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Well Installation Design Details <br /> The monitor well installation details for each shallow and deep well are presented as Map G-15. These <br /> details were prepared based on test pit information performed by Revenue mine personnel and <br /> provided to Buckhorn Geotech, Inc. Conceptually,the monitor well design was intended to account for <br /> the expected highly permeable and porous subsurface zones without loss of sand filter in order to <br /> produce suitable water quality samples long term. More specifically,this criteria was met by using an <br /> inner and outer well casing design. The outer casing is 8 inch diameter and the inner casing is 2 inch <br /> diameter. The 8 inch diameter outer casing provides confinement for the sand filter and a filter pack of <br /> nearly three inches around the inner well screen. <br /> The well casing(both inner and outer) should be constructed of minimum Schedule 40 PVC materials. <br /> The casing should be of the flush-mount threaded type, with "0-ring" seals used on the inner well casing <br /> joints. No gluing of inner or outer well sections is permitted. Slotted screen sections should be <br /> machine-slotted to 0.010 inch slot size. The filter sand should be inert 10/20 Premium Colorado silica <br /> sand. This sand is composed of rounded particles which will ensure a better distribution in the annular <br /> space when tremied. The sealed annular space above the sand filter may be accomplished with a layer <br /> bentonite pellets and/or bentonite/cement grout mix to the surface. <br /> While specific means and methods of well installation are the responsibility of the well drilling <br /> contractor,we offer the following general guidelines and recommendations. <br /> 1. The well drilling contractor selected should have demonstrated experience in installation of <br /> groundwater monitoring wells in difficult subsurface conditions. <br /> 2. Because a portion of the subsurface materials to be penetrated are man-made "waste rock", <br /> etc., decontamination procedures for all materials used apply. Therefore, all permanent well <br /> materials(casings, screen sections, centralizers, etc.)should be decontaminated prior to <br /> installation andall temporary installation materials(auger,tremie pipe, bits, etc) must be <br /> thoroughly decontaminated between well installations. High pressure steam cleaning is the <br /> preferred method of decontamination. Acid washes are not recommended for PVC materials. <br /> 3. Once the outer casing is set,the inner casing should be lowered into place using centralizers to <br /> keep the inner pipe centered in the outer casing. <br /> 4. The sand filter(10/20 Premium Colorado silica sand)should be tremied in such a manner to <br /> completely fill the annular space around the well screen section and avoid plugging and clogging <br /> Revenue Mine TR-03 Appendix 15 Page 3 <br />