As one of the largest metropolitan areas in the country, downtown Dallas is home to big buildings, mass transit, and bustling streets. To avoid road closures, costly traffic maintenance and utility conflicts, engineers chose a trenchless installation of 1,800 linear feet of 36” prestressed concrete cylinder pipe. Arredondo, Zepeda & Brunz Project Manager Steve Hardy is an experienced engineer who knows the area. “You can’t get big equipment in,” he says. “Anytime you’re dealing with downtown, its much more complex.” The project pathway was adjacent to a 50-story skyscraper and a light rail transit line. Concerns about heavy loads, vibrations and stray currents led the engineering firm to recommend PCCP.
Tunnel depths were a maximum of 40 feet. Thompson Pipe Group engineers designed PCCP to withstand up to 150 feet of cover. The unique design concept of PCCP, featuring a steel cylinder for watertightness and a rugged, high-strength concrete structural core circumferentially prestressed with high strength steel wire, makes it the best option. To protect against corrosion the portland cement-rich mortar coating provides a passivating alkaline environment for the steel cylinder, joint rings and prestressing wire. Additionally, vibrations from the adjacent light rail tracks will not impact on the pipe.
Installation Benefits of PCCP
To assist with ease of installation, Thompson Pipe Group manufactures trenchless PCCP with raised mortar coated skids. These integral mortar coated skids eliminate supplemental casing spacer failures. Additionally, PCCP can be restrained by Thompson Pipe Group Snap Rings® or harness clamps. Neither require welding and are protected by portland rich cement. Plus, testable joints eliminate the time and effort to seal and fill the completed line with water. Contractors air test joints in the field to confirm leak-free joints.