Business Description

1. DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION Description of the Business —Montrose Environmental Group, Inc. ("Montrose" or the "Company") is a corporation formed on November 2013 , under the laws of the State of Delaware. The Company has approximately 120 offices across the United States, Canada, and Australia and approximately 3,500 employees as of December 31, 2025. Montrose is an environmental services company serving the recurring environmental needs of a diverse client base, including Fortune 500 companies and federal, state and local governments through the following three segments: Assessment, Permitting and Response segment provides scientific advisory and consulting services to support environmental assessments, environmental emergency response and recovery, toxicology consulting and environmental audits and permits for current operations, facility upgrades, new projects, decommissioning projects and development projects. The Company works closely with clients to navigate the regulatory process at the local, state, provincial and federal levels, to identify the potential environmental and political impacts of their decisions and develop practical mitigation approaches, as needed. In addition to environmental toxicology and given the Company's expertise in helping businesses plan for and respond to disruptions, the Company's scientists and response teams have helped clients navigate their preparation for and response to emergency response situations. Measurement and Analysis segment is one of the largest providers of environmental testing and laboratory services in North America. The Company's highly credentialed teams test and analyze air, water and soil to determine concentrations of contaminants, as well as the toxicological impact of contaminants on flora, fauna and human health. The Company's offerings include source and ambient air testing and monitoring, leak detection, and advanced multi-media laboratory services, including air, soil, stormwater, wastewater and drinking water analysis. Remediation and Reuse segment provides clients with engineering, design, and implementation services, primarily to treat contaminated water and remove contaminants from soil. The Company's team, including engineers, scientists and consultants, provides these services to assist clients in designing solutions, managing products and mitigating environmental risks and liabilities at their locations. The Company does not own the properties or facilities at which it implements these projects or the underlying liabilities, nor does the Company own material amounts of the equipment used in projects. Basis of Presentation —The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP). Intercompany balances and transactions are eliminated. Reclassifications— Certain prior year amounts, which are not material, have been reclassified to conform to current year presentation in the consolidated statements of cash flows and notes to the consolidated financial statements.