PORTSMOUTH, N.H. – The Department of Defense has sent a letter to the chairman of the Base Realignment and Closure commission reiterating the department’s reasons for supporting the closure of the Portsmouth Naval Shipyard in Kittery.

In a letter of their own, Maine and New Hampshire’s congressional delegations responded that the facts are not on the department’s side.

The 92-page Department of Defense letter, sent to Anthony Principi on Tuesday, outlines all of the department’s realignment and closure recommendations for military facilities nationwide.

The letter states that the Defense Department still strongly endorses shutting down the shipyard, and dismissed arguments that the Navy doesn’t have enough capacity to absorb the work now done at the shipyard at other facilities.

“Excess capacity increases each year as workload requirement decreases throughout the closure period,” the letter reads. “In [fiscal year 2009], aggregated excess capacity will be greater than 17 percent overall in three remaining shipyards.”

The letter said any risks in closing the shipyard would be “manageable,” and that keeping the facility open “would obligate the department to significant future costs.”

In response, the Maine and New Hampshire congressional delegations said they have demonstrated “that there is no excess capacity at any of our nation’s four shipyards and closure of Portsmouth would irrevocably damage our nation’s naval war fighting capability.

“With so many of the BRAC commissioners questioning the Defense Department’s cost-savings numbers, it is increasingly clear that DOD’s rationale for closing Portsmouth cannot be substantiated,” said the letter, signed by Maine Sens. Olympia Snow and Susan Collins, New Hampshire Sens. Judd Gregg and John Sununu, Maine Reps. Tom Allen and Mike Michaud and new Hampshire Reps. Jeb Bradley and Charles Bass.

Retired Navy Capt. William McDonough, a former Portsmouth Naval Shipyard commander who now heads the Save Our Shipyard group, said the Department of Defense letter’s reference to the shipyard appears to be a final-hour attempt to sway commissioners who may be thinking about keeping the shipyard open.

“They’re trying desperately to get in there with the last word,” McDonough said. “They’re trying to make sure the commissioner who is sitting there wrestling with the decision does not decide in our favor.”

McDonough said he’s concerned that commissioners will put more stock in the Defense Department’s opinion than in arguments made by shipyard supporters because the Defense Department is the supposed expert.

The commission is scheduled to vote on the closure and realignment recommendations beginning Wednesday. McDonough said he expects a vote on the shipyard by the end of Thursday.

The commission will also vote on the future of two other Maine facilities: the Brunswick Naval Shipyard and the Defense Finance Accounting Service office in Limestone.

The commission will forward its final recommendations by Sept. 8 to President Bush, who has until Sept. 23 to accept or reject the recommendations in their entirety.