Boston readying new fee for handling storm runoff, says most homeowners won't have to pay more, but many businesses will

The Boston Water and Sewer Commission says it plans to start levying a new "stormwater charge" next year to expand and improve the city's current 600-mile, 30,000-catchbasin storm-runoff network, both to reduce the amount of contaminants that flow into our rivers and Boston Harbor and to handle greater surges from increasingly heavy rainfall spurred by climate change.

The commission says its current estimates are that most homeowners - and small multi-family buildings of up to six units - will not see any change in their overall bills, because the new charge will be accompanied by a reduction in the monthly sewage fee. The commission says it is also working on a grant program to help homeowners who do see an overall increase reduce the amount of impermeable surfaces on their land.

However, the commission says other property owners could see increases or, in many cases new monthly bills - including landowners who do not currently use BWSC services but whose land is covered in large amounts of surfaces from which rain now runs into catch basins, such as parking lots.

Charging this way will mean that thousands of properties - like parking lots - that place a demand on the stormwater system, but don’t receive water and sewer service from BWSC, will be charged for stormwater services in the future. BWSC is in the process of notifying these customers of the importance of stormwater management and their shared responsibility in supporting these critical services.

All properties with more than 400 square feet of impervious areas will be charged because they contribute pollutants that are transported into BWSC’s stormwater system, requiring BWSC to manage runoff and ensure compliance with regulations. Charges will be based on the amount of impervious surface on the property. Properties paying the charge include, but are not limited to, residential properties, commercial and industrial properties, non‐profit organizations, schools, colleges/universities, houses of worship, state and federal-owned properties, and parking lots.

The commission says it's spent $9.2 million over the past five years in bolstering the city's 207 outfalls into the Charles, Mystic and Tobin and Boston Harbor but that the new fee will let it boost that amount to $44.6 million over the next two years, both to repair and expand the current network and to add new systems to "recharge" rainwater right into the ground, rather than letting it flow into waterways. This is on top of the roughly $12.7 million the commission says it spends annually just on maintaining the existing system.

Stormwater is generated when precipitation falls on hard impervious surfaces like roofs, driveways, roads, or sidewalks and "runs off," rather than absorbing into the ground as it would in nature. When stormwater flows over hard surfaces, it collects litter, sediment, and other pollutants, like motor oil and fertilizer. Catch basins in our roadways capture stormwater and convey it through a network of underground pipes called storm drains. Storm drains then release stormwater into our water bodies via stormwater outfalls. Stormwater does not receive treatment at the Deer Island wastewater treatment plant, which means that all the pollutants carried by stormwater enter our lakes, rivers, streams, and Boston Harbor.

In a city that receives an average of 48 inches of rainfall annually, stormwater runoff also contributes to inland flooding. Due to climate change, storms are becoming more frequent and more intense, which will result in more flooding in the coming years if BWSC and the City do not begin to adapt now.

The commission says that in addition to more traditional systems, such as pipes and outfalls, it is also working on "green" systems to keep runoff from getting into those pipes to begin with.

Green infrastructure acts like nature and catches rainwater at the point where it falls, allowing it to soak into the ground slowly. This method
enhances infiltration, improves water quality and groundwater levels, and creates green spaces within urban areas, among other benefits.

The commission says Boston already has several such installations, which include "rain gardens, porous paving materials, and stormwater bioswales that allow stormwater to filter into the soil around trees instead of running off into streets," including at the new City Hall Plaza, Harrison Avenue "tree trenches," a "rain garden at South and Bussey streets in Roslindale and at several BPS schools.

The commission provided details of how it plans to figure out the monthly fee for each property in the city:

The Commission will use Geographic Information System (GIS) data and pictures taken from planes or satellites above our City to determine the amount of impervious (hard) surface on each property. The greater the amount of impervious surface, the larger the charge. ...

The stormwater charge will be billed based on the customer's property classification as small residential or non-small residential. Small Residential Properties (SRP) have one to six units. Non-Small Residential Properties (NSRP) include all other property types, including residential with more than six units, institutional, industrial, and commercial.

To calculate the stormwater charge, a unit called the Equivalent Residential Unit (ERU) will be used. One ERU represents the amount of impervious area on a typical Small Residential Property in Boston, which is 2,164 square feet. The Commission is currently determining how much the charge per ERU will be.

• Properties with less than 400 square feet of impervious surface will not be charged for stormwater.
• Small Residential Properties will be charged a single rate for one ERU.
• Non-Small Residential Properties will be charged per ERU of impervious area on the property. To calculate the stormwater charge, BWSC will divide the total impervious area of the property by 2,164 square feet to determine the number of ERUs and round up. For example, a property with 45,000 square feet of impervious area will be charged for 21 ERUs.

Working with property owners to reduce storm runoff into sewers is not a new idea in Boston. The Back Bay, the South End, Bay Village, Chinatown and parts of the Fenway, East Boston, the North End, downtown and Beacon Hill are covered by "groundwater conservation overlay" zoning, in which property owners proposing new buildings or significant changes to existing ones have to install "groundwater recharge" systems to inject rainwater into the ground, rather than letting it flow into storm drains - to protect the hundreds of buildings that sit on wood pilings that would begin to rot should they dry out if the water table falls too much.