This depends on many factors: dredging method (hydraulic would be the most efficient in this case), availability of large and sufficiently close dewatering sites, and availability of sufficiently close sites which would accept/use the dewatered material. The material is free of toxic materials and is good topsoil.
The initial posting indicated a very broad range. Our engineering professional services contractor, GRAEF, is investigating the feasibility of a number of options, some of which could result in significant cost savings. The opinion of probable cost presented by GRAEF at a public meeting on June 28, in the range $8.4 million to $10.4 million, was based on the options under investigation at that time and preliminary information on those options. Since the opinion was prepared, the Conservancy Bay Peninsula extension, which was considered the most economical alternative, has been removed from further consideration due to the proposed regulatory restrictions, and the Conservancy Bay Upland, will be of limited use based on site constraints due to wetlands, forested areas, soils, and topography.
Details on this estimate are posted on the Ecosystem Restoration page, under Committee Documents, with the title “GRAEF Opinion of Probable Cost, June, 2014” .Please note that this informed opinion was based on many assumptions on conditions, which have changed and will continue to change as the investigation continues.
THE ACTUAL COST WILL NOT BE KNOWN UNTIL WE HAVE ACTUAL BIDS FROM CONTRACTORS. The riparian owners will NOT be asked to cast an up or down vote on this project based on estimates, but on bids from contractors. Meanwhile, preliminary estimates, based on similar projects elsewhere, help keep the public informed, although they give only “ball park” numbers.
As always, the cost of doing something should be measured against the cost of doing nothing. If dredging were not to be performed there would be a lot of hidden costs, not only to the riparians but to the surrounding community.
Please see these two related FAQ’s: