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Environmental Restoration Services <br /> Site Investigations * Fuel Tank Closures and Installations * Site R�rQ6it!b4i*9.4plWry Reporting <br /> Fier-'r €�t;1/'0r: <br /> 03 OCT - I PH 2: 14 <br /> San Joaquin County September 29, 2003 <br /> Environmental Health Department <br /> 304 E Weber Ave Third Floor <br /> Stockton, CA 95202-2708 <br /> Attn Harlin Knoll,R E H S <br /> Re Groundwater Monitoring Event <br /> 260�W'Thornton Rd , Thornton, CA <br /> 7&5b <br /> On September 8, 2003, a single round of groundwater samples were obtained from <br /> monitoring wells MW3 and MW4 Groundwater samples were collected as follows <br /> Each well was bailed until the volume of water withdrawn was equal to at least three <br /> casing volumes To assure that a representative groundwater sample is collected periodic <br /> • measurements of the temperature, pH and specific conductance were made An individual <br /> log sheet was maintained throughout the sampling operations The sample was collected <br /> only when the temperature, pH, and/or specific conductance reached relatively constant <br /> value and the well had recharged to a minimum of 80% of its per purge volume <br /> A hand operated bailer was used for evacuating the well casing (purging) of the monitor <br /> well Water samples were collected using a new disposable bailer An effort was made to <br /> minimize exposure of the sample to air <br /> Subsequent to collection, the samples were immediately stored on crushed ice in an <br /> appropriate ice chest and maintained at a constant 4 degrees Celsius Samples were <br /> transported under Chain-of-Custody procedures to North State Labs (NSL) of South San <br /> Francisco, CA, on the day of their collection <br /> Care was taken to collect all excess water resulting from the sampling and cleaning <br /> procedures The excess water is contained in a pre-labeled 55-gallon drum on-site <br /> pending receipt of laboratory analyses <br /> The following analyses were performed by NSL on the groundwater samples obtained <br /> from each monitor well <br /> TPH-gasoline (EPA Method 8015M) <br /> BTEX and Fuel Oxygenates and Additives (EPA Method 8260) <br /> 500 Santa Cruz Avenue * Menlo Park California * Phone 6501325-3216 * Fax 6501327-2984 <br />