Conservation Commission Regular Meeting Materials (linked)

Stormwater Management Design Report 
Pequot Apartments 
908 Hartford Turnpike (Conn. Route 85) 
Waterford, Connecticut 
 
 
July 1, 2021 
 
 
Prepared for: 
 
Cohanzie Partners, LP 
325 Spalding Gates Court 
Atlanta, Georgia  30328 
 
 
 
 
 
 
 
 
 
 
 
 
Prepared by: 
 
 
 
Civil Engineers & Land Surveyors, P.C. 
60 Wall Street 
P.O. Box 708 
Madison, Connecticut 06443-0708 
Telephone: (203) 245-0722 
Summer Hill 

21-07 Stormwater Management Design Report 
                                                                                            Table of Contents   i 
Pequot Apartments 
Waterford, Connecticut 
Stormwater Management Design Report 
Pequot Apartments 
908 Hartford Turnpike (Conn. Route 85) 
Waterford, Connecticut 
 
 
Table of Contents
 
Section 
 
Page No. 
 
Title Page 
Table of Contents ......................................................................................................................................................................... i 
1.0  Introduction ......................................................................................................................................................................... 1 
2.0  Hydrologic Model Development ........................................................................................................................................ 2 
3.0  Stormwater Management System ..................................................................................................................................... 3 
 
List of Tables
 
Table No. 
       Description 
Page No. 
 
Table 1  24–Hour Rainfall Depths for the Project Site Vicinity  ................................................................................................ 3 
Table 2  Summary Comparison of Peak Discharges and Reservoir Routings ..................................................................... 4 
 
List of Figures
 
Figure No. 
    Description 
Page No. 
 
Figure 1  Project Location .......................................................................................................................................................... 1 
Figure 2  Flood Insurance Rate Map ........................................................................................................................................ 1 
 
Appendices
 
Appendix A  Design Computations 
Appendix B  Hydrologic Model Input Data and Results 
Appendix C  NRCS Soils Information 
Appendix D  NOAA Atlas 14 Precipitation Information 
Appendix E  General Site Operation and Maintenance Plan 
Appendix F  Drainage Area Maps 
 

 
21-07 Stormwater Management Design Report 
                                                                                                                      Page 1 
Pequot Apartments 
Waterford, Connecticut 
1.0  Introduction 
 
This Stormwater Management Design Report has been prepared on behalf of Cohanzie Partners, LP who has 
submitted an application to the Town of Waterford Conservation Commission seeking approval to develop a portion of 
an approximate 16.5 acre land parcel located in the central portion of the Town on Hartford Turnpike (Conn. Route 85).  
The parcel is located on the west side of Hartford Turnpike approximately 0.5 miles southeast of its intersection with 
Cross Road(Figure 1).   
 
 
 
Figure 1.  Project Location 
U.S.G.S. Palmertown and Niantic Connecticut Quadrangles 
 

 
21-07 Stormwater Management Design Report 
                                                                                                                      Page 2 
Pequot Apartments 
Waterford, Connecticut 
The planned development proposal is a multi-family residential complex that will provide 40 - 1 and 2 bedroom rental 
apartments in two buildings.  The proposal will also include a community building and driveway, parking area, 
sidewalk, lighting, and landscape improvements. 
 
The site is located within an Industrial Multi-Family (I-MF) zoning district.  The existing land uses adjacent to and in the 
vicinity of the site are commercial and retail.  A single family residence and several out buildings are currently located 
on the site.  The undeveloped portion of the site is wooded. 
 
The site is served by the City of New London public water system, the Town of Waterford municipal sanitary sewer 
system, and public communication, electric, and gas utilities within the Hartford Turnpike highway. 
 
The site is located within the Jordan Brook subregional drainage basin (HUC 2201).  Jordan Brook flows through the 
southerly portion of the site and an un-named tributary to Jordan Brook is located on the site immediately south of the 
planned development area.  Surface water runoff from the planned development area drains to an inland wetland 
associated with the un-named tributary which joins Jordan Brook approximately 600 feet south of the planned 
development area.   
 
A special flood hazard area zone is located on the project site land parcel associated with Jordan Brook.  The planned 
development portion of the site is not located within the special flood hazard area zone (Figure 2).  
 
An identified Connecticut Department of Energy and Environmental Protection Natural Diversity Database Area 
associated with Jordan Brook and its tributaries is located on the site. 
 
The Natural Resources Conservation Service Soil Survey of the State of Connecticut indicates that the upland surficial 
soil types on and in the near vicinity of the planned development portion of the site are classified as Canton and 
Charlton fine sandy loams (62D) and Charlton-Chatfield complex (73C).   
 
The topography within the planned development area of the site is sloping and ground surface elevations range 
between 150 - 170 feet along the sites Hartford Turnpike frontage to 120 feet along the Jordan Brook Tributary, 
 
2.0  Hydrologic Model Development 
 
The site stormwater management system has been designed in accordance with standard hydrologic and hydraulic 
engineering practices. 
 
HydroCAD Version 10.10 hydrologic modeling software (HydroCAD Software Solutions, LLC) was used to create the 
hydrologic models and estimates of peak rates of discharge of stormwater runoff.  The U.S. Department of Agriculture 
Soil Conservation Service (now Natural Resources Conservation Service) Technical Release 20 Computer Program for 
Project Formulation Hydrology methodology was used within the HydroCAD software program.  TR-20 is a single 
event, lumped parameter surface water hydrologic model that simulates the precipitation-runoff relationships of a 
drainage area.  The model uses the Soil Conservation Service Curve Number and Unit-Hydrograph methods to 
represent infiltration losses and to transform excess precipitation into runoff, and the Modified Puls (Storage-Indication) 
method to perform reservoir routing. 
 
NOAA Precipitation Frequency Atlas 14 for the Northeastern States 24-hour rainfall depths in the project site vicinity 
shown in Table 1 were accessed from the NOAA precipitation frequency data server and entered into the models. 
 
