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.
