Stormwater Information

Stormwater Basics

What is stormwater runoff?

Hydrology is the study of the circulation of water between the earth and the atmosphere. This endless circulation of water is known as the hydrologic cycle.

Water is found on the earth’s surface (surface water) and within the sub-surface (groundwater).  The movement of water between the surface and groundwater make up a component of the hydrologic cycle.   Another component is the cycling of water movement of water in the atmosphere.

water cycle

Water, which exists in the atmosphere as water vapor, reaches the ground by precipitation (rain, snow, hail, and fog).  Once it reaches the ground, it follows one of three possible fates: 

· it evaporates;

· it runs off into wetlands, rivers, and other water bodies; or

· it can percolate into the soil.

When water infiltrates into the ground, a portion of it is stored in the soil as soil moisture, and is used by plants.  The rest continues to flow downward into the ground by gravity.  At some point it reaches a depth where all of the soil and rock spaces are saturated with water.  This location is referred to as the water table, and water that infiltrates to this depth is said to recharge the groundwater.  The groundwater flows through spaces in soils and rocks below the ground surface and eventually discharges into springs, wetlands, streams, and other water bodies.

Water that does not percolate through the soil and recharge the groundwater forms runoff.  Stormwater runoff is ultimately discharged to downstream waterbodies, such as ponds and rivers.  In developed areas, stormwater runoff is often collected from paved surfaces in catch basins and manholes and then piped to downstream waterbodies. 

Impacts of development

The development of a previously undeveloped site for another use can alter the physical features affecting runoff.  Specifically, the creation of impervious surfaces (pavements and roofs) can increase the volume and rate of stormwater runoff as compared to natural conditions, as discussed below:

  • Increase in volume of runoff. The volume of water available for runoff increases because the impervious area created by roofs, parking lots, streets, and other surfaces reduces the amount of infiltration that can occur. Note that this increase in runoff volume is directly associated with a decrease in recharge of the groundwater.
  • Increase in runoff rates. Urban development involves changes in surface cover, and the introduction of channels, curbing, gutters, and storm drainage collection systems. These changes result in hydraulic efficiencies that increase the velocity of runoff as it flows to the watershed outlet. This results in higher peak rates of stormwater discharge as compared to natural watersheds.

Ultimately, development-related increases in the stormwater runoff rates and volumes, and alterations to the natural hydrologic regime can substantially increase the potential for downstream flooding problems. 

EPA

Impervious surfaces also have other impacts:

  • Impervious surfaces absorb more heat than natural surfaces.  When the heat is released it raises the air temperature, contributing to the urban “heat island” effect.
  • Because they absorb heat, the runoff that is generated on them tends to have a higher temperature than natural runoff.  Even minor temperature differences in runoff can have significant impacts on aquatic life.
  • Some impervious surfaces, primarily paved surfaces and particularly roadways, generate more pollution than natural surfaces.  Some of these pollutants include:  motor oil and grease; heavy metals; nutrients in fertilizers and pet waste; and sediment from sanding operations, erosion, and construction sites.

Stormwater Pollutants

The daily activities of humans and wildlife can result in the deposition of pollutants on roads, parking lots, lawns, and naturally vegetated areas.  As stormwater flows over these surfaces and is collected in the municipal drainage system, it can pick up a variety of pollutants from the ground surface.  This runoff is ultimately discharged untreated to outfalls at the edge of our lakes, ponds, and rivers.  While there may be some attenuation of pollutants in the runoff before it enters the receiving waterbody, pollutants, particularly in urbanized areas, are often found in large enough quantities to impair these receiving waters.  A discussion of the most common pollutants found in stormwater runoff is provided below.   

Bacteria

Bacteria are one-celled micro-organisms that are present everywhere in the environment; they even live within our own bodies.  They vary in shape, oxygen and nutritional requirements, and movement.  Most microorganisms are beneficial to their hosts, but some cause diseases.  Disease-causing micro-organisms are called pathogens, and some common diseases pathogens cause are acute diarrhea (caused by a specific type of Escherichia Coli) and typhoid fever (which is caused by Salmonella typhosa).

It is impossible to monitor water for the presence of all pathogenic micro-organisms.  Instead, standard practice is to test for fecal indicator bacteria.  These indicator species are associated with human waste, which often carries pathogenic organisms.  Fecal indicators inhabit the intestines of humans and other animals, and are excreted in digestive waste material.  Although the indicators are not pathogenic, they often live with other micro-organisms that do cause disease.  Therefore, if high levels of indictors are measured in water, it is likely that feces or disease-causing micro-organisms are present as well.  In additional to the public health issues associated with fecal material, they can also cause cloudy water, unpleasant odors, and an increased oxygen demand (which causes algal blooms).

