Arlington County police and sheriff’s deputies have taken their firearms training since 2008 either at a site without bathrooms or running water, or at a range where the equipment was considered substandard. That was after they left the Alexandria range because of constraints on noise and available time.

So the County Board’s unanimous decision Tuesday night to spend $7 million toward building a $17.7 million police firing range and training center with the Metropolitan Washington Airports Authority at Dulles International Airport came as welcome news.

“This will solidify a permanent solution for us for the next 25 years,” said Arlington Police Chief Doug Scott. “A police officer discharging a firearm is low probability, but high risk.”

It’s been difficult to squeeze the 192 police training days and the 76 sheriff’s department training days in, either at the existing Dulles training range where besides the lack of fixed restrooms there is minimal class space, but also at the Loudoun County Sheriff’s Range, which Arlington officials described as “antiquated.”

The new facility will have two 25-lane, 50-yeard open firing ranges, and a 300-yard rifle deck, as well as a secure storage area and classrooms. Arlington had set aside $7 million in its capital improvement budget for the construction; officials estimate it will cost about $105,000 a year to operate, money that will come from the police department’s seized assets fund.

The Metropolitan Washington Airports Authority, which leases the federal land where the facility is to be built, will share the new range, but Arlington has priority. MWAA is donating the $5.9 million cost of the land in its portion of the cost. The jurisdictions hope to lease the facilities when possible to other police agencies as well.

County officials said there is no room in the 27-square-mile county for a firing range.