Severe erosion was discovered on an October 2008 inspection of Allegheny River Lock and Dam No. 6 near Pittsburgh, PA, a US Army Corps of Engineers structure. In the Q1 2009 issue of PileDriver Magazine from the PDCA, a project spotlight describes the $2.9 million Sheet Piling and Grouting Emergency Repair project performed by Brayman Construction Corporation to repair the dam and lock. (Illustration from PileDriver Magazine, Q1 2009, V6, No. 1)
The dam and lock was built in 1927-1928 and is 992-ft wide by 12.4-ft high. The lock itself is 56-ft by 360-ft. The foundations for the concrete dam structure consisted of timber pilings with a steel frame on top.
The survey performed by divers had found more erosion than was anticipated and the worst section extended approximately 29-ft underneath the dam in a 200-ft section, threatening to undermine the dam. Brayman Construction began the repair work in early November of 2008 and was completed with most repairs by mid-January of 2009. The fixes included installation of a sheet pile wall on the downstream side of the dam along with erosion protection on the downstream side. Concrete was tremied into the eroded portion and through drilled holes in the dam at other locations to ensure that the voids were filled.