On 20 Sep 06, an Associated Petroleum Products (APP) fuel truck slid off the road and over an embankment at Howard Hanson Dam. Incident resulted in the release of approximately 600 gallons of #2 diesel fuel into the soil. The tanker truck has been removed from site.
Initial soil analysis predicted that the fuel would quickly move vertically through the soil until it reached the water table.
This fuel has traveled from the spill site to the reservoir shore. Temporary measures have been put in place to minimize the fuel impact to the water. This has been accomplished with a series of trenches dug with absorbent materials placed in them and also a combination of oil only absorbents and rigid containment boom.
PAST 24 Hours:
• Tiered containment trenches, cut into the slope below the point of seepage to prevent fuel from reaching the water, are being inspected on a regular schedule. Absorbent materials were replaced this morning by NRC Environmental Services (NRCES), checked again around lunchtime, and will be replaced again this evening (23 Sep 06).
• Containment booms and absorbent materials remain in the water as a preventative measure.
• Corps personnel continue to perform periodic visual assessments to look for additional signs of fuel seepage or sheen in the water.
• NRCES, the response contractor submitted their remedial design/proposal, which was discussed during a conference call this afternoon (see “other efforts” below).
• Tacoma Public Utility (TPU) representative Brian King was briefed by telephone and both he and Chris McKeen will attend the meeting Monday morning.
NEXT 24 Hours:
• NRCES will continue to prepare their equipment for deployment and will begin making improvements to the access road surface – required before any remedial work can begin – as early as this afternoon (24 Sep 06).
• Meeting with key parties and stakeholders scheduled for 0900 Monday morning at Howard Hanson Dam (25 Sep 06).
• NRCES will bring in a hydro/geological engineer either today or tomorrow to work the slope stability issue -- Monte Kaiser (CENWS-EC-DB-CS) will assist.
The removal of contaminated soil and restoration activities are to be performed in four phases:
Phase 1: Water protection, access road repair
Phase 2: Slope Stabilization
Phase 3: Contaminated soil removal, confirmation sampling
Phase 4: Backfill and restoration
NRC Environmental Services’ (NRCES) approach will be to control petroleum runoff to minimize the impact to the watershed, throughout the course of the project. NRCES will then remove all of the contaminated soil from the site and sample the area to confirm that all of the contamination has been remove per Washington State Department of Ecology’s MTCA regulations. Once all of the contamination has been removed NRCES will then restore the site to its original state.
• Remedial action will likely be a combination of Plan A (excavation of the lower slope area) and Plan B (trenching/French drains in the lower slope and extraction wells between the accident site and the lower slope). Final decision to be made after evaluation of the slope stability issue.
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