20081121 Ver 2_More Info Received_20100129

Summey Engineering Associates, PLLC
SEA Engineering- Land Planning • Consulting
PLLC PO Box 968 - Asheboro, NC 27204
[phone] / Fax: [phone] / [e-mail]
TRANSMITTAL / ?f c? pocko s
Date: January 27, 2010
To:
NCDENR-Division of Water Quality
401 Oversight & Express Permits Unit
2321 Crabtree Boulevard, Suite 250
Raleigh, NC 27604
ATTN: Ms. Annette Lucas, PE
Phone: [phone]
We are sending you attached the following items:
? Shop Drawings ? Samples
? Prints ? Specifications
® Plans ? Disk
Re:
os- l la.I U a'
Diamonds Keep S/D
DWQ Project #08-1121 V2
Randolph County, NC
Revised Plans
SEA Job No. E-1524
? Copy of Letter
? Other
# Copies Drawing # Description Disposition
1 ea. Response Letter
2 sets Revised Plans & Supporting Documentation 11ff@[q0V@
JAN 2
2
V
010

Remarks:
Annette, here are the revised plans and supporting documentation for this project. If
you need anything else just let me know.
Thanks!
Mack
By: aZ4-'.'
H. Mack ummey, PE
II
c: File
Summey Engineering Associates, PLLC
Engineering - Land Planning - Consulting
P.O. Box 968
Asheboro, NC 27204
Phone: [phone] - Fax: [phone]
January 26, 2010
Re: Diamonds Keep Subdivision
Response Letter
DWQ # 08-1121v2
Randolph County, NC
SEA Job No. E-1524
Ms. Sue Homewood
North Carolina Division of Water Quality
Winston-Salem Regional Office
585 Waughtown Street
Winston-Salem, North Carolina 27107
Dear Sue:
Enclosed are two (2) sets of revised plans and supporting material you requested per your
letter dated November 25, 2009. Posted below are your Comments and our Responses to
your letter.
DWO Comments:
Comment: 1. Please provide cross sectional details showing the provisions for aquatic life
passage (burial of culvert 20% for culverts < 48 inches, and 1-foot for culverts > 48
inches).
Response: Cross sectional details are now provided to show how Arch pipe is being
placed to allow for aquatic life passage. The Arch pipe carries the base flow for the
creek. The two (2) 72" pipe are specifically designed to function only during high
flow storm events and will remain dry most of the time. See Details on Sheet 18.
Comment: 2. Per the requirements of the General Certification, all work shall be done "in
the dry". Therefore, dewatering methods will be necessary to temporarily dewater the
stream channels during structure installations. Please provide a construction sequence
that details the method of dewatering to be utilized at the site and the sequence of
construction events to be followed to ensure compliance with this condition.
Response: Detailed plans and a Detailed Sequence of Construction are now
provided to outline to order of construction activities to ensure all work is done in
the dry. This will be utilized by a by-pass channel and coffer dams sequenced to
allow for the work to be done in the dry. See Sheet 19 for plan views, elevations and
the Sequence of Construction.
Comment: 3. Per the requirements of GC 3705, please enumerate all temporary impacts
(in addition to permanent impacts already indicated) to the stream channel. Temporary
impacts include areas of disturbance necessary for proper pipe installation, proper
dewatering, as well as any impacts from temporary erosion control measures or fill
stabilization. Please note that temporary impacts should be minimized to the maximum
extent practical.
Response: The temporary impacts include the placement of coffer dams in the
stream channel to dewater the work area. This area adds 2 areas approximately 15
ft wide by 10 ft long or a total of 20 if of additional temporary impacts. This
Temporary disturbance feature has been added to the PCN Form under Section C.3
- Stream Impacts. The method by which is being proposed for construction
minimizes the amount of disturbed area to the creek bed. All rip rap will be
removed once coffer dams are no longer needed. Total permanent length is 138',
temporary is 20' and is indicated on the PCN Form.
