Dollar General - Salisbury - STORMWATER_CALCS_SAND_FILTER_REVISED

BREC

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1

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 2
1.0 General Information

This document contains stormwater calculations demonstrating compliance with
post-construction state and local stormwater regulations for the construction of a
9,100 ݂ݐ ଶ Dollar General retail store at the intersection of Grace Church Road
and U.S. Highway 29 in Salisbury, NC. Specifically, regulations for this area
require water quality treatment of the first flush ሺ1"ሻ storm and the attenuation of
the 1 year, 24 hour storm to pre-construction discharge rates. Larger storms are
also required to pass the system. An above ground sand filter will be utilized to
meet these requirements.
2.0 Methodology

The water quality volume ሺܹܳ௩ ሻ required to be treated from the first flush was
calculated using the Schueler method outlined in the NCDENR Stormwater BMP
Manual. The Schueler method utilizes the following equations:

ܴ௩ ൌ 0.05 ൅ 0.9ܫ஺
ܹܸܳ ൌ 3630ܴ஽ ܴ௩ ܣ

Where ܫ஺ is the impervious fraction of the drainage area, ܴ௩ is a runoff coefficient,
ܴ஽ is the rainfall depth, ܣ is the drainage area, and ܹܳ௩ is the runoff volume.
The calculated ܹܳ௩ is 2,758 ݂ݐ ଷ . To route the ܹܳ௩ through the sand filter, it is
necessary to calculate a modified SCS curve number to avoid underrepresenting
the first flush. The modified curve number is calculated as follows:

ܥܰ௠ ൌ 1000/ቂ10 ൅ 5ܴ஽ ൅ 10ܹܳ௩ െ10ඥܹܳ௩ଶ ൅ 1.25ܹܳ௩ ܴ஽ ቃ

The modified curve numbers were used to route the first flush using an SCS 6
hour balanced storm distribution. The 1 year, 24 hour and larger storms were
routed with standard curve numbers and an SCS type II 24 hour storm
distribution.

One pre-construction drainage area and five post-construction drainage areas
were identified.

Table 1 - Pre-Construction Drainage Area(s)
ࡺࢇ࢓ࢋ ࡭࢘ࢋࢇ ሺࢇࢉ࢘ࢋ࢙ሻ ࡯ࡺ ࡯ࡺ࢓ ࢀࢉ ሺ࢓࢏࢔࢛࢚ࢋ࢙ሻ
PRE-CONSTRUCTION:1 2.46 70.33 N/A 5

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 3
Table 2 - Post-Construction Drainage Area(s)
ࡺࢇ࢓ࢋ ࡭࢘ࢋࢇ
ሺࢇࢉሻ
࡯ࡺ ࡯ࡺ࢓ ࢀࢉ
ሺ࢓࢏࢔ሻ
ࡾ࢜ ࢃࡽࢂ
ሺࢌ࢚૜ ሻ
POST-CONSTRUCTION:1 0.17 98.00 99.57 5 0.95 585
POST-CONSTRUCTION:2 0.21 98.00 99.57 5 0.95 727
POST-CONSTRUCTION:3 0.33 94.20 98.44 5 0.83 1135
POST-CONSTRUCTION:4 0.05 71.01 81.89 5 0.11 311
POST-CONSTRUCTION:5* 0.40 81.13 92.51 5 0.43 1464

*Drainage area POST-CONSTRUCTION:5 consists of on site and off site
vegetated areas and highway asphalt on the down slope side of the stormwater
BMP; therefore, it is not routed through the BMP; however, runoff from this
drainage area is included in the peak attenuation calculations.

Routing of the required storms through the sand filters was performed using
Autodesk Storm and Sanitary Analysis (SSA) 2015.

2.1 Sand Filter Calculations

The standard and adjusted water quality volumes are calculated as follows:

ܹܸܳ ൌ 2,758 ݂ݐ
ଷ
ܹܸܳ௔ௗ௝ ൌ 0.75ܹܸܳ ൌ
ሺ0.75ሻሺ2,758ሻ ൌ 2,069 ݂ݐ
ଷ

There are multiple ܣ௙ and ܣ௦ size combinations that provide a working solution to
the design requirements for the calculated water quality volume. Possible
options are summarized in the table below.

