CAD cells are special permitted disposal areas that receive clean sand and material from dredging. CDF’s are generally located in close proximity to the dredge site, which minimizes the transportation component. CDF’s resemble a landfill in their basic design with exceptions.
CDF’s are special permitted landfills and CAD’s are deep – water disposal areas commonly found in the ocean. Methods for disposal include onsite and offsite landfills, confined disposal facilities (CDF) and confined aquatic disposal (CAD). The list of regulatory compliance requirements is long when it comes to managing dredge spoils. Clean sediments that are properly conditioned can create opportunities for beneficial use options near most dredge projects. Chemical technology, when performed separately or in combination with other dewatering processes, will further treat and modify the sediments to achieve soil like characteristics. Chemicals such as quicklime, cement, Calciment LKD (lime kiln dust) or other products with pozzolanic properties may be required to dry, modify and stabilize unworkable sediments.Other methods may include pug mills, custom soil-mixing boxes and excavators with an assortment of mixing head attachments for introducing reagents into the dredge spoils. Plate and frame filter presses, belt presses, centrifuges and hydrocyclones are options on large-scale dredging projects. Mechanical equipment of various types is used to physically remove excess water from sediment.In some large applications, the sediment remains sealed in the Geotubes in an onsite landfill. The use of lime-based reagents and other products commonly used to condition the sediment to achieve an optimum strength and moisture content. When opening a Geotube it is common for the sediment to need additional drying or stabilization to meet a required specification. The overall effectiveness of the dewatering process will depend on the sediment type. Geotubes are large membrane fabric bags that hold sediment to allow the solids settle while water slowly drains out over a period of months.What are the Different Types of Dredging? Federal, state or local laws govern the decision-making process for proper management of contaminated sediments. The type and levels of the contamination present will determine the options that are available for beneficial use or disposal. The proper management of contaminated sediments is a complex process. Contaminants enter waterways from many sources including surface runoff, municipal and industrial discharges, historical industrial practices, chemical spills and other sources. These dredge projects serve a critical role in protecting human life, water treatment systems, property and environment while ensuring safe shipping of goods to the market.Įnvironmental dredging targets the reduction of additional contaminate exposure by preventing the spread of contaminated sediments to other areas. Every year, the USACE must oversee the removal and management of millions of cubic yards of dredge spoils. Navigational dredging is an ongoing maintenance initiative that is under the direction of the US Army Corp of Engineers (USACE). Flood control and management during high flow conditions through a watershed.
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