SW3191202_2020_02_11 Northgate Stormwater Report_2/11/2020

Storm Drainage, Riprap Apron, & Water Quality Calculations
FOR
THE RESIDENCE AT NORTHGATE
Statesville, North Carolina
Residence Housing Associates, LLC
1109 Davie Avenue
Statesville, NC 28677
Date: 04/02/19
Revised: 02/11 /2020
00 URBAN
DESIGN
PARTNERS
1318 Central Avenue, Suite E6
Charlotte, NC 28205
NCBELS Firm #: P-0418
SC COA #: C-03044
Project No: 19-039
Calculations By: LBT
�N CARD
ESSjo�%:
q/ . D
2/11/2020

Project Location
Old Wilkesboro Road & Bradley Farm Road, Statesville, NC 28625
Project Narrative
Residence Housing Associates, LLC. is developing a single senior apartment
building along with the associated parking, walking paths, and utilities. On -site
stormwater will be managed using a pipe network and sand filter.
The sand filter will be above ground and located at the southern side of the site.
The outfall of the sand filter is at the natural low elevation of the site. The
drainage area for the sand filter is 4.93 acres and the proposed built -upon area
is 43%.
The NCDEQ Stormwater Design Manual was used to design the proposed sand
filter. The design calculations can be found in this report. A plan view of the
sand filter and the details and notes to accompany it can be found in the
construction documents on sheet C-5.1, SCM Plan & Details.

STORM DRAINAGE PIPE
CALCULATIONS

Northgate Urban Design Partners
JOB NO.: 19-039 BY: udp 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Ibt Charlotte, NC 28205
REVISED: 10.25.19 STORM DRAINAGE DESIGN DATA
LOCATION
FROM TO
DRAIN
AREA
(acres)
RUNOFF
C I Q inlet Q pipe
(cfs) (cfs)
PIPE
REQ'D ROUNDED
n SLOPE LENGTH SIZE SIZE
(%) (ft) (inches) (inches)
ACTUAL
CAPACITY VEL.
(cfs) (fps)
INVERT ELEV.
INV INV
OUT IN
(FROM) (FROM)
RIM COVER
ELEVATION DEPTH
CB-17 CB-16
CB-16 CB-12
0.38
0.59
0.80
0.80
7.03
7.03
2.1 2.1
3.3 5.4
0.013
0.013
1.11 %
1.52%
59
119
9.7 15
13.0 15
6.81 4.72
7.98 7.08
913.25
912.50
912.60
910.70
917.00
916.70
2.25
2.70
YI-15 CO-14
0.34
0.60
7.03
1.4 1.4
0.013
1.13%
49
8.3 12
3.79 4.30
913.75
913.20
916.50
1.50
CO-14 CB-13
CB-13 CB-
0.00
0.80
0.80
7.03
7.03
0.0 1.4
0.0 1.5
0.013
0.013
1.07%
1.00%
37
8.4 12
8.6 15
3.70 4.19
4.00
913.10
912.60
912.70
910.70
919.78
919.49
5.43
5.39
CB-12 CB-11
0.19
0.08
0.80
0.80
7.03
7.03
1.1 8.0
0.4 8.4
0.013
0.013
1.67%
1.27%
54
63
14.7 15
15.8 18
8.36 8.18
11.87 7.52
910.60
909.60
909.70
908.80
915.78
914.69
3.68
3.30
CB-11 CB-10
CB-10 CB-3
0.24
0.80
7.03
1.3 9.7
0.013
1.16%
60
17.0 18
11.35 7.58
908.70
908.00
913.00
2.51
YI-9 CB-8
CB-8 JB-7
0.90
0.85
0.60
0.80
7.03
7.03
3.8 3.8
4.8 8.6
0.013
0.013
1.61 %
2.33%
75
60
11.2 15
14.2 15
8.21 6.15
9.89 9.51
914.50
913.20
913.30
911.80
917.50
917.50
1.50
2.80
JB-7 CB-6
CB-6 CB-5
0.00
0.27
0.80
0.80
7.03
7.03
0.0 8.6
1.5 10.1
0.013
0.013
0.83%
1.16%
60
90
17.2 18
17.2 18
9.62 6.43
11.36 7.59
911.70
911.10
911.20
910.05
918.90
918.25
5.41
5.36
CB-5 CB-4
CB-4 CB-3
0.07
0.09
0.80
0.80
7.03
7.03
0.4 10.5
0.5 11.0
0.013
0.013
1.12%
1.11 %
103
108
17.6 18
17.9 24
11.14 7.57
23.91 7.00
909.95
908.70
908.80
907.50
918.59
915.60
6.85
4.59
CB-3 FES-2
0.28
0.80
7.03
1.6 22.3
0.013
1.40%
36
22.4 24
26.84 9.91
906.50
906.00
911.70
2.89
OCS-2 FES-0 ]LLL__]j
0.80
7.03
6.0 6.0
0.013
0.95%
52
14.7 18
10.29 6.00
902.50
902.00
1 910.00
5.71

RPRAP
CALCULATIONS
(STORM DRAINAGE OUTLET PIPES

Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
20
10
r%
3 0
��
Outlet y Iw - Do + �-a
Pipe i
diameter (Do)
La —
`0ilwater { 0.5Do
o1 Pp 60
`MVP
fit
ItII 54
5 10 20 50 100 200 500
Discharge (ft3/sec)
.0 0
1000
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from around pipe flowing full, minimum taiiwater condition (T. c 0.5 diameter)
Rev. 12, 93
tFES-0:
Q=6cfs
do =
18"
3do
= 4.5'
La =
10' (min)
w =
11.5'
v =
6.0 fps
d,o
= 0.6'
8.0.3

Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
2U
10
3 0
��
Outlet y Iw - Do + �-a
Pipe i
diameter (Do)
La —
`0ilwater { 0.5Do
o1 Pp 60
`MVP
fit
ItII 54
5 10 20 50 100 200 500
Discharge (ft3/sec)
r
= m
2 Cn
Q
a
1 LO
.0 0
1000
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from around pipe flowing full, minimum taiiwater condition (T. c 0.5 diameter)
Rev. 12, 93
tFES-2:
Q =
22.1 cfs
do =
24"
3do=6'
La =
14'
w =
16'
v =
9.91 fps
d,o
= 0.6'
8.0.3

Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
20
10
0
3 0
��
Outlet y Iw - Do + �-a
Pipe i
diameter (Do)
La —
`0ilwater { 0.5Do
o1 Pp 60
`mud`
fit
ItII 54
10 20 50 100 200 500
Discharge (ft3/sec)
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum taiiwater condition (T. c 0.5 diameter)
Rev. 12, 93
'RIP -RAP:
Q =
1.4 cfs
do =
15"
3do
= 3.75'
La =
10' (min)
w =
11.25'
v =
5.0 fps
d,o
= 0.4'
r
2 Cn
C.
M
Q
a
1 U')
8.06.3

CALCULATIONS

507590
35o 48' 37" N
35o 48' 28" N
Hydrologic Soil Group—Iredell County, North Carolina
(Northgate Soil Map)
507620 507650 507680 507710 507740
507590 507620 507650 507680 507710 507740
Map Scale: 1:1,450 if printed on A portrait (8.5" x 11") sheet.
Milers
$ N 0 20 40 80 120
Feet
0 50 100 200 300
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
507770
507770
507800
35o 48' 37" N
1
35o 48' 28" N
507800
a
3/6/2019
Pagel of 4

Hydrologic Soil Group—Iredell County, North Carolina
(Northgate Soil Map)
MAP LEGEND
Area of Interest (AOI)
0
Area of Interest (AOI)
Soils
Soil Rating
Polygons
0
A
0
A/D
0
B
0
B/D
0
C
0
C/D
0
D
0
Not rated or not available
Soil Rating
Lines
r 0
A
r 0
A/D
B
r
B/D
N 0
C
r 0
C/D
r 0
D
r 0
Not rated or not available
Soil Rating
Points
0
A
0
A/D
0
B
0
B/D
❑ C
0 C/D
0 D
❑ Not rated or not available
Water Features
Streams and Canals
Transportation
— Rails
­0 Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:12,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Iredell County, North Carolina
Survey Area Data: Version 23, Sep 10, 2018
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Apr 8, 2015—Nov 28,
2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Group—Iredell County, North Carolina
Northgate Soil Map
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
CmB2
Clifford sandy clay loam,
B
2.8
37.0%
2 to 6 percent slopes,
moderately eroded
CmC2
Clifford sandy clay loam,
B
3.5
46.6%
6 to 10 percent
slopes, moderately
eroded
CrC
Clifford -Urban land
B
1.2
16.3%
complex, 2 to 10
percent slopes
Totals for Area of Interest
7.6
100.0%
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Iredell County, North Carolina
Northgate Soil Map
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 4 of 4

507570
35o 48' 37" N
o_
35o 48' 28" N
Hydrologic Soil Group—Iredell County, North Carolina
(Northgate SCM Drainage Area Soil Map)
507600 507630 5076M 507690 507720
507570 507600 507630 507660 507690
Map Scale: 1:1,310 if printed on A portrait (8.5" x 11") sheet.
Meters
$ N 0 15 30 EO 90
Feet
0 50 100 200 500
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
507720
507750
35o 48' 37" N
o_
"03
0
35o 48' 28" N
507750
0
3/6/2019
Pagel of 4

Hydrologic Soil Group—Iredell County, North Carolina
(Northgate SCM Drainage Area Soil Map)
MAP LEGEND
Area of Interest (AOI)
0
Area of Interest (AOI)
Soils
Soil Rating
Polygons
0
A
0
A/D
0
B
0
B/D
0
C
0
C/D
0
D
0
Not rated or not available
Soil Rating
Lines
r 0
A
r 0
A/D
B
r
B/D
N 0
C
r 0
C/D
r 0
D
r 0
Not rated or not available
Soil Rating
Points
0
A
0
A/D
0
B
0
B/D
❑ C
0 C/D
0 D
❑ Not rated or not available
Water Features
Streams and Canals
Transportation
— Rails
­0 Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:12,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Iredell County, North Carolina
Survey Area Data: Version 23, Sep 10, 2018
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Apr 8, 2015—Nov 28,
2017
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Group—Iredell County, North Carolina
Northgate SCM Drainage Area Soil
Map
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
CmB2
Clifford sandy clay loam,
B
2.7
54.6%
2 to 6 percent slopes,
moderately eroded
CmC2
Clifford sandy clay loam,
B
1.2
24.9%
6 to 10 percent
slopes, moderately
eroded
CrC
Clifford -Urban land
B
1.0
20.5%
complex, 2 to 10
percent slopes
Totals for Area of Interest
6.0
100.0%
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Iredell County, North Carolina
Northgate SCM Drainage Area Soil
Map
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 3/6/2019
Conservation Service National Cooperative Soil Survey Page 4 of 4

North ate Urban Design Partners
JOB NO.: 19-039 BY: 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Charlotte, NC 28205
REVISED: 11.26.19 IMPERVIOUS CALCULATIONS
Existing Impervious
Building:
8,706 sf
Concrete:
0 sf
Asphalt:
0 sf
Total Impervious Area:
Drainage Area:
Impervious Percentage:
8,706 sf
0.20 ac.
6.40
3%
Proposed Impervious
Building:
34,064 sf
Concrete:
Asphalt:
9,381 sf
48,669 sf
Total Impervious Area:
Drainage Area:
92,114 sf
2.11 ac.
4.93
Impervious Percentage:
43%
Proposed Impervious Site
Building:
32,274 sf
Parking/Sidewalk:
71,693 sf
Total Impervious Area:
Site Area:
Impervious Percentage:
103,966 sf
2.39 ac.
7.53
32%

19:1 Northgate Urban Design Partners
JOB NO.: 19-039 BY: udp 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Ibt Charlotte, NC 28205
REVISED: 11.26.19 TIME OF CONCENTRATION WORKSHEET
PRE -DEVELOPED
SHEET FLOW
Max. Elevation:
937
Min. Elevation:
933
Flow Length (ft):
150
Slope:
2.67%
Mannings:
0.4 Table 3-12 SWDM
Precipitation:
3.12 2-yr, 24-hr rainfall
Travel Time:
0.45 hr Eq. 3.17 SWDM
SHALLOW CONCENTRATED
Max. Elevation:
933
Min. Elevation:
902
Flow Length (ft):
655
Slope:
4.73%
Velocity (fps):
3.51 Eq. 3.23 SWDM
Travel Time:
186.61 sec
0.052 hr
CHANNEL FLOW
Flow Length (ft):
0
Velocity (fps):
3 assumed 3 ft/sec
Travel Time:
0.00 sec
0.000 hr
TIME OF CONCENTRATION
Total: 0.50 hr
30 min
Page 2 of 8

Northgate Urban Design Partners
JOB NO.: 19-039 BY: 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Charlotte, NC 28205
REVISED: 11.26.19 PRELIMINARY CALCULATIONS
INTRODUCTION:
SUMMARY
DRAINAGE AREAS:
SOIL TYPES:
(see attached drainage area map)
Predeveloped Drainage Area 6.40 acres
Postdeveloped SCM Drainage Area 4.93 acres
Postdeveloped Bypass Drainage Area 1.48 acres
(see attached soils map)
Area (ac) Area (%)
Soil Type
Hydrologic Soil Group
3.39
53%
CmB2
B
1.60
25%
CmC2
B
1.41
22%
CrC
B
Total
6.40
100%
1
B
CURVE NUMBER:
Predeveloped CN
Cover Type
Area (ac)
% CN Wtd. CN
Wooded
6.20
97%
53.28
Impervious
0.20
3%
3.06
Total
6.40
56.34
Composite CN
Use CN = 56.00
Postdeveloped CN
Cover Type
Area (ac)
%
CN
Wtd. CN
Impervious
2.11
43%
98
42.05
Grass/Open Space
2.20
45%
61
27.28
Wooded
0.61
12%
55
6.80
Total
4.93
76.13
Composite CN
Use CN =
76.00

HYDROLOGIC CALCULATIONS
Pre -developed
Drainage area (DA) 6.40 ac.
Cuve Number (CN) 56
Modified Curve Number (CN) n/a
Time of Concentration 0.50 hr.
Impervious Percentage 3%
WATER QUALITY VOLUME (1 ")
Volume must be released over a period of 2-5 days
Using the runoff volume calculations in the "Simple Method"
Rv = 0.05 + .009 (1)
Rv= 0.44 in/in
WQv = (Design rainfall) (Rv) (Drainage Area)
WQv = 1 " rainfall x Rv in/in x 1/12 in/ft x Da =
WQv= 0.179 ac-ft
7,803 ft3
0.44 in
75% WQv=
MODIFIED CURVE NUMBER
CNm= 1000/(10+5P+10WQV-10(WQv^2+1.25WQVP)^0.5)
P= rainfall, in inches (use1.0 inches) = 1.00
WQv= water quality volume, in inches = 0.33
CNm 90.2
CHANNEL PROTECTION VOLUME
0.134 ac-ft
5,852 ft3
0.33 in
Q= (P-0.2S)^2/(P+0.8S)
Q= accumulated runoff volume, inches
P= accumulated rainfall (potential maximum runoff), inches 2.58 in
S= potential maximum soil retention, inches = 1000/CN-10 = 3.16 in
CN= SCS curve number
Q= 0.74 cfs
Compute Watershed Runoff
CPv= 0.31 ac-ft = 13,301 cf
50% CPv= 0.15 ac-ft = 6,651 cf
Channel Protection Volume Release Rate (1 yr, 24 hr storm)
1.5 day
36 hour
Release= 0.103 cfs
50% Rel= 0.051 cfs
Post -developed
4.93 ac
76
90
0.08 hr.
43 %

Determine Orifice Size for drawdown
IF— Q=
CA x sgrt(2gh)
orifice equation
aA=
Area of orifice
a sqft
t=
Time to drawdown
129,600 sec 36 hour
g=
Gravity constant
32.2 ft/sA2
h=
Change in head
1.00 ft
C=
Orifice constant
0.6
Maximum orifice area =
0.0213 sq ft
Maximum orifice size =
1.98 in.

