Carrying Capacity Study-1983

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CARRYING
CAPACITY
STUDY
Currituck County 0utex Banks

CURRITUCK COUNTY OUTER BANKS
CARRYING CAPACITY STUDY
by
Christopher R. Bell
M. Candice Brisson
Ira P. Costel
Marc A. Fink
Susan A. Jones
Robert H. Pederson
C. Luther Propst
Stephen Sizemore
Sue K. Snaman
Nanette Vignola
Eric P. Vlk
Jane W. Wheeler
Diana S. Young—Paiva
(Students)
and
guided by
David Brower
David R. Godschalk
Edward J. Kaiser
(Instructors)
Department of City and Regional Planning
The University of North Carolina
Chapel Hill, N.C.
June 1983

TABLE OF CONTENTS
Page
I Introduction and Summary of Findings 1
II Potential Buildout Based on Availability and 7
Suitability of Land
III Hurricane Evacuation 28
IV Road Network 33
V Wastewater Disposal 37
VI Water Supply 55
Appendices
A Method for Calculating Potential Buildout A-1
B Miscellaneous Information About Major Developments on A-12
the Currituck Outer Banks -- As of February 20, 1983
C Description of Six Environmental Processes and A-15
Sensitive Areas on the Banks, and Thier Implications
for Development
D Method Used in Hurricane Evacuation Analysis A-25
E Method for Analysis of Road Network Capacity and Demand A-30
F Method for Wastewater Disposal Analysis A-34
G Notes on Drinking Water Supply A-50
References

FIGURES AND TABLES
Page
6
Figure
I-1
10
Figure
II-1
11
Figure
II-2
16
Table
II-1
17
Table
II-3
18
Table
II-4
19
Table
II-5
20
Table
II-6
21
Table
II-7
22
Figure
II-3
25
Figure
II-4
26
Figure
III-1
31
Table
III-1
32
Table
IV-1
36
Table
V-1
41
Figure
V-1
43 and 44
Figure
V-2
42
Table
V-2
53
Figure
VI-1
57
Figure
VI-2
58
Table
VI-1
69
Appendices
Table
E-1
A-33
Table
F-1
A-36
Table
F-2
A-38
Table
F-3
A-39
Table
F-4
A-44
Table
F-5
A-47

CHAPTER I
INTRODUCTION AND SUMMARY OF FINDINGS
This is a carrying capacity study of the Currituck County Outer Banks,
a beautiful but environmentally sensitive stretch of barrier island. By
carrying capacity we mean the reasonable limits of the natural and man—made
systems on the banks to absorb new development. Building beyond these
limits will endanger the health, safety or welfare of the residents,
degrade the natural environment, or pose a danger to the fiscal health of
local government. The report estimates the number of dwelling units that
could be built before exceeding the reasonable limits that we call carrying
capacity.
The report analyzes five factors that are important to the island's
capacity to absorb growth — availability and suitability of land for
development, the possible need for hurricane evacuation, road network for
access and internal circulation, wastewater treatment, and drinking water
supply. Each of these factors implies its own carrying capacity.
It should be emphasized that the carrying capacities of these five
factors are not fixed numbers, but depend on assumptions as well as facts.
They also can change with altered perceptions, knowledge or public
investment. For example, greater expenditures for infrastructure will,
within limits, permit more development to occur before carrying capacity is
reached. Of course, increasing the capacity of one of the five

2
determinants of capacity does not necessarily increase that of any other
determinant, and may in fact decrease it. The assumptions made in this
analysis are clearly stated in the text and appendices of the report.
Overall, assumptions generally lean toward allowing more development rather
than less.
The study does not consider the impacts of possible retail or
hotel/motel development. Such development would reduce the carrying
capacity of the island for dwelling units and create additional impacts on
man-made and natural systems.
The purpose of this report is not to make recommendations. Instead,
it is to provide data and a framework that will inform elected and
appointed officials in formulating and administering growth management
policy on the Currituck County Outer Banks.
The analyses reported here have been done by thirteen graduate
students as part of a course in the Department of City and Regional
Planning at the University of North Carolina at Chapel Hill. The class was
guided by three faculty members of that department. Expenses for the study
were paid by Currituck County.
Summary of Findings
o Under present county land use regulations, 15,580 dwellings can be
built on the available acreage on the banks. About 10,000 dwellings,
approximately two-thirds of this buildout capacity, could be built on the
southern half of the island. Approximately 60 percent of the total
potential buildout has already been platted or otherwise approved, at least
preliminarily, for development. Currently 409 dwellings exist on the banks.

3
o The figures above are based on existing plats plus a development
density of three dwellings per net acre on unplatted buildable land, as
allowed by present county land use policy. There are environmental
processes, such as beach erosion, and sensitive areas, such as moving sand
hills, that can constrain development, but which are not presently
regulated. These could be taken into partial account on a site by site
basis under appropriate regulations and review procedures.
o Under present arrangements for hurricane evacuation, 9060 dwellings
can be built on both the Currituck and northern Dare County outer banks,
and still allow for safe evacuation of residents and visitors in the event
of a hurricane. Even if no further development occurs on northern Dare
County Outer Banks, only 3790 additional dwellings could be built on
Currituck Outer Banks before hurricane evacuation capacity is reached.
Potential buildout on the Currituck Outer Banks under current regulations
will exceed the present hurricane evacuation capacity by 11,390 dwellings.
Further development on the northern Dare County Outer Banks, from Rill
Devil Hills north, would reduce capacity available to the Currituck Outer
Banks.
o The present road system can handle 5590 additional dwellings.
Buildout exceeds this capacity by 9990 dwellings. Two additional two—lane
highways would be required to adequately serve the potential buildout level
of development, at an estimated cost of one million dollars per mile.
o Soils on the Banks can accommodate a total of 2670 septic systems.
This is 12,900 less than would be required under potential buildout, which
would endanger drinking water supply, if served by on —site septic systems.

4
Alternative wastewater treatment systems must be able to handle 7.5 million
gallons of effluent per day. Actual water use could be substantially less
than 7.5 mgd, but wastewater disposal regulations require a wastewater
system to handle effluent produced at peak periods. This margin of safety
is incorporated into calculations to compensate for poor soil conditions,
periods of extreme wetness, etc.
There are no accurate data on water supply. Test wells should be
drilled and monitored to provide what may be the most crucial missing data
about the Banks. Whatever alternative drinking water supply systems are
used, they will have to supply between 5.3 and 7.5 million gallons per day
to adequately serve the island at potential buildout.
The diagram on the next page provides a graphic indication of the
situation. (See Figure I-1) There currently exist 409 dwellings on the
Currituck Outer Banks, as indicated near the bottom of the figure. The
first limit to further development will be encountered at 2680 dwellings,
if only septic tanks on suitable soils are used to treat wastewater. This
limit can be eased by providing alternative wastewater treatment systems.
The next limiting factor will be hurricane.evacuation, which will be
encountered at the level of 4,200 dwellings, less if further development
occurs on the northern Dare County portion of the Outer Banks.
If hurricane evacuation and wastewater treatment limitations are
alleviated, the existing road network will impose a limit of approximately
6,000 dwellings.
The available land imposes the ultimate constraint at a level of
15,580 dwellings -under current policy. This could be lowered, or raised,

�I
by a change in policy, or by an increase or decrease in the land made
available for development, e.g., by the sale of Nature Conservancy land for
development.
There is insufficient data on drinking water supplies on the
banks, but they could well impose an additional constraint on development.

0
FIGURE 1-1
CARRYING CAPACITY LIMITS ON DEVELOPMENT OF THE
15,580
Dwellings
6,000 DUs
4,200 DUs
2,680 DUs-
409 DUs
CURRITUCK COUNTY OUTER BANKS
Potential Buildout on Available Upland
Under Current Land Use Policy
Capacity of Existing Road Network, Maintaining
an Acceptable Level of Service
Capacity of Existing Hurricane Evacuation System
(Less if Further Development Occurs on northern
Dare County Outer Banks)
Capacity if On-site/Septic Tanks are Used for
Wastewater Treatment on Suitable Soils
Existing Level of Development on the Currituck
County Outer Banks
Water Supply

7
CHAPTER II
POTENTIAL BUILDOUT BASED ON AVAILABLILITY AND SUITABILITY OF LAND
Land is perhaps the most basic factor limiting growth on the Currituck
Outer Banks. The availability and suitability of developable land places
limits on the ultimate capacity for growth and certainly affects the
location, timing, and manner of development on the Banks.
The analysis of land availability and suitability presents three de—
velopment scenarios. All three scenarios assume that land currently owned
by conservation organizations will remain undeveloped. The first scenario
is buildout of all available lands defined as "uplands" by the county tax
office for assessment purposes. This scenario applies the county's density
limit of three dwelling units per acre to the total area of "upland"
located on undeveloped property, then adds the total number of already
platted, or otherwise approved, dwelling units to produce the total
potential buildout. The figure of three dwelling units per acre, derived
from the county's density limit, can be adjusted to project buildout
figures under higher or lower permissible density levels. This first
scenario represents buildout under relatively unrestricted conditions
and the existing density policy of the county.
The second and third scenarios exclude land that may be subject to
regulatory prohibitions on residential development. As prescribed by
Currituck County Planned Unit Development (PUD) regulations, the second
scenario applies a density limit of three dwelling units per acre to all

8
undeveloped land not classified as wetland under the Coastal Area
Management Act (CAMA). The resulting potential for additional development
is added to the total number of already approved dwelling units developable
under CAMA wetlands regulations, to yield the total potential buildout.
This second scenario represents the best estimate of maximum buildout under
current development regulations.
The third scenario represents the most restrictive estimate of
buildout. It applies a density limit of three dwelling units per acre to
all undeveloped land not designated as a CAMA Area of Environmental Concern
(AEC), or as wetlands according to Section 404 of the Clean Water Act.
ABCs under the Coastal Area Management Act include ocean hazard areas and
estuarine shoreline setbacks, as well as the CAMA defined wetlands included
in the second scenario. The resulting figure approved is added to the
total number of already approved dwelling units developable under CAMA
regulations and Section 404 wetlands regulations, to yield the total
potential buildout. Again, the density limit of three dwelling units per
acre can be adjusted to project buildout under higher or lower permissable
density limits.
Figures II-1 and II-2 show the areas regulated as CAMA AEC and 404
wetlands. The methodology used to define and delineate regulated areas and
calculate buildout is explained in Appendix A.
Several provisos should be noted regarding county PUD regulations,
CAMA regulations, and Section 404 wetlands regulations. First, although the
PUD density limit is applied to all land area outside CAMA wetlands, some
of the PUD net acreage remains subject to the development prohibitions of

9
Section 404 and other CAMA AEC regulations. For example, building within
the ocean erodable area is prohibited, but the area can be counted in
computing density limits for the overall development. Also, there are
instances where 404 wooded swamplands are inland of CAMA wetlands, and can
be counted in calculating the allowable number of dwellings, although the
land cannot be built upon. Therefore, the actual density of new
development under PUD regulations may substantially exceed three dwelling
units per developable acre. Second, the jurisdiction of either CAMA or
Section 404 regulations may be modified independently of the other, and
therefore a change in either will affect what development is or is not
allowed. Third, a permitting authority's application of the regulations toa
a specific project may affect the delineation of regulated and buildable
areas and thus the number of permissible dwellings in ways that can not be
completely foreseen in a general analysis such as ours. However, it is
believed that our estimates are both sound and reasonable, given current
information.
For the purpose of this analysis, the Currituck Banks are divided into
a northern and a southern section. The northern section extends from the
Virginia state line to the southern boundary of the Nature Conservancy's
Monkey Island holding. The southern section extends south from this point
to the Dare County line, and consists of that part of the Banks that has
access by existing paved road. This division also separates the southern
portion, which is under more intensive development pressures, from the less
intensely pressured northern portion of the Banks.

Legend
- CAMA Wetlands
® 404 Wetlands
® Ocean Erodible Areas/Estuarine Shorelines
REGULATORY CONSTRAINTS
u1..a. 0....
s
North Half
Currituck County Outer Banks
0

Figure II-2
REGULATORY CONSTRAINTS
u,..... a.... r r r r —
■ \ / w .f sr .....� ._• r 1r tt If s r Tt r tt �7
r7i.pnw■wIrtr's.or7llirw�111■ltlfrti<!r" i ..,_
ot
t.;-r,U
C.,."... s....
Legend
- C:AMA Wetlands
® 404 Wetlands
® O....Erodible Areas/Estuarine Shorelines
it
Ar4Z" -qm%�
c..•,r... s....
South Half
Cu rrituck County Outer Banks
.�• ► 8n�rd rol (bmmss,Or+ery III MARK 71.1►f1
_ Cwnluch Ca.nly, Norin (:a roi,na -

Legend
Approved for Development
- Conservation
QLlndevelopea
II-3
PROPERTY OWNERSHIP/STATUS
North' Half
Currituck County Outer Banks

Legend
® Approved for Development
- Conservation
e
Undeveloped
II-4
PROPERTY OWNERSHIP/STATUS
VON
WRI
K.
ii "n'.'. r� S .1 • -- mac,':
b
J\, r.""red for ...-
Board of Corr "loners LIRMARDT CAPPS '
.±-- CurrilucR Courtly..01, Caro�ina
South Half
Currituck County Outer Banks

13
There are several environmentally sensitive areas, including the beach
and dune system, washover areas, inlet hazard areas, aquifer recharge
areas, maritime forests, and the estuarine system, which can further limit
development. To assure their consideration, specific standards and
practices should be incorporated into the development review and permitting
process. They have not been used as a limit to the number of dwellings
allowed under current policy in this analysis.
Each scenario assumes that no development will occur on the Monkey
Island South and Swan Island tracts held by The Nature Conservancy on the
northern section of the island or on the Audubon Society's land in the
southern section. If these parcels are not withheld from development, the
potential buildout figures would be substantially higher. Figure II-3 and
II-4 show ownership patterns on the banks, including the parcels held by
The Nature Conservancy and Audubon Society, the areas already approved for
development, and the undeveloped but presumably available areas.
Tables II-2 through II-7 show the developable acreage and/or buildout
capacity (in dwelling units) of each parcel of both undeveloped land and
already approved developments, for each of the three scenarios. More
information about major developments (as of February 20, 1983) is contained
in Appendix B.

12
This analysis also identifies several natural features that do not act
as outright prohibitions on development, but that do have implications for
development management on the Currituck Outer Banks. Land features that
present constraints to development include the following; 1) the beach and
dune system, 2) washover areas, 3) inlet hazard areas, 4) aquifer recharge
areas, 5) maritime forests, and 6) the estuary and salt marshes. -
Findings
The first scenario, buildout of uplands as defined by the county tax
office, would allow up to 15,720 dwelling units to be built on the
Currituck Banks. Of this figure, 6200 dwelling units could be expected in
the northern section and 9520 units in the southern section.
The second scenario, maximum buildout under current development
regulations, including CAMA wetlands regulations, would allow up to 15,580
dwelling units to be built. Of these, 5480 dwelling units could be
expected in the northern section and 10,100 units in the south.
The third scenario, buildout of only that land on which actual
residential development is permitted under CAMA AEC regulations and
section 404 wetlands regulations, would allow up to 13,150 dwelling units
on the Banks. Of these, 4330 units could be expected in the northern
section and 8820 units in the southern section
Table II-1 displays these potential buildout figures. It also shows
that 55 to 60 percent of the potential buildout has already been platted or
otherwise approved for development. Vested rights represented in each ap-
proved development will limit the potential effect of any changes in growth
policy.

I
TABLE II-1
POTENTIAL BUILDOUT BASED ON LAND AVAILABILITY AND SUITABILITY
(In Dwelling Units, rounded to nearest 10)
Scenario, and Potential Buildout Potential Buildout Total Potential
section of the In Existing on Undeveloped Buildout
Banks (1) Development Property
Scenario I (2)
North
3010
3190
6200
South
6390
3130(5)
9520(5)
Total
9400
6320
15,720
Scenario II (3)
North
2610
2870
5480
South
6090
4010(5)
10,100(5)
Total
8700
6880
15,580
Scenario III (4)
North 2600 1730 4330
South 5790 3030 8820
Total 8390 4760 13,150
15 Each scenario excludes land belonging to conservation organizations,
i.e., The Nature Conservancy and the Audubon Society.
2) Scenario I is buildout of undeveloped land at three dwelling units
per acre of "upland", as defined by the county tax records.
3) Scenario II is buildout of undeveloped land at three dwelling units
per "net acre", as defined by the county PUD ordinance (gross acreage
minus CAMA wetlands).
4) Scenario III is buildout of undeveloped land at three dwelling units
per acre of land actually developable after deleting Section 404 (of
the Clean Water Act) wetlands, and areas regulated by CAMA Area of
Evironmental Concern regulations (wetlands, ocean erodible areas,
estuarine shoreline).
5) Buildout figures for the undeveloped south section of the island are
"unexpectedly" larger under Scenario II than for Scenario I, because
CAMA wetlands under Scenario II allow more buildable land for several
large parcels than did tax record determinations.

17
TABLE II-2
POTENTIAL BUILDOUT FOR NORTH CURRITUCK UNDER SCENARIO I: FULL BUILDOUT
Tax Office Uplands Potential
Property Identification (Acres) (1) Dwelling Units(2)
Existine Development
A. Seagull 37
B. Swan Beach 539
C. North Swan Beach 414
D. Carova Beach 2,019
Subtotal 3,009
Undeveloped Property
1.
Hall, Ballantine,
33
99
& Woodhouse
2.
Ocean Beach &
223.5
670
Misc. Lots
3.
Lewark/Bender
41
123
4.
Parker
14
42
5.
Ocean Associates
150
450
6.
White Estate
0
0
7.
Unknown Owner
2.5
7
8.
Friedman
36
108
9.
Swan Island Club
26
78
10.
White Estate
22
66
11.
Gray/Gray
110
330
12.
Swan Beach Corp.
160
480
13.
Carova Corp.
200
600
14.
Construction Assoc.
0
0
15.
Atlantic & Gulf
0
0
16.
Ganaway & Gray
46
138
Subtotal
1,064
3,191
TOTAL BUILDOUT
6,200
1 Upland acres as shown on the property tax valuation records.
2 Approved PUD dwelling units plus subdivision lots approved and pending
approval, with one dwelling unit per subdivision lot; or tax records
upland acreage times three dwelling units per acre.

