OR/17/009 Introduction

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Tye, A M, Kirkwood, C, Dearden, R, Rawlins, B G, Lark, R M, Lawley, R L, Entwistle, D, and Mee, K. 2017. Environmental factors influencing pipe failures. British Geological Survey Internal Report, OR/17/009.

This report details the results from two NERC grants examining the impacts of geological, environmental and landscape factors on the resilience of underground pipe networks. Our major partner in these Knowledge Exchange grants was Yorkshire Water (YW); one of the largest water and sewerage companies in the UK supplying 1.24 billion litres of drinking water per day. YW manage 31 300 km of clean water mains and respond to 6000–7000 bursts per year. Pipeline failures can result in loss of supply to properties, damage and closure of the public highway, closures or other inconveniences to business and the general public. Leakage (estimated to be about 275 Ml/day) from the mains water network results in loss of pressure, increased demands on water demand and treatment works (increasing carbon emissions) and water-related ground instability. YW also operate ~53 000 km of sewage pipe and respond to 200–300 sewer collapses per year. Sewer failures result in the flooding of homes and businesses with foul water and potential increases in insurance premiums for those properties affected. Importantly, sewerage leaking from collapsed sewers, also contributes to diffuse pollution of rivers and groundwater. Yorkshire Water expect to invest £140 m on clean water pipe renewal, repair and cleaning in the next 5-year asset management program (AMPs) and a similar amount is anticipated to be invested in maintaining and repairing the waste water network.

YW currently utilize a Below-Ground Asset Surveyor Predictor (BGASP) model to aid maintenance of their clean and waste water pipe networks. The BGASP model uses pipe age, material, diameter, previous failure locations, temperature and basic soil properties (i.e. type) to assess whether replacement pipe is needed. The overall model assessments are suitable for YW's planning of total investment value over the AMP cycle. This project aims to develop complementary models to those currently used by YW, with the aim of providing greater understanding of how pipe networks interact with their broader environments. Information used will include spatial soil characteristics (physical and chemical), landscape analysis, geological hazard properties and additional network or environmental factors. The project draws on BGS’s wealth of 1:50 000 datasets on soil properties (e.g. texture, depth, and chemistry), groundwater depth and geohazards. Algorithms applied to high-resolution digital terrain models will be used to predict indices such as local soil wetness (related to local topographic position and changes in topography). The project will utilize comprehensive datasets of clean and waste water failures supplied by YW (about 100 000 entries) that includes a range of pipe materials (cast iron, plastic, clay and concrete). These data are assessed using statistical methods to refine and quantify a conceptual model of the factors that control pipe failure. A key aim is to examine how the models developed may yield information relevant to water companies that will enhance the maintenance and resilience of pipe networks.