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		U. S. COAST GUARD
ENVIRONMENTAL ASSESSMENT
FOR
	IMPLEMENTATION OF DIFFERENTIAL GLOBAL POSITIONING SYSTEM (DGPS)
SERVICE, INCLUDING SITING, INSTALLATION OF ANTENNA,
GROUND PLANE, EQUIPMENT HUT, AND THEIR OPERATION,
AT U.S. NAVAL AIR STATION KEY WEST, GEIGER KEY, FL
	This Environmental Assessment (EA) was prepared in accordance with 
Coast Guard Commandant's Instruction M16475.1B and is in compliance
with the National Environmental Policy Act of 1969 (P.L. 91-190) and 
the Council of Environmental Quality Regulations (40 CFR Parts 1500-1508.
This EA serves as a concise public document to provide sufficient 
evidence and analysis for determining the need to prepare an 
environmental impact statement or a finding of no significant 
impact.
This EA concisely describes the proposed action, the need for the 
proposal, the alternatives, the environmental impacts of the proposal 
and alternatives, comparative analysis of the action and alternatives, 
a statement of environmental significance, and lists the agencies and 
persons consulted during its preparation.
	Date        Preparer                     Title/Position
	Date        Environmental Reviewer       Title/Position
	Date        Responsible Official         Title/Position
	U. S. COAST GUARD
FINDING OF NO SIGNIFICANT IMPACT
FOR
	IMPLEMENTATION OF DIFFERENTIAL GLOBAL POSITIONING SYSTEM (DGPS)
SERVICE, INCLUDING SITING, INSTALLATION OF ANTENNA,
GROUND PLANE, EQUIPMENT HUT, AND THEIR OPERATION,
AT U.S. NAVAL AIR STATION KEY WEST, GEIGER KEY, FL
This action has been thoroughly reviewed by the Coast Guard and it has 
been determined, by the undersigned, that this project will have no 
significant effect on the human environment.
This finding of no significant impact is based on the attached 
U.S. Coast Guard prepared Environmental Assessment which has been 
determined to adequately and accurately discuss the environmental 
issues and impacts of the proposed action and provides sufficient 
evidence and analysis for determining that an environmental impact 
statement is not required.
	Date        Preparer      Title/Position
	Date        Environmental Reviewer        Title/Position
	Date        Responsible Official          Title/Position
	ENVIRONMENTAL ASSESSMENT FOR 
IMPLEMENTATION OF DIFFERENTIAL GLOBAL POSITIONING SYSTEM (DGPS)
SERVICE, INCLUDING SITING, INSTALLATION OF 
ANTENNA, GROUND PLANE, EQUIPMENT HUT
AND THEIR OPERATION, AT THE U.S. NAVAL
AIR STATION KEY WEST, GEIGER KEY, FL
	PURPOSE AND NEED FOR THE PROPOSED ACTION:
Background:  To aid navigation and prevent collisions and wrecks of 
vessels and aircraft, the Coast Guard is charged under 14 USC 81 with 
establishing, maintaining, and operating electronic aids to navigation 
to serve the needs of U.S. armed forces, maritime commerce, and air 
commerce (as requested by the Federal Aviation Administrator).  
Starting back in 1921 with the introduction of radiobeacons, the 
first electronic aid to navigation, and continuing through the 
development of LORAN-A, LORAN-C, and Omega, those responsibilities 
have been met to the extent that technology would allow.  With the 
introduction of each new system, navigators were able to improve 
their efficiency while increasing the safety of navigation.
Electronic or radio aids provided all-weather navigation services 
that met the accuracy requirements for ocean crossings through 
Omega and for offshore and coastal navigation using LORAN-C.  
But these systems did not meet the required navigational accuracies 
of 8-20 meters for harbor approach and harbor navigation as described 
in the Federal Radionavigation Plan (FRP).  To meet these needs, 
differential techniques were developed to provide local corrections 
to the existing signals, resulting in much higher accuracies. 
(A differential system uses a receiver at a precisely known location 
to measure the local errors in radionavigation signals.)  Due to the 
nature of both LORAN-C and Omega signals, differential corrections 
were valid for only a small area, requiring extensive ground 
equipment to provide coverage for all harbors and harbor approaches.  
It was not economically feasible to build such an extensive system.  
Also, the accuracies achieved with these systems fell short of most 
requirements.  Differential Omega achieved approximately 1/4 mile 
accuracy, and Differential LORAN-C could do no better than approach 20 
meters accuracy for limited periods of time.
Now technological advances have provided a new method of meeting 
navigational requirements through the satellite based Global 
Positioning System (GPS).  Developed and operated by the U.S. 
Department of Defense, GPS provides two levels of service:  Standard 
Positioning Service (SPS) and Precise Positioning Service (PPS).  
While SPS accuracy can be better than 54 meters (95% probability), 
with the activation of Selective Availability (SA) that accuracy 
is degraded to 100 meters (95% probability) for civil users.  
Nevertheless, GPS provides all-weather global coverage, 24 hours/day 
at unprecedented accuracies.  The Standard Positioning Service (SPS), 
is available to all users worldwide.  PPS will provide 21 meter (95% 
probability) accuracy to military and approved civil users.  Yet even 
GPS, with its remarkable accuracies, still does not meet the 
needs of harbor and harbor approach navigation.  But by applying 
differential techniques, as used with Omega and LORAN systems, 
navigational accuracies of better than 10 meters can be achieved.  
For the first time, an economical, all-weather system is possible 
to meet the extremely accurate navigation requirements of mariners 
in our environmentally sensitive harbor and harbor approach areas.
In addition to providing a highly accurate navigation signal, 
Differential GPS (DGPS) also provides a continuous integrity check on 
GPS satellite health.  Integrity is the ability of a system to provide 
timely warnings to users when the system should not be relied upon for 
navigation.  System integrity is a real concern with GPS.  With the 
design of the ground control of GPS, a satellite can be transmitting 
a bad navigation signal for 2 to 6 hours before it can be detected 
and corrected by the Master Control Station or before users can be 
warned not to use the signal.  But with the continuous, real-time 
messages generated by DGPS, unhealthy satellites can still be used, 
or the navigator's receiver is directed not to use a particular 
satellite.  This can eliminate the danger of the navigator 
unintentionally relying on an erroneous signal.
