Infinity - Project Infinity Storm Water Calc Report 2.28.2018 (2)

TABLE OF CONTENTS
I. NARRATIVE

Introduction
Storm Water Management Requirements
Existing Site Conditions
Proposed BMP Design
Conclusions

II. MAPS AND FIGURES

HydroCAD Model Diagram
Pre and Post Drainage Area Maps
NOAA Rainfall Data
Location Map
Soils Map
USGS Map
FEMA FIRM Map

III. HYDROCAD MODEL OUTPUT

Hydrocad: 1-Inch Storm Event (Modified P)
Hydrocad: 10-yr 6-hr Storm Event
Hydrocad: 50yr 6-hr Storm Event

IV. STORM WATER Hydraulic Calculations

Storm Sewers Design

INTRODUCTION
TKC Land Development II, LLC is proposing the construction of a new 100,000 SF industrial facility with a
future 50,000 SF expansion option located at 115 Summit Park Drive in the Summit Corporate Center in
Rowan County, North Carolina. The purpose of this report is to show that the proposed storm water
management BMP associated with these improvements will meet or exceed the state of North Carolina’s
storm water requirements as well as the requirements of the Rowan County and the Summit Corporate
Center.

STORM WATER MANAGEMENT REQUIREMENTS
The proposed BMP shall meet or exceed the rules as defined in the NCDEQ Stormwater Design Manual
Chapter A-1. Runoff Treatment and Volume Match and be designed to meet or exceed the Minimum
Design Criteria (MDC) as outlined in Chapter C-0. The BMP chosen for these improvements is a Sand Filter
as designed per Chapter C-6. These are the requirements this sand filter must meet per the rules of 15A
NCAC 02H .1056: MDC for Sand Filters:

Objective: Remove urban stormwater pollutants including TSS, BOD, fecal coliform, hydrcarbons, and
metals. Sand filters are designed to treat 0.75 times the design volume.

Design Volume: The design storm depth for high density projects [greater than 24% Built Upon Area (BUA)]
shall be 1-inch of storm water runoff from the BUA of the site.

Discharge Flow: Stormwater outlets shall be designed so that they do not cause erosion downslope of the
discharge point during the peak flow from the 10-year storm event as shown by engineering calculations.

EXISTING SITE CONDITIONS
The 14.54-acre parcel is currently being mass-graded as Project Infinity under approval from the State of
North Carolina (Project ID: ROWAN-2018-007). The disturbed area is 12.89 acres. The project is bordered
to the West and North by the Summit Park Drive 60’ R/W, to the South by undeveloped property in the
Corporate Park owned by Rowan County, and to the East by industrial land owned by TKC XCI,LLC and a
Church. There is an existing sanitary sewer easement along the eastern property line and an unnamed
tributary to Town Creek east of that, which runs parallel and through the sewer easement. The site is located
approximate 1.1 miles from Town Creek in the Yadkin Pee Dee River basin. The site’s existing contours had
a ridge along approximately the middle of the site as it runs from south to north. The mass grading will drain
the disturbed area to a sediment basin located along the western side of the site, in the location of the
proposed BMP Sand Filter. The sand filter will discharge to an existing roadside ditch that drains to an existing
yard inlet and piped to an existing culvert under Summit Park Drive. The pre-development conditions for
runoff are a wooded site and approximately 7.2 acres draining to the discharge point of the BMP. The site is
graded to be balanced and so it will not require the import nor export of material. The soils are 80% Helena
Sandy Loam (HSG C) and 20% Armenia Loam (HSG C along the eastern property line, near the sewer
easement).

See the Maps & Figures section of this report for Drainage Area and Soils Maps.

Figure: Pre-development Drainage Area (HydroCAD Model)

PROPOSED SITE CONDITIONS
The proposed improvements include the development of approximately 12.89 acres. The site will consist of
a 100k SF industrial building with a 50k SF future building expansion. The building will have employee
parking to the north which will include 170 parking spaces and an expandable truck court with future trailer
parking on the west. This high impervious area gives the site a curve number (CN) of 91 with a drainage
area to the sand filter of 10.77 acres. Sand filters are best used when the curve number is high, which was
one of the reasons why it was chosen as the BMP for this site.

