Groundwater
Water is the lifeblood of every living creature on
earth. Approximately 70 percent of the earth's
surface is covered with water. Through the
wonders of nature, water can take on many
different forms, from the water we drink, to the
ice we use to chill a glass of lemonade, to the
water vapor used to steam clean equipment. It is
easy to understand the significance water plays in
our lives. It may be much more difficult to
understand the groundwater that exists below the
Earth's surface.
When it comes to water, there is no place like
Wisconsin. We are water rich. Between the
mighty Mississippi River and the Great Lakes of
Michigan and Superior, there are more than
15,000 lakes, 7,000 streams and five million acres
of wetland. And that just scratches the surface.
Below our feet Wisconsin has a buried treasure –
1.2 quadrillion gallons of ground-water. It is hard
to grasp just how much water is stored
underground unless you look at how much we use
every day.
Each year about 29 trillion gallons of water fall as
rain or snow on Wisconsin’s 36 million acres.
Plants and animals consume some, some is
returned to the atmosphere by evaporation,
liquid changing into gas on the surface, or by
transpiration, moisture given off from plants to
the atmosphere. Some water becomes runoff,
flowing into rivers, lakes and streams. The rest
becomes groundwater by infiltrating or
percolating, soaking into and through the soil,
into groundwater aquifers. Aquifers are large
areas of sand, gravel and rock that store water for
later use.
about the quantity of good quality groundwater
available for municipal (city, village, town),
industrial, agricultural and domestic use. There is
also concern about adequate base flow; the
groundwater that sustains our lakes, streams and
wetlands.
Getting a clean glass of water isn’t as easy as
turning on the tap!
In Wisconsin, the quality and quantity of
groundwater varies from place to place. The
difference is caused by a combination of geology,
varying precipitation and use. Cities and towns in
the North Central and Northeastern third of
Wisconsin receive the most precipitation in the
state, but they are underlain by crystalline
bedrock; a type of rock formation notorious for
yielding only small quantities of water. Even
though there may be plenty of rain, finding
enough groundwater to supply municipalities in
these regions can be difficult. Groundwater
levels have been going down by hundreds of feet
around some of Wisconsin’s growing
metropolitan areas.
At last estimate, there were more than 850,000
private wells in Wisconsin. In areas where water
moves through aquifers very slowly, private wells
can still yield enough water for residential use.
You can drill a hole just about anywhere in
Wisconsin and find water. But is this water
drinkable? Not necessarily. Ground-water can be
contaminated in many ways. Clean groundwater
is Wisconsin’s buried treasure that needs to be
cared for and protected.
Hydrologic Cycle
If you could somehow pour all the water below
ground on top, you'd need to trade in your ranch
house for a houseboat: Wisconsin's groundwater
could cover the whole state to a depth of 100 feet.
Despite this abundance of groundwater, there is a
growing concern in certain areas of the state
Water might be called our most recycled
resource. The water you showered in this
morning may have contained the same water
molecules that gave a dinosaur a cool drink
during prehistoric times or carried the early
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explorers across our country. The distribution of
the Earth's total supply of water changes but the
quantity has remained constant. Remember, the
water we use today is the water we will need in
the future too.
Surface water and groundwater are part of the
hydrologic cycle. The hydrologic cycle is the
constant movement of water above, on and below
the Earth’s surface. The cycle has no beginning
and no end. You can understand it best by tracing
it from precipitation.
Precipitation
occurs in
several forms,
including:
rain, snow,
sleet, dew,
fog and hail.
Wisconsin
receives an
average 30 to
32 inches of
precipitation
per year.
Rain can do
three things
once it
reaches the
Earth’s surface. It can filter into the ground,
runoff into water bodies or evaporate. Rain, for
example, wets the ground surface. As more rain
falls, water begins to filter into the ground
(infiltration). Approximately 70 to 90 percent of
the water that falls to the earth's surface enters the
soil. This water can become groundwater but
most of it evaporates from the soil surface or is
used by vegetation. How fast water soaks into, or
infiltrates the soil depends on soil type, land use,
slope of the land and the intensity and length of
the storm. Water infiltrates faster into soils that
are mostly sand rather than those made mostly of
clay or silt. Almost no water filters into paved
areas. Rain that cannot be absorbed into the
ground flows across the surface forming runoff
streams.
