Research on Key Problems of New Environmental Protection Dredging

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The biggest difference between polluted sediment dredging and ordinary engineering dredging is that the former is integrated with the environmental protection concept and requirements, aiming at the removal of pollutants from the sediment and the change and improvement of water environment indicators. But the majority of the planning and implementation of the environmental protection dredging process, the starting point for the sediment pollutant removal and control of pollutants in the process of dredging relief, rarely considers the ecological problems caused by dredging and ecological protection. Study on ecological environmental protection dredging optimal control factor, water ecological restoration and protection of aquatic is conducive to the follow-up research, it is extremely necessary and urgent. Based on the focus on environmental protection dredging sediment pollutant removal currently, water ecological restoration after the dredging reconstruction are concerned about the problem of not enough analysis filter control factor affecting aquatic ecosystem survival, growth. And combined with the new ecological dredging method of terrain model is put forward for the subsequent ecological restoration build appropriate depth and basal conditions are needed to provide the solution.

1. Environmental dredging and ecological conservation paradox

In dredging construction practice, some ecological and environmental problems are increasingly prominent. Rational analysis, deep reflection, and comprehensive understanding of the impact of dredging are of great significance to the revision or promulgation of dredging regulations for sediment removal.

 1.1 Full section removal, surface removal and seed bank retention of sediment

The spatial difference in sediment pollution determines the layout of dredging. Under natural conditions, the pollutants in the bottom sediment are mainly concentrated in the sediment layer with a thickness of 20~50cm on the surface layer. However, due to the influence of external pollution and hydrodynamic environmental conditions, the distribution characteristics of pollutants in different regions are different, and the vertical horizon of the pollution layer is different. The thin layer of surface dredging not only removes the pollution but also completely removes the aquatic plants and large benthic seed banks that live in this layer, affecting the germplasm resources for subsequent ecological restoration. The larger the dredging section and scale, the more serious the influence is.

 1.2 Dredging depth and ecological restoration difficulty

There are no mature methods and accepted standards for the determination of ecological dredging depth of rivers and lakes for the purpose of reducing endogenous pollution. The sediment deposition rate and stratification characteristics can be used as reference factors to determine dredging depth. At present, the reference methods mainly include empirical value method, concentration control value method, background value comparison method, inflection point method and stratified release rate method. Too shallow dredging cannot effectively remove pollutants, and too deep dredging will change the shape of the bottom and adding the difficulty of repairing aquatic plants after dredging. The deeper the dredging, the more difficult the ecological restoration is under the same conditions.

 1.3 Minimize dredging size with maximum removal benefit

The ideal dredging scale of sediment is to remove the heavily polluted part of sediment with a small amount of dredging on the basis of full protection of the existing ecological good section, and to seek the best dredging effect, so as to realize the unification of environmental benefits, economic benefits and ecological benefits. The scale is a function of the dredging area and dredging depth. The more sample points and sections are monitored, the higher the upfront cost will be and the higher the construction accuracy will be required. The precision of dredging is closely related to the advancement of dredging equipment and the level of construction technology. According to the investigation and analysis of dredging equipment of ecological dredging projects at home and abroad, the control precision of vertical depth is generally 5~10 cm in practical construction.

 1.4 In situ cleaning and remote pollution

The pollutants in the bottom and overlying water in the ecological dredging area of the river and lake have been effectively controlled. However, some surface pollutants in the dredging process will have adverse effects on the surrounding water during the agitation and diffusion of construction. The dredged sludge and tail water of the sludge disposal site are external pollution to the storage site and the receiving water body, and there is a risk of leakage in long-distance transportation. The larger the scale of sediment removal, the higher the degree of pollution to other places, and the greater the risk of pollution to the water around the pipeline.

1.5 Dredging projects are lagging behind the scientific research support

After partial and small scale demonstration or experimental dredging, there is a trend of large-scale dredging in some areas. However, the research on key and mechanical problems, such as pollution division of supporting sediment, dredging scale and layout indicators and methods, is still in progress, especially on the evaluation of the dredging effect and monitoring of ecological restoration, which is relatively backward. Of course, this is related to the fact that river and lake dredging is an organic part of comprehensive water treatment, and it is difficult to quantify the comprehensive effect of dredging on water quality improvement and its contribution rate. However, it is the best way to make up for the lack of support and guide ecological dredging.

2. Research on key issues of dredging measures based on ecological protection and subsequent ecological restoration

 2.1 Ecological assessment objectives of environmental dredging

The effect of dredging should be evaluated comprehensively by the degree of completion of dredging target and the effect of dredging. While affirming its positive effects on the effective removal of pollutants and the increase of flood control and storage capacity, the adverse impact on ecology should not be ignored or avoided. At present, environmental protection dredging can only be used as an effective means to remove pollutants in an emergency. The long-term maintenance and improvement of water quality mainly depend on the purification of water quality of the water ecosystem and the play of ecological carrying function. Specifically, the proportion of aquatic vegetation must be certain after dredging. Therefore, the planning and design should focus on the dredging disturbance area and the area suitable for habitat construction after dredging, compare the changes of the habitat suitable for ecological restoration before and after dredging, increase the assessment of the suitable habitat construction after restoration and make up for the ecological damage caused by dredging. In principle, the area suitable for the growth of aquatic organisms should be maintained unchanged or improved to some extent.

 2.2 Selection of suitable ecological factors and construction of suitable habitat for aquatic organisms

2.2.1 Selection of ecological optimal control factors

The function of water ecological purification is closely related to the biological area after dredging. The ecological limiting factors affecting the water ecological restoration in dredging areas are the external habitats closely related to their living and growing, including water quality, water depth, bottom quality, illumination, wind waves, etc. For the aquatic organisms in the dredging area, the main difference is the change of water depth and the physical and chemical properties of the substrate before and after dredging. Under the same conditions, if the water depth is increased than before dredging, the underwater light field will be insufficient, making the underwater vegetation restoration more difficult. However, for shallow water bodies, the increase of water depth means that the disturbance effect of wind waves on sediment can be reduced to some extent, and the transparency will be improved accordingly. Underwater light intensity is closely related to water transparency, water depth and physicochemical properties of water quality, which can be reflected by water quality and water depth. The nutrient concentration in the water will become the threshold value for the growth and survival of aquatic organisms. Dredging can alleviate this situation to a certain extent, so it is not an important limiting factor after dredging. Under the influence of wind and waves, the bottom material will be suspended or disturbed and released to the overlying water. Its physical and chemical properties will affect the growth and distribution of immortal organisms. To sum up, the water depth and bottom quality can be used as the optimal control factors for ecological restoration after environmental dredging.

