Encyclopedia Dubuque
"Encyclopedia Dubuque is the online authority for all things Dubuque, written by the people who know the city best.”
Marshall Cohen—researcher and producer, CNN
Affiliated with the Local History Network of the State Historical Society of Iowa, and the Iowa Museum Association.
LOCKS: Difference between revisions
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LOCKS. A navigational device used to raise or lower boats. Along with twenty-nine dams on the Upper [[MISSISSIPPI RIVER]], locks create a water staircase that drops two hundred forty feet from St. Paul and Minneapolis, Minnesota, to St. Louis, Missouri. Below St. Louis, the water is naturally deep enough that dams and locks are not needed. | LOCKS. A navigational device used to raise or lower boats. Along with twenty-nine dams on the Upper [[MISSISSIPPI RIVER]], locks create a water staircase that drops two hundred forty feet from St. Paul and Minneapolis, Minnesota, to St. Louis, Missouri. Below St. Louis, the water is naturally deep enough that dams and locks are not needed. | ||
Locks are based on the principle that water seeks a lower level. Underground tunnels and valves are used to fill and empty the locks with water. For boats headed downstream, the lock is filled by opening the filling valve. The upper and lower gates, along with the emptying valve, are closed to allow the water level to reach the upstream level. When this level is reached, the upper gate is opened. | [[Image:locks-1.gif|left|thumb|250px|]]Locks are based on the principle that water seeks a lower level. Underground tunnels and valves are used to fill and empty the locks with water. For boats headed downstream, the lock is filled by opening the filling valve. The upper and lower gates, along with the emptying valve, are closed to allow the water level to reach the upstream level. When this level is reached, the upper gate is opened. | ||
The upper gates are closed behind the boat. The filling valve is closed, and the emptying valve is opened. Water pressure alone drains the lock; no pumping is necessary. When the water level inside the lock equals the water level on the downstream side of the lock, the lower gates are opened and the boat is able to resume its journey. The process is reversed for boats headed upstream. | The upper gates are closed behind the boat. The filling valve is closed, and the emptying valve is opened. Water pressure alone drains the lock; no pumping is necessary. When the water level inside the lock equals the water level on the downstream side of the lock, the lower gates are opened and the boat is able to resume its journey. The process is reversed for boats headed upstream. | ||
Revision as of 01:33, 5 August 2008
LOCKS. A navigational device used to raise or lower boats. Along with twenty-nine dams on the Upper MISSISSIPPI RIVER, locks create a water staircase that drops two hundred forty feet from St. Paul and Minneapolis, Minnesota, to St. Louis, Missouri. Below St. Louis, the water is naturally deep enough that dams and locks are not needed.
Locks are based on the principle that water seeks a lower level. Underground tunnels and valves are used to fill and empty the locks with water. For boats headed downstream, the lock is filled by opening the filling valve. The upper and lower gates, along with the emptying valve, are closed to allow the water level to reach the upstream level. When this level is reached, the upper gate is opened.
The upper gates are closed behind the boat. The filling valve is closed, and the emptying valve is opened. Water pressure alone drains the lock; no pumping is necessary. When the water level inside the lock equals the water level on the downstream side of the lock, the lower gates are opened and the boat is able to resume its journey. The process is reversed for boats headed upstream.
Between 1.5 and 2.0 hours are needed to lock through a fifteen-barge tow holding the equivalent of 870 semi-truck loads of grain, farm chemicals, or petroleum. Barges, from 105 feet to 108 feet long, have a tight squeeze in the lock that is only 110 feet long. The depth of the water drops eleven feet with the gates open.
Watching the locking process is a favorite pastime for thousands of visitors to Dubuque. Between June and July of 1988 an estimated 77,448 people watched Lock and Dam 11, many of whom used the vantage point of EAGLE POINT PARK to observe the locking procedures.