BANGOR – City councilors this week entered a development agreement with Eastern Maine Healthcare Systems, which is gearing up to build a $3 million ambulance and office facility at 931 Union St.

Proposed is a three-story structure that would be located at the former Harold S. Slager Memorial U.S. Army Reserve Center, a 7-acre, city-owned property adjacent to the EMHS Healthcare Mall on Union Street.

Existing buildings on the site will be demolished.

EMHS, which acquired the adjacent former Westgate Mall in the mid-1990s and transformed it into a complex of medical, business and related health care offices, now wants to redevelop the Slager property next door.

“I believe we’ve all seen the benefits of [work EMHS has done so far] on Union Street, and I believe this would be a great project for the city of Bangor,” Councilor Richard Stone said Monday night, just before the council’s unanimous vote in favor of the agreement.

EMHS officials also looked forward to the project.

“I see it as a win-win for us and for the city,” EMHS Executive Vice President Kenneth Hews said Thursday in a telephone interview.

The Slager property, acquired by the U.S. Army in 1956, once was used for medical screening and administrative activities.

Two brick buildings there were constructed between 1956 and 1959. One of the buildings housed administrative offices, unit supply rooms, an arms room, a drill hall and a limited kitchen, according to federal documents. The other housed a maintenance shop.

The U.S. Army Reserve occupied the building until 1993. In the late 1990s, the property was deemed to be excess to the military’s needs and conveyed to the city, originally for educational purposes.

The deal provides EMHS the space it needs for Meridian Mobile Health, its ambulance operation. Meridian now operates out of a Harlow Street building that is not adequate to its needs.

In addition, Hews said, moving Affiliated Healthcare Systems into the new building will free up space at the health-care mall for outpatient medical services.

In return, the city will receive lease and property tax income from the parcel, which has been vacant for years.

Though Hews said the project is still in the conceptual phase, plans call for a more than 20,000-square-foot facility that would house Meridian Mobile Health on the ground level and Affiliated Healthcare Systems on the two upper floors.

Meridian and Affiliated are for-profit divisions of EMHS and as such are taxable, city officials confirmed earlier.

The agreement councilors approved during their meeting Monday night calls for:

. The immediate development of a building of at least 20,000 square feet at a cost of at least $3 million.

. Construction of a new entrance and exit, and the installation of a traffic signal to provide safer access to both the Slager parcel and the health-care mall.

. A lease of at least three years, with an option to renew for five more years.

. Annual rent of $16,640 during the first term of the lease, with an annual 8 percent increase in following years.

The development pact also provides for a zone change for the property and a lease with an option to purchase.

The option to purchase, however, hinges on a waiver from the federal government, which gave the property to the city with several conditions attached regarding resale.