Air quality which is generally referred to as "Air Pollution", refers to one or more chemical substances that degrade the quality of the atmosphere. Individual air pollutants degrade the atmosphere by reducing visibility, damaging property, reducing the productivity or vigor of crops or natural vegetation, and/or reducing human or animal health. Air quality is a term used to describe the amount of air pollution the public is exposed to.
The pollutants that are most important to this project are those that can be traced to motor vehicles and heavy-duty diesel trucks. These are carbon monoxide (CO) and particulate matter 2.5 microns in diameter or less (PM2.5).
CO is a colorless gas that interferes with the transfer of oxygen to the brain. CO is emitted almost exclusively from the incomplete combustion of fossil fuels. Prolonged exposure to high levels of CO can cause headaches, drowsiness, loss of equilibrium, or heart disease. CO concentrations can vary greatly over relatively short distances. Relatively high concentrations of CO are typically found near congested intersections, along heavily used roadways carrying slow-moving traffic, and in areas where atmospheric dispersion is inhibited by urban "street canyon" conditions. Consequently, CO concentrations are predicted on a localized, or microscale, basis.
Particulate pollution is composed of solid particles or liquid droplets that are small enough to remain suspended in the air. In general, particulate pollution can include dust, soot, and smoke. Particulate matter is in part the product of fuel combustion processes. PM2.5 refers to particulates that are 2.5 microns or less in the aerodynamic diameter, roughly 1/28th the diameter of a human hair. PM2.5 results from fuel combustion (from motor vehicles, power generation, and industrial facilities), residential fireplaces, and wood stoves. PM2.5 can penetrate the human respiratory system's natural defenses and damage the respiratory tract when inhaled. In vehicular exhaust and particularly from the diesel-fueled vehicles, PM2.5 is the main pollutant of concern.
In the recent years due to the stringent engine emission standards in Canada and US applied to the new vehicles and the renewal of the vehicular fleet, emissions of carbon monoxide decreased so significantly that it is rare that they cause any health concern. The biggest concern is currently particulate emissions, especially of the fine particles generated by diesel engines.
Mitigation measures, such as reducing traffic congestion, vehicle queues at intersections, and improving traffic flow can be used to reduce impacts from vehicular emissions.
Measures that take advantage of dispersion of pollutants in the atmosphere (i.e., mixing with the ambient air) can also lower pollutant concentrations. The greater the distance between the source of emissions and the sensitive land use, the lower the impact of that source on nearby sensitive land uses (e.g., residences, parks, schools, etc).
Dispersion in the atmosphere depends on a number of atmospheric conditions that could either enhance or inhibit it. High winds and unstable turbulent conditions enhance dispersion while stable atmospheric conditions and low wind speeds don't promote mixing. In addition, pollutants tend to disperse downwind.
London, Ontario airport meteorological data is considered representative of the Southwestern area of Ontario and recommended by the Ontario Ministry of Environment to use for dispersion modeling in this area. The wind rose for data collected at this airport in the year 2000 demonstrates that the prevailing winds in the area are coming from the west.
The impacts of this project (i.e., predicted air quality levels) were compared for the project's opening year (2015) under three scenarios: the future No Action scenario, the proposed DRIC Land Bridges alternative, and the proposed Greenlink alternative.
The future No Build scenario represents local pollutant levels if nothing changes except for the growth of traffic volume associated with business development other than those caused by the proposed Detroit River Crossing. Future decreases in vehicular emissions as a result of the new and stricter emission and fuel standards were taken into account.
The proposed DRIC Land Bridges alternative is a depressed roadway with series of short tunnels as presented by DRIC partners at the Fifth public Information Open House in August of 2007.
The Greenlink alternative is the alternative with significantly expanded short tunnels that connect neighborhoods as proposed by the city of Windsor.
The air quality analysis focused on the PM2.5 as the most significant pollutant of concern from the heavy-duty diesel truck traffic that will increase in the future.
The area of the existing intersection of the Cabana Road and Todd Lane with Highway 3 was selected for analysis. This is one of the major intersections along the project corridor and the site of the longest of the proposed short tunnel under the Greenlink alternative.
The results of the analysis indicate that the impacts under the No Build scenario will be the greatest of the three alternatives analyzed. Moving and idling at the traffic signal vehicles at the at-grade roadway intersections would generate more emissions and have bigger impacted areas than the free-flow vehicles in the depressed roadway. Emissions generated inside the tunnel and exhausted out of the exit portal under the longer Greenlink alternative are greater than emissions generated under the much shorter Land Bridge. However, the impacted area under the Greenlink alternative is limited to the area surrounding the portal of the proposed tunnel, whereas impacts under Land Bridge alternative extend along the proposed roadway alignment. In addition, tunnel portals could be located in areas with no nearby sensitive land uses to avoid or minimize impacts.
View the full air quality report (pdf format)