July 19-21, 2024: Site Updates
MN Power updated the estimated
release volume from approximately 1 million gallons of coal residual
slurry water to approximately 5.4 million
gallons.
A review and shovel test were performed
by an archeological team of the proposed excavation site. Results were reviewed
by MP, MPCA, LLBO, and the MN Historical Society and determined excavation
would produce no adverse effects. Excavation of source-area soils began Saturday,
July 20.
Excavation of the affected soil,
subdivided into four zones, zone one being closest to the point of discharge,
fanning out along the discharge path towards the edge of Blackwater Creek.
Excavation began at zone three working inwards toward zone one. Affected
material was excavated down to about six feet below ground surface.
Conductivity readings of the soil were intermittently sampled and compared to a
baseline sample taken away from the affected area to assess the condition of
affected soil.
As of Sunday, July 22, about 256 tons
of material was removed from the excavation site.
Water monitoring
and sampling efforts continued. Preliminary results of samples taken in Blackwater
creek water showed an elevated concentration for sulfate. A sulfate analyzer
instrument was requested to provide more immediate concentration levels in the
creek.
An ecological survey of the
Blackwater Creek was conducted by Barr Industries to assess the condition of
the wild rice beds.
July 18, 2024:
Site Update
EPA received the first preliminary
analytical results for surface water sampling. Preliminary data did not
indicate concerns with metals with the exception of elevated boron. Elevated sulfates
were found at the point of discharge and diminished further away from the
discharge point.
EPA met with representatives from the Leech Lake Tribe
to view the potential excavation area to remove affected soils from the spill.
A cultural/historical/archeological review is currently underway to determine
whether an adverse effect from the excavation is possible. Once the review is
complete, EPA and MPCA will work with the Tribe to determine next steps.
July 17, 2024: Site Update
EPA
continues to work with the MPCA, the Leech Lake Band of Ojibwe, U.S. Fish and
Wildlife Service, Minnesota Department of Natural Resources, U.S. Department of
the Interior, and MN Power on response efforts. MN Power continues to conduct
surface water monitoring and sampling with EPA and MPCA oversight. EPA is still
waiting for sample results to determine next steps for in-water mitigation if
needed. Source area mitigation efforts include on-going slurry water collection
which has been augmented with additional recovery pits for groundwater
collection and planned soil removal.
Protection boom has been placed near the discharge area to prevent
Blackwater Creek flow from disturbing potentially contaminated areas until
sampling results are received.
EPA
issued a Notice of Federal Interest to MN Power under the agency’s Superfund
and Clean Water Act authorities.
July 16, 2024:
Site Update
On Tuesday, July 16, Minnesota Power determined that approximately 1 million
gallons of coal residual slurry water (otherwise called supernate), from a
discontinued coal ash slurry pond was discharged from a return-water reuse
pipeline over several days. The discharge flowed overland into the backwaters
of Blackwater Creek which feeds into Blackwater Lake, a backwater lake of the
Mississippi River near Cohasset. This area is nearby and downstream of the
Leech Lake Band of Ojibwe Reservation and within the 1855 Treaty Rights Area.
EPA arrived at the
site to begin coordinating with the Minnesota Pollution Control Agency (MPCA),
the Leech Lake Band of Ojibwe, the U.S. Fish and Wildlife Service, U.S. DOI, and
MN Power. On July 16, all recoverable material from the spill area and pipeline
back-drain was collected. Surface water samples were collected to be analyzed
for contaminants of concern such as sulfides, metals, total suspended solids,
chloride and carbonaceous biochemical oxygen demand, or CBOD.
MN Power installed an earthen berm to contain slurry
water near the leak and will recover water that will be sent back to the plant
systems. MN Power also installed silt fencing further down the slope to retain
any solids as well as installed a line of floating boom across the creek just
downstream of the release where it empties into Blackwater Lake.
MN Power will conduct water quality monitoring and
sampling with EPA and MPCA oversight. EPA and MPCA are working on a sampling
and analyses plan for the incident and reviewed previous analyses of the slurry
water. EPA has identified wild rice areas throughout the system and downstream.
Mitigation needs will be reassessed as more data is available.
MN Power will
continue to conduct hourly visual inspections of the area for any signs of
stressed vegetation or wildlife or unusual water quality.
