20000404 Ver 1_COMPLETE FILE_20000328

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
Mr. Todd Smith
Hite Associates
1530 East Fourteenth Street
Greenville, NC 27858
Dear Mr. Smith:
4?
AMMON now
NCDENR
Division of Water Quality
September 5, 2000
Subject: West Johnston County High School
DWQ Project No. 000404
Johnston County
The Wetlands Unit staff reviewed the stormwater management plans for the subject project and determined
that additional information is necessary to complete the technical review process. The required additional
information is as follows:
Forebay
The berm for the forebay (whether above or below the surface of the pond) should extend across the
pond so the forebay will contain sediment. Please revise the engineering plans to reflect the change.
Wet Detention Pond and Dry Detention Pond Calculations
The dimensions of both basins have changed. Please submit updated sizing information (see attached
worksheets).
4. Level Spreader
The level spreaders should be designed to discharge along the length of the berm in order to
maximize the length of buffer utilized for stormwater assimilation. The plans do not show this.
Please feel free to call me at [phone] to discuss this matter.
Division wetlands unit staff will strive to complete a final technical review within 10 working days of
receipt of the requested information. If you have any questions or would like to discuss this project, please
contact me at [phone].
Attachments
cc: John Dorney, Wetlands/401 Unit
Raleigh Regional Office
File
Sincerely,
odd St. ?h , APE
Environmental Engineer
4401 Reedy Creek Road, Raleigh, NC 27607 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper
State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
e??
NGDENR
Division of Water Quality
June 26, 2000
Mr. Todd Smith
Hite Associates
1530 East Fourteenth Street
Greenville, NC 27858
Subject: West Johnston County High School
DWQ Project No. 000404
Johnston County
Dear Mr. Smith:
The Wetlands Unit staff reviewed the stormwater management plans for the subject project and determined
that additional information is necessary to complete the technical review process. The required additional
i formation is as follows:
1. Forebay
All stormwater wet detention basins are required to have a forebay to facilitate TSS removal. The
forebay should be approximately 20% of the total basin volume. Reference Stormwater Best

Management Practices Manual, April 1999 (http://h2o.enr.state.nc.us/su/Manuals_Factsheets.htm).
Please revise the engineering plans to meet this requirement.
Inlet/Outlet Structure Location
The inlet and outlet structures must be placed to minimize short circuiting. A long flow path will
help to maximize the settling efficiency of the water quality structure. The submitted design of the
pond labeled "wet detention #1" will be subject to short circuiting. This issue may be addressed
through structure relocation, baffles, forebays, etc.
Vegetated Side Slopes
The basin side slopes of the basin labeled "stormwater detention #2" indicate the side slopes are 3:1.
The plans appear to actually have side slopes of 2.5:1. The side slopes should be no steeper than 3:1
(horizontal to vertical). Also, please specify landscape/seeding information on engineering the plans
for both ponds.
Level Spreader
The level spreaders should be designed to discharge along the length of the berm in order to
maximize the length of buffer utilized for stormwater assimilation. Please provide calculations to
show that the length of the level spreaders is adequate. Also, the use of properly sized forested
buffers as filters strips may allow both basins to be designed as dry detention basins and still meet
the 85% TSS removal required in the subject Water Quality Certification. Also, please feel free to
call me at [phone] to discuss this matter.
4401 Reedy Creek Road, Raleigh, NC 27607 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper
5. Vegetative Shelf
A vegetative shelf around the perimeter of the wet detention pond (#1) is required. The shelf shall be
gently sloped (6:1 or flatter) and shall consist of native vegetation. Please specify this on the
engineering plans.
6. Sediment Removal
If the basins are proposed to be used as sediment basins during construction, the plans must clearly
indicate that accumulated sediment will be removed prior to implementation as a stormwater basins.
7. Operation and Maintenance Agreement
An operation and maintenance agreement is required. '
A stormwater control structure will not operate as designed without regular maintenance. Typical
requirements for an operation and maintenance plan include the following:
• Vegetation management/mowing schedule
• Semi-annual inspections
• Debris check after every storm event
• Benchmark for sediment removal (specific elevations listed)
• Designation of a responsible party
The operation and maintenance agreement must also be signed by the responsible party and
notarized.
Division wetlands unit staff will strive to complete a final technical review within 10 working days of
receipt of the requested information. If you have any questions or would like to discuss this project, please
contact me at [phone].
Sincerely
Todd St. John, P
Environmental gineer ^
cc: John Dorney, Wetlands/401 Unit
Raleigh Regional Office
File

nspection and Maintenance Agreement
3ond name:
_ocation:
vlonthly inspection
A. Remove debris from primary and emergency spfilways
B , Check groundcover fot signs of erosion or failure
1. 6n embankment
2 in pond
C. Check draw down pipe for blockage
IWaY and underdratn for signs of seepage or erosion
? D. lnsped the embankment, primary sp<
1. If seepage Is found, note•approximate flow rate, color of discharge, location of slumps, wetness on slope, eta
2 Draw a map of the structure noting any erosion, wetness, slumps, eta
Quarterly Inspedion
A. Remove debris
for undercutting. Replace rip rap and repair broken pipes.
p B. Check pipes
p C. Reseed grass swaies, the dwml between the forebay and permanent pool, and the pond embankment
r'
6 Month Inspection
A. Remove accumulated sediment from the permanent pool, time forebay and the outlet of the pond.
oral maintenance
Mow the side slopes for the embankment and the ponded area (not including the shelf) according to the growing season of
?e grass.
m cattails from dogging the pond and spillways.
-inane Requirements
s
Pape 1 o(2
57
v.
.....:aa7 Tf_ ANDS GROUP
i
West Johnston High School
8-04-00
Calculations for level spreader
Wet De tention in the front of the School
Q = 27.7 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLHA1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (013.OL)A0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
Detenti on Behind the Athletic Fields
Q = 27.2 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH^1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)^0.66
H = 0.18 ft
V = Q/A A = LH = 21.82 sf
V = 1.25 fps OK less than 3 fpsr.

1
nspection and Maintenance AgreementO
pond name: j ??l r ?.?fLf L?flir.l er
_ocation:i
vtonthly Inspection
A. Remove debris from primary and emergency spillways
B. Check groundcover for signs of erosion or failure
1. On embankment
2 In pond
3 C. Check draw down pipe for blockage
3 D. Inspect the embankment, primary spillway and underdrain for signs of seepage or erosion
1. If seepage is found, note-approximate flow rate, color of dirge, Iocation of slumps, wetness on slope, eta
2 Draw a map of the structure noting any erosion, wetness, slumps, eta
:)uarteriy Inspection
A. Remove debris
3 g, Check pipes for undercutting. Replace rip raP and repair broken pipes-
3 C. Reseed grass swales, the dhannel between the forebay and permanent pool, and the Pond embankment
3 Monti (nspedion
A. Remove accumulated sediment from the permanent pool, the forebay and the outlet of the pond.
-iral maintenance
Mow the side slopes for the embankment and the ponded area (not including the shelf) according to the growing season of
v grass.
I cattails from dogging the pond and spillways.
finance Requirements
Page 1 o(2
57
ijgE 'LANDS GROUP

A hereby acknowledge that I am the financially responsible party for
maintenance and inspection of this detention pond I will perform the maintenance as outlined above, to comply with the
Johnston County Stormwater Management Ordnance and the Stormwater Management permit received for this project
Furthermore, I attest that this Inspection and Maintenance Agreement is on file with the Register of Deeds.
Signature

Alf All I 'Y Y/ fjA" J a Notary Public for state of
I,
Co of , do reby certify that _
personally before me this day of ,1c9 '? and aclmo a the due execution of the foregoing
instrument Witness my hand and official seal,
My commission
?a?`°? 'E W.
c ?0TA
zlc?p to

Page 2 of 2
63

revised 10/98

West Johnston High School
8-04-00
Calculations for level spreader
Wet De tention in the front of the School
Q = 27.7 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH"1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)°0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
Detenti on Behind the Athl etic Fields
Q = 27.2 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH"1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)"0.66
H = 0.18 ft
V=Q/A A=LH=
V= 1.25 fps
21.82 sf
OK less than 3 fps
Nx?

Hite associates
ARCHITECTURE / ENGINEERING / PLANNING
LETTER of TRANSMITTAL
T g
TO: NCDENR - Division of Water Quality
4401 Reedy Creek Road
Raleigh, NC 27607
ATTN: Mr. Todd St. John, PE
DATE: August 23, 2000
RE: West Johnston High School
We are sending via UPS the following plans:
COPIES DWG DATE DESCRIPTION NOTES:
3sets Site Plans/Grading and Erosion Control/Details
1 Letter from Division of Water Quality response
1 Reports from Engineer J.S. Janowski
l SnsPcc.fia?, MA7n?u,anc?. ?gvtt?rl?'E
This information is transmitted for approval unless noted otherwise.
REMARKS:
Drawings:
0001-Overall Site Key Plan
0002-Site Phasing Plan
C201-Site Grading and Erosion Control - South
C202-Site Grading and Erosion Control - North
C203-Site Grading and Erosion Control - Entrance
C204-Site Grading and Erosion Control
C401-Site Details: Storm Sewer/ Sanitary Sewer
C402-Site Details: General Notes / Erosion Control
C403-Site Details: Storm Water Detention Boxes
C404-Site Details: Wet Detention / Storm Water Detention
C405-Site Details: Curb and Gutter / Asphalt & base / Parking
C406-Site Details: Athletic Field Improvements
C407-Site Details: Athletic Field Improvements / Misc.
IGNED:
ith
copy: Steve Janowski, P.E.
Ms. Ann Williams, Johnston County Schools
Mr. Ray Debruhl, TPFG
file:
C408-Site Details: Dugouts
C409-Site Details: Water Services
C410-Site Details: Concrete Steps
C501-Road Widening
9 h
a - G 2 52000
WIRLANDS GROUP
M QWLl -?r SECT!^"
2600 Meridian Drive / Greenville, NC 27834 / tel [phone] / fax [phone] / e-mail: [e-mail]

Project No. DWQ
Project Name: W. Johnston High pond 1
SUBMITTED DESIGN: REQUIRED DESIGN:
elevations status
Bottom of Basin (ft) 194
Permanent Pool (ft) 198 4 ft. depth ok
Temporary Pool (ft) 199.12 1.12 ft. depth ok
areas
Permanent Pool SA (sq ft)
37324
19476 sq. ft.
ok
Drainage Area (ac) 23
Impervious Area (ac) 13.14 57.1 %
volumes
Permanent Pool (cu ft) 39228
Temporary Pool (cu ft) 130153 47103 cu. ft. ok
Forebay (cu ft) 0.0 % check forebc
other parameters
SA/DA 0 1.94 -
Orifice Diameter (in) 3 0.18 cfs drawdown -
Design Rainfall (in) 1 8.5 day drawdown check drawc
Linear Interpolation of Correct SA/DA***
% Impervious
Next Lowest 50
Project Impervious 57.1
Next Highest 60
4 ft. Permanent Pool Depth
SA/DA from Table
1.73
1.94
2.03
State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
Mr. Todd Smith
Hite Associates
1530 East Fourteenth Street
Greenville, NC 27858
Dear Mr. Smith:
A 4?
Ad 111111111111L
NCDENR
Division of Water Quality
October 11, 2000
Subject: West Johnston County High School
DWQ Project No. 000404.
Johnston County
The Wetlands Unit staff reviewed the stormwater management plans for the subject project and determined
that additional information is necessary to complete the technical review process. The required additional
information is as follows:
1. Forebay
The berm for the forebay (whether above or below the surface of the pond) should extend across the
pond so the forebay will contain sediment. Please revise the engineering plans to reflect the change.
Please refer to page 9 of the NC DENR Stormwater Best Management Practices Manual, April 1999.
2. Level Spreader
The level spreaders should be designed to discharge along the length of the berm in order to
maximize the length of buffer utilized for stormwater assimilation. The plans do not show this.
Please feel free to call me at [phone] to discuss this matter. Please refer to page 77 of the NC
DENR Stormwater Best Management Practices Manual, April 1999.
Division wetlands unit staff will strive to complete a final technical review within 10 working days of
receipt of the requested information. If you have any questions or would like to discuss this project, please
contact me at [phone].
Sincerely 14?_
;1/l,,/ „ n ?t
To t. John, PE
Environmental Engineer
cc: John Dorney, Wetlands/401 Unit
Raleigh Regional Office
File
4401 Reedy Creek Road, Raleigh, NC 27607 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper
State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
Mr. G. Douglas Jones
PO Box 1132
Edenton, NC 27932-1132
Dear Mr. Jones:
NCDENR
Division of Water Quality
September 15, 2000
Subject: Albemarle Baptist Church
DWQ Project No. 991266
Chowan County
This Office is in receipt of the plans dated September 1, 2000 for the stormwater
management basin and grassed Swale at the subject facility submitted to the Division on
September 5, 2000. Staff from the Wetlands Unit reviewed the plans and found them acceptable
as long as the stormwater facilities are constructed and functioning before any structure
associated the proposed fill is occupied per the subject 401 Water Quality Certification dated
December 2, 1999. Also, for this approval to be valid, a signed and notarized Operation and
Maintenance Agreement must be approved in writing by this Office. Please note that this
approval shall not be construed as an approval of the dam design for Dam Safety purposes.
If you have any questions regarding this matter, please contact Mr. Todd St. John at (919)
733-9584.
4etl R. Domey
ands Unit Su ervisor
cc: Mr. Todd St. John, Wetlands
Washington Regional Office
File
4401 Reedy Creek Road, Raleigh, NC 27607 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper
Project No. DWQ 1 (to be provided by DWQ)
DIVISION OF WATER QUALITY -401 WEB DE?TON BASIN WORKSHEET
DWO Stormwater Management Plan Review:
A complete stormwater management plan submittal includes a wet detention basin worksheet for each basin,
design calculations, plans and specifications showing all basin and outlet structure details, 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.
1. PROJECT INFORMATI (please complte the following information):
Project Name :
Contact Person: Phone Number: Z ?' lv '07
For projects with multiple basins, specify which basin this worksheet applies to: 1.x/04.I
Basin Bottom Elevation
Permanent Pool Elevation
Temporary Pool Elevation
Permanent Pool Surface Area
Drainage Area
Impervious Area
IQ?•m ft.
ft.
199.•/ ? ft.
r?
sq. ft.
ac.
ac.
(average elevation of the floor of the basin)
(elevation of the orifice invert out)
(elevation of the outlet structure invert in)
(water surface area at permanent pool elevation)
(on-site and off-site drainage to the basin)
(on-site and off-site drainage to the basin)
Permanent Pool Volume
Temporary Pool Volume
Forebay Volume
?? 2 28 cu. ft.
cu. ft.
cu. ft.
(combined volume of main basin and forebay)
(volume detained on top of the permanent pool)
SA/DA used 2.41 hlof ' -;,W X 144M(surface area to drainage area ratio)
Diameter of Orifice in. (draw down orifice diameter)
H. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices manual
(N.C. Department of Environment, Health and Natural Resources, November 1995) and Administrative Code
Section: 15 A NCAC 2H .1008. 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.
The temporary pool controls runoff from the 1 inch storm event.
The basin length to width ratio is greater than 3:1.
The basin side slopes are no steeper than 3:1.
KA submerged and vegetated perimeter shelf at less than 6:1 is provided.
Vegetation to the permanent pool elevation is specified.
An emergency drain is provided to drain the basin.
The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
The temporary pool draws down in 2 to 5 days.
E) E The forebay volume is approximately equal to 20% of the total basin volume.
Sediment storage is provided in the permanent pool.
j ._ Access is provided for maintenance.
A minimum 30-foot vegetative filter is provided at the outlet.
A site specific operation and maintenance (O&M) plan is provided.
A vegetation management/mowing schedule is provided in the O&M plan.
Semi-annual inspections are specified in the 0&M plan.
A debris check is specified in the 0&M plan to be performed after every storm event.
A specific sediment clean-out benchmark is listed (elevation or depth) in 0&M plan.
A responsible party is designated in the O&M plan.
100 09/97 Page 1 of 1
Project No. DWQ_ (to be provided by DWQ)
DIVISION OF WATER QUALITY
401 EXTENDED DRY DETENTION BASIN WORKSHEET
DWQ Stormwater Management Plan Review:
A complete stormwater management plan submittal includes a dry detention basin worksheet for each
basin, design calculations, plans and specifications showing all basin and outlet structure details, 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.
I. PROJECT INFORMATION (please complete the following information):
Project Name :
Contact Person: > Phone Number: /
For projects with multiple basins, specify which basin this worksheet applies to:J?rtg T (p ?L
Drainage Area: Zf, lJ acres Percent Impervious Area: L %
H. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices
Manual (N.C. Department of Environment, Health and .Natural Resources, November 1995) and
Administrative Code Section: 15 A NCAC 2H.1008. 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.
Applicants Initials
1-2 Either capture runoff from 1 yr., 24 hour storm and release over a 48 hour period, or
capture runoff from 1 inch storm and draw down over a period of 2 to 5 days.
9fl The basin length to width ratio is greater than 3:1.
The basin side slopes are no steeper than 3:1.
A small, permanent pool atoutlet orifice is provided to reduce clogging.
An emergency drain to completely empty the basin is provided.
-0Wegetation plan prepared by a licensed professional is specified.
Basin-to be stabilized within 14 days of construction is specified.
11, d l*, Z ` . Sediment storage (20% of detention volume) in addition to detention volume is provided.
Inlet and outlet erosion control measures to prevent scour are provided.
Additional treatment to meet the 85% TSS removal efficiency is provided.
Access for clean-out and maintenance is provided.
Inlet plunge pool or other energy dissipation is provided.
V or --I Forebay is provided to capture sediment and minimize clean-out problems.
Uncompacted natural soils are utilized to promote vegetation and reduce sedimentation.
Seasonal high water table is at least 1 foot below bottom of basin.
:Z#E If used as a temporary basin, plans indicate clean-out prior to final operation.
A site specific operation and maintenance plan with the following provisions is provided.
- Mow grass at least twice annually
- Remove trash and debris upon accumulation and at least twice annually
- Inspect for proper operation at least twice annually including:
- outlet clogging or too rapid a release
- erosion on banks
a- , _. . i
not indicate that we received them. Please provide us with documentation that
that was done.
Please review the DWQ Interim Internal Guidance documents for mitigation
monitoring protocols (http://h2o.enr.state.nc.us/ncwetlands/) or contact Todd St.
John or Dave Penrose with my staff for additional details. However, we
recommend that you consider assessing the following items as part of any
mitigation monitoring plan:
¦ Determination of dominant channel forming discharge.
¦ Determination of proper bed, banks, and flood plain cross-section geometry.
¦ Determination of morphological stream classification.
¦ Determination of sediment transport, yield, and delivery budgets.
¦ Determination proper bed, bank, slope, and flood plain planform.
geometry. mmum information should include specific numbers for the
reference reach and design channels.
¦ Establishment of riparian buffer zones.
¦ Proper selection, density, and placement of vegetation.
¦ Briefly discuss basic soil types and properties.
Recall that the 401 Certification for this project specifically mentions that
mitigation monitoring protocols shall include assessment of channel stability and
benthic macroinvertebrate communities. These monitoring protocols must be
included in the mitigation plan.
? Section 7 of the 401 Certificate mentions that DOT shall submit a stormwater and
on-site stream enhancement plan to DWQ by 6 June, 1998 for written DWQ
approval. Our files indicate that this has not been done. Again if you find that
DWQ has been delinquent in our record keeping, please note these delinquencies
and provide us with dated material addressing this.
Thank you for your attention to these matters and we look forward to working with you
on this project.
Sincerely,
o Dorney
Cc: Todd St. John and Dave Penrose, Wetlands Unit
Mark Cantrell, US Fish and Wildlife Service, Asheville
Bob Johnson, US Army Corps of Engineers, Asheville
Frank McBride, NC Wildlife Resources Commission
Cynthia Van Der Wiele, Wetlands Unit
Bill Gilmore, NC Department of Transportation .
File Copy
Central Files
. , -w I.

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
1••
NOOK
NC ENR
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
15 September, 2000
Mr. Mark Ashness
CE Group
P.O. Box 219
Pittsboro, North Carolina 27312
Dear Mr. Ashness;
Regarding: Environmental Monitoring Program
Harris Tract, Chatham County
DWQ # 991233
Thank you for the opportunity to review the Environmental Monitoring Program for the
Preserve at Jordan Lake Golf Club (DWQ # 991233). This appears to be a very
comprehensive monitoring program that will address most of the concerns noted during
the public hearing 27, April 2000 and addressed in the 401 Certification. Staff members
of the Division of Water Quality have reviewed this document and have the following
comments/concerns. Please respond to these issues by October 31, 2000.
Many of the potential water quality problems associated with this project are non-point
source perturbations and as such will be most noticeable during, or immediately
following, spate events. Sections 2.2 and 3.2 discuss the sample frequency for surface
water samples. We recommend that these samples be collected during each of the four
collection periods during both Phase I and Phase II of this monitoring program. We
recognize that water levels may present problems with collection at some stations during
low rainfall periods. Every attempt should be made to collect these samples following
significant rain events to effectively assess the non-point source perturbations. In
addition, baseflow conditions also should be sampled and noted. These latter data will
serve as low-flow background information.
Other comments include the following:
? Please add a List of References to this document where appropriate.
It is strongly recommended that surface water samples also be collected from the
collection location noted on Figure 1 as Sediment 3/Monitoring Well 3 near the
western portion of the project.
Wetlands/401 Unit 1621 Mail Service Center Raleigh, North Carolina 27699-1621
. Telephone [phone] FAX # [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10%n post consumer paper
v
61
STORM WATER MANAGEMENT PLAN
WEST JOHNSTON HIGH SCHOOL
JOHNSTON COUNTY, NORTH CAROLINA
Proj. No. 20013
June 6, 2000
'f- vov
prepared by:
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
[phone]

Narrative
This site is a proposed high school. It is situated on a 101 acre tract of land off the east
side of SR 1330 and south of Beaverdam Branch. The property is not located in the
ESOD. The site is classified as commercial in accordance with the classification that
Johnston County Director of Infrastructure and Engineering assigned to this school in a
joint meeting on April 4, 2000. The impervious limits for commercial areas is 60%. The
existing slopes of the land are between 5 and 10 % with drainage in two directions. The
proposed drainage plan also manages storm water in the two separate basins. There is a
total of 22.70 acres of impervious area on this site which is 22.5% impervious.
In the front of the site, a wet detention basin is designed to attenuate the post development
peak discharge of the 2 year 24 hour storm to that of the predeveloped flow and to detain
the first 1" of runoff and release it between 2 and 5 days. The estimated predevelopment
peak rate of runoff is 28.6 cfs: The estimated postdevelopment rate of runoff is 81.9 cfs.
The effluent pipe into the basin is a 54"RCP at a flat slope of 0.5% to minimize velocities.
The outlet control pipe is a 3" pvc pipe with a small 3.5 R weir opening to control the 2
year storm. The principal spillway is an 8'x8' concrete box. The dam is approximately 15'
wide 3:1 front side slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut
around the north of the basin to handle the 100 year design storm. The basin is designed to
remove 85% TSS prior from the runoff. The downstream impacts are mitigated as a result
of the detention basin.
In the athletic field site, another detention basin is designed to attenuate the post
development peak discharge of the 2 year 24 hour storm to that of the predeveloped flow.
The estimated predevelopment peak rate of runoff is 36.6 cfs. The estimated
postdevelopment rate of runoff is 62.7 cfs. The effluent pipe into the basin is a 3" pvc
pipe to detain the first 1" of runoff and release it over a 2 to 5 day period. This basin is
designed as an extended dry detention basin to remove 50 % TSS. It has a level spreader
downstream of the outlet to remove another 35% TSS for a total of 85% TSS removal.
The outlet control pipe is a 54" RCP with a small, 10 foot wide dam, with 3:1 front side
slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut around the west of
the basin to handle the 100 year design storm. A 6.5 foot weir is formed into an 8'x8' box
in order to control the 2 year storm. The basin is designed such vegetation will be allowed
to grow freely and provide for additional nutrient intake. Maintenance for the facility will
include inspections of the dam and control devices. The downstream impacts are mitigated
as a result of the detention basin.
SOIL EROSION
AND
SEDIMENTATION CONTROL
PLAN
NARRATIVE
WEST JOHNSTON HIGH SCHOOL
JOHNSTON CO , NORTH CAROLINA
20013
J.S. JANOWSKI AND ASSOCIATES
105 C EAST VICTORIA COURT
GREENVILLE, NC 27858
252-756-8918
This project includes the construction of appro)dmately 205,630 5F of new buildings for the school on a portion
of a 101 acre site. Approximatey 75.5 acres of land will be disturbed.
The site has slopes averaging 5-10%. Overall, elevations vary from a high point of 242 msl to a low point of less
than 176 msl. The site is currently farmed . The soil type is a silty day.
III ADJACENT PROPERTY
The property is bourxled on the , south and east by undeveloped property, bounded on the west by Raleigh Rd
(SR 1330) and on the North by Beaver Branch.
IV. PLANNED NORM WATER MANAGEMENT AND EROSION AND SEDIMENTATION CONTROL
MEASURES
TEMPORARY GRAVEL CONSTRUCTION ENTRANCE
A Temporary Gravel Construction Entrance is to be used at street connection to SR 1330
TEMPORARY SILT FENCE
Temporary Silt Fences are to be placed at the toe of fill sites adjacent to the property line to collect sediment
laden runoff. Due to the abundance of fill slopes the silt fence will provide an excellent barrier to protect off-site
facilities from sediments.
Sediment fence will be installed around all catch basins and drop inlets to prevent sediment from entering the
storm drainage system.
L: ; I:M:IN1 L*]3-Ml
Temporary Rods Check Dam will be used in the Consbvction of new ditches.
STORM INLET SEDIMENT TRAP
Storm inlet sediment traps will be used at concentrated runoff points associated with drop inlets as shown on
plans.
GRASS LINED CHANNEL
Grass lined channels with temporary straw-net liners will be constructed in roadside ditches.
STORM WATER DETENTION BASIN AND ROCK DAM SEDIMENT TRAP
At the end of the major storm drainage outfall a storm water detention basin including a sediment trap will be
installed in order to reduce the peak outflow and to trap sediment that may escape inlet control measures. A
rock dam will be placed at the inlet of the outlet pipe for the detention facilities to trap sediment.
1.OBTAIN PLAN APPROVALS AND ALL APPLICABLE PERMITS.
2. FLAG LIMITS OF ROUGH GRADING FOR BUILDING SITE, PARKING LOTS AND ESTABLISH GRADE LIMITS AS NEEDED.
3. HOLD PRECONSTRUCTION MEETING WITH GRADING CONTRACTOR, EROSION CONROL ADMINISTRATOR, PROJECT ENGINEER AND OWNER.
4. INSTALL SEDIMENT TRAPS AND THE PERIMETER SEDIMENT FENCES AS THE FIRST CONSTRUCTION ACTIVITY.
5. INSTALL STORM DRAINAGE FOR OUTFALL, INSTALL RELATED EROSION CONTROL MEASURES AND END OF DAY MEASURES
6. PREPARE TEMPORARY CONSTRUCTION ENTRANCE, STRIP AREA OF TOP SOIL AND STOCKPILE AS NEEDED FOR FINAL LANDSCAPING.
INSTALL SEDIMENT FENCES AROUND PERIMETER OF STOCKPILE AREAS.
7. INSTALL RIP RAP OUTLET PROTECTION OUTLET.
8. BEGIN AND COMPLETE ROUGH GRADING OPERATIONS INCLUDING ENTRY ROADS.
9. INSTALL TEMPORARY SEDIMENT CONTROL MEASURES IN THE ROADSIDE DITCHES.
10. INSTALL STORM DRAINAGE FOR PARKING AREA, AND BUILDING PERIMETER INSTALL RELATED EROSION CONTROL MEASURES AND END OF
DAY MEASURES
11. BRING BUILDING AND PARKING AREA TO WITHIN 2" OF FINAL SUBGRADE, TEMPORARILY SEED THESE AREAS TO PREVENT EROSION UNTIL
SUCH TIME OWNER 15 READY TO PROCEED WITH FINAL CONSTRUCTION.
12. BRING LANDSCAPED AREAS TO WITHIN 6" OF FINAL GRADE, RE-DISTRIBUTE 6" OF TOP SOIL.
13. INSTALL TEMPORARY STAW-NET LINERS IN ROADSIDE SWAIES
14. FINE GRADE, PERMANENTLY SEED AND MULCH ALL LANDSCAPED AREAS.
15. STABILIZATION SHALL OCCUR WITHIN 15 DAYS OF COMPLETION OF GRADING OPERATIONS.
16. REMOVE SEDIMENT TRAP AND INSTALL REMAINING STORM DRAINAGE, REGRADE AREA AND SEED AND MULCH.
17. ADDITIONAL EROSION AND SEDIMENTATION CONTROL MEASURES MAY BE REQUIRED BY THE STATE OR OWNER IF DEEMED
NECESSARY.
18. AFTER SITE IS STABIMED, REMOVE ALL TEMPORARY MEASURES, FINE GRADE DISTURBED AREAS, AND INSTALL PERMANENT VEGETATION
ON THE DISTURBED AREAS.
19. MAINTAIN PERMANENT VEGETATION BY TOP DRESSING WITH 700 LBS PER ACRE OF FERTILIZER EVERY 6 MONTHS UNTIL THE
COMPLETION OF THE PRO3ECr.
20. REMOVE ALL TEMPORARY EROSION AND SEDIMENTATION CONTROL MEASURES UPON COMPLETION AND STABILIZATION OF PROJECT.
VI. MAINTENANCE PLAN
1. All erosion and sediment control practices will be dlecked for stability and operation following every
run-off producing rainfall but in no case less than once every week. Any needed repairs will be made
immediately to maintain all practices as designed.
2. Sediment will be removed from behind the silt fence when it becomes 0.5 feet deep.
3. Sediment will be removed from the sediment trap when the storage has been approbmately 50%
filled. Gravel will be deaned and replaced when the sediment pool no longer drains properly.
4. All seeded areas will be fertilized, re-seeded as necessary, and mulched according to specifications in
the vegetative plan to maintain a vigorous, dense vegetative cover.
Yll. VICINITY PLAN
See Erosion Control Plan
VIII. VEGETATION PLAN
A. PERMANENT SEEDING AFTER APRIL 15 AND BEFORE SEPTEMBER 15
SEEDING MIXTURE
COMMON BERMUDAGRASS 80 (2 LB/1000 SF)
SOIL AMENDMENTS
APPLY 3000 LEI/ACRE GROUND AGRICULTURAL LIMESTONE AND 500 LB/ACRE
10-10-10 FERTILIZER.
MULCH
USE JUTE, EXCELSIOR MATTING OR OTHER EFFECTIVE CHANNEL LINING
MATERIAL TO COVER THE BOTTOM OF CHANNELS AND DITCHES. THE
LINING SHOULD EXTEND ABOVE THE HIGHEST CALCULATED DEPTH OF FLOW.
ON CHANNEL SIDE SLOPES ABOVE THIS HEIGHT, AND IN DRAINAGE NOT REQUIRING
TEMPORARY LINING, APPLY 4000 LB/ACRE GRAIN STRAW BY STAPLING NETTING OVER THE TOP.
MULCH AND ANCHORING MATERIAL MUST NOT BEALLOWED TO BE WASH DOWN SLOPE WHERE
THEY CAN CLOG DRAINAGE DEVICES.
MAINTENANCE
A MINIMUM OF 3 WEEKS IS REQUIRED FOR ESTABLISHMENT. INSPECT AND REPAIR MULCH
FREQUENTLY. RE-FERTILIZE THE FOLLOWING APRIL WITH 50 LB/ACRE NITROGEN.
B. PERMANENT SEEDING AFTER SEPTEMBER 15 AND BEFORE APRIL 15:
SEEDING MIXTURE
TALL FESCUE 80 LB/ACRE
COMMON BERMUDA GRASS 40 LB/ACRE
KOBE LESPEDEZA 40 LB/ACRE
SEEDING DATES
FROM SEPT. 1- MARCH 1, USE UNSCARIFIED BERMUDA GRASS
SEEDING DATES
BEST
POSSIBLE
EARLY SPRING. FEB. 15 - MAR. 20 FEB. 15 -APRIL 30
FALL SEPT I - SEPT. 30 SEPT. 1- OCT. 31
SOIL AMENDMENTS
APPLY LIMEAND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 5000 LB/ACRE
GROUND AGRICULTURAL LIMESTONE AND 1000 LBIACRE 10-10.10 FERTILIZER
MULCH
APPLY 4000 LBIACRE GRAIN STRAW ON EQUIVALENT COVER OF ANOTHER SUITABLE
MULCH. ANCHOR STRAW BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY STRAIGHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELYRE-FER77UZE IN THE SECOND YEAR
ACCORDING TO THE SOIL TEST OR TOP DRESS WITH 500 LBIACRE 10-10-10 FERTILIZER
AND MOW AS NEEDED. WHEN SERICEA IS OMITTED FROM THE MIXTURE, RE-SEED,
FERTILIZE, AND MULCH DAMAGED AREAS IMMEDIATELY.
C. TEMPORARY SEEDING AFTER SEPTEMBER 15 AND BEFORE APRIL 15.
SEEDING MIXTURE
RYE GRAIN 120 LB/ACRE
KOBE LESPEDEZA 50LBIACRE
OMIT ANNUAL LESPEDEZA WHEN DURATION OF TEMPORARY COVER IS NOT TO EXTEND BEYOND
JUNE
SEEDING DATES
COASTAL PLAIN -DEC. 1-APRIL 15
SOIL AMENDMENTS
APPLY UME AND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 2000 LBIACRE
GROUND AGRICULTURAL LIMESTONEAND 750 LB/ACRE 10.10-10 FERTILIZER
MULCH
APPLY 4000 LB/ACRE GRAIN STRAW ON EQUIVALENT COVER OF ANOTHER SUITABLE
MULCH. ANCHOR STRA W BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY SR41GHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELY RE-FERTILIZE RE-SEED, RE-FERTILIZE AND
MULCH IMMEDIATELY FOLLOWING EROSION OR OTHER DAMAGE.
D. TEMPORARY SEEDING BEFORE SEPTEMBER 15 AND AFTER APRIL 15.
SEEDING MIXTURE
GERMAN MILLET 40 LBIACRE
SEEDING DATES
APRIL 15-AUGUST 15

