Coal Age Magazine - For nearly 100 years, Coal Age has been the magazine that readers can trust for guidance and insight on this important industry.
Issue link: https://coal.epubxp.com/i/131326
transport tips continued Figure 2: Thebes Reach between Mile Points 44 and 46 (Black dots represent rock pinnacles) wide channel that is 9 ft deep, but they cannot manage water when it is not available. Based on the National Weather Service forecast, low Mississippi River stages were forecast to impact the St. Louis Districts' ability to maintain the navigation channel at authorized project dimensions, especially in the Thebes Reach in the mid-December 2012 timeframe. As Figure 2 shows, this would have narrowed the channel to 150 ft near the bend. Less than a mile downstream the channel is a little wider (170 ft), but the rock dangers are so much greater. Construction companies hired to remove rock pinnacles from the river have used a number of different methods: (1) backhoe on barge; (2) drilling and blasting; and (3) hydro-hammer. Oddly enough, they cannot work when the water gets too deep, and recent rains have caused a cessation of work. The higher water that is good news to the barge companies is a delaying factor for the Corps' rock removal effort. The first rock removal contract used drilling and blasting technology, and was done in 1988 and 1989. It took advantage of low water (-4.2 St. Louis gage). The Coast Guard closed the channel for 30 days at Thebes, but the work was not completed. There is no doubt that navigation problems in the St. Louis-to-Cairo reach seriously affect grain haulage from the Illinois Waterway and the Twin Cities. Some may argue that coal is not so seriously affected, but that is not true. Coal docks on the Mississippi River include Cora, Kellogg, Cahokia, Hall Street (St. Louis); the Illinois River has the Havana Dock. All would argue they would be seriously affected. Temporary Problems at Lock and Dam 27 Lock and Dam 27 consists two locks. The main lock is 1,200 ft long; the smaller auxiliary lock is 600 ft long. On Jan. 22, the main lock was already closed for repairs. At about 0500 the operator was raising the auxiliary chamber with the first cut of the MV CAPT W.D. Nunley. As the chamber was filling there was apparently enough slack in the lines to allow the front barges to get up under the nap section of the downstream lift gate. [The nap section is the "lip" that goes across the top of the gate.] The rising barges caused the gate to be raised out of the water and become skewed in the slot. It could become a serious problem if the lock operator had not noticed and acted quickly. Figure 3: Barge Tow Clearing Thebes Reach near Mile Point 46 26 www.coalage.com The operator almost immediately took action to lower the chamber water level. However, this is a slow process. There is a culvert on both sides of the lock used to fill the chamber. Each culvert is 12 ft x 12 ft so there is a lot of water rushing into the chamber. To reverse the process the operator had to first close the large valves on the upstream end of this culvert. These valves are operated through motor gear driven machinery and take several minutes to close; meanwhile the chamber continued to fill after these valves were closed (by then the gate was high enough that it no longer "overlapped" with the seal on the other gate and the chamber continued to fill from water leaking between the two gate leaves). Next the operator opened the lower valves, which took just as long, and began to drain the chamber. Eventually the barges lowered, but the gate remained wedged in its slot with significant slack in the hoisting chains. The maintenance crew immediately began running the gate machinery to take out the slack, and the gate dropped about 2.5 ft with the chains stopping it. This kind of shock to the mechanical system required complete inspection of the chains, connections, and hoisting sprockets as well as the gate itself. Fortunately, the Corps found only minor damage, which they were able to repair in less than 24 hours. A section of the seal required 48 hours for parts, but Corps engineers made the decision the lock could be safely operated, and the seal was repaired two days later after backed-up tows were allowed through. Operations resumed at 2000 hours on Jan. 23. Dave Gambrel is a coal consultant and writer. The former director of transportation for Peabody Energy, his background includes coal terminals and all modes of transportation in the U.S. and abroad. He may be reached at bunkgambrel@earthlink.net. Figure 4: Lift Gate at Auxiliary Lock and Dam 27 (Source: USACE) March 2013