Problem Drainage Area Evaluation-2000

1
TVt/N
Town of Kitty Hawk
Problem Drainage Area Evaluation
Submitted by
URS
5606B Virginia Beach Blvd
Virginia Beach, VA 23462
[phone]

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•
September 22, 2000
Town of Kitty Hawk
Mr. Timothy W. Owens
Assistant Town Manager
101 Veterans Memorial Drive
Post Office Box 549
Kitty Hawk, North Carolina 27949
Dear Mr. Owens:
As agreed to per your telephone conversation with James,Peaco on September, 12, 2000,
URS Corporation (URS) is pleased to submit six (6) final copies of the enclosed Problem
Drainage Area Evaluation. As you will see, the.evaluation includes recommendations
and cost estimates for drainage improvements, at,nine sites, including the Austin
Cemetery Road Area.
URS appreciates being given the opportunity to assist the Town in meeting its stormwater
management needs. Please call Bud Curtis at [phone] or James Peaco at (757)
321-1255 if you have any questions.
Sincerel
LWC.jmj
Enclosure
URS Corporation
Executive Cove Center
5606B Virginia Beach Boulevard
Virginia Beach, VA 23462-5631
Tel: [phone]
Fax: [phone]

FUNDING CREDIT
•
The preparation of this document 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 Resources Management, National Oceanic and
Atmospheric Administration.
•

TOWN OF KITTY HAWK
PROBLEM DRAINAGE AREA EVALUATION
EXECUTIVE SUMMARY
LO INTRODUCTION
The Town of Kitty Hawk (Town) is located in the Tidewater region of the coastal
plain in northeastern North Carolina. The Town was incorporated in 1981 and is
located in Dare County. The Town contains approximately 8.2 square miles of land
area and is bordered by the towns of Southern Shores and Kill Devil Hills.
Surrounding surface waters include the Atlantic Ocean, Currituck Sound, and Kitty
Hawk Bay.
Currently, the Town experiences nuisance flooding in some areas 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 greater intensity occurring on the average of once every five to ten
years. Major flooding regularly occurs during northeasters and hurricanes
The Town contracted URS Corporation (URS) to evaluate areas identified by the
Assistant Town Manager that experience stormwater-related problems such as street
flooding, ponding of runoff, and ocean overwash. This report contains descriptions
of the problem areas and provides conceptual recommended design alternatives with
cost estimates for alleviating site -specific drainage problems.
2.0IDENTIFICATION AND EVALUATION OF PROBLEM DRAINAGE
AREAS
Areas in the Town identified as experiencing recurring drainage problems are shown
in Figure 1. The individual areas and the associated drainage problems are listed as
follows:
(1) Kitty Hawk Estates — Poor drainage and standing water.
(2) Ponding of Runoff at the Byrd Avenue/Lindbergh Avenue intersection.
(3) Ponding of ocean overwash between U.S. 158 and N.C. 12.
(4) Ponding of street runoff on Ascension Drive and Tateway Road near U.S.
158.
(5) Lot flooding on Lightkeepers Way due to street runoff from Beacon Drive.
(6) Flooding on U.S. 158 at Beacon Drive.
(7) Kitty Hawk Village — Roadway flooding and blockage of emergency vehicle
access during coastal storms.
(8) Poor street drainage on Kitty Hawk Road near Austin Cemetery.
(9) Kitty Hawk Landing — Poor street drainage on Ivy Lane.

• 3.0 PRIORITIZED RECOMMENDATIONS
Based on a review of the identified problem drainage areas in Kitty Hawk, URS has
developed a priority ranking for the implementation of the proposed drainage
improvements. Protection of public health and safety and conformance with North
Carolina stormwater management regulations were the primary considerations in the
ranking analysis. As shown in Table I on the following page, the Beacon Drive/U.S.
158 intersection was ranked No. 1 by URS. As shown in Photograph 3, a significant
potential for accidents exists at this location during routine storm events due to
inundation of the road surface and the moderately high speed limit.
The areas of ocean overwash between U.S. 158 and N.C. 12 were ranked No. 2 by
URS. Although a significant public health and safety concern, the ocean overwash
events occur only during moderate to severe storm events and the potential for
repetitive automobile accidents is much lower than the Beacon Drive/U.S. 158
intersection.
Ascension Drive/Tateway Road and Light Keepers Way were ranked Nos. 3 and 4,
respectively, due to the potential for repetitive problems during routine to moderate
storms and the potential for damage to private property. Kitty Hawk Estates was
ranked No. 5 due to its significant drainage problem but moderately low potential for
detriment to public safety or private property.
• Kitty Hawk Village was ranked No. 6 because its location in an area of low-lying
topography precludes a cost-effective method for significantly minimizing repetitive
flooding; however, the poor existing condition of culverts should be addressed.
n
U
Byrd Street, Kitty Hawk Road near Austin Cemetery, and Kitty Hawk Landing are
ranked Nos. 7 through 9, respectively, due to their location in residential areas with
low speed limits and a low potential for detriment to public safety or private property.
it

•
•
Table I
Prioritized'Recommendations
Rank
Site Number and ID
Recommended
Estimated Cost
Alternative
1
Site 6 — Flooding at
Swale
$1,507,000
intersection of Beacon
improvements and
Drive and U.S. 158
pump station.
2
Site 3 — Ponding of
Sump boxes and
$280,500
ocean overwash
pipe stands for
between U.S. 158 and
connecting portable
N.C. 12
pumps.
3
Site 4 — Ponding of
Construction of
$7,900
street runoff on
roadside infiltration
Ascension Drive and
swales.
Tateway Road
4
Site 5 — Lot flooding at
Construction of
$1,000
105 Light Keepers Way
roadside infiltration
due to street runoff.
swales.
5
Site 1 —Poor drainage
Culvert
$33,500
and standing water in
replacement and
Kitty Hawk Estates
improvement.
6
Site 7 — Roadway
Culvert
$62,500
flooding in Kitty Hawk
replacement and
Village
improvement.
7
Site 2 — Ponding of
Removal of
<$200
runoff at the Byrd
existing berm and
Street/Lindbergh
utilization of
Avenue intersection.
existing swale.
8
Site 8 — Poor street
Construction of
$5,300
drainage on Kitty
roadside infiltration
Hawk Road near
swales.
Austin Cemetery.
9
Site 9 — Poor street
Construction of
$2,600
drainage on Ivy Lane in
roadside retention
Kitty Hawk Landing.
swales.
0
TOTAL COST: $1,900,500

• 3.1 Cost Considerations
As can be seen below Table I, the total cost of the recommended drainage
improvements is $1,900,500. Typically, the alternatives recommended in Table I
have the lowest associated costs. The recommended alternative for the Beacon
Drive/U.S. 158 intersection does not have the lowest associated cost. A
discussion of this location is provided as follows.
Beacon Drive/U.S. 158 Intersection
As discussed in Sections 2.2.1.1 through 2.2.1.3 of the report, the drainage
alternatives and associated costs for this location include:
• Swale improvements and pump station $1,507,000
• Swale improvements and infiltration basin $1,512,000
• Swale improvements alone $33,700
The infiltration basin alternative was not recommended due to the high cost and
safety considerations associated with a relatively deep (4 feet) basin in an area
prone to public access.
Although the least expensive alternative, swale improvements alone provide
• roadway protection for only routine storms and do not meet the NCDOT 50-yr
storm design criteria for primary roads. Following moderate to severe storms, the
roadway would still be subject to inundation and no method currently exists to
remove standing water at this location. In addition, the proposed expansion of
U.S. 158 to six lanes would further limit space availability for swale
improvements in the future.
•
The swale improvement and pump station alternative was recommended because
it provides the highest level of roadway and water quality protection. During
and/or following moderate to severe storms, the pump station can be utilized to
remove standing water from the roadway surface. For routine storms, the
recommended use of overflow -type inlet structures in the swales will allow most
or all of the runoff to be retained and infiltrated.
Additionally, if desired, the design and construction of the pump station and
HDPE force main can be performed in conjunction with the highway widening
project. If space limitations associated with the widening project prevent the
construction of swales, a curb and gutter system can be utilized in this area to
convey runoff to the pump station.
IV

TOWN OF KITTY HAWK
PROBLEM DRAINAGE AREA EVALUATION
1.0 INTRODUCTION................................................................................................................... 1
2.0 IDENTIFICATION AND EVALUATION OF PROBLEM DRAINAGE AREAS ..................... 1
2.1 Kitty Hawk Estates........................................................................................................ 2
2.1.1 Recommendations....................................................................................... 3
2.2 Intersection of U. S. 158 and Beacon Drive................................................................. 5
2.2.1 Potential Drainage Alternatives.................................................................. 6
2.2.1.1 Option 1-Piped Ocean Outfall......................................................... 6
2.2.1.2 Option 2-Constructed Infiltration Basin ........................................ 11
2.2.1.3 Option 3-Infiltration Swales and Culvert Improvements .............. 14
2.3 Areas Between U. S. 158 and N. C. 12....................................................................... 15
2.3.1 Intersection of Lindbergh Avenue and Byrd Street ................................... 15
2.3.1.1 Potential Drainage Alternatives.................................................... 17
2.3.1.2 Option 1-Regraded (Crowned) Road Surface and Constructed
Infiltration Swales......................................................................... 18
2.3.1.3 Option 2-Taffic-Rated Trench Drains and Constructed Infiltration
Swales........................................................................................... 19
2.3.1.4 Option 3-Constructed Infiltration Basin and Piped Collection System
(Location A).................................................................................. 21
2.3.1.5 Option 4-Constructed Infiltration Basin and Piped Collection System
(Location B).................................................................................. 22
2.3.1.6 Option 5-Berm Removal and Utilization of West Parking Area
Swale............................................................................................ 23
2.3.2 Sea Dunes Condominium Complex.......................................................... 24
2.3.2.1 Jointly Maintained Infiltration Basin ............................................ 25
2.3.3 Areas of Ocean Overwash......................................................................... 26
2.3.3.1 Potential Drainage Alternatives.................................................... 27
2.3.3.2 Piped Collection System and Gravity Ocean Outfall.................... 28
2.3.3.3 Piped Collection System With Pumping Station and Ocean
Outfall.......................................................................................... 28
2.3.3.4 Sump Boxes and Portable Pumps ................................................. 28
2.4 Kitty Hawk Village..................................................................................................... 31
2.4.1 Recommendations.....................................................................................33
2.4.2 Cost Estimates........................................................................................... 34
2.5 Austin Cemetery Road Area....................................................................................... 34
2.5.1 Recommendations.....................................................................................35
2.5.2 Cost Estimates........................................................................................... 36
2.6 Kitty Hawk Landing................................................................................................... 36
2.6.1 Recommendations.....................................................................................37
2.6.2 Cost Estimates........................................................................................... 38

• 2.7 Tateway Road and Ascension Drive........................................................................... 38
2.7.1 Recommendations.....................................................................................40
2.7.2 Cost Estimates........................................................................................... 40
2.8 Light Keepers Way..................................................................................................... 41
2.8.1 Recommendations.....................................................................................42
2.8.2 Cost Estimates........................................................................................... 43
3.0 PRIORITIZED RECOMMENDATIONS............................................................................. 43
3.1 Cost Considerations.................................................................................................... 45
•
•

•
Figure
FIGURES
Follows
1
Problem Drainage Areas
Page 1
2
Kitty Hawk Estates
Page 2
3
Proposed Pond Outlet Structure and Drainage Culvert
Page 4
4
Beacon Drive-U.S. 158 Intersection
Page 6
5
Beacon Drive Drainage (Option 1)
Page 8
6
Beacon Drive Drainage (Option 2)
Page 12
7
Byrd Avenue Drainage (Option 1)
Page 18
8
Byrd Avenue Drainage (Option 2)
Page 19
9
Byrd Avenue Drainage (Option 3)
Page 21
10
Byrd Avenue Drainage (Option 4)
Page 22
11
Type I Sump Box
Page 28
12
Type H Sump Box
Page 28
13
Proposed Sump Box Locations
Page 29
14
Proposed Sump Box Locations
Page 29
15
Proposed Sump Box Locations
Page 29
16
Austin Cemetery Road Area
Page 35
• 17
Kitty Hawk Landing
Page 38
18
Tateway Road and Ascension Drive
Page 40
19
Light Keepers Way
Page 43

r 1
L_J
Table
TABLES
Page
2.1
Cost Estimates for Kitty Hawk Estates
4
2.2
Cost Estimates for Beacon Drive/U.S. 158 (Option 1)
11
2.3
Cost Estimates for Beacon Drive/U.S. 158 (Option 2)
14
2.4
Cost Estimates for Beacon Drive/U.S. 158 (Option 3)
15
2.5
Cost Estimates for Byrd Street (Option 1)
19
2.6
Cost Estimates for Byrd Street (Option 2)
20
2.7
Cost Estimates for Byrd Street (Option 3)
22
2.8
Cost Estimates for Byrd Street (Option 4)
23
2.9
Cost Estimates for Areas of Ocean Overwash
31
2.10
List of Culverts in Kitty Hawk Village Study Area
32
2.11
Cost Estimates for Kitty Hawk Village
34
2.12
Cost Estimates for Austin Cemetery Road Area
36
2.13
Cost Estimates for Kitty Hawk Landing
38
2.14
Cost Estimates for Tateway Road and Ascension Drive
41
2.15
Cost Estimates for Light Keepers Way
43
3.1
Prioritized Recommendations
44

171
TOWN OF KITTY HAWK
PROBLEM DRAINAGE AREA EVALUATION
1.0 INTRODUCTION
The Town of Kitty Hawk (Town) is located in the Tidewater region of the coastal
plain in northeastern North Carolina. The Town was incorporated in 1981 and is
located in Dare County. The Town contains approximately 8.2 square miles of land
area and is bordered by the towns of Southern Shores and Kill Devil Hills.
Surrounding surface waters include the Atlantic Ocean, Currituck Sound, and Kitty
Hawk Bay.
Currently, the Town experiences nuisance flooding in some areas 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 greater intensity occurring on the average of once every five to ten
years. Major flooding regularly occurs during northeasters and hurricanes
The Town contracted URS Corporation (URS) to evaluate areas identified by the
Assistant Town Manager that experience stormwater-related problems such as street
flooding, ponding of runoff, and ocean overwash. This report contains descriptions
• of the problem areas and provides conceptual recommended design alternatives with
cost estimates for alleviating site -specific drainage problems.
2.0IDENTIFICATION AND EVALUATION OF PROBLEM DRAINAGE
AREAS
Areas in the Town identified as experiencing recurring drainage problems are shown
in Figure 1. The individual areas and the associated drainage problems are listed as
follows:
(1) Kitty Hawk Estates — Poor drainage and standing water.
(2) Ponding of Runoff at the Byrd Avenue/Lindbergh Avenue intersection.
(3) Ponding of ocean overwash between U.S. 158 and N.C. 12.
(4) Ponding of street runoff on Ascension Drive and Tateway Road near U.S.
158.
(5) Lot flooding on Lightkeepers Way due to street runoff from Beacon Drive.
(6) Flooding on U.S. 158 at Beacon Drive.
(7) Kitty Hawk Village — Roadway flooding and blockage of emergency vehicle
access during coastal storms.
(8) Poor street drainage on Kitty Hawk Road near Austin Cemetery.
(9) Kitty Hawk Landing — Poor street drainage on Ivy Lane.
• Evaluations, cost estimates, and recommended alternatives for the individual problem
areas are provided in the following sections.

