Groundwater Exploration in Tennessee's Karst Terrane

Groundwater Exploration in
Tennessee’s Karst Terrane
Thomas E. Ballard, PG
Southeast Hydrogeology, PLLC
Murfreesboro, TN

Distribution of Limestone
in Tennessee

Karst Hydrogeology
• Two thirds of Tennessee is underlain by limestone.
• Karst is an important groundwater source in those areas.
• Primary porosity is low in limestone.
• Secondary porosity, i.e. solution cavities and fractures, are an
important groundwater source.
• Karst aquifers best developed near surface and in relatively pure
limestones.

Karst Aquifers
• Openings forming the karst aquifer may be partly or completely
water-filled.
• The elevation where all pores are filled with water in an aquifer is the
water table.
• Water tables in karst areas can be highly irregular in elevation,
because water-carrying conduits can develop at various elevations.

Primary vs. Secondary Porosity
The porosity that
represents the original
pore openings when a
rock or sediment
formed
The porosity
developed in a rock
after its deposition as
result of fracturing or
solution; usually not
uniformly distributed.
EXAMPLE: Karstic Limestone has relatively low primary
porosity, but can have high secondary porosity due to
development of solution cavities and channels.
Primary Porosity Secondary Porosity

Primary vs Secondary Porosity
• Limestone generally
has poor primary
porosity
• Secondary porosity
provided by karst
development
• Solution openings
along fractures and
bedding planes
• Caverns and conduits

Anisotropy
Exhibiting properties with
different values when measured in
different directions, such as
groundwater flow rates along
fracture zones or solutional
cavities in a karst aquifer,
compared to groundwater flow
rates at a right angle to the
fracture flow direction.

Anisotropy Example
• Solution channels developed
along bedding plans or linear
fracture zones.
• Groundwater flow controlled by
the openings in the rock

Asperity and Aperture
Asperity – roughness of the
surface in solutional cavities
developed along fractures or
bedding plans that can impede
groundwater flow.
Aperture – the opening created
by solutional cavities developed
along bedding plans or fractures
that can allow for groundwater
flow.

Groundwater Flow to Wells in Karst
Conceptual model of groundwater
flow to a well pumping in a karst
formation consisting of solutional
openings and a network of diffuse
fractures.

Asperity and Aperture Example
• Compositional differences in the
bedrock will result in uneven
development of solution
channels
• Channels can squeeze shut due
to collapse of channels
• Best groundwater movement
requires a network of
interconnected fractures or
solution channels

Example Karst Features
Spring at Limestone-Shale Interface
Epikarst Development
Sinking Stream

Groundwater Movement Through Fractures

Karst Water Table
• Surface water infiltration can be
rapid in karst terrane
• Groundwater flow rates can be
high.
• Groundwater table and flow
rates are highly variable
depending on precipitation

Karst Development
• Karst is a set of geological features
shaped by the dissolution of
carbonate rock, such as limestone
or dolomite.
• The primary driver of karst is mildly
acidic water, such as rainwater,
acting on weakly soluble carbonate
rock.
• Persistent exposure to the acidic
water will begin to dissolve away
the carbonate rock and form
epikarst or sinkholes.
• Over time these features become
significantly larger as the process
continues.
• Karst features can also develop
underground on buried carbonate
rock, forming massive caves and
cavern systems.
• Karst development generally
limited to within 300 feet of the
surface.

Carbonic Acid Process
Carbonic acid (H2CO3), which is a
weak acid, forms two kinds of
salts: the carbonates and the
bicarbonates. In geology, carbonic
acid causes limestone to dissolve,
producing calcium bicarbonate,
which leads to many limestone
features such as stalactites and
stalagmites.

Idealized Diagram of Karst
Development

Karst Wisdom
• The only thing certain about groundwater flow in karst terranes is
that it is uncertain.
• We can narrow the odds, though.

Locating Wells in Karst Terrane
• Geology Counts
• Geomorphological Features (springs, sinkholes, etc.)
• Fracture Trace and Lineament Analysis
• Well Data
• Dye Tracer Tests?
• Geophysics?

