SW8050841_COMPLIANCE_20051012

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE
�ZO/
YYYYMMDD

Design Calculations
Infiltration System
for
Live Oaks at Topsail
September 3, 2005
I. Project Description
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The project consists of construction of a 22-unit residential waterfront community. This site is located adjacent
to the Intracoastal Waterway, SA;HQW.
2. Design Requirements
Project will be designed in accordance with NC Administrative Code Section 15A NCAC 2H.1000 —
Stormwater Management (hereinafter "Regulations". This site is in the category of "development activities
within coastal counties except those areas draining to Outstanding Resource Waters or within one-half mile of
and draining to SA water". Due to density, the project is considered "high density development". In
accordance with Section .1105(2)(b) of the Regulations, an infiltration system designed to accommodate 1-112"
of rainfall will be required. Furthermore, runoff in excess of the design volume must flow overland through a
vegetative filter.
3. Impervious Surface Areas
On -site Buildings
On -site Streets
On -site Parking
On -site Sidewalk
Reserve for Future
Total
Drainage Area
Percent Impervious
4. Design Volume
= 43,568 sf161,037 sf
= 71.38 %
22,392 sf
11,762 sf
7,155 sf
2,259 sf
-0- S
43,568 sf
61,037 sf
In accordance with Section .1008(c)(1), the required design volume is computed as follows:
Using Schuler "Simple Method":
Rv = 0.05 + 0.009(I) where I = Percent Impervious (71.38%)
= 0.6924 in/in
Design Volume = Design Rainfall (1.5") x Rv x Drainage Area
= 1.5" x 0.6924 x 61,037 sf
= 63,393 in-sf or 5,282.8 cf

5. Storage Volume
The "Storage Area" is sized accommodate the Design Volume in a series of 60" HDPE pipes, 36" HDPE
manifold and 24" HDPE inlets drains:
By Pass Structures
24" HDPE Drains
36" HDPE Manifold
60" HDPE Pipe
12" HDPE Outlet
4' Diameter Wetwell
6. Infiltration Area
2 @ 20 cf/ea
40 cf
153 if @ 3.16 cf/If
483 cf
50.1 If @ 7.07 cf/If
354 cf
2201f @ 19.37 cf/If
4,261 cf
661f @ 0.78 cf/If
51 cf
7.66' depth @ 12.56 cf/vf
96 cf
Total Storage Volume 5,285 cf
Infiltration area is sized to accommodate actual storage volume (5,285 co pumped down in 2.0 days. Required
infiltration rate (and associated stormwater pumping rate) is computed as follows:
Infiltration (Pump) Rate = 5,285 cf / (2.0 day x 24 hr/day)
= 110.1 cf/hr (13.7 gpm)
Stormwater Pump Station shall be designed and adjusted to deliver 13.7 gpm to the infiltration system which is
sited upland from the Storage Area in order to comply with required separations from SHWT.
The Soil and Site Evaluation Report (copy attached) indicates that existing soils are clean, well graded, coarse
to medium sands with hydraulic conductivites ranging from 10-20 in/hr. Assuming conservatively that existing
soils have a minimum hydraulic conductivity of 8.0 in/hr, required infiltration area is computed as follows:
Req'd Infiltration Area = 110.1 cf/hr / (8.0 in/hr / 12 in/ft)
= 165.2 sf
Use ten (10) standard "Infiltrator" units which provides 177 sf surface area.

R
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.J-
INFl��TOR
,.Walali

-
1 4Y• iti; 1
r 1 �
Standard Infiltrator' Chamber
The Standard Infiltrator chamber is a low -profile unit with a 6-inch
sidewall for shallow placement.
Standard SideWinder Chamber
The Standard SideWinder chamber combines the shallow -placement advantages
of the Standard Infiltrator chamber with the revolutionary SideWinder sidewall.
g� -
rage Capacity . �n
ivered,SidewalllHeight�
Equalizer® 24 Chamberu
The Equalizer 24 chamber system is the optimal choice for narrow trenches
and utilizes SideWinder technology to maximize infiltrative area.
Contour" Wedge
The innovative Contour Wedge provides extra flexibility to accommodate natural terrain features
and to avoid obstacles. The 15' angled unit interlocks securely to chambers or other Contour
Wedges. Available in Standard and High Capacity models for left or right turns, it can be used
with Infiltrator and SideWinder chambers_

leir aChamber
a
i�
Ease of
Installation
Infiltrator chambers can be
delivered to the site in a pickup
truck and hand -carried into
position. For most jobs, two
people can install a system in
less than half the time it takes
for a comparable stone and
pipe leachfield.
.: Cost Savings
t,W yp„ No stone or geotextiie is
typically required, and cham-
istaflations use far less pipe. Because installations
ester with chambers, you save on heavy equipment
ition and eliminate the need for heavy trucks used to
)ort stone
It to Last
ide from PolyTuffTM, a proprietary blend of recycled
lyolefin resins
emical-resistant and UV -stable
werful arch design supports loads of 16,000 Ibs,
h 12 inches of compacted cover, equivalent to
AASHTO rating of H-10
products carry a limited warranty
Itrator Systems has a comprehensive quality -control
igram and is an ISO 9001: 2000 certified company
s Site Disruption
Infiltrator chambers typically occupy a smaller total
ran stone and pipe leachfields, and use less heavy
lent, there is less damage to landscaping. Elimination
e means cleanup at the job site is much easier too,
itor is flee numbeyone s±rpaleachfreldcham
ved in al150states; 45'slateswith_upt#o a 5C
i systems.instatled (and`countrng) andamore�.
.�. -:
United States 'an ��3�othe?,countrieess Ov Re',
t is an Intiltrator syste i,:.ylhfiltrat6t�bh� iMbe(s
fished history of', erformar,_ b and>reiiabrlity k
)tic system performance and.f3il�irraaratac:ch�
Superior Technology
M A solid top prevents infiltration of
rainwater and the intrusion of fines
■ MicroLeachingTM sidewall louvers
reduce fines intrusion and promote
sidewall leaching and evapotrans-
poration
■ An inspection port cutout permits
monitoring and maintenance
O Patented chamber interlocks with an advanced design
connect chambers end -to -end with a precise fit
Longevity and Reliability
Infiltrator chambers have a proven success rate, which
is better than stone and pipe, giving homeowners and
installers extra confidence.
Product Availability
Infiltrator Systems has an extensive network of distributors
throughout North America. These knowledgeable professionals
maintain inventories of our products and also provide contrac-
tors and installers with product delivery and +'installation support.
ti
Responsive Service $
Our technical staff and local sales representatives maintain
a strong presence where it counts, in the field. You will
also have the full assistance of our customer support team,
which can answer your product and ordering questions and
supply you with marketing materials.
Training and Education
We offer installer training and authorization classes and field
demonstrations to make installing Infiltrator chambers the most
efficient and effective solution for you and your customers.
tprrnt Theresare more tha
ro,milliot� chambers in=arc

