Olson, one of the largest ad agencies in Minneapolis, announced Tuesday that it has agreed to be acquired by ICF International, a Washington, D.C.-area firm that specializes in technology consulting for commercial and government clients.

Olson and ICF officials said the 545-person agency would operate as a stand-alone unit of ICF under the proposed arrangement and that no management changes or layoffs were expected. ICF said it would pay $295 million in cash to Olson's parent, private equity firm KRG Capital Partners, and other minority shareholders.

The acquisition gives ICF access to Olson's expertise in advertising, marketing, digital and social media and analytics.

Olson, in turn, could see growth opportunities from both domestic and international clients served by the $1 billion firm, based in Fairfax, Va.

The announcement was a surprise to Olson's staff but not totally unexpected, since KRG has owned Olson since 2009, about the maximum length of time for private equity investors.

The deal faces approval by the Federal Trade Commission, but a mid-November close is expected.

"This increases our breadth and depth to add services for our clients," said Sudhakar Kesavan, ICF's chief executive, in an interview. "We see the service landscape changing. Our clients are asking for more digital and social media and transactional services."

ICF provides management consulting and economic analysis to clients in government, health care, energy and aviation. The firm has a strong international presence with 70 offices across the globe.

Historically most advertising agency acquisitions have been by holding companies already in the advertising environment.

That Olson is being acquired by a business-to-business consulting firm is a bit out of the norm.

"It's pretty typical to have different owners over the years, but these guys are a different flavor. I guess they want the kind of magic that a creatively oriented agency brings to their very heavy data-intensive analytical business." said Steven Wehrenberg, a University of Minnesota advertising professor and former CEO of the Minneapolis agency Campbell Mithun. "It could end up being a pretty good thing for Olson. It will give them a platform to have international clients and international offices."

Kesavan said Olson's strength in analytics and social and digital media will be of good use to its clients in energy and health care.

He said ICF works with electric utilities, for instance, that want to connect directly with consumers about energy usage, as do health care providers dealing with the "consumerization of health care" brought on by the Affordable Care Act.

Olson has a broad client base in retail, tourism and consumer products. In recent months, Olson became the loyalty agency of record for Hyatt Hotels & Resorts, landed work with P.F. Chang's China Bistro and was named social media agency of record for Reynolds Consumer Products.

Olson CEO John Partilla called the partnership with ICF "additive and innovative."

"It drives value creation for our clients and future growth for us domestically, internationally and across client categories," Partilla said in a statement.

New York-based AdMedia Partners served as Olson's primary adviser on the transaction. The investment bank Jefferies also advised in the deal.