ARCHIVED REPORTS_XR0006783 - Laserfiche WebLink

Home Browse Search

1 Fourth Quarter 2002 Monitoring and Sampling Report 3 7-Eleven, Inc, Store#21756,853 E Yosemite Avenue,Manteca, CA December 10 2002 ' An SVE test was conducted on April 24, 2002, by applying a vacuum to well SPV-1 Magnehelic gauge measurements of resulting pressure changes in wells MW-1, MW-2, MW-3, and SPV-1 indicated an estimated radius of vapor extraction influence (ROI)of 25 to 30 feet around the extraction point, and low extracted vapor concentrations (Shaw, 2002) An additional SVE test was conducted on October 17, 2002, by applying a vacuum to wells SPV-2 and MW-1, to determine if higher levels of extracted vapors ' could be generated by extracting from a different part of the site Results (page 4 of this document) verified that the SVE ROI is about 20-30 feet, and Indicated that there Is little residual gasoline mass available in the vadose zone for SVE Air and/or oxygen sparging maybe applicable as a remediation ' method to address residual gasoline constituents in the saturated zone ' Geology/Hydrogeology The shallow stratigraphy in the study area consists of Quarternary alluvium Materials underlying the site ' consist largely of fine-to medium-grained sand Interbedded below about 13 feet bg with clayey silt Depth to groundwater is encountered during drilling at about 16 to 19 feet bg During the current sampling 1 event, equilibrated depth to groundwater ranged from 17 12 to 20 57 feet below top of casing (TOC) Historic groundwater flow is to the northwest at a hydraulic gradient of about 0 002 foot per foot Sensitive Receptors ' A well search for public water supply wells located within one mile of the site indicates that the nearest well is an active municipal well located 1,987 feet downgradient of the site, it is 155 feet deep, with top of screen at approximately 65 feet bg The site is therefore considered to be of relatively low risk to sensitive ' receptors ' Groundwater Monitoring Data Before monitoring, the well caps were opened to allow the water in each well to stabilize to atmospheric pressure The DTW was measured to the nearest 0 01 foot from the top of the well casing using an interface probe ' A potentiometric surface map prepared using the quarterly groundwater elevation data Is shown in Attachment 1, Figure 2 Based on the groundwater elevation data, groundwater flow is toward the northwest at a gradient of 0 002 foot per foot Quarterly groundwater monitoring results and historical data ' are summarized in Tables 1 and 1A, respectively (Attachment 2) Field data sheets are Included in Attachment 3