I have never copied and posted a large amount of test on this blog before. Yet below I do. I do this because the issue is fascinating and the information a trifle tedious to find.
The topic is a call from MSHA for comments on ways to make mine tailings dams safer.
I urge you to comment if you can. My first comment is that you need but two things to make safe tailings dams:
- A Professional Engineer of Record (PE) who personally inspects the dam at least twice a year and who has trusted subordinates record and report on conditions every month.
- A Peer Review Board that meets at least twice a year to review conditions. The peer reviewers must be totally independent of the professional engineer and his firm and must report to the highest possible level of mine management. There should be at least three peer reviewers, all from different organizations and of varying, but relevant disciplines.
My second comment is that no tailings facility is safe unless it is like those Cahokia Mounds. These are 1,000-year old soil mounds just east of St. Louis, Missouri.
The only modern tailings disposal facility I know of that meets my criterion for stability and safety is the Greens Creek, Alaska tailings disposal facility.
The fact is that only way to achieve safe tailings disposal is to dry, filter press, or ammend the tailings to become a solid as Suncor is doing in Alberta. As long as we insist in discharging liquid tailings, we risk failure. This, I believe, is true regardless of the robustness of the embankment dam that may be constructed to retain the liquid tailings. For earth dams or embankments fail. The record of such failures is long. If the retained slimes are fluid, they will, and have, flowed out and caused incredible environmental impact and death.
Maybe the way we did it on the UMTRA Project is another example, another way to ensure safe tailings dams. At least, UMTRA is an example of the best way to close a tailings impoundment. It will take a genius to incorporate its principles into the design and operation of a new tailings facility.
I strongly recommend against more volumes of guidelines. There are enough of those already and they add nothing. They are mostly the product of consultants who have never managed a tailings facility, and they are generally no more than out-of-date checklists. Avoid them completely, whatever their proponents may claim. I personally cringe when I read them or hear them cited as examples of good tailings practice.
Maybe at the Conference in Vail in October on Tailings & Mine Waste we should spend a whole session talking about this. We have a paper in the conference on this very topic which pretty much says what I say above. In our paper we reject all the fallacious theories of why slimes dams fail. It all boils down to the failure to have responsible PEs, very frequent intelligent inspections, and independent peer reviewers. Just think how many taxpayer dolloar could be saved, if our paper were read and our recommendations implemented.
The paper will appear in the conference proceedings, but if you want a copy now, e-mail me at email@example.com.
Now if you click the text saying continue reading, you will be able to read the totality of MSHA’s statement. And it is worth reading.
I. Background Back to Top
MSHA’s database contains information on nearly 2000 dams at metal and nonmetal mines. Mine operators have constructed these structures for various purposes, such as disposing of tailings or mine waste, processing minerals, treating or supplying water, and controlling run-off and sediment. Although many of these dams are designed, constructed, operated, and maintained according to accepted dam safety practices, others are not and dam failures and near failures continue to occur.Show citation box
Since 1990 to the present, MSHA investigated dam failures at metal and nonmetal mines in virtually every region of the country and at small and large operations. Failures or near failures have occurred at copper, phosphate, sand and gravel, trona, gypsum, and limestone mines, among others.Show citation box
Failures have damaged property and equipment, but no deaths or serious injuries have occurred. Examples of dam failures include:Show citation box
- A 1990 failure of a 100-foot high dam at a limestone mine in Puerto Rico released over 10 million gallons of water and tailings. The failure flooded eight lanes of a major highway, depositing tailings up to eight feet thick. The dam failed about 2 a.m. when no miners were present. The mine operator did not use an engineer to design the dam; several design and construction deficiencies, such as poor compaction, steep slopes, and absence of internal drains, contributed to the failure. Show citation box
- A 70-foot high tailings dam failed at an andesite quarry in Wisconsin in 1992, tearing apart a railroad track and leveling a power line at the mine. The dam failed at 3 a.m. when no miners were present. The dam was not designed by an engineer. After a slope failure in 1987, the mine operator installed instruments in the dam to monitor internal water pressures. Pressures beyond a certain level would lead to structural instability. In the 18 months before the 1992 failure, however, the operator checked the instruments only twice. A combination of steep slopes and high internal water pressure contributed to the failure. Show citation box