Northgate Urban Design Partners
JOB NO.: 19-039 BY: udp 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Ibt EL Charlotte, NO 28205
REVISED: 1.22.201 SAND FILTER DESIGN
Sand Filter Desian Requirements
Design Method
Design Method
TSS
Detention Time
2.0 days
Filter Bed Depth
2.5 ft
Underdrain System Thickness
1.0 ft
Hydrologic Calculations
Pre -developed
Post -developed
Drainage area to pond (Da)=
6.40 ac.
4.93 ac
Cuve Number (CN)
56
76
Modified Curve Number (CNm)
n/a
90
Time of Concentration
0.50 hr.
0.08 hr.
Impervious Percentage
3%
43%
Water Quality Volume (WQv)
-
7,803 cf
75% WQv
-
5,852 cf
Calculate Pretreatment System Requirements
sedimentation chamber must be equal to sand chamber
Volume= 9,210 cf (required)
Chamber Approximate Dimensions
Depth=
3 ft
Length=
52 ft
Width=
12 ft
Area=
624 sf
Volume=
9,225 cf (provided)
Determine Suface Area to Treat WQv
Surface Area based on Darcy's Equation
Af= (WQv)(df)/((k)(h+d)(t))
Af= surface area of ponding area (sq ft)
WQv= water quality control volume
5,852 cf
d= filter bed depth
2.5 ft
k= coefficient of permeability of filter media
3.5 ft/day
h= average height of water above filter bed (ft)
1 ft
t= design filter bed drain time (days)
2.00 day
Af= 597 sf (required)
Determine Dimensions
Length= 30.0 ft
Width= 20.0 ft
Area= 600 sf (provided)
Stage/Storage Table
24" max for WQ storm event
Elevation Forebay
(msl) Area (sf)
Main Pond
Area (sf)
Total Area
(sf)
Total Area
(ac)
Forebay Main Pond Total Volume
Vol (cu-ft) Vol (Cu-ft) (Cu-ft)
Total Volume
(ac-ft)
905 0
600
600
0.014
0 0 0
0.000
906 2,200
1,865
4,065
0.093
0 1,173 1,173
0.048
907 2,760
2,380
5,140
0.118
2,472 3,288 5,760
0.153
908 3,370
2,955
6,325
0.145
5,529 5,948 11,477
0.284
909 4,040
3,585
7,625
0.175
9,225 9,210 18,435
0.444
910 -
-
9,615
0.221
- - 27,027
0.641
911 -
-
10,845
0.249
- - 37,241
0.876

Northgate Urban Design Partners
JOB NO.: 19-039 BY: udp 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Ibt Charlotte, NO 28205
REVISED: 1.22.201 SAND FILTER DESIGN
Forebay Weir
Elevation =
Q= 3.33lh^3/2
Q= 2 yr. storm runoff
21.0 Cfs
1= weir length
I ft
h= elevation over weir
1.00 ft
1= 0/(3.33 x h^3/2)
Weir Length
10 ft (min.)
Stage/Discharge Table (Sand Bed)
Q= Af(k)(h+d)/(d)
Af= surface area of ponding area (sq ft)
d= filter bed depth
k= coefficient of permeability of filter media
h= average height of water above filter bed (ft)
Elevation Height
(msl) (ft)
Fow
(cf/day)
Flow
(cfs)
905 0
0
0.000
906 1
2,940
0.034
907 2
3,780
0.044
908 3
4,620
0.053
909 4
5,460
0.063
910 5
6,300
0.073
911 6
7,140
0.083
Peak Flow Summary
Flow Calculations:
Drainage Area:
4.93 Ac.
Runoff Coefficient:
0.8
2-yr Intensity:
5.32 in/hr
2-yr Flow:
20.98 cfs
600 sf
2.5 ft
3.5 ft/day
Design Storm
Pre
Post
Routed
Peak Attenuated?
WSE
cfs
cfs
cfs
Y/N
1-year
0.28
8.21
0.23
Y
907.59
2-year
1.03
12.11
0.62
Y
907.94
10-year
4.89
23.64
1.41
Y
909.58
25-year
8.07
30.97
5.17
Y
910.17
50-year
10.94
36.98
17.27
N
910.45
1 00-ear
1 14.05
1 43.13
1 23.27
1 N
910.74
I op of dam elevation: 911.00
WQv Water Surface Elevation: 906.67
Sand Bed Elevation: 905.00
Size Underdrain - based on Section 5.7 of NCDENR BMP Manual
Determine Design Flow
Design Flow= SA*k'SF
SA= surface area of sand filter 600 ft2
k= coefficient of permeability of filter r 3.5 ft/day
SF= safety factor 10
Q= 0.24 cfs
Calculate diameter of single pipe
D= 16*((Q'n)/(s^0.5))^(3/8)
Q= design flow 0.24 cfs
S= slope of underdrain pipe (0.5% rec 0.005 ft/ft
n= roughness (0.011 recommended) 0.011
D= 4.69 in
6" pipes required for sand filter
use area of bottom
contour

North ate Urban Design Partners
JOB NO.: 19-039 BY: udp 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Ibt Charlotte, NC 28205
REVISED: 11.26.19 1W FLOATATION CALCULATIONS
Calculations Given Data Standard Footing Assumptions
Buoyant Weight of Concrete 87.6 Ibs/ft^3 1. Footing base to be 1 ft. wider than structure
Weight of Water 62.4 Ibs/ft^3 on all sides.
Safety Factor (S.F.) 1.25 2. Footing depth to be a minimum of 8 inches in depth.
Equations used:
Outlet Structure Weight, W(s)
= 4(w + t) x t x h x W(bc)
where, w = outlet box inside dimension, ft.
t = structure wall thickness, ft.
h = height of structure, ft.
W(bc)= buoyant weight of concrete, Ibs/ft^3
W(w)= weight of water, Ibs/ft^3
S.F.= safety factor
Displaced Water Weight, W(w) = 4 x (w + 2t) x W(w) x h
Required Base Weight, W(b) = (W(w) x S.F.) - W(s)
Required Footing Volume, V(f) = W(b) / W(bc)
ut et Structure
Structare Dimensions
Object Weights
Height of structure, h =
5 ft.
Outlet Structure Weight, W(s) =
3942
Structure wall thickness, t =
6 in.
Displaced Water Weight, W(w) =
6240
Outlet box inside dimension, w =
4 ft.
Req'd Base Weight, W(b) =
3858
Footing Size 11
Required Footing Volume, V(f) =
44 cf
Standard Footing Length, L =
7.00
Provided Footing Volume, V(f) =
74 cf
Standard Footing Width, W =
7.00
Footing Check
okay
Minimum Footing Depth, D =
1.50
Footing Size to be used:
Length =
7.00 ft.
Width =
7.00 ft. Outlet Structure #1
Depth =
1.50 ft.

1" ROUTING
CALCULATIONS

Predeveloped
3
2m I Sand Filter/Dry
Postdeveloped (CNm)
Subcat Reach on Link
• 0j

Northgate SCM
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 2
Area Listing (selected nodes)
Area CN Description
(acres) (su bcatch me nt-n u mbe rs)
0.200 98 Impervious (1)
6.200 55 Wooded (1)
4.930 90 modified CN for WQv (2m)
11.330 71 TOTAL AREA

Northgate SCM
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 3
Soil Listing (selected nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000
HSG A
0.000
HSG B
0.000
HSG C
0.000
HSG D
11.330
Other 1, 2m
11.330
TOTAL AREA

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment 1: Predeveloped
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 6-hr 1-Inch Rainfall=1.00"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
N
3
0
LL
Subcatchment 1: Predeveloped
Hydrograph
Type MI
6-h r
1-I6ch Rainfall='1.0011
Runoff Area; 6.400 arc
Runoff Volume=0.000 of
Runoff Depth=0.007
Tc=30.0 mill
CN=56
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)
■ Runoff

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 5
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.08
0.00
0.00
3.00
0.73
0.00
0.00
4.50
0.92
0.00
0.00
6.00
1.00
0.00
0.00
7.50
1.00
0.00
0.00
9.00
1.00
0.00
0.00
10.50
1.00
0.00
0.00
12.00
1.00
0.00
0.00
13.50
1.00
0.00
0.00
15.00
1.00
0.00
0.00
16.50
1.00
0.00
0.00
18.00
1.00
0.00
0.00
19.50
1.00
0.00
0.00
21.00
1.00
0.00
0.00
22.50
1.00
0.00
0.00
24.00
1.00
0.00
0.00
25.50
1.00
0.00
0.00
27.00
1.00
0.00
0.00
28.50
1.00
0.00
0.00
30.00
1.00
0.00
0.00
31.50
1.00
0.00
0.00
33.00
1.00
0.00
0.00
34.50
1.00
0.00
0.00
36.00
1.00
0.00
0.00
37.50
1.00
0.00
0.00
39.00
1.00
0.00
0.00
40.50
1.00
0.00
0.00
42.00
1.00
0.00
0.00
43.50
1.00
0.00
0.00
45.00
1.00
0.00
0.00
46.50
1.00
0.00
0.00
48.00
1.00
0.00
0.00
49.50
1.00
0.00
0.00
51.00
1.00
0.00
0.00
52.50
1.00
0.00
0.00
54.00
1.00
0.00
0.00
55.50
1.00
0.00
0.00
57.00
1.00
0.00
0.00
58.50
1.00
0.00
0.00
60.00
1.00
0.00
0.00
61.50
1.00
0.00
0.00
63.00
1.00
0.00
0.00
64.50
1.00
0.00
0.00
66.00
1.00
0.00
0.00
67.50
1.00
0.00
0.00
69.00
1.00
0.00
0.00
70.50
1.00
0.00
0.00
72.00
1.00
0.00
0.00
73.50
1.00
0.00
0.00
75.00
1.00
0.00
0.00
76.50
1.00
0.00
0.00
78.00
1.00
0.00
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
1.00
0.00
0.00
81.00
1.00
0.00
0.00
82.50
1.00
0.00
0.00
84.00
1.00
0.00
0.00
85.50
1.00
0.00
0.00
87.00
1.00
0.00
0.00
88.50
1.00
0.00
0.00
90.00
1.00
0.00
0.00
91.50
1.00
0.00
0.00
93.00
1.00
0.00
0.00
94.50
1.00
0.00
0.00
96.00
1.00
0.00
0.00
97.50
1.00
0.00
0.00
99.00
1.00
0.00
0.00
100.50
1.00
0.00
0.00
102.00
1.00
0.00
0.00
103.50
1.00
0.00
0.00
105.00
1.00
0.00
0.00
106.50
1.00
0.00
0.00
108.00
1.00
0.00
0.00
109.50
1.00
0.00
0.00
111.00
1.00
0.00
0.00
112.50
1.00
0.00
0.00
114.00
1.00
0.00
0.00
115.50
1.00
0.00
0.00
117.00
1.00
0.00
0.00
118.50
1.00
0.00
0.00
120.00
1.00
0.00
0.00
121.50
1.00
0.00
0.00
123.00
1.00
0.00
0.00
124.50
1.00
0.00
0.00
126.00
1.00
0.00
0.00
127.50
1.00
0.00
0.00
129.00
1.00
0.00
0.00
130.50
1.00
0.00
0.00
132.00
1.00
0.00
0.00
133.50
1.00
0.00
0.00
135.00
1.00
0.00
0.00

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 6
Summary for Subcatchment 2m: Postdeveloped (CNm)
Runoff = 4.26 cfs @ 2.97 hrs, Volume= 0.132 af, Depth= 0.32"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 6-hr 1-Inch Rainfall=1.00"
Area (ac) CN Description
4.930 90 modified CN for WQv
4.930 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2m: Postdeveloped (CNm)
Hydrograph
I ■Runoff
4.26 cfs
--- ---- ---- }----+----+----+---- ---- ---- ---T pe ll-
4
6-h r
1-16ch Rainfall='�1.00'7
L - - - - L - - - - L - - - - L - - - - L - - - - 1 - - - - 1 - - - - 1 - - - - L - - - - L - -
3 Runoff area''=4.9$0 aq
Runoff Volume=0.1,32 of
LL 2 L--- L ----L 1-Runoff-�}epth=0.32"-
Tr,=5.o min
C�,N=9p
----------;----
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 7
Hydrograph for Subcatchment 2m: Postdeveloped (CNm)
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.08
0.00
0.00
3.00
0.73
0.16
3.87
4.50
0.92
0.27
0.22
6.00
1.00
0.32
0.14
7.50
1.00
0.32
0.00
9.00
1.00
0.32
0.00
10.50
1.00
0.32
0.00
12.00
1.00
0.32
0.00
13.50
1.00
0.32
0.00
15.00
1.00
0.32
0.00
16.50
1.00
0.32
0.00
18.00
1.00
0.32
0.00
19.50
1.00
0.32
0.00
21.00
1.00
0.32
0.00
22.50
1.00
0.32
0.00
24.00
1.00
0.32
0.00
25.50
1.00
0.32
0.00
27.00
1.00
0.32
0.00
28.50
1.00
0.32
0.00
30.00
1.00
0.32
0.00
31.50
1.00
0.32
0.00
33.00
1.00
0.32
0.00
34.50
1.00
0.32
0.00
36.00
1.00
0.32
0.00
37.50
1.00
0.32
0.00
39.00
1.00
0.32
0.00
40.50
1.00
0.32
0.00
42.00
1.00
0.32
0.00
43.50
1.00
0.32
0.00
45.00
1.00
0.32
0.00
46.50
1.00
0.32
0.00
48.00
1.00
0.32
0.00
49.50
1.00
0.32
0.00
51.00
1.00
0.32
0.00
52.50
1.00
0.32
0.00
54.00
1.00
0.32
0.00
55.50
1.00
0.32
0.00
57.00
1.00
0.32
0.00
58.50
1.00
0.32
0.00
60.00
1.00
0.32
0.00
61.50
1.00
0.32
0.00
63.00
1.00
0.32
0.00
64.50
1.00
0.32
0.00
66.00
1.00
0.32
0.00
67.50
1.00
0.32
0.00
69.00
1.00
0.32
0.00
70.50
1.00
0.32
0.00
72.00
1.00
0.32
0.00
73.50
1.00
0.32
0.00
75.00
1.00
0.32
0.00
76.50
1.00
0.32
0.00
78.00
1.00
0.32
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
1.00
0.32
0.00
81.00
1.00
0.32
0.00
82.50
1.00
0.32
0.00
84.00
1.00
0.32
0.00
85.50
1.00
0.32
0.00
87.00
1.00
0.32
0.00
88.50
1.00
0.32
0.00
90.00
1.00
0.32
0.00
91.50
1.00
0.32
0.00
93.00
1.00
0.32
0.00
94.50
1.00
0.32
0.00
96.00
1.00
0.32
0.00
97.50
1.00
0.32
0.00
99.00
1.00
0.32
0.00
100.50
1.00
0.32
0.00
102.00
1.00
0.32
0.00
103.50
1.00
0.32
0.00
105.00
1.00
0.32
0.00
106.50
1.00
0.32
0.00
108.00
1.00
0.32
0.00
109.50
1.00
0.32
0.00
111.00
1.00
0.32
0.00
112.50
1.00
0.32
0.00
114.00
1.00
0.32
0.00
115.50
1.00
0.32
0.00
117.00
1.00
0.32
0.00
118.50
1.00
0.32
0.00
120.00
1.00
0.32
0.00
121.50
1.00
0.32
0.00
123.00
1.00
0.32
0.00
124.50
1.00
0.32
0.00
126.00
1.00
0.32
0.00
127.50
1.00
0.32
0.00
129.00
1.00
0.32
0.00
130.50
1.00
0.32
0.00
132.00
1.00
0.32
0.00
133.50
1.00
0.32
0.00
135.00
1.00
0.32
0.00

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 8
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area =
4.930 ac, 0.00% Impervious, Inflow Depth = 0.32" for 1-Inch event
Inflow =
4.26 cfs @ 2.97 hrs, Volume= 0.132 of
Outflow =
0.04 cfs @ 6.10 hrs, Volume= 0.132 af, Atten= 99%, Lag= 187.5 min
Primary =
0.04 cfs @ 6.10 hrs, Volume= 0.132 of
Routing by Stor-Ind
method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 906.67'
@ 6.10 hrs Surf.Area= 4,782 sf Storage= 5,281 cf
Flood Elev= 911.00'
Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 1,347.3 min calculated for 0.132 of (100% of inflow)
Center -of -Mass det.
time= 1,347.1 min ( 1,560.4 - 213.3 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)
(sq-ft) (cubic -feet) (cubic -feet)
905.00
600 0 0
906.00
4,065 2,333 2,333
907.00
5,140 4,603 6,935
908.00
6,325 5,733 12,668
909.00
7,625 6,975 19,643
910.00
9,612 8,619 28,261
911.00
10,845 10,229 38,490
Device Routing
Invert Outlet Devices
#1 Primary
902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1
905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1
907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1
910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=0.04 cfs @ 6.10 hrs HW=906.67' (Free Discharge)
L1=Outlet Pipe (Passes 0.04 cfs of 15.73 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.04 cfs)
3=Orifice ( Controls 0.00 cfs)
4=Grate Top ( Controls 0.00 cfs)

