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r, R^-'_ ` a= °' ,c= " i feet <br /> IJs down the n , s ' Lz _ - - - _ _n foot <br /> riprap section cf the down drain _ �._ _ ppe�rs stable. <br /> Lower sections of the gully appear to be healing in most areas , but some <br /> recent downcutting was evident. <br /> 30. The Culvert F-2 cutfa] 1 at 65+70 is savereIy eroded. The approved plan <br /> specifies a 30" culvert at this location but an 18" CMP was installed. A <br /> gully with a vertical headwall flush with the culvert cutlet which <br /> averages 15 feet deep, with an 8 foot wide base and 25 foot top width <br /> extends for approximately 30 feet directly below the culvert to the lower <br /> edge of the road fill . The gully continues into a meadow for <br /> approximately 50 feet, averaging 4 feet de•ip by 4 feet wide. Soil and <br /> rock eroded from the gully has been ae'oesited in the meadow below. Some <br /> rock has been placed in the outfall section , but much of it is 2" x 10" <br /> material which is obviously insufficient to dissipate the erosive force <br /> of water which free falls 10 to 12 feet from the culvert outlet to the <br /> base of the gully. For short term remediation, the outfall will need to <br /> be properly armored . A sedimentation pond at the lower end of the long <br /> meadow adjacent to the road may need to be a component of the long term <br /> erosion/siltation control plan for the upper portion of Road F, if it is <br /> to have future operational use. <br /> 31 . Culvert F-4N conveys flows from gullies which extend from Culvert F-3 and <br /> the two culvert set. The gullies converge a short distance above the <br /> lower road segment and empty into the road ditch. Flow at this point is <br /> forced to make a right angle turn, since the culvert inlet is 30 to <br /> 40 feet down the ditch from the gully terminus and gully debris has <br /> accumulated in the ditch along this segment. The culvert is rusted and <br /> leaking approximately 4 feet in from the outlet. The channel .20 feet <br /> below the outfall has been properly riprapped . Below that, downcutting <br /> up to 6 feet deep extends for approximately 100 feet, with sediment <br /> deposition in the meadow below. <br /> 32. Culvert F-3N, depicted on Road F Drainage Plan Map as an 18" CMP at <br /> Sta. 52+40 was either completely buried or was never installed. It could <br /> not be found. <br /> Road E <br /> 33. The RD-1 ditch relief drain is well riprapped an d has not eroded despite <br /> the fact that drainage form approximately 3 ,500 feet of road is <br /> discharged at this point. However, a gully up to 2 feet deep is evident <br /> for several hundred feet on the aspen covered hillslope below. Severe <br /> erosion has resulted at the toe of the hillslope immediately above Coal <br /> Creek. The lower gully segment is 25 feet :,ride , 15 to 20 feet deep, and <br /> extends approximately 100 to 150 feet above the depositional fan at its <br /> base. <br /> 34. The outfall section immediately below Culvert E-3 has eroded 4 to 5 feet <br /> deep for a distance of 15 to 20 feet , and will need to be stabilized . <br /> /ern 8163F <br /> -4- <br />