Annual precipitation at a landfill in the town of Fremont is 100 mm per year, and 50 percent of this water runs off the landfill without infiltrating the surface. The landfill has a surface area of 5,000 m². Underneath the landfill, the town installed a leachate collection system that is 80 percent effective. Any leachate not collected by the system enters the surrounding soil and groundwater. This leachate contains cadmium and other toxic metals.

Calculate the volume of water in cubic meters (m³) that infiltrates the landfill per year.

100 mm/year = 0.1 m/year

0.1 m/year × 5,000 m² × 50% = 250 m³

So the volume of leachate in m³ that is treated per year is: 250m³ × 80% = 200m³

Your Turn In a neighboring landfill, 70 percent of annual precipitation runs off without infiltrating the surface and the leachate collection system is 90 percent effective. Calculate in cubic meters (m³) the volume of leachate that is treated each year.