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Appendix C <br /> Refuse Pile Expansion East <br /> Sampling, Testing, and Monitoring Plan <br /> Mountain Coal Company, LLC <br /> May 2014 <br /> The monitoring plan for the Refuse Pile Expansion East (RPEE) includes installation of <br /> instrumentation to monitor and analyze the following relevant design aspects: seepage/groundwater <br /> conditions, deformation/stability, and geotechnical properties of refuse material and colluvium. <br /> These are relevant aspects associated with the design assumptions used in the geotechnical design <br /> and analysis which need to be verified during construction. The design of the RPEE is based on the <br /> Observational Approach (R.B. Peck, 1969), and thus, in accordance with this approach, the design <br /> assumptions should be verified during construction. The results of the monitoring program will be <br /> compared to design parameters established in the permit application and analyses performed as <br /> required. The following describes in detail the anticipated monitoring plan of these aspects for the <br /> site. <br /> Seepage/Groundwater <br /> Piezometers will be installed in the RPEE to monitor groundwater (i.e. pore-water pressure) at <br /> locations where inclinometers are placed. The proposed piezometers for this monitoring plan will be <br /> installed along the centerline of the pile alignment in the intermediate benches in the approximate <br /> locations shown on Figure C-1. Two piezometer tips will be attached to the outsides of each <br /> inclinometer casing, with one located within the refuse pile material and one within the colluvium at <br /> each location as shown in the facility centerline profile (Figure C-2). It is anticipated that a total of <br /> 13 piezometers will be installed. <br /> It is anticipated that the piezometers will be installed using the fully-grouted method. In the fully <br /> grouted method, the piezometers tips are placed in a column of cement-bentonite grout mix. The <br /> piezometers will be installed as construction of the pile advances. Pore-pressure readings will be <br /> collected using data loggers and the data will be downloaded quarterly. Data from the piezometers <br /> will be used to update the stability model, as needed, as described under the analysis section. <br /> PA\Mpls\06 CO\26\06261003 MCC Refuse Pile Site Review&Permit\WorkFiles\Permit Application\2014 Revision\Appendix C Monitoring <br /> Plan\App C Monitoring Plan 2014-05.doc <br />