the third feedwater pump subsequently tripping. The loss of feedwater and sudden trip from the high power level caused the reactor water level to drop below -46 inches. After passing this point, the emergency core cooling system automatically activated. Operators using the RCIC and HPCI systems promptly restored the reactor water level to normal. Ironically, it was found that the pumps were tripped due to a design flaw in a recent SCRAM reduction program intended to make the pumps less likely to trip. Quick action by the operators prevented a more serious low-water incident. It was the first time in the station's history that reactor water level reached a low-low condition and activated emergency core cooling systems. On January 27, 2015, the plant underwent a storm-induced unplanned shutdown. The plant was shut down May 31, 2019 and began the process of decommissioning. Electricity Production Surrounding population The Nuclear Regulatory Commission defined two emergency planning zones around nuclear power plants: a 10 mile (16 km) plume exposure pathway zone, 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. In 2010, 75,835 people lived within of Pilgrim, an increase of 40.5% in a decade (according to an analysis of U.S. Census data for msnbc.com). 4,737,792 people lived within 50 miles (80 km), an increase of 10.2% since 2000. Cities within 50 miles included Boston (35 miles to city center). Environmental impacts on Cape Cod Bay PNPS operated a single reactor unit with a boiling water reactor and a steam turbine generator. The cooling and service water systems operated as a once-through cooling system, with Cape Cod Bay being the water source. The water was circulated in the plant's heat exchanger in the same manner as any fossil-fuel powered power plant, using the seawater to remove heat from primary coolant away from sources of radioactive contamination. Approximately 480 million gallons of seawater were withdrawn daily from the bay through an intake embayment formed by two breakwaters, and then re-deposited into the bay causing a change in temperature at peak times (ΔT) of 3 °C (5.4 °F). During that process, the greatest environmental impact to the bay occurred through impingement and entrainment (I&E) of sea organisms and species. Entrainment occurs when small aquatic life forms are carried into and through the cooling system