Backing Them Up – Staging Inline Storage and Green Infrastructure as Low-Cost Steps Towards Controlling a Big CSO

Municipal utilities are challenged to develop cost-effective wet-weather compliance plans funded mostly by ratepayers. As an alternative to traditional plans, Sanitation District No. 1 of Northern Kentucky chose a staged approach for reducing overflows at their largest CSO. Relying on inline storage of wet weather flows and basin-wide green infrastructure demonstration projects, the Willow Run CSO overflow abatement program showcases short-term improvements that will complement any potential long-term direction. With extensive green and watershed-based control opportunities and a major highway/bridge system upgrade greatly affecting the drainage basin for the next 15 to 20 years, such flexibility is essential for cost-effectively addressing a big CSO.This paper will provide guidance for municipal utilities in developing a staged approach for reducing overflows based on lessons learned from the Willow Run CSO. First, the paper will discuss challenges and opportunities for the Willow Run drainage basin within the context of SD1's regional priorities and Consent Decree requirements. Second, this paper will consider planning and implementation issues for static and dynamic controls for inline storage of wet weather flows, including risk-based evaluations of potential surface/basement flooding locations and assessments of both local and system-wide overflow impacts. Features of SD1's green infrastructure concept plan for the I-71/I-75 corridor, which falls within Willow Run CSO boundaries, will also be summarized.