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' GeologuaecFinus Inc Page 2 GW Monitonng Report ' Ted Peters-AST Project No 70I 2 . March 14,2001 correspondence In his letter, Mr Mello also included the requirement that the site's wells be monitored on a semi-annual basis starting with the first quarter of 2001 This report details the completion of the first semi-annual monitoring event performed on February 16, ' 2001 2.0 GROUNDWATER MONITORING 2.1 Site Hydrology ' Site-specific groundwater gradients and bearings were calculated from the depth to water measurements taken during the event Two separate gradients were calculated for the three wells in the former UST location (MW-1, MW-2 and MW-3) and the three wells in the former AST location (MW-4, MW-5 and MW-6) Table 1 in Appendix A is a summary of water level elevations, gradient slopes and bearings Figure 2 is a groundwater gradient map for the site Historical groundwater direction and slope data are summarized in Figure ' 3 Groundwater Gradient Rose Diagram The average groundwater elevation of the AST wells was 13 83 feet above mean sea level The direction and gradient of groundwater in this area was N371E at 0 03 ft/ft As seen in Figure 3, the northeast direction is anomalous when compared to the southwesterly directions noted on July 30, 1999, and February 17, 2000 It is noted that free product was present in well MW-5, which may have resulted in a depressed water table level Nmeasurement in the well A gradient was also calculated from the three wells installed at the front of the site to ' investigate the UST area The gradient in this area was 0 001 ft/ft flowing N64°W This gradient is identical to the May 1, 2000 data recorded for the UST wells and similar to the other monitoring events ' This is the third event where groundwater elevations were measured in both sets of wells on the property Although it is not known why groundwater gradients are different in the two sets of wells, a possible explanation is that there are a large number of domestic wells west ' of the site that may influence the gradient at the site A domestic well survey within 2,000 feet of the site was completed on August 16, 2000 ' The survey efforts resulted in the identification of numerous domestic wells on the residential properties to the southwest, west and northwest of the site Ten wells were located in the properties to the immediate west of the subject site and their locations are identified in our "Well Receptor Report" dated September 11, 2000 (submitted to the SJC- ' PHS/EHD and the CRWQCB-CVR) 2.2 Groundwater Sampling Procedure ' On February 16, 2001, Don Light of Del Tech Geotechnical Support arrived on-site, opened the wells, and measured the depth to water with an electrically actuated sounding tape The ' water level reading was recorded to an accuracy of 0 01 foot During this monitoring event free product was noted in well MW-5 and an accurate reading of groundwater depth was not . obtained