20050949 Ver 1_More Info Received_20081009

4-4
41??MCKEM&CREED
To: DWQ
2321 Crabtree Blvd, Suite 250
Raleigh, NC27604
ATTENTION: Ms. Annette Lucas
WE ARE SENDING: ® Originals
? Specifications
LETTER OF TRANSMITTAL
Date: October 9, 2008 O 5- O q L4 q V Z
PROJECT NO: 03403.0001 PHASE NO:
RE: Partners Equity Group
TRANSMITTAL NO: PAGE 1 OF 1
? Prints
? Calculations
? Shop Drawings ? Samples
? Other -
Quantity I Drawing No. I Rev. I Description
2 I I 1401 DWQ Certification Partners Equity Group Subdivision -
Permit Request
Status
H.
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 find the above enclosed document on behalf of Jonathan Smith. Feel free to call with
any questions concerning the above project.
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*TI NDS APID STORM,N TER 3Ft0.Nsr'i
1730 Varsity Drive Suite 500, Raleigh, NC 27606 919/233-8091 Fax [phone]
cc:
McKIM & CREED, PA
Signed
`'lVV
Nicole G. Pennington
C: \ Documents and Settings \ npennington \ Desktop \ LETTER OF TRANSMITTAL 2006.doc
Updated 1-1-08
v MCKIM&CREED
v
ENGINEERS
S U R V E Y O R S
P L A N N E R S
Venture IV Building
Suite 500
1730 Varsity Drive
Raleigh, NC 27606
919.233.8091
Fax [phone]
www.mckimcreed.com
October 9, 2008
Annette Lucas
2321 Crabtree Blvd
Suite 250
Raleigh, NC 27604
M&C: 03403.0001 (40.48)
RE: 401 DWQ Certification Partners Equity Group Subdivision
Dear Ms. Lucas:
In response to your Verbal Request for Information (RFI) dated October 7, 2008
for the Partners Equity Group 401 WQ Certification application enclosed you
will find additional information related to your request. We have provided two
(2) 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 the prior version. Note that this additional information
does not involve significant changes to the project concept. The only
modification to the previously submitted plans is the replacement of the
drawdown orifice of the pond with a 5" drawdown orifice. We have included a
revised detail sheet showing this modification. Please do not hesitate to contact
me if you have any questions concerning these documents.
Sincerely,
McKIM & CREED, P.A.
Jo than T. Smith PE, CPSWQ, CPESC
cc: file
John Shallcross
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WETLA'VO ANN) 3 r Mdll4T b C11
Partners Equity Group Subdivision q °'. M9
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Stormwater Management Narrative
For NCDWQ 401 Certification = Sit °
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Revised October 9 2008 y .t ?. V, - Az '
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Introduction Io ?V
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 110,, 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
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
understand that 401 WQ certification requirements at that time included treatment and
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
2
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 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 was used and
represents the most conservative methodology for sizing of Stormwater BMP
parameters.
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 (@ 70 % imp) is approximately 111,819 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 82 %. Note that the required water quality volume calculation is based on the
maximum impervious limit for the entire 45.3 acre drainage basin (70% 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 70 n/a
Average Depth 5.65 ft
Required Surface Area (90% SA/DA) 54,857 S q. ft.
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 QualiStora e(WQS) 203,930 Cu ft
3
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
Required Water Quality Volume** (WQV) 111,819 Cu ft
Excess WQ storage 92,111 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 sized according to the 85% TSS removal guidance 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 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, such as larger size. The method utilizes a
4
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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 aoint 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)
The pond at Partners Equity will be enlarged to meet the 90% TSS removal requirements
for Piedmont region of North Carolina. As a result the pond will be sized considerable
larger than the sizing typically credited with 25% N removal. As a result we understand
the pond can be credited with 30% removal of Nitrogen
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 "wet swales" which convey runoff from South Equity drive across the center
of the development to North Equity Drive and into the wet detention pond (figs 9-10).
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
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
5
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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
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%.
6
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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
swales and other conveyances on-site have been dedicated to the Town of Smithfield
and are maintained by the town.
7
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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:
1. Temporary and Permanent Seeding
Temporary and permanent seeding will be used to establish a dense and
vigorous ground cover in exposed soil areas.
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
temporary storage volume which exceeds the standard by 82 %. 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.
8
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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.
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.
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
Representative Photo's from Project Site
10
1) View of outlet structure from west bank of pond January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)

