In early 2011 Cargill AgHorizons awarded Kajima Building & Design (KBD) Group Inc. the bid to overhaul its outdated Hales Point, TN, barge-loading facility located on the banks of the Mississippi River. The plan involved expansion of its storage and handling capacity and a structural foundation capable of meeting the demands of river terminal operation. However, given the unpredictable nature of Ol’ Man River, the Atlanta, GA-based design/build firm had to overcome unique challenges.
KBD Group began preliminary construction in the spring of 2011; however, early into the project, the Mississippi River experienced flooding greater than in the 80-year recorded history for this area. During this time, 6 to 10 feet of floodwater engulfed the project site. As a result, the expansion suffered a number of setbacks: The design/build firm’s jobsite trailers, temporary gravel roads, a silt fence and the preliminary grading work were destroyed.
Construction was halted for weeks (during this time the site was only accessible by boat), which gave Cargill an opportunity to reconsider some of the parameters of the project. For example, the company changed the location of the office building by increasing the grading work and placing it higher to avoid future damage.
After the water receded, the team remobilized in June of 2011.
“Our team worked closely with Cargill, Inc. to get the original existing facility cleaned up and back in working order. Cargill’s goal was to complete the facility by July 1, 2012 prior to the end of summer and fall wheat, corn and bean harvest,” KBD Group’s regional manager Jack Yates explains, noting how all entities — subcontractors, equipment suppliers, vendors — worked diligently to meet this goal.
The riverfront location posed two challenges: variable water level and unstable soil. While weather and river level challenges vary, the installation of a solid foundation could be navigated with expert engineering.
Preparing for future floods
Since annual flooding was generally predictable at the Hales Point facility, KBD Group took it into consideration during every phase of the design process. For example, access from the barge tower to the adjacent work platform has several levels so that the walkway can be raised or lowered based on the river level. Pits and tunnels were designed with sump pits and waterproofing membranes to protect from the rising ground water.
“The large pit at the receiving tower was designed with buoyancy in mind to protect from the uplift forces that would be imposed by extremely high groundwater levels,” Yates notes, having analyzed the river’s historical data to determine flood levels.
With its location so close to the river, the site’s soil condition was not ideal.
Yates explains: “To compensate for the poor soil quality, we analyzed several foundation options and determined the most appropriate system would be an array of rammed aggregate piers, known as Geopiers, placed in several separate mobilizations to allow for the construction of the different subsurface levels. We also had to use sheet piling for the construction of the deeper tunnels and pits, which required close coordination to work with the existing structures. In addition to the Geopiers, the new large bins were placed on up to 10 feet of engineered structural fill. This was required to raise their bottom elevation enough to allow for the underground tunnel and conveyor system.”
The facility required a considerable amount of soil built up to support the expansion, which in addition to an added 855,000 bushels of storage space, included the installation of a 32-foot-deep concrete pit, multiple below-grade tunnels and foundations, and the demolition of two existing buildings.
The dirt work on a project of this scope would have been costly; however, a nearby landowner wanted to level his mound-filled property into an agricultural field.