Massachusetts regulations state that waters can be used for swimming or boating only when bacteria levels in the water are below specific limits.

Sources of bacteria in surface waters, such as the Aberjona River, are varied.  They include urban runoff, domestic and wild animal waste, and on-site septic systems. 

Nutrients

Nutrients, especially nitrogen and phosphorous, occur naturally and are essential for plant growth.  However, man-made sources of nutrients, from fertilizers and failing septic systems, for example, can lead to excessive amounts of nutrients in our waterbodies. 

Nutrients contribute to algal blooms.  Algal blooms occur when algae, which are single-celled organisms, feed on the nutrients and rapidly reproduce.  Algal blooms can be recognized by discoloration of the water, which is caused by the high density of their pigmented cells.  When the algae die, they sink to the bottom of the water bottom and are consumed by bacteria.  This can result in reductions in oxygen levels in the water and the release of chemicals from the sediment, which can lead to fish kills.

Heavy Metals

Many people associate heavy metal pollution with intensive industrial use.  However, roadways and automobiles are now considered to be one of the largest sources of heavy metals.  Zinc, copper, and lead are three of the most common heavy metal pollutants released by automobile use.  All cars, even the cleanest of vehicles, shed small amounts of metals, fluids, and other pollutants. 

Heavy metals are deposited on the road surface, where they bind with dust, sediment, and other particulates.  When it rains, these metals either become soluble (dissolved) or are washed off with the sediments.

Listed in the table below are the common heavy metals that are encountered in roadway runoff.

table

Once in the environment, heavy metals have a number of effects.  Most heavy metals are harmful or deadly to both humans and aquatic life.  Some metals, such as cadmium and mercury, can bioaccumulation.  Many people are familiar with “No fishing” signs posted due to high levels of mercury in the environment.

Sediments

Sediments collect on our roadways and are flushed by stormwater runoff and end up in our waterbodies.  Exposed soils, such as during construction activities, are highly susceptible to erosion and can contribute significant amounts of sediment to urban runoff.  Sediment may also accumulate on roadways and sidewalks as a result of winter sanding activities. 

Sediments, when suspended in water, contribute to high levels of turbidity.  Turbidity limits the penetration of sunlight into the water column, thereby limiting or prohibiting growth of algae and rooted aquatic plants.

Eventually, when sediment-laden water slows down, the sediment begins to settle out of the water and deposits at the bottom of our rivers, streams, and ponds.  This can reduce the ability of our waterways to convey water and may impact flooding.  In spawning rivers, gravel beds are blanketed with fine sediment which inhibits or prevents spawning of fish.

In addition to the effects of sediment itself, other pollutants, such as heavy metals and phosphorous mentioned above, can be chemically “attached” to sediment, so sediment can provide another source of these pollutants.

Residents & Property Owners

Below are a list of simple tips that property owners can follow to help reduce their impact on stormwater quality and reduce the amount of runoff leaving their property. 

 General Tips

  • Never dump or throw anything in a catch basin or the storm drain.  Only stormwater runoff should enter these systems.
  • Pick up pet waste and dispose of it properly.  Throwing pet waste in the trash is the best disposal method.  Leaving pet waste on the ground increases public health risks by allowing harmful bacteria and nutrients to wash into storm drains, and ultimately our waterbodies.
  • Check your vehicle for leaks and repair quickly.  Safely dispose of motor oil at a certified recycling location.
  • Use a commercial car washing facility or wash your car on the grass.  The soap used to wash cars includes high nutrient loads, which are detrimental to our receiving waterbodies.

 Lawn Care and Landscaping

  • Use fertilizers sparingly and avoid chemical fertilizers. 
  • Store all fertilizer and pesticide containers safely to prevent spills, and dispose of the empty containers properly.
  • Landscape only with native plants and water lightly and frequently to reduce the potential for disease and insect damage.  A 15 to 20 minute watering during dry weather after sunset or before sunrise is usually sufficient.
  • Consider replacing pervious surfaces, such as paved driveways and walkways, with more pervious treatments, such as crushed stone or porous pavers.

rain garden

  • Use compost as an alternative to fertilizer.  Compost contributes organic matter and gradually releases nutrient to the soil.
  • Minimize the use of pesticides in order to keep your lawn safe for earthworms and other “good” insects. 
  • Whenever soils are disturbed or laid bare, utilize a silt fence or other appropriate methods of erosion control to keep eroded soils from migrating off-site.  As soon as possible, re-establish vegetation over the area.  Mulch the exposed areas to provide temporary cover and protect the soils from rain.
  • If you are re-grading your land, create softer or shorter slopes that have less potential for erosion.
  • Maintain wide buffer strips of natural vegetation.  Buffer strips help to filter out pollutants and reduce flow velocities.
  • Consider planting a rain garden on your property to intercept and infiltrate runoff from grassy or paved surfaces, or from rooftop areas. 
  • Consider purchasing a rain barrel to intercept clean runoff from your rooftop area that can be reused to water plants and lawns.

