LONG-TERM DATALOGGING
Continuous Monitoring of Pipe-to-Soil Potentials in Dynamic Stray Current Environments
Stray currents from DC-powered light rail transit (LRT) systems can have a significant effect on the integrity of nearby buried pipelines. The current that escapes from the rails into the surrounding soil follows paths of least resistance, picks up metallic structures, and eventually discharges back toward the substation. At the points of discharge, accelerated corrosion can shorten the service life of an otherwise sound pipeline by decades.
The challenge is that LRT stray current is dynamic, not steady-state. Single-point pipe-to-soil potential
measurements (the "snapshots" most corrosion programs rely on) tell you what was happening at one moment in time on one location on the pipe. They do not tell you what happens at peak train operations, under different seasonal conditions, or during scheduled LRT maintenance activities. Long-term datalogging captures all of that, and it is the only practical way to characterize the real interference environment a pipeline is operating in.
Cell-to-cell potential monitoring equipment installed near a light rail transit system to detect DC stray current on nearby buried pipelines
Long-term datalogging plot showing seasonal precipitation influence on pipe-to-soil potentials near a light rail transit corridor
Remote datalogger collecting continuous DC stray current and pipe-to-soil potential data along a light rail transit system
Cell-to-cell potential monitoring equipment installed near a light rail transit system to detect DC stray current on nearby buried pipelines
What Long-Term Datalogging Captures
A well-designed datalogging program runs continuously over days, weeks, or months, recording pipe-to-soil potential and other electrical parameters at intervals that resolve the dynamic patterns single-point surveys miss. The data ICG collects regularly reveals:
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Operational variation. Train movement patterns, traction power substation switching, and rail current return path changes all show up clearly in continuous data.
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Seasonal effects. Soil moisture, freeze-thaw cycles, and precipitation events shift the stray current picture in ways that a one-time survey cannot represent.
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Maintenance impacts. LRT track work, substation maintenance, and pipeline cathodic protection adjustments all produce signatures in the data that help diagnose root causes.
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Peak interference levels. The worst-case stray current conditions for a pipeline often occur during brief operational windows that snapshot surveys are statistically unlikely to capture.
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Mitigation effectiveness. Once mitigation is installed, datalogging is the only way to verify that the interference is actually under control across the full range of operating conditions.
How ICG Approaches Datalogging Programs
ICG designs and operates datalogging programs end-to-end. A typical program includes:
Site Selection
Choosing the right monitoring locations is the foundation of a useful program. ICG works with utility owners and transit agencies to identify points along the pipeline where interference is most likely, where mitigation is most likely to be effective, and where data will best support engineering decisions.
Equipment Installation
ICG installs remote dataloggers at each monitoring location, configured to record at intervals appropriate to the dynamics of the system being monitored. Most installations include cell-to-cell potential monitoring and pipe-to-soil potential measurements.
Data Collection and Management
Loggers record continuously over the duration of the study. ICG manages data retrieval, storage, and quality control, including identifying gaps, outliers, and instrumentation issues that need to be addressed in the field.
Data Analysis and Correlation
Raw data becomes useful only after it is correlated with environmental and operational variables. ICG analyzes datalogger results alongside LRT operating schedules, precipitation records, soil resistivity, and pipeline cathodic protection conditions to identify the factors driving stray current activity.
Reporting and Recommendations
Final deliverables include graphical presentation of the data in formats that engineering staff and non-technical management can both understand, written analysis of the findings, and specific recommendations for mitigation, additional monitoring, or operational changes.
Why It Matters
Long-term datalogging programs are not the cheapest option for assessing stray current on a pipeline. They are usually the most informative one. For pipeline owners, the cost of a well-designed monitoring program is a small fraction of the cost of either an unexpected stray-current-driven failure or a poorly justified mitigation project.
For transit agencies, datalogging serves a different purpose: documenting that stray current is being managed responsibly, supporting cooperative agreements with neighboring utility owners, and providing the technical record needed to defend the system if questions arise later.
ICG works on both sides of the equation, often as a neutral technical partner helping transit agencies and utility owners build the kind of shared understanding that makes long-term cooperation possible.