Stormwater Management Plan Review Comments:
Comment: 4. Overall, the DWQ accepts your approach of treating offsite area in lieu of
providing stormwater treatment for drainage areas 7 and 8. However, please describe the
current and future uses of the land in the offsite drainage area as well as an estimation of
the current and future imperviousness of the offsite area.
Response: The current use of the off-site property is a single family residential
subdivision called Windemere Heights. This has been the use of the property for
many years. It is our understanding that there are a few lots that have not built out
due to the lack of sewer in the area. Sewer in proposed within the next 5-10 years so
Single family homes may be constructed. Zoning for Windemere Heights is limited
to Single Family Units so no Multi-Family or high density developments could be
built. Below we summarize the current and possible proposed state of the offsite
areas:
Overall Offsite Drainage Area = 21.24 Acres
Current Offsite Impervious Area = 2.45 Acres
Future Offsite Impervious Area = 3.42 Acres ((max. build out) assuming 2500 sf
home, driveway and out building for lots not developed) {This is not 3.42 Ac.
additional to the 2.45 Ac but would be a total estimated build out meaning only 0.97
acres of Impervious area would be added to the existing 0.97 Ac. in the future
equaling 3.42 Ac.}.
Comment: 5. For all proposed stormwater BMPs, please provide soils test that has been
conducted within the footprint of every proposed BMP to document the level of the
SHWT. This information should be attached. Also, the BMP Supplement Forms and
plan sheets should be updated to reflect the new information. The DWQ will not approve
these BMPs without a soils test that has been sealed by an appropriately qualified
individual.
Response: Enclosed is a signed & sealed report detailing the SHWT levels provided
by a Licensed Soil Scientist who performed the work on-site.
Comment: 6. For all proposed BMPs, please provide a construction sequence that
explains how the BMP will be protected during the project construction.
Response: The rough grading is complete for the entire project so there will not be
a major earth moving operation being performed. However, the wet detention
ponds will be used as sediment basins with skimmers for each phase until
construction is complete. Once the fine grading/seeding/mulching and paving is
complete on each phase, the basins will be cleaned out, wetland plantings installed
and pond or sand filter will be converted to its permanent function. A sequence of
construction is detailed for each BMP. The BMP will not be put into operation until
the site is stabilized since this is basically an "after the fact" project.
Comment: 7. For all Wet Detention Ponds, please fill out the "Volume, temporary pool"
blank in the Supplement Forms.
Response: This has been provided as requested on the Supplement Forms.
Comment: 8. Please show the level of the temporary pools on the wet detention pond
profiles.
Response: This has been provided on the detail sheets for each pond.
Comment: 9. Please correct all discrepancies and errors in the Supplement Forms and
plan sheets. For example, for Basin 1, the size of the orifice on the Supplement Form is
stated to be 2 inches, but the plan sheet says 2.5 inches.
Response: These items have been corrected.
Comment: 10. Please correct errors in the values of driving head that have been entered
into the Wet Detention Basin Supplement Forms. The driving head is equal to the
Temporary Pool elevation minus the Permanent Pool elevation.
Response: This item has been corrected.
Comment: 11. For the sand filters, please provide specifications for the sand media
material that is to be used.
Response: The sand specification is located on the plan but has been shown at each
section on the detail sheets for clarification.
We appreciate your working with us on this project and we are dedicated to its
completion. Please note that no further phases of the project will be disturbed until all
approvals from your office have been obtained. Once these approvals are obtained, the
pond for Phase 1 will be installed and each additional BMP as necessary for each specific
phase.
Should you have any questions or concerns or require any additional information,
please do not hesitate to contact me directly at 336-328-0902.
Very Truly Yours,
Summey Engineering Associates, PLLC
H. Mack Summey, Jr., PE
HMSJ/hmsj
Cc: Mr. Gary White, Diamond W Builders, LLC
File
R{ % seof S.1--k
08-aka 1 L)a-
C. Proposed Impacts Inventory
1. Impacts Summary
1a. Which sections were completed below for your project (check all that apply):
® Wetlands ® Streams - tributaries ? Buffers
? Open Waters ? Pond Construction
2. Wetland Impacts
If there are wetland impacts proposed on the site, then complete this question for each wetland area impacted.
