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�} Mr Harlin Knoll ORION San Joaquin County Environmental Health Division 7 July 2000 • Page 3 ' The remainder of the well annulus above the top screened interval in the wells was filled with bentonite grout to approximately 1 foot below grade ' The wells were developed on 25 January 2000 by surging and bailing to (1 ) remove fines from the filter pack and well screen and (2) reduce sediment in the water At least 5 casing volumes of water were removed from each well during development, totaling approximately 36 gallons The well development logs are included in Attachment 2 Soil Sampling and Analytical Results Soil sampling and analytical procedures were conducted in accordance with Orion's work plan Details of the drilling and sampling activities are included in Attachment 3 Soil samples were collected at 5 feet below ground surface and at approximate 5-foot intervals thereafter Selected soil samples were analyzed by Positive Lab Service of Los Angeles, California (Positive), a State-certified laboratory The samples were analyzed for TPHg using modified EPA Method 8015, and for BTEX and MTBE using EPA Method 8260 Analytical laboratory reports and chain-of-custody forms for the January 2000 drilling activities are included in Attachment 4 and are summarized on Table 1 �`• One soil sample was selected and analyzed from each boring during drilling activities The soil sample from MW-1 , at a depth of 20 feet below grade, contained the only detectable concentration of MTBE at 99 micrograms per kilogram (µg/kg) The soil samples analyzed from MW-2 and MW-3 for MTBE were below detection limits at depths of 35 and 15 feet below grade, respectively TPHg and BTEX were not detected in any of the other soil samples analyzed from the borings Groundwater Sampling y and Analytical Results p Groundwater sampling and analytical procedures were conducted in accordance with Orion's work plan Details of the groundwater sampling procedures are included in Attachment 5 Groundwater samples were analyzed by Positive Lab Service The ' samples were analyzed for TPHg using modified EPA Method 8015, and for BTEX and MTBE using EPA Method 8260 Analytical laboratory reports and chain-of-custody forms for the January 2000 (first round) and May 2000 (second round) sampling activities �t are included in Attachment 4 and are summarized on Table 2 The monitoring wells were sampled immediately after their development in January 2000 and again in May 2000 Depth to groundwater was measured before sampling using a Solinst water level meter Approximately 5 casing volumes were purged from ' the wells before sampling during the first round and 3 casing volumes from the second round Throughout purging and lust before sampling the wells, pH, specific conductivity, and temperature of the evacuated groundwater were measured and S\BFS\STOCKTON\LTR\LTR004 DOC 7/7100