SW7 Inlets - City of Fort Wayne

City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
SW7.01 Introduction
Stormwater inlets are a vital component of the urban stormwater collection
and conveyance system. Inlets intercept excess stormwater from streets and
developed areas and transition surface flow into storm sewers.
Proper inlet design includes both the proper inlet hydraulic capacity and
appropriate inlet placement.
If too few inlets are provided, if inlets are placed in the wrong location, or if
inlets do not have adequate hydraulic capacity then even amply sized pipes in
the storm sewer system will not function as intended.
The purpose of this section is to establish a basis for inlet design utilizing City
of Fort Wayne standard inlets and castings.
Methods for determination of stormwater runoff are presented in the Fort
Wayne Design Manual, Chapter 5, Section 2, Hydrology.
SW7.02 Standard Inlets
SW7.03 Inlet Location (Inlet Placement)
There are three general types of inlets acceptable for use in Fort Wayne,
including curb opening, valley (grate), and combination inlets. They can be
made of cast-iron, steel, concrete, and/or pre-cast concrete and are installed
on the edge of the street adjacent to the street gutter or in the bottom of a
swale. Water Resources has approved the following inlet types and castings
for use. The standard structure type is provided for each casting.
The standard inlets permitted for use in Fort Wayne are provided in Table
5.4.2.
Inlets must be placed at each location where surface runoff flow should be
interrupted and transitioned into storm sewer system pipe flow. Inlets can
be placed in roadside ditches, grass or lined swales, parking or pavement area
depressions, and under (in) roadway or parking area curb and gutters.
The following location requirements must be considered during the design of
inlets.
In developed areas, inlets shall be located in all pavement and green space
depression areas where surface runoff collects and should transitioned to
storm sewer pipe flow.
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
TABLE 5.4.2 STANDARD INLETS
APPLICABLE
SETTING
INLET TYPE
DRAWING
NO. CASTING AutoCAD File Name
30" x 30" Beehive Grate
Neenah R-4215 with grate C C8-1
East Jordan 6610 with grate O C8-2
2'x2' Curb and Gutter Casting
Neenah R-3010 with grate A, R, or S C10-1, C10-3, C10-5
Swale or Channel 30" Round Inlet East Jordan 7010ZM1T1 with grate M1, M5, or M3 C10-2, C10-4, C10-6
Green space Precast 30" Round Inlet STR 26 2'x2' Alley Casting
Pavement Field Created 30" Round Inlet STR 27 Neenah R-3036-B with grate S C9-1
East Jordan 5100ZM1 with grate M1 5105 C9-2
Neenah R-3036-B or East Jordan 5105 C-11
33" Round Curb & Gutter Casting
East Jordan 7020Z with grate M1 or M2 C12-1, C12-2
Neenah R-3159 with grate S C12-3
33" Round Inlet 33" Round Curb & Gutter Casting
Swale or Channel Precast 33" Round Inlet STR 28 East Jordan 7020Z with grate M1 or M2 C12-1, C12-2
Field Created 33" Round Inlet STR 29 Neenah R-3159 with grate S C12-3
24" Beehive Casting
Swale or Channel Neenah R-1772 with grate R-4351-D C7-1
Green space 24" Inlet STR 30 East Jordan 1022Z1 with grate 6509-0 C10
Pavement
24" Storm Manhole Casting
Neenah R-2502 with grate D C6-1
East Jordan 1022Z1 with grate M1 C6-1
2'x2' Curb and Gutter Grate
Neenah-3010 or East Jordan 7010 C-12
2'x2' Curb and Gutter Casting
Neenah R-3010 with grate A, R, or S C10-1, C10-3, C10-5
Curb 2' x 2' Inlet STR 31 East Jordan 7010ZM1T1 with grate M1, M5, or M3 C10-2, C10-4, C10-6
Pavement
2'x2' Alley Casting
Neenah R-3036-B with grate S C9-1
East Jordan 5100ZM1 with grate M1 5105 C9-2
Neenah R-3036-B or East Jordan 5105 C-11
2'x3' Curb and Gutter Casting
Curb 2' x 3' Inlet STR 32 Neenah R-3067 with grate C or R C11-1, C11-3
East Jordan 7030Z1 with grate M2, M3, or M5 C11-2, C11-4, C11-5
Neenah R-3067 or East Jordan 7030 M5
C13
30" x 30" Beehive Grate
Neenah R-4215-C
C14
Swale or Channel 30" x 30" Inlet STR 33 East Jordan 6610 C14
Neenah R-4215 with grate C C8-1
East Jordan 6610 with grate O C8-2
24" Beehive Casting
