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Taking of Marine Mammals Incidental to Specified Activities; Brunswick Harbor Deepening Project, Glynn County, Georgia

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National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.


Notice of receipt of application and proposed authorization for a small take exemption; request for comments.


NMFS has received a request from the U.S. Army Corps of Engineers-Savannah District (Corps) for an Incidental Harassment Authorization (IHA) to take small numbers of marine mammals, by harassment, incidental to deepening the inner harbor portion of the Brunswick Harbor in Glynn County, GA to a depth of -36 ft (-11 m) mean low water (MLW) in the inner harbor and -38 ft (-11.6 m) MLW across the bar channel. Under the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue a 1-year IHA, to the Corps to incidentally take, by harassment, small numbers of bottlenose dolphins (Tursiops truncatus) as a result of conducting this activity.


Comments and information must be received no later than February 17, 2004.


Comments on the application should be addressed to Michael Payne, Chief, Marine Mammal Conservation Division, Office of Protected Resources, NMFS, 1315 East-West Highway, Silver Spring, MD 20910-3225. Comments cannot be accepted if submitted via e-mail or the Internet. A copy of the application may be obtained by writing to this address or by telephoning the contact listed here. Publications referenced in this document are available for viewing, by appointment during regular business hours, at this address.

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Kenneth R. Hollingshead, NMFS, (301) 713-2322, ext 128.

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Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) direct the Secretary of Commerce to allow, upon request, the incidental, but not intentional, taking of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are issued or, if the taking is limited to harassment, a notice of a proposed authorization is provided to the public for review.

Permission may be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for subsistence uses and that the permissible methods of taking and requirements pertaining to the monitoring and reporting of such takings are set forth. NMFS has defined “negligible impact” in 50 CFR 216.103 as “an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.”

Subsection 101(a)(5)(D) of the MMPA established an expedited process by which citizens of the United States can apply for an authorization to incidentally take small numbers of marine mammals by harassment. The MMPA defines “harassment” as:

any act of pursuit, torment, or annoyance which (i) has the potential to injure a marine mammal or marine mammal stock in the wild [Level A harassment]; or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering [Level B harassment].

Subsection 101(a)(5)(D) establishes a 45-day time limit for NMFS review of an application followed by a 30-day public notice and comment period on any proposed authorizations for the incidental harassment of small numbers of marine mammals. Within 45 days of the close of the comment period, NMFS must either issue or deny issuance of the authorization.

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Summary of Request

On November 6, 2003, NMFS received a request from the Corps for an IHA to take bottlenose dolphins incidental to deepening the inner harbor portion of Brunswick Harbor during the Brunswick Harbor Deepening Project in Glynn County, GA. The Corps is proposing improvements to the existing navigation facilities at Brunswick Harbor. The proposal is a 6-ft (1.8 m) deepening of the navigation channel from the inner harbor across the bar channel to the ocean. The new authorized depth would range from a depth of -36 ft (-11 m) MLW in the inner harbor and -38 ft (-11.6 m) MLW across the bar channel. Completion of the dredging project is likely to employ a cutterhead dredge and confined blasting.

The Corps' proposed action is to modify the Brunswick Harbor Deepening Project to allow pretreatment (blasting) to improve performance of dredging. The proposal to allow blasting during dredging operations is limited to only the central section of the inner harbor work. The potential blast area runs primarily in a section of the South Brunswick River from near the mouth of Turtle River into St. Simons Sound, a length of approximately 26,500 ft (8077 m), and includes the first 2,250 ft (685.8 m) in East River and an addition 1000-ft (304.8 m) section about 6000 feet (1829 m) further upstream in East River. Approximately 590,000 cubic yards of material has been identified that may require blasting. No blasting would be allowed outside the reaches designated for blasting.

Pretreatment may include punch barge or blasting. Impacts from punch barge operations are expected to be similar to those for hydraulic cutterhead dredging. Material removed by dredging after pretreatment will be placed in the nearshore deposition areas near Jekyll Island or other areas approved by the resource agencies.

The Corps expects the contractor will employ underwater dredging and confined blasting to construct the project. Blasting has the potential to have adverse impacts on bottlenose dolphins inhabiting the area near the project. While the Corps does not presently have a blasting plan from the contractor, which will specifically identify the number of holes that will be drilled, the amount of explosives that will be used for each hole, the number of blasts per day (usually no more than three per day) or the number of days the construction is anticipated to take to complete, the Corps has provided a description of a completed project in San Juan Harbor, Puerto Rico to use as an example. For that project, the maximum weight of the explosives used for each event was 375 lbs (170 kg) and the contractors detonated explosives once or twice daily from July 16 to September 9, for a total of 38 individual detonations. Normal practice is for each charge to be placed approximately 5 - 10 ft (1.5 - 3 m) deep depending on how much rock needs to be broken and how deep a depth is sought. The charges are placed in the holes and tamped with rock. Therefore, if the total explosive weight needed is 375 lbs (170 kg) and they have 10 holes, they would average 37.5 lbs (17.0 kgs)/hole. However, the weight for the Corps' project in Brunswick Harbor is likely to be significantly less. Charge weight and other determinations are expected to be made by the Corps and the contractor approximately 30-60 days prior to commencement of the construction project. Because the charge weight and other information is not presently available, NMFS will require the Corps provide this information to NMFS, including calculations for impact/mitigation zones (for the protection of marine mammals and sea turtles from injury), prior to issuance of the IHA.

