20211442 Ver 1_NC SHPO_ILM Airport_Project Review 7 22 2020_20210429

PROJECT REVIEW
Project Name: Replacement of Visual Omnidirectional Range Tactical Air Navigation System
(VORTAC), Wilmington International Airport (ILM), New Hanover County
Project Location: 4900 Holly Shelter Road, Castle Hayne, NC 28429 (New Hanover County)
Project Contact Information:
Name: Karen Dorrell, Senior Environmental Engineer
Company: Parsons/Technical Support Services Contractor for the Federal Aviation
Administration (FAA)
Address: 3800 Camp Creek Parkway, Building 2400, Suite 106, Atlanta, GA 30331
Phone: [phone] Email: [e-mail]
Project Description
The ILM Visual Omnidirectional Range Tactical Air Navigation System (VORTAC) facility is
located approximately 6 miles north/northeast of the Wilmington International Airport, New
Hanover County in southeastern North Carolina at 4900 Holly Shelter Road, Castle Hayne. The
ILM VORTAC facility is accessed through a metal gate along an unpaved road about 1584 ft.
long (0.3 miles) (Figure 1) and is situated within a vegetative cleared area, with a 1000-foot
radius, surrounded by wetlands. The existing access road and facility were constructed on fill
approximately 1.5 ft. above the surrounding wetlands and the existing impervious area is 0.24
acres (Figure 2). Large trees and other vegetation surround the cleared area, obscuring the ILM
VORTAC facility from Holly Shelter Road to the north (with the exception of the narrow
opening in the trees for the access road alignment), from the industrial/commercial facilities
along Barbados Boulevard to the west and south, from Blue Clay Road to the east, and from
residences along Sunray Road to the southeast.
The proposed project consists of replacing the existing Visual Omnidirectional Range Tactical
Air Navigation System (VORTAC) with an elevated Doppler VORTAC. The existing VORTAC
has several radials that are no longer functional due to interference/obstruction from the mature
tree growth located at the edge of the 1000-foot radius cleared area. Converting to a Doppler
VOR will raise the counterpoise up 55 ft. in the air and will eliminate any interference from
anything on the ground and from obstructions (mature trees) below 80 ft. at the 1000-foot
radius. (The mature height of Southern White Pine is approximately 80 ft.)
The existing VOR antenna and shelter, and propane tank will be removed; the existing
transformer and back-up emergency communication (BUEC) will be relocated (Figure 2).
VORTACs are a combination of a VOR and TACAN, providing bearing and distance from the
navigation aid. Like a VOR, they are ground -based electronic navigation aids transmitting very
high frequency signals, 360 degrees in azimuth oriented from magnetic north. The TACAN
component is used to measure, in nautical miles, the slant range distance of an aircraft from the
navigation aid. A VORTAC provides VOR azimuth, TACAN azimuth, and TACAN distance
measuring equipment at one site. VORTACs transmit right -left information to pilots (bearing on
a specified course) as well as "distance to go" (Spohnheimer 2019). A VOR and VORTAC site
are very similar in layout and facility design. The site plot, equipment building, central cone

