When the original Elmhirst Parkway structure over a tributary of Rock Creek was deteriorating, weight restricted, and deemed insufficient, a new stream crossing was needed. It was imperative that the new structure be aesthetically pleasing, while also minimizing construction and stream dewatering times. Furthermore, Montgomery County also wanted a structure that was easy to maintain.
“Elmhirst Parkway bridge was originally constructed in 1940 and is located in the Locust Hills subdivision in Bethesda, Maryland,” stated Bill Sittinger, Construction Manager with Montgomery County Department of Transportation (MCDOT). “Research found that a precast concrete segmental style span system would provide the dynamics of the existing bridge and would give the bridge the unlimited weight restriction that we were looking for.”
As the best solution, a 16' x 5' CON/SPAN® B-Series® Bridge System, 69.75' in length, was selected because it was aesthetically pleasing and a complete system, including precast superstructure, precast EXPRESS® Foundations, headwalls, and wingwalls. All of the components were installed via crane in just four days.
“Having the elements precast reduced the timeline for construction, saved on labor costs, and provided a cleaner and safer way to construct the infrastructure,” added Sittinger.
The biggest design/construction challenge with this project was that due to County and State scour design requirements, the bottom of the foundations needed to be set approximately 11 feet below the stream bed elevation. In addition, the MDOT and County wanted to utilize precast as much as possible to minimize roadway closure time. In order to meet both requirements, Contech Engineered Solutions also provided an EXPRESS Foundation system that included footings and 10’ tall precast concrete pedestal walls.
“In completion, the wall facing was designed to have a stone finish look much like the existing bridge,” concluded Sittinger. “MCDOT worked in conjunction with Maryland National Capital Park and Planning Commission to complete this project. This project was completed on time and under budget and should be around for many years to follow.”