20081265 Ver 2_More Info Received_20090609

ENGINEERING • SURVEYING • DESIGNING • DRAFTING
Larry King & Associates R.L.S., P.A.
Post Office Box 53787 -1333 Morganton Road, Suite 201
Fayetteville, North Carolina 28305
Ir=
[phone] • Fax: [phone] ??0 V
www.LKandA.com
JUN 0 9 2009
O ' ?1 Lo$ Y 2- DENR - WATER QMM
June 8, 2009 0. WERMDSANDSTORMWATERORMCH
Ms. Cyndi Karoly, Supervisor
401 Oversight/Express Review Permitting Unit
North Carolina Department of Environment and Natural Resources
Division of Water Quality
1650 Mail Service Center
Raleigh NC 27699-1650
Re: Two Bale Lane at Cotton Square
Little Rock fish Creek [030615,18-31-24-(7), C]
Additional Information Provided (Five Copies)
Dear Ms: Karoly:
We have provided additional information requested involving the
stormwater runoff from the Two Bale lane Roadway that removes 85% TSS.
BMP supplement forms with required items are enclosed.
We were successful in proving wet ponds to treat most of the stormwater
before reaching the low point near the major wetland crossing for the
roadway. This is the section where the roadway narrows and has retaining
walls on each side to reduce the wetland impact. The drainage pipes for this
area are too deep in relation to the topography to provide a BMP at this
crossing. We did discuss this with Annette Lucas to get her input before we
provide you our best option for our conditions.
Please contact us with questions you may have.
Sincerely,
Larry King & Associates R.L.S., P.A.
Thomas S. Speig rt,Jr.,vPE, PLS
Cc. John Gillis, Partner Two Bale Road
Tony Beasley Withers and Ravenel
Ken Averitte, DWQ Fayetteville Regional Office
r
Permit No.
AG"A"NCDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information.
(to be provided by DWQ)
o?OF W AT?RQG
5 y
C> YYIIIII lIY/ C
t. PROJECT INFORMATION
Project name Two Bale Lane
Contact person Tom Speight, PE
Phone number 910-4834300
Date 6/2/2009
Drainage area number Wet Pond-1
II. DESIGN INFORMATION
Site Characteristics
Drainage area 25,700 ftz
Impervious area, post-development 24,415 ft2
% impervious 95.00 %
Design rainfall depth 1.0 in
Storage Volume: Non-SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre-development 1-yr, 24-hr runoff
Post-development 1-yr, 24-hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the pre/post control of the lyr 24hr storm peak flow required?
1-yr, 24-hr rainfall depth
Rational C, pre-development
Rational C, post-development
Rainfall intensity: 1-yr, 24-hr storm
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Pre/Post 1-yr, 24-hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 1 Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state-required temp. pool?
Elevation of the top of the additional volume
1,940 ft3 OK
3,098 ft3
OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
0 ft3
ft3
(Y or N)
3.0 in
0.30 (unitless)
0.95 (unitless)
1.00 in/hr OK
0.18 ft3/sec
0.56 ft3/sec
0.38 ft3/sec
166.01 fmsl
165.50 fmsl
fmsl
166.00 fmsl
165.00 fmsl
161.00 fmsl
160.00 fmsl
1.00 It
(Y or N)
166.0 fmsl OK
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
III. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Page/ Plan
Initials Sheet No.
1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
- Off-site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement.
n 2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing:
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross-section,
- Vegetation specification for planting shelf, and
- Filter strip.
L 3. Section view of the wet detention basin (1" = 20' or larger) showing:
- Side slopes, 3:1 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures.
4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin.
5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
6
A construction se
th
t
h
.
quence
a
s
ows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
FActo5eA 7. The supporting calculations.
E? ?se[[y 8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
9. A copy of the deed restrictions (if required).
0Ae 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County
soil maps are not an acceptable source of soils information,
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Part III. Required Items Checklist, Page 1 of 1
Permit Number:
(to be provided by DWQ)
Drainage Area Number: W9- I
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
? does M does not
This system (check one):
? does ? does not
incorporate a vegetated filter at the outlet.
incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be minimized to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problem: How I will remediate the problem:
The entire BMP Trash/ debris is resent. Remove the trash/ debris.
