How do you decide whether to spend $12 million replacing a 93-year-old water main or far less in targeted repairs? For the City of Baltimore, that question became urgent when a critical 36-inch cast-iron transmission main beneath Clifton Park Golf Course began experiencing recurring joint leaks.
The pipeline, built in 1932 and cement-lined in 1982, remains a vital link in the City’s water distribution network with many decades of remaining service life. While the City could continue repairing nuisance leaks as they surfaced, their frequency pointed to a deeper question:
Was the pipeline’s barrel beginning to fail due to age, or were the joints the primary source of trouble?
Answering that question was essential. The City needed a reliable, non-disruptive assessment to guide decisions about rehabilitation or full replacement, with the goal of minimizing costs, service interruptions, and traffic control impacts for the surrounding community.
To evaluate the condition of this transmission main, RJN deployed AVA, a non-invasive solution that measures the pipe’s dynamic response to controlled vibrations, powered by KenWave’s Dynamic Response ImagingTM. Unlike traditional inspection methods that require the line to be taken out of service or equipment to be inserted inside, AVA allows data to be collected while the pipeline remains fully operational.
RJN captured readings at 500-foot intervals along the main, using seven existing appurtenances and nine new potholes. This spacing achieved sub-pipe-stick resolution, providing a detailed view of wall thickness for each 6.6-foot pipe segment.
Through a series of controlled frequency tests, a wave generator excited the pipe while sensors recorded its response. RJN’s team correlated those vibration patterns to the pipe’s wall stiffness. This mapping revealed changes in wall thickness and hoop stress (the circumferential stress acting around the pipe wall along the entire alignment.
To validate the analysis, RJN compared the AVA results to a pipe segment removed during a 2023 hydrant installation. This sample showed a remaining wall thickness of 1.175 inches, which closely aligns with the results and provides strong confidence in the assessment's accuracy.
The technology proved very accurate. We recovered a pipe segment from a 2023 hydrant installation, and its measured thickness aligned perfectly with the AVA results—the data was spot on."
--Carlos Espinosa, PE - RJN Project Manager
The AVA analysis provided clear answers. Despite its age, the pipeline remains structurally strong. AVA testing revealed wall loss ranging from roughly 4-27%, with no segments showing distress levels that would indicate imminent failure. Approximately 15% of the pipeline fell into the good category (<10% wall loss), while the remaining 85% showed moderate loss between 10-30%. None of the sections exceeded the 30% threshold that would warrant immediate action.
In short, the data indicated that the pipeline remains structurally sound with decades of remaining useful life. The true vulnerability lies at the joints, where minor but persistent leaks have driven maintenance needs and raised operational concerns.
These findings raised an important question: if the pipeline is sound, how much longer can it be expected to serve? While precise remaining useful life prediction was not the goal of this study, RJN’s engineers modeled linear deterioration rates across all tested segments to better understand remaining structural capacity. The analysis indicated that the pipeline retains robust overall wall thickness and should continue to provide reliable service well beyond its original design life under current operating conditions.
These figures are not literal forecasts but rather indicators of the barrel’s significant safety margin and remaining service life. The results confirmed that the cast iron pipeline retains ample wall thickness and strength to continue performing well beyond its original design life.
The KenWave technology reaffirmed the City’s belief in targeted condition assessment of the pipe over wholesale replacement, by allowing to assess condition at pipe-level basis, which helped in decision making to address critical pipeline infrastructure at a fraction of the cost over replacement."
--Harpreet Singh - City of Baltimore Project Supervisor
From a risk perspective, the primary operational concern is not catastrophic failure of the pipe wall, but nuisance joint leaks that contribute to maintenance costs and localized service disruptions. These joint-related issues can lead to traffic impacts and recurring field repairs, but they do not represent a structural risk to the transmission main itself.
With the barrel’s condition confirmed, RJN could present the City with rehabilitation alternatives. The AVA investigation not only verified the main’s structural integrity but also opened the door to a range of rehabilitation options. By verifying the barrel’s strength, RJN gave the City confidence to pursue targeted solutions instead of defaulting to full pipeline replacement.
Several feasible strategies were evaluated, including internal joint seals, lining, and structural renewal methods. To support final design decisions, RJN recommended broadband electromagnetic (BEM) testing on segments with slightly higher wall loss to refine wall thickness estimates, and hydraulic modeling to confirm flow capacity if sliplining were to be pursued. When paired with the affordability of AVA testing, each rehabilitation option achieved significantly lower total investment savings compared to the costs of full replacement and far fewer construction and traffic impacts.
AVA allowed the City to shift from a single, high-cost replacement plan to a suite of informed rehabilitation choices. This approach provided the utility with peace of mind for a critical asset, while maximizing value and focusing on only impactful rehabilitation options.
RJN’s application of AVA technology reframed long-held assumptions about the condition of one of Baltimore’s most critical transmission mains. The results showed that the 93-year-old pipe remains structurally sound and that recurring maintenance issues stem from leaky joints rather than impending pipe failure.
This project marked more than a successful assessment. It represented a paradigm shift in how aging infrastructure can be managed. By applying modern, non-invasive diagnostics to legacy assets, the City demonstrated how innovation and pragmatism can coexist. With data guiding each decision, Baltimore turned a potential multimillion-dollar replacement into a targeted rehabilitation strategy that preserves capacity, minimizes disruption, and upholds responsible stewardship of public funds.
In a broader sense, this outcome illustrates the evolution of infrastructure management: a move from reactive maintenance to intelligent reinvestment. Through technology and insight, cities can extend the life of their buried assets, direct capital where it’s most effective, and sustain the systems that keep communities running for generations to come.