- In 1997, a dam at an Arizona copper mine released tailings for over a half mile downstream and to depths of 30 feet. Four miners, one in a haul truck, one in a bulldozer, and two in a pickup truck, were carried down-slope with the slide. One miner injured his back running from the pickup but the others were not injured. The dam was designed by an engineer; however, the mine operator’s rate of placement of waste rock on top of the tailings created pressures that contributed to the failure. Show citation box
- In August 2002, a 450-foot section of dam failed at a sand and gravel mine in Georgia, sending a wave of water and tailings through the shop area. The 30-foot high dam failed shortly after 8 p.m. The wave of water and tailings moved a scraper, backhoe and front-end loader, which were parked in the area. Three miners, near the shop, saw the dam failing and escaped in a pickup truck. The dam, built without being designed by an engineer, had a weak foundation, among other deficiencies. Show citation box
- In 2004, a dam failure at a sand and gravel mine in California released over 200 million gallons of water and tailings, inundating a hydraulic excavator in an adjacent pit. The failure occurred shortly after 6 p.m., at the start of the maintenance shift. About 15 minutes before the failure, the excavator operator had gone home and a bulldozer operator had parked his machine on the top of the dam. A miner who lubricated the equipment was driving into the pit when he noticed the rising water, halted his truck, and backed up the access road. The dam was not properly designed. The investigation revealed that the design of the dam failed to include an evaluation of the foundation and embankment material strengths, and stability analyses to verify that the slopes of the dam would have adequate factors of safety. Show citation box
MSHA investigators have found that design, construction, operation, or maintenance deficiencies have contributed to failures of dams at metal and nonmetal mines and exposed miners to hazards.Show citation box
Since the early 1970’s, Congress has enacted laws to create a national program to reduce the risks of dam failures. The Federal Emergency Management Agency (FEMA) is charged with administering the national dam safety program and has issued a series of Federal Guidelines for Dam Safety (Guidelines) (http://www.fema.gov/library/viewRecord.do?id=1578).Show citation box
The Guidelines address, among other things, practices and procedures for the design, construction, operation, and maintenance of all types of dams. In the Guidelines, FEMA recommends that dams:Show citation box
- Be designed by a competent engineer; Show citation box
- Be constructed under the general supervision of a competent engineer knowledgeable about dam construction; Show citation box
- Be inspected and monitored at frequent intervals by a person trained to recognize unusual conditions; be inspected by a competent engineer with knowledge of dam safety at a frequency consistent with the dam’s hazard potential; and Show citation box
- Have an emergency action plan, if dams are classified as having high or significant hazard potential in the event of failure. Show citation box
Every two years, MSHA reports on the status of its dam safety program to FEMA, which then sends Congress an evaluation of each Federal agency’s program and how it complies with the Guidelines. FEMA has recommended, in biennial reports to Congress and in meetings of the Interagency Committee on Dam Safety, that MSHA promulgate standards to encompass all aspects of design, construction, and inspection for dams at metal and nonmetal mines.Show citation box
The existing requirements for dams at metal and nonmetal mines, 30 CFR 56.20010 and 57.20010, are derived from the Metal and Nonmetallic Mine Safety Act of 1966. The standards state: “If failure of a water or silt retaining dam will create a hazard, it shall be of substantial construction and inspected at regular intervals.” The standards promulgated for coal mines under the Federal Coal Mine Health and Safety Act of 1969 were similar, but specified that the mine operator inspect the dams at least once per week and record inspection findings.Show citation box
The requirements for coal mines were revised in 1975 after the Buffalo Creek dam failure. For dams which can present a hazard or are of a certain size, the existing standards require a coal mine operator to:Show citation box
- Have a registered professional engineer certify the dam’s design; Show citation box
- Develop plans for the design, construction, maintenance, and abandonment of the dam and have the plans approved by MSHA; Show citation box
- Have a qualified person inspect the dam weekly; Show citation box
- Have instrumentation monitored weekly; Show citation box
- Correct any hazardous conditions and make required notifications; and Show citation box
- Submit an annual report with a registered, professional engineer’s certification that construction, operation, and maintenance of the dam have been in accordance with approved plans. Show citation box
II. Key Issues on Which Comment Is Requested Back to Top
MSHA is asking interested parties to comment on measures to assure that mine operators design, construct, operate and maintain dams to protect miners against the hazards of a dam failure.Show citation box
