ACTT Workshop: Rhode Island
Pawtucket Bridge No. 550 - Building a Foundation for the Future
Chapter 3: Skill Set Recommendations
The structures group recommended that the bridge be replaced instead of repaired: the advantages of higher capacity and lower long-term maintenance costs outweigh the higher initial cost and longer construction time associated with replacing the structure. The team's priority recommendations follow.
- Close the George Street/I-95 northbound on-ramp during construction. Consider permanent closure as well.
- Keep all three traffic lanes together in each direction. Avoid lane splitting.
- Detail longitudinal deck joints to accommodate deflection differentials between construction phases.
- Use multi-span continuous girders for the bridge framing.
- Three span (requiring the closure of Pleasant Street) - 140'/225'/140'.
- Three span (requiring re-alignment of Pleasant Street) - 230'/260'/150'.
- Four span (requiring re-alignment of Pleasant Street) - 100'/130'/260'/150'.
Construction Option 1 - Horizontal Skidding
- Eliminate the skewed west abutment at Pleasant Street. Pleasant Street should be re-aligned to accommodate this.
- Erect temporary jacking towers along both the north and south sides of the bridge.
- Construct a new three-lane superstructure to the south of the existing bridge on the temporary shoring towers.
- After diverting northbound traffic onto the newly constructed structure and southbound traffic onto the existing northbound section, demolish the existing southbound structure.
- After constructing the replacement southbound structure and moving traffic onto it, demolish the existing northbound structure.
- Close northbound I-95 for one evening and horizontally skid the previously constructed section into place.
Construction Option 2 - Longitudinal Launching
- Use construction staging similar to that used for the horizontal skidding option.
- Construct a launching pit at the east end of the bridge, and launch the new bridge beams from east to west.
The team noted that a major benefit to this option is that cranes would not be required for erecting the bridge. Cranes would still be needed to remove the existing structure.
Construction Option 3 - Conventional Construction
- Use staged construction methods similar to the first option.
- Use prefabricated substructures and slabs.
- Provide contractor incentives and disincentives to accelerate the construction schedule.
The team noted that viable crane locations are a concern.
Recommended Cost Reduction Options
- Shorten bridge length. The two eastern-most spans are located over vacant space and are unnecessary. This area could be filled, reducing the area of new bridge construction and future maintenance requirements.
- Eliminate the west abutment skew; all beams could be fabricated identically, maximizing economy and efficiency.
- Re-use as many of the original substructures as possible.
- Maximize girder spacing: this would require less steel and fewer bearings and connections.
- Utilize constant depth beams, and consider using high performance steel (hps) for the major bridge framing.
- Use high performance concrete (HPC) for the pier caps and deck.
- Consider integral abutments.
- Need to remove lead paint from the existing bridge.
- Need to keep construction out of the river: this would eliminate costly dewatering and the time-consuming permits necessary for this type of work.
- Minimize excavation and the potential for encountering contaminated soil.
- Eliminate, or least minimize, deck drains.
- Build off-line.
- Consider night and weekend work.
- Close the roadway on the weekend.
Of the three options presented, the structures group preferred horizontal skidding to the others. This option provides the most construction time outside the traffic stream and, therefore, the least adverse impacts to traffic.
Citing the same reasons as the structures group, the construction skill set recommended that the bridge be replaced rather than repaired.
- Shorten bridge length.
- Investigate closing the northbound or southbound direction for three months to perform a "hyperfix" and open the roadway to traffic much sooner.
- Consider beam launching to minimize crane usage.
- Upgrade secondary roadways so School Street traffic could be detoured.
- If School Street traffic is maintained, five construction phases will be necessary.
- If School Street is closed, the work can be completed much more quickly.
- Utilize A-plus-b bidding to solicit the best contract package, i.e., the lowest price and the shortest construction timeframe.
Construction Option 1 - Conventional Construction
- Use smaller cranes and shorter beam lengths.
- Use existing piers for temporary support.
Construction Option 2 - Horizontal Skidding
- Use a modified version of the method developed by the structures group.
- Construct the new bridge in three phases:
- Build the northbound structure off-line south of the current structure.
- Shift the northbound traffic to the new superstructure, and demolish the northbound section.
- Move the northbound section into place and build another section off-line.
Phased Construction Alternatives
- Consider the following phasing plan:
- Phase 1 - traffic improvements.
- Phase 2 - substructure contract (acting concurrently with phase one).
- Phase 3 - superstructure replacement contract.
- Close George Street/I-95 northbound on-ramp.
- Change Division Street to one-way traffic (eastbound).
- Contract local roadway improvements concurrently with advanced substructure work: interstate traffic would not be affected.
- Limit work to outside of the flood plain.
- Address difficult access from the north.
- Devise scenarios where working in the river is permissible.
