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Salt and De-icer

When snow melts, salt and deicer flow down storm drains and straight into our waterways. Help keep these chemicals out of our water by shoveling snow first, using acetate-based deicers instead of chloride-based, and using deicer sparingly!

Picture of a shovel in a pile of snow









Photo © Like the Grand Canyon 2010 via Flickr

Recommended techniques for snow and ice removal:

Shovel: Shoveling snow should always be implemented first to remove as much snow and ice as possible, thereby reducing the use of de-icing salts.

De-ice: Acetate-based salts, such as CMA or calcium magnesium acetate, have an impact on wetland ecosystems compared to their chloride-based counterparts.

Brine vs. Rock Salt: If using chloride-based salts to de-ice pavements, salt brines should be used rather than rock salt. Applying the liquid is more effective at melting areas of ice relative to the amount of salt applied.

Use Acetate-based Salts such as Calcium Magnesium Acetate (CMA) and avoid Salts with Chloride (CI) like Sodium Chloride, Calcium Chloride and Magnesium Chloride.


The use of de-icing salt is a ubiquitous and effective means of ensuring passage and safety on many of our nation’s roads, but it comes at a cost to the health of our natural environment, in particular our waterways. The high amounts of salt being applied to our roads every winter and, consequently, draining into natural environments has resulted in increased concentration levels that make it difficult for our ecosystems to thrive. Concentrated amounts of chloride and other components of these road salts cause biochemical imbalances to occur, harming flora and fauna found within freshwater environments that are not adapted to highly saline conditions. As climate change continues to shift seasonal weather patterns and conditions, it has resulted in a staggering increase in road salt application; unsurprisingly, this has further strained local governments tasked with treating environments plagued with salt toxicity and correcting its corrosive damage to both vehicles and infrastructure. Although some areas have begun to implement environmentally conscious alternatives, large-scale adoption of a safe de-icer solution is necessary to reach goals for protecting green spaces and infrastructure budgets as climate change continues to force human populations to adapt to more variable weather conditions. (Kane, Ryan “Environmentally conscious de-icers: Chemical capabilities in the environment and municipalities” Nov 30, 2022 Prepared for the Mystic River Watershed Association)



What You Can Do

Child walking a small dog down a city sidewalk

Scoop the Poop

Did you know that stormwater can carry bacteria and nutrients from your dog’s poop from anywhere in the watershed to the Mystic or Charles River? Pick up your dog’s poop and properly dispose of it in the trash. (Brochure) (Video: English | Español)

City-issued trash tote

Keep a (Trash) Lid on It

Trash can be picked up by runoff when it rains and ends up in the Mystic River or Charles River. Properly dispose of trash in your trash carts or dumpsters and keep the lid securely on. (Video: English | Español)  

Leaf bags lined up for collection

Leave the Leaves & Yard Waste  

Be a Leaf Hero and leave leaf and yard waste in your yard as a natural habitat for native pollinators. Any excess leaf and yard waste can be collected and placed at the curb for City pick up between April and December! Check out the yard waste collection calendar!

Bag of lawn fertilizer

Use Fertilizer Responsibly

Curious about what you can do to keep our water clean? Watch this video! And then visit to learn more! Keep our waterways clean, use fertilizer responsibly! (Video: English | Español)

What the City Is Doing

Somerville at a Glance

  • Combined Sanitary Sewer: 72 miles
  • Separated Sanitary Sewer: 64 miles
  • Storm Drain: 48 miles
    • # of Catch Basins: 3,617
    • # of Drain Manholes: 1,478

Stormwater Management Plan

Somerville’s Stormwater Management Plan (SWMP) describes and details the activities and measures that will be implemented to reduce pollutants that enter the drainage system to the maximum extent practicable (MEP). These control measures are based on the requirements of the National Pollutant Detection Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permit.

See the full Stormwater Management Plan here. Any questions or comments can be sent to Lucica Hiller, Stormwater Program Manager, at

Minimum Control Measures


What Is the City Doing?

Public Education and Outreach

Implement an education program that includes educational goals based on stormwater issues of significance within the MS4 area

Check out the What Can You Do tab, Twitter account, and mailers for more information on stormwater messages for residents, businesses, industrial users, and developers.

