Getting ready for a larger panama canal - assessing a critical large diameter force main


Opened in 1905, the Government Cut is a manmade shipping channel between Miami Beach and Fisher Island, which allows better access to the Port of Miami in Miami, Florida. Before the Cut was established, a single peninsula of dry land stretched from what is now Miami Beach to what is now Fisher Island, and boats destined for the port at the mouth of the Miami River had to pass around Cape Florida, to the south of Key Biscayne. The now-famous South Beach is to the north of the cut.

Unseen on most maps and aerial photos are the water and sewer mains that traverse the Cut to service the citizens of Miami-Dade County. These pipelines are being replaced as part of a project that will see the Cut being deep-dredged by 2014 at which time the Port of Miami will be one of only three East Coast ports capable of accepting larger “New Panamax” ships.

The project consists of the fast tracked design-build of a (-) 142’ deep and 1,600’ long 24-inch diameter Horizontal Direction Drill from the Port of Miami to Fisher Island to replace an existing 20” water main and a 72-inch diameter micro-tunnel from Fisher Island to an in-water shaft south of South Beach. The 1,200’, 72-inch micro-tunnel, installed at a depth of (-) 80 feet, will carry a new 54-inch diameter sewage force main, replacing the existing force main which transmits wastewater from various municipalities to the Miami-Dade Water and Sewer Central District Wastewater Treatment Plant on Virginia Keys.

Being such an important part of the economy for Miami-Dade County and because of the sensitive nature of Biscayne Bay, the Miami-Dade Water and Sewer Department (WASD) implemented a comprehensive assessment of the force main prior to any dredging and pipeline replacement activities. The 54-inch force main in particular is Prestressed Concrete Cylinder Pipe that was manufactured by Interpace in 1978 and used Class IV prestressing wire. Assessing the condition of this pipeline was a critical path item in the overall Government Cut dredging program because a failure during construction activities could have damaging and costly consequences to WASD and the County.

To mitigate the risk of damaging the pipeline during the Government Cut expansion, Pure Technologies US, Inc. (Pure) was contracted to provide inspection, condition assessment services and recommendations for portions WASD’s Prestressed Concrete Cylinder Pipe (“PCCP”) Government Cut Force Main. The 54-inch PCCP Force Main conveys wastewater from the City of Miami Beach to the Central District Wastewater Treatment Plant (“WWTP”) on Virginia Key.

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