The Norman Transcript

April 6, 2014

Greening up the urban hardscape

By Joy Hampton
The Norman Transcript

NORMAN — Native plantings, wildlife habitat and rippling waters aren’t just descriptors of a country life anymore. In Norman, green infrastructure practices are bringing the beauty of nature to the urban setting but repurposed to do the work that cement and rip rap used to do.

“Even in an urban environment, we can have a natural wetland. We don’t have to mow everything down,” City Engineer Scott Sturtz said.

Using a low impact development approach reduces development-related impacts on water resources and also saves money.

The Brookhaven Creek project is one example. Leveraging $150,000 in grant funding from the Oklahoma Conservation Commission, Norman invested $100,000 and in-kind services worth $50,000 as a matching contribution.

The city planted 200 trees and 600 other plants. Education is part of the process. Often residents will ask why the center portion is not mowed. Established natural wetlands help slow down storm water to protect stream banks from erosion. Those native plants also work to filter out pollutants such as excess nutrients — for example, phosphorus — and keep them from entering the Lake Thunderbird watershed.

Green infrastructure also creates recreational opportunities such as trails along the city’s creeks.

The Brookhaven Creek project included the construction of basins, wetland plantings, Newberry riffles and stream crossings. Newberry riffles use rocks to slow water down and prevent erosion.

“In the long run, for the health of the stream and the area, I think it was a good investment,” Sturtz said.

These “soft armory techniques” are less costly than concrete and result in a savings of 20 to 50 percent.

“When we did the Brookhaven project, we literally had to train the contractors,” O’Leary said. “When the industry catches up, we’ll see even more savings.”

Other innovations the city is looking at using includes log veins which help deflect the water from hitting the bank. The city’s new storm water engineer, Joe Wellingham is looking at using them for some future projects. The logs run at odd angles to bank.

“It’s a very counter intuitive design,” Sturtz said. “We’d love to use a tree fall. We want to get away from taking everything in a stream and removing it. Obviously, we want our streams to be natural.”

There are over 300 miles of stream corridors in Norman.

O’Leary said if the city moves forward with a storm water utility fee and it is approved by voters, the fee would provide a funding source for future work in this area.

On a Merkle Creek tributary severe erosion was treated with ScourStop and turf reinforcement mat rather than using a concrete liner. ScourStop mats are made of a polymer that protects the soil from erosion. The green mats have holes that allow vegetation to grow through, helping to anchor the soil, providing a buffer from erosion and a filter for pollutants.

Local builders are already starting to use low impact development infrastructure. Examples include the Carrington Lakes Addition and Trailwoods.

“You have to educate all people — even your own maintenance people,” O’Leary said.

In one instance a builder had maintenance mow plantings that had been put in to create a rain garden effect. In other instances, the city has had staff mow wetlands and trees.

But the ideas are catching on.

Many Norman codes and ordinances support low impact development including the landscape ordinance with buffers along arterial frontage and recommended plant materials that are drought resistant. Detention requirements, engineering and design criteria and standards and the water quality protection zone are among Norman’s proactive measures to lesson the impact of development and use the natural environment to protect stream corridors and the lake’s watershed.

The city’s fertilizer ordinance has become particularly important as the city moves to comply with new standards based on the recent TMDL study done on Lake Thunderbird.

In the future, the city will take a hard look at city codes to eliminate outdated codes that hinder low impact development.

“We’re going to try to do a lot of things looking at our own rules,” Sturtz said. “It’s going to be a lot of education and working with developers.”

Joy Hampton



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