26 OCTOBER 2026 WorldWide Drilling Resource® A Clay-and-Water Mixture Adapted from Information by Enbridge As the 41-mile Line 5 Wisconsin Segment Relocation Project moves forward, some of the most crucial operations are taking place dozens of feet below rivers, streams, wetlands, and roadways. This method, known as horizontal directional drilling (HDD), is a specialized technique used globally to install pipelines below sensitive environmental areas without the need for open trenches. A common question asked is what exact materials are used in HDD construction. The answer is quite simple. The drilling process relies on a mixture predominantly comprising around 96% water and 4% bentonite clay. “People hear the term “drilling mud” and sometimes imagine something complicated,” said Christopher Pope, Manager of Mainline Construction for Enbridge’s Line 5 Wisconsin Segment Relocation Project. “In reality, the primary ingredients are water and bentonite clay - materials that have been used safely in drilling applications for decades, including the construction of drinking water wells.” Bentonite is a natural, nontoxic clay originating from weathered volcanic ash. During the drilling operation, this clay-water mixture is pumped through the drilling line and circulated back to the surface. This fluid serves multiple purposes: it lubricates and cools the drill bit, stabilizes the underground borehole, transports soil, and diminishes friction as the pipeline is inserted. In most HDD projects, the bentonite-water mixture is sufficient on its own. In instances where specific site conditions require enhanced drilling capabilities, only additives approved by the Wisconsin Department of Natural Resources (DNR) may be utilized. “Environmental protection is built into every aspect of this work,” said Pope. “The DNR permit for the project requires that any additives must meet Wisconsin’s regulatory requirements. If an additive is needed, that additive has already been approved by DNR for HDD use.” HDD avoids surface disruption by drilling a pilot hole deep beneath these features and subsequently pulling the pipeline through the completed borehole. This technique offers numerous environmental advantages, including: • Reduced disturbance to aquatic habitats • Protection of riverbeds and streambanks • Minimized impact on water quality • Less disruption to wetlands and vegetation • Decreased risks of erosion and sedimentation For the communities along the Line 5 route, HDD represents one of the most carefully engineered aspects of the project. The drilling process is continuously overseen by experienced professionals. In the event of pressure drop, drilling is halted until corrective measures are completed. Should there be a release of the clay-water mixture, Enbridge follows DNR-approved response plans to minimize the impact and has equipment positioned nearby for quick respond cleanup efforts. Editor’s Note: In between our print issues, the WWDR Team prepares an electronic newsletter called E-News Flash by WorldWide Drilling Resource by WorldWide Drilling Resource®. This newsletter is filled with articles not included in our print issue. Based on readership, this was the most popular article of the month. Get in on the action and subscribe today at: worldwidedrillingresource.com Horizontal Directional
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