Reducing Runoff Pollution: DEQ Funds Portland Library Eco-roof

DEQ awarded federal grant funds to Multnomah County so they could install an eco-roof on the Central Library building in downtown Portland. An eco-roof is a vegetated roof system used in place of a conventional roof. An eco-roof is comprised of several layers that include a root barrier, waterproof membrane, drainage, soil system and plants.

DEQ expects the librarys eco-roof to reduce rainwater runoff pollution by 70 percent annually and reduce carbon emissions. This is the first library in Oregon, and the first historic building in the state, to have an eco-roof. Constructed in 2008 to replace the conventional roof with over 17,000 plants, the eco-roof absorbs rain water like a meadow in a natural setting.

Reducing rainwater runoff

By capturing rainfall, eco-roofs reduce stormwater runoff by storing water in the soil for later use by the plants. Stormwater runoff can carry pollutants including automobile engine fluids and heavy metals to rivers and streams. 

Reducing energy costs and air pollution

During the winter significant amounts of heat can be lost through conventional roofs and during the summer rooftop temperatures can reach 175 degrees. The new eco-roof is expected to offset carbon emissions by lowering building heating costs by 50 percent in winter and cooling costs by 6 to 8 percent in summer.

Eco-roofs filter dust, particulates and other harmful pollutants, and bind them in the soil where they are broken down into useful plant nutrients.  A 1,000-square-foot eco-roof can remove an estimated 41 pounds of airborne particles per year.

More ecoroofs in Portland

The library project is the second Multnomah County ecoroof DEQ has helped fund. (See Multnomah County's Library Eco-Roof page for more information and tours). In 2003, the county used a DEQ grant to install an accessible eco-roof that blooms beautiful wildflowers in spring and summer on its main office building in southeast Portland.

Portland has other eco-roofs in bloom, design and under construction. Projects include a completed 23,000-square-foot lightweight roof on Portland State Universitys Broadway Housing Complex and an eco-roof caf and soccer field on an industrial building in design.

 

 

 

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