But a low-head dam that delivered irrigation water also blocked fish movement.

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This problem was avoided in 2004, but unfortunately, on that occasion, the volume of sand available behind the dam was too low to rebuild the sandbanks.

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With the water level critically low, it is difficult to see how the turbinated flow of the dam is reaching the high levels that the state agency is claiming.

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The MTA took extensive measures before the storm to limit the amount of water flooding into tunnels, including by boarding up ventilation grates in low-lying stations, piling sandbags at station entrances, inflating a rubber dam in the Long Island Rail Road's West Side yards in Manhattan and hastily erecting a floodwall across the mouth of the No. 3 train tunnel near East 148th Street in Harlem.

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