Ground Water Contamination

A High School Level Presentation on How

We Can Clean Up After OurselvesPresented by:

Catherine Charnawskas and Margaret MilliganGeospheres November 17, 2004

Aquifers found in the continental US

Ground Water Basics

What is Ground Water?

An Aquifer is a formation, a group offormations, or part of a formation thatcontains sufficient saturated permeable material to yield significantquantities of water to wells or springs.

Ground water is water that is found anywhere from close to the earth’s surface (such as a marsh) to hundreds of feet below the surface. Ground water is stored and moves through aquifers.

The Silurian – Devonian Aquiferwhich includes Detroit

How does Ground Water form?

Ground water is replenished by precipitation – rain fall or snow melt

The unsaturated zone contains little water, but may become saturated but will dry out again after a period of little precipitation.

When the biological needs of the unsaturated zone are fulfilled, excess water can infiltrate the saturated zone. This water will travel through the aquifer towards streams, springs, or wells where water is being withdrawn.

Replenishment of Aquifers

Natural replenishment is a very slow process because the water must move through the unsaturated zone and the aquifer.

Aquifers can also be recharged artificially. This can be done in two ways.

-Spread water over pits, furrows, or ditches. Construct small dams in stream channels to detain runoff to allow it to infiltrate the aquifer.

-Construct recharge wells to inject water directly into the aquifer.

Artificial recharge of an aquifer

How much can an Aquifer hold?The amount of water held by an aquifer is dependant on the porosity of the rock. Porosity is the measure of pore size between the grains of the rock

Principal aquifers by rock typeIf pores are connected, water can flow through the spaces and the rock is said to be permeable. Water can also move through more solid rocks such as granite if there are cracks or fissures present.

Quality of Ground Water

Sources of ContaminationTypes of ground water

contamination:

- Agricultural

- Residential

- Industrial

- Natural

Types of Contamination

Sources of ground water contamination

Animal burial areas, feedlots, chemical storage or usage areas, irrigation sites, manure storage and spreading.

Agricultural Contamination

Residential Contamination

Sources of ground water contamination

Fuel oil, household chemicals, lawn and garden chemicals, septic systems, sewer lines, pools, cars products.

Types of Contamination

Industrial Contamination

Natural Contamination

Sources of ground water contamination

Improper waste disposal, cesspools or dry holes, underground storage tanks, mining.

Sources of ground water contamination

Depends on the type of geological material that the water is flowing through. The water can pick up magnesium, arsenic, chloride, iron, lead, mercury, sulfate, or zinc to name a few.

Natural purification of groundwater

Pollution of groundwater is a serious problem especially where aquifers provide a large part of the water supply.

Problem: Sewage

Sewage contaminated with bacteria can enter the groundwater system can be naturally filtered if the correct soil composition is present.

Extremely permeable aquifers do not allow enough time for purification to occur. Aquifers made of sand or permeable sandstone. Since the pores are large enough to allow water movement, but the movement is slow enough to allow purification.

E. coli

Prevention of ContaminationThe best way to clean groundwater is to prevent the contamination in the first place.

Options to restore a contaminated aquifer

-Inground treatment

-Aboveground treatment

-Remove or Isolate contaminated area

-Abandon the supply

-Ignore the problem

Inground Treatment

One possibility to treat polluted ground water is to isolate the water supply. There are several possible/proposed methods in order to do this

-Constructing vertical barriers that prevent the flow of clean ground water into the site. Examples include Slurry walls, grout curtains, or even biobarriers. The Ecosystem Restoration website gives a full run down of what each of these types of prevention are.

Many sites of groundwater pollution qualify for Superfund money that was created in 1980 to clean up hazardous waste sites that pose an unacceptable risk to human or ecological health.

Superfund site at Silver Bow Creek. Water pollution was caused by metal mining in the area.

Above Ground Treatment Many industries are recognizing the importance of cleaning water before releasing the water back into the groundwater supply.

-Ford Motor Company is using plants and trees to help clean up hydrocarbon soil contamination that could potentially affect the groundwater supply.

-Microorganisms (such as Geobacter sulferreducens) are currently being studying to test their effectiveness to clean up groundwater that has been contaminated by uranium from underground holding areas.

These plants can degrade hydrocarbons in the root zone. This is known as phytoremediation.

Underground uranium holding facility.

Resourceshttp://news.nationalgeographic.com/news/2004/09/0924_040924_phytoremediation.html

http://www.cepis.ops-oms.org/muwww/fulltext/repind46/restora/restora.html

http://capp.water.usgs.gov/GIP/gw_gip/index.html

http://capp.water.usgs.gov/aquiferBasics/index.html

http://water.usgs.gov/ogw/

http://www.nationalatlas.org

Essentials of Geology 7th Edition, Lutgens and Tarbuck

Physical Geogrpahy 6th Edition, McKnight