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Ms. Laurie Cotulla <br /> July 26, 1991 <br /> Page 2 <br /> • Proposed investigation: Since the site is clean, no further investigation is proposed <br /> or needed. <br /> • Monitoring well data: Since the site is clean, no data, with the exception of <br /> groundwater levels,have been collected since 1988. Groundwater level measurements <br /> have been taken yearly, with the exception of 1990, since 1988. Groundwater level <br /> information is shown below: <br /> well Groundwater depth, Groundwater elevation, <br /> Date number feet below top of casing feet above mean sea level <br /> 8/26/88 AL-1 10.36 89.8 <br /> AL-2 8.93 89.97 <br /> AL-4 8.81 90.06 <br /> 4/10/89 AL-1 NM° <br /> AL-2 9.72 89.18 <br /> AL-4 9.68 89.19 <br /> 5/23/91 AL-1 10.43 89.73 <br /> AL-2 9.28 89.62 <br /> AL-4 9.34 89.53 <br /> VNI cover stuck. <br /> • Analytical results: All analytical results to date have been provided in previous <br /> reports. <br /> • Downgradient well: Since there is no "source of contamination," it is not imperative <br /> that a downgradient well be confirmed or verified. The groundwater flow direction <br /> on May 23, 1991 was to the southeast under a gradient of 0.0022 ft/ft, or 11.6 <br /> feet/mile, a very flat gradient. If the previous waste oil excavation is considered a <br /> "source of pollution," then there is no groundwater monitoring well immediately <br /> downgradient. However, groundwater flow directions in this area are influenced by <br /> seasonal groundwater pumping and fluctuate greatly. The groundwater flow direction <br /> on August 26, 1988 was in just the opposite direction as May 23, 1991. The flow <br /> direction on August 26, 1988 was to the northwest under a gradient of 0.0035 ft/ft, or <br /> 18.5 feet per mile, still a relatively flat gradient. Given this flow direction, then <br /> groundwater monitoring well AL-1 is immediately downgradient of the former waste <br /> oil tank excavation. Groundwater from well AL-1 has never contained petroleum <br /> hydrocarbons. I reiterate that there is no "source of contamination" on this site, <br /> therefore, the location of the wells relative to such a source is mute, especially given <br /> the wide range of flow directions due to agricultural pumping. <br /> Brown and Caldwell <br /> Consultants <br />