Proposed Specifications for submitting documents to the Dams ...

Proposed Specifications for submitting documentsto the Dams Safety CommitteeDraft Guidance Sheet UsageThese draft Guidance Sheets have been prepared primarily for review and commentONLY and at this stage they give an indication of the DSC’s intentions for futurepolicies and procedures. It should not be assumed that these draft Guidance Sheetswill be adopted in the future. In all cases users should refer to the currentInformation Sheet for information on the Committee’s current policy and procedures.However until these Guidance Sheets are finalized, the DSC will consider, on acase-by-case basis any reasoned and substantiated proposals by dam ownersbased on either the existing DSC Information Sheets or the proposed GuidanceSheets.How to make your commentsThe preferred method is by email to comments@damsafety.nsw.gov.au. You mayalso fax or mail your comments to:Dams Safety CommitteePO Box 3720PARRAMATTA NSW 2124Fax: (02) 9895 7354Please indicate which draft Guidance Sheet yourcomments refer to and if possible which section (e.g.DSC2A Section 2.1).Deadline for comments: 30 November 2009

NSW DAMS SAFETY COMMITTEE (DSC)GUIDANCE SHEET DSC4DMINING NEAR PRESCRIBED DAMSCONTINGENCY PLANSTABLE of CONTENTSITEMPage1. Introduction 22. DSC Mining Safety Goal & Key Requirements 23. General DSC Requirements 34. DSC Legal Powers in an Emergency 45. Role of the DSC 46. Contacting the DSC in the Event of an Emergency 47. Possible Triggers (Action Indicators) 48. Contingency Actions 69. Contingency Plan Presentation 7CONSULTATION DRAFT (August 2009)The following document is a draft for consultation purposes only. If a copy ofthis document has been received, it should be used for information only. Theguidance and requirements of the document are under discussion and are notyet endorsed by the NSW Dams Safety Committee (DSC).- 1 -

1.0 INTRODUCTIONThe normal requirements of the NSW Dams Safety Committee (DSC) are set out in itsguidance sheets with its principal guidance sheet, DSC Background, Functions andOperations (DSC1A),outlining the DSC’s general operations and authority.One of the DSC’s main functions is the surveillance of mining within the Notification Area ofany Prescribed Dam in NSW (see DSC4A for definitions) to ensure the safety of thePrescribed Dam and the security of its stored water. This process involves makingrecommendations to the Minister responsible for the Mining Act 1992 in respect ofapplications to mine within Notification Areas of prescribed dams. These recommendationsspecify the extent and type of mining which may be undertaken in the vicinity of the dam andfor mining near stored waters usually require a contingency plan to be formulated.Accordingly this Guidance Sheet, supersedes DSC35, June 1998, and is provided for theguidance and direction of mining companies on items to be included in contingency plans tominimise dam damage or storage loss as a result of mining under, or near, stored waters.Companion guidance sheets indicate:• Definitions and administrative procedures involved in obtaining consent for mining withinNotification Areas (DSC4A). It includes details of the types of supporting material to beincluded with an application;• Aspects the DSC will consider before making recommendations on a mining application,and provides guidelines on the extent and type of mining which the DSC mayrecommend to the Minister administering the Mining Act (DSC4B); and• Some guidelines on the types of monitoring and management conditions normallyrecommended by the DSC to the Minister (DSC4C). These guidelines are an indicationonly as variations will occur as a result of local conditions.The DSC Mining Safety Goal and Key Requirements (Section 2) are a summary-the wholesheet is to be read for a proper understanding of DSC considerations on contingencyplanning for mining near prescribed dams.2.0 DSC MINING SAFETY GOAL & KEY REQUIREMENTS2.1 DSC Mining Safety GoalThe primary goal of the DSC, relevant to this sheet, is that mining risks to prescribeddams and their storages are demonstrated to be tolerable with all these risks:• Identified and assessed;• Reduced as low as reasonably practicable (ALARP), and as soon as reasonablypracticable, in a way that best serves community interests; and• Kept under review throughout the life cycle of the mining operations.The following sections of this sheet aim to provide direction and guidance to assistmining companies in achieving the DSC’s goal.2.2 DSC Key RequirementsThis section summarises the DSC requirements outlined in this sheet3.0 GENERAL DSC REQUIREMENTSThe DSC requires that the approval of mining under stored waters will include arequirement that an appropriate Contingency Plan be developed to ensure water losswill be kept within tolerable limits.The Contingency Plan is required to be an “action plan”The DSC, the Department of Primary Industries (DPI) and the dam owner are to belisted as parties to be notified at an appropriate trigger level.- 2 -