Table 1.  24-Hour Rainfall Depths for the Project Site Vicinity 
Recurrence Interval 
Rainfall Depth 
Year 
Inches 
2 
3.45 
5 
4.37 
10 
5.13 
25 
6.18 
50 
6.96 
100 
7.79 
 

 
21-07 Stormwater Management Design Report 
                                                                                                                      Page 3 
Pequot Apartments 
Waterford, Connecticut 
Partial duration series precipitation frequency data was also accessed from the NOAA precipitation frequency data 
server and entered into the models to create a synthetic rainfall distribution specific to the project site vicinity. 
 
Drainage area boundaries were delineated using the existing conditions mapping for the site.  The delineations were 
checked and adjusted based on a field inspection. 
 
Drainage area composite runoff curve numbers and times of concentration were computed using procedures and 
parameter values presented in the National Engineering Handbook, Section 4 - Hydrology (1985). 
 
Antecedent moisture condition II was used to represent the soil moisture condition in the drainage areas prior to the 
modeled rainfall events. 
 
3.0  Stormwater Management System 
 
The site stormwater management system consists of a typical catch basin inlet structure and storm sewer collection 
and conveyance system that will direct stormwater runoff from the developed sites building roofs, sidewalks, driveway, 
and parking areas to both stormwater treatment and peak discharge control facilities. 
 
The site stormwater collection and conveyance system has been designed in accordance with the procedures outlined 
in the Connecticut Department of Transportation Drainage Manual.  Drainage structure inlets and storm sewers have 
been designed for peak discharges generated from a 25-year design frequency rainfall event computed using the 
Rational Method.  Outlet protection measures were designed for the 25-year design frequency peak discharge and 
checked for the 100-year discharge.  All times of concentration were assumed to be 5 minutes and the following runoff 
coefficients were used: 
 
Pavements: C = 0.90 
Lawn and landscaped areas: C = 0.30 
 
Stormwater runoff will be directed from the conveyance and collection system to a stormwater infiltration basin 
designed to temporarily store stormwater runoff and allow it to infiltrate into the underlying natural soils.  The elevation 
of the two basin riser outlets has been set such that the storage volume below the outlets exceeds both the computed 
water quality volume and annual groundwater recharge volume for the developed site.  The top of berm elevation of 
each of the basin is 1.5 feet above the elevation of the riser outlets. 
 
The stormwater infiltration basin has been designed to meet the water quality volume and annual groundwater 
recharge volume requirements of the Connecticut Department of Energy and Environmental Protection Stormwater 
Quality Manual.  As noted above, the available storage volume within the basin below the riser outlets exceeds the 
computed design values for these hydrologic sizing criteria.   
 
During less frequent, greater depth rainfall events, when the ponded water surface within the basin exceeds the 
elevation of the riser outlets, stormwater will be directed to a subsurface stormwater detention system located below 
the site parking area. 
 
The subsurface stormwater detention system consists of multiple ADS StormTech MC-4500 manufactured chambers 
providing a storage reservoir and a precast concrete outlet control structure that will control the design rainfall events 
peak rates of stormwater discharge leaving the system such that they are equal to or less than the computed peak 
discharge rates for the design rainfall events in the existing condition.  The discharges from the system will be directed 
to a stone riprap lined preformed scour hole at the discharge location from the outlet control structure before entering 
the adjacent tributary to Jordan Brook. 
 
 
 
 
Remainder of this page left blank 
 
 
 
 
 

 
21-07 Stormwater Management Design Report 
                                                                                                                      Page 4 
Pequot Apartments 
Waterford, Connecticut 
A summary comparison of the rates of peak discharges and the reservoir routing results for the system is given below. 
 
Table 2.  Summary Comparison of Peak Discharges and Reservoir Routings 
 
Recurrence Interval
 
       2-yr 
5-yr 
10-yr 
25-yr 
50-yr 
100-yr 
   Existing Condition (cfs) 
0.1 
0.5 
0.9 
1.5 
2.0 
2.6 
   Developed Condition (cfs) 
5.7 
8.1 
10.2 
13.0 
15.1 
17.4 
   Routed Outflow (cfs) 
0.4 
0.5 
0.6 
1.5 
2.0 
2.5 
   SWMB Peak Stage (ft) 
138.4 139.1 
139.7 
140.4 
140.9 
141.6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Remainder of this page left blank 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Appendix A 
Design Computations 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Civil Engineers & Land Surveyors, P.C. 
 
BY:    MJO  .   
DATE:   7-1-21  . 
SUBJECT:    Pequot Apartments Waterford, Connecticut                    .   SHEET No.:    1   OF   2  . 
 
 
 
 
CHECKED:    LJM  .   DATE:   7-1-21  . 
  Stormwater Management System Design Computations                        .   PROJECT No.:    21-07  . 
Summer Hill 
1.  Water quality volume computed using the CT Stormwater Quality Manual equation 
 
     WQV = 1.0 in(R)(A)/12, where: 
 
     WQV, Water Quality Volume (Ac-ft) 
     R,  Volumetric Runoff Coefficient = 0.05 + 0.009(I) 
     I,   Percent impervious cover 
     A   Site area (Ac.) 
 
     I = 56% 
     R = 0.05 + 0.009(56) = 0.55 
     A = 117,230 ft2 = 2.69 Ac. 
 
     WQV = 1 in(R)(A)/12 = (1 in)(0.55)(2.69)/12 = 0.1233 Ac-ft = 5,370 ft3 
 
2.  Groundwater recharge volume computed using the CT Stormwater Quality Manual equation 
 
     GRV = D(A)(I)/12, where: 
 
     GRV, Groundwater Recharge Volume (Ac-ft) 
     D,  Depth of runoff to be recharged (in) 
     A   Site area (Ac.) 
     I,   Net increase in percent of impervious cover 
 
     For Hydrologic Soil Group B, D = 0.25 in 
 
     A = 117,230 ft2 = 2.69 Ac. 
 
