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Title: Supplemental Environmental Assessment: Removal of Concrete Sill, U.S. Marine Corps Support Facility - Blount Island, Duval County, Jacksonville, Florida
Authors: United States. Army. Corps of Engineers. Jacksonville District.
Keywords: Dredging
Dredging spoil
Jacksonville (Fla.)
Publisher: United States. Army. Corps of Engineers. Jacksonville District.
Abstract: The Federal action being evaluated in this document is the construction/modification of harbor features within the Congressionally authorized project at U.S. Marine Corps Support Facility – Blount Island (MCSF-BI), Duval County, Florida. The evaluation shall be consistent with the Council on Environmental Quality regulations that define Federal actions to include those actions “subject to federal control and responsibility” (40 CFR 1508.18). A detailed description of the proposed construction/modification of harbor features at MCSF-BI can be found in the Final Environmental Assessment (EA), Removal of Concrete Sill and Advance Maintenance Dredging of Marine Corps Facility – Blount Island, Jacksonville, Duval County, Florida (2010) and is incorporated herein by reference. This Supplemental Environmental Assessment (SEA) only considers the removal of the concrete sill located within the Marine Corps Terminal slip using a diamond wire saw. All other alternatives to remove the sill, as well as effects associated with each alternative, have been previously considered within the aforementioned 2010 EA. The concrete sill located at MCSF-BI would be cut into sections using a diamond wire saw, and the sections removed using an excavator type and/or large clamshell dredge. The reinforced concrete sill is 32.6 feet wide by 426.5 feet long and 14.5 feet deep. Currently the crest elevation is at -37.6 feet Mean Lower Low Water (MLLW). The diamond wire saw would be used to cut into the sill facilitating the removal of the concrete and rebar contents, resulting in an upper sill elevation of approximately -47 feet MLLW. Equipment such as a hydraulic power unit and the diamond wire saw are expected to be staged on a barge located over the particular area being cut. Operations may occur 24 hours a day using multiple saws, staff, and safety equipment for night operation. Dredging of approximately 3,000 cubic yards of material around the sill will be necessary in order to access the structure. It is assumed the dredging will be to approximately -47 feet MLLW and dredged material will be offloaded to the upland placement area at Dayson Island Dredged Material Management Area. Any sedimentary rock and sill material will be either placed at the upland disposal area or another pre-approved alternative location and the rebar will be disposed of at a local recycling facility.
Description: Environmental Assessment / Finding of No Significant Impact
Rights: Approved for Public Release; Distribution is Unlimited
Size: 42 pages / 3.297 Mb
Types of Materials: PDF/A
Appears in Collections:Environmental Documents

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