11
2) View of southeast corner of pond from west bank January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
12
3) View of existing "feeder swale" between Lot 2 and 3 looking west. January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
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 Oct, 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 Oct, 2008)
January 2007
7) 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.
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
8) View of Road swale along West side of South Equity drive looking south January 2007

16
9) View of road swale along west side of South equity drive looking south January 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 2008)
17
10) View of Connector swale along south Equity Drive looking north. June 2007
Partners Equity Group Subdivision
Stormwater Management Narrative
Proposed Stormwater BMP Retrofits
July, 2008 (Rev Oct, 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 Oct, 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 Oct, 2008)
20
15) View of Cross-connection Swale between lots 16 and 17 looking east June 2007
Permit No
(to be provided by DWQ)
O?O?WAT?9?G
© y r
w?-A o
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.
PROJECT IWORMATIOtI
Project name Partners Equity Subdivison Stormwater Management
Contact person Jonathan Smith
Phone number 919-233-8091
Date 1019!2008
Drainage area number Wet Pond
A D111 00ATI011ill
Site Characteristics
Drainage area 1,973,268.00 ft2
Impervious area 1,381,288.00 ft2
% impervious 70.00 %
Design rainfall depth 1.00 in
Storage Volume: Non-SR Waters
Minimum volume required 111,819.00 ft3
Volume provided 203,930.00 ft3
Storage Volume: SR Waters
1-yr, 24-hr runoff depth in
Pre-development 1-yr, 24-hr runoff ft3
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 0.82 (unitless)
Rainfall intensity: 1-yr, 24-hr storm 2.75 in/hr
Pre-development 1-yr, 24-hr peak flow 24.90 ft3lsec
Post-development 1-yr, 24-hr peak flow 102.00 ft3lsec
Pre/Post 1-yr, 24-hr peak flow control 77.10 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 144.44 ft
Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
N. AESfG14 ! ORIA[tON
Volume and Surface Area Calculations
SA/DA ratio 2.78 (unitless)
Surface area at the bottom of shelf 50,416.00 fie
Volume at the bottom of shelf 223,531.00 ft3
Permanent pool, surface area required 54,857.00 fte
Permanent pool, surface area provided 60,792.00 fie OK
Permanent pool volume 251,333.00 ft3
Average depth for SA/DA tables 4.13 ft OK
Surface area at the top of shelf 68,015.00 fte
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 fie
Drawdown Calculations
Treatment volume drawdown time
Treatment volume discharge rate
Pre-development 1-yr, 24-hr discharge
Post-development 1-yr, 24-hr discharge
Additional Information
Diameter of orifice
Design TSS removal
Basin side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build-out?
Drain mechanism for maintenance or emergencies
2.71 days OK
0.79 ft3/s
24.90 ft3/s OK
21.80 ft3/s OK

