U.S. Department of the Interior

U.S. Geological Survey

Review of Aquifer Test Results for the Lansdale Area,

Montgomery County, Pennsylvania, 1980-95

Open-File Report 98-294

prepared in cooperation with the

U.S. ENVIRONMENTAL PROTECTION AGENCY

0.001

0.01

0.1

1

101

10

-1

10

0

10

1

10

2

10

3

10

4

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 1,300 m2/d

S = 0.00004

W = 1,700 m
U.S. Department of the Interior

U.S. Geological Survey

Review of Aquifer Test Results for the Lansdale Area,

Montgomery County, Pennsylvania, 1980-95

by Daniel J. Goode and Lisa A. Senior

Open-File Report 98-294

prepared in cooperation with the

U.S. ENVIRONMENTAL PROTECTION AGENCY

Lemoyne, Pennsylvania

1998
ii

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

840 Market Street Box 25286

Lemoyne, Pennsylvania 17043-1584 Denver, Colorado 80225-0286

Email: dc_pa@usgs.gov
iii

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Hydrogeologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Study methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Aquifer testing in the Lansdale area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Aquifer test of Mg-67 and Mg-80, March 1980. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Drawdown in pumped well Mg-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Drawdown in second pumped well Mg-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Drawdown in observation wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Aquifer-isolation testing of Mg-67 and Mg-68, January 1983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Aquifer test of Mg-624 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Aquifer test of Mg-625, March 1980. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Aquifer test of Mg-1125, October 1982 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Aquifer test of Mg-1125, February and October 1989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Aquifer testing at Merck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Aquifer test of Mg-125, May 1986. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Aquifer test of Mg-128, November 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Aquifer test of Mg-1198, September 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Aquifer test of Mg-1659, September 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Aquifer test of Mg-1199, April 1989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Aquifer test of Mg-1423, February 1994. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Aquifer test of Mg-1424, February 1994. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Aquifer-isolation testing at Ford, March 1992 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Mg-89, zone 1, 19 - 54 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Mg-135, zone 3, 86 - 116 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Mg-135, zone 4, 109 - 146 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Mg-147, zone 1, 19 - 44 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Mg-151, zone 4, 107 - 137 m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Aquifer test of Mg-924, April 1980. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

CONTENTS

Page
iv

Figure 1. Map showing location of study area and wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2-20. Graphs showing:

2. Log-log and semi-log plots of theoretical drawdown (s) as a function of time (t)

for several conceptual models: (A) confined; (B) unconfined; (C) leaky;

(D) double porosity; (E) single vertical fracture; (F) permeable dike

in less-permeable aquifer; (G) confined with recharge boundary;

(H) confined with impermeable boundary.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3. Drawdown in pumped well Mg-67, Lansdale area, March 1980, and

estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4. Drawdown in pumped well Mg-67, Lansdale area, March 1980, and estimates

of transmissivity and storage coefficient by Theis method. . . . . . . . . . . . . . . 8

5. Drawdown during recovery in pumped well Mg-67, Lansdale area,

March 1980, and estimate of transmissivity by method of Goode. . . . . . . . . . 9

6. Drawdown in pumped well Mg-80 in Lansdale area, March 1980. . . . . . . . . . . . 10

7. Drawdown in pumped well Mg-80 in Lansdale area, March 1980, and

estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8. Drawdown during recovery in pumped well Mg-80 in Lansdale area,

March 1980, and estimate of transmissivity by method of Goode . . . . . . . . 11

9. Drawdown in observation wells Mg-157, Mg-162, Mg-163, and Mg-164 during

pumping of Mg-67 and Mg-80 in Lansdale area, March 1980, and

estimates of transmissivity and storage coefficient from drawdown at

Mg-163 and Mg-164 by Theis method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

10. Drawdown in Mg-150 during pumping of Mg-67 and Mg-80 in Lansdale area,

March 1980, and estimates of transmissivity and storage coefficient

 by superposition of Theis solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

11. Drawdown in pumped well Mg-624 in Lansdale area, and estimates of

transmissivity and storage coefficient by Theis method. . . . . . . . . . . . . . . . . 16

12. Drawdown in pumped well Mg-624 in Lansdale area and estimates of

transmissivity and storage coefficient by Cooper-Jacob method . . . . . . . . . 17

13. Drawdown during recovery in pumped well Mg-625 in Lansdale area,

March 1980, and estimate of transmissivity by method of Goode . . . . . . . . 18

14. Drawdown in pumped well Mg-1125 in Lansdale area, October 1982,

and estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

15. Drawdown during recovery in pumped well Mg-1125 in Lansdale area,

October 1982, and estimate of transmissivity by Theis method . . . . . . . . . . 21

16. Drawdown during recovery in pumped well Mg-1125 in Lansdale area,

October 1982, and estimate of transmissivity by method of Goode . . . . . . . 21

17. Drawdown in pumped well Mg-1125 in Lansdale area, October 1982,

during step test with pumping rates of 380, 770, and 1,150 liters per

minute. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

ILLUSTRATIONS

Page
v

Figure 2-20. Graphs showing—Continued:

18. Drawdown in pumped well Mg-1125 in Lansdale area, February and

October 1991, and estimates of transmissivity and storage

coefficient by Cooper-Jacob method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

19. Drawdown in observation wells Mg-1124, Mg-1126, and Mg-1270 during

pumping of Mg-1125 in Lansdale area, October 1991, and estimate of

transmissivity and storage coefficient from drawdown in Mg-1126 by

Theis method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

20. Drawdown in observation well Mg-1124 during pumping of Mg-1125 in

Lansdale area, February 1991, and estimates of transmissivity and

storage coefficient by image well method for a strip aquifer of

infinite length but uniform finite width, based on Theis solution . . . . . . . . 25

21-22. Maps showing:

21. Locations of pumping and observation wells at Merck, Sharpe & Dome

facility, near Lansdale, Pa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

22. Drawdown in wells in the area of pumped well Mg-128 in Lansdale area,

November 1993, at end of 48-hour aquifer test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

23-53. Graphs showing:

23. Cross-section showing regional dip of bedrock and drawdown in wells

in the area of pumped well Mg-128 in Lansdale area, November 1993,

at end of 48-hour aquifer test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

24. Drawdown in observation well Mg-1555 and pumped well Mg-128 in

Lansdale area, November 1993, in log-log format . . . . . . . . . . . . . . . . . . . . . . 30

25. Drawdown in observation well Mg-1555 and pumped well Mg-128 in

Lansdale area, November 1993, in semi-log format . . . . . . . . . . . . . . . . . . . . 31

26. Drawdown in observation well Mg-1565 during pumping of Mg-1198

in Lansdale area, September 1988, and estimates of transmissivity

and storage coefficient by Cooper-Jacob method . . . . . . . . . . . . . . . . . . . . . . 32

27. Drawdown in observation well Mg-1565 during pumping of Mg-1198

in Lansdale area, September 1988, and estimates of transmissivity

and storage coefficient by Theis method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

28. Drawdown in observation wells Mg-1660, Mg-1562, and Mg-1563

during pumping of Mg-1199 in Lansdale area, April 1989, in log-log

format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

29. Drawdown during recovery in observation wells Mg-1660, Mg-1562,

and Mg-1563 and in the pumped well Mg-1199 in Lansdale area,

April 1989, in log-log format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

30. Drawdown and pumping rate in pumped well Mg-1199 in Lansdale area,

April 17, 1989, during step test, in semi-log format. . . . . . . . . . . . . . . . . . . . . 35

31. Sum of incremental drawdown divided by pumping rate as a function

of pumping rate for step test in Mg-1199, Lansdale area, April 1989,

for estimation of linear (formation loss) and nonlinear (well loss)

components of drawdown by Hantush and Bierschenk method . . . . . . . . . 36

ILLUSTRATIONS—Continued

Page
vi

Figure 23-53. Graphs showing—Continued:

32. Drawdown in pumped well Mg-1423 in Lansdale area, during step

test on February 15, 1994, in semi-log format. . . . . . . . . . . . . . . . . . . . . . . . . . 37

33. Sum of incremental drawdown divided by pumping rate as a function of

pumping rate for step test in Mg-1423, Lansdale area, February 15, 1994,

for estimation of linear (formation loss) and nonlinear (well loss)

components of drawdown by Hantush and Bierschenk method . . . . . . . . . 37

34. Drawdown in observation wells Mg-1556, Mg-1654, Mg-1655, Mg-1568,

and Mg-1570, and in pumped well Mg-1423 in Lansdale area during

step test and subsequent 48-hour aquifer test, February 1994, in

log-log format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

35. Drawdown during recovery in observation wells Mg-1556, Mg-1654,

Mg-1655, Mg-1568, and Mg-1570, and in pumped well Mg-1423 in

Lansdale area after step test and subsequent 48-hour aquifer test,

February 1994, and estimation of transmissivity by method

of Goode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

36. Drawdown in observation well Mg-1656 during pumping of Mg-1424

in Lansdale area, February 1994, and estimates of transmissivity

and storage coefficient by Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . 40

37. Drawdown in pumped zone 1 and unpumped underlying zone during

aquifer-isolation testing of Mg-89 in Lansdale area, March 1992 . . . . . . . . . 43

38. Drawdown in pumped zone 1 and unpumped underlying zone during

aquifer-isolation testing of Mg-89 in Lansdale area, March 1992,

and estimates of transmissivity and storage coefficient by

Theis method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

39. Drawdown in pumped zone 1 and underlying unpumped zone during

aquifer-isolation testing of Mg-89 in Lansdale area, March 1992,

and estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

40. Drawdown during recovery in pumped zone 1 and underlying unpumped

zone during aquifer-isolation testing of Mg-89 in Lansdale area,

March 1992, and theoretical drawdown by method of Goode . . . . . . . . . . . 46

41. Drawdown in pumped zone 3 and overlying and underlying unpumped

zones during aquifer-isolation testing of Mg-135 in Lansdale area,

March 1992, in log-log format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

42. Drawdown in pumped zone 3 and unpumped overlying and underlying

zones during aquifer-isolation testing of Mg-135 in Lansdale area,

March 1992, and estimates of transmissivity and storage

coefficient by Cooper-Jacob method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

43. Drawdown during recovery in pumped zone 3 and overlying and underlying

unpumped zones during aquifer-isolation testing of Mg-135 in Lansdale

area, March 1992 and transmissivity by method of Goode . . . . . . . . . . . . . . 49

44. Drawdown in pumped zone 4 and unpumped overlying zone during

aquifer-isolation testing of Mg-135 in Lansdale area, March 1992 . . . . . . . . 50

ILLUSTRATIONS—Continued

Page
vii

Figure 23-53. Graphs showing—Continued:

45. Drawdown in pumped zone 4 and unpumped overlying zone during aquiferisolation testing of Mg-135 in Lansdale area, March 1992 in log-log

format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

46. Drawdown in pumped zone 4 and overlying unpumped zone during

aquifer-isolation testing of Mg-135 in Lansdale area, March 1992,

and estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

47. Drawdown during recovery in pumped zone 4 and unpumped overlying

zone during aquifer-isolation testing of Mg-135 in Lansdale area,

March 1992 and transmissivity by method of Goode . . . . . . . . . . . . . . . . . . . 53

48. Drawdown in pumped zone 1 and underlying unpumped zone during

aquifer-isolation testing of Mg-147 in Lansdale area, March 1992 . . . . . . . . 54

49. Drawdown in pumped zone 1 and unpumped underlying zone during

aquifer-isolation testing of Mg-147 in Lansdale area, March 1992,

and estimates of transmissivity and storage coefficient by

Theis method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

50. Drawdown in pumped zone 1 and unpumped underlying zone during

aquifer-isolation testing of Mg-147 in Lansdale area, March 1992, and

estimate of transmissivity and storage coefficient by CooperJacob method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

51. Drawdown during recovery in pumped zone 1 and unpumped underlying

zone during aquifer-isolation testing of Mg-147 in Lansdale area,

March 1992, and estimate of transmissivity by method of Goode . . . . . . . . 56

52. Drawdown in pumped zone 4 and unpumped overlying zone during

aquifer-isolation testing of Mg-151 in Lansdale area, March 1992 . . . . . . . . 57

53. Drawdown in pumped zone 4 and unpumped overlying zone during

aquifer-isolation testing of Mg-151 in Lansdale area, March 1992,

and estimates of transmissivity and storage coefficient by

Cooper-Jacob method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

54. Map showing locations of wells and drawdown in meters at end of 48-hour aquifer

test in the area of pumped well Mg-924 in Lansdale area, November 1993. . . . . . . . 59

55-59. Graphs showing:

55. Drawdown in observation well Mg-876 during pumping of Mg-924 in

Lansdale area, April 1980, and estimates of transmissivity and storage

coefficient by Theis method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

56. Drawdown during recovery in observation well Mg-876 after pumping

of Mg-924 in Lansdale area, April 1980, and estimates of transmissivity

 by method of Goode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

57. Drawdown in observation well Mg-1661 during pumping of Mg-924 in

Lansdale area, April 1980, and estimates of transmissivity and storage

coefficient by Theis method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

58. Drawdown during recovery in observation well Mg-1661 after

pumping of Mg-924 in Lansdale area, April 1980, and estimate of

transmissivity by method of Goode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

ILLUSTRATIONS—Continued

Page
viii

Figure 55-59. Graphs showing—Continued:

59. Drawdown in observation well Mg-1662 during pumping of Mg-924 in

Lansdale area, April 1980, and estimates of transmissivity and

storage coefficient by Theis method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

60. Map showing distribution of transmissivity values in square meters per day estimated

from review of existing well testing information in the Lansdale area. . . . . . . . . . . . 65

TABLES

Table 1. Transmissivity and storage coefficient estimates from water levels during pumping

of Mg-67 and Mg-80 in March 1980 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2. Summary of results of aquifer-isolation testing in Mg-67. . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3. Summary of results of aquifer-isolation testing in Mg-68. . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4. Transmissivity and storage coefficient estimates from drawdown during pumping

of Mg-125, Merck & Co., West Point, Pennsylvania, May 1986 . . . . . . . . . . . . . . . . . . 26

5. Summary information on packer tests at Ford Plant, Lansdale, Pennsylvania . . . . . . . . . 41

6. Estimates of horizontal transmissivity of individual depth intervals from packer

tests at Ford Plant, Lansdale, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7. Estimates of transmissivity and storage coefficient determined from open-hole

aquifer tests in wells near Lansdale, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

8. Summary of aquifer-isolation tests in wells near Lansdale, Pennsylvania . . . . . . . . . . . . 68

9. Estimates of well loss determined from step tests and recovery analyses in wells near

Lansdale, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

ILLUSTRATIONS—Continued

Page
ix

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—a geodetic

datum derived from a general adjustment of the first-order level nets of the United States and Canada,

formerly called Sea Level Datum of 1929.

