How Parking Lots Cause Nonpoint Source Pollution

Nonpoint source (NPS) pollution is a type of diffuse contamination that affects water or air and arises from numerous sources, including runoff from parking lots, roads, highways, and bridges. This runoff water picks up various contaminants, such as dirt, dust, metal, oil, pesticides, fertilizers, and litter, which are then deposited into nearby lakes, rivers, and streams. NPS pollution is a significant issue, impacting aquatic habitats, drinking water quality, recreation, fisheries, and wildlife. It is challenging to control due to its multiple sources, and it can have economic and social consequences for coastal communities. To address NPS pollution, various programs and regulations have been implemented, including the Nonpoint Source Management Program under the Clean Water Act, which aims to identify affected water sources and implement management practices to mitigate pollution.

Urban runoff

Impervious surfaces, such as roads, parking lots, and sidewalks, constructed during urbanization play a significant role in this process. When it rains or snows, these surfaces, often made of asphalt or concrete, channel contaminated water toward storm drains. This water picks up various pollutants, including gasoline, motor oil, heavy metals, trash, fertilizers, and pesticides, from roadways and parking lots.

Parking lots, in particular, contribute to urban runoff. They are major sources of polycyclic aromatic hydrocarbons (PAHs), which are byproducts of gasoline combustion and other fossil fuel uses. Parking lots also contribute to the presence of heavy metals such as nickel, copper, zinc, cadmium, and lead in urban runoff. To mitigate this, bioretention techniques, such as landscape islands, can be installed below parking lots to collect and treat stormwater before it becomes runoff.

The impact of urban runoff extends beyond just environmental concerns. It can lead to urban flooding, causing repetitive and costly issues for communities, even in areas not traditionally associated with flooding. Additionally, the increased temperatures in streams caused by runoff can harm fish and other organisms, impacting the commercial fishing industry and the overall quality of life in coastal communities.

Addressing urban runoff requires a combination of strategies. Implementing citywide maintenance programs, such as street sweeping, can help collect particles and solids that contribute to runoff. Educational programs can also raise awareness among local businesses and individuals about the importance of proper disposal practices to reduce pollution. Additionally, thermal pollution from runoff can be mitigated through the use of stormwater management facilities, including bioretention systems and infiltration basins.

Diffuse contamination

Nonpoint source (NPS) pollution refers to diffuse contamination of water or air that does not originate from a single discrete source. Diffuse contamination, in the context of NPS pollution, refers to the cumulative effect of small amounts of contaminants gathered from a large area. This is in contrast to point source pollution, which results from a single source.

In the case of parking lots, diffuse contamination occurs when rainwater or snowmelt washes over the paved surfaces, picking up various contaminants such as oil, pet waste, pesticides, fertilizers, road salt, bacteria, and sediment. These contaminants are then carried away as runoff, eventually depositing them into nearby water bodies such as lakes, rivers, or streams. The impervious nature of asphalt and concrete surfaces in parking lots contributes to the runoff problem, as water cannot penetrate these surfaces and instead flows directly into storm drains.

The impact of diffuse contamination from parking lots can be mitigated through various methods. Buffer strips, for instance, can be implemented to create a grass barrier between the parking lot and the nearest body of water, allowing the soil to absorb pollutants before they reach the aquatic environment. Retention ponds can also be constructed to trap and settle contaminants, preventing them from entering the water bodies. Additionally, the use of porous pavement can help reduce runoff by allowing rainwater and stormwater to drain into the ground beneath the pavement.

Overall, diffuse contamination from parking lots contributes to NPS pollution, which has significant environmental and economic impacts. It affects the health and beauty of coastal lands and waters, influencing tourism and the well-being of coastal communities. The cumulative nature of NPS pollution, with contaminants originating from multiple sources, makes it a challenging issue to address.

Stormwater management

One approach to stormwater management in parking lots is to implement best management practices (BMPs) that control the flow of stormwater and reduce pollution. These practices can include structural and non-structural measures. Structural BMPs involve the use of engineered structures such as retention ponds, infiltration trenches, and porous pavements. Retention ponds are designed to collect and temporarily store stormwater runoff, allowing pollutants to settle and be treated before controlled release into water bodies. Infiltration trenches promote the infiltration of stormwater into the soil, reducing the volume of runoff. Porous pavements, also known as permeable pavements, allow stormwater to permeate through the surface and be absorbed into the underlying base layer, reducing the amount of runoff.

