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<br />Mr. Stephen G. Rathbun -2- August 26, 1994 <br />In regard to Item No. 2, the August 12, 1994 inspection report states on page 1 of Section III that <br />the minesite received 2.99 inches of rain in 24 hours on August 3, 1994. This exceeded the <br />10-year, 24-hour event of 2.90 inches. Of that 2.99 inches of rain, the inspection report states that <br />2.6 inches fell in 4 hours. For the entire week preceding the August 12 inspection, the mine site <br />received a total of 3.65 inches of rain. It was this rainfall intensity that caused a wooden retaining <br />wall beneath the refuse conveyor to fail, allowing disturbed area drainage to go into the Purgatoire <br />River. The retaining wall was in place and functional at the time of the May 9, 1994 State <br />inspection, although this was not specifically stated in the inspection report. When we came upon <br />this area during the August 12 inspection, we cited the violation. <br />As for Item No. 3, the May 9, 1994 inspection report states, on page 6 of Section III, that the <br />operator was just beginning to finish up work at the recently installed weigh bin east of the coal <br />silo, and that cleanup work would follow. Installation of an upgraded sediment control system was <br />occurring at the time of the May 9, 1994 State inspection. Temporary sediment control measures <br />(straw bales) had been taken at that time and were completely functional. <br />As observed during the July 14, 1994 State partial inspection, the new sediment control system <br />was in place and functioning at that time, although a minor refinement was advised at that time. <br />After the July 14 State inspection, but before the August 12 inspection, the operator performed <br />grading operations in the area east of the coal silo that rendered portions of the sediment control <br />system nonfunctional, resulting in an out-0f-compliance situation. The State cited this during the <br />August 12 inspection. <br />Finally, referring to Item No. 4, the Reno Mattress Ditch on the west side of the refuse disposal <br />area was in compliance at the time of the May 9, 1994 State inspection, although not specifically <br />noted in the inspection report. As stated in Item No. 2 above, considerable rain fell at the mine <br />site during the week before the August 12, 1994 oversight. Although the Reno Mattress Ditch <br />cross section was designed for the 100-year, 24-hour event, the heavy rains caused the rocks held <br />within the Reno Mattresses to shift and bunch up, thereby reducing the cross sectional area of the <br />ditch, and allowing disturbed area drainage to breach the ditch and ultimately flow offsite. When <br />the Division conducted its inspection on August 12, the violation was cited. <br />The Division believes that this letter provides a satisfactory response to the OSM letter of <br />August 18, 1994. If you have any further questions, please contact me. <br />Sincerely, <br />J seph J. Du sh <br />Environmental Protection Specialist <br />ce: Dan Hernandez, DMG <br />M:\OSS\emmVL\hb~m,jjd <br />