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'aquifer will have minimal or no affect on the water level in the confined aquifer. The reverse is also true. However, if the well in the confined aquifer is not properly sealed through the confining layer and unconfined zone, leakage can occur and pumping from one aquifer could affect the water level in the other aquifer. Occasionally there will be a slight change in the water level in the confined aquifer owing to pressure adjustments due to slight compaction of material in the unconffned aquifer as water is withdrawn. CONCEPT 17: Human activities at or near the earth's surface can contaminate qroundwater. Action: Use one of the wash bottles containing diluted dye to add colored water to the lagoon. Discussion: The dye should move out of the lagoon, into the unsaturated sand and into the groundwater. The dye may move toward the lake. The lagoon represents various sources of groundwater contamination and could be a landfill, a chemical disposal site, a sewage lagoon, or a manure storage area. Action: Use one of the wash bottles containing a different colored diluted dye. Add colored water to the underground storage tank. Discussion: The dye should move out of the storage tank and into the sand. The underground storage tank represents another source of groundwater contamination and could be a gasoline tank or a septic tank. Action: Use 3 different wash bottles to add diluted dye to the injection wells. The injection well ~earest the edge of the model will inject dye into the confined aquifer, the middle injection well should add dye to the lens of coarse sand, and the remaining injection well should add dye to the fine sand about 3 inches below the surface. Watch closely for the color to show up (not easy to see if use very diluted dye). Discussion: Injection wells represent another source of groundwater contamination. Contamination can occur if the contaminant is injected directly into the aquifer through an injection well. Improperly sealed wells can allow surface contamination to enter the aquifer through seepage down the outside of the well casing. Action: Use one of the wash bottles containing diluted dye. This time carefully squirt the diluted dye on the surface (can add to the sand as well as the lake). The dye will move into the sand. Discussion: This is a good opportunity to talk about what we do in our homes and everyday lives that can lead to groundwater contamination. Consider littering, boating, use of fertilizers and pesticides, improper disposal of household chemicals, etc. 6