Outdoor Warning System


Pierce County Department of Emergency Management (PCDEM) has 40 sirens in the Puyallup River Valley and the Nisqually River Valley. These sirens are meant to get the attention of people who are outside during certain emergencies so they know to get more information.

The warnings from the siren towers include voice warnings in English and Spanish, flashing lights to reach additional vulnerable populations and alert tones based on the emergency.

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Emergency Management

2501 S. 35th St. Suite D
Tacoma, WA 98409

For Emergencies:
Call 9-1-1
Ph: (253) 798-6595  
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  1. Monthly Tests
  2. An Emergency

Monthly Tests

Testing happens the first Monday of each month. The test sound the siren makes is similar to a Westminster chime on a clock. You can hear the tone and verbal instructions for the test below. The chime tone is used for the system test instead of the regular alert tone based on feedback from the community. The feedback was the alert tones used during testing were mistaken as a real emergency.


One of the natural hazards facing residents of Pierce County is volcanic activity from Mt. Rainier. Experts consider it one of the most dangerous volcanoes in the world, largely because of the threat of a lahar. A lahar is a large volcanic mudslide, stemming from snow and ice melt; given the sheer number and volume of glaciers on Mt Rainier, and proximity of residents to the mountain, the damage could be catastrophic.

The Puyallup River Valley is at greatest risk. Tens of thousands of people live in areas that may have as little as 40 minutes to as much as 3 hours to move to safety once a large lahar is detected. This robust system was originally created to notify people promptly and widely, they were in harm’s way and how to prepare and take protective actions.

Lahar Whos At Risk_PP Slide Image_061118 Presentation

In response to this hazard, PCDEM has worked closely with our partners to create an integrated lahar warning system. The Mt. Rainier Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. Residents will also receive warning via PCALERT and other alerting mechanisms.

There are currently Acoustic Flow Monitor sites on the Puyallup River, plus two radio repeaters. The United States Geological Survey (USGS), in coordination with PCDEM, has made plans to upgrade the Acoustic Flow Monitors (AFM) detection technology. The USGS is working on a multiyear project to enhance the system and create new sites called Lahar Monitoring Stations (LMS) with software, real-time transmission of signals and cameras. The upgrade project will focus first on the Puyallup drainage. Both systems will run in tandem to ensure operability before the old AFMs are removed.

What Is A Lahar_PP Slide Image_061118 Presentation

System Components

Acoustic Flow Monitors (AFM): An automated system detects lahar flows by using a network of small sensors called acoustic flow monitors (AFMs) embedded underground to measure ground vibrations made by passing lahars. Computer base stations located in the Washington State Emergency Operations Center (EOC) and South Sound 9-1-1 continuously analyze signals from the field stations. Upon detection of a lahar, the computer alerts the 24 hour emergency monitoring and notification centers, who then initiate the warning component of the system. Warning messages would trigger immediate, preplanned emergency response actions.

Lahar Detection How It Works_PP Slide Image_ 061118 Presentation

All Hazard Alert Broadcast (AHAB) Sirens: The siren component is one aspect of that pre-planned emergency response. When imminent danger threatens, the outdoor sirens will be activated. Citizens will be advised to evacuate the valley floor and head to higher ground. The sirens are made for outdoor warning and used to alert residents in the Puyallup River Valley of the need to evacuate due to a lahar or other volcanic event. The outdoor sirens are tested at noon on the first Monday of every month. The outdoor sirens chime during testing and a voice announcement follows in English and Spanish. During a real event, the outdoor sirens will continuously wail until the batteries die or they are destroyed.

Lahar Detection Instrumentation Package


PCEM works in partnership with the United States Geological Survey (USGS), the Pacific Northwest Seismic Network (PNSN), Washington Military Department’s Emergency Management Division, South Sound 9-1-1  and Orting, Puyallup, Sumner, Fife, and the Port of Tacoma to monitor and operate the systems.