Meghan Hodges
The growth of roadway infrastructure has led to concerns about the impact of stormwater runoff on the environment. Pavements and roads are impervious surfaces that prevent stormwater from soaking into the ground, altering natural river flow patterns and groundwater supplies. Instead, stormwater flows over pavements, picking up oil and other pollutants before flowing into nearby water bodies. This has led to an increase in flooding, erosion, and habitat degradation. To mitigate these issues, the use of permeable pavements has been proposed as a green infrastructure solution. Permeable pavements are porous surfaces that allow water to infiltrate and drain through lower layers, filtering pollutants and reducing runoff volume.
| Characteristics | Values |
|---|---|
| Pavement type | Asphalt, concrete, interlocking pavers |
| Pavement porosity | High initial porosity can plug over time |
| Pavement sealers | Coal tar pitch has high levels of polycyclic aromatic compounds, negatively impacting aquatic life |
| Pavement maintenance | Regular restorative maintenance can improve infiltration capacity |
| Stormwater runoff | Picks up oil and other pollutants from pavements, vehicles, and atmospheric deposition |
| Permeable pavement impact | Reduces runoff volume, decreases pollutant loads, increases infiltration |
| Natural stormwater management | Rain gardens, green roofs, preservation of natural features, permeable paving |
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What You'll Learn
- Porous pavements can reduce stormwater pollution by trapping and slowly releasing precipitation
- Pavement sealers containing coal tar pitch can negatively impact aquatic life
- Atmospheric pollutants and materials dispersed by vehicles on pavements impact stormwater quality
- Permeable pavements can reduce the concentration of some pollutants physically, chemically, or biologically
- Natural stormwater management approaches can help maintain a more natural watershed
Porous pavements can reduce stormwater pollution by trapping and slowly releasing precipitation
The urbanization of landscapes has had a negative impact on the quality of runoff water entering lakes and streams. Replacing natural land covers, such as grasslands and forests, with impervious surfaces like parking lots and streets, has resulted in a loss of the water-retaining capacities of soil and vegetation. This has led to an increase in runoff, causing dangerous floods, severe erosion damage to stream channels, diminished groundwater recharge, and degraded habitats for fisheries.
Porous pavements, also known as permeable pavements, are designed to mitigate these issues by allowing water to infiltrate and drain to lower layers, filtering pollutants in stormwater runoff. This type of pavement acts as a reservoir, catching precipitation and surface runoff and slowly releasing it into the soil below, rather than allowing it to flow directly into storm drains. By slowing down the process, porous pavements can also reduce the temperature of urban runoff, minimizing the stress and impact on the surrounding stream or lake environment.
The effectiveness of porous pavements in reducing stormwater pollution has been evaluated in various studies. One such study, conducted by the U.S. Geological Survey, compared the performance of three permeable pavement surfaces: asphalt (PA), concrete (PC), and interlocking pavers (PIP). The 24-month monitoring period revealed that all three types of porous pavements helped reduce the amount of pollutants and runoff volume.
Another challenge is preventing the high initial pavement porosity from becoming plugged over time. While porous pavements can improve water quality, they require maintenance to ensure their effectiveness. Additionally, the reuse of old pavements at the end of their life tends to have minimal environmental impact when recycled, although the deposition of pollutants on these materials can impact their reuse in certain applications.
Overall, porous pavements offer a promising solution to reducing stormwater pollution by trapping and slowly releasing precipitation, improving water quality, and mitigating the negative impacts of urbanization on our natural water bodies.
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Pavement sealers containing coal tar pitch can negatively impact aquatic life
The intensive growth of roadway infrastructure worldwide has led to growing concerns over the health impacts of stormwater runoff and leachate from roadways. While normally constructed asphalt and concrete pavements were found to release low levels of contaminants during their life, deposition from atmospheric pollutants and materials dispersed by vehicles on pavements do have a measurable impact on stormwater quality.
Pavement sealers containing coal tar pitch have been found to negatively impact aquatic life. Coal tar and coal-tar pitch, used in sealcoat products, have extremely high concentrations of polycyclic aromatic hydrocarbons (PAHs), which are known human carcinogens. PAHs are toxic to mammals, amphibians, fish, and birds. In lakes, PAHs accumulate in sediment, making them particularly dangerous to animals living in the mud. More than one-third of urban lakes studied had sediment concentrations of PAHs above the level expected to negatively affect aquatic life. Runoff from areas treated with coal tar sealant can have very high levels of PAHs. The sediment from their runoff can contain as much as 3,500 milligrams of PAH per kilogram of sediment, compared to only 54 milligrams per kilogram in runoff from unsealed pavement.
Mortality in small aquatic life, such as minnows and water fleas, reached 100% when exposed to runoff from pavement sealed with coal tar within 42 days. In contrast, minnows and water fleas exposed to runoff from unsealed pavement experienced no more than 10% mortality. When exposed to simulated sunlight, which intensifies the toxicity of some PAHs, runoff collected 111 days after sealcoat application caused 100% mortality in both species, and 100% mortality to water fleas even when diluted to 10% of its original strength.
The use of permeable pavement has been proposed as a potential solution to managing stormwater runoff and reducing the impact of pollutants. Permeable pavement can reduce the concentration of some pollutants by trapping them in the pavement or soil, or through biological and chemical processes. By slowing down the process of stormwater runoff, permeable pavements can also reduce the impact on stream or lake environments.
