Stormwater FAQs

stormwater runoff depiction

Why should we care about stormwater runoff?

Studies by the U.S. Environmental Protection Agency (EPA) have demonstrated that stormwater runoff is one of the most significant sources of water pollution. Rain or snow melt can pick up pollutants and wash them into the town’s drainage system, and this polluted stormwater runoff can be discharged into local rivers and streams without adequate treatment.

Common pollutants include:

  • motor oils, fuels, greases, and metals from vehicles
  • pesticides,lawn fertilizers, and yard waste
  • construction dust and sediment
  • litter such as dog waste, cigarette butts, paper wrappers, and plastic bottles

In combination, these pollutants can clog waterways, degrade animal habitat, and contaminate drinking water. The increased volume and rate of flow can contribute to increased flooding, causing erosion of streambeds and siltation of waterways, and decreasing the amount of water recharged to aquifers. Why Stormwater Matters Presentation (PDF).

Why is it important to control stormwater?

When land is cleared or built upon, the stormwater that once infiltrated into ground must go somewhere else. Oftentimes, this creates adverse impacts to abutting properties, wetlands and streams, as more stormwater, dirt, or pollutants run offsite. 

Stormwater runoff represents the state’s single largest source responsible for water quality impairments. In an attempt to lessen these impacts, Massachusetts has mandated that towns regulate stormwater runoff.

What is Weston doing about stormwater?

In 2012, Weston adopted the Stormwater and Erosion Control By-law. Stormwater is managed through a combination of engineering, construction, maintenance and public outreach to address the quality and quantity of runoff. Much of the stormwater that flows onto Weston’s roads is directed to ponds, wetlands, and streams through a Municipal Separate Storm Sewer System (MS4).

The Town is authorized to discharge stormwater through the Phase II National Pollutant Discharge Elimination System (NPDES) general permit for small MS4s.

What types of projects trigger the Stormwater By-law?

The By-law requires the following types of land disturbance and construction activities to apply for a Stormwater Permit:

  • Creation of new impervious surfaces greater than 750 square feet
  • Construction of new or replacement dwelling
  • Reconstruction of public or private way (and parking)
  • Reconstruction of existing non-residential parking lots and driveways great than 2,500 square feet
  • Repair/replacement of septic systems
  • Land disturbance (e.g. tree cutting, grading, earthwork) greater than 5,000 square feet
  • Addition/on-site redistribution of greater than 250 cubic yards of earth material
  • Land disturbance exceeding 20% of the parcel 

For additional information and resources, please visit the Stormwater Resources and Information web page.