Land Subsidence Due To

Ground-Water Withdrawal

in the Los Banos Kettleman City Area,

California, Part 2. Subsidence and

Compaction of Deposits

GEOLOGICAL SURVEY PROFESSIONAL PAPER 437-F

Prepared in cooperation with the 

California Department of Water Resources
Land Subsidence Due To

Ground-Water Withdrawal

in the Los Banos-Kettlemari City Area,

California, Part 2. Subsidence and

Compaction of Deposits

By WILLIAM B. BULL

STUDIES OF LAND SUBSIDENCE

GEOLOGICAL SURVEY PROFESSIONAL PAPER437-F

Prepared in cooperation with the 

California Department of Water Resources

UNITED STATES GOVERNMENT PRINTING OFFICE, W AS H I NGTO N : 1 975
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Bull, William B. 1930-

Land subsidence due to ground-water withdrawal in the Los Banos-Kettleman City area, California.

(Studies of land subsidence) (Geological Survey Professional Paper 437-E-G)

Pt. 2 by W. B. Bull; pt. 3 by W. B. Bull and J. F. Poland.

Includes bibliographies and indexes.

CONTENTS: pt. 1. Changes in the hydrologic environment conducive to subsidence. pt. 2. Subsidence and compaction 

of deposits, [etc.]

Supt. of Docs. No.: I 19.16:437-F 

1. Subsidences (Earth movements) California San Joaquin Valley. 2. Aquifers California San Joaquin Valley. 3.

Water, Underground California San Joaquin Valley. I. Miller, Raymond E. II. Poland, Joseph Fair-field, 1908- III.

California. Dept. of Water Resources. IV. Title. V. Series. VI. Series: United States. Geological Survey. Professional

Paper 437-E-G. 

QE75.P9 No. 437-E-G [GB485.C2] 557.3'08s [551.3'5] 74-28239

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402

Stock Number 024-001-02610
CONTENTS

Page

Glossary ______________________________ V

Abstract _____________________________ Fl

Introduction ______________________________ 1

Purposes ___________________________ 2

Acknowledgments______________________ 2

Subsidence of the land surface ___ ______ _______ _ 2 

Sources of vertical-control data _______________ 4 

Topographic mapping program of the U.S. Geological

Survey ________________________ 4 

Bench-mark survey program of the U.S. Coast and Geodetic Survey ____________________ 4 

Changes in the altitude of the land surface _________ 6 

Tectonic movements____________________ 7 

Apparent uplift of Anticline Ridge, 1962-63 __ 7 

Subsidence due to withdrawal of petroleum ______ 8 

Near-surface subsidence _________________ 8 

Subsidence due to withdrawal of ground water ___ 10 

Extent and magnitude of subsidence in the Los

Banos-Kettleman City area _________ 10 

History of subsidence _______ _________ 19 

Rate of subsidence _________________ 22

Compaction of the ground-water reservoir ___________ _ 29

Field measurements of compaction _________ ____ 29

Types of compaction gages used ____________ 29

Analysis of friction in a compaction recorder _____ 31

Cumulative compaction at multiple compaction-recorder

sites __________________________ 33 

Cumulative compaction at single compaction-recorder

sites __________________________ 36 

Unit compaction at the multiple compaction-recorder

sites __________________________ 38

Shortening and increased protrusion of well casings __ 41

Shortening of an oil-well casing __________ 42

Shortening of water-well casings __________ 43

Compaction of the ground-water reservoir Continued 

Field measurements of compaction Continued 

Shortening and increased protrusion of well

casings Continued 

Casing-failure study _____________ _ F45

Proportions of compaction occurring in the upper and lower

zones___-____________________________ 46

Geologic factors influencing compaction of the unconsolidated

deposits ________________________________ 49

Local relations ____________________ 49

Overburden load _______________ 49 

Petrology________________________ 51

Bedding ____________________________ 54 

Sierra flood-plain deposits __ 56 

Diablo alluvial-fan deposits ________ 57 

Diablo flood-plain deposits 57 

Sierra deltaic deposits 58 

Lacustrine deposits ____________ 59 

Lateral extent __ _ _____ _____ 59

Comparison of bed-thickness factors 60

Compaction characteristics _______________ 62

Regional relations __________________ 63

Age of the deposits ____________ -_ 63 

Specific unit compaction of the lower-zone deposits __ 64 

Geologic factors influencing specific unit compaction_______________ 67

Prior total applied stress ________ _ 67 

Stress-compaction products _____ 70 

Mean lithology _______________ 76

Source and mode of deposition ___ 79

Variation in excess pore pressure ________ 82

Distribution of well-casing failures ______ 83

Summary and conclusions ___________ 84

References __________ 87

Index __________________________________ 89

ILLUSTRATIONS

FIGURE

 Page

1. Map showing bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in

this report __________________________________________________________ F3

2. Map showing level-line network of the U.S. Coast and Geodetic Survey, 1963 __________________ 5

3. Maps showing extent and times of principal leveling by the U.S. Coast and Geodetic Survey ______ 8

4. Graph showing apparent net uplift of Anticline Ridge along State Highways 33 and 198, between March 1962 and

March 1963_____________________________________________________________ 8

5. Graph showing change in altitude of bench marks in Pleasant Valley (T156), Anticline Ridge (W156), and the west

edge of the San Joaquin Valley (Y156), 1933-66 __________________________________ 8 

6-13. Maps showing:

6. Location of oil and gas fields in western Fresno County ____________ 9

7. Areas of major land subsidence in the San Joaquin Valley, as of 1963 _____________ _____ 11

8. Land subsidence due to artesian-head decline, 1920-28 to 1943 ______________________ 12

9. Land subsidence, 1920-28 to 1966 __________________________________ _____ 13 

Land subsidence due to artesian-head decline, 1943-59 ____________________ _ 15 

Land subsidence, 1955-56 ________________ ___________ ___-_ ____ ____ 16 

Land subsidence, 1959-63 ________________________________________ _____ 17 

Land subsidence, 1963-66 ________________________________________ ______ 18

ill

10.

11.

12.

13.
IV CONTENTS

Page

FIGURE 14. Graph showing distribution of intensity of subsidence, 1920-28 to 1966 _________ _________________ _ F19

15. Graphs showing subsidence for selected bench marks _____________________________ --- ---- 20

16. Profile of subsidence that has occurred since 1943, Tumey Hills to Mendota ______________ __ -___ - 21

17. Profile of subsidence that has occurred since 1943, Anticline Ridge to Fresno Slough __________________ 22

18-21. Maps showing:

18. Average yearly rate of subsidence, 1959-63 ______________-____-______ - - _ 23

19. Average yearly rate of subsidence, 1963-66 ___________________________________ __ 24

20. Change in rate of subsidence between the 1943-53 and 1959-63 periods.________ ___ 25

21. Change in rate of subsidence between the 1959-63 and 1063-66 periods_______________________ _ 27

22. Graphs showing subsidence rates for selected bench marks __________________ ________ _ ____ 28

23. Diagram of recording compaction gage ______________________________________________ 29

24. Diagrammatic sketch of a compaction-recorder system with casing-cable friction _________ __ ______ 32

,25-35. Graphs showing:

25. Interpolation of part of the cumulative compaction record from well 16/15-34N1 ______ _ ____ 32

26. Compaction and subsidence at the Oro Loma site, 1958-66, and Mendota site, 1961-66 _ 34

27. Compaction and subsidence at the Cantua site, 1958-66 __________________ __ 35

28. Decrease in the percentage of subsidence measured in the 0-2,000-foot depth interval at the Cantua site,

1959-67 ____-___________________________________________________ 35

29. Compaction and subsidence at the Westhaven site, 1962-66, and well 13/12-20D1, 1961-66 _________ 36

30. Compaction and subsidence at well 19/16-23P2, 1959-66 _____________________ __ 37

31. Mean annual unit compaction in three depth intervals at the Oro Loma site for 2-year periods, 1960-65 _ 38

32. Mean annual unit compaction in two depth intervals at the Mendota site for 2-year periods, 1962-65 ___ 39

33. Mean annual unit compaction in three depth intervals at the Cantua site for 2-year periods, 1960-65- 40

34. Unit compaction in three depth intervals at the Westhaven site for 1-year periods, 1963-65 ____ 40

35. Decrease in annual compaction for selected depth intervals at multiple compaction-recorder sites 40

36. Photograph showing compressional rupture of an irrigation-well casing _______________ _ __. 41

37. Graph showing relation of increased casing protrusion to casing diameter for observation wells that are not gravel

packed ______________________________________________________________ 42

38. Diagrammatic sketch of wells used for measuring water levels and compaction, wells 20/18-11Q2 and 11Q3 _ __ 42

39. Photograph showing compaction gage and casing separation at wells 20/18-11Q2 (inner casing) and 11Q3 (outer

casing) __________________________________________________________________________________ 43

40-44. Graphs showing:

40. Shortening of 11%-inch casing, wells 20/18-11Q2 and 11Q3 __________________ __________ 44

41. Subsidence of well bench marks and reference bench marks within 17-193 feet of the well bench mark 45

42. Effect of pumping on differences of changes in altitudes of reference and well bench marks 45

43. Unit casing-failure ratio for 50-foot intervals above and below the Corcoran Clay Member of the Tulare

Formation __ __ ____ _ ___ ____ ______ _____ ______ __ ______ _ _ _______ _ _ 46

44. Comparison of unit compaction at the Mendota, Cantua, and Westhaven sites and unit casing-failure ratios

in the same depth intervals of nearby irrigation wells _________ __ _ 47

45. Map showing proportions of compaction occurring in the upper and lower water-bearing zones ____ _ __ 50

46. Graphs showing relation of applied stress, sorting, and particle size on void ratio and porosity of selected suites of

samples of alluvial sediments from three core holes in the Los Banos-Kettleman City area _ _ __ 52

47. Electric log of the deposits at well 18/19-20P1 ____________________________________________ 55 

48-52. Graphs showing bedding, lithology, and vertical permeability:

48. Sierra flood-plain deposits, Cantua site, depth 978-1,134 feet _________ _ 56

49. Diablo alluvial-fan deposits, Mendota site, depth 350-500 feet __________________ __ 57

50. Diablo flood-plain deposits, Mendota site, depth 1,040-1,205 feet __________________ 58

51. Fine-grained facies of the Sierra deltaic deposits, Huron site, depth 2,000-2,114 feet ____ __ 58

52. Corcoran Clay Member of the Tulare Formation and adjacent deposits at the Mendota site, depth 600-721 feet __ 59 

53-58. Maps showing:

53. Maximum thickness of the perforated interval of the lower zone __ _ __ __ _ _ _ 65

54. Specific unit-compaction for the lower water-bearing zone, 1943-60 ________ __ 66

55. Depth to the middle of the lower zone________i_________________________-___ 68

56. Applied stress due to the>unsaturated condition of the deposits above the water table as of 1951 ___ __ 69

57. Seepage stress on the lower zone as of 1943 _______________ ___ --- -------- 71

58. Total applied stress on the middle of the lower zone as of 1943 __________ _ ___ _ 72

59. Graph showing reduction of the effect of variable effective stress through use of compressibility-effective stress

products for core samples from the Cantua site ______________ ___ __ 73

60. Map showing variations in stress-compaction products __________________ __ _ _ 75

61. Lithofacies map based on the mean corrected resistivities of the lower zone ____________ _ __ 78

62. Graph showing variation in mean particle size with depth for alluvial deposits below the Corcoran in cores from the

Mendota and Huron sites _____________________________________ __ 79

63. Graphs showing relation of mean corrected resistivity to the product of specific unit compaction and total applied

stress, lower zone ________________________________________ __________ ___ 79

64. Map showing relation of stress-compaction products to the sources and modes of deposition of the lower-zone deposits _ 80
CONTENTS V

Page

FIGURE 65. Section showing relation of stress-compaction products to types of lower-zone deposits _______ ___________ F81 

66. Graph showing relation of well-casing failures to hydrologic unit and type of adjacent deposit ___ ___ 84

TABLE

TABLES

Page

1. Summary of compaction-recorder installations ___ _____ ____________________ -- __ - F31

2. Annual compaction rates at multiple compaction-recorder sites __ __ __ ___ __ __ _______ 38

3. Variation in the deepest annual water levels for selected depth zones at the multiple compaction-recorder sites,

1959-63 _____________________________________________________ _________ 41

4. Proportions of compaction occurring in the upper and lower water-bearing zones _________ - 48

5. Amount of clay in deposits from Diablo and Sierra sources in the Mendota, Cantua, and Huron cores __ _ _ 53

6. Mean vertical permeabilities of the different types of deposits as determined from consolidation tests of samples in the

load range 400-800 Ib in~2 at the four core-hole sites __ __ _____ __ __ __ 56

7. Summary of lower-zone weighted mean bed -thickness factors of aquitards for types of deposits and Inter- Agency Committee core-hole sites ___ _____ _____ ___ ___ __ __ _____ __ _________ _ - 60

8. Weighted mean bed-thickness factors of aquitards for lower-zone deposits at Inter-Agency Committee core-hole sites 61

9. Mean consolidation characteristics of the Corcoran and the different types of lower-zone deposits in the load range

400-800 Ib in~2 __ _______ _ _______________ _ ______________________________ 62

GLOSSARY

The geologic and engineering literature contains a variety of terms 

that have been used to describe the processes and environmental 

conditions involved in the mechanics of stressed aquifer systems and 

of land subsidence due to withdrawal of subsurface fluids. The usage of 

certain of these terms in reports by the U.S. Geological Survey research staff investigating mechanics of aquifer systems and land 

subsidence is denned and explained in a glossary published separately 

(Poland and others, 1972). Several terms that have developed as a 

result of the Survey's investigations are also denned in that glossary.

The aquifer systems that have compacted sufficiently to produce 

significant subsidence in California and elsewhere are composed of 

unconsolidated to semiconsolidated clastic sediments. The definitions 

given in the published glossary are directed toward this type of sediments; they do not attempt to span the full range of rock types that 

contain and yield ground water. In denning the components of the 

compacting stresses, the contribution of membrane effects due to 

salinity or electrical gradients has been discounted as relatively 

insignificant in the areas studied.

In our research reports, pressures or stresses causing compaction 

are usually expressed in equivalent "feet of water head" (1 foot of 

water = 0.433 Ib in ~ 2 (pounds per square inch)).

A committee on redefinition of ground-water terms, composed of

 members of the Geological Survey, recently issued a report entitled

"Definitions of Selected Ground-Water Terms" (Lohman and others,

1972). The reader is referred to that report for definitions of many

ground-water terms.

Five terms used in this report which have not been defined elsewhere are given in the following list.

APPARENT COMPRESSIBILITY. A time-dependent parameter 

derived from field observations that indicates the amount of shortening, per unit thickness of deposits, per unit change in applied stress. 

Parameters such as specific unit compaction and stress-compaction 

products are apparent compressibilities because the degree to which 

applied stresses have become effective is not known. 

COMPRESSIBILITY-EFFECTIVE STRESS PRODUCT. The product of compressibility and effective stress, as determined by laboratory consolidation tests. The resulting product is a true compressibility for which the effects of variable effective stress have been largely 

eliminated.

^CRITICAL DEPTH. The depth below which friction between the 

casing and the adjacent deposits exceeds the shear strength of the 

casing.

STRESS-COMPACTION PRODUCT. An apparent compressibility 

for which the effect of prior total applied stress has been removed. In 

this paper, the stress-compaction product was computed by multiplying specific unit compaction by total applied stress. The resulting 

product is only an apparent compressibility of the deposits, because 

the degree to which applied stresses have become effective is not 

known.

SUBSIDENCE, NEAR-SURFACE. The vertical downward movement of the land surface that occurs when moisture-deficient deposits 

compact as they are wetted for the first time since burial (Bull, 1964a).

STUDIES OF LAND SUBSIDENCE

LAND SUBSIDENCE DUE TO GROUND-WATER WITHDRAWAL

IN THE LOS BANOS KETTLEMAN CITY AREA, CALIFORNIA,

PART 2. SUBSIDENCE AND COMPACTION OF DEPOSITS

By WILLIAM B. BULL

ABSTRACT

Pumping of ground water has increased the stresses tending to 

compact unconsolidated deposits by as much as 50 percent, thereby 

creating the world's largest area of intense land subsidence in the 

west-central San Joaquin Valley, Calif. As of 1966,2,000 square miles 

had subsided more than 1 foot, and the area that had subsided more 

than 10 feet was 70 miles long. Maximum subsidence was 26 feet. 

Subsidence rates increased until the mid-1950's when the maximum 

observed rate was 1.8 ft yr~* (feet per year), but have decreased since 

then. During the 1963-66 period the maximum subsidence rate was 

only 1.1 ft yr .

Subsidence due to artesian-head decline is of greater extent and 

magnitude than three other types of subsidence in the area. Tectonic 

subsidence is difficult to separate from other types of subsidence. Net 

uplifts of less than 0.1 foot have occurred at three places at the front of 

the Diablo Range. Subsidence due to pumping of petroleum appears to 

be minor. The Coalinga oil field subsided only 0.25 foot in 20 years. 

About 120 square miles adjacent to the Diablo Range is susceptible to 

near-surface subsidence, where compaction due to wetting of 

moisture-deficient alluvial-fan deposits has caused as much as 15 feet 

of subsidence. Subsidence of 3-10 feet is common.

Subsidence due to artesian-head decline occurred first in the northern part of the area, where, by 1943, subsidence was as much as 10 

feet. By 1963, 20 feet of subsidence had occurred in both the northern 

and southern areas. Maximum subsidence, as of 1968, was estimated 

to be 28 feet.

Special compaction recorders in wells penetrating most of the 

aquifer system tapped by wells initially measured as much as 99 

percent of the subsidence. Since 1963, most recorders have been 

measuring progressively less of the subsidence, which indicates that 

compaction due to pore-pressure decline is occurring at greater depths 

than previously.

Unit compaction of as much as 1.2 x 10 feet per foot per year has 

been measured at the Cantua site. Casing-failure distribution indicates that amounts of unit compaction increase to depths of roughly 

200 feet below the Corcoran Clay Member of the Tulare Formation in 

response to progressively larger head declines with depth. Below a 

depth of about 200 feet below the Corcoran, unit compaction decreases 

with depth, probably in response to minimal change of head decline 

with depth and to the decreasing compressibilities of the deposits 

caused by progressively greater prior effective stresses.

Compaction mainly shortens water-well casings, but also causes 

increased casing protrusion above the land surface of as much as 10 

percent of the compaction. Bench marks within 17-193 feet of active 

irrigation wells subside less than the tops of the well casings despite 

increased casing protrusion. Maximum compaction occurs at pumping wells, because they are points of maximum applied stress.

In most of the area about 70-95 percent of the compaction occurs in 

the lower zone below the Corcoran confining bed. As much as 30-40 

percent of the compaction occurs in the upper zone in the southern 

part of the area.

Geologic factors that cause differences in specific unit compaction 

include total applied stress, lithofacies, and source and mode of 

deposition factors that were assessed by removing the effect of prior 

load. The specific unit compaction of the lower-zone deposits, 1943-60, 

in the northern part of the area is four times that in the central and 

southern parts of the area, suggesting a marked difference in the 

compressibility of the deposits. About one-third of the apparent difference in compressibilities between the northern and southern areas is 

real and is due to differences in total applied stress prior to 1943. 

Deeply buried deposits that have been subjected to large prior applied 

stresses are less compressible, per unit of additional stress increase, 

than are deposits at moderate depths.

The other two-thirds of the compressibility difference is only apparent and is attributed chiefly to hydraulic differences between genetic 

types of deposits that affect the rate of expulsion of water from 

aquitards for a given applied-stress increase. When compared with 

the Diablo (derived from Diablo Range) and Sierra (derived from 

Sierra Nevada) flood-plain deposits, the Diablo alluvial-fan deposits 

have a higher clay content and are more poorly sorted, which results 

in lower permeabilities and slower consolidation rates. Fine-grained 

beds generally are thicker in the lacustrine and fan deposits than in 

the flood-plain deposits. (Respective mean bed-thickness factors are 

61, 24, and 14, where bed-thickness factor is (aquitard thickness/2)2 ). 

Thus, conditions in the alluvial-fan aquitards in the southern part of 

the area and thick lacustrine sequences in the central part of the area 

are favorable for development of large residual excess pore pressures 

and high values of ultimate specific unit compaction. These same 

conditions also are responsible, in part, for the lower apparent compressibilities (stress-compaction products) during the 1943-60 period 

in the areas of thick alluvial-fan and lacustrine deposits than in the 

areas of thick flood-plain deposits.

Variations in the mean lithology (corrected mean resistivities) of 

the lower zone are not as important as either prior overburden load or 

mode of deposition in determining the apparent compressibilities of

the deposits.

INTRODUCTION

By increasing the stress tending to compact the unconsolidated deposits by as much as 50 percent, man has 

created the world's largest area of intense land subsidence in the west-central San Joaquin Valley. Withdrawal of ground water for agriculture has caused more 

than 2,000 square miles to subside more than 1 foot. As

Fl
F2 STUDIES OF LAND SUBSIDENCE

of 1966, the area that had subsided more than 10 feet 

was 70 miles long, and the maximum subsidence was 26 

feet. The land subsidence, compaction of the saturated 

deposits that caused the subsidence, and the geologic 

factors influencing the compaction which are the topics of this paper will be presented for one of four major 

areas of intense land subsidence due to ground-water 

withdrawal in California.

This paper is the second of three reports discussing 

land subsidence due to ground-water withdrawal in the 

Los Banos-Kettleman City area, California. Part 1 

(Bull and Miller, 1974) is a factual presentation of the 

hydrologic factors conducive to land subsidence in the 

study area. Part 3 (Bull and Poland, 1974) discusses the 

interrelations of water-level change, change in 

aquifer-system thickness, and the concurrent changes 

in land-surface altitude as well as the criteria for prediction of subsidence.

The introduction to all three parts can be found in 

Part 1 (Bull and Miller, 1974). That introduction includes descriptions of the extent of the study area and 

the geographic setting, as well as sections about the 

Inter-Agency Committee on Land Subsidence and the 

scope of the field and laboratory work for the Cooperative and Federal subsidence programs. The principal 

areas of land subsidence in California due to groundwater withdrawal and the topographic and cultural features of the Los Banos-Kettleman City subsidence area 

are shown in figures 1 and 2 of Part 1 (Bull and Miller, 

1974). For a resume of the hydrologic environment and 

the man-induced changes in the hydrologic environment, the reader is referred to the summary and conclusions of Part 1.

The boundaries of the Los Banos-Kettleman City 

study area, bench marks, observation wells, compaction 

recorders, core holes, and lines of section referred to in 

this report are shown in figure 1. The northeast boundary as shown in figure 1 is along the valley trough, but 

as of 1966, as much as 8 feet of subsidence had occurred 

east of the valley trough. Therefore, in much of the 

study, the 1-foot subsidence line (figs. 9,14) was used as 

the east boundary of the subsidence system.

The bulk of the information presented in this paper 

concerns the events before April 1966, which was a time 

of complete leveling of the bench-mark network by the 

U.S. Coast and Geodetic Survey (since 1970, the National Geodetic Survey, a component of the National 

Ocean Survey). Where post-March 1966 data are presented and discussed, it is done only to present facts or 

concepts that cannot be demonstrated with the earlier 

data.

PURPOSES

The scope of this paper is to discuss the compaction of 

unconsolidated deposits and the resulting land subsidence in the many different geologic and hydrologic 

environments present in the west-central San Joaquin 

Valley. Within this scope, the paper has three specific 

purposes. The first is to show the extent, magnitudes, 

and rates of subsidence due to artesian-head decline; to 

show the changes of these aspects during the agricultural development of the area; and to compare the extent, magnitudes, and rates of subsidence due to 

artesian-head decline with concurrent subsidence 

caused by compaction due to wetting, withdrawal of 

petroleum, and tectonic activity. The second purpose is 

to describe the measurement of compaction, the proportions of subsidence being measured by compaction recorders, and the rates and amounts of compaction occurring within specific depth intervals. The third purpose 

of this paper is to assess the geologic factors influencing 

compaction of the deposits of differing lithology, source, 

mode of deposition, and depth of burial. Both those 

geologic factors described in the literature and consideration of new factors will be included in the geologic 

appraisal of compaction.

ACKNOWLEDGMENTS

The cooperation of numerous ranchers, landowners, 

and companies is acknowledged for supplying essential 

information to the subsidence project and for giving 

permission to install and maintain wells and equipment 

for obtaining water-level and compaction information. 

Particular assistance was given by the Pacific Gas and 

Electric Co., Westlands Water District, and Russell Giffen, Inc.

The financial cooperation of the California Department of Water Resources made this study possible, and 

information provided by the U.S. Bureau of Reclamation from core holes and observation wells contributed 

significantly to the essential data.

This work could not have been completed without the 

discussions, interest, and assistance of many people 

who have been associated with the land-subsidence 

studies since 1956.1 appreciate particularly the helpful 

discussions and review of the manuscript by the project 

chief, J. F. Poland, and my colleagues, G. H. Davis, B. E. 

Lofgren, and F. S. Riley. I enjoyed working together 

with R. L. Ireland and R. G. Pugh on a variety of jobs in 

the field and appreciate their extensive help in collection and assembling of field data. Particular credit is 

due Mr. Ireland for his meticulous care and thoughtful 

foresight in the installation and operation of the equipment for recording compaction and water-level changes 

during the entire period of record.

SUBSIDENCE OF THE LAND SURFACE

Several parts of the Los Banos-Kettleman City area 

have subsided more than 20 feet, and subsidence rates
R. 10 E

LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

12 13 120°30' 14 15 16 17 120°00'

F3

37°00

_,--. ~-' ,., XH Madera

Boundary of deformed 

rocks

Boundary of the Los BanosKettleman City area

034 N1

Core hole and well number

Compaction recorder; if more than one, 

number indicated inside symbol

Observation well and well number; if more 

than one, number indicated inside symbol

Irrigation well from which water-level record has been obtained and well number

X V692

Bench mark and number 

C C'

 <±^- oW805--

Line of section or profile shown in succeeding illustrations

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 1. Bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in this report.

-1 have exceeded 1 ft yr (foot per year). The main purpose of this section is to discuss the extent, rate, and 

magnitude of subsidence due to artesian-head decline.

Three other types of subsidence also will be discussed to 

indicate their extent, rate, and magnitude in relation to 

the areas of subsidence due to artesian-head decline.
F4 STUDIES OF LAND SUBSIDENCE

SOURCES OF VERTICAL-CONTROL DATA

The two main sources of vertical-control data are 

maps made by the Geological Survey and bench-mark 

altitudes of the Coast and Geodetic Survey. The Bureau 

of Reclamation and the California Department of Water 

Resources also have surveyed bench marks along canals 

and future canal alinements.

TOPOGRAPHIC MAPPING PROGRAM 

OF THE U.S. GEOLOGICAL SURVEY

The first detailed topographic mapping of 71/2-minute 

quadrangles in the Los Banos-Kettleman City area was 

done mainly during the 1920's. Surveys for detailed 

topographic maps were made in the following periods: 

between latitudes 36°30' and 37°00', 1919-23; between 

36°15' and 36°30', 1924-28; and between 36°00' and 

36°15', 1926-33. These maps had a 5- or 10-foot contour 

interval based on planetable surveys.

The Geological Survey was first confronted with the 

subsidence problem in the Los Banos-Kettleman City 

area in 1953-54 when a map revision program was 

undertaken (Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1958, p. 33-35). Normally a revision for the purpose of bringing culture up 

to date would not present many problems. However, the 

surveyors had difficulty in closing stadia traverses and 

in reconciling topography with cultural changes. It was 

apparent that a useful topographic map for engineering 

purposes would not result from a mere cultural revision.

The situation was brought to the attention of the 

members of the Inter-Agency Committee, and it was 

agreed that completely new topographic maps were 

necessary to show the amount of subsidence that had 

occurred since the 1920's, especially for large areas between the existing level lines. The Coast and Geodetic 

Survey gave full cooperation to a coordinated program 

of establishing vertical control for the areas to be remapped topographically. The topographic mapping 

immediately followed the leveling of SeptemberNovember 1955, and 28 quadrangles were remapped 

during the winter of 1955-56; by 1962, 43 maps within, 

or partly in, the Los Banos-Kettleman City area had 

been revised and then remapped where necessary. The 

contour interval for these maps ranges from 5 to 40 feet.

A comparison of the maps made in the 1920's and the 

1950's showed that more than 10 feet of subsidence had 

occurred over large areas and that the maximum subsidence was about 18 feet in an area west of Mendota. 

Because of the large areas between level lines prior to 

1955, this comparative subsidence map is used, in part, 

for all the subsidence maps that portray subsidence 

prior to 1955. Maps that portray only post-1955 subsidence are based entirely on bench-mark control.

BENCH-MARK SURVEY PROGRAM OF THE 

U.S. COAST AND GEODETIC SURVEY

The Coast and Geodetic Survey has been the key 

agency in fulfilling the following vertical-control elements proposed by the Inter-Agency Committee on 

Land Subsidence in the San Joaquin Valley (1955, p. 

16-17).

1. Maintenance of a basic network of first-order levels 

surrounding the San Joaquin Valley, with crossties between bedrock in the Sierra Nevada, Coast 

Ranges, and Tehachapi Mountains, and to oceantide gages. (This network provides an overall 

datum and helps determine the general stability of 

the local bedrock reference points.)

2. Establishment of a network of first- and second-order 

levels within the basic network to form a base for 

topographic mapping and special surveys, which 

will provide information on the extent of subsidence areas and on the development of new subsidence areas.

3. Periodic releveling of a comprehensive network of 

lines in the areas of known major subsidence to 

define the amount and rate of subsidence. (The Los 

Banos-Kettleman City area was releveled every 2 

years between 1955 and 1959 and every 3 years 

between December 1959 and March 1966.) 

The level-line network of the Coast and Geodetic Survey is shown in figure 2, which also shows the quadrangle boundaries and numbers. Only part of the lines 

outside of the Los Banos-Kettleman City area are 

shown. Additions to this network have not been proposed except for short spur lines to compaction recorders.

The first Coast and Geodetic Survey leveling in the 

Los Banos-Kettleman City area was made in 1933 

(prior levelings were made by the Geological Survey) 

and was followed by releveling or new leveling in 1935, 

1942-43, 1947, 1948, and in every year from 1952 

through 1968 except 1956 and 1961. In some of these 

years, the extent of the leveling was small because the 

work consisted mainly of establishing bedrock ties for 

work being done outside the Los Banos-Kettleman City 

area. The extent of the eight principal levelings is 

shown in figure 3. The complete subsidence network 

that was established in 1955 has been releveled four 

times, the latest being in the winter of 1966.

Leveling accuracy is difficult in an area that subsides 

as rapidly as the Los Banos-Kettleman City area. Attainment of precise results is hindered by movement of 

reference bench marks within the mountains and by 

subsidence of bench marks during the leveling of the 

valley areas. For purposes of adjusting the results of a 

leveling program, certain bench marks set in bedrock
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F5

37°00

f ~1t» * 

112^1 I

Kl

Boundary of deformed 

rocks

Level line that usually is leveled to firstorder accuracy

Level line that usually is leveled to secondorder accuracy

U.S. Coast and Geodetic Survey quadrangle 

boundary and number. The level-line number for each quadrangle is that published 

by the Coast and Geodetic Survey. Some 

line numbers change at quadrangle 

boundaries

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 2. Level-line network of the U.S. Coast and Geodetic Survey, 1963.

within the mountains are regarded as stable (not undergoing changes in altitude). It is important to tie the

subsidence network to bench marks set in bedrock at 

several places because, in general, bench-mark move-
F6 STUDIES OF LAND SUBSIDENCE

Los Banos

1943

December 1942-April 1943

Kettleman City

Los Banos

1947

February-May

Kettleman City

Los Banos

1953

December 1952-February 1953

Kettleman City D

Los Banos

1954

February-July

Kettleman City

Los Banos 1955

September-November

Los Banos

1957

January-May

Kettleman City

Los Banos 1959

November 1959- 

January 1960

Los Banos 1963, 1966

February-April

Kettleman City Kettleman City

Kettleman City'* \-J

10 20 MILES

FIGURE 3. Extent and times of principal leveling by the U.S. Coast and Geodetic Survey.

ment in the mountains is minor compared to the settlement of areas of active land subsidence. Even the stable 

bench marks may undergo changes in altitude due to 

tectonic movement or to mass movements such as soil 

creep. Evidence presented in the next section suggests 

that some of the bench marks in the mountains may 

have been uplifted tectonically about 0.1 ft yr (fig. 4). 

Even outside control brought into the area may be complicated by natural or man-induced subsidence of 

tidal-gage reference bench marks.

The rate of subsidence due to artesian-head decline 

varies with both time and place. The times of most 

active subsidence are associated with the times of maximum head decline, or maximum rates of head decline, 

of the lower zone, which commonly are in March and 

June-September. During the times of maximum applied 

stress, 0.001-0.004 foot of subsidence occurs each day 

throughout most of the area. The best time to level the

Los Banos-Kettleman City area is between October and 

February because during this period the potentiometric 

levels are rising or are declining slowly from the winter 

high water levels. If leveling must be scheduled during 

the times of most rapid subsidence, it may be advisable 

to level those areas of most intense subsidence by 

second-order, rather than by first-order, methods. Less 

time is needed for second-order leveling; therefore, the 

cumulative error caused by subsidence between times of 

leveling ties to stable bench marks will be less.

CHANGES IN THE ALTITUDE OF THE LAND. SURFACE

In addition to subsidence due to the withdrawal of 

ground water, changes in land-surface altitude in the 

study area are caused by tectonic movements, withdrawal of petroleum, and application of irrigation water 

to dry clayey alluvial-fan deposits.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F7

TECTONIC MOVEMENTS

Pronounced uplift and subsidence caused by tectonic 

forces have occurred in the study area during the Late 

Quaternary. These movements are continuing, but are 

small in rate and are hard to discern from changes in the 

altitude caused by man's activities.

Both the Diablo Range and the west edge of the San 

Joaquin Valley have been subject to intermittent uplift 

which culminated in the Coast Range orogeny in the 

Pleistocene Epoch. The Coast Range orogeny was preceded by several periods of uplift (Taliaferro, 1943, p. 

151-158), one or more of which resulted in the deposition of the Tulare Formation of Pliocene and Pleistocene 

age. The orogeny resulted in the monoclinal and anticlinal folds that form the foothill belt east of the main 

Diablo Range (Bull, 1964b, p. 93). Remnants of the 

Tulare Formation capping the foothills and the folding 

of the Pleistocene Corcoran Clay Member of the Tulare 

Formation to 45° (Carpenter, 1965) attest to the magnitude of the uplift.

In the San Joaquin Valley, the western parts of the 

Corcoran were raised several hundred feet relative to 

the Corcoran east of the trough of the valley. The Corcoran and associated sediments have been folded gently 

throughout much of the area. The structure on the top of 

the Corcoran is described in detail by Miller, Green, and 

Davis (1971, fig. 11).

Uplift of the mountains has continued since the formation of the foothill belt to at least 3,000 years ago. 

Detailed studies of stream terraces and segmented alluvial fans (Bull, 1964b) show that the uplift was intermittent both in time and place and that the zone of 

maximum differential uplift generally was near the 

mountain front.

Large-scale subsidence of the San Joaquin Valley 

geosynclinal trough was concurrent with the deposition 

of several thousand feet of continental deposits after the 

ocean receded in the Pliocene Epoch. The rates of deposition were rapid. More than 900 feet of deposits accumulated in the Tulare Lake basin and elsewhere in 

the Los Banos-Kettleman City area in the 600,000 

years (Janda, 1965) after the pluvial period associated 

with the Corcoran. Tulare Lake has remained a basin of 

interior drainage despite the rapid accumulation of 

fine-grained deposits (Davis and Green, 1962), and 

deep-seated subsidence and compaction have moved the 

top of the Corcoran to more than 700 feet below present 

sea leveL_

The facts that 900 feet of deposits have accumulated 

in parts of the Tulare Lake basin since Corcoran time 

and that it is still a basin of interior drainage indicate a 

large tectonic subsidence. The 600,000-year age for the 

deposits immediately above the Corcoran indicates a

mean post-Corcoran depositional rate of about 1.5 feet 

per 1,000 years. Assuming the topographic features of 

the basin were the same as at present, the room for the 

900 feet of deposits would be caused by subsidence of the 

bedrock floor under the basin and to a lesser extent by 

post-Corcoran compaction of the deposits between the 

bedrock floor and the top of the Corcoran.

