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Despite the DNR's best efforts to provide accurate data, there may be errors and
omissions. There may also be delays in adding new data or correcting older data
that is found to be incorrect or incomplete.
Listed below are steps in groundwater monitoring data collection and analysis at
which data accuracy could be compromised.
- Sample collection: groundwater samples may not have been collected and preserved
properly in the field according to standard protocols.
- Sample storage: samples collected in the field may not have been stored properly
according to standard protocol prior to and during shipment to laboratories for
analysis.
- Sample analysis: samples may not have been analyzed properly for contaminants
in the laboratory according to standard laboratory methodologies.
- Data transcription and loading: in the course of transmitting data from laboratories
and various intermediaries, including consultants and municipal officials, to the
DNR, data may be inadvertently lost, omitted, or uploaded to the GEMS database incorrectly
(Prior to 1996, many sites submitted data on paper forms with increased risk of
transcription error. Therefore, older data is more likely to contain transcription
errors).
The facility or lab representative or consultant that submits environmental monitoring
data to the DNR must sign a certification form stating that to the best of their
knowledge the data is correct. Nevertheless, it is not possible to prevent all errors.
It is very important that the user not make conclusions based on limited information,
such as one piece of data from one monitoring point. Instead, the data as a whole
should be evaluated by a scientist who is experienced with such evaluations and
considers changes over time and takes into account the location of each monitoring
point as well as the natural variability of water quality. Data that appears to
be elevated may be caused by naturally occurring substances or by a contaminant
source other than the facility being monitored.
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