5 in
90 %
3.00 :1 OK
10.00 :1 OK
10.00 ft OK ,
3.87 :1 OK
2.49 :1 OK
Y (Y or N) OK
1.17 ft OK
N (Y or N) Design must be based on 90% TSS removal
N (Y or N) Need a recorded drainage easement
Y (Y or N) OK
Form SW401-Wet Detention Basin-Rev.4 Parts I. & II. Design Summary, Page 2 of 2
Permit No.
(to be provided by DWQ)
Ill, REQUWD I[TEMS CHECKUST
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.
In'
0A
?Q
r7^[?
Pagel Plan
Sheet No.
C?
C?
0)
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.
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.
w 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.
A' I } s`i" ;r 7. The supporting calculations.
PPeyioss w A copy of the signed and notarized operation and maintenance (0&M) agreement,
C 5 9. A copy of the deed restrictions (if required).
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.
Form SW401-Wet Detention Basin-Rev.4 Part III. Required Items Checklist, Page 1 of 1
Project: Partners Equity Stormwater Improvements
Project No.: 3403-0001
Client: Partners Equity Group
Location: Smithfield, NC
Designer: MJB Date: 10/8/2008
Reviewer: JTS Date: 10/9/2008
v, MCIQM&CREED
Objective: Determine Water Quality Volume (WQV) using Simple Method
WQV = P* Rv *A
12
Rv = 0.05 + 0.009 Ia
Given: Find:
Rainfall depth 1 in Rv 0.68 in
Wtrshd Area 45.3 ac WQV 111,819 cu ft
Impervious % 70 % *
ytt? Mfr
?(?V
SEa! S
0265
i v1N
* Conservative estimate based on maximum built upon area per Town of Smithfield requirements.
Project: Partners Equity Stormwater Improvements V
Project No. 3403-0001 v,
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 10/9/2008
Reviewer: JTS Date: 10/9/2008
Objective: Determine the SCS Curve Number for the project site.
MC CREED
01/4-, =.
0
EPa-
S '
026523
r? ? ?n'T?y G•?```M
Curve Number Calculation ( D
SCS Method
Impervio us Percentage 70%
Landuse Soil Group RCN Area Product of RCN
Commercial B 87.1 11.9 1037.70069
Commercial C 90.7 11.2 1018.96008
Commercial D 92.7 22.2 2053.46259

Totals 45.3 4110.1
Total (Weighted) Curve Number 90.73
=Total Product/Total Area
Estimated Curve Number 91
CN Interpolation from TR55 suggested curve numbers
Soil Group
o B C D
0 72% 88 91 93

¢ 65% 85 90 92
Interpolation for 70% Imperious
70% 87.1 90.7 92.7
Project: Partners Equity Stormwater Improvements V
Project No.: 3403-0001 v? MCKIM&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 Segment ID AB
1. Surface description (Table 3-1) dns grass
2. Manning's roughness coeff., n (Table 3-1) Hi Pt 154 0.240
3. Flow length, L (Total < 300 ft) Lo Pt 150 ft 40
4. Two-year 24-hour rainfall, P in 3.7
5. Land slope, S T = 0.007(,L)- ft/ft 0.100
6. Travel time, T 1 o..s ' hr 0.06
Shallow Concentrated Flow Segment ID BC
7. Surface description (Paved or Unpaved) Paved
8. Flow length, L Hi Pt 0 ft 0
9. Watercourse slope, S Lo Pt 0 ft/ft #DIV/0!
10. Average velocity, (Figure 3-1) c„ = 20.3282( ft/sec #DIV/0!
Il.Travel time, T v, = 16.1345(shr1 0.00
Storm Culvert Channel Flow
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R =
15. Channel slope, S
16. Manning's roughness coeff., n
17. Channel velocity, V
18. Flow length, L
19.Travel time, T t
Drainage Channels
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R =
15. Channel slope, S
16. Manning's roughness coeff., n
17. Channel velocity, V
18. Flow length, L
19.Travel time, T c
Connector Channels
12. Cross sectional flow area, A
13. Wetted perimeter, P
14. Hydraulic radius, R =
15. Channel slope, S
16. Manning's roughness coeff., n
17. Channel velocity, V
18. Flow length, L
19.Travel time, T c
Segment ID
ft^2
ft
ft
S=N/A ft/ft
ft/sec
V = 1.49R ft
n hr
Segment ID
ft^2
ft
ft
S=N/A ft/ft
ft/sec
1 Y' = 1.49R21s12 ft
n hr
Segment ID
ft^2
ft
ft
S=N/A ft/ft
ft/sec
Y' = JAIR 21Y12 ft
n hr
Time of Concentration = 20 min
J?"t I'fa?7
g SE
0265AL23
4 \ • ?,: l
'rj?iiL77f AN
rl"I'll ltl? jO 1
l?.
Lag Time = (0.6)(Tc) = 12 min
CALCULATION
Project i : t"' f: r ,r1 5:4rM ;,g? Cr ,.,T1Y/yVoVg1,4f1J- g Proj. No.
Client < Dated
Subject kel'a e _G fJ -_c P-Qrvl pool t t Des. By
Chk. By
I ?? ? ?? _ ?, 2 J da?" Stie?F -l- E+. r-??t;+?? ? ?s? ?oon? ? a..-?--a?
Fer'r"r. ?2>.?e bOT ant
?:..: x?? ! t rt' So, old /?.? {? ??) l?
4,

