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: December 31, 2010

Point of Contact:
Sharon Fang
USEPA 1650 Arch Street
Mail Code: 3HS21
Philadelphia PA 19103-2029 
Tel: 215-814-3018 
Email: fang.sharon@
epa.gov

Commodore Semiconductor Group
Lower Providence Township, PA


Hydrogeology:

The Site is underlain by the middle member of the Triassic age Stockton formation. The Stockton formation is characterized by siltstone, fine-grained and medium-grained sandstone, red shale, very fine-grained red sandstone, and a few beds of coarse-grained sandstone and conglomerate. The strata have a regional dip of five to eighteen degrees to the northwest. Fractures within the bedrock appear to be vertical, and for the most part, evenly distributed.

The unconsolidated overburden deposits consist of predominantly red-brown silt and clay. Overburden thickness ranges from six feet to 22.5 feet. The soil/bedrock interface is gradational. Soil gradually grades into consolidated material where relict bedding is visible, and then into weathered
bedrock.

Two units that are not isolated hydraulically were identified beneath the Site: a shallow (perched) water-bearing zone in soil and shallow bedrock and a deeper bedrock unit. The saturated thickness of the shallow zone varies seasonally and is dependent upon
precipitation. The bedrock water-bearing zone does not appear to respond to precipitation.

Groundwater movement through the heterogeneous anisotropic bedrock water-bearing zone occurs through a combination of primary and secondary porosity. Groundwater movement and hence
migration of the site-related contaminants is influenced by the pumping of the bedrock public water
supply wells: VFCC-2, VFCC-3, VFCC-4, Aud-3, and Aud-5, as well as the gravel bed of the Transco pipeline. The regional groundwater flow is to the southeast; however, groundwater in the
vicinity of the Site appears to be moving south-southwest as well.

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

Original plume where MCLs were exceeded was approximately 3,200 feet long and 2,000 feet wide.

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (640 µg/L)
  • - 1,2-Dichloroethene (280 µg/L)
  • - 1,1,1-Trichloroethane (51 µg/L)
  • - Tetrachloroethene (30 µg/L)

Site Characterization Technologies:

No technologies selected.


Remedial Technologies:

  • - Chemical Oxidation (In Situ)
    • Permanganate
  • - Pump and Treat
  • - Soil Vapor Extraction
    • In Fractured Bedrock Vadose Zone
Comments:
The local water authority's VFCC-2 was found to be contaminated 1979 and was capturing a large part of the site plume. This well was fitted with an air stripper in 1984 and used for cleanup until 2007 when the water authority shut it down. Also as part of the ROD the facility installed extraction wells for the deeper plume. This system, which includes seven extraction wells came on line in August 2000.

A full scale SVE system began operated August 2003  March 2005 to cleanup vadose zone overburden and bedrock.

Permanganate was injected between August 2003 and October 2003 into the shallow soil and bedrock beneath a site building.

In January 2007, the Audubon Water Company stopped accepting treated water from the groundwater treatment system. The site currently sends treated water to the sanitary sewer system.
Remediation Goals:

MCL (ppb)
Bromodichloromethane 80*
Chloroform 80*
1,2 Dichlorobenzene 600
1,4 Dichlorobenzene 75
1,1 Dichloroethane 810**
1,2 Dichloroethane 5
1,1 Dichloroethene 7
1,2 Dichloroethene 70
Tetrachloroethene 5
1,1,1 Trichloroethane 200
Trichloroethene 5
Vinyl Chloride 2
* Contaminant with updated MCL
**Non- carcinogenic health-based concentration


Status:

The pump and treat system continues operation. An overall decrease in contaminant concentrations has been observed. As of March 2010, more than 657 million gallons of water had been treated and 481 pounds of COCs had been removed via the recovery wells and the French drain.

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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