Seeing through the Ground: The Potential of Gravity Gradient as a Complementary Technology

In the UK there is a huge legacy of buried utility service pipelines and cables beneath our streets and new services, such as fibre optic cables, are being added all the time. Much of this utility network is poorly mapped and recorded. It is therefore important to accurately locate and map these services to aid the installation of new, and repair and maintenance of existing, assets. This will help avoid damage to adjacent services and reduce the direct and social costs associated with finding buried utilities. This paper describes two major UK initiatives—Mapping the Underworld (MTU) and Gravity Gradient Technologies and Opportunities Programme (GG-TOP)—that aim to improve the way that we locate, map, and share information on buried utility services. MTU aims to develop a multisensor device to locate buried services, while GG-TOP aims to develop gravity gradient technology to deliver a (three orders of magnitude) step change in performance. 1. Introduction Most utility services, including electricity, water, gas, and telecommunications, are distributed using buried pipelines or conduits, or via directly buried cables, and the majority of this buried utility infrastructure exists beneath roads. Trenching is usually required whenever they need maintenance, repair, replacement, or extension and this often causes disturbance (and sometimes damage) to other utility services, delays to traffic and/or damage to the environment. Inaccurate location of buried pipes and cables results in far more excavations than would otherwise be necessary, thereby creating a nuisance and increasing the direct costs of maintenance to the service providers, while greatly increasing the costs to others, the most important being the enormous direct cost of traffic delays to business and direct and indirect costs to private motorists. These “social costs” of congestion in the UK alone are estimated to be as high as billion per annum [1], 5% ( million) of which is attributed to street works. There are also very considerable environmental “costs” due to traffic congestion, a significant proportion of the damage to the planet due to motor transport deriving from vehicles that are delayed. Nevertheless, utility service providers, who are under enormous pressure from the regulators to improve performance in all sorts of ways and minimize costs to customers, retain the open cut approach and accept the inconvenience of “dry holes” (excavations that miss the target service) as a marginal cost addition. It is important that this attitude changes, but it will only do so when the utility