Need:  There is a crucial need to reduce the number of current 
navigation-related vessel groundings, collisions, personal injuries, 
fatalities, and potential hazardous cargo spills resulting from the 
inadequateness of current and previous navigation methods.  Our 
nation's waterways support the transportation of vast amounts of 
commercial products and resources, vital to the support of our economy.  
Our ports and harbors serve as gateways to the rest of the world for 
increasing our trade.  The safe and efficient transport of these 
materials is critical to our nation's well-being.  There is also a 
crucial need for an all weather system to meet the extremely accurate 
navigation requirements of mariners in our environmentally sensitive 
harbor and harbor approach areas.  Additionally, the most reliable 
all weather navigation system is needed to:  increase navigation 
safety and efficiency through environmentally sensitive areas, 
position aids to navigation, track properly equipped vessels, 
perform more precise charting activities, and more efficiently 
maintain dredged channels, etc.  Making our maritime transportation 
mode work better - increasing the safety, environmental security, 
and economic efficiency - is a critical need of the U.S.  
Purpose:  The purpose of the proposed action is to improve current 
navigation systems by implementing the best system capable of 
improving the condition of nationwide navigational safety, 
environmental security, and economic efficiency.
The critical need for an improved all weather navigation system 
was recognized by Congress.  Consequently, Congress has mandated 
specific funding for the navigation system known as DGPS in the 
Coast Guard Budget.
The use of DGPS provides the enabling technology to modernize the 
existing infrastructure to meet the rapidly increasing demands 
on our ports and waterways.  Integration of precise navigation 
information from DGPS with the radar picture and electronic 
charts will increase navigation safety and efficiency through 
environmentally sensitive areas.  Other applications use DGPS 
to position aids to navigation, track properly equipped vessels, 
perform more precise charting activities, more efficiently 
maintain dredged channels, etc.  DGPS is the only available 
technology that meets the 8 to 20 meter accuracy required 
for Harbor and Harbor Approach (HHA) electronic navigation.  
This requirement is documented in the Federal Radionavigation 
Plan (current edition).  For the purposes of navigation safety, 
sites have been proposed to ensure coverage of major ports and 
vessel navigation routes.Additionally, other government agencies 
with maritime safety responsibilities will improve service to 
the public through the use of the Coast Guard's DGPS service.  
Dredging operations and other waterway maintenance activities are 
being carried out more efficiently by the U.S. Army Corps of 
Engineers without the need to set up temporary positioning systems.  
Hydrographic surveys conducted by the Coast and Geodetic Survey 
are being done faster and more accurately.  These agencies are 
already using the Coast Guard's prototype DGPS sites and intend 
to expand their use of DGPS as the rest of the Coast Guard's 
service is implemented.
This Environmental Assessment (EA) assesses the impact of the proposed 
implementation (siting, constructing, and operating) of a Differential 
Global Positioning System (DGPS) facility at the preferred alternative 
on the U.S. Naval Air Station (NAS) property on Geiger Key, Monroe 
County, FL and at alternative sites capable of providing DGPS 
service coverage of the Southwest coast and Florida Keys.
PROPOSED ALTERNATIVES FOR DETAILED ANALYSIS:
a.  DGPS implementation at NAS Key West, Geiger Key, Monroe County, FL.
The proposed site at NAS Key West, alternative (a), is the preferred 
alternative.  The Coast Guard has coordinated with NAS and applicable 
Federal agencies to ensure the project is planned, constructed, and 
operated to assure protection, preservation, and enhancement of 
wetlands, floodplains, and endangered species to the fullest extent 
possible.  The site is in the 100 Year Flood Zone AE with a base 
flood elevation of +9' NGVD (1929).  The encroachment of the DGPS 
site on the floodplain is consistent with the guidelines for 
NEPA and COMDTINST M16475.1B and should not have an adverse 
impact on the natural and beneficial floodplain values.  Planned 
mitigation/enhancement measures (enclosure (8)) will reduce the 
disturbances caused by the site construction and will provide long 
term improvements to the existing ecosystem.  The project site is 
immediately adjacent to known Lower Keys marsh rabbit habitat.  
This rabbit (Sylcilagus palustris hefneri) is currently listed as a 
Federal and State endangered species.  A Vegetation Survey and 
Habitat Assessment (enclosure (7)) of the project area was performed.  
Sensitive areas were delineated and design plans have placed the 
transmitting antenna and equipment shelter to avoid these sensitive 
areas.  Some clearing of woody and herbaceous vegetation for the 
installation and maintenance of the site will be required but is 
limited to the area of the radiobeacon antenna and its ground 
plane.  No threatened or endangered plant species will be affected.  
b.  DGPS implementation at USCG Base Key West, Key West, Monroe 
County, FL 
	The proposed site at USCG Base Key West, alternative (b), has 
many of the same environmental concerns as those outlined in 
alternative (a).  The site is in the 100 Year Flood Zone AE with 
a base flood elevation of +9' NGVD (1929).  
Some clearing of woody and herbaceous vegetation for the installation 
and maintenance of the site may be required but would be limited to 
the area of the radiobeacon antenna and its ground plane.  No 
threatened or endangered plant species will be affected and no 
known Lower Keys marsh rabbit habitat would be disrupted.
c.  No-action.
The No-action alternative:  Possible adverse environmental impact. 
Implementation of the DGPS service is expected to reduce the number of 
navigation-related vessel groundings which have resulted in the 
severe damage to the sensitive coral formations within the Florida 
Keys National Marine Sanctuary, collisions, personal injuries, 
fatalities, and potential hazardous cargo spills resulting from 
such incidents by 50 percent over existing navigation methods.  
