20020577 Ver 1_More Info Received_20070530

r

SO1L
HORIZONS
P.O. Box i o63
Youngsville, North Carolina 27596
Phone: (9~9~ 554-2363
May 29, 2007
North Carolina Division of Water Quality
401 Wetlands Unit
2321 Crabtree Boulevard, Suite 250
Raleigh, North Carolina 27604-2260
Attention: Ms. Amy Chapman
Reference: Level Spreader Design
Lot 9 Dove Landing, Franklin County, NC
DWQ# 2002-0577v2
Dear Ms. Chapman:
Please find attached a stand alone level spreader design worksheet, calculations, site plan, details,
and operation and maintenance agreement. In summary, this site has a very small area of
drainage area that flows toward the proposed Tar-Pamlico forested buffer. This level spreader
design assumes that if this lot is ever developed, the entire drainage area would be covered with
concrete. Also, it is designed to handle the 10 year storm event which is approximately 2 inches
per hour. Please review these documents to determine if they contain the appropriate material
that you are looking for per your letter dated March 28, 2007.
Also, if you have any questions regarding this information, please give me a call at 919-818-5087.
Sincerely,
J
_ ~~"
ohn R. Davis, Jr., RS
Licensed Soil Scientist
Enclosures: Level Spreader Worksheet
,{
,: ~1 i~ r
Design Calculations
Figures 1, 2 and 3
NOAA Precipitation Estimates
Notarized Operation and Maintenance Agreement
Soil Evaluations For On-Site Wastewater Disposal Systems
Wastewater System Design, Inspection and Operation
Wetland Delineations

DWO Project
2-00~.- OS `77 v~
DIVISION OF WATER QUALITY -LEVEL SPREADER WORKSHEET (112007)
I. PROJECT INFORMATION (please complete the following information):
Project Name : Lof 9 ,hove r' G ~ d
Contact Person: ~T h ~ovis Phone
Level Spreader ID: 1
Level Spreader Length ~ ~
Drainage Area Q. ! 3
Impervious Area 03.13
Forebay Area
Maximum Filter Strip/Buffer Slope 5
grass
ft.
ac.
ac.
cu ft.
(perpendicular to flow)
(on-site and off-site drainage to the level spreader)
(on-site and off-site drainage to the level spreader)
(0.2% of the contributing impervious surface area)
(6% for forested, leaf littler cover, 8% for thick ground cover
Max. Discharge from 1"/Hr Storm ~• / ~ cfs
Max. Discharge to Level Spreader . / ~ cfs
Filter Strip/ Zone 2 Buffer Vegetation ~o res (thick ground cover or grass; canopied forest with leaf litter
groundcover)
Pre-treatment or Bypass Method Used /l//Q ~Nv-ee .S'~+ZC ~ ~t~r .~U ~ ~' ~~^~ ~ b 2~ rfs
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.
A licants Ini' I
Project Site was visited prior to designing level spreader. S~Kt /9reui o tisf
4-`t -a7 Date of the Site visit. PLEASE ATTACH TIME-DATED DIGITAL PHOTO OF EXISTING~UFFER CONDITIONS.
Level spreader is at least 13 ft. per cfs for thick ground cover or grass or 65 ft per cfs in canopied forest with leaf
litter for 50-foot buffer; 50 ft per cfs for 100-foot buffer, or 40 ft. per cfs for 150-foot buffer.
Pre-Formed Scour Holes are on flat slopes only.
No structures are located in protected buffers (must meet no practical alternatives criteria).
Design Alternative (if any) and Bypass method used:
Ivy Bypass conveyance method is specified and plan details and calculations are provided.
~2 lce oye.-sr-Zed ~'a LioN~~e /Dyv eve,.-.~~'-
Alternative design option is specified and plan details and calculations are provided.
Discharge to level spreader and subsequent filter strip is hydraulically and spatially separate from the bypass
discharge.
No structures are located in protected buffers.
Plan details for the bypass and outlets are provided.
The operation and maintenance agreement includes annual erosion and vegetation repair.
The operation and maintenance agreement signed and notarized by the responsible party is provided.

