ACWP UPPER TANNEHILL/MANOR HILLS WASTEWATER LINE

Austin, Texas

The Upper Tannehill-Lower Fort Branch & Manor Hills Sanitary Sewer Rehabilitation Project is part of the Austin Clean Water Project. Trenchless construction methods (microtunneling and pipe jacking) were required to construct approximately 721 ft of the pipeline, due to the depth of installation and potential for third party disruption at the ground surface if open trench construction were used. The new pipeline consists of 21-in.-diameter fiberglass reinforced polymer-mortar pipe (FRPM). Depth to pipeline invert varies from 8-ft to 24-ft-below the existing ground surface (bgs.). Soil conditions consist of clays and sands located below the groundwater table.

Lyman Henn performed a subsurface investigation at the site, which included six test borings and one groundwater monitoring well. The geologic information gathered was used to develop a feasibility report for the project, which provided recommendations on proposed construction methods, alignment, and shaft locations. Lyman Henn also prepared a Geotechnical Baseline Report. In addition, Lyman Henn reviewed technical specifications for microtunneling portions of the project.

Construction of the project began in October 2004, and the trenchless section was completed by February 2005. The Contractor elected to use a microtunneling machine to construct all three trenchless segments. Lyman Henn provided full-time construction observation of the microtunnel.