Earth Tech was founded in 1970 when its primary focus was geotechnical engineering. In the 1980's the company's services expanded to include the environmental services market. Entering the 1990s, Earth Tech was recognised as one of the leading providers of environmental, earth sciences, and waste management consulting. In 1996 Earth Tech became a wholly owned subsidiary of Tyco International Ltd, a public traded, worldwide service provider and manufacturer.

As Earth Tech focused on expansion a number of highly specialised and well-regarded engineering, construction and environmental firms were brought together. These acquired companies have added important technical capabilities and strengthen existing ones, including engineering, remediation, construction, contract operations and management, air quality management, water and wastewater engineering, solid waste management.