Blanket of green on Providence St. Mary Medical Center roof

A rooftop project at Providence St. Mary Medical Center promises a variety of benefits for the hospital and environment.

A mix of sedum plants is expected to provide colorful blooms come spring.

A mix of sedum plants is expected to provide colorful blooms come spring. Photo by Matthew Zimmerman Banderas.

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On a large section of the Providence St. Mary Medical Center roof, Troy Culp, project manager for Enviroscapes Northwest, tends to a newly planted green roof by placing river rock around a drain while hospital staff and others reflected in a window, look on,

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On top of a section of the Providence St. Mary Medical Center roof, hospital employees and green roof specialists, reflected in a patient window, check out the facility’s new 10,000-square-foot green roof made up of a mix of nine different types of sedum plants.

WALLA WALLA -- On the rooftop of Providence St. Mary Medical Center a sort of secret garden is taking root.

It is a virtual 10,000-square-foot blanket of succulents that will only ever be seen by a relative few but should be felt throughout the hospital for years to come, officials say.

The "living roof" started as a replacement concept for a roof at the end of its life. But it is also expected to have benefits far beyond being environmentally friendly. It is also expected to cut power costs and provide a better overall experience for patients whose windows look out over the carpet of blooming sedums.

Finishing touches were being put last week by Enviroscapes Northwest on what is believed to be the community's first such living commercial rooftop.

"We really think there's going to be a benefit for our patients," said Larry Baer, the hospital's facilities director.

The project, he said, started simply enough. "We had a roof that needed to be replaced," Baer said.

Rather than change it out with a traditional roof and gravel covering, officials began to explore whether a more environmentally sustainable option was available, an approach that has become a flagship strategy for the hospital.

They found Tremco Roofing and Maintenance, an Ohio company that specializes in green roofs and contracts with landscape firm Enviroscapes Northwest.

The roofing method, which has taken hold in larger cities for a number of years, is expected to at least double the life of the roof because the plants protect the roofing membrane from the sun's ultraviolet rays, Baer said.

It also adds insulation to the roof and is expected to provide relief to the power system, he said. On a typical 90-degree Walla Walla day, the rooftop reaches about 170 degrees, he said. With the new vegetation it will actually be cooled to 75 or 80 degrees. That reduction in heat will result in less work from the facility's heating and cooling units. Furthermore, the green roof is expected to bring stormwater savings of 70 percent by absorbing runoff.

All of those savings would have been enough to justify the reported $600,000 price of the project, officials said.

But there's another benefit particular to health care facilities, added Liz Hart, sustainable technologies specialist for Tremco.

Unlike other sectors that are major users of living roofs -- municipal and education sectors, in particular -- green roofs at medical centers have been known to provide a source of comfort and healing for patients.

Studies are showing that patients able to look out on the waves of blooms and greenery have reduced stress, lower blood pressure, may need fewer narcotics and report fewer overall complaints and discomforts. The result is a more positive overall experience, Hart said.

At St. Mary, the new roof is visible for patients in the hospital's new Intensive Care Unit on the fourth floor, as well as the lower-level maternity ward.

Around April or May the sedums -- popular for green roofs because of their water retention properties, hardiness and beauty -- should begin to bloom and will stagger throughout the warm months with white, pink and yellow flowers. The garden will need little maintenance, another selling point.

Hart said it may need weeding once or twice a year. Tremco representatives will monitor the roof with visits the first couple of years. The shallow 2 1/2-inch beds are watered through an automated irrigation system. "It really takes care of itself," Hart said.

The new roof may be just the beginning. A living wall of growing plants may be next to help block the hospital's radiation wall. As other roofs at the property need replacement, operators may choose to replace them with the living roofs.

The change at the hospital is part of an ongoing history in recent years to embrace sustainability whenever possible. Initiatives have included everything from low-flow toilets and soy ink in the photocopiers to an overhaul of lighting and changeover to a digital control system and variable-speed fans to the air handling system.

"Our hope is that these changes here will 'go viral,' raising environmental awareness in our homes, families and communities," said Linda Herbert, a nurse and co-chair of the hospital's Green Team.

She said the efforts recently garnered the Facilities Department a letter of commendation from the American Society of Healthcare Engineers. Energy savings at St. Mary from the various initiatives was five times the average savings for all 44-member hospitals in the region from 2010 to 2011, she said.

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