housing the VOR antenna, and surrounding monitor antennae are identical. A VORTAC differs
with the addition of the TACAN mounted on a collar usually connected to the VOR cone.
Doppler technology was introduced in the 1950s and, although it provides an improvement over
conventional VOR technology, it has not been as widely adopted because the antennae are more
expensive to build (Pellessier 2019; Spohnheimer 2019). Doppler VORs are less susceptible to
terrain reflections than conventional VORs. The different antenna technologies result in
differences in building dimensions or configurations at VOR sites nationwide. A typical Doppler
antenna array includes 51 instead of 4 antenna mounted on a larger counterpoise (roof) structure
than conventional sites (Pellessier 2019).
The elevated Doppler VORTAC facility will consist of expanded gravel/impervious surfaces
along the east and west sides of the existing gravel pad and construction of a 4-foot wide gravel
path extending 150 ft. from the east side of the expanded pad (approximately 0.31 acres), a new
VOR shelter measuring 11.5 ft. x 30 ft., a concrete engine generator (EG) pad measuring 10 ft.
by 12 ft., a disconnect/transfer switch rack, relocation of the transformer and back-up emergency
communication (BUEC) antenna, and the installation of new conduit lines from the VOR shelter
- to the TACAN monitor (which will be situated in the same location as the existing monitor),- to
VOR monitor and relocated BUEC, and -to the disconnect/transfer switch rack and transformer
(Figure 3). The elevated Doppler VORTAC will be/remain 55 ft. high; the relocated BUEC will
be 60 ft. high.
Ground Disturbing Activity
Ground disturbing activities include demolition of existing VORTAC concrete pads and
foundations, the addition of fill around the existing gravel pad and along the 150 ft. long path to
the relocated BUEC; excavation for twenty 7 ft. x 7ft. x 1 ft. footings with a base footing depth
equal to 24 inches, and open trenching to a depth of 3 ft. to install conduit for power and control
cables. As the proposed excavated depths most likely will exceed the current thickness of fill
(1.5 ft.) and extend into the saturated soils below, engineering fill will be added at these
locations.
Existing Site Structures
The ILM VORTAC is housed in a one-story square wood frame building, measuring 36 ft. x 36
ft. (1,296 sq. ft.) constructed prior to 1956 (Nationwide Environmental Title Research [NETR]
1956) and placed in service in 1958. The building design is similar to the standardized Type B'
plan (Figure 4). The building features an approximately 52 ft. diameter flat, round roof with
eaves overhanging the facades of the building. The underside of the roof (soffit) is covered in
corrugated aluminum siding. The disc -like roof is approximately 12 in. thick; the roof was
replaced with a poured roof system in 2016. The edge of the roof is covered with metal flashing.
Rising from the center of the roof is an approximately 16 ft. high white fiberglass `cone' or
`teepee' housing the set of four VOR antennae. The exterior walls are corrugated aluminum
siding. Ancillary structures associated with the ILM VORTAC facility are the VOR monitor on a
wood treated 18 in. diameter utility pole (40 ft. high), BUEC antenna (fiberglass tilt -down
tower), transformer, and propane tank. Navigational system components were updated in 1985.

Area of Potential Effects
The Area of Potential Effects (APE) consists of the project limits (0.67 acres) within which
ground disturbing activities such as demolition of existing facilities, excavation of concrete
footings, the addition of fill, and utility trenching will occur (Figure 5). Because large trees and
other vegetation obscure the view of the ILM VORTAC facility from surrounding parcels and
the heights of the elevated Doppler VOR and relocated VOR monitor and BUEC antenna are less
than 60 ft., the proposed project will not create any additional visual intrusions to Holly Shelter
Road (north), to the industrial/commercial facilities along Barbados Boulevard (west and south),
to Blue Clay Road (east), and to residences along Sunray Road (southeast).
Site Files Search
A site files search was conducted by a qualified archaeologist on May 29, 2020, using the online
North Carolina State Historic Preservation Office HPOWEB Geographic Information System
(GIS). No documented architectural resources are located within a 1/2 mile radius of the ILM
VORTAC facility project area.
As indicated by the 1947 USGS quadrangle, the APE represents a swampy area feeding
numerous small drainages flowing in all directions from the area (NETR United States
Geological Survey [USGS] 1947). A recent wetlands assessment defines the cleared area
surrounding the APE as a zone of heavily saturated soils with little standing water. Prehistoric or
historic occupations would occur in dry areas surrounding wetlands rather than within an area of
saturated soils. Because this area around the APE was historically a wetlands, the probability for
the presence of prehistoric or historic archaeological sites is unlikely.
The configuration of the ILM VORTAC building has remained unchanged since its construction;
alterations to the ILM VORTAC building include upgrades to the navigational equipment in
1985 and replacement of the roof in 2016. The ILM VORTAC building is a typical example of
approximately 961 facilities constructed across the United States to house air navigational aids.
Constructed of standard plans, of which variations exist, the common features of a VORTAC
building include the flat, multi -sided polygon roof with central cone constructed on a square or
rectangular building housing equipment and back-up power supply. Variations occur in building
footprint and style, height, and shape of the VORTAC antenna cone and monitor antennae.
Eighty-nine navigational aid locations are present within North Carolina (PilotNav 2020).
Sixteen locations contain VOR or VORTAC navigational systems.
Because VORTAC buildings dating from the late 1950s to the early 1960s are ubiquitous across
the country and were constructed of a simple, utilitarian design based on standardized plans, they
are not likely to be considered eligible for the National Register of Historic Places (NRHP). The
FAA has determined that the ILM VORTAC is not eligible for the NRHP.
Assessment of Effects
The existing VORTAC facility will be demolished and some equipment will be relocated.
Addition of the fill will occur around the existing VORTAC facility and in areas of adjacent
wetlands. Excavation of concrete footings will occur within the existing and new impervious
surfaces to depths of no more than 24 inches and may extend into saturated soils. Trenching for
the conduit containing the power and control cables will occur at depths no greater than 3 ft. and
may also extend into saturated soils.

