San Miguel Lignite Mine
On January 1, 2011, Kiewit was awarded a contract to provide management services to mine and deliver lignite from the San Miguel Mine. Approximately 3.3 million tons of lignite coal is delivered to the adjacent 400-MW San Miguel Electric Cooperative, Inc. power plant, which is the owner of the mine. San Miguel Electric Cooperative, Inc. furnishes power and energy to South Texas Electric Cooperative, Inc.
The mining process consists of clear and grub, topsoil and overburden removal, lignite mining, and regrade. The overburden removal is achieved using two draglines, a 76-cubic-yard machine and an 80-cubic-yard dragline. The 76-cubic-yard dragline moves nearly 17 million yards per year of overburden, while the 80-cubic-yard dragline moves about 20 million yards per year. Assisting the overburden operation is a 19-cubic-yard mass excavator with a fleet of 100-ton end dump trucks. The lignite is mined using a specialized mining tool called an Easy Miner. These machines resemble milling machines used to remove and recover asphalt and concrete highway surfaces and provides tight depth control to selectively mine the lignite or remove the parting, as well.