2020-06-24_REVISION - C1981035 (2)

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ENVIRONMENTAL ASSESSMENT 7:00 p.m.) and 50 dBA nighttime at 25 ft from the property line.The standards include further limitations for periodic, impulsive, or shrill noise such as back-up alarms and warning devices. As a result of these studies, Wave evaluated the potential effectiveness of noise barriers using a model that assumed a 12-foot-high wall and a break for a driveway (which greatly decreases barrier effectiveness). GCCE prepared a noise and visual buffering plan for site-specific conditions at 2541 and 3230 (McCue and Hunzeker) CR 120. As a result of this, the following measures have been and are currently being implemented: • Damper has been installed on the main fan; • Warning signals on load-out equipment have been adjusted to lowest legal levels; • Mining has been eliminated within 300 ft of residences; and • All of the conditions of the LPC Special Land Use permit regarding noise have been complied with, including a noise barrier at the Hunzeker residence. Vibration Adjacent landowners perceived vibration sources from the mine were associated with the ventilation fan and underground miner equipment. The EDI study(2013)tested for the presence of vibration and sound emanating from mining activities near neighboring residences. Vibration studies reported no detectable ground motion near adjacent landowners'test locations and only low-level ground motion levels within 10 ft of the mine ventilation fan and conveyor located on surface. The study also indicated that this low-level ground vibration would not transmit beyond the immediate vicinity. These results would also be expected to apply to mining in the Project Area and equipment and vehicle operation through the low-cover crossing. In response to surrounding residents' requests, the study was extended to include acoustic analyses to test for low-frequency sound transmitted to neighboring residences—acoustic waves that would be perceived as a vibration. The study concluded that noise from the mine did not transmit low-frequency sound to nearby residences. These results would also be expected to apply to mining in the Project Area and equipment and vehicle operation through the low-cover crossing. A supplemental vibration study (CDS 2014) addressed adjacent landowner concerns that measurements in the 2013 noise and vibration study were made too far from production activity and covered too short of a time span. This supplemental study conducted noise and vibration measurements for 19 days continuously on the surface immediately above the active mining area where two continuous miners operated one or two shifts per day throughout the test period (CDS 2014).This study concluded that any vibration or noise attributable to mining activity was well below the threshold of human perception. The typical high levels reported were at or below one-quarter of the perception limit.These results would also be expected to apply to mining in the Project Area. 3.4.4.2 Environmental Effects The noise and vibration effects of the Proposed Action would be associated with mining and loading equipment operating at the miners surface facilities and underground as well as from semi-trucks Dunn Ranch Area Coal Lease by Application COC-78825 and Mine Plan Modification EA 3-22