2.2.2 Aquatic organisms are suitable for deepwater habitat.

Biology and environment are coevolutionary, and aquatic plants and benthic animals in particular water bodies have their suitable living conditions. In rivers dredging depth, all kinds of aquatic plants arguably suitable growth conditions of water depth data are its pre-conditions. Rich and varied underwater terrains should be determined and shaped based on the current topography, bottom elevation, current water depth and the changes before and after dredging, so as to provide a good external habitat for the water ecosystem to play its ecological purification function.

2.2.3 Basal-textured habitat

Physical and chemical properties of substrates, such as hardness, the thickness of loam, and sediment characteristics, all affect the biological distribution of growth and habitat on them. At low nutrient concentration, organic substances, mineral elements and nutrients in the substrate are necessary for the normal growth of submerged plants. But at high nutrient concentration, the substrate may exert stress and inhibition on the growth of submerged plants. According to research, too hard or too soft sediments are not conducive to the growth of aquatic plants, high nutrient concentration will cause damage to aquatic plants, and eutrophication water is not conducive to the growth of aquatic plants to a large extent. When dredging depth, suitable depth and basement properties cannot be taken into account, the following treatment methods and sequence are recommended: It is better to meet the maximum pollution removal requirements first and then backfill loam according to the appropriate water depth. Next, according to the physical and chemical properties of the soil in the dredging area, the dredging depth should be reduced appropriately, and the suitable soil layer inherent in the bottom mud should be used as the new growing substrate after dredging. Finally, it is necessary to remove pollutants to the maximum extent, so that the water ecosystem can recover slowly after the water quality improves and transparency increases in the future. However, phased dredging should be adopted to create conditions and buffer time for water ecological restoration.

 2.3 Relationship between dredging pattern, layout and scale, and ecological protection and restoration

2.3.1 Relationship between dredging and other control measures

Sediment dredging is an organic unit in the comprehensive measures of river and lake pollution. On the basis of economic benefit analysis, the sequence and combination of various control projects in the comprehensive treatment of river and lake water environment are reasonably arranged, and the external source control and management are studied to ensure the dredging effect.

2.3.2 Influence of dredging layout on water ecosystem construction

The function of water ecological purification after dredging is closely related to the total area and layout of the water ecosystem. Under the premise that guarantees effectively remove endogenous pollution of lakes, combined with good ecological protection, is advantageous to the aspects such as ecological restoration after dredging, choose chip dredging, spacing strip dredging, local dot pit way dredging in rivers upstream and downstream, the full reasonable layout, forming different shades, habitat for a variety of underwater terrain to lay the foundation for the follow-up of ecological restoration.

2.3.3 The establishment of a water ecosystem in water level fluctuation zone combined with bank line regulation and bank revetment construction.

Under the influence of water diversion in the plain area, river basin flood control and season, the water level of rivers and lakes fluctuates within and between years, forming the water-level fluctuation zone. In combination with the regulation of river and lake shorelines, the form of bank protection is adjusted. The dredged silt is used in the underwater shoreline shorelines to build the habitat of different shorelines, so as to form the natural wetlands of river and lake shorelines and make up for the impact of bank protection construction on the encroachment of natural shoal wetlands.

3. Conclusion

The underwater topography is an important habitat for aquatic life. River and lake dredging will change the underwater topography. The reconstruction is an important means to adjust the elements of lakes and rivers. On the basis of analyzing the purpose, effect and influence of dredging, and from the perspective of environmental protection and subsequent ecological restoration, the optimal control factors of environmental dredging of sediment are selected as water depth and substrate. A new type of dredging measure, which can be combined with the dredging of sediment, is put forward to provide a new idea for the transition from environmental protection dredging to ecological dredging.

 

Influence of Estuarine Dredging on Environment

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Dredging is conducive to flood discharge and navigation and can eliminate pollution hazards after removing silt containing pollutants. At the same time, it will have many adverse effects, including local turbidity, saltwater wedge retrogression, ecological environment changes, etc.

1. Abstract

The estuary is the confluence area of the sea and river. The dynamic conditions and the evolution process of the riverbed are complicated due to the dual action of tidal wave and river. When the estuary is dredged and the soil is disposed of, it will have more complicated impacts on the surrounding environment. With the development of dredging technology, the concept of dredging not only refers to the navigation dredging at the shoal reach but also is an important measure for flood control, disaster reduction and elimination of environmental pollution. However, during the dredging process of estuaries, it is inevitable to have negative impacts on the environment. For example, mechanical agitation or excavation may cause the bottom sand to rise, resulting in local turbidity and so on. In addition, the dredging depth of the channel in the estuary will affect the upstream distance of the salt wedge, thus changing the distribution of salt in the upstream, and having some adverse effects on the surrounding ecological environment.

2. Environmental impact of dredging

Dredging is the use of dredging equipment to move sediment underwater to other waters or land. Since dredging changes the local environment, flood control dredging in water conservancy, navigation dredging in shipping, and environmental dredging in environmental protection will have a positive or negative impact on the environment.

 2.1 The positive dredging effects

2.1.1 Dredging for flood control

Estuarine shrinkage is a serious sediment problem in recent years. All estuaries have tidal gates to hold back the tide, to control salinization, and to store freshwater. The establishment of tidal sluice changed the dynamic condition of the estuary area and brought serious siltation to the downstream of the sluice. In order to be able to open the sluice normally to drain flood, the silt under the floodgate must be removed every year. After dredging the river mouth, it can stabilize the river mouth, and ensure the smooth discharge of the flood of these rivers, protect the safety of people’s lives and property, and avoid the water logging disaster.

2.1.2 Navigation dredging

With the development of economy and trade, the demand for water transportation is constantly expanding, especially with the increasingly busy coastal transport and Marine transport and the transport ships are gradually developing to large scale, while the lack of water depth in the channel at the mouth of the river often becomes the bottleneck of regional social and economic development.

