JAXPORT Bartram Island Cell C Restoration and Capacity Improvement

Abstract: Bartram Island, located in the St. Johns River in Jacksonville, Florida, consists of several dredged material management areas (DMMAs). The DMMAs provide dredged material storage for maintenance of the Federal navigation channel and Jacksonville Port Authority’s (JAXPORT’s) marine terminals. In 2021, a study assessing the dredged material disposal needs of Jacksonville Harbor over the next 20 years predicted that JAXPORT would exceed its immediately available capacity within 2 years. Based on this, the study proposed several alternatives to create capacity. One alternative, JAXPORT’s Bartram Island Cell C Restoration and Capacity Improvement project, would create 1,224,000 CY of dredged material management capacity. One year after design and permitting began, construction commenced in February of 2022, and work concluded in mid-2024.

Data collection for design and permitting included a natural resources survey, topographic and hydrographic survey, and geotechnical investigation. Based on the natural resources survey, the design avoided wetland impacts. As a result, permit review and issuance timelines were significantly reduced. The geotechnical investigation consisted of vibracore borings to evaluate stored dredged material for suitability as a borrow source as well as Standard Penetration Test (SPT) and wash borings to evaluate engineering properties of foundation and embankment soils.

By offloading all historically placed dredged material within the DMMA and reconstructing and raising the dike by 10 feet, the design achieved the increased dredged material management capacity. As required under Florida Department of Environmental Protection Environmental permit review criteria for DMMAs, a seepage and slope stability analysis improved dike design and safety. The design implemented an internal gravel dike drain, discharging along the exterior toe, to control seepage. In addition, geosynthetic reinforcement through a section of the new dike foundation improved slope stability in an area where subgrade soils were particularly problematic. Another JAXPORT DMMA on the island and three newly constructed storage cells adjacent to Cell C received offloaded dredged materials that were not suitable for dike construction. The unique project location presented difficulties when sourcing suitable material for the dike construction. To avoid importing fill to the island, the design required separation of suitable stored dredged material from unsuitable materials; excavating 5.5 feet below the historical basin bottom generated additional suitable borrow materials. Noteworthy challenges addressed during construction included geosynthetic reinforcement installation around a curve and variable geotechnical site conditions with a deficit of suitable construction fill.

How does this project / topic contribute to the advancement of the industry and profession?: The dredging of navigation channels and ship terminals is one of many measures taken to maintain a port. Dredged Material Management Areas (DMMAs) provide disposal capacity for continual dredging operations. For this project, an inactive DMMA with no remaining capacity was transformed into a fully restored and expanded DMMA with capacity for 1,224,000 CY of dredged material. The design featured solutions to challenging geotechnical site conditions and the construction phase lessons learned which offer opportunities of advancement of the industry and profession.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The constructed storage cells allowed for efficient offloading of about 150,000 CY of dredged material (from the DMMA) that was unsuitable for construction of the new dike. The internal gravel dike drains, designed to control seepage, feature about 5,000 linear feet of custom 12” perforated HDPE pipe that conveys water to 24 different outfall locations. Half of the outfall locations include a 100’ long gravel toe drains to prevent point discharge of seepage into the adjacent wetlands.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The most challenging aspect was the project’s location. The DMMA is located on an island in the St. Johns River. To avoid expensive barging costs, all unsuitable earthen material was separated and offloaded to other containment cells on the island with suitable material used to construct the new dike. With little to no room to expand on the island, the new dike had to be located within the original footprint to avoid wetland impacts. Poor subsurface soil layers within the footprint presented slope stability issues for the increased dike height which were addressed through internal seepage drains and geosynthetic reinforcement.

Who is the target audience for this paper?: The target audience for this paper would be those engineers and Port Authorities/Operators interested in dredged material management, geotechnical engineering, and earthwork construction. Dredging plays an important role in ensuring a port stays operational. The dredged material can be disposed of in several ways, but capacity is never unlimited. This paper will outline the design and construction process that created 1,224,000 CY of capacity by the restoration and improvement of JAXPORT’s DMMA.