Table 3 - Sand Filter Sizing
ࢎࡹࢇ࢞ࡲ࢏࢒࢚ࢋ࢘ ሺࢌ࢚ሻ ࢎ࡭ ሺࢌ࢚ሻ ࡭࢙ ൅ ࡭ࢌ ሺࢌ࢚૛ ሻ
1.0 0.5 2,069
2.0 1.0 1,034
3.0 1.5 690

Given the site constraints, ݄ெ௔௫ி௜௟௧௘௥ was selected as 1.0 ݂ݐ. Together with the
requirement to make the filter chamber and the sediment chamber proportionally
sized yields the following calculations.

݄ெ௔௫ி௜௟௧௘௥ ൌ1.0 ݂ݐ
݄஺ ൌ ݄ெ௔௫ி௜௟௧௘௥
2 ൌ 1
2 ൌ 0.50 ݂ݐ

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 4
݇ൌ4 ݂ݐ
݀ܽݕ
ݐ ൌ 1.66 ݀ܽݕݏ
݀ி ൌ1.5 ݂ݐ
ܣ௙ ெ௜௡ିோ௘௤௨௜௥௘ௗ ൌቆ ሺܹܸܳሻሺ݀ி ሻ
ሺ݇ሻሺݐሻሺ݄஺ ൅݀ி ሻቇൌቆ ሺ2,758ሻሺ1.0ሻ
ሺ4ሻሺ1.66ሻሺ0.50 ൅ 1.5
ሻቇ ൌ 312 ݂ݐ
ଶ
ܣ௦ ெ௜௡ିோ௘௤௨௜௥௘ௗ ൌ 0.066ܹܸܳ ൌ 0.066
ሺ2589ሻ ൌ 182 ݂ݐ
ଶ
ܣ௙ ௉௥௢௩௜ௗ௘ௗ ൌ 1,137 ሺ324 ݏܽ݊݀ሻ ݂ݐ
ଶ ൐ܣ௙ ெ௜௡ିோ௘௤௨௜௥௘ௗ
ܣ௦ ௉௥௢௩௜ௗ௘ௗ ൌ 1,437 ݂ݐ
ଶ ൐ܣ௦ ெ௜௡ିோ௘௤௨௜௥௘ௗ
ቀܣ௦ ௉௥௢௩௜ௗ௘ௗ ൅ܣ௙ ௉௥௢௩௜ௗ௘ௗ ቁ ൌ 1,137 ൅ 1,437 ൌ 2,574 ݂ݐ
ଶ
ቀܣ௦ ௉௥௢௩௜ௗ௘ௗ ൅ܣ௙ ௉௥௢௩௜ௗ௘ௗ ቁݔ݄ெ௔௫ி௜௟௧௘௥ ൌ ሺ2,574ሻሺ1.0ሻ ൌ 2,574 ݂ݐ
ଷ ൐ܹܸܳ௔ௗ௝
3.0 Results

The pre- and post-construction peak runoff rates at each pre-construction outfall
are summarized below for the storms requiring peak attenuation.

Table 4 - Peak Runoff Rates for PRE-CONSTRUCTION:1
ࡿࢀࡻࡾࡹ ࡼࡾࡱ െ ࡯ࡻࡺ ቆ
ࢌ࢚૜
࢙ ቇ ࡼࡻࡿࢀ െ ࡯ࡻࡺ ቆ
ࢌ࢚૜
࢙ ቇ
1 year, 24 hour 1.92 1.69

Model outputs from SSA are included in the Appendix for verification.