P.Brunn (1976) pointed out that it is impossible to maintain navigable water depth in estuaries without necessary dredging. It can be seen that dredging is a major measure to improve the navigable water depth of estuaries. The deepening of navigable water depth will certainly produce better social benefits and, from a certain point of view, will also have a beneficial impact on the environment. For example, the natural depth of the Yangtze estuary channel is only 6m, 1000 tons of ships have to enter the port by the tide or load reduction. After the first phase of the Yangtze estuary deepwater channel regulation project, the water depth has been increased to 8.5m, and the fourth-generation container ship carrying 4,000 teu only needs to unload 1,000 teu before entering the port. Before regulation, 2000 teus need to be removed. Meanwhile, the channel after regulation can be two-way navigation, and the speed is also increased from 8kn to 12kn. It is expected that after the second and third phases of the dredging project, the water depth can continuously reach 10.0m and 12.5m, and the fifth and sixth generation containers and 10,000-ton cargo ships can enter the port by the tide.

2.1.3 Environmental dredging

With the enhancement of environmental protection awareness, the harm of underwater pollutants to the environment has gradually attracted people’s attention. Environmental dredging is an important measure in water environment comprehensive remediation, and its status and function have been revealed. Environmental dredging plays an important role in ecosystem restoration. Dredging also removes heavy metal pollution and reduces the release of nutrient solutions over time. Estuarine is the intersection of river and sea. Pollutants from river runoff and ocean tide often accumulate and deposit in the estuarine area, causing environmental pollution. However, estuarine areas， where the economy is prosperous and the population is dense will cause greater harm and people should pay attention.

 2.2 Negative dredging effects

2.2.1 Suspension of bottom sediment

Mechanical agitation during dredging will cause the suspension of bottom sediment, and during the transfer of dredged material, the sand will also cause local water turbidity. There are main measures to control such pollution: (1) the dredging with the rake suction dredger (the rake head is installed with movable closing plate) can not only avoid the sediment from falling, but also prevent the water from flowing inwards. (2) Using the often-used lake dredging methods, a closed net curtain is used to enclose several layers in the dredging area to prevent muddy water from flowing out. However, since the high flow velocity in the estuarine area, the practicability of this method needs to be discussed.

2.2.2 Retransport of polluting substances

During dredging and dredging operations, bottom sediments are disturbed and re-suspended. Suspended particles may release toxic substances and remain in the water, posing a potential hazard to local aquatic life. Moreover, the dual effects of the tidal waves and rivers in estuaries are more likely to cause the re-transport of toxic substances. At the same time, excavated silt containing toxic substances will also cause secondary pollution if not properly handled.

2.2.3 The saltwater wedge goes up

After the estuary is dredged, the siltation position will move up with the saltwater wedge upstream. Usually, the upstream of the saltwater wedge is controlled by many factors, but water depth is the most important. The lower reaches of tidal estuaries are usually dredged to improve navigation conditions. But any deepening and small changes in the channel affect the distribution of salt in the upper reaches and may lead to greater changes in the length of the saltwater wedge upstream. For example, the Mississippi River in the United States is a high-stratified river estuary. Before treatment, the gate sand ratio is relatively stable, the water depth can be maintained at 2.74m, and the saltwater wedge is not far upstream. After the estuary was dredged to a depth of 12.2m (southwest passage), the saltwater wedge went up to 160~200km, and the silt position also moved up and down with the saltwater wedge. However, the change of the distribution of the upstream salt content will inevitably affect the freshwater supply and drinking water quality of towns on both sides of the river, and cause the corresponding land salinization and ecological environment changes. To control or improve these problems, some guidance projects must be taken. It means that the combination of regulation and dredging is an effective way to control tidal estuary, but the negative impact of dredging on the environment and the countermeasures taken still need to be further studied.

2.2.4 Enormous pressure on the environment generated by dredged material

Dredging is accompanied by a large amount of dredging spoil. For example, the whole project in the Yangtze estuary deepwater channel regulation will produce 243.86 million cubic meters of dredging spoil. If placed on land, it will require a large area of compressed wasteland, and the fine particles in the dredging soil after drying will move with the wind, causing air pollution; If cast into the water, it will lead to the increase of sediment concentration in local waters of the sludging area, and may also cause sediment deposition in other estuaries under the action of coastal sediment transport.

2.2.5 Fertilization of water quality

When dredging, mechanical agitation causes fine particles to be suspended, this may release ammonia and phosphates and “fertilize” the water, resulting in environmental dredging not achieving the desired results. For example, during environmental dredging in the Taihu lake basin, although certain measures have been taken to prevent the spread of suspended sediment, the “fertilization” of water quality has not been effectively prevented, causing the proliferation of plankton and algae, which consume a large amount of dissolved oxygen in the water, resulting in hypoxia of water quality and aggravating other types of pollution. Therefore, dredging sediment is not a necessary and sufficient condition for controlling lake eutrophication. Moreover, in estuaries, where the flow rate is relatively high, dissolved contaminants are more likely to be carried away. It’s equivalent to diluting the concentration of dredged areas which results in more dissolved contaminants into the water and causes more widespread pollution. Therefore, attention should be paid to the cost-benefit ratio of dredging as an environmental engineering and its possible negative impact on ecological restoration.

2.2.6 Other effects

The environmental effects of dredging estuaries are complex and have many aspects. The change of runoff into the sea with the nutrient salt and pollutant flux it carries, and the change of bed bottom will also lead to the change of the ecological environment will affect the reproduction and growth of aquatic animals and plants or the migration conditions of birds. There are also environmental problems caused by dredging: (1) Oxygen consumption. (2) Reduce sea life. (3) Changing the nutrient levels of seawater, etc.

3. Environmental impact of dredging material

There is a lot of dredging waste with the dredging process. The environmental impact of dredging results is obvious: proper disposal can turn waste into treasure and obtain huge economic and social benefits; Bad or improper treatment can become a burden, causing greater damage to the environment. Therefore, the disposal and utilization of dredged soil should be emphasized when discussing the impact of dredged soil on the environment. This research emphasizes on how to minimize the adverse impact of dredged soil on the environment and maximize its utilization value.

 3.1 Make the most of dredging soil

Dredging has many uses and many benefits. In determining the dredging scheme, the properties of dredging soil should be carefully analyzed and the utilization value of dredged soil should be explored as much as possible. Generally speaking, dredging uses can be divided into three categories: engineering uses, agricultural and product uses and landscaping uses. Its uses can be divided into the following categories: (1) Construction and other engineering uses, including port, airport construction, urban and residential construction, etc. Such as Bordeaux, Le Havre, Rouen and other ports in France, dredging soil will be used to fill the land for port construction and development of industrial and agricultural land. (2) Building materials, such as cement added to solidify them, are made into building blocks. (3) Replacement backfill. (4) Coastal protection and erosion control. (5) Artificial fill beach. (6) Covering, i.e. using clean dredged material to cover the contaminated dredging material in the offshore backfill. (7) Wildlife habitat expansion. (8) For fishing. (9) Building national parks and recreation areas. (10) Used in agriculture, forestry and horticulture. (11) Backfill of open-pit mine and management of solid waste.