No archaeological sites are likely to occur in the APE as the area has been historically a
wetlands; no archaeological sites would be disturbed by the proposed undertaking. No
architectural resources occur within a 1/2 mile radius of the APE and the ILM VORTAC is not
considered eligible for the NRHP due to its ubiquitous nature throughout the US, construction
based on standardized plans, and loss of physical integrity.
In accordance with Section 106 (54 USC 306108) of the National Historic Preservation Act
(NHPA), the FAA requests the North Carolina State Historic Preservation Officer' s concurrence
with this Finding of "No Historic Properties Affected" for the Replacement of Visual
Omnidirectional Range Tactical Air Navigation System (VORTAC), Wilmington International
Airport (ILM), New Hanover County.
References Cited
Nationwide Environmental Title Research (NETR). 1956. Aerial Photograph of the area around
4900 Holly Shelter Road, Castle Hayne, North Carolina. Available on-line at:
https://www.historicaerials.com/viewer. Accessed May 29, 2020.
NETR United States Geological Survey (USGS). 1947. Topographic Quadrangle showing the
area around 4900 Holly Shelter Road, Castle Hayne, North Carolina. Available on-line at:
https://www.historicaerials.com/viewer. Accessed May 29, 2020.
PilotNay. 2020. Navaids in North Carolina. Available on line at:
www.pilotnay.com/browse/Navaids/continent/North America/country/UNITED
STATES/state/NORTH CAROLINA . Accessed May 29, 2020.
Pellessier, Richard. 2019. Electronic mail to Steve Locher regarding Demolition of the GAL
VOR Building, dated June 4, 2019.
Spohnheimer, L. Nelson. 2019. Personal Communication between L. Nelson Spohnheimer,
Federal Aviation Administration (retired) and Spohnheimer Consulting, with Rachael Mangum,
Cultural Resources Specialist, Parsons.
Vanhoenacker, Mark. 2012. "What's That Thing? Pastoral Doodad Edition," published in
Browbeat, Slate' s Culture Blog. Electronic document,
http://www.slate.com/blogs/browbeat/2012/06/07/strange_ white_ cones_ out infields what are
they_.html, accessed November 9, 2017.

Figure 1. ILM VORTAC Replacement Project Location, Castle Hayne, New Hanover County, North Carolina

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Site Photographs
Figure 6. ILM VORTAC Facility, East and North Elevations, VOR Monitor and BUEC Antenna
at Left, Looking Southwest.

Figure 7. ILM VORTAC Facility, Transformer and Propane Tank at Right, Looking South.

Figure 8. ILM VORTAC Facility, East Elevation, Area Proposed for the Relocation of the VOR
Monitor and BUEC Antenna, Looking West.

Figure 9. Access Road and Tree Line Surrounding the Cleared Area Around the ILM VORTAC
Facility, Looking North Toward Holly Shelter Road.