This 50 percent reduction is based on accuracy, availability, 
and integrity requirements derived from a risk allocation model 
which used historical data from a busy waterway with a history 
of groundings and collisions.  The reduction will equate to 
yearly savings of approximately $21 million in commercial 
vessel/cargo damages alone and prevent approximately 400 
fatal injuries.  It will also provide cost avoidance to the U.S. of 
responding to such incidents (cleanup, restoration, investigation, 
etc.) and avoid the resulting environmental damage.  If no-action 
is taken the potential savings described above can not occur.  
The U.S. Coast Guard could be found negligible if we did not 
implement the DGPS system and a serious collision or grounding 
resulted in a spill of hazardous cargo that caused environmental 
damage, loss of life, or property damage that could possibly have 
been avoided if DGPS coverage was available.  For these reasons 
no-action is not a feasible alternative.
	ALTERNATIVES CONSIDERED BUT DISMISSED FROM DETAILED ANALYSIS:
Other radionavigation systems were considered but eliminated from 
detailed discussion because they do not meet the accuracy and 
integrity requirements for harbor and harbor approach navigation.  
These other systems were: GPS, LORAN-C, Omega.
DGPS SITES CONSIDERED BUT NOT SELECTED:
Other sites were considered but not selected.  Three additional 
sites were final candidates but were disqualified for the 
following reasons.
	Site 1:  East end of Trumbo Point Annex Facility, Key West, FL
         Vacant lot.  Property use was not attainable from 
         owner.
Site 2:  North side of Key West International Airport at an 
         old missile site.  DGPS site would be collocated with 
         Next Generation Weather Radar (NEXRAD) site.  Reflection 
         of the GPS signals and RF interference due to the close 
         proximity of the NEXRAD antenna to the DGPS equipment 
         would severely impede DGPS operations.  Grounding and 
         bonding methods will not successfully mitigate problems. 
         This site does not meet selection criteria.
Site 3:  On Naval Regional Medical Clinic, Key West, FL at 
         mile marker 4.  Property use was not attainable from 
         owner.
By comparing the alternatives the Coast Guard believes that 
alternative (a) will provide the best coverage area, be the most 
cost effective in terms of operation and maintenance, have no 
affect on resident personnel, and have only minor environmental 
impacts related to the installation of the antenna, ground 
plane, and equipment hut.  For these reasons it is our 
preferred alternative.
LOCATION AND DESCRIPTION OF PROPOSED SITES:
U.S. Naval Air Station (NAS) Key West, FL:  The proposed facility 
will be an unmanned installation, established on unimproved U.S. 
Navy property at NAS Key West, FL.  The site is located on a 
portion of 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 the 
Public Records of Monroe County, Florida (enclosure 1).  
This property is not a homestead property.  This 
proposed site is associated with alternative (a). 
U.S. Coast Guard Base Key West, FL:  The proposed facility will 
be an unmanned installation, established on U.S. Coast Guard 
property at USCG Base Key West, FL.  The land is owned by the 
Coast Guard and is within the security fence line of the Coast 
Guard Base.  This proposed site is associated with alternative (b). 
DGPS TECHNOLOGY:
Differential GPS is based upon knowledge of the accurate geographic 
location of a reference station, which is used to compute corrections 
to GPS parameters.  A DGPS reference station is fixed at a 
geodetically surveyed position.  From this position, the reference 
station tracks all satellites in view and computes corrections 
based on its measurements and geodetic position.  These 
differential corrections are then transmitted to GPS users, 
who apply the corrections to their received GPS signals.  For a 
civil user of SPS, differential corrections can improve 
navigational accuracy from 100 meters (95% probability) to 
better than 10 meters (95% probability).
DGPS TRANSMISSION MEDIUM:
Marine Radiobeacons (LF/MF) were chosen as the transmission 
medium for the differential corrections after considerable 
analysis.  Working closely with the Radio Technical Commission 
for Maritime Services (RTCM) beginning in 1983, the Coast Guard 
reviewed radio frequencies allocated in the U.S. for radionavigation 
and analyzed their suitability for use with DGPS.  It was 
concluded that the radiobeacon band of 285-325 kHz was the only 
band that met the needs of DGPS for radionavigation use without 
requiring changes in international frequency allocations.  In 
addition, the beacons were already located in sites where 
marine navigators needed coverage, the effects of blockage 
and multipath were small in this band compared to higher 
frequencies, radiobeacons had already been used successfully 
for other differential navigation applications, and the range 
of the radiobeacon signal roughly corresponded to the 
applicable range of the DGPS corrections.  International 
radionavigation standards also recommend the use of radiobeacons 
for differential corrections in support of maritime navigation.  
For the Coast Guard's implementation, radiobeacons also offer 
the only cost effective communications medium by allowing the 
maximum use of existing infrastructure - an infrastructure 
that is already providing a public radionavigation service.  
Consideration of site costs, user equipment cost, site 
availability, site locations, equipment availability, frequency 
spectrum availability, transmission range, international radio 
regulations, and international standards resulted in the 
radiobeacon network being the only feasible communications 
medium for transmitting the Coast Guard's DGPS corrections.  
DGPS BENEFITS TO NAVIGATION:
Coast Guard maritime safety activities will be more efficient 
through the use of DGPS, improving service to the public.  
Buoy tenders and Aid to Navigation Teams will be able to 
position navigation aids in a more expedient and precise 
manner and allow all-weather, 24-hour a day operations.  
This is a significant improvement over current visual positioning 
methods that are easily hindered by fog, clouds or darkness.  
And any vessel can be quickly configured with a DGPS system to 
perform buoy positioning checks after a major storm or hurricane 
to ensure the waterway is safe to resume navigation as soon as 
possible.  Rescue aircraft and vessels will be able to execute 
search patterns more effectively.  Cutters and aircraft 
conducting law enforcement operations can more accurately and 
more reliably fix their positions to determine law enforcement 
jurisdiction and the geographic limits of areas requiring 
special enforcement, such as closed fishery areas.
	Use of DGPS coupled with transponder equipment permits highly 
accurate tracking of law enforcement vessels, aircraft, 
search and rescue craft, or vessels carrying hazardous 
cargoes or pollutants.  This will allow Coast Guard 
Vessel Traffic Services (VTS) to more effectively monitor 
vessel traffic in major harbors or ports.
