Prepared in cooperation with the New York State Office of the Attorney General

Simulated Flow of Groundwater and Brine from a Flooded 

Salt Mine in Livingston County, New York, and Effects 

of Remedial Pumping on an Overlying Aquifer

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

This northwest aerial view shows sinkholes above room 11-Yard West (left foreground) and room 2-Yard South (right center, 

partially obscured by trees) of the Retsof salt mine. The Retsof main plant is located about 4 miles northwest of the sinkholes.

Simulations of the movement of brine from a flooded salt mine near Geneseo, New York into an overlying aquifer indicate the 

following effects, if remedial pumping were discontinued: 

►Saline water from bedrock would flow upward toward an overlying aquifer through rubble chimneys in bedrock that hydraulically 

connect the flooded salt mine to the aquifer. Halite brine from the mine would eventually reach the aquifer along the same path. 

►Dense saline water that reaches the aquifer through the rubble chimneys would migrate southward along the sloping bedrock 

surface to its lowest point south of the mine. 

►A pool of saline water would form in this depression and extend northward and southward as the flow continues; however, the high 

relative density of the saline water would probably prevent it from rising into other overlying aquifers. 

►The fate of mine water (brine) that enters bedrock fracture zones that intersect the rubble chimneys is uncertain. Some might emerge 

updip to the north, where a limestone subcrop area intersects the bedrock surface. The traveltime, however, cannot be calculated 

from available information. 

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1286

Ver. 1.1 August 2012
2

Introduction

Two ceiling collapses in the Retsof salt mine near 

Geneseo in upstate New York (fig. 1) in spring 1994 resulted 

in the upward propagation of two columns of rubble through 

600 feet of overlying shale and carbonate bedrock (fig. 2). 

This upward propagation formed a hydraulic connection 

between the lower confined aquifer (LCA) and the mine and 

allowed water from the aquifer and bedrock fracture zones that 

intersected the rubble columns to flow into the mine at a rate of 

18,000 gallons per minute (gal/min) (fig. 3, steps 1–2). All salt 

mining ceased in September 1995, and the mine was completely 

flooded by January 1996 (figs. 1B; fig. 3, step 3). 

The flow of water from the lower confined aquifer into the 

mine caused widespread drawdowns, and water levels in the 

aquifer declined by as much as 400 feet near the collapse area 

and by more than 50 feet at wells 7 miles to the north and south. 

Within 3 to 4 weeks of the collapses, water levels in about a 

dozen domestic and industrial wells had declined severely, 

and some wells went dry. Water levels in at least 58 wells 

in the lower and middle confined aquifers were affected by 

mine flooding. Groundwater in the upper unconfined aquifer 

and surface water in streams were unaffected by water-level 

drawdown, but channels of the Genesee River and Beards 

Creek (fig. 1) were altered by land subsidence related to the 

mine collapse.

Water levels recovered from 1996 through 2006 (fig. 3, 

step 4), but the mine is now filled with about 16 billion gallons 

of saturated halite brine. The weight of the overlying rock and 

sediment is expected to cause the salt beds to deform and fill the 

mine cavity during the next several hundred years; this in turn 

could displace as much as 80 percent of the brine and cause it to 

move upward through the rubble chimneys, rendering the LCA 

unusable as a source of water supply. Saline water was detected 

in the LCA in 2002 but was found to be derived primarily from 

fractures in the limestone and shale units between the mine and 

the LCA, rather than from the mine. 

In September 2006, the mine company began a brinemitigation project that entailed pumping five wells finished in 

limestone and shale units within the collapse areas to alter the 

flow gradient and thereby prevent further movement of brine 

and saline water into the LCA (fig. 3, step 5). The pumped brine 

was routed to an onsite desalination plant. At the same time, the 

U.S. Geological Survey (USGS) began a study in cooperation 

with the New York State Office of the Attorney General 

to construct numerical models to analyze the groundwater 

chemistry and delineate the directions of flow. Specific 

objectives of the study were to: 

» Assess the sources of salinity within the collapse area and 

identify the factors that control the movement and mixing of 

freshwater, saline waters from fracture zones, and brine; 

» Evaluate the likelihood that the pumping will induce 

anhydrite dissolution and lead to continued land subsidence; 

» Construct variable-density groundwater flow models to 

predict the effect of remedial pumping on salinity within 

the LCA;

» Evaluate the effectiveness of remedial pumping in preventing 

the movement of saline water into the LCA; and

» Predict the extent of brine migration 8 years after a 

hypothetical shutdown of all pumping in 2008. 

This report (1) summarizes the hydrogeologic setting and 

effects of mine flooding, (2) describes the geochemical and 

variable-density model simulations and their principal results, 

(3) discusses the implications of (a) continued pumping and 

desalination to protect the LCA and (b) a full shutdown of 

pumping after 2008, and (4) suggests further research that could 

lead to refinement of model predictions. Additional information 

may be found in Yager and others (2001 and 2009). These 

reports can be accessed at http://pubs.usgs.gov/pp/pp1611/ and 

http://pubs.usgs.gov/pp/pp1767/, respectively. A summary of 

simulation results can be accessed at http://ny.water.usgs.gov/

projects/Coram/seawat/seawat.html.

