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Tech Forum – Don’t Be Found Dead in a Manhole

Tom Suiter

Suiter


For most wastewater operators, working in manholes is a principal feature of their job; however, it is also a key culprit in instances of their sickness, injury and death.

With fatal occupational injuries related to “confined spaces” (including manholes) peaking in 2018 , operator safety protocol is being increasingly scrutinized by wastewater agencies across the nation. Therefore, it is pivotal to address the hazards facing workers in sewers and manholes—whether these risks be the possibility of bacterial infection or a sustaining a serious fall—in order that workplace injury can be minimized to the furthest extent possible. Considering the seriousness of working in manholes, here are five tips for safely accessing them.

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1. Ventilate the Workspace


According to the CWA, “Poor natural ventilation is one of the characteristics of a confined space.” Therefore, after properly coning-off the work site and erecting all necessary warning signs to alert passersby in the area, the first step for a safe workspace is employing a ventilator and fan in the manhole to ensure a continuous supply of fresh air to the operator. This process, which adjusts the atmosphere of a confined space to acceptable standards for humans, is known as “purging.” Once the manhole has been successfully purged via a mobile ventilation system, it is safe to continue.

2. Test the Air Quality


Next, operators need to verify the manhole’s air quality after the purging process and before someone descends into the workspace by using an air monitoring device. Typically, operator injury and/or death in manholes is due to the inhalation of potentially deadly sewer gasses like hydrogen sulfide and carbon monoxide, among others. The possibility of combustible gasses or vapors like methane is also a concern. Using an air monitoring device (or, “sniffer”) after purging the workspace is extremely important when preparing to work in a manhole, as it will give an accurate reading of a safe atmospheric oxygen content (anywhere between 19.5 and 23.5 percent). Anything less, or more, than this acceptable oxygen ratio, will be alerted to you by the device.

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3. Use Proper Safety Equipment


After verifying acceptable atmospheric oxygen content, it is safe for the operator to descend into the manhole. However, before he does so, it is important that the proper safety equipment be employed—typically a body harness and tripod. Per the NSC’s sewer pipe inspecting and cleaning guidelines, “All employees entering sewer manholes must wear a full-body harness with lifelines attached to a winch or tripod device to permit rapid removal in case of collapse.” Even with purging, the atmosphere inside a manhole can change instantaneously and without warning; therefore, proper safeguards to remove an unconscious worker must be employed. Tragically, more would-be rescuers die attempting to save an incapacitated coworker than the original victims of a poisonous atmospheric change.

4. Never Work Alone


Per OSHA and the NSC, at least two workers should be present for any sewer maintenance job, with one operator always above ground acting as a supervisor and lookout for the operator inside the manhole. In the case of an atmospheric change in the manhole that incapacitates a worker, it is pivotal that the above-ground lookout be present to remove him via the harness, winch, and tripod.

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5. Maintain Sanitized Equipment


Finally, wastewater operators need to maintain sanitized tools on the jobsite. This is often the most overlooked precaution when working with wastewater and one that needs to be addressed. A new study assessing the threat of microbes in sewer pipes found that, even with standard cleaning agents like bleach, antibiotic-resistant “biofilms” on pipe (and manhole) walls still pose a serious threat to maintenance workers. Some agencies employ additional anti-bacterial safety equipment, like Vanguard Pathogen Defense technology , to more effectively eliminate pathogens and bacteria on jet hoses and hand tools. However, regardless of the cleaning agent(s) employed, it is important that operators be cognizant of the hazardous environment in which they work and have a comprehensive understanding of what can be done to minimize personal risk.


Tom Suiter is operations team member at Hydro Products Corp.



Sources


“Fact Sheet | Fatal Occupational Injuries Involving Confined Spaces | JULY 2020,” U.S. Bureau of Labor Statistics (U.S. Bureau of Labor Statistics, July 15, 2020), https://www.bls.gov/iif/oshwc/cfoi/confined-spaces-2011-18.htm.

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“CWA Occupational Safety and Health Fact Sheet #12: Confined Spaces & the Workplace,” cwa-union.org, 2017, https://cwa-union.org/sites/default/files/osh-fact-sheet-12-confined_spaces_and_the_workplace.pdf, 2.

CWA, 2.

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CONFINED SPACE ENTRY TRAINING GUIDE,” https://www.oakland.edu/Assets/upload/docs/EHS/CSE_trainingguide.pdf (Oakland University Office of Environmental Health and Safety, March 2005), 2.

“Sewer Pipe Inspecting and Cleaning,” nsc.org (National Safety Council, 2017), https://www.nsc.org/getmedia/3db0e168-32d8-4252-ac9f-4ecb57b2631b/sewer-pipe-inspecting-cleaning.pdf.aspx, 3.

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NSC, 3.

“Harmful Microbes Found on Sewer Pipe Walls,” ScienceDaily (ScienceDaily, July 6, 2020), https://www.sciencedaily.com/releases/2020/07/200706094128.htm.

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Luke Laggis, “Guarding Wastewater Workers,” Municipal Sewer & Water Magazine, June 2021, https://www.mswmag.com/editorial/2021/06/guarding-wastewater-workers.

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