Wasco County Landfill Landslide - Operational Stability
The Dalles, Oregon
For over 20 years LT has provided landfill development support for multiple owners of the Wasco County Landfill. The nearly 200-acre landfill site is situated on marginally-stable ancient landslide terrain and receives over 600,000 cubic yards of refuse annually. Several of these ancient landslides have been reactivated as a result of construction activities during expansion of the active portion of the landfill. Our services have included performing subsurface investigations, monitoring of landslide movement, stability analyses of existing conditions and final landfill configuration, assisting with permit compliance for site development, and providing recommendations on refuse placement in active landslide terrain.
The placement of landfill liner and refuse on moving ground presents a risk to the landfill liner system being damaged. To avoid this risk, construction of new landfill liner does not take place on moving ground as required by DEQ. LT has provided guidance to Waste Connections on expansion of the active filling area to minimize the potential of reactivating slide movement. Subgrade cuts and fills are minimized for liner placement and refuse is placed in a bottom-to-top sequence starting on stable ground outside of the ancient slide limits. Mitigation measures implemented to reduce or stop landslide movement include construction of a rockfill key trench, placement of a soil buttress or re-routing of haul roads.
An observational approach has been utilized to closely monitor slide movement and evaluate the effectiveness of implemented mitigation measures. Slope inclinometers are monitored on a quarterly basis to ensure slide movement does not impact landfill operations. Large cost savings have been realized by using the observational approach to construct only what is necessary to stop slide movements.
The placement of landfill liner and refuse on moving ground presents a risk to the landfill liner system being damaged. To avoid this risk, construction of new landfill liner does not take place on moving ground as required by DEQ. LT has provided guidance to Waste Connections on expansion of the active filling area to minimize the potential of reactivating slide movement. Subgrade cuts and fills are minimized for liner placement and refuse is placed in a bottom-to-top sequence starting on stable ground outside of the ancient slide limits. Mitigation measures implemented to reduce or stop landslide movement include construction of a rockfill key trench, placement of a soil buttress or re-routing of haul roads.
An observational approach has been utilized to closely monitor slide movement and evaluate the effectiveness of implemented mitigation measures. Slope inclinometers are monitored on a quarterly basis to ensure slide movement does not impact landfill operations. Large cost savings have been realized by using the observational approach to construct only what is necessary to stop slide movements.
Wasco County Landfill Reactivated Landslide Mitigation