SOIL AMENDMENTS
APPLY LIME AND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 2000 LB/ACRE
GROUND AGRICULTURAL LIMESTONEAND 750 LB/ACRE 10-10-10 FERTILIZER
MULCH
APPLY 4000 LB/ACRE GRAIN STRAW ON EQUIVALENT COVER OF ANOTHER SUITABLE
MULCH. ANCHOR STRAW BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY SRAIGHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELY RE-FERTILIZE RE-SEED, RE-FERTILIZE AND
MULCH IMMEDIATELY FOLLOWING EROSION OR OTHER DAMAGE.
IX. SPECIFIC ATIONS AND DETAILS
A. 6.02 ....................................................Land Grading
B. 6.06 ....................................................Temporary Gravel Construction Entrance
C. 6.14 ....................................................Mulching
D. 6.30 . ...................................................Grass- lined channels
E. 6.51 . ....................................................Fabric Drop Inlet Protection (Temporary)
F. 6.60 ....................................................Temporary Sediment Trap
G. 6.62 .....................................................Temporary Sediment Fence
H. 6.83 . ....................................................Rock Check Dam

CULVERT CROSSING DESIGN
FOR
WEST JOHNSTON HIGH SCHOOL
MAIN ENTRY ROAD
100 YR - 24 HOUR
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
%kill
ZAq SEALS 'v
?- 12324
FN?
West Johnston High School 20013-1

Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
0.95
0.3
CN=
CN=
C.
187.00 acres
98 37.00 acres
73 150.00 acres
C
5000 feet
79 feet
8.4 inches
Design Hydrograph Formulation
Composite CN
S=10001CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
77.9
2.83
5.76 inches
Time of Concentration
channel flow (not overland)
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
27.2
R 9 h
2 132 18
10 203 22
25 246 23
100 302 25
27.2 minutes
0.43
5.8 inches per hr
Peak Discharge Q=CIA 463.7 cfs
Time to peak
Tp= Vol/(1.37 Qp) 102.5 minutes
Based on Analysis of a 2 - 72" culverts the Headwater Elevation = 197.73
Top of the Road = 198.84 Road is designed to not overtop in the 100 year storm
Outlet Velocity = 8.8 fps Design Outlet Protection
Use Chart pg 8.06.3
for 232 cfs per barrel and 72" dia pipe use La = 30 feet
West Johnston High School -20013-2
PIPE CULVERT ANALYSIS
COMPUTATION OF CULVERT PERFORMANCE CURVE
June 5, 2000
PROGRAM INPUT DATA
DESCRIPTION
Culvert Diameter (ft) .......................................
FHWA Chart Number ...........................................
FHWA Scale Number (Type of Culvert Entrance) ................
Manning's Roughness Coefficient (n-value)..... ' ..............
Entrance Loss Coefficient of Culvert Opening ................
Culvert Length (ft) .........................................
Invert Elevation at Downstream end of Culvert (ft)..........
Invert Elevation at Upstream end of Culvert (ft)............
Culvert Slope (ft/ft) .......................................
Starting Flow Rate (cfs) ....................................
Incremental Flow Rate (cfs) .................................
Ending Flow Rate (cfs) ......................................
Starting Tailwater Depth (ft) ...............................
Incremental Tailwater Depth (ft) ............................
Ending Tailwater Depth (ft) .................................
COMPUTATION RESULTS
Flow Tailwater Headwater (ft) Normal Critical
Rate Depth Inlet Outlet Depth Depth
(cfs) (ft) Control Control
-
---- (ft)
--------- (ft)
----------
-------
100.0 ----------
4.0 -----------
3.82 ----
-
3.99 1.94 2.69
150.0 5.0 4.92 5.18 2.41 3.33
200.0 6.0 6.0 6.45 2.83 3.87
250.0 7.0 7.22 7.99 3.23 4.33
300.0 8.0 8.47 9.65 3.63 4.73
350.0 9.0 10.09 11.43 4.03 5.07
400.0 10.0 11.96 13.33 4.47 5.33
450.0 11.0 14.07 15.35 5.03 5.53
500.0 12.0 16.44 17.49 6.0 5.67
550.0 13.0 19.05 19.75 6.0 5.77
600.0 14.0 21.91 22.13 6.0 5.83
VALUE
6.0
1
1
0.012
0.1
55.0
188.0
188.51
0.0093
100.0
50.0
600.0
4 0
1.0
14.0
Depth at Outlet
Outlet Velocity
(ft)
--------- (fps)
---------
4.0 4.99
5.0 5.96
6.0 7.07
6.0 8.84
6.0 10.61
6.0 12.38
6.0 14.15
6.0 15.92
6.0 17.68
6.0 19.45
6.0 21.22
---- - -----------
HYDROCALC Hydraulics for Windows, Version 1.2a Copyright (c) 1996
Dodson & Associates, Inc., 5629 FM 1960 West, Suite 314, Houston, TX 77069
Phone:[phone], Fax:[phone], Email:[e-mail]
All Rights Reserved.
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722 32'30" 1 7pgooom.? • INTERIOR-GEOLOGICAL SURVEY, RESTON• VIRGINIA-199
FOUR OAKS 6 M/.-Ik;,
1 MILE ROAD CLASSIFICATION
000 5000 6000 7000 FEET
Medium-duty ...... _.._ Light-duty >a
1 KILOMETRE Unimproved dirt
0 FEET O State Route
%ATUM OF 1929 1
i
West Johnston High School
8-04-00
Calculations for level spreader
et De tention In the front of the School
Q = 27.7 cis outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH"1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (013.OL)"0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
Detenti on Behind the Athl etic Fields
Q = 27.2 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH"1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)"0.66
H = 0.18 ft
V = Q/A A = LH = 21.82 sf
V = 1.25 fps OK less than 3 fps
A
SLOPE
?. •: _ _ _ _ ...'.. : _ :.. • TRANSMON TO
3 A8-' _
..
/.` ............... ......
Design Flow
(cfs) Entrance Width Depth End Width Length
10

2D-3. ,
'11 2 I.0 3' ?o
LEVEL SPREADER
SCALE: NONE
c1C5 - GJ U H
t
Wet Detention Study front of School-2 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
2 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
6-6-00
rev 9-13-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
`????ruur
N s 2324
b? 0 .?
JANO
??nnr0M0
West Johnston High School -20013-1
t
Site Conditions Predevelopment
Wet Detention Study front of School-2 year 24 hour
Total watershed area
Area Impervious C=
Area grass or woods C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L"3/H)A0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.9 X
23.00 acres
CN= 98 0.00 acres
CN= 73 23.00 acres
C
1220 feet
40 feet
3.7 inches
OVERLAND
2
E 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-2
13.9 minutes
0.3
4.1 inches per hr
28.6 cfs

Storage Required
Wet Detention Study front of School-2 year 24 hour
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface diff.
Elevation am gift
198.00 37924
2.00
200.00 43925
2.00
202.00 51021
accum.
StOEM strM Elevation
0 198
81849
81849 200.00
94946
176795 202.00
Z
Std SUM LN(st rno LN(UWJ SUV
0 0 ERR ERR 0.00
81,849 2 11.31 0.69 2.00
176,795 4 12.08 1.39 4.00
b= 1.1110408
Ks= 37892.807
1/b
Z= (S/K,)^
Predicted Water Surface Elevation for 2 year 24 hour storm=
Predicted Surface Area= elev = 198.00
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00°
28.6 cis
81.9 cfs
94,699 cf
RM
0 198.00 =water surface
2
4
200.28 feet msl
37924 sf
West Johnston High School -20013-4
1 4
Wet Detention Study front of School-2 year 24 hour
Average pool depth = 3 ft
SAIDA= 2.30% Required Surface Area= 23023 sf
Surface Area Provide= 37924.0 sf
Volume to be controlled by 1" storm =1"(Rv=0.05 + 0.009(I))(DA) = 47005 cf
Temporary Water Quality Pool Elevation = 199.12
Discharge of volume in 48 hours = 0.3 cfs
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev.
available head (h) _
discharge (d) = 0.3 -
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)"1/2
0.0
198.00 feet mst
198.10 feet msl
200.28 feet msl
2.18 feet
0.3 cfs
0.6
0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 28.6 cfs L = 8 ft
Q=CwLH^3/2 H = 1.12 ft
Top of Emergency Spilivr a 1.12 msl
5
West Johnston High School -20013-5

Inflow HWkOgmph
Peak Inflow =
Time to Peak =
I Wme min)
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
Wet Detention Study front of School-2 year 24 hour
Additional Row
81.9
29.6
37.0368384
0 (cfA
0
2.1
8.0
17.2
28.9
41.7
54.5
65.8
74.7
80.3
81.8
79.3
72.9
64.2
56.3
49.3
43.2
37.9
33.2
29.1
25.5
22.4
19.6
17.2
15.1
13.2
11.6
10.2
8.9
7.8
6.8
6.0
5.3
4.6
4.0
3.5
3.1
2.7
2.4
0.0
West Johnston High School -20013-6
Wet Detention Study front of School-2 year 24 hour
L= 3.5
Stormwater routing
3 Spillway
inch 199.12
L(time min) Q(dj) Stomas egg O utflow Elevation orifice bL?iC
0 0 0 0.00 0.0 198.00
3 2.1 0 0.00 0.0 198.00 0.0 0.0
6 8.0 369 0.02 0.0 198.02 0.0 0.0
9 17.2 1809 0.06 0.0 198.06 0.0 0.0
12 28.9 4913 0.16 0.0 198.16 0.0 0.0
15 41.7 10110 0.30 0.0 198.30 0.0 0.0
18 54.5 17616 0.50 0.0 198.50 0.0 0.0
21 65.8 27417 0.75 0.2 198.75 0.2 0.0
24 74.7 39236 1.03 0.2 199.03 0.2 0.0
27 80.3 52650 1.34 1.3 199.34 0.3 1.1
30 81.8 66855 1.67 4.6 199.67 0.3 4.3
33 79.3 80760 1.98 8.7 199.98 0.3 8.4
36 72.9 93468 2.25 13.0 200.25 0.3 12.6
39 64.2 104261 2.49 17.2 200.49 0.4 16.8
42 56.3 112717 2.67 20.6 200.67 0.4 20.3
45 49.3 119130 2.80 23.3 200.80 0.4 22.9
48 43.2 123823 2.90 25.3 200.90 0.4 24.9
51 37.9 127048 2.97 26.8 200.97 0.4 26.4
54 33.2 129044 3.01 27.7 201.01 0.4 27.3
57 29.1 130043 3.03 28.1 201.03 0.4 27.7
60 25.5 130226 3.04 28.3 201.04 0.4 27.9
63 22.4 129722 3.03 28.1 201.03 0.4 27.7
66 19.6 128691 3.01 27.7 201.01 0.4 27.3
69 17.2 127242 2.98 27.0 200.98 0.4 26.6
72 15.1 125473 2.94 26.2 200.94 0.4 25.8
75 13.2 123477 2.90 25.3 200.90 0.4 24.9
78 11.6 121298 2.85 24.3 200.85 0.4 23.9
81 10.2 119014 2.80 23.3 200.80 0.4 22.9
84 8.9 116659 2.75 22.2 200.75 0.4 21.9
87 7.8 114261 2.70 21.2 200.70 0.4 20.9
90 6.8 111845 2.65 20.2 200.65 0.4 19.9
93 6.0 109433 2.60 19.3 200.60 0.4 18.9
96 5.3 107044 2.55 18.3 200.55 0.4 18.0
99 4.6 104693 2.50 17.4 200.50 0.4 17.0
102 4.0 102394 2.45 16.5 200.45 0.4 16.1
105 3.5 100159 2.40 15.6 200.40 0.4 15.2
108 3.1 97996 2.35 14.7 200.35 0.4 14.3
111 2.7 95914 2.31 14.0 200.31 0.3 13.6
114 2.4 93888 2.26 13.1 200.26 0.3 12.8
117 2.1 91955 2.22 12.5 200.22 0.3 12.1
120 1.8 90090 2.18 11.8 200.18 03 11.5
123 1.6 88297 2.14 11.2 200.14 0.3 10.8
126 1.4 86580 2.10 10.5 200.10 0.3 10.2
129 1.2 84940 2.07 10.1 200.07 0.3 9.7
132 1.1 83353 2.03 9.4 200.03 0.3 9.1
West Johnston High School -20013-7
Wet Detention Study front of School-2 year 24 hour
135 1.0 81849 2.00 9.0 200.00 0.3 8.7
138 0.8 80402 1.97 8.5 199.97 0.3 8.2
141 0.7 79013 1.94 8.1 199.94 0.3 7.8
144 0.6 77684 1.91 7.7 199.91 0.3 7.4
147 0.6 76415 1.88 7.3 199.88 0.3 7.0
150 0.5 75208 1.85 6.9 199.85 0.3 6.5
153 0.4 74061 1.83 6.6 199.83 0.3 6.3
156 0.4 72953 1.80 6.2 199.80 0.3 5.9
159 0.3 71906 1.78 5.9 199.78 0.3 5.6
162 0.3 70898 1.76 5.7 199.76 0.3 5.4
165 0.3 69928 1.74 5.4 199.74 0.3 5.1
168 0.2 68997 1.71 5.1 199.71 0.3 4.8
171 0.2 68127 1.70 4.9 199.70 0.3 4.6
174 0.2 67274 1.68 4.7 199.68 0.3 4.4
177 0.2 66460 1.66 4.5 199.66 0.3 4.2
180 0.1 65684 1.64 4.2 199.64 0.3 3.9
183 0.1 64947 1.62 4.0 199.62 0.3 3.7
186 0.1 64247 1.61 3.9 199.61 0.3 3.6
189 0.1 63565 1.59 3.7 199.59 0.3 3.4
192 0.1 62921 1.58 3.6 199.58 0.3 3.3
195 0.1 62294 1.56 3.3 199.56 0.3 3.1
198 0.1 61704 1.55 3.2 199.55 0.3 3.0
201 0.1 61131 1.54 3.1 199.54 0.3 2.9
204 0.0 60575 1.53 3.0 199.53 0.3 2.8
360 0.0 32579 0.87 0.2 198.87 0.2 0.0
720 0.0 28161 0.77 0.2 198.77 0.2 0.0
1080 0.0 24047 0.66 0.2 198.66 0.2 0.0
1440 0.0 20298 0.57 0.2 198.57 0.2 0.0
1800 0.0 16875 0.48 0.1 198.48 0.1 0.0
2160 0.0 13813 0.40 0.1 198.40 0.1 0.0
2520 0.0 11113 0.33 0.1 198.33 0.1 0.0
2880 0.0 8775 0.27 0.1 198.27 0.1 0.0
3240 0.0 6798 0.21 0.1 198.21 0.1 0.0
3600 0.0 5268 0.17 0.1 198.17 0.1 0.0
3960 0.0 4127 0.14 0.0 198.14 0.0 0.0
4320 0.0 3405 0.11 ERR 198.11 ERR 0.0
4680 0.0 ERR ERR ERR ERR ERR 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 28.3 cis
Peak Stage= 3.04 ft
Water Elevation= 201.04 msl
Peak Storage = 130226 cf
Design Spillway 199.12 ms!
Length of weir 30 ft
West Johnston High School -20013-8
Inflow outflow hydrograph
......:........................;........................; ...................
90 ............................ ................ ...:......................... ............. ............................
80
...................................................................
70 ...................... ........... ....................... ............ ........................
60 ..................... ...... ................ ................. ............................... ................................................. ....................... ...................
50 ..................... .. .......................................... ` ..........--------- ........................ '..-........... ...........................-. _ .................
i
0
LL
40 ..................... . ----------------------- ............................... ................ ................................................. ........................ ................---
30 ........................................ .................. ..... ........................ ........................ ..................... ...................
20
10
0
0 15 30 45 60 75 90 105
. Time (minutes)
-?- Inflow Hydrograph -A- Outflow Hydrograph
Wet Detention Study front of School-100 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
100 YR - 24 HOUR
NCDENR BMP
FIRST V OF RUNOFF
20013
5-25-00
rev 9-13-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918

West Johnston High School -20013-1
Wet Detention Study front of School-100 year 24 hour
Site Conditions Predevelopment
Total watershed area
Area Impervious
Area grass or woods
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
To=(L^3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
C= 0.95
C= 0.3
6.9 X
23.00 acres
CN= 98 0.00 acres
CN= 73 23.00 acres
C
1220 feet
40 feet
8.4 inches
OVERLAND
2
B 9 h
2 132 18
10 203 22
25 246 23
100 302 25
13.9 minutes
0.3
7.8 inches per hr
53.6 cis
West Johnston High School -20013-2
. t
Storage Required
Wet Detention Study front of School-100 year 24 hour
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface dill.
Elevation area AY stomp.
198.00 37924
2.00 81849
200.00 43925
2.00 94946
202.00 51021
accum.
stomp
0
81849
176795
Y
Stomp S-Ug LN orM) LN(Stage) Rap
0 0 ERR ERR 0.00
81,849 2 11.31 0.69 2.00
176,795 4 12.08 1.39 4.00
b= 1.1110408
Ks= 37892.807
1/b
Z= (g/KS)n
Predicted Water Surface Elevation for 100 year 24 hour storm=
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00%
53.6 cfs
120.2 cfs
231,990 cf
Elevation
198 0 198.00 =water surface
200.00 2
202.00 4
203.11 feet msl
West Johnston High School -20013-4

Wet Detention Study front of School-100 year 24 hour
Average pool depth = 3 ft
SA/DA= 2.30% Required Surface Area=
Surface Area Provide=
Volume to be controlled by 1" storm =1"(Rv=0.05 + 0.009(I))(DA)
Temporary Water Quality Pool Elevation =
Discharge of volume in 48 hours =
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) = 0.3 -
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)^1/2
0.0
23023 sf
37924.0 sf
47005 cf
199.12
0.3 cfs
198.00 feet msl
198.10 feet msl
203.11 feet msl
5.01 feet
0.3 cfs
0.6
0.18 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 53.6 cfs L = 8 ft
Q=CwLH^3/2 H = 1.71 ft
Top of Emergency Spiiiwc 1.71 msl
West Johnston High School -20013-5
Wet Detention Study front of School-100 year 24 hour
135 25.4 131061 3.06 30.7 201.06 0.4 28.4
138 23.8 130104 3.04 29.3 201.04 0.4 27.9
141 22.2 129118 3.01 27.7 201.01 0.4 27.3
144 20.8 128136 2.99 27.3 200.99 0.4 26.9
147 19.4 126972 2.97 26.8 200.97 0.4 26.4
150 18.2 125642 2.94 26.2 200.94 0.4 25.8
153 17.0 124201 2.91 25.5 200.91 0.4 25.1
156 15.9 122662 2.88 24.9 200.88 0.4 24.5
159 14.9 121039 2.84 24.1 200.84 0.4 23.7
162 13.9 119379 2.81 23.5 200.81 0.4 23.1
165 13.0 117658 2.77 22.6 200.77 0.4 22.3
168 12.1 115921 2.74 22.0 200.74 0.4 21.7
171 11.4 114141 2.70 21.2 200.70 0.4 20.9
174 10.6 112364 2.66 20.4 200.66 0.4 20.1
177 9.9 110596 2.62 19.7 200.62 0.4 19.3
180 9.3 108844 2.58 18.9 200.58 0.4 18.5
183 8.7 107114 2.55 18.3 200.55 0.4 18.0
186 8.1 105378 2.51 17.6 200.51 0.4 17.2
189 7.6 103677 2.47 16.8 200.47 0.4 16.5
192 7.1 102013 2.44 16.3 200.44 0.4 15.9
195 6.6 100360 2.40 15.6 200.40 0.4 15.2
198 6.2 98753 2.37 15.0 200.37 0.4 14.7
201 5.8 97165 2.33 14.3 200.33 0.4 14.0
204 5.4 95631 2.30 13.8 200.30 0.4 13.5
360 0.2 17175 0.49 0.1 198.49 0.1 0.0
720 0.0 17560 0.50 0.1 198.50 0.1 0.0
1080 0.0 14334 0.42 0.1 198.42 0.1 0.0
1440 0.0 11447 0.34 0.1 198.34 0.1 0.0
1800 0.0 8947 0.27 0.1 198.27 0.1 0.0
2160 0.0 6843 0.21 0.1 198.21 0.1 0.0
2520 0.0 5151 0.17 0.1 198.17 0.1 0.0
2880 0.0 3801 0.13 0.0 198.13 0.0 0.0
3240 0.0 2917 0.10 0.0 198.10 0.0 0.0
Results of routing the 100 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 118.7 cfs
Peak Stage= 3.59 ft
Water Elevation= 201.59 msl
Peak Storage = 156828 cf
Design Spillway 199.12 msl
Length of weir 3.5 ft
Emergency Spillway 201.01 msl
Length of Weir 58.5 ft 30 Boot emergency spillway plus 32'-3.5' of design
spillway = 30'+28.5'= 58.5'
2.0
0.9
0.0
0.0
West Johnston High School -20013-8
Wet Detention Study front of School-100 year 24 hour
Size Oudet Pipe for Spillway
100 yr. flow for principal spillway =
Effective Length of Emergency spillway for outlet pipe =
Water Surface Elevation for 100 year Storm =
Top of Emergency Spillway at box =
Q=CLH^1.5 =
Design flow for 100 year storm for outlet pipe =
Slope of outlet pipe =
Material of outlet pipe =
n=
d = 16 (QNS"0.5)"0.375
Use =
40.8 cfs
28.5 ft
201.59 msl
201.01 msl
37.8 cfs
78.5 cfs
0.005 fttft
concrete
0.012
42.26 inches
48 inch
West Johnston High School -20013-9
J.
Inflow outflow hydrograph
....; ......................:............-.......:..............................................,.......................:...................
140 .................................... .......
120 ............................................................... ' ........................................................................................
100 ............................................................................................................. €... ............. .................. ................
..............................................................
80
v
1
LL
60
40 --------------------- <............ ........... ....................... _........ ............... >....................... ........................ ....................... .............
20
0
0 15 30 45 60 75 90 105
Time (minutes)
-+- Inflow Hydrograph - Outflow Hydrograph
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
2 YR - 24 HOUR
NCDENR BMP
FIRST V OF RUNOFF
20013
5-25-00
rev 9-13-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918

nP-4L
N?p%° C' 1
West Johnston High School -20013-1
I l
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions Predevelopment
Total watershed area
Area Impervious C=
Area grass or wooded C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.7 X
29.00 acres
CN= 98 0.00 acres
CN= 73 29.00 acres
C
1280 feet
51 feet
3.7 inches
OVERLAND
2
B Q b
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-2
13.3 minutes
0.3
4.2 inches per hr
36.6 cfs
{
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L^3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= Vol/(1.37 Qp)
0.95
0.3
6.7
CN= 98
CN= 73
C.
E 9 11
2 132 18
10 203 22
25 246 23
100 302 25
29.00 acres
9.56 acres
19.44 acres
C
1280 feet
51 feet
3.7 inches
81.2
2.31
1.89 inches
13.4 minutes
0.51
4.2 inches per hr
62.7 cfs
38.6 minutes
West Johnston High School 20013-3
.
Storage Required
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface diff. accum.
Elevatiop area AL" Storage stoma
179.00 5673 0
1.00 6400
180.00 7127 6400
2.00 18160
182.00 11033 24560
2.00 26047
184.09 15014 50607
2.00 33772
186.00 18758 84379
2.00 42466
188.00 23708 126845
1.50 38900.25
189.50 28159 165745.25
Z
C
d
Stodge L N(sttc, gel LNOtag_e) ompute
egg
0 0 ERR ERR 0.00
6,400 1 8.76 0.00 1.24
24,560 3 10.11 1.10 3.00
126,845 9 11.75 2.20 8.81
165,745 10.5 12.02 2.35 10.50
b= 1.5240975
Ks= 4603.0858
1/b
Z= (S/K.y)A
36.6 cis
62.7 cfs
60,364 cf
Elevation
179 0
180.00 1
182.00 3
184.00 5
186.00 . 7
188.00 9
189.50 10.5
Predicted Water Surface Elevation= 184.41 feet msi
To capture the first 1" of runoff
volume= DA x 43560 x 1" 112 106270 cf 186.80 feet msl
set spillway elevation at this elevation
West Johnston High School -20013-4
I V i ?
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) _
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)"1/2
0.61 cfs
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
0.5 -
SAY
179.00 feet msl
179.30 feet msl
186.80 feet msl
7.50 feet
0.5 cfs
0.6
0.22 feet
3 inches
0.0
Determine Weir length for 2 year 24 hour discharge
Q = 36.6 cfs stimate L = 8 ft
Q=CwLH"3/2 H =
Top of Emergency Spillwc,
1.33 ft
188.12 msl
West Johnston High School -20013-5
5
1 )
Mow Fiydm ph
Peak Mow =
Mme W Peak =
48.26564414
T (dme min)
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCE)ENR BMP
2Ad
AdMonal Pow
62.7
38.6
0
0.9
3.7
8.0
13.8
20.6
28.0
35.6
43.0
49.7
55.3
59.5
62.0
62.7
61.5
58.6
54.0
48.9
44.2
39.9
36.1
32.6
29.5
26.7
24.1
21.8
19.7
17.8
16.1
14.5
13.1
11.9
10.7
9.7
8.8
7.9
7.2
6.5
5.9
West Johnston High School 20013-6
0.0
I .
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour NCDENR BMP
L= 6.5
Stormwater routing
3 Spillway
inch 186.80
T (time min) Q (sh) Stomp S#.M Outflow FLevation orifice wl[
0 0 0 0.00 0.0 179.00
3 0.9 0 0.00 0.0 179.00 0.0 0.0
6 3.7 167 0.11 0.0 179.11 0.0 0.0
9 8.0 826 0.32 0.0 179.32 0.0 0.0
12 13.8 2271 0.63 0.0 179.63 0.0 0.0
15 20.6 4751 1.02 0.2 180.02 0.2 0.0
18 28.0 8423 1.49 0.2 180.49 0.2 0.0
21 35.6 13420 2.02 0.3 181.02 0.3 0.0
24 43.0 19781 2.60 0.3 181.60 0.3 0.0
27 49.7 27459 3.23 0.4 182.23 0.4 0.0
30 55.3 36333 3.88 0.4 182.88 0.4 0.0
33 59.5 46206 4.54 0.5 183.54 0.5 0.0
36 62.0 56824 5.20 0.5 184.20 0.5 0.0
39 62.7 67888 5.85 0.5 184.85 0.5 0.0
42 61.5 79072 6.46 0.6 185.46 0.6 0.0
45 58.6 90044 7.04 0.6 186.04 0.6 0.0
48 54.1 100480 7.56 0.6 186.56 0.6 0.0
51 48.1 110098 8.03 2.9 187.03 0.6 2.2
54 44.2 118247 8.41 10.1 187.41 0.7 9.4
57 39.9 124387 8.70 17.5 187.70 0.7 16.8
60 36.1 128433 8.88 22.7 187.88 0.7 22.0
63 32.6 130843 8.99 26.1 187.99 0.7 25.5
66 29.5 132009 9.04 27.8 188.04 0.7 27.1
69 26.7 132320 9.06 28.4 188.06 0.7 27.7
72 24.1 132003 9.04 27.8 188.04 0.7 27.1
75 21.8 131343 9.01 26.8 188.01 0.7 26.1
78 19.7 130442 8.97 25.5 187.97 0.7 24.8
81 17.8 129394 8.93 24.3 187.93 0.7 23.6
84 16.1 128233 8.87 22.4 187.87 0.7 21.7
87 14.5 127096 8.82 20.9 187.82 0.7 20.2
90 13.1 125951 8.77 19.4 187.77 0.7 18.8
93 11.9 124818 8.72 18.0 187.72 0.7 17.3
96 10.7 123715 8.67 16.6 187.67 0.7 15.9
99 9.7 122656 8.62 15.3 187.62 0.7 14.6
102 8.8 121655 8.57 14.0 187.57 0.7 13.3
105 7.9 120721 8.53 12.9 187.53 0.7 12.3
108 7.2 119819 8.49 12.0 187.49 0.7 11.3
111 6.5 118958 8.45 11.0 187.45 0.7 10.3
114 5.9 118146 8.41 10.1 187.41 0.7 9.4
117 5.3 117391 8.37 9.2 187.37 0.7 8.5
120 4.8 116696 8.34 8.5 187.34 0.7 7.8
123 4.3 116029 8.31 7.9 187.31 0.7 7.2
126 3.9 115393 8.28 7.2 187.28 0.7 6.6
129 3.5 114795 8.25 6.6 187.25 0.7 6.0
132 3.2 114238 8.23 6.2 187.23 0.7 5.6
West Johnston High School -20013-7
1 1 1
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
135 2.9 113689 8.20 5.7 187.20 0.7 5.0
138 2.6 113188 8.18 5.3 187.18 0.7 4.6
141 2.4 112704 8.15 4.8 187.15 0.7 4.1
144 2.1 112270 8.13 4.4 187.13 0.7 3.8
147 1.9 111858 8.11 4.1 187.11 0.7 3.4
150 1.7 111469 8.09 3.8 187.09 0.7 3.1
153 1.6 111104 8.08 3.6 187.08 0.7 3.0
156 1.4 110738 8.06 3.3 187.06 0.6 2.7
159 1.3 110400 8.04 3.0 187.04 0.6 2.4
162 1.2 110091 8.03 2.9 187.03 0.6 2.2
165 1.1 109785 8.01 2.6 187.01 0.6 1.9
168 1.0 109509 8.00 2.5 187.00 0.6 1.8
171 0.9 109239 7.99 2.3 186.99 0.6 1.7
174 0.8 108977 7.97 2.1 186.97 0.6 1.4
177 0.7 108744 7.96 1.9 186.96 0.6 1.3
180 0.6 108520 7.95 1.8 186.95 0.6 1.2
183 0.6 108305 7.94 1.7 186.94 0.6 1.1
186 0.5 108100 7.93 1.6 186.93 0.6 1.0
189 0.5 107904 7.92 1.5 186.92 0.6 0.9
192 0.4 107719 7.91 1.4 186.91 0.6 0.8
195 0.4 107543 7.91 1.4 186.91 0.6 0.8
198 0.3 107360 7.90 1.3 186.90 0.6 0.7
201 0.3 107189 7.89 1.2 186.89 0.6 0.6
204 0.3 107027 7.88 1.1 186.88 0.6 0.5
360 0.0 99185 7.50 0.6 186.50 0.6 0.0
720 0.0 85717 6.81 0.6 185.81 0.6 0.0
1080 0.0 72899 6.13 0.6 185.13 0.6 0.0
1440 0.0 60792 5.44 0.5 184.44 0.5 0.0
1800 0.0 49450 4.75 0.5 183.75 0.5 0.0
2160 0.0 38931 4.06 0.4 183.06 0.4 0.0
2520 0.0 29303 3.37 0.4 182.37 0.4 0.0
2880 0.0 20659 2.68 0.3 181.68 0.3 0.0
3240 0.0 13125 1.99 0.3 180.99 0.3 0.0
3600 0.0 6896 1.30 0.2 180.30 0.2 0.0
3960 0.0 2332 0.64 0.1 179.64 0.1 0.0
4320 0.0 423 0.21 0.0 179.21 0.0 0.0
4680 0.0 423 0.21 0.0 179.21 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 28.4 cfs
Peak Stage= 9.06 ft
Water Elevation= 188.06 ms!
Peak Storage = 132320 d
Design Spillway 186.80 msl
Length of weir 6.5 ft
West Johnston Nigh School -20013-8

