Conservation Commission - 185 (03/09/2023)

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Board/CommissionConservation Commission
Meeting DateMarch 09, 2023
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Supplemental Storm Drainage Report 
Proposed Affordable Housing Development 
Clark Lane 
Waterford, Connecticut 
 
 
 
Prepared for 
 
Kingstown Properties LLC 
 
 
 
February 5, 2023 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Prepared by: 
 
Provost & Rovero, Inc.
Provost & Rovero, Inc.
Provost & Rovero, Inc.
Provost & Rovero, Inc. 

Table of Contents 
Section 1 – Executive Summary 
Section 2 – Storm Sewer Design Calculations 
Section 3 – Water Quality Design Calculations 
Section 4 – Hydrologic Analysis Calculations 
Section 5 – Erosion and Sediment Control Design 

 
 
 
 
 
 
Section 1 
Executive Summary 
 

SUPPLEMENTAL NARRATIVE 
 
This supplemental report presents additional information in prepared in response to review 
comments during the public hearing process before the Waterford Conservation and Inland 
Wetlands Commission. 
 
HYDROLOGIC ANALYSIS 
 
The design of the detention basin and bioretention basin have been revised.  The previously 
submitted hydrologic model did not account for any stormwater detention provided by the 
bioretention basin.  The detailed hydrologic calculations presented in Section 4 include the 
detention effects of the bioretention basin and reflect ground cover and elevation adjustments in 
the model.  The following is a summary of existing and proposed peak flow rates at the analysis 
point: 
 
Storm Event 
 
Existing Peak Flow (cfs) 
Proposed Peak Flow (cfs) 
2 year  
 
 
36.89  
 
 
31.56 
5 year  
 
 
67.20  
 
 
57.96 
10 year  
 
 
87.01  
 
 
75.20 
25 year  
 
 
114.72  
 
 
99.40 
50 year  
 
 
136.23  
 
 
126.74 
100 year 
 
 
165.57  
 
 
162.75 
 
The following is a summary of proposed peak flow rates at the detention basin discharge: 
 
Storm Event 
 
Proposed Peak Flow (cfs) 
2 year  
 
 
1.98 
 
 
 
 
5 year  
 
 
2.95 
 
 
 
 
10 year  
 
 
3.46 
 
 
 
 
25 year  
 
 
7.60 
 
 
 
 
50 year  
 
 
14.15  
 
 
 
100 year 
 
 
23.78  
 
 
 
 
 
The detention basin outlet is equipped with a riprap lined plunge pool and concrete weir level 
spreader.  The discharge from the detention basin during a 100 year storm was analyzed to ensure 
that the level spreader would not result in erosive flow velocities.  The 100 year detention basin 
discharge is 23.78 cfs which will result in a flow velocity from the level spreader of 1.70 ft/sec.  
Per the 2002 Connecticut Guidelines for Soil Erosion and Sediment Control, the allowable 
velocity for sandy loam soils consistent with those observed on site is 2.5 ft/sec.  Based on this 
analysis, downstream erosion of native soils is not anticipated as a result of the detention basin 
discharge. 
 
Detailed hydrologic calculations are presented in Section 4. 
 
WATER QUALITY DESIGN 
 
The design of the bioretention basin has been revised to reflect 2020 guidance from the 
University of New Hampshire Stormwater Center.  The revised basin design is enhanced with an 
internal storage reservoir (ISR) which essentially functions as a subsurface gravel wetland system 
below the biofiltration system.  The primary benefit of the ISR system is enhanced nitrogen 

removal.  Additionally, the bioretention soil mix has been revised to further enhance phosphorus 
removal.  Actual removal rates for nitrogen and phosphorus are anticipated to be approximately 
85% and 87% respectively based on testing by the UNHSC.  Revised design and sizing 
calculations are presented in Section 3. 
 
STORM SEWER DESIGN 
 
Revised storm sewer summary calculations are presented in Section 2. 
 
TEMPORARY EROSION AND SEDIMENTATION CONTROL DESIGN 
 
The temporary sediment basin has been revised to coincide with the updated hydrologic cover 
conditions and the permanent configuration of the stormwater basins.  Revised design 
calculations are presented in Section 5. 
 
 

 
 
 
 
 
Section 2 
Storm Sewer Design Calculations 
 


 
 
 
 
 
Section 3 
Water Quality Design Calculations 
 


Enhanced Biofiltration is a practice the provides temporary storage of runoff for filtering through an 
engineered soil media, augmented for enhanced phosphorus removal, followed by detention and 
denitrification in a subsurface internal storage reservoir (ISR) comprised of gravel.  Runoff flows are routed 
through filter media and directed to the underlying ISR via an impermeable membrane for temporary storage.  
An elevated outlet control at the top of the ISR is designed to provide a retention time of at least 24 hours in 
the system to allow for sufficient time for denitrification and nitrogen reduction to occur prior to discharge.  
The design storage capacity for using the cumulative performance curves is comprised of void spaces in the 
filter media, temporary ponding at the surface of the practice and the void spaces in the gravel ISR.  The 
cumulative phosphorus load reduction curve for this control is intended to be used for systems in which the 
filter media has been augmented with materials designed and/or known to be effective at capturing 
phosphorus.  If the filter  media is not augmented to enhance phosphorus capture, then the phosphorus 
performance curve for the Bio-Filter should be used for estimating phosphorus load reductions.  The 
University of New Hampshire Stormwater Center (UNHSC) developed the design of this control practice and 
a design templated can be found at UNHSC’s website.
Enhanced Biofiltration with Internal Storage Reservoir (ISR) Factsheet
Source Category by Land Use
Land Surface Cover
P Load Export Rate1
(lbs./acre/year)
N Load Export Rate2
(lbs./acre/year)
Commercial (COM) and Industrial (IND)
Directly connected impervious
1.78
15
Multi-Family (MFR) and High-Density 
Residential (HDR)
Directly connected impervious
2.32
14.1
Medium-Density Residential (MDR)
Directly connected impervious
1.96
14.1
Low-Density Residential (LDR) - "Rural"
Directly connected impervious
1.52
14.1
Prepared By:
University of New Hampshire
Stormwater Center
Durham, NH
www.unh.edu/unhsc
January 2020
General Equations
Pollutant Export Rate by Land Use1
1 From NH Small MS4 General Permit, Appendix F
Physical Storage Capacity: Depth of Runoff * Drainage Area
Cost: Physical Storage Capacity * Cost Index * Adjustment Factor1
Yearly Pollutant Removal: Pollutant Load Export Rate * Drainage Area * Efficiency
Cost
https://www.unh.edu/unhsc/sites/default/files/media/undersized_systems.pdf
1 EPA Memorandum “Methodology for developing cost estimates for Opti-Tool.” Februrary 20, 2016
2 Converted from 2010 to 2020 dollars using U.S. Department of Labor (USDOL). (2012). Bureau of Labor Statistics 
consumer price index inflation calculator. http://www.bls.gov/data/inflation_calculator.htm
Materials and Installation 
Cost ($/ft3) (2020)
Design Cost ($/ft3) 
(2020)
Total Cost ($/ft3) 
(2020)1,2
Rural
10.42
5.61
16.02
Mixed
20.83
11.22
32.05
Urban
31.25
16.83
48.07

