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1 <br />Aggregate Industries - F Street Site Characterization Report <br />Project Number IOOIOl8 PnRncoN <br />' October 9, 2001 <br />Page 5 <br />engineer. Those logs contain visual and tactual classifications of the materials encountered <br />' during drilling, as well as the driller's interpretation of subsurface conditions based on <br />drilling resistance. The descriptions of the soils encountered in the borings are in general <br />t accordance with the General Notes included in Appendix D. Final boring logs included in <br />this report represent an interpretation of the field logs. The stratification boundaries shown <br />on the enclosed boring logs represent the approximate locations of changes in soil types; in- <br />' situ, the transition of materials may be gradual. <br />' 4.2 Groundwater Observations <br />Historic groundwater elevations are summarized in Table 1 in Appendix B. As seen from <br />Table 1, groundwater was observed at depths ranging from approximately 5.6 to 24.7 feet <br />' below the top of casings (TOC) in MW-l through MW-4 and EW-1 on July 25, 2001; <br />August 10, 2001; August 17, 2001; and September 19, 2001. It should be noted that well <br />' MW-1 is located approximately 17 feet above the spill area since the overburden from the <br />spill area had been previously removed from that area of the site during mining activities. <br />Free-phase petroleum has not been observed in the monitoring wells during the four (4) <br />' groundwater elevation measurement events. <br />On September l9, 2001, the depth to groundwater was also measured in four (4) observation <br />' wells which were previously installed by Aggregate Industries. Those observation wells are <br />generally located south of the spill area along F Street as shown on Figure 4 in Appendix A. <br />' As seen from Table 1, groundwater was observed at depths of approximately 7.8 to 18.7 feet <br />below TOC in wells OW-1 through OW-4 on September 19, 2001. <br />' 4.3 Piezometric Surface <br />Piezometric surface diagrams for groundwater elevations observed on September 19, 2001 <br />t are included as Figures 4 and 4a in Appendix A of this report. The piezometric surface for <br />the overall site, including wells OW-1 through OW-4, is shown on Figure 4 while the <br />pie,%ometric surface in the vicinity of the spill area is shown on Figure 4a. The piezometric <br />' surfaces were estimated using the computer program Surfer® which is distributed by Golden <br />Software. As seen from Figure 4, the regional groundwater flow generally appears to be in a <br />northeasterly direction with a more northerly component on the east side of the site. As <br />' seen from Figure 4a, the local groundwater flow direction appears to be to the east-northeast <br />in the vicinity of the spill area. The hydraulic gradient was estimated to range from <br />' approximately 0.006 to 0.03 for the overall site while the hydraulic gradient was estimated <br />to range from approximately 0.002 to 0.006 for the spill area. It should be noted that local <br />geohydrologic characteristics such as flow direction and gradient may change due to <br />t <br /> <br />