This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 1 1 Prob 4 4 5 Drawdown was measured during a pumping test in a confined aquifer at frequent intervals in an observation well 200 ft from a well that was pumped at a constant rate of 66 84 ft3 min 500 gpm The data for this pump test is listed below Determine T and S for this aquifer using the Theis curve overlay method Time min Drawdown ft 1 0 05 2 0 22 3 0 4 4 0 56 5 0 7 7 0 94 10 1 2 20 1 8 40 2 5 100 3 4 300 4 5 1000 5 6 4000 7 Solution Step 1 Plot the t vs s data on log log graph Step 2 Superimpose the data plot on the 1 u vs W u plot blue line and align data red points This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 2 Step 3 Select a match point and determine the values where s drawdown One possible match point yellow star W u 1 s 1 ft 1 u 1 t 2 min Step 4 Determine T Step 5 Determine S 2 Prob 4 4 6 For the time drawdown data listed below for a confined aquifer calculate T and S using Jacob s approximation After computing T and S check to see that the basic assumptions of this approximation are satisfied For the values of T and S that you computed after how many minutes of pumping would Jacob s approximation be valid The discharge is Q 1 500 gpm and the radius is r 300 ft Time min Drawdown ft Time min Drawdown ft 1 0 45 50 2 3 2 0 74 60 2 34 3 0 91 80 2 5 4 1 04 100 2 67 6 1 21 200 2 96 8 1 32 400 3 25 10 1 45 600 3 41 30 2 02 800 3 5 40 2 17 1000 3 6 1440 3 81 Solution Step 1 Plot the data log t vs s on semi log graph Step 2 Fit a straight line to the data This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 3 Step 3 Find t0 0 42 min using equation of line at y 0 to solve for x Step 4 Find s for times one log cycle apart s 2 56 1 48 ft 1 08 ft for t1 10 min and t2 100 min us equation of line from linear regression of data to get exact values of s at 10 and 100 min Step 5 Compute T Step 6 Compute S Step 7 Check assumption at 1440 min problem did not state which time to check One log cycle in time S This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 4 Jacob s approximation is valid for 3 4 4 7 For the time drawdown data recorded during the recovery phase of a pump test determine the transmissivity of the confined aquifer The pumping rate is 162 9 ft3 min and the pump is shut off at 800 min Recovery of test well Recovery of Observation well Time min s ft Time min s ft 800 12 50 800 1 86 803 20 00 805 1 78 808 5 00 810 1 64 813 0 50 815 1 53 820 1 50 820 1 45 880 1 00 825 1 37 940 0 80 830 1 32 995 0 69 840 1 22 1055 0 59 850 1 15 1115 0 51 860 1 09 1175 0 49 870 1 03 1235 0 46 880 0 97 1295 0 38 890 0 94 1360 0 34 900 0 90 1416 0 33 910 0 87 1418 0 33 920 0 85 1527 0 22 980 0 70 1600 0 22 1040 0 61 1100 0 54 1160 0 49 1220 0 46 1280 0 40 1340 0 36 1400 0 36 1460 0 34 1520 0 31 1600 0 29 This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 5 Solution The value of T can be determined using the recovery data of the test well or the observation well Values of t t are plotted on semilog paper against the residual drawdowns see figures below Note that the first three data points in the recovery data of the test well are excluded in the analysis Q 162 9 ft3 min From the above plot of the Test Well data s 0 97 ft per log cycle in this example from t t 2 to t t 20 is determined then This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 6 From the above plot of the Observation Well data s 0 81 ft per log cycle is determined then 00 10 20 30 40 50 60 70 80 911 11 21 31 41 51 61 71 81 90 11 010 0100 01000 0Residual cid 9 Drawdown cid 9 s ft Time cid 9 Ratio cid 9 t t 1 11 cid 9 0 31 cid 9 cid 9 0 8 cid 9 ft This study source was downloaded by 100000823171538 from CourseHero com on 10 05 2023 07 09 09 GMT 05 00 https www coursehero com file 40098721 CE374L HW 6 Solution Pump Test 2019pdf Homework 6 Spring 2019 CE374L 7 4 4 6 1 The drawdown versus time data for an observation well 160 feet from the pumping well of the same aquifer as in Example 4 6 1 pumping rate Q 600 ft3 min confining layer thickness b 14 ft is given below Use the spreadsheet to estimate the transmissivity and storage coefficient of the confined aquifer and the hydraulic conductivity of the aquitard Compare the results with the answers to Example 4 6 1 Time min Drawdown ft 4 2 15 6 2 86 8 3 46 10 3 78 15 4 58 20 5 09 25 5 49 30 5 85 40 6 37 50 6 64 60 6 80 70 6 96 80 7 16 90 7 36 100 7 44 110 …