One of the major population centers along the Ohio River is the city of Louisville, Kentucky. Every day, Louisville Water Company (LWC) produces millions of gallons of drinking water for its customers by pulling surface water from the Ohio River.

The Ohio River is an amazing natural water resource for Louisville as well as other cities and towns throughout the Ohio River Valley. However, its other uses—for transportation, industry, and recreation—can result in water pollution and contaminants that make it challenging to use the river to supply drinking water.

To make sure that the surface water is safe for people, the LWC sends it to a treatment plant where it is filtered to remove contaminants and sediment. In looking for a more efficient and “greener” way to produce drinking water, the company began investigating a process called riverbank filtration that allows for the use of groundwater instead of surface water in the municipal water system.

In 1999, the LWC began riverbank filtration at their B.E. Payne Plant with one well that pulls 20 million gallons a day from an aquifer. An aquifer is an underground layer of rock, gravel, sand, or soil that holds water. In this case, the aquifer is located near the bank of the Ohio River, so the river water filters through the bank into the aquifer.

Based on the success of the Payne Plant, the LWC decided to expand the project by digging four additional wells and a mile-long collection tunnel that can produce up to 70 million gallons of water a day from the riverbank aquifer. The videos in the Tunneling for Water collection document this engineering feat and look at science and engineering concepts related to the project.

The process of riverbank filtration has several advantages over pulling surface water from the river. They include the following:

• The water is cleaner because it is naturally filtered by the sand and gravel it passes through from the river to the aquifer. So less treatment is needed to insure its safety.
• The water is at a constant temperature of 55˚ degrees Fahrenheit. Surface water temperatures vary from 37 to 70 degrees, and this variation can cause water main breaks.
• The aquifer beside the Ohio River is perfect for a riverbank filtration system; every day, millions of gallons of river water naturally move from the river into the ground.

The LWC tunnel and well system—the first of its kind in the world—consists of four wells that collect water from the aquifer. They are located above the tunnel, which is 150 feet below the surface of the ground. When water collects in the wells, gravity causes it to flow down into the tunnel. Then electric pumps pull the water from the tunnel back to the surface, where it is processed and distributed to Louisville households and businesses.

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