River Water Intrusion Phase I & II

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SD1’s combined sewer system is impacted on a regular basis by high river levels, on both the Ohio River and Licking River. This is not uncommon in combined sewer systems, but is especially pronounced in Northern Kentucky given that many of the CSO outfalls were constructed prior to construction of the Markland Dam in the mid-1960s (downstream from SD1’s service area), which raised the pool elevation to 25.4 feet.

River water intrusion has the effect of increasing flows in the combined sewer system during high-river stage conditions, resulting in earlier triggering of CSOs during rainfall events, an increase in CSO volume when flood stations are activated and utilization of treatment plant capacity to treat river water.

To mitigate the effects of river water intrusion, SD1 has developed a multi-phase program to prevent river water intrusion up to a design river elevation. Phases I & II will be implemented by 2023, and will include the installation of a flap gate or check valve on 19 CSO outfalls along the Ohio and Licking rivers, as shown above. 

Once complete, this project will allow the Bromley Pump Station, 8th Street Pump Station and Patton Street Pump Station to remain in normal operation up to a river stage of 47 feet. These pump stations can thus remain in operation and not inundate the Dry Creek Wastewater Treatment Plant with river water and highly dilute sewage.

The River Water Intrusion Mitigation Program is expected to reduce typical-year combined sewer overflows by about 116 million gallons.