High-Risk, 610 mm (24 in.) Diameter, 1, 645 m (5, 400 ft.) HDD Project—A Case Study

The Middlesex Water Company (MWC) is a 113-year-old, publically traded company providing water, wastewater and related utility services to a population of nearly 400,000 in central New Jersey and Delaware. Recently, MWC completed the planning, design and construction of a new 610 mm (24-inch), 1,768 m (5,800-foot) long water main to replace an existing 610 mm (24-inch) cast iron water main more than 100 years old. The existing water main conveys water from MWC's northern distribution system near the city of Perth Amboy, across the Raritan River, and into MWC's South River Basin system in southern Middlesex County, New Jersey. Due to the age, corrosivity and unstable nature of the surrounding environment, the existing main experienced several breaks, requiring costly emergency repairs on an increasing frequency. These outages caused major operations disruptions and repairs were costly due to access impediments associated with the river, soft sediments adjacent to and under the river, and regulatory considerations associated with adjacent wetlands and river navigation. Alternative construction methods for crossing the 1,463 m (4,800-foot) wide Raritan River were evaluated. Studied options included open-cut trenching, microtunneling, pipe jacking, conventional tunneling and horizontal directional drilling (HDD). Factoring in construction schedule, cost, sustainability, impacts to the environment and marine traffic, and permitting requirements, HDD and fusible polyvinyl chloride pipe (FPVCP) were recommended for the river crossing. The final design consisted of an HDD crossing, approximately 1,635 m (5,365 feet) long, using 610 mm (24-inch) FPVCP. The completion of this HDD and pipe pullback makes this the longest FPVCP pullback for a diameter of 610 mm (24 inches) or greater completed to date in the world. This paper highlights the planning, design and construction of this 1,635 m (5,365-linear-foot), 610 mm (24-inch) FPVCP water main installed using HDD techniques across the Raritan River. Elements of this high-risk project that are discussed include the geotechnical investigation, HDD construction techniques, staging and fusing of the FPVCP, and startup. This paper also discusses the design process and compares pulling forces predicted by the design with the actual pulling forces recorded during pipe installation This project was awarded the 2010 Project of the Year for New Installation by Trenchless Technology.