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 29, 2003

Point of Contact:
Florin Gheorghiu
Golder Associates Inc.
1951 Old Cuthbert Rd.
Cherry Hill NJ 08034 
Tel: 856-616-8166 
Fax: 856-616-1874
Email: fgheorghiu@
golder.com

Modern Landfill
York County, PA


Hydrogeology:

Low grade metamorphic rocks of Cambrian age including Harpers Formation phillite, Antietam Formation meta-sandstone, and Vintage Formation crystalline dolostone.

The rock materials have a low primary porosity. Consequently, the flow of ground water is controlled by the rock mass discontinuities. The most important structural features which control ground-water flow are:(i) the main fracture systems identified by drilling, trenching, and interpretation of aerial photographs and lineament analysis,(ii) the geologic contacts between different rock units,(iii)the foliation within the Harpers Formation phyllite which causes the anisotropic flow patterns and (iv) the alternating low and high permeability zones within the dolomite strata which also cause anisotropic flow conditions. In all geologic units beneath the site, the range of hydraulic conductivity is greatest above a depth of 100 ft. Below this depth, the range of the values decreases with at least one order of magnitude as a result of a decrease of fracture frequency and fracture porosity with depth. The aquifer is estimated to be limited to a maximum depth of about 200 ft. below ground surface. The generalized relationships between hydraulic conductivity and main fracture systems for the upper 100 ft. of the aquifer is; (i) at the intersection between main fracture systems the hydraulic conductivity is in the range of 10(-3) cm/sec, (ii) along the main fracture systems, 10(-4) cm/sec, and (iii) areas between the main fracture systems, 10(-5) cm/sec and lower.

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (var)

Site Characterization Technologies:

  • - Vertical Chemical Profiling
    • Packer Isolation

Comments:
Constant rate pumping tests, slug tests and drill stem packer tests (a total of about 260 hydrogeologic tests)


Remedial Technologies:

  • - Fracturing
  • - Pump and Treat
Comments:
Controlled rock blasting was installed in 1999 to increase hydraulic conductivity to allow conveyance and collection of leachate-impacted ground water. Accumulated ground water at the downgradient end of the 2,800-foot long blast trench is extracted by a well field.

Hydraulic conductivity was increased by at least two orders of magnitude, thereby promoting ground water collection and a preferential flow pathway using natural horizontal gradients and induced upward vertical gradients.
Remediation Goals:

None provided

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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