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 5
Appendix

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 6
Pre‐construction Routing

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 7
1 year, 24 hour Routing

Project Description
PRE-CON-ROUTING.SPF
Project Options
CFS
Elevation
SCS TR-55
User-Defined
Hydrodynamic
YES
YES
Analysis Options
Aug 28, 2017 00:00:00
Aug 31, 2017 00:00:00
Aug 28, 2017 00:00:00
0 days
0 01:00:00 days hh:mm:ss
0 00:05:00 days hh:mm:ss
0 00:00:15 days hh:mm:ss
15 seconds
Number of Elements
Qty
1
1
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
Rainfall Details
SN Rain Gage Data Data Source Rainfall Rain State County Return Rainfall Rainfall
ID Source ID Type Units Period Depth Distribution
(years)(inches)
1 SALISBURY Time Series 1YR-24HR Cumulative inches North Carolina Rowan 1 2.73 SCS Type II 24-hr
Orifices ...................................................
Weirs ......................................................
Outlets ...................................................
Pollutants ........................................................
Land Uses ......................................................
Inlets ......................................................
Storage Nodes .......................................
Links................................................................
Channels ................................................
Pipes ......................................................
Pumps ....................................................
Rain Gages ....................................................
Subbasins........................................................
Nodes..............................................................
Junctions ................................................
Outfalls ...................................................
Flow Diversions .....................................
Start Reporting On .........................................
Antecedent Dry Days ......................................
Runoff (Dry Weather) Time Step ...................
Runoff (Wet Weather) Time Step ..................
Reporting Time Step ......................................
Routing Time Step ..........................................
Time of Concentration (TOC) Method ............
Link Routing Method ......................................
Enable Overflow Ponding at Nodes ...............
Skip Steady State Analysis Time Periods ......
Start Analysis On ............................................
End Analysis On .............................................
File Name .......................................................
Description .....................................................Z:\CURRENT_PROJECTS\316_TERAMORE_DEVELOPMENT\3160082016_DOLLAR_GENERAL_SALISBURY\PRO
DUCTION_DWGS\3160082016_C100-STORMWATER.dwg
Flow Units .......................................................
Elevation Type ................................................
Hydrology Method ..........................................
Subbasin Summary
SN Subbasin Area Weighted Total Total Total Peak Time of
ID Curve Rainfall Runoff Runoff Runoff Concentration
Number Volume
(ac)(in)(in)(ac-in)(cfs)(days hh:mm:ss)
1 {PRE-CONSTRUCTION}.PRE-CONSTRUCTION : 1 2.46 70.00 2.73 0.57 1.40 1.92 0 00:05:00
Node Summary
SN Element Element Invert Ground/Rim Initial Surcharge Ponded Peak Max HGL Max Min Time of Total Total Time
ID Type Elevation (Max)Water Elevation Area Inflow Elevation Surcharge Freeboard Peak Flooded Flooded
Elevation Elevation Attained Depth Attained Flooding Volume
Attained Occurrence
(ft)(ft)(ft)(ft)(ft²)(cfs)(ft)(ft)(ft)(days hh:mm)(ac-in)(min)
1 OUTFALL Outfall 790.50 0.00 0.00
Subbasin Hydrology
Subbasin : {PRE-CONSTRUCTION}.PRE-CONSTRUCTION : 1
Input Data
Area (ac) .....................................................2.46
Weighted Curve Number ............................70.00
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-2.46 -70.00
Composite Area & Weighted CN 2.46 70.00
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................0.57
Peak Runoff (cfs) ........................................1.92
Weighted Curve Number ............................70.00
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {PRE-CONSTRUCTION}.PRE-CONSTRUCTION : 1

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 8
Post‐construction Routing

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 9
First Flush (1”)

