Arlington County will spend $17.6 million to design, build and oversee the construction of a building to wash, fuel, park and maintain its 60-bus fleet, the County Board unanimously decided Saturday.

The Arlington Transit bus maintenance facility will be built on the site of a county-owned lot at South Eads and 32nd St. in Crystal City, adjacent to a WMATA structure where buses are currently washed and fueled between 3 and 6 a.m. at a high cost, county officials said.

W.M. Schlosser Co. was awarded a $12.4 million construction contract, which will start this summer and take 18 months to complete. Another $5.2 million will be needed for design, construction management and related costs, officials said. Part of the plan is to improve the appearance of the property along Jefferson Davis Highway. Money for the project comes from a combination of state and regional funds and local commercial real estate tax revenue that can only be used for transportation.

The building will not be able to handle “heavy” maintenance, which will continue to be done outside the county, nor will it house the existing fleet or the 30 additional buses expected to be in use by 2022.

The ART buses, started to supplement WMATA’s Metrobus service, have seen ridership grow from 650,000 in 2004 to nearly 3 million this year.

A county facilities study now underway is looking for places to park those additional buses, as well as public school buses. The county just last week announced plans to buy six acres of land near Washington-Lee High School that might be used in part for that purpose.

Another major county construction project, the $9 million homeless services center, has fallen months behind schedule, and the County Board agreed Saturday to spend another $116,842 to oversee its continued work. Like the bus facility decision, the shelter delay attracted no discussion from the County Board nor from the public.

The homeless shelter, which is supposed to occupy two floors of a renovated commercial building at 2020 14th St. North in the Court House neighborhood, was supposed to have been finished in March. A previously announced completion date of June will also be missed, said County Manager Barbara Donnellan, who visited the site Friday.

“No one is more disappointed than me because I wanted this to be done before I leave,” she said. Donnellan is retiring at the end of June.

The construction contractor is being charged $1,250 per day he is late, Donnellan said, and that money along with the project’s contingency funds will pay for the additional construction oversight that is needed.

The cost of renovating the other four floors of the building for county offices (first-floor retail space will be retained) is not included in the construction cost. The total cost of buying the building, renovation and relocation was in 2012 expected to be $37 million.