2017-01-30_PERMIT FILE - C1981041 (8)

Home Browse Search

Roadside Mine #00489-0004 Huddlestan-Beefy 08/25/16 The recent survey also identifies a horizontal anomaly north of the air shaft. However, the anomaly does not appear to connect to the air shaft. In addition, no surface sinkhole expression was observed in this area. Although the survey identified two horizontal anomalies, the data did not identify any horizontal anomaly extending from the rock pile feature discussed in the report. As indicated in the referenced Fugro report, water was dumped into this feature and as a result, HBET would have anticipated that any horizontal anomaly extending from this location would be identified during the survey. Recommendations As outlined in the referenced May 9, 2016 report, the recommended mitigation measures included excavation / backfilling of the sinkhole / shaft and compaction grouting. Based upon the results of the recent geophysical survey, both alternatives are still appropriate. The survey indicated that the connection between the horizontal anomaly and air shaft occurs at a depth of approximately 5 in (-16.5 ft). This is within the reach of a large excavator. However, in order to adequately close the pathways using this method, significant ground disturbance would be required. As a result, it may be preferable to utilize compaction grouting to seal off the shaft / horizontal pathway. Based upon the geophysical survey results, the grout hole depth of 25 feet recommended in the referenced report is still believed to be valid. As mentioned previously, the geophysical survey identified a second horizontal anomaly north of the air shaft. Although the data did not show a connection between this horizontal anomaly and vertical anomaly (air shaft), HBET recommends that trenches be excavated perpendicular to this horizontal anomaly in an effort to expose the feature creating this anomaly and further evaluate any potential impacts on the mine workings and/or need for mitigation. General The conclusions and recommendations above available information, and upon our experience. only for the subject project. are based upon our observations at the site, The conclusions and recommendations are valid We are pleased to be of service to your project. Please contact us if you have any questions or comments regarding the contents of this report. Respectfully Submitted: Huddleston -Berry Engineering and Testing, LLC Michael A. Berry, P.E. Vice President of Engineering X:\2008 ALL PROJECTS\00489 - JE Stover Associates Inc\00489-0004 Roadside Mine\200 - Geo\00489-0004 LR082516.doc N TR -69 A14-15-2 09/16