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L LJanuary 19,2006 NOA Project Number: E05161A i" Examination of these maps indicates that no water level data is available for the Tracy/Banta area, which includes the Site, and no definite comments as to depth or gradient flow direction can be Lmade. Based on our experience in the area, our office estimates that, at its shallowest,the ground water in the area lies between 10 and 15 feet below the ground surface. Test holes were drilled on the subject property to a depth of 10 feet in March of 1994; no groundwater was encountered. 6' On March 24, 2005,our office drilled a groundwater boring approximately '/2 mile north of the subject property. The groundwater boring was drilled 10 feet;no groundwater was encountered. LNo ground water was encountered by the staff of Neil O.Anderson&Associates, Inc. during the drilling of the percolation test hole to a depth of 3 feet on December 7,2005. 4.2 Potential Ground Water Contamination Issues Identifying potential ground-water contamination sources was not part of the scope of work for the soil suitability study. Potential ground-water contamination can occur from a number of sources which often include leaky underground storage tanks, agricultural activities,dairies, septic systems, and storm water infiltration. Any past agricultural activities and the present use of septic systems in the area should be considered Lpotential ground-water contamination sources. In the Tracy area, the 448-acre Tracy Defense Depot site was an Army Supply Depot from 1942 to 6. 1963 when it was turned over to the Defense Logistics Agency as a source of potential groundwater contamination. Operations at the facility included repackaging of leaking chemical containers, fumigating shipping materials,maintaining vehicles,painting, storing chemicals,preserving metal parts, operating chemical and photographic laboratories, storing and mixing pesticides and storing bw and treating liquid and solid wastes. Currently, all solid hazardous waste is hauled off site to Federally-approved disposal facilities.The shallow aquifer below the site is contaminated with volatile organic compounds (VOCs);i.e.,TCE,PCE and DCE. (U.S. EPA,2005) 6. According to an interview with Marcus Pierce,project manager for the Tracy Defense Depot cleanup, on April 5,2005 from the CVRWQCB, since 1995 there has been active remediation for the groundwater plume released from the Tracy Defense Depot. Through several methods including "soil vapor extraction" and"pump and treat" there has been significant progress to stabilize the plume with concentrations dropping from 50-100 micrograms per liter, down to 10 micrograms per liter. Pierce reported that there has been an agreement with numerous water quality control regulatory agencies not to treat groundwater east of Banta Road and to let the plume assimilate naturally over time.There is a network of groundwater monitoring wells in the path of the northeastern migration of the plume. The most recent monitoring has revealed that the plume's current"maximum levels of concentration" are being reported from the monitoring wells located near the subject property. 5 L L