• 6 strips of wide-range pH paper (litmus paper) (Note: 100 strips are available for less than $5 at many chemical supply companies, such as Auspex Scientific at http://store.yahoo.com/auspexcorp/phpaper.html)
• 7 numbered small plastic cups for samples
• Plastic spoon for mixing
• 2 copies of the Finding Pollution Worksheet
• 1 12-in. ruler

Part I

• 6 Ziploc® bags or plastic bins
• ~12 cups of playground sand
• 1 marker or Sharpie®
• 1 roll of masking tape
• 6 teaspoons
• 1 container of unsweetened powdered lemonade mix
• 6 soil samples (made from sand and lemonade mix; see Procedure Section for preparation instructions)
• Jug of water

Part II

• 1 bottle of vegetable oil
• 1 box of baking soda
• 1 bag of (any-sized) cotton balls
• 6-10 coffee filters (any size, kind)
• 6-10 plastic spoons
• 1 bottle of liquid dishwashing soap (any kind)
• Plastic disposable gloves (optional)

• Using a marker and masking tape, label the six Ziploc® bags (or plastic bins) with the numbers 1-6.
• Create six bags of equal amounts of sand (about 2 cups each) using Ziploc® bags or plastic bins. These are your soil samples.
• Mix the soil samples in the appropriately-numbered bags/containers with different concentrations of lemonade according to the map below (Figure 1; the highest concentrations of lemonade should be the numbers located in the yellow oval of the map). Samples 1 and 2 should have no lemonade, sample 3 should have the highest concentration of lemonade, sample 6 should have the lowest concentration and samples 4 and 5 should be equal concentration higher then sample 6 but lower then sample 3.

Figure 1. Map showing the direction of groundwater flow. click for copyright

• Make the highest and lowest concentration samples, and then test the pH to make sure they are indeed different and in the range of the pH paper.
• Make a copy of the Groundwater Pollution Worksheet for each student.
• Set up a supply station in the classroom. The station should have the six samples clearly labeled, a teaspoon and a water source for Part I. This station can also have all of the treatment methods for Part II. Alternatively, this can be done at lab stations and each station can have all six samples.
• Next, make a batch of polluted water for Part II by mixing water, lemonade and vegetable oil. Test the water sample to make sure that the pH of the water sample matches the pH of the #3 Soil Sample. (Note: You can also add dirt, cocoa or food coloring to make the sample "muddy.")

Part I - Finding the Contaminant Spill

1. Explain to the students that they are professional environmental engineers and have been asked by the state to detect and treat a contaminant plume. Here is the situation (note: provide the students with as much or as little detail you feel necessary):

A French chemical company created a chemical called Le Chimique. Le Chimique is a highly toxic, highly acidic cleaning agent, which became illegal to use in 1990. The company is now bankrupt, and the government wanted to redevelop the land; however, when they started digging, traces of highly acidic Le Chimique were found in the soil. They did some research and found that there was a spill, but they did not know where or when it occurred. The local community heard about the newly discovered spill and is worried that it might affect their water supply. In response, the government has taken several samples of soil in the area over the course of the year. They have hired your class to test the samples and find where the spill occurred, predict in what direction the groundwater is moving, and how fast, so they can best determine how to clean up the spill. They have taken six soil samples from the groundwater and then dried them to make transport easier.

2. Pass out the Finding Pollution Worksheets, 7 cups, pH (litmus) paper and a plastic teaspoon to each student group. Show students where the six soil samples are located.
3. Have students label 6 of the cups #1 - #6. The 7th cup should be labeled "Water."
4. Explain to students what pH is and how to use pH paper. Explain concentration. It is helpful to remind the students that the contaminant they are looking for is highly acidic. In other words, if the sample has a low pH, then it will be highly acidic, and they can conclude that there is a high concentration of Le Chimique in that sample.
5. Explain and demonstrate the following procedure to the students.
6. Students should take the water cup, plastic soon and two other cups to the samples station. Have the students fill the water cup with water and the two numbered cups with one teaspoon of the corresponding soil sample. For example, put a teaspoon of Sample 1 in cup #1, Sample 2 in cup #2.
7. Then, have students return to their seats and add two spoonfuls of water to each sample. They should mix it up and then test it with the pH paper. Have students record the pH of each sample in the first column of their worksheets. Students should repeat this process until they have tested all of their samples.
8. After students have measured all the samples, have them fill out the second column of their worksheet with relative concentrations of the contaminant in the sample. Samples that have a high pH have low acidity and a low concentration of Le Chimique. Samples that have a low pH are highly acidic and have a high concentration of Le Chimique.
9. Finally, students should put a star on their maps showing where they thought the spill occurred, an arrow indicating direction of groundwater flow and a rough outline of what they think the plume looks like. (This should become apparent with the varying levels of pH.)
10. Finally, have the students determine the velocity (v) and flow rate (Q) of the plume, using the distances and times provided on the Groundwater Pollution Worksheet. The students should use this information to predict when the flow will reach the community at point A.