With the deepening of the work, the utilization scope of dredging soil will be expanded, and the economic and social benefits will be improved.

 3.2 Problems to be paid attention to when dredging soil utilization

In some estuarine areas, pollutants are found in underwater sediments due to the influence of industrial wastewater and pesticides. In the process of dredging soil utilization, we should not ignore the possible pollution and simply pursue dredging soil utilization. Direct application of contaminated dredged soil, resulting in the diffusion of pollution; the negative effects caused by environmental changes should not be emphasized unilaterally. Dredging soil should be treated as secondary pollution. This requires a correct assessment of the degree of contamination of dredged materials, and appropriate treatment of dredged soil that is indeed contaminated, such as the application of restrictive dredging technology, so that it can be applied in the construction of harbors and cities.

 

Progress in environmental dredging of river sediment

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Progress in environmental dredging of river sediment

With the increasing number of environmental dredging projects, the environmental protection dredging of river sediment has become a worldwide concern. The removal of nutrients, heavy metals and persistent organic compounds from sediment by dredging are obvious. Environmental dredging of sediment is time-effective for controlling river pollution. Dredging methods, dredging depth and dredging equipment are the main factors for dredging project design. This paper reviews the research progress of environmental dredging of sediment in order to deepen the understanding of environmental dredging of sediment.

Channel sediment is not only the central link of the nutrient cycle but also the main accumulation reservoir of nutrients, persistent organic pollutants and heavy metals. Even if exogenous sources are effectively controlled, the release of sediments by biological or physical factors may still lead to the poor state of water eutrophication or deterioration of water quality for a long period of time. Sediment dredging completely removes pollutants from the water system, which can greatly reduce the contribution rate of sediment to the overlying water, so as to solve the secondary pollution caused by endogenous release under biological or physical effects.

1.The concept of environmental dredging

Environmental dredging is the dredging projects aim at environmental protection. Environmental dredging refers to the technical method of removing surface sediments rich in nutrients, toxic chemicals and toxin bacteria by manual or mechanical means to reduce the endogenous load and pollution risk of sediment. Environmental protection dredging refers to a kind of dredging technique and technology that has the least impact on the environment and surrounding water during dredging, transportation and disposal of soil with no region. According to Kleeberg A and Kohl J G, environmental dredging is a technique to remove phosphorous rich surface sediments and control the release of phosphorus in order to obtain phosphorus constraints for algae growth. In conclusion, environmental dredging is an environmentally friendly dredging technique that USES mechanical methods to remove polluted sediment from rivers and lakes to provide phosphorus restriction conditions for algae growth.

2.Reference factors for the design of environmental dredging project

Environmental dredging is a new industry developed in the recent 30 years, and it is the edge engineering technology of water conservancy engineering, environmental engineering and dredging engineering. It is necessary to consider the technical feasibility and economic rationality of the dredging construction and meet the requirements of environmental protection. The main factors considered in the design of the project scheme are as follows.

2.1 Dredging depth

Usually, the polluted sediment thickness in the water is uneven and varies greatly. In dredging, not only the polluted bottom sediment should be removed, but also the over-excavation of non-polluted bottom sediment should be reduced as far as possible, so as to avoid damage, and at the same time, the treatment quantity and treatment cost of polluted bottom sediment should be reduced. Therefore, the dredging precision of dredging equipment is much higher than that of general channel dredging or water conservancy dredging. The bottom mud structure can be divided into three layers from the top to the bottom: the upper mud layer, the middle mud layer, the bottom soil layer. The upper floating layer is the main factor that most easily pollutes the overlying water body in the bottom mud and is the main object of environmental protection dredging. The middle silt layer should also be removed during dredging. The old soil layer at the bottom is a natural structure layer, which should be retained when dredging. Based on the analysis of the layered structure of sediment and its pollution characteristics, the dredging thickness of sediment is usually determined by the “inflection point method”, that is, the “inflection point” (the point where the pollutant concentration suddenly decreases) is found from the vertical distribution characteristics of pollutants along the thickness direction of sediment, and the thickness above the “inflection point” is taken as the dredging thickness. The determination of dredging depth should consider comprehensively the effects of removing endogenous pollution, controlling on higher aquatic plants and benthic animals, as well as the benefits to ecological restoration. In areas with low water tables, dredging should be prevented from damaging the impermeable layer of water and causing leakage. In addition, the impact of dredging on river safety should be considered and evaluated, such as the damage and collapse of shoreline and coastal buildings caused by dredging.

 2.2 Dredging measures

Dredging measures of sediment can be divided into two basic types: dry bed dredging and water dredging. Dry bed dredging is the draining of water prior to dredging. It is usually suitable for small ponds, reservoirs, or small river channels, and the sediment can be removed by manual cleaning, mechanical (bulldozer) cleaning, or hydraulic (water gun with a buoy and dredge pump) cleaning. Dry bed dredging is convenient for human and mechanical operation, and it is quite thorough, but it has a great impact on the ecology of the water body, and sometimes affects the safety of shoreline and surrounding buildings. In contrast, the operation with water has a wide range of applications, including river dredging and lake dredging.

 2.3 Dredging equipment

River dredging project has the characteristics of technology-intensive, capital intensive and management intensive. River dredging project relies on the dredging equipment (dredging vessel) that belongs to the non-standard equipment with high technical content. There are basically two types of dredging equipment for water operation: special dredging equipment and conventional dredger transformation. In the conventional dredger transformation, the main purpose is to develop the environmental protection reamer for dredging. The selection of dredging equipment needs to consider the availability of equipment, project time requirements, sediment transport distance, discharge head and physical and chemical characteristics of sediment, etc. The appropriate equipment should also be selected according to specific local conditions.

3. Major problems in the environmental dredging process presently

 3.1 Sediment disturbance

During dredging, mechanical agitation causes sediment to hang up. Sediments are the main storage sites for hydrophobic pops. The sediment overhang causes the release of ammonia and phosphates, which “fertilizes” the water and makes dredging less effective. For example, the concentration of herbicides in the water after dredging at Brighton harbor is higher than before. In addition, toxic substances such as heavy metals that are re-suspended due to disturbance can be potentially harmful to local aquatic life.

