Stormwater Management Plan Update-1988

/'
PIS+Ee'/�/f;��/
—
I-•�
r �r
� i�% c MI ���r a
�1
� �
��► �.
� � ! ,
I A
97�
ram'
'J
rev ''
!," �`"' //' /�, i�r
';��,,�.
,
•�.

TOWN OF KILL DEVIL HILLS
STORMWATER MANAGEMENT PLAN UPDATE
1988
Planning Board
William Schmidt, Chairman Tom Taylor, Vice -Chairman
Phillip L. Tate Torrence L. Gray Tom Casey
Kenneth Barlow (alternate) Claire Waterfield (Clerk)
Department of Planning and Development
William G. Loy, Director
L. Ralph Allen, Assistant Planner
Consultant
William C. Overman Associates,-P. C.
��� Cak0
G F�,
Sandra M. Weir
Certified as
Planner -in -Charge
North Carolina
Division of Coastal Management
The preparation of this report was financed in part through
a grant provided by the North Carolina Coastal Management Program
through funds provided by the Coastal Zone Management Act of 1972
as amended which is administered by the Office of Ocean and
Coastal Resource Management of the National Oceanic and
Atmospheric Administration.

11
I
u
I
U
William C. Overman Associates, P.C.
August 29, 1988
Honorable Chairman and Members
Town Planning Board
Town of Kill Devil Hills
Post Office Box 719
Kill Devil Hills, North Carolina 27948
Gentlemen:
Engineers . Planners
We take pleasure in presenting our report entitled Kill
Devil Hills Stormwater Management Plan Update in accordance with
our subcontract of April 5, 1988.
The report describes progress towards implementing the 1983
stormwater management plan, documents existing and buildout
conditions under current policies, -identifies alternatives and
viable combinations for managing stormwater and improving
receiving water quality, and lists recommendations and their
priorities and costs. Tables and maps are included to support
and illustrate the work. Maps are provided under separate cover.
We appreciate your having authorized this study and the
thoughtful, timely review and comments from you and your staff.
We will be pleased to assist you with additional work at any
time.
Very truly yours,
WILLIAM C. OVERMAN ASSOCIATES, P. C.
7el
By
Garland L. Page, Jr., P. E.
Director of Planning
GLP:dmg
380 Cleveland Place • Virginia Beach, VA 23462 9 [phone]-

ACKNOWLEDGEMENTS
We express our sincere appreciation to the Planning Board of
Kill Devil Hills for their timely review and comments, to Mr.
William G. Loy, Director of Planning and Development and Mr. L.
Ralph Allen, his assistant, for their valuable guidance and
counsel, and to Mr. C. A. Smith, _Director of Public Works, for
the maps, data and other information he provided about the town
and finally, to Mr. Stephen R. Gabriel, Coastal Land Use Planner
with the Department of National 'Resources and Community
Development, for his overall assistance and particularily his
guidance in matters of water quality improvement.

KILL DEVIL HILLS
STORMWATER MANAGEMENT PLAN
UPDATE, 1988
TABLE OF CONTENTS
Page No.
Letter of Transmittal
Acknowledgements
Table of Contents i
List of Tables, List of Exhibits, List of Maps ii
Chapter
I. Executive Summary
1
A. Statement of the Problem
1
B. Recommended Solutions
2
C. Water Quality Effects
5
D. A Note About Methods
6
II. 1983 Storm Water Management Plan
Implementation Progress
8
III. Existing Conditions and Buildout Conditions
Resulting from Current Policy 11
A. Existing System Inventory 11
B. Existing Land Use 15
C. Buildout Land Use 24
D. Current Stormwater Policies and Regulations 28
E. System Capacity 36
F. Water Quality 56
IV. Alternatives 58
A. Do Nothing 59
B. Correct Existing Deficiencies 61
C. Require Open Space 67
D. Require Detention 76
E. Combinations of the Alternatives 80
V. Recommendations 95
A. General Recommendations 95
B. Specific Recommendations 97
C. Water Quality Effects 104
D. Design Criteria 106
- i -

i
List of Tables
ITable
1
Land Use Estimates and Projections:
Housing Units and Business Establishments
16
'
Table
2
Acres of Land Used by Each Category of
Development
20
Table
3
Land Use in Each Portion of Each Zoning
District (in Acres)
21
Table
4
Estimated Total Rainfall (Inches)
39
Table
5
Summary of Existing Runoff Conditions
42
Table
6
Summary of Future Runoff Conditions
49
Table
7
Summary of Impacts of Storms on Existing
Systems
55
Table
8
Summary for Correcting Existing System
Deficiencies
64
Table
9
Two Options for Required Open Space, Summary
70
Table
10
Lot Coverage Limits
71
Table
11.
Two Options for Required Open Space,
iTable
RA-6 Zone
Open Space,
72
12
Additional Options for Required
RA-6 Zone
73
Table
13
Recommended System Improvements -
Cost and Priority
99
List of Exhibits
Exhibit
1
Index of Land Use Intensity
17
18
Exhibit
2
Land Use Inventory Data Sources
Exhibit
3
Assumptions Used for Buildout Projection
24
jExhibit
4
Open Space Vocabulary
68
List of Maps
(Maps Provided -Under Separate Cover)
Map 1
Existing System Inventory
1
Map 2
Existing Land Use Intensity 1988
Map 3
Project Land Use Intensity 2000
Map 4
Recommended Improvements
- ii -

IEXECUTIVE SUMMARY
I
u
A. Statement of the
Problem The Town of Kill Devil Hills, North
Carolina currently experiences nuisance
flooding when there is a storm of an
intensity that occurs on the average of
once every two years. The town currently
experiences more serious, but still
relatively minor flooding problems when
there are storms of a greater intensity
occurring on the average of once every
five to ten years. Major flooding would
occur in the event of an intensive
rainfall or hurricane. The town has
undertaken natural hazard planning
independently of this stormwater
management project to prepare for such
events.
While the flooding problem in the
town has generally not been frequent or
serious to date, the problem would worsen
as the town develops rapidly in the next
few years unless additional stormwater
management measures are put into place.
In addition to the salient stormwater
problems such as flooded buildings and
roads, other important aspects of the
stormwater problem must be considered.
With more intensive development a given
level of rainfall will result in more
flooding because of the increased runoff
from the developed land, and there will
be more structures and persons at risk of
damage to life, limb and property.
88-19 - 1 -

�I
1
EXECUTIVE SUMMARY
Meanwhile, the town has a policy of
support for protection of the estuarine
and oceanic water quality. The town
supports state Coastal Area Management
Program guidelines and the state Coastal
Area Management Act goals for water
quality protection. Unchecked stormwater
runoff would pollute the estuaries and
the ocean. Stormwater systems that would
effectively relieve flooding could
pollute even more severely than,
unchanneled runoff since they could allow
the water to flow at a rapid enough rate
for it to carry a maximum amount of
sediment and chemical pollutants directly
to the coast.
Rapid stormwater removal and
prevention of pollution from the
stormwater are in some ways competing
goals so it is challenging to devise
satisfactory solutions to the combined
problem.
B. Recommended
Solutions The solution recommended in this
report comprises several methods to
reduce the amount of stormwater runoff
from each lot, to detain runoff so that
less sediment will reach the coastal
waters, and to remove runoff quickly from
developed areas. Adoption and
implementation of all of the recommended
improvements would reduce flooding under
88-19 - 2 -

IEXECUTIVE SUMMARY
build -out conditions to a nuisance level
for the two year storm event without
worsening and in some cases improving
estuarine water quality. The solution
would also lessen flooding and pollution
problems from the five and ten year
storms.
The components of the recommended
solution are summarized below and are
' presented in more detail in Chapter V,
Recommendations.
B.1.
' 88-19
General
Recommendations
There are three general
recommendations for adoption and
implementation throughout the town.
First, stormwater management should
become one of the town's major categories
of capital expenditure. The Dare County
Carrying Capacity Commission reports of
1986 did not include stormwater as one of
six major categories of improvements for
which the Commission made detailed cost
projections through the year 2000. As
the town works toward determining its
capital budget priorities certain
benefits of the recommended stormwater
management program should be kept in
mind.
Stormwater management will reduce
flooding and preserve water -quality,
contribute to the solution of certain
transportation and public safety problems
- 3 -

d
EXECUTIVE SUMMARY
and in certain cases reduce the intensity
of development of the type that would
have been particularly demanding of
government services. The costs of the
program will be shared by the town, the
private sector, and federal and state
agencies.
Second, the town should have an on-
going operations and maintenance program
to correct existing and prevent future
erosion and sedimentation problems in the
town's system. Silt should be removed,
ditches should be cleaned and vegetated
and the town should only accept for
maintenance vegetated ditches that have
been properly constructed by private
developers.
Third, zoning ordinance regulations
should be adopted for (1) lot coverage
limits, (2) primary yards, (3) channeling
of runoff into primary yards, and (4)
land disturbing activity limits. Design
guidelines closely related to the zoning
regulations should be distributed and
promoted for use by private developers
and for the town government's own
development projects.
B.2. Specific
Improvements Specific improvements are
recommended for each drainage area (Map
4). These improvements include the
upgrading of the three existing ocean
88-19 - 4 -

1 EXECUTIVE SUMMARY
outfalls and the establishment of two new
ocean outfalls and one outfall to Kitty
Hawk Bay. The remainder of the
improvements consist of the upgrading or
establishment of internal collection
systems consisting primarily of open
ditches. In addition, two major
' detention facilities are recommended to
accommodate the future development in the
' southern portion of the town.
The recommended solutions include
elements of every alternative considered
including improvements to the town's
'
collection system and outfall system,
zoning and other related regulations, and
off -site detention. The various elements
are combined in every drainage -area. On -
'
site detention was recommended for use in
only a few cases. New state stormwater
regulations, however, will require on -
site detention for many developments of
over one acre in size.
C. Water Quality
Effects
The program will have beneficial
effects on water quality. No runoff from
any developed area is directed to the SA
high quality waters of Roanoke Sound and
Buzzard Bay.
Existing outfall points would be
used for almost all of the runoff to the
'
SC waters of Kitty Hawk Bay. Detention
of runoff would provide for infiltration
88-19
- 5 -

1
�I
I
EXECUTIVE SUMMARY
of sedimentation before the water would
reach the sound. Water quality in the
bay would be preserved or improved.
The oceanside waters classed as SB
would have their quality maintained as
'would the Fresh Pond watershed that is a
source of public drinking water.
D. A Note About
Methods The recommendations in this report
result from a sound planning process. It
included a thorough inventory of existing
land use and stormwater conditions and
projections of growth to the time when
every buildable lot is developed in some
way (Chapter III) .
The existing conditions analysis
phase considered the capacity of the
town's system as it now exists and -
identified the severity of flooding that
would occur in each drainage area, under
current and future development
conditions, for various storm intensities
(Table 7) .
The alternatives phase (Chapter IV)
considered the major options for
improving the stormwater management
situation, first independently, and then
in combination. Each alternative was
described in terms of related issues, the
regulatory framework, implementation,
financial considerations and the effects
of the alternative.
88-19 - 6 -

EXECUTIVE SUMMARY
88-19
Finally, general and area specific
improvements were recommended (Chapter V)
based upon the best combinations of
alternatives for implementation in the
town overall, and then in specific
drainage areas. Cost estimates are
provided for the recommended improvements
(Table 12) .
- 7 -

I
I
1983 STORM WATER MANAGEMENT PLAN IMPLEMENTATION PROGRESS
The Storm Water Management -Plan for
the Town of Kill Devil Hills, North
Carolina, May 1983, McDowell &
Associates, P.A. had as its purposes to
evaluate potential drainage problem areas
and to accomplish the following
objectives:
"1. To identify current surface water drainage problems.
2. To anticipate future drainage problems in Kill Devil
Hills.
3. To help guide growth in an orderly manner consistent
with the Town's Land Development Plan.
4. To help prevent the loss of life and property as the
result of drainage problems.
5. To help reduce existing.and future maintenance and
capital cost for the necessary storm water drainage
systems in and around the town.
6. To help coordinate associated regulations as soil
erosion and flood plain management.
7. To assist the town to set up cooperative agreements
with the North Carolina Department of Transportation
(N.C.D.O.T.) in protecting and maintaining the area's
drainage system."
The plan identified drainage
problems at fifty-eight locations and
devised proposed solutions to each
problem. Thirteen of the areas were
evaluated as having major problems. The
problems were listed in order of
priority, and had preliminary cost
estimates prepared for their
correction. The report also set the
following goals:
88-19 - 8 -

1983 STORM WATER MANAGEMENT PLAN IMPLEMENTATION PROGRESS
1
1
1
1
1
1
1
1
1
1
1
i
1
1
i
1
i as-,9
1#1. Review the referenced field problems and set up the
town's priorities on corrective action using this
report's priorities as a guide.
2. - Establish sources of -financing for corrective action
through property owner assessments, developer
requirements, general taxes, joint venture arrangements
with D.O.T., and mosquito control funds.
3. Establish lines of responsibilities for drainage
maintenance and construction between the town and
D.O.T.
4. Develop a drainage ordinance.
5. Develop a storm water drainage design manual."
The plan was adopted by the Kill
Devil Hills Board of Commissioners and it
serves as the official "storm drainage
written policy" referenced in the town
zoning ordinance. The.use of the 1983
plan in the site plan review process is
described more fully in this plan in III.
D. Current Stormwater Policies and
Regulations, p. 22. Adoption of the 1988
plan herein would update and amend the
1983 plan as appropriate.
The major problems in several of the
thirteen areas were substantially solved
by the drainage system improvements
described in this plan in III. A.
Existing System Inventory, pp. 2-4.
Priority problem areas that have not
received improvements since they were
identified in 1983 have been incorporated
into the recommendations contained
herein.
- 9 -

1983 T S ORM WATER MANAGEMENT PLAN IMPLEMENTATION PROGRESS
iThe drainage ordinance and storm
water drainage design manual recommended
in the 1983 plan were not instituted.
1
-
i
I
i
1
i
I -
i
1 _
88-19 - 10 -

I
I
I
F
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
A. Existing System
Inventory Information pertaining to the
existing stormwater system for the Town
of Kill Devil Hills has been compiled
from field investigations, information
provided by the town, and North Carolina
Department of Transportation (NCDOT)
highway plans, and is displayed on Map
1.
The field information was obtained
by reconnaissance of the entire town
performed in April, 1988. Information
from NCDOT included as -built plans for
Croatan Highway (Rte. 158 Bypass).
Information from the town included pipe
sizes and locations for residential site
plan development since 1983. Information
from these sources has been shown
schematically. (Map 1). The Map was
prepared from the existing zoning.map for
the town, revised March, 1988. The
information shown includes the location,
size and material type for all pipes, the
location of endwalls, flared end
sections, catch basins and -junction boxes
and the location and typicial sections for
major open ditches. The locations of the
improvements shown are intended to be
illustrative of their approximate
locations and are not exact.
88-19 - 11 -

