The projected stripping ratio for this ore is about 2.6 : 1.
2.
As the mines expand the stripping ratio will increase.
3.
Low stripping ratios make this coal attractive but access to the coal deposit will be difficult ."
4.
It has an average mining depth of 65 metres ( 90m at the deepest point ) and a very low stripping ratio.
5.
When the operation reaches a predetermined stripping ratio ( tons of overburden / tons of coal ), it is not profitable to continue.
6.
The second lignite mine that Gipco is negotiating for, is 20 km away from the plant but has a better stripping ratio of 1 : 5.
7.
When compared to surface mining, which requires overburden removal prior to ore extraction, underground mining operations tend to have lower stripping ratios due to increased selectivity.
8.
The power plant is based on the pithead but the mines have a higher stripping ratio of 1 to 10 ( to extract 1 tonne of lignite 10 tonnes of overburden has to be cleared ).
9.
After considering stripping ratios and production costs, the USGS concluded that at the time of the economic evaluation, only 6 percent of the original resource, or 10.1 billion short tons of coal, was currently economically recoverable.
10.
Presently the approximately 15 mines in the Powder River Basin are working in areas where the stripping ratio is between 1 : 1 ( i . e . one ton of rock for one ton of coal ) and 3 : 1.
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