Project Description
POST-CON-ROUTING-BALANCED.SPF
Project Options
CFS
Elevation
SCS TR-55
User-Defined
Hydrodynamic
YES
YES
Analysis Options
Aug 28, 2017 00:00:00
Aug 31, 2017 00:00:00
Aug 28, 2017 00:00:00
0 days
0 01:00:00 days hh:mm:ss
0 00:05:00 days hh:mm:ss
0 00:00:15 days hh:mm:ss
15 seconds
Number of Elements
Qty
1
5
4
2
1
0
0
1
4
0
2
0
1
0
1
0
0
Rainfall Details
SN Rain Gage Data Data Source Rainfall Rain State County Return Rainfall Rainfall
ID Source ID Type Units Period Depth Distribution
(years)(inches)
1 SALISBURY Time Series 1IN-6HR-BALANCED Cumulative inches 0.00
Orifices .................................................................
Weirs ....................................................................
Outlets ..................................................................
Pollutants ......................................................................
Land Uses .....................................................................
Inlets .....................................................................
Storage Nodes .....................................................
Links..............................................................................
Channels ..............................................................
Pipes ....................................................................
Pumps ..................................................................
Rain Gages ...................................................................
Subbasins......................................................................
Nodes............................................................................
Junctions ..............................................................
Outfalls .................................................................
Flow Diversions ....................................................
Start Reporting On ........................................................
Antecedent Dry Days ....................................................
Runoff (Dry Weather) Time Step ..................................
Runoff (Wet Weather) Time Step .................................
Reporting Time Step .....................................................
Routing Time Step ........................................................
Time of Concentration (TOC) Method ..........................
Link Routing Method .....................................................
Enable Overflow Ponding at Nodes ..............................
Skip Steady State Analysis Time Periods .....................
Start Analysis On ..........................................................
End Analysis On ...........................................................
File Name .....................................................................
Description ....................................................................Z:\CURRENT_PROJECTS\316_TERAMORE_DEVELOPMENT\3160082016_DOLLAR_GENERAL_SA
LISBURY\PRODUCTION_DWGS\3160082016_C100-STORMWATER.dwg
Flow Units .....................................................................
Elevation Type ..............................................................
Hydrology Method .........................................................
Subbasin Summary
SN Subbasin Area Weighted Total Total Total Peak Time of
ID Curve Rainfall Runoff Runoff Runoff Concentration
Number Volume
(ac)(in)(in)(ac-in)(cfs)(days hh:mm:ss)
1 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1 0.17 99.57 1.00 0.95 0.16 0.35 0 00:05:00
2 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2 0.21 99.57 1.00 0.95 0.20 0.44 0 00:05:00
3 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3 0.38 98.44 1.00 0.83 0.31 0.74 0 00:05:00
4 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4 0.76 89.81 1.00 0.31 0.24 0.60 0 00:05:00
5 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5 0.94 81.13 1.00 0.10 0.09 0.15 0 00:05:00
Node Summary
SN Element Element Invert Ground/Rim Initial Surcharge Ponded Peak Max HGL Max Min Time of Total Total Time
ID Type Elevation (Max)Water Elevation Area Inflow Elevation Surcharge Freeboard Peak Flooded Flooded
Elevation Elevation Attained Depth Attained Flooding Volume
Attained Occurrence
(ft)(ft)(ft)(ft)(ft²)(cfs)(ft)(ft)(ft)(days hh:mm)(ac-in)(min)
1 BMP-RISER Junction 791.50 797.00 791.50 0.00 0.00 0.02 791.54 0.00 5.46 0 00:00 0.00 0.00
2 SITE-OUTLET Junction 791.00 797.00 791.00 0.00 0.00 0.16 791.10 0.00 5.90 0 00:00 0.00 0.00
3 OUTFALL Outfall 790.50 0.17 790.59
4 SAND-FILTER Storage Node 794.00 797.00 794.00 0.00 2.12 794.97 0.00 0.00
Link Summary
SN Element Element From To (Outlet)Length Inlet Outlet Average Diameter or Manning's Peak Design Flow Peak Flow/Peak Flow Peak Flow Peak Flow Total Time Reported
ID Type (Inlet)Node Invert Invert Slope Height Roughness Flow Capacity Design Flow Velocity Depth Depth/Surcharged Condition
Node Elevation Elevation Ratio Total Depth
Ratio
(ft)(ft)(ft)(%)(in)(cfs)(cfs)(ft/sec)(ft)(min)
1 BMP-BARREL Pipe BMP-RISER SITE-OUTLET 10.00 791.50 791.00 5.0000 18.000 0.0120 0.02 25.45 0.00 2.14 0.07 0.04 0.00 Calculated
2 VIRTUAL-LINK Pipe SITE-OUTLET OUTFALL 10.00 791.00 790.50 5.0000 18.000 0.0120 0.17 25.45 0.01 3.69 0.09 0.06 0.00 Calculated
3 PRINCIPAL-SPILLWAY Orifice SAND-FILTER BMP-RISER 794.00 791.50 36.000 0.00
4 FILTER-MEDIA Outlet SAND-FILTER BMP-RISER 794.00 791.50 0.02
Subbasin Hydrology
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1
Input Data
Area (ac) .....................................................0.17
Weighted Curve Number ............................99.57
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.17 -99.57
Composite Area & Weighted CN 0.17 99.57
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.95
Peak Runoff (cfs) ........................................0.35
Weighted Curve Number ............................99.57
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2
Input Data
Area (ac) .....................................................0.21
Weighted Curve Number ............................99.57
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.21 -99.57
Composite Area & Weighted CN 0.21 99.57
