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Over-the-line Potential Surveys for Indirect Condition Assessment of Water/Waste Water Pipelines: Case Studies

Picture for Over-the-line Potential Surveys for Indirect Condition Assessment of Water/Waste Water Pipelines: Case Studies
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Failure of water/wastewater mains can result in high visibility repairs customer inconvenience and replacement costs. Preventive measures such as condition assessment for early recognition of corrosion in aging infrastructures is crucial for agencies from resiliency safety and economic standpoints but is not regulated as in the oil & gas industry. Internally deployed tools/technology or external excavations for direct assessment techniques provide valuable insight on the existing condition of buried structures but at a significant cost in terms of shutdown and technology expenses in addition to safety concerns for manned entries into confined spaces. Because of the cost and safety implications large diameter cement mortar lined (CML) pipe extensive and recurring direct assessments are less common in the water and wastewater industries. Indirect assessment techniques particularly the over-the-line potential surveys for condition assessment of water/wastewater lines can be conducted to determine active external corrosion areas. Traditionally over-the-line potential surveys were applied to electrically continuous pipelines. Most water/wastewater pipeline designs utilize rubber gasket bell-and-spigot joints. Unless electrical continuity is intentionally designed for the pipeline such joints result in a pipeline with no electrical continuity. This paper presents multiple case studies where over-the-line potential surveys were successfully applied on electrically discontinuous water pipelines. The results of over-the-line surveys correlated well with direct assessment techniques. The paper presents the methodology and results of such assessments and findings for various pipe materials.

Product Number: 51319-13003-SG
Author: Mersedeh Akhoondan
Publication Date: 2019
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$20.00
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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.
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Retrofit and Management of Water Pipelines with Cathodic Protection: Case Studies

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ISBN: 9089 2017 CP
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Corrosion of metallic pipelines is a significant source of failures to drinking water utilities. Cathodic Protection has been used for buried metallic pipelines for decades but not widely used in the water industry. Preliminary findings of the on-going Water Research Foundation project.

 
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Cathodic Protection Retrofit for Rehabilitation of Aging Reinforced Concrete Municipal Water Infrastructure: A Case Study

Product Number: 51319-13002-SG
Author: Mersedeh Akhoondan
Publication Date: 2019
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Reinforced concrete towers in a water reservoir contain gates and the equipment to control the water entering the system. Any interruption in the operation of these towers may cause a huge disruption in the municipal water distribution system. Continuous operation in an aggressive environment often contributes to corrosion of aging water infrastructure. A failure due to corrosion would necessitate extensive repair or replacement costs and unacceptable system downtime. This paper presents a case study focused on a comprehensive condition assessment and corrosion mitigation of an aged forebay outlet tower in Southern California. The inspected tower - in operation since 1941 - is a crucial structure in a water distribution system serving most of the 19 million people in Southern California. The tower illustrated significant concrete deterioration and corrosion of the reinforcement above the operating water surface elevation. An impressed current cathodic protection (ICCP) system was designed and installed on the tower to extend the life of the structure. Field activities and ICCP installation were dictated by restricted shutdown schedules and operational constraints. The paper addresses the methodology for condition assessment and cathodic protection design as well as challenges encountered due to schedule/operational constraints.
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