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i • k4 KLEINFELDER • Other general water quality data showed the TDS concentrations ranging from 260 mg/L to 710 mg/L across the site. The TDS concentrations exceeded the recommended level SMCL for TDS of 500 mg/L in MW-2, MW-4, and MW-9, but did not exceed the SMCL upper level of 1 ,000 mg/L. TDS concentrations are cumulative results of many of the individual constituents dissolved in the groundwater, which include anions and cations. The concentrations of specific conductance in the groundwater samples ranged from 540 to 1,110 umohs/cm were the highest in MW-2 and MW-4. The SMCL for specific conductance is 900 umhos/cm, with a SMCL upper level of 1,600 umhos/cm. Kleinfelder also observed the drilling and installation of one exploratory boring to a total depth of 400 feet bgs. Three zones were tested by installing three temporary wells within the three discrete zones. The zone tests showed that Zone #3 (the shallowest zone — 163 feet to 183 feet) displayed concentrations of most analytes greater than two times the concentrations shown in the two deeper zones. The concentrations of nitrate as NO3 exceeded the MCL in Zone #3. The concentrations of sodium in all three zones exceeded the SNARL of 2 mg/L. The manganese concentration in Zone #1 exceeded the MCL for manganese. It should be noted that although the concentrations of most analytes were elevated in Zone #3, the concentrations did not exceed applicable water quality goals, unless otherwise noted. • Maximum contaminant levels (MCLs) are a part of the drinking water standards adopted by the California Department of Health Services (DHS). The United States Environmental Protection Agency (USEPA) also adopts MCLs under the Safe Drinking Water Act. DHS' drinking water standards must be at least as stringent as those adopted by the USEPA. Primary MCLs are derived from health-based criteria (e.g., cancer risk). Secondary MCLs are derived from human welfare considerations (e.g., taste, odor, laundry staining). MCLG's are promulgated by the USEPA as part of the enforceable Primary Drinking Water Regulations. MCLG's may be useful in interpreting narrative water quality objectives. 5.2. RECOMMENDATIONS To confirm the preliminary groundwater sample analytical results obtained as part of Kleinfelder's assessment, each of the eight monitoring wells should be re-sampled and tested for at least the following: • Nitrate as NO3 • Total and fecal coliform bacteria . . Organic analyses by EPA Methods 507 and 632 Before collecting the coliform bacteria samples, the wells should be disinfected to reduce the potential for inadvertent contamination as a result of the sampling process. Page 17 of 20 63138.H01/ST06R312/JDZ:Iv April 7, 2006 ©2006 Kleinfelder, Inc.