Utility infrastructure systems, designed well, have a pivotal role to play in improving the sustainability of cities due to their critical functionality in urban environments. Equally, utility streetworks – installation, maintenance and upgrading activities – can adversely impact the local and global economies. The inaccurate location of pipes and cables lengthens streetworks operations and can exacerbate traffic congestion, notably resulting in major delays in cases of third-party utility damage, while vehicle emissions and wasted energy are other examples of the adverse impacts of congestion caused by streetworks operations. The total impact of utility infrastructure projects can be assessed only by evaluating all economic (both direct and indirect), social and environmental costs of streetworks. A dedicated tool for evaluating the sustainability impacts of utility streetworks is required. This paper provides the basis for utility streetworks sustainability assessments, and hence full costing, by critically reviewing existing sustainability assessment tools and making recommendations for developing a total sustainability costing model and indicator system.

The underground utility infrastructure (UUI) will play a crucial role in meeting the demand for creating sustainable and resilient urban developments that are fit for purpose today and in the far future. The utility streetworks operations, an important feature of the UUI system, include placement, maintenance, rehabilitation, renewal and upgrading of UUI, which can have adverse economic, social and environmental impacts. A key challenge, and one that will lead to lost opportunities for the best use of the near surface for utility provision for future cities, is the lack of a sustainability indicator system and assessment method for evaluating different utility streetworks solutions. To address this shortfall, this paper presents a new suite of indicators, or performance criteria, bespoke to utility streetworks projects as well as a pre-appraisal method based on the adaptation of the Arup SPeAR ® sustainability evaluation framework. An example of the application of the modified system is provided for a trenchless against trenching case study, and the lessons that flow from this are discussed in the wider context of the synthesis of utility service operations into sustainable, resilient, smart and liveable cities of the future.

Cast iron water distribution pipes are used widely in the UK and worldwide. Corrosion of these cast iron pipes often occurs due to an electrochemical process where the pipe is buried directly in a chemically aggressive ground (as is the case for some clays). The electrochemical process changes the pH environment and releases iron ions into the clay. This can cause chemical alteration of the clay minerals and 'corrosion products', such as iron oxide, hydroxide and aqueous salts, to form in the soil. These chemical interactions are complex and time dependent, and can potentially result in pipe failure, and thus the conditions under which they occur need to be understood. Ground Penetrating Radar (GPR) has been proposed for routinely detecting, assessing and monitoring buried cast iron pipes, and thus it is important to know how these chemical changes affect the electromagnetic properties of soil. A bespoke set of laboratory experiments was devised to simulate and accelerate cast iron corrosion (using electrokinetics) and ion migration processes in two types of clay, namely Kaolin Clay and Oxford Clay. Tests were conducted for periods of up to 3 months using both inert electrodes and a cast iron disc as the anode. The changes in the geotechnical properties (undrained shear strength, moisture content and Atterberg limits), the geophysical properties (permittivity) and the geochemical properties (iron content, pH and conductivity) were monitored. The results indicated that the Oxford Clay was much more aggressive in terms of the corrosion activity compared to the Kaolin Clay. The laboratory results were used in GPR simulations in relation to the detection of a buried cast iron pipe. The results showed that the chemically induced changes to the Kaolin Clay did not materially affect the performance of GPR to detect the cast iron pipe, whereas a pipe buried in Oxford Clay the (greatly accelerated) chemically-induced changes were sufficiently advanced after approximately 7-8 weeks to cause the GPR to be unable to detect the corroded pipe.

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