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Evanston Green Infrastructure

What is green infrastructure?

Green infrastructure is an approach to managing precipitation by reducing and treating stormwater at its source while delivering environmental, social and economic benefits. Examples of green infrastructure include permeable pavement, rain barrels, rain gardens, green roofs and more.

Why is it important?

Green infrastructure reduces stormwater runoff, which can carry waste, bacteria and other pollutants and is a major cause of urban water pollution.


greenroof

Green Roofs

Green roofs consist of a vegetative layer that grows in specially designed soil, which sits on top of a drainage layer.

There are two types of green roofs: extensive and intensive.

An extensive roof consists of a shallow soil depth up to six inches, has limited plant species, and requires limited maintenance and irrigation.
An intensive roof consists of soil six inches or greater in depth, more plant options, and requires more maintenance and irrigation.

Benefits

  • Reduces stormwater runoff
  • Improves insulation and lowers utility bills
  • Provides habitats for urban wildlife

Location

Green roofs can be implemented on any residential or commercial roof that can structurally support the added load.

Costs

High. Costs are dependent on size, material and design, and location.

Lifespan

30–50 years with proper maintenance


raingardens

Rain Gardens

Rain gardens are small-scale, vegetated depressions that receive stormwater from small contributing areas and are used to slow, store, and treat stormwater runoff.

Benefits

  • Reduces stormwater runoff
  • Plants provide habitat for local wildlife
  • Reduces erosion
  • Absorbs and filters rainwater

Location

Home rain gardens can be in one of two places—near the house to catch only roof runoff or farther out on the lawn to collect water from the lawn and roof. View the Iowa Rain Garden Installation Manual and University of Wisconsin - Extension How-To Manual.

Costs

Moderate. Rain garden installation information can be found on the city’s website.

Lifespan

Roughly 20 years with proper maintenance


rainbarrel

Rain Barrels

Rain barrels are a type of rainwater harvesting system that collect water from a surface (usually a roof) for re-use within a building or for landscaping.

Benefits

  • Decreases flooding
  • Reduces tap water usage
  • Collects/stores rainwater that can then be used for watering lawns, gardens and plants

Location

Be sure to install the rain barrel underneath a clear downspout with a level surface underneath your rain barrel.

Costs

Low. Evanston residents can purchase 55-gallon rain barrels from the Metropolitan Water Reclamation District (MWRD). MWRD includes an installation guide with every rain barrel purchased.

Lifespan

Rain barrels and system components have a lifespan of about 20 years with proper maintenance


bioswale

Bioswales

A bioswale is a channel designed to treat stormwater flowing horizontally through vegetation. Bioswales also have permeable bottoms that may be beneficial in recharging groundwater.

Benefits

  • Absorbs stormwater runoff
  • Habitat for local wildlife
  • Removes pollutants by filtering stormwater runoff through natural vegetation and soil-based systems

Location

Bioswales work best when installed in parking lots, along roadways and sidewalks; however they may be constructed in any location provided there is a mild slope (no greater than five percent).

Costs

High. Costs are dependent on size,  material and design, and location.

Lifespan

20–50 years


drywells-01

Drywells

A drywell is an excavated depression filled with uniformly graded washed rock that temporarily stores stormwater runoff until it infiltrates into the underlying soils.

Benefits

  • Allows for groundwater recharge
  • Easy for new development and retrofit areas
  • Good for drainage and irrigation needs for plants/trees

Location

Drywells should be situated at least 10 feet from the property foundation and 3 feet from any property line. This structure requires a hole that is 4 feet deep and wide. It also requires a trench that is 1 foot deep and 6 inches wide that gradually slopes towards the hole.

Costs

Moderate. Costs are dependent on size, materials and design, and location.

Lifespan

If properly maintained, a drywell can work effectively for more than 30 years.


permeable pavement

Permeable Pavement

Permeable pavement is a porous urban surface composed of open pore pavers, concrete, or asphalt with a stone reservoir underneath it. The permeable pavement catches precipitation and surface runoff, storing it in the reservoir while slowly allowing it to infiltrate into the soil or discharge via a drain.

Benefits

  • Can help filter out pollutants that contribute to water pollution
  • Helps reduce the need to apply road salt for deicing in the winter time
  • Reduces stormwater runoff volume

Location

Permeable pavement is commonly used on roads, paths and parking lots subject to light vehicular traffic, such as cycle paths, service or emergency access lanes, road and airport shoulders, and residential sidewalks and driveways.

Costs

High. Costs are dependent on size,  material and design, and location.

Lifespan

When properly maintained, permeable pavement typically has the lifespan of 20-50 years.


EPA Defines Green Infrastructure

The range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters.


Other Resources

Environmental Protection Agency (EPA)

Local and Regional Groups

Citizens’ Greener Evanston-Watershed Collective
greenerevanston.org/water

Friends of the Chicago River
chicagoriver.org

The Alliance for the Great Lakes
greatlakes.org