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.