Figure: Post Developed Drainage Area to BMP (HydroCAD Model) 

PROPOSED SAND FILTER DESIGN
The BMP for this site is a Sand Filter, designed per the rules of 15A NCAC 02H .1056: MDC for Sand
Filters by NCDEQ. The sand filter is designed to treat the water quality volume from the 1-inch runoff over
1.77 acres congruently through the storm events. The Forebay of the sand filter has a 48”x48” concrete
outlet structure which is designed so that the entire water quality volume will be treated through the sand
filter and drained within 24 hours. Here is a detail of the outlets in the forebay, which control the water
quality volume and discharge from the site:

Figure: Details of discharge outlets from BMP forebay (HydroCAD Model)

There are two-10 ft wide riprap berms within the earthen dam separating the forebay from the sand filter,
which allows the 1” runoff storm water volume to infiltrate the filter area at a controlled rate. Level
spreaders evenly distribute the flow across the grassed area on the filter side to prevent erosion of the
sand media. The BMP is designed to discharge at or below the 10-year, 6hr storm flow rate. The forebay
and sand filter can detain a 50-Yr six hour storm with six inches of freeboard.

CONCLUSIONS
The requirements of the North Carolina Department of Environmental Quality (NCDEQ), the covenants of
the Summit Corporate Center, and the ordinance of Rowan County are met in the proposed design.

MAPS & FIGURES
HydroCAD Model Routing Diagram
Drainage Area Maps
NOAA Rainfall Data
Location Map
Soils Map
USGS Map
FEMA FIRM Map