18
TABLE II-3
POTENTIAL BUILDOUT FOR SOUTH CURRITUCK UNDER SCENARIO I: FULL BUILDOUT
Tax Office Uplands Potential
_Property Identification (Acres) (1) Dwelling Units (2)
Existina Develooment
A.
Pine Island Estates
12
B.
Sealoft
30
C.
Ocean Sands
3,600
D.
Ocean Breakers
600
E.
Whalehead
858
F.
Whalehead - Phase 2
455
G.
Whalehead Hunt Club
278
H.
Corolla
128
I.
Ocean Hills
340
J.
Monkey Island South
84
Subtotal 6,385
Undeveloped Property
1. Pine Island Club
290
870
2. Davis
35
105
3. Currituck Club
567
1,701
4. Unknown Owner
5.5
16
5. Whalehead
146
438
Subtotal
1,043.5
3,130
TOTAL BUILDOUT 9,515
1 Upland acres as shown on the property tax valuation records.
2 Approved PUD dwelling units plus subdivision lots approved or pending
approval, with one dwelling unit per subdivision lot; or tax records
upland acreage times three dwelling units per acre.

19
TABLE II-4
POTENTIAL BUILDOUT FOR NORTH CURRITUCK UNDER SCENARIO II: CURRENT POLICY
Potential PUD
Property Identification PUD Net Acreage(l) Dwelling Units(2)
Existing Develovment
A. Seagull 27
B. Swan Beach 489
C. North Swan Beach 217
D. Carova Beach 1,884
Subtotal 2,614
Undeveloped Property
1.
Hall, Ballantine,
5
15
& Woodhouse
2.
Ocean Beach &
182
546
Misc. Lots
3.
Lewark/Bender
31.5
94
4.
Parker
31
93
5.
Ocean Associates
98
294
6.
White Estate
36.5
109
7.
Unknown Owner
2.5
7
8.
Freedman
15
45
9.
Swan Island Club
17.5
52
10.
White Estate
4
12
11.
Gray/Gray
47
141
12.
Swan Beach Corp.
47
141
13.
Carova Corp.
228
844
14.
Construction Assoc.
20
60
15.
Atlantic & Gulf
106
318
16.
Ganaway & Gray
31.5
94
Subtotal
902.5
2,865
TOTAL BUILDOUT
5,479
l Land not restricted by CAMA wetlands regulations; from the National
Wetlands Inventory Classification.
2 Existing dwelling units or lots not subject to CAMA wetlands
restrictions; or undeveloped land not subject to CAMA wetlands
regulations times three dwelling units per acre.

20
TABLE II-5
POTENTIAL BUILDOUT FOR SOUTH CURRITUCK UNDER SCENARIO II: PRESENT POLICY
Potential PUD
Property Identification PUD Net Acreage(l) Dwelling Units(2)
Existing Development
A.
Pine Island Estates
12
B.
Sealoft
30
C.
Ocean Sands
3,483
D.
Ocean Breakers
600
E.
Whalehead
730
F.
Whalehead — Phase 2
443
G.
Whalehead Hunt Club
262
H.
Corolla
118
I.
Ocean Hills
325
J.
Monkey Island South
84
Subtotal 6,087
Undeveloped Property
1. Pine Island Club
468
1,404
2. Davis
27
81
3. Currituck Club
523.5
1,570 '
4. Unknown Owner
5.5
16
5. Whalehead
315
945
Subtotal
1,339
4,016
TOTAL BUILDOUT
10,103
l Land not restricted by CAMA wetlands regulations; from the National
Wetlands Inventory Classification.
2 Existing dwelling units or lots not subject to CAMA wetlands
restrictions; or undeveloped land not subject to CAMA wetlands
regulations times three dwelling units per acre.

21
TABLE II-6
POTENTIAL BUILDOUT FOR NORTH CURRITUCK UNDER SCENARIO III:
FULL CONSIDERATION OF CAMA AECS AND 404
CAMA/404 Potential Dwelling
Property Identification Developable Land(1) Units under CAMA/404(2)
Existing Development
A. Seagull 27
B. Swan Beach 489
C. North Swan Beach 213
D. Carova Beach 1,875
Subtotal 2,604
Undeveloped Property
1.
Hall, Ballantine,
5
15
& Woodhouse
2.
Ocean Beach &
138
414
Misc. Lots
3.
Lewark/Bender
28
84
4.
Parker
23.5
70
5.
Ocean Associates
80
240
6.
White Estate
5
15
7.
Unknown Owner
2.5
7
8.
Friedman
13
39
9.
Swan Island Club
15
45
10.
White Estates
4
12
11.
Gray/Gray
39
117
12.
Swan Beach Corp.
45
135
13.
Carova Corp.
127
381
14.
Construction Assoc.
20
60
15.
Atlantic & Gulf
31
93
16.
Ganaway & Gray
0
0
Subtotal
576
1,727
TOTAL BUILDOUT
4,331 .
1 From CAMA and 404 wetlands delineation on the National Wetlands
Inventory Map and CAMA AEC setback regulations.
2 Existing dwelling units or lots not subject to CAMA AEC or 404
development restrictions: or CAMA/404 developable land acreage times
three dwelling units per developable acre.

E*A
TABLE II-7
POTENTIAL BUILDOUT FOR SOUTH CURRITUCK UNDER SCENARIO III:
FULL CONSIDERATION OF CAMA AECs AND 404
CAMA/404 Potential Dwelling
Property Identification Developable Land(l) Units under CAMA/404(2)
Existing Development
A.
Pine Island Estates
12
B.
Sealoft
28
C.
Ocean Sands
3,483
D.
Ocean Breakers
560
E.
Whalehead
702
F.
Whalehead — Phase 2
436
G.
Whalehead Hunt Club
261
H.
Corolla
114
I.
Ocean Hills
125
J.
Monkey Island South
64
Subtotal 5,785
Undeveloned Prooerty
1. Pine Island Club
389
1,167
2. Davis
16.5
49
3. Currituck Club
401
1,203
4. Unknown Owner
4.5
13
5. Whalehead
198.5
595
Subtotal
1,009.5
3,027
TOTAL BUILDOUT 8,812
l From CAMA and 404 wetlands delineation on the National Wetlands
Inventory Map and CAMA AEC setback regulations.
2 Existing dwelling units or lots not subject to CAMA AEC or 404
development restrictions; or CAMA/404 developable land acreage times
three dwelling units per developable acre.

23
Additional Environmental Constraints to Development
This final section pertaining to land availability and development
suitability addresses environmentally sensitive features as factors in
development management. The natural features and areas discussed here do
not act as absolute barriers on development within an area, and have not
been reflected in the preceding analysis. However, they do have
implications for development regulations on the Currituck Banks.
Currituck Banks is a barrier spit, and as such, is a single ecological
system in a state of dynamic equilibrium with the ocean and the natural
forces that shape the land on the spit. The various land features or areas
are tied to each other by natural processes that affect the coastal
environment, such as sand and water movement. Changes in one part of the
system, such as in the maritime forest or the salt marsh, affect all the
other parts of the island. Thus, for the purposes of development
management, the separate coastal features should not be treated separately.
For example, management of the maritime forest can simply not be addressed
without consideration for the future subsurface water supply of the
island.
Any land suitability analysis must consider the importance of
maintaining the long-term viability of the natural systems and land
features that protect the Currituck Sound and the economic activities
dependent on the Sound and that give the banks their appeal as a place to
live and work, to vacation, or to retire.

24
Specific development densities, performance standards, or regulations
for each land area are not recommended here. Often these standards and
regulations involve value judgements where present benefits of development
must be weighed against -future costs of the development. The quantity of
development that is desirable will depend on several factors, including:
the quality of site design, site specific characteristics, and the
technology utilized to mitigate impacts of development.
The brief discussion here is limited to major implications for
development regulations and site design practices. More complete
descriptions and discussions of the natural processes and their
implications for development may be found in Appendix C.
The beach and dune system. Land management implications of the dune
and beach system require that development be prohibited from the frontal
dune and the area within the ocean erosion zone immediately landward
of the frontal dune. Access to the ocean over the frontal dune should
require boardwalk overpasses. Homes and roads should be kept out of the
path of migrating sand hills. (See Figures II-5 and II-6 for
locations of migrating sand hills). Natural plant species tolerant to
salt spray and saltwater flooding should be utilized in landscaping
standards.
Washover areas. Damage done by storm washover can be minimized by
limiting alterations'to topography, controlling density, and particularly
by controlling the amount of impervious surface. Impervious surfaces may
require expensive measures to keep them free of sand and water, and serves
to funnel flood waters into areas that would not otherwise be flooded.

:y;
44, 1
J,
IJ
Legend
Maritime Forests
Active Dunes
H-5
OTHER NATURAL CONSTRAINTS
TOTAL
PARTIAL ov,RWASM 196
2 OVIRWASH TOTAL OtEENAEX
F
T ' - -- i -A 5- - , !. i j, + F
T
41
�-Xlx
0.4"
s'
14
.4r
.17
North Half
Currituck County Outer Banks
PARTIAL
VIRWAS]
1962
r')
Ln

PARTIAL
ova"RRH
1902
♦ W. :�•
(
AUu,I. 0....
`^w
C.,.,-& 9n.1
Legend
Maritime Forests
Active Dunes
PARTIAL
OVRRWAR
1062
Figure II-6
OTHER NATURAL CONSTRAINTS ] POTLATIAL INLET SITE
PARTIAL OvRRMARH 1e62
.i�r ^�.� •-_'lM A ✓,�` _jtF .yJ:.. 1.��.r, a.___,�-_ 1 �y ��•'.•.�„ "�. �,-�(�i e_ � l�•1
`7!♦w •I_ " ..1- �7, ,•n�t(G %`, 7~ ^•�.. �_! �.i
_r r _—✓••"— .�`../.—....—�-.---�--.,,_ • •� •• •• f�i VI ".'_�`,� ram. [ S� •• �' , . � L� � Li .,,.' �
FRS -' -/ .. \:��• t C. � ��� V i�
It, ..: �.%' t �:..h ✓'1' ... ; t '. r —_
}
P
C.,H,.d R..M
South Half
Currituck County Outer Banks
- \ prepared for _.
i Board of Comn.ss,oners
►t5
Currituck County. North Carolina iq¢A0.D T CA
N
ON

27
Sand hills in washover areas should not be removed. Washover areas on the
Banks are shown in Figures II-5 and II-6.
Potential inlet hazard areas. Public and private investment should be
minimized in the two locations having the highest susceptability to storm
surges forming a new inlet. one of these areas is Carova Beach, where
canals have narrowed the island and provide a funnel for water to surge
from the sound side. The other is at the former Caffey's Inlet, near the
Dare County line.
Aquifer recharge areas. Within known shallow aquifer areas, design
criteria should minimize impervious surfaces and retain natural drainage
patterns, and should discourage removal of vegetation.
Maritime forests. While the forest areas are the safest parts of the
island to develop, they are also critical for aquifer and terrain
stability. Site design standards should minimize removal of trees or their
exposure to salt spray and wind shear. Areas of maritime forest vegetation
are shown in Figures II-5 and II-6.
The estuary system and salt marshes.. Development regulations should
serve to minimize overintensive development near the sound; poor septic
system design, installation, or maintenance; poorly designed storm
drainage; and cutting and filling in order to protect the estuarys and salt
marshes.

_W
CHAPTER III
HURRICANE EVACUATION
Hurricane evacuation is one of the critical factors in determining the
carrying capacity of the Currituck Outer Banks. All persons wanting to
evacuate should be able to do so safely, in event of a major storm hazard.
The Outer Banks of Currituck County are subject to the periodic
passage of hurricanes, with heavy rain and winds ranging from 74 to 250
miles per hour (Rogers, Golden and Halpern, 1981). North Carolina's
coastal population has grown more than 88 percent since the last major
hurricane, in 1960. Therefore, most coastal residents have not experienced
the destructive power of a hurricane. Further, the potential loss in lives
and property is much greater than it was in 1960.
There are a number of destructive components of a hurricane, such as
high winds, flooding, wave action and erosion. The vast majority of
property damages and fatalities resulting from hurricanes are a consequence
of flooding. In addition, flooding from rains can begin before tidal
inundation and thereby wash -out escape routes and cause flooding in areas
not reached by the storm surge (McElyea,.Brover, and Godschalk, 1982).
Aside from contributing to flooding, waves can also destroy property and
threaten lives by battering action.
The likelihood that North Carolina will be struck by a major hurricane
in any one year is about one in 40. The chance of a less -than -major

29
hurricane is one in ten (McElyea, Brower, and Godschalk, 1982). However,
it must be remembered that this is only a statistical probability. Between
1954-1960 eight hurricanes hit North Carolina, including three within five
weeks in 1955. The lack of a major storm has led some to conclude that
coastal residents now have a "false sense of security" (Stone, 1983).
Stone points out that many have forgotten, or were not around when
Hurricane Hazel killed nineteen people'and caused $100 million worth of
property damage in 1954.
Findings
The carrying capacity of the Currituck Outer Banks is limited by the
road capacity of the escape route over the Wright Memorial Bridge (Highway
158) during hurricane evacuation. The bridge would serve upper Dare
County's Outer Banks (from Rill Devil Hills to Duck) as well as the
Currituck County Outer Banks. See Figure III-1. The causeway represents
the critical point over which all evacuating vehicles must travel.
Eight hours was assumed to be the available time for safe evacuation
during the 12 hour warning period. The capacity of the bridge over an eight
hour evacuation period is 12,600 vehicles. This translates to 7,240 to
12,080 dwelling units being able to evacuate safely (depending on the
number of vehicles assumed to be evacuating per dwelling) from Currituck
Outer Banks and the northern part of Dare County's Outer Banks. These
figures also assume that approximately fifteen percent of the population
leave early (see Appendix D for a more complete explanation of the calcula-
tion of evacuation capacity.)

30
There are now only 409 dwelling units on Currituck Outer Banks and
4,860 dwellings on northern Dare County Outer Banks, so evacuation capcity
is not a problem. Excess capacity must be allocated between future Dare
and Currituck growth, because both areas use the same causeway.
Potential buildout far exceeds what the current evacuation route can
handle. Table III-1 shows the number of dwelling units in excess of the
evacuation capacity, assuming three different numbers of vehicles leaving
per dwelling unit.
If the entire island is developed to the 15,580 dwelling unit
potential on Currituck, evacuation demands will be vastly over capacity.
Vehicles needing to evacuate at this level of buildout will range from
24,530 to 40,880 vehicles. This includes the 4860 dwelling units existing
in Dare County needing to use the same evacuation route as Currituckians
(see Figure III-1).

31
ONO •4r4
a
�VIRGINIA—
NORTH CAROLINA
STATE LINE
COROLLA
FIGURE III-1
HURRICANE EVACUATION SHED
AND
EVACUATION ROUTE
KILL DEVIL HILLS
EVACUATION
SHED
air ROADWAY

32
TABLE III-1
SUMMARY OF INADEQUATE HURRICANE EVACUATION CAPACITY AT BUILDOUT
Vehicle/DU Evacuation Additional DUs Excess DUs Over
Assumed Capacity that can be built Evacuation Capacity
in DUsl before capacity at Buildout Leve13
is reached2 (20,440 DUs)
1.2 12,080 6,810 8,360
1.6 9,060 3,790 11,390
2.0 7,240 1,870 13,200
l Based on dividing 14,490 vehicles by the assumed vehicle/dwelling unit
level.
2 This is the difference between evacuation capacity and existing numbeis
of dwelling units (4,860 dwelling units in Dare County and 409 dwelling
units in Currituck County).
3 Buildout assumes 15,580 dwelling units on Currituck Banks and 4,860
dwelling units in the Dare County section of the Outer Banks (assumes no
additional development in Dare County) or a total of 20,440. Figures
Tn-
this column are obtained by subtracting 20,440 from column 2.

33
CHAPTER IV
ROAD NETWORK
The carrying capacity analysis of the Currituck Banks reported in this
chapter is based on the existing road network and on the implications of
potential buildout for capital improvements in the road network. This
analysis is important because the road network is a vital and necessary
part of the everyday functioning of the community. Increased development,
without a concurrent increase in road capacity, will lead to congestion,
noise, and air pollution. This chapter makes the connection between
demand, based on the number of dwelling -units, and the supply, or capacity,
of the road network.
The findings focus on how much buildout can occur without running into
excess demand on the existing network capacity. Buildout Scenario II,
based on current land policy, is utilized to determine whether the capacity
of the existing network is great enough to handle the traffic demand that
would result .
Findings
The findings are broken down according to two levels of development;
existing development and potential buildout under current policy (15,580
dwellings).
Current development is 409 dwelling units. The existing road network
is more than adequate to deal with the trip demand that is presently
generated. It is estimated that an additional 5590 dwelling units could be

34
built without putting a strain on the existing road network's capacity.
Potential buildout, based on land availability under current policy,
is 15,580 dwellings. Given the capacity of the existing road network, it
is estimated that there would be an excess demand on the road network of
about 10,540 trips. (See Appendix E for amplification of the methodology.)
This number is the equivalent of 9580 dwelling units too many. The road
network would be severely strained. In order to meet the increased demand
that would exist if the full buildout occurs, 3.2 lanes, or almost two new
roads similar to what now exists, would have to be built. The cost of this
would be about one million dollars per mile, not counting right of way
(Goode, 1983). Findings are summarized in Table IV-1.
Conclusions
The above analysis is based on two further assumptions. First, it
assumes that the main road from the Dare County line to Corolla will become
public. If it remains in private hands, however, with access to the Banks
controlled by guards hired by private developers, development even to road
capacity may not occur because of lack of confidence by potential
homeowners about access to their homes. This assumption ultimately has an
effect on all of the capacity analysis in this report. The question of
public acquisition of the road was not explicitly addressed in the report
because the political situation involved is outside the report's scope.
Public acquisition, or lack of it, will, however, have an effect on the
final level of development.

K61
The second assumption, regarding full buildout, is that road access
from Corolla north to Carova Beach will be provided. If it is not provided,
the existing situation -- in which people living north of Corolla must drive
four—wheel drive vehicles up the beach at low tide to reach their homes --
will severely constrain development north of Corolla. This situation was
not explicitly dealt with because it goes beyond the charge of this study.
It must, however, be considered in the final analysis.

