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F-1 <br /> <br />APPENDIX F <br />GROUNDWATER DIRECTION AND FLOW RATE CALCULATIONS <br /> <br />Groundwater elevations in the monitoring wells were obtained this semiannual period. <br />These measurements were used to define the direction and gradient of groundwater flow <br />in the vicinity of the North County Sanitary Landfill. The average groundwater velocity in <br />this area was calculated using the following equation (Darcy’s Law): <br /> V = Ki <br /> n <br />Where <br /> V = maximum linear velocity <br /> K = permeability <br /> = 9.8 x 10-3 centimeters per second (cm/s) <br /> = 10,100 feet per year (ft/yr) <br /> i = hydraulic gradient <br /> = (difference between groundwater elevations) / distance between <br />measuring locations) in foot per foot (ft/ft) <br /> n = porosity <br /> = 0.30 <br />Permeability coefficients determined with a slug test in well G-1 ranged from 8.3 x 10-3 to <br />9.8 x 10-3 cm/s in the water-bearing zone beneath the landfill. The highest measured <br />permeability value of 9.8 x 10-3 cm/s was selected because it would produce the greatest <br />groundwater velocity. An average porosity value of 0.3 was used, based on published <br />porosity values for similar geologic materials. <br />First Quarter 2025 <br />The hydraulic gradient (0.003 ft/ft) to the southwest was calculated by dividing the <br />difference in groundwater elevations between wells G-8 and G-13 by the horizontal <br />distance between the two wells (~2,070 feet). <br />The groundwater flow velocity of 101 ft/yr was calculated as follows: <br /> V = 10,100 ft/yr (0.003 ft/ft) = 101 ft/yr <br /> 0.30 <br /> <br />Second Quarter 2025 <br />The hydraulic gradient (0.002 ft/ft) to the west-southwest was calculated by dividing the <br />difference in groundwater elevations between contours -63 and -65 by the horizontal