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The City of Portland, Oregon

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Ave, Suite 613, Portland, OR 97204

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Before and After: Thanh Thao Restaurant Rain Garden


Environmental Services works with private property owners in targeted areas to manage stormwater and keep runoff out the combined sewers. Rain gardens, stormwater planters, swales, ecoroofs, and pervious pavement collect runoff from roof and paved areas and allow it to soak into the ground instead of flowing into the sewer system. Using natural processes to manage stormwater at its source helps control combined sewer overflows to the Willamette River and reduces the risk of sewers filling to capacity and backing up into basements during heavy rains. These kinds of stormwater management facilities also reduce sewage treatment costs, replenish groundwater supplies and beautify neighborhoods. The city provides substantial financial and technical assistance with project construction and the facilities remain private property and are privately maintained.

This new rain garden at Thanh Thao on SE Hawthorne Boulevard is a great example. In addition to the asphalt removed to make space for the facility, the building’s roof and the western parking lot now drain to the rain garden. The result is 4,840 sf of impervious area managed through this project. In an average water year of 37”, this project will keep approximately 106,000 gallons of stormwater out of the combined sewer. With over 56” of rainfall in 2017 so far, it’s already managed over 160,000 gallons of runoff!

Thanh Thao parking lot, before construction

Thanh Thao parking lot concrete getting removed 

Thanh Thao rain garden prior to planting 

Thanh Thao parking lot rain garden complete 

You can learn more about Environmental Services’ Private Property Retrofit program and see more examples here. Also, click here for a list of programs and resources for clean rivers and streams. 



Add a Comment


Marsha Hanchrow

September 2, 2017 at 3:40 PM

I'd love to know how this project came to be. Did painfully high stormwater management costs in their water/sewer bills lead the restaurant to ask for help or advice? How much did the project cost, and how much do they save on their quarterly bills?

It sure looks better than before.


Matt Burlin

September 5, 2017 at 3:42 PM

Hi Marsha,

Thanks for your questions. Stormwater projects and partnerships such as Thanh Thao are implemented to address local sewer capacity issues. This particular site is located in a sewer basin where heavy rain events can impact sewer service and cause sewage backup to basements and street inlets. To eliminate these issues, Environmental Services implements pipe improvements, installs green street facilities that remove street runoff from the sewer, and partners with private property owners to remove roof and parking lot runoff from the sewer. Properties with appropriate site conditions and willing partners in targeted areas can participate in partnerships that assist with sewer improvement goals. Outreach letters are mailed to properties within the targeted sewer basin with program participation being voluntary.

These private property partnerships are used in targeted locations where there is both a sewer system need and it is identified that private facilites will reduce public costs. All property owners in the targeted area are eligible for participation. Every dollar spent on partnerships to manage stormwater on private properties saves the Bureau three dollars on the overall project cost. This is due to the reduction in sewer and green street construction that would otherwise be necessary, and because these private facilities are maintained by the property owner over the long-term, rather than the City. The Thanh Thao rain garden manages close to 5,000 square feet of private runoff at a cost of around $5/square foot of area managed.

All properties in the targeted sewer basin are eligible for partnership with the city, depending on site conditions ( ). All properties that safely manage stormwater runoff in the City of Portland qualify for a rate reduction on their stormwater fees through the city’s stormwater discount program, Clean River Rewards (

Thanks, Matt
Environmental Services

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