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

Boggs Mountain Demonstration State Forest Draft Management Plan, June 2008
Work Site Descriptions
ROAD 100
Mileage begins at the junction of Road 300(west) and proceeds eastward
Site1: Mile 0.0 to 0.5 (2640 ft.)
Priority: High
This section of road is insloped with an outside berm and an inboard ditch. The most significant
problems are the serious erosion that is occurring with the inboard ditch and surface erosion of
the roadbed. Drainage structures from Road 300, which is upslope approximately 100-200 feet,
are having a significant impact on the amount of concentrated runoff accumulating on this section
of Road 100. As a result, the ditch relief culverts are overwhelmed and are highly susceptible to
plugging. In some places the inboard ditch has eroded to 5 feet wide and 6 feet deep, while in
other downslope locations, the inboard ditch has filled with fine sediment and is non-existent. The
headwall for the culverts, in some cases, is non-existent or is badly degraded. The berm on the
outside road edge channels surface runoff back onto the roadbed. Even where the road surface
is level, crowned or slightly outsloped, the outside berm prevents free-flow drainage of the road
surface. There are several waterbars that drain surface runoff, but the main problem is with the
inboard ditch. Most of the sediment yield is dissipated on the downhill slopes, but a fair
percentage is delivered to Mill Creek. Parent rock exposed first .05 miles of road and then at .15,
.5-.7 miles. Inboard ditch is filled in and the berm deteriorating in some spots. Runoff flows
downhill from culvert #4.
Remedial treatments include:
1. Outslope road surface
2. Remove ditch relief culverts and replace with rolling dips or rocked fords
3. Excavate outside berm and use spoil to fill inboard ditch
4. Upgrade culvert #2 to 18” diameter or install rocked ford and armor outfall
5. Retain inboard ditch, mile 0.7 to 0.75
Site 2: Mile 0.75
Priority: High
Mill Creek Stream Crossing
There are currently two 30” diameter culverts at this stream crossing with a headwall of approx. 5
feet. A waterbar drains the overflow but does not direct the runoff back into the watercourse (High
Diversion potential). Slope erosion into inboard ditch just past Mill Creek.
Remedial treatments include:
1. Replace and install larger culvert (diameter 72”, length 40 feet)
2. Install Pipe Arch culvert (72” diam.)
3. Increase headwall height
4. Maintain vegetation control at inlet
5. Install Trash Rack to prevent debris from plugging culverts
6. Install Critical dip
Site 3: Mile 0.75 to 1.2 (2376 ft.)
This section of road is insloped with an outside berm and an inboard ditch. The berm on the
outside road edge channels surface runoff back onto the roadbed. There are several waterbars
that drain surface runoff, but the main problem is with the inboard ditch. The inboard ditch has
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