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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />, I <br /> <br />9.4.2. Risk to Life. <br /> <br />There is no consensus or risk standard which <br />specifically considers whether risk to life <br />criteria, relating to the overall risk over the <br />long life of the dam, is equally applicable to <br />the short term construction period. Compliance <br />with RA94 and ANCOW 98 risk to life <br />criteria would generally result in very <br />conservative construction flood provisions <br />compared with historical practice. <br /> <br />At this stage of development of risk <br />assessment for dams, it is considered that <br />comparisons of risk to life estimates with life <br />safety criteria should only be used to assist in <br />considering construction flood options. <br /> <br />9.43. Remedial Works. <br /> <br />With an existing dam, the stored volume <br />usually poses a more severe hazard for <br />downstream areas over the construction period <br />than the water progressively stored during <br />river diversion during construction of a new <br />dam. <br /> <br />It is possible that, because of the practical <br />problems of maintaining supplies and existing <br />spillway capacity during works to increase <br />flood capacity (or remediate other <br />inadequacies), higher risks of dam flood <br />failure than the existing provisions could apply <br />during remedial works. This will be <br />particularly so if the existing spillway <br />operation is restricted during construction, ' <br /> <br />If the increase in flood capacity is to be <br />provided by construction of a separate <br />supplementary spillway and/or fuse plug, then <br />it is possible the works will not restrict the <br />existing flood capacity. <br /> <br />Consideration can be given to mItIgating <br />effects of staged construction with mesh <br />protection, and with an existing dam, lowering <br />of the storage level at critical phases, and <br />selection of appropriate lesser flow season or <br />periods for critical phases of construction. <br /> <br />9.4.4. Flood Warnilf' PlllfJs. <br /> <br />Specific flood forecasting and site warning <br />plans should be provided during construction, <br />in conjunction with appropriate warning and <br />evacuation plans developed with the <br />community downstream and relevant <br />emergency authorities. <br /> <br />9.4.5. Risk Assessment. <br /> <br />Each case will require consideration of the <br />specific site and operational restrictions and <br />practicability of handing floods during <br />construction. The basic risk process can assist <br />in identifying and comparing relative risks for <br />construction options, <br /> <br />In general, the aim, as far as practicable, <br />should be: <br />. With proposed dams for the flood <br />risks during the short construction <br />period to be equivalent to the adopted <br />flood risk over the long term life of the <br />dam subject to the owner being <br />satisfied that risks imposed on the <br />population are acceptable and <br />defensible. <br />. For remediation of existing dam <br />spillways, to not increase the existing <br />risk. <br /> <br />All these factors are usually considered for <br />insurance of works and third party insurance. <br /> <br />9.5. Mining Dam Spillway Provisions. <br /> <br />9.5.1. Scope <br /> <br />Dams constructed for a mining works to store <br />water for supply or re-use, as distinct from <br />tailings, should meet the general AFC <br />requirements of these guidelines. <br /> <br />9.5.2. Tailing Dam Water Management. <br /> <br />Aspects of water management for mining dams <br />such as tailings dams with different <br />requirements to water supply dams, relate to <br />staged construction, enviromnental <br />restrictions, and proposed life, including: <br /> <br />24 ANCOLD Guidelines on Selection of an Acceptable flood Capacity for Dams <br />