to the now high water level by manually reducing feedwater flow. At this point, the operator manually opened a steam line relief valve to reduce rising reactor pressure. However, due to the earlier introduction of water into the main steam lines, a hydrostatic shock occurred in the steam lines, which caused a safety valve to open, admitting steam and water into the drywell causing drywell pressure to increase. This caused the initiation of safety injection systems, and for the next 30 minutes reactor water level and pressure seesawed as the operators attempted to stabilize the reactor. It was not until two hours later that reactor level, reactor pressure and drywell pressure were reduced to normal. The movie The China Syndrome bases its initial plot device on this event, with the needle becoming unstuck when the operator taps the recorder. December 8, 1971: Events similar to the ones the year earlier on Dresden II occur on Dresden III. May 15, 1996: Lowering water levels around the nuclear fuel in unit 3 reactor's core prompt a shut down at Dresden Generating Station and placement on the NRC's "watch list" that merit closer scrutiny by regulators. Dresden was on the NRC watch list six out of nine years between 1987-1996, longer than any of the 70 other operating plants in the nation. July 15, 2011: Plant declared an Alert at 10:16 a.m after a chemical leak of sodium hypochlorite restricted access to a vital area that houses plant cooling water pumps. Surrounding population The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of , concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about , concerned primarily with ingestion of food and liquid contaminated by radioactivity. The 2010 U.S. population within of Dresden was 83,049, an increase of 47.6 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within was 7,305,482, an increase of 3.5 percent since 2000. Cities within 50 miles include Chicago (43 miles to city center). Ownership Both currently operating units are owned and operated by Constellation Energy following separation from Exelon, which also owns and is responsible for the decommissioning of Unit 1. Prior to August 3, 2000, all three units were owned by Commonwealth Edison. Seismic risk The Nuclear