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RULE 2 PERMITS <br />impacts to surrounding areas, and will be designed in such a manner to safely pass peak runoff from a 10 <br />year, 24 hour precipitation event (Please see Exhibit 24, Item 1 — Collom Access Road Culverts). <br />Additional design information for the Collom Access Road is listed in the Construction Notes section of <br />Sheet 3 of 9, on Map 25E. This road is specifically designed to meet the applicable haul road regulations <br />as well as Rio Tinto internal road design guidelines while minimizing additional disturbed area and <br />preventing environmental damage. As shown on Map 25E, the maximum sustained road grade is about <br />5.1 %. Cross fall slopes between centerline and road shoulders shall be between 1 and 2 percent as <br />directed by the field engineer. The road shall have an overall width of 100 feet, with a 24 foot paved <br />running surface as shown on the cross - sections. The road length is about 29,000 feet. <br />Asphalt pavement specifications shall be based on a 30 year design life with a 15" thick base course <br />(gravel) and 8.5" asphalt thickness. The pavement design is based on 50 ton coal haul trucks with axle <br />loads of about 81 psi. This specification assumes an R -20 silty sand subgrade material. Base course shall <br />be CDOT Class 6 aggregate. A 6 foot high berm shall be used at all locations where the roadway is <br />elevated. Cut slopes shall be 0.5H: IV or less when completed in competent rock. Elsewhere, cut slopes <br />in unconsolidated materials shall be laid back at 2H:IV or less as directed by the field engineer. <br />Requirements for fill placement shall be as specifically described in Rule 4.03.1 Haul Roads (3) (e) `Road <br />embankments ". A ditch shall be installed at toe of all cut slopes. If needed, temporary erosion control <br />measures shall be implemented during construction to minimize sedimentation and erosion until <br />permanent control measures can be established. <br />There are three main haul roads that will be built to haul overburden materials from the pit to the <br />temporary overburden stockpile. These are shown on Map 25D and are designated as the West, Central, <br />and East Haul Roads. The East Haul Road will also be used from the pit to haul coal to the truck dump. <br />This road configuration is needed given the valley configuration, the planned depth of the pit, and the <br />spoilpile design. These three roads have been designed to meet the applicable portions of Colorado <br />DRMS Rule 4.03.1 for Haul Roads. <br />All three roads are designed with an overall width of 120 feet as shown on the cross - sections. The West <br />Haul Road has a design length of about 5,300 feet and a maximum sustained slope of about 3.0 percent. <br />The Central Haul Road is the lowest in elevation and will eventually tie into the floor of the pit. It is <br />about 6,200 feet in length and has a maximum sustained slope of 8.3 percent. The East Haul Road is <br />about 5,200 feet in length with a maximum slope of 5.8 percent. These roads are also specifically <br />designed to meet Rio Tinto internal road design guidelines while minimizing additional disturbed area <br />and preventing environmental damage. Other design requirements are presented in the Construction <br />Notes section of Map 25D and are summarized below. Cross fall slopes between centerline and road <br />shoulders shall be between 1 and 2 percent as directed by the field engineer. <br />Upon completion of these three roads, the entire running surface of the road shall be surfaced with <br />approximately 1.0 to 1.5 inches of rock or crushed gravel for traction. Additional crushed gravel surfacing <br />shall be reapplied as necessary throughout the life of the roadway. A 6 foot high berm shall be used at all <br />locations where the roadway is elevated. Cut slopes shall be 0.5H:1 V or less when completed in <br />competent rock. Elsewhere, cut slopes in unconsolidated materials shall be laid back at 1.5H:1 V or less <br />as directed by the field engineer. Drainage from haul road shall be directed to the pit(s) wherever <br />possible. A ditch shall be installed at toe of all cut slopes. If needed, temporary erosion control measures <br />shall be implemented during construction to minimize sedimentation and eresicn until permanent control <br />measures can be established. The field engineer shall determine the need for control measures during <br />construction. Such temporary and permanent control measures would include silt fences, straw bales, <br />straw wattles, rock check dams, or other measures such as downstream sediment ponds. <br />Collom — Rule 2, Page 93 Revision Date: 1/23/09 <br />Revision No.: PR -03 <br />