During times of heavy rain, the intersection of Ebinport Road and Northgate Lane in Rock Hill, S.C., would cause yard flooding and property damage to five residences. A box culvert was installed under the intersection in 2007, but the yards continued to be damaged. After an analysis, it was found that the culvert was undersized, which was resulting in roadway overtopping.
A project was implemented to limit overtopping of the existing creek banks to assist with flood mitigation and minimize property damage. The team decided to go with a large, regional impoundment area to control flows to a newly constructed dam and culvert with the advantages of additional flood control for a majority of the 70-acre watershed the intersection drained into, which also established a natural floodplain and wetland area.
After the easement acquisition and Phase 1 environmental assessment were completed, construction began with the installment of sediment and erosion control BMPs. Once the dam was completed, the site was fine-graded, seeded and strawed or matted for stabilization purposes.
At first, the culvert opening was determined to be larger than the design intended, the excavated areas were not as deep as required and several trees that had been planted within the existing sewer easement needed to be shifted. After the models were re-run, a steel plate was designed for the front of the culvert to restrict flow and velocity downstream.