I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
The base map shows all known
dedicated rights -of -way within the limits
of the township -regardless of their
development condition.
While reviewing the existing system
in the field, it was noted that several
pipes are partially to fully silted
thereby drastically reducing the capacity
of the drainage system. This is not
unusual for a coastal area where the
soils are primarily sands with sparse
vegetation. However, if system capacity
is to be maintained periodic maintenance
must be performed to remove the silt and
vegetation must be established -along
ditches and waterways to reduce erosion
and sedimentation.
In addition, a review of the town's
records indicates that pipes have been
installed underneath driveways and roads
within several of the residential
areas. Reconnaissance showed no evidence
of these facilities indicating that they
are probably completely ineffective due
to silting over. Accordingly, these
facilities are not shown on Map 1.
Some changes have occurred since the
1983 Storm Water Management Plan was
prepared. Of particular importance are
the revised drainage systems along
Croatan Highway (U.S. Route 158 Bypass)
which were constructed in conjunction
88-19 - 12 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
with the NCDOT roadwaywidening
9
1 projects. Portions of Croatan Highway at
both the north and south ends of town
have been widened to five lanes and curb
and gutter and underground storm drainage
systems constructed. These new systems
' consist of a piped trunk line along
Croatan Highway with cross pipes
approximately every other block. Curb
inlets intercept the runoff from the
roadway and stub pipes with flared end
sections intercept the runoff from areas
outside the roadway which are collected
by ditches.
The system at the northern end of
town outfalls into the existing Bickett
Street ditch which discharges into Kitty
jHawk Bay.
The system at the southern end of
town outfalls through a pipe system along
Lake Drive which discharges through a new
j36-inch
reinforced concrete pipe into the
Atlantic -Ocean. This outfall system was
constructed since the 1983 plan and
replaced the 30-inch pipe outfall which
discharged on the beach behind Tanya's
Ocean House. The old 30 inch outfall was
subject to burial by shifting beach sands
and did not have a means of preventing
backflow of ocean waters during a tide
surge. The new outfall was constructed
on piles and extended to the low water
'
line thereby preventing beach sands from
1 88-19 - 13 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
blocking the pipe. The system also
1
includes a flap gate to prevent the
backflow west of the first drainage
structure near Virginia Dare Trail. The
rim of this structure is set at an
elevation which prevents the 100 year
itidal
flood from overtopping the
structure and breaching the dune line.
Another change in the drainage
system since 1983 is the construction of
the Holly Street- ditch from Shay Street
to Croatan Highway. This facility was
recommended in the 1983 Plan. In
addition, new developments in Wright
Woods and The Landing are served by new
pipe and open ditch drainage systems
outfalling into Kitty Hawk Bay. These
jsystems
are relatively small serving only
the immediate development area. Numerous
driveway crossings have also been
installed for both residential and
commercial properties. (Map 1).
Discussions with NCDOT personnel
indicate that another project for
widening Croatan Highway within Kill
Devil Hills is scheduled for construction
in the very near future. This project
will complete the widening of Croatan
Highway to five lanes through the town.
The project will include some revisions
to the storm drainage system along the
roadway but no detailed plans are
available.
1 88-19 - 14 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
In addition, the NCDOT will be
constructing a new 36-inch ocean outfall
along Oregon Avenue. This pipe will be
attached to the pilings used for the
proposed desalination plant discharge
line and will utilize a flap gate similar
to the one at the Lake Drive outfall to
prevent tide surge. This new outfall is
proposed to replace the Baum Street
outfall which consists of a 30-inch pipe
buried on the beach. NCDOT indicated
that the existing outfall would be
abandoned in place.
B. Existing Land Use A land use inventory provides a
tabulation of units in buildings
completed in Kill Devil Hills through
July 1988 (Table 1). The inventory
categorizes units as.follows: single
family, duplex, and mobile home units;
apartment and condominium units; hotel
and motel rooms; and commercial and
industrial establishments. For purposes
of this study, apartments, condominiums,
hotels and motels appear as separate
categories and are not included in the
commercial totals.
88-19 - 15 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING
FROM CURRENT POLICY
TABLE 1
LAND USE ESTIMATES AND PROTECTIONS: HOUSING UNITS AND BUSINESS ESTABLISHMENTS
Single Family, Apartment and
Commercial
Duplex and Condominium
Hotel/Motel
& Industrial
Mobile Hone Units Units
Roans
Establishments
19852
19881
3,000 402
1,006
280
19902
3,670 650
1,150
320
19952
4,058 836
1,672
N/A
5,550 1,551
2,275
N/A
20002
7,069 1,892
2,775
N/A
20003 (Alternate)
9,891 3,608
2,952
N/A
1 Number
of units, July 1988, estimated
by William C.
Overman
Associates.
occupancy
Based upon field surveys
permit information added to
and building
the units existing
and
in
1985 as
reported in Dare County Service Requirements
and
Development
Options Cost Report.
2
Dare County
Service Requirements and Development Options
Cost
Report,
1986, Scenario II.
3 Ibid.,
Scenario III..
I
1 88-19 - 16 -

1
I
I
I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
The inventory also yields land use
intensity in general (Exhibit 1, Map 2).
EXHIBIT 1
INDEX OF LAND USE INTENSITY
An index of land use intensity was devised to show the
development status of areas in Kill Devil Hills in summary
form. The same index was used for Map 1 (Existing Land Use
Intensity 1988) and Map 2 (Future Land Use Intensity 2000). The
index is based upon the information in Table 3, p. 6, which
indicates the acreage of each category of land use in each
portion of each zoning district. The index is calculated as
follows:
1. Each land use category is. assigned a weight based on the
average impact in terms of drainage, traffic or disturbance
of vegetation. The resulting assignment of weights is
Single family, mobile home, duplex - 1
Apartment, condominium, or light industrial in Fresh
Pond AEC - 2
Hotel or motel - 3
Other commercial or light industrial - 4
For each portion of a zoning district, acreages of each land
use are multiplied by the appropriate weight and summed.
2. The results from step 1 are divided by the total area
available for development after subtracting areas reserved
for right-of-way. An example is the calculation for 1988
for the Business district, portion 12:
30(1) + 5(2) + 10(3) + 110(4) = 2.1
245
The map and tabular information,
taken together and supplemented by this
narrative, are tailored to stormwater
management planning. For example,
detailed information was gathered for
various geographic areas of the town,
including typical lot sizes, lot
1 88-19 - 17 - -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
coverages by structure and impervious
surface, and total land disturbing
activity caused by development.
Many sources of data were used to
complete the inventory (Exhibit 2). In
addition, town, county, and state
policies affecting stormwater management
were reviewed by looking at documents and
conducting interviews. Key documents
were the 1987 Town of Kill Devil Hills
Land Use Plan, Kill Devil Hills Town
Code, Chapter 17 (Streets and Sidewalks)
and Chapter 20, (Zoning), A Handbook for
Development in North Carolina's Coastal
Area, and the various reports prepared
for the Dare County Carrying Capacity
Commission by Booz, Allen & Hamilton,
Inc.
I
EXHIBIT 2
LAND USE INVENTORY DATA SOURCES
1. Existing Land Use Map, p. 28a, 1987 Town of Kill Devil Hills
Land Use Plan
2. Dare County Carrying Capacity Commission, reports by Booz,
Allen & Hamilton, Inc.
3. Soil Survey of the Outer Banks_, North Carolina.
4. Building Inspector's Occupancy Permits (Monthly Summaries).
5. Building Permit Information (Monthly -Summaries).
6. Individual Building and Occupancy Permits files, all 1988
files, selected previous files.
7. Field inspection.
8. Kill Devil Hills Subdivision Index Map.
1 88-19 - 18 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
I
The acreage devoted to each category
of development in 1988 is displayed in
summary (Table 2) and by each separate
portion of each zoning district (Table
3). Significant land use characteristics
by land use category are the following:
1. Kill Devil Hills contains about
3,800 acres of land. Areas not
available for private -sector
development (1,164 acres).include
the portion of the maritime forest
owned by the North Carolina Nature
Conservancy, the areas forward of
the setback line in the ocean
erodible area of environmental
concern, the entire Government and
Institutional Zone, and the Wright
Memorial.
2. There are 965 acres of land
currently developed into one of the
four land use categories. About 30%
of current development is on
"marginal" or "unsuitable" soils, as
classified by the Soil Conservation
Service. Much of the development
-not on "suitable" soils is served by
septic systems.
3. Of the remaining 2,636 acres of
land, 263 acres, or 10%, are
allocated for purposes of this study
to existing or projected roads and
other rights -of -way.
1 88-19
- 19 -

TABLE 2
0
L
ACRES OF LAND USED BY EACH CATEGORY OF DEVELOPMENT
ko
Grand Total
Single Family,
Apartment and
Commercial
Developed
Right of
Duplex and
Condominium
Hotel/Motel
& Industrial
Land
Day
Mobile Home Units
Units
Rooms
Establishments
1985
910
90
520
40
60
200
1988
11070
105
630
50
65
220
1990
1,215
120
710
60
75
250
1995
1,790
180
1,115
95
90
310
2000
2,365
265
1,535.
110
105
350
Buildout
2,635
265
1,770
120
115
370
If buildout
is assumed
to be at 2,635
acres (development plus rights -of -way), according
to the
Ngrowth
policies
assumed
and with
no redevelopment, the
year 2000 situation would represent
buildout
o
in all areas
except 270
acres of
RA-6 where the market
would not yet have demanded the
necessary
investment in
central wastewater.
The total area of Kill Devil Hills
including areas not
developable
is 3,800 acres.

N
TABLE 3
LAND USE IN EACH PORTION
OF EACH ZONING DISTRICT
(IN ACRE.S)1
Estimated Development
1988
Projected Development,
2000
Total
Area Not
Right of
SF,Ki,
Apt.
Hotel
Ind.
SF,MH,
Apt.
Hotel
Ind.
8 of Buildout
Zoning District Portion
Area
Developable
Way
Duplex
Condo
Motel
Comm.
Duplex
Condo
Motel
Camm
2000
RA-6 Residential
1
920
90
270
645
80
2
230
25
75
0
5
180
5
5
90
3
770
255
50
90
400
85
RA-5 Residential
4
5
0
0
100
5
20
0
5
5
5
5
5
5
100
OIR Ocean Impact Residential
6
295
95
20
60
30
55
20
60
40
60
20
100
LB-1 Limited Business
7
60
5
20
55
100
Business
8
285
30
95
5
40
175
20
10
50
100
9
5
0
0
100
10
25
0
5
20
100
11
5
0
0
100
12
275
30
30
5
10
110
70
20
30
125
100
LI Light Industrial
13
10
0
5
5
5
10
100
14
45
5
5
5
5
35
100
LI-2 Light Industrial
15
50
5
10
45
100
G & I Gov't. & Inst.
16
435
435
0
Wright Memorial
17
375
375
0
Town Total
3,800
1,165
265
630
50
65
220
1,535
110
105
350
1 Each entry rounded to nearest 5 acres. Column and row totals may not agree with sum of entries due to rounding.
Zero entries indicate land use exists but at fewer than 2 acres.
2 Right-of-ways are included as builtout land. \

11
I
1
I
11
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
4. Existing single-family, duplex, and
mobile home development is at an
average density of 5.8 units per
acre (7,500 square feet per lot).
While the RA-6 zone containing the
bulk of potential single-family
housing areas has a minimum lot size
for newly platted lots of 15,000
square feet, the great majority of
that area was platted into smaller
lots previous to adoption of the
current ordinance. Such lot sizes
are "grandfathered" and the actual
limiting factor on lot sizes is
their ability to receive a septic
system permit. As of 1988,
residential lots receiving septic
system permits ranged upward from
5,000 square feet.
5. Existing condominiums and apartments
are concentrated in the Ocean Impact
Residential (OIR) zone. Very recent
multi -family housing development has
been in the OIR and Business
zones. Typically, each phase of a
condominium project ranges from 6 to
36 -units.
6. Hotels and motels are concentrated
in the OIR zone, while others are
across Virginia Dare Trail (U.S. 158
business) in the Business zone.
Current unit densities are at 15 to
20 rooms per acre. _
I
88-19 - 22 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
I
I
I
I
1
d
11
7. Commercial and industrial
establishments include all
industrial development and all
commercial development except multi-
family housing, hotels, and
motels. Recently the uses that have
been most numerous are offices,
restaurants, retail stores, and
warehouses. The average commercial
or industrial parcel size is 30,000
square feet; a typical small office
building is on a 10,000 square foot
parcel while a warehouse typically
uses a 65,000 square foot parcel.
8. While none of the G & I zone is
available for private -sector
development, the public sector uses
it for several facilities that have
an impact upon stormwater systems.
It is already used for some
institutional buildings and the
building permit has been filed for
the Kill Devil -Hills desalination
plant. Its development area has a
runoff coefficient similar to that
for small lot, single-family
residential uses. Given the
relatively few developed acres out
of a total 333 acre parcel, its land
use intensity computes to J0.
1
88-19
- 23 -

I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
IC. Buildout Land Use
I
I
The buildout projection for this
study used the following definition of
buildout: buildout is achieved when
every developable parcel in the town is
occupied by a structure(s) that is
buildable within the current or
grandfathered zoning and subdivision
regulations of the town. Further, the
density of development will be driven by
the market, within the constraints of the
town regulations existing in 1988; those
market conditions used were those that
underly 1988 development densities and
the Carrying Capacity Study. There were
several important assumptions used in
making the projections. (Exhibit 3).
EXHIBIT 3
ASSUMPTIONS USED FOR BUILDOUT PROJECTION
1. The "Moderate" growth policy selected for the town's land
use planning purposes, which is Scenario II from the Dare
County Carrying Capacity Study, is a realistic growth
projection for the town through the year 2000. Therefore,
the housing projections -of Scenario II are used for purposes
of this study.
Scenario II was compared to actual development from
1985 to 1988. Actual -development of single family and
apartment units was almost identical, while fewer hotel
rooms were built than Scenario II projected. However, hotel
construction is accelerating and should soon be at the
projected rate.
2. Projections for commercial and industrial establishments
were made for this study, since they were not available from
the Carrying Capacity Study. They were made, however, by a
method that related them to the Carrying Capacity Study
(CCS). The number of commercial establishments in 1985 by
1 88-19 - 24 -

