D.C. Mayor Vincent Gray has warned key lawmakers that the D.C. Fire and Emergency Medical Services Department's staffing protocols are leaving the District at risk in the event of a Boston-style attack against the city.

"The existing shift structure permits many personnel to commute extraordinary distances to report for work," Gray wrote in a letter to two legislators. "Should a serious emergency situation impact the District of Columbia, as it did [on April 15] in Boston, it would be almost impossible for many off-duty FEMS workers, who would be desperately needed, to respond in a timely manner to meet the needs of our residents."

Firefighters currently work 24-hour shifts before receiving three days off, but the Gray administration has used contract negotiations to seek a new arrangement of shorter shifts.

Where D.C. firefighters live
In the District: 24 percent
Within 30 miles: 48 percent
More than 30 miles: 28 percent
Source: D.C. Fire and Emergency Medical Services Department

"I know that the shift change will mean that some workers may need to rearrange their schedules for second jobs they may hold. It also may mean that some workers may have to decide between moving closer to the District or leaving employment at FEMS," Gray said. "While I certainly don't take these changes lightly, I cannot let the adherence to the status quo prevent us from implementing a change that is necessary to more safely serve our residents."

District government statistics show that 28 percent of the approximately 2,000 uniformed FEMS employees live more than 30 miles from D.C. Fifty-five workers reside at least 100 miles outside of Washington, with six traveling at least 200 miles into the city for work.

Edward Smith, the union's president, said firefighters are sufficiently close to the District, and he dismissed Gray's contention that the current shift structure poses a public safety threat.

"I think he's playing on people's emotions," Edward Smith said. "I don't believe those claims at all."

Smith added: "We'd be able to respond initially to any emergency."

Ward 6 D.C. Councilman Tommy Wells, the chairman of the council committee that oversees the fire department, said Gray's letter alarmed him after city officials repeatedly reassured him the District was prepared for a crisis.

"The mayor and his staff are not on the same page," Wells told The Washington Examiner. "If they're now saying they can't be accountable in the case of an emergency, then we have a problem."

Wells also said that the Gray administration had not complied with a request he made more than a month ago for data about where first responders reside.

Gray's willingness to invoke the Boston Marathon bombings came as the District prepares to enter binding arbitration proceedings with firefighters after years of negotiations and mediation failed to produce a new deal.

Firefighters have been without a contract since 2007, and their relationship with city leaders has become increasingly hostile in recent months, culminating in a March vote of "no confidence" against Chief Kenneth Ellerbe.SClBThe union mounted its formal complaint after a series of high-profile fire department failures, including an episode in which an injured D.C. police officer had to wait for an ambulance from Maryland because the city did not have one available.

Ellerbe was also a target of criticism after he acknowledged that he used flawed data about the readiness of the District's emergency fleet to lead his department for about a year.