	ENVIRONMENTAL APPROACH:
	While the benefits of the planned implementation of the 
Coast Guard's DGPS service are many, before decisions on 
final site locations could be made, potential negative 
impacts had to be assessed.  Pursuant to the National 
Environmental Policy Act, other federal laws, and the 
resulting implementing regulations as guidelines, the 
Coast Guard has investigated the impacts of the 
implementation plan.  
	First, site surveys were conducted to determine the 
suitability and viability of potential sites.  
An important consideration in choosing our proposed sites 
was the availability and condition of existing infrastructure.  
Not only does use of existing infrastructure reduce 
implementation costs, but it also reduces the disruption 
to the local environment.  
	In the development of the engineering plan for the actual 
installation of equipment, methods were sought to install 
needed equipment with minimal disruption to the environment.  
An excellent example of mitigating disruption is the use of 
a pavement saw to lay ground radials, 3" PVC pipe, and telephone 
lines. Ground radials and telephone service will be laid in 
a 1-2" wide x 1-2" deep slot. The 3" PVC pipe will be laid 
in a slot 4" wide and 2',4" deep. Excavated material will 
be contained on plastic sheeting.  Parent material will be 
used for backfill. Surplus material will be removed from the 
site.  A necessary element for a transmitting antenna system, 
a ground plane consists of copper radials (6 gauge copper wire) 
installed 2 inches or less beneath the soil and projecting 
outward from the antenna base.
	To assess the other impacts our plans might have, records 
searches were conducted within the Coast Guard to collect 
information about the proposed sites.  To ensure that expert 
knowledge from outside the Coast Guard was considered, we wrote 
to the officials in each state that will host the proposed 
sites describing the DGPS project, the construction necessary 
in their state, and requesting their review and comment on our 
proposed actions.  The state officials responsible for historic 
preservation, environmental protection, and fish and wildlife 
management were consulted.  The regional federal officials of 
the Environmental Protection Agency and the Fish and Wildlife 
Service were also consulted.
	Based on all of the information collected from all sources, 
the environmental assessment was conducted and is described 
below.
	DGPS IMPLEMENTATION AT A PROPOSED SITE:
To provide DGPS service at a proposed site, DGPS reference 
station and integrity monitoring equipment (including 
backup equipment) would need to be installed at the site.  
A radiobeacon installation with satisfactory antenna 
is also required.  Existing infrastructure would be used 
wherever possible.  The equipment at each site would need 
to be supplied with electrical power and a telephone line 
for connection of the site into a DGPS control network, but 
no additional backup power would be installed (i.e., no 
installation of generators with fuel tanks).  The actual 
DGPS broadcasts consist of low power signal transmissions 
at frequencies already authorized for maritime navigation 
information (285 to 325 kHz).  The sites operate automatically, 
with no technicians or watchstanders needed at the site, 
but they are monitored remotely by a control station.  
Personnel would occasionally visit the site to correct 
anomalies and/or perform preventive/corrective maintenance 
and/or grounds maintenance as necessary.  Such maintenance 
may include any of the following:
      - remove and manage exotic vegetation/growth from above the 
        site.
      - renovate/replace the antenna ground plane system
      - replace/repair the antenna
      - repair/replace the electronic equipment
      - repair/replace/renovate the equipment room or shelter
      - mowing will be eliminated or minimized to allow for the 
        natural growth of native vegetation. 
      - vehicle traffic will be restricted to the designated roadway
      - the antenna area will be monitored for evidence of bird 
        strike mortality during the life of the project.
PROPOSED MEASURES AND ANCILLARY FEATURES AT EACH SITE:
a.  Radiobeacon Antenna - Typically, one of two antenna designs is 
installed at a DGPS site.  The first design is a 90 foot high guyed 
tower.  This is the preferred design due to its superior electrical 
efficiency, but it requires more frequent technician visits for 
maintenance.  The second design is a 74 foot high self 
supporting whip antenna.  The second design has rough half the 
electrical efficiency of the first, but requires much less 
maintenance.  Both antenna designs require the installation of a 
ground plane which consists of up to 120 copper radials (6 gauge 
copper wire) installed 6 inches (or less) beneath the soil and 
projecting outward from the antenna base.  The desired radial length 
is 150ft.  Wherever possible, a very effective cable plow method 
would be utilized in the radial installation to minimize soil 
disturbance.  Installation of the ground plane will require some 
clearing of brush and vegetation.
b.  DGPS Antennas - The site would require the installation of two 
masts with a maximum height of 30ft to support six small receiving 
antennas.  The masts would be installed on a concrete foundation.  
	The antennas support the primary and backup reference receivers and 
integrity monitors.  The location of the two masts would be in the 
vicinity of the electronic equipment building or hut, but at least 
50ft to 100ft from existing structures.
	c.  Equipment Shelter - A new 10x16ft equipment shelter would be 
required to house the radiobeacon transmitter and DGPS equipment. 
The equipment hut will be elevated on six 6 foot columns.
d.  Utilities - Available commercial power would be used as the 
primary power source for the electronic equipment.  A telephone 
line would be required to allow remote monitoring and operation.  
IMPACTS OF ALTERNATIVES (a), (b), and (c):
1. AIR QUALITY
Alternative a.
	The generation and transmission of DGPS signals does not produce 
emissions or by-products, therefore no adverse impact is 
anticipated.  Short-term localized changes in noise levels 
and air quality would occur during construction, but these 
are expected to be brief in duration and limited in scope.
	Alternative b.
	The generation and transmission of DGPS signals does not 
produce emissions or by-products, therefore no adverse 
impact is anticipated.  Short-term localized changes in noise 
levels and air quality would occur during construction, but 
these are expected to be brief in duration and limited in scope.
Alternative c.
No impact, but the crucial need to reduce the number of current 
navigation-related vessel groundings, collisions, personal 
injuries, fatalities, and potential hazardous cargo spills 
resulting from such incidents would go unmet.
	2. WATER QUALITY
Alternative a.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse 
impact to water quality is anticipated due to its operation.  
