New type of water system lets nature work

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Al Key/DRC
The sidewalks in the parking lot feature plants like Rosemary along with ornamental grasses and trees, and curb cuts to promote drainage at Rayzor Ranch Wednesday.
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To shoppers, it looks like a simple bed of native grasses and trees with a slightly unusual border.

But what appears to be landscaping at the Rayzor Ranch Marketplace development is actually a complex water system that allows storm water drainage to be treated on-site before it continues downstream.

The system is among the first to implement the North Central Texas Council of Governments’ new integrated storm water program and is also the largest, said Deborah Viera, an environmental compliance coordinator for the city of Denton.

Viera said the program reflects a new attitude toward dealing with storm water.

“It is a way to combine water conveyance and water quality components of a project into one structure,” she said.

Natural filters

The Rayzor Ranch developer,Allegiance Hillview, agreed to build the system to treat storm water on-site,one that slows the water and allows it to filter through a series of vegetation strips and water quality ponds.

Rayzor Ranch, a mixed-use development, is upstream of North Lakes Park, which is a recreation area and home to a city-controlled dam and reservoir. Officials were concerned that the new homes, apartments and shopping centers in the area would eliminate a wetland and change the floodplain.

So at Rayzor Ranch, water flowing across acres of concrete finds places where it can penetrate the earth. Slotted curbs allow water to flow into special medians filled with plants, rock and engineered soil.

Cleaned by the grasses and plants on the surface, the water percolates through several feet of soil before finding its way to an underground pipe that carries it to retention areas with specially selected plants for further filtering before moving through a series of water quality ponds.

When a storm subsides and the water is still, sediments settle out. Fencing skims debris off the surface. Ducks, turtles, fish and even pesky, tree-eating beavers frequent the site,according to Tom Galbreath, a registered landscape architect and executive vice president at Dunaway Associates, who managed the Rayzor Ranch site design and planning.

A treatment wetland dense with aquatic plants filters the water one last time before runoff from the next storm sends it traveling under Bonnie Brae Street to flow into the reservoir at North Lakes Park.

“You have to design the landscape ordinance — the planting that cities require anyway — to work in concert with the integrated storm water management plan,” Galbreath said. “So you let the site dictate where things need to be, not an ordinance. If you know that you have landscaping on a site and you need landscape elements to clean up the water, then let water treatment needs guide the landscape criteria, rather than dealing with each of them independently.”

Future developments

Storm water runoff is a different problem to manage than permitted discharges by manufacturers and other industries.

The NCTCOG program offers a technical manual, workshops and classes to teach builders, architects and landscapers how to incorporate water quality features into their projects.

The program also provides technical details on ways to treat storm water where it falls, through filter strips, rain gardens, grass channels, storm water ponds, porous concrete, pipe systems and features.

Capturing the water where it falls lessens the chance it will pick up pollutants such as oil and gasoline as it travels over concrete surfaces.

Denton has secured two Environmental Protection Agency grants in the past decade to develop a protection plan for the Hickory Creek watershed and implement the design and construction of demonstration projects.

The plans and projects were completed together with researchers at the University of North Texas, Texas A&M University, Upper Trinity Regional Water District, North Texas Municipal Water District and consultants.

The city built demonstration water quality sites at Denton Enterprise Airport, Denton Fire Station No. 7, Wiggly Field Dog Park, Cross Timbers Park, the Denton County Road and Bridge facility on East McKinney Street, and at South Lakes Park downstream of a gas well pad site on neighboring land at Acme Brick.

In addition, a rain garden at the Pecan Creek Wastewater Treatment Facility was constructed in cooperation with the Texas A&M AgriLife Extension Service.

The more complicated site at Rayzor Ranch serves as a large-scale example of integrated storm water management standards and practices. Denton’s goal is to make such projects a normal partof development, according to David Hunter, the city’s watershed protection manager.

“When developers come to town, the first thing they should ask is, ‘What do I need to do for water quality?’” Hunter said. “It is a process where you have to not only educate developers, politicians and the decision-makers in your city, you have to start making your citizenship aware of it.”

Lessons learned

With lessons learned at Rayzor Ranch, the city hopes for bigger and better water quality systems to accompany larger projects.

The low-impact development keeps the land functioning more naturally while people continue to build for their needs, officials said. Implementing such designs that mimic the natural cycle of water through the land minimizes pollution and the cost of keeping local waters clean.

“There is an environmental component but it has a huge economic component to it as well,” Viera said.“When we talk about protecting streams, creeks and lakes, it is seen as damage to valuable infrastructure that will be costly to repair, and it is something we’ll pay for in water quality down at the lake.

“We have a responsibility to be good stewards of the resources at our disposal, that includes the environment and financially.”


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