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CONESTOGA-ROVERS Mr. Michael Infuma at ASSOCIATES November 26, 2008 EXISTING MONITORING WELL NETWORK EHD requested information to demonstrate the existing monitoring well network is appropriate for this site. Presented below is a summary of the monitoring well locations, well construction details, and chemical concentration data, along with a conclusion of the effectiveness of the existing monitoring well network. Shallow (A-Zone) Groundwater: Historical depth to water at the site has generally ranged from approximately 4 to 12 fbg. The groundwater gradient at the site is generally flat, averaging 0.008 over the last four quarters. The groundwater flow direction is generally toward the southwest. When the groundwater extraction (GWE) system was operating at the site the groundwater flow direction was affected by pumping activities and showed groundwater flow toward the GWE wells. There are 15 shallow groundwater monitoring wells associated with the site; 8 onsite wells and 7 offsite wells (Figure 3). The wells are generally between 20 and 25 feet deep. The one exception to this is extraction well RW-lA which is screened to 31 fbg. The well construction details for each well are included in Table 2. Deep (B-Zone) Groundwater: There are 3 deep (B-zone) groundwater monitoring wells (MW-12, MW43, and MW44) associated with the site. Two of these deep wells are located on site and one (MW-14) is located southeast of the site. These deep zone wells are screened between 68 and 84 fbg. The specific screened interval for each well is shown on Table 2. The three deep monitoring wells are located generally in a line and are not well suited for creating groundwater contours and monitoring groundwater flow direction. However the groundwater elevation data from these three wells shows that typically MW44 has a higher groundwater elevation than MW42 and Nff43 which indicates a general groundwater flow toward the northern hemisphere in the deep groundwater zone. Plume Delineation: The gasoline constituent plume associated with this site appears to be confined to the shallow groundwater zone. The deep wells typically have not contained any gasoline constituents. There have been some detections of MTBE in the deep zone, but all of these detections have been below the MCL for MTBE. The chemical analytical data referenced below is contained in Blaine Tech Services, Inc Well Concentrations table for the third quarter of 2008 (Attachment B) The shallow gasoline constituent plume is primarily located onsite and more specifically in the 240783 9 Worldwide Engineering, Environmental. Construction, and IT Services