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Rvle 2.' <br />• The crushed gravel will be durable to withstand the anticipated volume of traffic. No acid- or <br />toxic-forming substances will be used in haul road surfacing. In addition to the gravel running <br />surface, this measure will provide stability to the haul road. <br />• <br />u <br />The triangular-shaped berm on the outside edge of the roadway will be no less in height than the <br />mid-axle height of a haul truck with side slopes no steeper than 2h:ly. The berm does not <br />infringe upon the gravel travel way. Gaps in the berm will be provided at cross-culvert locations, <br />but in no case does spacing exceed 1,500 feet. The controlled spacing will provide positive <br />drainage off the roadway to promote stability. <br />Drainage ditches will be placed at the toe of all cut slopes and intercept flows before switchbacks <br />or large fills. Ditches will be sized to accommodate 10-year 24-hour design flows with 0.3 feet of <br />freeboazd. Flow velocities will be limited to the characteristics of soils without recourse to <br />design riprap or other ditch linings by relief drains (culverts) crossing under the roadway. <br />Culverts will be placed at crossings of watershed drainages and ditch relief cross-culverts <br />transfer runoff across (under) the roadway. Culverts will be designed to sustain the vertical soil <br />pressure, foundation conditions, and weight of vehicles. A minimum of 1 foot of cover over <br />culverts is specified by the regulations, but may be lazger based on Table 2.05.3-I. Culverts <br />across watershed natural drainages will be placed at channel grade to promote conveyance of <br />design flow, to not affect the normal flow or gradient of the stream, and to not adversely affect <br />aquatic habit or related environmental values. Cross-culverts will be placed at an invert slope of <br />2%. <br />TABLE 2.05.3-1 <br />LORENCITO CANYON MINE <br />MINIMUM COVER RECOMMENDATIONS' <br />Diameter of Culvert (inches) Minimum Cover (feet <br />12-42 3.0 <br />48-72 4.0 <br />78-120 4.0 <br />'Handbook of Steel Drainage & Highway Construction Products, American Iron and Steel <br />Institute (172 Kip maximum for 777C tractor rear axle reduced to 150 or less for coal loads.) <br />Culverts will be designed to transfer peak runoff from a 10-year, 24-hour precipitation event. If a <br />design culvert end azea exceeds 35 square feet, capacity is increased to a 20-yeaz, 24-hour <br />precipitation event. All culverts will be sized to accommodate design flows without a head over <br />the conduit. However, the minimum diameter is 18 inches to minimize plugging and <br />accommodate maintenance. Some drainage structures will be located on ephemeral, intermittent, <br />or perennial streams with watersheds of more then one square mile. <br />Page 2.05-22 and 23 Rule 2 Permits (Fe6.19.03).doc 2.05-22 (Revised 02/19/03) <br />