20070208 Ver 2_More Info Received_20071107

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• Soil & Environmental Consultants, PA
11010 Raven Ridge Road Raleigh, North Carolina 27614 Phone: [phone] Fax: [phone]
www.SandEC.com
November 7, 2007
S&EC Project #4716.W6
DWQ EXP Project #07-0208v2
Department of Environment and Natural Resources
Division of Water Quality
Attn: Cyndi Karoly/Lia Myott ~~
2321 Crabtree Boulevard, Suite 250 p ~~~
Raleigh, NC 27604 ,~
Re: Reply to the Division of Water Quality's Request for More Information N`'i~ 7 /~~~
Heritage High School-EXPRESS REVIEW PROGRAM
Wake Count , NC '~ ~ ~` ~`~" :~~~LITY,
y ~1~ ~~s~ r~ X41 @ I'
To Whom It May Concern:
The purpose of this letter is to respond to your Request for More Information letter dated October 31,
2007. The original questions/requests are copied below as they appear within letter and are then followed
by our response.
Additional Information Requested:
1. Please provide full size plans at a scale of 1 " = 50' or larger that details the entire site including
drainage area boundaries, impacts to waters of the state, and stormwater drainage system.
As per the engineer, attached are copies of the Site Grading Plans, stormwater Management
Plans and details containing the information requested.
2. Please label and identify the types of BMP's on the plans.
As per the engineer, the BMP's are labeled on the attached plans. The wet detention ponds on
the site were designed to provide pre-post stormwater detention and water quality treatment
based on previous DWQ design guidelines. Detailed calculations are not attached as these
BMP's are not intended to meet nitrogen removal requirements. Diffuse flow into the riparian
buffers is provided to meet NSW watershed requirements.
3. Where applicable on the plans, please include BMP system component details such as Inflow and
Outflow Structures, Pretreatment Systems (Forebays), High Flow Bypass Structures, Overflow and
Emergency Spillway, Erosion and Sediment Control and Monitoring devises such as Energy
Dissipaters and sediment Accumulation/Depth Markers. Please provide supporting calculations
for sizing each component.
As per the engineer, details of the proposed Level Spreader are provided on sheet C7.16 of the
attached plans. Details of the proposed wet detention ponds are also provided although these
devises are not being utilized to meet nutrient removal requirements.
4. The drainage area where the new High School and Student parking are located is considered a pocket
of high density. Therefore the Division of Water Qualify requires that the BMP in Area 4 meet both
85% TSS and 30% TN removal efficiencies such as bioretention structures, stormwater wetlands or
ponds followed by forested filter strips designed according to the latest version of the NCDENR
Sformwater Best Management Practices Manual.
Charlotte Office:
236 LePhillip Court, Suite C
Concord, NC 28025
Phone: [phone]
Fax: [phone]
Greensboro Office:
3817-E Lawndale Drive
Greensboro, NC 27455
Phone: [phone]
Fax: [phone]

The application submitted to the NCDWQ for this project requested written concurrence for the
use of Water Quality Certification 3625 for temporary impacts associated with utility line
construction, in addition to a Riparian Buffer Authorization for the impacts of anon-electric
utility line perpendicular crossing of a stream subject to the Neuse River Basin Buffer Rule.
Water Quality Certification 3625 does not include a condition requiring a stormwater
management plan to treat 85% TSS and 30% TN, or specific BMP's such as bioretention
structures, stormwater wetlands or ponds followed by forested filter strips therefore a
stormwater management plan to meet the 85% TSS and 30% TN removal has not been designed
and should not be required.
5. Since the project is located in a NSW watershed, all stormwater outflow through the riparian buffer
shall meet diffuse flow provisions such as discharging over a level spreader located outside the riparian
buffer with down slope not to exceed 6% or 8% for grass or forested filter strip respectively. On the
other hand, BMP's that meet conditions specified in item 4 above may substitute for diffuse flow
provisions that will allow direct discharge into stream channels. Please provide supplements for each
level spreader along with all items in the corresponding Required Items Checklist.