PROBLEM DRAINAGE AREAS
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KITTY HAWK r;
ESTATES_ ll
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KITTY HAWK
LANDING
THE INFORMA TION SHO WN IN THIS
FIGURE WAS REFORMATTED BY UR S
GREINER WOOD WARD CL YDE FROM
Y MAPPING PR 0 VIDED BY OTHERS IN
04
lt-
THE KITTY HA WK LAND USE PLAN.
a
CULVERT (TYP)
KITTY HAWK
VILLAGE
GRAPHIC SCALE
1000' 0 1000'
1 " = 1000'
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77
OKITTY HAWK ESTATES —POOR DRAINAGE AND
STANDING WATER
OPONDING OF RUNOFF AT THE BYRD AVE/LINDBERGH
AVE INTERSECTION
OPONDING OF OCEAN OVERWASH BETWEEN U.S. 158
AND N.C. 12
OPONDING OF STREET RUNOFF ON ASCENSION DRIVE
AND TATEWAY ROAD NEAR U.S. 158
OLOT FLOODING ON LIGHT KEEPERS SPAY DUE TO
STREET RUNOFF FROM BEACON DRIVE
O6 FLOODING ON U.S. 158 AT BEACON DRIVE
OKITTY HAWK VILLAGE — ROADWAY FLOODING AND
BLOCKAGE OF EMERGENCY VEHICLE ACCESS
DURING COASTAL STORMS
D 3OPOOR STREET DRAINAGE ON WEST KITTY HAWK
ROAD AT AUSTIN CEMETERY
OKITTY HANK LANDING —POOR STREET DRAINAGE
9 AND STANDING WATER ON IVY LANE
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5
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3
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THE PREPARATION OF THIS FIGURE 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 RESOURCES MANAGEMENT,
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION.
TOWN OF KITTY HAWK
DARE COUNTY, NORTH CAROL[NA
KITTY HAWK STORMWATER MANAGEMENT PLAN
PROBLEM DRAINAGE AREAS
FIGURE 1
URS Greiner 5606E VIRGINIA BEACH BOULEVARD
Wood ward — CI yd e VIRGINIA BEACH, VIRGINIA 23462

•
•
2.1 Kitty Hawk Estates
As can be seen in Figure 1, the Kitty Hawk Estates subdivision is located in
northern Kitty Hawk adjacent to U.S. 158. A visual inspection of the subdivision
performed by URS Corporation indicated that the existing drainage system for
Kitty Hawk Estates includes lot -line grassed swales, driveway culverts, and
residential lakes. The grassed swales along Windsor Place, Sycamore Lane,
Poplar Court, Locust Court, and the east side of Birch Lane appeared to have been
designed to collect and discharge street and yard runoff to two lakes generally
bounded by Birch Lane, Treasure Street and Windsor Place (see Figure 2). Lot -
line grassed swales along the west side of Birch Lane appeared to convey runoff
to the southwest side of the intersection of Birch Lane and Treasure Street, where
the runoff tended to pool. Two additional lakes, located west of Birch Street,
were located in a wooded section of Kitty Hawk Estates that was undeveloped at
the time of the visual inspection.
Existing drainage problems identified in Kitty Hawk Estates by URS Corportation
included standing water in lot -line swales as shown in Photograph 1 and high lake
water surface elevations as shown in Photograph 2.
The visual inspection of the subdivision revealed that the lake drainage problems
appeared to have been created by the failure of existing corrugated metal lake
inlet and outlet culverts due to a combination of corrosion and sedimentation.
With no effective drainage outlets, the water surface elevations in the two
residential lakes had apparently risen and caused water to pond in swales along
Treasure Street. In addition to the lake drainage issues, some of the driveway
culverts in Kitty Hawk Estates appeared to be plugged due to lack of maintenance
or blocked by residents.
Generally, standing water in swales was observed in all areas of Kitty Hawk
Estates except for the northeast quadrant, which was characterized by high ground
2

•
Ir I
THE PREPARATION OF IRIS FIGURE WAS FINANCED IN
PART THROUGH A GRANT PROVIDED BY IRE 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 RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
LJ
G
19
0
a
WMDSOR
SCALE. 1 =300'
U.S. 158
'9 Ir�.11Un
PROPOSED CORRUGATED
IPAi HDPE REPLACEMENT CULVERT
PROPOSED RIPRAP FO
EROSION ONTROL ( )
PROPOSED CORRUGATED
HDPE REPLACEMENT CULVERT
KRIY HAWK
WOODS
D

surface elevations relative to the rest of the subdivision, steep swale slopes and
• sandy soils. This was confirmed by a review of the Soil Survey of Dare County,
North Carolina, which was prepared by the U.S. Soil Conservation Service
(SCS). The Dare County soil survey indicates that the northeast quadrant of Kitty
Hawk Estates is characterized by Fripp fine sand, which drains readily due to high
infiltration capacity and has a seasonal minimum depth to the high groundwater
table elevation of greater than 6 feet. The northwest, southwest, and southeast
quadrants of Kitty Hawk Estates are generally characterized by Ousley fine sand,
which drains poorly when wetted due to slow infiltration capacity and has a
seasonal minimum depth to the high groundwater elevation of 1.5 to 3 feet. It
should be noted that the current Dare County soil survey was prepared from aerial
photography completed in 1982. At that time, Kitty Hawk Estates had not been
developed; therefore, the drainage capacity of the subdivision soils has likely been
reduced by the subsequent placement of imported fill material during the
construction of house foundations and streets.
2.1.1 Recommendations
When Kitty Hawk Estates was constructed, the two lakes within the developed
portion of the subdivision were utilized to receive street and yard drainage. Outlet
culverts for the two lakes discharged into the northern end of the current Kitty
Hawk Woods Conservation Easement, which is consistent with the original
natural drainage pattern. Kitty Hawk Woods is approximately 461 acres of
• maritime forest for which the Town owns the title to the lands and the State holds
the conservation easement. The culvert discharge points are currently located in a
privately owned tract of land on the south side of Treasure Street.
Kitty Hawk Estates is currently located in Town zoning district BR-1 (Low -
Density Beach Residential). Stormwater Best Management Practices (BMPs) in
coastal county low -density zoning districts are limited by North Carolina
regulations to predominantly vegetated conveyances and/or curb and gutter
systems which discharge to vegetated buffers. Kitty Hawk Estates meets State
low -density BMP requirements because all street and yard drainage are conveyed
by grassed swales and ultimately is discharged to the heavily wooded and
vegetated "buffer area" comprised by Kitty Hawk Woods. In addition, State low -
density BMP design criteria are exceeded in Kitty Hawk Estates because the
majority of the grassed swale drainage enters two residential lakes, which
essentially serve as wet detention ponds for stormwater discharges prior to
entering Kitty Hawk Woods.
Because of the water quality protection provided by the existing drainage system,
the following improvements are recommended for the Kitty Hawk Estates
drainage system:
(1) It is recommended that the existing lake inlet and outlet culverts be replaced
• for the two lakes in the developed area of Kitty Hawk Estates. Replacing these

culverts will reinstate positive drainage for the subdivision, lower the existing
• lake water surface elevations, and improve driving conditions in low-lying areas
of the neighborhood during storm events. By lowering the lake water surface
elevations, the adjacent swales will be able to drain more freely and the amount of
standing water will be reduced. Because of its strength and corrosion resistance,
corrugated HDPE piping is recommended for the replacement culverts. Inlet weir
structures are recommended for the culverts to minimize the introduction of
vegetation, sediment and debris. Outlet protection for erosion control should be
provided by the placement of rip -rap at the culvert discharge points. Proposed
outlet culvert replacement locations are shown in Figure 2 and a conceptual cross
section for the culvert and weir structures is shown in Figure 3.
(2) It is recommended that existing street and driveway culverts should be cleaned
and/or replaced as necessary. New culverts should be installed for all driveway
entrances that do not have existing culverts and block the swale drainage system.
New culverts and replacement culverts should be constructed of corrugated HDPE
and have a minimum diameter of 15 inches. Metal culverts should not be used.
(3) Following the restoration of the lake outlet culverts, regrading of the existing
swale system should be accomplished, as required, to provide positive drainage
for all lot -line swales. In the absence of current survey mapping, the extent or
cost of potential swale regrading requirements cannot be accurately estimated at
this time.
• Cost Estimates
•
Costs for the replacement of the existing lake drainage culverts are provided as
follows in Table 2.1. Costs for cleaning and repairing driveway/street culverts
and regrading lot -line swales are considered maintenance items and cannot be
accurately estimated at this time
Table 2.1
Cost Estimates for Drainage Improvements
Katy Hawk Estates, ,.
Unit Amount Cost
Total
Weir Inlet Structures
ea.
4 $2,500
$10,000
Headwalls
ea.
4 $1,900
$7,600
Corrugated HDPE (24-inch)
l.f.
200 $10.50
$2,100
Pavement Removal
S.Y.
54 $7.30
$400
Pavement Replacement
S.Y.
54 $35.00
$1,900
Trenching
C.Y.
108 $10.00
$1,100
Backfill/Compaction
C.Y.
90 $40.00
$3,600
Rip Rap
c.y.
40 $30.00
$1,200
Subtotal
$27,900
20% Contingency
$5,600
Total
$33,500
4

•
• 8
FRP GRATING
5'-0"
MOUNTED ON
EXTERIOR OF 2'xl'
S-8"
ROAD SURFACE
SIDE OPENING
8„
2 —0'
(TYP)
2'-0„
2'-0"
POND OVERFLOW
W.S.E. e
=
CORRUGATED HPDE
2'-6"
TRANSITION FITTING
FERNCO COUPLING
NORMAL POND
sz
W.S.E.
2'-0"
HEADWALL
SS PIPE CLAMPS
H-25 TRAFFIC RATED CORRUGATED HDPE
MOLDED HOPE
SELECTED BACKFILL
FLOW---
STUB END
RIP RAP
MOLDED HDPE
DISCHARGE TO
(T�) -�
STUB FND L �T 11 II
II
II
UPPER KITTY
HAWK WOODS
SELECTED BACKFILL
RIP RAP
; (TYP)
CONCRETE PIPE
CORRUGATED HPDE
HDPE SPOOL PIECE
e
SUPPORT
TRANSITION FITTING
CONCRETE PIPE
\�FERNCO
COUPLING
SUPPORT
DPE SPOOL PIECE
SCALE: 1 "=50'
THE PREPAAATON OF THIS FIGURE WAS FINANCED IN
TOWN OF KITTY HAWK
n
r
CAROLNA'COASTAL MANAGEMENT PROGRAM. IHRRO GII
DARE COUNTY, NORTH C.AROLINA
IOITTHAyM glpgMp,KiER MAN 'X'TPI„1N
pROP05®PoND OVRGf SDtUCI11RE AND DRAINAGE CUINE
�O FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1972. AS AMENDED, MICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
FIGURES
6 MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
i2
ADMINISTRATION.
�x,
0� a
W

• 2.2 Intersection of U.S. 158 and Beacon Drive
As can be seen in Figure 1, the intersection of U.S. 158 and Beacon Drive is
located in the southeast portion of Kitty Hawk. A more detailed view of the study
area is provided in Figure 4, The mapping shown in Figure 4 was generated by
URS Corporation using digital base mapping provided by the Town and
topographic mapping of the beach area, provided by the U.S. Army Corps of
Engineers (COE), from a 1996 Dare County Feasibility Study For Shore
Protection. As can be seen in Figure 4, the boundary of the topographic beach
mapping provide by the COE is the southwest edge of U.S. 158. Current
topographic mapping for areas in Kitty Hawk located southwest of U.S. 158 was
not in existence at the time of this evaluation.
•
Existing drainage problems observed by URS Corporation include localized
ponding and inundation of the U.S. 158 road surface during a moderate (1.3-inch)
rainfall event on April 15, 2000. As shown in Photograph 3, runoff from Beacon
Drive and the south -bound lanes of U.S. 158 tends to pond on the shoulder near
the Beacon Drive intersection. Town administrators indicated that several
accidents have occurred at this location due to automobiles hydroplaning at
approximately 50 miles per hour on the standing water. Additionally, U.S. 158 is
a designated hurricane evacuation route and the potential for restricted travel
capability due to roadway inundation is a critical safety issue for the Outer Banks
as a whole.
A visual inspection performed by URS Corporation indicated that the existing
drainage system at the intersection consists of shallow grassed swales along U.S.
• 158 (see Photograph 3). Runoff discharged to these swales includes sheetflow
from the U.S. 158 road surface, piped outlet discharges from adjacent commercial
5

parking lots, and swift downhill flow from the section of Beacon Drive that
• originates in relatively high (approximately 30 ft.) dune areas.
The drainage along U.S. 158 in the area between West Kitty Hawk Road and the
first driveway crossing southeast of the Noland Corporation appeared to be poor
due to (1) the limited storage capacity of the existing swales, (2) the inability of
runoff to pass through or across the grassed road shoulder into the existing swales,
and ineffective or non-existent roadway entrance culverts. Because of these
conditions, runoff is confined to the southwest side of U.S. 158 in the general area
of the Beacon Drive intersection.
2.2.1 Potential Drainage Alternatives
Potential drainage alternatives for this location include (1) A piped ocean outfall
(2) a constructed infiltration basin, and (3) improvement of roadside swales and
culverts. Discussions of each alternative are provided in the following
paragraphs.
2.2.1.1 Option 1- Piped Ocean Outfall
A piped roadway inlet drainage system with curb -and -gutter and a gravity -flow
ocean outfall does not appear to be feasible at this location because, as can be
seen in Figure 4, the invert of a junction box outlet on the southwest side of U.S.
• 158 would have to be set at an elevation of approximately 6 feet or less.
Progressing toward the ocean, the next location where an elevation of 6 feet
occurs is the surf zone (approximately 130 feet northeast of N.C. 12). In addition
to the lack of differential elevation required for substantial gravity flow, a storm
sewer outlet in the surf zone would pose a high risk of flooding on U.S. 158 due
to backflow during a storm surge (which could potentially generate tidal
elevations of 11-16 feet during a 100-year storm event). Although "Tide -flex'""
type flexible check valves (duckbills) are frequently used for coastal outfall
applications, they typically are susceptible to damage in areas prone to severe
storm surges and wave action.
An existing 36-inch diameter gravity stormwater outfall in nearby Kill Devil Hills
(the Lake Drive outfall) is shown in Photograph 4. As can be seen in Photograph
4, the outfall invert is located in the surf zone. The Lake Drive outfall is
constructed of reinforced concrete pipe, which is mounted to wooden piles using
U-shaped metal saddles and stainless steel bolts. A town maintenance employee
from Kill Devil Hills indicated that although originally installed with a flexible
check valve when constructed, the check valve was damaged during storms and
not subsequently replaced. Currently, the Lake Drive outfall reportedly tends to
become plugged with sand following severe storm events and the concrete storm
sewer pipeline has experienced joint separation due to settlement in the dune and
beach sand.
is

