With the People’s Committee of Da Nang City in principle agreeing to the Vietnam Maritime Administration (Ministry of Transport) to research, survey and implement procedures for submerging 200,000 m3 of material in the sea of ​​Da Nang, experts say. There is a need for a careful assessment of the environmental impact (EIA).

Danang’s marine ecosystem is in decline

Associate Professor-Dr. Vo Van Minh, Chairman of the Council of Da Nang Pedagogical University, said that if there is no other dumping site, there is only way to sink into the sea. However, where to sink, in EIA techniques, it is necessary to determine which sea is the safest, least damaging to the environment.

“Currently, the waters of Danang are not included in the group of protected areas, so it can be submerged. However, from an environmental perspective, falling there will certainly affect immediately, especially coral reefs and seagrass areas. These areas are very important for their habitat and breeding grounds for marine life. Surely it will disturb the environment, affect species of marine fauna and flora “- Mr. Minh said.

Mr. Minh emphasized that in the EIA technique, it is only said to minimize to the lowest level, in the permitted level, not say that it is not impacting. Da Nang’s marine ecosystem is in decline, especially the coral system due to poor conservation, tourism and wastewater impacts.

“I want the EIAs to consult with scientists, but if they do not do well, it is dangerous for the environment” – Mr. Minh worried.

According to Dr. Nguyen Tac An, former Director of Nha Trang Institute of Oceanography, in order to carefully analyze the EIA capacity of submerging, it is necessary to understand the dredging method and the submerged technique. It can be said that all the material in the sea when lying still is okay, but when touched and bounced, many problems occurred. Therefore, it is okay to say just taking this place and leaving that place.

Mr. An said that the submergence principle must stay away from sensitive areas such as residential areas, fishing grounds, protected areas and special values ​​of the sea. In addition, when submerged, it is necessary to avoid seas with strong motivations.

“Actually we dumped it, but it will run away. Submerging techniques must be very attentive. Must see if the quality of sediment and chemicals in the area we scraped up is toxic or not. This EIA agency is aware of both. The dynamic maps in Vietnam nowadays all have them. Therefore, when pouring, it must be considered and calculated. The EIA agency will have to take physical samples for testing, calculate the propagation pattern, size, dredging and dredging time “- Mr. An noted.

Mr. An emphasized: Dredging the sea channel is very important for economic development. Dredging cannot be helped. However, how to minimize the impact of the dredger to increase the overall economic value.

Experts believe that when evaluating the EIA, it is necessary to determine which sea area is safe, with the least damage to the environment. Photo: LE PHI

Dredging the sea channel into Tien Sa port will create 200,000 m3 of material and be calculated to submerge in the waters of Da Nang. Photo: TAN VIET

Worry about coral reefs

Talking about the material submerged in Da Nang sea, Dr. Nguyen Thi Minh Phuong, Dean of the Faculty of Environment – Chemical Technology (Duy Tan University), assessed that 200,000 m3 of material is much and will definitely affect the system. marine ecology.

“The affirmation is always going to impact the ecosystem. When we poured like that, we thought it would lie there, but in fact it was not there at all, it had extremely large currents, so it would be swept away. Must see under that sea there are corals or not, because the most fear is the influence of the coral. When pouring like that, the coral cannot withstand the mud, when the water is too turbid, the symbiotic algae of the coral dies and makes the entire coral carpet die “- Ms. Phuong said.

Ms. Phuong further analyzed the great possibility that the sea area is expected to be submerged deep enough that there are no live corals. Most worrying, however, is that the currents will sweep matter around. Especially sediments, if heavy sediments will be deposited, and fine-grained sediments will be swept away.

“Saying a 100-hectare sea area, it will actually wash away very far. The sediment in the dredging site is likely to be fine-grained, not coarse-grained sediment. Fine means it is light, can be washed away, coarse grain is deposited in place and moves slowly. In a period of a few years it will be swept away everywhere and swept seasonally, because the flow changes with the seasons. Wherever the flow is, the coral will die there. The symbiotic algae of the coral needs light, the coral ecosystem is extremely important. And the bottom ecosystem will be temporarily destroyed for a while, then recover “- Ms. Phuong said.

Ms. Phuong added that from a management perspective, any project will have an impact on the environment. If you consider the environmental impact less than the likelihood of economic development, that’s okay, it’s worth the tradeoff.

“Also saying no effect is not right. The impact at sea is difficult to control. If other ecosystems can recover over time, the corals will not, die will die ”- Ms. Phuong affirmed.

177 species of corals around Son Tra peninsula From 2016 to 2018, the Southern Institute of Ecology had the topic “Research on conservation and biodiversity restoration of terrestrial and underwater ecosystems in Son Tra Nature Reserve”. After nearly three years of restoration, the live coral cover increased by more than 10% compared to baseline. There is an increase in organisms living in the reef. The coverage of seagrass beds increases about 20% -30%. According to research by the Southern Institute of Ecology in 2019, the sea surrounding Son Tra peninsula has 177 species of coral belonging to 17 families and 52 varieties. There are also 130 species of fish living in coral reefs, belonging to 32 families and 65 varieties. This sea also has three species of seagrass distributed over a total area of ​​1 ha and 108 species of extremely diverse seaweed. However, the marine ecosystem here is seriously degraded.

As Law of Ho Chi Minh City informed, the Vietnam Maritime Administration plans to dredge and sink 200,000m3 of material in the waters of Da Nang, which worries many people.

We have an interview with Associate Professor, Dr. Vu Thanh Ca (Senior Lecturer, Hanoi University of Natural Resources and Environment) about this sinking plan.