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 9
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
C Inflow
4.26 cfs I ❑ Primary
--- ------ffrf1ow'',�T0a=4.93';0-ac,--
4 Pe4k Elev 900.67,'
- - - - Stor-a e=5 281-e -
I I I I I I� I� I I
3
y I I I I I I I I I I I I I
U I I I I I I I I I I I I I
3
p
a 2
1 I I I I I I I I I I I I
0.04 cfs
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 10
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
3.87
2,029
905.92
0.03
6.00
0.14
5,261
906.66
0.04
9.00
0.00
4,865
906.58
0.04
12.00
0.00
4,440
906.49
0.04
15.00
0.00
4,025
906.40
0.04
18.00
0.00
3,620
906.30
0.04
21.00
0.00
3,225
906.21
0.04
24.00
0.00
2,840
906.12
0.04
27.00
0.00
2,464
906.03
0.03
30.00
0.00
2,103
905.94
0.03
33.00
0.00
1,774
905.85
0.03
36.00
0.00
1,477
905.77
0.03
39.00
0.00
1,211
905.68
0.02
42.00
0.00
977
905.60
0.02
45.00
0.00
772
905.52
0.02
48.00
0.00
597
905.44
0.01
51.00
0.00
450
905.36
0.01
54.00
0.00
329
905.30
0.01
57.00
0.00
232
905.23
0.01
60.00
0.00
158
905.17
0.01
63.00
0.00
104
905.13
0.00
66.00
0.00
65
905.09
0.00
69.00
0.00
39
905.06
0.00
72.00
0.00
23
905.03
0.00
75.00
0.00
14
905.02
0.00
78.00
0.00
8
905.01
0.00
81.00
0.00
5
905.01
0.00
84.00
0.00
3
905.00
0.00
87.00
0.00
2
905.00
0.00
90.00
0.00
1
905.00
0.00
93.00
0.00
1
905.00
0.00
96.00
0.00
0
905.00
0.00
99.00
0.00
0
905.00
0.00
102.00
0.00
0
905.00
0.00
105.00
0.00
0
905.00
0.00
108.00
0.00
0
905.00
0.00
111.00
0.00
0
905.00
0.00
114.00
0.00
0
905.00
0.00
117.00
0.00
0
905.00
0.00
120.00
0.00
0
905.00
0.00
123.00
0.00
0
905.00
0.00
126.00
0.00
0
905.00
0.00
129.00
0.00
0
905.00
0.00
132.00
0.00
0
905.00
0.00
135.00
0.00
0
905.00
0.00

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 11
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type II 6-hr 1-Inch Rainfall=1.00"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 12
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

1 YR ROUTING
CALCULATIONS

Predeveloped
2
Postdeveloped
Sand Filter/Dry Pond
Subcat Reach on Link

Northgate SCM
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 2
Area Listing (selected nodes)
Area CN Description
(acres) (su bcatch me nt-n u mbe rs)
2.270
61
Grass/Open Space (2)
2.250
98
Impervious (1, 2)
6.810
55
Wooded (1, 2)
11.330
65
TOTAL AREA

Northgate SCM
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 3
Soil Listing (selected nodes)
Area Soil Subcatchment
(acres) Group Numbers
0.000
HSG A
0.000
HSG B
0.000
HSG C
0.000
HSG D
11.330
Other 1,2
11.330
TOTAL AREA

Northgate SCM Type 11 24-hr 1-yr Rainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment 1: Predeveloped
Runoff = 0.28 cfs @ 12.47 hrs, Volume= 0.094 af, Depth= 0.18"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 1-yr Rainfall=2.84"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
Subcatchment 1: Predeveloped
Hydrograph
0.3 0.28 cfs
0.28 TXpe JJ _24 Ja'r-
------ --------------------------------- Ir�r-Fein#-aN=2:847-
0.24
--- ---i �----i i i i---- - a-i-c-
0.22 t --- ]Runb Area=8.400
0.2-----I',-----I',-----I',----- Runoff,,, VAo[p e=-0rd94-cjf-
w 0.18
-- -- --- --- --- RUnofi-©epfh-0.98„_
3 0.16
LL 0.14 Tc=*0.0 mih
0.12-------------------------------------------------- O,WN-
0.1
-r----r-------------------r-----------------------------i--
0.08
0.06
0.04
0.02
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)
■ Runoff

Northgate SCM Type 1124-hr 1-yrRainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 5
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.05
0.00
0.00
3.00
0.10
0.00
0.00
4.50
0.16
0.00
0.00
6.00
0.23
0.00
0.00
7.50
0.31
0.00
0.00
9.00
0.42
0.00
0.00
10.50
0.58
0.00
0.00
12.00
1.88
0.01
0.01
13.50
2.27
0.06
0.16
15.00
2.42
0.08
0.11
16.50
2.53
0.10
0.09
18.00
2.62
0.12
0.08
19.50
2.68
0.14
0.06
21.00
2.74
0.15
0.06
22.50
2.79
0.16
0.05
24.00
2.84
0.18
0.05
25.50
2.84
0.18
0.00
27.00
2.84
0.18
0.00
28.50
2.84
0.18
0.00
30.00
2.84
0.18
0.00
31.50
2.84
0.18
0.00
33.00
2.84
0.18
0.00
34.50
2.84
0.18
0.00
36.00
2.84
0.18
0.00
37.50
2.84
0.18
0.00
39.00
2.84
0.18
0.00
40.50
2.84
0.18
0.00
42.00
2.84
0.18
0.00
43.50
2.84
0.18
0.00
45.00
2.84
0.18
0.00
46.50
2.84
0.18
0.00
48.00
2.84
0.18
0.00
49.50
2.84
0.18
0.00
51.00
2.84
0.18
0.00
52.50
2.84
0.18
0.00
54.00
2.84
0.18
0.00
55.50
2.84
0.18
0.00
57.00
2.84
0.18
0.00
58.50
2.84
0.18
0.00
60.00
2.84
0.18
0.00
61.50
2.84
0.18
0.00
63.00
2.84
0.18
0.00
64.50
2.84
0.18
0.00
66.00
2.84
0.18
0.00
67.50
2.84
0.18
0.00
69.00
2.84
0.18
0.00
70.50
2.84
0.18
0.00
72.00
2.84
0.18
0.00
73.50
2.84
0.18
0.00
75.00
2.84
0.18
0.00
76.50
2.84
0.18
0.00
78.00
2.84
0.18
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
2.84
0.18
0.00
81.00
2.84
0.18
0.00
82.50
2.84
0.18
0.00
84.00
2.84
0.18
0.00
85.50
2.84
0.18
0.00
87.00
2.84
0.18
0.00
88.50
2.84
0.18
0.00
90.00
2.84
0.18
0.00
91.50
2.84
0.18
0.00
93.00
2.84
0.18
0.00
94.50
2.84
0.18
0.00
96.00
2.84
0.18
0.00
97.50
2.84
0.18
0.00
99.00
2.84
0.18
0.00
100.50
2.84
0.18
0.00
102.00
2.84
0.18
0.00
103.50
2.84
0.18
0.00
105.00
2.84
0.18
0.00
106.50
2.84
0.18
0.00
108.00
2.84
0.18
0.00
109.50
2.84
0.18
0.00
111.00
2.84
0.18
0.00
112.50
2.84
0.18
0.00
114.00
2.84
0.18
0.00
115.50
2.84
0.18
0.00
117.00
2.84
0.18
0.00
118.50
2.84
0.18
0.00
120.00
2.84
0.18
0.00
121.50
2.84
0.18
0.00
123.00
2.84
0.18
0.00
124.50
2.84
0.18
0.00
126.00
2.84
0.18
0.00
127.50
2.84
0.18
0.00
129.00
2.84
0.18
0.00
130.50
2.84
0.18
0.00
132.00
2.84
0.18
0.00
133.50
2.84
0.18
0.00
135.00
2.84
0.18
0.00

Northgate SCM Type 11 24-hr 1-yr Rainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 6
Summary for Subcatchment 2: Postdeveloped
Runoff = 8.21 cfs @ 11.97 hrs, Volume= 0.373 af, Depth= 0.91"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 1-yr Rainfall=2.84"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
9 ■Runoff
8.21 cfs
-i ---- T ---- T ---- T ---- T ---- T ---- T ---- 7 ---- 7Type II z4-1--
8
-- - --- --- --- --- ---- ---- ---1 yr-Rainfall--2.84"-
7 1
L----L----L----L----1---- 1 ---- Run-off Area-4.930-ac-
6 Runoff Vo1ume=0.$73 pf
w 5 Runoft Depth=',0.91I"
3 -- Min 4
---r----r----+----r----+----+----+----+----------+---C --7-6-
3 1
--- --- ---- ---- ------------------ ---- ---- ------------- --
2
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 1124-hr 1-yrRainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 7
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.05
0.00
0.00
3.00
0.10
0.00
0.00
4.50
0.16
0.00
0.00
6.00
0.23
0.00
0.00
7.50
0.31
0.00
0.00
9.00
0.42
0.00
0.00
10.50
0.58
0.00
0.00
12.00
1.88
0.36
7.34
13.50
2.27
0.56
0.39
15.00
2.42
0.65
0.26
16.50
2.53
0.71
0.19
18.00
2.62
0.77
0.16
19.50
2.68
0.81
0.13
21.00
2.74
0.84
0.11
22.50
2.79
0.88
0.11
24.00
2.84
0.91
0.10
25.50
2.84
0.91
0.00
27.00
2.84
0.91
0.00
28.50
2.84
0.91
0.00
30.00
2.84
0.91
0.00
31.50
2.84
0.91
0.00
33.00
2.84
0.91
0.00
34.50
2.84
0.91
0.00
36.00
2.84
0.91
0.00
37.50
2.84
0.91
0.00
39.00
2.84
0.91
0.00
40.50
2.84
0.91
0.00
42.00
2.84
0.91
0.00
43.50
2.84
0.91
0.00
45.00
2.84
0.91
0.00
46.50
2.84
0.91
0.00
48.00
2.84
0.91
0.00
49.50
2.84
0.91
0.00
51.00
2.84
0.91
0.00
52.50
2.84
0.91
0.00
54.00
2.84
0.91
0.00
55.50
2.84
0.91
0.00
57.00
2.84
0.91
0.00
58.50
2.84
0.91
0.00
60.00
2.84
0.91
0.00
61.50
2.84
0.91
0.00
63.00
2.84
0.91
0.00
64.50
2.84
0.91
0.00
66.00
2.84
0.91
0.00
67.50
2.84
0.91
0.00
69.00
2.84
0.91
0.00
70.50
2.84
0.91
0.00
72.00
2.84
0.91
0.00
73.50
2.84
0.91
0.00
75.00
2.84
0.91
0.00
76.50
2.84
0.91
0.00
78.00
2.84
0.91
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
2.84
0.91
0.00
81.00
2.84
0.91
0.00
82.50
2.84
0.91
0.00
84.00
2.84
0.91
0.00
85.50
2.84
0.91
0.00
87.00
2.84
0.91
0.00
88.50
2.84
0.91
0.00
90.00
2.84
0.91
0.00
91.50
2.84
0.91
0.00
93.00
2.84
0.91
0.00
94.50
2.84
0.91
0.00
96.00
2.84
0.91
0.00
97.50
2.84
0.91
0.00
99.00
2.84
0.91
0.00
100.50
2.84
0.91
0.00
102.00
2.84
0.91
0.00
103.50
2.84
0.91
0.00
105.00
2.84
0.91
0.00
106.50
2.84
0.91
0.00
108.00
2.84
0.91
0.00
109.50
2.84
0.91
0.00
111.00
2.84
0.91
0.00
112.50
2.84
0.91
0.00
114.00
2.84
0.91
0.00
115.50
2.84
0.91
0.00
117.00
2.84
0.91
0.00
118.50
2.84
0.91
0.00
120.00
2.84
0.91
0.00
121.50
2.84
0.91
0.00
123.00
2.84
0.91
0.00
124.50
2.84
0.91
0.00
126.00
2.84
0.91
0.00
127.50
2.84
0.91
0.00
129.00
2.84
0.91
0.00
130.50
2.84
0.91
0.00
132.00
2.84
0.91
0.00
133.50
2.84
0.91
0.00
135.00
2.84
0.91
0.00

Northgate SCM Type 11 24-hr 1-yr Rainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 8
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area =
4.930 ac, 41.58% Impervious, Inflow Depth = 0.91" for 1-yr event
Inflow =
8.21 cfs @ 11.97 hrs, Volume= 0.373 of
Outflow =
0.23 cfs @ 15.42 hrs, Volume= 0.373 af, Atten= 97%, Lag= 207.0 min
Primary =
0.23 cfs @ 15.42 hrs, Volume= 0.373 of
Routing by Stor-Ind
method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 907.59'
@ 15.42 hrs Surf.Area= 5,843 sf Storage= 10,192 cf
Flood Elev= 911.00'
Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 1,523.5 min calculated for 0.373 of (100% of inflow)
Center -of -Mass det.
time= 1,523.5 min (2,382.1 - 858.6 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet)
(sq-ft) (cubic -feet) (cubic -feet)
905.00
600 0 0
906.00
4,065 2,333 2,333
907.00
5,140 4,603 6,935
908.00
6,325 5,733 12,668
909.00
7,625 6,975 19,643
910.00
9,612 8,619 28,261
911.00
10,845 10,229 38,490
Device Routing
Invert Outlet Devices
#1 Primary
902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1
905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1
907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1
910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=0.23 cfs @ 15.42 hrs HW=907.59' (Free Discharge)
L1=Outlet Pipe (Passes 0.23 cfs of 17.73 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.05 cfs)
3=Orifice (Orifice Controls 0.18 cfs @ 1.75 fps)
4=Grate Top ( Controls 0.00 cfs)

Northgate SCM Type 11 24-hr 1-yr Rainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 9
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
❑ Inflow
9 8.21 cfs - - ■ Primary
Inflow'Area=4.930 ad,
8
7
-- -------;- -- - -- Storage=10;1-92 cf--
6 I 1 I I 1
--- ---- ---- - --
y
U 5 I I I I I I I I I I I I
3 I I I I I I I I I I I I
p
E 4
3
2
-- -1-----1----t----t----t----t----1-----1----t----t----+----r--
1 1 1 1 1 1 1 1 1 1 1 1 1
0.23 cfs
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 1124-hr 1-yrRainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 10
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.00
0
905.00
0.00
12.00
7.34
4,795
906.56
0.04
15.00
0.26
10,174
907.59
0.23
18.00
0.16
9,965
907.55
0.19
21.00
0.11
9,664
907.50
0.13
24.00
0.10
9,514
907.48
0.11
27.00
0.00
8,786
907.35
0.05
30.00
0.00
8,281
907.25
0.05
33.00
0.00
7,785
907.16
0.05
36.00
0.00
7,299
907.07
0.04
39.00
0.00
6,821
906.98
0.04
42.00
0.00
6,353
906.89
0.04
45.00
0.00
5,896
906.79
0.04
48.00
0.00
5,448
906.70
0.04
51.00
0.00
5,010
906.61
0.04
54.00
0.00
4,582
906.52
0.04
57.00
0.00
4,163
906.43
0.04
60.00
0.00
3,755
906.34
0.04
63.00
0.00
3,357
906.24
0.04
66.00
0.00
2,968
906.15
0.04
69.00
0.00
2,589
906.06
0.03
72.00
0.00
2,221
905.97
0.03
75.00
0.00
1,881
905.88
0.03
78.00
0.00
1,573
905.79
0.03
81.00
0.00
1,297
905.71
0.02
84.00
0.00
1,052
905.62
0.02
87.00
0.00
838
905.54
0.02
90.00
0.00
653
905.46
0.02
93.00
0.00
496
905.39
0.01
96.00
0.00
367
905.32
0.01
99.00
0.00
262
905.25
0.01
102.00
0.00
181
905.19
0.01
105.00
0.00
120
905.14
0.00
108.00
0.00
76
905.10
0.00
111.00
0.00
47
905.07
0.00
114.00
0.00
28
905.04
0.00
117.00
0.00
17
905.02
0.00
120.00
0.00
10
905.01
0.00
123.00
0.00
6
905.01
0.00
126.00
0.00
3
905.00
0.00
129.00
0.00
2
905.00
0.00
132.00
0.00
1
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type 1124-hr 1-yrRainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 11
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type 1124-hr 1-yrRainfall=2.84"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 12
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

