Installation of 3,000-plus-ft of 54-in. HDPE Overcomes Numerous Obstacles
Dozens of people lined the street.
Up and down Euclid Avenue, less than a mile from Miami’s famous South Beach, crowds were forming. With camera phones at the ready, they watched a 54-in. high-density polyethylene (HDPE) pipe readied and pulled underground. Most onlookers had no idea what exactly they were watching, but each one of them could tell it was something remarkable. It was the culmination of years of work.
An existing 54-in. pre-stressed concrete cylinder pipe (PCCP) sanitary sewage force main (FM) was constructed in 1977 in the City of Miami Beach. The FM served as the sole means of wastewater conveyance through the City. By 2012, it was clear that it was aging and deteriorating like much of the infrastructure in coastal communities. Faced with the potential threat of failure, the City embarked on a Capital Improvements Program, totaling $750 million over five years. In 2013, the City invested in a non-destructive condition assessment. Using Pure Technologies’ PipeDiver, the assessment was performed on the PCCP FM. It was determined that it was, indeed, on the verge of catastrophic failure.
Failure of this force main, which is the sole means of wastewater conveyance, would be disastrous. It would potentially discharge millions of gallons of raw sewage along the urbanized corridor of one of the most popular tourist destinations in the world. It would impact residents and commercial operations while contaminating the pristine and ecologically sensitive waterways and beaches. The economic impact of forced closures of hotels, restaurants and beaches would devastate the City.
The City worked with consultant AECOM to develop a creative, cost-effective solution that would use the design-build method. The first step was to procure a contractor. David Mancini & Sons Inc. (DMSI) worked with AECOM to develop a constructible project using horizontal directional drilling (HDD) that pushed the boundaries of current technology, utilized innovative load reduction techniques, and was embraced by the tourist-driven community as being non-invasive versus open-cut trench methods.
The project was not without several challenges and risks. First, the geological makeup of the drill site, typical of south Florida, presented an obstacle. The drill would work through the Fort Thompson Formation composed of non-fossiliferous quartz fine sand, fossiliferous quartz sandy limestone, coralline limestone, freshwater limestone, and quartz limestone. DMSI brought significant knowledge of the geology and had successfully drilled through it many times before.
DMSI retained Brian Dorwart of Brierley and Associates as a consultant on the project. Previously, the City’s experience with HDD was limited to smaller diameters and shorter drill lengths. In this case, the plan involved 3,300 ft of 54-in. DR 17 HDPE weighing approximately 225 lbs per linear foot. The installation of 750,000 lbs of HDPE required creativity, experience and teamwork. ISCO Industries provided the pipe, as well as technical assistance, pipe fittings, and fusion services. “Their technical support helped maximize the construction efficiency and minimize the social impact of this project,” said Dorwart. HDPE was ideal for the job because of its low life cycle cost and monolithic features, as well as its lightweight and ductile properties.
It was determined that the pipe would be pulled in two segments, Drill No. 1 of approximately 3,100 ft and Drill No. 2 of 1,240 ft. DMSI used a dual-stringing approach which consisted of staging two segments of 1,650 ft of pipe in the center of the roadway. This allowed local access to residents while reducing the nuisance of having to extend the impact of the construction to more intersections. DMSI even constructed a pedestrian bridge over the pipe so that locals and tourists could cross above the staged pipe.
The fusion on the project was completed using a McElroy MegaMc 2065 provided by ISCO and operated by an ISCO fusion technician. The highlight was joining the two segments of 1,650-ft strings of pipe during the pullback process. “It was an incredible process,” said ISCO sales rep Bryan Fletcher. “It required a lot of patience and persistence. Our technician, Andre Joiner was able to complete the complex fusion.”
DMSI brought in Hardrock Directional and Spartan Directional, LLC to complete two pulls of the HDPE underground. “Spartan’s involvement was to provide all necessary man power and equipment to successfully complete these drills,” explained Boyd Simon, P.E., manager at Spartan, “This project had the potential to advance HDD methods like they’d never been propelled before. We had the combined experience to make it happen.”
A significant issue was the management of the supply and disposal of the large amounts of drill fluid that were used during the drilling process and during the pipe installation. Conditions limited the volume and size of trucks that were allowed to support the pipe installation and the management of drill fluid that was needed. The solution was to store the drill fluid inside the pipe while the pipe was being pulled in order to significantly reduce the amount of fluid needing to be disposed of quickly. The project planning team dug a series of relief wells to manage the drill fluid pressure during the pipe installation process. This would prevent pressure from fracturing the ground and releasing the drill fluid to the ground surface.
Another challenge for the project was working with limited space. “This type of drill takes plenty of large equipment,” Simon explained. “Having to work on a two-lane road under power lines was challenging.”
Spartan brought in a 1 million-lb Vermeer drill rig (D1000x900), mud pumps (American Auger P-750 and Tulsa Rig Iron TT-660), cleaning systems (American Auger MDC 1000 & Tulsa Rig Iron MCS 1000), a drill pipe (6-5/8-in. full hole, double shoulder), and hole openers (Horizontal Tech Jumbo Viper Rockreamers (30-, 42-, 54-, 66- and 72-in.).
The pull required the crew to open a 6-ft hole for 3,000 ft in order to pull the 54-in. pipe. The final set up for the drill was put in place at night. As the sun came up the next morning, the pull had started. It was slow at first, picking up speed by late afternoon. The pull was slow, but successful. It took ingenuity and innovation to master a pull that long. It started at 6:30 in the morning and was completed before the sun went down that evening.
HDPE has become a tested and proven solution for force main rehabilitation. Projects like this push the limits of what we know about the material’s capabilities and strength in action. This project is another example that there’s more ground to cover when it comes to the ability of plastic pipe.
A pull like this is literally and figuratively groundbreaking. The time and money it would have taken to dig up and replace the existing line would have made this project unrealistic. The disruption to the city, its residents and visitors, would’ve been enormous. Instead, a dedicated team pulled together to pool their experience and come up with a creative, innovative, and cost-effective solution to provide the City of Miami Beach with a reliable force main that will last for decades.
Chelsea Rabideau is public relations coordinator at ISCO Industries Inc.