Length

centimeter (cm) 0.3937 inch (in)

meter (m) 3.281 foot (ft)

Area

square centimeter (cm2) 0.001076 square foot (ft2)

square meter (m2) 10.76 square foot

Volume

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 264.2 gallon (gal)

Flow rate

meter per second (m/s) 3.281 foot per second (ft/s)

meter per day (m/d) 3.281 foot per day (ft/d)

meter per year (m/yr) 3.281 foot per year (ft/yr)

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

cubic meter per day (m3/d) 35.31 cubic foot per day (ft3/d)

liter per second (L/s) 15.85 gallon per minute (gal/min)

liter per minute (L/min) 0.2642 gallon per minute (gal/min)

cubic meter per day (m3/d) 264.2 gallon per day (gal/d)

Specific capacity

liter per second per meter [(L/s)/m] 4.831 gallon per minute per foot

[(gal/min)/ft]

meter squared per day (m2/d) 0.0559 gallon per minute per foot

[(gal/min)/ft]

Hydraulic conductivity

meter per day (m/d) 3.281 foot per day (ft/d)

Transmissivity

meter squared per day (m2/d) 10.76 foot squared per day (ft2/d)

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain
1

Review of Aquifer Test Results for the Lansdale Area,

Montgomery County, Pennsylvania, 1980-95

Daniel J. Goode and Lisa A. Senior

ABSTRACT

Aquifer and aquifer-isolation test results in and around North Penn Area 6 Superfund Site, Lansdale,

Montgomery County, Pa., are reviewed to provide estimated aquifer properties for use in a numerical model of

ground-water flow. This review was made to support remedial action investigations by U.S. Environmental

Protection Agency (USEPA), Region III, Philadelphia. The data reviewed are from files of the U.S. Geological Survey,

USEPA, and water companies, and from unpublished consultant reports prepared for USEPA and corporations in the

Lansdale area. Tested wells are in fractured sedimentary rocks of the Brunswick Formation, which are Triassic-aged,

dipping shales and sandstones. Review procedures include, in some cases, new analyses of drawdown during

pumping and recovery by use of analytical models of flow to wells. Estimated aquifer transmissivities (T) range from

zero to about 1,300 m2/d (meters squared per day); most tests indicate T between 10 and 100 m2/d. Aquifer-isolation

testing results indicate that most flow enters wells at a few discrete zones, probably fractures or bedding-plane

openings. The vertical connection between the zones in a single borehole with multiple producing zones commonly is

negligible. This suggests that the formation is vertically anisotropic; the hydraulic conductivity is much larger in the

horizontal direction than in the vertical direction. Some evidence of well-field-scale horizontal anisotropy exists, with

maximum transmissivity aligned with the regional northeast strike of bedding, but this evidence is weak because of

the small number of observation wells, particularly wells screened in isolated depth intervals. Analysis of recovery

data after constant-pumping-rate aquifer tests and of drawdown during step tests suggests that a significant fraction,

perhaps as much as 85 percent, of the drawdown in some production wells is due to well loss or skin effects in or very

near the pumped well and is not caused by resistance to flow in the surrounding formations.

INTRODUCTION

Water-supply and industrial wells in the area around Lansdale, Pa., have been contaminated with

low concentrations of organic solvents (CH2M Hill, Inc., 1991). In the past, water pumped from these wells

was treated at significant cost before use. Recently, wells have been abandoned as more economical water

sources become available. The removal of these wells from service will result in changes in ground-water

flow directions in the area of contamination and may result in further spreading of contaminants. In

cooperation with the U.S. Environmental Protection Agency (USEPA), the U.S. Geological Survey (USGS)

is developing a ground-water flow model of subsurface formations beneath the North Penn Area 6 (NP6)

Superfund Site (fig. 1) to examine current and past hydrologic conditions and to estimate response of the

ground-water system to pumping changes.

Purpose and Scope

Records of aquifer and aquifer-isolation tests in the Lansdale area are reviewed and analyzed to

provide estimates of hydraulic properties, primarily transmissivity (T) and storage coefficient (S), of the

fractured-rock aquifer. Reviewed and analyzed information includes data collected by USGS and from

USEPA and private corporation files and unpublished reports. Data sets are analyzed quantitatively to

estimate aquifer T and, in most cases, S.
2

Figure 1. Location of study area and wells. (Boundary of North Penn Area 6 Superfund Site from CH2M

Hill, Inc. (1991)).
3

Acknowledgments

Reports and data files on aquifer testing in the Lansdale area were provided by USEPA, Region III,

Philadelphia, Pa., as part of the NP6 project managed by Greg Ham. Kathryn Davies, also of USEPA,

provided guidance during this review. Additional information was provided by North Penn Water

Authority, Lansdale, Pa.

Numerous USGS staff contributed to this report. Kevin E. Grazul and James E. Bubb prepared some

graphics for this report. Charles R. Wood assisted with well database information. Ronald A. Sloto, Todd S.

Miller, and Keith J. Halford are acknowledged for their helpful reviews of this report. Analyses in this

report reflect contributions by and discussions with Dennis W. Risser.

HYDROGEOLOGIC SETTING

Lansdale, Pa., is in the Triassic Lowlands Section of the Piedmont Physiographic Province. Lansdale

and the surrounding area are underlain by sedimentary rocks of the Brunswick Group (lower beds) and

Lockatong Formation of the Newark Supergroup (Lyttle and Epstein, 1987). Contacts between the

Brunswick Group and the underlying Lockatong Formation are conformable and gradational, and the two

formations may interfinger. The lower beds of the Brunswick Group consist predominantly of

homogeneous, soft, red to reddish-brown and gray to greenish-gray mudstones and clay- and mud-shales.

Bedding is irregular and wavy. Some beds are micaceous. Interbedded silt-shales and siltstones are fairly

well sorted. Mudcracks, ripple marks, crossbeds, and burrows are common in all beds. The Brunswick

Group rocks contain detrital cycles of medium- to dark-gray and olive- to greenish-gray, thin-bedded and

evenly bedded shale and siltstone, similar to the underlying Lockatong Formation. Rocks of the Lockatong

Formation contain detrital cycles of gray to black calcareous shale and siltstone, with some pyrite, and

chemical cycles of gray to black dolomitic siltstone and marlstone with lenses of pyritic limestone, overlain

by massive gray to red siltstone with analcime (Lyttle and Epstein, 1987). The beds of the Brunswick

Group and Lockatong Formation strike northeast and dip about 15 ̊ to the northwest in the vicinity of the

site. The bedrock is covered by a thin weathered zone, generally less than a few meters thick, and by an

equally thin soil layer.

The Lockatong Formation commonly is relatively resistant to erosion and tends to form ridges that

rise above flat or rolling topography underlain by rocks of the Brunswick Group. Lansdale and the

surrounding area are underlain mostly by rocks of the Brunswick Group and are on relatively flat upland

terrain that is a surface-water divide between the Wissahickon Creek to the southwest, Towamencin Creek

to the west, and tributaries to the West Branch Neshaminy Creek to the north and northeast.

Ground water beneath Lansdale originates from infiltration of local precipitation and discharges to

streams and to pumping wells. After infiltrating through soil and saprolite, ground water moves through

vertical and horizontal fractures in the shale and siltstones (Newport, 1971). The aquifer transmissivity is

controlled by the size of the openings, or aperture, and by the degree of interconnectedness of openings

(Sloto, 1994). Primary porosity is very low or nonexistent. Permeability and storage are very low. Ground

water in rocks of the Brunswick Group and Lockatong Formation may be under confined, unconfined,

and(or) perched conditions. Ground water in the aquifer generally is under confined or partially confined

conditions, resulting in local artesian conditions.

The ground-water flow system can be characterized as a multi-aquifer system composed of highpermeability layers separated from each other by semi-confining layers. Shallow and deep ground-water

flow systems may exist at the site. Ground-water levels fluctuate with pumping and seasonal variations in

recharge. Water from the upper system may drain locally to streams and also leak downward to a deeper

ground-water flow system. Wells constructed as open-hole boreholes penetrate both systems, and water

levels measured in these wells represent composite heads. Where differences in potentiometric head are

present, water in the borehole flows from zones of higher head to zones of lower head. Ground water

generally flows in a direction similar to the topographic gradient. The natural direction of flow can be

altered by pumping. Pumping from deep zones may induce downward flow from shallow zones.

Longwill and Wood (1965) report that maximum well yields in the Brunswick Formation are generally
4

obtained at depths from about 60 m (200 ft) to about 170 m (550 ft) below land surface. The variable nature

of the subsurface permeability is reflected in variable well yields; nearby wells drilled to similar depths

commonly have very different yields (Rima, 1955).

STUDY METHODS

Results of aquifer tests conducted from 1980 to 1995 are reviewed and summarized. In addition,

water-level and drawdown (initial water level minus water level during testing) data from several

previously conducted well tests are reanalyzed by use of standard methods (Theis, 1935; Cooper and

Jacob, 1946). For some tests, this analysis is done with graphs from original reports. For other tests, printed

water-level or drawdown records were input manually or scanned and converted to digital data for reanalysis. Although a number of datapoints were lost during this process, sufficient data were retained to

adequately characterize the drawdown during the tests. Digital data files created for this study are

archived at the USGS Pennsylvania District office and are available on request.

Several graphical-analysis techniques are used to portray the hydraulic response of tested wells or

tested intervals within wells and, in some cases, to estimate aquifer properties (primarily T and S) from

drawdown data. Plots of linear-drawdown as a function of linear time are useful for portraying ‘real-time’

features of the test and for identifying borehole storage effects, which occur when all or most of the water

pumped from the well is derived from water stored in the borehole and not from inflow to the well from

the tested formation.

A standard method for analyzing well tests involves plotting log-drawdown as a function of logtime and using the Theis (1935) type-curve-matching procedure to estimate aquifer properties. This plot

emphasizes the early-time part of the test and can be used with several different conceptual mathematical

models of ground-water flow, such as those described by Reed (1980). Theoretical drawdown as a function

of time for several different conceptual models is shown in figure 2. For example, a straight line with half

slope on the log-log plot is characteristic of linear flow, commonly observed in fractured-rock systems

(fig. 2F). Although the hydrogeologic assumptions of the Theis model are never completely satisfied in the

field, this model provides a common framework to compare boreholes. Use of more realistic and more

complicated models commonly yields large-scale and late-time T and S similar to the Theis method (for

example, Dagan, 1967; Neuman, 1975). For an analysis of one test, a more complicated model for an

aquifer limited in extent in one direction is used. This model is based on image well theory and the Theis

model, and its application is described in the section “Aquifer Test of Mg-1125, February and October

1989.” Linear superposition of two Theis solutions is used to analyze drawdown in a well affected by two

pumped wells in the section “Aquifer Test of Mg-67 and Mg-80, March 1980.”

A derivative of the Theis method, suitable for large-dimensionless-time response, is based on a plot

of linear-drawdown as a function of log-time (Cooper and Jacob, 1946). A straight line on this plot is

indicative of Theis or infinite, confined-aquifer response at large-dimensionless time.

A new procedure (Goode, 1997) was employed for analysis of water-level recovery data for a few

tests. This type-curve method employs a plot of log-drawdown as a function of normalized time (time

since pumping stopped divided by duration of pumping) and allows estimates of T at the pumped well

that are not affected by well loss. This method is similar to the Theis (1935) method for recovery but

incorporates early-dimensionless-time response, particularly useful for observation wells. Recovery of

observation wells commonly does not satisfy the large-dimensionless-time approximation because

dimensionless time is inversely proportional to radial distance squared.

Step-test data are analyzed by use of procedures of Hantush and Bierschenk (see Kruseman and de

Ridder, 1990, p. 200). The incremental head change due to each pumping-rate increment is determined

graphically by extrapolation on a semi-log plot of drawdown (linear) as a function of time (logarithmic).

The linear and nonlinear (well-loss) terms for the drawdown equation are determined from the plot of the

sum of incremental drawdowns divided by pumping rate as a function of pumping rate. Theoretically, the

linear part of the drawdown is due to resistance to flow in the formation and the nonlinear term is due to

turbulent flow in or very close to the borehole.
5

Figure 2. Log-log and semi-log plots of theoretical drawdown (s) as a function of time (t) for

several conceptual models: (A) confined; (B) unconfined; (C) leaky; (D) double porosity;

(E) single vertical fracture; (F) permeable dike in less-permeable aquifer; (G) confined with

recharge boundary; (H) confined with impermeable boundary (modified from Kruseman and

de Ridder, 1990, and published with permission by International Institute for Land Reclamation

and Improvement, Wageningen, The Netherlands).

s lin

s log

t log t log t log

t log t log t log

t log t log t log

t log

t log t log

t log

s lin s lin

s lin s lin

s log

s log s log s log

s lin s lin s lin

s log s log s log

A B C

A' B' C'

D E F

D' E' F'

G H

G' H'

t log t log t log
6

Information on antecedent and background water-level trends is not available for most of the tests

reviewed. The analyses here are based on the assumption that measured water-level changes are caused

by pumping at the test well. Measured water-level changes may also be caused by recharge, drainage,

pumping at other wells, air pressure fluctuations, and other processes. Generally these water-level

changes are small compared to those caused by test-well pumping; hence, errors in estimated hydraulic

properties are correspondingly small. However, some amount of uncertainty in these estimated properties

is caused by our inability to remove antecedent and background water-level changes using available

information.

Well identifiers used here generally correspond to the USGS Pennsylvania well-numbering system.

The letters “Mg” refer to Montgomery County, and the numbers are sequential as wells are scheduled in

the USGS database. Local well identifiers also are given parenthetically in most cases. A limited number of

wells used in this report are not in the USGS Pennsylvania well database and are referred to here by their

local identifier.

AQUIFER TESTING IN THE LANDSDALE AREA

Aquifer Test of Mg-67 and Mg-80, March 1980

 Water-level measurements were made in eight observation wells and in the pumped wells during

pumping of Mg-67 (local well L 8) and Mg-80 (Allied Paint #1) beginning on March 25, 1980 (U.S.

Environmental Protection Agency, unpublished data files). Pumping at an average rate of 370 L/min

(98 gal/min) began in Mg-67 at 0900 on March 25, 1980. At 1100 on the same day, pumping began in Mg-80

at an average rate of 280 L/min (74 gal/min). Pumping in Mg-80 stopped at 1700 on the same day; hence

Mg-80 was pumped for a total of 6 hours. Pumping in Mg-67 continued until 0900 on March 27, 1980,

hence, Mg-67 was pumped for a total of 48 hours.

Estimated T and S from the aquifer test of Mg-67 and Mg-80 are summarized in table 1. Some

characteristics of drawdown in different wells are discussed below in separate sections.The pumping of

two separate wells during the same tests can be incorporated in models of drawdown during pumping to

estimate T and S from drawdown. However, these procedures are much more complicated and time

consuming than traditional Theis or Cooper-Jacob analyses. With one exception, the analyses in this

section are based on single pumped well models, which are considered to be only rough approximations

of the field situation. Drawdown in one well (Mg-150) is analyzed with a preliminary model accounting

for two pumped wells.