Inflow outflow hydrograph
............:............................................
70 ........................................... ...._.............................. ...................,........ ................:............
so ................................................................................................................. ................... .................
50
40
w
v
LL
30
20
10
0 4 4 4 4
0 15 30 45 60 75 90 105
Time (minutes)
+- Inflow Hydrograph Outflow Hydrograph
.
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
100 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
NH CAA
23 4.2
??''r+? aNN OV_`??
%,?FNf JAN ???..
West Johnston High School -20013-1
1 1 .
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions Predevelopment
Total watershed area
Area Impervious C=
Anna grass or wooded C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intensity
Peak Discharge
0.95
0.3
6.7 X
CN= 98
CN= 73
OVERLAND
2
8 9 h
1= g/(h+T) 2 132 18
10 203 22
25 246 23
100 302 25
Q=CIA
29.00 acres
0.00 acres
29.00 acres
C
1280 feet
51 feet
8.4 inches
13.3 minutes
0.3
7.9 inches per hr
68.5 cfs
West Johnston High School -20013-2

Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L"3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= Vol/(1.37 Qp)
0.95
0.3
CN=
CN=
C
29.00 acres
98 9.56 acres
73 19.44 acres
C
1280 feet
51 feet
8.4 inches
81.2
2.31
6.15 inches
6.7
B 9 h
2 132 18
10 203 22
25 246 23
100 302 25
13.4 minutes
0.51
7.9 inches per hr
117.3 cfs
67.1 minutes
West Johnston High School -20013-3
r 4 1 4
Storage Required
Storm Water Detention Study Behind Athletic f=ields-100 year 24 hour-NCDENR BMP
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface diff. accum.
Elevation area slu stomp storm
179.00 5673 0
1.00 6400
180.00 7127 6400
2.00 18160
182.00 11033 24560
2.00 26047
184.00 15014 50607
2.00 33772
186.00 18758 84379
2.00 42466
188.00 23708 126845
1.50 38900.25
189.50 28159 165745.25
Z
C
d
Storage Rap L Njstor Pagel LN( m) ompute
StW
0 0 ERR ERR 0.00
6,400 1 8.76 0.00 1.24
24,560 3 10.11 1.10 3.00
126,845 9 11.75 2.20 8.81
165,745 10.5 12.02 2.35 10.50
b= 1.5240975
Ks= 4603.0858
1/b
Z= (5/Ks)^
68.5 cfs
117.3 cfs
196,465 cf
Elevation
179 0
180.00 1
182.00 3
184.00 5
186.00 7
188.00 9
189.50 10.5
Predicted Water Surface Elevation= 190.74 feet msl
To capture the first 1" of runoff
volume= DA x 43560 x 1" !12 106270 cf 186.80 feet msl
set spillway elevation at this elevation
West Johnston High School -20013-4
I r 1 f
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP _ _ __ _
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) = 0.5 -
coefficient of discharge =
Determine the orifice diameter
Orifice equation
0.61 cfs
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
179.00 feet msl
179.30 feet msl
186.80 feet msl
7.50 feet
0.0 0.5 cis
0.6
Q = Cd(A)(2gh)"1/2 0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 68.5 cfs stimate L = 8 ft
Q=CwLH"3/2 H = 2.01 ft
Top of Emergency Spiilwc 188.81 msl
5
West Johnston High School -20013-5
I k + •
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Mftw HWmgraph
AdditWW Flow 0.0
Peak 1n8ow = 117.3
Time W peak = 67.1
83.92897444

0 0
3 0.6
6 2.3
9 5.1
12 9.0
15 13.8
18 19.6
21 26.1
24 33.2
27 40.9
30 48.9
33 57.0
36 65.2
39 73.3
42 81.1
45 88.5
48 95.2
Si 101.3
54 106.5
57 110.8
60 114.0
63 116.2
66 117.2
69 117.1
72 115.8
75 113.4
78 109.9
81 105.5
84 100.1
87 94.5
90 89.1
93 84.1
96 79.3
99 74.9
102 70.6
105 66.7
108 62.9
111 59.3
114 56.0
West Johnston High School -20013-6
f * 1 0,
Stone Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
L= 6.5 55.5
Stormwater routing Emergency
3 Spillway Spillway
inch 186.80 187.78
L(time min) Q { ds) Storage Ran Qutfl?c Elevation orifice Wilt WAk
0 0 0 0.00 0.0 179.00
2 0.3 0 0.00 0.0 179.00 0.0 0.0
4 1.0 31 0.04 0.0 179.04 0.0 0.0
6 2.3 154 0.11 0.0 179.11 0.0 0.0
8 4.1 429 0.21 0.0 179.21 0.0 0.0
10 6.3 916 0.35 0.0 179.35 0.0 0.0
12 9.0 1671 0.51 0.0 179.51 0.0 0.0
14 12.1 2751 0.71 0.1 179.71 0.1 0.0
16 15.7 4193 .0.94 0.2 179.94 0.2 0.0
18 19.6 6054 1.20 0.2 180.20 0.2 0.0
20 23.8 8380 1.48 0.2 180.48 0.2 0.0
22 28.4 11212 1.79 0.3 180.79 0.3 0.0
24 33.2 14587 2.13 0.3 181.13 0.3 0.0 0.0
26 38.3 18538 2.49 0.3 181.49 0.3 0.0 0.0
28 43.5 23090 2.88 0.4 181.88 0.4 0.0 0.0
30 48.9 28265 3.29 0.4 182.29 0.4 0.0 0.0
32 54.3 34080 3.72 0.4 182.72 0.4 0.0 0.0
34 59.8 40544 4.17 0.5 183.17 0.5 0.0 0.0
36 65.2 47663 4.64 0.5 183.64 0.5 0.0 0.0
38 70.7 55435 5.12 0.5 184.12 0.5 0.0 0.0
40 76.0 63853 5.62 0.5 184.62 0.5 0.0 0.0
42 81.1 72905 6.13 0.6 185.13 0.6 0.0 0.0
44 86.1 82573 6.65 0.6 185.65 0.6 0.0 0.0
46 90.8 92833 7.18 0.6 186.18 0.6 0.0 0.0
48 95.2 103656 7.72 0.6 186.72 0.6 0.0 0.0
50 99.4 115009 8.26 6.8 187.26 0.7 6.2 0.0
52 103.1 126114 8.78 19.7 187.78 0.7 19.0 0.0
54 106.5 136122 9.23 84.5 188.23 0.7 33.5 50.3
56 109.5 138767 9.34 107.9 188.34 0.7 37.4 69.8
58 112.0 138953 9.35 110.1 188.35 0.7 37.8 71.7
60 114.0 139172 9.36 112.4 188.36 0.7 38.2 73.5
62 115.6 139366 9.37 114.7 188.37 0.7 38.5 75.5
64 116.6 139473 9.38 117.0 188.38 0.7 38.9 77.4
66 117.2 139433 9.37 114.7 188.37 0.7 38.5 75.5
68 117.2 139735 9.39 119.3 188.39 0.7 39.3 79.3
70 116.8 139490 9.38 117.0 188.38 0.7 38.9 77.4
72 115.8 139466 9.38 117.0 188.38 0.7 38.9 77.4
74 114.3 139326 9.37 114.7 188.37 0.7 38.5 75.5
76 112.4 139283 9.37 114.7 188.37 0.7 38.5 75.5
78 109.9 139005 9.36 112.4 188.36 0.7 38.2 73.5
80 107.1 138709 9.34 107.9 188.34 0.7 37.4 69.8
82 103.8 138607 9.34 107.9 188.34 0.7 37.4 69.8
84 100.1 138110 9.32 103.5 188.32 0.7 36.7 66.1
86 96.3 137704 9.30 99.1 188.30 0.7 36.0 62.4
88 92.6 137366 9.28 94.8 188.28 0.7 35.3 58.9
West Johnston High School -20013-7
? ? • fY
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
90 89.1 137102 9.27 92.7 188.27 0.7 34.9
92 85.7 136670 9.25 88.6 188.25 0.7 34.2
94 82.5 136331 9.24 86.5 188.24 0.7 33.9
96 79.3 135849 9.22 82.4 188.22 0.7 33.2
98 76.3 135477 9.20 78.5 188.20 0.7 32.5
100 73.4 135220 9.19 76.5 188.19 0.7 32.1
102 70.6 134850 9.17 72.7 188.17 0.7 31.4
104 68.0 134607 9.16 70.8 188.16 0.7 31.1
106 65.4 134268 9.14 31.1 188.14 0.7 30.4
108 62.9 138383 9.33 37.8 188.33 0.7 37.1
110 60.5 141398 9.46 42.6 188.46 0.7 41.9
112 58.2 143549 9.55 46.0 188.55 0.7 45.3
114 56.0 145010 9.62 48.8 188.62 0.7 48.1
116 53.9 145878 _9.66 50.4 188.66 0.7 49.6
118 51.8 146299 9.67 50.8 188.67 0.7 50.0
120 49.9 146427 9.68 51.2 188.68 0.7 50.4
122 48.0 146270 9.67 50.8 188.67 0.7 50.0
124 46.1 145934 9.66 50.4 188.66 0.7 49.6
126 44.4 145428 9.64 49.6 188.64 0.7 48.8
128 42.7 144807 9.61 48.4 188.61 0.7 47.7
130 41.1 144126 9.58 47.2 188.58 0.7 46.5
132 39.5 143392 9.55 46.0 188.55 0.7 45.3
134 38.0 142611 9.51 44.5 188.51 0.7 43.8
136 36.6 141835 9.48 43.3 188.48 0.7 42.6
138 35.2 141023 9.44 0.7 188.44 0.7 0.0
140 33.8 145160 9.63 0.7 188.63 0.7 0.0
142 32.6 149137 9.80 0.7 188.80 0.7 0.0
144 31.3 152958 9.96 0.7 188.96 0.7 0.0
146 30.1 156630 10.12 0.7 189.12 0.7 0.0
148 29.0 160158 10.27 0.7 189.27 0.7 0.0
150 27.9 163549 10.41 0.7 189.41 0.7 0.0
152 26.8 166806 10.54 0.7 189.54 0.7 0.0
154 25.8 169936 10.67 0.8 189.67 0.8 0.0
156 24.8 172943 10.80 0.8 189.80 0.8 0.0
158 23.9 175832 10.92 0.8 189.92 0.8 0.0
Results of routing the 100 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 117.0 cfs
Peak Stage= 9.38 ft
Water Elevation= 188.38 msl
Peak Storage = 139490 cf
Design Spillway 186.80 ms!
Length of weir 6.5 ft
Emergency Spillway 187.78 ms!
Length of Weir 55.5 k
57.1
53.6
51.9
48.6
45.3
43.7
40.6
39.0
0.0
West Johnston High School -20013-8
t A. 0 W
Inflow outflow hydrograph
......,.............................................................................................
120 .........................................
100 ' ..............................................`.....................................................................'-.......•••........... ................
80 ............................................ ....................... ...................... ........ ..............s....................... ................
w
U
60 .......................... ....................... ........ ............v............ ..... ...............................................................
O
tl
.
40 ............ .............. ............... ............................... ....................... ..... ................. ...................... ...................
20
0
0 10 20 30 40 50 60 70
Time (minutes)
-?- Inflow Hydrograph- Outflow Hydrograph
- erosion at inlet and outlet
- sediment accumulation/removal
- condition of emergency spillway
- woody vegetation in the embankment
A responsible party is designated in the O&M plan.
FORM SWU109 04198 Page 1 of 1
r'
- erosion at inlet and outlet
- sediment accumulation/removal
- condition of emergency spillway
- woody vegetation in the embankment
A responsible party is designated in the O&M plan.
FORM SWU109 04/98 Paae 1 of 1

Project No. DWQ (to be provided by DWQ)
DIVISION OF WATER QUALITY - 401 WET DETENTION BASIN WORKSHEET
DWO Stormwater Management Plan Review:
A complete stormwater management plan submittal includes a wet detention basin worksheet for each basin,
design calculations, plans and specifications showing all basin and outlet structure details, 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.
1. PROJECT INFORMATI (please compl to the following information):
Project Name
Contact Person: Phone Number:
For projects with multiple basins, specify which basin this worksheet applies to:.
Basid Bottom Elevation
Permanent Pool Elevation
Temporary Pool Elevation
Permanent Pool Surface Area
Drainage Area
Impervious Area
Permanent Pool Volume
Temporary Pool Volume
Forebay Volume
I0_6v ft.
l va ft.
199. / ft.
, 9 sq.
Z 7P.O ac.
11,14- ac.
(average elevation of the floor of the basin)
(elevation of the orifice invert out)
(elevation of the outlet structure invert in)
ft. (water surface area at permanent pool elevation)
(on-site and off-site drainage to the basin)
(on-site and off-site drainage to the basin)
?? Z 28 cu. ft.
I ?iD,ly cu. ft.
cu. ft.
(combined volume of main basin and forebay)
(volume detained on top of the permanent pool)
SA/DA used 2 •?? Y ?,' /446(surface area to drainage area ratio)
Diameter of Orifice in. (draw down orifice diameter)
H. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices manual
(N.C. Department of Environment, Health and Natural Resources, November 1995) and Administrative Code
Section: 15 A NCAC 2H .1008. 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.
The temporary pool controls runoff from the 1 inch storm event.
The basin length to width ratio is greater than 3:1.
The basin side slopes are no steeper than 3:1.
7/ A submerged and vegetated perimeter shelf at less than 6:1 is provided.
f -Vegetation to the permanent pool elevation is specified.
An emergency drain is provided to drain the basin.
The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
The temporary pool draws down in 2 to 5 days.
The forebay volume is approximately equal to 20% of the total basin volume.
Sediment storage is provided in the permanent pool.
7 Access is provided for maintenance.
A minimum 30-foot vegetative filter is provided at the outlet.
A site specific operation and maintenance (O&M) plan is provided.
A vegetation management/mowing schedule is provided in the O&M plan.
Semi-annual inspections are specified in the 0&M plan.
A debris check is specified in the 0&M plan to be performed after every storm event.
A specific sediment. clean-out benchmark is listed (elevation or depth) in 0&M plan.
-A responsible party is designated in the O&M plan.
100 09/97 Page 1 of 1
I/
Project No. DWQ 09 be provided by DWQ)
DIVISION OF WATER QUALITY
401 EXTENDED DRY DETENTION BASIN WORKSHEET
DWQ Stormwater Management Plan Review
A complete stormwater management plan submittal includes a dry detention basin worksheet for each
basin, design calculations, plans and specifications showing all basin and outlet structure details, 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.
1. PROJECT INFORMATION (please complete the following information):
Project Name :
Contact Person: C > Phone Number: /
For projects with multiple basins, specify which basin this worksheet applies to:_ 1_ ?r7( ?jp 2
Drainage Area: Zf.,v acres Percent Impervious Area: Ali , ? 7 %
II. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices
Manual (N.C. Department of Environment, Health and .Natural Resources, November 1995) and
Administrative Code Section: 15 A NCAC 2H.1008. 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.
Applicants Initials
Either capture runoff from 1 yr., 24 hour storm and release over a 48 hour period, or
n capture runoff from 1 inch storm and draw down over a period of 2 to 5 days.
97The basin length to width ratio is greater than 3:1.
The basin side slopes are no steeper than 3:1.
-A smali• permanent pool at outlet orifice is provided to reduce clogging.
An emergency drain to completely empty the basin is provided.
4-v-Wegetation plan prepared by a licensed professional is specified.
Basin'to be stabilized within 14 days of construction is specified.
v I9. S' Sediment storage (20% of detention volume) in addition to detention volume is provided.
Inlet and outlet erosion control measures to prevent scour are provided.
Additional treatment to meet the 85% TSS removal efficiency is provided.
<< _ E Access for clean-out and maintenance is provided.
Inlet plunge pool or other energy dissipation is provided.
i Forebay is provided to capture sediment and minimize clean-out problems.
Uncompacted natural soils are utilized to promote vegetation. and reduce sedimentation.
Seasonal high water table is at least 1 foot below bottom of basin.
If used as a temporary basin, plans indicate clean-out prior to final operation.
A site specific operation and maintenance plan with the following provisions is provided.
- Mow grass at least twice annually
-Remove trash and debris upon accumulation and at least twice annually
- Inspect for proper operation at least twice annually including:
- outlet clogging or too rapid a release
- erosion on banks

STORM WATER MANAGEMENT PLAN
WEST JOHNSTON HIGH SCHOOL
JOHNSTON COUNTY, NORTH CAROLINA
Proj. No. 20013
June 6, 2000
leiA/. 'T• -a oo
oljkV C
age"
? F
E
AD
24
?IN .
V JAND`.``??
prepared by:
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
[phone]

Narrative
This site is a proposed high school. It is situated on a 101 acre tract of land off the east
side of SR 1330 and south of Beaverdam Branch. The property is not located in the
ESOD. The site is classified as commercial in accordance with the classification that
Johnston County Director of Infrastructure and Engineering assigned to this school in a
joint meeting on April 4, 2000. The impervious limits for commercial areas is 60%. The
existing slopes of the land are between 5 and 10 % with drainage in two directions. The
proposed drainage plan also manages storm water in the two separate basins. There is a
total of 22.70 acres of impervious area on this site which is 22.5% impervious.
In the front of the site, a wet detention basin is designed to attenuate the post development
peak discharge of the 2 year 24 hour storm to that of the predeveloped flow and to detain
the first 1" of runoff and release it between 2 and 5 days. The estimated predevelopment
peak rate of runoff is 28.6 cfs. The estimated postdevelopment rate of runoff is 81.9 cfs.
The effluent pipe into the basin is a 54"RCP at a flat slope of 0.5% to minimize velocities.
The outlet control pipe is a 3" pvc pipe with a small 3.5 ft weir opening to control the 2
year storm The principal spillway is an 8'x8' concrete box. The dam is approximately 15'
wide 3:1 front side slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut
around the north of the basin to handle the 100 year design storm. The basin is designed to
remove 85% TSS prior from the runoff. The downstream impacts are mitigated as a result
of the detention basin.
In the athletic field site, another detention basin is designed to attenuate the post
development peak discharge of the 2 year 24 hour storm to that of the predeveloped flow.
The estimated predevelopment peak rate of runoff is 36.6 cfs. The estimated
postdevelopment rate of runoff is 62.7 cfs. The effluent pipe into the basin is a 3" pvc
pipe to detain the first 1" of runoff and release it over a 2 to 5 day period. This basin is
designed as an extended dry detention basin to remove 50 % TSS. It has a level spreader
downstream of the outlet to remove another 35% TSS for a total of 85% TSS removal.
The outlet control pipe is a 54" RCP with a small , 10 foot wide dam, with 3:1 front side
slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut around the west of
the basin to handle the 100 year design storm A 6.5 foot weir is formed into an 8'x8' box
in order to control the 2 year storm The basin is designed such vegetation will be allowed
to grow freely and provide for additional nutrient intake. Maintenance for the facility will
include inspections of the dam and control devices. The downstream impacts are mitigated
as a result of the detention basin.
SOIL EROSION
AND
SEDIMENTATION CONTROL
PLAN
NARRATIVE
WEST JOHNSTON HIGH SCHOOL
JOHNSTON CO , NORTH CAROLINA
20013
J.S. JANOWSKI AND ASSOCIATES
105 C EAST VICTORIA COURT
GREENVILLE, NC 27858
252-756-8918
This project includes the construction of approximately 205,630 SF of new buildings for the school on a portion
of a 101 acre site. Approximatey 75.5 awes of land will be disturbed .
11. SITE DESCRIPTION
The site has slopes averaging 5-10%. Overall, elevations vary from a high point of 242 msl to a low point of less
than 176 msl. The site is currently farmed . The soil type is a silty day.
The property is bounded on the , south and east by undeveloped property, bounded on the west by Raleigh Rd
(SR 1330) and on the North by Beaver Branch.
IV. PANNED S'T'ORM WATER MANAGEMENT AND EROSION AND SEDIMENTATION CONTROL
MEASURES
TEMPORARY GRAVEL CONSTRUCTION ENTRANCE
A Temporary Gravel Construction Entrance is to be used at street connection to SR 1330
TEMPORARY SILT FENCE
Temporary Silt Fences are to be placed at d'ie toe of fill sites adjacent to the property line to Collect sediment
laden runoff. Due to the abundance of fill slopes the silt fence will provide an excellent barrier to protect off-site
facilities from sediments.
Sediment fence will be installed around all catch basins and drop inlets to prevent sediment from entering the
storm drainage system.
_ Y \ .. ci-x ..Lt,i7:lYJ
Temporary Rods Check Dam will be used in the Construction of new ditches.
STORM INLET SEDIMENT TRAP
Storm inlet sediment traps will be used at concentrated runoff points associated with drop inlets as shown on
plans.
GRASS LINED CHANNEL
Grass lined channels with temporary straw-net liners will be Constructed in roadside ditches.

At the end of time major storm drainage outfall a storm water detention basin including a sediment trap will be
installed in order to reduce the peak outflow and to trap sediment that may escape inlet control measures. A
rock dam will be placed at the inlet of the outlet pipe for time detention facilities to trap sediment:.
1. OBTAIN PLAN APPROVALS AND ALL APPLICABLE PERMITS.
2. FLAG LIMITS OF ROUGH GRADING FOR BUILDING SITE, PARKING LOTS AND ESTABLISH GRADE LIMITS AS NEEDED.
3. HOLD PRECONSTRUCTION MEETING WITH GRADING CONTRACTOR, EROSION CONROL ADMINISTRATOR, PROJECT ENGINEER AND OWNER.
4. INSTALL SEDIMENT TRAPS AND THE PERIMETER SEDIMENT FENCES AS THE FIRST CONSTRUCTION ACTIVITY.
5. INSTALL STORM DRAINAGE FOR OUTFALL, INSTALL RELATED EROSION CONTROL MEASURES AND END OF DAY MEASURES
6. PREPARE TEMPORARY CONSTRUCTION ENTRANCE, STRIP AREA OF TOP SOIL AND STOCKPILE AS NEEDED FOR FINAL LANDSCAPING.
INSTALL SEDIMENT FENCES AROUND PERIMETER OF STOCKPILE AREAS.
7. INSTALL RIP RAP OUTLET PROTECTION OUTLET.
8. BEGIN AND COMPLETE ROUGH GRADING OPERATIONS INCLUDING ENTRY ROADS.
9. INSTALL TEMPORARY SEDIMENT CONTROL MEASURES IN THE ROADSIDE DITCHES.
10. INSTALL STORM DRAINAGE FOR PARIONG AREA, AND BUILDING PERIMETER INSTALL RELATED EROSION CONTROL MEASURES AND END OF
DAY MEASURES
11. BRING BUILDING AND PARIMG AREA To WITHIN r OF FINAL SUBGRADE, TEMPORARILY SEED THESE AREAS TO PREVENT EROSION UNTIL
SUCH TIME OWNER IS READY TO PROCEED WITH FINAL CONSTRUCTION.
12. BRING LANDSCAPED AREAS TO WITHIN 6' OF FINAL GRADE, REDISTRIBUTE 6" OF TOP SOIL.
13. INSTALL TEMPORARY STAW-NET LINERS IN ROADSIDE SWALES
14. FINE GRADE, PERMANENTLY SEED AND MULCH ALL LANDSCAPED AREAS.
15. STABIIMTION SHALL OCCUR WITHIN 15 DAYS OF COMPLETION OF GRADING OPERATIONS.
16. REMOVE SEDIMENT TRAP AND INSTALL REMAINING STORM DRAINAGE, REGRADE AREA AND SEED AND MULCH.
17. ADDITIONAL EROSION AND SEDIMENTATION CONTROL MEASURES MAY BE REQUIRED BY THE STATE OR OWNER IF DEEMED
NECESSARY.
18. AFTER SITE IS STABILIZED, REMOVE ALL TEMPORARY MEASURES, FINE GRADE DISTURBED AREAS, AND INSTALL PERMANENT VEGETATION
ON THE DISTURBED AREAS.
19. MAINTAIN PERMANENT VEGETATION BY TOP DRESSING WITH 700 Las PER ACRE OF FERTILIZER EVERY 6 MONTHS UNTIL THE
COMPLETION OF THE PR03ECT.
20. REMOVE ALL TEMPORARY EROSION AND SEDIMENTATION CONTROL MEASURES UPON COMPLETION AND STABILIZATION OF PROJECT.
VI. MAINTENANCE PLAN
1. All erosion and sediment control practices will be checked for stability and operation following every
run-off producing rainfall but in no case less than once every week. Any needed repairs will be made
immediately to maintain all practices as designed.
2. Sediment will be removed from behind the silt fence when it becomes 0.5 feet deep.
3. Sediment will be removed from the sediment trap when the storage has been appro)amately 50%
filled. Gravel will be cleaned and replaced when the sediment pool no longer drains properly.
4. All seeded areas will be fertilized, re-seeded as necessary, and mulched according to specifications in
the vegetative plan to maintain a vigorous, dense vegetative cover.
Al. VICINITY PLAN
See Erosion Control Plan
VIII. VEGETATION PLAN
A. PERMANENT SEEDING AFTER APRIL 15 AND BEFORE SEPTEMBER 15
SEEDING MIXTURE
COMMON BERMUDAGRASS W (2 LB11000 SF)
SOIL AMENDMENTS
APPLY 3000 LB(ACRE GROUND AGRICULTURAL LIMESTONE AND 500 LB/ACRE
10-10.10 FERTIL)ZER.
MULCH
USE JUTE, EXCELSIOR MATTING OR OTHER EFFECTIVE CHANNEL LINING
MATERIAL TO COVER THE BOTTOM OF CHANNELS AND DITCHES. THE
LINING SHOULD EXTEND ABOVE THE HIGHEST CALCULATED DEPTH OF FLOW.
ON CHANNEL SIDE SLOPES ABOVE THIS HEIGHT, AND IN DRAINAGE NOT REQUIRING
TEMPORARY LINING, APPLY 4000 LB/ACRE GRAIN STRAW BY STAPLING NETTING OVER THE TOP.
MULCH AND ANCHORING MATERIAL MUST NOT BE ALLOWED TO BE WASH DOWN SLOPE WHERE
THEY CAN CLOG DRAINAGE DEVICES.
MAINTENANCE
A MINIMUM OF 3 WEEKS IS REQUIRED FOR ESTABLISHMENT. INSPECT AND REPAIR MULCH
FREQUENTLY. RE-FERTILIZE THE FOLLOWING APRIL WITH 50 LB/ACRE NITROGEN.
B. PERMANENT SEEDING AFTER SEPTEMBER 15 AND BEFORE APRIL 15.
SEEDING MIXTURE
TALL FESCUE 80 LB(ACRE
COMMON BERMUDA GRASS 40 LB/ACRE
KOBE LESPEDEZA 40 LB/ACRE
SEEDING DATES
FROM SEPT. 1- MARCH 1, USE UNSCARIFIED BERMUDA GRASS
SEEDING DATES
BEST
POSSIBLE
EARLY SPRING: FEB. 15 - MAR. 20 FEB. 15- APRIL 30
FALL- SEPT I - SEPT. 30 SEPT. 1- OCT. 31
SOIL AMENDMENTS
APPLY LIME AND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 5000 LB/ACRE
GROUND AGRICULTURAL UMESTONEAND.1000 LB/ACRE 10-10-10 FERTILIZER
MULCH
APPLY 4000 LB/ACRE GRAIN STRAW ON EQUIVALENT COVER OF ANOTHER SUITABLE
MULCH. ANCHOR STRAW BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY STRAIGHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELY RE-FERTILIZE IN THE SECOND YEAR
ACCORDING TO THE SOIL TEST OR TOP DRESS WITH 500 LB/ACRE 10-10-10 FERTILIZER
AND MOW AS NEEDED. WHEN SERICEA IS OMITTED FROM THE MIXTURE, RE-SEED,
FERTILIZE, AND MULCH DAMAGED AREAS IMMEDIATELY.
C. TEMPORARY SEEDING AFTER SEPTEMBER 15 AND BEFORE APRIL 15:
SEEDING MIXTURE
RYE GRAIN 120 LB/ACRE
KOBE LESPEDEZA 50LBIACRE
OMIT ANNUAL LESPEDEZA WHEN DURATION OF TEMPORARY COVER IS NOT TO EXTEND BEYOND
JUNE
SEEDING DATES
COASTAL PLAIN - DEC. 1- APRIL 15
SOIL AMENDMENTS
APPLY UMEAND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 2000 LB/ACRE
GROUND AGRICULTURAL LIMESTONEAND 750 LB/ACRE 10-10-10 FERTILIZER
MULCH
APPLY 4000 LB/ACRE GRAIN STRAW ON EQUIVALENT CO VER OF ANOTHER SUITABLE
MULCH. ANCHOR STRAW BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY SR41GHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELY RE-FERTILIZE RE-SEED, RE-FERTILIZE AND
MULCH IMMEDIATELY FOLLOWING EROSION OR OTHER DAMAGE.
D. TEMPORARY SEEDING BEFORE SEPTEMBER 15 AND AFTER APRIL 15.
SEEDING MIXTURE
GERMAN MILLET 40 LB/ACRE
SEEDING DATES
APRIL 15 -AUGUST 15
I
SOIL AMENDMENTS
APPLY LIME AND FERTILIZER ACCORDING TO SOIL TESTS OR APPLY 2000 LB/ACRE
GROUND AGRICULTURAL LIMESTONE AND 750 LB/ACRE 10-10-10 FERTILIZER
MULCH
APPLY 4000 LB/ACRE GRAIN STRAW ON EQUIVALENT COVER OF ANOTHER SUITABLE
MULCH. ANCHOR STRAW BY TACING WITH ASPHALT, NETTING, OR ROVING OR
BY CRIMPING WITH A MULCH ANCHORING TOOL A DISK WITH BLADES SET
NEARLY SRAIGHT CAN BE USED AS AN ANCHORING TOOL
MAINTENANCE
IF GROWTH IS LESS THAN FULL ADEQUATELY RE-FERTILIZE RE-SEED , RE-FERTILIZE AND
MULCH IMMEDIATELY FOLLOWING EROSION OR OTHER DAMAGE.
IX.
A. 6.02 ......................
B. 6.06 ......................
C. 6.14 ...........................
D. 6.30 ..........................
...................Land Grading
...................Temporary Gravel Construction Entrance
...................Mulching
....................Grass- lined channels
E. 6.51 .....................................................Fabric Drop Inlet Protection (Temporary)
F. 6.60 ....................................................Temporary Sediment Trap
G. 6.62 .....................................................Temporary Sediment Fence
H. 6.83 .....................................................Rock Check Dam

CULVERT CROSSING DESIGN
FOR
WEST JOHNSTON HIGH SCHOOL
MAIN ENTRY ROAD
100 YR - 24 HOUR
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
%%till
12324 :
West Johnston High School -20013-1

Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
0.95
0.3
CN=
CN=
C
187.00 acres
98 37.00 acres
73 150.00 acres
C
5000 feet
79 feet
8.4 inches
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))"2 / (P+0.8(s))
77.9
2.83
5.76 inches
Time of Concentration
channel flow (not overland)
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
27.2
R3 9 h
2 132 18
10 203 22
25 246 23
100 302 25
27.2 minutes
0.43
5.8 inches per hr
Peak Discharge Q=CIA 463.7 cfs
Time to peak
Tp= Vol/(1.37 Qp) 102.5 minutes
Based on Analysis of a 2 - 72" culverts the Headwater Elevation = 197.73
Top of the Road = 198.84 Road is designed to not overtop in the 100 year storm
Outlet Velocity = 8.8 fps Design Outlet Protection
Use Chart pg 8.06.3
for 232 cfs per barrel and 72" dia pipe use La = 30 feet
West Johnston High School -20013-2
PIPE CULVERT ANALYSIS
COMPUTATION OF CULVERT PERFORMANCE CURVE
June 5, 2000
------------------
------------------
PROGRAM INPUT DATA
DESCRIPTION VALUE
Culvert Diameter (ft) .......................................
FHWA Chart Number ...........................................
FHWA Scale Number (Type of Culvert Entrance) ................
Manning's Roughness Coefficient (n-value)..... ' ..............
Entrance Loss Coefficient of Culvert Opening ................
Culvert Length (ft) .........................................
Invert Elevation at Downstream end of Culvert (ft)..........
Invert Elevation at Upstream end of Culvert (ft)............
Culvert Slope (ft/ft) .......................................
Starting Flow Rate (cfs) ....................................
Incremental Flow Rate (cfs) .................................
Ending Flow Rate (cfs) ......................................
Starting Tailwater Depth (ft) ...............................
Incremental Tailwater Depth (ft) ............................
Ending Tailwater Depth (ft) .................................
6.0
1
1
0.012
0.1
55.0
188.0
188.51
0.0093
100.0
50.0
600.0
4-.0
1.0
14.0
----- --------------- - ------------
COMPUTATION RESULTS ---------- - ---- - - -----
Flow Tailwater Headwater (ft) Normal Critical Depth at Outlet
Rate Depth Inlet Outlet Depth Depth, Outlet Velocity
(cfs) (ft) Control Control
---
--- (ft)
--------- (ft)
---------- (ft)
---------- (fps)
---------
-----------
100.0 -----------
4.0 -----------
3.82 --
-
3.99 1.94 2.69 4.0 4.99
150.0 5.0 4.92 5.18 2.41 3.33 5.0 5.96
200.0 6.0 6.0 6.45 2.83 3.87 6.0 7.07
250.0 7.0 7.22 7.99 3.23 4.33 6.0 8.84
300.0 8.0 8.47 9.65 3.63 4.73 6.0 10.61
350.0 9.0 10.09 11.43 4.03 5.07 6.0 12.38
400.0 10.0 11.96 13.33 4.47 5.33 6.0 14.15
450.0 11.0 14.07 15.35 5.03 5.53 6.0 15.92
500.0 12.0 16.44 17.49 6.0 5.67 6.0 17.68
550.0 13.0 19.05 19.75 6.0 5.77 6.0 19.45
600.0 14.0 21.91 22.13 6.0 5.83 6.0 21.22
HYDROCALC Hydraulics for Windows, Version 1.2a Copyright (c) 1996
Dodson & Associates, Inc., 5629 FM 1960 West, Suite 314, Houston, TX 77069
Phone:[phone], Fax:[phone], Email:[e-mail]
All Rights Reserved.
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722 32'30" ?24?'" E • INTERIOR-GEOLOGICAL SURVEY, RESTON, VIRGINIA-199:
FOUR OAKS 6 M/.y
1 MILE ROAD CLASSIFICATION
000 5000 6000 7000 FEET
Medium-duty_ Light-duty
1 KILOMETRE Unimproved dirt
0 FEET O State Route
)ATUM OF 1929 i
' a
West Johnston High School
8-04-00
Calculations for level spreader
Wet De tention in the front of the Sghool
Q = 27.7 cis outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH^1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (013.OL)°0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
Detenti on Behind the Athl etic Fields
Q = 27.2 cis outflow from 2year 24 hr storm
L = 120 It length of level spreader on plans
Q = CLH"1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)"0.66
H = 0.18 It
V = Q/A A = LH = 21.82 sf
V = 1.25 fps OK less than 3 fps
k
j... _.. - SLOPE
yi?•!
' ?. .•:::
- - - - - TRANSMON TO
O'GRAOf
S AP_= .. --
ZIIS-Ilparl
---------- --- ---
OUTL-'
..... --••..
/..` .................
Design Flow
(cfs) Entrance Width Depth End Width Length
0-'C SV 0.? _T '?

