Stormwater Management

Town of Somerset Stromwater Management Plan and Illicit Discharge Detention & Elimination (IDDE) Plan

Each Community with a municipal separate storm sewer system (MS4) in designated urbanized areas must develop a Stormwater Management Program (SWMP) That will guide its acitivities under the 2016 MS4 general permit. All documents are available for review and coment.

Comments on the plan may be submitted in the following ways:

  • In writting - 140 Wood Street, Somerset, MA 02740 Attention: Nancy Durfee, Town Planner
  • Phone 508-646-2809

Documents and information may be downloaded in PDF or HTML format using the links provided below. Requests for alternative formats may be directed to Nancy Durfee by calling 508-646-2809, or by email at

Illicit Discharge Detection & Elimination (IDDE) Plan:

Town of Somerset Stormwater Management Plan:


Stormwater is water originating from a rain event or snowmelt. Stormwater runoff occurs when the ground is unable to absorb all of the water. Impervious surfaces (such as buildings, driveways, parking lots, sidewalks, roads, and even compacted gravels and soils) prevent most of the runoff from infiltrating into the ground. As such, the runoff is often directed into physical drainage systems (such as catch basins), and then discharged into local rivers, streams, and other water bodies.


As the stormwater runoff flows, it picks up pollutants (such as fertilizer, oils, salt, sediment, and trash), carries them into those drainage systems, and eventually into our local water bodies. These pollutants can cause algae blooms among other aesthetic, health, and environmental issues. Unlike wastewater, stormwater runoff is often untreated or only pretreated before they are discharged into our local water bodies. Therefore, it is very important that we work as a community to keep our stormwater clean.


The Highway Department manages the Town’s storm drainage system, also known as 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 Stormwater Discharges from Small MS4s in Massachusetts. The U.S. Environmental Protection Agency (EPA) oversees the NPDES program. To comply with the permit, the Town must follow six Minimum Control Measures (MCMs):

  • 1. Public Education & Outreach: Provide educational material about stormwater to four audiences (residents, industry, commercial, and construction). The purpose of the educational material is to provide the targeted audience information about stormwater and how their actions may impact it.
  • 2. Public Participation: Provide an opportunity for the public to participate in the Town’s Stormwater Management Program (SWMP).
  • 3. Illicit Discharge Detection and Elimination: Find and eliminate sources of non-stormwater discharges (e.g. sewage) from the storm sewer system. Part of this requirement includes development of a system wide storm sewer map:
  • 4. Management of Construction Site Runoff: Adopt an ordinance and procedures for site plan review as well as erosion and sediment control on construction sites that disturb one or more acres of land.
  • 5. Management of Post-Construction Site Runoff: Address stormwater runoff from new development and redevelopment projects that disturb one or more acres of land. The goal of this measure is to try to management stormwater where it falls and retain it on site. This control measure encourages the use of low impact design techniques and requires the retention or treatment of runoff on site using green infrastructure practices.
  • 6. Good Housekeeping in Municipal Operations: Implement good housekeeping practices in municipal operations such as vehicle maintenance, open space, buildings and infrastructure. The permit requires street sweeping twice per year, optimization of catch basin cleaning, and pollution prevention at the Highway Garage.



Rake up your leaves to reduce water pollution and prevent flooding!

Fallen leaves are loaded with natural fertilizer, which can cause water pollution that harms people and animals. Leaves that are left near the side of the road can cause flooding when they block storm drains and waterways.

Keep the ponds and waterways in your community clean and healthy this fall with a few simple steps:

  • Never dump leaves in wetlands or waterways (it’s harmful and illegal)
  • Bag leaves in paper bags for disposal by your town (check your town’s disposal schedule)
  • Or compost your yard waste at home in an area away from wetlands and storm drains
  • Keep paved areas and storm drains clear of leaves
  • Make sure your lawn service is properly disposing of all your waste
  • Mow your leaves with a mulching mower and let them stay them on the lawn as a natural fertilizer

Leaves as Water Pollution? Really?

What could be more natural than leaves in the fall? The problem isn’t the leaves. It’s what people do with their leaves and the way our stormwater infrastructure works.

Freshly fallen leaves contain a natural fertilizer called phosphorous. When phosphorous gets added to streams, ponds and wetlands, it serves as an especially powerful fertilizer in the water. It encourages lush growth of pond weeds and algae in the spring that can interfere with swimming, reduce the amount of oxygen in the water needed to sustain fish and aquatic life, and in severe cases, can contribute to the growth of cyanobacteria “blooms” that can be toxic to people and animals.

When leaves fall in the autumn, they quickly begin to decompose, and rain washes the natural fertilizers out of them. When leaves fall in a forest or on your lawn, these fertilizers get recycled into the soil and trapped there, helping plants grow in the spring.

But when leaves, grass clippings or other organic materials, get dumped into wetlands, waterways or ponds, those natural fertilizers go right into our water and cause problems.

Similarly, when leaves or other yard waste are left on paved areas, rain washes those natural fertilizers into storm drains in your neighborhood that lead right to our waterways without first going to a water treatment plant.

Dumping of leaves can also cause blockages in storm drains and waterways that can cause flooding.

Business owners and residents can do their part to keep Massachusetts' waterways clean.