The Shetland Islands are a subarctic archipelago off the northeast coast of Scotland at the virtual crossroads of the North Sea and Atlantic Ocean. The islands have spectacular cliffs, deep-sea inlets, rock-strewn hillsides, miles of peat bogs, and underground caverns that open to the sea. Beautiful, arable land and heather-covered slopes are also part of the islands’ allure.

The islands, which belong to Scotland and are subject to Scottish laws, are part of the United Kingdom, governed by UK traffic regulations, and are part of the UK postal network. The population speaks standard English, although the old Shetland dialect can still be heard.

Much of the Shetlands’ appeal is its remoteness, yet residents enjoy most of the services and benefits of larger cities—except a high-speed connection to the Internet.

However, this is in the process of changing.

Thirteen miles of fiber-optic cable has been laid between Lerwick, Shetland’s largest town, and Sandwick. Shetland Telecom, a unit of the Shetland Islands Council (SIC), hopes that the fiber network will transform communications between Shetland and the wider world to help attract new businesses by giving private telecommunications firms the capability of offering super-fast Internet speeds to their customers.

The fiber route is along road A970, and the use of an innovative new construction technique significantly lowered the cost of placing the cable underground.

Shetland-based contractor Tulloch Developments used a new microtrenching machine to cut a narrow trench in the paving adjacent to the roadway in which the cable was placed.

Not only does the equipment make it faster and less expensive to install the cable, it is more environmentally friendly, said Shaun Tulloch, project manager. Because the cut is only 20 mm (0.75 inches) wide and about 115 mm (4.5 inches) deep, there is less damage to the surface, which reduces disruption of road traffic and makes filling the trench faster and less costly, compared to other types of construction.

Equipment used for the project is a Ditch Witch^® MT12 MicroTrencher, a specially equipped four-wheel-drive RT45 trencher with a saw blade using replaceable carbide bits for cutting asphalt.

Tulloch said production averaged 450 meters (1476 feet) per day. “We are laying four to six times more cable in a day compared to normal open-cut excavation,” said Tulloch. “The slot we cut in the road is only 20 mm wide compared to 200-300 mm (7.9-11.8 inches) wide with an excavator. The cost per meter is slightly more, but our output is far higher, so overall cost is lower.”

Tulloch describes the process.

“First, a trench is cut with the Ditch Witch machine. Then we have a powerful Ditch Witch FX20 vacuum excavator that we use to clean the trench. We then use a fiber screed lance, which is a combination of compressed air and a propane burner, to further clean and dry the trench.

“A foam packer is then laid in the trench followed by the preloaded fiber cable, which is preloaded in HDPE duct, and then a stainless steel tracer wire is attached to the duct, and then another foam packer applied.”

Crack fill material is placed in the remaining void to complete reinstating the road surface.          

“Once cable is in the ground, we subcontract a telecommunications company to join and test each section of cable. Then it’s handed over to the council for connection to their network.”

Tulloch said the Ditch Witch MT12 MicroTrencher has performed well.

“Teeth and blade wore more than we anticipated,” he said. “There’s no consistency. Some days we would get 200 meters (656 feet) out of a set of teeth. Then the next day we might only get 60 to 80 meters (197 to 263 feet). We believe it’s caused by a variation of the abrasiveness of the surface dressing aggregate. We’ve seen this before with our ready-mix concrete.”

The teeth mount on a circular blade is enclosed in a shield. Blades are available in three width sizes: 19 mm, 25 mm and 32 mm (0.75, 0.95 and 1.25 inches). Trenching depth can be altered by raising and lowering the cutting motor on the saw in 25 mm increments. Tulloch said the minimum cutting depth on the saw used on the project was 150 mm (5.9 inches), but because project specifications allowed to cut to a maximum depth of 120 mm (4.7 inches), a steel packer was welded to the underside of the skid that floats on the road surface to provide the cutting depth of 115 mm (4.5 inches).

The blade can hydraulically travel 610 mm (24 inches) to right of the center point for cutting adjacent to curbs or other obstacles and can be manually tilted six degrees to the right or left for working on slopes. The blade is powered by a direct-coupled, high-torque digging drive motor.

During trenching, the microtrencher system’s Ditch Witch FX20 vacuum unit can be positioned either in front of the trencher or to the rear, removing spoils as they are created by the saw blade, reducing cleanup time and labor expense. In addition to its vacuum capabilities, the FX20 also is a “soft” excavation machine, using high-pressure water to displace soil for making “potholes” to uncover existing utilities. 

Shetland broadband deployment had been a special project for economic development official Marvin Smith, who has been working on how to improve broadband for several years. He said the next step would be transferring the benefits to every remote area of Shetland.

Based in the Shetland Islands, Tulloch Developments Ltd. was established in the 1970s as a builder of private homes, and their building expertise grew to include council housing schemes, care homes and leisure centers.

 In the mid 1990s, company directors made the decision to switch to the civil engineering side of construction. Since then, the company has completed major contracts for various national organizations in different disciplines of engineering.

“We are currently constructing a new berthing facility for the Lerwick Port Authority in Lerwick, clearing sites to enable works for new houses for the SIC, and restoring an old stone pier for the Sandsayre Pier Trust,” said Tulloch.

In addition to the Shetland fiber project, utility-related contracts have included a series of transformer upgrades for Scottish & Southern Energy, and laying the Faroese Fibre cable from the west side of Shetland to the east side. This cable links Faroe, Shetland & Orkney with the UK mainland, and the cable for Shetland telecom will be connected to this network.

The M12 MicroTrencher is manufactured in the United States by The Charles Machine Works, Inc. Other products in the DitchWitch line include a variety of sizes of trenchers and vibratory plows and attachments; horizontal directional drilling equipment, drill pipe, downhole tools, and electronic tracking systems; compact utility equipment, vacuum excavators, pipe and cable locators, and related equipment.

Assisting Tulloch on the project was Mark Davies at Ditch Witch of the United Kingdom.