Public Involvement & Participation

Provide opportunities to engage the public to participate in the review and implementation of the City’s Stormwater Management Plan (SWMP)

Every year the public is provided opportunities to review and submit comments on the SWMP through public meetings and events. Check out the most recent SWMP under the Annual Reports and Resources tab.

Illicit Discharge Detection Elimination (IDDE)

Implement a program to systematically find and eliminate sources of non-stormwater discharges to the City’s separate storm sewer system and implement procedures to prevent such discharges

The City has:

  • mapped over 99% of the City’s MS4 system
  • completed outfall screening
  • continued annual staff training
  • continued ongoing catchment investigations to identify and correct illicit connections.

Check out the Final IDDE Plan and results from past IDDE work under the Annual Reports and Resources tab.

Construction Site Stormwater Runoff Control

Minimize or eliminate erosion and maintain sediment on-site so that it is not transported in stormwater and allowed to discharge to the Mystic River or Charles River through the City’s MS4 system and outfalls

The City has implemented Site Construction Permit Rules and Regulations to review site plans, inspect active sites, and enforce site plan review requirements.

Post Construction Stormwater Management for New Development & Redevelopment

Reduce the discharge of pollutants found in stormwater through the retention or treatment of stormwater after construction on new or redeveloped sites

The City has:

  • approved Stormwater Ordinances to enforce post-construction stormwater management
  • developed a street design report
  • developed a green infrastructure report with retrofit opportunities

Good Housekeeping & Pollution Prevention for Permittee Owned Operations

Implement an operations and maintenance program for City-owned operations that has a goal of preventing or reducing pollutant runoff and protecting water quality from all City-owned operations

Every year, the City:

  • removes debris from catch basins
  • sweeps the streets between April and November

Additional Control Measures


What is the City doing?

Discharges to Water Quality Limited Waterbodies

If there is a discharge from the MS4 area to a water quality limited waterbody, additional requirements are required to reduce pollutants in discharges from the impaired catchment(s). Somerville currently only discharges to the Mystic River and Alewife Brook (a tributary of the Mystic River). The Mystic River and Alewife Brook have the following impairments:

  • Phosphorus
  • Bacteria/Pathogens
  • Solids/Oil/Grease/Metals

The City has:

  • increased public education and outreach for specific messages, such as pet waste and leaf/yard waste
  • increased street sweeping frequency of all municipal-owned streets and parking lots
  • identified a prioritized list of catch basins for inspection and maintenance to ensure catch basins are no more than 50% full

Stormwater Management

The City of Somerville's sewer and drain collection systems consists primarily of combined stormwater and sewer systems. Some areas of the City along the Alewife Brook and the Mystic River have separate systems. Combined systems are common in older cities such as Somerville. During significant rainstorms, combined sewer systems may fill up beyond their capacity with a mixture of sanitary waste and rainwater. Combined Sewer Overflows (CSO) act like a relief valve allowing sewerage to discharge into waterways preventing sewerage backups into homes, businesses, and streets. Somerville’s combined sewer system ties into the Massachusetts Water Resources Authority's (MWRA) wastewater collection system which is treated and discharges at Deer Island. During periods of heavy rain, both MWRA and Somerville’s wastewater systems can become overwhelmed by rainwater releasing CSOs into both the Mystic River and the Alewife Brook.

Municipal separate storm sewer systems (MS4) use separate pipes for sanitary sewage and stormwater flows. Combined sewer systems (CSS) use the same pipes.

NPDES / Stormwater Management Program

As part of the Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) permitting program, Somerville is required to take steps to reduce the impact of stormwater pollution. Portions of Somerville's stormwater drainage system operate as a Municipal Separate Storm Sewer System (MS4) under this permit.

The City's program includes the following elements:

  • Public Education and Outreach
  • Public Involvement and Participation
  • Illicit Discharge Detection and Elimination (IDDE) Program
  • Construction Site Stormwater Runoff Control
  • Post Construction Stormwater Management in New Development and Redevelopment
  • Good Housekeeping and Pollution Prevention for Permittee Owned Operations

2016 General Permit

The EPA issued a new, updated general permit effective July 1, 2018. This permit replaces the 2003 permit and contains updated and new requirements that the Town will have to meet. The entire contents of the permit are available at the EPA’s website:

Annual Reports & Resources

FAQ & Acronyms

What is a catch basin?