?
190
LEVEL SPREADER
SCALE: NONE
jo,5 - LJ JH 5
r
Wet Detention Study front of School-2 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
2 YR - 24 HOUR
NCDENR BMP
FIRST V OF RUNOFF
20013
6-6-00
rev 9-13-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
` ,`
4 ?t
?A?' ` . ? /NEE 4 . . r ' *?? ?. ? ?•
F .?
N JANE %??•.
West Johnston High School 20013-1

Site Conditions Predevelopment
Wet Detention Study front of School-2 year 24 hour
Total watershed area
Area Impervious C=
Area grass or woods C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
Tc=(L"3/H)"0.385
128
Composite C =
37
Rainfall Intensity = 1= g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.9 X
13.9 minutes
0.3
4.1 inches per hr
23.00 acres
CN= 98 0.00 acres
CN= 73 23.00 acres
C
1220 feet
40 feet
3.7 inches
OVERLAND
2
S 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-2
28.6 cfs
Y 1
Storage Required
Wet Detention Study front of School-2 year 24 hour
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface diff.
Elevation am sky
198.00 37924
2.00
200.00 43925
2.00
202.00 51021
28.6 cis
81.9 cfs
94,699 cf
accum.
stomp StOEM Elevation egg
0 198 0 198.00 =water surface
81849
81849 200.00 2
94946
176795 202.00 4
Z
Stodge LN(stamv) LNStM)
0 0 ERR ERR 0.00
81,849 2 11.31 0.69 2.00
176,795 4 12.08 1.39 4.00
b= 1.1110408
Ks= 37892.807
i/b
Z= (g/Ks)A
Predicted Water Surface Elevation for 2 year 24 hour storm= 200.28 feet msi
Predicted Surface Area= elev = 198.00 37924 sf
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00%
West Johnston High School -20013.4
Wet Detention Study front of School-2 year 24 hour
Average pool depth = 3 ft
SAIDA-- 2.30% Required Surface Area=
Surface Area Provide=
Volume to be controlled by 1" storm = 1"(Rv=0.05 + 0.009(I))(DA) _
Temporary Water Quality Pool Elevation =
Discharge of volume in 48 hours =
Size Outlet Device for Control Structure
invert elevation -
estimated orifice center elev.
proposed water surface elev.
available head (h) _
discharge (d) _
coefficient of discharge =
0.3 -
0.0
23023 sf
37924.0 sf
47005 of
199.12
0.3 cfs
198.00 feet msl
198.10 feet ms]
200.28 feet msl
2.18 feet
0.3 cfs
0.6
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)^1/2
0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 28.6 cfs L = 8 ft
Q=CwLH^312 H = 1.12 ft
Top of Emergency Spiilvir 1.12 msi
5
West Johnston High School -20013-5

Inflow Hydroyrob
Peak Inflow =
Time to Peak =
Wet Detention Study front of School-2 year 24 hour
Additlwial Flow
81.9
29.6
37.0368384
I [ymm min)
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
0 C(s)
0
2.1
8.0
17.2
28.9
41.7
54.5
65.8
74.7
80.3
81.8
79.3
72.9
64.2
56.3
49.3
43.2
37.9
33.2
29.1
25.5
22.4
19.6
17.2
15.1
13.2
11.6
10.2
8.9
7.8
6.8
6.0
5.3
4.6
4.0
3.5
3.1
2.7
2.4
0.0
West Johnston High School -20013-6
Wet Detention Study front of School-2 year 24 hour
L= 3.5
Stormwater routing
3 Spillway
inch 199.12
T (time min) o r Ohl Stone S O utflow Elevation orifice tic
0 0 0 0.00 0.0 198.00
3 2.1 0 0.00 0.0 198.00 0.0 0.0
6 8.0 369 0.02 0.0 198.02 0.0 0.0
9 17.2 1809 0.06 0.0 198.06 0.0 0.0
12 28.9 4913 0.16 0.0 198.16 0.0 0.0
15 41.7 10110 0.30 0.0 198.30 0.0 0.0
18 54.5 17616 0.50 0.0 198.50 0.0 0.0
21 65.8 27417 0.75 0.2 198.75 0.2 0.0
24 74.7 39236 1.03 0.2 199.03 0.2 0.0
27 80.3 52650 1.34 1.3 199.34 0.3 1.1
30 81.8 66855 1.67 4.6 199.67 0.3 4.3
33 79.3 80760 1.98 8.7 199.98 0.3 8.4
36 72.9 93468 2.25 13.0 200.25 0.3 12.6
39 64.2 104261 2.49 17.2 200.49 0.4 16.8
42 56.3 112717 2.67 20.6 200.67 0.4 20.3
45 49.3 119130 2.80 23.3 200.80 0.4 22.9
48 43.2 123823 2.90 25.3 200.90 0.4 24.9
51 37.9 127048 2.97 26.8 200.97 0.4 26.4
54 33.2 129044 3.01 27.7 201.01 0.4 27.3
57 29.1 130043 3.03 28.1 201.03 0.4 27.7
60 25.5 130226 3.04 28.3 201.04 0.4 27.9
63 22.4 129722 3.03 28.1 201.03 0.4 27.7
66 19.6 128691 3.01 27.7 201.01 0.4 27.3
69 17.2 127242 2.98 27.0 200.98 0.4 26.6
72 15.1 125473 2.94 26.2 200.94 0.4 25.8
75 13.2 123477 2.90 25.3 200.90 0.4 24.9
78 11.6 121298 2.85 24.3 200.85 0.4 23.9
81 10.2 119014 2.80 23.3 200.80 0.4 22.9
84 8.9 116659 2.75 22.2 200.75 0.4 21.9
87 7.8 114261 2.70 21.2 200.70 0.4 20.9
90 6.8 111845 2.65 20.2 200.65 0.4 19.9
93 6.0 109433 2.60 19.3 200.60 0.4 18.9
96 5.3 107044 2.55 18.3 200.55 0.4 18.0
99 4.6 104693 2.50 17.4 200.50 0.4 17.0
102 4.0 102394 2.45 16.5 200.45 0.4 16.1
105 3.5 100159 2.40 15.6 200.40 0.4 15.2
108 3.1 97996 2.35 14.7 200.35 0.4 14.3
111 2.7 95914 2.31 14.0 200.31 0.3 13.6
114 2.4 93888 2.26 13.1 200.26 0.3 12.8
117 2.1 91955 2.22 12.5 200.22 0.3 12.1
120 1.8 90090 2.18 11.8 200.18 0:3 11.5
123 1.6 88297 2.14 11.2 200.14 0.3 10.8
126 1.4 86580 2.10 10.5 200.10 0.3 10.2
129 1.2 84940 2.07 10.1 200.07 0.3 9.7
132 1.1 83353 2.03 9.4 200.03 0.3 9.1
West Johnston High School -20013-7
Wet Detention Study front of School-2 year 24 hour
135 1.0 81849 2.00 9.0 200.00 0.3 8.7
138 0.8 80402 1.97 8.5 199.97 0.3 8.2
141 0.7 79013 1.94 8.1 199.94 0.3 7.8
144 0.6 77684 1.91 7.7 199.91 0.3 7.4
147 0.6 76415 1.88 7.3 199.88 0.3 7.0
150 0.5 75208 1.85 6.9 199.85 0.3 6.5
153 0.4 74061 1.83 6.6 199.83 0.3 6.3
156 0.4 72953 1.80 6.2 199.80 0.3 5.9
159 0.3 71906 1.78 5.9 199.78 0.3 5.6
162 0.3 70898 1.76 5.7 199.76 0.3 5.4
165 0.3 69928 1.74 5.4 199.74 0.3 5.1
168 0.2 68997 1.71 5.1 199.71 0.3 4.8
171 0.2 68127 1.70 4.9 199.70 0.3 4.6
174 0.2 67274 1.68 4.7 199.68 0.3 4.4
177 0.2 66460 1.66 4.5 199.66 0.3 4.2
180 0.1 65684 1.64 4.2 199.64 0.3 3.9
183 0.1 64947 1.62 4.0 199.62 0.3 3.7
186 0.1 64247 1.61 3.9 199.61 0.3 3.6
189 0.1 63565 1.59 3.7 199.59 0.3 3.4
192 0.1 62921 1.58 3.6 199.58 0.3 3.3
195 0.1 62294 1.56 3.3 199.56 0.3 3.1
198 0.1 61704 1.55 3.2 199.55 0.3 3.0
201 0.1 61131 1.54 3.1 199.54 0.3 2.9
204 0.0 60575 1.53 3.0 199.53 0.3 2.8
360 0.0 32579 0.87 0.2 198.87 0.2 0.0
720 0.0 28161 0.77 0.2 198.77 0.2 0.0
1080 0.0 24047 0.66 0.2 198.66 0.2 0.0
1440 0.0 20298 0.57 0.2 198.57 0.2 0.0
1800 0.0 16875 0.48 0.1 198.48 0.1 0.0
2160 0.0 13813 0.40 0.1 198.40 0.1 0.0
2520 0.0 11113 0.33 0.1 198.33 0.1 0.0
2880 0.0 8775 0.27 0.1 198.27 0.1 0.0
3240 0.0 6798 0.21 0.1 198.21 0.1 0.0
3600 0.0 5268 0.17 0.1 198.17 0.1 0.0
3960 0.0 4127 0.14 0.0 198.14 0.0 0.0
4320 0.0 3405 0.11 ERR 198.11 ERR 0.0
4680 0.0 ERR ERR ERR ERR ERR 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 28.3 cfs
Peak Stage= 3.04 ft
Water Elevation= 201.04 msl
Peak Storage = 130226 cf
Design Spillway 199.12 msl
length of weir 30 ft
West Johnston High School -20013-8

Inflow outflow hydrograph
......:.................._
90 ........................................... ....:......................................... ......._ .......................:..........................................
80 ..................................................................................................................................... ................... .................
70 ...................................................................................................................
60 .... ............ v.......................................................---.................................................---..........................
50 ............................................-----...------..................------...............---......---......----.............--- - .................
U
12
v
O
LL
40 ............................................................................................€.................................................................... _ .................
30 ........... € ....................... ............................................. .................
20
10
0
0 15 30 45 60 75 90 105
Time (minutes)
-+- Inflow Hydrograph -- Outflow Hydrograph
A
Wet Detention Study front of School-100 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
100 YR - 24 HOUR
NCDENR BMP
FIRST V OF RUNOFF
20013
5-25-00
rev 9-13-00
Prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
...trot
"'rN J
?brUtt?
West Johnston High School -20013-1
i e
Site Conditions Predevelopment
Total watershed area
Area Impervious
Area grass or woods
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intensity = 1= g/(h+T)
Peak Discharge Q=CIA
Wet Detention Study front of School-100 year 24 hour
C= 0.95
C= 0.3
6.9 X
23.00 acres
CN= 98 0.00 acres
CN= 73 23.00 acres
C
1220 feet
40 feet
8.4 inches
OVERLAND
2
8 a h
2 132 18
10 203 22
25 246 23
100 302 25
13.9 minutes
0.3
7.8 inches per hr
53.6 cfs
West Johnston High School -20013-2

Wet Detention Study front of School-100 year 24 hour
Storage Required
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface diff.
Elevat*o n am a" stoma
198.00 37924
2.00 81849
200.00 43925
2.00 94946
202.00 51021
accum.
storm
0
81849
176795
Z
Storage Uap LN oma) LN(St_t__ angel
0 0 ERR ERR 0.00
81,849 2 11.31 0.69 2.00
176,795 4 12.08 1.39 4.00
b= 1.1110408
Ks= 37892.807
1/b
Z= (S/Ks) A
Predicted Water Surface Elevation for 100 year 24 hour storm=
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00%
53.6 cfs
120.2 cfs
231,990 cf
Elevation Ran
198 0 198.00 =water surface
200.00 2
202.00 4
203.11 feet ms]
West Johnston High School -20013-4
1 1
Wet Detention Study front of School-100 year 24 hour
Average pool depth = 3 ft
SA/DA= 2.30% Required Surface Area=
Surface Area Provide=
Volume to be controlled by 1" storm =1"(Rv=0.05 + 0.009(I))(DA) _
Temporary Water Quality Pool Elevation =
Discharge of volume in 48 hours =
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) _
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)^1/2
0.3 -
0.0
23023 sf
37924.0 sf
47005 cf
199.12
0.3 cfs
198.00 feet msl
198.10 feet msl
203.11 feet msl
5.01 feet
0.3 cfs
0.6
0.18 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 53.6 cfs L = 8 ft
Q=CwLH^3/2 H = 1.71 ft
Top of Emergency Spillwc, 1.71 msl
West Johnston High School -20013-5
Wet Detention Study front of School-100 year 24 hour
135 25.4 131061 3.06 30.7 201.06 0.4 28,4
138 23.8 130104 3.04 29.3 201.04 0.4 27.9
141 22.2 129118 3.01 27.7 201.01 0.4 27.3
144 20.8 128136 2.99 27.3 200.99 0.4 26.9
147 19.4 126972 2.97 26.8 200.97 0.4 26.4
150 18.2 125642 2.94 26.2 200.94 0.4 25.8
153 17.0 124201 2.91 25.5 200.91 0.4 25.1
156 15.9 122662 2.88 24.9 200.88 0.4 24.5
159 14.9 121039 2.84 24.1 200.84 0.4 23.7
162 13.9 119379 2.81 23.5 200.81 0.4 23.1
165 13.0 117658 2.77 22.6 200.77 0.4 22.3
168 12.1 115921 2.74 22.0 200.74 0.4 21.7
171 11.4 114141 2.70 21.2 200.70 0.4 20.9
174 10.6 112364 2.66 20.4 200.66 0.4 20.1
177 9.9 110596 2.62 19.7 200.62 0.4 19.3
180 9,3 108844 2.58 18.9 200.58 0.4 18.5
183 8.7 107114 2.55 18.3 200.55 0.4 18.0
186 8.1 105378 2.51 17.6 200.51 0.4 17.2
189 7.6 103677 2.47 16.8 200.47 0.4 16.5
192 7.1 102013 2.44 16.3 200.44 0.4 15.9
195 6.6 100360 2.40 15.6 200.40 0.4 15.2
198 6.2 98753 2.37 15.0 200.37 0.4 14.7
201 5.8 97165 2.33 14.3 200.33 0.4 14.0
204 5.4 95631 2.30 13.8 200.30 0.4 13.5
360 0.2 17175 0.49 0.1 198.49 0.1 0.0
720 0.0 17560 0.50 0.1 198.50 0.1 0.0
1080 0.0 14334 0.42 0.1 198.42 0.1 0.0
1440 0.0 11447 0.34 0.1 198.34 0.1 0.0
1800 0.0 8947 0.27 0.1 198.27 0.1 0.0
2160 0.0 6843 0.21 0.1 198.21 0.1 0.0
2520 0.0 5151 0.17 0.1 198.17 0.1 0.0
2880 0.0 3801 0.13 0.0 198.13 0.0 0.0
3240 0.0 2917 0.10 0.0 198.10 0.0 0.0
Results of routing the 100 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 118.7 cfs
Peak Stage= 3.59 ft
Water Elevation= 201.59 msl
Peak Storage = 156828 cf
Design Spillway 199.12 msl
Length of weir 3.5 ft
Emergency Spillway 201.01 msl
Length of Weir 58.5 ft
30 foot emergency spillway plus 32'-3.5' of design
spillway = 30'+28.5'= 58.5'
West Johnston High School -20013-8
2.0
0.9
0.0
0.0
Wet Detention Study front of School-100 year 24 hour
Size Outlet Pipe for Spillway
100 yr. flow for prindpal spillway = 40.8 cfs
Effective Length of Emergency spillway for outlet pipe = 28.5 ft
Water Surface Elevation for 100 year Storm = 201.59 msl
Top of Emergency Spillway at box = 201.01 msl
Q=CLH^1.5 = 37.8 cfs
Design flow for 100 year storm for outlet pipe = 78.5 cfs
Slope of outlet pipe = 0.005 ft/ft
Material of outlet pipe = concrete
n = 0.012
d = 16 (Qn/S^0.5)"0.375 42.26 inches
Use = 48 inch
West Johnston High School -20013-9
A
Inflow outflow hydrograph
140 ............................................................................................................................................................................................
120 .................................................................................... ...................... ....................... ............................................
100
80 .
v
0
LL
60
40 --------------------- ............ .......... ...................... .......... ....... :.................-----.'s...............................................i...........-.
20
0 4 4
r 'r 'r T 'r
0 15 30 45 60 75 90 105
Time (minutes)
-+- Inflow Hydrograph --*- Outflow Hydrograph
0
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
2YR-24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
5-25-00
rev 9-13-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
;it?.tdctsj>;;

West Johnston High School -20013-1
I .
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions Predevelopment
Total watershed area
Area Impervious C=
Area grass or wooded C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L^3/H)`0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.7 X
CN= 98
CN= 73
OVERLAND
2
R 9 h
2 132 18
10 203 22
25 246 23
100 302 25
29.00 acres
0.00 acres
29.00 acres
C
1280 feet
51 feet
3.7 inches
13.3 minutes
0.3
4.2 inches per hr
36.6 cfs
West Johnston High School -20013-2
4 i
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L"3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= Vol/(1.37 Qp)
0.95
0.3
6.7
CN= 98
CN= 73
C.
R 9 h
2 132 18
10 203 22
25 246 23
100 302 25
29.00 acres
9.56 acres
19.44 acres
C
1280 feet
51 feet
3.7 inches
81.2
2.31
1.89 inches
13.4 minutes
0.51
4.2 inches per hr
62.7 cfs
38.6 minutes
West Johnston High School 20013-3
r i
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Storage Required
Allowable release at impoundment = 36.6 cfs
Peak rate of inflow at impoundment = 62.7 cis
Sr = (Qi - Qo)Tp 60,364 cf
STAGE STORAGE DATA
surface diff. accum.
Elevation area glgY storage Storm Elevation stm
179.00 5673 0 179 0
1.00 6400
180.00 7127 6400 180.00 1
2.00 18160
182.00 11033 24560 182.00 3
2.00 26047
184.00 15014 50607 184.00 5
2.00 33772
186.00 18758 84379 186.00 7
2.00 42466
188.00 23708 126845 188.00 9
1.50 38900.25
189.50 28159 165745.25 189.50 10.5
Z
C
d
Storage Rao LN(st_ orage) LNMM) ompute
UM
0 0 ERR ERR 0.00
6,400 1 8.76 0.00 1.24
24,560 3 10.11 1.10 3.00
126,845 9 11.75 2.20 8.81
165,745 10.5 12.02 2.35 10.50
b= 1.5240975
Ks= 4603.0858
1/b
Z= (S/Ks)^
Predicted Water Surface Elevation= 184.41 feet ms]
To capture the first 1" of runoff
volume= DA x 43560 x V 112 105270 of 186.80 feet msl
set spillway elevation at this elevation
West Johnston High School -20013-4
r ,
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) = 0.5 -
coefficient of discharge =
Determine the orifice diameter
orifice equation
0.61 cfs
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
179.00 feet msl
179.30 feet msl
186.80 feet msl
7.50 feet
0.0 0.5 cfs
0.6
Q = Cd(A)(2gh)^1/2 0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 36.6 cfs Omate L = 8 ft
Q=CwLH"3/2 H = 1.33 ft
Top of Emergency Spillwc- 188.12 msl
5
West Johnston High School -20013-5

Peak Ldtow
Time W Peak =
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
AddMortal Flow
62.7
38.6
48.26564414
T jdme mini
0
3
6
9
12
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
0
0.9
3.7
8.0
13.8
20.6
28.0
35.6
43.0
49.7
55.3
59.5
62.0
62.7
61.5
58.6
54.0
48.9
44.2
39.9
36.1
32.6
29.5
26.7
24.1
21.8
19.7
17.8
16.1
14.5
13.1
11.9
10.7
9.7
8.8
7.9
7.2
6.5
5.9
0.0
West Johnston High School -20013-6
. 1 i i
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR SMP
L= 6.5
Stormwater routing
3 Spillway
inch 186.80
T (time min) Qf cW Storage W O utflow F evation orifice W&
0 0 0 0.00 0.0 179.00
3 0.9 0 0.00 0.0 179.00 0.0 0.0
6 3.7 167 0.11 0.0 179.11 0.0 0.0
9 8.0 826 0.32 0.0 179.32 0.0 0.0
12 13.8 2271 0.63 0.0 179.63 0.0 0.0
15 20.6 4751 1.02 0.2 180.02 0.2 0.0
18 28.0 8423 1.49 0.2 180.49 0.2 0.0
21 35.6 13420 2.02 0.3 181.02 0.3 0.0
24 43.0 19781 2.60 0.3 181.60 0.3 0.0
27 49.7 27459 3.23 0.4 182.23 0.4 0.0
30 55.3 36333 3.88 0.4 182.88 0.4 0.0
33 59.5 46206 4.54 0.5 183.54 0.5 0.0
36 62.0 56824 5.20 0.5 184.20 0.5 0.0
39 62.7 67888 5.85 0.5 184.85 0.5 0.0
42 61.5 79072 6.46 0.6 185.46 0.6 0.0
45 58.6 90044 7.04 0.6 186.04 0.6 0.0
48 54.1 100480 7.56 0.6 186.56 0.6 0.0
51 48.1 110098 8.03 2.9 187.03 0.6 2.2
54 44.2 118247 8.41 10.1 187.41 0.7 9.4
57 39.9 124387 8.70 17.5 187.70 0.7 16.8
60 36.1 128433 8.88 22.7 187.88 0.7 22.0
63 32.6 130843 8.99 26.1 187.99 0.7 25.5
66 29.5 132009 9.04 27.8 188.04 0.7 27.1
69 26.7 132320 9.06 28.4 188.06 0.7 27.7
72 24.1 132003 9.04 27.8 188.04 0.7 27.1
75 21.8 131343 9.01 26.8 188.01 0.7 26.1
78 19.7 130442 8.97 25.5 187.97 0.7 24.8
81 17.8 129394 8.93 24.3 187.93 0.7 23.6
84 16.1 128233 8.87 22.4 187.87 0.7 21.7
87 14.5 127096 8.82 20.9 187.82 0.7 20.2
90 13.1 125951 8.77 19.4 187.77 0.7 18.8
93 11.9 124818 8.72 18.0 187.72 0.7 17.3
96 10.7 123715 8.67 16.6 187.67 0.7 15.9
99 9.7 122656 8.62 15.3 187.62 0.7 14.6
102 8.8 121655 8.57 14.0 187.57 0.7 13.3
105 7.9 120721 8.53 12.9 187.53 0.7 12.3
108 7.2 119819 8.49 12.0 187.49 0.7 11.3
111 6.5 118958 8.45 11.0 187.45 0.7 10.3
114 5.9 118146 8.41 10.1 187.41 0.7 9.4
117 5.3 117391 8.37 9.2 187.37 0.7 8.5
120 4.8 116696 8.34 8.5 187.34 0.7 7.8
123 4.3 116029 8.31 7.9 187.31 0.7 7.2
126 3.9 115393 8.28 7.2 187.28 0.7 6.6
129 3.5 114795 8.25 6.6 187.25 0.7 6.0
132 3.2 114238 8.23 6.2 187.23 0.7 5.6
West Johnston High School -20013-7

Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP _ _
135 2.9 113689 8.20 5.7 187.20 0.7 5.0
138 2.6 113188 8.18 5.3 187.18 0.7 4.6
141 2.4 112704 8.15 4.8 187.15 0.7 4.1
144 2.1 112270 8.13 4.4 187.13 0.7 3.8
147 1.9 111858 8.11 4.1 187.11 0.7 3.4
150 1.7 111469 8.09 3.8 187.09 0.7 3.1
153 1.6 111104 8.08 3.6 187.08 0.7 3.0
156 1.4 110738 8.06 3.3 187.06 0.6 2.7
159 1.3 110400 8.04 3.0 187.04 0.6 2.4
162 1.2 110091 8.03 2.9 187.03 0.6 2.2
165 1.1 109785 8.01 2.6 187.01 0.6 1.9
168 1.0 109509 8.00 2.5 187.00 0.6 1.8
171 0.9 109239 7.99 2.3 186.99 0.6 1.7
174 0.8 108977 7.97 2.1 186.97 0.6 1.4
177 0.7 108744 7.96 1.9 186.96 0.6 1.3
180 0.6 108520 7.95 1.8 186.95 0.6 1.2
183 0.6 108305 7.94 1.7 186.94 0.6 1.1
186 0.5 108100 7.93 1.6 186.93 0.6 1.0
189 0.5 107904 7.92 1.5 186.92 0.6 0.9
192 0.4 107719 7.91 1.4 186.91 0.6 0.8
195 0.4 107543 7.91 1.4 186.91 0.6 0.8
198 0.3 107360 7.90 1.3 186.90 0.6 0.7
201 0.3 107189 7.89 1.2 186.89 0.6 0.6
204 0.3 107027 7.88 1.1 186.88 0.6 0.5
360 0.0 99185 7.50 0.6 186.50 0.6 0.0
720 0.0 85717 6.81 0.6 185.81 0.6 0.0
1080 0.0 72899 6.13 0.6 185.13 0.6 0.0
1440 0.0 60792 5.44 0.5 184.44 0.5 0.0
1800 0.0 49450 4.75 0.5 183.75 0.5 0.0
2160 0.0 38931 4.06 0.4 183.06 0.4 0.0
2520 0.0 29303 3.37 0.4 182.37 0.4 0.0
2880 0.0 20659 2.68 0.3 181.68 0.3 0.0
3240 0.0 13125 1.99 0.3 180.99 0.3 0.0
3600 0.0 6896 1.30 0.2 180.30 0.2 0.0
3960 0.0 2332 0.64 0.1 179.64 0.1 0.0
4320 0.0 423 0.21 0.0 179.21 0.0 0.0
4680 0.0 423 0.21 OA 179.21 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 28.4 cfs
Peak Stage= 9.06 ft
Water Elevation= 188.06 msl
Peak Storage = 132320 cf
Design Spillway 186.80 msl
Length of weir 6.5 ft
West Johnston Nigh School -20013-8
1 1 1 y
Inflow outflow hydrograph
70 ........................................... .. ..................
60 ............................................ ......................................................................................................................................
50 .................. .. .......... ..................
40
w
LL
30
20 ................................................... --------- ...................... f.--........................................s...........................................
10
0
0 15 30 45 60 75 90 105
Time (minutes)
+- Inflow Hydrograph -- Outflow Hydrograph
1
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
100 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
, 1
ryt H C,a c
Z AZ J0
West Johnston High School -20013-1
1
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions Pnedevelopment
Total watershed area
Area Impervious
Area grass or wooded
SCS Sal Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
Tc=(L"3/H)`0.385
128
Composite C =
Rainfall Intensity
Peak Discharge
C= 0.95
C= 0.3
6.7 X
CN= 98
CN= 73
OVERLAND
2
B 9 h
1 = g/(h+T) 2 132 18
10 203 22
25 246 23
100 302 25
Q=CIA
29.00 acres
0.00 acres
29.00 acres
C
1280 feet
51 feet
8.4 inches
13.3 minutes
0.3
7.9 inches per hr
68.5 cfs
West Johnston High School -20013-2

Stone Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area 29.00 acres
Area Impervious C= 0.95 CN= 98 9.56 acres
Area grass C= 0.3 CN= 73 19.44 acres
SCS Soil Group (Craven) C. C
Hydraulic Length 1280 feet
Vertical Relief 51 feet
24-hr, 2 yr rainfall 8.4 inches
Design Hydrograph Formulation
Composite CN 81.2
S=1000/CN -10 2.31
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L"3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= Vol/(1.37 Qp)
6.7
E S h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-3
6.15 inches
13.4 minutes
0.51
7.9 inches per hr
117.3 cfs
67.1 minutes
l P ,
Storage Required
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface dill. accum.
Elevation Wea 21" stoma stoma
179.00 5673 0
1.00 6400
180.00 7127 6400
2.00 18160
182.00 11033 24560
2.00 26047
184.00 15014 50607
2.00 33772
186.00 18758 84379
2.00 42466
188.00 23708 126845
1.50 38900.25
189.50 28159 165745.25
Z
d
Storage Ltgp L N(gorM) S(NUM) Compute
0 0 ERR ERR 0.00
6,400 1 8.76 0.00 1.24
24,560 3 10.11 1.10 3.00
126,845 9 11.75 2.20 8.81
165,745 10.5 12.02 2.35 10.50
b= 1.5240975
Ks= 4603.0858
1/b
Z= (S/Ks)^
68.5 cfs
117.3 cfs
196,465 cf
Elevation
179 0
180.00 1
182.00 3
184.00 5
186.00 7
188.00 9
189.50 10.5
Predicted Water Surface Elevation= 190.74 feet msl
To capture the first 1" of runoff
volume= DA x 43660 x 1" 112 105270 cf 186.80 feet msl
set spillway elevation at this elevation
West Johnston High School -20013-4
( 0 ),
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev. _
proposed water surface elev. _
available head (h) _
discharge (d) = 0.5 -
coefficient of discharge =
Determine the orifice diameter
Orifice equation
0.61 de
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
179.00 feet msl
179.30 feet msl
186.80 feet msl
7.50 feet
0.0 0.5 cfs
0.6
Q = Cd(A)(2gh)"1/2 0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 68.5 cfs stimate L = 8 ft
Q=CwLH"3/2 H = 2.01 ft
Top of Emergency Spillwe 188.81 ms!
5
West Johnston High School 20013-5

