Cities' Drainage Systems: Pollution Control Strategies

Stormwater runoff is a major cause of water pollution in cities, as water flows over hard surfaces, it collects pollutants such as fertilizer, oil, pesticides, dirt, bacteria, and trash before entering storm drains and ditches untreated, eventually contaminating streams, rivers, lakes, and oceans. To combat this, cities employ various strategies, including regular maintenance and cleaning of storm drains, street sweeping, and implementing green infrastructure solutions like rain gardens and permeable pavements. Public education and volunteer initiatives also play a crucial role in preventing pollution and keeping drains clear.

Green infrastructure and low impact development

Green infrastructure and low-impact development (GI/LID) are effective ways for cities to manage stormwater and reduce pollutants entering drains. GI/LID mimics nature by infiltrating rainwater into the soil, rather than allowing it to become stormwater runoff that enters drains untreated.

In natural environments, rainwater soaks into the ground. However, in urban areas, rainwater often becomes stormwater runoff due to buildings, pavements, and other impervious surfaces that water cannot penetrate. Green infrastructure and low-impact development techniques aim to slow down and spread out stormwater runoff, allowing it to infiltrate into the ground and be filtered by plants.

Examples of green infrastructure techniques include rain gardens, pervious pavement, rain barrels, and green roofs. Rain gardens, for instance, capture rainwater and allow it to filter through the soil and be cleaned by vegetation before entering the groundwater system. Green roofs and roadside plantings also help to capture and filter rainwater, reducing the amount of stormwater that enters drains. These techniques not only reduce flooding but also improve water quality by removing pollutants from runoff.

The implementation of GI/LID can be seen in Boston, where it has been installed in five public schools to reduce pollutant loading in the Charles River. Additionally, the Bluebelt project in Staten Island and Brooklyn has preserved streams, wetland areas, and other drainage corridors that use natural mechanisms to capture, store, and filter stormwater effectively.

Overall, green infrastructure and low-impact development provide a more sustainable approach to stormwater management by mimicking natural hydrological processes. By capturing, infiltrating, and filtering rainwater, these techniques help to reduce the amount of pollutants that enter drains and improve the quality of local water supplies.

Street sweeping and highway sweeping

Street and highway sweeping is an important step in clearing pollutants from drains and is considered a best management practice under the EPA Clean Water Act and Clean Air Act. The practice helps remove debris and pollutants from road surfaces, including sediment, vegetation, vehicle debris/waste, industrial emission particle deposition, litter, metals, organics, nutrients, and particulate matter.

Street sweeping has evolved from simply removing large "cosmetic" debris to focusing on the removal of coarse sand particle-sized street dirt and smaller particles that contribute to instream sediment and nutrient pollution. This is especially important as these pollutants can wash into waterways, leading to aquatic habitat degradation, nuisance algal growth, low dissolved oxygen, and toxicity in receiving water bodies.

Cities like Minneapolis, Minnesota, perform street sweeping activities on a large scale, covering over 1,100 miles of streets and additional alleys twice annually, with routine sweeping at other times. Their reasons for street sweeping include the seasonal removal of trash and debris, winter road maintenance, keeping the community clean, and preventing storm drain clogs and waterway pollution. Smaller cities like Forest Lake, Minnesota, have similar goals but operate on a smaller scale.

Some cities, like Rochester, have implemented formal street-sweeping programs with goals in stormwater management, public safety, street maintenance, and aesthetics. They also focus on educating residents about proper debris and waste management and fostering sustainable behaviors. Other cities like Lakeville, Mankato, and St. Cloud have developed unique strategies, such as using sweepers in tandem with education initiatives, providing multiple leaf disposal options, and capitalizing on cost-sharing.

To optimize their street-sweeping efforts, cities like Fridley prioritize sweeping in pollutant hotspots, including construction sites and streets with runoff discharging into water bodies impacted by sediments and pollutants. They also consider implementing GPS tracking technology to increase efficiency and make data-driven decisions about priority sweeping routes. Additionally, cities like Anderson and Mount Pleasant have partnered with universities to educate communities about water quality and the cumulative effects of stormwater.

Regular drain inspection and maintenance

Inventory and Inspection: Cities should create a detailed inventory of their storm drainage system, including maps and information on drainage pipes, catch basins, and outfalls. This inventory serves as a foundation for developing a structured inspection and maintenance program. It is also essential to identify areas prone to flooding during heavy rainfall, as these areas may require more frequent and rigorous maintenance.

Routine Maintenance: Street sweeping, weed eating, and clearing ditches are essential aspects of routine maintenance. This involves manually removing debris, leaves, sediment, and plant material from gutters, storm drain grates, ditches, and driveway tiles. Regular maintenance ensures that drains are clear of blockages that can impede water flow and cause flooding.

