Page 437 - Civil Engineering Formulas

STORMWATER, WASTEWATER, AND ENVIRONMENTAL PROTECTION 363

Joint
Manhole cover filler Curb
Normal gutter line
6"
12 1
Opening
Depressed
gutter
6"
5' 3' wide
Rungs-14"
C. to C. Minimum
inside
width 2'-6"

Pipe

6"
Invert shaped with
concrete fill
FIGURE 13.1 Storm-water inlet with opening in a curb. (Merritt—Standard Handbook for
Civil Engineering, McGraw-Hill.)

When a grate inlet is used to collect the storm water, an opening of 18 in, or
more, is recommended. With a flow depth of up to 4.8 in, the inlet capacity is

Q 3Py 3/2 (13.7)
where P perimeter, ft, of grate opening over which water may flow, ignoring
the bars.
If the flow depth exceeds 1 ft 5 in, the capacity is
Q 0.6A 2 2gy (13.8)

where A total area of clear opening, ft 2
g acceleration due to gravity, 32 ft/s 2

Controlling Sewer-Water Flow
Controls used to regulate sewer-water flow include side weirs, siphon spill-
ways, and leaping weirs (Fig. 13.2). Flow diversion for a side weir is, in cu ft/s:
Q 3.32l 0.83 1.67 (13.9)
h