[Federal Register Volume 60, Number 21 (Wednesday, February 1, 1995)]
[Notices]
[Pages 6345-6347]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-2493]



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DEPARTMENT OF TRANSPORTATION
Coast Guard
[CGD 91-202]
RIN 2115-AE10


Escort Vessels for Certain Oil Tankers

AGENCY: Coast Guard, DOT.

ACTION: Notice of availability.

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SUMMARY: A two-part study assessing the capability of escort tugs to 
control disabled tankers in Prince William Sound, Alaska, was 
commissioned by the Disabled Tanker Towing Study Group. The study 
specifically reviewed the present equipment, personnel, and procedures 
aboard the tankers and escort vessels operating in Prince William 
Sound, as well as the assist capabilities of the vessels presently in 
service for escorting these tankers. Both parts of the study have now 
been completed, and the U.S. Coast Guard has been granted permission to 
make it available to the public through the National Technical 
Information Service (NTIS).

ADDRESSES: The study is published as two separate parts, which may be 
ordered from the National Technical Information Service, Springfield, 
VA 22161 (phone orders (703) 487-4650; MasterCard, Visa, and American 
Express are accepted).

FOR FURTHER INFORMATION CONTACT: Thomas Jordan, Project Manager, OPA 90 
Staff, at U.S. Coast Guard Headquarters, 2100 Second Street, SW., 
Washington, DC 20593-0001, or by phone at (202) 267-6751. 
[[Page 6346]] 

SUPPLEMENTARY INFORMATION:

Background

    In the aftermath of the EXXON VALDEZ grounding, the state of Alaska 
established a contingency plan that includes provisions requiring laden 
tankers to be escorted through Prince William Sound. The escort vessels 
are expected to provide immediate assistance to a tanker in the event 
it suffers a propulsion or steering failure. The escort vessels also 
have some spill response capabilities. At present, there are 11 tugs 
and escort vessels in this service, operating out of Port Valdez and 
escorting tankers to Hinchinbrook Entrance.
    The Disabled Tanker Towing Study Group (DTTSG) was formed to review 
the present escort vessel practices in Prince William Sound. The DTTSG 
is formed of representatives from the Regional Citizen's Advisory 
Council (RCAC) for Prince William Sound, the Prince William Sound 
Tanker Association, the Alyeska Pipeline Service Company, the Alaska 
Department of Environmental Conservation, and the U.S. Coast Guard.
    The DTTSG commissioned The Glosten Associates, Inc., to prepare a 
two-part study. The first part conducted an expert review and 
evaluation of the emergency towing equipment aboard the tankers and 
escort vessels operating in Prince William Sound. The second part 
determined, by means of actual tanker/tug trials and computer 
simulation analyses, the capabilities of the escort vessels to actually 
control disabled tankers within the navigational limits of Prince 
William Sound, under various weather and operating conditions.
    Part 1 of the study was previously announced in a notice of 
availability published by the Coast Guard (59 FR 1411; January 10, 
1994). This present notice announces the availability of Part 2 of the 
study.

Ordering Information

    A synopsis of each part of the study is given here in order to 
provide the public with an overview of the study and its findings. 
Persons interested in obtaining full copies of the study may order it 
from the National Technical Information Service. The NTIS publication 
number for Part 1 of the study is PB94-120961 (price $27.00 for paper 
copy, or $12.50 for microfiche copy). The publication number for Part 2 
is PB95-147617 (price $119.00 for paper copy, or $52.00 for microfiche 
copy). A separate shipping and handling charge of $8.00 per order also 
applies. It generally takes 3 to 6 weeks to fill an order, unless a 
customer opts to pay for 24-hour turnaround.

Summary of Part 1

    Part 1 of the DTTS, entitled ``Evaluation of Existing Equipment, 
Personnel and Procedures,'' is summarized as follows:
    The DTTS is an objective evaluation by an experienced salvage 
towing master of the existing tugs, emergency towing equipment, towing 
practices, and discussion of alternate tug types.
    The Part 1 investigation was performed by subcontractor Smit Tak 
BV, based in Rotterdam. Captain Jan ter Haar, a senior Smit Tak salvage 
master, conducted interviews and observed normal operations and 
emergency drills in the Valdez area.
    All tankers calling at Valdez are required to carry specific 
emergency towing gear for rapid deployment and connection to a rescue 
tug. This ``Prince William Sound Emergency Towing Package'' is stowed 
and deployed differently on various vessels. Captain ter Haar 
recommends that all vessels adopt systems that can be readied for 
deployment in 15 minutes or less by a crew of two without using winch 
power.
    Captain ter Haar demonstrated, in drills, several effective 
alternative methods of making towing connections with the tugs' own 
gear, without deploying the ship's Prince William Sound Towing Package. 
Drills were also used to assess crew skills in towing large tankers in 
adverse weather with multiple tugs. He concludes that additional drills 
and training, both in the makeup and towing operations, would be 
beneficial.
    Captain ter Haar concludes that the vessels presently under 
contract are suitable for rescue towing in Prince William Sound under a 
full range of weather conditions. In the open waters of the Gulf of 
Alaska, at and beyond Hinchinbrook Entrance, he concludes that a larger 
salvage tug would improve the capability to prevent a major casualty.

