A major portion of the Seattle metro area comprehensive sewage collection and treatment plan launched in 1958, included improvements to an existing combined sewer system within Seattle's city limits. Initial plans included interception and treatment of raw sewage flowing to saltwater points, regulation of combined flows to utilize all available trunk storage, and construction of temporary storage tanks at freshwater overflow points. Construction has been completed to demonstrate the feasibility of applying computer-control concepts to make maximum use of all available storage within a collection system.