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Geologual TeCluucs int Page 2 GW Monitoring Report Ted Peters-AST Project No 7012 September 19,2001 ' 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 second semi-annual monitoring event performed on August 1, ' 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 three wells in the former AST location (MW-4, MW-7 and MW-8) 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 01 feet above mean sea level The direction and gradient of groundwater for the August 2001 monitoring event was ' N52°W at 0 008 ft/ft As indicated in Figure: 3, a northwest direction was calculated for the second consecutive event since wells MW-7 and MW-8 were installed in March 2001 These data are offset by 90° 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 obverted in the other monitoring events ' It is noted that free product has been present in well MW-5, which may have resulted in an anomalous water table level measurement in the well Well MW-5 data is anomalous for the August 1, 2001 event and is omitted from the contour diagram included in Figure 2 ' 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 0 005 ft/ft flowing N831W This data is similar to the other monitoring events ' A comparison of the two areas indicates that for the last two events the gradient was northwesterly in both locations 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 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) 1 1