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Step 2: AssLvn PFMs to Screening Categories After each potential failure mode was identified and preliminarily evaluated, it was assigned to a screening category as summarized on Table 3. All Category I (Highlighted) and Category II (Considered, but not Highlighted) potential failure modes were carried forward for quantitative annualized failure probability estimation. Table 3 PFMA Screening Categories Category Description Definition I Highlighted Those PFMs of greatest significance considering need for awareness, potential for occurrence, magnitude of consequence and likelihood of adverse response. Highlighted (Category 1) PFMs are those for which physical possibility is evident, fundamental flaw or weakness is identified and conditions and events leading to failure seemed reasonable and credible. Category l potential failure modes should be carried forward into a risk analysis. Short -term emergency action -increased monitoring or other interim risk reduction measures may be warranted while risk estimates and documentation are being completed, II Considered, but Category 11 PFMs are also considered credible, in that they are physically possible, not Highlighted but are not highlighted for one or more reasons. Category II potential failure modes are judged to be of lesser significance and likelihood than Category I potential failure modes. A PFM may be placed in Category II because there is no direct or indirect evidence or any indication of problem development; the loading required to initiate the potential adverse response is not as likely as for Category I; or the magnitude of consequences is not as significant as Category I potential failure modes. These potential failure modes are slgnifcant enough that they should be carried forward into a risk anal sis, but do not appear to require immediate (short -term) action. III Insufficient These PFMs to some degree lacked information sufficient to allow a confident Information judgment of significance. As a result, a dam safety investigative action or analyses can be recommended. Because action is required before resolution, the need for this action may also be highlighted. There is insufficient information to make a. judgment on whether these PFMs should be carried forward for risk analysis (in which case either, 1) risk estimates for different failure modes may help focus what information will be most valuable in estimating the risks, or 4 a decision can be made to collect and evaluate the data prior to beginning a risk analysis). Increased monitoring may be an appropriate interim risk management activity while information is being collected. IV Ruled Out Candidate PFMs may be ruled out because the physical possibility does not exist, information came to light which eliminated the concern that had generated the development of the PFM, or the PFM is clearly so remote a possibility as to be non - credible or not reasonable to postulate. These PFMs are clearly so remote that the likelihood of failure is negligible, and hence do not need to be carried forward for risk estimates. However, they still need to be documented along with the reasons they are considered to be negligible risk contributors. Monitoring is likely not warranted for these po tentia/failure modes. San Luis Project Miller Geotechnical Consultants Tailing Dam Data Report 37 February 2014