Laserfiche WebLink
Avoidance of DHS standards allows for setting artificially <br /> high detection limits, in some instances. This effectively <br /> creates a window of nondetection between the lower <br /> established MCL and the higher established laboratory <br /> detection limit, possibly resulting in false negatives. <br /> It is also important to note that the risk assessment could <br /> establish a cleanup goal lower than the MCLS. <br /> Parameter WCC (D. Limit) EPA State <br /> Detection MCL MCL <br /> Limit (µg/P) (µg/E) (µg/P) <br /> 1, 2 Dichloroethane 0. 9 5.0 0. 5 <br /> Vinyl Chloride 1. 0 2 . 0 0. 5 <br /> Chlordane 0. 5 2. 0* 0. 1 <br /> Heptachlor 0. 1 0. 4* 0. 01 <br /> Heptachlor Epoxide 0. 1 0. 2* 0. 01 <br /> Polychlor. Biphenyls 1. 0-2 . 0 0. 5* - <br /> * Effective 7/92. <br /> Of these compounds, both vinyl chloride and 1, 2- <br /> dichloroethane (DCA) are biodegradation products of <br /> tetrachloroethylene (PCE) and trichloroethylene (TCE) , the <br /> major contaminants in the groundwater at DDRW-Tracy. <br /> • All detection limits should be, at a minimum, lower <br /> than the applicable MCLS. <br /> • The Project Managers need to discuss the possibility <br /> for setting lower detection limits (e.g. , to <br /> characterize the outer reaches of the GW plume and in <br /> anticipation of potential cleanup goals lower than <br /> MCLS. ) . <br /> 3 . For the overall RI/FS process, these data by themselves are <br /> of insufficient quality to meet EPA's Contract Laboratory <br /> Program (CLP) standards. More rigorous quality <br /> assurance/quality control (QA/QC) protocol must be followed <br /> and, in some cases, lower detection limits must be attained. <br /> • These overall data quality concerns must be addressed <br /> in future quarterly monitoring reports. <br /> 2 <br />