Thirsty Duck® Rating Curve Development

The University of Minnesota, St. Anthony Falls Laboratory (SAFL) was contracted by Thirsty Duck, Ltd to conduct a testing program on a buoyant flow control device. The focus of the study was to develop rating curves and analyze debris performance for the ER-200 series device. Debris performance testing included leaves, grass (hay), aluminum cans, plastic bottles, and sticks/vines. The rating curves were monitored during debris performance tests to determine if the select debris impaired the function of the device. The ER-200 device was designed to be installed in a concrete inlet. For this study the device was designed for a Florida Department of Transportation (FDOT) Type C standard inlet (Appendix A). A diagram of the ER-200, provided by Thirsty Duck, Ltd, is provided in Figure 1. There are four primary components to the device. The first is a stationary sleeve which fits inside the concrete inlet. The second component is a moving flow restrictor that has both an orifice in the center and a flared base that creates the annulus between the flow restrictor and the stationary sleeve. Third is a set of floats that raises the moving flow restrictor such that the pressure head between the pond surface and the orifice and annulus is constant. Finally, a skimmer plate is attached to the floats to prevent floatable debris from entering the device.