Bridge Construction: Water Pollution Risk And Mitigation Strategies

Bridges are often constructed over bodies of water to improve road connectivity for transportation. However, the construction of bridges can have a detrimental impact on the environment, including water pollution. The construction process can result in the destruction of vegetation, an increase in suspended solids, and the discharge of sewage and construction wastewater, which can directly affect water quality. Additionally, the use of large construction vehicles can tear apart natural environments and contaminate water sources. The impact of bridge construction on water pollution is influenced by various factors, including the construction location, bridge properties, and atmospheric deposition. To mitigate these effects, it is essential to implement runoff controls and carefully plan and schedule construction projects to minimize environmental damage.

Construction runoff and spillage

The construction of bridges can cause water pollution through runoff and spillage. Runoff controls are essential to preventing polluted water from roads, highways, and bridges from reaching surface waters. During construction, heavy metals, oils, toxic substances, and debris from construction traffic and spillage can be absorbed by the soil and carried with runoff water to lakes, rivers, and bays. These pollutants can have detrimental effects on water quality, fish habitats, and public health.

To mitigate these issues, runoff-control measures can be implemented during the construction phase. Such measures can effectively reduce the entry of pollutants into surface and groundwater sources. Additionally, thoughtful planning and scheduling can limit pollution and damage during construction. For instance, project managers can sequence activities to reduce the amount of equipment used on-site and shorten project durations.

Furthermore, modern construction techniques, such as Accelerated Bridge Construction (ABC), can significantly reduce environmental impacts. ABC involves using prefabricated bridge elements, allowing for less disruptive installation and limiting the need for end-to-end on-site construction. This approach decreases overall development time and enables most of the work to be done off-site in controlled spaces, minimizing pollution and damage.

To further limit environmental impacts, bridge projects can utilize Geosynthetic-reinforced soil (GRS) abutments and walls. GRS technology reduces the need for large equipment, which can tear apart natural environments and pollute the air and water. By employing innovative solutions and following regulatory guidelines, bridge construction projects can minimize their impact on water sources and the surrounding ecosystem.

Suspended solids and water quality

The construction of bridges and tunnels has been shown to have a detrimental impact on the environment, particularly on water sources. One notable consequence is the increase in suspended solids in the water, which can have a significant effect on water quality.

Suspended solids, or Total Suspended Solids (TSS), are particles that float or are suspended in water. This includes substances such as sand, sediment, silt, clay, plankton, and decaying organic matter. When the construction of bridges and tunnels disturbs the land, it can cause these solids to enter water sources, increasing TSS levels.

TSS affects water clarity, also known as turbidity, which is an important indicator of water quality. As TSS levels increase, the water becomes less clear and more cloudy or murky in appearance. This reduced transparency is due to the light being scattered by the particles in the water, impeding light penetration. Consequently, this can hinder the vision of aquatic organisms, making it more challenging for them to locate food sources.

Additionally, TSS can absorb and retain heat from the sun, leading to increased water temperatures. Warmer water has a reduced capacity to hold dissolved oxygen, resulting in lower oxygen levels. This can create hypoxic conditions, posing survival threats to small fish and other organisms living in the water. Furthermore, the presence of suspended solids can block sunlight, hindering the process of photosynthesis and further diminishing oxygen levels as plants and algae are affected.

The increase in TSS can also have indirect ecological implications. For instance, higher TSS levels can cause issues with plumbing and water-based appliances, as well as impede navigation for boats and ships due to reduced water clarity and increased flooding risks.

Ecological conditions of groundwater

The construction of bridges and tunnels can have a significant impact on the ecological conditions of groundwater. While bridges and tunnels improve road connectivity for transportation, they can also lead to disturbances in the underground area, affecting the quality and availability of groundwater.

Groundwater refers to water that collects or flows beneath the earth's surface, percolating through porous spaces in soil, sediment, and rocks. It is a critical source of fresh water, especially in arid and semi-arid regions, supporting municipal, industrial, domestic, and agricultural activities. Half of the US population relies on groundwater for their daily needs, and it is essential for drinking, irrigation, industry, and livestock.

The ecological conditions of groundwater are influenced by various factors, including natural processes and human activities. Natural stressors that impact groundwater conditions include high levels of naturally occurring dissolved solids (salinity) and metals such as arsenic found in natural rock formations. These natural stressors can affect water quality and the ecological systems that depend on groundwater, such as fish habitats and spawning grounds.

