MPCA Posts PolyMet Draft Water Quality Permit and Section 401 Certification

Agency releases draft permits to Tribes, EPA and PolyMet prior to public
meetings

ST. PAUL, Minn.–(BUSINESS WIRE)–The Minnesota Pollution Control Agency has informed Poly Met Mining
Inc., a wholly-owned subsidiary of PolyMet Mining Corp. (together
“PolyMet” or the “company”) TSX: POM; NYSE AMERICAN: PLM – that it has
posted the draft water quality permit and draft Section 401
Certification and supporting permit documentation on its website for the
NorthMet copper-nickel-precious metals project.

As previously announced by the MPCA, public meetings on the draft air
and water permits and the draft Permit to Mine will be held jointly
February 7 and 8, 2018, in Aurora and Duluth, respectively. The public
comment period for MPCA’s draft permits will begin prior to the February
public meetings. The draft Permit to Mine was released for public
comment by the Minnesota Department of Natural Resources on January 5,
2018.

The water quality permit establishes specific limits and requirements to
protect Minnesota’s surface and groundwater quality for a variety of
uses, including drinking water, aquatic life and recreation. It is also
known as an NPDES/SDS (National Pollutant Discharge Elimination
System/State Disposal System) permit.

The 401 Certification is a proposed approval by the MPCA that the
company’s plans, as submitted or with conditions written by the MPCA,
will protect water quality.

“With the release of the draft Permit to Mine earlier this month and now
the draft water quality permit and draft 401 Certification, we move ever
closer to fulfilling our commitment to build an environmentally
responsible mine and to provide the jobs, mineral diversity, and
tremendous economic benefits that this project will bring to the Iron
Range and the state,” said Jon Cherry, president and CEO.

The draft water quality permit and 401 Certification posted by the MPCA,
including related conditions and other permit documentation, are found
at https://www.pca.state.mn.us/northmet.

About PolyMet
PolyMet Mining Corp. (www.polymetmining.com)
is a publicly traded mine development company that owns 100 percent of
Poly Met Mining, Inc., a Minnesota corporation that controls 100 percent
of the NorthMet copper-nickel-precious metals ore body through a
long-term lease and owns 100 percent of the former LTV Steel Mining
Company site, a large processing facility located approximately six
miles from the ore body in the established mining district of the Mesabi
Iron Range in northeastern Minnesota. The NorthMet Final Environmental
Impact Statement was published in November 2015, preparing the way for
decisions on permit applications. NorthMet is expected to require
approximately two million hours of construction labor, create
approximately 360 long-term jobs directly, and generate a level of
activity that will have a significant multiplier effect in the local
economy.

PolyMet Disclosures
This news release contains certain
forward-looking statements concerning anticipated developments in
PolyMet’s operations in the future. Forward-looking statements are
frequently, but not always, identified by words such as “expects,”
“anticipates,” “believes,” “intends,” “estimates,” “potential,”
“possible,” “projects,” “plans,” and similar expressions, or statements
that events, conditions or results “will,” “may,” “could,” or “should”
occur or be achieved or their negatives or other comparable words. These
forward-looking statements may include statements regarding the ability
to receive environmental and operating permits, job creation, and the
effect on the local economy, or other statements that are not a
statement of fact. Forward-looking statements address future events and
conditions and therefore involve inherent known and unknown risks and
uncertainties. Actual results may differ materially from those in the
forward-looking statements due to risks facing PolyMet or due to actual
facts differing from the assumptions underlying its predictions.

PolyMet’s forward-looking statements are based on the beliefs,
expectations and opinions of management on the date the statements are
made, and PolyMet does not assume any obligation to update
forward-looking statements if circumstances or management’s beliefs,
expectations and opinions should change.

Specific reference is made to risk factors and other considerations
underlying forward-looking statements discussed in PolyMet’s most
recent Annual Report on Form 40-F for the fiscal year ended January 31,
2017, and in our other filings with Canadian securities authorities and
the U.S. Securities and Exchange Commission, including our Report on
Form 6-K providing information with respect to our operations for the
three and nine months ended October 31, 2017.

The Annual Report on Form 40-F also contains the company’s mineral
resource and other data as required under National Instrument 43-101.

The TSX has not reviewed and does not accept responsibility for the
adequacy or accuracy of this release.

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Contacts

PolyMet Mining Corp.
Media
Bruce Richardson,
+1-651-389-4111
Corporate Communications
[email protected]
or
Investor
Relations
Tony Gikas, +1-651-389-4110
Investor Relations
[email protected]