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Section 1 Introduction and Background 1.3.3 SHALLOW GROUNDWATER OCCURRENCE AND QUALITY According to preliminary hydropunch work conducted by ENGEO, shallow groundwater is expected at a depth of approximately 16 feet below ground surface (bgs). Additionally, ENGEO collected hydropunch water quality samples for TDS from three boreholes and at various depths (12-16, 20-24, and 26-30 ft. bgs). Initial hydropunch water quality samples indicate that the uppermost 12 to 16 foot interval had reported TDS values of between 460 to 1,700 mg/L at the three locations assessed. The 20 to 24 foot interval contained TDS at a reported range of 1,100 to 1,800 mg/L while the lowermost 26 to 30 foot interval had TDS at concentrations ranging from 1,100 to 1,200 mg/L (only two samples were collected at this depth as there was not sufficient water to sample one of the boreholes). ENGEO further identified the California Department of Corrections, Deuel Vocational Institute, located adjacent to and west of the Main Stone Property as having water quality data available. According to ENGEO, quarterly monitoring of wells associated with reclamation of disinfected tertiary-treated wastewater indicates that groundwater TDS ranges from 2,800 to 4,300 mg/L. ENGEO further identified a 22-acre onsite spray field used for discharging treated groundwater from a contaminated fire pit. Accordingly, groundwater impacted with chlorinated solvents from this pit was extracted via a pump and treat remediation system (treated with granular activated carbon) and then discharged to the spray field. ENGEO also reports that the Deuel site has monitoring wells associated with fuel releases from two leaking underground storage tank incidents, one from a gasoline release near the Deuel Maintenance Building and the other a diesel release near the sewage treatment plant. May 2006 Main Stone Property 13 Effluent Storage and Disposal Site Hydrogeologic Invesfigation Workplan