What is a Mudboil?

The Tully Valley mudboils are volcanolike cones of fine sand and silt that range from several inches to several feet high and

from several inches to more than 30 feet in diameter. Active mudboils are dynamic ebb-and-flow features that can erupt and form a

large cone in several days, then cease flowing, or they may discharge continuously for several years.

Remediation of Mudboil Discharges in

the Tully Valley of Central New York

Mudboils have been observed in the

Tully Valley in Onondaga County,

in central New York State, since the late

1890’s. Mudboils have continuously

discharged sediment-laden (turbid) water

into nearby Onondaga Creek, which

flows to Onondaga Lake. The discharge

of sediment causes gradual land-surface

subsidence (fig. 1) that, in the past,

necessitated rerouting a major petroleum

pipeline and a buried telephone cable,

and caused two road bridges to collapse.

The water discharged from mudboils can

be either fresh or brackish (salty).

Mudboil activity was first reported in

the Syracuse, NY Post Standard, in a

short article dated October 19, 1899:

“Tully Valley—A Miniature Volcano This newspaper article accurately

describes Tully Valley mudboils and

presages the collapse of the Otisco Road

bridge 92 years later in 1991. The article

indicates that land subsidence occurred

nearby, but gives no indication that

Onondaga Creek was turbid; this was

either an oversight by the reporter or was

not a concern.

In 1991, the Onondaga Lake

Management Conference identified the

Tully Valley mudboils as the major

source of turbidity being discharged into

Onondaga Lake. Beginning in the fall of

1991, the Conference created the

Mudboil Working Group (representing

local, State, and Federal agencies) to

Remediation of Mudboil Discharges in

the Tully Valley of Central New York

Few people are aware of the existence of

a volcano in this town. It is a small one,

to be sure, but very interesting. In the 20-

rod gorge where the crossroad leads by

the Tully Valley grist mill the hard

highway bed has been rising foot after

foot till the apex of a cone which has

been booming has broken open and

quicksand and water flow down the

miniature mountain sides. It is an ever

increasing cone obliterating wagon

tracks as soon as crossed. The nearby

bluff is slowly sinking. Probably the

highway must sometime be changed on

account of the sand and water volcano,

unless it ceases its eruption.”
of the valley at the Tully Moraine and from the alluvial fans at

the mouth of Rattlesnake Gulf and Rainbow Creeks.

The flow of water from the mudboils changes seasonally in

response to changes in artesian pressure in the two aquifers. In

the spring, when ground-water recharge is greatest, the

mudboils in the main mudboil/depression area (MDA) (fig. 3,

inset map) can discharge 400 gallons per minute or more. As

recharge to aquifers declines during the summer, artesian

pressure in the aquifers also declines, and flow from mudboils

typically decreases to 200 gallons per minute or less. The rate

of mudboil flow does not change in response to individual

rainstorms but does respond to seasonal variations in

precipitation.

Suspended-sediment discharge from the MDA to Onondaga

Creek was measured between October 1991, and September,

1996. The daily average suspended sediment load for water

years1

 1992-96 are shown in fig. 2. Most of the suspended

sediment is very fine clay and silt with a small fraction of very

fine sand.

Chemical analyses of mudboil discharge in the MDA

indicate that the source of water is either the confined

freshwater aquifer or an underlying brackish-water (salty)

aquifer (fig. 4). Chloride concentrations in the upper,

(1) develop a plan of study to identify the cause of mudboil

activity, and (2) formulate ways to reduce or eliminate

mudboil discharges, and thereby decrease or stop associated

turbidity in Onondaga Creek, and nearby land subsidence. The

U.S. Geological Survey in co-operation with researchers from

the New York State Department of Environmental

Conservation and Syracuse University, began the first

comprehensive, long-term study of mudboil activity in the

Tully Valley. The study plan was to: (1) define the mechanism

and extent of mudboil development; (2) drill test wells to

define the glacial stratigraphy (layering of glacial materials)

and thereby delineate ground-water flowpaths within the

valley, including drilling a deep test well to penetrate the salt

beds below the mudboil area; (3) monitor the flow and

sediment concentrations of mudboil discharges to calculate the

amount of water and sediment discharged to Onondaga Creek;

(4) identify remedial actions to reduce those discharges; and

(5) monitor the results of those actions.

Flow from a mudboil is driven by artesian pressure that

forces water and sediment upward from two sand and gravel

aquifers through a 60-foot-thick layer of dense silt and clay.

The artesian pressure within the aquifer can lift water 20 feet

above land surface within most of the valley floor and 30 feet

above land surface near Onondaga Creek. The source of the

artesian pressure is surface water entering the ground-water

system along the valley walls — primarily at the southern end

1Water year - This is the 12-month period from October 1 through

September 30. The water year ending on September 30, 1996 is the 1996

water year.

