By the PICA Corp Engineering Team  |  Updated June 2026  |  Est. reading time: 9 min

A wastewater force main failure is not a maintenance problem. It is a public health incident. Sewage reaches the surface, enters waterways, and triggers EPA enforcement before the utility has finished locating the break. These failures generate headlines and consent orders, not just repair bills. They happen more often than utilities want to admit, because force mains are among the most under-inspected assets in any wastewater system.

The reason is structural. Force mains operate under continuous positive pressure, with few access points and nothing like the manhole spacing of a gravity sewer. The pipe is mostly buried metallic — ductile iron, lined steel, or bare steel — and the deterioration that causes failure develops inside and through the pipe wall. A conventional CCTV camera, even deployed after service isolation, does not see it. You need electromagnetic NDT that detects wall loss and corrosion through the pipe material itself, not just what is visible on the interior surface.

This page documents real force main inspection projects PICA has completed for utilities across North America. They range from a 40-year-old main running beneath a drinking water reservoir in San Diego to a sub-aqueous crossing in Florida to a comprehensive ductile iron assessment for Milwaukee’s regional sewer district. In each case, the inspection data changed how the utility understood its risk and allocated its capital resources. Full technical papers are available for download on each project.

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Why Wastewater Force Mains Are Hard to Inspect

Force mains sit in a different inspection category than gravity sewers. The practical gap is wider than most utilities realize when they first try to apply standard inspection tools to a pressurized main.

Gravity sewers are accessible. You pull a manhole lid every few hundred feet, insert a CCTV crawler, and drive it downstream to collect a video record of the pipe surface. You see cracks, joint gaps, infiltration, root intrusion, and structural deformation. The method works because the pipe flows by gravity and is not under pressure.

Force mains offer none of these conditions. The pipe operates under continuous positive pressure — typically 30 to 150 PSI depending on pumping head and topography. Access is limited to pump station inlets, isolation valve vaults, and occasional cleanouts, not a series of evenly spaced manholes. The critical deterioration modes — H2S gas causing internal corrosion, internal tuberculation in ductile iron, pitting corrosion in steel, external corrosion from aggressive soil chemistry — develop through the pipe wall and are invisible to a camera. And shutting down a force main for inspection is not straightforward when it is the only collection route from a pump station to a treatment plant.

The right tool for force main condition assessment is electromagnetic NDT: Remote Field Technology (RFT) for most metallic force main configurations. This technique passes an electromagnetic signal through the pipe wall and detects changes in wall thickness and metal integrity — not just surface defects, but actual through-wall material condition. PICA’s technology roots trace to Russell NDE Systems Inc., which developed the electromagnetic through-transmission methodology that underpins all of the projects below.

A detailed account of the specific operational challenges of force main inspection is available separately. What follows are the projects.

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Featured Case Studies

San Diego, California: The Force Main That Could Not Fail

The most constrained force main inspection project in PICA’s publicly documented work was a 40-year-old force main running beneath an active drinking water reservoir in San Diego, California.

The engineering firm Brown & Caldwell, working with the City of San Diego Public Utilities Department (A. Elden, P.E.; G. Skipper, P.E.; D. Gordon, CEP; and E. Fernandez, P.E.) alongside PICA Corp’s C. Garrett, took on an inspection problem with no margin for error. The force main was aging with no baseline condition data, and its location — directly beneath a major potable water supply — meant a catastrophic failure was not just a sewage overflow risk. It was a potential drinking water contamination event.

PICA deployed electromagnetic inspection tools to assess the pipe’s internal condition and remaining wall strength without requiring full service isolation. The project was presented at WEFTEC (Water Environment Federation Technical Exhibition and Conference) under the title “Inspecting the Uninspectable: Failure is Not an Option,” and later documented at the NASTT No-Dig Show 2018 in Palm Springs, where the full methodology and findings are published.

The title was accurate, not marketing. For a pipe in that configuration, with that consequence profile, the only acceptable outcome was inspection data that enabled a real engineering decision about where to direct rehabilitation resources first. The project demonstrated that electromagnetic NDT could deliver that data even when conventional inspection options were impractical. Download the full technical paper: Inspecting the Uninspectable (WEFTEC).

Milwaukee Metropolitan Sewerage District: Ductile Iron Force Main Assessment

The Milwaukee Metropolitan Sewerage District manages wastewater infrastructure for one of the largest urban regions in the Great Lakes basin. When the District needed to understand the actual condition of its ductile iron force mains, a multi-party project team was assembled: PICA Corp (M. Korz) provided the electromagnetic inspection services, Donahue & Associates served as engineering consultant, and Corrosion Control Technologies contributed pipe corrosion expertise.

