ODOR CONTROL FOR LARGE DIAMETER DEEP SEWER TUNNELS - THE CITY OF COLUMBUS OHIO

The Upper Scioto West Interceptor (USWI) tunnel has only recently been put into service but has already exhibited sewer air ventilation characteristics that make it prone to odor release. The USWI tunnel is approximately 31,000 feet long and reaches depth of 75 feet. The tunnel diameter ranges from 72 to 84 inches and the connecting sewers range in size from local 6-inch diameter gravity sewers up to the 54-inch diameter Dublin sewer. The USWI tunnel was constructed with the best available drop structure designs which reduced the magnitude of drop structure ventilation but did not eliminate it. The USWI system has 14 access shafts, of which 2 are vortex type drop manholes with deaeration chambers and 4 are vortex type drop manholes without deaeration chambers.Deep tunnel wastewater collection systems have become popular over the past several years primarily due to the elimination of pumping facilities and the associated operation and maintenance cost. The ventilation characteristics exhibited by the Upper Scioto West Interceptor are unique to deeply buried primary sewers. This problem has been identified in several deep tunnel sewers but is usually most severe where drop structures consist simply of vertical shafts with little consideration given to designs that reduce ventilation. The ventilation problem also occurs, although to a lesser extent, even when drop structures are designed to reduce forced ventilation. To identify and correct the odor releases a study of the ventilation dynamics and odors was performed.