--> Abstract: Use of Groundwater Gradient Calculations in the Prediction of Volatile Organic Compound Distribution in Groundwater: Examples from Santa Clara Valley Superfund Sites, by J. Hillenbrand; #90958 (1995).
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Abstract: Use of Groundwater Previous HitGradientNext Hit Calculations in the Prediction of Volatile Organic Compound Distribution in Groundwater: Examples from Santa Clara Valley Superfund Sites

John Hillenbrand

Between 1981 and 1994 the San Francisco Regional Water Quality Control Board has overseen completion of many groundwater investigations of volatile organic compound contaminated sites including all 19 Regional Board-lead superfund sites in Santa Clara Valley. Two of these sites are associated with Stanford Research Park in Palo Alto.

At the first site, located at 640 Page Mill Road, interbedded proximal fan and floodplain or bay deposits between San Francisquito and Matadero Creeks interweave to create depositional fabric that is oblique to the expected and measured groundwater Previous HitgradientNext Hit. At the second site, located at 1501 Page Mill Road, tilted beds of the Santa Clara formation combine with deposits similar to those mentioned above to create a post depositional fabric that is also oblique to the expected and measured groundwater Previous HitgradientNext Hit.

Since advectively transported contaminants are expected to flow with the Previous HitgradientNext Hit, it was predicted that the calculated Previous HitgradientNext Hit would indicate where the contaminants would be found. After each site installed more then 150 wells during 12 years of investigation, both sites found chemical paths were at angles approaching 90 degrees to the measured Previous HitgradientNext Hit in portions of the sites. The problem of not recognizing the difference between calculated and actual groundwater Previous HitgradientNext Hit (and therefore chemical distribution) has been a major contributor to protracted site investigations.

This problem can be recognized by a flattening of an otherwise consistent groundwater Previous HitgradientNext Hit. The solution may lie in either the placement of at least three wells in close proximity to each other within the relatively flatter Previous HitgradientTop area or a conscious effort to confirm lateral boundaries of the groundwater plume.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California