Regional tectonic subsidence probably is continuing 

in the San Joaquin Valley, but the rate is so small that it 

cannot be differentiated from the rapid subsidence due 

to artesian-head decline.

Present-day tectonic movement of the mountain front 

was evaluated on the basis of leveling data. Two approaches were used changes in the adjusted altitudes 

of individual bench marks were studied and changes in 

the unadjusted altitudes of pairs of bench marks were 

compared. Neither approach indicated net uplifts in 

excess of 0.1 foot during the history of leveling. Tectonic 

analysis is complicated by the fact that most, if not all, 

of the mountain-front area has been affected by minor 

amounts of subsidence due to man's activities.

Adjusted leveling results suggest minor net uplifts 

between certain periods of leveling at the mountain 

front of the Laguna Seca Hills, near the mountain front 

at Little Panoche Creek, and on Anticline Ridge. The 

amounts of apparent uplift are not listed because values 

of uplift of less than 0.1 foot may be within the amount 

of survey error in a subsidence region. These three sites 

are mentioned as areas of possible tectonic uplift on the 

basis of several lines of evidence, such as is presented in 

figures 4 and 5. Bench marks at all these sites show a 

net subsidence over the entire period of record, and net 

uplift is suggested only for one to three periods between 

levelings. Subsidence due to withdrawal of ground 

water is lowering the bench marks near the Laguna 

Seca Hills; subsidence due to application of water is 

affecting the areas near the mouth of Little Panoche 

Creek; and subsidence due to withdrawal of petroleum 

is affecting the Anticline Ridge area.

Adjusted leveling results for bench marks on lines 

crossing the mountain front indicate that net subsidence, in amounts of less than 1 foot, has occurred in the 

mountains near the mountain front at Warthan Canyon, Cantua Creek, Monocline Ridge, and Panoche 

Creek. With the exception of Warthan Canyon, these 

are areas of known tectonic uplift in the recent geologic 

past, and the present subsidence is most likely related 

to the withdrawal of ground water in the adjacent San 

Joaquin Valley.

APPARENT UPLIFT OF ANTICLINE RIDGE, 1962-63

Between March 1962 and March 1963, several bench 

marks on the crest of Anticline Ridge rose almost 0.1
F8 STUDIES OF LAND SUBSIDENCE

foot. The variation in the amount of altitude change 

along the highway crossing Anticline Ridge is shown in 

figure 4. The uplift was at a maximum at the crest and 

decreased toward the northeast and southwest flanks of 

the anticline. Bench marks in Pleasant Valley and the 

San Joaquin Valley subsided during the same period, 

although two bench marks adjacent to Anticline Ridge 

in Pleasant Valley underwent minor amounts of net 

uplift. The model used for movement occurring during a 

single year is one of "locked in" strain in an active 

structural element strain that is released occasionally 

during short time periods.

, Ul

I uli

I * 

o oc

+0.10 

+0.08 

+ 0.06 

+0.04 

+0.02 

0.00

-0.02

-0.04

W156

V156 J929

X156

San - 

Joaquin 

Valley

Y944

T156

4 6 

DISTANCE, IN MILES

FIGURE 4. Apparent net uplift of Anticline Ridge along State Highways 33 and 198, between 

March 1962 and March 1963.

Bench-mark graphs showing changes in altitude in 

Pleasant Valley, Anticline Ridge, and the west edge of 

the San Joaquin Valley are shown in figure 5. All three 

graphs show a net subsidence for the period of record, 

but the graphs for bench marks Y156 and T156 do not 

show a decrease in the subsidence rate for the 1962-63 

period. Therefore, the marked reversal in trend shown 

by W-156 and four other bench marks on the crest of the 

anticline is not the result of the 1963 leveling being in

1933 1940 1950 1960 1968

FIGURE 5. Change in altitude of bench marks in Pleasant Valley (T156), Anticline Ridge 

(W156), and the west edge of the San Joaquin Valley (Y156), 1933-66.

error by an amount equal to the net amount of uplift. 

The graphs also indicate that the amount of measured 

surface uplift is less than the true amount of tectonic 

uplift because of continuing long-term compaction.

SUBSIDENCE DUE TO WITHDRAWAL OF PETROLEUM

Some areas of intense land subsidence are associated 

with withdrawal of petroleum (Poland and Davis, 

1969). Many oil and gas fields are adjacent to the Los 

Banos-Kettleman City area, but, of the large fields, 

only the 11-mile-long Helm field occurs entirely within 

the study area. The location and extent of the areas of 

petroleum production are shown in figure 6.

The amounts of subsidence due to withdrawal of petroleum appear to be minor, but are difficult to differentiate from the subsidence due to withdrawal of water 

that occurs within or adjacent to the oil-producing 

areas. Bench mark W156, in the Coalinga oil field, subsided 0.26 foot between 1943 and 1962 (fig. 5). Part of 

the subsidence of bench marks east of bench mark W156 

may be the result of withdrawal of ground water by 

wells tapping the Tulare and Etchegoin Formations in 

the adjacent San Joaquin Valley. Bench mark W156, 

however, is situated on the Jacalitos Formation, which 

is stratigraphically below the formations tapped for 

ground water. Because the bench mark is within the 

Coalinga oil field, it is presumed that most of the net 

subsidence is the result of extraction of petroleum.

NEAR-SURFACE SUBSIDENCE

The extent and magnitude of near-surface subsidence 

in the Los Banos-Kettleman City area are exceeded 

only by the subsidence due to artesian-head decline. 

Near-surface subsidence is the result of application of 

water to clayey moisture-deficient alluvial-fan deposits. 

Because compaction due to wetting occurs above the 

water table, it is independent of the subsidence due to 

artesian-head decline. As of 1964, near-surface subsidence had occurred in about 90 square miles or about 6 

percent of the Los Banos-Kettleman City area (fig. 9). 

An additional 30-40 square miles, mainly upslope from 

the areas of known near-surface subsidence, probably 

would subside if irrigated. The upslope and middle parts 

of the small fans susceptible to this type of subsidence 

have about the same magnitude of potential subsidence, 

but the amount of subsidence generally decreases from 

the middle to the lower parts of the fans.

More than 500 square miles of the study area was 

subject to prehistoric near-surface subsidence resulting 

from intermittent streamflow on the large alluvial fans 

of streams that head in the main Diablo Range (Bull, 

1972).

Near-surface subsidence characteristically varies 

markedly within short distances; it has destroyed or 

damaged ditches, canals, roads, pipelines, electric-
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F9

37°00' 

36°30' 

36° 00

Location and name of oil 

or gas field

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 6. Location of oil and gas fields in western Fresno County. (From California Division of Oil and Gas, 1960).

transmission towers, and buildings and has made the 

irrigation of crops difficult. Subsidence of 3-5 feet is 

common, and 10-15 feet of subsidence has occurred

within small areas. The rate of subsidence is as much as 

0.25 foot per day and is controlled partly by the rate at 

which the water front advances through the deposits.
F10 STUDIES OF LAND SUBSIDENCE

Subsidence cracks which are typical of this type of 

subsidence are vertical fissures that may or may not 

have offset of the bedding on opposite sides of the crack.

Near-surface subsidence results chiefly from the 

compaction of deposits by an overburden load as the clay 

bond supporting the deposits is weakened by water percolating through the deposits for the first time since 

burial. Two requirements are necessary for compaction 

due to wetting to occur: first, that after much of the 

water has been removed from the deposits by evapotranspiration, the moisture-deficient state of the deposits be maintained by absence of percolation of water 

from rainfall or streamflow as the deposits are buried to 

progressively greater depths; second, that the deposits 

have enough clay so as to undergo a decrease in compressive strength when they are wetted for the first time 

after burial. Most of the known compaction due to wetting has occurred in the upper 200 feet of deposits.

The amount of subsidence is dependent mainly on the 

overburden load, natural moisture conditions, and the 

amount and type of clay in the deposits. Test-plot data 

show that the compaction due to wetting varies directly 

with amount of overburden load under uniform gross 

lithologic and moisture conditions (Bull, 1964a, p. 48).

The type, amount, and moisture condition of clay 

influence the amount of subsidence. The predominant 

clay mineral in the subsiding fans is montmorillonite 

(Meade, 1967, fig. 14), which is stronger, at a given 

moisture content, than other clay minerals (Trask and 

Close, 1958).

Small fans (derived from the foothill belt of the Diablo 

Range) that are susceptible to subsidence usually have 

higher clay contents than nonsubsiding fans of the same 

size. The clay is derived from the marine sedimentary 

rocks of the Diablo Range. Soft clay-rich rocks predominate in the drainage basins of subsiding fans; there, 

they underlie an average estimated 67 percent of the 

area as compared to an average 38 percent for the 

drainage basins of nonsubsiding fans.

Fan deposits with low clay contents do not have 

enough dry strength to preserve voids supported by a 

sparse clay binder as the overburden load increases 

naturally; moreover, deposits with high clay contents 

do not compact much because the clay, even when wetted, partly supports the voids and because the clay 

swells. Maximum compaction due to wetting occurs at 

intermediate clay contents (Bull, 1964a).

Detailed studies of near-surface subsidence, the deposits that compact when wetted, and the source areas 

of the deposits have been made by Bull (1964a), and 

prehistoric near-surface subsidence is described by Bull 

(1972). Other studies, in conjunction with the planning 

and construction of the San Luis Canal section of the 

California Aqueduct, have been made by the California

Department of Water Resources and the Bureau of Reclamation. As a result of these various studies, the deposits along the route of the San Luis Canal section of 

the California Aqueduct that were believed to be susceptible to compaction due to wetting were preconsolidated by ponding.

SUBSIDENCE DUE TO WITHDRAWAL OF GROUND WATER

About a third of the San Joaquin Valley is subsiding 

because of ground-water withdrawals. The three principal subsidence areas are between the towns of Los 

Banos and Kettleman City, Tulare and Wasco, and 

Arvin and Maricopa (fig. 7).

The extent and the magnitude of the subsidence as of 

1962-65 are shown in figure 7. The total area within the

1-foot subsidence line is about 3,800 square miles. The 

Los Banos-Kettleman City area is not only the largest 

but is the most intense of the three subsidence areas 

 subsidence has exceeded 20 feet, as compared with a 

maximum of 12 feet for the Tulare-Wasco area, and 8 

feet for the Arvin-Maricopa area. In general, the boundaries of the three areas coincide with the areas of 

pumpage from confined and semiconfined aquifer systems. Since 1955, the rate of subsidence has been accelerating in the vicinity of Hanford, between the Los 

Banos-Kettleman City and Tulare-Wasco areas. 

Post-1963 leveling indicates that the rate of subsidence 

has increased along the trough of the valley for 20 miles 

north of Mendota and that much of this area has subsided more than 1 foot.

EXTENT AND MAGNITUDE OF SUBSIDENCE IN THE 

Los BANOS-KETTLEMAN CITY AREA

The two periods of topographic mapping and the 

many relevelings of bench marks in the area permit 

assessment of the changes of the extent, magnitude, and 

rate of subsidence. Many subsidence maps have been 

made, but only the most pertinent maps are included in 

this report.

The extent and magnitude of the early subsidence in 

the area are shown in figure 8, which was compiled by 

subtracting the 1943-59 subsidence from the 1920-28 

to 1959 subsidence. The area of intense subsidence west 

of Mendota was mapped topographically in 1920, and 

about three-fourths of the area within the 2-foot 

subsidence line of figure 8 was mapped in 1920-21. The

2-foot subsidence line is close to, and parallels most of, 

the south, east, and north boundaries of the area 

irrigated with ground water as of 1937-42 (Pt. 1, Bull 

and Miller, 1974, fig. 21). Along the west side of the 

irrigated area, the 2-foot line is 2-6 miles west of the 

boundary of land that was being irrigated in 1937-42. 

In contrast to the 10 feet of subsidence that had 

occurred in the northern part of the area, little
121°

LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°

Fll

119 C

37° -

36° -

35° 

San Luis 

Reservoir

Hanford 

1933-62

EXPLANATION

Outline of valley

Drawn chiefly on boundary 

of consolidated rocks

Line of equal subsidence

Dashed where approximately lo 

cated. Interval, in feet, variable

California Aqueduct 

1933-62

Period of vertical control 

Compiled from leveling of the 

U.S. Coast and Geodetic Survey 

and topographic mapping by 

U.S. Geological Survey

10 20 30 40 KILOMETRES o Wheeler Ridge

FIGURE 7. Areas of major land subsidence in the San Joaquin Valley, as of about 1963. (From Poland and Evenson, 1966.)

subsidence had occurred as of 1943 in the southern part, 

where agricultural development was limited. Even in 

the largest area irrigated with ground water, subsidence was minor. For example, bench mark PTS21S, 

north of Westhaven, subsided only 1.2 feet between 

1923 and 1947.
F12 STUDIES OF LAND SUBSIDENCE

120° 30' 120°00'

37°00'-

River \ ,'

Madera

EXPLANATION

Boundary of deformed 

rocks

Line of equal subsidence 

Interval 2 feet. Compiled as the difference 

between the 1943-1959 subsidence map 

(fig. 10 ) and the 1920-28 to 1959 subsidence map (compiled chiefly as the sum 

of (1) a comparison of topographic mapping by the U.S. Geological Survey done 

between 1920 and 1928 and in 1955 and 

(2) leveling of the U.S. Coast and Geodetic Survey in 1955 and 1959). The 

estimated near-surface subsidence component has been subtracted from total 

subsidence

Coalinga

VALLEY

15 KILOMETRES

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 8. Land subsidence due to artesian-head decline, 1920-28 to 1943.

The date 1920-28 was used for figure 8 and the 

1920-28 to 1966 map because nearly all the areas of 

early subsidence were surveyed between these dates.

The areas that were mapped prior to 1920 never have 

subsided much, and the areas first mapped between 

1928 and 1933 did not subside much until the middle
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F13

37°00

EXPLANATION

'ive Points ^

77777777777,

Boundary of deformed

rocks

Line of equal subsidence 

Interval in feet, variable. Compiled chiefly 

as the sum of (1) a comparison of 

topographic mapping by the U.S. Geological Survey done between 1920 and 1928 

and in 1955, and (2) leveling of the U.S. 

Coast and Geodetic Survey in 1955 and 

1966. Controlled in part by leveling of 

1943 and 1959

Boundary of near-surface subsidence areas 

as of 1961

San Luis Canal section of the California 

Aqueduct

ettleman BED 

10 15 KILOMETRES City

36°30' 

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 9. Land subsidence, 1920-28 to 1966.

1940's, as is indicated by the subsidence history of bench 

mark PTS21S.

The 1920-28 to 1966 subsidence map (fig. 9) shows the

magnitude and extent of the long-term subsidence 

within the Los Banos-Kettleman City area. The basic 

pattern of the lines of equal subsidence is an elongate
F14 STUDIES OF LAND SUBSIDENCE

oval. The area that has subsided more than 10 feet is 70 

miles long, and the area within the 1-foot subsidence 

line exceeds 2,000 square miles. Maximum subsidence 

was about 26 feet at bench mark S661, southwest of 

Mendota. Within the main subsidence area, smaller 

elongate areas of locally intense subsidence occur. The 

southern part of the area had subsided as much as 22 

feet by 1966, largely as a result of the accelerated 

compaction of deposits between the mid-1940's and the 

mid-1950's.

Near-surface subsidence occurred chiefly after 1950 

and varied markedly within short distances. Local 

pockets of intense near-surface subsidence have not 

been included. Although some of the subsidence shown 

is the result of compaction due to wetting of alluvial-fan 

deposits, the amount is not large, and the trends of the 

lines of equal subsidence do not change upon entering or 

leaving areas of near-surface subsidence.

The San Luis Canal section of the California 

Aqueduct passes through the areas of most intense 

subsidence, but between the intense subsidence areas 

the canal passes through an area that had subsided only 

4 feet as of 1966.

The 1943-59 map (fig. 10) shows only the subsidence 

due to artesian-head decline. The general pattern of 

subsidence is much the same as for the 1920-28 to 1966 

map, but the maximum amounts of subsidence shown 

are 16 feet for both the northern and southern parts of 

the area. Because the dates of leveling control for this 

map are the same as the dates for the best available 

long-term water-level control, this map will be used 

later in this report to make a specific unit compaction 

map (fig. 56).

The near-surface subsidence component was estimated and removed from the differences in altitude for 

14 bench marks used in the construction of the 1943-59 

map. Several lines of evidence were used to estimate the 

amounts of near-surface subsidence. Some of the bench 

marks, although they are adjacent to areas of 2-10 feet 

of near-surface subsidence, probably have not been 

subjected to near-surface subsidence because they are 

in areas such as cotton gins, oil pumping stations, and 

farm buildings that are removed from the effects of 

irrigation water. By plotting subsidence profiles along 

level lines in near-surface subsidence areas, it was 

apparent that the protected bench marks had subsided 

less than nearby bench marks known to have been 

affected by near-surface subsidence. In some cases it 

was possible to draw a profile of the deeper seated 

subsidence due to artesian-head decline by using bench 

marks that were assumed not to have been affected by 

near-surface subsidence.

The history of irrigation within the area provided a 

second approach for estimating amounts of near-surface

subsidence. Surveys by the California Department of 

Water Resources and the Bureau of Reclamation 

provided information on how long the land had been 

irrigated and on the type of crops grown. Test holes 

drilled by these agencies provided information about 

the depth of the wetted front near some of the bench 

marks known to have been affected by near-surface 

subsidence. This information was used to make estimates of the thickness of the dry fan deposits wetted 

since 1943 and the clay content of the deposits. The 

relation between (1) overburden load and compaction 

due to wetting and (2) the effect of clay content on 

compaction due to wetting (Bull, 1964a, fig. 27, p. 

48-63) were applied to the data to make estimates of the 

near-surface subsidence component at those bench 

marks known to have settled as a result of compaction 

due to wetting.

With the establishment of the level-line network in 

1955, which was designed specifically to provide control 

on land subsidence, maps could be made that were based 

entirely on the results of leveling by the Coast and 

Geodetic Survey. The 1955-66 map (fig. 11) shows that 

more than 12 feet of subsidence occurred during these 

11 years (13.1 ft at bench mark S661). In the northern 

part of the area, the area of most intense subsidence had 

moved 8-10 miles south since the 1920-43 period.

Because topographic remapping of the areas of most 

rapid subsidence was done in 1955, the 1955-66 

subsidence map is the most useful map, at the time of 

the writing of this report, for correcting the 1955 map 

altitudes within the subsidence area.

The 1959-63 map (fig. 12) shows maximum subsidence was almost 4Vz feet and a 54-mile-long area that 

had subsided more than 2.5 feet. In general, the area in 

the vicinity of the Delta-Mendota Canal subsided less 

than 1 foot, indicating a deceleration of subsidence rate 

from prior years. The 0.5-foot subsidence line extended 

half way between Mendota and Kerman, and north of 

the Kings River in the vicinity of Highway 41, indicating an acceleration of subsidence in the eastern part of 

the area when compared with the 1957-59 map (not 

included in this report).

The subsidence during the next 3-year period is 

shown in figure 13. Although the same time interval 

occurred between the 1959-63 and 1963-66 periods of 

bench-mark leveling, the amounts of subsidence in the 

1963-66 period were substantially less than during the 

1959-63 period. Maximum subsidence was only 3 feet, 

and the area having more than 2.5 feet of subsidence, 

instead of being a continuous 54-mile-long area, 

consisted of four isolated areas. The maximum subsidence was near the town of Cantua Creek in the central 

part of the study area, instead of being southwest of 

Mendota as in previous years. The subsidence rate
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F15

37°00

EXPLANATION

Boundary of deformed 

rocks

Line of equal subsidence 

Interval 2 feet except for the 1-foot line. 

Compiled chiefly from leveling of the 

U.S. Coast and Geodetic Survey in 1943 

and 1959, but in part extrapolated from 

leveling in 1947. Configuration between 

bench-mark control based partly on comparison of topographic surveys made by 

the U.S. Geological Survey in 1920-28 

and 1955

Boundary of near-surface subsidence areas 

as of January 1960

The estimated near-surface subsidence component has been subtracted from total 

subsidence in these areas Coalinga 

VALLEY

San Luis Canal section of the California 

Aqueduct

15 KILOMETRES

36°30' -

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 10. Land subsidence due to artesian-head decline, 1943-59.

remained the same northeast of Mendota, but decreased 

markedly from the 1959-63 rate in the vicinity of the 

Kings River, owing to the greater availability of

surface-water imports (Pt. 3, Bull and Poland, 1974, fig. 

49). 

Additional leveling was done during the winter of
F16 STUDIES OF LAND SUBSIDENCE

120°30'

37°00

,

Boundary of deformed 

rocks

Line of equal subsidence 

Dashed where approximately located. Interval in feet varies. Compiled from leveling 

of the U.S. Coast and Geodetic Survey, 

September-November 1955 and FebruaryMarch 1966

Boundary of near-surface subsidence areas, 

as of 1961

Canal section of the California

Annediict

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 11. Land subsidence, 1955-66.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F17

37°00'

EXPLANATION

Boundary of deformed 

rocks

Line of equal subsidence

Interval 0.5 foot. Compiled chiefly from Y^ 

leveling of the U.S. Coast and Geodetic 

Survey, November 1959-January I960, 

and February-April 1963. The bench 

marks south of Highway 198 were leveled 

in December 1958-January 1959 and 

1963, but not in 1959-60. January 1960 

altitudes for these bench marks were 

estimated to the nearest 0.1 foot, from 

an analysis of bench-mark graphs, and 

comparisons with graphs of bench marks 

along highway 198, which were leveled 

every year from 1954 to 1963 except 

1956 and 1961

Boundary of near-surface subsidence areas 

as of 1961

San Luis Canal section of the California 

Aqueduct

15 KILOMETRES

36°30' -

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 12. Land subsidence, 1959-63.
F18 STUDIES OF LAND SUBSIDENCE

120°30' 120° 00'

37°00

EXPLANATION

Boundary of deformed 

rocks

Line of equal subsidence 

Interval 0.5 foot. Compiled from leveling 

of the U.S. Coast and Geodetic Survey, 

February-April 1963 and February-March 

1966

Boundary of near-surface subsidence areas 

as of 1961 Coalinga 

VALLEY

San Luis Canal section of the California 

Aqueduct

10 15 KILOMETRES

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 13. Land subsidence, 1963-66.

1968-69, when bench marks along the completed San

Luis Canal were leveled with the rest of the network.

The areas of most intense subsidence constitute only

a small part of the Los Banos-Kettleman City area. The 

graph of distribution of subsidence intensity (fig. 14) is 

based on the 1920-28 to 1966 subsidence map and
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F19

28

24

20

16

12

400 800 1200 1600 2000

AREA, IN SQUARE MILES 

FIGURE 14. Distribution of intensity of subsidence, 1920-28 to 1966.

includes areas that are northeast of the Los Banos 

-Kettleman City area as defined in figure 1. As of 1966, 

almost 2,000 square miles had subsided more than 1 

foot, but only 50 square miles had subsided more than 

20 feet.

The total volume of subsidence within the 1-foot 

subsidence line in the Los Banos-Kettleman City area 

between 1920-28 and 1966 was 8,500,000 acre-feet. 

This is the volume of water derived from compaction of 

the unconsolidated deposits and for the most part 

represents a permanent decrease in storage of the 

confined aquifer systems. However, because the compaction has occurred mostly in the fine-grained 

aquitards, usable storage in the aquifers has not been 

reduced appreciably.

HISTORY OF SUBSIDENCE

Past subsidence in an area as large as the Los 

Banos-Kettleman City area is likely to be highly variable. Subsidence graphs show a variety of trends, and 

subsidence profiles show that in some places the loci of 

maximum subsidence have migrated.

Nine graphs of cumulative subsidence are shown in 

figure 15. Bench marks in areas of ground-water pumping at the time that the bench mark was established do 

not show abrupt changes in the slopes of cumulative 

subsidence plots. Examples would be bench marks 

F678, H237 (reset), and the three bench marks at Mendota. Along the western and southern parts of the area, 

subsidence was minor until the agricultural expansion 

after World War II. For example, the plot of bench mark 

E220 southwest of Mendota shows little subsidence 

from 1935 to 1947 and then a large amount of subsidence distributed evenly over the two decades since that 

time. Marked changes in subsidence rates after 1947 

also occurred at bench marks Q237, P692, and N692. At 

bench mark V805, steepening of the slope of the 

cumulative subsidence plot occurred after 1953. At 

bench mark W805, which is only 1 mile south of V805, 

the slope of the cumulative subsidence plot steepened 

gradually during the period of record.

The plot for bench mark L157 in the southeastern 

part of the area also shows the acceleration of the rate of 

subsidence after 1947. However, bench marks in this 

area show periods of little or no subsidence in 1956 and 

1958, which is in contrast with the pattern of the 

bench-mark histories in the rest of the area. The 

reasons for variation of the rate of subsidence at bench 

mark L157 are discussed in detail in Part 3 (Bull and 

Poland, 1974).

The amounts of subsidence can vary within short 

distances, as is shown by bench marks P692 and N692. 

These bench marks are only 1 mile apart, yet the total 

subsidence at N692 is about four times the 4% feet of 

subsidence at P692.

Some bench-mark plots indicate a decreasing subsidence rate since 1950. The plot for N692 indicates a 

decreasing rate of subsidence, but the record at Mendota shows a gradually increasing rate of subsidence 

since 1919.

Two transverse subsidence profiles illustrate the histories of subsidence southwest of Mendota and Five 

Points. The locations of these profiles are shown in 

figure 1. Subsidence profile A-A' (fig. 16) extends from 

the edge of the foothills of the Diablo Range to Mendota, 

passing through the center of maximum subsidence 

shown in figure 9. The series of profiles shows the different amounts of subsidence at seven times between 1943 

and 1966. As much as 3 feet of subsidence occurred 

along the line of profile between 1935 and 1943 (fig. 8). 

From 1947 to 1957 the point of maximum subsidence 

migrated toward the southwest, and by 1966, 24 feet of 

subsidence had occurred at one point.

Subsidence profile B-B' (fig. 17) extends from Anticline Ridge through Five Points to Fresno Slough. The 

maximum subsidence in the 1943-66 period was 18 feet. 

The profiles are highly assymetric as compared with 

those shown in figure 16. The persistent steepness of the
F20 STUDIES OF LAND SUBSIDENCE

120°30'

37°00

1940 1950 1960

1940 1950 1960

1920 1930 1940 1950 1960

174} Y661, B1042

1940 1950 1960 1940 1950 1960

1940 1950 1960 EXPLANATION

4 ^ FRESNO CO 

Boundary of deformed 0 ICINGS CQ_

rocks

TIME,IN YEARS

0 1930 1940 1950 1960

4

XQ237

Bench-mark number 

and location

Kettleman BED 

10 15 KILOMETRES City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000. 1958

FIGURE 15. Subsidence of selected bench marks.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F21

8 12 

DISTANCE, IN MILES

16 20

FIGURE 16. Profiles of subsidence that has occurred since 1943, Tumey Hills to Mendota.
F22 STUDIES OF LAND SUBSIDENCE

Anticline 

Ridge

Fresno

4 8 12 16

DISTANCE, IN MILES

FIGURE 17. Profiles of subsidence that has occurred since 1943, Anticline Ridge to Fresno Slough.

20 24

southwest side of the profiles is suggestive of a sudden 

change in the compaction characteristics of the sediments, or in the rate of withdrawal of ground water, or 

both.

RATE OF SUBSIDENCE

Changes in the slope of cumulative subsidence 

graphs, such as those shown in figure 15, provide a 

general indication of changes in subsidence rate. In this 

section, the areal variations in subsidence rate will be 

discussed first, then the changes in subsidence rate, 

both regionally and at specific bench marks, will be 

discussed.

The trends of most lines of average yearly subsidence

rate for the 1959-63 period (fig. 18) are similar to the 

trend of the lines of equal subsidence of the 1959-63 

subsidence map (fig. 12). However, in the areas of 

widely spaced lines of equal subsidence, such as between Mendota and Five Points, the patterns of the 

lines of equal subsidence and the lines of equal subsidence rate are different.

Subsidence rate maps are useful in that they permit 

the designers of engineering structures, such as canals, 

to see at a glance the mean amount of subsidence that 

has occurred each year during a period of record. If the 

same units are used, rate maps are also useful in comparing the magnitude of subsidence occurring in differ-
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F23

37°00

EXPLANATION

Boundary of deformed 

rocks

Line of equal rate of subsidence. Interval 

0.25 foot per year. Derived from figure 12

Boundary of near-surface subsidence areas 

as of 1961

San Luis Canal section of the California 

Aqueduct

Coalinga

VALLEY

Kettleman BED 

10 15 KILOMETRES City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 18. Average yearly rate of subsidence, 195JM53.

ent areas. Figure 18 shows that the alinement of the 

San Luis Canal-California Aqueduct passes through 

several areas that subsided more rapidly than 1 ft yr" 1

and through one area that subsided between 1.25 and 

1.50 ft yr" 1 during the 1959-63 period. During this 

period, 480 square miles subsided more than 0.5 ft yr~ 1 ,
F24 STUDIES OF LAND SUBSIDENCE

120°30'

37°00

Five Points \

EXPLANATION

Boundary of deformed 

rocks

Line of equal rate of subsidence 

Interval 0.25 foot per year. Compiled from 

leveling of the C/.S. Coast and Geodetic 

Survey, February-April 1963 and February-March 1966

Boundary of near-surface subsidence areas, 

as of 1961 Coalmga

VALLEY

San Luis Canal section of the California 

Aqueduct

Kettleman RFn 

10 15 KILOMETRES City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 19. Average yearly rate of subsidence, 1963-66.

and 63 square miles subsided more than 1 ft yr-1 .

The rate of subsidence during the most recent period 

of leveling, as of the time of writing of this paper, is 

shown in figure 19. Only a small area subsided at a rate

greater than 1.0 ft yr~i, and the area of most rapid 

subsidence shifted from southwest of Mendota to 

southwest of the town of Cantua Creek. Comparison of 

the 1959-63 and 1963-66 subsidence rate maps reveals
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30f 120°00'

F25

37°00'-

EXPLANATION

Five Points y

Boundary of deformed 

rocks

Line of equal increase in rate of subsidence 

Interval 0.20 foot per year, except for the 

0.10 foot line. Compiled chiefly from levelings of the U.S. Coast and Geodetic 

Survey in 1943, 1953, 1954,1958, 1959, 

and 1963

Areas in which the rate of subsidence was 

less during the 1959-63 period than during the 1943-53 period

Boundary of near-surface subsidence areas 

as of 1961 Coalinga 

VALLEY

San Luis Canal section of the California 

Aqueduct

Kettleman RFn 

10 15 KILOMETRES City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 20. Change in rate of subsidence between the 1943-53 and 1959-63 periods.

a general decrease in subsidence rate that is discussed 

later (fig. 21).

A 1943-53 subsidence rate map (not included in this 

report) was compared with the 1959-63 rate map to

determine the changes in rate between early and recent 

periods. Figure 20 shows that the rate of subsidence 

increased in most of the Los Banos-Kettleman City 

area between the 1943-53 and 1959-63 periods. In most
F26 STUDIES OF LAND SUBSIDENCE

of the area, the rate increased 0.1-0.4 ft yr-1 . In two 

areas, one southwest of Mendota and the other southeast of Huron, the subsidence rate increased more than 

0.8 ft yr" 1 . The rate decreased in two areas, a small area 

east of the town of Cantua Creek and a large area 

between Los Banos and Mendota.

The changes in the rate reflect changes in the many 

factors influencing increase in applied stress, compaction, and subsidence. The large area of decreased subsidence rate lies within the service area of the DeltaMendota Canal. Although some of the wells in the service area continued to be pumped after large-scale 

canal-water deliveries began in 1953, the net effect was 

for the artesian head to decline less rapidly than before, 

or to rise slightly, thereby causing a decrease in the 

compaction rate of the deposits. Some areas were already receiving surface water from other canals before 

the construction of the Delta-Mendota Canal. However, 

the area of decreased subsidence rate lies almost entirely within the area that has been receiving large 

amounts of surface water only since 1953. An area adjacent to the north end of the Panoche Hills has been 

receiving canal water since 1959 and shows little 

change from the subsidence rate that prevailed in the 

1943-53 period. In contrast, the adjacent areas to the 

southeast that did not receive any surface water underwent a doubling of subsidence rate.

Most of the areas with a rate increase of more than 

0.40 ft yr~! were areas that were unirrigated before 

1940 but that were developed agriculturally with the 

aid of ground water between 1940 and 1950 (Pt. 1, Bull 

and Miller, 1974, fig. 22). In these areas, the change in 

rate is due largely to the fact that large manmade applied stresses persisted throughout the 1959-63 period, 

but were developed only during the latter part of the 

1943-53 period.

Subsidence rates in much of the area irrigated with 

ground water throughout both periods increased from 

0.1-0.4 to 0.2-0.8 ft yi-1 . The large increase in subsidence rates in areas already irrigated with ground 

water in 1943 probably is due to a combination of factors. Factors contributing to an increase in subsidence 

rate would include increases in the rates of artesianhead decline for the zones being pumped and increases 

in excess pore pressures in the aquitards.

Several aspects regarding the withdrawal of ground 

water were considered, but do not seem to explain fully 

the increased subsidence rate in those areas irrigated 

with ground water throughout both the 1943-53 and 

1959-63 periods. The overall amount of ground water 

pumped within the area has not changed much since 

1953 (Pt. 1, Bull and Miller, 1974, fig. 23). In general, 

the wells were perforated in the same intervals during 

both periods, which would indicate that the head decline was occurring in the same zones during both 

periods. An increase in the rate of head decline within 

the area would explain the increase in subsidence rate, 

but pumping levels have been declining at a progressively slower rate in much of the area.

The factor that accounts for the increased subsidence 

rates is increased excess pore pressures in the 

aquitards. Evidently, the head in the aquifers has been 

drawn down more rapidly than aquitard excess pore 

pressures could decay, and hence the differential between the head in the aquifers and average excess pore 

pressures in adjacent aquitards has increased. The rate 

of subsidence is a function of this head differential.

The change in subsidence rate between the two most 

recent periods of leveling of the bench-mark network is 

shown in figure 21. In contrast to the comparison shown 

in figure 20, subsidence rates during the 1963-66 period 

were less than during the 1959-63 period throughout 

most of the area. Within about 80 square miles in the 

northern part of the area, the subsidence rate had decreased more than 0.25 ft yr-1 between the 1959-63 and 

1963-66 periods. In the central and southern parts of 

the area, the subsidence rate decreased more than 0.25 

ft yr~l only in small local areas. The dashed line connects the outermost points of no change in subsidence 

rate between the two periods, but intersection of rate 

lines of the two maps show that isolated points of no 

change in rate occur within the dashed line. Some small 

areas of minor increase in subsidence rate in the southern part of the area were suggested by comparison of the 

two maps (figs. 18,19), but in these areas the suggested 

increases in rate were less than 0.25 ft yr-1.

The contrast between the trend of subsidence rates in 

figures 20 and 21 is the result of a decrease in the rates 

of increase of stress being applied to the aquifer system, 

as indicated by decreasing rates of artesian-head decline (Pt. 1, Bull and Miller, 1974, fig. 45). Rates of 

artesian-head decline have decreased markedly in recent years and have been accompanied by slight to moderate decrease in subsidence rates. Some of the geologic 

reasons for the greater decrease in subsidence rate in 

the northern part of the area are discussed in the section 

"Geologic Factors Influencing Compaction of the Unconsolidated Deposits."

Bar graphs of subsidence rates for five bench marks 

(fig. 22) show the changes in subsidence rate better than 

the changes in slope of the cumulative subsidence 

graphs of figure 15. Both the amounts and patterns of 

changes of subsidence rate are highly variable in the 

different parts of the study area.

