FEATURE ARTICLE The Cannelton Lock and Dam is a US Army Corps of Engineers (USACE) facility located 1,170 km (727 mi) below Pitts- burgh on the Ohio River. Built between 1962 and 1974, it has a main chamber 34 m (110 ft) wide and 366 m (1,200 ft) long, with one auxiliary lock structure. The non- navigable part of the structure is 427 m (1,400 ft) long with 12 tainter gates. Under normal river conditions the upper and lower pool average elevations above mean sea level are 383 ft (116.7 m) and 358 ft (109 m), respectively. This 7.6 m (25 ft) elevation difference is a potential source of clean renewable energy that is being developed by American Municipal Power (AMP), a nonprofit, 128-member power producing co-op. The renewable power will come from the 3 horizontal 29.3 MW bulb-type turbines and generating units housed in the concrete power plant scheduled to be completed early 2014. Cannelton Hydroelectric Cofferdam Cut-Off Wall The project was procured in separate contracts based on specialized scopes of work and schedule constraints. The estimated construction value is estimated to be over $400 million. The Kiewit- Traylor JV was awarded the $63 million contract for the design and construction of the cofferdam on February 17, 2009. The team was in a race against time to get the design completed and approved and build the cofferdam, one-third of which was in the Ohio River, along with the cut-off wall and flooding system before the Ohio River reached its normal yearly highs, typically January through April. To meet the schedule, the job team worked on the landside portion of the cut- off wall while the marine dike was under construction. The cut-off wall operation started at the dam, arriving just as the marine dike was completed. The key decision made by the team was to select an innovative technique to constructing the cut- off wall — a hydromill/clam combination excavated under self-hardening slurry CB, or cement bentonite, in this case slag and bentonite. This technique allowed the cut- off wall to be completed in time to avoid risk of flooding during construction. However, the mix design was critical; it had to be sufficiently viscous to carry cutting sand to the desander, but not so viscous that it wouldn’t allow desanding or pumping for long distances. Ground breaking was in August, 2009, followed by environmental controls, tempo- rary roads and the work platform. The work consisted of: 154,000 sm (515,000 sf) CB cut-off wall to depths of 44.2 m (145 ft), marine dike construction – (600,000 tons of stone and sand), powerhouse excavation – 948,000 cm (1,233,000 cy), instrumentation, dewatering system – up to 19,000 lpm (5,000 gpm), flooding system and temporary roads. AUTHORS Dwight Metcalf, P.E., Area Manager, Foundations, Kiewit Infrastructure Co. and James Tantalla, Ph.D., P.E., MRCE 82 • DEEP FOUNDATIONS • NOV/DEC 2013
