WWTP Access Drive Bridge Replacement

Project Overview

NTH was retained by the City of Ann Arbor for the evaluation and design of a new bridge to provide access over the Huron River to the City’s Wastewater Treatment Facilities Plant. The current access structure is a two-span, reinforced concrete deck on rolled steel beams bridge, built in 1935 to provide access to the City’s Treatment Facilities Plant. The current bridge is well past its designed life span and is functionally obsolete (it is too narrow to safely provide two-way traffic on the bridge).

As part of our initial evaluation, NTH was tasked with evaluating two schemes for addressing the goal of providing safe, efficient two-way traffic access to the existing treatment plant. One scheme involved designing a new two-lane bridge to convey all traffic in and out of the facility and allow the existing bridge to be closed to vehicular traffic. The second scheme is to design a new, one-lane bridge to work in combination with the existing bridge (which will be utilized as a 1-lane bridge).

Project Scope

We performed a visual inspection of the existing bridge to determine what repairs might be needed for use in the scheme where it is retained in service for one-way vehicular traffic.

Construction of the new bridge will require a new easement for the shifted alignment and bridge’s location. Finally, as part of the design, environmental considerations for 100-year floodplain and wetlands within the new footprint are also part of the contract.

Client Benefit

NTH’s ability to design a foundation that would not penetrate the pressurized aquifer saved the client extra expenses for relief of the ground water that would be continuously rising through any foundation that would penetrate this layer (such as driven piling) and could undermine the stability of the bridge’s foundations over its designed life span.