Hydraulic vs. Mechanical
"Environmental and public health experts are concerned that mechanical dredging poses health risks more significant than those calculated by the Environmental Protection Agency.
Mechanical dredging of the harbor has been opposed by the environmental group Buzzards Bay Coalition because it results in burying PCB-contaminated soil beneath the harbor, instead of trucking it to an approved disposal site in Michigan, as is done in hydraulic dredging."
Health risks posed by mechanical dredging worry experts South Coast Today, May 2, 2012,
http://www.southcoasttoday.com/apps/pbcs.dll/article?AID=/20120502/NEWS/205020345/-1/NEWS10
"Local newspapers report that the U.S. Army Corps of Engineers is considering changing the proposed method of dredging the Indiana Harbor and Shipping Canal. The Corps of Engineers announced at a meeting earlier this week at Riley Park that a hydraulic dredging method is being considered. Residents have criticized the plan that originally called for using a clam shell to remove dredged material from barges. Hydraulic dredging is potentially cheaper, cleaner, and safer, according to the Corps of Engineers officials."
Alternatives sought for Indiana Harbour dredging project Dredging News Online, May 7, 2004,
http://www.sandandgravel.com/news/article.asp?v1=5159
"Hydraulic dredging is typically used because it is generally cheaper than mechanical dredging for large amounts of sand."
Best Management Practices for Soft Engineering of Shorelines, Chapter 5, Constructing Islands for Habitat Rehabilitation in the Upper Mississippi River (Barry Johnson, U.S. Geological Survey and Jeff Janvrin, Wisconsin DNR).
"Sediment was successfully removed from a Peabody Coal Company pond near Macon, Missouri, by a hydraulic dredge. Previous attempts using land-based equipment had been unsatisfactory. They hydraulic-powered auger and submerged pump easily removed 882 m/sup 3/ (1154 yd/sup 3/) and pumped the slurry a distance of 305m (1,000 ft.) to a disposal area. The hydraulic dredge was more effective and cheaper to operate than land-based equipment. The dredge cost was $1.31/m/sup 3/ ($1.00/yd/sup 3/), the dragline cost was $6.54/m/sup 3/ ($5.00/yd/sup 3/) and the front end loader cost was $15.70/m/sup 3/ ($12.00/yd/sup 3/), under optimum conditions"
Hydraulic dredging, a sediment removal technique. Journal Article from Univ. Ky., Off. Eng. Serv., (Bull) Symposium on surface mining hydrology, sedimentology and reclamation; Spotts, J.W., Pgs. 91-95 1980 Dec 01
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