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for, and magnitude of, losses of freeboard that may result from settlement of the levee and that demonstrates that the minimum required freeboard will be maintained 7. Interior Drainage -- An engineering analysis of the potential hazards associated with floodwaters that originate on the landward side of the levee 8. Operations A formal levee operation plan 9. Maintenance A formal levee maintenance plan Occasionally, exceptions to the minimum freeboard requirements cited in Items 1 and 2 for riverine and coastal levees may be approved. Any request for an exception must be supported by appropriate engineering analyses which show that, even with the lesser freeboard, a high level of certainty for 100-year flood protection exists. For riverine levees, the supporting analyses must evaluate the uncertainty in the estimated BFE and must assess, at a minimum, the statistical confidence limits of the 100-year peak discharge; stage-discharge relationshi ps for floods larger than the 100-year flood; and the sources, potential, and magnitude of debris, sediment, and ice accumulation that may affect those relationshi ps. The analyses must also show that the levee will remain structurally stable during the base flood, when such additional loading conditions are imposed. Freeboards of less than 2 feet will not be accepted. For coastal levees, the supporting analyses must evaluate the uncertainty in the estimated base flood loading conditions. particular emphasis must be placed on the effects of wave attack and overtopping on the stability of the levee. Freeboards of less than 2 feet above the computed stillwater surge elevation will not be accepted. In lieu of the data described in Items 1 through 6 above, the requestor may submit a certification by a Federal agency with the responsibility for levee design that the levee has been adequately designed and constructed to provide 1 GO-year flood protection. Although a Federal agency certification may be submitted in lieu of Items 1 through 6, it will not satisfy the requirement for an interior drainage analysis (Item 7). Therefore, if a Federal agency certification is submitted it must be accompanied by one of the following: 1. An additional certification -- also by a Federal agency with the responsibility for levee-design -- that either states that no 100-year flood hazard associated with interior drainage exists in the protected area or identifies areas subject to 100- year flooding caused by inadequate interior drainage. 2. A complete interior drainage analysis as described in Item 7. In addition, a certification by a Federal agency does not waive the requirement for the levee operations and maintenance plans (Items 8 and 9). Map Revision Procedures In its review of a Map Revision request, FEMA will communicate by letter and, as necessary, by telephone directly with the person who submitted the request. If that person is a private party, copies of all letters to that person from FEMA wi II be sentto the CEO. After a revision request has been received from the CEO or from a private party, FEMA will perform a preliminary review of the request and the supporting data submitted with it. The purpose of the preliminary review is to determine whether at least the basic supporting data required for a Map Revision have been provided and, if the request was submitted to 27