As per the engineer, the points of stormwater outflow are addressed below starting with the
discharge from Dry Detention Pond A in the northeast corner of the site and progressing
counter-clockwise around the site:
Discharge Point 1-Outfall from Drv Detention Pond A
Discharge from this outlet is directed into an old drained pond bed (isolated wetland). There is
a distance of approximately 320 linear feet between the outlet structure and the riparian buffer
located below the old pond dam of the drained pond.
Discharge Point 2-Outfall from Wet Detention Pond G
Outflow from this discharge point flows to an existing, expansive wetland/floodplain area that,
due to the natural existing topography, will provide natural diffuse flow of stormwater into the
stream buffer. There is a distance of approximately 360 linear feet between the outlet structure
and the jurisdictional wetland and an additional 3001inear feet (totaling an approximate 660
linear feet) to the riparian buffer of Smith Creek.
Discharge Point 3-Outfall from Storm Drain Outlet B6
A level spreader has been added to the plans where discharge from this outlet approaches the
stream buffer. A Level Spreader Supplement from and draft 18~M Agreement are attached, this
draft 18~M Agreement has been sent to Wake County Public School System for signature and to
be notarized. Please note that a signed and notarized 18~M agreement and deed restriction will
be provided following DWQ acceptance of the proposed devise.
Discharge Point 4-Outfall from Wet Detention Pond B
Outflow from this discharge point flows to an existing, expansive wetland/floodplain area that
due to natural existing topography, will provide natural diffuse flow of stormwater into the
stream buffer located more than 1,500 linear feet from the pipe outlet.
Discharge Point 4-Outfall from Wet Detention Pond C
Outflow from this discharge point flows to an existing, expansive wetland/floodplain area that
due to natural existing topography, will provide natural diffuse flow of stormwater into the
stream buffer located more than 800 linear feet from the pipe outlet.
Discharge Point 4-Outfall from Wet Detention Pond D
Outflow from this discharge point flows to an existing, expansive wetland/floodplain area that
due to natural existing topography, will provide natural diffuse flow of stormwater into the
stream buffer located more than 1751inear feet from the pipe outlet.

We anticipate that this answers all of the DWQ's questions in order to complete the final review process
for Water Quality Certification 3625 and Riparian Buffer Authorization. If you have any further questions or
any additional explanation is needed, please don't hesitate to call.
Sincerely,
Debbie Edwards
Environmental Specialist
CC:
Susan Holt-LS3P Associates
Attachments:
1) Overall Grading Plan (sheets C3.0-C8.2)
2) Level Spreader 66 Supplement, Checklist & Calculations
3) Draft Inspection and Maintenance Agreement

~~~
NCDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
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LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER SUPPLEMENT
This form must he filled out, printed and submitted.
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L PRDJECT tNfORMATIQN - l -l
Project name Heritage High School
Contact name Steve Miller, PE
Phone number 919-319-6716
Date November 6, 2007
Drainage area number B6
11. DESIGN INFORMATION
For Level Spreaders Receiving Flow From a BMP
Type of BMP ~ i
Drawdown flow from the BMP cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Where Does the Level Spreader Discharge?
To a bioretention cell?
To a wetland?
To a filter strip or riparian buffer?
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass
Width of dense ground wver
Width of wooded vegetation
Total width
Slope (from level lip to to top of bank)
Are any draws present?
Level Spreader Design
Forebay surface area
Feet of level lip needed per cfs
Answer "Y" to one of the following:
Length based on the 1 inlhr storm?
Length based on the 10-yr, 24-hr storm?
Length based on the BMP discharge rate?
Design flow
Is a bypass device provided?
Length of the level lip
Are level spreaders in series?
108,400 ftZ
33,970 fiz
0.31
0.51
1.269146006 cfs
min
7.22 in/hr
9.16323416 cfs
N (Y or N)
Y (Y or N) Do not need to complete filter strip characterization below.
N (Y or N)
rl/~ ft
ft
ft
ft
N (Y or N) OK
68 sq ft OK
fUcfs
Y (Y or N)
N (Y or N)
N (Y or N)
1.27 cfs
Y (Y or N) OK
26 ft
N (Y or N)
Form SW401-Level Spreader, Finer Strip, Restored Riparian Buffer-Rev.2
#VALUE!
#VALUE!
