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' 0 4 . GROUNDWATER FLOW DIRECTION ' In order to choose boring locations for sampling groundwater up- and down-gradient from suspected source areas of contamination, it was necessary to determine the flow direction of groundwater. ' Therefore, borings B-1 through B-3 were drilled first, on October 20, and top-of-casing elevations were leveled. After stabilizing overnight, depths to water were measured with an electronic depth gauge on the morning of October 21 . The table below lists rela- tive top-of-casing elevations (Etoc) , depths to water (DTW) , and water elevation (Ew) , on the morning of October 21, 1994 . BORING Etoc DTW Ew B-1 94 . 79 22 . 92 71 . 87 B-2 96 . 05 23 . 99 72 . 06 ' B-3 95 . 85 23 . 85 72 . 00 *Etoc assuming level had elevation of 100 feet iThese water elevations were used to compute the flow azimuth in the vicinity of the three borings, which was 1870 (S 70 W) , as ' plotted in Figure 2 . 5 . CHEMICAL ANALYSES 5 . 1 Priority Metals and Cyanide Priority metals and cyanide analyses, listed in Table 1, were of principal concern due to the electroplating operations conducted ' by Shinko. All nine samples collected for chemical analysis were tested for 13 priority metals (EPA Method 6010) and for cyanide (EPA Method 9010) . In all five soil samples, arsenic, cadmium, selenium, thallium, silver, and mercury were not detected (shown in Table 1 as ND< #, with # representing the value of the detection limit) . ' The remaining six metals were present at low levels, with zinc having the highest concentration, up to 56 mg/kg. These are considered background concentration levels for soils in the San ' Joaquin Valley. Among the four water samples, only three metals were detected -- chromium, copper, and zinc -- and these were extremely low in ' concentration. Zinc was the highest, up to 0 .30 mg/1, while chromium and copper were less than or equal to 0 . 010 mg/1 . These concentrations are considered to represent background levels . It is noteworthy that groundwater from borings B-2 and B-4, located up- and down-gradient of the chemical operations area, had essen- ' 4