The project site is located in the 100 yr floodplain.  The 
encroachment has been evaluated as required by DOT Order 5650.2 
and determined to be "not significant".  Minor mitigation/enhancement 
measures (enclosure 8) are planned to restore and preserve the 
natural and beneficial floodplain values as required by the Water 
Resources Council's "Unified National Framework for Flood Plain 
Management" and NEPA (42 U.S.C. 4321).
	Alternative b.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to water quality is anticipated due to its operation.  The 
project site is located in the 100 yr floodplain.  Minor 
mitigation/enhancement measures will be necessary to restore 
and preserve the natural and beneficial floodplain values 
as required by the Water Resources Council's "Unified National 
Framework for Flood Plain Management" and DOT Order 5650.2.
Alternative c.
Adverse impact to water quality due to greater incidence of 
groundings.  The area is within a National Marine Sanctuary.  
The establishment of a better navigation system not only protects 
the ships from damage but protects the sensitive coral habitat 
and resulting fishery from damage from groundings.
3. FISHERY RESOURCES
Alternative a.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to fisheries is anticipated.  No impacts anticipated to fisheries 
due to site preparation, construction and maintenance of the site.  
The accurate navigation signal of DGPS will assist USCG vessels 
in the enforcement of closed fishery areas, helping to ensure 
our valuable fishery resources are effectively managed.
	Alternative b.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to fisheries is anticipated.  No impacts anticipated to fisheries 
due to site preparation, construction and maintenance of the site.  
The accurate navigation signal of DGPS will assist USCG vessels 
in the enforcement of closed fishery areas, helping to ensure our 
valuable fishery resources are effectively managed.
	Alternative c.
Adverse impact to water quality due to greater incidence of 
groundings.  The area is within a National Marine Sanctuary.  
The establishment of a better navigation system not only 
protects the ships from damage but protects the sensitive 
coral habitat and resulting fishery from damage from groundings.
4. WILDLIFE RESOURCES
Alternative a.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact to 
wildlife is anticipated.  The impacts to wildlife resources due to 
site preparation, construction, and maintenance are minimal.  The 
Lower Keys marsh rabbit (Sylcilagus palustris hefneri) is the only 
federally or state listed threatened or endangered species known to 
exist in the proposed project area.  The shrubbery and vegetation 
that will be temporarily modified to construct the site will not 
adversely impact the rabbit habitat. Exotic vegetation will be 
eliminated and the native vegetation will be allowed to reinvade 
the area improving the natural habitat.  The NAS Key West Lower 
Keys Rabbit Habitat Plan, and Florida G&FWF biologists in Monroe 
County have provided guidance. The Fish and Wildlife Service has 
notified the Coast Guard that the proposed project is not 
expected to impact the species (see enclosure 5; U.S. Dept of 
Interior letter dated 09 JAN 96).
Wetland areas are adjacent to the proposed project area.  The 
wetlands do not support a large bird (raptor) population but the 
site in within known migratory bird routes.  One of the adjacent 
wetlands is freshwater and could provide a suitable rest area for 
migrating birds.  The Coast Guard choose to install the 74 foot 
self supporting radiobeacon antenna vice the 90ft guyed tower at 
this site.  The 74 foot design will be used to eliminate the hazard 
of migratory birds striking a tower or its guy wires.  The 74 foot 
whip radiobeacon antenna also requires a smaller site footprint and 
therefore the removal of less site vegetation.  In addition the 74 
foot antenna design requires less annual maintenance; only one 
site visit per quarter by one technician for 30 minutes per visit.  
The 90 foot guyed tower requires quarterly maintenance visits by 
four to five technicians for up to eight hours per visit.  These 
antenna designs are discussed in the Radiobeacon Antenna 
paragraph on page 8.Alternative b.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to wildlife is anticipated.  The impacts to wildlife resources 
due to site preparation, construction and maintenance are minimal.  
The Lower Keys marsh rabbit (Sylcilagus palustris hefneri) is the 
only federally or state listed threatened or endangered species 
known to exist in the area.  No known marsh rabbit habitat 
is located in the proposed project area.Alternative c.
Adverse impact to wildlife habitat (if no alternative (a)) since 
the projects net result will improve the marsh rabbit habitat 
and enhance native vegetation through the removal of exotic 
vegetation and solid waste.
5. VEGETATION Alternative a.
	A "Vegetation Survey and Habitat Assessment" was conducted on 
Sept 22, 1995 (enclosure (7)) and concluded that no threatened 
or endangered plant species would be effected by the proposed 
project.  To minimize vegetation disturbance, the 74 foot self 
supporting whip radiobeacon antenna design will be used vice 
the 90 foot guyed tower.  The vegetation within a 120 foot radius 
on the 74 foot antenna will not be mowed.  The native grasses will be 
disturbed during the placement of the ground radials and buried PVC 
pipe and utility service (enclosure (1)). Exotic vegetation will 
be permanently removed on the site.  Shrubs on the north aspect 
of the ground radials  within the 110 foot radius are predominantly 
Brazilian pepper and will be removed.  Mangrove which have 
reestablished in the previously disturbed area along the two canals 
will not be disturbed.  The equipment hut and the two reference masts 
have been relocated for this purpose.  The site design plan delineates 
vegetation types (see site design drawing, enclosure (1)) and locations 
of the radiobeacon antenna, the utility poles, and the limits of the 
buried ground radials.  These items will be staked just prior to 
construction.  The Marathon office of the Florida Department of 
Environmental Protection (DEP) will be notified so an inspection 
to ensure compliance can be performed and an Environmental Resource 
Permit (ERP) can be granted.  (See Florida DEP letter dated 17 NOV 
95; enclosure 6). Alternative b.
	The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to vegetation is anticipated.  The impacts to vegetation due to 
site preparation, construction and maintenance are minimal.  No 
threatened or endangered plant species are known to be in the 
proposed project area.  Minimal clearing of vegetation is 
required to install and maintain the ground plane and antenna.
Alternative c.
Adverse impact to vegetation (if no alternative (a)) since the 
projects net result will improve the area by enhancing native 
vegetation through the removal of exotic vegetation and solid waste.
	6. WETLANDS
Alternative a.