2a. 2b. 2c. 2d. 2e. 2f.
Wetland impact Type of jurisdiction
number - Type of impact Type of wetland Forested (Corps - 404, 10 Area of impact
Permanent (P) or (if known) DWQ - non-404, other) (acres)
Temporary T
W1 ®P ? T Fill Bottom of pond ? Yes ? Corps 254
removed ® No ? DWQ .
W2 ? P ®T Fill - Temporary Forrested ® Yes
? No ? Corps
? DWQ .001
W3 ®P ? T Fill Bottom of ? Yes ? Corps 140
removed pond ® No ? DWQ .
W4 ®P ? T Fill Forrested ® Yes
? No ? Corps
? DWQ .051
W5 ? P ? T ? Yes ? Corps
? No ? DWQ
W6 ? P ? T ? Yes ? Corps
? No ? DWQ
2g. Total wetland impacts .446
2h. Comments: " .001 Ac. included but is temporary impact for Sewer.
3. Stream Impacts
If there are perennial or intermittent stream impacts (including temporary impacts) proposed on the site, then complete this
question for all stream sites impacted.
3a. 3b. 3c. 3d. 3e. 3f. 3g.
Stream impact Type of impact Stream name Perennial Type of jurisdiction Average Impact
number - (PER) or (Corps - 404, 10 stream length
Permanent (P) or intermittent
DWQ -non-404,
width
(linear
Temporary (T) (INT)? other) (feet) feet)
S1 ®P ? T Culvert Caraway Creek ® PER
? INT ® Corps
® DWQ 15' 66'
S2 ®P ? T Rip Rap Caraway Creek ® PER
? INT ® Corps
® DWQ 15' 72'
S3 ? P ®T Rip Rap -
Temporary Caraway Creek ® PER
? INT ® Corps
® DWQ 15 10"
S4 ? P ®T Rip Rap -
Temporary Caraway Creek ® PER
? INT ® Corps
® DWQ 15 101*
S5 ? P ? T ? PER ? Corps
? INT ? DWQ
S6 ? P ? T ? PER ? Corps
? INT ? DWQ
3h. Total stream and tributary impacts 138' (*20')
3i. Comments: 138' Involves crossing of creek with pipe, "2 -10' sections are temporary coffer dams that will be removed.
Page 5 of 11
PCN Form - Version 1.3 December 10, 2008 Version
Scott F. Cole
Licensed Soil Scientist
312 Copple's Road Ext.
Asheboro, NC 27205-0711
H: [phone]; M: [phone]
Summey Engineering Associates
Attn: Mr. Mack Summey
1342 E. Salisbury Street
Asheboro, NC 27203
January 26, 2010
Re: Identification of the seasonal high-water table for storm-water devices in the Diamonds Keep subdivision
located on Archdale Road, Randolph County, NC.
Mr. Summey,
Per your request, soil conditions were evaluated at multiple locations on the above-referenced property to
determine the depth of the seasonal high-water table. Work was conducted to satisfy requirements set forth in
the North Carolina Division of Water Quality Stormwater Best Management Practices Manual.
Soil borings around proposed wet ponds and future sand filters were evaluated. Samples were collected with
hand augers.
The seasonal high-water table is determined by a field evaluation for soil wetness conditions. Soil wetness
conditions are determined by the presence of colors with a chroma of 2 or less (in Munsell color notation) in
mottles or the horizon matrix. Colors of chroma 2 or less due to relic minerals from the parent material
(underlying rock) are not considered as indicators for soil wetness conditions.
RESULTS
0 Site 1: Wet pond (lot #5) i'0 rj I
Base elevation: 742.69'
Seasonal high-water observed 6.5' below surface
Seasonal high-water elevation: 736.19'
• Site 2: Wet pond (behind lot #21) ?0 r1j 2
Base elevation: 721.02'
Seasonal high-water not observed within 7' of surface (714.021)
Note: Base elevation is 1.25' (15 inches) above bottom of pond.
