Contractors are mobilized on a Missouri mountaintop, awaiting notice to proceed on reconstruction of a pumped-storage reservoir whose impoundment collapsed in December 2005. The roller-compacted concrete structure will be the continent's largest RCC dam, sources claim. The 450-MW peaking hydroelectric powerplant that the reservoir drives could be back on line by the end of 2009.

Ozark Constructors LLC, a venture partnership formed by ASI Constructors Inc. and St. Louis-based Fred Weber Inc., on Nov. 7 was named construction contractor on the Taum Sauk upper reservoir in Reynolds County, Mo. AmerenUE, St. Louis, the Missouri utility operating company of Ameren Corp., did not disclose the contract value. Pueblo West, Colo.-based ASI is a heavy civil contractor specializing in major water projects. AmerenUE also named Paul C. Rizzo Associates Inc., Monroeville, Pa., engineer of record and project manager.

The 1.5-billion-gallon upper reservoir's enclosure will contain 3 million cu yd of roller-compacted concrete in a design approved by the Federal Energy Regulatory Commission (FERC). ASI project manager Lee Scherm­erhorn says it will be North America’s largest RCC dam at 6,750 ft long and reaching between 85 ft to 160 ft in height. Fares Abdo, water resources program manager for Skokie, Ill.-based Portland Cement Association, agrees. The world’s largest RCC dam will be China’s 630-ft-high Long Tan, with 7.9 million cu yd, says a spokes­man for Black & Veatch, Kansas City. The firm is the design and construction consultant for the project, due for completion in 2010.

The contractor is conducting tests on a 40-ft x 60-ft x 12-ft-high RCC pad as required by the FERC permit pending final settlement of a state civil lawsuit against AmerenUE. The reservoir’s failure dumped 1.3 billion gallons of water through a 600-ft-wide gap in the 84-ft-high, rock-filled, concrete-lined dam.

In October 2006, AmerenUE agreed to pay a $10-million civil penalty, fund $5 million in improvements and adopt a comprehensive safety program for its hydroelectric facilities in a settlement with FERC. Settlement of the state’s lawsuit, which sources say is imminent, will clear the way for reconstruction to begin.