Groundwater
Basics
Purpose
Every community needs a clean source of drinking
water. More than 44 percent of Michigan's
residences rely on groundwater as their primary
source of drinking water. Groundwater is also
our primary source of drinking water in the
Greater Lansing Area. The Cities of East Lansing
and Lansing as well as Delhi, Delta, Lansing
and Meridian Township’s all rely on
groundwater for their public water supplies.
Approximately 225 production wells are drawing
groundwater from the Saginaw Aquifer, which
covers a large portion of the Lower Peninsula.
Groundwater is also important
to the environment because it replenishes
streams, rivers, and wetlands and helps to
support wildlife habitat. Groundwater is also
used for irrigation and industry. Groundwater
needs to be protected because once it is contaminated
it can be very costly and difficult to clean.
In some cases it is almost impossible to do
the remediation to a level that is acceptable
for potable use.
There are a number of reasons
for everyone to be trained in wellhead protection.
The people that can make the biggest difference
to protect our groundwater are the people
who live and work in the Wellhead Protection
Area (WHPA).
What
is groundwater?
Groundwater is water beneath the surface of
the earth, which saturates the pores, and
fractures of sand, gravel, and rock formations.
Groundwater occurs in the zone of saturation
in an aquifer or in the soil.
Where does groundwater
come from?
Groundwater begins as precipitation that is
absorbed into the ground. Some of it is taken
up immediately by plant roots and evapotranspired.
The precipitation that makes it beyond the
root zone is pulled down by gravity until
it reaches the water table. Below the water
table, all the pore spaces in the soil are
filled with water. This is the saturated zone.
How
can groundwater be contaminated?
As groundwater infiltrates it can pick up
contaminants from the ground surface or underlying
soil. The water may dissolve the contaminant
or just carry it in to the aquifer. Some contaminants
can be transported great distances from their
source. Normally, groundwater travels very
slowly. Therefore, little dilution or dispersion
of the contaminant usually occurs. The contaminant
forms a concentrated plume that follows the
groundwater flow path.
What
are the potential sources of contamination?
There are many different potential sources
of contamination. Any site that has or uses
chemicals can be considered a potential source.
Some of the commonly known sources are underground
storage tanks (USTs), septic tanks, surface
impoundments, agricultural activities, landfills,
industries, drycleaners, abandoned wells,
highway de-icing, accidents, and illegal dumping.
What
are the types of contamination?
There are three basic types of contaminants.
They are microorganisms, inorganic chemicals,
and organic chemicals.
- Microorganism
contaminants include bacteria (i.e. E. coli
and Salmonella), viruses, protozoa (i.e.
Cryptosporidium and Giardia lamblia) and
parasites. They are usually just a concern
for shallow wells as the soil does a fairly
good job of trapping them.
- Inorganic chemicals are
chemical such as nitrate, arsenic, and metals.
Many of these chemicals are found naturally
in the soil and are not in high enough concentrations
to cause harm. Public Water Suppliers are
required to monitor for them. Many land
uses can increase their concentrations.
For examply, applying too much fertilizer
can increase the amount of nitrate in the
groundwater.
- Organic chemicals
are chemicals that contain carbon, such
as fuels, solvents, and pesticides. It only
takes a small amount of these chemicals
to cause health concerns. These chemicals
have a tendency to do one of three things
when they come into contact with water.
How they react is based on their physical
and chemical properties.
- The first type has
the tendency to dissolve into the water.
In this way they are able to travel
long distances from their source. They
can also be distributed from the top
of the aquifer to the bottom.
- The second way a
chemical may act would be to float on
the surface and follow the flow pattern
at the water table. An example of this
type of chemical would be gasoline.
- The third tendency
of some chemicals is to sink down to
the bottom of the aquifer and flow along
the bottom because they are heavier
than water. These include chlorinated
chemicals such as (transformer oil,
perchloroethlene, and dry cleaning fluids.)
What is Wellhead Protection?
Wellhead Protection is a preventative program
to protect public water supply systems. The
goal is to prevent contaminants from entering
public supply wells.
What
is a Wellhead Protection Plan?
It is a program written by a local team to
protect public water supply systems from potential
sources of groundwater contamination. It is
done by forming a wellhead protection team
to delineate the area that needs protection,
taking an inventory of potential sources of
contamination, identifying appropriate management
strategies, developing contingency plans,
planning for future wells and public involvement
in the process.
What is the Wellhead
Protection Area?
A Wellhead Protection Area (WHPA) is a geographically
designated surface and subsurface area surrounding
a water well or well field, supplying a Public
Water System, through which contaminants are
reasonably likely to move toward and reach
the water well or well field. This is an area
where groundwater protection is emphasized.
A WHPA includes at least the delineated capture
zone area, but could be influenced by other
factors such as existing land use and zoning,
site and facility identification and location,
political boundaries, natural features, and
environmentally sensitive areas. The dark
tan area in the below graphic shows an example
of a WHPA.
How large is the
Wellhead Protection Area (WHPA)?
A WHPA can be many varying sizes depending
on a number of factors. Some of these factors
include the pumping rate, the surrounding
geology and characteristics of the aquifer,
the time of travel for pollutants. Michigan's
WHPP requires a 10 year time of travel (TOT)
to insure that if the groundwater outside
of the WHPA were to become contaminated there
would be adequate time to devise a plan to
deal with the contamination before it reached
the well. WHPAs may extend several thousand
feet upgradient of the well to protect it.
