WorldWide Drilling Resource®

Small-Diameter TBM Makes a Big Impact Adapted from The Robbins Company A small-diameter (8-foot) tunnel boring machine (TBM) completed 11,400 feet of boring with no intermediate access, making it the longest rock tunnel ever bored by a Double Shield TBM under 8.2 feet in diameter. Contractor S.J. Louis Construction used the TBM for the Parmer Lane Wastewater Interceptor in Austin, Texas. Advance rates were good despite two tight 500-foot-radius curves and ground conditions requiring modification to the cutterhead while in the tunnel. “The pairing of this tunnel length, which is on the longer side, and the diameter, which is on the smaller side, is challenging. The survey in a small tunnel with tight radius curves and limited surface access for over two miles is very dif- ficult,” said Zach West, project manager for S.J. Louis. Through one stretch, the tunnel advanced directly between a 12-inch-diameter, high-pressure gas main, and fuel tanks for a gas station with limited as-built information. “I would say that I am most proud of our ability to guide the machine success- fully through these obstacles and into our retrieval shaft within our expected tolerances,” West added, saying the space was too small for an automated guidance system, so they manually surveyed the front of the machine at every push to ensure it was on track. The tunnel is located in an environ- mentally-sensitive aquifer, with ground conditions ranging from soft dolomite with clay, to limestone. Advancement rates were close to 3 feet per hour through the soft material and over 17 feet per hour through the limestone. The crew’s best advancement day was 81 feet in a single shift. The Parmer Lane Wastewater Interceptor connects to two existing lift stations at Lake Creek and Rattan Creek. The tunnel allows for these lift stations to be decommissioned; it will provide additional flow capacity by grav- ity, reducing operating costs for the City of Austin. 40 JULY 2020 WorldWide Drilling Resource ® The Qwater Well Developer (QWD) utilizes the surge block method and ball valve to develop wells faster and more effectively, while maximizing yield and lowering water turbidity in small-diameter monitoring and production wells. Its flexible wiper seals the tool to the casing/screen, creating a suction to pull water into the screen. The Environmental Series (right) is offered in five sizes from 3/4-inch to 2 inches, and is capable of lifting water with a ball valve over 50 feet. The Production Series (left) comes in 4-, 5-, and 6-inch sizes, and is capable of lifting water with a ball valve over 100 feet. Qwater is a Valued WWDR Advertiser. C&G