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Who: The United States Geological Survey (USGS)
What: Completed two studies to measure phosphorus levels in receiving water bodies with and without leaf removal from streets and if frequency or removal methods impacted these levels
When: 2016 and 2020
Where: Madison, WI
Results:
1) Timely removal of leaf litter from streets can reduce phosphorus loads by 80%. This assumes biweekly street cleaning which may not be realistic for all municipalities.
2) Weekly removal of leaves is recommended. If resources are limited, target streets with high canopy cover for largest impact.
3) No significant differences were measured between phosphorus levels and methods of leaf collection (e.g., transfer to community mulch pile, vacuum-mulch) or street cleaning (e.g., mechanical, regenerative air).
Why is this important?
Wisconsin legislation (NR102.06) identifies acceptable levels of phosphorus in different water bodies to maintain healthy freshwater resources. Elevated phosphorus levels can lead to algae blooms which kill aquatic plants, clog gills of fish, lower dissolved oxygen levels, and can produce toxins that are harmful if ingested by people or pets.
How can your municipality help?
Remove leaves from streets prior to rainfall. Leaves leach phosphorus into stormwater even if the leaves do not physically make their way to the nearest water body.
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