20090204 Ver 1_More Info Received_20090618

--- M U L K EY
ENGINEERS & CONSULTANTS
PO Box 331 27
RALEIGH, NC 27636
.PHONE: 919-S51-1912
FAx: [phone]
LETTER OF TRANSMITTAL
To: NCDENR-DWQ
Cyndi Karoly
Attn: Annette Lucas.,
401 Permitting Unit
2321 Crabtree Blvd., Suite 250
Raleigh, NC 27604
Re: DWQ Project # 09-0204
WCU-Health & Gerontology
I am sending you the following item(s):
@L9W9 1
JUN 1 8P 2009
DENR -WATER QUALITY
WETLA.WDS AND ST0RMQWUj?TER BRANCH
Oq- 1)a p,+
Date: June 18, 2009
** HAND DELIVER **
Job No.: 2007047.00
COPIES DATE NO. DESCRIPTION
2 Response to Request for more information
2 Calculations associated with Response to Request for
more information
2 Revised plan sheets (C-2.10, C-2.15 & D-1.06)

These are transmitted as checked below:
? As requested
® For approval
? For review and comment
® For your use
? For Signatures
Remarks:
Please let me know if there are any questions or comments. You can contact me at [phone] or
[e-mail]. Thank you for your time and assistance.
Copy to: US Army Corps-Ashville Signed:
NC Wildlife-David McHenry Warren M. ugg, P
Jackson County Planning Project Engineer
Pti
4-eMULKEY
ENGINEERS & CONSULTANTS
PO Box 331 27
RALEIGH, NC 27636
PHONE: C319-851-1912
FAx: 919-B51-1918
LETTER OF TRANSMITTAL
To: NCDENR-DWQ
Roger Edwards
Attn: Susan Wilson
2090 U.S. Highway 70
Swannanoa, NC 28778
1-828-296-4500
Date: June 18, 2009
** FEDERAL EXPRESS **
Re: DWQ Project # 09-0204
WCU-Health & Gerontology
I am sending you the following item(s):
Job No.: 2007047.00
COPIES DATE NO. DESCRIPTION
1 Response to Request for more information

1 Calculations associated with Response to Request for

more information
1 Revised plan sheets (C-2.10, C-2.15 & D-1.06)

These are transmitted as checked below:
? As requested
® For approval
? For review and comment
® For your use
? For Signatures

Remarks:
Please let me know if there are any questions or comments. You can contact me at [phone] or
[e-mail]. Thank you for your time and assistance.
Copy to: US Army Corps-Ashville Signed:
NC Wildlife-David McHenry Warren M. Sugg, PE
Jackson County Planning Project Engineer
#roly 919-858-1811
MULKEY
ENGINEERS & CONSULTANTS
June 17, 2009
North Carolina Department of Environment & Natural Resources
Division of Water Quality
Roger C. Edwards, Regional Office Supervisor
Surface Water Protection Section
2090 U.S. Highway 70
Swannanoa, North Carolina 28778
Subject: Response to June 11, 2009 Request for More Information
DWQ Project # 09-0204
Western Carolina University School of Health and Gerontology
Response to Request for More Information
Mr. Edwards:
Mulkey Engineers and Consultants is serving WCU as the site/civil for the above reference project.
Below we have provided the formal response to the request for more information by your office.
Please find these response along with the associated and included documentation to verify the
responses.
Please address the following issues with the design of the sand filters:
a. Volume in excess of the design volume must bypass the sand filter (ie the sand filter
should have a splitter device so that the first inch of rainfall is captured for treatment).
Response: Sputter boxes have been shown on the plan sheet (C-2.10) and on the detail sheet
(D-1.06). The boxes are numbered 15, 15a, 13, 13a, 11, & 28 and have been noted under the
drainage table as double width box VNrith special weirs that have been designed for the first
inch of rainfall. The weir dimensions have been shown in the detail on D-1.06 and the
design calculations for each splitter box weir have been included in this submittal. Please
refer to C-2.10, D-1.06 and included calculations for all sand filter references.
b. These systems require under drains. The under drains should be designed in accordance
with Section 5.7 of the DWQ BMP Manual.
Response: Underdrains have now been shown in the details of the sand filters on D-1.06.
The calculations for these underdrains have followed the design from section 5.7 of the 2007
DWQ BMP manual and have been included in this submittal.
c. Show the boundaries of the recorded drainage easement on the plan sheets.
Response: The DWQ drainage easement has been shown on C-2.10 from all sand filters and
bioretention to the public ROW.
