HomeMy WebLinkAbout20061214 Ver 2_Stormwater Info_20070705•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
__
ol~- i2,~'~ v 2
WITHERS t.~ RAVEN EL
WOODCREEK -Amenity Center Phase
Stormwater Management Report
Holly Springs, North Carolina
Prepared For:
Preston Development Company
ioo Weston Estates Way
Cary, NC 27513
Prepared By:
WITHERS & RAVENEL, INC
Zit MacKenan Drive
Cary, North Carolina 27511
June, Zoo?
W&R Project No. 02040232.80
<~. ~`~
°~,.
.a
~'~ ~ l
~~~ ~ 1~ .
xe
~~
N.CAR~IJ
aQ SEAL 9~'~ 2 ~
w
n; 28421 ;ter
_ .,.
C. Heath Wadsworth, P.E.
!~
DWO Project No. 06-1214
*
DIVISION OF WATER QUALITY - 401 EXTENDED DETENTION (and POCKET
) WETLAND WORKSHEET
• I. PROJECT INFORMATION (please complete the following information):
"
"
Recreation Tract
in certification docsl
Project Name : Woodcreek -Amenity Center Phase (a.k.a.
• Contact Person: C. Heath Wadsworth PE Phone Number: (919) 238-0323
• For projects with multiple basins, specify which basin this worksheet applies to: N/A
• Permanent Pool Elevation 366.00 ft. (elevation of the orifice invert out)
Temporary Pool Elevation 367.00 ft. (elevation of the outlet structure invert in)
Permanent Pool Surface Area 11,850 sq. ft. (water surface area at permanent pool elevation)
Drainage Area 10.42 ac. (on-site and off-site drainage to the basin)
• Impervious Area 5.21 ac. (on-site and off-site drainage to the basin)
Forebay Surface Area 1.788.5 sq. ft. (at permanent pool elevation approximately 15%)*
• Marsh 0"-9" Surface Area 4.148 sq. ft. (at permanent pool elevation approximately 35%)*
Marsh 9"-18" Surface Area 4,143 sq. ft. (at permanent pool elevation approximately 35%)*
1
*
Micro Pool Surface Area 1,778.5 sq. ft. (at permanent pool elevation approximately
5%)
•
Temporary Pool Volume 22,956 cu. ft. (volume detained on top of the permanent pool)
• SAIDA used 2.06 (surface area to drainage area ratio}*
• Diameter of Orifice 2.0 in. (draw down orifice diameter)
II. REQUIRED ITEMS CHECKLIST
• Initial in the space provided to indicate the following design requirements have been met and supporting documentation is attached. If a
requirement has not been met, attach an explanation of why. At a minimum, a complete stormwater management plan submittal includes
• a worksheet for each BMP, design calculations, plans and specifications showing all BMPs and outlet structure details, a detailed
drainage plan and a fully executed operation and maintenance agreement. An incomplete submittal package will result in a request for
• additional information and will substantially delay final review and approval of the project
Applicants Initials
LIhJ The temporary pool controls runoff from the 1 inch rain.
Gldrl The basin side slopes are no steeper than 3:1.
Lei A planting plan for the marsh areas with plant species and densities is provided.
~r/L Vegetation above the permanent pool elevation is specified.
(a¢fJ An emergency drain is provided to drain the basin.
~,! The temporary pool draws down in 2 to 5 days.
GifL~ Sediment storage is provided in the permanent pool.
~~/ A sediment disposal area is provided.
1,~/r./ Access is provided for maintenance.
~~rk./ A site specific, signed and notarized operation and maintenance agreement is provided.
-l d~/ The drainage area (including any offsite area) is delineated on a site plan.
Nr/ Access is provided for maintenance.
Plan details for the wetland are provided.
Plan details for the inlet and outlet are provided.
~~[!/ A site specific operation and maintenance agreement, signed and notarized by the responsible party is provided (see
http:llh2o.ehnr.state.nc.uslncwetland s/oand m.doc).
* Pocket Wetlands have different design parameters and are only assumed to remove 35% TSS - See pp. 19 and 20 of the NC DENR
stormwater BMP Manual, April 1999. 10% open water, 50% high marsh, 40% low marsh.