Purpose of the Onondaga Lake Management Conference:

“To prepare and implement a comprehensive Management Plan to define a cleanup strategy for Onondaga Lake,

rehabilitate the Lake ecosystem, and restore beneficial uses of the Lake to the citizens of Onondaga County.”

—Statement from: Citizens Advisory Committee, General Goals and Objectives, April 1991

Figure 1. (right) Mudboil/

Depression Area, known as

the ‘’MDA‘’, as of November,

1994. View of land surface

subsidence is toward the

west from the MDA dam.

(Location shown in fig. 3).

Figure 2. (left) Yearly average suspendedsediment load discharged to Onondaga Creek from

the mudboil/depression area, water years 1992-96.

YEARLY AVERAGE SUSPENDED

SEDIMENT LOAD, in tons per day

1992 1993 1994 1995 1996

0

10

20

30

40

29.8

9.75

1.41 1.8 2.78
Surface-Water Diversion

Flow from the upper 0.7 square miles of the Tributary 6

drainage was diverted south to Tributary 5, (fig. 3) in June

1992. This diversion reduced total annual surface water inflow

to the MDA by about two-thirds, which, in turn, reduced

sediment loading to Onondaga Creek by half — from about 30

tons per day before diversion to about 15 tons per day

thereafter.

Aquifer Depressurizing Wells

Depressurizing wells were installed near the collapsed

Otisco Road bridge during the winter of 1992-93 in an effort to

reduce artesian pressures in the upper aquifer and thereby slow

nearby mudboil activity. The wells were drilled to the base of

the freshwater aquifer, and 10-foot-long well screens were

installed to allow artesian-pressured water to flow out of the

well while holding the fine-grained sand and silt in place.

These wells have a combined discharge of about 25 gallons per

minute of sediment-free water and have modestly reduced

artesian pressure in the freshwater aquifer by about 1 pound

per square inch, or about 2.5 feet of hydraulic head. Nearby

mudboil activity did not increase, and no new mudboils have

developed since the wells were installed. Furthermore, the

discharge of nearby mudboils has been sediment free,

indicating possible stability in the area.

Eight additional wells were installed in the aquifers

underlying the MDA and Onondaga Creek in the summer of

1996 to further reduce artesian pressure and slow mudboil

activity. Total ground-water discharge from all wells averages

about 350 gallons per minute. The chemical quality of water

discharged from these wells varies with position around the

MDA; most of the flows from depressurizing wells screened in

the upper aquifer around and downgradient from the MDA are

slightly brackish to salty, indicating that water from the lower

aquifer is migrating upward into the base of the upper,

freshwater aquifer. Water quality upgradient (south) of the

MDA, is generally fresh. Discharge from individual wells

range from less than 5 gallons per minute to more than 100

DIVERSION CHANNEL, 

 from Tributary 6 to 

 Tributary 5

ACTIVE MUDBOIL

 AREAS

DEPRESSURIZING 

 WELL

EXPLANATION

STREAM CHANNEL, 

 arrow shows 

 direction of 

 streamflow

EDGE OF VALLEY

 FLOOR

LINE OF GEOLOGIC 

 SECTION, see 

 Figure 4.

Otisco Road

Onondaga Creek

U. S. Route 20

BARE MOUNTAIN

Rain bow Creek

Rattlesnake Gulf

Tribut ary 6

Tributary 5

Onondaga Cr

New York Route 11-A

A A'

0 0.5 1.0 1.5 MILES

0 0.5 1 2 KILOMETERS

Onondaga Cr

Tully

Fam

s Road

Brine Field

Brine Field

Syracuse

ONONDAGA

COUNTY

Study Area

NEW YORK

Onondaga Creek 

Mudboils

Collapsed Otisco 

Road Bridge

Mudboil/Depression Area 

(MDA)

TULLY 

MORAINE

A A'

Onondaga

Creek

Detail

MDA Dam 





Tributary 6

Figure 3. Principal geographic features of Tully Valley, N.Y.,

and locations of brine field, diversion channel, and mudboil

areas. Inset map shows detail of MDA and locations of

several depressurizing wells and outlet dam.

