Centralia Chronicle: "Weyco’s Clear-Cut Mudslide Could Prompt New Rules"
By Dan Schreiber
BOISTFORT -- Dozens of mudslides still scar the landscape of forested hills above the Boistfort Valley, a stark reminder of relentless rain dropped by the December 2007 storm that showed no mercy when it befell West Lewis County.
The most noted of the slides is on Little Mountain, a tree-stripped slope on Weyerhaeuser land in the Stillman Creek drainage basin.
Members of the state Forest Practices Board toured the Little Mountain site on Tuesday. The board is commissioning a slope study that could mean changes in how timber is harvested on the state’s hillsides.
The clear-cut slide was vividly captured in a Seattle Times aerial photograph taken a few days after the natural disaster that brought hurricane-force winds to the coast and Lewis County’s worst flooding on record.
The image quickly spurred questions over whether clear-cut logging practices on the timber company’s large holdings in the Willapa Hills contributed to the flood damage.
The rain intensity was concentrated in the higher elevations, with an estimated 15 to 20 inches falling over 48 hours in the hills, compared to about eight inches in the Twin Cities.
The storm sent a torrent of mud down hillsides into the Chehalis River and its tributaries. It eventually came to rest as a thick, sticky blanket in the homes and farm fields of the valley.
Tuesday’s tour led by Weyerhaeuser scientists was attended by several state officials, members of conservationist groups and timber industry advocates.
They saw a part of what the state Department of Natural Resources estimates to be 1,600 December storm-related slides.
Much of the landscape is characterized by clayish soils that rest on bulky bedrock. When rain gets into cracks between the landforms, slides occur. Scientists said slides shaped the hills over the course of history.
Commissioner of Public Lands Doug Sutherland emphasized that much more needs to be learned before rules are set on slopeside logging.
“Unstable slopes is a broad term,” Sutherland said. “We have to ask some questions. Under what circumstances is it unstable? Is it a function of geology? Is it the rock? The soils?”
Last winter, the U.S. Geological Survey called the storm a 500-year event based on Chehalis River flow gauges. Sutherland noted that the state generally sets practices based on the possibility of less intense 100-year events, and said there might not be any way to prevent damage from storms of December’s magnitude.
“Was this storm an anomaly?” Sutherland asked rhetorically of the 500-year designation, which simply means that the possibility of an equally devastating storm is one in 500 during any given year. “Is there something that happened that obliges us to change the rules?”
DNR communications director Patty Henson said department officials have done aerial surveys since the storm, and found 60 to 65 percent of the slides to have occurred in areas with standing timber.
“There was no particular correlation between the slides and areas that were harvested or not harvested,” Henson said.
Weyerhaeuser officials contended in 2008 legislative hearings that the company was powerless to do anything to prevent damage from such an extreme event. Weyerhaeuser’s chief environmental scientist Bob Bilby said based on company data, 60 percent of the slides happened in areas considered in models to be moderate or low risk for slide potential.
University of Washington Professor David Montgomery also addressed the tour group, perched on an adjacent hillside with a clear view of the Little Mountain slide. Montgomery said computer models are not necessarily the final arbiter of truth about geological structures.
“You can tweak those models to get whatever results you want,” said Montgomery, who specializes in soils and erosion. “Models are only as good as the data that go into them.”
Just over 100 acres of logging was approved on the 50-degree Little Mountain slope in 2004. Although state surveys said the land contained highly erodible and unstable soils, DNR approved the operations. A Weyerhaeuser geologist who walked the site said there were “no potentially unstable slopes.”
The application process was all legal, according to Henson.
“Rules were not broken,” Henson said.
Jack Shambo, DNR’s Chehalis district manager, originally inspected the site. He explained to the tour group how Weyerhaeuser’s harvest application was approved.
“I had a very high confidence level in the assessment,” Shambo said, mentioning that 500-year-old stumps on the land suggested it could withstand heavy cutting of old-growth trees. “I figured if it survived that harvest, it’s a pretty stable slope.”
Shambo said he consulted a 1994 watershed analysis that listed Little Mountain as part of a larger moderate risk area for potential slides.
“We felt the proposal Weyerhaeuser had laid out was adequate to protect the slope,” Shambo said.
Montgomery questioned the old-growth stump criteria.
“The idea that old growth stumps tell you something about the potential for stability is not something geologists believe,” Montgomery said.
Montgomery said root structures inherently stabilize slopes, but Weyerhaeuser officials argued that based on the depth of the slides, the relatively shallow root base of conifers would have been ripped out of the ground.
Montgomery said the hillside was misidentified by Weyerhaeuser.
“We can quibble about the definition of potentially unstable in a regulatory or scientific sense,” Montgomery said. “But the slopes speak for themselves. They, in fact, failed, and were therefore potentially unstable.”
Sutherland said Tuesday’s exercise was not designed to assign blame for the slides.
“I’m not looking to point fingers and the governor is not looking to point fingers,” Sutherland said. “I want to know what it is we can learn from this and how that is applicable to other circumstances.”
During a special February meeting, the Forest Practices Board approved $400,000 in federal grant money for a statewide slope stability study, and the Legislature approved an additional $200,000 for the effort that is expected to yield data next winter.
DNR officials are not sure if the Stillman site will be studied specifically, but they said the new information will inform the debate, and have a big influence on how the board looks at its rules.
Eric Schroff, the DNR Pacific Cascade region manager who has been working in the area since the flood, said no matter what ultimately caused the slides, people shouldn’t underestimate the complexity of forest practices and regulatory procedures.
“It’s a lot easier to assess that slope now that the trees are off of it,” Schroff said.
Dan Schreiber covers county government and environmental issues for The Chronicle. He may be reached at 807-8239 or firstname.lastname@example.org.