sentences:  Many of the early safety procedures and waste disposal practices were inadequate, and government documents have since confirmed that Hanford's operations released significant amounts of radioactive materials into the air and the Columbia River, which still threatens the health of residents and ecosystems.The weapons production reactors were decommissioned at the end of the Cold War, but the decades of manufacturing left behind of high-level radioactive waste, an additional of solid radioactive waste, of contaminated groundwater beneath the site and occasional discoveries of undocumented contaminations that slow the pace and raise the cost of cleanup.The Hanford site represents two-thirds of the nation's high-level radioactive waste by volume.