nt i?
C
• , 5Ei t..
• y? r
JJJJJfJ1111111?
?`7
V'?
v-_

Project: Partners Equity Stormwater Improvements
Project No.: 3403-0001
Client: Partners Equity Group v, McKIM&CREED
Location: Smithfield, NC
Designer: JDH Date: 10/9/2008
Reviewer: JTS Date: 10/9/2008
Objective: Determine the pond sizing required to meet 90%o TSS removal guidelines
Drainage Area 45.3 acres
Impervious Precentage 70%
Taken from SADA Table 10-3 of 2007 NC Stormwater BMP Design Guide
Permanent Pool Average Depth
4.0 4.5 5.0 5.5 6.0
Impervious % 70% 3.3 3.1 2.8 2.7 2.5
Calculation of Surface Area Required for various Avg Depths
Permanent Pool Average Depth
I 4.0 I 4.5 I 5.0 5.5 6.0
Surface Area 65,118 61,171 55,252 53,278 49,332
Design Check
Design Average Depth* 5.65 ft
SADA Ratio 2.70
Reqd Perm. Pool SA @ 5.5 ft avg depth 53,278 sqft
Design Permanent Pool SA 60,792 sqft
r`,:?*?tsatrrrr?r,?
'0.R" a `',Y • , ?v"l ' i
"R
" use 5.5 ft as conservative
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Project: Partners Equity Stormwater Improvements
Project No.: 3403-0001 V MCIQM&CREED
Client: Partners Equity Group
Location: Smithfield, NC
Designer: MJB Date: 10/9/2008
Reviewer: JTS Date: 10/9/2008
Objective: Runoff Routing through wet pond structure for the 1 year rainfall event
1 Year Calcs for Wet Pond
Watershed Description
Area 45 acres
Hydraulic L 1464 ft
A elev. 9 It
Rainfall Data
24 hr. P 3.2 in
peak i 2.75 1
in/hr
In uts
Time of Concentration Outpvts
Tc A,•`min
Rainfall Data
g 108 in
h 19 in/hr
CN 60
Rational C 0.2
Rational Equation
QP 24AI cfs
Ti- to Pcak
Tp 32.35 min
NRCS Curve Number Method
S 6
Q 0.4
Q in
vol 671 d f[a
v
fa. f'
yt r= ret.. _ '
?. 4 7
S"•
lU-?-off
g & h Values obtained from Johnston County
Stormwater Design Manual
Ks 3252.402662
Stage-Storage Relationship b 2.114539484
(fp (W) (W) (a3) (a) (ft)
Description Counlour Elev Countour Arc lncr Vol .A--, Veil Stage In S In Z Zest
bottom 135 19,392 - 0 U - - 0.000
136 21,820 20606 20606 1 9.9333 0.01100 2.394
137 25,536 23678 44284 2 10.6984 0.6931 3.438
138 28,637 27086.5 71370.5 3 11.1756 1.0986 4.309
139 31,935 30286 101656.5 4 11.5294 1.3863 5.(193
140 36,326 34130.5 135787 5 11.8188 1.6094 5.84t1
141 41,930 39128 174915 6 12.0721 1.7918 6.583
142 47,537 44733.5 219648.5 7 121998 1.9459 7.332
142.5 50,416 24488.1825 244136.6825 7.5 12.4055 2.0149 7.708
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 114111 8.552
144 70,762 34694.25 338834.615 9 12.7333 2.1972 9.000
145 98,355 84558.5 423393.115 10 12.9561 2.3026 10.000
shelf 6u0om 146 115b17 1116986 530379.115 11 13.1813 2.3979 11.124
normal pool 147 137,611 126614 656993.115 12 13.3954 2.4849 12310
Wri
Length 25
Elevation 145.35
Cw 3.0
Storage Below 455339.9
Orifice
t Radius 6 in Peak Pre-inflow 24.9
't Center Elcv. 143.25 it Peak Weir Flow 31.3
Cd 0.60 Max WSE 145.91
V Storage Below . 281891.75 ft3
PRE POST
Time Inflow Inflow Storage Vol. Stage WSE Orifice Ou Weir Out
(min) (ft3/s) (fP/s) (£o) (ft) (ft) (ft3/s) (ft3/8)
U U.ll(I ll.lill LU413J.bb O.W . ? ?. 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 8.00 143.00 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 0A0
0.2 0.00 0.01 264125.65 800 14100 0.67 0.00
I'
? i
fD '
O
O
I
OI
7
O
CD
N
N
O
Flow (cfs)
1 ?
N O co O N
O O O O O O O
X
G
(D
rr
T
O
CL
X
O
C
to
(11) 3SM
N W ?I? C?37 v
Project: Partners Equity Stormwater Improvements V
Project No. 3403-0001 v? WKIM&CREED
Client: Partners Equity Group
Location: Smithfield, NC
Designer: MJB Date: 10/9/2008
Reviewer: JTS Date: 10/9/2008
Objective: Runoff Routing through wet pond structure for the 10 year rainfall event
10 Year Calcs for Wet Pond
W
h
d D
i
i
aters
e
es
Area cr
pt
on
45
acres
Hydraulic L 600 ft
4 elev. 9 ft
Rainfall Data
24 Ir. P 5.8 in
peak i 4.73 in/hr
P ArL
! o ?
! u (?.T'Jla1 u
1 ?
S ? y
a i
Inputs .+ y. afa.. a r{'?`E': a ?.. ?
Time of Concentration Outputs i.i °<.?,'.:,?i .?4' ?ti?•'r?
Tc ? min YY,. ?'•-.iv°°Y``yiq?\' ('+?•,'?`\?
Rainfall Data i i+ f f f f l l 1 l l l l' a
g E51 in g It Values obtained from Johnston County
h 23 in/hr Stormwater Design Manual II
rre
CN 60
Rational C 0.2
Rational Equation
Qp cis
Time to Peak
Tp Smin
NRCS Curve Number Method
S G`
Q l in
Qv 29 N'
in
ft'