I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
EXHIBIT 3 (Continued)
the CCS (430) was estimated to include 150 housing
establishments, and 280 other. -commercial and industrial
establishments. That same proportion of "housing" to
"other" establishments prevailed in newly permitted
development in the time 1985 to 1988. It was assumed that
the proportions would prevail through the year 2000. With
that assumption, it was possible to use a ratio to derive
"other" commercial projections from commercial housing
projections.
3. Apartment and condominium units are projected to be built at
an average density,of 20 units/acre from 1988 on, while
hotel and motel rooms will be built at a density of 40
rooms/acre. Average existing apartment densities are 10
units per acre, while respective hotel densities are 17
units per acre.
It is assumed that very few conditional use permits will be
granted for multi -family housing in the RA-6 zone.
4. Single family housing -units are assumed to be_able to be
built (able to receive septic system permits, if needed) at
lot sizes similar to those used for construction in 1988.
The smaller lots, platted earlier, will be fewer of the
total building lots as time passes, giving way to the newly
platted 15,000 square foot lots. Houses newly built in the
time period 1995-2000 will be on an average of 12,000 square
foot lots.
5. It was assumed that no conversion of structures from one'use
to another and no redevelopment of currently developed
properties will occur through the year 2000. There is
currently some conversion and redevelopment occurring.
While it might be more realistic to assume some conversion
and redevelopment, it was felt that projecting the amount
could not be done adequately with available data. If such a
projection is done, it should be considered whether to alter
the market assumption rather than using Scenario II.
Note that the above definition of
buildout does not mean that every parcel
is developed to its highest permissible
density. That density could only be
achieved with the use of community -wide
1
88-19
- 25 -

i
EXISTING CONDITIONS AND BOILDOOT CONDITIONS
RESULTING FROM CURRENT POLICY
wastewater. Very few lots in Kill Devil
Hills are currently developed to such
densities, so that achieving them would
require massive redevelopment. In
addition, the market would not demand
buildout defined in that way for at least
50 years. Given that Kill Devil Hills
has evidence that complete coverage of
' the town by development (the first
definition of buildout, above) might
occur before the year 2005, it seems more
appropriate to focus upon the stormwater
management problems that will arise by
.2005 than to compute the greatest -
possible development that regulations
would allow.
'
The buildout projections (Table 2,
10)
p. are the acreages represented by
the development according to the market
demand indicated in the Carrying Capacity
Study. Note that projections in detail
(Table 3, p. 11; Map 3) showing each area
of each zoning district, are carried
through the year 2000, at which time all
areas except the RA-6 areas are built
out. The most likely scenario, to begin
before the 2000 to
year and continue
until buildout, would shift residential
iuses
from the.Business zone through
conversion and redevelopment.
The following description of trends
in each land use category summarizes data
'
from Tables 1 through 3 and reflects
88-19
- 26 -

IEXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
1
current market conditions and zoning
policy.
1. Projected single-family, duplex, and
mobile home development will
comprise 3,399 new units and consume
905 acres between 1988 and 2000.
The bulk of the development will be
'
on land zoned RA-6. The remainder
will be on land in other zones.
1
Total single-family category
development at buildout, occurring
'
at about the year 2003, would
1,769
comprise total acres, 67% of
Kill Devil Hills' total developable
'
land.
2. Apartment and condominium
construction will peak in 1990-1995,
according to the market projections
from the Carrying Capacity Study.
Such uses will be concentrated in
'
the Ocean Impact Residential (OIR)
District and some Business areas.
3:_ -Hotel and Motel development will
enjoy a strong market through
buildout. While the OIR zone will
still have the greatest number of
t-otal hotel and motel units at
buildout, the Business zone will
receive the greatest number of new
hotel and motel units between the
1988 2000. In the
years and OIR
zone, zoning limits on room density
1
88-19 - 27 -

' EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
I
11
D. Current Stormwater
Policies and
Regulations
5.
and the unavailability of land will
limit the market, while the market
will be strong across U.S. 158
Business in the Business zone.
Industrial and commercial
establishments will be built in the
appropriate zones. The recent surge
in industrial building permits will
continue and the LI zones will be
built out in industrial uses by the
year 2000. Commercial construction
will continue at the rapid pace of
the late 1980's, but it appears that
buildout of the Business zone will
include both new commercial and new
- residential units.
In the G & I zone it is likely that
the town will erect some municipal
services facilities and Dare County
may build two schools. It is
anticipated, however, that retention
of much of the parcel in an
undeveloped state will yield a land
use intensity of j6 in the year 2000.
_There are several existing policies
and -:regulations that have a direct effect
upon stormwater management in Kill Devil
Hills. Stormwater management is the
chief purpose of some of the policies and
regulations, while stormwater management
is an indirect benefit of other
policies. The regulations are widely
88-19 - 28 -

EXISTING CONDITIONS AND BOILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
available so they will not be repeated
word-for-word in this stormwater
management plan. There is, however, a
brief description of each below with
additional comments as to the effect of
the regulation.
Several of the regulations are a
' part of the Town of Kill Devil Hills
Zoning Ordinance. The major amendments
to the town's zoning ordinance in 1985
included a restructuring of the zoning
districts and their related
regulations. A stated major purpose of
the zoning ordinance overhaul was to
' limit development in areas that are both
susceptible to storm impacts and where
high -intensity development would have
jeopardized water quality. The 1985
zoning ordinance changes, therefore, put
low intensity and high -intensity
districts in the proper arrangement to
improve stormwater management. The new
high -intensity districts, however, are
zoned for increased densities, which
impact upon the drainage systems. Also,
1 the zoning ordinance will have a less
profound effect upon limiting development
than the zoning map would suggest because
much of Kill Devil Hills was already
carved into subdivisions with
"grandfathered" small lots still eligible
for development.
' 88-19 - 29 -

iEXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
i -
The only explicit limitations on lot
i coverage are in the Light Industrial Zone
II and the Government and Institutional
Zone. In the Light Industrial Zone II no
lot may be developed "in such a manner
that more than sixty-five percent of the
existing vegetation is removed or altered
from its natural state". In the
Government and Institutional district
impermeable surface is limited to "the
i minimum amount necessary for normal
operation of the site. Should lot
coverage exceed 65 percent of the site,
all surface alterations in excess of 65
percent of the site shall be constructed
in semi -permeable paving blocks."
The Ocean Impact Residential zoning
regulations, while not expressing a
coverage limit, clearly state that
useable land on an oceanfront lot does
not include any areas east of the first
line of vegetation. In addition, there
is direct reference to the setback
multipliers for ocean hazard areas of
environmental concern. The regulations
affecting the ocean hazard, public water
supply, and estuarine shoreline areas of
environmental concern are covered below
1
in the section on state coastal
regulations.
The off-street parking and loading
portion of the zoning ordinance sets
forth detailed off-street parking
1
88-19 - 30 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
t t requirements for all land uses. It hen
sets forth three types of parking
reduction factor incentives available to
multi -family and commercial
developments. These incentives are for
visual and acoustic buffers, interior
ilandscaping, and the use of semi -pervious
paving block. The latter two amenities
and buffers made of certain materials
would reduce stormwater runoff from a
site.
The town zoning ordinance requires
1 that a building permit be obtained for
all development in the town. The
building permit application for single-
family detached units and multi -family
residential buildings containing four or
fewer dwelling units must describe, among
other items, ". . .(2) conditions
existing on the lot; and, (5) any other
matters which may be necessary to
determine conformance with, and provide
for the enforcement of this chapter."
1 For multi -family, group development
projects, group housing projects, and
commercial buildings, a site plan must be
approved by the planning board and board
of commissioners before a building permit
for construction may be issued. The site
plan must contain several features
relevant to stormwater management: (1)
site improvements, from which may be
calculated the proportion of impermeable
88-19 - 31 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
surface on the property; (2) the
percentage of land disturbing activity;
and, (3) finished grades for the site and
edge of adjacent properties. Also "storm
drainage shall be provided in accordance
with the duly adopted written policy, as
iamended from time to time, of the Board
of Commissioners, on file with the Town
Clerk."
The "storm drainage written
policy" of reference as of 1988 is the
Storm Water Management Plan for the Town
of Kill Devil Hills, North Carolina, May
1983, McDowell & Associates, P.A. Its
I section IV., "Stormwater Drainage Design
and Construction Criteria" indicates
drainage management information to be
included in site plans. Those criteria
include a basic performance standard that
j"All water drainage leaving the site
under development shall be channelled to
points of approved discharge, such as a
natural or manmade watercourse, a lake,
pond, ditch, or storm drainage system."
Systems should be designed to handle a
10-year storm. The 1983 criteria also
refer to North Carolina Department of
Transportation and Dare County Health
' Department standards as appropriate.
Dare County Health Department's
involvement in stormwater management
consists largely of assuring that
wastewater facilities are properly
1 88-19 - 32 -

1
, . I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
separated from stormwater facilities and
that wastewater systems are above the 10-
year flood level.
The State of North Carolina has
three primary sets of regulations that
affect stormwater management in coastal
land development projects, namely the
Coastal Area Management Act permit
requirements, the erosion and sediment
control regulations of the Sedimentation
Pollution Control Act of 1973, and the
Stormwater Runoff Disposal regulations,
effective 1988, under the authority of
G.S. 143-214, 215.
The Coastal Area Management Act
permit requirements apply to development
in designated Areas of Environmental
Concern (AEC's).in Kill Devil Hills. The
town's AEC's are of three types: the
Ocean Hazard AEC, the Estuarine System
AEC, and the Public Water Supply AEC.
Those permit requirements most
closely associated with stormwater
management in the Ocean Hazard AEC are
the limitations on the siting of
structures and the restrictions that
protect dunes, permitting dunes to
perform their natural function as erosion
buffers. The average annual shoreline
erosion rate is the basis for defining
Ocean Hazard AEC boundaries and the basis
for the siting regulations. Updated
88-19 - 33 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
erosion rates are under review at the
time of writing of this plan.
A major purpose of the estuarine
system AEC rules is to prevent stormwater
damage to the water quality of the
estuary. Impervious surfaces are limited
to 30 percent of a lot's area. In
addition, development must meet the
referenced standards of the Sedimentation
Pollution Control Act of 1973 and
drainage ditches in estuarine areas must
comply with the state Dredge and Fill
Act.
The erosion and sediment control
regulations of the Sedimentation
Pollution Control Act of 1973 mandate
that t-emporary and permanent control
measures be taken to.prevent accelerated
erosion and off -site sedimentation as a
result of land -disturbing activity. The
regulations apply to all development
activity, regardless of its extent, but
specify that a control plan be filed for
development areas of more than one acre
to provide protection from the calculated
.-_10-year storm. The 10-year storm
performance standard must be met during
construction of the project and
permanently upon the projectIs
completion. In Kill Devil Hills such
plans must be filed for land -disturbing
activity throughout the town.
1 88-19 - 34 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
Effective 1988, additional specific
stormwater control measures are required
for any development activities in Kill
Devil Hills which require a Coastal Area
Management Act (CAMA) major development
permit or a sedimentation/erosion control
plan. The permit approval processes for
the CAMA permits and
sedimentation/erosion control permits
are, in fact, to be used for the specific
stormwater control measures. The
specific measures for an individual
development are not required if the
Ldevelopment "controls runoff through an
off -site stormwater system meeting
provisions of this Rule and permitted in
accordance with G.S. 143-215.1(d)" an
example of an off -site system would be
any Town of Kill Devil Hills system that
serves a development.
For those developments that would
require on -site control measures, the
rule specifies design criteria for
stormwater infiltration systems and wet
detention ponds. The rule has separate
design criteria for areas draining into
Class SA water (Roanoke Sound/Buzzard
Bay) and other classes of waters (the
ocean, Kitty Hawk Bay).
The Town of Kill Devil Hills and the
State of North Carolina recognize that
the U.S. Environmental Protection Agency
is expected to issue additional
1 88-19 - 35 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
stormwater regulations during the summer
of 1988, namely "permit requirements and
best management practices for stormwater
point sources pursuant to the Federal
Water Pollution Control Act as amended."
E. System Capacity The existing drainage systems as
shown on the inventory map, along with
information obtained from the 1983 plan
and USGS quadrangle maps were reviewed to
determine the existing drainage patterns
within the town. The major outfall
systems along with the approximate
drainage boundaries for each system were
determined from the available
information.
The stormwater management system for
Kill Devil Hills is comprised of five
major outfall systems of which three
outfall into the Atlantic Ocean and two
outfall into Kitty Hawk Bay. Three minor
systems located in the Wrights Wood and
The Landing subdivisions also discharge
into Kitty Hawk Bay. The approximate
boundaries for each of these systems are
shown along with an area designation.
(Map 4). The area designation consists
of a letter representing the ultimate
outfall of the drainage system (i.e. O
for ocean outfall, S for sound) and a
number.
After determining the approximate
boundary for each system, the existing
88-19 - 36 -

IEXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
land uses within each drainage area were
reviewed and this information used to
estimate runoff values for sub -watershed
areas. Factors considered in determining
runoff values include the type of
development (i.e. residential,
commercial, industrial, etc.), the
average percent of impervious land cover
due to buildings, pavement, etc., and the
predominant soil types in the area.
The type of development and average
percent of impervious land cover were
determined from a review of the town's
records as described in Section III.B of
this report. Information regarding the
predominant soil types was obtained from
Soil Survey of .the Outer Banks, North
Carolina as prepared by the Soil
Conservation Service. The runoff factors
are used to compute the peak runoff rate
and total runoff volume for each of the
sub -watersheds analyzed based on a
specific rainfall amount.
Rainfall information was extracted
from rainfall maps prepared by the U.S.
Weather Bureau as published in Technical
Paper No. 40, Rainfall Frequency Atlas of
the United States. Rainfall amounts for
intermediate return periods and durations
were estimated using the procedures
outlined in Technical Memo NWS Hydro 35,
a
Precipitation Frequency for the eastern
and Central United States. The estimated-
88-19
- 37 -

