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01 October 2013 <br />AGE Project No. 99-0559 <br />Page 2 of 6 <br />2.0. PROCEDURES <br />On 16 September 2013, a groundwater monitoring event was conducted utilizing site wells <br />MW-1 through MW-7 and MW-9; wells MW-10, MW-11, and MW-12 were inaccessible <br />during the September 2013 sampling event and were not monitored. Work was performed <br />in accordance with guidelines established by the California Regional Water Quality Control <br />Board (CRWQCB) - Central Valley Region for subsurface investigation of underground <br />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 MW-7 <br />and MW-9. Groundwater samples were collected from wells MW-1 through MW-4, <br />MW-5A/B, MW-6A/B, and MW-7B. <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 16 September 2013 sampling event, AGE concludes the following: <br />HU1 and HU2: <br />Depth to groundwater measured in wells MW-1 through MW-4, MW-5A, MW-6A, <br />and MW-7A ranged between 53.72 (MW-4) and 55.50 (MW-6A) feet below the top <br />of casing (btoc). Groundwater elevation ranged between 28.17 feet below North <br />American Vertical Datum 88 (NAVD88) in well MW-4 and 30.15 feet below NAVD88 <br />in well MW-7A indicating an average decrease of 6.18 feet since the previous <br />monitoring event in December 2012. <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 hydraulic gradients <br />ranging between 0.025 and 0.003 foot per foot (ft/ft) [Figure 3]. <br />Total petroleum hydrocarbons quantified as gasoline (TPH-g) were detected in <br />groundwater samples collected from wells MW-1, MW-2, MW-3, MW-4, and MW-5A <br />at a maximum concentration of 12,000 micrograms per liter (pg/l) in well MW-2. <br />Advanced GeoEnvironmental, Inc.