36
TABLE IV-1
SUMMARY OF ROAD NETWORK CAPACITY FINDINGS
Implication of Implication of
Information Existing level Potential
Category of Development Buildout Under
Current Policy
Current Capacity 6,600 vehicles 6,600 vehicles
of Road
# of DUs 409 dwellings 15,580 dwellings
Demand 450 trips 17,140 trips
( trips)
Demand 6,150 trips 10,540 trips
Under/Over under capacity over capacity
Capacity
Demand 5,590 dwellings 9,580 dwellings
Under/Over under capacity over existing capacity
Capacity —
# of DUs
Capacity 3.2 lanes;
Expansion 2 new roads
Needed to
Meet Demand
Costs of $1,000,000
Capacity per mile
Expansion

37
CHAPTER V
WASTEWATER DISPOSAL
Wastewater disposal will be a critical factor in determining the
future growth and development of the Currituck Banks. Natural features
such as extremely porous soils, high seasonal water table and other factors
have already led to contamination of groundwater and shell -fish beds in
other North Carolina coastal communities.
In addition to the major consideration of cost, other important
considerations must be included in the analysis of wastewater disposal
alternatives. Among these are:
• Flexibility
• Reliability
• Environmental Impact
• Public Health Considerations
• Social Impact
• Economic Impact
Flexibility is the ability to meet changes in treatment requirements,
respond to changes in wastewater characteristics, expand capacity, adapt to
changing land uses, and upgrade in response to technological advances.
Reliability is the ability of a wastewater system to meet or exceed
discharge requirements, have a low failure rate, not be vulnerable to
natural disasters, and be assured of the adequacy and availability of
critical materials and repair services.

38
Environmental Impact pertains to the effects upon soil, vegetation,
groundwater, surface water, animal and insect life.
Public Health Considerations refer to groundwater quality, potential
runoff from the site, and airborne overspray from applications methods.
Social Impact refers to public acceptance of the treatment method,
aesthetic concerns, and the market for any harvested crop from a land
application site.
Economic Impact is concerned with the change in value for land used
for application or land adjacent to the site, ability of government to
purchase suitable tracts, conservation of resources used in treatment
processes, and energy conservation.
Five wastewater systems were selected for study as potentially
feasible solutions for the Currituck Banks:
(1) on -site disposal using conventional septic system technologies
(2) package treatment plants with disposal by land application
(3) .package treatment plants with ocean outfall disposal
(4) package treatment plants with collection by pressure sewers and
disposal by land application
(5) collection of wastewater from the Banks for land disposal on the
mainland
The fifth option is discussed in less detail due to limited
information. This option is currently used at Onslow Beach for a private
development of 600 condominiums.

39
Findings
On -Site Wastewater Disposal Alternatives. On -site alternatives
include the conventional septic system and other ground disposal or
alternative septic system methods that are appropriate for conditions found
on Currituck. In the conventional septic system, wastes from a residence
are collected in a septic tank where solid particles settle out and the
liquid effluent moves by gravity out to a system of subsurface trenches.
Treatment is achieved by bacteria in the soil. The advantage of septic
systems is the use of natural aeration and filtration to treat wastewater
close to the source. The main disadvantage is the potential for
groundwater contamination if a septic system fails due to improper
installation or maintenance, or its location in unsuitable soils.
Capacity Implications of On -Site Alternatives. Due to Currituck
Banks' predominant natural soil characteristics of high water table
(ranging from 0 to 6 feet from the surface), wetness, and frequent flooding
in many parts, extensive use of on -site disposal systems is not feasible.
Using criteria set by North Carolina for ground absorption sewage treatment
systems, it has been determined that a total of 1,338 acres of Currituck
Banks is suitable for on -site systems. See Figure V-1 for a mapping of
"suitable" soils. Subtracting acreage with already improved lots and the
Ocean Sands development served by a package treatment facility,
approximately 1,125 acres of Currituck Banks (approximately 13 percent of
the total 8,800 acres) remain suitable for on -site wastewater disposal
systems.

40
This suggests that some additional dwellings could be accommodated
using conventional septic systems on suitable soils. This additional
capacity is approximately 2,390 dwellings, assuming two dwellings per acre,
for a total capacity using on -site systems of 2,680 dwelling units,
excluding existing units in the Ocean Sands development.
Although up to three dwelling units per acre using septic tanks are
allowed under North Carolina Coastal Zone regulations, the actual number of
dwelling units allowed would depend on the amount of land required for
setbacks for each lot. Conservative setback requirements and an allowance
for protection of groundwater sources could reduce the amount of available
space below three dwellings per acre; Hence the assumption of two dwellings
per acre.
Buildout Scenarios: Demands on On -Site Systems. Chapter II indicates
that a total buildout on Currituck Banks under current policies would
result in 15,580 dwelling units. The capacity to handle residential
wastewater by on -site systems would be exceeded at buildout by 12,910
dwellings. Table V-1 presents a detailed analysis.

41
TABLE V-1
POTENTIAL BUILDOUT IMPLICATIONS FOR CONVENTIONAL ON -SITE
WASTEWATER SYSTEMS CARRYING CAPACITY
Under
Current Policy
North(1)
South(2) Total
Section
Section
(DUs)
(DUs) (DUs)
Total Buildout
Potential
On -Site Systems
Carrying Capacity:
Existing Units
plus Additional
Possible on
Suitable Soils
Potential
Development
in Excess of
On -Site System
Capacity
5,480 10,100
1,410 1,270
4,080 8,830
15,580
2,680
12,910
Source: Information contained in Chapter II of this report and on the
1"=2000' working map of Currituck soils (a 1"=2000' version of Figure V-1)
1 Southern border of Monkey Island north to the Virginia state line
2 Dare County line to the southern border of the Nature Conservancy's
Monkey Island tract.

42
From Figure V-1 (next page) general patterns of areas of soils
suitable for on -site disposal of wastewater can be noted. Suitable soils
are located generally 200 feet inland from the ocean shore to midway across
the island. Relatively large areas of contiguous suitable soils are in
Swan Beach, Whalehead, and Ocean Sands developments. Note the conspicuous
lack of suitable soils in the Carova Beach area.
Suitable soil types are Beaches, Dune land, Dune land-Newhan complex,
and Newhan. Figure V-2 indicates the relative location of these soil
types, with respect to a cross section of the Banks, and suggests that
suitable soils are found in areas of shrub and foredune beach on the
seaward half of the island.
FIGURE V-2
THE RELATIONSHIP OF SOILS AND LANDSCAPE ON CURRITUCK OUTER BANKS
Vegetation Zone
Marsh I Maritime Forest I Shrub Foredune-
Beach
Currituck
Sound
Dominant Soils
Currituck
Soils
/ ocean
Ousley and Newhan, Corolla Newhan soils
Osier Soils and Duckston soils and Dune land
Source: Soil Survey of Currituck County, 1982.

f al • a p ,,.
Figure V-1
SOIL SUITABILITY.FOR ON -SITE WASTEWATER DISPOSAL SYSTEMS
" ".01. a....
Legend
Suitable, Soils
r'1 Unsuitable Soils
°vw1.0 8....
t�,:,•�,�� - -� «. �° .. , '�• %�1�,t. Ito:• KI �. `��•
�' f _ •_.;:`?cam
rr
North Half ('e6.o..a:: ;...o: t
lIa/.�. ..a e.0
Currituck County Outer Banks Io.Bl.�k�o24Q 200
Y #
s. 1...., lsea DCALS 1N RR
i
4-
W

Figure V-1
SOIL SUITABILITY FOR ON -SITE WASTEWATER DISPOSAL SYSTEMS
.n..n. o..•. -
ocean Sands Package Treatment Plant
Z.
`� '1 =n_i^• - �Y� - }�� 1, ~ __.-�_:••--.•.f �,��1'�i/>•�.�•
'\mot J l yl'�' * _ I ...... �— � •�_` 1 � '�j ....._ .. `�'\;••'�'~,� '•',7 �!•5�/ <,..,,v` .':�
-+ o c�(t. � k o 1�.e_i_•.__-_.:..1-�_- '." .' 1. � �-^�Rrl ,.,� y,J U j°j^�. � (• . --
Yea' •�fF �� _`,:,. ; .,<•, j ,�• �',: , v
yv-
Legend
Suitably. Soils
L�Unsuitable, Soils
D
C.... Wh s..N
South Half
Currituck County Outer Banks
Prepared for .
Board of Commissioners 1)(?nARD T�CAPPS
Curriluck County. North Carolina 1 Ot 1
I.

45
Many sites on Currituck Banks which were unsuitable for conventional
on -site disposal systems in their natural state have been improved by
filling with imported soil in order to increase the distance from the water
table. Studies conducted by the North Carolina Department of Health
Services have shown that filling is adequate to protect the groundwater
from contamination.
It should be noted that even soils -that are rated as suitable for
wastewater disposal and included in the acreage totals may pose problems
due to extreme permeability, a property not specifically addressed in North
Carolina state regulations. This is a reason for the discrepancy between
state regulations and the Soil Survey of Currituck County, which rates all
Banks soils as "severe" for on -site system development.
Alternative ground on -site absorption systems are not currently in use
on Currituck. The only feasible alternative may be the low pressure pipe
distribution system. This system also uses a septic tank to settle out
solid particles with distribution via small -diameter, shallowly placed
pipe. The effluent is pumped under low-pressure (2 - 4 foot pressure head)
through this network of perforated pipe. The low pressure pipe system
would require a smaller area of land for the on -site nitrification field
than does the conventional system.
Another alternative, the "mound" system, does not appear to have much
success on the Outer Banks. In a mound system, liquid effluent is
discharged to a raised bed for distribution throughout the upper layer of
suitable soil. This system is best used in locations with shallow or rocky
soil where suitable soil can be brought in for the mound system. Staff at

46
the state Health Department note that the limiting disadvantage of mounds
has been the tendency of the sides to breach.
The conclusion that must be drawn from this analysis is that where
surficial aquifer groundwater is used for water supplies, as it is on the
Currituck outer Banks, the contamination of groundwater is a major concern.
While current evidence indicates that the water systems being used (both
public and private) are generally not contaminated, continued use of
conventional on -site systems in this area will eventually result in the
contamination of the freshwater lens. The danger increases with additional
development, especially if it occurs outside areas of suitable soils. If
potential buildout levels under existing policy are realized, on -site
sewage treatment is not feasible. As density and levels of development on
Currituck Banks increases, community systems for wastewater disposal must
be considered.
Community wastewater disposal options, like the community water supply
alternatives which will be discussed in Chapter VI, lend themselves less to
derivation of a carrying capacity figure than other determinants of the
capacity analysis for Currituck Banks. For community wastewater disposal,
capacity is more a question of how much Currituck residents are willing and
able to pay for an alternative system which will adequately treat
wastewater.
The following options for community -wide systems for handling domestic
wastewater will need to be considered if development continues to take
place on the Banks.

47
Package treatment facilities are pre -fabricated by a manufacturer and
delivered as complete units to the site. Package plants are built to
comply with general design criteria so that accessory equipment such as
additional aerators and chlorinators can be added without major
renovations. In most cases, additional treatment units can be easily
provided, thus increasing plant capacity. In general, capacity for these
small community systems ranges from 5,000 to 100,000 gallons per day.
The advantages of package treatment plants are many: relatively small
acreage required for the actual plant and therefore security from public
intrusion; ease of installation; capability of modular expansion to extend
capacity to a certain maximum; and the possibility for a private developer
to lease capacity at a privately -owned facility. The disadvantages are: a
relatively high cost per unit, especially for designs less than 10,000
gallons per day; difficulty in assuring that the plant consistently meets
design specificiations; extreme sensitivity to seasonal fluctuations of
wastewater flows due to nutrients needed to maintain the biological
process; requirement of a licensed operator or consultant for operation and
maintenance; and the need for careful engineering in the design, selection,
and supervision of the installation.
Land application uses the soil and sometimes plants (usually an
inedible cover crop) to remove harmful substances from effluent or to
provide final disposal of treated wastewater. The amount of wastewater
applied to the soil must be carefully regulated, and a crop must be
selected that is compatible with the wastewater load and soil type.
Therefore extensive initial investigations are required to select and
evaluate a desired site and process.

48
Ocean outfall refers to the disposal of treated effluent offshore,
depending on dilution by ocean waters for final disposal. Careful ,
consideration of wastewater plume drift must be made as influenced by
current, temperature, offshore depth, and other factors. A primary
objective in the design of ocean outfall is to protect bathing beaches for
swimming. Higher quality effluents can mean a shorter, shallower outfall.
The feasibility report prepared for Dare County by Brown and Caldwell
(1982) provides a possible point of comparison to projected growth levels
for Currituck Banks.
A report by the N.C. Water Resources Research Institute states that
"despite the high cost of the ocean outfall option, this is no more
expensive and generally less costly than other options. Ocean outfall for
the northern study area can conveniently and economically serve the entire
(Outer Banks) population" (Nierstedt, et al., 1980). However, if the
Currituck Banks water supply continues to come from the Banks itself,
groundwater mining would be a serious drawback to selection of an ocean
outfall system for Currituck. Water would be drawn from the freshwater
lens, used in wastewater disposal, and discharged to the ocean rather than
recharging the groundwater table.
Pressure sewage collection systems pump household wastes in small
diameter plastic pipe and deliver the waste to a central treatment
facility, which in this case involves land treatment. Individual grinder
pumps or septic tank effluent pumps provide low pressure to move the
effluent. The use of pumps overcomes topographic limitations which would
normally require expensive lift stations. Installation is substantially

49
cheaper than a traditional gravity collection system due to lower cost of
plastic pipe, and because trenches can be made narrower and shallower.
Since the trench will not be deep enough to reach groundwater on the
Currituck Banks, leaching onto the trenches will not be a construction
difficulty. The plastic pipe is also less vulnerable to breaching or to
infiltration from groundwater.
Advantages of pressure sewers include the ability to connect them to
existing homes with or without septic tanks, low capital cost when compared
to conventional sewers, adaptability to a wide range of topographic and
demographic situations, and simple installation techniques. Disadvantages
are substantial maintenance requirements in addition to pumping of septic
tank sludge, and supervision by a licensed operator preferably within the
framework of a public or private management agency.
A fifth community system, piping wastewater to the mainland, is also
feasible for Currituck Banks. A condominium development at Onslow Beach
recently received a permit to collect wastewater from the island, and
transport the effluent through piping secured to the underside of a bridge
crossing Bogue Sound. The pipe continues 5 to 6 miles inland to property
already owned by the developer, and is"treated by land application.
The permit allows 1.5 million gallons per day (mgd) wastewater flow,
which accomodates 600 units already built. The developer requested 3 mgd
treatment capacity in order to treat wastewater generated by the buildout
level of 2,000 units. The consulting engineer estimated a total cost of
$7 million for a system to be privately -owned and operated. Operation and
maintenance costs are not availble.

50
If such a system was publicly owned and managed for the Currituck
Banks, several advantages are apparent. The system could protect
groundwater sources for the Banks by transporting effluent to an area with
a soil type best suited for land treatment of wastewater. On the other
hand, as with ocean outfall, this approach would not replenish the
surficial aquifer. Commercial foresters could be interested in using the
nutrient -rich effluent as an irrigation source for hard and softwood
timber. Such a community -wide system shares the costs over a wider tax
base. One disadvantage associated with the transport would be the
potential destruction of shellfish beds in Currituck Sound if, the transport
pipe ever breached. In the Currituck situation, since a bridge does not
exist, engineering studies would have to be performed regarding the laying
of pipe across the shallow part of Currituck Sound.
To evaluate the four options Table V-2 was developed from varying
sources. More detailed information including actual calculations appear in
Appendix F. Table V-2 compares the four options on the following criteria:
• capital costs, per lot
• land area requirements for the treatment unit and disposal system
• annual operation and maintenance costs
• design life
• sensitivity to seasonal fluctuations in wastewater flow
When considering solely capital cost, irrespective of operating costs,
the conventional septic system appears most cost-effective. However, for
most of the Currituck Banks, and for higher buildout levels, on -site
disposal is not a feasible long run solution.

51
Both options which rely on land application for disposal require over
750 acres of suitable land. This land area need not be contiguous, for it
is possible to allocate land away from the treatment unit itself as long as
tracts of 50 - 100 acres are reserved for this use.
Use of ocean outfall wastewater disposal is dependent upon a minimum
threshold population of 10,000 dwelling units in order to distribute the
extemely high capital costs over more residents. One possibility would be
for several Outer Bank communities to develop an ocean outfall regional
service authority. Ocean outfall, however, could have serious impacts on
a groundwater source which is not replenished by this approach.
The figures contained in Table V-2 are intended to be used as
relative indicators only. Evaluation of wastewater treatment options
requires further detailed study. Where noted, assumptions could affect
calculations; certain data gaps (e.g., operation and maintenance estimates
for ocean outfall) have made direct comparison of these options
unreliable.
Whatever treatment option is selected, it is important to integrate
water conservation and wastewater system practices. The less wastewater
introduced to a treatment system, the less capacity that would be required.
Demonstration projects by the North Carolina Extension Service and Sea
Grant program have shown water conservation to decrease hydraulic load of a
wastewater system by at least one-third. The basic components of a
voluntary water conservation program include: installation of toilet dams
low -flow showerheads, and aerating faucet devices; public education as to
the benefits of common sense water use; consideration of reduced flush and

52
composting toilets; and public information that reduced water use means
less expensive water supply systems and wastewater disposal systems as well
as longer lasting capacity.
Conclusions
• continued use of septic systems beyond buildout level of 2,670
dwelling units on suitable soils would result in groundwater
contamination
• interim use of package treatment plants, similar to the Ocean Sands
treatment works, with a modified land application disposal system,
will serve growing wastewater disposal needs
• ocean outfall is a potential treatment option for development in
excess of 10,000 homes
• potential buildout will require capacity to treat 7.5 million
gallons per day
• not enough is known about groundwater supplies underneath Currituck
Banks to be able to judge the impact of wastewater absorption from
land application options or the impact that transporting effluent
out to sea or to the mainland would have on replenishment of
aquifers on the Outer Banks.
Underpinning the conclusions for wastewater treatment options is the
assumption that each system will be properly managed and operated to meet
design specifications.

