Mitch,

Try the book by Adams and Papa (2000): Urban Stormwater Management Planning with analytical probabilistic Models (John Wiley and Sons). I guess a good way to go about this is to look at rainfall characteristics, do a statistical analysis on these and try to come up with years with average characteristics and, finally, run these 2 or 3 years with continuous simulation. The book mentioned has good discussion on rainfall analysis and provides equations that enable you to use the rainfall characteristics to obtain information about CSO, detention volumes and spills. It is derived from the approach started out at the end of the 1970s by Charles Howard (in B.C.) and that has been extended by Dr. Adams at U. of Toronto for the last 20 years or so.

Hope this helps.

Gilles Rivard, ing. M. Sc.
grivaquapraxis@VIDEOTRON.CA