Project Specifics

A low-head dam, originally constructed in the 1800’s, was scheduled for removal in order to increase free movement of aquatic organisms.

Geosyntec Scope of Services

Pre-existing data included available hydrology and hydraulic models and data from the owner, Federal Emergency Management Agency (FEMA), United States Army Corps of Engineers (USACE), National Oceanic and Atmospheric Administration (NOAA), United States Geological Survey (USGS), and the area’s county, as well as proposed conditions outlined in the owner removal drawings.

To evaluate potential impacts of the dam removal on a bridge pier, Geosyntec conducted site visits to collect data, which was used in conjunction with pre-existing data to create a hydrology assessment; an impact analysis of existing versus proposed conditions (including pier and abutment scour analysis as well as velocity and water surface elevation comparison); and mitigation recommendations, including dam alteration alternatives and bridge pier armoring.

Our team developed a hydraulic model by selecting and simulating hydrologic scenarios to evaluate pier impacts, including the selection of creek and river reoccurrence interval coincidental flood events. Dam removal impacts were evaluated for both immediate and long-term removal conditions. Geosyntec also developed alternative pier scour protection measures and proposed alternative dam removal options.

Notable Accomplishments

In the face of challenges including limited hydrologic data of a creek and river reach near the area’s confluence and a tight time frame, Geosyntec successfully completed the development of the detailed hydraulic model that fitted the needs of the project. After completing a comprehensive analysis of the low-head dam removal impacts on the bridge, Geosyntec provided the owner with an affordable pier scour mitigation approach.

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