Photograph by Richard Young, Geological Sciences, 

State University of New York Geneseo, May 1994

In April and May 1994, sinkholes formed when rubble chimneys 

extended upward from the Retsof salt mine to land surface (about 

1,100 feet). The formation of the sinkholes lowered the streambed 

of Beards Creek (shown above), a tributary of the nearby Genesee 

River, and water from the creek flooded the sinkholes. Eventually, 

both sinkholes measured 200 feet in diameter (cover photo).

Photograph by William Kelly, New York State Geological Survey, June 199

Picture shows rising water in the Retsof salt mine in June 

1995, following the collapse of two ceiling areas in the mine 

near Cuylerville, New York, on March 12, 1994. A pump out was 

attempted and abandoned. Mining ceased in September 1995, 

and the mine was flooded by January 1996.

5
3

RETSOF SALT MINE

MODEL

 DOMAIN

Conesus

Creek

Genesee

River

Genesee

River

Beards

Creek

Creek

Keshequa

Creek

Canaseraga

Conesus

Lake

Dansville

Nunda

Mount

Morris

Leicester

Geneseo

Livonia

Avon 20 20

15

39

390

20A

256 20A

15

256

255

256

436

258 408

408

39

36

20A COLLAPSE

AREAS

0 2

0 2

4 MILES

4 KILOMETERS

LOCATION MAP

NEW YORK

Study

area

A

B A’

B’

EXPLANATION

Aquifer-system boundary

Approximate extent of

 lower confined aquifer 

Line of geologic section A A’

Base from U.S. Geological Survey digital data, 1:100,000, 1983

Universal Transverse Mercator projection, Zone 18

Sonyea

77°52'30" 77°45'

42°37'30"

42°45'

42°52'30"

390

Rochester

City of Rochester

16 miles

EXPLANATION

Room and pillar mining

Yielding pillar mining

Collapse

March 1994

Collapse

Panel Room

11-Yard West

Panel Room

2-Yard South

B. Mine extraction technique

C. Progression of mine flooding

June 1994

Oct. 1995

April

1994

Sept. 1994

Mine shaft

Jan. 1996

Extent of

Retsof Salt Mine

A

Figure 1. A, Map showing locations of the Retsof salt mine and the two ceiling-collapse areas, and the extents of aquifers near 

Geneseo in Livingston County, New York. Adapted from Yager and others (2009, fig. 1.) B, Plan view showing small pillars in panel 

rooms 2-Yard South (2YS) and 11-Yard West (11YW) where ceiling collapse occurred. C, Map showing extent of Retsof salt mine and 

progression to complete flooding of the 5-mile by 5-mile mine in January 1996. 
4

A–A'

Lv 369 Gas well

16108

Gas well

 17445

Lv 442

(projected)

Lv 422 Lv 346 Lv 360 Lv 399 Lv 365 Lv 46

Lv 29 Lv 21Lv 13

Fowlerville

moraine

Avon Geneseo Collapse

area

Dansville Sonyea

Older Silurian shales,

siltstones, and sandstones

Retsof salt bed (B6 salt unit)

Camillus Shale, Syracuse Formation, and Vernon Shale

Bertie Limestone

Onondaga Limestone

Devonian shales

(undifferentiated)

Unconformity

EXPLANATION

Unconsolidated deposits

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

and gravel

 Lacustrine sand, silt, and clay

 Till—Silt and clay embedded with pebbles

 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

Yager and others, 2001. Numbers for gas wells were assigned

by New York State Department of Environmental Conservation 

Lv349

200

NAVD 88

–800

–600

–400

–200

400

600

800

FEET

NORTH

200

NAVD 88

–800

–600

–400

–200

400

600

800

FEET

SOUTH

5 10 MILES

0

0

5 10 KILOMETERS

VERTICAL SCALE GREATLY EXAGGERATED

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 unconfined aquifer

Upper confining layer

Middle confined aquifer

Lower confining layer

Lower confined aquifer

Deltaic deposits

Till

Direction of water flow

during mine flooding

Water table

800

600

400

200

NAVD 88

–200

–400

–600

–500

–300

–100

100

300

500

700

800

600

400

200

NAVD 88

–200

–400

–600

–500

–300

–100

100

300

500

700

VERTICAL EXAGGERATION x10

FEET

WEST

A FEET

EAST

A'

2,000 4,000 FEET

0

0

500 1,000 METERS

Mineral content in core

 from borehole Lv343

▲ Clay minerals (> 20 percent)

Anhydrite (> 20 percent)

▼ Fe-dolomite (> 30 percent)

+ Halite (> 30 percent)

Direction of water flow during mine flooding

Figure 2. The upper stratigraphic cross-section A–A’ shows one rubble chimney above the collapsed ceiling and the directions 

of groundwater flow into the Retsof salt mine, Livingston County, New York. The map view of the location of cross section A–A’ is 

shown in figure 1 (from Yager and others, 2009, fig. 2). The lower cross section shows a view from north to south under the valley 

from Avon to Dansville, New York (see fig. 1), describing the unconsolidated deposits and direction of water flow in the lower 

confined aquifer during mine flooding. 
5

Effects of Mine Flooding

The flooded salt mine lies beneath a glacially scoured 

bedrock valley that contains the Genesee River in western 

New York (fig. 1). The mined salt bed is within Silurian shale 

overlain by nearly 600 feet of Devonian shale and limestone 

units that underlie a 500-foot-thick glacial aquifer system 

containing an upper unconfined aquifer, a middle confined 

aquifer, and a lower confined aquifer (LCA). These aquifers are 

separated by thick confining layers (fig. 2).