4.0 DSC’s LEGAL POWERS IN AN EMERGENCYSection 18 (2) of the Dams Safety Act 1978 empowers the DSC to issue a noticerequiring any person (relevant authority, etc) to do such things as necessary toensure the safety of a prescribed dam. Section 21 of the Dams Safety Act 1978empowers the Minister to declare a state of emergency in certain circumstances.5.0 ROLE OF THE DSCThe DSC’s role, having been alerted to an unexpected inflow is to monitor thesituation, ensure that the developed Contingency Plan is implemented by the mineowner, and to offer technical assistance where possible.6.0 CONTACTINNG THE DSC IN THE EVENT OF AN EMERGENCYMining companies are required to liaise with the DSC to obtain the contact details forpertinent DSC officers for inclusion in the Contingency Plan.7.0 POSSIBLE TRIGGERS (Action Indicators)Triggers should be based on physical parameters which are relevant, reliable, andreadily measured. The DSC has standard criteria for a trigger requiring notification(i.e. a low level trigger) based on water inflows.8.0 CONTINGENCY ACTIONSTable 1 lists some generic contingency actions, and provides some specificexamples relevant to the loss of stored water.9.0 CONTINGENCY PLAN PRESENTATIONThe Contingency Plan should contain details of all relevant procedures,specifications and actions. The actual type and timing of actions will depend on theoperational requirements of the particular mine, the capacity for pumping and storingwater underground, and the value of the stored water.3.0 GENERAL DSC REQUIREMENTSThe purpose of a Contingency Plan is to provide effective procedures that will assist inminimising dam structure damage, or minimising water loss from the mining affected storagethrough a major inflow (or inrush) into the adjacent mine workings, in the event thatunexpected conditions are encountered during mining operations. The plan is not asubstitute for adequate pre-mining investigation nor does the existence of a plan allowmining in areas that would otherwise have an unacceptable risk. Accordingly, the DSCrequires that the approval of mining under stored waters will include a requirement that anappropriate Contingency Plan be developed to protect the dam structure and ensure waterloss will be kept within tolerable limits.This document is intended as a guide only. Where contingency or emergency plans alreadyexist for other reasons it may be more appropriate to extend one of these plans rather thandevelop a completely new plan.The Contingency Plan is required to be an ‘action plan’ and include:Relevant, reliable and readily measured parameters identified for use as ‘triggers’;• Identified levels or events for triggers;• Explanation of the monitoring or other information supporting each trigger level;• An explanation of the actions required to be implemented at each trigger level. Forexample, for mine inflows, procedures will specify levels of inflow above which keypersonnel, both at the mine and in other organisations, are to be informed of thesituation, and what actions are required of these personnel;• Definition of the roles, responsibilities and contacts for persons involved in any trigger oraction;- 3 -