•
10
N. G 12
BLACK PELICAN
RESTAURANTCZD
oD
POST
POST
OFFIC
t 1
^ 20 a
THE PRBPARATION OF THIS FIGURE WAS FINANCED IN
! PART THROUGH A GRANT PROVIDED BY THE NORTH
CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1972, AS AMENDED, WHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
0
ATLANTIC OCEAN
l
!mu
F-1W
PONDING AREA
ON U.S. 158
U.S. 158
SCALE: 1 "=200'

Photograph 4 — Lake Drive storm sewer outfall (36-inch diameter
reinforced concrete) in Kill Devil Hills.
In lieu of a gravity storm sewer outfall, a stormwater pump station and ocean
outfall force main that would include approximately 1,000 feet of high density
polyethylene (HDPE) piping could be constructed to the beach on the northeast
side of N.C. 12. Due to the lack of space availability on the southwest side of U.S.
158 , the proposed pump station location is on the northeast side of U.S. 158 in
• an open area that is currently part of U.S. Post Office property.
To convey roadway runoff to the proposed stormwater pump station, swale
improvements and collector inlets will be required on the southwest side of U.S.
158 between West Kitty Hawk Road and the first driveway entrance southeast of
the Noland Corporation property. By widening and deepening the existing
swales, the runoff storage volume of the existing swales can be significantly
increased. By utilizing an overflow -type weir configuration and filter screens for
the drainage system inlet structures, the increased storage capacity of the swales
can be utilized to retain and infiltrate the runoff from light to moderate storm
events without activation of the stormwater pumps. Infiltration in the swales is
feasible at this location because of the high permeability (> 20 inches per hour) of
the Newhan sands present and the associated minimum seasonal depth to the high
ground water table of greater than 6 feet (as listed in the SCS Dare County Soil
Survey). For intense storm events during which runoff enters the pump station
sump pit, the pumps will cycle on -and -off based on level controllers.
Preliminary Design Criteria
The preliminary design criteria utilized for developing cost estimates for Option I
are listed as follows:
0

• The estimated impervious asphalt surface area contributing runoff to the
• site is 5 acres. This estimate conservatively includes impervious surfaces
on the Noland Corporation facility, which currently utilizes an on -site
infiltration basin to retain runoff. The runoff generated by Newhan sand in
elevated dune areas southwest of U.S. 158 and is considered minimal.
• Using the Rational Method with a 50-year design storm (to meet North
Carolina primary road drainage standards) and a minimum time of
concentration (Tc) of 10 minutes, the associated design storm intensity is
7.0 inches/hour (as derived from the Hatteras rainfall intensity duration
curve in the North Carolina Erosion and Sediment Control Design
Manual). Using an intensity of 7.0 in./hr, a runoff factor (C) of 0.95 for
asphalt, and a contributing watershed of 5 acres yields a peak runoff rate
of 33.3 cubic feet per second (cfs). This is equivalent to 14,920 gallons
per minute (gpm) or 21.4 million gallons per day (mgd).
• Approximately 1,175 feet of swale improvements are possible between
West Kitty Hawk Road and the first driveway entrance southeast of the
Noland Corporation. The conceptual Swale design is V-shaped (due to the
sandy soils) with a top width of 18 feet, a depth of 3 feet, and a cross -
sectional area of 27 square feet (ft). The control elevation for the
drainage system inlet screens relative to the swale bottom is 2 feet, which
provides 21,255 cubic feet (ft) of storage volume in the swales prior to
runoff entering the stormwater pump station. Note: 21,255 ft3 of storage
volume in the infiltration swales is equivalent to the runoff volume
• generated by 1.2 inches of rainfall on the five estimated acres of
impervious surface in the study area. 1.2 inches exceeds State BMP
design criteria requirements for coastal county infiltration devices, which
must have sufficient volume to retain the first (1) inch of rainfall.
• Two 11-mgd stormwater pumps (vertical turbine or submersible) are
proposed in a lead/lag configuration. Using a peak design flow of 22-mgd
and a design velocity of 10 feet per second (fps) in the force main, a pipe
diameter of 24 inches (2 feet) is required for the outfall pipe.
A conceptual plan view of the stormwater pump station system layout, along with
section views of the proposed overflow -type inlet structures, are shown in Figure
5. Potential benefits and drawbacks of the ocean outfall force main alternative are
listed as follows:
Benefits
• Flooding problems on U.S. 158 at this location can be minimized
during routine to moderate storm events, which will substantially
improve driver safety and reduce accidents caused by hydroplaning.
Boring and jacking with a concrete carrier pipe or horizontal directional
drilling (HDD) with an SDR 11 wall thickness can potentially be used
• to route the HDPE pump station inlet and discharge pipes under U.S.

•
•
b
f
FORCE MAIN_
—IJ•
ILI
I
CJ EXISTING SE I
Q DRAIN FIELD
� 1
SEA DUNES
CONDOMINIUM
POSTorric
0
PROPOSED PAR 0 A
PROPOSED MW R
PUMP STAT11
LtDJ t
t
U.S. ISB PROPOSED HPDE GRAVITY
COLLECTION SY
p ROPO D SWA
2 Q MPROV EN P
1 NOUN
I� � CORP.
�O
HE PREPARATION OF THIS FIGURE WAS FINANCED IN SCALE: 1 "=200'
" PART THROUGH A GRANT PROVIDED BY THE NORTH
3 CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
" FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1`072. AS AMENDED, WHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
MANAGEMENT, NATIONAL OCF"IC AND ATMOSPHERIC
ADMINISTRATION.
1
�umoblkr•
FRP GRATING
STANDARD MANHOLE COVER
MOUNTED ON
EXTERIOR OF 8'zf'
SIDE OPENING
TOP OF
�'
(TYP)
SHALE
7' -0.
S.-O.2'-0' •�
BOTTOM OF
Z'-O"
HALE
MOLDED
45'
EDPE FI777NO HOPE
STUB
END
CONCRETE INLET
NCONC
STRUCTURE
NDPE FLANOE
RETE PIPE
ADAPTER (TYP
SUPPORT
TO
FROM UPSTREAM
JUNCTION
DUCTILE COLLECTION
MANHOLE f
IRON WYE INLETS
SECTION B—B
La.
SECTION A —A
T
TOWN OF KITTY HAWK
DARE COUNTY. NORTH CAROLINA
I WEND KITTY HAWK SDORMWATER MANAGEMENT PLAN
O PROPOSE, JUNCTION BEACON BEACON DRIVE DRAINAGE (OPTION II
❑ PROPOSE, (NUT STRUCNRE
- HOPE SUC1`10H UNE _ - FIGURES

• 158 and N.C. 12 with minimal traffic disruption. In addition, boring
and jacking or horizontal directional drilling (HDD) can be used to route
the force main underneath the frontal dunes on the northeast side of N.C.
12 without damaging them. Conventional excavation can be utilized for
constructing the force main between U.S. 158 and N.C. 12. The HDPE
force main will require concrete anchor collars in areas of conventional
excavation to prevent pipe movement due to thrust and buoyancy. At the
outfall end, the HDPE force main can be mounted on pilings similar to the
Lake Drive outfall shown in Photograph 4; however, stainless steel clamps
must be provided on the pilings for thrust support and to prevent floatation
of the HDPE pipe.
Unlike a gravity storm sewer outfall, mechanical check valves can be
installed on the force main discharge header at the pump station. The
check valves will prevent potential backflow and flooding of the pump
station due to storm surge, and eliminate maintenance issues associated
with a flexible check valve located in the surf zone. By utilizing a force
main system, sand that enters the open-ended HDPE pipeline will be
flushed out during pump operating cycles due to the scouring action of the
6 fps discharge design velocity. Currently, a buried 16-inch HDPE force
main outfall is used in Kill Devil Hills for the discharge of concentrate
(brine) from the Dare County North Reverse Osmosis (RO) Water
• Treatment Plant. The RO force main flow is typically between 500 to 600
gpm (0.72 to 0.86 mgd) and no check valve is used at the discharge point.
The outfall point for the RO discharge line, located in the surf zone, is
shown in Photograph 5. The high corrosion resistance and inherent
flexibility of HDPE piping minimize the potential for storm damage to the
buried beachfront force main discharge point.
•
0

• • Because HDPE pipe sections are joined by heat -fusion, there are no joints
that can separate and allow sand or septic tank effluent to infiltrate into the
pipeline.
• The Town has indicated that the Outer Banks Chapter of the Surfrider
Foundation, a non-profit environmental organization "dedicated to the
protection of the world's oceans, waves, and beaches," is adamantly
opposed to the construction of ocean outfalls in the Outer Banks.
According to Town administrators, the Surf Rider Foundation successfully
opposed the construction of a recent North Carolina Department Of
Transportation (NCDOT) gravity storm sewer ocean outfall design to
alleviate drainage problems at this same location. The stormwater pump
station/HDPE force main proposed by URS Corporation is conceptually
designed as an intermittent discharge used to alleviate severe driving
safety hazards along U.S. 158 during moderate to severe storm events. It is
not a gravity -type concrete storm sewer that can unintentionally serve as a
conduit for continuous discharges of septic tank effluent due to joint
infiltration. As previously described, the proposed pump station alternative
exceeds North Carolina design criteria for infiltration devices by providing
sufficient storage volume to retain more than the required first (1) one inch
of rainfall. This is accomplished through the proposed use of roadside
infiltration swales and drainage system inlet elevation control. Based on
• the combination of water quality protection and critical public safety
improvements associated with this design alternative, the Surfrider
Foundation may be amenable to its acceptance.
Drawbacks
• High cost for facilities, equipment and construction easements.
• Maintenance for the pump station, swales, inlet structures, and force main
discharge point would have to be provided on an on -going basis. NCDOT
funding and participation for this effort would be expected because the
flooding issue effects U.S. 158.
• The Surfrider foundation is opposed to stormwater system ocean outfalls
in the Outer Banks.
• Space availability for the proposed swale improvements and inlet
structures may be limited by a proposed expansion of U.S. 158 to six lanes
and existing utility systems.
• Potential power outages during severe storm events would require that a
diesel generator be included as a permanent part of the pump station
design.
is

• Cost Estimates
Cost estimates for this design alternative are listed in Table 2.2.
Table 2.2
Cost Estimates for Drainage Improvements
Beacon Drive/U.S. 158—Option I
Cnit
Amount
Cost
I old
Excavation (Sw.des and Basin)
C.Y.
1,500
$2.00
$3,000
Hauling
C.Y.
1,450
$3.50
$5,100
Inlet Structures/Manholes
ea.
6
$2,100
$12,600
HDPE Piping (24-inch SDR-I1)
I.f.
2,300
$40.00
$92,000
Horizontal Directional Drilling
1. 1.
300
S400
$120,001)
Pavement Removal(Replacement
I.S.
1
$2,000
$2,000
Trenching/Dewatering
I.S.
1
$80,000
$80,000
Backfill/Compaction
C.Y.
1400
$40.00
$56,000
Rip Rap/Headwalls
I.S.
1
$16,000
$16,000
Pump Station
ea.
1
$700,000
$700,000
Property/Easement Acquistion
s.f.
37,000
$3.00
$1I1,00(I
Outfall Pile Supports
I.S.
1
$8,000
$8,000
Subtotal
$1,205,700
25% Contingency
$301,400
Total
$1,507,000
2.2.1.2 Option 2 - Constructed Infiltration Basin
• Infiltration basins are currently utilized to capture and treat stormwater discharges
from the Kitty Hawk post office parking lot (which is located on the opposite
[northeast] side of U.S. 158 from the Beacon Drive intersection) and from the
Noland Corporation building and parking lots (which are located at the
intersection of Beacon Drive and U.S. 158). Photograph 6 shows the Noland
Corporation infiltration basin during a 1.3-inch rainfall event on April 15,2000.
•
Photograph 6 — Noland Corporation infiltration basin during 1.3-
inch rain event on April 15, 2000.

