Siren Information


The Occoquan Dam Siren system exists to alert persons below the Occoquan Dam of a structural failure of the Occoquan dam (an extremely unlikely event). If the siren sounds, seek higher ground if you live/work/are visiting inside the IMPACT ZONE. The impact zone is a small area adjacent to the banks of the Occoquan River between the Town of Occoquan and Belmont Bay that will flood if the Occoquan Dam experiences a structural failure.


Fairfax Water owns and operates the Occoquan Reservoir as a drinking water source for Northern Virginia. The Occoquan Reservoir holds approximately 8.3 billion gallons of water. The Occoquan Dam was built in the early 1950s to create the Occoquan Reservoir. The dam is inspected and maintained on a routine basis. The structural integrity of the Occoquan Dam is very sound. In fact, through rigorous maintenance and improvements, it is even stronger today than when it was constructed. As a precaution in the extremely unlikely event of a structural failure, Fairfax Water has installed a siren warning system to alert persons downstream of the dam in the event of dam failure. The sirens will only sound for two reasons: