Kenduskeag East CSO Storage Facility in Bangor, Maine

Abstract

Bangor, Maine, a community of 33,000, is one of several hundred communities nationwide undertaking projects to control Combined Sewer Overflows. The City's Long Term Control Plan recommends several control technologies for Bangor's CSO situation, including the construction of CSO storage facilities in three locations. In 1998, Bangor constructed the 1.2 million-gallon Davis Brook CSO Storage Facility, an inline tunnel-like structure constructed of pre-cast concrete box sections and located under a future waterfront park area. The project was extremely successful from a construction and operational perspective, and very cost-effective with a construction cost at about $1.3 million. In September 2000, construction commenced on the City's second CSO storage project, the 1.2 million-gallon Kenduskeag East CSO Storage Facility. Bangor again utilized pre-cast concrete box sections to construct this off-line structure underneath an existing public parking lot in the downtown area. At a cost to the City of less than $2.2 million, this project is $3.1 million less than a proposed cast-in-place tank. By utilizing precast sections, the entire structure was installed within a threemonth time frame, with only minimal disruption to the public. The precast units were manufactured locally under a separate contract; with over half of the units manufactured by the time installation began. Units were delivered to the project on an as needed basis. The facility fit nicely under a public parking lot, thereby requiring no additional land area. The project includes a flushing system to remove settled solids from the bottom of the tank. The facility is connected to the City's Supervisory Control and Data Acquisition (SCADA) system, which will provide real time monitoring and remote control by Treatment Plant personnel. The local economy benefited with design, precast manufacturing, and construction all accomplished locally. This paper discusses several issues that should be of interest to other CSO (or SSO) communities contemplating storage projects, including design considerations, advantages of precast concrete, low costs, ease and speed of construction, and operational experience.