INFILTRATION SITE VISIT REQUEST
Name of the Project :
Location (attach a clear vicinity map):AlC_ /14/--/ '_� o
Street address, SR number, community, etc. ,e
Directions from the nearest major intersection: 1'rort-7 IF? 1-L-Ger 1/C2_ o f AL 2-10
Cr
yr7//-1, 5!le-- a� /-G�i/il
Owner/Applicant Name: 16nv 2 Za �r�r /1vrY1
Consultant Name:C'-'�z.-!,7- C421" - EA&Me rx
Consultant Contact Information:
Phone, fax, email, etc.
Existing ground elev. @basin/trench=
SHWT elev.=
krzac. //. C-'T
#1 #2 #3 #4 #5 #6 #7 #8
SHWT plus 2' (max, bottom elev.)6///��
Date/Time of Soils Investigation .10
,63
Summa/ryl�Comme1n��: �!1 � - �,� v�cr�� , I y �`-•���
e" � C> 'f L/
All proposed infiltration areas and existing, active utility lines located within the proposed basin/trench
must be marked and flagged. If these areas are not flagged, the Soils Scientist reserves the right to
decline to do the investigation. If the proposed infiltration system will be located in an area of existing
pavement and there is no open area nearby, equipment capable of breaking through the impervious
layer must be provided. The soils investigation does not take the place of a soils report prepared by
an appropriate professional. The Soils Scientist will only verify the soil conditions that are reported in
the Soils Report, and make a determination as to the suitability of the site to meet the infiltration
design requirements under NCAC 2H.1000, and assumes no liability should the system fail.

ep 27 05 11:52a CrystalCoastEngineering
9 1 U-"3'25-0060 p.5
Cn`�Qa`u Gzl
TOPSAIL SOUND
Vicinity Map
NO SCALE

INFILTRATION TRENCH ANALYSIS
Filename: S:\WPDATAYWQG\|NTRENCH\050841
Project # SVV8050841
Project Name Live Oaks at Topsail
ReovngStream |CVVVV
Drainage Basin Cape Fear
Site Area 5.98 mcnwn
Impervious Area Calculation
Buildings
22392
Streets
11763
(]5PrkQ
7155
OS n|devvo|ke
2259
Total
Volume/Storage Calculation
If Rational Method is used, place a 1 in this box
Required
Provided
Design Storm
RV
Volume to Store
Date 28-Oot-05
Reviewer P.Eartlett
Classification SA'. HC)VV
Index # 18-87-(5.5)
Drainage Area 80,8843F
1.40 Acres
Rational Cc(list Cafter each BUA>
1
1
1
%|mpamious:
1.5 in
0.00
W83,!lCF
��
�+\.
04
71.4% |q)-o/ ��
^
Pipe Size Y
Pipe Size 2
Pipe Diameter
1.9
Paot
Length Of Single run of Pipe
81.25
Feet
Number ofPipe Runs inTrench
3
each
Storage In Piping
177
0 Cubic Feet
Total Storage in Piping
|
Cubic Feet
Cross -Sectional Area DfPipe Runs
5.671
0D00SF
Length OfTrench
31.25
Feet
Width [)fTrench
5.667
Feet
Height OfTrench
| 1|
Fee{
Cross -Sectional Area Of Trench
5.67
0.00 SF
Voids Volume, 4O%
Total Voids Volume
Total Volume Provided
/Tot.Vol. Provided from all StorageStructures)
Elevation OfBottom [fTrench
Elevation OfSHVVT
Overflow Elevation
Exffltra tion Rate /Dra wdown
Infiltration Pump Rate, Tot. VoiPnuv/2dayn~24hr/dey\
Reported Hydraulic Conductivity
Req'd.Infiltration Area =|nfi|trPump Rate/Hyd Cond
Provided Infiltration Area /8ottunn Surface Area)
Dnawdoxvn Time
25YEAR 34HOUR STORM NIA
Intensity, i=.33inches /hour
Qr=CiA=
Qp through the bottom of the basin=
0.34 CFG
O.8330CF8
CF
CF
Cubic Feet
5285
8.18 Mean Sea Level
7.16 Mean Sea Level
7.D2Mean Sea Level
1101 Cubic Feet Per Hour
0.87 Cubic Feet Per Hour Per Sq Ft
Square Feet
Square Feet '
hours
Must bo> Qr
1OYEAR 10MIN HIGH INTENSITY EVENT
|ntanohv. i=6.3inches /hour
Volume for 10yr. 10 min. event =
177 CF