Sediments like sand and silt naturally accumulate at the bottom of bodies of water. Dredge spoils are the organic matter removed during dredging, including sand, soil, silt, clay, debris and other organic sediment. Dredging happens for several reasons — maintaining channels for navigation, maintaining natural bodies of water like ponds, managing floods, protecting shoreline infrastructure, and removing contaminated sediment for environmental reasons. In all these forms of dredging, sediment is removed from the water and must then be properly reused or disposed of to minimize any environmental impact.
Understanding what dredge spoil is and knowing the best sediment management strategies should be a vital part of your dredging projects.
Sediment Management in Dredging
Though dredge spoils are typically composed of sand, soil and silt, the sediment may also contain heavy metals, nutrients and other contaminants. With this in mind, managing dredge spoils is vital for several reasons:
- Environmental conservation: Properly managing dredge spoils is key to protecting habitats that could be affected by sediments. Proper management can also help with conservation efforts by using spoils to rebuild wetlands.
- Water quality: Sediments can contain heavy metals and nutrients that can degrade water quality and affect the water’s appearance and aquatic life.
- Compliance: Some jurisdictions have regulations governing the disposal of dredge spoils. Adhering to these standards is vital for avoiding fines and other legal concerns that could delay projects.
- Health and safety: Some dredge soil may be contaminated with toxins that can pose a health and safety risk to humans and marine life. Proper sediment management is essential for reducing these risks.
Dredge Spoils Disposal
The most important part of disposing of dredging spoils is doing so responsibly and according to local or federal regulations. In the United States, you need a permit in compliance with the Marine Protection, Research and Sanctuaries Act (MPRSA) to dispose of uncontaminated dredge spoil material. The U.S. Army Corps of Engineers (USACE) is the federal body that authorizes and issues these kinds of permits.
Sediment is a natural part of the ecosystem, and most dredge spoils that are disposed of offshore come from dredging local harbors and channels. The dredge spoils are typically disposed of at established sites. Permits are required for all disposal of offshore dredge spoils and the dredging spoils must be properly treated before disposal. Additionally, dumping sewage sludge and other contaminated sediments is forbidden. When sediment is contaminated, one must follow regulatory procedures to dump the spoils legally at an appropriate landfill or plant.
Recycling and Reusing Dredge Spoils
While dumping dredge spoils is the most appropriate route in some circumstances, there are several other ways to use dredge spoils, including for construction projects, wetland restoration efforts and island creation.
Applications in Construction
Dredging can be an integral part of construction projects, especially along harbors and other waterways. The dredge spoils may be dewatered and treated before reuse — even as construction material. Additionally, a recent academic study on managing dredge spoils from construction and demolition concluded that promoting the reuse and recycling of dredge spoils could significantly contribute to yearly greenhouse gas reductions and possibly economic savings.
Wetland and Island Creation Projects
Dredge spoils can be used for conservation efforts like wetland restoration. An academic article from the Journal of Great Lakes Research documented restoration methods for two Lake Ontario wetland sites by dredging and using spoils.
Environmental dredging and using dredge spoils also have wonderful applications in creating small islands. One real-life case study that perfectly highlights the benefits of dredge spoils for natural restoration and creation projects is the dredge spoil islands in Mexico.
The project, which took place in 2012, used dredge spoils from creating the main canal of Bahía Tóbari, Sonora, Mexico, to create 11 small islands. The project was a success, as 12 breeding species of birds were surveyed on these islands.
Another beneficial use of dredge spoils was restoring a vanishing island called Sandbag Island in the channel between the Cape Lookout Lighthouse and Harkers Island. The human-made island was constructed using dredge spoils, and its creation dates back to at least 1970.
Waterbirds nested and foraged on the island, but it has slowly shrunk from 18 acres to 0.1 acres in 2019. Thankfully, a large-scale sediment removal project recently took place. The dredge spoils were used to restore the island and help ensure the waterbird colonies and the brown pelicans that had been spotted at Sandbag Island continued to thrive.
Advanced Tools for Sediment Management
Dredging and managing dredge spoils requires advanced tools. There are different types of dredging methods and equipment, but using submersible pumps is one of the most effective ways to dredge and manage spoils. The benefits of submersible pumps in dredging and dredge spoils management include:
- Using submersible pumps allows you to handle and remove large volumes of water and sediment continuously.
- While dredging, you experience lower turbidity since submersible pumps can reduce sediment disturbances.
- Submersible pumps make it easier to accomplish targeted sediment removal that minimizes environmental impact.
- These pumps can used to dredge in various settings, from coastal areas and rivers to lakes and ponds.
- They are suitable for dredging various sediment types, from mud and slurries to solid materials like rocks and debris.
- Since submersible pumps operate underwater, there is less risk of sediment spills or leaks and less equipment on the surface that can pose a hazard to operators.
- Submersible pumps have an accessible design with more variable speed options and quieter operation.
At GeoForm International, our Dino6 and Dino8 dredges and submersible pumps allow you to manage inaccessible projects and maintain a variety of waterbodies, from retention points to small marinas. These dependable and durable portable hydraulic dredges are easy to operate and feature low mobilization costs and a smaller environmental footprint than large excavators.
Contact GeoForm International for Submersible Pumps and Dredgers
Dredge spoils have unique applications in construction and conservation efforts, like wetland restoration and island creation. With the correct permits, dredge spoils can also be disposed of safely. Understanding how to manage dredge spoils is key to compliance and minimizing your projects’ environmental impact.
If you want to manage your dredging projects more effectively and find ways to be more efficient, GeoForm International can assist. You can rely on our knowledgeable team to consider your industry’s specific needs and provide you with industry-leading sediment removal equipment. Our dredges, dredge systems and submersible pumps are designed with innovation and quality in mind for the most efficient way to remove sediment and debris from water.
Contact GeoForm International today to learn more about our Dino6 and Dino8 Sediment Removal Systems and to discuss renting or buying our dredges or submersible pumps.