Laserfiche WebLink
Addendum to the Well Installation and <br /> Hydraulic Testing Report and Additional <br /> ARCADIS Well Installation Work Plan <br /> Former Occidental Chemical Corporation <br /> Lathrop, California <br /> b = Aquifer thickness, equal to approximately 30 ft <br /> K = Hydraulic conductivity, in ft/day <br /> After measuring drawdown in each observation well, drawdown was plotted on an arithmetic scale <br /> along the y-axis.The distance from each observation well to the pumping well was plotted on a <br /> logarithmic scale along the x-axis(Figure 4).A line was then fit through the data points and extended to <br /> the distance axis.The intercept of the line and the distance axis(ro) is the distance beyond which the <br /> pumping well has no effect. Storativity was calculated using the following equation: <br /> S=T*t/640 roe (Equation 3) <br /> where <br /> T = Transmissivity, in ft2/day, calculated to be 1137.5 ft2/day using Equation 1 <br /> t = Time in minutes, equal to 27 hours <br /> ro = Distance beyond which the pumping well has no effect, measured as 800 ft using Figure 4 <br /> S = Storativity, dimensionless <br /> A summary of aquifer parameters calculated from the hydraulic testing is shown in Table 1 below. <br /> Aquifer parameters are consistent with published values for flow through sandy aquifers(e.g., typical <br /> hydraulic conductivity of sandy aquifers ranges from 0.001 to 0.1 centimeters per second[cm/sec]). <br /> Hydraulic testing results were used to estimate the zone of influence of water table zone extraction <br /> wells. By plotting distance versus drawdown as shown on Figure 4,the distance beyond which the <br /> pumping well had no effect was estimated to be 800 ft.Assuming that the radius of influence is defined <br /> by a drawdown of 0.1 ft or less, the radius of influence corresponding to an extraction rate of 65 gpm is <br /> approximately 750 ft. Using drawdown and distance measurements during pumping at 30 gpm,the <br /> radius of influence was estimated to be approximately 700 ft. <br /> Table 1.Aquifer Parameters from Hydraulic Testing Data <br /> Aquifer Parameter Site-Specific Value Units <br /> Transmissivit 1137.5 ft2/da <br /> Storativity 0.0045 -- <br /> Hydraulic conductivity 37.9 ft/da <br /> 0.013 cm/sec <br /> 2012-09-13 addendum well install work plan_hy test rpt.dxx 4 <br />