20050949 Ver 2_More Info Received_20080912

v?MCKJTW&CREED
To: Ms. Annette Lucas
2321 Crabtree Blvd
Raleigh NC, 27604
ATTENTION: Ms. Annette Lucas
o5-ogL4 0? 4 2
LETTER OF TRANSMITTAL
DATE: September 12, 2008
PROJECT NO: 03403-0001 TASK NO: 1
RE: Partners Equity Subdivision
TRANSMITTAL NO: PAGE 1 OF 1
WE ARE SENDING: ? Originals ® Prints ? Shop Drawings ? Samples
? Specifications ? Calculations ? Other -
Quantity Drawing No. Rev. Description Status
5 Report and Plans for Partners Equity Stormwater Improvements G
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1. No Exceptions Taken 2. Make Corrections Noted 3. Other
4. Amend & Resubmit 5. Rejected - See Remarks
REMARKS:
Please feel free to contact us if you have any questions regarding the plans or our responses, 919-
233-8091.
cc:
SEP 12 2008
DENR - WATER UiJALI Y
WETLANDS AND STORMWATER BRANCH
S: \ 3403 - Partners Equity Group \ 0001 \ 10-Comm\ LOT_20080912.doc
Updated 2-15-07
200 MacKenan Cowt, Cary, NC 27511 919/233-8091 Fax [phone]
McKIM & CREED, PA
Signed
Jonathan Hinkle, EI
1 05 -EA49W2
v MCKIM&CREED ENGINEERS
1 v
S U R V E Y O R S
1 PLANNERS
1 September 12, 2008 M&C: 03403.0001 (40.48)
1
Annette Lucas
1 2321 Crabtree Blvd
Suite 250
Raleigh, NC 27604
1 RE: 401 DWQ certification Partners Equity Group Subdivision
1 Dear Ms. Lucas:
1 In response to your Request for Information (RFI) dated August 19th, 2008 for the
Partners Equity Group 401 WQ Certification application enclosed you will find
additional information related to your request. We have provided five (5) copies
of the supplemental information which your office has requested. The enclosed
documents should be considered supplemental to the original application and
where duplicate documents exist the most recent should be considered to replace
1 the prior version. Since the additional information involved some significant
changes to the project concept we have revised the project narrative for
additional information. Please do not hesitate to contact me if you have any
1 questions concerning these documents.
Sincerely,
1 McKIM & CREED, P.A.
1
1
Venture IV Building Jo than T. Smith PE, CPSWQ CPESC
Suite 500 cc: file
1 John Shallcross
1730 Varsity Drive
Raleigh, NC 27606
' 919.233.8091 SEF
1 2 2008
Fax [phone] WET Sr?r WATER OU4LIT .
AND STORMWATER BRAS{
1 wwvv.mckimcreed.cam
Partners Equity Group Subdivision
Stormwater Management Narrative
For NCDWQ 401 Certification
Introduction
The Partners Equity Group subdivision encompasses 45.3 acres of commercial lots and
associated transportation areas in Smithfield, NC. The subdivision is located to the
Northeast of the intersection of NCSR 2398 and Venture Drive. The drainage boundary
for the subdivision runs approximately along the perimeter of the project boundary. The
site drains generally to the Northeast and eventually into Buffalo creek, a tributary to the
Neuse River Basin.
' There are 19 commercial lots in Partners Equity subdivision. The majority of these lots
are currently occupied or are in various states of development. Two lots, however (Lots
18 and 19) have not been developed due to areas which have previously been classified
' as jurisdictional wetlands. This project involves the limited development of portions of
lots 18 & 19 resulting in impacts to 1.53 acres of wetlands.
It should be noted that proposed development on lots 18 and 19 has been minimized
and configured to retain a contiguous area of wetlands along the boundary of these two
lots and lots 10 and 11 to the east (see exhibits).
Project History
401 WQ certification was originally approved for the Partners Equity Subdivision (as
project # 970656) on February 11f, 1998. Extensive research and document tracking was
conducted in order to understand the project history and obtain original design
parameters. Unfortunately, due to the time which has elapsed since the original 401
certification permit was approved, a limited amount of the original application
documentation has been located. As a result, information regarding the existing
conditions of the stormwater management system is based principally on construction
drawings prepared in 1999 and supplemented by information provided in a series of
communications between the NCDWQ wetlands unit staff and McKim & Creed staff
between 1998 and 2001. We understand that at the time of original permitting the project
was required to meet the section 401 WQ certification requirements in place at that time.
To meet these needs a system of vegetated conveyances was designed to route
stormwater runoff from individual parcels and into the single large treatment pond at
the northeast corner of the project site. This pond was designed to meet both 401 WQ
requirements as well as Town of Smithfield stormwater management requirements. We
understand that 401 WQ certification requirements at that time included treatment and
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
removal of 85% of TSS. This performance standard was accomplished via the existing
stormwater wetpond.
Retrofitting the Existing Stormwater Management System
In the intervening years since the project was originally approved 401 WQ certification
requirements have changed significantly. We understand that current NC 401 WQ
certification rules require that projects located within NSW watersheds and resulting in
impacts to jurisdictional waters must be designed with stormwater BMPs which have
been shown to remove nitrogen from runoff with a removal efficiency of 30%.
Discussions with NCDWQ staff have revealed that any activities which result in impacts
to the remaining wetlands on the project site will require compliance with current NC
401 WQ certification regulations. Currently, the only stand alone BMP's which have
been approved to meet this standard per NCDENR BMP manual (NCDENR 2007) are
stormwater wetlands, bioretention areas, and wetponds used in conjunction with
forested filter strips (standard wet ponds without forested filter strips are credited with
25% removal of Nitrogen). Each of these BMP types have certain configuration
requirements related to dimensions, configuration, and other design parameters which
are necessary in order to be credited with 30% Nitrogen removal. As a result of the pre-
existing drainage network, configuration of existing development areas, and other site
conditions the use of these three pre-approved BMPs are not suitable for use in meeting
the requirement for the Partners Equity Group Subdivision.
Difficulties lie in modifying the existing drainage infrastructures and overall sizing since
' a significant portion of the subdivision is currently either built or under construction. In
addition a number of parcels within the subdivision have been sold and are no longer
owned or under the management of the applicant. The project site is not a suitable
candidate for bioretention due to concerns over high groundwater and difficulties in
retrofitting bioretention cells into existing drainage easements.
In addition the design team has taken every effort to look at methods of converting the
existing pond to a standard wetland design In order to get it up to the standard (30%
removal of Nitrogen) and found the available area insufficient to achieve this goal. The
' pond discharges directly into an existing conveyance channel with no opportunity to
utilize a forested filter strip.
' Where stand alone BMPs aren't suitable to meet pollutant reduction requirements, the
use of multiple hybrid BMPs can be used to enhance overall pollutant removal
' performance based on the performance of each BMP type. This improvement is a result
of the various treatment processes that each BMP uses to treat stormwater. We propose
that the existing drainage infrastructure with enhancement of existing facilities as
1
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
described below will be capable of obtaining and/or exceeding 30% reduction of
Nitrogen from stormwater runoff.
Existing project Area
Currently, stormwater runoff originating on the site is routed via open conveyances into
a manmade pond at the northeast corner of the 45.3 acre watershed. Local planning
regulations as administered by the Town of Smithfield Planning Department restrict
individual lot imperviousness to not greater than 70% (Embler 2008). Therefore the use
of 70% imperviousness as a runoff calculation input for individual lots would represent
the most conservative methodology for sizing of Stormwater BMP parameters.
Determinations of impervious percentages for lots which are already developed was
conducted using a grid method (min. grid points 200/lot). For lots which have not yet
been fully developed the maximum allowable of 70% was assumed. The resulting
design imperviousness for the project site was 61%. This imperviousness was used as an
input parameter for all water quality calculations. It should be noted that the use of 61%
imperviousness for calculation purposes does not indicate actual imperviousness of the
project area but only maximum future imperviousness allowed by local regulations as
existing lots are developed.
Pond Modifications
In order to achieve necessary Nitrogen removal, modification of the existing pond is
proposed. The proposed modifications include enlarging the pond size to exceed the
required sizing requirements. Based on the construction documents and other project
information as described above, the temporary water quality storage for the existing
pond is 147,247 cu ft. The required water quality volume (WQV) for the 45.3 ac
watershed ( @ 61 % imp) is approximately 98,498 cu ft as calculated using the Simple
Method detailed by NCDENR( 2007). By enlarging the existing pond as detailed below
the temporary storage volume will increase to 203,930 cu ft. and will exceed the required
by 107 %. Note that the required water quality volume calculation is based on the
maximum impervious limit for the entire 45.3 acre drainage basin (61% impervious).
However, BUA for each lot may be lower than this level.
Table 1: Wet Detention Basin Proposed Condition
Parameter Value Units
Watershed Area 45.3 Acres
% Impervious 61 n/a
Average Depth 4.13 ft
Required Surface Area (90% SA/DA) 57,855 S q. ft.
3