Lot 9 Dove Landing Level Spreader Design and Calculations
RUNOFF ESTIMATE FOR LEVEL SPREADER
Rational Method Q=CiA
Q =peak runoff in cfs.
0.95 C =Coefficient
1 I = ave. intensity of rainfall, in/hr. for a storm equal to Tc.
Tc =time of concentration in minutes.
0.13 A =drainage area in acres.
Q~- = 0.12 cfs for 1"rain 8.03 Ft. Length of Level Spreader at 65 feet per 1 cfs on slope <6%
Q10yr = 0.26 cfs for 10 yr. Storm 16.90 Ft. Length of Level Spreader at 65 feet per 1 cfs on slope <6%
Design utilizes two spill areas 20 feet long.
LEVEL SPREADER DESIGN
On this site, since potential impervious area that would flow toward the newly established riparian buffer is small,
and stormwater runoff into a pond may compromise the water quality, an oversized divided level spreader design
is used to ensure that sheet flow will not concentrate in the forested filter strip and allow a shallower
channel reservoir.
Also, this level spreader is designed to handle the 10 year storm (2.11 inch) instead of the 1 inch rainfall.
A divided level spreader utilizes a raised section approximately 2 inches high in the middle of the lip
to help spread out the flow.
Divided Level Spreader Profile
S ill Area S illp Area
60' ~~
20' ~~ 20' ~ 20'
20' > 8.45' 20' > 8.45'
See attached Figure 2 for a perspective view of a typical level spreader without the raised lip in the middle.
See attached Figure 3 for a profile view and details of a level spreader.
See attached notorized Operation and Maintenance Agreement

