SW1200502_NC Arboretum EX Spreadsheet_5/14/2020

1.00
1.39
1.88
2.22
2.66
3.79
4.48
5.03
5.58
Highlighted Storm is Design Storm
6.52 acres 1.27 acres
0.00 acres 59%
0.00 acres
Complete the breakdown of impervious area for the project
Yes
NOTE: Please use the Storm-EZ calculation sheets to document the stormwater design
and create the O&M Agreement.
Discrete SCS Method,
Pre - PostCalculation Method
Entire Site
Impervious Surface Area
Offsite Drainage Area (sf)
Stream Index Number
Stream Class
Receiving Stream name
Basin Information
Future (sf)
Off-site (sf)
Existing BUA (sf)
55,321Total
Other On-Site (sf)
53,521
1,800
On-Site Parking (sf)
On-Site Sidewalks (sf)
On-Site Buildings/Lots (sf)
On-Site Streets (sf)
0
0
Proposed Impervious Area (sf)
% Impervious Area (total)
0
55,321
59%
Total Drainage Area
On-Site Drainage Area (sf)
6-67-10
93,668
93,668
Data in italics is derived from application
forms and land use data worksheets and
cannot be changed by user.
Wesley Creek
B
Use Worksheet Data?
Total Property Area
Total Coastal Wetlands Area
Total Surface Water Area
Depth
(inches)
P90
First Flush / WQV
P90
P95
50-yr, 24-hr
Design Storm:
Asheville
1-yr, 24-hr
The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County
French Broad River Basin
RAINFALL & CALCULATION DATA
Rainfall Source:
Project County:
Project City:
BUNCOMBE
Asheville
Asheville
100-yr, 24-hr
PROJECT INFORMATION
Total Impervious Area
Project % impervious area
ALL AREAS ARE IN SQUARE FEET
Entire Site
2-yr, 24-hr
Storm Event
10-yr, 24-hr
25-yr, 24-hr(Minimum Design Storm = P90 for non-SA, 1-yr, 24-hr for SA)
Loaded Rainfall:
STORM-EZ
Version 1.4 Project Data
5/14/2020
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Pre-Development Land Use:
HSG CN %
B 98 7.23%
B 61 92.77%
Note: Enter BUA Draining to
Permeable Pavement Below
HSG
Select HSG 0.00 21.66% 0.00%
Select HSG 0.00 0.00%
Select HSG 0.00 0.00%
2.15 7.23%
Existing Permeable Pavement (Infiltration):
Pavement Area Additional BUA
Soil
Infiltratio
n Rate
Gravel Void
Space
Total
Gravel
Depth
Orifice
Dia.
Orifice
Height
(sf) (sf) (in/hr) (%) (in) (in) (in)
100
DSD PAW Dgr
(in) (%) (in) (sf) (acres)
150 1.39 0.00
2.15 acres
0.00 acres
0.00 acres
0.00 acres
0.00 acres
2.15 acres
Pre-Development SCMs:
Imp. Open
(sf) (sf)
(cf) HSG 6775 86893
200
Rainfall Volume =2.99 cf
Natural Infiltration & ET =-2.80 cf
Disconnected Impervious Surfaces =0.00 cf
SCM Infiltration =0.00 cf
Permeable Pavement Infiltration =0.00 cf
Green Roof ET =0.00 cf
Post Filtration Discharge =0.00 cf
Total Runoff Reduction =-2.80 cf
Treated SCM Outflow =0.00 cf
Untreated Surface Runoff =0.19 cf
D.S.
BMP
SCM Type
Has Synthetic
Liner?
Permeable Pavement + Additional BUA:
Green Roofs :
0
Existing Green Roofs:
HSG
SCM #
Area DS SCM #
0
Downstream
SCM
Description
Total Site Area:
Land Use Summary:
Description
Preserved Coastal Wetlands :
Notes
Drainage Area
93,668 2.15
% Imp
Area (sf.)
