Collins, as a subconsultant, provided underwater inspections of a four-span bridge over the Raquette River in Madrid, New York, and a six-span bridge over the Grass River in Norwood, New York. Both bridges are located on the New York & Ogdensburg Railway. The purpose of the inspections was to aid in the bridges’ rehabilitation.
The underwater inspection consisted of a close visual and tactile examination (Level I and partial Level II, as needed) of the entire submerged surface of the bridges’ piers and the west abutment of the six-span bridge to locate and document all significant areas of damage, deterioration, apparent distress, and local scour. Due to recent rain causing strong currents and the high intensity of the inspection, surface-supplied air was used to keep the diver in constant communication with topside during the inspection of the six-span bridge. Scuba diving techniques were employed at the four-span bridge with dive depths reaching up to 20 feet.
Local scour evaluation channel bottom elevations were measured at 5-foot intervals along the perimeter of each substructure unit and along the upstream and downstream fascia of the bridge. The channel bottom adjacent to the substructure units was probed and identified. The submerged portion of the west abutment was inspected and an additional sounding profile was taken along the fascia of the bridge. Following the completion of the field inspections, Collins prepared detailed condition assessment reports including descriptions of the inspection findings and photographs. Underwater photography documented structural conditions below water.