7/2/2007
•
Response to DWQ comments (from Annette Lucas)
DWQ Project # 06-121!}, Ver. z
• Wake County
Subject Property: Recreation Tract of Woodcreek (formerly Wild Acres)
• UT to Middle Creek [03040327-43-15-(I), C, NSW]
REQUEST FOR MORE INFORMATION: STORMWATER MANAGEMENT PLAN
•
1. The acreage of the impervious surfaces and open space reported on the enhanced
aerial photograph do not match the acreages reported in the Extended Detention
Worksheet. Please explain the discrepancy.
Response: The discrepancy in the impervious surfaces and open space has been
corrected.
•
i. Please provide an overall site plan that shows lot layouts and the footprints of the
i
f
h
rom t
e s
te
impervious surfaces. The site plan must show that all of the stormwater
will be routed to the extended detention wetland.
Response: An overall site plan that shows the lot layouts and the footprints of
the impervious surfaces has been included, The stormwater conveyance system
• is shown on the exhibit map in the report.
3. The roadside drainage from the proposed new street may not be directed to a level
spreader without first being treated by an allowable BMP for Nutrient Sensitive
• Waters (NSW) as described in General Certification 3631.
Response: Per discussion with DWQ representatives and the 401 Water Quality
• Certification and Authorization Certificate additional conditions, the roadside
drainage does not require treatment as described in General Certification 3631
since it is not in Tract D, Tract F, Tract J, or the Recreation Tract (a.k.a. Amenity
~ Center Phase). The permit states that constructed wetlands or bio-retention
ponds must be used to treat stormwater for the above Tracts due to their
• proposed percent imperviousness. The roadside drainage is not located in one
of the above Tracts; therefore the discharge is diffused with a level spreader.
4. Please revise the drainage system to the extended detention wetland so that all of
the stormwater is routed to the forebay at the north end of the constructed wetland.
• The forebay that is currently proposed in the center of the wetland will reduce the
treatment capability of the wetland and likely result inshort-circuiting.
•
Response: The drainage system has been revised so that all of the stormwater is
• routed to the forebay at the north end of the constructed wetland.
5. Please provide all of the information under listed in the "Required Item Checklist" in
• the DWQ Extended Detention Worksheet. Some ofthe omitted items include a
~iaizoo~
planting plan, a delineation of the drainage area, and plan details for the inlet and
outlet structures.
Response: The above mentioned information from the "Required Item Checklist"
has been included. The planting plan and inlet and outlet details are included
on the constructed wetland detail sheet (22" X 34.") that is included in the
appendix. The delineation ofthe drainage area is shown on the project exhibit
map (ii" Xi7").
The signed and notarized site specific operation and maintenance agreement
was included with the previous submittal; it was not re-submitted with this
submittal.
6. The outflow from the extended detention wetland may not be directed to a scour hole
in the currently proposed location. A scour hole is only allowable in areas where the
downslope is less than or equal to two percent. (See the Level Spreader BMP Manual
Chapter at:
http:l/hzo.enr.state.i~c.us/i~cwetlands/docu111ents/Levels~readerBMPManualclia
vter.doc.). Please replace the scour hole with a properly designed level spreader. In
your resubmittal, please include level spreader plans, calculations and a DWQ level
spreader worksheet so that DWQ staff can evaluate the design of the level spreader.
Response: A ditch has been designed to carry the outflow from the extended
detention wetland through the buffer, directly into the receiving stream. The
ditch is shown on the construction drawing which is included in the appendix of
the report.
The estimated io-yearvelocity in the ditch is 3.o ft/s; as a result rip rap was only
used at the pipe outlet, the remainder of the ditch will be grass. Also, the ditch
grade ties to the receiving stream's invert. With the slow ditch velocities and the
backwater influences from the receiving stream, it is not anticipated that erosion
will be a problem at the ditch outlet.
