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5.3 GROUNDWATER ELEVATIONS AND CONTOURS Prior to purging and sampling, each well was sounded for water depth using a weighted electronic sounder, and the static water level was recorded on a Well Data Sheet (Appendix Q. The groundwater elevations were calculated for each well by subtracting the depth-to-water measurement from the top-of-casing reference elevation. The current groundwater elevation data for the French Camp Landfill are summarized in Table 5. The groundwater elevation data obtained during this quarterly monitoring period were used to generate the groundwater elevation contour map shown on Figure 1,which ' indicates that groundwater flows to the east with an average hydraulic gradient of approximately 0.004 ft/ft. To calculate the approximate linear groundwater flow velocity for the site, conservative assumptions were used,including a hydraulic conductivity of 300 gallons per day per square foot(0.014 cm/sec), and an estimated effective porosity of 35 percent(CH2M Hill ' 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: Ki cm 0.004 sec– ft V = —=[(0.014 —)* ]*2835 0.454 ft/day ne sec 0.35 cm –day where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.014 cm/sec). i=Hydraulic gradient: is:;0.004 for the site during the current monitoring period. ne=Effective porosity(n,=0.35);an estimated value. The groundwater flow rate is calculated to be 0.454 feet/day(166 feet/year). 5.4 DETECTION MONITORING PROGRAM Second quarter 2006 field and laboratory results for DMP monitoring wells (MW-6A, ' MW-7A,MW-8A, MW-9A,MW-9B, and MW-lOA) are summarized in Table 2 and time-series plots are presented in Appendix D. As shown in the time-series plots, the general chemistry and metals constituents are generally consistent with historical ' concentrations. Of note,no organic constituents were detected in DMP monitoring wells during the current monitoring period. ' Concentration Limits For DMP monitoring wells at the French Camp Landfill, concentration limits (CLs) are ' used for the water quality protection standards (WQPS). The CLs shown in Table 2 were calculated by Herst &Associates using Sanitas , a state-approved statistical software program,using historical data from background wells MW-6A and MW-7A, and are ' presented in Appendix D. Based on a comparison of the data obtained during the second quarter 2006 monitoring period, the following analytes were found to exceed a CL: D:UO03_021\FC_spKdoc 3 Geologic Associates