ACWP
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-inch 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.