MSHA seeks comments on the questions below. If a commenter refers to a particular dam as an example, please identify the mine, or provide the number of miners and the mine’s commodity. Also, include the dam’s storage capacity, height, and hazard potential and characterize its complexity. Provide enough detail with the comments that the Agency can understand the issues raised and give them the fullest consideration. Comments should include alternatives, rationales, benefits to miners, technological and economic feasibility, impact on small mines, and supporting data. Please include any information that supports your conclusions and recommendations: Experiences, data, analyses, studies and articles, and standard professional practices.Show citation box
1. MSHA is seeking information concerning current dam safety practices at metal and nonmetal mines. What measures do mine operators currently take to design, construct, operate, and maintain safe and effective dams? What measures do mine operators currently take to safely abandon their dams? For mine operators with dams, please provide your experiences.Show citation box
2. MSHA is required to inspect every mine in its entirety, which includes dams of all sizes and hazard potential. A common approach for dam safety is to have tiered requirements based on a dam’s size and hazard potential. How should MSHA determine safety requirements based on a dam’s size and hazard potential? Please include specific recommendations and explain your reasoning.Show citation box
3. What non-Federal authority regulates the safety of dams at metal and nonmetal mines in your state, territory, or local jurisdiction? Please discuss the specific requirements, including the principles that they address. If possible, please provide information about relevant non-federal dam safety requirements through a hyperlink or other means.Show citation box
4. What records should be kept of activities related to the safety of dams? Please be specific and include your rationale. What records should be provided to miners if hazardous conditions are found?Show citation box
Design and Construction of Dams
MSHA’s existing standards do not include specific requirements for design of dams. MSHA found that inadequate design contributed to some of the metal and nonmetal dam failures. In responding to the following questions, please discuss how any requirements should vary according to the size or hazard potential of a dam, and why.Show citation box
5. How should mine operators assure that dams are safely and effectively designed? Please suggest requirements that MSHA should consider for safe design of dams. Please be specific and include your rationale.Show citation box
6. Please suggest requirements for review of dam designs by mine operators and MSHA and include your rationale for specific recommendations and alternatives.Show citation box
7. With new standards, operators may need to evaluate and upgrade existing dams. Please elaborate on how the safety of existing dams should be addressed.Show citation box
8. MSHA’s existing standards for dams at metal and nonmetal mines do not address whether a dam is constructed as designed. What measures are necessary to ensure that mine operators construct dams as designed?Show citation box
9. How should MSHA verify that dams have been constructed as designed? Please explain your rationale.Show citation box
Operation and Maintenance of Dams
MSHA’s existing standards do not contain specific requirements addressing the operation and maintenance of dams.Show citation box
10. What should a mine operator do to operate and maintain a safe dam? How should MSHA verify that dams are safely operated and maintained? Please be specific.Show citation box
MSHA’s existing standards require dams to be inspected at regular intervals if failure would create a hazard. Inspections can identify hazardous conditions, allowing a mine operator to take corrective action to prevent a failure. The Agency will be referring to two types of inspections in this document, “routine” and “detailed.” Mine operators should perform frequent, routine dam inspections, which may include monitoring instrumentation, to identify unusual conditions and signs of instability. Personnel with more specialized knowledge of dam safety should conduct detailed inspections to identify less obvious problems and evaluate the safety of the dam. Detailed inspections, occurring less often, would include an examination of the dam and a review of the routine inspections and monitoring data. The Guidelines recommend that inspection personnel be qualified for their level of responsibility and trained in inspection procedures.Show citation box
11. What measures should mine operators take to assure that dams are adequately inspected for unusual conditions and signs of instability?Show citation box
12. How often are routine inspections of dams conducted? How often should they be conducted? What determines the frequency? Who conducts the routine inspections? Please be specific and include your rationale.Show citation box
13. Instruments, such as weirs, provide information on the performance of a dam. How frequently should mine operators monitor dam instrumentation? Please provide your rationale.Show citation box
14. What information should be documented during routine dam inspections? Please provide your rationale.Show citation box
15. Does a competent engineer inspect your mine’s dam? If so, at what frequency? Please explain the rationale for these inspections and what is evaluated.Show citation box
16. How often should detailed inspections be conducted? Please include your rationale.Show citation box
17. What information and findings should be documented during detailed dam inspections? Please be specific and include your rationale.Show citation box
