TNRRAT:

Please note that the assessment tool has not yet been revised to correspond to the new MS4 general permit (issued September 30, 2016), but the original version of the tool is still available.

The Tennessee Runoff Reduction Assessment Tool (TNRRAT) was designed to help engineers, landscape architects, and other designers to create successful permanent stormwater management designs that protect water quality and meet the Tennessee MS4 Permanent Stormwater Permit requirements.

It is expected that you will download this the first time while going through the set of four basic videos, available on this website under the Video button. It is recommended that you do not run the TNRRAT without going through those videos, as it is not likely to make much sense.

The registration link below provides access to the most recent version of the TNRRAT, which is updated periodically as bugs are fixed and new features added. You will be asked to register before downloading, in large part to enable us to inform you of new versions as they are posted.

The TNRRAT description, also available for download, is a more detailed overview of the science behind the TNRRAT. It is not necessary to read this in order to successfully use the TNRRAT for designs, but it does help in understanding why it behaves as it does. This description is intended for design professionals with a substantial background in hydrology, rather than more general user.

Download the TNRRAT Tool

You must first register to download the tool.  If you have previously taken a class at tnepsc.org before, you may register with a couple of clicks by finding your name using the tool below.   Otherwise, click the Click Here to Register button below.