N

Sinkhole above 11-Yard West

Sinkhole above

2-Yard South

Route 20A

Cuylerville

Sterling mineshafts

Retsof main plant and mine

Courtesy of Ron Pretzer/LUXE, May 1994

Simulated Effects of 1994 Salt-Mine Collapse 

on Ground-Water Flow and Land Subsidence 

in a Glacial Aquifer System, 

Livingston County, New York

U.S. Department of the Interior

U.S. Geological Survey

Professional Paper 1611

Prepared in cooperation with the Livingston County Department of Health
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Simulated Effects of Salt-Mine Collapse 

on Ground-Water Flow and Land Subsidence 

in a Glacial Aquifer System, Livingston County, 

New York

By Richard M. Yager, Todd S. Miller, and William M. Kappel

Professional Paper 1611

Prepared in cooperation with the Livingston County Department of Health
Library of Congress Cataloging-in-Publications Data

Any use of trade, product, or firm names in this report is for

identification purposes only and does not constitute endorsement 

by the U.S. Government.

For sale by U.S. Geological Survey, 

Branch of Information Services

Box 25286, Federal Center

Denver, CO 80225

Reston, Virginia 2001

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Yager, Richard M.

Simulated effects of salt-mine collapse on ground-water flow and land subsidence in a glacial 

aquifer system, Livingston County, New York / by Richard M. Yager, Todd S. Miller, and William 

M. Kappel.

p. cm. – (Professional paper ; 1611)

Includes bibliographical references (p. ).

ISBN 0-607-95033-1

1. Groundwater flow–New York (State)–Livingston County–Comp;uter simulation. 2. Subsidences (Earth movements–New York (State)–Livingston County–Computer simulation. I. Miller, 

Todd S. II. Kappel, William M. III. Geological Survey (U.S.) IV. Livingston County (N.Y.). Dept. 

of Health. V. Title. VI. U.S. Geological Survey professional paper ; 1611.

QE75 .P9 v. 1611

[GB1025.N]

557.3 s

[551.49’0974785] 00-060049
Contents III

CONTENTS

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

Introduction .......................................................................................................................................................................... 3

Purpose and scope ...................................................................................................................................................... 4

Previous studies .......................................................................................................................................................... 4

Methods of investigation ............................................................................................................................................ 6

Seismic surveys ................................................................................................................................................ 6

Water-level and streamflow measurements ....................................................................................................... 7

Ground-water quality ........................................................................................................................................ 7

Acknowledgments ....................................................................................................................................................... 7

Geologic setting .................................................................................................................................................................... 7

Bedrock units .............................................................................................................................................................. 8

Silurian units ..................................................................................................................................................... 8

Devonian units .................................................................................................................................................. 8

Glacial and postglacial geology .................................................................................................................................. 8

Erosion of bedrock by ice .................................................................................................................................12

Unconsolidated deposits ...................................................................................................................................12

Subglaciofluvial sand and gravel ............................................................................................................12

Englacial and glaciolacustrine sediments ...............................................................................................16

Supraglacial sand and gravel ..................................................................................................................16

Glaciolacustrine and deltaic sediments and till ......................................................................................16

Alluvial sediments ..................................................................................................................................17

Hyrdologic setting ................................................................................................................................................................17

Aquifers and confining units .......................................................................................................................................17

Upper aquifer ....................................................................................................................................................17

Upper confining layer and deltaic deposits .......................................................................................................17

Middle aquifer ..................................................................................................................................................17

Lower confining layer .......................................................................................................................................18

Lower aquifer ....................................................................................................................................................18

Bedrock aquifers ...............................................................................................................................................19

Ground-water flow patterns before the collapse .........................................................................................................19

Upper aquifer ....................................................................................................................................................19

Middle and lower aquifers ................................................................................................................................19

Bedrock aquifers ...............................................................................................................................................21

Ground-water quality ..................................................................................................................................................21

Salinity ..............................................................................................................................................................22

Isotopic composition .........................................................................................................................................24

Natural gas ........................................................................................................................................................24

Effects of mine collapse and flooding ...................................................................................................................................25

Collapse of mine ceiling .............................................................................................................................................25

Land subsidence .........................................................................................................................................................28

Surface water ..............................................................................................................................................................28

Ground-water hydrology ............................................................................................................................................30

Ground-water levels ..........................................................................................................................................30

Ground-water quality ........................................................................................................................................33

Natural gas exsolution ................................................................................................................................................37

Simulation of ground-water flow...........................................................................................................................................38

Model design ..............................................................................................................................................................38

Model layers and grid .......................................................................................................................................38
IV Contents

Boundary conditions ........................................................................................................................................ 42

Model layer 1 ......................................................................................................................................... 42

Model layers 3 and 5 .............................................................................................................................. 42

Model layers 2 through 5 ....................................................................................................................... 42

Model calibration ....................................................................................................................................................... 43

Calibration procedure ....................................................................................................................................... 43

Steady-state simulations ......................................................................................................................... 44

Transient-state simulations ..................................................................................................................... 44

Precollapse conditions ...................................................................................................................................... 44

Head distribution .................................................................................................................................... 44

Recharge and discharge .......................................................................................................................... 46

Aquifer properties .................................................................................................................................. 46

Postcollapse conditions (flooding and water-level recovery) ........................................................................... 47

Drawdowns ............................................................................................................................................. 48

Water budget .......................................................................................................................................... 51

Estimates of aquifer properties ............................................................................................................... 52

Model bias .............................................................................................................................................. 54

Model results .............................................................................................................................................................. 55

Effect of natural gas on specific storage ........................................................................................................... 55

Water-level recovery ......................................................................................................................................... 60

Effect of mine collapse on saline water intrusion ............................................................................................ 60

Simulation of land subsidence .............................................................................................................................................. 65

One-dimensional simulations ..................................................................................................................................... 65

Model design .................................................................................................................................................... 65

Model calibration ............................................................................................................................................. 68

Three-dimensional simulation .................................................................................................................................... 71

Summary .............................................................................................................................................................................. 72

Hydrogeologic setting ................................................................................................................................................. 73

Effects of mine collapse ............................................................................................................................................. 74

Simulation of ground-water flow ............................................................................................................................... 75

Simulation of land subsidence ................................................................................................................................... 76

References cited .................................................................................................................................................................... 77

FIGURES

1. Shaded-relief map showing locations of selected geologic features in western New York 

and of study area ................................................................................................................................................................... 3

2. Map showing principal geographic features of Genesee Valley study area, Livingston County, N.Y.,

and location of mined area and of collapse.......................................................................................................................... 5

3. Photo showing view from southeast of sinkholes that formed in the collapse area, Retsof salt mine,

Genesee Valley, Livingston County, N.Y., 1994. .................................................................................................................. 6

4. Map showing bedrock geology and bedrock surface altitudes in modeled Genesee Valley aquifer area, 

Livingston County, N.Y., and locations of wells in ground-water-monitoring network....................................................... 9

5. Generalized columnar geologic section of Paleozoic rocks in Retsof salt mine vicinity, 

Livingston County, N.Y......................................................................................................................................................... 10

6. Generalized geologic sections A-A′ across the valley near collapse area, and B–B′ 6 miles north 

of collapse area at Retsof salt mine, Livingston County, N.Y............................................................................................... 11

7. Generalized geologic section C-C′ along Genesee valley axis, Livingston County, N.Y. ............................................... 13

8. Map showing the surficial geology of Genesee Valley from Avon to Dansville, N.Y....................................................... 14

9. Schematic diagram showing glacial-deposition processes in Genesee Valley, Livingston County, N.Y. ........................ 15

10. Aquifers and confining layers along geologic section A–A′ in Genesee Valley, Livingston County, N.Y..................... 18

11. Map showing water-table altitude in upper aquifer prior to mine collapse in March 1994, and locations

of wells for which water-level meaurements are available ................................................................................................... 20
Contents V

12. Trilinear diagram showing percentage of major cations and anions in water from confined aquifers and OnondagaBertie Limestones in Genesee Valley, Livingston County, N.Y. .......................................................................................... 21

13. Map showing locations of water-sampling sites I through V in Genesee Valley, 

Livingston County, N.Y., with (1) specific conductance, and (2) ratios of chloride-to-bromide concentrations, 

in wells screened in the lower aquifer. .................................................................................................................................. 23

14. Graphs showing concentrations of stable isotopes and tritium in confined aquifers in Genesee Valley, 

Livingston County, 1995–96. A. δD in relation to δ18O. B. Tritium in relation to δ18O. ..................................................... 25

15. Map showing locations of rooms and pillars in Retsof salt mine, Livingston County, N.Y.,

and extent of flooding in April and June 1994 ...................................................................................................................... 26

16. Stratigraphic section A–A′ depicting rubble zones over collapsed rooms in Retsof salt mine,

Livingston County, N.Y. ....................................................................................................................................................... 27

17. Map showing land subsidence in vicinity of the Retsof salt mine, Livingston County, N.Y., 

February 1996 ....................................................................................................................................................................... 29

18. Map showing drawdown in lower aquifer, Genesee Valley, Livingston County, N.Y., in January 1996, 

hydrographs showing hydraulic head in selected wells, and bar graph showing precipitation at 

Mt. Morris, 1994–97 ............................................................................................................................................................. 31

19. Map showing locations of sampled wells in Genesee Valley, Livingston County, N.Y., and wells in which

saline water was detected in April 1997................................................................................................................................ 33

20. Trilinear diagram showing percentage of major cations and anions in water from northern end of

Genesee Valley, Livingston County, N.Y., April 1997 .......................................................................................................... 36

21. Boxplot showing specific conductance of water from northern end of Genesee Valley, Livingston County, N.Y.,

April 1997 ............................................................................................................................................................................. 36

22. Graph showing relation between chloride and bromide concentrations in water from 

the lower aquifer and the Onondaga and Bertie Limestones in Livingston County, N.Y., and the Bass Islands 

carbonate brine in western New York.................................................................................................................................... 37

23. Graph showing measured brine level (altitude) in the mine, estimated brine levels in the collapse area 

(location II), and water levels in the collapse area, Livingston County, N.Y., January 1996 through March 1997.............. 37

24. Schematic diagrams showing: A. Vertical section of model with hydraulic properties assigned to

each layer and representation of vertical hydraulic connections between model layers along valley walls. 

B. Cell dimensions and variables used in computation of flow rates between cells ............................................................. 40

25. Map showing boundary conditions in ground-water-flow model of aquifer system in Genesee Valley, 

Livingston County, N.Y.: A. Upper aquifer (model layer 1). B. Confined aquifer system (model layers 3, 4 and 5)........... 41

26. Map showing distribution of hydraulic head and weighted residuals computed by steady-state 

simulation (model 3D-A) for Genesee Valley, Livingston County, N.Y.: A. Upper aquifer (model layer 1).

B. Lower aquifer (model layer 5).......................................................................................................................................... 45

27. Map showing distribution of drawdown in lower aquifer in Genesee Valley, Livingston County, N.Y. 

in January 1996, and range of weighted residuals computed with values from transient-state simulation 

(model 3D-A)........................................................................................................................................................................ 49

28. Hydrographs showing water levels measured in middle and lower aquifers in Genesee Valley, 

Livingston County, N.Y. during 29 months after collapses at Retsof salt mine, and values simulated by transient-state 

simulation (model 3D-A): A. Location II, wells Lv348 and Lv368. B. Location III, wells Lv351 and Lv350.

C. Location IV, wells Lv361 and Lv360. D. Location V, wells Lv366 and Lv367. E. Site near Fowlerville 

moraine, wells Lv483 and Lv496 ......................................................................................................................................... 50

29. Hydrographs showing water levels measured in the lower aquifer in Genesee Valley, Livingston County,

N.Y. during 29 months after collapses at Retsof salt mine, and values simulated by transient-state simulation 

(model 3D-A) from two alternative values of specific storage: A. Location II, well Lv368. B. Location V, 

well Lv367. C. Site near Mt. Morris, well Lv91. D. Site near Fowlerville moraine, well Lv425. ....................................... 54

30. Graphs showing simulated heads and weighted residuals computed from transient-state simulation 

(model 3D-A) of aquifer system in Genesee Valley, Livingston County, N.Y...................................................................... 55

31. Graph showing effect of gas exsolution and expansion on specific storage values in lower aquifer
VI Contents

during drawdown at location II near collapse area in Genesee Valley, Livingston County, N.Y., March 1994

through January 1996............................................................................................................................................................ 57

32. Graph showing change in specific storage during drawdown and recovery at selected wells

screened in lower aquifer in Genesee Valley, Livingston County, N.Y., during 29 months after collapses 

at Retsof salt mine................................................................................................................................................................. 57

33. Hydrographs showing water levels measured in lower aquifer in Genesee Valley, Livingston County, N.Y.

during 29 months after collapses at Retsof salt mine, and values simulated by transient-state simulations with models 

3D-A (constant specific storage) and 3D-B (variable specific storage values based on gas exsolution with methane

concentrations below saturation): A. Location II, well Lv368. B. Location V, well Lv367. C. Site near Mt. Morris, 

well Lv91. D. Site near Fowlerville moraine, well Lv425.................................................................................................... 59

34. Hydrographs showing water levels measured in lower aquifer in Genesee Valley, Livingston County, N.Y. 

during first 900 days after collapses at Retsof salt mine, and water levels simulated for 1994 through 2006 by model 

3D-A: A. Location II, well Lv368. B. Location V, well Lv367. C. Site near Fowlerville moraine, well Lv496 .................. 60

35. Hydrographs showing water levels measured in lower aquifer in Genesee Valley, 

Livingston County, N.Y. during 29 months after collapses at Retsof salt mine, and water levels simulated for 1994 

through 2006 by model 3D-A with vertical conductance increased and decreased by one order of magnitude:

A. Location II, well Lv368. B. Location V, well Lv367. C. Site near Fowlerville moraine, well Lv496 ............................. 61

36. Map showing hydraulic-head distribution in the lower aquifer in northern part of the Genesee Valley, 

Livingston County, N.Y. and ground-water flow paths from time of first Retsof mine collapse (March 1994) through 

August 1996 (29 months):

A. Under precollapse (March 1994) conditions; flow paths computed with steady-state simulation (model 3D-A);

B. In August 1996; flow paths computed with transient-state simulation (model 3D-A) .......................................... 62

C. In August 1996; flow paths computed with transient-state simulation (model 3D-A) assuming highpermeability paths and with specific storage value (2.3 × 10-6 ft-1) calculated from published values 

obtained in land-subsidence studies ........................................................................................................................... 63

37. Generalized stratigraphic sections showing relative thickness of units and the depths of 

confined aquifers at borehole XD1 (location II) and monument survey K10 (2,800 ft south of the collapse area), 

in Genesee Valley, Livingston County, N.Y. ........................................................................................................................ 66

38. Graphs showing examples of consolidation curves for: A. Compressible clays in California. 

(Modified from A. I. Johnson, 1984, fig. 4.16, corehole 14/13-11D1). B. Confining-layer sediments from 

well Lv346 at location II near the collapse area, Livingston County, N.Y. .......................................................................... 67

39. Graph showing relation of compressibility to depth as derived from consolidation curves of confininglayer sediments in Genesee Valley aquifer system, Livingston County, N.Y........................................................................ 68

40. Hydrograph showing pressures in upper confining layer at location II in Genesee Valley, 

Livingston County, N.Y. as computed by one-dimensional model 1D-A and measured at borehole XD-1......................... 70

41. Graphs showing results of one-dimensional model 1D-B simulations of land subsidence at monument 

K10 in Genesee Valley, Livingston County, N.Y.: A. Computed and measured subsidence. B. Simulated hydraulic 

head as a function of depth in upper and lower confining layers, April 1994 through August 1996.................................... 70

42. Graph comparing land subsidence measured 1994–96 at monument K10 in Genesee Valley, 

Livingston County, N.Y., values computed by one-dimensional model 1D-B for 1994–2006, and values obtained 

from alternative regressions in which land subsidence was assumed to result only from elastic compression.................... 71

43. Graph showing land subsidence along survey line K in Genesee Valley, Livingston County, N.Y.,

as measured in February 1996 and as computed by three-dimensional model 3D-C........................................................... 72

44. Map showing distribution of land subsidence in Genesee Valley, Livingston County, N.Y. 

in February 1996, as computed by three-dimensional model 3D-C ..................................................................................... 73
Contents VII

TABLES 

1. Concentrations of inorganic constituents of water from confined aquifers in the Genesee Valley, 

Livingston County, N.Y......................................................................................................................................................... 22

2. Concentrations of stable isotopes and tritium in water sampled confined aquifers in the Genesee Valley, 

Livingston County, N.Y......................................................................................................................................................... 24

3. Concentrations of inorganic onstituents in water sampled from confined aquifers in the Genesee Valley, 

Livingston County, N.Y., April 1997 .................................................................................................................................... 34

4. Summary of models of ground-water flow and land subsidence in the Genesee Valley, 

Livingston County, N.Y., assumptions used in defining storage coefficients, and applications of each............................... 39

5. Numbers of parameters representing hydraulic properties in model 3D-A estimated and fixed in nonlinear 

regression for Genesee Valley aquifer system, Livingston County, N.Y............................................................................... 43

6. Simulated water budget for Genesee Valley aquifer system, Livingston County, N.Y., under average

steady-state conditions before collapses of Retsof mine ceiling in March and April 1995 .................................................. 46

7. Parameter values estimated for model layer 1 (water-table aquifer in Genesee Valley aquifer system, 

Livingston County, N.Y.) through nonlinear regression; also model error in steady-state simulation 3D-A and 

measured mean stream discharges ........................................................................................................................................ 47

8. Simulated water budget for aquifer system in Genesee Valley, Livingston County, N.Y. during 

period of mine flooding, March 1994 to January 1996. A. Entire aquifer system. B. Confined-aquifer system .................. 51

9. Optimum parameter values estimated for confined aquifer system (model layers 2 to 5)

in Genesee Valley, Livingston County, N.Y., through nonlinear regression in transient-state simulation 

(model 3D-A), and their aproximate confidence intervals at 95-percent level, and discharge to mine estimated 

from volume of flooded area in Marhc and September 1994................................................................................................ 52

10. Fixed parameter values used in nonlinear regression for transient-state simulation (model 3D-A) 

for confined aquifer system in Genesee Valley, Livingston County, N.Y. ........................................................................... 53

11. Optimum parameter values estimated for confined aquifer system (model layers 2 to 5) 

in Genesee Valley, Livingston County, N.Y., through nonlinear regression in transient-state simulation with 

models 3D-A (constant specific storage) and 3D-B (variable specific storage values based on gas exsolution) ................. 58

12. Optimum parameter values estimated for confining layers in Genesee Valley aquifer system,

Livingston County, N.Y. through nonlinear regression in one-dimensional models 1D-A (location II) and 

1D-B (mounment K10), their approximate confidence intervals at 95-percent level, and the mean values specified 

in three-dimensional model 3D-C (entire aquifer system).................................................................................................... 69

APPENDIX

13. Wells in the monitoring network in Genesee Valley, Livingston County, N.Y................................................................ 82
VIII Contents

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

Length

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

acre 0.4047 hectare

square mile (mi2) 2.590 square kilometer 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second 

cubic foot per day (ft3/d) 0.02832 cubic meter per day

gallon per minute (gal/min) 0.06309 liter per second

Temperature

degrees Farenheit ( ̊F) 5/9 ( ̊F-32) degrees Centigrade ( ̊C)

Density

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter

Pressure

ton per square foot (ton/ft2) 95.77 kilopascal 

pound per square inch (psi) 6.895 kilopascal 

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day

Transmissivity

foot squared per day (ft2/d) 0.09290 meter squared per day 

Specific storage

per foot (ft-1) 3.281 per meter

Other abbreviations

picocurie per millimeter pCi/ml

microsiemens per centimeter μS/cm

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—a geodetc datum derived from a general 

adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929.
Abstract 1

Simulated Effects of 1994 Salt-Mine Collapse on GroundWater Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

By Richard M. Yager, Todd S. Miller, and William M. Kappel

ABSTRACT

The bedrock ceiling in parts of the Retsof salt 

mine in the the Genesee Valley, Livingston County, 

N.Y. collapsed on March 12, 1994 and water from 

overlying aquifers began to flow into the mine at a rate 

of 5,500 gal/min (gallons per minute), and the rate 

increased to as much as 20,000 gal/min after a second 

collapse 3 weeks later in April 1994. Efforts to save the 

mine were abandoned by the end of 1994, and the mine 

was completely flooded by January 1996.

The Genesee Valley (including the tributary 

Canaseraga Valley) is about 40 miles long and contains 

as much as 750 feet of glacial sediment and recent alluvium, which rest on mostly carbonate bedrock along 

the valley axis near and north of the collapse site, and 

on shale in areas farther south. The mined salt bed lies 

within Silurian shale and is overlain by 600 feet of 

Devonian shale and limestone. Rock-rubble zones and 

fractures that formed within units overlying the collapse resulted in about 45 feet of subsidence at the bedrock surface and the formation of sinkholes as much as 

70 feet deep at land surface.

The glacial aquifer system in the Genesee Valley 

generally consists of an unconfined alluvial aquifer 

(upper) and two confined glacial aquifers (middle and 

lower) separated by two confining layers. The underlying carbonate bedrock also contains water-bearing 

fracture zones in which water flowed northward before 

the collapse. The salinity of ground water generally 

increases with depth; specific conductance ranges from 

430 to 1,390 μS/cm (microsiemens per centimeter) in 

the middle aquifer and from 2,980 to 39,300 μS/cm in 

the lower aquifer. Concentrations of tritium in the 

lower aquifer indicate the water to be generally more 

than 45 years old.

Subsidence at land surface ranges from 15 feet 

over some parts of the mine (through shrinkage of the 

mine cavity in response to deformation of salt beds) to 

more than 70 feet over two areas within the mine, and 

is as much as 0.8 ft outside the mined area as a result of 

compaction of fine-grained sediments in the confining 

layers. By January 1996, when the mine was completely flooded, drawdowns in the lower aquifer were 

as much as 400 feet near the collapse area, as much as 

50 feet in an area 7 miles to the north, and as much as 

135 feet in an area 8 miles south of the collapse area. 

The northward direction of ground-water flow in the 

confined aquifers north of the collapse was reversed, 

and five domestic wells 7 miles north of the collapse 

began to produce saline water from the lower aquifer, 

apparently because the drawdown either induced the 

inflow of saline water from bedrock, or allowed saline 

water from further north to flow southward. Ratios of 

chloride to bromide concentrations in ground-water 

samples indicate two sources of salinity in the lower 

aquifer: (1) saline water from carbonate bedrock and 

(2) halite-bearing water from an unknown source. Both 

thermogenic and biogenic gases (methane and sulfide) 

were produced by wells screened in confined aquifers 

as a result of exsolution as water-level declines lowered 

the pore pressure.

A five-layer ground-water flow model based on 

generalized geologic sections was used to simulate 

flow conditions within the unconsolidated sediments 

before and after the mine collapse. The model represents a 61.3 square-mile section of the Genesee Valley 

that extends from the Village of Avon in the north to the 

Village of Dansville, 40 miles in the south. Nonlinear 

regression was used to calibrate the model to (1) 

assumed water-table altitudes and estimated base flows 

in steady-state simulations representing precollapse 

conditions, and (2) measured water levels in wells and 

estimated ground-water discharges to the mine in transient-state simulations that represent the flooding of the 

mine and water-level recovery thereafter. 
2 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

The computed water budget indicated that 

ground water released from storage in the lower aquifer 

accounted for about 11 percent of the total inflow to the 

model, and most of the water discharged to the mine. 

Values of specific storage estimated by regression for 

the two confined aquifers (2.9 x 10-4 and 6.9 x 10-5

ft-1) were much larger than values typically estimated 

for other sand and gravel aquifers affected by land subsidence (1 x 10-6 to 3 x 10-6 ft-1); this could be 

explained by the exsolution of natural gas (methane) 

from ground water during the period of drawdown; 

exsolution also could account for part of a bias in the 

head distribution computed in model simulations. A 

gas-partitioning equation developed to compute specific storage in the presence of a gas phase indicates 

that specific storage was not constant, as assumed in 

the flow model, but varied temporally and spatially as 

a function of pressure. Computations of specific storage in the lower aquifer near the collapse area, where 

the maximum drawdown occurred, included the effects 

of gas exsolution and ranged from 2.4 x 10-5 to 1.8 x 

10-4 ft-1; the maximum pore volume occupied by gas 

was estimated to be 7 percent. Including (1) gas exsolution and (2) aquifer compressibility typically associated with aquifer-system compaction, decreased model 

error by about 15 percent and slightly reduced model 

bias.

Hydraulic heads computed in 12.4-year transient-state simulations indicate that water levels will 

return to precollapse conditions by about the year 

2006, but the recovery would be completed by 1999 if 

the specific storage were smaller (2.3 x 10-6 ft-1). 

Ground-water flow paths computed from model results 

indicate that the reversal of the northward hydraulic 

gradient in the northern part of the valley allows saline 

water to migrate southward toward the collapse at a 

velocity of 1 to 2 ft/d (feet per day). The time between 

the collapse and the onset of salinity in two domestic 

wells indicates a greater velocity (8 ft/d), however, and 

suggests that the saline water could have traveled along 

discrete flowpaths with a larger hydraulic conductivity 

(2,000 ft/d) than the 300 ft/d estimated by regression 

for the lower aquifer. The present southward gradient 

(1.2 x 10-3 ft/ft) is about 3 times larger than the northward gradient (3.9 x 10-4 ft/ft) that will develop once 

the natural hydraulic gradient is reestablished. The calculated northward velocity indicates that, if saline 

water migrates southward for 10 years after the mine 

collapse, about 30 years will be required for freshwater 

to flush the area into which the saline water has 

intruded.

Transient-state simulations with one- and threedimensional models were conducted to estimate the 

extent of land subsidence due to dewatering of finegrained sediments outside the mined area, where subsidence measurements were not made. The one-dimensional models represent vertical flow and compression 

in the upper and lower confining layers at two locations—one near a borehole with pressure transducers 

screened in the upper confining layer near the collapse 

area, and the second at a survey monument 2,800 ft to 

the south. Vertical hydraulic conductivity of the upper 

confining layer, and specific storage of both confining 

layers, were estimated through nonlinear regression 

from observations of pore pressure and subsidence. 

Both elastic and inelastic storage were represented in 

both confining layers. Elastic storage was assumed, 

from an observed relation between compressibility and 

depth computed from consolidation tests of confininglayer sediments, to be inversely proportional to effective stress (or depth); inelastic storage was assumed, 

from published values, to be 30 times greater than elastic storage.

Computed pressure changes in the upper confining layer near the collapse were in close agreement 

with measured pressures changes, and the maximum 

computed subsidence was about 94 percent of the 

observed subsidence (0.78 feet). About 92 percent of 

the computed subsidence was the result of drainage and 

compression in the lower confining layer; 90 percent of 

this compression was estimated to be inelastic, nonrecoverable compaction. Representing drainage of confining-layer sediments by elastic storage gave pressure 

and maximum-subsidence values that matched 

observed values as closely as those based on inelastic 

storage; elastic storage also simulated land-surface 

rebound after water-level recovery, which had not 

occurred by 1999. Hydraulic properties of the confining-layer sediments estimated by the one-dimensional 

models that represented only elastic compression were 

incorporated in the three-dimensional model and 

resulted in close agreement between computed subsidence and subsidence measured along a survey line. 

Simulated subsidence closely matched the actual subsidence in Mt. Morris, 3 mi south of the collapse, where 

as much as 0.3 ft of subsidence was measured. Model 

results indicate that at least 0.1 ft of subsidence 

occurred by February 1996 over the 16 square-mile 
INTRODUCTION 3

area that extended 5 miles north of the collapse area 

and 7 miles south of the collapse.

INTRODUCTION

A collapse of the bedrock ceiling in parts of the 

Retsof salt mine in Livingston County, N.Y. (fig. 1) in 

March and April 1994 allowed water from overlying 

aquifers to flood the mine. All mining activity was 

halted in September 1995, and the mine shafts were 

sealed. The mine was completely flooded by January 

1996, eliminating a major commercial source of rock 

salt. The flooding of the mine caused widespread 

water-level declines in the overlying aquifer system, 

which lies within the valley drained by the Genesee 

River and Canaseraga Creek in Livingston County; this 

is referred to herein as the Genesee Valley study area.

The Retsof salt mine is about 30 mi southwest of 

the City of Rochester (fig. 1) and adjoins the western 

NIAGARA

ORLEANS

MONROE

WAYNE

ERIE

GENESEE

LIVINGSTON

ONTARIO

YATES

CATTARAUGUS ALLEGANY STEUBEN

WYOMING

NIAGARA

ORLEANS

MONROE

WAYNE

ERIE

GENESEE

LIVINGSTON

ONTARIO

YATES

CATTARAUGUS ALLEGANY STEUBEN

WYOMING

Avon

Geneseo

Mt. Morris

Dansville

Rochester

Avon

Geneseo

Mt. Morris

Dansville

Rochester

L A K E

E R I E

L A K E O N T A R I O

Niagara

River

Salt Mine

A P P A L A C H I A N U P L A N D S

O N T A R I O – E R I E L O W L A N D S

Study Area

ONONDAGA ESCARPMENT

ONONDAGA ESCARPMENT



Base from U.S. Geological Survey digital data, 1:250,000, 1983

42 ̊30'

43 ̊

79 ̊ 78 ̊ 77 ̊

0 10 20 MILES

0 10 20 KILOMETERS

78°30' 77°30'

NEW YORK

LOCATION MAP

Study

area

Map area

EXPLANATION

Subcrop area of the Onondaga Limestone

Valley Heads moraine

Boundary of the Genesee Valley

Boundary of the ancestral Genesee Valley

Onondaga escarpment

Figure 1. Locations of selected geologic features in western New York and of study area.
4 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

edge of the Village of Geneseo (fig. 2). The mine began 

operations in 1885 and became the largest rock-salt 

mine in the western hemisphere; it now underlies an 

area of more than 6,000 acres (about 11 mi2). Most of 

the mined salt was used for road deicing in 14 northeastern States. The abandoned Sterling mine (fig. 2) 

was connected to the Retsof mine to improve ventilation.

On March 12, 1994, the mine ceiling collapsed 

in a 650- by 650-ft mining panel (2 Yard South) which 

consists of 40 ft-wide rooms separated by 25-ft-square 

pillars located 1,100 ft below land surface (fig. 2). The 

collapse allowed water from overlying aquifers to drain 

into the mine at a rate of about 12 ft3/s (7.9 Mgal/d). 

Less than a month later, on April 8, 1994, the bedrock 

overlying a nearby panel (11 Yard West) collapsed, and 

total ground-water inflow to the mine increased to 47 

ft3

/s (30.2 Mgal/d), which is equivalent to 5.6 percent 

of all ground water pumped by municipalities (535 

Mgal/d) in New York State (Solley and others, 1993).

Subsidence of rock and sediment above the collapsed areas propagated to land surface, causing two 

300-ft-diameter sinkholes (fig. 3) to develop, around 

which ring fractures developed with vertical offsets 

ranging from 1 to 10 ft. Land surface subsidence was 

as much as 20 ft in the first sinkhole and as much as 70 

ft in the second. The sinkholes caused the closure of a 

highway bridge over Beards Creek on State Route 20A 

(fig. 2); an alternate route was established to detour 

traffic around the collapse area.

Water levels in domestic and industrial wells 

within the valley declined rapidly within eight weeks 

after the collapses, and at least a dozen wells went dry. 

By January 1996, when the mine was completely 

flooded, ground-water levels had declined about 400 ft 

near the collapse area and more than 50 ft in areas 7 mi 

to the north and 8 mi to the south within the valley. 

Since 1994, the mine owner has supplied water to residents whose wells went dry, has monitored water levels 

in a network of more than 100 wells and has measured 

land subsidence at monument surveys. A Memorandum of Understanding among the mine owner, Livingston County, and the State of New York in December 

1994 provided funds for test-well drilling to characterize the aquifer system and to support the development 

of a ground-water flow model.

In 1995, the U. S. Geological Survey (USGS), in 

cooperation with the Livingston County Department of 

Health, began a 2-year study to define the effect of the 

ceiling collapse on the Genesee Valley aquifer system. 

The study used information from field surveys, including (1) stratigraphic logs from test drilling (Alpha Geoscience, 1995a,b,c and 1996a,b,c); (2) seismicreflection and refraction surveys, (3) drillers’ logs and 

records of ground-water levels; (4) measurements of 

land-surface altitude; and (5) chemical analyses of 

ground-water samples to develop a three-dimensional 

ground-water-flow model of the aquifer system. The 

model results were compared with actual water-level 

declines to simulate (1) the time required for water levels to return to precollapse conditions and (2) the extent 

of land subsidence caused by compression of finegrained sediments.

Purpose and Scope

This report describes the hydrogeology of the 

Genesee Valley and the effects of the ceiling collapse 

on the aquifer system. It discusses (1) the origin and 

character of glacial sediments, (2) the occurrence, flow 

directions, and chemical quality of water in the aquifer 

system before the collapse, (3) the effects of the collapse on the aquifer system in terms of land subsidence, 

water-level declines, changes in water quality, and 

exsolution of natural gas, and (4) design and calibration 

of the ground-water-flow model; it also presents (1) 

results of flow-model simulations, including an estimated ground-water budget and graphs showing the 

simulated water-level recovery, and (2) results of subsidence simulations, including maps and graphs showing the extent of land subsidence.

