U.S. EPA Contaminated Site Cleanup Information (CLU-IN)


U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Fractured Bedrock Project Profiles

Last Updated: January 2, 2011

Point of Contact:
Joseph McDowell
USEPA 1650 Arch Street
Mail Code: 3HS20
Philadelphia PA 19103-2029 
Tel: 215-814-3192 
Email: mcdowell.joseph@
pa.gov

Stanley Kessler
King of Prussia, PA


Hydrogeology:

The Cambro-Ordovician carbonate sequence dominates the geology and hydrogeology at, and in the immediate vicinity of, the Site. This sequence of carbonate rocks consists of three distinct geologic formations which are, from oldest to youngest, the Ledger (dolomite), Elbrook (limestone), and Conestoga (limestone). The bedding
strike of this carbonate sequence is reported as N80E in the vicinity of the Site with bedding dip at 50 - 55
degrees to the south-southeast.

The Site is underlain by the Conestoga Formation which consists of blue to gray, granular, thin-bedded, micaceous limestone, a middle dark graphitic member and basal beds that are conglomeratic containing pebbles
and masses of marble in a limestone matrix. Underlying the Conestoga Formation and mapped as subcropping to
the north of the Site is the Elbrook Formation. The Elbrook Formation is described as a thinly-bedded, light
to light blue limestone. There are some beds of finely laminated, fine-grained marble as well. The Ledger Formation underlies the Elbrook Formation and is mapped as subcropping immediately north of the Elbrook Formation. The Ledger Formation mainly consists of a light gray to white dolomite that is often massive.

The Site geology, based on monitoring well data, consists of saprolite and underlying limestone bedrock. Saprolite is the chemically weathered product of bedrock and ranges in thickness from 30 to 70 feet. The saprolite consists of brown, orange-brown, and olive green sandy silts, clayey silts, and silty clays with phyllite and limestone fragments.

The carbonate aquifer underlying the site has been described as anisotropic with a principal axis of highest transmissivity trending east-northeast.

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

The highest concentration of TCE was in the 149 to 160 foot bgs interval. The ROD and 5-year reviews do not indicate plume extent.

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (600 µg/L)
  • - 1,1,1-Trichloroethane (340 µg/L)
  • - 1,1-Dichloroethene (37 µg/L)
  • - 1,2-Dichloroethene (5 µg/L)
  • - Benzene (7 µg/L)

Site Characterization Technologies:

  • - Vertical Chemical Profiling
    • Packer Isolation
  • - Pumping Tests
  • - Fracture Trace Analysis

Remedial Technologies:

  • - Pump and Treat
Comments:
The pump and treat system started October 1998. In 2003 the system consisted of two open hole pumping wells (40 gpm total) and a liquid carbon filter.
Remediation Goals:

Cleanup goals were MCLs.


Status:

TCE levels continue to decrease or remain stable in most monitoring wells and extraction well MW-8. Extraction well RW-l and monitoring well MW-4 located in the vicinity of a former source area are showing increasing trends (2009).

http://cfpub.epa.gov/supercpad/cursites/csitinfo.cfm?id=0300862

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For more information on Fractured Bedrock, please contact:

Ed Gilbert
Technology Assessment Branch

PH: (703) 603-8883 | Email: gilbert.edward@epa.gov