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NORWEST ENGINEERING EVALUATION OF LTC ROAD <br /> JULY 28,2016 <br /> COR PORAT ION PAGE 2 OF 10 <br /> that is 20 inches in diameter. This culvert appears to have been installed correctly. Comments received <br /> from landowners indicate that the culverts historically could not pass the seasonal high flows in springtime, <br /> and flows would overtop the culvert and roadway eroding the road. It is not known if this flooding and <br /> overtopping occurred with the current culverts or culverts that were replaced after one of the flooding events. <br /> Regardless,the culverts are undersized for peak flows in Little Turkey Creek. The peak flow resulting from <br /> the 10-year, 24-hour storm event is 422 cfs, and each 30-in culvert can safely convey 50 cfs using a <br /> nomograph for concrete pipe culverts prepared by the Bureau of Roads (U.S. Department of Commerce, <br /> 1963). The nomograph is attached at the end of this document.The flow calculations are included in Exhibit <br /> G of the July 21,2016 permit submittal. The culverts do not contain debris protection devices. Photographs <br /> showing the Little Turkey Creek culvert crossings are included on Figures 3,4,and 5,and a photograph of <br /> the Deadman Creek culvert crossing is included on Figure 6. <br /> Public comments also suggest that rock falls are common along portions of Little Turkey Creek Road, <br /> particularly where there are high cliffs. The locations of these rock falls were not indicated in the comments, <br /> but the most likely location for rock falls is along the rock cliffs located east of the quarry area. This area <br /> will not be mined, and these cliffs are located mostly outside the study area. <br /> It is unknown if the road or culverts were engineered in any fashion, but the lack of a crown or drainage <br /> features,small size of the culverts,the crossing installations,and the road surface suggests that the road was <br /> minimally engineered. <br />