ARCHIVED REPORTS_1988 - Laserfiche WebLink

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KLEINFELDER m t Of the 25 metals quantified m the analysis, only ,,� calclu„ ifin, man anese, potassium, and were detected in the sample. Primary drinking water maximum contaminant levels (MCLS) do not currently exist for these constituents. Iron and manganese were detected in the ground water sample at 0.4 and 2.5 mg/l, respectively, exceeding the secondary drinking water MCLS of.3 and .05 mg/l. The ground water sample was also relatively high in SWQdft and total dissolved cAlMe The reported c oride concentrations7Qy_ and the total dissolved solids rnncentr ion i 930 m 1 These concentrations exceed the secondary drinking water MCLS for chloride and total dissolved solids, which are 250 mg/l and 500 mg/1, 7 respectively. Based on the reported concentration of major ions, the ground water appears to be a sodium/chloride water type. The Stiff diagram for this sample is shown on Plate 9. The regional ground water in San Joaquin County was investigated by the U.S. Geological Survey in June 1981, (USGS, 1981). The ground water in the vicinity of the site during 1981 was a calcium-sodium/bicarbonate type with total dissolved solids concentrations generally less than 500 mg/l and chloride concentrations under 100 mg/l. However, the USGS study also indicated that the ground water just 2 to 6 miles south and west of the site had total dissolved solids concentrations of 500 mg/l to more than 1,000 mg/kg, and chloride concentrations of 100 mg/l to more than 250 mg/1. The general water chemistry observed in MW-1 is more consistent with the regional ground water observed south and west of the site in 1981. This may indicate that: the water quality zone depicted west of the site in the USGS study may have migrated or spread eastward; or the shallow water quality at the site differs from the deeper water quality. No well construction details are provided in the USGS report, but it is likely that most of the wells, which include domestic, industrial, and irrigation wells, are perforated at greater depths than MW-1. The USGS study also noted that manganese concentrations ranged from 0.0 mg/l to 3.1 mg/l over the study area. Several wells with manganese concentrations above the 0.05 mg/l drinking water criteria were located in the central part of the area near Stockton and Lodi. Observed iron concentrations in the study area ranged between 0.0 and .67 mg/l, but only exceeded .3 mg/l in two of the wells sampled. 137-88-1663 16