BMP Performance Curve for Enhanced Biofiltration w/ ISR
Enhanced Biofiltration w/ ISR BMP Performance Table: Long-Term 
Phosphorus & Nitrogen Load Reduction
BMP Capacity: Depth of Runoff  
from Impervious Area (inches)
0.1
0.2
0.4
0.6
0.8
1.0
1.5
2.0
Cumulative TSS Phosphorus Load 
Reduction
44% 69% 91% 97% 98% 99% 100% 100%
Cumulative Phosphorus Load 
Reduction
19% 34% 53% 64% 71% 76% 84% 89%
Cumulative Nitrogen Load 
Reduction
32% 44% 58% 66% 71% 75% 82% 86%
Cumulative Zinc Phosphorus Load 
Reduction
68% 88% 95% 96% 96% 97% 98% 99%

Type III 24-hr  2 year Rainfall=3.20"
WATER QUALITY OUTLET ORIFICE
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 1
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 1P: Bioretention Basin
Inflow
=
0.00 cfs @ 
0.00 hrs,  Volume=
0.000 af
Outflow
=
0.20 cfs @ 
0.00 hrs,  Volume=
0.456 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
0.20 cfs @ 
0.00 hrs,  Volume=
0.456 af
Routing by Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs
Starting Elev= 96.86'   Surf.Area= 11,330 sf   Storage= 19,844 cf
Peak Elev= 96.86' @ 0.00 hrs   Surf.Area= 11,330 sf   Storage= 19,844 cf
Plug-Flow detention time= (not calculated: no plugs found)
Center-of-Mass det. time= (not calculated: no inflow)
Volume
Invert
Avail.Storage
Storage Description
#1
95.00'
21,436 cf
Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic-feet)
(cubic-feet)
95.00
9,768
0
0
96.00
10,848
10,308
10,308
97.00
11,408
11,128
21,436
Device
Routing     
Invert
Outlet Devices
#1
Primary
93.25'
2.0" Vert. Orifice/Grate    C= 0.600   
Primary OutFlow  Max=0.20 cfs @ 0.00 hrs  HW=96.86'   (Free Discharge)
1=Orifice/Grate  (Orifice Controls 0.20 cfs @ 9.04 fps)

Type III 24-hr  2 year Rainfall=3.20"
WATER QUALITY OUTLET ORIFICE
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 2
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pond 1P: Bioretention Basin
Inflow
Primary
Hydrograph
Time  (hours)
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
0.22
0.21
0.2
0.19
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
Peak Elev=96.86'
Storage=19,844 cf
0.00 cfs
0.20 cfs

Type III 24-hr  2 year Rainfall=3.20"
WATER QUALITY OUTLET ORIFICE
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 3
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Hydrograph for Pond 1P: Bioretention Basin
Time
(hours)
Inflow
(cfs)
Storage
(cubic-feet)
Elevation
(feet)
Primary
(cfs)
0.00
0.00
19,844
96.86
0.20
1.00
0.00
19,137
96.80
0.20
2.00
0.00
18,437
96.74
0.19
3.00
0.00
17,742
96.67
0.19
4.00
0.00
17,054
96.61
0.19
5.00
0.00
16,373
96.55
0.19
6.00
0.00
15,698
96.49
0.19
7.00
0.00
15,029
96.43
0.18
8.00
0.00
14,367
96.37
0.18
9.00
0.00
13,711
96.31
0.18
10.00
0.00
13,061
96.25
0.18
11.00
0.00
12,419
96.19
0.18
12.00
0.00
11,782
96.14
0.18
13.00
0.00
11,153
96.08
0.17
14.00
0.00
10,529
96.02
0.17
15.00
0.00
9,913
95.96
0.17
16.00
0.00
9,303
95.91
0.17
17.00
0.00
8,699
95.85
0.17
18.00
0.00
8,103
95.79
0.16
19.00
0.00
7,513
95.74
0.16
20.00
0.00
6,930
95.68
0.16
21.00
0.00
6,353
95.63
0.16
22.00
0.00
5,784
95.57
0.16
23.00
0.00
5,221
95.52
0.16
24.00
0.00
4,666
95.47
0.15
25.00
0.00
4,117
95.41
0.15
26.00
0.00
3,575
95.36
0.15
27.00
0.00
3,040
95.31
0.15
28.00
0.00
2,513
95.25
0.15
29.00
0.00
1,992
95.20
0.14
30.00
0.00
1,479
95.15
0.14
31.00
0.00
973
95.10
0.14
32.00
0.00
474
95.05
0.14
33.00
0.00
66
95.01
0.05
34.00
0.00
5
95.00
0.00
35.00
0.00
0
95.00
0.00
36.00
0.00
0
95.00
0.00

 
 
 
 
 
Section 4 
Hydrologic Analysis Calculations 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

1S
P-2
2S
P-1
3S
E-1
3R
Overland Flow
3P
CB
Level Spreader
4P
Bioretention Basin
5P
CB
Weir MH 103 WQF
6P
Detention Basin
7P
CB
Weir MH 103 to Det
 Basin
2L
Design Point
Routing Diagram for 213009 REV 2-4-23
Prepared by Provost & Rovero, Inc.,  Printed 2/5/2023
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Subcat
Reach
Pond
Link

213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 2
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Project Notes
CarlsonStageIncrement|1.0000|

