Confined Aquatic Disposal Cell Capping Design, Construction and Monitoring: The Case of Piaçaguera Channel – Santos – SP – Brazil
WODCON XXIII - Dredging is changing - The Practice. The Science. The Business.
M. Torronteguy, J.J. Menegucci, M.R. Palermo
"During the years 2016 to 2020, a Confined Aquatic Disposal (CAD) cell was implemented in the Santos Estuary, São Paulo, Brazil, for confinement of 2.8 million cubic meters of sediments not suitable for oceanic disposal from the Piaçaguera Channel clean-up project. The CAD's implementation was executed in three distinct phases: i) opening, ii) filling and iii) capping. All phases were completed and resulted in the removal of a large mass of contaminants (PAHs and metals) which were adequately confined and isolated allowing for the establishment of better environmental quality and implementation of more favorable and safe navigation conditions along the Piaçaguera Channel. The CAD cap was placed after the hydraulically dredged sediments disposed inside the CAD had enough time to consolidate and gain strength to support the weight of the cap layer, providing geotechnical stability. A series of surveys were executed with the objective of monitoring the consolidation process before the placement of the cap. The use of existing material from Port of Santos navigation channel was deemed appropriate for the CAD cap based on strict technical criteria, following recommendations of the USACE, PIANC, Brazilian regulations and others. The CAD capping ended in September 2020 with the beneficial use (BU) of approximately 300,000 cubic meters of clean sediments dredged from the Port of Santos channel entrance. Since then, the cap has been monitored through regular surveys. This article presents details of the design and the execution of CAD capping, as well as the preliminary results of the cap monitoring, contributing to the understanding of the behavior of subaqueous caps for a large CAD site over time."
Keywords: Confined Aquatic Disposal (CAD); Contaminated Sediments; Capping; Dredging; Beneficial Use (BU)