Table 1. Transmissivity and storage coefficient estimates from water levels during pumping of Mg-67 and Mg-80

in March 1980

[L/min, liters per minute; m2/d, square meters per day; m, meters; m bls, meters below land surface; Q, pumping rate]

Well Transmissivity

(m2/d)

Storage

coefficient

Radial

distance

(m)

Open

interval

(m bls)

Method Pumping rate used

in analysis

Mg-67 31 0.0014 0.1 6-87 Cooper-Jacob Q= 370 L/min, Mg-67 only

Mg-67 25 .012 Theis Q= 370 L/min, Mg-67 only

Mg-67 99 Recovery (Goode) Q=370 L/min, Mg-67 only

Mg-157 99 .0004 310 14-87 Theis Q=370 L/min, Mg-67 only

Mg-162 99 .00009 366 9-232 Theis Q=370 L/min, Mg-67 only

Mg-163 85 .00015 339 9-92 Theis Q=370 L/min, Mg-67 only

Mg-164 85 .00013 366 9-123 Theis Q=370 L/min, Mg-67 only

Mg-80 202 40-98 Cooper-Jacob Q=280 L/min, Mg-80 only

Mg-80 79 Recovery (Goode) Q=280 L/min, Mg-80 only

Mg-150 150 .0002 r1=161

r2=56

13-123 Theis; 2 wells Q1=370 L/min; Mg-67

Q2=280 L/min; Mg-80
7

Drawdown in Pumped Well Mg-67

Drawdown in pumped well Mg-67 is analyzed by the Cooper-Jacob method (fig. 3). A straight line is

visually fit to the data in a linear-drawdown as a function of log-time format. The slope of this line yields

an estimated T = 31 m2/d (330 ft2/d). Analysis by use of the Theis model in log-log format yields T =

25 m2/d (270 ft2/d) (fig. 4). All of the plotted data fall on the large-time part of the Theis curve, supporting

application of the Cooper-Jacob method. However, the value of S = 0.012 by use of the Theis method is too

high for confined or semi-confined fractured-rock aquifers in general. If well loss or a low-permeability

skin is present, the Theis estimate would be low. Well loss is generally a pressure drop caused by turbulent

flow between the formation just outside the borehole and the measurement location within the borehole. A

skin is a thin zone at the borehole that has a permeability distinct from that of the surrounding formation.

A low-permeability skin causes an exaggerated drawdown in the pumped well compared to the formation

drawdown.

0

5

10

15

20

0.1 1 101

102103104

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 2.3 Q / 4 π ∆

= 2.3 (535 m3/d) / (4 π 3.2 m)

= 31 m2/d

S = 2.25 T t0 / r2

= 2.25 (31 m2/d) (2 x 10-7 d) / (0.1 m)2

= 0.0014

Figure 3. Drawdown in pumped well Mg-67, Lansdale area, March 1980, and estimates of

transmissivity (T) and storage coefficient (S) by Cooper-Jacob (1946) method.
8

The recovery method of Goode (1997) yields an estimated T = 99 m2/d (1,070 ft2/d) from recovery

data in Mg-67 (fig. 5). The early recovery is very rapid and probably is caused by well loss or a lowpermeability skin, which causes the drawdown in the well to be much greater than that in the nearby

formation during pumping. However, after pumping stops, flow rates dissipate quickly, and the water

level in the well is much closer to that in the formation. The higher T estimated with this method is three to

four times that from the pumping-period data and indicates that well loss during pumping accounts for

about 75 percent of the drawdown in the pumped well.

0.1

1

10

100

DRAWDOWN, IN METERS

OBSERVED DRAWDOWN

THEORETICAL DRAWDOWN

T = 25 m2/d

S = 0.012

Figure 4. Drawdown in pumped well Mg-67, Lansdale area, March 1980, and estimates of transmissivity

(T) and storage coefficient (S) by Theis (1935) method.

1 10 110 210 3

ELAPSED TIME, IN MINUTES
9

0.1

1

10

100

1

10

100

0.01 0.1 1 10

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

230

0.23

OBSERVED

DRAWDOWN

THEORETICAL

DRAWDOWN

T = 99 m2/d

Figure 5. Drawdown during recovery in pumped well Mg-67, Lansdale area, March 1980, and estimate of

transmissivity (T) by method of Goode (1997).
10

Drawdown in Second Pumped Well Mg-80

Drawdown in Mg-80, which was pumped at 280 L/min for 6 hours during the aquifer test of Mg-67,

also is analyzed to estimate T. Drawdown of between 0 and 0.26 m (0.85 ft) was observed in Mg-80 prior to

pumping, while Mg-67 was pumped (fig. 6). When the pump in Mg-80 was started, the drawdown

increased rapidly to about 12 m (40 ft) and increased very slowly after about 15 minutes of pumping.

The Theis log-log plot of drawdown as a function of time of pumping in Mg-80 is too flat to match

with the theoretical Theis response. Application of the Cooper-Jacob method yields T = 202 m2/d

(2,170 ft2/d) (fig. 7). The match of the short-recovery (after Mg-80 pump was turned off) data to the Theis

curve of Goode (1997) is marginal but yields T = 71 m2/d (770 ft2/d). Projecting the theoretical drawdown

during recovery back in time (fig. 8), the formation drawdown of Mg-80 when pumping stopped is

estimated to be closer to 3 m (10 ft) than to 12 m (40 ft), suggesting significant well loss or skin effects,

about 75 percent of the total drawdown, during pumping. All these results are considered to only

approximately characterize the formation; better estimates of T could be derived from a more complicated

model that matches the field data better than the analyses presented here.

0

2

4

6

8

10

12

14

0 100 200 300 400 500 600

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

MG-67 PUMP ON AT t = 0 minutes

MG-80 PUMP ON AT t = 120 minutes

Figure 6. Drawdown in pumped well Mg-80 in Lansdale area, March 1980.

PUMP OFF AT t = 480 minutes
11

Figure 7. Drawdown in pumped well Mg-80 in Lansdale area, March 1980, and estimates of

transmissivity (T) and storage coefficient (S) by Cooper-Jacob (1946) method.

0

5

10

15

20

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 202 m2/d

S ≈ 0

1 10 110 210 3

Figure 8. Drawdown during recovery in pumped well Mg-80 in Lansdale area, March 1980,

and estimate of transmissivity (T) by method of Goode (1997).

1

10

1

10

100

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

0.45

45

THEORETICAL DRAWDOWN

OBSERVED DRAWDOWN

T = 71 m2/d
12

Drawdown in Observation Wells

Water levels also were measured in eight observations wells. Wells Mg-624 (Rex #2), Mg-625

(Rex #1), and Mg-81 (L-27) were not substantially affected by the pumping in Mg-67 and Mg-80. However,

water levels in Mg-162, Mg-163, Mg-164 (Rybond 2, 3, 4), Mg-157 (former F.M. Weaver), and Mg-150

(Allied Paint #2) responded to the pumping.

The drawdown in wells Mg-157, Mg-162, Mg-163, and Mg-164 and a match between the Theis

model and drawdown at wells Mg-163 and Mg-164 are shown in figure 9. This match and a similar match

to Mg-157 yield T ranging between 88 and 114 m2/d (950 and 1,230 ft2/d) by use of the pumping rate from

well Mg-67 alone. Only this well’s pumping rate is used in this analysis because the drawdown trends do

not respond significantly to pumping in Mg-80. The momentary increases in drawdown in the observation

wells correspond to short-duration pumping of the observation wells to collect water-quality samples.

Soon after this sampling, the water level in the observation wells returns to levels consistent with presampling levels. Nonetheless, these fluctuations in the water levels caused by sampling may have a minor

effect on estimated T and S.

0.01

0.1

1

10

Mg-157

Mg-162

Mg-163

Mg-164

DRAWDOWN, IN METERS

THEORETICAL

ELAPSED TIME, IN MINUTES

DRAWDOWN DURING INTERMITTENT

ONE-MINUTE PUMPING FOR SAMPLE

Mg-80 ON

AFTER 120 MINUTES

ELAPSED TIME

DRAWDOWN

T = 85 m2/d

S = 1.3 x 10-4

Figure 9. Drawdown in observation wells Mg-157, Mg-162, Mg-163, and Mg-164 during pumping of

Mg-67 and Mg-80 in Lansdale area, March 1980, and estimates of transmissivity (T) and storage

coefficient (S) from drawdown at Mg-163 and Mg-164 by Theis (1935) method.

1 10 110 210 3 4

10

ACQUISITION
13

In contrast to other observation wells, drawdown in observation well Mg-150 (Allied Paint #2) had

distinct periods of response to Mg-67 pumping and to both Mg-80 and Mg-67 pumping after Mg-80

pumping began (fig. 10). Applying Theis’ theory, the total drawdown in an observation well affected by

two pumped wells is the superposition or sum of the drawdown due to each pumped well separately.

Drawdown in Mg-150 appears to agree well with the Theis model (fig. 10) and the match yields an

estimated T = 150 m2/d (1,610 ft2/d), similar to T from the other observation wells. The estimated

S = 4 × 10-4 is at the upper end of the range expected for fractured rock.

0.01

0.1

1

10

1 10 100 1,000

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 150 m2/d

S = 0.0002

Figure 10. Drawdown in Mg-150 during pumping of Mg-67 and Mg-80 in Lansdale area, March 1980,

and estimates of transmissivity (T) and storage coefficient (S) by superposition of Theis (1935) solutions.
14

Aquifer-Isolation Testing of Mg-67 and Mg-68, January 1983

Sutton (1983) describes aquifer-isolation tests and associated sampling carried out by Earth Data,

Inc., on wells Mg-67 (L 8) and Mg-68 (L 9) for North Penn Water Authority (NPWA). Hydraulic testing was

accomplished by pumping an isolated zone in each borehole between a pair of inflatable packers.

Drawdown was measured in the pumped zone and in the borehole zones above and below the inflated

packers. If there is no leakage around the inflated packers in the borehole, and there is no highpermeability connections between the isolated zone and the rest of the borehole in the rock near the

borehole, then drawdown would be expected in only the isolated, pumped zone. Tests also were run

without packers inflated and with only one packer inflated to estimate production from zones that were

not isolated for testing. This review focuses on tests of isolated zones with both packers inflated.

The results of aquifer-isolation testing in Mg-67 are summarized in table 2. Drawdown in nonpumped zones above and below the pumped zone was essentially zero, suggesting very low vertical

hydraulic conductivity in the vicinity of the borehole.The estimates of T by Sutton (1983) using the Theis

method should be considered as only rough approximations because of the short duration of pumping

(less than 30 minutes). The Theis method is not applicable to drawdown in the 14.3 - 20.1 m depth zone

because the drawdown was essentially constant in time.

Specific capacities (table 2) are based on pumping between 30 and 60 minutes. The open-hole

specific capacity is estimated as about 85 m2/d (4.75 (gal/min)/ft), about 20 percent higher than the sum

of the isolated zone specific capacities. This suggests that about 20 percent of the well yield is from parts of

the borehole that were not tested. Examination of the composite specific-capacity data (Sutton, 1983, p. 62)

indicates that this additional yield is approximately split between depth intervals 42.7 - 46.3 m and 52.1 -

55.5 m. These data also suggest that essentially zero yield occurs below the bottom tested zone.

Sutton (1983) provides estimates of specific capacity after 30-60 minutes of pumping for similar

aquifer-isolation testing in well Mg-68 (table 3). For this test, hydraulic head was recorded graphically

from pressure transducers, but analyses of these data by Theis or Cooper-Jacob methods was not

attempted (Sutton, 1983). Two tests were done in each zone such that the isolated zone drawdown was

approximately 2 and 3 m; only the 3-m-drawdown results are presented here. With packers inflated, static

water levels in lower zones were higher than the open-hole static water level, implying an upward

gradient in hydraulic head in the formation. Sutton (1983) observes evidence of either leakage between

isolated zones in the borehole or actual hydraulic connection between isolated zones outside the borehole.

In contrast to results for Mg-67, a significant part of the well yield is from depths more than 70 m below

land surface. The estimated open-hole specific capacity is 77 m2/d. The tested zones include almost all

parts of Mg-68.

.
15

Table 2. Summary of results of aquifer-isolation testing in Mg-67 (Sutton, 1983)

[m2/d, square meters per day; m bls, meters below land surface; --, no data available]

Depth interval of

isolated zone

(m bls)

Specific

capacity1

(m2/d)

Percent of openhole specific

capacity

Transmissivity

(m2/d) U.S. Geological Survey notes

8.5 - 14.3 0 0 --

14.3 - 20.1 14.1 17 -- Almost constant drawdown

21.3 - 27.1 28.3 33 8.6 Theis method

36.9 - 42.7 18.4 22 2.5 Theis method

46.3 - 52.1 2.7 3 --

55.5 - 61.3 4.8 6 --

76.8 - 82.6 0 0 --

Open hole 85 100 -- Specific capacity of open hole larger

than sum of individual zones

(68.3 m2

/d)

1 Specific capacity after pumping between 30 and 60 minutes.

Table 3. Summary of results of aquifer-isolation testing in Mg-68

(Sutton, 1983)

[m2/d, square meters per day; m bls, meters below land surface]

Depth interval of

isolated zone

(m bls)

Specific

capacity1

(m2/d)

Percent of openhole specific

capacity

23 - 29 0 0

31 - 37 34.5 45

39 - 45 14.4 19

47 - 54 15.7 21

68 - 74 0 0

74 - 142 11.8 15

Open hole 276.4 100

1 Specific capacity is based on pumping between 30 and 60 minutes.

2 Estimated as sum of zone values.
16

Aquifer Test of Mg-624

Drawdown was measured in Mg-624 (Rex #2) during 25 minutes of pumping at a rate of about

45 L/min (12 gal/min) (U.S. Environmental Protection Agency, unpublished data files). The pump was set

at 27 m (90 ft) below land surface, and the well was pumped until the water level dropped to the pump

intake in about 25 minutes. Recovery measurements are not available.

The late-time part of the drawdown record agrees fairly well with the Theis theory and yields an

estimated T = 0.53 m2/d (5.8 ft2/d) (fig. 11). However, the best fit also yields an estimate of S = 0.26,

implying unconfined or water-table conditions. Similar values of T = 0.59 m2/d (6.4 ft2/d) and S = 0.21 are

obtained from the Cooper-Jacob straight-line semi-log fit (fig. 12).

0.1

1

10

100

0.1 1 10 100

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

Figure 11. Drawdown in pumped well Mg-624 in Lansdale area and estimates of transmissivity (T) and

storage coefficient (S) by Theis (1935) method.

T = 0.53 m2/d

S = 0.26
17

0

5

10

15

20

25

30

35

40

0.1 1 10 100

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

Figure 12. Drawdown in pumped well Mg-624 in Lansdale area and estimates of transmissivity (T)

and storage coefficient (S) by Cooper-Jacob (1946) method.

