This activity was designed for classrooms with access to an erosion table. However, if unavailable, instructions are provided below for alternate materials.

Each group needs:

• LEGO EV3 Intelligent Brick (such as part #45500 for $197.99, available at https://shop.lego.com/en-US/EV3-Intelligent-Brick-45500)
• LEGO MINDSTORMS EV3 Color Sensor, available at https://shop.lego.com/en-US/EV3-Color-Sensor-45506 for $41.99
• 8 clear plastic cups, 8-ounce size or larger; 1 empty, 1 for water, 1 for sand and 5 for different contaminated sand samples that are labeled and prepared with drops of dye
• 6 plastic spoons; 1 for each of the 5 contaminated sand samples plus 1 for adding sand and water
• Soil Contamination Pre-Evaluation, one per student
• Soil Contamination Post-Evaluation, one per student
• Soil Contamination Worksheet, one per student

To share with the entire class:

• simulation of river flow, via an erosion table with hydraulic bench OR a stream table OR a homemade erosion table; see below for details about these options
• 10 pounds fine sand (~$5)
• roll of aluminum wire mesh, 7 feet in length such as this New York Wire 24-in (61 cm) wide aluminum screening at https://www.zoro.com/phifer-screen-bright-aluminum-24in-w-x-100ft-l-3000727/i/G9554736/?q=New+York+Wire+24-in+wide+aluminum+screening
• heavy-duty scissors or tin snips, to cut wire mesh
• permanent marker, to write on plastic cups
• box of liquid food color dye ($9), such as https://www.amazon.com/MCCORMICK-FOOD-AND-COLORING-Colors/dp/B004G7PLJI/ref=sr_1_2?ie=UTF8&qid=1401487149&sr=8-2&keywords=food+coloring+mccormick%20OR%20http://www.amazon.com/McCormick-486204917497-Mccormick-Color-1-Ounce/dp/B006K3RKEU/ref=pd_sim_gro_3?ie=UTF8&refRID=1GPATVZ1NK8VJCQM4ATX
• access to water and sink

River Simulation Options

1. Erosion table with hydraulic bench for academic purposes, such as the Hydro-Geology Stream Table - Hubbard (#Z06394M) for $1,330 from Nasco at https://www.enasco.com/p/Z06394M; the recommended table dimensions are 26-in wide X 66-in long X 6-in deep; the author used the erosion table shown in Figure 1.
2. Alternatively, use a stream table, such as, such as the Stream Table Kit (#SB01704M) for $80 from Nasco at https://www.enasco.com/p/SB01704M; its heavy plastic tray is 14-in wide X 48-in long X 3-in deep with a drain hole.
3. Alternatively, create a homemade erosion table, such as the one shown in Figure 4. Although a bit more work, it is an efficient low-cost alternative that can be created for ~$34 using the following supplies:

• a large plastic box of similar dimensions to the erosion and stream tables; manually create a drain (hole) on one end, such as this 16.25-in wide X 23-in long X 6-in deep 28-quart storage bin for ~$7 at http://www.homedepot.com/p/Sterilite-28-Qt-Latch-Box-16551010/100671079
• a second pan or bucket to collect the water, such as a five-gallon bucket for ~$3
• a filter, such as a piece of cheesecloth, to keep soil from escaping the pan, ~$4
• a pump, with velocity or flow meter if possible, so students can observe differences in erosion effects due to flow rate changes, ~ $20