TABLE V-2
COMPARISON OF ALTERNATIVE WASTEWATER SYSTEMS
Evaluation
On -Site
Pkg. Treatment
Pkg. Treatment
Pressure Collection,
Criteria
Septic
Land Disposal
Ocean Outfall
Land Disposal
System
collection: $3,000 to
Capital
$500-1,200 per lot
unit:(2) $41.4 M,
unit:(2) $41.4 M,
$7,500 per hook-up, plus
Costs
for conventional
$2,660 per unit
$2,660 per unit
$2,660 per unit
per lot septic system
Land Area 1/2 acre is usually
Requirements adequate for
Currituck soils but
depends on the site
Operation & $50-$100 for
Maintenance inspection and
Costs (annual) septage pumping
Design Life 20-plus years with
proper intallation
& maintenance
Sensitivity
to Seasonal
Fluctuations
depends on
distance to
groundwater
table
disposal:(7) $5.86 M
hard costs plus
4.5 M land=$665/lot(4)
unit:(2) 5-7 acres
for 15,000 homes -
disposal:(5) 757
acres for 15,580
homes
disposal:(3) Dare Co.
estimate=$8.85 M
for 1-10 MGPD or
$568 per lot(7)
unit:(2) 5-7 acres
for a plant to
serve 15,000 homes
disposal: not
applicable
unit:(6) $615,000/yr unit:(6) $615,000/yr
or $40 per lot or $40 per lot
disposal:(7) $105,700 disposal: data
/yr or $7 per lot not available
unit: 20 years unit: 20 years
pipe: 50-plus yrs pipe: 115-20 years
land: 20 years
treatment requires
certain level of
organic material to
remain aerobic
treatment requires
a certain level of
organic material to
remain aerobic
disposal:(1) $5.8 M
hard costs plus
$4.5 M land=$665/lot(4)
collection:(2) 10-20 ft.
of linear right of way
disposal:(5) 757 acres
for 15,580 homes
collection:(2) approx.
$150/yr per lot; plus
$40 per lot for unit
disposal:(7) $105,700
or $7 per lot
grinder pumps:0) 14 yrs
pipe: 50-plus years
land: 20 years
collection: pumps
run only as flow
warrents
disposal: not sensi- disposal: not disposal: not sensitive
tive since irrigation sensitive since irrigation occurs
occurs when flow when flow warrants
warrants
w

54
Notes to Table V-2
(1) Design life of Myer grinder pump = 10,000 on/off cycles, which at 2
cycles per day for 365 days per year results in a design life of
approximately 13.7 years.
(2) Figures taken from National Association of Home Builders,
Alternatives to Public Sewer: $3.75/gallon using 7.47 mgd = $28
or $1,800 per lot using 15,580 dwelling units as total buildout.
These 1977 figures are converted to 1982 dollars, resulting in
$2,660 per lot.
(3) Taken from Final Report: Preliminary Design and Marine Survey for
Ocean Outfall, Dare County, N.C. prepared by Brown and Caldwell
Consulting Engineers, September 1982.
(4) Use of a land cost of $6,000/acre per the WRRI methodology
(5) Land requirements are based on the higher of a) hydraulic capacity,
or b) nutrient requirements of cover crop. Nutrients (specifically
N = nitrogen, P = phosphorous, K = potassium) are the limiting factor
for the coastal soils with the P most limiting. The cover crop is
assumed to be coastal bermuda because of the soil stabilizing benefit
and high uptake of P at 150 lbs/year.
(6) Total operation and maintenance cost vs. annual flow at secondary
level of treatment (activated sludge) for EPA Region IV expressed in
1977 dollars. Taken from Analysis of operations and Maintenance
Costs for Municipal Wastewater Treatment Systems 430 9-77-015)
issued by EPA Office of Water Program Operations, May 1977. Assume
8 mgd domestic flow.
(7) Expressed in constant dollars. Taken from Technical Report: Costs
of Wastewater Treatment by Land Application EPA 430/9-75-003
developed by U.S. EPA Office of Water Program Operations, June 1976.
Assumes application rate of 3 inches per week for center pivot
application sytem. Cover crop given as corn.

55
CHAPTER VI
WATER SUPPLY
In a coastal environment such as the Currituck Outer Banks, sufficient
supply of fresh water is a major problem and could impose an important
constraint to future development.
Findings
The main conclusions drawn from this study of water supply on the
Currituck Outer Banks are:
1. It is not possible to estimate the quality or quantity of
groundwater, due to the absence of test well data. Test wells and
monitoring of water quality and yield are required for any further
analysis of drinking water supply.
2. For the existing popluation and moderate growth, the water table
aquifer is able to meet the demand for fresh water. But in order to
support a large increase in population, high cost alternatives will
have to be considered. These alternatives include desalinization and
pipeline supply from the mainland.
3. Continued use of on -site septic systems may contaminate the water
table aquifer.
4. For the potential buildout of dwelling unts, demand will be between
5.3 and 7.0 million gallons per day. (Water demand was estimated using

56
the buildout figure of 15,580 dwellings. Calculations were made
assuming an average of 4.5 persons per dwelling unit (Coastal
Consultants, 1980), and a consumption range of 75 — 100 gallons per
capita per day.)
Water Supply Alternatives
Several water supply alternatives have been considered in terms of
their capacity to meet the estimated demand. These alternatives are:
groundwater, individual household rainwater collection, desalinization,
and mainland pipeline supply. Groundwater wells and rainwater collection
are the current sources of fresh water on the Currituck Outer Banks.
Desalinization and pipeline supply are examined as potential sources to
meet the high buildout demand. Each of these alternatives is discussed
below.
Groundwater supply. The groundwater system underlying the Banks is
divided into aquifers, which vary in thickness and fresh water content.
Little is known about the quality or quantity of water in the aquifers due
to absence of test well data on the Banks. Most of the information on the
lower water zones is extrapolated from aquifer studies on the mainland.
The concensus of most investigators is that the deepest aquifers contain
only saltwater beneath the Banks. There is a possibility, however, that
fresh water is available from the Upper Yorktown Aquifer, which supplies
fresh water on the mainland (Moore, Gardner and Associates). This aquifer
dips and thickens as it proceeds easterly (Figure VI-1). Therefore,
projections of data from the mainland may not be valid on the Currituck
Outer Banks. A deep test well is needed before conclusions can be drawn
about the quality or quantity of water available from this aquifer.

57
FIGURE VI-1
SCHEMATIC DIAGRAM OF UNDERLYING AQUIFERS
(in cross section)
MAINLAND CURRITUCK
OUTER BAN CS
UPPER (YORKTOWN) AQUIFER
IMESTONE
aniITFGR
SEA
LEVEL

58
SOUND
SIDE
FIGURE VI-2
SCHEMATIC DIAGRAM OF WATER TABLE AQUIFER
(in cross section)
OCEAN
SIDE
SURFICIAL,
WATER TABLE
SALTWATER
INTERFACE
Note: the shape of the lens varies with location on the
Currituck Outer Banks

59
The surficial, or water table, aquifer occurs as a lens -shaped body
overlying saltwater (Figure VI-2). This aquifer supplies water to all
wells drilled on the Currituck Outer Banks. In most areas, the fresh water
table is only a few feet below the land surface. However, the quality of
water obtained from wells is highly variable within a small geographic
area. The best quality water is found above sea level; wells drilled below
sea level yield water with high concentrations of dissolved minerals.
Water quality also varies with location on the,Banks. Highest quality
water is associated with the highest dunes nearest the ocean.
Unfortunately, these areas are also the best sites for septic systems.
Proceeding westerly towards the sound, concentrations of many contaminants,
particularly iron, increase. Therefore, water obtained from these areas
will generally require more treatment than water obtained from wells near
the ocean.
One of the most serious problems associated with the water quality of
the surficial aquifer is the leaching of sewage pollution into the aquifer.
As the number of on -site septic systems and package treatment plants
increases, the potential for pollution of the groundwater also increases.
The amount of water available from the surficial aquifer depends on
the level of the water table. The water table rises as a result of
precipitation recharge and falls in response to ocean/sound discharge,
infiltration to lower aquifers, and well -pumping (Moore, Gardner and
Associates). Each of these variables must be quantified in order to
estimate the water available from the water table aquifer.

60
The average annual rainfall on the Currituck Outer Banks is 45-55
inches (USGS, 1966). According to the Geological Survey, only about 25
percent of the annual precipitation is recoverable by wells from the
surficial aquifer. In order to translate this figure into available supply
(number of gallons per day), the number of acres available for aquifer
recharge must be calculated. Recharge areas exclude marsh, foredunes, and
areas subject to ocean overwash. In addition, septic system drain fields
and impervious surfaces (such as parking lots, roads, buildings) are
unavailable for aquifer recharge. Therefore, in calculating recharge
acreage, all of these areas must be subtracted. As the amount of
development increases the recharge area decreases, particularly if
wastewater systems requiring land discharge are utilized.
Another variable affecting the water table aquifer is drawdown. The
elevation of the water table relative to sea level is influenced by the
extent and distribution of well withdrawals. Excessive withdrawal lowers
the water table so that saltwater encroaches into the freshwater supply.
Thus, spacing of wells and amount of pumping are extremely important in
determining the safe yield from the surficial aquifer. Safe yield may
decrease with increased development as more wells are drilled. Each well
drilled may have impact on neighboring wells; therefore continuous
monitoring of strategically spaced observation wells is necessary. Data
from these wells would warn of salt water intrusion.
Because of the variability of the surficial aquifer and the lack of
test well data, it is not possible to estimate available supply from this
source. Nor is it possible to estimate fresh water available from the

61
lower aquifers. Because of the uncertainties associated with the
groundwater supply, use of this system to meet the buildout demand should
not be considered until test well data are available.
Individual household rainwater collection. Many of the first
inhabitants of the Outer Banks collected rainwater from their roofs into
cedar barrels. These early settlers lived near the soundside of the
barrier island, where trees provided protection against harsh winds and
storms. Rainwater provided a pure and abundant supply alternative to the
poor quality groundwater characteristic of the soundside.
The old Coast Guard life-saving stations which are scattered along the
North Carolina coastline, stored rainwater in elevated cedar barrels. Some
of the original barrels still remain. The elevated barrels provided a
gravity -induced pressure to*the outlets; no electricity or pumping was
required.
Utilization of other materials and unique design features for a
rainwater storage system may be seen at the house of the lighthouse keeper
in Corolla. Cisterns constructed of brick and wood are located on both
ends of the house. Part of the container is submerged into the ground
which prevents winter freezing and cools the water in the summer.
Wood -slat louvered walls and a small hip roof shade and protect the
cisterns from the weather.
Rainwater is still a feasible water supply source for residents living
on the soundside of the Currituck Outer Banks. Four families in Corolla
presently rely on rainwater collection systems to supply all of their
domestic needs. While all four systems use a roof and gutters to collect

62
water, the type of storage containers and the volume of storage differ
considerably.
Two of the families collect water in buried fiberglass tanks
(originally designed for septic systems). One of the families, consisting
of two adults and one child, has two tanks--1,100 gallons each --for their
storage. This gives them an adequate supply, provided they practice
conservation.
The other two families collect and store water in above -ground storage
tanks constructed of 1/4-inch plate steel and supported on treated pilings.
Both families have a 4,000 gallon capacity tank. The family of four, two
adults and two children, does not make special conservation efforts.
Major problems with rainwater systems include low storage capacity,
freezing, and pump pressure loss. All four families reported that
their storage supply was low during the early fall drought period
(September to October). Freezing of the underground tanks does not occur,
but the families with above -ground tanks reported that their tanks
"froze -up" two or three times during the cold winter of 1977. Generally,
however, freezing does not occur.
The 45 to 55 inches of rainfall annually (USGS, 1966) is more than
adequate. Supply depends on the effective surface area of the rainwater
collector (roof) and on the volume of storage used to hold water during
periods without rainfall.
Available information on the chemical composition of rainwater is
dated from August, 1962 to July, 1963 (USGS, 1966). At that time, the
water quality was very good, many times cleaner than the Outer Banks'

63
groundwater. (Chemical analysis is provided only; no measurement of
radioactivity is given.) Industries developed since these tests may have
adverse effects on the current quality of rainwater. Updated tests are
needed.
The systems in Corolla were built nine to fourteen years ago. At the
time of installation in 1974, the cost of the fiberglass tank system was
between 600 and 700 dollars for the tanks, piping and pump. The cost of
the above -ground systems was around 400 to 500 dollars in 1969. All
families provided their own labor, a cost which needs to be considered for
evaluation purposes.
Rainwater collection is most suitable for single dwelling units which
are occupied year-round. Such a system would not be feasible as a supply
for buildout demand.
Desalinization. The Moore Gardner feasibility study recommends that
desalinization of brackish or seawater not be considered as a water supply
alternative until other means prove uneconomical. However, because of the
uncertainty of supply from underlying aquifers, desalting techniques
warrant further study.
Desalinization may be an attractive option for water supply on the
Currituck Outer Banks for two reasons. First, the process has the
potential to convert seawater, brackish waters from the Currituck Sound, or
brackish deep ground water, into potable water. Because of the virtually
limitless supplies from these sources, water quantity is not a constraint.
Second, desalting has great potential as an intermittent supply for
seasonal or peak use, since its costs are related more to time of operation

Gig
than to construction expenses. The fixed capital cost represents only 20 to
50 percent of the total operating cost; at full output, operating costs
account for most of the desalting cost. This contrasts with many other
water supply sources which have a high ratio of capital to operation cost
(Millikan and Taylor, 1981).
But operating cost is also a major drawback of desalinization. This
high cost is primarily due to the high consumption of energy required for
salt removal. However, there are ongoing research efforts to reduce this
cost.
There are two broad categories of desalinization processes. One
category involves water purification through a change of water state
(vaporization or freezing of water). The second category involves use of
thin, filmlike sheets, or membranes, that act as separators of saltwater
and freshwater.
The processes involving a change of water state are:
1. Distillation: the saline feedwater is boiled, leaving behind the
unwanted solids (including salt). The resulting steam is then cooled
so that it condenses as freshwater. The main advantage th this
process is that it can produce high quality water. The main
disadvantage is the high consumption of energy.
2. Freezing: the saline water is frozen so that fresh water crystals
are separated from salt crystals. The two advantages of this process
are separated from salt crystals. The two advantages of this process
are a lower energy consumption than distillation, and suitability for
a wide range of salinities (brackish water to seawater). However,

65
these systems are still in the research stage.
Processes using membranes are expected to dominate the desalting
market by the year 2000 (Fluor Engineers, 1978). These processes include:
1. Electrodialysis: a direct electric current is used to separate
fresh water from saline water. From a standpoint of research and
development, this process is the most advanced of the membrane
processes. However, economical application is limited to brackish
water.
2. Reverse osmosis: pressure is applied to brackish water on one side
of a membrane. This causes "fresh" water molecules to pass through
while the unwanted solids (called brine) are left behind (see Appendix
G for a detailed illustraion). The brine may be discharged by
pipeline to the ocean. This desalting process uses less energy than
any of the other processes. In addition, the processing equipment is
relatively simple. The major disadvantages of this system are the
high membrane replacement costs, and the required pretreatment of the
feedwater.
There are several reverse osmosis plants operating in North Carolina.
Two of these plants are located near Wrightsville Beach, but are only
demonstration plants. Ocracoke Island has a reverse osmosis system which
has been in operation since June, 1977. Information on the operation,
capacity, and cost of this system was obtained from sources at the Ocracoke
Water Association. These data may be useful in determining the feasibility
of a similar system on the Currituck Outer Banks. (Refer to Appendix G for
more detailed information on costs and operation.)

66
The feedwater supply for the Ocracoke plant is brackish groundwater,
which has a saline content equal to about half the salinity of the adjacent
Pamlico Sound. The plant has a maximum output capacity of 150,000 gallons
per day. During the summer peak —usage months (July and August), output is
about three times the winter output. Some pretreatment and posttreatment
of the water is necessary. The product water chloride concentration is
within drinking water standards.
According to Mr. Frank Wardlow of the Ocracoke Water Association,
reverse osmosis is the only desalting technique which can economically
produce the needed volumes of potable water. Last year's operating
expenses were about $115,000 (expenses are detailed in Appendix G).
Capital cost of the plant was $1,003,140 in 1977 dollars. Twenty—six
million gallons of water were sold last year (July 1, 1981 —June 30, 1982)
for $117,000. Thus, costs of operation were matched by water sales.
The feasibility of any desalting system on the Banks depends on the
cost of the water produced. Three factors influence cost:
1. The size of the plant (i.e., production capacity); the larger
the plant, the higher the capital investment and maintenance costs.
2. The type and amount of energy used in the desalting process.
3. The salt content in the feedwater. Generally, the higher the salt
content of the water, the higher the cost to reduce the concentration
to acceptable levels.
The first step, then, in designing a desalinization system for the
Currituck Outer Banks is to determine the dissolved solid (salt) content of
the possible sources. These sources include seawater, water from the

67
Currituck Sound, and groundwater. The advantage to use of sound or
seawater is the unlimited supply. However, desalting costs may be very
high. The quantity of water available from groundwater aquifers is
unknown. Thus, the feasibility of groundwater supply for desalting is
questionable.
It is beyond the scope of this report to recommend a particular
desalting technique for use on the Banks. However, if large-scale plans
for Banks development are pursued, desalinization may be a viable option
for water supply.
Pipeline from the mainland. The Moore Gardner feasibility study
discusses an alternative of piping water from the mainland to the Outer
Banks. This 16 inch submerged water main would cross Currituck Sound from
Poplar Branch on the mainland to Ocean Sands on the Banks.
According to the Moore Gardner study, the cost for the pipeline alone
would be approximately 1.8 million dollars in 1985. Other costs to
complete the system would include the costs of two water towers, one on
each end of the pipeline. Two water towers would cost $400,000 (Moore
Gardner). This does not include the costs of distribution lines on the
Currituck Outer Banks. Distribution costs would vary with the level of
development.
A well field in Poplar Branch, which draws from the Upper Yorktown
Aquifer, would supply the pipeline. From the USGS investigation (1978),
both fresh and saltwater exist in the Upper Yorktown in the eastern area
of North Carolina. The possibility of drawing saltwater may be increased
by the influence of other well -pumping in the area.