Geology Counts:
Tennessee Karst Regions

Geology Counts!
• Limestones that are prone to
fractures, solution cavities,
caves, conduits.
• Aligned springs
• Sinkhole density
• Shale contacts can result in poor
quality water

Springs As An Indicator of Karst Development

Inner Central Basin – Karst Characteristics
Physiography Aquifer Characteristics Typical Lithologic Units
High sinkhole density; thin soil
cover; low relief and few hills.
Relatively pure limestone, <30
meters thick, separated by shaley
limestones; minor confinement
throughout.
Carters Limestone, Lebanon
Limestone, Ridley Limestone,
Pierce Limestone, Murfreesboro
Limestone; Knox Group
(paleokarst).

Conceptual Groundwater Model
Inner Central Basin

Outer Central Basin – Karst Characteristics
Moderate sinkhole density and
fluvial drainage, variable soil
thickness; numerous hills (knobs).
Relatively pure limestones, <30
meters thick, overlain and
underlain by shaley limestone;
major confinement at base
(Hermitage Formation).
Leipers and Catheys Formations,
Bigby and Cannon Limestones,
Hermitage Formation.

Conceptual Groundwater Model Outer
Central Basin

Fort Payne Fm – Chattanooga Shale contact
• Fort Payne can generally be
considered an aquifer
• Chattanooga Shale is generally
considered an aquitard
• Springs common along Fort Payne
– Chattanooga Shale contact
• Chattanooga Shale tends have
sulfur, metals, radionuclides
• Generally poor water quality
although it is often used for
residential drinking water source

Eastern Highland Rim

Groundwater Flow Along Bedding Planes in
the Fort Payne Formation

Western Highland Rim – Karst Characteristics
Sinkholes and caves well developed
in upper units, decreasing down
section; thick soils; relief extremely
variable--well dissected over much
of Western Highland Rim.
Upper units thick, relatively pure
limestone with many large
openings, lower units increasingly
impure limestones grading to chert
and shale with relatively weak
dissolution porosity; major
confinement at base (Chattanooga
Shale; locally Fort Payne
Formation).
St. Louis Limestone, Warsaw
Limestone, Fort Payne Formation;
Chattanooga Shale.

Pennyroyal Plateau– Karst Characteristics
Numerous sinkholes, sinking
streams, caves and other karst
features well developed in
limestone units, relief nearly flat
throughout the Tennessee portion
of the plateau.
Ste. Genevieve Limestone -
contains a broad variety of mainly
thin-bedded limestones and
dolomites which readily form
solution channels and cavities.
Maximum preserved thickness 70
feet. St. Louis Limestone - grayish-
brown, medium-bedded limestone
with many chert beds. Maximum
preserved thickness about 50 feet.
Well developed karst features in
Ste. Genevieve Limestone.
Ste. Genevieve Limestone overlying
St. Louis Limestone.

Cumberland Plateau – Coves and
Escarpments

Cumberland Plateau – Karst Characteristics
Sandstone caprock over cavernous
limestone; steep-sided coves and
escarpments; thick, coarse-grained
colluvium at base of slopes.
Relatively thick, pure limestones
interbedded with minor shale,
sandstone, and chert, large springs
and cave streams; minor
confinement throughout.
Bangor Limestone, Hartselle
Sandstone, Monteagle Limestone,
St. Louis Limestone, Knox Dolomite
in Sequatchie Valley east of
Sequatchie Fault.

Generalized Cross Section
Northern Cumberland Plateau

Cumberland Plateau
Groundwater moves primarily through fractures in clastic rocks and solution
openings in limestone. Fractures in shale confining units allow rapid
downward movement. Shallow near-surface fractures yield the most water to
wells.

Valley and Ridge – Karst Characteristics
Parallel, structurally controlled
valleys and intervening ridges;
significant cavern development.
Dolomites and dolomitic
limestones of varying thickness,
porosity, and composition; many
large springs; major confinement at
several stratigraphic horizons
(Pumpkin Valley Shale, Nolichucky
Shale, Athens Shale, Ottosee Shale,
Bays Formation, and Martinsburg
Shale).
Conasauga Group, Knox Group,
Chickamauga Group, Jonesboro
Limestone, Newman Limestone.

Valley and Ridge Province
Generalized Cross Section

Valley and Ridge Province
Groundwater moves
downward through
interstitial pore spaces in
residuum and alluvium
into the consolidated
rocks, where it moves
along fractures, bedding
planes and solution
openings. The general
direction of flow is from
ridges to toward springs
and streams in the
valleys.

