environmental assessment for the hog lake road improvement project

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Ramona Hog Lake Road Improvement Project August 2011 Figure 13: Jurisdictional Drainages L & L Environmental, Inc., 2009 Vehicle use increases erosion rates and sedimentation through detachment, abrasion and changes to the road surface, making the local sandy and cohesionless soils susceptible to transport. Four-wheeled vehicles and motorcycles apply a shear stress parallel to the soil surface and a compression stress perpendicular to the surface. These stresses are most destructive on uphill route segments, on curves or route segments in which the tires may spin. Erosion and sedimentation will be prevented through the implementation of an Erosion Prevention Plan for the Project. In order to address The Santa Ana Regional Water Quality Control Board’s requirement to demonstrate how the Proposed Action would affect sedimentation movement in the watershed, the WEPP model (http://forest.moscowfsl.wsu.edu/fswepp/) was used to generate estimates of erosion. Using the WEPP model the amount of erosion generated was calculated for Hog Lake Road at various locations as an unpaved road (current condition), and Frank Springer & Associates, Inc. Page 75 of 79 Environmental Assessment
Ramona Hog Lake Road Improvement Project August 2011 those amounts were compared to the amount of erosion generated for Hog Lake Road as a paved road (condition after Proposed Action): An unpaved road 24’ wide at 94+77 to 84+77 yielded 1,155.63 lb of road prism erosion and 679.96 lbs of sediment leaving buffer. At 84+77 to 74+77, an unpaved road 24’ wide yielded 1,386.99 lb of road prism erosion and 850.06 lbs of sediment leaving buffer. At 74+77 to 64+77, an unpaved road 24’ wide yielded 1,397.17 lb of road prism erosion and 852.71 lbs of sediment leaving buffer. At 64+77 to 54+77, an unpaved road 24’ wide yielded 1,544.53 lb of road prism erosion and 950.69 lbs of sediment leaving buffer. At 54+77 to 44+77, an unpaved road 24’ wide yielded 1,397.17 lb of road prism erosion and 852.71 lbs of sediment leaving buffer. At 44+77 to 34+77, an unpaved road 24’ wide yielded 1,559.57 lb of road prism erosion and 954.76 lbs of sediment leaving buffer. At 24+77 to 14+77, an unpaved road 24’ wide yielded 1,096.78 lb of road prism erosion and 612.56 lbs of sediment leaving buffer. At 14+77 to 4+77, an unpaved road 24’ wide yielded 372.92 lb of road prism erosion and 188.37 lbs of sediment leaving buffer. At all of the above locations, a paved road 24’ wide yielded 0 lb of road prism erosion and 0 lbs of sediment leaving buffer. Clearly, paving the road will greatly reduce the quantity of sediment entering Canyon Lake/Lake Elsinore (TMDL 303 listed water bodies). Although runoff would increase erosion with a paved road, the implementation of mitigation measures/design features should reduce the amount of erosion to a level that is less than significant. For the Proposed Action, the Project would reduce federal/ACOE jurisdictional area by an additional 4,288 sf (0.098 acres), and state/CDFG jurisdictional area by an additional 6,429 sf (0.148 acres); however, these losses will be made up through the purchase of at least 0.15 acres of approved mitigation bank credit. If the Proposed Action is implemented with mitigation measures / design criteria employed, impacts to jurisdictional drainages and Canyon lake/Lake Elsinore and downstream in the watershed if the Proposed Action was implemented would be reduced to being less than significant. Cumulative Effects Projects and general development within the Forest, District and the Riverside Extended Mountain Area Plan (REMAP) area outlined in the Riverside County Frank Springer & Associates, Inc. Page 76 of 79 Environmental Assessment
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FINAL FRANK SPRINGER & ASSOCIATES,
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LIST OF TABLES Table 1: Mitigation
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