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Community Warning System

Contra Costa County's Community Warning System (CWS) helps you, your family and your community learn how to best prepare for and handle emergencies.

Overview of the System

The Community Warning System (CWS) is an emergency warning system that consists of alert, notification and education. The alert and notification features are linked by a radio frequency network, and are designed to function when telephone systems fail. Signals carried by radio frequency activate every part of the emergency system.

Contra Costa County's Community Warning System (CWS) alerts the community and emergency responders when there is a hazardous materials incident. The CWS includes a system of outdoor sirens that can be quickly sounded by an large industry in the event of a chemical release that could impact the public. Emergency response agencies can also activate the warning system for transportation and other types of incidents.

The system's design features multiple safe guards-such as back-up power at each broadcast point, operation on multiple radio frequencies, and four broadcast towers within the county to receive and broadcast signals so that there is an excellent chance that the system will survive an earthquake. Emergency Alert Receivers (EARs) will be placed in all schools (public and private), hospitals, daycare centers, convalescent hospitals and other sensitive receptors in the industrial corridor of the county. The EARs can be used for any emergency. For example, if a school is in a flood plain during a flash flood alert, the county can send them a message to evacuate or tell the school the that evacuation busses are on the way. It can be set to alert only for a section of the county – click here for instructions.

Contra Costa County is one of the first locations in the country to utilize National Weather Service radios to receive hazardous materials alerts. These radios are now available with technology that allows them to be programmed to receive notifications for a specific geographic location within the county, in addition to receiving regional weather information. Residents of Contra Costa County may purchase a weather radio with Specific Area Message Encoding (SAME) from electronic suppliers such as Radio Shack, and program it to receive Shelter-In-Place advisories issued by the County.

CAER funded weather radios for both public and private schools, child care centers, hospitals, senior citizen facilities, and nursing care facilities in the County's industrial corridor running along Highway 4 from Richmond to Oakley. While the safety sirens in this zone provide an outdoor alert that means to go indoors and shelter-in-place, the weather radios now provide an indoor alert tone and voice message that will be received in the facility's office

The weather radios needed to receive Contra Costa shelter-in-place alerts offered by several manufacturers. After purchasing a radio, it can be programmed to receive alerts for the geographic location where it is being used, or for a broader area. Click here for instructions on how to program a weather radio to receive shelter-in-place alerts in Contra Costa County.

How Does it Work?

sirenSirens have been placed in the industrial corridor of the county. They are intended to be used for chemical accidents and used to notify the community to Shelter, Shut & Listen.

Pagers for emergency response personnel which operate via the radio network (independent of the phone system) can be used for any emergency. The County can order a coordinated deployment of emergency responders via CWS to areas of need during a disaster.

Why Provide the CWS?

Our mission is to provide an alert and notification system that is able to:

  • Immediately alert adjacent residents (one mile radius) to Shelter-in-Place in response to an emergency that may be harmful to their well being
  • Notify appropriate emergency response agencies concerning the emergency
  • Provide on-going updates about the incident and additional protective measures that may be required

Guiding Principles

  1. Recognize that people's safety during an emergency is the highest priority.
  2. Implement an alert and emergency notification system to reduce adverse impact for individuals affected during an emergency situation.
  3. Foster an awareness of the alert and notification system throughout the county, and provide support for on-going education about "Shelter-in-Place" emergency measures.
  4. Implement project in Phases, Phase I to be funded by a broad base of industries, and Phase 2 and all additional phases to be funded by public and other community agencies.
  5. Gift the project to Contra Costa County at the completion of Phase I implementation.

How can I receive instant emergency notification messages on
the Internet?

For latest messages posted, visit the EDIS at

You may want to obtain a free subscription with the EDIS automated e-mail messaging system, to receive the messages on your computer or email enabled pager, by subscribing at

CAER helped write the National Strategy for Public Warning

Efraim Petel, of Hormann America, Inc., takes Contra Costa CWS experience to Partnership for Public Warning. . .

“Help write the National Strategy for Public Warning.” was the heading of the email that I received on October 30, 2002. The heading looked so impressive that I was sure that this was just another “spam” e-mail. When I finally opened it, I found a sincere call from the Partnership for Public Warning (PPW), a non-profit organization. I was being invited to join a public effort to improve our national public warning capability.

Six weeks later, I was seated with 20 other volunteer experts for four days, at the National Emergency Management Institute Headquarters in Mary-land amidst a heavy snowstorm, debating and drafting a “National Strategy for Integrated Public Warning Policy and Capability.”

Valuable experience and staff work completed in Contra Costa County will be used for developing the national system. During the implementation of the Contra Costa County Community Warning System, the CAER group had done a great job of getting all ends together: the community demands were high and unforgiving, the County’s procedures demanding, and the industry willingness to comply with all this was compromised by technological capabilities.

CAER conducted endless meetings to clarify procedures and polish technological solutions – great work that resulted in a system that has proved itself many times in the last few years. This system is very comprehensive and enables the established procedures to be followed automatically in any chemical disaster to the benefit of the County’s residents. The experience gained during the implementation process is considered valuable by the PPW, and they are considering implementing a pilot project in Contra Costa County for the national system, which will integrate the existing system and the new technologies. CAER Executive Director Tony Semenza and County staff personnel Lew Pascalli, Randy Sawyer, Elizabeth Klute and Debbie Vanek joined me in presenting information on our warning system to Dr. Peter Ward (PPW Chairman) in January. We discussed implementation of a pilot project in our county as part of the National Warning System development.

U.S. Senator John Edwards (D-NC) has introduced legislation that would adopt key recommendations made by the PPW. The Emergency Warning Act, Senate Bill 118, was introduced on Jan. 9, 2003 and was referred to the Committee on Commerce, Science, and Transportation

Download and read the committee's National Strategy Document (PDF, requires Adobe Acrobat)