Valley and Ridge

Principal Aquifers in Valley and Ridge
• Principal aquifers are carbonate
rocks of Cambrian and
Ordovician Age
• Some Mississippian aquifers in
western Valley and Ridge

Western Toe – Karst Characteristics
Coalesced alluvial and colluvial fans
over carbonate rocks.
Fractured, cavernous carbonates
between overlying alluvial/colluvial
deposits and lowpermeability,
underlying shale and quartzites;
large springs; major confinement at
base (Chilhowee Group).
Shady Dolomite, Honaker
Dolomite.

Western Toe

Sinkholes
• Sinkholes are surface
manifestations of underlying
conduits, caves and solution
cavities
• Abundance of sinkholes indicate
well developed karst
• Alignment of sinkholes can
indicate fracture zones

Types of Sinkholes
• Sinkholes typically develop from
the bottom up.
• As sinkholes develop, they can
become unstable and collapse
• Usually distinguished by some
sort of topographic depression.
• Buried sinkholes are the most
difficult to identify.

Springs
• Springs are surface indications of
groundwater flow
• Tubular springs most productive
and indicate subsurface karst
development
• Impermeable rock fracture
springs and contact springs less
productive
• Contact springs can have water
quality issues

Bedding Plane Flow
• Groundwater infiltrates into
ground through fractures and
epikarst features.
• Flows laterally along bedding
planes if there are no significant
solution channels developed
• Small joints between bedding
planes contribute to vertical flow

Other Karst Features
• Dolines
• Karrens
• Sinking streams
• Pinnacles
• Epikarst
Indicators of karst conduit
development and groundwater
flow potential

Fracture Trace and Lineament
Analysis

Fracture Trace and Lineament Analysis
• Fracture zones vs inter-fracture zones
• Fractures vs lineaments
• Relationship of fracture zones to conduit development in the subsurface
• Stress relief fracturing vs faulting
• A " fracture trace" is a natural linear feature less than one mile long, seen
best on aerial photographs. These features are dark or light lines in the soil,
alignments of vegetation, topographic sags, aligned gaps in ridges, and
other similar features. Fracture traces have been mapped in all types of
terrain and are believed by several authors to be the surface manifestation
of almost vertical zones of fracture concentration

Stress Relief Fracturing
• Stress relief fractures develop as
a result of relief of
compressional stress due to
erosion of overburden above
valleys and streams
• Removal of the weight of the
overburden causes the valley
bottoms to flex upward, creating
stress relief fractures.
• Also called unloading fractures

Stress Relief Fracturing – Relation to Yields
• Wells in valleys typically have the
highest yields
• Wells on hillsides have
intermediate yields
• Wells on hilltops typically have
the lowest yields.
• There are exceptions to every
rule, of course.

Stress Fractures Caused By Folding
• The stress of folding rocks can
cause stress fracturing on the
crests of anticlines
• This fracturing can enhance karst
development and groundwater
flow
• Example:
• Western Toe of the Blue Ridge

Faults
• A fracture in the bedrock
accompanied by a displacement of
one side of the fracture with
respect to the other usually in a
direction parallel to the fracture.
• Faults can result in significant
fracturing of the bedrock within
the fault zone.
• Fracturing increases the porosity of
the bedrock, allowing for greater
groundwater flow and storage.

Faulting Associated with Folds
• Compressional stresses causing
folding can also induce faulting
• Normal faults can occur on the
crest of the anticline
• Thrust faults can also develop in
the inner area of the anticline
• Example:
• Sequatchie Valley

Fracture Trace & Lineament Analysis Methods
Desktop Review
• Aerial Photography
• Satellite Imagery
• Topographic Maps
• LIDAR
• Digital Elevation Models
• Geological Maps
• Well Logs
Field Methods
• Drone photography
• Follow up with ”ground
truthing”
• Verify whether linear trends are
faults or fracture zones
• Prioritize areas for drilling based
on fracture zones and geology

