2015-10-19_REPORT - C1996083 (2)

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970-249-6828 ■ 800-865-9847 (fax) ■ 222 South Park ■ Montrose, CO 81401 ■ wew.dowl.com tilaska ■ Arizona ■ Colorado ■ Montana ■ North Dakota ■ Oregon ■ Washington ■ Wyoming �M October 8, 2015 Huddleston -Berry Engineering and Testing, LLC 640 White Avenue Grand Junction, CO 81501 Attention: Mike Berry, PE SUBJECT: Third Quarter Monitoring Report, Vibrating Wire Line Piezometers, Bowie Mine No. 2, Coal Waste Disposal Area No. 3 Dear Mr. Berry, DOWL has conducted quarterly monitoring of installed vibrating wire piezometers on September 26, 2015 for the second quarter reporting period, 2015 at Coal Waste Disposal Area No. 3 (CWDA No. 3). A graphic plot of measured pore pressures over time is presented on the attached Figure 1, and numerically in Table 1 below. Table 1 summarizes the initial, prior and current readings and the difference in individual pore pressures since installation and prior readings. Table 1. Summary of Pore Pressures VWP ID # Initial Pore Pressure 10/31/14 (psi) 6/26/15 Pore Pressure (psi) 9/26/15 Pore Pressure (psi) Difference Since Installation (psi) Difference Since Last Reading (psi) VWP-A Deep 10.4 6.0 6.0 -4.4 0 VWP-A Shallow 4.7 4.5 4.9 +0.2 +0.4 VWP-B Deep 1 0.2 1 0.4 1 0.3 1 +0.1 -0.1 VWP-B Shallow 13.9 14.9 15.6 +1.7 +0.7 VWP-D 7.1 6.6 7.4 +0.3 +0.8 If you have any questions regarding this letter or the instrumentation monitoring at CWDA No. 3, please don't hesitate to contact me at (970) 497-8827 or w,nanaforf afowlxom. Respectfully Submitted, DOWL Wayne Pandorf, P.E. Sr. Geotechnical Engineer Enclosure: Figure 1 — Vibrating Wire Piezometer Data Graph Bowie CDWA 3 Q3 VWP Report 10-8-15 Project #7131.74108.01 Page 1 of 1