Clark Seif Clark, Inc. (CSC), a part of J.S. Held
Environmental ServicesCalifornia, United States11-50 Employees
Clark Seif Clark, Inc. (CSC) is an environmental services firm whose work centers on environmental consulting and industrial hygiene, with particular emphasis on indoor environmental quality and the regulatory aspects of soils and groundwater. Its services cover investigations, project monitoring, remediation closure testing, bid management, litigation support, and expert testimony for a diverse client base. Based in Chatsworth, Southern California, CSC serves clients nationwide and operates multiple offices, offering around-the-clock response for scheduled or emergency engagements. Its expertise spans a broad set of environmental concerns, including asbestos, mold, mercury, lead-based paint, and other hazards, and it serves property managers, insurers, hospitals, schools and universities, attorneys, construction firms, and state or municipal agencies. In May 2026, CSC was acquired by J.S. Held, situating its environmental consulting and industrial hygiene capabilities within the broader platform of the acquiring firm.