Previous Studies

Ground-water resources of the Genesee River 

Basin were described by Kammerer and Hobba (1967) 

in a report that includes drillers’ logs and chemical 

analyses of water. The history of glacial deposition in 

the area has been described by Muller and others 

(1988) and by Brennan (1988) and Young and Sitkin 

(1994).

Various engineering studies addressed leakage 

of ground water into an access shaft to the abandoned 

Sterling mine. Langill and Associates (1981) traced the 

leakage to joints and bedding-plane fractures at the 

contact between the Onondaga and Bertie Limestones 

and identified the source of water as the glacial aquifer 

underlying the Genesee River. Dunn Geoscience Corporation (1992) discussed the hydrogeology of uncon-
INTRODUCTION 5

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

   

Conesus

Creek

Conesus

Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga

Creek

Genesee

River

Avon

Dansville

Geneseo

RETSOF SALT MINE

Collapse areas:

Mount

Morris

Cuylerville

2 Yard South

11 Yard West

Former Sterling

Salt Mine

Sonyea

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 0 2 4 MILES

0 2 4 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Model area (Genesee Valley)

Figure 2. Principal geographic features of Genesee Valley study area, Livingston County, N.Y., and location of mined 

area and of collapse. (Location is shown in fig. 1.)
6 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

solidated deposits and bedrock in the vicinity of the 

Retsof and Sterling mines as part of a proposal for an 

incinerator-ash-processing facility.

After the roof collapses, Nittany Geoscience 

(1995) summarized ground-water levels and chemical 

quality in the vicinity of the collapse in an effort to 

identify which wells were affected by drainage of 

ground water to the mine. Ground-water levels measured by the mine owner and Livingston County in the 

monitoring network from March 1994 through May 

1996 are reported in Akzo Nobel Salt Salt, Inc. (ANSI, 

1996), and land-surface-subsidence measurements 

from August 1994 to September 1996 are given in 

monthly reports by the mine owner (Kenneth Cox, 

Akzo Nobel Salt Salt, Inc. (ANSI), written commun., 

1996). Stratigraphic logs from test drilling at five locations in the Genesee Valley, and results of hydraulic 

tests performed in the field and in the laboratory, are 

included in Alpha Geoscience (1995a,b,c and 1996a,b). 

The hydrogeology of the Genesee Valley, as indicated 

by test drilling and by records of gas wells and drilling 

logs prepared in previous studies, is summarized in 

Alpha Geoscience (1996c).

Methods of Investigation

Data from (1) seismic-reflection and seismicrefraction surveys, (2) water-level measurements, and 

(3) analyses of ground-water quality in this study were 

used with hydrogeologic information from previous 

studies to develop a conceptual model of the aquifer 

system and to design a three-dimensional groundwater-flow model.

Seismic Surveys

Seismic-reflection profiling was done by boat in 

the Genesee River to define the stratigraphy of unconsolidated deposits within the Genesee Valley. The survey began downstream from a small hydroelectric dam 

at the west side of the valley, where the Genesee River 

exits a bedrock gorge (Letchworth State Park), 1 mi 

N

Sinkhole above 11-Yard West

Sinkhole above

2-Yard South

Route 20A

Cuylerville

Sterling mineshafts

Retsof main plant and mine

Courtesy of Ron Pretzer/LUXE, May 1994

Figure 3. View from southeast of sinkholes that formed in the collapse area, Retsof salt mine, Genesee Valley, 

Livingston County, N.Y., 1994. (Location is shown in fig. 2.)
GEOLOGIC SETTING 7

north of the Village of Mt. Morris (fig. 2), and proceeded eastward across the valley. A description of the 

equipment, field technique, and theory is given by Reynolds and Williams (1987), and the application of the 

method to the delineation of hydrogeologic boundaries 

is described by Haeni (1986).

A seismic-refraction survey was conducted in 

the northern part of the study area to supplement bedrock-elevation data from well records. A continuous 

record of depth to bedrock was obtained along the survey line. Seismic-refraction techniques used in this 

study are described by Haeni (1988). A two-layer analysis of the saturated unconsolidated sediments and the 

bedrock (Scott and others, 1972) was used to calculate 

depths to bedrock.

Water-Level and Streamflow 

Measurements

Water levels were measured in more than 100 

wells bimonthly or monthly (appendix 1 and fig. 4) 

from April 1994 to the present (1998) with electric 

tapes or chalked steel tapes. Water levels in eight wells 

were measured continuously with float-driven graphical recorders or pressure-transducers with data loggers. 

The altitude of measuring points was measured 

through transit surveys on some wells; the rest were 

estimated from 1:24,000-scale topographic maps. 

Wells listed in appendix 1 are included in the U. S. 

Geological Survey’s Ground-Water Site Inventory data 

base; aquifers screened by wells for which no stratigraphic logs were available were assigned on the basis 

of well depth, estimated depth to bedrock and groundwater level. Streamflow measurements were made in 

Beards Creek and the Genesee River by standard 

USGS techniques (Rantz and others, 1982).

Ground-Water Quality

Ground-water samples were collected by Alpha 

Geoscience (1996c) from the 14 wells installed in 

1994. A centrifugal pump was used to purge the wells 

and collect the samples. pH, specific conductance, and 

alkalinity were measured in the field; analyses for principal inorganic ions were done by Lozier Laboratories, 

Inc., of Rochester, N.Y. through standard techniques. 

Splits of the same samples were analyzed by the USGS 

for hydrogen-isotope (δD) values with a hydrogenequilibration technique at 30 ̊C (Coplen and others, 

1991), and for oxygen-isotope (δ18O) values by the 

CO2-equilibration technique of Epstein and Mayeda 

(1953) at 25 ̊C, followed by mass spectrometry. Stableisotope ratios of deuterium to hydrogen and of 18O to 

16O are reported in per mil relative to Vienna Standard 

Mean Ocean Water (V-SMOW) and normalized such 

that the δD and δ18O values of Standard Light Antarctic Precipitation (SLAP) are -428‰ and -55.5‰, 

respectively (Coplen, 1994). The uncertainty of δD and 

δ18O values, expressed as twice the standard deviation 

of the measurements, is 2‰ and 0.2‰, respectively.

Acknowledgments

Ralph VanHouten of the Livingston County 

Department of Health provided water-level and wateruse data. ANSI staff provided water-level and geologic 

data, and access to the collapse area and to the rest of 

the mine. Dr. Richard Young and Dr. William Brennan 

of the Geology Department at State University of New 

York (SUNY) at Geneseo provided geologic data and 

advice. Dr. John Fountain of the Geology Department 

at SUNY at Buffalo helped derive the analytical 

expression used to describe the effect of gas exsolution 

on specific storage of the aquifer material. Many homeowners provided access to their water wells for measurement of water levels and collection of water 

samples.

GEOLOGIC SETTING

The Genesee Valley was formed through several 

geologic processes, including: (1) tectonic uplift of 

Paleozoic sedimentary rocks and subsequent fluvial 

downcutting, (2) glaciation that resulted in erosion of 

bedrock and subsequent deposition as much as 750 ft 

of glacial sediments, and (3) erosion and deposition by 

postglacial streams. Structural control within bedrock 

may account for the present alignment of the valley, 

which bends 60 ̊ from N30 ̊W in the south to N30 ̊E in 

the north (see fig. 2) (Isachsen and McKendree, 1977). 

The stratigraphy and composition of the glacial 

deposits are more complex than described in this 

report. The data available are insufficient to describe 

the geologic framework of the Genesee Valley in detail, 

but the ground-water flow model (described further on) 

was based on the geologic framework as described 

herein, and seems adequate to simulate the generalized 

ground-water flow conditions in the valley.
8 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Bedrock Units

The mined salt bed and overlying rocks are sedimentary units of Silurian and Devonian age. The age, 

formation names, lithologic description and average 

thickness of bedrock units in the vicinity of the mine 

are summarized in figure 5. Bedrock units affected by 

the ceiling collapses include the mined B6 salt unit 

within the Vernon Shale and the following overlying 

units, in ascending order: the Syracuse Formation, 

Camillus Shale, Bertie Limestone, and Onondaga 

Limestone (fig. 6). The younger Devonian units (Marcellus Shale, Skaneateles Shale, Ludlowville Shale, 

and Moscow Shale), which form the valley walls and 

uplands (fig. 6), were probably not greatly affected by 

the collapses. All bedrock units dip less than 1 ̊

 to the 

south. A regional unconformity separates the late Silurian Bertie Limestone from the Middle Devonian 

Onondaga Limestone (figs. 5, 6). The Onondaga Limestone subcrop forms most of the buried bedrock surface 

in the northern and central part of the Genesee Valley 

(figs. 4 and 7).

Silurian Units

The Vernon Shale is typically 420 ft thick in the 

Genesee Valley (Dunn Geoscience Corporation, 1992) 

and consists of calcareous shales interlayered with salt 

beds. The mine owner mined a salt bed within the Vernon Shale known as the B6 salt unit, which ranges from 

13 to 30 ft in thickness (figs. 5 and 6). Salt unit B6 

slopes southward from an altitude of -260 ft in the 

northern part of the mine to -540 ft in the southern part. 

This unit is about 1,100 ft below land surface in the collapse area at the south end of the mine.

The Syracuse Formation typically is 185 ft thick 

in the study area; it consists mainly of dolomitic shale 

and shale interbedded with some salt and anhydrite 

beds and rests conformably on the Vernon Shale. It was 

referred to as the “Syracuse Salt” by Newland and 

Leighton (1910). It is conformably underlain by the 

Camillus Shale, a mostly dolomitic and calcareous 

shale that typically is 70 ft thick in the study area (Dunn 

Geoscience Corporation, 1992). Gamma and drillers’ 

logs indicate that the upper 15 to 20 ft of the Camillus 

shale contains some dolomite and evaporite beds, but 

the lower 50 ft is almost entirely shale.

The uppermost Silurian unit is the Bertie Limestone, which in the Genesee Valley is typically 72 ft 

thick and, despite its name, consists mainly of dolomitic shale and dolomite with some limestone.

Devonian Units

The Silurian Bertie Limestone is unconformably 

overlain by the Devonian Onondaga Limestone. This 

unit is mostly limestone, but some layers are as much 

as 50 percent insoluble, hard chert. The massive beds of 

chert-bearing limestone make this formation one of the 

most erosion-resistant sedimentary units in New York. 

The Onondaga Limestone is a major aquifer in parts of 

western and central New York where it crops out at land 

surface or underlies thin glacial drift (fig. 1). Large 

amounts of ground water can be pumped from the 

Onondaga wherever dissolution along vertical joints 

and bedding planes has resulted in major water-bearing 

zones (Staubitz and Miller, 1987). The Onondaga 

Limestone averages 137 ft thick beneath the uplands 

where it has not been eroded, but is thinner in the north 

part of the Genesee Valley, where the top was eroded by 

glaciers.

The Onondaga Limestone is overlain by about 

750 ft of younger Devonian rock in the uplands and 

along the sides of the Genesee Valley; these units, in 

ascending order, are the Marcellus Shale, Skaneateles 

Shale, Centerfield Limestone, Ludlowville Formation, 

Tichenor Limestone, and Moscow Shale (fig. 6, section 

A-A′). The contact between the Moscow Shale and the 

Ludlowville Formation was formerly placed 50 ft or 

more above the Tichenor Limestone (Cooper, 1930; 

Bradley and Pepper, 1938; Rickard, 1975), but more 

recently has been placed at the base of the Tichenor 

Limestone (Dunn Geoscience Corporation, 1992; 

Mayer ,1994; Baird, 1979). All of these units have been 

removed by erosion along the valley axis near and 

north of the collapse area. The three shale units, while 

capable of yielding a few gallons per minute to wells in 

most places, are probably less permeable than the thin 

limestone units, which contain solution-widened joints 

and openings. Water levels in wells that tap these units 

were generally unaffected by the flooding of the mine. 

Few data on water levels in bedrock wells prior to the 

collapse are available, however.

Glacial and Postglacial Geology

The glacial history of the Genesee River Basin is 

described by Muller and others (1988); discussion in 

this report is limited to glacial sediments in part of the 

valley that was affected by the mine collapse. The interpretation of glacial geology in the Genesee Valley is 

based on recent subsurface information collected during this investigation and results of seismic-reflection 
GEOLOGIC SETTING 9

FOLD FOLD





408

408

258

436

63

39

15

255

256

256

36

36

20

A

390



600

700

500

300

400

600

100

100

0

0

500

400

–100

–100

100

0

200 300 400 500

0 100

200

300

400 500

200

200

.

. .

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

. .

.

.

.

. .

.

.

.

.

.

.

.

. .

.

.

.

.

. . . .

.

.

. .

.

.

Lv 398 Lv 407

Lv 451

Lv 408 Lv 410

Lv 419

Lv 417

Lv 301

Lv 399

Lv 46

Lv 29

Lv 21

Lv 13

Lv 467

Lv 477

Lv 455

LOCATION V

Lv 366

Lv 367

Lv 365

Lv 428

Lv 429

Lv 91

Lv 420

Lv 449

Lv 446

Lv 413

Lv 411

Lv 404

Lv 405

Lv 401

Lv 416

Lv 403

Lv 415

Lv 402

Lv 424

Lv 414

Lv 423

Lv 406

Lv 484

Lv 434

Lv 433

Lv 472

Lv 445 LOCATION II

Lv 309

Lv 348

Lv 346

Lv 368

Lv 441

LOCATION III

Lv 349

Lv 350

Lv 351

LOCATION IV

Lv 360

Lv 361

Lv 362

Conesus

Canaseraga

Creek

Keshequa

Creek

Beards

Creek

Genesee

River

A

A'

C'

Cuylerville

Mount

Morris

Dansville

Sonyea

Groveland

EXPLANATION

Bedrock geology

 Devonian shales

 Onondaga Limestone

 Bertie Limestone

 Salina Group

Bedrock contour—

 Shows altitude of 

 bedrock surface. 

 Contour interval 

 100 feet. Datum 

 is sea level

Line of section (figures 

 6 and 7)

300

Well in monitoring network—

 Number is Livingston County

 well number

 Well with ground-water level data

 Well with ground-water quality data

 Well with both ground-water level 

 and ground-water quality data

 Well cluster with stratigraphic logs 

 and water analyses in Alpha 

 Geoscience (1996c)

API gas well

Mine collapse area

A A'

. Lv 472

. Lv 520

. Lv 500

.

LOCATION IV

Lv 360

Lv 361

Lv 362

. API 04149

NEW YORK

LOCATION MAP

Study

area

42° 37' 30"

45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 4 MILES 2 0

0 2 4 KILOMETERS

 area, Livingston County, N.Y., and locations of wells in ground-water-monitoring network.
10 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

studies conducted by Mullins and others (1991) in parallel Finger Lake valleys to the east that were similarly 

deepened by glacial scour.

Glaciation altered stream courses in western 

New York, removed preglacial sediments, deepened 

valleys, and deposited large amounts of sediment. Glaciers typically transport large amounts of sediment (1) 

at the base of the ice as subglacial material, (2) within 

the ice as englacial material, and (3) on top of the ice as 

supraglacial material. Test drilling revealed as much as 

















yyyy

SYSTEM GROUP FORMATION LITHOLOGY

AVERAGE

THICKNESS,

IN FEET

DESCRIPTION

SILURIAN DEVONIAN

Salina Hamilton

Onondaga

Limestone

Vernon

Syracuse

Formation

Shale

Camillus

Shale

Bertie

Limestone

Marcellus Shale

Skaneateles

Shale

Ludlowville

Formation

Moscow

Shale

420

185

70

72

137

27

237

118

120

Unconformity

Shale and siltstone, gray and black;

Tichenor Limestone (8 feet thick) at

base of unit

Shale and siltstone, gray, calcareous;

Centerfield Limestone (8 feet thick)

at base of unit

Shale and siltstone, gray, brown, and

black, calcareous; commonly 

contains thin limestone beds

Shale and limestone, gray

Limestone, gray, massive bedding;

contains abundant chert

Dolomite and dolomitic shale, gray

to grayish brown

Shale, gray and green, dolomitic;

contains anhydrite concretions

Shale, salt, gypsum, and anhydrite

gray shale, white and pink to

yellowish-brown salt, gypsum, and

anhydrite

Shale, interbedded with salt, brown,

green and gray shale; clear white, gray,

and orange salt

Retsof mine in B6 salt unit

 (13-30 feet thick)

Geology modified from Dunn Geoscience Corporation , 1992

Figure 5. Generalized columnar geologic section of Paleozoic rocks in Retsof salt mine vicinity, Livingston 

County, N.Y.
GEOLOGIC SETTING 11



Moscow

Shale

Tichenor Limestone

Centerfield Limestone

Marcellus Shale Marcellus Shale

Ludlowville

Formation

Skaneateles

Shale

Onondaga Limestone

Bertie Limestone

Camillus Shale

Syracuse Formation

(mostly shale with some salt beds)

Vernon Shale

(with some salt beds)

Vernon Shale

Retsof salt mine (salt unit B6)

Unconformity

1

2

3

4

5

Delta Till

Genesee River Valley flood plain

(Extent of seismic-reflection survey)

Channels of the Genesee River

Lv 360 Lv 349 SECTION C–C'

Seismic-refraction

survey

Seismic-refraction

survey

Lv 496

Lv 188 (projected)

Gas well 4363

(projected)

Gas well 3283

(projected)

Genesee River

SECTION

C–C'

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

Unconsolidated deposits (undifferentiated)

Onondaga Limestone and older rocks

Devonian

shales

(undifferentiated)

4

5

EXPLANATION

Unconsolidated deposits—Numbers are geohydrologic 

 units referenced in text (Geologic Setting)

 Alluvial-fan and flood-plain deposits—Silt, sand,

 and gravel

 Lacustrine sand, silt, and clay

 Till—Silt and clay embedded with pebbles

 Deltaic deposits—Pebbly sand

 Supraglacial debris—Silty sand and gravel

 Englacial meltout material and subaqueous-fan

 deposits—Mix of clay, silt, and sand and gravel

 Subglacial meltwater deposits—Sand and gravel

Well and U.S. Geological Survey well number—

 Dashed where projected. Numbers with Lv prefix 

 were assigned by USGS. Well data are given in 

 appendix 1. Numbers for gas wells were assigned 

 by New York State Department of Environmental 

 Conservation

2

2

1

Lv349

3

800

600

400

200

SEA LEVEL

–200

–400

–600

–500

–300

–100

100

300

500

700

800

600

400

200

SEA LEVEL

–200

–400

–600

–500

–300

–100

100

300

500

700

VERTICAL EXAGGERATION × 10

FEET

WEST

A FEET

EAST

A'

2,000 4,000 FEET

0

0

500 1,000 METERS

800

600

400

200

300

500

700

FEET

WEST

B

VERTICAL EXAGGERATION × 10

800

600

400

200

300

500

700

FEET

EAST

B'

2,000 4,000 FEET

0

0

500 1,000 METERS

Figure 6. Generalized geologic sections A–A′ across the valley near collapse area, and B-B′ 6 miles north of collapse 

area at Retsof salt mine, Livingston County, N.Y. (Lines of sections are shown in fig. 4.)
12 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

750 ft of gravel, sand, silt, and clay in the Genesee Valley (Alpha Geoscience, 1996c). These sediments were 

deposited in (1) glaciofluvial environments (where 

meltwaters discharged at the base of the ice when ice 

occupied the valley), (2) glaciolacustrine environments 

(where proglacial lakes occupied the valley in front of 

the retreating ice), and (3) flood-plain environments 

(along the riverbank during recent postglacial time).

Erosion of Bedrock by Ice

Glacial erosion deepened the preglacial Genesee 

Valley by as much as 600 ft and widened it, creating a 

concave, north-south bedrock profile (fig. 7). The 

eroded bedrock surface (Onondaga Limestone) slopes 

southward from Fowlerville at the north end of the valley where it subcrops at an altitude of 400 ft. The deepest part of the bedrock basin (177 ft below sea level) is 

estimated to be in the central part of the valley, near 

Sonyea, 9.5 mi south of Fowlerville. The bedrock surface rises from Sonyea southward and reaches an altitude of about 580 ft at Dansville.

The erosion-resistant Onondaga Limestone limited the depth to which ice could scour, and thus, controlled to a large extent the resulting bedrock-surface 

configuration in the valley. Ice in the northern part of 

the valley, where depth to the Onondaga Limestone 

was relatively shallow (150-500 ft below land surface), 

eroded the soft overlying shales but could not erode 

through the entire limestone unit; therefore it slid 

southward atop the limestone to the point at which this 

unit was too deep to reach (750 ft below land surface 

near Sonyea) or to where it encountered harder bedrock 

units to the south, where the Appalachian Plateau 

begins. The ice was deflected upward through a bedrock saddle about 5 miles south of Dansville.

Much of the published literature describes glaciated valleys in central and western New York as being 

U-shaped. Seismic-reflection work by Mullins and others (1991) in the Finger Lakes of New York indicates, 

however, that the major north-south valleys change 

from broad and relatively shallow in the north to Ushaped in the middle, and are narrower and V-shaped in 

the south. The mine collapse area is in the U-shaped 

middle reach of the Genesee Valley (fig 6, section A–

A′). A seismic-refraction survey conducted 6 mi north 

of the collapse area indicated that the bedrock valley 

floor is broad and relatively shallow (fig. 6, section B–

B′), a finding consistent with that of Mullins and others 

(1991). South of Sonyea, the buried bedrock valley 

appears to become V-shaped, but subsurface data are 

insufficient to verify this conclusion.

Glaciation probably removed much of the 

weathered bedrock that had presumably formed at the 

bedrock surface before the the Wisconsinan glaciation. 

Subsequent weathering of the bedrock surface (after 

glaciation) was probably limited because the bedrock 

was protected by thick overlying deposits of glacial 

sediments.

Unconsolidated Deposits

The unconsolidated sediments that partly fill the 

Genesee Valley were deposited during glacial advances 

and retreats and, to a lesser extent, during postglacial 

time. The distribution of surficial deposits in the Genesee Valley from Avon to Dansville is generalized in figure 8. Although the valley was covered by continental 

glaciers several times during Pleistocene time, each 

glaciation removed most evidence of prior glaciations. 

Most of the glacial sediments in the region are probably 

from the late Wisconsinan stage (Muller and others, 

1988), but remnants of older glacial deposits are found 

north of the study area (Young and Sirkin, 1994). 

Subglaciofluvial Sand and Gravel

A layer of coarse sand and gravel overlies the 

bedrock valley floor, as indicated by drillers’ stratigraphic logs, gamma logs from wells drilled by the 

mine owner and by water-well drillers in the Genesee 

Valley. This basal layer is 10 to 40 ft thick in the collapse area and 460 to 500 ft below land surface (fig 6). 

Drillers reported that the clasts were predominantly 

limestone, presumably derived from the underlying 

Onondaga Limestone. All deep wells in the valley that 

extended to, or close to, bedrock penetrated a basal 

coarse-grained deposit, but the permeability of this unit 

varies from place to place. This unit was probably 

deposited by subglacial meltwaters (fig. 9B, unit 5) that 

formed eskers and subglacial outwash fans at the base 

of the ice. Eskers were found in several Finger Lake 

valleys by Mullins and others (1991), who hypothesize 

that major north-south valleys between Lake Ontario 

and the Allegheny Plateau were principal routes of sediment transport by subglacial meltwater. Some of the 

subglacial sediment that was transported southward 

through the Genesee Valley near the base of the ice was 

deposited south of Dansville where it forms the Valley 

Heads Moraine, which plugs the valley (fig. 8).
GEOLOGIC SETTING 13

   

SECTION

B–B'

SECTION

A–A'

Lv 369 Gas well

16108

Gas well

 17445

Lv 442

(projected)

Lv 422 Lv 346 Lv 360 Lv 399 Lv 365 

Fowlerville

moraine

Avon Geneseo

Collapse

area

BEND IN

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

Sonyea

BEND IN

SECTION

Older Silurian shales,

siltstones, and sandstones

Retsof salt bed (B6 salt unit)

Camillus Shale, Syracuse Formation, and Vernon Shale

Bertie Limestone

Onondaga Limestone 

5

4

3

2

1

Unconformity

4

5

EXPLANATION

Unconsolidated deposits—Numbers are geohydrologic  units referenced in text (Geologic Setting) Alluvial-fan and flood-plain deposits

—Silt, sand,

 and gravel Lacustrine sand, silt, and clay Till

—Silt and clay embedded with pebbles

 Deltaic deposits

—Pebbly sand

 Supraglacial debris

—Silty sand and gravel

 Englacial meltout material and  deposits

—Mix of clay, silt, 

 Subglacial meltwater deposits

—

Well and U.S. Geological Surve Dashed where projected. Num were assigned by USGS. Well  appendix 1. Numbers for gas  by New York State Departme Conservation

2

2

1

Lv349

3

200

SEA LEVEL

–800–600–400–200

400600800

FEET

NORTH

C

5 

0

0

5 

VERTICAL SCALE GREATLY EXAGGERATED

Figure 7. Generalized geologic section C–C′ along Genesee valley axis, Livingston County, N.Y. (Line of section is shown 
14 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

   

Conesus

Creek

Conesus

Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga

Creek

Genesee

River

Avon

Dansville

Geneseo

SALT MINE

COLLAPSE

AREA

Mount

Morris

Cuylerville

C

C'

A

A'

B B'

Mt. Morris

Delta

Valley

Heads

Moraine

Fowlerville

Moraine

Sonyea

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 Geology modified by T.S. Miller (1998) from

E.H. Muller and D.H. Cadwell (1986 and 1988)

0 2 4 MILES

0 2 4 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Alluvial deposits—Fans

 consist of sand and gravel.

 Flood-plain deposits con-

 sist of fine sand and silt

Outwash gravel

Fowlerville Moraine—Clayey

 silt matrix with embedded 

 stones

Delta—Pebbly sand and silt

Lacustrine fine sand, silt, 

 and clay

Kame deposits—Silty sand

 and gravel

Till moraine—Clayey, sandy, 

 silt matrix with embedded 

 stones

Till overlying bedrock

Bedrock

Line of geologic section A A'

Figure 8. Surficial geology of Genesee Valley from Avon to Dansville, N.Y. (Location is shown in fig. 1.)
GEOLOGIC SETTING 15











 



.

.

.

.

.

.

. .

.. ..

.

. .

.. .

4

5

4 4 3

5

5

5

Alluvium

1. Preglacial Genesee River valley

Ice

2. Intense bedrock scouring during continental glaciation;

gravel (5) deposited by subglacial meltwater

Floating ice near

terminus

Subglacial lake

3. Discharge of subglacial meltwater sediments and

rainout of debris (4) from melting ice into subglacial lake

Crevasse

filling

Delta

4. Supraglacial material (3) deposited in lake as ice melts;

deltas deposited where upland streams empty into lake

Devonian siltstone, shale,

and thin limestone units

Onondaga Limestone

Retsof (B6) salt layer

Proglacial

lake

6. Readvance of ice deposits over lacustrine deposits

Proglacial

Lake

7. More lacustrine sediments are deposited in late-stage lake

Genesee River

Canaseraga

Creek

8. Postglacial streams deposit alluvial fans and floodplain sediments (1)

5. Fine-grained lacustrine sediments (2) deposited into

proglacial lake

3

2 Till

Subglacial

meltwaters

Older Silurian shales

4 5

3

2

4 5

3

2

4 5

3

2

1

3

4

5

EXPLANATION

Unconsolidated deposits—Numbers are geohydrologic 

 units referenced in text (Geologic Setting)

 Alluvial-fan and flood-plain deposits—Silt, sand,

 and gravel

 Lacustrine sand, silt, and clay

 Till—Silt and clay embedded with pebbles

 Deltaic deposits—Pebbly sand

 Supraglacial debris—Silty sand and gravel

 Englacial meltout material and subaqueous-fan

 deposits—Mix of clay, silt, and sand and gravel

 Subglacial meltwater deposits—Sand and gravel

2

2

1

Figure 9. Glacial-deposition processes in Genesee Valley, Livingston County, N.Y.
16 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Englacial and Glaciolacustrine Sediments

As the ice retreated northward from the Valley 

Heads moraine near Dansville, it formed a temporary 

dam that impounded drainage to form a proglacial lake 

that declined through several stages in the valley 

between the retreating ice and the moraine. The proglacial lakes were sufficiently deep to allow the thinning 

ice front to float. As much as 250 ft of sediment was 

deposited in the proglacial lakes from several sources, 

which included (1) subaqueous fans deposited by subglacial meltwater at the submerged part of the ice front, 

and (2) englacial sediment (referred to as flowtill and 

rainout material) that dropped from floating ice to form 

a poorly sorted deposit of variable thickness (fig. 9C, 

unit 4). Core samples collected by Alpha Geoscience 

(1995a,b,c and 1996a,b) indicate that these sediments 

consist of interbedded coarse sand and gravel, silty 

gravel, till, and lacustrine fine sand, silt and clay. The 

precise geometry of all these sedimentary units is more 

complex than shown in figures 5 and 6.

Supraglacial Sand and Gravel

Water-well drillers’ logs and results of a 1994 

marine-seismic-reflection survey (fig. 6) conducted by 

the USGS in the Genesee River northeast of Mt. Morris 

indicate a relatively thin layer of sand and gravel (typically less than 10-ft-thick but as much as 60-ft-thick) 

that overlies the englacial and glaciolacustrine sediments in many places. The extent of this deposit is 

uncertain, but several domestic wells in the Fowlerville 

Moraine area tapped similar sand and gravel zones 

before they went dry after the collapse. These wells 

were subsequently deepened to tap the lower aquifer. 

The seismic-reflection record south of the collapse 

contains strong reflectors that clearly delineate an 

undulating surface across most of the valley; this surface is assumed to correspond to the sand-and-gravel 

layer that lies 250 to 310 ft below land surface near the 

collapse area. This layer probably consists of (1) 

supraglacial sediments deposited by meltwater, (2) 

upland inwash that settled in the proglacial lake during 

the recession of the ice margin, and (3) material derived 

from coarse-grained subaqueous fans (fig. 9D, unit 3). 

Glaciolacustrine and Deltaic Sediments and Till

A series of proglacial lakes formed in the Genesee Valley in front (south) of the receding glacier margin. The lake levels were controlled by natural 

spillways at topographic lows on the watershed perimeter. A detailed account of the various lake levels and 

spillways is given in Muller and others (1988). The oldest and highest spillway was across the Valley Heads 

Moraine, south of Dansville (fig. 8); several successively lower spillways to the north, between 1,400 and 

900 feet, were exposed as the ice margin retreated 

northward. Lake levels probably dropped abruptly as 

each successive spillway was exposed. As much as 250 

ft of fine-grained sediment from the receding ice margin and upland streams (fig. 9E, unit 2) was deposited 

above the supraglacial sediments in the middle and 

southern parts of the valley, and deltas were deposited 

along the edges of the valley where upland streams 

flowed into the lakes. The largest delta in the valley 

(locally known as the Mt. Morris Delta) was deposited 

near Mt. Morris (fig. 8), where the Genesee River 

flowed from the Letchworth Gorge into the GeneseeCanaserga valley. The Mt. Morris Delta consists mostly 

of silt, sand, and pebbly sand. Other deltas are either 

buried by flood-plain sediment or are small and above 

the present water table and, therefore, are not shown in 

figure 8.

Drillers’ logs and seismic-reflection surveys 

indicate an apparent till layer within the glaciolacustrine sediments (fig. 6A). The presence of till suggests 

that the ice readvanced southward into the lake after it 

had retreated to the northern part of the valley, and 

overrode the glaciolacustrine sediments (fig. 9F). The 

till layer consists of compacted and reworked lacustrine sediments with some stones embedded in a finegrained matrix. The hydraulic properties of the till are 

similar to those of the lacustrine sediments, and the till 

is considered part of the lacustrine deposit (unit 2) in 

this report. The subsequent northward retreat of the ice 

left the till submerged in the proglacial lake, and additional lacustrine sediments were deposited on top of the 

till. Several drill logs indicate a 5- to 15-ft-thick sandand-gravel layer beneath the till in some locations. 

These small, discontinuous sand-and-gravel layers 

could have been deposited by subglacial meltwater at 

the readvancing ice margin before deposition of the till. 

The Fowlerville Moraine (figs. 7 and 8) was 

deposited during the final and lowest proglacial lake 

stage and fills the valley in the northern part of the 

study area. A lake formed in the 27-mi reach between 

this moraine and the Valley Heads Moraine near Dansville to the south (Young, 1975), and glaciolacustrine 

sediments were deposited over the till layer described 

above (fig. 9G). The glaciolacustrine sediments above 

the till are finer grained and better sorted than those 
HYDROLOGIC SETTING 17

below the till and consist mostly of rhythmically bedded silt and clay, whereas the glaciolacustrine sediments below the till consist of fine sand, silt, and clay, 

and contain some ice-rafted sand and gravel and dropstones that probably dropped into the lake when the ice 

melted. The glaciolacustrine and till deposits are 200 to 

250 ft thick and extend to depths of 250 to 310 ft below 

land surface. The most recent proglacial lake drained as 

the outlet stream gradually eroded a spillway through 

the Fowlerville Moraine.

Alluvial Sediments

The upper 20 to 60 ft of the valley-fill sediments 

are Holocene deposits (fig. 9H, unit 1) that consist of 

mixed coarse- and fine-grained sediments deposited by 

the Genesee River, Canaseraga Creek, and small 

upland tributaries that flow into the valley. The coarse 

fraction of the alluvial sediment consists of sand and 

gravel deposited as fans and within stream channels; 

the fine-grained fraction includes fine sand, silt, and 

clay laid down as point bar and overbank deposits during floods, which were frequent in the Genesee Valley 

until the Mt. Morris Dam was completed in 1954.

