Project Location: Town of Plymouth in Windsor County on Vermont Route 100 over Reservoir Brook. Culvert 115 is located approximately 1.4 miles south of the intersection of VT Route 100 and US Route 4 in Bridgewater, VT, at approximately mile marker 9.34.

Background: The Plymouth Culvert 115 project includes the replacement of the existing corrugated steel multi-plate pipe culvert. The existing culvert was installed in 1971, and is 80 feet in length. The structure has a clear span of 8 feet, providing a waterway area of approximately 64 square feet. The structure currently has a rating of 4, “poor”, with deterioration in the form of large perforations throughout the entire length of the structure. It was also determined that the structure does not meet hydraulic standards.

Engineering Study: VTrans evaluated alternatives for the rehabilitation or replacement of the culvert in an engineering study completed in March, 2017. This study assessed the proposed design criteria for the structure, right-of-way, rare/threatened/endangered species impacts, hydraulics, archeological resources, and wetland impacts. Several alternatives were considered, including: no action, rehabilitation, and replacement with a bridge or buried structure. Complete replacement alternatives were considered for different traffic maintenance options: short term road closure with detour, temporary bridge, or phased construction with traffic maintained.

Recommendation: Based on the age of the structure, site constraints, and current conditions, the engineering study recommended replacement of the culvert with an open bottom buried structure: concrete arch or combination structure of metal arch with concrete pedestals. It is suggested that traffic be maintained on an official signed detour. Closure duration will be approximately 3 weeks, during which time the detour will add 7.2 miles to the thru route. There is no local bypass route. Update: Project will be contracted with Bridge 114 with a 28 day closure period to include both bridges.

Roadway: The existing roadway meets most of the geometric provisions of the Vermont State Standards. The only known roadway deficiency in the project area is the lane and shoulder widths for the approach and bridge lanes. This is not a high crash location, therefore no changes to the approach lanes are proposed. However, the replacement will include building out the lane and shoulder widths over the structure, to accommodate any future increase of approach roadway width.