Stormwater Pollution: Understanding The Sources Of Contamination

Stormwater pollution is a pressing issue that affects the cleanliness of the water we drink and swim in. Stormwater is rainwater or snowmelt that, instead of soaking into the ground, flows over streets, parking lots, and roofs, picking up pollutants such as oil, trash, and excess nutrients from fertilizers, and carrying them into nearby waterways. This polluted runoff can have adverse effects on aquatic plants, fish, animals, and people, causing physical damage, lowering oxygen levels, and leading to health hazards. The management of stormwater is crucial, and implementing green infrastructure and natural water management techniques can help reduce runoff, filter pollutants, and protect water resources.

Stormwater runoff picks up trash, debris, and chemicals from streets, parking lots, and lawns

Stormwater runoff is a significant contributor to water pollution, particularly in urban and suburban areas. When rain or snowmelt, known as stormwater, falls on streets, parking lots, and other impervious surfaces, it cannot soak into the ground and instead flows directly into nearby waterways or storm drains.

As stormwater runoff flows across these surfaces, it picks up trash, debris, and chemicals, becoming polluted. Streets and parking lots often contain pollutants such as oil, excess nutrients, heavy metals, and other toxins, which are then carried by the runoff. This can include litter like plastic bags, cigarette butts, and beverage bottles, as well as chemicals and contaminants from fertilizers, pet waste, and yard waste.

The impact of stormwater runoff on water pollution is exacerbated by the increase in impervious surfaces in urban and suburban areas. As areas become more developed, the amount of paved surfaces, such as roads, sidewalks, and parking lots, increases, leading to higher volumes of stormwater runoff. This alteration in the landscape affects the natural water cycle, as water that would typically soak into the ground is redirected, picking up pollutants along the way.

The accumulation of trash, debris, and chemicals in stormwater runoff has significant environmental implications. The polluted water flows into local waterways, including streams, rivers, lakes, and oceans, contaminating these water sources and harming aquatic life. Additionally, stormwater runoff can overwhelm local infrastructure, causing sewage overflows that further pollute the water with pathogens and other harmful substances.

To mitigate the issue of stormwater runoff pollution, communities can employ various management practices and green infrastructure solutions. This includes the use of rain gardens, pervious pavement, rain barrels, and green roofs, which help to slow down and filter stormwater, allowing natural processes to remove pollutants. Educating homeowners and businesses on proper waste disposal, equipment maintenance, and responsible lawn care can also help prevent pollution at its source.

Fertilizers, pet and yard waste, and improperly disposed of animal waste can contaminate stormwater

Stormwater is the water from rain or snow storms that, instead of being absorbed into the ground, flows over streets, parking lots, and roofs and into a body of water or storm drain. This stormwater often becomes contaminated due to human activities, picking up excess nutrients and pollutants as it flows over impervious surfaces. Fertilizers, pet waste, yard waste, and improperly disposed of animal waste are common sources of stormwater pollution.

Fertilizers are a significant contributor to stormwater pollution, particularly those containing water-soluble phosphorus. When excess fertilizer is applied to lawns, plants may not be able to absorb all of it, leading to runoff. This runoff carries fertilizers and their nutrients, such as phosphorus, across lawns, roads, and into waterways. The phosphorus acts as a ""junk food" for algae, causing excessive growth that can disrupt the delicate ecological balance in these habitats. Chemical fertilizers can also introduce pesticides and other agrochemicals into the water, further contributing to water pollution. To mitigate this issue, it is recommended to use water-insoluble fertilizers, apply fertilizers carefully and only when needed, and avoid getting them on impervious surfaces like driveways and sidewalks.

Pet waste is another source of stormwater pollution. It contains phosphorus and other nutrients that can contaminate waterways if not properly disposed of. Responsible pet owners should clean up after their pets regularly and dispose of the waste in designated trash receptacles or pet waste stations. By doing so, they can help prevent the spread of pollutants and ensure a healthier environment for future generations.

Yard waste, such as leaves, grass clippings, and other organic debris, can also contribute to stormwater pollution. When yard waste decays in water, it consumes oxygen and releases pollutants. These pollutants can be harmful to plants and other organisms living in creeks, streams, lakes, and rivers. To prevent yard waste from entering stormwater systems, it is important to properly dispose of yard waste, avoid piling it near storm drains, and consider participating in loose leaf collection programs or taking waste to designated centers.

Improperly disposed of animal waste, particularly from confined animal feeding operations (AFOs), can contaminate stormwater during flooding events. Animal waste and wastewater from AFOs can introduce pathogens, such as E. coli, and other pollutants into surface water and the environment. These contaminants can affect both groundwater and drinking water sources, posing significant health risks to humans and livestock. To minimize these risks, it is crucial to follow guidelines for protecting workers and the public from livestock and poultry wastewater during and after floods.

