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ENVIRONMENTAL ASSESSMENT <br /> transporting coal along CR 120. Temporary noise effects would also occur from heavy equipment <br /> operation during construction of the low-cover crossing in The Gulch. A total of approximately 20 acres <br /> would be disturbed by the Project over the life of the mine. This would include 10 acres for construction <br /> of the low-cover crossing at the outset of the Project and 10 acres cumulatively for all other dispersed <br /> surface disturbances of variable sizes that would occur over the life of the mine. The affected area for <br /> noise and vibration focuses on the sensitive receptors or residences that have identified noise and <br /> vibration issues during scoping. <br /> Effects of Alternative A—Proposed Action <br /> Direct and indirect Effects <br /> Noise <br /> Due to an adjacent landowner's concerns about noise and vibration from the existing mining operations, <br /> measures included in Design Features such as installing dampers on the ventilation fan, reducing alarm <br /> sounds to the lowest level required to meet safety and legal standards, using modified load-out <br /> procedures to minimize the need for"back-up" warning alarm signals, and eliminating mining within 300 <br /> ft of existing residences have been implemented to decrease noise and vibration effects. Similar levels of <br /> impacts would be reasonably expected to occur from underground mining in the LBA.The same modified <br /> load-out procedures to reduce the need for"back-up"warning alarm signals and eliminating mining within <br /> 300 ft of existing residences at the existing mine would be implemented for mining in the LBA to decrease <br /> noise and vibration effects. <br /> Construction of the low-cover crossing through The Gulch would create temporary noise effects during <br /> the approximate six month associated construction timeframe.Construction of the crossing would involve <br /> operation of 2 haul trucks, 2 excavators, a frontend loader, a small bulldozer, a water truck, and a Skid <br /> Steer, not necessarily at the same time, during daylight hours. Noise generating components would <br /> include the engine, cooling fan, air intake, exhaust, transmission, tires, tracks, hydraulics and moving <br /> mechanical parts. Direct noise impacts may include local disturbance of wildlife. These effects would be <br /> expected to range from minor to moderate and would be temporary in nature. Noise from heavy <br /> equipment operation may also be audible at times and at some residences in the Vista de Oro Subdivision. <br /> Of the equipment used for the construction of the crossing,the average noise level, measured at 50 ft, is <br /> between 76 and 82 dB. The inverse square law describing the attenuation of noise over distance states <br /> the for each doubling of distance from a point source, the sound pressure level decreases by <br /> approximately 6 dB. Given the nearest home to the location of the low-cover crossing (approximately <br /> 3,300 ft),the sound level of the loudest machinery used in the cover construction would attenuate from <br /> 82 dB to 45 dB. It would likely be lower than this due to surrounding topography and vegetation further <br /> attenuating the noise produced.Therefore,the noise effects would be negligible to minor and temporary. <br /> In addition, daily passage of three construction worker vehicles, and infrequent passage of a water truck <br /> for dust control and equipment maintenance vehicles, to and from the construction site along the <br /> proposed access route would create temporary and intermittent noise in the immediate area of the access <br /> route. Direct impacts may include local disturbance of wildlife.These effects would be expected to range <br /> from minor to moderate and would be temporary in nature. <br /> Dunn Ranch Area Coal Lease by Application COC-78825 and Mine Plan Modification EA 3-23 <br />