The operation of infiltration devices is successful at these locations because of the
• high permeability (> 20 inches per hour) of the Newhan sands present, and the
associated minimum seasonal depth to the high ground water table of greater than
6 feet (as listed in the SCS Dare County Soil Survey).
It appears that sufficient land area may be available on the southern end of the
Post Office property to construct an infiltration basin of sufficient size to
accommodate problem runoff generated near the U.S. 158 and Beacon Drive
intersection. As previously described in Option 1, the topography of the study
area and the required surf zone discharge location are not considered suitable for a
gravity storm sewer system at this location. As such, Option 2 also requires the
construction of a stormwater pump station and HDPE force main, improvements
to the existing swales on the southwest side of U.S. 158, and the installation of
overflow -type inlet structures. A conceptual layout of the stormwater pump
station, HDPE force main, and constructed infiltration basin is shown in Figure 6.
Preliminary Design Criteria
The preliminary design criteria utilized for developing cost estimates for Option 2
are listed as follows:
• Pump station, force main, and Swale/culvert criteria are the same as in
Option 1.
• • An evaluation of aerial photography provided with the 1996 COE
shoreline protection study indicates that an area of approximately 48,750
ft2 (1.12 acres) on the existing post office property could potentially be
used as a site for a constructed infiltration basin. Assuming a basin depth
of 4 feet and a water depth of 3 feet, an infiltration device of this size
could hold approximately 146,250 ft3 of runoff with one foot of freeboard
elevation. The retention volume associated with 3 feet of water depth in
the basin is sufficient to capture 8 inches of rain from the study area
impervious surface of 5 acres. The one foot of freeboard elevation would
account for the 8 inches of rain that would fall directly on the infiltration
basin.
Potential benefits and drawbacks of Option 2 are listed as follows:
Benefits
• Flooding problems on U.S. 158 at this location can be minimized during
routine to moderate storm events, which will substantially improve driver
safety and reduce accidents caused by hydroplaning.
• Boring and jacking or HDD technology can potentially be used to route
the HDPE force main under U.S. 158 with minimal traffic disruption. A
concrete carrier pipe may be needed for structural protection of the HDPE
•
12

•
ATLANTIC OCEAN
t 1
o
N. C. 12 1
BLACK PELICAN cj
RESTAURANT a
G:3 1
0 �
1 ter
EXISTING SEP i O ❑
Q � DRAIN FIELD
t
SEA DUNES a
CONDOMINIUM
PRO OSED I FILTRATION BASIN
POST
OFFIC �
s
PROPOSED HD
STORMWATER
FORCE MAIN
PROPOSED OR TE PROP SED PA NO AREA
PUMP STATI
t
1
1
U.S. TSC PROPOSED HPDE GRAVITY
COLLECTION SY
-------------------
ROPO D SWALE
PROM MENT (TYP) NOLAN
CORP.
00
THE PREPARATION OF THIS FIGURE WAS FINANCED IN
n PART THROUGH A GRANT PROVIDED BY THE NORTH
r CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1972, AS AMENDED. IFIIICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
SCALE: 1 "=200'
FRP GRATING
STANDARD MANHOLE COVER
MOUNTED ON
EXTERIOR OF 2'x1'
SIDE OPENING
TOP OF
"'''
(TYP)
SHALE
0
1-0-
s'-0•
2'_O•
t+
BOTTOM OF
2'-0-
,
SWALE
MOLDED
46•
HOPE FITTING
HDPE
STUB
END
CONCRETE INLET
STRUCTURE
;• +
HDPE FLANGE
CONCRETE PIPE
ADAPTER (TYP
SUPPORT
TO
FROM UPSTREAM
JUNCTION
DUCTILE
COLLECTION
f
MANHOLE
IRON IIYE INLETS
SECTION B—B
La.
SECTION A —A
i EG=
O PROPOSED JUNCTION MANHOLE
0 PROPOSED INLET STRUCTURE
HDPE SUCTION LINE

pipe at this road crossing. Conventional excavation can be utilized for
• construction on the northeast side of U.S. 158.
• This option provides complete retention and pumping capacity for the 50-
year design storm, which meets North Carolina highway drainage
requirements for primary roads, and does not require an ocean outfall.
Additional retention volume capacity is provided in the improved roadside
infiltration swales through the use of pump station inlet elevation control.
Runoff volumes generated by precipitation totals of approximately 1.2
inches or less are confined in the improved roadside infiltration swales,
which meets North Carolina standards for infiltration basin design.
• Because the infiltration basin should normally be dry, public safety issues
and the potential for mosquito breeding should be minimized.
• Sand excavated during construction can be used to bolster the frontal
dunes along N.C. 12.
Drawhacks
• High cost for facilities, equipment, property and construction easements.
• Maintenance for the pump station, swales, inlet structures, and infiltration
basin would have to be provided on an on -going basis. NCDOT funding
and participation for this effort would be expected because the flooding
issue effects U.S. 158.
• Space availability for the swale improvements and inlet structures may be
• limited by a proposed expansion of U.S. 158 to six lanes.
• Potential power outages during severe storm events would require that a
diesel generator be included as a permanent part of the pump station
design.
• In addition to the flooding problem on the southwest side of U.S. 158, the
Sea Dunes condominium complex, located across U.S. 158 from Beacon
Drive (see Figure 4), also experiences flooding problems during moderate
to severe rainfall events. As an infiltration basin is also a remedial
drainage alternative for the apartment complex, land space availability
options adjacent to the post office become more limited. During a site
inspection by URS, a large septic tank drain field was observed on the post
office property (see Figure 6) adjacent to the condominium complex,
which may preclude the use of an infiltration basin at this location.
• The proposed site of the infiltration basin has been inundated by ocean
overwash in the past, and public safety/access issues must be considered.
13

• Cost Estimates
Cost estimates for this design alternative are listed on the following page in Table
2.3.
Table 2.3
Cost Estimates for Drainage Improvements
Beacon Drive/U.S. 158 — Option 2
Unit
Amount
Cost
Total
Excavation (Swales and Basin)
C.Y.
8,750
$2.00
$17,500
Hauling
C.Y.
8,750
$3.50
$30,600
Inlet Structures/Manholes
ea.
6
$2,100
$12,600
HDPE Piping (24-inch SDR-11)
I.f.
1,500
$40.00
$60,000
Horizontal Directional Drilling (U.S. 158)
11
200
$400
$80,000
Pavement Removal/Replacement
I.s.
1
$2,000
$2,000
Trenching/Dewatering
I.s.
1
$60,000
$60,000
Backfill/Compaction
C.Y.
900
$40.00
$36,000
Rip Rap/Headwalls
I.S.
I
$16,000
$16,000
Pump Station
ea.
1
$700,000
$700,000
Property Acquisition
s.f.
65,000
$3.00
$195,000
Subtotal
$1,209,700
25% Contingency
$302,400
Total
$1,512,100
• 2.2.1.3 Option 3 - Infiltration Swales and Culvert Improvements
As described in Option 1, swale and culvert improvements on the southwest side
of U.S. 158 could provide sufficient retention and infiltration volume to
accommodate precipitation totals of approximately 1.2 inches or less. Used alone,
this option would not provide highway inundation protection for the 50-year
storm as required by NCDOT for primary roadways; however, a significant
improvement in drainage would be obtained for more frequent storms. A
precipitation total of 1 inch or more is considered a significant rain event, and the
ability to provide drainage capacity for a 1-inch rainfall event would improve
driving conditions considerably at this location for routine storm events. Existing
shallow swale conditions at the intersection of Beacon Drive and U.S. 158 are
shown in Photograph 7.
is
14

Cost Estimates
• Cost estimates for this design alternative are listed in Table 2.4.
Table 24
✓ Cost Estimates for=Drainage improvements
;Beacon Drive%U.S.158= O
tion 3
Unit Amount
Cost
Total
Excavation
C.Y.
1,175
$2.00
$2,350
Hauling
C.Y.
1,175
$3.50
$4,100
Pavement Removal
S.Y.
40
$7.30
$300
Pavement Replacement
S.Y.
40
$35.00
$1,400
Corrugated HDPE Piping (304nch) l.f.
150
$21.00
$3,150
Trenching
C.Y.
81
$10
$800
BackfilUCompaction
C.Y.
54
$40.00
$2,150
Rip Rap
C.Y.
60
$30
$1,800
Headwalls
ea.
6
$2,000
$12,000
Subtotal
$28,050
20%
Contingency
$5,600
Total
$33,700
2.3 Areas Between U.S. 158 and N.C. 12
• As shown in Figure 1, various areas generally bounded by U.S. 158 and N.C. 12
experience periodic flooding due to poor drainage or ocean overwash. Areas with
poor drainage include (1) the intersection of Lindbergh Avenue and Byrd Street
and (2) the Sea Dunes condominium complex. Alternatives to alleviate the
drainage problems at these locations are provided in the following sections.
2.3.1 Intersection of Lindbergh Avenue and Byrd Street
Typical streets in residential areas between U.S. 158 and N.C. 12 do not have
storm sewer collector systems, ditches or swales. Street runoff is typically
confined to the roadway surface due to the higher relative elevation of street
shoulders and yards. In most areas, street runoff eventually migrates to a low
point on the road surface where it leaves the street and enters open sandy areas
between homes. In these areas, street runoff generated by routine storm events is
typically conveyed, retained and infiltrated without significant inundation of the
road surface.
As shown in Photographs 8 and 9 on the following page, a fenced public beach
access parking area has been constructed at the intersection of Lindbergh Avenue
and Byrd Street. Street runoff from Lindbergh Avenue and Byrd Street tends to
pool in a low point at the intersection of the two roads. This is caused by the
existing downward road surface slopes, which converge at the intersection, and
• the lack of an outlet point.
15

• Prior to the construction of the parking area, it is likely that most of the street
runoff migrated from the intersection road surface into the formerly open area on
which the parking lot is now located. As part of the parking lot design, sidewalks,
fencing and infiltration swales were constructed around the perimeter of the
parking lot. The swales, which are linked by culverts, do not have an outlet
system and receive runoff from the paved parking lot surface. Because no outlet
system is provided, the swales essentially operate as infiltration devices in which
runoff percolates into the sand.
•
As shown in Photographs 8 and 9, it was observed by URS during a 1.3-inch rain
event on April 15, 2000, that street runoff at the intersection of Lindbergh Avenue
and Byrd street tended to flow into the infiltration swale on the south comer of the
public parking area.
As can be seen in the center of Photograph 9, the infiltration swale at the south
comer of the public parking area is separated from a larger infiltration swale,
located on the western side of the parking area, by a grassed berm underneath a
section of fencing. As shown in Photograph 10 on the following page, the larger
infiltration swale on the western side of the parking area remained dry while the
smaller infiltration swale at the south end of the parking area was filled with street
runoff from Byrd Street and Lindbergh Avenue.
The fact that the infiltration swale on the western side of the parking area
remained dry during a 1.3-inch rain event, while the infiltration swale on the
south side of the parking area flooded due to the inclusion of street runoff,
indicates that: (1) The runoff generated by the parking area during a 1.3-inch
precipitation event did not produce a significant volume of water in the western
infiltration swale. This likely indicates that the storage capacity of the parking lot
• infiltration swale system as constructed is significantly higher than that required
by North Carolina BMP design criteria, which require that an infiltration device
16

• be able to accept the first 1-inch of rainfall (on a volumetric basis) from the
associated drainage area. (2) The available storage capacity in the western
infiltration swale could be used to receive street runoff from the Lindbergh
Avenue and Byrd Street intersection for routine to moderate storms. This could
be accomplished by removing the existing berm (see Photograph 9) between the
south and western swales or by installing a culvert that connects the two swales.
2.3.1.1 Potential Drainage Alternatives
Piped storm sewer collection systems and gravity ocean outfalls are generally not
desired by the Town in beachfront areas due to their high construction costs and
tendency to become filled with sand. As described earlier in this report, the
Surfrider Foundation opposes gravity ocean outfalls due to the potential for
surface water pollution caused by the infiltration of septic tank effluent. The
ponding of street runoff at this location is considered by URS to be of the
"nuisance" variety and does not justify the construction of a gravity storm sewer
system or a stormwater pump station and force main outfall system.
Having eliminated the ocean outfall options, the removal of runoff at the
intersection can be accomplished by: (1) re -grading the road surface and directing
runoff to constructed infiltration swales, similar to those used for the public
access parking area, which are located in the Town right-of-way along Lindbergh
Avenue and Byrd Street; (2) utilizing traffic -rated trench drains, in lieu of
regrading the road surface, to capture sheet flow runoff from the road surface and
direct it into constructed infiltration swales along Lindburgh Avenue and Byrd
Street; (3) utilizing a constructed infiltration basin, located in an open lot on the
southwest comer of the Lindburgh Avenue and Byrd Street intersection, and a
• piped collection system; and, (4) utilizing a constructed infiltration basin, located
in an undeveloped area on the north side of Byrd Street near its intersection with
17

U.S. 158 and, (5) removing the berm between the south and west parking area
• swales and utilizing the excess storage capacity of the west swale to accept street
runoff from the Lindbergh Avenue and Byrd Street intersection. The benefits and
drawbacks of these options are described in the following paragraphs.
2.3.1.2 Option 1 - Regraded (Crowned) Road Surface and Constructed
Infiltration Swales
As shown in Figure 7, Option 1 includes constructed infiltration swales in Town
right-of-ways along Lindbergh Avenue and Byrd Street. Crowning (regrading) of
the road surface is recommended to ensure that runoff flows to infiltration swales
on both sides of the road. Because of the downward slope of Lindbergh Avenue
and Byrd street toward their intersection, intermittent check dams or berm
dividers are recommended in the swales to prevent runoff from flowing downhill
and continuing to pond at the intersection.
Preliminary Design Criteria
• The estimated impervious surface area contributing runoff to the study site
is 48,960 square feet (1.12 acres). This area was determined using a
combination of visual inspection during a rainfall event on April 15, 2000
and topographic mapping provided in the aforementioned 1996 COE
shoreline protection feasibility study. The contribution of runoff from
• yards is considered minimal.
• Linear street footage, which can accommodate the installation of swales
along Lindbergh Avenue and Byrd Street within the study area drainage
boundary, is estimated to be 3600 ft. A parabolic swale design with a top
width of 6 feet and a depth of 2 feet yields a total swale storage capacity of
43,200 cubic feet. The retention volume associated with 43,200 cubic feet
of swale storage capacity is sufficient to capture 10.6 inches of rain from
the estimated study area impervious surface area of 48,960 square feet.
The ability to capture 10.6 inches of rain is well in excess of the 10-year,
24-hr precipitation total of 6.5 inches for Kitty Hawk. As such, Option 2
meets Kitty Hawk BMP drainage design criteria for town roads (10-yr
storm) and North Carolina BMP design criteria for infiltration devices,
which must capture the first (1) inch of rainfall.
Benefits
• Low cost for construction and maintainenance.
• Meets Town and State BMP design criteria.
• Provides roadway protection for severe (up to approximately 10.5-inch)
rainfall events.
• Sand excavated during construction can be used to bolster frontal dunes
along N.C. 12.
•
18

