Hoke County Cooperative Extension Office Building - Stormwater Report

HOKE COUNTY COOPERATIVE
EXTENSION OFFICE BUILDING
663 EAST PALMER STREET
RAEFORD, NORTH CAROLINA
STORMWA TER REPORT
4
DATE: 23 APRI�°j�""19
A """ff Ay7w
E3 I G I Q - B L.1 I L-
600 GERMANTOWN ROAD
RALEIGH, NC 27607
TELEPHONE [phone]
FAX 91 9-851 - 1982

PROJECT NARRATIVE
This project is for a ±16,000 sf government office and associated access, parking,
and utilities. The project is located in Raeford, North Carolina on an existing ±20-acre
parcel. There are no 100-year floodplains or lumber basin riparian buffers on the
property. Storm water runoff is collected and directed via erosion and sedimentation
control measures to a temporary sediment basin during grading. In the final condition, a
majority of the developed area will be directed to a stormwater infiltration basin. The
infiltration basin will reduce run-off from the developed areas to below pre -
development levels for the 1-yr, 24-hour storm events. Permanent stormwater devises
release overflow events through either a 15' spillway (infiltration basin 1) a flared end
section to existing grade (infiltration basin 2).
There are no special or experimental erosion control devices and construction
sequence is state of NC standard with the following exception: none

SUPPLEMENT-EZ

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
FORMS LOADED
27
Name and Title:
Blair Pittman, PE
28
anization:
Bobbin Design Build, Inc.
29
Street address:
600 Germantown Road
30
Cit , State, Zip:
Raleigh, NC 27607
31
Phone numbers):
919 851-1980
32
Email:
hnittm—Mkl khiH ..--
Certification Statement:
I certify, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or
supervision; that the information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and
that the engineering plans, specifications, operation and maintenance agreements and other supporting information are consistent
with the information provided here.
iyi� �rft� nature of Designer
IWNr.
�s a{! Date

DRAINAGE AREAS
1 Is this a high density project? Yes
2 If so, number of draina a areasISCMs 2
Is ail/part of this project subject to previous rule
3 versions? No
FORMS LOADED
DRAINAGE AREA INFORMATION
Entire Site
7
2
4
T e of SCM
NA
Infiltration
Infiltratio
5
Total BUA in project s ft
I
265355 sf
25185 sf
34360 s
6
New BUA on subdivided lots (subject to permitting)
(sq ft
7permitting)
New BUA outside of subdivided lots (subject to
s
60755 sf
25185 sf
30215 sl
8
Offsite total area (sq ft
9
Offsite BUA (sq ft
10
Breakdown of new BUA outside subdivided lots:
Parking (sq ft
38590 sf
14910 sf
19790 sf
Sidewalk (sq ft
6165 sf
2275 sf
2425 sf
Roof (sq.ft
16000 sf
8000 sf
8600 sf
Roadway s ft
Future (sq ft
Other, please specify in the comment box
below (sq ft
New infiltrating permeable pavement on
11 subdivided lots (sq ft
New infiltrating permeable pavement outside of
12 subdivided lots (sq ft
Exisitng BUA that will remain (not subject to
13 1 permitting)ft
204600 sf
4145 sf
Existin BUA that is alreadypermitted s ft
Existing BUA that will be removed s ft
Percent BUA
N18
31%
Design storm inches
1 in
1 in
1 in
Desi n volume of SCM cu ft
3870 cf
4040 of
Calculation method for design volume
Simple
Simple
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
20 1drainaue area(s):