     I (Existing) = 0 ft2  (neglect existing building structures) 
 
     I (Proposed) = 66,235 ft2 / 117,230 ft2 = 0.56 
 
     Net increase = 0.56 – 0 = 0.56 
 
     GRV = (0.25 in x 2.69 Ac. x 0.56)/12 = 0.0314 Ac-ft = 1,367 ft3 
 
3.  Stormwater infiltration basin storage volume 
Stage-Storage 
Elevation   
ft 
Area             
ft2 
Average Area     
ft2 
Incremental Volume   
ft3 
Cumulative Volume   
ft3 
Cumulative Volume      
Ac-ft 
140.00 
2,210 
2,210 
0 
0 
0.0000 
141.00 
2,735 
2,473 
2,473 
2,473 
0.0568 
142.00 
3,295 
3,015 
3,015 
5,488 
0.1260 
142.50 
3,680 
3,488 
1,744 
7,231 
0.1660 
143.00 
3,885 
3,783 
1,891 
9,123 
0.2094 
144.00 
4,495 
4,190 
4,190 
13,313 
0.3056 
 
     Storage volume at top riser elevation 142.50 = 7,231 ft3  
 
 
 
 
 
 

Civil Engineers & Land Surveyors, P.C. 
 
BY:    MJO  .   
DATE:   7-1-21  . 
SUBJECT:    Pequot Apartments Waterford, Connecticut                    .   SHEET No.:    2   OF   2  . 
 
 
 
 
CHECKED:    LJM  .   DATE:   7-1-21  . 
  Stormwater Management System Design Computations                        .   PROJECT No.:    21-07  . 
Summer Hill 
4.  Outlet Protection Computations 
 
     Infiltration Basin Outlet 
 
     Riprap apron dimensions based on ConnDOT Drainage Manual design procedure: 
 
     Using critical depth (dc) as tailwater depth (TW), dc for design discharge (Q25) = 7.6 ft3/s = 1.0 ft 
 
     1.0 ft > 0.5Rp = 0.5(1.5) = 0.75 ft 
 
     Type B Riprap Apron (maximum tailwater condition) dimensions: 
 
     La = (3.0(Q - 5)/Sp 
1.5)+ 10 
     W1 = 3 Sp (min.) 
     W2 = 3 Sp + 0.4 La  
 
     Q   Design Discharge (ft3/s) 
     Sp  Pipe Span (ft) 
     Rp  Pipe Rise (ft) 
     La  Length of Apron (ft) 
     W1  Width of Apron at Pipe Outlet (ft) 
     W2  Width of Apron at Apron Outlet (ft) 
 
     Q100 = 7.4 ft3/s 
     Sp = 1.5 ft  
     Rp = 1.5 ft  
     La = 3.0(7.4 – 5)/1.51.5 + 10 = 13.9 ft – Use 14 ft 
     W1 = 3(1.5) = 4.5 ft 
     W2 = 3(1.5) + 0.4(14.0) = 10.1 ft – Use 10 ft 
 
     Use modified riprap (D50 = 0.42 ft) 
 
     Depth (d) = 1.0 ft 
 
     Subsurface Detention System Outlet 
 
     Type I Preformed Scour Hole dimensions based on ConnDOT Drainage Manual design procedure: 
 
     Q                  Design Discharge (ft3/s) 
     TW                 Tailwater Depth (ft) 
     D50 = (0.0125Rp
2/TW) (Q/Rp
2.5)1.333 Median Stable Stone Diameter (ft) 
     d                  Riprap Thickness (ft) 
     B = 2Sp + 6F           Width (ft) 
     C = 3Sp + 6F           Length (ft) 
     Sp                 Culvert Span (ft) 
     Rp                 Culvert Rise (ft) 
     F = 0.5Rp             Type I Scour Hole Depression (ft) 
 
     Q100 = 17.4 ft3/s 
     TW = 1.5 ft (using critical depth) 
     Sp = 2.0 ft  
     Rp = 2.0 ft  
     D50 = (0.0125(2.02)/1.5 (17.4/2.02.5)1.333 = 0.10 ft  –  Use modified riprap (D50 < 0.42 ft) 
     d = 1.0 ft 
     B = 2(2.0) + 6(1.00) = 10.0 ft  
     C = 3(2.0) + 6(1.00) = 12 ft 
     F = 0.5 (2.0) = 1.00 ft 

PROJECT:   Pequot Apartments
SHEET No.:    1    OF   2 
DATE:   7-1-21
PROJECT No.: 21-07
DESIGNED:   MJO
CHECKED:    LJM
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Impervious
1,500
0.03
Impervious
5,720
0.13
Lawn
5,995
0.14
Lawn
17,385
0.40
7,495
0.17
23,105
0.53
Weighted Runoff Coefficient (Cw)
0.42
Weighted Runoff Coefficient (Cw)
0.45
Catchment Area CB 2 
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Impervious
3,609
0.08
Impervious
920
0.02
Lawn
0.00
Lawn
960
0.02
3,609
0.08
1,880
0.04
Weighted Runoff Coefficient (Cw)
0.90
Weighted Runoff Coefficient (Cw)
0.59
Catchment Area CB 3 
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Impervious
1,418
0.03
Impervious
1,260
0.03
Lawn
0.00
Lawn
1,300
0.03
1,418
0.03
2,560
0.06
Weighted Runoff Coefficient (Cw)
0.90
Weighted Runoff Coefficient (Cw)
0.60
WEIGHTED RUNOFF COEFFICIENT COMPUTATION SHEET
Catchment Area CB 1
Catchment Area CB 4  
Runoff Coefficent (C)
Product A x C
                   Waterford, Connecticut
Runoff Coefficent (C)
Product A x C
0.90
0.03
0.90
0.12
0.30
0.04
0.30
0.12
0.07
0.24
Runoff Coefficent (C)
Product A x C
Runoff Coefficent (C)
Product A x C
Catchment Area CB 5
0.90
0.07
0.90
0.02
0.30
0.00
0.30
0.01
0.07
0.03
Runoff Coefficent (C)
Product A x C
Runoff Coefficent (C)
Product A x C
Catchment Area CB 6 
0.03
0.03
0.90
0.03
0.90
0.03
0.30
0.00
0.30
0.01

