From Water and Wastewater Calculations Manual, Second Edition
10 Sewer Appurtenances
The major appurtenances used for wastewater collection systems include street (stormwater) inlets, catch basins, manholes, building connection, flushing devices, junctions, transitions, inverted siphons, vertical drops, energy dissipators, overflow and diversion structure, regulators, outlets, and pumping stations.
10.1 Street Inlets
Street inlets are structures to transfer stormwater and street cleansing wastewater to the storm sewers. The catch basin is an inlet with a basin which allows debris to settle. There are four major types of inlet, and multiple inlets. Location and design of inlets should consider traffic safety (for both pedestrian and vehicle) and comfort. Gutter inlet is more efficient than curb inlet in capturing gutter flow, but clogging by debris is a problem. Combination inlets are better. Various manufactured inlets and assembled gratings are available.
Street inlets are generally placed near the corner of the street, depending on the street length. The distance between inlets depends on the amount of stormwater, the water depth of the gutter, and the depression to the gutter. The permissible depth of stormwater in most U.S. cities is limited to 6 in (15 cm) on residential streets.
Flow in the street gutter can be calculated by the Manning formula, modified for a triangular gutter cross section (McGhee, 1991):
where Q =
gutter flow, m 3/ s or ft 3/s
= 22.61 m 3/(min m) = 0.38 m 3/(s m)
= 0.56 ft 3/(s ft)
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