Deformation of the overlying bedrock layers after the 

collapse resulted in land-surface subsidence that ranged from 

15 feet over some parts of the mine to more than 70 feet 

above the rubble chimneys. As much as 0.8 feet of subsidence 

occur south of the mined area as a result of dewatering and 

compaction of fine-grained sediment in the confining layers 

of the glacial aquifer system. Two sinkholes that appeared 

over the rubble chimneys in April and May of 1994 each 

measured 200 feet in diameter and deepened as surficial 

sediment subsided into the sinkholes. The subsidence also 

damaged nearby structures, including a State highway bridge. 

Dissolution of salt pillars within the flooded mine increased 

the rate of mine-cavity closure and resulted in continued land 

subsidence that ranged from 1 to 16 feet over several parts of 

the mine (subsidence survey map shown on page 9).

Borehole geophysical surveys and drilling in the limestone 

units in April 1994 and March 2004 indicated that water in the 

bedrock units above the mine was initially flowing toward the 

rubble chimneys through two main horizontal fracture zones, 

and that the collapses had caused increased fracturing within 

these zones. These zones are designated the O/B fracture zone 

between the Onondaga and Bertie Limestones and the B/C 

fracture zone between the Bertie Limestone and the Camillus 

Shale (fig. 4). A less extensive Syr fracture zone is also present 

in the upper part of the Syracuse Formation. 

Groundwater levels recovered and the hydrostatic pressure 

within the mine increased, thereby slowing the rate of land 

subsidence to less than 0.8 inches per year by 2006. After the 

mine was flooded, saturated halite brine was displaced from the 

mine by the weight of the overlying material. The only outlet 

for displaced brine is upward through the rubble chimneys, 

although some brine could be diverted laterally into the bedrock 

fracture zones above the mine (fig. 4).

Modeling Studies

The chemistry of groundwater in the collapse area reflects 

the hydraulic and chemical processes that have occurred since 

mine flooding began in 1994. Geochemical models were 

developed to assess the sources of salinity (the flooded mine 

and the fracture zones within the overlying bedrock units) 

and to predict whether groundwater-quality changes induced 

by pumping would lead to mineral dissolution and additional 

land subsidence. Variable-density flow models were developed 

to (1) calculate the rates and directions of groundwater flow, 

(2) assess the effectiveness of mitigation pumping (from 2006 

through 2008) in preventing migration of brine into the LCA 

and (3) predict the lateral extent of potential brine migration 

within the LCA if the pumping were terminated. 

Geochemical Models

Geochemical models for seven water samples in the 

collapse area were developed through PHREEQC (Parkhurst 

and Appelo, 1999) to analyze the variation in chemical 

composition of water in the collapse area and identify the 

mixing proportions of waters from three sources—halite brine 

from the flooded mine, saline water from the overlying bedrock 

units, and freshwater from the LCA. The models also were 

used to identify reactions between water and rock that explain 

the observed water chemistry in the collapse area. Additional 

geochemical models were used to assess the potential for 

mineral dissolution and land subsidence caused by the mixing 

of saline water and brine in the collapse area as induced by 

brine-mitigation pumping. 

Photograph by Richard Young, Geological Sciences, 

State University of New York Geneseo, March 1995

An Earth fissure ruptures a field above the western edge of the 

mine, northwest of 2-Yard South sinkhole. The field surrounding 

the fissure had subsided almost 1 foot.

U.S. Route 20A bridge and utilities in April 1996 showing effects of 

surface subsidence.

Photograph by William Kelly, New York State Geological Survey, April 1996
6

600

400

200 NAVD 88

200

400

600

Moscow Shale Ludlowville Formation Skaneateles Shale 

Onondaga Limestone Bertie Limestone Camillus Shale Syracuse Formation Vernon Shale Retsof salt mine Unconformity (fracture zone)

Collapse structure (rubble chimney)

600

400

200

NAVD 88

200

400

600

Cuylerville

Geneseo

Genesee River

Top of bedrock

20A

N

Marcellus Shale 

Unmined salt (unit B6)

Unconsolidated sediments

Upper unconfined aquifer Upper confining layer Middle confined aquifer Lower confining layer Lower confined aquifer

Sinkholes

Unconsolidatedsediments

Unconformity

Top of bedrock

(fracture zone)

Retsof salt mine

Unmined salt (unit B6)
7

(1) March, 1994— Collapse at the Retsof salt mine. Inflow of saline water into mine through rubble zone.

(3) January, 1996—Salt mine is completely flooded. Minimum water levels in wells. Brine and saline water begin to move upward through rubble chimney.

