OUSTER'S LAST CAMP NORTHERN CHEYENNE INDIAN RESERVATION BUSBY, MONTANA March 2009 ACCOMPLISHMENTS • Removed 3 USTs and ancillary equipment • Excavated and removed 3,481 yd3 of PCS • Installed new drinking water well • Conducted site assessments • Installed 5 MWs • Groundwater monitoring • Conducted AS/SVE pilot study • Evaluated feasibility of AS/SVE system as remedial strategy • Designed full-scale AS/SVE system EPA Region 8 performed this work in partnership with the Northern Cheyenne Tribe and with contract support from Avanti Corporation. PLANNED ACTIVITIES/ FUTURE STRATEGIES • Install and operate AS/SVE system • Groundwater monitoring SITE HISTORY A gas station and associated store once operated at the Custer's Last Camp (CLC) site. In 1991, the domestic well located at CLC was found to be contaminated with volatile organic compounds (VOC), including benzene and 1,2 DCA. In 1993 and 1994 the Montana Department of Environmental Quality (MTDEQ) con- ducted site investigations with leaking underground storage tank (LUST) Trust funds. Carbon filtration sys- tems were installed in two domestic wells. Site activities determined the source of the contamination of one of the domestic wells to be from the underground stor- age tank (UST) located in the Montana Department of Transportation (MDT) right-of-way. Four hundred fifty-five yd3 of petroleum contaminated soil (PCS) were removed from the right-of-way. However, additional sampling results indicated contamination from other sources. MTDEQ notified the owners of the CLC site that the state would no longer being funding clean-up activities at the site. EPA inspectors visited the site in 1996 and CLC became eligible for federal LUST funding in 1998. The fuel dispenser, associated piping, 3 USTs and 3,481 yd3 of PCS were removed from the site in 2003. Soil samples taken during the excavation activities indicated elevated concentrations of petroleum hydro- carbons in the soil. A new domestic drinking water well was installed in 2003. Two additional monitoring wells (MWs) were installed in 2004. Groundwater samples continued to show high contaminant concentrations in the vicinity of the former USTs while soil samples showed low levels of contaminants in the vicinity of the former USTs. In 2008, a site assessment was conducted at the site. Three additional MWs were installed, devel- oped and sampled. Results from the site assessment indi- cated that petroleum hydrocarbons present in the soil were limited to the vicinity of the former pump islands. An AS/SVE pilot study was designed and performed. Design work on a full-scale AS/SVE system was com- pleted in January 2009. EPA is planning to install the remedial system in April 2009. TIMELINE Busby ii id LIU ii nrbL ue Let, Leu in *-i_*- uuniebLit, wen Phase 1 Investigation conducted by MTDEQ • 4 MWs installed r Installation of passive free product recovery system in MW-3 * Groundwater monitoring 3,481 yd3 of PCS removed and landfarmed on-s CLC drinking water well plugged and abandoned 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 -Phase II Investigation •> 3 MWs installed » UST in MTD right-of-way determined to be affecting 2nd drinking water well« 455 yd3 PCS removed from MDT right-of-way and land farmed « Carbon filtra- tion systems installed in CLC domestic well and a 2nd well * Free product discovered in MW near pump island *- 3 USTs removed *- Federal LUST funding eligibility determination - MT ceases expenditure of LUST Trust Funds ° EPA conducts site inspection I CUSTER'S LAST CAMP ? EPA Region 8 UST Program Technical Contact | Mr. Raymond Faliskie | (303) 312-6124 or faliskie.raymond@epa.gov | www.epa.gov/region8/ust/ ------- |