INFILTRATION SYSTEM
1
Drainage area number
1
2
2
GENIERM
3 Its
Design volume of SCM (cu ft)
MP& F
the SCM sized to treat the SW from all surfaces at build -out?
3870 cf
Yes
4040 cf
Yes
4 Its
the SCM located away from contaminated soils?
Yes
Yes
5 1
What are the side slopes of the SCM (H:V)?
3:1
3:1
6
Does the SCM have retaining walls, gabion walls or other engineered side slopes?
No
No
7 Are the inlets, outlets, and receiving stream protected from erosion (I0-yearstorm)?
Yes
Yes
8 Is there an overflow or bypass for inflow volume in excess of the design volume?
Yes
Yes
9 What is the method for dewatering the SCM for maintenance?
Pump (preferred)
Pump (preferred)
10 If applicable, will the SCM be cleaned out after construction?
Yes
Yes
11 Does the maintenance access comply with General MDC (8)?
Yes
Yes
12 Does the drainage easement comply with General MDC (9)?
if the SCM is on a single family lot, does (will?) the plat comply with General MDC
13 (10)?
14 Is there an 0&M Agreement that complies with General MDC (11)?
Yes
Yes
15 Is there an O&M Plan that complies with General MDC (12)?
Yes
Yes
16 Does the SCM follow the device specific MDC?
Yes
Yes
17 Was the SCM designed by an NC licensed professional?
N
Yes
Yes
18 Proposed slope of the subgrade surface (%)
Q%
0%
19 Are terraces or baffles provided?
No
No
20 Type of pretreatment:
Other
Other
Soils Data
Was the soil investigated in the footprint and at the elevation of the infiltration
21 system?
[2-2
Yes
Yes
ISHWT elevation (fmsl)
245.00
241.00
23 1 Depth to SHWT per soils report (in)
48.00
120.00
24 lGround elevation at boring in soils report (fmsl)
249.00
251.00
25 Is a detailed hydrogeologic study attached if the separation is between 1 and 2 feet?
26 ISoil infiltration rate (in/hr)
2.00
2.00
27 1 Factor of safety (FS) (2 is recommended):
2.00
2.00
29 113ottom elevation (fmsl) _
247. R
247 ft
30 IStorage elevation (fmsl)
248 ft
248 ft
31 1 Bypass elevation (fmsl)
248, ft
248 ft
For Basins Only
32 Bottom surface area, ft�;
2937 ft
3172 ft
33 Storage elevation surface area (ft2)
4810 ft
4977 ft
For Trenches Only
34 Lengih (ft)
35 Width (ft)
36 Perforated pipe diameter, if applicable (inches)
37 Number of iaterals
38 Total length of perforated piping
39 Stone type, if applicable
40 Stone void ratio (%)
41 Is stone free of fines?
42 Is the stone wrapped in geotextile fabric?
43 1 Has at least one infiltration port been provided?
Volumes/Drawdown
filtration 1 i -an ven ahihma

DRAINAGE AREA RUN-OFF SUMMARY

Drainage Area Run-off Summary
Hoke County Cooperative Extension Office Buildin —
663 East Palmer Street
663 East Palmer Street is a developed property that is used for county government
services, mainly the Hoke County Health Department. The proposed developed area is at
the top of the drainage area and runoff from the existing developed area does not flow
onto the new development, except for a portion of the existing driveway. The run-off
from the existing driveway sheet flows into a proposed infiltration basin. This run-off is
accounted for in peak flow calculations but is not included in the required treatment
calculations. The other drainage basins on this property are not modeled as there will be
no changes in these areas.
The project is located in located in one drainage area. The drainage area sheet flows off
site. The point of analysis for the drainage area is the same for pre -development and post -
development conditions. This point is chosen because it allows for modeling of
stormwater that includes discharge from the proposed BMP. See Exhibit DA-1 for pre -
development drainage map.
Two infiltration basins are proposed for stormwater quantity and quality control. The
infiltration basins are primary stormwater control measures (SCM) and are sized to meet
run-off treatment requirements. They are also sized for extended detention to control
peak flow for the l -year, 24 hour storm. In the post -development condition, the
infiltration basins will serve most of the proposed project impervious area as well as a
portion of the existing driveway. See Exhibit DA-2 for post -development drainage map.
Drainalle Areas
Total drainage area pre -development = 5.34 Acres
Total drainage area post -development = 5.42 Acres
Drainage area post -development (routed through infiltration 1) = 0.91 acres
Drainage area post -development (routed through infiltration 2) = 1.17 acres
Drainage area post -development (by-pass infiltration) = 3.34 acres
Proposed Curve Numbers
Proposed Coefficient (C-Values)
C (open space, graded, and landscaped)
C (impervious)
= 0.35
= 0.95