Onondaga Creek Rainbow Creek

WEST EAST

A A'

ALTITUDE, IN FEET

DISTANCE, IN FEET

0 1,000 2,000 3,000 4,000 5,000

800

700

600

500

400

300

200

100

Rattlesnake

Gulf

Upper (Freshwater) Aquifer

Confining Clay/Silt Layer

Bedrock Valley

Confining Till Layer

Lower (Brackish-water) Aquifer

Figure 4. West-east geologic section between Rattlesnake Gulf

and Rainbow Creek along Otisco Road, showing upper and

lower glacial aquifers and confining clay layers.

freshwater aquifer range from 37 to 430 milligrams per

liter (mg/L) and from 2,000 to 7,100 mg/L in the lower,

brackish-water aquifer. The difference in chloride

concentration between these two aquifers is due partly to the

greater density of the saltwater, which causes the brackish

water to concentrate in the lower aquifer.

 Remedial efforts near the Tully Valley mudboils include:

(1) diverting flow from the tributary that feeds the MDA to an

adjacent tributary; (2) installing depressurizing wells at several

locations around the MDA and along Onondaga Creek to

decrease the artesian pressure; and (3) constructing a dam and

sediment-settling impoundment to detain mudboil sediment

that would normally discharge to Onondaga Creek.
January 1998 United States Department of the Interior — U.S. Geological Survey Fact Sheet FS 143-97

Sources of Technical Information

Kappel, W.M,. Sherwood, D. A.,. and Johnston, W.H,

Hydrogeology of the Tully Valley and characterization of

mudboil activity, Onondaga County, New York: U.S.

Geological Survey Water Resources Investigations Report

96-4043, 1996, 71 p.

Haley and Aldrich of New York, 1991, Report on mudboil

occurrence in the Tully Valley, Onondaga County, New York:

Rochester, N. Y., Haley and Aldrich of New York, prepared for

Allied Signal Inc., 28 p.

Getchell, F.A., 1983, Subsidence in the Tully Valley, New

York, unpublished thesis, Syracuse University, Syracuse, NY,

108 p.

Waller, R.M,. Subsidence in New York related to groundwater discharge in Geological Survey Research 1977, U.S.

Geological Survey Professional Paper 1050, p. 258.

gallons per minute, depending on location and the aquifer

material —flow from a coarse sand is much greater than flow

from a fine-grained sand.

Impoundment Dam

A temporary dam was constructed at the outlet of the MDA

(fig. 3, inset map) in July 1993 to reduce the average daily load

of sediment discharging to Onondaga Creek. The impounded

water covered several mudboils and allowed most of the silt

and sand to settle out before flowing to Onondaga Creek. Also,

the weight of water over active mudboils, and the additional

weight of sediment settling on the mudboils decreased mudboil

discharge. The impoundment, in conjunction with the

depressurizing wells, has slowed mudboil activity in the MDA,

and should slow land subsidence in this area as well.

The impoundment reduced the average daily load of

sediment discharged from the MDA to Onondaga Creek, from

15 tons per day in 1992 to about 1.5 tons per day during water

years 1993 and 1994, but by 1995, the entire impounded area

was filled with sediment. Consequently, sediment loading to

Onondaga Creek increased from 1.8 tons per day in water year

1995 to 2.8 tons per day in water year 1996 (fig. 2).

The dam was reconstructed to allow the outflow elevation to

be raised in the summer of 1996. The intent is to slowly

increase the height of water over the remaining mudboils in the

Figure 5. Depressurizing well flowing more than

100 gallons per minute near the MDA.

MDA while the surrounding depressurizing wells are in

operation. The increased amount of water and sediment over

the active mudboils are expected to slow mudboil activity and

cause the wells to discharge increased amounts of sedimentfree water to the Creek.

Conclusions

 The Onondaga Lake Management Conference’s primary

goal is to restore the lake’s ecological integrity. As one of seven

major issues identified by the Conference, the Tully Valley

mudboils “must be controlled to improve the water quality of

the Creek and Lake, and their habitats.” The Conference has

funded the study of the mudboils within the mudboil/

depression area and along Onondaga Creek since 1991 and has

funded these remediation projects which should, in time, slow

mudboil activity.

 Mudboils will persist in the Tully Valley as long as the

two confined aquifers have artesian pressure that will ‘push’

water above land surface. The remediation projects are designed

to (1) reduce artesian pressure that drives mudboil activity, and

(2) decrease the discharge of sediment. These projects are

expected to slow, but not stop, mudboil activity. As a result,

turbidity in Onondaga Creek will decline, as will the rate of land

subsidence in the Tully Valley. The results of this work will assist

the Onondaga Lake Management Conference in improving the

water quality of Onondaga Creek and Onondaga Lake.

—William M. Kappel and Wendy S. McPherson—

For more Information:

Subdistrict Chief

U.S. Geological Survey

903 Hanshaw Rd

Ithaca, N.Y. 14850

This fact sheet and related

information can be found on

the World Wide Web at:

http://ny.usgs.gov