Giardia – A protozoan parasite.  Occurrence in water sample must be confirmed by identification of two or more morphological
characteristics, nuclei, axoneme and/or median body.

How are MPA groundwater tests conducted?

Samples are collected in accordance with the EPA “Consensus
Method for Determining Groundwaters Under the Direct Influence
of Surface Water Using Microscopic Particulate Analysis (MPA).”
Two sampling events are recommended, one during a dry period and
a second during a wet period.  Turbidity, temperature, rainfall and
stream flow records, and conductivity etc. may be used for guidance
for when to test.

What is MPA and how can it be used to differentiate ground water under surface influence?

What is MPA and how can it be used to differentiate ground
water under surface influence?
The premise behind the use of microscopic particulate analysis
(MPA) is that surface waters are subject to contamination by
pathogens such as Giardia and that there are other organisms whose
natural habitat is limited to surface waters.  If these surface water
organisms are found in ground water, then the water is subject to
contamination with Giardia cysts and other pathogens.  Indicators of
surface water contamination of ground waters include: Giardia,
coccidia including Cryptosporidium, diatoms and certain other algae,
rotifers, green plant material, and insect parts. 

What information is useful in MPA classification?

Historical water quality records
1.  At least three years of Total Coliform and/or Fecal Coliform data.
2.  Turbidity and temperature records including those of nearby
surface water sources.
3.  No history of a known or suspected outbreak of Giardia,
Cryptosporidium or other pathogenic organisms associated with
surface water that has been attributed to the source.
4.  No evidence of particulate matter associated with surface water.
On site inspection
1.  No evidence for surface water infiltration.
2.  Sufficient distances from surface water sources.Cryptosporidium
Cymbella (Diatom)

MPA – What is GWUDI – “a ground water source under direct influence of surface water”?

The EPA Guidance Manual defines a ground water source under
direct influence of surface water as water in which there is either:
“significant occurrence of insects or macroorganisms, algae, organic
debris, or large-diameter pathogens such as Giardia lamblia.”
“significant and relatively rapid shifts in water characteristics such
as turbidity, temperature, conductivity, or pH which closely correlate
to climatological or surface water condition.”


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