There are many publications reporting the performance of isolated stormwater controls, but relatively few that have examined how the use of many of these controls function at larger scales and for long periods of time. Researchers, stormwater managers and regulators need to know answers to such questions as:

• Are source area distributed controls effective in reducing outfall discharges?
• Can results from small-scale laboratory and pilot-scale field experiments be up-scaled to large, long-term installations?
• How robust are stormwater controls for extended periods?
• How do local groundwater conditions affect bioretention performance, and what is the potential for groundwater contamination?

This presentation summarizes the results from several research projects that Bob Pitt and their students have been involved with that address scaling issues and these questions. Specifically, they have found that carefully conducted small-scale and short-term laboratory and pilot-scale tests can be useful when extrapolated to full-scale installations. These tests need to use actual stormwater and the tests need to be conducted in a manner that accurately represent expected conditions. Obviously, scaling up these results are also highly dependent on the amount of the stormwater directed to the controls. Small “hot spots” need priority treatment, but since they usually only represent small runoff amounts, moderately contaminated areas representing greater amounts of the runoff are also usually needed for effective watershed-scale benefits. Also, unintended consequences of large-scale implementation of infiltration may adversely affect the local groundwater, and/or poorly understood local soil and groundwater conditions may adversely affect the performance of the stormwater controls.