• Site 3: Wet pond (behind lots #195-197) PO ri I 2
Base elevation: 726.15'
Seasonal high-water observed 1.5' (18 inches) below surface
Seasonal high-water elevation: 724.65'
• Site 4: Wet pond (south of lot #201) ?v r A \'?
Base elevation: 704.66'
Seasonal high-water not observed within 7' of surface (697.661)
Site 5: Sand filter (front of lots #67 & 68) 5O.W,a ?: 1-?_ ( 5
Base elevation: 707.9'
Seasonal high-water not observed within 16' of surface (691.9')
• Site 6: Sand filter (front of lots #64 & 65) So,,. a N--z \-?_ e 4-
Base elevation: 704.14'
Seasonal high-water not observed within 13' of surface (691.14')
The attached map shows the location of each sampling point, its elevation, and the elevation at which the
seasonal high-water table was observed (if applicable).
I am pleased to be of service in this matter and will be available, if necessary, to provide additional services that
may aid in the successful completion of this project.
Thank you,
C
Scott F. Cole
North Carolina Licensed Soil Scientist
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Permit No.
(to be provided by DWQ)
OF WA149
A*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 III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name Diamond Keep Subdivision
Contact person H. Mack Summey, Jr., PE
Phone number 336-328-0902
Date 1/27/2010
Drainage area number 1
II. DESIGN INFORMATION
Site Characteristics
Drainage area 691,733 ftz
Impervious area, post-development 203,860 ftz
% impervious 29.47 %
Design rainfall depth 1.0 in
Storage Volume: Non-SA Waters
Minimum volume required 18,200 ft3 OK
Volume provided 19,050 ft3
OK, volume provided is equal to or in excess of volume required.
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
ft3
ft3
ft3
ft3
ft3
(Y or N)
2.8 in
0.30 (unitless)
0.50 (unitless)
0.12 in/hr OK
0.57 ft3/sec
0.96 ft3/sec
0.39 ft3/sec
739.25 fmsl
737.50 fmsl
736.19 fmsl
739.25 fmsl
fmsl
734.50 fmsl
fmsl
734.50 ft
N (Y or N)
fmsl
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Parts I. & II. Design Summary, Page 1 of 2
Permit
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 12,590 ftz
Area REQUIRED, permanent pool
SA/DA ratio
Area PROVIDED, permanent pool, Apenpwl
Area, bottom of 1 Oft vegetated shelf, Abot shelf
Area, sediment cleanout, top elevation (bottom of pond), Abd wd
Volumes
Volume, temporary pool
Volume, permanent pool, Vpem-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 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, Vperm-pool
Area provided, permanent pool, Aperm_pool
Average depth calculated
Average depth used in SA/DA, dav, (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Aperm pool
Area, bottom of 1 Oft vegetated shelf, Abot shelf
Area, sediment cleanout, top elevation (bottom of pond), Abet-pond
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment)
Average depth calculated
Average depth used in SA/DA, deV, (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 (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 is:
9,131 ftz
1.32 (unitless)
9,181 ftz OK
12,500 ft`
5,163 ftz
19,050 ft3 OK
59,088 ft3
11,450 ft3
19.4% % OK
85 %
N (Y or N)
Y (Y or N)
1.32 (unitless)
Y (Y or N)
59,088 ft'
9,181 ftz
3.00 ft OK
3.0 ft OK
N (Y or N)
9,181 ftz
12,500 fe
5,163 ftz
-734.50 ft
3.00 ft OK
ft
Y (Y or N)
2.50 in
inz
0.60 (unitless)
1.75 ft
N (Y or N)
(unitless)
(unitless)
ft
ft
ft3/sec
ft3/sec
ft3/sec
3.00 days OK, draws down in 2-5 days.