Like the structures group, the construction team preferred the horizontal skidding approach, as this method minimizes crane usage. Due to space and right-of-way constraints, the team felt that southbound traffic should not be shifted outward (north of the bridge). They stated that traffic improvements to local roadways, the use of Intelligent Transportation Systems (ITS) and other detour methods would reduce construction time and lane closures.
Like the first two groups, the geotechnical/materials group recommended replacing versus repairing the bridge. Based on the information available, the group found no abnormal soil conditions that would require extensive foundation design. As a result, the team felt that, with micropile retrofitting, the existing foundations could possibly be re-used. They also noted that mechanically stabilized earth (MSE) retaining walls would allow for unlimited aesthetic treatments.
- Evaluate foundation types depending on loading condition:
- Consider spread footings on rock.
- Consider spread footings on MSE.
- Use micropiles - they have low headroom requirements and would allow access to difficult areas.
- Use drilled shafts. (There may be issues with boulders and other obstructions.)
- Use mse wall structures.
- Consider the impacts of fill on existing structures:
- EPS geofoam.
- Lightweight foamed concrete.
- Shredded tires.
- Numerous facing treatments.
- Consider fill placement under existing structure - use flowable fill for final lift in tight areas.
Material Issues: Re-Use of Existing Piers
- Determine viability of removing concrete deck and reusing existing piers.
- Evaluate condition/deterioration of the existing steel beams.
- Determine the extent of lead paint on the steel beams.
- Determine foundation capacity needs.
- Restore the concrete facing on the existing piers and abutments.
- Determine the condition of the underground footings before final design: their current condition is unknown.
- Determine the presence/absence of contaminated soils.
- Address traffic maintenance during construction: it is a large concern.
- Consider the equipment necessary to place large beams when locating access and staging areas.
- Utilize CSS.
- Determine the best suited contracting mechanism.
- Check material availability before final design.
- Make worker/public safety a priority.
Like the other groups, the geotechnical/materials group recommended structure replacement over repairing the existing bridge. They saw foundation re-use as a viable option but noted that the existing substructures must be evaluated in regards to their condition, structural capacity and retrofit/strengthening practicality. The team noted that utilities are not an issue on this project.
The traffic/safety/ITS/PR group focused on project needs and constraints in order to facilitate traffic flow and public information on the Pawtucket Bridge No. 550 project. They outlined a number of key issues in their list of recommendations and advocated a 24-hour construction workday.
Overarching Traffic Concerns
The team noted the following constraints on the project area:
- Maintaining three full-width traffic lanes in each direction.
- Maintaining School Street/I-95 northbound off-ramp traffic and access to the Pawtucket Memorial Hospital.
- Putting traffic on the historic Division Street Bridge.
- Rerouting traffic: local one-way street patterns complicate potential detour routes, and narrow local streets may not be able to accommodate large traffic volumes.
The team recommended using the following tools to mitigate traffic concerns:
- Movable traffic barriers.
- Management of acceptable traffic delays using Quick Zone.
- An incident detection system.
- Portable smart zones featuring cameras, signs and detectors on alternate routes.
- Better traffic signal coordination on local roads for detoured/rerouted traffic.
- Traffic law enforcement for speed control.
- Off-peak rolling road closures.
- Lane rentals.
- Contractor incentives/disincentives.
- Consider closure of both the George Street/I-95 northbound on-ramp and the School Street/I-95 northbound off-ramp, permanently if possible. This would eliminate conflicts between merging and exiting traffic and reduce the number of crashes on the bridge.
- Improve local streets to handle traffic loads.
An effective public relations campaign is necessary to keep motorists informed of construction activities.
Intelligent Transportation Systems (ITS)
- Provide real time traffic information.
- Expand the existing network.
- Provide additional coverage for Division Street.
- Utilize Smart Zone.
- Use Highway Advisory Radio (HAR) to broadcast current information.
- Use the 511 National traveler information system.
- Use message signs to display travel time.
- Portable message signs and dynamic message signs (DMS): northbound, southbound, on I-295 in Massachusetts.
- Advanced trailblazer signs for Pawtucket Memorial Hospital.
- Conduct bi-weekly incident management meetings.
- Provide around-the-clock tow trucks in the work zone.
- Maintain records of pre-accident data, a history of the work area and construction monitoring.
- Use highway cameras.
- Monitor work zone safety.
- Promote alternate routes.
- Define the target audience:
- Traveling public.
- Local businesses.
- Residents in the project area.
- Civic and community leaders.
- Elected officials.
- Keep the lines of communication open. Establish a point of contact person.
- Provide information on the ridot web site.
- Consider proposals for a public awareness program.
- Use television and radio traffic reports.
- Encourage flexible work schedules and working at home for commuters.
- Take advantage of public transportation; increase bus routes.
