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U.S. Environmental Protection Agency

Missouri Water Science Center


Summary of RI-FS results for the Front Street site (OU1):

  1. There is substantial tetrachloroethene (PCE) contamination in soils along Front Street and beneath the southeast part of the Front Street building to depths greater than 20 feet. More than 5,200 cubic yards of soils are contaminated with PCE concentrations greater than 19,000 ug/kg (micrograms per kilogram). The largest PCE concentration detected was 6,200,000 ug/kg.
  2. A plume of PCE contaminated ground-water is migrating in the Missouri River alluvial aquifer from the south side of the Front Street building northeast about 600 feet to the Missouri River. The plume contains an estimated 5.7 million gallons of water with PCE concentrations above the maximum allowable level of 5.0 ug/L (microgram per liter). The largest PCE concentration detected was 11,000 ug/L.
  3. PCE use and disposal at OU1 is probably not the cause of the PCE contamination that closed city wells W1 and W2.
  4. PCE in soils at OU1 may present a carcinogenic risk to future residents, occupational workers, and recreational visitors.
  5. The use of ground water at OU1 by future residents and occupational workers pose excess carcinogenic and non-carcinogenic risks from PCE and other contaminants.
  6. PCE contamination at OU1 does not present an unacceptable risk to ecological receptors (animals and plant life).
  7. The Feasibility Study (FS) for OU1 has identified 8 potential strategies for addressing the PCE contamination in soils and ground water at OU1.

Reference:

U.S. Environmental Protection Agency, 2003, Focused remedial investigation of operable units OU1 and OU3, Riverfront Superfund Site, Franklin County, Missouri: U.S. Environmental Protection Agency Region VII, DW1495217301-2, Kansas City, Kansas.

Summaries and excerpts of studies related to Operable Unit OU1 are available for downloading.


The following is a graphical summary of the extent and magnitude of PCE contamination at the Front Street Site (Operable Unit OU1). The illustrations are from the Focused Remedial Investigation of Operable Units OU1 and OU3 (USEPA, 2003).

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Early in the RI, analysis of core samples from trees was used to screen area of potential subsurface PCE contamination. Analysis of these samples indicated subsurface PCE contamination near the Front Street Building extending northeast toward the Missouri River.   PCE distribution in trees in the downtown area near OU1
  PCE distribution in trees in the downtown area near OU1 (368 kb pdf)
PCE was detected at 128 of 144 soil sampling locations at OU1. The largest concentrations were along and beneath Front Street south of the Front Street building and beneath the southeast part of the building.   Figure showing maximum PCE concentration at soil sample locations (128 kb pdf)
  Figure showing maximum PCE concentration at soil sample locations (128 kb pdf)
Soils stained black with PCE and other contaminants were found in some areas beneath Front Street.   Figure showing PCE stained soil beneath Front Street (361 kb pdf)
  Figure showing PCE stained soil beneath Front Street (361 kb pdf)
A computer program was used to assist in compiling all of the soil sample data into a series shaded contour maps. The maps show the PCE concentration every 2 feet in depth across OU1.   Figure showing PCE in soils at 6-8 feet (171 kb pdf)
  Figure showing PCE in soils at 6-8 feet (171 kb pdf)
  PCE at 14-16 feet (160 kb pdf)
  PCE at 14-16 feet (160 kb pdf)
  Images showing PCE versus depth
  Images Showing PCE Versus Depth
PCE was detected in 22 of 28 ground-water sampling locations at OU1. A plume of PCE contamination exists in the alluvial aquifer about 20 to 50 feet below the land surface at OU1. The contamination is moving northeast to the Missouri River at several feet per year   Figure showing PCE versus depth
  Figure showing the PCE plume in the alluvial aquifer (319 kb pdf)
Using a combination of data collected from the site, a hydrogeologic cross-section was drawn between Front Street and the Missouri River. The section is along the center of the PCE plume and shows the PCE contaminated soils and sandy sediments transporting dissolved PCE from the site.   Hydrogeologic section between Front Street and the Missouri River.
  Hydrogeologic section between Front Street and the Missouri River (257 kb pdf)
Samples collected every 5 feet during the drilling of bedrock monitoring wells indicate that a plume of PCE contaminated ground-water is moving in the bedrock beneath OU1 from an unknown source somewhere south (upgradient) of city well W2. This data indicates that it is unlikely that PCE dumped at OU1 is the source of the PCE detected in the contaminated city wells because OU1 is downgradient (north) of city well 2.   Figure showing PCE distribution in bedrock monitoring wells near OU1
  Figure showing PCE distribution in bedrock monitoring wells near OU1.

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