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.
• 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 are being replaced twice a day and will be weighed to estimate quantity of fuel absorbed.
• Containment booms and absorbent materials remain in the water as a preventative measure – the pool level has dropped slightly and there is NO sheen present in the water.
• Periodic visual assessments are being performed to look for additional signs of fuel seepage or sheen in the water. None observed to date.
• NRCES has mobilized to 24-hour operations, effective today.
• The trench opened on the access road, in an attempt to catch fuel during the emergency phase of the response, was filled in.
• NRCES has begun work to remove contaminated soil from the lower slope area. It is expected that all contaminated soil can be removed from the site and backfilled with clean material within 7-10 days.
• A “super sucker” was used to remove surface soil contamination from the accident site on the upper slope. Appropriate method of treatment of the residual hydrocarbons has not yet been determined. Jute mat will likely be used to stabilize the slope when work in that area is completed.
• APP has been provided with a list of items for inclusion into the revised NRCES action plan.
• Harold Cashman (Whatcom Environmental) has been identified as the single POC for all site Operations. He will arrive on site each afternoon for night shift. Jason Potts will provide updates to Brian Pettitt during day shift, but all official reports will be made through Mr. Cushman.
• The excavator operator suffered a minor ankle sprain from stepping on a rock, but was able to continue working. No lost time.
• Traffic safety issue was addressed with the deployment of several “construction in progress” type warning signs on the main road, at each end of the worksite.
• Whatcom Environmental is working with surveyors from Tacoma Public Utilities (TPU) to take elevations to more accurately map out the spill/cleanup site.
• Silt fencing was installed at the bottom of the lower slope to prevent material from sliding into the water.
• A public news release regarding this incident was released this afternoon (http://www.nws.usace.army.mil/Template/Display/More_New_News.cfm?recno=283)
• Exploratory “potholes” were dug in line with the suspected fuel flow and residual fuel was successfully located at approximately 18’ depth on the third attempt. This spot, located near the switchback on lower access road, was then trenched and appears to have cut off the flow of residual fuel between the upper and lower slopes. A French drain or extraction well may be installed (TBD).
• NRCES has been building up the access road surface with crushed gravel; as of 1500, all material was in place and only compaction remained -- it should be completed early this evening.
• An extraction system is being installed in the trench between the upper and lower slopes. Once installed, the trench will be backfilled and the area stabilized.
• Vacuum operations should begin on the extraction system; a vacuum truck will be used until a portable system can be installed.
• NRCES will continue staging to begin soil removal operations on the lower slope. Contaminated soil removal could begin as early as tomorrow morning and be completed within 7-10 days.
• The lower slope surface will continue to be monitored and absorbent materials replaced twice a day.
• A mobile laboratory will be brought to the site to conduct on-site soil analysis during the removal phase. Sample turnaround is expected to be approximately one hour.
• NRCES and Whatcom will coordinate directly with Traylor Brothers to replenish the materials that they supplied during the emergency phase of response operations.
• NRCES will coordinate with NW Erosion Control to determine an appropriate means of seeding/treating the upper slope.
• Large rocks removed during excavation will be set aside for later use; they will not be used during backfill.
• Appropriate method of treating the residual hydrocarbons on the upper sloe must be discussed further. Jute mat will be used to stabilize the slope when work in that area is completed.
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