September-October 2000

Miners Ridge Road-to-Trail Restoration Project at Prairie Creek State Park

The Miners Ridge Road-to-Trail Restoration Project was implemented to improve a popular hiking trail and reduce erosion hazard in Prairie Creek State Park.

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By Ethan Casaday

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The initial move-in up Miners Ridge Road began on September 21, 1999, and took 12 hours because of the necessity for brush removal. On September 23, the John Deere excavator was moved in and began work at upper station 25+00. This walk-in took three hours from Gold Bluffs Beach campground. During this time, the older Komatsu was moved down the road to upper station 00+00. The old Komatsu was then moved out on October 4, and a shorter transport vehicle was able to make the pickup at Gold Bluffs Beach. The new John Deere was then moved out on October 6, and the shorter transport vehicle was again able to make the pickup at Gold Bluffs Beach. On October 7, the new Komatsu was moved in to replace the John Deere and began work at lower station 22+20. The new Komatsu was then moved out on October 18, and the shorter transport vehicle was again able to make the pickup at Gold Bluffs Beach.

To protect the historic corduroy road, and because of wetland conditions in some areas, a 4x4 vehicle with a truck-bed fuel tank was not permitted to travel to the upper end of the project. For fuel supply, a 500-gal. off-highway diesel fuel tank was placed at the lower end of Miners Ridge Road. The tank was filled two times by a Renner fuel truck during the project. The tank was placed in a small depression lined with plastic for secondary-spill confinement. The tank was originally going to be placed farther up the road at lower station 00+00. However, an old bridge constructed of redwood logs with unknown weight limitations forced the tank location to be farther down the road. During the first week of the project, equipment work was 2 mi. from the fuel tank.

The excavator was filled daily by two park employees who transported fuel in 5-gal. cans on a motorized wheelbarrow from the tank to the work location. The park employees filled the excavator daily during the operator lunch break. The arrangement relieved the operator of all fueling responsibilities.

Upper Road Removal in Old-Growth Forest

The upper portion of this project involved the complete removal of 2,600 ft. of narrow forest road. The road removal took 83.5 hours over a 10-day period and included excavation of 1,840 yd.3 of roadfill and 140 yd.3 from four stream crossings (see Figure 2). The average production rate was 24 ft.3/hr. and 260 ft./day for the road removal.

Figure 2. Fill Volume Percentages
Fill volume percentages

A full recontour to the natural slope was obtained along the entire road-removal length. Organic material was separated from the fill and placed on the recontoured surface to protect against raindrop splash and sheet erosion. Because of the heavy load of organic material associated with the old-growth section of road, we were able to distribute a thick layer of logs, brush, and rotten material over most of the disturbed surface. Logs and large pieces of organic material were placed parallel to the slope and were tamped down to provide contact with the soil surface. In some places, the organic material placed on the final surface has 100% coverage and may be up to 3 ft. thick. At station 26+00, numerous logs were piled up to completely block the view of the road recontour from hikers traveling down the new trail reroute.

Stream crossings were excavated to recontour the natural channel shape, and an attempt was made to locate natural channel features. Additional logs were placed against the upper banks of stream crossings to prevent soil detachment from concentrated flow. The excavation of stream crossings involved locating buried stumps, boulders, logs, and black organic rich soil as indicators of the natural stream channel.

The road bench at wet areas and seeps at stations 4+00, 4+50, and 16+00 was outsloped and fill was moved down the road to a dry, more stable storage location. Past projects have indicated that fill material should not be placed on top of springs or seeps because this can cause saturation of the fill resulting in slope failure.

The main difficulty with this road pull was the result of the numerous large old-growth redwood trees. The trees greatly limited excavator swing room and reduced available roadfill for recontouring, especially at station 24+50. Extra travel is necessary to fill the cutbank behind a giant redwood tree because the typical swing pattern is altered. Instead of the typical scoop, swing, and dump pattern, the excavator was forced to rake a large pile of material along with him while moving down the road to an area behind a large tree, or material was hauled up the road one bucketload at a time from sites up to 50 ft. away.

Road-to-Trail Conversion

Similar to road removal, a road-to-trail conversion involves excavating the roadfill from the outside edge and placing it against the cutslope to create a natural-looking, recontoured slope. The trail conversion involves leaving a 4-ft.-wide portion of the road bench to serve as the new trail tread. It is important to note that the excavator cannot simply deconstruct the road and then tamp in a trail tread. Rather, the trail tread must be located on a portion of the original roadbed. This allows the trailbed to be located on a previously compacted surface and eliminates the oversteepened trail cutbank that would be created if the trail were recut into the fully recontoured material.

The lower portion of this project involved the reconstruction of 2,600 ft. of forest haul road into a gently curving hiking trail. The road removal took 84 hours over a nine-day period and included excavation of 2,445 yd.3 of roadfill and 280 yd.3 from eight stream crossings. The average production rate was 32 ft.3/hr. and 289 ft./day of road-to-trail reconstruction.

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Stream crossings were excavated to recontour the natural channel shape, and an attempt was made to locate natural channel features. A Humboldt crossing with numerous large logs was removed to expose the active stream channel at station 13+00. The logs removed from this crossing were placed against the east streambank to provide armor from high flows. This streambank needed additional excavation to remove some perched fill, and the logs blocked a more desirable trail-crossing location. Two cubic yards of small angular boulders were placed as bed armor in each of the two larger stream crossings. The rock armor provided a low water crossing for the Sweco bulldozer to cross without sinking into deep mud. The road bench at wet areas and seeps was excavated similarly to a stream crossing by creating a gentle swale, and fill was moved down the road to a dry, more stable storage location.

During the road-to-trail conversion, over 100 spruce and alder trees of 6-18 in. diameter at breast height (dbh) that were growing in the roadfill or against the cutslope were pushed over by the excavator. Trees and brush removed from the road right of way were pushed downslope into the surrounding forest. The material was not used as mulch on the rehabilitated road because of the need to do additional work with the Sweco and a trail hand crew. Next Page >

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