HYDROCAD OUTPUT
1-inch Design Volume Storm Event

D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 2HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 0S: PRE - DEVELOPMENT
Runoff = 0.29 cfs @ 3.65 hrs, Volume= 0.037 af, Depth= 0.06"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"
Area (ac) CN Description
7.200 73.0 Woods, Fair, HSG C
7.200 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.2 200 0.0335 0.27 Sheet Flow,
Range n= 0.130 P2= 3.32"
13.6 716 0.0310 0.88 Shallow Concentrated Flow,
Woodland Kv= 5.0 fps
25.8 916 Total
Subcatchment 0S: PRE - DEVELOPMENT
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)0.32
0.3
0.28
0.26
0.24
0.22
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
Charlotte 6-hr 1-Inch
1" WQ Rainfall=1.25"
Runoff Area=7.200 ac
Runoff Volume=0.037 af
Runoff Depth=0.06"
Flow Length=916'
Tc=25.8 min
CN=73.0
0.29 cfs
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 3HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: POST TO SAND FILTER
[49] Hint: Tc<2dt may require smaller dt
Runoff = 13.52 cfs @ 3.12 hrs, Volume= 0.487 af, Depth= 0.54"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"
Area (ac) CN Description
10.770 91.0 Urban industrial, 72% imp, HSG C
3.016 28.00% Pervious Area
7.754 72.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment 1S: POST TO SAND FILTER
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Charlotte 6-hr 1-Inch
1" WQ Rainfall=1.25"
Runoff Area=10.770 ac
Runoff Volume=0.487 af
Runoff Depth=0.54"
Tc=5.0 min
CN=91.0
13.52 cfs
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 4HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 2P: FOREBAY
Inflow Area = 10.770 ac, 72.00% Impervious, Inflow Depth = 0.54" for 1" WQ event
Inflow = 13.52 cfs @ 3.12 hrs, Volume= 0.487 af
Outflow = 0.02 cfs @ 6.12 hrs, Volume= 0.113 af, Atten= 100%, Lag= 180.3 min
Primary = 0.01 cfs @ 6.12 hrs, Volume= 0.001 af
Secondary = 0.01 cfs @ 6.12 hrs, Volume= 0.111 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 767.73' @ 6.12 hrs Surf.Area= 17,506 sf Storage= 21,063 cf
Plug-Flow detention time= 3,386.7 min calculated for 0.113 af (23% of inflow)
Center-of-Mass det. time= 3,353.2 min ( 3,567.6 - 214.4 )
Volume Invert Avail.Storage Storage Description
#1 766.00' 78,624 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
766.00 1,854 0 0
767.00 15,816 8,835 8,835
768.00 18,119 16,968 25,803
769.00 20,481 19,300 45,103
770.00 22,968 21,725 66,827
770.50 24,218 11,797 78,624
Device Routing Invert Outlet Devices
#1 Primary 765.00'24.00" Round RCP_Round 24"
L= 38.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 765.00' / 764.50' S= 0.0132 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1 767.72'24.00" W x 4.00" H Vert. 10 YR. ORIFICE C= 0.600
#3 Device 1 769.60'48.00" x 48.00" Horiz. TOP OF OUTLET STRUCTURE C= 0.600
Limited to weir flow at low heads
#4 Secondary 765.34'FLOW THROUGH RIPRAP BERM (Q=KIA) X 2.00
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00
Disch. (cfs) 0.000 0.003 0.005 0.008 0.011 0.013
Primary OutFlow Max=0.01 cfs @ 6.12 hrs HW=767.73' TW=0.00' (Dynamic Tailwater)
