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• Rule 1: Pelmiis <br />inches before compaction, and compacted within acceptable levels ofmoisture content. Material consisting <br />oflazge-size rock will be place inuniformlayersnotexceedingtheaveragesizeofparticles,liftsnotin <br />excessof36inches,andplacedinamannertominimizevoids,pockets,andbridging. The finallayerwill <br />contain material which has less than 25%ofrock largerthan 6 inches in largest dimension in a uniform laver <br />not exceeding 12 inches. <br />The crushed gravel will be durable to withstand the anticipated volume oftraffic. No acid- or toxic-fomung <br />substances will be used in access road surfacing. In addition to the gravel wearing surface, this measure <br />will provide stability to the access road. <br />Drainage ditches will be placed at the toe ofall cut slopes and intercept flows before switchbacks or large <br />fills. Ditches are sized to accommodate design flows with 0.3 feet offreeboazd. Ditch reliefcross~ulverts <br />(to transfer ditch flows across the roadway) or swales and berm reliefgaps remove storm nmofffrom the <br />roadway. Culverts (drainage structures), placed at natural grades, are used to cross drainages of <br />watersheds. <br />Culverts will be sized to accommodate design flows without a head over the conduit. However, the <br />minimum diameter is 18 inches to minimize plugging and accommodate maintenance. Al l culverts will have <br />mitered inlets, unless additional protection is needed to minimize erosion. Culverts are designed to sustain <br />• the vertical soil pressure, foundation conditions, and weight ofvehicles. Culverts will be covered by <br />compacted sill to a minimum depth of 1 foot to minimize collapse. <br />Cross culverts and berm gaps will be placed at spacings commensurate with grades and small natural <br />upland drainages to reduce flow velocities, inhibit erosion, and provide positive drainage to promote <br />stability. Exact locations will be sited in the field to coincide with natural upland drainages. The cross <br />culverts are placed at an invert slope oft to 3%. Cross-culvert and gap exit channels are riprapped down <br />fill embankments and discharge into riprap orstraw bales to dissipate energy. Plastic sleeves (elephant <br />trunks) are a design option to riprap cross-culvert exit channels. <br />The access road does not alter or relocate natural drainages. Upland watershed discharges are transferred <br />by culverts placed in established natural drainages. Culverts are designed to transfer peak runofffrom a <br />10-year, 24 hour event. In the event a design culvert end area exceeds 35 square feet, capacity is <br />increased to a 20-yeaz, 24-hour event. Culverts are at natural channel slopes to promote conveyance of <br />design flow, to not affect the normal flow orgradientofthe stream, and to not adversely affect fish migration <br />and aquatic habit or related environmental values. <br /> <br />~R-o <br />w.~<~~oam~-rnrgnsp~iyxoai »ya 2.05-28 (Revised 7/25/01) <br />