3 :1 OK
10 :1 OK
10.0 ft OK
3 :1 OK
2.0 :1 OK
Y (Y or N) OK
1.5 It OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Shear Gate is provided to drain pond.
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Parts I. & II. Design Summary, Page 2 of 2
Permit
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, 9O
? r
? y
1. PROJECT INFORMATION
Project name Diamond Keep Subdivision
Contact person H. Mack Summey, Jr., PE
Phone number 336-328-0902
Date 10/14/2009
Drainage area number
II. DESIGN INFORMATION
Site Characteristics
Drainage area 871,200 ft2
Impervious area, post-development 336,719 ft2
% impervious 38.65 %
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 1Oft 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
29,200 ft3 OK
29,702 ft3
OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
(Y or N)
2.8 in
0.30 (unitless)
0.50 (unitless)
0.12 in/hr OK
0.72 ft3/sec
1.20 ft3/sec
0.48 ft3/sec
717.20 fmsl
717.20 fmsl
714.02 fmsl
715.50 fmsl
fmsl
712.50 fmsl
fmsl
712.50 ft
(Y or N)
fmsl
Form SW401-Wet Detention Basin-Rev.e-9/17/09 Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 19,671 ft'
Area REQUIRED, permanent pool 13,678 ft'
SA/DA ratio 1.57 (unitless)
Area PROVIDED, permanent pool, Aperm
pool 15,272 fe OK
_
Area, bottom of 1Oft vegetated shelf, Abot shelf 19,650 ft
Area, sediment cleanout, top elevation (bottom of pond), Abot?ohd 7,939 ft
Volumes
Volume, temporary pool 29,702 ft3 OK
Volume, permanent pool, Vperm-pool 88,046 ft3
Volume, forebay (sum of forebays if more than one forebay) 17,610 ft3
Forebay % of permanent pool volume 20.0% % OK
SAIDA Table Data
Design TSS removal 85 %
Coastal SA/DA Table Used? N (Y or N)
Mountain/Piedmont SA/DA Table Used? Y (Y or N)
SA/DA ratio 1.57 (unitless)
Average depth (used in SA/DA table):
Calculation option 1 used? (See Figure 10-2b) Y (Y or N)
Volume, permanent pool, Vpenpool 88,046 ft'
Area provided, permanent pool, Aperm_pool 15,272 ft
Average depth calculated 3.00 It OK
Average depth used in SA/DA, day, (Round to nearest 0.5ft) 3.0 It OK
Calculation option 2 used? (See Figure 10-2b) N (Y or N)
Area provided, permanent pool, Aperm-pool 15,272 ft`
Area, bottom of 1 Oft vegetated shelf, Abut shelf 19,650 ft
Area, sediment cleanout, top elevation (bottom of pond), Abot_p0ed 7,939 ff
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment) -712.50 ft
Average depth calculated 3.00 ft OK
Average depth used in SA/DA, day, (Round to nearest 0.5ft) ft
Drawdown Calculations
Drawdown through orifice? Y (Y or N)
Diameter of orifice (if circular) 3.00 in
Area of orifice (if-non-circular) in'
Coefficient of discharge (CD) 0.60 (unitless)
Driving head (Ho) 1.70 ft
Drawdown through weir? N (Y or N)
Weir type (unitless)
Coefficient of discharge (Cw) (unitless)
Length of weir (L) ft
Driving head (H) It
Pre-development 1-yr, 24-hr peak flow ft3/sec
Post-development 1-yr, 24-hr peak flow ft3/sec
Storage volume discharge rate (through discharge orifice or weir) ft3/sec
Storage volume drawdown time 3.00 days OK, draws down in 2-5 days.
Additional Information
Vegetated side slopes 3 :1 OK
Vegetated shelf slope 10 :1 OK
Vegetated shelf width 10.0 It OK
Length of flowpath to width ratio 3 :1 OK
Length to width ratio 2.0 :1 OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1.5 It OK
Vegetated filter provided? Y (Y or N) OK
Recorded drainage easement provided? Y (Y or N) OK
Capures all runoff at ultimate build-out? Y (Y or N) OK
Drain mechanism for maintenance or emergencies is: Shear Gate Provided to drai n pon
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Parts I. & II. Design Summary, Page 2 of 2
Permit
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)
OF W A 7-f;,?