1
1
1
1
i
1
1
1
1
1
1
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
88-19
total rainfall for various durations and
frequencies for the Kill Devil Sills area
are summarized. (Table 4). These
rainfall amounts were used in determining
the runoff rates and volumes used in this
analysis.
- 38 -

m m m m m m m m m i m m m m m m m m
TABLE 4
ESTIMATED TOTAL RAINFALL IN INCHES
Kill Devil Hills, North Carolina
DURATION
FREQUENCY
5 MIN.
10 MIN.
15 MIN.
30 MIN.
1 HR.
2 HRS.
3 HRS.
6 HRS.
12 HRS.
24 HRS.
2-Year '
0.4
0.8
1.0
1.5
1.9
2.2
2.6
3.5
4.2
5.0
5-Year
0.5
0.9
1.2
1.8
2.4
2.9
3.3
4.4
5.4
6.4
10 Year
0.55
1.0
1.3
2.0
2.8
3.3
3.8
5.1
6.3
7.4
25-Year
0.6
1.1
1.5
2.4
3.3
3.9
4.5
6.1
7.4
8.8
50 Year
0.7
1.2
1.6
2.6
3.7
4.4
5.1
6.8
8.4
9.9
100 Year
0.8
1.3
1.8
2.9
4.1
4.9
5.6
7.6
9.3
11.0
0

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
k
1
1. Existing Conditions:
After compiling the runoff factors
and drainage area for each sub -watershed,
computations were performed to estimate
the peak rate of runoff within each
watershed. These computations used the
Soil Conservation Service's TR-55
Computer program which utilizes the
methodology presented in Technical
Release No. 55 (TR-55) Urban Hydrology
for Small Watersheds. The size and
nature of the drainage areas dictated
selection of this methodology. This
methodology also provides a convenient
method for estimating storage volumes to
reduce peak flowrates to a predetermined
level. Peak runoff rates were computed
for each drainage area for the 2, 5 and
10-year return frequency storms (10-year
storm). The rainfall amounts for each
storm are shown in Table 4.
Estimates of each system's outfall
capacity were computed along with
estimates of the capacity of critical
internal system pipes such as the
crossings of Croatan Highway based upon
the field information previously
obtained. In estimating the capacity of
these systems and their components the
following assumptions were made:
1. All silt, trash and other debris has
been completely removed from all
pipes.
1 88-19
- 40 -

IEXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
2. The outfall pipes are not subjected
to extreme tidal surges caused by
strong wind storms (i.e. hurricanes,
tropical storms, northeasters, or
southwesters) which completely
inundate the outfall structure.
3. Normal high tide conditions caused
by lunar and solar movements are
imposed on the outfalls.
The peak runoff rates and outfall
systems capacities for each of the
drainage areas were compared to determine
the adequacy of the existing system under
' existing conditions. A summary of the
results of this analysis is presented in
Table 5 and further described herein.
Included in the table is the outfall
designation, the total area of the
existing watershed, the.outfall system
capacity and the peak flowrate generated
by each of the storms analyzed.
Also included in the table is the
estimated storage volume that would be
required to detain the runoff thereby.
reducing the peak rate to a level
equivalent to the outfall capacity. This
volume is an indication of the amount of
flooding that will occur within the
watershed for the storm specified.
' 88-19 - 41 -

ww ■w w■� w w ww ww ww aw sr ww sw ww w ww w wr ws ww
00 TABLE 5
00
to
SUMMAM OF EXISTING RUNOFF
CONDITIONS
Drainage
Outfall
Peak
Runoff Rate
Required
Storage
Volume
Area
Capacity
2 Yr.
5 Yr.
10 Yr.
2 Yr.
5 Yr.
10 Yr.
System
(Acres)
(CFS)
(CFS)
(CFS)
(CFS)
(Ac-Ft)
(Aa-Ft)
(Ac-Ft)
0-1
92.3
60
114
172
215
4.5
8.8
12.4
0-2
178.0
30
98
170
225
7.1
15.0
21.6
0-3
112.6
35
92
156
206
4.6
9.9
14.3
60*
92
156
206
3.1
7.5
11.4
S-1
416.2
260
96
195
272
-
-
-
S-2
139.6
95
95
162
212
-
6.8
10.7
w
S-3
31.6
18
9
24
35
-
0.7
1.4
S-4
7.4
10
3
7
11
-
-
-
S-5
21.3
20
7
16
24
-
-
-
*Based on proposed 36-inch outfall by NCDOT.

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
Storage will occur first in the pipes and
open ditches and will then spread to the
lowest surrounding ground. In some
' instances parking lots, roadways and
portions of yards will become involved.
Based on the available information we
have estimated available storage volumes
within the pipe and open ditch systems.
' However, without more detailed
topographic information of the area it is
not possible to specifically delineate
those areas that will flood under given
conditions. Therefore, judgement has
' been used to ascertain the seriousness of
the anticipated flooding. This
information is presented for each system.
System 0-1 has a total drainage area
of 92.3 acres of this area approximately
34 acres are business, 26 acres are a mix
of residential and light industrial uses
and the remaining area is undeveloped.
The outfall system is controlled by the
existing 36-inch pipe which discharges
into the ocean at the end of the Lake
Drive which has a capacity of 60 cubic
1
feet per second (cfs). The estimated
2-
peak runoff from this watershed for a
year storm is 114 cfs. Therefore, the
existing drainage system is inadequate to
accommodate existing runoff conditions.
This is not surprising since the NCDOT
has clearly stated that the intent of the
1
ocean outfalls is to provide a means for
88-19 - 43 -

1
1
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
relieving the watershed without providing
the full capacity required to accommodate
a design storm.
Since the peak runoff exceeds the
outfall capacity, the excess runoff will
be forced to pond in low lying areas
within the watershed. The required
storage volumes listed in Table 5 are an
estimate of the volume of this excess
runoff. For the 2-year storm this volume
is 4.5 acre-feet. Estimates of the
available storage within ditches and pipe
systems within this watershed indicate
that approximately 1.0 acre-foot can be
accommodated in these areas. The
remaining 3.5 acre-feet will pond in
other areas such as parking lots and
yards. This amount of ponding is
considered minimal and would amount to
nuisance level only. The estimated
flooding resulting from a 10-year storm
would be 12.4 acre-feet. This may result
in flooding within 40 percent of the
watershed of 4 to 6 inches. This would
be considered more than nuisance flooding
but would not seriously hamper emergency
access.
System 0-2 has a total drainage area
of 178.0 acres. Of this area
approximately 44 acres are business, 31
acres are residential and the remaining
103 acres are undeveloped. The outfall
system for this watershed is controlled
by the existing 27-inch pipe which
11
88-19
- 44 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
discharges into the ocean just south of
Martin Street. This outfall has a
capacity of 30 cfs. The estimated peak
runoff from this watershed for a 2-year
storm is 98 cfs. Therefore, the system
is inadequate to accommodate existing
' runoff conditions.
Irunoff
The estimated volume of excess
be
which will ponded within the
watershed is,7.1 acre-feet. With the
'
extensive amount of open ditches within
this area, especially along Holly Street,
'
Memorial Avenue, Harding Street and
Boundary Street, it is estimated that 5.0
1
acre-feet can be accommodated within
these systems. Therefore, the resulting
flooding from a 2-year storm would be
considered nuisance flooding in spot
locations throughout the area. The
effects of a 10-year storm will be more
noticeable with approximately 40 percent
of the watershed having ponded water.
Since the majority of the runoff is
generated in the business area between
Croatan Highway and .Virginia Dare Trail
it is anticipated that the majority of
the flooding will also occur in this
area. However, the flooding should not
be of a nature that would hamper
emergency access or cause major problems
in the area.
System 0-3 has a total drainage
area of 112.6 acres of which 56.4 acres
88-19 - 45 -

1
IEXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
1 are a mix of residential and business
1 development and 56.2 acres are
undeveloped. The present outfall for
this watershed is the 30-inch pipe which
discharges on the beach just north of
Baum Street. This outfall is estimated
to have a capacity of 35 cfs. As
mentioned previously, the NCDOT is
' planning to construct a new 36-inch
outfall in conjunction with work involved
with the proposed desalination plant.
This new outfall is intended to replace
1 the Baum Street outfall. The new outfall
will have a capacity of-60 cfs.
1
As indicated in Table 5 neither the
present or new outfalls for this
watershed can accommodate the estimated
peak runoff resulting from a 2-year or
greater storm. Therefore, ponding within
the watershed will occur similar to areas
0-1 and 0-2. Although the new outfall
proposed by NCDOT will provide some
additional relief to the area, it will
not eliminate all of the anticipated
impact is
ponding. The of the ponding
estimated to be of a nuisance nature for
the 2-year storm with slightly more
severe flooding for t-he 10-year storm.
Emergency access should not be a problem.
System S-1 has a total drainage area
of 416.2 acres and is by far the town's
largest system. The drainage area
includes a portion of the Wright Memorial
1 88-19 - 46 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
I
Li
I
I
I
Park along with primarily residential
development. The outfall system includes
the Highway Commission ditch which
extends from Croatan Highway to Kitty
Hawk Bay and has a capacity of 260 cfs.
This system is adequate to accommodate
the estimated runoff from this watershed
resulting from a 10-year storm with only
minor problems. It should be noted that
although the outfall system is adequate,
portions of the internal system,
especially along Carolina Avenue, may be
inadequate for their immediate area.
These areas are limited in size producing
minor problems resulting in nuisance
flooding with average depths of 2 to 4
inches.
System S-2 has a total drainage area
of 139.6 acres comprised of 71 acres of
residential and business development and
68.6 acres of undeveloped land. The
outfall system is the open ditch along
Bickett Street which is controlled by a
48-inch pipe under Bayview Drive. The
capacity of the outfall pipe is 95 cfs.
The runoff from a 2-year storm can be
accommodated by the outfall system. The
available storage within the Bickett
Street ditch and the Raymond Avenue ditch
system can provide the storage needed to
accommodate the 5-year storm. It is
anticipated that the 10-year storm will
result in nuisance flooding at various
1 88-19
- 47 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
Systems S-3, S-4 and S-5 are small
' systems which serve very localized
residential areas. These systems appear
I to be adequate for the 2-year storm with
only nuisance flooding caused,by the 10-
year storm.
2. Future Conditions:
'
After analyzing the impacts of
runoff from existing conditions, each of
the systems was analyzed to determine the
impacts of future development based on
buildout as described in Section III.C.
herein. Each of the watersheds were
'
reviewed to determine the increased
development within the existing .watershed
1
in addition to expansion of the watershed
incorporate
to areas which are not
presently served by established storm
drainage systems. Drainage boundaries
were then revised to show the expanded
watersheds. (Map 5). The methodology
for determining runoff factors, peak
runoff rates and volumes for this
scenario are the same as described for
the existing conditions. Table 6. The
following
narrative reviews the impacts
of these future runoff conditions on the
existing systems.
1 88-19 - 48 -

TABLE 6
SUMMARY OF FUTURE RUNOFF CONDITIONS
Drainage
Outfall
Peak
Runoff
Rate
Area
Capacity
2 Yr.
5 Yr.
10 Yr.
stem
(Acres)
(CFS)
(CFS)
(CFS)
(CFS)
0-1
153.8
60
238
350
434
0-2
208.8
30
268
396
493
0-3
438.0
60
241
395
519
S-1
823.8
260
338
606
817
S-2
139.6
95
185
269
331
S-3
51.4
18
22
48
68
S-4
7.4
10
5
10
14
S-5
21.3
20
13
23
32
Required Storage Volume
2 Yr.
5 Yr.
10 Yr.
(Aa-Ft)
(Ac-Ft)
(Ac-Ft)
13.8
23.4
30.8
22.3
40
50
23.1
44.6
62.1
15.5
43.0
68.2
8.3
15.3
21.1
-
2.3
3.8
0.3
1.1

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
Under future conditions, the
drainage area for System 0-1 has been
expanded by 61.5 acres. The additional
area encompasses the light industrial and
residential areas west of Croatan
Highway. The estimated peak runoff rate
resulting from a 2-year storm is 238
cfs. This is slightly higher than the
j10-year storm under existing
conditions. The resultant flooding from
the 2-year storm will be noticeable in 30
percent of the watershed with ponding
depths averaging 4 to 6 inches. Due to
the variation in elevations in the
watershed it is anticipated that some
localized areas especially within the
business zone could experience flooding
of a foot in depth or more. The 10-year
storm would result in flooding in 60
' percent of the watershed with many areas
experiencing depths of 6 to 12 inches.
Although none of the analyzed storms are
anticipated to hamper emergency access on
the main roads there may be problems on
minor streets within the residential and
light industrial areas.
■ The drainage area for System 0-2 was
expanded to include 30.8 acres of
primarily light industrial zoning in the
westernmost portion of the watershed.
The estimated peak runoff from the 2-year
storm of 268 cfs exceeds the outfall
capacity by a factor of 8. This will
1 88-19 - 50 -

I
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
1
result in a required storage volume of
22.3 Ac-ft. Since the majority of the
available ditch storage is in the
residential area west of Croatan Highway
it is anticipated that only minor street
and yard flooding will occur in this
area. The more severe flooding will
occur in the Business zone primarily
between Wrightville Avenue and Virginia
Dare Trail where depths may vary from 6
to 12 inches. The resultant flooding
from the 10-year storm will require
storage in excess of 42 acre-feet. It is
anticipated that this storm will so
severely overtax the existing system that
approximately 50 percent of the runoff
generated will be ponded in the areas
generating the runoff and will not reach
the downstream system for several
hours. Once again the flooding is not
anticipated to create problems for
emergency access but will cause flooding
over 40 to 50 percent of the watershed.
The future conditions for System 0-3
include expanding the drainage area by
325 acres. This expansion includes the
Residential, Business and G&I zoning
areas west of Croatan Highway. The
estimated peak runoff rate resulting from
the 2-year storm is 241 cfs of which 134
cfs is generated by the area west of
Croatan Highway. It is anticipated that
the existing system will be able to .
1
88-19
- 51 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
accommodate the runoff from the area east
of Croatan Highway with only minor
flooding. The area west of the highway
will be forced to detain its runoff until
the downstream peak has subsided.
Therefore, the majority of the estimated
23.1 Ac-ft. of storage will occur in this
area. Depending upon the improvements
constructed in this area to expand the
drainage system flooding may not be a
problem. This area is addressed in more
detail in later sections of this report.
The drainage area for System S-1 was
expanded to include additional area in
the Wright Memorial Park and the First
Flight Village subdivision as well as an
additional 104 acres of residential area
east of Croatan Highway. The revised
total drainage area is 823.8 acres. The
peak runoff rate from the 2-year storm is
estimated to be 338 cfs which can be
easily accommodated by the existing
outfall system utilizing the storage
Iavailable
in the Highway Commission
-ditch. The 5-year storm with a peak of
606 cfs would require 43.0 acre-feet of
storage which is within the estimated
available storage within the ditch
1
systems throughout this watershed,
therefore, no real flooding is
anticipated as a result of this storm.
The 10-year storm will generate 817 cfs
and will require 68.2 acre-feet of
88-19
- 52 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
storage. It is anticipated that the
majority of the flooding will occur in
the residential zone east of Croatan
Highway due to the restricted capacity of
storm pipes across the highway.
The initial analysis of future
conditions for System S-2 does not
consider any expansion of the existing
drainage area as this is addressed under
other sections of this report. Based on
the existing drainage area and future
buildout conditions the 2-year storm will
result in a peak runoff rate of 185 cfs
with a storage requirement of 8.3 acre-
feet. This storm can be accommodated
considering the available storage within
the open ditch systems along Bickett
Street and Raymond Avenue. The 331 cfs
peak runoff and 21.1 acre-feet storage
requirement generated by the 10-year
storm will cause flooding primarily in
the upstream reaches of the northern end
of the watershed. This flooding will be
more severe than nuisance flooding but
should not be detrimental to emergency
access.
The future conditions for Systems
S-3, S-4 and S-5 will not present a
problem under the 2-year'storm. The
runoff generated by a 10-year storm will
casue some minor nuisance flooding
primarily in the areas directly adjacent
to the roadside ditches. Therefore,
1 88-19 - 53 -

