Nov 2003 - No-Dig International
by Ian Clarke
NDI Editor
As part of its ongoing development, The University of Cardiff in Wales, U.K. is currently undertaking a major investment programme to install a high speed fibre optic cable network linking all of its educational facilities and campuses around the city, as well as the Cardiff Hospital which is also a medical training unit. The internal network will enable instant communication across the University which has various facilities and operational sites across Cardiff. A 48-core single mode fibre cable is being installed which is designed to accommodate both current and projected use.
PROJECT
The basic scheme to install the fibre network was put to tender amongst some 4 or 5 different contractors. On examining the installation bids the University found that one bid came in not only significantly below all other offers but also allowed the University to complete the installation in a much-reduced period of time. The project was awarded to contractor Neo Networks which placed a bid to use the TeraSpan installation system across a significant proportion of the planned 7.25 km project route. In all some 3 km would be installed using the TeraSpan technology, with 2.25 km being completed using conventional open cut and finally re-cabling of 2 km of existing ducting. TeraSpan Networks itself is undertaking the installation of its system on site.
The open cut section was completed as such due to various requirements including the existence of other services on the route and other installations, which were also required under the terms of the contract.
TERASPAN
TeraSpan comprises what is essentially a digging technology but one which uses the very minimum of excavation, which is why it can be classed as a 'trenchless' technology. The system, which was designed in North America, basically uses a circular road saw to cut a narrow (6 mm) groove in the road or walkway surface along the required route. Into this groove the fibre cable is laid and back filled completing the installation.
A typical installation section would run as follows: The utility and services plans for the route to be worked are obtained from the various utility companies, including Gas, Water and Wastewater, Power and Telecoms, to obtain information about existing buried equipment. The route is then surveyed using a CAT and Ginnie to confirm expected positions. Where services cannot be detected using the electronic survey the plan positions of services are marked on surface.
The circular road saw is brought in and set up to cut the required groove on the marked route. The speed of this operation also ensures that any traffic disruption is kept to an absolute minimum. For example, during the visit of No-Dig International to site in Cardiff, cutting of a full crossing of a busy access route in to the City Centre was completed in less than 1 hour from curb to curb using single lane traffic control with 'Stop/Go' boards. There was also no need to cover the narrow groove once cut as traffic could pass over it with ease, allowing the road to be fully open whilst awaiting cable installation.
Once cut and available for cable installation the groove is jetted clean to remove any debris that could cause cable damage. The cable is then installed directly from the cable drum. A foam packer is then installed above the cable for protection and the groove is finally filled with a bitumen compound to surface.
Where cable connections or spare cable is to be installed the 6 mm groove is simply opened out to about 15 mm width, over a length of about 500 mm. In this box slot a cable storage device is placed which can store several metres of cable, allowing for damaged sections to be replaced or tie in connections to be made in a short space of time.
SPEED
One of the main advantages to the TeraSpan system is its speed compared to more conventional systems. At the time of NDI's visit to the site the TeraSpan systems had been working for just 4 days with almost 700 m of cable installed and backfilled to finished surface requirements. TeraSpan's aim is to complete the work at an average of 160 to 200 m/day over the duration of the project, which compares to averages of around 30 to 40 m/day conventionally.
At the time of writing it had just been announced that TeraSpan had been awarded a DTI (Department of Industry) Telecom operators license (with Code Powers) for the U.K.