Ductile iron force mains have a specific deterioration profile. The material is susceptible to internal tuberculation — deposits of iron oxides that form on the interior surface as corrosion proceeds — and to external corrosion in aggressive soil environments. Both mechanisms reduce wall thickness over time. Neither announces itself visually until the pipe is already leaking or has failed.

PICA’s electromagnetic inspection produced a continuous wall condition dataset mapped to linear pipe position, identifying locations of significant metal loss and providing a basis for repair and rehabilitation prioritization. The project delivered the transition from “we don’t know what condition our force mains are in” to a ranked list of pipe segments with supporting condition data. Download the technical paper: Comprehensive Inspection and Condition Assessment of DI Force Main Pipes.

Mount Pleasant Waterworks, South Carolina: From Inspection Data to Infrastructure Planning

Mount Pleasant Waterworks serves one of the fastest-growing municipalities in the Southeast. When the utility was building a more systematic infrastructure management approach, it recognized the planning process was only as good as its condition data — which, for the force mains, was largely absent.

Working with Brown & Caldwell (K. Derr) and Mount Pleasant Waterworks (D. Niesse), PICA Corp’s C. Garrett led a force main condition assessment that produced the data inputs needed for a capital plan. The project was documented twice: as a technical paper by PICA’s E. Brain and C. Garrett, “Using Direct Condition Assessment to Improve Your Infrastructure Management Plan,” and as a NASTT No-Dig 2014 presentation, “Leveraging Condition Assessment to Improve Your Asset Management Plan.”

The core argument of both papers holds for any utility in a similar position: capital expenditures planned on estimated pipe condition — using age and material type as proxies — carry significant uncertainty. Direct electromagnetic inspection replaces an estimate with a measurement. The difference in resource allocation is often substantial, both in which pipes get prioritized for action and which can be deferred with documented confidence rather than unease.

Both papers are available: Direct Condition Assessment for Infrastructure Management (Mt. Pleasant) and Leveraging Condition Assessment for Asset Management (NASTT No-Dig 2014).

Pinellas County Utilities, Florida: Sub-Aqueous Crossing Assessment Using RFT

In summer 2008, Pinellas County Utilities commissioned PICA to assess an abandoned 12-inch force main at a sub-aqueous crossing, using an electromagnetic inspection tool that was newly developed at the time. The pipe was out of service — making this a condition assessment ahead of a rehabilitation or permanent decommissioning decision.

Sub-aqueous force main crossings present access constraints that onshore mains do not. Excavation to create inspection access points is complicated by the water environment. The crossing is typically installed by horizontal directional drilling, at variable depth, and is not designed for routine in-line entry. Conventional above-ground inspection methods give you nothing useful about internal conditions.

PICA’s electromagnetic inspection delivered a continuous wall condition dataset for the full length of the 12-inch crossing — data that answered the decision question directly: did this pipe have remaining structural life that justified rehabilitation and return to service, or was replacement the better path? That is the exact output of the inspect-before-you-replace framework applied to an end-of-life asset. Download the case study: Case Study: 12″ Force Main Sub-Aqueous Crossing, Pinellas County, Florida.

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The Electromagnetic Technology Behind These Assessments

All four projects above relied on the same foundational NDT approach: electromagnetic through-transmission inspection. A signal transmitter inside the pipe generates a field that passes through the pipe wall and is captured by a receiver. Changes in signal amplitude and phase indicate variations in wall thickness, metal loss, and internal corrosion — detected through the material, not just from the surface.

The technique was developed by Russell NDE Systems Inc. — the technology developer behind PICA’s tool lineup — with foundational methodology documented by David Russell and Dr. Yuwu Yu in “Condition Assessment of Force Main Lines Using Electromagnetic Through-Transmission NDT Technique.” Download the methodology paper: EM Through-Transmission for Force Main Condition Assessment.

PICA’s current tool lineup for force main work includes RFT tools for most metallic force main and configurations profiles where electromagnetic propagation characteristics differ. Tool selection is determined by pipe diameter, wall construction, and operating conditions. PICA’s SeeSnake & Chimera platforms are the RFT tools to be deployed. For an overview of how these tools apply across all supported pipe types and applications, the service applications page documents the full matrix.

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Why CCTV Inspection Alone Misses the Most Critical Force Main Defects

CCTV inspection is the standard tool for gravity sewer condition assessment, and it works well in that context. Applied as the primary method for force main condition assessment, it misses the failure mechanisms that actually cause force mains to fail.

CCTV shows what is visible on the pipe interior surface: cracks in liner material, deposits, joint gaps, infiltration, visible surface pitting. It does not measure wall thickness. It does not detect metal loss developing through the pipe wall from external soil-side corrosion. A pipe can look visually intact on the inside while the exterior face is corroding from aggressive ground chemistry or stray electrical current — and the camera gives no indication of it.