C

1
1

11

1
1

G

Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
Permanent Pond Elev 143 Ft
Permanent Pool Surface Area 60,792 S q. ft.
Permanent Pond Volume 251,333- Cu ft
Temporary Pool Elev 145.35 Ft
Temporary Pool Surface Area 103,225 S q. ft.
Temporary Pool Volume (includes Perm Vol) 455,263 Cu ft
Temporary Water Quality Stora e(WQS) 203,930 Cu ft
Required Water Quality Volume** (WQV) 98,498 Cu ft
Excess WQ storage 105,502 Cu. Ft.
Littoral Shelf Vegetated Area 17,599 S q. ft
- Does not include sediment storage of 1' on bottom of pond.
** Per NCDENR design guidelines, R/O from 1" rainfall see design calculations.
At the time of construction of the wet detention basin, littoral shelf design standards
were poorly developed with guidelines generally suggesting water depths ranging from
0-12" and no guidance on required planting soil. Subsequent research and anecdotal
experience has indicated that wetland plants do not survive well where normal depths
exceed 6" and planted in poor subsoil conditions. The littoral shelf at the Partners Equity
likewise exhibits poor vegetation on the basin edges (Fig 1-2). In order to improve the
function of the wet detention basin so that it can attain maximum pollutant removal we
propose to improve the existing littoral shelf by raising the bottom elevation of the
littoral shelf so that it ranges from 142.5' to 143.5'. The soil to be used in raising this
elevation will be of sufficient quality to ensure vegetation growth. In addition, obligate
wetland species will be planted in the submerged portion of the improved littoral shelf
on a spacing of 3' and a wetland planting mix will be applied to the non submerged
portion of the aquatic shelf. Enhancement of the littoral shelf in this fashion will result in
a wet detention pond which satisfies littoral shelf design parameters to achieve 25%
nitrogen removal efficiency as detailed by the current NCDENR BMP design manual.
After enhancement activities, littoral shelf area will be approximately 17,599 sq ft. Due to
the unique configuration of the pond establishment of the littoral shelf results in a
considerable portion of the total pond area in a vegetated state. As a result the proposed
pond relies heavily on wetland removal processes to accomplish Nitrogen pollutant
removal. We propose that the wet pond system be considered as a wetland/wet pond
hybrid and have utilized the wetland supplement form in this documentation.
Pollutant Removal Performance
Currently wet ponds are credited with removing 25% of Nitrogen from stormwater
runoff by NCENR. Other agencies and organizations credit wet ponds with higher
removal efficiencies. Specifically "Urban Stormwater Retrofit Practices", which is
4
1

i

Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
manual #3 of the urban watershed restoration series by the Center for Watershed
Protection (2007) which provides guidance on retrofitting stormwater BMPs in
developed areas. This manual uses the latest BMP performance data from the mid-
atlantic region which credits wetponds with TN removal of 30%. The manual also
provides a methodology for obtaining additional pollutant removal for various BMP
types through the use of designs which exceed standard parameters. Wetponds for
instance are credited with TN removal of up to 40% if certain additional design
parameters are met. The method utilizes a design point process whereby a particular
proposed retrofit achieves "points" for specific design components. Points are then
tallied and used in conjunction with an adjustment equation which relates design points
to median, high and low removal percentages for specific pollutants. High and low
pollutant removal efficiencies are not available readily for NC. Therefore the standard N
removal efficiency was adjusted proportionately to the high and low removal
efficiencies as reported by CWP in order to obtain high and low removal efficiencies for
use in the design point method.
Table 2 Nitrogen removal rates used in the design point method
CWP NC Standards
High 40% 33%*
Medium 30% 25%
Low 15% 12.5%**
* High efficiency is exceeds median by 33% (matches CWP ratio)
** Low efficiency is 50% lower than Median (matches CWP ratio)

