Problem/Challenge:

The Zenza–Cacuso section of the Luanda–Malanje Railway in Angola faces significant operational issues due to degraded infrastructure, including numerous sharp bends, steep gradients, and damaged tracks and bridges. Thus, the Zenza – Cacuso section requires urgent renovation/upgrades involving sophisticated construction and engineering, to improve the existing line by introducing the necessary improvements. The proposed upgrades aim to improve safety, reliability, and performance. However, the project raises concerns about potential impacts on air quality from construction and operational emissions, particularly from dust (PM10 and PM2.5) and vehicle exhaust gases (NOX, SO2, CO).

Solution/Approach Taken:

To address these concerns, an Air Quality Impact Assessment (AQIA) was conducted. The approach included:

• Baseline air quality monitoring at key locations along the railway.
• Emissions inventory for both construction and operational phases.
• Dispersion modelling using Screen3 and AERMOD tools to predict pollutant concentrations under various scenarios.
• Comparison of model results with World Health Organization (WHO) air quality guidelines.

The modelling assessed emissions from construction vehicles and locomotives, estimating how pollutants would disperse in the atmosphere. Two construction phases (Zenza–N’dalatando and N’dalatando–Cacuso) were modelled. Additionally, a localised study focused on N’dalatando station to evaluate impacts in denser areas.

Role of Air Quality Specialist (Rayten Engineering):

Rayten Engineering Solutions was the air quality specialist responsible for the entire AQIA. Their role included:

• Conducting site assessments and identifying sensitive receptors.
• Compiling and analysing baseline air quality data.
• Developing emissions inventories and performing dispersion modelling.
• Interpreting results to assess the potential impact on ambient air quality.
• Recommending mitigation measures and monitoring protocols to manage dust and emissions during the construction phase.

Rayten Engineering’s assessment concluded that although daily concentrations of PM10 and PM2.5 could exceed WHO interim targets near the railway during construction, the overall impact was rated as low to medium. Their detailed evaluation enabled informed decision-making to minimize environmental and health risks.