68
More information and research are required before the feasibility of
the pipeline can be determined. Environmental costs of the pipeline
crossing the Sound and reliability of the groundwater source need further
study.
Summary
Table VI-1 summarizes the significant characteristics of the four
alternatives, including cost, quantity and quality of water supply,
suitability of alternatives for certain development patterns, and the
reliability of the alternatives under extreme weather conditions and
seasonal variations. A category is also included to indicate the type of
further information that is required for proper evaluation of the
alternatives. The more important points made in the table include:
1. The quality and quantity of groundwater available on the Currituck
Outer Banks are uncertain. Test wells and monitoring wells are
needed.
2. Rainwater collection is a viable alternative for permanently
occupied, family residences on the soundside of the Banks, but is not
a long run solution.
3. Desalinization may be viable for meeting high water demand, but is
expensive. The cost of water supplied by the Ocracoke system is $4.50
per 1,000 gallons (not including capital costs).
4. Pipeline supply is expensive (in excess of 2 million dollars in
capital costs), and there are many uncertainties about the quantity
and quality of water available from the mainland groundwater system.

TABLE VI-1
TABLE OF WATER SUPPLY ALTERNATIVES - SUMMARY OF MAJOR CONSIDERATIONS
Evaluation
Considerations
Rainwater Collection
Alternatives
Surficial Aquifer Wells
Desalinization
Pipeline
Monetary cost
lowest operating cost
less expensive
depends on plant
probably
of all alternatives
then pipeline or
capacity and amount
highest
desalinization
of salt in feed-
capital cost
water; capital
of all
cost low relative
alternatives
to operating cost
Quantity of
depends on storage
unknown
virtually limitless'
depends on
supply
capacity of tanks
if seawater or sound
source
water used as source
Quality of
updated tests needed
highly variable within
depends on feed-
depends on
supply
small geographic area
water
source
and with depth
Best suited
individual lots;
not suitable as supply
cluster type to
cluster type
development
low density
for large-scale
minimize distribu-
to minimize
development due to
tion costs
distribution
uncertainties of supply
costs
Seasonality of
not suitable for
increased pumping during
not a constraint
not a
supply (seasonal
seasonal residents
peak periods may cause
contraint
vs. year-round)
salt water intrusion
Susceptibility
may have to conserve
storm overwash may
not a constraint
possible
breaks in
to interruption
during dry periods
contaminate supply;
if seawater or
(storms,dry periods)
low water table in
sound water used
water main
hot periods
during storms
Further informa-
test/monitoring wells
test/monitoring
HIS probably
tion requirements
needed; calculation of
wells needed for
required
recharage area and
determining ground
amounts needed
water source

A-1
APPENDIX A
METHOD FOR CALCULATING POTENTIAL BUILDOUT
This appendix explains how the area restricted from development by the
Coastal Area Management Act (CAMA) and Section 404 of the Clean Water Act
was computed.
The CAMA ocean erodible area for those areas developed or platted
before 1979 extends 60 feet landward of the vegetation line. For areas
undeveloped or unplatted in 1979, the ocean erodible setback is determined
by the Office of Coastal Management based on 30 year erosion rates and 100
year floodplain. The setbacks and erosion rates currently in effect in
Currituck County were used in this study. The recently revised erosion
rates adopted by the Coastal Resources Commission can be substituted for
the existing setbacks if they are adopted by the County.
The estuarine shoreline area, as defined under CAMA, is that area
extending from the mean high water level along the estuaries or the sound
to a distance 75 feet landward.
Wetlands that are subject to regulation under CAMA are defined as "any
salt marsh or other marsh subject to regular or occasional flooding by
tides, including wind tides (whether or not the waters reach the marshland
areas through natural or artificial watercourses), provided this shall not
include hurricane or tropical storm tides. Salt marshland or other marsh
shall be those areas.upon which grows some, but not necessarily all, of the

A-2
following salt marsh and marsh plant species:
(1) smooth or salt water cordgrass (Spartina alterniflora),
(2) black needlerush (Juncus roemerianus),
(3) glasswort (Salicornia spp.),
(4) salt grass (Distichlis spicata),
(5) sea lavender (Limonium spp.),
(6) bullrush (Scirpus spp.),
(7) saw grass (Cladium jamaicense),
(8) cat -tail (Tgpha spp.),
(9) salt -meadow grass (Spartina patens), and
(10) salt reed grass (Spartina cynosuroides)."
Wetlands subject to the regulatory authority of the Army Corps of
Engineers pursuant to Section 404 of the Clean Water Act are defined as
"areas that are inundated or saturated by surface or ground water at a
frequency or duration sufficient to support, and that under normal
circumstances do support, a prevalence of vegetation typically adapted for
life in saturated soil conditions" 33 C.F.R. 4 323.2 (1981).
The delineation of both types of wetlands is done by permit officers
on a site -specific, lot -by -lot basis as development is proposed and
approval is sought. There is no map that indicates what land is subject to
dredge or fill permitting for either type of wetland. The criteria applied
by the Army Corps of Engineers under Section 404 is particularly
subjective. The discretion to define a specific area as a wetland under
the definition used by the Corps, and therefore subject to restrictions on
residential construction, is vested with a permit officer who considers the

A-3
vegetation of the area, the soil type and conditions, and the hydrology of
the area, and applies guidelines set forth by the Environmental Protection
Agency. Both the Office of Coastal Management, which enforces CAMA, and
the Army Corps of Engineers can be expected to deny permit applications for
large-scale residential development within their respective jurisdictions.
The areas designated as wetlands in our projections were derived from
the National Wetlands Inventory Classification Maps, which were prepared by
the U.S. Fish and Wildlife Service. The wetlands inventory is vegetation
based, as are the definitions of wetlands for CAMA and Section 404. Short
of an exhaustive field survey of the entire banks, interpretation of the
National Wetlands Inventory Classification produces the best available,
mappable estimates of what land is subject to regulatory constraints. The
vegetation families that represent the various wetland conditions were
overlayed onto a 1 inch equals 400 feet scale map of the banks.
Unresolvable doubt was settled on the side of classifying an area as
developable.
The areas within the CAMA definition of wetland are identified by the
inventory as: E2EM1P, E2SS1/EM1P, PEM1C, and PEM1F. These areas may be
subject to flooding on a regular or irregular basis, and some, but not all,
of the ten specified marsh plant species are established in the area. For
those areas delineated as E2EM1P, or E2SS1/EM1P the dominant marsh species
include black needlerush (Juncus roemerianus), cordgrasses (Spartina,
spp.), cat -tails (Typha, app.), bullrush (Scirpus olnevi), and sawgrass
(Cladium jamaicense). The areas delineated as PEM1C and PEM1F are fresh
water areas whose dominant marsh plant species include bullrush

A-4
(Scirpus spp.), rushes (Juncus, spp.), salt meadow cordgrass
(Spartina patens), and cat -tails (Typha, spp.).
Areas interpreted as Section 404 wetlands are delineated by the
wetlands inventory system as PSS1C, PSS1R, PSS3C, PFOIA, and PFO1C. These
areas are seasonally or semipermanently flooded. Dominant plants in these
areas include shrubs and water resistant trees. Species such as waxmyrtles
(Myrica spp.), sweet bay (Magnolia virginiana), red bay (Persea borbonia),
greenbriar (Smilax spp.), black gum (Nyssa sylvatica), and cypress
(Taxodium distichum) are common. These species identify wetlands in
addition to those regulated under CAMA.
It should be noted that all designated wetlands under CAMA satisfy the
definition of wetlands under Section 404, but not all wetlands under
Section 404 are designated as wetlands under CAMA.
The following areas described by the wetlands inventory classification
as wetlands do not fulfill the requirements set forth in either the CAMA or
404 definition of wetland: M10WL, MOL, E2FLM, R10WL, POWH, PFO1F, PF04A,
PF04F, and PF01B. These areas, although wet, are for the most part devoid
of vegetation or when vegetation does exist, the species are not "typically
adapted for life in saturated soil conditions."
An explanation of the National Wetlands Inventory Maps is attached. A
copy of the maps for the Currituck County area and a working map at a 400
foot scale and outlining CAMA and 404 lands have been given to the
Currituck County Planning Office. In addition, a 1 inch- to-2000 foot scale
map of CAMA and 404 wetlands, ocean erodable areas and estuarine shorelines
have been given to the Planning Office.

A-5
NATIONAL WETLANDS.INVENTORY
NOTES TO USERS
for the
Currituck Sound 1:100,000 Scale Map Area
INTRODUCTION
In 1974, the U.S. Fish and Wildlife Service directed its Office of
Biological Services to conduct an inventory of the nation's wetlands. This
National Wetlands Inventory (NWI) became operational in 1977.
Wetland delineations depicted on these maps were produced by
stereoscopically interpreting high altitude aerial photography and then
transferring this information with a zoom transfer scope to an overlay
using the U.S. Geological Survey 7.5' or 15' map series as base
information.
Wetlands were identified on the photography by vegetation, visible
hydrology, and geography, and subsequently classified in general accordance
with Cowardin et al. Classification of Wetlands and Deep Water Habitats of
the United States. Where, for pragmatic reasons, strict adherence to this
classification system was not possible, mapping conventions developed by
NWI were used.
MAP PREPARATION
The wetland maps of the Currituck Sound 1:100,000 scale map area were

A-6
produced using 1:80,000 scale quad —centered U.S. Geological Survey black
and white photography captured during March of 1977 and April of 1978.
Photo interpretation was done by the University of Massachusetts located at
Amherst, Massachusetts. Additional information was obtained from available
soil surveys produced by the Soil Conservation Service. Limited
ground—truthing was performed during August and October of 1979 and April
of 1981.
SPECIAL MAPPING PROBLEMS
A problem concerning wetland identification was encountered with the black
and white emulsion. This was most apparent in identifying interdunal
wetlands where there was high reflectivity from beach sands and in forested
areas where dense canopies limited interpretation ability. Intertidal
bars/flats and aquatic beds were also not generally identifiable on this
photography.
Additional complications were encountered due to droughty conditions at the
time of ground—truthing, inaccessability of field check sites and locally
intensive development with associated drainage efforts.
STUDY AREA
The Currituck Sound 1:100,000 scale map area is located in the extreme
northeast area of North Carolina and includes portions of the;Outer Banks,
the Currituck Sound estuary, and the mainland of North Carolina.
Bailey in Description of the Ecoregions of the United States describes this
area as part of the Southeastern Mixed Forest Province (2320). This area

A-7
generally occurs on the irregular Gulf Coast Plains and Piedmont, where 50
to 80 percent of the area slopes gently. Local relief of these flat
Coastal Plains is generally less than 100 feet.
The climate is approximately uniform throughout this area. Mild winters
and hot humid summers are the rule with the average annual temperature
being 600 to 700 F. Precipitation averages 40 to 60 inches annually. It
is rather evenly distributed throughout the year, but peaks slightly in
midsummer or early spring when it falls mostly during thunderstorms.
Precipitation exceeds evaporation, but droughts do occur. The growing
season is long (200 to 300 days), but frost occurs nearly every winter.
Snow falls rarely but melts almost immediately.
Utisols are the dominant soils of the area with vertisols, formed from
marls of soft limestones, being locally conspicuous. The vertisols are
clayey soils that have wide, deep cracks when dry. Inceptisols on flood
plains of the major streams are among the better soils for crops.
WETLAND COMMUNITIES
Marine System
M10WL - Open high-energy, high salinity, ocean typically devoid
of vegetation.
EIOWL - Open low -energy waters with reduced salinities of bays,
sounds, and stream channels typically devoid of
vegetation.
E2FLM - Irregularly exposed intertidal flats typically devoid of
vegetation.

A-8
E2EM1P —Irregularly tidally flooded persistent emergents.
Dominant marsh plants include Black Needle Rush (Juncus
roemericanus), Cordgrasses (Spartina spp.), Cattails
(Typha spp.) Bullrush (Scirpus olneyi), and Sawgrass
(Cladium jamaicense).
E2SS1/EM1P — Irregularly flooded intertidal wetland with 30% or
more of the canopy consisting of broad—leaved
deciduous shrubs, usually Marsh Elders (Iva spp.)
and/or Groundsel trees (Baccharis spp.). The
remaining canopy consists of marsh plants as
described above.
E2SS3/EM1P — As above, but with broad—leaved deciduous shrubs
being replaced by broad—leaved evergreen shrubs,
usually Waxmyrtles (Myrica spp.). Emergents are
similar to those decribed under E2EM1P.
Riverine System
R10WL — Tidally influenced open freshwater streams.
Palustrine System
POWH — Small permanently flooded fresh water ponds typically
devoid of vegetation.
PEM1C, PEM1F — Fresh water marshes seasonally.to semipermanently
flooded. Dominant persistent emergents include
Bullrushes (Scirpus spp.), Spikerushes (Eleocharis
spp.), Rushes (Juncus spp.), Beakrushes

A-9
(Rhynchospora spp.), Sedges (Cyperus spp; Carex
spp.), Panic Grasses (Panicum spp.), Salt Meadow
Cordgrass (Spartina patens), Cattails (,Typha
spp.), and Arrowheads (Sagittaria spp.).
PSS1C, PSS1R - Seasonally flooded broad-leaved deciduous shrub
swamps with the latter indicating tidally
influenced fresh water. Dominant shrubs include
Willows (Salix spp.), Coastal Pepperbush (Clethra
alnifolia), Blueberries (Vaccinium spp.),
Groundsel Trees (Baccharis spp.), and Buttonbush
(Cephalanthus occidentalis).
PSS3C, PSS3R - Seasonally flooded broad-leaved evergreen shrub
swamps with the latter indicating tidally
influenced fresh water. Dominant shrubs include
Waxmyrtles (Myrica spp.), Sweet Bay (Magnolia
virginiana), Red Bay (Persea borbonia), and
Greenbriars (Smilax spp.). A special
alpha -numeric of PSS3/v indicates interdunal areas
that not be individually mapped and were therefore
lumped with interspersed upland.
PFOIA, PF01C - Temporarily to seasonally flooded bottomlands and
swamps. Typically, Red Maple (Acer rubrum) and
Sweetgum (Liquidambar styraciflua) dominate the upper
canopy with Tulip Tree (Liriodendron tulipifera),
Laurel Oak (Quercus laurifolia), Water Oak ( uercus

A-10
ni ra), Swamp Chestnut Oak (Quercus michauxii), Black
Gum (Nyssa sylvatica), and Cypress (Taxodium distichum)
also being prevalent. The latter two are particularly
asociated with wetter areas. Typical understory
vegetation includes cane (Arundinaria gigantica),
Blueberries (Vaccinium spp.), Greenbriars (Smilax
spp.), Hollies (Ilex spp.), Waxmyrtles (Myrica spp.),
Grapes (Vitas spp.), Sweet Bay (Magnolia virginiana)
and Coastal Pepperbush (Clethra alnifolia). In wetter
areas, Fetterbush (Lyonia lucida), Red Bay (Persea
borbonia), and Sphagnum spp. moss become prevalent.
PF01F - Semipermanently flooded swamps dominated by broad-leaved
deciduous trees, usually Black Tupelo (Nyssa sylvatica).
PF04A - Temporarily flooded needle -leaved evergreen flats
usually dominated by Loblolly Pine (Pinus taeda). This
dominance type typically occurs as a mixture with
hardwoods (PFO1/4A; PF04/1A).
PF04F - Semipermanently flooded needle -leaved forested swamp
dominated by Pond Pine (Pinus serotina).
PFO1B, PF01/4B, PF04/1B, PF04B - The saturated water regime (B)
was used to indicate Carolina
Bays. Dominant vegetation is
similar to that described under
PFO1 and PF04.

A-11
SPECIAL MODIFIERS EMPLOYED
"x" — The excavated modifier was usually used to indicate small
dugouts/ponds (POWHx) or ditches (7,10WLx; R10WLx).

A-12
APPENDIX B
MISCELLANEOUS INFORMATION ABOUT MAJOR DEVELOPMENTS ON THE CURRITUCK
OUTER BANKS --AS OF FEBRUARY 20, 1983
Carova Beach 2019 platted lots
162 improved lots
200 additional acres of upland according to
tax office
North Swan Beach 414 platted lots — 244 sold
9 improved lots
Swan Island Tract 812 acres, of which 771 are classed as upland
(The Nature Conservancy) 5095 acres of marshland owned by conservation
easement, on which the Hunt Club retains
certain rights, including the right to
construct a 4000 square foot lodge.
Swan Beach 539 platted lots — 450 sold
Less than 6 lots with improvements
Ocean Beach and Seagull 71 platted lots (37 of thse are in Seagull)
Less than 6 lots with improvements
Monkey Island Tract 991 acres, of which 119 acres are considered
(The Nature Conservancy) upland

A-13
Monkey Island South This parcel is in subdivision sketch plan
review
Ocean Hills This tract is in three sections; 1 to 3 south
to north
Sections 3 and 2 have received preliminary plat
approval for 227 lots on 104 acres
Section 1 has been approved
113 platted lots
4 improved lots
Corolla 128 platted lots
46 improved lots (including 4 on the Whalehead
Hunt Club property)
Lighthouse Property 400 foot strip ocean to sound owned by the
state
Whalehead Hunt Club Sketch plan approval for a PUD that includes
Development 278 units in three tracts on 66 acres
Would include 52 one bedroom units, 194 two
bedroom units, and 32 three bedroom units
Whalehead — Phase 2 Preliminary plat approval for 455 units,
including 247 single family, and 104
duplex units
Whalehead 229 acres of undeveloped property

A-14
858 lots of which all are sold
52 lots are improved
Whalehead — Phase 1 Recorded proposal of 803 dwelling units
including 181 single family units, 49
duplex units, and 524 multi —family units
Ocean Breakers Proposed Development of 600 units
Ocean Sands 600 acres, 400 are developed and 200 are open
space
1168 platted lots
3600 total dwelling units
112 improved lots
Sealoft 30 lots
8 improved lots
Currituck Shooting Club 2168 acres total
Pine Island 700 acres
Pine Island Estates 12 lots
4 improved lots
Audubon Society Tract 1084 total acres

A-15
APPENDIX C
DESCRIPTION OF SIX ENVIRONMENTAL PROCESSES AND SENSITIVE AREAS
ON THE BANKS, AND THEIR IMPLICATIONS FOR DEVELOPMENT
This appendix describes six environmental processes and sensitive
areas on the Currituck Outer Banks and makes recommendations for
development policies that properly respect them. They are the beach and
dune system, washover areas, potential inlet areas, aquifer recharge areas,
maritime forests, and the estuary system and salt marshes.
The Beach and Dune System
The Currituck Banks have wide flat beaches, along with a low and
somewhat discontinuous frontal dune system. A relatively high row of
continuous dunes has been constructed on parts of the island.
The beach is shaped by the repetitive onshore movement of waves, by
longshore currents generated when waves hit the beach at an angle, and by
the world—wide rise in sea level occurring in the current geologic period.
These three forces result in constant movement of the sand that constitutes
the beach. The shape of the beach at any given time is closely tied to the
direction and the intensity of water movement (since the water movement
moves the sand), and to the supply of sand to the beach. The beach and
frontal dunes make up a dynamic system that changes considerably over time.
Dunes also shift constantly and migrate inland along with the shoreline.

