This project is for the design, engineering and permitting of a concrete box culvert with a 14’ span, 8’ width, and 35’ in length on Slate Rock Road where it crosses the Fall River, approximately 0.5 miles from the intersection of Slate Rock Road and US-5. The concrete box culvert will be buried 3’ feet, resulting in a clear height of 5’ feet above streambed and providing approximately 70 square feet of waterway area. Bed retention sills 12” inches in height should be placed no more than 8’ feet apart across the width of the structure, with one sill placed at both the inlet and the outlet. The box culvert shall be filled level to the streambed with E-Stone, Type III in order to provide the conditions necessary for aquatic organism passage. The specifications for this structure are based on the recommendation of Vermont Agency of Transportation and Agency of Natural Resources staff in a 2022 Hydraulics Study. The box culvert will be designed to meet all VTrans Hydraulics Manual standards for stream equilibrium and bank full width. This project is intended to improve flood resiliency, prevent future wash outs of Slate Rock Road and reduce sedimentation of the Fall River, as well as improve aquatic organism passage. The existing boiler tube culvert (#762-05) is undersized and prone to failure. The culvert has regularly overtopped during high water events, most recently in July 2023, causing major wash outs that cut off all vehicle access for the approximately 30 households located on Slate Rock Road beyond the location of the existing structure. The new box culvert, designed to the standards of the VTrans Hydraulic Manual, will be capable of handling flows from increasingly frequently large stormwater events. This project is intended to limit future damage to Slate Rock Road, reduce sedimentation and protect water quality in the Fall River, currently rated by the Agency of Natural Resources as a B-1 Very Good waterway for aquatic biota and fisheries. Slate Rock Road is located off of US-5 approximately 1.5 miles north of the Massachusetts border and is a dead-end road with no outlet other than the State Highway. Plans to maintain access to Slate Rock during construction and any resulting right-of-way impacts must be included as part of the design, engineering and permitting process.