The record for bench mark 97.68 (USER) shows increasing subsidence rates from 1937 to 1954 and decreasing rates since then. The marked reversal in the 

trend of subsidence rate coincided with the delivery of
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F27

37°00

EXPLANATION

Boundary of deformed 

rocks

Area in which the subsidence rate during 

1963-66 decreased more than 0.25 foot 

per year from the rate during 1959-63

Outer line through the points of no change 

in subsidence rate between the 1959-63 

and 1963-66 periods

Boundary of near-surface subsidence areas 

as of 1961 Coahnga

VALLEY

San Luis Canal section of the California 

Aqueduct TULARE 

LAKE

Kettleman BED

10 15 KILOMETRES

36°30' -

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 21. Change in rate of subsidence between the 1959-63 and 1963-66 periods.

Delta-Mendota Canal water to the area. The dotted line 

showing the interpolated general subsidence rate is an 

integration of the bar-graph data. There is only one line

of best fit because it is based on equal areas above and 

below the line. The post-1963 line is tentative, for post1966 data are necessary to complete the integration.
F28 STUDIES OF LAND SUBSIDENCE

12CT30' 120° 00'

37°00'b

1920 / 1930 1940 1950 1960 1970

1940 1950 1960 1970

EXPLANATION

.

Boundary of deformed 

rocks

Bench-mark number 

and location

Interpolated general 

subsidence rate Coalinga

VALLEY

Kettleman BED 

City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 22. Histories of subsidence rates for selected bench marks.

Subsidence rates have increased steadily since 1919 

at Mendota. Some minor fluctuation of subsidence rate 

occurred during the middle 1950's, and the rate increased the most rapidly in-the 1963-66 period.

Bench mark S661 has subsided more than any other 

bench mark in the San Joaquin Valley. The altitude of 

this bench mark declined 24 feet in the 23 years prior to 

1966. The rate of subsidence has not been uniform,
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F29

although, at first glance, the cumulative subsidence 

graph (Pt. 3, Bull and Poland, 1974, fig. 30) appears to 

have a fairly constant slope since 1947. The subsidence 

rate increased rapidly between 1943 and 1953 as 

ground water was pumped in the vicinity for the first 

time. The interpolated general subsidence rate line indicates that the maximum rate of subsidence was in 

1954 and was more than 1.8 ft yi*" 1 . Since 1955, subsidence rates have been decreasing, and by 1965 the rate 

was only 0.7 ft yr" 1 . Bench mark S661 is in the large 

area of recent decrease in subsidence rate (fig. 21). At 

this bench mark, the subsidence rate decreased 0.51 ft 

yr" 1 between the 1959-63 and 1963-66 periods.

The increased subsidence rates at bench mark W805, 

in the southern part of the area, also are associated with 

agricultural expansion since 1947. In contrast with the 

record of S661, however, the rates do not define a peak 

until 1964 (fig. 22).

The record at bench mark L157, in the southeastern 

part of the area, shows three periods of little or no 

subsidence and two periods of subsidence rates of about 

0.4 ft yr~l. Subsidence in this part of the area since 1955 

is influenced by changing proportions of the sources of 

irrigation water, which include surface water from the 

Kings River and ground water from above and below 

the Corcoran.

COMPACTION OF THE GROUND-WATER 

RESERVOIR

In the preceding section, most of the subsidence in the 

Los Banos-Kettleman City area was attributed to excessive withdrawal of water from confined aquifer systems. This section describes the compaction of the 

ground-water reservoir and compares the amounts of 

compaction and subsidence.

The best information regarding the amounts, rates, 

and vertical distribution of compaction is obtained from 

specially drilled wells or unused irrigation wells that 

are equipped to measure shortening of the deposits between the land surface and a designated depth. A second 

source of information is provided by studies of wellcasing shortening and rupture that occur as a result of 

compaction.

FIELD MEASUREMENTS OF COMPACTION

TYPES OF COMPACTION GAGES USED

The methods of measuring compaction used by the 

Geological Survey have evolved from relatively simple 

to refined equipment that is adaptable to the problems 

encountered at individual locations. The basic type of 

recording compaction gage is shown diagrammatically 

in figure 23. A heavy weight is lowered to the bottom of 

the well on a Vs-inch cable. Where possible, the anchor 

weight is set below the casing bottom to measure the 

vertical shortening of the deposits rather than the concurrent shortening of the well casing. At the land surRecorder

Sheaves mounted 

in teeter bar

Counterweights

Compaction tape

Steel table

Bench mark /Con-icrete slab

Cable, 1/8-inch stainless 

steel, 1 x 19 stranded, 

reverse lay

Well casing, 

4 to 13 inches

Anchor weight, 

200 to 300 pounds

FIGURE 23. Diagram of recording compaction gage.

face, the cable is passed over two ball-bearing sheaves 

and is counterweigh ted to keep it taut. The sheaves are 

mounted in a metal rack set on a 1-foot-thick concrete 

foundation that does not touch the well casing. A 

mechanically driven hydrographic recorder (Stevens, 

type F) set in the rack is connected to the %-inch cable 

with a small diameter cable that is clamped to the main 

cable and passes over the drive pulley of the recorder. As 

compaction occurs, the concrete slab and the recorder 

move downward relative to the cable clamp, because 

(ideally) the length of the cable remains constant as the 

thickness of the aquifer system decreases. The movement of the recorder relative to the small-diameter 

cable rotates the recorder pulley and chart drum, producing a graph of compaction at a scale of 1:1. The 

principal limitation upon the accuracy of the system is 

friction between the well casing and the down-hole 

cable.

Many improvements have been made since the first 

recorders were installed. In wells where the amount of 

friction between the casing and cable is small, an 

expanded-scale record is obtained directly in the field 

through the use of a second recorder linked to the first 

by an amplifying gear train. A 12- or 24-times expansion of the record is useful in observing the finer details
F30 STUDIES OF LAND SUBSIDENCE

of the compaction record, provides more accurate measurements of short-term compaction, and permits determination of the times of changes from recorded compaction to record expansion of the aquifer system.

Friction in the above-ground components of the system has been reduced to a negligible level by mounting 

the sheaves in a teeter bar. As compaction occurs, the 

teeter bar tilts on a knife-edge fulcrum, but the sheaves 

do not rotate. The sheaves rotate when the bar is leveled 

each time the recorder is serviced. Errors caused by 

seasonal swell due to changes in surface moisture conditions have been largely eliminated by the use of concrete and steel, instead of wood, in the tables and foundations. Changes due to seasonal soil swell have not 

been eliminated entirely, but can be measured when 

necessary.

Compaction of the enclosing deposits shortens and 

destroys well casings. Slip joints installed in some 

compaction-recorder wells apparently have been successful in preventing or delaying major casing damage.

The characteristics of the cable are of paramount 

importance. Even small unit changes in cable elongation due to fatigue or untwisting are significant if they 

affect much of the length of a 2,000-foot cable. Changes 

in the position of the top cable clamp due to these factors 

cannot be distinguished from changes due to compaction unless special measurements are made. The effect 

of temperature changes is not considered important, 

because below a depth of a few feet the temperature 

remains uniform.

The first cable used for compaction recorders in the 

study area consisted of 7 x 7 stranded Vs-inch galvanized 

steel, but corrosion caused failure of cables at several 

sites within a few months. This cable was replaced with 

stainless steel, plastic coated, 7x7, Vs-inch stranded 

cable, which resisted corrosion, but had more casingcable friction than the uncoated cable. Also, the cable 

tended to untwist as indicated by rotation of the counterweights. As of 1968, Vs-inch, 1x19 stranded, uncoated, stainless steel, reverse-lay cable had been found 

the most desirable for compaction-recorder use. It resists corrosion, has low stretch and friction characteristics, and little tendency to untwist. The low tendency to 

untwist under load is due to the fact that the six strands 

about the center strand spiral in the opposite direction 

from the outer twelve strands.

A different type of compaction gage was installed in 

well 15/13-35D5. It consists of a iy2-inch pipe inside a 

casing. The bottom of the 1 Mi-inch pipe was set 7 feet 

below the bottom of the enclosing 4-inch casing. 

Changes in aquifer-system thickness are determined at 

monthly intervals by measuring the distance between 

the top of the IVk-inch pipe and a steel frame bolted to a 

concrete foundation that encloses but does not touch the

4-inch casing. Wells 20/18-11Q2 and 16/15-34N4, at 

the Westhaven and Cantua sites, also operate as a 

compaction-pipe type of gage. (See description of the 

Westhaven site under section "Shortening of an OilWell Casing.")

The first compaction recorder was installed in September 1955 in well 19/17-35N1. The site was an unused irrigation well 2,030 feet deep, having 16-, 12-, and 

9-inch casing. The compaction record from this installation is shown in Part 3 (Bull and Poland, 1974, fig. 11).

Attempts to install compaction recorders in the three 

core holes drilled in 1957 were unsuccessful. As an 

experiment and an economy measure to eliminate casing costs, side wall anchors were installed in core hole 

12/12-16H1, which was uncased. The hole collapsed 

during installation of the equipment, even though it 

was filled with a special mud to inhibit caving. Later 

attempts to install compaction recorders in uncased 

holes 14/13-11D2 and 19/17-22Jl, 2 used y4 -inch iron 

tubing to protect the cables. These compaction recorders 

were unsuccessful because of excessive friction between 

the tubing and cable and because of corrosion and 

cementation.

By January 1968, 21 wells were providing information about compaction in the Los Banos-Kettleman 

City area. Groups of recorders with bottom-hole weights 

set at different depths are at 12/12-16H near Oro Loma, 

at 14/13-11D west of Mendota, at 16/15-34N near the 

town of Cantua Creek, and at 20/18-11Q near Westhaven. Twelve of the recorders operate in groups, and 

nine operate singly.

Descriptions of the compaction-recorder installations 

are summarized in table 1, and their locations are 

shown in figure 1. Where possible, the anchor was set 

below the casing bottom, and, in the unperforated wells, 

the anchors were set as much as 49 feet below the 

bottom of the casing. In most of the perforated wells, 

however, the anchor weight was set on sand in the 

casing; in most of these the sand was brought into the 

well as a result of development to observe water-level 

changes. Attempts to bail the sand from the casing 

usually resulted in a continuing influx of sand through 

the perforations. However, useful compaction records 

are obtained because the casings are shortened almost 

the same amount as the sediments that encase them 

and because the amounts of compaction that do not 

cause casing shortening cause measurable increased 

casing protrusion above the land surface.

Compaction that has occurred at the sites is shown in 

figures 26 through 32. Data from multiple compactionrecorder sites will be discussed first. Inverted bar 

graphs showing monthly compaction for most of the 

sites are given in Part 3 (Bull and Poland, 1974, figs. 

13-17).
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F31

TABLE 1. Summary of compaction-recorder installations

Date Agency 

Well installed drilled by 

12/12-16H2 __ 2/26/58 (M

12/12-16H3 _ _ 2/26/58 C 1 )

12/12-16H4 __ 2/26/58 (*)

13/12-20D1 _ _ 7/27/61 (2 )

13/15-35D5 _ _ 5/13/66 (3 )

14/12-12Hl____12/10/64 (2)

14/13-11D4 __ 9/28/60 ( 3)(4 )

14/13-11D6____ 4/14/61 ( 3 )(4 )

15/13-11D2 __ 12/28/64 (2 )

15/16-31N3. _ 3/23/67 ( 3 )

16/15-34N1 __ 4/16/58 f 1 )

16/15-34N2 _ _ 4/16/58 (M

16/15-34N3 _ _ 4/16/58 (')

16/15-34N4 __ 8/11/60 ( 3)(4 )

18/16-33 Al____ 12/1 1/64 (2 )

18/19-20P2 _. 3/24/67 (3)

19/16-23P2 ____ 4/30/59 ( 5 ) 

19/17-35N1 __ 9/1/55 (7 )

20/18-6D1 _ .12/11/64 ( 2 )

20/18-11Q1 __ 6/ 6/64 ( 4 )

20/18-11Q2____ 8/16/62 («)

20/18-11Q3____ 8/16/62 ( 10 )

Casing 

diameter

(in.)

4

4

4

4

4

6

8

8

6

6

4

4

4

8

8,6,4

6

13 

16, 12, 9

6,4

4

11

4, 11

Depth of 

cased hole

964

320

470

665

433

936

774

1,329

960

595

1,951

660

457

1,112

1,070

577

2,406 

2,130

1,007

710 (9 )

2,004

Anchor depth 

when 

installed 

(ft below 

land surface)

1,000

350

500

681

440

913

780

1,358

958

596

2,000

703

503

1,096

1,029

578

2,200 

2,030

867s

710 8459

1,930

Position of 

anchor 

above ( + ) or 

below (-) 

bottom of 

casing (ft)

-36

-30

-30

-16

-7

+23

-6

-29

+2

-1

-49

-43

-46

+ 16

+41

-1

+ 100

+ 140

0

(9 )

("I

Perforated 

interval 

(ft below 

land surface)

None

None

None

425-665

373-433

740-936

714-774

1,133-1,196

900-960

497-537

Not perforated

Not perforated

Not perforated

1,052-1,112

858-1,070

497-537

Unknown 

608-2,130

716-736

760-835

851-872

650-710

755-805

1,885-1,925

Depth interval 

Corcoran Clay 

Member 

(ft below 

land surface)

379-465

379-465

379-465

304-418

428-476

615-719

625-700

625-700

768-860

585-648

565-575

565-575

565-575

565-575

781-805

567-634

Not present 

860-870

811-820

715-745

715-745

715-745

Remarks

Water-level records obtained from

12/12-16H5 (perforated interval

670-712 ft) and 12/12-16H6

(perforated interval 770-909 ft).

Compaction-pipe type of recorder.

Water level not representative of zone.

Water-level records obtained also from

14/13-11D3 (perforated interval

180-240 ft).

Gravel packed; water-level records also

obtained from 15/16-31N2

(perforated interval 667-747 ft).

Water-level records obtained also from

16/15-34N5 (perforated interval

240-300 ft).

Water-level records obtained from

18/19-20P1 (perforated interval

647-687 ft).

Cable failed October 1960; casing

broken; not repaired.

Compaction-pipe type of recorder.

'Inter-Agency Committee on Land Subsidence in the San Joaquin Valley.

2U.S. Bureau of Reclamation.

California Department of Water Resources.

4U.S. Geological Survey.

5Shell Oil Company.

6Anchor set on cement plug in casing.

'Russell Giffen, Inc.

8Anchor set on top of 140 ft of 4-in. casing.

9Mid-depth of cement plug between 4-in. and 11-in. casing.

10Texaco Oil Company.

ANALYSIS OF FRICTION IN A COMPACTION RECORDER

The accuracy of the recorded compaction data is in 

large part dependent on the amount of friction within 

the compaction recording system. Friction occurs both 

in the recording equipment above the land surface and 

between the cable and the well casing below land surface. However, friction in the recording equipment is 

negligible, in comparison to casing-cable friction. The 

inaccuracies resulting from casing-cable friction are 

minimized by large-diameter straight casings and 

through the use of cables with minimum friction 

characteristics and high elastic modulus (minimum 

stretch per unit length per unit tension).

If the tension gradient due to the unit weight of the 

cable is neglected, the tension in a free-hanging cable 

may be considered uniform. However, a typical compaction cable does not hang freely, and the tension is approximately uniform only in the parts of the cable suspended between points of frictional contact with the 

casing. Tension above the uppermost point of contact 

between cable and casing equals the counterweight. 

Below this point the tension is different in each suspended segment.

Figure 24 illustrates, diagrammatically, a 

compaction- recorder system that has friction between

the casing and the cable, owing to a bend in the casing. 

For simplicity, only the uppermost point of contact between the casing and the cable is shown (B), and it is 

assumed that the cable does not touch the casing between point B and the anchor weight. Actually, the 

cable may be partly or wholly in contact with the casing 

below point B.

In the situation portrayed in figure 24, any change in 

aquifer-system thickness above point B will be recorded 

accurately if friction in the above-ground components of 

the instrument is negligible. Above point B, constant 

cable tension is maintained at all times by the counterweights.

Below point B, cable tension will, in general, not 

remain constant. During compaction, cable tension between B and C will decrease until the cable stress betweenB and C, plus the friction at pointB, is exceeded by 

the cable stress induced by counterweighting above the 

land surface. Relative upward cable movement past 

point B will then occur, and concurrently stress in the 

cable between B and C will increase rapidly until friction at B prevents further movement. The cable between B and C may never attain the same stress as the 

cable between A andB, as long as compaction continues.

An opposite relation exists during times of net
F32 STUDIES OF LAND SUBSIDENCE

Af land surfaceWell casings

Sheave

Counterweight

uppermost point of 

contact between 

ceble and casing

anchor weight

FIGURE 24. Diagrammatic sketch of a compaction-recorder system with casing-cable

friction.

aquifer-system expansion. During expansion of the deposits and well casing below point B, cable tension will 

increase until it exceeds the cable stress between A and 

B, plus the friction at B. Downward cable movement 

past point B will then occur, and stress in the cable 

between B and C will decrease rapidly until friction 

prevents further movement past point B. The cable between B and C may remain more highly stressed than 

between A and B, as long as expansion continues.

Expansion or compaction below the uppermost friction point will not be recorded unless unbalanced cable 

stresses across that point exceed the friction at that 

point. Installations having little friction generate a 

moderately smooth and reasonably accurate compaction record. Installations with large amounts of friction 

generate a stepped compaction record, with most or all 

of the compaction recorded at times when differences in 

cable stress exceed the friction. If undisturbed, recorders with large amounts of casing-cable friction may 

show no compaction for many months and then suddenly record several tenths of a foot of compaction.

A partial solution to the problem of excessive friction 

is to change the stress on the cable artificially each time 

the instrument is serviced. This is done simply by pushing the counterweights down about 1 foot, or less, and 

allowing them to rise gently as the force is relaxed. This 

operation temporarily increases the stress imbalance 

across friction points enough to allow the cable to move 

upward against friction, thereby removing those differences in cable tension that have accumulated as a result 

of compaction since the last application of stress. When 

the cable comes to rest after relaxation of the load, a new 

vertical distribution of stresses will have been imposed 

in the cable. The difference between the old and new 

stress distributions is a measure of the compaction that 

has occurred since the last time the cable was loaded in 

the same way. If the periodic loading of the cable is done 

in a highly consistent way and if the elastic properties of 

the cable and the friction characteristics of the casingcable contacts change little with time, then the vertical 

distribution of stress within the cable should be nearly 

the same after each loading. Thus the cable length corresponding to this characteristic distribution of stress 

constitutes a nearly unchanging reference against 

which to measure compaction of the aquifer system.

An example of a record from a compaction recorder 

with large amounts of casing-cable friction is shown in 

figure 25. The amount of friction within this well probably is as severe as for any in operation and is caused by 

the use of a cable with high friction characteristics 

(plastic coated) in a deep well (2,000 ft) that has a small 

diameter casing (4 in.). During the first year of operation, before the cable was stressed monthly, this installation would record no compaction for 6 months and 

then would record more than 0.5 foot of compaction at 

one time. The record shown in figure 25 is stairstepped 

because compaction is recorded only at the time of each

3.0

3.5

4.0

4.5

Interpolated general 

compaction curve ./Unadjusted field 

data

S O N D

1960

FMAMJ JASOND

1961

FIGURE 25. Interpolation of part of the cumulative compaction record from well

16/15-34N1.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F33

monthly stress increase. For most of the record, an interpolated cumulative compaction curve can be drawn 

through the low points of the stairstepped record. When 

the cable appears to have been overstressed (mid-1961) 

or understressed (late 1961), the value for that month 

(or months) is omitted, and the amount of compaction 

for two or more months is combined, as shown by the 

dashed lines. The method is accurate for determining 

compaction that has occurred for periods longer than 2 

or 3 months because the cable probably returns to a 

similar distribution of stresses after most monthly 

stress increases.

CUMULATIVE COMPACTION AT MULTIPLE 

COMPACTION-RECORDER SITES

Plots of cumulative compaction and subsidence for 

those sites where two or three compaction recorders are 

operating are shown in figures 26-28. The plots are 

interpretations of stairstepped records similar to that 

shown in figure 25, and the dashed parts of the record 

indicate where more than one month's record has been 

combined. By mid-1968, 10 feet of cumulative compaction had been measured by one recorder. The unit compaction of the deposits in the different depth zones is 

discussed later.

Compaction and subsidence at the Oro Loma site in 

the northern part of the area are shown in figure 26. 

About 12 feet of subsidence occurred at this site between 

1920 and 1966 (fig. 9). The maximum rate of subsidence 

was in 1954 (0.9 ft yr" 1 ), and since then the rate has 

decreased steadily (fig. 22). The change in slope of the 

plot for bench mark 97.68 (USER) reflects the decreasing subsidence rate for the 1958-66 period.

The compaction anchors at the Oro Loma site were set 

at depths of 350, 500, and 1,000 feet. The 1958-66 compaction was less than half a foot for the two shallow 

recorders, but more than 2 feet of compaction occurred 

in the 0-1,000-foot interval. The large amounts of apparent compaction that occurred during the first 3 

months of operation in 1958 probably were caused by 

initial cable stretch and foundation settlement. If the 

first few months of record are omitted, the total compaction in the upper 350 feet has been only 0.1 foot in the 7 

years since 1958.

The plots for wells 16H3 and 16H4 show periods of 

apparent net expansion of the aquifer materials prior to 

1963. Similar effects are noticeable for the plot of well 

16H2, but they are not as obvious as in the records from 

the other two recorders because of the greater compaction rate. The expansion is not real, but is chiefly a 

combination of soil and lumber swell during the winter 

rainy season. In April 1962, the installations for wells 

16H3 and 16H4 were rebuilt, using steel racks set on 

large concrete pads that are not in contact with the 

casings. Little apparent aquifer-system expansion has

occurred during the rainy season since the site was 

rebuilt. The recorder for well 16H2 was rebuilt in a 

similar fashion in October 1960.

A seasonal effect is noted for some years in the compaction record of well 16H2. For example, in 1963 the 

maximum compaction rate occurred in February and 

July-September the months of large demand for irrigation water.

A comparison of the compaction in the upper 1,000 

feet to the total amount of subsidence can be made by 

examining the record for well 16H2 and the plot for 

nearby bench mark 97.68 (USER). If all the subsidence 

were the result of compaction in the upper 1,000 feet, 

the two plots would parallel each other.

The Oro Loma site has experienced a change in the 

amount of compaction being measured compared with 

subsidence, as is indicated by the divergence of the 

subsidence and compaction plots after 1961. During the 

period October 1958-October 1961, about 90 percent of 

the subsidence was the result of compaction in the upper 

1,000 feet. The percentage decreased to about 55 percent for the period October 1961-October 1965 when 

about 45 percent of the compaction occurred below 1,000 

feet.

Compaction and subsidence plots for the Mendota site 

(about 8 mi west-southwest of the town of Mendota) are 

shown in figure 26. The site, which subsided about 23 

feet between 1920 and 1966, is in one of the areas of 

most intense land subsidence in the study area. The rate 

of subsidence increased until the mid-1950's and has 

decreased since then. The 1961-66 subsidence trend is 

shown by the plot of bench mark GW4.

Compaction anchors at the Mendota site were set at 

depths of 780 and 1,358 feet. During the period shown in 

figure 26, 0.9 foot of compaction occurred in well 11D4, 

and 2.85 feet of compaction occurred in well 11D6.

The Mendota site recorders were built using concrete 

pads and steel racks and do not show the effects of soil 

and lumber swell as noted during the first few years of 

record at the Oro Loma site.

The compaction rate varies with the season. Both 

wells show a pronounced reduction of compaction rate 

during the winter months. The times of maximum compaction vary from year to year, but in general roughly 

correspond with the times of irrigation in the summer 

and late winter-early spring.

The lesser overall slope of the compaction plot for well 

11D6 as compared with the bench-mark plot reveals 

that part of the subsidence is occurring below 1,358 feet. 

During the period September 1961-August 1965, about 

69 percent of the subsidence occurred as compaction 

between the land surface and 1,358 feet, and about 31 

percent of the subsidence was attributed to compaction 

of deposits below 1,358 feet. About 23 percent of the
F34 STUDIES OF LAND SUBSIDENCE

Subsidence, 

Bench mark 97.68 (USER

1958 1959 1960 1961 1962 1963 1964 1965 1966

1961 1962 1963 1964 1965 1966

FIGURE 26. Compaction and subsidence at the Oro Loma site, 1958-66 (upper graph), and Mendota site, 1961-66 (lower graph).

compaction occurred between the land surface and a 

depth of 780 feet, and 46 percent between depths of 780 

and 1,358 feet.

Compaction and subsidence plots for the Cantua site 

in the central part of the Los Banos-Kettleman City 

area are shown in figure 27. About 19 feet of subsidence 

occurred at the site between 1924 and 1966, but more 

than 9 feet has occurred since 1957. The subsidence rate 

has been rapid and fairly constant since the early 

1950's.

In 1958, compaction anchors were set at depths of 503, 

703, and 2,000 feet. In 1961, an additional anchor was 

set at 1,096 feet in a well that was drilled primarily to 

obtain lower-zone water-level information. All the recorders were rebuilt on concrete pads in April 1962. 

Records were interrupted when corrosion caused the 

galvanized cables to break in May 1959 in well 34N1 

and in December 1959 in well 34N2. The record for the 

0-1,096-foot depth interval in well 34N4 was terminated in June 1963 when attempts to repair casing 

breaks caused by subsidence failed. Separation of two 

casings (a compaction-pipe type of gage) has provided

compaction information for the 0-900-foot depth interval for well 34N4 since February 1965. The casing for 

well 34N1 has not failed, apparently because of the slip 

joints placed at several depths, even though 10 feet of 

casing shortening had occurred by mid-1968.

In contrast with the Mendota site, the Cantua site 

record shows less variation of compaction with the season of the year, although in some years the compaction 

rate decreased moderately during the winter.

The 2,000-foot recorder measures most of the subsidence that is occurring. For the period December 

1959-December 1962, about 99 percent of the compaction was occurring in the upper 2,000 feet. About 10 

percent of the compaction was measured above 503 feet, 

and about 26 percent of the compaction was measured 

above 703 feet. During the next 3-year period, December 1962-December 1965, the amount of subsidence 

remained about the same. However, the 2,000-foot recorder measured only about 88 percent of the subsidence, indicating that about 12 percent of the compaction was occurring below 2,000 feet. During this second 

3-year period, about 8 percent of the compaction was
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F35

1.0

2.0

3.0

4.0

5.0

ui 

O

Z 

Ul

g OT

CD

O

v> 

DC 

o

1,0

o

<

Q.

z

8 7.0

8.0

9.0

10.0

x /Well 34N1, 2000 feet deep

New cable installed

X 

__ Casing failure _

Casing repair

1958 1959 19GO 1961 1962 1963

FIGURE 27. Compaction and subsidence at the Cantua site, 1958-66.

1964 1965 1966

measured in the upper 503 feet, and about 22 percent of 

the compaction was measured in the upper 703 feet of 

the deposits. The percentage of subsidence being measured decreased still further during the March 

1966-November 1967 period, being only 79 percent of 

the subsidence. The decrease in the percentage of subsidence measured in the 0-2,000-foot depth interval at 

the Cantua site between 1959 and late 1967 is shown in 

figure 28.

Three compaction recorders two cable type and one 

pipe type are operating at the Westhaven site in the 

southern part of the Los Banos-Kettleman City area. 

The instrumentation of well 20/18-11Q2 consists of a 

4-inch pipe cemented inside an 11-inch pipe at a depth of 

830-860 feet. Compaction is measured by observing the 

amount of shortening of the 11-inch casing as compared 

with a reference point on the 4-inch casing and adding 

the minor amounts of change in protrusion of the 

11-inch casing. The construction of this abandoned oil

Q

uj 1 00

oc

1Ul

Ul

o

z

Ul

Q

cn 50

o

<fi

u.

O

Ul

0

1-

z

Ul

O 

uj 0

-

-

L-

| ^ ^ | ^ ^-t I I I

/ / > y ^|

/

/ y

/ /-

/ .

' /

"

/

/ /

,/ X. / X X,X XiX X /:/ Xi/

*r\f*r* An**r* 4 r\e* A 1 ACC 1960

FIGURE 28. Decrease in the percentage of subsidence measured in the 0-2,000-foot depth 

interval at the Cantua site, 1959-67.

well is described in detail in the section "Shortening and 

Increased Protrusion of Well Casings."
F36 STUDIES OF LAND SUBSIDENCE

Compaction and subsidence plots for the Westhaven 

site are shown in figure 29. About 13 feet of subsidence 

occurred at the site between 1928 and 1963. The plot of 

subsidence in figure 29 is taken from two subsidence 

maps because vertical control was not extended to the 

site until the 1966 leveling. The amount of subsidence 

shown for the 4-year period probably is within 0.2 foot of 

the amount that would have been observed if a bench 

mark at the site had been surveyed, because a level line 

is located 1 mile west of the site.

Compaction is being measured above depths of 710, 

830, and 1,930 feet. All three plots show pronounced 

seasonal variations in the rate of compaction. Maximum compaction rates occur in the summer and in late 

winter. Compaction virtually ceases in early winter and 

early spring.

The plots of subsidence and of compaction in the 

upper 1,930 feet are nearly parallel, and probably more 

than 95 percent of the compaction is occurring above 

this depth.

CUMULATIVE COMPACTION AT SINGLE 

COMPACTION-RECORDER SITES

As of 1968, single compaction recorders were operating at 9 sites throughout the Los Banos-Kettleman 

City area. Only two of the records are sufficiently long to 

warrant illustration in this report, and at most of the 

sites, bench-mark altitudes were not established until 

1966.

Well 13/12-20D1 was one of many wells drilled by the 

Bureau of Reclamation to obtain geologic and hydrologic information along the alinement of the San 

Luis Canal. About 10 feet of subsidence has occurred in 

the area between 1920 and 1966. Leveling has not been 

extended to the site itself, but subsidence maps provide 

a fairly accurate estimate of the amounts and rates of 

subsidence because of level lines 1 mile to the west, and 

to the south of the site.

The plot for well 20D1 (fig. 29) shows a steadily decreasing compaction rate into 1965, but the excessive 

compaction rate in the first 3 months of record may be 

the result of initial cable stretch and foundation settlement. Consistent seasonal fluctuations of compaction 

are not readily apparent in the record from this well, 

and long-term and seasonal changes in artesian head of 

the upper part of the lower zone have been minor.

The well is in an area of near-surface subsidence, and 

compaction due to wetting of unsaturated deposits has 

occurred in addition to the compaction of saturated deposits. A Bureau of Reclamation evaluation of the 

amount of compaction due to wetting in a 230-foot well 

at the site indicates that virtually no net compaction 

due to wetting occurred during the 4-year period. Apparently, percolation of irrigation water has thoroughly 

wetted all the deposits above the water table.

COMPACTION ORUBSIOENCE. IN FEET

to 3o

^

----._

^____^We,i 3/12-20D1.690

Approximate subsidence at 

_ 13/12-20D1, from 1959- 

and 1963-66 subsidence 

maps ,

feet deep

^/Compaction

 - -- -___

 v 

1965 1966

FIGURE 29. Compaction and subsidence at the Westhaven site, 1962-66 (upper graph), and 

well 13/12-20D1, 1961-66 (lower graph.)

Comparison of compaction with estimated subsidence 

for the period December 1961-December 1965 indicates 

that about 90 percent of the compaction during the 4 

years occurred above 690 feet and that 10 percent of the 

compaction occurred below 690 feet.

Well 19/16-23P2 is an oil test abandoned in 1950, in 

which a cement plug has been set in the casing at 

2,200-2,406 feet. Seven feet of subsidence occurred at 

the site during the 1928-66 period. The use of the well 

has provided the Geological Survey with the deepest 

compaction recorder in the study area. The 13%-inch 

casing greatly reduces the casing-cable friction. Despite 

the potential of the site, the recorder has had many 

problems. The recorder has been rebuilt several times, 

and the cable has been removed from the well five times 

because of corrosion failure or replacement or to make 

other changes in the equipment. In 1966, the recorder 

was rebuilt completely, using the most advanced equipment available, and since then a record of both aquifersystem compaction and expansion have been obtained 

without changing the cable stress by monthly oscillations of the counterweight. The record of net expansion 

is discussed in Part 3 (Bull and Poland, 1974).

Compaction at 19/16-23P2 and subsidence at bench 

mark Z888 about 500 feet southwest of 23P2 are 

shown in figure 30. Because of the months of recorded 

net expansion and the instrumentation problems, many 

of the monthly records have been combined and are 

shown by a dashed line. Casing shortening is being 

measured because the anchor weight is set at a depth of 

2,200 feet on af concrete plug in the casing. However, 

shortening of the casing is virtually the same as the 

concurrent shortening of the deposits that encase it, as
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F37

H 

UJ 

UJ 

LL

2 1.0

ul 

O 

2 

lil 

Q 

w 2.0

GQ

Compaction, 

..well 19/16-23P2, 2200 feet deep

3.0

Subsidence, 

bench mark Z88£

H 

O 

< 

0.

84-0

Cable failure

D

New cable 

installed

1959 1960 1961 1962 1963 1964

FIGURE 30. Compaction and subsidence at well 19/16-23P2, 1959-66.

1965 1966

is shown by negligible amounts of increased casing 

protrusion above the land surface. Consistent seasonal 

patterns of compaction do not occur at this site because 

the compaction is dependent to a large extent on the 

pumping schedule of well 23P1, about 500 feet to the 

southwest. Well 23P1 pumps more often during the 

winter months than most of the wells in the Los 

Banos-Kettleman City area.

Comparison of compaction at well 23P2 and subsidence at bench mark Z888 suggests that compaction is 

being measured in excess of subsidence. During the 

period December 1959-December 1965, measured compaction was about 122 percent of the subsidence at 

bench mark Z888. The compaction cable was not removed from the well between the times of leveling in 

March 1963 and March 1966. Compaction was about 

120 percent of the subsidence during the 1963-66 

period. Subsidence rates change rapidly from west to 

east in the vicinity of 23P2 (fig. 13). Less subsidence 

should occur at bench mark Z888 because it is 500 feet to 

the southwest of 23P2. Steep subsidence gradients are 

not uncommon in the Los Banos-Kettleman City area. 

An example would be the' subsidence of bench marks 

P692 and N692 (fig. 15), where bench marks 1 mile 

apart have subsided 4 and 16 feet, respectively.

Post-1966 leveling substantiates the presence of a 

marked subsidence gradient in the vicinity of well 

19/16-23P2. The bench mark in the concrete pad of the 

recorder site was first leveled in March 1966 and was 

releveled in March 1967 and December 1967. Neither of 

the post-1966 periods indicates that the measured compaction exceeds subsidence. Measured compaction 

above a depth of about 2,200 feet is only slightly less 

than the subsidence. For the period from March 1966 to

March 1967, the data indicate that about 98 percent of 

the subsidence is being measured. Thus the presence of 

abrupt lateral changes in subsidence rate have been 

verified at the site. The leveling record shows that from 

March 1966 to March 1967 about 20 percent more subsidence occurred at the compaction-recorder well than 

at bench mark Z888.

In September-December 1964, the Bureau of Reclamation drilled four wells, principally for the purpose of 

monitoring lower-zone potentiometric head changes 

along the San Luis Canal (wells 14/12-12H1, 

15/13-11D2, 18/16-33A1, 20/18-6D1). The wells are 

868-1,070 feet deep, and compaction recorders have 

been installed in them by the Geological Survey in order 

to provide information regarding the maximum amount 

of compaction that might be occurring in the upper 

water-bearing zone. The compaction recorders are 

operating satisfactorily, and the preliminary results 

from them are used in the discussion of compaction 

above and below the Corcoran Clay Member. (See section "Proportions of Compaction Occurring in the Upper 

and Lower Zones.")

In 1965, the California Department of Water Resources drilled well 13/15-35D5, and in 1966, wells 

15/16-31N2, 3 and 18/19-20P1, 2. The Geological Survey has installed equipment to observe compaction and 

water-level changes in these wells. At each site, a well 

was drilled to the Corcoran and a compaction recorder 

was installed in order to measure the amount of compaction between the land surface and the Corcoran. 

