Laserfiche WebLink
surficial is geologically defined as: `Characteristic of, pertaining to, formed on, situated at, or <br />occurring on the earth's surface; especially, consisting of unconsolidated residual, alluvial, or glacial • <br />deposits lying on bedrock." <br />The primary area of concern, as noted by CDMG, is in the 1995-1999 Yoast mining area, and more <br />specifically, within the area of proposed Haul Road "B" Extension. This area was mapped as Ools - <br />Quaternary unconsolidated older surficial landslide deposits -from aerial photos <br />ISee Exhibit 6-1, Site Specific Geology, and Exhibit 12-1, Operations Plan, for locationsl. Based on <br />this mapping and physical investigations/observations, the mapped surficial materials appear to have <br />already slid and are now in a stable configuration, otherwise there would 6a evidence of recent <br />movement. SCC removed and stockpiled the topsoil from this area in the Fall of 1998, thereby <br />unloading and removing any potentially unstable material remaining, and has not observed any signs of <br />further instability to date. A physical investigation of the disturbed areas was conducted in May of <br />1999 and no indication of movement or instability was observed except in one area at the nose of a <br />small ridge where a minor tension crack was observed. This minor tension crack is approximately 20 <br />feet in length and varies from h to 2 f+ inches in width. See Attachment 13-14, Haul Road B <br />Extension Instability Investigation, for documentation of existing conditions including photographs of <br />[he area were topsoil was removed and the existing topsoil stockpile H. <br />SCC has not made a final determination relative to whether to establish the Haul Road B Extension, <br />begin mining in the area to the south, and then mine the `Neck Pit" on retreat or to mine the "Neck •, <br />Pit" area initially and establish the Haul Road 8 Extension in the resulting spoils area. Designs for <br />initial establishment of the Haul Road B Extension on natural ground have been prepared based on <br />available information and previous geotechnical evaluations and represent a 'worst case' situation <br />relative fo potential road grades and construction configuration. Key factors relative to the stability of <br />the Haul Road B Extension, if constructed as designed on natural ground, include the fact that the <br />mapped historic landslide area was composed of materials that had alreatly moved and were in what <br />appeared to be a stable configuration, and previous removal of any potentially unstable surficial <br />materials during topsoil stripping operations in 1998, <br />If SCC elects to mine this area first and then establish the Haul Road B Extension on the resulting <br />spoils, road location and construction will differ from the design included in the permit. The additional <br />information required for design of the road in the spoils, however, including alignment, elevation, <br />material characteristics, and ground water conditions, will then be available. The advantages of <br />constructing the haul road in spoils would be that all surficial materials of concern would either be <br />removed Itopsoill or replaced in a stable configuration loverburden or spoil materialsl~ If mining <br />precedes construction of the Haul Road B Extension, SCC commits to design and construct this haul <br />road in the same manner as SCC's existing haul roads in mine spoil areas. SCC will complete and <br />obtain DMG approval of a haul road design prior to initiation of road construction. <br />A number of preventative measures can be instituted to "head off" or rectify potential failures. These • <br />measures can include: <br />9a Revised 7/99 <br />