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.95
Peak Runoff (cfs) ........................................0.44
Weighted Curve Number ............................99.57
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3
Input Data
Area (ac) .....................................................0.38
Weighted Curve Number ............................98.44
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.38 -98.44
Composite Area & Weighted CN 0.38 98.44
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.83
Peak Runoff (cfs) ........................................0.74
Weighted Curve Number ............................98.44
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4
Input Data
Area (ac) .....................................................0.76
Weighted Curve Number ............................89.81
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.76 -89.81
Composite Area & Weighted CN 0.76 89.81
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.31
Peak Runoff (cfs) ........................................0.60
Weighted Curve Number ............................89.81
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5
Input Data
Area (ac) .....................................................0.94
Weighted Curve Number ............................81.13
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.94 -81.13
Composite Area & Weighted CN 0.94 81.13
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.10
Peak Runoff (cfs) ........................................0.15
Weighted Curve Number ............................81.13
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5
Junction Input
SN Element Invert Ground/Rim Ground/Rim Initial Initial Surcharge Surcharge Ponded Minimum
ID Elevation (Max)(Max)Water Water Elevation Depth Area Pipe
Elevation Offset Elevation Depth Cover
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft²)(in)
1 BMP-RISER 791.50 797.00 5.50 791.50 0.00 0.00 -797.00 0.00 0.00
2 SITE-OUTLET 791.00 797.00 6.00 791.00 0.00 0.00 -797.00 0.00 0.00
Junction Results
SN Element Peak Peak Max HGL Max HGL Max Min Average HGL Average HGL Time of Time of Total Total Time
ID Inflow Lateral Elevation Depth Surcharge Freeboard Elevation Depth Max HGL Peak Flooded Flooded
Inflow Attained Attained Depth Attained Attained Attained Occurrence Flooding Volume
Attained Occurrence
(cfs)(cfs)(ft)(ft)(ft)(ft)(ft)(ft)(days hh:mm)(days hh:mm)(ac-in)(min)
1 BMP-RISER 0.02 0.00 791.54 0.04 0.00 5.46 791.52 0.02 0 06:09 0 00:00 0.00 0.00
2 SITE-OUTLET 0.16 0.14 791.10 0.10 0.00 5.90 791.02 0.02 0 03:08 0 00:00 0.00 0.00
Pipe Input
SN Element Length Inlet Inlet Outlet Outlet Total Average Pipe Pipe Pipe Manning's Entrance Exit/Bend Additional Initial Flap No. of
ID Invert Invert Invert Invert Drop Slope Shape Diameter or Width Roughness Losses Losses Losses Flow Gate Barrels
Elevation Offset Elevation Offset Height
(ft)(ft)(ft)(ft)(ft)(ft)(%)(in)(in)(cfs)
1 BMP-BARREL 10.00 791.50 0.00 791.00 0.00 0.50 5.0000 CIRCULAR 18.000 18.000 0.0120 0.5000 0.5000 0.0000 0.00 No 1
2 VIRTUAL-LINK 10.00 791.00 0.00 790.50 0.00 0.50 5.0000 CIRCULAR 18.000 18.000 0.0120 0.5000 0.5000 0.0000 0.00 No 1
Pipe Results
SN Element Peak Time of Design Flow Peak Flow/Peak Flow Travel Peak Flow Peak Flow Total Time Froude Reported
ID Flow Peak Flow Capacity Design Flow Velocity Time Depth Depth/Surcharged Number Condition
Occurrence Ratio Total Depth
Ratio
(cfs)(days hh:mm)(cfs)(ft/sec)(min)(ft)(min)
1 BMP-BARREL 0.02 0 06:02 25.45 0.00 2.14 0.08 0.07 0.04 0.00 Calculated
2 VIRTUAL-LINK 0.17 0 03:08 25.45 0.01 3.69 0.05 0.09 0.06 0.00 Calculated
Storage Nodes
Storage Node : SAND-FILTER
Input Data
794.00
797.00
3.00
794.00
0.00
0.00
0.00
Storage Area Volume Curves
Storage Curve : SAND-FILTER
Stage Storage Storage
Area Volume
(ft)(ft²)(ft³)
0 2589 0.000
1 3526 3057.50
2 4520 7080.50
3 5571 12126.00
Evaporation Loss .................................................................................
Invert Elevation (ft) ..............................................................................
Max (Rim) Elevation (ft) .......................................................................
Max (Rim) Offset (ft) ............................................................................
Initial Water Elevation (ft) ....................................................................
Initial Water Depth (ft) .........................................................................
Ponded Area (ft²) .................................................................................
Storage Node : SAND-FILTER (continued)
Outflow Orifices
SN Element Orifice Orifice Flap Circular Rectangular Rectangular Orifice Orifice
ID Type Shape Gate Orifice Orifice Orifice Invert Coefficient
Diameter Height Width Elevation
(in)(in)(in)(ft)
1 PRINCIPAL-SPILLWAY Bottom Rectangular No 36.00 36.00 795.25 0.63
Output Summary Results
2.12
2.12
0.02
0.00
794.97
0.97
794.32
0.32
0 06:03
0.000
0
0
0.00
Total Time Flooded (min) ....................................................................
Total Retention Time (sec) ..................................................................
Max HGL Depth Attained (ft) ...............................................................
Average HGL Elevation Attained (ft) ...................................................
Average HGL Depth Attained (ft) .........................................................
Time of Max HGL Occurrence (days hh:mm) .....................................
Total Exfiltration Volume (1000-ft³) ......................................................
Total Flooded Volume (ac-in) ..............................................................
Peak Inflow (cfs) ..................................................................................
Peak Lateral Inflow (cfs) ......................................................................
Peak Outflow (cfs) ...............................................................................
Peak Exfiltration Flow Rate (cfm) ........................................................
Max HGL Elevation Attained (ft) ..........................................................

