United states department of interior bureau of ocean energy management



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2.6General Construction Methods


The proposed method to construct the beach and dune platforms on East Timbalier Island and the West Belle Headland would entail the placement of sediment in the Restoration Areas. Sediment would be excavated by dredges in the Borrow Areas and either pumped directly to the Restoration Areas through pipelines located in designated conveyance corridors or transported by barge or hopper dredge from the borrow area to a pump-out area where it will be unloaded and pumped to the Restoration Areas through a pipeline in a designated conveyance corridor. Bulldozers would be used to move and place the pipeline and to shape the sand for the dune and beach portions of the project. Bulldozers would shape pumped sand to create training dikes to help retain hydraulically dredged and placed sediment. Survey crews would place grade stakes to locate the Project features’ horizontal and vertical limits.

The proposed construction method to construct the marsh platforms on East Timbalier and the West Belle Headland would require construction of containment dikes to help retain hydraulically dredged sediment within the footprint of the marsh platform.

On East Timbalier Island, the marsh containment dike will be constructed from sand excavated from the Ship Shoal or South Pelto Borrow Areas, transported to the pump-out area, offloaded via the sediment pipeline, and deposited to create the dike. The sediment would be mechanically shaped.

The marsh containment dike for the West Belle Headland Restoration Area will be constructed with in-situ sediments excavated and placed by a barge mounted bucket excavator or track mounted articulated arm bucket excavators (marsh buggies). Sediment to create the marsh platform would be transported via pipeline and positioned within the marsh fill area with a marsh buggy. The containment dikes help retain hydraulically dredged sediment while the marsh platform undergoes compaction and dewatering and are expected to degrade naturally over time. If necessary, dikes would be gapped within the first three years to allow for tidal exchange with the created marsh and to prevent ponding of water within the containment area. Considerations regarding if and when mechanical gapping will be conducted will be based on site inspections and determinations will be made in cooperation with natural resource agencies.

Equipment would be transported to the construction site via barges, tugboats, and crew boats. In addition, there may be a quarter’s barge on site for housing the crew. Construction access to East Timbalier Island and the West Belle Headland will be limited to the permitted construction access corridors. Personnel transport would be facilitated by use of boats and/or small all-terrain vehicles.

Sand Fencing

The dune platform of all of the Project features will have sand fencing installed along the centerline. The single row of sand fence will promote deposition of windblown sand and conserve sand placed within the fill template. The sand fencing will be constructed of wooden slats, appropriately spaced laterally, and secured with fence wire to wooden posts to form a porous barrier constructed four (4) feet in height above the dune platform. Offset distance at fencing overlap locations vary from 3ft to 8ft, which allows for wildlife movement across the island.



Vegetative Plantings

Vegetative planting of the dune and marsh is a vital component of barrier island habitat restoration. All of the Project features include establishment of vegetation along the entire length of the dune and marsh platform at a planting density and composition similar to recent barrier island restoration projects in Louisiana. The entire dune platform will be planted immediately following construction. Vegetative plantings will be a separate contract and will be installed after construction during fall through early spring pending final completion, out of bird nesting season. The marsh will be planted in spring and the dune will be planted fall through early spring.

The vegetative plantings would include a mixture of some or all of the following herbaceous species: Bitter Panicum (Panicum amarum var. amarum ‘Fourchon’), Seashore Paspalum (Paspalum vaginatum ‘Brazoria’), Seacoast Bluestem (Schizachyrium maritimum ‘Timbalier’), Seashore Dropseed (Sporobolus virginicus), Sea Oat (Uniola paniculata ‘Caminada’), Marshhay Cordgrass (Spartina patens ‘Gulf Coast’), and Gulf Cordgrass (Spartina spartinae). Woody species would be planted landward of the restored dune and supratidal back berm area, at a planting density of fifteen (15) percent to mimic the sparsely vegetated native vegetative assembly that typically occurs in this area. Woody species for the dune and supratidal areas would primarily be Matrimony Vine (Lycium barbarum). After construction and consolidation, the newly created marsh platform will be planted with Smooth Cordgrass (Spartina alterniflora var. ‘Vermilion’) and other appropriate species.