Description of the Marine Mammals Affected by the Activity

General information on marine mammal species found off the

East Coast of the United States can be found in Waring et al. (2001, 2002). This report is available at the following location:​prot_​res/​PR2/​Stock_​Assessment_​Program/​sars.html

The only marine mammal species likely to be found in Brunswick Harbor is the bottlenose dolphin and West Indian manatee (Trichechus manatus latirostris). Take authorizations for manatees are issued by the U.S. Fish and Wildlife Service (FWS). There is no stock assessment available concerning the status of bottlenose dolphins in the inshore and nearshore waters off Georgia. The Dolphin Project conducts surveys for dolphins along the GA coast, but they have not conducted any scientific surveys within the project area. Anecdotal information from Georgia Department of Natural Resources indicates there may be up to about 30 individuals within the project area. The defined stocks of bottlenose dolphins that reside closest to the project area are the western North Atlantic coastal and offshore stocks of bottlenose dolphins, with minimum populations estimated to be 2,482 for the coastal stock and 24,897 for the offshore stock. Additional assessment information for these two stocks is available at the previously mentioned URL.

Potential Effects on Marine Mammals

Potential impacts to marine mammals from explosive detonations could include both lethal and non-lethal injury, as well as Level B harassment. Marine mammals may be killed or injured as a result of an explosive detonation due to the response of air cavities in the body, such as the lungs and bubbles in the intestines. Effects are more likely to be most severe in near surface waters where the reflected shock wave creates a region of negative pressure called “cavitation.”

A second possible cause of mortality is the onset of extensive lung hemorrhage. Extensive lung hemorrhage is considered debilitating and potentially fatal. Suffocation caused by lung hemorrhage is likely to be the major cause of marine mammal death from underwater shock waves. The estimated range for the onset of extensive lung hemorrhage to marine mammals varies depending upon the animal's weight, with the smallest mammals having the greatest potential hazard range.

NMFS' criteria for determining non-lethal injury (Level A harassment) from explosives are the peak pressure that will result in: (1) the onset of slight lung hemorrhage, or (2) a 50-percent probability level for a rupture of the tympanic membrane. These are injuries from which animals would be expected to recover on their own. NMFS has also established dual criteria for what constitutes Level B acoustic harassment: (1) an energy-based TTS (temporary threshold shift) criterion from received sound levels 182 dB re 1 microPa2-sec cumulative energy flux in any 1/3 octave band above 100 Hz for odontocetes (derived from experiments with bottlenose dolphins (Ridgway et al., 1997; Schlundt et al., 2000)); and (2) 12 psi peak pressure cited by Ketten (1995) as associated with a safe outer limit for minimal, recoverable auditory trauma (i.e., TTS). The Level B Harassment zone therefore is the minimum distance at which neither criterion is exceeded.

Mitigation and Monitoring

In the absence of these acoustic measurements (because of the high cost and complex instrumentation needed), in order to protect endangered, threatened and protected species (manatees, dolphins, sea turtles), the following equations have been proposed by the Corps for blasting projects to determine zones for injury or mortality from an open water explosion and to Start Printed Page 2335assist the Corps in establishing mitigation to reduce impacts to the lowest level practicable. These equations are believed to be more conservative than the dual criteria since they are based on (1) a species more sensitive than dolphins (humans) and (2) unconfined charges and the proposed blasts in Brunswick Harbor will be confined (stemmed) charges. The equations are:

Caution Zone radius = 260 (lbs/delay)1/3

Safety Zone radius = 520 (lbs/delay)1/3

The caution zone represents the radius from the detonation beyond which mortality is not expected from an open-water blast. The safety zone is the approximate distance beyond which non-serious injury (Level A harassment) is unlikely from an open-water explosion. These zones will be used for implementing mitigation measures.

In Brunswick Harbor (or any area where explosives are required to obtain channel design depth), marine mammal/sea turtle protection measures will be employed by the Corps. For each explosive charge, the Corps proposes that detonation will not occur if a marine mammal is sighted by a dedicated marine mammal/sea turtle observer within an area that is two times the caution zone (called the marine mammal safety zone) where the caution zone is a circular area around the detonation site with the following radius: R = 260(W)1/3 (260 times the cube root of the weight of the explosive charge in pounds) where: R = radius of the caution zone in ft; W = weight of the explosive charge in lbs).

