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n <br />Water Quality Monitoring Report <br />Forward Landfill <br />percent or less. Review of laboratory analysis dates and required holding times <br />indicates that all samples were submitted and analyzed within the required holding <br />times during the second quarter 2014. Based on the results of the laboratory blank and <br />duplicate analyses, it is concluded that acceptable QA/QC procedures were exercised <br />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 Q. 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 <br />(including offsite EMP wells that were gauged for groundwater elevation in April 2014) <br />were used to generate the groundwater elevation contour map shown on Figure 3-1, <br />which indicates that groundwater along the northern perimeter of the Austin Unit and <br />offsite EMP wells generally flows to the northeast at a hydraulic gradient of 0.001 ft/ft, <br />to the north at a gradient of 0.002 ft/ft, and to the northeast at a gradient of 0.003 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 (CH2M Hill <br />2000). An estimated groundwater flow velocity was calculated using Darcy's Law: <br />Ki cm 0.001 sec — ft <br />V = — = [( 0.04 —) * ] * 2835 = .324 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 = 0.001 to 0.003 at the site during the second quarter <br />2014. <br />ne= Effective porosity (ne = 0.35); an estimated value. <br />The estimated groundwater flow rate is calculated to be 0.324 to 0.972 feet/day (118 to <br />355 feet/year). <br />M:\ 2014.0012\FA_2Q14.docx 10 <br />7/29/2014, Rev. 0 <br />