Canadian Underground Infrastructure Logo

Addressing the challenges of inspecting corrugated metal pipe

Backscatter Computed Tomography (BCT) provides non-destructive method for imaging in-situ soil voids

In the city of Levis, Quebec, one section of a storm water drainage system comprised of corrugated metal pipe was identified as high concern. After a visual and acoustic assessment, two anomalies were chosen for BCT imaging.
In the city of Levis, Quebec, one section of a storm water drainage system comprised of corrugated metal pipe was identified as high concern. After a visual and acoustic assessment, two anomalies were chosen for BCT imaging.

Company info

711 Woodstock Road, Unit B
Fredericton, NB
CA, E3B 5N8

Website:
inversasystems.com

Read more

Corrugated metal pipe (CMP) is heavily reliant on supporting soil for structural integrity. As such, a condition assessment must include an evaluation of the supporting soil to be considered complete. Previously there was no conclusive and quantifiable way to assess soil condition without damaging the pipe wall – further compromising the structural condition of the pipe.

Backscatter Computed Tomography (BCT) has been applied to this unmet inspection challenge and is capable of providing diagnostic imaging to enhance the understanding of structural soil conditions around CMP assets. BCT allows a full structural condition assessment and is the only non-destructive method for imaging in-situ soil voids and undermining around CMP. As part of a comprehensive assessment protocol, this technology can be used in asset management programs, rehabilitation planning, safe replacement or deferral, post construction QA/QC, or in emergency situations.

Collapse, replacement and maintenance planning have been identified as areas of concern in transportation, stormwater and flood control systems comprised of CMP. Time and environmental conditions wear away the supporting soil around the pipe. As these pipes are considered flexible conduits, the structural integrity is dependent on the supporting soil. An improperly supported pipe will experience mechanical stress and deformation which can eventually result in a catastrophic failure. As a result soil voids and undermining must be considered when evaluating the structural condition of the asset.

Conventional pipe inspection methods are subjective and speculative, often lacking descriptive evidence of the condition of the pipe’s supporting soil. Until now, testing methods have been limited to visual appraisals, acoustic assessment and destructive testing. Visual appraisal, either in person or by remotely-controlled CCTV, is effective in identifying corrosion, joint failure, misalignment, deformation and ovality. However, this method fails to provide information regarding the degree of soil loss in the supporting soil envelope of the CMP. Acoustic testing is done by striking the pipe and identifying anomalous regions by sound. This method is subject to frequent false positives due to soil compaction variability and soil composition. Destructive testing is conclusive; however, it exacerbates potential soil void and corrosion problems by introducing avenues for soil ingress to the pipe.

The introduction of Backscatter Computed Tomography, in the form of insight to CMP evaluation, is the final critical step in full and conclusive structural condition assessment. The system is suited to evaluate corrugated metal, plastic and composite pipe (lined or coated) in nominal diameters 900 mm and larger.

To achieve this, a three-part assessment protocol is employed which can be broken into two tiers. Tier 1 includes a rigorous visual assessment and an acoustic testing process which screens 100 percent of the pipe for anomalies. Tier 2 consists of BCT imaging to conclusively identify, visualize and quantify all anomalies and identify soil voids around CMP structures identified during Tier 1 assessment.

Backscatter Computed Tomography (BCT)

BCT is a form of industrial diagnostic imaging that provides information similar to that of a medical CT scan. It creates a relative map of density, which allows the system to distinguish between materials of different density and map their location. The resulting image allows the verification of soil presence or void behind a CMP wall, the quantification of any presented voids and the visualization of the geometric shape of the void.

Utilizing results from the visual and acoustic assessment, areas for diagnostic BCT imaging are selected. The BCT scanner is positioned against the pipe wall and a region of up to 30 cm per position is imaged and assessed. BCT images provide a cross-sectional view behind the pipe wall.

The head of the application unit during the centrifugally cast concrete pipe application.

Case study: City of Levis, Quebec

The City of Levis owns and operates a significant storm water drainage system that serves the city and surrounding areas. Some of this system is comprised of corrugated metal pipe. One section in particular was of high concern and was requested for immediate condition assessment to guide rehabilitation efforts.

A visual and acoustic assessment was carried out, four anomalies were identified and two anomalies were chosen for BCT imaging. Locations were measured from manhole access (STA0+000) to the outlet (STA0+180).

Seams throughout the storm drain were in poor condition, several with visible voids, above and below the pipe, allowing water to run underneath causing flow-related soil failure. The ovality of the pipe diameter is greater than 10 percent, the majority of issues being underneath Autoroute #73. Several rock impingements were noted, the largest located directly beside the entrance of the manhole located on route #73 (STA0+137) from the access manhole on Avenue de la Rotonde. The bitumen coating throughout the pipe had become dried out and brittle, chipping during hammer testing. The outlet of the storm drain (STA0+156) to (STA0+180) was in very poor condition; two acoustic anomalies were found. Evidence of buckling and significant scour was noted. The outlet of the pipe was damaged with several large indentations.

