The metallurgical coal is mined using longwall extraction technology with development support from continuous miners. Mine No. 7 - underground operation with two longwall systems.
The mining plan at the No. 7 Mine incorporates continuous and longwall underground mining methods similar to the No. 4 Mine, however there is a change in the mineable seam horizon. The Blue Creek seam and the Mary Lee seam are further apart as the middleman thickness increases to several feet in the No. 7 Mine area. The Blue Creek seam is the primary focus of the longwall mining operation. The Mary Lee seam which lies several feet above the Blue Creek is not mined unless it facilitates roof support for long term stability as in the Main developments which must remain stable for the life of all the longwall panels in a reserve area. The Blue Creek seam is being mined at a depth ranging from approximately 1,500 to 2,000 feet. The Blue Creek seam is suitable for metallurgical purposes and as a compliance steam coal.
Description:
- Seam - Blue Creek/Mary Lee;
- Seam height - 53 inches;
- Cutting height - 69 inches and 80 inches;
- Panels width - 1,060 ft and 1,040 ft;
- Panels length - 7,000-8,000 ft and 4,000-13,000 ft;
- Over-burden - 1,600 ft;
- No. of gate entries - 4 and 4;
- Depth of cut - 36 inches;
- Shearers - Joy 7LS-1D;
- Haulage systems - Ultratrac 2000;
- Roof support yield (tons) - Joy 1,150 and Joy 1, ........
