The city has also agreed to take other steps to prevent a terrorist from punching a hole in the edifice that could cripple the city's water system and flood an area where 200,000 people live.
Since the 11 September 2001 terrorist attacks, New York City and Westchester officials have been in agreement that the road on top of the dam should be closed to improve security. It is not clear what will happen if the study does not conclusively show that a truck or sport utility vehicle carrying a bomb could compromise the dam.
Both the county and the city say they own the road and have the final power to decide whether vehicles should be allowed to drive on it.
