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Reports of Worker Fatalities during Flowback Operations

May 19th, 2014 9:10 am ET  -  John Snawder, Ph.D, DABT; Eric Esswein, MSPH, CIH; Bradley King, MPH, CIH; Michael Breitenstein, BS; Marissa Alexander-Scott, DVM, MS, MPH; Kyla Retzer, MPH; Max Kiefer, MS,CIH and Ryan Hill, MPH.

Although worker safety hazards in the oil and gas extraction industry are well known, there is very little published data regarding occupational health hazards (e.g., types and magnitude of risks for chemical exposures) during oil and gas extraction operations. To address the lack of information, NIOSH requests assistance from oil and gas stakeholders in further characterizing risks for chemical exposures during flowback operations and, as needed, develop and implement exposure controls. This article briefly describes flowback operations and addresses reports made known to NIOSH of recent worker fatalities related to or located at flowback operations.

Worker Fatalities

NIOSH learned about several worker fatalities associated with flowback operations through media reports, officials with the Occupational Safety and Health Administration (OSHA), and members of the academic community. According to our information, at least four workers have died since 2010 from what appears to be acute chemical exposures during flowback operations at well sites in the Williston Basin (North Dakota and Montana). While not all of these investigations are complete, available information suggests that these cases involved workers who were gauging flowback or production tanks or involved in transferring flowback fluids at the well site. Often these fatalities occurred when the workers were performing their duties alone.

Potential Exposures during Flowback Operations

Hydrogen sulfide (sour gas) is well recognized as a toxic exposure hazard associated with oil and gas extraction and production (1,2). However, less recognized by many employers and workers is that many of the chemicals found in volatile hydrocarbons are acutely toxic at high concentrations. Volatile hydrocarbons can affect the eyes, breathing, and the nervous system (3,4,5,6,7) and at high concentrations may also affect the heart causing abnormal rhythms (8,9). Recently, NIOSH conducted exposure assessments to identify chemical hazards to workers involved in flowback operations. Results from initial field studies suggest that certain flowback operations/activities can result in elevated concentrations of volatile hydrocarbons in the work environment that could be acute exposure hazards. The results, conclusions, and recommendations based on these evaluations will be detailed in a peer-reviewed journal article, a future NIOSH Science Blog posting, or other communication products.

Potential Exposures during Flowback Operations

Flowback refers to process fluids from the wellbore that return to the surface and are collected after hydraulic fracturing is completed. In addition to the hydraulic fracturing fluids originally pumped, returned fluids contain volatile hydrocarbons from the formation. After separation, flowback fluids are typically stored temporarily in tanks (figure 1) or surface impoundments (lined pits, ponds) at the well site. Liquid hydrocarbons from the separation process are routed to production tanks (figure 2). Workers periodically gauge the fluid levels in flowback and production tanks with hand-held gauges (sticks and tapes) through access hatches located on the top of the tank.

Preliminary Recommendations

Based on the limited information on fatalities and initial NIOSH exposure assessments, NIOSH researchers have identified preliminary recommendations to reduce the potential for occupational exposures:

1) Develop alternative tank gauging procedures so workers do not have to routinely open hatches on the tops of the tanks and manually gauge the level of liquid.

2) Provide hazard awareness training to ensure flowback technicians, water haulers, and drivers understand the potential hazards and risks for volatile chemical exposures when working on and around flowback and production tanks.

3) Monitor workers to determine their exposure to volatile hydrocarbons and other contaminants. Employers should consult with an occupational safety and health professional trained in industrial hygiene to ensure an appropriate sampling strategy is used.

4) Ensure workers do not work alone in potentially hazardous areas.

5) Use appropriate respiratory protection in areas where potentially high concentrations of volatile hydrocarbons can occur as an interim measure until engineering controls are implemented. Employers should consult with an occupational safety and health professional trained in industrial hygiene to determine the appropriate respirator to be used. Note that OSHA regulations (29 CFR 1910.134External Web Site Icon) require a comprehensive respiratory protection program be established when respirators are used in the workplace. NIOSH guidance for selecting respirators can be found at http://www.cdc.gov/niosh/docs/2005-100/default.html

6) Establish emergency procedures to provide medical response in the event of an incident.


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