 3.2 Secondary contamination of sediment

Under the condition of leaching, the heavy metals, nitrogen, phosphorus and organic pollutants contained in the sediment may diffuse and transfer, causing secondary pollution to the environment. Especially the rosy metal in the bottom sediment has environmental persistence. The improper disposal will cause a serious consequence which is difficult to make up. Some developed countries even require an ecological risk assessment of contaminated sediment before dredging.

 3.3 Destruction of the physical structure at the bottom of the channel

The urban river, especially the river with a long history, has formed a good natural impermeable layer at the bottom because of historical accumulation. If it is not properly disposed of in the dredging process of bottom sediment, it will lead to the destruction of the natural impermeable layer, and thus destroy the physical structure at the bottom of the river. For example, the Sanjiadian reservoir in Beijing broke the seepage prevention layer at the bottom of the reservoir during the dredging process, resulting in serious leakage accidents.

 3.4 Destruction of benthic ecosystems

Due to the interference of various factors, environmental protection dredging will damage the benthic ecosystem. After the completion of the dredging project and before the establishment of the new benthic cattle system, the river ecosystem is fragile and prone to cause algal bloom.

4.Major directions for environmental dredging research

 4.1 Research on dredging technology of hydraulic mud suction and centrifugal dehydration

According to the characteristics of sediment pollution and the conditions of river dredging construction in the central built-up area, the combined dredging technology of hydraulic suction and site dewatering of dredged mud is an applicable technology for the cleaning of polluted sediment in urban river channels. The advantages are as follows: (1) Hydraulic dredging systems can effectively dredge the pollution accumulates sediment with a high content of organic matter and close specific gravity to water. (2) On-site centrifugal dewatering can greatly reduce the amount of dredged material to be transported and absorbed, which is suitable for the construction environment of the built-up area of the center. (3) The inherent shearing and particle hydraulic classification function of centrifugal dewatering can make the logistics after centrifugal dewatering split according to the degree of pollution, which can significantly reduce the amount of material to be disposed of. The technology is being rolled out in engineering practice.

 4.2 Precise improvement of cutter suction dredger

The research on precise dredging and high-concentration dredging technology of contaminated sediment is carried out abroad, the core of which is the development and introduction of advanced dredging equipment. At present, the more advanced environmental dredging method is to use the cutter suction dredger, which is directed by the pipe under the action of the mud pump to lift the surface sediment and long-distance transport to the land accumulation area (yard). High-precision technologies such as RTK-DGPS and underwater camera are gradually being widely used in the field of dredging in developed countries.

 4.3 Study on post-treatment of dredging sediment

In order to avoid secondary pollution, the research of sediment post-treatment focuses on the following aspects.

4.3.1 Disposal and utilization of contaminated sediment

The treatment of polluted bottom sludge has abandoned the previous single method of disposal of soil and is gradually developing towards the direction of resource utilization, reduction and harmless utilization. The main methods are storage and closure, containerization of contaminated sludge, bioremediation, and resource utilization. The combination of sludge disposal and comprehensive utilization should be encouraged when possible, and the waste bottom mud should be used to exchange soil with mud, make bricks, improve soil and fill lowland, etc. and to turn waste into treasure, which is not only beneficial to the protection of the ecological environment but also can produce certain economic and social benefits.

4.3.2 Storage yard surplus water treatment

The excess water discharged from the storage yard after the polluted sediment is deposited naturally is called surplus water. The remaining water contains a large number of organic compounds, nitrogen, phosphorus, heavy metals and other pollutants, which attach to fine particles and are suspended in the remaining water. The methods of residual water treatment include filtration, centrifugation, flocculation and sedimentation. Flocculation and sedimentation is the most commonly used method for residual water treatment. The advantages of flocculation precipitation method are that it does not need power, has great flexibility of operation, has strong adaptability to the change of water quality and quantity, is convenient for the supply of agents, and the treatment facilities cover a small area, and the facilities are simple, low cost and easy to build.

4.3.3 The desiccation of dredging mud

Polluted sediment belongs to silty soil with high organic content and the natural drying and consolidation process of silty soil is slow. Manual enhanced dehydration measures can be used when the drying process needs to be accelerated. The common methods of accelerating solidification in blowing-filling engineering include vacuum preloading method, stack-loading preloading method, dosing sedimentation method, mechanical dewatering method, active dewatering method in the storage yard, etc. In recent years, geotechnical bag filtration and dehydration technology have been gradually used in the sludge dehydration treatment of rivers, lakes and seas.

 4.4 The combination of dredging and ecological restoration

At present, the main research direction of river and lake eutrophication control is to combine dredging with river ecological reconstruction from the perspective of river ecological protection, and to give full consideration to the growth conditions and distribution of large aquatic plants when determining the dredging area and dredging depth.

 

Dredging of Inland Waterway Based on Environmental Protection

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Description: This article points out that the concept, content and core of inland waterway dredging problems combined with a section dredging renovation project and discusses the way of inland waterway dredging.

The ecological maintenance problems of channel dredging projects are becoming more and more obvious, and the challenges they face keep increasing. On the international scale, the real purpose of clearing the polluted silt from the lakes is to restore the ecology of the lakes, but the environmental dredging problem in the channel dredging level is not extensive. On the basis of discussing the nature of the action mechanism of waterway dredging on the natural environment, this study gives the definition of the corresponding environmental dredging of the waterway and provides the reference and theoretical basis for the corresponding environmental dredging of the waterway.

1.Definition, connotation and key problems of channel environmental dredging

 1.1 Definition of channel environmental dredging

The significance of environmental dredging lies in the removal of contaminated silt from the water. The foundation after dredging can continuously create more basic conditions for ecological restoration work. Its source is the integration of the project, environment and nature, and the sustainable deepening of the lake or the restoration of the lake “ecological niche”. The waterway dredging project joins the concept of environmental dredging. In the process of the deepened channel, pay attention to clean, properly solve sediment pollution in course; reduce the operation on the ecological environment pollution and damage. The secondary pollution in the whole process of dredging should be strictly managed to create corresponding conditions for the maintenance and restoration of the aquatic ecosystem in the waters where the shipping line is located.

