City of Frisco Engineering Standards

Engineering Standards
• Column 18: Enter the selected pipe size for circular pipe.
• Column 19: Enter the selected width for box pipe.
• Column 20: Enter the selected height for box pipe.
• Column 21: Enter the appropriate Manning’s roughness coefficient “n” (0.013 for
concrete pipe and box culverts).
• Column 22: Enter the slope of the frictional gradient (hydraulic gradient) determined by
Manning’s equation. In a partial flow condition, the friction slope is the slope of the
water surface and should follow the slope of the pipe.
• Column 23: This is the upstream HGL before the structure and is calculated as Column
24 plus the friction loss (Column 3 times Column 22).
• Column 24: This is the beginning hydraulic gradient of the line. It is equal to the Design
HGL (Column 32) for the next downstream segment, or the beginning HGL of the system
as described above.
• Column 25: Velocity of flow in incoming pipe at the junction, inlet or manhole at the
design point identified in Column 2.
• Column 26: Velocity of flow in outgoing pipe (i.e. the pipe segment being analyzed) at
junction, inlet or manhole at design point identified in Column 2.
• Column 27: Velocity head of the velocity in Column 25.
• Column 28: Velocity head of the velocity in Column 26.
• Column 29: Head loss coefficient “Kj”, at junction, inlet or manhole at design point from
Table 4.5.
• Column 30: Multiply Column 27 by Column 29.
• Column 31: Head Loss at Structure. At a junction or change in pipe size, this is Column
28 minus Column 30. At a bend or inlet, this is Column 26 times Column 29. In all cases
this is 0.10’ minimum.
• Column 32: Design HGL at the design point identified in Column 2. Column 24 plus
Column 31. This is the beginning HGL (Column 24) for any upstream pipe discharging
into that junction.
• Column 33: Invert elevation for the pipe being analyzed at the downstream storm drain
station in Column 1.
• Column 34: Invert elevation for the pipe being analyzed at the design point (upstream
storm drain station) in Column 2.
• Column 35: Top of curb elevation at the design point in Column 2.
• Column 36: Comments regarding pipe being analyzed.
Section 4 – Drainage Design Requirements May 2012 Page 4-24