Peak Inflow =
Time W Peak =
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP _
AdMonal Flow '
1173
67.1
83.92897444
T (Nmm min)
0
3
6
9
12
Y5
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
0 (cfsl
0
0.6
2.3
5.1
9.0
13.8
19.6
26.1
33.2
40.9
48.9
57.0
65.2
73.3
81.1
88.5
95.2
101.3
106.5
110.8
114.0
116.2
117.2
117.1
115.8
113.4
109.9
105.5
100.1
94.5
89.1
84.1
79.3
74.9
70.6
66.7
62.9
59.3
56.0
0.0
West Johnston High School -20013-6
M J ? f
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
L= 6.5 55.5
Stormwater routing Emergency
3 Spillway Spillway
inch 186.80 187.78
T (time min) Q-(sh) Storms g Outfl ?C Elevation orifice w1k We![
0 0 0 0.00 0.0 179.00
2 0.3 0 0.00 0.0 179.00 0.0 0.0
4 1.0 31 0.04 0.0 179.04 0.0 0.0
6 2.3 154 0.11 0.0 179.11 0.0 0.0
8 4.1 429 0.21 0.0 179.21 0.0 0.0
10 6.3 916 0.35 0.0 179.35 0.0 0.0
12 9.0 1671 0.51 0.0 179.51 0.0 0.0
14 12.1 2751 0.71 0.1 179.71 0.1 0.0
16 15.7 4193 .0.94 0.2 179.94 0.2 0.0
18 19.6 6054 1.20 0.2 180.20 0.2 0.0
20 23.8 8380 1.48 0.2 180.48 0.2 0.0
22 28.4 11212 1.79 0.3 180.79 0.3 0.0
24 33.2 14587 2.13 0.3 181.13 0.3 0.0 0.0
26 38.3 18538 2.49 0.3 181.49 0.3 0.0 0.0
28 43.5 23090 2.88 0.4 181.88: 0.4 0.0 0.0
30 48.9 28265 3.29 0.4 182.29 0.4 0.0 0.0
32 54.3 34080 3.72 0.4 182.72 0.4 0.0 0.0
34 59.8 40544 4.17 0.5 183.17 0.5 0.0 0.0
36 65.2 47663 4.64 0.5 183.64 0.5 0.0 0.0
38 70.7 55435 5.12 0.5 184.12 0.5 0.0 0.0
40 76.0 63853 5.62 0.5 184.62 0.5 0.0 0.0
42 81.1 72905 6.13 0.6 185.13 0.6 0.0 0.0
44 86.1 82573 6.65 0.6 185.65 0.6 0.0 0.0
46 90.8 92833 7.18 0.6 186.18 0.6 0.0 0.0
48 95.2 103656 7.72 0.6 186.72 0.6 0.0 0.0
50 99.4 115009 8.26 6.8 187.26 0.7 6.2 0.0
52 103.1 126114 8.78 19.7 187.78 0.7 19.0 0.0
54 106.5 136122 9.23 84.5 188.23 0.7 33.5 50.3
56 109.5 138767 9.34 107.9 188.34 0.7 37.4 69.8
58 112.0 138953 9.35 110.1 188.35 0.7 37.8 71.7
60 114.0 139172 9.36 112.4 188.36 0.7 38.2 73.5
62 115.6 139366 9.37 114.7 188.37 0.7 38.5 75.5
64 116.6 139473 9.38 117.0 188.38 0.7 38.9 77.4
66 117.2 139433 9.37 114.7 188.37 0.7 38.5 75.5
68 117:2 139735 9.39 119.3 188.39 0.7 39.3 79.3
70 116.8 139490 9.38 117.0 188.38 0.7 38.9 77.4
72 115.8 139466 9.38 117.0 188.38 0.7 38.9 77.4
74 114.3 139326 9.37 114.7 188.37 0.7 38.5 75.5
76 112.4 139283 9.37 114.7 188.37 0.7 38.5 75.5
78 109.9 139005 9.36 112.4 188.36 0.7 38.2 73.5
80 107.1 138709 9.34 107.9 188.34 0.7 37.4 69.8
82 103.8 138607 9.34 107.9 188.34 0.7 37.4 69.8
84 100.1 138110 9.32 103.5 188.32 0.7 36.7 66.1
86 96.3 137704 9.30 99.1 188.30 0.7 36.0 62.4
88 92.6 137366 9.28 94.8 188.28 0.7 35.3 58.9
West Johnston High School -20013-7
? JS A •
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
90 89.1 137102 9.27 92.7 188.27 0.7 34.9 57.1
92 85.7 136670 9.25 88.6 188.25 0.7 34.2 53.6
94 82.5 136331 9.24 86.5 188.24 0.7 33.9 51.9
96 79.3 135849 9.22 82.4 188.22 0.7 33.2 48.6
98 76.3 135477 9.20 78.5 188.20 0.7 32.5 45.3
100 73.4 135220 9.19 76.5 188.19 0.7 32.1 43.7
102 70.6 134850 9.17 72.7 188.17 0.7 31.4 40.6
104 68.0 134607 9.16 70.8 188.16 0.7 31.1 39.0
106 65.4 134268 9.14 31.1 188.14 0.7 30.4 0.0
108 62.9 138383 9.33 37.8 188.33 0.7 37.1
110 60.5 141398 9.46 42.6 188.46 0.7 41.9
112 58.2 143549 9.55 46.0 188.55 0.7 45.3
114 56.0 145010 9.62 48.8 188.62 0.7 48.1
116 53.9 145878 .9.66 50.4 188.66 0.7 49.6
118 51.8 146299 9.67 50.8 188.67 0.7 50.0
120 49.9 146427 9.68 51.2 188.68 0.7 50.4
122 48.0 146270 9.67 50.8 188.67 0.7 50.0
124 46.1 145934 9.66 50.4 188.66 0.7 49.6
126 44.4 145428 9.64 49.6 188.64 0.7 48.8
128 42.7 144807 9.61 48.4 188.61 0.7 47.7
130 41.1 144126 9.58 47.2 188.58 0.7 46.5
132 39.5 143392 9.55 46.0 188.55 0.7 45.3
134 38.0 142611 9.51 44.5 188.51 0.7 43.8
136 36.6 141835 9.48 43.3 188.48 0.7 42.6
138 35.2 141023 9.44 0.7 188.44 0.7 0.0
140 33.8 145160 9.63 0.7 188.63 0.7 0.0
142 32.6 149137 9.80 0.7 188.80 0.7 0.0
144 31.3 152958 9.96 0.7 188.96 0.7 0.0
146 30.1 156630 10.12 0.7 189.12 0.7 0.0
148 29.0 160158 10.27 0.7 189.27 0.7 0.0
150 27.9 163549 10.41 0.7 189.41 0.7 0.0
152 26.8 166806 10.54 0.7 189.54 0.7 0.0
154 25.8 169936 10.67 0.8 189.67 0.8 0.0
156 24.8 172943 10.80 0.8 189.80 0.8 0.0
158 23.9 175832 10.92 0.8 189.92 0.8 0.0
Results of routing the 100 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 117.0 cfs
Peak Stage= 9.38 ft
Water Elevation= 188.38 msl
Peak Storage = 139490 d
Design Spillway 186.80 msl
Length of weir 6.5 ft
Emergency Spillway 187.78 msl
Length of Weir 55.5 It
West Johnston High School -20013-8

Inflow outflow hydrograph
..:.......................:...................
120 ............................................. .; ...............................................; .......................:.....................
100 ................................................................................................................ .... ...... ..............
80 ........................................................................................... ...................... ........ .............. ..........................................
w
....................... .........
60 ..............................................................................._......... .......
0
LL
40 ............ ............. =............... ...... ........................ ............................. ............... .................. ................
20
0
0 10 20 30 40 50 60 70
Time (minutes)
-?- Inflow Hydrograph -*- Outflow Hydrograph
hereby acknowtedgg that I am the financially responsible party for
maintenance and inspection of this detention pond. I will perform the maintenance as outlined above, to comply with the
Johnston County Stormwater Management Ordinance and the Stormwater Management permit received for this project
Furthermore, I attest that this inspection and Maintenance Agreement is on file with the Register of Deeds.
'? Signature

A4 AA I "f Y/ . J I,
IUYA" he __, a Notary Pubfic for state of
Co of do reby certify that
personally Weared before me th is day of 19,A0 and acl n a the due execution of the foregoing
instrument Witness my hand and official seat,
,. •..........

My commission
,O,OTA1,j a
ems, CA
°° ?CN COU

Hite associates
ARCHITECTURE / BrGNEEW6 / PLANNN6
LETTER of TRANSMITTAL

TO: NCDENR - Division of Water Quality
4401 Reedy Creek Road
Raleigh, NC 27607
DATE: October 5, 2000, tf r
q
9 2000
ATTN: Mr. Todd St. John, PE RE: West Johnston. High 80=1
We are sending via UPS the following plans:
r,nPiFS mr. DATF DESCRIPTION
NOTES:
2sets Site Plans/Grading and Erosion Control/Details
2 Extended D Detention Basin work sheet
2 Operation and Maintenance manuals
2 Storm water management plans
This information is transmitted for approval unless noted otherwise.
REMARKS:
Drawings:
0001-Overall Site Key Plan
0002-Site Phasing Plan
C201-Site Grading and Erosion Control - South
C202-Site Grading and Erosion Control - North
C203-Site Grading and Erosion Control - Entrance
C204-Site Grading and Erosion Control
C401-Site Details: Storm Sewer/ Sanitary Sewer
C402-Site Details: General Notes / Erosion Control
C403-Site Details: Storm Water Detention Boxes
C404-Site Details: Wet Detention / Storm Water Detention
C405-Site Details: Curb and Gutter / Asphalt & base / Parking
C406-Site Details: Athletic Field Improvements
C407-Site Details: Athletic Field Improvements I Misc.
NED
C G
NTodd Smith
copy: Steve Janowski, P.E.
Ms. Ann Williams, Johnston County Schools
Mr. Ray Debruhl, TPFG
3
C408-Site Details: Dugouts
C409-Site Details: Water Services
C410-Site Details: Concrete Steps
C501-Road Widening
2600 Meridian Drive / Greenville, NC 27834 / tel [phone] / fax [phone] / e-mail. [e-mail]
:a-
OPERATION AND MAINTENANCE MANUAL
AND
AGREEMENT
for
West Johnston High School
Wet Detention Basin No. 1 and Dry Detention Basin No. 2
, 7No
INS
proj no 20013
prepared by
J.S. Janowski, PE
105 C East Victoria Court
Greenville, NC 27856
252-756-8918
West Johnston High School - 1
14
Wet Detention Basin
Checklist and Schedule
Monthly Inspection
1. T Remove debris from primary and emergency spillways
2. _ Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. _ Check draw down pipe for blockage
4. _ Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. _ Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment, and the emergency spillway.
6 Month Inspection
1. _ Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool =194.00
fore bay = 192.00
outlet of pond =193.00
2. _ Check emergency spillway for erosion.
General Maintenance
1. Mow the side slopes for the embankment and the ponded area (not including
the shelf) according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. _ Check bar grating to make sure it is secure and locked down.
5. _ Turn gate valve. to make sure it is operable
6. _ Remove any woody trees growing in the embankment.
West Johnston High School - 2
Dry Detention, Basin
Checklist and Schedule
Monthly Inspection
1. _ Remove debris from primary and emergency spillways
2. _ Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. Check draw down pipe for blockage
4. - Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. _ Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment.
6 Month Inspection
1. _ Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool =178.00
fore bay =178.00
outlet of pond =177.00
General Maintenance
1. - Mow the side slopes for the embankment and the ponded area (not including
the shel) according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. _ Check bar grating to make sure it is secure and locked down.
5. _ Turn gate valve to make sure it is operable
West Johnston High School - 3
hereby acknowledge that I am the financially responsible party for
maintenance and ispection of this detention pond. I will perform the maintenance as outlined above, to comply with the
Johnston County Stormwater Management Ordinance and the Stormwater Management permit received for this project
Furthermore, I attest that this Inspection and Maintenance Agreement is on file with the Register of Deeds.
Signature

I, a Notary PubC?c for state of ? '
p?e of, do reby certify that
sonally befofte is da y of YL'Ig ,1c9 ldG, and ackno a the due execution of the foregoing
instrument Wiliness my hand and official seal,
?. ..........
My commission
c t\.OTA,g
ec*42 - CA
o AVS?IG
"N t'
•.,._ COU

OPERATION AND MAINTENANCE MANUAL
AND
AGREEMENT
for
West Johnston High School
Wet Detention Basin No.1 and Dry Detention Basin No. 2
proj no 20013
prepared by
J.S. Janowski, PE
105 C East Victoria Court
Greenville, NC 27856
252-756-8918
West Johnston High School - 1
Dry Detention Basin
Checklist and Schedule
Monthly Inspection
1. _ Remove debris from primary and emergency spillways
2. - Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. _ Check draw down pipe for blockage
4. _ Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. - Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment.
6 Month Inspection
1. Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool =178.00
fore bay =178.00
outlet of pond = 177.00
General Maintenance
1. _ Mow the side slopes for the embankment and the ponded area (not including
the shelf) according to the growing season of the grass
2. - Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. - Check bar grating to make sure it is secure and locked down.
5. _ Turn gate valve to make sure it is operable
West Johnston High School - 3

OPERATION AND MAINTENANCE MANUAL
AND
AGREEMENT
for
West Johnston High School
Wet Detention Basin No.1 and Dry Detention Basin No. 2
%'rN JA'
ii1+A
proj no 20013
prepared by
J.S. Janowski, PE
105 C East Victoria Court
Greenville, NC 27856
252-756-8918
West Johnston High School - 1
14
Wet Detention Basin
Checklist and Schedule
Monthly Inspection
1. T Remove debris from primary and emergency spillways
2. _ Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. _ Check draw down pipe for blockage
4. _ Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. T Check pipes for undercutting. Replace rip rap and repair broken pipes
3. _ Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment, and the emergency spillway.
6 Month Inspection
1. _ Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool = 194.00
fore bay = 192.00
outlet of pond = 193.00
2. _ Check emergency spillway for erosion.
General Maintenance
1. Mow the side slopes for the embankment and the ponded area (not including
the shel fl according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. _ Check bar grating to make sure it is secure and locked down.
5. Turn gate valve to make sure it is operable
6. _ Remove any woody trees growing in the embankment.
West Johnston High School - 2
Dry Detention. Basin
Checklist and Schedule
Monthly Inspection
1. - Remove debris from primary and emergency spillways
2. _ Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. _ Check draw down pipe for blockage
4. _ Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. _ Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment.
6 Month Inspection
1. Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool =178.00
fore bay =178.00
outlet of pond = 177.00
General Maintenance
1. _ Mow the side slopes for the embankment and the ponded area (not including
the shelf) according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. _ Check bar grating to make sure it is secure and locked down.
5. - Turn gate valve to make sure it is operable
West Johnston High School - 3
hereby acknowledge that I am the financ*k* responsible party for
maintenance and inspection of this detention pond. I will perform the maintenance as outlined above, to comply with the
Johnston County Stormwater Management Ordinance and the Stormwater Management permit received for this project
Furthermore, I attest that this Inspection and Maintenance Agreement is on file with the Register of Deeds.
Signature
1.1?lr111 Gy
Adp'AM le f,
. a Notary Public for state of
Cou of , do reby certify that
personalty *before me th is day of ,1c9, and ac(mo Nlete the due execution of the foregoing
instrument. Witness my hand and official seal,
My commission
W.
c 40 TAq
AUSLIG
'''+unnm??a

r
OPERATION AND MAINTENANCE MANUAL
AND
AGREEMENT
for
West Johnston High School
Wet Detention Basin No. I and Dry Detention Basin No. 2

proj no 20013
prepared by
J.S. Janowski, PE
105 C East Victoria Court
Greenville, NC 27856
252-756-8918
West Johnston High School - 1
Wet Detention Basin
Checklist and Schedule
Monthly Inspection
1. , Remove debris from primary and emergency spillways
2. Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. - Check draw down pipe for blockage
4. - Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment, and the emergency spillway.
6 Month Inspection
1. _ Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool =194.00
fore bay = 192.00
outlet of pond = 193.00
2. _ Check emergency spillway for erosion.
General Maintenance
1. Mow the side slopes for the embankment and the ponded area (not including
the shelf) according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. _ Check bar grating to make sure it is secure and locked down.
5. - Turn gate valve to make sure it is operable
6. _ Remove any woody trees growing in the embankment.
West Johnston High School - 2
Dom' Detention Basin
Checklist and Schedule
Monthly Inspection
1. - Remove debris from primary and emergency spillways
2. - Check groundcover for signs of erosion or failure
1. on embankment
2. in pond
3. _ Check draw down pipe for blockage
4. _ Inspect the embankment, primary spillway and undeerdrain fro signs of seepage or
erosion.
1. If seepage is found, note approximate flow rate, color of discharge, location
of slumps, wetness on slope, etc.
2. Draw a map of the structure noting any erosion, wetness, slumps, etc.
Quarterly Inspection
1. _ Remove debris
2. _ Check pipes for undercutting. Replace rip rap and repair broken pipes
3. _ Reseed grass swales, the area between the forebay and permanent pool, and
the pond embankment.
6 Month Inspection
1. Remove accumulated sediment from the permanent pool, the fore bay and the
outlet of the pond.
Note: the following are the benchmark elevations for the sediment pools.
permanent pool = 178.00
fore bay ° 178.00
outlet of pond =177.00
General Maintenance
1. _ Mow the side slopes for the embankment and the ponded area (not including
the shelf) according to the growing season of the grass
2. _ Keep the cattails from clogging the pond and spillways.
3. _ Check debris at the inlet after each storm event.
4. - Check bar grating to make sure it is secure and locked down.
5. , Turn gate valve to make sure it is operable
West Johnston High School - 3
.; j?
.ems _
IE,^C7A _O _.- •? -
'. : • .. - : STAB'LZED
' •?- SLOF?
TRANSMON '0
. r r '- T TRADE
%...-"
S 7A 6L
OUTLE- ......_.. .......
Design Flow
(cfs) Entrance Width Depth End idth Length

20
2C-3.
?1 2 I.0 3' 20
LEVEL SPREADER 1
SCALE: NONE

Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
135 2.9 114550 7.97 5.9 186.97 0.6 5.3
138 2.6 114002 7.94 5.4 186.94 0.6 4.7
141 2.4 113504 7.92 5.0 186.92 0.6 4.4
144 2.1 113026 7.90 4.7 186.90 0.6 4.0
147 1.9 112571 7.88 4.3 186.88 0.6 3.7
150 1.7 112140 7.86 4.0 186.86 0.6 3.4
153 1.6 111735 7.84 3.7 186.84 0.6 3.0
156 1.4 111359 7.83 3.5 186.83 0.6 2.9
159 1.3 110982 7.81 3.2 186.81 0.6 2.6
162 1.2 110636 7.79 2.9 186.79 0.6 2.3
165 1.1 110321 7.78 2.8 186.78 0.6 2.1
168 1.0 110011 7.77 2.6 186.77 0.6 2.0
171 0.9 109708 7.75 2.4 186.75 0.6 1.7
174 0.8 109436 -7.74 2.2 186.74 0.6 1.6
177 0.7 109173 7.73 2.1 186.73 0.6 1.5
180 0.6 108919 7.72 2.0 186.72 0.6 1.4
183 0.6 108675 7.71 1,9 186.71 0.6 1.2
186 0.5 108442 7.69 1.6 186.69 0.6 1.0
189 0.5 108239 7.69 1.6 186.69 0.6 1.0
192 0.4 108028 7.68 1.5 186.68. 0.6 0.9
195 0.4 107827 7.67 1.4 186.67 0.6 0.8
19& 0.3 107638 7.66 1.3 186.66 0.6 0.7
201 0.3 107460 7.65 1.2 186.65 0.6 0.6
204 0.3 107294 7.64 1.1 186.64 0.6 0.5
360 0.0 99184 7.27 0.6 186.27 0.6 0.0
720 0.0 85939 6.64 0.6 185.64 0.6 0.0
1080 0.0 73295 6.00 0.6 185.00 0.6 0.0
1440 0.0 61328 5.36 0.5 184.36 0.5 0.0
1800 0.0 50079 4.71 0.5 183.71 0.5 0.0
2160 0.0 39610 4.06 0.4 183.06 0.4 0.0
2520 0.0 29982 3.40 0.4 182.40 0.4 0.0
2880 0.0 21292 2.74 0.4 181.74 0.4 0.0
3240 0.0 13655 2.06 0.3 181.06 0.3 0.0
3600 0.0 7282 1.38 0.2 180.38 ti
. . 0.2 0.0
3960 0.0 2495 0.70 0.1 ,
179.70 0.1 0.0
4320 0.0 213 0.15 0.0 179.15 0.0 0.0
4680 0.0 213 0.15 0.0 179.15 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 271 cfs
Peak Stage= 8.78 k
Water Elevation= 187.78 msl
Peak Storage = 133491 d
Design Spillway 186.55 msl
Length of weir 6.S ft
West Johnston High School -20013-8
West Johnston High School
8-04-00
Calculations for level spreader
Wet Detention in the front of the School
0 = 27.7 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
0 = CLHw1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (013.OL)A0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
Detention Behind the Athleljc Fields
0 = 27.2 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
0 = CLH°1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (0/3.OL)AO.66
H = 0.18 ft
V = 0/A A = LH = 21.82 sf
V = 1.25 fps OK less than 3 fps,,.
West Johnston High School
8-04-00
Calculations for level spreader
Wet Detention in the front of the School
Q = 27.7 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLH111.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (0/3.OL)"0.66
H = 0.18 ft
V = Q/A A = LH = 22.08 sf
V = 1.25 fps OK less than 3 fps
nd the Athletic Fiel
Q = 27.2 cfs outflow from 2year 24 hr storm
L = 120 ft length of level spreader on plans
Q = CLHw1.5 Weir equation
C = 3 constant
H = ?ft to be computed
H = (Q/3.OL)"0.66
H = 0.18 ft
V = Q/A A = LH = 21.82 sf
V = 1.25 fps OK less than 3 fps,.
....
%ESE A ,u - :! .
Oil/ 3EZI
SLOPE
. - .. -..... ... • • • • ' TRANSMON TO
O'GRADE
S AELE .. /?..._....... ... -
_. '
OUTLE- ?.. j'.. ---•••• ..
016
................. .....•
Oesign Flow
(cfs) Entrance Width Oepth End Width Length

Z^ 2?
V. 3
'l1 2 ?, 0 3' 2v'
LEVEL SPREADER `
SCALE: NONE
rln.?_ r.)t l u?
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
135 2.9 114550 7.97 5.9 186.97 0.6 5.3
138 2.6 114002 7.94 5.4 186.94 0.6 4.7
141 2.4 113504 7.92 5.0 186.92 0.6 4.4
144 2.1 113026 7.90 4.7 186.90 0.6 4.0
147 1.9 112571 7.88 4.3 186.88 0.6 3.7
150 1.7 112140 7.86 4.0 186.86 0.6 3.4
153 1.6 111735 7.84 3.7 186.84 0.6 3.0
156 1.4 111359 7.83 3.5 186.83 0.6 2.9
159 1.3 110982 7.81 3.2 186.81 0.6 2.6
162 1.2 110636 7.79 2.9 186.79 0.6 2.3
165 1.1 110321 7.78 2.8 186.78 0.6 2.1
168 1.0 110011 7.77 2.6 186.77 0.6 2.0
171 0.9 109708 7.75 2.4 186.75 0.6 1.7
174 0.8 109436 ..7.74 2.2 186.74 0.6 1.6
177 0.7 109173 7.73 2.1 186.73 0.6 1.5
180 0.6 108919 7.72 2.0 186.72 0.6 1.4
183 0.6 108675 7.71 1.9 186.71 0.6 1.2
186 0.5 108442 7.69 1.6 186.69 0.6 1.0
189 0.5 108239 7.69 1.6 186.69 0.6 1.0
192 0.4 108028 7.68 1.5 186.68 0.6 0.9
195 0.4 107827 7.67 1.4 186.67 0.6 0.8
19$ 0.3 107638 7.66 13 186.66 0.6 0.7
201 0.3 107460 7.65 1.2 186.65 0.6 0.6
204 0.3 107294 7.64 1.1 186.64 0.6 0.5
360 0.0 99184 7.27 0.6 186.27 0.6 0.0
720 0.0 85939 6.64 0.6 185.64 0.6 0.0
1080 0.0 73295 6.00 0.6 185.00 0.6 0.0
1440 0.0 61328 5.36 0.5 184.36 0.5 0.0
1800 0.0 50079 4.71 0.5 183.71 0.5 0.0
2160 0.0 39610 4.06 0.4 183.06 0.4 0.0
2520 0.0 29982 3.40 0.4 182.40 0.4 0.0
2880 0.0 21292 2.74 0.4 181.74 0.4 0.0
3240 OA 13655 2.06 0.3 181.06 0.3 0.0
3600 0.0 7282 1.38 0.2 180.38 0.2 0.0
3960 0.0 2495 0.70 0.1 179.70 0.1 0.0
4320 0.0 213 0.15 0.0 179.15 0.0 0.0
4680 0.0 213 0.15 0.0 179.15 0.0 0.0
Results of routing the Z year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 271 cfs
Peak Stage= 8.78 ft
Water Elevation= 187.78 msl
Peak Storage = 133491 cf
Design Spillway 186.55 msl
Length of weir 6.5 ft
West Johnston High School -20013-8
Wet Detention Study front of School-2 year 24 hour
135 1.0 84006 2.00 9.0 200.00 0.3 8.7
138 0.8 82559 1.97 8.5 199.97 0.3 8.2
141 0.7 81170 1.94 8.1 199.94 0.3 7.8
144 0.6 79841 1.91 7.7 199.91 0.3 7.4
147 0.6 78572 1.88 7.3 199.88 0.3 7.0
150 0.5 77364 1.86 7.0 199.86 0.3 6.7
153 0.4 76194 1.83 6.6 199.83 0.3 6.3
156 0.4 75085 1.81 6.3 199.81 0.3 6.0
159 0.3 74015 1.78 5.9 199.78 0.3 5.6
162 0.3 73006 1.76 5.7 199.76 0.3 5.4
165 0.3 72037 1.74 5.4 199.74 0.3 5.1
168 0.2 71106 1.72 5.2 199.72 0.3 4.9
171 0.2 70214 1.70 4.9 199.70 0.3 4.6
174 0.2 69361 -1.68 4.7 199.68 0.3 4.4
177 0.2 68546 1.66 4.5 199.66 0.3 4.2
180 0.1 67771 1.65 4.3 199.65 0.3 4:1
183 0.1 67013 1.63 4.1 199.63 0.3 3.8
186 0.1 66293 1.61 3.9 199.61 0.3 3.6
189 0.1 65611 1.60 3.8 199.60 0.3 3.5
192 0.1 64947 1.58 3.6 199.58. 0.3 3.3
195 0.1 64320 1.57 3.5 199.57 0.3 3.2
198 0.1 63710 1.56 3.3 199.56 0.3 3.1
201 0.1 63119 1.54 3.1 199.54 0.3 2.9
204 0.0 62563 1.53 3.0 199.53 0.3 2.8
360 0.0 34567 0.89 0.2 198.89 0.2 0.0
720 0.0 30091 0.79 0.2 198.79 0.2 0.0
1080 0.0 25914 0.69 0.2 198.69 0.2 0.0
1440 0.0 22062 0.59 0.2 198.59 0.2 0.0
1800 0.0 18563 0.51 0.1 198.51 0.1 0.0
2160 0.0 15377 0.43 0.1 198.43 0.1 0.0
2520 0.0 12536 0.35 0.1 198.35 0.1 0.0
2880 0.0 10088 0.29 0.1 198.29 0.1 0.0
3240 0.0 7985 0.24 0.1 198.24 0.1 0.0
3600 0.0 6217 0.19 0.1 198.19. 0.1 0.0
3960 0.0 4867 0.15 0.0 198.15 0.0 0.0
4320 0.0 3983 0.12 0.0 198.12 0.0 0.0
4680 0.0 3983 0.12 0.0 198.12 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 27.7 cfs
Peak Stage= 3.01 ft
Water Elevation= 201.01 msl `
Peak Storage = 131446 d
Design Spillway 199.12 msl
Length of weir 30 ft
West Johnston High School -20013-8
??- . .
9E OE TA,
SLOPE
?:':._ . "- " • ::: .. • TRANSITION TO
- •'- :::.' 0' GRADE
S AB-= .
OUTLET -•--._-.. -..-•--.. - / :. ................
.•- :.... .••:.:. ......
------------- ---
........... _
i ... ............... ......
._
Oesign Flow
(cfs) Entrance Width Oepth End %dth Length
C t0 0.? 0

24
?1 2 1.0 3
LEVEL SPREADER
SCALE: NONE
,in.<_ ?.1(iu<
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
135 2.9 114550 7.97 5.9 186.97
138 2.6 114002 7.94 5.4 186.94
141 2.4 113504 7.92 5.0 186.92
144 2.1 113026 7.90 4.7 186.90
147 1.9 112571 7.88 4.3 186.88
150 1.7 112140 7.86 4.0 186.86
153 1.6 111735 7.84 3.7 186.84
156 1.4 111359 7.83 3.5 186.83
159 1.3 110982 7.81 3.2 186.81
162 1.2 110636 7.79 2.9 186.79
165 1.1 110321 7.78 2.8 186.78
168 1.0 110011 7.77 2.6 186.77
171 0.9 109708 7.75 2.4 186.75
174 0.8 109436 .7.74 2.2 186.74
177 0.7 109173 7.73 2.1 186.73
180 0.6 108919 7.72 2.0 186.72
183 0.6 108675 7.71 1.9 186.71
186 0.5 108442 7.69 1.6 186.69
189 0.5 108239 7.69 1.6 186.69
192 0.4 108028 7.68 1.5 186.68
195 0.4 107827 7.67 1.4 186.67
198 0.3 107638 7.66 13 186.66
201 0.3 107460 7.65 1.2 186.65
204 0.3 107294 7.64 1.1 186.64
360 0.0 99184 7.27 0.6 186.27
720 0.0 85939 6.64 0.6 185.64
1080 0.0 73295 6.00 0.6 185.00
1440 0.0 61328 5.36 0.5 184.36
1800 0.0 50079 4.71 0.5 183.71
2160 0.0 39610 4.06 0.4 183.06
2520 0.0 29982 3.40 0.4 182.40
2880 0.0 21292 2.74 0.4 181.74
3240 0.0 13655 2.06 0.3 181.06
3600 0.0 7282 1.38 0.2 180.38
3960 0.0 2495 0.70 0.1 179.70
4320 0.0 213 0.15 0.0 179.15
4680 0.0 213 0.15 0.0 179.15
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 271 cfs
Peak Stage= 8.78 R
Water Elevation= 187.78 msl
Peak Storage = 133491 d
Design Spillway 186.SS msi
Length of weir 6.S k
0.6 5.3
0.6 4.7
0.6 4.4
0.6 4.0
0.6 3.7
0.6 3.4
0.6 3.0
0.6 2.9
0.6 2.6
0.6 2.3
0.6 2.1
0.6 2.0
0.6 1.7
0.6 1.6
0.6 1.5
0.6 1.4
0.6 1.2
0.6 1.0
0.6 1.0
0.6 0.9
0.6 0.8
0.6 0.7
0.6 0.6
0.6 0.5
0.6 0.0
0.6 0.0
0.6 0.0
0.5 0.0
0.5 0.0
0.4 0.0
0.4 0.0
0.4 0.0
0.3 0.0
0.2 0.0
0.1 0.0
0.0 0.0
0.0 0.0

West Johnston High School -20013-8
Wet Detention Study front of School-2 year 24 hour
135 1.0 84006 2.00 9.0 200.00 0.3 8.7
138 0.8 82559 1.97 8.5 199.97 0.3 8.2
141 0.7 81170 1.94 8.1 199.94 0.3 7.8
144 0.6 79841 1.91 7.7 199.91 0.3 7.4
147 0.6 78572 1.88 7.3 199.88 0.3 7.0
150 0.5 77364 1.86 7.0 199.86 0.3 6.7
153 0.4 76194 1.83 6.6 199.83 0.3 6.3
156 0.4 75085 1.81 6.3 199.81 0.3 6.0
159 0.3 74015 1.78 5.9 199.78 0.3 5.6
162 0.3 73006 1.76 5.7 199.76 0.3 5.4
165 0.3 72037 1.74 5.4 199.74 0.3 5.1
168 0.2 71106 1.72 5.2 199.72 0.3 4.9
171 0.2 70214 1.70 4.9 199.70 0.3 4.6
174 0.2 69361 _1.68 4.7 199.68 0.3 4.4
177 0.2 68546 1.66 4.5 199.66 0.3 4.2
180 0.1 67771 1.65 4.3 199.65 0.3 4.1
183 0.1 67013 1.63 4.1 199.63 0.3 3.8
186 0.1 66293 1.61 3.9 199.61 0.3 3.6
189 0.1 65611 1.60 3.8 199.60 0.3 3.5
192 0.1 64947 1.58 3.6 199.5a 0.3 3.3
195 0.1 64320 1.57 3.5 199.57 0.3 3.2
198 0.1 63710 1.56 3.3 199.56 0.3 3.1
201 0.1 63119 1.54 3.1 199.54 0.3 2.9
204 0.0 62563 1.53 3.0 199.53 0.3 2.8
360 0.0 34567 0.89 0.2 198.89 0.2 0.0
720 0.0 30091 0.79 0.2 198.79 0.2 0.0
1080 0.0 25914 0.69 0.2 198.69 0.2 0.0
1440 0.0 22062 0.59 0.2 198.59 0.2 0.0
1800 0.0 18563 0.51 0.1 198.51 0.1 0.0
2160 0.0 15377 0.43 0.1 198.43 0.1 0.0
2520 0.0 12536 0.35 0.1 198.35 0.1 0.0
2880 0.0 10088 0.29 0.1 198.29 0.1 0.0
3240 0.0 7985 0.24 0.1 198.24 0.1 0.0
3600 0.0 6217 0.19 0.1 198.19 ?; . 0.1 0.0
3960 0.0 4867 0.15 0.0 198.15 " 0.0 0.0
4320 0.0 3983 0.12 0.0 198.12 0.0 0.0
4680 0.0 3983 0.12 0.0 198.12 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 27.7 cfs
Peak Stage= 3.01 ft
Water ©evatlon= 201.01 msl `
Peak Storage = 131446 d
Design Spillway 199.12 msl
Length of weir 30 It
West Johnston High School -20013-8

n Lm U, A 9nn0
STORM WATER MANAGEMENT PLAN
WEST JOHNSTON HIGH SCHOOL
JOHNSTON COUNTY, NORTH CAROLINA
Proj. No. 20013
June 6, 2000
...1,...
J?
prepared by:
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
[phone]

