Tetra Tech Inc. on Wednesday said it reached an agreement to buy the U.S.-based international development consulting business practice of PA Consulting Group., a London company.

The Pasadena construction services provider said the unit provides international energy and infrastructure consulting services, and would roughly double its energy management consulting business. The 125 PA employees in the unit, which is based in Arlington, Va. and has offices in Madison, Wis., will become part of the company’s technical support services division.

Terms of the deal were not disclosed. Tetra Tech expects to close the deal in the fourth quarter.

In a separate announcement, the company said its Tetra Tech/Mead & Hunt joint venture was awarded a $95 million contract to provide architectural and engineering services to the National Guard Bureau at Air National Guard and Army National Guard locations across the United States and its territories.

Shares were down 10 cents, or less than a percent, to $18.75 in midday trading on the Nasdaq.