The known wetlands would be impacted by the site construction.  
Mitigation and enhancement measures have been included in the 
permit application letter.  As required by DOT Order 5660.1A, 
the Coast Guard has determined that DGPS implementation would 
not adversely effect the Florida coastal zone and consequently 
would be consistent with the Florida Coastal Zone Management 
Plan.  Per E.O. 11990 (Protection of Wetlands) both federal 
and state wetland permits are required for this site.  
Application for these permits have been made.  Guidelines 
are being complied with during site planning and will be 
adhered to during construction.
	Alternative b.
The generation and transmission of DGPS signals does not produce 
emissions, effluents or by-products, therefore no adverse impact 
to wetlands is anticipated.  There are no impacts to wetlands due 
to site preparation, construction and maintenance.  As required by 
DOT Order 5660.1A, the Coast Guard has determined that DGPS 
implementation would not adversely effect the Florida coastal 
zone and consequently would be consistent with the Florida 
Coastal Zone Management Plan.
	Alternative c.
Adverse impact to wetlands (if no alternative (a)) since the 
projects net result will improve wetland habitat through the removal 
or scraping of artificially high areas in the project area.  Also, 
adverse impact to wetlands due to greater incidence of groundings.  
The establishment of a better navigation system not only protects 
the ships from damage but protects the wetlands from the damage 
that can result from groundings.
7. NOISE LEVEL
Alternative a.
	The generation and transmission of DGPS signals under normal 
operations does not produce noise, therefore no impact is anticipated.  
Short-term localized changes in noise levels and air quality would 
occur during construction, but these are expected to be brief in 
duration and limited in scope.
	Alternative b.
	The generation and transmission of DGPS signals under normal 
operations does not produce noise, therefore no impact is 
anticipated.  Short-term localized changes in noise levels and 
air quality would occur during construction, but these are 
expected to be relatively brief in duration and limited in scope.
Alternative c.
No impact, but the crucial need to reduce the number of current 
navigation-related vessel groundings, collisions, personal 
injuries, fatalities, and potential hazardous cargo spills 
resulting from such incidents would go unmet.
	8. SOCIOECONOMIC RESOURCES
Alternative a.
	Construction would result in minor short term increases in sales 
and hotel business.  Once implemented, our DGPS service is 
expected to increase the safety, environmental security, and 
economic efficiency of our harbor and harbor approach areas.  
Avoidance of hazardous cargo spills in our coastal areas helps 
preserve our socioeconomic resources.
	Alternative b.
	Construction would result in minor short term increases in sales 
and hotel business.  Once implemented, our DGPS service is expected 
to increase the safety, environmental security, and economic 
efficiency of our harbor and harbor approach areas.  Avoidance 
of hazardous cargo spills in our coastal areas helps preserve 
our socioeconomic resources.
Alternative c.
Adverse impact to socioeconomic resources since the projects net 
result will protect the sanctuary recreational resources from 
damage from grounding.
9. CULTURAL RESOURCES
Alternative a.
	There are no properties in the project area of historic, 
architectural, or archaeological significance, therefore 
no impact is anticipated.  (See Florida 
SHPO letter dated 31 OCT 95; enclosure 6).
Alternative b.
	There are no properties in the immediate project area of 
historic, architectural, or archaeological significance, 
therefore no impact is anticipated.
Alternative c.
No impact, but the crucial need to reduce the number of 
current navigation-related vessel groundings, 7 collisions, 
coral damage, personal injuries, fatalities, and potential 
hazardous cargo spills resulting from such incidents 
would go unmet.
10. RECREATIONAL RESOURCES
Alternative a.
The project site is not located in or near a recreation area, 
therefore no impact is anticipated.  DGPS service is expected 
to increase the safety, environmental security, and economic 
efficiency of our harbor and harbor approach areas.  
Avoidance of hazardous cargo spills in our coastal areas 
helps preserve our recreation resources.
Alternative b.
	The project site is not located in or near a current recreation area, 
therefore no immediate impact is anticipated.  However, the 
recently completed Key West master plan for future base 
reconstruction/expansion did not rule out the use of the 
proposed project site as a future recreation area.
Alternative c.
Adverse impact to recreational resources since the projects 
net result will protect the sanctuary recreational resources 
from damage from grounding.
11. ENERGY
Alternative a.
	Construction of a new antenna and ground plane at the proposed 
project site would result in the minor short-term use of energy.  
The radiobeacon transmitter and DGPS electronic equipment to 
be installed would result in a minor increase in the use of energy.
	Alternative b.
Construction of a new antenna and ground plane at the proposed site 
would result in the minor short-term use of energy.  The radiobeacon 
transmitter and DGPS electronic equipment to be installed would 
result in a minor increase in the use of energy.
Alternative c.
No impact, but the crucial need to reduce the number of current 
navigation-related vessel groundings, collisions, coral damage, 
personal injuries, fatalities, and potential hazardous cargo spills 
resulting from such incidents would go unmet.
12. LONG TERM IMPACTS
Alternative a.
The impacts on the natural environment are minimal.  No threatened or 
endangered plant or wildlife will be negatively impacted.  The natural 
and beneficial values of the floodplain will be preserved and the 
wetlands will be unaffected. 
	DGPS provides the enabling technology to modernize the existing 
infrastructure to meet the rapidly increasing demands on our ports 
and waterways.  It will increase navigation safety, environmental 
security, and economic efficiency resulting in major long-term 
benefits of significant reductions in the number of 
navigation-related vessel groundings and collisions, reduced personal 
injuries, fatalities, and potentially hazardous cargo spills.  
DGPS capability will enhance maritime safety in keeping with the 
National Transportation Policy by providing an all-weather 
radionavigation service to supplement existing radar and visual 
techniques.  It will fulfill the 8-20 meter accuracy requirement 
for harbor and harbor approach navigation with availability of up 
to 99.9%.  It will also meet the requirements of the Coast Guard, 
the Coast and Geodetic Survey, and the Army Corps of Engineers to 
provide more accurate and efficient maritime services to the public.
	Alternative b.