Drains a Areas 1 yr. Rational method
Peak Discharge of Runoff --1-year storm
Point of Pre-Dev
Post-Dev
Post-Dev
Post-Dev
Post-Dev
Analysis Peak
By-pass
Routed
Routed
Peak
Discharge
Pond
through
through
Discharge
Infiltration 1
Infiltration 2
Drainage Area 2.25 cis
j 1.42 cfs
0.00 cfs
0.00 cfs
1.42 cfs
Drains a Areas 2 yr. Rational method
Peak Discharge of Runoff -- 2-year storm
Point of Pre-Dev
Post-Dev
Post-Dev
Post-Dev
Post-Dev
Analysis Peak
By-pass
Routed
Routed
Peak
Discharge
Pond
through
through
Discharge
Infiltration
Infiltration
1
2
Drainage Area 2.76 cfs
1.73
0.00 cfs
0.00 cfs
1.73 cfs
Drainage Areas 10 r. Rational method
Peak Discharge of Runoff — 10-vear storm
Point of
Pre-Dev
Post-Dev
Post-Dev
Post-Dev
Post-Dev
Analysis
Peak
By-pass
Routed
Routed
Peak
Discharge
Pond
through
through
Discharge
Infiltration
Infiltration
1
2
Drainage Area
3.95 cfs
2.48 cfs
0.00 cfs
0.00 cfs
2.48 cfs
Drainage Areas (100 vr. Rational method
Point of Pre-Dev
Post-Dev
Post-Dev
Post-Dev
Post-Dev
Analysis Peak
By-pass
Routed
Routed
Peak
Discharge
Pond
through
through
Discharge
Infiltration
Infiltration
1
2
Drains e Area I 5.77 cfs
3.63 cfs
0.00 cfs
10.00 cfs
3.63 cfs

Watershed Model Schematic
1
Leaend
tiyd. Origin
1 Rational
Pre -development
2 Rational
Post -development DA-1
3 Rational
Post -development DA-2
a Rational
Past-development-SCM By-pass
5 Reservoir
Infiltration 1 (DA-1)
6 Reservoir
Infiltration 2 (DA-2)
7 Combine
Post -development
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
2 3 4
V111111-
77
7
Project: Infiltration Basin.gpw � Tuesday, 04 / 23 / 2019

Pond Report
Hydraflow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12 Tuesday, 04/23/2019
Pond No. 1 - Infiltration 1
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 247,00 ft
Stage 1 Storage Table
Stage (ft)
Elevation (ft)
Contour area (sgft)
Incr. Storage (tuft)
Total storage (tuft)
0.00
247.00
2,937
0
0
1.00
248.00
4,880
3,867
3,867
1.50
248,50
5,890
2,688
6,656
Culvert 1 Orifice Structures
Weir Structures
[A]
[B]
[C]
[PfiRsr]
[Al
[Bl
[C]
[Dl
Rise (in)
= 0.0D
0.00
0.00
0.00
Crest Len (ft)
= 15.00
0.00
0.00
0.00
Span (in)
= 0.00
0,00
0.00
0.00
Crest El. (ft)
= 247.50
0.00
0.00
0.00
No. Barrels
= 0
0
0
0
Weir Coeff.
= 3.33
3.33
3.33
3.33
Invert El. (ft)
= 0.00
0.00
0.00
0.00
Weir Type
= Ciplti
-
---
---
Length (ft)
= 0.00
0.00
0.00
0.00
Multi -Stage
= No
No
No
No
Slope (*A)
= 0.00
0.00 0.00
nla
N-Value
= .013
.013 .013
nla
Orifice Coeff.
= 0.60
0,60 0.60
0.60 Exfrl.(inthr) = 1,000 (by Contour)
Multistage
= n/a
No No
No TW Elev. (ft) = 0.00
Note: CulverilOrifice oul tows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage (ft)
Stage 1 Discharge Elev (ft)
Z.
1.8(
1.6(
1 AC
110
1,00
0.80
0.60
0.40
0.20
0 nn
249.OD
248.80
248.60
248.40
248.20
248.00
247.80
247.60
247.40
247.20
24700
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00
Total Q Discharge (cfs)

