Water is admitted into and drained from the lock by culverts cast in the base. These are 8 by 10 feet, narrowing at the opening to 8 by 8 feet, and closed by 8 sluice gates, each operated by a 52-horsepower electric motor. It will be possible to fill or empty the lock in ten minutes. There are five sets of gates to the lock. They are built of steel plates and rolled shapes, four and a half feet thick and weighing 200 tons each. And there is an emergency dam weighing 720 tons, which in case of necessity can be used as a gate. Four pairs of the gates are of 55-foot size; one of 42-foot. Each gate is operated by a 52-horsepower electric motor. When open, the gates fit flush into the walls of the locks. In the emergency dam is the refinement of precaution--designed as it was to save the city from overflow in the remote event of the lock gates failing to work during high water, and to insure the uninterrupted operation of the lock in normal times, if the gates should be sprung by a ship, or otherwise put out of commission. This dam consists of eight girders or sections, 80 feet long, 3 feet wide and 6 feet high. They weigh 90 tons each. They are kept on a platform near the river end of the lock. Nearby is the crane with a 300-horsepower motor, that picks up these girders and drops them into the slots in the walls of the lock. To set this emergency dam is the work of an hour. A ship passing through the lock will not proceed under her own power. There are six capstans, two at each end of the lock and two at the middle, each operated by a 52-horsepower electric motor, and capable of developing a pull of 35,000 pounds, which will work the vessels through. The lock complete, counting the bridge and approaches, cost $7,500,000. One and a half million of this is for machinery, and $56,000 for the approaches. Henry Goldmark, the New York engineer who designed the gates of the Panama Canal and the New Orleans Industrial Canal, in a letter of March 24, 1921, to the engineering department of the Dock Board, comments as follows on the remarkable lock: "I was much impressed by the uniformly high grade of construction of the lock, the systematic and energetic way in which the work was being carried on, and especially by the admirable spirit of team work, shown by the employees of the Dock Board, of different grades, as well as the contractors, superintendents and foremen. "The desire to get the best possible results in all the details, at the least cost, was manifest throughout. "The unique method used for carrying on the very difficult and risky work of excavation has attracted much professional attention in all parts of the country. Its successful completion is very creditable to all concerned, in the inception and carrying out of the method used.