Salt & De-Icers

When the snow melts, do you ever wonder where all that salt and de-icer goes? You guessed it! It flows over our driveways, sidewalks, and roads, into the nearest catch basin, and directly (untreated!) into our waterways.

Salt in our fresh water is harmful to plants, wildlife, and people. Birds can mistake salt crystals for food, eating them and getting sick. Salt can be toxic to fish and others in aquatic systems. Salt is not good for our plants, and in many wetlands salt-tolerant invasives are crowding out our native vegetation, which then affects the wildlife that lose their food sources. And of course salt in our water supplies is not good for us -- we all know that salt is linked to high blood pressure and heart disease. Salt includes sodium chloride, as well as calcium and magnesium chloride.

Some use sand, and while it doesn’t carry chemicals into our waterways, it does clog catch basins and cause flooding. It can also carry other pollutants into our waterways. If used, excess sand should be swept up.

De-icer is a preferable alternative to both salt and sand, but it is still not perfect, and should be used smartly and sparingly. De-icers include Sodium or Potassium Acetate and Calcium Magnesium Acetate.

What can YOU do to keep your pavement safe while also keeping your water clean?

  • Use de-icer (sodium acetate, potassium acetate, and calcium magnesium acetate) instead of salt (sodium chloride, calcium chloride, and magnesium chloride).
  • Shovel early and often. Remove as much snow and ice as you can, and only use de-icer on what you can’t take care of with a shovel.
  • Follow product instructions and only use as much de-icer as you need. More is not better.
  • For heavy snowfalls, shovel early and often to avoid the snow compacting and forming ice.
  • For wet snow or sleet and freezing rain, apply de-icer product early on to prevent snow from bonding or ice from building up.

Development & Construction

The term “Best Management Practices” or BMPs describe control measures that are taken to mitigate the effects of urban runoff, namely increased peak runoff rates and volumes, as well as impaired water quality.  They can be “structural,” such as something that is constructed or installed, or they can be “non-structural,” such as street sweeping or using no-phosphorous fertilizer.

There are many examples of BMPs within the Town of Winchester.  Typically, new projects will incorporate BMPs to meet state and local standards.  A few examples of BMPs are discussed below:

deep sump


Deep Sump Catch Basins

Deep sump catch basins are a device that improves water quality, though they do not reduce the peak flow or volume of runoff.  In this case, a catch basin contains a sump, which is a pit below the outlet pipe, and the outlet pipe has a hood over it.  When runoff flows into the catch basin, instead of immediately going out the outlet, it first sits in the sump, which allows sediments to settle out.  The hood prevents floatable materials, such as trash and oil, from flowing down the drain.  They need to be maintained by cleaning out the sump routinely.

Porous Pavement

Porous pavement is a permeable pavement surface with a stone reservoir underneath. The reservoir temporarily stores surface runoff before infiltrating it into the subsoil. Runoff is therefore infiltrated directly into the soil and receives some water quality treatment. Porous pavement often appears the same as traditional asphalt or concrete but is manufactured without "fine" materials, and instead incorporates void spaces that allow for infiltration.

Bioretention/Raingardens

Bioretention areas use soils, plants, and microbes to treat stormwater before it is infiltrated or discharged.  They are typically shallow depressions that are filled with sandy soils and covered with mulch and dense native vegetation.  When stormwater enters the bioretention area, the soil acts as a filter that removes pollutants.

A bioretention area captures runoff from an impervious surface and allows that water to infiltrate through the soil media. As the water infiltrates, pollutants are removed from the stormwater runoff through a variety of mechanisms including adsorption, microbial activity, plant uptake, sedimentation, and filtration. Some of the incoming runoff is temporarily held by the soil of the bioretention area and later "leaves" the system by way of evapotranspiration or exfiltration to the groundwater.

filtration


Infiltration

Infiltration is one of the best BMPs available as it reduces peak runoff rates and volumes and also improves water quality.  However, it is not suitable for all locations. 

