Two local environmental consulting and site assessment firms have agreed to merge.

Long Beach-based McAlister GeoScience Inc., which specializes in site assessments for environmental hazards and remediation plans, last month agreed to buy Pasadena-based Orswell and Kasman Inc., which also provides site assessments and has compiled a database that can be used for due diligence property investigations. Financial terms of the deal were not disclosed.

The acquisition is set to close on Jan. 1, when Orswell and Kasman will become the Pasadena office of McAlister GeoScience. The combined firm will have roughly 21 employees.

David McAlister, founder and current principal of McAlister GeoScience, will become principal of the combined company. Marty Kasman, the current principal of Orswell and Kasman, will stay on as principal in charge of the Pasadena office.

McAlister, who had spent his early career working for environmental firms including Pasadena-based Tetra Tech Inc., founded McAlister GeoScience in 2012.

The firm does some phase 1 site assessments that characterize the nature of any contamination that may be at a specific site. But its specialty is phase 2 assessments that determine the level of contamination on a site through soil samples. The firm also designs cleanup plans, known in the industry as remediation.

Merging businesses

Orswell and Kasman was founded in 1990 by Jack Orswell, a former FBI special agent, and joined in 1998 by Kasman, a former Los Angeles County Fire Department hazardous materials supervisor. The pair developed a regulatory database of aerial photos and records of sites known to have contamination, among other hazards. The database provides a starting point for most phase 1 site assessments. When Orswell retired several years ago, Kasman took the helm.

McAlister said in an interview last week that these different areas of specialization were a prime factor in the acquisition decision.

“We offer complementary services, so it makes sense to combine them,” he said.

He added that while much of the firms’ work is in Southern California, they also do site work in other states. “We have agents in every major metro area in the United States,” he said.

While declining to give specific revenue figures, McAlister did provide a range, saying the combined revenue of the two companies was “in the seven figures.”