Port of Jacksonville, FL
The Jacksonville Port Authority has requested that the U.S. Army Corps of Engineers study the feasibility of deepening the Port of Jacksonville, Duval County, Florida. The Corps has considered dredging of about 21 miles extending from the mouth of the river at Mayport upriver to the vicinity of the Mathews Bridge. Alternative dredging depths under consideration were 39 to 45 feet. Economic analysis of the 21 miles of main channel resulted in justification for deepening about 15 miles of the main channel to a depth of 40' and 2 miles of the West Blount Island Channel to a depth of 38'.
The preferred plan (Plan A3) calls for dredging (without blasting) of this 15 miles of existing channel to a project depth of 40' and and 2 miles of the West Blount Island Channel to 38' under the locally preferred option (15 miles to 39' and 2 miles to 38' deep = NED Plan). Also a side shoal at the east entrance to Mill Cove would be removed and advanced maintenance zones would be dredged from within several areas of the channel. Material dredged from these efforts would be disposed of in existing disposal sites (Buck Island, east Bartram Island, and west Bartram Island), off-shore artificial reef (rock material), the beach or nearshore south of the harbor's entrance, or the Jacksonville Harbor ODMDS (if any material is not suitable for other disposal methods). The existing dikes at Bartram Island would be raised (within the existing foot print) to increase capacity. Dredging would be accomplished by hydraulic and/or mechanical dredging. Various alternatives were considered but those involving more dredging (entire 21 mile segment) were not economically justified. Widening was considered at some locations where passing or turning is required.
Impacted areas include the channel reaches, pipeline crossings to the disposal sites, and the disposal sites themselves. Upland sites considered are Bartram Island, several sites north of the river near the old Imeson Airport and the JEA site, Buck Island and the beach south of the south jetty at Mayport. Impacts from dredging and filling activities include loss of emergent vegetation around Bartram Island and river bottoms where fill occurs, possible effects on manatees from dredging and blasting (not in preferred plan). Mitigation for some of the alternatives that impact wetlands would have to include creation of marsh areas around Bartram Island and creation of habitat suitable for natural marshland creation. Wetland impacts from the preferred plan (unlike some alternatives) would be minimal since existing disposal areas would be used. Effects of discharge into waters of the United States is evaluated under Section 404 (Clean Water Act) guidelines. Other options for beneficial use of dredged material will be considered during the design phase.
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