2 YR ROUTING
CALCULATIONS

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 13
Summary for Subcatchment 1: Predeveloped
Runoff = 1.03 cfs @ 12.36 hrs, Volume= 0.193 af, Depth= 0.36"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 2-yr Rainfall=3.45"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
1.03 cfs
M!
Subcatchment 1: Predeveloped
Hydrograph
' ' ' ' ' ' ' ' ' ■Runoff
I ---- I ---- i ---- i ----------
Type II �z4-r
2 yr Rainfall=3.457
Runoff Area=6.400 ad
Runoff Vol'ump=0.1193 clf
Runoff Depth=,0.361"
TcT30.0 min
CN=56
----------------------------------------------
Time (hours)

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 14
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.06
0.00
0.00
3.00
0.12
0.00
0.00
4.50
0.19
0.00
0.00
6.00
0.28
0.00
0.00
7.50
0.38
0.00
0.00
9.00
0.51
0.00
0.00
10.50
0.70
0.00
0.00
12.00
2.29
0.06
0.07
13.50
2.76
0.16
0.32
15.00
2.94
0.20
0.20
16.50
3.07
0.24
0.15
18.00
3.18
0.27
0.13
19.50
3.26
0.30
0.11
21.00
3.33
0.32
0.09
22.50
3.39
0.34
0.09
24.00
3.45
0.36
0.09
25.50
3.45
0.36
0.00
27.00
3.45
0.36
0.00
28.50
3.45
0.36
0.00
30.00
3.45
0.36
0.00
31.50
3.45
0.36
0.00
33.00
3.45
0.36
0.00
34.50
3.45
0.36
0.00
36.00
3.45
0.36
0.00
37.50
3.45
0.36
0.00
39.00
3.45
0.36
0.00
40.50
3.45
0.36
0.00
42.00
3.45
0.36
0.00
43.50
3.45
0.36
0.00
45.00
3.45
0.36
0.00
46.50
3.45
0.36
0.00
48.00
3.45
0.36
0.00
49.50
3.45
0.36
0.00
51.00
3.45
0.36
0.00
52.50
3.45
0.36
0.00
54.00
3.45
0.36
0.00
55.50
3.45
0.36
0.00
57.00
3.45
0.36
0.00
58.50
3.45
0.36
0.00
60.00
3.45
0.36
0.00
61.50
3.45
0.36
0.00
63.00
3.45
0.36
0.00
64.50
3.45
0.36
0.00
66.00
3.45
0.36
0.00
67.50
3.45
0.36
0.00
69.00
3.45
0.36
0.00
70.50
3.45
0.36
0.00
72.00
3.45
0.36
0.00
73.50
3.45
0.36
0.00
75.00
3.45
0.36
0.00
76.50
3.45
0.36
0.00
78.00
3.45
0.36
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
3.45
0.36
0.00
81.00
3.45
0.36
0.00
82.50
3.45
0.36
0.00
84.00
3.45
0.36
0.00
85.50
3.45
0.36
0.00
87.00
3.45
0.36
0.00
88.50
3.45
0.36
0.00
90.00
3.45
0.36
0.00
91.50
3.45
0.36
0.00
93.00
3.45
0.36
0.00
94.50
3.45
0.36
0.00
96.00
3.45
0.36
0.00
97.50
3.45
0.36
0.00
99.00
3.45
0.36
0.00
100.50
3.45
0.36
0.00
102.00
3.45
0.36
0.00
103.50
3.45
0.36
0.00
105.00
3.45
0.36
0.00
106.50
3.45
0.36
0.00
108.00
3.45
0.36
0.00
109.50
3.45
0.36
0.00
111.00
3.45
0.36
0.00
112.50
3.45
0.36
0.00
114.00
3.45
0.36
0.00
115.50
3.45
0.36
0.00
117.00
3.45
0.36
0.00
118.50
3.45
0.36
0.00
120.00
3.45
0.36
0.00
121.50
3.45
0.36
0.00
123.00
3.45
0.36
0.00
124.50
3.45
0.36
0.00
126.00
3.45
0.36
0.00
127.50
3.45
0.36
0.00
129.00
3.45
0.36
0.00
130.50
3.45
0.36
0.00
132.00
3.45
0.36
0.00
133.50
3.45
0.36
0.00
135.00
3.45
0.36
0.00

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 15
Summary for Subcatchment 2: Postdeveloped
Runoff = 12.11 cfs @ 11.97 hrs, Volume= 0.546 af, Depth= 1.33"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 2-yr Rainfall=3.45"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
' � � � � � � � � � � � � ■Runoff
13 12.11 cfs 1--------- ---- ---- ---- ------------------------ ---
12 Type -I I-24-h r -
------r----r----+----+----------------- 2-yx Rai nfall=145---
10 - - - - - 'Runo#f-Are&4.J3aac--
--- ---r----r----r------ --- rr----r----r
- - Rp noff Vo(umq=O: $46- # -
H $ ---
7 -Runoff-Depfh=1.33.r-
LL 6 --- -- ----------------;---- T�=5.© mil
- - - - - - L - - - - L - - - - L - - - - L - - - - L - - - - - - - - L - - - - -'- - - - -'- - - - -'- - - - -'- - - - -'- - -
5 -- C'N=76
-- --- ---- ---- --------+---- ---- ----- - - -
4
--- --- ---- ---- ---- ---- ---- ---- ----------------------------
3
-- ---r----r----+----+----rt--------y-------------------------r--
2
- - - - r - - - - T - - - - T - - - - T - - - - 7 - - - - - - - - - -
20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 16
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.06
0.00
0.00
3.00
0.12
0.00
0.00
4.50
0.19
0.00
0.00
6.00
0.28
0.00
0.00
7.50
0.38
0.00
0.00
9.00
0.51
0.00
0.00
10.50
0.70
0.00
0.03
12.00
2.29
0.57
10.68
13.50
2.76
0.85
0.54
15.00
2.94
0.98
0.35
16.50
3.07
1.07
0.26
18.00
3.18
1.14
0.22
19.50
3.26
1.19
0.17
21.00
3.33
1.24
0.15
22.50
3.39
1.29
0.14
24.00
3.45
1.33
0.14
25.50
3.45
1.33
0.00
27.00
3.45
1.33
0.00
28.50
3.45
1.33
0.00
30.00
3.45
1.33
0.00
31.50
3.45
1.33
0.00
33.00
3.45
1.33
0.00
34.50
3.45
1.33
0.00
36.00
3.45
1.33
0.00
37.50
3.45
1.33
0.00
39.00
3.45
1.33
0.00
40.50
3.45
1.33
0.00
42.00
3.45
1.33
0.00
43.50
3.45
1.33
0.00
45.00
3.45
1.33
0.00
46.50
3.45
1.33
0.00
48.00
3.45
1.33
0.00
49.50
3.45
1.33
0.00
51.00
3.45
1.33
0.00
52.50
3.45
1.33
0.00
54.00
3.45
1.33
0.00
55.50
3.45
1.33
0.00
57.00
3.45
1.33
0.00
58.50
3.45
1.33
0.00
60.00
3.45
1.33
0.00
61.50
3.45
1.33
0.00
63.00
3.45
1.33
0.00
64.50
3.45
1.33
0.00
66.00
3.45
1.33
0.00
67.50
3.45
1.33
0.00
69.00
3.45
1.33
0.00
70.50
3.45
1.33
0.00
72.00
3.45
1.33
0.00
73.50
3.45
1.33
0.00
75.00
3.45
1.33
0.00
76.50
3.45
1.33
0.00
78.00
3.45
1.33
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
3.45
1.33
0.00
81.00
3.45
1.33
0.00
82.50
3.45
1.33
0.00
84.00
3.45
1.33
0.00
85.50
3.45
1.33
0.00
87.00
3.45
1.33
0.00
88.50
3.45
1.33
0.00
90.00
3.45
1.33
0.00
91.50
3.45
1.33
0.00
93.00
3.45
1.33
0.00
94.50
3.45
1.33
0.00
96.00
3.45
1.33
0.00
97.50
3.45
1.33
0.00
99.00
3.45
1.33
0.00
100.50
3.45
1.33
0.00
102.00
3.45
1.33
0.00
103.50
3.45
1.33
0.00
105.00
3.45
1.33
0.00
106.50
3.45
1.33
0.00
108.00
3.45
1.33
0.00
109.50
3.45
1.33
0.00
111.00
3.45
1.33
0.00
112.50
3.45
1.33
0.00
114.00
3.45
1.33
0.00
115.50
3.45
1.33
0.00
117.00
3.45
1.33
0.00
118.50
3.45
1.33
0.00
120.00
3.45
1.33
0.00
121.50
3.45
1.33
0.00
123.00
3.45
1.33
0.00
124.50
3.45
1.33
0.00
126.00
3.45
1.33
0.00
127.50
3.45
1.33
0.00
129.00
3.45
1.33
0.00
130.50
3.45
1.33
0.00
132.00
3.45
1.33
0.00
133.50
3.45
1.33
0.00
135.00
3.45
1.33
0.00

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 17
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area = 4.930 ac, 41.58% Impervious, Inflow Depth = 1.33" for 2-yr event
Inflow = 12.11 cfs @ 11.97 hrs, Volume= 0.546 of
Outflow = 0.62 cfs @ 13.23 hrs, Volume= 0.546 af, Atten= 95%, Lag= 75.7 min
Primary = 0.62 cfs @ 13.23 hrs, Volume= 0.546 of
Routing by Stor-Ind method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 907.94' @ 13.23 hrs Surf.Area= 6,251 sf Storage= 12,275 cf
Flood Elev= 911.00' Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 1,085.8 min calculated for 0.546 of (100% of inflow)
Center -of -Mass det. time= 1,085.7 min ( 1,932.7 - 847.0 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
905.00 600 0 0
906.00 4,065 2,333 2,333
907.00 5,140 4,603 6,935
908.00 6,325 5,733 12,668
909.00 7,625 6,975 19,643
910.00 9,612 8,619 28,261
911.00 10,845 10,229 38,490
Device Routing Invert Outlet Devices
#1 Primary 902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1 905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1 907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1 910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=0.62 cfs @ 13.23 hrs HW=907.94' (Free Discharge)
L1=Outlet Pipe (Passes 0.62 cfs of 18.42 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.05 cfs)
3=Orifice (Orifice Controls 0.57 cfs @ 2.88 fps)
4=Grate Top ( Controls 0.00 cfs)

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 18
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
■ Inflow
12.11 CfS------------------4----+------�---- ---�-- ❑ Primary
13 -------''I-----''I------------------ !anflowArea= 930ar
12
11 ---------------------T---- T ---- T---- 'Peo-E'',1ev=9o-7--94' -
10 -------'I-----'I----JI----JI----1----1--- L-L----I--- -I-- '- - J
- Storaae=12,275 cf
9 ---------------- --------+----------------- -----i----------
8 --- ----I -----
--- T---- T---- T----T- - --
----i ---- --
y I I I I I I I I I I I I � I
w
`-' 7 I I I I I I I I I I I I
3
LL
i
4 ___ _____________T----T----T____T---- r---- r------------------T--
i
3 �I
I I I I I I I I I I I I
-I- - - - J - - - - J - - - - 1 - - - - 1 - - - - L - - - - L - - - -I- - - - -'- - - - -I- - - - J - -
2 I I I I I I I I I I I I
1 0.62 cfs
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 19
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.00
0
905.00
0.00
12.00
10.68
7,920
907.19
0.05
15.00
0.35
11,456
907.80
0.50
18.00
0.22
10,362
907.62
0.27
21.00
0.15
9,915
907.55
0.18
24.00
0.14
9,748
907.52
0.15
27.00
0.00
8,879
907.36
0.05
30.00
0.00
8,365
907.27
0.05
33.00
0.00
7,868
907.18
0.05
36.00
0.00
7,380
907.09
0.04
39.00
0.00
6,901
906.99
0.04
42.00
0.00
6,432
906.90
0.04
45.00
0.00
5,972
906.81
0.04
48.00
0.00
5,523
906.72
0.04
51.00
0.00
5,083
906.62
0.04
54.00
0.00
4,653
906.53
0.04
57.00
0.00
4,233
906.44
0.04
60.00
0.00
3,823
906.35
0.04
63.00
0.00
3,423
906.26
0.04
66.00
0.00
3,033
906.17
0.04
69.00
0.00
2,652
906.08
0.03
72.00
0.00
2,282
905.99
0.03
75.00
0.00
1,936
905.90
0.03
78.00
0.00
1,622
905.81
0.03
81.00
0.00
1,341
905.72
0.02
84.00
0.00
1,091
905.64
0.02
87.00
0.00
872
905.56
0.02
90.00
0.00
682
905.48
0.02
93.00
0.00
521
905.40
0.01
96.00
0.00
387
905.33
0.01
99.00
0.00
278
905.26
0.01
102.00
0.00
193
905.20
0.01
105.00
0.00
129
905.15
0.01
108.00
0.00
83
905.10
0.00
111.00
0.00
51
905.07
0.00
114.00
0.00
30
905.04
0.00
117.00
0.00
18
905.03
0.00
120.00
0.00
11
905.02
0.00
123.00
0.00
6
905.01
0.00
126.00
0.00
4
905.01
0.00
129.00
0.00
2
905.00
0.00
132.00
0.00
1
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 20
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type/1 24-hr 2-yr Rainfall=3.45"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 21
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

10 YR ROUTING
CALCULATIONS

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 22
Summary for Subcatchment 1: Predeveloped
Runoff = 4.89 cfs @ 12.29 hrs, Volume= 0.580 af, Depth= 1.09"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 10-yr Rainfall=5.09"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
Subcatchment 1: Predeveloped
Hydrograph
■Runoff
4.89 cfs ---- ---- ---- ---- ---- ---- ---- ---- -- -
5 Type 11 124-1l'r
- L L --------i--10,-yr-Rainfal1-,5.09
4 Runoff Area=6.400 ad
Runoff Vol'umq=0.580 elf
3 Runoft Depth=1.0"
Tc:*0.0 min
2 C,N=56
1
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 23
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.08
0.00
0.00
3.00
0.18
0.00
0.00
4.50
0.28
0.00
0.00
6.00
0.41
0.00
0.00
7.50
0.56
0.00
0.00
9.00
0.75
0.00
0.00
10.50
1.04
0.00
0.00
12.00
3.37
0.34
1.05
13.50
4.07
0.60
0.85
15.00
4.34
0.72
0.49
16.50
4.54
0.81
0.36
18.00
4.69
0.89
0.30
19.50
4.81
0.95
0.25
21.00
4.91
1.00
0.21
22.50
5.00
1.04
0.20
24.00
5.09
1.09
0.19
25.50
5.09
1.09
0.00
27.00
5.09
1.09
0.00
28.50
5.09
1.09
0.00
30.00
5.09
1.09
0.00
31.50
5.09
1.09
0.00
33.00
5.09
1.09
0.00
34.50
5.09
1.09
0.00
36.00
5.09
1.09
0.00
37.50
5.09
1.09
0.00
39.00
5.09
1.09
0.00
40.50
5.09
1.09
0.00
42.00
5.09
1.09
0.00
43.50
5.09
1.09
0.00
45.00
5.09
1.09
0.00
46.50
5.09
1.09
0.00
48.00
5.09
1.09
0.00
49.50
5.09
1.09
0.00
51.00
5.09
1.09
0.00
52.50
5.09
1.09
0.00
54.00
5.09
1.09
0.00
55.50
5.09
1.09
0.00
57.00
5.09
1.09
0.00
58.50
5.09
1.09
0.00
60.00
5.09
1.09
0.00
61.50
5.09
1.09
0.00
63.00
5.09
1.09
0.00
64.50
5.09
1.09
0.00
66.00
5.09
1.09
0.00
67.50
5.09
1.09
0.00
69.00
5.09
1.09
0.00
70.50
5.09
1.09
0.00
72.00
5.09
1.09
0.00
73.50
5.09
1.09
0.00
75.00
5.09
1.09
0.00
76.50
5.09
1.09
0.00
78.00
5.09
1.09
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
5.09
1.09
0.00
81.00
5.09
1.09
0.00
82.50
5.09
1.09
0.00
84.00
5.09
1.09
0.00
85.50
5.09
1.09
0.00
87.00
5.09
1.09
0.00
88.50
5.09
1.09
0.00
90.00
5.09
1.09
0.00
91.50
5.09
1.09
0.00
93.00
5.09
1.09
0.00
94.50
5.09
1.09
0.00
96.00
5.09
1.09
0.00
97.50
5.09
1.09
0.00
99.00
5.09
1.09
0.00
100.50
5.09
1.09
0.00
102.00
5.09
1.09
0.00
103.50
5.09
1.09
0.00
105.00
5.09
1.09
0.00
106.50
5.09
1.09
0.00
108.00
5.09
1.09
0.00
109.50
5.09
1.09
0.00
111.00
5.09
1.09
0.00
112.50
5.09
1.09
0.00
114.00
5.09
1.09
0.00
115.50
5.09
1.09
0.00
117.00
5.09
1.09
0.00
118.50
5.09
1.09
0.00
120.00
5.09
1.09
0.00
121.50
5.09
1.09
0.00
123.00
5.09
1.09
0.00
124.50
5.09
1.09
0.00
126.00
5.09
1.09
0.00
127.50
5.09
1.09
0.00
129.00
5.09
1.09
0.00
130.50
5.09
1.09
0.00
132.00
5.09
1.09
0.00
133.50
5.09
1.09
0.00
135.00
5.09
1.09
0.00