A catch basin, also known as a storm drain, is a large underground box-like structure with an opening at the top. The function of a catch basin is to take water from streets and other paved areas and move it through the storm drainage system into the nearest water body. Catch basins are designed to trap stormwater pollutants, such as sediment and oils. Regular maintenance to clean out the catch basins removes these pollutants from our system and our water bodies.

Where can I report someone dumping trash, oil, or other pollutants into a catch basin?

Only rain belongs down the storm drain system. Dumping into catch basins is illegal. Report illegal dumping using the 311 system.

Which watershed do I live in?

Somerville is part of the Mystic River watershed to the north and west and part of the Charles River watershed to the south and east. Any drop of rainfall that lands in either watershed will end up in either the Mystic River or Charles River.

What is the difference between an impervious area and a pervious area?

Impervious area is typically artificial surfaces that are covered in water-resistant materials, such as concrete, asphalt, or the rooftop of a building. These areas do not allow stormwater to infiltrate into the soils. Rather, stormwater runs along the surface, picking up pollutants or debris, and enters the drainage system through catch basins that discharge to a waterbody.

Pervious areas are typically natural surfaces that allow water to be filtered through various media, often soils, into the earth. Different media can provide different levels of treatment of the stormwater.

What is stormwater?

Stormwater originates from any form of precipitation (rain, snow, or hail) that runs off any surfaces, such as streets, roofs, yards, and other sites. Stormwater can be absorbed into pervious areas or run along impervious areas, typically toward catch basins, and be transported to waterways.

What are stormwater pollutants and where do they come from?

Stormwater pollutants are:

  • Oil from vehicles and equipment,
  • Excess nutrients, such as phosphate from fertilizers,
  • Bacteria, such as E. coli from pet waste, and
  • Debris, such as trash or sediment from construction sites

Proper disposal can help reduce pollutants entering our waterways. Check out the What You Can Do tab for more information and tips to help protect the Mystic River and Charles River.


Aren’t sewer and drain systems the same?

The sewer and drain systems are not the same. The sewer system should only carry sewage to the Deer Island Treatment Facility, and the drain system should only carry clean stormwater to our waterways. The City does have combined sewers, where sewer and stormwater can both collect and be treated at the treatment facility or overflow to either the Alewife Brook or the Mystic River. The City is committed to reducing overflows through various methods, including separating combined sewer systems, removing inflow and infiltration in the sewer system, and working with our neighboring communities to improve water quality.

Does the City have a rain barrel program?

The City, through the OSE Department, has offered discounted rain barrel in partnership with a rain barrel vendor in the past. Typically, these programs are held once a year. We will update this page if a rain barrel event will be held this year.

Common Acronyms

CB: Catch basin

EPA: Environmental Protection Agency

IA: impervious area

IDDE: Illicit Discharge Detection and Elimination

MassDEP or DEP: Massachusetts Department of Environmental Protection

MEP: Maximum extent possible

MH: Manhole

MS4: Municipal Separate Storm Sewer System

NOI: Notice of Intent

NPDES: National Pollutant Detection Elimination System

SWMP: Stormwater Management Plan

TMDL: Total Maximum Daily Load


Leaf Litter and Yard Waste

Leaves and grass clippings that are dumped or stored near waterways or paved areas add to water pollution and clog storm drains causing flooding.


Be a Leaf Hero and leave leaf and yard waste in your yard as a natural habitat for native pollinators. Any excess leaf and yard waste can be collected and placed at the curb for City pick up between April and December! Check out the yard waste collection calendar!


Here is what you can do about it:

  • Consider composting yard waste.
  • Keep paved areas and storm drains clear of leaves.
  • Keep bagged, piled, and mulched leaves on natural soil, a few feet back from paved areas.
  • Ensure that your lawn service is properly disposing of yard waste.
  • Reduce excessive lawn chemical use and always follow manufacturer’s directions.

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