Laserfiche WebLink
7 <br /> •M LEEDSHILL•HERRENHOFF, INC. <br /> } AMENDED WORKPLAN FOR GROUNDWATER ASSESSMENT <br /> LINCOLN VILLAGE CENTER, STOCKTON <br /> The following discussion is LEEDSHILL-HERKENHOFF, INC. 's response to the <br /> Central Regional Water Quality Control Board's concerns regarding the previ- <br /> ously submitted Lincoln Village Center groundwater assessment Workplan. <br /> PHASE I <br /> As discussed in the original Workplan, LEEDSHILL-HERKENHOFF (LH) has divided <br /> the investigation into several phases, primarily due to a lack of site- <br /> specific hydrogeologic and background water quality data. The original <br /> monitoring well conceptual layout was designed to define the extent of <br /> suspected contamination by using a phased, cost-effective approach. LH's <br /> original Workplan provided water quality data regarding upgradient, back- <br /> ground conditions, and downgradient, offsite migration from Lincoln Village <br /> Center, if any. Although there has been documented TCE and PCE contamina- <br /> tion in Lincoln Village (LV) Well #1, the source of this contamination has <br /> yet to be determined. In that regard, although site specific solvent leak- <br /> age from sewer lines is a possible source, potential upgradient contaminant <br /> sources may or may not be contributing to this problem. Since no upgradient <br /> background water quality data representative of the shallow aquifer exists, <br /> it is important to establish this baseline condition so that all responsible <br /> parties can be identified and be provided the opportunity to participate in <br /> this investigation. Currently, the downgradient and/or offsite extent, if <br /> any, of the suspected TCE and PCE groundwater contamination is unknown, and <br /> must be established during Phase I. LH's original monitoring well locations <br /> were established to determine groundwater gradient and direction of flow, <br /> and determine whether offsite (off Lincoln Village Center) migration is <br /> occurring. If representative samples from these perimeter wells show no <br /> contamination, then the focus of subsequent phases of this investigation can <br /> be narrowed to source identification and mitigative strategies within Lin- <br /> coln Village Center. If initial and confirmation samples show TICE and/or <br /> PCE migration offsite, then existing downgradient wells within one-half mile <br /> which are used for domestic consumption will be located, sampled and ana- <br /> lyzed for TICE and PCE. LH's specific modifications to the original Workplan <br /> are presented by task as follows. <br /> Task 1: Site History <br /> As discussed in LH's original Workplan, determination of historic product <br /> usage and disposal practices will be documented through interviews with <br /> operators of the dry cleaners and other establishments that are identified <br /> as possible sources of contamination. Additionally, based on information <br /> obtained during this Task and after evaluating the existing data obtained <br />