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3.3.3 East Panel Landslide Geotechnical Evaluation <br />An East Panel landslide occurred on October 8, 2006. A geotechnical evaluation program <br />was designed by Agapito Associates Inc (AAI). This program was designed to determine <br />the slide plane and to determine parameters for future development of G and K pit. This <br />program also included sites in Z dip pit. A description of the sites is shown on Tables <br />3.3 -1 and 3.3 -2. <br />A total of three sites were completed with inclinometers, four sites with piezometers and <br />several sites with surface benchmarks. Surface benchmarks are used to monitor changes <br />in down -dip displacements over time. Data retrieved from inclinometers is deflection of <br />casing as a function of depth below the collar. Plots are developed of deflection versus <br />depth. Piezometers are used to monitor water levels. Planned instrumentation is shown <br />in Table 3.3 -3 <br />The monitoring was performed in accordance with the recommendations of Agapito <br />Associates Inc. as described below: <br />• Once per month during the dry season <br />• Once per week during the wet months of spring (April -May) and fall (September - <br />October). <br />Once per day after major precipitation (rainstorm) events >0.50 inches for 3 -4 <br />days transitioning to weekly for 1 -2 weeks and back to a normal schedule <br />thereafter. <br />In September of 2008, the required monitoring frequency was reduced (by AAI) to the <br />guidelines shown below: <br />• Once per month <br />• Once per week for two weeks following a major rainstorm event ( >0.5 inches) <br />In October of 2009, the original monitoring program was replaced with a state -of -the -art <br />program that was developed as a part of a new ground control plan submitted to MSHA <br />in advance of resuming mining operations in the land slide area. The monitoring plan was <br />developed with the assistance of AAI and Applied Geomechanics. <br />With the new system, three GPS stations were constructed in the slide zone. A fourth <br />station located outside the slide area acts as a reference and repeater station. Four <br />boreholes were drilled. These holes were drilled for instrumentation installation only; no <br />characterization core holes were completed at these sites. Each hole was cased with <br />inclinometer casing. Each borehole contains two fully grouted piezometers and three in- <br />place inclinometers. Each instrumentation station is equipped with audible sirens and <br />strobe light alarm systems, radio equipment, solar panel and batteries. <br />3 -27a <br />t7�,so� <br />s! «!mow <br />