The Role of Surface and Subsurface Geophysics in Enhancing the Ground Model on a Deep Sewer Tunnel

Abstract

g the Strategic Tunnel Enhancement Programme (STEP) to improve the sewerage systems in Abu Dhabi city. STEP comprises a deep sewer tunnel, link sewers and an underground pumping station. The city has experienced vigorous economic and social growth since the 1970’s, when the majority of its sewer system was designed and constructed. Today this growth continues under the framework of Abu Dhabi’s long term master plan, referred to as ‘Plan Abu Dhabi 2030’. The growth is acute in the metropolitan area, where large scale development is occurring on an aggressive timescale and the population is expected to double within ten years. As a result, ADSSC sees many of its sewerage assets being overloaded and approaching the end of their intended service life. Two key drivers for ADSSC’s consideration of a deep tunnel sewer system were limited available land within Abu Dhabi for development and the need to build an efficient, cost-effective and reliable sewerage infrastructure to ensure it could support long term population and industrial growth. STEP is intended to have a design life of 80 years. The deep sewer tunnel is designed to be self-cleansing and to meet the hydraulic design criteria the tunnel alignment will fall at a gradient of 1 in 1300 from north to south. At the southern end of the alignment, a new pump station (PS) will lift the sewerage and discharge into an independent sewerage treatment plant (ISTP), where it will be treated and reclaimed as treated sewage effluent (TSE) for return to the metropolitan area for irrigation purposes.