The port-channel dredging industry is a project to excavate the sand and stones in the surrounding waters of the port or waterway, which aims to improve the water condition of the port and waterway and reduce dredging ecological impacts. Due to the large amount and long construction time of the port and river dredging project, it is easy to destroy the original ecological environment and change the beach appearance. Therefore, we should adhere to the concept of environmental protection, scientific treatment of dredged materials, and protect the ecological environment of the construction area.

1.The significance of environmental protection in the dredging project

Environmental protection usually refers to in order to be able to effectively solve the existing or potential environmental problems, humanity will give them effectively coordinate the relationship between the human and the environment. To people’s living environment and ensure the social and economic sustainable development and implementation of a series of actions. At the same time, the environmental protection of the construction of the project belongs to a comprehensive performance for a long time and higher activity. It cannot be carried out from a single aspect in the specific implementation process, and cannot be limited to a stage. At present, with the increasing development of society and the differences in different construction aspects, it is impossible to successfully protect the environment in the project at once. We should pay close attention to the related changes and make continuous improvement at the same time. During this period, environmental protection and social stability and development can be effectively combined, and on this basis, social and economic construction can be developed. Once social and economic development is driven, corresponding protection measures will be taken for the environment. In this way, we can have both “fish and bear’s paw” and keep the ecological environment in a relatively stable state. However, special attention should be paid to the fact that human society cannot destroy the environment as the dredging cost in the process of continuous development, which will bring untold consequences.

Channel dredging projects have direct or indirect impacts on the ecological environment due to the changes in the water area, the depth, width and direction of the channel, and sometimes even chain effects. Therefore, during the implementation of the dredging project, it is necessary to ensure that a dredging operation not only meets the design requirements but also effectively protects the ecological environment.

2.Ecological impact of dredging construction

With the development of the dredging industry, the number of pollutants in rivers and lakes increases year by year. For example, bottom sediment and nutrient uptake of the contaminants often sediments. To clean up the water and sediment during the period of dredging, it will exacerbate bottom mud churn, cause pollutants released into the water and nutrient of sediment, cause water pollution and eutrophication. A series of biological reproduction and growth of survival in water bring great threat, even lead to negative dredging effects on fishes. Therefore, in the dredging construction, the pollutants in the channel must be treated to reduce the pollution of water quality. In addition, during the dredging of the channel, the construction noise and the application of ships will also bring great pollution to the water area. During the construction process, it may cause some dredging disadvantages. Different levels of noise will be generated. However, it will have a relatively large impact on the aquatic life around the port channel, and even cause the death of aquatic life in serious cases. In addition, engineering ships are usually docked in the water around the construction channel, and some ships may leak oil after long-term application. All kinds of garbage are often collected around the ships, which will cause pollution to some water bodies. Special attention should also be paid to the fact that once the dredging engineers abandon the soil at will during the dredging process, it will bring very serious consequences, which will pollute the water quality of the whole abandoned soil area, thus causing great damage to the local environment, and also prevent secondary pollution caused by the leakage of sediment during transportation.

3.Environmental protection measures to be taken in the waterway dredging business

 3.1 Certain construction measures shall be taken according to environmental protection requirements before construction starts

Before the construction starts, the possible pollution sources in the construction waters should be investigated to understand the composition of sediments at the bottom of the channel, and relevant construction technology schemes should be formulated accordingly. The dripping sediment should be calculated on the base of all the survey data, and then the various links of channel dredging should be studied and formulated, and the scale, scope, and methods of channel dredging should be formulated and divided one by one. In addition, according to the breeding cycle of aquatic organisms, the construction time of the channel dredging project should be adjusted accordingly to avoid the breeding season of aquatic organisms as far as possible. According to experience, since most aquatic organisms have migrated away in winter, the best construction time of general channel dredging is the best at that time.