The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to
detention basin erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
Vegetation is too short or too Maintain vegetation at a height of
long. approximately six inches.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 1 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: WP- I
BMP element: Potential problem: How I will remediate the problem:
The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the
swale sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged.
Erosion is occurring in the Regrade the swale if necessary to
swale. smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
The forebay Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design depth for possible. Remove the sediment and
sediment storage. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The vegetated shelf Best professional practices Prune according to best professional
show that pruning is needed practices
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The main treatment area Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design sediment possible. Remove the sediment and
storage depth. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Algal growth covers over Consult a professional to remove
50% of the area. and control the algal growth.
Cattails, phragmites or other Remove the plants by wiping them
invasive plants cover 50% of with pesticide (do not spray).
the basin surface.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 2 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: Wf -
BMP element: Potential problem: How I will remediate the problem:
The embankment Shrubs have started to grow Remove shrubs immediately.
on the embankment.
Evidence of muskrat or Use traps to remove muskrats and
beaver activity is present. consult a professional to remove
beavers.
A tree has started to grow on Consult a dam safety specialist to
the embankment. remove the tree.
An annual inspection by an Make all needed repairs.
appropriate professional
shows that the embankment
needs repair. if applicable)
The outlet device Clogging has occurred. Clean out the outlet device. Dispose
of the sediment off-site.
The outlet device is damaged Repair or replace the outlet device.
The receiving water Erosion or other signs of Contact the local NC Division of
damage have occurred at the Water Quality Regional Office, or
outlet. the 401 Oversight Unit at 919-733-
1786.
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads 1u(0.6 feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads o feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
ill in the blanks)
Sediment Removal
Bottom
0 Permanent Pool Elevation 1tn5.50
r (? I Pe anen Pool
--------------- -- Volume Sediment Removal Elevation 1(vl Volume
-------------------------------------------- ------
i uo - Min.
Sediment Bottom Elevation IinO 1-ft r
Storage Sedimei
Storage
FOREBAY MAIN POND
Form SW401-Wet Detention Basin O&M-Rev.4 Page 3 of 4
Permit Number:
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name: -fWo goa'e LAVte.
BMP drainage area number: W el P,nrl - I
Print name:John M. Gillis Jr.
Title:Partner
Address: 8623 Galatia Church Rd
Phone: [phone] LY)
Signature:
-Zoo
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
a Notary Public for the State of
y c f , , County of r_,; eJ , do hereby certify that
`J? personally appeared before me this -64
day-bf ,l_, and acknowledge the due execution of the
r
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,

Notary Public
pler
Cumberland County
k nrtb Carolina

SEAL
My commission expires l I - l11- ,'46t)
Form SW401-Wet Detention Basin O&M-Rev.4 Page 4 of 4
Permit
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 7,128 ft2
Area REQUIRED, permanent pool 961 ft2
SA/DA ratio 3.74 (unitless)
Area PROVIDED, permanent pool, Aperm-pool 5,262 ft2 OK
Area, bottom of 1Oft vegetated shelf, Abot shelf 3,720 ft2
Area, sediment cleanout, top elevation (bottom of pond), Abotpond 1,079 ft2
Volumes
Volume, temporary pool
Volume, permanent pool, VP,. Pod
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SAIDA Table Data
Design TSS removal
Coastal SA/DA Table Used?
Mountain/Piedmont SAIDA Table Used?
SAIDA ratio
Average depth (used in SA/DA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, Vpermpoo,
Area provided, permanent pool, Apermpooi
Average depth calculated
Average depth used in SA/DA, day, (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Apermpooi
Area, bottom of 1Oft vegetated shelf, Abot-shelf
Area, sediment cleanout, top elevation (bottom of pond), Abotpond
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment)
Average depth calculated
Average depth used in SA/DA, day, (Round to nearest 0.5ft)
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if-non-circular)
Coefficient of discharge (CD)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (CW)
Length of weir (L)
Driving head (H)
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build-out?
