R655-11-8. Spillway Requirements

A. On all spillway control structures, provisions should be made for aeration of the nappe.

B. All spillways excavated in soils or soft rock should include a check structure to avoid headcutting and lowering of the spillway flowline.

C. All spillway channels should have suitable armor to prevent erosion.

D. If the spillway has concrete sidewalls, adequate weepholes should be provided or the walls should be designed with full hydrostatic loads in conjunction with the soil loads.

E. For spillways in remote areas where significant snowfall occurs, efforts should be made to maximize the southern exposure of the spillway to prevent ice blockage. In many cases elimination of tall trees will be required.

F. All construction joints should be provided with adequate water stops.

G. Design provisions should be made so that downstream spillway channel flows cannot encroach on the dam.

H. All spillways draining reservoirs with large amounts of floating debris should include a log boom to avoid plugging the spillway.

I. Spillway designs should provide for energy dissipation so that waters returned to the natural channel will not cause erosion.

J. For spillways with concrete floors, provisions should be made to control uplift pressures.

K. Stop logs or flashboards which restrict the design spillway capacity will not be allowed.