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Stormwater- & street-runoff harvesting case study

Portland, Oregon Green Streets.
Portland, Oregon, USA.
Latitude 45.5˚N.
Elevation 33 feet (10 meters).
Average annual precipitation 42 inches (1084 mm)

Portland, Oregon has long had a problem common to many cities around the world: they have a combined sewer, meaning both stormwater and sewage go to the same pipe. This becomes an issue in big storm events with lots of runoff water entering the sewer, resulting in more water than the combined sewer pipe can handle. At that point, turds can pop up through home basement drains or onto the street via man holes.

That is heinous, but it is also awesome. Because few things motivate people like a brown trout popping up into their basement or street. Folks start calling Mayor and Council to demand that they get rid of the turds.

So the City created a new map of the city delineating neighborhoods by their subwatershed boundaries. Then they identified the subwatersheds/neighborhoods with the highest need, such as those with high turd to basement drain ratios and combined sewer overflows (see image below). These subwatersheds/neighborhoods were then prioritized for interventions.

A neighborhood watershed identified as having a high turd to basement drain ratio and other combined sewer overflow issues. Image courtesy of City of Portland Environmental Service, Sustainable Stormwater Management.

But the first draft plan attempting to address the issue was costly, conventional, and not very enlightened as it did not utilize the stormwater at all. Instead it would’ve disappeared the stormwater by sending it out of sight and out of mind in more and bigger underground stormwater pipes that would just kick more of the water and various contaminants down to the river potentially increasing flooding downpipe. Estimated cost was $144 million. See image below.

Conventional drainage plan calling for more and bigger underground pipes to kick the stormwater and problems downpipe/downstream. Cost estimate $144 million. Image courtesy of City of Portland Environmental Service, Sustainable Stormwater Management.

Thankfully, thinking at the city changed before the conventional drainage plan was implemented. New thinking led to a more integrated, more effective, and less costly plan that utilized the stormwater in above ground Sustainable Stormwater strategies such as stormwater harvesting, infiltration, and reuse as a free irrigation source for plantings. This has reduced flooding throughout the subwatersheds and downstream, while also improving water quality.

This new plan with Sustainable Stormwater strategies cost $86 million—a $58 million savings over the conventional plan, with much of these savings due to a reduction of needed pipe replacement. See the new plan below.

Enlightened Sustainable Stormwater plan calling for the harvest of stormwater within surface level rain gardens. Cost $86 million—a $58 million savings over the conventional plan. Image courtesy of City of Portland Environmental Service, Sustainable Stormwater Management.

Unlike storm drain pipe that only conveys water, the Sustainable Stormwater strategies are beautiful and provide multiple benefits. For example, stormwater-harvesting rain gardens placed within streets double as traffic-control, beautify neighborhoods, make walking and bicycling safer, naturally bioremediate or filter contaminants, and freely irrigate associated plantings that grow to shade and cool neighborhoods in summer. See images below.

Traffic-calming, water-harvesting chicanes or pull outs that narrow the width of the road, and protect on-street parking. The curb used to be along the edge of the grass, but has now been moved further into the street. Image courtesy of City of Portland Environmental Service, Sustainable Stormwater Management.
Street trees grow bigger and healthier with such stormwater-harvesting installations since they get more water and nutrients. Note the curb cut stormwater inlet to the rain garden in the foreground. The resulting shade reduces the heat-island effect (above normal temperatures caused by exposed pavement that absorbs and reradiates heat of the sun. Photo: Brad Lancaster
Such stormwater-harvesting traffic calming makes neighborhoods safer for all ages such as this young cyclist. Photo: Brad Lancaster
Note how these stormwater-harvesting, traffic-calming rain gardens were installed upstream of the stormdrain (grate in foreground) to utilize, naturally filter, and reduce the amount of water entering the drain. Photo: Brad Lancaster

These sustainable stormwater-harvesting strategies have turned problem neighborhoods into desirable neighborhoods, and increased financial resources for the city by both saving money and making more money as business in these neighborhoods has increased, while improving the quality of life for all.

Thank you to Dave Elkin former City of Portland Environmental Service, Landscape Architect in Sustainable Stormwater Management who guided me on tours of these installations, shared the City’s evolutions, and provided the statistics in this section.

For more:

Book Cover #2

Volume 2

See Rainwater Harvesting for Drylands and Beyond, Volume 2, 2nd Edition —available at deep discount direct from the author—for additional examples in Portland and elsewhere along with step-by-step how to installation guides.

Buy the Book Now

And for still more on Portland, Oregon efforts see the links and images below…
• In-street water-harvesting traffic-calming image gallery

• Water-harvesting parking lot, garage, and driveway image gallery

•  Portland, Oregon, Green Infrastructure & Green Streets Resources

•  Portland, Oregon, Green Infrastructure & Green Streets Case Studies

Passive SystemsStormwater & Street Runoff Harvesting