Rapid Removal and Replacement of the 4500 South Bridge over I-215 in Salt Lake City

Project Overview and Lessons Learned

Project Overview

The 4500 South Bridge on State Route (SR) 266 in Salt Lake City, UT, was built in 1971. The four-span bridge crossed Interstate 215 and served as an important access point for local businesses and residents. The bridge was in very poor condition, with delaminated, distressed concrete columns, pier caps, girders, and decks, as well as badly exposed and corroded reinforcing steel. On a scale of 0 to 100, the overall sufficiency rating for the structure was 40.3. The condition of the bridge prompted UDOT to expedite the removal and replacement of the bridge. After exploring alternatives and evaluating project and user costs, UDOT selected innovative accelerated bridge construction (ABC) and project delivery strategies to remove and replace the bridge. These strategies include the following:

• Use of the construction manager general contractor (CMGC) project delivery strategy, which allowed fast-tracking of the project.
• Offsite construction of the entire superstructure, including girders, deck, curb, gutter, side railings, etc. The single-span deck was 172 feet (ft) (52.4 meters (m)) long.
• Offsite construction of other bridge components, such as sleeper slabs and approach panels.
• Construction of substructures beneath the 4500 South Bridge and outside the bounds of I-215 with little to no impact on I-215 traffic. The construction of the substructure consisted of building the abutments with aesthetic murals on cast-in-place (CIP) spread footing foundations with extended wing walls.
• Dramatic reduction in user costs and increase in motorist and worker safety and user satisfaction through the use of a revolutionary construction engineering aid—the self-propelled modular transporter (SPMT). This tool made it possible to remove the old bridge and replace it with the new bridge over a weekend.
• Employment of a short-term full lane closure on I-215 to reduce construction time and user impact and improve safety.
• Implementation of an effective public information campaign involving both outreach and communication efforts.

The innovations employed on the project represented many firsts for UDOT, including the use of an SPMT and several of the substructure elements. The biggest innovation was the removal and replacement of the bridge using an SPMT. The entire operation took a mere 53 hours and has significantly raised customers' future expectations of UDOT on highway project delivery methods and time frames.

Equipped with 256 wheels and operated remotely by a single operator using a joystick control, the SPMT made two trips to complete the removal of the existing two-span superstructure (one trip per span). The entire removal took about 4 hours on Saturday, October 26, 2007. After moving both parts of the existing superstructure to the demolition area, work on rubblizing the existing columns and bent caps began over I-215. The remaining time on Saturday was spent removing the rubblized materials and preparing the abutments for placement of the new superstructure

On Sunday, October 28, the SPMT moved the new single-span superstructure to its final destination supported by the newly built abutments. The new 172-ft-long (52.4-m-long) superstructure, which weighed about 16,000 tons (14,514 metric tons), was the longest bridge ever moved by an SPMT in the United States. Many local residents and professionals from UDOT and other highway agencies observed the process. Local and national news outlets, including CNN, were also at the site. I-215 reopened to traffic on Monday, October 29, at 1 a.m. The 4500 South Bridge reopened to traffic about 10 days later, after the precast approach slabs and bridge detail work were completed. UDOT estimated that under conventional construction, which would have employed partial lane closures, the user impact would have been felt for 120 days over a 4- to 6-month period.

Data Collection

Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that accelerated bridge technologies can be used to achieve the HfL performance goals in these areas.

No worker injuries or motorist incidents were reported during construction, which means UDOT exceeded the HfL requirements for worker safety. A segment of I-215 that included the 4500 South Bridge on SR 266 and part of the pavement on either side of this structure was selected to determine the operational safety of the structure before construction. The 3-year crash histories revealed numerous crashes, but none that could be attributed directly to the structure that was replaced. Finally, no motorist incidents have been reported since the construction of the new bridge structure.

Under conventional construction, the impact on both roads from construction-related congestion was estimated at 40 to 50 weeks. With the use of ABC techniques, the impact was reduced to a weekend for I-215 and 10 days for SR 266. There was minor impact on I-215 for 8 weeks during construction of the spread footing (foundation for the abutments), abutments, and wingwalls. During the removal and replacement of the 4500 South Bridge, I-215 was closed to all traffic for 48 hours. Essentially, the major impact on I-215 was for only a weekend.

Quality was measured in terms of noise (OBSI) and smoothness (IRI) both before and after construction. The sound intensity data suggest that pre- and postconstruction noise levels did not differ significantly. Both were excellent and exceeded the HfL target values. Preconstruction IRI was 223 inches per mile for the existing bridge deck, and postconstruction IRI was 265 inches per mile. However, the final riding surface had not been placed before postconstruction IRI data collection. Although the thin riding surface is not expected to decrease the IRI dramatically, it is expected to provide a better match between the pre- and postconstruction test results. Nevertheless, the HfL goal for IRI of 48 inches per mile, while reasonably attainable on long, open stretches of pavement, was not met on this project. It is difficult to attain this level of average ride quality on a short-span bridge because the inevitable bumps at each end of the bridge have so much influence on the average.
During the planning and construction of the 4500 South Bridge, UDOT implemented an aggressive, comprehensive communication effort with residents and businesses in the affected zones. Through fliers, newsletters, e-mails, and a dedicated hotline, the public was kept aware of key project schedules and milestones on a weekly or as-needed basis. In addition, a project summary page posted on the UDOT Web site was updated periodically to reflect project progress. A postconstruction survey indicated that residents and businesses were extremely satisfied with the construction approach and the final product. As a result, UDOT exceeded the HfL customer satisfaction expectation by a large margin.

