Laserfiche WebLink
<br />The "key" requirements are for the material to be (1) durable, (2) non-slaking, and (3) <br />chemically inert. To satisfy these requirements, field sampling and mechanical and chemical <br />laboratory testing has been performed on the granite that will be excavated within the footprint <br />of the valley leach facility because we proposed, as you are aware from your Office's approval <br />of representative sampling sites (given on April 18, 1994), to use this material to supplement <br />the waste rock currently located below the site of the Economic Mill. <br />Sampling <br />In April 1994, five borings were drilled in the granite in the higher elevations of the leach <br />facility footprint to garner samples for geotechnical characterization. The location of these five <br />holes are shown on Attachment 1. Drilling locations were also dictated by the fact that the sites <br />had to avoid cultural resource features. The borings were advanced as 2.5-inch diameter holes <br />to 50 feet below the ground surface using an air-track drill rig. Two samples were collected to <br />represent each boring, each comprised of a representative sample from a 25-foot interval of <br />cuttings. As a example, sample number CPR-10-25 was collected from cuttings generated from <br />drilling Boring CPR-10 from 0 to 25 feet and sample number CPR-10-50 was collected from <br />cuttings generated from drilling Boring CPR-10 from 26 to 50 feet. A total of ten samples were <br />collected. <br />Because the finely-ground sample cuttings were inappropriate for use for the mechanical <br />laboratory (ASTM C535 LA Abrasion and ASTM D4644 Slake Durability), the sample for this <br />test was collected from the freshest surface outcrop sample of the granite in the leach pad area <br />that could be collected. <br />A copy of the letter transmitting your Office's approval of the 5 boring locations and your <br />approval is included as Attachment 2. <br />Geochemical Laboratory Testing and Results <br />The ten samples collected from the five bore holes were tested for chemical characteristics using <br />the acid generation assessment or Acid-Base Accounting ("ABA") and the Meteoric Water <br />Mobility Procedure ("MWMP", Nevada procedure). Both tests were performed by American <br />Assay Laboratories, Inc. located in Sparks, Nevada. The results of the ABA tests are provided <br />in the Table of Attachment 3. The net neutralization of each of the ten samples is positive. <br />Only one of the granite samples shows measurable acid generation potential. <br />The results of the MWMP tests are presented in Attachment 4. These are compared with the <br />numeric values normally used to evaluate the relationship between the test data and the receiving <br />streams. Of course, this granite material is the material through which the stream currently <br />passes throughout Arequa Gulch downstream of the volcanic material. <br />The Laboratory data report sheets for these data are provided in Attachment 5. <br />2 <br />