41 APRIL 2022 WorldWide Drilling Resource® Tunnel Boring to Mitigate Flood Risks in Phoenix, Arizona Compiled by Amy White, Associate Editor, WorldWide Drilling Resource® The Cave Buttes Dam is a flood-control structure in Phoenix, Arizona. The dam, along with a system of three earthen dikes, diverts stormwater runoff from Cave Creek Wash. Built by the U.S. Army Corps of Engineers, the dam system has protected thousands of downstream properties from floods since 1980. On two occasions in the dam’s history, seepage was detected through the embankment when flood pool impoundments were holding more water than usual. Since the leaks indicated a potential safety threat, the Flood Control District of Maricopa County decided to take proactive measures to protect people and infrastructure in the area. The district designed a safety plan which involved building a 61-foot supplemental outflow structure for the dam. Contractors were hired to create a tunnel below the dam to decrease the time it took water to drain. A 68-inch tunnel boring machine (TBM) was used to create a pathway for a new outflow pipe. Underground conditions were highly variable and unpredictable. As the TBM pressed forward, it encountered soft dirt, hard rock, and clay. In some areas along the path, ground conditions changed every five feet, creating quite a challenge for workers. Due to variations in the ground, daily production varied, ranging from a high of 40 feet to a low of 2 feet in a day. Once the tunnel was complete, 943 feet of 60-inch pipe was placed inside. Grout was used to form a seal around the pipe to prevent leaking. After the pipe was set, intake and outlet structures were built, and a gate was installed to control water discharge from the dam. Increasing flood safety measures for the Caves Butte Dam required extensive planning, design, permitting, and approval processes which took almost a decade to complete before construction could begin. Now that the flood control pipeline is finally a reality, residents and businesses in Phoenix will have a greater level of protection from floods for years to come. Some things to think about . . . Have fun! Why do dogs always race to the door when the doorbell rings? It’s hardly ever for them. (Thanks - Harry Hill, Comedian) We’ve begun to long for the pitterpatter of little feet, so we bought a dog. It’s cheaper and you get more feet. (Thanks - Rita Rudner, Comedian) I spend three minutes every day choosing a TV channel to leave it on for my dog. Then I go to work, and people take me seriously as an adult. (Thanks - Damienfahey) A Canadian psychologist is selling a video that teaches you how to test your dog’s IQ. Here’s how it works: If you spend $12.99 for the video, your dog is smarter than you. (Thanks - Jay Leno, Comedian) C&G
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