HYDROLOGIC SETTING

The shallow unconsolidated deposits in the Genesee Valley are recharged by precipitation on the valley 

floor and by runoff from upland areas. Prior to the mine 

collapse, ground water discharged to streams or flowed 

northward. The salinity of ground water generally 

increases with depth in the valley, and the low tritium 

concentrations indicate that most of the water in the 

two confined aquifers is more than 45 years old.

Aquifers and Confining Units

The glacial aquifer system in the Genesee Valley 

is underlain and bounded laterally by bedrock and consists of three aquifers separated by two confining layers. The degree of hydraulic connection among these 

three aquifers in areas along the edges of the valley, 

where the confining layers are thin or absent, is 

unknown because the stratigraphy of glacial sediments 

in the Genesee Valley is complex. (The general conceptualization of aquifer geometry presented in this section may not conform to actual aquifer conditions at all 

locations.) The underlying carbonate bedrock contains 

water-bearing zones that are bounded on the north by 

the Onondaga escarpment, where the outcrop ends (fig. 

1), and extend southward (downdip) beyond the end of 

the valley, as well as eastward and westward (crossstrike).

Upper Aquifer

The unconfined (upper) aquifer consists of sandand-gravel layers within the 20-to-60-ft thick Holocene 

alluvial sediments at land surface (fig. 10). The bottom 

of the upper aquifer conforms to the nearly flat-lying 

lacustrine sediments (upper confining layer) below. 

Several domestic wells are screened in the upper aquifer.

Upper Confining Layer and Deltaic Deposits

The upper confining layer separates the upper 

aquifer from the middle aquifer (fig. 10) and consists of 

glaciolacustrine sediment and till. It is about 250 ft 

thick along the axis of the valley and could be locally 

absent or coarse-grained near the valley walls. The 

hydraulic conductivity of the lacustrine sediment, calculated from the geometric mean of 11 permeameter 

test samples, is about 9 x 10-5 ft/d (Alpha Geoscience, 

1996c). 

The confining layer is assumed to be bounded 

laterally by permeable deposits of coarse materials that 

in some places mantle the sides of the bedrock valley, 

and provide vertical hydraulic connections between the 

upper aquifer and the middle aquifer. For example, a 

wedge-shaped deltaic deposit of mostly sand mantles 

the west valley wall near Mt. Morris and slopes eastward to the center of the valley (figs. 6, 8 and 10). Several domestic and commercial wells along the valley 

wall are screened in presumed deltaic or ice-marginal 

deposits and have yields ranging from 20 to 400 gal/

min. A kame deposit mapped at land surface near Sonyea (fig. 8) also might extend to the top of the middle 

aquifer, but no stratigraphic logs are available to support this hypothesis.

Middle Aquifer

The middle aquifer underlies the upper confining 

layer and consists of sand and gravel, typically less 

than 10 ft thick, that was deposited in a proglacial lake. 

The upper surface is undulating as a result of the varied 

depositional processes that formed this aquifer. Several 

domestic wells are screened in this aquifer beneath the 

Fowlerville Moraine; a well screened in this aquifer 

near Sonyea (Lv366), where it is 60 ft thick and has a 
18 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

hydraulic conductivity of 80 ft/d, yielded 300 gal/min 

(Alpha Geoscience, 1996c). 

Lower Confining Layer

A lower confining layer of fine-grained sediments as much as 250 ft thick separates the middle 

aquifer from the lower aquifer (fig. 10). The lower confining layer consists of glaciolacustrine sediment and 

till with lenses of coarse materials that were deposited 

in a proglacial lake from the floating ice margin. The 

hydraulic conductivity of fine-grained sediments in the 

lower confining layer, as calculated from the geometric 

mean of four permeameter test samples, was 3 x 10-4

ft/d (Alpha Geoscience, 1996c). Kame deposits, if 

present, would provide hydraulic connections between 

the middle and lower aquifers, but no stratigraphic logs 

are available to confirm their presence.

Lower Aquifer

The lower aquifer overlies the bedrock valley 

floor and consists of glaciofluvial sand and gravel about 

25 ft thick that was deposited in tunnels beneath the ice 

and on fans where subglacial streams flowed into the 

proglacial lake at the ice front. Two industrial wells and 

several domestic wells are screened in the lower aquifer; their yields range from 20 to 500 gal/min. Industrial 

well Lv91 in Mt. Morris (fig. 11) yields 500 gal/min 

resulting in a drawdown of about 15 ft. Aquifer transmissivity at this location is about 10,000 ft2

/d as estimated from the specific capacity of 33 (gal/min)/ft, 

calculated from a relation given in Todd (1980, eq. 

4.70). This transmissivity value corresponds to a 

hydraulic conductivity of 500 ft/d. Well Lv46, which 

was drilled 2 mi north of Dansville (fig. 11), yielded 

about 3,000 gal/min from this aquifer under flowing 

artesian conditions.

Fractures at the bedrock surface where the aquifer overlies the Onondaga Limestone increase the 

effective thickness of the lower aquifer and increase 

ground-water flow through it. Well Lv346, 900 ft west 

of the collapse, is finished from 7 to 17 ft below the 

Onondaga surface and yielded 100 gal/min during a 

pumping test in November 1994, from which the 

hydraulic conductivity was estimated to be 75 ft/d 

(Alpha Geoscience, 1996c). If the Onondaga LimeDevonian shale

with thin limestone

units

Onondaga Limestone

SECTION

C–C'

Recharge from precipitation

Runoff from

upland areas

Runoff from

upland areas

Leakage through

Discharge to river fractured bedrock surface

Leakage through

fractured bedrock surface

EXPLANATION

Upper aquifer

Upper confining layer

Middle aquifer

Lower confining layer

Lower aquifer

Deltaic deposits

Till

Direction of water flow

Water table

800

600

400

200

SEA LEVEL

100

300

500

700

800

600

400

200

SEA LEVEL

100

300

500

700

VERTICAL EXAGGERATION × 10

FEET

WEST

A FEET

EAST

A'

2,000 4,000 FEET

0

0

500 1,000 METERS

Figure 10. Aquifers and confining layers along geologic section A–A′ in Genesee Valley, Livingston 

County, N.Y. (Line of section is shown in fig. 8.)
HYDROLOGIC SETTING 19

stone at this location is highly fractured from the collapse, this value is higher than in in other areas. 

Fractures in the shales that form the valley walls could 

provide hydraulic connections between the lower aquifer and bedrock aquifers in uplands that border the 

Genesee Valley (fig. 10).

Bedrock Aquifers

Several water-bearing zones in the bedrock 

underlying the Genesee Valley were identified through 

borehole geophysical surveys (Williams, 1996). Borehole geophysical logs indicate that most of these zones 

are nearly horizontal bedding planes at stratigraphic 

contacts. The principal water-bearing zone that subcrops within the Genesee Valley is a fracture zone near 

the contact between the Onondaga and Bertie Limestones, previously identified as the source of leakage 

into a shaft drilled to the Sterling salt mine (Langill and 

Associates, 1981).

Few wells are finished in bedrock beneath the 

Genesee Valley because the water quality is generally 

poor, except in subcrop areas near the Onondaga 

Escarpment, where recent fresh recharge enters the 

bedrock. Well yields outside the Genesee Valley range 

from 10 to 160 gal/min in subcrop areas but are generally less than 10 gal/min in areas south of the subcrop, 

where the weight of overlying sediments compresses 

the fracture apertures. Leakage from the Onondaga/

Bertie contact to the Sterling shaft has increased 

steadily since the 1930’s and was estimated to be 300 

gal/min in 1986. This increase indicates that fracture 

apertures near the shaft have probably been widened by 

dissolution and are, therefore, not representative of 

fractures in other areas (Acres International, 1986).

Ground-Water Flow Patterns Before the 

Collapse

Ground water within the valley originates as precipitation on the valley floor and the surrounding 

uplands, and discharges to the Genesee River and 

Canaseraga Creek and their tributaries, or as underflow 

to downgradient areas. It generally flowed northward 

through the aquifer system prior to the mine collapse. 

Upper Aquifer

Most of the ground-water levels recorded prior 

to the roof collapse in the Retsof mine were measured 

in wells screened in the upper aquifer (Kammerer and 

Hobba, 1967). These measurements, together with 

mapped elevations of springs and perennial streams, 

were used to construct a map showing the altitude of 

the water table prior to the collapse (fig. 11). This map 

is assumed to be representative of undisturbed, steadystate conditions with no change in ground-water storage, because no large withdrawals that could cause 

water-level fluctuations were being made prior to the 

collapse.

Water in the upper aquifer generally flows northward and to major streams in the valley. Recharge is 

derived from precipitation over the valley floor and 

runoff from the surrounding uplands (fig. 10), it also 

enters as lateral underflow from the surrounding bedrock uplands. The rate of recharge is largest in the 

north, where the aquifer is bounded by Onondaga 

Limestone, because fracture zones in the limestone 

probably transmit more water than fracture zones in the 

shales that border the rest of the valley. Recharge also 

enters the upper aquifer as upland runoff (Morrissey 

and others, 1988), which is potentially significant 

everywhere in the valley. Most of the water in the upper 

aquifer discharges to the Genesee River and Canaseraga Creek, although some discharges northward as 

underflow.

Middle and Lower Aquifers

Recharge enters the two confined aquifers 

through the Valley Heads moraine south of Dansville 

and along the sides of the valley in some areas (fig. 10). 

The rate of recharge along the sides of the valley is 

probably largest where locally permeable deposits, 

such as the Mt. Morris delta, provide a hydraulic connection with the upper aquifer. Water flowing through 

the confined aquifer in the Beards Creek Valley, west of 

Mt. Morris, also discharges to the middle aquifer. 

Ground water discharges from the confined aquifers 

primarily as underflow to the area north of the study 

area and possibly to the upper aquifer along the edges 

of the valley in some areas.

The hydraulic-head distribution in the confined 

aquifers under precollapse conditions was probably 

similar to that in the upper aquifer, but the heads in the 

confined aquifers beneath the valley floor were probably higher than the water table. This interpretation is 

supported by drillers’ logs that note confined conditions at several locations in the lower aquifer (see 

fig. 11), including well Lv46 near Dansville , well 

Lv421 at an industrial facility near Cuylerville (H&A 

of New York Consulting Engineers, 1988), and well 
20 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

   

Conesus

Creek

Conesus

Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga

Creek

Genesee

River

Avon

Dansville

Geneseo

SALT MINE

COLLAPSE

AREA

Mount

Morris

Cuylerville

Lv 421

Lv 397

Lv 526

Lv 91

Lv 46

Sonyea

520

545

545

560

580

600

545

580

600

560

700

600

580

560

560

580

600

600

580

600

610

620

660 700710

720 760

800

.

.

.

.

. .

. .

.

. .

.

.

.

. ... .

.

. . . .

.

. . . .

.. . .

.

.

.

. .

.

. . . . . .. . . . . . . . . .

.

. .

.

. .

.

. .

.

.

.

. .

.

.

.

. .

.

.

.

. .

. .

.

.

.

.

. . .

.

. .

..

.

.

.

. .

.

.

.

.

.

.

.

.

.

. . .

.

. .

.

.

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 0 2 4 MILES

0 2 4 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Model area (Genesee Valley)

Water-table contour—Shows

 altitude of water table before

 mine collapse. Contour 

 interval, in feet, is variable.

 Datum is sea level

Well in monitoring network

Well in U.S. Geological 

 Survey database

.

.

580

Figure 11. Water-table altitude in upper aquifer prior to mine collapse in March 1994, and locations of wells for which 

water-level meaurements are available. (Location is shown in fig. 1.)
HYDROLOGIC SETTING 21

Lv397 near the Geneseo airport (Dunn Geoscience 

Corporation, 1992). Heads at other wells screened in 

the lower aquifer, including well Lv526 near the collapse area and well Lv91 in Mt. Morris, were within a 

few feet of land surface before the collapse.

Bedrock Aquifers

Little information is available on ground-water 

flow in the bedrock underlying the valley. La Sala 

(1968) suggested that circulation of deep ground water 

flowing northward from the Appalachian uplands to the 

Erie-Ontario lowlands brought highly mineralized 

water into shallow aquifers in Erie County, west of Livingston County (fig. 1). The similarity of the bedrock 

stratigraphy and topographic setting in Livingston 

County to that in Erie County suggests northward flow 

in this area as well, but the rate of flow is unknown. 

Water in fracture zones near the Onondaga/Bertie 

Limestone contact probably discharges upward into the 

lower aquifer near the Bertie Limestone subcrop in the 

Genesee Valley north of the Fowlerville Moraine (fig. 

4); water in these fracture zones also discharges to 

springs along the Onondaga escarpment east and west 

of the Genesee Valley. The Onondaga/Bertie contact 

along the escarpment is higher than the water table in 

the Genesee Valley and ground water in this area probably flows laterally (eastward or westward) to the Genesee Valley, rather than to the escarpment through the 

fracture zone.

Ground-Water Quality

The middle and lower aquifers in the Genesee 

Valley differ in chemical composition of ground water. 

Water in the middle aquifer is relatively fresh and has a 

low specific conductance (430 to 1,390 μS/cm, table 1). 

The principal chemical constituents are calcium and 

bicarbonate, which probably result from dissolution of 

calcite in glacial sediments derived from the underlying carbonate bedrock (fig. 12). The relatively high 

concentrations of sodium and potassium at some wells 

could reflect the exchange of calcium for sodium and 

potassium on the surface of clay particles through ion 

exchange.

Water in the lower aquifer generally is more 

saline than water in the middle aquifer—specific conductance values during 1995-96 ranged from 1,450 to 

39,300 μS/cm, except near well Lv367 at location V 

near Sonyea (fig. 13), where it was 460 μS/cm (table 

1). Water from this well was a calcium-bicarbonate 

type, similar to that in the middle aquifer (fig. 12). 

Water from other wells screened in the lower aquifer 

was a calcium/sodium-chloride type that probably 

reflects mixing with water from water-bearing zones in 

the underlying bedrock. Williams (1996) measured 

specific conductance values of 1,000 to 2,500 μS/cm in 

the lower aquifer during borehole conductance logging 

of five wells drilled near the collapse.

Fracture zones in the Onondaga and Bertie 

Limestones generally contain saline water with high 

specific conductance (72,000 to 106,200 μS/cm) (table 

1). Williams (1996) measured specific conductance 

Lv397

Lv367

Lv346

0

20

40

60

80

100 0

20

40

60

80

20

40

60

80

100

100

80

60

40

20

0

CALCIUM

MAGNESIUM

SODIUM + POTASSIUM

PERCENT

100

80

60

40

20

20

0

0

20

40

60

80

100

100

80

60

40

20

0

0 0

100

40

60

80

20

40

60

80

100

80

60

40

20

Bass

Islands

carbonate

brine SULFATE + CHLORIDE

CALCIUM + MAGNESIUM

CARBONATE + BICARBONATE

SULFATE

CHLORIDE

PERCENT

PERCENT

EXPLANATION

Observation well screened in:

 Middle aquifer

 Lower aquifer 

 Onondaga–Bertie Limestones

Specific conductance—Circle diameter

 indicates log of specific conductance

 Middle aquifer

 Lower aquifer 

 Onondaga–Bertie Limestones

.

.

.

1 5

microsiemens per

centimeter

Figure 12. Percentage of major cations and anions in 

water from confined aquifers and Onondaga-Bertie 

Limestones in Genesee Valley, Livingston County, N.Y.
22 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

values of 10,000 to 50,000 μS/cm in these zones during 

borehole conductance logging of a well drilled near the 

collapse. The saline water is a calcium/sodium-chloride type (fig. 12) that is chemically similar to brines 

from oil-bearing zones in the Bass Island carbonates in 

western New York (New York State Department of 

Environmental Conservation (NYSDEC), 1992). The 

Bass Island carbonates, which are stratigraphically 

equivalent to the Rondout Formation (Rickard, 1969), 

overlie the Bertie Limestone in the southern part of the 

Genesee watershed but have been eroded within the 

study area. The lowest specific conductance value 

obtained from bedrock wells (3,040 μS/cm) was in a 

sample from well Lv346, screened in the upper part of 

the Onondaga Limestone at location II near the collapse (fig. 13). The water in this well probably originated from the overlying lower aquifer and, therefore, 

is not representative of other water-bearing zones in the 

bedrock.

Salinity

The ratio of chloride to bromide concentrations 

in saline water from the Onondaga and Bertie Limestones (120 to 180) is close to the average ratio of 110 

reported for brines from oil-bearing zones in the Bass 

Island carbonates in western New York (NYSDEC, 

1992). Samples from three of the wells screened in the 

lower aquifer (Lv370, Lv350 and Lv360) had chlorideto-bromide ratios of about 100, which indicates mixing 

with water from the Onondaga and Bertie Limestones. 

Water from well Lv370 at location I, near the subcrop 

of the Bertie Limestone near Avon, had the highest specific conductance (12,400 μS/cm) of these three wells 

(fig. 13). Water from Lv203, also screened in the lower 

aquifer near the Bertie subcrop, had a specific conductance of 12,100 μS/cm in 1966 (Kammerer and Hobba, 

1967). The highest specific conductance measured in 

the lower aquifer (39,300 μS/cm) was in a sample from 

well Lv397, which had a chloride-to-bromide ratio of 

Table 1. Concentrations of inorganic constituents of water from confined aquifers in the Genesee Valley, Livingston 

County, N.Y.

[Locations are shown in fig. 4. Concentrations are in milligrams per liter except as noted. μS/cm, microsiemens per centimeter at 25 ̊C. 

Ca, calcium; Mg, magnesium; Na, sodium; K, potassium; SO4, sulfate; Cl, chloride; Br, bromide; CaCO3, calcium carbonate; <, less than.] 

Location

Well 

number

Sampling 

date

Constituent or physical property

Ca Mg Na K

Alkalinity, 

as 

CaCO3 SO4 Cl Br

Specific 

conductance 

(μS/cm)

Middle aquifer:

I Lv371 11/95 180 66 58 36 370 150 140 < 1 1390

III Lv351 11/95 22 8.6 97 8.7 150 11 130 1.7 700

IV Lv361 10/95 44 29 61 4 240 8 100 1.6 790

IV Lv362 8/96 15 6.8 74 110 260 8.2 67 < 1 870

V Lv366 11/95 16 8.8 64 2 190 6.2 23 < 1 430

Lower aquifer:

I Lv370 8/96 450 230 1,400 67 86 182 4300 44 12,400

II Lv368 8/96 180 44 280 140 460 < 14 840 2.2 2980

III Lv350 10/95 530 220 880 27 430 19 2100 22 6670

IV Lv360 11/95 62 34 150 7.2 320 7.7 300 2.8 1450

V Lv367 8/96 19 18 45 7.9 240 13 24 < 1 460

— Lv397 10/95 1000 30 8,100 64 460 120 14,300 32 39,300

Onondaga and Bertie Limestone

I Lv369 11/95 4600 1500 10,600 360 440 2100 29,400 230a

a

Sampled 8/96

72,200

II Lv346 10/95 150 71 310 13 410 7.3 750 7.6 3040

III Lv349 8/96 6800 2100 16,000 780 270 320 47,000 260 106,200

V Lv365 8/96 3900 1600 11,000 450 240 49 32,500 260 72,000
HYDROLOGIC SETTING 23

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

   

Conesus

Creek

Conesus

Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga

Creek

Genesee

River

. .

.

. .

.

.

.

. .

.

.

.

.

Lv 203

--:12,100

LOCATION I

Lv 370

98:12,400

Lv 397

445:39,300

LOCATION II

Lv 368

382:2,980

Lv 346

99:3,040

LOCATION III

Lv 350

95:6,670

LOCATION IV

Lv 360

107:1,450

LOCATION V

Lv 367

--:460

Area shown

in figure 15

Area shown

in figures 17 and 44

Area shown

in figures 19 and 36

Avon

Dansville

Geneseo

SALT MINE

COLLAPSE

AREA

Mount

Morris

Cuylerville

Sonyea

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 0 2 4 MILES

0 2 4 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Bedrock geology

 Devonian shales

 Onondaga Limestone

 Bertie Limestone

 Salina Group

Salt well

Well screened in lower 

 aquifer—Number to left is

 chloride-to-bromide ratio; 

 number (bold) on right is

 specific conductance, in

 microsiemens per 

 centimeter. -- indicates

 data not available

.

LOCATION I

Lv 370

98:12,400

.

Figure 13. Locations of water-sampling sites I through V in Genesee Valley, Livingston County, N.Y., with (1) specific 

conductance, and (2) ratios of chloride-to-bromide concentrations, in wells screened in the lower aquifer.
24 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

445. This ratio and that of well Lv368 (382) at location 

II near the collapse is much higher than the ratio in 

water from the Onondaga and Bertie Limestones; this 

suggests that the ground water in this area has mixed 

with water containing dissolved halite, which has a 

chloride-to-bromide ratio of over 1,000 (Whittemore, 

1988; Davis and others, 1998). Halite from the Salina 

salt beds has been mined by solution through several 

wells in the Genesee Valley in the past 100 years (fig. 

13), and leakage from mining operations or brine disposal could have contaminated the lower aquifer in 

some areas. Improperly abandoned gas wells that penetrate the Salina salt beds could also allow upward 

leakage of saline water into the lower aquifer.

Isotopic Composition

Waters from the two confined aquifers have similar isotopic compositions of hydrogen (δD) and oxygen (δ18O) (table 2), and most samples plot along the 

global meteoric water line (GMWL) with a mean isotopic values of -75 ‰ δD and -10.8 ‰ δ18O (fig. 14A). 

These values are near the mean composition for samples from a shallow dolomite aquifer in Niagara Falls 

(fig. 1) (-75 ‰ δD and -10.4 ‰ δ18O; Yager and Kappel, 1998) and, therefore, reflect the average values for 

recharge in western New York. Water samples from the 

Genesee River in January 1996 also plot near the 

GMWL, but the isotopic values are more negative 

(depleted) than those from the confined aquifers 

because are lower in winter than in summer. The δD 

and δ18O values of samples from two wells screened in 

the middle and lower aquifers at location III, 1.2 mi 

southeast of the collapse (Lv350 and Lv351), are more 

depleted than in other wells in the valley; this suggests 

poor hydraulic connection with other parts of the confined-aquifer system; the depletion also suggests that 

recharge in this area occurred at lower temperatures 

than in other parts of the confined-aquifer system, but 

the reason is unknown.

The low tritium concentration in 9 of the 15 samples from the confined aquifers (less than 3 pCi/L, fig. 

14B), indicates that most of the recharge entered the 

system before atmospheric testing of nuclear weapons 

began in 1953 (Michel, 1989). The slightly elevated tritium concentration in 5 of the 6 remaining samples (3 

to 11 pCi/L) suggests either that (1) recharge in these 

areas entered the confined aquifer after atmospheric 

testing of nuclear weapons began in 1953 but before 

peak tritium concentrations were recorded in 1962 

(Michel, 1989), or (2) post-1962 recharge, which had 

an elevated tritium concentration, has mixed with older 

water to yield the observed intermediate concentration. 

The sample with the highest tritium concentration (67 

pCi/L) is from the middle aquifer at location I, near 

Avon (Lv371); this indicates that the most recent 

recharge entered this shallow part of the confined-aquifer system after 1962.

Natural Gas

Natural gas is commonly encountered during 

drilling in confined aquifers in the Genesee Valley 

(Ronald Hall, Dansville Water Wells, oral commun., 

1996). Methane and hydrogen sulfide were reported 

during the sampling of several wells screened in confined aquifers in 1966 (Kammerer and Hobba, 1967). 

Gas from four wells sampled in 1994 had a δ13C value 

of -55.1‰ and methane-to-ethane ratios of 54 to 135 

(John C. Fountain, Geology Department, State University of New York, Buffalo, written commun., 1995). 

The relatively light isotopic composition of carbon in 

Table 2. Concentrations of stable isotopes and tritium in

water from confined aquifers in the Genesee Valley,

Livingston County, N.Y.

(‰, per mil; pCi/L, picocuries per liter; —, unnamed location. 

Locations are shown in fig. 4)

Location

Well 

number

Constituent

δD (‰) δ18O (‰)

Tritium

(pCi/L)

Middle aquifer:

I Lv371 -71.1 -10.24 66.9

II Lv348 -74.4 -10.75 1.3

III Lv351 -104.8 -14.76 10.6

IV Lv361 -73.8 -10.82 1.3

IV Lv362 -75.1 -10.85 1.3

V Lv366 -78.6 -11.31 .3

Lower aquifer:

I Lv370 -71 -10.26 7

II Lv368 -76.6 -11.07 -1.3

III Lv350 -102 -14.41 10.9

IV Lv360 -73.8 -10.8 6.4

V Lv367 -76 -11.07 1.9

— Lv397 -74.5 -11.2 1.6

Onondaga and Bertie Limestones

I Lv369 -76.9 -11.11 -0.3

II Lv346 -73.8 -10.52 6.7

III Lv349 -79.7 -10.98 2.6
EFFECTS OF MINE COLLAPSE AND FLOODING 25

the methane (δ13C), and the low ethane content of gas 

from wells screened in the confined aquifers, indicate 

that the gas is produced by microbial decomposition of 

organic matter. In contrast, gas produced from thermal 

decompostion of organic matter in western New York 

typically has δ13C values of -32 to -40.9‰, a methaneto-ethane ratio less than 20, and average methane and 

ethane contents of 85 percent and 7 percent, respectively (John C. Fountain, written commun., 1995; Mark 

Pearce, Gypsum Energy, written commun., 1995). The 

gas produced by microbial decomposition probably 

enters the ground water through diffusion from the 

Devonian shale bedrock that borders the confinedaquifer system.

EFFECTS OF MINE COLLAPSE AND 

FLOODING

The collapse within the salt mine affected hydrogeologic conditions not only in the sedimentary bedrock units overlying the mine (including the mined salt 

unit), but in the overlying glacial deposits. The collapses propagated upward through 600 ft of bedrock 

and 530 ft of unconsolidated sediments to land surface. 

Ground water began to flow into the mine from above 

after the collapses, and the fall of rock eventually 

caused a vertical zone or “chimney” of rock rubble to 

form within the overlying bedrock and glacial aquifer 

system. This rubble zone provided a major vertical 

pathway for ground-water flow from overlying waterbearing units.

The collapse and mine flooding resulted in 15 to 

70 ft of land subsidence over the two mining panels and 

as much as 15 ft of subsidence over other parts of the 

mined area. Water levels in the lower aquifer had 

declined as much as 400 ft by January 1996, by which 

time the mine was completely flooded. Water-level 

declines of 50 ft and 135 ft were recorded at wells 7 mi 

north of the collapse area and 8 mi south of it, respectively, and over a dozen domestic wells screened in the 

middle aquifer in the collapse area went dry.

The decline in water levels decreased the pressure in the aquifers, causing (1) compression of finegrained sediment in confining layers, which in turn 

resulted in land subsidence of 0.8 ft 2,900 ft south of 

the collapse and as much as 0.3 ft in Mt. Morris, 3 mi 

south of it, (2) exsolution of natural gas from ground 

water (three or four water wells began to produce gas), 

and (3) a reversal in the direction of ground-water flow. 

This southward reversal is probably the reason for the 

apparent intrusion of saline water into the lower aquifer 

at the north end of the Genesee Valley.

Collapse of Mine Ceiling

The salt bed that was mined at Retsof is 13 to 30 

ft thick and slopes from an altitude of about 280 ft 

below sea level in the northern part of the mine to 560 

ft below sea level in the southern part. Salt was mined 

Lv351

Lv350

Deuterium Genesee Valley

aquifer system

mean: -10.8, -75

Location III

Global meteoric water line

Genesee

River

Tritium

Lv350 Lv351

Lv371

Pre-1953

waters

Tritium concentration in 1953

Genesee

River

–15.0 –14.0 –13.0 –12.0 –11.0 –10.0

–70

–110

–105

–100

–95

–90

–85

–80

–75

A. Relation between deuterium and oxygen-18.

B. Relation between tritium and oxygen-18.

δ 18OV-SMOW , per mil

δ 18OV-SMOW , per mil

–15.0 –14.0 –13.0 –12.0 –11.0 –10.0 –10

70

0

10

20

30

40

50

60

TRITIUM CONCENTRATION,

IN PICOCURIES PER LITER δDV-SMOW , in per mil

EXPLANATION

Middle aquifer

Lower aquifer

Onondaga/Bertie limestone

Genesee River

Figure 14. Concentrations of stable isotopes and tritium 

in confined aquifers in Genesee Valley, Livingston 

County, 1995-96: A. δD in relation to δ18O. B. Tritium in 

relation to δ18O.
26 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

at a depth of about 1,100 ft below land surface (altitude 

of 540 ft below sea level) in the collapse area. Most of 

the salt from the mine was extracted by a “room-andpillar” technique that leaves large pillars (at least 75 ft 

by 75 ft) spaced about 65 ft apart (fig. 15). A different 

mining method—a “yielding pillar” technique—was 

used after 1990 in the southern part of the mine to control rockfalls and floor buckles (John T. Boyd Company, 1995; Denk and others, 1994). The yieldingpillar technique allowed excavation of large mining 

panels as much as 1,000 ft long, consisting of 40-ftwide rooms separated by many small pillars (20 ft by 

20 ft) that are designed to deform readily and transfer 

the roof load onto the walls and into the overlying rock. 

Both collapses occurred in yielding-pillar areas, but 

whether this technique contributed to the ceiling collapse, or whether the collapse resulted from structural 

weakness in the overlying bedrock, is uncertain. 

Reports that discuss possible causes for the collapses 

are summarized in NYSDEC(1997).

408

63

39

39

36

36

390

20A

20A 

0 2 4 MILES

0 2 4 KILOMETERS

Geneseo

Mount

Morris

SALT MINE

MAP AREA

0 1 2 KILOMETERS

0 1 2 MILES

42°47'16"

46'52"

46'18"

77°53'29" 52'30" 51'35" 50'37" 49'42"

Collapse

Sterling Mine

Retsof Mine

April 1994

June 1994

Panel Room

11-Yard West

Panel Room

2-Yard South

EXPLANATION

Room and pillar mining

Yielding pillar mining

Approximate limit of

 flooding

Figure 15. Locations of rooms and pillars in Retsof salt mine, Livingston County, N.Y., and extent of flooding in April 

and June 1994. (Location is shown in fig. 13.)
EFFECTS OF MINE COLLAPSE AND FLOODING 27

On March 12, 1994, the ceiling collapse in a 

panel containing yielding pillars (2-Yard South, fig. 15) 

caused a seismic event (magnitude 3.6) that was 

recorded by several siesmograph stations (NYSDEC, 

1997). The resultant fracturing of shale overlying these 

panels formed a vertical rubble zone that propagated 

upward to the Bertie and Onondaga Limestones and 

allowed water from water-bearing zones to drain into 

the mine (fig. 16). The leaking ground water was 

undersaturated with respect to halite and caused rapid 

dissolution of salt, further weakening the pillars that 

supported the mine ceiling. The weight of the glacial 

sediments overlying the carbonate rocks caused the latter to collapse, allowing water from the lower aquifer 

to flow down through the rubble zone and into the 

mine. Subsequent seismic surveys indicated that the 

bedrock surface over part of the collapsed area subsided about 45 ft (Dobecki Earth Sciences, Inc., 1994). 

The upward propagation of subsidence through the glacial sediments caused a sinkhole to form at land surface 

on April 6, 1994 over panel 2-Yard South (fig. 3). The 

rate of ground-water flow into the mine increased 

abruptly after a second seismic event on April 8, 1994 

(NYSDEC, 1997). The appearance of a second sinkhole over panel 11-Yard West on May 25, 1994, several 

weeks after the initial collapse, indicated that additional collapses had occurred either within the second 

panel or within cavities in the overlying shale bedrock.

 





Devonian shale

with thin limestone units

Onondaga Limestone

Bertie Limestone

Camillus Shale

Syracuse Formation

Vernon Shale

Vernon Shale

Retsof salt mine

Unconformity

Channels of the Genesee River

Rubble zone

Subsidence zone

Recharge from precipitation

Runoff from

upland areas

Runoff from

upland areas

Leakage through

Discharge to river fractured bedrock surface

Leakage through

fractured bedrock surface

Discharge

to mine

Sinkhole

EXPLANATION

Upper aquifer

Upper confining layer

Middle aquifer

Lower confining layer

Lower aquifer

Deltaic deposits

Till

Direction of water flow

Water table

800

600

400

200

SEA LEVEL

–200

–400

–600

–500

–300

–100

100

300

500

700

800

600

400

200

SEA LEVEL

–200

–400

–600

–500

–300

–100

100

300

500

700

VERTICAL EXAGGERATION × 10

FEET

WEST

A FEET

EAST

A'

2,000 4,000 FEET

0

0

500 1,000 METERS

Figure 16. Stratigraphic section A–A’ depicting rubble zones over collapsed rooms in Retsof salt 

mine, Livingston County, N.Y. (Line of section is shown in fig. 8.)
28 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

In an attempt to save the mine, over thirty wells 

were drilled in April 1994 to either pump water from 

the mine or to inject grout into panel 11-Yard West to 

strengthen the weakened mine pillars. The pumping 

efforts were discontinued by the end of April 1994, 

however, after the rate of flooding exceeded the pumping capability, and attempts to prevent leakage of 

ground water to the mine by injecting grout into the 

rubble zone were unsuccessful and were abandoned 

after the second sinkhole appeared over panel 11-Yard 

West on May 25.

