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<p>This paper examines the planning, design, and construction of the 15.3&#xa0;km Headrace Tunnel (HRT) in Sri Lanka’s Uma Oya Multipurpose Development Project (UOMDP). The project was approved under a USD 514&#xa0;million EPC contract, with a benefit-cost ratio (BCR) of 1.328 and an expected internal rate of return (EIRR) of 13.06%, based on a 10% oil price increase. However, limited geological analysis and planning led to unanticipated socio-political challenges, resulting in a nine-year delay, and an additional USD 39&#xa0;million in direct costs. Excavation, conducted using two Tunnel Boring Machines (TBM), encountered excessive groundwater ingress - highlighting the need for advanced geoengineering solutions and expertise to stabilize the HRT. This study explores the geoengineering, environmental, and financial challenges involved, and evaluates the risk management and decision-making processes used to address them. Technical interventions, including post excavation angled hole grouting and pre-excavation grouting were effective in controlling water ingress and securing tunnel integrity. The delay resulted in estimated revenue losses of USD 700&#xa0;million from power generation, USD 110&#xa0;million from irrigation, and USD 12.7&#xa0;million from drinking water supply. The findings underscore the necessity of proactive on-site management and continuous monitoring to mitigate risks that could lead to social unrest and financial setbacks. The analysis highlights the integration of geo-engineering strategies, financial planning, and effective management as essential components for successful project delivery and long-term profitability. These insights serve as a valuable reference for future tunnelling projects to avoid delays and optimize outcomes.</p>

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Challenges and implications of deep tunnel construction in Uma Oya: a geo-engineering, environmental, and socio-political perspective

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月27日

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  • M. G. S. Jayanath,
  • H. A. H. Jayasena,
  • B. Gunaratna

摘要

This paper examines the planning, design, and construction of the 15.3 km Headrace Tunnel (HRT) in Sri Lanka’s Uma Oya Multipurpose Development Project (UOMDP). The project was approved under a USD 514 million EPC contract, with a benefit-cost ratio (BCR) of 1.328 and an expected internal rate of return (EIRR) of 13.06%, based on a 10% oil price increase. However, limited geological analysis and planning led to unanticipated socio-political challenges, resulting in a nine-year delay, and an additional USD 39 million in direct costs. Excavation, conducted using two Tunnel Boring Machines (TBM), encountered excessive groundwater ingress - highlighting the need for advanced geoengineering solutions and expertise to stabilize the HRT. This study explores the geoengineering, environmental, and financial challenges involved, and evaluates the risk management and decision-making processes used to address them. Technical interventions, including post excavation angled hole grouting and pre-excavation grouting were effective in controlling water ingress and securing tunnel integrity. The delay resulted in estimated revenue losses of USD 700 million from power generation, USD 110 million from irrigation, and USD 12.7 million from drinking water supply. The findings underscore the necessity of proactive on-site management and continuous monitoring to mitigate risks that could lead to social unrest and financial setbacks. The analysis highlights the integration of geo-engineering strategies, financial planning, and effective management as essential components for successful project delivery and long-term profitability. These insights serve as a valuable reference for future tunnelling projects to avoid delays and optimize outcomes.