ARCHIVED REPORTS_XR0009517 - Laserfiche WebLink

Home Browse Search

' 3.0 GROUNDWATER MONITORING 3.1 Groundwater Sampling Activities JJW Geosciences, Inc. (JJW) conducted groundwater monitoring and sampling activities on November 27, 2001. Prior to purging the wells and collecting groundwater samples, we ' measured and recorded the depth to static groundwater in the five wells. We present current groundwater gradient and flow directions in Table I and Figure 3. Following water depth measurements, we used a 12-volt DC pump to purge the groundwater monitoring wells until at least two or more of the readings for temperature, pH, conductivity, and oxidation-reduction potential (ORP) approximately stabilized or three well volumes were purged. Following well purging and recharge, we collected groundwater samples with polyethylene, well-dedicated disposal bailers and poured the collected groundwater into precleaned 40 milliliter glass vials and 250 milliliter amber glass jars. JJW experienced no ambient petroleum-like odors above the monitoring wells. Following collection, we immediately placed the water samples on ice in a cooler. Specific site conditions and sampling parameters can be found in the Well Sample ' Field Logs included in Appendix A. JJW transported the groundwater samples under chain-of-custody to TEG-Northern California, Inc., a State of California certified analytical laboratory (Certification No. 1671) The samples were analyzed for the following parameters: ' - Total petroleum hydrocarbons as gasoline (TPH-g) (EPA method 8015 modified); - The aromatic volatile fuel components benzene, toluene, ethylbenzene, and xylenes (BTEX) and MTBE (EPA method 8020A); Cumulative groundwater analytical results are summarized in Table 11. The analytical laboratory data sheets can be found in Appendix B. t3.2 Groundwater Sample Laboratory Analytical Results Laboratory analyses indicated that aromatic volatile hydrocarbons (BTEX) and total petroleum hydrocarbons as gasoline (TPH-g) were detected in monitor well MW-2 above the method reporting limits. Benzene was the only compound detected in monitor well MW-5. Groundwater samples collected from MW-1, MW-3 and MW-4 did not contain TPH-g or BTEX ' components above the method reporting limits. San Joaquin County Environmental Health Division no longer required the water samples to be analyzed for the petroleum oxygenate MTBE since it has not been a factor at this site. The samples were analyzed one more time, ' however, to confirm that MTBE is not detected above the method reporting limit. No MTBE was detected above the method reporting limit in any of the five wells. ' Monitor well MW-2 contained 130 µg/L of TPH-g and 4.1 pg/L of benzene. MW-5 had benzene at 0.62 µg/L. _See Table II for Cumulative Groundwater Analytical Results. The analytical .laboratory data. ' sheets can be found-in Appendix B. ' JJW GEOSCIENCES Inc. 2