Soil physical characteristics related to failure of stormwater biofiltration devices

The main theme of this dissertation research was to investigate and test solutions to overcome common failure mechanisms of bioinfiltration stormwater devices. Bioinfiltration can be an effective option for the management of stormwater runoff from urban areas, mainly through enhanced infiltration of the runoff to better balance the urban hydrologic cycle. There are increasing interests in the use of bioinfiltration practices for managing stormwater runoff, as infiltration practices promote groundwater recharge, reduce runoff peak flow rates and volumes, and can reduce pollutant discharges to surface water bodies. However, there are known problems causing failure of these devices (such as clogging, under-sizing, improper underdrain use, and inefficient treatment media). In addition, few quantitative guidelines are available for the design of biofilters and bioinfiltration devices for specific treatment goals while minimizing these operational problems. Some types of stormwater control practices are intended to include standing water for varying lengths of time for enhanced sedimentation and scour protection. In areas having restrictive soils, underdrains are used to minimize long periods of standing water (less than 3 days) to minimize nuisance conditions such as breeding of mosquitoes.. Alternatives that result in greater flexibility and efficiency in the design of biofiltration and bioretention devices were tested and developed during this research. The drainage rate in biofiltration devices (having an underdrain) is usually controlled using an underdrain that is restricted with a small orifice or other flow-moderating component. These orifices used for flow control frequently fail, because they are very small (