Communities Address Non-Point Source Pollution

It's the Last Frontier on Road to Clean Waterways

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Posted: Tuesday, November 2, 2010 3:33 pm

Non-point source (NPS) pollution is considered by many to be the "last frontier" in the decades-long campaign to clean up America's rivers, lakes and streams. By definition, NPS pollution comes from a wide variety of sources. From lawn fertilizer to oil drippings and heavy metals flushed from our roadways into municipal storm sewer systems, NPS pollution leads to concentrations of contaminates in detention basins and waterways.

There are several ways communities can address NPS pollution. The city of Key West, Fla. is one community that has been actively addressing the problem.

The city has installed 27 filtered gravity wells into the bedrock of the island and five pollution control devices at the end of outfall pipes. The city also modified its construction requirements to accommodate the use of berms and porous surfaces on parking areas.

Bioswales, rain gardens, wetlands and other land features can naturally filter stormwater before it makes its way into lakes and streams.

Bioswales are landscape elements designed to remove silt and pollution from surface runoff water. They consist of a swaled drainage course with gently sloped sides that are filled with vegetation, compost and/or riprap. The water's flow path, along with the wide and shallow ditch, is designed to maximize the time water spends in the swale, which aids the trapping of pollutants and silt. Depending on the geometry of land available, a bioswale might have a meandering or almost straight channel alignment. Biological factors also contribute to the breakdown of certain pollutants.

A common bioswale application is around parking lots, where substantial automotive pollution is collected by the pavement and then flushed by rain. The bioswale, or other type of biofilter, wraps around the parking lot and treats the runoff before releasing it to the watershed or storm sewer.

There are several classes of water pollutants that can be arrested with bioswales. These fall into the categories of silt, inorganic contaminants, organic chemicals and pathogens. In the case of silt, these effects are resultant turbidity to receiving waters. Inorganic compounds might be metallic compounds such as lead, chromium, cadmium and other heavy metals.

Other common inorganic compounds are macronutrients such as phosphates and nitrates. Principal sources of these nutrients are excess fertilization, which can cause eutrophication in receiving waters. The primary organic chemicals are pesticides, frequently overdosed in agricultural and urban landscaping. These chemicals can lead to a variety of organism poisoning and aquatic ecosystem disturbance. Pathogens typically derive from surface runoff containing animal wastes and can lead to a variety of diseases in humans and aquatic organisms.

"Those are some of the features that are being used to address non-point source pollution," said Alyson Crean, communications manager for the city of Key West. "When there is new development or redevelopment, that's part of what our planning department looks at. They look at different ways to deal with groundwater run-off. We still have a ways to go on that, because we have places that were built long before people thought about non-point source pollution. But, as places are being redeveloped, there are newer and higher criteria and guidelines that they must abide by in order to make sure that they are upgrading and protecting the waters," Crean said.

The state of Kentucky is also actively addressing NPS pollution issues.

"We generally do projects called ‘watershed planning,'" said Jim Roe, non-point source and basin team section supervisor for the Kentucky Division of Water. "In other words we try to sample water quality and interpret that data and use certain different factors to make management decisions about what types of best management practices should be put on the ground to reduce or eliminate non-point source pollution," Roe said.

The Kentucky Division of Water is within the Kentucky Department of Environmental Protection. "We have those types of projects around urban areas," he added.

"The other types of projects that we do are called ‘best management practice demonstrations.' We put a best management practice on the ground, which includes helping to pay for an installation of a best management practice. There is an educational outreach component that goes with that, such as pervious pavement, rain gardens and any kind of storm water detention," Roe said.

The idea is to demonstrate that practice to the surrounding communities, the region and the state.

"We work with all of our communities and advise them on technologies, techniques and what they can do to address non-point pollution. Typically, we're somewhat reactive. Being a government agency, we try to be as proactive as we can when it comes to educating the public and the municipalities, but we're also somewhat reactive in that we respond to requests from municipalities," Roe said.

The city of Cleveland, Ohio has NPS pollution problems that are similar to other older cities where the sewers were built over 100 years ago. Approximately 92 percent of Cleveland's system is a combined storm water and sanitary sewer system. The system experiences overflows.

"We have tried to control as much as possible, the volume and peak flow coming from private property by controlling the point of discharge and making sure that stormwater flow that is generated from a particular site does not exceed existing capacity," said Rachid Zoghaib, deputy commissioner for the Cleveland Water Pollution Control department. "We have built underground detention tanks and have installed other water quality control measures," he said.

"In addition to attempting to control the volume and peak flow, we are also trying to improve the quality of the discharge going into the system, especially where we have separate storm and sanitary sewers, where the storm flow goes directly into the storm sewer pipes and then into creeks and eventually into the lake.

"We're trying to improve the quality of the water by using best management practices and educating residents and commercial property owners and making recommendations during the planning and review process."

Zoghaib said the city is also employing stormwater best management practices on its projects. They're trying to control sediments and erosion, and they're doing stream work using bio-engineering techniques. Environmentally friendly materials are being used on construction projects.

"We also received a grant from the U.S. Environmental Protection Agency to do a demonstration project on the Water Pollution Control department property. This includes using some best management practices such as replacing approximately 10,000 square feet of asphalt pavement with pervious asphalt pavement and approximately 4,200 square feet of concrete pavement with pervious concrete pavement. We will also construct two rain gardens on one side of the facility to pick up downspouts from a trough on an 18,000 square-foot roof. Right now, the downspouts discharge directly to the sewer," Zoghaib said.

"We will be constructing bioswales and a water reuse system, where we will harvest clean stormwater for reuse at our facility. Tours will be held for the community so that they can see what improvements can be achieved by using these methods." The project is expected to be completed by the summer of 2011 and ready for public tours by next fall.

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