Browsing by Subject "Washout"
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Item Assessment and Recommendations for the Operation of Standard Sumps as Best Management Practices for Stormwater Treatment (Volume 2)(Minnesota Department of Transportation, 2012-05) McIntire, Kurtis D.; Howard, Adam; Mohseni, Omid; Gulliver, John S.In order to improve the performance of standard sumps as a best management practice (BMP) in treating stormwater runoff, a baffle was designed to be installed as a retrofit in standard sumps. The retrofit is a porous baffle called “SAFL Baffle”. The effect of the SAFL Baffle on the performance of standard sumps was assessed by conducting laboratory tests on small scale as well as full scale straight flow-through standard sumps equipped with the baffle. In addition, a number of tests were conducted to determine the performance of standard sumps with the SAFL Baffle when the baffle is clogged with debris like trash and vegetation. Furthermore, the performance of two other configurations of the baffle was studied: (1) the SAFL Baffle in a sump with an outlet pipe 90 degrees to the inlet pipe, and (2) the SAFL Baffle in a sump with some water entering the sump through an overhead inlet grate. Standard sumps equipped with the SAFL Baffle were evaluated using two metrics: (1) How well the system captures sediment during low flow conditions (Removal Efficiency Testing), and (2) how well the system retains the previously captured sediment during high flow conditions (Washout Testing). The results of the tests showed that the SAFL Baffle dissipates the energy of water entering the sump and as a result, at low flow rates, it captures sediment better than a standard sump with no baffle. More importantly, at high flow rates, the washout of the previously captured sediment reduces to near zero.Item Hydrodynamic separator sediment washout testing.(2010-07) Saddoris, David AllanHydrodynamic separators are widely used in urban areas for removal of suspended sediments and floatables from stormwater due to limited land availability for the installation of above ground stormwater best management practices (BMPs). Hydrodynamic separators are often sized based on relatively frequent storm events. However, during less frequent storm events, device design treatment rates are exceeded and previously captured sediments can be washed out of the devices. To study the potential for scour and washout of previously deposited sediments in the sumps of hydrodynamic separators under high flow conditions during infrequent storm events, sediment washout testing methods using mass balance were developed for both controlled field testing and laboratory testing. The developed testing methods were utilized to conduct sediment washout testing on three full scale hydrodynamic separators: 1) an Environment21 V2B1 Model 4, 2) a STC1200 Stormceptor and 3) a 6-ft Downstream Defender. All three devices were tested in the laboratory. The Environment21 V2B1 device was also tested in the field. In addition to full scale testing, two scale models were constructed and tested in the laboratory. Previous work by others on describing sediment washout in standard stormwater sumps was applied to data obtained from the sediment washout tests to develop sediment washout functions which incorporate non-dimensional parameters. Washout functions were developed for each of the devices tested in the laboratory and the field, as well as for a modified ecoStorm device previously tested by others. The washout functions that were developed can be incorporated, along with removal efficiency functions, into continuous urban runoff models to predict maintenance schedules for hydrodynamic separator devices.