When the soil is completely saturated additional
water moves slowly down through the
unsaturated zone (drier, upper soil layers) to the
saturated zone (wet lower layers or aquifer)
replenishing or recharging the groundwater. The
distance water has to travel to reach groundwater
can range from a few feet to hundreds of feet.
Water movement toward groundwater may take
hours or years depending on the depth to the
aquifer and the characteristics of the unsaturated
zone. Water then moves through the saturated
zone to groundwater discharge areas such as
springs or artesian wells.
Evaporation occurs when water from such
surfaces as oceans, rivers and ice is converted to
water vapor. Evaporation, together with
transpiration from plants, rises above the Earth’s
surface, condenses, and forms clouds.
Transpiration is the process by which plants
release water to the atmosphere. Water from both
runoff and from groundwater discharge moves
toward streams and rivers and may eventually
reach the ocean. Oceans are the largest surface
water bodies that contribute to evaporation. It is
estimated that 39 inches of water annually
evaporates from each acre of ocean.
After water vapor is drawn into the atmosphere it
can be transported over hundreds of miles by
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large air masses. When water vapor cools, it
condenses to form clouds. As water condenses
within clouds, water droplets increase in size until
gravity pulls them to the Earth's surface as
precipitation.
What is Groundwater?
Groundwater is fresh water (from rain or
melting ice or snow) that soaks into the soil and is
stored in the pores (tiny spaces) between rocks
and particles of soil. Approximately 70% of
Wisconsin’s residents and 97% of Wisconsin’s
communities rely on groundwater to meet their
water supply needs. Groundwater can stay
underground for hundreds of thousands of years
or it can come to the surface and help fill rivers,
streams, lakes, ponds and wetlands. Groundwater
can also come to the surface as a spring, artesian
well or be pumped from a well.
How Does the Ground Store Water?
Groundwater is stored in the tiny open spaces
between rock, sand, soil and gravel. How well
loosely arranged rock (such as sand and gravel)
holds water depends on the size of the rock
particles. Layers of loosely arranged particles of
uniform size (such as sand) tend to hold more
water than layers of rock with materials of
different sizes. This is because smaller rock
materials settle in the spaces between larger rock
materials, decreasing the amount of open space
that can hold water. Porosity is how well rock
material holds water. Porosity is dependent on the
shape of the rock particles and the amount of pore
space available. Round particles will pack more
tightly than particles with sharp edges. Material
with angular-shaped edges has more open space
and can hold more water.
Groundwater is found in two zones. The
unsaturated zone, also called the vadose zone, is
immediately below the land surface. It contains
water and air in the open spaces or pores. The
saturated zone, a zone in which all the pores and
rock fractures are filled with water, is below the
unsaturated zone. The boundary between the
unsaturated and saturated zones is called the
water table. The water table is the top of the
saturated zone and may vary in depth from place
to place and year to year. It may be a few feet
below the surface or hundreds of feet below the
land surface. The water table may rise or fall
depending on many factors. Heavy rains or
melting snow may cause the water table to rise, or
an extended period of dry weather may cause the
water table to fall. Extensive pumping of water
by high capacity wells can lower the water table.
How Groundwater Moves
What is an Aquifer?
An aquifer can form where groundwater moves
rapidly, such as through gravel
and sandy deposits. An aquifer
has enough groundwater so that
it can be pumped to the surface
and used for drinking water,
irrigation, industry or other
uses. An aquifer is the area
where groundwater is stored
naturally before being used or
discharged to the surface.
For water to move through
underground rock, pores or fractures in the rock
must be connected. If rocks have good
connections between pores or fractures and water
can move freely through them. These rocks are
referred to as being permeable. Permeability
refers to how well a material transmits water. If
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the pores or fractures are not connected, the rock
material cannot produce water and is therefore
not considered an aquifer. When water does not
readily move through
material, the material is
considered impermeable. A
layer of such material would
be considered a confining
layer. Confining layers are
often made of clay or shale.