 1.2 The connotation of environmental dredging of the waterway

The content of environmental dredging of air route mainly includes the following four levels: (1) Accurate dredging: high precision positioning and high accuracy mining to achieve the dredging requirements and minimize the corresponding over-excavation value, that is, to minimize the excavation of native soil under the precondition of the benefit of the bag-cutting dredging project. Normal hull operation accuracy is between 20cm and 50cm, and environmental dredging usually requires accuracy of less than 10cm. (2) diffusion benefits in dredging management: with the help of sophisticated dredging equipment and its corresponding technology, it can ensure its own high concentration of inhalation and manage the thick consistency of suspended solids. (3) Manage the leakage process of dredging soil transportation: carry out the corresponding detection on the dredging soil transportation process, control the total amount of leakage within the minimum range, and prevent the secondary pollution of water caused by the leakage in the transportation process. (4) Disposal and reuse of dredging soil: the materials contained in dredging soil are relatively complex and have different properties. Therefore, reasonable treatment is required to reduce the effect of dredging soil on the environment, so as to avoid secondary pollution and maximize the use of waste soil resources.

 1.3 The key problem of channel environmental dredging

Channel dredging mainly consists of three stages: dredging, transportation, and dredging disposal. How to reduce the secondary pollution caused by dredging and how to solve the dredging with high quality and high efficiency is the main content in the course of environmental dredging. The form of environmental dredging proposed in recent years is the main means to implement the ecological channel dredging. In this process, the detection of operation links and the disposal of dredging soil are the core of the environmental dredging process.

2.Construction process control of environmental dredging of the waterway

 2.1 Determine the appropriate construction period

It is relatively important to determine the dredging time of sediment, and the proper dredging time can minimize the dredging effect on the benthos. It is required to avoid the deterioration of water bodies in accordance with the pollution conditions in the areas waiting for dredging routes, and to avoid the regenerating period and breeding period of underwater species. Proper dredging time can effectively reduce the consistency of dredging suspended matter and reduce its effect on the water quality of the shipping line. The development of the project links the dredging to the corresponding sections of the operation, increases the construction period, minimizes the intensity of its operation and contributes to the restoration of the damaged natural environment. When dredging operations avoid the period of abundant water, the density of suspended matter decreases, and the effect on water quality is relatively weak.

 2.2 Strict control of secondary pollution

Secondary pollution is effectively controlled in the operation: (1) In order to reduce the pollution and diffusion of suspended substances, the relatively advanced harrow suction dredger is selected to carry out high-pressure flushing according to the consistency of fine sand and silty clay in each river section. DGPS (differential global positioning system) is used to carry out the corresponding plane management, and its positioning accuracy is within the error range of 3m. Strict management of the link and regular inspection of its equipment can ensure dredging accuracy. According to the soil condition, high-pressure flushing is opened to reduce the diffusion and pollution of pollutants. All discharge pipe flanges belong to cast steel members and have strong water-tight property. The rubber hose in the operating time is also stable and both ends of the flange turn into a general to prevent the former clamp connection leakage situation.

 2.3 Transport and disposal of dredged soil

The project reduces pollution in the dredged soil environment by limiting overflow time and avoiding overflows in transportation and limiting pumping areas. In the process of dumping sediment, the total amount of sediment should be controlled, and the independent inspection system of dredging vessel assembly should be carried out in time. After sediment casting, it is strictly forbidden to carry out relevant pumping work in the sediment casting section, so as to minimize the remaining water in the cabin and strengthen the tightness of the cabin.

 2.4 Effect testing after dredging

After the dredging process has been carried out, relevant assessments are carried out in the corresponding sections of the project to facilitate timely ecological restoration. After the project is carried out, the vegetation will be restored and the existing land environment will be restored in terms of the operation area. In the course of operation, consistent with the aquatic units, the operation of fishermen in the surrounding environment of the salvage work is limited.

3.Disposal of channel environmental dredging soil

 3.1 Analyze the properties of dredging soil

In the process of environmental dredging, it is not only necessary to study the sediment mechanism of the river bed, but also to establish the pollution status of dredging waste soil. A simple, efficient test to determine whether dredged soil is contaminated is: The bed wet sediment of the dredged site and the water in the sludging area were proportionally mixed at 1:4 and violently shaken. After 30min, the supernatant was allowed to precipitate for 1h, and then the corresponding filtration was carried out on the supernatant. Or it can be disposed of by centrifugation to remove granular ions and test for soluble contaminants and determine the total amount of oxygen required by the organism.

 3.2 How to deal with dredging soil

Dredging operations depend largely on their physical and chemical properties. According to the different functions of dredging sediment, with the help of the corresponding treatment properties, pollution can be prevented and its reuse can be realized.

3.2.1 Ordinary sediment

For conventional soils that are not contaminated nor have very low levels of contamination, they can be directly dumped or reused. In the process of dredging, the dredged soil is relatively clean and basically unloaded in the nearest dam field.

3.2.2 Polluted sediments

If the sediment is polluted, special treatment technology is required to prevent ecological pollution to the environment. Nowadays, the conventional treatment forms of contaminated dredging soil mainly include: (1) Store the contaminated sediment to the bottom of the sediment storage site or carry out the corresponding sediment puddle sealing measures. In the project of river section disposal, the corresponding landfill work is carried out on the soil quality of serious pollution. The actual means of operation is secondary segregation of the bottom sediment: The dirt is first separated from the garbage, and then the sediment from the sludge is separated from the sewage. The separated solid waste is transported to the “solid waste treatment plant of old ports” for relevant landfills, and the other mud is transported to the mud warehouse through a 5km pipeline with the help of a mud pump, and the corresponding organic treatment is carried out. Sewage can be recycled after treatment, but the sludge requires the corresponding landfills to be developed after sedimentation, including dredging waste soil with local pollution level in the standard category which is regarded as the soil used for greening. Such a form of disposal has relatively strong disposal benefits, and it has been widely used nowadays. It is suitable for all contaminated soil, and its corresponding cost is not large. (2) The contaminated sediment is excavated and transported to the factory for corresponding treatment and recycling. The dredging vessel only dredged mud to the corresponding processing plant. In the factory, the pollutants are removed in the form of physical, chemical, or biological forms, and then related recycling work is carried out on the treated soil. This treatment project has carried out relevant research and application on the reuse technology of contaminated sediment, including the use of cement materials in local dredging soil, which are used in the cement production process. This treatment form is relatively expensive and its corresponding treatment performance is poor.

4.Conclusion

In conclusion, the ecological effects of channel dredging are mainly reflected in the continuous deterioration of the living environment of aquatic organisms caused by the increase of suspended matter density and the re-suspension of polluted sediment during dredging. In the treatment project of this construction, with the help of control operation link and scientific selection of corresponding operation form, the density of suspended matter and its effect on the ecological environment are effectively controlled, the natural ecology of the project section is maintained, and the experience reference is provided for the disposal of polluted sediment by inner navigation environmental dredging.

