Wayne,

I appreciate your help. Since I sent that email, I have discovered that the error is related to the maximum intensity of the event. That is, I have compared the flow and fecal coliform loads in (that is, the loads that are supposed to be going in) versus total model-predicated load out and found that the difference increases as the maximum event rainfall intensity increases (we're running a series of design events as well as a typical year continuous simulation). Below, say an inch or so an hour, the difference appears negligible. Based on this and some cursory examination of the inputs, I am thinking it may be at least partially due to some instabilities in the R1 inputs we received from the other consultant.

Also, the reason we have to use the R1 cards in the first place is because we have to assign FC concentrations to the flows based on a dry weather/wet weather concentration assignment scheme we're using.

Thanks again,
Scott