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1 ' 30 July 2003 AGE-NC Project No 99-0584 ' Page 4 of 8 2 4 GROUND WATER MONITORING Initial ground water samples were collected on 28 February 2000 Prior to April 2003, six ground water monitoring events have been conducted at the site Depth to ground water has ranged between 9 77 and 12 80 feet bsg, ground water flow direction has been consistently northeast at a relatively low gradient of approximately 0 002 f1/$ Petroleum hydrocarbon compounds was detected during three monitoring events, 100 µg/1 TPH-g, 2 7 µg11 benzene, 0 92 µg/1 ethylbenzene, 3 4 µg/1 xylenes and lfi µg/1 MTBE in sample MW-1 in March 2002, 4 2 µg/l MTBE in sample MW-1 and 77 µg/1 TPH-d in sample MW-3 in November 2000, and 4 9 µg/1 MTBE in sample MW-1 and 110 µg/l TPH-d in sample MW-5 in March 2001 ' Currentgr ound water data indicates a minor MTBE detection in well MW-1 near the former UST area The consistently low concentrations of MTBE in only one well indicate a small, stable contaminate plume The mass of dissolved MTBE is not readily determinable due to the limited detections and low concentrations 25 SENSITIVE RECEPTOR SURVEY AGE conducted a sensitive receptor survey to identify the location and use of wells potentially affected by the UST release, including municipal, domestic, irrigation or ground water monitoring wells within a 2,000-foot radius of the site Furthermore, a search was performed to locate septic systems that could potentially serve as vertical conduits ' On 05 June 2001,an AGE representative conducted a search of well dnllers'reports at the California Department of Water Resources - Central District for water wells located in the surrounding area Dnller's reports for five water wells located within a 2000 ft-radius were found Copies of the well ' driller's reports are included in Appendix B, a summary of water wells located from the review of well driller's reports is included in Table 1 ' On 09 August 2001 Mr Ben Guzman of San Joaquin County Utilities was contacted by an AGE representative According to Mr Guzman, domestic wells supplied drinking water to properties in the vicinity of the site In addition,sewer systems were also local,and septic tanks were used During ' the telephone conversation Mr Guzman stated no municipal water wells were located near the site On 09 August 2001, an AGE representative performed an area reconnaissance for visually observable potential sensitive receptors located within a2,000-foot radius of the subject site During ' Advanced GeoEnvironmental,ine. 1