SITE INFORMATION AND CORRESPONDENCE

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Rl KLEINFELDER File No. 20-3978-01.W 10 July 26, 1997 Arsenic was not detected in the stock (cattle pen) well, Production Wells 5 and 7, Monitoring Well 3 (downgradient of a portion of the wastewater ponds), Monitoring Well 4 (downgradient from the mud ponds), and Monitoring Well 5 (off-site upgradient well). Arsenic was detected above the MCL in Monitoring Well 1 and 2 (downgradient from the lime ponds). The concentrations present were similar to those revealed in past monitoring events at the site. Arsenic is a naturally occurring element and can exist in groundwater in very high concentrations such as that in the west side of the San Joaquin Valley. Barium concentrations exceed the MCL in monitoring wells MW-1 and MW-2 (downgradient from the lime ponds). Both concentrations, 1.4 mg/L and 1.1 mg/L respectively, only slightly exceed the MCL of 1.0 mg/L. The source of the barium is unknown. However, it should be noted that barium concentrations in the off-site upgradient monitoring well (MW-5) have exceeded the MCL for barium during past monitoring events associated with the ponds. The concentrations present were similar to those revealed in past monitoring events at the site. 3. The concentrations of bicarbonate alkalinity, boron, calcium, magnesium, potassium and sodium appear to indicate a "hard water" condition to be present in the samples obtained. This condition is evident in all of the samples. The highest concentrations present appear to be located adjacent to the lime ponds. However, hard water was also present in the upgradient, off-site well. No MCLS or SMCLs are listed for any of these analytes in 22CCR§64431 or 22CCR§64449, respectively. 4. Slightly elevated chloride concentrations existed on site. Water samples obtained from Monitoring Wells 2 and 4 exceeded the recommended SMCL as expressed in 22CCR§64449. In addition, the chloride results for the water sample taken from Monitoring Well 4 matched the "Upper" SMCL of 500 mg/L as expressed in 22CCR§64449. 5. Specific Conductance (EC) in the groundwater samples obtained exceeded the recommended SMCL (900 µmhos/cm) as expressed in 22CCR§64449 in all but the samples obtained from the stock(cattle pen)well. The exceedances also occurred for the off-site, upgradient well MW-5. Additionally, water samples obtained from Production Wells 5 and 7 matched the upper SMCL of 1600 µmhos/cm, while Monitoring Wells 1 through 5 exceeded it. In addition, Monitoring Wells 1, 2 and 4 exceeded the short term SMCL (2,200 µmhos/cm) Total Dissolved Solids (TDS) in groundwater were high in all but one of the samples obtained (stock (cattle pen) 20-3978-OI.WI012O17L155 Page 35 of 5O Copyright 1997,Kleinfelder,Inc.