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Martin "AgAD <br /> Marietta <br /> MAY 0 g 2018 <br /> May 2, 2018 , DMOMOF <br /> LAIWA <br /> Via U.S. Mad and e-mail <br /> "WAND ,O <br /> Mr. Tim Cazier <br /> Colorado Division of Reclamation, Mining, and Safety <br /> 1313 Sherma Street, Room 215 <br /> Denver, CO 8�203 <br /> RE: YODER PIT, PERMIT NO. M-1980-189 <br /> EL P4SO COUNTY, COLORADO <br /> TEC NICAL REVISION (TR-02) <br /> CLARIFICATION IN RESPONSE TO ADEQUACY REVIEW <br /> Dear Mr. Cazier, <br /> Martin Marietta filed a request for a Technical Revision (TR-02) to modify the reclamation plan <br /> for Yoder Pit in El Paso County, Colorado, Colorado Department of Reclamation, Mining, and <br /> Safety, (DRMS) Mine ID# M-1980-189. On May 2, 2018, DRMS issues in a letter requesting <br /> clarification on two issues, as follows: <br /> 1. Rationile for removal of the riprap rundown on the north side of the pit; and <br /> 2. Clarification of the seeding method and discussion of the seed rate (per square foot). <br /> Rationale for emoval of the Riprap Rundown on the North Side of the Pit <br /> The topograph on the north side of the Yoder mine pit generally drains to the southwest, away <br /> from the pit slope. Therefore the water that drains down the slope is primarily that which falls on <br /> the slope. The soil making up the site is Bijou Sandy Loam, which the Natural Resources <br /> Conservation Service describes as a somewhat excessively drained soil with a slight erosion hazard <br /> and a "K" eros on factor (susceptibility to sheet and rill erosion by water) of 0.2, which is at the <br /> low end of low to moderate susceptibility. The pit wall has an approximate 4.5 to 1 horizontal to <br /> vertical slope i the location where the riprap rundown is proposed in the'current reclamation plan. <br /> Based on the slope angle and low to moderate susceptibility of the soil to sheet and rill erosion by <br /> water, the riprap rundown is judged to be unnecessary once vegetation is established on the slope. <br /> Prior to the establishment of vegetation in the area of the riprap rundown, the slope will be <br /> monitored for �rosion. If significant erosion is occurring on the slope, temporary erosion control <br /> measures, such as the installation of straw wattle or erosion control blanketing will be installed. <br /> Martin Marietta <br /> Rocky Mountain Di ision <br /> 1627 Cole Boulevar4,Suite 200 <br /> Westminster,Colorado 80401 <br /> (720)245-6400 <br />