Sanitary Sewer Overflows May Be Linked to Outdated Technology, Faulty Inspections

Electro Scan Inc. recently informed the California Environmental Protection Agency, State Water Resources Control Board, and the Office of Enforcement that sanitary sewer overflows experienced by California cities and counties may be due to reliance on older visual-based technologies and faulty inspections by city crews and independent contractors.

“California’s record rainfall has put a spotlight on sewer agencies that have not made the necessary investment in new technologies needed to combat SSOs,” said Chuck Hansen,  Chairman, Electro Scan Inc. “Traditionally, cities have relied on Closed-Circuit Television (CCTV) cameras – a visual-based inspection technique – to identify and catalog cracks, defective joints, and poorly connected service connections. But, the inability to differentiate superficial cracks from cracks that go through a pipe wall, have frustrated efforts to accurately prioritize critical pipes and certify repairs, contributing to SSOs and flooding.”

California SSOs are tracked statewide by an interactive map maintained by the CalEPA State Water Resource Control Board.

Studies conducted by Electro Scan consisted of work at more than sixty California sewer agencies where CCTV inspection results were compared to an innovative machine-intelligent technology that accurately locates and measures defects.

The findings presented to the State Water Board’s Office of Enforcement included:

• One study found CCTV inspections had missed eighty-eight percent (88%) of all sewer defects, including several CCTV reports on the same pipe that showed materially different assessments, completed by the same person working for the same company, just months apart.
• Several agencies with major defects in recently repaired sewers – leaking more after repair, than before repair.
• Major damage in a newly lined pipe caused by a contractor’s acceptance inspection; however, its final report showed ‘Zero Defects.’
• Two connected pipes that showed the newly relined pipe leaking more than the existing 50-year old pipe; both certified by CCTV inspection.
• A Northern California agency showing ‘Zero Defects’ on a sewer located in an area prone to flooding. Yet, on re-inspection, the pipe was more than half-full of water – on a clear day, mid-week, and in mid-afternoon – showing major leaks at every joint, undetected by CCTV inspection.
• A re-inspected sewer with an 11-million-gallon water main break; missed by two previous CCTV inspections conducted in 2011 and 2014. One survey had been conducted by an independent contractor, while another was completed by city staff, respectively.

A New Inspection Method Emerges

In December 2015, new guidelines were published for Inspecting and Testing Collection Systems, Seventh Edition, Volume 1, OPERATIONS AND MAINTENANCE OF WASTEWATER COLLECTION SYSTEMS, ISBN 978-1-59371-066-8, recommending Electro Scanning Inspection, in place of CCTV inspection, to assess all pre- and post-repair, rehabilitation, and relining projects.

Referred by the EPA as Focused Electrode Leak Location (FELL) inspection, the new inspection standard is being adopted by sewer utilities to provide an unbiased way to find sources of infiltration and to certify repairs.

FELL technology uses a high frequency, low voltage, focused electric current to evaluate 360-degrees of a pipe wall to find and measure openings that provide a clear path for water to enter or exit a pipe through defects. No operator judgment or third-party data interpretation is required, with each defect provided with an estimated defect flow in gallons per minute.

Tested by several independent studies funded by the US EPA, the new technology is compliant with ASTM F2550-13 Standard Practice for Locating Leaks in Sewer Pipes By Measuring the Variation of Electric Current Flow Through the Pipe Wall.

In the first twelve months of the new inspection standard, Electro Scan found defects in 69% of Cured-In-Place Pipe  – a leading alternative to dig and replace pipe rehabilitation – traditionally inspected by visual inspection.

Overall, 21% of CIPP surveyed in 2016 using new testing standards had defect flows of 20 gallons or more, after rehabilitation.

“CCTV was the best we had for a long time, but now there is a better tool to certify point repairs, service reconnections, and trenchless rehabilitation,” said Hansen.

As a result of these findings, the Office of Enforcement plans on encouraging Regional Water Boards to use Electro Scanning Inspection at various upcoming project and demonstration locations throughout California.

 

 

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