Water flows from rooftop to rain garden

Oregon Convention Center funnels millions of gallons a year to Willamette

By Kari Hastings

The Gresham Outlook, Nov 3, 2006, Updated Oct 30, 2009

Above: Wild roses trail over the terrace at the start of the Oregon Convention Center’s rain garden on Thursday, Nov. 2. Five drains send water into the rain garden, where it is filtered of pollutants by the soil and piped to the Willamette River.

Carole Archer / The Gresham Outlook

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There’s a hidden wellspring of sustainability under our noses in the form of the roofs over our heads. In the rainy state of Oregon, billions of gallons of often polluted rainwater runs off roofs every year and directly into our stormwater systems.

This taxes water treatment plants, costs money and uses unnecessary resources.

As our state becomes more environmentally aware, new codes require bio-swales, or large holes to be dug near impervious surfaces like streets and parking lots.

But there are pioneers in dealing with water run-off. Progressive companies like the Oregon Convention Center, which decided that instead of boring bio-swales, they’d build a rain garden.

The stunning, artistic garden, which rings the south end of the 17-acre center, was the receptacle for nearly 4.5 million gallons of water during Portland’s 2005 wet season (November through May).

A main advantage of such a system is soil filtration, which removes pollutants from the rainwater before it is directed into pipes that drain into the Willamette River. Clean water being injected into the Willamette is a lot better for the environment than polluted water heading to water treatment plants.

Besides the positive environmental impact, the rain garden is also an economic bonus for the convention center.

“It has really helped us in selling the Oregon Convention Center to clients,” said Assistant Executive Director Karen Totaro. “When we tell them about all the green aspects of the building and grounds, it’s really an ‘a-ha’ moment for them. It has sold us on at least six recent conferences we’ve done.”

In this way, Totaro said, the sustainability of the center matters for the growth of Portland as a whole.

“It’s labor intensive, but that’s where we see our return, when clients see our commitment to being sustainable and choose to do business here,” Totaro said.

In 2004, the convention center became the first structure of its kind in the nation to be certified by the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) Existing Buildings (EB).

The center’s 2003 expansion added 5.5 acres of rooftop to the structure, bringing the total rooftop acreage to 9. The new roof area was built with five drains that flow into a trough that resembles a waterfall when it’s raining.

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