (10,354) (2,273) (18,394) Fair value changes in business acquisition contingencies(4) — 13 (697) 844 Rebranding expenses 587 — 3,110 — Proceeds from insurance settlement related to business combination(5) (3,700) — (3,700) — Other losses and expenses(6) 741 372 3,356 1,857 Consolidated Adjusted EBITDA $ 35,903 $ 33,661 $ 85,606 $ 92,276
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© Onterris • 3Q26 Earnings • Onterris, Inc. Reconciliation of Revenue to Net Service Revenue 19 For the Three Months Ended September 30, For the Nine Months Ended September 30, 2026 2025 2026 2025 Revenue $ 203,044 $ 224,888 $ 558,223 $ 637,265 Subconsultants and non-labor direct costs, including intercompany (46,307) (67,247) (113,114) (168,851) Intercompany portion of subconsultants and non-labor direct costs 5,762 2,842 12,642 9,530 Net Service Revenue $ 162,499 $ 160,483 $ 457,751 $ 477,944
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© Onterris • 3Q26 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 20
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© Onterris • 3Q26 Earnings • Thank You 21