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Atmospheric pollutants and materials dispersed by vehicles on pavements impact stormwater quality
The intensive growth of roadway infrastructure worldwide has led to growing concerns over the health impacts of stormwater runoff and leachate from roadway materials. Atmospheric pollutants and materials dispersed by vehicles on pavements have a measurable impact on stormwater quality.
Normally constructed asphalt and concrete pavements release low levels of contaminants during their life. However, atmospheric pollutants and materials dispersed by vehicles on pavements can significantly impact stormwater quality. These pollutants are often expressed in the initial flush from stormwater events.
Permeable pavements have been identified as a potential solution to managing stormwater runoff and reducing the impact of pollutants. Permeable pavements, such as porous asphalt, pervious concrete, and interlocking pavers, allow stormwater to infiltrate through surface voids into an underlying stone reservoir, where it is temporarily stored and filtered. This process removes sediment and other contaminants, improving water quality.
The use of permeable pavements can also help reestablish a more natural hydrologic balance by reducing runoff volume. By trapping and slowly releasing precipitation into the ground, permeable pavements prevent large, fast pulses of water from entering the stormwater system. This, in turn, reduces the stress and impact on streams and lakes, helping to maintain a healthy aquatic environment.
In addition to the benefits of permeable pavements, proper management of the watershed, which is the surrounding land that provides rivers with water, is crucial. Natural stormwater management approaches, such as rain gardens, green roofs, and preserving natural features like floodplains, can effectively slow, filter, and store polluted runoff. These techniques help protect the natural water cycle and maintain clean rivers and healthy communities.
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Permeable pavements can reduce the concentration of some pollutants physically, chemically, or biologically
Urbanization has had a negative impact on the quality of runoff water entering lakes and streams. The replacement of natural land covers with impervious surfaces like parking lots and streets has resulted in the loss of water-retaining soil and vegetation. This has led to an increase in runoff, causing dangerous floods, severe erosion damage to stream channels, diminished groundwater recharge, and degraded habitats for fisheries.
Permeable pavement is a porous urban surface that catches precipitation and surface runoff, storing it in a reservoir and slowly allowing it to infiltrate the soil below. This helps to reduce the amount of runoff and improve water quality. By slowing down the process, permeable pavements can cool the temperature of urban runoff, reducing the stress and impact on the stream or lake environment.
Permeable pavements can reduce the concentration of some pollutants in stormwater physically, chemically, or biologically. Physically, permeable pavements can trap pollutants in the pavement or soil, preventing them from entering water bodies. Chemically, bacteria and other microbes can break down and utilize some pollutants, reducing their concentration. Additionally, plants that grow between certain types of pavers can trap and store pollutants biologically.
The implementation of permeable pavement can also reduce the need for road salt during winter deicing. Researchers at the University of New Hampshire found that permeable asphalt requires significantly less salt compared to normal asphalt. By controlling runoff at its source, permeable pavement can decrease the necessity for regional best management practices (BMPs), such as wet detention ponds, resulting in cost and effort savings.
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Natural stormwater management approaches can help maintain a more natural watershed
The growth of roadway infrastructure is causing concern over the health impacts of stormwater runoff and leachate from roadways. Pavements with high levels of polycyclic aromatic compounds, such as those containing coal tar pitch, can negatively impact aquatic life and produce sediment buildup in bodies of water. However, natural stormwater management approaches, also known as green infrastructure, offer a sustainable way to tackle these issues and maintain a more natural watershed.
Green infrastructure encompasses a range of water management practices that capture, filter, and reduce stormwater runoff. This includes vegetated rooftops, roadside plantings, absorbent gardens, rain gardens, bioswales, and blue roofs. By using vegetation, soil, and natural systems, green infrastructure mimics natural hydrological processes, allowing rainfall to infiltrate and be stored or evaporated, rather than becoming runoff. This reduces the volume of stormwater and the pollutants it carries, such as raw sewage, trash, and toxins, which can enter waterways and cause environmental and health issues.
Permeable pavements are another natural stormwater management approach that can help maintain a more natural watershed. Unlike impermeable surfaces such as asphalt or concrete, permeable pavements allow stormwater to infiltrate through porous surfaces into the soil and groundwater. This prevents large volumes of water from flowing into storm drains and receiving waters as effluent, reducing the risk of flooding. Permeable pavements also reduce the concentration of pollutants in stormwater, either by trapping them in the pavement or soil or through biological processes where plants growing between pavers trap and store pollutants.
Constructed wetlands are another nature-based solution that can help manage stormwater. They mimic natural wetlands by capturing and filtering stormwater, creating diverse wildlife habitats. Riparian buffers are a type of constructed wetland that protect aquatic areas from disturbance and can act as a right-of-way during floods, preserving aquatic ecosystems. These natural stormwater management approaches work with nature to maintain a more natural watershed, reducing pollution and mitigating flooding.
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Frequently asked questions
Pavement stormwater runoff has been found to release low levels of contaminants during its life. However, the deposition of pollutants from the atmosphere and materials dispersed by vehicles on pavements does have a measurable impact on stormwater quality.
Pavement affects stormwater pollution by acting as an impervious surface that prevents stormwater from soaking into the ground. This changes natural river flow patterns and increases the amount and speed of water entering rivers and other water bodies. This can result in more frequent floods, the destruction of habitats for water-dependent species, and a decrease in base flows in streams.
Permeable pavement helps reduce stormwater pollution by allowing water to infiltrate and drain to lower layers, filtering pollutants. Permeable pavement can also reduce the volume of stormwater runoff by trapping and slowly releasing precipitation into the ground.
