What you learned in school
Environmental science classes taught that properly designed landfills with clay liners and collection systems would safely contain waste without affecting groundwater supplies. Students learned about multiple barrier systems that would prevent any contamination from reaching drinking water sources. Textbooks presented landfills as engineered solutions that could permanently isolate waste from the environment. The long-term effectiveness of containment systems was presented as proven and reliable technology.
What we know now
Environmental science classes taught that properly designed landfills would safely contain waste without affecting groundwater supplies. Students learned about clay liners and other barriers that would prevent contamination. Many landfills, even those designed with barriers, have contaminated groundwater with toxic chemicals, heavy metals, and other pollutants. Liner systems can fail over time, and some older landfills had no protective barriers. Groundwater contamination from landfills has affected drinking water supplies and required expensive cleanup efforts. The long-term effectiveness of containment systems was overestimated.