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The water sample tests results from the recreational water quality monitoring programme are assessed against the national microbiological water quality guidelines published by the
Ministry for the Environment and the Ministry of Health (2003). These guidelines use bacteriological indicators associated with the gut of warm-blooded animals to assess the risk of faecal contamination and therefore the potential presence of harmful
pathogens. Compliance with the guidelines should ensure that people using water for contact recreation are not exposed to significant health risks. The bacteriological indicators used are:
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Freshwater (including estuarine waters):
Escherichia coli (E. coli)
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Marine waters: Enterococci
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Recreational shellfish-gathering waters: faecal coliforms
The guidelines are "trigger" values to help water managers determine when management intervention is required. The "trigger" values underpin a three-tier management framework analogous to traffic lights.
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Mode
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Management Response
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Green/Surveillance
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Routine monitoring
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Amber/Alert
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Increased monitoring, investigation
of source and risk assessment
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Red/Action
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Closure, public warnings, increased monitoring and investigation of source
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When water quality falls in the “surveillance mode”, this indicates that the risk of illness from bathing is acceptable (19/1000 risk for marine waters and 8/1000 risk for fresh waters). If water quality falls into the “alert” category, this indicates an increased risk of illness from bathing, but still within an acceptable range. However, if the water quality enters the “action” category, then the water poses an unacceptable health risk from bathing. At this point, warning signs are erected at the bathing site, and the public is informed that it is unsafe to swim at that site.
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