Additionally, it has been shown that deeper lakes are less prone to eutrophication (and algae growth) than shallow lakes. The subsequent effect on water quality can represent a cost burden to water treatment for potable purposes. These nutrients partition from the sediment into the water in the lake. For example, sediments can be laden with phosphate and other nutrients. Removal of lake sediment can have a positive impact on water quality. Reservoir costs include land for the lake, embankment, mitigation lands, appurtenances to the dam, such as pump stations, and pipelines to connect the lake to the treatment plant or raw water users. These variables are such that dredging cost estimates need to be based on site-specific circumstances. ThisĮxcavation is accomplished by lowering the lake water or waiting until drought conditions have caused the water surface to lower sufficiently to allow access by heavy highway equipment.Ĭomparing Dredging Costs to Construction of New Reservoirsĭredging costs are highly variable and driven by pipeline distance to dewatering sites, land costs for dewatering sites, weather, topography, and characteristics of bottom sediments. Mechanical dredging can also include the use of heavy highway equipment. This operation requires double handling of sediment and does not compare to hydraulic dredging on the basis of efficiency. The barges are moved to shore to unloading areas where the material is loaded on trucks for disposal. These operations use support barges to temporarily store dredged material. Mechanical dredging may involve draglines or clamshells that are mounted on barges. The hydraulic cutterhead dredge is the most common of the hydraulic dredges. Water jets, augers, or cutterheads are used to loosen the sediment. The pumped water creates a negative pressure that allows the sediment to be moved in slurry form through the pump and pipeline system. Hydraulic dredging is conducted by pumping water from the head of the dredge back through the vessel and out a pipeline to a dewatering area. Dredging can be done mechanically or hydraulically
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