INSPEC41648 - Laserfiche WebLink

Home Browse Search

III. COMMENTS -COMPLIANCE Below are comments on the inspection. The comments include discussion of observations made during the inspection. Comments also describe any enforcement actions taken during the inspection and the facts or evidence supporting the enforcement action. obscuring the riprapped channel (particularly in the vicinity of points of confluence with steep drainage chutes). Because the ditch itself is 10 feet or more lower than the crest of the refuse pile, upland flows were still conveyed away from the refuse, with no impact to the disposal pile. The steep riprap energy dissipater segments at the lower end of both wings of the Upper Diversion were impacted by the high flows; riprap was dislodged and washed downslope, and gully erosion resulted. Photo 2675 is at the east Upper Diversion outlet energy dissipater, 2681 is a view looking down from the upper end of the west Upper Diversion outlet energy dissipater, 2682 is a view up the slope toward the west outlet. Photos 2676 through 2679 depict various segments along the Upper Diversion where the riprapped ditch was largely or completely sifted in. Impacted segments of the CRDA-2 upper diversion and outlet energy dissipater structures will need to be restored to design condition. There was some sediment deposition along the lower 40 feet of the second terrace drain, at the west end. The drain apparently overtopped at the lower end near junction with the West Collection Ditch. Maintenance warranted to remove sediment deposition, restore design capacity. The drainage along the toe of the reclaimed powder magazine road had eroded but had been regraded since the storm. Graded segments will need to be seeded; also a steep cobble lined segment at the curve above the old concrete structure will need to be repaired. Coal Creek Channel Vicinity There was evidence of recent flow down the Coal Canyon channel, but no problems were evident along the channel itself. The riprap transition zone segment near the Pond 13 outlet has held up well; primary flow path is through the center portion of the riprap channel. Further upstream along the segment between Pond 6 outlet and Pond 10 outlet, it was noted that operator had recently installed riprap along the scoured segment of the left bank upstream from Pond 10, as requested in the previous inspection report. The repair work has held up and functioned well. The channel segment downstream of the repair area appears to have developed a wider and shallower primary flow channel, with reduced bank scour. Flow now appears to be dispersed across the channel, rather than concentrated along the left bank. The channel depth at the Pond 10 primary discharge pipe outlet is now approximately 5' below the pipe elevation; prior to upstream channel repairs and recent flow, the primary flow channel bottom was approximately 7.5' to 8' lower than the pipe elevation. Photo 2695 is a view upstream, with the Pond 10 outlet pipe in right center of photo. Photo 2696 is a downstream view, with Pond 10 pipe outlet at left center of photo. On Haul Road 4, a short distance up-gradient of the Coal Creek crossing between the North Portal area and the CRDA refuse areas, there is a 24" culvert that conveys undisturbed drainage beneath the road and down to Coal Creek (the culvert is at the lower end of the North Portal Area West Diversion Ditch). The culvert was partially blocked with sediment and had overtopped, with flow running across and down Haul Road 4, spilling off the road at various locations (Photo 2683). The culvert needs to be restored to design condition; ditch segment between culvert outlet and the riprapped downdrain to Coal Creek needs to be cleaned out, and the segment of Haul Road 4 affected by deposition needs to be graded. Further south along the road, the ditch outlet segment that runs adjacent to CBA-1 sediment sump, down to Coal Creek, had partially silted in and needs to be cleaned out. Road grading and ditch maintenance is warranted in various locations along most of the roads within the areas impacted by the storm event. There was a shallow pool of water in Pond 6, elevation well below primary discharge elevation. Pond 10 was muddy at both ends, but contained no water. High water marks were approximately 6 inches below the primary discharge pipe elevation. 6