The Metropolitan District (MDC) of Hartford, CT is constructing the $500 million South Hartford Conveyance and Storage Tunnel, which will run from West Hartford to the Hartford Water Pollution Control Facility. It is a key element of the MDC’s 20-year Clean Water Project that aims to safeguard the future of the Connecticut River by cleaning up Combined Sewer Overflow (CSO) discharges to streams and reducing oxygen-depleting nitrogen in the river. The tunnel will include odor control systems located at each of the ventilation shafts and droptubes to handle the emittance of foul air from the tunnel.
Alden performed CFD model studies to predict the quantity of foul air exiting through each of the droptubes and ventilation shafts during two scenarios:
1) A buoyant condition where colder ambient air would create an upflow of the warmer tunnel foul air
2) A storm condition where the incoming water would displace the tunnel foul air
Time-dependent Computational Fluid Dynamic (CFD) models of the planned tunnel system were developed. The models used historical temperature and storm data in the surrounding area of each droptube and ventilation shaft to define the test conditions for each simulation. The buoyancy model simulated the time-lapsed effect of the warm foul air rising out of the tunnel and being displaced by the colder ambient air. The storm model simulated the duration of an extreme storm case with water entering each droptube based on the local water flow data for the area. Each model provided the flow rate versus time of foul air exhausting (or ambient air drawn in) at the droptubes and ventilation shafts.
Results of these simulations were used to properly size the odor control systems.