WOODCREEK -Amenity Center Phase
Stormwater Management Report
Holly Springs, North Carolina
INTRODUCTION
The purpose of this study is to document the Stormwater management plan for the Amenity Center
Phase of the proposed development in accordance with the 401 Water Quality Certification and
Authorization Certificate's Additional Conditions (DWQ Project # o6-12i4; designated as "Recreation
Tract" in Additional Condition #7). The plan includes the design of one constructed wetland in the
Amenity Center Phase in order to treat Stormwater runoff. The site is located in the Neuse River Basin
and all of the site drainage is received by Middle Creek.
SITE .J
w !~, CLIF REE K,t: "~
(rt ..
Fgure i. Site outlined in
The proposed constructed wetland is designed to draw down the first inch of runoff over a 2 to 5 day
period and is sized according to the Division of Water Quality surface area requirements in order to
achieve 85% Total Suspended Solids and 40% total nitrogen reduction. The area draining to the
proposed constructed wetland consists of the amenity center and townhomes; the drainage area is
50% impervious (see attached map).
The future phases of this development that require Stormwater management will employ the use of
constructed wetlands, bioretention areas, and/or wet detention basins followed by a forested filter
strip in order to meet Water Quality Certification #3402 in order to manage Stormwater (from 4oi
Water Quality Certification the Tract D, Tract F, Tract 1, and the Recreation Tract phases require a
Stormwater management plan). These BMPs will be designed and submitted at a later date.
WOODCREEK -Amenity Center Phase i W&R Project ozogoz3z.8o
Stormwater Management Report lune, zoo?
WOODCREEK -Amenity Center Phase
Stormwater Management Report
Holly Springs, North Carolina
METHODOLOGY
The Stormwater study was conducted using the natural drainage features as depicted by the Wake
County aerial topographic information (2-ft contours), field survey data and proposed development
within the drainage areas.
The scope of work included the following analyses:
~d ro logy
^ Simulation of the io-year and ioo-year rainfall events for the Holly Springs area
^ Formulation of the 1o-year, and ioo-year flood hydrographs for the proposed developed
drainage area
Hydraulic
^ Routing the io-year and ioo-year flood hydrographs for post development runoff through
the proposed Stormwater BMPs
The results of the hydrologic calculations are used in the hydraulic analyses. The hydraulic design
requires the development of stage-storage and stage-discharge functions for the wet detention
basins. The rainfall/runoff hydrographs, stage-storage and stage-discharge functions have been
compiled to create a routing computer simulation model using Haestad Methods PondPack vio.o
software. This PondPack model was then used to assess the impact of the peak discharges for the
design rainfall events. The PondPack modeling results are provided as appendices to this report.
HYDROLOGY
The SCS Method was used to develop runoff hydrographs for the io-year and ioo-year storm events.
• NOAA Atlas i4 rainfall data for Raleigh-Durham International Airport was used to determine the z4-
hour duration rainfall for the io-year and Soo-year storm events. This method requires three basic
• parameters: a curve number (CN), time of concentration (t~), and drainage area.
i
•
•
•
Curve numbers were based on soil type and land use. Soil types were delineated from the Soil
Survey of Wake County, North Carolina (November i97o). Land use data was determined using aerial
photography and the most recent site plans for the proposed site. The curve numbers used in this
study are listed in the appendix of this report.
Times of concentration were estimated to have a time of concentration of 5 minutes to account for
shallow paved flow, and piping.
HYDRAULICS
Computer simulated reservoir routing of the io-year, and ioo-year design storms utilized stage-
storageand stage-discharge functions. Stage-storage functions were derived from the proposed
contours for the wet detention basins. Anon-linear regression relation for surface area versus
elevation was derived for the BMP. This relation estimates the incremental volume of the basin to
the stage or elevation of the basins. Stage-discharge functions were developed to size the outlet
structures for the wetlands.
WOODCREEK -Amenity Center Phase
Stormwater Management Report
W&R Project o2o4oz3z.8o
tune, 2007
WOODCREEK -Amenity Center Phase
Stormwater Management Report
Holly Springs, North Carolina
CONCLUSIONS
Based on the routing study, the outlet proposed for the constructed wetland passes the ioo-year
storm with at least one foot of freeboard. The results for the run are included in the appendix of this
report. The drainage area map on Sheet i of the appendix includes the outlet design for this phase's
BMP. Planting schedules and more detailed outlet design information is included on the
Construction Drawing "Woodcreek - Lockley Drive Extension" submitted with this report.
