[citation needed] In 1977 Tetra Tech offered common stock on the American Stock Exchange and used this capital to expand its services, from developing methods to predict the level and frequency of floods and causes of acid rain to environmental impact studies of gas pipeline construction and installing Hydro Products equipment for the United States Navy.

[9] As part of the Company's anniversary it launched the Global Clean Water Fund grant program in partnership with Engineers Without Borders.

[11] The remainder of the decade to 2014 involved growth by acquiring firms in Canada, Australia, and South America in its core (water and infrastructure) and new markets (mining and energy).

These new acquisitions focused on implementing sustainable strategies for water, energy, and the environment in Africa, Asia, and South America and facilitating stability and growth in countries in the aftermath of social conflicts or failed governing institutions.

[15] In February 2021 Tetra Tech acquired Coanda Research and Development Corporation, a Canadian engineering consulting company specializing in computational fluid dynamics, physical and predictive modeling, data analytics, process engineering, analytical chemistry, and instrument development.

[18] In July 2021 Tetra Tech acquired UK-based Hoare Lea, a sustainable engineering design firm.

[20] In February 2024 Tetra Tech announced the acquisition of LS Technologies, a Fairfax Virginia based contracting firm.

Tetra Tech CEO Dan Batrack said, “We believe that any concerns can be directly addressed by actually re-testing and analyzing the areas in question.”[29] In May 2018, two former supervisors involved in the cleanup of radioactive contaminants at the old Hunters Point Naval Shipyard pleaded guilty to falsifying soil sample results.

[30] In January 2019, the U.S. Justice Department sued Tetra Tech, accusing the engineering company of submitting false billing claims to the U.S. Navy that were based on falsified soil and building test data.

In July 2019, the San Francisco Office of Community Investment and Infrastructure Commission approved initial plans for the construction of more homes at Hunters Point Naval Shipyard, citing the California Department of Public Health’s certification that the area is clean and safe for residents.