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Sampling and Monitoring

Groundwater is monitored annually to target high seasonal groundwater. Transducers have been installed in many wells to better understand seasonal fluctuations. EPA and Montana DEQ groundwater teams continue to evaluate trends and spatial patterns of contaminants in groundwater. Groundwater monitoring will continue. Each year, EPA evaluates groundwater results and makes changes to the next year’s groundwater monitoring plan. These changes address data gaps and provide a better understanding of contaminant impact on groundwater.

Addendum 11a(pdf) (19pp, 5.4 MB) and Addendum 12 included groundwater sampling of additional wells and for additional contaminants, such as all 209 PCB congeners, in 2024.

Addendum 12:

Appendix A(pdf) (99pp, 8.8 MB)
Appendix B(pdf) (122pp, 19.1MB)
Appendix C(pdf) (97MB, 10.9 MB)

Sampling and Monitoring

Smurfit-Stone Mill