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Based on this information, it was accepted that mine operation vibrations do not pose a significant impact <br />from the proposed project, and therefore do not require further mitigation. <br />Subsidence Associated with Underground Mine Activities <br />Residents expressed concern about subsidence due to mining activities. Subsidence is regulated by <br />CDRMS and CDRMS regulations do not allow mining within 300 feet of residential structures. For added <br />assurance, GCC proposed to not mine within 1,000 feet of existing residences. <br />The County's noise and vibration consultant, Aimone-Martin Associates, noted that subsidence is easily <br />measured with mine personnel and survey equipment via either (1) a total survey station where x,y,z <br />ground surface positioning is measured on regular intervals or (2) existing groundwater monitoring wells <br />where a sudden drop in water level may indicate subsidence. <br />GCC has been required, by CDRMS, to identify groundwater monitoring well locations for water quality <br />and hydrologic regulations. GCC indicated that quarterly subsidence monitoring via recordation of <br />groundwater levels and posting of this data on their website would be performed. <br />Noise and Vibration Associated with Truck Trac on CR 120N <br />Relevant reports provided by GCC include: <br />1. Noise Assessment King II Coal Mine, Engineering Dynamics Inc, November 2013 <br />2. King II Coal Mine Haul Truck Noise Assessment, Wave Engineering, January 4, 2016 <br />(Attachment 13) Appendices A -F (Attachment 14) <br />Aimone-Martin Associates, engaged by the County to analyze noise and vibration, provided the following <br />reports: <br />1. Review of Noise and Vibrations from CRI 20 Truck Traffic and Mining Operations at the GCC <br />Energy King II Coal Mine, Dr. Catherine Aimone-Martin, September 7, 2015 (Attachment 12) <br />2. Letter, Dr. Catherine Aimone-Martin, January 15, 2016 (Attachment 1 S) <br />Noise as quality of life measurement is a primary area in which there are compatibility concerns expressed <br />and identified. <br />The scope of GCC's original noise evaluations was largely limited to assessing noise levels and <br />comparing those to existing noise standards. Data was collected at the onsite mine ventilation fan, at <br />seven residences, and at the intersection of CR 120 and the mine driveway access. The data collection <br />effort did not evaluate noise as a compatibility issue or provide mitigation measures and had several <br />technical limitations. Upon review of this data, Aimone-Martin Associates provided a set of parameters <br />for a second study (Attachments 12 & 15). <br />GCC engaged Wave Engineering to conduct the second study (Attachments 13 & 14). Wave Engineering <br />took short-term measurements at eight locations and long-term measurements (2 consecutive days, to <br />capture background conditions) at four locations. The following items from Wave Engineering's report, <br />King II Coal Mine Noise Assessment, dated January 4, 2016 is noted: <br />1. Measurements were taken at approximately 50' from CR 120 centerline and at a second location <br />near residences <br />2. Baseline noise at residences is well below noise from traffic, with the highest background value <br />being recorded at 10 dBC, due to wind gusts exceeding 10 mph <br />3. As expected, travel uphill and with a loaded haul truck, increased noise considerably <br />Project No. 2012-0089 PC <br />4852-5627-2942, v. 3 <br />Page 22 of 32 <br />(DM, VS, DP) <br />