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Emergency Alert Testing

Executive Summary - Sonoma County Operational Area Alert and Warning Functional Exercise

The Sonoma County Fire and Emergency Services Department, Division of Emergency Management conducted a first of its kind alert and warning test on the West Coast of the United States, on September 10th and 12th.

  • The scope of this exercise was to test the SoCoAlert, federal Wireless Emergency Alert (WEA) and Emergency Alert System (EAS).
  • The tests allowed Emergency Managers and residents to experience a live test of the communication methods that the County and City of Santa Rosa will use in the event of an emergency.
  • The test showed how alerts perform in the varied threat hazards, topography, demographics and urban densities of Sonoma County.

The County of Sonoma coordinated the tests to measure variables that might create communication gaps, including:

  • Human error
  • Limitations of software
  • Limitations of proprietary information
  • Limitations of telecommunications infrastructure

Emergency Management implemented the test in four phases:

  • Pre-Exercise Coordination and Public Education
  • SoCoAlert (All-Call)
  • WEA and EAS (Live Code)
  • Post-Exercise Assessment

SoCoAlert All Call Test

On September 10, 2018, there were 290,052 phone numbers in the SoCoAlert database, including landlines and subscribers. The call achieved a 51% success rate in delivering the message to a person or answering machine. Between 6:04 pm and 8:53 pm, the SoCoAlert system attempted 426,390 phone calls. Based on the time and number of calls completed, the system was able to initiate approximately 2,500 calls per minute.

The publicity of the tests resulted in the 38% increase of subscribers shown below.

Online RegistrationsSeptember 3, 2018September 9, 2018September 25, 2018Increase
Phone Numbers36,31447,06050,16738%

Federal Wireless Emergency Alert and Emergency Alert System Test

On September 12, 2018, five geographical areas were targeted for a WEA test to represent different threat hazards, topography, demographics and urban densities. Immediately following the WEA warnings, an EAS message was delivered via participating local radio stations and television providers.


Location Description

Message 1

Message 2


Selected due to a river flood hazard scenario. Is in a mountainous area with a somewhat rural community in the unincorporated area.

10:00 AM

10:01 AM

Glen Ellen/ Kenwood

Selected due to a Wildland Urban Interface (WUI) hazard scenario. The area is part of the valley floor with rural communities in the unincorporated area.

10:16 AM

10:20 AM


Selected to test the entire city boundary. It has multiple hazards with a high tourist population area.

10:30 AM

10:31 AM


Selected due to a train accident/hazardous materials release threat scenario. The target area is small and linear within the unincorporated area.

10:46 AM

10:47 AM


Selected as a community within a city. It is an urban setting with high population density. This target area has significant Spanish speaking population.

11:01 AM

11:02 AM

County Wide

Emergency Alert System Test

Issued in English and Spanish within the same message at 11:15 AM

The WEA test included an online survey component, which asked residents to provide feedback on the test. The survey was designed to measure variables that might impact the effectivity and reliability of the WEA system. The Survey received 3,678 responses.

Key Findings

The survey results demonstrate that the two major mobile phone carriers in Sonoma County, AT&T and Verizon, have different methods, policies, and algorithms for distributing WEAs.

  • Verizon stated that they require a cell tower to be within the boundaries of the alert area in order to broadcast the alert.
  • The survey data for AT&T users shows a larger bleed over area, which indicates that if an AT&T cell tower provides any amount of coverage to the alert area, all users connected to cell tower could receive the alert, even if the user is outside the alert boundary.

The differences in how the telecommunications providers distribute WEA messages causes significant issues for alert and warning officials when delivering alerts. Inconsistent policies amongst telecommunications providers for issuing alerts is challenging for emergency management officials to target specific areas with confidence.

The survey results demonstrate limited geo-fencing abilities. As an example of this exercise, when the test alert was issued to the Glen Ellen/Kenwood area, Sonoma Valley and Rohnert Park were alerted as well (Appendix C: Maps, page C-4). If geo-fencing were to work as publicized, the cities of Petaluma, Rohnert Park, most of Santa Rosa, Sonoma and Windsor should not have received the alert.

Distance from Call Out Areas

Number of Respondents

Percentage of Total Respondent

Total Respondents As Distance Increases

Respondents Not In Call Out Area

Within Area





Area to ¼ mile





¼ to ½ mile





½ to 1 mile





1 to 2 miles





2 to 5 miles





5 to 10 miles






This exercise demonstrated that each of the tools available have specific strengths and weaknesses. The SoCoAlert system saw a significant increase in subscriptions and the vendor was able to establish a baseline for how quickly notifications can be initiated. This along with feedback from the public will help emergency management officials create messages that are more effective and develop protocols to more efficiently target and send messages.

This exercise verified the need for improvement of the federal WEA system capabilities as it relates to conditions on the ground in Sonoma County. The exercise findings indicate that significant challenges remain regarding the effective use of the federal warning systems, including WEA and EAS. These challenges include incomplete and inconsistent alerting across telecommunication providers, significant bleed over when targeting specific geographic locations, and the performance of the technology across various wireless devices. These shortcomings significantly conflict with the public’s expectations for service. Local government emergency managers will have to continue to take into account these shortcomings in developing and conducting alert and warning efforts. It is critical that local governments, Cal OES, FEMA, and the FCC engage telecommunications providers to continue to improve the reliability and effectiveness of these systems.

To ensure that the lessons learned from this exercise improve both our local and national federal alert and warning capabilities and increase the effectiveness of emergency messaging to the public, Sonoma County developed a comprehensive improvement plan (Appendix B: Improvement Plan) that incorporates all of our response partners. It will be critical for each of these partners to participate in developing and addressing the improvements identified.

There remains no perfect solution to the complicated challenge of alert and warning. This exercise demonstrated that each of the tools available have specific strengths and weaknesses. Alert and warning officials cannot afford to rely on only one system to communicate in a time of disaster. Everyone, local government and the public, needs to understand how the various emergency warning systems work and how they connect to them. 

The County of Sonoma is committed to improving internal warning systems and maximizing the capabilities of federal systems in coordination with state and federal partners.

Contact Information

Jim Colangelo
Interim Department Director
Business Hours
Monday – Friday
8:00 AM – 5:00 PM
Contact us by Phone
2300 County Center Drive
Suite 220 B
Santa Rosa, CA 95403
38.46229, -122.725377