Assessing Environmental Impacts – Air Quality

Often times when the noise quality is affected, so too is the air quality. For example, when a sound wall is built to reduce traffic noise, that same sound wall can “trap” vehicle emissions, and have a derogatory impact on the air quality. It can be useful to have a single firm assess both noise and air impacts.

As you may know, government agencies have enacted laws, ordinances and regulations to achieve air quality. An air quality analysis must indicate, in quantitative terms, whether a proposed project will cause pollutant levels to exceed the air quality standards. Although emissions from the proposed project may not exceed the standards, the total emissions from the proposed project and other sources in the project environment may produce degradation in air quality sufficient to exceed the standards. Air impacts at air sensitive receptors can be computed using air quality models. These models require the input of accurate emission factors, meteorological data, such as wind speeds and directions, mixing heights, stability classes, and air chemistry information.

The first step in developing an air impact assessment is to understand the existing air quality environment. Monitoring ambient air quality at the project site, reviewing current air quality regulations, and determining existing and future air sensitive receptors achieve this.

The second step is to understand the air impacts during the construction stage. The most likely air impacts from construction activities are dust nuisance and gaseous emissions from construction vehicles. If the total air impacts exceed the statutory requirements, then appropriate mitigation measures are recommended. These can include water sprays to control dust emissions from the construction site, buffer distances between construction activities and air sensitive receptors, avoidance of simultaneous dust emission activities, reduction in the numbers of equipment operating in critical areas, etc.

The third step is to understand air impacts after the project is completed. Air quality models can predict air impacts at existing and future air sensitive receptors. Most air quality models can calculate the 1- hour, 24-hour and annual air quality levels. If the total air quality impacts exceed the statutory requirements, different mitigation measures should be recommended, such as effective buffer distances between the project site and the air sensitive receptors, suitable stack heights for industrial plants, appropriate land use planning, etc.

The forth step is to evaluate the economic benefits of all the recommended mitigation measures, and choose the most cost-effective mitigation measures. The final report is then submitted for agency approval.

TA is pleased to offer this additional service to our clients. In another blog post will finalize this series on Assessing Environmental Impacts by discussing water quality.