Allega Cos. answers Corps contract commanding nearly 120,000 tons of wave-worthy precast
Article excerpt from the January 2017 issue of Concrete Products
A weather front emanating from Superstorm Sandy in October 2012 tested infrastructure well inland of metro New York and New Jersey, the area hardest hit by precipitation, wind and storm surge. Among federal and state agencies contending with long-term responses to Sandy-level exposure is the U.S. Army Corps of Engineers Buffalo District. It capped the 2015 and 2016 construction seasons closing repair and upgrade contracts—Oswego Harbor Detached Breakwater, New York; Cleveland Harbor East Breakwater, Ohio—using non-proprietary precast concrete structures known as dolosse, in tandem with limestone or granite armor block.
District engineers outlined finished structure air content, flexural and compressive strength, plus surface quality specifications for respective Oswego and Cleveland project precasters, Lakelands Concrete Products of Lima, N.Y., and Allega Cos. of Valley View, Ohio. Both determined that highly fluid, self-consolidating mixes are the best solution for accelerated production of structures that will be submerged or subject to frequent Great Lakes wave exposure through a service life plausibly extending into the next century. Early indicators suggest the dolosse installations contribute to a Corps roster proving the efficacy of SCC for structures prone to extreme weather or temperature events, sharp freeze-thaw cycles, and rare, but catastrophic loads.
Dolosse resist breakwater or shoreline erosion from waves and undercurrent through their mass and energy-dissipating geometry. Known as dolos individually, the monolithically cast structures comprise three members of octagonal cross section: Uniformly sized shanks connect fluke ends. The latter are flared, tapered members running in opposite directions, along X and Y axes. Dolosse are fabricated in four- to 16-ton sizes, sans lifting hardware, and placed by sling so each structure interlocks such that even the most forceful waves or undercurrents meet long plain or reinforced precast concrete chains of inordinate tonnage.
The Corps Buffalo District used a formula factoring statistical 20-year wave height and 10-year water level to determine 16-ton and 6.5-ton dolos sizes for the New York and Ohio installations. Located near the southeastern corner of Lake Ontario and serving the first U.S. port from the St. Lawrence Seaway, the upgraded Oswego Harbor structure marks the District’s first use of 16-ton dolosse. Lakelands Concrete fabricated 997 of the 11-ft. long structures with conventional reinforcement (Concrete Products, July 2015). The dolosse represented the bulk of a $19 million contract Michigan’s Durocher Marine completed in November 2015.
Slightly trailing the New York engineering and casting schedule were preliminaries for the much more ambitious Cleveland Harbor work, centered in Lake Erie about two miles east and one-half mile north of downtown Cleveland. Buffalo District engineers specified the 6.5-ton dolosse, plain and 8.3-ft. long, for 4,400 feet of breakwater structure, which sustained more than $31 million in damage attributable to the Superstorm Sandy-spurred weather system. The Corps found that the intensity of the winds over Lake Erie created extraordinarily rare waves, measured at nearly 18 feet offshore of Cleveland.
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