Unknown Event Classification; Usepa Guidance On Event Response - Hach Event Monitor Trigger System Manual Básico Del Usuario

• There was a change in the corrosion control program (dose, compound, etc.).
• Maintenance was done on the plant or distribution system.
• There was any unusual water demands (e.g., major fire fighting or hydrant flushing).
• There was a water main break.
• The control systems for pH or chlorine function normally.
• There was a change in source water (e.g., service from a neighboring utility interconnect or back
flow from another source because of maintenance).
• Other monitoring sites resulted in a similar manner and the response distribution is such that it
could show a change in the source water.
• The event happened elsewhere upstream of the location.
• The event was seen downstream of the location.

Unknown event classification

If no obvious cause for the event can be found, identify if this change in water quality is harmful or
not and if is it deliberate.
Test for toxicity
Get water samples and analyze them for toxicity. Make sure that there are sufficient safety measures
in place to handle samples that could be poisonous or infectious.
Evaluate the volume of affected water
Deviations that last only a few minutes suggest that only a small volume of water may be effected. A
change that is continuous and persistent probably shows a large volume of changed water.
Do a chemical analysis of classified agents
When the Event Monitor supplies a classification of an agent
until it is shown to be accurate by more tests. The Event Monitor classification offers a valuable first
pass at the identification of the cause of a water quality upset and can be used to point to more
forensic analysis.
Adjust tests according to the class of agent identified by the monitor. Agent library event matches are
not necessarily exact. For example, an event match to Ethoprophos may not necessarily be caused
by the agent Ethoprophos. The agent could be another organophosphate with a fingerprint similar to
Ethoprophos that is not in the agent library. In this case, do tests to make sure that this is the correct
class of compounds (organophosphates) and to get more specific as testing continues. The agent
library is an optional item for the Event Monitor.
Do a chemical analysis of unclassified agents
Although an event match may not be identified by the agent library, the event may not necessarily be
benign. There are thousands of contaminants that could be added into the distribution system by
deliberate or accidental methods.
The agent library contains a subset of some of the most dangerous and likely compounds. Many
others are not contained in the library. The ability of the system to supply an alert to potentially
dangerous compounds that are not in the agent library is one of the great strengths of the system.
While no classification is given on these types of alarms, the information supplied by the individual
parameters measured can be important in forensic analysis guidance. For example, if an event
occurs because of changes in conductivity alone with no noticeable change in TOC or chlorine
demand, it would not be logical to test for organic compounds. Such common sense in testing can
save valuable time in an emergency.

USEPA guidance on event response

The USEPA supplies guidance on forensic testing in their emergency response protocols. Both core
and advanced field-testing can be done on the collected samples. In addition, samples can be sent to
the laboratory for more in depth analysis. The manufacturer supplies ready to use kits for core field-
testing (2884100) and advanced field-testing including toxicity testing (2886800). Do not stop water
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The monitor can only classify an agent when the optional agent library is available.
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, the classification is only tentative
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