Infiltration BMPs can consist of an above-ground excavated basin or perforated underground units that store stormwater and allow it to slowly infiltrate into the ground.  In Winchester, most of the municipally-owned infiltration systems are subsurface, such as at Manchester Field and Davidson Park.

By storing and slowly infiltrating runoff, these types of BMPs reduce peak runoff rates and the total volume of runoff from a site.  The systems recharge the groundwater and better mimic natural hydrologic conditions.  Pre-treatment of runoff is often required to prevent pollutants from entering the groundwater or clogging the infiltration systems.

Although infiltration BMPs can be highly effective, they are not suitable everywhere and require careful design.  Some soils are simply not capable of infiltrating large amounts of water, due to poor soil composition (such as high clay or silt content).  Also, there needs to be a separation between the BMP and the water table so that that the system doesn’t back up. 

Sedimentation Tanks

Sedimentation tanks are underground storage tanks with three chambers designed to remove heavy particulates, floating debris and oil from stormwater.

Stormwater enters the first chamber where heavy sediments and solids drop out.  The flow moves into the second chamber where oils and greases are removed.  Oil and grease are stored in the second chamber for future removal.  After moving into the third outlet chamber, the clarified stormwater runoff is then discharged to a pipe and another BMP.

Sedimentation tanks provide water quality treatment to stormwater, but does not control runoff peak rates or volumes.  They require routine maintenance to remain effective.  There are several publicly-owned sedimentation tanks located throughout Town, including on Mystic Valley Parkway, Washington Street, and in the parking lot at Town Hall.

Business

Parking Lot Maintenance

Regular sweeping of your parking lot improves the appearance for clients and customers, while also keeping pollution out of our waterways. During a storm, rain can carry trash, oil, grease, and even heavy metals across the parking lot, into the catch basin, through our pipes, and into our rivers and lakes. Remember, anything that goes into our storm sewer system will flow untreated into the water we use for swimming, boating, fishing, and drinking.

Regular sweeping also reduces the need for and cost of catch basin cleaning and prolongs the life of your asphalt.

Some tips to keep in mind:

  • Use dry cleaning methods (e.g., sweeping, vacuuming) to keep pollutants out of our catch basins and eventually our waterways. Sweeping is the most efficient method for removing coarse particles, leaves, and trash.
  • Determine the frequency of sweeping based on usage of space.
  • Dispose of parking lot sweeping debris in a landfill.
  • Provide plenty of trash cans. Empty trash on a regular basis to prevent spillage. Consider signs to discourage littering.
  • Clean out catch basins on a regular basis. Improperly maintained catch basins not only allow debris to reach our streams, rivers, and oceans, but clogged catch basins can result in the ponding of water in your parking lot after storms, negatively impacting your customers.
  • Repair cracks and potholes right away.

Remember, your parking lot is the first thing your clients and potential customers see. Keep it clean, and keep our waterways clean, too!

Dumpster & Trash Maintenance

Protect our streams and rivers and comply with health codes by following these simple maintenance tips:

  • Cover: Keep dumpsters and compactors under cover to keep rain out.
  • Close : Close and dumpster lids every day and repair them right away to prevent wildlife and              rainfall from entering.
  • Clean: Inspect dumpsters regularly to ensure they are clean and don’t leak. Keep them away from storm drains!
  • Contain: Fix leaks and use a spill kit to immediately clean up spills.

Salt & De-Icers

When the snow melts, do you ever wonder where all that salt and de-icer goes? You guessed it! It flows over our driveways, sidewalks, and roads, into the nearest catch basin, and directly (untreated!) into our waterways.

Salt in our fresh water is harmful to plants, wildlife, and people. Birds can mistake salt crystals for food, eating them and getting sick. Salt can be toxic to fish and others in aquatic systems. Salt is not good for our plants, and in many wetlands salt-tolerant invasives are crowding out our native vegetation, which then affects the wildlife that lose their food sources. And of course salt in our water supplies is not good for us -- we all know that salt is linked to high blood pressure and heart disease. Salt includes sodium chloride, as well as calcium and magnesium chloride.

Some use sand, and while it doesn’t carry chemicals into our waterways, it does clog catch basins and cause flooding. It can also carry other pollutants into our waterways. If used, excess sand should be swept up.

De-icer is a preferable alternative to both salt and sand, but it is still not perfect, and should be used smartly and sparingly. De-icers include Sodium or Potassium Acetate and Calcium Magnesium Acetate.

snow

What can YOU do to keep your pavement safe while also keeping your water clean?