A-16
The beach and dune system serves two important functions: sand supply
and storm protection. Sand is taken from the dunes during periods of high
wave energy (i.e., storms), and is stored on off -shore sand bars. This
usually occurs in the winter, which explains why the beach is more narrow
in the winter. These off -shore sand bars act as a drag on incoming waves
to dissipate their energy. The dunes are rebuilt with the sand from these
off -shore bars in the summer when the wave energy is lower.
The dunes also serve to prevent flooding of the interior of the
island. In the more severe storms, dunes and the wide beach act as the
off -shore sand bars do in the winter, dissipating the energy of the waves
as they washover, and thereby reducing storm damage to the interior of the
island.
Activities of man can interfere with this system in two important
ways: by destroying the dunes or by building up and stabilizing the dunes.
Destruction of the dunes eliminates storm protection provided by the dunes
and increases erosion. The sand stored in the dunes will also be removed
from the on-shore/off-shore transport system. This reduction in sand
supply will also increase beach erosion at the site and downcurrent from
the site. Attempts to stop or slow down beach erosion with seawalls,
jetties, and other coastal construction projects usually increase erosion
and destroy the beach either at the site or downcurrent, depending on the
structure constructed. The expense of such efforts often exceeds the
benefit of the efforts.
The building up and stabilizing of a row of high, continuous dunes was

A-17
done on large parts of the North Carolina Outer Banks and on parts of the
Currituck Banks during the 1930s. Although such projects may provide an
initial period of better storm protection, they have several detrimental
after effects.
A high, continuous dune system, like a seawall, refracts wave energy
back onto the beach at the base of the dune. This increases beach erosion
and steepens the beach profile, which further increases erosion. The
steeper and more narrow beach profile caused by the row of high dunes
reduces the desirability of the beach for recreation and reduces the
usefulness of the beach for vehicular access or for commercial fishing.
A row of high foredunes also protects the interior of the island from
salt spray and overwash. This in turn allows the proliferation of
vegetation that is less tolerant to salt spray and salt —water flooding or
to sand burial. Therefore, when storm waves do overwash the foredunes, the
damage to the island will be more severe because little vegetation will
survive to stabilize sand.
In preventing or reducing the possibility of overwash, a high row of
foredunes hinders an important process allowing barrier island migration
and replenishment of the marshes. The process of overwash will be
discussed in the next section.
Behind the frontal dunes are a series of secondary dunes, including
large stationary and migrating sand hills. These dunes serve several
important functions. They are a major storehouse for sand, providing sand
both to the primary dunes on the beach and to the sound for replenishment
of the marsh. As with the primary dunes, they also provide storm

A-18
protection. Finally, the secondary dunes serve to increase the capacity of
the water table and the availability of freshwater supplies. The importance
of these areas to subsurface water supplies will be discussed in the
section on aquifer recharge areas.
Interference with secondary dunes has serious impacts on the entire
island. Removal of the dunes reduces the subsurface water supply of the
island. Removal or stabilization of the dunes removes sand from ,the
transfer system and increases erosion both to the beach and on the
soundside. Therefore, the dunes are important to maintaining the entire
natural system.
Management implications presented by the dune and beach system recog-
nize that development should occur neither directly on the dune nor in
areas within the ocean erosion zone of the frontal dunes. Setback lines
should take into consideration the average annual rates of migration within
the area.
Many of the sand hills on the Currituck Banks are migrating, usually
in a southwesterly direction at a rate of 18 to 39 feet annually (Guttman,
1978). obviously homes, roads, or other structures built within the path
of migrating dunes should take that fact into consideration.
The growth of exotic plant species around the dunes and low laying
areas of the island should be discouraged. Instead, natural species that
are adapted to salt spray and saltwater flooding, such as sea oats and
beach grass, should be utilized.
Alteration of the surface of major dunes should be discouraged, as
should the removal of dunes. Access to the ocean over the dunes should be

A-19
over boardwalk overpasses, to prevent storm waters from channeling though a
narrow gap in the row of dunes and causing severe local erosion.
Washover Areas
Although the beach, the dune fields, and the interior of the island
are distinct geographic areas, the washover is a major feature that cuts
across all three of these barrier island environments. A washover connects
the beach with the sound, and may become a temporary or permanent inlet.
Washover areas may be recognized by low, often broad, passes running from
the ocean to the sound.
The washover process is a critical factor in a barrier island system.
It enables the barrier island to migrate. By migrating, the island
maintains its elevation in the face of the rising sea level. In a sense,
this migration occurs as the island rolls over on itself. Washovers also
enhance the productivity of the marshes in the sound by depositing sand in
the marsh to form new substrate for the growth of new marsh. Wave heights
during a storm may carry over the beach ridge and erode the foredune, or
may pass through the dune system at a gap in the dunes. Water and sand is
then carried over the island by the increased elevation of the ocean water
over the calmer water in the sound. If the barrier island is wide and
includes extensive barrier flats, a washover fan (a delta -shaped feature
that spills out over the sound) results. If the flow is narrow or the
island is flat and narrow, an inlet may be cut. Sand is transferred from
the beach to the sound, thus effectuating the migration necessary to keep
the island above the sea.
By preventing washover, the artificial row of high dunes prevents new

A-20
substrate from forming on the soundside of the island. This eventually
reduces the productivity of the marshes and of the sound. It also causes
the island to narrow because without replenishment, the soundside erodes
nearly as much as the ocean.
The damage done by storm washover can be minimized by limiting
alterations to an area's topography, by controlling density, and
particularly by controlling the amount of impervious surface within a.
washover area. Roads built within a washover area increase the impervious
surface within the area, may be expensive to keep free of sand and water,
and serve as flood channels that funnel water into areas that would not
otherwise by badly flooded. Large sand hills within washover areas should
not be removed because an inlet is more likely to form within a washover
area if the land across the island is low.
Potential Inlet Hazard Areas
The opening, closing, and migration of inlets are well—known to
coastal observers and to coastal historians. Inlet formation is caused by
the tidal surge associated with storm activity. Inlets may form from ocean
or soundside surge. They form from the oceanside if a storm surge is
concentrated within a small area or is across a narrow part of the island.
If the island or spit is wide and relatively flat as it slopes into the
sound a washover fan is more likely to develop. Inlets may form from the
soundside when mainland runoff and extraordinary storm surge seek a way to
the ocean and break through a low part of the island.
There are two potential inlet areas on the Currituck Banks. The first
of these is Carova Beach where the canals provide a funnel for water and

A-21
have narrowed the island. A second and more likely area for an inlet is at
the site of the former Caffey's Inlet. This area is near the Dare County
line where the island is low and narrow, where there is little marsh to
dissipate wave energy and form an overwash fan, and where there is a deep
waterchannel leading to the area.
The dynamic nature of inlets must be considered in barrier island
development decisions. An inlet would upset transportation flow across the
banks and would render the immediate area around the inlet undevelopable
due to the migratory nature of inlets. Public investment decisions, such
as road or pipeline construction, should consider the possibility of inlet
formation.
Aquifer Recharge Areas
Aquifers are naturally occurring, water -bearing bodies of permeable
rock, sand, or gravel. The known shallow aquifers on the Currituck Banks
are lens -shaped bodies of freshwater floating on saltwater that has
intruded into underlying sediments. This freshwater is concentrated in the
maritime forest areas and in pockets within the larger dune and sand hill
areas. The root systems of forest vegetation play an important role in
retaining this shallow groundwater. The groundwater also serves to sustain
the vegetation that grows in the forest, thereby stabilizing the island and
providing other amenities.
Because freshwater on the Currituck Banks is limited, proper
management of these subsurface aquifer areas takes on added importance.
Without adequate hydrological data, it is prudent to conserve the areas
that are known to contain water suitable for household use. Recharge of

A-22
these subsurface water supplies depends heavily upon the vegetation growing
above the aquifer. Therefore withdrawal of groundwater should be closely
monitored to insure that water is not drawn down to the point of causing
the vegetation to die, and development should avoid removing vegetation
over the areas that contain subsurface groundwater in shallow deposits.
Outside of known aquifer areas, design criteria for site development should
minimize impervious surfaces and retain natural topography and drainage
patterns.
Martime Forests
The forest plays an important role in the island environment. In
addition to its aesthetic importance, the forest buffers the impacts of
high winds and storms, retains rainfall as subsurface water, and stabilizes
the loose sandy soil of the island.
Early settlements on the Outer Banks almost always were placed within
the maritime forest because it is generally higher, safer, and more
sheltered from the temperature extremes than areas outside the forest area.
Developers along the coast are rediscovering the benefits of development
within the forest and are making tremendous demands on these areas.
Intensive development in maritime forests that requires cutting large
numbers of trees within the area is not compatible with the natural
processes served by the forests. Removal of the trees reduces the water
retaining capacity of the area. Possible septic tank contamination from
development in the area also reduces the usefulness and the desirability of
the groundwater for household consumption. Large-scale tree removal also
exposes the area to wind erosion that may cause relic dunes to become

A-23
active again and threaten other areas of the forest as well as human
development in the area. Excessive demands on the subsurface freshwater
lens may lower the water table or cause saltwater intrusion and completely
destroy the vegetation within an area. The amount of water that can be
pumped from a forested area before the area loses the vegetative cover is
unknown. Once the vegetative cover is killed, the amount of groundwater
available is reduced.
The forest is the safest area of the island for development.. It is
also the most critical for stability of the island. Meticulous site design
of development is thus necessary. The construction of roads and public
service lines through a forest area enables salt spray and wind shear to
kill a large number of road —side trees. An unfortunate example of this
forest destruction can be seen on the Bogue Banks along the Salter Path
Road, which was widened in 1977.
The Estuary System and Salt Marshes
The Currituck Sound and the associated marshes provide a vital service
as a nursery for sport and commercial fish species, and as a breeding and
migration area for a wide variety of birdlife. The individual land areas,
such as the tidal marshes, may be valuable in themselves, but their real
contribution occurs when they interact with the larger system of the
estuary and sound. The marshes are a vital part of the sound because the
productivity of the entire sound is supported by nutrients from these tidal
marshes. The populations of fish, seafood, and birdlife are directly tied
to the productivity and health of the marshes.
The marshes on the sound are also valuable in protecting upland areas

A-24
from soundside flooding and erosion. They absorb large amounts of water
and act as a barrier between the open sound and the upland during storm
activity. In this role they absorb wave energy and storm surges.
Man's activity can adversely affect the marsh by destroying the land
area of the marsh or by polluting the marsh. Filling or bulkheading a
marsh changes the area into upland and destroys its value to the sound.
The deposition of spoil and dredge material may have the same effect.
Water quality in the sounds and marshes is related to the rivers that
flow into the sound from the mainland because the estuary is the bottom of
the river drainage area and the water in the sound flows slowly. Land use
management in the upstream river basins is important to the productivity of
the marshes and sound. However, development on the island also plays an
important role in maintaining the productivity of the sound. Overintensive
development near the sound and poor septic tank selection or performance
will create runoff into the sound and could adversely affect its
productivity.

A-25
APPENDIX D
METHOD USED IN HURRICANE EVACUATION ANALYSIS
Hurricane evacuation capacity is based on the capacity of the one
evacuation route for Currituck Outer Banks and upper Dare County Outer
Banks (from Duck to Kill Devil Hills). This is the Route 158 causeway, the
Wright Memorial Bridge, at Kitty Hawk (see Figure III —I). This causeway
represents the critical point over which all evacuating vehicles must
travel.
Under ideal conditions, with 12 foot lanes and free flowing traffic, a
roadway has a capacity of 1,000 vehicles per lane per hour (Institute of
Traffic Engineering, 1965). During times of evacuation the roadway will be
utilized beyond what would allow free flow. Therefore, the number is
increased to 1,500 vehicles per lane per hour (Rogers, Golden, and Halpern,
1981). Since both lanes will be used for evacuation to the mainland, the
capacity is doubled to 3,000 cars per hour. Due to storm conditions,
stalled cars and emergency vehicles, however, the capacity is reduced to
1,575 vehicles per hour. This figure was obtained in the following
fashion: a 35 percent weather reduction factor was used to account for
slick roads, slower driving, and frequent stops (Rogers, Golden and
Halpern, 1981) bringing road capacity to 975 vehicles per lane per hour.
This figure was further reduced by 15 percent to 830 vehicles per lane per
hour, to allow for stalled cars (Rogers, Golden and Halpern, Stone, 1983).

A-26
Finally, capacity was set at 1,575 vehicles per hour for both lanes, by
accounting for closure of one lane 10 percent of the time to allow
emergency vehicles through (Stone, 1983).
The next step is determining a time constraint, and relating that to
the number of dwelling units that can be built. The official National
Weather Service warning is assumed to be 12 hours before the eye of the
storm reaches land. The North Carolina Department of Transportation
reports indicate that flooding and gale force winds will effectively shut
down the transport network three to five hours before the eye actually hits
land. Thus, using an average cutoff point, between three to five hours, it
was determined that all people would have to be evacuated four hours before
the storm's eye hit. This leaves a total of eight hours in which to
evacuate. It was assumed that people would be aware of what was occurring
and some would begin to evacuate as soon as the weather service warning was
issued (Goode, Personal Interview, 1983). This evacuation time could be
even less, however, if people take longer preparing to evacuate. Eight
hours at 1,575 vehicles per hour will result in an evacuation capacity of
12,600 vehicles that could be transported over the bridge during the
evacuation period.
Another assumption incorporated into the analysis was that additional
vehicles would leave prior to the official warning, i.e., before the eight
hour evacuation period. This assumption adds fifteen percent to the total
capacity of the bridge. It reflects the fact that some persons will leave
the island early due to inclement weather. This effectively raises the
total amount of vehicles that can be safely evacuated to 14,490. This
figure represents a maximum threshold of vehicles that, if on the island,

A-27
could escape the island (given that fifteen percent of the vehicles leave
in advance of the official warning).
The next step was to determine the demand which would be made on the
evacuation route. Demand was calculated in terms of dwelling units and the
number of vehicles which would be leaving each dwelling unit during a
hurricane. Rill Devil Hills and points north in Dare County also will use
the same route. Data from the North Carolina Department of Transportation
evacuation report and the Environmental Impact Statement written for the
Currituck Outer Banks indicate a total number of 5,270 existing dwelling
units for the entire evacuation area (including 409 dwellings on the
Currituck Outer Banks).
A range of vehicles per dwelling unit was used: 1.2, 1.6, and 2.0.
The 1.2 figure was based on the Sanibel, Florida, hurricane evacuation
study. The 1.6 number was based on findings of the Transportation Research
Board. The highest figure of 2.0 vehicles per dwelling unit was based on
the possibility that in a beach area, more than one family often share a
house and each family would evacuate in its*own vehicle.
Demand, or evacuation capacity in terms of dwelling units can be found
by dividing the number of vehicles on the island by the assumed vehicle per
dwelling unit figure. This is a general approach used to derive the
figures in Table III-1.
The analytic process is illustrated with actual figures below.
Process Used in Calculations of Road Capacity
A) (1500 veh/lane/hr.) x (.65 weather reduction factor) - 975
veh/lane/hr.

A-28
B) (975 veh/lane/hr.) x (.85 blockage factor) = 828.75 veh/lane/hr.
C) (828.75 veh/lane/hr.) x (.90 factor closure for emergency vehicles)
- 745.88 veh/lane/hr. (This is done for only one of the two lanes.)
D) 828.75 veh/lane/hr. + 745.88 veh/lane/hr. = 1575 veh/2 lanes, the
total road capacity for hurricane evacuation.
E) (1575 veh/2 lanes) x (8 hr. evacuation period) - 12,600 vehicles
during 8 hr. "peak".
F) 12,600 vehicles (8 hr. peak) x 1.15 (15% early leavers) - 14,490
vehicles that can safely evacuate during entire hurricane incident.
This represents the capacity of the hurricane evacuation system.
Process Used in Calculations of Evacuation Demand (measured in dwellings,
not vehicles)
A) (# of Currituck d.u.'s) x (# of veh/d.u.) - total Currituck vehicles
to be evacuated including early leavers.
B) (# of Dare County d.u.'s) x (# of veh/d.u.) - total Dare County
vehicles to be evacuated including early leavers.
C) (Currituck vehicles) + (Dare vehicles) - total vehicles leaving area
(8 hr. evacuation period and early leavers).
D) (Total from Step C) - (14,490 vehicles*) - # of vehicles over or
under capacity during total evacuation process.
E) (# of vehicles under or over capacity) / (vehicles/d.u.) = d.u.'s
under or over minimum threshold.
This figure is the minimum threshold level; the 12,600 vehicles at
Bridge during 8 hr. evacuation factored for assumption that 15% of the
population will leave before the 12 hr. warning, due to foul weather
(Goode, 1983).

