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Fish Ladder and Dam Improvements and Repairs

Relocated Route 403
East Greenwich and North Kingstown, Rhode Island
Owner: Rhode Island Department of Transportation

The Relocated Route 403 project is located within a very sensitive wetland and water resources area which includes the Hunt River, Frenchtown Brook and Fry Brook, as well as the Hunt-Annaquatucket-Pettaquamscutt (HAP) sole source aquifer. The development of a viable transportation solution for this corridor required a delicate balance between transportation needs and environmental protection. As part of the environmental mitigation for wetland impacts, GRA designed fish ladders and fish ladder improvements at locations within the project vicinity.

GRA designed improvements at the Forge Road Dam (right) on the Hunt River in North Kingstown, Rhode Island. The improvements consisted of removal of rock and cobbles in the tidal zone below the Forge Road fishway to create a defined, unobstructed channel to the base of the fishway, and the construction of a downstream passage chute at the top of the dam to help prevent juvenile fish mortality.

GRA designed improvements at Potowomut Dam (below) on Potowomut Pond and the Hunt River in North Kingstown, Rhode Island. The improvements consisted of a downstream passage chute at the top of the dam to help prevent juvenile fish mortality, and modifications to the existing fish ladder to accommodate a 14-inch water surface elevation change resulting from the installation of new and additional weir boards at the Potowomut Dam. GRA's design consisted of installing filler pieces within each baffle to adjust the fishway slope, thereby eliminating a hydraulic jump at the fishway exit. The filler sections steepened the hydraulic gradient of the fishway, but provided a constant and continuous hydraulic gradient from the fishway entrance, Hunt River, to the exit, Potowomut Pond.

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