Given the data below, design a section of sanitary sewer to carry these flows at

Question

Given the data below, design a section of sanitary sewer to carry these flows at minimum velocity of 2.5 fps. Assume that the minimum depth of the sewer below the street must be 8.5 ft and that an n value of 0.013 is applicable. Make a plan and profile drawing. ( Note: the invert into Manhole F must be 937 ft. Assume an invert drop of 0.2 ft across each manhole. ) Manholes (M) Distance between M (ft) Flow (gmp) Street elevations at M (ft) A-B 180 1200 A- 978 B-C 300 1450 B- 972 C-D 450 2200 C- 964 D-E 300 2500 D- 958 E-F 400 3000 E- 954 F- 949

Explanation / Answer

THIS WILL BE HELPFUL FOR YOU Minimum Sanitary Sewer Slopes By Thomas Gail Haws, P.E. New in 2009. Use the FREE pipe flow calculator at hawsedc.com. INTRODUCTION Minimum sanitary sewer slopes are established to provide a minimum cleansing velocity (usually 2 or 3 feet per second) at full flow or half-full flow. (The physics of hydraulic flow are such that a sloped pipe will carry flow by gravity half full at the same velocity as full.) Table 1 below gives minimum sewer slopes to provide 2 feet per second velocity assuming a Manning pipe roughness (n) of 0.013. For larger diameter pipes, considerations other than minimum cleansing velocity (such as construction tolerances and potential ground subsidence) may govern the minimum slope selection. Table 2 is a more generalized table with a range of common values: MINIMUM SANITARY SEWER SLOPE TABLE 1 (Standard Arizona Practice) Pipe Diameter (inches) Minimum Slope S={V/[1.486/n*(D/4)^(2/3)]}^2 4 0.0084 6 0.0049 8 0.0034 10 0.0025 12 0.0019 15 0.0014 18 0.0011 21 0.00092 24 0.00077 30 0.00057 36 0.00045 42 0.00037 48 0.00031 54 0.00026 60 0.00023 66 0.00020 72 0.00018 84 0.00015 96 0.00012 MINIMUM SANITARY SEWER SLOPE TABLE 2 PIPE SIZE MINIMUM SLOPE (in) (mm) FOR 2.0 ft/s (0.6 m/s) FOR 2.5 ft/s (0.75 m/s) Manning's n --> 0.010 0.013 0.015 0.010 0.013 0.015 8 200 0.0020 0.0034 0.0045 0.0031 0.0052 0.0070 10 250 0.0015 0.0025 0.0033 0.0023 0.0037 0.0052 12 300 0.0011 0.0019 0.0026 0.0018 0.0030 0.0040 15 380 0.00085 0.0014 0.0019 0.0013 0.0022 0.0030 18 450 0.00067 0.0011 0.0015 0.0010 0.0017 0.0023 24 600 0.00045 0.00077 0.0010 0.00071 0.0012 0.0016 30 760 0.0003 0.00056 0.00074 0.00052 0.00088 0.0012

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