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FIELD MEASUREMENTS OF CONTAMINANT FLUX BY INTEGRAL PUMPING TESTS (SAN FRANCISCO, CA)
Citation:
BROOKS, M. M., C. G. ENFIELD, M. D. ANNABLE, AND A. L. WOOD. FIELD MEASUREMENTS OF CONTAMINANT FLUX BY INTEGRAL PUMPING TESTS (SAN FRANCISCO, CA). Presented at AGU Conference, San Francisco, CA, December 13 - 17, 2004.
Impact/Purpose:
To inform the public.
Description:
Current remedial techniques are unable to completely eliminate all dense nonaqueous phase liquid (DNAPL) from source zone areas and conflicting views on the benefits of partial DNAPL source zone remediation exist in the literature. A comparison of flux measurements before and after remedial activities is one metric that has been proposed to elucidate benefits of partially alleviating DNAPL source-zones. Historically, contaminant flux has been estimated from distinct field measurements of hydraulic gradient, hydraulic conductivity, and contaminant concentration. The objective of this work is to investigate the use of integrated pump tests for field flux measurements. This technique consists of extracting water from a series of wells aligned perpendicular to the groundwater flow direction. Analytical solutions to pumping well(s) in a uniform flow field are used with head measurements and pumping rates to directly estimate the Darcy velocity (without independent estimates of hydraulic gradient and hydraulic conductivity), which is used with analytical chemistry results to estimate the contaminant flux. Results are presented from four test sites located in Fort Lewis, Washington; Borden, Ontario; Jacksonville, Florida; and Hill Air Force Base, Utah. A comparison is made to an independent flux measurement technique based on tracer-laden absorbent material placed in the same well series. Both techniques give similar order-of-magnitude results, and better agreement between the techniques may be hampered by differences in the underlying spatial scales of measurement between the techniques. Overall, the results to date indicate that integrated pump tests may provide an order-of-magnitude or better measure of mass flux.