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4075 Main St. <br /> Page 2 of 3 <br /> Diligent and timely remediation efforts are imperative at this site in order to reduce the <br /> petroleum contamination in soil and groundwater and prevent further off site migration. The <br /> lateral and vertical extent of groundwater contamination must be determined. PHS/EHD <br /> recommends cone penetrometry technology(CPT) to investigate the lithology at the site and to <br /> determine preferential pathways for contaminant migration. Based on information derived from <br /> CPT data, additional monitoring wells will need to be installed at the site and screened at discrete <br /> depths in the aquifer to monitor and evaluate the vertical and lateral extent of the contaminant <br /> plume. <br /> The well survey report showed the locations of nearby water wells but did not identify additional <br /> wells easily observed near this site. The survey also failed to depict a prominent nearby <br /> waterway(Mormon slough). PHS/EHD staff found additional water wells near the site. An <br /> apparent out-of-service well was located by PHS/EHD staff at 4126 E. Main St. south of the <br /> above referenced site. Two irrigation wells were located by PHS/EHD at 4400 E. Main St. and a <br /> third irrigation well was located on the property to the east of 4400 E. Main Street. Furthermore, <br /> a San Joaquin County Flood Control District map shows the existence of water well #SB 1 near <br /> the site. There may be other nearby water wells that have not been identified. A ground-truth <br /> physical survey for these additional water wells and any other wells within a 2,000-foot radius of <br /> the site must be conducted. Also, although the well survey report refers to well construction <br /> information for water wells listed in the report, no well logs were provided to PHS/EHD. Plot all <br /> wells on a site map and provide available well logs to PHS/EHD. Information regarding the use <br /> and pumping rates of these wells must also be provided to PHS/EHD. <br /> Quarterly groundwater monitoring must be continued until otherwise directed by PHS/EHD. <br /> Quarterly monitoring reports must be submitted within 60 days of the quarterly monitoring <br /> event. Please refer to the PHS/EHD letter dated June 30, 2000 regarding quarterly monitoring <br /> and report submittal directives. 1,2-Dichloroethane, ethylene dibromide, ethanol and methanol <br /> must be added to the current analytical sampling regime at this site. During the next quarterly <br /> monitoring event, a groundwater sample must also be collected from the nearest downgradient <br /> water well. Analyze the water well sample for all constituents of concern using EPA Method <br /> 524.2 (the drinking water analytical method equivalent to EPA Method 8260). Confirmation <br /> sampling of the nearest water well must occur during the following quarterly sampling event. <br /> Additional sampling of downgradient water wells may be necessary. <br /> The site map included in the report was deficient. The site map did not show previously located <br /> underground storage tanks or current underground storage tank locations. Site maps must show <br />