O?
? y
o
I. PROJECT INFORMATION
Project name Diamond Keep Subdivision
Contact person H. Mack Summey, Jr., PE
Phone number 336-328-0902
Date 10/14/2009
Drainage area number
12
II. DESIGN INFORMATION
Site Characteristics
Drainage area 747,054 ftz
Impervious area, post-development 165,528 ft2
% impervious 22.16 %
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 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 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
31,250 ft3 OK
32,635 ft3
OK, volume provided is equal to or in excess of volume required.
to
ft3
ft3
ft3
ft3
(Y or N)
2.8 in
0.30 (unitless)
0.50 (unitless)
0.12 in/hr OK
1.40 ft3/sec
2.30 ft3/sec
0.90 ft3/sec
728.25 fmsl
726.50 fmsl
726.50 fmsl
726.50 fmsl
fmsl
723.50 fmsl
fmsl
723.50 ft
(Y or N)
fmsl
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Paris I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 21,335 ftz
Area REQUIRED, permanent pool 7,097 ftz
SA/DA ratio 0.95 (unitless)
Area PROVIDED, permanent pool, Apes Pool 15,887 ft` OK
Area, bottom of 1 Oft vegetated shelf, AW shelf 21,300 ft`
Area, sediment cleanout, top elevation (bottom of pond), Abotyond 5,531 ft`
Volumes
Volume, temporary pool 32,635 ft3 OK
Volume, permanent pool, Vperm-pool 129,904 ft3
Volume, forebay (sum of forebays if more than one forebay) 25,990 ft3
Forebay % of permanent pool volume 20.0% % OK
SAIDA Table Data
Design TSS removal 85 %
Coastal SA/DA Table Used? N (Y or N)
Mountain/Piedmont SA/DA Table Used? Y (Y or N)
SA/DA ratio 0.95 (unitless)
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b) Y (Y or N)
Volume, permanent pool, Vperm-pwl 129,904 ft'
Area provided, permanent pool, Apen-pool 15,887 ft
Average depth calculated 3.00 ft OK
Average depth used in SA/DA, day, (Round to nearest 0.5ft) 3.0 ft OK
Calculation option 2 used? (See Figure 10-2b) N (Y or N)
Area provided, permanent pool, Aperm_pool 15,887 ft`
Area, bottom of 1 Oft vegetated shelf, AW shelf 21,300 ft`
Area, sediment cleanout, top elevation (bottom of pond), Abot pod 5,531 ftz
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment) -723.50 ft
Average depth calculated 3.00 ft OK
Average depth used in SAIDA, da,, (Round to nearest 0.5ft) ft
Drawdown Calculations
Drawdown through orifice? Y (Y or N)
Diameter of orifice (if circular) 3.25 in
Area of orifice (if-non-circular) in2
Coefficient of discharge (CD) 0.60 (unitless)
Driving head (Ho) 1.75 ft
Drawdown through weir? N (Y or N)
Weir type (unitless)
Coefficient of discharge (CW) (unitless)
Length of weir (L) ft
Driving head (H) ft
Pre-development 1-yr, 24-hr peak flow ft3/sec
Post-development 1-yr, 24-hr peak flow ft3/sec
Storage volume discharge rate (through discharge orifice or weir) ft3/sec
Storage volume drawdown time 3.00 days OK, draws down in 2-5 days.
Additional Information
Vegetated side slopes 3 :1 OK
Vegetated shelf slope 10 :1 OK
Vegetated shelf width 10.0 ft OK
Length of flowpath to width ratio 3 :1 OK
Length to width ratio 2.0 :1 OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1.5 ft OK
Vegetated filter provided? Y (Y or N) OK
Recorded drainage easement provided? Y (Y or N) OK
Capures all runoff at ultimate build-out? Y (Y or N) OK
Drain mechanism for maintenance or emergencies is: Shear Gate is provided to drain pond.
