Abstract: Session D 3:55 pm (Back to Session D)
Hoosier Dam Removal Project: Sediment Management Before, During, and After Removal
Angela Allen, PE
Wildlands Engineering, Inc.
Co-Authors: Aaron Collins, Schnabel Engineering
Angela Allen and John Hutton, Wildlands Engineering
Unique Places, LLC
The Hoosier Dam is a 94-year-old hydroelectric dam located on the Rocky River 5 ½ miles upstream of its confluence with the Deep River in Chatham County, North Carolina. The dam removal is part of a National Fish and Wildlife Foundation grant to restore the Rocky River from its currently impounded state back to a lotic state. The dam and associated impoundment significantly disconnect two critical habitat areas for the federally listed endangered Cape Fear shiner. The disconnection has blocked the aquatic species from dispersing freely and exchanging genetic material with neighboring populations, and as a result, USFWS has documented declines in the shiner population upstream of the dam. The removal of the Hoosier dam opens over 3.4 miles of habitat between these two critical habitat areas and meets the habitat recovery goals outlined for the Cape Fear shiner. The project is also beneficial to several mussel species of concern that have been identified in the trailrace of the dam.
With endangered species and species of concern located within the project area, coordination with the USACE, NCDEQ, USFWS, and WRC was critical through every stage of this project. The presence and treatment of sediment wedged behind the 25-foot-tall, 235-foot long dam was the largest variable within the project, and the most concerning item for all agencies involved. The creation of a sediment management plan included a bathymetric survey of the wedge, a Tier 1 evaluation for potential contamination, the dewatering of the impoundment to access the wedge, and the mechanical sampling of the sediment to determine sediment texture. Once this data was gathered, a biological assessment was performed for the USFWS that included a sediment management plan for removal. The management plan included a series of protocols set in place to protect sensitive mussel populations as well as the Cape Fear shiner. After much agency deliberation, the dam was removed in September 2018 allowing sediment to pulse through the system without mechanical removal while TSS was constantly monitored.