(2) April, 1994—Rubble chimney extends to land surface, creating sinkholes. Inflow of freshwater from lower aquifer. Water levels drop in wells in unconsolidated sediments.

(4) 1996 to 2006—Water levels recover to precollapse levels (near land surface). Brine and saline water in rubble chimney, saline water at top of bedrock. Inflow of saline water from bedrock upward through rubble chimney.

(5) 2006 to present— Pumping of brine and saline water from deep well. Continued inflow of saline water and brine. Water levels in wells remain constant.

Waterlevelin well

Perspective three-dimensional views showing Figure 3.

geologic setting, Retsof salt mine, rubble chimneys and 

ork. Inset views collapse areas, Livingston County, New Y

depict timeline from March 1994 to present (2010): (1) collapse of ceiling areas in March 1994, resulting in the inflow of saline water from fractured bedrock into the mine; (2) appearance of sinkholes at land surface in April 1994, inflow of fresh water from the lower confined aquifer, and decreases in water levels in wells; (3) salt mine completely flooded by January 1996, with water levels in most wells near minimum and brine beginning to move upward through the rubble chimneys; (4) recovery of water levels and continuing flow of saline water and brine upward through rubble chimneys from 1996 through 2006; and (5) operation of the brine mitigation project, including the pumping of saline water and brine from deep wells, from 2006 to present.
8

Lv534Lv309

B

South North

B'

Lv527Lv526Lv533Lv532

Lower confined aquifer

 (LCA)

Lower confining layer

Syracuse Formation

Vernon Shale

Onondaga Limestone

Bertie Limestone

Camillus Shale

Fracture zone and label

Direction of flow

 Freshwater in LCA

 Saline water in bedrock

 Halite brine in mine and 

 rubble chimneys

Monitoring well and number—

 Cased interval shown in gray;

 packer denoted by bold line

Lv309

O/B-FZ

Closure of mine cavity

Brine displacement

O/B-FZ

B/C-FZ

Syr-FZ

VERTICAL EXAGGERATION × 6

Flooded salt mine 

Rubble chimney 

Deformation zone 

EXPLANATION

-180

-160

-140

-120

-100

-80

-60

-40

-20

NAVD 88

20

METERS FEET

NAVD 88

–200

–400

–600

–500

–300

–100

2,000 FEET

0

0

500 METERS

Figure 4. Stratigraphic cross-section B–B’ showing rubble chimneys, the deformation zone in the collapse 

area above the flooded salt mine, and the direction of groundwater flow during water-level recovery, January 

1996 through August 2006. Water flows toward the collapse area from the lower confined aquifer and the 

fracture zone (FZ) between the Onondaga and Bertie (O/B) Limestones. Brine from the mine is displaced 

upward into the chimneys by closure of the mine cavity. Location is shown in figure 1. From Yager and others, 

2009, fig. 7. B/C-FZ, fracture zone between Bertie Limestone and Camillus Shale; NAVD 88, North American 

Vertical Datum of 1988. 
9

 The results of the simulations indicated that the halite 

brine in the flooded mine is a mixture of aquifer water 

(81 percent), bedrock water (16 percent), and bromide-rich 

brine (3 percent) assumed to have formed following deposition 

of the salt during the Silurian Period. The halite brine from 

the mine cavity has become diluted with bedrock water as 

it flows upward through the rubble chimneys, whereas the 

saline water above the O/B fracture zone is a mixture of saline 

bedrock water and aquifer water—an indication that brine 

from the flooded mine had not reached the LCA in 2006. The 

geochemical models indicated that land subsidence in the 

collapse area through anhydrite dissolution would not occur 

under prepumping (2005) conditions, and that subsidence 

through dissolution could occur but would be unlikely if 

pumping were kept at a lower rate than the upward flow of 

halite brine from the mine. 

Groundwater-Flow Models

Analytical and numerical models were used to simulate 

the movement of aquifer water, bedrock water, and halite brine 

within the rubble chimneys and the surrounding deformation 

zones during the 10.7-year period of water-level recovery that 

followed the period of mine flooding (January 1996 through 

August 2006). Several one- and three-dimensional (1D and 

3D) models were constructed through SEAWAT (Langevin and 

others, 2007), which simulates flow and solute transport. 

The 1D models were used to simulate upward flow of 

brine to the LCA through a single rubble chimney to (1) obtain 

an estimate of the rate of upward brine migration and the 

longitudinal dispersivity of the rubble material and (2) indicate 

the number of model layers needed for the 3D simulations, 

which were designed to predict the movement of the transition 

zone between saline water and brine during the 10.7-year waterlevel-recovery period. 

The 3D models simulated flow through both rubble 

chimneys and the surrounding deformation zone and 

represented the mixing of brine with bedrock water where 

fracture zones intersected the rubble chimneys. These models 

were used later to simulate the movement of aquifer water, 

bedrock water, and mine water in response to mitigation 

pumping from the collapse area that began in September 2006.

