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Onterris, Inc. operates as an environmental services company in the United States, Australia, Canada, and internationally. It operates in three segments: Assessment, Permitting and Response; Measurement and Analysis; and Remediation and Reuse. The company offers 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. It also provides environmental testing and laboratory services, including source and ambient air testing and monitoring, leak detection, and advanced multi-media laboratory services, including air, soil, stormwater, wastewater and drinking water analysis; and engineering, design, and implementation services comprising treatment technologies which treat contaminated water or soil remediation. The company serves oil and gas, utilities, local, state, provincial and federal government entities, technical services, industrial manufacturing, transportation, chemicals, renewable energy generation, telecommunications, and engineering industries. The company was formerly known as Montrose Environmental Group, Inc. and changed its name to Onterris, Inc. in May 2026. The company was founded in 2012 and is headquartered in North Little Rock, Arkansas.