Drain mechanism for maintenance or emergencies
3,098 ft3 OK
11,482 ft3
2,113 ft3
18.4% % OK
85 %
N (Y or N)
Y (Y or N)
3.74 (unitless)
N (Y or N)
ft'
ft2
ft
ft
Y (Y or N)
5,262 ft2 OK
3,720 ft2 OK
1,079 ft2 OK
4.00 ft OK
2.23 ft OK
3.0 ft OK
Y (Y or N)
0.75 in
in2
0.60 (unitless)
0.51 ft
N (Y or N)
(unitless)
(unitless)
It
ft
0.18 ft3/sec OK
0.56 ft3/sec OK
0.01 ft3/sec
2.13 days OK, draws down in 2-5 days.
OK, drawdown time is correct.
3 :1 OK
10 :1 OK
10.0 ft OK
5 :1 OK
5.0 :1 OK
Y (Y or N) OK
1.0 ft OK
Y (Y or N) OK
Y (Y or N) OK
N (Y or N) Required to capture all runoff from the ultimate build-out
Pump out pond
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts 1. & If. Design Summary, Page 2 of 2
Permit No.
(to be provided by DWQ)
" OF W ATF?,
..... *v y
NCDENR Y
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information.
1. PROJECT INFORMATION
Project name Two Bale Lane
Contact person Tom Speight, PE
Phone number 9104834300
Date 6/2/2009
Drainage area number Wet Pond-2
II. DESIGN INFORMATION
Site Characteristics
Drainage area 20,909 ft2
Impervious area, post-development 19,863 ft2
% impervious 95.00 %
Design rainfall depth 1.0 in
Storage Volume: Non-SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre-development 1-yr, 24-hr runoff
Post-development 1-yr, 24-hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the prelpost control of the 1yr 24hr storm peak flow required?
1-yr, 24-hr rainfall depth
Rational C, pre-development
Rational C, post-development
Rainfall intensity: 1-yr, 24-hr storm
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Pre/Post 1-yr, 24-hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 1 Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state-required temp. pool?
Elevation of the top of the additional volume
1,590 ft3 OK
1,747 ft3
OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
0 ft3
ft3
N (Y or N)
3.0 in
0.30 (unitless)
0.95 (unifless)
1.00 in/hr OK
0.14 ft3/sec
0.46 ft3/sec
0.32 ft3/sec
165.92 fmsl
165.50 fmsl
fmsl
166.00 fmsl
165.00 fmsl
161.00 fmsl
160.00 fmsl
1.00 ft
N (Y or N)
165.9 fmsl OK
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts I. & II. Design Summary, Page 1 of 2
Permit
(to be provided by DWQ)
IL DESIGN INFORMATION
Surface Areas
Area, temporary pool 5,000 ft2
Area REQUIRED, permanent pool 782 ft2
SA/DA ratio 3.74 (unitless)
Area PROVIDED, permanent pool, APerm Pod 5,042 ft2 OK
Area, bottom of 1 Oft vegetated shelf, Abot_shelf 3,319 ft2
Area, sediment cleanout, top elevation (bottom of pond), Abotyond 734 ft2
Volumes
Volume, temporary pool
Volume, permanent pool, VPenpod
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SA/DA Table Data
Design TSS removal
Coastal SA/DA Table Used?
Mountain/Piedmont SA/DA Table Used?
SA/DA ratio
Average depth (used in SA/DA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, VPenpod
Area provided, permanent pool, APerm-pod
Average depth calculated
Average depth used in SA/DA, da,, (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Aperr-pod
Area, bottom of 1 Oft vegetated shelf, Abot shelf
Area, sediment cleanout, top elevation (bottom of pond), Abotyond
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment)
Average depth calculated
Average depth used in SA/DA, d., (Round to nearest 0.5ft)
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if-non-circular)
Coefficient of discharge (Cc)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (C.)
Length of weir (L)
Driving head (H)
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build-out?