	The impacts on the natural environment are minimal.  No threatened or 
endangered plant or wildlife will be negatively impacted.  The natural 
and beneficial values of the floodplain would be preserved and the 
wetlands would not be affected.
Same positive long term impact as described in alternative (a).  
Strong possibility of long term negative impact on daily operations 
at Group Key West.  The proximity of fuel, ordinance and personnel 
to the transmitting site would require the Coast Guard to perform 
extensive hazards studies  prior to the installation of the DGPS 
equipment.  If the potential for hazards is found to exist, at a 
minimum, a "hazard reduction" program would need to be implemented 
and maintained.  The resources required to support such a program 
do not exist at the Group.  Obtaining additional resources is not a 
viable option.
Alternative c.
Adverse impact to all resources mentioned since the projects net result 
will protect the sanctuary resources from damage from groundings.  
The accumulative impacts from inferior navigational systems could 
result in the long range deterioration of the coral resource 
which is the main attraction in the area.  The 
Sanctuary, Fish & Wildlife Service, National Park Service, State, 
County, and private environmental organizations can use DGPS to 
increase the accuracy of their research and the management of 
their resources in the area.
	13. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES
Alternative a.
	Time, electrical energy, and fuel would be used to construct, operate, 
and maintain the site.
Alternative b.
	Time, electrical energy, and fuel would be used to construct, operate, 
and maintain the site.  This site will take several months longer to 
complete than alternative (a) due to the complexity of the systems 
and services available at Group Key West.  The potential for hazards 
to personnel, fuel and ordinance will increase if a DGPS site (or any 
transmitting site) is installed.  Significant hardening of the physical 
plant (bonding and grounding) as well as a "hazard reduction" program 
may need to be implemented and maintained to minimize risk.  
Alternative c.
No resources would be committed, but the crucial need to reduce the 
number of current navigation-related vessel groundings, collisions, 
personal injuries, fatalities, and potential hazardous cargo spills 
resulting from such incidents would go unmet.
14. UNAVOIDABLE ADVERSE IMPACTS
Alternative a.
	Based on our evaluation, we conclude the proposed siting, facility 
construction, operation, and maintenance would not have  any 
unavoidable adverse impacts.
	Alternative b.
	Based on our evaluation, we conclude the proposed siting, facility 
construction, operation, and maintenance would have unavoidable 
adverse impacts on the personnel working at Group Key West.  The 
proximity of the project site to other base facilities will have 
a short term impact on the working and living conditions of the 
personnel during installation and construction.  The possibility 
of electromagnetic radiation hazards may require the implementation 
of a "hazard reduction program" to mitigate any negative effects.  
The implementation of such a program will adversely impact the 
life-styles of the base residents and would result in an increased 
workload for vessels and personnel using the facilities at the base.
	Alternative c.
Adverse impact due to the crucial need to reduce the number of current 
navigation-related vessel groundings, collisions, coral reef damage 
personal injuries, fatalities, and potential hazardous cargo spills 
resulting from such incidents would go unmet.
15. LOCAL SHORT TERM IMPACTS VS LONG TERM PRODUCTIVITY
Alternative a.
	Short-term localized increases in noise levels during installation or 
construction.  Short-term and very localized changes in air quality 
during construction from fugitive dust, operation of equipment, 
and vehicular exhausts.  Short-term impact on vegetation, 
floodplain, and wildlife habitat during early phase of construction.  
Offset factors are:
(a) Decreased environmental damage.  Major long-term productivity 
increase for transportation of commercial products and resources 
in U.S. waters.  Integration of precise navigation information from 
DGPS with the radar picture and electronic charts will meet the 
rapidly increasing demands on our ports and waterways.  The long 
term gains to transportation productivity of the avoidance of 
50% of navigation-related vessel groundings, collisions, personal 
injuries, fatalities, and potential hazardous cargo spills resulting 
from such incidents, is significant.  It will also avoid the cost 
to the U.S. of responding to such incidents (cleanup, restoration, 
investigation, etc.) and avoid the resulting environmental damage.
(b) Increased resource management.  Major long-term productivity 
increase for the U.S. Coast Guard, other federal agencies, and 
some state agencies will result.  Coast Guard effectiveness and 
productivity will be significantly enhanced in areas such as 
Aids To Navigation (ATON), ice operations, search and rescue (SAR), 
and law enforcement.  (For example, the Coast Guard buoy 
tender fleet will realize a 30% increase in productivity 
compared to manual methods now used.)  Other government 
agencies will benefit from similar productivity improvements 
and operating cost reductions.  The Coast and Geodetic Survey 
can use DGPS for precise positioning during hydrographic 
surveying for nautical charts.  The U.S. Army Corps of Engineers 
can use the precise positioning from DGPS for dredging operations 
and mat laying in rivers.  State agencies can use DGPS's accurate 
positioning in resource management.
(c) Socioeconomic increase.  Local short-term increase in sales and 
hotel business for local residents.
Alternative b.
Short-term localized increases in noise levels during installation or 
construction.  Short-term and very localized 
changes in air quality during construction from fugitive dust, operation 
of equipment, and vehicular exhausts.  Short-term impact on vegetation 
and floodplain during early phase of construction.  Offset factors are 
same as described in alternative (a).
Alternative c.
The local short term impacts without the project are minimal.  The long 
term adverse impacts would be significant due to the increased 
probability of damage to the marine ecosystem in the area.
SUMMARY
Alternative a.
	Consideration has been given to the various environmental impacts that 
the proposed site may have.  No socioeconomic impacts are anticipated 
with the proposed action.  No effects on local transportation patterns 
or volume is anticipated.  Short-term localized changes in noise levels 
and air quality will occur during construction, but these are expected 
to be brief in duration and limited in scope.  Mitigation/enhancement 
measures (enclosure (8)) address the impacts we will have on vegetation, 
floodplain, and wildlife in or adjacent to the proposed site.  Based 
on our evaluation, we conclude the proposed siting, facility 
construction and operation would have positive environmental 
benefits.  Furthermore, based upon the enhancement measures 
incorporated into our site planning, the site area will benefit 
significantly due to a reduction in negative human activity in 
that area (dumping, off-road vehicle traffic, etc.).
