1. (a) Periodic re-evaluation of existing dams. Existing dams, as defined in §299.1 of this title (relating to Definitions), are subject from time to time to re-evaluation in consideration of continuing downstream development. Hydrologic criteria contained in §299.14, Table 3 of this title (relating to Hydrologic Criteria for Dams) are the minimum acceptable spillway evaluation flood (SEF) for re-evaluating dam and spillway capacity for existing dams to determine whether upgrading is required. Dams not meeting minimum criteria are considered to be below acceptable limits and are subject to action as necessary under §299.2 of this title (relating to General).
2. (b) Exemptions from minimum hydrologic criteria. Existing low hazard dams are exempt from the minimum hydrologic criteria as given in Table 3 and any other existing structure may be exempt from the minimum hydrologic criteria if properly prepared dam breach analyses show that existing downstream improvements or known or planned future improvements will not be adversely affected. A properly prepared breach analysis should include at least three events, the normal storage capacity nonflood event, the barely overtopping event, and the PMF event. Data on additional flood magnitudes may be provided as necessary to document other conditions or conclusions. Downstream flooding differentials of one-foot or less between breach and nonbreach simulations are not considered to be adverse.
3. (c) Structural evaluation. Evaluating the structural condition of an existing dam includes, but is not limited to, visual inspections and evaluations of potential problems such as seepage, cracks, slides, conduit and control malfunctions, and other structural and maintenance deficiencies which could lead to failure of a structure. An active and progressive deteriorating condition is sufficient for a finding that an existing dam is structurally inadequate.

Source Note:The provisions of this §299.15 adopted to be effective May 13, 1986, 11 TexReg 1978.