Deepening a Complex Channel: Contaminated Dredging, Wreckage Removal and Compacted Soil
Type:
Presented during:
WODCON XXII - Enhance the Harmony between Dredging and Ecology
Authors:
T.M. Tessler, L.C.Q.C. Melo , A.S. Vieira
Abstract
"The increased occupancy of the Brazilian coast, which includes population and logistic infrastructure, resulted in the inevitable interaction between waterways and sewage disposal, of home and industrial origin. At the same time, environmental guidelines and legislation are very strict in Brazil, encouraging port owners to increase existing operational units instead of investing in greenfield developments. This has resulted in an ever-increasing occurrence of contaminated sediment and waterway obstructions within dredging prisms, such as fishing apparatus, anchors and shipwrecks. One specific waterway extension project faced these difficulties. Access channel deepening of the Niteroi harbor access channel and maneuvering basin, located in Rio de Janeiro, was a complex task; which involved dredging of contaminated and non-contaminated sediment, partial removal of a late 1800`s shipwreck, compacted soil and sedimentary rock. Over 53,136 m3 of contaminated sediment was removed with a 12-inch cutter suction dredger and pumped to a sealed barge, without overflowing. The material was removed from the barge with a pump and, after mixed with polymer, confined in geotextile tubes. Residual wastewater was treated with a custom-made filtering system and disposed. The contaminated sediment was disposed on a classified landfill. The non-contaminated portion (193,525 m3) was removed with a large clamshell dredge and disposed in oceanic area supported by split hopper barges. Compacted soil and sedimentary rock were disaggregated with hydraulic breakers, collected with boarded long-reach excavators and carried to oceanic disposal. The shipwreck was partially removed by hoisting parts previously cut by divers and disposed in a deep section of the channel. In addition to the multidisciplinary operation, the waterway contour was very close to the coastline and rigid structures, such as piles, quays and riprap. The research and studies developed for this project comprehends and presents sediment sampling, decontamination process, geophysical and geotechnical survey, as well as the methodology implied on each work front and the final results."
Keywords: Dredging, Contaminated Sediment, Sediment treatment, Wreck removal.