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Water Quality Monitoring Report Forward Landfill 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 F). 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 on November 14, 2016, were used to generate the groundwater elevation contour map shown on Figure 2-1 for the fourth quarter 2017 monitoring period, which depicts groundwater beneath the northern half of Forward Unit generally flowing to the east-northeast at an average hydraulic gradient of 0.001 to 0.004 ft/ft, while groundwater beneath the southern half of Forward Unit generally flowing to the southeast at an average 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 (CH2M Hill, 2000). The maximum groundwater flow rate is calculated to be 2.9 feet per day(1064 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the Forward Unit groundwater monitoring wells for the fourth 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 fourth quarter 2017 monitoring period, non-statistical indications of a release was identified at well MW-17 as a result of a trace concentrations of 1,1-dichloroethane (1,1-DCA), dichlorodifluoromethane (DCDFM); tetra chloroethene (PCE), trichloroethene (TCE); and quantifiable concentrations of chloroform, carbon tetrachloride, and trichlorofluoromethane (TCFM). In a letter dated January 30, 2018, the RWQCB was notified of the CNSDAM exceedances in well MW-17. Quantifiable VOC constituents were place in "tracking mode" and are being evaluated quarterly for temporal trends (discussed below). Project No.5017.1030 I Water Quality Monitoring Report 6 January 2018