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 24
Summary for Subcatchment 2: Postdeveloped
Runoff = 23.64 cfs @ 11.96 hrs, Volume= 1.072 af, Depth= 2.61"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 10-yr Rainfall=5.09"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
26 --------+----+----+---- +---- +----+----+-------------------------r-- ■Runoff
25 23.64 cfs ----- ---- ---- ----
24 ------r----r----r----+----r----r----r-----------T--/�i-p------w---r--
23 ------'----- i ---- -'----------'------------------ - -' Type �A-hr _
22 --- r----r----+----+----7---------------------------------�--
------L---- 1---- 1---- 1----
1----
I/
---- --9-0= 1r RC-flrfafr��
------------------------------ - -- - -
- ---- --- ---- ---- ---- --
19
Run
ff Area"-4.930ac
18 ----------+--------------------�i -i -
17 ------+----+----+----+----+----+--��0 1'�-Y���u- 1�l-072- -
16 --- -----------------------------
w 15 ------+----+----+----+----+----+----+-- ---- - ---- c ---
14 ----------- ----- ---- ---- ---- -------Runoff DepthI2.fT17 -
3 13 ------+----+----+----+----+----+----+----+-----1---yy�,.�
a11 --- -- -- -- -- -- -- ------------ T � -- I- -
19 --- -- -- -- -- -- -- -- ----- --- --'i- VN�76_
-r- -
r- -r- -+- -r- -r- -r- -i-- -I-- -i-- -I- -r
--- ---
6 --- --- ---- ---- ---- ---- -----------------------------'-----L
4 ---X,--- ---- ---- ---- ---- ---- ---- ----------------------------
3 ------r----r---- + ---- + --------------------------------------i --
2 ------+----+----+-- +----+----+----+----------i---------i-- -i---
20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 25
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.08
0.00
0.00
3.00
0.18
0.00
0.00
4.50
0.28
0.00
0.00
6.00
0.41
0.00
0.00
7.50
0.56
0.00
0.00
9.00
0.75
0.00
0.05
10.50
1.04
0.05
0.26
12.00
3.37
1.28
20.42
13.50
4.07
1.79
0.96
15.00
4.34
2.01
0.61
16.50
4.54
2.16
0.44
18.00
4.69
2.28
0.37
19.50
4.81
2.38
0.30
21.00
4.91
2.46
0.26
22.50
5.00
2.54
0.25
24.00
5.09
2.61
0.23
25.50
5.09
2.61
0.00
27.00
5.09
2.61
0.00
28.50
5.09
2.61
0.00
30.00
5.09
2.61
0.00
31.50
5.09
2.61
0.00
33.00
5.09
2.61
0.00
34.50
5.09
2.61
0.00
36.00
5.09
2.61
0.00
37.50
5.09
2.61
0.00
39.00
5.09
2.61
0.00
40.50
5.09
2.61
0.00
42.00
5.09
2.61
0.00
43.50
5.09
2.61
0.00
45.00
5.09
2.61
0.00
46.50
5.09
2.61
0.00
48.00
5.09
2.61
0.00
49.50
5.09
2.61
0.00
51.00
5.09
2.61
0.00
52.50
5.09
2.61
0.00
54.00
5.09
2.61
0.00
55.50
5.09
2.61
0.00
57.00
5.09
2.61
0.00
58.50
5.09
2.61
0.00
60.00
5.09
2.61
0.00
61.50
5.09
2.61
0.00
63.00
5.09
2.61
0.00
64.50
5.09
2.61
0.00
66.00
5.09
2.61
0.00
67.50
5.09
2.61
0.00
69.00
5.09
2.61
0.00
70.50
5.09
2.61
0.00
72.00
5.09
2.61
0.00
73.50
5.09
2.61
0.00
75.00
5.09
2.61
0.00
76.50
5.09
2.61
0.00
78.00
5.09
2.61
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
5.09
2.61
0.00
81.00
5.09
2.61
0.00
82.50
5.09
2.61
0.00
84.00
5.09
2.61
0.00
85.50
5.09
2.61
0.00
87.00
5.09
2.61
0.00
88.50
5.09
2.61
0.00
90.00
5.09
2.61
0.00
91.50
5.09
2.61
0.00
93.00
5.09
2.61
0.00
94.50
5.09
2.61
0.00
96.00
5.09
2.61
0.00
97.50
5.09
2.61
0.00
99.00
5.09
2.61
0.00
100.50
5.09
2.61
0.00
102.00
5.09
2.61
0.00
103.50
5.09
2.61
0.00
105.00
5.09
2.61
0.00
106.50
5.09
2.61
0.00
108.00
5.09
2.61
0.00
109.50
5.09
2.61
0.00
111.00
5.09
2.61
0.00
112.50
5.09
2.61
0.00
114.00
5.09
2.61
0.00
115.50
5.09
2.61
0.00
117.00
5.09
2.61
0.00
118.50
5.09
2.61
0.00
120.00
5.09
2.61
0.00
121.50
5.09
2.61
0.00
123.00
5.09
2.61
0.00
124.50
5.09
2.61
0.00
126.00
5.09
2.61
0.00
127.50
5.09
2.61
0.00
129.00
5.09
2.61
0.00
130.50
5.09
2.61
0.00
132.00
5.09
2.61
0.00
133.50
5.09
2.61
0.00
135.00
5.09
2.61
0.00

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 26
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area =
4.930 ac, 41.58% Impervious, Inflow Depth = 2.61" for 10-yr event
Inflow = 23.64 cfs @ 11.96 hrs, Volume= 1.072 of
Outflow =
1.41 cfs @ 12.83 hrs, Volume= 1.072 af, Atten= 94%, Lag= 52.3 min
Primary =
1.41 cfs @ 12.83 hrs, Volume= 1.072 of
Routing by Stor-Ind
method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 909.58'
@ 12.83 hrs Surf.Area= 8,783 sf Storage= 24,423 cf
Flood Elev= 911.00'
Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention
time= 648.2 min calculated for 1.072 of (100% of inflow)
Center -of -Mass det.
time= 648.1 min ( 1,475.5 - 827.4 )
Volume Invert Avail.Storage Storage Description
#1 905.00'
38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area
Inc.Store Cum.Store
(feet)
(sq-ft) (cubic -feet) (cubic -feet)
905.00
600 0 0
906.00
4,065 2,333 2,333
907.00
5,140 4,603 6,935
908.00
6,325 5,733 12,668
909.00
7,625 6,975 19,643
910.00
9,612 8,619 28,261
911.00
10,845 10,229 38,490
Device Routing
Invert Outlet Devices
#1 Primary
902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1
905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1
907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1
910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=1.41 cfs @ 12.83 hrs HW=909.58' (Free Discharge)
L1=Outlet Pipe (Passes 1.41 cfs of 21.41 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.07 cfs)
3=Orifice (Orifice Controls 1.34 cfs @ 6.81 fps)
4=Grate Top ( Controls 0.00 cfs)

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 27
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
-------------------------- ----
■ Inflow
26 23.64 CfS---------1----I--L---- I --- -- ❑ Primary
24 �'I -------------------------- ---- 1nflowArea=4.-93aac--
' --- -----------------rt-
22 - - - �Pea- E'jev=90�.-58 -
20 -------r----I---- --------7----T----r----r --
___ ___- torage=24 4Z3_cf -
18 ,�I i i i i i i I I I I '� I I
,
' - - - -'- - - - -'- - - - 1 - - - - 1 - - - - 1 - - - - 1 - - - - L - - - - L - - - -'- - - - -'- - - - -'- - - - 1 - -
16 ___ I I I I I I I I I I I I
N
14 ------------------------ ---- - - - -i - - - -i ------------------
--
3
I I I I I I I I I I
LL
I I I I I I I I I I I I I
8 -
,
6 4 �II II II II II II II -- - - - III ---- - III ----
1.4
--
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 28
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.05
57
905.08
0.00
12.00
20.42
18,153
908.80
1.11
15.00
0.61
20,672
909.13
1.24
18.00
0.37
14,351
908.26
0.83
21.00
0.26
10,974
907.73
0.41
24.00
0.23
10,299
907.61
0.26
27.00
0.00
9,039
907.39
0.06
30.00
0.00
8,497
907.29
0.05
33.00
0.00
7,997
907.20
0.05
36.00
0.00
7,507
907.11
0.04
39.00
0.00
7,025
907.02
0.04
42.00
0.00
6,553
906.93
0.04
45.00
0.00
6,091
906.83
0.04
48.00
0.00
5,639
906.74
0.04
51.00
0.00
5,197
906.65
0.04
54.00
0.00
4,765
906.56
0.04
57.00
0.00
4,342
906.47
0.04
60.00
0.00
3,930
906.37
0.04
63.00
0.00
3,527
906.28
0.04
66.00
0.00
3,134
906.19
0.04
69.00
0.00
2,751
906.10
0.04
72.00
0.00
2,378
906.01
0.03
75.00
0.00
2,023
905.92
0.03
78.00
0.00
1,701
905.83
0.03
81.00
0.00
1,412
905.75
0.03
84.00
0.00
1,153
905.66
0.02
87.00
0.00
926
905.58
0.02
90.00
0.00
729
905.50
0.02
93.00
0.00
560
905.42
0.01
96.00
0.00
419
905.35
0.01
99.00
0.00
304
905.28
0.01
102.00
0.00
213
905.22
0.01
105.00
0.00
144
905.16
0.01
108.00
0.00
93
905.12
0.00
111.00
0.00
58
905.08
0.00
114.00
0.00
35
905.05
0.00
117.00
0.00
21
905.03
0.00
120.00
0.00
12
905.02
0.00
123.00
0.00
7
905.01
0.00
126.00
0.00
4
905.01
0.00
129.00
0.00
3
905.00
0.00
132.00
0.00
2
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 29
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type 11 24-hr 10-yr Rainfall=5.09"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 30
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

25 YR ROUTING
CALCULATIONS

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 31
Summary for Subcatchment 1: Predeveloped
Runoff = 8.07 cfs @ 12.28 hrs, Volume= 0.877 af, Depth= 1.64"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 25-yr Rainfall=6.08"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
Subcatchment 1: Predeveloped
Hydrograph
----r----r----r-----r----r----r--- ----r----r----r--
9
8.07 CfS ■Runoff
Type 11 124-1l'r
----------------------------------
7 -2 -yr-Fain an=6.08"-
---r---- T---- T---- T---- T----T ---- Runoff Area=6.400-ao-
6
------ Runoff
Vol�umq=0.077-Of-
5 Runoff Depth=1.64,"
--------------------------
4 Tc:*0.0 mire
--—----T———— T———— T———— T———— T——— —T ---- ---- -------GN=56-
3
2
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 32
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.10
0.00
0.00
3.00
0.21
0.00
0.00
4.50
0.34
0.00
0.00
6.00
0.49
0.00
0.00
7.50
0.66
0.00
0.00
9.00
0.89
0.00
0.00
10.50
1.24
0.00
0.00
12.00
4.03
0.59
2.34
13.50
4.86
0.97
1.21
15.00
5.19
1.14
0.68
16.50
5.42
1.26
0.50
18.00
5.60
1.37
0.42
19.50
5.75
1.45
0.35
21.00
5.87
1.52
0.29
22.50
5.98
1.58
0.28
24.00
6.08
1.64
0.26
25.50
6.08
1.64
0.00
27.00
6.08
1.64
0.00
28.50
6.08
1.64
0.00
30.00
6.08
1.64
0.00
31.50
6.08
1.64
0.00
33.00
6.08
1.64
0.00
34.50
6.08
1.64
0.00
36.00
6.08
1.64
0.00
37.50
6.08
1.64
0.00
39.00
6.08
1.64
0.00
40.50
6.08
1.64
0.00
42.00
6.08
1.64
0.00
43.50
6.08
1.64
0.00
45.00
6.08
1.64
0.00
46.50
6.08
1.64
0.00
48.00
6.08
1.64
0.00
49.50
6.08
1.64
0.00
51.00
6.08
1.64
0.00
52.50
6.08
1.64
0.00
54.00
6.08
1.64
0.00
55.50
6.08
1.64
0.00
57.00
6.08
1.64
0.00
58.50
6.08
1.64
0.00
60.00
6.08
1.64
0.00
61.50
6.08
1.64
0.00
63.00
6.08
1.64
0.00
64.50
6.08
1.64
0.00
66.00
6.08
1.64
0.00
67.50
6.08
1.64
0.00
69.00
6.08
1.64
0.00
70.50
6.08
1.64
0.00
72.00
6.08
1.64
0.00
73.50
6.08
1.64
0.00
75.00
6.08
1.64
0.00
76.50
6.08
1.64
0.00
78.00
6.08
1.64
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
6.08
1.64
0.00
81.00
6.08
1.64
0.00
82.50
6.08
1.64
0.00
84.00
6.08
1.64
0.00
85.50
6.08
1.64
0.00
87.00
6.08
1.64
0.00
88.50
6.08
1.64
0.00
90.00
6.08
1.64
0.00
91.50
6.08
1.64
0.00
93.00
6.08
1.64
0.00
94.50
6.08
1.64
0.00
96.00
6.08
1.64
0.00
97.50
6.08
1.64
0.00
99.00
6.08
1.64
0.00
100.50
6.08
1.64
0.00
102.00
6.08
1.64
0.00
103.50
6.08
1.64
0.00
105.00
6.08
1.64
0.00
106.50
6.08
1.64
0.00
108.00
6.08
1.64
0.00
109.50
6.08
1.64
0.00
111.00
6.08
1.64
0.00
112.50
6.08
1.64
0.00
114.00
6.08
1.64
0.00
115.50
6.08
1.64
0.00
117.00
6.08
1.64
0.00
118.50
6.08
1.64
0.00
120.00
6.08
1.64
0.00
121.50
6.08
1.64
0.00
123.00
6.08
1.64
0.00
124.50
6.08
1.64
0.00
126.00
6.08
1.64
0.00
127.50
6.08
1.64
0.00
129.00
6.08
1.64
0.00
130.50
6.08
1.64
0.00
132.00
6.08
1.64
0.00
133.50
6.08
1.64
0.00
135.00
6.08
1.64
0.00