A-29
E,g.Total Build —out, Using 1.6 veh./d.u.
A) (15,580 DUs) x (1.6) a 24,931 vehicles
B) (4,860 DUs) x (1.6) = 7,776 vehicles
C) (24,931) + (7,776) = 32,707
D) (32,707) — (14,490) = 18,217 vehicles
E) (18,217) / (1.6) = 11,385.6, rounded up to 11,390 DUs

A-30
APPENDIX E
METHOD FOR ANALYSIS OF ROAD NETWORK CAPACITY AND DEMAND
The method for determining carrying capacity based on the road network
is similar to that used in the hurricane evacuation analysis. Both employ
the capacity of a critical point in the transport network as the
determining factor in the network's ability to handle traffic. The
differences between the two are based on traffic generation during a normal
day and traffic generation during a hurricane evacuation.
The first step in our road network analysis is to determine the
critical point in the transportation network. This point is one over which
most people making an auto trip will cross to get to their final
destination. In the Currituck network it was determined that point would
be at the Dare—Currituck county line.
Given this critical point, the next step was to determine its
capacity. We started with an ideal roadway and ideal, or free flowing,
traffic. These two factors woud result in a capacity of about 700 cars per
lane per hour (Highway Research Board, 1965). That number was factored up
to 1375 cars per lane per hour (Highway Research Board, 1965), which in
turn is based on a change in the assumptions on traffic flow. Rather than
assuming the free flow associated with 700 cars per lane per hour, or a
total of 1400 for two lanes, capacity was calculated using a "stable"
traffic flow. In a stable flow situation, traffic has not yet reached a

A-31
point of stop and go movement, but driver speed and manuverability are
somewhat constrained (Highway Research Board, 1965). This is a tolerable
traffic level which most drivers and residents would accept. In essence,
we are making a tradeoff between freer flowing traffic and more capacity.
A final factor brought down that capacity slightly, based on the fact that
the 11 foot lanes present on Currituck's roads are less than the ideal
condition of 12 foot lanes (Highway Research Board, 1965). The final
capacity of the road, then, was 1320 cars per lane per hour. The entire
process is summarized in Table E-1.
After calculating the capacity of the critical point, which may
effectively be called supply, the next step was to determine demand on that
point using the number of dwelling units. Greatest demand on the critical
point will be during some peak hour when a majority of people are
travelling. For a typical community that will be in the evening from 3:30
to 6:00. On Currituck, the peak may encompass different times of the day,
but the length of it, that is 2 1/2 hours, and the demand generated during
that time, should be similar.
Traffic, or trip, generation per dwelling is based on the density of
housing. Since Currituck's land use ordinance allows three dwelings per
acre, that density figure was utilized. The average trip generation rate
for each household at three dwellings per acre is 1.1 (Sosslau, 1978).
That means that on the average, 1.1 trips will be made for each household
during the 2 1/2 hour peak period. Given the trip generation rate per
dwelling, it was a simple process to determine total demand during the peak
hour by multiplying trip generation by the total number of dwellings (See
Table E-1).

A-32
Given a peak period of 2.5 hours, it was necessary to determine the
road capacity for the entire period. The first step in this calculation
was to get the entire hourly critical point capacity. This entails
multiplying the hourly per lane capacity by the number of lanes, in our
case, two. The next step was to multiply that hourly critical point
capacity by 2.5, which is the length of the entire peak period. The final
figure is peak period capacity of the roadway.
The final step in the analysis was to relate demand generated by the
buildout figure discussed earlier to the capacity which now exists, and
indicate the consequences of buildout on roadway capacity strain.

A-33
TABLE E-1
SUMMARY OF METHOD FOR ANALYSIS OF ROAD NETWORK
Capacity
1) Determine critical point
2) Determine capacity of critical
point
a) ideal conditions
700 cars/lane/hour(1)
b) factor up ideal conditions(2)
1375 cars/lane/hour
c) factor down based on 11 ft.
lanes 1375 x .96 = 1320(3)
3) Determine peak capacity for
entire road
a) - determine hourly capacity
for entire road
1320 x 2 (# of lanes) = 2640
b) determine entire peak capcity
2640 x 2.5 (# of hours in
peak) - 6600
Demand
1) Determine # of d.u.'s: 15,580
2) Determine trip generation rate(4)
per household in peak period: 1.1
3) Determine total peak period
demand:
15,580 d.u.'s x 1.1 trips/d.u.
17,140 trips
1Highway Research Board, 1965, pp. 252-253.
2Highway Research Board, 1965, pp. 252-255.
3Highway Research Board, 1965, p. 256.
4Sosslau, 1878.

A-34
APPENDIX F
METHOD FOR WASTEWATER DISPOSAL ANALYSIS
On -Site Systems
A map of Currituck Banks soil units (scale 1"=2000'), suitable for
individual on -site wastewater treatment systems was developed using the
Soil Survey of Currituck County and criteria outlined in North Carolina
Laws and Rules for Ground Absorption Sewage Treatment and Disposal Systems.
Total acreage of suitable land according to existing regulation was
determined from the map with a planimeter. This acreage was multiplied by
two dwelling units per acre which is the average lot size on Currituck and
one which allows for adequate setback. The resulting figure yields the
number of dwelling units with on -site systems that could be supported on
Currituck Banks. The steps involved in this process are:
Step 1: soil survey information used to produce 1"=2000' base map of
Currituck Banks soil units
Step 2: unsuitable soils for on -site systems identified based on N.C.
regulations
Step 3: 10 year flood elevation denoted on map; soils within this zone
added to unsuitable cateogry
Step 4: final map of remaining suitable soils developed
Step 5: acreage of suitable soils determined using planimeter
Step 6: acreage (of suitable soils) served by Ocean Sands community waste-
water system subtracted
Step 7: remaining acreage multiplied by two dwellings per acre to yield
carrying capacity

A-35
Detailed Explanation of Soil Suitability Classification
Table F-1 denotes soils information needed to determine suitability of
each soil type for on -site systems, according to North Carolina
regulations. The following categories of information are considered:
topography and landscape position; soil drainage; soil texture, structure,
and consistence; and available space.
Topography/landscape position is a major limiting factor for on -site
systems. Unsuitable soils are those susceptible to frequent flooding (the
10 year flood level) based on interpretations of the State Division of
Health Services staff. Ten year flood zones based on tidal flooding have
been recommended by the U.S. Army Corps of Engineers (based on a National
Oceanographic and Atmospheric Administration report) to be defined by the 5
to 6 foot elevation on ocean and sound sides of Currituck Banks.
Unsuitable soils based on flooding potential cannot be reclassified
"provisionally suitable" under state regulations due to any site
modifications.
Soil drainage is the other major limiting quality of Currituck soils
according to state regulations. Soils with a water table less than 12
inches from the land surface are unreconcilably unsuitable for individual
systems. With a water table 12 to 18 inches from the surface,
modifications like adding fill approved by the State Health Department can
be considered, and a soil may be reclassified "provisionally suitable".
Soil texture, structure, and consistence are unsuitable only for the
Currituck mucky peat classification. Texture refers to the relative
proportions of sand, silt, and clay particles in a mass of soil. Structure

A-36
TABLE F-1
SOIL INTERPRETATIONS FOR ON -SITE DISPOSAL SYSTEMS
Soil Soil Name
Symbol
Slope
7.
Soil Organic
Texture Soil
Soil
Structure(1)
Depth to
High Water
Table(feet)
Depth
To Rock
(feet)
BN
Beaches-Newhan Association
0-25
Fine
sand
0,(sg)
CoB
Corolla
0-6
Fine
sand
0,(sg)
1.5-3
6+
CrB
Corolla-Duckston complex
0-6
Fine
sand
0,(sg)
1-3
6+
Cu
Currituck
0-2
Mucky peat yes
massive
+1-1
5+
Dt
Duckston
0-2
Fine
sand
0,(sg)
1-2
6+
Du
Dune land
*
Fine
sand
0,(sg)
DWD
Dune land-Newhan complex
2-40
Fine
sand
0,(sg)
*
6.25+
NeC
Newhan
0-10
Fine
sand
0,(sg)
>6
6.25+
NhC
Newhan-Corolla complex
0-10
Fine
sand
0,(sg)
1.5-6
6-6.25+
Os
Osier
*
Fine
sand
granular,(sg)(3)
0-1
5+
OuB
Ousley
0-6
Fine
sand
0,(sg)
1.5-3
6.7+
Soil
Symbol
equency
ground Water
Duration
Flooding
Months
10 Year
Soil
Rating
Survey Septic System Evaluation
Reasons
BN
*,
*
*
no
severe
poor filter
CoB
rare
*
*
yes
severe
wetness, poor filter
CrB
common-
brief-
Jan -Dec
yes
severe
wetness, poor filter, flooding
frequent
v. long
Cu
frequent
v. long
Jan -Dec
yes
severe
wetness, poor filter, flooding
Dt
common
brief
Jan -Dec
yes
severe
wetness, poor filter, flooding
Du
*
*
*
no
DWD
*
*
*
no
NeC
none -rare
*
*
no
severe
poor filter
NhC
*
*
*
yes/no
severe
wetness, poor filter
Os
rare -common brief
Dec -Apr
yes
severe
flooding, wetness, poor filter
OuB
common
brief
Dec -Apr
yes
severe
flooding, wetness, poor filter
Sources: Soil Survey of Currituck County and National Cooperative Soil Survey
* too variable to rate, or no information available
(1) 0 = no observable aggregation; sg = single -grained; massive = a coherent soil
mass; granular = small aggregations of individual soil particles
(2) rare, common and frequent flood designations may all be interpreted as 10
year frequency areas,

A-37
is the arrangement of primary soil particles into aggregates. Consistence
refers to the ease with which a lump of soil can be crushed by the
fingers.
Space requirement. State regulations also identify sizes of
nitrification fields adequate for proper functioning based on wastewater
application rates determined per bedroom.
In addition to accomodating a nitrification field, a lot must be large
enough to include a house, septic tank, and any setbacks required by state
and local governments. Examples of setbacks which must be accomodated by
Currituck Banks lots are:
Currituck County: structures must be 20 feet from improved roads
North Carolina: ground absorption disposal systems must be 100 feet
from any water source; 50 feet from marshes,
streams, and coastal waters; 10 feet from any
property line
N.C. Coastal Area Management Act: oceanfront set —back requirement for
structures is a distance landward from the first
line of stable vegetation, based on ocean erodable
rates
Areas remaining which must accomodate such set —backs have been calculated
for selected Currituck developments in Table F-2.

A-38
TABLE F-2
EXAMPLES OF GROUND ABSORPTION SYSTEMS SPACE REQUIREMENTS FOR
SELECTED CURRITUCK DEVELOPMENTS
Development Avg. Lot Size Avg. House Nitrific. Field Remaining Space
(ft2) Size (ft2) Space Require.") 3 BR 4 BR
3 BR 4 BR (ft2)
(ft2)
Whalehead 22,000 2000 900-1350 1200-1800 18650- 18200-
19100 18800
Ocean Hill 22,000 1500-2000 900-1350 1200-1800 18950 18500-
19400 19100
Swan Beach 15000-20000 1000-1500 900-1350 1200-1800 13950- 13500-
14400 14100
N. Swan Beach 15000-20000 1000-1500 900-1350 1200-1800 13950- 13500-
14400 14100
Carova Beach 15000-20000 1000-1500 900-1350 1200-1800 13950- 13500-
14400 14100
lAccording to state regulations, flow rate per bedroom is assumed to be
120 gpd. These calculations also assume 100 foot pipe lengths in trenches.
Source: Personal communication with Larry Riggs, Riggs Realty (March 1983).
Space requirement calculations based on North Carolina Laws and Rules
for Ground Absorption Sewage Treatment and Disposal Systems.
The overall suitability of a site is determined by the lowest
uncorrectable site characteristic outlined in Table F-3. Only two
characteristics, soil drainage and landscape position, are deemed uncor-
rectable by state regulations.
An alternative methodology would be to evaluate soil suitability for
on -site wastewater disposal systems using recommendations from the Soil
Conservation Service (SCS), Soil Survey of Currituck County (1982). The
last two columns of Table F-1 indicate rating and the soil properties that

TABLE F-3
GROUND ABSORPTION SEWAGE. TREATMENT SYSTEM SUITABILITY
ACCORDING TO NORTH CAROLINA REGULATIONS
Soil
Soil Name Topography/
Soil
Characteristics
Soil
Soil
Restric-
Overall
Symbol(1) Landscape
Texture
Consistence
Structure
Drainage
Depth
tive
Suit-
Position(2)
Horizons
ability(3)
BN
Beaches-Newhan Asso. -
s
s
s
-
s
s
s
CoB
Corolla u
s
s
s
ps
s
s
u
CrB
Corolla-Duckston Comp. u
s
s
s
ps
s
s
u
Cu
Currituck u
u
u
u
u
s
s
u
Dt
Duckston u
s
s
s
ps
s
s
u
Du
Dune land -
s
s
s
-
s
s
s
DND
Dune land-Newhan Comp. -
s
s
s
-
s
s
s
NeC
Newhan -
s
s
s
s
s
s
s
NhC
Newhan-Corolla Complex u
s
s
s
ps
s
s
u
OS
Osier u
s
s
s
u
s
s
u
OuB
Ousley u
s
s
s
ps
s
s
u a
w
Sources: N.C. Laws and Rules for Ground Absorption Sewage Treatment and Disposal (1982)
Soil Survey of Currituck County 1982
u = unsuitable ps = provisionally suitable s = suitable
1 as used in the Soil Survey of Currituck Count
2 Dash indicates that soils are suitable (no groundwater flooding of 10 year frequency),
but tidal flooding may remove some of the soils from consideration. Figure V-1 has
excluded those soils below 6 feet in elevation, which according to the Army Corps of
Engineers is the limit for 10 year frequency tidal flooding.
3 For those soils meeting available space requirements (See Table V) and with no danger of
10 year tidal flooding. The lowest uncorrectable characteristic determines overall
site characteristics.

A-40
limit on -site development for each soil type. All Currituck Banks soils
are rated "severe" for septic tank nitrification fields according to SCS
criteria. This means that soil properties are so unfavorable or so
difficult to overcome that special system design, significant increase in
construction costs, and possibly increased maintenance are required for
proper sewage treatment. There is a discrepancy in acreage termed suitable
using the SCS criteria (zero acres) and the methodology allowing state
regulations (1338 acres). The methodology based on state regulations was
chosen for this carrying capacity study, because it reflects existing
practice. The conflict between the acreages of suitable land resulting
from the two approaches is discussed in the following section.
Comments About the Method Used to Determine Carrying Capacity
With On -Site Systems
The difference between the amount of land considered suitable for
on -site systems under state regulations and according to soil survey
recommendations exists because state regulations allow individual systems
in extremely porous (sandy) soils where depth to water table is greater
than 12 inches. Soil Conservation Service recommendations, however, are
based on the assumption that when wastewater percolates rapidly through the
soil, adequate time is not allowed for proper filtering and biological
treatment of the waste. Installers and owners of septic systems in
Currituck beach sands (soils named Beaches-Newhan association, Dune land,
and Dune land/Newhan complex) should be made aware of the fact that rapid
permeability may lead to groundwater contamination.

A-41
Due to errors inherent in calculating suitable lands using graphic
methods, the figure given in the text for developable land for on -site
wastewater disposal systems should not be viewed as a precise figure.
Possible sources of error are: loss in accuracy from changing scales of the
soil survey to the Currituck base map, estimating the location of the
6-foot contour in order to designate the 10-year flood zone, and planimeter
error.
Sensitivity analysis performed on available space requirement figures
suggests that area remaining after allowing for septic tank, nitrification
field, and house on a lot would be adequate to accommodate any setback
requirements, given that soil otherwise meets all standards. However,
allowing three dwelling units per acre in this analysis would reduce
available space to an amount questionable for accommodating setbacks, so
this option has not been included in the calculation of total suitable
land. Whether or not the remaining available space is adequate for
setbacks is highly dependent on lot configuration, as well as proximity of
adjacent lots and structures, and their water and wastewater systems.
However, the approach used here remains a reasonable method of estimating
the interpretation of state regulations requirements on an island wide
basis.
Community Systems
For systems which require land treatment, daily wastewater flows are
assumed to be 120 gallons/person/day, as specified in the North Carolina
Laws and Rules for Ground Absorption Sewage Treatment and Disposal Systems.

A-42
Buildout levels as detailed in Chapter II were determined to be
15,580 dwelling units under existing policy. It is assumed that 4
persons would occupy each dwelling for 365 days per year. (Regulations
do not recognize seasonal occupancy).
Methodology for Community System Cost Determination
In calculating the criteria appearing in Table V-2 in Chapter V, a
methodology was derived from standard engineering practices:
STEP 1: Determine wastewater flow generated at a buildout level of
15,580 dwelling units
STEP 2: Calculate the land area required for ground absorption
systems
STEP 3: Compute the hydraulic loading rate for the predominant soil
type
STEP 4: Determine the nutrient capacity for the given cover crop.
(Coastal bermuda is recommended as a cover crop. Although
it is not a native grass, this species requires little
maintenance, is well adapted to the soil and hydraulic
conditions founds on a barrier island, supports two or more
harvests per year, and provides soil stabilization and a high
nutrient uptake.)
STEP 5: Derive capital costs (various sources) and allocate a portion
of the cost to each dwelling unit
STEP 6: Estimate operation and maintenance costs and allocate to each
unit
STEP 7: Document design life specifications for each option and
ascertain sensitivity to seasonal fluctuations.
The remainder of this appendix discisses calculations for steps 1 though 4.
Steps 5,6 and 7 are performed by researching the sources sited in the notes
to Table V-2.
Calculations for Land Area Requirements: Land Application System. Assume:
120 gallons/person/day as wastewater loading rate; dwelling unit occupancy
for 365 days; 4 persons per dwelling unit.