Stormwater can be polluted by oil on the streets, which is filtered out through the soil of a bioswale

Stormwater is rain or melting snow that flows over the ground and into nearby water bodies or storm drains. In urban areas, stormwater runs over pavement and parking lots, picking up oil and other pollutants before flowing into a nearby river or stream. This is known as stormwater runoff, which is often worsened by human activities. As the amount of impervious surface increases, the amount of land for infiltration decreases, resulting in increased runoff and potentially more pollution into surface water.

Bioswales are engineered systems used to manage stormwater runoff and improve water quality. They are typically long, narrow channels or shallow drainage ditches that slow down stormwater runoff using berms or check dams. The design of a bioswale helps remove particulates, including silt, oil, metals, and nutrients from the water, allowing a portion of the runoff to infiltrate the soil. The longer stormwater stays in the bioswale area, the more pollutants are filtered out.

The soil mix in a bioswale is specifically designed to optimize infiltration and permeability rates, pH, soil texture, organic content, nutrient levels, salinity, toxicity, and minerals. This blend of sand, soil, and compost helps remove pollutants and filter runoff. The topsoil component is classified by USDA Soil Texture class and optimized for pH and organic matter content, while the compost component is a mature, stable compost with high organic matter content.

Bioswales are frequently placed near parking lots to capture pollutants from cars, preventing them from entering nearby waterways. They are also located near waterways to prevent stormwater runoff from entering and polluting those areas. By reducing the amount of stormwater runoff and filtering out pollutants, bioswales play a crucial role in protecting local waterways and improving water quality.

Sewage overflows can pollute stormwater with pathogens, excess nutrients, heavy metals, and other toxins

Stormwater runoff is often worsened by human activities and can contain pollutants from fertilizers, pet and yard waste, and bacteria from human sewage. When rain or snowmelt overwhelms the wastewater systems, they are designed to occasionally overflow and discharge excess untreated sewage directly into nearby streams, rivers, or other bodies of water. This results in stormwater being contaminated with sewage.

Sewage overflows can introduce pathogens into stormwater, which can cause waterborne illnesses, especially in children. These pathogens can include harmful bacteria, viruses, and parasites, which can cause gastrointestinal symptoms, rashes, skin and eye infections, and flu-like symptoms.

Sewage overflows can also introduce excess nutrients into stormwater, such as nitrogen and phosphorus from fertilizers. These excess nutrients can cause eutrophication, harmful algal blooms, and fish kills, which can further put human health at risk.

In addition to pathogens and excess nutrients, sewage overflows can also introduce heavy metals into stormwater. Heavy metals, such as lead, copper, zinc, and aluminium, can be toxic to aquatic organisms even at low concentrations. These metals can accumulate in the environment and pose risks to both ecological and human health.

Furthermore, sewage overflows can introduce other toxins into stormwater. These toxins can include bacteria, viruses, and chemicals that are harmful to both the environment and human health. With climate change predicted to bring more intense rain events, the risk of sewer overflows and the subsequent release of these toxins into stormwater is likely to increase.

Stormwater can cause streambank erosion and loss of fish habitat when too much water enters a creek or river too quickly

Stormwater can have a detrimental effect on natural water sources, such as creeks and rivers, and the wildlife that inhabits them. When too much water enters a creek or river too quickly, it can cause streambank erosion and the loss of fish habitats.

Streambank erosion is a natural phenomenon, but human activities can accelerate it. For example, in urban areas, rainwater cannot soak into the ground due to the prevalence of hard surfaces like buildings, roads, and parking lots. As a result, water runs off these surfaces and into nearby water sources, picking up pollutants along the way. This runoff can carry excess nutrients, heavy metals, and other toxins, which can kill aquatic life and create algal blooms that suffocate fisheries.

The speed of the water entering a creek or river can also cause streambank erosion. Ideally, streams should have gently sloping, fully vegetated banks. When water enters too quickly, it can wash away the fines, sand, and small gravel that make up the streambank, leaving a coarse cobble lag. This process can be exacerbated by landslides and debris flow, which provide a large quantity of coarse material to streams, accelerating erosion as the river flanks the coarse deposit.

Sediment from erosion can smother stream habitats, alter stream flow, and increase nutrient levels to harmful degrees. Sources of sediment include uncovered soil, slumping streambanks, muddy construction sites, poorly maintained dirt and gravel roads, and careless logging practices.

To mitigate the effects of stormwater on streambank erosion and fish habitats, it is essential to slow down the water and allow it to soak into the ground. This can be achieved through the use of green infrastructure, such as rain gardens, pervious pavement, rain barrels, and green roofs. These techniques help to reduce the amount of water that enters creeks and rivers too quickly and allows plants to filter out pollutants.

Frequently asked questions