The Walk Bridge Program will be developed and constructed in phases to maintain rail service and reduce impacts to the public.
The Conceptual Design developed and considered a broad range of alternatives to identify the most feasible design options for further evaluation. Initially, 69 bridge replacement options were identified and screened to identify five that best met the Program goals. The screening considered aesthetics relating to the surrounding environment and historic image of the bridge, navigational clearances, and resiliency to withstand extreme weather and storm surges, and constructability.
At this time, three alternatives have been advanced for further evaluation. These alternatives are:
- 170' Rolling Bascule Bridge — a pair of 170-foot rolling bascule trusses carrying four tracks total. Span opens at a 50degree angle with a height range of 70ft (closed) to 140 ft (open). Vertical clearance ranges from 27ft (closed) to 60 ft (open). Horizontal clearance of 120 ft.
- 170' Vertical Lift Span — a pair of 170-foot vertical lift spans carriying four tracks total. Tower height ranges from 105 ft to 140 ft. Vertical clearance ranges from 27ft (closed) to 60 ft (open). Horizontal clearance of 120 ft.
- 240' Vertical Lift Span — a pair of 240-foot vertical lift spans carriying four tracks total. Tower height ranges from 105 ft to 140 ft. Vertical clearance ranges from 27ft (closed) to 60 ft (open). Horizontal clearance of 200 ft.
All three alternatives require new retaining walls and a west approach rebuild.
The Environmental Assessment/Section 4(f) Evaluation/Environmental Impact Evaluation (EA/EIE) identifies a preferred alternative: the 240' Vertical Lift Bridge. The selection of a Long Span Vertical Lift Bridge as the preferred alternative was based on a comparison of factors such as construction duration, risk, navigation and local road impacts, environmental footprint, long-term performance, aesthetic flexibility and cost as they relate to the project’s Purpose and Need Statement. The Long Span Vertical Lift Bridge is the only alternative with both foundations proposed outside of the existing swing span limits, allowing the existing bridge to remain operational longer during construction and requiring a shorter rail track outage.
The environmental review for the Walk Bridge is being conducted in accordance with the requirements of the National Environmental Policy Act (NEPA) and the Connecticut Environmental Policy Act (CEPA). Under this joint NEPA/CEPA process, a combined Environmental Assessment/Environmental Impact Evaluation (EA/EIE) will be prepared. The goal of the environmental review is to promote informed decision-making by considering a range of reasonable alternatives and the analysis leading to selection of the preferred alternative. In addition, separate environmental reviews will be completed for the CP243 and the Dockyard projects. Since these projects are not expected to have a significant effect on the environment, Categorical Exclusions will be prepared.
Purpose and Need
The Purpose and Need Statement, one of the first steps completed in the environmental review, identifies the reasons for the Program and establishes the objectives the Program is intended to address. The Purpose and Need Statement is part of the EA/EIE and is considered in evaluating the alternatives.
The Purpose for the Walk Bridge Program is "to restore or replace the existing deteriorated bridge with a resilient bridge structure which will enhance the safety and reliability of rail service, offer operational flexibility and ease of maintenance, and provide for increased capacity and efficiencies of rail transportation along the New Haven Line/Northeast Corridor, while maintaining or improving navigational capacity and dependability for marine traffic in the Norwalk River."
The Need for the Program focuses on the age and deteriorating condition of the existing structure, its decreasing reliability, lack of resiliency, inconsistency with current safety standards, lack of redundancy, limited operational flexibility, difficulty of maintenance, reduced rail capacity and efficiency, reduced dependability and capacity for marine traffic, and lack of sustainability. In addition, the Need for the Program is also based on its importance to the local and regional economy as a vital link in the NEC rail corridor, and to environmental quality, by providing an alternative to travel on congested Interstate I-95 which serves the same corridor as the NEC.
During the environmental review, alternatives are developed and screened, and the most viable alternatives are advanced for further evaluation. Existing conditions of environmental resources and the potential impacts and benefits of the alternatives on these resources are documented as well as measures to avoid, minimize, or mitigate impacts.
A Section 4(f) assessment, under the U.S. Department of Transportation Act of 1966, is also being prepared to assess potential impacts to public parks, recreation areas, wildlife refuges and historic sites. Under Section 4(f), use of these resources for transportation projects can be approved only if there is no prudent or feasible alternative and if measures are taken to minimize harm to the Section 4(f) resource.
The Walk Bridge is listed on the National and State Registers of Historic Places and is subject to Section 106 of the National Historic Preservation Act. A preliminary historic assessment was conducted as part of the Section 106 Process to identify the Area of Potential Effect, or the area within which the Program may directly or indirectly affect historic properties. A design charrette was held in August 2015 to identify potential impacts and mitigation for historic resources, and a second charrette was held in February 2016.
The EA/EIE will identify a preferred alternative. When the EA/EIE is complete, a 45-day public comment period will be held in late 2016 during which the public will be invited to review and comment on the EA/EIE. A public hearing held during the public comment period will include a presentation on the EA/EIE and opportunity for public comment.
Construction Manager/General Contractor
CTDOT is utilizing the innovative Construction Manager/General Contractor (CM/GC) project delivery method for the Walk Bridge Program. With the CM/GC process, the contractor acts as Construction Manager during design and advises CTDOT on schedule, phasing, constructability, materials availability, risk, and cost. This integrated team approach of involving the Contractor early in the project adds value by reducing construction duration, reducing impacts, improving construction sequencing, and reducing risk.
The Walk Bridge Program also strives to use innovative Accelerated Bridge Construction (ABC) techniques to reduce the duration of construction and impacts to the public. One potential example of this approach would be to construct bridge components offsite and rapidly assemble them in place.
Construction of the complex Walk Bridge Program will be phased to allow rail service to continue throughout construction and to reduce impacts to the community. The schedule for construction is still preliminary since the project is in the Design phase.