SW7051115_HISTORICAL FILE_20051114

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
P2 HISTORICAL FILE
DOC DATE
ar5L//_�
YYYYMMDD

Stormwater Management Plan Narrative RECEIVED
New Hope Foundation Daycare / Office NOV 14 2005
November 1, 2005
General DWQ-WAR®
The following narrative will detail the stormwater management system to serve proposed built -upon area for the New
Hope Foundation Daycare / Of ice site. A high density permit is being pursued for this project.
New Hope Foundation Daycare 1 Off -ice site consists of a proposed 7,770 sf daycare & office building, with
associated parking and infrastructure. As per state regulations, a high density permit will be pursued. The New
Hope Foundation Daycare 1 Office site is situated on a 2.21 acre site located in the northeast quadrant of the
intersection of Interpath Parkway and Beau Parkway East, approximately 865 feet southeast of the intersection of'
Interpath Parkway and U.S. 17 in Mount Hermon Township, Pasquotank County. The proposed stormwater
management method to serve the facility will consist of a wet pond with enough temporary storage capacity to store
the runoff generated by a 2.61 inch rainfall event. The following narrative will summarize the parameters of this
design which will illustrate an effective stormwater management system in full compliance with all state regulations.
Summary of Existing Conditions
The New ]lope Foundation Daycare / Office site is currently vacant. The vacant site is bounded by drainage ditches
to the north, west, and south which drain to the north. There are currently no BMP's to address stonmwater from the
site.
Summary of Proposed Conditions
Stormwater management improvements will be needed to control the runoff Boni proposed impervious construction.
Runoff from all new impervious areas is proposed to be collected via curb and gutter and storm sewer and conveyed
to a proposed stormwater wet basin located in the southwest corner of the site. The drainage area containing all of
the proposed improvements will consist of 33,814 sf of area (73.3% impervious) which will generate 2,084 cf of
runoff from a l" rainfall event. The proposed wet basin will have temporary storage capacity of 5,467 of (equivalent
to the runoff produced from a 2.61" rainfall event). Considering that the temporary storage available will provide for
a rainfall of 2.61 inches, the temporary storage proposed is exceedingly adequate.
Stormwater Collection, Treatment, Storage and Disposal
Collection
The stormwater runoff will be collected and directed via site grading, curb and gutter, and storm sewer to discharge
to the wet detention pond. Roof runoff is required by the plan to be collected via gutter and downspout and piped to
the storm sewer.