1=RCP_Round 24" (Passes 0.01 cfs of 19.92 cfs potential flow)
2=10 YR. ORIFICE (Orifice Controls 0.01 cfs @ 0.38 fps)
3=TOP OF OUTLET STRUCTURE ( Controls 0.00 cfs)
Secondary OutFlow Max=0.01 cfs @ 6.12 hrs HW=767.73' TW=765.38' (Dynamic Tailwater)
4=FLOW THROUGH RIPRAP BERM (Q=KIA) (Custom Controls 0.01 cfs)
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 5HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Pond 2P: FOREBAY
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=10.770 ac
Peak Elev=767.73'
Storage=21,063 cf
13.52 cfs
0.02 cfs0.01 cfs0.01 cfs
Pond 2P: FOREBAY
Total
Primary
Secondary
Stage-Discharge
Discharge (cfs)
302520151050Elevation (feet)770
769
768
767
766
10 YR. ORIFICE
TOP OF OUTLET STRUCTURE
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 6HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 3P: SAND FILTER
[78] Warning: Submerged Pond 2P Secondary device # 4 by 0.75'
Inflow = 0.01 cfs @ 6.12 hrs, Volume= 0.111 af
Outflow = 0.01 cfs @ 89.12 hrs, Volume= 0.055 af, Atten= 10%, Lag= 4,979.8 min
Primary = 0.01 cfs @ 89.12 hrs, Volume= 0.055 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 766.09' @ 89.12 hrs Surf.Area= 3,582 sf Storage= 2,484 cf
Plug-Flow detention time= 3,560.7 min calculated for 0.055 af (49% of inflow)
Center-of-Mass det. time= 1,774.8 min ( 5,382.9 - 3,608.0 )
Volume Invert Avail.Storage Storage Description
#1 765.34' 22,648 cf SAND FILTER STORAGE (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
765.34 3,093 0 0
766.00 3,519 2,182 2,182
767.00 4,256 3,888 6,069
768.00 5,055 4,656 10,725
769.00 5,933 5,494 16,219
770.00 6,925 6,429 22,648
Device Routing Invert Outlet Devices
#1 Primary 766.00'FILTER MEDIA
Head (feet) 0.00 2.50 5.00
Disch. (cfs) 0.000 0.327 0.532
Primary OutFlow Max=0.01 cfs @ 89.12 hrs HW=766.09' TW=0.00' (Dynamic Tailwater)
1=FILTER MEDIA (Custom Controls 0.01 cfs)
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 7HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Pond 3P: SAND FILTER
Inflow
Primary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)0.013
0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0
Peak Elev=766.09'
Storage=2,484 cf
0.01 cfs
0.01 cfs
Pond 3P: SAND FILTER
Primary
Stage-Discharge
Discharge (cfs)
0.50.450.40.350.30.250.20.150.10.050Elevation (feet)771
770
769
768
767
766
FILTER MEDIA
D
Charlotte 6-hr 1-Inch 1" WQ Rainfall=1.25"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 8HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 4P: TOTAL
[40] Hint: Not Described (Outflow=Inflow)
Inflow Area = 10.770 ac, 72.00% Impervious, Inflow Depth > 0.06" for 1" WQ event
Inflow = 0.01 cfs @ 89.12 hrs, Volume= 0.056 af
Primary = 0.01 cfs @ 89.12 hrs, Volume= 0.056 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Pond 4P: TOTAL
Inflow
Primary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)0.012
0.011
0.011
0.01
0.01
0.009
0.009
0.008
0.008
0.007
0.007
0.006
0.006
0.005
0.005
0.004
0.004
0.003
0.003
0.002
0.002
0.001
0.001
0.000
0
Inflow Area=10.770 ac
0.01 cfs0.01 cfs

