2012-02-28_REVISION - M1980244 (71)

Home Browse Search

February 7, 2007 - -7- 063 -2140 indeterminately sized features will be drilled to define those requiring further investigation during the confirmatory drilling program. Various approaches and criteria were used to select the locations of the drill holes, including the following: • General trends in the underground workings can be noted from surface disturbance observations developed during the field reconnaissance program and from the historical mining records. This information provides an indication of possible connections between shafts. Holes should be drilled across these lineaments between shafts to determine if the underground workings between shafts have been mined close to the surface. • Underground workings of moderate to shallow depth may have been mined close to the surface. Holes should be drilled across the alignment of such workings. • Some areas that have been mined or have caved through to the surface have local indications that shallow stopes extended away from the area. Holes should be drilled to provide an indication of how far such stopes might extend away from the open surface features. • Areas indicated in the mining records as having been excavated with wide open stopes, and areas observed in the field where multiple openings appeared to be very close together may have caved up to close to the surface. Holes should be drilled into these areas to determine if open voids are present close to the surface. • Lateral extensions that were observed in the field to extend from open shafts are inherently shallow, and may represent potentially unstable excavations. Holes should be drilled across such features to determine the approximate geometry and thickness of the crown pillar. • Some of the features identified in the surface reconnaissance program as collapsed shafts may not, in fact, be collapsed shafts. Similarly, some of the depressions noted in the field logs may be indications of collapsing drifts or stopes. Where the designation of these features isn't certain, they should be drilled or excavated in order verify the type and extent of these workings. • In some cases, no features were identified during the surface reconnaissance at locations where historical mining records show major shafts or adit openings. These locations were targeted to verify or refute the historical records and confirm the presence or absence of mining disturbance. As in previous CC &V drilling programs, the target depth for remediation of underground workings is anticipated to be approximately 50 feet below the finished soil liner fill subgrade. In general, the objective of the preliminary and confirmatory drilling programs is to identify workings for L`96 \21,PDaW1P11DUSl WORK.¢ NOS- FNI. O+ FF90TP10 DISfORICALVIOR[NOSFNIAIFEHOi DOC Golder Associates