Rates of flow into the mine were estimated to be 

5,500 gal/min on March 14, 1994 and 20,000 gal/min 

on April 8, 1994, as calculated from the rate of waterlevel rise within the mine and from estimates of the volume of flooded area (L.D. Milliken, ANSI, written 

commun., 1996). Estimated flow rates remained relatively constant at about 20,000 gal/min over the next 20 

months but became less certain as older parts of the 

mine became flooded. Methane and hydrogen sulfide 

concentrations in the mine increased as the flooding 

progressed; in May 1995, gas was flared (burned) from 

three wells drilled in the collapse area. Mining ceased 

in September 1995, and the mine was completely 

flooded by January 1996. By this time all shafts leading 

to the mine had been sealed, and gas emissions from 

the three flare wells had ceased. Gas seeps in streambeds overlying the mine perimeter were observed during and after flooding of the mine.

Land Subsidence

Land subsidence within the Genesee Valley, 

whether caused directly or indirectly by the mine collapse, extended more than 3 mi north and south from 

the collapse area. Subsidence directly over the mine 

area ranged generally from 1 to 15 ft by February 1996 

(fig. 17), except in the two sinkholes, where it was estimated to be as much as 70 ft (NYSDEC, 1997). Surface 

subsidence of 0.1 to 0.8 ft extended southward beyond 

the mine to Mt. Morris, 3 mi south of the collapse, 

where as much as 0.3 ft of subsidence was measured.

Most of the subsidence over the mine was caused 

by closure of the mine cavity; this process was accelerated by the dissolution of the salt pillars by water that 

flooded the mine. Mining engineers expect the land 

surface above most of the mine to subside 8 to 9 ft over 

the next 100 years, but the future rate of subsidence 

could decrease because the mine is now filled with 

brine that will support part of the weight of overlying 

sediment (van Sambeek, 1994; Shannon and Wilson, 

1995). The subsidence is expected to cause fractures at 

land surface along the margins of the mined area (John 

T. Boyd Company, 1995). These fractures, and the tilting of the land surface in the direction of the mine, have 

damaged a highway bridge and four houses over the 

mined area; continued subsidence could damage other 

structures.

Additional subsidence above and beyond the 

mined area is expected to result from the compression 

of fine-grained sediments in the confining layers within 

the aquifer system (fig. 10). The compression results 

from the drainage of water from the fine-grained sediments as the intergranular stress (effective stress) 

increases in response to the declining water levels (pore 

pressure) in the aquifer system. Effective stress σe is 

defined as

(1)

where σ = geostatic pressure [FL-3] that results from 

the weight of the sediment and water above 

a given depth, and

p = pore pressure [FL-3].

As the pore pressure decreases, the effective 

stress increases, and more of the weight is borne by the 

sediment matrix. Consequently, the pore volume n in 

the sediment decreases in proportion to the increase in 

effective stress ∆σe and the compressibility of the 

material α. The pore-volume decrease ∆n is

. (2)

The reduction in pore volume results in compression of 

the sediment and the expulsion of pore water, and the 

cumulative result of compression of sediments at various depths is subsidence of the land surface. The compressibility of fine-grained sediments is 2 or 3 orders of 

magnitude greater than that of coarse sediments and 

accounts for most of the subsidence (Freeze and 

Cherry, 1979). The simulation of this process in 

response to the collapse is described further on.

Surface Water

Land subsidence over the mined area lowered 

the channel of the Genesee River as much as 4.5 ft 

along a reach extending about 1.5 mi upstream from 

the mouth of Beards Creek (fig. 17) and widened the 

σe = σ – p

∆n α∆σe = –
EFFECTS OF MINE COLLAPSE AND FLOODING 29

10-year flood plain by about 340 acres (Musetter Engineering, Inc., 1996). Increased sediment deposition in 

this area could temporarily decrease the sediment supply to downstream reaches and cause a slight increase 

in bank erosion and a widening of the channel. 

Increased bank erosion along the bend in the Genesee 

River just south (upstream) of the mined area along 

Route 20A (fig. 17) is expected and could necessitate 

repairs to a road embankment (Musetter Engineering, 

Inc., 1996).

Subsidence also altered the course of Beards 

Creek, causing it to flow through the collapse area and 

create a pond in each of the sinkholes that formed over 

the collapses. The subsidence of the creekbed initiated 

headward erosion of a knickpoint, which had progressed about 0.5 mi upstream by June 1995, lowering 

the creekbed by as much as 12 ft and widening it by 

about 40 ft (Musetter Engineering, Inc., 1996). 

Upstream progression of the knickpoint could undermine a highway bridge along River Road (fig. 17); 

therefore, grade-control structures were constructed to 

protect the bridge.

Streamflow measurements were made along 

Beards Creek and along the Genesee River from Mt. 

Morris to Avon to assess whether surface water was 

discharging into the mine. Measurements in Beards 

Creek on May 3, 1994 indicated that streamflow in the 

reach within the collapse area (Location II, fig. 17) 

     

20A

390

408

36

63

39

20A

0.1

0.1

0.1

1

5

.

. .

.

.

Lv 398

LOCATION II

(Lv 368 and

borehole XD-1) Line K

Monument K10

Lv 428

Lv 91

River Road

Canaseraga

Creek

Keshequa

Creek

Beards Creek

Genesee

River

Genesee

River

Geneseo

Cuylerville

Mount

Morris

SALT MINE

COLLAPSE

AREA

EXPLANATION

Model area (Genesee Valley)

Line of equal subsidence—Contour 

 interval, in feet, is variable

Survey line

Gas-producing well (1994)

0.1

. Lv 398

NEW YORK

LOCATION MAP

Study

area

77° 56' 15" 52' 30"

45'

42°48'45"

Base from U.S. Geological Survey digital data,

1:100,000, 1983

2 4 MILES

0

0

2 4 KILOMETERS

48' 45"

Figure 17. Land subsidence in vicinity of the Retsof salt mine, Livingston County, N.Y., February 1996. (Location is 

shown in fig. 13).
30 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

increased about 15 percent—from 16.4 to 18.8 ft3/s; 

this indicates that ground water was discharging to the 

creek and that no streamflow was infiltrating through 

the sinkholes to the mine. On July 14, 1994 all of the 

flow in Beards Creek (0.39 ft3

/s) was lost through infiltration to the underlying alluvial sediments upstream of 

the collapse area, and reappeared in the stream downstream from the collapse area; this indicates further that 

streamflow was not infiltrating to the mine.

The low vertical hydraulic conductivity (9 x 

10-5 ft/d) and large thickness (250 ft) of the finegrained material that underlies streams in the Genesee 

Valley probably prevents downward flow of water from 

the streams to the confined aquifers and the mine. 

Some reaches of the Genesee River lie adjacent to the 

valley wall, however; where water from the river could 

infiltrate downward through bedrock surface fractures 

to the confined aquifers. Streamflow measurements 

were made along the Genesee River from Mt. Morris to 

Avon on August 28, 1995 to assess this possibility during a period of relatively low flow (69 ft3

/s), when 

streamflow was not affected by regulation at upstream 

dams. The measurements indicated an increase in 

streamflow (by ground-water discharge) of 19 ft3

/s, 

which is within the range of 15 to 20 ft3

/s estimated in 

this study for this reach in similar low-flow periods 

during a drought in the early 1960’s. The measurements indicate that the declining ground-water levels in 

the confined aquifers did not induce infiltration from 

the Genesee River and, again, indicate that water from 

the river did not enter the mine.

Ground-Water Hydrology

The collapses in the salt mine in March and April 

1994 resulted in new ground-water flow paths from the 

lower aquifer to the mine and away from any downvalley outlet(s) farther north along the Genesee Valley. 

Before the collapses, ground water discharged through 

the downgradient boundary of the study area near 

Avon, where the hydraulic head was about 520 ft, as 

calculated from the estimated water-table altitudes (fig. 

11). The formation of the rubble zone in the bedrock 

between the mine and the confined lower aquifer was 

analogous to “pulling the plug in a bathtub” and 

opened a drain in the bedrock surface at an altitude of 

about 80 ft. Water from the lower aquifer and bedrock 

fracture zones flowed through the permeable rubble 

zone and into the mine, which was at atmospheric pressure.

The rate of ground-water discharge to the mine 

exceeded the rate of recharge to the lower aquifer and 

caused water levels (hydraulic head) throughout the 

confined-aquifer system to decline. First the water levels declined abruptly, then continued to decline gradually for 2 years. Discharge from the lower aquifer to the 

rubble zone virtually ceased, however, once the 

hydraulic head in the mine had risen above the bedrock-surface altitude (80 ft above sea level) in January 

1996. Once the mine was completely flooded and the 

rubble zone saturated, hydraulic head in the lower aquifer began to recover near the collapse area, although 

hydraulic heads in areas 8 mi north of the collapse had 

still not yet begun to recover by June 1996.

The discharge of ground water into the mine 

altered the hydraulic gradient in the lower aquifer and 

reversed the direction of ground-water flow for at least 

9 mi north of the collapse area. After the gradient reversal, the former downgradient boundary of the study 

area near Avon became an upgradient boundary, and 

saline ground water from the north end of the valley 

flowed southward toward the collapse area. The 

decrease in hydraulic head in the lower aquifer also 

increased the vertical hydraulic gradient between the 

lower aquifer and the Bertie Limestone, and thereby 

enhanced upward migration of saline water from the 

bedrock to the aquifer. The intrusion of saline water 

caused increased salinity at five residential wells; this 

intrusion was first reported in March 1995 (Ralph VanHouten, Livingston County Department of Health, oral 

commun., 1996).

Ground-Water Levels

Water-level declines (drawdowns) resulted in 

both confined aquifers. Water levels in upland areas 

beyond the valley-fill aquifer system, and those at most 

of the wells screened in the upper aquifer, were unaffected by the mine collapse. Drawdowns at affected 

wells were calculated as the difference between measured water levels and those inferred for precollapse 

conditions. This calculation yielded conservative estimates of drawdown because hydraulic heads in the 

lower aquifer were probably higher than heads in the 

upper aquifer, as indicated by reports of artesian conditions in deep wells in the valley (Dr. Richard Young, 

Geology Department, State University of New York at 

Geneso, oral commun., 1996). The distribution of 

drawdown in January 1996, when water-level declines 

in the collapse area were greatest, is shown in figure 18, 
APSE AND FLOODING 31





408

408

258

436

63

39

15

255

256

256

36

36

20

A

100

390



150

200

200

250

150

100

50

300

350

50

.

. .

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

. .

.

.

.

. .

.

.

.

.

.

.

.

. .

.

.

.

.

. . . .

.

.

. .

.

.

Lv 410

Lv 91

Lv 413

Lv 402

Lv 406

Lv 348

Lv 368

Lv 360

Lv 361

Lv 407

Lv 349

Lv 367

Conesus

Canaseraga

Creek

Keshequa

Creek

Beards

Creek

Genesee

River

Cuylerville

Mount

Morris

Dansville

1994 1995 1996 1997

560

550

540

530

520

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv402

middle aquifer

1995 1996 1997

450

400

350

300

250

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv360

lower aquifer

1995 1996 1997

450

400

350

300

250

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv361

middle aquifer

1995 1996 1997

300

250

WATER LE

ABOVE 

1995 1996 1997

450

400

350

300

250

200

150

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv368

lower aquifer

1994 1995 1996

580

570

560

550

540

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv406

upper aquifer

1994 1995 1996 1997

7

6

5

4

3

2

1

0

MONTHLY PRECIPITATION,

IN INCHES

Precipitation

Mount Morris

1994 1995 1996 1997

550

500

450

400

350

WATER LEVEL, IN FEET

ABOVE SEA LEVEL

Well Lv91

lower aquifer

EXPLANATION

Model area (Genesee Valley)

Line of equal drawdown—Contour interval 50 feet.

Well in monitoring network—Number is Livingston 

 County well number

 Individual well

 Well cluster

Mine collapse areas

150

. Lv 425

. Lv 360

Lv 361

NEW YORK

LOCATION MAP

Study

area

42° 37' 30"

45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 4 MILES 2 0

0 2 4 KILOMETERS

1996, hydrographs showing hydraulic head in selected wells, and bar graph showing precipitation at Mt. Morris, 1994-97. (Location is shown in fig. 1.)
32 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

which includes hydrographs of water levels at selected 

wells.

The maximum drawdown in the lower aquifer 

was about 400 ft near the collapse area; drawdowns of 

50 ft and 110 ft were recorded 7 mi north of the collapse area, and 8 mi south of it, respectively. The water 

level in well Lv91, 3 mi south of the collapse area, had 

declined about 60 ft by the end of March 1994 and by 

a total of 140 ft by March 1996 (fig. 18). The water 

level in well Lv425, 8 mi north of the collapse area, had 

declined more than 30 ft by the end of May 1994 and 

had declined an additional 30 ft by March 1996. Part of 

the hydrograph for well Lv368 ( closest to the collapse 

area, location II) is missing because the well was 

capped and, therefore, no water levels could be measured after it began to produce gas after an attempt to 

obtain a water sample in October 1995. The 

hydrograph for well Lv346, screened in the Onondaga 

Limestone at the same location, indicates that recovery 

of the aquifer system began at the beginning of January 

1996.

The maximum drawdown in the middle aquifer 

was about 250 ft in the collapse area; drawdowns of 50 

ft and 135 ft were recorded 7 mi north of the collapse 

and 8 mi south of it, respectively. Despite the large 

drawdowns, the water level in the collapse area 

remained above the top of the middle aquifer, and confined conditions were maintained. Eight to ten wells 

screened in an aquifer in the Beards Creek valley east 

of state highway 36 (fig. 18) went dry by the end of 

March 1994, however, and about six wells 8 mi north 

of the collapse area in the Genesee Valley went dry 

between May and November 1994. Hydraulic heads in 

the middle aquifer near the collapse area (well Lv348) 

began to recover in February 1996, about 1 month after 

heads in the lower aquifer began to recover.

Water levels in water-bearing zones in the Onondaga and Bertie Limestone declined about 210 ft at 

location III (well Lv349), about 1.2 mi southeast of the 

collapse (fig. 18). Drawdown in the water-bearing 

zones was greater south of the collapse than to the 

north of it; drawdowns totaled about 70 ft at location V 

near Sonyea (well Lv365, about 7 mi south of the collapse) and only 7 ft at location I near Avon (well Lv369, 

8 mi north of the collapse). The water level in each of 

these three wells was converted to freshwater hydraulic 

head, hfw, by the following relation, to correct for the 

higher density of the saline water in these aquifers:

(3)

where p = pressure at the bottom of the well screen 

[ML-1T-2],

γfw = specific weight of freshwater [ML-2T-2], and

z = altitude of the bottom of the well screen [L].

The pressure p is given as

(4)

where γ= specific weight of the saline water 

[ML-2T-2], and

l = depth of water above the bottom of the well 

screen [L].

Substituting equation 4 into equation 3 indicates 

that the freshwater head is higher than the measured 

head by a factor of γ/γfw. This factor was computed to 

be 1.01 for the saline water in the Onondaga and Bertie 

Limestones, from the measured density of water samples from wells Lv369 and Lv371 at location I near 

Avon. The corrected freshwater head was 8.2 ft higher 

than the measured head at location V near Sonyea, 4.4 

ft higher than that at location III 1.2 mi southeast of the 

collapse, and 1.6 ft higher than that at location I.

Water levels in wells located in the bedrock 

uplands (Lv413 and Lv410) and in the upper aquifer 

(Lv406 and Lv407) near the collapse area fluctuated 

seasonally from 1994-97, declining through the summer and fall, then rising in response to recharge 

through the following winter and spring (see fig. 18). 

Water levels in the upland wells showed no persistent 

decline from March 1994 through January 1996 (when 

those in the confined aquifers declined), and began 

their seasonal rise in October or November 1995, 2 

months before ground-water discharge to the mine 

ceased; this suggests that upland areas were not 

affected by the mine collapse. Water levels in the upper 

aquifer reached a minimum in November 1995, however, and did not recover to a seasonal maximum until 

the end of January 1996, after ground-water discharge 

to the mine had ceased. Water levels in the upper aquifer also were lower in the winter of 1995-96 than in the 

following winter (1996-97), despite the greater amount 

of precipitation in 1995. These observations indicate 

that water levels in the upper aquifer near the collapse 

area were affected by the mine collapse but were lowered by only about 5 ft from March 1994 through January 1996.

h fw

p

γ fw

= ------- + z

p = γl
EFFECTS OF MINE COLLAPSE AND FLOODING 33

Ground-Water Quality

Five domestic wells screened in the lower aquifer in the northern part of the Genesee Valley south of 

Fowlerville Road (fig. 19) began to produce water in 

1995 whose salinity rendered the water unsuitable for 

consumption. Well Lv457 on Little Road (fig. 19) 

yielded freshwater when it was drilled in September 

1994 (Ronald Hall, Dansville Water Wells, oral commun., 1996), but the elevated specific conductance 

(12,500 μS/cm) in March 1995 indicated that saline 

water had entered the well during the winter of 1994-

95. The specific conductance of water samples from 

well Lv500, which is 3,700 ft southwest of Lv457 on 

Hogmire Road (fig. 19), increased from 4,700 to 

 

39

550

525

500

475

.

.

.

.

.

.

.

.

.

. .

.

.

.

.

.

.

.

.

.

. .

.

.

..

.

. .

.

. .

.

.

.

.

.

.

Lv 493

Lv 443

Lv 436

Lv 479Lv 469

Lv 459

Lv 517 Lv 515

Lv 516

Lv 523

Lv 518

Lv 524

Location I

(Lv 370)

Lv 525

Lv 425

Lv 498Lv 457

Lv 513

Lv 522

Lv 512

Lv 203

Lv 480

Lv 500

Lv 427

Lv 514

API 04288

Lv 519

Lv 510

Lv 511 Lv 483 Lv 454 Lv 430

Lv 520

Lv 521

Lv 442

Lv 461

Lv 437

Lv 471

API 04149

Genesee

River

Conesus

Creek

Avon

Fowlerville Road

Hogmire Road

Little

Road

Nations Road

400

375

350

325

425

450475

500

525 550

575

600

625

650

675

700

725

750

775

800

825

300

275

250

225

200

325

350

375

400

425

450

475 500

525

550

575

600

625

600

575

625

650



EXPLANATION

Lower aquifer

Bertie Limestone

Potentiometic contour—Contour interval 25 feet. Datum is sea level

Bedrock contour—Contour interval 25 feet. Index contours every 100 feet. Datum is sea level

Boundary of model area

Sampled well

Wells at which specific conductance exceeded 2,500 microsiemens per centimeter

Abandoned gas well

Well at which water level was measured, April 1997

500

325

300

. Lv 500

. Lv 524

API 04149 .

. Lv 436

42°54'

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

77° 52' 51' 50' 49' 48' 47' 46' 45'

53'

52'

51'

0 2 4 MILES

0 2 4 KILOMETERS

Figure 19. Locations of sampled wells in Genesee Valley, Livingston County, N.Y., and wells in 

which saline water was detected in April 1997. (Location is shown in fig. 13.)
34 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

12,400 μS/cm between June 1995 and January 1996. 

Six wells in the northern part of the Genesee Valley had 

elevated specific conductance values (greater than 

2,500 μS/cm) in April 1997 (fig. 19); a seventh well 

along Fowlerville Rd. (Lv203) had a specific conductance of 12,100 μS/cm in 1966, as mentioned previously.

Water samples were obtained from 29 wells and 

1 spring in the northern end of the Genesee Valley in 

April 1997 to investigate the source of salinity (fig. 19 

and table 3). Nine of the wells were screened in the 

middle aquifer and 17 wells were screened in the lower 

aquifer. The remaining wells and the spring produced 

water from bedrock. Analyses of water from three other 

wells in this area are also available: Lv371 and Lv397 

(middle and lower aquifer, respectively, at location I), 

sampled in 1995, and Lv203 (lower aquifer), sampled 

in 1966. Specific conductance values are generally 

lower in the middle aquifer than in the lower aquifer; 

the median specific conductance of samples unaffected 

by saline water was 600 μS/cm in the middle aquifer 

and 1300 μS/cm in the lower aquifer (groups 1 and 2 in 

figs. 20 and 21). Specific conductance values greater 

2,500 μS/cm of water from six wells screened in the 

lower aquifer (group 3, figs. 20 and 21) are attributed 

to saline water migration.

Table 3. Concentrations of inorganic constituents in water from confined aquifers in Genesee Valley, Livingston 

County, N.Y., April 1997.

[Locations are shown on fig. 19. Concentrations are in milligrams per liter except as noted. μS/cm, microsiemens per centimeter at 25 ̊ C;

Ca, calcium; Mg, magnesium; Na, sodium; K, potassium; SO4, sulfate; Cl, chloride; Ba, barium; Sr, strontium; Br, bromide; CaCO3, 

calcium carbonate; <, less than.; —, not analyzed]

Well

number Owner

Constituent or physical property

Ca Mg Na K

Alkalinity, as 

CaCO3 SO4 Cl Ba Sr Br

Specific 

conductance 

(μS/cm)

Dissolved

solids

Middle aquifer:

Lv442a Millard 36 48 72 1.6 180 96 24 .033 9.7 .13 890 513

Lv443b Cullinan 52 37 15 < 5 310 7 13 1.7 3.7 < 1 550 450

Lv458b Crandall 64 41 37 < 5 250 60 43 < .2 2.6 < 1 620 378

Lv493b Kelly 24 37 20 < 5 260 < 7 20 1.7 4.7 < 1 480 287

Lv513a McKeown 17 16 84 2.1 150 8.1 44 3.0 34 .4 610 389

Lv518b Orologio, B. 42 34 38 < 5 290 30 36 2 8. < 1 620 319

Lv523 McMahon 64 56 151 8 246 42 296 2.2 14 2.7 1800 751

Lv524 Striker 41 34 43 < 5 254 8 36 .8 8.3 < 1 590 325

Lv525 Housed 101 41 23 < 5 301 46 48 < .2 .17 < 1 844 400

Lower aquifer:

Lv203c Croston — — — — — 1,430 3,540 — — — 12,100 —

Lv370b Akzo Nobel 370 190 1400 190 40 33 3300 .9 35 39 15,100 7000

Lv425a Hollinger 43 37 84 2.4 130 7.2 160 3.3 7.7 .66 950 511

Lv454a Holt 24 16 83 2.0 140 29 23 .1 4.5 .15 550 347

Lv461a Wadsworth 9.9 7.1 160 1 96 200 82 .014 3.5 .24 1010 627

Lv469a Orologio, V. 74 52 160 5.9 160 25 290 .75 11 2.0 1620 867

Lv479a Ward 68 52 150 5.4 160 33 280 .61 10 1.8 1800 839

Lv498a Davis #3 120 110 280 4.4 120 12 840 9.4 22 2.5 3600 1630
EFFECTS OF MINE COLLAPSE AND FLOODING 35

Ratios of chloride to bromide concentrations in 

water samples from the lower aquifer indicate two 

sources of saline water. Eight of the 17 samples from 

the lower aquifer contained chloride-to-bromide ratios 

of 84 to 154, similar to ratios measured in Bass Island 

carbonate brine in western New York (110) and saline 

water from the Onondaga and Bertie Limestones (120 

to 180). These data plot close to a line representing the 

average ratio in waters from the Onondaga and Bertie 

Limestones (150:1, fig. 22). Saline water at well Lv512 

(dissolved solids concentration 6,710 mg/L) had a 

much higher chloride-to-bromide ratio (920), which is 

close to those characteristic of waters affected by halite 

dissolution (greater than 1,000:1) (Davis and others, 

1998). Ratios for the remaining wells plot between the 

lines representing these two extreme ratios (fig. 22); 

this result indicates that the salinity of this water results 

from the mixing of saline water from the Onondaga and 

Bertie Limestones with water affected by halite from 

an unidentified source.

Saline bedrock water probably enters the lower 

aquifer where the Bertie Limestone subcrops north of 

Fowlerville Road (fig. 19). Before the mine collapse, 

saline water entering the lower aquifer probably flowed 

northward with the horizontal hydraulic gradient. The 

documented saline water at well Lv203 along Fowlerville Road (specific conductance 12,100 μS/cm in 

1966, Kammerer and Hobba, 1967) marks the approxTable 3. Concentrations of inorganic constituents in water from confined aquifers in Genesee Valley, Livingston 

County, N.Y., April 1997—Continued

[Locations are shown on fig. 19. Concentrations are in milligrams per liter except as noted. μS/cm, microsiemens per centimeter at 25 ̊ C;

Ca, calcium; Mg, magnesium; Na, sodium; K, potassium; SO4, sulfate; Cl, chloride; Ba, barium; Sr, strontium; Br, bromide; CaCO3, 

calcium carbonate; <, less than.; —, not analyzed]

a

Analysis by New York State Department of Health, Wadsworth Center, Albany, N.Y.

b

Analysis by Lozier Laboritories, Rochester, N.Y.

c

Analysis by Kammerer and Hoba, 1967.

d

Aquifer uncertain.

Well

number Owner

Constituent or physical property

Ca Mg Na K

Alkalinity, as 

CaCO3 SO4 Cl Ba Sr Br

Specific 

conductance 

(μS/cm)

Dissolved

solids

Lower aquifer:

Lv500b Baker/ Wadsworth 590 530 2400 39 130 240 5300 5.0 86 8.5 25,800 11,800

Lv510a Jones (house) 80 86 260 3.8 110 7.8 700 7.6 23 1.5 3000 1430

Lv511a Jones (barn) 42 42 160 2.9 110 11 300 1.5 14 .76 1300 753

Lv512a Halpin 390 170 1500 20 120 490 3500 .23 47 3.8 18,400 6710

Lv514a Banker 17 5.3 61 1.3 93 15 12 .14 2.5 .12 380 255

Lv515a Klimasewski 56 43 110 3.9 150 18 240 1.8 11 1.7 1300 705

Lv516a Zander 58 44 110 4.3 150 14 230 1.4 12 1.6 1280 844

Lv517b Sullivan 71 53 120 9.4 320 48 220 .91 9.8 1.5 1420 676

Lv519b Elliot 88 80 270 8.9 220 9 630 4.3 15.0 1.9 2600 1260

Lv521b Harris 110 41 26 42 330 90 48 .32 .55 < 1 800 592

Lv522b O’Connelld 128 41 60 41 330 79 89 < .2 2.6 < 1 1047 672

Bedrock:

Lv430b Lloyd 68 73 76 5.3 432 60 69 .58 4.8 < 1 1020 641

Lv450b Morabito 58 35 20 < 5 210 40 40 < .2 .36 < 1 590 345

Lv520b Morss 83 62 33 5 380 54 80 .2 .67 < 1 950 546
36 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

imate southward limit of saline-water movement at that 

time because domestic wells further south produced 

potable water. After the mine collapse, the reversal of 

the horizontal hydraulic gradient in this area allowed 

saline water to flow southward from the Bertie subcrop 

toward the collapse area. The drawdown in the lower 

aquifer also increased the upward hydraulic gradient 

from below, thereby enhancing the potential for 

upward migration of saline waters through high-angle 

fractures in the bedrock south of the Bertie subcrop. 

These changes are probably the reason for the intrusion 

of saline water into areas south of Fowlerville Road.

The halite detected in water samples from the 

lower aquifer probably originated from the Salina salt 

beds. Two abandoned gas wells that penetrated the 

Salina salt beds are near the five domestic wells that 

yielded water with specific conductance values greater 

than 2,500 μS/cm (fig. 19). Halite-bearing water could 

have flowed upward through the gas wells or outside 

the well casing and leaked into the lower aquifer if the 

wells were not properly sealed when abandoned. Past 

solution mining of halite could explain the salinity in 

the sample from well Lv397 (fig. 13), but the other 

affected wells are north of the only known locations of 

solution mining, and the recent changes in salinity 

appear to have originated from the north; therefore, the 

salinity probably was not derived from these solutionmining sites. Halite-bearing water from road-salting 

0

20

40

60

80

100 0

20

40

60

80

20

40

60

80

100

100

80

60

40

20

0

CALCIUM

MAGNESIUM

SODIUM + POTASSIUM

PERCENT

100

80

60

40

20

20

0

0

20

40

60

80

100

100

80

60

40

20

0

0 0

100

40

60

80

20

40

60

80

100

80

60

40

20

SULFATE + CHLORIDE

CALCIUM + MAGNESIUM

CARBONATE + BICARBONATE

SULFATE

CHLORIDE

PERCENT

PERCENT

Lv370

Lv512

Saline water from

Onondaga/Bertie

Limestones

EXPLANATION

Specific conductance values at observation

 wells—Size of circle is proportional to value

 Group 1: Middle aquifer

 Group 2: Lower aquifer, less than 2,500

 microsiemens per centimeter

 (unaffected by saline water)

 Group 3: Lower aquifer, greater than or

 equal to 2,500 microsiemens per

 centimeter (affected by saline water)

.

.

.

1 5

Log specific conductance

(microsiemens per

centimeter)

Figure 20. Percentage of major cations and anions in 

water from northern end of Genesee Valley, Livingston 

County, N.Y., April 1997.

n = 7

n = 11

n = 7

Group 1

Group 2

Group 3

100

100,000

200

300

400

500

700

1,000

2,000

3,000

4,000

5,000

7,000

10,000

20,000

30,000

40,000

50,000

70,000

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

EXPLANATION

Data values less than or equal to 1.5 times

 the interquartile range outside the quartile

75th percentile

Median

25th percentile

Groups

 1—Middle aquifer

 2—Lower aquifer, unaffected by saline water

 3—Lower aquifer, affected by saline water

n Number of samples

Figure 21. Specific conductance of water from northern 

end of Genesee Valley, Livingston County, N.Y., April 

1997.
EFFECTS OF MINE COLLAPSE AND FLOODING 37

operations could migrate through bedrock fractures to 

wells near the valley walls, but the highest salinity values were at the center of the bedrock valley and, therefore, probably did not result from road salting. 

Although the source of halite-bearing water in the 

lower aquifer remains uncertain, the inflow of this 

water probably resulted from change in hydraulic gradient that followed the mine collapse.

The potential for intrusion of saline water also is 

a concern near the collapse area, where the rubble zone 

forms a permeable pathway between the flooded mine 

and the lower aquifer. The flooded mine is filled with 

brine, which is heavier than freshwater and has a specific gravity (γbrine/γfw) of about 1.2. The brine will be 

forced upward through the rubble zone as the mine cavity closes under increasing geostatic pressure and could 

eventually enter the lower aquifer in the collapse area; 

it also might flow laterally through fracture zones in the 

Onondaga and Bertie Limestones. The level (altitude) 

of brine is being monitored through a water-level comparison of a well that penetrates the mine (Lv396) with 

one that is screened in the Onondaga and Bertie Limestones in the collapse area (Lv309; Akzo Nobel Salt, 

Inc., 1996). Records indicate that the brine level in the 

collapse area was over 120 ft below the bottom of the 

Bertie Limestone in 1998 (fig. 23).

Natural Gas Exsolution

Methane and hydrogen sulfide were detected in 

the mine after the collapses and accumulated to unsafe 

levels periodically throughout the summer of 1994. 

Five or six wells, originally drilled as part of a grouting 

program to save the mine, were used to vent the gas 

from the mine, and three of the wells were flared in 

May 1995. The gas probably originated from a fracture 

zone in the Bertie Limestone, where gas had previously 

been detected in other boreholes (L. D. Milliken, 

ANSI, oral commun., 1996). The methane-to-ethane 

ratio in gas samples from three wells screened in the 

rubble zone in the collapse area ranged from 5 to 21, 

which indicates that the gas was produced primarily by 

thermogenic decomposition of organic matter (John C. 

Fountain, Dept. of Geology, State University of New 

York at Buffalo, written commun., 1995).

Some water wells screened in the middle aquifer 

as far as 6 mi from the collapse area began to produce 

gas after the collapse. Gas was flared from two wells 

screened near bedrock—Lv398 on the west side of the 

Halite ratio 900:1

Carbonate brine ratio 150:1

Lv512

0.1 1 10 100 1,000 10,000

BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

10

106

105

104

103

102

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

EXPLANATION

Lower aquifer with specific conductance

 Less than 2,500 microsiemens per centimeter—Group 2

 Greater than 2,500 microsiemens per centimeter—Group 3

Onondaga and Bertie Limestones

Bass Island carbonate brine

Figure 22. Relation between chloride and bromide 

concentrations in water from the lower aquifer and the 

Onondaga and Bertie Limestones in Livingston County, 

N.Y., and the Bass Islands carbonate brine in western 

New York.

 

Bertie Limestone

glacial sediments

land surface

Onondaga Limestone

Salina Shale

J F M A M J J A S O N D J F M

1996 1997

500

600

–500

–400

–300

–200

–100

0

100

200

300

400

ALTITUDE, IN FEET ABOVE SEA LEVEL

EXPLANATION

Estimated brine level in collapse area (well Lv 309)

Brine level in mine (well Lv 396)

Water level in collapse area (well Lv 309)

Figure 23. Measured brine level (altitude) in the mine, 

estimated brine levels in the collapse area (location II), 

and water levels in the collapse area, Livingston County, 

N.Y., January 1996 through March 1997.
38 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

valley in Cuylerville, and Lv428 on the east side of the 

valley in Groveland (fig. 17), after the wells went dry 

in April and July 1994, respectively. Gas also was produced in well Lv91 screened in the lower aquifer in Mt. 

Morris beginning in December 1994. The methane-toethane ratio in gas samples from these three wells 

ranged from 54 to 135, indicating that the gas was produced primarily through biogenic decomposition of 

organic matter (J. C. Fountain, State University of New 

York, Buffalo, written commun., 1995).