WOODCREEK -Amenity Center Phase
Stormwater Management Report
3
W&R Project ozo4oz3z.8o
tune, zoo?
__ ~
~ °'
. R
- w
U
Q ~ ~ ~~
o
~
_~-
-
.--
~ ~
- --
~ z
Op~w ~ so
-
-
_. -
--'- '~=-- w ~cn
~-y
Q ~ ~<
/y
y
~ ~
LL
Q LUL 1
6~L
~
d
cn a p m
~
~" g
'Q
rt,::, „
-p ~
Z o Z
x
~ ~ n
?
a~. ~
U`nc~v
ai
U
f6 ~;
Q
C
y
.-_
_~~_ ,;
tip---t_~-' ?;~ ~{I'G
_.v~_~__ ~- ~ . ' d
F~ -~1_ ,~
~ ~. ~ `~
w ~!!
L ; ~ ~ -`7
t~ 7~~~~
_"---~
(~ ~
~~
a
m
E
0
z~
3 /
~ ~~
~ to
~, „. ..r'
~f
~~~ l t I
- ~
.,~"'-
rr
7 r
/~ /
7
f i~ - - _
~,
`~ ~ --
` ~~---~
~ 'ti
~ t t
Ifl l
~-
~~
~- ~ ~ __
v ~ ~ ~~~~
_~
_ ___
t
~ ~ ~ w..~
~'_ ?
o ~ ~ : ~~.e
~ ~ ~ ~~ o
Q ~ ~ ~ o ~ ~.
~ ~ ~ O ~ ass ~ F
t,~
~ N ~ ~ u~ ~° ` ;`~ ~ ~ f
Q
~ ~ U ~ N _ C :'" Vr i
oLS co ~ ~ (~ ~ ~ ~ Q 3
~ ~ ~, ,
~ ~+ ~ ~ C C ~ Z 0 ~ I
i
~ U ~ N Q 0 H ~ (n ~~~s ~ o
~ , ~r; ~ i
c a ~~
a, ~ ~ ~ ~ ~~: ~~
~ V J __ ~ ~-
'~
BMP SIZING
CALCULATION S
Project Name: Woodcreek -Amenity Center Phase
City/State: Holly Springs, NC
Project #: 2040232
Date: 21-Jun-0 7
Table 1.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant
Removal Efficiency in the Piedmont
Impervious
Cover Permanent Pool Depth (feet)
3.0 4.0 5.0 6.0 7.0 8.0 9.0
10 0.59 0.49 0.43 0.35 0.31 0.29 0.26
20 0.97 0.79 0.70 0.59 0.51 0.46 0.44
30 1.34 1.08 0.97 0.83 0.70 0.64 0.62
40 1.73 1.43 1.25 1.05 0.90 0.82 0.77
50 2.06 1.73 1.50 1.30 1.09 1.00 0.92
60 2.40 2.03 1.71 1.51 1.29 1.18 1.10
70 2.88 2.40 2.07 1.79 1.54 1.35 1.26
80 3.36 2.78 2.38 2.10 1.86 1.60 1.42
90 3.74 3.10 2.66 2.34 2.11 1.83 1.67
Source: NCUtNWUWCI Stormwater Best Management Practices, pg. 5, April 1999
STORMWATER BMP 1 -CONSTRUCTED WETLAND (40% TN Removal)
Land Use Area
(ac) % IA Imp. Area
(ac)
Im ervious 5.21 100 5.2
O en S ace 5.21 0 0.0
Totals 10.42 5.2
Total % Impervious Surface Area = 50.0
Surface Area of Permanent Pool:
Assumed depth = 3 feet
SA/DA ratio = 2.06 % From Table 1.1
Minimum pond surface area (SA) _ (DA * SA/DA ratio)/100
SA = 0.215 acres
9350 sq. ft.
