Lesson 5: Cases of Contamination

Grade 5-9 (health, science and social studies)
Grade 10-12 (health, science and social studies)

Topic: Recent cases of drinking water contamination.

Time: 60 minutes

Space Requirement: Regular classroom

Methodology: PowerPoint presentation, class discussion

Materials: Projector and computer, case study handouts

Objectives: The students will look at four recent waterborne illness outbreaks in Canada and the United States. They will use the knowledge from the two previous classes to explain the outbreaks and elaborate on questions regarding the outbreaks.

For the Teacher: It is advisable for the teacher to be familiar with the four cases prior to the presentation. The handout sheets give general information and provide links for further research.


  1. Hand out information sheets for each of the four cases. These sheets elaborate on the information in the presentation.
  2. Play the PowerPoint presentation for the class. This can be done either in presentation format or as overheads. There are notes for each slide that will elaborate on certain points. (40 min)
  3. The last slide is a question-answer page. This page is designed for oral questioning and class discussion. (20 min)

Evaluation: Active listening skills and being respectful for the person speaking can be assessed in this lesson. The answers given and points raised can also be used as evaluation criteria.

Resources: The PowerPoint presentation of Contamination Case Studies.
The following resources and handouts are found below:
- Milwaukee Case Study
- New Orleans Case Study
- North Battleford Case Study
- Walkerton Case Study

Extension Activity: If possible, obtain a sample of pond or dugout water and a black light (from the science department), to see if the water glows when exposed to the light. If it glows, this is an indication of the presence of biological contaminants.

The Safe Drinking Water Foundation has other educational programs that can be taught with this set of lessons. Operation Water Drop examines the chemical contaminants that can be found in water; this program is designed for a science class. Operation Water Flow explores the use of water and where it comes from; this program is designed for a Social studies and Math collaboration. Operation Water Spirit presents a First Nations perspective of water and water issues and is designed for a Native Studies or Social Studies class. Operation Water Health explores common health issues surrounding drinking water in Canada and around the world and is designed for a Health, Science and Social Studies collaboration. To access more information on these and other educational activities visit the Safe Drinking Water Foundation website at www.safewater.org.

Sources and Related Links:
- Cost-Benefit Analysis: Treat the Illness or Treat the Water? – a SDWF fact sheet

Milwaukee Case Study:

Milwaukee in the early 1990s was home to 1.61 million people. The households were served by two water treatment plants but only one plant (the Howard Avenue Water Treatment Plant) was the source of the Cryptosporidium contamination.

Milwaukee receives its water from Lake Michigan. The origin of the contamination was found to be sewage that passed through the plant’s filtration system. Where the sewage came from is still unknown but it might have been run off from a farm or feed lot.

During the time when sewage was passing through the system, turbidity levels were abnormal. There was no attempt at correcting the turbidity levels. Therefore, from March 23 to April 9, a total of 18 days, Cryptosporidium oocysts were free to contaminate the water system.

As a result of the outbreak, 403,000 people became ill and over 100 people died. The plant was shut down shortly after the outbreak occurred.

The estimated cost of this outbreak, as calculated by the Centers for Disease Control and Prevention, was $96.2 million: $31.7 in medical costs and $64.6 million in lost productivity.


New Orleans Case Study:

The city of New Orleans, Louisiana was one of the areas devastated by Hurricane Katrina in August 2005. The bustling city was flooded as the levees protecting the city failed. The flood waters filled the streets with almost every imaginable type of contamination. Fuel, chemical, and biological products combined to make what some people referred to as a “toxic soup”.

Although the chemicals and fuel made the water dangerous to walk through, it was the biological contamination that made the water hazardous to drink. When the levees failed, the sewage treatment plant flooded and released raw sewage into the streets.

The E. coli levels in the water were measured to be 45,000 times the acceptable limit for swimming in a lake or pond. In fact, one scientist demonstrated the extent of the contamination by holding a vial of pond water up to a black light. The pond water produced a very faint glow as a result of the biological contaminants in the water. When he repeated this experiment with water taken from the flooded streets of New Orleans, the vial glowed fluorescent yellow.

The number of people who became ill as a result of drinking the contaminated water or even walking through the water is unknown. It is estimated to be in the thousands though. There were five deaths attributed to Vibrio vulnificus, a form of cholera. These five people were elderly. Their deaths are linked to the water. It is probable that many more people died as a result of consuming the water but the actual number will never be known.


