Laserfiche WebLink
r`. Mr. Harlin Knoll <br /> San Joaquin County Environmental Health Division ORION <br /> + 1 May 2001 <br /> L Page 3 <br /> 1LThe samples from cross-gradient well MW-3 did not contain detectable concentrations <br /> of TPHg, BTEX, and MTBE during any round of groundwater sampling. <br /> Groundwater Sampling and Analytical Results <br /> The monitoring wells were sampled on 19 April 2001 ; the groundwater sampling and <br /> analytical procedures were conducted in accordance with Orion's work plan. Depth to <br /> groundwater was measured before sampling using a Solinst water level meter. <br /> Approximately 3 casing volumes were purged from the wells prior to sampling. <br /> L. Throughout purging and just before sampling the wells, pH, specific conductivity, and <br /> temperature of the evacuated groundwater were measured and recorded. These <br /> measurements were made to confirm that the well was purged sufficiently. Water <br /> L samples were collected after the measurements stabilized to within 10 percent of the <br /> previous readings or a baseline was established. Purging and sampling logs are provided <br /> T <br /> in Attachment 1 . Purging and sampling was performed using a 2-inch-diameter Teflon <br /> L and disposable polyethylene bailers suspended from a nylon line. The Teflon bailer was <br /> decontaminated between each well use. The bailers were equipped with a bottom- <br /> release device for sample collection. <br /> Water samples were collected from the wells in new 40-milliliter glass bottles with <br /> Teflon-lined caps provided by the analytical laboratory. These samples were collected <br /> so that no headspace was present in the bottle. A field blank was not collected because <br /> + the wells were sampled using disposable bailers. The samples were delivered to Positive <br /> L, Lab Service of Los Angeles, California, a State—certified laboratory. <br /> The samples were analyzed for TPHg using modified EPA Method 8015; for BTEX and <br /> d• MTBE using EPA Method 8021 . Analytical laboratory reports and chain-of-custody <br /> forms for the April 2001 sampling activities are included in Attachment 2. <br /> �— In April 2001, groundwater samples from well MW-1 (installed near the former source <br /> t area, Figure 2) contained no detectable amounts of TPHg or BTEX. A small amount of <br /> L MTBE was detected in MW-1 at a concentration of 5.0 µg/I. Upgradient well MW-2 <br /> contained a TPHg concentration of 170 µg/1. The samples from cross-gradient well MW- <br /> 3 did not contain detectable concentrations of TPHg, BTEX, and MTBE. Newly installed <br /> downgradient monitoring well MW-4 contained no detectable amounts of TPHg or <br /> BTEX. A small amount of MTBE was detected in MW-4 at a concentration of 2.4 µg/I. <br /> L Analytical results from this and the four previous rounds of groundwater sampling are <br /> summarized in Table 1 . Groundwater elevations are summarized in Table 2. Details of <br /> Ithe groundwater sampling procedures are included in Attachment 3. <br /> r <br /> L <br /> LIABF5\STOCKTON\LTRIM1108.DOC 511/01 <br />