Bioswale, trees help control storm runoff at Mount Alvernia in Millvale

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TreeVitalize has been on a tree-planting mission since 2009, first in Pittsburgh and now throughout Allegheny County. From 250 trees that first spring, the organization has been planting 4,000 trees a year.

Millvale has received 850 trees since last fall, when a partnership offered TreeVitalize an opportunity to branch out, with results that demonstrate "the direction we are going in, using multiple components to control storm water," said Jeff Bergman, director of TreeVitalize, a public-private partnership managed by the Western Pennsylvania Conservancy.

On property owned by the Sisters of St. Francis at Mount Alvernia, one of the largest bioswales in the country is being completed by Best Feeds Design, the contractor that's also working on a smaller catchment area off a parking lot on the Sisters' hilltop campus. Both are expected to be completed in time for a public ceremony and reception from 5 to 7 p.m. Oct. 9 at the site, 146 Hawthorn Road.

The traditional ribbon cutting will be replaced by a ceremonial curb cutting.

A bioswale is a sunken portion of land engineered to divert storm water and absorb it or slow its movement toward eventual absorption.

The bioswale along Hawthorn Road is almost 400 feet long by 15 feet wide -- a strip of plants, rocks and boulders with a 16-foot curb cut.

It was dug to mimic a natural stream's series of riffles and pools. Flow and volume monitors will be placed in two weirs, one in the middle and one at the end, where a raised drain would take overflow.

"This was a massive project," he said. "There's really nothing like this in the country on a grade like this."

Heavy rains cascade down Hawthorn Road, which bends where the bioswale begins and slopes conveniently from the middle to feed it water.

"The primary concern is its ability to survive a really big flooding event," said Art Gazdik, the project design engineer from Groundwork Civil. "There will be times when it will fill and water will go into the storm drain at the bottom end.

"In six to eight months, we will have pretty good numbers" that show the bioswale's capacity in storms of various intensity. "There aren't a lot of bioswales in the area and not on steep slopes like that," about an 8 percent grade.

The Allegheny County Conservation District is funding the Northern Area Environmental Council to monitor the site to find out how much water it can divert from the combined sewer system.

Sewage overflows are among several regional concerns surrounding storm water.

The U.S. Environmental Protection Agency mandated in 2008 that Alcosan prevent sewage overflows, and numerous groups have been promoting green infrastructure as a cost-effective and job-creating part of the solution.

Millvale was heavily damaged when Girty's Run rose up from its normal trickle to send 8 feet of water through the borough in the wake of Hurricane Ivan in 2004.

"We are extremely excited to be a part of such a progressive project at a time when water and sewage issues are becoming part of a larger conversation," said Brian Wolovich, a member of the borough council.

The conservancy will maintain the 850 trees and the bioswales for two years, which Mr. Wolovich said "ensures the survival of the trees and plants."

Tree Pittsburgh has held training sessions for residents to become tree tenders, and the borough's public works staffers will also get maintenance training to take over the role, he said.

"I'm thrilled about this project," said Mr. Wolovich, who lives at the bottom of Hawthorn and near Girty's Run. "We couldn't have started off with a better one. Now we're looking at where we can grow from there."

TreeVitalize is a partnership among the state Department of Conservation and Natural Resources, the city of Pittsburgh, Allegheny County, Tree Pittsburgh and the Western Pennsylvania Conservancy.

The conservancy has raised more than $8 million for TreeVitalize projects from foundations, government agencies and corporations. Of that, $3.9 million has come from the state's Infrastructure and Investment Authority for large projects in Pittsburgh, Wilkinsburg and Millvale, Mr. Bergman said.

"This is one of my favorite projects since TreeVitalize was launched," he said of Millvale. "We were looking for an institution to partner with. The sisters have an environmental focus, so the stars aligned."

Sister Donna Zwigart has been TreeVitalize's go-to representative at Mount Alvernia.

"I've always had an interest in the environment," she said. "Most of our sisters do, as Franciscans. Rain comes down Hawthorn pretty fast, and houses at the bottom get flooded. We wanted to see what we could do to help."

The bioswale on the campus will be "like a water garden that we want to share with the children in our day care and all the people who come here for peace and quiet," she said. "The sisters are all excited about this project, and I am too."

environment - neigh_north

Diana Nelson Jones: or 412-263-1626. Read her blog City Walkabout at


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