If you don't hear a siren at 11:45 a.m. tomorrow, it could be because you are in one of the many gap areas around the state.

The most recent state civil defense analysis concluded there is a need for 147 new warning sirens in locations across the state that are not covered by the existing 355 sirens or where coverage needs to be enhanced.

Continued population growth coupled with a renewed awareness of the importance of alert warning sirens in the wake of last October's earthquake are helping drive a push for more sirens to be installed or upgraded statewide.

State officials are asking the Legislature for a record $5 million in each of the next two years to upgrade the siren system.

On O'ahu, the analysis identified the need for 50 new sirens and 78 replacements. The list contains areas where new residential neighborhoods have sprung up in recent years such as Kapolei, 'Ewa and Mililani Mauka, but also includes remote coastal areas that are seeing more visitors, such as Mokule'ia.

"These are areas where the population has sprung up in recent years (or there are) more beachgoers," said Harold Buckle, communications officer for the city Department of Emergency Management, formerly the O'ahu Civil Defense Agency.

Both state and city civil defense officials stressed that the sirens aren't the only way to notify residents about a disaster or emergency.

While these areas are commonly referred to as siren gap areas, "we do have these areas covered by other means," said Peter Hirai, the city's acting emergency management director.

For instance, Hirai said, the last time there was a tsunami watch, police, fire and civil defense volunteers physically went into gap areas to notify people about the possibility of impending disaster.

"Although there are gaps in our audible siren system, we don't consider them gaps as far as emergency preparedness goes," Hirai said.

PLANS TO UPGRADE

The main function of the alert sirens, said O'ahu civil defense spokesman John Cummings III, is to alert the public that there may be imminent danger and that they should turn on their TVs and radios for the most current information.

But that's not to say the need for additional sirens is not a priority, Hirai said.

"In general, it is a concern to us, as I'm sure it is with residents who don't hear the sirens," Hirai said. "We are trying to make it a priority to install these sirens."

That concern and the worry that old-fashioned sirens tied to the electric company's power grid wouldn't work during an outage were both heightened Oct. 15, when two major earthquakes off the Big Island left O'ahu without electricity for hours.

The plan to upgrade the system calls for converting 132 of the existing sirens to solar-powered electronic battery systems.

"Ever since Oct. 15 — I think that made the issue come to the forefront," Hirai said. "Before the earthquake, we were just looking at replacing the old ones. Since then, we decided all the electric sirens would have to be replaced so that they could work in a non-electricity system."

Ray Lovell, state civil defense public information officer, said the annual budget for sirens statewide was about $300,000 from about the mid-1990s to the early part of this decade. It then increased to about $500,000 annually and is $1.24 million in the current fiscal year. The $5 million for each of the next two years would be substantially more, Lovell said.

"There was already a scaling up, but I think the momentum greatly increased after Oct. 15," he said.

The sirens cost about $86,250 each including the cost of installation, depending on where they are located and any logistical issues involved, Lovell said. It will take an additional $3 million in fiscal 2010 and $2 million in 2011 to address today's needs.

By then, of course, new sirens will be needed, he said. "There will always be a need for new and replacement sirens," Lovell said.

INSTALLATION FACTORS

Getting a siren installed doesn't happen quickly and can take from two to six years, civil defense officials said, depending on funding availability, the types of permits needed and give-and-take with the community about where it should be located.

People want to have a siren near enough so they can hear it but often don't want it too close to their homes because they worry about the loud blaring. Hau'ula Elementary School officials even asked that one just outside their campus be removed because it was too loud for their students, Hirai said.

It took a while before the community agreed where the siren should be relocated — on the roof of a commercial shopping center.

While many residents don't like the notion of a siren being placed near their homes, Cummings urged people to think twice before opposing the siting of one on that basis.

"When you look at the reality of it, it's once a month, 12 times a year, for 30 seconds," he said. "That's a small price to pay to ensure people's safety during an emergency."

Also delaying the installation of new sirens is the fact that there are only two or three contractors in the state capable of putting them up, civil defense officials said.

A number of factors go into the prioritizing of new or replacement sirens.

Coastal areas are the priority, Buckle said. That's because alert sirens are most critical in the event of a tsunami, which may require people to react extremely quickly. In other disasters, like a hurricane, science today allows for more advance warning — hours and sometimes even more than a day — giving the public much more time to react and be prepared.

SOURCE OF WARNING

Hirai said stretches of coastline with sparse populations have been served by Civil Air Patrol airplanes equipped with sirens and loudspeakers in the event of a tsunami warning situation. Now civil defense officials want to put sirens in some of those areas such as Mokule'ia.

Areas of extensive home or apartment development are also high on the priority list. Hirai listed Kapolei, Makakilo, Wai'anae Valley, 'Ewa, Mililani Mauka and Kahuku in that category.

While there's a general principal that the sirens should be placed about 3,000 feet from one other, Buckle said that determining where new alert sirens should go is an inexact science and determined by a large and constantly changing set of variables.

"Sometimes due to the way a place is built, we may have to put in a smaller siren that has a lesser range because you can't have 121 decibels blowing into someone's bedroom window from a hundred feet away," Buckle said. "And when you have to put smaller sirens in, you have to put in more sirens."

And then there's a place like Mililani Mauka. While the neighborhood may be close to being built out as a housing development, civil defense officials have reassessed and determined that there may be a need for more sirens to take into consideration new factors. Buckle said those may include the inability of residents to hear sirens because of trees or more homes capable of being cooled by central air conditioning where the windows are shut to outside noise.

He also encouraged people to have on hand radio receivers that key on the Emergency Alert System broadcasts through AM and FM radio stations and through the National Oceanic & Atmospheric Administration Weather Radio network.

Hirai said while the alert siren system is important, the public should not rely on it as their only source of warning that a disaster may hit.

"Especially as hurricane season (June through November) is approaching, they need to be situationally aware," Hirai said. "Just follow the news, read the newspaper, be aware of what's going on around. If the siren sounding is the first thing that tells them there's a hurricane, that's really bad."

Lovell said that civil defense officials are looking into new technology that can help them alert people in an emergency including the use of cellular phones and pager alerts that use voice or text messaging, or both.

Reach Gordon Y.K. Pang at gpang@honoluluadvertiser.com.