Abstract: Session E 3:10 pm (Back to Session E)
Urban Stream Mitigation: Negotiations, Bridges, Bugs and BMPs
Butterfly Branch flows through downtown Spartanburg, SC. Its restoration provides permittee-responsible mitigation to offset unavoidable stream impacts associated with the Spartanburg Downtown Memorial Airport’s runway expansion. Restoration activities included “daylighting” approximately 1,125 lf of closed drainage system and restoring an additional 710 lf of channel.
The project has improved bank stability, provided water quality improvements, and improved in-stream and riparian habitat. Because of unavoidable project constraints, the upstream-most reach includes an integrated series of cascade/pools. The downstream reaches utilize more traditional boulder and log grade control structures, natural meander patterns, and aquatic habitat enhancements.
The City of Spartanburg and the Northside Development Corporation are redeveloping this area of downtown. The Butterfly Branch Restoration Project is its centerpiece. Public trails, informational signage, and outdoor classrooms have been integrated into the restoration design. The pedestrian bridge traverses a triple A-vane in the restored stream. In addition to providing pedestrian connectivity, the bridge is an aesthetically pleasing centerpiece that illustrates the importance of water quality within the community.
As a result of extended permit negotiations with the US Army Corps of Engineers’ Charleston District, the project is required to document/demonstrate its functional uplift by meeting both numeric ambient water quality, as well as numeric benthic macroinvertebrate performance metrics during its five-year monitoring period. The Butterfly Branch site is the first mitigation project in the Southeast to be held to such standards. In order to fulfil this requirement, an innovative habitat enhancement and reference reach benthic relocation effort has begun to be implemented. Year 1 monitoring results indicate that a diverse range of benthic taxa have begun to colonize the site.
The project received a 2019 ACECNC Engineering Excellence Grand Award.