PASADENA, CALIF. — Tetra Tech, Inc. has signed a definitive agreement to purchase the U.S.-based international development consulting business practice from London-headquartered PA Consulting Group (PA). Tetra Tech intends to acquire the portions of PA that focus on international energy and infrastructure consulting services, a practice that generates about $35 million of annual revenue. Tetra Tech plans to close the transaction during the fourth quarter of its fiscal 2010. The terms of the acquisition were not disclosed.

This transaction will add about 125 employees to Tetra Tech’s Technical Support Services segment. It will double Tetra Tech’s energy management consulting business, expanding Tetra Tech’s customer base with key utilities and government agencies and adding technical skills in utility performance improvement, market research, and modeling. About half of the business serves the U.S. Agency for International Development, focusing on energy sector reform, regulation, and utility performance improvement in emerging economies.