Total subsidence will be obtained by periodic leveling to 

a bench mark set in the concrete pad. These wells should 

help evaluate compaction rates in areas where ground 

water is mostly pumped from the upper zone.
F38 STUDIES OF LAND SUBSIDENCE

UNIT COMPACTION AT THE MULTIPLE 

COMPACTION-RECORDER SITES

The setting of compaction anchors at various depths 

at a given site affords a means of measuring the 

amounts of compaction occurring in the depth intervals 

between the anchors. The amounts of compaction per 

foot of deposits for each calendar year are given in table 

2, and unit compaction for 1-year or 2-year intervals is 

shown for the multiple compaction-recorder sites in 

figures 31 through 34. The thickness values exclude 

deposits above the water table. Changes in the position 

of the water table have been minor during the period of 

record at all the multiple compaction-recorder sites.

Although the percentage compaction for the various 

depth zones is shown to the nearest percent, it is probable that the measurements are accurate to only within 

several percent. Errors can be introduced by initial 

cable stretch and foundation settlement, casing-cable 

friction, untwisting of the cable, and leveling to the 

bench mark. In general, the percentage compaction is 

more accurate at those sites with the most compaction.

Amounts of unit compaction vary from 0 for the 

350-500-foot interval at the Oro Loma site to 0.00115 

foot per foot per year for the 503-703-foot-depth zone at 

the Cantua site (table 2). Amounts of unit compaction 

vary by as much as 100 percent between various years.

Changes in unit compaction with depth for the Los 

Banos-Kettleman City area are the result of two 

factors the increase in head decline to and across the 

Corcoran in much of the area and the decrease in compressibility with depth because of increasing prior 

overburden loads. Both upper- and lower-zone wells 

commonly are perforated in the first 100-200 feet below 

the Corcoran (Miller and others, 1971, pis. 3, 4), which 

suggests that this depth interval may have undergone

the maximum head decline. The combined effects of 

both factors should result in increasing unit compaction 

to a depth of a couple of hundred feet below the Corcoran 

and then decreasing unit compaction below that depth. 

It is not economically feasible to install a sufficient 

number of compaction recorders at any one site to define 

the change in unit compaction within the lower zone. 

However, the variation in unit casing-failure ratio (fig. 

45) suggests that unit compaction decreases below a 

depth of about 200-400 feet below the bottom of the 

Corcoran.

Variation in unit compaction above the Corcoran is a 

function of the degree of confinement as well as variation in compressibility of the deposits. Compaction has 

not occurred in those deposits containing unconfined 

water where the position of the water table has not 

changed. With increasing depth, the upper-zone waters 

generally become better confined, and in the southern 

part of the area, good confinement is provided by several 

extensive lake clays above the Corcoran. Considerable 

variation in applied stress and unit compaction should 

be expected for the different lithologic and genetic units 

of the upper zone.

The mean annual unit compaction in three depth 

zones at the Oro Loma site are shown in figure 31. The 

unit compaction was computed as the mean of two consecutive calendar years to reduce the year-to-year variation and to illustrate trends in unit compaction. The 

largest amounts of unit compaction have been in the 

500-1,000-foot-depth interval which is entirely below 

the Corcoran Clay Member. A progressive and rapid 

decrease in unit compaction has occurred in this 

interval the values of unit compaction for the 1964-65 

period are only one-third those for the 1960-61 period. 

The reduction of compaction rate within this depth inTABLE 2. Annual compaction rates

Well

12/12-16H3 __

16H4 __

16H2 __

16H2 __

14/13-11D4 ___

11D6 ____

11D6 ____

16/15-34N3 __

34N2 ____

34N1 ____

34N1 ____

20/18-11Q1 _ __

11Q2 __

11Q23 -

11Q3 ____

11Q3 _____

j- .

Anchor 

depth

installed

(ft)

350

500

 1,000

1,000

780

1,358

1,358

503

703

 2,000

 2,000

710

845

845

- 1,930

- 1,930

Depth

(ft)

0-350

350-500

500-1,000

0-1,000

0-780

780-1,358

0-1,358

0-503

503-703

703-2,000

0-2,000

0-710

0-845

710-845

845-1,930

n_i Q^ift

Thickness 

of

zone 

(ft)

*340

150

500 1999

!660

578

*l,238 *313

200

1 9Q7

^SIO

^50 *785

i ^^

1,080

'1,870

1959

0.05

.10

.29

.44

.12

.23

.86

1 91

1960

0

.01

.30

.31

.10

.12

.72

.94

Compaction

(ft)

1961

0.01

0

.33

.34

.31

.08

.20

.86

1.14

1962

2 0.04 2 .0

2 .16

.20

.20

.45

.65

.14

.16

.71

1.01

1963

0.00

.01

.19

.20

.23

.25

.48

.08

.17

.71

.96

.32

.29

.61

'Only saturated deposits included in the compactingthickness. Depth to water table in 1965 was 10ft adjacent to 12/12-16H3,120 ft adjacent to 14/13-11D4,190 ft adjacent to 16/15-34N3,

and 60 ft near 20/18-11Q3.

^Approximate values.

"Compaction measured as casing separation between well 20/18-11Q2 and well 20/18- 11Q3 plus increased protrusion of casing of 20/18-11Q3.
LOS BANGS KETTLEMAN CITY AEEA, CALIFORNIA, PART 2 F39

MEAN ANNUAL

COMPACTION RECORDERS UNIT COMPACTION, IN 

12/12-16 FEET PER FOOT

H3 H4 H2 20 40 60 80x10"

500

1000

\l

X1965 v\

:¥j : i ;';;:: V5 --8

' 

later t

& - *

: ' ' - .- /. : -:; " : . :' 

Lowar/ 

confining 

clay J

eble l

i Corcoran Clay 

_^J _ /Member IfT] ': '- '' 'If/1 '' ;;: i " : .';.;;; " : .' '^'I'-'.^i'^

I 

i

: ' . : ,- ' ' . .;.' : | : : -:-"''' '. - ' ' '.-:' : " : / : : '. ' ' '. ' : 

I 

I

I I I I I I I

1960 and 1961

EXPLANATION

1962 and 1963 1964 and 1965

FIGURE 31. Mean annual unit compaction in three depth intervals at the Oro Loma site for 

2-year periods, 1960-65.

terval has been largely responsible for the decreasing 

rate of subsidence indicated by bench mark 97.68 USER 

(fig. 22).

The mean unit compaction values in the upper two 

depth intervals at the Oro Loma site do not show a 

progressive change with time and have never exceeded 

half the unit compaction of the deepest interval. The 

largest unit compaction in the 10-350-foot-depth interval was during the 1962-63 period, and the largest unit 

compaction for the 350-500-foot interval was during the 

1964-65 period. The amounts of compaction were only a 

few hundredths of a foot per year, at most, and never 

exceeded the amounts of compaction recorded in 1959.

The mean annual unit compaction at the Mendota 

site is shown in figure 32. The unit compaction in the 

780-1,358-foot-depth interval (table 2) ranged from 

0.00043 to 0.00078 foot per foot per year for the 1962-65

at multiple compaction-recorder sites

COMPACTION RECORDERS 

14/13-11

D4 D6 (

MEAN ANNUAL

UNIT COMPACTION, IN

FEET PER FOOT

20 40 60 80x10"

hUi

OJ 500

Z

i" 

huj 1000 

Q

-

,

1965 water table

/Corcoran Clay

11111 '

Membe^

KmiK^v^mt^^x'X'v'tfffit^KfiK*}

\

-

i i i i i i

EXPLANATION

1962 and 1963 1964 and 1965

FIGURE 32. Mean annual unit compaction in two depth intervals at the Mendota site for 

2-year periods, 1962-65.

period. When the data are grouped into 2-year periods, a 

slight increase in the lower-zone compaction rate is 

suggested. The 0-780-foot-depth interval has had a decreasing rate of compaction, and the rate of compaction 

in the 0-1,358-foot-depth interval, although variable, 

has been decreasing (table 2).

The largest values of unit compaction in the study 

area have been measured at the Cantua site (fig. 33). 

Although the unit compaction for each depth interval is 

highly variable from year to year, the 1964-65 amounts 

are less than the 1960-61 amounts of compaction. The 

subsidence rate has decreased, and more compaction 

has been occurring below 2,000 feet in recent years, as 

was pointed out in the discussion of figure 28. The 

highest unit compaction has been consistently in the 

503-703-foot interval, which includes the deposits immediately above and below the Corcoran Clay Member, 

and in the Corcoran, which is only 10 feet thick at this 

site.

Compaction Continued

(ft)

1964

0.00

.02

.17

.19

.19

.39

.58

.10

.17

.83

1.10

"~34

"20

.54

1965

0.01

.01

.06

.08

.10

.35

.45

.08

.11

.63

.82

.26

.31

.05

.35

.66

1959

15

67

58

"38

115

66

____

I960

0

7

60

~~32

60

56

____

1961

3

0

66

~~47

~~26

100

66

____

Unit Compaction 

(xlO-5ft/ft)

1962

12

0

32

30

78

"45

80

55

____

1963

0

7

38

~~35

43

26

85

55

~~41

~~27

____

1964

0

13

34

~~29

68

~~32

85

64

~~43

~~19

__

1965

3

7

12

~~15

61

~26

55

49

~~40

39

36

32

____

Interval 

of 

Corcoran 

Clay

Member

(depth

in ft)

379-465

625-700

565-575

715-745
F40 STUDIES OF LAND SUBSIDENCE

COMPACTION RECORDERS 

16/15-34

N3 N2 N1 0

MEAN ANNUAL

UNIT COMPACTION. IN

FEET PER FOOT

20 40 60 80 100X10"'

500

1000

-

^d£« 5 water t

I 

able\

i i l i

ri 

] Corcoran Clay 

| /Member

EXPLANA 

 196(

1dC'

i l i

J

-

TION 

)and 1961 

2 and 1963 

land 1965

i l I

FIGURE 33. Mean annual unit compaction in three depth intervals at the Cantua site for 

2-year periods, 1960-65.

The unit compaction for the Westhaven site has been 

plotted for 1-year intervals in figure 34. Trends in the 

rate of compaction are not readily apparent for the 3 

years considered. The site is the only one that definitely 

shows larger amounts of unit compaction in the upper 

water-bearing zone than in the lower water-bearing 

zone, a subject that is discussed further at the end of 

the section "Casing-Failure Study."

Overall decrease in amounts of annual compaction for 

selected depth intervals at the multiple compactionrecorder sites is shown in figure 35. The data are from 

table 2 and plot with large amounts of scatter. Despite

COMPACTION RECORDERS 

2O/18-11

ANNUAL UNIT COMPACTION, 

IN FEETPER FOOT

Q1 Q2 Q3 20 40 60X10"

500

H 

UJ 

UJ

u. 

- 1000

DEPTH

1500 

*>ne\n

-

^19 35 waill l

er table/

Corcoran Clay

/Member

1

-

_

l 1 l 1

1963

EXPLANATION

1964 1965

FIGURE 34. Unit compaction in three depth intervals at the Westhaven site for 1-year 

periods, 1963-65.

1.0

0.8

0.6

O

o 

_J 

< 0.4

Z

z

0.2

Cantua Creek site 

703 to 2000- foot depth interval

Mendota site 

0 to 1358-foot depth interval

Westhaven site 

0 to 850-foot depth interval

_ Oro Loma site

500 to 1000-foot depth interval

1960 1962 1964

FIGURE 35. Decrease in annual compaction for selected depth intervals at multiple 

compaction-recorder sites.

the scatter, the overall trend toward decreasing rates of 

unit compaction appears to be real. The rate of decrease 

in the amounts of annual compaction appears to be more 

rapid for the two sites in the northern part of the study 

area (Oro Loma and Mendota) than for the two sites in 

the central and southern parts of the area (Cantua and 

Westhaven). Possible geologic factors influencing the 

differences in decrease of compaction rate are discussed 

in the section "Geologic Factors Influencing Specific 

Unit Compaction." The decreases in compaction rate 

shown are not the result of hydrologic changes for at 

least three of the sites, as indicated by minimum potentiometric levels for the lower-zone aquifer system, during the periods of record in table 3. At the Oro Loma and 

Cantua sites, the maximum annual depth to water in 

lower-zone wells had a range of only 3 feet, and at the 

Mendota site, the range was only 7 feet during the 

period of record. About 26 feet of head decline occurred
LOS BANDS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F41

TABLE 3. Variation in the deepest annual water levels for selected 

depth zones at the multiple compaction-recorder sites, 1959-63

Compaction-recorder site 

and depth interval 

(ft)

Oro Loma, 500-1,000

Mendota, 780-1,358

Cantua Creek, 703-2,000 

Westhaven, 0-850

Depth to annual low 

water level, 

in feet, and year

High

__ 202, 1963

__ 496, 1962

__ 600, 1961 

_ 450, 1963

Low

205, 1964 

503, 1965 

603, 1962 

476, 1965

Beginning of 

water-level 

record

9/60 

4/61 

8/60

"Potentiometric level at base of upper zone.

at the Westhaven site after the compaction gage was 

installed, which may account, in part, for the low slope 

of the line showing decrease in annual compaction for 

the upper-zone depth interval at the Westhaven site in 

figure 35.

SHORTENING AND INCREASED PROTRUSION 

OF WELL CASINGS

Shortening and increased protrusion of well casings 

and the distribution of casing failures provide valuable 

information about the compaction of the water-bearing 

deposits. Compaction resulting from water-level 

change is deforming well casings throughout the Los 

Banos-Kettleman City area. More than 3,000 irrigation wells have been drilled during 50 years of expanding agricultural development, but only 1,100 active irrigation wells existed as of 1960 (Ireland, 1963). Most of 

the wells that have been abandoned or destroyed were 

damaged by the compaction of the sediments that encase them. Compaction has caused tens of millions of 

dollars of damage to well casings. For example, in 1965 

it cost about $30,000 to drill, case, and gravel-pack a 

2,000-foot well (maximum water-well depth in the area 

is 3,800 feet). Where subsidence rates exceeded 0.75 ft 

yr-1 (fig. 18), the average well has been abandoned or 

has undergone extensive repairs after only about 8 

years. In areas where subsidence rates have not exceeded 0.5 ft yr" 1 , many wells are still in operation after 

15 years of use, but casing repairs commonly are necessary.

An underwater photograph of a casing failure is 

shown in figure 36. The light source was suspended 

under the camera. Machine-cut slotted perforations can 

be seen at the top of the photograph, and the circular 

cross section of the casing has been changed to a distorted oval. Compressional forces have ruptured the 

casing, and pebbles from the gravel pack can be seen on 

top of plates of sheared casing jutting into the well. 

Many water wells are ruptured in several places. Some 

ruptures can be repaired by swaging deformed parts of 

the casing and installing steel liners, but such repairs 

are costly.

Frictional resistance between the casing and adjacent 

deposits is cumulative with depth. Nonelastic deformation occurs after a critical stress is exceeded. The depth

FIGURE 36. Compressional rupture of an irrigation-well casing. (Photograph courtesy of 

Laval Underground Surveys, Inc.)

at which the critical stress is exceeded is a function of 

well factors such as mode of construction and casing 

diameter and strength as well as geologic factors such 

as lithology of the adjacent deposits and depth distribution, magnitudes, and rates of compaction. Above the 

critical depth, the enclosing sediments may move 

downward relative to the casing and result in increased 

casing protrusion at the land surface.

The combined effects of depth of the compacting interval and casing diameter as related to increased casing protrusion are shown in figure 37. The upper limit of 

increased casing protrusion (dashed line, fig. 39) for the 

various casing diameters shows a progressive decrease 

with increasing casing diameter. Thus, in the Los 

Banos-Kettleman City area, large-diameter (large 

sediment-casing contact area) casings may deform more 

readily than do small-diameter (small sediment-casing 

contact area) casings. The data are from compactionrecorder wells operated by the Geological Survey, and 

the data for only one well were plotted for each multiple 

compaction-recorder site. The period of measurement 

was from September 1965 to September 1966. None of 

the wells are gravel packed, and none were pumped 

during the measurement period.
F42 STUDIES OF LAND SUBSIDENCE

x P

UJ (j

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o o

EC UJ

o. o

(0 UJ

< o

0 EC 0 UJ S°-

w to

< <

UJEC 

u

z

60

20

EXPLANATION

 

Steel casing

o

Steel casing with 

cement jacket

8 12 16

CASING DIAMETER, IN INCHES

FIGURE 37. Relation of increased casing protrusion to casing diameter for observation 

wells that are not gravel packed.

The range in amounts of increased protrusion for a 

given casing size is largely a function of the depth of the 

compacting interval. For example, well 12/12-16H2 

(point A, fig. 37) is 1,000 feet deep, but 90 percent of the 

compaction occurs below 500 feet (fig. 31). During the 

period of measurement for figure 37, compaction apparently occurred entirely below the critical stress depth, 

and increased protrusion of the casing at the land surface did not occur, even though this well has a 4-inch 

casing. For most wells, some compaction due to waterlevel change occurs close enough to the land surface so 

that casing strength exceeds the cumulative casingsediment friction and small amounts of increased casing protrusion are noted. For three observation wells 

shown in figure 37, increased casing protrusion exceeded 20 percent of the measured compaction.

SHORTENING OF AN OIL-WELL CASING

Observations of an oil-well casing at the Westhaven 

site (20/18-11Q3) show that even a heavy oil-well casing encased in a cement jacket is too weak to resist the 

compressional force of the compacting sediments and is 

being shortened virtually in accord with the compaction. Instrumentation of the well has resulted in the 

obtaining of data about casing shortening and protrusion, compaction, and water-level changes. Preliminary 

results were presented by Poland and Ireland (1965).

When the oil test was drilled by the Texas Co. in 1957, 

a surface string of 11%-inch casing with a wall thickness of 0.44 inch was set from the land surface to a depth 

of 2,004 feet. The seal to prevent contamination of the 

fresh ground water was completed by pumping cement 

into the annular space around the casing. When the oil

test was abandoned, a cement plug was placed in the 

well between 1,930 and about 2,030 feet.

The Geological Survey converted the blank casing 

into a dual water-level well in April 1958. The casing 

was gun perforated from 755 to 805 and 1,885 to 1,925 

feet. Hydraulic separation of the two intervals was done 

by the following method. A four-inch pipe with a packer 

attached was lowered inside the casing to a depth of 860 

feet. A cement plug was placed on top of the packer, thus 

sealing the space between the 4- and 11%-inch casings 

in the depth interval 830-860 feet. A diagram of the 

converted well is shown in figure 38.

Initially, the 4-inch casing was suspended by a casing 

hanger resting on top of the 11%-inch casing. Four 

months after installation, the casing hanger appeared 

to be rising off the top of the 11%-inch casing, indicating 

shortening of the 11%-inch casing above the cement 

bond between the casings at a depth of 830-860 feet. The 

cumulative separation (top of the 11%-inch casing is 

below the top of the concrete pad in figure 39) was 

measured monthly, and by November 1969 the 

11%-inch casing had been shortened 3.30 feet.

Shortening of 1,930 feet of casing was measured, 

starting in August 1962, by setting a compaction anchor 

on top of the cement plug. Measurements of changes in 

the protrusion of the 11%-inch casing above the land 

surface were started in February 1963.

The measurements just described made it possible to 

measure casing shortening for the depth intervals 

0-845, 845-1,930, and 0-1,930 feet. Compaction to

Distance from clamp on cable to 

top of steel rack decreeses as 

distance from lower cement 

Reference clamp plug to land surface decreases

on cable ^Casing hanger on 4-inch casing

- -Separation of 4-inch and 11%-

inch casings 

::rProtrusion of 11%-inch casings

 11%-inch casing with cement seal

 -.' " outside

^Confining bed, 

715-745 feet

.= _ _ j \3un perforations, 755-805 feet

5

^Packer and cement plug, 830-860

feet

perforations, 1885-1925 feet

nchor weight at 1930 feet, at 

lower end of compaction cable 

Cement plug, top at 1930 feet

FIGURE 38. Diagrammatic sketch of wells used for measuring water levels and compaction; 

wells 20/18-11Q2 and 11Q3. (From Poland and Ireland, 1965.)
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

SHORTENING OF WATER-WELL CASINGS

F43

FIGURE 39. Compaction gage and casing separation at wells 20/18-11Q2 (inner casing) and 

11Q3 (outer casing).

1,930 feet was measured by movement of the land surface relative to the reference clamp on the cable; it was 

equivalent to the amount of increased casing protrusion 

above the land surface added to the amount of casing 

shortening. The results are shown in figure 40. The plot 

of increased protrusion shows a reversal of about 0.015 

foot late in 1963. Most of the reversal was due to soil and 

lumber swell which raised the table that was used as a 

reference point to measure changes in the position of the 

top of the casing. A concrete pad was poured in May 

1964, and reversals of increased casing protrusion have 

been minor since then.

Between August 1962 and October 1965, the total 

compaction above 1,930 feet was 1.98 feet. The total 

shortening of the 11%-inch casing and its cement jacket 

from the land surface to a depth of 1,930 feet was 1.83 

feet (1.98 ft minus 0.15 ft of increased casing protrusion). Casing shortening was 0.92 foot in the 

0-845-foot-depth interval (casing separation) and 0.91 

foot in the 845-1,930-foot-depth interval (1.83 ft minus 

0.92 ft). For the 3-year record plotted in figure 40, casing 

shortening was equal to 92 percent of the compaction. 

Roughly 95 percent of the subsidence is being measured 

by the 1,930-foot compaction recorder. (See end of section "Cumulative Compaction at Multiple CompactionRecorder Sites.")

The oil-well casing at 20/18-11Q3 had an increased 

protrusion equal to 8 percent of the measured compaction. Well 19/16-23P2 also is an abandoned oil test and 

has an increased protrusion equal to about 3 percent of 

the measured compaction. These values of increased 

protrusion are about the same as for water-well casings 

of similar diameter.

The main effect of compaction on well casings in the 

Los Banos-Kettleman City area has been to shorten the 

casings; amounts of increased protrusion have been 

minor. In contrast, in at least one subsiding area, Mexico City, observed protrusion of water-well casings has 

been as much as 18 feet in response to subsidence of 

about the same magnitude (Poland and Davis, 1969, p. 

227-228 and pi. 6), showing that under certain physical 

conditions, the friction between the compacting sediments and the well casing may not be sufficient to overcome the casing strength. However, in Mexico City, the 

observed protrusion of well casings almost as great as 

the total subsidence is believed to be due in part to the 

fact that wells are drilled using several casing sizes. The 

maximum protrusion is observed for inner casings 

separated from the formation for part of their length by 

outer casings of larger diameter.

General information about the shortening of waterwell casings in the Los Banos-Kettleman City area is 

available through bench-mark surveys made by the 

Coast and Geodetic Survey. During the mid-1950's, 

many well bench marks were established by chiseling a 

cross on top of the well casings or casing hangers of 

active and unused irrigation wells. For about 40 of these 

wells, reference bench marks consisting of a standard 

disk set in a concrete post were established within 0.1 

mile of the wells.

It has been demonstrated that bench marks on well 

casings are not stable even though the casing may extend beneath the compacting sediments (Poland and 

Ireland, 1965). Also, increased protrusion of a casing 

above the land surface should not be considered a reliable measure of either land subsidence or compaction. 

The unreliability of well bench marks stems from the 

fact that the proportions of casing shortening and increased casing protrusion are unknown, unless detailed 

measurements are made such as were described for the 

Westhaven site.

Some useful generalities, however, can be made by 

comparing well bench marks and nearby reference 

bench marks. A comparison of 18 pairs of well and 

reference bench marks is shown in figure 41. These 

selected pairs included only those pairs in which reference bench marks were 17-193 feet from the well bench 

marks, and excluded all those pairs of bench marks in 

near-surface subsidence areas. The surface casing 

diameter of the selected irrigation wells ranged from 12 

to 20 inches. The periods between bench-mark surveys 

ranged from 2 to 9 years.

The comparison in figure 41 shows that the amounts 

of subsidence at the well and reference bench marks are 

not greatly different, as is shown by the way in which 

the points plot close to the line of equal subsidence for
F44 STUDIES OF LAND SUBSIDENCE

2.0

1962 1963 1964 1965

FIGURE 40. Shortening of 11%-inch casing, wells 20/18-11Q2 and 11Q3.

the two types of bench marks. From this can be stated 

that, in general, water-well casings in the Los Banos 

-Kettleman City area are being shortened in amounts 

roughly equal to the compaction of the deposits within 

the well depth.

The small amounts of increased casing protrusion 

make the measured amounts of subsidence at well 

bench marks less than the true amounts of subsidence. 

Where increased protrusion has occurred, all the points 

should plot below the line of equal subsidence in figure 

41. Actually, 7 of the 18 points plot above the line, which 

means that some well bench marks subsided more than 

the reference bench marks despite the tendency of increased casing protrusion to reduce the amount of

measured subsidence. Apparently, amounts of subsidence vary considerably for distances of less than 200 feet 

from wells.

The plot shown in figure 42 was made to determine 

whether the pumping of wells had any relation to the 

variation of subsidence measured at well and reference 

bench marks. The differences of subsidence between the 

two types of bench marks were as much as 9 percent. 

The differences are influenced to a small extent by the 

amounts of regional subsidence gradients between the 

two bench marks. However, the effect of regional subsidence trends probably is negligible for distances of 

17-193 feet. In every case where the well was not 

pumped between levelings, the well bench mark sub-
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F45

I 

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Subsidence of well bench 

mark equals subsidence 

of reference bench markN

0246 

SUBSIDENCE OF REFERENCE BENCH MARKS, IN FEET

FIGURE 41. Subsidence of well b^nch marks and reference bench marks within 17-193 feet 

of the well bench mark.

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EXPLANATION

o

Well pumped between 

levelings

Well not pumped 

between levelings

12 16

CASING DIAMETER, IN INCHES

20

FIGURE 42. Effect of pumping on differences of changes in altitudes of reference and well 

bench marks. o=well pumped between levelings; »=well not pumped between levelings.

sided less than the reference bench mark. This can be 

explained in two ways: First, part of the compaction

adjacent to the well casing results in increased casing 

protrusion instead of subsidence; second, if a well has 

become unused within the past few years, the applied 

stresses in the prior drawdown cone near the well may 

still exceed the maximum stresses that have been applied to the deposits beneath the reference bench mark. 

Where this situation exists, prior larger compaction 

amounts near the well may have made the deposits less 

susceptible to compaction, relative to the deposits beneath the reference bench mark, during the period between bench-mark surveys.

This evidence suggests that because the wells are 

point sources of maximum applied stress, maximum 

compaction occurs at or near the wells and that differences of subsidence between closely spaced bench marks 

near pumped wells should be expected. The magnitude 

of subsidence dimples around pumping wells should be 

larger than indicated in figure 42 because subsidence of 

well bench marks is reduced by any increased protrusion that has occurred. For several pairs of wells, the 

increased protrusion was sufficiently large that the 

subsidence of the well bench mark was less than subsidence of the reference bench mark, even though the well 

was pumped between bench-mark surveys.

CASING-FAILURE STUDY

Many of the water-well casings that are ruptured by 

compacting deposits are repaired. Before repairs are 

attempted, a survey of the damage to the well casing 

commonly is made with an underwater camera to locate 

the damage and to evaluate the feasibility of repairing 

the casing break. A photograph of a casing break is 

shown in figure 36. A study of the types, distribution, 

and relation of casing breaks to the adjacent deposits 

has been made by W. E. Wilson (written commun., April 

1968) in about 650 square miles of the study area between townships 13 and 21 south. Selected parts of 

Wilson's work are included here and in the section 

"Geologic Factors Controlling Compaction of the Unconsolidated Deposits" because they provide information about compaction that cannot be obtained by compaction recorders.

Wilson's study included more than 1,100 reported 

casing failures in 275 irrigation wells. Most of the 

breaks were compressional types that resulted in the 

casing shortening. The data were obtained by the Laval 

Underground Surveys, Inc., and from pump company 

repair records.

The vertical distribution of casing failures with respect to the Corcoran Clay Member of the Tulare Formation is shown in figure 43. All the casing breaks have 

been included, and the number of failures per 1,000 feet 

of well casing surveyed is plotted for each 50-foot increment above and below the Corcoran. The unit casing-
F46 STUDIES OF LAND SUBSIDENCE

1000

04 8 12 16 

FAILURES PER THOUSAND WELL-FEET SURVEYED

FIGURE 43. Unit casing-failure ratio for 50-foot intervals above and below the Corcoran 

Clay Member of the Tulare Formation. (From W. E. Wilson, written commun., April 1968).

failure ratio increases to a depth of about 200 feet below 

the bottom of the Corcoran. The depth to the base of the 

Corcoran within Wilson's study area ranged from 500 to 

more than 900 feet. Below a depth of about 200 feet 

below the bottom of the Corcoran, the values of unit 

casing-failure ratio decrease. Part of the fluctuation of 

the plot below a depth of 300 feet below the Corcoran 

probably can be attributed to the decrease in footage of 

well casing surveyed at the greater depths. Only 20 

percent of the total footage of well casing surveyed was 

at depths of more than 300 feet below the bottom of the 

Corcoran (W. E. Wilson, writtencommun., April 1968). 

The vertical distribution of unit casing-failure ratio 

permits some useful general conclusions regarding the 

variation of compaction with depth in the Los Banos 

-Kettleman City area, if one makes the assumption 

that casing failures are most common in depth intervals 

that are compacting the most. From 300 feet above the 

Corcoran to land surface (depth interval ranges of 0-100

to 0-600 ft), the sparseness of casing failures indicates 

that little compaction is occurring. Maximum unit compaction is suggested in the interval between 50 feet 

above the Corcoran and 250 feet below the Corcoran. 

The unit casing-failure ratio for this interval is about 

twice that of the deposits above and below the interval. 

The Corcoran has a unit casing-failure ratio of only 5, 

indicating that the Corcoran either is not compacting as 

much as the deposits above and below it or that the clay 

does not grip the casing and gravel pack of the wells 

tightly enough to result in shortening of the casing 

equal to the shortening of the deposits of the Corcoran. 

The lower values of unit casing-failure occurrence below a depth of 400 feet below the bottom of the Corcoran 

suggest that deposits at these depths have a lower 

specific unit compaction than the deposits above them. 

Some reasons for the increasing and decreasing trends 

of unit casing-failure ratio are discussed in the section 

"Distribution of Well-Casing Failures."

Wilson found that the casing failures were most 

common in the areas that had subsided the most (W. E. 

Wilson, written commun., April 1968). A comparison of 

unit compaction at multiple compaction-recorder sites 

and unit casing-failure occurrences in the same depth 

intervals of nearby irrigation wells is shown in figure 

44.

At the Mendota and Cantua sites, the variation in 

unit casing-failure ratio agrees very well with the variation in unit compaction for the same depth intervals. 

The agreement is not good at the Westhaven site. Casing failures are more common per unit well foot surveyed in the lower zone, yet figure 34 indicates that the 

upper zone has the largest unit compaction. One explanation for this apparent anomaly is that the lower-zone 

deposits may grip the well casings more tightly than the 

upper-zone deposits.

PROPORTIONS OF COMPACTION OCCURRING IN THE 

UPPER AND LOWER ZONES

General information about the proportions of compaction occurring in the upper and lower zones is available at 12 compaction-recorder sites in the Los Banos 

-Kettleman City area. The upper zone is 300-900 feet 

thick, and the lower zone is 400-2,400 feet thick. The 

amounts of water pumped and the resulting compaction 

of the two zones vary greatly in the different parts of the 

area.

Most compaction-recorder wells do not have anchors 

set in the top of the Corcoran. The main purpose of the 

Bureau of Reclamation wells along the San Luis Canal 

was to monitor lower-zone head changes. In some cases, 

a suitable sand was not found within 200 feet of the 

bottom of the Corcoran. The main purpose of the Department of Water Resources wells at the Yearout,
800

Ul U-

>Z

m - 400

Ul DC 

00

<tc

OJH 400

o m z-

_i cc

ui O

ta o

h O

a! O

800

1200

ui ui u.

m - 400

Ul oc

z° 

<tc

OTy 

Q

o 400

h

OZ CQ 

0< 800

ui O m u

h O 

<L O

ni 1200

LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 

MENDOTA SITE CANTUASITE WESTHAVEN SITE

F47

Corcoran

Clay 

Member^

20 40 60 0 20 40 60 80 0 20 

A. MEAN ANNUAL UNIT COMPACTION X 10*1963-65, IN FEET PER FOOT

40 60

Corcoran

Clay 

Member

12 12 16 12

B. UNIT CASING-FAILURE RATIO, IN FAILURES PER 1,000 FEET

FIGURE 44. Comparison of unit compaction at the Mendota, Cantua, and Westhaven sites and unit casing-failure ratios in the same depth intervals of nearby irrigation 

wells. A, Mean annual unit compaction, 1963-65. B, Variation of unit casing-failure ratio with depth. (From W. E. Wilson, written commun., April 1968.)

Tranquillity, and Lemoore sites was to determine the 

proportion of compaction occurring above and below the 

Corcoran. The compaction recorders at these sites have 

anchors set near the top of the Corcoran to measure

shortening of the deposits between the land surface and 

the Corcoran. Total subsidence and lower-zone compaction are obtained as a result of periodic surveys of the 

bench marks at the sites.
F48 STUDIES OF LAND SUBSIDENCE

Estimates of the proportions of compaction occurring 

in the two zones are based on compaction-recorder data 

and bench-mark surveys. The proportions of subsidence 

in the two zones described in this section are based on 

information obtained since 1958, but the proportions 

are generally applicable for pre-1960 periods, such as 

the 1943-59 period, because the proportions of water 

pumped from the two zones in the different parts of the 

area (based on well-perforation data) have not changed 

greatly since 1943. Estimated proportions of the compaction occurring in the upper and lower zones are 

given in table 4. The Corcoran has been included in the 

lower zone in this discussion.

Several correction procedures were necessary to compute the rough estimates because the compaction anchors were not set in the top of the Corcoran at most 

sites. Estimates at those sites where the well does not 

bottom near the top of the Corcoran may overestimate 

the proportion of upper-zone compaction by as much as 

10 percent. Estimates of the unit compaction between 

an anchor and the top of the Corcoran were made as 

follows. At multiple compaction-recorder sites

12/12-16H and 16/15-34N, the unit compaction was 

determined for the interval between the bench marks 

set above and below the Corcoran. At the single compaction sites where the anchor was set above or below the 

Corcoran, the unit compaction for the interval between 

the water table and the anchor was used to interpolate 

or extrapolate amounts of unit compaction in order to 

estimate the amount of compaction between the water 

table and the top of the Corcoran. Corrections based on 

these procedures provided estimates of the maximum 

proportion of compaction occurring above the Corcoran 

because values of unit compaction are larger for the 

lower zone than for the upper zone, except at the south 

end of the study area (figs. 33, 36).

The proportions of compaction in the upper and lower 

zones given in table 4 and shown in figure 45 indicate 

that, in general, north of Cantua Creek less than 20 

percent of the compaction occurs in the upper zone, but 

south of Cantua Creek about 30-40 percent of compaction is occurring in the upper zone. Northeast of the 

town of Cantua Creek, most of the water is pumped from 

upper-zone aquifers, which in that area yield the best

TABLE 4. Proportions of compaction occurring

Well

1O/1O 1 £UQ

16H4__ 

i Q/I o onTn

13/15-35D5 __.

1 A /I O 1 OTJ1

14/13-11D4

15/13-11D2 __ .

15/16-31N3

16/15-34N3 __ .

