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595 Fast I 1 th Street Tracv CR June 6 1994 <br /> • The a%erage depth to groundwater was reported to be approximaleh 8-feet below surface grade with an <br /> inferred groundwater flow direction to the north-west with a gradient of approximately 0 003 %enical per <br /> horizontal feet According to site activit} records the wells had not been sampled again until October <br /> 1993 when RRM initiated a new quarterly sampling program <br /> In October 1993 RRM performed the first quarteriv groundwater sampling of monitor wells MW-1 <br /> through MW-3 Groundwater samples were analyzed for TPHg and BTEX TPHg concentrations of <br /> 5 500 (5 5 ppm) and 2 900 (2 9 ppm) parts per billion (ppb) along with BTEX compounds were found at <br /> wells MW-2 and MW-3 respectively TPHg and BTEX were not detected in well MW-1 The average <br /> depth to groundwater was measured at approximately 8-feet below surface grade with an inferred <br /> groundwater flow direction to the north-east <br /> In Januan 1994 RRM performed the second quarterl) grourrdwater sampling of monitor wells MW-1 <br /> through MW-3 Groundwater samples were analyzed for TPHg and BTEX TPHg concentrations of <br /> 20 000(20 ppm)and 14,000(14 ppm) parts per billion (ppb)along with BTEX compounds were found at <br /> wells MW-2 and MW-3, respectively TPHg and BTEX were not detected in well MW-1 The average <br /> depth to groundwater was measured at approximately 7 5 to 8-feet below surface grade with an inferred <br /> groundwater flow direction to the north-east <br /> OBJECTIVES <br /> The objective of this third quarterly groundwater sampling event was to monitor the extent of petroleum <br /> hydrocarbon impacts to groundwater and to establish the current groundwater flow direction and gradient <br /> as required b) the State of California Underground Storage Tank Regulations <br /> PROCEDURE <br /> Monitor wells MW-1, MW-2, and MW-3 were sampled on Mav 12, 1994 The locations of the wells are <br /> shown in Figure 2 Sampling activities consisted of a depth to water measurement, and then purging and <br /> sampling groundwater from each well Depth to water measurements were used to calculate the elevation <br /> of the groundwater level at each well to determine the groundwater gradient and flow direction. Details of <br /> the sampling procedures are descnbed below <br /> 1 Measure the static depth to groundwater at each well using a Sohnst electronic water level <br /> indicator <br /> 2 Using a pre-cleaned Teflon bailer purge each well a minimum of 5 well casing%olumes or until <br /> pH,conductivity, and temperature levels have stabilized <br /> 3 Following purging, re-measure static depth to groundwater at ea,.h well to determine that <br /> groundwater has recovered to within 80%of the initial level <br /> 4 Using a pre-cleaned Teflon bailer collect a groundwater sample from each well and transfer <br /> the samples into presened 40-m1 VOA sample vlais <br /> 5 Seal and label each sample and place into iced storage <br /> 6 Following chain of custody documentation, transport samples to a State Certified analytical <br /> laboratory <br /> All samples were subrrutted to Anametnx Laboratories of San Jose, Caltfonua for certified analyses for <br /> TPHg and BTEX using modified EPA Methods 8015/8020 <br /> 2 <br />