Narrative
This site is a proposed high school. It is situated on a 101 acre tract of land off the east
side of SR 1330 and south of Beaverdam Branch. The property is not located in the
ESOD. The site is classified as commercial in accordance with the classification that
Johnston County Director of Infrastructure and Engineering assigned to this school in a
joint meeting on April 4, 2000. The impervious limits for commercial areas is 60%. The
existing slopes of the land are between 5 and 10 % with drainage in two directions. The
proposed drainage plan also manages storm water in the two separate basins. There is a
total of 22.70 acres of impervious area on this site which is 22.5% impervious.
In the front of the site, a wet detention basin is designed to attenuate the post development
peak discharge of the 2 year 24 hour storm to that of the predeveloped flow and to detain
the first 1" of runoff and release it between 2 and 5 days. The estimated predevelopment
peak rate of runoff is 28.6 cfs. The estimated postdevelopment rate of runoff is 81.9 cfs.
The effluent pipe into the basin is a 54"RCP at a flat slope of 0.5% to minimize velocities.
The outlet control pipe is a 3" pvc pipe with a small 3.5 ft weir opening to control the 2
year storm. The principal spillway is an 8'x8' concrete box. The dam is approximately 15'
wide 3:1 front side slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut
around the north of the basin to handle the 100 year design storm The basin is designed to
remove 85% TSS prior from the runoff. The downstream impacts are mitigated as a result
of the detention basin.
In the athletic field site, another detention basin is designed to attenuate the post
development peak discharge of the 2 year 24 hour storm to that of the predeveloped flow.
The estimated predevelopment peak rate of runoff is 36.6 cfs. The estimated
postdevelopment rate of runoff is 62.7 cfs. The effluent pipe into the basin is a 3" pvc
pipe to detain the first 1" of runoff and release it over a 2 to 5 day period. This basin is
designed as an extended dry detention basin to remove 50 % TSS. It has a level spreader
downstream of the outlet to remove another 35% TSS for a total of 85% TSS removal.
The outlet control pipe is a 54" RCP with a small , 10 foot wide dam, with 3:1 front side
slopes and 3:1 back side slopes. A 30 foot emergency spillway is cut around the west of
the basin to handle the 100 year design storm A 6.5 foot weir is formed into an 8'x8' box
in order to control the 2 year storm The basin is designed such vegetation will be allowed
to grow freely and provide for additional nutrient intake. Maintenance for the facility will
include inspections of the dam and control devices. The downstream impacts are mitigated
as a result of the detention basin.
CULVERT CROSSING DESIGN
FOR
WEST JOHNSTON HIGH SCHOOL
MAIN ENTRY ROAD
100 YR - 24 HOUR
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
111111
12924 z
s _
INES'S`• 5
West Johnston High School 20013-1
r a
Site Conditions postdevelopment
Total watershed area
Area Impervious C= 0.95
Area grass C= 0.3
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
187.00 acres
CN= 98 37.00 acres
CN= 73 150.00 acres
C C
5000 feet
79 feet
8.4 inches
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))"2 / (P+0.8(s))
Time of Concentration
channel flow (not overland) 27.2
Tc=(L"3M)^0.385
128
Composite C =
B
Rainfall Intensity = I = g/(h+T) 2
10
25
100
9 h
132 18
203 22
246 23
302 25
77.9
2.83
5.76 inches
27.2 minutes
0.43
5.8 inches per hr
Peak Discharge Q=CIA 463.7 cfs
Time to peak
Tp= Vol/(1.37 Qp) 102.5 minutes
Based on Analysis of a 2 - 72" culverts the Headwater Elevation = 197.73
Top of the Road = 198.84 Road is designed to not overtop in the 100 year storm
Outlet Velocity = 8.8 fps Design Outlet Protection
Use Chart pg 8.06.3
for 232 cfs per barrel and 72" dia pipe use La = 30 feet
West Johnston High School -20013-2

PIPE CULVERT ANALYSIS
COMPUTATION OF CULVERT PERFORMANCE CURVE
June 5, 2000
PROGRAM INPUT DATA
DESCRIPTION
Culvert Diameter (ft) .......................................
FHWA Chart Number ...........................................
FHWA Scale Number (Type of Culvert Entrance) ................
Manning's Roughness Coefficient (n-value) ...................
Entrance Loss Coefficient of Culvert Opening ................
Culvert Length (ft) .........................................
Invert Elevation at Downstream end of Culvert (ft)..........
Invert Elevation at Upstream end of Culvert (ft)............
Culvert Slope (ft/ft) .......................................
Starting Flow Rate (cfs) ....................................
Incremental Flow Rate (cfs) .................................
Ending Flow Rate (cfs) ......................................
Starting Tailwater Depth (ft) ...............................
Incremental Tailwater Depth (ft) ............................
Ending Tailwater Depth (ft) .................................
VALUE
6.0
1
1
0.012
0.1
55.0
188.0
188.51
0.0093
100.0
50.0
600.0
4-.0
1.0
14.0
COMPUTATION RESULTS
Flow Tailwater Headwater (ft) Normal Critical Depth at Outlet
Rate Depth Inlet Outlet Depth Depth Outlet Velocity
(cfs) (ft) Control
- Control
--------- (ft)
--------- (ft)
---------- (ft)
---------- (fps)
---------
-----------
100.0 -----------
4.0 ----------
3.82 3.99 1.94 2.69 4.0 4.99
150.0 5.0 4.92 5.18 2.41 3.33 5.0 5.96
200.0 6.0 6.0 6.45 2.83 3.87 6.0 7.07
250.0 7.0 7.22 7.99 3.23 4.33 6.0 8.84
300.0 8.0 8.47 9.65 3.63 4.73 6.0 10.61
350.0 9.0 10.09 _ 11.43 4.03 5.07 6.0 12.38
400.0 10.0 11.96 13.33 4.47 5.33 6.0 14.15
450.0 11.0 14.07 15.35 5.03 5.53 6.0 15.92
500.0 12.0 16.44 17.49 6.0 5.67 6.0 17.68
550.0 13.0 19.05 19.75 6.0 5.77 6.0 19.45
600.0 14.0 21.91 22.13 6.0 5.83 6.0 21.22
HYDROCALC Hydraulics for Windows, Version 1.2a Copyright (c) 1996
Dodson & Associates, Inc., 5629 FM 1960 West, Suite 314, Houston, TX 77069
Phone:[phone], Fax:[phone], Email:[e-mail]
All Rights Reserved.
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7? 32'30" 724 "'-E • INTERIOR--GEOLOGICAL SURVEY, RESTON. VIRGINIA-1*1
FOUR OAKS 6 Ml."*,
1 MILE ROAD CLASSIFICATION
\
Mo 5000 6000 7000 FEET Medium-duty- Light-duty -,
1 KILOMETRE Unimproved dirt ====a=:=.
T• ?1 n._._ n_.-•_
Wet Detention Study front of School-2 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
2 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
6-6-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
324
West Johnston High School -20013-1

Site Conditions Predevelopment
Wet Detention Study front of School-2 year 24 hour
Total watershed area
Area Impervious C=
Area grass or woods C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
Tc=(L"3/H)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.9 X
CN= 98
CN= 73
OVERLAND
2
S 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-2
23.00 acres
0.00 acres
23.00 acres
C
1220 feet
40 feet
3.7 inches
13.9 minutes
0.3
4.1 inches per hr
28.6 cfs

Site Conditions postdevelopment
Wet Detention Study front of School-2 year 24 hour
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))"2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(LA3M)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
0.95
0.3
CN=
CN=
C
23.00 acres
98 13.14 acres
73 9.86 acres
C
1220 feet
40 feet
3.7 inches
87.3
1.46
2.39 inches
6.9
R S h
2 132 18
10 203 22
25 246 23
100 302 25
6.9 minutes
0.67
5.3 inches per hr
Peak Discharge Q=CIA 81.9 cfs
Time to peak
Tp= Vol/(1.37 Qp) 29.6 minutes
West Johnston High School -20013-3
Wet Detention Study front of School-2 year 24 hour
Storage Required
Allowable release at impoundment =
Peak rate of inflow at impoundment =
Sr = (Qi - Qo)Tp
STAGE STORAGE DATA
surface dill.
Elevation area A" stoma
198.00 38922
2.00 83904
200.00 44982
2.00 95795
202.00 50813
accurm
storms
0
83904
179699
Z
Storms Ran LN(stoorrw) LN(kno RAP
0 0 ERR ERR 0.00
83,904 2 11.34 0.69 2.00
179,699 4 12.10 1.39 4.00
b= 1.0987709
Ks= 39175.962
1/b
Z= (S/KS)n
Predicted Water Surface Elevation for 2 year 24 hour storm=
Predicted Surface Area=
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00%
28.6 cfs
81.9 cfs
94,699 cf
Elevation Ran
198 0 198.00 =water surface
200.00 2
202.00 4
200.23 feet ms]
=35607 sf
West Johnston High School -20013-4
A ?
Wet Detention Study front of School-2 year 24 hour
Average pool depth = 3 ft
SA/DA= 2.30% Required Surface Area=
Surface Area Provide=
Volume to be controlled by 1" storm =1"(Rv=0.05 + 0.009(I))(DA) _
Temporary Water Quality Pool Elevation =
Discharge of volume in 48 hours =
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev.
proposed water surface elev. _
available head (h) _
discharge (d) =
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)"1/2
0.3 -
0.0
23023 sf
35607.0 sf
47005 cf
199.12
0.3 cfs
198.00 feet msl
198.10 feet msl
200.23 feet msl
2.13 feet
0.3 cis
0.6
0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 28.6 cfs L = 8 It
Q=CwLH^3/2 H = 1.12 ft
Top of Emergency Spillwc- 1.12 msl
5
West Johnston High School 20013-5
K
Wow Hydmgraph
Peak MOW =
Time to Peak
L(time mW
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
7S
78
81
84
87
90
93
96
99
102
105
108
111
114
Wet Detention Study front of School-2 year 24 hour
37.0368384
Ud
Additlorwi Flow
81.9
29.6
0
2.1
8.0
17.2
28.9
41.7
54.5
65.8
74.7
80.3
81.8
793
72.9
64.2
563
493
43.2
37.9
33.2
29.1
25.5
22.4
19.6
17.2
15.1
13.2
11.6
10.2
8.9
7.8
6.8
6.0
53
4.6
4.0
3.5
3.1
2.7
2.4
West Johnston High School -20013-6
0.0
Wet Detention Study front of School-2 year 24 hour
Stormwater routing
j (time min) Q-(-Q
0 0
3 2.1
6 8.0
9 17.2
12 28.9
15 41.7
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
117
120
123
126
129
132
54.5
65.8
74.7
80.3
81.8
79.3
72.9
64.2
56.3
49.3
43.2
37.9
33.2
29.1
25.5
22.4
19.6
17.2
15.1
13.2
11.6
10.2
8.9
7.8
6.8
6.0
5.3
4.6
4.0
3.5
3.1
2.7
2.4
2.1
1.8
1.6
1.4
1.2
1.1
Storage
0
0
369
1809
4913
10110
17616
27417
39237
52652
66896
80884
93722
104635
113224
119777
124581
127918
130030
131146
131446
131061
130147
128814
127162
125242
123139
120892
118574
116212
113832
111455
109101
106784
104518
102316
100153
98071
96045
94112
92247
90454
88736
87097
85510
RM
0.00
0.00
0.01
0.06
0.15
0.29
0.48
0.72
1.00
1.31
1.63
1.93
2.21
2.45
2.63
2.77
2.87
2.94
2.98
3.00
3.01
3.00
2.98
2.95
2.92
2.88
2.84
2.79
2.74
2.69
2.64
2.59
2.54
2.49
2.44
2.40
2.35
2.31
2.26
2.22
2.18
2.14
2.10
2.07
2.03
Outflow
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.2
1.1
4.1
8.0
12.3
16.5
19.9
22.6
24.7
26.2
27.0
27.5
27.7
27.5
27.0
26.4
25.8
24.9
24.1
23.0
22.0
21.0
20.1
19.1
18.1
17.2
16.3
15.6
14.7
14.0
13.1
12.5
11.8
11.2
10.5
10.1
9.4
Elevation
198.00
198.00
198.01
198.06
198.15
198.29
198.48
198.72
199.00
199.31
199.63
199.93
200.21
200.45
200.63
200.77
200.87
200.94
200.98
201.00
201.01
201.00
200.98
200.95
200.92
200.88
200.84
200.79
200.74
200.69
200.64
200.59
200.54
200.49
200.44
200.40
200.35
200.31
200.26
200.22
200.18
200.14
200.10
200.07
200.03
L= 3.5
3 Spillway
inch 199.12
orifice WAk
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.2
0.3
0.3
0.3
0.3
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.9
3.8
7.7
11.9
16.1
19.5
22.3
24.3
25.8
26.6
27.1
27.3
27.1
26.6
26.0
25.4
24.5
23.7
22.7
21.7
20.7
19.7
18.7
17.8
16.8
15.9
15.2
14.3
13.6
12.8 .
12.1
11.5
10.8
10.2
9.7
9.1
West Johnston High School -20013-7
Wet Detention Study front of School-2 year 24 hour
135 1.0 84006 2.00 9.0 200.00 0.3 8.7
138 0.8 82559 1.97 8.5 199.97 0.3 8.2
141 0.7 81170 1.94 8.1 199.94 0.3 7.8
144 0.6 79841 1.91 7.7 199.91 0.3 7.4
147 0.6 78572 1.88 7.3 199.88 0.3 7.0
150 0.5 77364 1.86 7.0 199.86 0.3 6.7
153 0.4 76194 1.83 6.6 199.83 0.3 6.3
156 0.4 75085 1.81 6.3 199.81 0.3 6.0
159 0.3 74015 1.78 5.9 199.78 0.3 5.6
162 0.3 73006 1.76 5.7 199.76 0.3 5.4
165 0.3 72037 1.74 5.4 199.74 0.3 5.1
168 0.2 71106 1.72 5.2 199.72 0.3 4.9
171 0.2 70214 1.70 4.9 199.70 0.3 4.6
174 0.2 69361 1.68 4.7 199.68 0.3 4.4
177 0.2 68546 1.66 4.5 199.66 0.3 4.2
180 0.1 67771 1.65 4.3 199.65 0.3 4.1
183 0.1 67013 1.63 4.1 199.63 0.3 3.8
186 0.1 66293 1.61 3.9 199.61 0.3 3.6
189 0.1 65611 1.60 3.8 199.60 0.3 3.5
192 0.1 64947 1.58 3.6 199.58 0.3 3.3
195 0.1 64320 1.57 3.5 199.57 0.3 3.2
198 0.1 63710 1.56 3.3 199.56 0.3 3.1
201 0.1 63119 1.54 3.1 199.54 0.3 2.9
204 0.0 62563 1.53 3.0 199.53 0.3 2.8
360 0.0 .34567 0.89 0.2 198.89 0.2 0.0
720 0.0 30091 0.79 0.2 198.79 0.2 0.0
1080 0.0 25914 0.69 0.2 198.69 0.2 0.0
1440 0.0 22062 0.59 0.2 198.59 0.2 0.0
1800 0.0 18563 0.51 0.1 198.51 0.1 0.0
2160 0.0 15377 0.43 0.1 198.43 0.1 0.0
2520 0.0 12536 0.35 0.1 198.35 0.1 0.0
2880 0.0 10088 0.29 0.1 198.29 0.1 0.0
3240 0.0 7985 0.24 0.1 198.24 0.1 0.0
3600 0.0 6217 0.19 0.1 198.19 0.1 0.0
3960 0.0 4867 0.15 0.0 198.15 0.0 0.0
4320 0.0 3983 0.12 0.0 198.12 0.0 0.0
4680 0.0 3983 0.12 0.0 198.12 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 27.7 cfs
Peak Stage= 3.01 ft
Water Elevation= 201.01 msl
Peak Storage = 131446 cf
Design Spillway 199.12 msl
Length of weir 30 ft
West Johnston High School -20013-8
M I
Inflow outflow hydrograph
..
90 ...........................................
80 .......................................... ............ .................. .................. .................. ................... .................
70 ..................
......................... ....................... ....................... ....................... ...................
60 ..................... ...... ................. ................. ......
50 ...................... ........................ ........................ ........................ ....................... _ ...................
v
v
L
40 ........ ................ €....................... ......................... ....................... ...................
30 ............................................................................................................... ...........•----............................. ................
20 .......... ... ............. .................. .. ................. .............. ...................
10 .... ........ ................... ......................................... .................. ... ......
0
0 15 30 45 60 75 90 105
Time (minutes)
-+- Inflow Hydrograph- Outflow Hydrograph
K Wet Detention Study front of School-100 year 24 hour
WET DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
FRONT OF THE BUILDING
100 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
.u
24 =
jilk
110111111160,
West Johnston High School -20013-1

Site Conditions Predevelopment
Wet Detention Study front of School-100 year 24 hour
Total watershed area
Area Impervious C=
Area grass or woods C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L"3M)"0.385
128
Composite C =
Rainfall Intdnsity = I = g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.9 X
23.00 acres
CN= 98 0.00 acres
CN= 73 23.00 acres
C
1220 feet
40 feet
8.4 inches
OVERLAND
2
B 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School 20013-2
13.9 minutes
0.3
7.8 inches per hr
53.6 cfs
Wet Detention Study front of School-100 year 24 hour
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
0.95
0.3
CN=
CN=
C
23.00 acres
98 13.14 acres
73 9.86 acres
C
1220 feet
40 feet
8.4 inches
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L"3/H)"0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
87.3
1.46
6.87 inches
6.9 X2
S 9 h
2 132 18
10 203 22
25 246 23
100 302 25
13.8 minutes
0.67
7.8 inches per hr
Peak Discharge Q=CIA 120.2 cfs
Time to peak
Tp= Vol/(1.37 Qp) 58.1 minutes
West Johnston High School -20013-3
4 Storage Required
Wet Detention Study front of School-100 year 24 hour
Allowable release at impoundment = 53.6 cfs
Peak rate of inflow at impoundment = 120.2 cfs
Sr = (Qi - Qo)Tp 231,990 cf
STAGE STORAGE DATA
surface dill. accum.
Elevation area ALLY storage stoma Elevation
198.00 38922 0 198 0 198.00 =water surface
2.00 83904
200.00 44982 83904 200.00 2
2.00 95795
202.00 50813 179699 202.00 4
Z
C
d
Storage Stage L oma) L N(StM) ompute
Rage
0 0 ERR ERR 0.00
83,904 2 11.34 0.69 2.00
179,699 4 12.10 1.39 4.00
b= 1.0987709
Ks= 39175.962
1/b
Z= (S/KS)A
Predicted Water Surface Elevation for 100 year 24 hour storm= 203.05 feet msl
To capture the first 1" of runoff
Drainage Area = 23 ac
% imperv area = 57.00%
West Johnston High School -20013-4
t ,
Wet Detention Study front of School-100 year 24 hour
Average pool depth = 3 ft
SA/DA= 2.30% Required Surface Area= 23023 sf
Surface Area Provide= 35607.0 sf
Volume to be controlled by 1" storm =1"(Rv=0.05 + 0.009(I))(DA) = 47005 cf
Temporary Water Quality Pool Elevation = 199.12
Discharge of volume in 48 hours = 0.3 cfs
Size Outlet Device for Control Structure
invert elevation = 198.00 feet msl
estimated orifice center elev. = 198.10 feet msl
proposed water surface elev. = 203.05 feet msl
available head (h) = 4.95 feet
discharge (d) = 0.3 - 0.0 0.3 cfs
coefficient of discharge = 0.6
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)^1/2 0.18 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 53.6 cfs L = 8 ft
Q=CwLH^3/2 H = 1.71 ft
Top of Emergency Spillwc- 1.71 msl
West Johnston High School -20013-5
4
Wet Detention Study front of School-100 year 24 hour
Dftw HWYOWaph
AddRkmel Flow
Peak Inflow = 120.2
Time to Peak = 58.1
72.6105069
L(time min) 0 ! e6)
0 0
3 0.8
6 3.1
9 7.0
12 12.2
35 18.7
18 26.3
21 34.7
24 43.9
27 53.4
30 63.1
33 72.8
36 82.1
39 90.9
42 98.8
45 105.7
48 111.4
51 115.8
54 118.7
57 120.1
60 119.9
63 118.1
66 114.8
69 110.1
72 104.0
75 97.4
78 91.0
81 85.1
84 79.6
87 74.4
90 69.6
93 65.1
96 60.9
99 56.9
102 53.2
105 49.8
108 46.5
ill 43.5
114 40.7
0.0
West Johnston High School -20013-6
Wet Detention study front of School-100 year 24 hour
Stormwater routing
I (time min) 24- Storage egg Outflow Elevation
0 0 0 0.00 0.0 198.00
3 0.8 0 0.00 0.0 198.00
6 3.1 142 0.01 0.0 198.01
9 7.0 706 0.03 0.0 198.03
12 12.2 1961 0.07 0.0 198.07
15 18.7 4158 0.13 0.0 198.13
18 26.3 7516 0.22 0.1 198.22
21 34.7 12230 0.35 0.1 198.35
24 43.9 18461 0.50 0.1 198.50
27 53.4 26329 0.70 0.2 198.70
30 63.1 35912 0.92 0.2 198.92
33 72.8 47240 1.19 0.4 199.19
36 82.1 60264 1.48 2.5 199.48
39 90.9 74586 1.80 6.2 199.80
42 98.8 89824 2.13 11.0 200.13
45 105.7 105627 2.47 16.8 200.47
48 111.4 121623 2.80 23.3 200.80
51 115.8 137493 3.14 38.8 201.14
54 118.7 151354 3.42 83.1 201.42
57 120.1 157757 3.55 109.9 201.55
60 119.9 159597 3.59 118.7 20139
63 118.1 159804 3.59 118.7 201.59
66 114.8 159693 3.59 118.7 201.59
69 110.1 158990 3.58 116.5 201.58
72 104.0 157839 3.55 109.9 201.55
75 97.4 156793 3.53 105.5 201.53
78 91.0 155323 3.50 99.2 201.50
81 85.1 153857 147 93.0 201.47
84 79.6 152437 3.44 87.0 201.44
87 74.4 151101 3.42 83.1 201.42
90 69.6 149536 3.38 75.6 201.38
93 65.1 148455 3.36 72.0 201.36
96 60.9 147215 3.34 68.4 201.34
99 56.9 145852 3.31 63.3 201.31
102 53.2 144702 3.28 58.4 201.28
105 49.8 143771 3.27 56.8 201.27
108 46.5 142505 3.24 52.2 201.24
111 43.5 141485 3.22 49.3 201.22
114 40.7 140448 3.20 46.4 201.20
117 38.0 139409 3.17 42.5 201.17
120 35.6 138611 3.16 41.2 201.16
123 33.3 137596 3.14 38.8 201.14
126 31.1 136601 3.12 36.5 201.12
129 29.1 135626 3.10 34.4 201.10
132 27.2 134668 3.08 32.5 201.08
L= 3.5 58.5
Emergency
3 Spillway Spillway
inch 199.12 201.01
orifice New
0.0
0.0
0.0
0.0
0.0
0.1
0.1
0.1
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
2.3 0.0
5.9 0.0
10.7 0.0
16.5 0.0
22.9 0.0
30.1 8.2
36.6 46.1
39.8 69.6
40.8 77.5
40.8 77.5
40.8 77.5
40.5 75.5
39.8 69.6
39.3 65.8
38.6 60.2
37.8 54.8
37.1 49.5
36.6 46.1
35.7 39.5
35.2 36.3
34.7 33.3
34.0 28.8
33.3 24.6
33.1 23.3
32.4 19.4
32.0 16.9
31.5 14.5
30.8 11.2
30.6 10.2
30.1 8.2
29.7 6.4
29.3 4.7
28.8 3.3
West Johnston High School -20013-7
Wet Detention Study front of School-100 year 24 hour
135 25.4 133717 3.06 30.7 201.06 0.4 28.4
138 23.8 132760 3.04 29.3 201.04 0.4 27.9
141 22.2 131774 3.02 28.1 201.02 0.4 27.5
144 20.8 130721 2.99 27.3 200.99 0.4 26.9
147 19.4 129556 2.97 26.8 200.97 0.4 26.4
150 18.2 128227 2.94 26.2 200.94 0.4 25.8
153 17.0 126786 2.91 25.5 200.91 0.4 25.1
156 15.9 125247 2.88 24.9 200.88 0.4 24.5
159 14.9 123624 2.85 24.3 200.85 0.4 23.9
162 13.9 121927 2.81 23.5 200.81 0.4 23.1
165 13.0 120205 2.77 22.6 200.77 0.4 22.3
168 12.1 118468 2.74 22.0 200.74 0.4 21.7
171 11.4 116689 2.70 21.2 200.70 0.4 20.9
174 10.6 114911 2.66 20.4 200.66 0.4 20.1
177 9.9 113143 2.63 19.9 200.63 0.4 19.5
180 9.3 111356 2.59 19.1 200.59 0.4 18.7
183 8.7 109592 2.55 18.3 200.55 0.4 18.0
186 8.1 107857 2.51 17.6 200.51 0.4 17.2
189 7.6 106155 2.48 17.0 200.48 0.4 16.7
192 7.1 104458 2.44 16.3 200.44 0.4 15.9
195 6.6 102805 2.41 15.7 200.41 0.4 15.4
198 6.2 101166 2.37 15.0 200.37 0.4 14.7
201 5.8 99578 2.34 14.5 200.34 0.4 14.1
204 5.4 98012 2.30 13.8 200.30 0.4 13.5
360 0.2 19556 0.53 0.2 198.53 0.2 0.0
720 0.0 19782 0.54 0.2 198.54 0.2 0.0
1080 0.0 16398 0.45. 0.1 198.45 0.1 0.0
1440 0.0 13379 0.38 0.1 198.38 0.1 0.0
1800 0.0 10679 0.31 0.1 198.31 0.1 0.0
2160 0.0 8341 0.24 0.1 198.24 0.1 0.0
2520 0.0 6432 0.19 0.1 198.19 0.1 0.0
2880 0.0 4901 0.15 0.1 198.15 0.1 0.0
3240 0.0 3760 0.12 0.0 198.12 0.0 0.0
Results of routing the 100 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 118.7 cfs
Peak Stage= 3.59 ft
Water Elevation= 201.59 ms1
Peak Storage = 159804 cf
Design Spillway 199.12 msl
Length of weir 3.5 ft
Emergency Spillway 201.01 msl
Length of Weir 58.5 ft 30 foot emergency spillway plus 32'-3.5' of design
spillway = 30'+28.5'= 58.5'
2.0
0.9
0.2
0.0
West Johnston High School -20013-8
Wet Detention Study front of School-100 year 24 hour
Size Outlet Pipe for Spillway
100 yr. flow for principal spillway = 40.8 cfs
Effective Length of Emergency spillway for outlet pipe = 28.5 ft
Water Surface Elevation for 100 year Storm = 201.59 msl
Top of Emergency Spillway at box = 201.01 msl
Q=CLH"1.5 = 37.8 cfs
Design flow for 100 year storm for outlet pipe = 78.5 cfs
Slope of outlet pipe = 0.005 ftfft
Material of outlet pipe = concrete
n = 0.012
d = 16 (QNS^0.5)"0.375 42.26 inches
Use = 48 inch
West Johnston High School -20013-9
Worksheet
Worksheet for Circular Channel
Project Description
Worksheet Circular Channel - 2- Outlet Pipe for Wet Detention 100yr
Flow Element Circular Channel
Method Manning's Formula
Solve For Channel Depth
Input Data
Mannings Coefficient 0.012
Slope 0.005000 ft/ft
Diameter 48 In
Discharge 78.50 cis
Results
Depth 2.50 ft
Flow Area 8.3 ft=
Wetted Perimeter 7.29 It
Top Width 3.87 ft
Critical Depth 2.68 It
Percent Full 62.4 %
Critical Slope 0.004070 f tft
Velocity 9.51 ft/s
Velocity Head 1.41 ft
Specific Energy 3.90 It
Froude Number 1.15
Maramum Discharc 118.36 cis
Discharge Full 110.03 dfs
Slope Full 0.002545 tuft
Flow Type Supercritical
Project Engineer. Canon INNOVA MEDIA User
c:1..Istonn drainage for west johnston hs.fm2 J.S. Janowski and Associates FlowMaster %e.0 ]614e]
06/08/00 07:47:00 AM m Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA [phone] Page 1 of 1

