REV96047 - Laserfiche WebLink

Home Browse Search

S~ XII. GEOTECHNICAL STABILITY EXHIBIT ll3.01 Requirements 1.2u1e 6, Section 6.5 requires an applicant to provide a geotechnical evaluation of geologic hazards that might affect proposed improvements, slopes, embankments, highwalls or waste piles within the proposed affected ;area, [t also requires that where blasting is part of the proposed mining plan, off-site areas will not be adversely affected by blasting. 13.02 Highwall Slopes Amendment No. 3 for the Morrison Quarry was submitted in [993 largely in response to localized slope instability and bench failure occurrences on the east wall of the Central Quarry area. These problems were shown to be the result of constructing relatively steep slopes then loading them with backfill during reclamation in an area where a dominant, moderately shallow dipping, daylightingjoint set occurs with respect to the slope orientation. Appendix A of Amendment No. 3 provides a detailed slope stability study and remediation plan for the slope failure azea. Results of this study were extended in Exhibit D -Mining Plan of Amendment No. 3 to establish an "observational approach" to slope stability throughout the quarry whereby conservatively shallow slopes are excavated based on slope stability modeling results, additional geotechnical evaluations made, and steeper slopes constructed if updated stability modelingjustifies them. This approach is aUeady in place for the quarry and is proposed to remain the geotechnical stability process for future mined areas. Geotechnical stability updates were required by DMG after approval of Amendment No. 3 to be included in the facility Annual Reports. An updated summary of new geologic core hole data, ground water levels, geologic mapping and computer simulations of slope stability have been part of the Annual Report since 1994 and at the end of each subsequent operation year. Discussions of the stability of slopes, highwalls and benches are also included in Exhibit D -Mining Plan of this Amendment No. 4. Together, the special slope failure study for the east slope of the Central Quarry, the mining plans of this and the previous amendment, and the planned Annual Report geotechnical updates satisfy the geotechnical stability intent of Rule 6, Section 6.5. 13.03 Blasting Blasting has been a routine and ongoing part of operations at the quarry for over twenty years. Site personnel are trained and experienced in production blasting. Vibration monitoring is routinely performed and blast and G:VROlECf5~10:OQ~LOTTE%PAMFNDOS.TXT XII - I