Neenah R-1772 with grate R-4351-D C7-1
East Jordan 1022Z1 with grate 6509-0
C10
24" Storm Manhole Casting
Neenah R-2502 with grate D C6-1
East Jordan 1022Z1 with grate M1 C6-1
30" x 30" Beehive Grate
Neenah R-4215 with grate C C8-1
Swale or Channel East Jordan 6610 with grate O C8-2
Green space Standard 48" Manhole STR1, STR1a2'x2' Curb and Gutter Casting
Pavement Neenah R-3010 with grate A, R, or S C10-1, C10-3, C10-5
East Jordan 7010ZM1T1 with grate M1, M5, or M3 C10-2, C10-4, C10-6
2'x2' Alley Casting
Neenah R-3036-B with grate S C9-1
East Jordan 5100ZM1 with grate M1 5105 C9-2
Neenah R-3036-B or East Jordan 5105 C-11
33" Round Curb & Gutter Casting
East Jordan 7020Z with grate M1 or M2 C12-1, C12-2
Neenah R-3159 with grate S C12-3
Swale or Channel Trash Rack
Pavement
Trench Drain
Type I
Type II
STR35
STR36
Nyloplast Drain Basin
Pedestrian Area, (or approved equal)
Swale or Channel, 8" Drain Basin ?? 8"-10" Grate Assembly
Green space 10" Drain Basin ?? Standard Grate ??
(not allowed in 12" Drain Basin ?? Dome Grate ??
traffic areas) 15" Drain Basin ?? 12"-30" Grate Assembly
18" Drain Basin ?? Standard Grate ??
24" Drain Basin ?? Dome Grate ??
30" Drain Basin ?? Pedestrian Grate ??
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
1. Inlets shall be placed in grass or lined swales and open channels where
concentrated flow must be transitioned to storm sewer pipe flow.
2. Inlet grate capacities shall be designed to adequately pass the design 10-
year storm event flow with 50% of the inlet grate areas clogged.
3. Inlets shall be placed in all streets and roadway sags. For the 10-year
design storm, the depth of ponded water at the inlet shall not exceed the
valves shown in Table 5.4.3.1 (Allowable Use of Streets for Minor Storm
Runoff). For the 100-year design storm, the depth of ponded water at
the inlet shall not exceed the valves shown in Table 5.4.3.2 (Allowable
Use of Streets for Major Storm Runoff).
4. An emergency overland flow path shall be included at street and
roadway sags in the event that the inlet or storm sewer is not
functioning. The depth of ponded water at the inlet shall not exceed
twelve inches (12”).
5. Depth of ponded water shall not exceed eight inches (8”) in private
development parking areas, except in areas used as detention.
6. Depth of ponded water shall not exceed twenty-four inches (24”) in
green space areas, except in areas used as detention.
7. In streets and roadways, inlets shall be placed immediately upstream of
intersections, pedestrian walkways, and handicap ramps. Required inlets
shall be placed not closer than two feet (2') from the upstream edge of
walkways and handicap ramps. See Figure 5.4.3.1 Inlet Placement at
Intersections
8. In streets or roadways where opposing lanes are separated by a grass
median or concrete center curb, inlets shall be placed upstream of a
crossover.
9. On continuous roadway or street grades, inlet spacing is determined by
limiting maximum width of gutter flow (Tmax). Inlets shall be spaced to
collect a minimum of 75 percent (75%) of watershed design flow. Bypass
flow, flow not intercepted by an individual inlet, shall not exceed 25
percent (25%). Bypass flow shall be considered when determining the
location of the next downstream inlet. General inlet spacing on
continuous grades is 300 feet to 600 feet (300' to 600') provided the
Tmax criteria are not exceeded. Exact spacing shall be computed by the
designer. See the Section 5.4.5 Gutter Flow for more information on
Tmax design.
10. Uniform inlet and casting types should be used on individual street and
roadway projects. Uniformity limits confusion and misplacement of
proper inlet types during construction.
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
Street
Classification
Local
Table 5.4.3.1
Allowable Use of Streets for Minor Storm Runoff
Maximum Street
Encroachment
No curb overtopping.
Flow may spread to crown
of street
Street Width
Face of Curb to
Face of Curb,
(ft)
Maximum Top
Width from
Gutter, T max
(ft)
Maximum
Depth in
Gutter Flow,
d (ft)
30 15 0.30
32 16 0.32
Collector
Arterial
No curb overtopping.
