The Port of Seattle's offer to rescue Metro's waterfront streetcar still faces several unknowns, including price and schedule for extending the line, and building a new maintenance barn.

The Port, Metro, the city and the Seattle Art Museum are starting talks this week to figure out which entity would be responsible for which costs. Officials also will need to address a schedule for tearing down the current barn, which is on land the museum plans to remake into its Olympic Sculpture Park. The museum wants to start construction by this fall but might be asked to finesse its schedule so that the streetcar could continue operating for as long as possible.

Metro officials say it is too early to say when a replacement barn could be built. If the current barn is demolished before its replacement is ready, the streetcar service would have to be suspended temporarily. Metro officials say they want that interval kept to a minimum.

Erika Lindsay, museum spokeswoman, said museum officials believe much of the construction work for the sculpture park, including repairs to the seawall, can occur around the existing barn. They still hope, however, to open the park as originally designed, without the barn, in summer 2006.

"We are somewhat flexible on our construction schedule," she said. "We hope this can work out and still stay pretty much on target with our opening date."

The Port last week offered to donate land near its Elliott Bay grain silos for a new barn and to arrange for extending the line about 1.2 miles north, where it could serve businesses along Elliott Avenue West, including the Amgen biotechnology campus.

The extension also could allow the streetcar to continue operating during reconstruction of the Alaskan Way Viaduct, as far south as the Seattle Aquarium. Officials had assumed the streetcar would shut down during protracted waterfront reconstruction.

David Schaefer, Port spokesman, said the Port has not committed to pay for the track extension, but is committed to working with other landowners in the area to make it happen.

"We're not going to stick the county or city with the bill," he said.

Judy Riley, Metro's design and construction manager, said the cost of laying new track in that area could be as low as $500 a linear foot, which would mean a total cost of $3 million to $3.5 million depending on which of three alternative locations is chosen for the new barn.

Kevin Desmond, Metro's general manager, called the Port's offer last week "interesting and exciting," but noted that several issues remain unresolved.

They include selecting the location of the barn, designing the facility and determining the alignment of the 1.2-mile extension.

The northern extension of the streetcar line also has implications for Myrtle Edwards Park, and a cost would be involved if the existing bike path had to be moved to accommodate the streetcar. Another unknown is whether stations, or stops, would be built along the extension, and who would pay for them.

Other hurdles include the relocation of utilities along the line and the acquisition of necessary permits for building along the shoreline — a process that could take longer than the construction of the barn itself.

Metro likely would bear the costs for building the barn — including the outer shell, cranes, maintenance bays, concrete platforms and an overhead electricity network to power the streetcars.

Riley estimated that a bare-bones barn probably would cost about $2.5 million to build, with an additional $350,000 for the power network and $400,000 to lay new track that leads into the facility from the northernmost station. A new power substation also would need to be built in the area, and that could cost an additional $1.5 million, she said.

Stuart Eskenazi: 206-464-2293