This project was involves replacing the US-231 railroad bridge over the CSX Railroad at the Northern Bypass in the city of Montgomery. US-231 has an average daily traffic of 34,300 vehicles per day presently and is anticipated to grow to 74,338 vehicles per day in 2022. The existing roadway is a four lane divide highway with two narrow 28’ wide bridges over the CSX Railroad. The substandard vertical clearance over the railroad was only 20’ which restricted loads on that portion of the railroad. The challenge for this project was to raise the vertical grade to provide a minimum 23’ of vertical clearance and maintain two lanes of traffic in each direction during construction.
The approach was to build the two bridges on the outside of the northbound and southbound lanes at the new grade elevation, 2.5’ higher than the existing grade, while maintaining traffic in the middle on the existing lanes. This was accomplished by using concrete safety barrier not only to protect the construction crews from the traffic but also as a retaining wall. As the roadway fill was being raise to the final elevation the barrier was used to hold the roadway fill in place and not encroach on the existing roadway. Temporary inlets for drainage had to be installed on the edge of the existing roadway to prevent water from ponding next to the barrier and creating an unsafe travel area during rainfall events.
Once the roadway and bridge were completed on the outside the traffic was shifted to the outside and the existing bridges were removed and the roadway fill was brought up to final grade and the bridges were complete. The final product was a six lane bridge with barrier which provided over 23’ of clearance over the CSX Railroad and increase capacity on this section US-231.