T = 0.59 m2/d

S = 0.21
18

Aquifer Test of Mg-625, March 1980

A 4-hour constant-rate open-hole pump test was conducted in Mg-625 (Rex #1) by USEPA on March

18, 1980 (U.S. Environmental Protection Agency, unpublished data files). The pumping rate declined

during the test; average pumping rate was 320 L/min (85 gal/min). Water levels in the pumped well were

difficult to measure because of “cascading” inflow to the borehole above the free surface, and original data

sheets indicate that the water-level probe was malfunctioning. Maximum reported drawdown after

4 hours of pumping was 35 m (114 ft). Recovery of the pumped well was monitored for 90 minutes, and

drawdown decreased suddenly between 35 minutes [26 m (86 ft)] and 40 minutes [9.5 m (31 ft)] of

recovery.

For the analysis here, it is assumed that the drawdowns measured before 40 minutes are 16.6 m

(54.5 ft) too large because of measurement errors. After performing this correction, the late-time recovery

data matches the Theis theory (Goode, 1997) reasonably well (fig. 13), yielding T = 30 m2/d (320 ft2/d).

Analysis of these corrected data by use of Theis’ recovery method (not shown) yields T = 31 m2/d

(340 ft2/d). The drawdown during pumping is not considered reliable for estimation of aquifer properties

because of the probe malfunction, the erratic measured drawdown possibly caused by cascading water,

and probable well-loss effects indicated by the rapid early recovery of the pumped well water levels

(fig. 13).

0.1

1

10

100

0.1

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

82

0.082

T = 30 m2/d

Figure 13. Drawdown during recovery in pumped well Mg-625 in Lansdale area, March 1980,

and estimate of transmissivity (T) by method of Goode (1997).
19

Very recently, new monitor wells were installed near Mg-624 and Mg-625 in Lansdale (QST

Environmental, Inc., 1998). Aquifer-testing results reported by QST include T’s ranging from 14 to

62 m2/d (150 to 670 ft2/d). Although these data were not included in the review procedures for this report,

these values are similar to results from aquifer tests reviewed here.

Water levels were also monitored in Mg-624 (Rex #2) and Mg-82 (Lansdale Sewer Plant Well) on 8-

day strip charts (not shown). Both charts indicate that the water levels were not static prior to pumping of

Mg-625. A maximum drawdown of about 0.6 m (2 ft) was observed in Mg-624. Pumping in Mg-625 had

less effect on the water level in Mg-82; drawdown was more gradual, and the maximum drawdown was

about 0.09 m (0.3 ft). The water level in Mg-624 began to rise immediately after pumping in Mg-625

stopped, but water levels in Mg-82 continued to fall for 2 days, although at a noticeably slower rate than

during pumping. Measurable rainfall (5 mm (0.2 in) on the day of pumping) also may have influenced

water-level changes, especially in the observation wells. These nonideal conditions obviously have some

affect on estimated T and S, but sufficient data are not available to correct measured drawdowns.

Aquifer Test of Mg-1125, October 1982

A 48-hour aquifer test was conducted in Mg-1125 (NP 61) starting on October 19, 1982 (North Penn

Water Authority, unpublished data files). The well was pumped at a rate of 770 L/min (203 gal/min) for

48 hours and then at an increased rate of 1,100 L/min (289 gal/min) for 50 minutes. Drawdown during

pumping and recovery was monitored in the pumped well, and water levels in observation well Mg-1124

(NP 58) were recorded on a strip chart. Limited data also are available for a step test of Mg-1125 at rates of

380, 770, and 1,150 L/min (100, 203, and 305 gal/min).

A Cooper-Jacob (1946) analysis of drawdown in pumped well Mg-1125 yields T = 81 m2/d

(872 ft2/d) (fig. 14). The late-time part of the test data does not fall on the matched straight line, suggesting

intersection of a flow barrier (see fig. 3H’) or other conditions that would result in increased resistance to

flow towards the well. Except for this last part of the data, the Theis plot (not shown) is essentially a

straight line with slope less than 1/4 on the log-log plot. A large and relatively constant well loss could

cause drawdown in the pumped well to increase only slightly in time.
20

Recovery data yields T = 125 m2/d (1,345 ft2/d) by use of the standard Theis (1935) large-time

procedure (fig. 15) and T = 80 m2/d (860 ft2/d) by use of the Goode (1997) method (fig. 16). The rapid

initial decrease in drawdown during recovery suggests significant well loss or skin effect in the pumped

well. The late-time drawdown is higher than predicted by the theory. The intercept of the Theis recovery

method plot [at t/(t-tp)=1, where t is the time since pumping began and tp is the pumping duration; that is,

at very late time during recovery] is not at zero drawdown, and the log-log plot does not match the type

curves of Goode (1997) precisely. This sustained drawdown at late time during recovery could be caused

by a background trend of decreasing water levels. Examination of the strip chart in observation well

Mg-1124 indicates that water levels were dropping at a rate of about 0.15 m/d prior to the test. Assuming

that this rate of regional decline continued, water levels would not be expected to recover fully to prepumping levels.

Detailed analysis of the observation-well data was not conducted, but the general nature of the data

can be summarized. After the initial few minutes, drawdown increased almost linearly in time. The

maximum drawdown, not adjusted for the background trend, is approximately 2.5 m, and after a day of

recovery, the drawdown had decreased to about 1.9 m. Drawdown in the pumped well was about 2 m

after 1 day of recovery. Small drawdown differences between the pumped well and the observation well

during recovery is consistent with Theis late-time recovery theory.

0

5

10

15

20

0.1 1 101 102 103 104

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 81 m2/d

S = 0.007

Figure 14. Drawdown in pumped well Mg-1125 in Lansdale area, October 1982, and estimates of

transmissivity (T) and storage coefficient (S) by Cooper-Jacob (1946) method.
21

0

5

10

15

1 101

102103104

DRAWDOWN, IN METERS

TIME SINCE PUMPING BEGAN DIVIDED BY TIME SINCE PUMPING STOPPED

T = 125 m2/d

Figure 15. Drawdown during recovery in pumped well Mg-1125 in Lansdale area, October 1982,

and estimate of transmissivity (T) by Theis (1935) method.

0.1

1

10

100

0.1

1

10

0.0001 0.001 0.01 0.1 1 10

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

T = 80 m2/d

90

Figure 16. Drawdown during recovery in pumped well Mg-1125 in Lansdale area, October 1982,

and estimate of transmissivity (T) by method of Goode (1997).
22

Preliminary analysis of step-test data also suggests that the well loss or skin effect is significant in

Mg-1125 at prevailing pumping rates. The plot of linear drawdown as a function of log-time during three

sequential steps of increased pumping rate (fig. 17) shows that the drawdown does not increase

proportionally to the pumping rate but increases substantially more. Analysis of drawdown during

pumping rate steps of 380 and 770 L/min (100 and 203 gal/min) suggests that nonlinear well loss accounts

for about 65 percent of drawdown at the higher pumping rate. Thus, the drawdown in the pumped well is

likely to be about three times higher than levels in the formation close to the pumped well, when the

pumping rate is 770 L/min.

0

5

10

15

20

0.1 1 101 102

DRAWDOWN, IN METERS

ELAPSED TIME DURING EACH STEP, IN MINUTES

Q = 380 L/min

Q = 770 L/min

Q = 1,150 L/min

Figure 17. Drawdown in pumped well Mg-1125 in Lansdale area, October 1982, during step test with

pumping rates (Q) of 380, 770, and 1,150 liters per minute.
23

Aquifer Test of Mg-1125, February and October 1989

Two 48-hour aquifer tests were conducted in Mg-1125 in February and October 1991 (U.S. Geological

Survey, unpublished data). Mg-1125 was pumped at 770 L/min (203 gal/min), and water levels were

monitored in it and in observation wells Mg-1124 (NP 58) and Mg-1126 (NP 62). These observation wells

are on either side of the pumped well along regional strike of the dipping bedrock. The regional strike of

bedding is assumed to be about N45E in the area (Newport, 1971). An additional observation well,

Mg-1270, was installed for the October 1991 test south-east (up-dip) of the pumped well.

A Cooper-Jacob analysis of drawdown in the pumped well yields T = 120 m2/d (1,300 ft2/d)

(fig. 18). This result is similar to that from the 1982 test described in the previous section. Drawdown in the

pumped well during the two different aquifer tests was similar; drawdown was slightly more than 1 m

larger during the February test than during the October test. An abrupt shift in drawdown levels between

200 and 1,000 minutes was measured during the October test.

0

5

10

15

20

1 10 100 1,000 10,000

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

FEBRUARY

OCTOBER

T = 120 m2/d

S = 2 x 10-5

Figure 18. Drawdown in pumped well Mg-1125 in Lansdale area, February and October 1991,

and estimates of transmissivity (T) and storage coefficient (S) by Cooper-Jacob (1946) method.
24

Drawdown in the observation wells does not match the Theis theory in either the log-log plot

(fig. 19) or in the semi-log format (not shown). A Theis match to just the early-time part of the drawdown

at all three observation wells yields T values of 1,150, 930, and 580 m2/d (12,400, 10,000, and 6,200 ft2/d)

for wells Mg-1124, 1126, and 1270, respectively. Well Mg-1270, oriented in the assumed up-dip direction

from the pumped well, yields the smallest of these T values. The nearly linear trend in the log-log plot at

large time, at a slope of about 0.5, suggests ‘linear’ flow conditions. Linear flow conditions can be found

where there is horizontal flow in an infinite aquifer towards a finite-length vertical fracture, or in a narrow

fault zone of infinite length (fig. 2). Type curves are developed for the case of a homogeneous confined

aquifer bounded by two parallel no-flow boundaries by image well theory (Ferris and others, 1962;

Kruseman and de Ridder, 1990). The theoretical model assumes that the well is at the center of an aquifer

that is infinite in one coordinate direction and has uniform width (W) in the other direction. For the type

curve used here, it is assumed that the observation well is also on the centerline of this infinite-length,

finite-width aquifer. Drawdown in Mg-1124 (NP58) matches theoretical drawdown in a finite-width

aquifer (fig. 20). From the match shown (fig. 20), T = 1,300 m2/d (14,000 ft2/d), significantly higher than

estimates from the pumped well during both pumping and recovery. This estimate of T is similar to the

value from the standard Theis method (1,150 m2/d; 12,400 ft2/d).

0.01

0.1

1

10

0.00001 0.0001 0.001 0.01 0.1

Mg-1124

Mg-1126

Mg-1270

THEORETICAL

DRAWDOWN, IN METERS

ELAPSED TIME DIVIDED BY RADIAL DISTANCE SQUARED,

IN MINUTES PER SQUARE METER

T = 580 m2/d

S = 0.0002

Figure 19. Drawdown in observation wells Mg-1124, Mg-1126, and Mg-1270 during pumping of

Mg-1125 in Lansdale area, October 1991, and estimate of transmissivity (T) and storage coefficient

(S) from drawdown in Mg-1126 by Theis (1935) method.
25

Analysis of observation-well drawdown as a function of distance at large time yields T values

consistent with those from analysis of pumped well drawdown but much lower than the Theis and ‘linear’

flow estimates above. Hydraulic-head gradients between the observation wells and pumped well are near

equilibrium during the latter part of the test. For example, during the February test, the head difference

between observation well Mg-1124 and pumped well Mg-1125 at 10, 100, and 1,000 minutes is 12, 13, and

14 m (40, 44, and 46 ft), respectively. Hence, the flow system is near steady-state equilibrium at the wellfield scale. Applying Thiem’s steady-state method (Bear, 1979) to the observed drawdown as a function of

distance for each observation well separately yields T values ranging from about 50 to about 100 m2/d,

depending on the observation well used and the assumed effective pumped-well radius. The different

results for the early-time Theis match and the late-time Thiem analysis suggest that the underlying model,

which assumes confined horizontal flow in an infinite aquifer, is not an accurate characterization of the

flow system at the well-field scale.

0.001

0.01

0.1

1

101

10 -1 10 0 10 1 10 2 10 3 10 4

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 1,300 m2/d

S = 0.00004

W = 1,700 m

Figure 20. Drawdown in observation well Mg-1124 during pumping of Mg-1125 in Lansdale area,

February 1991, and estimates of transmissivity (T) and storage coefficient (S) by image well method

for a strip aquifer of infinite length but uniform finite width (W), based on Theis (1935) solution.
26

Aquifer Testing at Merck

Locations of pumped and observation wells at the Merck facility used in this report are shown in

figure 21.

Aquifer Test of Mg-125, May 1986

Roy F. Weston, Inc. (1986) conducted a constant-rate aquifer test in Mg-125 (PW-2) in May 1986.

Analysis of drawdown in observation wells Mg-123 (B), Mg-1658 (1-85), and Mg-1572 (11-85) by Theis and

Cooper-Jacob methods yielded T values ranging from 80 to 130 m2/d (900 to 1,400 ft2/d) (table 4).

Estimated S ranged from 2 x 10-4 to 7 x 10-4, consistent with confined conditions. Several wells located at

similar radial distances from the pumped well did not exhibit drawdown during the test, suggesting

heterogeneous or anisotropic hydraulic conductivity (Roy F. Weston, Inc., 1986).

Aquifer Test of Mg-128, November 1993

Nittany Geoscience Inc. (NGI) (1994a) conducted a 48-hour aquifer test of Mg-128 (PW-5) in

November 1993, pumping at an average rate of 380 L/min (100 gal/min), and monitored water levels in

the pumped well and in several observation wells. Analysis of drawdown in the pumped well by use of

the Cooper-Jacob large-time method yielded T = 7.2 m2/d on the basis of drawdown between about 150

and 1,500 minutes after the pump started (Nittany Geoscience Inc., 1994a). After 1,500 minutes, the

drawdown rate increased substantially (compared to the large-time model prediction) and this led to a

decreased estimated T = 2.9 m2/d for the latter part of the test. This increase in rate of drawdown also was

observed in most shallow observation wells (Nittany Geoscience Inc., 1994a). NGI (1994a) suggested that

this increased drawdown in the shallow observation wells could be caused by an increase in vertical

leakage downward to the deeper zone. An anisotropic horizontal-flow confined-aquifer (Theis) model was

used to estimate the transmissivity of the shallow zone [21 - 30 m (70 - 100 ft) below land surface (bls)]

because wells at similar radial distances had widely varying drawdowns (fig. 22). The maximum and

minimum components of the shallow zone T were estimated as 75 and 5 m2/d, respectively. The nondirectional effective T for the shallow zone (the geometric mean of the maximum and minimum

components) was 19 m2/d. Isotropic analysis of the drawdown observed in one deep zone [82 - 88 m (270

- 290 ft) bls] well yielded T = 3.5 m2/d.