I
1
1
1
I
I
1
1
1
EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
88-19
these systems are considered adequate for
all of the storm conditions analyzed.
Table 7 summarizes the impacts of
both existing and future runoff
conditions on the existing stormwater
systems. Listed in the table are the
different systems and a description of
the type of flooding anticipated for each
combination of runoff conditions and
storm frequency. The terms used to
describe the flooding are defined at the
end of the table.
- 54 -

TABLE 7
p SUMMARY OF IMPACT'S OF STORMS ON EXISTING SYSTEMS
0
zxisting
uonaitions
r,uture uonaitions
System
Area
Storm Frequency
Area
Storm Frequency
Designation
(Acres)
2 Yr. 5 Yr.
10 Yr.
(Acre)
2 Yr. 5 Yr.
10 Yr.
0-1
92.3
Nu
Nu
Mi
153.8
Mi Mi
Ma
0-2
178.0
Nu
Mi
Mi
208.8
Mi Ma
Ma
0-3
112.6
Nu
Nu
Mi
438.0
Mi Ma
Ma
S-1
416.2
Nu
Nu
Nu
823.8
Nu Nu
Mi
S-2
139.6
Nu
Nu
Nu
139.6
Nu Mi
Mi
S-3
31.6
Nu
Nu
Nu
51.4
Nu Nu
Mi
S-4
7.4
Nu
Nu
Nu
7.4
Nu Nu
Mi
S-5
21.3
Nu
Nu
Nu
21.3
Nu Nu
Mi
n Definitions - Nu - Nuisance - Frequent ponding for durations.up to 2 hours. and
depths up to 4 inches over up to 40% of the drainage area.
Mi - Minor - Occasional flooding for durations up to 6 hours and
depths up to 9 inches over up to 40% of the drainage area.
MA - Major - Periodic flooding for durations greater than 6 hours and
depths greater than 9 inches over at least 40% of the drainage area.

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
F. Water Quality The North Carolina Coastal Area
Management Act program has as a basic
goal the improvement of water quality in
the state's estuarine areas. The Coastal
Area Management Act sets a goal to
preserve coastal water quality overall,
including the estuaries, the Atlantic
Ocean, freshwater areas, and groundwater.
1
1
1
1
� 0a-19
This stormwater management plan
update must be responsive to the
standards of water quality for all waters
in or surrounding Kill Devil Hills. It
must address the current water quality in
each area and provide a plan for
stormwater systems that will contribute
to meeting water quality standards in the
future.
The current classification of water
quality assigns the waters of Kill Devil*
Hills into categories on the basis of
best use determined by the studies by the
Environmental Management Commission. The
Fresh Pond is classified as A -II (also
referenced as WS-II) by the Commission.
Its best use is defined as public
drinking water supply. The estuarine
waters of Roanoke Sound and Buzzard Bay
are classified as SA, suitable for
shellfish culture, commercial -
shellfishing, and all other tidal salt
water uses. The SA standards are the
highest water quality standards for tidal
salt water. The oceanside waters
- 56 -

EXISTING CONDITIONS AND BUILDOUT CONDITIONS
RESULTING FROM CURRENT POLICY
throughout the entire length of Kill
Devil Hills are classified as SB, with a
best use of primary recreation defined as
activities such as swimming involving
human body contact with water. Kitty
Hawk Bay is classified as SC, the lowest
quality classification for tidal salt
waters, with a highest and best use of
fishing and secondary recreation, defined
as boating and other uses not involving
human body contact with water.
M. MEM
- 57 -

I
ALTERNATIVES
There are several options available
to the Town of Kill Devil Hills to
improve its stormwater management
situation. The options are categorized,
below, as do nothing, correct
deficiencies, require open space, require
detention, and combinations of the
alternatives.
While each is first discussed
separately in this chapter, the options
are not independent of one another. For
example, an area could be specified to
have both open space and on -site
detention. The space occupied by a
detention system could be considered as
open -space. On a particular lot, a
'
required detention system might consume
40 percent of the lot, while the basic
open space requirement for the lot might
be 35 percent. In such a case, the
performance standard represented by the
on -site detention system could supersede
the open space requirement, and the
'
detention system could be required.
Such relationships among options
were considered as the options were
developed. The last section of this
' chapter presents some combinations of
alternatives.
88-19 - 58 -
I

IALTERNATIVES
Each alternative is described and
discussed in terms of related issues, the
regulatory framework, implementation,
financial considerations, and effects of
the alternative.
A. Do Nothing; Under this scenario no changes to
the storm drainage systems would be
implemented other than periodic
maintenance and the installation of new
facilities directly related to new
development. The major outfalls would
remain at their present capacity level.
No changes to the regulatory framework
would be required and development would
continue under its present guidelines.
Financial considerations would,
therefore, be restricted to the funding
necessary for maintenance purposes only.
The impacts of this scenario have
been discussed in detail in
Section III.E. - System Capacity. In
summary, the storm drainage systems in
the northern two-thirds of the town are
adequate to accommodate the 10-year storm
under existing conditions and the 2-year
storm under future developed conditions
with minimal nuisance flooding. The
combination of future developed
conditions and the 10-year storm will
cause some minor flooding of durations up
to 3 hours. The ocean outfall systems in
the southern third of the town will
88-19 - 59 -

ALTERNATIVES
experience minimal nuisance flooding
resulting from the 2-year storm under
iexisting
conditions. Both the 10-year
storm under existing conditions and the
2-year storm under future conditions will
result in minor flooding in 40 to 60
percent of the area. Ponded water depths
will average 6 inches with the duration
of flooding ranging from 3 to 9 hours.
For the 10-year
storm under future
conditions flooding of depths exceeding 6
to 12 inches for durations of 6 to 24
hours can be expected.
It should be noted that although the
.major drainage system watersheds were
'
expanded under the future conditions
scenario, some areas remain without a
storm drainage collection system or
outfall. The areas are primarily the
residential zones west of Croatan Highway
both
on the north and south sides of the
Bickett Street Outfall (S-2). Under the
jdo
nothing scenario it is assumed that
development will install the necessary
facilities to accommodate these areas or
they will remain without a system. If no
system is constructed the area will act
as a retention area with little to no
discharge into Kitty Hawk Bay and all
'
runoff ponding in the natural low areas
until the water either evaporates or
percolates into the subsurface.
88-19
- 60 -
1

ll
IALTERNATIVES
B. Correct Existing
Deficiencies
I
I
The current stormwater design
criterion for the Town of Kill Devil
Hills is based on t'he use of the 10-year
storm as specified in the 1983 Stormwater
Management Plan. Based on a review of
the existing system capacities and the
estimated runoff from future developed
conditions a change in this criterion
should be considered for the following
reasons.
First, the high runoff rates
generated by a 10-year storm will require
major expenditures to reconstruct and
enlarge the existing drainage systems.
These expenditures.which could reach into
the millions of dollars would severely
tax the ability of the town to provide
the necessary funding. Secondly, the
probability that a 10-year storm in this
area will be accompanied by strong winds
causing abnormally high tides is very
high. Under these conditions, any
outf all system that relies on gravity as
the impetus to move the water is going to
have a very difficult time overcoming the
backwater effects of the tidal surge.
With the majority of land in Kill Devil
Hills being in the lower elevations there
is a high probability that the generated
runoff will be forced to pond until the
abnormal tide recedes.. Since wind storms
can last for several days the flooding
may not recede for.up to a week or more.
- 61 -

ALTERNATIVES
There is also the possibility that a
major storm could pass through the area
causing considerable damage and forcing
certain areas to be abandoned or totally
' reconstructed.
With these factors in mind, it seems
prudent to consider a design criterion
that will provide relief to the area
1
during the more frequent rain storms
while maintaining the costs of
1
improvements at a level which would not
cause an undue burden on the town.
Therefore, for the purposes of this
scenario, the correction of existing
deficiencies will be directed toward
'
improvements which will -accommodate the
2-year storm under existing conditions.
'
The revised system capacity will then be
compared to future developed conditions
to determine the severity of expected
flooding under these conditions.
The areas which are the hardest
stressed in terms of runoff versus
capacity are the ocean outfall systems in
the
southern end of town. With the
installation of the new 36-inch outfall
'
proposed by NCDOT in the near future all
three ocean outfalls will be on pile
1
supports and will discharge directly into
the ocean. The simplest method of
'
improving these outfalls is to provide a
second pipe by expanding the pile support
'
structure. This approach will double the
88-19
- 62 -
I

IALTERNATIVES
I
1
outfall capacity for systems 0-1 and 0-3
and triple the capacity for system 0-2.
The proposed outfall capacity for each
system is shown (Table 8) along with a
summary of the peak flowrates and storage
volumes associated with the'2 and 10-year
storms for both existing and future
conditions. In addition to upgrading the
existing ocean outfalls, the proposed
program includes a new ocean outfall (0-
4) for the residential area east of
Croatan Highway from Third Street to
Prospect Avenue. This new outfall was
considered in order to help alleviate the
anticipated flooding conditions which
would occur if this area were directed
into System S-1 in the future as
previously considered. For this
scenario, Systems S-1 and S-2 were not
improved since they are capable of
accommodating the 2-year storm under
existing conditions.
88-19 - 63 -

m m m m r m m m m m m m m m mom m m m
TABLE 8
co
T
SLY4,PM
FOR CORRECTING EXISTING SYSTEM DEFICIENCIES
Lo
Outfall Capacity
Peak Runoff Rate (CFS)
Required Storage
Volume
(Ac-Ft)
Exist.
Prop.
2 Year Storm
10 Year Storm
2 Year Storm
10 Year Storm
System
(CFS)
(CFS)
Exist.
Future
Exist.
Future
Exist. Future
Exist.
Future
0-1
60
120
114
238
215
434
- 9.2 Mi
8.0
23.7 Ma
0-2
30
100
98
268
225
495
- 12.5 Mi
13.8
34.1 Ma
0-3
60
120
92
241
206
519
- 15.4 Mi
7.3
49.6 Ma
0-4
-
60
-
69
-
170
- -
-
8.2 Mi
S-1
260
260
96
290
272
700
- -
-
54.5 Mi
S-2
95
95
95
185
212
331
- 8.3 Nu
10.7
21.1 Mi

ALTERNATIVES
improvements
With the system
proposed with this scenario all of the
major outfall systems would be adequate
based on a 2-year design storm and
'
existing conditions. Under future
conditions systems 0-4-, S-1, and S-2 will
be adequate to handle the ,2-year storm
with only nuisance flooding. The three
existing ocean outfall systems (0-1
'
through 0-3) would experience minor
flooding primarily in the areas west of
'
Croatan Highway for durations up to 2
hours. Improvements that will address
1
the deficiencies under future conditions
will be discussed with the other
alternatives presented in this report.
As illustrated in Table 8, the 10-
year storm under existing conditions will
have the same impact on the systems as
the future conditions/2-year storm. The
future conditions/10-year storm will
jflooding
result in more areas being prone to
for longer durations.
1
The eventual community facilities
for the financing
plan scheduling and of
stormwater facilities will become a part
of the town's overall community
facilities plan. Realistic capital
budget limits and the competition for
funds among various capital facilities
must be considered as stormwater facility
recommendations are made. Stormwater
'
facilities are not currently part of the
improvements
town's capital plan.
88-19
- 65 -

L
1 ALTERNATIVES
The only projected programs
connected to stormwater already in the
capital improvements plan are
transportation improvements. Prospective
state -funded road projects would be
improvements to U.S. 158 By-pass and
Business. Such projects would include
drainage improvements. The 1987 Town of
Kill Devil Hills Land Use Plan indicated
a "dire need" for improvements to local
roads. Funding sources identified for
improvements were (1) special assessments
(2) the town's matching of street
residents' contributions of 50 percent of
the cost of paving roads, and (3) impact
fees, for which there was citizen
support. The Land Use Plan also
recommended revisions to local road
specifications for drainage.
Opportunities for funding from
sources other than the town's general
fund must be pursued if stormwater
management is to improve significantly.
The traditional source of funds for
system improvements would be Kill Devil
Hills' general fund, supported by Ad
Valorem taxes. That will remain the
appropriate funding source for partial or
total costs for some stormwater system
projects from which all town property
owners derive a benefit.
Another funding source is special
assessments, already recommended for use
88-19 - 66 -
1

IALTERNATIVES
1
1
for the town's road improvements.
Special assessments are especially useful
-for funding projects that benefit one
area with clearly -defined boundaries. An
advantage of assessments is that they can
be made against existing and new
development for funding of a single
project.
A third source of funds is facility
fees, a form of impact fees authorized
for use in Kill Devil Hills by the
General Assembly of North Carolina in
1985. Such fees are appropriate to
"place an equitable share of the cost of
providing new community service
facilities upon all new inhabitants and
upon those associated with the
development process".
C. Require Open Space The Town of Kill Devil Hills
currently has direct or implied lot
coverage limits in only three of its
zoning districts (Chapter I, D). It may
be advisable to impose lot coverage
limits in all zoning districts for
stormwater management, aesthetic,
recreational, and other purposes.
Specifying lot coverage limits in the
zoning ordinance is a direct way to
require open space.
' There must be a clear definition of
"lot coverage" and "open space" that can
be understood by developers and town
i
88-19 - 67 -
I