Flow spread must leave at
least one lane free of
water with 5-feet on
either side of the street
crown.
No curb overtopping.
Flow spread must leave at
least two 10-foot lanes
free of water with 10 feet
on each side of the street
crown.
36 18 0.36
36 13 0.26
40 15 0.30
44 17 0.34
Coordinate Allowable Use with agency having
jurisdictional authority on roadway.
Table 5.4.3.2
Allowable use of Streets for Major Storm Runoff
Maximum Depth and Inundated Area
Street Classification
The maximum Depth of water:
Local and Collector
1. shall not exceed 12-inches above the gutter flowline and,
2. shall not reduce the localized Flood Protection Grade to
less than 12-inches.
(Whichever is more restrictive)
The maximum Depth of water:
Arterial
1. shall not exceed 12-inches above the gutter flowline and,
2. shall not reduce the localized Flood Protection Grade to
less than 12-inches and,
3. shall not exceed the street crown (to allow for emergency
vehicles)
(Whichever is most restrictive)
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
June 15, 2012 (last draft date) 5

City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
SW7.04 Inlet Hydraulic Capacity
1. Introduction
All the stormwater runoff that enters a sump or gutter must pass
through an inlet to enter the storm sewer system. In most situations
stormwater is laden with debris and the inlet will be susceptible to
clogging. Therefore, the capacity of inlets must account for this clogging
potential.
Design of Inlet hydraulic capacity is separated into either a sump or
continuous grade situation. The follow section includes design
considerations and tables for inlet capacity for those two situations.
2. Sump Condition
Inlets in depressions or sumps function like weirs for shallow flow, but
as the depth of stormwater increases inlets begin to function like an
orifice. Following are tables showing the allowable inlet capacities in a
sump conditions.
Table assumptions:
Weir flow assumed for water depths below 2”
Weir Equation:
Q =3.30 x P x d 1.5
Q 1= Rate of flow into the inlet, cfs
P= perimeter of grate, ft
d = depth of water surface above inlet, ft
Orifice flow assumed for water depths above 4”
Orifice Equation:
Q =4.81 x A x d 0.5
Q 1= Rate of flow into the inlet, cfs
A= net open area of grate, ft
d = depth of water surface above inlet, ft
Transition flows assumed between 2” and 4” water depth
Clogging reduces weir length by 50%
Clogging reduces free open area by 50%
3. Continuous Grade Condition
Inlet Hydraulic Capacity on a continuous grade is designed as a function
of depth of water flow in the street gutter and the inlet grate constant.
The grate constant is determined empirically by the inlet manufacturer.
Note that inlets shall be spaced so that allowable inlet capacity
intercepts at least 75 percent (75%) of the gutter flow during the 10-
year rain event.
Following are tables showing the allowable inlet capacities in continuous
grade conditions:
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
16.00
Allowable Inlet Capacity, Q (cfs.)
Green Space Area - Depression Conditions
Neenah R-1772, With Type 'D' Beehive Grate
14.00
East Jordan 1022Z1, With 6509-O Beehive Grate
Neenah R-4215-C
12.00
East Jordan 6610
Inlet Capacity, Q (cfs)
10.00
8.00
6.00
4.00
2.00
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
17.0
17.5
18.0
18.5
19.0
19.5
20.0
20.5
21.0
21.5
22.0
22.5
23.0
23.5
24.0
Water Depth, D (inches)
8.00
Allowable Inlet Capacity, Q (cfs.)
Pavement Area - Depression Conditions
7.00
Neenah R-2502, With Type 'D' Grate
East Jordan 1022Z1M1
Neenah R-2580-C, With Type 'G' Grate
6.00
East Jordan 1585, With M Open Grate
Inlet Capacity, Q (cfs)
5.00
4.00
3.00
Neenah R-3036-B, With Type 'S' Grate
East Jordan 5100ZM1
2.00
1.00
0.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
Water Depth, D (inches)
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
6.00
Allowable Inlet Capacity, Q (cfs.)