Treatment
Runoff from paved areas will sheet flow to drop inlets, and be directed to the wet detention basin via a storm sewer
system. Large particulates and debris will accumulate at the drop inlet grates and at the storm sewer rip -rap outlet.
The storm sewer will discharge to the pond forebay via a rip -rap protected outlet. The riprap apron will act as
filtration areas screening pollutants and large particulate matter from the stormwater runoff prior to it reaching the
wet pond forebay area. Once (lie runoff reaches the basin it will pass through a vegetated shelf on its way into the
forebay area. This vegetated shelf will exist around the entire perimeter of the wet pond permanent pool It shall be
constructed at a 6:1 slope and have a width of 6 feet around the entire permanent pool and the majority of the
forebay area. This shelf is to be vegetated with the following native wetland species Tvpha emgustfolia, Tvphu
latijblia, Juncus roemerianus, Juncus of rsus and Baccharis halinafolia. The placement of the Tvphu ougtrstifolia,
Tvphu latifolia, Juncus roemerianus and Juncos of rsus will be on 2 foot centers and Baccharis halimifnlia on 5 foot
centers. The Baccharis halimrfoha shall be placed at the upper limit of the season high water table or on the dry side
of the season high water table elevation in order to ensure the successful growth of this organism. In other words the
root zone may be saturated and the organism can be subjected to occasional flooding but should not be submerged at
all times. This vegetative shelf will act as the point of primary pollutant filtration and nutrient uptake. As the
permanent pool undergoes seasonal fluctuations in water level and changes in depth due to precipitation, the
stormwater runoff will pass repeatedly throughout the vegetation of the shelf actually assisting in bringing pollutants
and nutrients in contact with the vegetated shelf as well as flushing this shelf periodically. This shelf will provide the
same natural filtration function as naturally occurring wetland fringes and salt water marsh areas. The forebay is a
pocket within the pond where the water enters a depression that allows for energy dissipation and sediment removal.
As the runoff exits into the water surface the energy is diffused by (lie relatively large body of stationary water and
therefore sediment removal occurs due to the particulates no longer being suspended by the turbulent flow. "Pile
forebay is surrounded by a forebay wall which consists of a submerged vegetated shelf existing approximately 1 foot
below the permanent pool elevation. The elevation of the forebay wall is necessary to sustain the wetland plant
species to be planted there. The species best suited for this area are those that can exist and flourish in water
saturated soils such as the Needle Rushes (Juncrts roemerianus, Juncus effcrsus) or the cattails (7vplm at�gt�slifolia,
T)lpha latifolia). Once the vegetated forebay wall becomes well established with plant growth this wall will act as a
strainer filtering the water prior to its entering the permanent pool. This vegetated forebay wall will act as a
secondary method of filtration. The season mean high water table, based on observation of subsurface soil conditions
as well as surrounding wetland, occurs at an elevation of approximately 10.2 feet MSL. The season mean high water
table will be considered the upper limit of the permanent pool. The storage provided by this system will exist from
the permanent pool elevation to the top of the temporary pool elevation. The side walls of the temporary pool will
be vegetated according to the general seeding specifications found in the enclosed plan set. When stormwater runoff'
begins to accumulate above the permanent pool elevation the pond level will increase and the vegetated side walls of
the temporary pool will provide further filtration of pollutants and nutrient uptake. The extended duration time
within the forebay will allow for particulate matter to settle to the bottom. In addition the entire pond, sired for
greater than a I inch storm, will offer an extensive storage time allowing for maximum settling. The wet pond has
been designed to accommodate 900 Total Suspended Solids (TSS) removal and storage. The surface area to
drainage area (SA/DA) calculations reflecting the 90% TSS removal have been enclosed and can be found within the
calculations section of the appendix. The wet pond as a stormwater management plan method will offer many
excellent opportunities for stormwater treatment.
Stogy
This wet detention pond system will offer temporary storage above the ground surface (calculated) and additional
storage within the void spaces available in the subsurface (not calculated). The runoff generated by a 1.0 inch storm
in the project drainage area will require 2,084 ft3 of storage. The wet pond system will temporarily store stormwa(er
above pennanent pond. The total temporary storage available above the pennanent pond surface is 5,467 ft3
(equivalent to runoff generated by a 2.61 inch storm). The provided volume of 5,467 W is greater than the 2,094 (13
referenced above, indicating complete storage of a 1.0 inch storm. Additional unaccounted storage is available

within the subsurface below the side slopes of the temporary storage down to the water table.
.Disposal
Stormwater runoff entering this management system will be disposed of in two manners; infiltration into the
subsurface and discharge to the adjoining drainage ditch via stormwater basin outfall structure. The system has been
designed with additional storage so that this site will have the capability to handle in excess of a 1.0 inch storm when
such a weather event should occur. The 2.61 inches of storage available within the wet pond represents excessive
storage within the wet pond with controlled discharge to the adjoining drainage ditch (as well as into the subsurface)
over a 3.8 day post -storm period with a maximum discharge rate of 0.029 cts.
In the event that the design storm is exceeded, the site's stormwater management system will overflow to the
adjoining drainage / outfall ditch.
Sods
After visits to the site by Quible & Associates staff soil borings indicate that the soils found throughout this site
consist of a dark loam underlaid by clay. These soil types will have poor infiltration rates in naturally occurring
soils. Observations of in -situ soils generally agree with the Pasquotank County Soils Maps which designate high -
ground soils on this site as follows:
13b - Bayboro loam, nearly level, poorly drained. Permeability is moderate to very slow.
The soil types found in the field correlate with the descriptions mapped and discussed in the United States
Department of Agriculture, Soil Conservation Service, Soil Survey of Pasquotank County, North Carolina. A
photocopied soils map with site location has been included within this narrative.
Calculations
A set of sample calculations can be found within appendix portion of this narrative.
Conclusions
The proposed stormwater management plan for this site will handle in excess of the 1_0 inches of stormwater runoff
generated by all surfaces, pervious and impervious proposed for this site by incorporating collection swales and a
wet detention pond. The proposed system will offer preliminary, primary and secondary methods of treatment as
well as an alternate method of disposal should the capacity be exceeded. This proposed design should more than
adequately serve the stormwater management requirements of this site.

