With the rains that occurred over the past several weeks, many of us have had to mow our lawns more often. These heavy rains can also contribute to grass clippings ending up in storm water runoff. Grass clippings that are blown into the street eventually enter the street storm drain.
When lawn clippings, fertilizers, soil, leaves, or animal wastes, are picked up by storm water runoff, they are carried directly to our local streams and lakes. All of these materials including grass clippings contain phosphorus. According to the U.S. EPA, phosphorus is one of the most troublesome pollutants in storm water runoff and it is considered the primary cause of water quality problems in our lakes, ponds and streams.
Grass clippings contribute nutrients such as nitrogen and phosphorous, which cause unwanted and uncontrolled growth of algae and aquatic weeds in the waterways. Increased algae growth is observed as green algae blooms or “scums” on lakes and ponds. Too much algae is harmful to a lake system. It blocks sunlight and prevents other plants from growing. When it dies and decays, it also takes much needed oxygen away from fish. Limiting phosphorus reduces algae blooms. According to the Northeast Wisconsin Stormwater Coalition, one bushel of fresh grass clippings can contain 0.1 pounds of phosphorus which if it ends up in lakes or ponds is enough to produce 30 to 50 pounds of algae.
When mowing your yard, make certain that you do not blow grass clippings into the street. Alsace Township has an MS4 Permit with the DEP which regulates stormwater and pollution which may enter the streams from the storm system. Also, we were required to adopt an MS4 Ordinance adhering to these regulations. Lawn clippings blown into the street and not cleaned up by the homeowner may enter the storm system and is a violation of the MS4 Ordinance and is a fine-able offense. When mowing, make the first few passes with the lawnmower blowing the grass clippings into the lawn not the street. If there are grass clippings on the street or sidewalk, use a broom or leaf blower to blow them back into the lawn. Do not use a hose to wash them into the street or storm drains. Keeping your leaves and lawn clippings out of the streets and gutters will have significant benefits for your local lake or stream. You can reduce the amount of phosphorus entering a lake or stream and keep one of our most precious renewable resources clean for the next generation.