McNeil Island Closeout Statement

According to information provided to Ecology by MICC, the 3,130 gallons discharged into the emergency generator building via the #2 emergency generator day tank cap flowed to the floor drain, into the underground oil water separator located outside the building, and then to the MICC waste water treatment plant. A portion of the 3,130 gallons was discharged to the Puget Sound following the treatment process and evaporation within the treatment plant.

The other 2,576 gallons, according to MICC information, discharged outside the emergency generator building via the #2 emergency generator day tank vent flowed to a wetland and penetrated into the ground. Of that amount, 1,610 gallons were recovered as free product from the excavation created during cleanup and 916 gallons was removed with contaminated soil. A balance of 50 gallons was estimated to have remained in the ground upon completion of cleanup operations.

Immediate Cause: The flow switch of the #2 emergency generator day tank failed to shutdown the refill pump. Due to the failure of the switch, the refill pump continued to pump diesel from the main 10,000-gallon storage tank located outside the emergency generator building and caused the #2 emergency generator day tank to overflow. Diesel escaped from the day tank through the cap vent hole and the tank vent pipe. The oil escaping inside the building from the vent cap overwhelmed the oil water separator and flowed to the MICC waste water treatment facility. The oil escaping outside the building from the tank vent pipe on the roof made its way to nearby stormwater piping and then to the adjacent wetland.

DOC is implementing the following measures to prevent similar incidents from occurring:

• Procedures for operating the emergency generator and fueling the day tank were revised. After each emergency generator test the pump will be disabled before DOC personnel leave the building. This will ensure that the DOC personnel are present when refill of the day tank occurs. Since the day tank can only provide approximately three hours of fuel for the emergency generator, response by DOC personnel to reactivate the refill pump power supply is required if there is a power outage.

• The fuel delivery control system was reconfigured to ensure that the fuel pump can not operate if the associated emergency generator is not running. The day tank may not be full when the generator shuts down, but a minimum fuel level in the tank will be maintained to provide two hours of generator run time.

• Replaced the oil/water separator outside the emergency generator building with a 300-gallon double-wall sump. The sump is equipped with an alarm that will alert the DOC personnel when a high level occurs due to a spill within the building and will automatically shut off the fuel transfer system to minimize the amount spilled.

DOC is considering the following additional preventive measures for the system:

• Reconfiguring the fuel delivery system by relocating the 10,000 gallon AST outside the building to lower elevation so that the day tank can use gravity to return fuel to the AST.

• Replacing all four day tanks and secondary containment systems equipped with pump-back systems to return fuel to the 10,000 gallon AST.

However, based on the available information, Ecology recommended that DOC implement the following preventive measures to minimize the potential for similar spills in the future:

• Establish a process to ensure that any future design or modification of the fuel delivery systems is evaluated and certified by a professional engineer.

• Establish quality control/quality assurance procedures to ensure that any modification or repair done on the fuel delivery systems is verified and certified by a qualified engineer before returning the systems to operational status.

• Establish an equipment inspection and maintenance schedule based on the manufacturers’ recommendations and specific operating conditions.

• Consult the manufacturer of the day tank to find out if the tank top opening with a cap that has a center vent hole should be removed or modified.

McNeil Island Incident Summary

On October 12, 2002, Department of Corrections employees discovered a release of No. 2 diesel fuel from the emergency generator building at McNeil Island Corrections Center. A small float valve had malfunctioned which caused a transfer pump to continue operating after a day tank was filled. This caused a release of almost 6,000 gallons of diesel fuel. McNeil staff notified the Department of Ecology Spill Response Program, and Ecology personnel responded to the site.

The source of the release was located and shut off. McNeil staff crews were mobilized to pump standing product from the spill site, and to excavate contaminated soil from a marshy area where fuel was discharged through a stormwater line. An undetermined quantity of fuel was also released to the sanitary sewer system and was processed through the wastewater treatment plant on the island, allowing a very small amount of diesel to be discharged into Puget Sound.

A metal sump was installed in the initial excavation to enhance the removal of product from the spill site. The excavation was expanded and backfilled with ½-inch gravel. McNeil Island staff have been pumping oil from the excavation sump daily. Approximately 2,000 gallons of diesel had been recovered as of October 29, 2002.

If you have questions, please contact Spill Responder Doug Stolz, Department of Ecology, at 360-407-6377 or Corrina McElfish at the Department of Corrections at 253-512-6602.

McNeil Island Photos
All photos provide by Doug Stolz, Ecology Spills program, Southwest Regional Office

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