(a) Spillway design flood.

1. (1) Existing dams will be evaluated periodically to determine if development of downstream areas warrants:

   1. (A) Change in hazard classification; and
   2. (B) Review of spillway design flood (SDF).

2. (2) Overtopping during the SDF may be allowed if properly prepared analyses demonstrate that:

   1. (A) Overtopping will have a return interval greater than twenty-five (25) years; and
   2. (B) The dam will withstand the projected overtopping without failure.

(b) Structural. A complete evaluation of the structural integrity may include the following:

1. (1) Geotechnical investigation;
2. (2) Structural stability;
3. (3) Seismic resistance;
4. (4) Horizontal and vertical alignments;
5. (5) Structural concrete reliability;
6. (6) Erosion controls;
7. (7) Inlet and outlet works;
8. (8) Stilling basins;
9. (9) Seepage; and
10. (10) Others.

(c) Operation and maintenance.

1. (1) Evaluation of an existing structure shall include, but not be limited to, visual inspections and evaluations of potential problems such as:

   1. (A) Leakage;
   2. (B) Seepage;
   3. (C) Cracks;
   4. (D) Slides;
   5. (E) Settlement;
   6. (F) Spillway blockages;
   7. (G) Conduit controls; and
   8. (H) Other operational and maintenance deficiencies that could lead to failure of the dam.
2. (2) There may be sufficient evidence for a finding that an existing dam is inadequate.