US 15 over Indian Field Swamp Bridge
The US 15 over Indian Field Swamp Bridge was load restricted and structurally deficient. SCDOT established the firm goal of minimizing environmental impacts by reconstructing the bridge and roadway in its existing location. This resulted in the need for a road closure detour, subsequently mandating an accelerated design and construction process. The Design-Build team of United Infrastructure Group Inc. (UIG) as lead contractor and Infrastructure Consulting & Engineering PLLC (ICE) as lead designer was shortlisted for the procurement and ultimately selected as the best-value proposer on January 29, 2020. This very expedited and time-critical project had a contract completion date of July 16, 2020.
The RFP included an incentive, $10,000 per day for a maximum of 15 days, for early reopening of US 15. To earn the maximum available early completion incentive, the UIG/ICE team planned to complete the new bridge 15 days ahead of the required opening date, on July 1, 2020. This required that RFC plans must be issued by April 1st to allow a minimum of 30 days for shop drawing approvals and material delivery. Closure of the road and activation of the off-site detour was scheduled for May 1st, which would be the construction start date. UIG used a comprehensive CPM schedule to plan crew daily assignments that would result in completion of the new bridge and reopening the road to traffic by July 1, 2020. Further acceleration of the work allowed UIG to open the new bridge to traffic on June 24, 2020, more than twenty days ahead of the required completion date and six days before the maximum incentive date.
ICE prepared a cost-effective solution and expeditiously provided designs that allowed for rapid construction. UIG worked with ICE to optimize material selection for schedule efficiency, collaboration that facilitated the implementation of multiple innovative approaches including:
- The use of 20″ square prestressed concrete piles at all bents reduced necessary submittals and reviews, and facilitated efficient equipment use on-site.
- The selection of a cast-in-place flat slab span allowed the entire bridge superstructure to be constructed at one time. This eliminated the need for off-site girder fabrication and subsequent erection activities.
- Layers of loosely compacted sands on the existing embankments are subject to liquefaction during a seismic event. Typical mitigation strategies would include earthquake drains and/or ground improvement that require specialty contractors and additional weeks of work that negatively impact the construction schedule. To improve the construction schedule and reduce cost, ICE designed a u-shaped sheet pile containment system around each end bent. This system met all seismic performance requirements and was installed by UIG in less than one week.
- The new bridge completely spans the stream channel, resulting in unimpeded water flow and maintaining the original condition of the stream.
These design elements saved time, improved safety, minimized environmental impacts, and reduced maintenance costs.
By advancing all aspects of design during the procurement phase, the Design-Build Team was able to greatly reduce their risk and risk to SCDOT. United procured and delivered materials to the staging area before the closure of US15, providing adequate time for SCDOT to sample and test the materials prior to incorporation into the completed work. This minimized quality risks to SCDOT and UIG by ensuring all quality control requirements were met and provided greater schedule assurance.
The UIG/ICE Design-Build Team worked as a cohesive unit responsible for all pre-construction engineering and design, construction, and all other services that were necessary for the completion of the Project. UIG’s Project Manager was cohabitated with ICE during the preconstruction phase to conduct continuous over-the-shoulder reviews and facilitate designer- contractor coordination. This resulted in improved approaches to constructability, enhanced plan quality, reduced field RFI’s, and reduced overall project cost and schedule.
The bridge embankment was increased to approximately nine feet in height with 2H:1V slopes. Additionally, 0.28 miles of roadway work involved improvements to tie into the new bridge. The site geotechnical screening indicated the existing fill and subsurface soils presented potential for liquefaction and shear strength loss. Seismic hazard mitigation was required at the end bents for the design to meet the required factors of safety and seismic performance limits.
The greatest challenge for the Design-Build Team was meeting the accelerated design and construction schedule. Based on the requirements, the Project was to be designed, reviewed, and approved by SCDOT and constructed in less than 163 days from Notice of Award. SCDOT also mandated construction occur on existing alignment to minimize environmental impacts and road closures / detours could last for no more than 75 calendar days. The RFC plans were approved on April 25, 2020, and construction was started April 27, 2020, with the installation of the detour. All require construction was completed on June 24, 2020, and open to traffic.
The Design-Build Team was also able to complete the project ahead of schedule, allowing the route to be open three weeks sooner than anticipated and maintain budget requirements. The completion of this bridge replacement also enhanced the lives of residents in the vicinity of the Project by significantly improving response times of local emergency services due to the new increased load rating of the replacement bridge. The original bridge was load restricted which caused tripled response times.
The US 15 Bridge over Indian Field Swamp has received a Design-Build Institute of America Merit Award and is a nominee for the National Award of Excellence in the Transportation Category. As an added honor, the project is also one of the 2 finalists for the nation’s Best in Small Projects Award which will be awarded at DBIA’s national conference in Denver, Co later this year.