Normal pool elevation = 366.0 feet
Surface area provided = 0.272 acres
11848 sq. ft.
1-Inch Runoff Volume Calculation
Using the runoff volume calculations in the "Simple Method" as described by Schueler (1987)
Rv = 0.05 + 0.009(1) where, Rv =Runoff coefficient, in./in.
I =Percent impervious
Rv = 0.50 in./in.
Total runoff volume from 1-inch precipitation:
Runoff volume, S = (Design rainfall) (Rv) (Drainage Area)
S = 0.434 acre-ft
18912 cu. ft.
Water quality pool elevation= 367.70 feet
Storage volume provided = 0.527 acre-ft
22956 cu. ft.
Project Name: Woodcreek -Amenity Center Phase Project #: 2040232
City/State: Holly Springs, NC Date: 21-Jun-07
STORMWATER BMP 1 -CONSTRUCTED WETLAND (40% TN Removal)
Orifice Calculator
Variables Constants
WQ Volume: 0.434167 Acre-ft 18912.3 cf g = 32.2 ft/sZ
Head: 1.70 ft 0.85 ft Cd = 0.6
Draw down time: 54 hrs 194400 s
Orifice Area =
0.021915 sq. ft
3.155782 sq. in
Orifice Diameter =
2.00 in
USE 2 INCH DIAMETER ORIFICE
ROUTING
CALCULATION S
DA1c (amen ctr)
~~-
0
wetland 1 c
Out 10
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Table of Contents
********************** MASTER SUMMARY ***r*****tt***r,rr*****
Watershed....... Master Network Summary ............. 1..01
****************** DESIGN STORMS SUMMARY *******************
RDU NOAA 19 Desi Design Storms ...................... 2.01
****tr*tr********t**** TC CALCULATIONS ********t************
DA1C (AMEN CTR) Tc Ca1cs ........................... 3.01
*****r*****r,t********* CN CALCULATIONS *********************
DA1C (AMEN CTR) Runoff CN-Area ..................... 4.01
**t*****r*****,t******** POND VOLUMES ************r**t****t**
WETLAND 1C...... Vol: Elev-Area ..................... 5.01
******************** OUTLET STRUCTURES *********************
Outlet lc....... Outlet Input Data .................. 6.01
i
S/N: DOYXYWH3NLBE
PondPack (10.00.015.00)
10:43 AM
Withers & Ravenel
6/21/2007
Type.... Master Network Summary Page 1.01
Name.... Watershed
File.... K:\04\04-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
MASTER DESIGN STORM SUMMARY
Network Storm Collection: RDU NOAA 14 Desi
Total
Depth
Return Event. in
2 3.4900
5 4.3000
10 9.9800
25 5.9000
50 6.6300
100 7.3700
1 3.0000
Rainfall
Type
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Synthetic Curve
RNF ID
RDU NOAA 2yr
RDU NOAA Syr
RDU NOAA l0yr
RDU NOAA 25yr
RDU NOAA 50yr
RDU NOAA 100yr
TypeII 24hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Return HYG Vol. Qpeak Qpeak
Node ID Type Event ac-ft Trun hrs cfs
--------
-----
DA1C -------
(AMEN -----
CTR) ----
AREA ------
2 ----------
1.380 -- ---------
12.1000 29.88
DA1C (AMEN CTR) AREA 5 1.990 12.1000 39.83
DAlC (AMEN CTR) AREA 10 2.497 12.1000 47.69
DA1C (AMEN CTR) AREA 25 3.205 12.1000 56.39
DA1C (AMEN CTR) AREA 50 3.781 12.1000 61.70
DA1C (AMEN CTR) AREA 100 9.379 12.1000 67.50
DA1C (AMEN CTR) AREA 1 1.085 11.9500 19.61
*OUT 10 JCT 2 1.358 R 12.3000 7.37
*OUT 10 JCT 5 1.968 R 12.2000 21.47
*OUT 10 JCT 10 2.474 R 12.2000 32.07
*OUT 10 JCT 25 3.181 R 12.1500 43.41
*OUT 10 JCT 50 3.757 R 12.1500 49.14
*OUT 10 JCT 100 9.349 R 12.1500 54.06
*OUT 10 JCT 1 1.065 R 12.6500 1.73
S/N: DOYXYWH3NLBE
PondPack (10.00.015.00) 10:43 AM
Max
Max WSEL Pond Storage
ft ac-ft
-------- ------------
Withers & Ravenel
6/21/2007
Type.... Master Network Summary Page 1.02
Name.... Watershed
