Ratio and Overburden Calculations

The SR grid is always included in the ratio and overburden calculations. If the SR grid is dropped to the top of the thickness TK grid (like ROM), and the coal variable is TK, then ALL inseam parting is included in the overburden in both the RT and OB calculations. If the SR grid is at the top of the ST grid, and the coal variable is ST, then NO inseam parting is included in the overburden in either the RT or OB calculations. All parting is included with the coal. If the SR grid is at the top of the ST grid, and the coal variable is TK, then NO inseam parting is included in any calculations. It is unaccounted for. The RT and OB grids will be wrong.

If a TK grid exists, it is ALWAYS used for coal thickness and volume calculations. If the TK grid does not exist, then roof and floor are used.

If the total mineable material (ST or TK) is made up of several different products, a Nominal Thickness grid should be created for each product type. The Nominal Thickness = Total thickness * Percent of Individual Product. The Nominal Thickness grids are substituted for the TK grids in the formulae below to get reserves in Tons/Acre units. Otherwise a percentage of the total reserves would have to be hand calculated for each product (Tons/ft2).