Summary of Part 2

    Part 2 of the DTTS, is entitled ``Computer Simulations of Escort 
and Rescue Towing Scenarios.'' Part 2 evaluates, using computer 
simulations, the capability of existing escort vessels in Prince 
William Sound, Alaska, and examines alternatives, if any, that could 
enhance escort and rescue towing capabilities in a worst case failure 
scenario. The study was subsequently expanded to include a parametric 
study to investigate the consequences of variants from the worst case. 
The parametric variables included wind speed, tanker speed, failure 
rudder angle, failure recognition time and tug notification time.
    Tug escort of laden tankers has been a feature of tanker operations 
in Valdez Narrows since the opening of Alyeska Valdez Marine Terminal 
in 1977. Shortly after the grounding of the EXXON VALDEZ in 1989, 
escorting was extended all the way through Prince William Sound to Seal 
Rocks in the Gulf of Alaska.
    Tankers calling in Prince William Sound range in size from 60,000 
to 265,000 DWT. Three representative sizes, 90,000 DWT, 170,000 DWT and 
265,000 DWT, were chosen for computer simulation.
    In developing the parameters of the study, it was decided that 
worst-case scenarios would be investigated because if the escort system 
was effective in worst cases it would be effective in all situations. 
The worst-case scenario was a combination of: a hard-over rudder 
failure, loss of power, extreme weather conditions, a failure 
recognition delay and a conservative definition of areas (red zones) 
where a response effort would be considered ineffective.
    The study investigated (via computer simulations) five geographic 
locations in Prince William Sound (PWS): Valdez Narrows; Valdez Arm; 
central Prince William Sound; Hinchinbrook Entrance; and the Gulf of 
Alaska near Seal Rocks. The climatology used for this study was the 
worst-case wind and sea state resulting from a 25-year return period 
storm or the defined closure condition in each of the study's 
geographic areas.
    The study defined the worst-case tanker failure scenario to be:

--A 35-degree locked rudder failure.
--A time delay for failure recognition.
--Simultaneous shutdown or loss of the propulsion system upon rudder 
failure recognition.

    The parametric study investigated less extreme variations to the 
failure scenario (rudder failures at 10 and 20 degrees, shorter time 
delays for failure recognition and tug notification, and reversing of 
the tanker engine).
    Each class of tugs currently on charter was modeled for use in the 
computer simulations, as well as four other tug designs as possible 
alternatives. These alternative vessels were:

--4000 BHP vertical axis propeller tractor tug.
--7600 BHP vertical axis propeller tractor tug.
--7110 BHP azimuthing propeller (Z-drive) pusher tug (sometimes called 
a reverse tractor).
--168-ton bollard pull deep sea salvage tug.

    1 [[Page 6347]] The ability of the various types and sizes of tugs 
to perform escort and emergency towing was determined based on existing 
performance data, computer simulations and available operating 
experience.
    A matrix of simulation cases was developed, representing a full 
range of combinations of tug types, deployments and associated time 
delays, geographic locations and tanker sizes and speeds. In addition 
to the matrix of worst-case scenarios, over 1,000 additional cases, 
involving parametric reductions in the severity of the defined 
variables, were performed.
    The study's results of the worst-case and parametric studies are 
summarized below.

--For the worst-case scenario, the larger tractor tug (with additional 
assist from an untethered ERV tug), or the largest conventional tug 
tethered as a rudder tug (with additional assist from another 
conventional tug and an ERV tug both tethered alongside), is capable of 
controlling all three modeled tankers in the Valdez Narrows if the 
tanker speed at failure is less than or equal 4 knots.
--All of the current escort tugs have adequate power to tow a disabled 
tanker in the worst-case climatology of Valdez Arm. However, the 
simulations show the need for increasing the sea room between the 
outbound track and Buoy 9 near Pt. Freemantle.
--Both the SEA VOYAGER and the ERV class tugs are capable of towing any 
of the three sizes of tankers to windward in the modeled worst-case 
(45-knot wind) conditions for central Prince William Sound. However, 
there is inadequate sea room from the TSS lane to Naked Island for the 
tug to rig its towline and begin towing. In lesser wind speed 
conditions, however, there would be adequate sea room for these tugs to 
begin towing before any of the three sizes of tankers reached Naked 
Island. A SEA SWIFT class tug requires additional assistance from an 
ERV tug to tow any of the three sizes of tankers to windward.
--There is insufficient sea room to accommodate arrival time delays of 
existing tugs on standby at the Pilot Station, Naked Island or Port 
Etches based on the worst-case parameters set for this study. This 
result supports the current escort policy in Prince William Sound.
--The simulations for Hinchinbrook Entrance in the worst-case 
climatology show the need for increasing the sea room between the 
outbound track and Montague Island. For all cases with a right rudder 
failure occurring in the center of the southbound separation lane, the 
tanker will enter the red zone around Schooner Rock before an escorting 
tug can provide effective assistance.
--However, the parametric study for Hinchinbrook Entrance identifies 
some successful combinations under reduced wind conditions that result 
in towing control before the disabled vessel enters the red zone.
--None of the tugs investigated in this study can tow the modeled 
170,000 and 265,000 DWT vessels to windward in the worst-case 
climatology identified for the Gulf of Alaska. However, both the 
simulated SEA VOYAGER class tug and the salvage tug at least have the 
capability to control its downwind drift direction.
--The simulations indicate that the salvage tug can tow the disabled 
90,000 DWT vessel to windward in the Gulf of Alaska given the assumed 
worst-case conditions.
--The parametric study of reduced wind conditions for the Gulf of 
Alaska show that all three sizes of tankers can be towed to windward by 
the SEA VOYAGER class tug in 30 knots of wind or less or by the salvage 
tug in 50 knots of wind or less.

    Dated: January 24, 1995.
Joseph J. Angelo,
Acting Chief, Office of Marine Safety, Security and Environmental 
Protection.
[FR Doc. 95-2493 Filed 1-31-95; 8:45 am]
BILLING CODE 4910-14-P