213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 3
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Area Listing (all nodes)
Area
(acres)
CN
Description
(subcatchment-numbers)
21.549
39
>75% Grass cover, Good, HSG A  (1S, 3S)
6.976
61
>75% Grass cover, Good, HSG B  (1S, 3S)
46.790
74
>75% Grass cover, Good, HSG C  (1S, 2S, 3S)
1.996
80
>75% Grass cover, Good, HSG D  (1S, 3S)
22.152
98
Paved parking HSG A  (1S, 3S)
1.644
98
Paved parking HSG B  (1S, 3S)
19.305
98
Paved parking HSG C  (1S, 2S, 3S)
1.046
98
Paved parking HSG D  (1S, 3S)
7.008
30
Woods, Good, HSG A  (1S, 3S)
7.864
55
Woods, Good, HSG B  (1S, 3S)
41.589
70
Woods, Good, HSG C  (1S, 2S, 3S)
21.166
77
Woods, Good, HSG D  (1S, 3S)
3.956
72
Woods/grass comb., Good, HSG C  (1S, 2S, 3S)
0.402
79
Woods/grass comb., Good, HSG D  (1S, 3S)
203.443
72
TOTAL AREA

213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 4
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Soil Listing (all nodes)
Area
(acres)
Soil
Group
Subcatchment
Numbers
50.709
HSG A
1S, 3S
16.484
HSG B
1S, 3S
111.640
HSG C
1S, 2S, 3S
24.610
HSG D
1S, 3S
0.000
Other
203.443
TOTAL AREA

213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 5
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Ground Covers (all nodes)
HSG-A
(acres)
HSG-B
(acres)
HSG-C
(acres)
HSG-D
(acres)
Other
(acres)
Total
(acres)
Ground
Cover
Subcatchment
Numbers
21.549
6.976
46.790
1.996
0.000
77.311
>75% Grass cover, Good
1S, 
2S, 3S
22.152
1.644
19.305
1.046
0.000
44.147
Paved parking
1S, 
2S, 3S
7.008
7.864
41.589
21.166
0.000
77.627
Woods, Good
1S, 
2S, 3S
0.000
0.000
3.956
0.402
0.000
4.358
Woods/grass comb., Good 1S, 
2S, 3S
50.709
16.484
111.640
24.610
0.000
203.443
TOTAL AREA

213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 6
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pipe Listing (all nodes)
Line#
Node
Number
In-Invert
(feet)
Out-Invert
(feet)
Length
(feet)
Slope
(ft/ft)
n
Diam/Width
(inches)
Height
(inches)
Inside-Fill
(inches)
1
5P
95.40
95.00
70.0
0.0057
0.013
12.0
0.0
0.0
2
6P
90.25
90.00
44.0
0.0057
0.012
30.0
0.0
0.0
3
6P
90.30
90.25
5.0
0.0100
0.012
10.0
0.0
0.0
4
7P
91.00
90.00
50.0
0.0200
0.013
36.0
0.0
0.0

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 7
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Muskingum-Cunge method  -  Pond routing by Dyn-Stor-Ind method
Runoff Area=87.970 ac   20.82% Impervious   Runoff Depth=0.88"
Subcatchment 1S: P-2
   Flow Length=4,420'   Tc=68.3 min   CN=71   Runoff=29.66 cfs  6.437 af
Runoff Area=13.736 ac   38.54% Impervious   Runoff Depth=1.61"
Subcatchment 2S: P-1
   Tc=26.0 min   CN=83   Runoff=15.55 cfs  1.842 af
Runoff Area=101.737 ac   20.18% Impervious   Runoff Depth=0.93"
Subcatchment 3S: E-1
   Flow Length=4,420'   Tc=68.3 min   CN=72   Runoff=36.89 cfs  7.882 af
Avg. Flow Depth=0.04'   Max Vel=1.05 fps   Inflow=1.98 cfs  1.383 af
Reach 3R: Overland Flow
n=0.400   L=760.0'   S=0.0368 '/'   Capacity=35.52 cfs   Outflow=1.98 cfs  1.378 af
Peak Elev=90.05'   Inflow=1.98 cfs  1.383 af
Pond 3P: Level Spreader
   Outflow=1.98 cfs  1.383 af
Peak Elev=96.90'  Storage=20,529 cf   Inflow=3.60 cfs  0.809 af
Pond 4P: Bioretention Basin
   Outflow=0.31 cfs  0.493 af
Peak Elev=97.21'   Inflow=15.55 cfs  1.842 af
Pond 5P: Weir MH 103 WQF
   Primary=3.60 cfs  0.809 af   Secondary=11.95 cfs  1.033 af   Outflow=15.55 cfs  1.842 af
Peak Elev=91.63'  Storage=23,893 cf   Inflow=12.21 cfs  1.526 af
Pond 6P: Detention Basin
   Outflow=1.98 cfs  1.383 af
Peak Elev=92.33'   Inflow=11.95 cfs  1.033 af
Pond 7P: Weir MH 103 to Det Basin
36.0"  Round Culvert  n=0.013  L=50.0'  S=0.0200 '/'   Outflow=11.95 cfs  1.033 af
   Inflow=31.56 cfs  7.815 af
Link 2L: Design Point
   Primary=31.56 cfs  7.815 af
Total Runoff Area = 203.443 ac   Runoff Volume = 16.161 af   Average Runoff Depth = 0.95"
78.30% Pervious = 159.296 ac     21.70% Impervious = 44.147 ac

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 8
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: P-2
CarlsonPlanXYPos|1171180.9301|691042.4469|
CarlsonSurface||
Runoff
=
29.66 cfs @ 12.98 hrs,  Volume=
6.437 af,  Depth= 0.88"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  2 year Rainfall=3.20"
Area (ac)
CN
Description
11.076
98
Paved parking HSG A
10.583
77
Woods, Good, HSG D
1.449
72
Woods/grass comb., Good, HSG C
0.201
79
Woods/grass comb., Good, HSG D
3.504
30
Woods, Good, HSG A
16.559
70
Woods, Good, HSG C
3.932
55
Woods, Good, HSG B
0.822
98
Paved parking HSG B
0.523
98
Paved parking HSG D
5.898
98
Paved parking HSG C
10.774
39
>75% Grass cover, Good, HSG A
3.488
61
>75% Grass cover, Good, HSG B
18.163
74
>75% Grass cover, Good, HSG C
0.998
80
>75% Grass cover, Good, HSG D
87.970
71
Weighted Average
69.651
79.18% Pervious Area
18.319
20.82% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
14.3
100
0.0200
0.12
Sheet Flow, 
Grass: Dense   n= 0.240   P2= 3.20"
3.6
980
0.0490
4.49
Shallow Concentrated Flow, 
Paved   Kv= 20.3 fps
6.8
1,230
3.00
Direct Entry, pipe flow
43.6
2,110
0.0260
0.81
Shallow Concentrated Flow, 
Woodland   Kv= 5.0 fps
68.3
4,420
Total