HYDROCAD OUTPUT
10-yr - 6-hour Storm Event

D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 16HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 0S: PRE - DEVELOPMENT
Runoff = 8.97 cfs @ 3.46 hrs, Volume= 0.668 af, Depth= 1.11"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"
Area (ac) CN Description
7.200 73.0 Woods, Fair, HSG C
7.200 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.2 200 0.0335 0.27 Sheet Flow,
Range n= 0.130 P2= 3.32"
13.6 716 0.0310 0.88 Shallow Concentrated Flow,
Woodland Kv= 5.0 fps
25.8 916 Total
Subcatchment 0S: PRE - DEVELOPMENT
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)10
9
8
7
6
5
4
3
2
1
0
Charlotte 6-hr 10-yr
10yr-6hr Rainfall=3.40"
Runoff Area=7.200 ac
Runoff Volume=0.668 af
Runoff Depth=1.11"
Flow Length=916'
Tc=25.8 min
CN=73.0
8.97 cfs
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 17HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: POST TO SAND FILTER
[49] Hint: Tc<2dt may require smaller dt
Runoff = 51.11 cfs @ 3.15 hrs, Volume= 2.196 af, Depth= 2.45"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"
Area (ac) CN Description
10.770 91.0 Urban industrial, 72% imp, HSG C
3.016 28.00% Pervious Area
7.754 72.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment 1S: POST TO SAND FILTER
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)55
50
45
40
35
30
25
20
15
10
5
0
Charlotte 6-hr 10-yr
10yr-6hr Rainfall=3.40"
Runoff Area=10.770 ac
Runoff Volume=2.196 af
Runoff Depth=2.45"
Tc=5.0 min
CN=91.0
51.11 cfs
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 18HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 2P: FOREBAY
Inflow Area = 10.770 ac, 72.00% Impervious, Inflow Depth = 2.45" for 10yr-6hr event
Inflow = 51.11 cfs @ 3.15 hrs, Volume= 2.196 af
Outflow = 8.77 cfs @ 3.58 hrs, Volume= 1.813 af, Atten= 83%, Lag= 26.0 min
Primary = 8.74 cfs @ 3.58 hrs, Volume= 1.696 af
Secondary = 0.02 cfs @ 3.58 hrs, Volume= 0.117 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 769.79' @ 3.58 hrs Surf.Area= 22,445 sf Storage= 62,048 cf
Plug-Flow detention time= 341.8 min calculated for 1.813 af (83% of inflow)
Center-of-Mass det. time= 324.9 min ( 531.1 - 206.1 )
Volume Invert Avail.Storage Storage Description
#1 766.00' 78,624 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
766.00 1,854 0 0
767.00 15,816 8,835 8,835
768.00 18,119 16,968 25,803
769.00 20,481 19,300 45,103
770.00 22,968 21,725 66,827
770.50 24,218 11,797 78,624
Device Routing Invert Outlet Devices
#1 Primary 765.00'24.00" Round RCP_Round 24"
L= 38.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 765.00' / 764.50' S= 0.0132 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1 767.72'24.00" W x 4.00" H Vert. 10 YR. ORIFICE C= 0.600
#3 Device 1 769.60'48.00" x 48.00" Horiz. TOP OF OUTLET STRUCTURE C= 0.600
Limited to weir flow at low heads
#4 Secondary 765.34'FLOW THROUGH RIPRAP BERM (Q=KIA) X 2.00
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00
Disch. (cfs) 0.000 0.003 0.005 0.008 0.011 0.013
Primary OutFlow Max=8.70 cfs @ 3.58 hrs HW=769.79' TW=0.00' (Dynamic Tailwater)
1=RCP_Round 24" (Passes 8.70 cfs of 29.44 cfs potential flow)
2=10 YR. ORIFICE (Orifice Controls 4.43 cfs @ 6.64 fps)
3=TOP OF OUTLET STRUCTURE (Weir Controls 4.28 cfs @ 1.42 fps)
Secondary OutFlow Max=0.02 cfs @ 3.58 hrs HW=769.79' TW=765.37' (Dynamic Tailwater)
4=FLOW THROUGH RIPRAP BERM (Q=KIA) (Custom Controls 0.02 cfs)
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 19HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Pond 2P: FOREBAY
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=10.770 ac
Peak Elev=769.79'
Storage=62,048 cf
51.11 cfs
8.77 cfs8.74 cfs
0.02 cfs
Pond 2P: FOREBAY
Total
Primary
Secondary
Stage-Discharge
Discharge (cfs)
302520151050Elevation (feet)770
769
768
767
766
10 YR. ORIFICE
TOP OF OUTLET STRUCTURE
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 20HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 3P: SAND FILTER
[78] Warning: Submerged Pond 2P Secondary device # 4 by 0.75'
Inflow = 0.02 cfs @ 3.58 hrs, Volume= 0.117 af
Outflow = 0.01 cfs @ 84.11 hrs, Volume= 0.060 af, Atten= 52%, Lag= 4,831.6 min
Primary = 0.01 cfs @ 84.11 hrs, Volume= 0.060 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 766.09' @ 84.11 hrs Surf.Area= 3,583 sf Storage= 2,490 cf
Plug-Flow detention time= 3,499.1 min calculated for 0.060 af (51% of inflow)
Center-of-Mass det. time= 1,743.5 min ( 5,229.8 - 3,486.3 )
Volume Invert Avail.Storage Storage Description
#1 765.34' 22,648 cf SAND FILTER STORAGE (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
765.34 3,093 0 0
766.00 3,519 2,182 2,182
767.00 4,256 3,888 6,069
768.00 5,055 4,656 10,725
769.00 5,933 5,494 16,219
770.00 6,925 6,429 22,648
Device Routing Invert Outlet Devices
#1 Primary 766.00'FILTER MEDIA
Head (feet) 0.00 2.50 5.00
Disch. (cfs) 0.000 0.327 0.532
Primary OutFlow Max=0.01 cfs @ 84.11 hrs HW=766.09' TW=0.00' (Dynamic Tailwater)
1=FILTER MEDIA (Custom Controls 0.01 cfs)
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 21HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Pond 3P: SAND FILTER
Inflow
Primary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)0.026
0.024
0.022
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
Peak Elev=766.09'
Storage=2,490 cf
0.02 cfs
0.01 cfs
Pond 3P: SAND FILTER
Primary
Stage-Discharge
Discharge (cfs)
0.50.450.40.350.30.250.20.150.10.050Elevation (feet)771
770
769
768
767
766
FILTER MEDIA
D
Charlotte 6-hr 10-yr 10yr-6hr Rainfall=3.40"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 22HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 4P: TOTAL
[40] Hint: Not Described (Outflow=Inflow)
Inflow Area = 10.770 ac, 72.00% Impervious, Inflow Depth > 1.96" for 10yr-6hr event
Inflow = 8.74 cfs @ 3.58 hrs, Volume= 1.756 af
Primary = 8.74 cfs @ 3.58 hrs, Volume= 1.756 af, Atten= 0%, Lag= 0.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Pond 4P: TOTAL
Inflow
Primary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)9
8
7
6
5
4
3
2
1
0
Inflow Area=10.770 ac
8.74 cfs8.74 cfs

