Hi. I'm Ginny Yingling and I'm a hydrogeologist at the Minnesota
Department of Health.
[music]
Today we're going to be talking about a category of
chemicals called Perfluoroalkyl substances or PFAS. You may have also have
heard them called PFC's. In this video we're going to be talking about why
we're sampling for PFAS, what the sampling process is, where we find PFAS
in southern Washington County and how we decide which private wells to sample. To
see this video again, or to find more information about PFAS, please visit the
Minnesota Department of Health website. Based on the levels of PFAS that we are
finding, there are no immediate health concerns, even if people are using water
that exceeds our current guidance values. The PFAS that we find in Minnesota is
typically well below levels that would pose concerns. Our goal is to lessen the
long term build-up - over many years - in the population of mothers-to-be. For more
information about PFAS health risks, please go to the Minnesota Department of
Health website. We understand people's concerns and their desire to have
answers quickly and that's why we have to focus our sampling in areas where the
evidence shows it is most needed at this time.
PFAS were manufactured in Minnesota. We know where they were disposed of in
South Washington County and we've been studying them since 2003. In light of new
evidence in 2017, the Minnesota Department of Health set new lower
guidance values for two of the PFAS, known as PFOS and PFOA. Again, the
levels of PFOS and PFOA that we find in most of southern Washington County
are not at levels of concern for most people. These new lower values are set to
protect our most sensitive groups. The state of Minnesota has been testing well
water in Washington County to identify any drinking water wells that exceed
these new lower health-based guidance values. We're targeting our investigation
to find wells that exceed these new lower values. That's why we prioritize
our sampling where the available evidence tells us it is most needed. We
determined that based on our understanding of the geology and
groundwater movement and almost 11,000 samples from over 2,700 wells in the
area. The PFAS in Washington County are water soluble which means they can move
quickly through the water. As a result, they quickly left the disposal sites,
entered the groundwater and moved in the direction that the groundwater is
flowing. This resulted in a large area of contamination that we refer to as a
plume. This map shows the location of the PFAS plumes in Washington County. The
blue arrows show the general direction, or gradient, of groundwater flow. South
Washington County sits on a ground water divide between two watersheds and this
controls the direction that groundwater flows. The approximate location of the
ground water divide is shown by this green dashed line. Groundwater on the
west side of the divide flows south-southwest towards the Mississippi
River, while water on the east side of the divide flows east southeast towards
the St. Croix River. Some of the PFAS also got into a surface
water system in Oakdale and Lake Elmo and this allowed them to be carried
across the divide and into parts of West Lakeland Township and northern Afton.
PFBA is another type of PFAS. It's the most soluble and so it doesn't stick
very well to soil or to bedrock and, as a result, it's created the largest area of
contamination shown here in brown. However, health studies suggest that
PFBA has lower toxicity and does not accumulate in our bodies so it has a
much higher health-based guidance value than PFOS or PFOA. In fact, only a
handful of wells very near the disposal sites have levels of PFBA that exceed
its health-based guidance value. PFOA and PFOS are slightly less water soluble
than PFBA and, to a certain degree, they will stick to soil and bedrock and, as a
result, they've created somewhat smaller plumes that are shown here in green for
PFOA and black hash marking for PFOS. You'll notice that those plumes are
elongated in the direction of the groundwater flow. In some places, the
plumes deviate from the groundwater flow because they're following features in
the bedrock, like faults or buried valleys, that channelize the flow of the
water and the contaminants. The white and purple dots on the map show all the
locations where we have sampled since 2003. The purple dots represent the over
880 private drinking water wells that exceeded our new lower health-based
guidance values and where we have issued drinking water advisories. Some areas on
the map don't have very many dots and that's because those areas are served by
city water or, in the case of Afton and Denmark Township, it's because they're
down gradient of areas where we have lots of sampling that show that
concentrations of PFAS are not anywhere near our drinking water guidance
values. Wells that come first for sampling are those that we've never
sampled before and that are located in or down gradient of areas where other
wells have been issued drinking water advisories and have higher levels of
PFOS or PFOA. That's why right now we're focusing our sampling in the areas of
West Lakeland Township and northern most Afton. We're also resampling wells that
have levels of PFOS or PFOA just slightly below our guidance values. As
we're able we're also sampling wells in Cottage Grove and St. Paul Park where
concentrations of PFOA and, to a lesser degree, PFOS are more widely scattered
and the concentrations tend to be lower than in West Lakeland Township and Afton.
Once we've completed that sampling, we'll be able to sample additional wells in
the lower risk area shown in brown. Well owners in the affected community can
request to have their well sampled by filling out an online form on the
Minnesota Department of Health website. Your well will then be placed on a list
and will be sampled in the order of the priority I just described. We'll try to
get it sampled as quickly as we can. You can find out more information about
PFAS at both the Minnesota Department of Health and the Minnesota Pollution
Control Agency web sites. You can also
call the Department of Health at six five one two zero one four eight nine seven.
[music]
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