Other Stormwater Infrastructure
As mentioned previously, stormwater runoff originating in the 45.3 acre commercial
development is routed to the wet detention pond via an extensive network of open
conveyances periodically interrupted by driveway and road crossing culverts. This
' drainage network originates as shallow grassed swales (See fig 3-7). These headwater
swales primarily occur between adjacent lots and exhibit slopes of less than 0.5 % and
side slopes of 3:1-5:1. These swales feed into collector swales which generally occur
adjacent to and on either side of North Equity and South Equity Drives (figs 8-12). These
swales are slightly deeper than the headwater swales and are dominated by grassed
vegetation. Some of these collector swales exhibit dense natural vegetation.

Collector swales from the majority of the watershed flow into one of two cross-
connection connection "wet swales" which convey runoff from South Equity drive across the center
10
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These "wet swales" are generally deeper than upstream conveyances and are dominated
' by cat-tails, rushes, and other diverse vegetation. These swales were originally designed

Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
to provide additional flood control storage during large storm events. Observed
standing water within these swales is estimated to range from 0-6". Similar to the
grassed swales described earlier these connector swales were not originally intended to
provide a water quality function. However, the low slope and presence of water have
lead to the conditions which mimic a stormwater wetland. The location of the connector
and cross-connection swales is shown on conceptual plan sheet 2. Additional
information concerning the drainage network is detailed in the table below.
Table 3: Drainage Conveyance System: Existing Condition
Parameter Headwater Swale Connector Swale Cross-connection
Swale (Wet Swale)
Cumulative Length Unknown 5700 1000
(ft)
Elevation Range (ft) 146+ 145-146 144-145
Typical Shape Triangular/Parabolic Parabolic/ Trapezoidal
Trapezoidal
Side slopes 3:1 + 3:1+ 2:1-3:1
Typical Width (ft) n/a 0-2 4-6
Slope (ft/ft) n/a 0-0.02 0-.001
Estimated Bottom n/a n/a 5000
Area (s ft)
Typical Vegetation Grassed, Bare, Grassed Misc vegetation:
Cattails cattails, rush, wax
myrtle
As shown in Table 2, swale elevations range from 143' to 147'. As mentioned previously
' during precipitation events the water level in the wet detention pond varies from
permanent pool elevation (143') up to as high as 147' (during flood control events). As a
result of the low slope and elevation of the swale system, portions of the swale system
' are inundated during larger events. This inundation of the wet swales and portions of
the connector swales limits velocity of flow during larger events. During runoff caused
by rainfall up to and including the water quality storm (1" rainfall) inundation of the
open conveyances is limited to the wet swales.
Grassed Swales are currently an approved Stormwater BMP for use in North Carolina
(NCDENR 1999). When designed per required guidelines, swales are considered to
remove 20% of Nitrogen originating from urban areas. They depend on infiltration,
physical filtration by vegetation and adsorption to soil particles for pollutant reduction.
As a result, water quality treatment is enhanced by vigorous vegetation and slow
velocities. Current design guidelines require that grassed swales provide 100 linear feet
' 6
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
of conveyance for each acre of development. Although the total length of headwater
swales is unknown, linear swale length of all connector swales is approximately 5700' or
111' per acre of development. As a result, the length of connector swales within the
development exceeds that required to achieve 20% nitrogen removal credit by 11%.
Wet swales are an additional BMP type that combines the conveyance function of a
swale with the improved pollutant removal function of stormwater wetlands. Wet
swales, however, are not currently an accepted stormwater BMP in North Carolina.
Some states and regions have accepted wet swales as pollutant removal structures. Yet
there are only a few monitoring studies available for review in which wet swales were
studied to determine pollutant removal (Strecker, 2003). Clayton and Schueler reviewed
2 monitoring studies and estimated TN removal associated with Wet swales of 40%
(1996). Other reviewers have noticed similar removal efficiencies. Generally pollutant
removal is believed to be enhanced by introduction of standard pollutant removal
mechanisms into the wet swales including; temporary storage of runoff, diversity of
species, and reduced velocity. Although design standards for wet swales vary widely,
the design standards typically require that velocities are limited to less than 2 fps. This
standard is very similar to accepted design standards for standard stormwater wetlands
in North Carolina. Similarly the wet swales in the cross-connection ditches at Partners
Equity resemble wetlands in many ways. There are many different design guidelines for
wetlands including volume capture, depth/area, and surface area/ watershed area ration.
Schueler suggests that shallow marsh wetlands should be sized so that wetland area is at
least 2% of watershed area to provide sufficient treatment (Schueler, 1992). Sufficient
treatment however is not defined in terms of nitrogen removal. Other research in North
Carolina found that a shallow marsh wetland of 0.4 % of watershed area without a
temporary storage component removed 20% of total nitrogen (Bass, 2000). Little
information is available on wetlands with smaller area/watershed ration. The cross-
connection "wet swales" at Partners Equity fall somewhat between exhibiting wet swale
and shallow marsh wetland characteristics. While we have not incorporated any
removal credit for the vegetated swales on the Partners Equity project as part of the
nitrogen removal estimate, it should be noted that pollutant removal mechanisms are
inherent to their operation and function.
Maintenance of Stormwater System
All existing and proposed stormwater components discussed above are contained
within existing drainage and utility easements. The easement surrounding the
stormwater pond is held by the applicant (see exhibits) and an Operation and
Maintenance agreement was submitted during the original 401 WQ certification. The
7

Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
swales and other conveyances on-site have been dedicated to the Town of Smithfield
and are maintained by the town.
Vegetated Conveyances

