King County officials say they're nearing the end of settlement negotiations with Snohomish County over lawsuits involving the planned Brightwater sewage-treatment plant, but that nothing has been finalized yet.

The two counties have been negotiating out of court for months to end a number of lawsuits and hearing-examiner appeals the two have filed against each other. Snohomish County officials have fought King County's placement of the plant within Snohomish County borders.

"The two counties are close to having an agreement, but we're not there yet," said Brightwater project manager Christie True.

Documents outlining one possible settlement, which were recently leaked to the press, suggest to Brightwater opponents that the two sides are close to an announcement. The possible settlement has King County paying $70 million in mitigation money to Snohomish County, which had initially requested $80 million.

According to the settlement outline, King County would spend more than $30 million on parks and green space, about $3 million for an on-site community-resource center and nonprofit use of that center, about $26 million for public-safety projects such as sidewalks and about $11 million for habitat improvements near the site.

In return, King County would be required to trench at the proposed site just once more, near the location of any chemical buildings. The Snohomish County Council had passed an emergency ordinance in April requiring reasonable control measures, including trenching, to protect the public from sewage or chemical spills that an earthquake could cause.

If a settlement is finalized, opponents of the sewage plant, such as the Sno-King Environmental Alliance (SKEA), fear they'll lose leverage in their own battle over the $1.5 billion plant's future.

For the grass-roots group, seismic concerns have been the crux of its argument against the 114-acre site north of Woodinville. U.S. Geological Survey studies suggest a fraction of the southern Whidbey Island fault zone crosses the northern corner of the Brightwater property.

SKEA has called for more trenching at the site to determine potential impacts of an earthquake.

"What King County doesn't know could hurt a lot of people," said SKEA member Corinne Hensley. "We'd rather have the proof in hand before they start doing anything."

"Any documents that might have been provided [to the public] are working drafts," Nelson said, confirming the released documents are one of several options under discussion. "Seismic issues are one of our main concerns, too."

Christopher Schwarzen: 425-783-0577 or cschwarzen@seattletimes.com