Greenhill Sewage Drop Shaft Odour Control

The City of Hamilton owns and operates one of the largest and most complex combined sewer systems (CSS) on the Great Lakes. The Greenhill CSS collects combined sewage from an area known as ‘Hamilton Mountain’, which is located on top of the Niagara Escarpment. Sewage and stormwater from a significant portion of Hamilton Mountain is collected by the Fennel Avenue Trunk Sewer and conveyed over the Niagara Escarpment by a large vertical drop shaft. From here, the sewage is conveyed east along Greenhill Avenue by the Greenhill Avenue Trunk Sewer to the Greenhill and Rosedale CSO storage tanks. Significant volumes of air are also conveyed by the drop shaft and trunk sewer, which can generate odours along Greenhill Avenue.A previous Class Environmental Assessment study recommended construction of a second sewage drop shaft at the east end of Fennell Avenue and a new trunk sewer along Greenhill Avenue, parallel to the existing sewer, to provide redundancy of sewage conveyance capacity over the escarpment, and to reduce odour emissions in the vicinity of the drop shaft and along Greenhill Avenue. The study proposed a single solution to address both of these issues, but it is also possible to deal with the odour and conveyance capacity issues separately, and do so in a manner that is still cost effective for the City, and does not limit their ability to address the conveyance capacity issue at any point in the future. Given the significant cost of the project as originally proposed, the City felt it was prudent to investigate such alternatives.Accordingly, Hatch Mott MacDonald (HMM), in association with Odor and Corrosion Technology Consultants, Inc. (OCTC), were retained by the City of Hamilton to provide engineering services to conduct an Odour Control Study for the Greenhill Sewage Drop Shaft, to determine whether there may be more cost effective approaches to controlling the existing odour problems in the vicinity of the existing Greenhill Sewage Drop Shaft.The paper documents the findings of the study and the recommended measures for controlling odours in the vicinity of the Greenhill Sewage Drop Shaft, along the Greenhill Avenue Trunk Sewer, and in the vicinity of the CSO storage tanks. The City is proceeding with the design/build of the recommended biofilter, and the paper also provides an update on the progress of this project.