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Great Sauk State/Walking Iron Trail – Bridge Feasibility Study Sauk and Dane Counties


Background Information Study Area, Existing Site and Project Criteria


Bridge Location

Dane County

Sauk County


Existing Site


Existing Site


Criteria

• Trail Bridge foundation design must meet AREMA standards and be “convertible” in the future for potential RR use • A H&H study is part of the scope to determine any floodplain impacts for the proposed trail and future RR bridge • Trail Bridge must exist within current corridor and allow future RR bridge to remain on alignment


Criteria

• Multi-modal use bridge (AASHTO and/or WisDOT standards) • Bike/ped/snowmobile • ADA compliance • Viewing platforms and fishing opportunities • Safety

• Recognize past railroad history


Public Input and Historical Context Study Area, Existing Site and Project Criteria


Summary of Leading Public Input

• What comes to mind when you hear of the “Driftless Region” • Topography, slower moving, small communities, agriculture • If built, what would the Wisconsin Recreation Bridge mean to you? • Safely getting across WI River, new viewpoints of river, access to more trails, more recreation options • Is the bridge part of the journey or is it the destination? • Part of the journey


Summary of Leading Public Input Which design do you prefer, traditional or modern? (1083 votes)

Traditional 67%

Modern 33%

• Safe, functional, and aesthetically pleasing. Not over the top • Safety and durability a top priority


Summary of Leading Public Input

What are your thoughts on building materials (315 votes)?

Timber 41%

Metal 59%


Summary of Leading Public Input

If the bridge is built, what type of lighting would you prefer? (588 votes)

Simple 76%

Multicolored 24%

*135 comments mostly related to “No Lights�


Public Input Meetings and Stakeholder Review Meetings

• Public Input Meetings (Sauk and Dane County) • 2 public input meetings were held • Bridge concept, aesthetics, and amenities were generally well received • Stakeholder Work Group Review Meetings • Bridge concept, aesthetics, and amenities were presented to the Stakeholder Work Group and were generally well received • Concept presented to Rail Commission with no objections.


Historic Context


Original Railroad Bridge – Historic Context


Original Railroad Bridge – Historic Context


Historic Context


Summary of Feasibility Study


Design Considerations


Design Considerations

• Substructure = AREMA Standards/Cooper E-80 Loading • Design for future potential conversion to rail • Ice loading/ice impact

• Superstructure = 13 ton load rating. AASHTO LRFD and WisDOT Bridge Manual guidelines • Snowmobile groomer, small maintenance vehicles, pedestrians

• Multi-use trail guidelines per AASHTO – Guide for The Development of Bicycle Facilities and the WisDOT Wisconsin Bicycle Facility Design Handbook.

• Fishing and Viewing Platforms/Aesthetic value


Existing Structure


Existing Structure

• Existing remaining pier, abutment, and span will need to be removed • Pier footing is proposed to be salvaged to provide bank stability, and fishing/mooring opportunities


Abutment and Pier Options


Abutment and Pier Options

• Span is approximately 500-feet • Typical maximum span for prefab pedestrian bridge is approx. 200-feet. Typical maximum span for TPG RR bridge is approx. 180-feet • Proposed design is a 3-span structure with spans of 165-feet to accommodate both pedestrian and future RR use • This requires 2 piers and 2 abutments • Abutments are designed for pedestrian use but piling can be salvaged for future RR use.


Abutment and Pier Options

• Proposed alignment is 10.5-feet “off-alignment” to accommodate future rail conversion • Piers are proposed as drilled shafts with steel casings • Piers will need to be socketed into bedrock • Drilled shaft piers are designed to withstand rail loadings, future scour, ice loading and river velocities and are the most feasible construction method • Fishing platforms are provided at each pier (4 total platforms) • Pier caps will support the superstructure. Pier caps will require demolition for future rail use.


Abutment and Pier Options


Abutment and Pier Options


Abutment and Pier Options


Abutment and Pier Options


Superstructure Options


Superstructure Options

• Prestressed girder and prefabricated bowstring options were initially considered but were not favorable to the stakeholder group or supported by subsequent public input • A prefabricated Warren Truss is proposed to provide a more historical railroad context and is supported by stakeholder and public input. 14-foot wide, 12 to 16foot tall, concrete deck • Middle span is taller to provide visual interest • Viewing platforms proposed at mid-span (6 total platforms) • Fishing platforms at each pier


Superstructure Options


Superstructure Options


Renderings


New Bridge – View 1


New Bridge – View 2


New Bridge – View 3


Pier Lookout


Mid-Span Lookout


Gateway


H&H and Scour Analysis


H&H and Scour

• Proposed bridge does not impact the floodplain/floodway • 100-yr event floodplain elevation • Project is permittable

• Potential scour is calculated per the 200-yr event • Potential scour is approximately 26.4-feet in the channel near piers • No substaintial scour anticipated at abutments, but banks should be armored • Pier design anticipates the max. scour


Permitting and Constructability


Permitting and Constructability

• Project is permittable, but will require extensive agency coordination • WisDNR, USACE, USFW, USCG

• Pier and abutment construction process • Access will be necessary from the east and west • Access through campground is necessary

• Road closures on Water Street • Staging area is required • Water levels and river velocities


Schedule and Sequence of Operations


Schedule

• Project is constructable within one construction season • No river access March 15th through June 15th

• If access work, demolition, and abutment work can be expedited there is potential for 4 to 6 weeks of schedule compression • Desired to avoid late season concrete deck pour


Schedule


Sequence of Operations • Build temporary access road on the west side of the Wisconsin River to install the temporary dock wall. • Use a barge to assist in placing equipment for the demolition of the existing west span and west abutment. The barge will help minimize the amount of debris from the demolition of the concrete abutment and pier column from reaching the river. • Construct the new west abutment. • Install the drilled shafts at pier 1 and pier 2 locations. • Set reinforcement within the drilled shaft casing and then pour concrete. • Form the top portion of the pier and place reinforcement in the formwork. • Pour concrete for the pier caps. • The east abutment can be completed at any time once the contractor is able to get access to the east abutment location. • Place riprap at abutments.


Sequence of Operations

• Trusses are delivered and assembled on site. • Float the trusses in on barges where available and make mid-air splices for the outside pieces of spans 1 and 3. • Anchor trusses to substructure. • Form and place reinforcement for the deck. • Pour concrete for the deck. • Miscellaneous bridge accessories such as railings can be installed at the pier lookouts and abutments. • Remove all the temporary access roads and dock wall. • Restoration of disturbed areas and clean-up of the project


Estimated Costs


Estimated Costs

• Bridge Construction = approximately $6.7 million • Aquatic Geotechnical Investigation = $140,000 • Final Design, Permitting, Construction Services = $1 million • ESTIMATED TOTAL PROJECT COST = $7.84 million


Estimated Costs – Potential Reductions • All Spans/Truss at 12-foot tall= ($45,000) • Remove mid-span lookouts= ($120,000) • Timber vs Concrete Decking= ($210,000) • Remove concrete staining and architectural surface treatments at piers and abutments = ($70,000) • Reduce Bridge Width to 12-ft = ($90,000) • Total = ($535,000)

• Estimated Cost Range = $7.3 - $7.84 million


Estimated 20 yr O&M Costs

• Bridge Inspections = $10,000 • Epoxy Deck Coating Replacement = $40,000 • Additional Recommended Contingency = $25,000



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