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cwkglutTeclmcslru Page 3 GW Monitoring Report Ted Peters-AST r Project No 701 2 May 15, 2003 2.0 GROUNDWATER MONITORING ' 21 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 five wells in the former AST location (MW-4, MW-5, MW-6, MW-7 and MW-8) Table 1 in Appendix A is a summary of water level elevations, gradient slopes and bearings and Table 4 includes well ' construction details 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 12 29 feet above mean sea level The direction and gradient of groundwater for the April 2, 2003 monitoring event was N46°W at 0 008 ft/ft As indicated in Figure 3, a northwest direction was calculated for the sixth consecutive event since wells MW-7 and MW-8 were installed in March 2001 These data are offset by 900 when compared to the southwesterly directions noted on July 30, 1999, and February 17, 2000 The northeasterly flow direction in February 2001 is ' anomalous to the dominant westerly direction observed for the other monitoring events The field technician has previously noted that free product was present in well MW-5 and during this event a heavy sheen was observed The groundwater elevation datum for MW-5 is anomalous for the April 2003 event and is omitted from the contour diagram included in Figure 2 ' Groundwater 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 0 004 ft/ft flowing N12% on April 2, 2003 This is anomalous with the other monitoring events completed during the investigation The gradient has consistently trended to the west to northwest in the past as evident in Figure 3 An examination of the AST area indicates that for the last six events the gradient was ' northwesterly This suggests that previous calculations were affected by the spatial orientation of the AST wells, the presence of free product in MW-5, or a combination of both It is also possible the local domestic wells located west of this property are influencing the gradients at the site A domestic well survey within 2,000 feet of the site was completed on August 16, 2000 ' The suivey 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) 22 Groundwater Sampling Procedure ' On April 2, 2003, 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