DEPARTMENT OF TRANSPORTATION
Coast Guard
[CGD 96028]
Differential Global Positioning System; Geiger Key, Florida: Environmental
Assessment and Finding.
AGENCY: Coast Guard, DOT.
ACTION: Notice of availability.

__________________________________________________________________________
SUMMARY: The Coast Guard has prepared an Environmental Assessment (EA)
and proposed Finding of No Significant Impact (FONSI) for its activating
of a broadcast site of the Differential Global Positioning System (DGPS)
service at Geiger Key, Florida. The EA concludes that there will be no
significant impact on the environment and that preparation of an
Environmental Impact Statement will not be necessary. This Notice
announces the availability of the EA and proposed FONSI and solicits
comments on them.
DATES: Comments must be received on or before July 12, 1996.
ADDRESS: Comments may be mailed to the Executive Secretary, Marine Safety
Council, U.S. Coast Guard Headquarters, 2100 Second Street SW., Washington,
DC 20593-0001, or may be delivered to room 3406 at the same address
between 8 a.m. and 3 p.m., Monday through Friday, except Federal holidays.
The telephone number is (202) 267-1477.
FOR FURTHER INFORMATION CONTACT: LCDR Gene Schlechte, United States Coast
Guard Navigation Center, at (703) 313-5888. Copies
of the EA and proposed FONSI may be obtained by calling Mr. Schlechte, or by
faxing him at (703) 313-5920. Copies of the EA--without enclosures--are also
available on the Electronic Bulletin Board System (BBS) at the Navigation
Information Service (NIS) in Alexandria, Virginia, at (703) 313-5910. For
information on the BBS, call the watchstander of NIS at (703) 313-5900.
SUPPLEMENTARY INFORMATION:
Request for Comments
Copies of the EA and proposed FONSI are available from the address given
in ADDRESS and from the numbers given in FOR FURTHER INFORMATION CONTACT. The
Coast Guard encourages interested persons to submit comments on these
documents. It may revise these documents in view of the comments. If it
does, it will announce their availability in revised form by a later notice in
the Federal Register.
Background
As required by Congress, the Coast Guard is preparing to install the
equipment necessary to implement the Differential Global Positioning System
(DGPS) service in the southeastern United States. DGPS is a new
radionavigation service that improves upon the 100 meter accuracy of the
existing Global Positioning System (GPS) to provide an accuracy of 8 to 20
meters. For vessels, this degree of accuracy is critical for precise
electronic navigation in harbors and harbor approaches and will reduce the
number of vessel groundings, collisions,
personal injuries, fatalities, and potential hazardous cargo spills resulting
from such incidents.
After extensive study, the Coast Guard has selected a preferred
alternative at Geiger Key, Monroe County, FL. Significant concerns were
raised about siting DGPS equipment at the alternative site at U.S. Coast Guard
Base Key West, Monroe County, FL. The close proximity to the docking
facilities to the transmitting antenna has the potential to adversely affect
CG and Naval vessels carrying ordnance. The RF radiation of the antenna also
has the potential of interfering with Group Key West communications adjacent
to the proposed project area. In addition, the density of existing structures
and the planned growth (new construction) of the base has the potential to
create satellite signal reception errors due to multipath distortion from the
buildings, vessels, and vehicles. Such reception errors will adversely effect
the performance and safety function of the DGPS service provided. DGPS signal
transmissions will be broadcast in the marine radiobeacon frequency band
(283.5 to 325 KHz) using less than 35 watts (effective radiated power).
Signal transmissions at these low frequencies and power levels have not been
found to be harmful to the surrounding environment.
Proposed Installation at Geiger Key, FL:
a) Site -- The Geiger Key, FL, site is located on the U.S. Naval Air
Station (NAS) Key West, FL. The site is located on Geiger Key lying and being
in the County of Monroe, State of
Florida being more particularly described as follows: Lot 1, 2, 3, 4, 5, 30,
31, 32, 33, 34, Block 16 of "Boca Chica Ocean Shores" as recorded in Plat Book
5 at Page 49 of Public Records of Monroe County, Florida.
b) Radiobeacon Antenna -- The Coast Guard will install a 74 foot self
supporting whip antenna with an accompanying ground plane. A ground plane for
this 90 foot antenna consists of approximately 120 copper radials (6 gauge
copper wire) installed 6 inches (or less) beneath the soil and projecting
outward from the antenna base. The optimum radial length is 300 feet, but
this length may be shortened to fit within property boundaries. Wherever
possible, a cable plow method will be used in the radial installation to
minimize soil disturbance.
c) DGPS Antennas -- Two 30 foot masts to support six small (4 inches by
18 inches diameter) receiving antennas will be required. The masts will be
installed on concrete foundations. The antennas support the primary and
backup reference receivers and integrity monitors.
d) Equipment shelter -- DGPS transmitting equipment will be housed in a
10 foot 8 inch by 16 foot 8 inch shelter.
e) Utilities -- The Coast Guard proposes to use available commercial
power as the primary source for the electronic equipment with battery power as
a backup. A telephone line and modem will be required at each site for remote
monitoring and operation.

Proposed Finding
Implementation of a DGPS service at Geiger Key, FL, is determined to have
no significant effect on the quality of the human environment or require
preparation of an Environmental Impact Statement.
Dated: June 6, 1996.

N. T. SAUNDERS
Rear Admiral, U.S. Coast Guard
Chief, Operations