The amount of water an
aquifer can hold depends on
the permeability and porosity
of the underground materials
present.
An aquifer may be a few feet
to several thousand feet
thick, less than a square mile
or hundreds of thousands of square miles in area.
For example, the High Plains Aquifer underlies
about 280,000 square miles in 8 states including:
Colorado, Kansas, Nebraska, New Mexico,
Oklahoma, South Dakota, Texas, and Wyoming.
How Does Water Fill an Aquifer?
Aquifers get water from precipitation (rain, snow,
etc…) that filters through the unsaturated zone.
Aquifers can also receive water from surface
waters such as lakes and rivers. This taking in of
water is called recharge. Recharge areas are
where aquifers take in water. When the aquifer is
full, and the water table meets the surface of the
ground, the water stored in the aquifer can appear
at the surface as a spring or artesian well. These
are known as discharge areas. Discharge areas
are where groundwater flows to the land surface.
Water moves from higher-elevation areas of
recharge to lower-elevation areas of discharge
through the saturated zone.
How do we get water from an Aquifer?
Wells are used to remove water from aquifers.
Basically, a well is a hole drilled into an aquifer.
A pipe and a pump are used to pull water out of
the ground. A screen filters out unwanted
particles that could clog the pipe. Wells come in
different shapes and sizes. It depends on the type
of material the well is drilled into and how much
water is being pumped out. Cities often store this
water for later use in water towers to provide
water pressure.
Removing water lowers the water level in the
well. The difference between the initial water
table depth or static water level (elevation of the
water table above sea level) and the pumping
water level causes water to move in the aquifer.
Since the pumped well water level is lowest the
water from the surrounding aquifer flows toward
the well to replace the water being removed.
Shallow wells may go dry if the water table falls
below the bottom of the well. Some wells, called
artesian wells, do not need a pump because of
natural pressures from the slope of the aquifer
and/or confining layers that force the water up
and out of the ground naturally under pressure.
Rate of Groundwater vs. Surface Water
Movement
Surface water generally flows in rivers or streams
at velocities of 2-8 miles per hour. Rate of surface
water flow is determined by slope of the land,
amount and rate of precipitation, rate of
infiltration and evaporation, amount and type of
vegetation and land use.
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Groundwater moves through the spaces (pores)
between particles of a saturated material
anywhere from 0.1 foot per day to 3 feet per day.
That translates into movement of 35 to 1,100 feet
per year for groundwater. Ground-water moves
only if sufficient pressure is available to force
water through the spaces between porous aquifer
materials. Geology helps to controls the rate of
groundwater movement. The size of the cracks in
rocks, the size of the pores between soil and rock
particles, and whether the pores are connected
determine the rate at which water moves into,
through and out of the aquifer. Water generally
moves quickly in coarse sand, sometimes as
much as several feet per day. Openings between
the grains are large and interconnected, resulting
in high permeability. Very fine-grained material
like clay has many pores where water can be
stored, but the pores are so small that moving
water through or out is difficult. Clay formations
are relatively impermeable -- water may move
only a few inches a year. Permeability in
limestone, on the other hand, primarily depends
not on pore spaces, but on the size, frequency and
distribution of fractures and cracks.
The slope of the aquifer also helps to determine
the rate of groundwater movement. In other
words, the slope of the water surface between two
points in an aquifer and the aquifer material
determines how rapidly groundwater moves from
one location to another.
Wisconsin's Aquifers
An aquifer is a rock or soil formation that can
store or transmit water. Wisconsin's groundwater
reserves are held in four principal aquifers: the
Sand and Gravel Aquifer, the Eastern Dolomite
Aquifer, the Sandstone and Dolomite Aquifer,
and the Crystalline Bedrock Aquifer.
Sand and Gravel
Aquifer
The sand and gravel
aquifer is the surface material
covering most of the state except for parts of
southwestern Wisconsin. It is made up mostly of
sand and gravel deposited from glacial ice or in
river floodplains. The glacial deposits are loose,
so they are often referred to as soil -- but they
include much more than just a few feet of topsoil.
These deposits are more than 300 feet thick in
some places in Wisconsin.
