1. (a) All low hazard, significant hazard, or high hazard dams constructed prior to February 19, 1981 shall pass the flows indicated below with one foot of freeboard and without manual operations:

   1. (1) Low hazard dams shall pass a 50-year design event;
   2. (2) Significant hazard dams shall pass the 100-year design event; and
   3. (3) High hazard dam shall pass the 1,000-year design event, or site specific inflow design flood approved by the department.
2. (b) All dams constructed after February 19, 1981 shall pass the flow required by the administrative rules in place at the time of the dam’s construction, in accordance with the dam’s current classification, or at the owner's option, the requirements in Env-Wr 303.10(a) above.

Source. #8414, eff 8-20-05; ss by #10510, eff 1-22-14; ss by #13980, eff 5-24-24 (formerly Env-Wr 303.11)