Faults and Fractures – Relation to Yields

Reviewing Well Data from Nearby Wells
• Knowledge of local geologic
conditions can assist in
identifying a prospective well
location
• Use this information together
with the other data to help zero
in on the best drilling location
and depth
STATE OF TENNESSEE
DEPARTMENT OF ENVIRONMENT AND CONSERVATION
DIVISION OF WATER RESOURCES – DRINKING WATER UNIT
William R. Snodgrass – Tennessee Tower
312 Rosa L. Parks Avenue, 11th
Floor
Nashville, Tennessee 37243-1102
THIS REPORT TO BE SUBMITTED BY DRILLER WITHIN 60 DAYS AFTER
COMPLETION OF DRILLING WATER WELL WITH REQUIRED FEE TO THE ABOVE ADDRESS:
TENNESSEE WATER WELL DRILLERS REPORT
PPRRIINNTT OORR TTYYPPEE OONNLLYY
I certify under penalty of law that this document and all attachments were prepared by me, or under my direction or supervision. The submitted information is to the best of my
knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and
imprisonment. As specified in Tennessee Code Annotated Section 39-16-702(a)(4), this declaration is made under penalty of perjury.
Signature of Licensee: __________________________________________________________________________________
Distribution: White – Central Office Canary – Driller Pink – Homeowner
CN-0825 (Rev. 10-12) RDA 1520
OFFICE USE ONLY:
Well No.: _________________________________
Date Rec’d: _______________________________
Check # __________________________________
Amount Rec’d: _____________________________
Receipt #: _____________CD#: _______________
(1) LICENSEE
Firm Lic
Name________________________________________________ No. _________
Rig
Operator___________________________________________________________
Driller Tag # _______________________________________________________
(2) WELL LOCATION
County _________________________________________________________
Driller Map No. ___________ _____________ W X Y Z
Number Letter Section
OR
Latitude ______ ______ ______ Longitude ______ ______ _______
Deg Min Sec Deg Min Sec
Address ________________________________________________________
City _______________________________________ Zip _________________
5
____________ mile(s) (N) (E) (S) (W) of _____________________________
LANDMARK
(3) TYPE OF WORK
Date Drill rig left site: _____/_____/_____
New Well Deepen Rework Backfill & Abandon
(11) PRIMARY CASING
Diameter_______ Inches Top Set __________ Inches Above Ground
From land Surface to _____________________________ Feet Below Ground
Type: Plastic Steel Galvanized Concrete Other None
Wall Thickness ____________________ or SDR # ________________________
(10) PROPOSED USE OF WELL
Residential Commercial Industrial Monitor Test
Farm Irrigation Heat Pump Municipal Other
(Specify other) ____________________________________________________
(12) WELL FINISH
Open Hole Screen Slotted or Perf. Pipe
From _________Feet To __________ Feet
If Screen, Plastic Metal Slot Size _____________Inches
Gravel Pack From __________ Feet To ____________ Feet
(7) FORMATION LOG
DEPTH IN FT.
FROM TO DESCRIPTION (DENOTE ROCK COLOR & TYPE OR CAVES)
(13) BACK FILL MATERIAL
Bentonite Portland Cement From 3 Feet to 10 Feet
From To From To
Cuttings _______ ________ Sand _______ _______
Portland
Bentonite _______ ________ Cement _______ _______
Other Other
(Specify)________ ________ (Specify) _______ _______
(14) LINER CASING Yes No
Type: Plastic Steel Diameter ________________Inches
From: __________________Feet To: ___________________Feet
Packers Installed? Yes No
Location: _________________ Feet and ____________________Feet
(9) WELL OWNER
Name_____________________________________________________________
First Last
Or Company _______________________________________________________
Address ___________________________________________________________
City __________________________, State ________________ Zip___________
Phone # (________) _________________________________________________
(4) WELL COMPLETION DATA
Date Completed _____/_____/_____ Static Level ________ Feet
Total Depth _______________ Feet Estimated Yield _________________GPM
Depth to Bedrock ____________ Feet
(5) WATER-BEARING ZONES
DEPTH IN FT. GPM WATER QUALITY
___________ _________ _________________
___________ _________ _________________
___________ _________ _________________
(6) WELL TEST
Tested By: Pumping Blowing Bailing
Static Level ________ Feet Pumping Level _________ After _________Hour(s)
________ Minute(s) At _____________________ GPM
Development Time _____________Hour(s)
________________________Minute(s)
(15) ANTICIPATED WATER QUALITY
Clear Cloudy Dingy Muddy
Good Fair Bad Iron Sulfur
Gas Oil Salt
Other (Specify) ________________________________________________
(16) GENERAL INFORMATION
Well Disinfected: Yes No Well Capped: Yes No
Well located greater than fifty feet from septic tank & field Lines: Yes No
From information provide by:
Property Owner (provide written statement by owner)
Driller determination
Health Department
Drilling process water obtained from:
Well Springbox Public Supply Surface Supply
Pump Installed by Driller: Yes No
Variance Issued: Yes No
(8) COMMENTS
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________

