Ground Water Quality Issues in a Karst Rock ... - Ohiowater.org

ohiowater.org

Ground Water Quality Issues in a Karst Rock ... - Ohiowater.org

Ground Water Quality Issues in

a Karst Rock Environment

Stuart Smith, MS, CGWP

Allen Comeskey, MS, CPG

© 2007 all rights reserved


or Understanding What’s Going

to Determine What Could be

Coming at You… or not

Not to be

confused with

the quality of

content of this

presentation

All opinions are

those of the authors


Topics:

• Basics of Ground Water – so

we can understand each other

• General Geology of the Area

• Implications of Local Geology

• General Advice for Dealing

With Your Concerns

Ground Water Science


Basic Ground Water

• What is an Aquifer

• Saturated vs. Unsaturated

Conditions

• Porosity and Permeability

• Confined vs. Unconfined

Conditions

• Types of Porosity

• Moving Water Through an Aquifer

Ground Water Science


“Aquifer” Defined:

For our purposes we will define an aquifer

as:

“rock or sediment that is

saturated and transmits

water in economic

quantities”

Ground Water Science


Of course, an “aquifer” for

a single farm well may not

be an “aquifer” for a

village or a city. What is

an “economic quantity”

for one is not the same for

the other.

Ground Water Science


Rock or sediment functions as an

aquifer because of the porosity,

the void space, within it.

In an aquifer the porosity is

completely filled with water, that

is, it is saturated.

If the porosity is filled with air or

only partially filled with water, the

rock or sediment is unsaturated.

Ground Water Science


Unsaturated vs. Saturated Pores

Ground Water Science


The porosity is, in part, what gives an

aquifer the property of permeability.

Permeability is a measure of how well a

rock or aquifer transmits water.

A rock can possess high porosity but

exhibit low permeability, or

it can exhibit high permeability, but

possess low porosity.

Ground Water Science


In an aquifer, the pores are connected

together to allow flow.

Ground Water Science


Porosity range of rocks :

Shale = 0 to 10 %

Limestone & Dolostone = 0 to 20 %

Sandstone = 5 to 30 %

Karst Limestone = 5 to 50 %

Fractured Granite = 0 to 10%

Ground Water Science

(from Freeze & Cherry, 1979)


Permeability range of rocks :

Rock Fractures = 5.0 -5 to 500 ft/day

Granite = 5.0 -10 to 5.0 -6 ft/day

Sandstone = 5.0 -7 to 5.0 -1 ft/day

Limestone = 5.0 -6 to 5.0 -2 ft/day

Dolomitic Limestone = 5.0 -2 to 5 ft/day

(from de Marsily, 1986)

Ground Water Science


Unconfined and Confined

Aquifers

Ground Water Science


Unconfined aquifer configuration:

water level within aquifer

Ground Water Science


Confined aquifer configuration: Water

level above top of aquifer

Under

pressure

Ground Water Science


Types of Aquifer Porosity

Ground Water Science


Ground Water Science

Inter-granular Porosity


Ground Water Science

Fracture Porosity


Fracture porosity in 3-dimensions

Ground Water Science


Fracture pattern in rock

Vertical

Fracture

Horizontal

Bedding

Plane

Ground Water Science


Flow through fractures and bedding

planes

Ground Water Science


Solution Enhanced Fracture Porosity

Ground Water Science


Solution Enhanced Fracture Porosity

to the extreme, a cave system

Ground Water Science


Solution enhanced porosity, a small cave!

Ground Water Science


Eroded out:

Bigger cave

Wittenberg University

Speleological Society


Really big

solution

enhanced

porosity!

Wittenberg University

Speleological Society

Ground Water Science


Ground water is usually on the move, from

its recharge area to its discharge area

Ground Water Science


Capture Zone:

Part of the ground

water flow is

towards the well.

The flow in the rest

of the aquifer

remains to the

northwest. A divide

is created between

the two flow paths.