The 3-D models, which represented 1.8-square-mile 

areas surrounding the rubble chimneys, were each divided into 

75 rows and 52 columns, with cell dimensions ranging from 

33 feet to 980 feet (fig. 5). The final model had 159 layers and 

238,558 active cells. The layers represent the regional bedrock 

dip from north to south, parallel to the flooded salt mine, with 

layer spacings that ranged from 13 ft in the bottom half of the 

domain to 2 ft in the upper half. 

Two nearly identical 3D models (models A and B) 

were constructed to assess the hypothesis that salinity in 

the upper part of the profile is derived from the inflow of 

bedrock water from the limestone units, as indicated by the 

geochemical models, rather than from brine from the mine. 

Model A represented only fracture zone O/B, whereas model 

B represented three fracture zones: O/B, B/C, and Syr, as 

indicated by the observed salinity profile. The thickness and 

elevation of the fracture zones were interpolated from well 

borings and borehole geophysical logs. Simulations by the two 

models gave similar results, but differed slightly in the predicted 

composition of waters in the collapse area and in the values of 

some estimated model parameters. 

A 1-day steady-state simulation with constant heads 

in the LCA and the flooded mine provided an initial head 

distribution for the transient-state simulation of the 10.7-year 

water-level recovery. The initial conditions were as follows: 

the mine was filled with brine; the LCA, the rubble chimneys, 

and the deformation zone were filled with freshwater; and the 

bedrock fracture zones were filled with saline water. The initial 

concentration of halite (halite saturation) of water in the rubble 

chimneys and deformation zone was specified as zero, and a 

constant saturation of 100 percent was specified for the bottom 

model layer (flooded mine). Constant heads were specified for 

each year during the 10.7-year recovery period according to 

those measured in the LCA. Injection of brine at 100-percent 

saturation was applied at the bottom model layer to represent 

brine being displaced from the flooded mine. The brinedisplacement rates were estimated through model calibration 

and were decreased from 110 gal/min at the beginning of the 

simulation to 25 gal/min at the end. These rates were consistent 

with the mean rate that was estimated through subsidence 

surveys during 1996–2001.

1 MILES

1 KILOMETERS

0

0

Modified from William M. Kelly, New York State Geological Survey, 2006

Retsof mine

Extent

of mine

Collapse

area

LAND SUBSIDENCE CONTOUR INTERVAL 1 FOOT

Land subsidence near the Retsof mine collapse area, in feet, 

from April 1995 to July 1996. Dissolution of salt pillars within 

the flooded mine increased the rate of mine-cavity closure and 

resulted in continued land subsidence that ranged from 1 to 

16 feet over several parts of the mine. After the mine was flooded, 

saturated halite brine was displaced from the mine by the weight 

of the overlying material continuing to close the mine cavity. 

The only outlet for displaced brine is upward through the rubble 

chimneys, although some brine could be diverted laterally into the 

bedrock fracture zones above the mine (fig. 4). 
10

Extent of 

 Retsof salt mine

Lower confined aquifer,

 model layers 1 to 6

Rubble chimney,

 model layers 7 to 158

Monitoring well

 and number

Pumped well

 and number Deformation zone,

 model layers 7 to 158

Inactive cell

Constant-head boundary,

 model layer 1

EXPLANATION

B B’ Line of geologic section

Lv534

Lv532

Lv309

Lv539

Lv542

B'

B

Lv537

Lv537

Lv538

Lv540

Lv309

Lv530

Lv529

Lv527

Lv528

Lv322

Lv526

0 2,000 FEET

0 500 METERS

Figure 5. Three-dimensional model domain with the extent of the salt mine and the locations of the stratigraphic crosssection B–B’, the lower confined aquifer, the rubble chimneys, the deformation zone, and pumped and monitoring wells. 

From Yager and others, 2009, fig.16.
11

Model Calibration

Both 3D models were calibrated through trial and error 

to match measured values of halite saturation in time-series 

plots and a salinity profile based on measurements made 

in September 2006. The models were intended to illustrate 

processes that control solute transport rather than to provide 

calibrated representations of the flow system. Values for 

hydraulic conductivity, percent porosity, and longitudinal 

dispersivity were specified for the LCA, the rubble chimneys, 

the deformation zone, and the three fracture zones. The 

models were most sensitive to rubble-chimney porosity, which 

determined the velocity of brine migration and the depth 

referenced to the North American Vertical Datum of 1988 

(NAVD 88), of the transition zone between brine and saline 

water at the end of the 10.7-year simulation. Different porosity 

values were estimated for model A (10 percent) and model B 

(6 percent) to match the salinity profile. The mean inflow rates 

of groundwater into the collapse area from the O/B fracture 

zone during the 10.7-year recovery period also differed 

(30 gal/min and 16 gal/min for models A and B, respectively.

Simulation Results 

Time-series plots and block diagrams were generated 

to depict (1) the progression of halite saturation; (2) changes 

in directions of groundwater flow and in proportions of mine 

water, bedrock water, and aquifer water at selected elevations; 

and (3) flow directions in and around the rubble chimneys and 

fracture zones as closure of the mine cavity forced mine water 

upward into the rubble chimneys and the fracture zones during 

1996–2006 (fig. 6). Model B predicted a lower rate of salinewater inflow from the O/B fracture zone than model A and 

indicated that mixing of waters from the other two fracture zones 

transported mine water higher in the water column than in model 

A. Both models indicated lateral diversion of brine into the B/C 

fracture zone. Model B also indicated possible intrusion of mine 

water into the LCA. Although the geochemical simulation results 

do not support this interpretation, it could be valid if parts of the 

aquifer that were not sampled contained mine water.