Illicit Discharge Prevention and Reporting: Illicit discharges, such as cigarette butts, trash, vehicle fluids, and yard waste, should be prevented from entering storm drains. Cities can implement public education programs to raise awareness about proper debris management and the negative consequences of dumping waste into drains. Additionally, cities can employ illicit discharge inspectors to investigate and address complaints of illicit discharge and waste dumping.

Water Quality Separator Vaults: Installing water quality separator vaults can effectively capture debris and pollutants before they enter the drainage system. These vaults should be cleaned regularly to ensure they function optimally, reducing the amount of sediment and pollutants that enter water bodies.

Green Infrastructure: Implementing green infrastructure techniques, also known as low-impact development, can help address stormwater runoff and sewer overflow issues. This includes the use of rain gardens, permeable pavement, rain barrels, and green roofs. Green infrastructure slows down stormwater runoff, allowing plants to naturally filter out pollutants as the water infiltrates the ground.

By implementing these measures and conducting regular inspections and maintenance, cities can help prevent water pollution, protect aquatic ecosystems, and ensure the efficient functioning of their drainage systems.

Public education and awareness

Providing Information and Resources:

Educate the public about the causes and impacts of water pollution. Informing people about the unique qualities of their local water sources is a good starting point. For instance, understanding the treatment process of wastewater, stormwater flow, and drought conditions in their area can help individuals identify specific actions that will have a significant impact. It is also important to promote proper disposal of chemicals, oils, medications, and non-biodegradable items to prevent them from entering drainage systems.

Community Outreach and Engagement:

Organise events, workshops, and educational sessions to raise awareness and encourage participation in addressing water pollution. This can include environmental justice programs that specifically target disadvantaged communities. Additionally, cities can collaborate with universities, such as the partnership between Anderson, Mount Pleasant, and Clemson University's Carolina Clear program, to develop comprehensive approaches to educating communities about water quality and the cumulative effects of stormwater.

Supporting Policies and Sustainable Practices:

Advocate for regulations and support sustainable practices to ensure water safety and conservation. Governments play a vital role in setting standards and regulations for water quality. By engaging with policy discussions, the public can spur solutions and hold industries accountable for their impact on water pollution. For example, the Clean Water Act in the United States has been instrumental in holding polluters accountable.

Environmental Education in Schools:

Integrate water pollution education into school curricula. This can be achieved through partnerships with educational institutions, such as universities, to develop informative resources for students. By educating younger generations about water pollution, we can foster a sense of environmental stewardship and encourage sustainable practices from an early age.

Utilising Digital Platforms:

Leverage digital tools, such as websites, social media, and electronic newsletters, to disseminate information and resources about water pollution. For instance, the New York State Department of Environmental Conservation (NYSDEC) offers various electronic newsletter topics and sponsors environmental education sessions. Digital platforms provide a wide reach and enable interactive ways to engage and educate the public about water pollution concerns.

Illicit discharge identification and reporting

Inventory and Inspection:

Cities should create a comprehensive inventory of their storm drainage system infrastructure. This includes mapping out the network of pipes, drains, and waterways that comprise the stormwater management system. By having a detailed understanding of the drainage system, cities can develop targeted inspection and maintenance programs. Regular inspections by trained personnel are essential for identifying illicit discharges and ensuring the proper functioning of the drainage system.

Public Education and Awareness:

Educating residents about proper debris management and the impacts of illicit discharges on the environment is vital. Cities can implement education programs and use various communication channels, including social media, direct mail, and websites, to spread awareness about the issue. Encouraging residents to report any suspected illicit discharges in their community can also help identify problem areas.

Illicit Discharge Inspector:

Employing dedicated illicit discharge inspectors is crucial for investigating complaints and reports of illicit discharges, such as yard waste dumping or illegal dumping of hazardous substances. These inspectors should have the necessary training and authority to respond to complaints promptly, conduct thorough investigations, and enforce relevant regulations to deter future violations.

Street and Drain Cleaning:

Regular street sweeping and drain cleaning are essential for removing pollutants and debris before they enter the drainage system. Cities can employ drainage canal maintenance crews to clear debris from main ditch systems and ensure that water quality separator vaults, which collect debris from stormwater, are cleaned regularly. Increasing the frequency of inspections and deploying additional drain cleaning crews can further enhance the effectiveness of these efforts.

Green Infrastructure:

Implementing green infrastructure techniques can help address stormwater runoff and remove pollutants. This includes the use of rain gardens, pervious pavement, rain barrels, and green roofs. Green infrastructure slows down stormwater runoff, allowing plants to naturally filter out pollutants as the water infiltrates the ground.

By combining these strategies, cities can proactively identify and address illicit discharges, reducing the impact of pollutants on their drainage systems and the surrounding environment. A holistic approach that involves public participation, dedicated resources, and innovative solutions is key to ensuring the long-term effectiveness of drainage systems and protecting water quality.

Frequently asked questions