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A watertight chamber connecting the upper and lower canals, and large enough to enclose one or more boats. The position of the chamber is fixed, but its water level can vary. A gate (often a pair of "pointing" half-gates) at each end of the chamber. A gate is opened to allow a boat to enter or leave the chamber; when closed, the gate is watertight.
The system depended on the submerged, sealed box (the "caisson", from the French for "large chest" [7]) being heavily ballasted to achieve neutral buoyancy, so it was never possible in ordinary operation to lift it to water level to allow a descending boat to float in. Instead, a masonry chamber ("cistern") was built with walls higher than the ...
Salt water began to make its way upstream toward Lake Union, requiring a system of siphons and flushing mechanisms. Because the Cedar River was the main water source both for the lakes and locks and for Seattle's potable water, at times there were problems maintaining an adequate water supply to maintain lake level and operate the locks.
Schematic cross section of a pressurized caisson. In geotechnical engineering, a caisson (/ ˈ k eɪ s ən,-s ɒ n /; borrowed from French caisson 'box', from Italian cassone 'large box', an augmentative of cassa) is a watertight retaining structure [1] used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, [2] or for the repair of ships.
Embedded in the side and center walls are three large water culverts that are used to carry water from the lake into the chambers to raise them, and from each chamber down to the next, or to the sea, to lower them. These culverts start at a diameter of 22 ft (6.71 m) and reduce to 18 ft (5.49 m) in diameter, large enough to accommodate a train.
The four paddles for equalising the water level are clearly visible, but guillotine gates without paddles exist too. In those, the entire gate is lifted a little bit to allow water in or out of the chamber. The Weurt lock has an additional gate near the centre of the chamber. When only a few short boats want to go through the lock, they can use ...
The Louth Navigation canal and parts of the old River Lud perform land drainage and water level control with a number of locks and pumping stations. A tilting weir controls water levels in the Riverhead Basin and includes a gauging station which measures the flow along the canal. Controlling the height of water within a chamber at water ...
The reference water levels are used on inland waterways to define a range of water levels allowing the full use of the waterway for navigation. [1] Ship passage can be limited by the water levels that are too low, when the fairway might become too shallow for large ("target", "design") ships, or too high, when it might become impossible for the target ships to pass under the bridges. [1]