South Carolina's I-85/I-385 Gateway Project Nears Final Stage
The early November opening of a new Interstate 85 northbound system-to-system bridge to Interstate 385 northbound marks another major milestone for South Carolina's massive I-85/I-385 Gateway Project. The $300 million project, owned by the South Carolina Department of Transportation (SCDOT), began construction in 2015 and is on schedule for completion in May 2019. It is the state's largest transportation infrastructure project in over a decade, and one of the largest in South Carolina road history.
The new Woodruff Road bridge is one of a dozen new bridges that are major components of the revamped interchange of Interstates 85 and 385 in Greenville County, designed to relieve congestion and increase safety along the state's third busiest interchange - average annual daily traffic (AADT) on I-85 is 131,000 vehicles per day (vpd) , and is projected to be 174,700 by the year 2035. On I-385, the AADT is 105,500 vpd, and projected to increase to 172,500 vpd by 2035.
As SCDOT Director of Communications Pete Poore relates, "In 2007, this department developed a priority ranking list of interstate interchanges that had unacceptable operating conditions and deficiencies that created safety concerns due to congestion, undesirable movements and vehicular conflicts. The I-85/I-385 interchange was listed as the second priority on that list, and in May 2008, the SCDOT Commission approved the inclusion of this project in the Statewide Transportation Improvement Program (STIP) with preliminary engineering funding available in fiscal year 2009."
In March 2011, the project was officially turned over to the Preconstruction Innovative Projects Group to develop as a design-build project. Environmental studies and preliminary engineering were completed in February 2013, and Design-Build Request for Qualifications were advertised in July 2013. The design-build contract was executed and Notice to Proceed 1 was issued to begin permitting and final engineering design in October 2014; Notice to Proceed 2 was issued in December 2015 to begin construction.
The project is replacing existing loop ramps with direct-connect, high-level flyover bridges and includes construction of a new collector-distributor roadway along the two interstates. Also part of the project are reconfiguration and replacement of existing ramps, construction of additional lanes along I-85 and I-385, and resurfacing and rehabilitation of I-85. In addition to the 12 new bridges being constructed, crews are constructing 56 walls within the interchange limits, including mechanically-stabilized earth retaining walls. Among the improvements included within the scope of the project:
"¢ The extension of the 4th auxiliary lane on I-85 Northbound and the addition of another lane Southbound between I-385 and Pelham Road. This means the road will be four lanes wide between these two exits.
"¢ The widening of I-385 from four-lanes to six-lanes between Butler Road to Roper Mountain Road.
"¢ The construction of new interchange bridges, including two flyovers that will replace the existing loop ramps that tie I-85 from and to I-385.
"¢ The reconstruction and enhancement of the traffic signal system on Woodruff Road between Ketron Court and Highway 14.
"¢ The construction of additional turn lanes and reconstruction of three intersections on Woodruff Road between I-85 and I-385.
"¢ Collector-distributor roads along I-385 through the I-85 interchange area.
"¢ New interchange bridges and new Roper Mountain Road bridge over I-85 are designed to accommodate a future widening of I-85 mainline to eight lanes.
"¢ I-85 pavement rehabilitation between mile markers 41 and 56
The project is being financed in part with funding from Act 98 of 2013, which provided the SCDOT with additional funding for bridge, resurfacing and mainline interstate projects. The legislation provides an annual appropriation of $50 million to SCDOT for interstate improvements. The Federal Interstate Improvement Program and Greenville-Pickens Area Transportation Study Committee (GPATS) is providing additional funding.
Poore explains, "Act 98, signed into law June 24, 2013, provided the SCDOT additional funding for bridge, resurfacing and interstate projects. Act 98 provided an annual appropriation of $50M to SCDOT, which in turn transferred an equivalent amount to the South Carolina Transportation Infrastructure Bank (SCTIB) to be utilized as a revenue source to finance an estimated $550M in bonding for existing mainline interstate projects. The Act required SCDOT to submit a list of projects to the SCTIB for approval, and required approval by the Joint Bond Review Committee (JBRC). In December 2013, the JBRC approved implementation of financial assistance to several interstate projects including the I-85/385 System to System Interchange Improvement. SCDOT was approved for and has received $80 million in SCTIB funds on the project to date."
An Experienced Project Team
The I-85/I-385 Gateway Project is an undertaking of a joint venture between Flatiron Construction Co. of Broomfield, Colorado, and Zachry Construction Corp. of San Antonio, Texas. The design team includes Civil Engineering Consultant Services, Inc. as the primary designer, along with Stantec, TYLin, and Mead and Hunt as major subconsultants. The Flatiron-Zachry Joint Venture was awarded the design and construction of the project in August 2014, and construction got underway the following year.
Independently, Flatiron and Zachry have experience constructing other major projects in South Carolina and the Southeast. Flatiron was part of the construction team that built the Arthur Ravenel Bridge over the Cooper River in Charleston, completed in 2005, and the Carolina Bays Parkway in Myrtle Beach, completed in 2002. Zachry completed the Interstate 20 widening project in Richland County in 2014 and is currently working on Interstate 40/Interstate 77 in Iredell County, North Carolina.
The I-85/I-385 Gateway Project is utilizing a design-build contract under which the Flatiron-Zachry Joint Venture was responsible for design, obtaining permits, acquiring right-of-way, coordinating utility relocation, and constructing the new interchange, all under the oversight of SCDOT and FHWA. This type of contracting can save time and money by encouraging innovative designs, materials, and construction practices.
Poore comments, "All projects developed by SCDOT begin as traditional design-bid-build projects, but are analyzed to determine their suitability for design-build. Primary consideration factors include the proposed delivery schedule, complexity of the project and the opportunity for innovation, level of design that has been completed on the project, and the project cost.
"In this highly urbanized area, SCDOT wanted to take advantage of the innovations that design-build delivery brings and let the developer maximize efficient construction and maintenance of traffic techniques while minimizing the overall project footprint."
Reducing Future Bridge Maintenance
During the design phase, the Flatiron-Zachry Joint Venture proposed replacing several bridges from the ground up as an alternative to the contractual requirement of only rehabilitating the concrete riding surface of those bridges, while leaving the beams and supports in-place. SCDOT evaluated this plan and ultimately decided to accept this $5.3 million proposal, as it reduces future maintenance costs and will push the need for another major bridge project within the interchange off into the distant future.
The project's scope meant creating a new interchange within the general footprint of the current interchange by staging construction of the new lanes, ramps, and bridges - while maintaining traffic. "The most challenging aspect related to this project is the volume of traffic utilizing this interchange," states SCDOT Resident Construction Engineer Kimberly Bishop. "The challenge arises from ensuring the safety of the motoring public along with minimizing the impact to traffic all while constructing the project. In order to minimize the effect on motorists, lane closures and detours are being conducted at night. Also during the day, access to the project is done during non-peak hours."
More than 135 utility conflicts were identified during the design phase, and the respective utility companies worked to relocate their impacted infrastructure. The project also encountered unexpected delays in securing all the required environmental permits for construction.
A Catalyst for Growth
Completion of the I-85/I-385 Gateway Project is expected to enhance commerce and serve as a catalyst for economic growth, Poore states. "During the environmental documentation stage of the project development, the project was evaluated for potential economic impacts to the surrounding communities. The project could provide beneficial economic impacts through improved operations, reduced travel delays, and safer conditions. These improvements would improve the overall quality of life by reducing time delays and providing safer driving conditions, which would encourage and sustain the existing retail centers. The project would also result in a direct saving to motorists by decreasing travel time and reducing the potential for traffic accidents and property damage."