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 9
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Subcatchment 1S: P-2
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type III 24-hr
2 year Rainfall=3.20"
Runoff Area=87.970 ac
Runoff Volume=6.437 af
Runoff Depth=0.88"
Flow Length=4,420'
Tc=68.3 min
CN=71
29.66 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 10
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 2S: P-1
CarlsonPlanXYPos|1170813.5231|690121.8114|
CarlsonSurface||
Runoff
=
15.55 cfs @ 12.37 hrs,  Volume=
1.842 af,  Depth= 1.61"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  2 year Rainfall=3.20"
Area (ac)
CN
Description
0.464
70
Woods, Good, HSG C
0.525
72
Woods/grass comb., Good, HSG C
5.294
98
Paved parking HSG C
7.453
74
>75% Grass cover, Good, HSG C
13.736
83
Weighted Average
8.442
61.46% Pervious Area
5.294
38.54% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
26.0
Direct Entry, Storm sewer TC
Subcatchment 2S: P-1
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type III 24-hr
2 year Rainfall=3.20"
Runoff Area=13.736 ac
Runoff Volume=1.842 af
Runoff Depth=1.61"
Tc=26.0 min
CN=83
15.55 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 11
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: E-1
CarlsonPlanXYPos|1171180.9301|691042.4469|
CarlsonSurface||
Runoff
=
36.89 cfs @ 12.98 hrs,  Volume=
7.882 af,  Depth= 0.93"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  2 year Rainfall=3.20"
Area (ac)
CN
Description
11.076
98
Paved parking HSG A
10.583
77
Woods, Good, HSG D
1.982
72
Woods/grass comb., Good, HSG C
0.201
79
Woods/grass comb., Good, HSG D
3.504
30
Woods, Good, HSG A
24.566
70
Woods, Good, HSG C
3.932
55
Woods, Good, HSG B
0.822
98
Paved parking HSG B
0.523
98
Paved parking HSG D
8.113
98
Paved parking HSG C
10.775
39
>75% Grass cover, Good, HSG A
3.488
61
>75% Grass cover, Good, HSG B
21.174
74
>75% Grass cover, Good, HSG C
0.998
80
>75% Grass cover, Good, HSG D
101.737
72
Weighted Average
81.203
79.82% Pervious Area
20.534
20.18% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
14.3
100
0.0200
0.12
Sheet Flow, 
Grass: Dense   n= 0.240   P2= 3.20"
3.6
980
0.0490
4.49
Shallow Concentrated Flow, 
Paved   Kv= 20.3 fps
6.8
1,230
3.00
Direct Entry, pipe flow
43.6
2,110
0.0260
0.81
Shallow Concentrated Flow, watercourse
Woodland   Kv= 5.0 fps
68.3
4,420
Total

