Canal pound
[2] The Chesapeake and Ohio canal had frequent cave-ins due to limestone sinkholes near Shepherdstown, near Two Locks above Dam No.
Pumping would contribute greatly to operating expense, especially at the summit level, hence gravity fed water is preferred.
The Chesapeake and Ohio put a steam pump near the South Branch, near mile 174, which had a capacity of about 25 cu ft/s (0.71 m3/s), since the water from Dam No.
[11] Exceptions to this would include wartime necessities, i.e. the Chesapeake and Ohio Canal was left open in the winters of 1861–1862 because of the American Civil War.
These boats carried clay straw, takes, rope, wooden boards, and tools (picks & shovels).
[16] For culverts and flood gates, a row of heavy planks, interlocked with tongue and groove, would be driven across the canal (similar to a cofferdam) above and below the break, and would swell when wet.
If the break was in the bank or berm of the canal, the crew would drive two rows of stakes, about a foot apart, across the breach, then weaving rope between them.
One reason for the present restriction on boat movements over the summit is that the water rights and associated works were sold to various local authorities in 1923 under the terms of the Oldham and Rochdale Corporations Water Act, as the subsequent increase in leisure traffic was not anticipated.
The summit pound was 5.2 miles (8.4 km) long, between Poyntz Pass and Terryhoogan, but its water supply was a cause of problems over many years.
[21] Pennsylvania's Union Canal suffered likewise on its summit level for lack of water.
The longest one is the 11.6-mile (18.7 km) Fenny Stratford pound on the Grand Union Canal, between Cosgrove Lock, which starts the ascent to the Braunston summit to the north, and Fenny Stratford lock, which starts the ascent to the Bulborne summit to the south.
[23] Every sump pound needs somewhere to discharge the surplus water, and in this case, a large viaduct and aqueduct immediately to the south of Cosgrove Lock carries the canal over the River Great Ouse, which serves that function.
[27] Canals have several devices used to keep the water level from rising too high in the pounds, causing floods, washouts, and other damage.
Waste weirs often had paddle valves at the bottom, allowing the canal to be completely drained for repairs, emergencies, or at the end of the boating season for winter.
This could be adjusted, similar to the waste weir by adding or removing boards to control the water level.
An "informal overflow" on American canals is a dip in the towpath which functions as a spillway, but usually lacking concrete or formal structure.
[29] Informal overflows were often replaced by a waste weir or lined with concrete or masonry to make a more "permanent" spillway.
On the Erie Canal, in the three mile long rock cut above Lockport, if a mule or horse fell into the canal pound, there were some escape "holes" cut in the towpath, a depression covered over by wooden boards, so that the animal could go into the "hole" and then be rescued.
It is common on English canals for boaters to carry a barge pole to help punt the boat off an obstruction.
Sometimes boatmen would ask the lockkeeper of the lock above for a swell, to raise the water in the level, so that they could get off the sand bar.
