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FEB 2 8 1989 ROOK FACE L.0% Once the water table is reached, the materials will be mined hydraulically by the use of a dredge, which siphons out the materials to stockpile and dry, and lets water drain back into the pit. The mining operation will achieve 100% recir- culation of water; thus, no dewatering will occur. 10. Restoration Plan: The applicant proposes the use of littoral zones with planted vegetation to create a lake from the remaining mining pit. This plan will conform to Section 25r(5) of Appendix A of the zoning code regarding mining reclamation. 11. Bond Requirements: Phase II: $ 8,650 compliance bond $ 3,500 restoration bond Both Phases: $47,460 compliance bond $16,100 restoration bond The applicant has indicated a completion date of January, 1994; these bonds should run through January of 1995 to ensure the work is complete and all restoration work is inspected and accepted by the County. 12. Roadway Protection: The applicant has agreed to install a paved apron at the access point to 27th Avenue with adequate site distance around the access point on to 27th Avenue and provide warning signs along 27th Avenue to alert traffic that trucks are entering the highway. The site plan conforms to all the requirements of Section 25(R) mining and excavation provisions. 13. Noise: The Planning and Zoning Commission has expressed some concerns over the level of noise generated by these op- erations. As a result of this concern, staff imposed a noise limit of no more than 90 dbl at one hundred feet from the property of the mining operation on Phase I. This specific level was derived through the research of county reference material. In response to the Planning and Zoning Commission request for additional information, staff visited another mine in full operation which uses a similar method of mining (24 hour hydraulic dredging). Staff took noise readings at this mine with a decibel meter and got readings in the 60 to low 70 decibel range. The 70 decibel range is comparable to the interior of a poor quality car at highway speeds, 85 dbl is what the Air Force considers safe working conditions. While 60-70 dbl's is not extremely loud, area residents have informed the County that the particular mine operation that was monitored could be heard late at night and in the early morning. This is probably due to a lack of background noises during these times. Under present regulations, there are no specific controls for noise abatement or duration of mining for sites in the A-1 zoning district. The Board of County Commissioners can attach additional or more restrictive conditions to the approval of this appli- cation which would limit thetime, level and intensity of the noise generated. These could be conditions such as restric- ting the noise level after or before a certain hour, requiring all equipment to be muffled, etc. Special Exception Criteria The following special land use criteria found in Section 25.1 of the zoning ordinance apply to the proposed Phase II: 1. Applicants operating in the A-1, Agricultural District, where the project does not abut a single-family residential dis- 42