The sand and gravel aquifer
was deposited within the
past million years. The
sand and gravel outwash
plains now form some of
the best aquifers in
Wisconsin. Many of the
irrigated agricultural lands
in central, southern and
northwestern Wisconsin use
the glacial outwash aquifer.
Because the top of the sand
and gravel aquifer is also
the land surface for most of Wisconsin, it is
highly susceptible to human and naturally
occurring pollutants.
Eastern Dolomite Aquifer
The eastern dolomite aquifer occurs in
Eastern Wisconsin from Door County to
the Wisconsin-Illinois border. It consists of
Niagara dolomite underlain by Maquoketa shale.
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These rock formations were deposited 400 to 425
million years ago. Dolomite is a rock similar to
limestone; it holds groundwater in interconnected
cracks and pores. The water yield from a well in
this aquifer mostly depends on the number of
fractures the well goes through. As a result, it's
not unusual for nearby wells to vary greatly in the
amount of water they can draw from this layer.
Where the fractured dolomite bedrock occurs at
or near the land surface, the groundwater in
shallow portions of the Eastern Dolomite Aquifer
can easily become contaminated. In those areas
(such as parts of Door, Kewaunee and Manitowoc
counties), there is little soil to filter pollutants.
Little or no filtration takes place once the water
reaches large fractures in the dolomite. This has
resulted in some groundwater quality problems,
such as bacterial contamination from human and
animal wastes. Special care is necessary to
prevent pollution.
The Maquoketa shale layer beneath the dolomite
was formed from clay that doesn't transmit water
easily. Therefore, it is important as a barrier or
shield between the Eastern Dolomite Aquifer and
the Sandstone and Dolomite Aquifer.
Sandstone and Dolomite Aquifer
The Sandstone and
Dolomite Aquifer
consists
of layers of
sandstone
and dolomite
bedrock that vary greatly in their water-yielding
abilities. In dolomite, groundwater mainly occurs
in fractures. In sandstone, water occurs in pore
spaces between loosely cemented sand grains.
These formations can be found over the entire
state, except in the North Central portion.
In Eastern Wisconsin, this aquifer lies below the
Eastern Dolomite Aquifer and the Maquoketa
shale layer. In other areas, it lies beneath the Sand
and Gravel Aquifer. These rock types gently dip
to the East, South and West, away from North
Central Wisconsin, becoming much thicker and
extending to greater depths below the land
surface in the Southern part of the state.
The rock formations that make up the Sandstone
and Dolomite Aquifer were deposited between
425 and 600 million years ago. The Sandstone
and Dolomite Aquifer is the principal bedrock
aquifer for the Southern and Western portions of
the state. In Eastern Wisconsin, most users of
substantial quantities of groundwater, such as
cities and industries, tap this deep aquifer to
obtain a sufficient amount of water.
Crystalline bedrock aquifer
The Crystalline Bedrock
Aquifer is composed of
various rock types
formed
during the
Precambrian Era,
which lasted from the time the Earth cooled more
than 4 billion years ago, until about 600 million
years ago, when the rocks in the Sandstone and
Dolomite aquifer began to be formed. During this
lengthy period, sediments, some of which were
rich in iron and now form iron ores, were
deposited in ancient oceans; volcanoes spewed
forth ash and lava; mountains were built and
destroyed, and molten rocks from the earth's core
flowed up through cracks in the upper crust. The
rocks that remain today have a granite-type
crystalline structure. These are the “basement”
rocks that underlie the entire state. In the north
central region, they are the only rocks occurring
beneath the Sand and Gravel Aquifer.
The cracks and fractures storing and transmitting
water in these dense rocks are not spaced
uniformly. Some areas contain numerous
fractures while others contain very few. To obtain
water, a well must pass through some of these
cracks; the amount of water available to a well
can vary within a single home site. The
crystalline bedrock aquifer often cannot provide
adequate quantities of water for larger
municipalities, large farms or industries.
Many wells in the Crystalline Bedrock Aquifer
have provided good water. However, most of
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these wells do not penetrate deeply into the rock.
