ARCHIVED REPORTS_XR0008889 - Laserfiche WebLink

Home Browse Search

FARR ASSOCIATES 3 3 4 September 1998 Groundwater Monitoring Event A final site monitoring event was conducted on September 8, 1998, under supervision of Laurie Duncan of PHS/EHD The results of this monitoring event are described in this section Groundwater Level Measurements Groundwater level elevations of all five (5) monitoring wells were measured on September 8, 1998 (Appendix D) No odors or sheen were observed during the field measurements Water- level measurements were made using an electric water-level probe, relative to the surveyed lowest point on the top of the open well casings Figure 5 presents the potentiometric surface as measured on September 8, 1998 This most recent water level data is presented with contours on Figure 4 and the entire record of historical groundwater measurements are presented on Table 2 The direction of groundwater flow is toward the east-northeast with a horizontal hydraulic gradient of approximately 0 002 foot/foot Groundwater Sampling After completion of the groundwater level elevation measurements, each well was purged of approximately 3 well-casing volumes (Appendix D) The purge water was contained within a labeled, DOT-approved, 55-gallon storage drum The sampling equipment was decontaminated between each use in order to prevent cross contamination After purging each well of three well casing volumes of water, a groundwater sample was collected from each well using a disposable polyethylene baiter The sample water from each well was carefully poured from the bailer into five 40 ml glass vials (VOA vials) The sample bottles were labeled, recorded on a chain-of custody form, and stored in a chilled ice chest for transportation to Kilt Analytical, a State certified laboratory in Davis, California A travel or "trip" blank was prepared using distilled water to evaluate potential sample contamination during storage and transport of the samples Transport and handing of samples were performed under strict chain-of-custody protocol The field data sheets, groundwater analytical data sheets, and chain-of-custody records are contained in Appendix D of this report Groundwater Anal3qtcal Results The groundwater samples and trip blank were analyzed for BTEX (EPA Method 8020), TPH-g, TPH-d, and TPH-k (Modified EPA Method 8015), and seven oxygenates (EPA Method 8260) Results of the groundwater chemical analyses are shown on Figure 8 for the September 1998 monitoring event Table 3 lists the results of these recent analyses, along with the historical data As shown on Table 3 and Figure 5, the only constituent which was detected at the site was MTBE at the very low concentrations of 0 70 ug/1 at MW-1 and 0 51 ug/1 at MW-5 ' C IM Files\Annelw wml ra ecls�umon\ClosureR f w d 4