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® 4.3 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 and historical groundwater elevation data for the French Camp Landfill is summarized in Table 5. The groundwater elevation data obtained during the monitoring period were used to generate the groundwater elevation contour maps shown on Figures 1 and 2, which indicates that groundwater flow varied from 0.002 ft/ft to the northwest during the first quarter 2008 monitoring period to 0.001 ft/ft to the southeast during the second quarter 2008 monitoring period. 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 range in groundwater flow velocity was calculated using Darcy's Law: Kicm 0.002 sec– ft V = —_ [(0.014 —)* ]*2835 0.227 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=Maximum Hydraulic gradient: i a 0.002 for the site during the monitoring period. ne=Effective porosity(ne=0.35);an estimated value. The maximum groundwater flow rate is calculated to be 0.227 feet/day (83 feet/year). 4.4 DETECTION MONITORING PROGRAM Field and laboratory results for DMP monitoring wells(MW-6A, MW-7A,MW-8A, MW-9A, MW-9B, and MW-lOA)from the current monitoring period are summarized in Table 2 and time-series plots are presented in Appendix D. As shown in the time-series plots, general chemistry and metals constituent concentrations are generally consistent with historical concentrations. During the monitoring period,no organic constituents were detected. 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 DA2005-0012TC_1SAOBro Ldot Geologic Associates