HYDROCAD OUTPUT
50-yr - 6-hour Storm Event

D
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 23HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 0S: PRE - DEVELOPMENT
Runoff = 15.22 cfs @ 3.41 hrs, Volume= 1.128 af, Depth= 1.88"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"
Area (ac) CN Description
7.200 73.0 Woods, Fair, HSG C
7.200 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
12.2 200 0.0335 0.27 Sheet Flow,
Range n= 0.130 P2= 3.32"
13.6 716 0.0310 0.88 Shallow Concentrated Flow,
Woodland Kv= 5.0 fps
25.8 916 Total
Subcatchment 0S: PRE - DEVELOPMENT
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Charlotte 6-hr 50-yr
50yr-6hr Rainfall=4.48"
Runoff Area=7.200 ac
Runoff Volume=1.128 af
Runoff Depth=1.88"
Flow Length=916'
Tc=25.8 min
CN=73.0
15.22 cfs
D
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 24HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: POST TO SAND FILTER
[49] Hint: Tc<2dt may require smaller dt
Runoff = 69.28 cfs @ 3.10 hrs, Volume= 3.122 af, Depth= 3.48"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"
Area (ac) CN Description
10.770 91.0 Urban industrial, 72% imp, HSG C
3.016 28.00% Pervious Area
7.754 72.00% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment 1S: POST TO SAND FILTER
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Charlotte 6-hr 50-yr
50yr-6hr Rainfall=4.48"
Runoff Area=10.770 ac
Runoff Volume=3.122 af
Runoff Depth=3.48"
Tc=5.0 min
CN=91.0
69.28 cfs
D
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 25HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 2P: FOREBAY
Inflow Area = 10.770 ac, 72.00% Impervious, Inflow Depth = 3.48" for 50yr-6hr event
Inflow = 69.28 cfs @ 3.10 hrs, Volume= 3.122 af
Outflow = 30.22 cfs @ 3.27 hrs, Volume= 2.739 af, Atten= 56%, Lag= 10.0 min
Primary = 30.19 cfs @ 3.27 hrs, Volume= 2.621 af
Secondary = 0.03 cfs @ 3.27 hrs, Volume= 0.118 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 770.22' @ 3.27 hrs Surf.Area= 23,509 sf Storage= 71,856 cf
Plug-Flow detention time= 240.4 min calculated for 2.738 af (88% of inflow)
Center-of-Mass det. time= 229.2 min ( 431.0 - 201.8 )
Volume Invert Avail.Storage Storage Description
#1 766.00' 78,624 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
766.00 1,854 0 0
767.00 15,816 8,835 8,835
768.00 18,119 16,968 25,803
769.00 20,481 19,300 45,103
770.00 22,968 21,725 66,827
770.50 24,218 11,797 78,624
Device Routing Invert Outlet Devices
#1 Primary 765.00'24.00" Round RCP_Round 24"
L= 38.0' RCP, square edge headwall, Ke= 0.500
Inlet / Outlet Invert= 765.00' / 764.50' S= 0.0132 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1 767.72'24.00" W x 4.00" H Vert. 10 YR. ORIFICE C= 0.600
#3 Device 1 769.60'48.00" x 48.00" Horiz. TOP OF OUTLET STRUCTURE C= 0.600
Limited to weir flow at low heads
#4 Secondary 765.34'FLOW THROUGH RIPRAP BERM (Q=KIA) X 2.00
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00
Disch. (cfs) 0.000 0.003 0.005 0.008 0.011 0.013
Primary OutFlow Max=29.52 cfs @ 3.27 hrs HW=770.21' TW=0.00' (Dynamic Tailwater)
1=RCP_Round 24" (Passes 29.52 cfs of 31.02 cfs potential flow)
2=10 YR. ORIFICE (Orifice Controls 4.89 cfs @ 7.33 fps)
3=TOP OF OUTLET STRUCTURE (Weir Controls 24.63 cfs @ 2.54 fps)
Secondary OutFlow Max=0.03 cfs @ 3.27 hrs HW=770.21' TW=765.36' (Dynamic Tailwater)
4=FLOW THROUGH RIPRAP BERM (Q=KIA) (Custom Controls 0.03 cfs)
D
Charlotte 6-hr 50-yr 50yr-6hr Rainfall=4.48"Infinity Sand Filter
Printed 2/28/2018Prepared by Burton Engineering
Page 27HydroCAD® 10.00-17 s/n 03513 © 2016 HydroCAD Software Solutions LLC
Summary for Pond 3P: SAND FILTER
[78] Warning: Submerged Pond 2P Secondary device # 4 by 0.75'
Inflow = 0.03 cfs @ 3.27 hrs, Volume= 0.118 af
Outflow = 0.01 cfs @ 83.25 hrs, Volume= 0.061 af, Atten= 55%, Lag= 4,798.8 min
Primary = 0.01 cfs @ 83.25 hrs, Volume= 0.061 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 766.09' @ 83.25 hrs Surf.Area= 3,583 sf Storage= 2,490 cf
Plug-Flow detention time= 3,492.6 min calculated for 0.061 af (52% of inflow)
Center-of-Mass det. time= 1,740.0 min ( 5,203.6 - 3,463.6 )
Volume Invert Avail.Storage Storage Description
#1 765.34' 22,648 cf SAND FILTER STORAGE (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
765.34 3,093 0 0
766.00 3,519 2,182 2,182
767.00 4,256 3,888 6,069
768.00 5,055 4,656 10,725
769.00 5,933 5,494 16,219
770.00 6,925 6,429 22,648
Device Routing Invert Outlet Devices
#1 Primary 766.00'FILTER MEDIA
Head (feet) 0.00 2.50 5.00
Disch. (cfs) 0.000 0.327 0.532
Primary OutFlow Max=0.01 cfs @ 83.25 hrs HW=766.09' TW=0.00' (Dynamic Tailwater)
1=FILTER MEDIA (Custom Controls 0.01 cfs)

STORM WATER HYDRAULIC CALCULATIONS
Storm Sewers Design