PROJECT:   Pequot Apartments
SHEET No.:    2    OF   2 
DATE:   7-1-21
PROJECT No.: 21-07
DESIGNED:   MJO
CHECKED:    LJM
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Impervious
14,660
0.34
Lawn
0
0.00
14,660
0.34
Weighted Runoff Coefficient (Cw)
0.90
Weighted Runoff Coefficient (Cw)
Catchment Area CB 8 
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Impervious
15,015
0.34
Lawn
5,425
0.12
20,440
0.47
Weighted Runoff Coefficient (Cw)
0.74
Weighted Runoff Coefficient (Cw)
Catchment Area 
Cover Type
Area (A)
Area (A)
Cover Type
Area (A)
Area (A)
Square Feet
Acres
Square Feet
Acres
Weighted Runoff Coefficient (Cw)
Weighted Runoff Coefficient (Cw)
WEIGHTED RUNOFF COEFFICIENT COMPUTATION SHEET
                    Waterford, Connecticut
Catchment Area CB 7
Catchment Area  
Runoff Coefficent (C)
Product A x C
Runoff Coefficent (C)
Product A x C
0.90
0.30
0.30
0.00
0.30
Catchment Area 
Runoff Coefficent (C)
Product A x C
Runoff Coefficent (C)
Product A x C
0.90
0.31
0.30
0.04
0.35
Catchment Area 
Runoff Coefficent (C)
Product A x C
Runoff Coefficent (C)
Product A x C

PROJECT:   Pequot Apartments Waterford, Connecticut
DATE:   7-1-21
 
PROJECT No.: 21-07
DESIGNED:   MJO
CHECKED:    LJM
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
Station
Station
Incr.
Total
Runoff 
Coefficient   
C
Incr.
Total
Inlet 
(min.)  
Section 
(min.)
Total    
Tc    
(min.)
Rainfall 
Intensity   
I         
(in/hr) 
Design 
Discharge   
Q         
(cfs) 
Diameter 
(in)
Length 
(ft)
Slope  
(ft/ft)
Roughness 
Coefficient  
n
Full 
Capacity  
(cfs)
Average 
Velocity  
(fps)
Design 
Discharge  
Velocity    
(fps)
U/S
D/S
CB 1
CB 2
0.17
0.17
0.42
0.07
0.07
5
-
5
6.70
0.48
12
21
0.0100
0.012
4.15
5.42
147.20
146.99
CB 2
CB 3
0.08
0.25
0.90
0.07
0.14
5
-
5
6.70
0.94
12
44
0.0705
0.012
11.02
14.39
146.99
143.89
CB 4
CB 3
0.53
0.53
0.45
0.24
0.24
5
-
5
6.70
1.61
12
21
0.0100
0.012
4.15
5.42
144.10
143.89
CB 3
CB 5
0.03
0.81
0.90
0.03
0.41
5
-
5
6.70
2.75
12
57
0.0349
0.012
7.76
10.12
143.89
141.90
CB 5
CB 6
0.04
0.85
0.59
0.02
0.43
5
-
5
6.70
2.88
12
21
0.0100
0.012
4.15
5.42
141.90
141.69
CB 6
MH 1
0.06
0.91
0.60
0.04
0.47
5
-
5
6.70
3.15
12
56
0.0155
0.012
5.17
6.75
141.69
140.58
CB 7
MH 1
0.34
0.34
0.90
0.31
0.31
5
-
5
6.70
2.08
12
92
0.0100
0.012
4.15
5.42
141.50
140.58
MH 1
CB 8
-
1.25
-
-
0.78
-
-
5
6.70
5.23
15
53
0.0100
0.012
7.53
6.29
140.58
140.05
CB 8
OUTLET
0.47
1.72
0.74
0.35
1.13
5
-
5
6.70
7.57
18
14
0.0036
0.012
7.35
4.26
140.05
140.00
STORM SEWER DESIGN COMPUTATION SHEET
SHEET No.:    1    OF    1 
Invert Elevation
(20)
Structure
Drainage Area A (Ac.)
A x C
Time of Concentration Tc
DESIGN FREQUENCY:    25 Year

Project
By
Date
7-1-21
Location
    Checked
Date
7-1-21
Circle one:
Present
Developed
Circle one:
Tc
Tt  through subarea
ft
in
ft/ft
  6.  Tt =
0.007 (nL)0.8
Compute Tt
hr
P2
0.5 s0.4
ft
ft/ft
ft/s
11.  Tt =
L
Compute Tt
hr
3600 V
ft2
ft
ft
                pw
ft/ft
17.  V = 
1.49 r2/3 s1/2
ft/s
n
ft
19.  Tt =
L
Compute Tt
hr
3600 V
hr =
0.01
13.  Wetted perimeter, pw
0.03
+
=
Pequot Apartments
0.0880
  9.  Watercourse slope, s
  8.  Flow length, L
250
Unpaved
0.16
  7.  Surface description (paved or unpaved)
100
3.45
Shallow concentrated flow
=
0.1300
Segment ID
0.16
Worksheet 3: Time of Concentration (T
c) or Travel Time (T t)
Segment ID
AB
Include a map, schematic, or description of flow segments.
NOTES:  Space for as many as two segments per flow type can be used for each worksheet.
0.400
Woods
   MJO
   LJM
Sheet flow (Applicable to Tc only)
14.  Hydraulic radius, r =  a
0.19
=
+
20.  Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19)
  1.  Surface Description (table 3-1)
  3.  Flow Length, L (total L < 300 ft)
4.8
Channel flow
Waterford, Connecticut
10.  Average velocity, V (figure 3-1)
12.  Cross sectional flow area, a
Segment ID
18.  Flow length, L
  2.  Manning's roughness coeff., n (table 3-1)
  5.  Land Slope, s
  4.  Two-yr 24-hr rainfall, P2
15.  Channel slope, s
16.  Manning's roughness coeff., n
BC
+
(After Soil Conservation Service TR-55, Second Edition, June 1986)

