Feeders[edit]
There were three streams used as feeders: Rocky Run feeder (section #9, around 7 Locks), Great Falls feeder (section #18) and the Tuscarora feeder (section #78). There was a contemplated feeder at the Monocacy (not built),.[97] Of course, the remains of the Potomac Company Little Falls skirting canal was used as a feeder also. Inlet lock #2 is called the Seneca Feeder in historic documents.[98]
The remains of the Tuscarora feeder can still be seen, but it was made redundant by Dam #3 and was no longer used.[99]
[edit]
Despite Charles F. Mercer, two slackwaters were used for navigation: Big Slackwater at Dam #4, and Little Slackwater at Dam #5. Big Slackwater is about 3 miles long, Little Slackwater is about ½ mile long. The boats had to navigate despite winds, currents, and debris in the channel. In February 1837, the board of directors discussed using steam power in the slackwater for the boats, but instead decided on a permanent towpath.[100] The towpath for Big Slackwater was completed in 1838 for $31,416.36, and the towpath for Little Slackwater was completed in 1839 for $8,204.40.[101]
Little Slackwater was a tricky place to navigate. Not only did it have a lot of hairpin turns, but also just before Guard lock #5, there was a strip of land in the water called "the pier" [which exists even today]: loaded boats going downstream would have to go outside the pier, and unloaded boats on the inside, thus making steering difficult for the loaded boats to get into the lock. If the current was fast in the river it could go as fast as the boat, rendering the tiller useless, and thus, a boat could be almost impossible to steer.[102] One man reported that at the slackwater, they had him sit at the front of the boat with a hatchet in case they had to cut the towline [since it would pull the mules into the river], and had a couple of [wooden] hatches turned upside down, so that they could escape to shore on the hatches.[103] On 1 May 1903, the towline to Boat No. 6 broke, with Captain Keim, Mrs. Keim, their two daughters, and Harry Newkirk aboard. One daughter drowned, another suffered a broken leg, and the captain died later of injuries. The rest (including the mules aboard) survived.[104]
Boatmen reported that it was easier to navigate in the slackwaters than the aqueducts, since there was room for the water to move around the boat. Places like aqueducts, where there was little room for the water to move, were difficult for the mules to pull the boat through.[105]
Waste weirs, spillways, and informal overflows (mule drinks)[edit]
To regulate the level of water in the canal prism, waste weirs, informal overflows, and spillways were used.
Waste weirs removed the surges of water from storms or excess when a lock was emptied.[106] Boards could be removed or added to adjust the amount of water in the level. If one had to empty the whole level for winter, repairs, or emergencies, waste weirs often had paddle valves (similar to those found in locks) at the bottom which could be opened to let the water out.
Waste weirs come in several styles. Originally they were made of concrete masonry with boards on top making a bridge with mules to pass over. A possible example of an old-style waste weir (abandoned) is at 39.49 miles, above Lock 26 (Wood's Lock). Most of these old waste weirs were replaced with concrete structures in 1906.[107] Another used to be at Pennyfield lock in 1909-1911.
Spillways are made of concrete, and can be on either side, but if on the towpath side, have a bridge so people (and mules) can cross without getting the feet wet. High water simply flows over the spillway and out of the canal. The longest spillway, near Chain Bridge, is 354 feet long, was made in 1830 (but has been worked on since).[108] Another spillway near Foxhall road[109] at mile 1.51, was made in 1835. The spillway and waste weir at Big Pool was built in the 1840s[110]
An informal overflow or mule drink was a dip in the towpath allowing water to flow over, similar to a spillway, but without the bridge or the concrete construction (hence, were more informal). The canalers called these "mule drinks".[111] There are documented informal overflows at mileage 10.76 (shown in the photograph), 49.70, and 58.08.[112] These usually had a drainage ditch which was riprapped with stone to prevent erosion. Historically the towpath dropped two feet to form this overflow.[113] Due to silting, construction, etc. many of these overflows are now difficult to find. Hahn states that clues to finding these overflows include: a gully without a culvert, a sudden lowering of the towpath, or the signs of riprap on the towpath or the gully itself.[114] Many of these (e.g. the one at Pennyfield lock) were replaced by a waste weir.[115]
Paw Paw tunnel[edit]
Main article: Paw Paw Tunnel
One of the most impressive engineering features of the canal is the Paw Paw Tunnel, which runs for 3,118 feet (950 m) under a mountain.[56] Built to save six miles (10 km) of construction around the obstacle, the 3/4-mile tunnel used over six million bricks. The tunnel took almost twelve years to build; in the end, the tunnel was only wide enough for single lane traffic.[116] One notorious incident included two captains who refused to budge for several days. The company official threw green cornstalks onto a roaring fire at the upwind portion of the tunnel, smoking the offenders out.[49]
Inclined Plane[edit]
Engineer William Rich Hutton was instrumental in getting the inclined plane built.[117] Starting in 1875, a canal inclined plane was built two miles (3 km) upriver from Georgetown, so that boats whose destination was downriver from Washington could bypass the congestion (and price gouging of independent wharf owners) in Georgetown.[118] Originally the company planned to build a river lock, but then discovered that such a lock occasionally would consume more water than the level could provide. They then planned to make an inclined plane, much like the Morris Canal.[119] The first boat went through in 1876; 1918 boats used the inclined plane that first year.[120] Usage reports conflict: Hahn reports that was only really used for two years, and sporadically in 1889,[120] yet Skramstad reports that due to flood damage in 1880 to the Rock Creek outlet, any boat until 1889 (when another flood wrecked the canal) going further down the Potomac than Georgetown, had to use the inclined plane.[121] Although Hahn says it was the largest inclined plane in the world at that time, it was 600 feet long,[122] which is short compared to Plane 9 West of the Morris Canal at 1,500 feet. It originally used a turbine to power it (like the Morris Canal) but was later switched to use steam power.[120]
The inclined plane was dismantled after a major flood in 1889 when ownership of the canal transferred to the B&O Railroad, which operated the canal to prevent its right of way (particularly at Point of Rocks) from falling into the hands of the Western Maryland Railway.[25]
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