Sediment and Erosion Control
Measures will be taken to ensure that no sediment will leave the site during
construction. All exposed surfaces will be seeded after final grades are established. The
following practices will be implemented on this site:
N 1. Temporary and Permanent Seeding
Temporary and permanent seeding will be used to establish a dense and
vi
orous ground cover in exposed soil areas
.
g
2. Sediment Basin
During construction activities the existing wet detention facility will act as a
large sediment basin for these construction activities. Upon project completion
accumulated sediment will then be removed from the BMP facility.
3. Outlet Stabilization Structure
Outlet stabilization will be installed on the downstream end of the proposed
driveway culvert to reduce the flow velocity and to dissipate energy
Summary
This project involves an impact to jurisdictional waters of 1.53 acres. In order to comply
with existing 401 WQ certification rules the stormwater management system for the
project site must be designed to remove 30% or nitrogen from stormwater runoff. Due to
the existing condition of the existing development including infrastructure and multiple
owners standard BMP stormwater management approaches are not suitable. A system
of stormwater management is proposed using a modified wet pond to address the 30%
N reduction requirement and augment by existing vegetated conveyances..
As stated previously wet detention basins are "credited" by NCDENR to achieve 25%
reduction of nitrogen runoff when designed to current NCDWQ standards. The existing
' pond will be enhanced by expanding the pond to the 90% TSS standard resulting in a
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
temporary storage volume which exceeds the standard by 107 %. This will result in
approximately 28 % of the pond surface being vegetated by wetland vegetation. As a
result of these improvements we believe that total nitrogen removal efficiency for the
enhanced stormwater management system will exceed the required 30% reduction of
nitrogen in stormwater runoff.
The resulting stormwater management system will rely heavily on multiple pollutant
removal mechanisms including physical filtration, plant uptake, and microbial
nitrification and denitrification. The system will be comprised of a diverse natural
system including; deep water, emergent aquatic wetlands, shallow land wetlands
habitats, and dense vegetation conveyance swales.
1
I References
Bass, K. L., 2000. Evaluation of Small In-Stream Constructed wetland in North Carolina's
Coastal Plain. Masters Thesis: North Carolina State University, Raleigh, NC
Center for Watershed Protection,2007, Urban Stormwater Retrofit Practices, Ellicott City
MD.
Embler, Paul, 2008, Personal Communication.
NCDENR, 2007, NC Stormwater BMP Manual. North Carolina Department of
Environment and Natural Resources, Raleigh, NC.
NCDENR, 1999, Stormwater Best Management Practices, N.C. Department of
Environment and Natural Resources, Raleigh, NC.
Schueler, T. R. , 1992, Design of Stormwater Wetland Systems: guidelines for creating
diverse and effective stormwater wetlands in the mid-Atlantic region. Anacostia
Restoration tea,,. Metropolitan Washington Council of Governments., Washington, DC.
Strecker, E. W., Quiqley, M. M., and Urbonas B., "A Reassessment of the
Expanded EPA/ ASCE National BMP Database." InTroceedings of the World
Water and Environmental Congress 2003, June 23-26, 2003, Philidelphia, PA
Edited by Paul Bizier and Paul DeBarry, ISBN 0-7844-0685-5, ASCE, Reston, Va.

1!

Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
Representative Photo's from Project Site
zr,
'F/r ..
' 1) View of outlet structure from west bank of pond January 2007

10
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
c
lob
kW
2) View of southeast corner of pond from west bank January 2007
11

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Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
{
FN Y n??1i wyi, 'T S 9 T#? {yE fC • + f (' i'3.VP?R v; ?Fr'a',r '+1'{ ,
§ y,. ?# S'}g..'?` 14?. ?i w,a ? i • Xya' +?'ra1"?? zl..? ?`.% ? a. tt rl J a ?yY s?`?"t
tae" X
3) View of existing "feeder swale" between Lot 2 and 3 looking west. January 2007
12
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
1 4) View of existing feeder swale between lots 2 and 3 looking west. June 2007
13
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
5) View of junction of "feeder" swale and connector swale along South Equity Drive looking
northwest. June 2007
14
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
17) View of "feeder swale" between Lots 3 and 4 looking west from South Equity drive January
2007
15
6) View of perimeter "feeder" swale along northwest corner of project site looking east.
January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
8) View of Road swale along West side of South Equity drive looking south January 2007
;a
01
9) View of road swale along west side of South equity drive looking south January 2007
16

Partners Equity Group Subdivision
' Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
17
10) View of Connector swale along south Equity Drive looking north. June 2007

Partners Equity Group Subdivision
t Stormwater Management Narrative
Proposed Stormwater SMP Retrofits
July, 2008 (Rev Sept, 2008)
12) View of "Cross connection wet swale" between lots 15 and 16 looking east January 2007
18
11) View of road swale on East side of North Equity Drive looking south January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)
19
13) View of Cross-connection swale between lots 15 and 16 looking east. June 2007
14) View of Cross-connection "Wet Swale" Between 16 and 17 looking east January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Sept, 2008)

WN, z _: 0, ?k ti/ r y
_
15) View of Cross-connection swale between lots 16 and 17 looking east June 2007
20
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11

