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Denison Announces Temporary Suspension of Wheeler River Environmental Assessment Amidst COVID-19 Disruptions

Mine Development & Operations Permits & Approvals

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Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

PRESS RELEASE

DENISON ANNOUNCES TEMPORARY SUSPENSION OF WHEELER RIVER

ENVIRONMENTAL ASSESSMENT AMIDST COVID-19 DISRUPTIONS

Toronto, ON – March 20, 2020. Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:

NYSE American) announced today a temporary suspensi on of activities related to the environmental

assessment (“EA”) for the Company’s 90% owned Wheeler River Uranium Project (“Wheeler River” or the

“Project”). An important element of the EA process is the completion of extensive in-person engagemen t

and consultation activities with various interested parties and community groups. The decision to suspend

the EA process and other discretionary activities i s motivated by the significant social and economic

disruption that has emerged as a result of the COVI D-19 pandemic and the Company’s commitment to

ensure employee safety, support public health effor ts to limit transmission of COVID-19, and exercise

prudent financial discipline.

David Cates, Denison’s President & CEO, commented, “Considering the interactive nature of the

engagement and consultation activities planned to s upport the Environmental Assessment process for

Wheeler River, and the considerable uncertainty tha t has impacted capital markets, we believe that the

decision to temporarily suspend the EA is in the best interest of all interested parties. Our team made great

progress in 2019 and early 2020 towards advancing t he EA and de-risking the proposed In-Situ Recovery

(‘ISR’) uranium mine planned for the Phoenix deposit. During the temporary suspension we expect to be

focused on making the most of our positive momentum and positioning ourselves to quickly resume the

process when appropriate.”

The duration of the temporary suspension is unknown at this time. The Company intends to monitor the

COVID-19 situation and will coordinate the resumpti on of the EA with the applicable regulators and

interested parties. Further information will be provided as appropriate.

Background on the Project’s Environmental Assessment Process

The EA is a planning and decision-making tool, whic h involves predicting potential environmental effec ts

throughout the project lifecycle (construction, ope ration, decommissioning and post-decommissioning) a t

the site, and within the local and regional assessm ent areas. During the first quarter of 2019, Denis on

submitted a Project Description to the Canadian Nuc lear Safety Commission (“CNSC”) and a Technical

Proposal to the Saskatchewan Ministry of Environmen t ('SK MOE') to support the advancement of an In-

Situ Recovery (“ISR”) uranium mine at Wheeler River. This work followed the release of the Pre-Feasibility

Study (“PFS”) completed for Wheeler River in late 2 018, considering the potential economic merit of

developing the Phoenix deposit as an ISR operation and the Gryphon deposit as a conventional

underground mining operation (see press release dated October 30, 2018) .

The Project Description and Technical Proposal were accepted in the second quarter of 2019, initiating the

EA process for the Project in accordance with the r equirements of both the Canadian Environmental

Assessment Act, 2012 ('CEAA 2012') and the Saskatchewan Environmental Assessment Act . In late

December 2019, Denison received a Record of Decisio n from the CNSC on the scope of the factors to be

taken into account for the Wheeler EA, which indicate that the EA will follow the CNSC's generic guidelines.

Significant progress has been made in collecting en vironmental baseline data in previous years, and th e

current focus of EA related activities is split between engagement with interested parties and the completion

of various environmental assessments and studies re lated to the predicted environmental effects of the

Project.

The Company identified the EA process as a key element of the Project's critical path. Accordingly, Denison

initiated various studies and assessments to suppor t the preparation of the Project Environmental Impa ct

Statement (“EIS”), following the decision to advanc e the Wheeler River project in late 2018 (see press

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release dated December 18, 2018). The decision to temporarily suspend the EA process is expected to

impact the project development schedule outlined in the PFS for Wheeler River. Given the uncertainty

associated with the duration of the suspension, the Company is not currently able to estimate the impact to

schedule. Further information, including a revised development schedule, will be provided as appropriate.

Impact on Outlook for 2020

The Company announced its plans for 2020 in its ann ual MD&A for the year ended December 31, 2019

(the “2020 Outlook”). Those plans identified two discretionary work programs related to the advanceme nt

of Wheeler River: (1) the continuation of the EA and submission of a draft EIS to the Federal and Provincial

regulators (approximately $7.0 million), and (2) the completion of further ISR field testing to support wellfield

designs for a future Feasibility Study (approximate ly $6.6 million). Given the decision to suspend th e EA,

and the current economic disruption associated with COVID-19, these work programs are not currently

expected to advance in 2020. Based on the 2020 Out look, the Company intends to maintain its

environmental and technical teams in 2020 and to se lectively advance certain scopes of work, outside o f

the discretionary work programs, to position the Company to quickly resume project development activities

in the future and minimize the impact to the project schedule.

About Wheeler River

Wheeler River is the largest undeveloped uranium pr oject in the infrastructure rich eastern portion of the

Athabasca Basin region, in northern Saskatchewan – including combined Indicated Mineral Resources of

132.1 million pounds U 3O8 (1,809,000 tonnes at an average grade of 3.3% U 3O8), plus combined Inferred

Mineral Resources of 3.0 million pounds U 3O8 (82,000 tonnes at an average grade of 1.7% U 3O8). The

project is host to the high-grade Phoenix and Gryph on uranium deposits, discovered by Denison in 2008

and 2014, respectively, and is a joint venture betw een Denison (90% and operator) and JCU (Canada)

Exploration Company Limited (10%).

