A water quality certificate is a prerequisite for a twenty-year renewal by the NRC. On April 3, 2010, the New York State Department of Environmental Conservation ruled that Indian Point violates the federal Clean Water Act, because "the power plant's water-intake system kills nearly a billion aquatic organisms a year, including the shortnose sturgeon, an endangered species." The state is demanding that Entergy constructs new closed-cycle cooling towers at a cost of over $1 billion, a decision that will effectively close the plant for nearly a year. Regulators denied Entergy's request to install fish screens that they said would improve fish mortality more than new cooling towers. Anti-nuclear groups and environmentalists have in the past tried to close the plant, which is in a more densely populated area than any of the 66 other nuclear plant sites in the US. Opposition to the plant increased after the September 2001 terror attacks, when one of the hijacked jets flew close to the plant on its way to the World Trade Center. Public worries also increased after the 2011 Japanese Fukushima Daiichi nuclear disaster and after a report highlighting the Indian Point plant's proximity to the Ramapo Fault.