1

Permit No.
(to be provided by DWQ)
Ad? o??F W A T?c9OG
y v
NCDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information.
L PROJECT INFORMATION
Project name Partners Equity Subdivison Stormwater Management
Contact person Jonathan Smith
Phone number 919-233-8091
Date 911212008
Drainage area number Wet Pond
11. DESIGN INFORMATION
Site Characteristics
Drainage area 1,973,268.00 ftz
Impervious area 1,203,693.48 ft2
% impervious 61.00 %
Design rainfall depth 1.00 in
Storage Volume: Non-SR Waters
Minimum volume required 98,499.00 if
Volume provided 203,930.00 ft3
Storage Volume: SR Waters
1-yr, 24-hr runoff depth in
Pre-development 1-yr, 24-hr runoff ft 3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required ft3
Volume provided ft3
Peak Flow Calculations
1-yr, 24-hr rainfall depth 3.20 in
Rational C, pre-development 0.20 (unitless)
Rational C, post-development 0.78 (unitless)
Rainfall intensity: 1 -yr, 24-hr storm 2.75 in/hr
Pre-development 1-yr, 24-hr peak flow 24.90 ft3/sec
Post-development 1-yr, 24-hr peak flow 94.60 ft3/sec
Pre/Post 1-yr, 24-hr peak flow control 69.70 ft3/sec
Basin Elevations
Basin bottom elevation 135.00 ft
Sediment cleanout elevation 137.00 ft
Bottom of shelf elevation 142.50 ft
Permanent pool elevation 143.00 ft
SHWT elevation 146.50 ft
Top of shelf elevation 143.50 ft
Temporary pool elevation 145.35 ft
Form SW401-Wet Detention Basin-Rev.4
Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
II. DESIGN INFORMATION
' Volume and Surface Area Calculations
SA/DA ratio 2.93 (unitless)
Surface area at the bottom of shelf 50,416.00 fe
Volume at the bottom of shelf 223,531.00 ft3
' Permanent pool, surface area required 57,892.00 ff
Permanent pool, surface area provided 60,792.00 fe OK
Permanent pool volume
Average depth for SA/DA tables 251,333.00
4.13 ft3
ft
OK
Surface area at the top of shelf 68,015.00 fe
Volume at the top of shelf 304,140.00 ft3
Forebay volume 38,024.00 ft3
Forebay % of permanent pool volume 15.13 % Must be approx. 20%, Adjust pond dimensions
Temporary pool, surface area provided 103,225.00 fe
Drawdown Calculations
Treatment volume drawdown time
2.71
days
OK
Treatment volume discharge rate 0.79 ft3/s
Pre-development 1-yr, 24-hr discharge 24.90 ft3/s OK
' Post-development 1-yr, 24-hr discharge 21.80 ft3/s OK
Additional Information
Diameter of orifice 6 in
Design TSS removal 90 %
' Basin side slopes 3.00 :1 OK
Vegetated shelf slope 10.00 :1 OK
Vegetated shelf width 10.00 ft OK
Length of flowpath to width ratio 3.87 :1 OK
Length to width ratio 2.49 :1 OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1.17 ft OK
' Vegetated filter provided? N (Y or N) Design must be based on 90% TSS removal
Recorded drainage easement provided? N (Y or N) Need a recorded drainage easement
Capures all runoff at ultimate build-out? Y (Y or N) OK
Drain mechanism for maintenance or emergencies

Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2

1
1
1
1
1
1
1
1
Permit No.
(to be provided by DWQ)
Ill. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Pagel Plan
I ' Sheet No.
C. I
Plans (1" - 50' or larger) of the entire site showing:
Design at ultimate build-out,
Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
Basin dimensions,
Pretreatment system,
High flow bypass system,
Maintenance access,
Proposed drainage easement and public right of way (ROW),
Overflow device, and
Boundaries of drainage easement.
2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing:
Outlet structure with trash rack or similar,
Maintenance access,
Permanent pool dimensions,
Forebay and main pond with hardened emergency spillway,
Basin cross-section,
Vegetation specification for planting shelf, and
Filter strip.
3. Section view of the dry detention basin (1" = 20' or larger) showing:
Side slopes, 3:1 or lower,
Pretreatment and treatment areas, and
Inlet and outlet structures.
101 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin.
n? ix 5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
_ 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
Aolpend;A 7. The supporting calculations.
P•sv.euSlY
Svbrn: h1ed 8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
(,5 9. A copy of the deed restrictions (if required). Qv.,:?+"
,?a_ L45e rv%e^+
10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County
soil maps are not an acceptable source of soils information.
I Form SW401-Wet Detention Basin-Rev.4 Part III. Required Items Checklist, Page 1 of 1
4
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Project:
t N
P Partners Equity Stormwater Improvements
3403
0001 v
MC M&CREED
rojec
o.: - v?
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 9/11/2008
Reviewer: JTS Date: 8111/2008

Objective: Determine Water Quality Volume (WQV) using Sim ple Method
AL

WQv = P * Rv * A =
_ ?.
12

Rv = 0.05 + 0.009 la
``
?
'
Its
Given: Find:
Rainfall depth 1 in Rv 0.599 in
Wtrshd Area 45.3 ac WQv 98,499 cu ft
Impervious % 61 %
* Conservative estimate based on maximum built upon area per Tow n of Smithfield requirements.
Objective: Given current Water Quality Storage (WQS) volume, Find Rainfall equivalent (Simple Method)
Given: Find:
Perm Pond Vol 89,394 cu ft Temp WQS 147,247 cu ft
Temp Pond Vol 281,569 cu ft Rain equiv 1.49 in
Findings: Existing pond conditions provide enough temporary storage to meet NCDENR design guidelines
(runoff from 1" rainfall). Temporary WQS is equivalent to runoff associated with a 1.17" rainfall.

l

1

1
1

C.
1

Project: Partners Equity Stormwater Improvements
Project No. 3403-0001
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 7/16/2008
Reviewer: JTS Date: 7/16/2008
v' MCKIM&CREED
Objective: Determine the SCS Curve Number for the project site. Based on computed impervious percentages
from GRID method calculations.
Curve Number Calculation
SCS Method
Impervious Percentage 61%
Landuse Soil Group RCN Area Product of RCN
Commercial B 83.3 11.9 992.42787
Commercial C 89.4 11.2 1004.35536
Commercial D 89.4 22.2 1980.36198

Totals 45.3 3977.1
Total (Weighted) Curve Number 87.80
=Total Product/Total Area
Estimated Curve Number 88
CN Interpolation from TR55 suggested curve numbers tet t #I

Soil Group
f
0-11
S
B C D
0
..
72% 88 91 93
w
`
EAL
65% 85 90 92 02652
Interpolation for 61% Imperious ??b±11?1•??4
61% 83.3 89.4 91.4

