Maintenance Dredging of the Isle au Haut Thoroughfare near Isle au Haut, Maine

The Isle au Haut Thoroughfare Federal Navigation Project, located between Isle au Haut, Maine and Kimball Island, Maine on the outskirts of Penobscot Bay, about six miles southeast of Stonington and 25 miles east of Rockland. The Federal Navigation Project consists of a -6-foot Mean Lower Low Water (MLLW) deep by 75-foot wide extending 1,200-foot in length through the shoal in the thoroughfare.

The proposed work consists of mechanically dredging approximately 3,355 cubic yards (cy) (1,183 cy required, plus 2,172 cy overdepth) of shoaled material consisting of highly compacted coarse sand and gravel, with areas of cobbles and isolated small boulders from the channel. Due to the material type, a mechanical dredge with the ability to dig highly compacted coarse sand and gravel will be required. The proposed action is to dredge to the authorized depth of -6-foot MLLW plus an additional 1-foot of required advance maintenance with an additional allowable 1-foot of overdepth (e.g. -7-foot MLLW required + 1-foot allowable OD). One-time, advanced maintenance is approved for the entirety of the 1200-foot long authorized channel. The dredged material will be placed at the Flake Island Disposal Site (FIDS) which is approximately 1 nautical mile northwest of the FNP. Placement of the dredged material (sand, gravel and cobble) at Flake Island Disposal Site will benefit both juvenile lobster habitat and juvenile cod by increasing the areas habitat complexity.

The anticipated allowable dredging window is between September 15 and April 1 to avoid impacts to spawning shellfish, benthic resources, Essential Fish Habitat (EFH) of federally managed species, threatened and endangered species and interactions with mobile fishing gear.