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This project, submitted by TenCate Geosynthetics, won an Award of Excellence in the 2013 International Achievement Awards(IAA) / Geosynthetics presented by the Industrial Fabrics Association International. Each project in its own special way, exhibits outstanding innovation, technical skill and design excellence.
Submissions of geosynthetics projects for the 2014 International Achievement Awards are being accepted now. Submit your projects by June 30, 2014.
Introduction
The Embraport Container and Bulk Liquid Terminal was permitted for construction on the north shore of the port of Santos, Brazil estuary in a tidal zone that would require importing approximately 1.5 million cubic meters of select fill material to reach a platform elevation of +3.5m, taking into consideration settlement of the in situ subgrade during and after construction.
Through the sediment sampling process, it was determined that the required access channel and turning basin were overlaid with 600,000m3 of contaminated sediments that had to be removed and deposited in a secure upland disposal facility. This finding and subsequent required action increased the cost and construction timeline of the project. The cost of these requirements threatened the economic viability of the project.
Economic alternative
The dewatering cell subcontractor had to provide and install geotextile tube units capable of filling to a height of 2.2m, with a capacity of 35.2m3 per meter of a slurry with a specific gravity=1.43, and provide an overall minimum factor of safety of 4.3 or greater against circumferential, axial, and fill port rupture.
The engineered textile captured 99.9% of all suspended solids while having an effluent quality discharge capable of being discharged back into the native estuary and generating internal dry solids equal to or greater than 55%.
The geotextile tube units containing the residual dewatered contaminated sediments were required to have sufficient tensile reinforcement to provide a factor of safety equal to or greater than 2.25 when a 0.80-m pavement section has been installed and subjected to a load of 187tonf/m2. The geotextile tube structure had to have a 50+-year service life when subjected to hydrocarbon concentrations of 50% at ambient temperatures of 30° C.
This beneficial use concept would eliminate the requirement for an upland disposal facility, which would require the purchase of additional land for this facility or use of part of the Embraport site as the facility, and eliminating the 600,000 cubic meters of expensive imported select fill.
The geotextile tube containment and dewatering beneficial-use concept had to demonstrate through performance testing that it could meet stringent environmental guidelines for performance during construction. This included testing containment removal efficiencies and consolidation, providing high factors of safety against rupture during construction, proving survivability when subjected to severe overburden loading conditions or up to seven stacked layers of 20-ft and 40-ft maximum loaded ocean containers, and ensuring longevity demonstrated through accelerated testing.
The containment and dewatering design concept proved that it met all environmental and geotechnical requirements by being subjected to severe preconstruction performance testing and during the installation and construction phase of the Embraport project. The dewatering cell and polymer dosing system had to perform, without interruption of the dredging operation, by receiving the dredged contaminated sediments at a rate of 1,400m3 per hour. This performance requirement was met and this phase of the project was completed within the 18-month allowable time frame.
Sustainable solutions
Because the owner selected and implemented the geotextile tube containment and dewatering solution for on-site beneficial use of dredged contaminated sediments, the owner realized a savings of more than $50 million USD.
The carbon footprint was reduced by 7,903 metric tons of CO2 equivalent by adapting the geotextile tube containment and dewatering technology to securely contain and consolidate the dredged contaminated sediments on-site.
This concept allowed completion of the construction within the allowable time frame and to meet all of the Brazilian environmental regulations with regard to removal and containment of the contaminated sediments, quality of effluent return to the native environment, and service life of the project.