Two methods of trenchless construction are being employed in a project to improve the water infrastructure on the island nation of Barbados. Using these trenchless methods on this segment of the project allows aging water mains to be replaced while greatly limiting the amount of excavation needed to bury pipes.
Barbados construction firm Infra Inc., an infrastructure specialist, used the technologies of horizontal directional drilling (HDD) and pipe bursting to limit surface damage and interruption of routine activities along the project route. Some of the pipe being replaced had been in the ground more than 100 years.
The project is the first in Barbados to use these trenchless methods.
To install pipe by HDD, the drill unit bores down to the necessary depth, and the operator levels the path to the exit point. The bore proceeds to the exit point where pipe is connected to the drill string and pulled back through the pilot hole.
With pipe bursting, a powerful winch pulls a bullet-shaped tool through existing pipe, breaking up the old pipe and pulling in new pipe behind it. Excavation is minimized because new pipe follows the path of the old pipe.
Infra Inc. is installing approximately 11 miles of pipe ranging in diameter from 6 to 16 inches using HDD and pipe bursting.
“Methods of construction were determined by project owner, Barbados Water Authority,” said Roger Gill, Infra Inc. general manager. “The directional drilling and pipe bursting segments are projected to be completed in December 2015.”
Gill said the project owner is very satisfied with the new technology being used.
“Directional drilling,” Gill said, “is used to install new mains primarily under existing services, including natural gas, electricity, telephone/data, and other water mains and where there is enough room for the expansion not to cause damage to these adjacent services.
“Pipe bursting is used where there is an existing main that can be shut off and water temporarily bypassed while the pipe is forced through the main.”
These two installation methods use high-density polyethylene (HDPE) pipe in sizes from 6 to 16 inches. Lengths of pipe are butt fused together prior to installation.
“HDPE pipe was used for the eastern part of the country and in the capital, Bridgetown,” Gill explained. “Soils in this area generally are clay, which is unstable making open cutting not appropriate. HDD is also used in the capital since open trenching would be too disruptive to both vehicular and pedestrian traffic.”
PVC pipe in diameters from 6 to 12 inches subsequently was used in areas where open-cut construction was employed.
A Ditch Witch® JT100 All Terrain (AT) directional drill was used on the project. The 268-horsepower (200-kW) machine develops 100,000 pounds (445 kN) of pullback and rotary torque of 12,000 foot pounds. The AT designation represents the dual-pipe mechanical drilling drive that equips the machine to drill through hard rock formations without the use of a mud motor.
“The AT model was selected for the project because of the rocky soil conditions,” said Gill. “Thus far, it has met our expectations.”
The drill unit used Ditch Witch downhole bits and backreamers, and Subsite® Electronics tracking equipment to guide the pilot bore.
According to Gill, the project is projected to include 12 bores ranging in length from 400 feet to 1,500 feet with the average bore being 900 feet.
Pipe bursting segments were done with a HammerHead® HB100 static pipe-bursting system, which develops 100 tons (89 tonnes) pulling power. When completed, 55 bursts will be made averaging 400 feet in length, with the longest being 450 feet.
The Barbados Water Authority (BWA) potable water infrastructure includes more than 2,000 miles of transmission and distribution lines. Water sources are springs, wells, and desalination to complement the general water supply. BWA also is responsible for wastewater treatment and disposal.
The JADA Group, headquartered at Spring Hall in St. Lucy, is the primary organizer of the HDD/pipe bursting segments of the project. JADA Builders is the primary contractor and Infra Inc. has been utilized for the specialized trenchless segments. Other JADA companies involved include Infra Rentals, Bess Mining, and Cemix.
In addition to directional drilling equipment, including drill pipe and downhole tools; the Ditch Witch factory manufactures trenchers, vibratory plows, vacuum excavators, and compact utility equipment. Subsite Electronics manufactures HDD tracking systems and utility locators. HammerHead products include pipe bursting, piercing tools, pipe rammers, CIPP liners, HDD downhole tools, and rock hammers. All are members of the Charles Machine Works, Inc. family of companies.
Barbados is considered the easternmost of the Caribbean islands and is a leading tourist attraction. Says the Lonely Planet travel guide: “Barbados has it all: beach resorts from humble to grand; smashing nightlife, Bridgeport, a UNESCO World Heritage capital; a beautiful interior dotted with gardens; wild surf on the lonely east coast, and a proud and welcoming populace.”
Twenty-one miles (34 km) long and 14 miles (23 km) across at its widest point, Barbados actually is in the Atlantic Ocean, 250 miles (400 km) northeast of Trinidad and Tobago and outside the principal Atlantic hurricane belt.
Barbados is an independent country within the Commonwealth of Nations (previously the British Commonwealth).