- Work with interested parties.
- Get the public involved with naming the bridge.
- Celebrate meeting project milestones.
- Keep the public informed!
The team noted the following barriers to implementation:
- Public acceptance of the project and its inconveniences.
- Traffic congestion and disruption to commuters.
- Availability of alternate routes.
- Local residents' concerns.
- Truck traffic.
- Road conditions - future resurfacing.
- Cost/funding availability.
- Coordination among all interested parties.
The team felt that challenging project constraints will require ridot to utilize the latest technology to mitigate potential traffic problems. Technologies such as HAR, DMS and traveler information systems should be used, along with an active public relations campaign, to inform the public far enough in advance that they can adapt to the construction project's limitations.
3.5. Roadway/Geometric Design
The roadway/geometrics group agreed with RIDOT's determination that the weaving condition at the interchange needs to be addressed, and they put forth their recommendations accordingly.
The team identified the following issues with the proposed C-D road:
- The close spacing between the George Street and Vernon Street on-ramps.
- The merging of the George Street on-ramp on a curve.
- The widening needed on the George Street overpass to accommodate the proposed C-D road.
- The lack of improvement to the conditions at the George Street/I-95 northbound on-ramp.
- The unnecessary weave on the proposed C-D road.
Alternative to C-D Road
- Eliminate George Street northbound on-ramp.
- Make Division Street a one-way traveling east.
- Westbound traffic would use Main Street in the downtown area.
- Improve the School Street area.
- Build a roundabout connecting Division Street, Prospect Street and School Street.
- Straighten the alignment of School Street.
- Reconfigure George Street and local service roads such as Grace Street eastbound and Marrin Street westbound, and connect Marrin Street to Pleasant Street.
The group cited the following advantages to this configuration:
- It eliminates on-ramp weaves.
- It allows for advance roadwork.
- The George Street bridge is not modified.
- There are fewer traffic control impacts on I-95 (no on-ramp traffic).
- There is no additional width needed on Bridge No. 550 for weaving.
- It provides improved access to Pawtucket Memorial Hospital and along Division Street.
They also noted the following issues:
- Keeping Pleasant Street open. Consider constructing an arch over Pleasant Street.
- Potential property takings.
- Achieving buy-in by stakeholders.
- Local roadway improvements.
- Local traffic rerouting.
Much of the proposed widening work at Pawtucket Bridge No. 550 can be reduced, if not eliminated, by making local traffic improvements and reconfiguring traffic patterns. The problematic weave present at the interchange can be totally eliminated by redirecting entering and exiting traffic to other ramps that already exist along I-95. For this to be successful, local roadway improvements would need to be made. Eliminating the George Street northbound on-ramp and redirecting the traffic from that ramp would solve the weaving problem while reducing the bridge widening needed for the proposed C-D road.
The environment group began by discussing key project needs, after which they focused on addressing environmental and permitting concerns in a streamlined manner, all with the purpose of accelerating the project.
Overview of Key Recommendations
- Form a multi-disciplinary project design team.
- Establish a project development process that integrates engineering, environmental analysis, agency coordination and public involvement in to a collaborative decision making process.
- Conduct a comprehensive internal and external scoping process to:
- Refine project purpose and need.
- Delineate and map the environmental context.
- Obtain agency and public input.
- Establish transportation and environmental performance measures that will support environmental streamlining and stewardship.
- Develop/analyze alternatives that meet the project purpose and need while meeting
- State and Federal transportation and environmental performance measures, and
- the needs of the regulatory agencies and the public.
- Develop mitigation measures for unavoidable environmental impacts.
- Document the project development process:
- Comprehensive project files.
- NEPA document.
- Categorical Exclusion or Environmental Assessment.
- Strive to satisfy as many of the regulatory permit requirements as possible as part of the project development process.
- Address project environmental issues:
- Surface water quality and storm water management.
- Traffic and construction noise.
- Air toxins and equipment emissions.
- Blackstone River Heritage corridor preservation.
- Historic sites and districts.
- Contaminated soils and groundwater.
- Environmental justice.
- Visual quality and aesthetics.
- Riverine vegetation and habitat connectivity.
- Construction waste management.
- Detours through residential and business communities.
- Nighttime construction lighting and noise pollution.
Context Sensitive Solutions (CSS)
- Use a project design team approach that includes the following:
- Project team leader.
- Engineering group.
- Environmental group.
- Public involvement group.
All proposed work should not only address the environmental regulatory requirements, but should also ensure that all parties involved (public agencies, contractors and citizenry) work together to complete as much of the permitting as possible in the early phases of the project. All work should address regulatory requirements. Limiting the environmental impacts, i.e., avoiding work in the river or placing new construction outside the 100-year flood plain, will help accelerate the project by avoiding possible permitting delays and unanticipated environmental issues.