Project
By
Date
7-1-21
Location
Checked
Date
7-1-21
Circle one:
Present
Developed
EC 1
Soil name
Product
and
of
hydrologic
x
acres 
CN x area
group
mi2     
% 
(appendix A)
1/  Use only one CN source per line.
total product
57.20
total area
1.04
2.  Runoff
Storm #3
(Use P and CN with table 2-1, fig. 2-1,
or eqs. 2-3 and 2-4.)
Worksheet 2: Runoff curve number and runoff
55
Storm #1
Fig. 2-3
Totals =
Use CN =
B
Woods (Good)
57.20
57.20
Storm #2
55
1.04
MJO
Cover description
(cover type, treatment, and
percent impervious;
Area
1.  Runoff Curve Number (CN)
Waterford, Connecticut
CN 1/
LJM
Pequot Apartments
unconnected/connected impervious
area ratio)
Fig. 2-4
hydrolgic condition;
Table 2-2
1.04
55.0
CN (weighted)
=
=
=
in
in
Rainfall, P (24-hour)
Runoff, Q
Frequency
yr
(After Soil Conservation Service TR-55, Second Edition, June 1986)

Project
By
Date
7-1-21
Location
Checked
Date
7-1-21
Circle one:
Present
Developed
DC 1
Soil name
Product
and
of
hydrologic
x
acres 
CN x area
group
mi2     
% 
(appendix A)
1/  Use only one CN source per line.
total product
201.16
total area
2.40
2.  Runoff
Storm #3
(Use P and CN with table 2-1, fig. 2-1,
or eqs. 2-3 and 2-4.)
in
in
Rainfall, P (24-hour)
Runoff, Q
Frequency
yr
83.8
CN (weighted)
=
=
=
0.92
unconnected/connected impervious
area ratio)
Fig. 2-4
1.48
hydrolgic condition;
Pavement, Building
98
Table 2-2
MJO
Cover description
(cover type, treatment, and
percent impervious;
Area
1.  Runoff Curve Number (CN)
Waterford, Connecticut
CN 1/
LJM
Pequot Apartments
Storm #2
84
2.40
201.16
56.12
145.04
B
Lawn
-
Fig. 2-3
Totals =
Use CN =
Worksheet 2: Runoff curve number and runoff
61
Storm #1
(After Soil Conservation Service TR-55, Second Edition, June 1986)

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Appendix B 
Hydrologic Model Input Data and Results 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 1
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Rainfall Events Listing (selected events)
Event#
Event
Name
Storm Type
Curve
Mode
Duration
(hours)
B/B
Depth
(inches)
AMC
1
2-yr
Waterford 24-hr S1
2-yr
Default
24.00
1
3.45
2
2
5-yr
Waterford 24-hr S1
5-yr
Default
24.00
1
4.37
2
3
10-yr
Waterford 24-hr S1
10-yr
Default
24.00
1
5.13
2
4
25-yr
Waterford 24-hr S1
25-yr
Default
24.00
1
6.18
2
5
50-yr
Waterford 24-hr S1
50-yr
Default
24.00
1
6.96
2
6
100-yr
Waterford 24-hr S1
100-yr
Default
24.00
1
7.79
2

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 2
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=0.33"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=0.11 cfs  0.029 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.029 af   Average Runoff Depth = 0.33"

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 3
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
0.11 cfs @ 12.24 hrs,  Volume=
0.029 af,  Depth= 0.33"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 2-yr  Rainfall=3.45"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
0.125
0.12
0.115
0.11
0.105
0.1
0.095
0.09
0.085
0.08
0.075
0.07
0.065
0.06
0.055
0.05
0.045
0.04
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
Waterford 24-hr S1 2-yr
Rainfall=3.45"
Runoff Area=1.040 ac
Runoff Volume=0.029 af
Runoff Depth=0.33"
Tc=11.0 min
CN=55
0.11 cfs

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 4
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=0.68"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=0.45 cfs  0.059 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.059 af   Average Runoff Depth = 0.68"

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 5
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
0.45 cfs @ 12.14 hrs,  Volume=
0.059 af,  Depth= 0.68"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 5-yr  Rainfall=4.37"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
0.5
0.48
0.46
0.44
0.42
0.4
0.38
0.36
0.34
0.32
0.3
0.28
0.26
0.24
0.22
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
Waterford 24-hr S1 5-yr
Rainfall=4.37"
Runoff Area=1.040 ac
Runoff Volume=0.059 af
Runoff Depth=0.68"
Tc=11.0 min
CN=55
0.45 cfs

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 6
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=1.05"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=0.85 cfs  0.091 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.091 af   Average Runoff Depth = 1.05"

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 7
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
0.85 cfs @ 12.12 hrs,  Volume=
0.091 af,  Depth= 1.05"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 10-yr  Rainfall=5.13"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
0.9
0.85
0.8
0.75
0.7
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Waterford 24-hr S1 10-yr
Rainfall=5.13"
Runoff Area=1.040 ac
Runoff Volume=0.091 af
Runoff Depth=1.05"
Tc=11.0 min
CN=55
0.85 cfs

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 8
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=1.62"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=1.48 cfs  0.141 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.141 af   Average Runoff Depth = 1.62"