18. How should MSHA verify that mine operators conduct routine and detailed inspections? Please explain how your suggestion would work. Show citation box
Qualifications of Personnel
A mine operator is responsible for the design, construction, operation, and maintenance of dams. For an effective dam safety program, an operator must use personnel who are knowledgeable about dam safety.Show citation box
19. What qualifications do mine operators currently require of persons who design, inspect, operate, and manage dams? In what capacities are engineers used? Please be specific in your response.Show citation box
20. The Guidelines recommend that dams be designed by competent engineers. What specific qualifications or credentials should persons who design dams possess? Please include your rationale.Show citation box
21. The Guidelines recommend that a dam be constructed under the general supervision of a competent engineer knowledgeable about dam construction. What specific qualifications or credentials should a person have who verifies that a dam is being constructed as designed? Please provide your rationale.Show citation box
22. What training should personnel receive who perform frequent, routine inspections and who monitor instrumentation at dams? In your response, please suggest course content and the frequency of the training, including the rationale for your recommendations.Show citation box
23. What qualifications or credentials should be required of persons who perform detailed inspections to evaluate the safety of a dam? Please be specific and include your rationale.Show citation box
Abandonment of Dams
24. Some regulatory authorities require that dam owners obtain approval of a plan to cap, breach, or otherwise safely abandon dams. What actions should mine operators take to safely abandon dams? Please include specific suggestions and rationale.Show citation box
25. How can MSHA verify that a mine operator has safely abandoned a dam?Show citation box
MSHA seeks information to assist the Agency in deriving the costs and benefits of any regulatory changes for dams at metal and nonmetal mines. In answering the following questions, please indicate the dam’s storage capacity, height, and hazard potential and characterize the complexity of each dam referenced. Also, please include the state where each dam is located, and the number of employees at the mine.Show citation box
26. What are the costs of designing a new dam? Please provide details such as hours, rates of pay, job titles, and any contractual services necessary. How often is the design of an existing dam changed? What are the costs of a redesign?Show citation box
27. What are the costs of constructing a dam? Please provide details based on: Size of dam; labor costs, including hours, rates of pay, job titles; costs of equipment and materials; and any contractual services necessary.Show citation box
28. Please describe the oversight you provide during dam construction to assure it complies with the design plan. How much does it cost per year per dam for oversight and quality control? What special knowledge, qualifications, or credentials do you require of those who provide oversight?Show citation box
29. How often do you add height to an existing dam or modify it in some other way? Who supervises the design and construction of these modifications, for example, a professional engineer, competent engineer, contractor, etc? Please be specific and provide rationale for your answer. How much does it cost? Please provide details such as labor costs, including hours, rates of pay, job titles, and costs of equipment and materials and any contractual services necessary.Show citation box
30. How much does it cost per year per dam for routine inspections? If you incur separate costs for monitoring instrumentation, how much is that cost? How often do you have a detailed inspection conducted? How much does it cost per year for these inspections?Show citation box
31. Does the state or local jurisdiction in which you operate require you to use a professional engineer? If so, when is a professional engineer specifically required? (If you have dams in more than one state please identify which states require a professional engineer and which do not).Show citation box
32. What are the costs associated with training personnel who conduct frequent, routine inspections and monitor instrumentation at dams?Show citation box
33. What costs are involved in capping, breaching, or otherwise properly abandoning a dam? Please provide details of your experience and what was involved when you properly abandoned a dam. Describe any impact of a properly abandoned dam.Show citation box
34. What are the costs to a mine operator if a dam fails? Please characterize other impacts such as loss of life, environmental damage, etc.Show citation box
35. Do you have insurance against a dam failure? If so, please specify cost and coverage. Does the insurance carrier require the use of a professional engineer for specific dam activities? If a professional engineer is not required, does the insurance carrier give a discount if one is used? Does your insurance company have any other requirements related to dam safety?Show citation box
36. What quantifiable and non-quantifiable costs and benefits for the downstream community are involved when a dam is properly designed and constructed? In addition, MSHA welcomes comments on other relevant indirect costs and benefits.Show citation box
Dated: August 9, 2010.
Joseph A. Main,
Assistant Secretary of Labor for Mine Safety and Health.
[FR Doc. 2010-19960 Filed 8-12-10; 8:45 am]