•
7
•
a
THE PREPARATION OF THIS FIGURE WAS FINANCED IN SCALE:
I" =200'
B
PART THROUGH A GRANT PROVIDED BY THE NORTH
TOWN OF KITTY HAWK
S i
CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
DARE COUNTY, NORTH CAROLINA
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1972, AS AMENDED, WHICH IS ADMINISTERED BY
ICITTYxAwR SICNtAtwaTER MANAceMeNT RLaN
STO N
W
THE OFFICE OF OCEAN AND COASTAL RESOURCES
gW AINAOE-NAGE I
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
FIGURE 7
on
ADMINISTRATION.
•- "
�4""
remer
��.
' j2
Woodward —CI a

• As with the existing public parking area infiltration swales, the proposed
• streetside swales should remain normally dry and not generate problems
with nuisance odors or mosquito breeding.
•
Drawbacks
Traffic disruption during construction.
Space availability may be limited by public utilities.
Even with proposed crowning of the roadway surface, the downward slope
of Lindbergh Avenue and Byrd Street may continue to channel sheetflow
to the drainage low point in the intersection, rather than into the proposed
infiltration swales. This tendency would significantly reduce the usable
storage volume of the total Swale system.
Cost Estimates
Cost estimates for this design alternative are listed in Table 2.5.
Table 2S
Cost ksthnates for Drainage Improvements
. _ r Llt dbergit-Ave.IBy>rd Street Innters'ection Opon
Unit
Amount Cost
Total
Swale Excavation C.Y.
1,600 $2.00
$3,200
Hauling C.Y.
1,600 $3.50
$5,600
Driveway Culverts (18-inch corrugated HDPE) LE
400 $7.00
$2,800
Pavement Removal S.Y.
160 $7.30
$1,200
Pavement Replacement S.Y.
160 $35.00
$5,600
Pavement Crown ton
578 $35.00
$20,200
Trenching C.Y.
213 $10
$2,100
Backfill/Compaction C.Y.
187 $40.00
$7,500
Crushed Stone (check dams) C.Y.
19 $25.00
$500
Subtotal
$48,700
20% Contingency
$9,700
Total
$58,400
2.3.1.3 Option 2 - Traffic -Rated Trench Drains and Constructed Infiltration
Swales
As shown in Figure 8, Option 2 includes constructed infiltration swales in Town
right-of-ways and traffic -rated trench drains along Lindbergh Avenue and Byrd
Street. Because of the downward slope of Lindbergh Avenue and Byrd street
toward their intersection, trench drains installed perpendicularly across the street
surface are proposed to intercept downhill sheetflow runoff and discharge it into
infiltration swales. As in Option 1, check dams or berms are proposed to prevent
water from flowing downhill, to the intersection of Lindbergh Avenue and Byrd
• Street, after entering the roadside infiltration swales.
19

Preliminary Design Criteria
• • Thepreliminary drainage design criteria are the same as in Option 1.
Benefits
• Runoff cannot migrate to the low point in the roadway intersection.
• Meets Town and State BMP design criteria.
• Provides roadway protection for severe (up to approximately 10.5-inch)
rainfall events.
• Sand excavated during construction can be used to bolster frontal dunes
along N.C. 12.
• As with the existing public parking area infiltration swales, the proposed
streetside swales should remain normally dry and not generate problems
with nuisance odors or mosquito breeding.
• Trench drains can be easily cleaned with pressurized water.
Drawbacks
• Space availability may be limited by public utilities.
• Traffic is disrupted because roadway cuts are required for construction.
• Trench costs are higher than road crowning.
isCost Estimates
•
Cost estimates for this design alternative are listed in Table 2.6.
Table 2.6
Cost Estimates iar Drainage Improvements
.
Lindbei� h:AveB
rd Street Intersection O"tion 2:'_
Unit
Amount
Cost
Total
Swale Excavation
C.Y.
1,600
$2.00
$3,200
Hauling
C.Y.
1,600
$3.50
$5,600
Driveway Culverts (18-inch corrugated
HDPE) l.f.
400
$7.00
$2,800
Pavement Removal
S.Y.
230
$7.30
$1,700
Pavement Replacement
S.Y.
207
$35.00
$7,200
Trench Grates
l.f.
210
$140.00
$29,400
Trenching
C.Y.
283
$10
$2,800
Backfill/Compaction
C.Y.
210
$40.00
$8,400
Crushed Stone (check dams)
C.Y.
19
$25.00
$500
Subtotal
$61,600
20%
Contingency
$12,300
Total
$73,900
20

2.3.1.4 Option 3 - Constructed Infiltration Basin and Piped Collection System
• (Location A)
As shown in Figure 9, Option 4 includes a proposed infiltration basin in an empty
lot at the southwest corner of the Lindbergh Avenue and Byrd Street intersection
(this lot is visible in the upper right-hand corner of Photograph 9 and is designated
as "Location A") and a localized storm sewer collection system.
Preliminary Design Criteria
• As previously described, the estimated impervious surface area
contributing runoff to the study site is 48,960 square feet (1.12 acres)..
The contribution of runoff from yards is considered minimal. Using the
Rational Method with a 10-year design storm (to meet Kitty Hawk
drainage criteria for subdivision streets) and a minimum time of
concentration (Tc) of 10 minutes, the associated design storm intensity is
5.5 in./hr (as derived from the Hatteras rainfall intensity duration curve in
the North Carolina Erosion and Sediment Control Design Manual). Using
an intensity of 5.5 in./hr, a runoff factor (C) of 0.95 for asphalt, and a
contributing watershed of 1.12 acres yields a peak runoff flow rate of 5.9
cfs. Assuming a pipe velocity of 3 fps to maintain internal scouring
capability, a pipe diameter of 2 ft (24 inches) is required for the inlet pipe
to the infiltration basin. For all other collection system pipes, a diameter
• of 1.5 ft (18 inches) can be used.
• Space availability at Location A is estimated to be 5,200 square feet (0.12
acres). With an assumed storage depth of 3 feet and one foot of freeboard,
an infiltration basin constructed at this location could hold the runoff
generated by 3.8 inches of rain on the study area impervious surface.
Benefits
• Meets North Carolina BMP design criteria for infiltration basins, which
must retain the runoff generated by the first (1) inch of rainfall.
• Provides roadway drainage for severe (up to approximately 3.8-inch)
rainfall events with one foot of freeboard.
• Sand excavated during construction can be used to bolster frontal dunes
along N.C. 12.
• Based on USGS soils data for Dare County, the proposed infiltration basin
should remain normally dry and not generate problems with nuisance
odors or mosquito breeding.
Drawhacks
• High cost for property acquisition.
• • Space availability may be limited by public utilities, septic tank drain
fields or repair areas.
21

• Proximity to ground -level residence foundations.
• • Traffic will be disrupted during installation of the storm sewer piping
system.
• Periodic cleaning of the piped collection system may be required to
remove sand.
•
•
Cost Estimates
Cost estimates for this design alternative are listed in Table 2.7.
Table 2.7
Cost,Estimates for Drainage improvements
Lindbergh Ave.Byrd ;Street Intersection _`
Optlon.3 ; ..
.
Unit
Amount
Cost
Total
Excavation C.Y.
819
$2.00
$1,600
Hauling C.Y.
819
$3.50
$2,900
Manholes/Drop Inlets ea.
3
$2,000
$6,000
Pavement Removal S.Y.
49
$7.30
$350
Pavement Replacement S.Y.
37
$35.00
$1,300
Trenching C.Y.
55
$10
$550
Backfill/Compaction C.Y.
40
$40.00
$1,600
Headwall/Rip Rap I.S.
1
$2,400
$2,400
18-inch and 24-inch corrugated HDPE piping I.S.
1
$1,100
$1,100
Property Acquisition SJ
7,500
$3.00
$22,500
Subtotal
$40,300
20% Contingency
$8,000
Total
$48,300
2.3.1.5 Option 4 - Constructed Infiltration Basin and Piped Collection System
(Location B)
As shown in Figure 10, Option 5 includes a proposed infiltration basin at Location
B, which is an undeveloped area on the north side of Byrd Street at its intersection
with U.S. 158.
Preliminary Desijln Criteria
• Runoff design criteria for Option 5 are the same as for Option 4.
• Space availability at Location B is estimated to be 12,750 square feet (0.29
acres). With an assumed storage depth of 3 feet and one foot of freeboard,
an infiltration basin constructed at this location could hold the runoff
generated by 9.4 inches of rain on the study area impervious surface.
22

Benefits
• • Meets North Carolina BMP design criteria for infiltration basins which
g ,
must retain the runoff generated by the first (1) inch of rainfall.
• Provides roadway protection for severe (up to approximately 9.4-inch)
rainfall events with one foot of freeboard.
• Sand excavated during construction can be used to bolster frontal dunes
along N.C. 12.
• The proposed infiltration basin should remain normally dry and not
generate problems with nuisance odors or mosquito breeding.
• Location B is adequately distanced from ground -level residence
foundations.
•
Drawbacks
• High cost for property acquisition.
• Space availability may be limited by public utilities, septic tank drain
fields or repair areas.
• Traffic will be disrupted during installation of the storm sewer piping
system.
• Periodic cleaning of the piped collection system may be required.
Cost Estimates
Cost estimates for this design alternative are listed in Table 2.8.
Table 2 8
- Cost Estimates for Drainage Improvements
Lindbergh Ave.Byrd Street=lntersectioin - Option 4 3
Unit
Amount Cost
Total
Excavation C.Y.
1,889 $2.00
$3,800
Hauling C.Y.
1,889 $3.50
$6,600
Manholes/Drop Inlets ea.
3 $2,000
$6,000
Pavement Removal S.Y.
110 $7.30
$800
Pavement Replacement S.Y.
86 $35.00
$3,000
Trenching C.Y.
137 $10
$1,400
Backfill/Compaction C.Y.
100 $40.00
$4,000
Headwall/Rip Rap I.S.
1 $2,400
$2,400
184nch and 24-inch corrugated HDPE piping I.S.
1 $2,100
$2,100
Property Acquisition s.f
34,700 $3.00
$104,000
Subtotal
$134,100
20% Contingency
$26,800
Total
$160,900
2.3.1.6 Option 5 - Berm Removal and Utilization of West Parking Area Swale
isThis option includes removing the berm shown in Photograph 9 and allowing
street runoff to enter the infiltration Swale on the west side of the public parking
23

• area. The benefits associated with this option are minimal cost and expedience of
implementation. The drawback associated with this option is reduced capacity of
the western swale to receive parking lot runoff, however, as shown in Photograph
10, sufficient capacity appears to be present for the western swale to accept street
runoff during routine to moderate storms. The cost of this option is considered
negligible (less than $200).
•
2.3.2 Sea Dunes Condominium Complex
As shown in Figure 1, the Sea Dunes condominium complex is located on N.C.
12 between East Kitty Hawk Road and Hurdle Street. The privately owned
complex is located in a topographic depression and has no stormwater collection
system. Historically, the complex has experienced problems with flooding and
standing water following incidents of ocean overwash and/or moderate to heavy
rainfall. As shown in Photograph 11, sheetflow runoff from Sea Dune streets and
parking areas tends to pond in a low area on the northwest side of the complex.
The Sea Dunes manager (Doug Young) indicated in April 2000 that a landscape
architect was working on a regrading plan to improve the site drainage, which
reportedly included allowing runoff to enter a drainage easement along a fence
line on the northern property boundary. During the conversation, URS noted that
an open area, on the western side of the complex near Hallet Street, appeared to
be suitable for the construction of an infiltration basin. Mr. Young indicated that
this area was reserved as a repair area for the on -site septic tank system.
As described in section 2.2.1.2, approximately 1.1 acres of empty land space
appeared to be available on Post Office property where an infiltration basin could
• potentially be constructed. This acreage excludes an area in which the Post Office
septic tank drain field is currently located. Although the Sea Dunes condominium
24

complex is a private development, the construction of an infiltration basin that
• could be used to capture runoff jointly from the Beacon Drive/U.S. 158
intersection and the Sea Dunes complex is possible at this location. A discussion
regarding a joint infiltration basin is provided in the following paragraphs.
2.3.2.1 Jointly Maintained Infiltration Basin
The construction of a jointly maintained infiltration basin to receive runoff from
the Beacon Drive/U.S. 158 intersection and the Sea Dunes condominium complex
is desirable because it could concurrently relieve poor drainage conditions for two
problem locations. Costs for construction and maintenance of the basin could be
shared between the Town and the Sea Dunes based upon a signed agreement.
Design issues related to a joint infiltration basin are discussed as follows.
Preliminary Desilln Criteria
• Runoff design criteria are the same as in section 2.2.1.2, with an estimated
impervious surface area of 332,000 square feet (7.62 acres) used for the
Sea Dunes complex and 217,800 square feet (5 acres) used for the Beacon
Drive/U.S 158 intersection impervious surface area. The corresponding
percentages of the combined total drainage area for the infiltration basin
are 60 percent for the Sea Dunes complex and 40 percent for the Beacon
Drive/U.S. 158 intersection.
• • With an assumed storage depth of 3 feet and one foot of freeboard, a 1.12-
acre infiltration basin constructed at this location could hold
approximately 146,250 cubic feet of runoff. Using 60 percent of the
available basin volume for the Sea Dunes complex and 40 percent for the
Beacon Drive/U.S. 158 intersection, the runoff generated by
approximately 3.2 inches of rainfall can be accepted from both sites.
is
Benefits
• Meets North Carolina BMP design criteria for infiltration basins, which
must retain the runoff generated by the first (1) inch of rainfall.
• Provides roadway protection and condominium drainage for moderately
severe (up to approximately 3.2-inch) rainfall events with one foot of
freeboard.
• Sand excavated during construction can be used to bolster frontal dunes
along N.C. 12.
• The proposed infiltration basin should remain normally dry and not
generate problems with nuisance odors or mosquito breeding.
• Construction and maintenance costs can be shared by the Town and the
Sea Dunes condominium complex.
25