2. Please address the following issues with the design of the bioretention cell:
a. Consider organizing the plan sheets so that the information for the bioretention cell
(plans, profiles, and planting plan) can be found conveniently on consecutive plan
sheets.
Response: The planting detail for the bioretention has been moved to the C-2.15 in addition
to being on D-1.06 to clearly state all bioretention items on C-2.15.
b. Plants should not be backfilled with engineered soil that has been amended with
compost(approved media should be used; in addition, compost may hinder nutrient
uptake)
Response: The planting details on C-2.15 have been updated to state that only engineered
bioretention media shall be used in the bioretention area plantings.
c. Import top soil should not be placed on top of plantings.
MULKEY INC. 6750 TRYON ROAD CARY, NC 2751 1 PO BOX 33127 RALEIGH, NC 27636 PH: 919-851-1912 FAX: [phone] www.MULKEYINC.COM
Response: The planting details on C-2.15 have been updated to state that only engineered
bioretention media shall be used in the bioretention area plantings.
d. Provide watering specifications to establish the vegetation.
Response: A note has been added to the plan sheet C-2.15 that speaks to the watering
requirement as once per week to adequately establish the bioretention planting both during
the construction warranty phase and afterwards by WCU staff.
e. Explain how the berm that conveys flow from the building into the bioretention cell will
be stabilized to prevent erosion (currently the slope is approximately 20 percent in this
swale).
Response: A detailed calculation of the swale has been provided under this submittal. The
slope in the s?vale is 12.6°, o given the flow path of 111 linear feet and vertical drop from
2225 to 2211 as it enters the bioretention. The calculations prove that established grass will
handle the 3.3 ft/sec velocity that is expected during the 10 year rain event. Please refer to
the calculation provided for more information on the Swale.
f. Space the underdrains such that they provide more even coverage for the bottom of the
bioretention cell.
Response: The four required underdrains have been spaces to provide even coverage for the
entire bioretention cell. Please refer to C-2.15 for all bioretention information.
g. Show the boundaries of the recorded drainage easement on the plan sheets.
Response: The DWQ drainage easement has been shown on C-2.10 from all sand filters and
bioretention to the public RONV.
Please let me know if you have any further questions, comments, or concerns. Thanks.
Warren M. Sugg, PE, LEED AP
Project Engineer
Mulkey Engineers & Consultants
Cc: US Army Corps of Engineers Ashville Field Office (one copy)
David McHenry- NC Wildlife Resources Commission (one copy)
Cyndi Karoly-401 Permitting Unit (2 copies per phone conversation with Annette Lucas)
Jackson County Planning (one copy)
--MULKEY
E N C=. 1 !y: E E: I< E t. [: CJ t" LJ L.7 r, 1
SAND FILTER
SPLITTER BOX
CALCULATIONS
MULKEY INC. 6750 TRYON ROAD CARY, NC 27511 PC BOX 33127 RALEI61, NO 27636 PH: 919-B51-1912 FAX: [phone] WWW.MULKEYINC.COM
-'- M U LKEY Calculation Sheet
ENGIWUERS & C01, G U IT A N I S
CLIENT SUBJECT SA,.NO
PROJECT No. gc;, Y. *.1 5
Flow from first inch to Sand Side of Sand Filter (Q,.,) = 4.69 cfs
WEIR DESIGN
Assumption for width of weir =
Q=Cw*B*H"
Cw= 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.68' 8.19
2.5'
Page OF
Prepared By Date
Reveiewed By Date
Values to be input by user
Use 8 In
4-*MULKEY Calculation Sheet
C N [; I N l E " R E F C O h S U LT 4 N 7 S
CLIENT SUBJECT SAND FAG TZ
PROJECT No. $Dx l-,
Flow from first inch to Sand Side of Sand Filter (Q,,,) = 0.96 cfs
WEIR DESIGN
Assumption for width of weir =
Q=CW*B-H'.e
Cw = 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.23' 2.80
2.5'
Page OF
Prepared By Date
Reveiewed By Date
Values to be input by user
Use 3 In
4!-MULKEY Calculation Sheet
E NI:I N[C R5 & CON GU LIA N / S
CLIENT SUBJECT SAND
PROJECT No. R?y+ iz,
Flow from first inch to Sand Side of Sand Filter (Q,,,) = 1.39 cfs
WEIR DESIGN
Assumption for width of weir =
Q=Cw*B*H1.e
Cw= 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.30' 3.64
2.5'
Page OF
Prepared By Date
Reveiewed By Date
Values to be input by user
Use 4 in
41-MULKEY Calculation Sheet
E N G I N E E R S S COIN S U L T A N T S
CLIENT SUBJECT SAO FIl.TEVAkL4
PROJECT No. B,!:W, 13A