Parts I. and II. Design Summary, page 1 of 2
( /

Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Dimensions of the channel (see diagram below):
M
B
W
Y
Peak velocity in the channel during the 10-yr, 24-hr storm
Channel lining material
(Y or N) Redesign channel to discharge to a dissipaior pad adjacent to the w
ft
ft
ft
ft
cfs
~~
I j------------
M
,~
1 B
Form SW401-Level Spreader, Fiker Strip, Restored Riparian Buffer-Rev2
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Parts I. and II. Design Summary, page 2 or 2

1N. flEQtlIREU ITEMS CHECKLIST.
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Page/ Plan
Initials Sheet No.
~~ ~~• Z ~ 1. Plans (1" - 50' or larger) of the entire site showing:
~ ~ ti -Design at ultimate build-out,
- Off-site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
-Forebay (if applicable),
- High flow bypass system,
- Maintenance access,
- Recorded drainage easement and public right of way (ROW), and
- Boundaries of drainage easement.
~!~ G T / ~ 2. Plan details (1" = 30' or larger) for the level spreader showing:
- Forebay (if applicable),
-High flow bypass system,
-One foot topo lines between the level lip and top of stream bank,
- Recorded drainage easement, and
- Design at ultimate build-out.
~ G 7• I c, 3. Section view of the level spreader (1 " = 20' or larger) showing:
- Underdrain system (if applicable),
- Level lip,
- Upslope channel, and
- Downslope filter fabric.
'~ 4. Adate-stamped photograph of the filter strip that clearly shows the type of vegetation that is present.
~_ 5. An assurance that the installed system will meet design specifications upon initial operation once the
project is complete and the entire drainage area is stabilized.
rv'1~ G y•o f 6. A construction sequence that shows how the level spreader will be protected from sediment until the entire
drainage area is stabilized.
~r
~~ sd~°~ 7. The supporting calculations.
Pb. ~-
D2roF'r' P~, L 8. A copy of the signed and notarized inspection and maintenance (I&M) agreement.
#-' 9. A copy of the deed restriction.

,e~v'iiww ~3 y DN'4 .
S>;~ u~rilrrrycJGP'io•J S~Q~~~ 1T3=M ~Z2 , cn/ G ~.O .
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.2
Part III, page 1 of 1
l.~

PROJECT NAME
Heritage High School
LOCATION
Wake Forest, NC
Storm Outlet Structure
FES No.= A10
Pipe Dia= 18 in
Qio = 5.83 cfs
Qfull = 15.40 cfs
Vfull = 8.70 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
- - - SI
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I- ~ ~"~ch --I
DATE DESIGN PHASE
11-5-07 PRELIM / X /
PROJECT NO CONSTR / /
1123 REVISION / /
BY RECORD / /
KAL OTHER / /
CHECKED BY (SPECIFY)
SJM
Quo/Qfull = 0.38
V/Vfull = 0.93
V = 8.1 fps
Zone = 2
Dso = 8 in
Dn~c = 12 in
Riprap Class = B
Apron Thickness = 18 in
Apron Length = 9 ft
Apron Width = 3xDia = 5 ft
Storm Outlet Structure
FES No.= LEVEL SPI SPREADER B6
Weir Wth= 36 in
Q~ o = 11.00 cfs
Ofull = 11.00 cfs
Vfull = 3.20 fps
From Fig. 8.06.b.1:
From Fig. 8.06.b.2:
s
Y
,__ 3
Quo/Qfull = 1.00
V/Vfull = 1.14
V = 3.6 fps
Zone = 2
Dso ~ = 8 in
Dix - 12 in
Riprap Class = B
Apron Thickness = 18 in
Apron Length = 18 ft
Apron Width = 3xDia = 9 ft

Appendices
_ NEW YORK DOT DISSIPATOR METHOD
I FOR USE IN DEFINED CHANNELS
(Source: 'Bank and channel lining procedures", New York Department
of Transportation, Division of Design and Conswcuon, 1971.)
Note: To use the following char you must know:
(1) Q full capacity
(2) Qto
(3) V full
(4) V1o
where Q =discharge in cfs and V =Velocity in FPS.
ESTIMATION OF STONE SIZE AND DIMENSIONS FOR
CULVERT APRONS
Step 1) Compute flow velocity Vo at culvert or paved channel outlet.
