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0 <br /> • between 9 and 19-feet bgs to monitor the first watei-bearing zone <br /> encountered Monitoring wells MW-7 and MW-9 are screened between <br /> 55-feet bgs and 70-feet bgs Monitoring well MW-8 is screened between. <br /> 100-feet bgs and 115-feet bgs Monitoring well MW-10 is screened <br /> between 105-feet bgs and 115-feet bgs <br /> Hydrocarbons and/or VOCs were detected in groundwater samples <br /> collected from all ten monitoiing wells The highest concentrations <br /> detected were in groundwater samples collected from monitoring wells <br /> MW-5 and MW-6 Both of these wells are screened in the first water- <br /> bearing zone encounteied with the bottom of the zone extending to a <br /> depth of no gieater than 19-feet bgs Monitoring well MW-5 is located <br /> between the USTS and the pump island near West Yosemite Avenue <br /> Monitoring well MW-6 is located between the USTS and the site building <br /> BTEX concentrations in groundwater samples collected from these two <br /> wells exceeded DHS MCLs for drinking watei Benzene concepti ations in <br /> groundwater samples collected fiom monitoring wells MW-7, MW-8 and <br /> MW-9, all screened in deeper zones, also exceeded the DHS MCLS foi <br /> drinking watei <br /> The groundwatei flow direction in the first zone (shallower than 19-feet <br /> bgs) was to the northwest at a gradient of between 0 008 to 0 01 - <br /> feet/foot Not enough wells were screened in the deeper zones to <br /> calculate the groundwater flow direction at these depths (since three non- <br /> linear points are needed) <br /> 2.. 8 August 1999_Quarterly Groundwater Monitoring <br /> In August 1999, ASE collected groundwater samples from the site <br /> groundwater monitoring wells, as well as the on-site drinking water well <br /> Free-floating hydrocarbons, believed to be gasoline, were present on the <br /> groundwater surface in monitoring well MW-5 A hydrocarbon sheen was <br /> present on the groundwater surface in monitoring well MW-6 The <br /> analytical results from the remaining wells showed a slight decrease from <br /> the initial sampling of these wells The only hydrocarbon concentrations <br /> which exceeded DHS MCLS for drinking water were the toluene, ethyl <br /> benzene and total xylene concentrations in groundwater samples <br /> collected from monitoring well MW-6, and the benzene concentration in <br /> groundwater samples collected from monitoring well MW-7 TPH-D was <br /> detected in several of the samples including a low concentration in the <br /> on-site drinking water well The groundwater flow direction in the first <br /> zone (shallower than 19-feet bgs) was to the north and northeast at a <br /> gradient of approximately 0 002-feet/foot <br /> Frank's One Stop Workplan — September 2000 <br /> -4- <br />