File.... K:\04\09-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
MASTER NETWORK SUMMARY
SC5 Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left.; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID Type Event. ac-ft Trun hrs cfs ft ac-ft
WETLAND 1C IN POND 2 1.380 12.1000 29.88
WETLAND 1C IN POND 5 1.990 12.1000 39.83
WETLAND 1C IN POND 10 2.497 12.1000 47.69
WETLAND 1C IN POND 25 3.205 12.1000 56.39
WETLAND 1C IN POND 50 3.781 12.1000 61.70
WETLAND 1C IN POND 100 4.379 12.1000 67.50
WETLAND 1C IN POND 1 1.085 11.9500 19.61
WETLAND 1C OUT POND 2 1.358 R 12.3000 7.37 367.98 .626
WETLAND 1C OUT POND 5 1.968 R 12.2000 21.47 368.28 .736
WETLAND 1C OUT POND 10 2.474 R 12.2000 32.07 368.46 .805
WETLAND 1C OUT POND 25 3.181 R 12.1500 93.41 368.63 .871
WETLAND 1C OUT POND 50 3.757 R 12.1500 49.14 368.71 .903
WETLAND 1C OUT POND 100 4.349 R 12.1500 59.06 368.78 .930
WETLAND 1C OUT POND 1 1.065 R 12.6500 1.73 367.80 .562
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00 .015.00) 10:43 AM 6/21/2007
Type.... Design Storms
Name.... RDU NOAA 14 Desi
Page 2.01
File.... K:\04\09-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
Title... Project Date: 10/18/2006
Project Engineer: CHW
Project Title: Woodcreek
Project Comments:
DESIGN STORMS SUMMARY
Design Storm File,ID = RDU NOAA 14 Desi
Storm Tag Name = 2
Data Type, File, ID
Storm Frequency
Total Rainfall Depth
Duration Multiplier
Resulting Duration
Resulting Start Time
Time-Depth Curve RDU NOAA 2yr
2 yr
3.4400 in
1
23.9909 hrs
.0000 hrs Step= .0833 hrs End= 23.9909 hrs
Storm Tag Name = 5
Data Type, File, ID = Time-Depth Curve RDU NOAA Syr
Storm Frequency = 5 yr
Total Rainfall Depth= 4.3000 in
Duration Multiplier = 1
Resulting Duration = 23.9904 hrs
Resulting Start Time= .0000 hrs Step= .0833 hrs End= 23.9904 hrs
Storm Tag Name = 10
Data Type, File, ID
Storm Frequency
Total Rainfall Depth
Duration Multiplier
Resulting Duration
Resulting Start Time
Time-Depth Curve RDU NOAA l0yr
10 yr
9.9800 in
1
23.9904 hrs
.0000 hrs Step= .0833 hrs End= 23.9904 hrs
Storm Tag Name = 25
Data Type, File, ID = Time-Depth Curve RDU NOAA 25yr
Storm Frequency = 25 yr
Total Rainfall Depth= 5.9000 in
Duration Multiplier = 1
Resulting Duration = 23.9904 hrs
Resulting Start Time= .0000 hrs Step= .0833 hrs End= 23.9904 hrs
Storm Tag Name = 50
Data Type, File, ID = Time-Depth Curve RDU NOAA 50yr
Storm Frequency = 50 yr
Total Rainfall Depth= 6.6300 in
Duration Multiplier = 1
Resulting Duration = 23.9904 hrs
Resulting Start Time= .0000 hrs Step= .0833 hrs End= 23.9904 hrs
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.015.00) 10:43 AM 6/21/2007
Type.... Design Storms
Name.... RDU NOAA 14 Desi
Page 2.02
File.... K:\04\04-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
Title... Project Date: 10/18/2006
Project Engineer: CHW
Project Title: Woodcreek
Project Comments:
DESIGN STORMS SUMMARY
Design Storm File,ID = RDU NOAA 14 Desi
Storm Tag Name = 100
Data Type, File, ID
Storm Frequency
Total Rainfall Depth
Duration Multiplier
Resulting Duration
Resulting Start Time
Time-Depth Curve RDU NOAA 100yr
100 yr
7.3700 in
1
23.9990 hrs
.0000 hrs Step= .0833 hrs End= 23.9990 hrs
Storm Tag Name = 1
Data Type, File, ID = Synthetic Storm TypeII 24hr
Storm Frequency = 1 yr
Total Rainfall Depth= 3.0000 in
Duration Multiplier = 1
Resulting Duration = 24.0000 hrs
