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Water Quality Monitoring Report <br /> Forward Landfill <br /> ® a RPD less than seven percent. Review of laboratory analysis dates and required holding <br /> times indicates that all samples were submitted and analyzed within the required <br /> holding times during the third quarter 2015. Based on the results of the laboratory <br /> blank and duplicate analyses, it is concluded that acceptable QA/QC procedures were <br /> exercised and the water quality samples collected from the Austin Unit appear to be <br /> representative of water quality at the site. <br /> 3.1.3 Groundwater Elevations and Contours <br /> Prior to purging and sampling, each well was sounded for water depth using a weighted <br /> electronic sounder, and the static water level was recorded on a well data sheet <br /> (Appendix F). The groundwater elevations were calculated for each well by subtracting <br /> the depth-to-water measurement from the top-of-casing reference elevation. The <br /> current groundwater elevation data for the Austin Unit are summarized in Table 3-6. <br /> The groundwater elevation data obtained during this quarterly monitoring period were <br /> used to generate the groundwater elevation contour map shown on Figure 3-1, which <br /> indicates that groundwater generally flows to the northeast with hydraulic gradients <br /> ranging from 0.001 to 0.002 ft/ft. <br /> To calculate the approximate linear groundwater flow velocity for the site, conservative <br /> assumptions were used, including a hydraulic conductivity of 875 gallons per day per <br /> square foot (0.04 cm/sec) and an estimated effective porosity of 35 percent (CH21VI Hill <br /> 2000). An estimated groundwater flow velocity was calculated using Darcy's Law: <br /> Ki cm 0.002 sec— ft <br /> V = —= [(0.04—)* ]* 2835 = 0.648 ft/day <br /> ne sec 0.35 cm —day <br /> where: V= Groundwater flow velocity. <br /> K= Hydraulic conductivity of the water-bearing unit (0.04 cm/sec). <br /> i= Hydraulic gradient: i=0.002 at the site during the third quarter 2015. <br /> ne= Effective porosity (ne= 0.35); an estimated value. <br /> The maximum groundwater flow rate is calculated to be 0.648 feet/day (237 feet/year). <br /> 3.1.4 Detection Monitoring Program <br /> Field and laboratory results for the Austin Unit DMP wells for the third quarter 2015 are <br /> summarized in Table 3-1. <br /> M:\2015.0014\FA 3Q15.docx 10 <br />