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 12
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Subcatchment 3S: E-1
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type III 24-hr
2 year Rainfall=3.20"
Runoff Area=101.737 ac
Runoff Volume=7.882 af
Runoff Depth=0.93"
Flow Length=4,420'
Tc=68.3 min
CN=72
36.89 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 13
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Reach 3R: Overland Flow
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 1.21"    for  2 year event
Inflow
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af
Outflow
=
1.98 cfs @ 13.32 hrs,  Volume=
1.378 af,  Atten= 0%,  Lag= 12.5 min
Routing by Dyn-Muskingum-Cunge method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Reference Flow= 26.64 cfs  Estimated Depth= 0.84'  Velocity= 0.62 fps
m= 1.648,  c= 1.03 fps,  dt= 0.6 min,  dx= 760.0' / 21 = 36.2',  K= 0.6 min,  X= 0.309
Max. Velocity= 1.05 fps,  Min. Travel Time= 12.1 min
Avg. Velocity = 0.99 fps,  Avg. Travel Time= 12.8 min
Peak Storage= 1,469 cf @ 13.23 hrs
Average Depth at Peak Storage= 0.04'
Bank-Full Depth= 1.00'  Flow Area= 51.0 sf,  Capacity= 35.52 cfs
50.00'  x  1.00'  deep channel,  n= 0.400
Side Slope Z-value= 1.0 '/'   Top Width= 52.00'
Length= 760.0'   Slope= 0.0368 '/'
Inlet Invert= 88.00',  Outlet Invert= 60.00'
‡
Reach 3R: Overland Flow
Inflow
Outflow
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
2
1
0
Inflow Area=13.736 ac
Avg. Flow Depth=0.04'
Max Vel=1.05 fps
n=0.400
L=760.0'
S=0.0368 '/'
Capacity=35.52 cfs
1.98 cfs
1.98 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 14
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 3P: Level Spreader
[57] Hint: Peaked at 90.05' (Flood elevation advised)
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 1.21"    for  2 year event
Inflow
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af
Outflow
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 90.05' @ 13.12 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
90.00'
56.0' long Sharp-Crested Rectangular Weir   2 End Contraction(s)   
1.0' Crest Height   
Primary OutFlow  Max=1.98 cfs @ 13.12 hrs  HW=90.05'  TW=88.04'   (Dynamic Tailwater)
1=Sharp-Crested Rectangular Weir  (Weir Controls 1.98 cfs @ 0.73 fps)
Pond 3P: Level Spreader
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
2
1
0
Inflow Area=13.736 ac
Peak Elev=90.05'
1.98 cfs
1.98 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 15
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 4P: Bioretention Basin
[80] Warning: Exceeded Pond 5P by 1.37' @ 25.07 hrs (2.87 cfs 0.197 af) 
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth = 0.71"    for  2 year event
Inflow
=
3.60 cfs @ 12.37 hrs,  Volume=
0.809 af
Outflow
=
0.31 cfs @ 14.98 hrs,  Volume=
0.493 af,  Atten= 91%,  Lag= 157.0 min
Primary
=
0.31 cfs @ 14.98 hrs,  Volume=
0.493 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 96.90' @ 14.98 hrs   Surf.Area= 11,856 sf   Storage= 20,529 cf
Plug-Flow detention time= (not calculated: outflow precedes inflow)
Center-of-Mass det. time= 333.4 min ( 1,201.1 - 867.7 )
Volume
Invert
Avail.Storage
Storage Description
#1
95.00'
34,250 cf
Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic-feet)
(cubic-feet)
95.00
9,768
0
0
96.00
10,848
10,308
10,308
97.00
11,968
11,408
21,716
98.00
13,100
12,534
34,250
Device
Routing     
Invert
Outlet Devices
#1
Primary
93.25'
2.5" Vert. Orifice/Grate    C= 0.600   
#2
Primary
97.00'
16.0' long  x 6.0' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00  1.20  1.40  1.60  1.80  2.00  
2.50  3.00  3.50  4.00  4.50  5.00  5.50   
Coef. (English)  2.37  2.51  2.70  2.68  2.68  2.67  2.65  2.65  2.65  
2.65  2.66  2.66  2.67  2.69  2.72  2.76  2.83   
Primary OutFlow  Max=0.31 cfs @ 14.98 hrs  HW=96.90'  TW=91.48'   (Dynamic Tailwater)
1=Orifice/Grate  (Orifice Controls 0.31 cfs @ 9.07 fps)
2=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 16
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pond 4P: Bioretention Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
4
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=96.90'
Storage=20,529 cf
3.60 cfs
0.31 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 17
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 5P: Weir MH 103 WQF
[57] Hint: Peaked at 97.21' (Flood elevation advised)
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth = 1.61"    for  2 year event
Inflow
=
15.55 cfs @ 12.37 hrs,  Volume=
1.842 af
Outflow
=
15.55 cfs @ 12.37 hrs,  Volume=
1.842 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
3.60 cfs @ 12.37 hrs,  Volume=
0.809 af
Secondary =
11.95 cfs @ 12.37 hrs,  Volume=
1.033 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 97.21' @ 12.37 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
95.40'
12.0"  Round Culvert   
L= 70.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 95.40' / 95.00'   S= 0.0057 '/'   Cc= 0.900   
n= 0.013  Corrugated PE, smooth interior,  Flow Area= 0.79 sf   
#2
Secondary
96.83'
60.0" Horiz. Orifice/Grate    C= 0.600   
Limited to weir flow at low heads   
Primary OutFlow  Max=3.60 cfs @ 12.37 hrs  HW=97.21'  TW=95.92'   (Dynamic Tailwater)
1=Culvert  (Barrel Controls 3.60 cfs @ 4.59 fps)
Secondary OutFlow  Max=11.95 cfs @ 12.37 hrs  HW=97.21'  TW=92.33'   (Dynamic Tailwater)
2=Orifice/Grate  (Weir Controls 11.95 cfs @ 2.01 fps)
Pond 5P: Weir MH 103 WQF
Inflow
Outflow
Primary
Secondary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=97.21'
15.55 cfs
15.55 cfs
3.60 cfs
11.95 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 18
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 6P: Detention Basin
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 1.33"    for  2 year event
Inflow
=
12.21 cfs @ 12.37 hrs,  Volume=
1.526 af
Outflow
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af,  Atten= 84%,  Lag= 44.9 min
Primary
=
1.98 cfs @ 13.12 hrs,  Volume=
1.383 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 91.63' @ 13.12 hrs   Surf.Area= 18,984 sf   Storage= 23,893 cf
Plug-Flow detention time= 201.7 min calculated for 1.383 af (91% of inflow)
Center-of-Mass det. time= 132.9 min ( 1,088.7 - 955.9 )
Volume
Invert
Avail.Storage
Storage Description
#1
90.30'
122,564 cf
Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic-feet)
(cubic-feet)
90.30
16,859
0
0
92.00
19,568
30,963
30,963
94.00
22,870
42,438
73,401
95.00
24,576
23,723
97,124
96.00
26,304
25,440
122,564
Device
Routing     
Invert
Outlet Devices
#1
Primary
90.25'
30.0"  Round Culvert   
L= 44.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 90.25' / 90.00'   S= 0.0057 '/'   Cc= 0.900   
n= 0.012,  Flow Area= 4.91 sf   
#2
Device 1
90.30'
10.0"  Round Culvert   
L= 5.0'   CPP, projecting, no headwall,  Ke= 0.900   
Inlet / Outlet Invert= 90.30' / 90.25'   S= 0.0100 '/'   Cc= 0.900   
n= 0.012,  Flow Area= 0.55 sf   
#3
Device 1
93.90'
30.0" Horiz. Orifice/Grate    C= 0.600   
Limited to weir flow at low heads   
#4
Primary
95.00'
20.0' long  x 13.0' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00  1.20  1.40  1.60   
Coef. (English)  2.60  2.64  2.70  2.66  2.65  2.66  2.65  2.63   
Primary OutFlow  Max=1.98 cfs @ 13.12 hrs  HW=91.63'  TW=90.05'   (Dynamic Tailwater)
1=Culvert  (Passes 1.98 cfs of 8.63 cfs potential flow)
2=Culvert  (Inlet Controls 1.98 cfs @ 3.64 fps)
3=Orifice/Grate  ( Controls 0.00 cfs)
4=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 19
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pond 6P: Detention Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=91.63'
Storage=23,893 cf
12.21 cfs
1.98 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 20
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 7P: Weir MH 103 to Det Basin
[57] Hint: Peaked at 92.33' (Flood elevation advised)
Inflow
=
11.95 cfs @ 12.37 hrs,  Volume=
1.033 af
Outflow
=
11.95 cfs @ 12.37 hrs,  Volume=
1.033 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
11.95 cfs @ 12.37 hrs,  Volume=
1.033 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 92.33' @ 12.37 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
91.00'
36.0"  Round Culvert   
L= 50.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 91.00' / 90.00'   S= 0.0200 '/'   Cc= 0.900   
n= 0.013  Corrugated PE, smooth interior,  Flow Area= 7.07 sf   
Primary OutFlow  Max=11.95 cfs @ 12.37 hrs  HW=92.33'  TW=90.96'   (Dynamic Tailwater)
1=Culvert  (Inlet Controls 11.95 cfs @ 3.93 fps)
Pond 7P: Weir MH 103 to Det Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Peak Elev=92.33'
36.0"
Round Culvert
n=0.013
L=50.0'
S=0.0200 '/'
11.95 cfs
11.95 cfs

