International Dredging Review

International Dredging Review
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Bath Iron Works (BIW) and the U.S. Department of the Navy are seeking permits from the U.S. Army Corps of Engineers New England District to conduct maintenance dredging in the Kennebec River in Bath, Maine.

Both entities are seeking to renew previous 10-year permits to conduct periodic maintenance dredging activities. Bath Iron Works requires deeper waters for its shipbuilding operations, while the Navy is asking for dredging to facilitate movement of their ships in and out of the river, to and from Bath Iron Works.

Bath Iron Works originally received a Corps permit in November 2009, that authorized dredging up to 70,000 cubic yards at its dry dock sinking basin; up to 4,000 cubic yards at its dry dock landing grid; and up to 12,000 cubic yards at berthing piers 1,2 and 3. Dredged material from the sinking basin has been disposed of at an in-river site just south of Bath at Bluff Head. Dredged material from the other sites has been disposed of at an upland, non-wetland location. This permit expires on December 31, 2019.

Dredge volumes are expected to remain the same on average and no changes in dredge footprints are proposed. Dredge material at these locations will continue to be disposed of in the same manner as previously authorized. All dredging will be conducted by mechanical dredge. Based on historic shoaling rates, current and projected shipbuilding schedules at Bath Iron Works, and current budget forecasts, maintenance dredging is anticipated to be needed and performed at 2- to 3-year intervals (sinking basin), and annually for the other locations.

The first maintenance dredging event is proposed to occur during the winter of 2019/2020 (dry dock sinking basin, Pier 2, and the dry dock landing grid).

According to the Navy’s application, based on historic shoaling rates and current and projected Navy shipbuilding schedules at BIW, maintenance dredging is anticipated to be needed and performed at about three-year intervals. It is estimated that up to 50,000 cubic yards will be dredged off Doubling Point, within a 45-acre area to a depth of -32 feet mean lower low water and disposed of in-river. Up to 20,000 cubic yards will be dredged within a 31-acre area to a depth of -29 feet mean lower low water and disposed of near Jackknife Ledge at the mouth of the river.

The in-river disposal site is located just south of Bluff Head in about 95-100 feet of water. The Jackknife Ledge site is located about 0.4 nautical mile south of Jackknife Ledge and in about 40 to 50 feet of water. Both disposal sites have been used repeatedly for similar dredging conducted by the Corps and at the Bluff Head site, also by Bath Iron Works. Dredging would be conducted by hopper dredge and/or mechanical dredge.