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Newhalem Penstock

CERCLA Response Action: Newhalem Penstock Site and Saddle Replacement

North Cascades National Park Service Complex » CERCLA Response Action: Newhalem Penstock Site and Saddle Replacement » Document List

Introduction:
The National Park Service (NPS) is completing 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 Newhalem Penstock within Ross Lake National Recreation Area. Seattle City Light (SCL) is performing the removal action under NPS oversight. On-site project work began in late September 2016 and is expected to be completed by the end of August 2017.

Background:
The Newhalem Creek Hydroelectric Project is located across the Skagit River from Newhalem, WA. Seattle City Light operates the project, comprising a powerhouse, penstock, bedrock power tunnel, and creek diversion structure, under a Federal Energy Regulatory Commission (FERC) license. The 30-inch diameter penstock is 1,122 feet long and conveys water to the Newhalem powerhouse. Approximately 904 feet of the penstock is above ground and historically rested on wood frame supports, or pedestals, with bases of wood, concrete, or stone. Built in the 1920s, the penstock is now over 75 years old and the wooden supports are/became no longer able of safely supporting the penstock.

In order to comply with FERC dam safety guidelines, SCL is replacing the badly deteriorated wooden saddles, the majority of which (52) are made from treated wood, which have deteriorated over time. Several of these saddles were burned in the August 2015 wildland fire and temporary supports were installed at four saddle locations as an emergency project to prevent the penstock from being damaged by buckling. SCL is now replacing the 52 wooden saddles, including the five temporary supports, with permanent cast-in-­place concrete saddles. Soils around the penstock are known to contain elevated levels of lead, arsenic, and polycyclic aromatic hydrocarbons (PAHs). The lead is from old paint on the penstock; the arsenic and PAHs are from the treated timbers used for the saddles. Contaminated soils will be excavated as part of removing the wooden saddles and constructing formwork for cast-in-place concrete footings and saddles. The approval of the TCRA authorized the removal and disposal of contaminated soil that had to be excavated to complete the scope of work during the penstock saddle replacement project.

The Administrative Record for this action is open for public inspection at any time. Please click on the "Document" link (at left) to review these documents and others related to this removal action.

Contact Information
Elizabeth Boerke, Environmental Protection Specialist, 360-854-7328