Drawbacks
• • High cost for property acquisition.
• Space availability may be limited by public utilities, septic tank drain
fields or repair areas.
• The ability to capture 3.2 inches of rainfall from the Beacon Drive/U.S.
158 intersection drainage area will provided a substantial improvement in
driving safety conditions; however, the ability to capture 3.2 inches of
rainfall (neglecting infiltration) is not sufficient to provide drainage for the
50-yr design storm (7.0 inches in 24 hours) as required by NCDOT for
primary roads.
• The proposed location of the infiltration basin has been inundated by
ocean overwash in the past.
Cost Estimates
Cost estimates for this design alternative are the same as shown in Table 2.3.
2.3.3 Areas of Ocean Overwash
As shown in Figure 1, the Town has identified six areas between Lindbergh
Avenue and N.C. 12 that are prone to ocean overwash and standing water during
northeasters and hurricanes. As identified by the Town, the general areas of
• standing water include the following:
• The intersection of Eckner Street and N.C. 12.
• The intersection of Bleriot Street and N.C. 12.
• The area west of N.C. 12 between Wilkins Street and Hawks Street.
• The intersection of Balchen Street and N.C. 12.
• The area west of N.C. 12 between Historic Street and "Unnamed" Street.
• The area west of N.C. 12 between East Kitty Hawk Road and the Sea
Dunes Condominium Complex.
These areas identified above are subject to flooding during coastal storms due to
the combined effects of periodic soil saturation caused by intense precipitation
and tidal surges that breach the frontal dunes along the east side of N.C. 12. As
shown in Photograph 12 on the following page, the potential for tidal surges to
cross N.C. 12 is enhanced by openings in the frontal beach dunes, which are
created by existing homes and cottages. In areas where houses no longer exist
and the frontal dunes have been re-established, such as across from the Black
Pelican Restaurant at the intersection of East Kitty Hawk Road and N.C. 12 (see
Figure 4), ocean overwash has been substantially minimized.
As part of an effort to further mitigate ocean overwash through the re-
establishment of it's frontal dune system, Town ordinances do not allow the
rebuilding of houses on the east side of N.C. 12 that have been destroyed by
26

• coastal storms. In addition, Town ordinances prescribe special flood protection
requirements in residential areas along N.C. 12. As time progresses and more of
the frontal dune system is re-established, instances of flooding in areas west of
N.C. 12 will become much less frequent. Even with re-established dunes,
however, some overwash can be expected during severe storms in areas where
dunes become destroyed by wave action.
•
Currently, when ocean overwash crosses to the west side of N.C. 12, it flows into
low areas of the natural topography where it often becomes trapped by existing
frontal dunes and/or the high relative elevation of the N.C. 12 road surface. With
no existing storm drainage system, the ocean water has no conduit by which to
return to the ocean and it may stand in lots and streets for several days before
evaporating or infiltrating into the sand. The two primary hazards of this standing
water are (1) public safety issues associated with impeded travel along N.C. 12,
which hinders evacuation efforts prior to major storms and the progress of
medical and rescue vehicles following these storms, and (2) public health issues
associated with the potential surcharge of submerged septic tank systems.
2.3.3.1 Potential Drainage Alternatives
Trapped ocean overwash at these locations is considered by the Town to be a
significant public safety and health issue. The removal of the standing overwash
should be accomplished as quickly as feasible in order to restore roadway access
and prevent surcharging of existing septic systems. Alternatives for removing
trapped ocean overwash are discussed in the following sections.
27

2.3.3.2 Piped Collection System and Gravity Ocean Outfall
• Piped storm sewer collections stems and gravity ocean outfalls are generally not
Y tY
desired by the Town in beachfront areas due to their high construction costs and
tendency to become filled with sand. As described earlier in this report, the
Surfrider Foundation opposes gravity ocean outfalls due to the potential for
surface water pollution caused by the infiltration of septic tank effluent into
separated joints. Although ocean overwash at these locations is considered by
URS to be a significant public safety and health issue, the implementation of this
alternative does not appear warranted due to high cost, maintenance
considerations, and the potential for beachfront water quality degradation.
2.3.3.3 Piped Collection System With Pumping Station and Ocean Outfall.
Although technically feasible, this alternative entails extremely high construction
costs and maintenance requirements for a collection system, pumping station and
ocean outfall in the Kitty Hawk beachfront area. Based on discussions with Town
administrators, this alternative is impractical from a budgetary and maintenance
standpoint and will not be evaluated in detail for the purpose of this report.
2.3.3.4 Sump Boxes and Portable Pumps
Having eliminated the gravity outfall and pump station options, the removal of
• overwash along the Kitty Hawk beachfront can be accomplished through the use
of concrete sump boxes with permanent pipe stand connections used to attach
portable pumps. Conceptual drawings of two options (Type I and Type II) for
sump box and pipe stand arrangements are shown in Figures 11 and 12,
respectively. Descriptions of the two types of sump boxes are provided in the
following paragraphs.
Type I Sump Boxes
As can be seen in Figure 11, the sump box consists of a concrete box with slot -
type openings on the sides and an square access port on top. The side openings are
covered with fiberglass reinforced polyethylene (FRP) grating to prevent access
by people and animals; and, to prevent debris such as vegetation or garbage from
entering the sump box during overwash pumping conditions. The access port on
top is covered by a removable steel grate also serves as an overflow -type inlet
during ocean overwash pumping operations. Type I sump boxes are
recommended for installation in easily accessible Town right-of-ways along
streets. Proposed locations for the installation of Type 1 sump boxes are shown in
Figures 13 through 15.
As shown in Figure 11, the sump box discharges to a vertical pipe stand using
buried HDPE piping. The buried HDPE suction piping is mounted to the sump
is
box and pipe stand foundation with stainless steel anchor straps and weighted
28

•
•
•
• •
PROPOSED 12" HDPE FLANGE ADAPTER
:EL CLAMP PAVEMENT CUT STANLESS STEEL CLAMP
DE SUPPORT
STUB END
.. ,., ..,. EXTERIOR
OF 2'x1' SIDE OPENING (TYP)
CONCRETE SUMP BOX
EL. 2.0
EL. 0.33
7'-8" 6'-4" ' SS CLAMP (TYP. OF 2)
5'-0" 4'_6" 12" SDR 17 HDPE PIPING
CONCRETE PIPE SUPPORT
MOLDED HDPE
STUB END
12"x8" REDUCER
N.C. 12 CONCRETE PIPE SUPPORT
BOLLARD (TYP)
ROAD SURFACE
G.S.E.=0.0
12" SDR 11 HDPE PIPING
8" SDR 17 HDPE PIPING
12" SDR 17 HDPE PIPING
CONCRETE ANCHOR COLLAR 12"x8" REDUCER
(SIZE AND SPACING AS
RECOMMENDED BY THE PIPE CONCRETE PIPE SUPPORT
MANUFACTURER)
TYPICAL ROAD CROSSING (N.C. 12)
SECTION A -A
PROPOSED SUMP BOX AND CONNECTION FOR PORTABLE PUMP
NOT TO SCALE
3
THE PREPARATION OF THIS FIGURE WAS FINANCED IN
n
PART THROUGH A GRANT PROVIDED BY THE NORTH
w
CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 197Z AS AMENDED, WHICH IS ADMINISTERED BY
yI
THE OFFICE OF OCEAN AND COASTAL RESOURCES
6
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
n�
ADMINISTRATION.
6'-0"
90' FLANGED
COUPLING
CONNECTION
" HDPE FLANGE ADAPTER
--BOLLARD (TYP OF 4)
-- 90' FLANGED 8"
COUPLING CONNECTION
12'-0"
2'-6"
14'-0'
6'-0" - L 8"

•
•
R
10'-4"
7'-$" 16'-4„ 5'-0"
4" WEEP HOLE (TYP)
10'-4"
•
•
omm
4'-6"
a
LTANLESS STEEL CLAMP
CONCRETE PIPE SUPPORT
MOLDED HDPE STUB END
FRPI GRATING MOUNTED ON EXTERIOR
OF 2'x1' SIDE OPENING (TYP)
CONCRETE SUMP BOX
-PROPOSED 12" HDPE FLANGE ADAPTER
PAVEMENT CUT STANLESS STEEL CLAMP
12"x8" REDUCER
N.C. 12 CONCRETE PIPE SUPPORT -
BOLLARD (TYP)
ROAD SURFACE
EL. 0.33
G.S.E.=0.0
-PEA GRAVEL
_SS CLAMP (TYP. OF 2) 8" SDR 17 HDPE PIPING
12" SDR 11 HDPE PIPING 12��SDR 17 HDPE PIPING
12" SDR 17 HDPE PIPING
L ui
_ I'L U
d
CONCRETE ANCHOR COLLAR
AS
CONCRETE PIPE SUPPORT REICOMMENDED ZE BANDIY THE PIPE
MOLDED HDPE MANUFACTURER)
STUB END
TYPICAL ROAD CROSSING (N.C. 12)
SECTION A -A
PROPOSED SUMP BOX AND CONNECTION FOR PORTABLE PUMP
NOT TO SCALE
3'-0"
12"x8" REDUCER -A
CONCRETE PIPE SUPPORT
THE PREPARATION OF THIS FIGURE 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 197Z AS AMENDED, WHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
90' FLANGED
COUPLING
CONNECTION
8" HDPE FLANGE ADAPTER
,,.--BOLLARD (TYP OF 4)
i- 90' FLANGED 8"
COUPLING CONNECTION
2'-6"
6'-0"
8"

with concrete collars. The concrete collars serve to prevent floatation of the
• buoyant HDPE and to allow flexibility in the pipeline to account for potential
thermal expansion and contraction.
For the vertical pipe stand, a fabricated 45-degree HDPE fitting and piping are
cast into a concrete block. The concrete block serves the dual purpose of
providing support for the vertical pipe stand and thrust restraint for the pipeline.
On top of the concrete support block, an HDPE flange adapter is used to attach a
90-degree galvanized steel connector coupling for the discharge line. The vertical
pipe stand is supported by a stainless steel collar with welded support legs and
surrounded by bollards for damage protection. The flanged connector coupling
can remain in place on a permanent basis or be installed when necessary by
utilizing a removable blind flange at the HDPE connection point.
Utilizing existing Town beach access right-of-ways, ponded ocean overwash will
be discharged back to the beachfront and ocean using a temporary pipeline
connected to a portable trash pump. The temporary pipeline is made of
interlocked galvanized steel segments and can be covered by protective portable
ramps at road crossings (if necessary).
Type II Sump Boxes
The proposed Type II sump box and pipe stand, shown in Figure 12, is
• substantially similar to the Type I sump box shown in Figure 11; however, the
Type II sump box is surrounded by a structural trash/sand sump. The proposed
Type II sump box is intended for installation in ponding areas between N.C. 12
and Lindbergh Avenue that are well removed from existing Town right-of-ways.
As can be seen in Figure 13, a Type II sump box is proposed in a natural
depression (shown in Photograph 13 on the following page) on the northwest side
of Hawks Street. The benefits of a structural trash/sand sump at this location
include:
• The ability to minimize the introduction of vegetation, debris, and sand
into the sump box during periods between severe storms.
0 The ability to capture and hold vegetation, debris, and garbage during
pumping activities as the water surface is drawn down.
• The ability to minimize the introduction of stormwater runoff into the
sump box during periods between severe storms.
• The ability to exfiltrate standing water using a gravel layer and weep
holes.
Proposed locations for sump boxes and valve stands to serve the six problem
drainage areas described above are shown in the following figures:
• • Eckner Street and N.C. 12. (Figure 13)
29

7
0
A
wm
h'n I u1
THE PREPARATION OF THIS FIGURE WAS FINANCED IN
3 n PART THROUGH A GRANT PROVIDED BY THE NORTH
CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF f 872, AS AMENDED, IIHICH IS ADMINISTERED BY
ly THE OFFICE OF OCEAN AND COASTAL RESOURCES
JANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
n ADMINISTRATION.
ATLANTIC OCEAN
l I I I I I 1 f TTl i t
UNDBERGH AVE 1 �'
4
fA
Z 1
m
a
c
SCALE: >"=200'
U. S 158
I EGEN
G PROPOSED SUMP BOX
O PROPOSED CONNECTION POINT
FOR PORTABLE PUMP
HDPE SUCTION LINE
TOWN RIOHT-OF-WAY W
1
TOWN OF KITTY HAWK
DARE COUNTY, NORTH CAROLINA
KITTY HAWK STORMWATER MANAGEMENT Ih AN
PROPOSED SUMP BOX LOCATIONS
FIGURE 19
dword -Clr a �'
i

•
0
3
ATLANTIC OCEAN
N.C. 12
t (�
❑ o o a
1 �l
o
t
❑ �t ❑
LJNDBERGH AVE.
1
E o
t
U.S. 158
0
1
4
�❑ao
THE PREPARATION OF THIS FIGURE 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 RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
a ADMINISTRATION.
Y
SCALE: 1=200'
Ful
IFGFNn
0 PROPOSED SUMP BOX
0 PROPOSED CONNECTION POINT
FOR PORTABLE PUMP
— HOPE SUCTION LINE
— TOWN RIGHT-OF-WAY
0

• Bleriot Street and N.C. 12. (Figure 13)
• Between Wilkins Street and Hawks Street. (Figure 13)
• Balchen Street and N.C. 12. (Figure 14)
• Between Historic Street and "Unnamed" Street. (Figure 14)
• Between East Kitty Hawk Road and the Sea Dunes Condominiums.
(Figure 15)
•
r
LJ
Preliminary Design Criteria
• The estimated size of an area (a typical block along N.C. 12) to be drawn
down with a single portable pump is 850 feet by 350 feet (840,000 square
feet). Assuming a standing water depth of 3 feet after an ocean overwash
event, 6.28 million gallons of water will need to be removed.
• Using a 2100 gpm pump, 6.28 million gallons of water can be removed in
approximately two days. Note: A draw down time of 2 days is consistent
with the North Carolina stormwater BMP design criterion of 2-5 days for
wet detention ponds. By utilizing a draw down time of 2 days, significant
water quality protection will be provided because suspended solids in the
ocean overwash will settle out of the water column prior to being pumped
back to the ocean. In addition, the draw down time of 2 days is
sufficiently expedient to minimize the potential for water quality
degradation associated with surcharging of submerged septic tanks.
U11

