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Daniel J. Goode, Claire R. Tiedeman, Thomas E. Imbrigiotta, Pierre J. Lacombe,
Eric W. Best, Francis H. Chapelle, Paul M. Bradley, Allen M. Shapiro,
Kinga M. Revesz, Carole D. Johnson, John H. Williams (all at U.S. Geological Survey, USA),
and Jeffrey M. Dale (U.S. Navy, Lester, Pennsylvania, USA)

Abstract

The U.S. Geological Survey (USGS), in cooperation with the U.S. Navy, is conducting a multidisciplinary investigation of the distribution and fate of trichloroethene (TCE) in gently-dipping fractured mudstones that underlie the 60-acre former Naval Air Warfare Center (NAWC), West Trenton, New Jersey. TCE, (a dense non-aqueous-phase liquid (DNAPL)) was released to the land surface during 1951-98 and natural microbial reductive dechlorination has partially transformed TCE to cis-1,2-dichloroethene (cisDCE), vinyl chloride (VC), and ethene. Maximum dissolved concentrations of TCE, cisDCE, and VC have slowly declined since the early 1990’s in waters from more than 70 bedrock monitoring wells (most with 15 to 20-ft open intervals) and are now about 200,000, 16,000, and 1,200 micrograms per liter, respectively. TCE and its degradation byproducts have also been removed from the ground water by a pump and treat system operating since the mid-1990's.   

NAWC West Trenton is underlain primarily by mudstones of the Triassic Lockatong Formation and to a lesser extent by sandstones and shales of the Stockton Formation of the Newark Basin. Extensive characterization of the geology and dissolved contaminant concentrations indicates that bedding-plane fractures and thin continuous fissile or laminated mudstone strata are major transport paths. Persistently high concentrations of TCE suggest that large contaminant mass lies in less-permeable fractured rock and perhaps in the primary porosity of unfractured rock. During drilling in 2005 DNAPL-detecting fabrics and elutions off of cuttings did not detect DNAPL.  DNAPL has not been observed in optical logs of or water samples from monitoring wells.

Extraction and analysis of dissolved concentrations of TCE and other volatile organic compounds (VOC's) from bulk-rock samples collected during coring of a 170-ft deep borehole indicate that TCE occurs within the primary porosity of the rock matrix adjacent to fractures at all depths. However, TCE was not detected in many sections, especially in unfractured massive red and light-gray mudstones. Below the weathered zone, detection of TCE in bulk-rock samples is correlated with lithology, with highest concentrations measured in black or dark-gray mudstones and fractured laminated rocks. Further detailed analysis will examine the correlation between bulk-rock VOC concentrations and rock properties, for example fracture transmissivity. The bulk-rock VOC results are qualitatively consistent with, but different from, observed concentrations in water samples pumped from isolated zones using temporary packers and diffusion-sampling devices installed in the borehole for about one year.

Current USGS research includes monitoring chemical, microbial, and hydraulic conditions following a biostimulation and bioaugmentation pilot study by the Navy, GeoSyntec, Inc. and ECOR Solutions, Inc. in July 2005. A culture containing Dehalococcoides and an electron-donor solution of emulsified oil and lactate was injected into four bedrock wells within a small (about half an acre) area. Initial results include nearly 100 percent reduction of TCE and increases in cisDCE and VC in water from the four wells. To date, only small changes in concentrations have been measured in water from down-gradient wells. Further analysis of these monitoring data will provide insight into the important mechanisms controlling transport and transformation of the contaminants in response to the injection of electron donor and microbes, and the conditions under which contaminant degradation is most effective.

Future multidisciplinary research at NAWC will focus on transport, transformation, and remediation of VOC’s in this highly heterogeneous, fractured-rock hydrogeologic framework. This research will include, for example, investigations of matrix diffusion processes, water-rock interaction and its impact on the biogeochemistry of the ground water, the ecology and degradation capabilities of indigenous and injected bacteria, and VOC transformation rates by natural and enhanced biodegradation.

Citation: Goode, D.J., Tiedeman, C.R., Imbrigiotta, T.E., Lacombe, P.J., Best, E.W., Chapelle, F.H., Bradley, P.M., Shapiro, A.M., Revesz, K.M., Johnson, C.D., Williams, J.H., Dale, J.M., 2006, Distribution and Fate of TCE in Fractured Sedimentary Rocks of the Newark Basin, NAWC, West Trenton , New Jersey: National Ground Water Association Focus Conference on Eastern Regional Ground Water Issues, Portland, Maine, September 2006 (http://pa.water.usgs.gov/projects/frhr/goode06.html).

Keywords: NAWC, West Trenton, New Jersey; Lockatong Formation; Stockton Formation; Newark Basin; EPA, NJDEP

Use of tradenames is for identification purposes only.

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U.S. Department of the Interior | U.S. Geological Survey
URL: http://pa.water.usgs.gov/projects/frhr/goode06.html
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To find out more about research on fractured rock hydrology in Pennsylvania, contact Daniel J. Goode
|| E-mail: djgoode@usgs.gov || Phone: (610) 321-2434 x203 || Fax: (610) 321-2509 ||
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