Flow from first inch to Sand Side of Sand Filter (Q,.,) = 1.25 cfs
WEIR DESIGN
Assumption for width of weir =
Q=CW*B*H'.s
Cw= 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.28' 3.39
2.5'
Page OF
Prepared By Date
Reveiewed By Date
Values to be input by user
Use 4 in
-?-MULKEY Calculation Sheet
E N G I NEERS & GCJ N SUi.1 AN'l S
CLIENT SUBJECT SAnt4 rlr,T tti `
PROJECT No. Rrr? 71
Flow from first inch to Sand Side of Sand Filter (Q,,,) = 7.16 cfs
WEIR DESIGN
Assumption for width of weir =
Q=Cw*B*H"
Cw= 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.90' 10.85
2.5'
Page OF
Prepared By Date
Reveiewed By Date
Values to be input by user
Use 11 in
-=- M U LK EY Calculation Sheet Page OF
ENGINEERS S GUN ?LUL1-A NJS /
CLIENT SUBJECT 5,4Nt F14TS0 '6 Prepared By Date
PROJECT No. Fo,, Reveiewed By Date
Values to be input by user
Flow from first inch to Sand Side of Sand Filter (Q,..) = 3.85 cfs
WEIR DESIGN
Assumption for width of weir = 2.5'
Q=Cw*B*H,.5
Cw= 3.33 for sharp-crested weirs
B = width of weir (assumed)
H = Height (solve for)
H = 0.60' 7.18
Use 8 in
I'uIULKEY
Ii t' i ?` G f F: c f" ('J p- cq LJ ? ? •, r.. 1 f
SAND FILTER
& BIORETENTION
UNDERDRAIN
CALCULATIONS
MULKEY INC. 6750 TRYON ROAD CARY, NC 27511 PO BOX 33127 RALEIGH, NC 27636 PH: 919-851-1912 FAX: [phone] WWW.MULKEYINC.COM
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NCDENR Stormwater BMP Manual
Table 5-1
Number of Pipes Required in the Underdrain
Revised 09-28-07
If D is less than # of 4" pipes If D is less than # of 6" pipes
5.13 2 7.84 2
5.95 3 9.11 3
6.66 4 10.13 4
7.22 5
7.75 6
8.20 7
5.8 Outlets
Outlets of BMPs are the devices that control the flow of stormwater out of the BMP to
the conveyance system (stormwater pipe, natural drainageway, etc.). While most of the
water quality treatment takes place within the BMP, the outlet design is often integral to
treatment efficiency, as well as being a critical factor in stormwater volume control.
Water quality is affected by how quickly the water is removed from the treatment unit,
thereby affecting sedimentation time and possibly causing resuspension of particles.
The depth from which the water is drawn also affects water quality, since the water is
typically cleaner the higher it is in the water column. Finally, the design of the outlet is
also the main means of controlling peak flow volumes and rates. Outlet designs are
specific for each BMP depending on the goals to be achieved. The following sections
will discuss many of the most common outlet designs. Hydraulic calculations for outlets
types as well as storage and drawdowns are provided in Section 3.0 Stormwater
Management and Calculations.
It should be noted that floatation issues should be considered with any structure (outlet
box, riser, etc.) placed within a BMP.
5.8.1 Outlet Boxes
Outlet boxes typically consist of a cast in place or precast concrete structure, with a free-
flowing weir providing the water control mechanism. They are typically employed on
smaller BMPs with lower flow volumes. The weirs can be made of various materials
(wood, metal, concrete, etc.), and there are several standard weir shapes, with
rectangular and v-notch being the most common. Each weir has a formula for
calculating the flow over the weir based on the height of the water column and shape of
the weir. A rectangular weir releases a relatively linearly increasing flow volume as the
level of water in the BMP rises. A v-notch weir releases a relatively exponentially
increasing flow volume as the level of water in the BMP rises. V-notch weirs allow more
accurate flow measurement and control at lower flows, but sometimes cannot handle
peak storm events. There are also "compound" weir designs, which incorporate aspects
of different weir designs to achieve specific results. For instance, a compound weir
might have a small v-notch in the lowest portion to provide lower release rates for
Common BMP Design Elements 5-12 July 2007
[''mot U L K E Y
D1XAINAGE SWALE
TO BIORETENTION
CALCULATIONS
MULKEY INC. 6750 TRYON ROAD CARY, NC 2751 1 PO BOX 33127 RALEIGH, NC 27636 PH: 919-851-1912 FAX: [phone] WWW.MULKEYINC.COM
Method for Sizinq Trapezoidal Channels
Project Name:
Operator:
Job Number:
Date:
Channel:
Description:
WCU
WMS
2007047.00
6/17/2008
Swale before entering bioretention
10-yr Design
Design Parameters ==>
*-MULKEY
I?IM 8 CONSULTANT„
P.O, BOX 33127
RALEIGH, NC 27836-312?
