Safety – Equipment & Systems: Arlington Valley Energy Facility – Combined Cycle Journal

Safety – Equipment & Systems: Arlington Valley Energy Facility

Meteorological data produces heat-stress caution and warning alarm

Arlington Valley Energy Facility
Owned by LS Power Group, Operated by NAES Corp

570-MW, gas-fired, 2 × 1 combined cycle located in Arlington, Ariz
Plant manager: Greg Nugent
Key project participants: Greg Heard, EH&S manager Ron Sager, production manager William “Jon” McCall (deceased), O&M technician, Arlington Valley O&M staff


The desert environment that our plant is situated in is well known for being a hot and inhospitable place during the summer months. Temperatures soar into the 110F to 120F range for months on end. The nighttime temperatures offer little relief. When the monsoon rains start in mid-summer, temperatures drop slightly but the humidity levels climb concurrently.Heat exhaustion, heat stress, and heat stroke can strike very quickly during the summer heat of the day. With such wide swings in temperature and humidity it is particularly important to take these in to account when considering heat exposure concerns.


Several key meteorological measurements for determining heat stress were already being measured at our plant—such as dry bulb temperature and relative humidity. The idea was presented that we could use these inputs to create cautions and warnings on the hottest days of the year in order to increase heat-stress awareness.An alarm was programmed in the plant’s DCS using a generally accepted heat index formula. When these heat-stress caution and warning alarms trigger, the CRO makes an announcement to all personnel onsite of the heat-stress alert level and reminds everyone to take necessary precautions.


The site has not encountered any heat-stress injuries or first-aid events since implementation. Some employees choose to employ ice vests and hydration backpacks or avoid staying outside for extended periods after a caution or alarm.

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