5.1 Each device has unique flow patterns and turbulence characteristics and may exhibit a wide range of efficiencies as discharge, particle-size distribution, particle density, and flow viscosity (that is, water temperature) changes. The testing procedures described in Section 8 provide a method of measuring the removal efficiency of these devices under a given flow condition, flow viscosity (water temperature), and particle-size distribution and density. Therefore, the results of testing represent the flow, viscosity, and particle-size distribution tested.

1.1 This test method concerns measurement of the efficiency of hydrodynamic separators and underground settling devices in removing suspended sediment from simulated stormwater runoff under conditions defined herein. This test method is not intended for use in determining field removal efficiency.

1.2 Units tested shall be of a size commonly manufactured, not a scale model. This test method is not intended to address product scaling.

1.3 This test method is not for measuring the removal efficiency of filters or the scouring potential of hydrodynamic separators and underground settling devices.

1.4 In this test method, only gravity flow operation is addressed—performance of units operating under pressurized conditions is not addressed.

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.