Innovative Sensor Array for Sewer Survey (ISASS) Sewer systems around the world are ageing and their performance is deteriorating. More frequent sewer blockages and collapses result in raw sewage flooding into houses and spilling into rivers more often and with increased severity, causing much damage, distress and pollution. Water companies need more information about their sewer systems so that they can plan where and when to carry out detailed inspection, cleaning and repair. Under Ofwat regulation, water companies in England and Wales have committed to meeting stretching flooding and pollution targets. If they succeed, they will gain financially to recognise the benefit that the communities they serve have benefitted from better service. If they fail, they will suffer financial penalties. The problem they all have to address is what to do and where to do it to control their sewer systems to meet and exceed the targets. The traditional CCTV inspection is slow and costly, which has resulted in only a small percentage of sewer system ever having been inspected even once. The use of acoustics for sewer survey has been developed in the UK over the last 10 years and provides a means for water companies to survey more of their sewer networks quickly and cheaply, and to do it more often. In the UK, Acoustic Sensing Technology (UK) Ltd has been providing the SewerBatt system since 2013\. The time is now right to bring together the experience gained since the company was established with the expertise of world-leading researchers at the University of Sheffield to develop the next generation of sensors. ISASS will use acoustic numerical simulation to produce digital prototypes of sensor arrays and simulate their performance in digital representations of many different configurations of sewers and the defects they contain. Bypassing the need to build multiple physical sensor arrays and test them in many different real, live, sewers will dramatically accelerate the delivery of the optimal next generation sensor. Once the design has been optimised by simulation the final design will be produced in the metal and field tested to confirm its performance. Finally, the ISASS project will develop a version of SewerBatt for long-term installation in manholes, designed to provide data for prioritising cleaning and repair of sewers and drains while minimising the need to physically access them.