DENBY STORE PINE RIDGE INDIAN RESERVATION DENBY, SOUTH DAKOTA March 2009 Denby ACCOMPLISHMENTS • Removed 5 USTs and ancillary equipment • Conducted site investigation • Soil and groundwater monitoring • On-site landfarming of 200 yd3 of PCS • Closure of landfarm EPA Region 8 performed this work in partnership with the Oglala Sioux Tribe. PLANNED ACTIVITIES/ FUTURE STRATEGIES • Conduct a chemical oxidation pilot study • Design and implement subsequent in-situ chemical oxidation (ISCO) injection events • Groundwater monitoring SITE HISTORY The former Denby Store operated as a gasoline station, post office and grocery store. In 1996, an initial investi- gation to assess soil and ground-water at the site was con- ducted by South Dakota Department of Environmental and Natural Resources (SDDENR) at the site prompted by reports of petroleum odors in the domestic water supply at the onsite residence of the store owner. As a result of the investigation, six monitoring wells (MWs) were installed and sampled along with the on-site domestic well. The on-site domestic water supply well was first charcoal filtered then plugged and abandoned. The ambient air was screened in the store, residence and adjacent property buildings using a PID, charcoal tubes with low flow pumps and a combustible gas indicator. Five underground storage tanks (USTs) were removed from the site in 1997 by EPA and the Oglala Sioux Tribe. In 1998, EPA performed additional investigations at the site including: resampling all existing MWs and domestic water wells; performing a soil gas survey; and performing indoor air monitoring. In 2007, the land- farmed soils were removed from the site. TIME LINE Onsite domestic well abandoned and plugged * Carbon filters installed in onsite domestic well ' Groundwater monitoring 6 MWs installed • Site assessment completed • Landfarmed soils removed from site • Collected soil samples from landfarmed soils 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 5 USTs removed from property ^•p jr "*»_ (SB) Groundwater monitoring •> Ground- water monitoring in adjacent prop- erty domestic wells • Soil gas surveys of store and residence " Indoor air surveys of store and residence and adjacent property buildings Groundwater monitoring •• DENBY STORE EPA Region 8 UST Program Technical Contact | Mr. Raymond Faliskie | (303) 312-6124 or faliskie.raymond@epa.gov | www.epa.gov/region8/ust/ ------- |