Neither model A nor model B indicated that saline water 

had migrated laterally beyond the collapse area within the LCA. 

The origin of salinity in the upper part of the collapse area in 

model A (only one fracture zone) is consistent with results 

from the geochemical models, whereas the origin of salinity 

in model B (three fracture zones) indicates movement of mine 

water into all three fracture zones and is consistent with original 

predictions from the 1995 geotechnical studies (John T. Boyd 

Company, 1995) and borehole flow-meter surveys. Whether 

model A or model B more accurately represents conditions in 

the collapse area is unknown because the lateral extents of the 

fracture zones beyond the collapse area are not well delineated 

and because the boundary conditions specified for the mine 

and fracture zones are uncertain. As a result of these and other 

uncertainties, both models may not accurately represent flow 

and transport in the collapse area. The results, however, provide 

a description of the major processes and groundwater sources 

that contributed to the migration of brine and saline water—

namely, the advection and dispersion of brine through the rubble 

chimneys and deformation zones—and the mixing of brine with 

saline water from fracture zones. 

Simulated Effects of Mitigation Pumping During 2006–11 

Models A and B were used to predict the changes in 

water levels and halite saturation that could be caused by the 

simulated pumping of the five brine-mitigation wells from 

September 2006 through August 2011 (fig. 5). Simulated 

results were compared with changes in water levels and halite 

saturation induced by pumping during 2006–08 and with the 

total mass of halite produced by the desalination plant. Both 

models simulated the movement of mine water, bedrock water, 

and aquifer water, and also the composition of water produced 

by each of the pumped wells. 

The mitigation-pumping simulations by both models 

indicated that the current rate of pumping (25 gal/min will 

cause halite saturation in the collapse area to decrease and also 

will alter the directions of groundwater flow; this in turn will 

halt the upward migration of brine and saline water toward 

the LCA. The 5-year simulations indicated that the rate of 

brine displacement from the flooded mine is currently (2009) 

25 gal/min or less and that as much as 5 gal/min is possibly 

being diverted laterally into the B/C fracture zone.

Results of simulations with model B (three fracture zones) 

matched the halite saturation of the influent to the desalination 

plant, the amount of halite produced, and the observed decline 

in saturation through time better than model A (one fracture 

zone). Both sets of simulations reflected some of the actual 

conditions in the collapse area, but only simulations by model B 

indicated that more than one fracture zone affects the migration 

of saline water and mine water in the collapse area. The actual 

amount of mixing and rate of flow from the fracture zones, 

however, could be less than indicated by model B.

A sensitivity analysis with both models identified the 

parameters to which the simulation results were most sensitive. 

The results indicated that the principal controls on saturation 

and water levels were the rates of brine displacement from 

the mine and the pumping rate, and that the simulated rate 

of brine displacement could be slower than the actual rate 

because the simulated declines in saturation were smaller than 

those observed at most wells from September 2006 through 

February 2008. 

Implications for Future Mitigation Efforts 

The simulations of water-level recovery (1996–2006) 

indicate that saline water has probably not moved laterally 

beyond the collapse area within the LCA. The simulations 

of pumping (2006–08) indicate that pumping has halted the 

upward migration of brine and saline water and that salinity 

within the upper parts of the rubble chimneys and deformation 

zones will decrease over the next few years if the current rates 

of pumping (36 gal/min) are maintained. 

Effects of Permanent Shutdown

Additional 10-year simulations were conducted to predict 

changes in halite saturation within the O/B fracture zone 

and the LCA if the brine-mitigation project had been halted 

in September 2008 after 2 years of pumping. Results of the 

simulations of a permanent shutdown with model A indicated 

that, in the absence of pumping, saturated brine would rise 

nearly to the O/B fracture zone in 3 years by September 2011 

and extend laterally throughout the O/B fracture zone within the 
12

South

B

North

B’

Direction of groundwater flow

Color of vector arrows indicates 

groundwater velocity, in feet per day 

Closure of mine cavity displaces brine 

 from flooded mine

10

0.1

1

Halite saturation, in percent

100

0

50

75

25

EXPLANATION

South

B

North

B’

Syr-FZ

Flooded

 salt mine

Rubble

 chimneys

B/C-FZ

O/B-FZ

LCA

EXPLANATION

A. January 1998

B. September 2006

 Figure 6. Examples of block diagrams along cross-section B–B’ in collapse area showing results simulated by model B for 

changing directions of groundwater flow (left) and changes in the spatial distribution of halite saturation (right) for A, January 1998 

and B, September 2006. The simulation results indicate groundwater-flow exiting the rubble chimney to both the lower confined 

aquifer and the Bertie-Camillus fracture zone (B/C-FZ) from January 1998 to September 2006, and a reversal in groundwater-flow 

direction along the Onondaga-Bertie fracture zone (O/B-FZ), initially as an inflow, but then becoming an outflow. The halite saturation 

results indicate increased levels of halite saturation in the chimneys and intersecting fracture zones (for example, the Syracuse 

fracture zone (Syr-FZ)), as brine is displaced from the mine cavity and moves upward. Saline water was detected in the confined 

aquifer in 2002. Animations of model simulation results can be seen at http://ny.water.usgs.gov/projects/Coram/seawat/seawat.html. 

