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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

A Green Street Overview

What is a Green Street and what are the benefits?

Glencoe School rain gardenA Green Street is a natural stormwater management approach that uses plants and soil to slow, filter, and cleanse stormwater from streets. Traditional stormwater management directs runoff into pipes. A Green Street manages stormwater at its source, where rain falls.

Green streets protect water quality in rivers and streams by removing up to 90% of pollutants. They replenish groundwater supplies, absorb carbon, improve air quality and neighborhood aesthetics, and provide green connections between parks and open space. Vegetated curb extensions improve pedestrian and bicycle safety, and calm traffic.

Green Streets reduce peak stormwater flows, free capacity in the pipes to carry more wastewater to the sewage treatment plant, and stop sewer backups in basements. They can eliminate the need to install or replace expensive underground collection, conveyance and treatment systems.

How does Environmental Services choose a location?

green street photoEnvironmental Services prioritizes Green Street implementation where there is a need to reduce or remove stormwater runoff flowing to the sewer system, protect water quality in nearby streams and rivers, improve pedestrian and bicycle safety and protect properties from sewer backup.

The Sustainable Stormwater Management Program keeps a list of people who have expressed interest in having a facility in their neighborhood. Contact Emily Hauth at 503-823-7378.

What kinds of plants will be in the Green Street facility?

Environmental Services selects plants that can tolerate wet soil water in the winter and dry conditions in the summer. The plants are a mix of native and non-native that grow two to three feet high, preferably evergreen. Rushes and sedges are commonly used. Flower bulbs add color. Street trees are planted whenever possible.

Who will maintain the Green Street?

green street photoEnvironmental Services maintains Green Streets as an important part of the city's stormwater infrastructure. City maintenance crews visit Green Street facilities as needed, but at least twice a year to weed, prune, clean out sediment, and replace plants. We welcome help from neighbors to keep Green Street facilities free of litter and leaves.

Will a Green Street breed mosquitoes?

Mosquitoes breed in standing water. Green streets are designed to drain in less than 48 hours to prevent breeding. The City of Portland works with Multnomah County Vector Control to monitor Green Street facilities for mosquito breeding. Vector Control has not found a facility yet that is a mosquito breeding ground. Make sure you remove any potential mosquito nurseries from your property. Look for standing water in buckets, barrels, old tires, wading pools or trash cans.

How do we know the Green Street is working correctly?

The city regularly monitors facilities, but if you see a problem, please report it to the City of Portland Maintenance Bureau 24 hours a day at 503-823-1700. Green Streets are designed to overflow to stormwater inlets when they reach capacity during heavy rain.

Does a Green Street collect pollutants?

green street photoPlant roots and soil organisms in green street facilities break down stormwater pollutants. The city is monitoring green street soil for pollutants of concern. Current soil analysis shows no evidence of pollutants accumulating in concentrations that pose a health risk. The city will continue to collect and analyze data.

Will you take out the existing street trees?

Trees catch and absorb rain, and are important to the city's sustainable stormwater management efforts. Environmental Services works closely with the City Forester's Office to determine possible impacts to existing trees. For more information on street trees, contact the City Forester's Office at 503-823-4489.

How can I manage stormwater on my property?

You may use ecoroofs, rain gardens, trees, downspout disconnection, parking lot swales, etc. to manage stormwater on your property. This may make you eligible for a discount on your onsite stormwater management bill. Go to www.cleanriverrewards.com or call 503-823-1371 for more information.

Will the Green Street remove parking?

It depends on the type of facility. Stormwater planters accommodate parking while curb extensions replace parking with landscape. Our goal is to not remove parking, but sometimes a curb extension is the only option. Curb extensions can enhance pedestrian safety by decreasing crossing distances, keeping site lines clear, and slowing traffic. The city continues to research a variety of design options to limit loss of parking.

Will a Green Street near our house cause basement seepage?

No. We have very strict criteria for determining how close a facility can be to a home. There is a separation of at least four feet between the bottom of the excavated facility and high groundwater, and at least a 4:1 slope between the bottom of the excavated facility and the lowest point of the nearest structure, usually a basement.

If I live on a steep slope or have poor infiltration, is a Green Street an option?

Yes. Typically in those situations the facility is lined. Lining prevents stormwater from soaking into the ground, but this type of Green Street still improves water quality and reduces peak flows.

Why can't you use pervious paving?

Pervious paving is a good option for reducing impervious surface on private property, but there are issues with maintenance, installation and long-term performance of pervious paving in public streets. In the future, the city may use pervious paving in public streets as a stormwater management option, but it is not an option right now.

What do Green Streets look like?

Sometimes it's hard to distinguish between a Green Street facility and simple landscaping. Generally you can tell if you're looking at a Green Street if the facility has an opening for stormwater to enter, and a depressed area where stormwater can pool.

Portland has been building green stormwater management facilities since 1992, and you can see many examples in your neighborhood.