34N9

1 Q/1 £ OOA1

1 8/1 Q_ 9ftP9

OA/1 Q CTI1

11Q1

Period 

of

measurement

._ _ 10/61 10/65

.__ _ 10/61 10/65

Q/££ 1 1 ICH

K.ICC C/£Q

Q/££ 1 1 ian

19/fi9 1O/fiP\

. __ - 9/65-9/66

o la n o ia o

1 o la o 1 o ia c

._ _ .12/62-12/65

Q/££ 1 1 IG.H

O/CT o/cn

Q/££ 1 1 IGTJ

12/64-12/65

Depth 

interval 

Corcoran

Clay 

Member 

(ft below 

land surface)

379-465

379-465

304-418

A OQ A na.

fi1 f^_71 Q

625-700

rr/jQ QCCl

KQK C.A O

KCCK7K

565-575

TQ1 QAC

CCT £Q>I

Q1 1 QOA

715-745

Anchor depth 

when

installed 

(ft below 

land surface)

OCA

500

690

440

Q1 Q

nsic\

QCQ

CQC

cnq

7fiQ

1 fl9Q

CTQ

ocn

710

Position 

of anchor 

above (+) 

or

below (-) 

top of 

Corcoran Clay 

Member

_i_oq

QQ£

19

OQQ

ICC

1QO

-11

i CO

1 QQ

948

-11

+ 5

Depth to 

water

table, 

1965

(ft)

10

10

1 Qf\

10

190

ion

990

1 ^

190

40

1 ^

IKfl

Compacting 

interval

(ft)

Compacting 

thickness

(ft)

10-350

340 

350-500

150 

180-690

510 

10-440

430 

190-913

723 

120-780

660 

220-958

738 

15-596

581 

190-503

313 

503-703

200 

40-1,029

989

15-578

563 

150-867

717 

60-710

650
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F49

quality water. Pore-pressure decline occurs in the lower 

zone mainly as a result of extensive lower-zone pumping in the vicinity of Cantua Creek. Southeast of Mendota, saline waters occur in the upper zone but not in the 

lower zone, and the combined effects of lower-zone 

pumping and lower-zone head decline more than 5 miles 

to the southwest result in more than 90 percent of the 

compaction occurring in the lower zone. Within the 

Delta-Mendota Canal service area, the wells supplementing the surface-water imports pump mainly 

lower-zone water. In addition, part of the head decline 

results from intensive lower-zone pumping to the south. 

Large proportions of lower-zone compaction occur at 

both the Yearout and Lemoore sites despite heavy 

upper-zone pumping at both sites. The upper-zone deposits being affected by pore-pressure decline are only 

200-350 feet thick and consist largely of sands which 

undergo little inelastic compaction (Pt. 3, Bull and Poland, 1974). At the Lemoore site, the fresh-water bearing deposits below the Corcoran are more than 800 feet 

thick; the lower-zone head decline to the west apparently has decreased artesian head at the site sufficiently

in the upper and lower water-bearing zones

to result in more than 80 percent of the compaction 

occurring in the lower zone.

GEOLOGIC FACTORS INFLUENCING

COMPACTION OF THE 

UNCONSOLIDATED DEPOSITS

The geologic factors affecting compaction of unconsolidated deposits can be evaluated on a local or regional basis. Within the Los Banos-Kettleman City 

area, sufficient data are available to assess the effect of 

overburden load, petrology, and bedding at core-hole 

sites and to assess areally the effect of prior total applied 

stress, age of the deposits, mean lithology, and source 

and mode of deposition on the susceptibility of the deposits to compaction upon increase in applied stress 

caused by ground-water pumping.

LOCAL RELATIONS

OVERBURDEN LOAD

The prior effective load on a given deposit partly 

determines the amount it has compacted in the geologic 

past and the potential for future compaction. In general,

Measured

(ft)

0.05

.04

.16

.03

.48

.52

.16

.20

.26

.45

qq

.07

.45

.25

Extrapolated 

compaction 

between

and 

top of 

Corcoran

0.01

.12

0

.20

.12

.04

' 0

.14

.08

0

.04

0

Estimated 

maximum 

compaction

above 

the 

Corcoran

0.06

.04

.03

.28

.40

.12

.20

.40

9^

.07

.41

.25

Subsidence 

during

P^f Maximum 

measurement upper-zone 

,A, compaction 

utl (percent)

Minimum 

Estimated; lower-zone 

Rpnch mark extrapolated compaction Bench-marK f 1963_66 (uercent) 

surveys subsidence (percent) 

map

1.30 ________ 95

.29 ........ ^

86 

........ .48 -f94 

.99 ........ &-

72 

2.14 ........ ^

81 

........ .90 J»

87 

________ .63 ZL

68 

3.15 ........ 2-

87

.56 *fi ________ 45^ 

________ .50 

86 

1.23 ________ f67 

.60 4f 58
F50 STUDIES OF LAND SUBSIDENCE

120°30' 120°00'

37°00

\o Cantua Creek EXPLANATION

Boundary of deformed 

rocks

Boundary of areas of near-surface subsidence 

as mapped in 1961

Approximate proportions of compaction in 

the upper and lower zones at compactionrecorder sites, in percent

Number above line is maximum upper-zone 

compaction; number below line is minimum lower-zone compaction 

 70 

Approximate line of equal proportion of 

lower-zone compaction to subsidence

Interval 20 percent. Based on computed 

estimates of minimum lower-zone compaction at recorder sites, a map showing 

the proportion of irrigation water pumped 

from the upper and lower zones, and the 

compressibility and thickness of the lower- and upper-zone deposits

15 MILES

Coalinga

VALLEY

36°30' 

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 45. Proportions of compaction occurring in the upper and lower water-bearing zones.

amounts of prior compaction increase with depth because prior applied stress increases with depth and because geologic time has been sufficient for applied stress 

increases to become effective, even in thick clay beds.

Several lines of evidence show that the compressibility of the deposits at the core-hole sites decreases with 

increasing depth of burial. Two examples of the decrease in compressibility with increasing effective
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F51

stress at the Cantua site, derived from one-dimensional 

consolidation tests of core samples, are discussed in 

conjunction with figure 59.

The upper-zone deposits should be more compressible 

than the lower-zone deposits at the core-hole sites because they have been subjected to less prior effective 

stress. Petrologic characteristics greatly affect compressibility, but samples from the core-hole sites do not 

show major petrologic changes with depth of the deposits of a given source and depositional environment.

The relation between prior effective stress and compressibility of the deposits in the upper and lower zones 

probably explains the higher unit compaction in the 

upper zone at the Westhaven site (fig. 34). The bulk of 

the deposits in both zones at the Westhaven site consists 

of Diablo alluvial-fan deposits, with minor lacustrine 

deposits (Miller and others, 1971). Hydrographs of the 

wells at the site (Pt. 1, Bull and Miller, 1974, fig. 14) 

show that the history of head change at the base of the 

upper zone is about the same as that in wells tapping 

different parts of the lower zone. In addition, the casings 

of many of the irrigation wells in the vicinity of the 

Westhaven site are perforated for 100 feet or more 

above the Corcoran, indicating that withdrawal of 

ground water and head decline are common in the upper 

zone.

Specific unit compaction in the upper zone at the Oro 

Loma, Mendota, and Cantua sites also probably exceeds 

the lower-zone specific unit compaction at the sites, but 

is not apparent in figures 31-33. The total compaction 

for the upper zone at these three compaction-recorder 

sites probably is small because (1) the proportion of the 

upper-zone deposits affected by substantial head decline is much less than in the southern part of the study 

area and (2) the change in applied stress has not been as 

large as in the lower zone.

The factors affecting the relation between applied 

overburden load and unit compaction also are apparent 

in the plot of unit casing-failure ratio versus vertical 

distance from the Corcoran (fig. 43, and W. E. Wilson, 

written commun., April 1968). Unit casing-failure ratio 

increases to a depth of about 200 feet below the Corcoran and then decreases with increasing depth for the 

rest of the lower zone. Wilson's plot can be interpreted 

as follows if it is assumed that unit casing-failure ratio 

is related directly to the unit compaction of the adjacent 

deposits. For a given suite of deposits, unit compaction 

decreases with depth and increases with increasing 

pore-pressure decline. Pore-pressure decline is related 

directly to the amounts of water pumped from the deposits and hence to the perforated interval of the wells. 

Most of the wells are perforated mainly in the lower 

zone, and many of the wells that tap mainly the upper 

zone also tap the uppermost 100-300 feet of the lower

zone (Miller and others, 1971, pis. 3, 4). Wells that tap 

both zones are most common in the southeastern, eastern, and northern parts of the area. Thus, the pattern of 

unit casing-failure ratio shown in figure 43 is logical. 

The upper part of the plot reflects the dominance of 

progressively greater pumping of confined water to a 

depth of about 200 feet below the Corcoran. The lower 

part of the plot reflects dominance of the other component decreasing compressibility of the deposits with 

depth because of the effect of the preexisting overburden loads and because of the moderately good hydraulic 

conductivity of the lower zone.

A detailed assessment of the properties of core samples from three sites in the Los Banos-Kettleman City 

area has been made by Meade (1968). Although the core 

samples reflect the selectivity of the coring process 

(more clays than sands are recovered), Meade's analysis 

provides a valuable insight into the factors influencing 

void ratio and porosity of sediments underlying areas of 

land subsidence.

The relation between the logarithm of applied stress 

at the time of coring and void ratio for 40 core samples 

consisting of clayey silt is shown in figure 46A. Meade 

segregated the cored alluvial sediments of the Los 

Banos-Kettleman City area into four lithologic groups 

to minimize the strong correlation between particle size 

and void ratio that also occurs in the suite of cores. The 

term "clayey silt" is based on Shepard's (1954) 

classification. The gap in the plot between applied 

stresses of 20 and 35 kilograms per square centimetre 

reflects the differential in artesian head across the Corcoran that exists in the northern and central parts of the 

area. The regression line shown in figure 46A suggests 

that for the alluvial clayey silts cored, the void ratio 

would decrease from about 0.8 to 0.6 upon an increase in 

applied stress from 20 to 80 kilograms per square centimetre.

PETROLOGY

Laboratory consolidation tests made by many workers have shown that, in general, clays are much more 

compressible than sands. On the basis of the large body 

of literature discussing the result of laboratory studies, 

it is only natural to assume that conditions in the field 

consist of (1) small amounts of chiefly elastic compaction that occur rapidly in sands and (2) large amounts of 

chiefly inelastic compaction that occur slowly in clays.

These assumptions, although probably true in a general sense, have yet to be fully verified in the field. 

Furthermore, the state of knowledge about laboratory 

consolidation of sands is not nearly as well known as for 

clays because of the difficulty of fitting a sand sample 

into a consolidometer ring without disturbing the sample to the extent that results are unreliable. Most of the 

deposits in the study area consist of thin beds that
F52 STUDIES OP LAND SUBSIDENCE

1.0

0.5

IIIIITT

i i i i i i i

50

40 gu 

cc i

30

10 20 40 80

APPLIED STRESS, IN KILOGRAMS 

PER SQUARE CENTIMETRE

SORTING (SO) 

2 4

1.0 50

O 

OC

1 2 3 

QUARTILE DEVIATION (QD0)

CC 

Q 

O 0.5

50

40

30

20

^n

0 j

O

4 16 64 

MEDIAN DIAMETER, IN MICRONS

250

FIGURE 4(j. Relation of applied stress, sorting, and particle size on void ratio and porosity of 

selected suites of samples of alluvial sediments from three core holes in the Los Banos 

-Kettleman City area. Figures are from Meade (1968, figs. 11C, 13A, 16); solid lines are the 

regression lines, dashed lines represent the 95 percent confidence limits. A, Relation 

between void ratio and applied stress for clayey silts. B, Relation between void ratio and

0 25 ^'75 

quartile deviation QD, = - in silty sands. C, Relation between void ratio and

median particle diameter for all samples.

contain clay. Compaction recorders have measured net 

change in thickness of suites of deposits. None of the 

compaction recorders have been positioned in pairs so as 

to measure specifically changes in the thicker lacustrine silty clays and clayey silts such as the Corcoran. 

Because of the lack of quantitative information about 

the compaction of different lithologies in the field, many 

of the interpretations about compaction in subsidence 

areas are based on assumptions derived from laboratory 

investigations.

Compaction of sands occurs as a result of elastic compression of the grains and by rearrangement of the

particles. Most of the laboratory studies about consolidation of sands have been made on clean quartz sands, 

and little work has been done on clayey sands, micaceous sands, and polymineralic sands. Meade (1968, p. 

9-14) reviewed the work that has been done regarding 

the void ratio characteristics of sands. In brief, void 

ratio of sands decreases with increase in median diameter, decrease in sorting, decrease in the angularity of 

the grains, and increase in overburden load.

Consolidation characteristics of sands that contain 

mica flakes are different from mica-free sands. The mica 

flakes act as elastic beams between some of the sand 

grains. Studies by Gilboy (1928) showed that only a 

small percentage of mica added to a clean quartz sand 

greatly increases the compressibility of the sand.

The variable presence of mica in the sediments of the 

Los Banos-Kettleman City area may explain, in part, 

the variations in net specific unit expansion that have 

been observed at compaction-recorder sites. According 

to Meade (1967, p. 5), sands derived from the Sierra 

Nevada contain 2-5 percent of fresh-looking biotite in 

large flakes, and sands derived from the Diablo Range 

contain 2 percent or less of weathered-looking mica in 

small flakes.

In his study of the fabric of sands, Meade (1968, p. 

32-34) concluded that distortion of compressible grains 

such as mica flakes and fragments of partly weathered 

shales and metamorphic rocks contributed to the compressibility of the sands represented by the core samples. He also concluded that the orientation of large 

mica flakes parallel to the bedding in the Sierra sands 

was more conducive to elastic changes in thickness of 

the deposits than the orientation of small mica flakes at 

roughly 45° to the bedding in the Diablo sands. Large 

mica flakes oriented parallel to the bedding should respond to an increase in applied stress by bending around 

the grains an elastic type of movement that is easily 

reversed upon decrease in applied stress. Small mica 

flakes oriented at 45° to the bedding should respond to 

an increase in applied stress by allowing particles to slip 

past one another into a denser state of packing an 

inelastic type of movement that is largely permanent. 

But, as Meade stated, the compressibility of both types 

of fabrics in micaceous sands provides a greater potential compressibility than in mica-free sands.

In general, silts are considered more compressible 

than sands, but not as compressible as clays, probably in 

part because the coarser silt fraction does not have 

sufficient surface area to absorb the large amounts of 

water typically absorbed by clays. Most well-sorted silts 

have larger void ratios than sands because of the greater angularity of individual grains. The poorer sorting of 

some silts, as compared with sands, tends to result in a 

lower void ratio.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F53

Detailed studies of the clay mineralogy of the sediments of 101 samples, 85 from deep core holes and 16 

from streams and alluvial-fan deposits to a depth of 70 

feet, have been made by Meade (1967, p. 18-24). There 

is a uniform preponderance of montmorillonite in the 

clay-mineral assemblages from the Sierra (derived from 

Sierra Nevada) as well as Diablo (derived from Diablo 

Range) source terranes. Calcium is the principal adsorbed cation in the clays. The percent of adsorbed 

sodium increases with depth, but does not exceed 38 

percent of the cations in any of the samples tested.

From studies of samples from core holes at the Mendota, Cantua Creek, and Huron sites, Meade (1967, p. 

22, table 5) estimated that the amount of material finer 

than 3 micrometres represented the proportion of clay 

minerals in the cores. The mean of the material finer 

than 3 micrometres in the 305 core samples is 26 percent. The mean was adjusted by Meade (1967, p. 22) to 

15 percent, as an estimate of the proportion of clay 

minerals in the sediments, because the coring process 

tended to recover more clays than sands. However, the 

3-micrometre size is 1 micrometre smaller than the size 

generally recognized as being the size between clay- and 

silt-size material. Therefore, for purposes of general 

comparison in this paper, the mean percentages of material finer than 3 micrometres are considered to be 

roughly equivalent to the amount of clay-size material 

(less than 4 micrometres in the deposits at each site).

The amounts of clay-size particles in the deposits of 

different source areas and depositional types at the 

three core-hole sites are summarized in table 5. Cores 

from the Diablo flood-plain deposits have the lowest 

clay content (21 percent), and the Sierra deltaic deposits 

have the highest clay content (32 percent). The mean 

clay contents of all the cores from the Diablo and Sierra 

sources are about the same 27 percent for the Diablo 

deposits and 25 percent for the Sierra deposits. Almost

TABLE 5. Amount of clay in deposits from Diablo and Sierra sources 

in the Mendota, Cantua, and Huron cores

Source and mode of deposition1

Diablo: 

Alluvial fan

All Diablo samples

Sierra: 

Flood Plain

Deltaic

All Sierra samples

Combined Diablo and Sierra: 

Lacustrine deposits

All cored samples

Number of 

samples

.___ 145

37

._ _ 182

58

16

74

44

3 305

Percent 

finer than 

3 micrometres2 

(mean)

28

21

27

23

32

25

27

26

iFrom Miller, Green, and Davis (1971, pi. 5).

2Data from Meade (1967, table 5).

3Includes five samples for which the source and mode of deposition were not determined.

half of the samples are Diablo alluvial-fan deposits, 

which have a mean clay content of 28 percent. The 44 

core samples taken from the lacustrine sands and clays 

represent both Diablo and Sierra sources. The lacustrine deposits varied from clean littoral sands to silty 

clays; the mean clay content for the 44 samples was 27 

percent.

The presence of clay adds greatly to the potential 

compressibility of the deposits of the study area. All 

clays tend to adsorb water, and the amount of water 

adsorbed is directly related to the surface area per unit 

volume of clay. Water farther away from the clay particles is not held as tightly as the water next to the clay 

minerals. Increase in applied stress removes the less 

tightly held water, causing a concurrent decrease in 

volume as water is expelled.

The rate of expulsion of water from aquitards and 

aquicludes is also a function of clay content. High clay 

contents tend to decrease the permeability and favor 

development of large residual excess pore pressures for 

a given applied-stress increase and bed thickness.

The fact that 7 parts out of 10 of the clay-mineral 

fraction consist of montmorillonite throughout nearly 

all the Los Banos-Kettleman City area is important. 

Because montmorillonite is very finely divided, it has a 

much larger specific surface than other clay minerals. 

Meade (1964, p. 6), in summarizing the studies of other 

workers, tabulated the following specific surface ranges 

in square metres per gram: montmorillonite, 600-800; 

illite, 65-100; and kaolinite, 5-30. Thus, montmorillonite can adsorb more water at a given applied stress and 

salinity than other clay minerals. This affinity for water 

permits montmorillonite to have a larger void ratio at 

a given effective stress than other clay minerals, and 

therefore more potential for compaction for a given increase in effective stress.

The void ratio of montmorillonite also is dependent, 

in part, on the electrolyte concentration and the nature 

of the adsorbed cations. Meade (1964, fig. 1), in his 

review of the literature concerning the clay-water system, pointed out that stronger osmotic pressures (and 

therefore larger void ratios) are associated with low 

electrolyte concentrations. He also pointed out (fig. 11) 

that at low effective stresses (<10 kg per cm2 ), montmorillonite saturated with sodium cations has a consistently larger void ratio than does montmorillonite saturated with calcium, magnesium, potassium, or alluminum cations. One would conclude, therefore, that 

the clayey deposits at shallow depth within the study 

area would be even more susceptible to compaction if 

the predominant adsorbed cation were sodium rather 

than calcium.

If the void ratio of a sample can be assumed to be a 

rough measure of potential compressibility, a strong
F54 STUDIES OF LAND SUBSIDENCE

correlation between potential compressibility and particle size can be demonstrated. Figure 46C is a plot of 

the logarithm of median diameter and void ratio for 135 

samples selected from alluvial deposits at the Mendota, 

Cantua, and Huron core holes. The semilogarithmic 

regression line suggests that the void ratio decreases 

from almost 0,8 for a median diameter of 1 micrometre 

to 0.6 for a median diameter of 250 micrometres.

Meade noted a significant simple correlation between 

void ratio and sorting of the cored sediments in the 

coarsest grained group of cores the silty sands. The 

results of his regression analysis of void ratio and quartile sorting are shown in figure 46B. Meade (1968, p. 25) 

pointed out that the degree of sorting also decreases 

with depth, and so the regression reflects the effect of 

some other factor(s).

The combined effects of the many physical and chemical factors influencing compaction of clays is difficult to 

assess. In an important statistical study, Meade (1968) 

made a multiple-regression analysis from core studies 

of the Richgrove site in the southern San Joaquin Valley of the pore volume, overburden load, particle size, 

clay-mineral type, type of adsorbed cations, total dissolved solids in leachate, pH, orientation of the montmorillonite flakes, and diatom content. He concluded 

that the effects of overburden load on the pore volume in 

the suite of sediments studied is completely obscured by 

petrologic factors, which were responsible for an increase of void ratio with inceasing depth. The pore volume was most closely related to particle size, diatom 

content, and the proportion of adsorbed sodium. Other 

factors thought to have a direct or indirect influence on 

pore volume were the dominant proportion of montmorillonite in the clay fraction, pH, and electrolyte concentration.

Although a similar study has not been made in the 

Los Banos-Kettleman City area, it is anticipated that 

the petrologic factors having a dominant influence on 

pore volume will not be greatly different from those 

defined by Meade. For example, the diatomaceous clays 

of the Corcoran lacustrine sequence characteristically 

have the maximum void ratios and compressibilities.

BEDDING

The bedding of the deposits is one of the most important geologic factors affecting the rate of compaction of 

unconsolidated sediments upon increase in applied 

stress.

If one considers units that are 50 to more than 1,000 

feet thick, a given type of deposit such as the Diablo 

alluvial-fan deposits is surprisingly homogeneous: 

vertical and lateral changes in lithology occur gradually for a given fan. However, if one considers units of 

only a few inches or feet thick, abrupt changes in lithology are characteristic of all genetic types of the deposits.

The interlayering of thin-bedded compressible finegrained sediments with permeable coarse-grained sediments has resulted in aquifer systems that compact 

rapidly and substantially in response to increase in 

applied stress. Variations from this typical condition 

occur within the study area. In those areas where most 

of the beds are consistently coarse grained, such as some 

sites near the Kings River, the values of specific unit 

compaction (fig. 54) are less than in the areas of heterogeneous interbedding, presumably because the coarsegrained sediments are less compressible than clayey 

sediments. In those areas where hundreds of feet of 

clayey deposits occur, such as northeast of the Big Blue 

Hills, the values of specific unit compaction also are 

smaller than in those deposits that have heterogeneous 

interbedding because the low vertical permeabilities of 

the thick clay beds result in slow compaction rates and 

small amounts of observed compaction.

The time, t, necessary for a specified percentage of 

compaction to be completed in a clay bed can be estimated from the following equation, which is based on 

the Terzaghi theory of consolidation (Terzaghi and 

Peck, 1948, p. 241):

Th2

t=

where

T = a dimensionless time factor that varies nonlinearly with the percentage of compaction 

completed;

h the thickness, in feet, of the compacting layer. 

If it is being drained through both upper and 

lower surfaces, the half thickness is used; 

cv the consolidation coefficient, in square feet 

per year, which is determined as part of the 

one-dimensional consolidation test. 

The Terzaghi equation illustrates the importance of 

the thickness of compressible clay beds on the amount of 

time necessary for compaction to occur. The time required for a stress to become effective varies directly as 

the square of the bed thickness. The variable thickness 

of the Corcoran within the study area can be used as an 

example to illustrate the importance of bed thickness. 

The Corcoran varies in thickness from less than 1 foot to 

more than 100 feet. Assuming homogeneity, that is the 

hydrologic properties are identical and that expulsion of 

pore water only occurs at the bottom, a 100-foot thickness of the Corcoran would require 10,000 times as long 

to undergo a given specific unit compaction as would the 

1-foot thickness. Even 15-foot-thick clay beds may have 

sufficient residual excess pore pressures that they continue to compact after water levels have risen more 

than 50 feet (Pt. 3, Bull and Poland, 1974). _

Electric logs of the wells within the area provide a 

means of evaluating the characteristic bed thicknesses
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F55

of the different types of deposits. An electric log is shown 

in figure 47, and micrologs are shown in figures 48-52.

An electric log of the upper-zone aquifer system at 

well 18/19-20P1 is shown in figure 47. Below a depth of 

200 feet, the resistivity log reveals three thick clay beds 

at about 240 feet, 290 feet, and below 565 feet. Two of 

these clays have been shown to be of lacustrine origin 

(Croft, 1972), the deepest clay being the Corcoran. The 

rest of the section consists almost entirely of waterbearing sands. The resistivity log reveals only general 

information about the gross thicknesses of large units, 

but the spontaneous-potential log shows that many of 

the units that appear to be thick-bedded sands on the 

resistivity log contain beds of finer grained material, 

perhaps having lithologies such as silty sand or clayey 

sand.

The beds of low resistivity on the spontaneouspotential log produce a negative deflection instead of 

the positive deflection commonly noted because of the 

relation of the mud and formation resistivities at this 

site. At the bottom-hole temperature of 21°C (694 ft), 

the mud resistivity was 1.68 ohm-metres (ohm-metres2 

per metre). Apparently, the mud had a much lower 

resistivity than the formation resistivity, hence the 

clays show as deflections to the left and the sands show 

as deflections to the right on the spontaneous-potential 

log. In many of the electric-log surveys made in the 

study area, ground water is used to mix the mud, and as 

a result the resistivity contrast between the mud and 

the formation is so slight that the spontaneouspotential log is virtually useless. Salt is added sometimes to the drilling mud to produce a spontaneouspotential log with characteristics similar to the log 

shown in figure 47.

The spontaneous-potential log of figure 47 shows that 

many of the beds in the Sierra flood-plain deposits between depths of 300 and 500 feet have the following 

thickness characteristics. Most of the sand beds are 

thick bedded, being 10-30 feet thick. Within the sand 

sequences are beds that are interpreted as being clayey 

or silty sand and, in general, are less than 10 feet thick.

Above a depth of 230 feet, the minute crenulations in 

the spontaneous-potential log suggest that the deposits 

are much more heterogeneous than the deposits in the 

depth interval from 300 to 550 feet. The deposits in the 

upper part of the log are interpreted as being alluvialfan deposits derived from the Diablo Range such as 

those noted in nearby core holes.

Detailed bedding of five different types of Sierra and 

Diablo deposits is shown in the micrologs (microinverse 

1" x 1" logs) of figures 48-52. The figures represent 

selected parts from logs made in the Inter-Agency 

Committee core holes at the Mendota, Cantua, and 

Huron sites. Samples from the intervals shown have

SPONTANEOUS

POTENTIAL 

IN MILLIVOLTS

5

-H +

RESISTIVITY, 

IN OHMSm/'m 

(64-inch normal)

200

300

400

500

600

FIGURE 47. Electric log of the deposits at well 18/19-20P1.

been studied petrographically by Meade (1967), and the 

genetic types of deposits have been correlated on a re-
F56 STUDIES OF LAND SUBSIDENCE

gional basis by Miller (Miller and others, 1971). The 

resistivities of the logs have not been corrected to a 

common salinity and temperature. The percent of 

clay-mineral material is from Meade (1967, table 5), 

and the percentage of sand and vertical permeabilities 

are from Johnson, Moston, and Morris (1968). The solid 

arrows represent the reported depths from which the 

samples were collected. Discrepancies between the reported depths and the microlog depths, in general, are 

less than 2 feet. For many of the depths reported in the 

field, the position of the sample had to be estimated 

because 100 percent recovery was not obtained in many 

of the cores. Where discrepancies in depth are apparent, 

a dotted arrow has been added to indicate the bed from 

which the author believes the sample was obtained.

The coefficients of vertical permeability for clayey 

sediments with permeabilities of less than 0.01 gal 

day" !ft~2 (gallon per day per square foot) obtained from 

a variable head permeameter are considerably higher 

than permeabilities obtained from consolidation-test 

data of adjacent core samples. The differences are due in 

part to the unloaded condition and the use of water of 

different chemical character from the pore water in the 

permeameter tests (Johnson and others, 1968, p. 26). 

Therefore, the permeability results shown in figures 

48-52 that are less than 0.01 gal day" 1 per ft~2 probably are higher than if the permeabilities had been computed from a time-consolidation test.

To provide the reader a rough comparison of the vertical permeabilities of the finer grained beds from the 

various types of deposits, mean permeabilities from 27 

consolidation tests are shown in table 6. Only results 

obtained from samples tested in the load range 400-800 

Ib in~2 (pounds per square inch) were used. The mean 

vertical permeabilities shown in table 6 indicate that 

fine-grained lithologies from both the lacustrine and 

alluvial-fan deposits have low permeabilities compared 

with the flood-plain deposits. The Diablo flood-plain 

deposits had the highest mean permeability, which is

TABLE 6. Mean vertical permeabilities of the different types of deposits as determined from consolidation tests of samples in the 

load range 400-800 Ib in ~2 at the four core-hole sites

Source and mode of deposition1

Diablo: 

Alluvial fan

Sierra:

Combined Diablo and Sierra: 

Lacustrine

Number 

of

tests

_ 10

_ 9

4

._ 5

Mean coefficient of permeability2

(gal day^ 1 

ft- 2 x!0^ 5 )

1.7 

5.7

4.0 

2.9

(ftday-'xlO-6 )

2.3 

7.6

5.3 

3.9

'From Miller.Green, and Davis (1971, pi. 5).

2Data from table 9, Johnson, Moston, and Morris (1968, p. 64, 65). Cubic feet times 

7.48 equals gallons.

consistent with the high silt content and low clay content of these deposits as compared with the fine-grained 

beds of the other types of deposits.

The performance characteristics of the wells in the 

northern and southern parts of the study area indicate 

that major differences exist between the transmissivities of the flood-plain and alluvial-fan deposits. Most 

of the wells are designed and pumped in such a manner 

as to yield 1,000-1,500 gallons per minute. In the northern area (such as T. 13 S., R. 13 E.), only 600-1,000 feet 

of perforated interval are needed to get sufficient yields, 

and seasonal lowering of the potentiometric level is only 

40-60 feet. In contrast, wells in the southern area (such 

as T. 20 S., R. 18 E.) have perforated intervals of 

1,200-1,600 feet, and the seasonal lowering of the 

potentiometric level exceeds 100 feet. Comparison of 

yield factors of lower-zone wells tapping different types 

of deposits indicates that the flood-plain deposits are 

three to five times as permeable as the alluvial-fan 

deposits.

SIERRA FLOOD-PLAIN DEPOSITS

Bedding of the Sierra flood-plain deposits at the 

Cantua site is shown in figure 48. The sand beds are

RESISTIVITY, 

IN OHMSm2/m

1000

1050

1100 

Vertical 

permeability in 

gallons per day 

per square foot

FIGURE 48. Bedding, lithology, and vertical permeability of the Sierra flood-plain deposits, 

Cantua site, depth 978-1,134 feet.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F57

thick. A 65-foot-thick sand section occurs between 

depths of 985 and 1,050 feet, but within the bed are two 

thin beds of fine-grained material one that is 1 foot 

thick and one that is 2 feet thick. Despite the large 

thickness of the overall bed, numerous thin beds having 

resistivities in excess of 10 ohm-metres are common, 

indicating the presence of many beds that are coarser 

grained, or have lower clay contents than most of the 

sand section. The lower part of the log also reveals sand 

beds ranging in thickness from 10 to 30 feet. Beds of 

fine grained material as much as 9 feet thick occur also. 

The lithology of the finer grained units is not uniform, 

but instead consists of alternating beds of different 

lithologies that have a mean bed thickness of about 1 

foot.

The lithologies of the Sierra flood-plain deposits have 

a wide range of particle-size distribution. The sand beds 

consist of about 90 percent sand, with virtually no clay. 

The fine-grained beds consist of almost half clay with 

less than 10 percent sand. The sample from a depth of 

981 feet was well sorted even though it contained 70 

percent silt.

DIABLO ALLUVIAL-FAN DEPOSITS

Bedding of the Diablo alluvial-fan deposits at the 

Mendota site is shown in figure 49. The bedding of the 

fan deposits is highly variable. Characteristically, the 

sand sections do not exceed 20-30 feet, and sand beds 

that are thicker than 10 feet appear to be less uniform in 

lithology than the Sierra sands. Sands predominate in 

the Sierra flood-plain deposits, but fine-grained deposits 

predominate in the Diablo alluvial-fan deposits. The 

finer grained sections of the alluvial-fan deposits range 

in thickness from less than 1 foot to more than 50 feet, 

but like the fine-grained sections of the Sierra 

flood-plain deposits, considerable lithologic variation of 

individual beds occurs.

The particle-size analyses indicate marked differences between the Sierra flood-plain deposits and the 

Diablo alluvial-fan deposits. Instead of containing 90 

percent sand, the sand beds of the fan deposits contain 

40-60 percent sand, and the clay content of the sand 

beds is 10-20 percent, instead of being less than 10 

percent as in the case of the Sierra sands. Similar 

percentages of sand and clay occur in the thick 

sequences of alluvial-fan deposits in the southern part 

of the Los Banos-Kettleman City area. The sands of the 

Diablo alluvial-fan deposits at the Huron site rarely 

contain more than 60 percent sand and generally have 

6-20 percent clay (Johnson and others, 1968, table 4).

The fine-grained beds in the alluvial-fan deposits 

contain large amounts of clay. The clay content of 61 

percent for the sample at the 397-foot depth in figure 49 

was the maximum noted for the samples taken from fan

RESISTIVITY,

IN OHMSm/'m

350

400

450 

500

 ^From consolidation test

FIGURE 49. Bedding, lithology, and vertical permeability of theDiablo alluvial-fan deposits, 

Mendota site, depth 350-500 feet.

deposits in the upper 600 feet. Clay contents in the 

30-50 percent range in the finer grained beds at both 

the Mendota and Huron sites are more common than 

clay contents of more than 50 percent.

The coarse-grained Diablo fan deposits are less 

permeable than the coarse-grained Sierra flood-plain 

deposits. The effect of the generally poor sorting of the 

fan deposits (Meade, 1967, fig. 12) tends to make the 

sand beds of the fan deposits have moderate to low 

permeabilities. For example, the sample from a depth of 

472 feet in figure 49 contained 47 percent sand, but had 

a vertical permeability of only 0.7 gal day"" 1 ft .

The minimum permeability measured (in a permeameter) in samples from the fine-grained beds in the 

fan deposits at the Mendota site was 7x 10~5 gal day" 1

ft"2 .

DIABLO FLOOD-PLAIN DEPOSITS

Bedding of the Diablo flood-plain deposits at the 

Mendota site is shown in figure 50. The Diablo 

flood-plain deposits have abundant thin clayey and 

sandy beds. Characteristically, 4-8-foot-thick beds of 

clayey materials are interbedded with sand beds that 

range in thickness from less than 10 feet to more than 

50 feet. The electric logs indicate that more abrupt
F58 STUDIES OF LAND SUBSIDENCE

RESISTIVITY, 

IN OHMSm2/m

1050 -

1200 -

FIGURE 50. Bedding, lithology, and vertical permeability of the Diablo flood-plain deposits, 

Mendota site, depth 1,040-1,205 feet.

changes in lithology occur in the Diablo flood-plain 

deposits than in the other types of deposits. Thin beds of 

clayey and silty materials within the thicker sand 

sections are much more common than in the Sierra 

flood-plain deposits, and the sand beds within the sand 

sections appear to be more variable in lithology than 

those in the Sierra flood-plain deposits.

The lithology of the sand beds appears to be that of 

clean sands, as in the case of the Sierra flood-plain 

deposits. In many of the sand beds, the amount of 

sand-size material ranges between 80 and 90 percent, 

and the amount of clay minerals is less than 10 percent. 

Only one sample from a fine-grained bed had a clay 

content of more than 36 percent, and the maximum clay 

contents for most of the fine-grained beds were about 

20-30 percent. However, the fine-grained beds do 

contain large amounts of silt. Half of the beds sampled 

(fig. 52) had silt contents between 40 and 68 percent.

The laboratory permeabilities of the Diablo 

flood-plain deposits also are different from those for the 

other types of deposits. For the sand beds, the 

permeabilities appear to vary with the degree of 

sorting. Well sorted beds have moderate permeabilities,

but sand beds that contain more than 15 percent silt and 

clay tend to have moderate to low permeabilities. Three 

sand beds that contained 72-76 percent sand had 

vertical permeabilities of only 1-2 gal day"" 1 ft~2 . The 

mean permeability of the fine-grained beds is three 

times the mean permeability of the more clayey Diablo 

alluvial-fan deposits (tables 5, 6).

SIERRA DELTAIC DEPOSITS

Beds that are considered to be deltaic deposits (Miller 

and others, 1971) derived from the Sierra Nevada are 

shown in figure 51. The bedding of the fine-grained 

deltaic deposits at the Huron site is distinctive when 

compared with the bedding of the other types of deposits. Thick beds of a dominant lithology do not occur; 

instead, alternating beds of silty clay and clayey silt 

seem to be typical of the Sierra deltaic deposits at this 

site. Between depths of 2,000 and 2,075 feet, the mean 

bed thickness is about 4 feet, but below 2,075 feet, the 

mean bed thickness is only 1 foot.

