ELMWOOD PARK, N.J. — Langan Engineering & Environmental Services, a privately held consulting firm with 500 employees in 14 offices around the world, has acquired Treadwell & Rollo, a premier geotechnical and environmental engineering firm based in San Francisco.

The acquisition, the first in Langan’s 40-year history, firmly establishes a nationwide footprint for the company by adding 70 high-caliber professionals from Treadwell & Rollo’s California offices in San Francisco, Oakland, San Jose, and Sacramento.

In an era where large public corporations have routinely acquired smaller firms, the Langan/Treadwell & Rollo deal signifies a strategy for growth and expansion between two independent firms. As a result, the combined forces of Langan and Treadwell & Rollo will instantly attain true nationwide reach; have access to shared technical resources; and remain privately held, which enables swift responsiveness to client needs on all projects.

Langan’s major projects include the New Meadowlands Stadium for the Giants and Jets, the Four Seasons Hotel (the tallest building in South Florida), and the Shops at Atlas Park, which won the 2007 Phoenix Award, EPA Region 2. The firm also supports development projects for academic institutions, hospitals, and governmental agencies, as well as large-scale national and international infrastructure projects. Additionally, Langan’s environmental practice specializes in compliance programs for major corporations in the petro-chemical, utilities and manufacturing industries, and is widely acknowledged as a leader in remedial design for brownfield and Superfund sites.

For more than 20 years, Treadwell & Rollo has been committed to consistently providing outstanding environmental and geotechnical engineering consulting and services to its numerous public and private clients. From initial site investigations, soil, soil vapor and groundwater remediation, and engineering design to providing expert witness testimony in court, the professionals of Treadwell & Rollo have demonstrated their skills throughout the United States and the Pacific Basin. Treadwell & Rollo provides high-quality consulting services during the planning, investigation, and construction stages of development projects, and has developed years of experience addressing the issues that property owners, architects, engineers, and planners are faced with during the full life cycle of projects.

Plans call for an interim period whereby Treadwell & Rollo will maintain its name, but will be branded as “A Langan Company.” In 2012, the firm will become known as Langan Engineering & Environmental Services. The financial terms of the agreement are not being disclosed.