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Dredging is a well-known and highly documented process. Perhaps the most controversial and talked-about aspect of dredging is the impact on reef corals, sea grasses, spawning grounds and the general ecosystem within the dredging area. However, in some circumstances, dredging is used to improve the environment when contamination is present. Whether to improve the water environment, for maintenance, flood prevention or in preparation for construction work, dredging is an important part of waterways management. Yet, as well as improving dredging processes to make them less disruptive to the ecosystem, we must also consider how dredge spoils can be better handled, disposed of and reused.
Dredge spoils are typically referred to as a ‘by-product’ of the excavation process. Typical this ‘by-product’ is made up of sediment, soil, rock, shell material and sand. These materials can also contain high levels of contamination, depending on human activity in the area. Disposal methods of these materials range from confined disposal facilities to oceans and rivers. Yet we shouldn’t see dredge spoils as merely material that has been ‘taken out to be put back in elsewhere’.
Dredge spoils that are highly contaminated, or are suspected to be contaminated, should be treated before being returned to any water body or sent to landfill. Otherwise the problem is being moved around, rather than solved. By processing spoils, contamination in the form of heavy metals, hydrocarbons and other harmful constituents, is removed which ensures no further damage to the ecosystem if disposed of in the ocean or no potential harmful leaching if disposed of in landfill. Reducing or eliminating the hazardous content and decreasing the weight of the spoils through treatment and dewatering of the materials is also much more cost-effective if disposing of the waste in landfill or confined disposal facilities.
Dredged spoils also shouldn’t be merely seen as a ‘by-product’ of a process when they contain such valuable resources. Sand is one of the most sought-after resources in the world, and it is depleting fast. As dredged materials are excavated, valuable resources such as sand and stone can be treated, separated and resold for reuse. Applications in which these resources can be used include construction, landscaping and bedding among others. The recovered excess water typically goes through a tertiary treatment process and can be returned to the original water channel.
Dredging is an important waterways management method that is often a necessity for many reasons. What is missing in the dredging process is the sustainability in how we deal with the ‘by-products’. Once we begin to see dredging differently, we’ll realise that contaminated dredgings can’t be disposed of safely before treatment and treated dredged spoils contain resources waiting to be unlocked.
For more information on the part CDEnviro play in the treatment of dredged spoils, get in touch.
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