The U.S. Census Bureau opened a headquarters in Bellevue today as part of its efforts to ramp up for the 2010 Census.

The new office, located at 636 120th Ave. NE, will serve as the agency’s base of operations for most of eastern King County.

John Saul, manager of the local office, said the Census Bureau expects to find a half million people, or one-third of the King County population, in that region.

Experts also predict that the census will show changing demographics in many Eastside cities, where high-tech jobs have attracted an increasing number of foreign-born residents to live and work.

Bellevue has seen its ethnic minority population rise dramatically in recent years to an estimated 30 percent.

Sammamish Mayor Don Gerend said his city has seen considerable change as well, with the overall population rising from 34,000 to an estimated 41,000 people in the last decade.

“I’m convinced this census is going to show a huge increase in the international spectrum of our community,” he said.

Census figures help determine federal funding for an assortment of programs, including roads, human services and education.

The data also determines apportionment for the U.S. Congress, and Washington – specifically east King County – stands to gain a 10th representative if the numbers shift just right nationally.

“That could make my job a little easier,” said Congressman Dave Reichert, who represents Bellevue and the politically mixed 8th District.

A new congressional district in east King County could leave Reichert, known as a moderate Republican, with a district more suited to his strengths.

The Census Bureau plans to mail out its questionnaires in mid-March.

The agency has switched to a shortened, 10-question survey – down from 46 – in an effort to encourage participation.

The 2010 Census will provide a short-lived stimulus for the regional economy, with the Bellevue headquarters planning to hire 1,000 people to collect data from May until July. Those workers will earn $17.50 per hour.

Certain populations tend to avoid the Census, making it difficult to get a completely accurate assessment of demographics. Many immigrants fear they could run into trouble with the law by making themselves known.

“There’s a lot of apprehension, but it’s just a head count, not an immigration check,” said Debadutta Dash, a member of the Washington State Commission on Asian and Pacific American Affairs.

Bellevue Deputy Mayor Conrad Lee, a native of China, said the counts are important for everyone because they bring about “power, money and justice” for those included.

“As immigrants, we tend not to understand that and not be counted,” he said. “It’s important for us to not be shy and encourage our neighbors to stand up and be counted.”

Each person not counted in the census causes an estimated loss of $1,400 a year in missed funding opportunities for their communities, according to Saul.

The Census Bureau brought in an ethnically diverse group of performers to help celebrate the opening of its new office in Bellevue with presentations that included a song by members of the Snoqualmie Indian Tribe and a prayer dance by an immigrant from Zambia.

The Civil Air Patrol’s Overlake squadron also attended the event for a presentation of colors.