What About Dye Tracer Tests?
• Typically designed for regional
studies as opposed to individual
wells
• Gives a general idea of flow
paths and rates
• Can be useful for contamination
studies
• Generally can’t be used for a
“drill here” approach for water
wells

Geophysical Methods
• Can “see” deeper than
boreholes and in between
• Can survey large areas relatively
quickly
• Can assist in placement of wells
• Can be expensive
• Sensitive to “noise”
Generally used for well fields or
municipal wells
Most common geophysical
methods for karst assessment
• Resistivity
• Ground Penetrating Radar (GPR)
• Electromagnetics (EM)
• Seismic Refraction
• E-Logs

Putting It All Together:
Groundwater Exploration in Karst

Relative Storage Capacity vs. Depth
• Alluvium generally has highest
storage capacity which is related
to sand and gravel content
• Bedrock storage capacity in TN is
highly dependent on fractures
and solution cavities in
limestone
• Fewer fractures with depth
• Karst development is limited
with depth

Karst Groundwater Model
The best production zones in karst
have the following characteristics
• High concentration of fractures
or joints
• Development of interconnected
solution channels and cavities
along bedding planes
• Located in valley bottoms where
stress relief fracturing is greatest

Types of Wells in Karst
A. Typically used for unstable
surface formations.
B. Typically used when there are
zones of non-karst sediments
or poor quality water.
C. Normal karst-type well with
open borehole and surface
seal.
D. Screened well in non-karst
environment

Typical Karst Well
• Generally less than 200-300 feet
in most areas
• Open borehole well
• Well casing and seal to minimize
surface water infiltration
• Fractures and conduits provide
the groundwater flow to the well

Location, Location, Location
• Inter-fracture zone areas are
dominated by matrix flow – very
poor production
• Zones of mild fracturing and
solution conduit development
can have modest yields
• Zones with high fracture
concentrations and solution
channels can yield high
quantities of water

Florida Lineament Analysis
• Map shows projected
lineaments mapped based on air
photos at a well field in Pinellas
County, Florida
• Follow up ”ground truthing”
indicates that only the linear
feature near Well 109 was
verified to be a fracture trace.

USGS Study – Jefferson County, West Virginia
Circle size
indicates relative
transmissivity of
well
Red is fracture
trace parallel to
bedding direction
Green is fracture
trace across
bedding direction
Black with teeth is
thrust fault
Black lines with
arrows are folds

Residential Well Site – Overton County
• Monteagle Limestone to west of
property
• St Louis Limestone on most of
the property
• Underlain by Warsaw Formation
• Springs and sinkholes in lower
St. Louis Limestone
• Linear trends indicate fracture
zones

Residential Well Site (continued)
• The St Louis Limestone just above
the contact with the underlying
Warsaw Formation is well know for
developing karst features
• Select well locations based on
linear trends, favorable geologic
units, spring and sinkhole
development.
• Used geologic map, air photo
(Google Earth), topographic map,
site visit

Video Log of a Well in Karst
• Water flows through solution
opening developed along
bedding plane.
• Note calcium carbonate being
deposited in the solution
opening

Jack Daniel Cave Water Source –
Bigby-Cannon Limestone

Tools
Google Earth
https://www.google.com/earth/
EarthPoint Topo (add in for
Google Earth)
http://www.earthpoint.us/TopoM
ap.aspx
TN Geologic Map overlay for
Google Earth
https://mrdata.usgs.gov/geology/
state/state.php?state=TN
National Geologic Map Database
(online) – USGS
https://ngmdb.usgs.gov/ngmdb/n
gmdb_home.html
USGS Topographic Maps (online)
https://nationalmap.gov/ustopo/
TN GIS – LIDAR
http://www.tngis.org/lidar.htm

Thomas E. Ballard, P.G., C.H.G.
Southeast Hydrogeology, PLLC
1715-K South Rutherford Blvd, #400
Murfreesboro, TN 37130
931-394-3233
tballard@sehydrogeology.com
tballard@groundwaterguy.com
www.sehydrogeology.com

Groundwater Exploration in Tennessee's Karst Terrane

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