BCT images at two locations were taken to verify soil structure. The largest confirmed void identified a void 14 centimetres in depth spanning more than three corrugations. The location of this void was concerning as it was located directly under Autoroute #73. The other images showed that there was adequate backfill supporting the pipe. Image B-2142 displayed discontinuous CMP wall and small soil void pocket behind a seam separation. Image C-2143 indicated a void in a single corrugation; it did not span corrugations.

A thorough review of the structural condition assessment of the storm water drainage section under Rotonde Avenue and Autoroute 73 in Levis was used to formulate a comprehensive rehabilitation plan. The main body of the pipe was referred to in Stages 1, 2 and 3 of this project (STA 0+000 to STA o+156). The downward sloping outfall section was considered Stage 4 of this project (outfall).

Two primary rehabilitation techniques have been identified as viable options for the rehabilitation of this pipe segment (STA 0+000 to STA o+156): Spray in Place Pipe (SIPP) polymer solution and Centrifugally Cast Concrete Pipe (CCCP) solution.

To begin rehabilitation, cleaning, sealing and void filling must be accomplished to achieve optimal results. This pipe is completely covered in a bituminous anti-corrosion coating. As noted in the condition assessment report, this coating is completely worn away in the invert of the pipe and deteriorated past the point of functionality elsewhere on the pipe wall. Removal is highly recommended and is a requirement for use of CCCP and SIPP.

A structural deficiency at STA 0+138 was identified. The nature and extent of this deficiency will require localized repair beyond the scope of either CCCP or SIPP. This localized repair must be addressed as a first action in Stage 2 prior to Stage 3 work. The deflection of the pipe wall at STA 0+138 represents a significant risk of pipe failure under Autoroute 73. It is recommended that galvanized steel tunnel plate be used to reinforce and stabilize the pipe in this specific location. This technique offers the advantage of being assembled in the host pipe, as well as providing a localized repair strategy providing excellent long-term stability. This technique will cause some flow restriction, but is an excellent tradeoff in risk mitigation and cost.

The main barrel of the pipe STA 0+000 to 0+156, is now considered prepared for lining. The two options are CCCP and SIPP. Both options are detailed in the full report with material, application and curing specifications.

This section will discuss the recommended action for the down-sloping outfall section of the pipe from STA 0+158 to STA 0+180. This segment of the pipeline was in a state of advanced deterioration. There are obvious signs of undermining throughout the entire invert, wall buckling failure in the invert, and severe damage to the pipe end.

The long-term viability of this segment is questionable, therefore replacement of this section is recommended. Due to the physical location on the roadway embankment and the difficulty of excavation at this site, this may not be a cost-effective project at this time.

Possible risk mitigation strategies can be undertaken to prolong the effective service of this segment of the pipeline. The invert of the outfall must be stabilized and soil stabilization will be of key importance to this effort. If the asset owner deems, maximum service life extension is a priority for this segment; a spray applied protective coating is highly recommended.

Joint caption separation witnessed on a section of corrugated metal pipe in Levis, Quebec.

Industry implications

CMP structures are subject to a variety of failure modes and each site presents unique conditions that impact the structural condition of the entire structure. By utilizing the best in condition assessment and combining the latest in trenchless techniques, the most responsible, cost effective and safe solution can be applied to aging infrastructure.

During projects across North America, other soil voids with unique geometry have been identified that offer previously unavailable information to guide decision making.

The unique nature of each asset, and the importance of identifying what sort of failure mode is present when planning and designing an effective rehabilitation, is now able to be more completely understood. By addressing this pipe trenchlessly as opposed to digging it up, cost saving of over 50 percent was proven.

By applying this condition assessment to large sections of inventory, Tier 1 screening can exclude structurally sound pipes from Tier 2 screening. Structurally sound pipes can then be monitored and deterioration trended over time. Assets that require further investigation into their structural condition undergo Tier 2 assessment for full asset diagnosis. This information not only optimizes individual rehabilitation projects, it optimizes the long-term asset management and rehabilitation planning of CMP assets. The information provided allows for the maintenance of assets to be either safely deferred or planned for future remediation activities.

More from Locating, Inspection

Pole camera from CUES lightweight, portable and wireless

CUES has developed a new lightweight, portable, wireless digital video inspection pole camera that can be operated by one person. The new QuickZoom III (QZIII) camera is designed to provide cable-free safe-viewing in industrial or environmental areas with no man entry. Perform swift inspections and surveys of pipelines, wet wells, manholes, sewer treatment plants, steam generators, tanks, vessels, and other areas that are difficult to reach. QZIII can also be used to locate lateral services or to identify blockages at manholes, access ports, or other entry points without entering the line or structure.