Non-structural BMPs focus on minimizing the impact of stormwater runoff through proper maintenance and management practices. This includes regularly cleaning and maintaining parking lots to prevent the buildup of pollutants such as oil, grease, and debris. Implementing erosion control measures, such as vegetated buffer strips or sediment basins, can help capture and filter sediments before they enter stormwater systems. Proper waste management practices, such as providing trash receptacles and regularly collecting litter, can also reduce the amount of debris and contaminants entering stormwater.

In addition to BMPs, stormwater permit programs play a crucial role in managing stormwater in parking lots. Regulatory bodies, such as the Washington State Department of Ecology, issue stormwater permits to businesses and industrial sites, including parking lot owners or operators. These permits outline specific requirements and best practices to control stormwater pollution. By obtaining and complying with these permits, parking lot owners can ensure that their facilities are properly managing stormwater runoff and reducing pollution.

Another important aspect of stormwater management in parking lots is public education and community involvement. Educating parking lot users about the impacts of nonpoint source pollution and simple practices they can adopt to reduce pollution can have a significant collective impact. This can include encouraging proper waste disposal, promoting the use of environmentally friendly products, and raising awareness about the importance of stormwater management. Community partnerships and collaborations with local organizations can also be established to implement stormwater management initiatives and enhance the overall health of water bodies in the region.

Retention ponds

Nonpoint source (NPS) pollution is a growing concern, particularly in the United States, where it is responsible for two-thirds of the total amount of pollution affecting water quality. NPS pollution is caused by various contaminants, including metals, organic materials, and microbes, which are transferred from urban, industrial, commercial, agricultural, and rural areas into water bodies. NPS pollution can damage aquatic habitats, harm aquatic life, and reduce the capacity of water resources for drinking and recreation.

One of the major sources of NPS pollution is urban runoff, which flows through storm drains and into lakes and streams without being treated. This includes runoff from city streets and parking lots, which can contain contaminants such as oil, pet waste, pesticides, fertilizers, road salt, bacteria, and sediment. To mitigate NPS pollution from parking lots, it is recommended to periodically sweep or vacuum these areas to remove trash and debris.

The use of retention ponds for NPS management is supported by various programs and guidelines, such as the Nonpoint Source Pollution Control Program in California. This program provides flexibility in meeting pollutant removal and hydrology criteria, allowing developers to choose from a range of technologies, including retention ponds, infiltration practices, filtration practices, and open channel practices.

In addition to retention ponds, other practices can be implemented to reduce NPS pollution. These include sustainable roadside maintenance, planning, design, construction, erosion control, contour grading, soil bioengineering, and vegetative restoration. Implementing these practices can help improve water quality and mitigate the impact of NPS pollution on human health and coastal ecosystems.

Contaminants

Nonpoint source (NPS) pollution refers to diffuse contamination of water or air that does not originate from a single discrete source. This type of pollution is often the cumulative effect of small amounts of contaminants gathered from large areas. NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrological modification (rainfall and snowmelt). As rainwater and snowmelt wash over impermeable surfaces like parking lots, they pick up various contaminants and deposit them into nearby water bodies as NPS pollution.

Sediment, a significant contaminant in NPS pollution, is produced when soil particles are eroded from the land and transported to surface waters. While natural erosion occurs gradually due to vegetation protection, human activities such as construction and road building can increase erosion rates. Sediment makes the water cloudy, impairing the vision and feeding abilities of aquatic organisms. It can damage fish gills, hinder aquatic insect breathing, and reduce sunlight penetration, affecting plant growth. Sediment can also carry other pollutants like metals and toxic chemicals.

Atmospheric deposition, another source of NPS pollution, includes inorganic and organic constituents transported from air pollution sources like industrial facilities to receptors on the ground. Vehicular traffic near highways and parking areas contributes to uncertainties in the magnitudes of various atmospheric sources in runoff.

The impact of NPS pollution extends beyond the environment to the social and economic realms. High-density populations along coastal regions stress the environment, particularly through NPS pollution. If left unchecked, NPS pollution can deteriorate the economies and social conditions of coastal communities, affecting the commercial fishing industry and driving down waterfront property values.

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