Location of section B–B’ is shown in figure 5. From Yager and others, 2009, (fig. 20).
13

September 2011 September 2016

South

Rubble chimneys

 and deformation 

 zone

LCA

North

South

North

South

North

South

North

B Plan view of O/B-FZ

A Section B–B’

C Plan view of LCA

100 Halite saturation, in percent

0

50

75

25

South

B

B

B’

North

B’

South

B

North

B’

O/B-FZ

Flooded 

 salt mine

VERTICAL EXAGGERATION × 5

EXPLANATION

Figure 7. Simulated halite saturations in 2011 and 2016 following shutdown of brine mitigation project after 

2 years of pumping from September 2006 through August 2008: (A) along section B-B’ through the 

collapse area, (B) plan view of fracture zone at Onondaga/Bertie contact (O/B-FZ) and (C) plan view 

of lower confined aquifer (LCA).

Figure 7. Simulated halite saturations in 2011 and 2016 following shutdown of brine-mitigation project after 2 years of pumping from 

September 2006 through August 2008: A, Along cross-section B–B’ through the collapse area, the brine would rise nearly to the OnondagaBertie fracture zone (O/B-FZ) by September 2011 and spread throughout the zone by September 2016; B, plan view of the O/B-FZ indicates 

that halite brine would fill the rubble chimneys and deformation zone by September 2011 and most of the modeled area of the zone by 

September 2016; and C, the plan view of the lower confined aquifer indicates that the halite saturation would increase to about 75 percent 

in the rubble chimneys and deformation zone by September 2016 and that a plume of saline water about 25 percent saturated would 

migrate southward along the sloping bedrock surface of the aquifer toward its lowest point, which is near Sonyea (figs. 1 and 2). 
14

Photograph by Samuel Gowan, Alpha Geoscience, February 2007

The brine-mitigation project, implemented in 2006, has stopped the 

upward migration of brine and saline water within the collapse 

area. Pumping brine and saline water from 5 deep wells (fig. 5), the 

desalination plant is capable of processing 100 gallons per minute 

of saturated brine, producing potable water and salt.

model domain in 8 years by September 2016 (fig. 7). The brine 

would continue to rise within the rubble chimneys and enter 

the LCA, whereupon a plume of saline water would migrate 

southward along the sloping bedrock surface. The predicted 

halite saturation would be about 10 percent at the southern 

model boundary (0.5 mile south of the collapse area) by 2011 

and 20 percent by September 2016.

Decreasing the estimated hydraulic conductivity of the O/B 

fracture zone from 50 feet per day to 25 feet per day decreased 

the predicted flow of saturated brine into the O/B fracture zone 

and increased the percent saturation in the LCA. This decrease 

in hydraulic conductivity would cause predicted saturation 

at the southern model boundary to increase to 30 percent by 

September 2016. 

Interpretation of the simulation results indicates 

the following:

» Cessation of pumping would allow saline water from bedrock 

to flow upward toward the LCA through the rubble chimneys. 

Halite brine from the mine would eventually reach the LCA. 

» Dense saline water that reaches the LCA through the rubble 

chimneys would migrate southward along the sloping 

bedrock surface to its lowest point, which is near Sonyea 

(figs. 1 and 2). 

» A pool of saline water would form in this location along the 

LCA and then extend northward and southward as the flow 

continues; however, the high relative density of the saline 

water would probably prevent it from rising into overlying 

aquifers or to the land surface in that location. 

» The fate of mine water (brine) that enters the bedrock fracture 

zones is uncertain. Some might emerge updip to the north 

near Avon, where the subcrop area of the Bertie Limestone 

intersects the bedrock surface (fig. 2). The traveltime, 

however, cannot be calculated from information available. 

Cost/Benefit Considerations for Continued Aquifer Protection 

The LCA is not currently used as a source of fresh water 

except for a few residential wells southwest of Avon (fig. 1). 

The estimated volume of water within the aquifer (37 billion 

gallons) is about 2.5 times the volume of brine expected to be 

displaced from the flooded mine; therefore, intrusion of saline 

water and brine into the aquifer can be expected to substantially 

increase the salinity of aquifer water and render it unusable as a 

source of supply.

The potential yield of the LCA is 3 million gallons per 

day, as estimated by steady-state simulations with the model 

of the glacial aquifer system developed by Yager and others 

(2001). The value of this resource represents its potential utility 

as a storage reservoir in addition to the volume of water it 

could provide.

The brine-mitigation project, implemented in 2006, can 

be considered a success because the pumping has stopped the 

upward migration of brine and saline water within the collapse 

area, and because the desalination plant produces potable water 

and salt that can be offered for sale. The value of these products 

is less than the cost of the plant operation, however (S.W. 

