CERCLA Response Action: Ladder Creek Falls Settling Tank
The National Park Service (NPS) is conducting a time-critical removal action (TCRA) in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to mitigate potential risks to public health, welfare, and the environment from the release or threat of release of hazardous substances along the Ladder Creek Settling Tank Site (Site) within Ross Lake National Recreation Area. Seattle City Light (SCL) is performing the work under NPS oversight. On-site project work began in late August 2017 and is expected to be completed by November 2018, if not sooner.
The Ladder Creek Settling Tank Site is located within Ross Lake National Recreation Area, in Whatcom County, Washington in a remote, forested area approximately 40 feet from Ladder Creek, a very steep and cascading stream, and approximately 100 yards upstream of the creek's confluence with the Skagit River. The Site is also approximately one quarter mile from the Gorge Powerhouse (operated by Seattle City Light) and across the Skagit River from Newhalem, WA.
The Site is comprised primarily of a steel settling tank which was historically used for sedimentation of creek water for the town of Newhalem' s domestic water supply. This tank was previously enclosed within a two-story protective structure, but in 2015, the Goodell wildfire burned through the area, completely destroying the housing structure and leaving a debris field in its wake. An assessment completed by the NPS following this wildfire found that the water tank, which was left intact but impacted with residue from the fire, is now uncovered and is collecting rainwater.
The assessment also found that the debris field on the ground surface surrounding the tank contains charred construction materials including paint, mastic coating, electrical
cables/insulation, lighting, molten/re-solidified metal roof shards, and unidentified materials. Soil in approximately the same area as the debris field also was impacted by the fire, primarily by airborne fallout during the burning of the building structure. Post fire sampling results indicate concentrations of lead and arsenic within the water tank and arsenic, chromium, lead, and carcinogenic polycyclic aromatic hydrocarbons (cPAHs) within the surrounding soil.
The settling tank and associated structures are located on approximately 0.09 acres of land that is owned by the United States and managed by the NPS, but the infrastructure is owned, operated, and maintained by SCL. The terrain surrounding the tank is steep, and ground access is limited to either walking/hiking along a rugged foot trail.
To mitigate potential risks to public health, welfare, and the environment from the release or threat of release of hazardous substances now present on Site, SCL will clean the inside of the settling tank, remove burned debris and contaminated soil from the Site, and undertake actions to restore the Site to its pre-removal contours and native vegetative conditions.
The main elements of the TCRA include: Clean inside of settling tank with post-removal confirmation sampling (Phase I); Remove debris and shallow surface contaminated soil resulting from the 2015 Goodell Creek wildfire with post-removal confirmation sampling (Phase II); Load, transport, and properly dispose of burned debris and contaminated soil at an approved disposal facility (Phase III); and Restore Site to its pre-removal contours and vegetative conditions (Phase III and IV).
Ultimately, this TCRA will entail excavation and disposal of burned debris and contaminated sediment within and soil located around the Ladder Creek Settling Tank, thereby minimizing risks to human health and the environment and mitigating, if not eliminating, the source of the contamination. Future response actions at the Site are not expected based upon available information.
Elizabeth Boerke, Environmental Protection Specialist, 360-854-7328