Casco Bay Estuary Partnership
Central Interior and Midcoast
Total Cost of Project:
Culvert replacement tidal flow enhancement
In this project, the Casco Bay Estaury Partnership (CBEP) replaced an undersized, failing concrete box culvert/bridge with a correctly sized structure where Wallace Shore Road crosses a small tidal creek. The failing concrete structure had partially collapsed, forming a series of steps/perches which restricted tidal flow in and out of the adjacent 13.5 acre estuarine tidal wetland, and impounded water upstream of the structure. Surface water hydrology monitoring (CBEP 2013) illustrated that the road created a severe restriction to tidal exchange between the New Meadows River and the wetland as evidenced by reduced tidal range, height, and inundation upstream, the effects of which were amplified during spring tides, and impoundment at low tide. Vegetation around perimeter of the wetland, which is predominantly salt marsh, appeared to have shifted, as indicated by the presence of freshwater scrub/shrub and Typha spp. in low-lying areas. Removing the restriction relieved the impoundment of water, enhanced wetland resiliency, and improved exchange of tidal water, freshwater, aquatic organisms, and sediments beneath the road, restoring natural function of the estuarine wetland.