PETALUMA -- Irvine-based Environmental Resources Inc., which has a 35-employee local office, merged with Cardno Limited of Australia.

The merger, effective June 9, was part of a $106.3 million deal that also included Houston-based environmental consulting firm Entrix Inc. ERI and Entrix executives became shareholders in Cardno and remain in place.

ERI (www.eri-us.com) has 155 employees in nine offices nationwide. The Petaluma office staff operates soil and groundwater remediation systems at a number of petroleum-contaminated sites in Sonoma County, according to Keith Romstad, vice president and chief operating officer. These sites include former and existing service stations, bulk fuel-storage facilities and former manufactured gas plants.

In addition, local staff handle environmental assessment and remediation at former and existing refineries outside the county.

Founded in 1989, ERI first came to the North Bay in 1994 with a Bay Area office in Novato, according to Mr. Romstad. The office moved to Petaluma in 2004.

Cardno (www.cardno.com.au) started in 1945 and now has 3,650 employees in offices and projects in 70 countries.