Preliminary Framework for Sustainable Beneficial use of Dredged Materials in Yangon River, Myanmar

Abstract

Yangon river has been facing with a problem of high rate of sedimentation as the reasons of deforestation, riverbank erosion, and flooding. A hundred million tons of sediments has been being dredged over 50 yr to maintain Yangon river waterway. Sediments daily produced from dredging work are directly dumped at a designated disposal area about 200 m far from dredging site to flash out these sediments by strong river flow. It may increase disposal-related turbidity disturbing sediment-settling into riverbed, and perhaps have a tendency to re-accumulate these materials into original dredging site because of the complex river flow at dredging site, known as inner bar area, where is close to a confluence of rivers and creek. This paper examines how to minimize the dredged amount at inner bar area by means of beneficial use. Therefore, sediment characteristics are needed to analyze because fine-grained sediments can easily attach pollutants giving an adverse effect to marine environment. Sediment samples from three different locations around inner bar area were collected with hand corer by diver, and analyzed U.S EPA methods: 10 129, 10 067, and 8000 for organic matters, inductive coupled plasma mass spectrometer for heavy metals, gas chromatography with mass spectrometer for persistent organic pollutants, and laser diffraction particle size analyzer. 14% of sand, 32% of silt, and 54% of clay were determined. The water contents in samples were 40.73%, 40.28%, and 31.40%. Lower values of harmful pollutants in samples than international standards were found. Therefore, sediments from inner bar may be supposed non-contaminated ones giving a better quality applied for beneficial use. Thus, without additional pollution-control treatments, appropriate technologies such as particle separation and dewatering techniques are described to produce commercial products, and to apply for engineering uses and environment enhancement as a sustainable practice.