Construction has started on a project to upgrade water and sewer lines serving Liberty Island, the site of the iconic Statue of Liberty, in New York City
Design is completed by engineering consultant Hatch Mott MacDonald – which was retained in 2012 by the Jersey City Municipal Utilities Authority to design replacements for the existing water and sewer lines. These are currently undersized and vulnerable to damage. Interruption of service would meant closing the island, which receives, via ferry services, more than four million visitors per year.
The Jersey City Municipal Utilities Authority provides the water and wastewater service to Liberty Island, which in turn is operated by the National Park Service.
The new design includes the use of horizontal directional drilling (HDD) to install separate 2,400ft long water and sewer lines through the bedrock of New York Harbor. Approximately 3,000ft of water pipe and a further 3,000ft of sewer force main will also be installed within Liberty State Park, using pipe-bursting techniques.
Pipe-bursting, one of a number of trenchless excavation methods, is a method of rehabilitating old water and sewer lines without having to dig them up from the surface. An air compression powered hammering tool is used to break apart the existing underground infrastructure, which is simultaneously replaced with a new pipe pulled in behind it from the opposite end of the line.
Nick DeNichilo, President and CEO of Hatch Mott MacDonald, said: “HMM looks forward to the successful completion of this important project. We are proud to help ensure safe and uninterrupted public access to one of the world’s most popular attractions and significant monuments.”
The project design is challenging due to the extremely limited construction area on Liberty Island. HMM performed eight geotechnical borings to determine the quality of bedrock, recommended the use of conductor casings on each end of the HDD crossings, designed temporary systems to maintain service during construction, obtained necessary permits, and coordinated with Liberty State Park and Liberty Island to maintain visitor access during construction.