CUES launches new pipeline inspection tool

CUES has developed a new pipeline inspection tool designed to significantly reduce unplanned downtime. The CUES REDI (Remote Evaluation Diagnostic Inspection) Kit is the first pipeline inspection troubleshooting kit available on the market today designed to help diagnose electrical issues, allowing for quicker and more accurate troubleshooting and repairs of problems while in the field. The release of this new product reflects CUES continuing commitment to offer the best customer support services in the business.

Cansel acquires Trenchless Utility Equipment precision locating business

Cansel, a software, hardware, and service provider to engineering, surveying, construction, architecture, government and printing industries announced today that it has acquired the precision location business of Trenchless Utility Equipment Inc. in Ontario and Alberta.  First established in 1992, Trenchless Utility Equipment Inc. was formed to specialize in the relatively new Horizontal Directional Drill Industry. Over the years the company has become a leader in protecting underground utility infrastructure. 

Robust, cost-effective downhole inspection camera from Hoskin

The dipper-See EXAMINER from Hoskin Scientific is a robust and cost effective vertical downhole inspection camera. Designed with portability in mind, this self-contained unit is ideal for viewing in wells, drains, vertical shafts, open bodies of water, boreholes and narrow tubes over 25mm (1") in diameter.

  • Versatile positioning arm
  • High Definition (HD) display screen
  • HD, detachable See-120 camera probe
  • Recordable video/audio
  • Designed to work in the harshest environments
  • Built in hanger - hands-free viewing while in the field

Latest in ground penetrating radar on display at World of Concrete

GSSI, the world's leading manufacturer of ground penetrating radar (GPR) equipment, will be highlighting its latest GPR technology at the 2018 World of Concrete conference, to be held January 23-26, 2018, at the Las Vegas Convention Center in Las Vegas, Nevada, Booth #C3719. On display will be a new affordable UtilityScan GPR System, StructureScan Mini XT all-in-one concrete inspection GPR system, and the new Palm XT miniaturized GPR antenna for the StructureScan Mini XT. 

New Sentinel Portable Inspection System

The new Sentinel Inspection System, from Aries Industries, Inc., is an integrated system with all components operated by an all-in-one controller. The compact, portable unit combines a lightweight reel, a quick set-up tractor and a state-of-the-art camera.

free-paper-airplane

Get our newsletter

Learn more

multiVIEW opens Kitchener office to expand service coverage across Southern Ontario

multiVIEW Locates Inc. a professional services firm that specializes in locating and mapping buried infrastructure has announced the opening of its’ fourth office location in Kitchener, Ontario.  The new location will allow multiVIEW to quickly deploy to deliver private and public utility locating services across the city and surrounding area, bridging the gap between the company’s existing Mississauga and London-based offices.

The Smarter Way to Locate

The Vermeer Verifier™ G3 utility locator by McLaughlin combines trusted precision with a user-friendly interface. Contractors face congested underground conditions, unmarked utilities and increasingly strict regulations, making accurate, timely locating more important than ever.  The Verifier G3 features include a combination peak and null screen, semiautomatic and manual gain adjustment, and automatic depth and current measurement index. The new compass icon simplifies the locating process by automatically calculating the peak signal and informing the user of the direction of the utility path. With the Verifier G3, users can expect the same core qualities of the Verifier G2 including: a durable design with antennas mounted in rubber isolators to standup to the toughest jobsite conditions and the exclusive McLaughlin three-year warranty and weather-proof guarantee. Users new to the locating profession will appreciate the streamlined design and simple interface; advanced operators have the option to capitalize on some of the industry’s most advanced locating technology — all in one device.  

GSSI announces flexible, configurable ground penetrating radar system for utility detection

GSSI, a leading manufacturer of ground penetrating radar (GPR) equipment, announces the release of the UtilityScan Pro, the latest addition to the company’s popular UtilityScan GPR product line. UtilityScan systems are the industry standard for efficiently identifying and marking the location and depth of subsurface utilities, including gas, sewer, and communication lines. Featuring the SIR 4000 control unit, the UtilityScan Pro delivers the configurability and flexibility to address a wide range of utility applications.

multiVIEW opens new office location to meet growing demand across Southwestern Ontario

multiVIEW, a leading professional services firm that specializes in locating and mapping buried infrastructure is pleased to announce the opening of its London, Ontario office. The strategically situated office location will allow multiVIEW to complete local contract-based work and quickly deploy to meet growing demand across Southwestern Ontario for utility locating, hydro-excavation and CCTV camera inspection services.

New guidelines for utility relocations

Utility relocations typically present one of the largest potential risks to delivering major capital infrastructure projects on time or on budget within urbanized areas. Until now there has been little in terms of a standardized process in place regarding the coordination of the utility impacts and the management of the effects of the utility relocations on a project.

