Response Procedures: Intentional Contamination of a Public Water Supply - EH: Minnesota Department of Health

Response Procedures:
Intentional Contamination of a Public Water Supply

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Public health will be protected from exposure to an intentionally contaminated public water supply.


MDH Environmental Health Division staff will promptly respond to a credible report of an intentionally contaminated public water supply in cooperation with law enforcement and emergency management staff.

Public water systems are strongly urged to establish a reporting protocol and relationship with local law enforcement before an incident occurs. Having local law enforcement aware of the water system, its critical components, and any areas of vulnerability is a key part of water system security.

When an incident or possible threat is reported to local law enforcement, the operator or superintendent, along with local law enforcement, will decide if there is any credible threat to the water supply system. The evaluation should include an inspection for physical evidence, such as containers or material, in an intrusion area; a quick check for chlorine residuals in all parts of the system; and a check of finished water for turbidity, odor, color, and pH.  Care should be taken with this assessment. An unusual event such as finding an unlocked door or hatch, without any other indication of the water quality being compromised, should not automatically be considered a credible threat to the water supply system.

No Credible Threat to System

If it is determined that there is no credible threat, local law enforcement will continue to investigate the potential threat, but there will probably be no need to notify the state health department or others. However, if operators have any special concerns about the situation, they should feel free to contact their Minnesota Department of Health district engineer or, for non-community systems, their district sanitarian.

Credible Threat to System

If it is determined that there is a credible threat to the water supply system, local law enforcement (or the operator/superintendent if for some reason local law enforcement is unable to do this) will report the threat to the state duty officer at 1-800-422-0798 and the local emergency manager. The local emergency manager may be the county sheriff or a member of the fire department.

  • Responses

    This will trigger the involvement of the Threat Assessment Group, a multi-agency team that includes the Minnesota Department of Health and the MDH district engineer. The Threat Assessment Group will evaluate the situation and determine appropriate responses, which may include sampling of the water supply. Sampling may include field testing conducted by the Civil Support Team, a National Guard group that specializes in these types of situations and has sophisticated field-testing kits.

  • Corrective Actions

    The MDH district engineer will advise the operator on corrective actions and assist with the implementation of such actions, including arranging an alternate water supply, if necessary, notifying the fire department if the system has to be shut down, and taking suspect facilities out of service.

  • Public Notification

    The public must also be notified about the situation and any precautions (such as not using the water or boiling it before using) that should be followed. Public notification will be done with the assistance of the district engineer and/or the Minnesota Department of Health’s Communications Office, if requested.

  • Closure

    The incident will be closed when the Threat Assessment Group declares it to be over and when corrective actions, including necessary notifications, have been completed and the water system is back in service. Flushing and resampling may be required before the incident is closed; the completion of a criminal investigation may not be necessary.

Updated Monday, August 17, 2015 at 11:16AM