Former gas station where one underground storage tank (UST) was removed and one UST cleaned out and left in place
- No Further Environmental Investigation under Current Land Use Notice issued by EPA February 2013
- 2011- 2013 Groundwater monitoring
- 2010-Groundwater monitoring, vapor intrusion investigation
- 2009- PCS removed, l soil samples taken; three groundwater monitoring wells were installed, developed, and sampled
- 2008-One UST removed, one UST cleaned out and left in place, soil samples collected, PCS landfarmed
- Work funded by EPA through LUST program
- Response actions ongoing
In 1951 two USTs with a 550 gallon capacity were installed at the Ferdinand Gas Station. One was located underground inside the gas stations exterior walls. In 1997 the USTs were pumped out and locked when the gas station closed. In 2008 the UST and product lines underneath the building could not be removed because they were located under the hydraulic lift in the shop building. A hole was cut in the top of the UST and the tank was cleaned out. A hole was cut through the bottom of the tank to sample the soil beneath, but groundwater entered the hole and the sample could not be collected. A second hole was cut through the side of the tank and a soil sample collected. The sample exceeded the Idaho Department of Environmental Quality’s (IDEQ) Initial Default Target Levels (IDTLs). The tank and product lines were filled with concrete grout (Bristol 2009).
The outside UST was located 13 feet below ground surface (bgs). The UST was inerted, cleaned, and removed. Fuel odor was apparent in the soil. The UST was in poor condition, rusted, and with obvious holes on one end. After removal of the UST, the excavation was dug to a depth of 15 feet bgs to remove the contaminated soil. Approximately 24 cubic yards of petroleum contaminated soil (PCS) was removed and stockpiled. The stockpile was covered with visqueen until it was loaded and transported to a disposal facility. The soil sample results from the outside UST indicated that two samples exceeded IDEQ’s IDTLs (Bristol 2009).
In 2009 Bristol removed an additional 190 cubic yards of PCS and disposed of it at Jackson’s Dirt Farm, collected soil samples; and installed, developed, and sampled three groundwater monitoring wells to assess the groundwater conditions beneath the site (Bristol 2010).
Based on the 2009 groundwater analytical results, groundwater beneath the site was impacted with benzene, ethylbenzene, and naphthalene. The well located near the residence was the most contaminated, it contained benzene, ethylbenzene, and naphthalene above the IDEQ IDTLs. The well located at the northwest corner of the shop had elevated benzene in the groundwater (Bristol 2010). In 2009, thru 2013 groundwater sampling continued.
In 2010 a vapor intrusion investigation was conducted by the Nez Perce Tribe Water Resources Division to determine if soil vapors pose a health risk to residents at the site. The air sampling results were inconclusive and a second vapor intrusion investigation is not warranted.