1
ALTERNATIVES
1
I
1 88-19
officials alike. The stormwater
management purposes of imposing the
limits should be kept in mind while
developing -the -definitions. There are
several concepts closely related to lot
coverage limits (Exhibit 4).
EXHIBIT 4
OPEN SPACE VOCABULARY
Terms associated with open space . . .
Open Space
Yard
Setback
Natural Vegetative Cover
Ground Cover
Interior Landscaping
Terms associated with lot coverage . . .
Lot Coverage
Built -upon Area
Impervious or Impermeable Surface
Other related terms .
Semi -permeable Cover
Pervious Surface
Land -disturbing Activity
Generally, lot coverage limits refer
to the developed area, covered
permanently by impervious surface, with
increased runoff compared with the runoff
from the undeveloped area. Remaining
open space generally represents pervious
surface that may have runoff amounts less
than, the same as, or greater than the
pre -development amounts. Open space
requirement recommendations from this
plan should be those that contribute most
to decreasing runoff.
- 68 -

ALTERNATIVES
Open
space requirements would apply
to new development. They could apply to
all sizes of lots within a district. The
actual percentage of required open space
could be the same for all lots within
each district or could differ according
to lot size. It is particularly
important for the town to address lots of
1
less than one acre, since lots of greater
than one acre will generally be subject
to the coastal area stormwater control
regulations.
New development in the town is
likely to consume about 1,135 acres
between the years 1988 and 2000
(Table 2) .
Of the 1,135 acres, approximately
260 acres, or 23 percent, is in about 35
lots of one acre or more. The remaining
875 vacant, developable acres are platted
into roughly 3,000 lots of less than one
acre. Some of these lots will likely be
packaged for developments of more than
one acre. Therefore, state -required
be filed
stormwater control plans will
for about 50 to 200 lots; any town open -
space requirements would be the sole open
space regulation for almost 3,000 lots.
Two alternatives for requiring open
space appear below (Table 9.)
i
u
88-19 - 69 -

IALTERNATIVES
ITABLE 9
TWO OPTIONS FOR REQUIRED OPEN SPACE,
With Resulting 2-Yr. Peak Runoff
SUMMARY
Rate
System Drainage
Outfall Peak Runoff Rate (2 Yr.) (CFS)
Area
Capacity Iusiness
Zone Limit
(Acres)
(CFS) 65%
85% 1
0-1 153.9
�60 170
226
0-2 208.9
30 196.
254
0-3 438.1
.60 257
293
S-1 720.4
2'60 260
287
S-2 139.6
95 165
236
1 The runoff rates
business zone is
indicated are those that would
built out with business uses
occur when the
exclusively.
That would result
from construction of businesses
and
conversion and redevelopment
to business uses.
That intensity
of development probably
would occur several years
after the
year 2000; it is
a higher intensity than that
represented in
previous tables.
IProposed lot coverage limits vary by
zoning
district.
The
lot coverage limit
for the
Business
zone
has been considered
at the
65 percent
and
85 percent level.
The lot
coverage
limit
for each other
zone is
the same
under
either
alternative,
as
follows
(Table 10):
- 70 -

1
IALTERNATIVES
ITABLE 10
LOT COVERAGE LIMITS
Zoning
% Impervious
District
Surface
RA-6
30
RA-5
55
'
OIR
LB-1
30
55
Business
65 or 85
LI
55
LI-2
30
G & I
551
1 Developed portion
' The lot coverage limit on the 75-
foot deep estuarine shoreline AEC is 30
percent regardless of zoning district.
Surfacing materials such as stone,
concrete pavers, compacted dirt, "semi -
porous" asphalt are included under the
' definition of impermeable surfaces.
Additional description of CAMA
regulations is in the previous Chapter
(Chapter I, D).
The alternatives were selected after
consideration of several additional
options, including different limits for
the Business and RA-6 zones. For the
'
Business zone, 100 percent lot coverage
(no limit) results were calculated. This
option was rejected because it yields
'
unacceptable peak runoff rates and
represents business development at a
'
higher lot -by -lot intensity than it is
currently occurring. Average retail lot
'
88-19
-71 -
1

vi
1 ALTERNATIVES
coverage for new development, 1988, is
roughly 85 percent.
Options initially considered in the
RA-6 zone were 20 percent and 30 percent
lot coverage. Thirty percent lot
coverage was selected. for Table 9 because
there was not a substantial difference
between peak runoff rates at the 20
percent and 30 percent level. Examples
'
of the insignificant differences in peak
runoff under the two residential lot
'
coverage limits, applied to systems 0-1,
0-2, and 0-3 appear below (Table 11).
'
TABLE _ 11
TWO OPTIONS FOR REQUIRED OPEN SPACE, RA-6 ZONE
Business Zone at 65% Limit l
' System Peak Runoff Rate (2 Yr.)
RA-6 Zone Limit
30% 20%
0-1 170 163
0-2 196 189
0-3 257 254
I
j
1
88-19
1 The business zone is assumed to be built
out with business uses exclusively as in
Table 9.
Additional calculations were made for
the system S-6 drainage area to consider a
possible range of RA-6 zone lot coverage
limits from 20% to 40%. The results of the
calculations of peak runoff rates and
required storage are as follows (Table 12):
- 72 -

ALTERNATIVES_
TABLE 12
ADDITIONAL OPTIONS FOR REQUIRED OPEN SP�CE, RA-6 ZONE
Business Zone at 65% Limit
RA-6 Zone Limit
System S-6 40% 35% 30% 25% 20%
Peak Runoff Rate
(2-Yr.), (CFS) 191 170 141 106 77
Required Storage
Volume (2-Yr.), (Ac-Ft.) 30.0 N/A 22.9 N/A 15.6
1 The business zone is assumed to be built out with business
uses exclusively as in Tables 9 and 11.
The peak flow rate and the required
storage -volume both increase as the lot
coverage limit increases. If a detention
facility were constructed to receive the
increased volume it would be more costly
than a smaller facility. In addition, the
runoff rate represented by the 40 percent
lot coverage limit would have more severe
water quality impacts than the rate at the
30 percent limit.
In the Business zone, new minimum lot
sizes, perhaps differing according to
principal use, and lot coverage limits could
be set at the same time.
The town has the authority to impose
additional regulations to assure that the
open space on each -lot will be used
optimally for stormwater management. The
group of regulations and related guidelines
suggested below represents one open space
88-19 - 73 -

IALTERNATIVES
solution. The particular figures specified
would work with the lot coverage limits
discussed above.
The first set of regulations and
guidelines would be applied to the zones
with predominantly business and industrial
uses, namely Business,.G & I, LB-1, LI, and
LI-2. In those areas, the purpose of the
regulations would be for the open area to
perform well as a vegetative filter. In
order to accomplish this, there could be a
strict requirement that at least 70 percent
of the required open space be concentrated
in one primary area. The requirement could
be in the zoning ordinance as a yard
requirement, without reference as to
placement on the -lot (no reference to rear
yard, front yard, side yard).
Further, there could be a site plan
requirement in the zoning ordinance that the
open area receive the runoff from at least
65 percent of the impervious surface on the
lot. Some flexibility in the site plan
review would be in order, especially if some
of the impervious surface runoff. could be
received in an open area on the lot other
than the "primary" yard.
Note that there would not be any limit
on land -disturbing activity. In areas of
intensive land use, regraded and revegetated
land could be designed to perform the
stormwater management function as well as or
88-19 - 74 -

IALTERNATIVES
better than natural areas; it would have to
be vegetated in order to absorb runoff
effectively for.it to be considered to be a
permeable surface by the state regulations.
The, second set of regulations and
guidelines would be applied to the two
predominantly residential zones, namely RA-6
and RA-5. The purpose of the regulations
would be to make the best use of natural
retention capabilities on each lot. The
zoning requirement would be that no more
than 60 percent of the lot's land could be
disturbed. Note that the regulations, if
coupled with a 30 percent lot coverage
limit, would allow for 30 percent of the lot
to be disturbed but not covered; that 30
percent could be graded and landscaped, etc.
The town could also issue a design
guideline recommending that the lowest area -
on the lot be the 40 percent or greater
portion left undisturbed, for maximum
retention benefit. There probably would be
legal and practical obstacles to regulating
which portion of the lot would be
undisturbed. For example, it might be
impossible on some lots to find places to
site the retention area, house, and required
yards. Still, design guidelines could.have
a significant effect even if they are not
all followed on every lot. Other design
guidelines could also be included, such as
suggestions as to how to receive runoff
control benefits from the space below the
- 75 -

I
I- ALTERNATIVES
Slowest floor of a structure in areas where
the floodway ordinance requires elevated
construction.
Similar regulations to the above do not
appear to be in order for the OIR zoning
district. Inland zoned OIR,'similar
purposes are served by existing zoning
regulations and CAMA permit regulations.
Imposition of lot coverage limits would
add to the town's administrative work. The
town would work with developers during the
site plan review process to assure
compliance with the limits as well as best
' use of the lot's open space. Additional
site design assistance might be necessary
' for town and developers; some of the
assistance could -be the state's forthcoming
planning and design manual for erosion and
sedimentation control measures and manuals
such as urban best management practices
handbooks.
' The costs of open space requirements
would be borne by the developer of a site.
However, the open space limits will be set
with consideration of removal of stormwater
by the town's stormwater system and, for
larger developments, on -site detention
systems.
D. Require Detention Possible regulations to require
detention of stormwater are considered with
regard to several issues. The amount of
88-19 - 76 -

IALTERNATIVES
rainfall used as a standard for the system
must be set. The detention can be on -site
or off -site. The ability to design an
adequate on -site system varies by lot
-size. The ability to design adequate off -
site systems varies by size and location of
land available for the systems. The
financing and scheduling of off -site systems
can be handled in several ways. The links
between requiring detention, improvements to
the town system and open space requirements
cannot be ignored.
The minimum rainfall standards set for
the infiltration control systems required by
the new state coastal area regulations are
one and one-half inches of rainfall for
development draining directly to Roanoke
Sound and Buzzard Bay and one -inch of
rainfall for all other drainage areas. It
appears that the town has the authority to
set higher standards in Kill Devil Hills.
The 2-year storm deposits 1.0 inch of rain
in the first 15 minutes and 1.5 inches of
rain in the first thirty minutes. North
Carolina statewide erosion and sediment
control performance standard requires
protection from the peak rate of runoff from
the 10-year storm.
The 2-year storm standard could be met
simply with well -maintained vegetation, with
lot coverage.and open -space regulation, in
low -density residential areas. Actually,
the above is a part of Alternative C,
- 77 -

ALTERNATIVES
IRequire
Open Space, since structurally there
is no detention facility at all. Some
residential areas could meet a higher
standard than the 2-year storm, freeing a
'
larger share of the town's total resources
to use for stormwater management in higher -
density areas. In higher -density areas,
generally control measures such as
infiltration systems, wet detention ponds,
and vegetative filters would be necessary.
Since detention would be required with
'
reference to a performance standard, such as
a 2-year storm design, the best choice of
control measure and the necessary dimensions
of those measures can only be determined on
a lot -by -lot basis. There would be a lower
limit to the lot size for which on -site
detention would be -practical.
As much on -site detention as possible
is generally preferable to off -site
detention because it keeps the
'
responsibility for the system with the
landowner, detention
private many stormwater
features increase the visual atrractiveness
of a site, and the open space can be used
for several purposes.
Where on -site detention of any
magnitude is impractical, off -site measures
must be employed. One situation calling for
off -site measures could be for infill,
small -lot, medium to high intensity
development in the northern part of town
1
88-19 - 78 -

ALTERNATIVES
where developed and undeveloped lots now
form a checkerboard pattern.
Off -site detention.for the development
pattern above could be provided in several
locations.- There are some clusters of
vacant lots within the checkerboard pattern
'
large enough to provide'a detention facility
that would serve from one to one hundred
developed lots. In most cases, though, such
clusters of lots are prime areas for new
development. The lot purchase prices would
be high. A single large location for an
off -site detention facility could be on a
large vacant area in the Government and
Institutional zone. It would be suitable
'
for such use and it is already owned by the
town.
'
The required storage volume for each
- drainage area, for future developed
1
conditions, if detention is the exclusive
control mechanism employed, appears in The
Summary of Future Runoff Conditions (Table
6). In some cases a single site might be
available to accommodate the runoff for an
entire drainage area. In other cases,
development patterns would call for several
1
sites.
The cost of required off -site detention
'
could be chargeable to each developer.
However, the town will have the option of
whether to allow for developers to install
and dedicate off -site facilities or to
88-19
- 79 -

LALTERNATIVES
require a developer to contribute to the
cost of a facility constructed by the
town. Facility fee financing seems
particularly appropriate to the funding of
' off -site detention.
Off -site detention systems to upgrade
stormwater management in already -developed
areas could be funded by the general fund or
by special assessments, depending upon who
benefits from the improvement.
E. Combination of the In this section are alternatives for
Alternatives
I
improving the' stormwater systems within the
Town of Kill Devil Hills which utilize
combinations of the options previously
addressed such as physical improvements to
the system, open space requirements as well
as on -site and/or off -site detention. Each
of the watersheds, both existing and
proposed, will be discussed in terms of the
available combinations of alternatives and
their impacts on anticipated flooding within
the area based on future conditions.
System 0-1: The total drainage area
proposed for this system is 153.9 acres
consisting of 81.3 acres in -the Business (B)
Zone, 24.6 acres in Light Industrial (LI-2),
41.0 Acres in Residential (RA-6) and 7.0
Acres in the Ocean Impact (OIR) Zone. The
existing outfall for the area is the 36-inch
pipe which discharges directly into the
ocean at the eastern end of Lake Drive.
COMM

ALTERNATIVES
iSince
53 percent of the land use within
this watershed is zoned for Business, this
area is ideally suited for implementation of
open space requirements within the zoning
ordinance. Of particular importance is the
restriction of new development in the
1
Business -zone to 65 percent impervious cover
of the developed land. As discussed in
Section III.C., this requirement will reduce
the runoff generated by a 2-year storm from
238 cfs to 170 cfs, a reduction of 40
percent.
In addition to the open space
'
requirements, the upgrading of the existing
outfall system is considered as part of this
alternative. Upgrading of the outfall
system would include the installation of a
second 36-inch ocean discharge pipe attached
to the existing trestle. This would result
I60
in an increase of the outfall capacity from
cfs to 120 cfs.
With the peak runoff reduced to 170 cfs
increased
and the outfall capacity to 120
cfs, 5.0 acre-feet of storage will be
jrequired
to prevent any flooding from
occurring within the watershed. This
storage could be provided in the form of a
1.5 to 2:0 acre detention facility. The
optimum location for such a facility will be
along the west side of Croatan Highway
between Fresh Pond Drive and Lake Drive.
it
This location .is recommended since would
allow for the collection of all runoff from
88-19
- 81 -

