1987-12-01_PERMIT FILE - C1981017 ‎(286)‎

• Permit No: C1981017
• IBM Index Class Name: PERMIT FILE
• Doc Date: 12/1/1987
• Section_Exhibit Name: Chapter V Table of Contents
• Media Type: D
• Archive: No

Chapter V
• This concept has been/will be implemented where practicable. Limiting site conditions
would include bedrock along the roads, or areas of narrow road width.
Riprap. Riprap has been/will be placed below culvert outfalls and road ditch outlets.
The riprap zone will extend approximately 8-10'. Riprap materials will consist of rock of
variable size and shape, mixed rather than segregated. Large size rock material will be
included for steeper slopes and areas of considerable flow velocity. The design is
indicated at Vol. 3-A, Map II-B-7 Att. 2.
Catchment Basins. Catchment basins will be installed where feasible along road
drainage ditches, to serve as sediment collection systems. The basins will be placed
across the road ditch, generally above the terminus of the road ditch outlet. Size,
depth and configuration will be determined by ground conditions and available space at
the respective sites. When ground conditions allow, the catchment basins will be
constructed as incised ponds, rectangular in shape, approximately 14' wide x 20' long x
4-6' deep.
Berms. Berms will be placed or retained along the outside portion of the roads when
necessary to prevent road drainage flowing over the outside and eroding the fill slope.
Areas of use would include portions of the road where the bedrock conditions prevent
excavation of a road ditch. In general, berms will not be used on roads or in sectors
• where winter snowplowing could knock berm material over the outside slope of the
road. Road maintenance will be done so as to avoid knocking berm material over the
outside slope of the road. Berms will generally be used in conjunction with water bars,
to direct flow of the road drainage.
Water Bars. Water bars of 6-12" in height are used at specified locations as necessary
to direct flows. Generally, water bars will be constructed at an angle, leading to the
inside ditch. Where feasible, however, water bars may be used to direct flows to the
outside edge of the road, for discharge onto moderate, well vegetated slopes. Water
bars to the outside will not be used where road drainage would discharge onto
unstable, steep, erosive or poorly vegetated slopes.
Culverts. Culverts are used at specified locations to convey road drainage. Where
possible, culvert outfalls should discharge onto vegetated slopes of moderate terrain,'
and avoid erosive soils. Riprap is placed beneath culvert outfalls.
Culvert downstructures are utilized as a means to convey drainage over unstable fills,
or unstable natural slopes. Downstructures may not be advisable in avalanche areas;
and in areas which normally receive heavy snowpack, as they are subject to snow
damage. The pressure of the snow tends to pull the downstructure apart from the
culvert at the band. Avalanches also compress, twist or otherwise damage the
• structure. In such circumstances alternative means, such as geowebbing, may be ,
employed.
18
Revised 7/92