Boggs Mountain Demonstration State Forest Draft ... - Cal Fire

Boggs Mountain Demonstration State Forest Draft Management Plan, June 2008
Q= .4(1.86)152 = 113.1 cfs
The suggested culvert size for Lower Mill Creek was determined to be 40”.
Upper Mill Creek:
The crossing at Upper Mill Creek has a 30” culvert, measures 2.5’ from the base of the culvert to
the headwall, and 3.5’ to the road grade. The headwater depth is 1.4 culvert-diameters.
A=114 acres L= 832 feet (.2 miles) H= 320 feet
Tc= [11.9(.2) 3 /320] .385 = .044 hours (2.6 minutes)
Q= .4(1.86)114
= 84.8 cfs
The suggested culvert size for Upper Mill Creek was determined to be 44”.
Lower Spikenard Creek:
The crossing at Lower Spikenard Creek has a 48” (4’) culvert, and measures 8’ from the base of
the culvert to the headwall as well as to the road grade. The headwater depth is 2 culvertdiameters.
A=248 acres L= 3980 feet (.75 miles) H=840 feet
Tc= [11.9(.75) 3 /840] .385 = .139 hours (8.4 minutes)
Q= .4(1.86)248
= 184.5 cfs
The suggested culvert size for Lower Spikenard Creek was determined to be 52”.
83