Methane also was detected near a plugged access 

shaft at the northern end of the mine in January 1996, 

shortly after the mine had become completely flooded 

and ground-water levels had begun to recover. Methane 

emissions continued through the summer of 1996 but 

gradually diminished. They were apparently vented 

through bedrock outcrops above the edge of the mine 

and probably resulted from the increased pressure that 

developed within the mine in response to the rising 

ground-water levels (J. C. Fountain, State University of 

New York, Buffalo, written commun., 1996).

SIMULATION OF GROUND-WATER FLOW

Ground-water flow through the aquifer system in 

the Genesee Valley was simulated with three-dimensional models with MODFLOWP (Hill,1992) to represent flow conditions before and after the ceiling 

collapses in the Retsof salt mine. The models were 

based on the generalized geologic sections presented 

earlier and used homogeneous distributions of hydraulic properties and, therefore, gave a simplified representation of actual aquifer conditions.

The first model (3D-A, table 4) was calibrated to 

measured water levels and flow rates in steady- and 

transient-state simulations and was used to calculate 

ground-water budgets and determine the time required 

for water levels to return to precollapse conditions. 

Results of transient-state simulations were used to 

assess the effects of the reversal of ground-water flow 

directions on the location and rate of saline-water intrusion into the lower aquifer in the northern part of the 

valley. Model 3D-A was later modified to create model 

3D-B, which was used to assess the effects of gas exsolution on the volume of water released from storage 

within the confined aquifers.

One-dimensional models (1D-A and 1D-B, table 

4) with MODFLOW (McDonald and Harbaugh, 1988) 

with the interbed-storage package (Leake and Prudic, 

1991) were then constructed to simulate compression 

of fine-grained sediments in the upper and lower confining layers, as described in the section “Simulation of 

land subsidence.” Estimated values for hydraulic properties of the confining layers obtained through calibration of the one-dimensional models then were 

incorporated in three-dimensional model 3D-A to create model 3D-C, which was used to depict the spatial 

distribution of land subsidence. Four different assumptions were made concerning the storage properties of 

confined aquifers and confining-layer sediments during 

calibration of the three-dimensional and one-dimensional models. A summary of the five models used, and 

the assumptions made concerning storage properties 

and applications of each model, is given in table 4.

Model Design

Three-dimensional model 3D-A was prepared 

with MODFLOWP , a computer program based on 

MODFLOW, which uses a nonlinear-regression 

method to estimate model parameter values. The modeled area extends 30 mi from Avon southward to the 

Valley Heads Moraine near Dansville and represents an 

area of 61.3 mi2

 (fig. 2). The modeled area generally 

coincides with the boundaries of the upper aquifer but 

also includes the Fowlerville Moraine, where the upper 

aquifer is extremely narrow.

Model Layers and Grid

The three aquifers and two confining layers that 

form the aquifer system (fig. 10) were represented by 

five model layers. Water-bearing zones in the bedrock 

were not represented in the model because little information on their hydraulic properties is available, and to 

include them would require a substantial increase in the 

size of the modeled area.

Model layer 1 represents the upper aquifer, 

which includes three components—the alluvial sediments that cover most of the valley floor, the deltaic and 

kame deposits along parts of the valley walls, and the 

Fowlerville Moraine and adjacent fine-grained lacustrine sediments (fig. 24). Model layer 2 represents the 

upper confining layer (lacustrine sediments and till), 

which separates the upper aquifer from the middle 

aquifer; layer 2 also includes the lower part of the 

Fowlerville Moraine. Model layers 3 and 5 represent 

the two confined aquifers, and model layer 4 represents 

the lower confining layer, which separates them. Model 

layers 3 and 4 include delta and kame deposits that are 
SIMULATION OF GROUND-WATER FLOW 39

assumed to extend from the confined aquifers to land 

surface. Model layer 5 implicitly represents fractures at 

the bedrock surface that are in hydraulic connection 

with the lower aquifer; the transmissivity of model 

layer 5 estimated in model calibration includes the contribution from bedrock fractures.

Each of the five model layers was divided into a 

uniformly spaced grid of 300 ft with 470 rows and 194 

columns. Model layers 1 and 2 (upper aquifer and 

upper confining layer) contain 19,005 active cells and 

represent a wider area (61.3 mi2

) than the other model 

layers because the bedrock valley narrows with depth 

(fig. 10). Layer 5 contains 17,024 active cells and represents an area of 55 mi2

 and its horizontal extent (fig. 

25B) coincides with the assumed horizontal extent of 

the lower confining layer.

The thickness of sediments represented by each 

cell in model layers 1 and 2 was calculated from isopach (thickness) maps of the upper aquifer and upper 

confining layer, respectively. The thickness of morainal 

and lacustrine sediments in the vicinity of the Fowlerville moraine was divided equally between model layers 1 and 2. The middle and lower aquifers were 

assumed to be of uniform thickness (10 ft throughout 

model layer 3 and 25 ft throughout model layer 5, 

respectively), except where these aquifers pinch out 

near the bedrock valley walls. The thickness of the 

lower confining layer (model layer 4) was computed as 

Table 4. Summary of models of ground-water flow and land subsidence in Genesee Valley, Livingston County, N.Y.,

assumptions used in defining storage coefficients, and the applications of each

 [Locations of seismic-survey monument K10 and location II are shown in fig.17]

Model 

Assumptions used in defining 

storage coefficients a

a

Variables:

ρg = specific weight of water [ML-2T-2],

α = compressibility of aquifer material [ML-1T-2]

-1,

Ssg = given in equation 18 [L-1],

m = a constant estimated by PEST regression [MT-2],

di

 = depth of cell i in models C and D [L],

b = thickness of confining layer [L], and

bi

 = unit thickness of cell i in models C and D [L].

Model applications

Three-dimensional model

3D-A Constant specific storage Ss in confined aquifers:

Ss = ρgα

Water-level drawdown and recovery

Saline-water migration

3D-B Variable specific storage Ss′ in confined aquifers:

Ss′ = Ss + Ssg

Gas exsolution from confined aquifers

3D-C Elastic specific storageb

in confining layers:

Ss = b-1ΣSse(i)bi, 

i = 1, b

b

Elastic storage Sse(i) estimated from PEST regression (Doherty and others, 1994) neglecting inelastic compression.

Spatial distribution of 

land subsidence

One-dimensional models

1D-A: upper confining layer at location II Elastic specific storage Sse and 

inelastic specific storage Ssin

in confining layers:

Sse(i) = ρgm/di

Ssin(i) = Sse(i)*30

Pore pressure at location II

1D-B: upper and lower confining layers at monument K10 Same as in model 1D-A Land subsidence at

monument K10
40 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Upland

runoff

Upland

runoff

Recharge Recharge

Valley wall

Model

Layer

1

2

3

4

5

K

K V

K V

K, S S

A. Vertical section of model. 300 feet

300 feet

10 feet

Q H

K V

K, S S

A H

model cell

A V

Q V

B. Cell dimensions and variables used in

computation of flow rates.

EXPLANATION

Units represented

 Upper aquifer

 Upper confining layer

 Middle aquifer

 Lower confining layer

 Lower aquifer

 Fractured bedrock (valley wall)

 No flow

Hydraulic connections within fractured bedrock

 (along valley wall)

Predominant flow direction within model layer

Hydraulic properties assigned to units

 Horizontal hydraulic conductivity

 Vertical hydraulic conductivity

 Specific storage

Horizontal flow

Vertical flow

Cross-sectional area for horizontal flow

Cross-sectional area for vertical flow

Direction of flow

K

K V

S S

EXPLANATION

Q H

A H

A V

Q V

Figure 24. A. Vertical section of model with hydraulic properties assigned to each layer and representation of vertical 

hydraulic connections between model layers along valley walls. B. Cell dimensions and variables used in computation 

of flow rates between cells.
SIMULATION OF GROUND-WATER FLOW 41

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

  

Conesus

Creek

Conesus Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga Creek

Avon

Dansville

Geneseo

SALT MINE

Mount

Morris

Cuylerville

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

0 4 8 MILES

0 4 8 KILOMETERS

408

408

258

436

63

63

39

39

36

15

15

255

256

256

36

36

256

5

390

20

20A

20

20A

20A

390

  

Conesus

Creek

Conesus Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga Creek

Avon

Dansville

Geneseo

SALT MINE

Mount

Morris

Cuylerville

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

0 4 8 MILES

0 4 8 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Model layer 1

 Alluvial deposits

 Fine-grained deposits

 Delta

 River and stream cells

 Head-dependendent boundary cells

 Upland runoff cells

Model layers 3, 4, and 5

 Lower aquifer

 Weathered bedrock in layer 3

 Weathered bedrock in layer 4

 Kame delta (layers 3 and 4)

 Ice-contact deposits (layers 3 and 4)

 Head-dependent boundary (layers 3 and 5)

 Collapse area (layer 5)

Figure 25. Boundary conditions in ground-water-flow model of aquifer system in Genesee Valley, Livingston County, 

N.Y.: A. Upper aquifer (model layer 1). B. Confined aquifer system (model layers 3, 4 and 5).
42 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

the difference between the altitude of the top of model 

layer 5 (altitude of bedrock surface plus thickness of 

model layer 5) and the bottom altitude of model layer 3 

(altitude of land surface less combined thickness of 

model layers 1 through 3).

Boundary Conditions

Boundary conditions that represent inflows and 

outflows of water to and from the aquifer system were 

specified in the three model layers that correspond to 

the upper aquifer and the two confined aquifers (model 

layers 1, 3, 5).

Model Layer 1

A constant-flow boundary was used to represent 

direct recharge to the upper aquifer from precipitation; 

recharge rates for cells along the valley walls were 

increased to account for the additional recharge that 

enters the upper aquifer along the valley edges from 

channeled and unchanneled runoff from upland areas 

(fig. 25A). Head-dependent boundaries were used to 

represent other inflows from upland areas, which 

include: (1) the thick glacial sediments in the Valley 

Heads Moraine at the south end of the valley, (2) the 

thick lacustrine sediments near the Fowlerville 

Moraine south of Avon, and (3) the subcrop of the 

Onondaga Limestone near the Fowlerville Moraine. 

Head-dependent boundaries also were used to represent outflow through the northern (downgradient) 

boundary, and flow to and from perennial stream channels, including the Genesee River, Canaseraga Creek, 

and their tributaries.

Head values along head-dependent boundaries 

were specified from assumed water-table altitudes or 

from estimates of stream stage. Stream-stage estimates 

were computed from land-surface altitudes derived 

from digital elevation model (DEM, U.S. Geological 

Survey, 1996) data with 34-ft (10-m) resolution. The 

conductance (C) for model cells representing headdependent boundaries was computed from the relation:

, (5)

where K= hydraulic conductivity (LT-1);

A = cross-sectional flow area (L2

); and

l = length of flowpath between cell center and 

model boundary (L).

Hydraulic properties of cells representing lateral flows 

through head-dependent boundaries were assigned as 

follows: 

K (hydraulic conductivity) was specified according to 

the type of material at the boundary;

A (cross-sectional area) was computed as the product 

of the cell width (w) and thickness (b); and

l (flowpath length) equaled w.

The K value for cells representing flows to and from 

perennial streams was assumed to be 1 ft/d, and the 

ratio A/l was based on the length, width, and thickness 

of the stream channel as follows: 

cells representing the Genesee River: 3×104

 ft; 

cells representing named creeks: 1×104

 ft; and 

cell representing unnamed tributaries: 3×103

 ft.

Model layers 3 and 5

Head-dependent boundaries were used in model 

layer 3 (middle aquifer) to represent inflow from 

upgradient areas at the Valley Heads Moraine and in the 

Beards Creek valley (fig. 25B); head-dependent boundaries were specified for model layers 3 and 5 (middle 

and lower aquifers) to represent underflow through the 

northern (downgradient) boundary. Drain boundaries 

were used in layer 5 to represent discharge from the 

lower aquifer to the rubble zone in the collapse area, as 

discussed in the section “Transient-state simulations.”

Model layers 2 through 5

No-flow lateral boundaries were used in model 

layers 2 through 5 to represent the contact between the 

aquifer system and the shale bedrock at the valley wall. 

Hydraulic connectivity in active cells near the perimeters of model layers 2 through 5 was increased to represent vertical leakage through permeable deposits, 

bedrock fractures, or both, along the valley wall (fig. 

24A). The ratio of horizontal to vertical hydraulic conductivity specified for these cells was scaled by a factor 

to account for differences in the cross-sectional flow 

area that result from the cell geometry. The flow rate 

(Q) between adjacent model cells is given by

, (6)

where i = hydraulic gradient between the cells.

The thickness of permeable deposits and(or) fractured 

bedrock along the valley walls was assumed to be 10 ft; 

as a result, the cross-sectional area for horizontal flow 

(AH) was 3×103

 ft2, and the cross-sectional area for 

C KA

l = ------- Q KiA =
SIMULATION OF GROUND-WATER FLOW 43

vertical flow (AV) was 9×104 ft2 (fig. 24B). The vertical 

hydraulic conductivity (KV) was, therefore, reduced by 

a factor of 30 in cells representing leakage along the 

valley walls, such that vertical anisotropy in these cells 

equaled 1.0.

Model Calibration

Parameter values representing aquifer properties 

were adjusted through steady-state and transient-state 

simulations to produce a model that would approximate the water levels and flow rates measured (1) prior 

to the collapses, (2) during the flooding of the mine, 

and (3) during the period of water-level recovery after 

the mine was filled. The steady-state simulation represented precollapse conditions, when no large stresses 

were imposed on the aquifer system; the resulting 

hydraulic heads provided initial conditions for a 29-

month (876-day) transient-state simulation (model 3DA in table 4) that began with the first collapse in March 

1994 and ended in August 1996, 8 months after the 

mine was flooded. The transient-state simulation represented the two postcollapse periods—drainage from 

the aquifer system to the mine (March 1994 to January 

1996), and recovery of water levels after the mine had 

completely filled (January 1996 through August 1996). 

Model parameters were estimated through a nonlinear 

regression method (Cooley and Naff, 1990) that minimized differences between measured and computed 

heads and flows.

Calibration Procedure

Initial estimates were specified for 25 parameters 

in model A (table 5), 12 of which were estimated 

through nonlinear regression.

Table 5. Numbers of parameters representing Genesee Valley aquifer properties in model 3D-A, as estimated and fixed 

in nonlinear regression for Genesee Valley aquifer system, Livingston County, N.Y.

[ —, no parameter specified] 

Model layer

Aquifer property

1

Upper

aquifer

2

Upper

confining

layer

3

Middle

aquifer

4

Lower

confining

layer

5

Lower

aquifer

Horizontal hydraulic conductivity:

Estimated 3—1—1

Fixed — 1 — 1 —

Vertical hydraulic conductivity:

Estimated — — — 2 —

Fixed —a

a

Vertical hydraulic conductivity value taken from underlying layer.

1 —a 2 —

Specific storage:

Estimated — —1—1

Fixed 1 1 — 1 —

Recharge:

Estimated 3 ————

Other fixed properties:

Streambed conductance 3 ————

Conductance along valley wallsb

b

Same value specified in model layers 2 through 5.

— 1 ———

Specific storage along valley wallsb — 1 ———

Total

Estimated: 12 60222

Fixed: 13 45040
44 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Steady-state simulations

Steady-state simulations were used to estimate 

values for six parameters that represent horizontal 

hydraulic conductivity (herein referred to as hydraulic 

conductivity) and recharge in the alluvial, deltaic, and 

fine-grained deposits in model layer 1 (upper aquifer) 

(fig. 25A). Hydraulic heads computed from the steadystate simulation were compared with the assumed 

water-table altitude at 29 locations chosen to represent 

the spatial distribution of head shown in figure 11, and 

ground-water discharges computed from the steadystate simulation were compared with base flows estimated from stream discharge measured during the 

spring or fall from 1973 through 1993 at USGS gaging 

stations on Canaseraga Creek and on the Genesee River 

at Jones Bridge Rd. and Avon (fig. 4). Base flow along 

two stream reaches was estimated from discharge measured during 15 five-day periods with steadily declining flow, when storm runoff and stream regulation were 

absent.

Improvements in model results were identified 

through comparison of the sum of squared errors (SSE) 

given by

, i = 1, n (7)

where ei

 = difference between the measured and calculated values of measurement i;

wi

1/2 = square root of the weight assigned to the 

error in the measured value of measurement 

i,

wi

1/2ei = weighted residual corresponding to measurement i; and

n = number of measurements; 

and the standard error of estimate (SE) given by

, (8)

where p = the number of model parameters estimated 

by the regression.

The weights, wi

, were chosen according to procedures in Hill (1992) to account for the different units 

associated with head measurements (130 to 680 ft) and 

flow measurements (1.0 × 106

 to 3.5 × 106 ft3/d). The 

wi

 values were adjusted such that all the head and flow 

measurements were weighted equally.

Transient-state simulations

The six parameter values obtained from the 

steady-state simulations were used in transient-state 

simulations to estimate values for six additional parameters representing hydraulic conductivity and specific 

storage of model layers 3 and 5 (middle and lower aquifers, respectively), and vertical hydraulic conductivity 

of model layer 4 (lower confining layer). These parameters were applied to all cells within these model layers 

except those representing the weathered bedrock (fig. 

25A). A value also was estimated for a separate parameter representing vertical hydraulic conductivity of the 

lower confining layer at two model cells in the collapse 

area to represent the increase in permeability that probably resulted from subsidence of sediments within the 

confining layer above the rubble zone in the bedrock. 

Results of transient-state simulations were compared 

with two estimates of ground-water discharge to the 

mine (March and September 1994), and with 354 

water-level measurements made at 51 wells from 

March 1994 through August 1996. Of these 51 wells, 

24 were screened in the lower aquifer, 26 were 

screened in the middle aquifer, and 1 was screened in 

the upper aquifer.

Additional steady-state simulations were then 

conducted with the six parameter values from the transient-state simulations to obtain new estimates for the 

six parameters used in model layer 1. These new estimates then were used in additional transient-state simulations to obtain a final set of six parameters values for 

model layers 3, 4 and 5.

Precollapse Conditions

The base flows and hydraulic-head distribution 

in the water-table aquifer computed with the steadystate simulation matched the measured heads and flows 

reasonably well, and the predicted directions of 

ground-water flow were consistent with the directions 

assumed for precollapse conditions.

Head distribution

The hydraulic-head distribution in the upper 

aquifer, as computed by the steady-state simulation 

with model 3D-A (fig. 26A) was similar to assumed 

water-table elevations prior to the collapses (fig. 11). 

The model overpredicted heads by 10 to 20 ft in areas 

where fine-grained sediments are present near the 

Fowlerville Moraine, but the simulated directions of 

ground-water flow were consistent with flow directions 

SSE Σ wi

1 2⁄

ei [ ]

2 =

SE SSE

n p – ------------

1 2⁄

=
SIMULATION OF GROUND-WATER FLOW 45

408

408

258

436

63

63

39

39

36

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15

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256

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36

256

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390

20

20A

20

20A

20A

390

  

Conesus

Creek

Conesus Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga Creek

Avon

Dansville

Geneseo

SALT MINE

Mount

Morris

Cuylerville

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

0 4 8 MILES

0 4 8 KILOMETERS

408

408

258

436

63

63

39

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15

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256

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256

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390

20

20A

20

20A

20A

390

  

Conesus

Creek

Conesus Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga Creek

Avon

Dansville

Geneseo

SALT MINE

Mount

Morris

Cuylerville

77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

0 4 8 MILES

0 4 8 KILOMETERS

640

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p p

e e

e

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e e

p

p

e

p

p e

p

e

p e

e

e p

p p

p

e

p

p

p

p NEW YORK

LOCATION MAP

Study

area

NEW YORK

LOCATION MAP

Study

area

EXPLANATION EXPLANATION

Model layer 1

 Alluvial deposits

 Fine-grained deposits

Water-table contour—

 Contour interval 20 feet.

 Datum is sea level. Arrow 

 indicates direction of

 ground-water flow

Collapse area

Model layer 5

 Lower aquifer

 Boundary of model area

Potentiometric contour—

 Contour interval 10 feet. 

 Datum is sea level. Arrow 

 indicates direction of

 ground-water flow

Collapse area

Difference between predicted

 and observed head, in feet

 Less than –20

 –10 to –20

 0 to –10

 0 to 10

 10 to 20

 Greater than 20

A. Upper aquifer (model layer 1). B. Lower aquifer (model layer 5).

p

p

p

e

e

e

560 560

Figure 26. Distribution of hydraulic head and weighted residuals computed by steady-state simulation (model 3D–A) 

for Genesee Valley, Livingston County, N.Y. A. Upper aquifer (model layer 1). B. Lower aquifer (model layer 5).
46 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

assumed for precollapse conditions. The standard error 

in heads was 8.7 ft, and the range in computed heads 

was 520 to 720 ft. The hydraulic-head distribution 

computed for the lower aquifer indicated northward 

flow from the Valley Heads Moraine to the northern 

model boundary (fig. 26B). The horizontal hydraulic 

gradient computed in the steady-state simulation was 

relatively flat (3 × 10-4 ft/ft) throughout most of the 

lower aquifer, but was steeper (2 × 10-3 ft/ft) near the 

model boundaries and was generally oriented outward, 

which would indicate upward discharge through the 

assumed permeable zone along the perimeter of the 

valley.

Recharge and discharge

More than half of the computed inflow to the 

aquifer system consisted of recharge from precipitation 

on the valley floor (51 percent); another 5 percent was 

derived from upland runoff (table 6). More than onethird of the inflow to the aquifer system consisted of 

infiltration from the Genesee River and Canaseraga 

Creek; the remainder (9 percent) was contributed as 

underflow from upgradient boundaries (Valley Heads 

and Fowlerville Moraines, Onondaga Limestone subcrop, and Beards Creek Valley). Almost all of the computed outflow (98 percent) was discharged to the 

Genesee River and Canaseraga Creek. The computed 

base flow (outflow minus inflow) of Canaseraga Creek 

(45 ft3

/s or 3.9 × 106 ft3/d) was 12 percent greater than 

the estimated baseflow (40 ft3

/s), and the computed 

base flow to the Genesee River (31 ft3

/s or 2.7 × 106

ft3/d) was 25 percent less than the estimated base flow 

in this reach (40 ft3/s).

Recharge through alluvial and deltaic sediments 

was estimated to be 20 in/yr (table 7), 50 percent 

greater than the estimate of 14 in/yr obtained from 

average annual runoff (Lyford and Cohen, 1988, fig. 3). 

The estimated rate of recharge through the fine-grained 

sediments was 3.9 in/yr. The recharge rate specified in 

model cells representing upland runoff was twice the 

recharge rate specified for alluvial and deltaic sediments and was equivalent to 0.2 ft3

/s per mile of valley 

wall—slightly smaller than the rate calculated by MacNish and Randall (1982) for recharge from unchanneled upland runoff in similar terrane immediately 

south of the Genesee watershed. The estimated rate of 

recharge from upland runoff (0.8 in/yr derived from 90 

mi2

 of upland area) is a relatively small fraction of the 

average precipitation (30 in/yr), and rates exceeding 

1.3 ft3

/s per mile of valley wall have been estimated for 

other areas in the glaciated northeast (Morrissey and 

others, 1988). The actual rate of direct recharge from 

precipitation probably is less than the estimated rate, 

and the actual rate of recharge from upland runoff 

probably is greater than the estimated rate, primarily 

because not all of the channeled runoff is explicitly represented in the model.

Aquifer properties

Estimated hydraulic conductivity values of the 

alluvial sediments was 280 ft/d, that for the deltaic sediments was 500 ft/d, and that for the fine-grained sediments was 0.93 ft/d . The estimated hydraulic 

Table 6. Simulated water budget for Genesee Valley aquifer system, Livingston County, N.Y., under average steadystate conditions before collapses of Retsof mine ceiling in March and April 1995

[Flow rates are in millions of cubic feet per day.]

Inflow Outflow

Source Rate

Percentage 

of total Location Rate

Percentage 

of total

Recharge from precipitation 5.30 51

Upland runoff .52 5

Genesee River 2.60 25 Genesee River 5.30 51

Canaseraga Creek 1.04 10 Canaseraga Creek 4.89 47

Underflow .94 9 Underflow .21 2

TOTAL 10.4 100 10.4 100
SIMULATION OF GROUND-WATER FLOW 47

conductivity value for alluvial sediments is reasonable 

for coarse-grained sediments but seems too large for 

the alluvial sediments that contain fine sand and silt. A 

lower value would decrease the simulated base flow, 

however, and would increase model error. Optimum 

values were obtained by the nonlinear regression for 

the recharge rate and hydraulic conductivity of the alluvial sediments. The approximate individual confidence 

intervals (at the 95-percent confidence level) for these 

values were 3 to 36 in/yr for recharge and 8 to 380 ft/d 

for hydraulic conductivity; these wide ranges indicate 

that the parameter values were not estimated precisely. 

The confidence intervals are approximate because the 

required assumptions on which they are based (an 

unbiased model that is effectively linear with normally 

distributed weighted residuals) are not strictly met by 

the steady-state simulation. The large uncertainty in 

parameter estimates probably results from the relatively small number of measured heads and flows for 

comparison with simulated values, and from the low 

sensitivity of the steady-state simulation to these measurements as a result of the extensive boundaries specified in model layer 1.

Despite the uncertainty in estimated values, the 

hydraulic-head distribution in the upper aquifer, and 

the base flows computed with the steady-state simulation, are reasonable; therefore, the head distributions 

computed for the lower model layers probably represent valid initial conditions for the transient-state simulation. Sensitivity analyses indicate that none of the 

model parameters obtained through steady-state simulations significantly affected the results of transientstate simulations.

Postcollapse Conditions (Flooding and WaterLevel Recovery)

Transient-state simulations of postcollapse conditions included additional boundary conditions in 

model layer 5 (lower aquifer) for the first simulation 

period, which represented ground-water discharge into 

the mine from the overlying aquifer system. Headdependent boundaries were specified in two model 

cells—one above each of the two rubble zones associated with the two collapses. The first of these additional 

boundaries, which represented the collapse over panel 

2-Yard South (fig. 15), was active at the start of the first 

simulation period (March 1994); the second boundary 

became active 1 month later to represent the collapse 

over panel 11-Yard West (April 1994). These boundaries were assigned heads equal to the aquifer-bottom 

(bedrock surface) altitude and arbitrary conductance 

(C) values (eq. 5) large enough that flow through the 

boundaries would be limited by the hydraulic conductivity of the lower aquifer, rather than that of the rubble. 

These boundary conditions were removed at the start of 

the second simulation period, which represented recovery of ground-water levels once the mine was filled.

The boundaries are considered reasonable representations of actual conditions during flooding because 

the mine was at atmospheric pressure, and the hydraulic gradient controlling discharge from the lower aquifer depended solely on the head in the aquifer. The 

hydraulic conductivity of the rubble zone connecting 

the aquifer to the mine is unknown but is assumed to be 

larger than that of the lower aquifer. Partial dewatering 

of the lower aquifer could have occurred above the rubble zone and formed a seepage face that, in effect, 

decreased the saturated thickness of the aquifer. Butler 

(1957) investigated the effects of seepage faces on 

ground-water flow and found that the saturated thickness could be decreased by as much as 50 percent at 

such boundaries. Decreasing the boundary conductance by 50 percent increased SSE more than 100 perTable 7. Parameter values estimated for model layer 1 

(upper aquifer in Genesee Valley aquifer system, 

Livingston County, N.Y.), through nonlinear regression; 

also model error in steady-state simulation 3D-A and 

measured mean stream discharges 

[ft3/s, cubic feet per second] 

Variable Value

Aquifer property

Recharge, inches per year

alluvial and deltaic sediments 20

fine-grained sediments 3.9

upland runoff 0.8a

a

Recharge derived from 90 square miles of upland area.

Hydraulic conductivity, feet per day

alluvial sediments 280

fine-grained sediments 0.93

deltaic sediments 500

Model error

Sum of squared errors, feet squared 2,351

Standard error in heads, feet 8.7

Mean stream discharge, ft3/s

Genesee River (40 ft3

/s measured) 31

Canaseraga Creek (40 ft3

/s measured) 45
48 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

cent, however, and decreased the simulated discharges 

into the salt mine to less than 40 percent of those measured; therefore, the saturated thickness over the collapse area was not appreciably decreased in transientstate simulations.

The middle aquifer was assumed to remain 

under confined conditions throughout the transientstate simulations, although unconfined conditions were 

measured in parts of this aquifer in the Beards Creek 

Valley and near the Fowlerville Moraine. The transition 

from confined to unconfined conditions was not represented in the model because the altitude of the top of 

the middle aquifer could not be estimated precisely. As 

a result, the storage coefficent specified for the middle 

aquifer is too low in these areas because more water is 

released from storage under unconfined conditions 

than under confined conditions. The additional volume 

of water released is probably insignificant, however, 

because these areas represent only a small part of the 

total aquifer area.

Drawdowns

The distribution of drawdowns in the lower aquifer in January 1996 as computed by transient-state simulation with model 3D-A (fig. 27) is similar to the 

measured distribution (fig. 18). Computed drawdowns 

in wells near the collapse area exceeded the actual 400-

ft drawdowns by less than 10 ft and are about 60 ft less 

than the actual 110-ft drawdowns in wells 7 mi to the 

south. Computed drawdowns also are generally about 

15 ft less than the actual 50-ft drawdowns in wells 8 mi 

north of collapse area, although they are underpredicted in some wells in this area and overpredicted in 

others. The standard error in heads computed for the 

confined aquifers was 33 ft, and the range in heads was 

100 to 735 ft.

Locations II and IV. The simulated change in 

drawdown with time is in close agreement with drawdowns measured at wells near the collapse area (location II). Computed and measured drawdowns in both 

the middle and lower aquifers match particularly well 

at locations II and IV (figs. 28 A, C). The maximum 

recorded drawdown at each of these locations is accurately simulated, but no data are available for comparison with drawdowns that occurred soon after the 

collapse because the wells were not completed until 1 

to 2 years thereafter. Water levels in well Lv368 (fig. 

28A) recovered more slowly than simulated early in the 

recovery period, perhaps because natural gas in the 

lower aquifer temporarily dewatered the aquifer at this 

location.

Location III. The model overpredicted drawdowns at location III (fig. 28B) and provided a particularly poor match in the middle aquifer (where 

measured drawdowns were relatively small) given its 

proximity to the collapse area. This disparity, and the 

differences in the isotopic content between waters near 

location III and from the rest of the confined-aquifer 

system, indicate that the confined aquifers at this location are hydraulically isolated. Stratigraphic information to document this lack of continuity is unavailable, 

however; therefore, no changes were made in the 

model design to decrease the error in computed drawdowns at this location. For this reason, measured drawdowns at well Lv351 (location III, middle aquifer) 

were not included in the nonlinear regression.

Location V. Computed drawdowns at location V, 

7 mi south of the collapse area (fig. 28D) were underpredicted by 80 ft in the middle aquifer and 60 ft in the 

lower aquifer. The drawdown distribution at this location is unusual in that measured drawdowns in the middle aquifer (135 ft) were 25 ft greater than in the lower 

aquifer (110 ft). This indicates that (1) the two confined 

aquifers are hydraulically connected near, or somewhere north of, this location, and (2) the hydraulic conductivity and (or) thickness and width of the lower 

aquifer decreases south or east of the area of hydraulic 

connection and thereby causes steeper gradients than in 

the middle aquifer. The kame deposit mapped near 

Sonyea (fig. 8) indicates that the ice margin temporarily halted there during a recession; if a large thickness of coarse-grained ice-contact material 

accumulated nearby during the deposition of the lower 

confining layer, this material would now form a 

hydraulic connection between the confined aquifers. 

The vertical hydraulic conductivity of the lower confining layer, which separates the middle aquifer from the 

lower aquifer, was increased locally by a factor of 10 in 

the model to represent the assumed hydraulic connection (fig. 25B). The computed drawdowns in the two 

confined aquifers were nearly equal as a result of this 

change in model design but were still less than the measured drawdowns.