To the east of the Huron site, the deltaic beds consist 

of thick bedded crossbedded micaceous arkosic sand 

(Miller and others, p. 107). The coarse-grained facies of 

the deltaic deposits is similar to the Sierra flood-plain 

deposits in that thick sand beds characterize much of 

the section.

Most of the cores of deltaic deposits at the Huron site 

have less than 20 percent sand and 15-60 percent clay. 

The typical lithology of the cores is that of poorly sorted

RESISTIVITY, 

IN OHMSm/m

2000

2050

2100 

0.002

Vertical 

permeability 

in gallons per 

day per square 

foot

FIGURE 51. Bedding, lithology, and vertical permeability of the fine-grained facies of the 

Sierra deltaic deposits, Huron site, depth 2,000-2,114 feet.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F59

mixtures of sand, silt, and clay. Most of the sand sections were not recovered during coring.

The permeabilities of both the silty clay beds and the 

clayey silt beds is low. For the five samples tested in a 

permeameter, the range in permeability was from 

4xlO~4 to 3xlO~2 gal day" 1 ft"2 . The mean of two 

permeabilities derived from consolidation tests in the

800-1,600-lb in"2 

day" 1 ft~2 .

load range was about 1x10 gal

LACUSTRINE DEPOSITS

A microlog of the Corcoran Clay Member of the Tulare Formation at the Mendota site is shown in figure 

52. Cores indicate that the Corcoran occurs between 

depths of 625 and 700 feet and that it is underlain by 

Sierra flood-plain deposits and overlain by Diablo 

flood-plain deposits. The 6-foot sand beds that occur 

immediately above and below the Corcoran may be 

equivalent to thicker lacustrine sands that Miller (Miller and others, 1971) found associated with the Corcoran south of the Mendota site.

The bedding of the Corcoran is closer to being massive 

than any of the other types of deposits. The lower 20 feet 

of the Corcoran is distinctly coarser grained and of more 

uniform lithology than the upper 55 feet, as is indicated 

by both the electric and core logs. The coarser grained 

basal part is typical of the Corcoran throughout the 

study area. The typical sequence of the upper part is

RESISTIVITY, 

IN OHMSm/Yn

600

650

700

-^From consolidation test

FIGURE 52. Bedding, lithology, and vertical permeability of the Corcoran Clay Member of 

the Tulare Formation and adjacent deposits at the Mendota site, depth 600-721 feet.

alternating beds of silty clay and sand-silt-clay, which 

commonly are less than 1 foot thick.

The lithology of the Corcoran and adjacent deposits, 

as indicated by the particle-size analyses, is as follows. 

In the upper part, the beds of silty clay contain more 

than 40 percent clay, and the beds of clayey silt contain 

30-40 percent clay. The clayey silt in the lower onefourth of the Corcoran contains about 25 percent clay. 

Sand was present in all the samples, but many beds 

have only 1 percent sand. The maximum sand content 

was 27 percent. The bed considered to be a lacustrine 

sand beneath the Corcoran is a clean well-sorted sand, 

containing 80 percent sand and only 3 percent clay.

The permeabilities of the beds within the Corcoran 

are consistently low, having a permeability of about 

5x10 gal day" ft (mean of three permeameter 

tests) or about 4xlO" 5 gal day" 1 ft"2 (mean of three 

consolidation tests, load range 400-800 Ib in"2). 

Minimum permeabilities from consolidation-test results of the Diablo fan deposits were about the same as 

the minimum permeability observed for a sample from 

the Corcoran.

LATERAL EXTENT

Lateral extent, as well as bed thickness, is important 

in determining drawdown and seasonal fluctuation in 

the vicinity of irrigation wells. Extensive aquifers as 

compared to a lensing aquifer system of variable 

permeability will tend to reduce drawdown at the 

wells and increase the seasonal head declines at the 

midpoints between the wells.

The general lateral extent of four of the types of deposits can be evaluated by study of their modern counterparts. Deltaic sediments are not being deposited in 

the San Joaquin Valley at the present time.

The deposits with the most extensive bedding are the 

lacustrine clays and sands. One of the diagnostic features of lacustrine clays such as the Corcoran is their 

unbroken continuity over thousands of square miles. 

The thin beds within the lacustrine clays commonly 

extend for distances of more than several hundred 

yards. The lacustrine sands are a littoral facies formed 

by the winnowing action of waves. The sands extend 

over great distances because they are deposited chiefly 

during expansions and contractions of a lake.

The flood-plain deposits consist mainly of point-bar 

deposits, overbank deposits, and quiet water deposits. A 

lensing nature is typical of these deposits, but considerable lateral continuity of permeability is provided by 

adjacent point-bar deposits of similar permeabilities. 

The extent and thicknesses of the lenses probably are 

greater for the Sierra than for the Diablo flood-plain 

deposits because the perennial streams from the Sierra 

Nevada were larger than the perennial streams from 

the Diablo Range.
F60 STUDIES OF LAND SUBSIDENCE

The modern Diablo alluvial-fan deposits lense more 

than the other types of deposits. Although individual 

beds may extend for more than 1,000 feet along the 

radial lines of deposition of a fan, the lateral extent 

along the fan contours generally is less than 500 feet.

COMPARISON OF BED-THICKNESS FACTORS

The Terzaghi theory of consolidation (see section 

"Bedding") states that the time, t, needed to establish a 

specified degree of compaction (pore-pressure decay) in 

an aquitard that is being drained through both the 

upper and lower surfaces is a function of the halfthickness of the bed, h,

t=c(h/2)2

The coefficient, c, is used for Tlcv because variations in 

the time factor and the coefficient of consolidation are 

not considered in the following bed-thickness evaluation. This section evaluates the effect of bed thickness 

on the relative time needed for a specified percentage of 

compaction to occur in lower-zone aquitards at the four 

Inter-Agency Committee core-hole sites. The results of 

the study are summarized in tables 7 and 8.

Micrologs (microinverse 1 inch x 1 inch logs) of the 

core holes were used to estimate quantitatively the effects of differences in bed thicknesses for the suites of 

deposits at each core-hole site. The bed-thickness study 

also provided a way of assessing the relative times 

needed for attainment of equilibrium pore pressures for 

the different types of deposits.

The procedure was as follows. The effect of temperature increase with depth on resistivity was accounted 

for by drawing a drift line on the electric log, touching 

the left edges of the beds of minimum resistivity. 

Aquitard bed thicknesses were measured along a line 

that was parallel to the resistivity drift line and was 

offset sufficiently to be to the right of low resistivity 

beds in the Corcoran.

Beds that extended to the left of the measuring line 

were classed as aquitards, and those parts of the miTABLE 7. Summary of lower-zone weighted mean bedthickness factors of aquitards for types of deposits and 

Inter-Agency Committee core-hole sites

Deposit or 

core hole

Weighted mean 

bed-thickness factor

Genetic type of deposit:

Lacustrine

Core-hole site: 

Oro Loma

. __ 11

________ 161

________ 111

. _ _____ 24

_ 61

________ 16 |

.__ __ _ 11 /

<3A \

________ 15 /

14

14

24

crolog to the right of the measuring line were classed as 

being chiefly aquifer material. It is unlikely that the 

"aquitard" beds have sufficient permeability to be considered aquifers. One way to illustrate the conservative 

approach used would be to check the amounts of silt and 

clay in the material classed as aquifer material. For 

example, in the depth range 1,265-1,342 feet in the 

Mendota core hole, both micrologs were to the right of 

the aquitard measuring line, and thus no aquitard beds 

were counted in this depth interval. The coring process 

recovered samples with the following amounts of 

fine-grained material (Johnson and others, 1968, p. 

A48):

Depth (top of 

0.5-ft sample)

Percentage silt 

and clay

1,269.5 ________________ 46

1,271.0 _________________ 29

1,284.0 _________________ 14

1,293.0 _________________ 46

1,300.0 ________________ 38

1,312.0 _________________ 75

1,319.4 ________________________ 37

1,330.8 _________________ 35

1,339.5 _________________ 83

Percentage clay 

<0.004 mm

24

16

21

21

25

17

19

21

The mean silt and clay content of the samples was 45 

percent, and the mean clay content was 19 percent. It is 

apparent that some beds to the right of the aquitard 

measuring line have permeabilities characteristic of 

aquitards.

The lateral extent of the "aquifers" adjacent to the 

aquitards also may be important in controlling expulsion of water from aquitards. If lensing reduces the 

permeability of the aquifers, but not to the extent of 

being equal or less than the vertical permeability of the 

aquitards, lateral changes in aquifer permeability are 

of little importance because water can be transmitted 

by the aquifers more rapidly than it can be expelled 

from the aquitards. If, however, clayey sand lenses are 

completely enclosed by aquitards, bed thicknesses (as 

measured on the microlog) are less than the effective 

thicknesses of the aquitards.

The degree of lensing, in decreasing order of importance, for the various types of deposits is alluvial fan, 

flood plain, deltaic, and lacustrine.

It was considered unlikely that beds a few inches to 1 

foot thick could maintain lateral hydraulic continuity 

to the nearest well (mean distance about one-half mile), 

particularly in the alluvial-fan deposits. Thus, 

intermediate- and high-resistivity beds less than 1 foot 

thick were included in the aquitard thicknesses.

The aquitard thicknesses were classed in 3-footthickness intervals, the percentage of aquitard beds in 

each thickness range was determined, and weighted 

mean bed-thickness factors were computed as bed-
TABLE 8. Weighted mean bed-thickness factors ofaquitardsfor lower-zone deposits at Inter-Agency Committee core-hole 

A. By genetic type

Aquitard Mean aquitard Bed-thickness 

thickness1 thickness factor2

Sierra deltaic Sierra flood plain Diablo flood plain Diablo alluvial fan 

(ft)

0-3 

3-6 

6-9 ______

9-12 ______

1 Q 91

21-24

24-27 ______

97 ^n

QA QQ

42-45

45-48 __ __

(ft)

1.5

4.5

7.5

10.5

i q c

1 Q C

99 <=_

25.5

9Q C

07 C

46.5

Weighted mean bed-thicknes

Aquitard 

thickness1

(ft)

0-3 _______

3-6 _______

&-9 _______

9-12 _______

12-15 __ _ _

1 Q O1

21 24 _______

24-27 _______

27 30

QA__ QQ

33-36 __ -

36-39

39 42

45-48 _______

(tt) Number3

0.56 25 

5.06 5 

14.1 2 

27.6 2

95.1 1 

127 ________

163 1 

203 ________

248 ________

qno

473 ________

540 ___ 

 _ _ 36

Mean aquitard Bed-thickness 

thickness factor2

(ft)

1.5 

4.5 

7.5 

10.5 

13.5 

16.5 

19.5 

22.5 

25.5 

28.5 

31.5 

34.5 

37.5 

40.5 

43.5 

46.5

Weighted mean bed-thickne

(ft) -. , , 

Number3

0.56 23 

5.06 5 

14.1 5 

27.6 4 

45.6 1

127 2 

163 1 

203 ________

248

298 ________

qno

540

_ ___ _ ___ 41

Percent4 Product5 Number

69.4 39 51 

13.9 70 18 

5.6 79 8 

5.6 154 4 

___ ___ 1

2.8 266 2

2.8 455 1

100.1 1,063 91 

_____________ 10.6

Oro Lorn a

Percent4 Product5

56.1 31 

12.2 62 

12.2 171 

9.8 270 

2.44 109

4.9 620 

2.44 396

100.1 1,656 

_______________________ 16.5

Percent

56.0 

19.8 

8.8 

4.4 

1.1 

3.3 

2.2 

2.2 

1.1

1.1

100.0

B.

Number

35 

9 

3 

1 

1

1

50

Product Number Percent

31 43 64.2 

100 9 13.4 

124 7 10.4 

121 4 6.0 

50 1 1.5 

224 ________ ______

209

278 2 3.0 

179 1 1.5

097

1,643 67 100.0 

16.4

For core-hole site

Mendota

Percent Product

70.0 39 

18.0 91 

6.0 84 

2.0 55 

2.0 91

2.0 703

100.0 1,063 

10.6

Product

36 

68 

146 

166

68

380

244

1,108

Number

74 

18 

11 

10 

3 

5 

4 

2 

4

3 

2

1 

1

138

Number

76 

23 

15 

9 

8 

3 

5 

1 

3

2 

1

1

147

Cantua

Percent

53.6 

13.0 

8.0 

7.2 

2.2 

3.8 

2.9 

1.45 

2.9

2.2 

1.45

.72 

.72

99.9

Percent

51.7 

15.6 

10.2 

6.1 

5.4 

2.0 

3.4 

.7 

2.0

1.4

.7

.7

99.9

Product

30 

66

112 

198 

100 

245 

276 

183 

471

546 

431

341 

384

3,383 

33.8

Prod

1

1

2

1

3

3

3

2

__

3

__

2,4

1From micrologs (microinverse 1 in. x 1 in. logs) of the Inter-Agency Committee core holes. Measured along the parallel to resistivity drift line and offset from the drift line sufficiently to be to the ri

Clay Member of the Tulare Formation. Intermediate and high resistivity beds less than 1 ft thick were included in the aquitard thicknesses.

2n j iu i r * ( acquitard thickness2 N 

2Bed-thickness factor = I - - I

3Number of aquitard beds in each thickness range counted along measurement line described in footnote 1. 

4Percentage of beds in each thickness range. 

5Product of percent and bed-thickness factor.
F62 STUDIES OF LAND SUBSIDENCE

thickness factor=(aquitard thickness/2)2 . Weighted 

mean bed-thickness factors for the lower-zone deposits, 

based on the data from the four core holes, are summarized in table 8.

The mean bed-thickness factors for the genetic types 

of deposits range from 11 for Sierra deltaic deposits to 61 

for lacustrine deposits. Although low, the value of 11 for 

the deltaic deposits probably is higher than that for the 

coarser grained Sierra deltaic deposits to the east and 

southeast of the Huron core-hole site (the only site 

where this type of deposit was penetrated).

The flood-plain deposits have a mean bed-thickness 

factor of 14, with thicker aquitards being present in the 

Sierra than in the Diablo flood-plain sequences. The 

thicker aquitards in the Sierra flood-plain deposits may 

be a function of larger rivers entering the area from the 

Sierra Nevada than from the Coast Ranges. Finegrained deposits, such as would accumulate in oxbow 

lakes and in backswamp areas, should have been proportionately thicker along the rivers from the Sierra 

Nevada than along the smaller streams from the Coast 

Ranges.

Diablo alluvial-fan deposits tend to have distinctly 

thicker aquitards than either the flood-plain or deltaic 

deposits. The bed-thickness factor of 24 results in part 

from the relatively large proportion of intermediateresistivity beds less than 1 foot thick in the fan deposits.

The thickest aquitards occur in the sequences of 

lacustrine sands and clays, as shown by the large mean 

bed-thickness factor of 61. The 86- and 75-foot Corcoran 

aquicludes at the Oro Loma and Mendota sites were not 

included, but the 3-14-foot-thick clayey beds within the 

Corcoran at the Cantua and Huron sites were included 

in the analysis of lacustrine bed thickness.

Other factors being equal, the mean bed-thickness 

factors for the different types of deposits indicate the 

potential for residual excess pore pressures within the 

lower zone. Flood-plain or deltaic sequences should 

compact rapidly, but lacustrine sequences can be expected to have maximum residual excess pore pressures. Alluvial-fan sequences are intermediate in the 

amount of time needed for pore-pressure equilibrium to 

be attained.

The mean bed-thickness factors at the core-hole sites 

reflect the types of lower-zone deposits. The deposits at 

the four core-hole sites consist of two to four genetic 

types of deposits. The lowest bed-thickness factor is for 

the Mendota site, where 80 percent of the aquitard beds 

are in flood-plain deposits.

The Oro Loma and Huron sites have similar mean 

bed-thickness factors, but greatly different types of deposits. At Oro Loma, flood-plain deposits predominate, 

but lacustrine beds are present also. At the Huron site, 

Sierra deltaic deposits in the deepest 400 feet of the core

hole reduce the effect of 1,000 feet of alluvial-fan deposits on the mean bed-thickness factor.

At the Cantua site, flood-plain, alluvial-fan, and 

lacustrine deposits are abundant in the lower zone. All 

three types of deposits have many thick aquitards, resulting in a high mean bed-thickness factor. On the 

basis of mean bed-thickness factors, the Cantua site has 

greater potential for residual excess pore pressures 

than the other three sites.

With only four sites evaluated in a 2,000-square-mile 

subsidence area, firm conclusions cannot be drawn regarding the effect of areal bed-thickness variations on 

residual compaction in the northern and southern parts 

of the study area. However, the mean bed-thickness 

factors of 14 for the northern and 24 for the southern 

parts of the area agree with other evidence that suggests greater amounts of residual excess pore pressure 

in the southern part of the area.

COMPACTION CHARACTERISTICS

Laboratory tests made on 18 samples from the Corcoran and the various types of lower-zone deposits provide some general information regarding the consolidation characteristics of the fine-grained beds in different 

genetic types of deposits. Table 9 gives the mean 

parameters of the compressibility (compression index) 

and the rate of consolidation (coefficient of consolidation) for the 18 consolidation tests. Most of the conclusions derived from the results of the tests should be 

regarded as tentative because of the small number of 

tests involved. The results indicate the following decreasing order of compressibility for the fine-grained 

beds: lacustrine, Diablo flood plain, Diablo alluvial fan, 

and Sierra flood plain. The rate of consolidation for the 

suites of samples decreases in the following order: Diablo flood plain, Sierra flood plain, lacustrine, and Diablo alluvial fan.

The consolidation tests suggest the following 

generalizations. The lacustrine deposits should undergo large amounts of compaction, but over long 

periods of time. The Sierra flood-plain deposits should 

undergo only moderate amounts of compaction, and the 

compaction should occur fairly rapidly. The Diablo

TABLE 9. Mean consolidation characteristics of the Corcoran and the 

different types of lower-zone deposits in the load range 400-800 Ib in ~2

[Samples from fine-grained beds at the four Inter-Agency Committee core-hole sites]

Source1

Diablo:

Sierra:

Combined Diablo and Sierra:

Number

of

tests

6

_____ 6

2

4

Mean

compression

index 2

(Cc )

0.37

.46

.33

.82

Mean

coefficient

of consolidation

(cv , in ft2/yr )

8.1

328.5

20.8

17.5

iFrom Miller, Green, and Davis (1971).

2From Johnson, Moston, and Morris (1968, table 9).

3Median instead of mean used because of one excessively large value.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F63

alluvial-fan deposits should undergo moderately large 

amounts of compaction, but long periods of time will be 

required for ultimate compaction to be achieved. The 

Diablo flood-plain deposits should undergo moderately 

large amounts of compaction, and the compaction 

should occur more rapidly than for either the alluvialfan or lacustrine deposits.

Evaluation of the bedding, lithology, permeability, 

and lateral extent of the five types of deposits discussed 

in figures 48-52 results in conclusions similar to those 

derived from the consolidation tests regarding the different amounts and rates of compaction in response to 

increase in applied stress. The following interpretations 

should be considered as generalizations.

The Sierra flood-plain deposits should compact the 

most rapidly because of their high permeability, but the 

total amount of compaction should be smaller than for 

the other types of deposits because sections of sand 

thicker than 50 feet that contain less than 10 percent 

clay are common. The presence of mica in the Sierra 

sands results in higher elastic and inelastic components 

of compaction than in sands containing no mica.

The Diablo alluvial-fan deposits contribute substantially to the large amounts of compaction that have 

occurred in the southern part of the area because of the 

fine-grained compressible nature of most of the fan deposits. The many coarser grained beds of varying thickness furnish a means of escape for the water being 

expelled from the slowly draining intercalated clay 

beds. However, the rate of compaction for a given increase in applied stress probably is less than for either 

the Sierra or Diablo flood-plain deposits. The combined 

effects of large amounts of clay, even in the aquifers, 

and the highly lensing character of the overall suite of 

fan deposits tends to retard the expulsion of water from 

the aquitards and create a condition favorable for large 

amounts of residual excess pore pressure.

The Diablo flood-plain deposits have characteristics 

that are almost ideal for large amounts of compaction to 

occur rapidly. Large amounts of compressible clayey 

material are present, and most of the beds of clayey 

material are only 4-8 feet thick. Almost 90 percent of 

these aquitards at the core-hole sites were less than 9 

feet thick (table 8A). Although they contain large 

amounts of silt and clay, the highly compressible 

fine-grained beds within the Diablo flood-plain deposits 

have higher permeabilities than the fine-grained beds 

of the alluvial-fan deposits. Sand beds with good to 

moderate permeability, and having large lateral extents, commonly occur between the clay beds, thus providing ready avenues of drainage for the water expelled 

from the clayey beds.

The fine-grained facies of the Sierra deltaic deposits 

might be expected to compact to a moderate extent over

a long period of time. The ultimate specific unit compaction of the Sierra deltaic deposits probably is less than 

that of beds with similar petrologic characteristics in 

the upper zone because of the large stresses that have 

been applied to the deeply buried deltaic deposits in the 

geologic past.

The compaction characteristics of the Corcoran 

should be opposite to those of the Sierra sands. The 

Corcoran is highly compressible, but the rate of compaction is very slow because of the great thickness and low 

permeability of this lacustrine unit (Miller, 1961). The 

low permeabilities of even the clayey silt beds more 

than offset the tendency of good lateral extent of the 

beds to cause a more rapid rate of compaction. Pore 

pressures in the middle of the thickest lacustrine clay 

beds may not have declined much, despite the large 

declines in pore pressures in the aquifers above and 

below the Corcoran. Analysis of the compaction and 

water-level record at the Lemoore site suggests that 

compaction may continue at a very slow rate in lacustrine clays after artesian-head recovery in the aquifers 

of 50 feet from the previous summer low.

REGIONAL RELATIONS

Areal variations in the age, prior total applied stress, 

mean lithology, and source and mode of deposition of the 

deposits are responsible for much of the areal variations 

in the amounts of compaction upon increase in applied 

stress caused by pumping of ground water in the Los 

Banos-Kettleman City area. Both the degree of variation of these geologic factors and their effect on mancaused compaction and subsidence will be the subject of 

this section.

AGE OF THE DEPOSITS

The older deposits in the study area have had more 

time in which to undergo diagenetic changes, which 

have increased their ability to withstand further increase in applied stress. Diagenetic changes not only 

include sufficient time for the compaction of thick clay 

beds, but also cementation of the sandy deposits resulting from precipitation of part of the dissolved solids 

from water passing through the deposits or from solution of part of the grains at the points of contact and 

redeposition in the areas of lesser grain-to-grain pressure. Mineralogic changes occur also with changing 

pressure, temperature, and chemistry of the contained 

waters.

Most of the Pleistocene deposits are considered to be 

unconsolidated, even though in part they are buried to 

depths of more than 1,000 feet. The Pliocene marine and 

continental deposits show more effects of time when 

compared with Pleistocene deposits of similar lithology. 

The clayey deposits, instead of being plastic when handled, are sufficiently brittle that samples will break
F64 STUDIES OF LAND SUBSIDENCE

when struck with a hammer. The sandy deposits, instead of being loose, are sufficiently cemented that they 

are cohesive, but friable to the touch. Lenses or concretionary nodules of calcareous sandstone are common. The degree of lithification of the Pliocene waterbearing deposits is not advanced, however, and weathered outcrops of Pliocene materials commonly appear to 

consist largely of unconsolidated materials.

The following stratigraphic and descriptive information about the deposits tapped by water wells in the 

study area is summarized from Miller, Green, and 

Davis (1971):

Formation Age

Tulare ________Pliocene and

Pleistocene.

San Joaquin____Pliocene. 

Etchegoin1 __-^Pliocene.

Kreyenhagen ____Eocene and 

Oligocene.

Lithology

Sand, silt, 

and clay.

_Clay, silt,

sandstone. 

_Sand and silt,

blue to

brown. 

Organic,

siliceous

shale.

Depositional environment

Continental alluvial fan, 

flood plain, lacustrine, 

deltaic.

Marine and continental.

Marine, fluviatile, 

lacustrine.

Marine.

'Upper part tapped by water wells south and west of Cantua Creek (town).

A map showing those parts of the area where wells 

tap the pre-Tulare marine and continental Pliocene deposits is shown in Part 1 (Bull and Miller, 1974, fig. 15). 

Two such areas are present adjacent to the foothills of 

the Diablo Range one opposite the Panoche Hills and 

the other opposite the Big Blue Hills and Anticline 

Ridge. In the northern area the wells are shallow, some 

of them reaching the Kreyenhagen Formation at depths 

of only 1,200 feet, and the bulk of the water pumped by 

the wells is derived from flood-plain deposits within the 

Tulare Formation. In the southern area, wells as deep 

as 3,500 feet tap the marine sands of the Etchegoin and 

San Joaquin Formations. Most of the ground water 

pumped within 5 miles of the Big Blue Hills probably is 

derived from these Pliocene deposits.

Amounts of subsidence have been minor where wells 

derive most of their water from the Etchegoin Formation or other pre-Tulare Pliocene deposits. The artesian 

head has declined as much as 500 feet in the area adjacent to the Big Blue Hills, but only about 1 foot of 

subsidence has occurred. The low specific compaction of 

these deposits indicates that the Pliocene deposits are 

much less compressible than the deposits of the overlying Tulare Formation. Part of the reason for the sharp 

decrease in subsidence on the west end of profile B-B' of 

figure 17 may be attributed to the fact that the wells 

derive their water in part from pre-Tulare formations.

SPECIFIC UNIT COMPACTION OF THE 

LOWER-ZONE DEPOSITS

In evaluating the long-term relations between 

change in applied stress and compaction, Bull (Pt. 3, 

Bull and Poland, 1974) derived a specific compaction 

map of the lower zone for 1943-60. In making the map,

the following factors were evaluated: (1) the one component of stress change caused by lower-zone artesianhead decline, (2) the three components of stress change 

caused by change in the position of the water table, and 

(3) total subsidence for the period and the proportion of 

subsidence that was due to lower-zone compaction. 

Compaction of the lower zone in the 1943-60 period was 

estimated, utilizing the observed proportions of compaction occurring in the lower zone in the 1960's (fig. 45; 

see also section "Proportions of Compaction Occurring 

in the Upper and Lower Zones," paragraph 3).

The specific unit compaction of the lower-zone deposits can be computed by dividing the specific compaction by the thickness of deposits undergoing porepressure decline. The perforated interval of the lower 

zone is used for this purpose. The maximum thickness of 

the lower-zone perforated interval is based on the well 

tabulation compiled by Ireland (1963), which lists the 

perforated-interval data for wells drilled before 1962. 

Since 1960, fewer wells have been tapping the brackish 

waters that occur at the base of the lower zone, but the 

tabulation is an excellent source of information regarding the distribution of perforated intervals of pumping 

wells during the 1943-60 period.

The maximum thickness of the perforated interval of 

the lower zone is shown in figure 532 . The thickness of 

lower-zone deposits being tapped ranges from less than 

400 feet to more than 2,400 feet. The general pattern is 

one of overall increasing thickness of perforated interval toward the southwest. Thicknesses of more than 

1,800 feet occur in the areas of pumpage from the Etchegoin Formation. In the vicinity of Fresno Slough and 

Kings River, the thickness of fresh-water-bearing deposits extends below the base of the perforated interval 

(Miller and others, 1971, pi. 4), but wells can obtain a 

sufficient yield without penetrating the full thickness of 

fresh-water-bearing deposits. Pore-pressure decline 

may be occurring below the base of the perforated interval in the vicinity of Fresno Slough and Kings River as a 

result of the large amounts of water being pumped from 

the deeper aquifers farther to the west. An example of 

this type of head decline is shown at the Yearout site by 

Bull (Pt. 1, Bull and Miller, 1974, fig. 24).

The specific unit compaction map for the lower zone, 

1943-60, is figure 54. The values would represent the 

variation in compressibility of the lower-zone deposits if 

pore-pressure equilibrium had existed throughout the 

aquifer systems in 1943 and 1960. The specific unit 

compaction ranges from about 0.5 to more than 

lO.OxlO"5 ft" 1 (foot per foot of aquifer-system thickness per foot of increase in applied stress). Because of 

the complexity of the many factors used in computing 

regional specific unit compaction, the purpose of the

2Same as figure 18, Part 1; construction of map described in Part 1 (Bull and Miller, 1974).
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F65

Los Banos

/

37°00 Dos 

Palos

Fresno^,-..

