Chester Engineers was contracted by the Jacksonville Port Authority (JAXPORT) to perform a study to address major concerns and opportunities related to the management of dredging resources, methods of dredge removal, management (capacity and structural) of current and potentially new spoil sites and the optimal use of such materials to the benefit of JAXPORT. All these activities were addressed, on a long-term basis, while maintaining a high degree of ecological interest and focus for the river as well as the adjoining environment. The primary focus of this study was to evaluate this activity for the long term with input from key stakeholders (City of Jacksonville, Port Terminal Operators and the Army Corps of Engineers).
The main challenges in this effort were:
The real estate available for expansion of the JaxPort terminal facilities was limited. In light of this, JAXPORT wanted to evaluate the conversion of some of the cleaner spoil sites, such as Buck Island, into terminal facilities. This conversion would, however, limit dredged material impoundment sites, thus further requiring the need for more creative dredging and impoundment plans.
There was still a need to identify and/or verify existing sediment transport models (computer simulation models) and historical sediment transport studies, which had been performed on the St. Johns River. If these models were found lacking, applicable models or studies would be performed for the river segment of interest.
The Interdisciplinary Approach
In order to achieve this objective by JAXPORT, Chester Engineers structured a comprehensive and detailed analysis of present and projected operational needs, developed and undertook efforts to develop an understanding of the physical limiting criteria and imposed conditions, assessed resource and manpower availability and allocation, identified alternative methodologies and/or technologies, and researched and qualified potential opportunities that could impact the JAXPORT facility to the 20-year horizon. Based on the information that had been acquired and the inferences which could be drawn from the information reviewed up to that point, Chester Engineers recommended that JAXPORT institute a rigorous review of the dredging program and implement a proactive dredging strategy for the future.
The Sustainable Result
JAXPORT immediately instituted a process to investigate and undertook efforts directed toward the creation of additional spoil sites.
Immediate implementation of a disposal handling cost-recovery program (tipping) in order to offset some of the anticipated inevitable development and operating costs. This was envisioned to assume the form of an “across-the-board tipping fee program” analogous to those implemented at other domestic port facilities.
Recommendations included potential alternative dredging technologies that could be envisaged for implementation to allow for larger vessels and also result in cost savings by only having to dredge every other year. The SedCon Turbo systems interrupt the sedimentation cycle by keeping the mud in its fully suspended state. At the same time, powerful water jets sweep the mud back into areas of active river transport. With a fall time of several hours, the sediment is carried far downstream by the ebbing tidal current. The system adds no new sediment to water columns and does not erode existing mud bottom. There has been no evidence of any increased shoaling adjacent to any SedCon Turbo system installations.