ARCHIVED REPORTS XR0000281 - Laserfiche WebLink

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Maximum methyl tert-butyl ether (MTBE) concentrations of 277 and 120 pg/l have been detected in groundwater samples analyzed by EPA Test Methods 8020 and 8260, respectively Historical groundwater flow beneath the Site is directed to the east and southeast A summary of historical analytical groundwater data is tabulated in Appendix A ' In February 2000, the mass of petroleum hydrocarbons in soil was estimated at approximately 485 pounds for TPHg and 8 pounds for benzene The mass of petroleum hydrocarbons in groundwater beneath the Site was estimated to be approximately 2 grams of TPHg and 0 7 grams of benzene The ' groundwater plume beneath the Site may extend beneath B Street Review of the historical soil analytical data indicates petroleum hydrocarbon impacts at intervals between 35 and 66 feet below the ground surface (bgs) with the exception of the tank removal soil samples collected between 12 and 14 ' feet bgs Approximate locations of the groundwater monitoring wells are depicted on Figure 2 FIELD ACTIVITIES ' Depth to Groundwater Measurements On May 27, 2004, representatives of Geocon measured the depth to groundwater in monitoring wells MW-1 through MW-12, VW-1 and VW-2 using a battery operated water level meter The measurements were obtained from a surveyed reference point at the top of the well casing (TOC) The approximate well locations and site features are depicted on Figure 2, Groundwater Elevation Map - May 2004 During the Second Quarter - 2004, the depth to groundwater in wells MW-1 through MW-12, VW-1 M and VW-2 was recorded between 51 21 and 52 86 feet below TOC Based on the May 2004 groundwater elevation data, the groundwater beneath the Site appears to be directed toward the south- southeast at an approximate gradient of 0 003, which is consistent with historical groundwater flow A ' review of the last reported groundwater level measurements for the Site indicates that from March to May 2004 the groundwater levels in each of the wells decreased an average of 0 71 foot A summary of the TOC elevations, depth to groundwater measurements and Mean Sea Level groundwater ' elevations is presented on Table 1 Well Purging and Sampling ' On May 27, 2004, approximately three well volumes of water (28 to 59 gallons) were extracted from each well utilizing a 2-inch diameter submersible pump During the well purging activities, the groundwater was monitored for pH, electrical conductivity, temperature and turbidity This information is included on the Monitoring Well Sampling Data Sheets presented in Appendix B Following the purging activities, groundwater samples were collected from the wells and decanted into ' four 40-milliliter volatile organic analysis vials and one one-liter amber glass bottle The samples were sealed, labeled, placed in an ice chest containing ice, and subsequently transported to the laboratory using standard chain-of-custody protocol ' The extracted groundwater was placed into 13 Department of Transportation-approved, 17-H, 55- gallon drums and temporarily stored onsite pending receipt of laboratory analysis The drums were transported by ABCO Environmental Services to an appropriate disposal facility on June 14, 2004 Project No S8471-06-24K -2- June 22,2004