Monroe County wanted to replace an aging three-sided concrete culvert carrying an unnamed Oatka Creek tributary (a regulated waterway) under North Road in Wheatland, NY. Erdman Anthony undertook the project with the goals of assessing and estimating alternatives and then designing a cost-effective and environmentally conscious solution.
Our design process considered several alternative materials, including metal, concrete, and plastic pipes. An option was identified that met two important goals: to fit within the county’s budget and to be hydraulically efficient.
The existing culvert was 4.75 feet wide by 5 feet high by 54 feet long. The replacement culvert is an 81-inch-span by 59-inch-rise by 99-foot-long corrugated-metal pipe-arch culvert. Its invert is buried 21 inches in order to provide a natural stream bottom through its entire length. The culvert’s length includes 4-foot-long sloped ends.
The plastic coating, laminated on both the interior and exterior of the corrugated metal pipe, extends the life of the pipe by as much as 80 years. This solution realized a 20 percent cost savings over a precast-concrete span. Additional cost savings were realized as the county performed the work using its own crews and equipment.
The replacement culvert is 45 feet longer, which provides for an additional 18 feet of improved and unobstructed roadside safety and a clear zone in accordance with current AASHTO and NYSDOT standards. The safety accrual realized by the dramatically increased length of the replacement culvert also meant that our design did not require guide rails.
Hydraulic analysis determined that the size of the culvert opening we designed would be hydraulically equivalent to existing conditions, mitigating impact on abutting landowners upstream and downstream, and contributing to balance in the ecosystem.
By burying the pipe invert below the stream bed, the North Road culvert design creates a natural creek bottom with a depth of water consistent with the upstream and downstream flows. Since the natural stream flow and bottom substrate are continuous throughout the crossing, the structure does not constrict or fragment the stream. This approach allows fish and invertebrates to continue to pass through the stream freely.