ARCHIVED REPORTS_XR0009516 - Laserfiche WebLink

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f1 f 4.0 SENSITIVE RECEPTOR SURVEY A sensitive receptor survey was conducted by Wm. J. Hunter & Associates (Hunter) and ' summarized in the December 1993 Problem Assessment Report prepared for San Joaquin County Department of Environmental Health Services (SJCDEHS) by Hunter. Hunter noted that within a mile radius of the site are three Department of Water Resources wells and one ' San Joaquin County well. No well records or details for these wells could be located by JJW. Hunter's map indicates that the closest well may be about 2000 feet northeast of the site. ' JJW reviewed well logs at the State of California Department of Water Resources (DWR) and found two sites within 2000 feet of Valley Showcase that contained wells. ' JJW discovered well logs for three monitor wells and a map indicating a fourth monitor well at 404 West Fremont Street, the Crystal Cream & Butter facility. The three monitor wells with logs were installed in 1993 and have a screened interval from 20 to 40 feet below the surface. ' The Crystal Cream & Butter facility is approximately 2000 feet east of the Valley Showcase site. JJW discovered well logs for six monitor wells at Colberg Boat Works. The site is located ' approximately 600 feet southeast of the Valley Showcase site at 858 West Fremont Street. The six monitor wells were installed in 1997 and have a screened interval from about 4 to 24 feet below the surface (figure 3). ' A field reconnaissance of the area by Hunter did not reveal any obvious domestic wells within several hundred feet of the site. Additionally, the Stockton Deep Water Channel is ' approximately 600 feet to the south. ' 5.0 MAXIMUM CONTAMINANT LEVELS FOR GROUNDWATER The Maximum Contaminant Levels (MCLs) are considered safe levels of contaminants in ' drinking water and are enforceable drinking water standards adopted into regulation under the Safe Drinking Water Act. The MCLs for BTEX are provided below for comparison with the current concentration levels of BTEX in the groundwater at the site: ' Constituent MCL (ppb) Benzene 1 ' Toluene 150 Ethylbenzene 70 Xylenes 1,750 t 6.0 RATIONALE FOR SITE CLOSURE Justification and rationale for site closure is discussed separately for soil and groundwater in the following sub sections. ' 6.1 Soil Based on historical site investigation activities at the site and the associated reports, lateral ' and vertical extent of contamination in soil appears to have been defined adequately. As ' 5 JJW GEOSCIENCES Inc.