Appendix

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(Sheet 18)

Quible SINCE 1959
Quible & Associates, P.C.
ENGINEERING • ENVIRONMENTAL SCIENCES • PLANNING • SURVEYING
8 Juniper Trail • P.O. Drawer 870 • kitty Hawk, NC 27949
Phone [phone] o FAX [phone] • E-Mail: [e-mail]
JOB_( 5,2 - .SW MCali _
SHEET NO. . OF
CALCULATED BY DATE
CHECKED BY
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DATE

Quible SINCE 1959
JOB PO 56yL
SHEET NO.
OF
Quible & Associates, P.C.
ENGINEERING • ENVIRONMENTAL SCIENCES • PLANNING • SURVEYING
8 Juniper Trail • P.O. Drawer 870 • Kitty Hawk, NC 27949
Phone [phone] • FAX [phone] • E-Mail [e-mail]
CALCULATED BY J7W/7 DATE 10' 31'DS
CHECKED BY
SCALE
DATE
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Quible SINCE 1959
SHEET NO.
OF
Qufble & Associates, P.C. CALCULATED BY 1JAn DATE
ENGINEERING • ENVIRONMENTAL SCIENCES • PLANNING • SUrNEYING
8 Juniper Trail • RID, Drawer 870 • Kitty Hawk, NC 27949 CHECKED 8Y DATE
Phone [phone] • FAX [phone] • E-Mall. [e-mail] SCALE

Quible SINCE 1959
Quibie & Associates, P.C.
ENGINEERING • ENVIRONMENTAL SCIENCES • PLANNING • SURVEYING
8 Juniper Trail • P.O. Drawer 870 • Kitty Hawk, NC 27949
Phone [phone] • FAX [phone] • E-Mail: [e-mail]
J08 D
SHEET NO. OF .Z _
CALCULATED BY DATE
CHECKED BY DATE
SCALE

Quible
Quible & Associates, P,C,
ENGINEERING • ENVIRONMENTAL SCIENCES • PLANNING • SURVEYING
SINCE 1959
November 1, 2005
Mr. Bill Moore
NCDENR
Division of Water Quality
943 Washington Square Mall
Washington, North Carolina 27889
RECEIVED
Nov 14 2005
DWQ-WARQ
Re: Stormwater Management Plan (High Density Application)
Proposed New I -lope f oundat ion Daycare / Ofhce site
I'asquotank County
Dear Mr. Moore:
P.O. Drawer $70
Kitty Hawk, NC 27949
Phone: [phone]
Fax; 252-26I -1260
PRINCIPALS
Sean C. Boyle, P.E.
Joseph S. Lassiter, C.E.P.
Eduardo J, VoldVeso. P.E.
ASSOCIATES
Joseph J. Anlout, P.E.
Katherine C Morchello. P.L.S.
On Behalf of New Hope Foundation, Inc., Quible and Associates, P.C. hereby submits for review and
approval a High Density, Stormwater Management Permit Application package 11or the above referenced
proposed daycare 1 office building in Pasquolank County.
'rhe project falls within the high density classification. The enclosed narrative will explain in detail the
stormwater management of this site.
The following items are included and shall be considered part ofthis submittal package:
. Review Fee Check for $420.00
2. Two (2) copies of the Stormwater Management Permit Application Fonn w/one (1) copy
of the Wet Detention Basin Supplement
3. Stormwater Management Plan Narrative
4. Two (2) copies of the following Plan Sheets
Sheet 1 - Site Plan
Sheet 2 - Grading & Drainage Plan
Sheet 4 - SESCP
Sheet 6 - Stormwater Details
If you have any questions, or require any additional information, please do not hesitate to contact me at
[phone].
Sincerely,
uible socVspr.
avid . I eel, L.
enc: as stated
cc: Mr. Robert Melton