Sanitation District No. 1 Partners with Development Community to Cost-Effectively Reduce Overflows into the Ohio River

The Sanitation District No. 1 of Northern Kentucky (District) provides sanitary and storm sewer services for 33 communities in Boone, Campbell, and Kenton Counties of Northern Kentucky. The District's sanitary sewer system covers approximately 200 square miles and serves a population of approximately 350,000, 12 square miles of which comprise their combined sewer service area.As part of their Watershed Consent Decree with the Kentucky Division of Water and USEPA Region 4 to address CSOs and SSOs, the District is required to develop Watershed Plans every five years. These Watershed Plans will determine a combination of affordable watershed and infrastructure controls to improve water quality, eliminate SSOs, and comply with the CSO Policy. The first Watershed Plans are due in June 2009.With the Watershed Planning in the very early stages, a local developer submitted plans to develop a portion of the Northern Kentucky Riverfront in Dayton, Kentucky over the upper 8,000 LF of the District's Ohio River Interceptor (ORI) and needs to be replaced. Initially, the developer proposed to replace the existing pipe with the same size (24″-30″), with the developer covering the costs. The District quickly realized that this was an opportunity to consider construction of facilities that could help reduce overflows instead of replacing in-kind with an undersized interceptor. This approach had two key advantages:The developer would pay for some portion of the project.Due to the nature of the development, construction would be very difficult if not cost-prohibitive in the future to upsize the interceptor and construct new facilities in this area.Construction in this area is likely very costly due to the proximity to the Ohio River and the extent of fill material on the site.The District decided to try to evaluate a range of alternatives and to evaluate the long and short term impacts of the alternatives on various future CSO control measures which included conveyance and local storage. The District's system-wide model was used to develop sizes for conveyance and storage facilities as well as identify the optimum locations for the future storage facilities.The selected alternative was to install an 84-inch pipe along the entire development to provide both increased conveyance and in-line storage capacity. This alternative best addressed both the short and long-term needs to bring CSOs into compliance in this area by providing for the needed conveyance in the future and short-term in-line storage. Therefore, the District's model was used to evaluate the current benefits of installing an 84-inch pipe along the entire development The final design of the sewer replacement also included new diversion structures that will prevent significant grit accumulation, prevent the intrusion of Ohio River water, and will serve to reduce solids and floatables from overflowing. This paper will present the analysis that was done to select the design as well as other key design features of the sewer.