VHB partnered with the Town of Penobscot and Maine Coast Heritage Trust to design a resilient, safer crossing on Route 175 at Mill Creek—an area prone to coastal flooding and constrained by an aging granite culvert. Fully funded through state and federal grants, the project improves roadway reliability for residents while protecting the stream and adjacent marsh system that supports prime alewife spawning habitat.
The design raises the roadway profile to reduce overtopping and flood-related closures, and replaces the compromised culvert with a larger concrete structure that improves hydraulic capacity and enhances fish passage. To support long-term ecological function, the crossing is designed to better align with natural stream processes and to promote restoration of the upstream salt marsh.
VHB used tidal monitoring and hydraulic modeling to evaluate site conditions and develop the roadway elevation and culvert replacement design in accordance with HEC-25 coastal highway design guidance, U.S. Fish and Wildlife Service aquatic organism passage (AOP) stream simulation guidance, and Maine Department of Marine Resources CoastWise guidance. The project also incorporates roadway safety improvements, a new parking area, and a pedestrian trail with stream access.
VHB designed the culvert alignment and construction sequencing to maintain tidal conditions and protect sensitive resources during installation. A scientific monitoring program—supported as part of the grant funding—will track performance during construction and provides Maine Maritime Academy students with hands-on experience in coastal resilience field work. Construction on the project began in April 2026.