Pond Report
Hydraftow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12
Tuesday, D4 / 23 12019
Pond No. 2 - Infiltration 2
Pond Data
Contours -User-defined contour areas. Conic method
used for volume calculation. Begining
Elevation = 247.00 ft
Stage / Storage Table
Stage (ft) Elevation (ft)
Contour area (sgft) Incr. Storage (cuft)
Total storage (cuff)
0,00 247.00
3,172
0
0
1,00 248.00
4,977
4,040
4,040
2.00 249.OD
6,839
5,883
9,923
3.00 250.00
8,757
7,777
17,701
Culvert / Orifice Structures
Weir Structures
[A] [Bl
[C]
[Pr(Rsr]
[A] [B]
[C]
[D]
Rise (in) = 15.00 0.00
0.00
0.00 Crest Len (ft)
= 0.00 0,00
0,00
0.00
Span (in) = 15.00 0,00
0.00
0.00 Crest El. (ft)
= 0.00 0.00
0.00
0.00
No. Barrels = 1 0
0
0 Weir Coeff.
= 3.33 3.33
3.33
3.33
Invert El. (ft) = 248.00 0.00
0.00
0.00 Weir Type
= - -
-
-
Length (ft) = 117.00 0.00
0.00
0.00 Multistage
= No No
No
No
Slope (%) = 0.50 0.00
0.00
n/a
N-value = .013 .013
.013
n/a
Orifice Coeff. = 0.60 0.60
0.60
0.60 Exfil.(in/hr)
= 1.000 (by Contour)
Multi -Stage = n/a No
No
No TW Elev. (ft)
= 0.00
Note:
CulvertlOrifice outflows are analyzed under inlet (ic) and outlet (oc) corrim]. Weir risers checked for orifice conditions (Ic) and submergence (s).
Stage (ft)
Stage / Discharge
Eiev (ft)
3.00
250.00
2.00
249.00
1.00
248.00
0.00
0.00 1,00
2.00
3.00
4.00 5.00
247.00
6.00
Total 0
Discharge (cfs)

I YEAR STORM

Hydrograph Summary Report
Hydraflow Hydrographs Extension for AutoCADO Civil 313® 2018 by Autodesk, Inc. v12
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type now interval Peak volume hyd(s) elevation strge used Description
(origin) 1(cfs) 1(min) (min) (tuft) I I (ft) I (tuft)
1 Rational
2.254
1
76
10.214 ----
------ Pre -development
2 Rational
2.976
1
5
893 -- ------
---- Post -development DA-1
3 Rational
3.931
1
5
1,179 ----
---- Post -development DA-2
4 Rational
1.418
1
75
6,379 ------ ------
------ Past-development-SCM By-pass
5 Reservoir
0.000
1
18
0 2 247.23
885 Infiltration 1 (DA-1)
6 Reservoir
0.000
1
33
0 3 247.29
1,169 Infiltration 2 (DA-2)
7 Combine
1.418
1
75
6,379 4, 5, 6 ------
------ Post -development
Infiltration Basin.gpw
Return Period: 1 Year I
Tuesday, 04/23 / 2019

Hydrograph Report
Hydrafiow Hydrographs Extension for AutoCADS Civil 3D® 2018 by Autodesk, Inc. 02
Hyd. No. 1
Pre -development
Hydrograph type
= Rational
Storm frequency
= 1 yrs
Time interval
= 1 min
Drainage area
= 5.340 ac
Intensity
= 1.172 in/hr
OF Curve
= mid_NC_1yr.IDF
2.0(
1.00
Tuesday, 04 / 23 / 2019
= 2.254 cfs
76 min
= 10,214 cult
= 0.36
= 75.54 min
= 1/1
Peak discharge
Time to peak
Hyd. volume
Runoff coeff.
Tc by TR55
Asc/Rec limb fact
Pre -development
Hyd. No. 1 — 1 Year
20 40 60 80 100 120 140
Hyd No. 1
Q (cfs)
3.00
2.00
1.00
,1.00
160
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCADO Civil 3D® 2018 by Autodesk, Inc. v12
Hyd. No. 2
Post -development DA-1
Hydrograph type
= Rational
Storm frequency
= 1 yrs
Time interval
= 1 min
Drainage area
= 0.910 ac
Intensity
= 4.480 inlhr
OF Curve
= mid_NC_1yr.IDF
2.0c
1.00
Tuesday, 04 / 2312019
= 2.976 cfs
= 5 min
= 893 cuft
= 0.73
= 5.00 min
111
Peak discharge
Time to peak
Hyd. volume
Runoff coeff.
Tc by User
Asc/Rec limb fact
Post -development DA-1
Hyd. No. 2 -- 1 Year
1 2 3 4 5 6 7 8 9
Hyd No. 2
Q (cfs)
3.00
2.00
1.00

