Appendix-JAppendix J
Table 1 Design
Criteria
TABLE 1
STORM DRAIN DESIGN CRITERIA
DESIGN CRITERIA LOS ANGELES COUNTY PUBLIC WORKS
Section 4.2 of LACPW 2006 Hydrology
Flood Protection Manual-Capital Flood Protection (50-year
frequency design)applies to canyons within
the County of LA that are subject to burning.
Where velocity exceeds 20 fps the total
horizontal angle of divergence or convergence
Maximum Velocity between the walls of a manhole and it's centerrvmax)line shall not exceed 5°45'
Extra thick walled pipe to increase cover over
interior steel
Minimum Diameter of 24-inch (standard conditions)
main line conduit 42-inch (serving a non-standard debris basin)
Minimum Slope (S min)0.1%
200ft (for S 30-inch)
Minimum Distance 400 ft (for 30-inch >d>45-inch)
Between Manholes 500 ft (for 45-inch and larger pipes)
MH's to be located outside of intersection
Manning's Roughness 0.013 for RCP
Coefficient (n)0.012 for HDPE
RCP -preferred
Drainage Pipe Material HOPE -allowed rarely (to date only for
"above ground"installations such as down a
slope face where movement is anticipated)
<45 0 and
<300 where:
Angle of Confluence 1.Qin of lateral exceeds 10%of mainline Q
2.V of lateral exceeds 20 fps
3.Size of lateral 2:60-inches
Allowable Computer 1.WMS for hydrology analysesPrograms(used for this
project study)2.WSPG for hydraulic analyses
MH NO.1 where mainline is :>;33"(2-D 102)
MH No.2 where mainline is ~36"(2-D 184)
Manholes Standards MH No.4 where lateral is 2:half the diameter
of the mainline except for mainlines are
:>;36"(2-D 113)
Minimum Cover over pipe 2ft
Project is in DPA Zone 6 (per 1-H 1.2 map
LACPW Sedimentation Manual)with a total
Sediment Production of 5,434 C.Y.per
Sediment Basin per Zone equation 3.3.3
Requires elevated Inlet per Table 4.1.1 of the
LACPW Sedimentation Manual Second
Edition dated March 2006
Page 1 of 1 -.8Harris &Associates