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Recommendations for any measures required to ensure the stability of these facilities will be <br />implemented during construction. • <br />The mining plan may be revised to minimize the disturbances in these areas based on the outcome of <br />the field surveys and the mining operations which will occur near these areas. In accordance with <br />Rule 4.12121, should any landslides occur, the Division will be notified immediately and a monitoring <br />and remediation plan submitted for approval and implementation. <br />SCC's experience at the Yoast Mine and at the Seneca II-W operation has shown few problems with <br />"surficial" landslide areas, none of which were significant or life threatening, The only slide of any <br />"consequence" occurred in the II-W area and resulted in a portion of a topsoil stockpile sliding into the <br />pit. An in-depth geological and geotechnical study, associated with pond embankments and haul road <br />construction, was conducted in the Seneca II-W area in 1992. This study served to reinforce the <br />applicability of the methods and measures that Seneca typically uses to design and construct facilities. <br />The strata generally dip steeply toward the west, while the area of concern occurs on an east-facing <br />slope indicating a potential for shallow surficial sloughing rather than deep-seated failure. As <br />mentioned in the Amuedo and Ivey report (1992) for the general area of II-W, the potentially unstable <br />areas do not exhibit the characteristics of catastrophic failure. The mapped landslide area exhibits <br />localized sloughing and hummocky ground, however, more significant rotational slides have not been • <br />observed in the area. The nature of the instability is characteristic of creep or slow-moving types of <br />shallow surficial failure (i.e., surficial landslides). <br />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 Qols - <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 be 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 yz to 2 yz inches in width. See Attachment 13-14, Haul Road B <br />9a TR-21 Revised 06/02 <br />