Design Considerations for a Sea Water Conveyance Pipeline in Chilean Mining: A Case Study

Abstract Chile, rich in mineral deposits, faces an acute water shortage in its arid mining regions. With increasing industrial and local demands, mining companies are aligning with the national mining policy for 2050 by investing in seawater conveyance infrastructure to reduce continental water consumption. The challenge lies in conveying this water from coastal facilities, traversing the challenging topography of the Andes to reach mining sites above 2,000 m.a.s.l, necessitating water conveyance pipeline infrastructure over extensions of 140 km. This paper focuses on the design complexities encountered in conveying seawater to a major copper mining operation in the region of Antofagasta, a hub of mining activity in Chile’s copper mining sector, addressing critical challenges associated with seawater corrosivity, variable flow capacities, energy efficiency, seismic risks, and steep topography. For the case study presented, the pipeline is in API 5L X70 bare steel, with corrosion allowance, NPS 36″, as the result of life cycle cost analysis. The study details the approach to optimize the hydraulic design, incorporating historical data analysis for internal pipe roughness and corrosion rate determination due to seawater’s corrosive nature. The pump selection process is explored, emphasizing the need for strict tolerance specifications to ensure design capacity and energy efficiency in the face of the pipeline’s dynamic design requirements. Practical insights are shared regarding pump and electric motor, utilizing Variable Speed Drives (VSD) to accommodate multiple duty points throughout the pipeline’s operational life. Given the seismicity of the project area, arising from the convergence of the Nazca and South American plates, the study underscores the necessity of a comprehensive seismic risk study to determine design parameters. Additionally, the pipeline’s route presents a unique construction challenge, due to steep elevation changes from coastal facilities to above 1,000 m.a.s.l through a coastal cliff range, within the first 30 km of the pipeline. The study addresses this by providing specific considerations for a specialized construction methodology suitable for high steep slopes. In conclusion, this case study presents key multifaceted design considerations required for a seawater conveyance pipeline in Chilean mining. by tackling the issues of corrosivity, variable flow capacities along with energy efficiency, seismic risks and pipeline construction in steep topography, the paper offers valuable insights for engineers and stakeholders involved in similar projects. The comprehensive approach presented ensures the resilience and robustness of the pipeline infrastructure throughout its operational life, contributing to a sustainable water availability for the mining operation. The information is presented in general terms, as not to disclose private information.