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2.2.4 DISTRIBUTION IN GROUNDWATER <br /> Groundwater samples have been collected from 19 groundwater monitoring wells <br /> (MW-1 through MW-19) in Neighborhood B and 15 groundwater monitoring wells <br /> (MW-2 through MW-16) in Neighborhoods C and D since September 2009. Five <br /> groundwater monitoring and sampling events have occurred between September 2009 <br /> and September 2010. TPHc, BTEX, and naphthalene concentrations in groundwater <br /> from all wells have been below their respective reporting limits during all five <br /> monitoring and sampling events. In March 2010,TPH as diesel (TPHd) was detected at <br /> 55 micrograms per liter (µg/1) in MW-19 (Neighborhood B) and ranged from 54 to <br /> 79 µg/l in MW-3, MW-4, MW-6, MW-9, MW-13, and MW-14 (Neighborhoods C and D). <br /> The laboratory noted for all TPHd detections the sample chromatographic patterns for <br /> TPH did not match the chromatographic patterns of the specified standard. The TPHd <br /> concentrations did not exceed the RWQCB water quality objective of 100 µg/l <br /> (Appendix A). No TPHd was detected above the reporting limit in any other sampling <br /> event. <br /> Since TPHc, TPHd, BTEX, and naphthalene concentrations in groundwater from all <br /> wells were historically and are currently below reporting limits, no trend graphs were <br /> prepared for the wells. <br /> 3.0 LOW RISK CASE CLOSURE <br /> The following criteria should be met for a site to qualify for closure per RWQCB's <br /> Interim Guidance on Required Cleanup at Low-Risk Fuel Sites. <br /> • The pipeline was historically removed and source soils have been excavated; <br /> • The site has been adequately characterized; <br /> • The dissolved hydrocarbon plume is not migrating; <br /> • Little or no groundwater impact currently exists,no contaminants are found at levels <br /> above established MCLS or other applicable water-quality objectives; <br /> • Based on the impact levels in groundwater, remaining soil impacts are not acting as <br /> a source to dissolved phase impacts; <br /> • No water wells, deeper drinking water aquifers, surface water, or other sensitive <br /> receptors are likely to be impacted; and <br /> • The site presents no risk to human health or the environment. <br /> 060222(11) 5 CONESTOGA-ROVERS&ASSOCIATES <br />