Table 4. Transmissivity and storage coefficient estimates from drawdown during pumping of Mg-125,

Merck & Co., West Point, Pa., May 1986 (Roy F. Weston, Inc., 1986)

[m2/d, square meters per day; m, meters; bls, below land surface; ? depths unknown]

Observation well Transmissivity

(m2/d)

Storage

coefficient

Radial distance

(m)

Open interval

(m bls) Analysis method

Mg-123 130 0.0004 91 10 - 168 Theis

156 .0003 Cooper-Jacob

Mg-1658 98 .0002 305 ? - ? Theis

143 .00014 Cooper-Jacob

Mg-1572 109 .00007 283 ? - 68 Theis

149 .00007 Cooper-Jacob
27

Figure 21. Locations of pumping and observation wells at Merck, Sharpe & Dome facility, near Lansdale, Pa.
28

Figure 22. Drawdown in wells in the area of pumped well Mg-128 in Lansdale area, November 1993, at end of 48-hour aquifer Geoscience, Inc., 1994a).
29

Several conceptual inconsistencies in the analysis methods used by NGI (1994a) are suggested.

Drawdown was estimated in each of the two separate depth zones by use of the total pumping rate.

Proper analysis would use only that part of the total pumping rate that entered the well from each zone.

Thus, if each zone contributed half of the total pumping rate, then the estimated T values of NGI (1994a)

would be twice the correct values. Moreover, in heterogeneous systems, the highest drawdown is

generally observed in the zones of highest T. Drawdown in the deep zone may be very close to the

drawdown in the pumped well because of the high permeability connection between the observation well

and the pumped well (fig. 23). If this conceptual model is appropriate, then most flow into the well would

be coming from the deep zone, and the T of the shallow zone could be overestimated. This conceptual

model could be verified with analytical (Papadopulos, 1966) or numerical models (Rutledge, 1991;

McDonald and Harbaugh, 1988), but these complex analysis methods are beyond the scope of the current

review. The uniformly increased drawdown throughout the shallow zone may also be due to vertical flow

downward to a system of high permeability fractures in a finite area at depth. Drawdowns within such a

fracture cluster might be essentially uniform in space and cause relatively uniform vertical leakage from

the overlying zones.

-50

0

50

100

150

0 200 400 600 800 1,000

ELEVATION, IN METERS ABOVE MEAN SEA LEVEL

DISTANCE, IN METERS

Land surface

0.31

8.59

0.63 -0.02

0.04

0.34

9.73

A A'

APPROXIMATE REGIONAL DIP 15 DEGREES

Figure 23. Cross-section showing regional dip of bedrock and drawdown in wells in the area of

pumped well Mg-128 in Lansdale area, November 1993, at end of 48-hour aquifer test (Nittany

Geoscience, Inc., 1994a). Drawdowns at wells not located on cross section are translated to the

cross section by moving along the strike direction.
30

The Theis log-log plot of drawdown in the pumped well and in deep zone well Mg-1555 (N20D)

[located near Mg-1554 (N20)] (fig. 24) shows that the Theis curve does not match the observed drawdown,

hence the basic assumptions of the large-time Cooper-Jacob analysis are not met. The log-log plot shows

essentially straight line response with a slope of about 1/3 for the pumped well. The difference between

the drawdown in the pumped well and in well Mg-1555 is consistently between 1.2 and 1.5 m (4 and 5 ft)

for the entire record (fig. 25). This suggests that the flow system between Mg-1555 and the pumped well is

in quasi-equilibrium. That is, the flow rate, which is proportional to head gradient, between Mg-1555 and

Mg-128 is essentially constant, and the increasing drawdown of both is due to depletion of storage in parts

of the flow system beyond (or above) Mg-1555.

The increased drawdown (a maximum of approximately 0.5 m (1.5 ft) of additional drawdown) in

the shallow zone at about 1,700 minutes after the test began may not be directly related to the pumping of

Mg-128. Possible causes for the sudden increased drawdown include initiation of pumping in a nearby

production well or a significant increase in atmospheric pressure. As postulated by NGI (1994a), this

increased rate of drawdown in the shallow zone may be caused by increased leakage downward to the

deeper zone where drawdowns are higher. However, the increase in drawdown rate in such a conceptual

model would probably not be so abrupt. Such a response would also indicate that most flow entering the

pumped well is coming from the deeper zone; only in this case will the effect of the leakage on water levels

be greater than the drawdown due to horizontal flow to the pumped well.

0.1

1

101

102

1 101 102 103 104

Mg-128

Mg-1555

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

HALF-SLOPE

ONE-THIRD

SLOPE

Figure 24. Drawdown in observation well Mg-1555 and pumped well Mg-128 in Lansdale area,

November 1993, in log-log format.
31

0

5

10

1 101 102 103 104

Mg-128

Mg-1555

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

Figure 25. Drawdown in observation well Mg-1555 and pumped well Mg-128 in Lansdale area,

November 1993, in semi-log format.

PUMPING ENDED
32

Aquifer Test of Mg-1198, September 1988

NGI (1988a) conducted a step test on Mg-1198 (PW-9) starting on September 19, 1988. Because of

problems with regulation of the discharge, the initial pumping rate was erratic, and the test was halted

temporarily. After re-starting the test, the pumping rate was about 265 L/min (70 gal/min). A subsequent

step change resulted in an increase to about 322 L/min (85 gal/min) with a declining rate in time.

Attempts to increase the rate for another step change were not successful. Drawdown was measured in the

pumped well and in observation well Mg-1565 (N30). Water-level measurements also were made in

observation wells Mg-1563 (N28) and Mg-1564 (N29), but the initial water level was not measured; hence,

drawdown cannot be computed. However, the drawdown at both these wells, which are about 150 m

(500 ft) from the pumped well, was greater than 0.3 m (1 ft) during the period that was measured. Several

non-standard features of this test limit the usefulness of the data for estimation of aquifer properties.

Analysis of the drawdown data from observation well Mg-1565 provides a rough estimate of aquifer

properties in the vicinity of Mg-1198. Cooper-Jacob analysis of the drawdown at observation well Mg-1565

yields an estimated T = 120 m2/d (1,300 ft2/d) (fig. 26). The Theis match yields T = 98 m2/d (1,050 ft2/d)

(fig. 27). From the Theis match, the storage coefficient is estimated as 2 × 10-4. Because of scatter in the

observed drawdown, the match for the Theis and Cooper-Jacob methods is not very good. Better estimates

of aquifer properties could be obtained from a more controlled test with a constant pumping rate and

measurement of drawdown at all affected observation wells.

0

0.5

1

1.5

2

1 10

1

10

2

10

3

10

4

DRAWDOWN, IN METERS

ELAPSED TIME, PERIOD 2, IN MINUTES

T = 120 m2/d

S = 0.0001

Figure 26. Drawdown in observation well Mg-1565 during pumping of Mg-1198 in Lansdale area,

September 1988, and estimates of transmissivity (T) and storage coefficient (S) by Cooper-Jacob

(1946) method.
33

Aquifer Test of Mg-1659, September 1988

Preliminary review of the drawdown data for a production step test of Mg-1659 (PW-10) in

September 1988 indicates that it is not suitable for aquifer-property estimation because of the erratic

drawdown observed in the pumped well during the test. The specific-capacity data estimated by NGI

(1988b) is probably not reliable because the quick recovery of the pumped well to water levels greater than

1.5 m (5 ft) above the initial level indicates that water-level fluctuations during the pumping period were

not due to pumping of the tested well. This well is believed to have been abandoned in October 1993.

Aquifer Test of Mg-1199, April 1989

NGI (1989) conducted step and constant-rate aquifer tests in April 1989 on Mg-1199 (PW-11). From

these results, NGI (1989) estimated a specific capacity of 20 to 23 m2/d (1.1 to 1.3 (gal/min)/ft) and

predicted an elongated (anisotropic) cone of depression caused by long-term pumping at a rate of

230 L/min (60 gal/min), the estimated “safe yield.”

0.1

1

10

101102103104

DRAWDOWN, IN METERS

ELAPSED TIME, PERIOD 2, IN MINUTES

OBSERVED DRAWDOWN

T = 98 m2/d

S = 0.0002

Figure 27. Drawdown in observation well Mg-1565 during pumping of Mg-1198 in Lansdale area,

September 1988, and estimates of transmissivity (T) and storage coefficient (S) by Theis (1935) method.

THEORETICAL

DRAWDOWN
34

Drawdown at observation wells Mg-1660 (N14), Mg-1562 (N26), and Mg-1563 (N28) (fig. 28) during

pumping of Mg-1199 does not match the Theis model type curve. The drawdown is close to a straight line

with a slope of about 0.4 on the log-log plot. A slope of 0.5 on this plot would be indicative of linear flow,

commonly observed in fractured rock. Deviation from the half slope at late time may be indicative of

recharge to the fractures from overlying or underlying formations.

Observed recovery also does not agree with the Theis model curves (fig. 29). The rapid initial

recovery of the pumped well suggests that a significant part of the drawdown in the pumped well is

caused by well loss or skin effects.

A step test was conducted in Mg-1199 on April 17, 1989. Measured water levels during four steps of

100 minutes each and subsequent recovery in Mg-1199 and in observation well Mg-1562 indicate that

drawdown during each step was essentially constant, partly because the pumping rate was decreasing

somewhat during each step (fig. 30). Analysis of step-drawdown data (fig. 31) indicates that at 300 L/min

(80 gal/min) about 50 percent of the drawdown measured in the pumped well is caused by head loss in

the formation and about 50 percent is caused by well loss or skin effects. This suggests that use of

pumped-well drawdown during pumping will underestimate T by a factor of about two, if well loss is

ignored during the analysis.

0.01

0.1

1

10

1 101 102 103 104

Mg-1562

Mg-1660

Mg-1563

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

Figure 28. Drawdown in observation wells Mg-1660, Mg-1562, and Mg-1563 during pumping of

Mg-1199 in Lansdale area, April 1989, in log-log format.
35

1

10

1

10

0.0001 0.001 0.01 0.1 1

Mg-1199

Mg-1563

Mg-1562

Mg-1660

THEORETICAL

DRAWDOWN

DRAWDOWN, IN METERS

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

DRAWDOWN WHEN

PUMPING STOPPED

75

0.75

30

0.3

DIMENSIONLESS DRAWDOWN

Figure 29. Drawdown during recovery in observation wells Mg-1660, Mg-1562, and Mg-1563 and

in the pumped well Mg-1199 in Lansdale area, April 1989, in log-log format.

0

2

4

6

8

10

12

14

0

20

40

60

80

100

1 101

102103

DRAWDOWN

PUMPING RATE

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

PUMPING RATE, IN LITERS PER MINUTE

Figure 30. Drawdown and pumping rate in pumped well Mg-1199 in Lansdale area, April 17, 1989,

during step test, in semi-log format.
36

Aquifer Test of Mg-1423, February 1994

NGI (1994b) conducted a combined step and constant-rate aquifer test in Mg-1423 (PW-12)

beginning on February 15, 1994. NGI (1994b) estimated the ‘sustained yield’ of the well as about

270 L/min (70 gal/min) on the basis of an extrapolation of the 48-hour drawdown to 90 days. After the

step tests and the immediately subsequent 48-hour test, maximum drawdown in the pumped well was

about 31 m (103 ft); drawdowns in nearby observation wells ranged from 0 to about 1 m (3 ft). The

maximum observed drawdown in the observation wells was in well Mg-1568 (6-85), oriented southwest

from the pumped well, approximately aligned with the assumed NE strike of formation bedding in the

area. NGI (1994b) did not analyze observed drawdown to estimate aquifer properties.

Drawdown in the pumped well during each step after 60 minutes (fig. 32) is used to estimate a

nonlinear well-loss term by use of procedures of Hantush and Bierschenk (see Kruseman and de Ridder,

1990, p. 200). Analysis of step-test results (fig. 33) suggest that, at the long-term pumping rate of

270 L/min, about 80 percent of the drawdown is from nonlinear well loss and 20 percent of drawdown is

head loss in the formation.

1,200

1,400

1,600

1,800

2,000

2,200

0 0.001 0.002 0.003 0.004 0.005 0.006

DRAWDOWN DIVIDED BY PUMPING RATE,

PUMPING RATE, IN CUBIC METERS PER SECOND

SLOPE = 2 x 105s2/m5

INTERCEPT = 1,109 s/m2

Figure 31. Sum of incremental drawdown divided by pumping rate as a function of pumping rate for

step test in Mg-1199, Lansdale area, April 1989, for estimation of linear (formation loss) and nonlinear

(well loss) components of drawdown by Hantush and Bierschenk method (Kruseman and de Ridder, 1990). IN SECONDS PER SQUARE METER
37

0

5

10

15

20

25

30

35

1 10 1

10 210 310 4

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

Q = 125 L/min

Q = 272 L/min

Q = 223 L/min

Q = 167 L/min

Figure 32. Drawdown in pumped well Mg-1423 in Lansdale area, during step test on February 15, 1994,

in semi-log format.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0 0.001 0.002 0.003 0.004 0.005

DRAWDOWN DIVIDED BY PUMPING RATE,

PUMPING RATE, IN CUBIC METERS PER SECOND

SLOPE = 1,245 s/m2

INTERCEPT = 1.085 x 106s2/m5

Figure 33. Sum of incremental drawdown divided by pumping rate as a function of pumping rate for

step test in Mg-1423, Lansdale area, February 15, 1994, for estimation of linear (formation loss) and

nonlinear (well loss) components of drawdown by Hantush and Bierschenk method (Kruseman and

de Ridder, 1990). IN SECONDS PER SQUARE METER
38

Drawdown in observation wells Mg-1556 (N21), Mg-1654 (N34D), Mg-1655 (PZS2), Mg-1568 (6-85),

and Mg-1570 (9-85) during the 48-hour aquifer test does not match the Theis theoretical curve (fig. 34). The

log-log plot of drawdown in the observation well with the highest drawdown is approximated by straight

segments with slope between 0.5 and 1.0. Drawdown follows a straight line of 0.5 slope on the log-log plot

for linear flow conditions, common in fractured-rock aquifers (see fig. 2E and 2F). A straight line of slope

1.0 corresponds to bounded aquifers at large time when all pumping comes from storage. The drawdown

in the pumped well is almost constant during the 48-hour test and cannot be used to estimate T.

0.001

0.01

0.1

1

10

100

1 10 1 10 2 10 3 10 4

Mg-1556

Mg-1654

Mg-1655

Mg-1568

Mg-1570

Mg-1423 (pumped well)

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

UNIT SLOPE

HALF SLOPE

Figure 34. Drawdown in observation wells Mg-1556, Mg-1654, Mg-1655, Mg-1568, and Mg-1570,

and in pumped well Mg-1423 in Lansdale area during step test and subsequent 48-hour aquifer test,

February 1994, in log-log format.
39

Analysis of pumped well recovery by use of the method of Goode (1997) yields T = 39 m2/d (fig. 35).

