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= <br />May 27, 2014 <br />H udd leston- Berry Engineering and Testing, LLC <br />640 White Avenue <br />Grand Junction, CO 81501 <br />Attention: Mike Berry, PE <br />Civil, Structural & Geotechnical Engineers <br />222 South Park Ave. • Montrose. C�) 8'140 t <br />Ph.. (970) 249 -6828 • FAX. (970) 249 -0945 <br />SUBJECT: Monthly Summary of Vibrating Wire Piezometers May 2014, <br />Bowie Mine No. 2, Coal Waste Disposal Area No. 2 <br />Dear Mr. Berry, <br />Buckhorn Geotech, Inc. (BGI) has conducted on -going monitoring of inclinometers and <br />vibrating wire piezometers previously installed at Coal Waste Disposal Area No. 2 (CWDA <br />No. 2) for Bowie Resources, LLC (Bowie) since 2005. The undersigned took over <br />responsibility of reporting this data last month. As part of this effort, a decision was <br />made to reformat the graphic data presented as the historic time line was making the <br />graphic display cumbersome. The reformatting process included review of all prior data <br />for quality control. During the review, it came to the attention of the undersigned that <br />the previously reported pore water pressure data for Vibrating Wire Piezometers VWP -08, <br />VWP -09 and VWP -10 was not accurate. It is our opinion that the corrected data would <br />increase the overall stability of the Gob pile. An explanation follows: <br />The formula for computing the pore water pressure with the vibrating wire piezometer is: <br />P, = A(Hz') + B(Hz) + C + Elevation Correction <br />where A, B, and C are Calibration Parameters Factors unique to each piezometer <br />and Hz is the frequency of the vibrating wire in the piezometer <br />For piezometers VWP -08, 09 and 10, the Calibration Factors used in the prior spread <br />sheet were incorrect. Therefore a new spreadsheet and graphic summary was prepared <br />for the current and future reporting periods. The undersigned also reviewed past data <br />from the damaged and abandoned piezometers VWP -01 thru VWP -04 and VWP -07 and <br />did not note errors in reported spread sheet calculations for these piezometers. Table 1 <br />below presents the correct unique parameter set for each remaining active piezometer. <br />Table 1— Individual Piezometer Parameters <br />Item <br />VWP -05 <br />VWP -06 <br />VWP -08 <br />VWP -09 <br />VWP -10 <br />A Factor <br />- 2.15200E -05 <br />- 1.17264E -05 <br />- 1.35819E -05 <br />- 1.97147E -05 <br />- 1.85558E -05 <br />B Factor <br />0.0074253 <br />- 0.01452294 <br />- 0.01331596 <br />0.007292937 <br />0.004180301 <br />C Factor <br />177.09 <br />137.8985 <br />144.6463 <br />142.7307 <br />139.7038 <br />Approx. Surface Elev <br />6015 <br />6126 <br />6110 <br />6017 <br />6020 <br />Approx. Piezometer Elev <br />5988 <br />6079 <br />6075 <br />5982 <br />5985 <br />Elev Correction (psi) <br />3.05 <br />3.09 <br />3.09 <br />3.05 <br />3.05 <br />May 2014 VWP report-5-27-14 PN #13- 231 -001 <br />Page 1 of 2 <br />