United States                                       .
          Environmental Protection       Office of Water          EPA 810-F-96-001
          Agency                     4601                  February 1996



 BACKGROUND: Many communities obtain their drinking water from underground sources
 called aquifers. Water suppliers or utility officials drill wells through soil and rock into
 aquifers for the groundwater contained therein to supply the public with drinking water.
 Home owners who cannot obtain their drinking water from a public water supply, will have
 their own private wells drilled on their property to tap this supply. Unfortunately, the
 groundwater can become contaminated by harmful chemicals such as lawn care products
 and cleaners that were used or disposed of improperly after use or any number of other
 pollutants. These chemicals can percolate down through the soil and rock and into the
 aquifer - and eventually the well.  Such contamination can pose a significant threat to
 human health.  The measures that must be taken by well owners and operators to either
 protect or clean up contaminated aquifers are quite costly.

 NOTE: This demonstration should follow a class discussion on potential sources of pollution
 to drinking water supplies.

 OBJECTIVE: To illustrate how water is stored in an aquifer, how groundwater can become
 contaminated, and how this contamination ends up in a drinking water source. Ultimately,
 students should get a clear understanding of how careless use and disposal of harmful
 contaminants above the  ground can potentially end up in the drinking water below the
 ground.  This particular experiment can be done by each student at their work station.


 1 clear plastic cup that is 2 3/4" deep x 3 1 /4" wide for each student
 1 piece of modeling clay or floral clay that will allow  a 2" flat pancake to be made by each
   student for their cup
 White play sand that will measure 1/4" in bottom of each student's cup
 Aquarium gravel (natural color if possible) or small pebbles (approximately Vz cup per
 student) HINT: As many  small rocks may have a powdery residue on them, you may wish
 to rinse them and dry on a  clean towel prior to use. It is best if they do not add cloudiness
 to water.
 Red food coloring
 1 bucket of clean water and small cup to dip water from bucket


 1.    Pour 1 /4" of white sand in the bottom of each cup completely covering the bottom
of the container.  Pour water into the sand, wetting it completely {there should be no
standing water on top of sand).  Let students see how the water is absorbed in the sand,
but remains around the sand particles as it is stored in the ground and ultimately forming
part of the aquifer.

 2.     Have each student flatten the modeling clay (like a pancake) and cover % of the
 sand with the clay (have each student press the clay to one side of the container to seal
 off that side). The clay represents a "confining layer" that keeps water from passes
 through it.  Pour a small amount of water onto the clay. Let the students see how the
 water remains on top of the clay,' only flowing into the sand below in areas not covered by
 the clay.

 3.     Use the aquarium rocks to form the next layer of earth.  Place the rocks over the
 sand and  clay, covering the entire container.  To one side of your cup, have students slope
 the rocks, forming a high hill and a valley (see illustration below).  Explain to students that
 these layers represent some of the many layers contained in the earth's surface. Now pour
 water into your aquifer until the water in the valley is even with your hill.  Students will see
 the water stored around the rocks.  Explain that these rocks are porous, allowing storage of
 water within the pours and openings between them.  They will also notice a "surface"
 supply of  water (a small lake) has formed.  This will give them a view of both the ground
 and surface water supplies which can be used for drinking water purposes.

 4.     Use the food  coloring and put a few drops on top of the rock hill as close to the
 inside wall of the cup as possible.  Explain to students that often old wells are  used to
 dispose of farm chemicals, trash and-used motor oils and other activities above their
 aquifer can end up in their drinking water.  They will see that the color, spreads  not only
 through the rocks, but also to the surface water and into the white sand at the  bottom of
 their cup.  This is one way pollution can spread throughout the aquifer over time.

 FOLLOW-UP:                             .

 Discuss with students other activities that could pollute their aquifer. Assign students the
task of locating activities around the school or their own homes that could pollute their
 drinking water sources if not properly maintained.  Allow students  to drain off the water in
their cups and carry home their container to refill with water and show their parents
 surface and  ground water and how the food coloring illustrates pollution activity above
their aquifer can affect all water. Students should discuss with parents what steps they
can take as  a household to prevent water pollution.