The plan is not effective

Sir, is the plan to dredge 200,000m3 of material and to sink in waters 4 nautical miles from Tien Sa Port is reasonable and effective?

Assoc.Prof. Dr. Vu Thanh Ca: I also do not know where the sinking area is. But with personal experience, I think that this drowning option is reasonable but not effective.

It should be noted that even though we see sand all around, sand is actually becoming an extremely rare resource. Beach sand is always very flexible and has a sand cycle near the coast. In winter, large waves with short cycles bring the sand from the shore outward to form near shore sand bars. In summer, storm waves are small but long cycle transport sand from these sand bars to the shore to reclaim the beach. However, the amount of sand brought into the beach is always smaller than the amount of sand carried out or in other words, a certain amount of sand is lost each year towards areas with great depths. Usually, this loss of sand is offset by sand brought out by rivers.

Assoc.Prof. Dr. Vu Thanh Ca (Senior Lecturer, Hanoi University of Natural Resources and Environment).

As many hydroelectric and irrigation dams are currently built on the upper reaches of rivers and block most of the sand flowing from the river basin. The amount of sand loaded into the sea by rivers is severely reduced and is no longer enough to compensate for the loss of sand at beaches. As a result, beaches suffer from a lack of sand, thus being transformed from an accretion state to an erosion, loss of beach state. Beach erosion is more serious because some localities have allowed to absorb sand near the shore for sea encroachment, thus causing a shortage of sand.

Sediment in Tien Sa port channel and basin originates from neighboring sandbanks and Han River, and is carried by long waves into the channel and port basin. If this amount of dredged sand is not submerged in locations with great depths but is dumped near the beach next to Nguyen Tat Thanh Street in Danang Bay, the use of sand will be very efficient.

There is no need to pour sand at the beach but rather sand in front of the beach, near where the sand bars are formed in winter. Long waves in summer will transport sand into the sediment to the beach, restore part of the beach that was eroded before.

Only immersed sand is not polluted

The waters surrounding Son Tra Peninsula have 177 species of coral, 130 species of fish living in coral reefs, 3 species of seagrass distributed over a total area of ​​1 ha and 108 species of seaweed. Warnings experts must be very careful when dumping 4 nautical miles from Tien Sa port. What are your comments on these concerns?

There have been many studies around the world on the environmental impact of dredged mud and sand. The first thing to emphasize is that if the dredged sludge is contaminated, special treatment is required to eliminate the pollution and only the immersion of non-contaminated dredged sludge into the sea is allowed.

The research results in the world show that, if the dredged sand is poured over sensitive ecosystems with high biodiversity such as corals, sea grass, the dredged mud and sand will kill the ecosystems. This state. In addition, if the dredged sediment is dumped near such ecosystems, the dumping of the sediment will change the seabed topography. The sea dynamics processes such as waves and currents will reset a new balance at the seabed by transporting mud and sand to sedimentation in other areas and can fill and cover areas with leveling ecosystems. coral, sea grass. Therefore, to avoid unnecessary damage, the dredged sediment submerged area must be significantly away from areas with high biodiversity sensitive ecosystems.

Da Nang seaport area.

If the dredged sludge is submerged in a rather remote location (for sure, more than 5 km) an area with a sensitive ecosystem with high biodiversity, the problem of turbid water becomes unimportant. . I would like to quote on this issue of the Committee of the OSPAR Convention, which is the Convention on the Protection of the Marine Environment of the Nordic Countries and Western European Countries: “Sediments are an essential part, the integrity and dynamics of the system. Ecological. Over 99% of the dredged material that has been submerged into the sea has been generated near the submerged site and is the result of dredging ports and access channels to ensure navigational operations. Most of the dredges were submerged at identified sites. They are also used for beach farming and encroachment ”and“ sediments are part of the marine environment and the movement of non-polluted sediments in the ocean supports natural sediment balancing. also has short-term effects on light-dependent organisms, but this effect is generally considered negligible. ”

It should be noted that the Nordic countries and Western Europe have very high standards of marine protection, and they concluded as such, we do not need to worry about this. Some countries also require dredged mud and sand submerged in the area with the mud and sand circulation system to support the mud and sand circulation, prevent coastal erosion.

Pouring sand to feed the yard, a double job

Do you have any advice for Vietnam Maritime Administration as well as Da Nang in sinking 200,000m3 of material?

I think that the dredger should be used to feed the beach, to compensate for erosion at the beaches of Danang. Over the years, a number of beaches in Da Nang, one of the most important tourism resources, are being eroded due to a shortage of sand. The use of dredged sand to feed the beach by dumping this sand into sandbanks just outside of the eroding beaches, although not fully addressing the problem of beach erosion, can also be mitigated. this problem.

If it is possible to use dredged sand to feed the beach and prevent erosion, the Vietnam Maritime Administration as well as Da Nang have done more than a double job. I want to say “more than a double job” because many places in Vietnam can not raise the beach to prevent erosion because there is no sand to feed the beach.

Associate’s views on material submersion into the sea? In the world, besides submerging material in the sea, is there any other option?

There is almost no other option to handle dredged sludge. Dumping dredged mud on shore is both costly and environmentally dangerous. It is expensive because you will need a large area of ​​land for dredging mud and sand. Dangerous for the environment because salt water from dredged mud and sand will pollute and destroy the ecosystem in a rather large area around the dredged mud and sand dump site.

Furthermore, I would like to emphasize again that the dredged sludge is part of the sea, and if the uncontaminated dredged sludge is submerged in the area within the sand circulation system of an eroding beach then I have helped the beach to protect itself according to the laws of nature.

Thank you Sir!.