Stage-Storage Relationship Ks
b 3252.402662
2.114539484
(h) JP) (ft') (ft') (ft) (fl)
Description CounI-r Bev Countour A- I.- A'ol A¢um Vol St,ige In S In I_ Z "t
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 3.438
138.0 28,637 27086.5 71370.5 3 11.1756 1.0986 4309
139.0 31,935 30286 101656.5 4 11.5294 1.3863 5.093
140.0 36,326 34130.5 135787 5 11.8188 1.6094 5.840
141.0 41,930 39128 174915 6 110721 1.7918 6.583
142.0 47,537 44733.5 219648.5 7 12.2998 1.9459 7.332
1415 50,416 244681825 244136.6825 7.5 12.4055 10149 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 84558.5 423393.115 10 129561 2.3026 10.000
146.0 115,617 106986 530379.115 11 13.1813 2.3979 11.124
shelf bottom 147.0 137,611 126614 656993.115 12 13.3954 24849 12.310
Wei
Length 25
Elevation 145.35
Cw 3
Storage Below 455339.9
Orifice
t Radius 3 in Peak Pre-Inflow 42.88
t Center Elev. 143.25 ft Peak Weir Flow 125.50
Cd 0.6 Maz WSE 146.76
N Storage Below ;'.281891.75 ft'
PRE POST
Time Inflow Inflow Storage Vol. Stage WSE Orifice Ou Weir Out
(min) (ft3/s) (f3/;) (W) (ft) (ft) (W/s) (ft-/s)