The model curve also suggests that drawdown in the formation near the pumped well when pumping

stopped was closer to 10 m than to the 31 m drawdown measured in the pumped well. This exaggerated

drawdown in the pumped well is consistent with the step-test analysis above. The general pattern of

almost no recovery in the observation wells at early-recovery time is consistent with the theory of Goode

(1997). On the basis of that theory, recovery in the observation wells would tend to be small until the

pumped well recovers to comparable levels.

DIMENSIONLESS DRAWDOWN (4πTs/Q)

0.1

1

10

100

1,000

1

10

100

1,000

10 -4 10 -3 10 -2 10 -1 10 0

PUMPED WELL Mg-1423

Mg-1568

Mg-1570

Mg-1556

Mg-1654

Mg-1655

THEORETICAL DRAWDOWN

DRAWDOWN, IN METERS

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

DRAWDOWN WHEN

PUMP STOPPED

0.125

1,250

T = 39 m2/d

Figure 35. Drawdown during recovery in observation wells Mg-1556, Mg-1654, Mg-1655, Mg-1568,

and Mg-1570 and in pumped well Mg-1423 in Lansdale area after step test and subsequent 48-hour

aquifer test, February 1994, and estimation of transmissivity (T) by method of Goode (1997).
40

Aquifer Test of Mg-1424, February 1994

NGI (1994b) conducted a combined step and constant-rate aquifer test in Mg-1424 (PW-13)

beginning on February 8, 1994. NGI (1994b) estimated the ‘sustained yield’ of the well as about 470 L/min

on the basis of the extrapolation of the 48-hour drawdown to 90 days. After the step tests and the

immediately subsequent 48-hour test, maximum drawdown in the pumped well was about 20 m (67 ft);

drawdowns in nearby observation wells ranged from 0 to over 6 m (20 ft). The maximum observed

drawdown in the observation wells was in well Mg-1656 (N32D), oriented E-NE from the pumped well,

approximately aligned with the assumed NE strike of formation bedding in the area. NGI (1994b) did not

analyze observed drawdown to estimate aquifer properties.

Application of the Cooper-Jacob method to drawdown observed in Mg-1656 (N32D) yields T =

44 m2/d (fig. 36). Unfortunately, the early-time drawdown, which is necessary to match the Theis model

curve, was not measured. Many observation wells at similar and even smaller distances from the pumped

well exhibited much smaller drawdown. Drawdown at all of the wells during recovery does not match the

Theis theory. The pumped-well drawdown during pumping does not appear to be on a large-time straight

line in the Cooper-Jacob semi-log plot.

4

5

6

7

102 103 104

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 44 m2/d

S = 1.4 × 10-5

Figure 36. Drawdown in observation well Mg-1656 during pumping of Mg-1424 in Lansdale area,

February 1994, and estimates of transmissivity (T) and storage coefficient (S) by Cooper-Jacob

(1946) method.
41

Aquifer-Isolation Testing at Ford, March 1992

Aquifer-isolation tests were conducted in five wells at the Ford Electronics and Refrigeration

Corporation (FERCO) facility, Lansdale, Pa., in March 1992 by Earth Data Incorporated (Converse

Consultants East, 1994). The tested wells were Mg-89 (well 1), Mg-90 (well 2), Mg-135 (well 3), Mg-147

(well 4), and Mg-151 (well 5). Well locations are shown in figure 1. Information about the tests and

hydraulic data reported by Converse Consultants East (1994) is summarized in table 5. A straddle-packer

system, consisting of two inflatable borehole packers with a pump between the packers, was used to

separately test three or four isolated zones within each borehole. Reported specific capacity of the 30 to

40 m (100 to 130 ft) zones isolated in the boreholes ranges from 0.41 to 82 m2/d (0.023 to 4.6 (gal/min)/ft).

Specific capacity decreases with depth in four of the wells (Mg-89, Mg-90, Mg-147 and Mg-151), but in

Mg-135, the specific capacity is greatest in the deepest zone. To estimate the open-hole specific capacity

(productivity coefficient), Converse Consultants East (1994) summed the specific capacities for the tested

zones in each borehole, with minor but unexplained adjustments. These estimates indicate that the openhole specific capacities of Mg-147 and Mg-151 are about one order of magnitude (a factor of 10 times)

greater than the specific capacities of the other wells. All depths in this section are from Converse

Consultants East (1994) and are assumed to be depths below top of casing (BTOC).

Table 5. Summary information on packer tests at Ford Plant, Lansdale, Pennsylvania (from Converse Consultants

East, 1994)

[m, meters; min, minutes; L/min, liters per minute; L, liters; m2/d, square meters per day; --, no data available]

U.S. Geological

Survey well

identification

number

Zone

Depth to

top of

interval

(m)

Depth to

bottom of

interval

(m)

Length of

interval

(m)

Duration of

test

(min)

Pumping

rate

(L/min)

Total

volume

pumped

(L)

Drawdown

(m)

Specific

capacity

(m2/d)

Mg-89 1 18.8 54.0 35.3 64 97 6,070 10.5 13.3

Mg-89 2 55.2 85.7 30.5 113 33 3,450 45.8 1.0

Mg-89 3 86.9 117.4 30.5 122 34 3,610 64.5 .8

Mg-89 4 106.7 146.6 39.9 83 42 3,280 60.1 1.0

Mg-90 1 17.6 51.8 34.2 65 79 5,180 14.6 7.8

Mg-90 2 51.8 82.3 30.4 71 55 4,090 31.2 2.5

Mg-90 3 82.3 112.8 30.4 84 48 4,110 35.7 1.9

Mg-90 4 112.8 150.8 38.0 -- -- 0 -- not tested

Mg-135 1 16.9 54.9 37.9 58 47 3,970 34.9 .3

Mg-135 2 54.9 85.3 30.4 71 55 3,350 47.8 1.6

Mg-135 3 85.7 116.1 30.4 58 66 3,620 19.9 4.8

Mg-135 4 109.5 146.0 36.5 57 71 3,620 15.0 6.8

Mg-147 1 18.6 43.9 25.3 51 87 4,391 2.6 48.1

Mg-147 2 43.9 74.4 30.4 48 83 4,020 5.5 21.5

Mg-147 3 74.4 104.9 30.4 143 20 2,949 69.5 .4

Mg-147 4 108.2 138.7 30.4 58 85 4,822 11.8 10.4

Mg-151 1 11.7 45.7 34.0 64 70 4,637 1.2 82.8

Mg-151 2 45.8 76.2 30.4 78 64 4,841 11.8 7.9

Mg-151 3 76.2 106.7 30.4 49 61 3,800 14.6 5.9

Mg-151 4 106.7 137.2 30.4 79 44 3,395 32.4 1.9
42

During the testing of zone 1 in each borehole, the upper packer was not inflated. This allowed the

storage of water in the borehole, which changes as the water surface in the well drops, to contribute to the

pumping. This borehole storage caused the drawdown in zone 1 of all wells to increase more gradually (at

early time) than the drawdown in the enclosed zones 2-4. Drawdown increased very rapidly immediately

after the pump was started in zones 2-4. When the upper packer was inflated, the water surface was

hydraulically isolated from the pumped middle zone. It is likely that the early-time response in zone 1 of

each well would have been more similar to the other zones if the upper packer had been inflated in the

open borehole or in the casing but below the water surface in the well.

Several of the datasets presented by Converse Consultants East (1994) are noted to have cyclic

fluctuations in reported drawdown. For example, the drawdown in the upper pumped zone 1 of Mg-151 is

dominated by a 0.3 m (1 ft) cycle in drawdown, which is large compared to the maximum drawdown of

1.2 m (4.0 ft). The cause of these oscillations in reported water levels is not apparent, and use of these data

to estimate aquifer properties may yield erroneous values. The drawdown datasets presented by Converse

Consultants East (1994) that have unexplained fluctuations are not used in this review.

Transmissivities estimated by use of several methods of analysis from these aquifer-isolation tests

are summarized in table 6. Some characteristics of drawdown during each test are discussed below in

separate sections. Methods of analysis include Theis match or Cooper-Jacob straight line fit of drawdown

data and Theis match of recovery data for the pumped zone only. Drawdown or recovery data for zones

other than the pumped zone are not used to estimate T.

Table 6. Estimates of horizontal transmissivity of individual depth intervals from packer tests at Ford Plant, Lansdale,

Pennsylvania. Test conducted by and drawdown data from Earth Data Inc. (see Converse Consultants East, 1994)

[L/min, liters per minute; m2/d, square meters per day; m, meters; --, not determined; >, greater than; dd, drawdown]

U.S.

Geological

Survey well

identification

number

Depth

interval

(m)

Pumping

rate

(L/min)

Transmissivity (m2/d)

Specific

capacity

(m2/d)

Comments

Theis Cooper/

Jacob Rg 1

1 Recovery type curve method of Goode (1997).

Mg-89 19-54 97 8.1 4.3 -- 13 perfectly flat dd 10-22 min;

bottom zone max dd >1 m,

straight line with 0.6 slope

in log-log plot

Mg-135 86-116 66 -- 10.0 9.1 4.8 dd too straight for Theis

match; bottom zone dd

max almost 1 m; recovery

too fast, short time for

recovery meas.

Mg-135 109-146 71 -- 6.2 13.5 6.8 dd too flat and straight for

Theis match; top zone dd

maximum 0.2 m

Mg-147 19-44 87 22 28 35 48 dramatic change in dd after

38 minutes pumping from

erratic to smooth; early

time Cooper-Jacob gives

16 m2/d;

Mg-151 107-137 44 -- 6 -- 1.9 dd not static when pumping

started; very flat dd; no fit

possible for Theis or

Recovery log-log plots
43

Mg-89, Zone 1, 19 - 54 m

Drawdown data collected during this test is suspect because of a period of perfectly constant

drawdown during the test. Drawdown in pumped zone 1 initially decreased at a rate of about 2 m in

5 minutes but then remained constant from about 10 minutes to about 22 minutes after pumping began

(fig. 37). There is no physically plausible explanation for this temporal pattern of drawdown during

constant-rate pumping. After this period, drawdown looks realistic. However, the early drawdown trend

and the trend after the constant drawdown period do not appear to be visually consistent. In contrast, the

observed drawdown in the underlying unpumped zone (55-147 m (181-481 ft)) gradually increases during

the entire pumping period. The fact that both zones recover to about the same level by about 95 minutes

after pumping started suggests that the drawdown during recovery in the pumped zone is representative

of field conditions. The maximum drawdown in the unpumped section of the borehole was more than

1 m, suggesting either leakage between the zones within the borehole or a hydraulic connection between

the upper pumped zone and the underlying zone through rock outside the borehole.

-2

0

2

4

6

8

10

12

-20 0 20 40 60 80 100

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

UNPUMPED UNDERLYING ZONE

55-147 m BELOW LAND SURFACE

PUMPED UPPER ZONE 1

19-54 m BELOW LAND SURFACE

Figure 37. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation testing

of Mg-89 in Lansdale area, March 1992.

PUMPING BEGAN

PUMPING ENDED 
44

The Theis log-log type curve match to the drawdown data indicates T = 8.1 m2/d (fig. 38). However,

the Theis fit is somewhat questionable because of the flat part of the drawdown curve. On the log-log plot

(fig. 38), an apparent slope of 0.6 is identified in the drawdown of the unpumped underlying zone of the

borehole. A slope of 0.5 in this format is indicative of ‘linear’ or one-dimensional flow. This linear response

can be generated by, for example, purely vertical flow from over and underlying rock to a large horizontal

fracture with essentially uniform drawdown. Alternatively, a finite vertical fracture with one-dimensional

flow in the surrounding rock can also generate this characteristic response.

0.01

0.1

1

10

100

0.1 1 10 1 10 2 10 3

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 8.1 m2/d

S = 0.41

PUMPED ZONE 1

UNPUMPED

UNDERLYING ZONE

THEORETICAL

DRAWDOWN

Figure 38. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation

testing of Mg-89 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage

coefficient (S) by Theis (1935) method.

PUMPING ENDED
45

A straight line can be fit to the drawdown before the flat part of the curve in semi-log or CooperJacob format (fig. 39), yielding T = 4.3 m2/d. After the flat part of the drawdown curve, a straight line is

not apparent, and if one is assumed at very large time, the slope is different from that exhibited by the

early time part of the data.

The match between the recovery data and the theoretical Theis recovery curve is poor; observed

recovery occurs faster than predicted by theory for the latter part of the monitored period (fig. 40). This

might be caused by recharge to the pumped zone by an over- or underlying lower-permeability leakage

source. The drawdowns in the pumped and unpumped zones are almost equal at the end of the recovery

monitoring period, indicating some hydraulic connection between the monitored zones.

-2

0

2

4

6

8

10

12

0.1 1 10 100

DRAWDOWN, IN METERS

UNPUMPED UNDERLYING ZONE

55-147 m BELOW LAND SURFACE

PUMPED ZONE 1

19-54 m BELOW LAND SURFACE

T = 4.3 m2/d

S = 0.37

Figure 39. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation testing

of Mg-89 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage coefficient (S) by

Cooper-Jacob (1946) method.

PUMPING ENDED

ELAPSED TIME, IN MINUTES
46

Mg-135, Zone 3, 86 - 116 m

A Theis match was not possible to the drawdown in the pumped zone (fig. 41) because the

drawdown curve is essentially a straight line after the first few minutes of pumping. This type of response

also occurs in other wells in the area, for example, Mg-67 (L8), in which the well loss was estimated to be

up to 80 percent of the total drawdown in the pumped well. Drawdown in the underlying zone follows a

straight line with a slope of 0.5 on the Theis plot, possibly indicating linear-flow conditions. The

drawdown in the overlying zone does not indicate significant hydraulic connection either within or

outside the borehole between the overlying and pumped zones. The stepped and fluctuating pattern in

drawdown for this zone is indicative of the resolution of the recorded water levels. A straight-line fit is

possible in the Cooper-Jacob plot (fig. 42), yielding T = 10 m2/d.

0.1

1

10

100

0.1

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs /Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

55

0.055

PUMPED ZONE 1

19-54 m BELOW LAND SURFACE

UNPUMPED UNDERLYING ZONE

55-147 m BELOW LAND SURFACE

Figure 40. Drawdown during recovery in pumped zone 1 and unpumped underlying zone during aquiferisolation testing of Mg-89 in Lansdale area, March 1992, and theoretical drawdown by method of Goode

(1997).
47

0.01

0.1

1

10

100

0.1 1 10 1 10 2 10 3

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

UNPUMPED

UNDERLYING ZONE

117-146 m

PUMPED ZONE 3

86-116 m

UNPUMPED

OVERLYING ZONE

17-85 m

Figure 41. Drawdown in pumped zone 3 and unpumped overlying and underlying zones during

aquifer-isolation testing of Mg-135 in Lansdale area, March 1992, in log-log format.

