Carolina TEA led a bridge replacement design team for the Richland County Conservation Commission in the middle of a wetland mitigation bank.

The site abuts the Congaree National Park and is routinely susceptible to flooding. The existing bridge at the site was noted to overtop often and had been damaged by previous floodwaters – including lifting and relocating the entire bridge deck.

Setting the bridge at an elevation above the 100-yr flood was not practical and would have created significant grade issues on the roadway as well as significant wetland impacts. Carolina TEA used a 25 yr design highwater for setting the bridge, but also grouted all bents and bearings to not allow the bridge to “float”.

The replacement bridge will be a single lane, single span cored slab bridge. The roadway approaches were designed as low speed driveways to minimize the wetland impacts at the site. 30 mph vertical curves were checked with the bridge profile to ensure future roadway improvements can be facilitated.

The project was required to be completed in 24 months including survey, hydraulic modelling, bridge and roadway design. The actual completion was 12 months ahead of schedule.