	Alternative b.
	Consideration has been given to the various environmental impacts 
that the proposed site may have.  Short-term localized changes in 
noise levels and air quality would occur during construction, but 
these are expected to be brief in duration and limited in scope.  
No socioeconomic impacts are anticipated with the proposed action.  
No effects on local transportation patterns or volume is anticipated.
Mitigation/enhancement measures would be required to address the 
impacts on vegetation, the floodplain, and wildlife in or adjacent 
to the proposed site.  The Coast Guards preliminary evaluation has 
concluded that the proposed siting, construction, operation, and 
maintenance would have not have a negative impact on the environment.  
However, additional time, money and studies will be required to ensure 
the site is acceptable.  The complexity of the systems and the diversity 
of operations performed at the base may be impacted by the installation 
of a DGPS site.  The proximity of the proposed site to other base 
facilities may make the electromagnetic signature of the DGPS station 
hazardous to normal station operations.  At a minimum, a hazard 
reduction program will probably be required.  
The resources required to implement and maintain such a program may not 
be available.  In addition, future base expansion may be impacted.  
For these reasons, the proposed site is determined to be unsuitable 
for the installation of a DGPS broadcast site.
	Alternative c.
	Implementation of the DGPS service is expected to reduce the number 
of navigation-related vessel groundings, collisions, coral reef 
damage, personal injuries, fatalities, and potential hazardous 
cargo spills resulting from such incidents by 50 percent over 
existing navigation methods.  This 50 percent reduction is based 
on accuracy, availability, and integrity requirements derived from 
a risk allocation model which used historical data from a busy 
waterway with a history of groundings and collisions.  The reduction 
will equate to yearly savings of approximately $21 million in 
commercial vessel/cargo damages alone and prevent approximately 
400 fatal injuries.  It will also provide cost avoidance to the 
U.S. of responding to such incidents (cleanup, restoration, 
investigation, etc.) and avoid the resulting environmental damage.  
If no-action is taken the potential savings described above can not 
occur.  For these reasons no-action is not a feasible alternative.







	ENCLOSURES
(1)  Boca Chica Ocean Shore Plat Book - 49
(2)  List of Organizations Contacted
(3)  Sample letter sent to state and federal officers 
(4)  DGPS Implementation Plans for NAS Key West, FL
(5)  Comments from U.S. Government Officials 
(6)  Comments from State of Florida Officials
(7)  Vegetation Survey and Habitat Assessment
(8)  Summary of Mitigation and Enhancement Measures
Organizations Contacted for Comments on DGPS Plans
	1.  U.S. Environmental Protection Agency, Region IV
2.  U.S. Fish and Wildlife Service
3.  Florida Dept of Environmental Regulation
4.  Florida Game and Fresh Water Fish Commission
5.  Florida Dept of Environmental Protection, Bureau of Beaches
    and Coastal Systems
6.  Florida Dept of State, Director, Division of Historical
    Resources
7.  U.S. Army Corp of Engineers, Regulatory Division
8.  Florida Division of Historical Resources, Compliance Review
    Section
9.  Florida State Clearing House, Office of Planning and
    Budgeting
10  Florida Keys National Marine Sanctuary
	SUMMARY OF MITIGATION AND ENHANCEMENT MEASURES
	Mitigation/Enhancement 
The following measures have been identified to mitigate Coast Guard 
caused impacts and further enhance the ecosystem associated with this 
project site;
- Alternatives to the planned ground plane system will be considered to 
minimize impacts to the area.
- The hut has been relocated to eliminate impact to mangrove wetlands and 
minimize impact to other native vegetation.
- Exotic species of plant will be removed and managed during the life 
of the project in accordance with NAS guidelines.
- Mowing will be eliminated or minimized to allow for natural growth 
of native vegetation.
- Vehicle traffic will be permitted on designated roadways only.
- Designated roadway will remain in it's natural state.
- Native vegetation will be reestablished through plantings or invasion 
through natural succession.
- Upon installation of structural components the remaining bare areas 
will be carefully scraped to reduce their elevation 2"-3" to form 
slight depressions for algal and native vegetation regrowth. 
- Solid waste will be removed from the site and disposed of according 
to State and local regulations.
- Roofing material dumped on the site is suspected to contain petroleum 
products and possibly asbestos. This waste stream will be tested and 
disposed of accordingly.
- A lockable gate will be placed at the entrance to the designated 
roadway to restrict entry to official vehicles.
- Brush removed for installation of the ground plane will be mulched and 
placed on the bare areas after scraping.
COMPLETENESS SUMMARY-DGPS SITE-KEY WEST FILE # 442822305
	1. An application fee of $600.00 payable to "Department of Environmental 
Protection" is being prepared.
	2. Vegetation within a 120 foot radius of the proposed 74 foot tall 
antenna will not be mowed. The native grasses will be disturbed 
during the placement of the ground radials and the buried 3" PVC 
pipe and utility service. Exotic vegetation will be permanently 
removed and shrubs on the north aspect of the ground radials 
within the 110' radius will be removed.
	3. Mangrove which have reestablished in this previously disturbed 
area along the two canals will not be disturbed. The equipment hut 
and the two reference masts had been relocated for this purpose.
	4. The application drawings will be sealed by a state registered 
Coast Guard Civil Engineer. As mentioned in our discussion of 
January 24, 1996 the Coast Guard Civil Engineers are registered 
in various states.
	5. The locations of the proposed 74 foot tall antenna, the utility 
poles, and the limits of the proposed buried ground radials will 
be staked just prior to construction. Ed Barham of the Marathon 
DEP office will be notified of the staking so that an inspection 
may be executed to verify compliance.
	6. The ground radials, 3" PVC pipe, and telephone line will be 
cut in with a pavement saw. Ground radials and telephone 
service will be laid in a 1-2" wide x 1-2" deep slot. The 3" 
PVC pipe will be laid in a slot 4" wide and 2', 4" deep. 
Excavated material will be contained on plastic sheeting. Parent 
material will be used for backfill. Surplus material will be 
removed from the site.