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 9
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
1.48 cfs @ 12.12 hrs,  Volume=
0.141 af,  Depth= 1.62"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 25-yr  Rainfall=6.18"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
1
0
Waterford 24-hr S1 25-yr
Rainfall=6.18"
Runoff Area=1.040 ac
Runoff Volume=0.141 af
Runoff Depth=1.62"
Tc=11.0 min
CN=55
1.48 cfs

Waterford 24-hr S1 50-yr  Rainfall=6.96"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 10
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=2.10"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=2.01 cfs  0.182 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.182 af   Average Runoff Depth = 2.10"

Waterford 24-hr S1 50-yr  Rainfall=6.96"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 11
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
2.01 cfs @ 12.11 hrs,  Volume=
0.182 af,  Depth= 2.10"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 50-yr  Rainfall=6.96"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
2
1
0
Waterford 24-hr S1 50-yr
Rainfall=6.96"
Runoff Area=1.040 ac
Runoff Volume=0.182 af
Runoff Depth=2.10"
Tc=11.0 min
CN=55
2.01 cfs

Waterford 24-hr S1 100-yr  Rainfall=7.79"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 12
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=1.040 ac   Runoff Depth=2.64"
Subcatchment 10: EC 1
   Tc=11.0 min   CN=55   Runoff=2.61 cfs  0.229 af
Total Runoff Area = 1.040 ac   Runoff Volume = 0.229 af   Average Runoff Depth = 2.64"

Waterford 24-hr S1 100-yr  Rainfall=7.79"
21-07 EC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 13
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 10: EC 1
Runoff
=
2.61 cfs @ 12.11 hrs,  Volume=
0.229 af,  Depth= 2.64"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 100-yr  Rainfall=7.79"
Area (ac)
CN
Description
*
1.040
55
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
11.0
Direct Entry, 
Subcatchment 10: EC 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)
2
1
0
Waterford 24-hr S1 100-yr
Rainfall=7.79"
Runoff Area=1.040 ac
Runoff Volume=0.229 af
Runoff Depth=2.64"
Tc=11.0 min
CN=55
2.61 cfs

21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 1
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Rainfall Events Listing (selected events)
Event#
Event
Name
Storm Type
Curve
Mode
Duration
(hours)
B/B
Depth
(inches)
AMC
1
2-yr
Waterford 24-hr S1
2-yr
Default
24.00
1
3.45
2
2
5-yr
Waterford 24-hr S1
5-yr
Default
24.00
1
4.37
2
3
10-yr
Waterford 24-hr S1
10-yr
Default
24.00
1
5.13
2
4
25-yr
Waterford 24-hr S1
25-yr
Default
24.00
1
6.18
2
5
50-yr
Waterford 24-hr S1
50-yr
Default
24.00
1
6.96
2
6
100-yr
Waterford 24-hr S1
100-yr
Default
24.00
1
7.79
2

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 2
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=2.400 ac   Runoff Depth=1.89"
Subcatchment 20: DC 1
   Tc=6.0 min   CN=84   Runoff=5.71 cfs  0.379 af
Peak Elev=138.35'  Storage=0.192 af   Inflow=5.71 cfs  0.379 af
Pond 25: SSDS
   Outflow=0.40 cfs  0.293 af
Total Runoff Area = 2.400 ac   Runoff Volume = 0.379 af   Average Runoff Depth = 1.89"

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 3
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 20: DC 1
Runoff
=
5.71 cfs @ 12.04 hrs,  Volume=
0.379 af,  Depth= 1.89"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 2-yr  Rainfall=3.45"
Area (ac)
CN
Description
*
2.400
84
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
6.0
Direct Entry, 
Subcatchment 20: DC 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)
6
5
4
3
2
1
0
Waterford 24-hr S1 2-yr
Rainfall=3.45"
Runoff Area=2.400 ac
Runoff Volume=0.379 af
Runoff Depth=1.89"
Tc=6.0 min
CN=84
5.71 cfs

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 4
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Pond 25: SSDS
Inflow Area =
2.400 ac,  Inflow Depth = 1.89"    for  2-yr event
Inflow
=
5.71 cfs @ 12.04 hrs,  Volume=
0.379 af
Outflow
=
0.40 cfs @ 13.38 hrs,  Volume=
0.293 af,  Atten= 93%,  Lag= 80.1 min
Primary
=
0.40 cfs @ 13.38 hrs,  Volume=
0.293 af
Routing by Stor-Ind method, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Peak Elev= 138.35' @ 13.38 hrs   Surf.Area= 0.155 ac   Storage= 0.192 af
Plug-Flow detention time= 288.0 min calculated for 0.293 af (77% of inflow)
Center-of-Mass det. time= 191.1 min ( 1,036.8 - 845.7 )
Volume
Invert
Avail.Storage
Storage Description
#1A
136.30'
0.230 af
46.67'W x 144.32'L x 7.00'H Field A
1.082 af Overall - 0.425 af Embedded = 0.658 af  x 35.0% Voids
#2A
137.30'
0.425 af
ADS_StormTech MC-4500 b +Cap  x 170  Inside #1
Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf
Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap
170 Chambers in 5 Rows
Cap Storage= +39.5 cf x 2 x 5 rows = 395.0 cf
0.655 af
Total Available Storage
     Storage Group A created with Chamber Wizard
Device
Routing     
Invert
Outlet Devices
#1
Primary
137.30'
4.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#2
Primary
139.70'
7.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#3
Primary
141.75'
4.0' long  x 0.5' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00   
Coef. (English)  2.80  2.92  3.08  3.30  3.32   
Primary OutFlow  Max=0.40 cfs @ 13.38 hrs  HW=138.35'   (Free Discharge)
1=Orifice/Grate  (Orifice Controls 0.40 cfs @ 4.53 fps)
2=Orifice/Grate  ( Controls 0.00 cfs)
3=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Waterford 24-hr S1 2-yr  Rainfall=3.45"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 5
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Pond 25: SSDS
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)
6
5
4
3
2
1
0
Inflow Area=2.400 ac
Peak Elev=138.35'
Storage=0.192 af
5.71 cfs
0.40 cfs

