tsli001 - You can code HEC22 in a weekend or less (depending on your excel experience). I recommend always coding your own spreadsheet because it can take longer to backcheck someone elses. As ccampttu states there are free software products outthere that will do this as well. Check out SWMM5.0. You may have software available as well, for instance, INROADS has Storm & Sanitary built in if your company uses that or ACAD uses Hydraflow built in now. You may want to check with your company first.