WORK PLANS - Laserfiche WebLink

Home Browse Search

CAM B R I A boidegradation. In general,the core wells will be sampled on a quarterly basis and the peripheral wells will be sampled on an annual basis. The specific analyses for each well and the frequency of these analyses are detailed on Table 1. Detection limits: SJCEHD specified particular detection limits for some of the requested analytes and did not specify detection limits for other analytes. We will work with our lab to meet the specific detection limits requested and will use standard reporting limits for the analytes where no detection limits were specified. Table 1 lists the requested detection limits and the standard reporting limits for each of the requested analyses. © Occasionally detection limits are elevated because the lab needs to dilute the sample. Sample dilution is necessary when one or more analytes are recent at moderate or high concentrations. Diluting the sample will result in the detection limit being elevated for the analytes that are not present or are present at low concentrations. Dilution is necessary to protect laboratory equipment from becoming contaminated with high concentrations of analytes. This is a standard laboratory practice and may result in elevated detection limits from time to time. Acetone: One of the analytes SJCEHD has asked us to analyze for is acetone. Acetone is a known breakdown product of tertiary butyl alcohol (TBA). If MTBE and TBA have been detected in a groundwater sample from a particular well, and acetone is also present then this may be an indicator that biodegradation is breaking down MTBE into TBA, and TBA into acetone. We believe SJCEHD has requested acetone analysis to determine if this process is happening. We also believe that acetone analysis is only appropriate for wells that contain, or have contained, TBA, simply because acetone cannot be present as a breakdown product unless TBA is (or was) present. Therefore we recommend only performing acetone analysis on groundwater samples from wells MW-1 and MW-2, which are the only wells at this site that have contained TBA. -�k"5 Ethylene Dibromide (EDB) and 1,2-Dichloroethane (1,2-DCA): EDB and 1,2-DCA analysis has been performed on groundwater samples from every well at this site and neither has ever been detected. We believe the reason they have not been detected is because they were not a component of the gasoline when the release occurred. Lead scavengers (EDB and 1,2-DCA) were added to gasoline prior to 1991. The USTs were installed west of the dispenser islands during 1996, well after the use of lead scavengers ceased. Based on the fact that EDB and 1,2- DCA have not previously been detected in groundwater beneath the site and that it is likely EDB and 1,2-DCA were not a component of the fuel release,we recommend no further analysis for EDB and 1,2-DCA be performed. 1015 2