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 6
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=2.400 ac   Runoff Depth=2.70"
Subcatchment 20: DC 1
   Tc=6.0 min   CN=84   Runoff=8.13 cfs  0.540 af
Peak Elev=139.07'  Storage=0.283 af   Inflow=8.13 cfs  0.540 af
Pond 25: SSDS
   Outflow=0.53 cfs  0.430 af
Total Runoff Area = 2.400 ac   Runoff Volume = 0.540 af   Average Runoff Depth = 2.70"

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 7
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 20: DC 1
Runoff
=
8.13 cfs @ 12.04 hrs,  Volume=
0.540 af,  Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 5-yr  Rainfall=4.37"
Area (ac)
CN
Description
*
2.400
84
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
6.0
Direct Entry, 
Subcatchment 20: DC 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)
9
8
7
6
5
4
3
2
1
0
Waterford 24-hr S1 5-yr
Rainfall=4.37"
Runoff Area=2.400 ac
Runoff Volume=0.540 af
Runoff Depth=2.70"
Tc=6.0 min
CN=84
8.13 cfs

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 8
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Pond 25: SSDS
Inflow Area =
2.400 ac,  Inflow Depth = 2.70"    for  5-yr event
Inflow
=
8.13 cfs @ 12.04 hrs,  Volume=
0.540 af
Outflow
=
0.53 cfs @ 13.40 hrs,  Volume=
0.430 af,  Atten= 93%,  Lag= 81.2 min
Primary
=
0.53 cfs @ 13.40 hrs,  Volume=
0.430 af
Routing by Stor-Ind method, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Peak Elev= 139.07' @ 13.40 hrs   Surf.Area= 0.155 ac   Storage= 0.283 af
Plug-Flow detention time= 304.2 min calculated for 0.429 af (80% of inflow)
Center-of-Mass det. time= 214.3 min ( 1,047.1 - 832.8 )
Volume
Invert
Avail.Storage
Storage Description
#1A
136.30'
0.230 af
46.67'W x 144.32'L x 7.00'H Field A
1.082 af Overall - 0.425 af Embedded = 0.658 af  x 35.0% Voids
#2A
137.30'
0.425 af
ADS_StormTech MC-4500 b +Cap  x 170  Inside #1
Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf
Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap
170 Chambers in 5 Rows
Cap Storage= +39.5 cf x 2 x 5 rows = 395.0 cf
0.655 af
Total Available Storage
     Storage Group A created with Chamber Wizard
Device
Routing     
Invert
Outlet Devices
#1
Primary
137.30'
4.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#2
Primary
139.70'
7.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#3
Primary
141.75'
4.0' long  x 0.5' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00   
Coef. (English)  2.80  2.92  3.08  3.30  3.32   
Primary OutFlow  Max=0.53 cfs @ 13.40 hrs  HW=139.07'   (Free Discharge)
1=Orifice/Grate  (Orifice Controls 0.53 cfs @ 6.10 fps)
2=Orifice/Grate  ( Controls 0.00 cfs)
3=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Waterford 24-hr S1 5-yr  Rainfall=4.37"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 9
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Pond 25: SSDS
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)
9
8
7
6
5
4
3
2
1
0
Inflow Area=2.400 ac
Peak Elev=139.07'
Storage=0.283 af
8.13 cfs
0.53 cfs

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 10
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=2.400 ac   Runoff Depth=3.39"
Subcatchment 20: DC 1
   Tc=6.0 min   CN=84   Runoff=10.18 cfs  0.678 af
Peak Elev=139.72'  Storage=0.361 af   Inflow=10.18 cfs  0.678 af
Pond 25: SSDS
   Outflow=0.63 cfs  0.537 af
Total Runoff Area = 2.400 ac   Runoff Volume = 0.678 af   Average Runoff Depth = 3.39"

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 11
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 20: DC 1
Runoff
=
10.18 cfs @ 12.04 hrs,  Volume=
0.678 af,  Depth= 3.39"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 10-yr  Rainfall=5.13"
Area (ac)
CN
Description
*
2.400
84
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
6.0
Direct Entry, 
Subcatchment 20: DC 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)
11
10
9
8
7
6
5
4
3
2
1
0
Waterford 24-hr S1 10-yr
Rainfall=5.13"
Runoff Area=2.400 ac
Runoff Volume=0.678 af
Runoff Depth=3.39"
Tc=6.0 min
CN=84
10.18 cfs

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 12
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Pond 25: SSDS
Inflow Area =
2.400 ac,  Inflow Depth = 3.39"    for  10-yr event
Inflow
=
10.18 cfs @ 12.04 hrs,  Volume=
0.678 af
Outflow
=
0.63 cfs @ 13.45 hrs,  Volume=
0.537 af,  Atten= 94%,  Lag= 84.6 min
Primary
=
0.63 cfs @ 13.45 hrs,  Volume=
0.537 af
Routing by Stor-Ind method, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Peak Elev= 139.72' @ 13.45 hrs   Surf.Area= 0.155 ac   Storage= 0.361 af
Plug-Flow detention time= 316.7 min calculated for 0.536 af (79% of inflow)
Center-of-Mass det. time= 225.4 min ( 1,050.0 - 824.6 )
Volume
Invert
Avail.Storage
Storage Description
#1A
136.30'
0.230 af
46.67'W x 144.32'L x 7.00'H Field A
1.082 af Overall - 0.425 af Embedded = 0.658 af  x 35.0% Voids
#2A
137.30'
0.425 af
ADS_StormTech MC-4500 b +Cap  x 170  Inside #1
Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf
Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap
170 Chambers in 5 Rows
Cap Storage= +39.5 cf x 2 x 5 rows = 395.0 cf
0.655 af
Total Available Storage
     Storage Group A created with Chamber Wizard
Device
Routing     
Invert
Outlet Devices
#1
Primary
137.30'
4.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#2
Primary
139.70'
7.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#3
Primary
141.75'
4.0' long  x 0.5' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00   
Coef. (English)  2.80  2.92  3.08  3.30  3.32   
Primary OutFlow  Max=0.63 cfs @ 13.45 hrs  HW=139.72'   (Free Discharge)
1=Orifice/Grate  (Orifice Controls 0.63 cfs @ 7.23 fps)
2=Orifice/Grate  (Orifice Controls 0.00 cfs @ 0.47 fps)
3=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Waterford 24-hr S1 10-yr  Rainfall=5.13"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 13
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Pond 25: SSDS
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)
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=2.400 ac
Peak Elev=139.72'
Storage=0.361 af
10.18 cfs
0.63 cfs