SCALE
0 SO 100'
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f
3;
,.....
~.~
~~~~,
:~
Date: 5-24-2007
~--
~ _
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n _, ~
s f ~
~s E
,, o t 9 ,~
_ .,
.~,r,, r
P ~~~sc~
New _.
rya
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~ 11,59 sq
0.265 Acres
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4 L~J

e
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North
LE_
(( Drainage Area = 5760 sgft.
l~._.
(~-1 New Riparian Buffer

Site Plan FIGURE 1
Lot 9 Dove Landing
DWQ# 2002-0577v2

Forested Fi{tef
...Strip
~:
r~~
~`
~~ ~..
In the event that lot 9 is ever developed, a level spreader similar to
this one will need to be installed to ensure stormwater runoff is
collected and discharged as sheet flow into the existing forested
filter strip.
Date: 5-24-2007
DWQ# 2002-0577v2
Stand Alone
Level Spreader
Without
Forebay
FIGURE 2
Lot 9 Dove Landing

Leve( ~5p~reader Lip
~" ~Y~t"
~,.~~~~ Stone
Flcarnr Pith.-°~ .._-..._.~,,
<'~~ ~ ~ ~~~~ ~>par~n
Buffer
~:r i
Channel
~- ~~ 3 ft Wide
No Underdrain Strap cif
needed for this ~ eater I^abr~e
design A~arapr-a~ly Stz~d
Cc-ncrete Facer
Date: 5-24-2007
Level Spreader
Profile and Details
FIGURE 3
Lot 9 Dove Landing
IDWQ# 2002-0577v2

Precipitation Frequency Data Server Page 1 of 4
POINT PRECIPITATION _~ r~,
' ~ FREQUENCY ESTIMATES
~'~ ~ FROM NOAA ATLAS 14
NASHVILLE, NORTH CAROLINA (31-6044) 35.9667 N 77.9667 W 203 feet
from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland, 2004
Extracted: Tue May 22 2007
Confidence Limits ~Seasonatity Location Maps Other Info. GIS data Maps Help Docs U.S. M:
Precipitation Intensity Estimates (in/hr)
ARI* ~ 10 15 30 60 120 ~~ 12 24 48 ~~ 10 20 30 45 60
years) mm mm mm mm mm mm hr hr hr hr hr day day day day day day day
4.63 3.70 3.08 2.11 1.32 0.76 0.54 0.32 0.19 0.11 0.06 0.04 0.02 0.02 0.01 0.01 0.01 0.0
5.17 4.13 3.47 2.39 1.50 0.88 0.62 0.37 0.22 0.14 0.08 0.04 0.03 0.02 0.02 0.01 0.01 0.0
5.62 4.50 3.79 2.69 1.73 1.01 0.72 0.43 0.25 0.17 0.10 0.06 0.04 0.03 0.02 0.02 0.01 0.0.
10 6.65 5.32 4.48 3.25 2.11 1.26 0.90 0.54 0.32 0.21 0.12 0.06 0.04 0.03 0.02 0.02 0.01 0.0.
25 7.46 5.95 5.03 3.72 2.48 1.51 1.08 0.65 0.39 0.26 0.15 0.08 0.05 0.04 0.03 0.02 0.02 0.0.
50 8.33 6.64 5.60 4.22 2.86 1.78 1.28 0.78 0.47 0.30 0.17 0.09 0.06 0.04 0.03 0.02 0.02 0.0:
100 9.04 7.18 6.05 4.63 3.19 2.02 1.47 0.90 0.54 0.35 0.20 0.10 0.07 0.05 0.03 0.02 0.02 0.0:
200 9.71 7.69 6.47 5.04 3.53 2.28 1.68 1.03 0.62 0.41 0.23 0.12 0.07 0.06 0.04 0.03 0.02 0.0:
500 10.39 8.22 6.90 5.49 3.94 2.60 1.94 1.19 0.73 0.50 0.27 0.14 0.09 0.06 0.04 0.03 0.02 0.0:
1000 11.26 8.86 7.41 6.00 4.38 2.95 2.23 1.38 0.86 0.57 0.31 0.16 0.10 0.07 0.04 0.03 0.03 0.0:
Text version of table These precipitation frequency estimates are based on a partial duration series. ARI is the Average Recurrence Interval.
Please refer to the documentation for more information. NOTE: Formatting forces estimates near zero to appear as zero.
Partial duration based Point IDF Curves Version: 3
35.9667 M 77.9667 W 203 ft
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http://hdsc.nws.noaa. gov/cgi-bin/hdsc/buildout.perl?type=idf&series=pd&units=us&statename=NORT... 5/22/2007

LEVEL SPREADER SYSTEM OPERATION AND MAINTENANCE AGREEMENT (112007)
A level spreader system includes: a forebay, diverter box, level spreader, riparian buffer/vegetated filter strip,
and flow bypass channel.
Name of Project:
Address:
9 wave Lan ~irq /`"Yanl~ 1i1~ ~D~r+~~l . ~~
Maintenance activities shalt be performed as follows:
MAINTENANCE ACTIVITY FREQUENCY
Post-construction monitoring-inspect for vegetation, Check after every heavy rainfall for first 6 months
settlin ,erosion, or concentrated flow. followin construction.
Inspect Diverter Box and clean and/or make repairs. Once a month and after heavy rainfalls/storms.
Look for:
• Clogged inlet or outlet pipes.
• Trash/debris in the box.
Inspect Forebay + Level Spreader. Clean and/or Once a month and after heavy rainfalls/storms.
make repairs. Look for:
• Sediment in forebay and along level spreader
lip;
• Trash and/or leaf buildup.
• Scour, undercutting of level spreader.
• Settlement of level spreader structure (no
longer level; you see silt downhill below level
spreader).
• Fallen trees on level spreader.
• #57 stone washin downhill.
Inspect the Riparian Buffer and the Bypass Swale Once a month and after heavy rainfalls/storms.
and make repairs as needed'. Look for:
• Damaged turf reinforcement or riprap rolling
downhill.
• Erosion within the buffer or swale.
• Concentrated flows downhill of level
s reader-look for ullies or sediment flows.
Mow grass to a 6" height. As needed during growing season.
Remove any weeds/shrubs growing on level spreader Once a year.
or in swale.
' NOTE: Contact NC Division of Water Quality, 401/Wetlands Unit at 919-733-1786 BEFORE any work
in Protected Riparian Buffers.
Page 1 of 2

LEVEL
SPREADER NO. LOCATION ON SITE (DESCRIBE) HOW WILL IT BE ACCESSED?
1
~
Jr'D -~cQ-f' rt or~~ 0~ v o as'Q d o
mow, Mot.1 vh i» Qove Lane,
2
3
4
5
6
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:

ov
Address: ~$lfi`/ G~avk .S~a~i®-~ ,/[c~. .,SQVevv~ /ti'1z~ all ~'4-
Phone: ~~,3' - ~ bs '" 3$~ ~'
Signature:
Date: 4~' f 2~ / ~ ~
Note: The legally responsible party should not be a homeowners association unless more than 50% of the
lots have been,~s~/old and a resident of the subdivision has been named the president.
I, la~ `E Ii~,~,~ J~ ©'"l~ l~t-~~ , a Notary Public for the State of /Sl~_
County of ~~ , do hereby certify that ,~~Zio ~,c/ .c~~,~A
personally appeared before me this day of , and acknowledge the due
execution of the forgoing wet [wetland] detention basin maintenance requirements. Witness my hand and
official seal,
SEAL
My commission expires /~-9~-~~
Page 2 of 2