Although the caution zone is considered to be an area where mortality is possible, the Corps believes that because all explosive charges will be stemmed (placed in a drilled hole and tamped with rock), the areas for potential mortality and injury will be significantly smaller than this zone and therefore it is unlikely that even non-serious injury would occur if, as is believed to be the case, monitoring this zone is effective. For example, since bottlenose dolphins are commonly found on the surface of the water, implementation of a mitigation/monitoring program is expected by NMFS to be close to 100 percent effective.

According to the Corps, bottlenose dolphins and other marine mammals have not been documented as being directly affected by dredging activities and therefore the Corps does not anticipate any incidental harassment of bottlenose dolphins by dredging.

The Corps proposes to implement mitigation measures and a monitoring program that will establish both caution- and safety- zone radii to ensure that bottlenose dolphins will not be injured during blasting and that impacts will be at the lowest level practicable. Mitigation measures include: (1) confining the explosives in a hole with drill patterns restricted to a minimum of 8 ft (2.44 m) separation from any other loaded hole; (2) restricting the hours of detonation from 2 hours after sunrise to 1 hr before sunset to ensure adequate observation of marine mammals and sea turtles in the safety zone; (3) staggering the detonation for each explosive hole in order to spread the explosive's total overpressure over time, which in turn will reduce the radius of the caution zone; (4) capping the hole containing explosives with rock in order to reduce the outward potential of the blast, thereby reducing the chance of injuring a dolphin, manatee, or sea turtle; (5) matching, to the extent possible, the energy needed in the “work effort” of the borehole to the rock mass to minimize excess energy vented into the water column; and (6) conducting a marine mammal/sea turtle watch with no less than two qualified observers from a small water craft and/or an elevated platform on the explosives barge, from at least 30 minutes before to 30 minutes after each detonation to ensure that there are no marine mammals or sea turtles in the area at the time of detonation.

The observer monitoring program will take place in a circular area at least three times the radius of the above described caution zone (called the watch zone). Particular attention will be placed in a circular area with a radius of two times the caution zone (the marine mammal safety zone). Any marine mammal(s) in the caution zone, marine mammal safety zone, or watch zone will not be forced to move out of those zones by human intervention. Detonation will not occur until the animal(s) move(s) out of the caution zone and safety zone on its own volition.


Because this project may take a period of time longer than 1 year, NMFS is proposing to issue a 1-year IHA with the possibility for renewal upon application from the Corps. NMFS proposes to require the Corps to submit a report of activities 120 days before the expiration of the proposed IHA if the Corps plans to request a renewal of its IHA (and the proposed work has started), or within 120 days after the expiration of the IHA if a renewal is not being requested.

In the unlikely event a marine mammal or marine turtle is injured or killed during blasting, the Contractor shall immediately notify the NMFS Regional Office.

Endangered Species Act

Under section 7 of the ESA, NMFS has begun consultation on the proposed issuance of an IHA under section 101(a)(5)(D) of the MMPA for this activity. The Corps is consulting with FWS regarding effects on manatees. Consultation will be concluded prior to issuance of an IHA.

National Environmental Policy Act (NEPA)

The Corps prepared an Final Environmental Impact Statement (FEIS) in 1998 for the Brunswick Harbor Deepening Project. A copy of this document is available upon request (see ADDRESSES). NMFS is reviewing this FEIS in relation to the Corps' application and will determine the appropriate action to take under NEPA prior to making a determination on the issuance of an IHA.

Preliminary Conclusions

NMFS has preliminarily determined that the Corps' proposed action, including mitigation measures to protect marine mammals, should result, at worst, in the temporary modification in behavior by bottlenose dolphins, including temporarily vacating the area, may be made by these species to avoid the blasting activity and the potential for minor visual and acoustic disturbance from dredging and detonations. This action is expected to have a negligible impact on the affected species or stocks of marine mammals. In addition, no take by injury and/or death is anticipated, and harassment takes will be at the lowest level practicable due to incorporation of the mitigation measures described in this document.

Proposed Authorization

NMFS proposes to issue an IHA to the Corps for the harassment of small numbers of bottlenose dolphins incidental to deepening the inner harbor portion of Brunswick Harbor during the Brunswick Harbor Deepening Project in Glynn County, GA, provided the previously mentioned mitigation, monitoring, and reporting requirements are incorporated. NMFS has preliminarily determined that the proposed activity would result in the harassment of only small numbers of bottlenose dolphins and will have no more than a negligible impact on this marine mammal stock.

Information Solicited

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NMFS requests interested persons to submit comments, information, and suggestions concerning this request (see ADDRESSES).

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Dated: January 8, 2004.

Laurie K. Allen,

Director, Office of Protected Resources, National Marine Fisheries Service.

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[FR Doc. 04-901 Filed 1-14-04; 8:45 am]