A gravel site that was once proposed to provide fill for the third runway at Sea-Tac International Airport will revert to public ownership.

Under the proposal, the fill would have been transported by barge from the site on Maury Island and be transported from the Des Moines Marina to the airport on a conveyor belt.

Strong community opposition helped kill the idea.

The site is the longest remaining piece of undeveloped Puget Sound shoreline in King County. It will be permanently protected under an agreement signed by King County Executive Dow Constantine and the CalPortland Company - and facilitated by Cascade Land Conservancy - for public purchase.

"The chance to permanently protect such a long stretch of undeveloped Puget Sound shoreline and uplands is the kind of opportunity that comes along once in a lifetime," said Executive Constantine in announcing the agreement last week in West Seattle. "After more than a decade of advocating for this habitat I could not be more pleased at this breakthrough. I thank the state, our citizens, the sellers, and Cascade Land Conservancy for helping make this happen."

"We are pleased to have reached an agreement with King County and Cascade Land Conservancy on the sale of our Maury Island site," said Ron Summers, senior vice president and general manager of the Materials Division for CalPortland Company, owner of the site. "The sale of this site at this time makes sense for our company from a business perspective, but we reach this agreement with somewhat mixed emotions as this region still needs readily-available sources of high-quality aggregates to meet its current and future needs."

"(The) announcement is the result of an historic, decade-long effort by leaders from across this region," said Gene Duvernoy, president of Cascade Land Conservancy. "Their unwavering commitment to our communities and a vibrant Puget Sound has brought this negotiation to a successful agreement."

The agreement calls for a purchase price of $36 million, on a property appraised at $39.7 million. Of the purchase price:

$14.5 million is presently set aside in the state budget from ASARCO settlement funds, as the property lies within the bulls-eye of the plume from the old copper smelter in Ruston.

$19.1 million is proposed to be advanced from the King County Conservation Futures Fund, which by state law can only be used to purchase open space or resource lands - with the expectation that $2 million will be paid back into the fund through private fundraising.

$2.4 million is attributed to the value of extending CalPortland's existing mining lease on another part of the island, royalty-free, from 2020 to 2030, to meet the island's own gravel needs.

"I am pleased that Executive Constantine has negotiated the public purchase of this invaluable piece of Puget Sound shoreline," said Council Chair Bob Ferguson. "After the Council completes the budget, my top priority as chair will be ensuring timely council review of this deal in order to meet the December 30 deadline stipulated in the agreement."

Acquisition of the Maury Island site would protect 250 acres of pure Madrone forests and a mile of marine shoreline with nearshore habitat for listed chinook salmon. Along with King County's 320-acre Maury Island Marine Park just north of the CalPortland property and its mile of shoreline, the two sites will represent the largest public holding of protected marine shoreline in all of Puget Sound.

To raise $2 million in contributions as the private share toward the acquisition, Cascade Land Conservancy, People for Puget Sound, Preserve Our Islands, Vashon-Maury Island Land Trust and Washington Environmental Council are launching a fundraising campaign, called "Save Maury Island Now." Supporters can make a tax-deductable contribution at www.cascadeland.org.

"We ask everyone who cares about quality of life in Puget Sound to join us, to take a leadership role themselves, by contributing what they can to Save Maury Island Now," said Duvernoy. "Working together, we can ensure that we will indeed have great communities side by side with healthy landscapes envisioned in The Cascade Agenda and championed by the Puget Sound Partnership. We can make sure our region continues to be a place worthy of our children."

King County Parks would manage the 250-acre site as protected open space and for passive recreation, much as it now manages Maury Island Marine Park. The county envisions some trail expansion, kayak access, picnic shelters, portable toilets, and parking.

The site proposed for purchase contains almost five miles of trails that connect to Dockton Forest's three miles of trails. Hikers, mountain bikers and equestrians have used the 8-mile network for many years. This trail network could be expanded to access Maury Island Marine Park's trail network, providing an opportunity to create a 13-mile network of soft surface trails on more than 700 acres of public lands that will connect Puget Sound on the east to Quartermaster Harbor on the west.

Purchase of the property must close by Dec. 30, and requires approval by the Metropolitan King County Council.