Published in the August 2009 Coal USA Magazine
Red-white-blue jobs: the perfect description for coal industry jobs. Nothing more needs to be said. Thanks to Brett Harvey of Consol Energy for coining that phrase.
There exist surface/highwall mining operations in southern Indiana where hard-working, safety-conscious miners extract coal reserves, restore mined areas and deliver coal to Vectren power plants to generate reliable and low-cost electricity which is critical to the betterment and growth of Midwestern communities.
Vigo Coal Company is a 100% employee-owned company in southern Indiana that produces approximately 2 million tons per year using highwall and surface mining methods. Its customers are primarily the Midwest utility industry and a few industrial accounts. While the region’s coal industry has experienced periods of both growth and contraction, Vigo has remained a key player. ICG Addcar highwall mining has proven to be an excellent and low-cost complement to Vigo’s operations.
Mining operations
Vigo’s business model is to provide the management and equipment to mine coal reserves. Vectren, a southern Indiana utility company, contracted Vigo to mine its reserves at the Cypress Creek and Red Brush mines. Vigo’s truck and shovel fleets extract the Indiana No. 5 and No. 6 seams, which range from 1.5 feet to 8ft in thickness. Highwall mining equipment extracts the Indiana No. 5 seam only.
Technology has created windows of opportunity for the extraction of reserves that would otherwise have been left and potentially sterilized. Highwall mining began in 2001 and has included both final pit walls and trench mining applications.
The highwall decision
Around 2001, Vigo was monitoring competitors and noticed highwall mining technology being used by Branham & Baker. This led to a negotiation with Mining Technologies, a precursor to ICG Addcar Systems, and the commencement of highwall mining at Cypress Creek.
The first project was concluded in 2003 and highwall mining was put on hiatus until additional highwall mining areas could be created.
Vigo’s next highwall mining phase happened from November 2004 through to July 2005. Steve Carter, a principal of Knight Hawk Coal Company, agreed to lease an idle Superior highwall mining system to Vigo.
Vigo’s employees rose to the challenge and learned to operate the system; however, when the next highwall mining window opened in 2006, Vigo chose ICG Addcar as its contract operator to provide turnkey highwall mining services.
Remaining reserves at Red Brush also had the potential for highwall mining. In 2008, it was becoming increasingly difficult for the surface mine to stay ahead of the highly productive highwall miner at Cypress Creek.
Vigo decided to rotate the highwall miner between its Red Brush and Cypress Creek reserves, and Red Brush was set up as a trench operation.
As markets soared in 2008, Vectren requested additional tonnage so Vigo brought on a second system. Addcar’s new narrow bench system was brought to Cypress Creek in January this year and will continue to operate throughout 2009, primarily in a trench.
Trench mining
In trench mining, a trench is excavated in the middle of a reserve and a highwall mining system mines outward from both sides of the trench. The concept was created to maximize the return dollars spent on overburden removal.
This approach also significantly reduces the environmental footprint and makes reclamation easier and more efficient. As a trench is nearing completion, often the ramp will be flipped so as to maximize reserve recovery.
The Midwest topography of gently rolling hills and a geology that includes shallow overburden are well suited for trench mining. It is the coalfield where trench mining is most common.
Ground control
Dr David Newman of Appalachian Mining and Engineering has undertaken all highwall mining and geotechnical design work at Vigo’s operations.
The western border of the Cypress Creek surface mine is a rail line. Dr Newman designed web-and-barrier pillars for ICG Addcar to successfully undermine the railroad without causing subsidence. However, Dr Newman’s design only has value if the highwall system can mine according to his recommended plan.
ICG Addcar uses a patented steering and guidance system that allows for mining to proceed along the predetermined azimuth and for incremental corrections (steering) to be made to keep on course. Three ring laser inertial gyroscopes located in the body of the continuous miner are the cornerstone technology for this guidance system.
Information from the gyroscopes is transmitted in real time to the operator’s cab and is displayed in a user-friendly format so the operator can make any requisite adjustments. ICG Addcar is the only manufacturer offering inertial guidance technologies to ensure conformity with the mine plan.
Clearly, these coal reserves would have been backfilled and likely never mined if not for these engineering designs and cutting-edge guidance technologies.
Changing regulatory environment
Over the last couple of years, the Mine Safety and Health Administration has begun requesting, via ground control applications, that surface-mined highwalls be laid back more and/or have more safety benches. This equates to more overburden having to be removed to access the coal reserves and obviously increases the cost of producing coal.
To put this in perspective, when ICG Addcar began mining at Cypress Creek the highwalls were laid back 5 degrees and the first safety bench usually occurred at 100ft. The bottom of the trench was 110ft wide.
The currently approved ground control plans at Cypress Creek and Red Brush require the installation of 25ft-wide horizontal benches at 50ft vertical intervals from the pit floor, with a maximum allowable height of unbenched highwall of 65ft. The bottom of the trench must be 150ft wide to provide the highwall miner crews with a safer work space.
Keys to success
In reflecting over the past eight years of highwall mining at Vigo, the following are the main factors that have contributed to Vigo’s and ICG Addcar’s mutual success: safety focus, spirit of dedication and cooperation, sound engineering practices, continuous technological advancements, good planning and communication, and Vigo’s exceptional abilities at dewatering the pits.
