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The groundwater elevation data obtained during second quarter 2006 monitoring period were used to generate the groundwater elevation contour map shown on Figure 2-1, which indicates that groundwater at the site generally flows to the west and north at an average hydraulic gradient of approximately 0.001 to 0.003 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). The estimated maximum groundwater flow velocity was calculated using Darcy's Law: Ki cm * 0.003 *2835 sec– ft 0.972 /da V = —= [(0.04 cm ] ft y 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 0.003 for the site during the second quarter 2006. ne=Effective porosity(ne=0.35);an estimated value. The groundwater flow rate is calculated to be 0.972 feet/day(355 feet/year). 2.1.4 Detection Monitoring Program Field and laboratory results for the groundwater monitoring wells for the second quarter 2006 are summarized in Table 2-2 and Appendix D presents time-series charts of select inorganic parameters. As shown on Table 2-2, one or more trace level VOCs were measured in the samples collected from wells MW-1B,MW-10,MW-14,MW-15, MW-16,MW-17,MW-19, MW-21, and DW-9690,while concentrations of tetrachloroethene(PCE) and trichloroethene(TCE)in well MW-1B and acetone in well DW-9690 were measured above the practical quantitation limit(PQL). 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 sporadic detection of low-level VOCs in groundwater and lysimeter samples at the Forward Landfill are most likely due to landfill gas from unlined unit WW-B. Forward has continued to minimize gas related impacts to groundwater by minimizing interim fill areas that promote ponding of water. Furthermore, in accordance with CCR Title 27, Section 20937,Forward continues to install additional landfill gas extraction wells. New Historical Intrawell Maximum Values As shown in the following table,the results of the second quarter 2006 monitoring period indicate that 16 new historical intrawell maximum values were measured, including seven first-time VOC detections, in samples collected from groundwater monitoring wells. D:\2003_021\ForwsrdAusdn_sp06.doc 6 GeoLogic Associates