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Risky Timber Practices Above Oso Landslide

March 26, 2014

March 2014 Oso Landslide

The Seattle Times reported yesterday that the Snohomish County’s own 2010 report called the slide area dangerous. It also reported that the State Department of Natural Resources (“DNR”) allowed logging on the plateau above the slope. The Seattle Times’ reporting mirrors what PCVA’s own independent research has yielded.

The triangle of land that was logged just before the 2006 Stealhead Mudslide can be seen in this image.

As the Seattle Times reported, the apex of this triangle cut facing down was only a mere 600 feet from the origin of the 2006 Sealhead Mudslide.  This is a particularly dangerous cut in land that has been known for years to be unstable.

DNR approved timber harvesting on this land even though its own maps showed that the Oso slide area is not only steep but also comprised of “Qls” soil, a type of unconsolidated sediment.

Upon further investigation, PCVA has discovered that the U.S. Department of Agriculture (“USDA”) has a database containing additional information about the unstable soil composition of the Oso Mudslide area.  According to the USDA maps, the soil where the mudslide occurred was comprised of fine to gravelly “loam,” a type of soil comprised of mostly sand and silt.  Perhaps more alarming is that the area where the Oso Mudslide occurred, as well as where timber cuts have been allowed, were labeled “ESB.”  According to the USDA’s website, “ESB” stands for “Escarpment, bedrock,” and is defined as “A relatively continuous and steep slope or cliff, which was produced by erosion or faulting, that breaks the general continuity of more gently sloping land surfaces.  Exposed material is hard or soft bedrock.”

Experts alike agree that risky timber activities increases landslide frequency.  In a paper published in Geology in April 2000, several landslide experts surveyed landslides in Washington and concluded that “evidence confirm[s] that forest clearing increases regional landslide frequency.”  They further remarked that a “fundamental change in landscape dynamics is particularly relevant to long-term forest planning, especially where urban areas are extending into landslide-prone terrain.”  A copy of this paper can be found here [176kb PDF].

Just as these experts concluded, another team of experts from Tetra Tech identified the Oso Mudslide area as being dangerous.  As the Seattle Times reported, Tetra Tech’s study, a portion of which can be found here, identified the Oso Mudslide area “spotlighted the risks of the hill.”  “[T]he Steelhead Drive area was identified not only because of the steep slope but also because of a soil type that has been linked to landslides.”

Other Landslide Lawsuits

In lawsuits against DNR and timber companies for negligent forestry practices, PCVA has uncovered a history of relaxed permitting and risky cutting driven by money that has caused numerous mudslides all across Washington.  Despite all experts agreeing that harvesting on or near unstable slopes is dangerous, the practice continues to this day.

In 2011, PCVA filed a lawsuit against DNR and Manke Lumber Company (“Manke”) for their negligent harvest of timber both on and near unstable soil and steep slopes. There, DNR cut on some slopes exceeding 110% in grade and cut on other slopes too close to ravine tops. DNR made these cuts even though a 1960 soil survey of the area identified the soil composition of Little Dewatto valley slopes as “Rough broken land,” which “has no agricultural value and should be left in its natural cover to prevent erosion.” Disregarding the studies, as well as common sense, DNR and Manke cut on extremely steep slopes comprised of unstable soil. These practices destabilized the area, and landslides have recurred every year for the last 5 years in the area, causing significant damage to the properties below.

Similar disregard for the high risk of mudslides is the basis of another lawsuit that PCVA is fighting against Manke. In that case, Manke knew or should have known that a logging road it was required to maintain was likely to fail and cause a landslide. The foreseeable happened on Jan. 7, 2009, when the road failure caused a massive mudslide that destroyed a home and nearly took several lives.