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• Assessment of the best available sources of course and fine aggregates;
• Creep and shrinkage testing conducted concurrently with compressive strength and modulus tests;
• Additional project specific long-term concrete and creep testing;
• Structural analyses of the composite wall, with various preliminary reinforcement schemes; and
• Load deflection tests on two test pipe sections, manufactured with the final proposed reinforcement, to verify the composite wall designs. This was done to ensure the pipe would not be compromised during handling and installation.
During manufacturing of the liner, the steel cylinders were hydrostatically tested and the weld seams were radiographically tested to ensure the water-tightness of the composite-wall liner. The joint welds required to seal the composite steel and concrete tunnel liner inside the tunnel were tested in conformance with the ASME pressure vessel code.
Further hydrostatic testing was conducted after the installation was completed as a final quality check before the tunnels were put into service.
It took nearly 10 years, and more than 2,500 pieces of the 144-inch diameter composite-liner pipe, to complete the East and West tunnels. The lengths of the east and west tunnels total approximately 30,000 and 20,000 feet long, respectively. They are now an integral part of the Metropolitan Water District of Southern California’s critical Inland Feeder pipeline.