 

Common difficulties of river dredging project and methods of silt treatment

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River has many advantages, such as flood control, drainage. However, in the course of river flow, there will be sediment deposition, not only raising the bed but also the long-term accumulation of silt that will cause eutrophication. This paper starts from the common difficulties of the river dredging project and then analyzes the methods of silt treatment, so as to provide relevant references for urban river dredging project and silt treatment.

River course plays a more and more important role in urban economic construction and development, which will inevitably result in the siltation of river course, bad dredging project, and increase eutrophication of the water body. Therefore, the quality of the river dredging project is related to the practical application effect of river dredging and the treatment measures of the mud generated in the dredging project are particularly important. A series of technical dredging methods must be taken to remove the dredging silt at the bottom of the river and properly dispose of the silt to improve water quality and enhance flood control and drainage capacity.

1.Common difficulties in river dredging

 1.1 Influence of construction back silting condition

Back-silting is the most difficult problem we often encounter in the course of river dredging construction, and the amount of back-silting is also the key to restrict the construction quality, which requires us to control the back-silting quantity within a certain threshold as much as possible. If the flow of the channel is large or the sedimentation rate is fast, the whole project may not be carried out and even the basic riverbed structure may be damaged.

 1.2 Influence of different bed layers

The riverbed is not all soil layer, construction often encounters special riverbed soil layer, such as clay layer and soft rock layer, etc. The construction of different bed layers is quite different. For example, the ordinary sediment bed contains special bed layers, which will reduce construction efficiency or even prevent construction and negatively affect the construction progress. Therefore, the change of soil layer should be paid attention to at any time in the excavation process. The depth of each excavation and installation should be determined to ensure the safety of dredging engineers and dredging equipment.

 1.3 Negative effects of hydro-meteorological conditions

River dredging projects are operated on water and are easily affected by hydro-meteorological conditions, which are mostly negative. Hydrological conditions are reflected by the river’s flow rate, flow direction, water level change, etc. While meteorological conditions are mainly reflected by wind, precipitation, etc., all of which are force majeure factors and will bring difficulties to the construction. For example, in areas where the water flow is relatively rapid, the water level changes rapidly, which deepens the difficulty of excavation depth control.

2.Treatment of silt in dredging works

 2.1 Sludge treatment in ecological dredging

Silt occurs in the course of river course operation and blocks the river course, and the silt generated has high water content, low hardness and deposition for a long time to form a large number of toxic and harmful substances, which must be treated effectively to avoid secondary pollution to the environment. The traditional way of dredging rivers is to dig up the silt and pile it on the empty land, which is relatively simple but will have a negative impact on the urban environment. Way at present, we are exposed to the dredging of river silt that exists in the first name, mixing with a different particle size of sludge and elutriation after separation. Then using physical methods for sludge dewatering and drying to moisture content is below 30%, so as to achieve the goal of slud to recycle. Environmental dredging is a sustainable economic means, which plays a positive role in promoting the optimal allocation of various resources.

 2.2 Measures to treat sludge in the process of resource utilization

The sludge treatment measures in dredging projects are generally divided into polluted sludge treatment and pollution-free sludge treatment according to the properties of sludge. After classification, the sludge will be transported to the storage yard for turnover, and the surface treatment of the silt will be dried quickly. If the pollutant exceeds the standard, the pollutant content must be reduced first, and the treated sludge will be used for filling soil or berm. If there is no heavy metal pollution, the storage yard can be recycled and used as soon as possible. At present, the specific situation of dredging silt in various areas of the country is not the same, combined with the current environmental protection policy, in line with the principle of resource utilization, the use of silt treatment measures mainly as garden green fertilizer, energy utilization and fill soil embankment.

2.2.1 Garden green fertilizer

Environmental dredging sediment fertilizer has made certain achievements in foreign countries, urban river dredging construction after the formation of the high content of organic matter, nutrient-rich organic fertilizer through the technical improvement of sludge compost. After the sludge drying and deodorization treatment, the moisture content is low, small volume, facilitate transportation and processing of goods used in farmland and green manure. It can also be used as fertilizer for the green belt along the river, providing organic fertilizer for the landscape along the river, saving freight, and achieving economic and social benefits.

2.2.2 Energy utilization

Sludge energy utilization technology is often adopted by many developed countries in the world, including incineration and utilization, production of building materials and so on. Sludge incineration process can kill pathogenic bacteria and organic pollutants, but the high cost and large energy consumption will also discharge pollutants exceed the standard of smoke, so we usually do not use this method. Commonly, “mud energy utilization” refers to the production of building materials, such as cement, brick, and ceramicist. In addition, a small amount of industrial waste, such as slag and construction waste can be added to the sludge with the addition of coagulant for unburned bricks. It is a kind of mud treatment method with relatively mature technology and obvious economic benefit.

2.2.3 The filled soil dike dam

The water content of sludge can be reduced by sludge drying technology, the drying technology to join curing material make it become the general degree of soil so that we can set biochemical sludge resources and silt but due to the nature, characteristics and the influence of the adding amount of curing material. The filling effect of silt is general and sludge solidification processing cost is high thus limiting the promotion.

3.Conclusion

Above all, the purpose of the river dredging project is unblocked and improved exhaust port of flood control and water quality. Due to the narrow channel and garbage pollutants, the dredged water must be surveyed in all directions and must choose the right means of dredging. Dealing with the silt generated in the dredging process is especially important. The utilization value of sludge treatment products should be continuously developed to improve the recycling of resources. Considering the environmental health and safety, secondary pollution, long-term economic benefits and other aspects, the practical sludge treatment measures are selected to reduce the cost and develop the available value of silt.

 

Management methods of channel dredging project

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Waterway dredging is a complicated system engineering, which is necessary to ensure the corresponding management measures of engineering quality. The particularity of waterway dredging engineering is that it is a dynamic management project. With the continuous development of the dredging industry, the internal and external conditions of engineering will also change accordingly. Under this premise, in order to guarantee the maximum investment benefit of the project, the project should be managed, cost management and quality management. Waterway dredging engineering management to promote the development of our country water transportation enterprise plays an important role, waterway dredging companies’ management target, uses the way of governance, the method also has certain differences. This paper puts forward the focus in the next article’s management methods, to improve the effectiveness of the management of waterway dredging construction.

Compared with other modes of transport, waterway transport has certain advantages. The main reason is that waterway transport has the advantages of large freight volume, low freight, saving resources, saving investment, etc.

