It's not just stormwater...It's a valuable natural resource...

Green infrastructure is a general term for a variety of methods that manage, convey, and treat stormwater runoff at the local level through the use of natural systems, or engineered systems that mimic natural systems. The primary goals of green infrastructure are to capture and store stormwater as close to where it falls so that it can be cleaned, infiltrated into the soil, and slowly released into rivers and streams. By slowing the release and reducing the amount of rain water into the sewer system, these strategies also help alleviate the problem of Combined Sewer Overflows.

The USEPA has made green infrastructure a priority in wet weather programs, encouraging cities to use innovative design: "Green Infrastructure can be both a cost effective and an environmentally preferable approach to reduce stormwater and other excess flows entering combined or separate sewer systems in combination with or in lieu of, centralized hard infrastructure solutions."

The City is beginning the process of evaluating Green (Sustainable) Infrastructure for the use in existing Wet Weather Programs and projects, and is encouraging the private development community to do the same. As a first step, the City has developed a Sustainable Infrastructure Initiative. Below is a list of examples of green infrastructure methods:

Rain Garden (Bioretention)
Bioretention is the use of a natural, biological system to remove contaminants from stormwater. Bioretention basins, also called rain gardens, use plants specifically capable of absorbing and cleaning stormwater, a graded depression for water retention, and soil conditions that serve as a filter media to collect, store, and treat stormwater.
Bioretention/Rain Garden (pdf)

Learn how to build your own rain garden.
Click here to learn about how bioretention is used in the Cultural Trail in downtown Indianapolis.

Green Roof
A green roof is a multifunctional roofing system that utilizes plants, a growing media, and waterproof membranes to collect and absorb stormwater, thereby reducing the amount of stormwater runoff from the site. These systems have been functioning in Europe and other countries for decades, and have increased in popularity in the US in recent years as an alternative to traditional roofing systems for their durability, reduction of first-flush storm events, and for their aesthetic qualities.
Green Roof Fact Sheet (pdf)

Permeable Pavement
Permeable pavement is a pavement surface that allows water to pass through its surface and sub base for infiltration into the native soil below. These types of pavement provide the structural support of traditional pavement materials, but also provide many stormwater and application benefits such as reduced runoff and impact to surrounding plantings.
Permeable Pavement Fact Sheet (pdf)

Cisterns & Rain Barrels
Rain barrels and cisterns are stormwater storage systems designed to capture rainwater for either slowed release into natural or engineered stormwater systems, or for reuse as irrigation or other non-potable uses such as toilet flushing. These systems are fed by downspouts and have a limited capacity for rain water storage, but provide excellent capture of first-flush rain water.
Cisterns and Rain Barrels (pdf)

Learn how to build your own rain barrel.

Filter Strips
Filter strips are a vegetated, natural method for capturing and slowing stormwater while also trapping sediments and pollutants and are often used adjacent to impervious surfaces. These systems are a pretreatment method for sheet flow stormwater and are very cost-effective.
Filter Strips (pdf)

Low Impact Retentive Grading
Low impact retentive grading is the use of topographic features such as berms and depressions in combination with specific soil types that slow the vertical movement of stormwater and increase the rate of infiltration into the groundwater. These grading techniques are designed to capture and infiltrate stormwater from small storm events, and require secondary stormwater conveyance & treatment methods in large storm events.
Low Impact and Retentive Grading (pdf)

Swales
Swales are vegetated channels that collect and convey stormwater and serve to slow its speed and increase its infiltration rate before reaching the outfall. The type of vegetation used in a swale impact both the speed of conveyance and the rate of infiltration, as turf grasses are not as effective as deep-rooted, taller grasses and/or shrubs.
Swales (pdf)

Subsurface Infiltration
Subsurface infiltration is a method for storing stormwater below grade for slow infiltration into the groundwater. Beds of gravel or other open-graded aggregate are used to create voids where stormwater can collect and are often covered by lawn and therefore are difficult to detect from the surface. Stormwater can be conveyed to a subsurface infiltration area by surface runoff, via an underground pipe, or downspout from a roof.
Subsurface Infiltration (pdf)

Inlet/Outlet Control
Inlet/outlet control is a method of manipulating the movement of stormwater on a site to increase its chances for sediment settling and infiltration, in combination with other stormwater storage/conveyance methods. For example, curb openings can be used to direct stormwater into a rain garden or filter strip.
Inlet Outlet Control (pdf)

Filters
Filters are structures or excavated areas that use layers of materials to remove sediments and other pollutants from stormwater before infiltration or release to a sewer or natural body of water. Filters can be very effective in removing contaminants from stormwater. This is especially important in urban areas where pollutant levels are significantly higher.
Filters (pdf)

Subsurface Vaults
Subsurface vaults are essentially underground storage structures, commonly used in urban areas with very high land values, and are constructed of either concrete or plastic. These vaults are specifically designed to accommodate both the stormwater storage capacity needed and the load-bearing needs of the land use above them, such as parking lots, athletic courts, or buildings.
Subsurface Vaults (pdf)

Detention Basins
Detention basins are a common form of surface stormwater storage and are characterized by a deep depression and an outflow structure. Detention basins vary in their size, depth, and amount of vegetation and can provide aesthetic qualities. Detention basins allow sediments to settle out, slow the flow of water, and allow for infiltration before being released into the storm sewer or natural water body.
Detention Basins (pdf)