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51318-11064-Application of Indirect Condition Assessment Techniques for Buried Water Pipelines: A Case Study

Indirect assessment techniques (special over-the-line potential and soil corrosivity surveys) were applied on an electrically discontinuous effluent sewer land outfall. Critical areas were excavated and direct assessment performed.  Mitigation methods were recommended.

Product Number: 51318-11064-SG
Author: Mersedeh Akhoondan / Brien Clark / Graham Bell
Publication Date: 2018
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Failure of water/wastewater mains incurs heavy repair and replacement costs, in addition to customer’s inconvenience. Taking preventive measures such as condition assessment for early determination of corrosion in aging infrastructures is crucial for agencies from both a safety and an economic standpoint. Direct assessment techniques provide valuable insight on the existing condition of any buried structures. In an ideal case, agencies would have enough time, budget, and resources to reveal, excavate, and conduct direct assessment of their entire aging assets (e.g., miles of pipelines). In practice, such extensive assessments seldom occur and are not necessary. Indirect techniques (special over-the-line potential and soil corrosivity surveys) for external condition assessment of water/wastewater lines can be conducted to determine the high risk corrosion areas for further direct evaluation. This paper presents a case study where such indirect assessment techniques were successfully applied on an electrically discontinuous effluent sewer land outfall. Additionally critical areas were identified for excavation and direct assessment was performed. The results of direct assessment were in agreement with the over-the-line survey findings. The 40-year old sewer pipeline was located in environmentally sensitive areas (no tolerance for breaks) and may have become affected by nearby construction loads due to a road widening project. After the existing condition of the pipeline was determined mitigation methods for in-situ protection of the pipeline was recommended.

Key Words: corrosion, cathodic protection, close interval potential survey (CIS), water and wastewater pipelines, indirect and direct condition assessment, life extension, leaks, joints, electrically discontinuous pipe.

 

Failure of water/wastewater mains incurs heavy repair and replacement costs, in addition to customer’s inconvenience. Taking preventive measures such as condition assessment for early determination of corrosion in aging infrastructures is crucial for agencies from both a safety and an economic standpoint. Direct assessment techniques provide valuable insight on the existing condition of any buried structures. In an ideal case, agencies would have enough time, budget, and resources to reveal, excavate, and conduct direct assessment of their entire aging assets (e.g., miles of pipelines). In practice, such extensive assessments seldom occur and are not necessary. Indirect techniques (special over-the-line potential and soil corrosivity surveys) for external condition assessment of water/wastewater lines can be conducted to determine the high risk corrosion areas for further direct evaluation. This paper presents a case study where such indirect assessment techniques were successfully applied on an electrically discontinuous effluent sewer land outfall. Additionally critical areas were identified for excavation and direct assessment was performed. The results of direct assessment were in agreement with the over-the-line survey findings. The 40-year old sewer pipeline was located in environmentally sensitive areas (no tolerance for breaks) and may have become affected by nearby construction loads due to a road widening project. After the existing condition of the pipeline was determined mitigation methods for in-situ protection of the pipeline was recommended.

Key Words: corrosion, cathodic protection, close interval potential survey (CIS), water and wastewater pipelines, indirect and direct condition assessment, life extension, leaks, joints, electrically discontinuous pipe.

 

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