1.Regulation method of the channel dredging project

 1.1 Shallow shoal maintenance dredging

Shallow shoal maintenance dredging is a kind of dredging measure to maintain the channel standard. When dredging by this method, the two main problems are the avoidance of ships and the disposal of silt. Therefore, the relationship between dredger and dredging vessel and between dredger and silt transport should be properly handled. Usually, the former is easier to solve, so this paper focuses on the latter. The relationship between dredger work and silt transport needs to be handled according to the following points: When using mud barges for outward transportation, it is strictly forbidden to dump the silt in the channel, and ensure that the mud is cast in the designated position or the mud throwing area; When using the cutter suction dredger for construction, attention should be paid to whether the dredging pipeline is across the navigable channel. If it is across the navigable channel, the traffic volume of the vessel in the channel should also be taken into account. If the channel traffic volume is small, it can be used to break or limit navigation construction.

 1.2 Heave and maintenance work on the rapine

Heave maintenance construction is also a dredging measure used to maintain the standard of the channel. This method is mainly applicable to the rapid beach where the ship cannot sail automatically. In general, the advantage of this method is that it is more economical and efficient than other ships with high-power engines. In addition, some rapids may be affected by the environment, which may lead to the deterioration of beach conditions and further hinder the navigation of ships. In this case, maintenance works such as dredging and beach inspection must be used.

 1.3 Infrastructure dredging

Infrastructure dredging is mainly to improve the size of shipping channels and flow conditions. Generally speaking, infrastructure dredging is more suitable for shoals or shallow sections with little annual change. By infrastructure dredging, the non-navigable inlet channels in development and in the declining state can be improved into navigable channels that meet the navigation standards, but only if they are accurately judged and reasonably designed. In addition, for some rapids, a straight channel can be opened up by cutting nozzles and bending and straightening, so as to improve the flow conditions. But usually, this method requires a long time of riverbed evolution analysis and does scientific and reasonable design.

 1.4 Damming to divert water

The damming water diversion project plays an important role in improving navigation and water flow conditions. Damming water diversion refers to the construction of regulation structures such as spur dam, along the dam, submerged dam, and guide dam on the river channel. Its main role is to guide the flow of water and through the beam of water to attack the sand deep channel and so on. Usually, damming is suitable for the control of shoal. The regulating structures may be used alone, but in order to improve their effectiveness, they are usually used together with centralized regulating structures. In addition, in recent years, regulating structures also began to be used for rapids’ governance. The general practice is to combine the dam with a reef explosion. For some of the complex rapids, when dam and reef explosion is difficult to completely eliminate the jet stream and steep ratio drop, but also should be rapids and steep ratio drop area set, so as to more than a stranded beach into one.

2.Channel dredging project management

 2.1 Management of project progress

In the construction of the channel dredging project, due to the influence of various factors, the dredging project will inevitably be delayed. In this case, the most important thing is to timely adjust the project plan which requires the dredging engineer to be able to reasonably predict the factors affecting the construction schedule of the dredging project, so as to adjust the dredging equipment and human resources planning, etc. and to keep the overall construction schedule of the dredging project within a reasonable range. Specifically, the available construction schedule management methods mainly include the following four aspects: First of all, the contractor of the channel dredging project shall make a sound construction schedule and make a specific daily, monthly and ten-day operation plan. Secondly, the contractor shall calculate the daily earthwork volume and monthly earthwork volume by calculating the footage and width of the excavation and the average elevation of the dredging surface before dredging, which can be calculated according to the completed sections of the dredging area. Third, during the construction period, an intermediate measurement should be made every month, and take it as the construction progress of the project. Fourth, need to statistics dredger daily, monthly completed project amount, using earned value analysis to master the progress of the project. Finally, if the gap between the actual project progress and the planned progress is too large, besides adjusting the project plan, dredging equipment and manpower should also be increased.

 2.2 Engineering cost management

The cost management of the channel dredging project involves the whole process of the project. Therefore, for the cost management of the channel dredging project, it is necessary to coordinate the communication and cooperation of multiple departments. Generally speaking, the cost management of the channel dredging project can be divided into two parts: one is the project cost budget; the other is project cost control. Project cost budget is the foundation of project cost management among them. To ensure the accuracy of the project budget cost, the relevant standards should be followed in the development of the project budget cost. When making the project cost budget, we should take the total cost estimate as the premise, and allocate the project cost to each item according to the design scheme, and finally get the total project budget through the summary. In terms of project cost control, the two most important aspects are project capital expenditure and the project completion quantity of dredging. Engineering cost control needs to be completed with the help of certain cost management technology, which usually includes the following three methods: change control management, performance measurement and deviation management. Change control management is mainly to manage the construction scope and cost change process of the project. The project construction capital expenditure can be effectively controlled by strengthening the management of design depth, control the construction scope and cost change process. And the performance measurement is mainly through the project performance evaluation and earned value management to measure the completion of the project. Deviation management is to use the cost performance measurement index to evaluate the cost benchmark and analyze the reasons for deviation from the cost budget, and then take corrective measures.

 2.3 Project quality management

The quality management of waterway dredging project has a direct impact on ensuring the dredging effect of waterway, and the quality management level of waterway dredging project directly reflects the level of engineering technology. Therefore, the quality management of channel dredging is a very important aspect for managers. Generally speaking, the quality management of channel dredging works is mainly carried out from the following aspects: Above all, the action that should strengthen project inspect manage. The main reason is that project supervision is the necessary premise to ensure the quality of channel dredging project. In practice, managers should choose qualified supervision units to supervise the whole construction process of channel dredging project. In the process of supervision, the supervision unit must abide by the contract and supervise the project according to the supervision and acceptance system stipulated in the contract, so as to control the construction quality of the project. Secondly, the management of subcontracting should be strengthened. In practice, some sub-projects of waterway dredging project will be subcontracted to labor construction team. Under this premise, the qualification of subcontractors must be strictly examined in order to ensure the quality of subcontracted projects. In addition, managers should also supervise the construction process of subcontractors, so as to ensure the quality of subcontractors’ construction. Thirdly, the construction plan, and process management should be strengthened. To be specific, the manager must carefully review the construction organization design and construction plan, and then the construction organization design and construction plan can be implemented.

3.Conclusion

To sum up, channel dredging project management can effectively ensure the quality of engineering construction, while channel engineering management measures are to improve the navigation conditions or flow conditions of the channel through reasonable methods and to further improve the effectiveness of channel dredging project, which is conducive to promoting the development of China’s waterway transportation.