Drain mechanism for maintenance or emergencies
1,747 ft3 OK
9,763 ft3
1,811 ft3
18.5% % OK
85 %
N (Y or N)
Y (Y or N)
3.74 (unitless)
(Y or N)
ft3
ft`
Y (Y or N)
5,042 ft` OK
3,319 ft` OK
734 ft2 OK
4.00 ft OK
2.80 ft OK
3.0 ft OK
Y (Y or N)
0.63 in
in2
0.60 (unitless)
0.42 ft
(Y or N)
(unitless)
(unitless)
ft
ft
0.15 ft3/sec OK
1,00 ft3/sec Insufficient post-development peak flow.
0.01 ft3/sec
2.77 days OK, draws down in 2-5 days.
OK, drawdown time is correct.
4 :1 OK
10 :1 OK
10.0 ft OK
4 :1 OK
3.5 :1 OK
Y (Y or N) OK
1.0 ft OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Pump out pond
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts I. & II. Design Summary, Page 2 of 2
Permit Number:
(to be provided by DWQ)
Drainage Area Number: %) P - a,
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
? does ® does not
This system (check one):
? does [Z does not
incorporate a vegetated filter at the outlet.
incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be minimized to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problem: How I will remediate the problem:
The entire BMP Trash/ debris is resent. Remove the trash/ debris.
The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to
detention basin erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
Vegetation is too short or too Maintain vegetation at a height of
long. approximately six inches.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 1 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: W p . ;L,
BMP element: Potential problem: How I will remediate the problem:
The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the
swale sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged.
Erosion is occurring in the Regrade the swale if necessary to
swale. smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
The forebay Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design depth for possible. Remove the sediment and
sediment storage. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The vegetated shelf Best professional practices Prune according to best professional
show that pruning is needed practices
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The main treatment area Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design sediment possible. Remove the sediment and
storage depth. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Algal growth covers over Consult a professional to remove
50% of the area. and control the algal growth.
Cattails, phragmites or other Remove the plants by wiping them
invasive plants cover 50% of with pesticide (do not spray).
the basin surface.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 2 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: wp- al
BMP element: Potential problem: How I will remediate the problem:
The embankment Shrubs have started to grow Remove shrubs immediately.
on the embankment.
Evidence of muskrat or Use traps to remove muskrats and
beaver activity is present. consult a professional to remove
beavers.
A tree has started to grow on Consult a dam safety specialist to
the embankment. remove the tree.
An annual inspection by an Make all needed repairs.
appropriate professional
shows that the embankment
needs repair. if applicable)
The outlet device Clogging has occurred. Clean out the outlet device. Dispose
of the sediment off-site.
The outlet device is damaged Repair or replace the outlet device.
The receiving water Erosion or other signs of Contact the local NC Division of
damage have occurred at the Water Quality Regional Office, or
outlet. the 401 Oversight Unit at 919-733-
1786.
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads ?. Cv . feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads b .ob feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
ill in the blanks)
Sediment Removal
Bottom Elev
Permanent Pool Elevation (a5. SO
r(p( 11
4 c t
teanen?pool
olume Sediment
------ Removal Elevation l(Pl ----- Volume
------------
-ft Min.
Sediment Bottom Elevation 4c0 1-ft r
Storage Sedimei
Storage
MAIN POND
FOREBAY
Form SW401-Wet Detention Basin O&M-Rev.4 Page 3 of 4
Permit Number:
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name: 1 t.1o 64e rxhe
BMP drainage area number: W e? ?or,d - a
Print name:John M. Gillis Jr.
Title:Partner
Address: 8623 Galatia Church Rd
Phone
Signat
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
a Notary Public for the State of
do hereby certify that
personally appeared before me this "?, C''_
day of , 7S Cccj , and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
Nc,ary Public
< rr sift'rPsox EpleT
Cumberland County
k?>
librtll Carolina
SEAL
My commission expires // - /,,/- - C'q
Form SW401-Wet Detention Basin O&M-Rev.4 Page 4 of 4
Permit No
(to be provided by DWQ)
ltl,. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Page/ Plan
Initials Sheet No.
1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
- Off-site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement.
2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing:
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross-section,
- Vegetation specification for planting shelf, and
- Filter strip.