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. 02
Tuesday, 04123 12019
Hyd. No. 3
Post -development DA-2
Hydrograph type
= Rational
Peak discharge
= 3.931 cfs
Storm frequency
= 1 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 1,179 cuft
Drainage area
= 1.170 ac
Runoff coeff.
= 0.75
Intensity
= 4.480 in/hr
Tc by User
= 5.00 min
OF Curve
= mid_NC_lyr.IDF
Asc/Rec limb fact
= 1/1
2.00
1.00
0.00
0 1
Hyd No. 3
Post -development DA-2
Hyd. No. 3 -- 1 Year
2 3 4 5 6 7 8 9
Q (cfs)
4.00
3.00
2.00
1.00
a0o
10
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3130 2018 by Autodesk, Inc. v12
Hyd. No. 4
Post-development-SCM By-pass
Hydrograph type
= Rational
Storm frequency
= 1 yrs.
Time interval
= 1 min
Drainage area
= 3.340 ac
Intensity
= 1.179 in/hr
OF Curve
= mid_NC_1yr.IDF
Q (cfs)
1.00
e ��
0 20 40
Hyd No. 4
Peak discharge
Time to peak
Hyd. volume
Runoff coeff.
Tc by TR55
Asc/Rec limb fact
Post-development-SCM By-pass
Hyd. No. 4 -- 1 Year
Tuesday, 0412312019
= 1.418 cfs
75 min
= 6,379 cult
= 0.36
= 75.00 min
= 1/1
60 80 100 120 140
Q (cfs)
2.00
1.00
J.00
160
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3DO 2018 by Autodesk, Inc. A 2
Tuesday, 04123 / 2019
Hyd. No. 5
Infiltration 1 (DA-1)
Hydrograph type
= Reservoir Peak discharge =
0.000 cfs
Storm frequency
= 1 yrs Time to peak =
18 min
Time interval
= 1 min Hyd. volume =
0 cuff
Inflow hyd. No.
= 2 - Post -development DA-1 Max. Elevation =
247.23 ft
Reservoir name
= Infiltration 1 Max. Storage =
885 tuft
Storage Indication method used.
ExWtration extracted from Outflow.
Q (cfs)
Infiltration "I (DA-1)
Hyd. No. 5 -- 1 Year
Q (cfs)
3.00
3.00
2.00
2.00
1.00
1.00
0.00
0 60
120 180 240 300 360
420
0.00
- Hyd No. 5
Hyd No. 2 Total storage used = 885 tuft
Time
(min)

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAEXD Civil 3D@ 2018 by Autodesk, Inc. 02
Tuesday, 0412312019
Hyd. No. 6
Infiltration 2 (DA-2)
Hydrograph type
= Reservoir Peak discharge =
0.000 cfs
Storm frequency
= 1 yrs Time to peak =
33 min
Time interval
= 1 min Hyd. volume =
0 tuft
Inflow hyd. No.
= 3 - Post -development DA-2 Max. Elevation =
247.29 ft
Reservoir name
= Infiltration 2 Max. Storage =
1,169 cult
Storage Indication method used. Ex<Itration extracted from Outflow.
Q (cfs)
Infiltration 2 (DA-2)
Hyd. No. 6 -- 1 Year
Q (cfs)
4.00
4.00
3.00
3.00
2.00
2.00
1.00
1.00
0.00
0 180 360
0.00
540 720 900 1080 1260 1440 1620 1800
Hyd No. 6
Hyd No. 3 Totai storage used = 1,169 cult
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3DO 2018 by Autodesk, Inc. 02
Tuesday, 04 12312019
Hyd. No. 7
Post -development
Hydrograph type
= Combine
Peak discharge
= 1.418 cfs
Storm frequency
= 1 yrs
Time to peak
= 75 min
Time interval
= 1 min
Hyd. volume
= 6,379 tuft
Inflow hyds.
= 4, 5, 6
Contrib. drain. area
= 3.340 ac
1.00
20 40 60
Post -development
Hyd. No. 7 -- 1 Year
80 100 120 140
Hyd No. 7 Hyd No. 4 — Hyd No. 5 Hyd No. 6
Q (cfs)
2.00
1.00
J.00
160
Time (min)