• Outlining the resources required to monitor the parameters and implement any requiredactions as is the process for obtaining these resources; and• Arrangement such that the plan can be implemented rapidly by someone in the event ofan emergency.The DSC, the Department of Primary Industries (DPI) and the dam owner are to be listed asparties to be notified at an appropriate trigger level.Where the plan calls for an action which requires the use or installation of equipment, suchas pumping inflow water or constructing bulkheads, the time required for deployment of theequipment shall be considered in the plan. Where necessary the equipment shall be storedor installed at the commencement of mining, to be readily available.4.0 DSC’s LEGAL POWERS IN AN EMERGENCYSection 18 (2) of the Dams Safety Act 1978 empowers the DSC to issue a notice requiringany person (relevant authority, etc) to do such things as necessary to ensure the safety of aprescribed dam. Note that this includes actions in the vicinity of a prescribed dam, andunder Section 16(1), land comprising a dam includes a reference to the water or othermaterial impounded by a dam. Where this notice requires work at a mine to cease, thenotice will be issued with the approval of the Premier. All other notices, for example noticesrequiring grouting, installation of bulkheads, etc, may be issued by the DSC.Section 21 of the Dams Safety Act 1978 empowers the Minister to declare a state ofemergency in certain circumstances. Once declared, the DSC, with the approval of theMinister, may “take full charge and control of … the environs under…the prescribed dam “,and can arrange all such works as are necessary.5.0 ROLE OF THE DSCThe DSC’s role, having been alerted to an unexpected situation (eg inflow) is to monitor thesituation, ensure that the developed Contingency Plan is implemented by the mine owner,and to offer technical assistance where possible. More direct action will be considered if theplan was not implemented or if it did not appear to be successful.In the event of a significant incident (eg inrush or dam distress) the DSC expects to beinformed immediately with DSC staff then to inform appropriate DSC members. At the sametime the DPI should be informed, as well as the appropriate dam owner’s representative.6.0 CONTACTING THE DSC IN THE EVENT OF AN EMERGENCYAs part of the Contingency Plan, the DSC will need to be contacted in the event of anemergency. Mining companies are required to liaise with the DSC to obtain the contactdetails for pertinent DSC officers for inclusion in the Contingency Plan.7.0 POSSIBLE TRIGGERS (Action Indicators)Triggers should be based on physical parameters which are relevant, reliable, and readilymeasured. When considering potential loss of stored waters as a result of undergroundmining, inflow into the workings is usually a prime candidate for an information source as it isrelevant, and usually readily measured. However, the possibility of flow paths which do notintersect the workings developing as a result of mining should be considered. Otherindicative parameters are:• Development of caving towards a known aquifer or flow path;• Changes in groundwater levels;• Water loss from reservoir;• Unexpected ground movements at the surface, particularly at the dam structure, orunderground; or• Deterioration of pillars.- 4 -

Typically a number of trigger levels would be set. Defined in terms of the broad actionsrequired at each level, these might include:1. Watch;2. Notify, increase surveillance, mitigate (pump);3. Investigate, slow mining;4. Prepare for remedial measures, stop mining; and5. Implement remedial measures progressively (there may be more than 1 stage ofremedial works)Levels for triggers may need fine tuning based on their performance in the first few months.This is particularly the case for low level triggers, such as a ‘watch’ or ‘notify’ trigger.Activating low level triggers too frequently may reduce their perceived importance. Howeveran occasional (say, less than 3 times in 12 months) low level trigger will provide evidencethat the system is working.7.1 Triggers for Inflow into Mine WorkingsAt the upper end of the scale, mining should cease when the rate or volume of loss ofstored water approaches the tolerable limits set by the DSC. At this stage,implementation of the remedial works should have begun. Consideration will be given torecommencing mining if the loss is reduced to tolerable levels and the risk of additionalloss is considered to be acceptable by the DSC.Levels could be set based on the rate of flow, rate of change of flow, appearance of flow(discolouration), etc. The DSC has standard criteria for a trigger requiring notification(i.e. a low level trigger) based on water inflows involving:• The volume or rate of flow, or the change in the volume or rate of flow, or the flowlocation causes surprise among persons familiar with the workings;• The volume or rate of flow doubles over a few days; and• The volume or rate of flow is more than 3 standard deviations above the meanvalue (i.e. larger than about 99% of recent readings, or in the top one percentile).In order to be reliable and readily measurable systems must be in place to determinethe background levels. Usually this would involve maintaining a water balance for anarea. It may also incorporate some form of water fingerprinting to allow discriminationbetween different sources of water. This might minimise the number of false alarmtriggers.Options for detecting water inflows include:• An awareness program for staff and an informal visual inspection program;• Formal visual inspections; and• Review of the water balance recordings for the mine (ie recording volume of waterpumped in an out of an area of the mine, recording volumes in holding and recordingmoisture lost from an area in coal or ore or from ventilation).Typically a program would be developed that incorporated a number of these options.The more reliability there is in a program, the smaller the chance that the operation isinterrupted by false alarms.The total volume of water is an important consideration too, in particular if there arelimited means of removing water from the workings. Access to certain areas will berestricted as the workings fill with water, so actions that require access to these areasneed to be scheduled before access is lost.Where water is to be stored behind plugs or dams in the workings, the pressure on theplug as a result of the height of water behind it may determine the schedule as well. For- 5 -