BREC, P.A. Dollar General – Salisbury | Stormwater Calculations 10
1 year, 24 hour Routing

Project Description
POST-CON-ROUTING.SPF
Project Options
CFS
Elevation
SCS TR-55
User-Defined
Hydrodynamic
YES
YES
Analysis Options
Aug 28, 2017 00:00:00
Aug 31, 2017 00:00:00
Aug 28, 2017 00:00:00
0 days
0 01:00:00 days hh:mm:ss
0 00:05:00 days hh:mm:ss
0 00:00:15 days hh:mm:ss
15 seconds
Number of Elements
Qty
1
5
4
2
1
0
0
1
5
0
2
0
1
1
1
0
0
Rainfall Details
SN Rain Gage Data Data Source Rainfall Rain State County Return Rainfall Rainfall
ID Source ID Type Units Period Depth Distribution
(years)(inches)
1 SALISBURY Time Series 1YR-24HR Cumulative inches North Carolina Rowan 1 2.73 SCS Type II 24-hr
Orifices ...................................................
Weirs ......................................................
Outlets ...................................................
Pollutants ........................................................
Land Uses ......................................................
Inlets ......................................................
Storage Nodes .......................................
Links................................................................
Channels ................................................
Pipes ......................................................
Pumps ....................................................
Rain Gages ....................................................
Subbasins........................................................
Nodes..............................................................
Junctions ................................................
Outfalls ...................................................
Flow Diversions .....................................
Start Reporting On .........................................
Antecedent Dry Days ......................................
Runoff (Dry Weather) Time Step ...................
Runoff (Wet Weather) Time Step ..................
Reporting Time Step ......................................
Routing Time Step ..........................................
Time of Concentration (TOC) Method ............
Link Routing Method ......................................
Enable Overflow Ponding at Nodes ...............
Skip Steady State Analysis Time Periods ......
Start Analysis On ............................................
End Analysis On .............................................
File Name .......................................................
Description .....................................................Z:\CURRENT_PROJECTS\316_TERAMORE_DEVELOPMENT\3160082016_DOLLAR_GENERAL_SALISBURY\PRO
DUCTION_DWGS\3160082016_C100-STORMWATER.dwg
Flow Units .......................................................
Elevation Type ................................................
Hydrology Method ..........................................
Subbasin Summary
SN Subbasin Area Weighted Total Total Total Peak Time of
ID Curve Rainfall Runoff Runoff Runoff Concentration
Number Volume
(ac)(in)(in)(ac-in)(cfs)(days hh:mm:ss)
1 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1 0.17 98.00 2.73 2.50 0.42 0.59 0 00:05:00
2 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2 0.21 98.00 2.73 2.50 0.52 0.75 0 00:05:00
3 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3 0.38 94.20 2.73 2.11 0.79 1.21 0 00:05:00
4 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4 0.76 71.01 2.73 0.61 0.47 0.65 0 00:05:00
5 {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5 0.94 81.13 2.73 1.12 1.05 1.67 0 00:05:00
Node Summary
SN Element Element Invert Ground/Rim Initial Surcharge Ponded Peak Max HGL Max Min Time of Total Total Time
ID Type Elevation (Max)Water Elevation Area Inflow Elevation Surcharge Freeboard Peak Flooded Flooded
Elevation Elevation Attained Depth Attained Flooding Volume
Attained Occurrence
(ft)(ft)(ft)(ft)(ft²)(cfs)(ft)(ft)(ft)(days hh:mm)(ac-in)(min)
1 BMP-RISER Junction 791.50 797.00 791.50 0.00 0.00 0.46 791.67 0.00 5.33 0 00:00 0.00 0.00
2 SITE-OUTLET Junction 791.00 797.00 791.00 0.00 0.00 1.69 791.38 0.00 5.62 0 00:00 0.00 0.00
3 OUTFALL Outfall 790.50 1.69 790.76
4 SAND-FILTER Storage Node 794.00 797.00 794.00 0.00 3.18 795.30 0.00 0.00
Link Summary