Water samples from deep mineral exploration
holes near Crandon and deep iron mines near
Hurley have yielded salty water.
Water Level Changes Associated with
Groundwater Pumping
The combination of intensive pumping and
several years of below-normal precipitation can
accelerate the downward trend in water levels.
This is true because below normal precipitation
often results in decreased groundwater recharge.
More importantly, below normal precipitation
generally results in increased groundwater
When pumping starts in an unconfined aquifer,
most of the water is removed from very near the
well. With continued pumping, water is removed
further from the well lowering the water level at a
greater distance from the well. This is referred to
as draw down. Draw down decreases with the
distance from the well until, at some distance, the
water level remains relatively unaffected by
pumping. Drawdown in the well continues to
increase slightly with pumping. The resulting
cone-like shape of the water surface is referred to
as a cone of depression.
The size and shape of the cone of depression is
determined by the aquifer materials and the
amount of water being removed from the aquifer.
Domestic wells typically have very little cones of
depression. Irrigation and municipal wells
typically have large cones of depression that may
be up to 100 feet deep. These cones of depression
can cause shallow neighboring wells to quit
pumping water.
Factors Affecting Groundwater Declines
Under natural conditions, a balance existed
between the volume of water entering an aquifer
and the volume of water being discharged from
an aquifer. With the development of water wells,
the natural balance between recharge rates and
discharge rates is disrupted. The overall
groundwater supply has been depleted due to
increased water usage or discharge.
Groundwater supplies also can be altered due to
natural causes. Years of below-normal
precipitation can alter the amount of water
entering the aquifer. Likewise, seasonal and yearto-year differences in regional stream flow can
cause fluctuation in localized groundwater levels.
pumping further reducing the water level.
There are areas in Wisconsin where streams are
not running and springs are not flowing anymore
because the groundwater feeding them is being
pumped dry. In a growing number of places
people are pumping groundwater faster than it
can be replenished. Local scarcity of water
sometimes pits communities against one another.
When a proposed water bottling plant in Adams
County was opposed by citizen groups in 1999,
the interest of policymakers and the public in
water quantity issues bubbled to the surface. It
became clear that state laws did not address the
effect of high-capacity wells on nearby springs,
wetlands or trout streams. The Big Springs case
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made people much more aware of the connection
between groundwater, surface water and human
activities.
How do you use groundwater?
In Wisconsin, we us use nearly 205 million
gallons of groundwater daily for drinking, doing
dishes, making food and bathing. That's 55
gallons of groundwater per person per day. Fiftyfive gallons of groundwater per person per day
may not seem like much, but there are hidden
costs for excessive water use. Your community
may have to install new wells or water and sewer
pipes to accommodate increasing demands.
Pumping more water from private or public wells
requires more energy, which costs more money.
Treating used water, referred to as wastewater or
effluent, to strict standards of purity requires
money, resources and skilled workers.
Thirsty Cities
97% of Wisconsin's cities and villages count on
groundwater to provide basic water-related
services such as fighting fires, cleaning streets,
filling the local pool, watering golf courses and
parks, drenching shade trees, supplying
commercial customers and satisfy the needs of
thirsty residents at home. The average daily cost
of supplying groundwater to a family of four in
2005 was between 26 and 35.2 cents – an
increase of only a few cents since 1983.
A Fluid Economy
Water is vital to Wisconsin’s economic health. Its
part of countless manufacturing processes, from
metal fabrication to paper production to leather
tanning. Some of our most important industries -fruit and vegetable processing, cheese-making,
dairy farming, meat processing and brewing -need pure, clean groundwater to make the goods
for which Wisconsin is famous.
Big operators aren't the only ones who need this
valuable resource. Consider your local
Laundromat, car wash, water bottlers, restaurants,
health clubs, hairdressers…scores of services and
products we use daily depend on groundwater.
Food processing soaks it up: processing one can
of corn or beans requires nine gallons of water.
Cars, fast or slow, also guzzle it up: six gallons of
water are needed to produce one gallon of
gasoline. And to manufacture that car and put
four tires on it takes 39,090 gallons of water!