PUMPING ENDED
48

The rapid recovery of the pumped zone at a rate faster than that predicted by the theory (fig. 43)

suggests that the drawdown in the pumped zone may be exaggerated with respect to the drawdown in the

formation. This could be caused by other nearby pumping or by a low-permeability skin or region

immediately around the borehole. Nonetheless, the estimated T = 9.1 m2/d from the recovery type curve

match is close to that identified from the Cooper-Jacob plot for the pumping-period drawdown. If the well

loss or skin causes a constant head loss during pumping (that is, the head loss is independent of the

drawdown), the Cooper-Jacob slope can be used to estimate formation T because the slope of the semi-log

drawdown line does not depend on a constant well loss or skin factor, but only on the formation T. The

recovery analysis is also independent of a constant well-loss term (Kruseman and de Ridder, 1990). The

negligible recovery of the non-pumped zones is similar to the Theis theory for observation wells at early

time (Goode, 1997). The pumped well recovers most quickly because flow is towards the well on all sides

and initial gradients are large. In observation wells, gradients are lower when pumping stops, and flow

occurs both towards the observation well and away from it towards the pumped well. The extent of

recovery depends on the net flow into the well. Unfortunately, recovery was not monitored for sufficient

time to address many of the possible alternative explanations for the observed early time response.

-5

0

5

10

15

20

25

0.1 1 10 1 10 2

DRAWDOWN, IN METERS

PUMPING TIME, IN MINUTES

T = 10.0 m2/d

UNPUMPED ZONES

17-85 m OVERLYING

117-146 m UNDERLYING

PUMPED ZONE 3

86-116 m

Figure 42. Drawdown in pumped zone 3 and unpumped overlying and underlying zones during

aquifer-isolation testing of Mg-135 in Lansdale area, March 1992, and estimates of transmissivity (T)

and storage coefficient (S) by Cooper-Jacob (1946) method.

S ≈ 0
49

The part of the borehole isolated in pumped zone 3 overlapped with that in zone 4, which is

discussed in the next section. In particular, the section of the borehole contained in both zones (109-116 m

(359-381 ft)) coincides with the contact between the upper Lockatong and lower Brunswick Formations

inferred by Converse Consultants East (1994, pl. 1). Numerous authors have suggested that openings

along bedding contacts account for most of the large-scale T in the Brunswick Formation (for example,

Michalski, 1990; Michalski and Britton, 1997), although high-angle cross-bed fractures may provide most

of the formation’s permeability at large depths (Morin and others, 1997). Furthermore, the contaminant

concentrations reported for samples collected from the isolated zones 3 and 4 are very similar. These data

suggest that the overlapping section of the borehole may be contributing a significant fraction of the yield

of both zones during pumping. That is, the estimated transmissivities may be largely dependent on the

relatively high T in the overlapping section of the borehole. Adding the T or specific capacities of zones 3

and 4 would overestimate the corresponding values for the entire borehole by counting this section twice.

0.01

0.1

1

10

0.1

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

0.012

PUMPED ZONE 3

86-116 m BELOW LAND SURFACE

UNPUMPED OVERLYING ZONE

17-85 m BELOW LAND SURFACE

UNPUMPED UNDERLYING ZONE

117-146 m BELOW LAND SURFACE

T = 9.1 m2/d

Figure 43. Drawdown during recovery in pumped zone 3 and unpumped overlying and underlying zones

during aquifer-isolation testing of Mg-135 in Lansdale area, March 1992, and transmissivity (T) by method of

Goode (1997).
50

Mg-135, Zone 4, 109 - 146 m

As discussed above, zone 4 overlaps somewhat with zone 3 in Mg-135. If this part of the borehole

has a significant part of the T of each zone, the hydraulic response of the two zones might be similar

during pumping.

Drawdown in zone 4 (fig. 44), pumped at 71 L/min, is less than that in zone 3 pumped at 66 L/min

(fig. 41). This suggests that the T of zone 4 is higher than that of zone 3, as quantified by the specific

capacities of 4.8 m2/d (0.268 (gal/min)/ft) for zone 3 and 6.8 m2/d (0.379 (gal/min)/ft) for zone 4.

However, the actual pumping rates may have been more similar than the rates identified by Converse

Consultants East (1994). An average pumping rate for the entire test can be calculated by dividing the total

volume of water pumped by the duration of pumping; this procedure suggests that the average pumping

rates for zones 3 and 4 were 62.5 and 63.6 L/min (16.5 and 16.8 gal/min), respectively. In these drawdown

data, as well as data for other zones, fluctuations and, more likely, gradual decreases in pumping rate will

influence the shapes of the drawdown curves. Drawdown in zone 3 is relatively constant after an initial

rapid increase (fig. 41), whereas the drawdown in zone 4 increases more rapidly at later time (fig. 45). This

rate of increase of drawdown in time is used to estimate transmissivity in the Theis and Cooper-Jacob

methods, and, hence, the relative T of the two zones may be opposite that of their specific capacities

reported by Converse Consultants East (1994).

-5

0

5

10

15

20

-20 0 20 40 60 80

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

PUMPED ZONE 4

109-146 m

17-108 m

Figure 44. Drawdown in pumped zone 4 and unpumped overlying zone during aquifer-isolation testing of

Mg-135 in Lansdale area, March 1992.

PUMPING ENDED PUMPING BEGAN

UNPUMPED OVERLYING ZONE
51

0.01

0.1

1

10

100

0.1 1 101

102

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

PUMPED ZONE 4

109-146 m

UNPUMPED OVERLYING ZONE

17-108 m

Figure 45. Drawdown in pumped zone 4 and unpumped overlying zone during aquiferisolation testing of Mg-135 in Lansdale area, March 1992, in log-log format.

PUMPING

 ENDED
52

As with zone 3, the drawdown in zone 4 is too flat to fit to the Theis log-log plot (fig. 45). Maximum

drawdown in the upper zone is about 0.2 m in response to pumping. This suggests either leakage between

the zones in the borehole or a low-permeability hydraulic connection between the pumped zone and

overlying rock outside the borehole.

The slope of the straight line (large time) part of the pumped zone drawdown on the Cooper-Jacob

plot indicates T = 6.2 m2/d for zone 4 (fig. 46), lower than the Cooper-Jacob estimate of T = 10 m2/d for

zone 3. This ranking of T’s, zone 3 greater than zone 4, is opposite the ranking of specific capacities.

Drawdown during recovery of pumped zone 4 does not match the theoretical curve exactly, but the

marginal match (fig. 47) yields T = 13.5 m2/d, about twice as high as the Cooper-Jacob estimate from

pumping-period data.

-5

0

5

10

15

20

0.1 1 10 100

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

T = 6.2 m2/d

S = 4 × 10-4

PUMPED ZONE 4

109-146 m

UNPUMPED OVERLYING ZONE

17-108 m

Figure 46. Drawdown in pumped zone 4 and unpumped overlying zone during aquifer-isolation

testing of Mg-135 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage

coefficient (S) by Cooper-Jacob (1946) method.

PUMPING ENDED
53

0.01

0.1

1

10

0.1

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

0.017

PUMPED ZONE 4

109-146 m BELOW LAND SURFACE

UNPUMPED OVERLYING ZONE

17-108 m BELOW LAND SURFACE

T = 13.5 m2/d

17

Figure 47. Drawdown during recovery in pumped zone 4 and unpumped overlying zone during aquiferisolation testing of Mg-135 in Lansdale area, March 1992, and transmissivity (T) by method of Goode (1997).
54

Mg-147, Zone 1, 19 - 44 m

The reported drawdown for the test in Mg-147 pumped zone 1 was erratic until about 38 minutes

after pumping started, and subsequent drawdown changes smoothly in time (fig. 48). This suggests that

the data may be poor. For the unpumped section of the borehole, the drawdown is essentially zero, except

for the erratic data at early time. As noted above, the drawdown in pumped zone 1 increases more

gradually at early time because the water surface is open to the atmosphere in the pumped zone, and

hence a much larger volume of water must be removed from the borehole to lower the water pressure.

A Theis plot match is chosen that goes through the smooth part of the drawdown data at large time

and that has a similar shape, but is offset from, the erratic part of the data (fig. 49). This fit yields a T =

15 m2/d.

The Cooper-Jacob plot yields a T = 28 m2/d for the smooth late-time part of the pumped zone

drawdown (fig. 50). A reasonable fit may also be made to the early-time (<10 minutes) part of the data that

yields a somewhat lower T = 16 m2/d.

The recovery data matches well with the Theis theory after about 3 minutes and yields an estimated

T = 35 m2/d (fig. 51). As noted in previous sections, the late-time recovery data are not affected by well

loss or skin effect, and the T estimated from recovery data will be higher than that estimated from

pumping period drawdown where such effects are present.

-1

0

1

2

3

4

-20 0 20 40 60 80 100

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

PUMPED ZONE 1

19-44 m

UNPUMPED

UNDERLYING ZONE

45-139 m

Figure 48. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation

testing of Mg-147 in Lansdale area, March 1992.

PUMPING ENDED PUMPING BEGAN
55

0.01

0.1

1

10

1 10 1 10 2 10 3

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

PUMPED ZONE 1

19-44 m BELOW LAND SURFACE

UNPUMPED UNDERLYING ZONE

45-139 m BELOW LAND SURFACE

T = 15 m2/d

S = 0.53

THEORETICAL

DRAWDOWN

Figure 49. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation

testing of Mg-147 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage

coefficient (S) by Theis (1935) method.

PUMPING ENDED 
56

-0.5

0

0.5

1

1.5

2

2.5

3

1 10 1 10 2

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 28 m2/d

S = 0.13

PUMPED ZONE 1

19-44 m BELOW LAND SURFACE

UNPUMPED UNDERLYING ZONE

45-139 m BELOW LAND SURFACE

Figure 50. Drawdown in pumped zone 1 and unpumped underlying zone during aquifer-isolation testing of

Mg-147 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage coefficient (S) by

Cooper-Jacob (1946) method.

PUMPING ENDED 

0.1

1

10

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

35

0.35

PUMPED ZONE 4

109-146 m BELOW LAND SURFACE

T = 35 m2/d

THEORETICAL

DRAWDOWN

Figure 51. Drawdown during recovery in pumped zone 1 and unpumped underlying zone during aquiferisolation testing of Mg-147 in Lansdale area, March 1992, and estimate of transmissivity (T) by method

of Goode (1997).
57

Mg-151, Zone 4, 107 - 137 m

Zone 4 was the interval from 106.7 m (350.1 ft) to the bottom of the borehole, 137.2 m (450 ft). The

reported specific capacity is low (1.95 m2/d; 0.109 (gal/min)/ft). The zone was pumped at the rate of

49 L/min (13 gal/min) initially, but the rate decreased somewhat during the test such that the average rate

during the 79 minutes of pumping was about 43 L/min (11.3 gal/min). The overlying zone of the hole did

not respond to pumping in any discernible way, indicating a good seal between the packer and the

borehole wall and low permeability outside the borehole in the vicinity of the packer. Drawdown in the

pumped zone jumped to over 30 m almost instantly and increased slightly from about 31 to about 32.5 m

during pumping (fig. 52). After the pump was turned off, the drawdown instantly decreased to about

19 m, and then decreased slightly to about 17.5 m after over 100 minutes of recovery (fig. 52). The rapid

recovery immediately after pumping was stopped, and the then almost static water level indicates that the

drawdown in the formation very close to the pumped zone was closer to 20 m than to 30 m. This may be

the result of a skin effect caused by a low-permeability zone immediately around the borehole.

Because the drawdown changed only slightly during both pumping and recovery periods, the Theis

log-log curve match and the log-log recovery curve match were not possible. For the pumping period, the

log-log plot of drawdown as a function of time was essentially flat and would only match the Theis plot at

very large dimensionless time. The drawdown during recovery does not match the shape of the Theis

recovery solution; the drawdown decreases too slowly compared to the theoretical curve.

Semi-log plots of drawdown as a function of time indicate linear parts that can be analyzed by use of

the Cooper-Jacob method. However, these methods are based on the Theis solution, and the data clearly

do not match the Theis model; hence, this procedure should be considered only a crude approximation.

Analysis of drawdown during pumping indicates a T of about 6 m2/d; the recovery period drawdown

slope indicates a T of about 3 m2/d (fig. 53). These estimates indicate only the general range of the actual T,

which is low relative to the other zones tested at this site.

-10

0

10

20

30

40

50

-50 0 50 100 150 200

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

PUMPED ZONE 4

107-137 m

UNPUMPED OVERLYING ZONE

12 -106 m

Figure 52. Drawdown in pumped zone 4 and unpumped overlying zone during aquifer-isolation testing of

Mg-151 in Lansdale area, March 1992.

PUMPING BEGAN PUMPING ENDED 
58

Aquifer Test of Mg-924, April 1980

An aquifer test was conducted in well Mg-924 (NP 21) in April 1980 (U.S. Environmental Protection

Agency, unpublished data files). Pumping began at 1000 on April 8 and continued for 48 hours to 1000 on

April 10. The average pumping rate was 1,510 L/min (400 gal/min). Water levels were measured in

several observation wells; most were relatively shallow test holes on the American Electronics Laboratory

(AEL) property (fig. 54). Raingage readings indicate 7 mm (0.3 in.) of precipitation between 0700 on 5 April

and 0700 on 9 April, and 20 mm (0.8 in.) between 0700 on 9 April and 0700 on 10 April. The pumped well

is 153 m (500 ft) deep and casing extends to 15 m (50 ft) below land surface. Observation well Mg-876 (AEL

Drink) is 91 m (300 ft) deep and the “AEL Test Hole” observation wells 1-18 range between 8.5 and 15.8 m

(28 and 52 ft) deep. The depth of Cloverdale Park Well is not known. Drawdown in the pumped well was

measured by air line and recorded on a circular chart; these graphical data are not analyzed in this review.

-10

0

10

20

30

40

50

1 10 100 1,000

ELAPSED TIME, IN MINUTES

DRAWDOWN, IN METERS

PUMPED ZONE 4

107-137 m BELOW LAND SURFACE

UNPUMPED OVERLYING ZONE

12-106 m BELOW LAND SURFACE

T = 6 m2/d

S ≈ 0

Figure 53. Drawdown in pumped zone 4 and unpumped overlying zone during aquifer-isolation

testing of Mg-151 in Lansdale area, March 1992, and estimates of transmissivity (T) and storage

coefficient (S) by Cooper-Jacob (1946) method.

PUMPING ENDED 
59

Figure 54. Locations of wells and drawdown in meters at end of 48-hour aquifer test in the area of pumped well Mg-924 in Lansdale (U.S. Environmental Protection Agency, unpublished data files).
60

Drawdown measured in observation well Mg-876, which is about 490 m (1,600 ft) from the pumped

well, matches the Theis theory and yields an estimated T = 400 m2/d (4,300 ft2/d) and S = 10-4 (fig. 55).

