Who’s the Contamination Culprit?

You live in a small town where the drinking water has become contaminated!

In your  town, most homes and businesses have their own private wells. By performing lab  tests on the groundwater, it is discovered that it is contaminated with a fuel that is  stored by three companies. Each suspected company has an argument as to why they  are not responsible for the contamination: 

• The Oil Production Company is the prime suspect because they store fuel and  supply it to the other suspected companies.  
• The Oil Production Company has recently tested their storage tanks for leaks and  knows they are safe. They think that the contamination is coming from the Trucking  Company. 
• The Trucking Company says there is no proof that they are responsible. They think  the pollution is coming from the Gas Station or the Oil Production Company.

You are an expert in this field and the town wants you to find the contamination culprit! 

HOW WOULD A LEAKING FUEL STORAGE TANK CONTAMINATE A WELL?  

• Something causes damage to an underground storage tank such as corrosion.
• The damaged tank then begins to leak fuel. 
• The fuel leaches through the soil and into the water table—contaminating the  groundwater. 
• Then the well pumps up the contaminated groundwater. 
• Since groundwater is typically assumed to be a very safe source of water, it goes  through very little treatment and testing. So, it is likely that the contamination will go  undetected for a little while and the residents will drink polluted water. 

WHAT SORT OF CONTAMINANTS ARE IN A FUEL SPILL?  

• Fuel contains a bunch of different hydrocarbons including butane, pentane,  isopentane, and BTEX (benzene, ethylbenzene, toluene, and xylene).
• The BTEX compounds are typically the biggest thing to worry about.
• Ingestion can lead to headaches, throat irritation, and breathing difficulties. Over a  long period of time, exposure can even lead to memory loss and impaired muscle  function. 
• Luckily, this contamination event was caught early on and with your help it’ll be  cleaned in no time!! 

WHY DOES IT MATTER WHO CONTAMINATED THE GROUNDWATER?  

• Ground water is EXPENSIVE to clean!!!!! 
• That means a lot could be at stake for the company responsible so it is important to  find the correct source of contamination.

Let’s get to it!!!

What you’ll need:  

• Ruler, pencil, pen, eraser 
• The activity sheet (available below to print!)

Objective: Create a topographical map to predict groundwater flow and identify the  culprit of the contamination.  

Procedure: The direction of groundwater flow can be used to determine the source of  pollution. Since groundwater typically flows downhill—the suspected source that is  furthest upstream is the source of contamination. You are given the elevations of seven  wells to create a contour map with. 

1. The contours of the landscape can be estimated with the seven elevations. Assume  there is a constant slope between the known points. For example, there are four  equal slope increases of 10ft between a 10ft point and a 50ft point. 
2. Start by lightly drawing lines with a pencil between wells with at least 20 ft of  elevation difference between them.  
3. Divide these lines into equal segments representing 10 ft elevation increases.  
4. Lightly draw smooth, curved lines connecting all of the wells and marks with the  same elevations. These are the contour lines. 
5. With a pen, draw short arrows perpendicular from the contour lines. The arrows can  be approx. ½ inches apart. These arrows represent the direction of groundwater  flow so it’s important to be careful to make them as perpendicular as possible.  Erase the contour lines and other penciled-in lines to give a better view of the flow  direction. You can draw longer arrows now if that helps. 
6. Draw a loop around all of the contaminated wells. From the flow arrows you should  be able to see what the source of contamination is. 

Hannah Groenwegen

Hannah is from London, Ontario and is an Alum of the 2017 SOI Arctic Expedition. She is currently finishing her last semester of Civil Engineering at the University of British Columbia’s Okanagan Campus. At UBC she has been involved with Geering Up Engineering Outreach and Global Brigades. Her interests are in water quality and treatment, and she is hoping to pursue graduate studies in Environmental Engineering. In her free time, Hannah’s favourite things to do are drawing, hiking, seeing her friends, and cooking!

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