L.A. engineering firm Psomas has returned to growth mode, acquiring Irvine environmental firm BonTerra Consulting.

BonTerra offers consulting and engineering services to developers and the acquisition is further evidence of the real estate industry’s recovery.

Under the deal announced late last week, the new firm will move its headquarters to Psomas’ downtown L.A. office, but not right away. BonTerra will keep its name for a few years and during that time will maintain its offices in Irvine and Pasadena.

Prior to the acquisition, which closed Dec. 31, Psomas had roughly 415 employees and BonTerra just over 60. Both firms are privately held.

Psomas Chief Executive Blake Murillo told the Business Journal last week that this deal marks Psomas’ return to acquisition mode. Between 2003 and 2006, it bought six firms; among them Daniel Boyle Engineering Inc. of Laguna Hills and MMLA of Tucson, Ariz. Then the housing bust and recession hit, and the company put growth plans on hold.

“With the real estate market picking up again, we’re back in growth mode,” he said.

Murillo said BonTerra will strengthen his company’s expertise in preparing detailed environmental impact reports.

“It adds a new skill set for us,” he said. “We can expand our services in the preconstruction phases of project planning, impact assessment, and natural and cultural re-sources evaluation.”

According to its website, BonTerra has a bench of experts that can weigh in on environmental impact reports for major projects in nonurban settings. The experts include ornithologists, restoration ecologists and paleontologists. For example, BonTerra recently started offering surveys of the threatened Mojave ground squirrel for clients.

Psomas specializes in a range of development-related services, including construction management, land-use and planning entitlements, planning and landscape architecture, and traffic engineering.