Called the “Gospel Swamps” a century ago for the church-revival gatherings popular there, the southern California city of Fountain Valley later took its name from the area’s large artesian wells and unusually shallow groundwater basin that quite literally gushed water fountains after poking a stick into the ground any deeper than one foot.
Heavy water demand and usage has gradually lowered Fountain Valley’s high-water table by a few feet since the arrival of pioneer settlers, and yesterday’s open irrigation ditches have been long since replaced by a modern water distribution system serving the 56,000 residents of the thriving Orange County commuter suburb located south of Los Angeles.
Constructed during the high-growth building boom of the 1960s and 1970s, Fountain Valley’s water pipelines include more than 200 miles of asbestos-cement and coated-steel main pipelines that have largely been trouble-free over the decades — even surviving the region’s massive 1994 Northridge earthquake virtually unscathed. However, Fountain Valley’s Water Division is now facing a new threat to their pipelines that even the best water distribution infrastructure cannot avoid: age.
“We’ve been lucky to have experienced very few main pipeline leaks or breaks over the years, but statistical survival curves for our system estimate about half of our deteriorated mains will need replacing in about 10 to 20 years,” says Mark Sprague, field service manager with the Fountain Valley Water Division. “Our goal was to keep ahead of our aging infrastructure and avoid the scenario of constantly chasing up to 30 pipeline breaks per year with our small staff and budget. That’s why we brought in the Echologics team to determine the true condition of our pipeline mains using their ePulse technology.”
Acoustic-based Condition Assessment Technology
“Fountain Valley was facing the same problem as most utilities that are grappling with an aging infrastructure: having insufficient data to determine which pipe segments are the best candidates for replacement, and which pipes still have plenty of service life remaining,” says Charlie Fricke, Echologics distribution manager. “Too many utilities are still relying solely on ‘desktop’ assessment methods based on pipe age, construction type, and leak history to make expensive pipe replacement decisions. However, historical data and statistical analysis doesn’t tell you where the truly degraded pipes are located — but ePulse does.”
ePulse technology uses acoustic wave propagation (AWP) technology to identify sections of pipeline with reduced structural stiffness, and estimate the average remaining structural strength or wall thickness of a pipeline. Non-invasive and non-intrusive, this technology enables rapid inspection of large areas of a water distribution network without removing the pipelines from service, avoiding service interruptions, pipeline dewatering/cleaning, or costly excavations.
The ePulse technology involves inducing low-frequency acoustic pressure waves inside pipelines, measuring the pressure waves using sophisticated acoustic sensors connected externally to the pipe or appurtenances, then analyzing the acoustic data to determine pipe condition. The pressure waves cause the pipe wall to “flex” on a microscopic level, affecting the speed of the pressure wave detected by the acoustic sensors.
Thicker pipe walls are resistant to this pipe flexing, causing the acoustic pressure wave to travel faster within pipes in good condition. In contrast, slower pressure waves indicate pipe wall degradation and internal corrosion. Using the captured ePulse acoustic data, Echologics field engineers apply advanced algorithms to calculate the average minimum wall thickness of the measured pipe segment without ever entering the pipe itself.
Leak Detection Benefits
“The majority of our pipelines are 6-in. and 8-in. diameter asbestos-cement pipe, but even our larger 12-in. and 16-in. diameter steel pipe transmission mains are still too small for some other condition assessment technologies that require inserting an inspection device inside the pipeline — making ePulse the best choice for us,” says Sprague. “When we learned that Echologics technology was chosen for assessing and monitoring the huge water mains running down the middle of the famous Las Vegas “Strip,” we figured a solution that works for a critical water distribution system serving millions of visitors every year would also work for us.”
Engaged in the third year of a five-year condition assessment project with Fountain Valley that began in 2016, the City methodically targets different portions of the city’s water distribution system to be surveyed each year, with Echologics field survey crews covering up to a mile of pipeline per day. Equipped with specialized acoustic correlation equipment, the field crews deploy multiple acoustic sensors positioned anywhere from 300 ft to 600 ft apart along pipe segments. Attaching sensors to connected fire hydrants, valves, or directly to the exterior pipe wall, the crew performs the acoustic testing and measurements to determine pipe condition, average wall thickness — and the presence of potential water leaks.
“A unique benefit of ePulse technology is that it simultaneously analyzes captured acoustic data for the presence of pipeline leaks during a condition assessment survey,” says Fricke. “Avoiding the need to conduct separate leak detection inspections boosts the overall value of a condition assessment program, especially when ePulse detects a tiny leak in critical transmission main long before it develops into a big expensive problem.”
Echologics field crews detected no leaks in Fountain Valley’s critical pipelines surveyed during the first two years of the project, which included the city’s largest water mains running directly underneath the I-405 interstate freeway. However, the condition assessment surveys determined precisely which pipe segments were in good shape, and those that most likely will need replacing in the near future.
Condition assessment ratings involve assessing the percentage of pipe-wall “hoop” thickness loss, measured by comparing the measured hoop thickness to the original design or nominal thickness of the pipe wall. A loss of hoop thickness less than 10 percent results in a “good” rating, a loss of 10 to 30 percent results in a “moderate” rating, and a loss greater than 30 percent results in a “poor” rating for that section of pipe. The condition assessment reports detailing the surveys performed during the first two years were welcome news for Fountain Valley.
Fountain Valley’s condition assessment surveys completed in the first two years of the project identified 18 percent of the pipe segments as being in “good” condition, 65 percent in “moderate” condition, and 17 percent in “poor” condition. The pipe segments assessed as being in “poor” condition are mostly situated in isolated locations, possibly indicating localized corrosion or site conditions. It’s a favorable pipeline condition assessment report for 50-year-old water distribution system, although Fountain Valley’s condition assessment program still has another three years to go.
“This is what I was hoping for — the best-case scenario,” says Sprague. “I was budgeting $1.5 million per year to prepare for future pipeline replacements, so spending a fraction of that amount on this multi-year condition assessment program has resulted in a big savings for Fountain Valley. The Echologics condition assessment program enables our city to plan and prioritize pipeline repairs and rehabilitation, and stay ahead of our aging infrastructure. That’s the best part — it enables us to be proactive instead of reactive.”