Ground Water Science


General Geology of the Area

Ground Water Science


Much of the

Sandusky

watershed is

developed on

Silurian and

Devonian-age

carbonate and

shale rock

Ground Water Science


Note the structure of the geology as

revealed by this east-west crosssection

Ground Water Science


Around here, ground water

comes from the bedrock

Ground Water Science


Limestone near Lima, Ohio

Note difference in rock

Ground Water Science


Limestone near Carey, Ohio

Note difference in rock

Ground Water Science


Ground Water Science


Fremont

geography

What

hydrogeologists

would suggest:

directional bores

in the N-reducing

zone


Glacial

sediments and

deposits in

Ohio

You are here…

Ground Water Science


Thickness of

glacial

sediments and

deposits in Ohio

You are here…

Ground Water Science


Till from Glaciers

Ground Water Science


Standing on the bedrock / glacial sediments

contact (Carey, Wyandot County)

Till (clay)

Sand & Gravel

Weathered Rubble

Limestone

Ground Water Science


Till (clay)

Sand & Gravel

Weathered Rock Rubble

Ground Water Science


echarge & discharge areas

Ground Water Science


Implications of Local Geology

Ground Water Science


Where are

you?

Let’s talk…

Ground Water Science


The thickness

of glacial

sediments are

really thin in

places in the

watershed

Ground Water Science


The weathered zone…

Till (clay)

Sand & Gravel

Weathered Rubble

Limestone

Ground Water Science


Northwest Ohio’s Karst

area…

Ground Water Science


Karst area

features:

• Very large channel

development

• Sinkholes

• Caves

Ground Water Science

Wittenberg University Speleological Society


Seneca Caverns…

Ground Water Science


Wittenberg University

Speleological Society


Ground Water Science

Blue Hole at Castalia


Karst systems are

lively ecosystems

Cave flowstones

are microbially

deposited

features

Wittenberg University

Speleological Society

Ground Water Science


Hazards: Junk filled

depression or sinkhole

NC Division of Water Quality

Groundwater Section


The Point Is…

ANYTHING put on

the ground here can

reach the aquifer

and move quickly

down-gradient

(that means you, too)

Ground Water Science


Ground Water Pollution

• Pesticides

• Bacteria

• Nitrates

• Fuel, lube oil

• Stuff from

landfills: multiple

choice


Pesticides: How big a

problem?

• Rarely detected in

Ohio ground

water

• Geology helps

• So does

knowledge of

how to make and

use the pesticides


Ground Water Pollution:

Animal waste: How big a

problem?

• Pesticides

• Bacteria

• Nitrates

• Phosphorus

• Hormones,

meds, etc.


Soluble reactive P

NOAA shot

showing Lake

Erie algal blooms

Potential huge P reservoirs in aquifers


N: Carey ground water source

water protection area

Ground Water Science


The Ridge as recharge area

There be

caves here

Above: From the

east

Right: From west

(Blanchard basin)

Ground Water Science


N source in Ridge dolomite?

Probably not the “obvious” ones:

Needs more study

Ground Water Science


Abandoned shallow SWL well

Ground Water Science


CAFO siting stirs strong

emotional reactions


It can be difficult to develop an

impartial and productive system for

monitoring impacts

But

necessary!

Thinking

long term

Ground Water Science


When well problems occur – How

do we distinguish sources of

bacteriological contamination?


Are they contaminating wells?

No, the markers

came back

showing it’s the

humans

themselves, eww!

The coliform

positives? I tell you,

it’s us!


But we did the nutrient

balance calculations!

Performing field hydrogeology

(NOT guessing, NOT using

textbook values) is a big part of

that picture. There is no technical

reason NOT to detail local and

areal hydrogeologic parameters,

just as we do for landfills

But to

understand

the long-term

impacts, we

need to know

the regional

flow regime


• How do we manage any large facility with

potentially serious environmental impact

without enough information to track impacts

(or conclusively show lack of impact)?

• Why do we treat LAFFs (CAFOs) differently

from other waste management facilities?

Ground Water Science


Concerns? First, get serious

1) DOCUMENT

pre-development conditions

2) CONTINUE to monitor:

Observe, document, sample,

analyze, with proper

methodology and QA/QC

Ground Water Science


IF

something

happens,

with data you

have a chance of

figuring it out

Ground Water Science


Don’t want to do that? Then

quit whining… Without DATA,

your cause is probably toast…

Ground Water Science


Any questions?

What’s good

today?

Giraffe’s

aging

nicely

Contacts:

Tel 419.209.0298

Info@groundwaterscience.com

www.groundwaterscience.com

More magazines by this user
Similar magazines