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insect/larvae, rotifers, pollen and (in a separate
test), Giardia and Cryptosporidium.
It must be conceded that water wells located very
close to surface water, at very shallow depth and
within a coarse-grained aquifer that does not provide
adequate filtration, should be considered GWUDI,
and that very basic bacteriological testing can be
used to verify this. However, as a hydrogeologist,
it is my opinion that the vast majority of wells,
especially those in sand and gravel aquifers, are
not GWUDI. Furthermore, turbidity in a well is very
different than turbidity in surface water. The turbidity
in a well is associated with fine-grained aquifer
material that gradually migrates through the aquifer
and into the well during pumping. Wells producing
water with high iron can also produce turbid water
when the iron oxidizes upon reaching the surface.
A properly constructed and maintained water well
should produce water with very low turbidity. In
turn, those wells that produce turbid water may be
poorly designed, physically damaged, or in need of
rehabilitation. Finally, if you talk to the laboratories
that do the analysis of filters from MPA testing, you
would discover that positive results for any of the
previously mentioned particulates or pathogens are
rare. My colleague at Western Water, Doug Geller,
has overseen numerous MPA sampling programs on
wells over the years, and has never seen one result
that is positive for Giardia or Cryptosporidium.
Regardless of the source of turbidity and the
outcome of MPA testing, it appears that groundwater
purveyors by default are being subjected to the
precautionary principle and, therefore, required
to invest in extensive GWUDI studies and/or dual
treatment. If turbidity in a well is relatively low
and the required chlorine residual is maintained
in the associated water distribution system, I am
suggesting (again, as a hydrogeologist) that there is
likely far more risk to water quality in the well as a
result of land use activities in the vicinity of the well.
Therefore, instead of making water purveyors spend
money on unnecessary GWUDI studies and expensive
treatment plants, more effort (and money) should go
toward source protection. I further suggest that the
costs of source protection should not be borne solely
by the water purveyor, but also by land users in the
area. Unfortunately, this argument directs us towards
the most obvious hurdle (mentioned in my previous
article), which is that groundwater protection
planning is politically complex.
In closing, I am suggesting that there needs to
be more discussion regarding the identification
of real risks to groundwater quality, and that
practical solutions need to be implemented for
the monitoring of water quality and treatment
required. These issues should be at the forefront of
groundwater protection planning.
Please note that the opinions represented in this
article are those of the author, and not necessarily
those of the BC Groundwater Association.
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