SN Element Element From To (Outlet)Length Inlet Outlet Average Diameter or Manning's Peak Design Flow Peak Flow/Peak Flow Peak Flow Peak Flow Total Time Reported
ID Type (Inlet)Node Invert Invert Slope Height Roughness Flow Capacity Design Flow Velocity Depth Depth/Surcharged Condition
Node Elevation Elevation Ratio Total Depth
Ratio
(ft)(ft)(ft)(%)(in)(cfs)(cfs)(ft/sec)(ft)(min)
1 BMP-BARREL Pipe BMP-RISER SITE-OUTLET 10.00 791.50 791.00 5.0000 18.000 0.0120 0.46 25.45 0.02 3.44 0.21 0.14 0.00 Calculated
2 VIRTUAL-LINK Pipe SITE-OUTLET OUTFALL 10.00 791.00 790.50 5.0000 18.000 0.0120 1.69 25.45 0.07 6.07 0.32 0.22 0.00 Calculated
3 PRINCIPAL-SPILLWAY Orifice SAND-FILTER BMP-RISER 794.00 791.50 36.000 0.43
4 FILTER-MEDIA Outlet SAND-FILTER BMP-RISER 794.00 791.50 0.03
5 EM-SPILLWAY Weir SAND-FILTER SITE-OUTLET 794.00 791.00 0.00
Subbasin Hydrology
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1
Input Data
Area (ac) .....................................................0.17
Weighted Curve Number ............................98.00
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.17 -98.00
Composite Area & Weighted CN 0.17 98.00
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................2.50
Peak Runoff (cfs) ........................................0.59
Weighted Curve Number ............................98.00
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 1
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2
Input Data
Area (ac) .....................................................0.21
Weighted Curve Number ............................98.00
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.21 -98.00
Composite Area & Weighted CN 0.21 98.00
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................2.50
Peak Runoff (cfs) ........................................0.75
Weighted Curve Number ............................98.00
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 2
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3
Input Data
Area (ac) .....................................................0.38
Weighted Curve Number ............................94.20
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.38 -94.20
Composite Area & Weighted CN 0.38 94.20
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................2.11
Peak Runoff (cfs) ........................................1.21
Weighted Curve Number ............................94.20
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 3
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4
Input Data
Area (ac) .....................................................0.76
Weighted Curve Number ............................71.01
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.76 -71.01
Composite Area & Weighted CN 0.76 71.01
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................0.61
Peak Runoff (cfs) ........................................0.65
Weighted Curve Number ............................71.01
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 4
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5
Input Data
Area (ac) .....................................................0.94
Weighted Curve Number ............................81.13
Rain Gage ID ...............................................SALISBURY
Composite Curve Number
Area Soil Curve
Soil/Surface Description (acres)Group Number
-0.94 -81.13
Composite Area & Weighted CN 0.94 81.13
Subbasin Runoff Results
Total Rainfall (in) .........................................2.73
Total Runoff (in) ..........................................1.12
Peak Runoff (cfs) ........................................1.67
Weighted Curve Number ............................81.13
Time of Concentration (days hh:mm:ss) .....0 00:05:00
Subbasin : {POST-CONSTRUCTION}.POST-CONSTRUCTION : 5
Junction Input
SN Element Invert Ground/Rim Ground/Rim Initial Initial Surcharge Surcharge Ponded Minimum
ID Elevation (Max)(Max)Water Water Elevation Depth Area Pipe
Elevation Offset Elevation Depth Cover
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft²)(in)
1 BMP-RISER 791.50 797.00 5.50 791.50 0.00 0.00 -797.00 0.00 0.00
2 SITE-OUTLET 791.00 797.00 6.00 791.00 0.00 0.00 -797.00 0.00 0.00
Junction Results
SN Element Peak Peak Max HGL Max HGL Max Min Average HGL Average HGL Time of Time of Total Total Time