11

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1
1
1
1

Project: Partners Equity Stormwater Improvements M&
Project No.: 3403-0001 v? McIQM&CREED
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 7/16/2008
Reviewer: JTS Date: 7/16/2008
Objective: Determine the Time of Concentration for the project site
Time of Concentration Calculation
SCS Segmental Method
Tc to Wet Pond
Sheet Flow
1. Surface description (Table 3-1)
2. Manning's roughness coeff., n (Table 3-1)
3. Flow length, L (Total < 300 ft)
4. Two-year 24-hour rainfall, P
5. Land slope, S T
6. Travel time, T t
Shallow Concentrated Flow
7. Surface description (Paved or Unpaved)
8. Flow length, L
9. Watercourse slope, S
10. Average velocity, (Figure 3-1) V
11.Travel time, T t V.
Storm Culvert Channel Flow
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R =
15. Channel slope, S S
16. Manning's roughness coeff., n
17. Channel velocity, V
Segment ID AB
dns grass
Hi Pt 154 0.240
Lo Pt 150 ft 40
in 3.7
= 0.007(nL)- ft/ft 0,100
P -SO' hr 0.06
Segment ID BC
Paved
Hi Pt 0 ft 0
Lo Pt 0 ft/ft ODIV/0!
=2o.32s2(s)°' ft/sec #DIV/0!
= 16.1345(s)°_s hr. 0.00
Segment ID CD
ft^2 6.28
ft 12.56
ft 0.5
N/A ft/ft 0.0023
0.0013
ft/sec =
34.6
18. Flow length, L V = 1.4982"a1/2 ft 84
19.Travel time, T t n hr 0.00
Drainage Channels
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R=
15. Channel slope, S S=N/A
16. Manning's roughness coeff., n
17. Channel velocity, V
18. Flow length, L V = 1.49R-771 I
19.Travel time, T t n
Connector Channels
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R=
15. Channel slope, S S=N/A
16. Manning's roughness coeff., n
17. Channel velocity, V
18. Flow length, L V = 1.498
19.Travel time, T t n
Time of Concentration =
Segment ID
ft^2
Segment ID
Lag Time = (0.6)(Tc) = 12 min
t AL
02M
AN \\
IsItI114110,
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20 min
Project: Partners Equity Stormwater Improvements
' Project No.: 3403-0001
Client: Partners Equity Group v? McKIM&CREED
Location: Smithfield, NC
Designer: JDH Date: 9/9/2008
Reviewer: JTS Date:
Objective: Determine the SADA Ratio's for this site designed for 90% TSS removal.
' Taken from SADA Table 10-4 of 2007 NC Stormwater BMP Design Guide
Permanent Pool Average Depth
3.0 3.5 4.0 4.5 5.0
0 50% 3.0 2.8 2.5 2.3 2.0
60% 3.5 3.2 2.8 2.7 2.5
a, 70% 4.0 3.7 3.3 3.1 2.8
80% 4.5 4.1 3.8 3.5 3.3
Drainage Area 45.3 acres
' Impervious Percentage 61%
Interpolation of published SADA Ratio in order to compute SADA ratio for 61% Impervious.
Permanent Pool Average Depth
3.0 3.5 4.0 4.5 5.0
Impervious % 61% 3.56 3.28 2.93 2.75 2.49
r Calculation of required surface area for various permanent pool depths.
Permanent Pool Average Depth
3.0 3.5 4.0 4.5 5.0
Surface Area 70,271 64,798 57,892 54,243 49,161
Design Check
' Interpolation of computed average permanent pool depth to determine SADA Ratio
Design Average Depth 4.13 ft
Assumed SADA Ratio at 4.0' ft average
depth. 2.93
From computed SADA ratio the following design requirement were computed.
Required Permanent Pool SA 57,892 sqft
Design Permanent Pool SA 60,792 sqft
' Design Pond Volume 239,343 cuft
Forebay Required Volume 47,869 cuft
Forebay Design Volume 38,024 cuft
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Project: Partners Equity Stormwater Improvements
Project No.: 3403-0001 v, McKIM&CREED
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 9/9/2008
Reviewer: JTS Date:
Objective: Runoff Routing through wet pond structure for the I year rainfall event
1 Year Calcs for Wet Pond
Watershed Description
Area 45 acres Inputs
Hydraulic L 1... If, Time of Concentration Outputs
D elev. 9 it Tc „„,; min
Rainfall Data Rainfall Data
F1%, P 3.2 -1 g 108 m G & H Values obtained from Johnston County
k i 2.75 in/hr h 19 Wbx Stormwater Design Manual
Pre
CN 60
Rational C 0.2
Rational Equat on
Qp' 24.9cfs
Time to Peak
Tp t 3239°. ,in
NRCS Curve Number Method
S 6.67
Rational Equation
Qp 9416 cfs
Time to Peak
Tp 41.6 min
Ks 3252.402662
Stale-Storage Relationship b 2.114539184
(ft) ([t') (ft? (ft) (ft) (ft)
Description Countour Elev Couutour Aro: Incr Vol Accmn Vol Stale In S In Z Z est
bottom 135 19,392 --- 0 0 --- --- 0.000
136 21,820 20606 20606 1 9.9333 0.0000 2.394
137 25,536 23678 44234 2 10.6934 0.6931 3.438
138 28,637 27086.5 71370.5 3 11.1756 1.0986 4.309
