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02 May 2013 <br />AGE-NC Project No. 99-0559 <br />Page 2 of 5 <br />2.0. PROCEDURES <br />On 17 December 2012, a groundwater monitoring event was conducted utilizing site wells <br />MW-1 through MW-4, MW-5A/B, MW-6A/B, MW-7A/B, MW-11 and MW-12. Work was <br />performed in accordance with guidelines established by the California Regional Water <br />Quality Control Board (CRWQCB) - Central Valley Region for subsurface investigation of <br />underground storage tank (UST) sites, and with the approved sampling schedule. <br />Monitoring was performed in accordance with AGE's standard monitoring and sampling <br />procedures, provided in Appendix B. Field data and logs are provided in Appendix C. <br />Depth to water measurements were recorded from monitoring wells MW-1 through <br />MW-5A/B, MW-6A/B, MW-7A/B, MW-11 and MW-12. Groundwater samples were collected <br />from wells MW-1 through MW-5A/B, MW-7A/B, MW-11 and MW-12. <br />3.0. FINDINGS <br />Groundwater elevation in each monitoring well at the time of the monitoring event was <br />calculated by subtracting the depth to groundwater from the surveyed casing elevation; <br />current and historical groundwater elevation results are provided in Table 1. Each <br />groundwater elevation is grouped according to the appropriate HU, on the assumption that <br />elevation will reflect hydrostatic conditions within designated HUs. Based on data collected <br />at the time of the 17 December 2012 sampling event, AGE concludes the following: <br />HUI and HU2: <br />Depth to groundwater measured in wells MW-1 through MW-4, MW-5A, MW-6A, <br />MW-7A, and MW-12 ranged between 44.70 (MW-2) and 50.00 (MW-6A) feet below <br />the top of casing (btoc). Groundwater elevation ranged between 19.58 feet below <br />North American Vertical Datum 88 (NAVD88) in well MW-2 and 24.60 feet below <br />NAVD88 in wells MW-6A; an average decrease of 0.4 feet since the last monitoring <br />event. <br />Groundwater flow within the water table interval wells was inferred to be flowing <br />toward a depression near the former UST release area, at a hydraulic gradient of <br />0.008 foot per foot (ft/ft) [Figure 3]. <br />Total petroleum hydrocarbons quantified as gasoline (TPH-g) were reported in <br />groundwater samples collected from wells MW-1, MW-2, MW-3, MW-4, MW-5A and <br />MW-7A at a maximum concentration of 9,400 micrograms per liter (pg/l) in well <br />MW-2. <br />Advanced GeoEnvironmental, Inc.