[phone]
(9191851.1918 {FA,? i
Cited tables and figures are from "NC Erosion & Sediment Control Planning and Design Manual"
Peak Flow, Q =
Channel Lining =
Max. Permissible Velocity, Vm,x =
VR =
Manning's Roughness Coefficient, n =
Longitudinal Slope of Channel, s =
Bottom Width, B =
Horizontal Side Slopes, M =
design channel depth, d =
normal water depth, dn =
Channel Physical Calculations ==>
12.51 CFS
EARTH
4.0 FPS (Table 8.05a)
1.37 for use in Figure 8.05c
0.02 from Figure 8.05c, using Retardance Classification "C"
0.126 FT/FT
6 FT
3 FT
1.0 FT
0.5 FT
Cross-Sectional Area, A = 3.75 SF
Wetted Perimeter, P = 9.16 FT
Hydraulic Radius, R = 0.41 FT
Find Normal Depth ==>
Zreq = 0.473
Zav = 2.067
Change values of B, M, and d until Zreq - Zav
Calculate Velocity ==>
Calculated Velocity, V = 3.34 FPS
Check to make sure V is less than Vmax OK
Check Freeboard ==> Need at least 6" of freeboard
Freeboard, d, = 6.00 in
OK
OK
NCDENR Stormwater BMP Manual Chapter Revised 09-28-07
3.2. Peak Flow Calculations
Some of the state's stormwater programs require providing attenuation of peak runoff;
for example, that the post development flow rate for the one-year, 24-hour storm may
not exceed the pre-development flow rate (Neuse and Tar-Pamlico NSW Programs). In.
addition, it is also important to compute flow rates from the watershed when designing
BMPs such as grassed swales, filter strips, and restored riparian buffers.
The primary method that is used to determine peak runoff rate for North Carolina's
stormwater programs is the Rational Method. The Rational equation is given as:
Q=C*I*A
Where: Q = Estimated design discharge (cfs)
C = Composite runoff coefficient (unitless) for the watershed
I = Rainfall intensity (in/hr) for the designated design storm in the
geographic region of interest
A = Watershed area (ac)
The composite runoff coefficient reflects the surface characteristics of the contributing
watershed. The range of runoff coefficient values varies from 0 -1.0, with higher values
corresponding to greater runoff rate potential. The runoff coefficient is determined by
estimating the area of different land uses within each drainage area. Table 3-2 presents
values of runoff coefficients for various pervious and impervious surfaces. The
Division believes that the Rational Method is most applicable to drainage areas
approximately 20 acres or less.
Table 3-2
Rational runoff coefficients (ASCE,1975; Viessman, et al., 1996; and Malcom, 1999)
Description of Surface Rational Runoff Coefficients, C
Unimproved Areas 0.35
Asphalt 0.95
Concrete 0.95
Brick 0.85
Roofs, inclined 1.00
Roofs, flat 0.90
Lawns, sandy soil, flat (<2%) 0.10
Lawns, sandy soil, average (2-7%) 0.15
Lawns, sandy soil, steep (>7%) 0.20
Lawns, heavy soil, flat (<2%) 0.15
Lawns, heavy soil, average (2-5%) 0.20
Lawns, heavy soil, steep (>7%) 0.30
Wooded areas 0.15
The appropriate value for I, precipitation intensity in inches per hour, can be obtained
from the NOAA web site at: http://hdsc.nws.noaa.gov/hdsc/-pfds/. This web site
Stormwater Management and Calculations 3-2 July 2007
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--=- M U L K E Y
REVISED
CONSTRUCTION
DRAWINGS
MULKEY INC. 6750 TRYON ROAD CARY, NO 27511 PO BOX 33127 RALEIGH, NO 27636 PH: 919-851-1912 FAX: [phone] WWW.MULKEYINC.COM