Cross bore problem in the crosshairs

They are two words no contractor or municipal engineer wants to hear: cross bore. A cross bore is what happens when one underground utility intersects another. Most worrying is when a gas line punches through a sewer main or lateral. Cross bore risk has risen with the use of trenchless technologies like horizontal directional drilling, because the operator can’t physically see what’s in the immediate vicinity of the drill bit.

Cost-effective site sampling tools for environmental assessments

Geophysical surveys can be the bedrock (pardon the pun) of today’s environmental projects, from locating abandoned underground storage tanks (USTs) and utilities, to complex mapping of geology in remedial investigations, to finding landfill boundaries and other buried unknown problems. In the past few decades, a variety of non-destructive testing methods have gained in popularity over expensive and time-consuming drilling and digging for environmental projects. Among these, the method of pairing ground penetrating radar (GPR) with electromagnetic (EM) induction instruments is one that shows great promise in significantly reducing survey time and costs.

free-magazine-subscription

Get Our Magazine

Paper or Digital delivered monthly to you

Subscribe or Renew Learn more

Montreal-based consultancy completes inspection and leak detection of six 1,200-mm steel watermains and one 1,500-mm PCCP main in Montreal

Since September 2013, GAME Consultants has been paving the way for the next generation of watermain condition assessment tools by using existing tools and working to improve the results with every project. The company’s position is to equip itself with a wide range of tools designed exclusively for use in watermains.

GSSI’s new 350 HS Antenna uses HyperStacking technology to improve performance while meeting GPR emissions limits

GSSI has announced its 350 HS Antenna, which greatly improves the depth and data resolution performance of traditional real time sampling technologies. The 350 HS is designed for use with new digital HyperStacking technology, which allows users to see deeper targets and operate in conditions considered too “noisy” for conventional systems. Easily configurable, the 350 HS antenna is ideal for archaeology, geophysics, and utility locating applications.

Trimble launches new version of its smart water management software to streamline utility field operations

Trimble has announced the latest version of its smart water mapping and work management software—Trimble Unity 3.0. Trimble Unity is a cloud-based, (GIS) centric software-as-a-service (SaaS) solution for smart water management. Version 3.0 includes new features and workflows and also offers an App Builder and new integration capabilities to simplify connecting mobile workers with maps and data from back office enterprise systems.

Prevent leaks and bring lead leaching into compliance with ePIPE

Pipe Restoration Inc., Technologies, LLC, (PRT), a world-leading pipe lining innovator and manufacturer of the patented, proven ePIPE pipe restoration technology, offers the fastest, 2 hour return to service barrier coating that prevents water pipe leaks, as well as bringing lead leaching into compliance. In honor of the United States' Environmental Protection Agency's national Fix a Leak Week, and United Nations' World Water Day on March 22, PRT announces that it is helping to combat the global issue of water conservation and access to clean water with the ePIPE patented leak protection process.

“Locatable Rope” from 3M

The Electronic Marker System (EMS) Rope 7700 series uses propriety 3M path marking technology to deliver more accurate and more reliable tracking of underground plastic pipe and fiber optic conduit. Designed as a high performance alternative to the current industry standard solution, the new EMS Rope series is available for use in the electrical utility industry. The EMS Rope Series is also available for gas, telco, wastewater and water utility applications.

free-paper-airplane

Get our newsletter

Learn more

Into the void

It’s not uncommon to use ground-penetrating radar (GPR) to map underground utilities, but some municipalities are using it to find, well, nothing at all.

Lead pipes still a problem in Canada

The shocking story of lead contamination in Flint, Michigan may seem like a one-off situation that most of us living in modern housing don’t need to worry about. But after reading with horror and sadness all the coverage of how officials in Flint failed to protect thousands of mostly poor Americans, including children, from ingesting dangerous levels of lead that leached from corroded water pipes, I decided to look at the situation north of the border. (Flint is only a two-hour drive from London, ON) The conclusion? While the lead pipe problem in Canada isn’t as dire as in Flint, admittedly an extreme example, neither should we turn a blind eye to it, because thousands of Canadians (the exact number is impossible to pinpoint) may also be unknowingly drinking lead-contaminated water because they live in older homes where lead pipes and fittings were commonly installed.

Robotic inspection goes 1/2-K deep

In June, ASI Marine (ASI) personnel conducted a remotely operated vehicle (ROV) underwater inspection of the Cheves Hydropower Tunnel in Peru and ended up breaking the ASI company record for the deepest flooded tunnel inspection at 570 metres water depth. The Cheves Hydropower Project is being developed by Empresa de Generacion Electrica Cheves S.A., a wholly-owned subsidiary of Statkraft, a Norwegian electricity company.

free-magazine-subscription

Get Our Magazine

Paper or Digital delivered monthly to you

Subscribe or Renew Learn more