In addition to natural stressors, human activities can also significantly impact the ecological conditions of groundwater. Human-induced stressors include the application of pesticides and fertilizers, waste from livestock and other animals, landfills, mining operations, and unintentional releases like chemical spills or leaks from storage tanks. These activities can lead to groundwater pollution, making the water unsuitable for drinking or other human needs without proper treatment.

The construction of bridges and tunnels can further exacerbate these stressors and impact the ecological conditions of groundwater. During the construction period, there is a disturbance in the underground area, leading to an increase in suspended solids, habitat destruction, and a decrease in water exchange. Additionally, the discharge of domestic sewage and construction wastewater can directly impact water quality. These impacts can have long-lasting effects on the ecological systems that depend on groundwater, and the pollutants can also find their way into rivers and streams, causing widespread ecological damage.

Timing of construction

The timing of bridge construction plays a crucial role in minimising its environmental impact. While bridges are often constructed over waterways to improve transportation connectivity, careful planning and scheduling are necessary to reduce potential water pollution and ecological damage.

The choice of construction timing depends on the specific site, circumstances, and species involved. For example, bridge projects should be scheduled to avoid affecting the incubation, rearing, and migration cycles of fish. Working closely with local officials and environmental experts is essential to making informed decisions about timing.

One approach to reduce the environmental impact of bridge construction is Accelerated Bridge Construction (ABC). ABC employs prefabricated bridge elements, allowing for quicker installation and less disruption to the surrounding environment. By using prefabricated components or even sliding finished bridges into place, construction time is reduced, and pollution and damage are limited.

Additionally, modern bridge design and construction techniques have led to lighter structures with reduced footprints. These designs can span wide rivers and streams with minimal or no contact with the waterways, which is beneficial for limiting the impact on aquatic life.

The use of Geosynthetic-reinforced soil (GRS) abutments and walls is another innovative solution. GRS technology reduces the need for heavy equipment, which can tear apart natural environments and pollute the air and water. By minimising the use of large machinery, GRS abutments contribute to a more environmentally friendly construction process.

In summary, the timing of bridge construction is crucial for reducing water pollution and ecological damage. By employing accelerated construction methods, modern design techniques, and innovative technologies like GRS, bridge projects can be completed more efficiently and with less environmental impact. Careful consideration of the local environment and collaboration with experts are key to successful and sustainable bridge construction projects.

Environmental impact of construction vehicles

Construction projects have a significant impact on the environment, and the construction of bridges is no exception. The construction industry is known for consuming vast amounts of resources and producing large amounts of waste, with construction vehicles contributing to these negative impacts. Here are some paragraphs detailing the environmental impact of construction vehicles:

Construction vehicles play a significant role in the high energy consumption and greenhouse gas emissions associated with the construction industry. They rely heavily on fossil fuels, such as gas and diesel, which contribute to the sector's carbon dioxide and methane emissions. In 2019, the construction and buildings sector accounted for approximately 36% of energy use and nearly 40% of carbon dioxide emissions. Construction vehicles, with their extensive use of heavy machinery, are major contributors to these figures.

The burning of fossil fuels by construction vehicles leads not only to greenhouse gas emissions but also to air pollution. This includes the release of carbon dioxide, methane, and other waste products that pollute the air. Construction sites, with their constant operation of heavy machinery, generate significant air pollution, affecting both the environment and the health of nearby residents and workers.

Construction vehicles are also responsible for noise pollution. The use of heavy machinery, such as excavators, dump trucks, and concrete mixers, produces high levels of noise that can disrupt the surrounding environment, especially in residential areas. This noise pollution can impact not only humans but also local wildlife, causing stress and behavioural changes.

Additionally, construction vehicles contribute to waste generation. The construction industry produces a significant amount of waste, with demolition waste making up a large portion of it. Construction vehicles are used in the demolition process, and the debris often ends up in landfills or is incinerated, both of which have detrimental effects on the environment.

Moreover, construction vehicles can have indirect environmental impacts. For example, during the construction of bridges, the movement of vehicles can cause disturbances to the underground area, affecting the ecological conditions of groundwater. This, in turn, can lead to water pollution and other environmental issues.

Frequently asked questions