Minnesota Power –
Boswell Energy Center Release
Minnesota Power (an
Allete, Inc. Company) operates the Boswell Energy Center (BEC) in proximity to
the Mississippi River in Itasca County near Cohasset, Minnesota. On July 16,
2024, a release of coal ash contact water was discovered from a pipeline leak
at the BEC which flowed overland into wetlands and open water in Blackwater
Creek. Blackwater Creek feeds into
Blackwater Lake, which is a backwater Lake of the Mississippi River. It was later determined that approximately
5.5 million gallons of supernatant ash slurry water was discharged from a decommissioned
treatment pond (pond 4).
Blackwater Creek, Blackwater Lake and the
Mississippi River in the “Mississippi headwaters area” contains an abundance of
sensitive natural resources and Tribal cultural resources. There are many dense
and sparse stands of wild rice throughout the area including Blackwater Creek
and Blackwater Lake. These wild rice beds are of significant ecological and
cultural importance to Minnesota Tribal Nations and to local communities. This
area is nearby and downstream of the Leech Lake Band of Ojibwe (LLBO)
Reservation and within the 1855 Treaty Rights Area. Water levels in this area
are controlled by the Pokegema Dam Reservoir System.
The decommissioned pond
was mainly affiliated with coal combustion residuals (CCR) and more
specifically from air scrubber residues. Initial sampling of the pond 4 water
for several potential contaminants of concern found significantly high sulfate
levels. Previous testing of the Pond 4 water had shown total sulfate in the
range of 14,000 mg/l. The initial sample collected from pond 4 during this
response found a concentration of 19,700 mg/l total sulfate. The State of MN
water quality standard for the protection of wild rice areas is 10 mg/l for
sulfates.
During the summer and
fall, MN Power conducted multiple mitigation efforts. Initial actions included release
stabilization, baseline vegetative imagery, a wild rice baseline ecological
survey, a resources at risk evaluation, emergency NHPA/NAGPRA consultations
with THPOs/SHPOs for excavation of soils, water quality monitoring and
sampling, and released water recovery (pumping from Blackwater Creek wetland).
On August 12th, the MPCA
issued a Notice of Violation (NOV) to Minnesota Power. The NOV required the
submission of a Remedial Plan (including ecological risk assessment, updated sampling
plan, and target remediation values). The NOV also required the submission of a
long-term monitoring and response plan (LTRMP). This was to include soil,
groundwater and surface water monitoring activities and wild rice
evaluation.
To-date (December 2024),
Soil excavation in the source area is complete and approximately 19.6 million
gallons of sulfate water has been recovered from the Blackwater Creek area.
Future efforts potentially include sediment dredging and ground water recovery
under State (MPCA) oversight.
