OLYMPIA — Washington’s growing population may earn the state another voice in the U.S. House of Representatives in 2012.

U.S. Census data released Wednesday shows the state had 6,664,195 residents as of July 1, nearly 100,000 more than a year earlier. Washington is the nation’s 13th most populous state.

If Washington state keeps adding population at the same rate when the 2010 census is complete, it is expected to gain its 10th seat in the lower chamber of Congress, according to an analysis of the federal data by a national expert on redistricting released Wednesday.

“We’re definitely thrilled at the expectation of getting greater representation in the other Washington,” said David Ammons, communications director for the Secretary of State’s Office.

“We’ve been tracking this for a decade. We didn’t think we were on the bubble,” he said. “To see this information today was quite a pleasant surprise.”

Ammons cautioned that it is the 2010 census, not the 2009 estimates, that will determine whether the state winds up with one more of the House’s 435 seats.

House membership is capped at 435, and the U.S. constitution guarantees every state at least one of those seats. Census population counts done every 10 years are used to allocate the other 385 among all states. Shifts in where people live can lead to some states gaining and others losing seats.

Each year, Election Data Services of Virginia crunches the federal agency estimates and predicts how reapportionment could play out when it does get under way. This report deals with the last count before the pivotal 2010 census and predicts up to 10 seats may change hands

Washington and six other states — Arizona, Florida, Georgia, Nevada, South Carolina and Utah — would each gain a seat and Texas would pick up three seats using the latest census population estimates, concludes the report by the company’s president, Kimball Brace.

Eight states including Illinois and New York would lose a seat while Ohio stands to lose two, according to Brace’s work.

A year ago Brace reported Oregon was on course for another seat. But the most recent analysis shows its population did not grow as rapidly relative to the other 49 states.

“The additional seat appears to have gone to its northern neighbor, the state of Washington,” the report says.

Should Washington add a seat, it will be located in Western Washington.

“Without a doubt, because Eastern Washington is not growing as fast as the west,” he said.

Precisely which districts it would be carved from will take some time to figure out.

The census will begin April 1, and the final tally of population, by state, is due to President Barack Obama by Dec. 31, 2010 at which point it will be clear which states will add or lose seats.

States will receive a detailed breakdown on population from the Census Bureau by April 1, 2011. That’s when a five-person citizen commission will begin drawing up boundaries for each congressional district as well as each of the 49 state legislative districts with an eye to balancing them by population.

Final boundaries will be decided by early 2012 and be in use for elections that year, Ammons said.

Washington picked up its 8th District seat following the 1980 census and the 9th District seat after the 1990 census, according to the Secretary of State’s Office.

Reporter Jerry Cornfield: 360-352-8623, jcornfield@heraldnet.com.