Heat Stress Solutions
May 7, 2008
It’s never easy beating the heat when you have to work outdoors during the summer. But on the U.S. Department of Energy’s Hanford Site in the desert of eastern Washington State, CH2M HILL has developed strategies to keep the workforce healthy and productive.
The Hanford Site stores the nation’s largest volume of radioactive waste left over from decades of producing plutonium for nuclear weapons.
CH2M HILL is responsible for safely managing 53 million gallons of radioactive and chemical waste stored in 177 underground tanks until the waste can be prepared for disposal. Workers at the site encounter the potential for heat-related illness because they often have to face complex projects wearing several layers of protective clothing as well as respiratory protection.
“We condition our workers for the hot weather, but to help them we have installed special equipment and facilities where they can cool down on breaks,” said Monica Kembel who manages CH2M HILL’s heat stress mitigation program. “We have also provided them with handy reference cards to carry to help them recognize heat stress symptoms in themselves and their co-workers,” said Kembel.
High temperaturesFor much of June, July, August and September, temperatures at the Hanford Site, which is just 500 feet above sea level, can range from the high 80s to low 90s. And in late July through early August, daytime temperatures typically exceed 100°F. The low humidity that accompanies the high heat rapidly strips away moisture.
Daily tasks in Hanford’s tank farms usually range from simple routine surveillance activities performed in shirt sleeves, to heavy industrial work that includes crane and rigging, erection of scaffolding and equipment maintenance, all while wearing personal protective equipment (PPE). Throughout the warm weather the company stresses hydration before, during and after work and provides an ample supply of drinking water and electrolyte replacement beverages on all outdoor projects.
“One of the obvious ways to beat the heat is to change work schedules to swing or graveyard shifts so the work is performed during the cooler nighttime temperatures. This is done at times, but workers don’t like it as well as working in the daylight, so we need to have other options,” said Kembel.
Brainstorming for ideasTo develop new methods of protecting workers from the heat the company formed a team of workers and managers and gave them the freedom to brainstorm additional ideas. The first solution was to avoid the heat. Second was to change the work environments. And third was to look at work practices, knowing that different tasks would require a choice of several different solutions.
“Our first priority was to ensure that the heat stress program requirements for engineering controls, personal hydration, good communication, work/rest regimens and self-monitoring are clearly understood and followed by all,” said Kembel. This included training for workers and managers on signs and symptoms of heat stress. It also included environmental monitoring to determine the potential for heat stress based on such things as temperature, humidity, wind, the level of physical exertion required, duration of the work and the type of protective equipment required.
Based on team input the company installed cool-down tents just inside the fence of tank farms where work takes place for extended periods. Since workers have the potential to come in contact with radioactive contamination, the cool-down tents, which feature misters, fans and air conditioners, gave them a place to get out of the sun, drink water or electrolyte replacement beverages and rest without having to remove all of their protective clothing for the duration of their break.
The team also focused on addressing the actual work environment. As an example, to control the potential spread of radioactivity in certain projects, large, temporary structures are routinely erected using scaffolding and plastic. Workers refer to these as greenhouses, and as their name implies, they often turn into hot, confined work areas. To mitigate the heat, recirculation air conditioning with HEPA filters are used inside containment tents where the work is being performed. Also, netting has been installed over the containment tents to break the sun, which has resulted in lowering the ambient temperature of the work site, according to Kembel.
The team also recommended the use of special lightweight cooling vests, and changing from heavy cotton protective coveralls that were not well suited to hot, dry climates to a lighter weight coverall that performs well under a variety of conditions.