After six years of often contentious negotiations with city officials, neighbors, and dogged environmental advocates on an expensive and high-wire plan to build a new shipping terminal on West Hayden Island, the Port of Portland announced this morning that it's pulling its proposal for now. And maybe forever.

Word came down to the port's commissioners this morning—with a letter (pdf) also delivered to Mayor Charlie Hales. Bill Wyatt, the port's executive director, said the city's conditions for blessing the port's plan—targeting one of the region's last great expanses of raw nature—were too costly for the proposed development project to pencil out.

The city's Planning and Sustainability Commission recommended last summer that Portland City Council approve the deal with the port, but with stringent requirements for offsetting environmental damage as well as public health and traffic impacts for nearby residents.

Those conditions were expected to cost tens of millions of dollars—raising the bar for a project whose prospects were already touchy based on economic reports drafted before the planning commission made its vote. Sources and others had been saying the council was loath to budge on those conditions. Wyatt, in his letter to Hales this morning, wrote Hales had told him pretty much the same thing during a meeting the two had last month.

The heart of the port's proposal was a plan to set aside 300 acres of the 800 it owns on West Hayden Island for a terminal and rail and road infrastructure—requiring fill and the disruption of some natural habitat—with the rest of the island's 500 acres mostly preserved but with paths and other amenities carved into it. The city needed to annex the land, long owned by the port, before approving the actual proposal for a terminal.

That 300/500 division was brokered by former Mayor Sam Adams' administration and set the table for discussions with groups like the Audubon Society and others about appropriate mitigation. If, indeed, such a thing existed. Adams tried to push through a deal before leaving office, but the planning commission balked over the compressed time frame and took much of 2013 to refine its findings and do further study.

A previous bid to annex and develop West Hayden Island fell apart in 2000, amid community outcry and partly because the port couldn't find a tenant for a new terminal.

"It would be a massive win for the environment and the community," the Audubon Society's Bob Sallinger said this morning, when asked about rumors the port was about to make an announcement. "It also would be the second time in 15 years they attempted to annex and rezone and failed, and it speaks to how flawed this project is and how strong the opposition is."

Wyatt, in a release sent out by the port this morning, said it's possible the port could try again.

Sallinger said that was unlikely—that the cost of mitigation and the hurdles of globalization, a big reason a new terminal might not deliver on promises of sustainable local jobs, would still be with us.

"It's not getting easier," he says. "It's getting more difficult."

Update 12:15 PM: Hales' spokesman, Dana Haynes, sent over a response when asked whether Hales was among the council majority supporting the planning commission's conditions or not. He said Hales was in presiding at city council when the letter came down.

"The mayor supports the commission.

It’s always been a question of jobs vs. open spaces. No decision was going to make everyone happy. No surprises here.

The mayor has heard the Port’s opinion and totally understands the perspective from which they approach this. But he hasn’t had the opportunity to read, analyze and respond to today’s letter."