Inflow outflow hydrograph
140 ...........................................................................................................................................................................................
120 .................................................................................... .........................................--- ....................... ;...................
100 ........................................................................................
80 .................. .................. .. ......... ........ .... .................. ....... .................. .......------•--
U
O
LL
60
40 ............ ........ ..........................i......... .... .................................. ............................................................
20 ............... ................ .................. ................
0
0 15 30 45 60 75 90 105
Time (minutes)
-+- Inflow Hydrograph -*- Outflow Hydrograph
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
2 YR - 24 HOUR
NCDENR BMP
FIRST 1" OF RUNOFF
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
_ 324
.,??>FA GI Nt.?ryy?
yFNt .' 0 %%
1111,
West Johnston High School -20013-1
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions Predevelopment
Total watershed area
Area Impervious C=
Area grass or wooded C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channel flow
Tc=(L"3/H)^0.385
128
Composite C =
Rainfall Intensity = 1= g/(h+T)
Peak Discharge Q=CIA
0.95
0.3
6.7 X
29.00 acres
CN= 98 0.00 acres
CN= 73 29.00 acres
C
1280 feet
51 feet
3.7 inches
OVERLAND
2
E 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School 20013-2
13.3 minutes
0.3
4.2 inches per hr
36.6 cfs
R Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
0.95
0.3
CN=
CN=
C
29.00 acres
98 9.56 acres
73 19.44 acres
C
1280 feet
51 feet
3.7 inches
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))"2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L^3M)"0.385
128
Composite C =
Rainfall Intensity = I = g!(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= VoV(1.37 Qp)
81.2
2.31
1.89 inches
6.7
13.4 minutes
8 9 h
2 132 18
10 203 22
25 246 23
100 302 25
0.51
4.2 inches per hr
62.7 cfs
38.6 minutes
West Johnston High School 20013-3
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Storage Required
Allowable release at impoundment = 36.6 cfs
Peak rate of inflow at impoundment = 62.7 cfs
Sr = (Qi - Qo)Tp 60,364 cf
STAGE STORAGE DATA
surface diff. accum.
Elevation area flu Storm storage Elevation
179.00 0 0 179 0
1.00 4362
180.00 8724 4362 180.00 1
2.00 20960
182.00 12236 25322 182.00 3
2.00 28541
184.00 16305 53863 184.00 5
2.00 37500
186.00 21195 91363 186.00 7
2.00 47429
188.00 26234 138792 188.00 9
Z
C
d
Stowage S LNG o omporte
0 0 ERR ERR 0.00
4,362 1 8.38 0.00 1.00
25,322 3 10.14 1.10 3.06
138,792 9 11.84 2.20 9.00
b= 1.5747347
Ks= 4362
1/b
Z= (S/Ks)^
Predicted Water Surface Elevation= 184.30 feet msl
To capture the first V of runoff
volume= DA x 43560 x 1" 112 106270 cf 186.55 feet msl
set spillway elevation at this elevation
West Johnston High School 20013-4
} f
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation
estimated orifice Center elev.
proposed water surface elev. _
available head (h) _
discharge (d) _
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)"1/2
0.61 afs
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
0.5 -
0.0
179.00 feet msl
179.30 feet ms]
186.55 feet msl
7.25 feet
0.5 cfs
0.6
0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 36.6 cfs stimate L = 8 ft
Q=CwLH^3/2 H = 1.33 ft
Top of Emergency Spiltwc 187.88 msl
5
West Johnston High School 20013-5
T i
Inflow Hydmgraph
Peak Mow -
Tiom to Peak -
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
AddMonal Flow 0.0
62.7
38.6
48.26564414
7 ftim mint
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
2-UM
0
0.9
3.7
8.0
13.8
20.6
28.0
35.6
43.0
49.7
55.3
59.5
62.0
62.7
61.5
58.6
54.0
48.9
44.2
39.9
36.1
32.6
29S
26.7
24.1
21.8
19.7
17.8
16.1
14.5
13.1
11.9
10.7
9.7
8.8
7.9
7.2
6S
5.9
West Johnston High School -20013-6
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
L= 6.5
Stormwater routing
3 Spillway
inch 186.55
L(time min) Q-(-Q Storage 2M Outflow Elevation orifice Wak
0 0 0 0.00 0.0 179.00
3 0.9 0 0.00 0.0 179.00 0.0 0.0
6 3.7 167 0.13 0.0 179.13 0.0 0.0
9 8.0 826 0.35 0.0 179.35 0.0 0.0
12 13.8 2271 0.66 0.1 179.66 0.1 0.0
15 20.6 4734 1.05 0.2 180.05 0.2 0.0
18 28.0 8405 1.52 0.2 180.52 0.2 0.0
21 35.6 13402 2.04 0.3 181.04 0.3 0.0
24 43.0 19762 2.61 0.3 181.61 0.3 0.0
27 49.7 27440 3.22 0.4 182.22 0.4 0.0
30 55.3 36314 3.84 0.4 182.84 0.4 0.0
33 59.5 46187 4.48 0.5 183.48, 0.5 0.0
36 62.0 56806 5.10 0.5 184.10 0.5 0.0
39 62.7 67871 5.71 0.5 184.71 0.5 0.0
42 61.5 79057 6.30 0.6 185.30 0.6 0.0
45 58.6 90029 6.84 0.6 185.84 0.6 0.0
48 54.1 100468 7.33 0.6 186.33 0.6 0.0
51 48.1 110088 7.77 2.6 186.77 0.6 2.0
54 44.2 118277 8.13 9.2 187.13 0.7 8.6
57 39.9 124564 8.40 15.9 187.40 0.7 15.3
60 36.1 128886 8.59 21.3 187.59 0.7 20.7
63 32.6 131544 8.70 24.7 187.70 0.7 24.0
66 29.5 132971 8.76 26.6 187.76 0.7 25.9
69 26.7 133491 8.78 27.2 187.78 0.7 26.6
72 24.1 133385 8.78 27.2 187.78 0.7 26.6
75 21.8 132817 8.75 26.3 187.75 0.7 25.6
78 19.7 132007 8.72 25.3 187.72 0.7 24.6
81 17.8 130993 8.68 24.1 187.68 0.7 23.4
84 16.1 129864 8.63 22.5 187.63 0.7 21.9
87 14.5 128704 8.58 21.0 187.58 0.7 20.4
90 13.1 127537 8.53 19.6 187.53 0.7 18.9
93 11.9 126382 8.48 18.1 187.48 0.7 17.5
96 10.7 125257 8.43 16.7 187.43 0.7 16.1
99 9.7 124178 8.39 15.7 187.39 0.7 15.0
102 8.8 123109 8.34 14.3 187.34 0.7 13.7
105 7.9 122109 8.30 13.3 187.30 0.7 12.6
108 7.2 121143 8.26 12.3 187.26 0.7 11.6
111 65 120219 8.22 11.3 187.22 0.7 10.7
114 5.9 119347 8.18 10.4 187.18 0.7 9.7
117 5.3 118533 8.14 9.5 187.14 0.7 8.8
120 4.8 117782 8.11 8.8 187.11 0.7 8.2
123 4.3 117059 8.08 8.2 187.08 0.7 7.5
126 3.9 116370 8.05 7.5 187.05 0.6 6.9
129 3.5 115720 8.02 6.9 187.02 0.6 6.3
132 3.2 115112 7.99 6.3 186.99 0.6 5.7
West Johnston High School 20013-7
Storm Water Detention Study Behind Athletic Fields-2 year 24 hour-NCDENR BMP
135 2.9 114550 7.97 5.9 186.97 0.6 5.3
138 2.6 114002 7.94 5.4 186.94 0.6 4.7
141 2.4 113504 7.92 5.0 186.92 0.6 4.4
144 2.1 113026 7.90 4.7 186.90 0.6 4.0
147 1.9 112571 7.88 4.3 186.88 0.6 3.7
150 1.7 112140 7.86 4.0 186.86 0.6 3.4
153 1.6 111735 7.84 3.7 186.84 0.6 3.0
156 1.4 111359 7.83 3.5 186.83 0.6 2.9
159 1.3 110982 7.81 3.2 186.81 0.6 2.6
162 1.2 110636 7.79 2.9 186.79 0.6 2.3
165 1.1 110321 7.78 2.8 186.78 0.6 2.1
168 1.0 110011 7.77 2.6 186.77 0.6 2.0
171 0.9 109708 7.75 2.4 186.75 0.6 1.7
174 0.8 109436 7.74 2.2 186.74 0.6 1.6
177 0.7 109173 7.73 2.1 186.73 0.6 1.5
180 0.6 108919 7.72 2.0 186.72 0.6 1.4
183 0.6 108675 7.71 1.9 186.71 0.6 1.2
186 0.5 108442 7.69 1.6 186.69 0.6 1.0
189 0.5 108239 7.69 1.6 186.69 0.6 1.0
192 0.4- 108028 7.68 1.5 186.68 0.6 0.9
195 0.4 107827 7.67 1.4 186.67 0.6 0.8
198 0.3 107638 7.66 1.3 186.66 0.6 0.7
201 0.3 107460 7.65 1.2 186.65 0.6 0.6
204 0.3 107294 7.64 1.1 186.64 0.6 0.5
360 0.0 99184 7.27 0.6 186.27 0.6 0.0
720 0.0 85939 6.64 0.6 185.64 0.6 0.0
1080 0.0 73295 6.00 0.6 185.00 0.6 0.0
1440 0.0 61328 5.36 0.5 184.36 0.5 0.0
1800 0.0 50079 4.71 0.5 183.71 0.5 0.0
2160 0.0 39610 4.06 0.4 183.06 0.4 0.0
2520 0.0 29982 3.40 0.4 182.40 0.4 0.0
2880 0.0 21292 2.74 0.4 181.74 0.4 0.0
3240 0.0 13655 2.06 0.3 181.06 0.3 0.0
3600 0.0 7282 1.38 0.2 180.38 0.2 0.0
3960 0.0 2495 0.70 0.1 179.70 0.1 0.0
4320 0.0 213 0.15 0.0 179.15 0.0 0.0
4680 0.0 213 0.15 0.0 179.15 0.0 0.0
Results of routing the 2 year 24 hour storm
Use orifice = 3.0 inches
Peak outflow = 273 cfs
Peak Stage= 8.78 ft
Water Elevation= 187.78 msl
Peak Storage = 133491 cf
Design Spillway 186.SS msl
Length of weir 6.S ft
West Johnston High School -20013-8
i
Inflow outflow hydrograph
.
70 ............................................
so ......................... .................................................. ................... .................
50 ................• ..------•---- - •-------....----.. .. ......... .................. ...-----.......... ................... ..............._
40 .................. ...... ...... ................• •---.....-- .................. .................. ...---•-----....... ........_.......
o?
L
30 .................. ---.......... .................. .................. . ---..... .----.-•--------- .........---.----- .................
....................
20 ------------------ ........................... ........................ .................. ........................ ...:.................... ........................
10 ................... <........... ... .................. ................ ........ ...
0
0 15 30 45 60 75 90 105
Time (minutes)
?- Inflow Hydrograph -A- Outflow Hydrograph
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
STORM WATER DETENTION
FOR
WEST JOHNSTON HIGH SCHOOL
BEHIND ATHLETIC FIELDS
100 YR - 24 HOUR
NCDENR BMP
FIRST T' OF RUNOFF
20013
5-25-00
prepared by
J.S. Janowski and Associates
105 C East Victoria Court
Greenville, NC 27858
1-252-756-8918
West Johnston High School 20013-1

Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions Predevelopment
Total watershed area
Area Impervious C=
Area grass or wooded C=
SCS Soil Group
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Time of Concentration
channelflow
Tc=(L"3/H)"0.385
128
Composite C =
Rainfall Intensity = I = gt(h+T)
Peak Discharge Q--CIA
0.95
0.3
6.7 X
29.00 acres
CN= 98 0.00 acres
CN= 73 29.00 acres
C
1280 feet
51 feet
8.4 inches
OVERLAND
2
13 9 h
2 132 18
10 203 22
25 246 23
100 302 25
West Johnston High School -20013-2
13.3 minutes
0.3
7.9 inches per hr
68.5 cfs

Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Site Conditions postdevelopment
Total watershed area
Area Impervious C=
Area grass C=
SCS Soil Group (Craven)
Hydraulic Length
Vertical Relief
24-hr, 2 yr rainfall
Design Hydrograph Formulation
Composite CN
S=1000/CN -10
Runoff
RO=(P-0.2(S))^2 / (P+0.8(s))
Time of Concentration
channel flow (not overland)
Tc=(L"3/H)^0.385
128
Composite C =
Rainfall Intensity = I = g/(h+T)
Peak Discharge Q=CIA
Time to peak
Tp= Vol/(1.37 Qp)
0.95
0.3
6.7
CN= 98
CN= 73
C
B 9 h
2 132 18
10 203 22
25 246 23
100 302 25
29.00 acres
9.56 acres
19.44 acres
C
1280 feet
51 feet
8.4 inches
81.2
2.31
6.15 inches
13.4 minutes
0.51
7.9 inches per hr
117.3 cfs
67.1 minutes
West Johnston High School -20013-3

Storage Required
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Allowable release at impoundment = 68.5 cis
Peak rate of inflow at impoundment = 117.3 cis
Sr = (Qi - Qo)Tp 196,465 cf
STAGE STORAGE DATA
surface diff. accum.
Elevation am 21a stomp, storage Elevation
179.00 0 0 179 0
1.00 4362
180.00 8724 4362 180.00 1
2.00 20960
182.00 12236 25322 182.00 3
2.00 28541
184.00 16305 53863 184.00 5
2.00 37500
186.00 21195 91363 186.00 7
2.00 47429
188.00 26234 138792 188.00 9
Z
d
Storage Stage LN(stomy) L N(S ) Compute
SUp
0 0 ERR ERR 0.00
4,362 1 8.38 0.00 1.00
25,322 3 10.14 1.10 3.06
138,792 9 11.84 2.20 9.00
b= 1.5747347
Ks= 4362
1/b
Z= (S/Ks)^
Predicted Water Surface Elevation= 190.22 feet msl
To capture the first 1" of runoff
volume= DA x 43560 x 1" !12 105270 cf 186.55 feet msi
set spillway elevation at this elevation
West Johnston High School -20013-4

Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Release rate over 48 hours=
Size Outlet Device for Control Structure
invert elevation =
estimated orifice center elev.
proposed water surface elev. _
available head (h) _
discharge (d) _
coefficient of discharge =
Determine the orifice diameter
Orifice equation
Q = Cd(A)(2gh)"1/2
0.61 cfs
pond will drain in greater than 2 days
in accordance with NCDENR BMP
This will provide removal of 50% TSS
with outlet swales TSS removal will be
at least 85%
0.5 -
0.0
179.00 feet msl
179.30 feet msl
186.55 feet msl
7.25 feet
0.5 cfs
0.6
0.22 feet
SAY 3 inches
Determine Weir length for 2 year 24 hour discharge
Q = 68.5 cfs stimate L = 8 ft
Q=CwLH"3/2 H = 2.01 ft
Top of Emergency Spillwc 188.56 msi
5
West Johnston High School -20013-5
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Peak Inflow
lime to Peak =
Adddonal Flow
1173
67.1
83.92897444
T Mme oriel
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
51
54
57
60
63
66
69
72
75
78
81
84
87
90
93
96
99
102
105
108
111
114
RI AI
0
0.6
2.3
5.1
9.0
13.8
19.6
26.1
33.2
40.9
48.9
57.0
65.2
733
81.1
88.5
95.2
101.3
1065
110.8
114.0
116.2
117.2
117.1
115.8
113.4
109.9
105.5
100.1
94.5
89.1
84.1
793
74.9
70.6
66.7
62.9
59.3
56.0
0.0
West Johnston High School 20013-6
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
L= 6.5 55.5
Stormwater routing Emergency
3 Spillway Spillway
inch 18635 187.78
T (time min) QJ.cK Storms, O utflow Elevation orifice wlr W-Ift
0 0 0 0.00 0.0 179.00
3 0.6 0 0.00 0.0 179.00 0.0 0.0
6 2.3 104 0.09 0.0 179.09 0.0 0.0
9 5.1 517 0.26 0.0 179.26 0.0 0.0
12 9.0 1438 0.49 0.0 179.49 0.0 0.0
15 13.8 3057 0.80 0.1 179.80 0.1 0.0
18 19.6 5526 1.16 0.2 180.16 0.2 0.0
21 26.1 9016 1.59 0.2 180.59 0.2 0.0
24 33.2 13666 2.07 0.3 181.07 0.3 0.0
27 40.9 19593 2.60 0.3 181.60 0.3 0.0
30 48.9 26886 3.17 0.4 182.17 0.4 0.0
33 57.0 35609 3.79 0.4 182.79 0.4 0.0
36 65.2 45798 4.45 0.5 183.45 0.5 0.0 0.0
39 73.3 57458 5.14 0.5 184.14 0.5 0.0 0.0
42 81.1 70565 5.86 0.5 184.86 0.5 0.0 0.0
45 88.5 85070 6.60 0.6 185.60 0.6 0.0 0.0
48 95.2 100891 7.35 0.6 186.35 0.6 0.0 0.0
51 101.3 117924 8.12 9.0 187.12 0.7 8.4 0.0
54 106.5 134533 8.82 40.0 187.82 0.7 27.9 11.4
57 110.8 146511 9.31 110.4 188.31 0.7 45.5 64.2
60 114.0 146571 9.32 112.7 188.32 047 45.9 66.1
63 116.2 146817 9.33 114.9 188.33 0.7 46.3 67.9
66 117.2 147049 9.34 117.1 188.34 0.7 46.7 69.8
69 117.1 147061 9.34 117.1 188.34 0.7 46.7 69.8
72 115.8 147050 9.34 117.1 188.34 0.7 46.7 69.8
75 113.4 146810 9.33 114.9 188.33 0.7 46.3 67.9
78 109.9 146544 9.32 112.7 188.32 0.7 45.9 66.1
81 105.5 146056 9.30 108.2 188.30 0.7 45.1 62.4
84 100.1 145555 9.28 103.9 188.28 0.7 44.3 58.9
87 94.5 144871 9.25 97.5 188.25 0.7 43.2 53.6
90 89.1 144316 9.23 93.41 188.23 0.7 42.4 50.3
93 84.1 143548 9.19 85.3 188.19 0.7 40.9 43.7
96 79.3 143326 9.19 85.3 188.19 0.7 40.9 43.7
99 74.9 142250 9.14 75.7 188.14 0.7 39.1 36.0
102 70.6 142097 9.14 75.7 188.14 0.7 39.1 36.0
105 66.7 141183 9.10 68.4 188.10 0.7 37.6 30.1
108 62.9 140865 9.09 66.7 188.09 0.7 37.2 28.7
111 59.3 140187 9.06 61.5 188.06 0.7 36.1 24.7
114 56.0 139798 9.04 58.2 188.04 0.7 35.4 22.1
117 52.8 139402 9.03 56.6 188.03 0.7 35.1 20.8
120 49.9 138729 9.00 51.9 188.00 0.7 34.0 17.2
123 47.0 138364 8.98 48.9 187.98 = 0.7 33.3 14.9
126 44.4 138031 8.97 47.4 187.97 0.7 33.0 13.8
129 41.9 137482 8.95 44.6 187.95 0.7 32.3 11.7
132 39.5 136988 8.93 41.9 187.93 0.7 31.6 9.7
West Johnston High School -20013-7
Storm Water Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
135 3
37 136553 8.91 39.4 187.91 0.7 30.9 7.8
138 .
2
35 136176 8.89 37.0 187.89 0.7 30.2 6.1
141 .
2
33 135854 8.88 35.8 187.88 0.7 29.9 5.3
144 .
31
3 135381 8.86 33.7 187.86 0.7 29.2 3.8
147 .
6
29 134962 8.84 31.7 187.84 0.7 28.5 2.4
150 .
27.9 134582 8.83 30.8 187.83 0.7 28.2 1.9
153 26.3 134067 8.80 28.4 187.80 0.7 27.2 0.5
156 24.8 133697 8.79 27.7 187.79 0.7 26.9 0.2
159 23.4 133173 8.77 26.9 187.77 0.7 26.2 0.0
162 22.1 132544 8.74 26.0 187.74 0.7 25.3
165 20.9 131851 8.71 25.0 187.71 0.7 24.3
168 19.7 131104 8.68 24.1 187.68 0.7 23.4
171 18.6 130314 8.65 23.1 187.65 0.7 22.5
174 17.5 129492 8.61 21.9 187.61 0.7 21.3
177 16.5 128700 8.58 21.0 187.58 0.7 20.4
180 15.6 127$91 8.54 19.9 187.54 0.7 19.2
183 14.7 127127 8.51 19.0 187.51 0.7 18.3
186 13.9 126360 8.48 18.1 187.48 0.7 17.5
189 13.1 125597 8.45 17.3 187.45 0.7 16.6
192 12.4 124844 8.41 16.2 187.41 0.7 15.5
195 11.7 124156 8.39 15.7 187.39 0.7 15.0
198 11.0 123440 8.35 14.6 187.35 0.7 13.9
201 10.4 122795 8.33 14.1 187.33 0.7 13.4
204 9.8 122133 8.30 13.3 187.30 0.7 12.6
360 0.5 89395 6.81 0.6 185.81 0.6 0.0
720 0.0 86908 6.69 0.6 185.69 0.6 0.0
1080 0.0 74222 6.05 0.6 185.05 0.6 0.0
1440 0.0 62201 5.41 0.5 184.41 0.5 0.0
1800 0.0 50894 4.76 0.5 183.76 0.5 0.0
2160 0.0 40362 4.11 0.4 183.11 0.4 0.0
2520 0.0 30667 3.45 0.4 182.45 0.4 0.0
2880 0.0 21903 2.79 0.4 181.79 0.4 0.0
3240 0.0 14181 2.11 0.3 181.11 0.3 0.0
3600 0.0 7707 1.44 0.2 180.44 0.2 0.0
3960 0.0 2760 0.75 0.1 179.75 0.1 0.0
Results of routing the
Use orifice =
Peak outflow =
Peak Stage=
Water Elevation=
Peak Storage =
Design Spillway
Length of weir
Emergency Spillway
Length of Weir
100 year 24 hour storm
3.0 Inches
117.1 cfs
9.34 ft
188.34 msl
147061 cf
186.55 msl
6.5 ft
187.78 msl
55.5 ft
West Johnston High School -20013-8
i
Sto?vvater Detention Study Behind Athletic Fields-100 year 24 hour-NCDENR BMP
Size Outlet Pipe for Spillway
100 yr. flow for principal spillway =
Effective Length of Emergency spillway for outlet pipe =
Water Surface Elevation for 100 year Storm =
Top of Emergency Spillway at box =
Q=CLH^1.5 =
Design flow for 100 year storm for outlet pipe =
Slope of outlet pipe =
Material of outlet pipe =
n=
d = 16 (QNS"0.5)^0.375
Use =
46.7 cfs
25.5 ft
188.34 msl
187.78 msl
32.1 cfs
78.7 cfs
0.005 ft/ft
concrete
0.012
42.30 inches
48 inch
West Johnston High School 20013-9
t
Worksheet
Worksheet for Circular Channel
Project Description
Worksheet Circular Channel - 3- Outlet Pipe for Extended Dry Detention 100 yr
Flow Element Circular Channel
Method Manning's Formula
Solve For Channel Depth
Input Data
Mannings Coefficient 0.012
Slope 0.005000 ft/ft
Diameter 48 in
Discharge 78.70 cis
Results
Depth 2.50 ft
Flow Area 8.3 ft2
Wetted Perimeter 7.30 ft
Top Width 3.87 ft
Critical Depth 2.69 ft
Percent Full 62.5 %
Critical Slope 0.004076 ft/ft
Velocity 9.52 ft/s
Velocity Head 1.41 ft
Specific Energy 3.91 ft
Froude Number 1.15
Mabmum Discharc 118.36 cis
Discharge Full 110.03 cfs
Slope Full 0.002558 ft/ft
Flow Type Supercritical
Project Engineer: Canon INNOVA MEDIA User
cA ..1stonn drainage for west johnston hs.fm2 J.S. Janowski and Associates FlowMaster v6.0 (614e]
06/08/00 08:03:00 AM 0 Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA [phone] Page 1 of 1
t 4 1 1
Inflow outflow hydrograph
....................:. .
........
120 ................................................ .......................;.............
100 ` ................:............................................................... ...................
................. ------............ .. ..... ............
.................. ...............................................
80
60 € ........ ..................................................................
...
........ ................ 40-
.......................
20 .................. ....... ..................
0 105
0 15 30 45 60 75 90
Time (minutes)
-+- Inflow Hydrograph -- Outflow Hydrograph
Talg®
? Ana. /L? JOB NO SH/
. s?. CLIENT ?r. DATE
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CONSULTING ENGINEERS
SUBJECT
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302 Sycamore Branches Close • Winterviile, NC 28590 • 919-756-8918

v y 1 r
Worksheet
Worksheet for Trapezoidal Channel
Project Description
Worksheet Trapezoidal Channel -1-Main Entry Road
Flow Element Trapezoidal Channel
Method Manning's Formula
Solve For Channel Depth
Input Data
Mannings Coefficient 0.030
Slope 0.025000 fttft
Left Side Slope 3.00 H : V
Right Side Slope 3.00 H : V
Bottom Width 1.00 ft
Discharge 1.10 cfs
Results
Depth 0.26 It
Flow Area 0.5 ft2
Wetted Perimeter 2.62 ft
Top Width 2.54 It
Critical Depth 0.26 ft
Critical Slope 0.024268 ftfft
Velocity 2.43 ftts
Velocity Head 0.09 ft
Spec Energy 0.35 It
Froude Number 1.01
Flow Type Supercritical
Project Engineer. Canon INNOVA MEDIA User
c:\..lztorm drainage for west johnston hs.fm2 J.S. Janowski and Associates FlowMaster v6.0 [614e]
06107100 03:33:50 PM 0 Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA [phone] Page 1 of 1
Worksheet
Worksheet for Trapezoidal Channel
Project Description
Worksheet Trapezoidal Channel - 2- Swales by pump station
Flow Element Trapezoidal Channel
Method Manning's Formula
Solve For Channel Depth
Input Data
Mannings Coefficient 0.030
Slope 0.050000 fttft
Left Side Slope 3.00 H : V
Right Side Slope 3.00 H : V
Bottom Width 1.00 ft
Discharge 1.00 cis
Results
Depth 0.20 ft
Flow Area 0.3 ftz
Wetted Perimeter 2.29 ft
Top Width 2.22 ft
Critical Depth 0.24 ft
Critical Slope 0.024596 fttft
Velocity 3.04 I'tts
Velocity Head 0.14 ft
Specific Energy 0.35 ft
Froude Number 1.39
Flow Type Supercritical
Project Engineer. Canon INNOVA MEDIA User
c:\..\storm drainage for west johnston hs.fm2 J.S. Janowski and Associates FlowMaster %6.0 [614e]
06108/00 07:14:44 AM ®Haestad Methods, inc. 37 Brookside Road Waterbury, CT 06708 USA [phone] Page 1 of 1
JOB NO
J.. jari6wski -JOB .

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ASS CLIENTS' ` BATE
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SUBJECT DES BY
CONSULTING ENGINEERS n
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302 Sycamore Branches Close • Winterville, NC 28590 • 919-156-8918
?4.
Worksheet
Worksheet for Circular Channel
Project Description
Worksheet Circular Channel -1- Slope Drain Calculation
Flow Element Circular Channel
Method Manning's Formula
Solve For Channel Depth
Input Data
Mannings Coefficient 0.012
Slope 0.005000 ft/ft
Diameter 12 in
Discharge 2.30 cis
Results
Depth 0.70 ft
Flow Area 0.6 ft2
Wetted Perimeter 1.99 ft
Top Width 0.91 ft
Critical Depth 0.65 It
Percent Full 70.4 %
Critical Slope 0.006235 ft/ft
Velocity 3.90 ft/s
Velocity Head 0.24 ft
Specific Energy 0.94 ft
Froude Number 0.85
Maximum DischaN 2.94 cis
Discharge Full 2.73 cis
Slope Full 0.003551 fttft
Flow Type Subcritical
Project Engineer: Canon INNOVA MEDIA User
c:G..'.storm drainage for west johnston hs.fm2 J.S. Janowski and Associates FlowMaster v6.0 [614e]
06/08100 07:18:01 AM Q Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA [phone] Page 1 of 1

302 Sycamore Branches Close • Winterville, NC 28590 • 919-756.8918 1`ri
Project No. DWQ
Project Name: West Johnston High Pond #2
SUBMITTED DESIGN: REQUIRED DESIGN:
elevations status
Bottom of Basin (ft) 0
Permanent Pool (ft) 179 179 ft. depth check depth
Temporary Pool (ft) 186.55 7.55 ft. depth ok
areas
Permanent Pool SA (sq ft)
0
#DIV/0! sq. ft.
#DIV10!
Drainage Area (ac) 38.56
Impervious Area (ac) 9.56 24.8%
-
volumes
Permanent Pool (cu ft) 0
Temporary Pool (cu ft) 105270 38231 cu. ft. ok
Forebay (cu ft) 0 #DIV/0! % #DIV10!
other parameters
SA/DA 0 #DIV/0! -
Orifice Diameter (in) 3 0.46 cfs drawdown -
Design Rainfall (in) 1 2.7 day drawdown ok
Linear Interpolation of Correct SAIDA***
179 ft. Permanent Pool Depth
% Impervious SA/DA from Table
Next Lowest 1 01
Project Impervious 24.8 #DIV/0!
Next Highest 1
r r
oq? err?
DP
/,i?

Hits associates
ARCHITECTURE i ENGINEERING / PLANNING
TO: NCDENR - Division of VI
1621 Mail Service Center
Raleigh, NC 27699-1621
ATTN: Mr. John Dorney

We are sending via UPS the following plans:
LETTER of TRANSMITTAL
FE: June 9, 2000
{
r,
JUN 14 2000
GROUP
-MAWS 'West Johnston SECTION
'OPIES _DWG DATE DESCRIPTION NOTE
3sets Storm Water Management Calcs
3sets Site Plans listed below
This information is transmitted forapproval unless noted otherwise.
REMARKS:
Drawings:
0001-Overall Site Key Plan
0002-Site Phasing Plan
C201-Site Grading and Erosion Control - South
C202-Site Grading and Erosion Control - North
C203-Site Grading and Erosion Control - Entrance
C401-Site Details: Storm Sewer/ Sanitary Sewer
C402-Site Details: General Notes / Erosion Control / Silt fence / End-of-day measures
C403-Site Details: Storm Water Detention Boxes
C404-Site Details: Wet Detention / Storm Water Detention Ponds
C405-Site Details: Curb and Gutter / Asphalt & base / Parking
C406-Site Details: Athletic Field Improvements
C407-Site Details: Athletic Field Improvements / Misc.
SIGNED(D??*
: Todd Smith
copy: Steve Janowski, P.E.
Mr. Tom Davis, Johnston County Schools
Mr. Ray Debruhl, TPFG
file
1530 East Fourteenth Street / Greenville, NC 27858 / tel [phone] / fax [phone] / e-mail: [e-mail]

Project No. DWQ
Project Name: West Johnston High Pond #1
SUBMITTED DESIGN..- REQUIRED DESIGN.
elevations status
Bottom of Basin (ft) 194
Permanent Pool (ft) 198 4 ft. depth ok
Temporary Pool (ft) 199.12 1.12 ft. depth ok
areas
Permanent Pool SA (sq ft) 35607 19436 sq. ft. ok
Drainage Area (ac) 23
Impervious Area (ac) 13.11 57.0%
-
volumes
Permanent Pool (cu ft) 0
Temporary Pool (cu ft) 47005 47005 cu. ft. ok
Forebay (cu ft) 0 #DIV/O! % #DIY/0!
other parameters
SA/DA 0 1.94 -
Orifice Diameter (in) 3 0.18 cfs drawdown -
Design Rainfall (in) 1 3.1 day drawdown ok
Linear Interpolation of Correct SAIDA * * *
K
Impervious
Next Lowest 50
Project Impervious 57.0
Next Highest 60
4 ft. Permanent Pool Depth
SA/DA from Table
1.73
1.94
2.03
,71

State of North Carolina ..
Department of Environme
:. lr4 Natural resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
Mr. Tom Davis
NC ENR
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
May 8, 2000
Johnston County
DWQ Project #: 000404
APPROVAL OF 401Quality Certification and ADDITIONAL CONDITIONS and Neuse River Buffer Rules
Johnston County Board of Education
Post Office Box 1336
Smithfield, NC 27577
:Dear Mr. Davis:
You have our approval, in accordance with the attached conditions and those listed below, to impact 0.40 acres of wetlands. 95
linear feet of stream for the purpose of constructing a road crossing for the new West Johnson High School at SRI 330 near SR1382 as
you described ir your revised application dated May 4, 2000. After reviewing your application, we have decided that this fill is covered
by General Water Quality Certification Number 3102. This certification allows you to use Nationwide Permit Number 14 when the
Corps of Engineers issues it. This approval is also valid for the Neuse River buffer rules (15A NCAC 2B .033). In addition, you shouid
get any other federal, state or local permits before you go ahead with your project including (but not limited to) Sediment and Erosion
Control, Coastal Stormwater, Non-Discharge and Water Supply Watershed regulations. This approval will expire when the
accompanying 404 or CAMA permit expires unless otherwise specified in the General Certification.
This approval is only valid for the purpose and design that you described in your application except as modified below. If you
change your project, you must notify us and you may be required to send us a new application.. If the property is sold, the new owner
must bc giv.r a copy of this Certification and approval letter and is thereby responsible for complying with all conditions. If total
wetland fills for this project (now or in the future) exceed one acre, compensatory mitigation may be required as described in 15A
NCAC 2H .0506 (h) (6) and (7). This approval shall expire when the corresponding Nationwide Permit expires or.as otherwise provided
in the General Certification. I-or this approval to be valid, you musi follow the conditions listed in the attached certification and any
additional conditions listed below.
1. Deed notifications or similar mechanisms shall be placed on all remaining jurisdictional wetlands and waters or areas within 50
feet of all streams and ponds to notify the state in order to assure compliance for future wetland and/or water impact. These
mechanisms shall be put in place within 30 days of the date of this letter or the issuance of the 404 Permit (whichever is later,.
?. Stormwater shall be directed to flow at non-erosive velocities across the entire protected stream buffers.
3. An additional condition is that a final, written stormwater management plan shall be approved by this Office before the impacts
specified in this Certification occur. The stormwater management plan must include plans and specifications for stormwater
management facilities designed to remove 85% TSS according to the most recent version of the NC DENR,Stormwater Best
Managectent Practices Manual. Also, before any permanent building is occupied at the subject site, the facilities, as approved by
this Office, shall be constructed and operational, and the stormwater management plan, as approved by this Office, shall be
implemented
If you do not accept any of the conditions of this certification, you may ask for an adjudicatory hearing. You must act within 60
days of the date that you receive this letter. To ask for a hearing, send a written petition, which conforms to Chapter 150B of the North
Carolina General Statutes to the Office of Administrative Hearings, P.O. Box 27447, Raleigh, N.C. 27611-7447. This certification and
its conditions are final and binding unless you ask for a hearing.
T} is letter completes the review of the Division of Water Quality under Section 401 of the Clean Water Act. If you have any
questions, please telephone John Dorney at 919-733-9646. ; ,
inc„ e y,l
Steven
Attachment
cc: Carps of Engineers Raleig, a Fic;ld Office—
J
Ra?cigh DWQ Re;?oval Office
Raleigh Division of Land Resources'
Merle Hall; Southwind Surveying & engineering
File copy
Central Files
Todd .*St. John
Divisicr. ^of Water C;uality o Non-Discharge Branch
162, Mail Seivice.Center Raleigh NC 27669-1621 Telephone [phone]
An Equal Opportunity Affirmative Action Employer
50%a recycled/10%a post consumer paper
FAX # [phone]
SOUTHWIND
SURVEYING AND ENGINEERING
201 Glen Road
Garner, North Carolina 27529
Phone: [phone] L.
Fax: [phone]
TO j;2m
4c- I%1Vt j n"d0I;FrU ATEr44 t''M
4%4vt F;E95r* Ce61G.?.
%::?% 6-C Fw--M, K4C- 74 77
LIEUTEM orF TRUSEDUML
DATE
ATTENTIO
WE ARE SENDING YOU ached Of ,vte cover via
? Shop drawings ? Prints ? Plans
? Copy of letter ? Change order ?
the following items:
? Samples ? Specifications
COPIES DATE NO.
Figoem> DESCRIPTION
.z " W
THESE ARE TRANSMITTED as checked below:
or approval ? Approved as submitted ? Resubmit copies for approval
? For your use ? Approved as noted ? Submit copies for distribution
? As requested ? Returned for corrections ? Return corrected prints
? For review and comment ?
? FOR BIDS DUE 19 -El PRINTS RETURNED AFTER LOAN TO US
REMARKS
COPY TO 1-1LC7
SIGNED:
If enclosures are not as noted, kindly notify us at once.
4c,
ss ?
l?

