The South Station Transportation Center (SSTC) in Boston, MA, is a major intermodal hub that includes a train terminal, regional bus terminal, and public parking garage. Planned development at SSTC involves constructing high-rise structures and expanding the bus terminal over existing train platforms, resulting in a fully enclosed station environment except for the south portal and the east edge along Track 13. 

Enclosing the tracks and platforms introduces significant ventilation and air quality concerns. Diesel exhaust from locomotive main engines and Head-End Power (HEP) units, combined with cooling fan flows, could accumulate within the enclosed space. The design needed to ensure compliance with health and safety standards for emissions and thermal comfort under worst-case operating conditions. 

Verdantas (formerly Alden Research Laboratory) conducted Computational Fluid Dynamics (CFD) simulations using ANSYS-Fluent® to evaluate ventilation system performance. Three locomotive/track configurations were modeled to represent critical scenarios with trains idling at the head end of the tracks. Analyses focused on: 

• Predicting dispersion of diesel exhaust and cooling fan flows. 

• Assessing the effectiveness of proposed exhaust hoods and general ventilation systems. 

• Verifying compliance with target emission concentration limits and ambient temperature requirements. 

Key Outcomes  

• Multiple exhaust hood configurations were tested to optimize pollutant capture and airflow distribution. 

• CFD modeling confirmed that the proposed ventilation design meets specification and code requirements for air quality and thermal conditions. 

• Robust system design accommodates variable operational scenarios, ensuring passenger and worker safety during station operations. 

This analysis provided critical validation for the South Station expansion, enabling safe enclosure of the platform areas without compromising regulatory compliance or operational efficiency.