Tiếng Việt


Environmental Concerns about Dredge Disposal in Sea

When several days ago three barges, a suction vessel, and an excavator entered the Tho Quang docks in Son Tra district, Danang, to conduct experimental dredging in construction area number 1 in the waters east of the docks, more than a few environmental experts voiced concerns about the disposal of dredge material in the sea off Danang.
On April 14, the Danang traffic construction investment project management board informed of the experimental dredging and long-term maritime disposal in the Tho Quang fishing port docks, as part of the effort to remove the site from the list of environmental pollution hotspots by 2025.
M?i lo môi tru?ng khi nh?n chìm bùn n?o vét xu?ng bi?n
Dredge material from the Tho Quang docks is transported by bottom-door barge to its disposal site in the sea
According to the approved environmental impact report, the successful bidders, 126 JVC JSC and Phu Xuan JSC, will divide the docks to simultaneously perform the work and assess effectiveness and impact based on supervision and follow-up by the relevant agencies: the Department of Natural Resources & Environment, the environmental police, the border guard, the Son Tra district People’s Committee, etc.
According to decision 1719/QÐ-UBND of May 18, 2019, by the Danang city People’s Committee, the extent of the Tho Quang dredging is 50.17 ha, the total volume of dredge material with refuse removed to be disposed of is 346,790 m³; the total cost is 99 billion VND. For the disposal of dredge material, three barges with capacity of 1,495 m³ per day (for six trips per day) each will be used to transport the dredge material to the disposal site, for an estimated total of 3,500 m³ of dredge material per day.
In recent days, however, public opinion and environmental experts have started asking questions right from the moment the Tho Quang dock dredging project started: This is the first time large quantities of material are dredged up and disposed of in the sea. It is expected the initial work will be accompanied by environmental impact assessment. Can safety be ensured this way?
When hundreds of thousands of cubic meters of dredge material from the Tho Quang docks are dumped in the sea, will this settle by itself or will it feel the impact of currents, be moved around, and cause harm to the ecosystem and the coral reefs in the sea off Danang? Of note is that ecosystems, maritime coral reefs, and the Son Tra peninsula coasts are being degraded and are in dire need of recovery and protection.
On April 14, Dr Nguyen Thi Minh Phuong, Dean of the Faculty of Environmental & Chemical Engineering at DTU, Danang, explained to us how the Tho Quang docks area has long been a hotspot of environmental pollution. The sediments which have been heaping up for many years have reduced the dock capacity, and waste disposal and dredging are required. The methods of dredging and disposal, however, are important problems requiring deep consideration.
As the dredge volume of rather high, almost 350 thousand m³, and is composed mainly of fine grains (mostly clay, powder, and fine sand), it easily moves around and dissolves in an aquatic environment, it does not readily sink to the bottom. The high liquid-form fraction (“mud fraction of up to about 50%”) causes even farther movement and more rapid dissolution in water.
Still according to Dr Nguyen Thi Minh Phuong, the coral reefs in the Bai Bac area, Son Tra peninsula, are now nearly completely destroyed, and those in the south of the peninsula are also dying in large numbers. One of the factors destroying the coral reefs is sediments. Coral reefs develop in symbiosis with algae. If sedimentation suddenly increases, symbiotic algae will die first due to a lack of light for photosynthesis, and the corals die after them.
If the above-mentioned pollution were to move close to the shores of the Son Tra peninsula, the few remaining coral reefs will certainly be destroyed, which will entail an impact on organisms in the coral reef ecosystems. This will obviously have negative consequences for local tourism and for the fishers whose livelihoods depend on this maritime area.
(Media Center)