ARCHIVED REPORTS_2016_1 - Laserfiche WebLink

Home Browse Search

C7 Water Quality Monitoring Report Forward Landfill 3.1.2 QA/QC Results The QA/QC program completed for the first quarter 2016 water quality monitoring event at the Austin Unit included analyses of two trip blanks, one field blank, laboratory method blanks, and one duplicate sample (well AMW-21). The field and trip blanks were analyzed for VOCs by EPA Method 8260 and method blanks were analyzed for all required analyses. The results of the QA/QC program indicate that no VOCs were detected in the QA/QC blank samples. Inorganic constituents including calcium and sodium were measured at trace concentrations in method blanks. However, these constituents were measured at very low concentrations that did not affect the interpretation of primary sample results. Results from the duplicate groundwater sample collected from well AMW-21 are presented along with the primary data in Table 3-2 yielded good correlation with quantifiable constituents having a RPD less than seven percent. Only nitrate -N had a RPD above seven percent (25 percent). Review of laboratory analysis dates and required holding times indicates that all samples were submitted and analyzed within the required holding times during the first quarter 2016. Based on the results of the laboratory blank and duplicate analyses, it is concluded that acceptable QA/QC procedures were exercised and the water quality samples collected from the Austin Unit appear to be representative of water quality at the site. 0 3.1.3 Groundwater Elevations and Contours n 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 E). 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 3-6. 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 generally flows in a east to northeast direction with hydraulic gradients ranging from of 0.001 to 0.004 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 0.004 Sec— ft V = — = [( 0.04 —) * 1 * 2835 = 1.296 ft / day ne sec 0.35 cm — day where: V = Groundwater flow velocity. M:\ 2016.0007\FA 1Q16.docx 10