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3.2.3. Piezometers <br />It is proposed to install piezometers in the boreholes described above. At Location 1, one (1) <br />piezometer will be installed. At Location 2, two (2) piezometers will be installed. These devices are <br />adept at measuring porewater pressures within the slope. High porewater pressures lead to lower <br />shear strengths within the soil and rock, which results in a higher likelihood of slope movement. <br />The devices should be attached to the inclinometer casing at each inclinometer. At Location 1, the <br />depth of the piezometer should be within the colluvium a few feet above the top of the rock drainage <br />blanket material. At Location 2, the lower piezometer should be within the colluvium a few feet <br />above the top of competent bedrock. The upper piezometer should be within the refuse a few feet <br />above the top of the colluvium. The piezometers should be finished using the fully grouted method. <br />3.2.4 Monitoring Schedule <br />Monitoring the performance of the RPE East refuse pile is deemed to be important to verify its long- <br />term stability. In -situ measurements relating to deformation and groundwater characteristics can <br />provide useful information as to the refuse pile's performance and give warning of possible <br />problems. <br />As stated in the original permit design in Exhibit 82, instrumentation will be placed in the refuse pile <br />after operations have started and enough material has been placed to reach design capacity grade at <br />each of the instruments shown in the monitoring plan (Exhibit 82, Appendix C). <br />For deformation monitoring, inclinometers will be placed along the refuse pile centerline within the <br />refuse pile. Additionally, mirrors will be placed on the toe buttress, refuse material, and /or outside <br />the refuse pile footprint. The advantages of mirrors are that they provide much more lateral coverage <br />than inclinometers typically provide and they can easily measure vertical deformations. The <br />disadvantages are that the precision of movement is far less than that for an inclinometer and mirrors <br />are often disturbed by animals, frost heave, and other environmental factors. <br />Groundwater monitoring will be carried out by installing piezometers to measure water pressures <br />within and possibly underneath the refuse pile. These instruments will consist of vibrating wire <br />piezometers. <br />Monitoring results will be analyzed for potential movement and elevated porewater pressures. <br />Monitoring will be conducted according to the schedule as follows: <br />P Mpis 06 CO 26 06261003 Haul Road Slide Repair WorkFiles Report MCC_Slump_ Repair - Instrumentation- DrainRev_2012-05 -25 docx <br />15 <br />