2-YEAR 10-YEAR, AND I00-YEAR RUN-OFF
S UMMARIE S

Hydrograph Summary Report
Hydraflow Hydrographs Extension for AutoCAD® Civil Mt 2018 by Autadesk, Inc. v12
Hyd.
Hydrograph
Peak
Time
Time to
Hyd.
Inflow
Maximum
Total
Hydrograph
No.
type
flow
interval
Peak
volume
hyd(s)
elevation
strge used
Description
(origin)
(cfs)
(min)
(min)
(cult)
(ft)
(tuft)
1
Rational
2.758
1
76
12,500
-- ------
------ Pre -development
2
Rational
3.821
1
5
1,146
------ ---
------ Post -development DA-1
3
Rational
5.048
1
5
1,514
------ ------
------ Post -development DA-2
4 Rational
1.734 1
75
7,804
---- ------ ------ Post-development-SCM By-pass
5 Reservoir
0,000 1
45
0
2 247.29 1,136 Infiltration 1 (CA-1)
6 Reservoir
0.000 1
137
0
3 247,37 1,502 Infiltration 2 (DA-2)
7 Combine
1.734 1
75
7,804
4, 5,6 ------ ------ Post -development
Infiltration 6asin.gpw f Return Period: 2 Year Tuesday, 04/23/2019

Hydrograph Summary Report
Hydrafiow Hydrographs Extension for AutoCAD® Civil 3Dfl 2D18 by Autodesk, Inc. v12
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) 1(min) 1(min) 1(cuft) (ft) (tuft)
1 Rational
3.477
1
76
15,756
------
------ Pre -development
2 Rational
4.372
1
5
1,311
------ ------
------ Post -development DA-1
3 Rational
5.775
1
5
1,732
------ ------
----- Post -development DA-2
4 Rational
2.186
1
75
9,835
------ ------
------ Post-development-SCM By-pass
5 Reservoir
0.000
1
93
0
2 247.34
1,300 Infiltration 1 (DA-1)
6 Reservoir
0.000
1
6
0
3 247.43
1,718 Infiltration 2 (DA-2)
7 Combine
2.186
1
75
9,835
4, 5, 6 ------
------ Post -development
IInfiltration Basin.gpw I Return Period: 5 Year I Tuesday, 04 / 23 / 2019

Hyd rog ra p h Summary Report Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v92

TIME OF CONCENTRATION

TR55 Tc Worksheet
Hydraflow Hydrographs Extension for AUtoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Hyd. No. 1
Pre -development
Description
A
B
C
Totals
Sheet Flow
Manning's n-value
= 0.400
0.011
0.011
Flow length (ft)
= 180.0
0.0
0.0
Two-year 24-hr precip. (in)
= 2.20
0.00
0.00
Land slope (%)
= 0.50
0.00
0.00
Travel Time (min)
= 72.16 +
0.00
+ 0.00
= 72.16
Shallow Concentrated Flow
Flow length (ft)
= 400.00
0.00
0.00
Watercourse slope (%)
= 1.50
0.00
0.00
Surface description
= Unpaved
Paved
Paved
Average velocity (ft/s)
=1.98
0.00
0.00
Travel Time (min)
= 3.37 +
0.00
+ 0.00 =
3.37
Channel Flow
X sectional flow area (sgft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope (%)
= 0,00
0.00
0.00
Manning's n-value
= 0.015
0.015
0.015
Velocity (ft/s)
=0.00
0.00
0.00
Flow length (ft)
((0))0.0
0.0
0.0
Travel Time (min)
= 0.00 +
0.00
+ 0.00 =
0.00
Total Travel Time, Tc..............................................................................
75.54 min

TR55 Tc Worksheet
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D®2018 by Autodesk, Inc. v12
Hyd. No. 4
Post-development-SCM By-pass
Description
A
Sheet Flow
Manning's n-value
= 0.400
Flow length (ft)
= 180.0
Two-year 24-hr precip. (in)
= 2.20
Land slope (%)
= 0.50
Travel Time (min)
= 72.16
Shallow Concentrated Flow
Flow length (ft)
= 290.00
Watercourse slope (%}
= 1.40
Surface description
= Unpaved
Average velocity (ft/s)
=1.91
Travel Time (min)
= 2.53
Channel Flow
X sectional flow area (sqft)
= 0.00
Wetted perimeter (ft)
= 0.00
Channel slope (%)
= 0.00
Manning's n-value
= 0.015
Velocity (ft/s)
=0.00
B
C Totals
0.011
0.011
0.0
0.0
0.00
0.00
0.00
0.00
+ 0.00
+ 0.00 = 72.16
0.00
0.00
0.00
0.00
Paved
Paved
0.00
0.00
+ 0.00
+ 0.00 = 2.53
0.00
0.00
0.00
0.00
0.00
0.00
0.015
0.015
1
0.00
Flow length (ft) ({0))0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00
TotalTravel Time, Tc..............................................................................
0.00
75.00 min

