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Results of Groundwater Pumping Tests - 152 East 11 th Street, Tracy Page 11 on the Figure, applying the Cooper and Jacobs (1946) equation to a straight line through the late-time data yields Transmissivity, T = 264 Q I As = 4,324 gpd/ft where Q = Steady State Pump Discharge Flow Rate (in GPM), and As = Slope of the Time-Drawdown Curve, (Expressed as the change in drawdown between any two times on the log scale whose ratio is ten ) Coefficient of Storage Although the maximum drawdown produced in the observation well, NAV 3, was small, it was measurable and, within the limitations imposed by the resolution of the water-level probe, it was also possible to plot the relationship between the logarithm of time since the pump was started and the drawdown in that well due to pumping in NAV 6 This is shown on Figure 9 for the data obtained on December 28th 1993 As shown on the Figure a straight line can be drawn on this plot to find the zero-drawdown intercept and an estimate of the Coefficient of Storage (Storativity) can be made from (Driscoll, 1986) Coefficient of Storage, S = 0 3 TA t1 /1 z = 00022 where TA = the apparent Tranmissivity (in gpf/ft ) (As computed from early drawdown in the observation well ) t�= Time Intercept (in days) of the straight line curve at zero drawdown, and r= The Distance (in feet) from the Pumped Well to the Observation Well The value computed (0 0022) falls within the expected range of 0 005 to 0 00005 for confined aquifers (Freeze and Cherry, 1979) but it is very close to the upper limit This finding confirms the assumption used to develop the hydrogeologic model, that the sand stratum may be assumed to act as a confined aquifer for the purpose of analysis of the pumping test data but, because the estimated storativity fall in the high end of the range, it also confirms the assessment that, except in the case of hydraulic perturbations of relatively short duration, there is some degree of communication between the strata