1
ALTERNATIVES
the watershed west of Croatan Highway with
the existing storm drainage system utilized
las
the outfall for the detention facility.
Under this scenario, the combination of
open space requirement, upgrading of the
outfall system and off -site detention for
1
the area west of the Bypass, the 2-year
storm would be adequately accommodated for
the future conditions. Implementation of
this Alternative would be accomplished by
1
revising the zoning ordinance and the
expenditures of capital funds for
acquisition of a site and construction of
the detention facility, as well as upgrading
the outfall system. The cost of installing
any additional facilities within the
watershed to collect runoff and transport it
to the outfall would.be borne by the
developments within the area.
The highest single cost factor in this
scenario would be the acquisition of a
suitable site for locating the detention
intended
facility. To provide the benefit
for this facility, the location should be
idirectly
adjacent to Croatan Highway.
Naturally this is prime development land and
the cost of acquisition will reflect the
loss of this use.
'
If, for reasons of cost, the
construction of this detention facility is
not -included with this Alternative, it would
result in nuisance flooding. It is
88-19
- 82 -

IALTERNATIVES
janticipated that most of the flooding would
occur in the open space areas of the
jbusiness zone and in the lower elevations of
■ the residential and light industrial areas
j west of the bypass.
Another alternative for this area would
be to require on -site detention of all new
development. However, the reduction of the
peak runoff rate would not be sufficient to
eliminate the upgrading of the outfall
pipe. At best, this requirement would limit
ponding to the areas of new development
thereby reducing and possibly eliminating
the nuisance flooding which would occur
elsewhere.
The third alternative for this area is
the upgrading of the entire storm drainage
1
system along Lake Drive, including the
outfall pipe, to provide a capacity of 170
j
cfs. Due to the length of the pipeline and
minimal gradient available, this upgrade
j
would be expensive. In addition, the rapid
collection and discharge of stormwater
runoff does not provide any benefits in
jterms
of stormwater quality. Therefore,
this alternative is not considered
appropriate.
System 0-2: The total drainage area
Lproposed
for this system is 208.8 acres
consisting of 77.8 acres in the Business (B)
j
zone, 81.0_acres in the Residential (RA-6)
zone, 11.3 acres in Light Industrial (LI-2),
88-19
- 83 -
i

ALTERNATIVES
36.6 acres in Light Industrial (LI) zone and
2.1 acres in the Ocean Impact (OIR) zone.
The existing outfall for this system is the
27-inch pipe which discharges directly_.into
the ocean just south of Martin Street.
Although the Business zone only
1
comprises 40 percent of the total watershed,
the runoff generated from this area is
significant enough that implementation of
the open' space requirements will provide a
37 percent reduction in the peak flowrate.
Therefore, the first combined alternative
for this -area will include this option.
tIn
addition, since the existing outfall
is severely limited in capacity, this
alternative includes the upgrading of this
system to provide a capacity of 100 cfs.
This can be accomplished by attaching a 36-
inch pipe to the existing trestle and
upgrading the road crossings between Croatan
Highway and Virginia Dare Trail.
The result will be a peak runoff rate
of 196 cfs and an outfall capacity of 100
cfs. Approximately 8.3 acre-feet of storage
will be required to reduce the peak runoff
rate to 100 cfs. This storage can be
by the ditch
provided open systems along
Holly Street, Boundary Street and Harding
Street. Therefore, this alternative would
provide the capacity necessary to
1
accommodate the 2-year storm under future
conditions.
88-19 - 84 -
I

i
ALTERNATIVES
A second alternative for this area is
to maintain the existing outfall capacity
and provide off -site detention to reduce the
peak runoff rate to 30 cfs. This will
require a total of 15.4 acre-feet of storage
at various locations in the watershed.
Approximately 5.2 acre-feet of storage could
be provided by acquiring 2.0 acres of
property along the north side of Holly
Street just west of Croatan Highway.
Another 6.1 acre-feet could be provided on
i2.5
acres of land between Fox Street,
Croatan Highway, Harding Street and Martin
Street. To provide the remaining 4.1 acre-
feet of storage, another 1.5 to 2.0 acres of
land would be needed in the area between
iMartin
and Atlantic Streets. The total
required acreage to be acquired is 6.0 to
�
6.5 acres.of prime development land of which
the.cost.will be.excessive.
The utilization of detention in this
area to the extent discussed would provide
the necessary capacity to accommodate the
future 2-year storm. This alternative would
1
also provide additional stormwater quality
benefits by allowing sediment to be
deposited in the detention facilities prior
to the runoff being discharged into the
ocean. Although the water quality benefits.
for this alternative are greater than for
the first alternative, the initial
construction and future maintenance costs
will also be greater.
88-19
- 85 -

ALTERNATIVES
System 0-3: The total drainage area
proposed for this system is 438.0 acres
consisting of 107.7 acres in the Business
(B) zone, 14.9 acres in Light Industrial
(LI) zone, 98.9 acres in residential (RA-6),
and 216.6.acres in the Government and
Institutional (G&I)..zone. The outfall for
this area will be the 36-inch ocean
discharge pipe proposed by NCDOT. This pipe
will be constructed in the near future in
conjunction with the proposed desalination
plant.
The first alternative for this area
includes the implementation of the open
space requirements in the zoning
ordinance. However, since the Business zone
is already heavily developed and comprises
only 25 percent of the total watershed, the
reduction in peak flowrate is not
significant. In addition there is little
available land for locating a detention
facility within the Business zone.
Therefore, this alternative includes the
upgrading of the outfall system by providing
a second 36-inch ocean discharge pipe
attached to the same trestle to be built
with the initial outfall by NCDOT. This
will provide for the increase of the outfall
capacity from 60- to 120 cfs.
The upgraded outfall would be capable
of accommodating the runoff from the
Business zone with little or no flooding.
This leaves the residential and government
88-19 - 86 -

ALTERNATIVES
I
1
I
and institutional areas to be accommodated
by other means. Since the G&I zone is owned
by the town and there is little present use
of the land, this area provides an ideal
location for a detention facility. A 12.5
acre detention pond with a storage volume of
35t acre-feet could detain the entire runoff
from the residential and G&I areas. This
would.allow the downstream system to collect
and discharge the runoff from the business
area and then relieve the detention pond.
In addition to eliminating the need for
massive upgrading of the stormwater system
east of Croatan Highway, this scenario would
provide excellent stormwater quality control
benefits for the area west of Croatan
Highway.
The only other feasible alternative for
this area is the complete reconstruction of
the stormwater system to accommodate the
peak runoff under future conditions.
However, the high cost of upgrading the
system along with the lack of water quality
benefits makes this alternative a low
priority.
System 0-4: The proposed drainage area
for this system consists of 98.8 acres of
Residential (RA-6) zone and 5.0 acres of.
Business (B) zone for a total of 103.8
acres. This area has no existing defined
stormwater collection system or outfall.
Although some of the area could be directed
across Croatan Highway into System S-1, this
- 87 -

ALTERNATIVES
U
1
I
I
area would be better served by constructing
a new ocean outfall. The location of the
outfall would be dependent upon the
availability of access to the ocean with the
first choice being.at the eastern end of
Landing Drive. Another suitable location
would be First Street east of Virginia Dare
Trail. The outfall would consist of a 36-
inch pipe on piles with direct discharge
into the ocean.
The peak runoff from this area of 69
cfs could easily be accommodated by the
proposed ocean outfall. In addition to the
outfall pipe, a collection system will need
to be established to direct the runoff to
the outfall. Whenever practical, this
collection system should use open ditches to
allow for infiltration and vegetative
filtering of the runoff thereby preventing
the degradation of the water quality in this
area.
Another alternative would be to reduce
the capacity of the proposed outfall pipe
and provide a detention facility to reduce
the peak rate of runoff. However, the
savings accrued by reducing the size of the
outfall pipe are minimal in comparison to.
the cost of the detention facility.
Therefore, this alternative is not.
considered practical.
CER-r-IM

ALTERNATIVES
System S-1: The total drainage
proposed for this area is 720.0 acres
consisting of 18.2 acres in the RA-5
Residential zone, 274.4 acres in the RA-6
Residential zone, 65.0 acres in the Business
(B) zone, 53.4 acres in the Light Business
(LB-1) zone and 309.0 acres of the Wright
Memorial Park. The existing outfall for
this area is the Highway Commission ditch
which extends from Croatan Highway to Kitty
Hawk.Bay.
With the redirection of area 0-4 to the
ocean, this system is capable of
accommodating the 2-year storm under future
conditions. Although the outfall system is
satisfactory, some improvements.will be
needed in the internal systems, primarily in
the First Flight Village subdivision which
presently does not have a system to collect
the runoff and direct it into the outfall
ditch.
System S-2 and Other Areas: The
existing S-2 system presently collects the
runoff from 139.6 acres in the northern
portion of the town. There are an
additional 626.7 acres of land in the
northern half of the town which presently do
not have a stormwater system. Therefore, in
addition to investigating the available,
alternatives for the S-2 area.it is
necessary to consider this additional area
and determine the alternatives which provide
the best overall solution.
88-19 - 89 -

IALTERNATIVES
1
1
1
1
i
1
1
1
1
1
1
1
' 0a-.s
Included in the existing S-2 drainage
area is 112.9 acres of land which is zoned
for business use. All of this area is
located around_Croatan Highway eastward to
Virginia Dare Trail. All of the
residentially zoned land is located west of
Croatan Highway over to Kitty Hawk Bay.
This setup lends itself to directing the
Business area eastward to an ocean outfall
and the residential area westward to one or.
more sound outfalls. Therefore, this was
considered as the first alternative.
The business area redirected to an
ocean outfall totals 172.0 acres and is
designated as area 0-5 (Map 4). This area
generates a peak runoff rate of 212 cfs.
The optimum method of accommodating this
runoff is to provide an outfall capacity of
120 cfs and 8.0 acre-feet of storage within
the open ditch system along Raymond
Avenue. This would require that the
existing ditch be enlarged to approximately
25 feet in width which may not be practical.
Another alternative to accommodate the
Business area is to provide an outfall
capacity of 120 cfs and require all new
development to provide on -site detention to
prevent the peak runoff from exceeding
existing runoff conditions. Under this
scenario, the existing Raymond Avenue ditch
would provide sufficient storage to reduce
the peak runoff from existing development to
an acceptable discharge level.
- 90 -

IALTERNATIVES
11
1
I
It should be noted that under either of
these alternatives, some nuisance flooding
will occur throughout the watershed. Due to
the high peak runoff from this zone it is
not practical to construct a stormwater
system and ocean outfall with a capacity to
handle the 2-year storm without resulting in
some ponding.
Assuming that the Business area is
redirected to an ocean outfall, the open
ditch system along Bickett Street has excess
capacity to accommodate additional
residential areas. The first alternative
considered for this system was expanding the
drainage area to include the residential
zone from the limits of the Business zone
westward to Bayview Drive. The northern
limit was initially set at -Wilkinson Street
and the southern limit along the imaginary
extension of Dock Street. The total for
this drainage area is 231.7 acres. The peak
runoff generated by this watershed is 98
cfs. The existing outfall capacity is 95
cfs, therefore, the outfall is adequate to
accommodate this scenario. Implementation
will require the construction of primarily
open ditch systems within the residential
areas with main collectors bisecting the
area and directing the runoff to the Bickett
Street ditch.
Since the aforementioned alternative
does not utilize the available storage
within the Bickett Street ditch, the next
88-19 - 91 -
'J

j
IALTERNATIVES
alternative investigated was to expand the
drainage area to include another 61.1 acres
of the residential zone in the area bounded
by the town limit on the north, Wilkinson
Street on the south, Bath Street on the west
and the Business zone on the east. This .
area would be directed to an open ditch
system along Lee Avenue which would outfall
into the Bickett Street ditch. The total
revised drainage area is 292.8 acres
generating a peak runoff of 128 cfs. With
the existing outfall capacity maintained at
95 cfs, a storage volume of 5.3 acre-feet
would be required. This volume can be
accommodated in the existing ditch and the
proposed ditch along Lee Avenue.
By utilizing the available storage
within the open ditch systems this
alternative will provide some benefits in
terms of water quality. The open ditches
will provide temporary detention of the
runoff allowing for greater infiltration and
the deposition of sediments suspended in the
water. Therefore, this alternative is
considered as optimizing the use of the
existing sound outfall located at Bickett
Street.
With the Business zone redirected to an
ocean outfall and the residential area north
of Dock Street utilizing the Bickett Street
Outfall, there are 248.7 acres of
residential area remaining to be
accommodated. The peak runoff generated by
88-19 - 92 -

ALTERNATIVES
tthis
area is 141 cfs. Utilizing a system of
open ditches within the watershed to collect
Ithe
runoff and provide detention wherever
practical, this area can be directed to a
single outfall into Kitty Hawk Bay. The
location of the outfall would be south of
5th Street with the control being a pipe
'
under Bayview Drive. Depending upon the
available storage developed within the
watershed the outfall capacity could vary
from 15 cfs to 95 cfs. The corresponding
'
storage volumes are 12.5 and 5.0 acre-feet,
respectively.
By restricting the outfall capacity and
providing as much detention storage as
practical, the proposed stormwater system
will provide definite water quality benefits
which will prevent the continued degradation
..of Kitty Hawk Bay. The system will also
provide a positive means of transporting
runoff out of the watershed thereby
effectively eliminating the potential for
major flooding problems in the future.
Two other drainage areas should be
mentioned at this time. The first is an
area of approximately 46 acres in the
northwest corner of the town designated S-7
(Map 4). This area is prohibited by
'
physical constraints such as dunes from
being diverted anywhere -other than directly
into Kitty Hawk Bay. It is anticipated that
as this watershed develops, the.new
stormwater regulations imposed by CAMA will
adequately address this area.
88-19
- 93 -

1
i
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
ALTERNATIVES
The second area is the 101.5 acres
designated as P-1 (Map 4) adjacent to the
Fresh Pond. This area is restricted by
physical constraints from outfalling to
either the west or north. In addition, due
to the nature of the existing outfall for
area 0-1 it is impractical to direct this
area to the ocean. Therefore, it is
proposed that this area be directed to the
Fresh Pond. It is anticipated'that the
proposed zoning restrictiions for the LI-2
and RA-6 zones applicable to this area will
adequately protect the pond. Additional
measures in the form of maximizing the use
of open ditches in this area will provide
additional protection.
88-19 - 94 -