Wet and Wild
Thousands of tourists travel to Wisconsin each
year to enjoy our fabulous water resources. They
spent an estimated 11.8 billion dollars in 2005
alone. That’s a lot of fishing, boating, and
swimming. What most people see is a favorite
fishing hole, a secret pond with an expanse of
cattails perfect for observing herons, or those
wild rapids waiting to devour the raft or roll the
kayak. What they don’t see is the groundwater
flowing into those water bodies. After seeping
through the soil and rock, groundwater discharges
through springs and artesian wells, in low places
where the water table meets the land surface, into
streams, lakes and wetlands.
Agriculture
Wisconsin's farms use about 100 million gallons
of groundwater a day to water livestock, maintain
a high level of sanitation in the milk house and
provide all-around cleanliness on the farm. A
dairy cow producing 100 pounds of milk daily
drinks 50 gallons of water each day. There are
roughly 1,235,000 dairy cows in the state. This
means they drink over 10.9 billion gallons of
water per year.
Wisconsin also has an estimated 390,000 acres of
irrigated farmland. Irrigation equipment uses
about 182 million gallons of water per day during
the growing season, almost all of it groundwater.
On average, 80 percent of the water is consumed
– it is used by plants and not returned
immediately to the soil under the fields.
While irrigation has helped formerly marginal
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lands turn a profit, there is a cost. Excessive
irrigation may leach nutrients, fertilizers and
pesticides into groundwater and lower the water
table.
Threats to groundwater
Unfortunately, groundwater is susceptible to
pollutants. Groundwater is generally a safe source
of drinking water. There are concerns that
contamination may increase as toxins dumped on
the ground in the past make their way into
groundwater supplies. The soil cannot filter
many manmade chemicals.
A well can be easily contaminated if it is not
properly constructed or if toxic materials are
released into the well or onto nearby soil. Toxic
material spilled or dumped near a well can leach
into (soak into) the aquifer and contaminate the
groundwater drawn from that well. Leaching is
the process where chemicals slowly pass through
the soil and mix into the groundwater.
Contaminated wells used for drinking water are
especially dangerous. Wells should be tested to
see what chemicals may be in the well and if they
are present in dangerous quantities.
Pollutants can sink into the groundwater in areas
where material above the aquifer is permeable.
Groundwater can be polluted by landfills, septic
tanks, leaky underground gas tanks and from
overuse of fertilizers and pesticides. If
groundwater becomes polluted, it will no longer
be safe to drink. It is important for all of us to
learn to protect our groundwater.
Sources of Contamination
Groundwater contamination occurs when manmade products such as gasoline, oil, road salts
and chemicals get into the groundwater and cause
it to become unsafe and unfit for human use.
Some of the major sources of these products,
called contaminants, are storage tanks, septic
systems, hazardous waste sites, landfills and the
widespread use of road salts and chemicals.
In rural areas, different threats to groundwater
quality exist; animal waste, onsite sewage
systems, fertilizers and pesticides are primary
pollution sources. Farmers also must be careful
about where and when they spread manure.
Spring snowmelt or excessive rainfall can lead to
fish kills and contamination of drinking water
wells due to bacteria in manure that has run off
from farm fields.
Air pollution can also lead to groundwater
pollution. Particles clouding the air from car
exhaust, smokestacks and dust from city streets or
farm fields can contribute to groundwater
contamination. These particles of hydrocarbons,
pesticides and heavy metals settle on the ground,
are washed into the soil by rain, and eventually
trickle into aquifers. Although a rain shower may
disperse the particles from the air, the rains can
carry the pollutants down into the ground as the
water hits land.
Accidents happen – over 1,000 spills of toxic or
hazardous materials are reported each year in
Wisconsin. Volatile organic compounds (VOCs)
such as petroleum products account for many of
the spills in the state. Topping the list is diesel
fuel. Other substances, such as pesticides, paint,
and ammonia, make up the rest. Most spills occur
at industrial facilities or during transport of
hazardous substances. Response efforts focus on
containing and removing the hazardous material
to a proper disposal facility. This protects
groundwater and surface waters.