139 31,935 302,86 101656.5 4 11.5294 1.3863 5.093
140 36,326 34130.5 135787 5 11.8188 1.6094 5.840
141 41,930 39128 174915 6 110721 1.7913 6.583
142 47,537 44733.5 219648.5 7 12.2998 1.9459 7.332
142.5 50,416 24488.1825 244136.6825 7.5 12.4055 10149 2708
143 60,792 27801.9325 271938.615 8 12.5133 2.0794 8.111
143.5 68,015 32201.75 304140.365 8.5 12.6252 2.1401 8.552
144 70,762 34694.25 338334.615 9 12.7333 2.1972 9.000
145 98,355 84558.5 423393.115 10 12.9561 2.3026 10.000
shelfbottom 146 115,617 106986 530379.115 11 13.1313 2.3979 11.124
nel pool 147 137,611 126614 656993.115 12 13.3954 2.4-949 12.310
Wei
Length 25
Elevation 145.35
Cw 3.0
Storage Below 455339.9
Orifice
t Radius 6 in Peak Pre-Inflow 24.9
t Center Elev. 10125 ft Peak Weir Flow 21.8
Cd 0.60 Max WSE 145.79
t3 Storage Below 281891.75 ft3
PRE POST
Time Inflow Inflow Storage Vol. Stage WSE Orifice Ou Weir Out
(min) tWls) (fN/s) (fN) (ft) (ft) (ft3/s) (fNls)
v.ov v.w cos .o u.oi u.uu
0.02 0.00 0.00 264132.85 8.00 143.00 0.67 0.00
0.04 0.00 0.00 264132.05 8.00 143.00 0.67 0.00
0.06 0.00 0.00 264131.25 8.00 143.00 0.67 0.00
0.08 0.00 0.00 264130.45 8.00 143.00 0.67 0.00
0.1 0.00 0.00 264129.65 8.00 143.00 0.67 0.00
0.12 0.00 0.00 264128.85 8.00 14100 0.67 0.00
0.14 0.00 0.00 264128.05 8.00 143.00 0.67 0.00
0.16 0.00 0.00 264127.25 8.00 143.00 0.67 0.00
0.18 0.00 0.00 264126.45 8.00 143.00 0.67 0.00
0.2 0.00 0.01 264125.65 8.00 143.00 0.67 0.00
Cl -r?,v
WSE (ft)
? ? ? ?
of
C
NO
fd.?
C
0
a
m
r
w
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L
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00 000 (D O O O O
(S.IO) MOB j
Project: Partners Equity Stormwater Improvements
Project No. 3403-0001 v! McKIMCREED
Client: Partners Equity Group
Location: Smithfield,NC
Designer: JDH Date: 9/9/2008
Reviewer: JTS Date:
Objective: Runoff Routing through wet pond structure for the 10 year rainfall event
10 Year Calcs for Wet Pond
i
i
W
h
d D
aters
e
es
Area cr
pt on
45
acres
Hydraulic L 600 It
A elev. 9 ft
Rainfall Data
24 hr. P 5.8 in
peak i 4.73 in/hr
Inputs
Time of Concentration Outputs
Tc 204 min
Rainfall Data
g 205 in G & H Values obtained from Johnston County
h 23 in/hr Stormwater Design Manual
Prc
CN 60
Rational C 0.2
Rational Equation
Qp(. 42.9 cfs
Time to Peak
Tp 82.40 min
MRCS Curve Number Method
S 6.67
Q 1.79 in
Qcot 294677 W
n ,.w
n
3
Y
V S
Div
?dEeettetittt??'°6
Rational Equation
Qp _.... cfs
Time to Peak
Tp 53.6 min
NRCS Curve Number Method
Ks 3252.402662
Stage-Storage Relationship b 2.114539434
(ft) (ft2) (ft3) (ft (ft) (ft)
Description Countour Elev Countour Are Ina Vol Accum Vol stage In S In Z Z est
bottom 135.0 19,392 - 0 0 --- --- 0.000
136.0 21,820 20606 20606 1 9.9333 0.0000 2.394
137.0 25,536 23678 44284 2 10.6984 0.6931 3.433
138.0 28,637 27086.5 713705 3 11.1756 1.0986 4.309
139.0 31,935 30286 101656.5 4 11.5294 1.3863 5.093
140.0 36,326 34130.5 135737 5 11.8188 1.6094 5.840
141.0 41,930 39129 174915 6 12.0721 1.7918 6.583
142.0 47,537 44733.5 219643.5 7 12.2998 1.9459 7.332
142.5 50,416 24488.1325 244136.6825 7.5 12.4055 2.0149 7.708
143.0 60,792 27801.9325 271938.615 8 12.5133 2.0794 8.111
143.5 68,015 32201.75 304140.365 8.5 12.6252 2.1401 8.552
144.0 70,762 34694.25 338834.615 9 12.7333 2.1972 9.000
145.0 98,355 84553.5 423393.115 10 12.9561 23026 10.000
146.0 115,617 106986 530379.115 11 13.1813 2.3979 11.124
shelfbottom 147.0 137,611 126614 656993.115 ]2 13.3954 2.4349 12.310
Weir
Length 25 It
Elevation 145.35 ft
Cw 3
Storage Below 455339.9 W
Orifice
Radius 3 in Peak Pre-Inflow 42.88
Center Elev. 143.25 ft Peak Weir Row 112.69
Cd 0.6 Max WSE 146.66
Storage Below 281891.75 ft'
PRE POST
Time Inflow Inflow Storage Vol. Stage WSE Orifice Ou Weir Out
(min) VV/s) UP/s) (W) (ft) (ft) (fN/s) (fN/s)
u.uu -o
0.02 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.04 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.06 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.08 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.1 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.12 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.14 0.00 0.00 264133.66 8.00 143.00 0.00 0.00
0.16 0.00 0.00 264133.67 8.00 143.00 0.00 0.00
0.18 0.00 0.00 264133.67 8.00 143.00 0.00 0.00
0.2 0.00 U1 264133.68 8.00 143.00 0.00 0.00
WSE (FT)
of
C
O
C
aO
a?
0
r

