WORK PLANS - Laserfiche WebLink

Home Browse Search

a Work Plan for Extended Site Ch cterizadon: 7500 West Eleventh Street, Tracy,CA. Page 8 Well MW-8 will have a total depth of 22 ft. and will be screened over a 15-ft.interval from just above the groundwater table to a depth of 21 ft. Its construction will be similar to that shown on Figure 7. 6.3.3 Definition of Down- adient Extent: Principal Plume of Affected Groundwater One small-diameter exploratory boring and two groundwater-quality monitoring wells are proposed to explore the down-gradient limits of the principal plume of affected groundwater. A groundwater-quality monitoring well that will be designated well MW-9 will be installed , on the eastern side of Chrisman Road some 230 ft. north of that street's intersection with West Eleventh Street. (See Figure 2 for location). This planned well will be used to investigate the distance that groundwater affected by fuel hydrocarbons has been transported down the groundwater gradient. Its planned location is on a projection of a line from the center of the pump island area of the former fueling station, beneath which the majority of the fuel hydrocarbons that leaked into the subsurface were released, and existing monitoring well MW-7. Groundwater in MW-7 is heavily affected by components of both gasoline and diesel. Based on the hydrogeology and geochemistry of the site, it appears that the alignment of Former Pump Island Location to MW-7 to MW-9 is closely followed by the principal axis of the plume of affected groundwater in that area. A small-diameter boring (to be designated boring PP-15) will be drilled on the west side of � g Chrisman Road some 520 ft. to the north of West Eleventh Street. Drilled to approximately 17 ft. BGS, it will penetrate beneath the groundwater table to allow assessment of groundwater quality and to guide selection of the location of a groundwater-quality monitoring well in that area. A grab sample of groundwater will be recovered from the boring immediately after it reaches its total depth. If that sample contains no detectable concentrations of analytes of concern, a groundwater-quality monitoring well, to be designated well MW-10, will be installed some 50 ft. to the south of the PP-15 boring i location on the same side of Chrisman Road. If the groundwater sample contains detectable concentrations of any of the analytes of concern, monitoring well MW-10 will be installed to the north of the boring location. The exact location will be guided by the type and concentrations of any analytes of concern detected in the grab sample of ground water from PP-15. Wells MW-9 and MW-10 will be constructed in the manner shown on Figure 7. Each will have a total depth of 22 ft, and will be screened over a 15-ft. interval from just above the groundwater table to a depth of 21 ft. 6.3.4 Explore Subsurface and Groundwater at Apparent Source of Seco ndqU Plume L.� Proposed monitoring well MW-11 is intended to investigate the condition of soil and groundwater at the apparent source of a secondary plume of affected groundwater that has been identified beneath the property. It will be located, as shown on Figure 2, on the southern boundary of the site near a structure that was formerly a truck service bay. That location is, as shown on Figure 3, at the southern end of Pipe Trench No. 2, from which piping of SIC L