PHOENIX--About 8,600 people live within 10 miles of the Palo Verde Nuclear Generating Station (PVNGS)—an area called the 10-mile Emergency Planning Zone (EPZ). Living in the 10-mile EPZ has its advantages—less noise and light pollution, and unobstructed desert views—and makes being informed about emergency alert and warning plans and procedures all the more important.

Residents of the 10-mile EPZ got their annual reminder of what an emergency siren sounds like when PVNGS, the Arizona Department of Emergency and Military Affairs (DEMA), the Maricopa County Department of Emergency Management (MCDEM) and local amateur radio groups tested the Emergency Siren Alerting System on Nov. 10. The 58 sirens in the system were activated at noon by MCDEM and again by at 12:30 p.m. by the Arizona Department of Public Safety (DPS). The sirens sounded for less than 3 minutes on both occasions.

The Nuclear Regulatory Commission and FEMA have required annual siren tests since before PVNGS opened in 1986. Bill Wolfe, Radiological Emergency Preparedness (REP) Branch Manager, said the Siren Alerting System has changed in several ways over the 32-year history of the siren test. For starters, there are now 58 (and counting) sirens spread across the 10-mile EPZ. An additional 10 new sirens are expected to go up within the year, with more coming online as new development dictates.

According to the Wolfe, some of the sirens are in remote areas inhabited only by cactus, jackrabbits and rattlesnakes. Although a few sirens are out of anyone’s earshot, they are part of a proactive plan to have siren coverage across the entire EPZ.

Siren technology has also changed. Wolfe says the first sirens were topped with a rotating speaker, were powered by the electrical grid and needed regular repairs. The new sirens, he added, have fewer “moving parts,” use multiple speakers and are solar-powered.

With 58 sirens to test simultaneously, PVNGS and its offsite response partners depend on the participation of amateur (or ham) radio operators to get “eyes on” all of them. About 80 “hams” from the West Valley Amateur Radio Club, the Tri-City Amateur Radio Club and Arizona ARES, and other unaffiliated volunteers turned out in support of the exercise.

Wolfe described the amateur radio community’s participation in siren test as essential to its success, and their abilities to be self-sufficient—they bring their own equipment—and “muster up a communication network seemingly overnight” as a significant response capability.

As part of the opening remarks, the radio operators were divided into small groups; each was assigned a siren. They were given ample time to drive out to their given siren where their job was to ensure it worked as advertised. Wolfe said some of the sirens are located down dirt roads in areas inaccessible except by four wheel drive. Operators were directed to radio into a controller located at the airport if their siren did not sound.

Wolfe explained that siren tests are not meant to cause a panic, but are instead “an opportunity for them (residents in the EPZ) to hear the sirens, and for us (state and local emergency management) to reinforce why we have sirens.”

The sirens are there to alert the residents of 10-mile EPZ in the unlikely event of an emergency at PVNGS. Residents in the EPZ know to tune to local radio or TV station for protective action instructions if the sirens go off at night and/or for longer than 3 minutes.

PVNGS, the State and the County use multiple media to notify residents and passersby of the siren test. PVNGS mails an annual Public Safety Calendar that lists the test date and—about a week prior—a follow-up reminder to each residence in the EPZ.

The Arizona Department of Transportation notified motorists traveling Interstate 10 west of Phoenix using their overhead message boards. I-10 cuts across the EPZ between about 427th Ave. and Johnson Road near Exit 264.

As important as it is to test the sirens annually, it is equally important to keep it to once a year. Aside from the logistical challenges of organizing the test, Wolfe said the sirens are activated only in November so residents in the EPZ don’t get accustomed to hearing (and start tuning out) the sirens.

Palo Verde has other inconspicuous ways to test the sirens throughout the year. The plant performs regular silent and “growl” tests of the sirens as part of its system maintenance plan. A silent test is one in which Palo Verde tests only its wireless connectivity with the individual sirens. In a growl test, Palo Verde activates the sirens for 5 to 15 seconds during which residents hear an audible chirp. Both types of tests are performed during the day, and often go unnoticed.

Wolfe further explained that Palo Verde handles the installation and maintenance of the sirens but under federal regulation is not authorized to trigger the system in an emergency. DPS, MCDEM or the Maricopa County Sheriff’s Office would activate the sirens in the unlikely event of an emergency at PVNGS.

If an emergency did occur at Palo Verde, Maricopa County would also trigger its reverse 9-1-1 system called the Community Emergency Notification System (CENS). CENS allows MCDEM to send recorded messages to home and cell phones in an impacted area but only if it is registered. Maricopa County residents can register their phone number with CENS online.

PVNGS occupies 4,080 acres near the town of Wintersburg, approximately 50 miles west of Downtown Phoenix. It is the largest nuclear energy facility in the United States, providing power for approximately 4 million residences in Arizona, California, New Mexico and Texas.