3. Section view of the wet detention basin (1" = 20' or larger) showing:
- Side slopes, 3:1 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures.
a 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin.
5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
rr 7. The supporting calculations.
Gn os e? 8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
9. A copy of the deed restrictions (if required).
o rye 10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County
soil maps are not an acceptable source of soils information.
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Part III. Required Items Checklist, Page 1 of 1
Permit No.
(to be provided by DWQ)
OF W AT?R
'Mi-
NCDENR o
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 111) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name Two Bale Lane
Contact person Tom Speight, PE
Phone number 910-4834300
Date 6/2/2009
Drainage area number Wet Pond-3
II: DESIGN INFORMATION
Site Characteristics
Drainage area 64,033 ft2
Impervious area, post-development 60,832 ft2
% impervious 95.00 %
Design rainfall depth 1.0 in
Storage Volume: Non-SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre-development 1-yr, 24-hr runoff
Post-development 1-yr, 24-hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the pre/post control of the lyr 24hr storm peak flow required?
1-yr, 24-hr rainfall depth
Rational C, pre-development
Rational C, post-development
Rainfall intensity: 1-yr, 24-hr storm
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Pre/Post 1-yr, 24-hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 1 Oft vegetated shelf elevation
Bottom of 1Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state-required temp. pool?
Elevation of the top of the additional volume
4,841 ft3 OK
7,948 ft3
OK, volume provided is equal to or in excess of volume required.
_ ft3
ft3
-ft3
0 ft3
ft3
N (Y or N)
3.0 in
0.30 (unitless)
0.95 (unitless)
1.00 in/hr OK
0.44 ft3/sec
1.39 ft3/sec
0.95 ft3/sec
157.80 fmsl
156.50 fmsl
fmsl
157.00 fmsl
156.00 fmsl
152.00 fmsl
151.00 fmsl
1.00 It
N (Y or N)
157.8 fmsl OK
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 7,186 ftz
Area REQUIRED, permanent pool 2,395 ft2
SAIDA ratio 3.74 (unitless)
Area PROVIDED, permanent pool, Aperm-pool 5,042 ft` OK
Area, bottom of 10ft vegetated shelf, Abot shelf 3,319 ft`
Area, sediment cleanout, top elevation (bottom of pond), Abot pond 734 ft1
Volumes
Volume, temporary pool
Volume, permanent pool, Vperm_pool
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SA/DA Table Data
Design TSS removal
Coastal SA/DA Table Used?
Mountain/Piedmont SAIDA Table Used?
SAIDA ratio
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, Vperm_pool
Area provided, permanent pool, Apen-pool
Average depth calculated
Average depth used in SAIDA, d.„ (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Apen-pool
Area, bottom of 1 Oft vegetated shelf, Abot shelf
Area, sediment cleanout, top elevation (bottom of pond), Abotyond
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment)
Average depth calculated
Average depth used in SAIDA, ddv, (Round to nearest 0.5ft)
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if-non-circular)
Coefficient of discharge (CD)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (Cw)
Length of weir (L)
Driving head (H)
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build-out?
Drain mechanism for maintenance or emergencies
7,948 ft3 OK
9,763 ft3
1,811 ft3
18.5% % OK
85 %
N (Y or N)
Y (Y or N)
3.74 (unitless)
N (Y or N)
ft3
ft`
ft
ft
Y (Y or N)
5,042 ft` OK
3,319 ft` OK
734 ftz OK
4.00 ft OK
2.80 ft OK
3.0 ft OK
Y (Y or N)
0.88 in
in2
0.60 (unitless)
1.30 ft
N (Y or N)
(unitless)
(unitless)
ft
ft
0.45 ft3/sec OK
1.39 ft3/sec OK
0.02 ft3/sec
2.45 days OK, draws down in 2-5 days.
OK, drawdown time is correct.
