Written by: Michael J. Dickey, PE, Director and Bryan Wedin, PE, Chief Design Engineer
On May 6, 2022, the Maritime Administration (MARAD) released an amended Notice of Funding Opportunity (NOFO), allocating over $234 million for port infrastructure development in 2022. Adding to the previously appropriated amount of $450 million from the Infrastructure Investment and Jobs Act (IIJA, or Bipartisan Infrastructure Law), this will bring the total amount available for port improvement projects to $684 million for FY2022.
The significance of this investment comes at a crucial time. According to the American Association of Port Authorities, the pandemic has laid bare the need for a transport system that is able to surge and stretch across all links—from sea, to land, to rail, to warehouse, to consumer. The question is, how can this funding be used to meet this need quickly and cost-effectively? The answer may lie in a strategy implemented in 2021 in the state of Georgia to alleviate congestion at the Port of Savannah. The Georgia Port Authority, in partnership with Norfolk Southern, implemented a solution that has caught the attention of other U.S. port authorities and Class I railroads using what is being referred to as “pop-up container yards”.
What Is a Pop-Up Container Yard?
In a recent article featured on Freightwaves.com, pop-up container yards are described as “mini-versions of inland ports where containers are brought to strategically located sites by intermodal rail, shortening the distance trucks have to travel to collect imports or drop off exports and reducing traffic in and around busy seaports. The concept essentially brings the seaport closer to manufacturing, agriculture and population centers.” While, on the surface, pop-up container yards may seem like a very pragmatic solution to a complex problem, developing one of these sites can come with its own set of unique challenges.
One such challenge relates to existing ground conditions. From a geotechnical perspective, the ground conditions may not be suitable for the heavy demands of container handling and storage operations. And unless an alternate location has been identified that is better suited, project engineers and designers must often evaluate the need for ground improvement options capable of supporting heavy vehicle loads over soft or unstable soils. The good news is that the GEOWEB® Soil Stabilization System was invented specifically for this purpose. The GEOWEB Cellular Confinement System (CCS) is an American-made geosynthetic product manufactured by Presto Geosystems that has been in use for over forty years.
GEOWEB Geocells Improve Bearing Capacity Over Soft or Unstable Soils
Created through a collaboration between the U.S. Army Corps of Engineers (USACE) and Presto Products Co., the GEOWEB system was designed to address the needs of the U.S. military to build access roads capable of supporting heavy vehicle loads over soft or unstable soils. The system’s deep cellular network controls both the horizontal and vertical movement of unstable base soils. In load-support applications, when a static or dynamic load is applied to a geocell-reinforced layer, lateral earth pressures are mobilized and transferred across a three-dimensional network of interconnected cells. The layer essentially performs like a composite material, facilitating a phenomenon known as the mattress effect.
Success Story: CSX Intermodal Facility in Charleston
The CSX Charleston Intermodal Yard required base reinforcement due to poor and unstable subgrade conditions. Shallow surficial soils comprised very loose sandy soils that were inadequate to support the operation of reach stackers used in regular lifting and moving containers. In addition, a similar condition was prevalent in another area of the site designated for chassis parking. Both areas were prone to significant rutting due to the inherent instability of shallow surficial soils.
The Presto Geosystems’ design staff worked closely with CSX to provide design recommendations based on sub base strength, vehicle loadings, and frequency of traffic. After a thorough review of the geotechnical report, it was determined that on-site material could be beneficially reused as infill in the GEOWEB system.
Eliminating the need to import costly aggregate and structural fill led to significant cost savings, and yard downtime was substantially reduced. Minimizing downtime was especially important due to the high volume of tractor-trailers the facility handles daily. The reach stacker area used an enhanced woven geotextile, three-inch base, six-inch GEOWEB panels, and a three-inch wearing surface. The chassis parking area utilized a high-strength woven geotextile, six-inch GEOWEB panels, and a two-inch wearing surface. The GEOWEB system stabilized a total of 1.75 acres. Both areas have required minimal maintenance and continue to function as designed. Both areas have required minimal maintenance and continue to function as designed.
Protect Your Project Schedule and Reduce Costs with GEOWEB® Geocells
As demonstrated by the success at the CSX intermodal facility, where a suitable source of clean sand is available, the GEOWEB cells can be infilled with on-site material in place of expensive aggregate, drastically reducing imported aggregate volumes altogether. Even at sites where a suitable source of clean sand is not readily available, geocells offer the potential to reduce the required thickness of the base layer in a load support application by as much as 50%. In both cases, project stakeholders can realize cost savings, as well as a potential reduction of schedule-related risks, particularly where the availability of suitable aggregate, or availability of truck drivers to transport said material, might otherwise be outside of the project decision-maker’s control.
Compared to planar geosynthetic products such as geogrids—which commonly rely on expensive, imported high-quality aggregate—geocells are highly versatile and can be filled with a variety of commonly available and economical infill options. Infill options include sand, crushed aggregate, recycled concrete, pulverized debris, recycled asphalt, or other locally sourced materials. The illustration below provides a comparison of four structurally equivalent aggregate sections over a subgrade with a CBR of 0.5%.
As illustrated, the unreinforced aggregate option would require more than 36 inches of aggregate to achieve minimal stability, and the planar geosynthetic option (geogrid + geotextile) would require 26 inches of aggregate. In contrast, the GEOWEB geocells reduce the total section thickness to only 15 inches, and where suitable on-site material (OSM) is available, it is possible to limit imported aggregate to just the wearing course.
A Value-Engineered Solution for Your Pop-Up Container Yard Project
The GEOWEB geocells can be added to pop-up container yard projects to provide a value-engineered solution for both paved and unpaved areas. This not only reduces construction costs, but can also help keep your project on track when aggregate shortages and limited availability of truck drivers threaten your project schedule.
Project-specific recommendations are influenced by loading, subgrade soils, traffic frequency, and infill type. The engineering team at Presto Geosystems works closely with engineers and project planners, offering free project evaluation services and on-site installation support. Our recommendations will deliver a technically sound, cost-effective solution based on over four decades of accredited research and testing data. Please contact our knowledgeable staff and network of qualified distributors and representatives to discuss your project needs today.
Contact: Bryan Wedin, PE, Chief Design Engineer