CDM, based in Cambridge, MA, has announced its acquisition of Wilbur Smith Associates (WSA) of Columbia, SC. CDM provides consulting, engineering, construction, and operations services in water, environment, transportation, energy, and facilities, while WSA’s professional services consulting portfolio covers transportation, infrastructure, and community development planning, engineering, and economics.

CDM has more than 4,600 employees in 123 offices, 85 of them in the U.S. WSA employs 1,182 people in its 54 offices, 42 of which are in the U.S. Engineering News-Record included both firms in its 2010 ratings of Top 500 Design Firms (CDM is 21st, WSA is 64th) and Top 200 International Design Firms (86th and 114th respectively).

With the transaction completed, the firms have begun the important transition process to integrate the two organizations.