4 :1 OK
10 :1 OK
10.0 ft OK
4 :1 OK
3.5 :1 OK
Y (Y or N) OK
1.0 ft OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Pump out pond
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Parts I. & It. Design Summary, Page 2 of 2
Permit Number:
(to be provided by DWQ)
Drainage Area Number: WP-3
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
? does ? does not
This system (check one):
? does ? does not
incorporate a vegetated filter at the outlet.
incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be minimized to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problem: How I will remediate the problem:
The entire BMP Trash/ debris is resent. Remove the trash/debris.
The perimeter of the wet Areas of bare soil and/or Regrade the soil if necessary to
detention basin erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
F Vegetation is too short or too Maintain vegetation at a height of
long. approximately six inches.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 1 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: K p _ ?
BMP element: Potential problem: How I will remediate the problem:
The inlet device: pipe or The pipe is clogged. Unclog the pipe. Dispose of the
swale sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged.
Erosion is occurring in the Regrade the swale if necessary to
Swale. smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
The forebay Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design depth for possible. Remove the sediment and
sediment storage. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The vegetated shelf Best professional practices Prune according to best professional
show that pruning is needed practices
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Weeds are present. Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying.
The main treatment area Sediment has accumulated to Search for the source of the
a depth greater than the sediment and remedy the problem if
original design sediment possible. Remove the sediment and
storage depth. dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Algal growth covers over Consult a professional to remove
50% of the area. and control the algal growth.
Cattails, phragmites or other Remove the plants by wiping them
invasive plants cover 50% of with pesticide (do not spray).
the basin surface.
Form SW401-Wet Detention Basin O&M-Rev.4 Page 2 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number: WP-3
BMP element: Potential problem: How I will remediate the problem:
The embankment Shrubs have started to grow Remove shrubs immediately.
on the embankment.
Evidence of muskrat or Use traps to remove muskrats and
beaver activity is present. consult a professional to remove
beavers.
A tree has started to grow on Consult a dam safety specialist to
the embankment. remove the tree.
An annual inspection by an Make all needed repairs.
appropriate professional
shows that the embankment
needs repair. if applicable)
The outlet device Clogging has occurred. Clean out the outlet device. Dispose
of the sediment off-site.
The outlet device is damaged Repair or replace the outlet device.
The receiving water Erosion or other signs of Contact the local NC Division of
damage have occurred at the Water Quality Regional Office, or
outlet. the 401 Oversight Unit at 919-733-
1786.
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads I S-7.oo feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads ISZ.oO feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Sediment Removal
Bottom
0 Permanent Pool Elevation 15(0. 5
15 a Pe anen Pool
--------------- -- Volume Sediment Removal Elevation IS a Volume
lSl -ft Min. -------------------------------------------- ------
Sediment Bottom Elevation IS I 1-ft n
Storage Sedimet
Storage
FOREBAY MAIN POND
Form SW401-Wet Detention Basin O&M-Rev.4 Page 3 of 4
Permit Number:
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name: wo Bale Lan-e
BMP drainage area number: L,Je ? pov,?_A - 3
Print name:John M. Gillis Jr.
Title:Partner
Address:8623 Galatia
Phone:
Signati
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
a Notary Public for the State of
`f L?1_ ?Cc Ch,)) , County do hereby certify that
(At . personally appeared before me this
da? of v> ` , a-q , and acknowledge the due execution of the
y'
forgoing et detention basin maintenance requirements. Witness my hand and official
seal,
.sb c?
LOPI pson Epler
Cum e: iaad County
it nr2:i Carolina
SEAL
My commission expires__
Form SW401-Wet Detention Basin O&M-Rev.4 Page 4 of 4
Permit No.
(to be provided by DWQ)
III. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Page/ Plan
Initials Sheet No.
1. Plans (1" 50' or larger) of the entire site showing:
- Design at ultimate build-out,
- Off-site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement.
2. Partial plan (1" = 30' or larger) and details for the wet detention basin showing:
- Outlet structure with trash rack or similar,
Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross-section,
- Vegetation specification for planting shelf, and
- Filter strip.
3. Section view of the wet detention basin (1" = 20' or larger) showing:
- Side slopes, 3:1 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures.
J 4. If the basin is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin.