A-43
(A) 120 gallons x 4 persons x 15,580 dwelling units = 7,478,400 gallons
wastewater per day
(B) 7,478,400 x 365 days
2,729,616,000 gal.
wastewater per yr.
(C) total available irrigation (from Hydraulic Capacity Table F-4) is
136.03 inches per year x 27,154 ACIN (volume of water to cover 1 acre
1 inch deep) = 3,693,759 gallons per acre
(D) result (B) 2,729,616,000 gallons - 739 acres needed.
result (C) 3,693,759 gallons per acre

TABLE. F-4
HYDRAULIC CAPACITY: COROLLA/DUCKSTON SOILS
Month
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
ET
Drainage
Total Runoff
Total
Avg.
S.D.
Irrigation
Storage
Cumulative
Rainfall
Rainfall
Storage
J
0.93
13.0
13.93
.37
14.30
3.70
4.59
9.71
1.63
3.07
F
1.68
13.0
14.68
.37
15.05
3.72
4.61
10.44
.90
3.97
M
2.79
13.0
15.79
.37
16.16
3.74
4.63
11.97
.63
4.6*
A
3.60
13.0
16.60
.29
16.89
2.94
3.83
13.06
-1.72
2.88
a
M
4.65
13.0
17.65
.41
18.06
4.13
5.02
13.04
-1.70
1.18 4-
J
5.10
13.0
18.10
.40
18.58
4.02
4.91
13.67
-2.33
-1.15
J
4.95
13.0
17.95
.53
18.48
5.26
6.15
12.33
-0.99
-2.14
A
4.34
13.0
13.34
.58
13.92
5.82
6.71
7.21
4.13
1.99
S
3.60
13.0
16.60
.41
17.01
4.10
4.99
12.02
-0.68
1.31
0
2.17
13.0
15.17
.33
15.50
3.28
4.17
11.33
0.01
"Empty Basin"
N
1.50
13.0
14.50
.28
14.78
2.79
3.68
11.10
0.24
0.25
D
0.93
13.0
13.93
.32
14.25
3.21
4.10
10.15
1.19
1.44
Total
46.71
57.35
136.03
136.03"
=
2.62"/wk application
rate
Mean 11.34
52
wks

A 45
Notes to Hydraulic Capacity Table
Column (1) ET = evapotranspiration capacity of soil type as given in
Hardy's Bulletin (Carney, Hardy, and Van Bavel, 1977)
Column (2) Drainage coefficient = estimated surface flow from a site.
WRRI Report #165 states: "In estimating drainage, it is
assumed that wastewater and/or rainfall is applied in
sufficient quantity to saturate the permeable horizons."
Column (3) Total = column (1) + column (2)
Column (4) Runoff coefficient estimates the amount of water that runs off
the surface without absorption. This figure is considered to
be 10% of average rainfall per month.
Column (5) Runoff total = column (3) + column (4)
Column (6) Average monthly rainfall taken from Soil Survey of Currituck
County, North Carolina, U.S. Department of Agriculture, Soil
Conservation Service.
Column (7) Rainfall data used to calculate hydraulic capacity. The
figures given as average mouthy rainfall were inflated by 1
unit standard deviation to build in further protection in
years with heavy rains.
Column (8) Allowable Irrigation = amount of water safely applied to the
land surface. Calculated by column (5) — column (7).
Column (9) Storage = mean irrigation of 11.34" — column (8). Negative
values appearing in this column indicate a reduction in total
storage volume.
Column (10) Cumulative storage begins with an "empty basin" in October
and accumulates the storage figures from month to month.

A-46
Nutrient Analysis
Nutrients present in the domestic effluent and of most concern in the
operation of the land treatment system include nitrogen and phosphorus.
Potassium (K) is generally considered of great importance in agricultural
systems but is usually not present in effluent to any significant level,
according to Bob Rubin, N.C. Extension Service specialist.
If average nitrogen (N) and phosphorus (P) levels are assumed for
domestic wastewater generated at Currituck, then available nutrients may be
calculated as:
N: 7.47 mgd x 15 parts per million (ppm) x 365 days x 8.34
(constant weight of 1 gallon wastewater) = 341,090 lbs
nitrogen/year
P: 7.47 mgd x 5 ppm x 365 days x 8.34 = 113,697 lbs
phosphorus/year
Using these calculations and the land are required for absorbing the
water load, the nutrient load per wetted acre may be calculated as:
N: 341,090 lbs nitrogren/year + 739 (number of wetted acres)
= 465 tolerable lbs nitrogen/acre/year
P: 113,697 lbs phosphorus/year + 739 wetted acres = 154 lbs
phosphorus/acre/year
Nutrients, especially phosphorus, place the most significant
constraint on rates of wastewater land application. Table
F-5 summarizes the nutrient requirements of various crops.

A-47
TABLE F-5
CROP NUTRIENT REQUIREMENTS
(per acre)
Crop _
Nutrient Corn Wheat Coastal Bermuda Fescue Hardwoods
N 165(250)
72 0 35)
400(600)
250(350)
120050)
P 30
13
150
80
10
K 150
14
160
250
26
Source: N.C. Extension Service ,
Values in parentheses reflect nitrogen volatilization. In general, a
maximum of 150% of the uptake loading can be applied on any agricultural
crop/soil system. This is due to the losses from volatilization.
Based on phorphorus as the limiting nutrient and coastal bermuda as
the acceptable cover crop with highest phosphorus acceptance, the land area
required to assimilate the phosphorus load is:
113,697 total lb /year or 757 acres
150 lb /acre/year
The maximum phosphorus loading requires 757 acres, which is greater
than the hydraulic requirement of 739 acres. Therefore, 757 acres will be
required for land absorption of effluent.

A-48
APPENDIX G
NOTES ON DRINKING WATER SUPPLY
Operation of a Reverse Osmosis Desalization Unit
General process:
1. Feedwater is pumped through a filter where suspended solids that would
foul the filter membranes are removed.
2. Water is raised to operating pressure by a second pump.
3. Water is introduced into the desalinization unit:
a. portion of water permeates the membrane and is collected as
product water at the bottom of the unit;
b. brine is discharged at the top of the unit.

A-49
The Ocracoke Desalinization System (Reverse Osmosis)
Plant Output (numbers in gallons per day):
maximum capacity 150,000
average winter output 45,000
average May -June output 100,000
peak output (July -August) 130,000
Chemical Properties of Feedwater:
Total dissolved solids: 4800-5200 ppm
Chloride concentration: 1800 ppm
Chemical Properties of Product Water: Chloride concentration: 1-200 ppm
Cost:
Capital cost: $1,003,140 (1977 dollars)
Operating Expenses (July 1, 1981-June 30, 1982):
salaries
$34,000
truck
2,591
chemicals
15,334
payroll taxes
3,145
utilities
33,960
rent
1,200
equipment
1,952
plant
9,901
accountant
2,565
insurance
6,135
office supplies
3,985
miscellaneous
116
depreciation schedule: $46,410
plant life: 50 years
building life: 20 years
equipment life: 10-20 years
The Ocracoke Water Association is a non-profit organization which sells
product water on a straight-line rate (i.e., regardless of operating
expenses). The rate is $4.50/1000 gal. 26 million gallons were sold from
July 1, 1981 to June 30,1982. Total sales (26 million gallons at
$4.50/1000 gal.) were $117,000.
Pretreatment of feedwater:
Raw water passes through a sand filter. Sulfuric acid, potassium
permanganate, and a flocculant are then added.
Posttreatment (after desalting):
Aeration/degasifying. As the product water passes into the distribution
system, chlorine is added.
Sources: Ronnie Burrus and Frank Wardlow of the Ocracoke Water Asso.
(per telephone conversation)

A-50
References
Land Availability and Suitability for Development
Brower, David, Dirk Frankenberg, and Frances Parker. 1976. Ecological
Determinants of Coastal Area Management. Raleigh, N.C.: North
Carolina Sea Grant Program.
Clark, John. 1976. The Sanibel Report: Formulation of a Comprehensive
Plan Based on Natural Systems. Washington, D.C.: The Conservati
Foundation.
Godschalk, David et al. 1974. Carrying Capacity: A Basis for Coastal
Planning. Chapel Hill, N.C.: Department of City and Regional
Planning.
Godfrey, P.J., and M. M. Godfrey. 1974. "The role of overwash and inlet
dynamics in the formation of the salt marshes on North Carolina
Barrier Islands" p. 407-27. In R. J. Reimold and W.H. Queen (eds.),
Ecology of Halophytes. New York: Academic Press.
U.S. Fish and Wildlife Service. 1979. Classification of Wetlands and
Deepwater Habitats of the United States. Washington, D.C.: U.S.
Department of the Interior.
U.S. Fish and Wildlife Service. 1980. Environmental Impact Statement on
Proposed National Wildlife Refuge on the Currituck Outer Banks.
Newton Corner, Ma.: U.S. Department ot the Interior.
Guttman, Andrew L. 1978. The Interaction of Eolian Sand Transport,
Vegetation, and Dune Geomorphology - Currituck Spit, Virginia -
North Carolina. Thesis. Williamsburg, Va.: College of William
and Mary.
Hurricane Evacuation
Baerwald, John E., editor. 1965. Traffic Engineering Handbook. Wash-
ington, D.C.: Institute of Traffic Engineering.
Currituck Land Advisory Committee. 1980. Currituck County 1980-1990 Land
Use Plan.
Dare County Civil Preparedness Agency. May 31, 1977. Dare County
Hurricane Evacuation Plan.
Goode, Larry. March, 1983. Phone Conversation. Division of Highway
Transportation. Planning Engineer: [phone].

A-51
Highway Research Board. 1965. Highway Capacity Manual. Washington, D.C.:
National Academcy of Sciences.
McElyea, William, David Brower and David Godschalk. 1982. Before the
Storm: Managing Development to Reduce Hurricane Damages. Chapel
Hill, N.C.: The Center for Urban and Regional Studies.
North Carolina Department of Transportation. 1981. Environmental Impact
Statement for Currituck County Outer Banks Access. Raleigh, N.C.:
The author.
--------- December 28, 1982. Memo regarding "Peak Season
Population Estimates for the Outerbanks Area of Dare County and
Estimated Evacuation Time." Raleigh, North Carolina.
Pignataro, Louis J. 1973. Traffic Engineering: Theory and Practice.
Englewood Cliffs, New Jersey: Prentice -Hall, Incorporated.
Jersey: Prentice -Hall, Incorporated.
Rogers, Golden and Halpern. 1981. Hurricane Evacuation and Hazard
Mitigation Study. Philadelphia, Pennsylvania: Roger, Golden and
Halpern.
Sosslau, Arthur B., editor. 1978. Quick -Response Urban Travel Estimation
Techniques and Transferable Parameters. Washington, D.C.: Trans-
portation Reseach Board.
Stone, John R. 1983. Hurricane Emergency Planning: Estimating Evacuation
Times for Non -metropolitan Coastal Communities. UNC Sea Grant
College Publication UNC-SG-83-2, Raleigh, N.C.
Road Network
Baerwald, John E., editor. 1965. Traffic Engineering Handbook.
Washington, D.C.: Institute of Traffic Engineering.
Goode, Larry. April, 1983. Phone Conversation. North Carolina
Department of Transportation, Division of Highway Transportation
Planning Engineer; [phone]
Highway Research Board. 1965. Highway Capacity Manual. Washington, D.C.:
National Academy of Sciences.
Pignataro, Louis J. 1973. Traffic Engineering: Theory and Practice.
Englewood Cliffs, New Jersey: Prentice -Hall, Incorporated.
Sosslau, Arthur B., editor. 1978. Quick -Response Urban Travel
Estimation -Techniques and Transferable Parameters. Washington,
D.C.: Transportation Research Board.

A-52
Wastewater Disposal
Brown and Caldwell Consulting Engineers. 1982. Preliminary Design and
Marine Survey for Ocean Outfall: Dare County, N.C. Wilmington,
N.C.: The author.
Coastal Plains Center for Marine Development Services. 1975. Water Supply
and Wastewater in Coastal Areas. Proceedings from the Southeastern
Conference.
Coastal Plains Regional Commission.
Wastewater Disposal Feasibilit
Department of Administration.
1979. Final Report: Ocean Outfall
yand Planning. Raleigh, N.C.:
Moore, Gardner and Associates, Inc. No date. Volume Two: Feasibility Study
on Wastewater Facilities for County of Currituck, North Carolina.
Greensboro, N.C.: The author.
National Association of Homebuilders.
Washington, D.C.: The author.
1977. Alternatives to Public Sewer.
National Association of Homebuilders. 1980. Residential Wastewater
Systems. Washington, D.C.: National Association of Homebuilders.
National Oceanographic and Atmospheric Administration. 1975. NOAA
Technical Manual NWS HYDRO-27. Washington, D.C.: The author.
Nierstedt, R. et al.. 1980. Wastewater Management in Coastal North
Carolina. WRRI Report #165. Raleigh, N.C.: Water Resources
Research Institute of the University of North Carolina.
North Carolina Department of Human Resources. 1982. Laws and Rules for
Ground Absorption Sewage Treatment and Disposal Systems. Section
.1900 of N.C. Administrative Code, Title 10, Chapter 10, Subchapter
10A. Raleigh, N.C.: Division of Health Services.
U.S. Department of Agriculture. 1982. Soil Survey of Currituck County,
North Carolina. Soil Conservation Service, National Cooperative
Soil Survey.
U.S. Environmental Protection Agency. 1976. Costs of Wastewater Treatment
by Land Application. Office of Water Program Operations.
U.S. Environmental Protection Agency. 1978. Analysis of Operations and
Maintenance Costs for Municipal Wastewater Treatment Systems.
Office of Water Program Operations.

A-53
Water Supply
Fluor Engineers and Constructors, Inc. 1978. Desalting Plans and
Progress. California: The author.
Milliken, J. Gordon and Graham C.Taylor. 1981. Metropolitan Water
Management. Washington, D.C.: American Geophysical Union. Series
6: pp. 98-103.
Moore, Garnder and Associates. No date. Volume One: Feasibility Study
on Water Facilities for the County of Currituck North Carolina.
Greensboro, North Carolina: The author.
U.S. Department of Interior, Office of Water Research and Technology.
1977. The A-B-C of Desalting. Washington, D.C.: The author.
USGS. 1966. Chemical Composition of Rainfall in Eastern North Carolina
and Southeastern Virginia. Geological Survey Water Supply Paper
1535-K. Raleigh, N.C.: USGS.
USGS. May, 1978. Water Resources of Northeast North Carolina. Raleigh,
N.C.: USGS Water Resources Division.
General Carrying Capacity References
Precursors
C. S. Holling adn M. A. Goldberg. "Ecology and Planning," American
Institute of Planners Journal, 37:221-230, 1971.
Ian L. McHarg. "An Ecological Method for Landscape Architecture,"
Landscape Architecture, 57(2):105-107, 1967.
The Carrying Capacity Concept in Urban Planning
A. B. Bishop, H. H. Fullerton, A. B. Crawford and others. Carrying
CaRacity in Regional Environmental Man a ement, Report No. EPA-600/
5-74-021 Washington, D.C.: U.S. Environmental Protection Agency,
1974), Chapter IV: "A Carrying Capacity Planning Process for
Regional Environmental Management."
"Carrying Capacity Analysis is Useful --But Limited," Conservation
Foundation Letter, June 1974.
David R. Godschalk and Francis H. Parker. "Carrying Capacity: A Key to
Environmental Planning?" Journal of Soil and Water Conservation,
30(4):160-165, 1975.

A-54
David R. Godschalk and Norman Axler. Carrying Capacity Applications in
Growth Management: A Reconnaissance, report to the U.S. Department
of Housing and Urban Development (Washington, D.C.: U.S. Department
of Housing and Urban Development, 1977), Chapter 1: "Background and
Issues" and Chapter 3: "Conclusions and Recomendations."
Devon M. Schneider, David R. Godschalk, and Norman Axler. "The Carrying
Capacity Concept as a Planning Tool," Planning Advisory Service
Report No. 338, 1978.
Applications to Specific Areas and Resources
Joan Browder, Charles Littlejohn, and Don Young. South Florida: Seeking
a Balance of Tian and Nature (Tallahassee, FL: Center for Wetlands,
The University of Florida, and Division of State Planning, Florida
Department of Administration, 1977).
Department of Planning and Economic Development, State of Hawaii. Carrying
Capacity Action Research: A Case Study in Selective Growth
Management, Oahu Hawaii, report to the U.S. Department of Housing
and Urban Development Washington, D.C.: U.S. Department of Housing
and Urban Development, 1978), Chapter II: "Summary and Synthesis of
Findings."
David R. Godschalk. "The Carrying Capacity Approach to Local Growth
Management: Social Equity, Mother Nature, and the Public Works
Department," paper presented at the 1977 ASPO National Planning
Conference, April 25, 1977, San Diego, CA.
David W. Lime and George H. Stankey. "Carrying Capacity: Maintaining
Outdoor Recreation Quality," in Northeastern Forest Experiment
Station, Recreation Symposium Proceedings (Upper Darby, Pa.:
Northeastern Forest Experiment Station, U.S. Department of
Agriculture, 1971), pp. 174-184.
Howard T. Odum. "Energy Quality and Carrying Capacity of the Earth,"
Tropical Ecology, 16:1-8, 1975.
Urban Research and Development Corporation. Guidelines for Understanding
and Determining Optimum Recreation Carrying Capacity, prepared for
the Bureau of Outdoor Recreation (Washington, D.C.: Bureau of
Outdoor Recreation, U.S. Department of the Interior, 1977), Abstract,
excerpts from Chapter III: "Guidelines You Can Use to Determine
Optimum Recreation Carrying Capacity," and Chapter IV: "The Basis
for Determining Optimum Recreation Carrying Capacity."

A-55
Bucks County Planning Commission. Performance Zoning (Bucks County, Pa.:
Bucks County Board of Commissioners, 1973), p. 1: Introduction and
"Amendments to Zoning Ordinance."
George H. Nieswand and Peter J. Pizor. "How to Apply Carrying Capacity
Analysis," in Frank Schnidman, .Jane Silverman and Rufus Young, Jr.,
eds., Management and Control of Growth, Vol. IV: Techniques in
Application (Washington, D.C.: The Urban Land Institute, 1978),
pp. 140-143.
Peter J. Pizor with others. Managing Growth in Developing Communities (New
Brunswick, N.J.: New Jersey Agricultural Experiment Station, 1982),
pp. 44-65.
Tahoe Region:
Public Law 96-551, 94 Stat. 3233.
Tahoe Regional Planning Agency, Resolution No. 82-11, "Resolution of
the Governing Body of the Tahoe Regional Planning Agency Adopting
Environmental Threshold Carrying Capacities for the Lake Tahoe
Region," adopted August 26, 1982.
Mark von Wodtke. "The Carrying Capacity of the Los Angeles Basin," Cry
California, 5:22-26, 1970.

A-56
Contacts for Wastewater Disposal Information
Bill Burnett (Dare County Ocean Outfall)
Von Oesen and Associates
Wilmington, N.C.
[phone]
Fred Kleinfelter
Cartographic Section, U.S. Geological Survey
Reston, Va.
[phone]
Pat McDowell
Currituck County Engineering Consultant
Elizabeth City, N.C.
[phone]
Ken Old
Floodplain Management Branch
U.S. Army Crops of Engineers
Wilmington, N.C.
[phone]
Dennis J. Osborne (Land Disposal Methods)
CMO Associates, Inc.
402 Willowbrook Dr.
Cary, N.C.
[phone]
John Pridgen (Onslow Beach)
Pridgen Associates
Raleigh, N.C.
[phone]
Larry Riggs
Riggs Realty
Kill Devil Hills, N.C.
[phone]
Bob Rubin
N.C. Agricultural Extension Service
N.C. State University
Raleigh, N.C.
[phone]
Steve Steinbeck
Environmental Health Section
North Carolina Department of Human Resources
Raleigh, N.C.
[phone]

A-57
Locations Where Pressure Sewers in Use
Fair Play, South Carolina
York, Virginia