iFirebaugh

~~^__River \ ,f

~~~ ~ \Madera

^1 t*&

NJ

a

^oo-

'*,

>V

°<., ' 

^

36° 30'

Kermanc

\

\

\

:V- 

\ \

j^

FRESNO :\<

^

H

\

^-X

;/ V2200v

EXPLANATION

Boundary of deformed 

rocks

 400 

Generalized line of equal maximum thickness of the perforated interval of the lower zone for wells drilled before 1962.

Short dashed where approximately located; 

long dashed for thickness below estimated 

stratigraphic equivalent where Corcoran 

is absent. Interval 200 feet

Western boundary of the Corcoran Clay 

Member of the Tulare Formation

0 5 10 15 MILES I i ' i H '

0 5 10 15 KILOMETRES

*s'

%2

V

9 \

» -».

» N V*\

x ^%

^

 V '

N Westhaven

Huron ;\

1°3.

\l

1600-

^Coalinga 

""" VALLEY /

J

\ I &

\/ &'c?

\ %.*'<<* IKettleman 

City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 53. Maximum thickness of the perforated interval of the lower zone.

map should be to illustrate general variations rather 

than to show precise values of specific unit compaction. 

In the southern and central parts of the study area,

values of specific unit compaction generally are between 1 and 3 x 10~5 ft" 1 , but in the northern part of the 

area values of specific unit compaction generally exceed
F66 STUDIES OF LAND SUBSIDENCE

120° 30' 120°00'

37°00'-

Five Points y

EXPLANATION

Boundary of deformed 

rocks

\sN. Westhaven 

Generalized line of equal compaction per Huron o _

unit increase in applied stress per unit 

thickness (maximum perforated interval 

of the lower zone). Interval, in feet per 

foot squared x lOf varies Coalinga 

VALLEY

Western boundary of the Corcoran Clay 

Member of the Tulare Formation

Kettleman Rpn 

10 15 KILOMETRES City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 54. Specific unit compaction for the lower water-bearing zone, 1943-60.

3xlO~5 ft" 1 ; northeast of the Delta-Mendota Canal, 

values of specific unit compaction generally exceed

Thus, the most important feature of the map is a 

distinct indication that the deposits in the northern part 

of the area apparently are four times as compressible as
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F67

the deposits in the central and southern parts of the 

study area. The maximum value of the line of equal 

specific unit compaction for the northern part of the 

study area is four times that for the southern part of the 

area. Means of specific unit compaction from a 91-point 

grid also show a fourfold difference when a subarea 

north of the north boundary of township 16 south is 

compared with a subarea south of that boundary.

Most of the rest of this section will be devoted to 

consideration of various geologic and hydro logic factors 

in an attempt to determine whether the deposits in the 

northern part of the area are indeed more compressible 

or whether other factors such as the rate of compaction 

of different genetic types of deposits are important in 

causing the contrast in specific unit compaction in the 

northern and southern parts of the study area.

GEOLOGIC FACTORS INFLUENCING SPECIFIC UNIT COMPACTION 

PRIOR TOTAL APPLIED STRESS

One of the geologic factors that might cause the lateral variation in specific unit compaction is the variation in stress that was applied on the lower-zone deposits in the northern and southern parts of the area 

before the 1943-60 period. In the northern part of the 

area, the depth to the base of the lower zone ranges from 

about 1,000 feet to about 2,000 feet, whereas in the 

central and southern parts of the area, the depth to the 

base of the lower zone ranges from about 1,300 to about 

3,000 feet.

The difference in depths to the base of the lower zone 

suggests the hypothesis that in the central and southern parts of the area, the greater prior total applied 

stress has already compacted the deposits to such an 

extent that they are less compressible per unit increase 

of additional applied stress than the deposits in the 

northern part of the area. The effect of prior total applied stress on compressibility of the deposits at the 

Westhaven site was discussed in the section "Overburden Load," paragraph 3. This hypothesis can be 

evaluated by determining the total applied stress on the 

middle of the lower zone and then by taking the product 

of the total applied stress on the middle of the lower zone 

and specific unit compaction to largely remove the effect 

of prior total applied stress.

The depth to the middle of the lower zone is shown in 

figure 55. The middle of the lower zone was selected as a 

reference surface on which to define the total applied 

stress as of 1943 the beginning of the 1943-60 period 

used for computation of specific unit compaction. Maximum depths to the middle of the lower zone are the 

same in the northern and southern parts of the area 

 about 1,500 feet. In the central part of the area, maximum depths exceed 2,000 feet in the area of pumpage

from the Etchegoin Formation. The minimum depths to 

the middle of the lower zone are less in the northern part 

of the area 600-800 feet than in the southern part of 

the area 800-1,000 feet.

The depth would be roughly proportional to the total 

applied stress on the middle of the lower zone if the 

entire section were saturated and if no confining beds 

were present to cause potential head differentials. Because unsaturated deposits and confinement exist in the 

study area, corrections have to be made to figure 55 to 

derive the total applied stress on the middle of the lower 

zone. The gravitational stress of the saturated deposits 

is roughly equal to 1 foot of water per foot of thickness.

The total applied stress of the deposits above the 

water table is about 1.8 foot per foot (assuming a moisture content of 0.2 the volume). The additional stress 

due to the unsaturated condition of the deposits above 

the water table is shown in figure 56. The lines of equal 

applied stress were computed by multiplying the thickness of deposits above the water table, as of 1951, by 0.8. 

The lack of saturation of these deposits results in a 

correction factor that locally increases the stress on the 

middle of the lower zone by more than 200 feet of water. 

The component of increased applied stress is minor in 

the northeastern part of the area, but in much of the 

area, the stress was 50-200 feet of water greater, as of 

1951, because of the large thicknesses of deposits above 

the water table.

The difference in applied stress on the lower zone 

resulting from differences in the position of the water 

table between 1951 and 1943 is minor. Although a 

water-table map is not available for 1943, spot checks 

indicate that the position of the water table was within 

40 feet of the 1951 position. Although 40 feet of watertable change would cause 32 feet of stress change in the 

water-table aquifer as a result of change of the saturated condition of the deposits, the net effect of watertable change on the total applied stress on the lower 

zone is minor. The change in seepage stress resulting 

from water-table change more than offsets the stress 

change due to change in saturation of the deposits. The 

net effect is only 0.2 foot of water per foot of change in 

position of the water table (Pt. 3, Bull and Poland, 

1974). Forty feet of water-table change would cause 

only 8 feet of net change in applied stress on the lower 

zone. If the maximum error introduced by using the 

1951, instead of the 1943, water-table data is 10 feet of 

net stress change on the lower zone, it can be readily 

concluded that the magnitude of the error is 

insignificant compared to the 200-foot interval used for 

the 1943 total applied stress map (fig. 58).

The other correction component that needs to be applied to figure 55 to get the total applied stress on the 

middle of the lower zone is the seepage stress caused by
F68 STUDIES OF LAND SUBSIDENCE 

120°30' 120°00'

37°00

EXPLANATION

Boundary of deformed 

rocks

Line of equal depth to the middle of the 

lower zone

Interval 200 feet. Compiled from map of 

half the thickness of the lower zone and 

map of the depth to the base of the 

Corcoran Coahnga

VALLEY

Western boundary of the Corcoran Clay 

Member of the Tulare Formation

15 KILOMETRES

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 55. Depth to the middle of the lower zone.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F69

37°00' -

36°30' -

36°00'

River \ S

Madera

EXPLANATION

Boundary of deformed 

rocks

Line of equal applied stress due to the unsaturated condition of the deposits above 

the water table as of 1951

Dashed where approximately located. Interval, in feet of water, varies. The applied 

stress is the sum of two components; an 

added stress due to lack of bouyant 

support equal to 0.6 foot per foot of unsaturated deposits, and an added stress 

due to the weight of water contained in 

the unsaturated deposits equal to 0.2 foot 

per foot of unsaturated deposits. The 

total applied stress of the deposits above 

the water table is 1.8 feet of water per 

foot of unsaturated deposits, but this map 

excludes the component of stress due to 

bouyant weight of the grains. Depth to 

the water table information is from Davis, 

Green.Olmsted, and Brown (1959, fig. 16)

Coalinga 

VALLEY

Kettleman Rpn 

City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 56. Applied stress due to the unsaturated condition of the deposits above the water table as of 1951.
F70 STUDIES OF LAND SUBSIDENCE

head differentials between the water table and the 

potentiometric surface of the lower zone. The 1943 position of the lower-zone potentiometric surface was used 

to define the magnitude of the seepage stresses present 

in the area at the beginning of the 1943-60 period. The 

water level in wells tapping the lower zone rises as 

much as 500 feet above the base of the Corcoran, and 

before 1925 the artesian head was sufficient to cause 

wells to flow in the eastern part of the area (Pt. 1, Bull 

and Miller, 1974, fig. 21). However, by 1943, the potentiometric surface was below the water table throughout 

the area, and the resulting seepage stress on the lower 

zone was caused by, and equal to, the head differential 

between the water table and the potentiometric surface 

of the lower zone.

The seepage stress on the lower zone, as of 1943, is 

shown in figure 57. Seepage stress exceeded 100 feet of 

water in most of the area and locally was more than 200 

feet of water. The areas of maximum seepage stress 

coincide with the areas of maximum pre-1943 pumping 

of ground water about midway between Fresno 

Slough and the Diablo Range. Not all the increase in 

stress applied to the lower zone as of 1943 had become 

effective in the fine-grained beds of low permeability at 

that date.

Head differentials occur in the area west of the Corcoran also, as shown by comparison of the position of the 

water table and water levels in wells perforated to 

depths of more than 2,000 feet. Variations of head 

differentials occur more abruptly in the area west of the 

Corcoran than in the rest of the area where the Corcoran is present to provide uniform confinement for the 

lower zone.

The total applied stress on the middle of the lower 

zone was obtained by adding the stress components 

shown in figures 56 and 57 to lines of equal depth to the 

middle of the lower zone, multiplied by 1.0 foot of water 

per foot of deposits. The combination of these three 

maps, figure 58, shows that the total applied stress on 

the middle of the lower zone, as of 1943, ranged from 600 

to 2,200 feet of water. Throughout most of the area, the 

total applied stress was 1,000-1,800 feet. The amounts 

of total applied stress are about the same in the northern and southern parts of the area, except that the area 

west of Firebaugh is the area of lowest total applied 

stress in the study area west of the valley trough. The 

total applied stress in the central part of the area, where 

wells tap the Pliocene deposits, is almost one-third 

greater than the maximum amounts of stress that occur 

to the north and south. The lines of total applied stress 

were not extended west of the Corcoran, but the total 

applied stress in the area to the west of Huron seems to 

be in a narrow range between 1,600 and 1,800 feet of 

water.

STRESS-COMPACTION PRODUCTS

The purpose of making the total applied stress map 

was to assess the influence of variation in prior applied 

stress on the apparent compressibility of the various 

types of deposits. The stress was determined as of 1943. 

The amounts of estimated compaction and increase in 

applied stress were obtained for the 1943-60 period. The 

effect of prior total applied stress on specific unit compaction for the 1943-60 period was removed by multiplying the specific unit compaction by the total applied 

stress.

The validity of the use of such a product needs to be 

examined critically. The use of a simple product of total 

applied stress and specific unit compaction assumes 

that an arithmetic linear relation exists between compressibility and effective stress. Laboratory consolidation tests show that compressibility decreases with increasing effective stress.

The exponential decrease in compressibility with increasing effective stress for both the laboratory and field 

ranges of stress for two consolidation tests is shown in 

figure 59. The compressibility plots are from J. F. Poland (written commun., 1968), and I have added compressibility-effective stress products to the plots to show 

how the effect of variable effective stress can be almost 

eliminated. Sample A is the test result for the Cantua 

site that has the most extreme change of compressibility-effective stress product with increasing effective 

stress. The sample for case A was taken from a thin bed 

within the Corcoran lacustrine sequence.

The compressibility-effective stress products for 

sample A range from 0.133 to 0.280, showing that for 

the laboratory (and extrapolated) range of stresses, the 

use of products does not eliminate the effect of different 

effective stresses. Although a 110 percent difference is 

shown by the two extreme compressibility-stress products, a substantial reduction in the effects of different 

effective stresses has been made because the difference 

in the compressibilities of the two points is 3,600 percent.

The results of case B are for a sample that is much less 

compressible than sample A but which has a compressibility that probably is greater than the lower-zone 

clayey sands from the Cantua site for which consolidation tests were not made. The change of compressibilityeffective stress products is much less than in case A; 

only a 7-percent change in the products occurs between 

the end-point values of 0.026 and 0.028. Thus, for deposits having compressibilities similar to that of sample 

B, the use of compressibility-effective stress products 

eliminates most of the effect of different effective stresses, even for the extreme range of load used in the 

laboratory.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F71

37°00'

EXPLANATION

Boundary of deformed 

rocks

Generalized line of equal sttess on the lowet 

zone resulting ftom attesian-head decline

Interval 50 feet of water. Dashed lines indicate the head differentials in the area 

southwest of the Corcoran. Compiled 

from a map showing the lower-zone 

potentiometrtc surface as of 1943, and a 

water-table map based on 1951 measurements supplemented with pre- 1951 

data. The seepage stress has been approximated by using the head differential indicated by the position of the water table 

and potentiometric surface

Coalinga

VALLEY

Western boundary of the Corcoran Clay 

Member of the Tulare Formation

15 KILOMETRES

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 57. Seepage stress on the lower zone as of 1943.

The reason that compressibility-effective stress products almost eliminate the variations due to effective 

stress is that the slopes of the lines in figure 59 are close

to unity. If the slopes had been substantially different 

from unity, exponential corrections (rather than simple 

products) would have been necessary to reduce the ef-
F72

37°00'-

36° 30' -

STUDIES OF LAND SUBSIDENCE

120° 30' 120°00'

36° 00'

EXPLANATION

Boundary of deformed 

rocks

Line of equal total applied stress on the 

middle of the lower zone, as of 1943

Interval 200 feet of water. Based on maps 

showing the depth to the middle of the 

lower zone, thickness of the deposits 

above the water table as of 1951, and the 

seepage stress on the lower-zone as of 

1943

\. Westhave 

Huron ^

Coalinga

VALLEY

Western boundary of the Corcoran Clay 

Member of the Tulare Formation

15 KILOMETRES

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 58. Total applied stress on the middle of the lower zone as of 1943.
1C>'

Q

Z 

D 

O 

Q.

tc 

111

Q.

V) 

111

O

Z

111 

tc<, -'

O 

w

10

I I I 

10

B. Depth, 1953 feet 

Percent

Sand 27

Silt 28

Clay 45

A. Depth, 637 fee

Percent 

Sand 26 

Silt 50 

Clay 24

Maximum historic 

increase of total 

aPP |ied stress in 

the study area

0.028

j___i i i i i i i i i i

10'

i__i 

EFFECTIVE STRESS, IN POUNDS PER SQUARE INCH

FIGURE 59. Reduction of the effect of variable effective stress through use of compressibility-effective stress products for core samples from the Cantua site
F74 STUDIES OF LAND SUBSIDENCE

feet of variable effective stress. If we let mv be the 

compressibility andPe the effective stress, then

ni m =

The values of n (the rate of change of mv with respect to 

Pe) generally are only slightly less than 1.00. The maximum departure from unity for all the samples tested 

from the Cantua site is that of sample A.

An appraisal of the changes of stress-compaction factors under field not laboratory load ranges is necessary to complete the assessment of the validity of the 

approach used in this paper. The maximum possible 

error introduced by assuming a linear compressibilityeffective stress relation can be estimated by using the 

maximum historic increase of total applied stress that 

has occurred at the Cantua core-hole site. The increase 

in applied stress is the result of 400 feet of head decline 

since about 1900 and, if taken a short distance below the 

Corcoran, indicates that a 52-percent increase in applied stress has resulted from man's change in the hydrologic environment. At the 600-foot depth at the Cantua site, the applied stress has increased from 330 to 

about 500 Ib in~2. By taking the extremes of compressibility (case A), and increase in applied stress, it can be 

seen that a change in the products of 0.155-0.167 

occurs an indication that only 92 percent of the effect 

of different stresses has been removed. However, in the 

case of less compressible materials (case B), 99.4 percent of the effect of different applied stresses has been 

removed. Thus, it is concluded that the use of stresscompaction products in this paper does not entirely 

eliminate the effects of variation in total applied stress 

within the study area but that more than 90 percent of 

the effects of variation of total applied stress are removed.

The stress-compaction products will be used in this 

paper to evaluate the effects of prior total applied stress, 

mean lithology, and source and mode of deposition on 

variations of specific unit compaction between the 

northern and southern parts of the area. The products 

are apparent compressibilities, for which the effect of 

prior total applied stress has been largely removed. The 

products are only apparent compressibilities because 

the degree to which applied stresses have become effective is not known precisely.

The product of lower-zone specific unit compaction 

and the total applied stress on the middle of the lower 

zone is shown in figure 60. As in the case of the specific 

unit compaction map (fig. 54), the maximum values of 

stress-compaction products occur in the northern part of 

the area. The maximum value of the line of equal 

stress-compaction products for the northern subarea is 

twice that for the southern subarea (south of township 

15 in fig. 1). Means of stress-compaction products from a

91-point grid indicate a 2^-fold difference between the 

northern and southern subareas. Thus, the difference in 

apparent compressibility between the subareas appears 

to have been decreased by removing the effect of prior 

total applied stress.

The amount of change, however, varies greatly in 

both subareas. Locally, the apparent compressibility 

has been decreased 50 percent in the northern subarea 

and increased 100 percent in the southern subarea, 

when changes in the apparent compressibility indices 

at selected points are compared with the mean indices of 

the other subarea. At other locations, little or no change 

in apparent compressibility resulted from the use of 

stress-compaction products instead of specific unit compaction. Thus, the effect of prior total applied stress is 

important at some locations, whereas at others the effect of prior stress on apparent compressibility is completely obscured by petrologic factors. A similar conclusion was reached by Meade (1968) regarding the factors 

affecting change of void ratio with depth at the 

Richgrove core-hole site in the southern San Joaquin 

Valley.

The mean values of specific unit compaction and 

stress-compaction products for the two subareas suggest that the overall difference in apparent compressibility between the subareas has been reduced from fourfold for the specific unit compaction to 2 1/£-fold for the 

stress-compaction products. Thus, in a general sense, it 

is concluded that roughly one-third of the compressibility difference between the subareas is the result of different prior total applied stresses. The remaining twothirds of the compressibility difference is ascribed to 

variations in lithologic and geologic factors.

Both the specific unit compaction and the stresscompaction products probably are anomalously high in 

the extreme northern part of the area because of the low 

values used for the thickness of the lower zone. Field 

evidence from compaction recorders indicates that the 

values of thickness of the perforated interval of the 

lower zone that are less than 700 feet are too low, but 

information is not available to indicate the true thickness of deposits subject to pore-pressure decline in the 

area. For example, the 1,000-foot depth for the deepest 

recorder at the Oro Loma site was selected as being 

representative of the deepest well perforations in the 

vicinity, but comparison of compaction and subsidence 

(see section "Cumulative Compaction at Multiple 

Compaction-Recorder Site," paragraph 7) shows that 

only 55 percent of the compaction was occurring in the 

depth interval 0-1,000 feet in 1961-65. The other 45 

percent of the compaction was occurring in the deposits 

below 1,000 feet, due to pore-pressure decline resulting 

from upward leakage or in response to large artesianhead declines in deep aquifers to the south.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2

120°30' 120°00'

F75

37°00' 

36° 30' 

36°00'

,--^ Fresno ,. ____

EXPLANATION

Boundary of deformed 

rocks

Products of the lower-zone specific unit 

compaction for the 1943-60 period times 

the total applied stress on the middle of 

the lower zone, as of 1943, X10? Based 

on maps of lower-zone specific unit compaction and total applied stress on the 

middle of the lower zone

: . >«* : .: : 

Sub area discussed in text

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 60. Variations in stress-compaction products.

The problem of lack of knowledge about the maximum depth interval in which pore-pressure decline is 

occurring along the fringes of the study area does not

invalidate the conclusions mentioned. Values of specific 

unit compaction of 5xlO~5 and stress-compaction 

products of 8xlO~2 (figs. 54, 60) occur in the middle of
F76 STUDIES OF LAND SUBSIDENCE

the large area of intense subsidence southwest of Mendota where lower-zone aquifer-system thicknesses are 

1,200 feet (fig. 55) almost the maximum for the northern part of the area.

The removal of the effect of prior total applied stress 

in the central part of the area reveals several interesting aspects regarding the apparent compressibility of 

the deposits. Extremely low values of specific unit compaction (fig. 54) occur adjacent to the Big Blue Hills. By 

removing the effect of prior total applied stress on the 

deposits of this subarea, the values on the products map 

of figure 60 are no longer anomalously low, but are in 

the same range 1-2 x 10~2 as about half of the area 

south of the town of Cantua Creek. The removal of the 

anomaly adjacent to the Big Blue Hills suggests that 

the Pliocene marine deposits would be only slightly less 

compressible or would have about the same general 

compressibility as the Diablo alluvial-fan deposits 

sputh of the Huron-Westhaven area if the prior total 

applied stress had been equal.

If a map showing variation in ultimate specific unit 

compaction (the true compressibility of the deposits) 

could be prepared and the total effective stress were 

entirely the result of differences in prior effective stress, 

such a map would show little variation in the values of 

products in areas of uniform geologic and lithologic 

conditions. Although figure 60 utilizes transient 

specific unit compaction, little variation in the products 

occurs in those areas of similar geologic conditions.

In the central part of the study area (subarea A in 

figure 60), the stress-compaction products occur in a 

very narrow range, despite large differences in total 

applied stress, as of 1943. The work maps used in the 

construction of figure 60 show that the range of values 

for the products in this 100-square-mile subarea range 

only from 2.4to2.8xlO~2 , even though the prior total 

applied stress on the middle of the lower zone ranges 

from 1,000 to 2,000 feet of water. The specific unit compaction for the same area decreases progressively with 

increasing total applied stress. The removal of the effect 

of prior applied stress eliminates the trend shown by the 

specific unit compaction and indicates that if it were not 

for differences in prior applied stress, the deposits 

within the subarea A would compact the same amount 

per unit of head decline. The situation described suggests that the deposits within subarea A in figure 60 

should be similar geologically. Sierra flood-plain deposits are the dominant lower-zone type of deposit in all 

of subarea A. The western extension of the subarea 

north of the town of Cantua Creek coincides with the 

area of maximum western extent of thick Sierra 

flood-plain deposits and is north of the ancestral alluvial fans of Los Gates and Cantua Creeks and south of 

the Panoche Creek fan. The Sierra flood-plain deposits

intertongue with alluvial-fan deposits in the northwest 

and southeast corners of subarea A.

MEAN LITHOLOGY

Another geologic factor that might be responsible, in 

part, for the fourfold difference of specific unit compaction (fig. 54) in the northern and southern parts of the 

study area is the overall lithology of the deposits. The 

particle-size analyses of the samples from the core holes 

should be used with caution for such purposes because of 

the tendency of the coring equipment to recover the 

cohesive fine-grained deposits but not the incohesive 

coarse-grained deposits.

More complete and unbiased information can be obtained through electric-log studies of the lower zone. A 

resistivity map of the lower-zone deposits was made to 

evaluate the effect of lithologic variations on the compressibility of the deposits within the study area.

Three important types of data are available in all 

parts of the study area to make a lithofacies map based 

on electric logs. Abundant electric logs can be obtained 

readily. The salinity and chemical character of the 

lower-zone waters can be assessed as a result of a chemical sampling program made in 1951 (Davis and Poland, 

1957). The water temperatures at the discharge points 

of the wells are determined at the times of each 

pump-efficiency test made by the Pacific Gas and Electric Co. Additional temperature information is available from the bottom-hole temperatures obtained at the 

times that the electric logs were made.

Thus, within the Los Banos-Kettleman City area 

abundant information is available to make a lithofacies 

map based on the mean resistivity of the lower zone, 

using electric-log data that are corrected for the effects 

of regional variations in salinity, chemical character, 

and temperature. Resistivity logs, instead of 

spontaneous-potential logs, were selected for the 

lithofacies study because of the lack of definition that is 

typical of the spontaneous-potential logs in this area. 

The mud used in drilling a new well usually is mixed 

with ground water from a nearby irrigation well; therefore, there is little contrast between the mud and formation resistivities, and the spontaneous-potential log approaches a straight line in which deflections do not 

occur for either the sand or clay beds.

The lateral resistivity log with a 19-foot spacing between electrodes was used for the lithofacies study. The 

short- and long-normal resistivity logs were not used 

because small variations in resistivity were unimportant in a study of mean resistivity of the entire lower 

zone and because the lateral log minimizes the effect of 

drilling mud resistivity. Most of the drilling mud resistivities, at 38°C, ranged from 3 to 6 ohm-metres, but the 

extremes in mud resistivities ranged from 1 to 20 

ohm-metres.
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F77

The temperature correction was based, in nearly all 

cases, on the temperature of the water being pumped 

from irrigation wells and ranged from 21 to 43°C. The 

coolest water temperatures were for wells along Fresno 

Slough, and the hottest water temperatures were for 

wells that tap the sands of the Etchegoin Formation 

opposite the Big Blue Hills.

Two corrections had to be made for variations in the 

chemical character of the lower-zone water. A salinity 

correction was made, using standard charts provided by 

the Schlumberger Co. However, the Schlumberger 

charts are for NaCl solutions, and the typical lowerzone water is a sodium sulfate water (Davis and Poland, 

1957). By using a procedure outlined by Schlumberger, 

correction factors were computed and applied to chemical analyses of lower-zone waters from different parts of 

the study area. The calculations showed that the resistivity of the lower-zone waters was only 0.72-0.76, the 

resistivity of the NaCl solutions of comparable concentration. Therefore, a correction factor of 0.75 was applied to the dissolved solids values used in all the salinity corrections.

The salinity of the lower-zone water at each electriclog site was estimated from a map of the dissolved solids 

for the study area (Pt. 1, Bull and Miller, 1974, fig. 19). 

The estimated dissolved solids at the 110 electric-log 

sites ranged from about 700 to 2,000 mg I" 1 (milligrams 

per litre). An NaCl salinity of 1,000 mg 1~ * was used as a 

standard for the study.

The mean resistivity of the lower zone based on electric logs, and corrected to 38°C and 1,000 mg I" 1 NaCl 

salinity, is shown in figure 61. A general guide to the 

lithologies of the resistivities can be made by comparing 

the particle-size analyses and electric-log corrected resistivities at several core-hole sites. Thick clay beds 

such as the Corcoran or the fine-grained beds associated 

with the Etchegoin Formation have corrected resistivities of about 3-4 ohm-metres (values that may be too 

low if the pore water in the clays has a higher salinity 

than the water pumped by the wells). At the other 

extreme, clean well-sorted coarse-grained sand beds 

have a corrected resistivity of 20-25 ohm-metres. Thick 

beds consisting of fine- to coarse-grained sand have a 

corrected resistivity of 10-15 ohm-metres. Silts and 

clayey sands have corrected resistivities of about 4-10 

ohm-metres. The low mean resistivities that prevail 

throughout most of the study area are indicative of the 

clayey nature of most of the compressible deposits that 

have compacted to cause the large amounts of subsidence within the area. The lithofacies map also shows 

why 800-2,000 lineal feet of casings have to be perforated in most of the wells in order to obtain sufficient 

water for irrigation.

The mean resistivity of the lower zone shown in figure

61 reveals some interesting lithofacies variations 

within the study area. Although fine-grained deposits 

occur throughout most of the area, the deposits in the 

northern part of the area appear to be less clayey than 

the deposits in the southern part of the area. The central 

part of the area appears to have deposits with an intermediate amount of clay.

In four parts of the study area, the lithofacies map 

shows a strong correlation between increasing resistivity (coarser deposits) and the areas where sediments 

were introduced into the area during the course of deposition. Coarse-grained deposits are most common 

where Panoche and Los Gatos Creeks and the San Joaquin and Kings Rivers entered the study area. The 

bands of equal range in resistivity are concentric about 

the points of discharge into the San Joaquin Valley of 

the ancestral streams of Panoche and Los Gatos Creeks.

The lines of equal sums of the determined constituents (approximately the dissolved solids) also are 

concentric about the ancestral mouths of Panoche, Los 

Gatos, and Cantua Creeks (Pt. 1, Bull and Miller, 1974, 

fig. 19), which might suggest, at first thought, that an 

incomplete salinity correction was made for parts of the 

area in preparing figure 61. This is not the case. Chemical analyses were available for lower-zone wells 

throughout the study area. Furthermore, the lines of 

equal mean resistivity (fig. 61) cut across the lines of 

equal dissolved solids (Pt. 1, Bull and Miller, 1974, fig. 

19). For example, in figure 61, the 7.5 mean resistivity 

line near the town of Cantua Creek passes through 

areas where the dissolved solids for lower-zone waters 

ranges from less than 800 mg 1 -1 to more than 2,000 mg 

I" 1 . The 10.0 mean resistivity line opposite the mouth of 

Panoche Creek passes through areas that range from 

less than 1,000 to more than 2,000 mg I" 1 dissolved 

solids for the lower zone. It is concluded that the sources 

of pre-Corcoran coarser grained deposits from the Diablo Range were also the source of younger waters of 

high dissolved solids that largely replaced the waters 

originally contained in the deposits.

The results of particle-size analyses of core-hole samples agree with the lithofacies map, even though a 

larger proportion of finer grained than coarser grained 

deposits were recovered in the coring process. Variation 

in mean particle size with depth for the deposits cored 

below the Corcoran at the Mendota and Huron core sites 

is shown in figure 62. The lithofacies map in figure 61 

indicates that the lower-zone deposits at the Mendota 

site are slightly coarser than the deposits at the Huron 

site. The particle-size data shown in figure 62 show that 

many of the cored sediments at the Mendota site are as 

fine grained as those at the Huron site, but samples with 

mean particle sizes of more than 125 microns are much 

more common in the Mendota core than in the Huron
F78 STUDIES OF LAND SUBSIDENCE

120°30' 120°00'

37°00' 

EXPLANATION

Boundary of deformed 

rocks

2.5-5.0

Mean resistivity of the lower zone, in ohmmetres; based on electric logs, and corrected to 38°C and 1000 milligrams per 

litre NaCl salinity

,14/13-1101 

Core hole for data in figure 62

Coalinga

VALLEY

15 KILOMETERS

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 61. Lithofacies map based on the mean corrected resistivities of the lower zone.

core. Meade (1967, p. 12) concluded that "the sediments 

from the Huron core are generally finer grained, less

well sorted, and less skewed than the sediments from 

the Mendota core."
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F79

MEDIAN DIAMETER, 

IN MICRONS

8 62 500

o 

O 

00

o

O r; °o cr

00

 o

o - 

o

 o

 

EXPLANATION

O 

Mendota site

Huron site

i i i i

500

1000

1500

FIGURE 62. Variation in mean particle size with depth for 

alluvial deposits below the Corcoran in cores from the 

Mendota and Huron sites. (Data from Meade, 

1967, p. 13.)

A comparison was made between the overall lithology 

(mean resistivity) and the stress-compaction products 

for the lower zone. Because of the marked difference in 

apparent compressibility in the northern and southern 

parts of the area, the northern-area data were plotted 

separately from the data for the rest of the area. Data for 

all points north of township 16 (fig. 63A), for which the 

products shown in figure 60 exceed 2.5xlO~2 (from 

work map), are plotted in figure 63A, and data for the 

points for the central and southern parts of the area are 

plotted in figure 63B.

The large amounts of scatter in figures 63A and 63B 

show that variation in gross lithology, as indicated by

H 4 

O

O 

O

6 8 10 12 

MEAN RESISTIVITY, IN OHM-METERS

B

4 6 8 10 

MEAN RESISTIVITY, IN OHM-METERS

12

FIGURE 63. Relation of mean corrected resistivity to the product of specific unit compaction 

and total applied stress, lower zone. A, North of township 16.B, South of township 15.

the mean resistivity of the lower zone, is not important 

in causing the fourfold variation in specific unit compaction from 1943 to 1960 between the northern and 

southern parts of the area (fig. 54) or the twofold variation in the stress-compaction products (fig. 60). The 

deposits in the northern part of the area are slightly less 

clayey than the deposits in the southern part of the area, 

but the twofold differences in the apparent compressibility of the deposits in the two subareas cannot be 

explained by variations in overall lower-zone lithology. 

Mean lithology may be highly significant in evaluating 

ultimate compaction amounts, but where aquitards 

have large residual excess pore pressures other factors, 

such as the thickness of a bed of a given lithology, are 

more important than average lithology.

SOURCE AND MODE OF DEPOSITION

The third geologic factor to be considered as a possible 

cause of the variation in specific unit compaction in the 

northern and southern parts of the study area is the 

relation of the sources of the lower-zone deposits, and 

their modes of deposition, to the apparent compressibility of the deposits. Different types of deposits intertongue with each other in much of the area, but the 

deposits can be grouped in three classes. The three 

categories of deposits shown in figure 64 are largely 

from Part 1 (Bull and Miller, 1974, fig. 16).
F80 STUDIES OF LAND SUBSIDENCE

120°30' 120°00'

37°00'

36° 30'

36° 00'

EXPLANATION

Boundary of deformed 

rocks

Diablo and Sierra flood-plain deposits, minor lacustrine and Diablo alluvial-fan deposits

Diablo alluvial-fan deposits, and Sierra 

flood-plain and deltaic deposits

Sierra flood-plain deposits

Generalized line of equal product of lowerzone specific unit compaction and total 

applied stress on the middle of the lower 

zone, x 102. Interval varies

10 15 MILES

10 15 KILOMETRES

Kettleman RFn 

City

Base from U.S. Geological Survey Central 

Valley map, 1:250,000, 1958

FIGURE 64. Relation of stress-compaction products to the sources and modes of deposition of the lower-zone deposits.

The northern area of Diablo and Sierra flood-plain 

deposits has the maximum apparent compressibility, as 

indicated by the lower-zone stress-compaction products.

Diablo flood-plain deposits predominate near the Diablo 

Range and the proportion of Sierra flood-plain deposits 

increases toward the east. East and north of Mendota,
LOS BANOS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F81

flood-plain deposits from the San Joaquin River constitute virtually all the lower-zone deposits tapped by 

wells.

In the southern part of the study area, most of the 

lower-zone deposits consist of alluvial-fan deposits. 

Near the Diablo Range, virtually all the lower zone 

consists of alluvial-fan deposits, except in those areas of 

pumpage from the Pliocene marine deposits. Farther to 

the east, Sierra flood-plain and deltaic deposits become 

increasingly more important in the basal part of the 

lower zone. Toward the north, Diablo and Sierra 

flood-plain deposits become progressively more common. In the vicinity of the town of Cantua Creek, 

alluvial-fan, lacustrine, and deltaic deposits, as well as 

marine sediments, are present. The unit that includes 

alluvial-fan deposits has only half the apparent compressibility (as indicated by the stress-compaction 

products) of the flood-plain deposits in the northern part 

of the area.

The Sierra deposits show considerable variation in 

apparent compressibility. South of the town of San Joaquin, the apparent compressibility of the lower-zone 

deposits, as indicated by the products map, ranges from 

less than 1 to about 3 x 10~2 an apparent compressibility that is less than the compressibilities in either of the 

two subareas adjacent to the Diablo Range. Most of the 

deposits in the southern part of the belt of Sierra

flood-plain and deltaic deposits were deposited by the 

Kings River.

In the northern part of the belt of lower-zone Sierra 

flood-plain deposits, the apparent compressibilities 

tend to be about the same as for the Diablo flood-plain 

deposits to the west. Most of the Sierra flood-plain deposits in this part of the subarea were deposited by the 

San Joaquin River. The lithofacies map in figure 61 

indicates that the lower-zone deposits in the vicinity of 

Mendota have a higher resistivity (less clay) than the 

lower-zone deposits of the Kings River farther south.

Prior discussions concluded that about one-third the 

fourfold difference in the values of specific unit compaction in the southern and northern parts of the study 

area was the result of actual differences in compressibility due to the lesser prior applied stress in the northern 

part of the study area. The coincidence between the area 

of Diablo and Sierra flood-plain deposits and the area of 

high values of the stress-compaction products in the 

northern part of the area indicates a strong correlation 

between genetic class of deposits and compaction per 

unit head decline for stresses applied during the 

1943-60 period.

The relation of the apparent compressibility (stresscompaction products) of the lower zone to the genetic 

classes of deposits is shown along a longitudinal profile 

of the study area in figure 65. Maximum values of apSaline water body 024 SMILES

0246 KILOMETRES 

VERTICAL EXAGGERATION X26

SEA LEVEL

3200'

Sierra flood-plain 

deposits

Corcoran Clay Member of the 

Tulare Formation

EXPLANATION

Diablo flood-plain deposits, interbedded with Sierre floodplain deposits near well 167 

15-34N1

Diablo alluvial-fan deposits 

and Sierra flood-plain and 

deltaic deposits

Marine sediments

FIGURE 65. Relation of stress-compaction products to types of lower-zone deposits.
F82 STUDIES OF LAND SUBSIDENCE

parent compressibility occur in the northern part of the 

area, where Diablo flood-plain deposits constitute 

nearly all the lower zone along the line of section.

The apparent compressibility decreases in the central 

part of the area. Stress-compaction products in the 

northern part of the area are about 8x 10 ~2 , but in the 

central part of the area, the products are only about 

3xlO~2 . The marked decrease of stress-compaction 

products of the deposits in the central part of the area 

coincides with marked changes in the source and depositional environment of the deposits tapped by wells. 

Coarse-grained Sierra flood-plain deposits constitute 

more than 400 feet of the lower zone (fig. 65), and below 

the Sierra flood-plain deposits are intermixed Sierra 

and Diablo flood-plain deposits. In addition, the 

Pliocene marine deposits of the Etchegoin and San Joaquin Formations are heavily pumped to the west. The 

increase in the proportion of sand, with increasing 

proportion of Sierra flood-plain deposits and the inclusion in the section of the deeply buried partly consolidated Pliocene marine deposits, account for the decrease in apparent compressibility in the central part of 

the study area.

As much as 20 feet of subsidence had occurred in the 

central part of the area as of 1966, but figure 65 shows 

that the large amounts of subsidence that have occurred 

are not the result of large values of unit compaction per 

unit change in applied stress during a given period of 

time such as the 1943-60 period. Instead, the large 

amounts of subsidence that have occurred south of Cantua Creek are the result of large pore-pressure declines 

in more than 2,000 feet of lower-zone deposits.

Southeast of well 16/15-34N1, the apparent compressibility shown in figure 65 increases to about 5xlO~~2 . 

Deposits from many sources occur in this area also, but 

Sierra flood-plain and deltaic deposits make up much of 

the lower zone. Diablo alluvial-fan deposits overlie the 

Sierra deposits, and the marine littoral and estuarine 

deposits underlie the Sierra deposits. In contrast to the 

deltaic deposits shown in figure 51, the Sierra deltaic 

