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Mr Ron Rowe <br /> co Page 2 of 5 <br /> I ' <br /> GROUNDWATER ACTiVIT>fES <br /> Groundwater Monitoring and Sampling <br /> Groundwater monitoring was conducted on February 2, 2000 Depth to groundwater was <br /> ' measured in wells MW1 through MW 10 and MW13) and subtracted from the wellhead elevations <br /> to determine groundwater elevation Monitoi ing wells MW 11 and MW 12 were not accessible <br /> The depth to groundwater was also measured in vapor wells VW 1 and VW3 through VW6 <br /> Wellhead elevations have not been determined for the vapor wells Water levels rose an average <br /> of 0 92 feet since last monitored on November 18, 1999 Groundwater flow was generally <br /> ' northeasterly with a gradient averaging approximately 0 003 feet per foot A groundwater <br /> gradient map generated using the February 2, 2000 monitoring data is shown on Figure 2 Recent <br /> groundwater monitoring data are summarized in Table 1 Monitoring logs and well construction <br /> information are included in Attachment A <br /> On February 2, 3 and 4, 2000 Ground Zero collected groundwater samples from groundwater <br /> ' monitoring wells MW 1 through MW 10 and MW13), and vapor wells VW 1 and VW3 through <br /> VW6 At least three well casing volumes were purged from each well prior to sampling Physical <br /> parameters (pH, conductivity, tempei atut e) wet e monitoi ed during purging and allowed to <br /> stabilize prior to sampling Samples wei e collected sifter groundwater recharged to 100% of the <br /> original level Purged water was contained in 55-gallon drums approved by the Department of <br /> Transportation and stored onsite in a locked enclosure Purge logs are included in Attachment A <br /> 1 <br /> Samples were placed on ice and transpoited under chain of custody to Argon Laboratories (DHS <br /> #2359) Samples were analyzed foi TPHg using modified EPA method 8415 and BTEX using <br /> ' EPA method 8020 Additional sample mat ix collected from monitoring wells MW 1 through <br /> MW10, and MW13 and vapor wells VW1, and VW3 through VW6 was analyzed for oxygenates <br /> ' using modified EPA method 8260 Analytical i esults for TPHg, BTEX and MTBE are <br /> summarized in Table 2, oxygenate results are summarized in Table 3 Attachment B contains <br /> laboratory reports and chain of custody documentation <br /> ' Groundwater Analytical Results <br /> ' Groundwater Monitoring Wells <br /> The groundwater surface was above the top of the screened intervals in all monitoring wells <br /> except MW2 and MW13 Petroleum hydiocaibons weie detected in groundwater samples <br /> ' collected from all monitoring wells except MW 10 (wells MW 11 and MW 12 which historically <br /> have been non-detect for petroleum hydi ocai bons wet e inaccessible) The highest concentrations <br /> of TPHg and BTEX were detected in samples collected from wells MW4 and MW13 Although <br /> increases relative to November 1999 were recorded in samples from some wells, hydrocarbon <br /> concentrations in general remained stable in wells affected by the onsite release <br /> rockk mrl i gm2000 <br /> i � <br />