Location I. The model variably underpredicted 

and overpredicted drawdowns at the site 8 mi north of 

the collapse area, near the Fowlerville moraine. The 

match for wells Lv483 and Lv496 (screened in the 

middle and lower aquifers near this location, respectively) was reasonable (fig. 28E). Drawdowns in the 
SIMULATION OF GROUND-WATER FLOW 49

408

408

258

436

63

63

39

39

36

15

15

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390

20

20A

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20A

20A

390

   

Conesus

Creek

Conesus

Lake

Genesee

River

Beards

Creek

Keshequa Creek

Canaseraga

Creek

Genesee

River

Avon

Dansville

Geneseo

SALT MINE

COLLAPSE

AREA

Mount

Morris

Cuylerville

Location I

Location II

Location III Location IV

Location V

Lv 436

Sonyea

25

50

75

100

125

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77° 52' 30"

42° 52' 30"

42° 37' 30"

45'

77° 45'

Base from U.S. Geological Survey digital data, 1:100,000, 1983 0 2 4 MILES

0 2 4 KILOMETERS

NEW YORK

LOCATION MAP

Study

area

EXPLANATION

Lower aquifer

Line of equal water-level

 decline—Contour interval

 25 feet

Boundary of model area

Multiple well cluster

Well in monitoring network

Difference between predicted

 and observed head, in feet

 Less than –20

 –10 to –20

 0 to –10

 0 to 10

 10 to 20

 Greater than 20

p

p

p

p

p

p

p

p

250

Figure 27. Distribution of drawdown in lower aquifer in Genesee Valley, Livingston County, N.Y. in January 1996, and 

range of weighted residuals computed with values from transient-state simulation (model 3D-A).
50 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

A. Location II, wells Lv348 and Lv368.

B. Location III, wells Lv351 and Lv350.

C. Location IV, wells Lv361 and Lv 360.

D. Location V, wells Lv366 and Lv367.

E. Site near Fowlerville moraine, wells Lv483 and Lv496.

Well Lv 348, middle aquifer Well Lv 368, lower aquifer

Well Lv 351, middle aquifer Well Lv 350, lower aquifer

Well Lv 361, middle aquifer Well Lv 360, lower aquifer

Well Lv 366, middle aquifer Well Lv 367, lower aquifer

Well Lv 483, middle aquifer Well Lv 496, lower aquifer

HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL 600

550

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350

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150

HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL 550

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HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL 600

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HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL 600

550

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450

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350

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HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL

HYDRAULIC

HEAD, IN FEET

ABOVE SEA LEVEL

HYDRAULIC

HEAD, IN FEET

ABOVE SEA LEVEL

600

550

500

450

400

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300

250

HYDRAULIC HEAD,

IN FEET ABOVE SEA LEVEL600

550

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250

0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900

0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900

0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900

0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900

0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900

600

550

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450

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HYDRAULIC

HEAD, IN FEET

ABOVE SEA LEVEL

HYDRAULIC

HEAD, IN FEET

ABOVE SEA LEVEL

600

550

500

450

400

600

550

500

450

400

TIME SINCE COLLAPSE, IN DAYS TIME SINCE COLLAPSE, IN DAYS

EXPLANATION

Hydraulic head, in feet above sea level

 Measured

 Simulated

Figure 28. Water levels measured in middle and lower aquifers in Genesee Valley, Livingston County, N.Y. during 29 

months after collapses at Retsof salt mine, and values simulated by transient-state simulation (model 3D-A): A. 

Location II, wells Lv348 and Lv368. B. Location III, wells Lv351 and Lv350. C. Location IV, wells Lv361 and Lv360. D.

Location V, wells Lv366 and Lv367. E. Site near Fowlerville moraine, wells Lv483 and Lv496. (Well locations are shown 

in figs. 4 and 18.)
SIMULATION OF GROUND-WATER FLOW 51

lower aquifer near the center of the valley and south of 

the Fowlerville moraine were generally underpredicted 

by 20 to 30 ft, whereas those on the west side of the valley near the hamlet of Fowlerville were overpredicted 

by 30 to 50 ft. The glacial stratigraphy in this area is 

poorly defined, and the simplified representation of the 

aquifer system in the model clearly does not accurately 

represent the distribution of drawdown in this part of 

the Genesee Valley.

Water budget

The computed water budget for the entire aquifer 

system during the first simulation period (March 1994 

to January 1996), which represented the period of 

drainage from the aquifer to the mine (table 8), was 

similar to that computed by the steady-state (precollapse) simulations (table 6). Ground water released 

from storage provided about 11 percent of the total 

inflow in the water budget for the entire aquifer system 

and provided most of the water that discharged to the 

mine. This result is consistent with measured tritium 

concentrations at location II (near the collapse area), 

which indicated the ground water is more than 40 years 

old, because ground-water age at location II would be 

younger (and tritium concentrations larger) if most of 

the water that discharged to the mine were derived from 

recent recharge. The computed water budget for the 

confined part of the aquifer system (model layers 2 

through 5) indicates that most of the inflow (58 percent) was derived from storage in the lower aquifer, and 

that 15 percent was derived from storage from the rest 

of the confined system; another 24 percent of the total 

inflow was derived from vertical leakage to the confined-aquifer system from the upper aquifer along the 

valley walls and through deltaic deposits.

Table 8. Simulated water budget for aquifer system in Genesee Valley, Livingston County, N.Y., during period of mine 

flooding, March 1994 through January 1996. A. Entire aquifer system. B. Confined-aquifer system 

[Flow volumes are in millions of cubic feet; <, less than] 

Inflow Discharge

Source Volume

Percentage 

of total Location Volume

Percentage 

of total

A. Entire aquifer system (model layers 1 through 5)

Storage 840 11 River and streams 6,390 84

Recharge and upland runoff 3,720 49 Underflow 190 3

River and streams 2,430 32 Salt mine 1,020 13

Underflow 610 8

TOTAL 7,600 100 TOTAL 7,600 100

B. Confined part of aquifer system (model layers 2 through 5)

Storage

Upper confining layer 7 < 1

Middle aquifer 66 6

Lower confining layer 90 9

Lower aquifer 614 58

Underflow Underflow 

Middle aquifer 20 2 Middle aquifer 1 < 1

Lower aquifer < 1 < 1 Lower aquifer 23 3

Vertical leakage: Vertical leakage:

Valley walls 203 19 Valley walls 6 < 1

Deltaic deposits 50 5 Salt mine 1,020 97

TOTAL 1,050 100 TOTAL 1,050 100
52 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Nearly all (97 percent) of the water discharged 

from the confined-aquifer system flowed into the salt 

mine. Computed discharge to the mine in March 1994 

(20 ft3

/s) was nearly twice the estimated discharge (11 

ft3

/s), and the computed discharge for September 1994 

(28 ft3

/s) was little more than half the estimated discharge (45 ft3

/s). The estimated volume of water discharged to the mine was 1.1 × 109

 ft3, which represents 

55 to 60 percent of the mine volume, as calculated from 

the tonnage of salt removed (1.34 × 108

 tons) and an 

extraction ratio of 0.66 (Henry Klugh, oral commun., 

Akzo Nobel Salt, Inc., 1998). An alternative estimate of 

the extraction ratio (0.55) based on maps of the mined 

area indicates that the volume of ground-water discharge is equal to about 70 percent of the mine volume 

(Richard Young, oral commun., Geological Sciences, 

State University of New York-Geneseo, 1997). The 

underprediction of discharge to the mine in September 

1994 indicates that drawdowns in the aquifer system 

were generally greater than simulated, particulary near 

location V at Sonyea, where they were underpredicted 

by 60 to 80 ft.

Estimates of aquifer properties

The parameter values estimated by nonlinear 

regression for the six aquifer properties are listed in 

table 9, together with their approximate individual confidence intervals and coefficients of variation. The 

parameter values were log-transformed to ensure that 

the values remained positive in the regression. The confidence intervals were computed based on the method 

described in Hill (1992) under the assumption that the 

model is correct and linear in the vicinity of the optimum set of values, and that the parameter values are 

normally distributed. The reported statistics are only 

Table 9. Optimum parameter values estimated for confined aquifer system (model layers 2 through 5) in Genessee 

Valley, Livingston County, N.Y., through nonlinear regression in transient-state simulation (model 3D-A), and their 

approximate confidence intervals at 95-percent level, and discharge to mine estimated from volume of flooded area in 

March and September 1994.

[ft/d, feet per day, ft2

, feet squared; ft-1, per foot; ft3/s, cubic feet per second.].

Variable Value

Approximate individual 

confidence interval

Coefficient of 

variation (percent)a

a

Coefficient of variation on log-transformed parameter.

Aquifer property

Hydraulic conductivity, ft/d 

Middle aquifer 3.7 1.3 - 11 30

Lower aquifer 300 180 - 480 26

Vertical hydraulic conductivity of 

 lower confining layer, ft/d 

Collapse area 2.7 × 10-2 2.3 × 10-4 - 3.1 37

Remainder of layer 1.2 × 10-3 4.1× 10-4 - 3.2 × 10-3 4

Specific storage, ft-1

Middle aquifer 6.9 × 10-5 1.3 × 10-5 - 3.6 × 10-4 5

Lower aquifer 2.9 × 10-4 1.4 × 10-4 - 6.2 × 10-4 3

Model error

Sum of squared errors, ft2 4.04 × 105

Standard error in heads, ft 32.9

Discharge to mine, ft3/s Simulated

Estimated from volume

of flooded area

March 1994 20 11

September 1994 28 45
SIMULATION OF GROUND-WATER FLOW 53

approximate, however, because the model does not 

meet these assumptions, but they indicate qualitatively 

the relative reliability of the optimum parameter values.

Hydraulic conductivity. Hydraulic conductivity 

(K) of the lower aquifer was estimated to be 300 ft/d, 

which is about 60 percent of the value estimated from 

specific-capacity data from well Lv91 in Mt Morris, 

and within the range of values reported for sand and 

gravel (Freeze and Cherry, 1979). The estimated 

hydraulic conductivity of the middle aquifer was about 

4 ft/d, which is equivalent to values commonly reported 

for silty sand. The coefficients of variation for the estimated log K-values (26 percent and 30 percent, respectively) indicate that the model was sensitive to these 

parameters and that changing the optimum values 

would increase model error.

The estimated transmissivity of the lower aquifer 

is 7,500 ft2

/d, of which 15 percent (1,100 ft2/d) could 

result from fractures at the bedrock surface where the 

aquifer is underlain by the Onondaga Limestone. A 

separate regression was done in which the hydraulic 

conductivity of the lower aquifer was assumed to be 15 

percent greater in areas overlying the subcrop area of 

the Onondaga Limestone than in the remainder of the 

valley. The addition of bedrock fracture transmissivity 

to the lower aquifer did not improve the model fit, however, and resulted in no significant change in model 

error or estimated parameter values.

The estimated vertical hydraulic conductivity 

(Kv) values for the lower confining layer were 2.7 ×

10-2 ft/d in the collapse area and 1.2 × 10-3 ft/d for the 

remainder of the layer. The larger Kv value estimated 

for the collapse area is consistent with the hypothesis 

that the permeability of the confining layer was 

increased by subsidence, but the large confidence interval and coefficient of variation associated with the estimate indicates that a reliable value cannot be 

determined from the available data.

Specific storage. Specific storage Ss of a confined 

aquifer equals the volume of water released from storage per unit volume of aquifer under a unit decline in 

hydraulic head. Specific storage (Ss) values estimated 

for the lower and middle aquifers were 2.9 × 10-4 ft-1

and 6.9 × 10-5 ft-1, respectively. Typical values of Ss

corresponding to elastic compression of similar aquifers range from 1 × 10-6 ft-1 to 3 × 10-6 ft-1, as indicated 

by extensometer measurements of land subsidence 

caused by pumping (Ireland and others, 1984; Riley, 

1998). Most of these values were derived from alluvial 

basins in the southwestern United States; a similar 

value (2.3 × 10-6 ft-1) was also calculated for a glacial 

sand and gravel aquifer in Alaska (Nelson, 1982). The 

coefficients of variation for the estimated log Ss values 

were extremely small (3 to 5 percent), and assigning 

the lower aquifer a lower specific storage value of 2.3 

× 10-6 ft-1 greatly increased model error. No combination of parameter values that include this low Ss value 

was found through nonlinear regression that provided 

an acceptable match to the measured water levels, 

especially during the recovery (see, for example, fig. 

29). The larger-than-expected values of specific storage 

obtained through nonlinear regression can be explained 

by the exsolution of natural gas, discussed in the next 

section.

Remaining aquifer properties. The values for 

seven remaining aquifer properties that were specified 

as fixed in the nonlinear regression are listed in table 

10. The vertical hydraulic conductivity value for the 

upper confining layer was based on permeameter tests 

that used core samples of the lacustrine sediments and 

till (Alpha Geoscience, 1996c). The horizontal hydraulic conductivity value specified for the lower confining 

layer, and the vertical hydraulic conductivity value 

specified for the valley walls, were obtained through 

preliminary regressions that decreased model error but 

did not converge to optimum values. Storage values 

specified in the model are within the range of those 

reported in Ireland and others (1984).

Table 10. Fixed parameter values used in nonlinear 

regression for transient-state simulation (model 3D-A) of 

confined aquifer system in Genessee Valley, Livingston 

County, N.Y.

[ft/d, feet per day; ft-1, per foot.]

Hydraulic property Value

Horizontal hydraulic conductivity, ft/d

Lower confining layer .1

Vertical hydraulic conductivity, ft/d

Upper confining layer 1.0 × 10-5

Valley walls 2.5

Specific storage, ft-1

Upper confining layer 1.0 × 10-5

Lower confining layer 5.0 × 10-6

Valley walls 1.0 × 10-6

Specific yield of unconfined aquifer .25
54 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Model bias

Model 3D-A, where optimum parameter values 

obtained through nonlinear regression were used, represents the drawdown and recovery of water levels reasonably well, and the computed maximum drawdown 

in the collapse area and the extent of water-level 

declines in the middle and lower aquifers match the 

measured values closely. The weighted residuals 

(wi

1/2ei

) indicate, however, that the model is biased and 

thus may not correctly represent certain unidentified 

processes or properties within the aquifer system. 

Although the mean of the weighted residuals (0.13 ft) 

is near zero, which indicates that the regression succeeded in minimizing parameter error, the distribution 

of residuals about the mean is not random, as would be 

expected if the model accurately represented all aspects 

of the aquifer system.

A plot of weighted residuals and simulated heads 

(fig. 30) shows two clusters of residuals. Residuals in 

cluster A indicate significant model bias—heads in 

wells near the collapse area are generally underpredicted (drawdowns were greater than measured), and 

those in wells far from the collapse area are overpredicted (drawdowns were less than measured). This discrepancy is partly the result of exsolution of natural gas 

from ground water—a process that was not represented 

in the model. Model bias also could result from the uniform hydraulic-conductivity distribution assumed in 

the model, particularly near location V, where residuals 

are largest and local variation in hydraulic conductivity 

could account for the overprediction of head. StratiWell Lv368

Well Lv91 Well Lv425

Well Lv367

A. Location II, well Lv368. B. Location V, well Lv367.

C. Site near Mount Morris, well Lv91. D. Site near Fowlerville moraine, well Lv425.

0 900 100 200 300 400 500 600 700 800 100

550

150

200

250

300

350

400

450

500

HEAD, IN FEET

0 900 100 200 300 400 500 600 700 800 150

600

200

250

300

350

400

450

500

550

HEAD, IN FEET

0 100 200 300 400 500 600 700 800 900

TIME SINCE COLLAPSE, IN DAYS

600

300

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500

550

HEAD, IN FEET

0 100 200 300 400 500 600 700 800 900

TIME SINCE COLLAPSE, IN DAYS

600

300

350

400

450

500

550

HEAD, IN FEET

EXPLANATION

Hydraulic head, in feet above sea level

 Measured

 Computed with specific storage values estimated by regression

 Computed with published value of specific storage 2.3 × 10–6

ft–1

Figure 29. Water levels measured in the lower aquifer in Genesee Valley, Livingston County, N.Y. during 29 months 

after collapses at Retsof salt mine, and values simulated by transient-state simulation (model 3D-A) from two 

alternative values of specific storage: A. Location II, well Lv368. B. Location V, well Lv367. C. Site near Mt. Morris, well 

Lv91. D. Site near Fowlerville moraine, well Lv425. (Well locations are shown in figs. 4 and 18.)
SIMULATION OF GROUND-WATER FLOW 55

graphic data are not available to support this hypothesis, however. Cluster B, in contrast, displays no 

apparent bias and generally corresponds to heads 

greater than 490 ft measured in wells near the Fowlerville Moraine and in the Beards Creek Valley. Autocorrelation in the residuals resulting from multiple 

measurements made at different times at the same location explains some trends in the cluster, but the effect 

of autocorrelation on regression estimates of parameter 

values is unknown.

Model Results

Results of model simulations indicate that exsolution of natural gas from ground water lessened the 

water-level declines near the collapse area and delayed 

the propagation of drawdowns into areas distant from 

the collapse. Hydraulic heads simulated by 12.4-yr 

transient-state simulations indicate that water levels 

will return to precollapse conditions by about the year 

2006. Ground-water flow paths computed from steadystate and transient-state simulations indicate that 

water-level declines in the confined aquifers after the 

mine collapse reversed the natural hydraulic gradient in 

the northern part of the Genesee Valley, inducing saline 

water from water-bearing zones in the bedrock to flow 

southward into the lower aquifer.

Effect of Natural Gas on Specific Storage

Specific storage values reported from studies of 

land subsidence are much smaller than those required 

to simulate the relatively slow decline and recovery of 

water levels measured in the Genesee Valley after the 

mine collapse. Specific storage Ss of a confined aquifer 

is usually a constant, defined as

, (9)

where ρg = specific weight of water γ [ML-2T-2],

α = compressibility of aquifer material 

[ML-1T-2]

-1,

β = fluid compressibility [ML-1T-2]

-1and

n = porosity [dimensionless].

A decrease in hydraulic head results in a decrease in 

fluid pressure p and an increase in effective stress σe

(see eq. 1). The release of water from storage in 

response to (1) aquifer compression through the 

increase in σe (ρgα), and (2) expansion of water 

through the decrease in p (ρgnβ) are accounted for in 

equation 9.

The larger Ss values obtained by the regression 

indicate that more water was released from storage 

than can be accounted for by the compressibility of 

water and aquifer material alone; therefore, the release 

of dissolved gas was examined as a factor in the discrepancy. The releases of biogenic gas from several 

wells affected by water-level declines indicate that gas 

had exsolved from ground water and was present as a 

free phase over a wide area in the lower aquifer. Exsolution of gas could significantly increase specific storage because (1) the exsolved gas would displace water 

in the pore volume, forcing additional releases from 

storage, and (2) gas compressibility is about 100 times 

greater than aquifer compressibility under the pressures measured in the confined-aquifer system. A gaspartitioning equation was developed to compute the 

contribution to specific storage provided by the exsolution of a free gas phase.

The gas-partitioning equation relates the volume 

of gas in the vapor phase Vv to the ambient pressure p

and can be derived from the mass equation for gas in an 

arbitrary volume of aquifer material Va

, (10)

where MT = total mass of gas [M],

Cw = concentration of gas in water [ML-3],

Vw = volume of water [L3

], 

Cv = concentration of gas in vapor [ML-3], and

Vv = volume of vapor [L3

].

Ss = ρg( ) α + nβ

MT = CwVw + CvVv

bias

A

B

Underpredicted heads (more drawdown than observed)

Autocorrelation

 at well Lv436

Overpredicted heads (less drawdown than observed)

80

100

–100

–80

–60

–40

–20

0

20

40

60

WEIGHTED RESIDUAL, IN FEET

100 200 300 400 500 600 700

SIMULATED HEAD, IN FEET ABOVE SEA LEVEL

Figure 30. Simulated heads and weighted residuals 

computed from transient-state simulation (model 3D-A) 

of aquifer system in Genesee Valley, Livingston County, 

N.Y.
56 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

The sum of the water- and vapor-filled volumes equals 

the volume of pore space and is expressed as

. (11)

Combining equations 10 and 11 and solving for Vv

gives the gas-partitioning equation

(12)

Methane solubility in water follows Henry’s law 

for the pressure range and temperature (150 to 240 psi 

and 60 ̊ F) that occurred during mine flooding (Lekvam 

and Bishnoi, 1997). From Henry’s law, the concentration of methane in water Cw at pressure p can be computed from the methane solubility C0 measured at a 

reference pressure p0 by

, (13)

and is related to the methane concentration in the 

vapor-phase pressure Cv by the dimensionless Henry’s 

law constant Kh as

. (14)

Assuming the pore space was initially saturated with 

water (Vw = nVa; Vv = 0), and the water was saturated 

with methane (MT = CwVw) at a pressure pinit that prevailed before the mine collapse, then from eqn. 13

. (15)

Combining equations 13, 14 and 15 with equation 12 

and simplifying gives

. (16)

or, in units of head h:

. (17)

The specific storage resulting from gas exsolution Ssg is the volume of gas produced (water released) 

from the volume of aquifer material Va under a unit 

change in pressure (hinit - h= 1) or

. (18)

where h = hydraulic head calculated above the midpoint of the aquifer.

Equations 17 and 18 indicate that the specific 

storage of a confined aquifer containing dissolved gas 

and undergoing a water-level decline is not constant, 

but is a function of head (pressure), which varies temporally and spatially. Increasing fluid pressure during 

water-level recovery would result in dissolution of the 

released gas and would lower Ssg values as the volume 

of free gas in the pore volume declined.

The potential magnitude of gas exsolution in the 

lower aquifer was calculated assuming that the methane concentration in water (Cw) was at saturation when 

the mine collapse occurred. Specific storage at a model 

cell near the collapse area (location II) was calculated 

for each time step from equation 18 with computed 

heads from the 29-month transient-state simulation 

(model 3D-A), and values of n = 0.3 and Kh = 27.02 

(Schwarzenbach and others, 1993). The combined specific storage Ss′ was computed as the sum of Ssg (eq. 

18) and Ss (eq. 9) and is expressed as

, (19)

where Ss = 2 × 10-6 ft-1, a value representative of aquifer compressibility.

Computed specific storage values Ssg in the 29-

month transient-state simulation decreased when water 

levels recovered to represent dissolution of the gas. 

This computation assumed that the gas was trapped 

within the confined aquifers and did not escape from 

the system, and that the time required for gas dissolution was shorter than the time steps used in the transient-state simulation (2 to 120 days).

The resulting Ss′ values near location II, the point 

of maximum water-level drawdown at the collapse area 

(fig. 31), ranged from 2.7 × 10-5 ft-1 to 1.8 × 10-4 ft-1. 

Vw + Vv = nVa

Vv

MT CwnVa –

Cv Cw – = -------------------------------

Cw C0

p

p0

= -----

Cv = KhCw

MT C0

pinit

p0

= ----------nVa

Vv

pinit ( ) – p nVa

p Kh ( ) – 1 = ----------------------------------

Vv

hinit ( ) – h nVa

h Kh ( ) – 1 = ---------------------------------

Ssg

n

h Kh ( ) – 1 = -----------------------

Ss′ Ss S = + sg
SIMULATION OF GROUND-WATER FLOW 57

The Ss′ value was initially greater (8.0 × 10-5 ft-1) near 

location I in the north (well Lv496 in fig. 32), where the 

lower aquifer (depth 210 ft) is shallower than at location II (depth 480 ft), because the lower pressure at 

location I allowed greater expansion of exsolved gas. 

The maximum Ss′ value at location I (1.2 × 10-4 ft-1) 

was less than the value at location II, however, because 

water-level declines were less than those near the collapse area. The value of Ss′ at location V in the south, 

where the aquifer depth was more than 700 ft, ranged 

from 1.8 × 10-5 ft-1 to 1.9 × 10-5 ft-1. Unlike specific 

storage values at location II, the values at locations I 

and V continued to increase after the mine was filled in 

January 1996 (fig. 32) because water levels continued 

to decline at these locations and did not begin to 

recover until about 6 months later. The maximum percentage of pore volume occupied by gas was calculated 

to be 7 percent at the collapse area (location II) and less 

than 1 percent at locations I and V.

The effects of gas exsolution were incorporated 

into the computer program MODFLOWP (model 3DB in table 4) in which the combined specific storage Ss′

(eq. 19) was computed in each model cell for every 

time step. Two simulations were run with model 3D-B. 

In the first simulation, Cw was assumed at saturation 

throughout the confined aquifers, so that gas exsolution 

began with the onset of water-level declines. In the second simulation, the methane concentration was below 

saturation in parts of the middle and lower aquifers, 

such that

, (20)

where h0 = head at which Cw is at saturation. In the second simulation gas exsolution did not occur until 

declining water levels reduced the solubility to the dissolved gas concentration at the threshold h0.

Optimum parameter values were estimated in 

these two simulations by nonlinear regression with 

UCODE (Poeter and Hill, 1998). The regression 

method in UCODE is similar to that used in the model 

3D-A, except that sensitivities of model parameters 

required by the UCODE method are estimated through 

a perturbation technique, rather than computed directly 

from an analytical expression, as in MODFLOWP. The 

set of parameters estimated in the first regression was 

the same set estimated in model 3D-A, while two additional parameters representing h0 values for the middle 

and lower aquifers were estimated in the second regression. Specific storage values estimated with model 3DB for both regressions (table 11) were similar and near 

the upper end of the range reported for sand and gravel 

aquifers (2.3 × 10-6 ft-1) in studies of land subsidence. 

Hydraulic conductivity of the lower aquifer was estimated to be 230 ft/d assuming methane concentration 

at saturation or 180 ft/d assuming methane concentraSsg 0 for h h0 = , ( ) <

Lv368, location II

0 50 100 150 200 250 300 350 400 450

DRAWDOWN, IN FEET

SPECIFIC STORAGE × 105, IN FEET–1

0.1

100

0.2

0.5

0.7

1.0

2

5

7

10

20

50

70

EXPLANATION

Specific storage

 Ss', water and gas

 Ss, without gas

Figure 31. Effect of gas exsolution and expansion on 

specific storage values in lower aquifer during 

drawdown at location II near collapse area in Genesee 

Valley, Livingston County, N.Y., March 1994 through 

January 1996. (Location is shown in fig. 4.)

Lv368

Lv496

Lv367

0 100 200 300 400 500 600 700 800 900

TIME SINCE COLLAPSE, IN DAYS

SPECIFIC STORAGE × 105, IN FEET–1

0.1

100

0.2

0.5

0.7

1.0

2

5

7

10

20

50

70

EXPLANATION

Specific storage

 Ss', water and gas, Lv368, location II

 Ss', water and gas, Lv496, near Fowlerville moraine

 Ss', water and gas, Lv367, location V

 Ss, without gas

Figure 32. Change in specific storage during drawdown 

and recovery at selected wells screened in lower aquifer 

in Genesee Valley, Livingston County, N.Y., during 29 

months after collapses at Retsof salt mine.
58 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

tion below saturation. These values are less than the 

300 ft/d estimated with model 3D-A, in which the initial specific storage value was larger and required a 

larger hydraulic conductivity to simulate the rapid 

propagation of drawdown through the lower aquifer. 

The methane concentrations corresponding to the estimated ho values in the second regression were 

65 mg/L in the middle aquifer and 390 mg/L in the 

lower aquifer.

Including the effects of gas exsolution in model 

simulations caused little change in model error (table 

11). Drawdowns simulated by model 3D-B were about 

the same as those computed with model 3D-A for areas 

near the collapse (fig. 33A) but matched more closely 

the measured drawdowns in areas farther away (fig. 

33B, C). Drawdowns far from the collapse area were 

underpredicted (fig. 33D), indicating that the computed 

Ss′-values were still too large in these areas. Computed 

water levels also recovered much sooner than those 

measured. Some of the free gas phase that accumulated 

in the lower aquifer near the collapse area was thermogenic and originated from deeper reservoirs, but the 

volume of thermogenic gas within the lower aquifer is 

unknown and cannot be accounted for in model simulations. As a result, model 3D-B underestimates the 

volume of water released from storage near the collapse 

area and overestimates the volume released far from the 

collapse, producing a trend of underpredicting drawdowns in wells far from the collapse area. Displacement of water from the pore volume by thermogenic 

gas and variability in the initial methane concentration 

within the lower aquifer probably account for much of 

the remaining model error.

The exsolution of natural gas from ground water 

adequately explains the response of water levels in the 

confined part of the aquifer system to the collapse 

within the mine. The release of additional water from 

storage in response to gas exsolution lessened waterlevel declines near the collapse area and slowed the 

propagation of drawdowns into areas away from the 

Table 11. Optimum parameter values estimated for confined aquifer system (model layers 2 through 5) in Genessee 

Valley, Livingston County, N.Y., through nonlinear regression in transient-state simulation with models 3D-A (constant 

specific storage) and 3D-B (variable specific storage values based on gas exsolution).

[ft/d, feet per day, ft2, feet squared; ft-1, per foot; —, not estimated].

Model 3D-B

with methane concentration:

Variable Model 3D-A At saturation Less than saturation

Aquifer property

Hydraulic conductivity, ft/d 

Middle aquifer 3.7 3.7 3.1

Lower aquifer 300 230 180

Vertical hydraulic conductivity of 

 lower confining layer, ft/d 

Collapse area 2.7 × 10-2 2.7 × 10-2 3.0 × 10-2

Remainder of layer 1.2 × 10-3 1.2 × 10-3 1.4 × 10-3

Specific storage, ft-1

Middle aquifer 6.9 × 10-5 2.6 × 10-6 2.3 × 10-6

Lower aquifer 2.9 × 10-4 2.5 × 10-6 2.3 × 10-6

Threshold head ho, ft

Middle aquifer — — 86

Lower aquifer — — 520

Model error

Sum of squared errors, ft2 4.04 × 105 4.17 × 105 3.93 × 105

Standard error in heads, ft 32.9 33.3 32.4
SIMULATION OF GROUND-WATER FLOW 59

collapse. Uncertainty remains, however, as to the initial 

distribution of gas concentrations within the confined 

aquifers, the fate of the exsolved gas and its effect on 

the relative permeability of the confined-aquifer system.

The slower-than-simulated recovery of water 

levels suggests that one or more unknown but important processes are not represented in model 3D-B. For 

example, although the rate of gas exsolution was probably rapid because gas was present throughout the pore 

volume, the rate of gas dissolution could be limited by 

the size of the interface separating gas-filled pores from 

water-filled pores. A relatively high rate of gas exsolution followed by a lower rate of gas dissolution could 

explain the measured rapid drawdown of water levels 

in the confined aquifers followed by a relatively slow 

water-level recovery. Some of the exsolved gas could 

have remained trapped within the pore volume, or 

migrated upward toward land surface, rather than redissolving as water levels recovered. Laboratory studies 

have shown that displacement of water by gas can 

cause gas to become trapped in pore spaces and thereby 

reduce the effective porosity of aquifer material 

(Czolbe, 1997). 

If gas occupied 7 percent of the pore volume in 

the lower aquifer at location II, as computed with 

model 3D-B, the relative permeability of aquifer material to water (Kw) could decrease by as much as 50 percent if the gas were distributed uniformly throughout 

the pore volume (Coats and Richardson, 1967). This 

would not prevail for long, however, because the gas 

would soon migrate upward and form bubbles that 

Well Lv368

Well Lv425

A. Location II, well Lv368.

D. Site near Fowlerville moraine, well Lv425.

Well Lv91

Well Lv367

B. Location V, well Lv367.

C. Site near Mount Morris, well Lv91.

0 900 100 200 300 400 500 600 700 800 100

550

150

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500

HEAD, IN FEET

0 900 100 200 300 400 500 600 700 800 150

600

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550

HEAD, IN FEET

0 100 200 300 400 500 600 700 800 900

TIME SINCE COLLAPSE, IN DAYS

600

300

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550

HEAD, IN FEET

0 100 200 300 400 500 600 700 800 900

TIME SINCE COLLAPSE, IN DAYS

600

300

350

400

450

500

550

HEAD, IN FEET

EXPLANATION

Hydraulic head, in feet above sea level

 Measured

 Computed with specific storage values estimated by regression

 Computed with gas exsolution

Figure 33. Water levels measured in lower aquifer in Genesee Valley, Livingston County, N.Y. during 29 months after 

collapses at Retsof salt mine, and values simulated by transient-state simulations with models 3D-A (constant specific 

storage) and 3D-B (variable specific storage values based on gas exsolution with methane concentrations below 

saturation): A. Location II, well Lv368. B. Location V, well Lv367. C. Site near Mt. Morris, well Lv91. D. Site near 

Fowlerville moraine, well Lv425. (Well locations are shown in fig. 4.)
60 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

would be trapped by the lower confining layer, and this 

would reduce the saturated thickness (and transmissivity) by only 7 percent. If the gas migration were 

impeded, however, the decreased relative permeability 

could delay water-level recovery in some parts of the 

lower aquifer. Additionally, the upward migration of 

gas along the valley walls could reduce the Kw of permeable sediments that provide hydraulic connection 

between the confined aquifers and land surface and 

thereby decrease the potential for recharge and slow the 

recovery of water levels.

A two-phase flow model that represents water 

and gas movement could be used to simulate gas 

migration and its potential effects on relative permeability, but the use of such a model for this setting 

would be impeded by uncertainty regarding the initial 

gas concentration, the migration pathways, and the altitude and topography of the bottom of the lower confining layer, which probably forms a barrier to upward gas 

migration.

Water-Level Recovery

Water-level recovery in the confined-aquifer system after the collapse within the salt mine was simulated through 12.4-year transient-state simulations 

beginning with the first collapse in March 1994. Water 

levels simulated by model 3D-A (constant storage, 

table 4) had recovered nearly 90 percent by the year 

2000 and returned to precollapse conditions at most 

locations by the year 2006 (fig. 34). Decreasing the 

specific storage value (to 2.3 × 10-6 ft-1) for the lower 

aquifer shortened the recovery to precollapse conditions by 7 years (1999) because the contribution of 

storage to the inflow decreased sharply (18 percent, as 

opposed to the initial 73 percent), whereas the contribution from vertical leakage along the valley walls 

more than doubled (55 percent of inflow, as opposed to 

the initial 24 percent).

The effect of the vertical leakage rate on waterlevel recovery was investigated through two additional 

simulations in which the conductance of cells (see eq. 

5) representing vertical leakage through permeable 

deposits and bedrock fractures along the valley wall 

was increased or decreased by 1 order of magnitude. 

Water levels simulated with the increased conductance 

returned to precollapse conditions by the year 2002, but 

those with the decreased conductance had not completely recovered by the year 2006 (fig. 35). Simulated 

water budgets indicated that a 1-order-of-magnitude 

increase in conductance caused the vertical leakage 

rate to increase by about a factor of 3.

