ARCHIVED REPORTS_XR0011211 - Laserfiche WebLink

Home Browse Search

Working To Restore Nature Nor-Cal Beverage Company Project No. 150005.01 Page 3 generally do not yield much water to wells and impede the vertical movement of water. The majority of groundwater used for irrigation and drinking water supply in the Stockton area is extracted from more permeable zones beneath the flood basin deposits. San Joaquin County Flood Control maps for Spring 1992, Fall 1992, and Spring 1993 were examined. The regional groundwater flow direction was consistently northeasterly toward a groundwater depression located east of Stockton. According to DWR records, 15 water wells are present within a one mile radius of the site, (Figure 3). These wells were installed to depths ranging from 55 to 660 feet. With the exception of the three monitoring wells (designated 1N/6E-IM) and an industrial well (designated 1N/6E-1L3), screened intervals within these wells begin at depths ranging from 140 to 345 feet below the surface. No gradient information was discernible from DWR documents. For the most part, DWR records of wells installed after 1990 were not yet available to the . public. Therefore, San Joaquin County PHS/EHD records were reviewed in order to identify shallow groundwater monitoring wells that were installed during petroleum hydrocarbon investigations at properties within a one mile radius of the Nor-Cal facility. Four sites with calculated groundwater gradients were identified (Figure 3). Gradient information for these sites is listed in Table 5. The groundwater flow directions at these sites varies from northwesterly to east-northeasterly with generally shallow magnitudes. The gradient for Site #1, located at 2185 E. Fremont, was noted in CRWQCB correspondence (September 22,1993) as varying from west to southeast to northwest between May 1992 and March 1993. A review of reports on file at PHS/EHD indicate that, in fact, the gradient has been consistently to the northwest between October 1992 and April 1993. Figure 3 illustrates that groundwater gradients from these four sites seem to converge in northeast Stockton, near the intersection of Cherokee and Waterloo Roads. This may be due to an influence exerted by a water supply well located near the intersection of Willow and Filbert Streets. CONCLUSIONS A review of groundwater gradients from shallow wells at underground storage tank sites - indicated a convergence in northeastern Stockton. This gradient convergence is also consistent with San Joaquin County Flood Control Maps, which show both northerly and easterly components of groundwater flow in the vicinity of the Nor-Cal site. I0 L1293-ML 3