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unless specifically authorized by the County Commission for good cause. This limitation, however, is somewhat moot because present county mining regulations (Code Sec.934.07(4)) provide a stricter standard of limiting mining operations to between the hours of 7:00 am and 5:00 pm on weekdays (unless specifically approved otherwise by the Board). Noise Standards by Zoning Districts County Code Section 974.05 contains a table with sound level maximums, measured in decibels, based on zoning district categories (see attachment #5). These zoning categories, in order from lowest maximum sound allowances to highest, are: conservation; residential; commercial; industrial; and agriculture. [An exception is that..,residential developments within agricultural zoning districts are subject -to decibel level thresholds for residential zoning districts..] Therefore, noise restrictions for mines will be stricter for operations proximate to residential or conservation zoned areas, compared to mines adjacent to (or in) other zoning districts. Factors taken into consideration in determining sound level maximums include time of day (day vs. night) and duration of sound. Generally, sound levels are measured at the property boundaries of off-site receiving parcels. In monitoring noise generated from mining operations, planning staff has relied upon complaints to initiate noise level tests. Such tests are performed by staff to ensure that noise levels from actual mining operating conditions do not exceed the established maximum levels. Staff has had noise complaints regarding one mining operation in the last several years. That operation used dewatering pumps on a 24 hour a day basis at that time. Staff's test of actual noise conditions at that site, adjusted for night-time conditions, indicated that the operation conformed to the Chapter 974 noise level standards. Staff's conclusion from past experience is that use of dewatering pumps generate noise problems, since such pumps run during the night. Even so, most newer mining operations do not use dewatering pumps and, based on the lack of noise complaints received to date, noise from actual mining operations does not appear to be a significant problem. If noise from operations is determined to be a problem despite current LDR separation distance and hours of operation requirements, then berming requirements could be added to the existing regulations to attenuate noise. Possible LDR changes, if current LDR noise -related requirements are determined to be insufficient, include the following: 1. Add a requirement for berms along all or portions of a mining site perimeter that is adjacent to residences, or require berms around noise -producing areas within the mining. operation site. 2. Increase separation distances between occupied structures and mining activities. 3. Restrict mining operation hours where mining sites are adjacent to residences, regardless of the zoning or land use designation of the adjacent property. 96 1196SEPTEMBER 219 1995 BOOK ' PAF