DES MOINES &#8212 Wellmark Blue Cross and Blue Shield has announced plans to build a new $175 million headquarters in downtown Des Moines.

The health insurer signed an agreement Friday to gain control of 6 1/2 acres of downtown property, most from Iowa Health-Des Moines, according to a copyright story in The Des Moines Register.

The project includes a 2,000-car parking garage and a 500,000-square-foot headquarters in either of two buildings.

Wellmark considered a move to West Des Moines and bought 66 acres of land there earlier this year, but decided instead to stay downtown with its 1,600 employees, said John Forsyth, Wellmark’s chairman and chief executive.

“We have gone through a rigorous selection process, weighed all the options and determined that remaining in downtown Des Moines made the best sense,” Forsyth said.

The project still needs approval from city and state government officials. The site also needs approval from environmental regulators. Construction is scheduled to start in 2008.

Des Moines will provide incentives to Wellmark that are similar to what the city gave to Wells Fargo Financial and Allied Insurance when those companies built new headquarters, said City Manager Rick Clark.

Cliff Gold, a Wellmark group vice president said the combination of state and local incentives exceeds $10 million.

Clark said the city’s incentives include straightening a street, extending the downtown skywalk to the building, a mass transit agreement to encourage Wellmark employees to take the bus and the use of tax increment financing to rebate some property tax money to Wellmark.