German microtunneling machine anchors to rock to bore water intakes under Georgia reservoir

Key points

• Huxted Trenchless used a Herrenknecht AVN1000HR microtunneling machine to bore three 51-inch water intake tunnels under the Dog River Reservoir in Douglas County, Georgia.
• The machine weighed approximately 8.4 tons and required hydraulic grippers to anchor against the rock, preventing the cutting wheel’s torque from rolling the unit over.
• Each tunnel ended at the bottom of the reservoir, necessitating diver recovery of the machine after it broke through the lakebed.
• The project involves raising the dam by 35 feet, increasing water storage from 1.9 billion to 6.5 billion gallons to ensure drought resilience.
• The new intake feeds a pump station with two 2,500-horsepower vertical turbine pumps, with completion targeted for 2029.
• Project costs vary by source, ranging from $390 million to $440 million, making it the largest public infrastructure project in Douglas County’s history.

Background

This project addresses long-standing concerns about the Dog River Reservoir’s capacity to sustain Douglas County’s drinking water supply during droughts. A decade-old study indicated the reservoir could not withstand another severe drought, prompting the expansion. The project is part of broader infrastructure upgrades in the region, including similar microtunneling efforts in Oklahoma for water intake systems. The expansion also led to the closure of the Dog River Recreational Complex, as the new water level will submerge the boat ramp and picnic areas.

Why it matters

The Dog River Reservoir expansion is critical for ensuring Douglas County’s drinking water supply remains resilient against droughts. The use of advanced microtunneling technology under a reservoir lakebed highlights the engineering challenges and innovations required for modern water infrastructure. The project’s scale and cost reflect the growing importance of securing water resources in the face of climate change and increasing demand. Additionally, the project sets a precedent for similar infrastructure upgrades in other regions facing drought capacity issues.

What to watch

The project is targeted for completion in 2029, with the goal of a fully filled reservoir by the end of that year. The new intake and pump station will be operational, ensuring the county’s drinking water supply can sustain 23 million gallons daily through severe droughts. The project’s success will likely influence similar infrastructure upgrades in other regions facing drought capacity issues.