5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
T a- 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
7. The supporting calculations.
'' J
Ea 8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
- 0 A 9. A copy of the deed restrictions (if required).
10. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. County
soil maps are not an acceptable source of soils information.
Form SW401-Wet Detention Basin-Rev.6-2/20/09 Part III. Required Items Checklist, Page 1 of 1
Supporting Calculations
For
Wet Pond-1, Wet Pond-2 & Wet Pond-3
Project:
Two Bale Lane
(DWQ Project # 08-1265 Ver. 2)
Owner:
Gillis Group Partnership
L '
o°
y `rte: A - a

(.-t-0'°
Prepared by:
ENGINEERING - SURVEYING - DESIGNING - DRAFTING
Larry King & Associates, R.L.S., P.A.
P.O. Box 53787
1333 Morganton Road, Suite 201
Fayetteville, North Carolina 28305
P. [phone] F. [phone]
www.LKandA.com
SC-1
Water Quality Volume
Required for Storage
Project Name: Two Bale Lane
Outlet: WP-1
Calculate Runoff Coefficient
A= 0.59 acres
Ai= 0.56
la= 0.95
Rv=0.05+0.9*la
Rv= 0.90
Watershed area
Impervious area
Impervious fraction
Runoff Coefficient
Calculate Runoff Volume Reauired to be Controlled
Rd= 1 in Design storm rainfall depth (typically 1" or 1.5")
V=3630*Rd*Rv*A
WQV= 1937 cf Volume of runoff that must be
0.53 Ac in controlled for specified design storm
SC-2
Drawdown Orifice Sizing
Project Name:
Outlet:
Pond Storage=
Pond Depth(h)=
Drawdown Time=
Two Bale Lane
Wet Pond-1
1,937 cf
0.51 ft
2.5 days
Cd= 0.6 Coefficient of Discharge (typical 0.6)
g= 32.2 ft/sec^2 Gravity
The Orifice Equation
Q= Cd A Sgrt(2 g h)
Rearrange to solve for A, the minimum orifice area needed to meet drawdown requirements
Q= 0.01 cfs Based on pond volume and desired drawdown time
A= 0.00261 sf 0.38 si
Number of Orifices= 1
Minimum diameter to meet area
d= 0.69 inch diameter orifice
Use: 0.76 " diameter orifice 0.0031 sf
Check Outflow time
Q= Cd A Sgrt(2 g h)
Q= 0.01 cfs
Drawdown time= 2.13 days OK
SC-3
Anti-Flotation Calculations
Project Name: Two Bale Lane
Pond Designation: WP-1
Riser Diameter = 8 in (circular)
Dimensions of Riser- ft
Depth of pond = 3 ft
Required Factor of Safety = 1.2
Cross Sectional Area of Riser
Circular = 0.348889 sf
Rectangular= 0 sf
Volume of Water Displaced
Depth of pond * Cross-sectional area
1.046667 cf
Weight of Water Displaced
(assuming weight of water = 62.4 Ib/cf)
62.4 * Volume of water Displaced
65.31 lb
Minimum Weight of Anti-Flotaton Device
FS * WoW Displaced
78.37 lb
Riser Base Provided
2 ft x 2 ft x 1.5 ft (depth)
Weight of concrete assumed 150 Ib/cf
Weight of Base Provided = 900.00 lb
FS Provided = 13.78 ok
SC-4
Water Quality Volume
Required for Storage
Project Name: Two Bale Lane
Outlet: WP-2
Calculate Runoff Coefficient
A= 0.48 acres
Ai= 0.46
la= 0.96
Watershed area
Impervious area
Impervious fraction
Rv=0.05+0.9*la
Rv= 0.91
Runoff Coefficient
Calculate Runoff Volume Required to be Controlled
Rd= 1 in Design storm rainfall depth (typically 1" or 1.5")
V=3630*Rd*Rv*A
WQV= 1590 cf Volume of runoff that must be
0.44 Ac in controlled for specified design storm