Sag Condition - Curb and Gutter
Neenah Foundry Castings
5.00
Neenah R-3010, With Type 'A' (Rectangle Grate)
Neenah R-3010, With Type 'R' (Diagonal Grate)
Neenah R-3010, With Type 'S' (Sinusoidal Grate)
Neenah R-3159-A, With Type 'A'(Rectangle Grate)
Neenah R-3067, With Type 'C' (Rectangle Grate)
Neenah R-3067, With Type 'R' (Diagonal Grate)
4.00
Inlet Capacity, Q (cfs)
3.00
2.00
1.00
0.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
Water Depth, D (inches)
Inlet Capacity, Q (cfs)
6.00
5.00
4.00
3.00
2.00
East Jordan 7010ZM1T1, (Rectangle Grate)
East Jordan 7010ZM5T1, (Diagonal Grate)
East Jordan 7010ZM3T1, (Sinusoidal Grate)
East Jordan 7020Z, With Type 'M1' (Rectangle Grate)
East Jordan 7020Z With Type 'M2' (Sinusoidal Grate)
East Jordan 7030Z1, With Grate Type M2 (Rectangle Grate)
East Jordan 7030Z1, With Grate Type M3 (Diagonal Grate)
East Jordan 7030Z1, With Grate Type M5 (Diagonal Grate)
Allowable Inlet Capacity, Q (cfs.)
Sag Condition - Curb and Gutter
East Jordan Foundry Castings
1.00
0.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
Water Depth, D (inches)
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
Allowable Inlet Capacity, Q (cfs.) - Continuous Grade Condition
2' x 2' Curb and Gutter Combination Casting
Neenah R-3010, Type 'A', 'R' and 'S' Grates
East Jordan 7010Z, Type M1T1, M5T1 and M3T1 Grates
Longitudinal Slope, SL = 0.50%
Longitudinal Slope, SL = 1.0%
Longitudinal Slope, SL = 2.0%
Longitudinal Slope, SL = 3.0%
Inlet Capacity, Q (cfs)
Longitudinal Slope, SL = 4.0%
Longitudinal Slope, SL = 5.0%
Longitudinal Slope, SL = 6.0%
Water Depth, D (inches)
Allowable Inlet Capacity, Q (cfs.) - Continuous Grade Condition
33" Round Curb and Gutter Combination Casting
Neenah R-3159-A, Type 'S' Grate
East Jordan 7020Z, Type M1 and M2 Grates
Inlet Capacity, Q (cfs)
Longitudinal Slope, SL = 0.50%
Longitudinal Slope, SL = 1.0%
Longitudinal Slope, SL = 2.0%
Longitudinal Slope, SL = 3.0%
Longitudinal Slope, SL = 4.0%
Longitudinal Slope, SL = 5.0%
Longitudinal Slope, SL = 6.0%
Water Depth, D (inches)
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
Allowable Inlet Capacity, Q (cfs.) - Continuous Grade Condition
2' x 3' Curb and Gutter Combination Casting
Neenah R-3067, Type 'C' and 'R' Grates
East Jordan 7030Z1, Type M2, M3 and M5 Grates
Inlet Capacity, Q (cfs)
Longitudinal Slope, SL = 0.50%
Longitudinal Slope, SL = 1.0%
Longitudinal Slope, SL = 2.0%
Longitudinal Slope, SL = 3.0%
Longitudinal Slope, SL = 4.0%
Longitudinal Slope, SL = 5.0%
Longitudinal Slope, SL = 6.0%
Water Depth, D (inches)
Continuous Grade Condition Table assumptions:
Inlet Capacity on a continuous grade Equation:
Qi = K x d5/3
Qi =
K =
d =
Rate of flow into the inlet, cfs
Inlet grate constant based on grade geometry and
longitudinal and transverse slopes (provided by
manufacturer)
(Neenah inlet constants are utilized for comparable East
Jordan grates)
maximum depth of water surface above inlet, ft
Casting capacity reduced by 50% for clogging.
Continuous grade capacity curves only apply when street flow is at the
maximum allowable depth. For lower gutter depths, the inlet
interception rate will decrease.
SW7.05 Gutter Flow
1. Introduction
The capacity of gutter flow in curbed pavement helps determine proper
inlet casting and inlet spacing designs. Many factors affect the flow
capacity of gutters. These factors work together to provide a safe limit
on stormwater encroachment into driving lanes and parking areas.
June 15, 2012 (last draft date) 10

City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
Longitudinal Gutter
Slope, S L (%)
2. Allowable Use of Streets for Stormwater Flows
See Table 5.4.3.1 and Table 5.4.3.2 for a description of the allowable
encroachment into driving lanes for various street types and widths.
The minor and major storm events are to be defined and calculated per
the methods described in Chapter 5, Section 2, Hydrology.
3. Gutter Flow Capacity
Following is the table for Allowable Gutter Capacity. This table may be
used in lieu of separate calculations unless the actual street design is
not represented by the assumptions listed below the table.