WQ Volume
Provided
Area
(ac.)Area (sf.)
Subtotal:
User Defined Drainage Areas:Comp.
CNDescription
Area
0.16Impervious 6,775
86,893
Asheville, NC BUNCOMBE County
French Broad River Basin
PRE-DEVELOPMENT LAND USE CALCULATIONS
Drainage Area #
(sf)Land-use (acres)
1.99Pasture or Open Space
e North Carolina Arboretum Parking Reconfiguration & Expans
Subtotal:
93,668
acre-inches =
Design Storm Runoff Fate Summary:
Runoff Reduction Components:
acre-inches =
10,850acre-inches =
SCM #
SCM #
From Land Use Tables: 93,668
Preserved Surface Waters & Non-Coastal Wetlands :
BUA %
acre-inches =
acre-inches =
acre-inches =
acre-inches =
acre-inches =
acre-inches =
SCM Treatment:
acre-inches =675
The Pre-Development project area contains 6775 sf of built upon area, resulting in an overall density of 7.23%.
0
0
0
-10,174
-10,174
0
0
0
93,668
STORM-EZ
Version 1.4 Pre-Development
5/14/2020
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Permeable Pavement:
Infiltration
Rate Void Space
Total
Gravel
Depth
Orifice
Dia.
Orifice
Height
(sf) (acres) (sf) (acres) (in/hr) (%) (in) (in) (in)
500 0.00 0.00 NO
DSD PAW Dgr
(in) (%) (in) (sf) (acres)
600 1.39 0.00 No
Residential Lot CN Calculator (Excluding R/W and dedicated open spaces):
Max Imp / Lot Woods / Lot
(ac.) (sf) (sf)
0.00
Remaining Land Use:
HSG CN (sf) (acres) %
B 98.0 54,784 1.26 58.49%
B 61.0 38,884 0.89 41.51%
N/A 0 0.00 0.00%
N/A 0 0.00 0.00%
93,668 2.15 100.00%
Land Excluded, or Partially Excluded, from Volume Calculations:(sf.) (ac.)
00.00
00.00
93,668 2.15
Rainfall Volume =2.99 cf
Natural Infiltration & ET =-1.51 cf
Disconnected Impervious Surfaces =0.00 cf
SCM Infiltration =-1.30 cf
Permeable Pavement Infiltration =0.00 cf
Green Roof ET =0.00 cf
Post Filtration Discharge =-0.17 cf
Total Runoff Reduction =-2.99 cf
Area
Open Space / Lot
(sf)
10,850
acre-inches =
0
acre-inches =
-630
acre-inches =
acre-inches =
acre-inches =
acre-inches = -5,494
acre-inches =
0
Area
Runoff Reduction Components:
Design Storm Runoff Fate Summary:
The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County
French Broad River Basin
Detention
Check
Has
Synthetic
Liner?
Infiltration
Check
POST-DEVELOPMENT LAND USE CALCULATIONS
Pvmt Type
SCM #
-4,726
0
-10,850
acre-inches =
Total Site Area:
Surface Waters & Non-Coastal Wetlands :
Green Roofs :
Coastal Wetlands :
Lot Area
Impervious
Green Roofs:
# of Lots
Land-Use
Open Space (Managed Open Space)
Permeable Pavement + BUA:
Sub-Total:
HSG
Avg Lot Size
Pavement Area
% Imp.(sf.)
