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

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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 62
Boggs Mountain Demonstration State Forest Draft Management Plan, June 2008 failed in several locations due to sediment deposition and dense vegetation within the ditch. This has directed runoff onto the roadway and has led to some surface erosion. Ditch relief culverts and waterbars have been functioning properly in this section of road. Exposed rock at .9 and 1.1 miles. Inboard ditch non-existent in some places. Tree growing over road at 1.15. 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 Site 4: Mile 1.2 to 1.7 (2640 ft.) This section of road is insloped with an outside berm and an inboard ditch. Due to high rock content of roadway, there is minimal surface erosion occurring. Most of the ditch relief culverts in this reach of road were plugged or partially plugged. The waterbars in this section of road have been functioning properly. Exposed rock at 1.45-1.5, and 1.7 miles. 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 Site 5: Mile 1.75 to 2.2 (2376 ft.) This section of road is insloped with an outside berm and an inboard ditch. Due to high rock content of roadway, there is minimal surface erosion occurring. Most of the ditch relief culverts in this reach of road were plugged or partially plugged. Exposed rock at 1.75-1.8, 1.9, 2.0, and 2.2 miles. 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 Site 6: Mile 2.3 to 2.7 (Jct. Rd. 300) East (2112 ft.) This section of road is insloped with an outside berm. There is minimal or no inboard ditch in this section. Existing waterbars are responsible for road surface drainage. There are no ditch relief culverts until the junction of Road 300. Berm on right side of road. Exposed rock most of the way, but especially around mile 2.4. Bad erosion near junction. Vegetation grown over road. Remedial treatments include: 1. Outslope road surface 2. Install rolling dips 3. Excavate outside berm and smooth over road surface Site 7: Mile 2.7 to 3.15 (Big Spring) (2376 ft.) This section of road is currently outsloped, level or crowned with an outside berm. There is no inboard ditch and consequently no ditch relief culverts. Even though the road surface is level, crowned or slightly outsloped, the outside berm prevents free-flow drainage of the road surface. Existing waterbars are responsible for road surface drainage. Exposed rock at 2.8 miles. 63
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Boggs Mountain Demonstration State Forest Draft ... - Cal Fire

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