Type III 24-hr  2 year Rainfall=3.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 21
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Link 2L: Design Point
Inflow Area =
101.706 ac, 23.22% Impervious,  Inflow Depth > 0.92"    for  2 year event
Inflow
=
31.56 cfs @ 12.98 hrs,  Volume=
7.815 af
Primary
=
31.56 cfs @ 12.98 hrs,  Volume=
7.815 af,  Atten= 0%,  Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Link 2L: Design Point
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=101.706 ac
31.56 cfs
31.56 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 22
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Muskingum-Cunge method  -  Pond routing by Dyn-Stor-Ind method
Runoff Area=87.970 ac   20.82% Impervious   Runoff Depth=1.53"
Subcatchment 1S: P-2
   Flow Length=4,420'   Tc=68.3 min   CN=71   Runoff=55.21 cfs  11.236 af
Runoff Area=13.736 ac   38.54% Impervious   Runoff Depth=2.46"
Subcatchment 2S: P-1
   Tc=26.0 min   CN=83   Runoff=23.87 cfs  2.817 af
Runoff Area=101.737 ac   20.18% Impervious   Runoff Depth=1.60"
Subcatchment 3S: E-1
   Flow Length=4,420'   Tc=68.3 min   CN=72   Runoff=67.20 cfs  13.581 af
Avg. Flow Depth=0.06'   Max Vel=1.05 fps   Inflow=2.95 cfs  2.345 af
Reach 3R: Overland Flow
n=0.400   L=760.0'   S=0.0368 '/'   Capacity=35.52 cfs   Outflow=2.95 cfs  2.339 af
Peak Elev=90.06'   Inflow=2.95 cfs  2.345 af
Pond 3P: Level Spreader
   Outflow=2.95 cfs  2.345 af
Peak Elev=96.96'  Storage=21,186 cf   Inflow=3.35 cfs  0.838 af
Pond 4P: Bioretention Basin
   Outflow=0.31 cfs  0.518 af
Peak Elev=97.37'   Inflow=23.87 cfs  2.817 af
Pond 5P: Weir MH 103 WQF
   Primary=3.35 cfs  0.838 af   Secondary=20.61 cfs  1.978 af   Outflow=23.87 cfs  2.817 af
Peak Elev=92.74'  Storage=45,921 cf   Inflow=20.90 cfs  2.497 af
Pond 6P: Detention Basin
   Outflow=2.95 cfs  2.345 af
Peak Elev=92.85'   Inflow=20.61 cfs  1.978 af
Pond 7P: Weir MH 103 to Det Basin
36.0"  Round Culvert  n=0.013  L=50.0'  S=0.0200 '/'   Outflow=20.61 cfs  1.978 af
   Inflow=57.96 cfs  13.574 af
Link 2L: Design Point
   Primary=57.96 cfs  13.574 af
Total Runoff Area = 203.443 ac   Runoff Volume = 27.633 af   Average Runoff Depth = 1.63"
78.30% Pervious = 159.296 ac     21.70% Impervious = 44.147 ac

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 23
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 1S: P-2
CarlsonPlanXYPos|1171180.9301|691042.4469|
CarlsonSurface||
Runoff
=
55.21 cfs @ 12.98 hrs,  Volume=
11.236 af,  Depth= 1.53"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  5 year Rainfall=4.20"
Area (ac)
CN
Description
11.076
98
Paved parking HSG A
10.583
77
Woods, Good, HSG D
1.449
72
Woods/grass comb., Good, HSG C
0.201
79
Woods/grass comb., Good, HSG D
3.504
30
Woods, Good, HSG A
16.559
70
Woods, Good, HSG C
3.932
55
Woods, Good, HSG B
0.822
98
Paved parking HSG B
0.523
98
Paved parking HSG D
5.898
98
Paved parking HSG C
10.774
39
>75% Grass cover, Good, HSG A
3.488
61
>75% Grass cover, Good, HSG B
18.163
74
>75% Grass cover, Good, HSG C
0.998
80
>75% Grass cover, Good, HSG D
87.970
71
Weighted Average
69.651
79.18% Pervious Area
18.319
20.82% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
14.3
100
0.0200
0.12
Sheet Flow, 
Grass: Dense   n= 0.240   P2= 3.20"
3.6
980
0.0490
4.49
Shallow Concentrated Flow, 
Paved   Kv= 20.3 fps
6.8
1,230
3.00
Direct Entry, pipe flow
43.6
2,110
0.0260
0.81
Shallow Concentrated Flow, 
Woodland   Kv= 5.0 fps
68.3
4,420
Total

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 24
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Subcatchment 1S: P-2
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
60
55
50
45
40
35
30
25
20
15
10
5
0
Type III 24-hr
5 year Rainfall=4.20"
Runoff Area=87.970 ac
Runoff Volume=11.236 af
Runoff Depth=1.53"
Flow Length=4,420'
Tc=68.3 min
CN=71
55.21 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 25
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 2S: P-1
CarlsonPlanXYPos|1170813.5231|690121.8114|
CarlsonSurface||
Runoff
=
23.87 cfs @ 12.36 hrs,  Volume=
2.817 af,  Depth= 2.46"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  5 year Rainfall=4.20"
Area (ac)
CN
Description
0.464
70
Woods, Good, HSG C
0.525
72
Woods/grass comb., Good, HSG C
5.294
98
Paved parking HSG C
7.453
74
>75% Grass cover, Good, HSG C
13.736
83
Weighted Average
8.442
61.46% Pervious Area
5.294
38.54% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
26.0
Direct Entry, Storm sewer TC
Subcatchment 2S: P-1
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type III 24-hr
5 year Rainfall=4.20"
Runoff Area=13.736 ac
Runoff Volume=2.817 af
Runoff Depth=2.46"
Tc=26.0 min
CN=83
23.87 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 26
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Subcatchment 3S: E-1
CarlsonPlanXYPos|1171180.9301|691042.4469|
CarlsonSurface||
Runoff
=
67.20 cfs @ 12.98 hrs,  Volume=
13.581 af,  Depth= 1.60"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type III 24-hr  5 year Rainfall=4.20"
Area (ac)
CN
Description
11.076
98
Paved parking HSG A
10.583
77
Woods, Good, HSG D
1.982
72
Woods/grass comb., Good, HSG C
0.201
79
Woods/grass comb., Good, HSG D
3.504
30
Woods, Good, HSG A
24.566
70
Woods, Good, HSG C
3.932
55
Woods, Good, HSG B
0.822
98
Paved parking HSG B
0.523
98
Paved parking HSG D
8.113
98
Paved parking HSG C
10.775
39
>75% Grass cover, Good, HSG A
3.488
61
>75% Grass cover, Good, HSG B
21.174
74
>75% Grass cover, Good, HSG C
0.998
80
>75% Grass cover, Good, HSG D
101.737
72
Weighted Average
81.203
79.82% Pervious Area
20.534
20.18% Impervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
14.3
100
0.0200
0.12
Sheet Flow, 
Grass: Dense   n= 0.240   P2= 3.20"
3.6
980
0.0490
4.49
Shallow Concentrated Flow, 
Paved   Kv= 20.3 fps
6.8
1,230
3.00
Direct Entry, pipe flow
43.6
2,110
0.0260
0.81
Shallow Concentrated Flow, watercourse
Woodland   Kv= 5.0 fps
68.3
4,420
Total

