ARCHIVED REPORTS XR0002613 - Laserfiche WebLink

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SITE ASSESSMENT AND INSTALLATION OF GROUND WATER MONITORING WELLS ' Over the assessment period,a total of eleven ground water monitoring/extraction wells and two soil borings have been installed at the site to assess the vertical and lateral extent of impacted soil and ground water.A total of 20 ground water monitoring events have occurred at the site.The following ' is a summary of milestone events at the site. a Three ground water monitoring wells MW-1,MW-2 and MW-3 were installed at the site in ' October 1993. During the development a surge block was lodged within well MW-3, MW-3 had ' consistently failed to produce sufficient ground water to meet the pre-sampling purge requirements,therefore,MW-3 was over'drilled on 07 December 1995 and grouted to surface grade with portland cement. Three additional ground water monitoring wells were installed ' in December 1995: MW-3R, MW-4 and MW-5. Petroleum hydrocarbons were not detected in soil samples collected during the installation ' of wells MW-4 or MW-5, however, hydrocarbon-impacted ground water was detected in samples collected from MW-3R. Results of installation procedures were included in the Quarterly Report-December 1995, prepared by AGE. a In January 2000, two soil borings were advanced at the site and two ground water wells (MW-6 and MW-7) were installed. The most intense TPH-ss impacted ground water was detected within the former UST area. a In Apri12001, monitoring wells EW 1, MW8, MW9 and MW 10 were installed. ' a TPH-ss was detected in the monitoring well samples on the site and was not detected in the down gradient, ground water monitoring wells at the edges and off-site (MW6, MW-7 and . MW-10). BTEX compounds were not detected in any of the ground water samples. t a PCE and TCE were detected in the water samples collected from wells MW6,MW7 and the newly installed well MW-10,at concentrations which exceeded the Maximum Contaminant Level (MCL) of 5 µg/l established by the State of California - Department of Health ' Services.Detected concentrations of cis 1,2-dichloroethene and vinyl chloride also exceeded the State MCL of 6 µg/l. ' a The lateral extent ofthe dissolved halogenated-hydrocarbon plume has not been defined east or north of wells MW-6 and MW-10. ' a Soil and ground water on the site have been impacted with petroleum hydrocarbons as stoddard solvents and BTEX.Additionally,tetrachloroethene(PCE),cis 1,2-dichloroethene (1,2 DCA)and vinyl chloride were detected in the water samples collected from wells MW- 4, MW-5, MW6 and MW7. a In August 2001 a ground water extraction test was conducted at the site. Ground water draw- down of at least 18 feet was observed in extraction well EW-1 following 720 minutes of ' continuous pumping (5 GPM); ground water draw-down was observed locally at 0.37 feet to 0.1 feet. Advanced GeoEnvironmental,Inc.