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2015WinterShotcreteEMag

2014 Outstanding Infrastructure Project McCormick Dam & Power Station: Submerged Concrete Repairs By Roger Côté, Harold Ferland, and Kevin Robertson Tthe Quebec and Ontario Paper Company and tion confirmed abundant surface scaling at and-The results of Groupe-conseil TDA’s inspecScope of Workhe McCormick Dam and power station wasbuilt in 1952 on the Manicouagan River by the Canadian British Aluminium Company. It was below the waterline along the entire length of named after Colonel Robert R. McCormick, who the reservoir (basin) retaining walls and the tail- owned and published the Chicago Tribune. It is race (spillway). The average depth of the repairs currently owned and operated by the Société en was approximately 2 in. (50 mm). Damage to the Commandite Hydroélectrique Manicouagan. The reservoir (basin) retaining walls equated to a dam is situated approximately 1.9 miles (3 km) surface area of approximately 10,763 ft2 west of Baie-Comeau, QC, Canada, in the Côte- (1000 m2), while the tailrace (spillway) required Nord area of the province of Quebec. approximately 6458 ft2 (600 m2) of repair Groupe-conseil TDA, a well-established and (Fig. 1). leading consulting firm from la Côte-Nord area, The location of the repairs created many logis- was hired to inspect the dam, the retaining walls tical and procedural challenges. To overcome of the reservoir, and the water discharge (tailrace) those challenges, Le Groupe-conseil TDA speci- to determine the condition of the concrete after fied that the damaged concrete be removed and 60 years of exposure to heavy water flow and replaced using pressure grouting techniques, freezing-and-thawing cycling and to formulate a through which nonshrink grout would be pumped plan to rehabilitate the structure. from surface into the forms. Divers would be The project was released for tender in early required to direct the pressure grouting process 2013 and was awarded to BBMarine. BBMarine and to ensure the watertight forms retained all of is a specialized marine contractor from la Côte- the grout. Nord with over 35 years of experience in the The thought of forming a total area of 17,221 ft2 construction, inspection, repair, and maintenance (1600 m2), much of it underwater (using divers), of marine structures. concerned the construction team because of cost implications and the effect it would have on the entire construction schedule. Logistics The logistical challenges continued after BBMarine mobilized on site. The majority of the areas to be repaired provided limited access or room for equipment, materials, and formwork. Access to the repair locations was therefore lim- ited to barges. BBMarine initiated discussions with Groupe- conseil TDA, Béton projeté MAH Inc., and King Shotcrete Solutions to investigate alternative solu- tions for completing the concrete repairs. The group reached consensus that if concrete replace- ment was executed using the shotcrete process, it would allow easier access to the repair areas and it would contribute to an accelerated construction schedule. More importantly, all agreed that replacing nonshrink grout with concrete (as a repair Fig. 1: Area to be repaired material) would result in much more durable and 36 Shotcrete • Winter 2015


2015WinterShotcreteEMag
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