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2. I observed the recently constructed diversion ditch and the slope upgrade of that ditch <br />for any adverse stability conditions. The ditch is located downslope from the historic <br />King Mine buildings on the Bowie property. Historic rock retaining walls for slope <br />protection of the former rail lines appear to be in good condition and performing well <br />with no failures noted during our visit. The ditch appears to be graded to allow water <br />flow downslope to established drainages and the slope above the ditch is beginning to <br />achieve its natural angle of repose. We do not recommend any additional slope <br />protection measures at this time, since erosion blankets and seeding are unlikely to <br />perform well in the coal fines that make up the slope composition. The ditch should be <br />inspected and cleaned periodically as the slope naturally vegetates itself to match <br />existing conditions above. Any significant slope failures or changes in conditions should <br />be brought to our attention for possible mitigations recommendations. <br />3. In general, the grading and compaction of CWDA No. 2 appears to be progressing well <br />and significant work has been done since our last site visit on March 25, 2013, as <br />indicated by our weekly compaction testing and observation reports. <br />Closing <br />On -going monitoring of inclinometers and piezometers at CWDA No. 2 provides an indication of <br />the stability of the refuse as well as an indication of probable performance for other refuse piles <br />at Bowie. For these reasons, we recommend continued monitoring of this instrumentation on a <br />quarterly basis. We sincerely appreciate the opportunity to work with you on this project. If <br />you have any questions regarding this letter or the instrumentation monitoring at CWDA No. 2, <br />please don't hesitate to contact me at (970) 497 -8852 or dan @buckhorngeo.com. <br />Sincerely, r •�`� <br />BUCKHORN GEOTECH, INC. <br />��_ v 38334 `? <br />Daniel C. Quigley, P.E `0 'S_ <br />_3 . <br />L <br />Enclosures: Instrumentation Site Plan, Inclinometer Cumulative Displacements, Summary of Pore <br />Pressure Monitoring <br />cc: Jim Stover, J.E. Stover and Associates — ELECTRONICALLY ONLY <br />2nd Qtr Monitoring Report.doc PN #05- 126 -GEO <br />Page 3 of 4 <br />