You might want to try the university of Alabama. Some of the professors have already produced some work on IDF curves for the State. Dr. "Rocky" Duran is an expert in the field of hydrology and can be a great help. Two other documents you may need to help you out are TP-20 and...
You can obtain SWMM through the EPA website. Yes I have used a similar method that you are using and found it to be very tedious and it is very easy to forget something when you are dealing with multiple pumps. The last time I talked with haestad, they indicated that they were integrating...
Have you tried SWMM? It is not the easiest to set up but once you have enter your pump curves and established their parameters, you don't have make any other adjustments. What programs are you using now?
For the application you are looking at, the Rational Method is an excellent choice. If you are forced to use TR-20 for this type of application, although your drainage area is too small, get a copy of the National Engieering Handbook. It will give you great examples on to calculate the time of...