By Adam Smith
In a field of tall hay off Carter Road in Limestone County, a crew worked in the hot sun Friday to install a new pole and warning siren on property owned by J.D. Swanner.
It was the 59th siren to be installed since the Tennessee Valley Authority began switching out older models on March 29. Officials with TVA expected to install the 60th siren Friday afternoon.
TVA owns and operates about 100 sirens within a 10-mile radius of the Browns Ferry Nuclear Power Plant. Fifty-four of the sirens were installed in 1982 and 46 more were installed in 1989. About 40 percent of the sirens are on public property, while 60 percent are on private property like Swanner’s.
TVA spokesman Ray Golden said the primary use of the sirens is to warn residents of an accident at the power plant, but the sirens are also used in the event of a weather emergency at the discretion of officials with the state and local Emergency Management Agency.
“That’s a side benefit because they were used on April 27 last year, so they can be used for non-nuclear emergencies,” he said. “The idea is, we sound the sirens and people would turn on their TVs or radios and receive a message from the (Emergency Management System).”
In case of an accident at Browns Ferry Nuclear Plant, the message could contain information regarding an evacuation or shelter-in-place. Golden said recommendations are based on a variety of factors, including the amount of radiation released and wind speed.
“It’s a coordinated effort with the state and county, and they have the ability to increase or reduce the (emergency) recommendation,” he said. “We may evacuate 2 miles out or shelter 10 miles. We have 30-plus years of planning now so all the coordination makes it that much easier.”
There are approximately 43,000 people who live within the Browns Ferry emergency planning zone. Golden said plans to replace the sirens were set into motion prior to the Fukushima nuclear accident in Japan and the April 27 tornado outbreak, but those two events did accelerate the process.
A common concern following the April storms was the widespread siren failure across the county because of storm damage or power loss. The new sirens installed by TVA operate off A/C power but switch to D/C power during an outage.
The backup consists of four batteries and two chargers, and batteries will remain charged for about one week while in “sleep mode” if no A/C power is available. A monitoring circuit alerts the utility if the siren is not working.
While operating from battery power only, the sirens can be sounded 10 times. Officials said batteries would have to be replaced every three-to-five years.
The new sirens, which are round and white, have a different look than the old square, cone-shaped models. As a new siren is replaced, crews immediately run tests to ensure performance.
The installation process takes about four hours, which includes cutting down the wooden pole with a chainsaw, digging a new hole and setting the siren. The new sirens are being installed on steel poles, which offers many advantages over the traditional wood poles, including the ability to house the wiring internally.
“We don’t have to worry about wood rot, woodpeckers and termites,” said Tom Adkins, manager of emergency preparedness systems for TVA. “Plus, we had a worker find a snake inside (a wiring box).”
The utility estimated the total cost of siren replacement to be $7 million, which includes the costs of engineering, testing and the sirens themselves. TVA said there would be no rate increases, as the cost has been built in to the 2012-2013 budget.
The sirens were manufactured by Federal Signal and are being installed by West Shore Services of Allendale, Mich.
Two emergency crews had been working six days per week and replacing four sirens each day. A recent equipment failure left only one crew replacing two sirens each day, but officials said operations should wrap up ahead of schedule in mid-May.