What is green infrastructure and how does it relate to stormwater?
Green infrastructure refers to a number of different stormwater management practices, which absorb, delay and treat stormwater, rather than have the water runoff from roads, parking lots, and other hard surfaces polluting or flooding waterways that feed into the Wabash River. Green infrastructure may also provide habitats to insects and small animals, and protect aquatic ecosystems from chemicals or nutrient overloads. Such practices, also called Best Management Practices (BMPs) include rain gardens, vegetated swales, permeable pavers, and more. Check out all the different BMPs that the City of Lafayette maintains.
On the map below, click on a grey circle to see what the various BMPs look like.
The various types of green infrastructure in the city are ordered below, by tab. Click on a tab to learn how each one works.
- Contech VortSentry®
- Conveyance Channel
- Permeable Pavers
- Ponds- Wet and Dry
- Porous Asphalt
- Rain Garden
- Sediment Basin
- Vegetated Filter Strip
- Vegetated Swale
Aqua-Swirl™ Stormwater Treatment System allows for the removal of sediment, debris, and oil using vortex separation to speed up the ability of the system to separate by means of gravity. Stormwater enters through the inlet, and the flow produces a circular flow pattern that allows for the settling of the contaminates to the base of the unit. Various drag forces encourage sediment and debris to drop out of the flow and move to the middle of the chamber where the velocities are the lowest. The flow that is treated exits through an outlet behind the arched baffle, as shown in the figure. There is a pipe that rises vertically to the baffle to expose the system to atmospheric conditions.
There are numerous Aqua-Swirls located throughout the city, and these structures are underground, covered by manhole covers. Locations include at the Columbia Park Zoo entrance, on Fortune Drive, and Greenbush Street.
The Contech VortSentry® is a device that speeds up the gravitational separation of settling and floating pollutants from the storm water that moves through the device. Water enters through a downward-facing pipe inlet and begins a swirling motion which encourages separation and the pollutants and debris are captured in the lower treatment chamber. The system is designed to handle low to medium flows, and has an internal flow diversion so that flows that are too high for the system to handle will be diverted away from the treatment chamber and out the outlet pipe.
These structures are located underground at St. Elizabeth East Hospital, and are covered with a manhole.
A conveyance channel is a permanent waterway that has been shaped and lined with appropriate material, either plants or structural material like concrete in order to safely carry storm water runoff within or out of an area that is being developed. The channel is designed in such a way as to transport concentrated runoff from roads, agriculture, or industry while preventing erosion and damage.
The conveyance channels that the city maintains are located at Fleet Maintenance.
Forebays are necessary parts of infiltration and retention-type storm water best management practices (BMPs). They are placed settling basins installed at the inlet of a BMP and require storm drain piping. These allow for heavy sediment and larger pollutants to settle out before draining into the BMP. Forebays allow for access from maintenance equipment, due to the fact that the rapid settling of sediment requires forebays to be cleaned out every three to five years.
There is a forebay located at Durkees Run Stormwater Park.
Permeable paver blocks generally consist of interlocking concrete units that have part of its surface area filled with permeable material, like sand or gravel. These blocks filter solids and sediment from storm water runoff before the water is routed to infiltration storage underneath. Permeable pavers require maintenance about two times per year to remove solids from the permeable material, to prevent clogging.
There are permeable pavers located at the Durkees Run Stormwater Park and on North Street from 7th to Erie.
Detention/retention ponds are effective practices to manage storm water, and they come in two types- wet and dry. These ponds allow storm water to settle and for pollutants and sediment to settle so as to reduce the pollutant load that enters into waterways. Wet (retention) ponds are used to store relatively large volumes of storm water for an extended period of time and can often look either like a regular pond, or have some landscaping around the edges, especially in urban areas. Dry (detention) ponds are smaller and hold significantly less water than wet ponds, due to the fact they are not meant to hold water for long periods of time. Dry ponds are meant to store excess storm water for a short period of time to encourage pollutants to settle to the bottom of the pond, and then the water is gradually discharged to land features such as streams or wetlands. Thus, dry ponds are, indeed, usually dry and may have vegetation in them.
