Modifying Conduit Outlet Protection

[CDO863]

My situation involves designing a preformed scour hole adjacent to an existing retaining wall. The end of the headwall (just beyong the outfall) is proposed to be tied into to retaining wall. In order to satisfy design criteria, the scour hole needs to be a certain width and length. Length is not a problem. However, due to the contraint of the retainining wall, a portion of the scour hole cannot be constructed on one side (a triangular section, approx. 10% of the total area of the entire scour hole). I am thinking of designing riprap along this area, basically cutting off the portion of the scour hole that will not fit. Riprap will be placed from the where the scour hole no longer "fits" up to the bottom of the wall. Any advise from anyone who may have encountered anything similar, or can offer a professional opinion would be welcomed. Thank you.

 

[blueoak]

If length isn't a problem you could also consider a flip bucket (USBR Stilling Basins Manual, EM 25) or baffles so you have less to worry about with a scour or plunge pool. As for ultimate design for scour holes it can be pretty different based on the method.

What is the total drop (vertical and slope) and what sort of drop structure is it?