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Study reveals groundwater contributed to massive slide at Ledgewood
Homeowners still living near the massive landslide area in Ledgewood are wary as more pieces of the bluff continue to slough off.
Ralph Young, a resident living near the landslide site, said a large piece of the bluff broke away last month.
“We were concerned it’ll slide again,” Young said.
Island County Public Works Director Bill Oakes said officials anticipated that more parts of the bluff would break off and that the debris field from the springtime landslide would remain unstable.
The massive landslide occurred in March 2013, destroying a portion of Driftwood Way and prompted the evacuation of several nearby houses.
Oakes said a final geology report concerning the landslide was completed in late 2013. That report described the incident as “unprecedented in recent history” and said it “represents one of the largest landslide events in the recorded history of the Puget Sound area.”
The report, which was compiled by GeoEngineers, Inc., highlighted several factors that likely triggered the collapse:
-The presence of pre-existing slide planes with low strength.
-Possible buildup of groundwater and hydrostatic pressure because of slide debris that may have impeded seepage.
-Erosion at the toe of the slide area regularly occurred during storm events, particularly during the 2012-13 winter.
-High seasonal and cumulative precipitation resulted in increased water infiltration, high amounts of surface water runoff, high groundwater levels and increased seepage into the slide area.
The report notes that groundwater was a significant factor to the slides that were recorded in spring 2013.
People still living near the area are still feeling the impacts of the disaster.
To provide access to the area, Island County installed a one-lane-wide access road that connects Fircrest Avenue with Driftwood Way.
Residents living in the neighborhood experienced the limitations of the road last week when a fire destroyed a condemned home. Fire engines weren’t able to maneuver down the road and smaller brush rigs had to be used to fight the blaze.
After the landslide, county officials red tagged two homes, which means they’re unsafe to enter and yellow-tagged three others, meaning people can’t stay overnight in those homes. The report recommended those homes retain those tags through the 2013-14 winter and spring seasons.
However, the homeowners could provide more studies to support a change in the status of the effected homes. A significant portion of Driftwood Way remains closed and buried under dirt, debris and fallen trees.
Oakes said there aren’t any plans to repair the road. The debris field is too unstable and work won’t take place until it stabilizes, he said. The county will continue to monitor the conditions of the landslide area.