Proprietary underground devices are often used for stormwater treatment in urban areas due
to tight space constraints. Most of these devices are designed to remove suspended solids
from stormwater runoff prior to discharge into lakes, rivers, and streams via the physical
separation process of sedimentation. Data on the performance of installed devices are limited
and existing data are questionable because of the problems associated with assessment via
monitoring. The objectives of this research were to: (1) investigate the feasibility and
practicality of field testing for assessing the performance of underground devices, (2)
evaluate the effects of sediment size and stormwater flow rate on the performance of four
devices from different manufacturers, and (3) develop a universal approach for predicting the
performance of a device for any given application. For the field testing, a controlled and
reproducible synthetic storm event containing sediment of a fixed size distribution and
concentration is fed to a pre-cleaned device. The captured sediment is then removed, dried,
sieved, and weighed. Universal performance models were developed from the results of this
work and parallel laboratory testing of two other full-scale devices using the Peclet number,
which explains two major processes in performance: (1) advection or settling of particles and
(2) turbulent diffusion or resuspension of particles. The universal performance models will
improve the selection and sizing of these devices and their overall performance after
Local Road Research Board; Twin Cities Metropolitan Council
Wilson, Matthew A.; Gulliver, John S.; Mohseni, Omid; Hozalski, Raymond M..
Performance Assessment of Underground Stormwater Treatment Devices.
St. Anthony Falls Laboratory.
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