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3.1.3 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 Austin Unit are summarized in Table 3-4. The groundwater elevation data obtained during this quarterly monitoring period were used to generate the groundwater elevation contour map shown on Figure 3-1,which indicates that groundwater beneath the Austin Unit generally flows to the north-northwest at an average hydraulic gradient of approximately 0.002 ft/ft. To calculate the approximate linear groundwater flow velocity for the site, conservative assumptions were used, including a hydraulic conductivity of 875 gallons per day per square foot(0.04 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 0.002 sec– ft V = — _ [(0.04—)* ]*2835 0.65 ft /day ne sec 0.35 cm – day where: K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). i=Hydraulic gradient: i�0.002 for the site during the current the third quarter 2009. ne=Effective porosity(ne=0.35);an estimated value. The groundwater flow rate is calculated to be 0.65 feet/day(237 feet/year). 3.1.4 Detection Monitoring Program Field and laboratory results for the DMP wells for the third quarter 2009 are summarized in Table 3-1. As shown in Table 3-1, DCDFM was measured above the PQL in the sample collected from well AMW-14 and at a trace concentration in the sample collected from well AMW-6. In addition,PCE was measured above the PQL in the sample collected from well AMW-6; and PCE and TCE were measured above the PQL in the samples collected from wells AMW-13 and AMW-14. For the DMP wells at the Austin Unit, CLs are calculated for the water quality protection standards (WQPS). The CLs shown in Table 3-1 were calculated by Herst&Associates using Sanitas®, a state-approved statistical software program. As shown on the table below, the following analytes were found to equal or exceed a CL during the third quarter 2009 monitoring period. The results of the statistical analyses performed by Herst& Associates are presented in Appendix D. D A2009_001 TFA_3Q09.doc 9 Geologic Associates