Opinion ID: 170445
Heading Depth: 2
Heading Rank: 2

Heading: Mining on the D-3 Panel

Text: Mining on the D-3 panel, the third longwall panel to be mined at Willow Creek, commenced on July 17, 2000. As mining progressed, the levels of methane being liberated in the mine increased. Increased methane liberation is to be expected in the early stages of longwall mining, for two reasons. First, there is a ramping-up period in longwall mining: at the start of mining, the shearer takes fewer passes across the face each shift than it does once the full coal-production level is reached. Because methane is released as the coal at the face fractures, an increase in the number of passes increases the liberation of methane. Second, the gob, from which methane seeps, grows larger as mining progresses. On July 18 and 19, 2.5 million cubic feet of methane were carried by the bleeder system each day. By July 31, the day of the accident, the level had risen to over 7 million cubic feet, although that level was lower than the predicted level for that stage of mining and lower than the mine's estimated capacity. The predicted levels and estimated capacity had been submitted to MSHA during the ventilation-plan approval process. With an increase in the amount of methane liberated, readings of the automated atmospheric monitoring systems (AMS) at certain measuring point locations (MPLs) showed rising methane concentrations. On July 19, two days after mining began, readings at MPLs 7 and 8, located where air exiting the gob entered the bleeder entries, ranged between 0.5% and 1.25%. Then, as Plateau increased its production level around the 29th of July, methane concentrations rose sharply. On July 31 they averaged between 2.5 and 3.0%; the highest point reached was a concentration of approximately 3.5% at MPL 8 early in the morning of July 31, approximately 20 hours before the accident. Such rising concentrations are expected in the beginning stages of longwall mining, although the rise is not linear, because sudden releases of methane cause spikes in the level, which drop as the methane clears. Plateau had a protocol that dictated its response when methane concentrations at the measuring point locations reached specified levels. The action level established by Plateau for MPLs 7 and 8 was 4.0%. At that level Plateau would cease production until methane levels dropped to 3.7%. If an MSHA inspector notes a level of approximately 4.5% at one of those locations, the inspector issues an imminent danger order, requiring the evacuation of most mine personnel until the hazard is corrected. Plateau had set the action level lower than MSHA's unofficial threshold so that it could stop production before dangerous levels were reached. The staff at Willow Creek had noticed a rise in methane levels at MPLs 7 and 8 but did not believe that the levels warranted a response because (1) the rise was expected, (2) the levels had not reached the action level, (3) the staff had the option of ceasing production if methane became excessive, and (4) the ventilation system at the time was exceeding the air-quantity requirements of the plan. In addition, the mine was experiencing fewer methane stoppages on the D-3 panel than it had on the previous longwall panel. Among other locations at which Plateau took methane-concentration readings was the MPL B1 point, which was also known as the § 75.323(e) measuring point. That section specifies that the measuring point be placed immediately before the air [in the bleeder system] joins another split of air. 30 C.F.R. § 75.323(e). In the Willow Creek mine that location was at the end of the D-1 panel's tailgate, approximately 8,000 feet from the D-3 gob. Section 75.323(e) prohibits methane concentrations above 2.0% at that measuring point. It is the only limit specifically set by regulation with respect to methane concentrations within the bleeder system. Under Plateau's protocol, production would cease if methane levels at MPL B1 exceeded 1.95% and would resume only when methane levels had dropped to 1.75%. At 2.5%, Plateau would evacuate the mine and notify MSHA. In the early morning of July 31  approximately 20 hours before the accident  methane levels twice exceeded 1.95%; on one of those occasions, the level rose slightly above 2.0%. These exceedances of the action level occurred when production was idle, likely because it took some time for the air to travel the distance from the gob to MPL B1. Plateau waited for the levels to drop before resuming production. MSHA did not issue Plateau a citation for the exceedance at the § 75.323(e) measuring point. An MSHA ventilation expert testified at the hearing before the ALJ that the readings at the § 75.323(e) measuring point would have been higher if not for an atypically large amount of fresh air leaking into the return entries that carried air away from the gob. The fresh air leaked into those return entries from an intake bleeder entry that ran parallel to them. Some of this fresher intake air leaked through electrical installations, which the mine operator was required to ventilate, and some leaked through stoppings, which seal off the connections between the different entries. MSHA's expert testified that air entering the return bleeder entries likely had methane concentrations around 2.3 to 2.6% but that leakage between that point and the § 75.323(e) measuring point diluted the methane to below 2.0%.
As mining progressed on the D-3 panel, airflow in the ventilation system decreased. This was to be expected as the roof of the gob caved in, increasing resistance to airflow within the gob. Plateau's ability to bring more air into the mine was limited because the mine fan was running at or near its maximum speed and the sliding doors of the ventilation control devices (called regulators) were open as far as possible. Plateau's former general mine manager testified at the hearing that there were changes that Plateau could have made to bring in more air, but that those changes had not been thought necessary because air quantities at the face were still substantially higher than required in the ventilation plan.
By July 31 the longwall panel had retreated a short distance, approximately 250 feet out of a projected 4200 feet. Plateau and the Secretary dispute the precise chain of events involved in the accident, but the cause of the accident is not an issue on appeal. According to the Secretary, on the night of July 31 a section of the roof collapsed in the gob, igniting a small pocket of methane. The Secretary believes that the flame from the initial ignition then came into contact with a small accumulation of methane in the explosive range. This explosion disrupted the ventilation system, which allowed more methane to accumulate, causing two subsequent explosions that resulted in the deaths of two miners and injuries to eight others. Both sides agree that neither the presence of some methane in the gob nor an explosion of methane in the gob is conclusive evidence of an ineffective ventilation system, because methane is liberated from coal at concentrations at or near 100% yet is explosive only at concentrations between 5 and 15% percent. As the methane is diluted to concentrations in the low single digits, there will necessarily be a period when methane is present in the explosive range, and an event such as a rockfall can ignite that methane. After the accident the mine was sealed. MSHA conducted an investigation, which led to the issuance of the citation that Plateau challenges on appeal.
The citation alleges that Plateau violated § 75.334(b)(1). The first paragraph mostly paraphrases the regulation but adds and distribute to the regulatory language: During pillar recovery of the D-3 longwall panel, the bleeder system being used did not control and distribute air passing through the worked-out area in a manner which continuously diluted and moved methane-air mixtures and other gases, dusts, and fumes from the worked-out area away from active workings and into a return air course or to the surface of the mine. Plateau Mining Corp., 25 FMSHRC 738, 743 (Dec.2003) (emphasis added). The next paragraph provides a bit more detail but is still rather vague: The following factors impaired the bleeder system's effectiveness at controlling and diluting the air passing through the worked-out area: a limited mine ventilating potential; the configuration and distribution of airflow in the bleeder system and worked-out area; and temporary controls installed within the worked-out area which restricted airflow through the pillared area. As production increased and pillared area expanded, methane liberation increased and airflow paths changed within the worked-out area. These changing conditions resulted in reduced airflow and elevated methane concentrations within the worked-out area at locations containing potential ignition sources and within close proximity to the active longwall face. Id. The citation further alleges that the accident occurred upon ignition of an explosive mixture that had accumulated in the worked-out area.