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<br />92 GROUNDWATER PUMPING TESTS <br /> <br />CASE STUDIES 93 <br /> <br />and the selected value of riB were used to calculate aquifer <br />transmissivity and storativity and aquitard vertical <br />hydraulic conductivity. Calculations for observation well 1 <br />are as follows: <br /> <br />100.0 . <br /> <br />Observation VeIl I <br /> <br />10.0 <br /> <br />Q = 25 gpm, r = 96 ft, m = 8 ft, m., = 14 ft <br /> <br />rIB = 0.22 <br /> <br />Match Pt. Coord. W{u,rlB)= 1.0, 1/u = 10, s = 1.9 ft <br />t = 33 min <br /> <br />T = 1.146 X 10'(25)1.0/1.9 T = 1508 gpd/ft <br /> <br />S = 1.51 X 10'(1 X 10")33/[2.693 X 103(9.2 X 103)] <br />S = 0.0002 <br /> <br />P, = 1.51 X 10'(14)4.8 X 10"/9.2 X 103 <br />P, = 0.1I gpd/sq It <br /> <br />..., <br />u.. <br />C <br />. <br />o <br />-0 <br />~ <br />a <br /> <br />1.0 <br /> <br /> <br />0.1 <br />1 <br /> <br />10 100 1000 <br /> <br />TimQ After Pumping Started <br />Time-drawdown graph for Case Study 5.4. <br /> <br />10000 <br />(Hin) <br /> <br />The time-drawdown graph for observation well 1 is pre- <br />sented in Figure 5.5. <br />Average values of transmissivity, storativity, and verti- <br />cal hydraulic conductivity are 1500 gpdlft, 0.0002, and 0.1 <br />gpdlsq ft, respectively. The 2D-hour test sampled a cylindri- <br />cal volume of the aquifer with a height of 8 ft and a radius <br />of 2000 ft. Well storage capacity impacts were appreciable <br />until 36 minutes after pumping started and were taken into <br />account in the analysis. Available geological data indicate <br />that Dietrich Creek is not a recharge boundary; 14 ft of <br />sandy clay separate the streambed and the aquifer. Steady- <br />state conditions prevailed at the end of the test. <br />A 31-day pumping test was conducted in Case Study 5.5 <br />using aquifer production and observation wells and <br />aquitard and source bed observation wells (Neuman and <br />Witherspoon, 1972, pp. 1292-1297). The production well <br />fully penetrates the aquifer which underlies the city of <br />Oxnard, California. An aquifer observation well was <br />located 100 ft from the production well. Aquitard and <br />source bed observation wells partially penetrate deposits. <br />An upper aquitard observation well was located 62 ft from <br /> <br />Figure 5.5. <br /> <br />the production well and was open 22 ft above the top of the <br />aquifer. A lower aquitard observation well was located 81 ft <br />from the production well and was open 6 ft below the aqui- <br />fer base. The upper source bed observation well was located <br />72 ft from the production well and the lower source bed <br />observation well was located 100 ft from the production <br />well. <br />The fine to coarse-grained sand and gravel aquifer with a <br />thickness of 93 ft is encountered at a depth of 105 ft below <br />land surface. The aquifer is overlain by a silty and sandy <br />clay aquitard 45 ft in thickness, which in turn is overlain by <br />a sand and gravel source bed. The aquifer is underlain by a <br />silty and sandy clay aquitard 30 ft in thickness, which in <br />turn is underlain by a source bed consisting of fine to <br />coarse-grained sand and gravel. The storativities of the <br />upper and lower aquitards were determined from labora- <br />tory consolidation tests and taken into account in pumping <br />test analysis. <br />The constant discharge rate from the production well <br />