Force main failures typically begin with through-wall processes: H2S corrosion internally from accumulations, internal tuberculation that progresses to pitting, external corrosion that reduces wall section on the soil side, or material degradation that leaves the pipe looking structurally sound while losing capacity. A camera survey on a dewatered force main catches surface symptoms. It does not characterize the wall condition that determines when the pipe will fail.

PICA matches the inspection method to what needs to be detected. Electromagnetic NDT is the primary tool for metallic force main wall condition assessment. For specific force main configurations involving lined pipe, plastic mains, or complex-wall structures, the full PICA technology applicability chart covers pipe type and method selection. The same methodology logic — match the tool to the failure mode — applies in PICA’s water main work, as illustrated in the TRWD PCCP inspection case study, where RFT was selected specifically because PCCP failures are a through-wall electromagnetic phenomenon, not a surface condition event.

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Frequently Asked Questions

How is a wastewater force main inspected?

Wastewater force mains are primarily inspected using electromagnetic NDT — Remote Field Technology (RFT) — which passes a signal through the pipe wall to detect metal loss, corrosion pitting, and wall thickness reduction. These methods work in most applications without full service isolation. The right combination depends on pipe material, diameter, access constraints, and what specifically needs to be detected. PICA’s pipeline condition assessment process begins with a tool selection review based on these variables.

Can force main failures be prevented?

Most force main failures are preventable with proactive condition assessment. The majority result from internal corrosion, structural deterioration, and material fatigue that develop over years or decades before a pipe fails. Electromagnetic inspection detects these conditions while the pipe still has structural capacity, giving utilities time to schedule targeted rehabilitation rather than responding to an emergency. The San Diego and Milwaukee projects above are examples where inspection data identified deterioration before failure occurred and informed specific decisions about where to act first. Waiting for symptoms is a higher-cost strategy than scheduled assessment.

How much does a force main condition assessment cost?

Electromagnetic force main condition assessment typically runs $20 to $40 per linear foot depending on pipe diameter, access spacing, and site conditions. The more useful comparison is against emergency repair: a force main failure typically costs $250,000 to over $2 million to remediate, plus EPA Sanitary Sewer Overflow fines of up to $37,500 per day per violation. A proactive inspection is a fraction of a single emergency response cost, and the condition data it produces is usable across multiple budget cycles. PICA provides project-specific estimates based on system configuration.

What does a force main condition assessment report include?

A PICA force main assessment report includes a continuous wall thickness dataset mapped to linear pipe position, identification of segments with significant metal loss or corrosion, a risk-prioritized summary of findings by severity, and recommendations for rehabilitation, continued monitoring, or replacement. The output is structured to feed directly into a capital plan — not a raw data file, but an actionable document with prioritization built in.

Can a force main be inspected while still in service?

Yes. PICA’s electromagnetic inspection tools are designed to operate in flowing, pressurized conditions for most force main applications although will require a significantly reduced flow rate. The tool enters through an access fitting or valve connection at both ends where a launch and receive barrels are installed, traverses the pipe under live or reduced-flow conditions, and collects continuous wall condition data without requiring full service isolation. This is a significant operational advantage over CCTV, which typically requires flow bypass or full dewatering. For pump station designs where full isolation is not practical — the situation in several of the projects documented above — live-operation electromagnetic inspection is often the only feasible option.

What is the difference between force main inspection and gravity sewer inspection?

Gravity sewers flow by slope and are inspected with CCTV crawlers via evenly spaced manholes. Inspection identifies visible surface defects: cracks, joint gaps, root intrusion, infiltration, deposits. Force mains operate under pressure, have limited access points, and fail primarily through through-wall metal deterioration rather than surface condition changes. CCTV can be used on a dewatered force main to check surface condition, but electromagnetic NDT is the primary assessment tool because it detects the wall loss that determines structural capacity — something a camera cannot measure. The wastewater pipeline inspection overview covers these differences in more detail.

What is a Sanitary Sewer Overflow and what are the regulatory consequences?

A Sanitary Sewer Overflow (SSO) occurs when untreated sewage exits the collection system before reaching a treatment plant, most commonly through a pipe failure, pump station backup, or capacity-exceeded event. Force main failures are a primary driver of significant SSOs. Under the US Clean Water Act, SSOs are reportable events subject to EPA enforcement action. Fines reach $37,500 per day per violation. Utilities with repeated SSO events face consent orders requiring capital improvements under regulatory oversight, along with third-party liability exposure from property damage and environmental contamination caused by the overflow.