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are measurable concentrations above the practical quantitation limit(PQL) indicates good agreement(within 10%), except for nitrate as nitrogen, which was within 15 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 I A and I B, which indicates that groundwater generally, flows to the south with an average hydraulic gradient of 0.0025 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 range in groundwater flow velocity was calculated using Darcy's Law: V = Ki = [(0.014 cin 0.0025 2835 sec- fit � 0.284 ft /day ne sec 0.35 cm — clay where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.014 cm/sec). i=Hydraulic gradient: i�0.0025 for the site during the monitoring period. n,=Effective porosity(n,=0.35); an estimated value. The groundwater flow rate is calculated to be 0.284 feet/day(104 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-I OA) 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, chloroform and trichlorofluoromethane(TCFM) were measured above the PQL in the samples collected from wells MW-6A and MW-9A, respectively. Similar concentrations of TCFM have been measured in samples collected from well MW-9A. In a letter dated January 16, 2007, the RWQCB was notified of the non-statistical indication of a release at well MW-9A, which has been attributed to the recent placement of a final cover system on the landfill and associated landfill gas generation. The measured result is consistent with previous TCFM concentrations measured in well MW-9A. Well MW-6A is a background well and chloroform is a common laboratory contaminant,however, retest D:\200&0012\FC_2SA08.doc 3 Geo Logic Associates