3.2 Choose reasonable construction method

When dredging the channel, construction vessels should reduce the frequency of agitation at the bottom of the channel to prevent the increased diffusion of organic salts and inorganic substances in sediments. It is required to strictly control the depth and precision of excavation in accordance with the design requirements for dredging boat construction and to minimize the frequency of shallow sweeping and avoid rework. If the rake suction vessel is used for dredging, the underwater overflow and environmental protection rake are adopted to reduce the impact on the water environment. When the excavated soil, sand and stone is transported by mud carrier and pipeline, the sealing inspection should be carried out in advance to prevent mud leakage. In areas with strict environmental protection requirements, anti-pollution screens and curtains can be set up in dredging areas and mud storage pits to reduce the scope of construction pollution.

 3.3 Scientific treatment of dredged soil

The depth of the pollutants deposited in the bottom layer of the water is usually 10-15 cm and kept within 1 m. The usual ways to treat dredged soil are mud throwing and blow filling. These two approaches also pose problems when dealing with underlying sediments. The mud disposal method is a low cost, but it will cause muddy water, and the settled soil will seriously affect the growth of underwater organisms. In particular, some construction ships are likely to have adverse effects on fishing grounds and other growing areas and bring economic losses when they are secretly abandoned to save costs. Therefore, some countries in the world have started to explicitly prohibit construction ships from carrying out mud disposal. Although the treatment method of blow filling reduces the pollution degree of water body and can be reused when blown to the land and it is a comprehensive treatment method compared with sludge disposal, it still brings about environmental problems. Due to the high moisture content of the soil underwater, the foundation is generally weak when it is blown to the land. If it needs to be developed and applied in the later stage, soft foundation treatment and other measures should be taken to solidify the foundation. Moreover, if the underwater soil contains pollutants, it is easy to cause secondary pollution around the land. In fact, the bottom of the sediment is rich in minerals, is a good renewable resource. If it is closed stacked after the centralized treatment, the development and reuse of resources, both can avoid environmental pollution, and can produce new resources. At present, the main areas of dredging reuse include building materials, agriculture, and forestry.

 3.4 Use environmentally friendly dredging equipment

Currently, the research and development of international environmental dredging equipment fall into two categories: 1. the original dredger is used for renovation to meet the requirements of environmental protection construction. 2. Special environmental protection dredging equipment. At present, the advanced dredging techniques are used in combination with the environmental protection reamer. Most of these dredging ships adopt DGPS for accurate positioning, which greatly improves the dredging accuracy and can reduce the suspension of sediments and release pollutants into the water.

 3.5 Enhance the environmental awareness of project managers

As an abstract ideology, the concept of environmental protection includes the level and degree of people’s awareness of environmental protection, needs to rely on people’s subjective initiative to complete. The above environmental protection measures are also based on the strong environmental awareness of managers to decide the implementation of environmental protection measures. At ordinary times, project managers need to strengthen their awareness of environmental protection through environmental training and lectures. At the same time, the company’s management training institutions should take environmental protection as an equally important position as quality, progress, and safety, and put it into the training content through brochures, slide shows, and video materials to enhance employees’ environmental awareness. At present, the construction units also pay more and more attention to the concept of environmental protection in the waterway dredging engineering bidding. For example, requires a specialized construction unit according to the construction technology of environment protection measures. When the construction organizations design the compilation to environmental protection as a separate list a link is highlighted, specific environmental supervision bidding, and so on. All these are effective measures to strengthen the importance of project managers for environmental protection.

4.Conclusion

Nowadays, environmental awareness is greater in China. To do a good job in environmental protection is to do a good job in economic progress and development. Port-channel is an important part of water transportation and plays an important role in the whole transportation system. However, port-channel is easy silting and needs to be dredged. However, while strengthening the dredging of ports and waterways, we should also adhere to the concept of environmental protection, minimize pollution in the construction process, realize the common development of economy and environmental protection, and promote the steady and healthy development of port and waterway dredging.