Effect of Mine Collapse on Saline-Water Intrusion

Hydraulic heads and flow rates computed by 

model simulations were used with a particle-tracking 

routine developed by Pollock (1989) to generate 

ground-water flow paths in the northern part of the 

Genesee Valley, which was affected by intrusion of 

saline water within the lower aquifer. Flow paths were 

generated to delineate the potential migration of saline 

water from suspected sources at the Bertie subcrop and 

A. Location II, well Lv368.

C. Site near Fowlerville moraine, well Lv496.

B. Location V, well Lv367.

1994 1996 1998 2000 2002 2004 2006 100

600

150

200

250

300

350

400

450

500

550

HEAD, IN FEET

1994 1996 1998 2000 2002 2004 2006

600

400

450

500

550

HEAD, IN FEET 600

450

500

550

HEAD, IN FEET

1994 1996 1998 2000 2002 2004 2006

EXPLANATION

Hydraulic head, in feet above sea level

 Measured

 Computed

Figure 34. Water levels measured in lower aquifer in 

Genesee Valley, Livingston County, N.Y. during first 

900 days after collapses at Retsof salt mine, and water 

levels simulated for 1994 through 2006 by model 3D-A: 

A. Location II, well Lv368. B. Location V, well Lv367. C.

Site near Fowlerville moraine, well Lv496. (Well 

locations are shown in fig. 4.)
SIMULATION OF GROUND-WATER FLOW 61

along Fowlerville Road (fig. 36) through the lower 

aquifer under both pre- and postcollapse conditions. 

The difference in density between fresh and saline 

waters was not considered in the flow-path delineation 

because its effect is small, as discussed below.

Whether saline water moved to the affected 

wells as horizontal flow in the lower aquifer or as 

upward leakage through fractures in the bedrock, or 

both, is uncertain. Horizontal migration would result in 

a continuous plume of saline water within the aquifer, 

whereas vertical migration would result in locally discontinuous areas with greater-than-average concentrations of dissolved solids. Flow paths were delineated 

through model simulations to assess the potential for 

horizontal migration through the lower aquifer.

Ground-water flow velocity. Ground water in the 

northern part of the Genesee Valley under precollapse 

conditions flowed northeastward through the lower 

aquifer at an estimated mean velocity of about 2 ft/d, if 

an effective porosity of 0.3 is assumed for the aquifer 

material (fig. 36A). The length of the vectors in 

figure 36A indicates the distance traveled from 

selected model cells in 29 months (the duration of the 

876-day transient-state simulation). The mine collapses caused the hydraulic gradient to reverse, and 

ground water began moving southward toward the collapse area. Estimates of the onset of the flow reversal 

and the velocity of ground-water flow are dependent on 

the assumed values for specific storage and effective 

porosity of the aquifer material.

Flow paths derived from the heads and flows 

computed by model 3D-A indicate that the reversal had 

begun by January 1996 and that the mean velocity was 

about 1 ft/d (fig. 36B). These flow paths indicate that 

saline water originating north of Fowlerville Road 

would not have reached the affected wells by the winter 

of 1994-95, when salinity first appeared in well Lv457. 

The specific storage value (2.9 × 10-4 ft-1) specified for 

the lower aquifer in this area in model 3D-A does not 

account for exsolution of natural gas, however, and is 

probably too large; therefore, an additional simulation 

was run in which the specific storage value was 

decreased more than 100-fold to 2.3 × 10-6 ft-1. Results 

indicated that ground water could have begun to flow 

southward at a mean velocity of 2 ft/d about 2 months 

after the first collapse with (fig. 36C); nevertheless, 

saline water would not have reached the affected wells 

by the winter of 1994-95, even at this faster flow rate.

The apparent velocity of saline water can be estimated from the time of the appearance of salinity in 

wells Lv457 and Lv500 along Little and Hogmire 

Roads, respectively (fig. 36C), if saline water is 

assumed to have moved southwestward from well 

Lv457. Water from well Lv457 was potable when this 

well was drilled in September 1994 but had a specific 

conductance of more than 12,000 μS/cm in March 

1995, and water from well Lv500 had a specific conA. Location II, well Lv368.

C. Site near Fowlerville moraine, well Lv496.

B. Location V, well Lv367.

1994 1996 1998 2000 2002 2004 2006 100

600

150

200

250

300

350

400

450

500

550

HEAD, IN FEET

1994 1996 1998 2000 2002 2004 2006

600

400

450

500

550

HEAD, IN FEET 600

450

500

550

HEAD, IN FEET

1994 1996 1998 2000 2002 2004 2006

EXPLANATION

Hydraulic head, in feet above sea level

 Measured

 Water level with conductance increased

 by one order of magnitude

 Water level with conductance decreased

 by one order of magnitude

Figure 35. Water levels measured in lower aquifer in 

Genesee Valley, Livingston County, N.Y. during 29 

months after collapses at Retsof salt mine, and water 

levels simulated for 1994 through 2006 by model 3D-A 

with vertical conductance increased and decreased by 

one order of magnitude: A. Location II, well Lv368. B.

Location V, well Lv367. C. Site near Fowlerville moraine, 

well Lv496. (Well locations are shown in fig. 4.)
62 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

 

 

39

39

530

540

550

560

570

550

560

590

570

560

520

530 540

550

560

570

600

590

580

610

620

510

500

490

480

530

540

550

560 570

540–610

570

560

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Genesee

River

Conesus

Creek

Genesee

River

Conesus

Creek

Avon

Fowlerville Road

Hogmire Road

Little

Road

Nations Road

Avon

Fowlerville Road

Hogmire Road

Little

Road

Nations Road

400

375

350

325

425

450475

500

525 550

575

600

625

650

675

700

725

750

775

800

825

300

275

250

225

200

325

350

375

400

425

450

475 500

525

550

575

600

625

600

575

625

650

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375

350

325

425

450475

500

525 550

575

600

625

650

675

700

725

750

775

800

825

300

275

250

225

200

325

350

375

400

425

450

475 500

525

550

575

600

625

600

575

625

650

A. Under precollapse (March 1994) conditions; flow paths computed with steady-state simulation (model 3D-A).

B. In August 1996; flow paths computed with transient-state simulation (model 3D-A).

42°54'

Base from U.S. Geological Survey digital data, 1:100,000, 1983

77° 52' 51' 50' 49' 48' 47' 46' 45'

53'

52'

51'

0 1 2 MILES

0 1 2 KILOMETERS

42°54'

Base from U.S. Geological Survey digital data, 1:100,000, 1983

77° 52' 51' 50' 49' 48' 47' 46' 45'

53'

52'

51'

0 1 2 MILES

0 1 2 KILOMETERS

Figure 36. Hydraulic-head distribution in the lower aquifer in northern part of the Genesee Valley, Livingston County, 

N.Y. and ground-water flow paths from time of first Retsof mine collapse (March 1994) through August 1996 (29 

months): A. Under precollapse (March 1994) conditions; flow paths computed with steady-state simulation (model 

3D-A). B. In August 1996; flow paths computed with transient-state simulation (model 3D-A).
SIMULATION OF GROUND-WATER FLOW 63

ductance of 4,700 μS/cm in June 1995 which had 

increased to 12,400 μS/cm in January 1996. The maximum traveltime between these two wells is 450 days 

(September 1994 through January 1996); therefore, the 

ground-water velocity is at least 8 ft/d (3,700 ft / 

450 d); this is 4 to 8 times the range (1 to 2 ft/d) indicated by model 3D-A. The effective porosity n can be 

computed from the relation

 

39

520

530 540

550

560

570

600

590

580

610

620

510

500

490

480

530

540

550

560 570

540–610

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Genesee

River

Conesus

Creek

Avon

Fowlerville Road

Hogmire Road

Little

Road

Nations Road

Lv 457

Lv 500

400

375

350

325

425

450475

500

525 550

575

600

625

650

675

700

725

750

775

800

825

300

275

250

225

200

325

350

375

400

425

450

475 500

525

550

575

600

625

600

575

625

650

March 1995 to

January 1996

March 1994 to

March 1995

C. In August 1996; flow paths computed with transient-state simulation (model 3D-A) assuming high-permeability paths and

with specific storage value (2.3×10–6 ft–1) calculated from published values obtained in land-subsidence studies.



EXPLANATION Lower aquifer

Bertie limestone

Simulated potentiometic contour—Contour interval 10 feet. Datum is sea level

Bedrock contour—Contour interval 25 feet. Index contours every 100 feet. Datum is sea level

Ground-water flow path—Indicates direction and distance travelled:

29 months after 1994 mine collapse;

March 1994 to March 1995

March 1995 to January 1996

Boundary of model area

Sampled well

Affected well—Specific conductance exceeded 2,500 microsiemens per centimeter

550

350

300

.

.

42°54'

Base from U.S. Geological Survey digital data, 1:100,000, 1983

77° 52' 51' 50' 49' 48' 47' 46' 45'

53'

52'

51'

0 1 2 MILES

0 1 2 KILOMETERS

Figure 36— Continued. Hydraulic-head distribution in the lower aquifer in northern part of the Genesee Valley, 

Livingston County, N.Y. and ground-water flow paths from time of first Retsof mine collapse (March 1994) through 

August 1996 (29 months): C. In August 1996; flow paths computed with transient-state simulation (model 3D-A) 

assuming high-permeability paths and with specific storage value (2.3 × 10-6 ft-1) calculated from published values 

obtained in land-subsidence studies. (Locations are shown in fig. 13.)
64 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

(21)

where v = ground-water velocity [LT-1],

K = hydraulic conductivity [LT-1], and

i = hydraulic gradient [LL-1].

The effective porosity of the lower aquifer is 

about 5 percent, as indicated by equation 21, and the 

hydraulic conductivity value estimated from the regression (300 ft/d), and the hydraulic gradient measured in 

January 1996 (1.2 × 10-3 ft/ft). When an effective 

porosity of 5 percent and a specific storage of 2.3 ×

10-6 ft-1 were specified, the resulting ground-water 

flow paths (fig. 36C) were consistent with the assumed 

traveltimes between Fowlerville Road and well Lv457 

(March 1994 through March 1995), and between wells 

Lv457 and Lv500 (March 1995 through January 1996). 

An effective porosity value of 5 percent is unreasonably low for the sand and gravel that forms the aquifer 

material, however; the commonly reported range is 25 

to 40 percent (Dennis LeBlanc, USGS, written commun.,1991).

Alternatively from that described above, the calculated velocity of 8 ft/d could be explained if the 

effective porosity along the flow path travelled by 

saline water were increased to a realistic value of 30 

percent and the hydraulic conductivity were increased 

to 2,000 ft/d . This hydraulic conductivity value, 

although much larger than the regression estimate of 

300 ft/d, is within the range reported for sand and 

gravel. Coarse deposits with hydraulic conductivity 

values of 2,000 ft/d could be present in the lower aquifer. Little stratigraphic information is available to confirm this result, however, and additional information 

would be needed for a detailed representation of 

hydraulic conductivity in the ground-water flow model. 

Direction of flow. The effect of water density on 

the direction of ground-water flow can be assessed 

through a comparison of local hydraulic and elevation 

gradients. The direction and rate of saline-water flow is 

given by the Darcy velocity vector v, defined as 

(Davies, 1989)

, (22)

where ∇hfw = gradient of freshwater hydraulic 

head[L•L-1],

∆ρ = density difference between saline water and 

freshwater (ρfw)[ML-3], and (23)

∇E = elevation gradient [L•L-1]. (24)

The Darcy velocity vector is the sum of two vectors—one defined by the hydraulic gradient ∇hfw, and 

the other by elevation gradient ∇E, scaled by the factor 

∆ρ/ρfw. This factor was computed as 4.5 × 10-3, from 

the measured density of water samples from wells 

Lv370 (dissolved solids concentration 7,000 mg/L) 

and Lv371 (dissolved solids concentration 410 mg/L) 

at location I, near the Fowlerville Moraine. The elevation gradient near well Lv500 (1.2 × 10-2 ft/ft) is almost 

100 times greater than the hydraulic gradients under 

both precollapse conditions (3.9 × 10-4 ft/ft) and postcollapse conditions of August 1996 (1.2 × 10-3 ft/ft). 

The density difference between the saline water and 

freshwater is small enough, however, that the elevation 

gradient is equivalent to about 10 precent of the 

hydraulic gradient after it is scaled by the factor 

∆ρ/ρfw; this confirms that the density difference has little effect on the direction of horizontal ground-water 

flow.

Sources of saline water. Several questions 

remain concerning the source of salinity, as well as the 

velocity, and direction of saline water migration in the 

lower aquifer. The source could be the Onondaga and 

Bertie Limestones, the Salina saltbeds, or a combination of both, as discussed previously. Saline water 

could have moved to the affected wells as horizontal 

flow in the lower aquifer or as upward leakage through 

fractures in the bedrock, or both. Estimates of the 

velocity of saline water ranged from 1 to 8 ft/d, depending on the values of hydraulic conductivity, specific 

storage, and effective porosity specified for the lower 

aquifer. Saline water also could migrate through paths 

of high permeability that are not represented in model 

3D-A.

Saline water will probably continue to move 

southward toward the collapse area until water levels in 

the confined aquifers recover to the point where gradients in the lower aquifer are once again northward—or 

until about the year 2006, as indicated by the simulations of model 3D-A (fig. 34). The saline water then 

will move northward with the hydraulic gradient 

v

Ki

n = -----

v K ∇h fw

∆ρ

ρ fw

= – + --------∇E
SIMULATION OF LAND SUBSIDENCE 65

because the small density difference between saline 

and fresh water is not large enough to alter the direction 

of horizontal flow. The northward gradient (3.9 ×

10-4 ft/ft) estimated for precollapse conditions is about 

one-third the southward gradient in August 1966 (1.2 ×

10-3 ft/ft); therefore, (1) the northward velocity of 

saline water will be one-third the southward velocity 

during postcollapse conditions, and (2) if saline water 

migrates southward for 10 years after the collapses, 

another 30 years will be required for freshwater to flush 

the area into which the saline water has intruded. This 

calculation is conservative because the southward gradient was not constant, but gradually increased to a 

maximum in January 1996, when drawdowns throughout the aquifer system were largest. Dispersive mixing 

of freshwater and saline water will probably dilute the 

saline water, however, and decrease the time required 

for ground water to become potable.

Additional study based on stratigraphic and 

geochemical information from new test holes would be 

needed to determine the source of salinity, velocity of 

saline-water migration, and the extent of saline-water 

intrusion; this study would provide the data needed to 

refine the ground-water flow model 3D-A to incorporate local variations in the hydraulic conductivity in the 

lower aquifer.

SIMULATION OF LAND SUBSIDENCE

As much as 0.8 ft of land subsidence developed 

south of the Retsof salt mine in response to water-level 

declines and the resulting compression of fine-grained 

sediments in the upper and lower confining layers after 

the mine collapse. Two 1-dimensional models (models 

1D-A and 1D-B, table 4) were developed with MODFLOW with the interbed-storage package (Leake and 

Prudic, 1991) to estimate hydraulic properties of the 

confining layers from observations of (1) pore pressure 

near the collapse area, and (2) land subsidence 2,800 ft 

south of the collapse area. The interbed-storage package (IBS1) allows the specification of two storage coefficients—one to represent elastic compression, and one 

to represent inelastic compression, of fine-grained sediments. Estimates of hydraulic values derived from calibration of the two 1-dimensional models were then 

substituted in the three-dimensional flow model 3D-A 

described earlier to depict the spatial distribution of 

land subsidence (model 3D-C, table 4).

One-Dimensional Simulations

One-dimensional, transient-state simulations 

were run to investigate vertical flow and compression 

in the confining layers at location II, where pressure 

transducers were installed in borehole XD1, and at 

monument K10 along survey line K, 2,800 ft south of 

XD-1 (fig. 17). Two pressure transducers were installed 

in borehole XD1 within the upper confining layer at a 

depth of 216 ft in September 1995. The transducers 

were placed within a saturated sand pack, and the borehole was sealed to land surface with an expansive grout 

to isolate the monitored interval from atmospheric 

pressure (Alpha Geoscience, 1996c). A datalogger 

monitored the transducers at 15-min intervals to provide a continuous record of pore pressure in the upper 

confining layer from September 1995 to the present 

(1998). Land-surface altitudes were surveyed monthly 

along survey line K from September 1994 through July 

1996, and then quarterly to the present (Akzo Nobel 

Salt, 1994-97; Kenneth Cox, ANSI, written commun., 

January 1997).

Model Design

Generalized stratigraphic sections (fig. 37) show 

the thickness and depth of the confining layers and the 

confined aquifers at both locations (location II and 

monument K10). The model for location II (model 1DA in table 4) represented only the upper confining layer 

and used a column of 257 cells of unit volume (1 ft3). 

The model for survey monument K10 (model 1D-B in 

table 4) represented both the upper and lower confining 

layers with a column of 446 unit-volume cells. Aquifer 

boundaries in both models were assigned hydraulic 

heads generated from transient-state simulations in 

model 3D-A. Subsidence resulting from compression 

of the confining layers was computed as the sum of the 

volume of water released from storage.

The confining layers in each model were 

assigned values of vertical hydraulic conductivity Kv

and specific storage Ss. The Kv value for the upper confining layer in both models was obtained through the 

nonlinear regression method described below, and the 

Kv value for the lower confining layer (model 1D-B) 

was fixed at the value estimated from model 3D-A 

(1.2x10-3 ft/d). The Ss values assigned to both confining layers were chosen to represent elastic and inelastic 

compression and were estimated by regression from 

the relation
66 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

, (25)

where β = compressibility of water (4.3 × 10-7 ft-1),

n = mean porosity measured in consolidation 

tests (0.3),

α = compressibility of the confining-layer sediments, defined as the ratio of the volumetric 

deformation undergone by sediments to the 

magnitude of the stress that causes deformation. 

The value α can be estimated from consolidation tests 

from the relation

, (26)

where ∆e = change in void ratio caused by a change in 

effective stress ∆σe, and

e0 = initial void ratio.

Consolidation-test results for compressible 

materials (such as clays) typically display a two-part 

curve corresponding to an elastic (recoverable) 

response at relatively low stress, and an inelastic (nonrecoverable) response at higher stresses that are greater 

than the previous maximum stress applied to the material (fig. 38A). The increase in effective stress in the 

lower confining layer near location II after the mine 

collapse (12 ton/ft2

 or 167 psi) also is indicated in fig. 

38A. Compressibility in the inelastic range is generally 

20 to 100 times greater than in the elastic range (Riley, 

1998). 

Consolidation curves for lower confining-layer 

sediments indicate that the stress resulting from waterlevel declines after the collapse corresponded to the 

transition from the elastic to the inelastic stress range 

(fig. 38B). The maximum stress applied in the consolidation tests was insufficient to cause an inelastic 

response of these sediments; therefore, the previous 

maximum stress undergone by the lower confininglayer sediments cannot be estimated from the consolidation curves. The increased stress in the upper confining layer was not much greater than the previous 

maximum stress because relatively little drawdown 

occurred in the upper confining layer.

Compressibility under ambient stress before the 

mine collapse was computed from consolidation 

curves for 15 samples of confining-layer sediments 

(Alpha Geoscience, 1995a,b,c; 1996a,b) through equation 26. The results (fig. 38B) indicate a decreasing 

void ratio during the compression phase of the test 

(increased stress ∆σc) and an increasing void ratio during the rebound phase (decreased stress ∆σr). Compressibility at the ambient stress σe was computed for 

the compression and rebound phases of the tests.

Compressibility of the sediments generally 

declined with increasing σe at increasing burial depths 

(d) , as expected from empirical relations given in Jorgenson (1980) and Neuzil (1986). The relation of compressibility to depth is

(27)

where m = constant (MT-2). 

For example, eq. 27 with an m-value of 5.5 ×

10-2 ft/psi gives the compressibility values computed 

from consolidation curves during compression with a 

correlation coefficient (r

2

) of 0.94 (fig. 39). Substituting eq. 27 into eq. 25 yields

. (28)

Ss = ρg( ) α + nβ

α

( ) ∆e 1 e + 0 ⁄ ( )

∆σe

= –----------------------------------

α

m

d = ---

Ss ρg

m

d

--- + nβ     =

UPPER

CONFINING

LAYER

UPPER AQUIFER

Pressure

transducer

MIDDLE

AQUIFER

LOWER

CONFINING

LAYER

LOWER

AQUIFER

Cement grout

Model 1D-A

(Collapse area)

Model 1D-B

(Survey line K)

MONUMENT K10

Land surface 2,800 feet

100 

0

200 

300 

400 

500 

BOREHOLE XD1

(Location II)

FEET

Figure 37. Generalized stratigraphic sections showing 

relative thickness of units and the depths of confined 

aquifers at borehole XD1 (location II) and monument 

survey K10 (2,800 ft south of the collapse area), in 

Genesee Valley, Livingston County, N.Y. (Locations are 

shown in fig. 17.)
SIMULATION OF LAND SUBSIDENCE 67

elastic range

inelastic range

Increase in effective stress in

lower confining layer at location

II in Genesee Valley, April 1994

through December 1995

∆σc

∆ec

∆σr

∆er

e0

–(∆e)/(1+e0) α = ∆σ

A

B

0.1 0.2 0.5 1 2 5 10 20 50 100 0.3

1.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

10 20 50 100 200 500 1,000 2,000 5,000 10,000

CONSOLIDATION STRESS (σ), IN TONS PER SQUARE FOOT

STRESS, IN KILOPASCALS

VOID RATIO (e)

0.1 0.2 0.5 1 2 5 10 20 50 100 0.3

1.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

10 20 50 100 200 500 1,000 2,000 5,000 10,000

CONSOLIDATION STRESS (σ), IN TONS PER SQUARE FOOT

STRESS, IN KILOPASCALS

VOID RATIO (e)

EXPLANATION

Sample and depth—Solid line is compression 

 phase (c), dashed line is rebound phase (r), 

 arrow indicates change in stress during test

 Upper confining layer

 ST-1, 53 feet, above till

 ST-2, 98 feet, above till

 ST-3, 218 feet, below till

EXPLANATION

Core samples from borehole in California—Sample number and depth below land surface (from Johnson, 1984)

 23L-83, 699 feet

 Lower confining layer

 ST-4, 401 feet

Increase in effective stress after mine collapse, 

 April 1994 though December 1995

Ambient effective stress before mine collapse, 

 April 1994

 23L-84, 746 feet 23L-85, 984 feet

Figure 38. Examples of consolidation curves for: A. Compressible clays in California. (Modified from A. I. 

Johnson, 1984, fig. 4.16, corehole 14/13-11D1). B. Confining-layer sediments from well Lv346 at location II near 

the collapse area, Livingston County, N.Y. (Location is shown in fig. 4.)
68 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Compressibility values computed from the 

rebound phase of the consolidation tests are about 1 

order of magnitude smaller than those computed from 

the compression phase. Possibly, the sediment samples 

had expanded under atmospheric conditions prior to 

the compression phase at the beginning of the consolidation test and, therefore, were not representative of 

ambient conditions. By the end of the compression 

phase, however, the samples had been recompressed to 

a state of stress that resembled ambient conditions 

more closely than at the begininning of the tests.

Values of elastic and inelastic storage were specified for cells in models 1D-A and 1D-B through the 

following procedure: an elastic storage value Sse(i) was 

computed for each cell i from equation 28 with the 

depth below land surface di and an m-value estimated 

by nonlinear regression (The product ρg was specified 

as 62.4 lb/ft3 or 0.434 psi/ft). The magnitude of stress 

(preconsolidation head Hpc) at which the transition 

from elastic to inelastic storage occurred was also estimated in the regression. Inelastic storage values Ssin(i)

were specified to be either 30 or 50 times greater than 

Sse(i) values. The sensitivity of model results to specific 

storage values that were estimated from the compression and rebound phases of the consolidation tests and 

that represented elastic and inelastic compression is 

discussed below.

Model Calibration

A nonlinear regression method (PEST; Doherty 

and others, 1994) was used to estimate three parameters (Kv, m, and Hpc) in models 1D-A (location II) and 

1D-B (monument K10). The perturbation method in 

PEST is similar to the UCODE method used in the 

three-dimensional model 3D-B. One feature of the perturbation method is that two separate models can be 

linked in the same regression; thus, eight observations 

of pressure at location II (model 1D-A) were combined 

with four observations of subsidence at monument K10 

(model 1D-B) to obtain values of Kv , m, and Hpc. 

Weights wi (see eq. 7) were assigned to the pressure 

and subsidence observations (1 ft and 10 ft, respectively) to account for differences in the measurement 

ranges (404 to 435 ft in pressure and 0.18 to 0.78 in 

subsidence). Parameters were estimated through a 

12.4-year transient-state simulation representing precollapse and postcollapse conditions—the same period 

used in the three-dimensional simulations of waterlevel recovery discussed earlier.

The parameter values were estimated by the 

PEST regression were considered reliable, and the Kvvalue was close to that specified in the three-dimensional flow model (table 12). The weighted residuals 

from models 1D-A and 1D-B do not indicate any 

unusual model bias and appear to be normally distributed. The individual confidence intervals given in table 

12 are approximate, however, because the assumption 

of model linearity was not verified. Mean elastic specific-storage Sse values for the upper and lower confining layers were computed from the following relation

, i = 1, n (29)

where bi

 = 1-foot thickness of each cell, 

b = confining-layer thickness, 

Sse

1

b

-- Sse i( )b = ∑ i

0.005 0.01 0.1 1 10 50

COMPRESSIBILITY,

IN (POUNDS PER SQUARE INCH)–1 x 105

700

0

100

200

300

400

500

600

DEPTH BELOW LAND SURFACE, IN FEET

COMPRESSIBILITY, IN PASCALS–1 x 105

0.04 0.1 1 10 100 300

EXPLANATION

Estimated m-values, in foot per psi relating 

 compressibility α to depth d—α = m / d (equation 27)

ID-B (table 4) with elastic and inelastic storage, 

 2.4 × 10–4

ID-B (table 4) with elastic specific storage, 6.5 × 10–3

Estimated from compression data, 5.5 × 10–2 

Consolidation tests

Compression

 Upper confining layer

 Lower confining layer

Rebound

 Upper confining layer

 Lower confining layer

Figure 39. Relation of compressibility to depth as 

derived from consolidation curves of confining-layer 

sediments in Genesee Valley aquifer system, Livingston 

County, N.Y.
SIMULATION OF LAND SUBSIDENCE 69

Sse(i) = elastic storage at depth i, and 

n = number of cells representing the confining 

layer in the subsidence model. 

The mean Sse value (2.3 × 10-6 ft-1) compares 

well with that estimated for a confining layer composed 

of glacial drift in Anchorage, Alaska (2.3 × 10-6 ft-1) 

from extensometer measurements during an aquifer 

test (Nelson, 1982). The preconsolidation head of 410 

ft corresponds to a prior loading of about 150 ft of 

water at land surface and indicates that the confininglayer sediments are overconsolidated; this result is consistent with the presence of till in the upper confining 

layer and suggests that underlying sediments had previously undergone higher stresses during a temporary 

glacial advance than under the ambient conditions 

before the mine collapse. Further evidence of overconsolidation is apparent in the consolidation curves (fig. 

38B), which indicate that samples from beneath the till 

had a lower void ratio e0, and were much less compressible, than those obtained from shallower depths 

above the till. Specifying values of inelastic storage 

that were either 30 or 50 times the Sse-values resulted 

in little difference in model error.

Computed pressure changes in the upper confining layer (model 1D-A) were in close agreement with 

pressures measured in borehole XD1 at location II during drainage of the confined aquifer system and the 

subsequent recovery once the mine was flooded in January 1996 (fig. 40). The maximum residual was about 

5 ft, and the mean error was 2.1 ft, less than 2 percent 

of the computed 145-ft drawdown. The first pressure 

measurement was not obtained until September 1995, 

however; thus, the abrupt pressure declines that folTable 12. Optimum parameter values estimated for confining layers In Genesee Valley aquifer system, Livingston 

County, N.Y., through nonlinear regression in one-dimensional models 1D-A (location II) and 1D-B (Monument K10), 

their approximate confidence intervals at 95-percent level, and the mean values specified in three-dimensional model 

3D-C (entire aquifer system)

[ft, feet; —, not specified or not computed. Locations are shown in fig. 17.]

Variable

Value estimated in 

one-dimensional 

models 1D-A and 1D-B

Approximate individual 

confidence interval

Mean values 

specified in threedimensional model 

3D-C

Aquifer property

Vertical hydraulic conductivity (feet per day)

Upper confining layer 6.8 × 10-6 4.2 × 10-6 - 1.1 × 10-5 3.6 × 10-5

Lower confining layer 1.2 × 10-3 a

a

Fixed value in regression.

— 1.2 × 10-3

Mean elastic specific storage (ft-1)

Upper confining layer 2.3 × 10-6 1.4 × 10-6 - 4.1 × 10-6 2.2 × 10-5

Lower confining layer 1.1 × 10-6 7.8 × 10-7- 1.7 × 10-6 7.9 × 10-6

Preconsolidation head (feet) 410 370 - 458 —

Error in heads in model 1D-A at location II

Sum of squared errors (feet squared) 35.4

Standard error (feet) 2.1

Subsidence at monument K10,

as computed in model 1D-B (feet) Simulated subsidence Measured subsidence

Upper confining layer .06 — .05

Lower confining layer .67 — .50

Total at monument K10 .73 .78 .55
70 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

lowed the collapses were not represented in the measured data.

The predicted subsidence at monument K10 

(model 1D-B) closely matched the observed subsidence, and the maximum simulated subsidence (0.73 ft) 

was about 6 percent less than that observed (0.78 ft) 

(fig. 41A). About 90 percent of the simulated compression was inelastic, nonrecoverable compaction. The 

consistent downward trend in subsidence measurements along the K survey line suggests that the measurements from February 1995 through January 1996 

were relatively accurate, but whether the land surface 

rebounded slightly once water levels began to recover 

in January 1996, as simulated in the model, is difficult 

to discern because the measured values have wide scatter. 

The response of the confining layers to drainage 

and recovery of the aquifer system is illustrated by profiles of hydraulic head at K10 as a function of depth, as 

computed with model 1D-B (fig. 41B). Pressure 

declines propagated more rapidly through the lower 

confining layer than through the upper confining layer 

because the vertical hydraulic diffusivity (κv = Kv/Ss) 

of the lower unit is much greater (1,100 ft2

/d and 3.0 

ft2

/d, respectively). Vertical hydraulic diffusivity governs one-dimensional propagation of pressure changes 

in confining layers and determines the attenuation and 

delay of the pressure response (for example, Keller and 

others, 1989; Yager and Kappel, 1998). About 92 percent of the computed subsidence (0.67 ft, table 12) was 

Location II, borehole XD-1

1994 1996 1998 2000 2002 2004 2006 400

560

420

440

460

480

500

520

540

HYDRAULIC HEAD, IN FEET

EXPLANATION

Measured

Computed

Figure 40. Pressures in upper confining layer at location 

II in Genesee Valley, Livingston County, N.Y. as 

computed by one-dimensional model 1D-A and 

measured at borehole XD-1. (Location is shown in fig. 

17.)

Monument K10

A. Computed and measured subsidence.

B. Simulated hydraulic head as a function of depth in 

upper and lower confining layers, April 1994 through 

August 1996.

1994 1996 1998 2000 2002 2004 2006 1

0

LAND SUBSIDENCE, IN FEET 0.5

200 600 250 300 350 400 450 500 550 600

0

100

200

300

400

500

DEPTH, IN FEET BELOW LAND SURFACE

HYDRAULIC HEAD, IN FEET

EXPLANATION

Measured

Elastic and inelastic specific storage

Elastic specific storage

Upper aquifer

Upper confining layer

Middle aquifer

Lower confining layer

Lower aquifer

Date and time since collapse

 April 1994, 24 days

 December 1995, 639 days

 August 1996, 876 days

 June 1998, 1,163 days

Direction of head change

Average head in three-dimensional model 

 3D-A, December 1995

EXPLANATION

Figure 41. Results of one-dimensional model 1D-B 

simulations of land subsidence at monument K10 in 

Genesee Valley, Livingston County, N.Y.: A. Computed 

and measured subsidence. B. Simulated hydraulic head 

as a function of depth in upper and lower confining 

layers, April 1994 through August 1996. (Location is 

shown in fig. 17.)
SIMULATION OF LAND SUBSIDENCE 71

the result of drainage and compression in the lower 

confining layer. Flow through the lower confining layer 

was nearly at steady state before the recovery of water 

levels in January 1996, as indicated by the approximately linear hydraulic gradient. The rate of flow 

through the upper confining layer was still increasing at 

this time, however, and drainage from the top of the 

upper confining layer continued through June 1998, 

long after water levels had recovered in the lower confining layer. A result of the relatively slow response of 

the upper confining layer to pressure changes was that 

sediments near the top of the layer were being compressed, whereas the underlying sediments near the 

bottom were expanding.

Elastic compressibility values computed from 

the m value of 2.4 × 10-4 ft/psi estimated by the regression were about 1 order of magnitude less than those 

calculated for confining layer sediments during the 

rebound phase of the consolidation tests (fig. 39). 

Model sensitivity to specific storage was investigated 

in two alternative regressions in which the observed 

subsidence was assumed to result solely from elastic 

compression. In both regressions, the Kv value was 

estimated, and m values were either estimated or specified (fig. 39). The Sse values obtained in these regressions (eq. 29) were larger than those computed in the 

initial regression, which represented both elastic and 

inelastic compression. Results of the two alternative 

regressions matched the pressure response observed at 

borehole XD-1 (model 1D-A) equally well, however, 

because estimated Kv-values were larger also than in 

the initial regression, so that the vertical hydraulic diffusivity was unchanged. This result indicates that a 

range of Kv and Sse values can be used to match the 

observed pressures in model 1D-A as long as the ratio 

of the values (κv= Kv/Ss) remains constant. 