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Parts I. & II. Design Summary, Page 2 of 2
Permit
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)
?OF W A
TF9QG
o
r
O Y
I. PROJECT INFORMATION
Project name Diamond Keep Subdivision
Contact person H. Mack Summey, Jr., PE
Phone number 336-328-0902
Date 10/14/2009
Drainage area number 13
II. DESIGN INFORMATION
Site Characteristics
Drainage area 478,724 ft
Impervious area, post-development 182,081 ftz
% impervious 38.03 %
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 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
15,700 ff3 OK
15,927 ff3
OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
Y (Y or N)
2.8 in
0.30 (unitless)
0.50 (unitless)
0.12 in/hr OK
0.39 ft3/sec
0.66 ft3/sec
0.27 ft3/sec
703.50 fmsl
701.50 fmsl
697.66 fmsl
701.50 fmsl
fmsl
698.50 fmsl
fmsl
698.50 ft
Is there additional volume stored above the state-required temp. pool? N (Y or N)
Elevation of the top of the additional volume fmsl
Form SW401-Wet Detention Basin-Rev.8-9/17/09
Parts I. & II. Design Summary, Page 1 of 2
Permit
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool 9,763 ftz
Area REQUIRED, permanent pool 7,899 ft'
SAIDA ratio 1.65 (unitless)
Area PROVIDED, permanent pool, Apen-pod 7,934 ft` OK
Area, bottom of 1Oft vegetated shelf, Abot shelf 9,723 fe
Area, sediment cleanout, top elevation (bottom of pond), Abot?ortd 3.027 ftL
Volumes
Volume, temporary pool 15,927 ft3 OK
Volume, permanent pool, Vperm pool 44,884 ft3
Volume, forebay (sum of forebays if more than one forebay) 8,980 ft3
Forebay % of permanent pool volume 20.0% % OK
SAIDA Table Data
Design TSS removal 85 %
Coastal SAIDA Table Used? N (Y or N)
Mountain/Piedmont SAIDA Table Used? Y (Y or N)
SAIDA ratio 1.65 (unitless)
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b) Y (Y or N)
Volume, permanent pool, Vperm-pool 44,884 ft'
Area provided, permanent pool, Apempwl 7,934 ft`
Average depth calculated 3.00 It OK
Average depth used in SAIDA, de,,, (Round to nearest 0.5ft) 3.0 It OK
Calculation option 2 used? (See Figure 10-2b) N (Y or N)
Area provided, permanent pool, Aperm-pool 7,934 ft`
Area, bottom of 1Oft vegetated shelf, Abot shelf 9,723 ft`
Area, sediment cleanout, top elevation (bottom of pond), Abot?or,d 3,027 ft2
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment) -698.50 ft
Average depth calculated 3.00 It OK
Average depth used in SAIDA, day, (Round to nearest 0.5ft) It
Drawdown Calculations
Drawdown through orifice? Y (Y or N)
Diameter of orifice (if circular) 2.25 in
Area of orifice (if-non-circular) in2
Coefficient of discharge (CD) 0.60 (unitless)
Driving head (Ho) 1.80 ft
Drawdown through weir? N (Y or N)
Weir type (unitless)
Coefficient of discharge (CW) (unitless)
Length of weir (L) ft
Driving head (H) ft
Pre-development 1-yr, 24-hr peak flow ft3/sec
Post-development 1-yr, 24-hr peak flow ft3/sec
Storage volume discharge rate (through discharge orifice or weir) ft3/sec
Storage volume drawdown time 3.00 days OK, draws down in 2-5 days.
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 is:
3 :1 OK
10 :1 OK
10.0 ft OK
3 :1 OK
2.0 :1 OK
Y (Y or N) OK
1.5 It OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Shear Gate is provided to drain p
Form SW401-Wet Detention Basin-Rev.8-9/17/09 Parts I. & II. Design Summary, Page 2 of 2