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 33
Summary for Subcatchment 2: Postdeveloped
Runoff = 30.97 cfs @ 11.96 hrs, Volume= 1.417 af, Depth= 3.45"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 25-yr Rainfall=6.08"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
34 ----i ---- i-----T---- i ---- i ---- i ---- i-----i-----i-----i-----i-----i-----li -- ■Runoff
32
30.97 cfs r----T----7----T----7---- ---- ----------------------------
------------------------------------------
30 L--------1----1----1--------J-----------T Pe _II 24-hr -
28 - -------- ---2-5-yr Rairtfall=&.08"--
26
----T---- T---- 7---- T---- 7 ----7 ----
24 _'Run'off-Area",4.S80 -ad-
w 20 =18 - --- --- -- __ RunoffDepfh=,3.45
T----T
-----7----T----7--------7-------------T}.— C /�
0 16 - 1 -t= i i0 -m !h- -
LL
-- ---r----r----r----+----r----r----r-----i-----i--
14 --- --- ---- ---- ---- ---- ---- -------------------i-- �+1 1
12 -Vi1�1��V
--- ---I---------------------------------------------------------
10 I I TT
I
--- --- -------- ---- ---- 7 ---- �-
--------------------------------
8
4
2
20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 34
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.10
0.00
0.00
3.00
0.21
0.00
0.00
4.50
0.34
0.00
0.00
6.00
0.49
0.00
0.00
7.50
0.66
0.00
0.01
9.00
0.89
0.02
0.13
10.50
1.24
0.10
0.44
12.00
4.03
1.76
26.56
13.50
4.86
2.42
1.21
15.00
5.19
2.69
0.77
16.50
5.42
2.88
0.56
18.00
5.60
3.04
0.47
19.50
5.75
3.16
0.37
21.00
5.87
3.26
0.33
22.50
5.98
3.36
0.31
24.00
6.08
3.45
0.29
25.50
6.08
3.45
0.00
27.00
6.08
3.45
0.00
28.50
6.08
3.45
0.00
30.00
6.08
3.45
0.00
31.50
6.08
3.45
0.00
33.00
6.08
3.45
0.00
34.50
6.08
3.45
0.00
36.00
6.08
3.45
0.00
37.50
6.08
3.45
0.00
39.00
6.08
3.45
0.00
40.50
6.08
3.45
0.00
42.00
6.08
3.45
0.00
43.50
6.08
3.45
0.00
45.00
6.08
3.45
0.00
46.50
6.08
3.45
0.00
48.00
6.08
3.45
0.00
49.50
6.08
3.45
0.00
51.00
6.08
3.45
0.00
52.50
6.08
3.45
0.00
54.00
6.08
3.45
0.00
55.50
6.08
3.45
0.00
57.00
6.08
3.45
0.00
58.50
6.08
3.45
0.00
60.00
6.08
3.45
0.00
61.50
6.08
3.45
0.00
63.00
6.08
3.45
0.00
64.50
6.08
3.45
0.00
66.00
6.08
3.45
0.00
67.50
6.08
3.45
0.00
69.00
6.08
3.45
0.00
70.50
6.08
3.45
0.00
72.00
6.08
3.45
0.00
73.50
6.08
3.45
0.00
75.00
6.08
3.45
0.00
76.50
6.08
3.45
0.00
78.00
6.08
3.45
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
6.08
3.45
0.00
81.00
6.08
3.45
0.00
82.50
6.08
3.45
0.00
84.00
6.08
3.45
0.00
85.50
6.08
3.45
0.00
87.00
6.08
3.45
0.00
88.50
6.08
3.45
0.00
90.00
6.08
3.45
0.00
91.50
6.08
3.45
0.00
93.00
6.08
3.45
0.00
94.50
6.08
3.45
0.00
96.00
6.08
3.45
0.00
97.50
6.08
3.45
0.00
99.00
6.08
3.45
0.00
100.50
6.08
3.45
0.00
102.00
6.08
3.45
0.00
103.50
6.08
3.45
0.00
105.00
6.08
3.45
0.00
106.50
6.08
3.45
0.00
108.00
6.08
3.45
0.00
109.50
6.08
3.45
0.00
111.00
6.08
3.45
0.00
112.50
6.08
3.45
0.00
114.00
6.08
3.45
0.00
115.50
6.08
3.45
0.00
117.00
6.08
3.45
0.00
118.50
6.08
3.45
0.00
120.00
6.08
3.45
0.00
121.50
6.08
3.45
0.00
123.00
6.08
3.45
0.00
124.50
6.08
3.45
0.00
126.00
6.08
3.45
0.00
127.50
6.08
3.45
0.00
129.00
6.08
3.45
0.00
130.50
6.08
3.45
0.00
132.00
6.08
3.45
0.00
133.50
6.08
3.45
0.00
135.00
6.08
3.45
0.00

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 35
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area =
4.930 ac, 41.58% Impervious, Inflow Depth = 3.45" for 25-yr event
Inflow =
30.97 cfs @ 11.96 hrs, Volume= 1.417 of
Outflow =
5.17 cfs @ 12.14 hrs, Volume= 1.417 af, Atten= 83%, Lag= 10.8 min
Primary =
5.17 cfs @ 12.14 hrs, Volume= 1.417 of
Routing by Stor-Ind
method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 910.17' @ 12.14 hrs Surf.Area= 9,818 sf Storage= 29,881 cf
Flood Elev= 911.00'
Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 532.5 min calculated for 1.417 of (100% of inflow)
Center -of -Mass det. time= 532.5 min ( 1,351.9 - 819.4 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation
Surf.Area Inc.Store Cum.Store
(feet)
(sq-ft) (cubic -feet) (cubic -feet)
905.00
600 0 0
906.00
4,065 2,333 2,333
907.00
5,140 4,603 6,935
908.00
6,325 5,733 12,668
909.00
7,625 6,975 19,643
910.00
9,612 8,619 28,261
911.00
10,845 10,229 38,490
Device Routing
Invert Outlet Devices
#1 Primary
902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1
905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1
907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1
910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=5.14 cfs @ 12.14 hrs HW=910.17' (Free Discharge)
L1=Outlet Pipe (Passes 5.14 cfs of 22.38 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.07 cfs)
3=Orifice (Orifice Controls 1.52 cfs @ 7.74 fps)
4=Grate Top (Weir Controls 3.54 cfs @ 1.33 fps)

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 36
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
-------------------------- ----
■ Inflow
34 � 30.97 CfS r--------------,---- ----------------------------------- ■Primary
32 Jn owArea � '0
26
24 ----------------------i---- li ---- li - - - -'i `1D1 age=29881 cif
22
w20 -------------------------- ---- ---- ---- ---------------------
-------r----r--- ---- --------T----r----r----r----r----i---- --
18
0 16
14
12
$ 5.17 cfs--------I-----7----T----r----r------------------�--
6
------------r----r----r----r----r----r----r-------------r--
4
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 37
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.13
301
905.28
0.01
12.00
26.56
25,220
909.67
1.44
15.00
0.77
25,044
909.65
1.43
18.00
0.47
17,652
908.73
1.08
21.00
0.33
12,461
907.97
0.64
24.00
0.29
10,703
907.68
0.35
27.00
0.00
9,124
907.41
0.07
30.00
0.00
8,559
907.31
0.05
33.00
0.00
8,059
907.21
0.05
36.00
0.00
7,567
907.12
0.05
39.00
0.00
7,085
907.03
0.04
42.00
0.00
6,611
906.94
0.04
45.00
0.00
6,148
906.84
0.04
48.00
0.00
5,695
906.75
0.04
51.00
0.00
5,251
906.66
0.04
54.00
0.00
4,818
906.57
0.04
57.00
0.00
4,394
906.48
0.04
60.00
0.00
3,980
906.39
0.04
63.00
0.00
3,576
906.29
0.04
66.00
0.00
3,182
906.20
0.04
69.00
0.00
2,798
906.11
0.04
72.00
0.00
2,423
906.02
0.03
75.00
0.00
2,065
905.93
0.03
78.00
0.00
1,739
905.84
0.03
81.00
0.00
1,446
905.76
0.03
84.00
0.00
1,184
905.67
0.02
87.00
0.00
953
905.59
0.02
90.00
0.00
752
905.51
0.02
93.00
0.00
580
905.43
0.01
96.00
0.00
435
905.36
0.01
99.00
0.00
317
905.29
0.01
102.00
0.00
223
905.22
0.01
105.00
0.00
151
905.17
0.01
108.00
0.00
99
905.12
0.00
111.00
0.00
62
905.08
0.00
114.00
0.00
37
905.05
0.00
117.00
0.00
22
905.03
0.00
120.00
0.00
13
905.02
0.00
123.00
0.00
8
905.01
0.00
126.00
0.00
5
905.01
0.00
129.00
0.00
3
905.00
0.00
132.00
0.00
2
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 38
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type/1 24-hr 25-yr Rainfall=6.08"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 39
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

SO YR ROUTING
CALCULATIONS

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 40
Summary for Subcatchment 1: Predeveloped
Runoff = 10.94 cfs @ 12.27 hrs, Volume= 1.142 af, Depth= 2.14"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 50-yr Rainfall=6.88"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
Subcatchment 1: Predeveloped
Hydrograph
12 ■Runoff
10.94 cfs T---- T---- T--- -T - -------T- - - -T
11 ----' TyRe-H-Z4-b'r -
10 ------+----+----+----+----+----+----+--5O-yrRainfall='6-88� -
-----L----1----1----1---- 1---- 1---- jiRuni'a#f-Ares-6.400 ac--
8 - - - - - -Rpnoff-V-0(EI mq=1. a'42 elf- -
N 7
.�V.. ------+----+---- ---- ---- -------- ---�\M. off DTeI-�.%`—2.UII"--
�° 6 ----- r---- T---- T---- T----T--------T------------rFi,��V�-�--
5 ^ ww'' CC
------+----+----+----+----+----+----+---------------i---
LiiY J6
4
-
--- ---+----+----+----+----+----+----+-----i-----i----+-----+----+--
3
- - - - - - + - - - - + - - - - + - - - - + - - - - 1 - - - - - - - - J - - - - -'- - - - -'- - - - -'- - - - -'- - - - -'- - -
2
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 41
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.11
0.00
0.00
3.00
0.24
0.00
0.00
4.50
0.38
0.00
0.00
6.00
0.55
0.00
0.00
7.50
0.75
0.00
0.00
9.00
1.01
0.00
0.00
10.50
1.40
0.00
0.00
12.00
4.56
0.82
3.61
13.50
5.50
1.31
1.52
15.00
5.87
1.52
0.85
16.50
6.13
1.67
0.61
18.00
6.34
1.80
0.52
19.50
6.50
1.90
0.42
21.00
6.64
1.99
0.36
22.50
6.76
2.07
0.34
24.00
6.88
2.14
0.32
25.50
6.88
2.14
0.00
27.00
6.88
2.14
0.00
28.50
6.88
2.14
0.00
30.00
6.88
2.14
0.00
31.50
6.88
2.14
0.00
33.00
6.88
2.14
0.00
34.50
6.88
2.14
0.00
36.00
6.88
2.14
0.00
37.50
6.88
2.14
0.00
39.00
6.88
2.14
0.00
40.50
6.88
2.14
0.00
42.00
6.88
2.14
0.00
43.50
6.88
2.14
0.00
45.00
6.88
2.14
0.00
46.50
6.88
2.14
0.00
48.00
6.88
2.14
0.00
49.50
6.88
2.14
0.00
51.00
6.88
2.14
0.00
52.50
6.88
2.14
0.00
54.00
6.88
2.14
0.00
55.50
6.88
2.14
0.00
57.00
6.88
2.14
0.00
58.50
6.88
2.14
0.00
60.00
6.88
2.14
0.00
61.50
6.88
2.14
0.00
63.00
6.88
2.14
0.00
64.50
6.88
2.14
0.00
66.00
6.88
2.14
0.00
67.50
6.88
2.14
0.00
69.00
6.88
2.14
0.00
70.50
6.88
2.14
0.00
72.00
6.88
2.14
0.00
73.50
6.88
2.14
0.00
75.00
6.88
2.14
0.00
76.50
6.88
2.14
0.00
78.00
6.88
2.14
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
6.88
2.14
0.00
81.00
6.88
2.14
0.00
82.50
6.88
2.14
0.00
84.00
6.88
2.14
0.00
85.50
6.88
2.14
0.00
87.00
6.88
2.14
0.00
88.50
6.88
2.14
0.00
90.00
6.88
2.14
0.00
91.50
6.88
2.14
0.00
93.00
6.88
2.14
0.00
94.50
6.88
2.14
0.00
96.00
6.88
2.14
0.00
97.50
6.88
2.14
0.00
99.00
6.88
2.14
0.00
100.50
6.88
2.14
0.00
102.00
6.88
2.14
0.00
103.50
6.88
2.14
0.00
105.00
6.88
2.14
0.00
106.50
6.88
2.14
0.00
108.00
6.88
2.14
0.00
109.50
6.88
2.14
0.00
111.00
6.88
2.14
0.00
112.50
6.88
2.14
0.00
114.00
6.88
2.14
0.00
115.50
6.88
2.14
0.00
117.00
6.88
2.14
0.00
118.50
6.88
2.14
0.00
120.00
6.88
2.14
0.00
121.50
6.88
2.14
0.00
123.00
6.88
2.14
0.00
124.50
6.88
2.14
0.00
126.00
6.88
2.14
0.00
127.50
6.88
2.14
0.00
129.00
6.88
2.14
0.00
130.50
6.88
2.14
0.00
132.00
6.88
2.14
0.00
133.50
6.88
2.14
0.00
135.00
6.88
2.14
0.00

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 42
Summary for Subcatchment 2: Postdeveloped
Runoff = 36.98 cfs @ 11.96 hrs, Volume= 1.705 af, Depth= 4.15"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 50-yr Rainfall=6.88"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
ao
38
'
cfs �;---- -----t----t---- rt----�----y-----I-----I-----I-----I--------
■Runoff
36.98
---
---
36
--- t---- t---- t---- t----t----t---- t----- ----------------=�r--
---T----T----T----T---- ---- --------------,-Type-ll- 4- x -
34
32
---
---
-------------,----
---'-----'------'----'----- +-----------50=yr _Rainfall=&.88 ---
30
---
---L----1----1----1----1----L----L-
Ru no#f-Area:4.930 ac- -
28
26
---
-------
---L----1----1----1----1----L- ---------------------------
+----+----+----+----+----+--
R rto#-V�l'I,t�-111�=� : II�S-Of -
N 24
22
--
-
---t----t----T----T----t----I----I-----I-----I-----I-----I-----I---
---r---- T---- T--- -T ----------------Ranof# Depth-=14.1-5I"--
0 20
FL18
-
-
--- T---- T---- T---- T----T---- ---- -- }, /� y,
------------- T ---- T ---- T ---- T------------------ 1V� .W_m�ll--
16
CIIY=7�
14
---
-- -- -- -- - -- --- --- --- --- --- -- -
I I I I I I I I I I I I
12
---
---L----1----1----1----L---- ----L-------------------------I---
10
---
I I I I I I I I I I I I
---+----+----+----+----+----+----+----+----+----+-----+----+--
8
---
---+----+----+----+----+----+----+----+----+----+-----+----+--
6
----t---- -----------------------I---
t---- t---- t---- t
4
i
T---- T----T - -- T----T----T----T----------I---------r-- -I---
20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 43
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.11
0.00
0.00
3.00
0.24
0.00
0.00
4.50
0.38
0.00
0.00
6.00
0.55
0.00
0.00
7.50
0.75
0.00
0.05
9.00
1.01
0.04
0.21
10.50
1.40
0.15
0.59
12.00
4.56
2.18
31.58
13.50
5.50
2.95
1.42
15.00
5.87
3.27
0.90
16.50
6.13
3.49
0.65
18.00
6.34
3.67
0.54
19.50
6.50
3.82
0.43
21.00
6.64
3.94
0.38
22.50
6.76
4.05
0.36
24.00
6.88
4.15
0.33
25.50
6.88
4.15
0.00
27.00
6.88
4.15
0.00
28.50
6.88
4.15
0.00
30.00
6.88
4.15
0.00
31.50
6.88
4.15
0.00
33.00
6.88
4.15
0.00
34.50
6.88
4.15
0.00
36.00
6.88
4.15
0.00
37.50
6.88
4.15
0.00
39.00
6.88
4.15
0.00
40.50
6.88
4.15
0.00
42.00
6.88
4.15
0.00
43.50
6.88
4.15
0.00
45.00
6.88
4.15
0.00
46.50
6.88
4.15
0.00
48.00
6.88
4.15
0.00
49.50
6.88
4.15
0.00
51.00
6.88
4.15
0.00
52.50
6.88
4.15
0.00
54.00
6.88
4.15
0.00
55.50
6.88
4.15
0.00
57.00
6.88
4.15
0.00
58.50
6.88
4.15
0.00
60.00
6.88
4.15
0.00
61.50
6.88
4.15
0.00
63.00
6.88
4.15
0.00
64.50
6.88
4.15
0.00
66.00
6.88
4.15
0.00
67.50
6.88
4.15
0.00
69.00
6.88
4.15
0.00
70.50
6.88
4.15
0.00
72.00
6.88
4.15
0.00
73.50
6.88
4.15
0.00
75.00
6.88
4.15
0.00
76.50
6.88
4.15
0.00
78.00
6.88
4.15
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
6.88
4.15
0.00
81.00
6.88
4.15
0.00
82.50
6.88
4.15
0.00
84.00
6.88
4.15
0.00
85.50
6.88
4.15
0.00
87.00
6.88
4.15
0.00
88.50
6.88
4.15
0.00
90.00
6.88
4.15
0.00
91.50
6.88
4.15
0.00
93.00
6.88
4.15
0.00
94.50
6.88
4.15
0.00
96.00
6.88
4.15
0.00
97.50
6.88
4.15
0.00
99.00
6.88
4.15
0.00
100.50
6.88
4.15
0.00
102.00
6.88
4.15
0.00
103.50
6.88
4.15
0.00
105.00
6.88
4.15
0.00
106.50
6.88
4.15
0.00
108.00
6.88
4.15
0.00
109.50
6.88
4.15
0.00
111.00
6.88
4.15
0.00
112.50
6.88
4.15
0.00
114.00
6.88
4.15
0.00
115.50
6.88
4.15
0.00
117.00
6.88
4.15
0.00
118.50
6.88
4.15
0.00
120.00
6.88
4.15
0.00
121.50
6.88
4.15
0.00
123.00
6.88
4.15
0.00
124.50
6.88
4.15
0.00
126.00
6.88
4.15
0.00
127.50
6.88
4.15
0.00
129.00
6.88
4.15
0.00
130.50
6.88
4.15
0.00
132.00
6.88
4.15
0.00
133.50
6.88
4.15
0.00
135.00
6.88
4.15
0.00