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 14
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=2.400 ac   Runoff Depth=4.37"
Subcatchment 20: DC 1
   Tc=6.0 min   CN=84   Runoff=13.01 cfs  0.873 af
Peak Elev=140.35'  Storage=0.432 af   Inflow=13.01 cfs  0.873 af
Pond 25: SSDS
   Outflow=1.48 cfs  0.704 af
Total Runoff Area = 2.400 ac   Runoff Volume = 0.873 af   Average Runoff Depth = 4.37"

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 15
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 20: DC 1
Runoff
=
13.01 cfs @ 12.04 hrs,  Volume=
0.873 af,  Depth= 4.37"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Waterford 24-hr S1 25-yr  Rainfall=6.18"
Area (ac)
CN
Description
*
2.400
84
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
6.0
Direct Entry, 
Subcatchment 20: DC 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)
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Waterford 24-hr S1 25-yr
Rainfall=6.18"
Runoff Area=2.400 ac
Runoff Volume=0.873 af
Runoff Depth=4.37"
Tc=6.0 min
CN=84
13.01 cfs

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 16
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Pond 25: SSDS
Inflow Area =
2.400 ac,  Inflow Depth = 4.37"    for  25-yr event
Inflow
=
13.01 cfs @ 12.04 hrs,  Volume=
0.873 af
Outflow
=
1.48 cfs @ 12.65 hrs,  Volume=
0.704 af,  Atten= 89%,  Lag= 36.9 min
Primary
=
1.48 cfs @ 12.65 hrs,  Volume=
0.704 af
Routing by Stor-Ind method, Time Span= 0.00-24.70 hrs, dt= 0.05 hrs
Peak Elev= 140.35' @ 12.65 hrs   Surf.Area= 0.155 ac   Storage= 0.432 af
Plug-Flow detention time= 281.9 min calculated for 0.703 af (80% of inflow)
Center-of-Mass det. time= 195.0 min ( 1,010.4 - 815.4 )
Volume
Invert
Avail.Storage
Storage Description
#1A
136.30'
0.230 af
46.67'W x 144.32'L x 7.00'H Field A
1.082 af Overall - 0.425 af Embedded = 0.658 af  x 35.0% Voids
#2A
137.30'
0.425 af
ADS_StormTech MC-4500 b +Cap  x 170  Inside #1
Effective Size= 90.4"W x 60.0"H => 26.46 sf x 4.03'L = 106.5 cf
Overall Size= 100.0"W x 60.0"H x 4.33'L with 0.31' Overlap
170 Chambers in 5 Rows
Cap Storage= +39.5 cf x 2 x 5 rows = 395.0 cf
0.655 af
Total Available Storage
     Storage Group A created with Chamber Wizard
Device
Routing     
Invert
Outlet Devices
#1
Primary
137.30'
4.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#2
Primary
139.70'
7.0" Vert. Orifice/Grate   C= 0.600   Limited to weir flow at low heads   
#3
Primary
141.75'
4.0' long  x 0.5' breadth Broad-Crested Rectangular Weir   
Head (feet)  0.20  0.40  0.60  0.80  1.00   
Coef. (English)  2.80  2.92  3.08  3.30  3.32   
Primary OutFlow  Max=1.48 cfs @ 12.65 hrs  HW=140.35'   (Free Discharge)
1=Orifice/Grate  (Orifice Controls 0.71 cfs @ 8.17 fps)
2=Orifice/Grate  (Orifice Controls 0.77 cfs @ 2.87 fps)
3=Broad-Crested Rectangular Weir  ( Controls 0.00 cfs)

Waterford 24-hr S1 25-yr  Rainfall=6.18"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 17
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Pond 25: SSDS
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)
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=2.400 ac
Peak Elev=140.35'
Storage=0.432 af
13.01 cfs
1.48 cfs

Waterford 24-hr S1 50-yr  Rainfall=6.96"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 18
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Time span=0.00-24.70 hrs, dt=0.05 hrs, 495 points
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN
Reach routing by Stor-Ind+Trans method  -  Pond routing by Stor-Ind method
Runoff Area=2.400 ac   Runoff Depth=5.10"
Subcatchment 20: DC 1
   Tc=6.0 min   CN=84   Runoff=15.13 cfs  1.020 af
Peak Elev=140.87'  Storage=0.487 af   Inflow=15.13 cfs  1.020 af
Pond 25: SSDS
   Outflow=1.98 cfs  0.834 af
Total Runoff Area = 2.400 ac   Runoff Volume = 1.020 af   Average Runoff Depth = 5.10"

Waterford 24-hr S1 50-yr  Rainfall=6.96"
21-07 DC
Prepared by Summer Hill Civil Engineers & Land Surveyors, P.C,
Page 19
HydroCAD® 10.10-4b  s/n 10862  © 2020 HydroCAD Software Solutions LLC
Summary for Subcatchment 20: DC 1
Runoff
=
15.13 cfs @ 12.04 hrs,  Volume=
1.020 af,  Depth= 5.10"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0