States in the Midwest and Northeast have recognized the important water-quality benefits of leaf collection and street cleaning in the fall. Recent research has provided a guide for regulatory agencies to develop phosphorus reduction credits that can be applied toward pollution reduction requirements for cities with approved leaf collection and street cleaning programs. This presentation will highlight results from nearly a decade of research that helped formulate these credits by illustrating the range of nutrient load reductions observed over a matrix of leaf collection and street cleaning technologies and frequencies. Overall, the performance of municipal programs was related to the frequency and not the form of treatment. Areas receiving weekly street cleaning by use of a regenerative-air street cleaner had the highest reduction in phosphorus load, ranging from 65 to 71 percent for total phosphorus and 57 to 70 percent for dissolved phosphorus. As the frequency of leaf collection and street cleaning decreased, so did the percent reduction in phosphorus load measured in stormwater runoff. Reduction in nitrogen load was generally mixed, with many of the study areas showing no statistically significant change after treatment. In general, nutrient concentrations, and subsequently percent reduction of nutrient loads, were positively correlated with street tree canopy. Most nutrient concentrations were in the dissolved fraction making source control through leaf collection and street cleaning more effective at reducing the amount of dissolved nutrients in stormwater runoff than structural practices. Therefore, municipal leaf management programs would be most effective with weekly street cleaning in areas of high street tree canopy, whereas the method and frequency of leaf pile collection is of less significance to the mitigation of nutrients in stormwater runoff.
