OSO — A timber company that over the years clear-cut and thinned trees above the hill that unleashed the Oso mudslide has asked a King County judge to spare it from being forced into court next year to fight claims that it is partially responsible for the tragedy.

Grandy Lake Forest Associates contends that neither liability law nor emerging evidence about the hill’s geology support the case brought against it by lawyers representing people who lost families and homes in the mudslide.

Attorneys for the Skagit County-based company have filed a summary judgment motion, now scheduled to be heard Oct. 16. They contend that the facts are so clearly in Grandy Lake’s favor that a trial would be unnecessary.

“Grandy Lake can only imagine the impact of this tragedy on its victims and their families. But Grandy Lake is not responsible for their pain, and it should be dismissed from this lawsuit,” the timber company’s attorneys said in court papers.

Lawyers for those suing Grandy Lake say clear-cutting in 2004 plus thinning and other work on the property in 2010 allowed more rain to percolate into a hill that already had a long history of slides.

The company should have known people living in the Steelhead Haven neighborhood below were placed at risk, the attorneys maintain.

“Grandy wrongly tells the court that it had no duty to the people below (the historic slide zone), even though Steelhead Haven was in the line of fire of that dangerous slide on Grandy’s land, Grandy knew of the growing danger on its own land, and its land eventually liquefied, rushed across the river and buried the community,” attorneys for the plaintiffs wrote.

A total of 43 people died and dozens of homes were destroyed in the March 22, 2014, disaster. The timber company is being sued along with the state and Snohomish County.

Trial is now scheduled for June. King County Superior Court Judge Roger Rogoff has been sorting through the issues to be decided by jurors.

Dueling motions filed ahead of the hearing focus largely on what lawyers contend is the law governing the timber company’s duties as a tree harvester and the owner of property with a landslide. The pleadings also provide some of the clearest glimpses yet of the type of evidence and scientific opinion likely to be explored during the trial.

In court papers, Grandy Lake says it followed state forest practice rules and is a party in the case largely because of media attention, particularly stories that blamed the disaster on the company’s 2004 clear-cut in an area known as the Whitman Bench.

The timber company had no unique legal duties to people living in the valley below the historic slide, the lawyers maintain.

The dirt also is on their side, they say.

“If it must, Grandy Lake will show in a future summary judgment motion or at trial that forestry on the Whitman Bench had noting to do with the Oso slide,” the lawyers wrote.

In support, they point to evidence that emerged last fall when drillers for the state punched a hole more than 650 feet deep into the hill above the slide. About 130 feet down, the drill hit a layer of glacially compacted soil known as till. The timber company has an expert prepared to testify this “concrete-like” layer, some 90 feet thick, effectively forms a barrier to rain percolating into the hill and directs water away into creeks that bordered the slide zone.

Attorneys for those harmed by the slide have experts of their own. One is prepared to testify that Grandy Lake’s clear-cutting was “a causal factor” in a 2006 slide that blocked the North Fork Stillaguamish River, and that slide “in turn set the table for 2014.”

An expert on surface water, meanwhile, is expected to testify that work Grandy did to redirect a stream on the bench in 2010 sent water to the toe of the slope of the historic slide area, contributing to instability, the lawyers say.

Meanwhile, an author of one of the most-detailed scientific reports on the Oso mudslide has provided attorneys with a declaration that questions conclusions reached by Grandy’s expert.

Springs and seeps visible two months after the slide provide “strong physical evidence” that water from the hill wasn’t simply flowing into creeks and away from the area that fell, Jean Benoit, one of the authors of the Geotechnical Extreme Events Reconnaissance report, said in court papers.

He also said it would be a mistake to reach conclusions based on the drilling result Grandy cites.

“A single borehole for any investigation is grossly insufficient given the complexity of the subsurface and additionally in this case the areal extent of the site,” Benoit wrote.

Assistant state attorneys general took a similar position earlier this year when they convinced Rogoff to put off the trial until June. They wanted their experts to conduct more drilling on the hill and within the slide mass. The aim is to develop a better understanding of conditions below ground, particularly how water moves through the hillside.

If Rogoff handles the timber company’s motion as he’s done with other issues, he’ll likely announce his decision in a written ruling.

The case is believed to be the largest-ever wrongful death action filed against the state. The judge understands the stakes.

“This Court has, several times, commented on its expectations that the lawyers in this case practice their craft in a manner consistent with the importance this case holds for the people, government and residents of Snohomish County,” he said in a recent ruling. “The lawyers have admirably done so. Similarly, this Court wants to ensure that any decision reached by a judge or jury after the June, 2016 trial is one in which the people, government and residents of Snohomish County can have confidence.”

Scott North: 425-339-3431; north@heraldnet.com. Twitter: @snorthnews.