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Sol]Boring and Monitoring Well Installation Report Page 6 Ranch Market Riverbank CA September 6 2000 5.2 Results of Groundwater Monitoring and Sampling Referring to Table 3, the depth to water at the site has ranged from 27 31 to 31 98 feet bgs The monitoring data posted on Figure 7 shows the groundwater has a north to south flow direction with an approximate gradient of 0 0028 feet/foot Laboratory analytical results for groundwater samples collected from MW-1 through MW-9, MW-5d, DW-1, DW-3, and DW-4 on August 16, 2000 indicate the highest concentrations of dissolved gasoline range petroleum hydrocarbons are found in MW-1, over the former UST pit location (Table 3 and Figure 9) Reported concentrations an MW-1 were TPHg at 80,000 parts per billion (ppb), benzene at 13,000 ppb, and MtBE at 1,600 ppb Figure 8 shows the concentrations in groundwater declining away from the source area to below detection limits, with the exception of MW-7 The August 16, 2000 monitoring and sampling event reported elevated concentrations of dissolved petroleum range hydrocarbons at MW-7, anomalous to the surrounding wells and grab water samples from the nearby borings DW-3, located 10 feet from MW-7, had no reportable dissolved petroleum range hydrocarbons above detection limits 6.0 SENSITIVE RECEPTOR SURVEY 6.1 Map Review A review of existing maps was performed to help identify possible sensitive receptors within a 2000-foot radius of the Site The map review also provided the necessary information to conduct the DWR records review and field search Possible sensitive receptors identified are the Stamslaus River and Jacob Meyers Park The Stanislaus River is located approximately 1200-feet down gradient of the Site The former USTs at Ranch Market were located at a higher elevation than the River and Park 6.2 Department of Water Resources Records Review A Department of Water Resources (DWR) records search was performed to identify industrial, municipal, or domestic wells within a 2000-foot radius of the Site Due to the presence of the Stanisluas River south of the site, and the fact that no wells were observed during the field search south of the river in Riverbank, California, the well search was limited to north of the Stamslaus River, in San Joaquin County Well logs were not found at the DWR for the wells on the properties adjacent to the Ranch Market (wells DW-I through DW-4,Figure 2) or the wells observed at distances greater than 1700 feet north of Ranch Market (Figure 10) Only three wells were identified during the records review within the 2000-foot search radius The wells identified are all south and down gradient from Ranch Market one at Jacob Meyers Park, approximately 700 feet away, one West of the Park, approximately 1000 feet from the Site, and one to the east of the Park and East of Santa Fe Road, approximately 1500 feet from the Site Table 5 presents a File R-Welllnstall&M&S rpt doc SECOR Intertiational Incorporated