• Portable "dry priming" trash pumps which can operate under net positive
• suction head conditions of up to 28 feet will be utilized for pumping
operations. The HDPE suction line between the sump box and pipe stand
will be 12 inches in diameter to minimize friction head loss. The suction
line will reduce to 8 inches in diameter at the pipe stand to match the
standard suction and discharge diameter for a 2,100 gpm portable pump.
is
Cost Estimates
Cost estimates for the proposed Type I and Type II sump boxes and pipe stands,
as shown in Figures 13 through 15, are provided in Table 2.9.
Table 29
.
Cost Estimates for'Drainage Improvements
Areas of Ocean Oyerwash,'Along N. C.12
Unit Amount Cost
Total
Trenching
Hauling
C.Y.
C.Y.
1,700
500
$10.00
$3.50
$17,000
$1,750
Type I Sump Box
Type II Sump Box
ea.
ea.
7
1
$2,100
$4,200
$14,700
$4,200
Pipe Stands
ea.
7
$2,000
$14,000
8-inch HDPE (SDR 11)
l.f.
80
$9.00
$700
12-inch HDPE (SDR 11)
l.f.
3,080
$20.00
$61,600
Concrete Anchor Collar
Pavement Removal
ea.
S.Y.
60
178
$500
$7.30
$30,000
$1,300
Pavement Replacement
S.Y.
178
$35.00
$6,200
Backfill/Compaction
C.Y.
1600
$40.00
$64,000
Property Acquisition/Easement
s.f
6000
$3.00
$18,000
Subtotal
$233,450
20% Contingency
$47,000
Total
$280,500
2.4 Kitty Hawk Village
As can be seen in Area 7 of Figure 1, Kitty Hawk Village is generally located in
the central sound -side area of the Town. The area, which is traversed by West
Kitty Hawk Road and populated mainly by longtime residents ("locals"), is
subject to tidal flooding during coastal storm events. Generally, any storm event
accompanied by significant winds that drive ocean water into Currituck Sound
can create flooding conditions in Kitty Hawk Village, which is connected to the
sound by a series of creeks and guts. The average ground surface elevation in the
area, obtained from 1982 USGS topographic mapping, is approximately 1.5
meters (4.9 feet). The area lies completely within the AE flood zone (100-yr
storm event elevation of 9 feet) and is characterized by poorly drained soils with
seasonal groundwater table elevations of 0 to 3 feet.
During on -site interviews conducted by URS, Village residents indicated that the
• watercourses that cross Kitty Hawk Road are not significantly influenced by
normal tides or routine rain events; however, when the surface elevation of
31

• Currituck Sound rises due to wind -driven tidal surge, significant flooding
routinely occurs. Reportedly, water depths of approximately 3 to 4 feet were
encountered on low-lying areas of Kitty Hawk Road during Hurricane Floyd in
1999. The presence of this water impeded the access of emergency vehicles to
residents on the western side of Kitty Hawk Village and to Kitty Hawk Landing.
The flooding reportedly began to subside after approximately 8 hours when low
tide reoccurred. Because of Kitty Hawk Village's unique location and low-lying
topography, there is little that can be done to prevent the inundation of Kitty
Hawk Road during periods of significant tidal surge. An inspection of Kitty
Hawk Road by URS revealed that there are six cross culverts (designated as A
through F) located in the study area shown in Figure 1. Table 2.10 lists the
culverts, their estimated size and material, and the associated drainage systems.
•
•
Table 2.1.0
List of Kitty Hawk Road Culverts in the Kitty Hawk Village Study Area
Culvert ID
Estimated Size and Material
Associated Drainage System
A
2 — 18" corrugated metal
Sage Swamp
B
I — 24" corrugated metal
Ash Swamp
C
1— 18" corrugated metal
1— 24" corrugated metal
Ash Swamp
D
1 — 36" corrugated metal
1— 42" corrugated metal
Duck Pond Swamp
E
2 — 24" corrugated metal
Sandy Run Swamp
F
2 — 36" corrugated metal
Minger's Ridge Creek
During the site inspection by URS, it was observed that many of the existing
corrugated metal culverts appeared to be in poor condition due to corrosion
caused by the existing brackish environment. An example of an existing culvert
(Culvert C located near the intersection of Kitty Hawk Road and Bob Perry Road)
with significant corrosion evident is shown in Photograph 14 on the following
page.As can be seen in Photograph 14, the culvert on the right has deteriorated to
the point where debris has become trapped in the missing crown section and
potentially impedes flow.
32

• In addition to the evidence of corrosion, recent road surface and shoulder repairs
(related to Hurricane Floyd) were observed at some of the culvert crossings. One
such location (Culvert E) is shown in Photograph 15.
is
As shown in Figure 1 and Photograph 15, Culvert E conveys drainage from Sandy
Run Swamp underneath West Kitty Hawk Road via Sandy Run Ditch. As shown
in Figure 1, Sandy Run Ditch runs parallel to West Kitty Hawk Road for
approximately 600 feet at the southeast end of Culvert E. Because of the parallel
orientation of the road and ditch, a significant portion of West Kitty Hawk Road
can be flooded during storms at this location due to northerly tidal surge and the
limited flow capacity of the existing culverts. In addition, water that crosses to
the north side of West Kitty Hawk Road will be restricted from draining back to
Kitty Hawk Bay in a southerly direction. As shown in Photograph 15, evidence
of damage and repair to the road shoulder at Culvert E is visible.
2.4.1 Recommendations
Due to Kitty Hawk Village's location in a coastal flood plain that is annually
subjected to tidal surge from hurricanes and northeasters, the complete prevention
of roadway inundation along West Kitty Hawk Road during severe storm events
is not economically feasible. However, URS believes that the ability to minimize
roadway damage and repair requirements by improving the drainage capability at
existing culvert locations is desirable.
Based upon the deteriorated condition of the existing corrugated metal culverts
• and evidence of roadway damage observed on -site, URS recommends that a
33

hydraulic analysis should be performed for Culverts A through F and that
isCulverts A, B, C, D, and F should be replaced with corrugated HDPE for
corrosion protection. Because of the potential for significant roadway flooding
due to the parallel orientation of Sandy Run Ditch to West Kitty Hawk Road at
Culvert E, and the observed condition of the existing road surface (Photograph
15), URS recommends the installation of a box culvert or bridge at this location.
•
2.4.2 Cost Estimates
Because a hydraulic evaluation of the existing culverts is not available at this
time, size requirements for replacement cost estimates are based on the existing
(estimated) culvert sizes shown previously in Table 2.10. Cost estimates for
replacing Culverts A-F are shown in Table 2.11.
Table 2»1
it Esttmates
fob 3ramage mprovemen
-ME y Kltty_Ha kYilla e,
s,,...., _... ,.
O
..,
,
Unit
Amount
Cost
Total
184nch Corrugated HDPE pipe
11.
150
$7.00
$1,050
244nch Corrugated HDPE pipe
1.f.
100
$10.50
$1,050
36-inch Corrugated HDPE pipe
LE
150
$25.00
$3,750
42-inch Corrugated HDPE pipe
I.f.
50
$40.00
$2,000
Pavement Removal
S.Y.
200
$7.30
$1,500
Pavement Replacement
S.Y.
200
$35.00
$7,000
Trenching
C.Y.
267
$10.00
$2,700
Backfill/Compaction
C.Y.
200
$40.00
$8,000
Box Culvert (Total Cost)
I.S.
1
$25,000
$25,000
Subtotal
$52,100
20% Contingency
$10,400
Total
$62,500
2.5 Austin Cemetery Road Area
As can be seen in Area 8 of Figure 1, Austin Cemetery is located on the west side
of Kitty Hawk Village in the central sound -side area of the Town. Austin
Cemetery is bordered by Austin Cemetery Road to the west, Rodger's Street to
the north, and West Kitty Hawk Road to the east and south. During an on -site
inspection performed by URS during a 1.3-inch rain event on April 15, 2000,
standing water was observed on the southeast side of Austin Cemetery along both
sides of West Kitty Hawk Road (see Photographs 16 and 17 on the following
page). Based on a visual assessment of the existing site topography, runoff from
all of the road surfaces surrounding Austin Cemetery tended to migrate to a low
point on the southeastern side of the cemetery at the intersection of West Kitty
Hawk Road and Ivy Lane. Excluding the impact of severe storms, the existing
drainage conditions observed at this site are considered by URS to be of the
is"nuisance" variety and not an immediate hazard to public safety.
34

• As can be seen in Photographs 16 and 17, the existing stormwater drainage
system at this location consists of shallow roadside swales with no outlet point.
The area is low-lying and is characterized by the USGS Dare County Soil Survey
as being located in an area of Fripp Fine Sand with seasonal high groundwater
• depths of greater than 6 feet. Based on a visual inspection of the area, the
drainage capability of the existing soils (which have been modified to some extent
by development) is moderate to poor.
2.5.1 Recommendations
Austin Cemetery is located in Low -Density Village Residential District VR-1.
Per State stormwater management regulations and existing town policy, piped
stormwater collection and conveyance systems are not permitted in this area. As
shown in Photographs 16 and 17, open land space is available on the southeast
side of the cemetery that could be utilized for the installation of a retention pond
or infiltration basin. Neither of these alternatives, however, is recommended at
this location due to the proximity of existing graves.
With the piped collection system and retention/infiltration basin options
eliminated, URS recommends that the existing swale system be improved in the
Town right-of-way along both sides of West Kitty Hawk Road between Rodger's
Street and Ivy Lane. As shown in Figure 16, recommended improvements
include (1) widening and deepening the existing grass swales to provide improved
runoff storage capacity (2) creating retention sections in the improved swales,
using intermittent check dams or berms, to prevent ponding near Ivy Land due to
the downhill migration of flow in the swale system and (3) the construction of
small concrete flumes used to enhance to ability to remove runoff from the
• roadway surface and to channel runoff into swale retention sections
M

•
•
I•
0
THE PREPARATION OF THIS FIGURE WAS FINANCED IN
S� PART THROUGH A GRANT PROVIDED BY THE NORTH
�r CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
3 ACT OF 1972, AS AMENDED, WHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
i2
AUSTIN
CEMETERY
O
Ko HPWK c:J ❑
SCALE: 1=200'
I
Y
3
PROPOSED SWALE OO
IMPROVEMENTS
I

•
2.5.2 Cost Estimates
Cost estimates for the recommended Austin Cemetery Road Area drainage
improvements are shown in Table 2.12.
Table 2.12
Cost Estimates for Drainage Improvements
Austin Cemetery Road Area
Unit Amount Cost Total
Swale excavation C.Y. 767 $2.00 $1,500
Hauling C.Y. 767 $3.50 $2,700
Subtotal $4,400
20% Contingency $900
Total $5,300
2.6 Kitty Hawk Landing
As can be seen in Area 9 of Figure 1, Kitty Hawk Landing is located in the
southwestern corner of Kitty Hawk. During an on -site inspection performed by
URS during a 1.3-inch rain event on April 15, 2000, standing water was observed
at two locations on the southern end of Ivy Lane (see Photographs 18 and 19).
Based on a visual assessment of the existing site topography, runoff from the
northern and southern ends of Ivy Lane appeared to migrate to low points at the
locations where standing water was observed.
As can be seen in Photographs 18 and 19, no existing drainage swales are present
Along Ivy Lane. With no swales present, street runoff is confined to the roadway
surface where it ponds near addresses 3921 and 3923. Excluding the impact of
severe storms, the existing drainage conditions observed at this site are considered
by URS to be of the "nuisance" variety and not an immediate hazard to public
safety.
01

• 2.6.1 Recommendations
Soils in the Ivy Lane section of Kitty Hawk Landing are classified in the USGS
Dare County Soil Survey as "Psamments," which are areas where most or all of
the natural soil (Currituck mucky peat) has been removed or covered with new
soil for building or construction activities. Coupled with low-lying elevation and
a continuously high ground water table, the altered soil conditions along Ivy Lane
tend to impede the natural percolation of runoff. Because of this, infiltration
devices cannot be used in this area. Because Kitty Hawk Landing is located in a
low -density zoning district (VR-1), the use of piped stormwater collection
systems is prohibited by Town Ordinance and State stormwater management
regulations.
With the piped collection system and infiltration basin options eliminated, the use
of wet detention ponds and/or swales must be considered. As shown in
Photographs 20 and 21 on the following page, empty lots are present on both
sides of Ivy Lane adjacent to the areas of existing street ponding. While
technically feasible, the construction of a wet detention pond on the eastern side
of Ivy Lane between addressed 3921 and 3923 (Photograph 20) would be
expensive due to land acquisition (approximately $130,000 per acre), construction
costs, and maintenance costs. In addition, URS believes that significant
opposition to this alternative would be encountered from adjacent residents along
Ivy Lane.
Photograph 20— View, looking southwest, of
Town right-of-way (see fire hydrant)
adjacent to empty lot beside 3921 Ivy Lane
in Kittv Hawk Landing.
The Assistant Town Manager, Mr. Tim Owens, indicated that residents on Ivy
Lane have historically been opposed to the construction of drainage swales due to
aesthetic concerns, mosquitoes, and the desire to preserve the ability to move boat
trailers into and out of yards. As can be seen in Photographs 20 and 21, there is
ample space present in the Town right-of-way (see location of fire hydrant in
Photograph 20) to construct localized shallow retention swales on both sides of
• Ivy Lane between addresses 3934 and 3942 to the west and 3921 and 3923 to the
east. The purpose of these swales is to provide retention volume capacity for the
37