0.02
0.00
0.00 -t".oo
264133.66 -
8.00 t-.uu
143.00 u.uu
0.00 u.eu
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 0.01 264133.68 8.00 143.00 0.00 0.00
WSE (FT)
ti CO LOS co N
W
U)
a°
m
0
O
LL
L
N
C
E O
E
o
o.
C:
m
^L I ?
O O O O O O O O O O O O
O 00 CO d N O 00 CO N N
N ? r ?- i
(S13) MOIj
Project: Partners Equity Stormwater Improvements
Project No.: 3403-0001
Client: Partners Equity Group
Location: Smithfield, NC
Designer: JDH Date: 9/8/2008
Reviewer: JTS Date:
v? McKIM&CREED
Objective: Determine the 1" runoff drawdown time for the wet pond structure.
Drawdown for Wet Pond
Bottom Elevation 135.00 ft
Initial Stage, Zi 9.44 ft
Initial Elevation 144.44 ft
D-Egiv orifice 5.0 in
No. orifices 1
Cd 0.6
Invert 0.00 If
Invert Elevation 143.00 ft
DWO Method (1/3 Driving Head)
Permanent Pool Volume 281,891.75 cu ft
Temporary Pool Volume 364,062.46 ou ft
Driving Head 1.44 ft
Orifice Size 5.00 in
Qorifice 0.45 cfs
Draw Down 2.09 days
1 0 372199.64 9.41 144.41 0.72
2 0 369614.16 9.38 144.38 0.71
3 0 36706225 9.35 144.35 0.70
4 0 364544.02 9.32 144.32 0.69
5 0 362059.62 9.29 14419 0.68
6 0 359609.16 9.26 144.26 0.67
7 0 357192.77 9.23 144.23 0.66
8 0 354810.58 9.20 144.20 0.65
9 0 352462.72 9.17 144.17 0.64
10 0 350149.30 9.14 144.14 0.63
11 0 347870.45 9.11 144.11 0.62
12 0 345626.31 9.08 144.08 0.61
13 0 343416.98 9.06 144.06 0.60
14 0 341242.60 9.03 144.03 0.59
15 0 339103.29 9.00 144.00 0.58
16 0 336999.18 8.98 143.98 0.57
17 0 334930.37 8.95 143.95 0.56
18 0 332897.00 8.93 143.93 0.55
19 0 330899.19 8.90 143.90 0.55
20 0 328937.06 8.87 143.87 0.54
21 0 327010.72 8.85 143.85 0.53
22 0 325120.30 8.83 143.83 0.52
23 0 323265.92 8.80 143.80 0.51
24 0 321447.68 8.78 143.78 0.49
25 0 319665.71 8.76 143.76 0.48
26 0 317920.13 8.73 143.73 0.47
27 0 316211.05 8.71 143.71 0.46
28 0 314538.58 8.69 143.69 0.45
29 0 312902.83 8.67 143.67 0.44
30 0 311303.92 8.65 143.65 0.43
31 0 309741.97 8.63 143.63 0.42
32 0 308217.07 8.61 143.61 0.41
33 0 306729.35 8.59 143.59 0.40
34 0 305278.91 8.57 143.57 0.39
35 0 303865.85 8.55 143.55 0.38
36 0 302490.28 8.53 143.53 0.37
37 0 301152.32 8.51 143.51 0.36
38 0 299852.06 8.49 143.49 0.35
39 0 298589.61 8.48 143.48 0.34
40 0 297365.08 8.46 143.46 0.33
41 0 296178.56 8.45 143.45 0.32
42 0 295030.16 8.43 143.43 0.31
43 0 293919.98 8.41 143.41 0.30
44 0 292847.27 8.40 143.40 0.28
45 0 291830.47 8.39 143.39 0.27
46 0 290865.85 8.37 143.37 0.25
47 0 289949.95 8.36 143.36 0.24
48 0 289079.61 8.35 143.35 0.23
49 0 288251.90 8.34 143.34 0.22
50 0 287464.13 8.33 143.33 0.21
51 0 28671182 8.32 143.32 0.20
52 0 285998.65 8.31 143.31 0.19
53 0 285316.50 8.30 143.30 0.18
54 0 284665.40 8.29 143.29 0.17
55 0 284043.51 8.28 143.28 0.17
56 0 283449.14 8.27 143.27 0.16
57 0 282880.71 8.26 143.26 0.15
58 0 282336.74 8.26 143.26 0.14

