Nuclear plants generate about 20 percent of the electricity for U.S. residents, and proponents say the energy is a cleaner alternative to coal-fired plants. But nuclear power, which runs on uranium, also has a toxic side. Cotter Corporation recently offered a plan to state regulators for the cleanup of old uranium mine contamination flowing into a creek that feeds Ralston Reservoir. But the Colorado Division of Reclamation Mining and Safety said late last week the plan would not prevent contaminants from entering the reservoir that supplies some of the Denver area’s drinking water, according to The Associated Press. As such, state officials will take enforcement action against the company. Meanwhile, Wednesday in Denver, leaders from the uranium mining industry gathered with federal regulators to discuss ways to better safeguard the environment—drawing a group of protesters, according to The Denver Post. American Indian demonstrators want mining to stop on Navajo land, where several operations have been permitted. “Our Navajo communities rely on the groundwater for everything. These new projects could contaminate the source of drinking water for 15,000 Navajo community members,” says Nadine Padilla of the Multicultural Alliance for Safe Environments. She adds that uranium companies and regulators “need to deal with the legacy of past contamination before we would even consider new mining.”