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/

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