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 44
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area = 4.930 ac, 41.58% Impervious, Inflow Depth = 4.15" for 50-yr event
Inflow = 36.98 cfs @ 11.96 hrs, Volume= 1.705 of
Outflow = 17.27 cfs @ 12.05 hrs, Volume= 1.705 af, Atten= 53%, Lag= 5.6 min
Primary = 17.27 cfs @ 12.05 hrs, Volume= 1.705 of
Routing by Stor-Ind method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 910.45' @ 12.05 hrs Surf.Area= 10,162 sf Storage= 32,669 cf
Flood Elev= 911.00' Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 455.9 min calculated for 1.705 of (100% of inflow)
Center -of -Mass det. time= 457.1 min ( 1,271.2 - 814.1 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
905.00 600 0 0
906.00 4,065 2,333 2,333
907.00 5,140 4,603 6,935
908.00 6,325 5,733 12,668
909.00 7,625 6,975 19,643
910.00 9,612 8,619 28,261
911.00 10,845 10,229 38,490
Device Routing Invert Outlet Devices
#1 Primary 902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1 905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1 907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1 910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=16.97 cfs @ 12.05 hrs HW=910.44' (Free Discharge)
L1=Outlet Pipe (Passes 16.97 cfs of 22.82 cfs potential flow)
�2=Sand Bed Exfiltration (Custom Controls 0.08 cfs)
3=Orifice (Orifice Controls 1.60 cfs @ 8.14 fps)
4=Grate Top (Weir Controls 15.29 cfs @ 2.17 fps)

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 45
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
36.98 cfS - - - -
- - - -
■ Inflow
■ Primary
40
38
--- ----'-----'-----'--------------------
----------------
------
'---
----'
----------------------'--
Inflow -AKea=4.93',o a ,
36
32
-------------
-------------------------------------
----
---- ----
---- - -- --------- --- - --
Pecjk-E'�,Ie-v-*1QA6','-
2$
----r----r---r----r----r----r-
---
----------------------,----
----
- - -r- --r----r----r--------r--
---- ��Storap=32,6&9-e -
26
-------------
----
---- ----
---- ---------------------- --
w 24
--- -------------+----+----+----+----+----+------------------+--
V 22
0 20
cfs-----------------',---
---
----', ----', ----I-----I-----I-----',--
17.27
a 18
--------------
--
---
-- - --' ----'-----'-----'-----'-----'-----'-----'--
16
------------
----
---- ----
---- ---------------------- --
14
- -------------+----+----+----+----+----+------------------+--
12
-----r----r---7----
----7----rt----r----r----Ir----Ir----li----7--
10
-- ---
--- ---
-- --
- -- --- --- --- --- ---
8
- ---
--- ---
-- --
-------- --- --- ------
6
-----------
----
---- ----
---- ---------------------- -
10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 46
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.21
622
905.45
0.02
12.00
31.58
30,885
910.27
8.92
15.00
0.90
26,004
909.76
1.47
18.00
0.54
19,017
908.92
1.16
21.00
0.38
13,449
908.12
0.75
24.00
0.33
11,088
907.74
0.43
27.00
0.00
9,192
907.42
0.07
30.00
0.00
8,605
907.31
0.05
33.00
0.00
8,104
907.22
0.05
36.00
0.00
7,611
907.13
0.05
39.00
0.00
7,128
907.04
0.04
42.00
0.00
6,654
906.94
0.04
45.00
0.00
6,190
906.85
0.04
48.00
0.00
5,735
906.76
0.04
51.00
0.00
5,291
906.67
0.04
54.00
0.00
4,856
906.58
0.04
57.00
0.00
4,432
906.49
0.04
60.00
0.00
4,017
906.39
0.04
63.00
0.00
3,612
906.30
0.04
66.00
0.00
3,217
906.21
0.04
69.00
0.00
2,832
906.12
0.04
72.00
0.00
2,457
906.03
0.03
75.00
0.00
2,096
905.94
0.03
78.00
0.00
1,768
905.85
0.03
81.00
0.00
1,471
905.76
0.03
84.00
0.00
1,206
905.68
0.02
87.00
0.00
972
905.60
0.02
90.00
0.00
769
905.51
0.02
93.00
0.00
594
905.44
0.01
96.00
0.00
447
905.36
0.01
99.00
0.00
327
905.29
0.01
102.00
0.00
231
905.23
0.01
105.00
0.00
157
905.17
0.01
108.00
0.00
103
905.13
0.00
111.00
0.00
64
905.08
0.00
114.00
0.00
39
905.06
0.00
117.00
0.00
23
905.03
0.00
120.00
0.00
14
905.02
0.00
123.00
0.00
8
905.01
0.00
126.00
0.00
5
905.01
0.00
129.00
0.00
3
905.00
0.00
132.00
0.00
2
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 47
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type/1 24-hr 50-yr Rainfall=6.88"
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 48
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

100 YR ROUTING
CALCULATIONS

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 49
Summary for Subcatchment 1: Predeveloped
Runoff = 14.05 cfs @ 12.26 hrs, Volume= 1.429 af, Depth= 2.68"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 100-yr Rainfall=7.69"
Area (ac) CN Description
6.200 55 Wooded
0.200 98 Impervious
6.400 56 Weighted Average
6.200 96.88% Pervious Area
0.200 3.13% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
30.0 Direct Entry, pre Tc
Subcatchment 1: Predeveloped
Hydrograph
--- ------------------=,-
� ■Runoff
1514.05 cfs---------------------------- -----------T--------------
14 ------ ---- -T - - -- - - -- - - -- --------------------i-ype-H-'24—hr -
13 / I I I I I I 1
-- -------+----+----+---- 41---- I-----1-10D- Rainfal[--7.6-97 -
12
11 Run6ff Area=6.400 ad
--- ---+----+----+----+----rt----+---------t-----i-----i-----i-----r--
10 --- --- ---- ---- ---- ---- ---- --R nef-V-oI=1R=1 09-CF'--
N 9 / I 1
-- -- ---- ---- ---- ---- ---- ;------Runof�Depth=',�687
LL --- --- ---- ---- ---- ---- ---- -- TcT30.© mih
-- -
-r----r----r----r----r----r----r---------------
-----r----r--
6
------------------------------------------------------ C'N =56--
5
- - - - T - - - - T - - - - T - - - - T - - - - 7 - - - - - - - - - -
4
3
- - - - - - T - - - - T - - - - T - - - - T - - - - 7 - - - --
2
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 50
Hydrograph for Subcatchment 1: Predeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.12
0.00
0.00
3.00
0.27
0.00
0.00
4.50
0.42
0.00
0.00
6.00
0.62
0.00
0.00
7.50
0.84
0.00
0.00
9.00
1.13
0.00
0.00
10.50
1.57
0.00
0.00
12.00
5.10
1.09
5.02
13.50
6.14
1.68
1.84
15.00
6.56
1.94
1.02
16.50
6.85
2.12
0.74
18.00
7.08
2.27
0.62
19.50
7.27
2.39
0.51
21.00
7.42
2.50
0.42
22.50
7.56
2.59
0.40
24.00
7.69
2.68
0.38
25.50
7.69
2.68
0.00
27.00
7.69
2.68
0.00
28.50
7.69
2.68
0.00
30.00
7.69
2.68
0.00
31.50
7.69
2.68
0.00
33.00
7.69
2.68
0.00
34.50
7.69
2.68
0.00
36.00
7.69
2.68
0.00
37.50
7.69
2.68
0.00
39.00
7.69
2.68
0.00
40.50
7.69
2.68
0.00
42.00
7.69
2.68
0.00
43.50
7.69
2.68
0.00
45.00
7.69
2.68
0.00
46.50
7.69
2.68
0.00
48.00
7.69
2.68
0.00
49.50
7.69
2.68
0.00
51.00
7.69
2.68
0.00
52.50
7.69
2.68
0.00
54.00
7.69
2.68
0.00
55.50
7.69
2.68
0.00
57.00
7.69
2.68
0.00
58.50
7.69
2.68
0.00
60.00
7.69
2.68
0.00
61.50
7.69
2.68
0.00
63.00
7.69
2.68
0.00
64.50
7.69
2.68
0.00
66.00
7.69
2.68
0.00
67.50
7.69
2.68
0.00
69.00
7.69
2.68
0.00
70.50
7.69
2.68
0.00
72.00
7.69
2.68
0.00
73.50
7.69
2.68
0.00
75.00
7.69
2.68
0.00
76.50
7.69
2.68
0.00
78.00
7.69
2.68
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
7.69
2.68
0.00
81.00
7.69
2.68
0.00
82.50
7.69
2.68
0.00
84.00
7.69
2.68
0.00
85.50
7.69
2.68
0.00
87.00
7.69
2.68
0.00
88.50
7.69
2.68
0.00
90.00
7.69
2.68
0.00
91.50
7.69
2.68
0.00
93.00
7.69
2.68
0.00
94.50
7.69
2.68
0.00
96.00
7.69
2.68
0.00
97.50
7.69
2.68
0.00
99.00
7.69
2.68
0.00
100.50
7.69
2.68
0.00
102.00
7.69
2.68
0.00
103.50
7.69
2.68
0.00
105.00
7.69
2.68
0.00
106.50
7.69
2.68
0.00
108.00
7.69
2.68
0.00
109.50
7.69
2.68
0.00
111.00
7.69
2.68
0.00
112.50
7.69
2.68
0.00
114.00
7.69
2.68
0.00
115.50
7.69
2.68
0.00
117.00
7.69
2.68
0.00
118.50
7.69
2.68
0.00
120.00
7.69
2.68
0.00
121.50
7.69
2.68
0.00
123.00
7.69
2.68
0.00
124.50
7.69
2.68
0.00
126.00
7.69
2.68
0.00
127.50
7.69
2.68
0.00
129.00
7.69
2.68
0.00
130.50
7.69
2.68
0.00
132.00
7.69
2.68
0.00
133.50
7.69
2.68
0.00
135.00
7.69
2.68
0.00

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 51
Summary for Subcatchment 2: Postdeveloped
Runoff = 43.13 cfs @ 11.96 hrs, Volume= 2.003 af, Depth= 4.88"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Type II 24-hr 100-yr Rainfall=7.69"
Area (ac)
CN
Description
2.050
98
Impervious
2.270
61
Grass/Open Space
0.610
55
Wooded
4.930 76 Weighted Average
2.880 58.42% Pervious Area
2.050 41.58% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, post Tc
Subcatchment 2: Postdeveloped
Hydrograph
48
----r----+----+----+----+----+----+----+----+--------------------+--
----
----,-----,-----,----,----?----,------------------------------,---
■ Runoff
43.13
46
cfs----+----+----+---- ---- ------------------------ -----'
44
42
+----+----+----+----7---- ---- T --
-------------------------------------------- -i-y pe-u-'24 h r -
---
40
38
---
---
---+----+----+----+----+----+----+-- I - - - -I - - - --I -- I-----I---
--- + ---- + ---- ---- ---- ---------'r1O0-y-r Rai nfall-;7.C8'7 -
36
34
---
---r----r----7----t--------------- R�unp#f-/'ire& .JVV ac--
30
---
-------------------
---+----+----+----+----+----+-- R� rto#-Vt�l'I r�t�=2:E O3-Of -
N 26
---
---
--- +----+-- -- �,--- - + -- -- �, - - -- �,-----,Rtit�af#-D---fFr=�'�.$8��'�--
-----------------------------------
3 24
LL
---
---+----+----+----+----+---- --------+----+---TT----LL--/----+--
------'--_ 11t=J.W IIIfh
20
18
---
-
-----------------------i ---- --- V� ��V
16
---
------------------------------ --------------------------------
---
- --
10
---
---L----1----1----1----1---- ----J-------------------------'---
6
20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 52
Hydrograph for Subcatchment 2: Postdeveloped
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
0.00
0.00
0.00
0.00
1.50
0.12
0.00
0.00
3.00
0.27
0.00
0.00
4.50
0.42
0.00
0.00
6.00
0.62
0.00
0.00
7.50
0.84
0.01
0.09
9.00
1.13
0.07
0.29
10.50
1.57
0.21
0.76
12.00
5.10
2.62
36.68
13.50
6.14
3.50
1.63
15.00
6.56
3.87
1.03
16.50
6.85
4.13
0.74
18.00
7.08
4.33
0.62
19.50
7.27
4.50
0.49
21.00
7.42
4.63
0.43
22.50
7.56
4.76
0.41
24.00
7.69
4.88
0.38
25.50
7.69
4.88
0.00
27.00
7.69
4.88
0.00
28.50
7.69
4.88
0.00
30.00
7.69
4.88
0.00
31.50
7.69
4.88
0.00
33.00
7.69
4.88
0.00
34.50
7.69
4.88
0.00
36.00
7.69
4.88
0.00
37.50
7.69
4.88
0.00
39.00
7.69
4.88
0.00
40.50
7.69
4.88
0.00
42.00
7.69
4.88
0.00
43.50
7.69
4.88
0.00
45.00
7.69
4.88
0.00
46.50
7.69
4.88
0.00
48.00
7.69
4.88
0.00
49.50
7.69
4.88
0.00
51.00
7.69
4.88
0.00
52.50
7.69
4.88
0.00
54.00
7.69
4.88
0.00
55.50
7.69
4.88
0.00
57.00
7.69
4.88
0.00
58.50
7.69
4.88
0.00
60.00
7.69
4.88
0.00
61.50
7.69
4.88
0.00
63.00
7.69
4.88
0.00
64.50
7.69
4.88
0.00
66.00
7.69
4.88
0.00
67.50
7.69
4.88
0.00
69.00
7.69
4.88
0.00
70.50
7.69
4.88
0.00
72.00
7.69
4.88
0.00
73.50
7.69
4.88
0.00
75.00
7.69
4.88
0.00
76.50
7.69
4.88
0.00
78.00
7.69
4.88
0.00
Time Precip. Excess Runoff
(hours)
(inches)
(inches)
(cfs)
79.50
7.69
4.88
0.00
81.00
7.69
4.88
0.00
82.50
7.69
4.88
0.00
84.00
7.69
4.88
0.00
85.50
7.69
4.88
0.00
87.00
7.69
4.88
0.00
88.50
7.69
4.88
0.00
90.00
7.69
4.88
0.00
91.50
7.69
4.88
0.00
93.00
7.69
4.88
0.00
94.50
7.69
4.88
0.00
96.00
7.69
4.88
0.00
97.50
7.69
4.88
0.00
99.00
7.69
4.88
0.00
100.50
7.69
4.88
0.00
102.00
7.69
4.88
0.00
103.50
7.69
4.88
0.00
105.00
7.69
4.88
0.00
106.50
7.69
4.88
0.00
108.00
7.69
4.88
0.00
109.50
7.69
4.88
0.00
111.00
7.69
4.88
0.00
112.50
7.69
4.88
0.00
114.00
7.69
4.88
0.00
115.50
7.69
4.88
0.00
117.00
7.69
4.88
0.00
118.50
7.69
4.88
0.00
120.00
7.69
4.88
0.00
121.50
7.69
4.88
0.00
123.00
7.69
4.88
0.00
124.50
7.69
4.88
0.00
126.00
7.69
4.88
0.00
127.50
7.69
4.88
0.00
129.00
7.69
4.88
0.00
130.50
7.69
4.88
0.00
132.00
7.69
4.88
0.00
133.50
7.69
4.88
0.00
135.00
7.69
4.88
0.00