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Soil Map —Hoke County, North Carolina Hoke County Cooperative Extension
Office
Map Unit Legend
rMap Unit Symbol
Map Unit Name
Acres in AOI
Percent of AOI
Co
Coxville loam
2.9
5.9%
Dn
Dunbar foam
7.6
15.1 %
DpA
Duplin sandy loam, 0 to 3
percent slopes
6.0
12.1%
FaB
NoB
Faceville loamy sand, 2 to 6
percent slopes
Norfolk loamy sand, 2 to 6
percent slopes
8.5
21.6
17.1%
43.2%
Pg
Pantego loam
3.3
6.7%
Totals for Area of Interest
50.1
100.0%
Natural Resources Web Soil Survey 4/1012019
Conservation Service National Cooperative Soil Survey Page 3 of 3

INFILTRATION BASIN CALCULATIONS

Infiltration Basin Sizing Summary
Hoke Coun Coo erative Extension Office Buildin
633 East Palmer Street
Infiltration sized per NC DEQ Minimum Design Criteria (MDQ Section C-l.
Infiltration Basin I
Drainage Area: 0.91 ac
Built Upon Area (BUA): 0.58 ac
RV = 0.05 + 0.9 x IA
1A = 0.64
RV = 0.05 + 0.9 x 0.64 — 0.63
Design Volume
DV=3630xRDx RVxA
RD = 1.0"
RV = 0.63
A = 0.91 ac
DV — 3630 x 1.0" x 0.63 x 0.91 ac 2,081 cu ft
Surface Area
SA=FSx
(DV X 121KxT)
FS=2
DV
= 2,081 cu ft
K =
2.0 inlhr
T =
72 hours
SA = 2 x (2,081 CF x 1212.0 x 72) = 347 SF
(2,937 SF Provided)
Infiltration Basin 2
Drainage Area: 1.17 ac
Built Upon Area (BUA): 0.69 ac
RV = 0.05 + 0.9 x IA
IA = 0.59
RV = 0.05 + 0.9 x 0.59 = 0.58
Design Volume
DV = 3630 x RD x RV x A
RD = 1.0"
RV = 0.58
A= 1.17 ac
DV=3630x 1.0"x0.58x 1.17ac=2,463cuft

Surface Area
SA=FSx(DVX12/KxT)
FS=2
DV = 2,463 cu ft
K = 2.0 in/hr
T = 72 hours
SA = 2 x (2,463 cf x 1212.0 x 72) = 411 SF
(3,172 SF Provided)

INFILTRATION BASIN OPERATION AND
MAINTENANCE MANUAL

Operation & Maintenance reement
Project Name:
Project Location:
Hoke County Cooperative Extension Office Building
'Raeford, NC
Maintenance records shall be kept on the following BMP(s). This maintenance record shall be kept in a log in a known set locatio
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 pollutant removal efficiency of the BMP(s).
The BMP(s) on this project include (check all that apply & correspc
Bioretention Cell
Quantity:
Dry Detention Basin
Quantity:
Grassed Swale
Quantity:
Green Roof
Quantity:
Infiltration Basin
Quantity:
2
Infiltration Trench
Quantity:
Level SpreaderNFS
Quantity:
Permeable Pavement
Quantity:
Proprietary System
Quantity:
Rainwater Harvesting
Quantity:
Sand Filter
Quantity:
Stormwater Wetland
Quantity:
Wet Detention Basin
Quantity:
0
Disconnected Impervious Area
Present:
No
User Defined BMP
Present:
No
O&M tables wil
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s).
Location(s):
Location(s):
Location(s):
Location(s):
2-East
I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed for
each BMP above, and attached O&M tables. I agree to notify NCDENR of any problems with the system or prior to any changes to
the system or responsible party.
" Responsible Party: Hoke County
Title & Organization: Hoke County Manager
Street address: 227 N. Main St
City, state, zip: Raeford, NC
Phone number(s): 910-875-8751
Email: [e-mail]
Sign t e: Dater
I, 6
(tin"
n r • f�- ' a Notary Public for the State of
County of - do hearby rtify that d r a " - t�
personally appeared before me this —day of I and
acknowledge the due execution of perations and Ma nterypn�Agreement .
Witness �y,hand �d official seal,, I��U',
o
, , . My commission expires
col ,:�-o12azA
STORM-EZ 4130l2019
Version 1.4 O&M Manual Page 1 of 1