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1 <br />t <br />APPENDIX A <br />PROPOSED PROCEDURE FOR DRILLING, TESTING, AND <br />PIEZOMETER INSTALLATION <br />The following general procedure is proposed for each of the piezo- <br />meters installed on the crest and downstream of the tailings dam. An <br />f experienced engineer thoroughly familiar with the purpose of the work <br />L will be present to supervise the work and record information. Changes in <br />the procedures will be made by the engineer if necessary, in the course <br />of the work in order to adapt the investigation to actual subsurface <br />conditions. <br />IDrilling <br />1. The borings will be advanced from the ground surface to a distance <br />at least 10 feet within relatively intact (unweathered) rock. <br />( 2. A hollow stem auger will be used for drilling in the soil, to allow <br />easy sampling and measurement of natural water level during drilling. <br />3. Rock coring will be used in the intact rock in order to obtain <br />samples for description of rock lithology and quality. <br />4. Measurements of water level in the boring will be made at 5 to <br />I 10 foot intervals, depending on the changes in materials encountered. <br />Sufficient time for stabilization of water level will be allowed <br />prior to measurement. <br />Sampling <br />1. Standard penetration test (SPT) samples will be taken at 10 foot <br />intervals within the dam fill material, and at 2.5 foot intervals <br />within the natural alluvial soils and the weathered rock. <br />Va 2. One or two undisturbed samples (thin walled tubes) of the more <br />1 pervious alluvial material may be attempted to be obtained. These <br />may be difficult to obtain, depending on grain size of the material. <br />I The samples can be used for laboratory permeability testing, if <br />needed. <br />3. Rock core samples will be retained from coring the intact rock. <br />4. All samples will be logged in the field, and a log of the boring <br />prepared by the engineer. <br />Testin <br />1. At least one falling head test will be performed during drilling <br />within the more pervious zones of the alluvium. The hollow stem <br />augers can be used as the test pipe. <br />