Developments in the Safety and Security of Mining Industry Dams

Transcription

1 Developments in the Safety and Security of Mining Industry Dams John W. Fredland, P.E. Civil Engineer / Dam Safety Officer Mine Safety and Health Administration Tailings and Mine Waste `08 Conference

2 Dam-Safety Topics: Lessons from Dam Incidents Emergency Action Plans Security Measures for Dams Updating of Engineering and Design Manual: Coal Refuse Disposal Facilities

3 MSHA s Inventory of Dams Number and Hazard-Potential Classification of Dams (March, 2008) Hazard-Potential Classification High Significant Low Totals Coal Mines Metal / Nonmetal Mines Totals National Inventory of Dams (NID) Inclusion Criteria: 25 feet in height or 50 acrefeet storage. MSHA Coal regulations criteria: Approved plan required if can impound 20 acre-feet or 20 feet above the upstream toe.

4 Topic 1: Lessons from Incidents

5 Problems Observed at Some Tailings Dams Lack of a properly engineered design: Steep embankment slopes; Lack of systematic compaction of embankment; Lack of internal drainage; Inadequate spillways and freeboard. Lack of effective quality control during construction.

6 Example Tailings pond embankment failure.

7 No injuries, but the railroad and power lines were damaged.

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9 Example Limestone tailings dam failure.

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11 Dam raised by centerline and upstream construction Tailings Starter Cross-section of dam

12 Problems Observed at Some Tailings Dams Performance problems not detected by dam inspections Possible causes: Inadequate frequency of inspections Personnel lacking adequate training / background to recognize problems Lack of supplemental inspections by an engineer

13 Example Tailings dam failure.

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16 Purpose of routine dam inspection: Identify signs of problems or instability.

17 Adequate Freeboard?

18 Summary of Concerns at Some Tailings Dams Lack of a properly engineered design; Lack of adequate quality control during construction; Inadequate dam inspections.

19 Stava Tailings Dam Failure Stava, Italy Lower Pond: 82 feet high. Upper Pond: 100 feet high.

20 Released ~ 53 Million Gallons Tailings flowed 4 miles 268 Fatalities

21 Topic 2: Emergency Action Plans

22 Emergency Action Plan (EAP) An Emergency Action Plan: specifies pre-planned actions to be followed to minimize loss of life and property damage in the event of a dam failure.

23 Goal for EAPs GOAL: All high-hazard-potential dams in the U.S. will have EAPs within 5 years.

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26 For each high-hazardpotential dam without an EAP - Ask the person in charge what they would do if they came to work the next day and found that an emergency condition had developed and it appeared that the dam was going to fail

27 -What action would they take? -Who would they contact and how would they contact them? -Do they know who would be affected downstream once the dam fails? -How would those people be warned and notified to evacuate? -Do they know how to contact local emergency response personnel? -Have they ever discussed the possibility of an emergency at the dam with local emergence response personnel? -An EAP provides answers to these questions.

28 Buffalo Creek Failure Of 125 deaths, 77 occurred 5 miles or more downstream of the failed dam. It took 45 minutes or longer for the flood wave to reach these locations Warning time for the people affected downstream is the most important factor affecting potential loss of life due to dam failure (USBR)

29 FEMA 64

30 FEMA 64 / Federal Guidelines for Dam Safety The Basic Elements of an EAP: 1. Notification Flowchart - who is to be notified, by whom, and in what priority. 2. Emergency Detection, Evaluation, and Classification - procedures for reliable and timely detection and evaluation of an emergency situation. 3. Responsibilities - Dam owners are responsible for developing, maintaining, and implementing the EAP; Emergency management officials are responsible for warning and evacuation 4. Preparedness - Actions to moderate or alleviate the effects of a dam failure and to facilitate response to emergencies. 5. Inundation Map - delineates the area that would be flooded as a result of a dam failure and timing of the flood wave to facilitate timely notification and evacuation.

