YAKIMA, Wash. — Work to move Yakima police and fire dispatch and 911 services into a county-owned building in Union Gap is expected to begin next month, thanks to a recent 30-year agreement between the city of Yakima and Yakima County.

Yakima County commissioners on Tuesday approved the agreement that requires the city to pay half the roughly $4.4 million cost of upgrading the building, known as the Community Restitution Center, to accommodate the 911 and dispatch services. Revenue from a 911 tax on phone services will be used to pay for the remaining cost of the upgrade. The back half of the building will be gutted, and a generator will be installed as well as antennas. The work is expected to be complete by April 2015, said Yakima County Commissioner Rand Elliott.

There will be enough space for the call center — now composed of 35 employees — to eventually add dispatch services from other agencies, such as the Yakima County Sheriff’s Office and Yakima County Fire District 5, Elliott said.

“We want to make that available.”

The 911 call center is currently housed in cramped upstairs quarters of the city’s Law and Justice center on South Third Street. The city operates 911 services, a county function, under an operating agreement with the county.

A few years ago, county officials began eyeing the former restitution center at 2403 S. 18th St. as a place to house the 911 call center and other administrative offices that were running short of space.

The county bought the 27,000-square-foot building in 1999 to house low-level offenders and inmates held under contracts with other communities, but it became idle when the new jail was built on Pacific Avenue in 2006.

Since that time, the Washington State University Extension and the Yakima Valley Office of Emergency Management have moved into the building. Both those entities lease the space. Next, the county’s Emergency Medical Services department will be moved into the building as well as the emergency call center.

Upgrades to the space needed for Emergency Medical Services will cost an additional $800,000, and will be paid in part by the agency and the county.

Work to add the call center is expected to begin next month, and should be complete by March 2015, Elliott said.

“It’s good for everybody,” he said. “It just drives the cost down and it’s just a good long-term home for 911.”