Gowan, Alpha Geoscience, oral commun., 2008).

The protection of the aquifer from the continuously 

rising brine from the flooded mine would necessitate 

continued pumping and operation of the desalination plant 

for the next several hundred years (John T. Boyd Company, 

1995). The decision as to whether to continue operation of 

the plant will therefore probably depend on comparing the 

costs of mitigation against the present and future value of the 

groundwater resource.

Suggestions for Further Research 

Continued data collection could allow model refinement 

and improved assessment of whether continued pumping 

and desalination are warranted. The following efforts could 

provide information vital to refine the model and improve the 

predictions of saline water and brine migration:

» Continued monitoring of the halite saturation of groundwater 

within the collapse area and fracture zones in the bedrock in 

response to pumping

» Drilling of additional test holes into the Syracuse Formation 

outside the collapse area to delineate the extent and hydraulic 

properties of the bedrock fracture zones, provide additional 

access points for groundwater sampling, and thus monitor 

the lateral movements of saline water from bedrock and brine 

from the mine

» Measurement of groundwater levels in the fracture zones 

with which to calculate the hydraulic gradients needed 

for refinement of the boundary conditions specified in 

model simulations

» Borehole flowmeter surveys during remedial pumping to 

provide information on flow to and from the fracture zones 

and the hydraulic properties of these zones
15

Selected References

John T. Boyd Company, 1995, Impact analysis—Retsof Mine, Akzo Nobel Salt, Inc.: Pittsburgh, PA, John T. Boyd Company, 50 p. 

Kelly, William, 2006, Geology and history of 1994 roof collapse of AKZO Salt Mine, Cuylersville, NY, in 2006 Interstate Technical 

Group on Abandoned Underground Mines Sixth Biennial Workshop, June 14-16, 2006, Rochester, New York, accessed April 23, 

2011, at http://www.dot.ny.gov/conferences/itgaum.

Langevin, C.D., Thorne, D.T., Jr., Dausman, A.M., Sukop, M.C., and Guo, Weixing, 2007, SEAWAT version 4: A computer program 

for simulation of multi-species solute and heat transport: U.S. Geological Survey Techniques and Methods book 6, chap. A22, 39 p. 

New York State Department of Environmental Conservation, 1997, Collapse and flooding of Akzo Nobel’s Retsof salt mine, 

Livingston County, N.Y.: Albany, N.Y., Division of Mineral Resources, 113 p. 

Parkhurst, D.L., and Appelo, C.A.J., 1999, User’s guide to PHREEQC (version 2)—A computer program for speciation, batchreaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Water-Resources Investigations 

Report 99–4259, 310 p. 

Yager, R.M., Miller, T.S., and Kappel, W.M., 2001, Simulated effects of 1994 salt-mine collapse on groundwater flow and land 

subsidence in a glacial aquifer system, Livingston County, New York: U.S. Geological Survey Professional Paper 1611, 85 p., at 

http://pubs.usgs.gov/pp/pp1611/. 

Yager, R.M., Misut, P.E., Langevin, C.D., and Parkhurst, D.L., 2009, Brine migration from a flooded salt mine in the Genesee Valley, 

Livingston County, New York—Geochemical modeling and variable-density flow: U.S. Geological Survey Professional Paper 1767, 

52 p., at http://pubs.usgs.gov/pp/pp1767/.

By Richard M. Yager, Todd S. Miller, William M. Kappel, Paul E. Misut, Christian D. Langevin, David L. Parkhurst, and M. Peter deVries

Selected USGS Reports Related to Salt Production, 

Brine, and Saltwater Intrusion in New York

» Salt - Statistics and Information (shown right) 

from USGS National Minerals Information Center, 

Mineral Commodity Summaries, January 2012 at 

http://minerals.usgs.gov/minerals/pubs/commodity/salt/.

» The Retsof Salt Mine Collapse—Widespread subsidence 

occurred after a mine collapse in the Genesee Valley, New 

York at http://pubs.usgs.gov/circ/circ1182/pdf/14Retsof.pdf.

» Salt production in Syracuse, New York ("The Salt City") 

and the Hydrogeology of the Onondaga Creek Valley at 

http://ny.water.usgs.gov/pubs/fs/fs13900/FS139-00.pdf.

» Halite brine in the Onondaga Trough near Syracuse, New 

York: Characterization and simulation of variable-density 

flow at http://pubs.usgs.gov/sir/2007/5058/.

» Chloride in groundwater and surface water in areas underlain 

by the glacial aquifer system, northern United States at 

http://pubs.usgs.gov/sir/2009/5086/.

» Evaluation of well logs for determining the presence of 

freshwater, saltwater, and gas above the Marcellus Shale 

in Chemung, Tioga, and Broome Counties, New York at 

http://pubs.usgs.gov/sir/2010/5224/.

» Simulation of variable-density ground-water flow and 

saltwater intrusion beneath Manhasset Neck, Nassau County, 

New York, 1905–2005 at http://pubs.usgs.gov/sir/2008/5166/.
Rock salt being unloaded off of a ship in Oswego, New York, October 2007

James Rajotte/The New York Times/Redux

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