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 27
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Subcatchment 3S: E-1
Runoff
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type III 24-hr
5 year Rainfall=4.20"
Runoff Area=101.737 ac
Runoff Volume=13.581 af
Runoff Depth=1.60"
Flow Length=4,420'
Tc=68.3 min
CN=72
67.20 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 28
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Reach 3R: Overland Flow
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 2.05"    for  5 year event
Inflow
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af
Outflow
=
2.95 cfs @ 14.04 hrs,  Volume=
2.339 af,  Atten= 0%,  Lag= 12.3 min
Routing by Dyn-Muskingum-Cunge method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Reference Flow= 26.64 cfs  Estimated Depth= 0.84'  Velocity= 0.62 fps
m= 1.648,  c= 1.03 fps,  dt= 0.6 min,  dx= 760.0' / 21 = 36.2',  K= 0.6 min,  X= 0.309
Max. Velocity= 1.05 fps,  Min. Travel Time= 12.0 min
Avg. Velocity = 0.99 fps,  Avg. Travel Time= 12.8 min
Peak Storage= 2,184 cf @ 13.93 hrs
Average Depth at Peak Storage= 0.06'
Bank-Full Depth= 1.00'  Flow Area= 51.0 sf,  Capacity= 35.52 cfs
50.00'  x  1.00'  deep channel,  n= 0.400
Side Slope Z-value= 1.0 '/'   Top Width= 52.00'
Length= 760.0'   Slope= 0.0368 '/'
Inlet Invert= 88.00',  Outlet Invert= 60.00'
‡
Reach 3R: Overland Flow
Inflow
Outflow
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
3
2
1
0
Inflow Area=13.736 ac
Avg. Flow Depth=0.06'
Max Vel=1.05 fps
n=0.400
L=760.0'
S=0.0368 '/'
Capacity=35.52 cfs
2.95 cfs
2.95 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 29
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 3P: Level Spreader
[57] Hint: Peaked at 90.06' (Flood elevation advised)
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 2.05"    for  5 year event
Inflow
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af
Outflow
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 90.06' @ 13.83 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
90.00'
56.0' long Sharp-Crested Rectangular Weir   2 End Contraction(s)   
1.0' Crest Height   
Primary OutFlow  Max=2.95 cfs @ 13.83 hrs  HW=90.06'  TW=88.06'   (Dynamic Tailwater)
1=Sharp-Crested Rectangular Weir  (Weir Controls 2.95 cfs @ 0.83 fps)
Pond 3P: Level Spreader
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=90.06'
2.95 cfs
2.95 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 30
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 4P: Bioretention Basin
[80] Warning: Exceeded Pond 5P by 1.35' @ 25.43 hrs (2.84 cfs 0.161 af) 
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth = 0.73"    for  5 year event
Inflow
=
3.35 cfs @ 12.25 hrs,  Volume=
0.838 af
Outflow
=
0.31 cfs @ 13.98 hrs,  Volume=
0.518 af,  Atten= 91%,  Lag= 104.3 min
Primary
=
0.31 cfs @ 13.98 hrs,  Volume=
0.518 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 96.96' @ 13.98 hrs   Surf.Area= 11,918 sf   Storage= 21,186 cf
Plug-Flow detention time= (not calculated: outflow precedes inflow)
Center-of-Mass det. time= 335.8 min ( 1,172.3 - 836.5 )
Volume
Invert
Avail.Storage
Storage Description
#1
95.00'
34,250 cf
Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic-feet)
(cubic-feet)
95.00
9,768
0
0
96.00
10,848
10,308
10,308
97.00
11,968
11,408
21,716
98.00
13,100
12,534
34,250
Device
Routing     
Invert
Outlet Devices
#1
Primary
93.25'
2.5" Vert. Orifice/Grate    C= 0.600   
#2
Primary
97.00'
16.0' long  x 6.0' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00  1.20  1.40  1.60  1.80  2.00  
2.50  3.00  3.50  4.00  4.50  5.00  5.50   
Coef. (English)  2.37  2.51  2.70  2.68  2.68  2.67  2.65  2.65  2.65  
2.65  2.66  2.66  2.67  2.69  2.72  2.76  2.83   
Primary OutFlow  Max=0.31 cfs @ 13.98 hrs  HW=96.96'  TW=92.74'   (Dynamic Tailwater)
1=Orifice/Grate  (Orifice Controls 0.31 cfs @ 9.14 fps)
2=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 31
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pond 4P: Bioretention Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=96.96'
Storage=21,186 cf
3.35 cfs
0.31 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 32
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 5P: Weir MH 103 WQF
[57] Hint: Peaked at 97.37' (Flood elevation advised)
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth = 2.46"    for  5 year event
Inflow
=
23.87 cfs @ 12.36 hrs,  Volume=
2.817 af
Outflow
=
23.87 cfs @ 12.36 hrs,  Volume=
2.817 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
3.35 cfs @ 12.25 hrs,  Volume=
0.838 af
Secondary =
20.61 cfs @ 12.36 hrs,  Volume=
1.978 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 97.37' @ 12.36 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
95.40'
12.0"  Round Culvert   
L= 70.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 95.40' / 95.00'   S= 0.0057 '/'   Cc= 0.900   
n= 0.013  Corrugated PE, smooth interior,  Flow Area= 0.79 sf   
#2
Secondary
96.83'
60.0" Horiz. Orifice/Grate    C= 0.600   
Limited to weir flow at low heads   
Primary OutFlow  Max=3.35 cfs @ 12.25 hrs  HW=97.32'  TW=96.28'   (Dynamic Tailwater)
1=Culvert  (Outlet Controls 3.35 cfs @ 4.26 fps)
Secondary OutFlow  Max=20.61 cfs @ 12.36 hrs  HW=97.37'  TW=92.82'   (Dynamic Tailwater)
2=Orifice/Grate  (Weir Controls 20.61 cfs @ 2.41 fps)
Pond 5P: Weir MH 103 WQF
Inflow
Outflow
Primary
Secondary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=13.736 ac
Peak Elev=97.37'
23.87 cfs
23.87 cfs
3.35 cfs
20.61 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 33
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 6P: Detention Basin
Inflow Area =
13.736 ac, 38.54% Impervious,  Inflow Depth > 2.18"    for  5 year event
Inflow
=
20.90 cfs @ 12.36 hrs,  Volume=
2.497 af
Outflow
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af,  Atten= 86%,  Lag= 88.1 min
Primary
=
2.95 cfs @ 13.83 hrs,  Volume=
2.345 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 92.74' @ 13.83 hrs   Surf.Area= 20,792 sf   Storage= 45,921 cf
Plug-Flow detention time= 222.9 min calculated for 2.345 af (94% of inflow)
Center-of-Mass det. time= 177.4 min ( 1,086.7 - 909.3 )
Volume
Invert
Avail.Storage
Storage Description
#1
90.30'
122,564 cf
Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic-feet)
(cubic-feet)
90.30
16,859
0
0
92.00
19,568
30,963
30,963
94.00
22,870
42,438
73,401
95.00
24,576
23,723
97,124
96.00
26,304
25,440
122,564
Device
Routing     
Invert
Outlet Devices
#1
Primary
90.25'
30.0"  Round Culvert   
L= 44.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 90.25' / 90.00'   S= 0.0057 '/'   Cc= 0.900   
n= 0.012,  Flow Area= 4.91 sf   
#2
Device 1
90.30'
10.0"  Round Culvert   
L= 5.0'   CPP, projecting, no headwall,  Ke= 0.900   
Inlet / Outlet Invert= 90.30' / 90.25'   S= 0.0100 '/'   Cc= 0.900   
n= 0.012,  Flow Area= 0.55 sf   
#3
Device 1
93.90'
30.0" Horiz. Orifice/Grate    C= 0.600   
Limited to weir flow at low heads   
#4
Primary
95.00'
20.0' long  x 13.0' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00  1.20  1.40  1.60   
Coef. (English)  2.60  2.64  2.70  2.66  2.65  2.66  2.65  2.63   
Primary OutFlow  Max=2.95 cfs @ 13.83 hrs  HW=92.74'  TW=90.06'   (Dynamic Tailwater)
1=Culvert  (Passes 2.95 cfs of 22.17 cfs potential flow)
2=Culvert  (Inlet Controls 2.95 cfs @ 5.41 fps)
3=Orifice/Grate  ( Controls 0.00 cfs)
4=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 34
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Pond 6P: Detention Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=13.736 ac
Peak Elev=92.74'
Storage=45,921 cf
20.90 cfs
2.95 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 35
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Pond 7P: Weir MH 103 to Det Basin
[57] Hint: Peaked at 92.85' (Flood elevation advised)
Inflow
=
20.61 cfs @ 12.36 hrs,  Volume=
1.978 af
Outflow
=
20.61 cfs @ 12.36 hrs,  Volume=
1.978 af,  Atten= 0%,  Lag= 0.0 min
Primary
=
20.61 cfs @ 12.36 hrs,  Volume=
1.978 af
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 92.85' @ 12.45 hrs
Device
Routing     
Invert
Outlet Devices
#1
Primary
91.00'
36.0"  Round Culvert   
L= 50.0'   CPP, square edge headwall,  Ke= 0.500   
Inlet / Outlet Invert= 91.00' / 90.00'   S= 0.0200 '/'   Cc= 0.900   
n= 0.013  Corrugated PE, smooth interior,  Flow Area= 7.07 sf   
Primary OutFlow  Max=20.61 cfs @ 12.36 hrs  HW=92.82'  TW=91.48'   (Dynamic Tailwater)
1=Culvert  (Inlet Controls 20.61 cfs @ 4.59 fps)
Pond 7P: Weir MH 103 to Det Basin
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Peak Elev=92.85'
36.0"
Round Culvert
n=0.013
L=50.0'
S=0.0200 '/'
20.61 cfs
20.61 cfs