Part II - Remediation of the Contaminated Groundwater

11. Now that the students have determined when the contaminant spill might reach community A, they will work on treating the spill. Explain to the students that the state has selected a "pump and treat" method of cleaning up the groundwater based on the recommendations of your engineering firm. They have hired your class to remove the contaminated water at the source of the spill and propose methods for cleaning the water before placing it back into the ground. While removing a sample of the contaminated groundwater to test, it was discovered that oil used in the packaging of Le Chimique was also found in the sample. Le Chimique is highly toxic, and special care will need to be taken for cleaning up the water. At the same time, the state has a tight budget for remediation of this site.
12. Show students the water sample taken from the source of the spill. Next, show them (hold up for display) the different "tools" (treatment type, as described in the table below) available for removal.

13. On their worksheet, have students brainstorm combinations of treatment methods that might clean up the contaminated groundwater.
14. Next, have students show the teacher their ideas. Have them obtain a small sample of the contaminated water in one of their plastic cups from Part I.
15. The students may try their methods of clean up while following along with the worksheet. If time and material permit, allow the students to improve on their ideas with another sample of contaminated water.
16. Lastly, have the students discuss as a class what worked well and why. Have the students also discuss the possible cost and environmental effects of the treatment methods they chose.

Concept Review: Review groundwater flow with students. Ask students the following questions to review their previous knowledge of groundwater flow.

1. What is an aquifer? (Answer: An aquifer is water under the ground that technically provides a useable amount of water when pumped.)
2. Why do engineers and many people care about groundwater? (Answer: because many people get their drinking water from the groundwater)
3. If a can of oil was spilled on the ground by the school, could it end up in the town well 5 miles south of the school? (Answer: Yes, the oil will infiltrate through the ground and then travel with the groundwater in the direction of groundwater flow. The oil will not end up in the town well, however if the groundwater dose not flow south.)

Groundwater Pollution Worksheet: Have the students record pH measurements, and follow along with the activity on their Groundwater Pollution Worksheet.

Class Discussion of Treatment Methods: Discuss with students the remediation choices listed on their worksheets and why they chose the ones they did (#10). There are many advantages and disadvantages to each treatment option, including cost, time and environmental effects. Ask students which efforts might have the biggest impact on the environment of those listed. (Answer: Chemical treatment and physical barriers.)

Class Discussion of PollutantTtransport: Show students an overhead of the site map or sketch the site map on the white/chalk board. Ask a student from each group draw where they think the plume is located on the map. Once all the data is on the board, discus the results through the following questions.

1. Did all the groups get the same exact answer? (Answers may vary.)
2. If no, why not? (Answers will vary)
3. Do you think this happens in the real world? (Answer: Yes, scientific data is highly variable and sometime yields different answers - especially in the environmental engineering field. The case the students looked at is very real. Most of the time when pollution has been detected, no one knows when or where it originated, or sometimes, they do not even know what was spilled. Environmental engineers are charged with cleaning up spills without much knowledge of what is under the ground.)
4. Often, contaminant plumes spread out in all directions. Why might our plume spread faster in one direction than the other? (Answer: The plume spreads in the direction of the groundwater. There is probably a hill or higher elevations on the left side of the map.) Another reason might include the type of soil/substrate — such as high concentrations of clay on the left side of the map.

Class Discussion of Groundwater Remediation: Have students discuss the treatment process that their team developed. Did it work? Why or why not? What would they do to improve their treatment method? (Answers will vary.) Discuss with students how engineers often iterate several different designs when developing a final process or product. In this case, environmental engineers may have to test several different methods of treatment to find one that works with both the highly acidic Le Chimique and the associated oil products. Engineers also often have to design within constraints, such as limited budget (cost) and environmental effects of the treatment process.