Down-
stream
SCM
Additional BUA
SCM #
Downstream
SCM #
Drainage Area #
Retrofit? Comments
STORM-EZ
Version 1.4 Post Development
5/14/2020
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The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County
French Broad River Basin
POST-DEVELOPMENT LAND USE CALCULATIONS
Drainage Area #
Treated SCM Outflow =0.00 cf
Untreated Surface Runoff =0.00 cf
Pre-Development Runoff =0.19 cf
Difference =-0.19 cfacre-inches =-675
acre-inches =675
The Post-Development project area contains 54784 sf of built upon area, resulting in an overall density of 58.49%.
acre-inches =
acre-inches =0
SCM Treatment:
0
STORM-EZ
Version 1.4 Post Development
5/14/2020
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Impervious
(sf)
54,784 (cf) (cf) (cf) (cf) (cf) (cf)
700 1S Bioretention w/ IWS B 27,147 50% 39%2123 2654 2654 2341 312 0 74%
701 2S Bioretention w/ IWS B 27,637 50% 61%1606 2703 2703 2385 318 0 99%
Rainfall Volume =2.99 acre-inches =cf
Natural Infiltration & ET =-1.51 acre-inches = cf
Disconnected Impervious Area =0.00 acre-inches = cf
SCM Infiltration =-1.30 acre-inches = cf
Permeable Pavement Infiltration =0.00 acre-inches = cf
Green Roof ET =0.00 acre-inches = cf
Post Filtration Discharge =-0.17 acre-inches = cf
Total Runoff Reduction =-2.99 acre-inches =cf
SCM Treatment:
Treated SCM Outflow =0.00 acre-inches =cf
Untreated Surface Runoff =0.00 acre-inches =cf
0.19 acre-inches =cf
-0.19 acre-inches =cf
Down-
stream SCM
#
Drainage
Area Inflow
Volume
-675
-10,850
-4,726
0
10,850
Pre-Development Runoff =
0
0
100% of total
impervious
area.
100% of
total
pervious
area.
Runoff Reduction Components:
-5,494
54784 sf impervious area entered
compared to 54784 sf total impervious.
675
Warnings:
Design Storm Runoff Fate Summary:
The Post-Development project area contains 54784 sf of built upon area, resulting in an overall density of 58.49%.
0
-630
**VOLUME MATCHING ACHIEVED**
Difference =
0
38881 sf open space entered
compared to 38884 sf total
open space.
Pervious
(sf)
38,884
The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County
French Broad River Basin
Enter only runoff volume below that will be infiltrated or drawn down over 2 to 5 days. Additional volume provided in devices should not be entered in this worksheet.
Drawdown time requirement applies to all storm events.
Drainage Area #
PROPOSED SIPs & STRUCTURAL RUNOFF VOLUME CONTROLS
Offsite Impervious
Area Treated
Infiltration &
ET
0 sf
Total
Inflow
Volume
14,976
% of Total
Impervious
Area
% of Total
Pervious
Area
Storage
Volume
23,905
Warning: Per Session Law 2012-200, Conventional BMPs which promote standing water are discouraged within 5 miles of public airports. Conventional BMPs should be replaced with alternative SIPs or underground
structures. Contact NCDWQ Regional Office for additional guidance.
Name / Location
Contributing Area
HSG
STORMWATER CONTROL MEASURES
% of SCM
Volume
Utilized
Post
Filtration
Outflow
Treated
Outflow
Type of Device
SCM
#
STORM-EZ
Version 1.4 Stormwater Controls
5/14/2020
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P90 Storm - Rainfall Depth = 1.39 inches
The"Fate of Rainfall" charts display the hydrologic processes to which rainfall volumes are subjected based on the combinations of land use, soil type, and stormwater controls entered by the user. The charts are designed to display the stormwater
plan in a form which illustrates changes to the hydrologic cycle which result from urbanization and various stormwater management strategies.