Resulting Start Time= .0000 hrs Step= .1000 hrs End= 24.0000 hrs
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.015.00) 10:43 AM 6/21/2007
Type.... Tc Calcs
Name.... DA1C (AMEN CTR)
Page 3.01
File.... K:\04\09-230\09232\H&H\Stormwater\PondPack\woodcreek.ppw
........................................................................
........................................................................
TIME OF CONCENTRATION CALCULATOR
........................................................................
........................................................................
Segment #1: Tc: User Defined
Segment #1 Time: .0830 hrs
Total Tc: .0830 hrs
Calculated Tc < Min.Tc:
Use Minimum Tc...
Use Tc = .0833 hrs
S/N: DOYXYWH3NLBE Withers & Ravenel.
PondPack (10.00.015.00) 10:43 AM 6/21/2007
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Type.... Tc Calcs
Name.... DAlC (AMEN CTR)
File.... K:\04\04-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
Tc Equations used...
___= User Defined =-----------------------------------------------------
Tc = Value entered by user
Page 3.02
Where: Tc = Time of concentration
S/N: DOYXYWH3NLBE
PondPack (10.00.015.00)
10:43 AM
Withers & Ravenel
6/21/2007
Type.... Runoff CN-Area
Name.... DA1C (AMEN CTR)
Page 4.01
File.... K:\04\04-230\09232\H&H\Stormwater\PondPack\woodcreek.ppw
RUNOFF CURVE NUMBER DATA
..........................................................................
..........................................................................
Impervious
Area Adjustment Adjusted
Soil/Surface Description CN acres °C oUC CN
Open space (Lawns parks etc.) - Goo 61 5.210 61.00
Impervious Areas - Paved parking lO 98 5.210 98.00
COMPOSITE AREA & WEIGHTED CN ---> 10.420 79.50 (80)
...........................................................................
...........................................................................
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.015.00) 10:43 AM 6/21/2007
Type.... Vol: Elev-Area
Name.... WETLAND 1C
Page 5.01
File.... K:\04\04-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
Elevation Planimeter Area Al+A2+sgr(A1*A2) Volume Volume Sum
(ft) (sq.in) (sq.ft) (sq.ft) (ac-ft) (ac-ft)
366.00 ----- 11853 0 .000 .000
367.00 ----- 13782 38916 .294 .294
368.00 ----- 15770 44295 .339 .633
369.00 ----- 17815 50346 .385 1.018
370.00 ----- 19915 56566 .433 1.451
POND VOLUME EQUATIONS
* Incremental volume computed by the Conic Method for Reservoir Volumes.
Volume = (1/3) * (EL2-EL1) * (Areal + Areal + sq.rt.(Areal*Area2))
where: EL1, EL2 = Lower and upper elevations of the increment
Areal,Area2 = Areas computed for EL1, EL2, respectively
Volume = Incremental volume between EL1 and EL2
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.01.5.00) 10:43 AM 6/21/2007
Type.... Outlet Input Data
Name.... Outlet lc
Paqe 6.01
File.... K:\04\09-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
REQUESTED POND WS ELEVATIONS:
Min. Elev.= 366.00 ft
Increment = .10 ft
Max. Elev.= 370.00 ft
OUTLET CONNECTIVITY
---> Forward Flow Only (Upstream to DnStream)
<--- Reverse Flow Only (DnStream t.o Upstream)
<---> Forward and Reverse Both Allowed
Structure No. Outfall E1, ft E2, ft
Inlet Box RO ---> CO 367.700 370.000
Orifice-Circular 00 ---> CO 366.000 370.000
Culvert-Circular CO ---> TW 362.000 370.000
TW SETUP, DS Channel.
