Stormwater forms when precipitation falls on the land and begins flowing downhill to the nearest river, stream, lake or pond. As it flows, it carries nutrients, sediments, other contaminants and things with it. How much is carried and how far it goes depends on the amount of precipitation, the steepness of the area, and how much chance the water has to sink into the ground along the way. To protect the quality of waters downstream, we must control both the amount of stormwater and the quality of that water.
The Vermont Clean Water Act directs the Agency of Natural Resources to regulate parcels of land with 3 or more acres of impervious surface (surfaces like concrete, asphalt and other materials that don’t allow precipitation to sink into the ground where it falls). The Agency anticipates that when the best management practices (BMPs) outlined in the 2017 Vermont Stormwater Management Manual are applied, the phosphorus load from new development will drop at least 70%, on average.
The new manual updates the existing 2002 version with new state-of-the art BMPs, provides information on site planning and design, protection of the existing natural landscape, and how to develop a comprehensive stormwater management approach for each site. Though focused on parcels 3 acres and larger, the BMPs and practices described in the manual are useful for smaller areas well.