Mears Sets Fusible PVC Pipe Installation Record

April 2010 Vol. 65 No. 4
Mears’ 500,000-pound rig on the entry side.

The completion of another record breaking pipe installation, this time at Parris Island, a marine training base in Beaufort, SC, marks a series of successful and lengthy crossings of Fusible PVC (FPVC) pipe. Beaufort Jasper Water & Sewer Authority (BJWSA) contracted Mears Group Inc. to horizontally directional drill two crossings, 6,400 feet of 16-inch DR 18 FPVC and 600 feet of 16-inch DR 21 FPVC under Archers Creek and Malecon Drive, respectively. Underground Solutions Inc. (UGSI) supplied and fused the PVC product pipe for this project.

These installations are part of a project to divert the Parris Island wastewater flows to a BJWSA regional facility. The military base, Marine Corps Recruit Depot, trains about 17,000 recruits each year. BJWSA had previous experience with both Mears Group and UGSI during installation of 5,120 feet of 10-inch FPVC in 2008 to deliver reuse water to the Secession Golf Course on Lady’s Island. For two years, that stood as the record breaking crossing in a single pull using thermoplastic pipe.

The first crossing of this most current project is the longest installation of fusible PVC with a drilled length of 6,400 feet. Installing the crossing from Jericho Island to Little Horse Island, the Mears’ crew drilled under tidal marshland on either side of Archers Creek, utilizing their 500,000-pound rig on the entry side at Jericho Island. They set up their 140,000-pound rig at the exit side of the crossing at Little Horse Island to assist in the pre-reaming operations. Mears used a jet sub with a 9 7/8 inch bit during the pilot hole drilling. Drilling through clays, cemented sands, shells and gravel took careful steering. During pre-reaming, Mears opened the hole in three stages starting off with an 18-inch hole opener, then 26 inches and finally 34 inches. Before attempting to install the pipeline in the drilled crossing a barrel reamer was used to swab the hole.

Pipe strings
Because of the space restrictions and a requirement to keep traffic flowing on a busy road on the military base until the last minute, two prefabricated pipeline strings had to be fused together the day before the pullback.

Down hole pressures and pull force were monitored carefully throughout the 20-hour installation period. For this project with known conditions and confidence in the experience of the HDD contractor, UGSI allowed a maximum pulling load of 175,000 pounds on the pipe – in practice, the maximum tensile load applied at the drilling rig was only 83,000 pounds.