,S"q4mL,jjQ-,--
ud-eA

sek
4?? AQ? y-4&
/C AI /J A 1 l
40 11 t,"S C
DtiVQ ID: CORPS ACTION ID:
NATIONWIDE PER;tifIT REQUESTED (PROVIDE NATIONWIDE PERyIIT #)
PRE-CONSTRUCTION NOTIFICATION APPLICATION
, FOR NATIONWIDE PERMITS THAT REQUIRE:
1) NOTIFICATION TO THE CORPS OF ENGINEERS
2) APPLICATION FOR SECTION 401 CERTIFCATION
3) COORDINATION WITH THE NC DIVISION OF COASTAL MANAGEMENT
SEND THE ORIGINAL AND (1) COPY OF THIS COMPLETED FORM TO THE APPROPRIATE
FIELD OFFICE OF THE CORPS OF ENG21EERS (SEE AGENCY ADDRESSES SHEET). SEVEN
(7) COPIES MUST BE SENT TO THE NC DIVISION OF WATER
QUALITY, ATTN: JOHN DORNEY, 4401 REEDY CREEK ROAD,
RALEIGH NC 27607. PLEASE PRINT OR TYPE.
1. OWNER'S NAME: JC L,5-,C eJ C,,A9 i?ZZ 7 CIE ic1?TT?.?-4
2. MAILING ADDRESS: F0 i gnY- F?-
SUBDIVISION NAME
CITY: Svc rTliFl STATE: t1l• G, ZIP CODE: Z7 V?5'?7
PROTECT LOCATION ADDRESS, INCLUDING SUBDIVISION NANIE (IF DIFFERENT FROM
MAILING ADDRESS ABOVE): ?t`l it C S i?? n?Xtv?nA`iELy 4Z?-
3. TELEPHONE NUMBER: (HOivfE) (WORK)gL '?c03
4. IF.APPLICABLE: AGEN"T"S N.?N(E OR RESPONSIBLE CORPORATE OFFICIAL. ADDRESS.
PHONE NZLN IBER:
--- E" 1 ?? ?? Pal C (t s'-tt ?1(- 2-7j5-7`7
C J lam) 'E-1:3 1- -CL651
5 LOC.AT(ON OF WORK (PROVIDE .A .MAP. PREFERABLY .-\ COP%' OF USGS TOPOGRAPHIC
M.- P OR AERIAL PHOTOGRAPHY ?VITH SCALE):
COUNTY V<5fr4E nt-A - NE.kREST TO?VN l l l? ?? .1
SPECIFIC LOCATION (INCLUDE ROAD NUMBERS. LANDNIARKS. ECT.)
?c?? ?? ?T? tr?t?'?-sc?'T[cr.! ?=? 1-1-,G• S.P, . t?-??-? ? rl-.C..S. o`?, f ?8?'
6. IMPACTED OR NEAREST STREAM RIVER: 1??1E 1?15?^'t ': ?OG.64
RIVER BASIN: KIE;u,Se?
7a. IS PROJECT LOCATED NEAR WATER CLASSIFIED AS TROUT, TIDAL SALTWATER, (SA),
HIGH QUALITY WATERS (HQW), OUTSTANDING RESOURSE WATERS (ORW), WATER
SUPPLY (WS-I OR WS-In? YES ( ) NO (tj IF YES, EXPLAIN:
7b. IS THE PROJECT LOCATED WITHIN A NORTH CAROLINA DIVISION OF COASTAL
MANAGEMENT AREA OF ENVIROMENTAL CONCERN (AEC)? YES ( ) NO (? )
7c. IF THE PROJECT IS LOCATED WITHIN A COASTAL COUNTY (SEE PAGE 7 FOR LIST OF
COASTAL COUNTIES). WHAT IS THE LAND USE PLAN (LUP) DESIGNATION?
8a. HAVE ANY SECTION 404 PERMITS BEEN PREVIOUSLY REQUESTED FOR USE ON THIS
PROJECT? YES ( ) NO ( ) IF YES, PROVIDE ACTION I.D. NUMBER OF PREVIOUS
PERMIT AND ANY ADDITIONAL INFORMATION (INCLUDE PHOTOCOPY OF 401
CERTIFICATION):
8b. ARE ADDITIONAL PERMIT REQUESTS EXPECTED FOR THIS PROPERTY IN THE
FUTURE? YES ( ) NO ( ) IF YES. DESCRIBE ANTICIPATED WORK:
9a. ESTIMATED TOTAL. NUNiBERS OF ACRES IN TRACT OF LAND: i © l ,
9b. ESTIMATED TOTAL. NLti(BER OF ACRES OF WETLA.vDS LOCATED ON PROJECT SITE:
I Zl (p,
10a. NUN(BER OF ACRES OF WETL kNDS IL(PACTEE,DD BY THE PROPOSED PROJECT BY:
0' -M'
FILLING: _ n ©v?
FLOODING:
DRAINAGE :
EXCAVATION:
OTHER:
TOTAL ACRES TO BE IMPACTED:
10b. (1) STREAM CHANNEL TO BE IN PACTED BY THE PROPOSED PROJECT (IF
RELOCATED, PROVIDE DISTANCE BOTH BEFORE AND AFTER RELOCATION:
LENGTH BEFORE: -1 ?-) FT AFTER: FT
v WIDTH BEFORE (based on normal high water contours):
FT
AVERAGE DEPTH BEFORE: FT AFTER: FT
(2) STREAM CHANNEL IMPACTS WILL RESULT FROM: (CHECK ALL THAT APPLY)
OPEN CHANNEL RELOCATION: PLACEMENT OF PIPE IN CH,,kNNEL: , ?
CHANNEL EXCAVATION: COONSTRUCTION OF A DA.M/FLOODl tG:
OTHER:
11. IF CONSTRUCTION OF A POND IS PROPOSED, WHAT IS THE SIZE OF THE WATERSHED
DRAINING TO THE POND?
POND SURFACE AREA?
WHAT IS THE EXPECTED
12. DISCTIPTION OF PROPOSED WORK INCLUDING DISCUSSION OF TYPE OF MECHANICAL
EQUIPMENT TO BE USED? (ATTACH PLANS; 81/2 BY 11 DRAWINGS ONLY)
??ytSi"7 G#?c rSSc ?ILF ^T'? ?'+?= 4 E `I? t? [k1-THE ?t'?"(1???

13. PLJWOSE OF PROPOSED WORK:
l4. STATE REASONS WHY IT IS BELIEVED THAT THIS ACTIVITY MUST BE CARRIED OUT IN
WETLANDS ( INCLUDE ANY :V[EASL,'RES TAKEN TO :?IINI?IIZE WETLAND IN[PACTS)
?C? <,Sr-S 'Tt-tE ?r?t??-?c ?^?C?? ©a-`?'zt?t?? Gi-?s?5t ??C-c--?-?t
GP,? tS
15. YOU ARE REQUIRED TO CONTACT THE US FISH AND WILDLIFE SERVICE AND/OR
NATIONAL ?iLARI1"IE FISHERIES SERIVE REGARDING THE PRESENCE OF ANY FEDERALY
LISTED OR PROPOSED FOR LISTING ENDANGERED OR THREATENED SPECIES OR
CRITICAL. HABITAT IN THE PERMIT AREA THAT ?IAY BE AFFECTED BY THE PROPOSED
PROJECT. DATE CONTACTED: _
16. YOU ARE REQUIRED TO CONTACT THE STATE HISTORIC PRESERVATION OFFICER
(SHPO) REGARDING THE PRESENCE OF HISTORIC PROPERTIES IN THE PERMIT AREA
WHICH MAY BE AFFECTED BY THE PROPOSED PROJECT. DATE CONTACTED
17. DOES THE PROJECT INVOLVE AN EXPENDITURE OF PUBLIC FUNDS OT THE USE OF
PUBLIC (STATE) LAND? YES ( ) NO (&,< (IF NO, GO TO' 16)
a. IF YES, DOES THE PROJECT REQUIRE PREPERATION OF AN ENVIRONMENTAL
DOCUMENT PURUANT TO THE REQUIREMENTS OF THE NORTH CAROLINA
ENVIRONI fENTAL POLICY ACT? YES( ) NO ( )
b. IF YES, HAS THE DOCUMENT BEEN REFIEWED THROUGH THE NORTH CAROLINA
DEPARTMENT OF ADMINISTRATION STATE CLEARINGHOUSE YES ( ) NO ( " )
IF ANSWER 17b IS YES, THEN SUBMIT APPROPRIATE DOCUMENTATIONFROM THE STATE
CLEARINGHOUSE WITH THE NORTH CAROLINA ENVIRONMENTAL POLICY ACT.
QUESTIONS REGARDING THE STATE CLEARINGHOUSE REVIEW PROCESS SHOULD BE
DIRECTED TO MS. CHRYS BAGGETT, DIRECTOR STATE CLEARINGHOUSE, NORTH
CAROLINA DEPARTMENT OF ADMINISTRATION, 116 WEST JONES STREET, RALEIGH,
NORTH CAROLINA 27603-8003, TELEPHONE [phone].
18. THE FOLLOWING ITEMS SHOULD BE INCLUDED WITH THIS APPLICATION IF PROPOSED
ACTIVITY INVOLVES THE DISCHARGE OF EXCAVATED OF FILL MATERIAL INTO
WETLANDS:
a. WETLAND DELINEATION MAP SHOWING ALL WETLANDS, STREAMS. LAKES, AND
PONDS ON THE PROPERTY (FOR NATIONWIDE PERMIT NUMBERS 14.18. 21, 26, 29,
li-D 38). ALL STREAM (INTER.MITTENT A?NfD PERNkZlIENT) ON THE PROPERTY
[UST BE SHOWN ON THE MAP. MAP SCALES SHOULD BE 1 [NCH EQUALS SO FEET
OF 1 INCH EQUALS 100 FEET OF THEIR EQUIVALENT.
b. IF AVAILABLE, REPRESENTATIVE PHOTOGRAPH OF WETLANDS TO BE IMPACTED
BY PRODUCT.
r. IF DELINEATION WAS PERFORMED BY A CONSULTANT. INCLUDE ALL DATA
SHEETS RELEVANT TO THE PLACEMENT OF THE DELINEATION LINE.
d. ATTACH A COPY OF THE STORMWATER ,\(.?.`lAGE?(ENT PLAN IF REQUIRED.
e. WHAT IS LAND USE OF SURROUND[NG PROPOERTY'

f. IF APPLICABLE. WHAT IS PROPOSED METHOD OF SEWAGE DISPOSAL?
F?cou< ' c?c? +- -p"-BuL ?
S. SIGNED AND DATED AGENT AUTHORIZATION LETTER, IF APPLICABLE.
NOTE: WTLANDS OR WATERS OF THE US MAY NOT BE IMPACTED PRIOR TO:
1) ISSUANCE OF A SECTION 404 CORPS OF ENGINEERS PERMIT,
2) EITHER THE ISSUANCE OR WAIVER OF A 401 DIVISION OF WATER QUALITY
CERTIFICATION, AND
3) (IN THE TWENTY COASTAL COUNTIES ONLY), A LETTER FROM THE NORTH
CAROLINA DIVISION OF COASTAL MANAGEMENT STATING THE PROPOSED
ACTIVITY IS CONSISTENT WITH THE NORTH CAROLINA COASTAL
MANAGEMENT PROGRAM,
-0 " X0'3v ??d -
OWNER'S/AGENT'S SIGNATURE" DATE
(AGENT'S SIGNATURE VALID ONLY
IF AUTHORIZATION LETTER FROM
THE OWNER IS PROVIDED).
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Radio Towers •? ?` Berea Ch . 56 .u •;? %i Z a.
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I. MILE

5000 7000 FEET
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ROAD CLASSIFICATION
Medium-duty Light-duty
Unimproved dirt = .:

k
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TOTAL AREA= 101.46 ACRES
TOTAL WETLANDS= 12.18 ACRES
AREA IN CROSSING= 0.40 ACRES
SCALE, 1'=400'
MCROSSING AREA REVISED 5/3/2000
WEST JOHNSTON
SOUTHWIND
HIGH
SCHOOL
SURVEYING AND 201 GLEN ROAD
ENGINEERING, INC. GARNER, N.C. 27529 OWNER JOHNSTON COUNTY BOARD OF EDUCATION
919-773-0183
919-773-0148 (FAX) PRO.. No, STATE CO.
j2URVE"'ANGANGINEERINGAMD PLANNING MARCH 2000 SW980438 NC JOHNSTON
------ ------ / - -----------
. . ? ' y J
1
i
ti. L
•L'
DISTURBED
AREA
.L, .y. .y , y. v .L 1f +/
JI V L y
DISTURBED WETLANDS
?- - -- 1 WETLANDS
OUTLET PROTECTION J
1 t NCS`330
WETLAND AREA TO BE DISTURBED= 17,484 S.F.(0.40 AC.)
LENGTH OF STREAM TO BE DISTURBED= 95 L.F.
SCALES 11=100'
*CROSSING AREA REVISED 5/3/2000
WEST JOHNSTON
SOUTHWIND HIGH SCHOOL
8
SURVEYING AND 201 GLEN ROAD
N ENGINEERING, INC. GARNER, N.C. 27529 OWNER JOHNSTON COUNTY BOARD OF EDUCATION
919-773-0183 PIL MW Mi. SMTWIn . NC M77
919-773-0148 (FAX) DATE Maj. No. STATE Ci7.
MARCH 2000 SW9 438 NC JOHNSTON
SOUTHWIND
SURVEYING AND ENGINEERING
201 Glen Road
Garner, North Carolina 27529
Phone: [phone] ()00404
Fax: [phone] TO C`j F$1? ??t=t(1?Q L?

L1 IEU M of URMS EDUML
DAT5 E JOB NO.
f 1?/
ATTENT ON
RE: tttt
YZ
MAR 2 8 2W
the?follol ing items:
WE ARE SENDING YOU [&,*ffa`ched ? Under separate cover via 1 if
WETUW
? Shop drawings ? Prints ? Plans E1: $am ??ER U ificatidns
? Copy of letter ? Change order ? r
COPIES DATE NO. DESCRIPTION

G ? - Nl ct,??

PAYMENT
RECEIVED

THESE ARE TRANSMITTED as checked below:
or approval ? Approved as submitted
? For your use ? Approved as noted
? As requested ? Returned for corrections
? For review and comment ?
? FOR BIDS DUE 19
? Resubmit copies for approval
? Submit copies for distribution
? Return corrected prints
? PRINTS RETURNED AFTER LOAN TO US
REMARKS
COPY TO
SIGNED:( Hw L
If enclosures are not as noted, kindly notify us at once.
PAYMENT
RECEIVED
000404
DWQ ID: CORPS :ACTION ID:
NATIONWIDE PERMIT REQUESTED (PROVIDE NATIoi 1411,1 I '""'°-
?EW __,
PRE-CONSTRUCTION NOTIFICATIOI`?ILT?01'?7?iµ
FOR NATIONWIDE PERMITS THAT REQUIRE: 2 8 2000
1) NOTIFICATION TO THE CORPS OF ENGINEERS ---
2) APPLICATION FOR SECTION 401 CERTIFCATION W TIANDS GROUP
,ATIER Qi)!ILITY^SEUION
3) COORDINATION WITH THE NC DIVISION OF COASTAL MANAGEMENT
SEND THE ORIGINAL AND (1) COPY OF THIS COMPLETED FORM TO THE APPROPRIATE
FIELD OFFICE OF THE CORPS OF EN024EERS (SEE AGENCY ADDRESSES SHEET). S_ N
(7) COPIES MUST BE SENT TO THE NC DIVISION OF WATER
QUALITY, ATTN: JOHN DORNEY, 4401 REEDY CREEK ROAD,
RALEIGH NC 27607. PLEASE PRINT OR TYPE.
1. OWNER'S NAME: LCN4a??? C',,-nN z'4E.7 CE ELILc1?Tic
2. MAILING ADDRESS: t?0 IF
SUBDIVISION NAME
CITY:: R Jul Eli FI Elm STATE: KI, G o ZIP CODE: Z2'E 7
PROJECT LOCATION ADDRESS, INCLUDING SUBDIVISION NAME (IF DIFFERENT FROM
MAILING ADDRESS ABOVE): QLA Lt, I TELEPHONE NUMBER: (HOME) (WORK) rq 19 ! ??'C73
4. IF APPLICABLE: AGEV?'S Y.-MME OR RESPONSIBLE CORPORATE OFFICIAL, ADDRESS.
PHONE LNUNIBER:
5. LOCATION OF WORK (PROVIDE A NIAP. PPEFER.-kBLY A COPY OF USGS TOPOGRAPHIC
OR AER(AL. PHOTOGRAPHY WITH SCALE):
COUN, TY: J0F4"'=5ZP'a - :.NEAREST TOW`):
SPECIFIC LOCATION (INCLUDE ROAD NUMBERS. LANDtvIARKS. ECT.)
?x Ce o? T t1 'gs i lc-nl e iJ-?G cp r: ?7 r? G S 1382
6. INIPACTED OR NEAREST STREAM(RIVER:
RIVER BASIN: i???]Sl
7a. IS PROJECT LOCATED NEAR WATER CLASSIFIED AS TROUT, TIDAL SALTWATER, (SA),
HIGH QUALITY WATERS (HQW), OUTSTANDING RESOURSE WATERS (ORW), WATER
SUPPLY (WS-I OR WS-In? YES ( ) NO (?) IF YES, EXPLAIN:
7b. IS THE PROJECT LOCATED WITHIN A NORTH CAROLINA DIVISION OF COASTAL
MANAGEMENT AREA OF ENVIROMENTAL CONCERN (AEC)? YES ( ) NO ( ? )
7c. IF THE PROJECT IS LOCATED WITHIN A COASTAL COUNTY (SEE PAGE 7 FOR LIST OF
COASTAL COUNTIES), WHAT IS THE LAND USE PLAN (LUP) DESIGNATION?
8a. HAVE ANY SECTION 404 PERMITS BEEN PREVIOUSLY REQUESTED FOR USE ON THIS
PROJECT? YES ( ) NO ( ) IF YES, PROVIDE ACTION I.D. NUMBER OF PREVIOUS
PERMIT AND ANY ADDITIONAL INFORMATION (INCLUDE PHOTOCOPY OF 401
CERTIFICATION:
8b. ARE ADDITIONAL PERMIT REQUESTS EXPECTED FOR THIS PROPERTY IN THE
FUTURE? YES ( ) NO ( ) IF YES, DESCRIBE ANTICIPATED WORK:
9a. ESTIMATED TOTAL NUMBERS OF ACRES IN TRACT OF LA,W: I O 1, 4'?&
9b. ESTIMATED TOTAL. NUMBER OF ACRES OF WETLANDS LOCATED ON PROJECT SITE:
10, IF?
10a. NUMBER OF ACRES OF WETLA.YDS IMPACTED BY THE PROPOSED PROJECT BY:
0, El) I /_1 " (-- ? 6S
FILLING: O.BI
FLOODING:
DRAINAGE :
EXCAVATION:
OTHER :
TOTAL ACRES TO BE IMPACTED: OI
10b. (1) STREAM CHANNEL TO BE IMPACTED BY THE PROPOSED PROTECT (IF
RELOCATED, PROVIDE DISTANCE BOTH BEFORE AND AFTER RELOCATION:
LENGTH BEFORE: 217-7 FT AFTER: FT
WIDTH BEFORE (based on normal high water contours): FT
AVERAGE DEPTH BEFORE: FT AFTER: FT
(2) STREAM CHANNEL IMPACTS WILL RESULT FROM: (CHECK ALL THAT APPLY)
OPEN CHANNEL RELOCATION: PLACEMENT OF PIPE IN CHANNEL: L,--'_
CHANNEL EXCAVATION: COONSTRUCTION OF A DAM/FLOODING:
OTHER:
11. IF CONSTRUCTION OF A POND IS PROPOSED, WHAT IS THE SIZE OF THE WATERSHED
DR4INING TO THE POND? WHAT IS THE EXPECTED
POND SURFACE AREA?
12. DISCTIPTION OF PROPOSED WORK INCLUDING DISCUSSION OF TYPE. OF MECHANICAL
EQUIPMENT TO BE USED? (ATTACH PLANS; 81/2 BY 11 DRAWINGS ONLY)
?-t roc ?t?
13. PURPOSE OF PROPOSED WORK: l? l??`?e7 ??`? kkl ?-:z ?L-
[4. STATE REASONS WHY IT IS BELIEVED THAT THIS ACTIVITY MUST BE CARRIED OUT IN
WETLANDS ( INCLUDE ANY iNIFASURES TAKEN TO :MINIMIZE WETLAND IMPACTS)
^1-(-?EG'??S?c??S?s'ThE,E r?'v?--CC-?'???©F`fiE'i??'i"? Cr??St?-?x-?-?F?
wN?CN U-C-tA L-y
F=CT
13. YOU ARE REQUIRED TO CONTACT THE US FISH AND WILDLIFE SERVICE AND/OR
NATIONAL MARINE FISHERIES SERIVE REGARDING THE PRESENCE OF ANY FEDERALY
LISTED OR PROPOSED FOR LISTING ENDANGERED OR THREATENED SPECIES OR
CRITICAL HABITAT IN THE PERMIT AREA THAT L*vfAY BE AFFECTED BY THE PROPOSED
PROJECT. DATE CONTACTED:
16. YOU ARE REQUIRED TO CONTACT THE STATE HISTORIC PRESERVATION OFFICER
(SHPO) REGARDING THE PRESENCE OF HISTORIC PROPERTIES IN THE PERMIT AREA
WHICH MAY BE AFFECTED BY THE PROPOSED PROJECT. DATE CONTACTED
17. DOES THE PROJECT INVOLVE AN EXPENDITURE OF PUBLIC FUNDS OT THE USE OF
PUBLIC (STATE) LAND? YES ( ) NO ( t/f (IF NO, GO TO 16)
a. IF YES, DOES THE PROJECT REQUIRE PREPERATION OF AN ENVIRONMENTAL
DOCUMENT PURUANT TO THE REQUIREMENTS OF THE NORTH CAROLINA
ENVIRONMENTAL POLICY ACT? YES( ) NO ( )
b. IF YES, HAS THE DOCUMENT BEEN REFIEWED THROUGH THE NORTH CAROLINA
DEPARTMENT OF ADMINISTRATION STATE CLEARINGHOUSE YES ( ) NO ( )
IF ANSWER 17b IS YES, THEN SUBMIT APPROPRIATE DOCUMENTATIONFROM THE STATE
CLEARINGHOUSE WITH THE NORTH CAROLINA ENVIRONMENTAL POLICY ACT.
QUESTIONS REGARDING THE STATE CLEARINGHOUSE REVIEW PROCESS SHOULD BE
DIRECTED TO MS. CHRYS BAGGETT. DIRECTOR STATE CLEARINGHOUSE, NORTH
CAROLINA DEPARTMENT OF ADMINISTRATION, 116 WEST JONES STREET, RALEIGH,
NORTH CAROLINA 27603-8003. TELEPHONE [phone].
18. THE FOLLOWING ITEMS SHOULD BE INCLUDED WITH THIS APPLICATION IF PROPOSED
ACTIVITY INVOLVES THE DISCHARGE OF EXCAVATED OF FILL MATERIAL INTO
WETLANDS:
a. WETLAND DELINEATION MAP SHOWING ALL WETLANDS. STREAMS. LAKES, AND
PONDS ON THE PROPERTY (FOR NATIONWIDE PERMIT NUMBERS 14, 18.21, 26, 29,
AN-D 38). ALL STREANN1(INTERMITTENT AND PERMANENT) ON THE PROPERTY
MUST BE SHOWN ON THE Nf..P. MAP SCALES SHOULD BE 1 Il CH EQUALS 50 FEET
OF 1 INCH EQUALS 100 FEET OF THEIR EQUIVALENT.
b. IF AVAILABLE. REPRESENTATIVE PHOTOGRAPH OF WETLA.WS TO BE IMPACTED
BY PRODUCT.
c. IF DELINEATION WAS PERFORMED BY A CONSULTANT. INCLUDE ALL DATA
SHEETS RELEVANT TO THE PLACEMENT OF THE DELINEATION LINE.
d. ATTACH A COPY OF THE STOR.viWATER MANAGEMENT PLAN IF REQUIRED.
e. WHAT IS LANvD USE OF SURROUNDING PROPOERTY"

f. IF APPLICABLE. WHAT IS PROPOSED METHOD OF SEWAGE DISPOSAL.'.'

g. SIGNED AND DATED AGENT AUTHORIZATION LETTER, IF APPLICABLE.
NOTE: WTLANDS OR WATERS OF THE US MAY NOT BE IMPACTED PRIOR TO:
1) ISSUANCE OF A SECTION 404 CORPS OF ENGINEERS PERMIT,
2) EITHER THE ISSUANCE OR WAIVER OF A 401 DMSION OF WATER QUALITY
CERTIFICATION, AND
3) (IN THE TWENTY COASTAL COUNTIES ONLY), A LETTER FROM THE NORTH
CAROLINA DIVISION OF COASTAL MANAGEMENT STATING THE PROPOSED
ACTIVITY IS CONSISTENT WITH THE NORTH CAROLINA COASTAL
MANAGEMENT PROGRAM,
'7 ?Y- 3 . ®--
OWNER'S/AGENT'S SIGNA URE DATE
(AGENT'S SIGNATURE VALID ONLY
IF AUTHORIZATION LETTER FROM
THE OWNER IS PROVIDED).
` i ?/ '?i?--'' ,., : `"`?• `?\ i ? _ ? 1. ?I ? ?,
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0 6000 7000 FEET Medium-duty Light•duty_
I KILOMETRE Unimproved dirt ::..:
F -

TOTAL AREA= 101.46 ACRES
TOTAL WETLANDS= 12.18 ACRES
AREA IN CROSSING= 0.81 ACRES
SCALE, 1'=400'
WEST JOHNSTON
SOUTHWIND HIGH SCHOOL
'A 93 SURVEYING AND 201 GLEN ROAD
ENGINEERING, INC. GARNER, N.C. 27529 13WNER JOHNSTON COUNTY BOARD OF EDUCATION
919-773-0183
919-773-0148 (FAX) DATE PROJ. Nm STATE Co.
S URVEYING/ENGINEERINGAAND PLANNING MARCH 2000 SW980438 NC JOHNSTON
f
AA

DISTURBED WETLANDS
- WETLANDS
- OUTLET PROTECTION
DISTURBED
AREA

1 t . NCS_ R 1330
WETLAND AREA TO BE DISTURBED= 35,648 S.F.(0.81 AC.)
LENGTH OF STREAM TO BE DISTURBED= 217 L.F.
SCALES 1'=100'
WEST JOHNSTON
SOUTHWIND HIGH SCHOOL

1 93 SURVEYING AND 201 GLEN ROAD
ENGINEERING, INC. GARNER. N.C. 27529 ?wt-" JOHNSTON COUNTY BOARD OF EDUCATION
919-773-0183 pn Em 13;&. OOTHFIEL D NC
919-773-0148 (FAX) JArE PROD No. STATE
MARCH 2000 SW980438 NC JOHNSTON
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Iuoidx.L •oouuualumw mjnaaa lnopm pauSisop su omodo lou lllm amlorms lonuoo plumuuols y
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suisuq taismuuols u su uoiluluautaldwi of .loud panouta.I oq llim luaunpros palulnuinoou lugs olumpui
Al.molo lsnui suuld oql `uoponAsuoo auimp suisuq luowipos su posn oq of posodoid aw suisuq ag13I
Iunouia2l luauiipaS
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Hite associates
AOfECf1RE / HCHRE / iMY JAN 2 `L/ 17 January 2001

Mr. John Dorney
Wetlands/401 Unit
NCDEHNR Division of Water Quality
4401 Reedy Creek Road
Raleigh, NC 27607 ?A-
RE: West Johnston High School - 99018
DWQ # 000404
Dear Mr. Dorney:Za?l?
Thank you for your letter of approval dated December 19, 2000.
Regarding to dam regulations, we have confirmed with our Site Engineer that the height of our dam is
8' maximum and does not (as he understands) fall underneath these particular regulations. If this is .
not the case, please advise.
James G. Hite, AIA, Project Architect
Hite Associates, PC
JGH:pg
xc: Tom Davis
Ray DeBruhl, P.E.
Steve Janowski, P.E.
2600 Meridian Drive I Greenville, NC 27834 / tel [phone] / fax [phone] / [e-mail]
127 South Third Street /Smithfield, NC 27577 / tel [phone] / fax [phone] / e-mail, [e-mail]
State of North Carolina
Department of Environment
and Natural Resources &14 • •
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director NCDENR
DIVISION OF WATER QUALITY
December 19, 2000
Mr. Tom Davis
Johnston County Board of Education
PO Box 1336
Smithfield, NC 27577
Subject: Stormwater Management Plans
West Johnston High School
Johnston County, NC
DWQ# 000404
Dear Mr. Davis:
This Office is in receipt of the plans dated August 1, 2000 and revised December 18,
2000 for the stormwater management ponds and level spreaders at the subject facility prepared on
your behalf by Hite Associates and submitted to the Division on December 18, 2000. Staff from
the Wetlands Unit reviewed the plans and found them acceptable. Please note that this approval
shall not be construed as an approval of the dam design for Dam Safety purposes.
If you have any questions regarding this matter, please contact Mr. Todd St. John at (919)
733-9584.
cc: Mr. Todd St. John, Wetlands
Raleigh Regional Office
File
R. DQ
ands Unit Sup i or
4401 Reedy Creek Road, Raleigh, NC 27607 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post-consumer paper
awn
NCDENR
DIVISION OF WATER QUALITY
December 19, 2000
Memorandum To: John Dorney
From: Todd St. Joh
1 0/
Subject: West Johnston High School
Johnston County
DWQ# 000404
I have reviewed the stormwater management plans for the subject High School.
They have proposed using a dry and a wet detention pond each followed by a level
spreader that will discharge before it reaches zone 2 of the buffer. The side slopes of the
wet pond are 3:1 above the permanent pool and 6:1 below the permanent pool. The level
spreaders should be adequate considering the fact that they are each preceded by a
detention pond. As such, I recommend that the stormwater management plans be
approved.
DEC-18-00 12:26 PM
J. 5. JanOwoki and 55001ate5
December 18, 2000
Todd St. John, PE
Environmental Engineer
NCDENR
Division of Watcr Quality
4401 Reedy Crock Road
Raleigh,, NC 27607
Re: FAX to 919-733-9959
DWQ Proj. No. 000404
West Johnston High School
Johnston County

Dear Todd-
I am faxing the following information per our cony tion this morning and in response
to comments in a letter dated October 11, 2000:
1. Plan view of wet detention basin in front o the school.
2. Section of wet detention basin in front of t e school,

.
3. Plan view of dry detention basin behind t athletic fields.
4. Section of dry detention basin behind the hletic fields.
In response to item 1 of the referenced letter I have clarified the separation of the forebay
area from the main detention area. Please note that a revision was made in the wet
detention pond in order to pronounce the definition of the Wrm. In response to item no. 2
there are notes on the plan view that have a bubble • ound them establishing the height of
the berm for the level spreader. This will provide on level elevation for the storm water to
discharge over. Each level spreader is 120 feet long and has a level berm with an elevation
of 194.00 for the wet detention pond and 178.2 for t c dry detention pond. The level
spreader will be constructed in accordance with sect n 402.6.
I hope this additional information satisfies the comin nts from the October 11, 2000 letter.
If you need additional information please call.
Sincerely;
J.S. J Ad and Associates
.S. owski, PE
105.C Emot Victorla Ct. • Greenville, NC 2746 @ phone & Fax [phone].
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State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
Mr. Todd Smith
Hite Associates
1530 Last Courtecnth Street
Greenville, NC: 27558
Dear Mr, Smith:
Division of Vj
October 11, 200
1
Subject: West J?p
nwQ
The Wetlands Unit staff reviewed the stormwater mana
that additional information is necessary to complete the
information is as follows:
Forebay

CDENR
Quality
nston County High School
)ject No. 000404
County
plans for the subject project and determined
at review process. The required additional
The berm for the forebay (whether above or below tBit urface of the pond) should extend across the
pond so the forcbay will contain sediment. Please nethe engineering plans to reflect the change.
Please refer to page 9 of the NC DENR stormwater Management Practices Manual, April 1999.
2. Level Spreader
The level spreaders should be designed to discharge ah ng the length of the berm in order to
maximize the length of buffer utilized for stormwnt_r °°Firnilation. The plans do not show this.
Please feel free to call me at [phone] to discuss ?this matter. Please refer to page 77 of the NC
DFNR Swrmwater Best Management Practices Manu: , April 1999,
Division wetlands unit staff will strive to complete a final
receipt of the requested information. If you have any +W.5
contact me at [phone].
cc: John Dorney. Wetlands/301 Unit
Raleigh Regional Office
File
Sinc reI
Todd t, o7 hn
,
Environmental
4401 Reedy Creek Road, Raleigh, NC 27607
An Equal Opportunity Affirmative Action Employer
heal review within 10 working days of
or would like to discuss this project. please
I L
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