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 53
Summary for Pond 3: Sand Filter/Dry Pond
Inflow Area =
4.930 ac, 41.58% Impervious, Inflow Depth = 4.88" for 100-yr event
Inflow =
43.13 cfs @ 11.96 hrs, Volume= 2.003 of
Outflow =
23.27 cfs @ 12.03 hrs, Volume= 2.003 af, Atten= 46%, Lag= 4.2 min
Primary =
23.27 cfs @ 12.03 hrs, Volume= 2.003 of
Routing by Stor-Ind
method, Time Span= 0.00-135.99 hrs, dt= 0.03 hrs
Peak Elev= 910.74' @ 12.04 hrs Surf.Area= 10,520 sf Storage= 35,670 cf
Flood Elev= 911.00'
Surf.Area= 10,845 sf Storage= 38,490 cf
Plug -Flow detention time= 401.9 min calculated for 2.003 of (100% of inflow)
Center -of -Mass det. time= 401.8 min ( 1,211.4 - 809.5 )
Volume Invert Avail.Storage Storage Description
#1 905.00' 38,490 cf Detention (Prismatic) Listed below (Recalc)
Elevation
Surf.Area Inc.Store Cum.Store
(feet)
(sq-ft) (cubic -feet) (cubic -feet)
905.00
600 0 0
906.00
4,065 2,333 2,333
907.00
5,140 4,603 6,935
908.00
6,325 5,733 12,668
909.00
7,625 6,975 19,643
910.00
9,612 8,619 28,261
911.00
10,845 10,229 38,490
Device Routing
Invert Outlet Devices
#1 Primary
902.50' 18.0" Round Outlet Pipe L= 50.0' Ke= 0.500
Inlet / Outlet Invert= 902.50' / 902.00' S= 0.0100 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Device 1
905.00' Sand Bed Exfiltration
Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 6.00
Disch. (cfs) 0.000 0.034 0.044 0.053 0.063 0.073 0.083
#3 Device 1
907.33' 6.0" Vert. Orifice C= 0.600
#4 Device 1
910.00' 3.0" x 3.0" Horiz. Grate Top X 16.00 columns
X 16 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=23.27 cfs @ 12.03 hrs HW=910.73' (Free Discharge)
L1=Outlet Pipe (Inlet Controls 23.27 cfs @ 13.17 fps)
�2=Sand Bed Exfiltration (Passes < 0.08 cfs potential flow)
3=Orifice (Passes < 1.68 cfs potential flow)
4=Grate Top (Passes < 32.68 cfs potential flow)

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 54
Pond 3: Sand Filter/Dry Pond
Hyd rog raph
48
43.13 CfS ------
- -
- - -
- -- - -- - -- -- -- -
■ Inflow
■ Primary
46
44
----------------------------------„o
----------------
----
----------In
--- -----pa� 93,a-------------------
fI w A .- - --
40
----------------1----J----
-------r----I----
----
----
----+----+----r
----=E'fev=9'I1:7`=
-r -
38
I-
36
34
------------'----
- - - - - - - -----I----
----
----
----1----1---
---- ----
L--- L----'--- - I--J
----Storap=M 67-0-cit-
32
--------------
-----
- - -----
----
---- ---- ---------------------
30
--- ----I-----I----+----+----+----+----r----+----I-----I-----I----+--
H28
-------
---- -T --
--
------- -
- - - -T -- - -T -- - -T -------------T--
z6
23.27 cfs
3 24
- -
----------
-----
---
---------
--------------------------------
0 22
- ----+--------+----+----+----+----+----
+----+----+---+----+--
LL
20
-
-------
---- -T ----
+
T----r----r----r----r--------T--
18
--------------
----
--------+----
---------------------- --
16
--------------
----
--------T----r----r------------------
--
14
- ---
---
---J----J----1----1----L----L------------------1--
12
-----r--------7----
----7----rt----r----r----li-----Ir----li----7--
10
-
-----------------------'
----1----1----L-------------------'--
$
-
------------y----y----1----t----r----r----+----+----li----y--
6
-
----------------------------------------------------------
4
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Time (hours)

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 55
Hydrograph for Pond 3: Sand Filter/Dry Pond
Time
Inflow
Storage
Elevation
Primary
(hours)
(cfs)
(cubic -feet)
(feet)
(cfs)
0.00
0.00
0
905.00
0.00
3.00
0.00
0
905.00
0.00
6.00
0.00
0
905.00
0.00
9.00
0.29
1,049
905.62
0.02
12.00
36.68
34,713
910.64
23.14
15.00
1.03
26,795
909.84
1.49
18.00
0.62
20,322
909.09
1.22
21.00
0.43
14,508
908.28
0.85
24.00
0.38
11,615
907.83
0.53
27.00
0.00
9,277
907.43
0.08
30.00
0.00
8,656
907.32
0.05
33.00
0.00
8,153
907.23
0.05
36.00
0.00
7,660
907.14
0.05
39.00
0.00
7,176
907.05
0.04
42.00
0.00
6,701
906.95
0.04
45.00
0.00
6,236
906.86
0.04
48.00
0.00
5,780
906.77
0.04
51.00
0.00
5,335
906.68
0.04
54.00
0.00
4,900
906.59
0.04
57.00
0.00
4,474
906.49
0.04
60.00
0.00
4,058
906.40
0.04
63.00
0.00
3,653
906.31
0.04
66.00
0.00
3,257
906.22
0.04
69.00
0.00
2,870
906.13
0.04
72.00
0.00
2,494
906.04
0.03
75.00
0.00
2,131
905.95
0.03
78.00
0.00
1,799
905.86
0.03
81.00
0.00
1,499
905.77
0.03
84.00
0.00
1,231
905.69
0.02
87.00
0.00
994
905.60
0.02
90.00
0.00
788
905.52
0.02
93.00
0.00
610
905.44
0.02
96.00
0.00
461
905.37
0.01
99.00
0.00
338
905.30
0.01
102.00
0.00
239
905.24
0.01
105.00
0.00
163
905.18
0.01
108.00
0.00
107
905.13
0.00
111.00
0.00
68
905.09
0.00
114.00
0.00
41
905.06
0.00
117.00
0.00
24
905.03
0.00
120.00
0.00
14
905.02
0.00
123.00
0.00
9
905.01
0.00
126.00
0.00
5
905.01
0.00
129.00
0.00
3
905.00
0.00
132.00
0.00
2
905.00
0.00
135.00
0.00
1
905.00
0.00

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 56
Elevation Primary
(feet)
(cfs)
905.00
0.00
905.04
0.00
905.08
0.00
905.12
0.00
905.16
0.01
905.20
0.01
905.24
0.01
905.28
0.01
905.32
0.01
905.36
0.01
905.40
0.01
905.44
0.01
905.48
0.02
905.52
0.02
905.56
0.02
905.60
0.02
905.64
0.02
905.68
0.02
905.72
0.02
905.76
0.03
905.80
0.03
905.84
0.03
905.88
0.03
905.92
0.03
905.96
0.03
906.00
0.03
906.04
0.03
906.08
0.03
906.12
0.04
906.16
0.04
906.20
0.04
906.24
0.04
906.28
0.04
906.32
0.04
906.36
0.04
906.40
0.04
906.44
0.04
906.48
0.04
906.52
0.04
906.56
0.04
906.60
0.04
906.64
0.04
906.68
0.04
906.72
0.04
906.76
0.04
906.80
0.04
906.84
0.04
906.88
0.04
906.92
0.04
906.96
0.04
907.00
0.04
907.04
0.04
907.08
0.04
Stage -Discharge for Pond 3: Sand Filter/Dry Pond
Elevation Primary
(feet)
(cfs)
907.12
0.05
907.16
0.05
907.20
0.05
907.24
0.05
907.28
0.05
907.32
0.05
907.36
0.05
907.40
0.06
907.44
0.08
907.48
0.11
907.52
0.15
907.56
0.19
907.60
0.24
907.64
0.29
907.68
0.35
907.72
0.40
907.76
0.45
907.80
0.50
907.84
0.53
907.88
0.57
907.92
0.60
907.96
0.64
908.00
0.67
908.04
0.69
908.08
0.72
908.12
0.75
908.16
0.77
908.20
0.80
908.24
0.82
908.28
0.85
908.32
0.87
908.36
0.89
908.40
0.91
908.44
0.93
908.48
0.95
908.52
0.97
908.56
0.99
908.60
1.01
908.64
1.03
908.68
1.05
908.72
1.07
908.76
1.09
908.80
1.11
908.84
1.12
908.88
1.14
908.92
1.16
908.96
1.17
909.00
1.19
909.04
1.21
909.08
1.22
909.12
1.24
909.16
1.25
909.20
1.27
Elevation Primary
(feet)
(cfs)
909.24
1.28
909.28
1.30
909.32
1.31
909.36
1.33
909.40
1.34
909.44
1.36
909.48
1.37
909.52
1.39
909.56
1.40
909.60
1.41
909.64
1.43
909.68
1.44
909.72
1.45
909.76
1.47
909.80
1.48
909.84
1.49
909.88
1.51
909.92
1.52
909.96
1.53
910.00
1.54
910.04
1.97
910.08
2.75
910.12
3.76
910.16
4.94
910.20
6.28
910.24
7.77
910.28
9.38
910.32
11.11
910.36
12.95
910.40
14.90
910.44
16.95
910.48
19.09
910.52
21.32
910.56
23.01
910.60
23.07
910.64
23.13
910.68
23.19
910.72
23.26
910.76
23.32
910.80
23.38
910.84
23.44
910.88
23.50
910.92
23.56
910.96
23.63
911.00
23.69

Northgate SCM Type 11 24-hr 100-yr Rainfall= 7.69 "
Prepared by Microsoft Printed 4/2/2019
HydroCAD® 10.00-24 s/n 10816 © 2018 HydroCAD Software Solutions LLC Page 57
Stage -Area -Storage for Pond 3: Sand Filter/Dry Pond
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
905.00
600
0
905.10
947
77
905.20
1,293
189
905.30
1,639
336
905.40
1,986
517
905.50
2,333
733
905.60
2,679
984
905.70
3,026
1,269
905.80
3,372
1,589
905.90
3,718
1,943
906.00
4,065
2,333
906.10
4,173
2,744
906.20
4,280
3,167
906.30
4,387
3,600
906.40
4,495
4,044
906.50
4,603
4,499
906.60
4,710
4,965
906.70
4,818
5,441
906.80
4,925
5,928
906.90
5,032
6,426
907.00
5,140
6,935
907.10
5,259
7,455
907.20
5,377
7,987
907.30
5,495
8,530
907.40
5,614
9,086
907.50
5,733
9,653
907.60
5,851
10,232
907.70
5,970
10,823
907.80
6,088
11,426
907.90
6,206
12,041
908.00
6,325
12,668
908.10
6,455
13,307
908.20
6,585
13,959
908.30
6,715
14,623
908.40
6,845
15,301
908.50
6,975
15,993
908.60
7,105
16,697
908.70
7,235
17,414
908.80
7,365
18,143
908.90
7,495
18,886
909.00
7,625
19,643
909.10
7,824
20,415
909.20
8,022
21,207
909.30
8,221
22,019
909.40
8,420
22,851
909.50
8,619
23,703
909.60
8,817
24,575
909.70
9,016
25,467
909.80
9,215
26,378
909.90
9,413
27,310
910.00
9,612
28,261
910.10
9,735
29,228
910.20
9,859
30,208
Elevation
Surface
Storage
(feet)
(sq-ft)
(cubic -feet)
910.30
9,982
31,200
910.40
10,105
32,204
910.50
10,229
33,221
910.60
10,352
34,250
910.70
10,475
35,291
910.80
10,598
36,345
910.90
10,722
37,411
911.00
10,845
38,490

EROSION CONTROL
CALCULATIONS

Northgate Urban Design Partners
JOB NO.: 19-039 BY: 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Charlotte, NC 28205
REVISED: 01.22.20 Skimmer Basin Design - EC Phase 1
SKIMMER BASIN
DRAINAGE AREAS/REQ'D STORAGE
DESIGN CRITERIA
Total drainage area (TDA)
4.78 ac
Proposed sediment depth
1.5 ft
Disturbed area(DA)
3.90 ac
Bottom elevation of basin
906 msl
Required sediment storage(1800xDA)
7,016 cf
Side slopes (H:V)
3 :1
Required surface area:
4,875 sf
Depth of flow over spillway
0.5 ft
BASIN CONFIGURATION
PLANNED BASIN SIZE
(REFER TO EROSION CONTROL PLAN)
Bottom elevation
906 msl
Sediment Storage elevation
907.5 msl
F Elev. Area (SF) Cumulative Volume (CF)
Spillway elevation
909.5 msl
906
5,115
0
Top of Berm
911 msl
907
6,060
5,588
908
7,065
12,150
BASIN EFFICIENCY
909
8,120
19,743
Sediment storage required: 7,016 cf
Sediment storage provided: 19,743 OKAY
Surface area required: 4,875 sq ft
Surface area provided: 8,678 OKAY
910
1 9,235
28,420
911
10,410
38,243
PRIMARY SPILLWAY DESIGN (2-YEAR STORM)
DESIGN FLOW (Q=CIA) PRIMARY SPILLWAY DESIGN
Bare soil coefficient 'C' = 0.45 Spillway design: (L=Q/(C*h^1.5)); C=3.0, h= 0.5
Area 'A' = 4.78 ac
2 yr. storm rainfall intensity, 'I' = 5.03 in/hr
2 yr Design flow, 'Q' = 11 cfs
10 yr storm rainfall intensity, 'I' = 7.03 in/hr Spillway length C flow depth 15 ft
Design flow from site, 'Q' = 15 cfs
ASIN DEWATERING - FLOATING SKIMMER
ediment storage required:
7,016 cf
ediment storage provided:
19,743 cf
kimmer Size
2.0 in
ead on Skimmer
0.17 ft
rifice Size
1.5 in
Dewatering of Required Volume
Dewater of Actual Volume
3.30 days
9.30 days

Northgate Urban Design Partners
JOB NO.: 19-039 BY: 1318-E6 Central Avenue
DATE: 04.02.19 P.M.: Charlotte, NC 28205
REVISED: 01.22.20 Skimmer Basin Design - EC Phase 2
SKIMMER BASIN
DRAINAGE AREAS/REQ'D STORAGE
DESIGN CRITERIA
Total drainage area (TDA)
4.98 ac
Proposed sediment depth
1.5 ft
Disturbed area(DA)
3.85 ac
Bottom elevation of basin
906 msl
Required sediment storage(1800xDA)
6,927 cf
Side slopes (H:V)
3 :1
Required surface area:
5,200 sf
Depth of flow over spillway
0.5 ft
BASIN CONFIGURATION
PLANNED BASIN SIZE
(REFER TO EROSION CONTROL PLAN)
Bottom elevation
906 msl
Sediment Storage elevation
907.5 msl
F Elev. Area (SF) Cumulative Volume (CF)
Spillway elevation
909.5 msl
906
5,115
0
Top of Berm
911 msl
907
6,060
5,588
908
7,065
12,150
BASIN EFFICIENCY
909
8,120
19,743
Sediment storage required: 6,927 cf
Sediment storage provided: 19,743 OKAY
Surface area required: 5,200 sq ft
Surface area provided: 8,678 OKAY
910
1 9,235
28,420
911
10,410
38,243
PRIMARY SPILLWAY DESIGN (2-YEAR STORM)
DESIGN FLOW (Q=CIA) PRIMARY SPILLWAY DESIGN
Bare soil coefficient 'C' = 0.45 Spillway design: (L=Q/(C*h^1.5)); C=3.0, h= 0.5
Area 'A' = 4.98 ac
2 yr. storm rainfall intensity, 'I' = 5.03 in/hr
2 yr Design flow, 'Q' = 11 cfs
10 yr storm rainfall intensity, 'I' = 7.03 in/hr Spillway length C flow depth 16 ft
Design flow from site, 'Q' = 16 cfs
ASIN DEWATERING - FLOATING SKIMMER
ediment storage required:
6,927 cf
ediment storage provided:
19,743 cf
kimmer Size
2.0 in
ead on Skimmer
0.17 ft
rifice Size
1.5 in
Dewatering of Required Volume
Dewater of Actual Volume
3.26 days
9.30 days