• removal of road surface runoff at the two observed ponding locations, without
conveying the runoff to the adjacent canals. Swales along the entire length of Ivy
Lane did not appear necessary because ponding was only observed at the two
locations shown in Photographs 18 and 19. To accommodate future development
of the existing empty lots, the recommended swales can be constructed in a
fashion that allows ample space for a wide driveway and boat trailer access. In
addition to the swales, the construction of small concrete flumes on the road
shoulder is recommened to enhance the ability to expediently remove runoff from
the roadway surface. The proposed locations of the recommended swales are
shown in Figure 17.
•
•
2.6.2 Cost Estimates
Cost estimates for the recommended Kitty Hawk Landing drainage improvements
are shown in Table 2.13.
Table 2.13
Cost Estimates for Drainage Improvements
Kitty Hawk Landing
Unit ,%mount Cost Total
Swale excavation C.Y. 400 $2.00 $800
Hauling C.Y. 400 $3.50 $1,400
Subtotal $2,20()
20% Contingency S400
Total $2,600
2.7 Tateway Road and Ascension Drive
As can be seen in Area 4 of Figure 1, Tateway Road and Ascension Drive are
located in the southeastern corner of Kitty Hawk near the border of Kill Devil
Hills. During an on -site inspection performed by URS during a 1.3-inch rain event
on April 15, 2000, standing water was observed at the eastern end of Tateway
Road and Ascension Drive near their respective intersections with U.S. 158. The
standing water observed on Tateway Road is shown in Photographs 22 and 23 and
the standing water observed on Ascension Drive is shown in Photographs 24 and
25 (following page). As illustrated in Photograph 22, the source of the standing
water at the two locations is runoff generated by impervious surfaces associated
with residential development in elevated dune areas.
38

•
•
CURRITUCK SOUND
PROPOSED RETENTION O
O SWALES
SHELUBANK POINT :1H
F—
MY =
O u
LONE
O �d 0 Ln O
a� O
TEIQ Ci C3
O � � ❑ PINEWAY
THE PREPARATION OF THIS FIGURE WAS FINANCED IN
PART THROUGH A GRANT PROVIDED BY THE NORTH
S CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
ACT OF 1972, AS AMENDED, WHICH IS ADMINISTERED BY
wd THE OFFICE OF OCEAN AND COASTAL RESOURCES
rc MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
ADMINISTRATION.
SCALE: 1=200'
I FQFNQ
O PROPOSED SUMP BOX
O PROPOSED CONNECTION POINT
FOR PORTABLE PUMP _
HOPE SUCTION TINE
TOWN RIGHT-OF-WAYw
TOWN OF KITTY HAWK
DARE COUMY. NORTH CAROLINA
KITTY HAWK STORMWATER MANAGEMENT PLAN
KITTY HAWK LAND[ NG
FIGURE fl
remer �;,,�ry
Woodward —CI e

During the site inspection by URS on April 15, 200 it was observed that runoff
from impervious street and driveway surfaces was channeled downhill along
Tateway Road and Ascension Drive to low points with no associated drainage
swales or outlets. The ponding problem appeared to be more severe on Tateway
Road, as evidenced by the vehicle shown in Photograph 23 and the "high water"
sign shown in Photograph 22.
Photograph 25 - Stalli ilo, auto on
Ascension Drive during 1.3-inch rain event
on April 15,2000.
2.7.1 Recommendations
Natural soils at the two problem sites are generally classified in the USGS Dare
County Soil Survey as Newhan/Corolla Complex fine sands, which have high
infiltration capacities and a seasonal maximum groundwater table depth of 6 feet
or less. Because of this, infiltration devices can be utilized successfully in this
area. Wet detention ponds are not recommended at this location due to the high
infiltration capacity of the existing soil and lack of land space. Because Tateway
Road and Ascension drive are located in a low -density zoning district (BR-1), the
use of piped stormwater collection systems is prohibited by Town Ordinance and
• State stormwater management regulations.
M

• With the piped collection system and wet detention basin options eliminated, the
use of infiltration basins and/or swales must be considered. As shown in
Photographs 22 through 25, empty wooded lots (privately owned) are present on
both Tateway Road and Ascension Drive adjacent to the areas of existing street
ponding. While technically feasible, the construction of infiltration basins in the
existing wooded lots at these locations would be expensive due to land acquisition
costs (approximately $130,000 per acre), construction costs, and maintenance
costs.
As can be seen in Photographs 22 through 25, there is ample space present in the
Town right-of-way (see location of telephone pedestal in Photograph 24) to
construct infiltration swales on both sides of Tateway Road and Ascension Drive
in the areas of existing ponding on the road surface. The purpose of these
proposed swales is to provide retention volume capacity for the removal and
infiltration of road surface runoff at the two observed ponding locations. In
addition to the swales, the construction of small concrete flumes on the road
shoulder is recommended to enhance the ability to expediently remove runoff
from the roadway surface.
As shown by the conditions observed in Photograph 23 during a 1.3-inch rain
event, the ability to remove runoff from Tateway Road and Ascension Drive by
utilizing infiltration swales during routine to moderate rain events will provide a
is significant improvement in public safety at these locations. The proposed
locations of the recommended swales are shown in Figure 18.
2.7.2 Cost Estimates
Cost estimates for the recommended Tateway Road and Ascension Drive drainage
improvements are shown in Table 2.14.
40

•
rm
a
. o
. ao
oa
v4SIDRNE
ACS ON ❑
�a
0 U ED
�u
z p:
TATEWAY ROAD
ID
PROPOSED INFILTRATION
5 SWALES (TYP.)
ON p
D W.-
El o I
THE PREPARATION OF THIS FIGURE 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, IIHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
r MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
1 ADMINISTRATION.
is
SCALE: 1=200'
IBM@
rcal
Efful
Now
ATLANTIC
OCEAN

•
•
•
2.8 Light Keepers Way
As can be seen in Area 5 of Figure 1, Light Keepers Way is located in the
southeastern corner of Kitty Hawk near the northern shore of Kitty Hawk Bay.
During an on -site inspection performed by URS during a 1.3-inch rain event on
April 15, 2000, standing water was observed at the intersection of Light Keepers
Way and Beacon Drive (see Photograph 26).
Photograph 26 — Runoff from Beacon Drive and Light Keepers
Way being channeled to front of residence at 105 Light Keepers
Way during 1.3-inch rain event on April 15, 2000.
The source of the standing water at the intersection of Light Keepers Way and
Beacon Drive was runoff generated by impervious surfaces associated with
residential development. During the site inspection by URS on April 15, 2000 it
was observed that runoff from impervious street and driveway surfaces in an
elevated dune area was channeled downhill in a southwesterly direction along
Beacon Drive. Upon reaching the intersection with Light Keepers Way, the runoff
stream followed the edge of the road surface in a southeasterly direction along
Light Keepers Way. Additionally, it was observed that street runoff from a cul-
de-sac at the end of Light Keepers Way flowed in a northwesterly direction and
converged with the runoff from Beacon Drive in front of a private residence (105
Light Keepers Way) near the intersection of the two roads (see Photograph 26).
The resident at 105 Light Keepers Way indicated to URS during an on -site
interview that, during severe storms, runoff from the ponding area on the street is
channeled into his backyard via his driveway. A visual inspection of the
resident's yard indicated that the existing ground surface elevation is well below
the roadway elevation and that a significant depression was present in the
backyard. Recent repairs to the landscaping near the depression were evident, and
the resident attributed them to damage caused by flooding during various storms
during the previous six months.
41

2.8.1 Recommendations
isNatural soils at this site are classified in the USGS Dare County Soil Survey as
Newhan fine sands, which have high infiltration capacities and a seasonal
maximum groundwater table depth of 6 feet or less. Because of this, infiltration
devices can be utilized successfully in this area. Wet detention ponds are not
recommended at this location due to the high infiltration capacity of the existing
soil and lack of land space. Because Light Keepers Was is located in a low -
density zoning district (BR-1), the use of piped stormwater collection systems is
prohibited by Town Ordinance and State stormwater management regulations.
With the piped collection system and wet detention basin options eliminated, the
use of infiltration basins and/or swales must be considered. A wooded depression
(privately owned) is present on the opposite (southwest) side of Light Keepers
Way from residence 105. During an on -site inspection by URS during a 1.3-inch
rainfall event on April 15, 2000, it was observed that water ponding in front of
residence 105 tended to migragte across the street toward the existing depression
when the water level became high enough (see Photograph 26). While technically
feasible, the construction of an infiltration basin in the depression on the
southwest side of Light Keepers Way would be expensive due to land acquisition
costs (approximately $130,000 per acre), construction costs, and maintenance
costs.
• As can be seen in Photograph 26, there is ample space present in the Town right-
of-way in on the east side of the Beacon Drive/Light Keepers Way intersection to
construct an infiltration swale in the area of existing ponding on the road surface.
The purpose of this proposed swale is to provide retention volume capacity for the
removal and infiltration of road surface runoff during routine to moderate storm
events. In addition to the swale, the construction of small concrete flumes on the
road shoulder is recommended to enhance the ability to expediently remove
runoff from the roadway surface.
�J
As shown by the conditions observed in Photograph 26 during a 1.3-inch rain
event, the ability to remove runoff from Light Keepers Way by utilizing
infiltration swales during routine to moderate rain events will provide a
significant improvement in public safety at these locations and help to prevent
street runoff from entering the lot at residence 105. The proposed location of the
recommended swale is shown in Figure 19.
42

0
0
KITTY HAWK BAY
THE PREPARATION OF THIS FIGURE PAS FINANCED IN
PART THROUGH A GRANT PROVIDED BY THE NORTH
CAROLINA COASTAL MANAGEMENT PROGRAM, THROUGH
FUNDS PROVIDED BY THE COASTAL ZONE MANAGEMENT
o ACT OF 1972, AS AMENDED, WHICH IS ADMINISTERED BY
THE OFFICE OF OCEAN AND COASTAL RESOURCES
Y MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC
1 ADMINISTRATION.
ul
m
DORY
.o
a � O
o
O�G o
O
�N
SWALE ED nOt�
SCALE: 1=200'
I FGFND
17 PROPOSED SUMP BOX
O PROPOSED CONNECTION POINT _
FOR PORTABLE PUMP K
— HDPE SUCTION LINE
— TOWN RIGHT-OF-WAY �'<a
O
O
O
\;,Xo
P
TOWN OF KITTY HAWK
DARE COUNTY, NORTH CAROLINA
KITTY HAWK STORMWATER MANAGEMENT PLAN
LIGHTKEEPERS WAY
FIGURE 19
relner W-M�
Woodward —CI e

2.8.2 Cost Estimates
• Cost estimates for the recommended Light Keeper's Way drainage improvements
g p
are shown in Table 2.15.
3.0 PRIORITIZED RECOMMENDATIONS
Based on a review of the identified problem drainage areas in Kitty Hawk, URS has
developed a priority ranking for the implementation of the proposed drainage
improvements. Protection of public health and safety and conformance with North
Carolina stormwater management regulations were the primary considerations in the
ranking analysis.. As shown in Table 3.1 on the following page, the Beacon
• Drive/U.S. 158 intersection was ranked No. 1 by URS. As shown in Photograph 3, a
significant potential for accidents exists at this location during routine storm events
due to inundation of the road surface and the moderately high speed limit.
•
The areas of ocean overwash between U.S. 158 and N.C. 12 were ranked No. 2 by
URS. Although a significant public health and safety concern, the ocean overwash
events occur only during moderate to severe storm events and the potential for
repetitive automobile accidents is much lower than the Beacon Drive/U.S. 158
intersection. Ascension Drive/Tateway Road and Light Keepers Way were ranked
Nos. 3 and 4, respectively, due to the potential for repetitive problems during routine
to moderate storms and the potential for damage to private property. Kitty Hawk
Estates was ranked No. 5 due to its significant drainage problem but moderately low
potential for detriment to public safety or private property.
Kitty Hawk Village was ranked No. 6 because its location in an area of low-lying
topography precludes a cost-effective method for significantly minimizing repetitive
flooding; however, the poor existing condition of culverts should be addressed.
43

•
•
•
Rank Site Number and ID Recommended Estimated Cost
Alternative
1
Site 6 — Flooding at
Swale
$1,507,000
intersection of Beacon
improvements and
Drive and U.S. 158
pump station.
2
Site 3 — Ponding of
Sump boxes and
$280,500
ocean overwash
pipe stands for
between U.S. 158 and
connecting portable
N.C. 12
pumps.
3
Site 4 — Ponding of
Construction of
$7,900
street runoff on
roadside infiltration
Ascension Drive and
swales.
Tateway Road
4
Site 5 — Lot flooding at
Construction of
$1,000
105 Light Keepers Way
roadside infiltration
due to street runoff.
swales.
5
Site 1— Poor drainage
Culvert
$33,500
and standing water in
replacement and
Kitty Hawk Estates
improvement.
6
Site 7 — Roadway
Culvert
$62,500
flooding in Kitty Hawk
replacement and
Village
improvement.
7
Site 2 — Ponding of
Removal of
<$200
runoff at the Byrd
existing berm and
Street/Lindbergh
utilization of
Avenue intersection.
existing swale.
8
Site 8 — Poor street
Construction of
$5,300
drainage on Kitty
roadside infiltration
Hawk Road near
swales.
Austin Cemetery.
9
Site 9 — Poor street
Construction of
$2,600
drainage on Ivy Lane in
roadside retention
Kitty Hawk Landing.
swales.
TOTAL COST: $1,900,500
44

Byrd Street, Kitty Hawk Road near Austin Cemetery, and Kitty Hawk Landing
• are ranked Nos. 7 through 9, respectively, due to their location in residential
areas with low speed limits and a low potential for detriment to public safety or
private property.
3.1 Cost Considerations
As can be seen below Table 3.1, the total cost of the recommended drainage
improvements is $1,900,500. Typically, the alternatives recommended in Table
3.1 have the lowest associated costs. The recommended alternative for the
Beacon Drive/U.S. 158 intersection does not have the lowest associated cost. A
discussion of this location is provided as follows.
Beacon Drive/U.S.158 Intersection
As discussed in Sections 2.2.1.1 through 2.2.1.3, the drainage alternatives and
associated costs for this location include:
Swale improvements and pump station $1,507,000
Swale improvements and infiltration basin $1,512,000
Swale improvements alone $33,700
The infiltration basin alternative was not recommended due to the high cost and
• safety considerations associated with a relatively deep (4 feet) basin in an area
prone to public access.
•
Although the least expensive alternative, swale improvements alone provide
roadway protection for only routine storms and do not meet the NCDOT 50-yr
storm design criteria for primary roads. In addition, the proposed expansion of
U.S. 158 to six lanes would further limit space availability for swale
improvements in the future.
The swale improvement and pump station alternative was recommended because
it provides the highest level of roadway and water quality protection.
Additionally, if desired, the design and construction of the pump station and
HDPE force main can be performed in conjunction with the highway widening
project. If space limitations associated with the widening project prevent the
construction of swales, a curb and gutter system can be utilized in this area to
convey runoff to the pump station.
45