Jimmy DeLoach Parkway Eases Flow of Panama Canal Freight: Relieves Truck Congestion

Jimmy DeLoach Parkway Eases Flow of Panama Canal Freight: Relieves Truck Congestion

Square piles behind Reinforced Earth mixed abutment MSE wall
Reinforced Earth Product in Field
Savannah, GA
Georgia Dept. of Transportation
Archer Western Contractors
The Reinforced Earth Company

Did you know that the Panama Canal flows all the way to Savannah, Georgia?  Maybe not literally, but the Port of Savannah has the largest single container terminal in North America and, in its fiscal year ending June 30, 2015, handled 3.66 million Twenty-foot Equivalent [container] Units, or TEUs. The TEU is the standard measure of containerized freight, equivalent to 20 ft. x 8 ft. x 8 ft., and containers based on this standard can be moved seamlessly between ships and trucks.

Fully one third of the containers arriving or departing the Port of Savannah passed through the Panama Canal, which is now undergoing a major expansion to add a third set of significantly wider and deeper locks (completion in 2016). The new locks will allow the transit of "post-Panamax" ships carrying 13,000 TEUs, or 260% of what Panamax ships now carry, requiring the port to dredge its waterways to handle these massive, deeper draft ships. On the land side, the growing number of containers moving into and out of the port by truck will seriously challenge the current roadway system, so the Georgia Department of Transportation (DOT) is building a new roadway, the Jimmy DeLoach Connector, to improve port access.

The current route to the port is via I-95 and GA SR 21, then onto local road Bourne Avenue for about a mile to the port entrance. With about 8,000 trucks now entering or leaving port facilities daily, there is already major traffic congestion throughout the area, even before the post-Panamax ships arrive. The new 3.1 mile Jimmy DeLoach Connector, beginning near the existing Jimmy DeLoach Parkway terminus at SR 21 and extending south to Bourne Avenue at a point close to the port gates, will relieve truck congestion, shorten travel time, and keep most port-associated trucks off Hwy 21 and local roads.

The Jimmy DeLoach Connector requires six new bridges and new interchanges at Grange Road and at Jimmy DeLoach Parkway, all under a $73 million design-build contract awarded to Archer-Western Contractors of Atlanta and their design partner, The LPA Group (now Michael Baker International) of Norcross. Five bridges each require 2 tall abutments, configured with a mechanically stabilized earth (MSE) retaining wall in front of a bridge seat supported on (square precast concrete) piles. This arrangement  is known as a "mixed" MSE abutment, because the MSE structure retains the soil while the piles carry the bridge load through the reinforced soil to the foundation below (compared to a "true" MSE abutment, in which the bridge seat bears directly on the MSE backfill, Figure 3). In addition to the new abutments, an existing Reinforced Earth® wall (where the original Jimmy DeLoach Parkway transitions into the Jimmy DeLoach Connector) had to be reconfigured and extended. Archer Western asked The Reinforced Earth Company (RECo) to design and supply the MSE structures for this project.

GDOT generally requires the use of mixed abutments in settlement-prone areas such as this coastal environment. To avoid formation of settlement-induced voids beneath these pile-supported bridge seats, and possible resulting undermining of the approach slabs, the DOT also requires a waiting period before pouring the bridge seat. Geotechnical engineer United Consulting, (Norcross), developed a table of short term (during construction) and long term (post-construction) estimated settlements for each abutment. Some settlement estimates were as much as 24 in. short term/30 in. long term. At some of the higher-settlement locations, United recommended a staged construction process, i.e., building the abutment wall to mid-height, waiting 30 days for settlement to take place, completing the wall, then the typical 30-day waiting period prior to casting the bridge seat. To further reduce the magnitude of settlement, several of the MSE walls were specified to be undercut by 18 in. and backfilled with granular material.  Having identified an excellent local source for the MSE structure backfill (well-graded sand, φ = 33°, unit weight 115 pcf. at optimum moisture content), the contractor simply backfilled the undercuts with the same material.

Archer Western stated a strong preference for the Reinforced Earth option offered by GDOT's contract, not only because of its many successful projects completed with RECo, but also because RECo is known for its thorough designs, attention to detail, and high quality precasting (in this case, provided by a company-owned precast plant in Newnan, GA). So it is no surprise that both the Archer-Western/RECo relationship and the construction process itself flowed so smoothly. RECo works hard to make and keep such relationships, because good products and good relationships benefit all parties.

The abutments were built in pairs, working mostly south to north along the project alignment. The contractor requested precast coping for the abutments and chose a precast half-connector  to serve as both the coping and the foundation for the cast-in-place traffic barrier atop the reconfigured and lengthened existing Reinforced Earth wall. Contractors like RECo's precast top-out units (copings, traffic barriers, and half-connectors) because they are precision-cast to fit correctly and they significantly reduce top-of-wall forming and labor, improving work flow, safety and the bottom line. The forms are owned and maintained by RECo, assuring timely production on every job.

One bridge spanned the Norfolk Southern Railroad (NSRR). Since the walls were outside the railroad's mandatory track clearance envelope and all wall erection work could be done on the backfill side of the wall face, there were no railroad-induced MSE construction delays. The only substantial railroad-related impact occurred during superstructure construction, when working directly the over the tracks, but of course that was long after the Reinforced Earth abutments had been completed.

It is no surprise that contractors opt for Reinforced Earth MSE structures again and again. They do so because they know, often from years of their own experience, that RECo's quality products and the predictability of the Reinforced Earth construction process help projects succeed. So whether you are receiving container shipments from the Panama Canal, building an airport or a highway or an industrial project, or retaining a simple cut or fill in your home town, be sure to take advantage of the quality, predictability and experience of The Reinforced Earth Company. You can rely on RECo to support the earth … and to support you.