Alley Fuels was a bulk fuel distributor and card-lock retailer on the Banks/Lowman Highway, approximately 5 miles west of Garden Valley, Idaho. The facility consisted of 5 above ground storage tanks (from approx. 5,000 to approx. 10,000 gallons) containing gasoline and diesel fuel. On April 15, 2003, Brico Oil, the supplier to Alley Fuels, reported to the Idaho Department of Environmental Quality (DEQ) that 5,000 gallons of unleaded gasoline was unaccounted for and suspected to have leaked into the ground from one tank at the Alley Fuels facility. Upon inspection, a hole was found in the bottom of the tank. The leaking tank is 470 feet from the Middle Fork of the Payette River, with an approximately 50 foot elevation drop to the River. The owner/operator of Alley Fuels indicated to DEQ and EPA that he did not have the resources to conduct necessary site investigation to determine the extent and migration of spilled gasoline in subsurface soils and groundwater. The facility has since ceased operation, the leaking tank removed, and other tanks emptied.
On 7/14/03, EPA and EPA's START contractor mobilized to the site to conduct site investigation to determine whether spilled gasoline presents an significant threat of discharge to waters of the U.S.. A survey of the river bank and seeps along the area did not indicate a present discharge to the Payette River. START contractor installed six monitoring wells to determine subsurface characteristics, including groundwater depth and flow direction and soils type, and to try to locate the spilled fuel. Groundwater was observed at approximately 25 feet below ground surface. Sample results showed highly contaminated soils at approximately 1 to 3 feet above the water table, indicated that groundwater had dropped significantly from the time of the spill, creating a smear zone, and that the gasoline plume was migrating in the direction of the Payette River. Free phase petroleum was not observed in any of the wells, indicating that spilled petroleum was still largely hung up in the smear zone and/or the slug of it had already migrated through the area of the monitoring wells.
On 4/8/2004, EPA and START contractor personnel re-mobilized to the Site to evaluate current conditions relative to discharge or threat of discharge to the Payette River. Previously installed wells were monitored to determine groundwater elevation and flow direction. From 4/8/04 through 4/12/04, START and drilling subcontractor installed 4 additional monitoring wells in locations down gradient of previous well installations. Two wells were located on the top edge of the embankment leading to the Payette River, and two more wells were located over the embankment along a dirt road that approaches the River. Groundwater and soil samples were collected at new well locations. Groundwater was monitored in all existing and new wells. An approximate 1 inch layer of product was observed in earlier installed MW01, which is the well closest to the former leaking tank. All personnel demobilized from site on April 12, 2004.
Analytical results did not reveal high concentrations of gasoline range hydrocarbons in vadose zone soils in downgradient well locations, however, there were high concentrations of gasoline-range TPX and BTEX in groundwater. Additionally, a sample collected from a seep discharge to the Payette River contained gasoline range hydrocarbons at a concentration of 20,000 micrograms per liter.
On July 21, 2004, the EPA FOSC visited the site with staff from the Bureau of Reclamation's Pacific Northwest Regional Office, Boise, ID. Water level data was collected from the 10 monitoring wells at the site. It was observed that free product in MW01 had increased from 0.07 foot to 0.30 feet since the April 5, 2004 monitoring event.
The FOSC had requested BOR's assistance in evaluating site data developed to date, and to develop a gasoline plume migration model, and provide recommendations regarding threat of release to the Payette River and potential actions to be taken. The FOSC authorized a Pollution Removal Funding Authorization (PRFA) with BOR in the amount of $10,000 for this work.
BOR's subsequent report, along with earlier data and reports from EPA's START contractor, provide sufficient information for the FOSC to determine that, if unmitigated, gasoline hydrocarbons that have have reached and will continue to migrate to shallow groundwater at the Alley Fuels site present a substantial threat of discharge to the Middle Fork of the Payette River, which is a water of the U.S..
A phased approach to cleanup of the Alley Fuel site is planned. The first phase will involve the following activities:
- Sampling of existing monitoring wells and seeps in order to monitor the movement of the contaminant plume;
- Installation of recording piezometers in four of the existing monitoring wells, to monitor seasonal variation in ground-water levels and gradients at the site;
- Construction of a shallow interception trench at the toe of the seep area, in order to intercept contaminated groundwater before it reaches the Payette River. Absorbent pads or a skimmer pump will be used to recover gasoline product from the interception trench, and;
- Installation of a skimmer pump in the well closest to the former leaking storage tank (MW01) in order to remove floating product.
- Use of push probe soil sampling to better define the boundaries of the gasoline smear zone near the former leaking storage tank.
Analysis of data and results from Phase I activities will be used to determine what, if any, Phase II cleanup actions will be required.
The FOSC will increase the FPN ceiling by an additional $110,000 in order to fund the above Phase I activities. These activities will be performed by BOR under an amendment to the existing PRFA. Work should begin as quickly thereafter as possible.
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