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Addressing water runoff on College Street

Infiltration planters filter and manage water the natural way

Photo Credit: GARY ALLEN - Nature's way - New infiltration planters on College Street are designed to catch and filter runoff water before it is directed to the main storm drain. Also known as bioswales, the planters manage water quality and quantity. During large storms the planters fill with water which slowly seeps into the ground, helping to prevent flooding as well.City projects on College Street have improved travel for just about everyone. Cyclists can take advantage of newly painted bike lanes, pedestrians will appreciate paved sidewalks, and even water runoff has a new path to take, thanks to fixtures on the west side of the street that are designed to catch and filter water from the road before it flows into the main waterline.

Beginning at Illinois Street, the “infiltration planters” continue up North College Street on the west side of the road, and end at about Columbia Drive.

Jay Harris, director of public works, said the planters, also known as bioswales, have two primary functions.

“They’re for water quality and water quantity control,” he said, adding that when it rains, the water runoff from the pavement collects oil, grease and other sediment as it flows into the planters. “The vegetation, the roots and leaves and microbes in the soil treat the storm runoff, similar to the way a wetland would treat surface water that runs into it, and that’s before the water gets into the main drainage ways.”

As far as the quantity control element of the planters, Harris said it’s all about managing large volumes of water intake. The bioswales are recessed below street level, making them the low point on the street and the natural destination for runoff.

“Those basins fill up with water in large storm events,” Harris said, adding the water collects in the basin and slowly seeps into the soil, preventing a large backup of water trying to drain in one location. “The goal is to try to cut high flows out of downstream areas.”

The stormwater fixtures are one component of a larger improvement project to make the street more pedestrian and bike friendly. This has focused on the installation of bike lanes and sidewalks joining the planters on the west side of the street.

While the improvements line the street for about a half-mile at present, there are plans to extend them further up College Street.

“We have gotten a ‘pre-award letter,’ not official but solid, that we’ll be able to take it from where it ends on Columbia to all the way to Foothills Drive,” said David Beam, the city’s former economic development director who is serving as an associate planner.

The extension would mean College Street would have a total of about 1.3 miles of continuous sidewalks, bike lanes and planters on the west side of the road.

“People will see that rolling out in the next few years,” Harris said. “The goal after that is to start improvements on the east side.”

Harris said the infiltration planters project on College Street is probably the largest in the city to date, although he added more and bigger projects are on the way.

“In the future ODOT is putting in significant quality and quantity ponds and swales as part of the bypass project,” he said. “That’s probably going to be the biggest one in the city.”

Rather than a new way of dealing with water filtration, bioswales utilize one of the oldest water treatment concepts in the book, Harris said.

“If you think about it, it’s really going back to the way nature has always done things,” he said. “Before we were here all these surfaces would run downhill and eventually run into small wetlands and filtration areas. That’s basically what we’re doing here, utilizing mechanisms that are already established by nature.”

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