On November 3rd, 2006, a Puget Sound Energy (PSE) generator above ground storage tank (AST) was overfilled when automatic shutoff valves failed. The storage tank is filled by three 12,000 gallon underground storage tanks (UST’s). It is estimated that 18,000 gallons of diesel fuel spilled onto the generator pad and drained downhill into a drainage ditch which flows under Crystal Mountain Drive to Silver Creek and the diesel fuel spilled down an access road close to ¼ of a mile in distance. The fuel spilled at a rate of approximately 18 gallons per minute.
Temporary containment measures were implemented in an attempt to minimize fuel moving offsite towards Silver Creek. Containment measures include a series of trenches, use of absorbent materials, and construction of an underflow dam with PVC pipes and earth. Additional interceptor trenches have been excavated to collect product seeping down gradient of the generator site.
Thursday, November 23, 2006
• All site activities were postponed and personnel were demobed for the Thanksgiving Holiday
Friday, November 24, 2006
• Normal operations have resumed, including traffic control, snow removal, and surface water sampling.
• NRC will provide estimates for the amount of acreage cleared to for the construction of Silver Creek access road.
• The oil/water separator for the interceptor trench arrived.
• USFS Guard House well, along State Route 410, was added to the drinking water sampling plan. This site will be sampled twice a week.
Saturday, November 25, 2006
Excavation Activities
(between the generator road and power line access road)
• 27 Single truckloads of excavated soil have departed offsite during the night, 27 soil samples and 2 duplicates were collected for NWTPH-Dx. 7 additional trucks were loaded during daylight operations.
• The excavation area was dug down to bedrock.
• Contaminated soil remains near the generator site, near the previous night’s excavation. The excavation is approximately 20-25 feet deep, the smell of diesel is present.
Trench Operations
• WADOE wants fill soil and discharge water at non-detect levels for diesel.
• Silver Creek Trench area has been cleared of trees, brush and leveled with dirt.
Sunday, November 26, 2006
• 36 single truckloads of soil were transported offsite during the night. 36 soil samples for NWTPH-Dx collected. No confirmation samples were taken.
• The Silver Creek access road is complete, and the bench above the proposed interceptor trench is near completion.
• Soil will continue to be removed from power line access road and generator access road.
Monday, November 27, 2006
• 34 single truckloads of soil were removed offsite during the night. No confirmation samples were collected.
• Five truckloads were removed from the Silver Creek interceptor trench.
• Technical personnel from PSE arrived onsite to evaluate generation station.
• Sample results from the excavation area below the generation station, range from 2000-10,000ppm.
• The proposed interceptor trench would be 4-5 feet deep, and connect to an oil/water separator with a batch tank, and carbon filter onsite.
Tuesday, November 28, 2006
• 45 single truckloads of soil were removed offsite during the night. 45 soil samples were collected for NWTPH-Dx. No confirmations samples were collected for lab analysis.
• No trucks were available today due to icy road conditions.
• NRC will divert a drainage stream near the trench operations to reduce the amount of moisture in the soil before excavating.
Wednesday, November 29, 2006
• No night operations were conducted. The two dump trucks that are onsite moved 16 loads of soil out of the interceptor trench area and stockpiled the soil at a contaminated location on the power line access road.
• PSE will design a return system for overflow from the day tank for the generator back into the underground storage tanks.
• PSE will continue to recover product from the ground and maintain all spill control measures.
• PSE plans to continue daily water sampling for both drinking water and surface water.
• PSE will continue to excavate the Power Line Access Road.
• PSE will continue to install the expanded recovery trench and the treatment system in the lower wetlands area.
• Soil borings and site geology characterization will continue.
• Diesel and diesel contaminated water collected by the interceptor trench will be treated.
• Discuss with WADOE and PSE the steps needed to transition from an emergency response into a long-term removal project.
• Awaiting the Installation of the treatment system in the trench area.
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