Type III 24-hr  5 year Rainfall=4.20"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
Page 36
HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Summary for Link 2L: Design Point
Inflow Area =
101.706 ac, 23.22% Impervious,  Inflow Depth > 1.60"    for  5 year event
Inflow
=
57.96 cfs @ 12.98 hrs,  Volume=
13.574 af
Primary
=
57.96 cfs @ 12.98 hrs,  Volume=
13.574 af,  Atten= 0%,  Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Link 2L: Design Point
Inflow
Primary
Hydrograph
Time  (hours)
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Flow  (cfs)
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=101.706 ac
57.96 cfs
57.96 cfs

Type III 24-hr  10 year Rainfall=4.80"
213009 REV 2-4-23
  Printed  2/5/2023
Prepared by Provost & Rovero, Inc.
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HydroCAD® 10.00-13  s/n 02606  © 2014 HydroCAD Software Solutions LLC
Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 points x 3
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Dyn-Muskingum-Cunge method  -  Pond routing by Dyn-Stor-Ind method
Runoff Area=87.970 ac   20.82% Impervious   Runoff Depth=1.97"
Subcatchment 1S: P-2
   Flow Length=4,420'   Tc=68.3 min   CN=71   Runoff=72.03 cfs  14.416 af
Runoff Area=13.736 ac   38.54% Impervious   Runoff Depth=2.99"
Subcatchment 2S: P-1
   Tc=26.0 min   CN=83   Runoff=28.99 cfs  3.427 af
Runoff Area=101.737 ac   20.18% Impervious   Runoff Depth=2.05"
Subcatchment 3S: E-1
   Flow Length=4,420'   Tc=68.3 min   CN=72   Runoff=87.01 cfs  17.338 af
Avg. Flow Depth=0.07'   Max Vel=1.06 fps   Inflow=3.46 cfs