The King County Library System has crafted a proposal for an expanded library on Vashon Park District property — a footprint that would extend north of the current library and could add up to 3,800 square feet to the one-floor structure.

The library system hasn’t begun designing the expansion and thus can’t nail down the exact square footage the library will have once it’s remodeled, but staff are trying to get as close to 10,000 as the site will allow, said KCLS facilities development director Kay Johnson.

The library system owns the Vashon Library and will own the expansion as well, but it leases the land beneath it at Ober Park from the Vashon Park District.

The park board was amenable to the library system’s proposal and is currently planning a lease proposal that library staff say they need to have signed before they design the expansion or apply for building permits.

Still, park board members said they’d like to know more about the library system’s plans for Ober Park.

“You need to know a few things before you can lease a piece of property — like what the footprint’s going to be, how the building’s going to fit within the park,” said park board member David Hackett, who chaired the board from 2007 to 2008.

Previously, the option of building a new library at Ober Park had been put on the table, but library officials will only consider remodeling the current building, he said.

“They claim they don’t have enough money for a new building,” Hackett said.

Hackett, a lawyer who has drafted leases before, is preparing a lease proposal for KCLS to review.

Both park and library officials hope to agree upon a lease by the end of September, so library staff can begin design work in October. The library system will then submit its designs to the county for permitting, and if all stays on schedule, construction could begin in early 2011.

“We’re all very motivated to get this done, because we’re worried that the current bidding climate won’t last,” Johnson said.

The expanded library will add up to 3,800 square feet to the existing 6,100-square-foot library while improving the existing building, she said, at a construction cost of $3.67 million. The expansion will be on the northern side of the current library building, extending into what is now a grassy berm abutting the building.

The library board is hoping for a 99-year lease on the proposed areas.

“We wanted to have a long-term commitment on the library, since we’re putting so much money into it,” Johnson said.

However, park officials are leaning in a different direction. At their Aug. 4 board meeting, board members suggested a different lease term: 30 years, with an option to renew as long as the building is used as a library.

Park board chair Mike Collins said he’d examined other leases, and 30 years seemed to be reasonable.

The lease should be “enough years to cover the bond” — long enough that the building has been fully paid off by tax dollars, Hackett said.

In this case, the library will be built with funds from a 20-year bond, Johnson said.

While the board mentioned using language that would allow the library to lease the Ober Park land as long as the building is used as a library, Hackett noted that a lease in perpetuity is illegal, thus the 30-year term was agreed upon.

“I’ve never heard of a 99-year lease,” he said. “I think that’s a little long.”

After drafting the lease, park officials will hand it off to the district’s lawyer for review before sending it to the library system, which will then have a chance to suggest amendments or alterations to the lease.

The lease is all new rather than amended from the original one drafted in 1982 between King County Library System and the King County Park District. The Vashon Park District did not exist at that time.

“Otherwise, we’re just patching on an old lease, which doesn’t make a lot of sense,” Collins said.