Army Corp says blasting and dredging for the 100 million dollar Port of Palm Beach expansion will adversely impact whales, sea turtles, sawfish, corals, seagrass, fishing and diving.
The project expected to last two years with construction 24 hours a day, seven days a week will produce silty water and dead sea life in the vicinity of Peanut Island and the Blue Heron Bridge.
Here are a few excerpts for Appendices D through G, available online at: http://www.saj.usace.army.mil/About/DivisionsOffices/Planning/EnvironmentalBranch/EnvironmentalDocuments.aspx#Palm_Beach
Biological Assessment to National Marine Fisheries Service Lake Worth Inlet Widening and Deepening Palm Beach County, Florida
The project proposes to widen and deepen Lake Worth Inlet navigation channel. The authorized project depths are as follows: entrance channel to a depth of 37 feet (from STA 30+00 to STA 47+00); from the inner channel to a depth of 33 feet; from the turning basin to a depth of 33 feet; and to a depth of 25 feet in the extended turning basin located north of the existing project basin. The existing settling basin and the extended settling basin are maintained at 35 feet and are located adjacent to the entrance channel and north jetty.
Where hard rock is encountered, the Corps anticipates that contractors could utilize other methods, including confined blasting or large cutterhead dredge equipment to pre-treat the rock prior to removal.
Protected Species Included in this Assessment
The Corps has reviewed the biological, status, threats and distribution information presented in this assessment and believes that the following species will be in or near the action area and thus may be affected by the proposed project: the five sea turtle species; humpback and sperm whales, Johnson’s seagrass and smalltooth sawfish.
Six species of endangered marine mammals may be found seasonally in the waters offshore southeastern Florida. The Corps believes that only the sperm and humpback whales may be adversely affected by activities associated with the proposed action. These effects would be a result of acoustic harassment.
The endangered Florida manatee (Trichecus manatus) and the American crocodile (Crocodylus acutus) also occur with the action area and the Corps has initiated consultation with the U.S. Fish and Wildlife Service concerning the effects of the proposed action on these species.
Effects of the Action on Protected Species.
As previously stated, the Corps believes that the loggerhead turtle, green turtle, smalltooth sawfish and Johnson’s seagrass have the potential to be effected by the proposed dredging project. The project may have the following adverse impacts on listed/protected species are:
-direct effect of blasting in the turning basin.
-direct effect of dredging activities
Sea turtles Specific information regarding the likely direct impact of explosives on sea turtles is not available. Studies regarding the impacts of relatively minuscule explosives on humans noted that minor injuries such as small bruises or perforations of the intestinal tract occasionally occur well beyond ranges in which human lung damage could occur (Christian and Gaspin, 1974). Christian and Gaspin (1974) note that these minor injuries could become serious if left unattended. Sea turtles with untreated internal injuries would have increased vulnerability to predators and disease. In the Environmental Impact Statement prepared by the Navy to consider the effects of explosives used in shipshock tests, nervous system damage was cited as a possible impact to sea turtles caused by blasting. Damage of the nervous system could kill sea turtles through disorientation and subsequent drowning.
Unconscious sea turtles that are not detected, removed and rehabilitated likely have low survival rates.
Blasting will affect nearby finfish and invertebrates and cause short-term changes to the physical characteristics of the benthos. Fish and invertebrates killed or injured by the blasting may provide a short-term enhancement of foraging opportunities for green and loggerhead sea turtles. Through new recruitment and local migrations, finfish and benthic invertebrates are expected eventually to repopulate the affected area.
Blasting rock underwater produces a pressure wave in water that can produce fish mortality. Different types of fish have different mortality thresholds. This depends on whether the fish dwell near the surface, on the bottom, or in between.
The magnitude of the pressure wave generated in greatly affected by the stemming of the blastholes, distance between holes, and the delay time of the holes.
Normally, mortality occurs in the range of 150-psi overpressure for fish. In practice this is a 75foot to 100-foot radius around the blasting area.
Johnson’s seagrass Areas of Johnson’s seagrass adjacent to construction activities may be temporarily affected by increased turbidity and lower water clarity during construction