3.0 -DESCRIPTION OF STATUS OF SPECIES


There are 23 animal and three (3) plant species under the jurisdiction of the USFWS and/or NMFS, presently classified as threatened or endangered within the State of Louisiana or GOM waters. Of the list of threatened or endangered species that inhabit Louisiana and the Northern Gulf of Mexico, only a few are known to occur in the Project area. Table 3-1 is a list of threatened and endangered species (USFWS, 2016a) within the Project area.

The following sections provide the Federal status, species descriptions, and habitat information for the threatened/endangered species and critical habitat found within the Project boundary. The Project boundary refers to Project features on East Timbalier Island, West Belle Pass Headland, borrow and pump-out areas. Much of this information was adapted from the Biological Assessments conducted for the Louisiana Coastal Area Terrebonne Basin Barrier Shoreline Restoration Feasibility Study (LCA TBBSR) (USACE, 2010) and Supplemental Biological Assessment for the Louisiana Island Restoration: Caillou Lake Headlands, Chenier-Ronquille and Shell Island (USFWS, 2014).


Table 3. Threatened and Endangered Species in Lafourche and Terrebonne Parish (Last Update: May 4, 2016)

Species

Scientific Name

Federal Status*

State Status

FISH

Sturgeon, Atlantic (Gulf subspecies)

Acipenser oxyrinchus desotoi

T

T

MARINE MAMMAL

Manatee, West Indian

Trichechus manatus

T

E

Whale, fin

Balaenoptera physalus

E

E

Whale, humpback

Megaptera novaeangliae

E

E

Whale, sei

Balaenoptera borealis

E

E

Whale, sperm

Physeter macrocephalus

E

E

REPTILE

Turtle, Green Sea

Chelonia mydas

T

T

Turtle, Hawksbill Sea

Eretmochelys impricate

E

E

Turtle, Kemp’s Ridley Sea

Lepidochelys kempii

E

E

Turtle, Leatherback Sea

Dermochelys coriacea

E

E

Turtle, Loggerhead Sea

Caretta caretta

T

T



Species

Scientific Name

Federal Status*

State

BIRD

Plover, Piping

Charadrius melodus

T, CH

T, E

Knot, Rufa Red

Calidris canutus rufa

T




* E=Endangered, T=Threatened, CH=Critical Habitat

Source: USFWS, last updated May 4, 2016; NMFS, accessed January 26, 2017

https://www.fws.gov/lafayette/pdf/LA_T&E_Species_List.pdf

http://sero.nmfs.noaa.gov/protected_resources/section_7/threatened_endangered/Documents/louisiana.pdf




Of the above-listed species potentially present in the action area, CPRA believes that only loggerhead, green, hawksbill, and Kemp's ridley sea turtles, and Atlantic sturgeon are vulnerable to injury and death from the use of hopper dredges for dredging the Ship Shoal borrow area for this project. In addition, CPRA believes that the piping plover and red knot are likely to be affected by the restoration portions of the Project.

Sperm whales occur in the GOM but are rare in inshore waters. Other endangered whales, including North Atlantic right whales and humpback whales, have been observed occasionally in the GOM. The individuals observed have likely been inexperienced juveniles straying from the normal range of these stocks. Blue, fin, or sei whales would not be adversely affected by hopper dredging operations; the possibility of dredge collisions is remote since these are deepwater species unlikely to be found near hopper dredging sites. There has never been a report of a whale taken by a hopper dredge. Based on the unlikelihood of their presence, feeding habits, and very low likelihood of hopper dredge interaction, the above-mentioned cetaceans are not considered further in this Assessment.



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