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Ross Lake Dam – Sediment Cleanup & Remediation

North Cascades, Washington, USA

Ross Lake Dam – Sediment Cleanup & Remediation

Ross Lake Dam Seattle City Light Remediation Project
Ross Lake Remediation and Sediment Clean Up
EC and the Sour Dough Mountain Wildfires
North Cascades Mountains Ross Lake
Remediation and Sediment Clean Up Demobilization
Electrocoagulation and Ultrafiltration Remediation and Sediment Clean Up

After a decade of planning, permitting and safety coordination, the remediation of a 300’ long submerged tunnel, housing two 72” diameter penstocks (enclosed pipes that deliver water used for lake level management) was finally ready to proceed in the spring of 2023. WaterTectonics worked with project partners on this complex cleanup project over a 14-week period.

Tunnel access, located at the base of a dam deep in the remote northern Cascade Mountains of Washington State, was only accessible by boat. The remediation plan involved suction dredging sediment from the floor of the tunnel and treating the slurry through an electrocoagulation (EC) system followed by ultrafiltration (UF) and polishing filtration media (granular activated carbon and zeolite) located on two 100’ anchored barges floating at the base of the dam.  Barge mounted treatment systems are logistical challenges in their own right, but this project also dealt with the Sour Dough Mountain wildfire, massive amounts of accumulated woody debris (previously unknown), regular crossings of the power plant tail race, continuous moderation of lake levels, and at the end freezing temperatures.  WaterTectonics who performed the role of GC and water treatment provider, partnered with Ballard Marine for all underwater services needed for an integrated solution to turnkey this project for the City of Seattle.

The project successfully removed approximately 30 cubic yards of contaminated sediment that was carefully transported down river and off loaded by crane for authorized disposal. In addition, approximately 1.2 million gallons of water were treated and met state water quality discharge standards for copper (5.3 ppb), lead (16.4 ppb), and zinc (40.1 ppb) with an average turbidity of 2.76 NTU’s.