Loudoun County will pay $1.9 million to help cover a nearly $3 million overrun in the county sheriff’s office’s fiscal 2013 budget, county leaders said Tuesday.

With the end of the fiscal year fast approaching and the Loudoun County Sheriff’s Office on pace to exceed its budget by about $2.77 million, county supervisors were left with little choice but to recommend an additional allocation to help cover costs and avoid missed paychecks for sheriff’s office employees.

At a county finance, government services and operations committee meeting Tuesday, Sheriff Mike Chapman offered a presentation to county supervisors to explain the overrun.

The biggest expenditure, according to the presentation, was overtime pay: while the sheriff’s office budgets $2.6 million in overtime pay, most of those funds go toward holiday pay and the cost of double-time pay for deputies who work when the government is closed. The remaining balance of just over $1 million is not enough to meet the department’s staffing needs, Chapman said.

The overtime costs were heightened this year by unusual circumstances, Chapman said – including severe weather such as the derecho storm and Hurricane Sandy, as well as a number of high-profile political campaign events during the national election cycle.

The budget overrun was first announced by Supervisor Ralph Buona (R-Ashburn) at a budget work session last week. Buona, who chairs the county finance committee, said he was equally troubled by the overspending and the fact that county leaders had not been informed of the problem sooner. He told Chapman, who was present at the work session, to expect “hard questions” at Tuesday’s finance committee meeting.

At the Tuesday meeting, Chapman emphasized one particular problem that he said was largely responsible for the sheriff’s office’s financial challenges: mandated vacancy savings.

The sheriff’s office is required to maintain 21 vacant positions, Chapman said, which results in financial and operations failures and excessive overtime pay.

The 21 mandated vacant positions do not include the naturally occurring position vacancies, he said.

“This is where we have our most heartburn… we’re down 30 positions that we have to then fill in some regard in order to provide some minimal level of service,” Chapman told the committee Tuesday. “That’s really where it starts costing us quite a bit.”

The forced vacancies leave the agency in a bind, because other deputies must be paid to fill the empty posts, Chapman said: “We don’t have the option of just not having it filled... we’re emergency service providers.”

The committee members acknowledged that the issue of mandated vacancy savings needs to be addressed, and said they would review the matter. Ben Mays, Loudoun’s chief financial officer, said it would cost the county about $5 million to eliminate vacancy savings across all county departments.

Board of Supervisors Chairman Scott K. York (R-At Large) said it may be necessary for the county to absorb that cost.

“This is something we’ve got to take up very quickly because quite frankly it doesn’t make any sense to tell somebody that they’ve got [full time employee positions] but no, you can’t use them,” York said. “We may at one time have to take a one-time hit so that public safety can actually get the power on the streets, and in the long term it’ll be savings if we don’t have to do overtime.”

During his presentation Tuesday, Chapman also highlighted other cost-cutting measures that the sheriff’s office has taken, and said his staff had identified about $800,000 in operations and maintenance savings that could be applied to the fiscal 2013 overrun.

The committee voted Tuesday to recommend that the full Board of Supervisors allocate an additional $1.9 million to the sheriff’s office to cover the remaining cost.