Unfortunately, early-time drawdown was not measured; the first reported drawdown is at 62 minutes

after pumping began. Furthermore, the assumed static water level was measured 19 hours before

pumping began. Nonetheless, the good agreement between drawdown and the Theis model, especially

the result of a low storage coefficient, suggests that the drawdown record is reasonably reliable. Analysis

of drawdown during recovery also matches the theory, except for the last recorded value, and yields

estimated T = 350 m2/d (3,800 ft2/d) (fig. 56). The more rapid recovery than predicted by theory for the

last recorded value may be due to recharge from precipitation.

Rising water levels were observed in AEL Test Holes 1, 3-9, 12, 14, and 18. Some of these wells

exhibited an initial response to pumping in Mg-924, but recharge from rainfall apparently contributed to

overall rising water levels by the latter part of the test. No apparent response to pumping was observed in

Mg-914 (NP 12).

Figure 55. Drawdown in observation well Mg-876 during pumping of Mg-924 in Lansdale area, April 1980,

and estimates of transmissivity (T) and storage coefficient (S) by Theis (1935) method.

0.01

0.1

1

10

101 102 103 104

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 400 m2/d

S = 10 -4

THEORETICAL

DRAWDOWN
61

Increasing drawdown consistent with response to pumping was observed in AEL Test Holes 10,

Mg-1661 (AEL Test Hole 13), Mg-1662 (AEL Test Hole 16), and AEL Test Hole 17 and in Cloverdale Park

Well. However, only data from Mg-1661 and Mg-1662 are analyzed in this review. The Cloverdale Park

Well data are recorded on a strip chart. Drawdown during the latter part of the test was not recorded

because of malfunctions in the float, pulley, or recorder system. Drawdown in AEL Test Hole 17, also

recorded on a strip chart, shows steps in the data that are not consistent with gradually increasing

drawdowns caused by constant-rate pumping. The initial static water level was not recorded in AEL Test

Hole 10, although the water level dropped several feet in a gradual manner consistent with response to

pumping.

Figure 56. Drawdown during recovery in observation well Mg-876 after pumping of Mg-924 in Lansdale

area, April 1980, and estimate of transmissivity (T) and storage coefficient (S) by method of Goode (1997).

0.1

1

10

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

23

0.23

T = 350 m2/d

S = 10-4

THEORETICAL

DRAWDOWN
62

The observed drawdown in Mg-1661 matches the Theis theory well, yielding an estimated T =

855 m2/d (9,200 ft2/d) and S = 0.06 (fig. 57). This well is approximately 6 m (20 ft) from the pumped well

but is much shallower (total depth is 14 m (46 ft)). Because of its shallow depth, it is likely that the

drawdown in Mg-1661 is smaller than that in the fractures or fracture-zones providing most flow to

Mg-924. Hence, this T estimate is likely larger than the actual T for the deeper primary production zone(s)

for Mg-924. The large S is also indicative of unconfined or water-table conditions. As with Mg-876,

drawdown during recovery also matches the model reasonably well, except for the last recorded

drawdown, which may reflect recharge (fig. 58). From the recovery match, the estimated T = 570 m2/d

(6,100 ft2/d).

Drawdown in Mg-1662 (AEL Test Hole 16) responds later to pumping because of its large radial

distance of almost 610 m (2,000 ft) from the pumped well (fig. 59), compared to Mg-1661. The Theis match

to the relatively few data collected yield estimated T = 195 m2/d (2,100 ft2/d) and S = 0.001. This storage

coefficient is between the values estimated from Mg-876 and Mg-1661.

The spatial pattern of drawdown (estimated for some wells) after 48 hours of pumping does not

suggest planar radial flow towards the pumped well (fig. 54). The fact that the deepest observation well

exhibits the largest drawdown strongly suggests a three-dimensional nature to the flow system with the

primary production zone or zones at depths in the bedrock below the screened interval of most

observation wells. The observed drawdowns do not exhibit an obvious anisotropic pattern.

0.01

0.1

1

10

0.1 1 10 1 10 2 10 3

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 855 m2/d

S = 0.06

THEORETICAL

DRAWDOWN

Figure 57. Drawdown in observation well Mg-1661 during pumping of Mg-924 in Lansdale area, April 1980,

and estimates of transmissivity (T) and storage coefficient (S) by Theis (1935) method.
63

0.1

1

10

1

10

0.001 0.01 0.1 1

DRAWDOWN, IN METERS

DIMENSIONLESS DRAWDOWN (4πTs/Q)

TIME SINCE PUMPING STOPPED DIVIDED BY PUMPING DURATION

34

0.34

T = 570 m2/d

Figure 58. Drawdown during recovery in observation well Mg-1661 after pumping of Mg-924 in

Lansdale area, April 1980, and estimate of transmissivity (T) by method of Goode (1997).

THEORETICAL

DRAWDOWN

0.01

0.1

1

10 1 10 2 10 3 10 4 10 5

DRAWDOWN, IN METERS

ELAPSED TIME, IN MINUTES

T = 195 m2/d

S = 0.001

THEORETICAL

DRAWDOWN

Figure 59. Drawdown in observation well Mg-1662 during pumping of Mg-924 in Lansdale area,

April 1980, and estimates of transmissivity (T) and storage coefficient (S) by Theis (1935) method.
64

SUMMARY AND CONCLUSIONS

Estimated aquifer transmissivity (T) ranges from zero to about 1,300 m2/d; most tests indicate T

between 10 and 100 m2/d (fig. 60, table 7). Drawdown data from several aquifer tests do not closely match

the theoretical Theis curves, indicating that, in those cases, the assumption of radial, confined flow is not

valid. Several of the test results exhibit straight-line features of half-slope on log-log plots of drawdown as

a function of time; these features are commonly associated with flow in fractures.

Aquifer-isolation testing results indicate that most flow enters wells at a few discrete horizons

(table 8), probably associated with fractures or bedding-plane openings. The depth of most productive

zones ranged from 18 to 146 m bls, and generally productivity decreased with depth, although few data

are available to evaluate depths below 150 m. The use of specific capacity to rank individual productive

zones may yield a different order than ranking by transmissivity (see table 6).

Within a single borehole with multiple producing zones, the vertical hydraulic conductivity

between the zones appears to be very low in many aquifer-isolation tests. This suggests a strong vertical

anisotropy in hydraulic conductivity with highest values in the horizontal direction. Some evidence of

well-field-scale horizontal anisotropy aligned with the assumed NE strike of bedding exists, but this

evidence is considered weak because of the small number of observation wells, particularly wells screened

in isolated intervals.

Analysis of water-level recovery after constant-rate aquifer tests and of drawdown during step tests

(table 9), suggests that a significant fraction, perhaps as much as 85 percent, of the drawdown in pumped

wells is due to well loss or skin effects in or very near the pumped well and is not caused by resistance to

flow in the surrounding formations.

The hydraulic conductivity, transmissivity, and storage coefficient values estimated here

approximate the properties of fractured rock in the Lansdale area. Simple aquifer-test analysis methods are

used here in order to efficiently estimate properties at many locations in and around Lansdale. More

accurate models of three-dimensional flow in these dipping beds could be developed to provide more

detailed characterization of flow conditions at particular locations, which might be required for

predictions of flow at local scales. The wide range of estimated transmissivities underscores the

heterogeneity of the fractured-rock formation; hydraulic properties at new well locations cannot be

accurately estimated because these properties vary by orders of magnitude over relatively small distances.

The accuracy of these estimates is further reduced by limitations in this review, including the lack of

antecedent and background water-level trend information, lack of accurate pumping-rate information,

and generally unknown data quality. Removing these limitations would reduce uncertainties associated

with these results, but it is considered unlikely that the overall regional-scale results would be significantly

different.
65

Figure 60. Distribution of transmissivity values in square meters per day estimated from review of

existing well testing information in the Lansdale area.
66

Table 7. Estimates of transmissivity and storage coefficient determined from open-hole aquifer

tests in wells near Lansdale, Pennsylvania

[L/min, liters per minute; m2/d, square meters per day; r, well radius for pumped well, radial distance from

pumped well for observation wells; m bls, meters below land surface; Method: C-J, Cooper-Jacob; T, Theis; R,

Recovery-Theis; Rg, Recovery-Goode; Source: USGS, U.S. Geological Survey; NGI, Nittany Geosciences

Incorporated, 1988a&b, 1989, 1994a&b; Weston, Roy F. Weston, Inc., 1986]

Pumped (left) and

observation

(right) well

U.S. Geological

Survey local

number

Pumping

rate

(L/min)

Pumping

duration

(hours)

Method

of

analysis

Transmissivity

(m2/d)

Storage

coefficient

r

1

(meters)

Open

depth

interval

(m bls)

Source of

analysis

Mg-67 370 48 C-J 31 0.0014 0.1 6-87 USGS

370 T 25 .012 USGS

370 Rg 99 USGS

Mg-157 370 T 99 .0004 310 14-87 USGS

Mg-162 370 T 99 .00009 366 9-232 USGS

Mg-163 370 T 85 .00015 339 9-92 USGS

Mg-164 370 T 85 .00013 366 9-123 USGS

Mg-80 280 6 C-J 202 40-98 USGS

Rg 79 USGS

Mg-1502 370

280

T-2 well 150 .0004 161

56

13-123 USGS

Mg-624 45 .42 T .53 .26 .1 26-187

C-J .59 .21 USGS

Mg-625 320 4 Rg 31 .1 13-122 USGS

Mg-11253 770 48 C-J 81 .007 .08-.13 18-122 USGS

1,110 .83

R 127 USGS

Rg 80 USGS

Mg-1125 770 48 C-J 120 .00002 .08-.13 18-122 USGS

Mg-1124 strip4 1,300 .00004 285 USGS

Mg-1124 T 1,150 .00005 USGS

Mg-1126 T 580 .0002 238 USGS

Mg-1270 T 927 .0001 189 USGS

Mg-1124 Thiem 83 285 USGS

Mg-1126 Thiem 78 238 USGS

Mg-1270 Thiem 83 189 USGS

Mg-123 380 24+?

Mg-123 T 130 .0004 91 Weston

Mg-123 C-J 156 .0003 91 Weston

Mg-1658 T 98 .0002 305 Weston

Mg-1658 C-J 143 .00014 305 Weston

Mg-1572 T 109 .00007 283 Weston

Mg-1572 C-J 149 .00007 283 Weston

Mg-1285 380 48 C-J 28; 11 .08-.15 10-134 NGI

Mg-128 R 17 NGI

shallow6 380 T 75 .002 21-30 NGI

shallow7 380 T-aniso 19; 292 .002 21-30 NGI

Mg-1555 380 T 14 .0005 208 82-88 NGI

Mg-1198 265,322 step

N30 C-J 120 .0001 82 USGS

N30 T 98 .0002 82 USGS

Mg-1423 270 step, 48 Rg 39 .1 24-137 USGS
67

Mg-1424 470 step, 48 0.1 25-137

Mg-1656 C-J 44 .00001 232 97-103 USGS

Mg-924 1,510 48

Mg-876 T 400 .0001 490 USGS

Mg-876 Rg 350 .0001 USGS

Mg-1661 T 855 .06 6 USGS

Mg-1661 Rg 570 USGS

Mg-1662 T 195 .001 600 USGS

1 Well radii and radial distances are estimates from reports, files and maps; not measured in field.

2 Top distance and pumping rates are for Mg-67, bottom values are for Mg-80.

3 Top pumping rate and duration are for first part of test, bottom values for second part of test.

4 Strip aquifer method, image wells based on Theis.

5 First transmissivity value is for 100 - 1,500 minutes, second value is for 1,500 - 2,880 minutes.

6 Transmissivity is effective nondirectional geometric mean; shallow zone observation wells Mg-884, Mg-1537,

Mg-1538, Mg-1552, Mg-1553, Mg-1554, Mg-1556, Mg-1560, Mg-1564, and Mg-1566.

7 First transmissivity is in minimum direction, second is in maximum direction; Shallow zone observation wells

Mg-884, Mg-1537, Mg-1538, Mg-1552, Mg-1553, Mg-1554, Mg-1556, Mg-1560, Mg-1564, and Mg-1566.

Table 7. Estimates of transmissivity and storage coefficient determined from open-hole aquifer

tests in wells near Lansdale, Pennsylvania—Continued

[L/min, liters per minute; m2/d, square meters per day; r, well radius for pumped well, radial distance from

pumped well for observation wells; m bls, meters below land surface; Method: C-J, Cooper-Jacob; T, Theis; R,

Recovery-Theis; Rg, Recovery-Goode; Source: USGS, U.S. Geological Survey; NGI, Nittany Geosciences

Incorporated, 1988a&b, 1989, 1994a&b; Weston, Roy F. Weston, Inc., 1986]

Pumped (left) and

observation

(right) well

U.S. Geological

Survey local

number

Pumping

rate

(L/min)

Pumping

duration

(hours)

Method

of

analysis

Transmissivity

(m2/d)

Storage

coefficient

r

1

(meters)

Open

depth

interval

(m bls)

Source of

analysis
68

Table 8. Summary of aquifer-isolation tests in wells near Lansdale, Pennsylvania

[--, transmissivity not estimated]

Pumped well

U.S. Geological

Survey local

number

(other identifier)

Depth of

open hole

(meters)

Specific capacity

of open hole or

total of zones

(square meters

per day)

Depth of most

productive zone

(meters)

Specific capacity

of most productive

zone

(percent of total)

(square meters per

day)

Transmissivity of

most productive

zone

(square meters per

day)

Transmissivity

method

Mg-67 89 85 21-27 28.3 (33) 8.6 Theis

Mg-68 152 77 31-37 34.5 (45) --

Mg-89 147 16 19-54 13.2 (83) 8.1 Theis

Mg-90 151 12.3 18-52 7.8 (63) --

Mg-135 146 13 109-146 6.8 (50) 6.2 Cooper-Jacob

Mg-147 139 81 19-44 48.0 (60) 22 Theis

Mg-151 137 99 12-46 83.0 (84) --

Table 9. Estimates of well loss determined from step tests and recovery analyses in wells near

Lansdale, Pennsylvania

[Data sources: NPWA, North Penn Water Authority files, Lansdale Pa.; NGI, Nittany Geosciences

Incorporated, 1988a&b, 1989, 1994a&b]

Pumped well

U.S. Geological

Survey local

number

(other identifier)

Pumping rates

(Liters/minute)

Duration of

each step

(minutes)

Maximum

drawdown

(meters)

Well loss,

percent of

drawdown

Source of

data

Step tests

Mg-1125 380 770 1,100 60 27 65 NPWA

Mg-1198 265 322 120 32 75 NGI

Mg-1199 113 155 265 300 100 12 50 NGI

Mg-1423 125 165 220 270 60 9.3 80 NGI

Recovery analyses

Mg-67 370 17,280 20 85 EPA

Mg-80 270 360 12 75 EPA

Mg-625 320 360 35 70 EPA
69

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