Page 557 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch14_500-554.qxd 8/7/10 8:56 PM Page 515

14.6 Design Information 515

Edwin
8´ sewer
Chadwick Street
82
Street
55.02
69.34
Limit of
assessment
Limit of
assessment
Mills 100´
Limit of assessment 6.7
#34
100´ #22 #24 #30 #40
#569 12˝ V.C. drain
Curb
Curb Curb 70 168.9
Curb 64.9
59.6 62.4 63.5 78.6
Hiram 106.5 14.8 13.5 41.6 89.6 109.5 142.5 15.2 7.7 44.5 73.6 116.0 140.2 206.0 5.6 23.0
38.8
76.7
86.5 85.5 133.5 148.8 157.0 39.6 58.6 83.8 110.8 135.0 191.7 214.1 21.0
98.5
7.5
58.5
29.4
33.5 70 70 48.0 37.0 70 84.1 80
6˝ C.I. water 25 46.0 50.7 37.8
10˝ C.I. water Limit of assessment 100´ #15 9.5 #27 #33 #41
#21
#555 100´ Limit of assessment
#31
10
N
Street
Lemuel Shattuck
Figure 14.13 Plan of Sanitary Sewer Shown in Profile in Fig.14.14. Conversion factor: 1 1 ft 0.3048 m; 1 1 in. 2.54 cm
25.4 mm

• End of design period. (d) Maximum daily flow 2 average daily flow. Critical
for capacity of treatment works. (e) Extreme maximum flow 1.5 maximum
daily flow. Critical for capacity of sewers and pumps.
The flow ratios in this outline are suggestive of small sewers and relatively rapidly
growing areas, the overall ratio of the extremes being (2 1.5 2 2 1.5 18) 18 to 1.
For large sewers and stationary populations the overall ratio is more nearly 4 to 1.
Important unknowns in necessary calculations are the entering volumes of groundwater
and stormwater. Their magnitude depends on construction practices, especially on private
property (house or building sewers).

14.6.2 Storm Drains and Combined Sewers
Storm drains are dry much of the time. When rains are gentle, the runoff is relatively clear,
and low flows present no serious problem. Flooding runoffs may wash heavy loads of silt
and trash into the system. However, most of the drains then flow full or nearly full and so
tend to keep themselves clean.