Water Quality Guidelines Online - Toxicant Guideline not met, or likely not to be met?

Toxicant Guideline not met, or likely not to be met?

First check how often the trigger value is not met, - it may be due to natural variation (see Vol1 7.4-3)

Comparing Test Data with Background data from a Reference site

Some surface waters will contain background concentrations ( i.e. natural not caused by human disturbance ) of toxicants
that may naturally exceed the default guideline trigger values tabulated. The minimum data set for using reference
monitoring to derive a site specific trigger is two years, with a minimum of monthly sampling. New trigger values should
be derived from the background data as the 80th percentile. A trigger for further investigation is deemed to have occurred
when the median concentration of n independent samples taken at a test site exceeds the 80th percentile of the same indicator
at a suitably chosen reference site.

Comparing test data with default guideline trigger values

<<<< Level below guideline value

Level exceeds guideline value >>>>

Test data exceed modified trigger value >>>>

<<<< Local study shows modified guideline met

Action is triggered when the 95th percentile of the distribution of the test data, complied as a 'running' estimate of the
last n observations, exceeds the default trigger value in the lists (or in other terms, no action is triggered
if 95% of the values fall below the guideline value).
Therefore a trigger for further investigation is deemed to have occurred when the 95th percentile of n independent samples
taken at a test site exceeds the default guideline trigger value in the lists.

Next conduct the risk assessment using the Decision Tree Framework for Toxicants (Vol 1 page 3.4-14)

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Define primary management aims ( see Vol 1 fig 3.1.1)

Determine appropriate guideline trigger values for selected indicators( see Vol 1. fig 3.1.1)

    Monitor to test total contaminant concentration
    against guideline 'trigger' values for ecosystem
    type ( marine or freshwater )

*Low Risk of Damage or Impairment of Use

#Potential Risk of Damage or Impairment of Use

    Examine whether site specific factors may be ameliorating the toxic effects
    at the trigger value concentration. Determine a site specific guideline value
    that accounts for these local conditions.

    Consider the following issues:
      1. High natural background levels - monitor to set new trigger level
      2. Analytical limits - set guideline at limit of detection
      3. Locally important species - set guideline values that protect these species
      4. Chemical water quality modifiers - modify guideline value for to account for these
      5. Mixture Interaction - set guideline values that consider these mixture effects

#Potential Risk of Damage or Impairment of Use

    Perform biological effects assessment using
    local species (e.g. Direct Toxicity Assessment
    or Laboratory Toxicity Tests)

Initiate Remedial Actions or Accept Level of Change

*Low Risk of Damage or Impairment of Use

Toxic >>>>

<<<< Non Toxic

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#High Risk of Damage or Impairment of Use

*Low Risk of Damage or Impairment of Use

WQG - Australian and New Zealand Water Quality Guidelines (ANZECC & ARMCANZ 2000)
* Possible refinement of trigger value after regular monitoring. # Further investigations are not mandatory; users may opt to proceed to remedial action.