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(n) Column 14: The proposed street slope is listed in this column.
(o) Column 15: The allowable capacity for the street is listed in this column.
Allowable capacities should be calculated in accordance with procedures set
forth in Section 7.10,  Streets, of these Standards.
(p) Column 16: List the proposed pipe grade.
(q) Column 17: List the required pipe size to convey the quantity of flow necessary
in the pipe.
(r) Column 18: List the capacity of the pipe flowing full with the slope expressed
in Column 16.
Effective: November 16, 2000 DESIGN AND CONSTRUCTION STANDARDS 7-31
(s) Column 19: Tabulate the quantity of flow to be carried in the street.
(t) Column 20: List the actual velocity of flow for the volume of runoff to be
carried in the street.
(u) Column 21: List the quantity of flow determined to be carried in the pipe.
(v) Column 22: Tabulate the actual velocity of flow in the pipe for the design Q.
(w) Column 23: Include any remarks or comments that may affect or explain the
design. The allowable quantity of carryover across the street intersections should
often be listed for the initial design storm. When routing the major storm
through the system, required elevations for adjacent buildings can often be listed
in the column.
(2) Hydraulic and Energy Grade Line, and Design Losses: Storm sewers shall be
designed to convey the initial storm flow peaks without surcharging the sewer, and the
final energy grade line shall be at or below the proposed ground surface. To ensure that
this objective is achieved, the hydraulic and energy grade line shall be calculated by
accounting for pipe friction losses and pipe form losses. Total hydraulic losses will
include frictions, expansion, contraction, bend, and junction losses. The methods for
estimating these losses are presented in the following sections.
(a) Pipe Friction Losses: The Manning s  n values to be used in the calculation of
storm sewer capacity and velocity are presented in Table 7-3,  Manning s  n for
Storm Sewers, of these Standards.
(b) Pipe Form Losses: Generally, between the inlet and outlet the flow encounters a
variety of configurations in the flow passageway such as changes in pipe size,
branches, bends, junctions, expansion, and contractions. These shape variations
impose losses in addition to those resulting from pipe friction. Pipe form losses
are the result of fully developed turbulence and can be generally expressed as
follows:
HL = K(V2/2g)
Where HL = Head Loss (feet)
K = Loss Coefficient
V2/2g = Velocity Head (feet)
g = Acceleration of Gravity (32.2 ft/sec2)
Separate form losses attributable to pipe expansions and contractions, junctions
and manholes, and at pipe outlets may be more specifically calculated in the
following equations:
(i) Expansion Losses: Expansion in a storm sewer conduit will result in a
shearing action between the incoming high velocity jet and the
surrounding sewer boundary. Much of the kinetic energy is therefore
dissipated by eddy currents and turbulence. The loss of head can be
calculated as follows:
HL = Ke (V12/2g) [1 - (A1/A2)]2
Where HL = Head Loss (Feet)
Ke = Loss Coefficient (1.0, Sudden Expansion, 0.17,
Gradual 10% Taper, Refer to Figure 7-5,  Storm
7-32 DESIGN AND CONSTRUCTION STANDARDS Effective: November 16, 2000
(Expansion/Contraction), of these Standards)
V1 = Pipe Velocity Upstream of Expansion (feet per second)
A1 = Pipe Cross-Sectional Area Upstream of Expansion (ft2)
A2 = Pipe Cross-Sectional Area Downstream of Expansion
(ft2)
(ii) Contraction Losses: The form loss of head due to contraction can be calculated
as follows:
HL = Kc (V22/2g) [1 - (A2/A1)]2
Where HL = Head Loss (Feet)
Kc = Loss Coefficient (0.5, Sudden Contraction, 0.1,
Gradual Contraction, Refer to Figure 7-5,  Storm Sewer
Energy Loss Coefficient (Expansion/Contraction), of
these Standards)
V2 = Outfall Velocity (feet per second)
A1 = Pipe Cross-Sectional Area Upstream of Expansion (ft2)
A2 = Pipe Cross-Sectional Area Downstream of Expansion
(ft2)
(iii) Junction and Manhole Losses: A junction occurs where one or more
branch sewers enter a main sewer, usually at manholes. The hydraulic
design of a junction is in effect the design of two or more transitions, one
for each flow path. Allowances should be made for head loss due to the
impact at junctions. The head loss for a straight through manhole or at
an inlet entering the sewer may be calculated from the general form loss
equation, HL = K(V2/2g), presented at the beginning of this paragraph.
The form loss of head at a junction can be calculated as follows:
HL = V22/2g - Kj V12/2g
Where HL = Head Loss (Feet)
V2 = Outfall Velocity (Feet Per Second)
Kj = Loss Coefficient (Refer to Figure 7-6, Manhole and
Junction Losses, of these Standards
V1 = Inlet Velocity (Feet Per Second)
(3) Storm Sewer Outlet Losses: When the storm sewer system discharges into an open
channel, additional losses occur at the outlet in the form of expansion losses. For a
headwall and no wingwalls, the loss coefficient Ke = 1.0 and for a flared-end section the
loss coefficient is approximately 0.5 or less.
Effective: November 16, 2000 DESIGN AND CONSTRUCTION STANDARDS 7-33
FIGURE 7-5
STORM SEWER ENERGY LOSS COEFFICIENT
(EXPANSION, CONTRACTION)
D2
(A) EXPANSION (K ) (B) PIPE ENTRANCE FROM RESERVOIR
e
D2 D2
0* 2
= 3 = 1.5 V
BELL-MOUTH H = 0.04
D1 D1
L
2 g
10 0.17 0.17
20 0.40 0.40 2
V
45 0.86 1.06 0* SQUARE-EDGE H = 0.5
L
2 g
60 1.02 1.21
90 1.06 1.14
GROOVE END U/S
120 1.04 1.07
FOR CONCRETE
180 1.00 1.00
V2
PIPE H L = 0.2
2 g
* THE ANGLE 0 IS THE ANGLE
IN DEGREES BETWEEN THE
SIDES OF THE TAPERING
D1
SECTION.
D2
(C) CONTRACTIONS (K )
c
D2
K
c
D1
0 0.5
0.4 0.4
0.6 0.3
0.8 0.1
1.0 0
D1
REFERENCE: LINSLEY AND FRANZINI "WATER RESOURCES ENGINEERING"
MC GRAW-HILL, 1964
7-34 DESIGN AND CONSTRUCTION STANDARDS Effective: November 16, 2000
FLOW
FLOW
FIGURE 7-6: MANHOLE AND JUNCTION LOSSES
Q
3
,V
3
Q ,V
Q ,V 2 2
Q ,V Q ,V 1 1
1 1 2 2
Q Q
3 4
PLAN NOTE: FOR ANY TYPE PLAN
OF INLET
Q Q
4
3
h
h
Q ,V Q ,V
1 1 1
1
Q ,V Q ,V
2 2 2 2
Q ,V
3 3
USE EQUATION USE EQUATION
SECTION SECTION
CASE I
CASE II
INLET OR STRAIGHT THROUGH
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