Fisher Associates provides biennial below-water inspections of NYS Canal structures, walls, dams, locks, and NYS Thruway bridge foundations. We have provided team leaders and fathometer surveys since 2004. Our team leaders monitor diving inspections and prepare reports on inspection findings.
Fishers conducted an in-depth inspection of 100 spans of the subway 198 spans to
assess and document the existing condition of the reinforced concrete roof slabs and walls within the abandoned subway tunnel. This inspection identified areas in need of immediate repair, and was used to develop a program for future repairs for the next 10 years. In addition to conventional visual inspection and concrete sounding techniques, the use of “impact echo” testing was employed to determine areas of hidden concrete distress and delaminations. Impact Echo is a non-destructive evaluation of concrete and masonry and is based on impact generated stress waves of low frequencies that propagate through the test element and are reflected by internal defects and external stress free boundaries. The results were summarized in a report to the City of Rochester and is currently being used to develop a rehabilitation program for the abandoned tunnel.
Fisher staff performed 100% hands-on inspection of the bridge superstructure and substructures above the water upstream and downstream of the dam crest, the submerged concrete apron, and the concrete spillway and dam face down-stream of the dam crest. Work included hammer sounding and visual inspection, concrete cores, underwater inspection via dive team. For the underwater inspection, Fisher hired out with two professional divers and a safety diver. Dive plans were prepared ahead of the work to identify deteriorated areas utilizing underwater video and communications equipment with our Team Leader on the bridge. Lastly, our surveyors performed 3-dimensional survey and mapping of concrete test markings on the arch undersides of the bridge.