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laboratory QA/QC analyses, it is concluded that the laboratory data generated for the first 0 quarter 2011 monitoring period are generally acceptable and the water quality samples collected from the Forward Unit appear to be representative of water quality at the site. 2.1.3 Groundwater Elevations and Contours Prior to purging and sampling, each well was sounded for water depth using a weighted electronic sounder to an accuracy of 0.01 foot, 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 Forward Unit is summarized in Table 2-3. The groundwater elevation data obtained during the first quarter 2011 monitoring period were used to generate the groundwater elevation contour map shown on Figure 2-1, which indicates that groundwater generally flows to the north-northeast towards the Austin Unit, at an average hydraulic gradient of approximately 0.002 Mt. 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 L1771 0.002 see- .1i I' J(0.04 —)* —1* 283-5 -- zz 0,648 ft , daY ne sec 0.35 c1n - daY where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.04 cm/sec). i=Hydraulic gradient: i�0.002 for the site during the first quarter 2011. n,=Effective porosity(n,=0.35);an estimated value. The groundwater flow rate is calculated to be 0.648 feet/day (237 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the groundwater monitoring wells for the first quarter 2011 are summarized in Table 2-2. The organic results for the Forward Unit indicate that isopropyl ether was measured at an estimated trace concentration(between the method detection limit [MDL] and the PQL) in the sample collected from well MW-2A; tetrachloroethene (PCE) was measured at a trace concentration in the sample collected from well W-14; and acetone was measured at a trace concentration in the sample collected from well MW-16. On behalf of Forward Inc., GLA prepared a letter report dated February 14, 2001 (RWQCB Case No. 2209),to assess the source and potential impacts of low-level VOCs in groundwater adjacent to the Forward Landfill. The letter report concluded that the D:U01 1_0050\FA—IQI I.dmx 5 GeoLogic Associates