HR: 1330h
AN: H42F-1152    [PDF]
TI: Geologic Controls on Groundwater Flow and Contaminant Transport in Fractured Bedrock
AU: * Warner, J
EM: jim.warner@erm.com
AF: Environmental Resources Management, 1777 Botelho Drive, Suite 260, Walnut Creek, CA 94598 United States
AU: Truskowski, M
EM: melinda.truskowski@erm.com
AF: Environmental Resources Management, 1777 Botelho Drive, Suite 260, Walnut Creek, CA 94598 United States
AU: Fieber, L
EM: lfieber@burnsmcd.com
AF: Burns & McDonnell, 2601 West 22nd Street, Oak Brook, IL 60523 United States
AU: Ernstmann, G
EM: gernst@burnsmcd.com
AF: Burns & McDonnell, 2601 West 22nd Street, Oak Brook, IL 60523 United States
AU: Tisoncik, D
EM: dan.tisoncik@ual.com
AF: United Airlines, 1200 E. Algonquin Road, Elk Grove Township, IL 60007 United States
AU: Wells, T
EM: ted.e.wells@ual.com
AF: United Airlines, 1200 E. Algonquin Road, Elk Grove Township, IL 60007 United States
AU: Stanhope, J
EM: jennifer.stanhope@ual.com
AF: United Airlines, 1200 E. Algonquin Road, Elk Grove Township, IL 60007 United States
AU: Henrich, B
EM: bill.henrich@norcal.com
AF: Norcal Geophysics, 1350 Industrial Avenue, Suite A, Petaluma, CA 94952 United States
AB: This project involves strategic hydrogeologic investigation and remediation of chlorinated solvents in fractured bedrock and overlying alluvium in Northern California. Primary contaminants include 1,1,1-TCA, 1,1-DCE and 1,1- DCA. The source area includes recoverable DNAPL, with a maximum accumulated thickness of 29 feet in a well, and dissolved concentrations in excess of 500 mg/L. The dissolved plume extends away from the source through an extensive fracture network to a depth of 450 feet. The investigation involved drilling monitoring wells to depths up to 700 feet, borehole geophysics, a seismic reflection survey, and aquifer testing. Optical and acoustic televiewer logging were used to map the fracture network, which is dominated by west, southwest, south, and east dipping features. The seismic reflection survey identified en-echelon, southeast dipping normal faults and antithetic, southwest dipping reverse faults that are generally consistent with the orientation of structures in the nearby San Andreas fault zone. The primary fault strikes are generally parallel to those of the dominant fracture sets. Notable lithologic discontinuities in the Franciscan bedrock were documented across major faults, possibly related to significant vertical and strike-slip offset. The seismic reflection survey provided a useful guide for drilling by predicting areas of higher fracture density. Slug tests and acoustic wave-form, conductivity, temperature, and static/dynamic heat pulse flow meter logging were used to establish that flow is primarily through the fractures and conductive portions of the alluvium. These data were used to install an effective multilevel well network, establish a ground water flow pattern that reflects geologic controls and regional gradient, and support remediation evaluations. Remediation evaluations include dissolved phase remediation bench tests, DNAPL recovery, and monitored natural attenuation (MNA). The dissolved phase bench tests are in progress. DNAPL has been periodically recovered from fractured bedrock for two years. DNAPL recovery rates declined over time except immediately following a 5.3 Richter magnitude earthquake, which apparently caused a temporary increase. A pilot test demonstrated that dewatering and applying a vacuum to the well increased the DNAPL recovery rate by approximately 2500 percent over rates prior to pilot testing. The MNA results indicate that abiotic and biotic degradation are active, consistent with the apparent steady state condition of the dissolved plume over two years of monitoring. Based on the results, the remedial strategy for the site includes periodic DNAPL recovery with monitored natural attenuation. This study demonstrates the effective use of combined geologic, geophysical, and hydrologic investigation methods to support remedial planning.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2003 Fall Meeting