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Third Party Testing at the St. Anthony Falls Laboratory

August 2012 (volume 7 - issue 8)

Contributed by Craig Taylor, Associate Engineer, St. Anthony Falls Laboratory, University of Minnesota

Third-party testing is a service provided by the St. Anthony Falls Laboratory (SAFL) to evaluate a stormwater product’s operational effectiveness. The goals of third-party testing are to:

1. confirm or refute that a manufacturer’s product works as they expect it to
2. verify that a product will work in a specific watershed or under unique conditions
3. help manufacturer and practitioners visualize the mechanisms by which a product functions, and
4. recommend improvements to enhance a product’s efficiency.

The most notable of the testing work has been the full-scale evaluation of a series of hydrodynamic separators. This work has focused on evaluating the sediment removal efficiency and the washout potential for each device over a wide range of sediment sizes and water flow rates. The results of these tests have been incorporated into a free design software called SHSAM©. SHSAM© was developed by Barr Engineering® and is available through their website at https://www.barr.com/WhatsNew/SHSAM/SHSAMapp.asp. The SHSAM© software allows for the side-by-side comparison of all the hydrodynamic separators tested by SAFL. SHSAM© will be a valuable tool for any designer looking for a fair comparison of several devices that may be applicable to their site.

Figure 1: Screenshot of SHSAM© software package (available at https://www.barr.com/WhatsNew/SHSAM/SHSAMapp.asp).

Beyond sediment testing, SAFL can also conduct dye tracer tests for hydrodynamic separators. Dye tracer tests are the most effective means of evaluating the retention time within a given hydrodynamic separator. Retention time is of major influence on a BMP’s ability to settle out suspended sediment. Dye tracer tests have been used to determine if the chambers in multi-chamber devices are actually hydraulically separate or if the device should be considered well-mixed. Finally, dye tracer tests have been used to corroborate numerical models of various devices. This allows the manufactures to develop better models of their products and make improvements more quickly.

Figure 2: Example results from device dye tracer testing.

SAFL also specializes in third-party hydraulic testing and rating curve development. A recent project was completed for the Thirsty-Duck. Ltd® ER-200 Buoyant Flow Control Device, shown in Figure 3. The ER-200 is a floating orifice designed to function as a stormwater pond outlet structure. The advantage of a floating orifice is that it quickly reaches peak discharge and will maintain that discharge regardless of the pond’s depth. Ultimately, the ER-200 is more efficient at passing water out of the pond than a traditional outlet structure. The net results are that the dead storage zone at the bottom of the pond can be increased and the overall pond surface area can be reduced.

Figure 3: Thirsty-Duck. Ltd® ER-200 Buoyant Flow Control Device.

The motivation for the ER-200 testing was to develop a rating curve for the device and evaluate the performance when the device is exposed to debris and highway trash. A figure of the device rating curve is given in Figure 4. The points are the experimental data and the solid line is the rating curve as calculated by Thirsty-Duck, Ltd. Attempts were also made to foul and/or disable the device by clogging it with debris. Test debris included leaves, tall grass, soda cans/bottle, and sticks. Debris not trapped by the trash barrier did not impair the device. Leaves, grass, and soda cans/bottles all passed through the device. The sticks (up to 1 inch in diameter) were not sufficiently strong to disable the device. As a direct result of this testing, the ER-200 has been added to the Florida DOT approved product list.

Figure 4: Rating curve from device testing of Thirsty-Duck. Ltd® ER-200 Buoyant Flow Control Device.

Flow visualization videos are one of the most effective methods to help a practitioner understand how a product is supposed to work. As examples, flow visualization videos were conducted for Hydro-International’s Downstream Defender® and Thirsty-Duck, Ltd’s ER-200. The Downstream Defender video is available through Hydro-International’s YouTube channel (http://www.youtube.com/watch?v=XKH7AgRIivg&list=UUk5fWYLukyTRjLTb857ai3A&index=3&feature=plcp). The ER-200 debris testing video is available by request.
In conclusion, the goal of SAFL’s third-party testing program is to facilitate open and honest conversation between manufactures, agencies, and practitioners by ensuring that all parties understand how proprietary products function in the real environment.

We want to hear from you!!!

Let us know your thoughts, experiences, and questions by posting a comment. To get you thinking, here are a few questions:

• What answers do you want to get out of third-party testing? Do the above methods provide those answers or are there other testing methods we should incorporate or consider?
• What other devices or treatment practices need third-party testing such as this?