PERMFILE130333 - Laserfiche WebLink

Home Browse Search

• Soil surrounding channel PM-4D will be graded back to existing topography that was not disturbed by the slide. • The soil contributing azea for channels PM-4C and PM-4D is reclaimed (vegetated, with a cover of approximately 70 percent) or regraded (baze). • The rock riprap for the energy dissipater is sized using the riprap channel utility subroutine with flow velocity equal to the flow velocity in channel PM-4D. Because the PADER Method tends to undersize rock in steep channels, three-inches was added to the calculated Dso to provide a conservative design. Model Inputs: Drainage basin azea and hydraulic lengths, drainage heights and slopes were measured directly from a 1"=100'map, with a contour interval of 10 feet (see Drawing 1, Neckpit Slide Remediation Plan Planview). Input parameters are presented at the end of the SEDCAD4 modeling results. Approved curve numbers (CN) for the II-W South Area are presented in Appendix 13-SB, Drainage and Sediment Control Plan. Procedures: Channels PM-4. PM-4A. PM-4B and PM-4C • The contributing watershed area for PM-4C was determined using AutoCAD. • The contributing watershed azeas for channels PM-4, PM-4A and PM-4B were known from previous hydrologic design analyses. • The peak runoff from a 10-year, 24-hour storm event was calculated using the SEDCAD4 model. • Culvert PM-10 was sized using the culvert utility subroutine; the calculated diameter can then be compared against the existing pipe diameter to determine if a new culvert pipe should be installed. • Channel PM-4C was designed to ensure there is sufficient capacity to safely convey the peak runoff from the design storm event. The vegetated channel utility subroutine in SEDCAD was used to determine design parameters. Channel PM-4D • The contributing watershed area for PM-4D was determined using AutoCAD. Two watersheds were identified: 1) the area above the existing ranch road; and, 2) the steep slope adjacent to channel PM-4D. • SCC used a conservation design: the slide body and regarded soils used a CN=86, while reclaimed areas used a CN=71. TR-55 20-B.B-2 Revised 12/06