Confidential Client, Pharmaceutical and Optical Instrument Manufacturer, Sunnyvale, California

We determined the source of volatile organic compounds detected in soil, soil gas, and shallow ground water at the client's two properties. The client's sites were downgradient from another site that had released volatile organic compounds to ground water, and were within the COC plume originating from the upgradient site. We conducted an extensive review of existing data and performed analytic modeling of compound partitioning and soil gas migration to demonstrate that the observed volatile organic compounds originated offsite. We also reviewed data from previous investigations of the two sites, as well as results of investigations of the upgradient property and area-wide COC plume, including years of ground water data. Based on existing data, we calculated the expected concentrations above the water table based on observed concentrations. None of the concentrations measured on the site indicated there was a release.

Based on the geology, boring logs, ground water flow, and water quality data, we were able to determine that a well upgradient of the client's properties had been improperly constructed, penetrating a well known aquitard separating two different water-bearing zones. This allowed the ground water concentrations to be diluted from the deeper water-bearing zone; consequently, it was not a valid well for measuring water quality in the upper ground water zone. We demonstrated that a purported increase in ground water concentrations of the client's properties was in fact an artifact of the compromised data from the improperly constructed well.

We also showed that when the data from the improperly constructed well was discounted, ground water concentrations actually decreased in the downgradient direction, substantiating that there was no evidence of a release at the client's sites.

Our modeling results and technical analysis demonstrated that concentrations in the soil samples and soil gas samples above the water table were attributable to partitioning of compounds generated offsite from ground water. This supported a previous determination by the regulatory agency that the client's former sites were not the source of ground water contamination. Staff from our El Dorado Hills, California location also participated in this project.

Confidential Client, Pharmaceutical and Optical Instrument Manufacturer, Campbell, California

We conducted a hydrogeologic and fate and transport studies to assess the source and responsible parties for the offsite presence of constituents of concern. We successfully presented the data to the regulatory oversight agency such that our client was not listed as a responsible party on the Cleanup and Abatement Order issued for constituents of concern identified at offsite locations.