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Mr. David C. Shelton <br /> September 4, 1985 <br /> Page - 2 <br /> rock dusting, escapeway management and control, roof support, <br /> clearance of airways in the event of obstruction, maintenance <br /> and operation of electrical, drainage, air movement and <br /> other safety systems. All of these activities require <br /> personnel working in and upon the property, and the trans- <br /> portation to and from the work place. <br /> In addition, it is necessary that we maintain <br /> security, communications and office activities in support of <br /> these essential functions. <br /> In our #1 Mine, we operate an advancing 800 ft. <br /> longwall face under some of the most adverse and difficult <br /> conditions to be found anywhere. This face operates under <br /> approximately 3, 200 ft. of cover, one of the deepest mines <br /> in the world. The mine liberates large quantities of methane <br /> gas and a ventilation current in excess of 100,000 cu. ft. <br /> per minute sweeping the face is required at all times . <br /> Under these extreme pressures, the rock mechanics are entirely <br /> different than under shallower cover. We have a dynamic <br /> situation, particularly in the tailgate area of the longwall <br /> face which is prone to coal outbursts, and to bumps, floor <br /> heaves and roof failures. Control measures include destressing <br /> the coal face by driving holes and infusing water under high <br /> pressure; volley firing where necessary; careful pressure <br /> monitoring, and selective forward movement of the face. We <br /> have found through experience that if the face stops pressures <br /> increase, and under certain unpredictable conditions the <br /> face will "go solid" in that the squeeze is greater than the <br /> capability of the hydraulic shields to withstand the pressure, <br /> which will damage or destroy the equipment. Most of the <br /> equipment in this case belongs to the United States govern- <br /> ment who have provided the face as an experiment in this <br /> type of mining and we have a contractual duty, as well as a <br /> responsibility to safeguard the equipment and prevent damage <br /> or loss as a result of failing to cope with the conditions <br /> encountered. <br /> To cope with these problems, we have put this face <br /> on a seven day a week operating schedule in which it is <br /> selectively advanced each day, determined by operating <br /> conditions. While pressure conditions vary, and we cannot <br /> predict with certainty the duration of time involved in the <br /> pressure buildup sufficient to severely damage the face, we <br /> have learned through experience that if we do not move the <br /> face forward on a daily basis, we are greatly increasing the <br /> chances or probability of the face or portions of the face <br /> going solid and we are also increasing the level of hazard <br />