Y

v

, ? t?
?i6 9
(0
s PROPOSED VEGETATIVE ENHANCEMENT
,----M.~.,,~...~.. ~ ~ i i SIDE SLOPES 3:1 (TYPICAL) PLANT SPACINGS SHOULD BE 2 FT OC VEGETATED SHELF
..a. ~ _ - ~ ~ (SEE DETAILS D-1) 10:1 (TYPICAL)
147 147
146 1 146
145 145
~ ~ i 144 144
y 143 = _ _ - NORMAL POOL ELEV. 143,OD FT 143
I _
I 142 ~;I_- _ PROPOSED GRADE 142
I 140 = - 3:1 (TYPICAL} 1140
I
138 APPRGXlMA1~E EXISTING GRADE PROPOSED WETLAND TOPSOIL 138
137 AMENDMENTS (SEE DETAILS 137
SHEET D-1} 136 136
Q 135 135
D PROPOSED ~ TYPICAL CROSS SECTION SEDIMENT ACCUMULATION
~ I ~ I ~ Q i 1" = 5' ZONE
\~l Q Q
J iI
TE EXISTING TOPO
it
~ ~ s I I REPLACE EXISTING 6"
~ ~ I ORIFICE WITH 5" ORIFICE, ~
~ ~ I Q ! v'cP I MAINTAIN EXISTING INVE T ELEVATION
~ ~ ~
6' ~ ~ c~ ~ u' TYPICAL CROSS- I N
~s 1C'r~ rL = ~ 19 ~h I
,1 I rtr~.F~~hR.G~ MA~TI4: {T7F_) y 1 ~
1 y I I
I f'' I ; ~ ~
f ~RIE~i~~ ~ ,Ili w L~~.G~'J f I ~
t 5 D I 44 _v ~ , Re}~.CYD i (IVr` tL {a3 t}?r I ! ~ `.Y
I.
I F 1 F;._ ~1-7
~~G i i iPIGA~ EXa"!i TIDE
EXISTING BUILDING
-AM L~ ~ -a
I
I ~a-da~
O I `€'C11+~~!
\
I I Rig I ~ fi~u Y~
i I I T~ ~GP~L~L
r 1i I
~ s~ III
~ \ 4 00
\ \ ~ \ PROPOSED DRAINAGE ~ ~ ~ ~ I III O~T~ET DETA ~ MOTES: II II
~ ~ \ EASEMENT \ \ \ \
\ ~ ~ IIII
I I 1. RISER BARREL DETAILS BASED ON RELEASED FOR
\ \ _ _ CONSTRUCTION DRAWINGS (McKIM & CREED, 1999 FOR
I + I I I THE PARTNER'S EQl11TY SUBDIVISION. REFLECTED
\ ~ ~ \ ~ I I INFORMATION NAS NOT BEEN FIELD VERIFIED.
~ ~
II ICI
I I I
TI P PROPOSED DETEN ON OND
1 WAT R UA ITY NHANCEMENTS: ° E Q L E o II
1 EXPAND POND TO MEET 90~ TSS II ~ ~ I
~ \ REQUIREMENTS AND OTHER WET
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N x 144 $ 0 1. EXISTING CONDITIONS MAP BASED ON RELEASED FOR 144
~ R 1999 FOR 142 9, CONSTRUCTION DRAWINGS McKIM & C EED, ) 142
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gl% THE PARTNER'S EQUITY SUBDIVISION. REFLECTED ~ 138 138
d ~ INFORMATION HAS NOT BEEN FIELD VERIFIED, 136 P 136
GCB 134 3 8 134
T 132 E 2. SWALE CROSSINGS FOR DRIVEWAY ACCESS NAVE NO ~n~ m ; 132
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