It is anticipated that the Spalding Drive overpass will be lengthened and relocated south of the existing overpass to allow enough space for the SR 400 Express Lanes to pass underneath the bridge. The existing two-through lane bridge would be replaced with a two-through lane bridge. The SR 400 Express Lanes project would not be adding access, capacity, or additional lanes to the Spalding Drive Bridge. As Spalding Drive is a local road, requests for additional project(s) to relieve traffic congestion have been forwarded to the City of Sandy Springs for their review.
Current traffic data are being used in close coordination with the City of Roswell and a review of its previous local studies to best design the Holcomb Bridge Road Interchange.
In an effort to seek public input on potential construction alternatives at the five PIOHs, the public was presented with and asked to indicate a preference between two options for how to rebuild the Pitts Road Bridge.
· The first option was to rebuild the bridge in place, which would require a detour.
· The second option includes building the new bridge alongside the existing bridge allowing the bridge to remain open during construction but would require additional right-of-way, including displacing residences.
There are many factors, one of which is public input, which will help in the final decision on how to rebuild the Pitts Road Bridge. The project team will work with the City of Sandy Springs to determine if there is a viable detour available for Pitts Road. Detour route viability will be determined with consideration of impacts to schools, first responders, and mobility. It is anticipated that feedback on public detour will take place during the Public Hearing Open House.
GDOT will coordinate the bridge construction schedule to reduce traffic impacts where feasible. Before bridge reconstruction begins, GDOT will work with the local municipalities to identify viable detours, if needed, which will consider and assess impacts to schools, first responders, and mobility.
While we know that elevated portions of the express lanes will be required, we are currently developing preliminary plans that will be finalized by the successful bidder/Developer. The project’s goal is to first avoid, and second minimize/mitigate, any right-of-way impacts, including evaluation of potential solutions such as elevated lanes. One of the benefits of elevated lanes includes a minimized project footprint, however, this needs to be balanced with costs and visual impacts as well as engineering constraints. Final design plans, including final elevations, are anticipated to be completed in 2024 and will meet the required design height standards.
Elevating the express lanes when they could otherwise be at-grade is cost prohibitive. The effort of this project is to incorporate express lanes as cost effective as possible. There are areas that require GDOT to elevate lanes due to the complexities of the system.
For the SR 400 Express Lanes project, elevated lanes are necessary but limited to select locations including access points and to bring the express lanes from the outside of the general purpose lanes to the inside of the general purpose lanes. As part of our alternatives analysis, the amount of required elevated lanes has been reduced. As part of the design process, the project team is reviewing the corridor to assess where elevated lanes are needed and in an attempt to minimize the number of locations.
As more lanes are added to SR 400 via the SR 400 Express Lanes project, additional stormwater runoff will occur along the corridor. Detention ponds are essential to reducing the risk of flooding on neighboring properties. The roadway’s drainage design will be brought to current standards, where possible, as part of the overall design process and conform to best management practices. The project corridor falls within a Municipal Separate Storm Sewer System (MS4) Permitted area which consists of a system of conveyances owned by the state or local municipalities that discharges to waters of the U.S. Therefore, this project is subject to the requirements of the MS4 Permit. The stipulations to comply with this permit will require treatment of the runoff and protection of area surface waters and water quality. To address drainage concerns, design features in this project include, but are not limited to: detention basins, curb inlets and pipes (e.g., a closed drainage system), and ditches along the corridor where feasible to convey stormwater away from the roadway.
The detention ponds are stormwater management systems that will be used to both remove some of the pollutants in the roadway runoff (improve water quality) during a storm as well as to prevent downstream flooding. They are not intended to be permanently wet but rather to detain the water and allow it to trickle out at a slow rate at or near the pre-widened roadway rate so as not to flood downstream. It is intended for these ponds to release all the water within 48 hours of most rain events and not to serve as permanently wet ponds. Stormwater retention ponds will include fencing to discourage unauthorized access to GDOT right-of-way.
The detention ponds are being designed by registered design professionals in accordance with GDOT policies and standards. All stream alignments will be designed to safely convey water back to the existing riverbed. As part of the installation of these basins, routine maintenance will be conducted. Being dry between rain events greatly reduces the attractiveness to nuisance species.
There are a number of local bike, pedestrian, and complete streets interests, plans, and projects near the SR 400 Express Lanes corridor. Bike, pedestrian, and complete streets facilities are not within the confines of the SR 400 Express Lanes project scope; however, GDOT will coordinate with local governments to determine if they wish to provide funding to advance portions of the bike, pedestrian, and complete streets facilities into this project. It is GDOT’s intent to replace existing overpasses in kind and in a manner that doesn’t preclude other pedestrian, cycling, and complete streets local projects. The SR 400 Express Lanes project is a managed lanes project and complete streets policies do not apply to managed lanes projects.
GDOT is closely coordinating the two projects to maintain seamless transition between the two projects; however, the exact project tie-in/transition points are still being determined. The SR 400 Express Lanes project would open to traffic prior to the construction completion of the I-285 Top End Express Lanes project. Before the I-285 Express Lanes open to traffic, the southbound SR 400 Express Lanes would provide a connection to the MARTA North Springs Station and back to southbound general purpose lanes to access I-285. Traveling northbound, motorists (personal vehicles and buses) from the MARTA North Springs Station are proposed to have a direct connection to the express lanes. There would also be an at-grade direct merge/slip ramp to allow traffic coming from downtown via SR 400 or I-285 to access the express lanes.
Once the I-285 Top End Express Lanes project is open to traffic, these access points will remain in use, but motorists will have the additional option of remaining in the express lanes southbound on SR 400 and continuing onto the I-285 Top End Express Lanes.