S/N: DOYXYWH3NLBE
PondPack (10.00.015.00)
10:43 AM
Withers & Ravenel
6/21/2007
Type.... Outlet Input Data
Name.... Outlet lc
Page 6.02
File.... K:\04\04-230\04232\H&H\Stormwater\PondPack\woodcreek.ppw
OUTLET STRUCTURE INPUT DATA
Structure ID = RO
Structure Type
------------------ = Inlet Box
-----------
-------
# of Openings = 1
Invert Elev. = 367.70 ft
Orifice Area = 16.0000 sq.ft
Orifice Coeff. _ .600
Weir Length = 16.00 ft
Weir Coeff. = 3.000
K, Reverse = 1.000
Mannings n = .0000
Kev,Charged Riser = .000
Weir Submergence = No
Structure ID = 00
Structure Type = Orifice-Circular
------------------------------------
# of Openings = 1
Invert Elev. = 366.00 ft
Diameter = .1700 ft
Orifice Coeff. _ .600
S/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.015.00) 10:43 AM 6/21/2007
Type.... Outlet Input Data
Name.... Outlet lc
OUTLET STRUCTURE INPUT DATA
Structure ID = CO
Structure Type
----------------- = Culvert-Circular
-------------------
No. Barrels = 1
Barrel Diameter = 2.5000 ft
Upstream Invert 362.00 ft
Dnstream Invert = 360.00 ft
Horiz. Length = 62.00 ft
Barrel Length = 62.03 ft
Barrel Slope = .03226 ft/ft
OUTLET CONTROL DATA...
Mannings n = .0150
Ke .5000
Kb = .01.2271
Kr = .5000
HW Convergence = .001
Page 6.03
(forward entrance loss)
(per ft of full flow)
(reverse entrance loss)
+/- ft
INLET CONTROL DATA,..
Equati on form = 1
Inlet Control K = .0098
Inlet Control M = 2.0000
Inlet Control c = .03980
Inlet Control Y = .6700
T1 ratio (HW/D) = 1..144
T2 ratio (HW/D) = 1.291
Slope Factor = -.500
Use unsubmerged inlet control Form 1 equ. below T1 elev.
Use submerged inlet control Form 1 equ. above T2 elev.
In transition zone between unsubmerged and submerged inlet control,
interpolate between flows at T1 & T2...
At Tl Elev = 364.86 ft ---> Flow = 27.16 cfs
At T2 Elev = 365.23 ft ---> Flow = 31.05 cfs
Structure ID = TW
Structure Type = TW SETUP, DS Channel
FREE OUTFACE CONDITIONS SPECIFIED
CONVERGENCE TOLERANCES ...
Maxi mum Iterations= 40
Min. TW tolerance = .O1 ft
Max. TW tolerance = .O1 ft
Min. HW tolerance = .O1 ft
Max. HW tolerance = .O1 ft
Min. Q tolerance = .00 cfs
Max. Q tolerance = .00 cfs
5/N: DOYXYWH3NLBE Withers & Ravenel
PondPack (10.00.015.00) 10:43 AM 6/21/2007
Appendix A
Index of Starting Page Numbers for ID Names
A-1
----- D -----
DAlC (AMEN CTR)... 3.01, 4.01.
----- 0
Outlet 1c... 6.01
----- R -----
RDU NOAA 14 Desi... 2.01.
----- W -----
Watershed... 1.01
WETLAND 1C... 5.01.
S/N: DOYXYWH3NLBE
PondPack (10.00.015.00)
10:43 AM
Withers & Ravenel.
6/21/2007