ARCHIVED REPORTS XR0008680 - Laserfiche WebLink

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it 1 S EC ® R ' Between June 6 and July 11, 2003, SECOR installed four B monitoring zone groundwater monitoring wells (MW-11 through MW-14) Each of the wells is off-site, and the purpose of the work was to delineate the lateral extent of the petroleum plume in the B monitoring zone Wells MW-11 and MW-14 were installed to a depth of 82 feet bgs and screened from 77 to 82 feet bgs Wells MW-12 and MW-13 were installed to a depth of 83 feet bgs and screened from 78 to 83 feet bgs TPHg, benzene, MtBE, and 1,2-DCA were not reported in any of the soil samples analyzed with the exception of 1,2-DCA reported at a concentration of 0 0071 mg/kg in sample MW-12@70' Between May 3 and May 7, 2004, SECOR supervised the drilling of two on-site borings (SB-1 D ' and SB-2D) to 120 feet bgs Soil samples were collected continuously from 80 to 120 feet bgs and selected soil samples at 10 foot intervals were submitted for laboratory analysis N Hydropunch groundwater samples were collected at depths of 100 feet bgs and 120 feet bgs in ,� ' boring SB-1 D and 110 feet bgs and 120 feet bgs in SB-21D No detectable concentrations of �y petroleum hydrocarbons were reported for the soil samples from borings SB-1 D and SB-21D Hydropunch groundwater samples SB-1 D(W)@100' and SB-1 D(W)@120' had concentrations of 1 TPHg of 110 ppb and 80 ppb, respectively Hydropunch groundwater samples SB-2D(W)@110' and SB-2D(W)@120' had TPHg concentrations of 92 ppb and 140 ppb, respectively Hydropunch groundwater sample SB-2D(W)@110' had a 1,2-DCA concentration of 0 72 ppb ' Based on the above data benzene, MtBE, and 1,2-DCA in groundwater has been delineated at 4 120 feet bgs by water samples and TPHg has been delineated to low levels The three new groundwater monitoring wells MW-15— MW-17 were installed to provide long-term groundwater ; • monitoring in this depth interval The site is currently monitored and sampled on a quarterly basis Second quarter 2005 groundwater sampling reported TPHg in three of the four A monitoring zone wells at a maximum{ concentration of 1,600 ppb, MtBE in three of the four A monitoring zone wells at a maximum concentration of 2,000 ppb, and 1,2-DCA in two of the four A monitoring zone wells at a q' ` maximum concentration of 6 5 ppb Benzene was not reported in any of the A monitoring zone wells during the second quarter 2005 MW-2 was not sampled during second quarter 2005 ' because the well was inaccessible due to drilling activities at the site r During the second quarter 2005, TPHg was reported in five of the ten B monitoring zone wells at a ' a maximum concentration of 7,100 ppb, benzene in two of the ten B monitoring zone wells at a maximum concentration of 100 ppb, MtBE in five of the ten B monitoring zone wells at a maximum concentration of 2,300 ppb, and 1,2-DCA in seven of the ten B monitoring zone wells at a maximum concentration of 26 ppb MW-8 was not sampled during second quarter 2005 because the well was inaccessible due to drilling activities at the site ' Newly installed C monitoring zone wells (MW-15 through MW-17) were sampled on April 20, 2005 following well development MW-15 was previously sampled during the first quarter 2005 and during second quarter 2005 TPHg and benzene were reported in the samples from all three wells collected on April 20, 2005 1,2-DCA was reported in two of the three wells at aF ' maximum concentration of 1 0 ppb in MW-15 MtBE was not reported in any of the wells Additional data will be needed to determine groundwater trends in the C zone wells pA rte.. The A, B, and C monitoring zones are discussed further in Sections 4 and 5 The historical groundwater gradient direction within the A monitoring zone at the site has been to the northeast with the gradient ranging between 0 001 to 0 019 feet per foot The historical Updated SCM 2005 doc 4 1 77CP 64409 05 0005 to