Step 2) For pipe culverts Do is diameter.
For pipe arch, arch and box culverts, and paved channel outlets,
Do=Ao, where A.= cross-sectional area of flow at outlet.
For multiple culverts, use Do=1.25xDa of single culvert.
Step 3) For apron grades of 10% or steeper, use recommendations
For next higher zone. (Zones 1 through 6).
zs
20 -
'~_
Q..
}
U
O
W t0 -
s-
~ I R' K 56' ~' eY ~ I I
0' S' 10' 15' 20' 25'
DIAMETER (Ft.)
;~~ ~~' ;~
11
' ~ I ~ ~ ~
~,
I 11111 II 111 111 I' II
1 1
II 1
1
111 11111 11111 11 1111 it1
X11
1 1
\I 1 ~ 1 ~
5 ~IIII
11
111 ~1 III 111 II 111111
~~ 1~
I
I 1 1 1 I
.z1 13 ~ ,4
111 II ill
1i II
~lil~ I 1lilil
I 111 11 111
111 I III X11
111 111
1
I
Figure 8.06.b.1
Rcv, 12h~3
8.06.5
C~

Filter Strip, Restored Riparian Buffer and Level Spreader
Inspection and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
Important maintenance procedures:
- Immediately after the filter strip is established, any newly planted vegetation
will be watered twice weekly if needed until the plants become established
(commonly six weeks).
-~eget~n-
- Stable groundcover will be maintained in the drainage area to reduce the
sediment load to the vegetation.
ngs
(1\TIPC, 1993). Forested filter strips do not require this type of maintenance.
- /.
After the filter strip is established, it will be inspected quarterly and within 24 hours
after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal County).
Records of inspection and maintenance will be kept in a known set location and will be
available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential roblem: How I will remediate the roblem:
The entire filter strip Trash/debris is present. Remove the trash/debris.
s stem
The flow splitter device The flow splitter device is Unclog the conveyance and dispose
(if applicable) clo ed. of an sediment off-site.
The flow splitter device is Make any necessary repairs or
damaged. replace if damage is too large for
re air.

BMP element: Potential roblem: How I will remediate the roblem:
The Swale and the level 'The Swale is clogged with Remove the sediment and dispose
lip sediment. of it off-site.
The level lip is cracked, Repair or replace lip.
settled, undercut, eroded or
otherwise dama ed.
There is erosion around the Regrade the soil to create a berm
end of the level spreader that that is higher than the level lip, and
shows stormwater has then plant a ground cover and
bypassed it. water until it is established. Provide
lime and aone-time fertilizer
a lication.
Trees or shrubs have begun Remove them.
to grow on the Swale or just
downslo e of the level li .
The bypass channel Areas of bare soil and/or Regrade the soil if necessary to
erosive gullies have formed. remove the gully, and then
reestablish ro er erosion control.
Turf reinforcement is Study the site to see if a larger
damaged or ripap is rolling bypass channel is needed (enlarge if
downhill. necessary). After this, reestablish
the erosion control material.
The filter strip Grass is too short or too long Maintain grass at a height of
(if a licable). a roximatel three to six inches.
Areas of bare soil and/or Regrade the soil if necessary to
erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer a lication.
Sediment is building up on Remove the sediment and
the filter strip. restabilize the soil with vegetation if
necessary. Provide lime and a one-
time fertilizer a lication.
Plants are desiccated. Provide additional irrigation and
. fertilizer as needed.
Plants are dead, diseased or Determine the source of the
dythg. ~ problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide aone-time
fertilizer a lication.
Nuisance vegetation is Remove vegetation by hand if
choking out desirable species. possible. If pesticide is used, do not
allow it to get into the receiving
water.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality local Regional Office, or the
outlet. 401 Oversi ht Unit at 919-733-1786.

I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Print name: Michael Burris Wake County Public School System
Title: Assistant Superintendent of Facilities Design and Construction
Address: 1551 Rock Quarry Road Raleigh NC 27610
Phone: [phone]
Signature:
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
I, , a Notary Public for the State of
County of , do hereby certify that
personally appeared before me this
day of ,and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires,
D