Economic Analysis

The benefits and costs of this innovative project approach were compared with those of a project of similar size and scope with a more traditional delivery approach. UDOT supplied most of the cost figures for the as-built project, and the cost assumptions for the traditional approach were determined from discussions with UDOT and FHWA Utah Division staff and national literature.

The economic analysis revealed that UDOT's approach realized a cost savings of about $3.24 million or 36 percent over conventional construction practices.¹ A significant amount of the cost savings was from reduced delay costs.

Lessons Learned

Through this project, UDOT gained valuable insights on the innovative processes deployed, both those that were successful and those that need improvement in future project deliveries. These were published in a UDOT report² and are excerpted below.

Contracting Process

Benefits of the CMGC contracting method used for this project include the following:

• The contractor was involved in the project early.
• Input and coordination on the schedule and cost were constant.
• The design considers contractor's inputs thereby improving constructability.
• All the answers were not required up front; they were developed throughout the project.
• The prime contractor was able to coordinate with subcontractors up front.
• The contractor was able to coordinate with utility companies early in the project.
• Flexibility allowed early action items and early release packages (structural steel procurement and temporary site construction) to be provided.
• The project was delivered on a tight schedule and was estimated to have been completed approximately 12 months earlier than the traditional (design-bid-build) approach to bridge construction.

Areas needing improvement include the following:

• Provide more design time to investigate alternatives, optimize design, and improve constructability.
• Define clearly the roles and responsibilities of the design engineer and the construction engineer.
• Determine a method for improving construction cost estimates early in the design process, since the cost of the project is determined as the design progresses.

Design

Benefits of the design process used on this project include the following:

• The designer and contractor worked as a team.
• The designer was able to visit the site constantly to ensure that the design requirements were met and the design schedule was maintained.
• Early communication and coordination occurred among the designer, contractor, and mover.

Areas needing improvement include the following:

• Know the design direction for the project up front with owner-defined goals.
• Plan up front for more design associated with temporary works.
• Obtain the contractor and subcontractor earlier in the process.

Construction

Benefits of the construction process adopted include the following:

• The designer and contractor worked as a team.
• A contingency plan was in place for unforeseen complications.
• Multiple pre-event meetings were held with the entire team to examine every step.

Areas needing improvement include the following:

• Limit the number of nonproject personnel on the job site to limit exposure, risk, and liability from the contractor. Coordinate more effectively between the owner and contractor on site access, and develop a protocol for site visitation for all individuals. Schedule tour times if necessary.
• Investigate cheaper alternatives for temporary work.
• Schedule adequate time for curing requirements of concrete work.
• Plan for adequate space at the staging area for the significant amount of SPMT equipment delivered to the site.
• Develop a checklist for items to evaluate during construction.
• Provide a more detailed plan for tasks to be done after the bridge move (grading plans, landscaping, staging area, and nonstructural items).

SPMT

Benefits of the SPMT process include the following:

• The designer, contractor, and subcontractor worked together as a team.
• UDOT gained experience with the use of SPMTs.
• The new bridge was erected quickly and traffic disruption was minimized.

Areas needing improvement include the following:

• Provide additional contingency in the conceptual cost estimate when a new technology is being implemented.
• Write specifications to promote ABC and the use of SPMTs.

Public Involvement

Benefits of the public involvement process include the following:

• Printed information was available to the public early in the project.
• The media and public were informed throughout the project.

Areas needing improvement include the following:

• Define project expectations and the timeline of the bridge move to the public more clearly.
• Provide more information in the public viewing area during the bridge move.
• Provide facilities for all public viewers.

In addition to the benedtis noted, the off-site construction enhanced motorist and worker safety and minimized traffic disruptions and related congestion.

Conclusions

From the standpoint of construction speed, motorist and user safety, cost, and quality, this project was an unqualified success and embodied the ideals of the HfL program. UDOT received AASHTO's Innovative Management award in the Small Project category for this project. More importantly, UDOT learned that careful planning—coupled with an aggressive public outreach and the use of innovative ABC technologies—can result in projects that serve as watershed events in the way they are delivered to the public. A postconstruction stakeholder survey conducted by UDOT clearly indicated that local residents and businesses were extremely satisfied with the construction approach and the final product.

Because of the success of this project, UDOT has taken several significant steps toward making ABC an integral part of its bridge construction projects and has set a goal of making ABC standard practice for all bridges by 2010. They are well and truly underway in their endeavor in becoming the first US highway agency to do so.

¹ These costs were estimated in consultation with UDOT engineers and FHWA Utah Division staff.

² HDR, Lesson Learned Report, I-215; 4500 South Structure Project, Project Number F-I215 (126) 13, Structure NO. C-953, January 2008.