The alternative regression with the estimated m

value of 6.5 × 10-3 ft/psi yielded a maximum subsidence of 0.66 ft at monument K10—about 85 percent of 

the measured value, and the elastic compressibilities 

matched reasonably well the values calculated for the 

rebound phase of consolidation tests (fig. 39). This 

simulation indicates that the land surface would 

rebound after water levels had begun to recover and the 

compressed sediments had expanded elastically—a 

result that is clearly unrealistic (fig. 41A). The other 

alternative regression—that with the specified m value 

of 5.5 × 10-2 ft/psi—resulted in a maximum subsidence 

of 5 ft, about 6 times greater than the measured value 

(fig. 42). These results suggest that compressibility values derived from consolidation tests do not accurately 

represent the actual compressibilities under field conditions.

Three-Dimensional Simulation

The one-dimensional models 1D-A and 1D-B 

indicate that land subsidence south of the Retsof mine 

was the result of both elastic and inelastic compression 

of confining-layer sediments, and that two values are 

required for accurate representation of water released 

from storage during the observed water-level decline. 

The program MODFLOWP, which was used to construct three-dimensional model 3D-A, allows only one 

storage value for each model cell, however. The Ss-values specified in model 3D-A for the upper and lower 

confining layers (1.0 × 10-5 ft-1 and 5.0 × 10-6 ft-1, 

respectively) were close to the mean Sse-values computed by the alternative regression with models 1D-A 

and 1D-B, in which elastic compression was assumed 

(2.2 × 10-5 ft-1 and 7.9 × 10-6 ft-1, respectively). In that 

regression, the close match between computed and 

maximum subsidence at monument K10 indicates that 

an approximate value for the volume of water released 

from storage in the confining layers can be obtained 

1994 1996 1998 2000 2002 2004 2006

LAND SUBSIDENCE, IN FEET 5.0

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

EXPLANATION

Measured

Elastic and inelastic specific storage

Elastic specific storage (estimated)

Elastic specific storage (specified)

Figure 42. Land subsidence measured 1994-96 at 

monument K10 in Genesee Valley, Livingston County, 

N.Y., values computed by one-dimensional model 1D-B 

for 1994–2006, and values obtained from alternative 

regressions in which land subsidence was assumed to 

result only from elastic compression. (Location is shown 

in fig. 17.)
72 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

from a single specific-storage value. In addition, the 

water released from storage in the two confining layers 

was estimated to be less than 10 percent of the total 

water budget for the confined-aquifer system (table 8). 

Representing the effects of elastic and inelastic storage 

by a single value, therefore, probably does not greatly 

affect the hydraulic head distribution computed by 

three-dimensional model 3D-A.

Values of Kv and Ss that were obtained through 

regression with one-dimensional models 1D-A and 

1D-B (assuming elastic compression) were incorporated into three-dimensional model 3D-C (tables 4 and 

12) to compute the spatial distribution of subsidence 

when water-level drawdown was a maximum. Model 

3D-C calculated the subsidence at each cell as the sum 

of the volume of water released from storage in each 

confining layer (model layers 2 and 4), divided by the 

horizontal cell area. Model 3D-C depicts only qualitatively the distribution of maximum subsidence, however, because (1) it used a single value to represent 

elastic and inelastic storage, and (2) it represents each 

confining layer by a single model layer, rather than by 

many 1-ft-thick layers as in models 1D-A and 1D-B. 

Vertical profiles of hydraulic head as a function of 

depth, as computed in model 1D-B (fig. 41B), indicate 

that the average head computed by the model 3D-C for 

the lower confining layer represents the vertical 

hydraulic gradient reasonably well, but the average 

head computed for the upper confining layer does 

not—the heads near the bottom of this unit, where most 

of the pressure decline occurred, were significantly 

overpredicted. As a result, model 3D-C underpredicted 

drainage from the upper confining layer and the subsequent compression of sediments (table 12). The maximum subsidence at monument K10 as computed by the 

three-dimensional model 3D-C (0.55 ft) is about 70 

percent of that observed (0.8 ft). The cumulative subsidence in February 1996 along survey line K as computed by model 3D-C was reasonably consistent with 

the measured subsidence (fig. 43), although offset 

3,000 ft to the east. The underprediction of maximum 

subsidence in model 3D-C is partly the result of representing the confining layers as single model layers, as 

discussed above. The 3,000-ft discrepancy in the location of maximum subsidence along survey line K suggests that the distribution of confining-layer thickness 

specified in model 3D-C does not accurately represent 

the actual thickness of fine-grained confining-layer 

sediments.

Results of model 3D-C indicate that as much as 

0.1 ft of subsidence had occurred by February 1996 

over an area covering about 16 mi2

 that extended 5 mi 

north, and 7 mi south, of the collapse area (fig. 44) and 

that as much as 0.5 ft of subsidence occurred over an 

area covering about 1.4 mi2

. Simulated subsidence 

closely matched the measured subsidence in Mt. Morris, 3 mi south of the collapse, where as much as 0.3 ft 

of subsidence was measured. Subsidence was greatest 

near the collapse area and in the center of the Genesee 

Valley, where deposits of fine-grained sediments are 

thickest. A more accurate depiction of subsidence and 

potential rebound of the land surface could be obtained 

by incorporating the ISB1 package into three-dimensional model 3D-C to represent both elastic and inelastic storage.

SUMMARY

Collapses over two panels in the Retsof salt mine 

in the Genesee Valley in Livingston County, N.Y., in 

March and April 1994 allowed water from overlying 

aquifers to flood the mine. Subsidence of the overlying 

rock and sediment propagated to land surface, leaving 

two 300-ft-diameter sinkholes that damaged nearby 

structures, including a State highway bridge. Within 3 

to 4 weeks of the collapses, water levels in about a 

dozen nearby domestic and industrial wells had 

declined severely, and some wells went dry. All mining 

Monument K10

0 6,000 12,000 18,000

1

0

0.5

LAND SUBSIDENCE, IN FEET

DISTANCE ALONG SURVEY LINE K, IN FEET

EXPLANATION

Measured

Computed

Figure 43. Land subsidence along survey line K in 

Genesee Valley, Livingston County, N.Y., as measured in 

February 1996 and as computed by three-dimensional 

model 3D-C. (Location is shown in fig. 17.)
SUMMARY 73

ceased in September 1995, and the mine was completely flooded by January 1996, by which time water 

levels had declined 400 ft near the collapse area and by 

more than 50 ft at wells 7 mi north and south of the collapse area.

Hydrogeologic Setting

The glacial aquifer system within the valley generally consists of three aquifers separated by two confining layers and is underlain by water-bearing zones in 

bedrock. The glacial aquifers are bounded laterally by 

the bedrock valley walls. The uppermost aquifer consists of alluvial sediments 20 to 60 ft thick; the middle 

aquifer consists of glaciofluvial sand and gravel less 

than 10 ft thick; and the lower aquifer consists of glaciofluvial sand and gravel about 25 ft thick overlying 

the bedrock valley floor. The mine lies 550 to 600 ft 

below the valley floor. The upper and middle aquifers 

are separated by an upper confining layer of lacustrine 

sediments and till as much as 250 ft thick, and the two 

confined aquifers are separated by a lower confining 

layer of undifferentiated glaciolacustrine sediments as 

much as 250 ft thick. The principal water-bearing zone 

in the bedrock overlying the mine consists of fractures 

near the contact between the Onondaga and Bertie 

     

20A

390

408

36

63

39

20A

0.1

0.2

0.3

0.4

0.5

0.6

0.5

0.4

0.3

0.2

0.1

0.1

.

.

XD-1

Line K

Monument K10

Canaseraga

Creek

Keshequa

Creek

Beards Creek

Genesee

River

Genesee

River

Geneseo

Cuylerville

Mount

Morris

SALT MINE

COLLAPSE

AREA

EXPLANATION

Model area (Genesee Valley)

Simulated subsidence—Contour 

 interval 0.1 foot

Survey line

Borehole with pressure transducer

0.1

XD-1 .

NEW YORK

LOCATION MAP

Study

area

77° 56' 15" 52' 30"

45'

42°48'45"

Base from U.S. Geological Survey digital data,

1:100,000, 1983

2 4 MILES

0

0

2 4 KILOMETERS

48' 45"

Figure 44. Distribution of land subsidence in Genesee Valley, Livingston County, N.Y. in February 1996, as 

computed by three-dimensional model 3D-C. (Location is shown in fig. 13.)
74 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Limestones. The glacial aquifers are hydraulically connected at the edges of the confining layers and in subcrop zones, where water-bearing zones in the bedrock 

intersect the bedrock surface.

Ground water within the valley generally flowed 

northward prior to the mine collapse. The hydraulic 

head distribution in the confined aquifers under natural 

(precollapse) conditions is assumed to have been similar to that in the upper aquifer before the collapse, but 

water levels in the confined aquifers were probably 

above the water table beneath the valley floor. Ground 

water at the Onondaga/Bertie Limestone contact probably flowed northward to the Bertie Limestone subcrop 

in the valley north of the Fowlerville Moraine.

Water salinity in the middle aquifer is relatively 

low (430 to 1390 μS/cm); that in the lower aquifer 

ranges from 2,980 to 39,300 μS/cm, and that in the 

Onondaga and Bertie Limestones ranges from 72,000 

to 106,000 μS/cm. The ratio of chloride to bromide 

concentrations in the confined aquifers is generally 

close to the ratio of 110 reported for brines from oilbearing zones in the Bass Island carbonates in western 

New York. Ratios greater than 400 in some areas indicate, however, that halite (which has a chloride-to-bromide ratio greater than 1,000) has entered the lower 

aquifer as a result of solution mining operations or 

leakage through abandoned gas wells. The deuterium 

and 18O content of waters from the two confined aquifers generally are similar to that of recharge in western 

New York, and concentrations of tritium suggest that 

the water is generally more than 45 years old. Water in 

the confined aquifers also contains biogenic gas (methane and hydrogen sulfide) that is probably derived from 

the Devonian shale bedrock.

Effects of Mine Collapse

The collapses and subsequent mine flooding 

caused land subsidence of 70 ft over the two collapsed 

panels; subsidence elsewhere ranged from 0.8 ft or less 

south of the mined area to as much 15 ft over the uncollapsed mined area. The subsidence south of the mine is 

attributed to compression of fine-grained sediments in 

the confining layers. Land subsidence also lowered the 

bed of the Genesee River by as much as 4.5 ft and 

altered the course of Beards Creek such that two ponds 

formed in the two sinkholes that developed over the 

collapses. Streamflow measurements in the Genesee 

River and Beards Creek did not indicate streamflow 

losses to the confined-aquifer system; this indicates 

that the water flowing into the mine did not originate as 

streamflow.

The collapses over the mine allowed water to 

drain from the lower aquifer into the mine at an altitude 

of 40 ft, which is 500 ft lower than the natural discharge 

area at the north end of the Genesee Valley. This drainage altered the hydraulic gradients in the lower aquifer, 

reversing the direction of flow north of the collapse 

area. Water levels in the lower aquifer had dropped as 

much as 400 ft by January 1996, when the mine was 

completely flooded, and about 15 domestic wells 

screened in the middle aquifer went dry. Drawdowns of 

50 ft were recorded at wells 7 mi north of the collapse 

area, and drawdowns of 135 ft were recorded at wells 8 

mi south of it. Water levels in upland areas and in most 

of the upper aquifer were unaffected by the collapse, 

although drawdowns of 5 ft in the upper aquifer may 

have resulted near the collapse area.

The reversal in the direction of ground-water 

flow north of the collapse appears to have caused intrusion of saline water into the lower aquifer at the north 

end of the valley. Salt concentrations of water from several domestic wells had become too high for human 

consumption within 12 months of the collapse. Ratios 

of chloride to bromide concentrations in ground-water 

samples indicate two possible sources of salinity in the 

lower aquifer—saline water from the Onondaga and 

Bertie Limestones, and halite-bearing water from an 

unknown source. The saline water probably flowed 

southward from areas near the Bertie subcrop toward 

the collapse area but also could have flowed upward 

from underlying saline-water-bearing zones in bedrock 

through high-angle fractures south of the Bertie subcrop under the vertical hydraulic gradient created by 

the drainage of water into the mine.

Declining water levels and the resulting 

decreases in pressure within the aquifer system caused 

exsolution of natural gas from water in the confined 

aquifers, and 2 or 3 water wells began to produce biogenic gas by July 1994. Thermogenic gas was detected 

within the mine and was flared from May 1995 until 

January 1996 through three wells drilled to the mine. 

Methane was detected near a plugged access shaft and 

around the mine perimeter at the northern end of the 

mine in January 1996, shortly after the mine was completely flooded, but the emissions gradually diminished 

through the summer 1996.
SUMMARY 75

Simulation of Ground-Water Flow

Ground-water flow within the aquifer system 

was simulated by a three-dimensional model with 

MODFLOWP to represent flow conditions before and 

after the mine collapses. The three aquifers and two 

confining layers within the unconsolidated deposits 

were represented by five model layers. The model was 

calibrated to observed water levels and flow rates 

through nonlinear regression, and was used to calculate 

ground-water budgets and simulate the time required 

for water levels to return to precollapse conditions.

Parameter values representing aquifer properties 

were adjusted through steady-state simulations representing precollapse conditions and through transientstate simulations representing the flooding of the mine 

and water-level recovery after the mine was filled. The 

base flows and hydraulic-head distribution in the upper 

aquifer computed with the steady-state simulation 

matched the measured water levels and flows reasonably well, and the predicted directions of ground-water 

flow were consistent with the directions assumed for 

precollapse conditions. The standard error in heads was 

8.7 ft, and computed base flows were nearly equal to 

the estimated base flow in Canaseraga Creek, but were 

only one-half the estimated base flow in the Genesee 

River. Optimum parameter values were obtained only 

for the recharge rate and hydraulic conductivity of the 

alluvial sediments. Neither of these values was precisely estimated because the numbers of head and flow 

observations were insufficient, and the sensitivity of 

the steady-state simulation to these measurements was 

limited as a result of the extensive boundaries specified 

in the top model layer (layer 1). Hydraulic heads computed with the steady-state simulation provided initial 

conditions for the transient-state simulations.

Transient-state simulations represented the 29 

months during and after the collapse, including the 

period of drainage from the aquifer system to the mine 

(March 1994 through January 1996) and a period of 

water-level recovery after the mine had filled (January 

1996 through August 1996). The computed distribution 

of drawdowns in January 1996 was similar to the measured distribution. The standard error in heads was 33 

ft, and computed drawdowns near the collapse area 

(405 ft) were overpredicted by less than 10 ft, whereas 

drawdowns 7 mi to the north (35 ft) and 8 mi to the 

south (50 ft) were underpredicted by about 15 ft and 60 

ft, respectively.

Computed discharges to the mine in April 1994 

(20 ft3

/s) were 100 percent greater than the values estimated from the observed rate of mine flooding, and the 

computed discharges to the mine in September 1994 

(28 ft3

/s) were 40 percent less than those estimated. 

The computed water budget indicated that ground 

water released from storage accounted for about 11 

percent of the total inflow to the aquifer system and 

provided most of the water that discharged to the mine. 

Most of the drainage to the mine (58 percent) was from 

storage in the lower aquifer; another 15 percent was 

from storage from the rest of the confined system . The 

estimated volume of water discharged to the mine 

(1.1 × 109

 ft3) was only 55 to 60 percent of the mine 

volume, probably because drawdowns in the southern 

part of the aquifer system were underpredicted by as 

much as 60 ft.

Although the calibrated model represents the 

drawdown and recovery of water levels reasonably 

well, the simulated drawdowns in the lower aquifer 

were generally greater than those measured near the 

collapse area and less than those measured away from 

the collapse area. This bias indicates that the model 

does not accurately represent other unidentified processes or local variations in the hydraulic-conductivity 

distribution that affect ground-water flow. Specific 

storage values estimated for the lower and middle aquifers were 2.9 × 10-4 ft-1 and 6.9 × 10-5 ft-1, respectively, 

much larger than the range of values (1 × 10-6 ft-1 to 3 

× 10-6 ft-1) estimated from studies of land subsidence 

in other regions underlain by sand and gravel aquifers. 

Assigning a lower value of specific storage (2.3 × 10-6

ft-1) greatly increased model error, however, and no 

combination of the remaining parameter values was 

found through nonlinear regression that provided an 

acceptable match to the measured water levels.

Exsolution of natural gas from ground water during water-level declines lessened drawdown near the 

collapse area and slowed the propagation of drawdowns into areas away from the collapse, and probably 

accounts for the large values of specific storage estimated by regression and for part of the bias in the 

model. A gas-partitioning equation was developed to 

compute specific storage in the presence of a gas phase 

and indicated that specific storage was not constant, as 

assumed in the flow model, but varied temporally and 

spatially as a function of pressure. Including the effects 

of gas exsolution in MODFLOWP and specifying values of aquifer compressibility derived from studies of 

land subsidence decreased model error by about 15 

percent and slightly reduced model bias.
76 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Hydraulic heads predicted by the model indicate 

that water levels will return to precollapse conditions 

by about the year 2006. Specifying a lower specific 

storage value (2.3 × 10-6 ft-1) for the lower aquifer 

speeded the simulated recovery and indicated that 

water levels would return to precollapse conditions by 

1999. Increasing the conductance of cells representing 

vertical leakage through permeable deposits along the 

valley walls by 1 order of magnitude caused predicted 

water levels to return to precollapse conditions by the 

year 2002, whereas decreasing the conductance by that 

amount delayed the predicted recovery until after the 

year 2006.

Ground-water flow paths computed from steadystate and transient-state simulations with the model 

indicate that the mine collapse reversed the natural 

hydraulic gradient in the northern part of the valley, 

allowing intrusion of saline water into the lower aquifer. The estimated velocity of saline-water migration 

ranged from 1 to 8 ft/d, depending on the values of 

hydraulic conductivity, specific storage, and effective 

porosity specified for the lower aquifer. The most likely 

interpretation is that saline water traveled along preferential flow paths with a hydraulic conductivity of 2,000 

ft/d and an effective porosity of 0.3. The density difference between the saline and fresh waters is relatively 

small and was found to have little effect on the direction of horizontal ground-water flow. 

Saline water will probably continue to move 

southward toward the collapse area until about the year 

2006, when water levels in the confined aquifers 

recover to precollapse conditions, and the northward 

hydraulic gradient becomes reestablished. The estimated magnitude of the northward gradient (3.9 × 10-4

ft/ft) is only one-third as large as the southward gradient in August 1996 (1.2 × 10-3 ft/ft); thus, the northward velocity of saline water will be only a third as 

rapid as the southward velocity. If saline water is 

assumed to migrate southward for 10 years after the 

collapse, about 30 years will be required for freshwater 

to flush the area into which the saline water has 

intruded.

Simulation of Land Subsidence

Water-level declines within the aquifer system 

that resulted from the mine collapse, and the accompanying increase in effective stress, caused compression 

of fine-grained sediments in the upper and lower confining layers and resulted in as much as 0.8 ft of land 

subsidence south of the mine. One-dimensional, transient-state simulations were conducted with MODFLOW and the ISB1 package to represent vertical flow 

and compression in the upper and lower confining layers at two locations. One model, which represented the 

collapse area, consisted of a column of 257 cells of unit 

volume (1 ft3

) to represent the upper confining layer at 

borehole XD1 containing pressure transducers, and a 

second model, which represented the upper and lower 

confining layers at survey monument K10 , about 2,800 

ft south of the collapse, consisted of a column of 446 

unit-volume cells. Boundaries in the upper aquifer and 

confined aquifers in both models were assigned 

hydraulic heads computed by the three-dimensional 

model, and subsidence was computed as the sum of the 

volume of water released from storage from each of the 

two confining layers.

Vertical hydraulic conductivity of the upper confining layer and specific storage of both confining layers were estimated through a nonlinear regression 

program (PEST), and the vertical hydraulic conductivity of the lower confining layer was fixed at the value 

estimated with the three-dimensional model (1.2 ×

10-3 ft/d). Both elastic and inelastic storage were repesented in the one-dimensional models. Elastic storage 

was assumed, from the observed relation between compressibility and depth as derived from consolidation 

tests of 15 samples of confining-layer sediments, to be 

inversely proportional to effective stress (or depth). 

Inelastic storage was assumed, on the basis of published values, to be 30 times greater than elastic storage. The two models were linked in the same 

regression, and observations of pore pressure and subsidence were used to estimate model parameters.

Reliable values of vertical hydraulic conductivity, specific storage, and the preconsolidation head at 

which the transition from elastic to inelastic storage 

occurred were estimated through regression. Computed pressure changes in the upper confining layer 

were in close agreement with pressures measured with 

the transducers, and the maximum computed subsidence at monument K10 (0.73 ft) was only about 6 percent less than that observed. About 92 percent of the 

computed subsidence was the result of drainage and 

compression in the lower confining layer, of which 90 

percent was inelastic or nonrecoverable compaction.

An alternative regression, in which subsidence 

was assumed to result solely from elastic compression, 

resulted in larger estimates of vertical hydraulic conductivity and specific storage than in the regression in 
REFERENCES CITED 77

which inelastic storage was assumed. Results of the 

alternative regression matched the observed pressure 

response and maximum subsidence reasonably well 

but indicated that the land surface would rebound during water-level recovery. The observed absence of 

land-surface rebound at monument K10 indicates that 

subsidence resulted mainly from inelastic compaction.

Values of vertical hydraulic conductivity and 

specific storage of confining-layer sediments estimated 

on the assumption of elastic compression in onedimensional models were incorporated into the threedimensional model, in which each confining layer was 

represented by a single model layer. This approximation had little effect on the simluated drainage and 

compression in the lower confining layer, which had a 

large vertical hydraulic diffusivity (150 ft2

/d) and 

responded relatively quickly to drawdown. Compression in the upper-confining layer was underpredicted, 

however, because this unit had a lower vertical hydraulic diffusivity (1.6 ft2

/d) and responded more slowly to 

drawdown.

The cumulative subsidence in February 1996 

along survey line K, as computed by the three-dimensional model, compared favorably with the measured 

subsidence. Simulated subsidence closely matched the 

measured subsidence in Mt. Morris, 3 mi south of the 

collapse, where as much as 0.3 ft of subsidence was 

measured. As much as 0.1 ft of the simulated subsidence had occurred by February 1996 over an area covering about 16 mi2

 that extended 5 mi north of, and 7 

mi south of, the collapse area. Subsidence was greatest 

near the collapse area and in the center of the valley, 

where deposits of fine-grained sediment are thickest. 

REFERENCES CITED

Acres International, 1986, Sterling Mine B shaft—Geotechnical summary report: Buffalo, N.Y., 20 p. (DEC–906).

Akzo Nobel Salt, Inc., 1994–97, Retsof Mine subsidence 

monitoring: Clarks Summit, Pa., Akzo Nobel Salt, Inc., 

unpublished data on file at Geneseo Public Library, 

Geneseo, N.Y.

———1996, Surface and groundwater impacts report: 

Clarks Summit, Pa., Akzo Nobel Salt, Inc., 20 p.

Alpha Geoscience, 1995a, Well 9446 report: Albany, N.Y., 

Alpha Geoscience, 8 p.

———1995b, Well 9449 report: Albany, N.Y., Alpha Geoscience, 8 p.

———1995c, Well 9460 report: Albany, N.Y., Alpha Geoscience, 12 p.

———1996a, Well 9565 report: Albany, N.Y., Alpha Geoscience, 9 p.

———1996b, Well 9569 report: Albany, N.Y., Alpha Geoscience, 8 p.

———1996c, Geologic and hydrogeologic investigation of 

the Genesee River valley: Albany, N.Y., Alpha Geoscience, 31 p.

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80 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

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APPENDIX 81

APPENDIX
82 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Appendix. Wells in the monitroing network in the Genesee Valley, Livingston County, N.Y., 1997

[Locations are shown in fig. 4. x; information collected] 

Well number

Owner

Land-surface 

elevation

(feet above 

sea level)

Well depth

(feet below 

land 

surface)

Affected 

by

mine 

USGS Local flooding? Aquifer

Water-level

hydrograph

Water

sample

Lv91a 18 Barber-Ag 569.6 329 yes x lower

Lv203b — Croston 565. 120 unknown x lower

Lv301a — ANSI-9401 556. 1,113 yes x Retsof mine

Lv309a — ANSI-9409 554. 877 yes x Onondaga/Bertie 

Limestone

Lv340a 40 ANSI-9440 565.0 366 yes x bedrock

Lv346 88 ANSI-9446(II)c 559.1 499 yes x x Onondaga Limestone

Lv348 101 ANSI-9448(II)c 559.5 383 yes x middle

Lv349 89 ANSI-9449(III)c 567.4 679 yes x x Onondaga/Bertie 

Limestones

Lv350 90 ANSI-9450(III)c 565.8 358 yes x x lower 

Lv351 91 ANSI-9451(III)c 567.2 254 yes x x middle

Lv360 52 ANSI-9460(IV)c 566.8 545 yes x x lower 

Lv361 102 ANSI-9461(IV)c 566.9 323 yes x x middle

Lv362 81 ANSI-9462(IV)c 566.9 260 yes x x middle

Lv365 104 ANSI-9565(V)c 573.1 910 no x x Onondaga/Bertie 

Limestones

Lv366 105 ANSI-9566(V)c 572.9 448 yes x x middle

Lv367 106 ANSI-9567(V)c 573.2 750 maybe x x lower 

Lv368 103 ANSI-9568(II)c 559.5 480 yes x x lower 

Lv369 107 ANSI-9569(I)c 599.9 257 maybe x x Onondaga/Bertie 

Limestones

Lv370 108 ANSI-9570(I)c 599.8 207 maybe x x lower and Onondaga Limestone

Lv371 109 ANSI-9571(I)c 601.0 100 maybe x x middle

Lv396 — ANSI-9572 610. 1170. yes x Retsof mine

Lv397a 75 ANSI-7901 560.0 505 yes x lower 

Lv398 — National Hotel 575. 132 yes middle?

Lv399 — Tubbs 570. 437 unknown middle?

Lv401 1 Rolison 622.0 72 dry x middle

Lv402 2 Gregg 626.6 97 yes x middle

Lv403 3 Rugatuso 611.7 72 dry x middle

Lv404 4 Lovelace 643.3 13 no x shale bedrock

Lv405 5 Baumgardner 565.0 12 no x upper

Lv406 6 American Legion 564.6 32 maybe x upper

Lv407 7 Christiano 562.1 32 maybe x upper

Lv408 8 Newman 666.4 140 no x middle?
APPENDIX 83

Lv409 9 Newman 675.5 116 no x middle?

Lv410 10 Farruggia 743.3 110 no x shale bedrock

Lv411 11 Hull 685.3 21 no x unknown

Lv413 13 Pendergast 760. 96 no x shale bedrock

Lv414 14 Barnhardt 628.2 78 dry x middle

Lv415 15 Werner 621.4 64 dry x middle

Lv416 16 Arend 574.8 24 dry x middle

Lv417 17 Falconer 639.1 42 no x upper?

Lv419 19 Montemarano 590. 35 no x upper

Lv420 20 Cipriano 580. 33 no x upper

Lv421a 21 Atochem 550. 130 yes x lower?

Lv422a 22 Atochem 550. 255 well 

plugged

x unknown

Lv423 23 Bailey 610. 82 dry x middle

Lv424 24 Hardy 630. 115 yes x middle

Lv425 25 Hollinger 580. 173 yes x x lower 

Lv426 26 Davis #1 580. 58 dry x middle

Lv427 27 Banker 590. 193 yes x lower 

Lv428 28 Koshchara 637. 54 dry x unknown

Lv429 29 Bryan 720. 112 no x shale bedrock

Lv430 30 Lloyd 645. 73 no x shale bedrock?

Lv431 31 Yull 755. 46 no x shale bedrock?

Lv432 32 Geary 830. 72 no x shale bedrock

Lv433 33 Scatterday 760. 99 no x shale bedrock

Lv434 34 private 680. 100 no x shale bedrock

Lv435 35 McCracken 640. 160 yes x middle?

Lv436 36 McCauley 685. 121 yes x lower ?

Lv437 37 Barrett 590. 103 dry x middle

Lv438 38 Colahan 690. 99 dry x middle

Lv439a 39 Cofield 600. 96 dry x middle

Lv441 41 private 560. 315 no x unknown

Lv442a 42 Millard 635. 166 yes x x middle?

Lv443 43 Cullinan 650. 103 yes x x middle

Lv444 44 Romano 670. 73 yes x middle

Lv445 45 Bucci 940. 125 no x shale bedrock

Lv446 46 Clinton 820. 295 no x shale bedrock

Lv447 47 Arrigenna 720. 90 no x unknown

Lv448 48 Jerris 660. 101 yes x middle

Well number

Owner

Land-surface 

elevation

(feet above 

sea level)

Well depth

(feet below 

land 

surface)

Affected 

by

mine 

USGS Local flooding? Aquifer

Water-level

hydrograph

Water

sample
84 Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, 

Livingston County, New York

Lv449 49 Vozzies 910. 59 no x shale bedrock

Lv450 50 Morabito 585. 80 no x shale bedrock

Lv451 51 Dueppengisser 1,050. 90 no x shale bedrock

Lv453 53 Susz 670. 74 maybe x middle

Lv454 54 Holt/Marsh 610. 205 yes x x lower 

Lv455 55 private 620. 119 no x unknown

Lv456 56 Yull 755. 120 no x shale bedrock

Lv457a 57 Davis #2 580. 163 yes x lower 

Lv458 58 Crandall 565. 65 maybe x x middle

Lv459a 59 Stone 580. 120 yes x lower 

Lv460 60 O’Neil 600. 51 no x Onondaga Limestone

Lv461 61 Wadsworth 620. 221 yes x x lower

Lv462 62 Preston 655. 80 yes x middle

Lv463 63 Castle 720. 59 no x shale bedrock?

Lv464 64 Seager 770. 40 no x shale bedrock?

Lv465 65 Ambourgey 935. 23 no x shale bedrock

Lv466 66 Ambourgey 935. 23 no x shale bedrock

Lv467 67 Love 810. 67 no x shale bedrock

Lv468 68 Quakenbush 735. 47 no x shale bedrock?

Lv469 69 Orologio, V. 580. 137 yes x x lower 

Lv470 70 Amorese 935. 127 no x shale bedrock

Lv471a 71 Barrett 590. 199 yes x lower

Lv472 72 Waide 1,140. 33 no x shale bedrock

Lv473 73 Olea 770. 17 no x unknown

Lv474 74 Olea 770. 51 no x unknown

Lv476 76 Barefoot 700. 68 no x shale bedrock

Lv477 77 Brassie 1,140. 87 no x shale bedrock

Lv478a 78 Fuller 610. 110 yes x middle

Lv479 79 Ward 580. 150 yes x x lower 

Lv480a 80 Cofield 608. 208 yes x lower 

Lv482 82 Wall 590. 36 yes x middle

Lv483 83 Carlson 610. 127 yes x middle

Lv484 84 Sanderson 610. 53 no x shale bedrock

Lv485 85 Young/Thorn 675. 126 maybe x unknown

Lv486 86 Wiley/Viola 630. 95 yes x middle

Lv487 87 Kane 685. 114 yes x lower?

Lv493 93 Kelly 600. 53 yes x x middle

Well number

Owner

Land-surface 

elevation

(feet above 

sea level)

Well depth

(feet below 

land 

surface)

Affected 

by

mine 

USGS Local flooding? Aquifer

Water-level

hydrograph

Water

sample
APPENDIX 85

Lv494 94 Viola 610. 154 yes x lower 

Lv496a 96 Carlson 610. 212 yes x lower 

Lv498a 98 Davis #3 580. 174 yes x x lower 

Lv500 100 Baker/Wadsworth 600. 219 yes x x lower 

Lv510 — Jones (house) 610. 215 yes x lower

Lv511 — Jones (barn) 610. 225 yes x lower

Lv512 — Halpin 580. 167 yes x lower

Lv513 — McKeown 575. 85 yes x middle

Lv514 — Banker 590. 193 yes x lower

Lv515 — Klimasewski 580 134 unknown x lower

Lv516 — Zander 580. 135 unknown x lower

Lv517 — Sullivan 585. 144 unknown x lower

Lv518 — Orologio, B. 580. 81 unknown x middle?

Lv519 — Elliot 600. 219 yes x lower 

Lv520 — Morss 750. — unknown x bedrock spring

Lv521 — Harris 610. 175 unknown x lower

Lv522 — O’Connell 575. — unknown x lower?

Lv523 — McMahon 580. — unknown x middle?

Lv524 — Striker 580 — unknown x middle?

Lv525 — House 555. spring unknown x middle?

a

 Log available from U.S. Geological Survey, Ithaca, N.Y.

b Log available from Kammerer and Hobba, 1967.

c

 Azko-Nobel Salt, Inc. company number (cluster location); log available from Alpha Geoscience, 1996c.

Well number

Owner

Land-surface 

elevation

(feet above 

sea level)

Well depth

(feet below 

land 

surface)

Affected 

by

mine 

USGS Local flooding? Aquifer

Water-level

hydrograph

Water

sample
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1970” are available in paperback book form and as a set of 

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“Publications of the U.S. Geological Survey, 1971–1981” is 

available in paperback book form (two volumes, publications 

listing and index) and as a set of microfiche.

Annual supplements for 1982, 1983, 1984, 1985, 1986, and 

subsequent years are available in paperback book form.
Yager, Miller, and Kappel—Simulated Effects of 1994 Salt-Mine Collapse on Ground-Water Flow and Land Subsidence in a Glacial Aquifer System, Livingston County, New York—PP 1611

Printed on recycled paper