deposits in this part of the area have extensive sand 

beds. The marine sediments are not tapped by wells 

along the line of section south of the northernmost limit 

of the lens of brackish water.

In the southern part of the area, wells are able to 

obtain sufficient quantities of water without having to 

tap the Pliocene marine section or the fresh-waterbearing deposits in the basal part of the overlying Tulare Formation. Although these deeper deposits contain 

fresh water, as indicated in figure 65, wells in the southern part of the area generally are not perforated more 

than 100 feet below the bottom of well 20/18-11Q3 (fig. 

65). The alluvial-fan deposits derived from the Diablo 

Range predominate within the interval tapped by irrigation wells along the line of section. The proportion of 

alluvial-fan deposits constituting the lower-zone deposits increases to the southeast and is coincident with a 

decrease in apparent compressibility from 4 to 2 x 10~2 .

VARIATION IN EXCESS PORE PRESSURES

Several lines of evidence indicate that the various 

genetic types of deposits differ in their ability to retain 

excess pore pressures because of the characteristics of 

their source materials and their modes of deposition. 

The following summary indicates that the Diablo 

alluvial-fan deposits should be slower to attain porepressure equilibrium after a given head decline than 

the Diablo and Sierra flood-plain deposits:

Evidence based on laboratory tests of core-hole samples

1. Particle-size analyses of 145 samples from alluvialfan deposits and 95 samples from flood-plain deposits indicate mean clay contents of 28 percent for 

the alluvial-fan samples and 22 percent for the 

flood-plain samples.

2. The alluvial-fan deposits are more poorly sorted 

than the flood-plain deposits (Meade, 1967, p. 12).

3. Mean vertical permeabilities for 23 samples, as determined by consolidation tests in the load range of 

400-800 Ib in~2 indicate that the fine-grained beds 

of the fan deposits are less permeable than the 

fine-grained beds of the flood-plain deposits. In gallons per day per square foot, the mean permeability values were 1.7 for the fan deposits and 5.7 and 

4.0 for the Diablo and Sierra flood-plain deposits.

4. Mean values of the coefficient of consolidation, cv , for 

14 samples tested in the load range of 400-800 Ib 

in indicate that the fine-grained beds of the 

alluvial-fan deposits consolidate at a much less 

rapid rate than the fine-grained beds of the 

flood-plain deposits. The mean values of cv ft yr~ 

were 8 for the fan deposits and 28 and 21 for the 

Sierra and Diablo flood-plain samples.

Field evidence

1. Study of the micrologs of the different types of deposits shows that the Diablo alluvial-fan deposits 

generally have thicker beds of fine-grained material than the flood-plain deposits. Weighted mean 

bed-thickness factors of aquitards penetrated by 

the four Inter-Agency Committee core holes were 

24 for the alluvial-fan deposits and 14 for the 

flood-plain deposits.

2. Mean well yield factors (Pt. 1, Bull and Miller, 1974, 

fig. 16) for the types of deposits range from 1 to 4 for 

fan deposits and are 9 and 11 for Diablo and Sierra 

flood-plain deposits. The slow water expulsion rate 

from the fine-grained beds of the alluvial-fan deposits is, in part, responsible for the perforated
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F83

intervals of 1,200-1,600 feet and drawdowns of 

100-120 feet in the southern part of the area. In 

contrast, the wells of similar yield in flood-plain 

deposits commonly are perforated for 600-1,000 

feet and have drawdowns of 40-60 feet. 

Thus, conditions in the alluvial-fan aquitards in the 

southern part of the area have been favorable for development of large residual excess pore pressures and 

high values of ultimate specific unit compaction. The 

same conditions also are responsible, in part, for the 

lower apparent compressibilities (stress-compaction 

products) in the alluvial-fan deposits than in the 

flood-plain deposits during the 1943-60 period.

The hypothesis of more rapid dissipation of excess 

pore pressures in the northern subarea can be checked 

by examining the changes in compaction rates at four 

compaction-recorder sites. The decrease in mean daily 

compaction rates at the four sites is shown by Bull and 

Poland (Part 3, fig. 40, 1974). The mean-dailycompaction-rate plots may be represented by a general 

exponential equation of the type

y=cemx,

in which c and m are determined by the data for each 

site. Taking the Cantua site data as an example, the 

equation for the plot of mean daily compaction rate (y) 

and the time since mid-1961 in years (x) is

3/=0.0028e-°-096x .

Computation of the values of m for the four regression 

lines for the sites gave the following results: Cantua 

site, 0.096; Mendota site, 0.21; Westhaven site, 

-0.091; and the Oro Loma site, -0.18. Although these 

values of m are approximations, a rough twofold contrast in m values is apparent for the compactionrecorder sites in the northern and southern subareas.

The contrasts between the northern and southern 

areas regarding aquitard thickness and mean daily 

compaction rates imply that, as of 1967, larger excess 

pore pressures for a given head decline existed in the 

lower-zone deposits of the southern than the northern 

subarea. The magnitudes of the above contrasts is about 

the same as the magnitude of contrast in stresscompaction products (fig 60).

Mean daily compaction rates might also be affected 

by the proportions of aquitards in the lower zone. The 

core-hole sites had the following percentages of 

aquitards in the lower zone: Oro Loma, 41; Mendota, 23; 

Cantua, 69; and Huron, 55. The means for the two pairs 

of core holes in the northern and southern subareas are 

32 and 62 percent, respectively. (The difference between 

these means is significant at the 0.88 probability level.) 

Thus, an inverse relation apparently exists between the 

compaction rates and the proportions of the lower zone

comprised of aquitards. This further underscores the 

effect of aquitard thickness on recorded compaction for 

an aquifer system that does not have a steady-state 

pore-pressure distribution.

It is concluded that the source and environment of 

deposition is at least as important a geologic factor as 

the prior applied stress in determining the rate and 

amount of subsidence within the Los Banos-Kettleman 

City area. The combination of extensive permeable 

sand beds and intercalated clayey beds that generally 

do not exceed 8 feet in thickness provide an ideal 

geologic environment for the rapid expulsion of large 

amounts of water from the fine-grained beds to cause 

the large amounts of subsidence during the 1943-60 

period. One-third of the difference between the apparent compressibility (specific unit compaction) in the 

northern and southern parts of the area is real and is 

due to differences in prior total applied stress as of 1943. 

The other two-thirds of the difference is indeed only 

apparent and is attributed chiefly to hydraulic and petrologic differences between genetic types of deposits 

that affect the rate of expulsion of water from aquitards 

upon increase in applied stress. The effects of the mean 

lithology of the lower zone are not considered nearly as 

significant as either the effect of total applied stress or 

bed thickness of the sediments laid down under different modes of deposition.

DISTRIBUTION OF WELL-CASING FAILURES

Studies of well-casing failures have provided useful 

information about the distribution of casing breaks in 

the different types of deposits. Figure 66 shows the 

variation of casing-failure occurrences for the upper 

and lower zones and for the various types of deposits. In 

the upper zone, most of the casing failures have occurred in the basal part of the zone, where pore-pressure 

declines have been greatest. In general, the casing failures are most abundant in the lower zone because, as a 

unit, it has undergone more compaction than the upper 

zone. West of the Corcoran in the southwestern part of 

the area, the unit casing-failure ratio is intermediate 

between the ratios for the upper and lower zones where 

the Corcoran is present.

The Diablo alluvial deposits have an overall casing 

failure ratio that is similar to that of the Corcoran. The 

Sierra sands have the highest casing-failure ratio of any 

of the types of deposits. The abundant casing failures 

opposite the Sierra sands probably are not indicative of 

a higher unit compaction in sands than in clays. They 

may be related in part to the removal of sand adjacent to 

the casing during the course of pumping. Removal of the 

sand providing lateral support for the well casing would 

provide potential weak sections that could be ruptured 

as a result of compressive stresses that were caused by
F84 STUDIES OF LAND SUBSIDENCE

compaction of overlying and underlying fine-grained 

deposits.

AIT zones

Upper zone

Lower zone

West of Corcoran

Diablo alluvial deposits

Sierra sand deposits

Corcoran Clay Member

Other deposits

^;fiWl^i:W^;!^:^:X^^fv^ ^.\

I i 1 1

0 2 4 6 8 10

UNIT CASING-FAILURE RATIO, 

IN FAILURES PER THOUSAND FEET

FIGURE 66. Relation of well-casing failures to hydrologic unit and type of adjacent deposit. 

(From W. E. Wilson, written commun., April 1968.)

SUMMARY AND CONCLUSIONS

Changes in the altitude of the land surface in the Los 

Banos-Kettleman City area have been caused by compaction due to wetting of moisture-deficient alluvial-fan 

deposits, withdrawal of petroleum, and tectonic movements, but have been caused mainly by ground-water 

withdrawal.

Two main sources of vertical-control data were used. 

The Geological Survey made surveys for detailed topographic maps of the entire area during the 1920's and in 

1955. Comparison of these maps provides regional subsidence information prior to 1955. Although the Coast 

and Geodetic Survey levelings provide valuable information as early as 1933, the establishment of a levelline network in 1955 and subsequent relevelings to 

specifically evaluate land subsidence provided a means 

of obtaining detailed information about the extent, 

magnitude, and rate of subsidence.

During the last million years, parts of the adjacent 

Coast Ranges have been elevated more than 2,000 feet, 

and parts of the San Joaquin Valley have subsided 

about 1,000 feet as a result of tectonic movements. Tectonic movements are continuing today, but at very slow 

rates compared with the rate of manmade subsidence. 

The amounts of intermittent uplift of parts of the mountain front are small and are superimposed on long-term 

subsidence due to nontectonic causes. About 0.1 foot of 

net apparent uplift of the crest of Anticline Ridge occurred between 1962 and 1963.

Subsidence due to the withdrawal of petroleum is 

minor in extent and magnitude and occurs, in part, in 

those areas of subsidence due to withdrawal of ground 

water. Bench marks on Anticline Ridge that are set in 

formations older than the fresh-water-bearing formations indicate about 0.25 foot of net subsidence due to 

withdrawal of petroleum from the Coalinga oil field 

since 1943.

Near-surface subsidence occurs within about 7 percent of the areas affected by subsidence due to 

artesian-head decline. About 130 square miles have 

subsided or would subside if irrigated. Subsidence of 

3-10 feet is common, and 10-15 feet of subsidence has 

occurred locally.

Near-surface subsidence results from the compaction 

of deposits by an overburden load as the clay bond supporting the voids is weakened by water percolating 

through the deposits for the first time since burial. The 

amount of compaction due to wetting is dependent 

mainly on the overburden load, natural moisture conditions, and the type and amount of clay in the deposits. 

The amount of compaction increases with an increase in 

the overburden load, but most of the near-surface subsidence has been caused by compaction in the upper 200 

feet of deposits. For compaction due to wetting to occur, 

the alluvial-fan deposits must remain moisturedeficient after burial, and the deposits must have 

sufficient clay so that they undergo a decrease in 

strength when water percolates through them for the 

first time.

Both the magnitude and extent of subsidence due to 

artesian-head decline are greater than near-surface 

subsidence. The pattern of subsidence is an elongate 

oval, in which the area (as of 1966) that had subsided 

more than 10 feet was 70 miles long. More than 1 foot of 

subsidence had occurred in 2,000 square miles of the Los 

Banos-Kettleman City area and the adjacent areas east 

of the trough of the valley. Maximum subsidence of 26 

feet occurred southwest of Mendota between 1920 and 

1966, and the 'maximum subsidence rate of a bench 

mark during this period was 1.8 ft yr"" 1 .

Intense subsidence occurred first in the northern part 

of the area. By 1943, as much as 10 feet of subsidence 

had occurred west of Mendota, but less than 2 feet of 

subsidence had occurred in most of the southern part of 

the area. The area of intense subsidence expanded after 

the middle 1940's as a result of rapid agricultural development during and after World War II. By 1963, 

more than 20 feet of subsidence had occurred in both the 

northern and southern parts of the area.

During the 1959-63 period, 480 square miles were 

subsiding more than 0.5 ft yr" 1 , and 63 square miles 

were subsiding more than 1.0 ft yr~ .

Histories of subsidence rates are highly variable in 

the different parts of the area. In general, subsidence 

rates were 0.1-0.8 ft yr" 1 greater during the 1959-63 

period than during the 1943-53 period. The area between Los Banos and Mendota was the only large area 

in which the subsidence rate decreased between the two 

periods. Subsidence rates increased until 1954, when 

deliveries of water from the Delta-Mendota Canal reduced the amount of ground water pumped, and have
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F85

decreased since then. Subsidence rates have increased 

steadily at Mendota and to the northeast, and south of 

Huron until 1963. In the area between Kettleman City 

and Fresno Slough, years of little or no subsidence occur 

between years of as much as 0.4 foot of subsidence.

Since the middle 1950's, subsidence rates have remained fairly constant or have decreased slightly in 

most of the area. During the 1963-66 period, only a few 

square miles were subsiding more than 1 ft yr" 1 .

Compaction gages, consisting of anchors set near the 

base of the fresh-water-bearing deposits and connected 

to the land surface with %-inch cables inside well casings, have been measuring as much as 99 percent of the 

compaction that is causing the subsidence. The proportion of the subsidence that is being measured is decreasing at most compaction-recorder sites, indicating that 

compaction is occurring at greater depths than previously. At the Oro Loma site, the percent of subsidence 

that is being measured by the 1,000-foot compaction 

recorder has decreased from about 90 to 55 percent. At 

the Cantua site, the percentage has decreased from 99 

to 78 percent.

Seasonal variations in the rate of compaction occur at 

most sites, but are not well defined at some sites such as 

the Cantua site. Subsidence rates tend to be greatest 

during the late winter and during the summer the 

times of maximum demand for irrigation water from 

the ground-water reservoir.

The use of several compaction recorders at one site 

provides a means of measuring the unit compaction in 

the intervals between the depths at which the anchors 

are set. Annual unit compaction has varied from zero for 

the 350-500-foot depth interval at the Oro Loma site to 

1.2xlO~3 foot per foot per year for the 503-703-foot 

depth interval at the Cantua site.

Variation of unit compaction with depth for the Los 

Banos-Kettleman City area is largely the result of two 

components the decrease in compressibility of the deposits with depth because of the increase in prior effective overburden load and the variations in the amounts 

of head decline that have occurred as a result of pumping. Perforated-interval data suggest that the amounts 

of head decline increase with depth to about 200 feet 

below the Corcoran and then remain about constant or 

decrease slightly with further increase in depth. The 

casing-failure data indicate that unit compaction increases to a depth of about 200 feet below the Corcoran 

because the trend of greater head decline with increasing depth dominates over the decreasing compressibility of the deposits with increasing depth. Below a depth 

of about 200 feet below the Corcoran, the effects of 

decreasing compressibility of the deposits dominate, 

and unit compaction decreases with increasing depth.

Water- and oil-well casings are being shortened in

amounts about equal to the amount of compaction of the 

deposits, even if they are encased in cement. For wells 

ranging in size from 4 to 13 inches that are not gravelpacked, resistance to compaction decreases with increasing casing diameter. Increased protrusion of the 

well casings above the land surface is common, but is 

less than 10 percent of compaction for most water wells. 

The use of tops of well casings as subsidence bench 

marks and the measuring of increased protrusion to 

obtain amounts of compaction are not reliable unless 

the proportions of casing shortening and increased casing protrusion are known.

Comparison of the subsidence of well bench marks 

and reference bench marks 17-193 feet from the wells 

indicates that casings of pumped wells subside more 

than reference bench marks despite increased protrusion of the well casings. Maximum compaction occurs 

at, or near, pumping wells because they are point 

sources of maximum applied stress.

Compaction has damaged or destroyed hundreds of 

well casings where subsidence rates have been more 

than 0.5 foot per year for more than 5-10 years. Wells in 

areas where subsidence rates are less than 0.5 ft yr~ 

commonly last 10-20 years, but repairs of well casings 

in such areas of lesser subsidence rate are common.

Most of the compaction is occurring below the Corcoran; only 5-30 percent of the compaction occurs above 

the Corcoran in most of the area. As much as 30-40 

percent of the compaction occurs above the Corcoran in 

the southern part of the area.

The rates, amounts, and distribution of subsidence 

within the Los Banos-Kettleman City area are highly 

dependent on regional variations of geologic factors 

influencing the compaction of unconsolidated deposits. 

The poorly sorted and clayey nature of many of the 

sands tends to increase the compressibility of the sands 

within the study area. The presence of large freshappearing mica flakes in the sands derived from the 

Sierra Nevada increases the potential for inelastic compaction and the potential for an elastic expansion or 

compaction of the aquifers.

The deposits of the study area contain about 20 percent of clay-size material, which consists mainly of 

montmorillonite with calcium as the principal adsorbed 

cation. Except for the uppermost 300 feet of the Oro 

Loma core, about 7 parts out of 10 of the clay minerals 

are montmorillonite (Meade, 1967). The presence of 

large amounts of montmorillonite clay adds greatly to 

the compressibility of the deposits upon change in effective stress, as compared with kaolinite or illite clays.

In general, the younger deposits are less consolidated 

than the older deposits. The partly consolidated nature 

of the older deposits may be due to large prior overburden loads, but time also has been important in
F86 STUDIES OF LAND SUBSIDENCE

influencing the degree of compaction or cementation of 

the deposits. The Pliocene marine deposits are noticeably more consolidated than the Pleistocene deposits. 

The Pliocene clayey deposits, instead of being plastic, 

are sufficiently brittle that samples will break when 

struck with a hammer. The Pliocene sandy deposits, 

instead of being loose, are sufficiently cemented that 

they are cohesive, but friable.

The specific unit compaction for the 1943-60 period 

was determined for the lower zone. The specific unit 

compaction was based on (1) the subsidence during the 

period, (2) the proportions of post-1960 lower-zone compaction in the various parts of the study area, (3) the 

change in applied stress on the lower zone as a result of 

change in lower-zone artesian head and change in the 

position of the water table, and (4) the thickness of the 

lower-zone deposits that have undergone large head 

decline.

The most important aspect of the lower-zone specific 

unit' compaction is that the values of specific unit compaction are about four times larger in the northern than 

in the central and southern parts of the area. The 

geologic factors that were evaluated to determine the 

causes of areal variation in specific unit compaction 

were prior total applied stress, mean lithology, and 

source and mode of deposition of the different genetic 

types of deposits.

The applied overburden load that was computed was 

the total applied stress on the middle of the lower zone 

at the beginning of the 1943-60 period. The components 

of the total applied stress included (1) the buoyant 

weight of saturated deposits, (2) the geostatic weight of 

deposits and contained water above the water table, and 

(3) the seepage stresses caused by head differentials 

resulting chiefly from artesian-head decline. The component of total applied stress on the middle of the lower 

zone that was present in 1943 owing to the buoyant 

weight of saturated deposits ranged from 800 to 1,800 

feet of water for most of the area, but locally the applied 

stress resulting from this component was less than 600 

feet or more than 2,000 feet.

The lack of buoyant support for the deposits above the 

water table and the weight of water contained in the 

unsaturated deposits were responsible for an additional 

load in 1943 that was equal to 50-200 feet of water in 

most of the area. By 1943, artesian-head decline had 

lowered the potentiometric surface of the lower zone 

below the water table in all parts of the area. The result 

was an increase in applied stress on the lower zone. As of 

1943, seepage stresses of 100-200 feet of water were 

being applied to the lower zone in most of the study area. 

The three components of applied stress resulted in a 

total applied stress on the middle of the lower zone as of 

1943 of 600-2,200 feet of water, but in most of the area

the range of total applied stress was 1,000-1,800 feet of 

water.

The effect of prior total applied stress on lower-zone 

specific unit compaction for the 1943-60 period was 

largely removed by multiplying specific unit compaction by total applied stress. The resulting product is an 

apparent compressibility of the deposits. By removing 

the effects of prior applied stress about a third of the 

fourfold difference in specific unit compaction between 

the northern and southern parts of the area was removed. Removal of the effects of prior stress eliminated 

the area of anomalously low values of specific unit compaction adjacent to the Big Blue Hills. In a 

100-square-mile area underlain chiefly by Sierra 

flood-plain deposits, the removal of the effects of prior 

total applied stress that ranged from 1,000 to 2,000 feet 

resulted in almost uniform stress-compaction products 

that ranged only from 2.4 to 2.8xlO~2 .

It is concluded that prior applied stress is an important factor in determining the compressibility of a deposit of a given lithology in response to unit increase in 

effective stress. Compaction-recorder data at the 

Westhaven site substantiate this conclusion. Values of 

unit compaction for the alluvial-fan deposits are larger 

at shallower depths than at greater depths, where much 

of the upper zone has undergone head declines of similar 

magnitude to those in the lower zone.

Variations in the overall lithology of the lower zone 

were evaluated by making a lithofacies map based on 

the mean electric-log resistivities corrected to 38°C and 

1,000 mg I" 1 NaCl salinity. The lithofacies map indicates that the deposits in the northern part of the area 

are coarser grained than the deposits in the southern 

part of the area. The low resistivities that prevail in 

most of the study area confirm the presence of abundant 

fine-grained material noted in core samples. The 

coarser grained deposits in the lower zone are most 

common where the ancestral streams of Panoche and 

Los Gatos Creeks and the San Joaquin and Kings Rivers entered the study area.

Plots of mean resistivity and stress-compaction products of the lower zone have a large degree of scatter. A 

relation between mean lithology and apparent compressibility does not exist. Although laboratory tests 

indicate that clays are more compressible than sands, a 

parallel relation could not be demonstrated for the 

amounts of compaction that occurred for different mean 

lithologies between 1943 and 1960 in response to the 

increase in applied stress during the same period. Apparently, insufficient time was available during the 

period for large amounts of compaction to occur in those 

sections of the lower-zone containing large amounts of 

clay. The areas having large amounts of sand are interpreted as having compacted rapidly, but the total
LOS BANGS KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F87

amount of compaction was less than for areas having 

intermediate amounts of sand.

Consideration of the mode and source of deposition of 

the lower-zone deposits (Miller and others, 1971, p. 

25-33) revealed that the northern part of the area consisted mainly of Diablo flood-plain deposits and that the 

southern part of the area consisted mainly of Diablo 

alluvial-fan deposits. The eastern part of the area has 

lower-zone deposits that consist chiefly of Sierra 

flood-plain and deltaic deposits from the Kings River in 

the south and Sierra flood-plain deposits from the San 

Joaquin River in the north.

The area of highest apparent compressibility of the 

lower-zone deposits coincides with the area of Diablo 

flood-plain deposits and Sierra flood-plain deposits derived from the San Joaquin River.

Several lines of evidence indicate that the bedding of 

the deposits is an important geologic factor controlling 

the magnitude and rate of compaction computed for the 

1943-60 period. The Diablo flood-plain deposits contain 

abundant and laterally extensive sand beds between 

fine-grained beds 4-8 feet thick. In contrast, the 

alluvial-fan deposits have a higher clay content and are 

more poorly sorted than the flood-plain deposits 

 characteristics that result in minimum permeabilities and consolidation rates for the fine-grained 

beds of the fan deposits. Fine-grained beds generally are 

thicker in the fan deposits (mean bed-thickness factor of 

24) than in the flood-plain deposits (mean bed-thickness 

factor of 14), where the bed-thickness factor equals 

(aquitard thickness/2)2 .

Thus, conditions in the alluvial-fan aquitards in the 

southern part of the area have been favorable for development of large residual excess pore pressures and 

high values of ultimate specific unit compaction. These 

conditions also are largely responsible for less unit 

compaction per givenamountof increase in applied stress 

in the southern part of the area between 1943 and 1960.

Thus, evaluation of several geologic factors indicates 

that the apparent fourfold higher compressibility 

(specific unit compaction) of the lower-zone deposits in 

the northern part of the area is part real and part apparent. About a third of the apparent difference in compressibility is real and is due to lesser amounts of total 

applied stress prior to 1943 in the northern areas. Most 

of the other two-thirds of the difference is only apparent. 

It is apparent because it can be attributed chiefly to 

geologic differences, such as thickness of bedding, that 

control the rate of expulsion of water from aquitards 

upon increase in applied stress in deposits of markedly 

different modes and sources of deposition.

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 1964b, Geomorphology of segmented alluvial fans in western

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85 p.

Bull, W. B., and Miller, R. E., 1974, Land subsidence due to groundwater withdrawal in the Los Banos-Kettleman City area, 

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conducive to subsidence: U.S. Geol. Survey Prof. Paper 437-E, 

71 p.

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California Part 3. Interrelations of water-level change, change 

in aquifer-system thickness, and subsidence: U.S. Geol. Survey 

Prof. Paper 437-G, 62 p.

California Division of Oil and Gas, 1960, Pt. 1, San Joaquin- Sacramento Valleys and northern coastal regions, in California oil 

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Carpenter, D. W., 1965, Pleistocene deformation in the vicinity of the 

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Sci. p. 142-145.

Croft, M. G., 1972, Subsurface geology of the late Tertiary and 

Quaternary water-bearing deposits of the southern part of the 

San Joaquin Valley, California: U.S. Geol. Survey WaterSupply Paper 1999-H, 29 p.

Davis, G. H., and Green, J. H., 1962, Structural control of interior 

drainage, southern San Joaquin Valley, California, in Geological Survey research 1962: U.S. Geol. Survey Prof. Paper 450-D, 

p. D89-D91.

Davis, G. H., Green, J. H., Olmsted, F. H., and Brown, D. W., 1959, 

Ground water conditions and storage capacity in the San Joaquin Valley, Calif.: U.S. Geol. Survey Water-Supply Paper 1469, 

287 p.

Davis, G. H., and Poland J. F., 1957, Ground-water conditions in the 

Mendota-Huron area, Fresno and Kings Counties, California: 

U.S. Geol. Survey Water-Supply Paper 1360-G, p. 409-588.

Frink, J. W., and Kues, H. A., 1954, Corcoran Clay A Pleistocene 

lacustrine deposit in San Joaquin Valley, Calif.: Am. Assoc. 

Petroleum Geologists Bull, v. 38, no. 11, p. 2357-2371.

Gilboy, Glennon, 1928, The compressibility of sand-mica mixtures: 

Am. Soc. Civil Engineers Proc., v. 54, p. 555-568.

Inter-Agency Committee on Land Subsidence in the San Joaquin 

Valley, 1955,Proposed program for investigating land subsidence 

in the San Joaquin Valley: Sacramento, Calif, open-file report, 

160 p. 

1958, Progress report on land-subsidence investigations in the

San Joaquin Valley, California, through 1957: Sacramento, 

Calif, open-file report, 160 p.

Ireland, R. L., 1963, Description of wells in the Los Banos-Kettleman 

City area, Merced, Fresno, and Kings Counties, California: U.S. 

Geol. Survey open-file report, 519 p.

Janda, R. J., 1965, Quaternary alluvium near Friant, California, 

in Guidebook for Field Conference I, Northern Great Basin 

and California Internat. Assoc. Quaternary Research, 7th
F88 STUDIES OF LAND SUBSIDENCE

Cong. USA 1965: Lincoln, Nebr., Nebraska Acad. Sci., 

p. 128-133.

Johnson, A. I., Moston, R. P., and Morris, D. A., 1968, Physical and 

hydrologic properties of water-bearing deposits in subsiding 

areas in central California: U.S. Geol. Survey Prof. Paper 

497-A, 71 p.

Lofgren, B. E., 1960, Near-surface land subsidence in western San 

Joaquin Valley, California: Jour. Geophys. Research, v. 65, no. 

3, p. 1053-1062.

 1968, Analysis of stresses causing land subsidence, in Geological Survey research 1968: U.S. Geol. Survey Prof. Paper 600-B, 

p. B219-B225. 

-1969, Land subsidence due to the application of water,

in Varnes, D. J., and Kiersch, George, eds., Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. America, 

p. 271-303.

Lohman, S. W., and others, 1972, Definitions of selected ground-water 

terms revisions and conceptual refinements: U.S. Geol. Survey 

Water-Supply Paper 1988, 21 p.

Meade, R. H., 1964, Removal of water and rearrangement of particles 

during the compaction of clayey sediments review: U.S. Geol. 

Survey Prof. Paper 497-B, 23 p.

 1967, Petrology of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey Prof. Paper 

497-C, 83 p. 

-1968, Compaction of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey Prof. Paper 

497-D, 39 p.

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consolidation tests and decline in artesian head, in Geological

Survey research 1961: U.S. Geol. Survey Prof. Paper 424-B, p.

B54-B58.

Miller, R. E., Green, J. H., and Davis, G. H., 1971, Geology of the

compacting deposits in the Los Banos-Kettleman City subsidence area, California: U.S. Geol. Survey Prof. Paper 497-E, 46 p.

Poland, J. F., and Davis, G. H., 1969, Land subsidence due to withdrawal of fluids, in Varnes, D. J., and Kiersch, George, eds., 

Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. 

America, p. 187-269.

Poland, J. F., and Everson, R. E., 1966, Hydrogeology and land subsidence, Great Central Valley, California, in Bailey, E. H., ed., 

Geology of northern California: California Div. Mines and Geology Bull. 190, p. 239-247.

Poland, J. F., and Ireland, R. L., 1965, Shortening and protrusion of a 

well casing due to compaction of sediments in a subsiding area in 

California, in Geological Survey research 1965: U.S. Geol. Survey Prof. Paper 525-B, p. B180-B183.

Poland, J. F., Lofgren, B. E., andRiley, F. S., 1972, Glossary of selected 

terms useful in the studies of the mechanics of aquifer systems 

and land subsidence due to fluid withdrawal: U.S. Geol. Survey 

Water-Supply Paper 2025, 9 p.

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Canal alignment, western Fresno County, California, in Abstracts for 1962: Geol. Soc. America Spec. Paper 73, p. 60.

Sharpe, C. F. S., 1938, Landslides and related phenomena: New York, 

Columbia Univ. Press., 137 p.

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Jour. Sed. Petrology, v. 24, p. 151-158.

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Coast Ranges of California: California Div. Mines Bull. 118, p. 

119-163.

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practice: New York, John Wiley & Sons, Inc., 566 p.

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strength of soils: Coastal Engineering Conf., 6th, Florida 1957, 

Proc., v. 6, p. 827-843.
INDEX

[Italic page numbers indicate major references]

A Page

Age of deposits __ _______________ __ F63

Alluvial-fan deposits, bedding ___ 54, 55,57, 82, 87

casing failure ______________________ 83

clay content ______________________________ 53

compaction ______________ 62, 63, 83, 87 

compressibility _______________ 76,82,83

consolidation ___________________ 62, 63

lateral extent _________________ 60

lower-zone constituent __________________ 81

moisture condition ______________________ 10, 14

permeability ______________________________ 56

stress-compaction product ________________ 76

Westhaven site______________________ 51

Anticline Ridge _______________ 7, 8, 19, 64, 84

Apparent compressibility, defined ____________ v

Applied stress, clay content ______________ 87

compaction ___________________ 64, 70

lithology _______________________ 83 

lower zone _______________________ 86

water-table change ____________________ 45, 57

Aquifers ____________________ 10, 19, 60 

Aquitards _________ 19,26,60,62,63,79,82,87

Artesian-head decline _________ 6, 8, 14, 26, 84, 86

Arvin ________________________________ 10

B, C

Bedding of deposits _________________ 54,87 

Bed-thickness factors _______________ 60,87 

Benchmarks____________ 4, 14, 19, 43, 45, 85

Big Blue Hills ___________-____ 55, 64, 76, 86

California Aqueduct _______________ 10, 14, 23 

Cantua Creek__________ 7, 14, 24, 26, 48, 76, 81 

Cantua site, bed thickness ___________________ 62

casing failure _____________________ 46

compaction ___ __________ 34, 38, 39, 40, 46 

compressibility _______________ 70, 74 

equipment _________________ 30, 34 

pore pressure______________________________ 83

subsidence ________________ 34,35,85 

water-level change __________________ 40

Casing-cable friction _______________ 31, 32

Clay _____________ 10, 53, 59, 63, 83, 84, 85, 87 

Coalinga oil field ____________________ 8, 84 

Coast Range orogeny ___________________ 7

Coast Ranges_______________________ 84 

Coefficient of consolidation ________________ 62

Compaction ______________'_ 2, 10,29, 83, 84 

Compaction, applied stress change ____ _____ 70

lower zone ____________________ 46,64

measurement ____________ 32,53,36,38 

relation to consolidation._____________ 62

relation to geologic factors ____________ 49

relation to well casing _________ __ 43, 44

upper zone ___________________,46

Compaction recorder ________29,33, 36, 38, 46, 85

Compressibility, apparent, defined _________ v

applied stress ________________ 74, 83

clay ___________________________ 53 

compaction ____________________ 38, 85

effective stress __________________________ 70

fine-grained beds ______________________ 62

lithology -_____________________ 79, 80

lower-zone deposits ______________ 87

overburden load________________ 50, 85

Page

Compressibility-effective stress product, defined. ___ v 

Compression index ________________________F63

Compressional forces __________________ 41

Consolidation _______________ 51,62,70,85

Terzaghi theory _________________ 54, 60 

Consolidation coefficient _______________ 82

Continental deposits __________________________ 63

Corcoran Clay Member of the Tulare

Formation 7,38,39,46,47,54, 59,63, 70,77 

Critical depth _________________ _____ 41

defined____________________________ v

D

Damage caused by subsidence ______________ 8

Damage to wells ________________ 41, 42, 45, 85

Deltaic deposits __________ 53, 58, 61, 63, 81, 82 

Delta-Mendota Canal____________ 14, 26, 49, 84

Deposition ______________________ 79, 87

Diablo alluvial-fan deposits, bedding ___ 54, 55, 57

casing failure _________________ 83

clay content ________________________ 53

compaction ________________^______ 60, 62

compressibility ______________ 76, 82, 83 

consolidation ____________________ 62, 63

lateral extent ________________________ 60

stress-compaction product ______________ 76

Westhaven site ________________________ 51

Diablo flood-plain deposits, bedding _________ 57, 87

clay content _______ _ __ ______ 53

compaction.____-__-_-____________ 63

compressibility _________________________ 87

deposition ____________________ 80

lateral extent ______________________ 59

permeability ______________________ 56

Diablo Range ______________ 7, 10, 64, 70, 81

Diagenetic changes ________________________ 63

Drawdown ______________________________ 59

E, F

Effective stress ___________________ 51,70 

Elastic compaction __________________ 51

Electric log ___________________ 55,57,76 

Equipment _________ 29, 31, 33, 36, 37, 38, 42, 85 

Etchegoin Formation ____________ 8, 64, 67, 77 

Expansion ____________________ 32

Firebaugh __________________________ 70

Five Points ______________________ 19, 22

Flood-plain deposits, bed thickness___________ 62

bedding ______________ 55,56,57,82,87, 

clay content ______________________________ 53

compaction._______________________ 63

compressibility ____________________ 87

deposition ___________________ 80, 87 

lateral extent _________________________ 59

stress-compaction product ____________ 76

Fresno slough ________________ 19,64,70,85

Friction in equipment _________________ 30, 31

G, H, I, J

Geologic factors, relation to compaction _____ 49

relation to specific unit compaction _____ 67

Ground-water withdrawal __ 1, 7, 10, 33, 45, 57, 67, 84

Hanford ___________________ ______ 10

Page 

Head decline ___________________ F6, 38, 59, 64, 70, 85

Helm oil field __________________________________ 8

Huron ________________________ 26, 85

Huron site ___________________ 57,58,62

Inelastic compaction ___________________ __ 51

Irrigation ________________________________ 14

Jacalitos Formation______________________ 8

K, L 

Kerman _______________________ ___ 14

Kettleman City _____________________ 10, 85

Kings River_________________ 15, 29, 64, 81, 86

Kreyenhagen Formation ________________ 64

Lacustrine deposits __________ 56, 59, 62, 63, 81

Laguna Seca Hills __________________________ 7

Land surface movement_________ ____ _ 6

Lateral extent of beds-__________--------_______ 59

Lemoore site __________________________ 49, 63

Level-line network _____________ 4,10,14,26 

Lithology _______-___ 54, 57, 58, 59, 76, 83, 86 

Little Panoche Creek __________________ 7 

Los Banos _____________________ 10, 26, 84 

Los Banos-Kettleman City, location ___________ 2

Los Gatos Creek ___ _______ ______ 76, 77, 86

Lower zone, artesian head decline ___________ 86

compaction _______________________ 39, 46

deposition ___________________ ___ 87

deposits ___________________ 51,64, 79 

lithology ___ _ ________ _ __________ 76

specific compaction _____ _ ___ 74, 86

M 

Mapping program _______________ ______ 4, 10, 14

Maricopa____________________ ____ _ 10

Marine deposits_______________ __ 63, 76, 81, 82, 86

Mendota ____________ 14,19,22,26,28,49,85

Mendota site, bed thickness _______ -___ 62

casing failure ___ _______ - 46

compaction ___________ _ _ _ 33, 39

equipment ____________________________ 30, 33

lacustrine deposits ___________ ________ 59

micrologs _______________________ _ 60

permeability __________________________ 57

pore pressure---.__________________ _____ 83

subsidence ___________________ ___ 33

water-level change ____ _______________ 40

Mica __________________________________ 51,63,85

Micaceous arkosic sand ________________________ 58

Micrologs ______________ ________ ____ 60

Moisture condition___________ __ 10, 14, 84

Monocline Ridge ____________________________ 7

Montmorillonite _________________ 10, 53, 85

O, P 

Oro Loma site, bed thickness _________________ 62

compaction _______________ 33, 38, 39, 74

equipment _________ _ 30, 33

pore pressure__________________________ 83

subsidence _______________ _ _ 33, 85

water-level change ____________________ 40

Overburden load __ _________ ______ 10,49, 84

Panoche Creek _______________ 7, 76, 77, 87 

Panoche Hills_____________________ 26, 64

F89
F90 INDEX

Page 

Particle-size analyses _______________________ F77, 82

Permeability __________________ 57, 58, 59, 63, 82

Petroleum withdrawal _________________ 7

Petrology ________________________ 51, 74 

Pleasant Valley _______________ _______ 8 

Pore pressure _________ 26,51,54,62,79,82,87 

Potentiometric level _____________ 6, 56, 70, 86 

Previous work ____________________________ 4

Purposes _______________________________ 2

Q, R, S

Quality of lower-zone water ________________ 77

Rate of compaction _______ 33, 36, 38, 40, 83, 85 

Rate of consolidation __________________ 62

Rate of subsidence ______ 2, 6, 8, 9, 10, 19,22, 33, 84

Resistivity._________________ 55, 76, 77, 86

Reversal of subsidence rate ______________ 26

Richgrove site ______________________________ 54

Salinity of the lower-zone water ____________ 77

San Joaquin _________________________________ 81

San Joaquin Formation _________________ 64

San Joaquin River ____________________ 86

San Joaquin Valley ________ 1, 7, 8, 10, 28, 59, 84 

San Luis Canal _____________ 10, 14, 18, 23, 37 

Sand ____________________ 52, 57, 59, 63, 83, 85

Seepage stress __________________ 67,70

Page

Sierra deltaic deposits ______ F53, 58, 62, 63, 82, 87 

Sierra flood-plain deposits, bedding_ 55,56, 82, 87 

bed thickness________________ ________ 62

compaction_________________________ 63

deposition ________________________ 80

lateral extent ________________________ 59

stress-compaction product __________________ 76

Silt ___________________________________ 52

Sorting of the fan deposits.--________________ 57

Specific-unit compaction________ 51, 54, 63, 64, 86

Stress-compaction product ________ 79, 80, 82, 86

defined____________________ _ v

Subsidence...________________________ 2, 82

damage _______________________ 8

near-surface __________________ 8, 14, 84

defined_________________________ v

relation to petroleum withdrawal ________ 8, 84

relation to tectonic movement ____________ 7

relation to well-casing shortening ______ 37, 44

relation to withdrawal of ground water______ 10

Surface-water imports_________ 15, 26, 27, 29, 84

T, U, V

Tectonic movement __________________ 6, 7, 84

Terzaghi theory of consolidation _____ _ __ _ 54,60

Page

Thickness of beds _________. ___ F54, 64, 83 

Tulare _________________ ______ _ _ _ _ 10

Tulare Formation ______________ 7,8,64,82

Tulare Lake basin _______________________ 7

Unconsolidated deposits ______________ 19,49,63

Unsaturated deposits ______________________ 86

Uplift of Anticline Ridge _____________.__ 7,84

Upper-zone compaction ______________________ 46

Upper-zone deposits____________________ 51

Vertical-control data ______________________ 4

Void ratio _______________________ 51,54

W, Y

Warthan Canyon ___________________ 7

Wasco ______________________________________ 10

Well-casing failure____________________ 45, 51, 83

Well-casing shortening and

protrusion ______.__ 36,41,42,43,85 

Westhaven _____________________________ 11

Westhaven site, compaction _________ 36, 40, 86

equipment _________________ 30,35,42 

head decline ______________-_________ 41

overburden load ____________________ 51

pore pressure__________________________ 85

subsidence __________________________ 35

Yearout site ___________________________ 49, 64

U.S. GOVERNMENT PRINTING OFFICE: 1975-0-689-905/12