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. ~ -30- <br />XVII. Backfil2ing and Grading - Rules 2,05.3(3), 2.05.3(4), 2.05.4(2)(a), <br />2.05.4(2)(c), 4.09, 4.13, and 4.19 <br />The Martinez Strip !-line is a truck and shovel operation. Overburden and <br />interburden are blasted and loaded by shovels into trucks, Overburden and <br />interburden are hauled by truck to areas designated for spoil deposition. <br />Coal is then ripped with a tractor and loaded into trucks For haulage to <br />a crusher. This cycle is repeated for each of the three seams being <br />extracted within the eastern area of the Martinez Strip. Overburden and <br />interburden from the initial cut within the western area of the Martinez <br />Strip.wilZ be transported to the eastern spoil area for temporary storage <br />and eventual per-.manent deposition. Overburden and interburden handling <br />techniques are in conformance with standard industry practices. <br />It is important, in order to determine the appropriate post-mining topography <br />for any surface mine,~to analyze the swell factors for overburden and <br />interburden process during mining at the site. Increase in volume of overburden <br />and interburden can be offset by removal of coal during the mining process. <br />Tl~e relative vo2c7metric effects of these is/o components must be definitively <br />understood in order to correctly project the volume of backfilI and the <br />appropriate resulting Trost-mining topography of the mined area. <br />In response to Division requests, Chimney Rock Coal completer) two aerial <br />photographic surveys during the fall of 1931. The purpose of these aerial <br />photographic surveys was to compare excavated volumes with swollen overburden <br />and interburden fill volumes during a crontro2led segment of the mining <br />operation. It was booed that this analysis would allow determination of <br />overburden and interburden swell factors to be used in the projection of <br />overall bulking at the Martinez Strip, <br />Chimney Rock Coal, did3determine the quantities of fill (224,253 yd3) and <br />excavation (168,315 yd ) created at the ~~fartinez Strip during the observed <br />rronth, as well as ,the quantity of coal removed from the mine during the same <br />period (29,359 yd'). lfowever, the company indicated that confusion existed <br />due to the fact that a portion of the excavated coal seam may have been <br />backfilled with spoil during the period observed, Asa result, the company <br />is croncerned that the surveyed cut and fill volumes may not accurately reflect <br />the actual quantities of overburden and coal excavated and the quantities of <br />fill deposited at the mina during that period. The company projected an <br />overburden/interburden swell factor of 33~ through a m.mparison of the net <br />fill volumes versus the net excavational volumes, In response to the Division's <br />continued concern, Chimney Rock Coal completed a comparative analysis of <br />Iithologic bore hole data, in order to perfect its swe_'1 factor and bul.ki.og <br />factor projections. The company analyzed bore hole data and electronic <br />lithologic logs to determine the rock types encountered tirouglnut the <br />.Martinez pit. Published swell factors for common roc.t _*yp?s r/ere then used <br />to calculate a projected swell factor of 39.7% for the combined overburden; <br />interburden at the Martinez Strip hli ne. Assuming 85= coal recovery, Chimney <br />Rock projects a bul.;ing factor at the Martinez Strip in excess of 209 (20,25°a). <br />The company has appropriately amended its post-mining topography to accommodate <br />this anticipated excess backfill volume. As such, the Martinez Strip mine <br />quaZifiad as a "thick overburden" operation, i~~ conformance c/ith Rule 4.14.5. <br />however, since the activities have been demonstrated to be conducted in conformance <br />with the provisions of Rule -l.I~{.1, the operation is no*_ subject to the <br />additional requirements of Rule 4.14,5, <br />