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C
W
0
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(S??) MO??
Project: Partners Equity Stormwater Improvements
MCKIM&CREED
_
Project No.: 3403-0001 M
Client: Partners Equity Group = O
26
Location:
Designer: Smithfield, NC
JDH Date: 9/8/2008 •
rf?,•e??
?
"J.,
Reviewer: JTS Date: f
?' (?
IJ?? ;•••• ?? !??
`
?
Objective: Determine the 1" runoff drawdown time for the wet pond structure. ;` \ ??
?
0F), Ii •
Drawdown for Wet Pond
Ks 3252.40 DWQ Method (1/3 Driving Head)
b 2.11 Permanent Pool Volume 281,891.75 cu ft
Zo 0.00 ft Temporary Pool Volume 364,062.46 cu ft
Bottom Elevation
Initial Stage, Zi 135.00
9.31 ft
ft Driving Head 1.31 ft
Orifice Size 6.00 in
Initial Elevation 144.31 ft Qorifice 0.62 cfs

D-Egiv orifice
6.0
in Draw Down 1.52 days
No. orifices 1
Cd 0.6
Invert
Invert Elevation 0.00
143.00 ft
ft
1 0 360489.09 9.27 144.27 0.95
2 0 357061.25 9.23 144.23 0.93
3 0 353704.52 9.18 144.18 0.91
4 0 350419.28 9.14 144.14 0.89
5 0 347205.90 9.10 144.10 0.87
6 0 344064.75 9.07 144.07 0.85
7 0 340996.21 9.03 144.03 0.83
8 0 338000.65 8.99 143.99 0.81
9 0 335078.43 8.95 143.95 0.79
10 0 332229.94 8.92 143.92 0.77
11 0 329455.52 8.88 143.88 075
12 0 326755.54 8.85 143.85 0.73
13 0 324130.36 8.81 143.81 0.71
14 0 321580.34 8.78 143.78 0.69
15 0 319105.84 8.75 143.75 0.67
16 0 316707.20 8.72 143.72 0.65
17 0 314384.77 8.69 143.69 0.62
18 0 312138.91 8.66 143.66 0.60
19 0 309969.94 8.63 143.63 0.58
20 0 307878.23 8.60 143.60 0.56
21 0 305864.09 8.57 143.57 0.54
22 0 303927.88 8.55 143.55 0.52
23 0 302069.92 8.52 143.52 0.49
24 0 300290.55 8.50 143.50 0.47
25 0 298590.10 8.48 143.48 0.44
26 0 296998.77 8.46 143.46 0.41
27 0 295513.16 8.44 143.44 0.39
28 0 29412432 8.42 143.42 036
29 0 292824.16 8.40 143.40 0.34
30 0 291605.44 8.38 143.38 0.32
31 0 290461.61 8.37 143.37 0.30
32 0 289386.77 8.35 143.35 0.28
33 0 288375.55 8.34 143.34 0.26
34 0 287423.12 8.33 143.33 0.25
35 0 286525.06 8.31 143.31 0.24
36 0 285677.37 8.30 143.30 0.22
37 0 284876.40 829 143.29 0.21
38 0 284118.83 818 143.28 0.20
39 0 283401.61 8.27 143.27 0.19
40 0 282721.96 8.26 143.26 0.18
41 0 282077.34 8.25 143.25 0.17
42 0 281465.39 8.24 143.24 0.16
43 0 280883.96 8.24 143.24 0.15
44 0 280331.10 8.23 143.23 0.15
45 0 279804.96 8.22 14122 0.14
46 0 279303.87 8.21 143.21 0.13
47 0 278826.27 8.21 14121 0.13
48 0 278370.74 8.20 14120 0.12
49 0 277935.95 8.20 143.20 0.12
50 0 277520.66 8.19 143.19 0.11
51 0 277123.73 8.18 143.18 0.11
52 0 276744.11 8.18 14118 0.10
53 0 276380.81 8.17 143.17 0.10
54 0 276032.91 8.17 143.17 0.09
55 0 275699.57 8.16 143.16 0.09
56 0 275379.97 8.16 143.16 0.09
57 0 275073.39 8.16 143.16 0.08
58 0 274779.13 8.15 143.15 0.08
Project: Partners Equity Stormwater improvements V
Project No.: 3403-0001 !F M?KIM£?CREED
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 9/8/2008
Reviewer: JTS Date:
Objective: Determine the temporary storage drawdown time for the wet pond structure
Drawdown for Wet Pond
al Stage, Zi 10.35 it
sl Elevation 145.35 0
qiv orifice 6 0 Ir
orifices
R 0.00 ft
d Elevation 143.00 ft
0 a Method (1/3 Driving Head)
Permanent Pool Volume 281,891.75 cu ft
Temporary Pool Volume 455,339.95 cu ft
Driving Head 2.10 ft
Orifice Si" 6 00 in
.orifice 0.79 cfs
Draw Down 2.54 days
1 0 450415.61 10.30 145.30
2 0 445553.92 10.24 145.24
3 0 440755.23 10.19 145.19
4 0 436019.92 10.14 145.14
5 0 431348.36 10.09 145.09
6 0 426740.91 10.04 145.04
7 0 422197.96 9.99 144.99
8 0 417719.87 9.94 144.94
9 0 413307.03 9.89 144.89
10 0 408959.80 9.84 144.84
11 0 404678.57 9.79 144.79
12 0 400463.71 9.74 144.74
13 0 396315.61 9.69 144.69
14 0 392234.65 9 64 144.64
15 0 388221.20 9.60 144.60
16 0 384275.64 9.55 144.55
17 0 380398.37 9.51 144.51
18 0 376589.75 9,46 144.46
19 0 372850.18 9,42 144.42
20 0 369180.02 9.37 144.37
21 0 365579.67 9.33 144.33
22 0 362049.50 9.29 144.29
23 0 358589.89 9.24 144.24
24 0 355201.22 9 20 144.20
25 0 351883.87 9.16 144.16
26 0 348638.21 9.12 144.12
27 0 345464.62 9.08 144.08
28 0 342363.46 9104 144.04
29 0 339335.13 9.01 144.01
30 0 336379.97 8.97 143.97
31 0 333498.37 8.93 143.93
32 0 330590 68 8.90 143.90
33 0 327957.27 8.86 143.86
34 0 325298.50 8.83 143.83
35 0 322714.73 879 143.79
36 0 320206.31 8.76 143.75
37 0 317773.60 813 14333
38 0 315416.95 8.70 143.70
39 0 313136.70 8.67 143.67
40 0 310933.21 8.64 143.64
41 0 308806.80 8.61 143.61
42 0 306757.83 8.59 143.59
43 0 304786.63 8.56 143.56
44 0 302893.53 8.54 143.54
45 0 301078.87 8.51
1 143.51
45 0 299342.98 84 1
47 0 297700.89 8.47 143.47
48 0 296168.90 8.45 143.45
49 0 294737.58 8.43 143.43
50 0 293398.48 8.41 143.41
51 0 292143.98 8.39 143.39
52 0 290967.23 8.37 143.37
53 0 289862.05 8.36 143.36
54 0 288822.84 8.35 143.35
55 0 287844.54 8.33 143.33
56 0 286922.54 8.32 143.32
57 0 286052.67 8.31 143.31
58 0 285231.12 8.30 143.30
59 0 284454.42 8.29 143.29
60 0 283719.41 128 1432
8
61 0 283023.19 8.27 143.27
fit 0 282363.11 8.26 143.26
63 0 281736.74 8.25 143.25
64 0 281141.84 8.24 143.24
65 0 280576.36 8.23 143.23
66 0 280038.42 8.22 143.22
67 0 279526.26
6 8.22 143.22
68 0 279038.2 8.21 14321
69 0 278573.00 8.20 143.20
70 0 278129.04 8.20 143.20
71 0 277705.12 8.19 143.19
72 0 277300.07 8.19 143.19
73 0 276912.79 8.18 143.18
74 0 276542.27 8.18 143.18
75 0 276187.55 8.17 143.17
76 0 275847.76 8.17 143.17
77 0 275522.07 8.16 143.16
78 0 275209.73 8.16 143.16
79 0 274910.01 8.15 143.15
B0 0 274622.25 8.15 143.15
81 0 274345.82 8.14 14114
82 0 274080.14 8.14 143.14
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