These ponds are located all around the city, with many in private residential or commercial areas, but the city maintains ponds at Durkees Run Stormwater Park and at Heron Bay.
Porous asphalt is a type of pavement that promotes infiltration, improves water quality, and has an expected life span of twenty years or more. It has various components/layers, including an open-graded asphalt mix that have small spaces through which water can move, a thin stone top filter that stabilizes the surface for paving, groups of large stones that allow storm water storage, and a fabric filter that lets water flow down to the soil. Porous asphalt has a high removal rate of total suspended solids, metals, and oils.
There is porous asphalt located along Prange Drive.
A rain garden is a planted depression that includes native plants and they take advantage of rain and storm water runoff to capture and infiltrate storm water and the sediment and pollutants that come with it. Rain gardens allow for about a 30 percent higher infiltration rate than a regular lawn, helping to recharge local aquifers. Additionally, they are aesthetically pleasing and provide habitat for birds and insects. Rain gardens are preferably located very close to where the storm water runoff it receives is coming from, such as next to a road or driveway.
Various rain gardens exist in private residential or commercial areas, but the city maintains the rain gardens located at Durkees Run Stormwater Park, along North Street from 7th to Erie, around the intersection of Alabama and 4th Street, at Vinton Elementary School, and at Fire Station No. 8.
A sediment basin is a temporary or permanent basin used to collect, trap, and store sediment produced from muddy runoff due to construction events, or as a flow confinement facility for lessening peak runoff rates. They are either designed to stay full of water or to be able to drain completely dry. The sediment is able to settle to the bottom of the basin. It is constructed in a low area and has either a gravel outlet or spillway to as a means to slow the release of runoff from entering waterways.
The city maintains the sediment basin located at the Vinton Woods pond, which is cleaned twice per year and feeds into the retention pond next to the basin.
The Stormceptor© System is a device that is used to improve water quality by treating pollution at its source. The device removes total suspended solids (TSS) and free oil from storm water run-off. The treatment process is such that the storm water flows into a small by-pass chamber either by the storm drain or the grated inlet and will then flow back into the by-pass chamber that is connected to the pipe at the storm drain outlet. Liquids with a lower density than water (oil, etc.) rise in the treatment chamber, and will become trapped under a fiberglass weir. Gravity forces the sediment to settle to the bottom of the chamber.
These structures are underground and covered with a manhole, and located along Kettle Circle, at the Holiday Inn Express, along McCarty Lane and on Mezzanine Drive.
The vegetated filter strip is a permanent strip of plants located between a body of water and a source of nonpoint source pollution, such as cropland or industrial sites, so as to reduce or eliminate the effects of the nonpoint source pollutants such as sediment, nutrients, oil, chemicals, etc. These strips have a gentle slope, and require healthy and dense plants to be an effective storm water management practice. Storm water flow is slowed and the water is filtered before entering a waterway. Maintenance is also required, to ensure that sediment and debris do not get trapped in the strip, and to inspect damage by foot or vehicles.
There is a vegetated filter strip located at Vinton Elementary School.
The vegetated swale is an effective storm water management practice in which storm water or surface runoff infiltrates through vegetation like grass or native plants, thus improving water quality and enhancing landscape aesthetics. Volumes of storm and surface runoff are captured and filtered through the soil and are then fed into an underground drain system, particularly when the soil is poorly drained or a large storm event occurs. The vegetation in the swale stabilizes the soil and encourages sedimentation.
There are vegetated swales located in many commercial and residential areas around the city, but the city maintains those located along Concord and Maple Point Drive to US 52, at Durkees Run Stormwater Park, and along Veterans Memorial Parkway and Concord.