IT WAS A DUMB assumption, but we truly thought we had an exclusive. A "personal invitation" had been extended to The Stranger to go up in a twin-engine plane last week. Local activists, calling themselves Deep Impacts, were going to show us how a new strip-mining plan was going to ruin their precious Maury Island -- ecologically, economically, and aesthetically. (Maury Island is located southeast of Vashon, across the water from Des Moines and Federal Way.)

Come, see the beautiful madrone trees before they are torn from their roots by Lone Star Northwest, an evil mining company. Gaze down upon the gentle land, before the earth is laid bare and ripped open, the flycatchers' nests destroyed, the eagles and peregrine falcons forced to forage elsewhere. And don't miss the beautiful, relatively undeveloped beaches, lapped calmly by the Puget Sound, where the eelgrass provides a cozy spawning ground for Chinook salmon, an endangered fish.

Upon arriving at a small airstrip at Boeing Field, we discover that the invite has been extended to a gaggle of local media. Reporters and cameramen from KING 5 and KOMO 4 are there. So is The Seattle Times. The Seattle P-I, it seems, couldn't make it, but the Beachcomber, an island-based publication, gladly takes its seat on the plane.

Why we're not getting the exclusive becomes obvious as soon as we arrive. Deep Impacts wants all the media attention they can get, because they're fighting both Lone Star and the clock on this issue. Next week, King County will sound the deadline for public comment on a draft environmental impact statement. If the report goes unopposed, Lone Star is almost guaranteed to get a grading permit to increase mining. The company used to mine a small plot of land on the six-square-mile island, a mere 10,000 tons of sand and gravel a year. They want to up the ante by 7.49 million tons of sand and gravel, spread out over 235 acres.

"Real estate prices are already going down on the island," says Deep Impacts spokeswoman Sharon Nelson. That can't please the 2,000 or so Maury Island residents. With a nine-hole golf course, at least 10 bed and breakfast establishments, and homes ranging in price from $150,000 to $1 million, the island has been growing, but not at the incredible, often undesirable pace of the rest of the Seattle area. Afraid that a bigger strip mine will destroy the community, even the local chamber of commerce has gotten involved, officially supporting Deep Impacts, which now boasts a staff of 15 volunteers and a mailing list of the entire island.

At a press briefing before the fly-over, Nelson outlines the problems her organization has with the voluminous draft impact statement. First, she says, the report is biased because two of the firms who heavily contributed information to the report were paid directly by Lone Star, instead of being paid by the consultant the county hired. Second, if the conflict of interest accusation is true, a million questions come up about the environmental impacts the mining will really have on Maury Island. The two biggest: What will happen to the heavy amounts of arsenic that are contained on the island's soil? What will happen to the island's single-source aquifer?

The environmental group's claims gained legitimacy earlier this year, when it was discovered by the county's environmental consultants that one of the firms Lone Star was paying, Associated Earth Sciences, Inc., fudged its numbers by diluting its arsenic sampling. "It's not an independent evaluation," Nelson asserts. "If the mine does the damage we predict, we will be out of our homes."

Unfortunately for Nelson, a 48-year-old former Seafirst bank exec, the official draft impact statement pooh-poohs her concerns.

· "No potential to breach aquifer."

· "Appropriate drainage and recharge designs would be used."

· "Not expected to significantly reduce eelgrass or kelp."

· "Applicant is proposing to fully contain contaminated [arsenic-laced] materials at the site within a sealed berm."

These results please Lone Star, a subsidiary of Japan-based Taiheiyo Cement. Ron Summers, Lone Star's general manager for aggregate operations in Washington, gloats a bit about the project. "Lone Star will have the only clean property in the neighborhood," he says. "[Arsenic] won't be spread around the whole site [as it is everywhere else]." As far as the allegations of bias go, Summers is duly unimpressed. "[The county's consultants] turned around and independently reviewed [all test results], and made their own decisions." And the activists were allowed to help select the consulting firm, Jones & Stokes, Summers points out.

King County officials won't wade into the middle of this battle. "The decision on the grading permit will not be made until after the final [impact statement] has been issued," says Gordon Thomson, senior planner for the county's Department of Development and Environmental Services. "Nobody around here is even talking about a grading permit decision yet."

Thomson, however, isn't buying the claim that the draft impact statement was partial to the company. "If we thought it was a conflict of interest, then we would have been on top of it a long time ago," he says. "We'll defend our position. There are a limited number of firms out there that do [that type of] work. It's not in their interest to be biased."

Where does this leave Deep Impacts? Nelson says the group will be submitting a 150-page response to the draft impact statement. The activists are also holding out the hope that the county will wait for the results of an independent study by the state: a $250,000 look at the island's arsenic problem and aquifer system. The group claims credit for successfully lobbying for the study's financing, but it may come too late. The study isn't expected to be out until June 30. The county doesn't seem willing to wait, however. Thomson says he expects a final impact statement to be done by this November.

It's a hard fight ahead, but in the glow of all the media attention, Nelson is already flush with success. "We've come a long way," she says during the news conference. "This [mining plan] is not going to happen."

Lone Star's Summers, however, is eager to move forward with the project. "[The impact statement] confirmed what we have always felt," he says.