Storm water from roofs, driveways, parking lots
and streets contains contaminants such as
gasoline, metals, and bacteria it must be cleaned
up or pretreated before it is put back in the
ground using engineered storm water infiltration
devices.
Thanks to recycling efforts since 1995, each year
we have diverted about 40 percent of the
Wisconsin generated solid waste from
Wisconsin’s landfills. However, landfills may
still be a major source of contamination. Modern
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landfills have protective bottom layers and
leachate collection systems to prevent
contaminants from getting into the water.
Leachate is the polluted liquid that forms when
water percolates through solid waste and mixes
with chemicals in the waste. Many old landfills
and dumps did not have protective liners or were
natural attenuation designs. The natural
attenuation designs hoped the soil would filter
the buried chemicals and prevent them from
leaching into the groundwater. If there was no
layer or it is cracked, contaminants from the
landfill (car battery acid, paint, household
cleaners, etc.) can make their way down into the
groundwater.
Dangers of Contaminated Groundwater
Drinking contaminated groundwater can have
serious health effects. Diseases such as hepatitis
and dysentery may be caused by contamination
from septic tank waste. People are often poisoned
by toxins that leach into their well water. The
poisons may be from surface contamination or the
result of natural sources. Some rocks contain
heavy metals such as lead, arsenic, mercury and
aluminum. These metals all have ill affects on
human health and wildlife. It is important to
remember that wildlife can also be harmed by
contaminated groundwater.
Pollution Prevention
Many steps are being taken to keep pollutants
from reaching groundwater supplies.
Manufacturers are using fewer toxic raw
materials. Consumers have switched to
phosphate-free detergents and other less polluting
household products. Pollution control measures
such as the Clean Water Act have also been a big
part of the protection of drinking water supplies.
Tips on Protecting and Conserving
Groundwater
1. Dispose of chemicals properly.
2. Take used motor oil to a recycling center.
3. Limit the amount of fertilizer used on plants.
4. Take short showers.
5. Shut water off while brushing teeth.
6. Run full loads of dishes and laundry.
7. Check for leaky faucets and have them
repaired.
8. Water plants only when necessary. It is best to
water before 10 a.m. or after 7 p.m.
9. Keep a pitcher of drinking water in the
refrigerator.
10. Get involved in water education.
Groundwater cleanup...Who Pays?
We all pay for contaminated groundwater.
Groundwater contamination can be linked to land
use. What goes on the ground can seep through
the soil and turn up in drinking water, lakes,
rivers, streams and wetlands. Tracking down and
stopping sources of pollution is a lengthy and
expensive process. It’s usually impossible to
completely remove all traces of a pollutant.
Conducting a partial cleanup of an aquifer to a
usable condition can cost a substantial amount of
money.
The owner or facility operator causing the
pollution should pay the cost. But what happens
when the owner is bankrupt, out of business or
dead? Taxpayers must step in. Federal and state
money is used for cleaning up sites and enforcing
laws governing waste disposal and hazardous
material spills.
When it comes to groundwater, prevention is the
best strategy. This means looking at the many
ways we pollute groundwater and finding
methods to keep those pollutants from entering
the groundwater. Landfills and wastewater
lagoons need to be designed and operated to
prevent infiltration to groundwater. Pesticides
must be applied according to need and label
instructions, and fertilizers and manure should be
applied in carefully calibrated amounts to
enhance crops without damaging the
environment. With vigilance and care, we can
protect our buried treasure.
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Why is Cleaning Up Groundwater So Hard?
Cleaning up contaminated groundwater often
takes longer than expected because groundwater
systems are complicated and the contaminants are
invisible to the naked eye. This makes it more
difficult to find contaminants and to design a
treatment system that either destroys the
contaminants in the ground or takes them to the
surface for cleanup. Groundwater contamination
is the reason for most of Superfund’s long-term
cleanup actions. A Superfund site is a site that
has sustained severe contamination. Most
Superfund sites are old landfills or industrial
areas.