Asheville, NC BUNCOMBE County
French Broad River Basin
P90
The North Carolina Arboretum Parking Reconfiguration & Expansion
Compliance Storm = P90 Storm - Rainfall Depth = 1.39 inches
Drainage Area #
FATE OF RAINFALL
Select Storm:
VOLUME MATCHING SCALE
Volume Matching Threshold
Basic Treatment Threshold
BASIC TREATMENT SCALE
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Infiltration and ET ‐ 10220 cf Treated Outflow from BMPs ‐ 0 cf Untreated Surface Runoff ‐ 0 cf% of Total Rainfall VolumePost Development Fates
Infiltration and ET ‐ 5494 cf Green Roof Evapotranspiration ‐ 0 cf
Disconnected Impervious Infiltration ‐ 0 cf Permeable Pavement Infiltration ‐ 0 cf
Infiltration by BMPs ‐ 4726 cf Other
Post Filtration Outflow ‐ 630 cf
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Infiltration and ET ‐ 10174 cf Treated Outflow from BMPs ‐ 0 cf Untreated Surface Runoff ‐ 675 cf% of Total Rainfall VolumePre Development Fates
Infiltration and ET ‐ 10174 cf Green Roof Evapotranspiration ‐ 0 cf
Disconnected Impervious Infiltration ‐ 0 cf Permeable Pavement Infiltration ‐ 0 cf
Infiltration by BMPs ‐ 0 cf Other
Post Filtration Outflow ‐ 0 cf
FATE OF RAINFALL GRAPHS
STORM-EZ
Version 1.4 Rainfall Fate Graph
5/14/2020
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TIME OF CONCENTRATION CALCULATIONS:
Pre-Development
Length (ft) Slope (ft/ft)Tt (hrs)
Length (ft) Slope (ft/ft) n-value
Flow Area
(ft2)Tt (hrs)
Channel Flow:
Channel Flow:
Pre-development Tc =5.00 min (Minimum 5 minutes)
Post Development
Length (ft) Slope (ft/ft)Tt (hrs)
Length (ft) Slope (ft/ft) n-value
Flow Area
(ft2)Tt (hrs)
Channel Flow:
Channel Flow:
Post-development Tc =5.00 min (Minimum 5 minutes)
ADJUSTED CURVE NUMBER CALCULATIONS:
Pre-Development
F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr
Rainfall (in) = 1.00 1.39 1.88 2.22 2.66 3.79 4.48 5.03 5.58
Q*(in) =0.06 0.09 0.17 0.26 0.40 0.91 1.30 1.63 1.99
CNadj =78 72 69 67 66 65 65 64 64
Post Development
F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr
Rainfall (in) = 1.00 1.39 1.88 2.22 2.66 3.79 4.48 5.03 5.58
Q*(in) =0.00 0.00 0.18 0.40 0.71 1.56 2.11 2.57 3.03
CNadj =67 59 69 72 74 76 76 76 76
PEAK FLOW CALCULATIONS:
F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr
Pre-Development
Q* (in) 0.06 0.09 0.17 0.26 0.40 0.91 1.30 1.63 1.99
qu (csm/in)385.00 385.00 385.00 512.90 809.52 931.69 931.69 931.69 931.69
Q (cfs) 0.07 0.11 0.22 0.44 1.10 2.86 4.06 5.11 6.23
Post Development
Q* (in) 0.00 0.00 0.18 0.40 0.71 1.56 2.11 2.57 3.03
qu (csm/in)385.00 385.00 385.00 809.52 931.69 1165.98 1165.98 1165.98 1165.98
Q (cfs) 0.00 0.00 0.23 1.10 2.23 6.12 8.28 10.06 11.87
-100.0% -100.0% 4.5% 150.0% 102.8% 113.8% 103.8% 96.7% 90.5%
French Broad River Basin
ADDITIONAL CALCULATIONS
The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County
Shallow Flow:
Drainage Area #
Surface Cover
Wetted Perimeter (ft)
Sheet Flow:
Surface Cover
Analysis Area = 2.15 Acres (0.003 sq. miles)
Wetted Perimeter (ft)
Sheet Flow:
Shallow Flow:
**Note: To decrease Post-development peak flows - increase storage volume being drawdown or infiltrated or lengthen post-
development time of concentration. See LID HELP for more information.
Analysis Area = 2.15 Acres (0.003 sq. miles)
Sheet Flow:
Shallow Flow:
Sheet Flow:
Shallow Flow:
STORM-EZ
Version 1.4 Peak Flow Calcs
5/14/2020
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