example, a plug may be designed for a maximum pressure equivalent to 10 m of head.A plan would need to assume that the plug will fail at this point, and that any action to bedone in the area that would be flooded by the failure of the plug needs to be completedwell before the pressure builds up to 10 m.8.0 CONTINGENCY ACTIONSTable 1 lists some generic contingency actions, and provides some specific examplesrelevant to the loss of stored water. (Note that a similar approach would be required forresponding to unexpected mining effects on the structural integrity of dam structures)GenericTriggerTABLE 1GENERIC ACTIONS RELATED TO TRIGGER LEVELSGeneric ActionWatch Visual inspection, orobservation of existingmonitoring data, conductedirregularly but frequentlyduring normal operations.Notify Formal advice that anevent has occurred, or isoccurring. There may beseveral levels ofnotification (internal, DSC,DPI).IncreasesurveillanceInvestigateImplement a higherfrequency of measurementor observation of existingdata streams, or implementadditional monitoringaimed at improving theunderstanding of thebehaviour of the event.Undertake desk or on-siteinvestigations to determinethe source, path, or causeof an event.Mitigate Implement measures toreduce the consequence ofthe eventRemediate Implement measures toreduce the causeExample of specific actions related to an inflowfrom surface stored waterArranging to walk past and look at an area of seepageor drippers a few times during a shiftContact the DSC and advise them that there ispersistent leakage from a heading, that it will continueto be monitored, and that an update will be providedtomorrow.Direct seepage water to a point where it can bemeasured and recorded, so that a clearerunderstanding develops of the rate and volume ofinflow from a particular point.Drill holes to determine if a flow path from the surfaceto underground existsUndertake water fingerprinting to determine thesourceRe-evaluation of geological/hydrogeological modelGeophysical testing to determine water bearingfissuresTurn on existing pumps, or install additional pumps;NB this mitigates the consequence to the operationbut does nothing to mitigate the loss of stored waterStop miningDraw down the reservoirInstall a grout curtain or sheet, or attempt to grout aspecific flow pathSeal the area of the mine where the stored water isentering- 6 -

9.0 CONTINGENCY PLAN PRESENTATIONThe Contingency Plan should contain details of all relevant procedures, specifications andactions. This would include:• the capacity of the pumping system;• capacity of the underground storage facilities;• design of the bulkheads;• the name, position, and role of key personnel; and a contact telephone list;• a statement of grouting procedures and the applicability of these procedures to likelyinflow mechanisms; and• A timeline for the implementation of critical elementsThe actual type and timing of actions will depend on the nature and severity of the event andthe operational requirements of the particular mine, the capacity for pumping and storingwater underground, and the value of the stored water.It is vital that Contingency Plans are understandable. Some basic principles might include:• A guide (flowchart, table, or brief explanation) which facilitates the use of the plan in anemergency situation should be included close to the front of the plan;• While some background in a plan is desirable, lengthy sections which are not essentialto the aim of the plan should be avoided. Details are best kept in an Appendix;• Text should be succinct. Where possible it should be augmented by clear diagrams;• Breaking a plan into sub-plans can facilitate preparation and maintenance of the plan.However usability may decrease if there are a large number of sub-plans;• The relationship between sub-plans and the main plan should be very clear, specified ineach of the sub-plans and in the main plan; and• The overlap between plans should be minimised as overlap will increase the likelihood ofconflicts between plans and present difficulties when the plan requires updating.Desk checks should be run on the plan. These can be done by assuming a scenario andrunning through the plans step by step. If a high level of confidence is required in the planthen a more exhaustive check, involving the team of people who would be required toimplement the plan, can be run.- 7 -