Movement of Contaminated Groundwater
Contaminants that can dissolve in groundwater
will move along with the water. These
contaminants can potentially make it to wells
used for drinking water. If there is a continuous
source of contamination entering moving
groundwater, an area of contaminated
groundwater, called a plume, can form. A plume
of contamination is an area of contaminated
groundwater that moves together. A combination
of moving groundwater and a continuous source
of contamination can, therefore, pollute very
large volumes and areas of groundwater. Some
plumes at Superfund sites are several miles long.
More than 88 percent of current Superfund sites
have some groundwater contamination.
An Introduction to On-site Wastewater
Treatment
In Wisconsin, more than 750,000 private septic
systems use on-site wastewater treatment systems
to meet their wastewater treatment and disposal
needs. Residents in towns and cities are typically
served by centralized drinking water systems and
wastewater treatment facilities. Homeowners
living in rural areas without access to municipal
water treatment systems must rely on private
wells to meet drinking water needs, and their own
"mini treatment plant" to meet wastewater
disposal needs.
The most common type of on-site wastewater
treatment is the septic system. A septic system
consists of four main components. The first
component is a home’s indoor plumbing. This is
simply the system of drains and pipes located
inside a home that transports wastewater outside
to the next major component, the septic tank. The
septic tank is an underground, watertight
container, made of concrete, fiberglass, or other
durable material that resists corrosion.
The septic tank serves as the primary place of
treatment for wastewater. Here, sludge (solids)
settle to the bottom of the tank and partially
decompose with help from bacteria. A layer of
soaps, greases and scum float on top of the liquid
wastewater. Over time, the floating scum and
submerged solids accumulate and must be
removed by a qualified septic contractor.
The liquid wastewater contained in the septic
tank is called effluent. The effluent exits the
septic tank and enters the next major component
of a septic system, the drain field.
The drain field allows wastewater to percolate
(infiltrate) into the surrounding soil through a
series of underground, perforated pipes. The
pipes are usually placed on top of a layer of
gravel and sand. Above the pipes is a layer of
clay or manmade impermeable barrier to prevent
to effluent from floating to the surface. In areas
where the water table is close to the surface or
adequate filtration depth cannot be achieved, a
mound system is used. A mound system is
constructed on the surface and therefore creates a
mound in the yard to process the effluent.
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Conserve Water – Hydraulic overload is a
major cause of septic system failure. Low
flow plumbing fixtures (faucets, toilets and
showerheads) will minimize the amount of
water entering a septic system.
Care of the Drain field – Trees and shrubs
with deep penetrating roots should not be
planted near the drain field because the roots
can plug the perforated pipe structure. Heavy
vehicles and equipment should not be driven
or parked over the drain field because their
weight can compact the soils and damage
drain field components.
The soil is the final and most important
component of a septic system. This is where the
majority of wastewater treatment actually occurs.
Through various physical and biological
processes, most bacteria and viruses in
wastewater, as well as some nutrients, are
consumed as the wastewater effluent travels
down through the soil layers.
Properly constructed and maintained septic
systems pose little threat to the environment and
human health. However, improperly functioning
systems pose a contamination risk to groundwater
and surface water supplies.
There are numerous ways for homeowners with
septic systems to minimize the potential impacts
that on-site wastewater treatment systems may
have on the environment. These include:
Regular Inspection – One of the most important
ways to care for your septic system is to have it
inspected on a regular basis. This extends the life
of a septic system and helps the homeowner
avoid unnecessary and expensive repair and
replacement costs. It is generally recommended to
have a septic system inspected every 2-3 years.
Household Waste Disposal – Limit the types and
amounts of wastes poured down the drain.
Garbage disposals can nearly double the amount
of solids added to the septic tank and should be
used sparingly, or not at all. Cooking oils and fats
harden after disposal and block the septic tank
inlet, or outlet, and even clog the soil pores
surrounding the drain field reducing its
effectiveness for filtrating wastewater. In
addition, chemicals like paints, solvents, and
pesticides should not be dumped down the drain.
These items may kill microorganisms living in
the septic tank and soil that help purify the
wastewater. Without the bacteria, the untreated
effluent can potentially enter the groundwater and
contaminate drinking water supplies.
Homeowners who have a septic system that is
properly designed and installed and correctly
operated and maintained should receive years of
reliable service with minimum risks to human and
environmental health.
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