Gutter Flow Equation (Modified Manning’s Equations)
Top Width of
Gutter Flow, T
(ft)
Depth of Gutter
Flow, d (ft)
Q = 0.56 (S x 1.67 S L 0.50 T 2.67 )/n,
Where:
Q = Flow, cfs
S x = pavement cross slope, (ft/ft)
S L = average longitudinal slope of gutter, (ft/ft)
T = top width of flow extending from face of curb to street, ft
n = Manning’s roughness coefficient
Table 5.4.5.3.1
Allowable Gutter Capacity
GUTTER CAPACITY, Q (cfs)
5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0.50 0.3 0.8 1.7 3.1 5.0 7.5 10.0 10.0 10.0
0.75 0.3 1.0 2.1 3.7 6.1 9.2 10.0 10.0 10.0
1.0 0.4 1.1 2.4 4.3 7.0 10.0 10.0 10.0 10.0
1.5 0.5 1.4 2.9 5.3 8.6 10.0 10.0 10.0 10.0
2.0 0.5 1.6 3.4 6.1 9.9 10.0 10.0 10.0 10.0
2.5 0.6 1.7 3.8 6.8 10.0 10.0 10.0 10.0 10.0
3.0 0.6 1.9 4.1 7.5 10.0 10.0 10.0 10.0 10.0
3.5 0.7 2.1 4.5 8.1 10.0 10.0 10.0 10.0 10.0
4.0 0.7 2.2 4.8 8.6 10.0 10.0 10.0 10.0 10.0
4.5 0.8 2.3 5.1 9.2 10.0 10.0 10.0 10.0 10.0
5.0 0.8 2.5 5.3 9.7 10.0 10.0 10.0 10.0 10.0
Gutter Capacity Table Notes and Assumptions:
Sx = 2.0% or 0.020 ft/ft
N = 0.016
A minimum o f 75% of design flow shall be intercepted by inlet
Gutter width 1.5 feet
Maximum allowable gutter flow for minor storm event 10 cfs
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City Utilities Design Standards Manual Chapter 7
Stormwater Design
Inlets
5.4.7 Standard Drawings Create Links to Detail Pages
STRUCTURES:
Manhole Structure
STR-1 Standard 48” Manhole (Page 1)
STR-1a Standard 48” Manhole (Page 2)
Stormwater Specific
STR-26 Precast 30” Round Inlet
STR-27 Field Created 30” Round Inlet
STR-28 Precast 30” Round Inlet
STR-29 Field Created 30” Round Inlet
STR-30 24” Inlet
STR-31 2’ x 2’ Inlet
STR-32 2’ x 3’ Inlet
STR-33 30” x 30” Inlet
STR-35 Trench Drain Type I
STR-36 Trench Drain Type II
?? 8” – 30” Nyloplast Drain Basin
CASTINGS:
Stormwater Specific
C 6-1 24” Storm Manhole Casting
C 7-1 24” Beehive Casting
C 8-1 30” x 30” Beehive Grate
C 8-2 30” x 30” Beehive Grate
C 9-1 2’ x 2’ Alley Casting
C 9-2 2’ x 2’ Alley Casting
C 10
24” Beehive Casting
C 10-1 2’ x 2’ Curb and Gutter Casting
C 10-2 2’ x 2’ Curb and Gutter Casting
C 10-3 2’ x 2’ Curb and Gutter Casting
C 10-4 2’ x 2’ Curb and Gutter Casting
C 10-5 2’ x 2’ Curb and Gutter Casting
C 10-6 2’ x 2’ Curb and Gutter Casting
C 11
2’ x 2’ Alley Casting
C 11-1 2’ x 3’ Curb and Gutter Casting
C 11-2 2’ x 3’ Curb and Gutter Casting
C 11-3 2’ x 3’ Curb and Gutter Casting
C 11-4 2’ x 3’ Curb and Gutter Casting
C 11-5 2’ x 3’ Curb and Gutter Casting
C 12
2’ x 2’ Curb and Gutter Grate
C 12-1 33” Round Curb & Gutter Casting
C 12-2 33” Round Curb & Gutter Casting
C 12-3 33” Round Curb & Gutter Casting
C 13
2’ x 3’ Curb and Gutter Casting
C 14
30” x 30” Beehive Grate
?? 8” – 10” Grade Assembly
?? 12” – 30” Grade Assembly
June 15, 2012 (last draft date) 12