North Battleford Case Study:

The small community of North Battleford, Ssaskatchewan is home to almost 14,000 people. The water source for the community is the North Saskatchewan River. The surface water is treated by the surface water treatment plant and is chlorinated, flocculated and settled.

In March 2001, the solids contact unit in the surface water treatment plant was emptied and all the sludge removed from the bottom in order to inspect, clean and repair a crack that had formed in the cement floor. This type of repair should normally be done in February, so that the spring breakup and runoff will not affect the system.

The repair was completed in the afternoon of March 20, 2001. A night employee was left with instructions to run the water to waste until the turbidity level was less than 5 NTU and the chlorine residual level was 2.0 free chlorine. He followed these instructions and when the turbidity level was 2.29 and free chlorine was 2.15, the employee pumped the water into the clear well (the water used by the community is drawn from this well).

However, there was no settling of solids in the solid contact unit. The plant employees tried different chemical doses but nothing seemed to work. The turbidity levels fluctuated and the filters required backwashing more often but this water was not run to waste. The plant manager was informed of the lack of settling and approved the purchase of bentonite to aid in settling. Even with this new chemical settling did not occur until April 24, 2001. The turbidity levels during this time were over 0.5 for 9 days and over 0.3 for 13 days. The maximum turbidity level is 0.3 NTU.

From March 20 to April 24, the people of North Battleford drank the water, not knowing there was a problem. The first people to become ill were the elderly and the children. All had similar symptoms including nausea, vomiting, and diarrhea. Over 7,000 people became ill. The majority of these people lived in the North Battleford- Battleford area but because the water was contaminated over the Easter break, people from outside the community became ill too. There were no deaths associated with the contamination.

An inquiry was held and the source of the contamination was found to be Cryptosporidium. The city of North Battleford contested that the outbreak was not linked to the water because some people became ill on or slightly before March 20th. However, the inquiry ruled that the water was indeed the source of the outbreak and recommended that the city build a new water treatment facility no later than 2003. The city was also to write a safe drinking water policy. The province was to standardize their water treatment guidelines for all Ecoregions.

Some people were not satisfied with the result and launched a lawsuit naming the city of North Battleford and the provincial government as responsible for the contamination. The lawsuit was settled out of court and the 700 claimants received $3.2 million for pain and suffering, loss of income, out-of-pocket expenses and legal fees.

Walkerton Case Study:

The town of Walkerton is located on the Saugeen River and is part of the Municipality of Brockton, which has a population of just under 10,000 people. The drinking water for the town of Walkerton is supplied from a series of wells located around the town. The water is treated at each well before is goes to the Walkerton Public Utilities Commission (PUC) and from there it is pumped to the households.

In May 2000, a waterborne disease outbreak occurred in Walkerton, Ontario. Over 2,300 people became ill and seven people died as a result of E. coli 0157:H7 and Campylobacter jejuni contamination in their drinking water. An inquiry was called to determine how the water had become contaminated and if charges should be laid against those directly involved with the treatment of water.

The inquiry determined that Well 5 was the source of the contamination. It is a shallow well that is close to a cattle farm. There had been a lot of rain (over 100 mm) the week before the outbreak occurred and manure was washed into the well.

The well was supposed to be inspected daily and water samples taken to determine the amount of free chlorine in the system. However, it was common practice for the person checking the well to not test the water and to make up the amount of free chlorine in the system. Also, the inquiry discovered that water samples sent to an analytical lab were not taken from three different sites as was required but that employees took the samples from the PUC.

The first people to get sick were children and then elderly people. Even when parents were calling to ask about the water, they were told it was fine. Eight days after the manure washed into the well, the manager, Stan Koebel, decided to flush out the system with lots of chlorine. For eight days, the people of Walkerton were drinking contaminated water without knowing it, even though the PUC manager knew. A Boil Water Advisory was issued nine days after the contamination but not everyone heard about it. Some people continued to drink the water without boiling it.

The Minister of the Environment’s Office began an investigation, but not much information was found until seven people had already died. The inquiry placed the majority of the blame on Stan Koebel and the foreman, Frank Koebel. The Ontario government was also to blame for not having standardized water requirements. The Inquiry recommended source water protection, the training and certification of operators, a quality management system for water suppliers, and more competent enforcement

As a result of the inquiry, Stan Koebel and Frank Koebel were charged under the Criminal Code of Canada. Stan Koebel was sentenced to one year in jail, but released early, and Frank Koebel was sentenced to 9 months under house arrest.


- http://www.archives.gov.on.ca/en/e_records/walkerton/index.html - Walkerton Inquiry Reports