SC-5
Drawdown Orifice Sizing
Project Name: Two Bale Lane"
Outlet: Wet Pond-2
Pond Storage= 1,590 cf
Pond Depth(h)= 0.42 ft
Drawdown Time= 2.5 days
Cd= 0.6 Coefficient of Discharge (typical 0.6)
g= 32.2 ft/sec^2 Gravity
The Orifice Equation
Q= Cd A Sgrt(2 g h)
Rearrange to solve for A, the minimum orifice area needed to meet drawdown requirements
Q= 0.01 cfs Based on pond volume and desired drawdown time
A= 0.00236 sf 0.34 si
Number of Orifices= 1
Minimum diameter to meet area
d= 0.66 inch diameter orifice
Use: 0.625 " diameter orifice 0.0021 sf
Check Outflow time
Q= Cd A Sgrt(2 g h)
Q= 0.01 cfs
Drawdown time= 2.77 days OK
SC-6
Anti-Flotation Calculations
Project Name: Two Bale Lane
Pond Designation: WP-2
Riser Diameter = 8 in (circular)
Dimensions of Riser= ft
Depth of pond = 3 ft
Required Factor of Safety = 1.2
Cross Sectional Area of Riser
Circular = 0.348889 sf
Rectangular= 0 sf
Volume of Water Displaced
Depth of pond * Cross-sectional area
1.046667 cf
Weight of Water Displaced
(assuming weight of water = 62.4 Ib/cf)
62.4 * Volume of water Displaced
65.31 lb
Minimum Weight of Anti-Flotaton Device
FS * WoW Displaced
78.37 lb
Riser Base Provided
2 ft x 2 ft x 1.5 ft (depth)
Weight of concrete assumed 150 Ib/cf
Weight of Base Provided = 900.00 lb
FS Provided = 13.78 ok
SC-7
Water Quality Volume
Required for Storage
Project Name: Two Bale Lane
Outlet: WP-3
Calculate Runoff Coefficient
A= 1.47 acres
Ai= 1.40
la= 0.95
Watershed area
Impervious area
Impervious fraction
Rv=0.05+0.9*la
Rv= 0.91
Runoff Coefficient
Calculate Runoff Volume Required to be Controlled
Rd= 1 in
Design storm rainfall depth (typically 1" or 1.5")
V=3630*Rd*Rv*A
WQV= 4841 cf
1.33 Ac in
Volume of runoff that must be
controlled for specified design storm
SC-8
Drawdown Orifice Sizing
Project Name: Two Bale Lane
Outlet: Wet Pond-3
Pond Storage= 4,841 cf
Pond Depth(h)= 1.3 ft
Drawdown Time= 2.5 days
Cd= 0.6 Coefficient of Discharge (typical 0.6)
g= 32.2 ft/sec^2 Gravity
The Orifice Equation
Q= Cd A Sgrt(2 g h)
Rearrange to solve for A, the minimum orifice area needed to meet drawdown requirements
Q= 0.02 cfs Based on pond volume and desired drawdown time
A= 0.00408 sf 0.59 si
Number of Orifices= 1
Minimum diameter to meet area
d=
Use:
Check Outflow time
Q= Cd A Sgrt(2 g h)
Q=
Drawdown time=
0.87 inch diameter orifice
0.875 " diameter orifice 0.0042 sf
0.02 cfs
2.45 days OK
SC-9
Anti-Flotation Calculations
Project Name: Two Sale Lane
Pond Designation: WP-3 "
Riser Diameter = 8 in (circular)
Dimensions of Riser= ft
Depth of pond = 3 ft
Required Factor of Safety = 1.2
Cross Sectional Area of Riser
Circular = 0.348889 sf
Rectangular= 0 sf
Volume of Water Displaced
Depth of pond * Cross-sectional area
1.046667 cf
Weight of Water Displaced
(assuming weight of water = 62.4 Ib/cf)
62.4 * Volume of water Displaced
65.31 lb
Minimum Weight of Anti-Flotaton Device
FS * WoW Displaced
78.37 lb
Riser Base Provided
2 ft x 2 ft x 1.5 ft (depth)
Weight of concrete assumed 150 Ib/cf
Weight of Base Provided = 900.00 lb
FS Provided = 13.78 ok
SC-10