ID Inflow Lateral Elevation Depth Surcharge Freeboard Elevation Depth Max HGL Peak Flooded Flooded
Inflow Attained Attained Depth Attained Attained Attained Occurrence Flooding Volume
Attained Occurrence
(cfs)(cfs)(ft)(ft)(ft)(ft)(ft)(ft)(days hh:mm)(days hh:mm)(ac-in)(min)
1 BMP-RISER 0.46 0.00 791.67 0.17 0.00 5.33 791.54 0.04 0 12:14 0 00:00 0.00 0.00
2 SITE-OUTLET 1.69 1.67 791.38 0.38 0.00 5.62 791.04 0.04 0 11:55 0 00:00 0.00 0.00
Pipe Input
SN Element Length Inlet Inlet Outlet Outlet Total Average Pipe Pipe Pipe Manning's Entrance Exit/Bend Additional Initial Flap No. of
ID Invert Invert Invert Invert Drop Slope Shape Diameter or Width Roughness Losses Losses Losses Flow Gate Barrels
Elevation Offset Elevation Offset Height
(ft)(ft)(ft)(ft)(ft)(ft)(%)(in)(in)(cfs)
1 BMP-BARREL 10.00 791.50 0.00 791.00 0.00 0.50 5.0000 CIRCULAR 18.000 18.000 0.0120 0.5000 0.5000 0.0000 0.00 No 1
2 VIRTUAL-LINK 10.00 791.00 0.00 790.50 0.00 0.50 5.0000 CIRCULAR 18.000 18.000 0.0120 0.5000 0.5000 0.0000 0.00 No 1
Pipe Results
SN Element Peak Time of Design Flow Peak Flow/Peak Flow Travel Peak Flow Peak Flow Total Time Froude Reported
ID Flow Peak Flow Capacity Design Flow Velocity Time Depth Depth/Surcharged Number Condition
Occurrence Ratio Total Depth
Ratio
(cfs)(days hh:mm)(cfs)(ft/sec)(min)(ft)(min)
1 BMP-BARREL 0.46 0 12:14 25.45 0.02 3.44 0.05 0.21 0.14 0.00 Calculated
2 VIRTUAL-LINK 1.69 0 11:56 25.45 0.07 6.07 0.03 0.32 0.22 0.00 Calculated
Storage Nodes
Storage Node : SAND-FILTER
Input Data
794.00
797.00
3.00
794.00
0.00
0.00
0.00
Storage Area Volume Curves
Storage Curve : SAND-FILTER
Stage Storage Storage
Area Volume
(ft)(ft²)(ft³)
0 2589 0.000
1 3526 3057.50
2 4520 7080.50
3 5571 12126.00
Evaporation Loss .....................................................................................
Invert Elevation (ft) ..................................................................................
Max (Rim) Elevation (ft) ..........................................................................
Max (Rim) Offset (ft) ...............................................................................
Initial Water Elevation (ft) ........................................................................
Initial Water Depth (ft) .............................................................................
Ponded Area (ft²) .....................................................................................
Storage Node : SAND-FILTER (continued)
Outflow Weirs
SN Element Weir Flap Crest Crest Length Weir Total Discharge
ID Type Gate Elevation Offset Height Coefficient
(ft)(ft)(ft)(ft)
1 EM-SPILLWAY Trapezoidal No 796.00 2.00 10.00 1.00 3.33
Outflow Orifices
SN Element Orifice Orifice Flap Circular Rectangular Rectangular Orifice Orifice
ID Type Shape Gate Orifice Orifice Orifice Invert Coefficient
Diameter Height Width Elevation
(in)(in)(in)(ft)
1 PRINCIPAL-SPILLWAY Bottom Rectangular No 36.00 36.00 795.25 0.63
Output Summary Results
3.18
3.18
0.46
0.00
795.30
1.3
794.66
0.66
0 12:14
0.000
0
0
0.00
Total Time Flooded (min) ........................................................................
Total Retention Time (sec) ......................................................................
Max HGL Depth Attained (ft) ...................................................................
Average HGL Elevation Attained (ft) .......................................................
Average HGL Depth Attained (ft) ............................................................
Time of Max HGL Occurrence (days hh:mm) .........................................
Total Exfiltration Volume (1000-ft³) .........................................................
Total Flooded Volume (ac-in) ..................................................................
Peak Inflow (cfs) ......................................................................................
Peak Lateral Inflow (cfs) ..........................................................................
Peak Outflow (cfs) ...................................................................................
Peak Exfiltration Flow Rate (cfm) ............................................................
Max HGL Elevation Attained (ft) ..............................................................