1 RECOMMENDATIONS
I
I
I
1
A. General
Recommendations
The town should adopt and implement three
kinds of general improvements that would
apply throughout the town.
First, stormwater management should
become one of the town's major categories of
capital expenditure. The Dare County
Carrying Capacity Commission reports of 1986
did not include stormwater as one of six
major categories of improvements for which
the Commission made detailed cost
projections through the year 2000. As the
town works toward determining its capital
budget priorities certain benefits of the
recommended stormwater management program
should be kept in mind.
Stormwater management will reduce
flooding and preserve water quality, will -
contribute to the solution of certain
transportation and public safety problems
and in certain cases reduce the intensity of
development of the type that would have been
particularly demanding of government
services. The costs of the program will be
shared by the town, the private sector, and
federal and state agencies.
The second recommendation is to correct
existing and prevent future erosion and
sedimentation problems that affect the
88-19 - 95 -

RECOMMENDATIONS
town's systems. Silt should be removed
wherever it currently has settled in the
town's system and ditches should be cleaned
and vegetated. The town should vegetate the
ditches and inspect them periodically.
Operational and maintenance funds would have
to be budgeted by the town for such work.
The town should vigorously enforce
those provisions of the statewide
Sedimentation Control regulations that are
the town's responsibility. For example,
developers must provide permanent
sedimentation control measures. No
permanent sedimentation control measure,
such as a vegetated ditch, should be
accepted for maintenance by the town unless
it is installed properly (N.C.A.C. Title 15,
Subchapter 4.0013).
The third recommendation is to adopt
and implement zoning ordinance requirements
for (1) lot coverage limits (2) primary
yards, (3) channeling of runoff into primary
yards, (4) land -disturbing activity
limits. All of these zoning ordinance
recommendations are described under
alternative III. c. Require Open Space. It
is recommended that the Business zone lot
coverage limits be set at 65 percent, the
more effective of two limits considered.
All of the specific lot coverage limits were
listed in III. c. (Table 10).
88-19 - 96 -

RECOMMENDATIONS
B. Specific
Improvements
88-19
The design guidelines closely related
to the zoning regulations described above
should also be implemented. A key guideline
would be to advise lot owners that the
portion of a residential lot left
undisturbed should be the area with the
lowest elevation.
Implementation of the zoning ordinance
and design guideline recommendations would
add to the town government's workload in a
review and administrative capacity.
Developers would bear the cost of designing
sites to fit the regulations. The town and
developers would experience the property tax
base and level of town services impacts of
limiting the intensity of development.
The above general improvements and all
of the specific improvements below should be
adopted.
In addition to setting limitations on
impervious cover within the.zoning
ordinance, physical improvements to the
stormwater systems are recommended. The
following is a summary of the recommended
improvements for each drainage area based on
the various alternatives discussed in
Chapter IV.
The recommendations have been further
subdivided into projects and assigned a
number for ease of description (Map 4).
- 97 -

RECOMMENDATIONS
Each project was then assessed in terms of
cost and priority of needs (Table 13). The
estimated costs are in 1988 dollars and
include -an allowance for
88-19 - 98 -

M M m wmr r � mom M r M M M M M
REOOMMENDED SYSTEM IMPROVEMENTS
Project
Drainage
Estimated
Priority
No.
Area
Description
Cost
No.
0-1
Upgrade Existing Ocean Outfall (Lake Drive)
$ 138,900
3
0-1
Construct 5.0 Ac-Ft. Detention Facility
103,000
14
/3\
0-2
Upgrade Existing Ocean Outfall (Martin Street)
107,100
1
& Upgrade Road Crossings (Memorial & Wtightville)
4
0-2
Regrading and Minor Modification of Existing
9,000
15
Ditches (Holly St., Boundary St. & Hardin St.)
5�
0-3
Upgrade New Ocean Outfall (Oregon St.)
112,500
4
0-3
Construct 35t Ac.Ft. Detention Facility
423,500
13
�7
0-4
Construct New Ocean Outfall (Landing Dr.)
115,000
6
88
0-4
Construct Internal Collection System
46,000
8
8
(Sir Walter Road)
0-5
Construct New Ocean Outfall (Bickett St.)
107,300
5
10
0-5
Widen Existing Ditch System (Raymond Ave.)
50,000
9
All
S-1
Construct Internal Collection System
110,500
10
(First Flight Village)
AS-2
Construct.Internal Collection System
35,200
7
(South of Bickett Street)
AS-2
Construct Internal Collection System
63,800
11
(North of Bickett Street)
AS-6
Construct Outfall and Northern Portion of
45,200
2
Collection System (5th Street)
AS-6
Construct Southern Portion of Collection System
43,000
12
(West 3rd Street)
Estimated costs are in 1988 Dollars and include an allowance for construction, engineering, iana ana
contingencies.

RECOMMENDATIONS
construction, engineering and
contingencies. Where applicable, land
acquisition costs have.also been included.
The priority for each project is based
on the need for improvements under existing
conditions, the lack of existing facilities
and the area being serviced. The
establishment or upgrading of outfall
systems was considered more important than
I
the establishment or upgrading of internal
collection systems. Those facilities that
are recommended to serve future developments
were considered the lowest priority since
jthe
burden of.constructing some of these
improvements may be shifted to the
'
individual developments.
System 0-1: The recommended
improvements for this drainage area include
upgrading the existing pipe system along
Lake Drive from Croatan Highway east to the
ocean. The recommended outfall capacity is
120 cfs. In addition, a detention facility
5.0+
capable of providing acre-feet of
storage should be constructed in the area
'
between Fresh Pond Drive and Lake Drive on
the west side of Croatan Highway. The total
estimated cost for these improvements is
$241,900.
System 0-2: The recommended
improvements for this drainage area include
upgrading the existing outfall to a capacity
of 100 cfs. The existing pipes under Martin
88-19 - 100 -

IRECOMMENDATIONS
Street, Wrightsville Avenue and Memorial
Avenue should also be upgraded to provide
the capacity necessary to serve their
respective sub -drainage areas. The
detention required to reduce the peak runoff
for the area west of Croatan Highway can be
provided by utilizing the existing ditch,
system along Holly Street, Boundary Street
and Harding Street with only minor regrading
and widening. The total estimated cost for
these improvements is $116,100.
System 0-3: The recommended
improvements for this drainage area include
upgrading the proposed NCDOT outfall system
along Oregon Avenue from Carolina Boulevard
to the ocean. The recommended outfall
capacity -is 120 cfs. All of the runoff from
areas west of Croatan Highway should be-
directed to a detention facility located
within the Government and Institutional ':
zone. This facility should have a storage
volume of 35+ acre-feet. The total
estimated cost for these improvements is
$536,000.
System 0-4: The recommendations.for
this drainage area consist of constructing a
new ocean outfall on piles in the vicinity
of Landing Drive. The outfall should be
designed for a capacity of 60 to 70 cfs. In
addition, a complete internal collection
system consisting primarily of open ditches
will need to be constructed due to the lack
of existing facilities in this area. The
88-19 - 101 -

IRECOMMENDATIONS
total estimated cost for these improvements
is $161,000.
System 0-5: The recommendations for
this drainage area consist of redirecting
the runoff from the Business Zone portion of
existing System S-2 to a new ocean
outfall. The physical improvements required
to accomplish this task include relaying the
48-inch pipe under Croatan Highway and
constructing an outfall system along Bickett
Street to the ocean. The outfall capacity
should be 120 cfs. In addition, the
existing ditch system along Raymond Avenue
_from Bickett Street north should be enlarged
to provide a storage volume of 8+ acre-
feet. The total estimated cost for these
improvements is $157.,300.
System S-1: The recommended
improvements for this drainage area consist
of establishing an internal collection
system for the First Flight Village
subdivision to direct the runoff to the
existing Highway Commission ditch. No
additional improvements are necessary
provided area 0-4 is redirected to an ocean
outfall as recommended. The total estimated
cost for these improvements is $110,500.
System S-2: With the business zone
redirected to a new ocean outfall (System 0-
5), it is recommended that this drainage
area be redefined to include the residential
area north and south of Bickett Street, (Map
1
88-19 - 102 -
I

1
I
RECOMMENDATIONS
4). No specific improvements to the Bickett
Street ditch and outfall pipe are
recommended other than general cleaning and
maintenance. Since the.residential areas
added to this watershed do not have.internal
collection systems, a system of ditches
should be constructed to direct the runoff
to the Bickett Street ditch.. The use of
open ditches should be utilized to the
maximum extent practical to allow for
infiltration and sediment deposition prior
to the stormwater reaching the outfall. The
total estimated cost for these improvements
is $99,000.
System S-3: No specific improvements
are required for this drainage area. The
existing system is adequate:for future
conditions.
System S-4: No specific improvements
are required for this drainage area. The
existing system is adequate for future
conditions.
System S-5: No specific improvements
are required for this drainage area. The
existing system is adequate for future
conditions.
System S-6: The recommended
improvements for this drainage area (Map 4)
consist of establishing a complete internal
collection system and the construction of a
new outfall into Kitty Hawk Bay south of 5th
Street. The stormwater collection system
88-19 - 103 -

RECOMMENDATIONS
should utilize open ditches wherever
practical to increase infiltration and
sedimentation prior to the runoff being
discharged into Kitty Hawk Bay.. The total
estimated cost for these improvements is
$88,200.
System S-7: No specific improvements
are recommended for this drainage area. It
is anticipated that as this watershed
develops, the new stormwater regulations
will adequately address the needs in this
area.
System P-1: No specific improvements
are recommended for this drainage area. It
is recommended that the use of open ditches
for infiltration and detention be emphasized
to preserve the water quality of the Fresh
Pond. It is anticipated that as this
watershed develops, the new stormwater
regulations as well as zoning ordinance
requirements will adequately address the
needs of this area.
C. Water Quality
Effects Implementation of the
recommendations outlined above, both general
and specific, will provide an ambitious,
cost-effective program to preserve the water
quality of theestuarinesystem and the
ocean. Some aspects of the program that
directly address water quality follow.
88-19 - 104 -
1

1
RECOMMENDATIONS
No stormwater runoff from any developed
area is directed to the SA waters of Roanoke
Sound.and Buzzard Bay.
Nearly all of the drainage areas
outfalling to the SC waters of Kitty Hawk
Bay would be accommodated at existing
outfall points. In every case, new
development would be subject to lot coverage
restrictions. Once the limited amount of
runoff would leave each lot, improved
functioning of existing town ditches and an
enlarged ditch system would detain water.
Infiltration and sedimentation in the
ditches would increase so that the water
that would reach the Bay would be of good
quality.
Much of the potential Business area
whose.runoff is now directed to Kitty Hawk
Bay would have its runoff redirected to
ocean outfalls.
Wastewater effluent from the imperfect
septic systems of current and future
development will cause most of the future
pollution of Kitty Hawk Bay. It is strongly
recommended that the town continue to work
toward central wastewater treatment, but
that all large -lot zoning and prospective
lot coverage limits remain in place when
central wastewater treatment becomes
operational.
The proposed program will not degrade
the oceanside waters, classifed as SB. The
88-19 - 105 -

IRECOMMENDATIONS
program calls for increased detention in
every ocean drainage area, lot coverage
limits,,and both expanded.and new outfalls.
D. Design Criteria The following stormwater drainage
design and construction criteria are
recommended to be continued to be used on
all future drainage systems within the
town. These criteria are basically the same
as presented in the 1983 Storm Water
Management Plan with minor proposed
amendments as highlighted in boldface.
1.
The developer shall provide a drainage system for
the proper drainage of all surface water using the
approved design criteria as stated in the following
paragraphs below. The design of such a system
shall be subject to the approval of the town
pursuant to these guidelines and to the North
Carolina Department of Transportation when the
proposed drainage system affects drainage coming
from or going into the State's Right -of -Way.
2.
All surface water drainage into the site being
developed, or generated on said site must be
provided for in accordance with these guidelines.
All surface water drainage leaving the site shall
be channelled to points of approved discharge, such
as a natural or manmade watercourse, a lake, pond,
ditch or storm drainage system.
3.
No surface water shall be channelled or directed
into a sanitary sewer or septic tank system.
Distances between open ditches and septic tank
systems must be specified on the plans and approved
by the Dare County Sanitarian. This .approval must
be obtained by the developer prior to final
approval of the drainage system by the Town of Kill
Devil Hills.
4.
The developer shall use retention, detention, and
infiltration techniques to reduce the runoff from
his site.
88-19
- 106 -

RECOMMENDATIONS
5. The drainage design criteria for open and closed
drainage systems shall generally conform to these
guidelin.e.s and Handbook of Design for Highway
Surface Drainage Structures prepared by the North
Carolina Department of Transportation, the.A.S.C.E.
Manual of Engineering Practice No. 37, and Urban
Hydrology for Small Watersheds (T.R. No. 55)
prepared by the Soil Conservation Service.
6. Development plans shall show size, -slope, invert
and rim elevations, and ditch cross sections in the
vicinity of the development and as is necessary to
properly evaluate the existing and proposed surface
Water drainage system.
7. Drainage calculations, drainage area maps, flood
routing calculations, infiltration calculations,
storm sewer back water curve calculations, etc.
shall be submitted to the town upon request.
8. Estimated runoff calculations may be computed by
the Rational Method (Q-CIA), the SCS method in-TR
No. 55, or other approved methodologies. Sizing of
structures will be based on the Manning Equation.
Culverts shall be evaluated for inlet and outlet
control as necessary.
9. Systems shall generally be designed for a 2 year
storm frequency. There may be some situations
which may warrant a different requirement due to
the size of the system. The design engineer is
encouraged to contact the town engineering in the
�. preliminary design stages to determine if a change
is warranted.
10. A modified Rational Method hydrograph procedure may
be used in sizing retention and detention systems
for sites up to l.acre in size. For sites greater
than 1 acre, a runoff hydrograph shall be computed
using the tabular method in SCS TR-55.
ll. All underground storm sewers, open drainage ways,
and related structures shall be constructed to the.
applicable provisions of Roadway Standard Drawings
and Standard Specifications for Road and Structures
produced by the North Carolina Department of
Transportation.
88-19
- 107 -
I

RECOMMENDATIONS
12. During the construction, preparation, arrangement
and installation of improvements and facilities in
developments, the developer shall maintain each
stream, creek, ditch, or channel contiguous to or
located within the subdivision in an unobstructed
state and shall remove from such watercourses and
the banks of the watercourses all debris, logs,
timber, junk and other accumulations that would, in
time of flood, clog or dam the passage of waters in
their downstream course. Installation of
appropriately sized conduit, culverts, bridges or
other required structures shall not be constructed
in a way which will obstruct the flow of drainage.
88-19
- 108 -