31 See NRCS website: - Sample EAP - Fillable Form

32 Table-Top EAP Exercise: Dam owners and emergency responders should develop a working relationship before an emergency occurs.

33 Topic 3: Security Measures for Dams

34 Indicators of Possible Surveillance People Related Persons using or carrying video/camera equipment. Person with maps or diagrams Persons parking in same area over multiple days Persons observed using night-vision devices Personnel being questioned off-site about the facility Persons not associated with the dam showing an increased interest in it

35 Indicators of Possible Surveillance Activities Related Unfamiliar contractor crews Seemingly abandoned vehicle on the dam Unusual maintenance activities near the dam Delivery of equipment or materials that is unexpected

36 A copy of Dams Sector Security Awareness Guide is available on web site of the Association of State Dam Safety Officials (ASDSO) Go to

37 Topic 4: Updating of Engineering and Design Manual AKA The Green Monster Original developed under contract to MESA in

38 Event: Buffalo Creek Date: February 26, 1972 Location: Saunders, WV Impact: 125 deaths; > 4000 homeless

39 Cross-section of dams in Middle Fork, Buffalo Creek Dam No. 3 Dam No. 2 Dam No. 1 Refuse Pile Dams No. 2 and No. 3 built on sediments / slurry Slurry discharged a couple thousand feet upstream from impoundments

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43 Manual Purpose: Pull together what was known about coal refuse and disposal practices, plus provide information on dam-safety basics The Manual s primary intent is to serve as a uniform guide to safe refuse disposal practices 1975

44 30+ years later - some of the design information in the Manual is outdated. Original Manual does not address in detail important design issues, such as: - Dealing with underground mine workings near an impoundment; - Liquefaction and seismicstability analyses; Safety measures during upstream push-outs -Emergency Action Plans

45 Breakthrough Location Additional impetus to update the Design Manual came following a breakthrough accident in Martin County, KY in October 2000 where over 300 million gallons of water and slurry was released.

46 After Accident After > $45 M Cleanup No deaths resulted, but coal fines flowed out of two mine portals and affected creeks and creek-side property for many miles on two watersheds.

47 MSHA issued a Request for Proposals Contract awarded to a team of contractors headed by D Appolonia Consultants. Final draft in process of being reviewed. 1975

48 Key features of contract Team includes experts on seismic stability / deformation Questionnaire sent to designers Interested parties provided opportunity to comment on draft

49 Seismic expertise Dr. William Marcuson, Consultant, retired from COE Dr. Gonzalo Castro, GEI Consultants Dr. Peter Robertson, Gregg Drilling and Testing Blaise E. Genes, Civil & Environmental Consultants (CEC) Michael Paster, GEI Consultants Rich Tobin, GEI Consultants Robert E. Snow, D Appolonia Christopher Lewis, D Appolonia William Johnson, D Appolonia

50 Chapter on Seismic Stability / Deformation SEISMIC DESIGN : STABILITY AND DEFORMATION ANALYSES General Considerations» Seismic Instability» Excessive Deformations» Sand-Like Versus Clay-Like Material» Susceptibility to Strength Loss» Basic Steps for Seismic Stability and Deformation Analysis (Flow Chart) Characterization of Subsurface Conditions & Material Properties Seismic Stability Analyses» Triggering Analysis» Evaluation of Post-Earthquake Strength» Analysis Steps (Flow Chart) Seismic Deformation Analyses» Preliminary Screening» Newmark-Type Analysis» Numerical Modeling Embankment Modifications to Improve Stability or Resistance to Deformations Seismic Hazard Assessment (Seismicity)

51 Current Status of Design Manual Final review is being completed Expect Manual to be available in March, Format: Searchable DVD with references

52 To Recap Mining dams need to be adequately engineered and inspected. All high-hazard-potential dams should have an EAP. A Dam Security Awareness Guide is available. Look for an updated coal Design Manual in March of Contact Information: John Fredland, Dam Safety Officer, MSHA Phone: fredland.john@dol.gov