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Water Quality Monitoring Report Forward Landfill 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 on May 30, 2017, were used to generate the groundwater elevation contour map shown on Figure 2-1 for the second quarter 2017 monitoring period, which depicts groundwater beneath the northeastern corner of Forward Unit generally flowing to the northeast at an average hydraulic gradient of 0.003 ft/ft, while groundwater beneath the remainder of Forward Unit generally flowing to the southeast at a hydraulic gradient of 0.002 ft/ft, potentially controlled by agricultural well pumping on adjacent properties. To calculate the approximate linear groundwater flow velocity for the Forward Unit, conservative assumptions were used, including a hydraulic conductivity of 255 feet per day (CDM, 1997) and an estimated effective porosity of 35 percent. An estimated groundwater flow velocity was calculated using Darcy's Law: Kr , fl 0.003 V = — = ( 255 ) * a 2.19 Jl / day ne day 0.35 where: V= Groundwater flow velocity. K = Hydraulic conductivity of the water -bearing unit (255 ft/day). i = Average hydraulic gradient: i ;:z 0.003 during the second quarter 2017. ne= Effective porosity (ne = 0.35); an estimated value. The maximum groundwater flow rate is calculated to be 2.19 feet per day (798 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the Forward Unit groundwater monitoring wells for the second quarter 2017 monitoring period are summarized in Table 2-2. Non -Statistical Data Analysis The California Non -Statistical Data Analysis Method (CNSDAM) was performed for VOCs detected less than 10 percent of the time in background samples. Under the CNSDAM, a measurably significant indication of release occurs in a given sample when: two or more VOCs exceed their respective Method Detection Limits (MDLs); or one or more VOCs equals or exceeds its respective practical quantitation limit (PQL). During the second quarter 2017 monitoring period, non -statistical indications of a release was identified at well MW -2A as a result of trace concentrations of 1,1-dichloroethane (1,1 -DCA) and of cis- l,2-dichloroethene (cis-1,2-DCE); MW -16 as a result of a quantifiable concentration of diisopropyl ether (DIPE); and at well MW -17 as a result of quantifiable concentrations of carbon tetrachloride, chloroform, 0 Project No. 5017.1030 I Water Quality Monitoring Report 6 July 2017