  • Use de-icer (sodium acetate, potassium acetate, and calcium magnesium acetate) instead of salt (sodium chloride, calcium chloride, and magnesium chloride).
  • Shovel early and often. Remove as much snow and ice as you can, and only use de-icer on what you can’t take care of with a shovel.
  • Follow product instructions and only use as much de-icer as you need. More is not better.
  • For heavy snowfalls, shovel early and often to avoid the snow compacting and forming ice.
  • For wet snow or sleet and freezing rain, apply de-icer product early on to prevent snow from bonding or ice from building up.

Industrial &Commercial

Automotive

Improper disposal of automotive waste materials is harmful to the environment, hazardous to public health and violates state law. Waste materials from automobiles include used motor oil and filters, antifreeze, chemi- cals, fuel, metal filings, and much more. Even water-soluble cleaning products contain chemicals that are harmful to aquatic life and drinking water supplies.

Preventing Leaks and Spills 

Avoid spills by emptying and wiping drip pans when you move them to another vehicle or when they are half-full. Routinely inspect equipment to wipe up sills and repair leaks. Place large pans or an inflatable portable berm under wrecked cars. Drain all fluids from wrecked vehicles or “parts” cars you keep on site.

Cleaning Spills 

Clean-up small spills immediately using shop rags. Keep dry absorbent materials and/or a wet/dry vacuum cleaner on hand for mid-sized spills. Contain large spills immediately; block or shut off floor and parking lot drains and notify the proper authorities. Train all employees to be familiar with hazardous spill response plans and emergency procedures.

Changing Automotive Fluids 

Designate an area away from storm or sanitary sewer drains to change automotive fluids. Collect, separate, and recycle motor oil, antifreeze, transmission fluid, and gear oil. Drain brake fluid and other non-recyclables into a proper container and handle as a hazardous waste. Use a radiator flushing fluid that can be recycled and add it to the waste antifreeze. Working on transmissions, engines, and miscellaneous repairs. Keep a drip pan or wide low-rimmed container under vehicles to catch fluids whenever you unclip hoses, unscrew filters, or change parts, to contain unex- pected leaks.

Cleaning work areas. Sweep or vacuum the shop floor frequently. Damp mop work area—do not hose down work areas into the parking lot, street or gutter. Do not pour mop water into the parking lot, street, gutter or storm drain system. Use non-toxic cleaning products whenever possible.

Cleaning Parts

Clean parts in a self-contained unit, solvent sink, or parts washer to prevent solvents and grease from entering the sewer or storm drain. Identify and control wastewater discharges. Ensure that shop sinks and floor drains are connected to the sanitary sewer system. Check with the local sewer authority regarding permitting or other requirements.

Parking Lot Maintenance

Regular sweeping of your parking lot improves the appearance for clients and customers, while also keeping pollution out of our waterways. During a storm, rain can carry trash, oil, grease, and even heavy metals across the parking lot, into the catch basin, through our pipes, and into our rivers and lakes. Remember, anything that goes into our storm sewer system will flow untreated into the water we use for swimming, boating, fishing, and drinking.

Regular sweeping also reduces the need for and cost of catch basin cleaning and prolongs the life of your asphalt.

Some tips to keep in mind:

  • Use dry cleaning methods (e.g., sweeping, vacuuming) to keep pollutants out of our catch basins and eventually our waterways. Sweeping is the most efficient method for removing coarse particles, leaves, and trash.
  • Determine the frequency of sweeping based on usage of space.
  • Dispose of parking lot sweeping debris in a landfill.
  • Provide plenty of trash cans. Empty trash on a regular basis to prevent spillage. Consider signs to discourage littering.
  • Clean out catch basins on a regular basis. Improperly maintained catch basins not only allow debris to reach our streams, rivers, and oceans, but clogged catch basins can result in the ponding of water in your parking lot after storms, negatively impacting your customers.
  • Repair cracks and potholes right away.

Remember, your parking lot is the first thing your clients and potential customers see. Keep it clean, and keep our waterways clean, too!

Dumpster & Trash Maintenance

Protect our streams and rivers and comply with health codes by following these simple maintenance tips:

  • Cover: Keep dumpsters and compactors under cover to keep rain out.
  • Close : Close and dumpster lids every day and repair them right away to prevent wildlife and              rainfall from entering.
  • Clean: Inspect dumpsters regularly to ensure they are clean and don’t leak. Keep them away from storm drains!
  • Contain: Fix leaks and use a spill kit to immediately clean up spills.