Paducah Water currently draws water directly from the Ohio River using a screen located below the river surface. Our water treatment system is therefore subject to fluctuating river conditions such as sediment, microorganisms, zebra mussels, debris, contaminants, etc. This situation is further impacted by the location of PW’s intake and the complex interaction of the Ohio River, Tennessee River and the dams that are immediately upstream of the intake. PW staff must recognize and respond to the ever-changing conditions in a natural river system. PW has successfully navigated the challenging source water conditions and provided safe and reliable drinking water for many decades. However, it is getting more difficult and costly to achieve this high standard of quality. This summer was one very recent example when algae presented significant problems to virtually all communities along the Ohio River, and PW staff worked tirelessly all summer to battle the algae’s effects. Water Quality and Distribution staff met weekly to review, modify and adjust our response to the constantly changing conditions, including modifying treatment processes, changing operational controls and procedures, evaluating new treatment technologies and chemicals, and enhancing monitoring and testing. Although we were eventually successful in mitigating the problem, PW violated the Stage 2 Disinfection Byproducts Rule for Trihalomethanes (TTHMs) in July 2015.
The algal bloom of 2015 clearly illustrates the challenge of providing safe and reliable drinking water with a water source that can change wildly and rapidly. This event also illustrates the need for PW to be proactive in evaluating technologies and strategies that enable us to maintain the highest levels of quality and reliability in the drinking water we provide.
YouTube RBF video informational video
In order to address the challenges of a conventional river intake, PW is currently evaluating an alternate method of withdrawing source water called Riverbank Filtration (RBF). With RBF, a well (Ranney Well; named for Texas petroleum engineer Leo Ranney) is constructed adjacent to the riverbank. River water is drawn downward through the existing sediment, sand and gravel before collecting the filtered water in radial, horizontal wells. As the name RBF implies, the river water is filtered through the existing material below the river before entering the treatment plant. This pre-filtration results in a significant reduction in the cost of conventional treatment, and provides a buffer to some of the current challenges of the existing river intake including contaminants, microorganisms, temperature fluctuations and debris.
Currently, PW is working to examine the feasibility and construction cost of RBF. A potential site for an RBF Ranney Well has been identified and we are working to determine if geologic conditions are favorable through a series of borings and test wells. If the site is determined to be feasible, engineers and geologists will prepare a preliminary design with estimate of construction cost for consideration. PW will then make a determination of feasibility and assess the cost/benefit and funding options. The total process from evaluation through construction is expected to take between 24 and 30 months to complete.