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C404kal reckg1a Inc Page 3 Groundwater Momtonng Report Project No 723 2 June 20,2005 1.0 GROUNDWATER MONITORING ' In November, 2003, three new continuous multi-chambered tubing (CMTrm) wells were installed to further define the vertical and lateral extent of the soil and groundwater plumes ' (see Figure 13 for well locations and Table 8 for well construction details) The boreholes for the new wells' were installed to the north, east, and southwest of the site across E Castle, N El Dorado Street and W Adams Street, respectively ' As previously reported by GTI, the CMTS wells were so tightly coiled for shipping that it was difficult to install the wells without the tubing corkscrewing in the borehole, even when ' the casing was stretched out on the ground in the sun to warm and relax the coils The result of this twist in the tubing is that depth to water measurements could not be made because the instrument probe becomes lodged in the small chambers of the tubing But Del-Tech ' Geotechnical Support procured a new mucro-water level meter that can be used in the CMTrm wells The first quarter of 2005 was the first time that the well chambers were sounded ' The ability to sound the wells resulted in changes in quarterly monitoring reports The wells have been grouped according to the aquifer interval that the screened section intercepted (see Figure 14 for well screen intervals) Shallow Wells (screened 35 —55 feet bgs) MW-4, 5, 6, 7, 8 & 9 Intermediate Wells (screened 43 —70 feet bgs) MW-1, 2, 3, 107, 108 & 109 ' Deep Wells (screened 76—80 feet bgs) MW-207, 208 & 209 Deepest Wells (screened 94—97 feet bgs) MW-101, 307, 308 & 309 The aquifer was divided in four horizons based on the screened intervals and groundwater gradient contour maps constructed for each horizon shallow, intermediate, deep and deepest 1.1 Hydrogeology of Site ' Horizontal Groundwater Gradients The calculated gradients for the April 2005 monitoring event are as follows ' Aquifer Zone Screen Interval Gradient Bearing MW No Water table 35 to 55 ft bgs 0 0034 ft/ft N590E 4, 5 & 6 Intermediate 43 to 70 ft bgs 0 004 ft/ft N530E 1, 2, 3, 107, 108 7 109 ' Deep 76 to 80 ft bgs 0 0038 ft/ft N550E 207, 208 & 209 Deepest 94 to 97 ft bgs 0 0025 ft/ft S31°W 101, 307, 308 & 309 ' Figures 2A through 2D illustrate four aquifer groundwater gradient maps for the April 2005 event Figure 3, Groundwater Gradient Rose Diagram, includes the historical shallow groundwater directions and gradients