EMERGENCY INVESTIGATION OF COAL WASTE EMBANKMENTS

[Music] Coal, essential to industrial development in the 18th and 19th centuries, is just as essential today. An estimated 500 million tons were used nationwide in 1971. For every ton of coal produced, coal refues and wastes are also produced. But whereas coal is consumed, the refuse accumulates over the years. As coal mining and coal processing methods have changed, the relative amount of refu has increased. This refu may consist of mine rock, lowgrade coal, silt, and sludge randomly mixed with other refues and vegetation and is often burning as a result of spontaneous combustion or accidental ignition. To dispose of this coal waste, a mining company dumps it in an isolated area. The method of dumping is usually by aerial tram or dump truck. When this waste material is graded by a bulldozer, it is usually done only to allow access or gain additional space for dumping and not to achieve uniform compaction and stability. The most common types of deposits or impoundments formed by dumping are sidehill dumps, [Music] cross valley fills, [Music] sludge ponds, and waste heaps. Many of these dumps have long since been abandoned. [Music] But abandoned or active, these embankments can constitute a serious hazard. Few people realized this until the February 26th coal waste dam failure near Saunders, West Virginia that caused the Buffalo Creek flood disaster. [Music] To asssure that a similar failure does not occur in the future, the general and engineering characteristics of waste materials need to be thoroughly studied and defined before known principles in earth dam design, soil mechanics, and engineering geology can be applied to constructing adequate coal refu banks and empoundments. Following the Saunders waste dam failure, the Department of the Interior created a special task force to study coal waste hazards with the lead role assigned to the Bureau of Mines. The objectives were to analyze the Saunders Dam failure, identify other potentially hazardous sites, determine on a longer range basis the modes of failure and the means by which hazardous conditions can be recognized, and develop means for the safe disposal and storage of coal mine wastes. [Music] Faced with the job of trying to solve a problem quickly that had built up over many years, the task force implemented a plan to meet its immediate objectives by first calling on the bureau's coal mine inspection districts to inventory all significant waste embankments in the country. And from information provided in this inventory, 139 sites were identified for immediate field investigation. [Music] To meet the goal of investigating these sites within four weeks, eight ground teams and three helicopter teams were organized and sent to the field. These teams were made up of mining engineers and engineering geologists from the Bureau of Mines, Bureau of Reclamation, and special consulting firms. At the same time, the US Geological Survey, which participates in the interior task force assignment, was requested to develop hydraological and geologic information on each of the sites to be investigated. [Music] All the teams operated from mobile headquarters units used to coordinate both air and ground investigations. [Music] The air teams were made up of two engineering geology specialists and a federal coal mine inspector to locate the sites. Their assignment was to identify any embankment that showed signs of possible imminent failure and to set priorities for more detailed investigation by the ground teams. Within a 3-week period involving hundreds of flying hours, the helicopter survey teams flew over the Appalachian coal fields. These flights were carried out on schedule and without mishap even during the height of Hurricane Agnes. [Music] The majority of the sites were located in West Virginia and Kentucky, the rest in Pennsylvania, Virginia, Alabama, and Ohio. The investigations had to be fast. They were conducted at the reconnaissance level for the specific and limited purpose of quickly identifying any sites that might be imminent hazards or require immediate corrective measures. [Music] A basic criterion was formulated to evaluate the impoundments and to develop a priority classification system. One of the most common shortcomings or deficiencies found of the coal waste embankments investigated was improperly designed spillways or no spillways at all. Most dumps showed improper methods of construction when used for water retention. In some of them, the dumped materials formed an embankment with a slope approximately equal to the angle of repose of the material. This type of slope has a minimum factor of safety even before the forces of seepage are added to the already existing loads. Impoundments and dumps are subject to natural forces that can affect their structural stability, sheer strength, density, void ratio, and permeability. [Music] The low densities obtained by aerial or other types of dumping without adequate compaction and other structural controls make these embankments susceptible to failure by any one of several mechanisms or combinations thereof. [Music] In the matter of sludge disposal, very often the water and slime are released at the upper end of the impoundment rather than directly behind the upstream face of the dam. This causes the coarse material to settle immediately near the upper end, leaving the fines and water to accumulate against the embankment, where unless the embankment has been properly engineered, they create the greatest hazard. Another deficiency found at many of the coal waste embankments was inadequate freeboard. That is they did not provide adequate height between the pond level and the top of the embankment. In these cases, high storm runoff could cause dam overtopping which can cause sudden and potentially catastrophic failures. [Music] If the embankment impounds a large volume of water and sludge and does not have adequate spillway or diversion facilities to handle heavy storm runoff, a high potential for failure exists. Even if it does not impound water, sliding or slipping can occur, and such failure may block main channels, resulting in the rapid damning and release of large quantities of water. [Music] Burning is another deficiency. It causes a reduction in the volume of refuge material which in turn causes slumping or cracking of the dam surface. This can open seepage channels and cause internal erosion or piping. Saturation of the burning areas can also cause explosions which may severely damage the structure and cause local or complete failure. This is particularly hazardous if the refuge pile is situated on a steep hillside. [Music] Following the first day of the aerial survey, ground investigation teams were mobilized to be dispatched to the sites immediately. After orientation and briefing by members of the air team, the ground crews visited the dump and empoundment sites to obtain detailed evidence to confirm or dispute the air team's findings. At the waste sites, they checked in with site managers, and after picking up questionnaires left with them by a federal coal mine inspector, the ground teams went to work. They inspected, photographed, and measured the dumps, impoundments, slopes, and freeboards, sampled, and checked the deposits to determine as far as possible by surface evidence present the characteristics of material making up the waste. They examined the waste dumps closely to determine the extent of erosion, deposit movement, slumping or sliding and for seepage, internal erosion and piping. [Music] When obvious immediate hazards were verified, the review board was alerted to the need for immediate action. They sent daily reports to the task force in Washington on the investigation's progress and its findings. Tentative at first, then finalized as sufficient data was accumulated. [Music] The review board was responsible for determining which sites were obviously hazardous, which might be hazardous, and which were probably safe. [Music] [Applause] [Music] I like to be educated, but I'm so frustrated. Hello to my loneliness. I guess that ignorance is bliss. Take me back to before the new rewind. Take it out of queue. Innocence can be a young man's game. Send up for the hall of shame. I wish I knew how much I miss. I know [Music] that we're all screwed. We play our roles and ignore the problems. [Music] I like to be way more patient. Stay up. I feel so outdated. How can we look the other way? Sun is out, but the sky is gray. What would happen if I took a chance? It's always hard at first glance. I don't want to, but I know I got to do it. The truth is hard to swallow. I think I'll chew it. [Music] [Applause] [Music] [Applause] I wish I knew how much I missed. [Music] The primary long range goal of the Department of the Interior and the Bureau of Mines relative to mine waste is the permanent control of its disposal and storage to asssure that a disaster such as Buffalo Creek will never again threaten human life in any part of our country. To reach this goal will require the fullest cooperation between federal, state, and civilian agencies to develop new technology in the fields of civil engineering, soil mechanics, and engineering geology, and to develop and apply more comprehensive regulations for the construction and control of waste embankments.