WORK PLANS - Laserfiche WebLink

Home Browse Search

S Ec0R --, ,-- _ --- _ Confrimation Soil and Groundwater Sampling Work Plan 7-Eleven Store#21756 July 27, 2007 Page 2 On December 20, 1999, three groundwater monitoring wells (MW-1 to MW-3) were installed to depths of 25 feet bgs, and screened from 10 to 25 feet bgs (IT Corporation, February 2000). Benzene and TPHg in soil were not detected above laboratory reporting limits. Groundwater analytical data indicated dissolved concentrations of benzene (up to 0.32 tag/L), TPHg (up to 55 pg/L), MtBE (up to 230 fag/L), and tert-butyl alcohol (TBA) (3,710 pg/L). The reported TBA detection appears to be anomalous, as TBA has not been detected in subsequent quarterly samples. The MtBE plume was defined downgradient of the hydrocarbon source area (the former LIST and pump island locations) (IT Corporation, 2000). On April 1-3, 2002, monitoring well MW-4 was installed to 30 feet bgs and screened from 15 to 30 feet bgs (Shaw, August 2002). Dual-nested sparge/vent wells (SPV-1 and SPV-2) were drilled to 29 feet bgs, and screened from 12 to 22 feet bgs as soil vapor extraction (SVE) wells, and also screened from 24 to 29 feet bgs as sparge wells. A Geoprobe soil boring (GP-6) was advanced to a depth of 40 feet bgs. Soil samples collected from GP-6 and MW-4, and a grab groundwater sample from GP-6, did not contain BTEX, TPHg, and fuel/oxygenates above laboratory reporting limits. An SVE test was conducted on April 24, 2002, by application of vacuum to well SPV-1. Magnehelic gauge measurements of wells MW-1, MW-2, MW-3, and SPV-2 indicated an estimated radius of vapor extraction influence of 25 to 30 feet around the extraction point. A second SVE test was conducted on October 17, 2002. Vapor extraction was performed on SPV-2 and MW-1, which resulted in an estimated radius of influence of 25 to 30 feet. Influent vapor concentrations, as measured via a flame ionization detector (FID), ranged from 3 to 8 parts per million by volume (ppmv). On December 2, 2003, SECOR submitted a Request for Reduction in Groundwater Sampling with the SJCEHD. SECOR requested reducing sampling from quarterly to annually. The SJCEHD approved a reduction from quarterly to semi-annually in an e-mail dated March 12, 2004. SCOPE OF WORK SECOR proposes to advance one direct push soil boring (GP-7) as shown in Figure 2 and summarized in Table 1. The borings will be used to collect soil and grab groundwater samples for analysis of current conditions in the vicinity of groundwater monitoring well MW-1. HEALTH AND SAFETY SECOR will modify our existing site-specific Health and Safety Plan (HASP) for the proposed scope of work as required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120). The document will be reviewed and signed by all SECOR personnel and subcontractors prior to performing work at the site. 21756 Confirmation GP 7-27-07.doc SECOR International, Inc.