ATLANTA PREPARES FOR DELIVERY OF ITS NEW TBMS

This article profiles the West Area CSO (WCSO) and Nancy Creek tunnel projects in Atlanta, Georgia. The WCSO project involves the construction of a dedicated stormwater tunnel facility for conveying CSO flows such that untreated combined sewer flow is not discharged tin to the tributaries of the Chattahoochee River. The Nancy Creek project is a high profile sanitary sewer facility that passes directly beneath or close to 200 private homes in an affluent neighborhood. There are a number of similarities between the two jobs, such as the 8.3 miles length for Nancy Creek and the 8.7 miles length for the WCSO, as well as the fact that both projects needed two tunnel boring machines (TBMs) to complete excavation with very tight construction schedules. However, while the Nancy Creek project involves an 18 ft. 4 in. cut in diameter, the WCSO tunnels are 27 ft. in diameter. As such, the latter project required special ordering two new TBMs from Switzerland. The article notes that these projects have demanded significant capital investment by the City of Atlanta as a result of past state and city governments having ignored these needs.