Installation of track on the now-operating section of Metro's Blue Line will cost $9.5 million more than the original contract, a cost overrun of 76 per cent, the Metro board was told yesterday.

That overrun, caused by construction delays, strikes and engineering modifications, is proportionately the largest in the history of Metro, accoding to William Alldredge, Metro's director of construction. There have been larger over runs in terms of dollars

Lessons learned have resulted. Alldredge said in a revised Metro procedure for trackwork contracts.

It may be possible, he told the board, to recover some of the overrun from other contractors who did work preparatory to laying track. In any case, months of administrative or legal actions remain, he said.

The board had previously approved payment of some of the overrun. Yesterfay, the Metro staff recommended a final payment of $5.2 million to the contractor, a joint venture of four firms operating as Metro Track Constructors.

Board members told Metro general manager Theodore Lutz that they wanted a more detailed accounting of exactly what went wrong and where recovery might be made before reaching a final decision. They deferred action for two weeks.

The $5.2 million was a negotiated out-of-court settlement between Metro and the contractor.Metro has 30 days to pay the settlement or a lawsuit will be reinstated, Alldredge said.

Joseph Wholey, board member from Arlington, said "I think we should probe harder, in public, but I have no reason to believe that the settlement is not the most advantageous to the authority."

The original low bid for the contract was $12.5 million, the board members were told, and that included the acquisition of the track by the contractor. The contractor was guaranteed access to various sections of Metro tunnel on certain dates, but lead time of 18 months had to be given so the contractor could acquire the rail. Alldredge said.

What happened in the interval was that six months of construction strikes, a court-ordered requirement to install elevators for the handicapped in already designed Metro stations and other construction delays combined to deprive the contractor of access on the scheduled dates.

The track is laid in 1/4-mile welded sections, and significant stretches of tunnel must be available before the contractor can do anything meaningful, Alldredge said.

While the contractor waited, the price of both labor and materials sky-rocketed during the inflation of 1975.

Once the contractor was in the tunnel, it was discovered that the concrete pads on which the rails are set could not withstand the pressure. They had to be redesigned and replaced.

Further, several segments of the completed tunnel were not perfect, and corrections had to be made in the track-laying process to put the track at proper grade and alignment. It is in these areas that Metro can seek relief from other contractors, Alldredge said.

As a result of these and other factors, the final negotiated price on the contract is $22.1 million. Alldredge said that an audit of the contractors' books had been completed "and we have determined that he will suffer about a $7 million loss" including the overrun.

As a result of the experiences with that contract, Metro has redesigned the concrete blocks on which the tracks sit and now purchases the track directly from the steel mill itself, then issues it to the contractor. That process has meant, Alldredge said, that the lead time on track needs could be reduced substantially. Thus, access to trackbeds could be guaranteed with more certainly.