2010-10-21_REVISION - C1982057 - Laserfiche WebLink

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Elev. 5.9 7697.3 4470218.2 310359.0 40.620 7737.921 7736 -1.921 7733 0+00 7703.7 4470202.5 310366.3 40.620 7744.288 7746 1.712 7741 0+92 7735.8 4470183.9 310410.2 40.620 7776.418 7776 -0.418 7768 2+49 7781.9 4470166.1 310477.1 40.620 7822.540 7820 -2.540 7811 4+75 7808.4 4470188.0 310521.7 40.620 7848.988 7850 1.012 7845 6+59 - Channel PM-6 runs on the north side of the Seneca II-W South area and is south of channel PM-3A, along an undisturbed area (north of this undisturbed area). Channel PM- 6 flows into channel PM-213 at approximately station 8+06. The as-built channel length is approximately 1,162 feet and the designed length is approximately 1,816 feet. The channel design specifies a bottom width of 3 feet, an overall depth of 0.75 feet and a lining of either 6 inch riprap or TRM, depending on the location. The observed channel bottom width was between 3 and 6 feet, its depth was between 1 and 2 feet and its lining was 6 inch riprap or TRM, depending on the location. The upper half of the as-built channel is approximately 30 feet farther south than the designed location. The as-built location for the lower portion of the channel, however, differs significantly from the designed location. The as-built channel PM-6 intercepts channel PM-2A approximately 500 feet farther up the slope than the designed channel (and enters at a right-angle as opposed to flowing into channel PM-2A at a more acute angle). The entire length of the channel had riprap and vegetation and no erosion was noted. Based on the location changes for the as-built channel PM-6 noted above, the as-built channel profile differs significantly from the designed channel profile. The as-built elevations are between 14 and 50 feet higher than the design elevations. The as-built channel does not appear to be steeper than the designed profile, although the location of the steep grades has changed. The following chart shows the GPS data for post-mining channel PM-6. GPS Height Northing Easting Z Corr. Correct Z Exh D Elev. Z Diff. Exh 20- 5.9 Station 7609.6 4469844.7 310135.6 40.6 7650.2 7658 7.8 7600 0+00 7616.9 4469853.7 310151.9 40.6 7657.6 7662 4.4 7607 0+61 7621.9 4469882.6 310162.1 40.6 7662.5 7666 3.5 7623 1+62 7630.1 4469928.6 310202.2 40.6 7670.7 7670 -0.7 7660 3+62 7660.2 4469975.5 310284.2 40.6 7700.9 7704 3.1 7693 6+72 7699.5 4469997.9 310346.5 40.6 7740.1 7742 1.9 7709 8+89 7730.0 4470017.2 310378.8 40.6 7770.6 7772 1.4 7728 10+12 7746.8 4470029.2 310422.8 40.6 7787.5 7790 2.5 7756 11+62 - The post-mining channels discussed above have all been constructed as designed with regards to channel bottom width, channel depth and channel lining. There are, however, sometimes significant variations in channel location, channel profile and channel length. While the as-built channel profiles measured on the ground matched the information provided in SL-03 Exhibit D, there were some significant variations from the approved channel profiles provided in Exhibit 20-5.9 in both channel length and grade. There were also differences in the channel locations shown on Exhibit 20-2 (see Inspection Map 5).