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Water Quality Monitoring Report Forward Landfill The groundwater elevation data obtained on May 19, 2015, were used to generate the groundwater elevation contour map shown on Figure 2-1 for the second quarter 2015 monitoring period, which indicates that groundwater beneath the majority of the Forward Unit generally flows to the south-southwest at a hydraulic gradient of 0.001 to 0.004 ft/ft, while groundwater beneath the southeastern corner of the Forward Unit flows to the west-northwest at a hydraulic gradient of 0.004 ft/ft. To calculate the approximate linear groundwater flow velocity for the Forward Unit, 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— fit V = —= [(0.04—)* 1 2835 � 1.30ftlday, ne sec 0.35 cm — day, where: V= Groundwater flow velocity. K= Hydraulic conductivity of the water-bearing unit (0.04 cm/sec). i= Hydraulic gradient: i z�0.004 at the site during the second quarter 2015. ne= Effective porosity (ne =0.35); an estimated value. The maximum groundwater flow rate is calculated to be 1.30 feet per day (473 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the Forward Unit groundwater monitoring wells for the second quarter 2015 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 2015 monitoring period, non-statistical indications of a release were identified at well MW-16 as a result of a quantifiable concentration of diisopropyl ether (RIPE) and a trace-level concentration of acetone; and at well MW-17 as a result of a quantifiable concentration of chloroform and trace-level concentrations of carbon tetrachloride, dichlorodifluoromethane (DCDFM), and trichlorofluoromethane (TCFM). In a letter dated July 16, 2015, the RWQCB was notified of these exceedances and retesting is scheduled for July 2015. The results of the verification sampling will be reported under M:\2015.0014\FA 2Q15.docx 6 7/31/2015, Rev.0