Pursuant to the PFS, the Project is estimated to have mine production of 109.4 million pounds U 3O8 over a

14-year mine life, with a base case pre-tax NPV of $1.31 billion (8% discount rate), Internal Rate of Return

("IRR") of 38.7%, and initial pre-production capita l expenditures of $322.5 million. The Phoenix ISR

operation is estimated to have a stand-alone base c ase pre-tax NPV of $930.4 million (8% discount rate ),

IRR of 43.3%, initial pre-production capital expend itures of $322.5 million, and industry leading aver age

operating costs of US$3.33/lb U 3O8. The PFS is prepared on a project (100% ownership) and pre-tax basis,

as each of the partners to the Wheeler River Joint Venture are subject to different tax and other obligations.

Further details regarding the PFS, including additional scientific and technical information, as well as after-

tax results attributable to Denison's ownership int erest, are described in greater detail in the NI 43 -101

Technical Report titled "Pre-feasibility Study for the Wheeler River Uranium Project, Saskatchewan,

Canada" dated October 30, 2018 with an effective da te of September 24, 2018. A copy of this report is

available on Denison's website and under its profil e on SEDAR at www.sedar.com and on EDGAR at

www.sec.gov/edgar.shtml.

About Denison

Denison is a uranium exploration and development company with interests focused in the Athabasca Basin

region of northern Saskatchewan, Canada. In additio n to the Wheeler River project, Denison’s Athabasca

Basin exploration portfolio consists of numerous pr ojects covering approximately 305,000 hectares.

Denison’s interests in the Athabasca Basin also include a 22.5% ownership interest in the McClean Lake

joint venture (“MLJV”), which includes several uranium deposits and the McClean Lake uranium mill, which

is currently processing ore from the Cigar Lake mine under a toll milling agreement, plus a 25.17% interest

in the Midwest and Midwest A deposits, and a 66.57% interest in the J Zone and Huskie deposits on the

Waterbury Lake property. Each of Midwest, Midwest A, J Zone and Huskie are located within 20 kilometres

of the McClean Lake mill.

Denison is also engaged in mine decommissioning and environmental services through its Closed Mines

group (formerly Denison Environmental Services), wh ich manages Denison's Elliot Lake reclamation

projects and provides post-closure mine care and ma intenance services to a variety of industry and

government clients.

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Denison is also the manager of Uranium Participatio n Corp., a publicly traded company which invests in

uranium oxide and uranium hexafluoride.

For more information, please contact

David Cates (416) 979-1991 ext 362

President and Chief Executive Officer

Sophia Shane (604) 689-7842

Investor Relations

Follow Denison on Twitter @DenisonMinesCo

Cautionary Statement Regarding Forward-Looking Statements

Certain information contained in this news release constitutes ‘forward-looking information’, within the meaning of the applicable United

States and Canadian legislation concerning the business, operations and financial performance and condition of Denison.

Generally, these forward-looking statements can be identified by the use of forward-looking terminolog y such as ‘plans’, ‘expects’,

‘budget’, ‘scheduled’, ‘estimates’, ‘forecasts’, ‘intends’, ‘anticipates’, or ‘believes’, or the negatives and/or variations of such words and

phrases, or state that certain actions, events or r esults ‘may’, ‘could’, ‘would’, ‘might’ or ‘will be taken’, ‘occur’, ‘be achieved’ or ‘has

the potential to’.

In particular, this news release contains forward-looking information pertaining to the following: the EA process, including its intended

scope, objectives and timing; the results of the PFS and expectations with respect thereto (including potential for delays as a result of

the temporary suspension of the EA and other discre tionary programs and expenditures); evaluation and development plans and

objectives generally and in Denison’s 2020 Outlook; and expectations regarding its joint venture ownership interests and the continuity

of its agreements with its partners.

Forward looking statements are based on the opinions and estimates of management as of the date such statements are made, and

they are subject to known and unknown risks, uncert ainties and other factors that may cause the actual results, level of activity,

performance or achievements of Denison to be materi ally different from those expressed or implied by s uch forward-looking

statements. For example, if market conditions remai n volatile and/or COVID-19 mitigation measures resu lt in more social and

economic disruptions, Denison may need to further re-assess its discretionary and non-discretionary expenditures and programs for

2020 and beyond, which could have significant impacts on Denison and/or the development of the Project. Denison believes that the

expectations reflected in this forward-looking information are reasonable but no assurance can be given that these expectations will

prove to be accurate and results may differ materia lly from those anticipated in this forward-looking information. For a discussion in

respect of risks and other factors that could influence forward-looking events, please refer to the factors discussed in Denison’s Annual

Information Form dated March 13, 2020 under the hea ding ‘Risk Factors’. These factors are not, and should not be construed as

being exhaustive.

Accordingly, readers should not place undue relianc e on forward-looking statements. The forward-lookin g information contained in

this news release is expressly qualified by this cautionary statement. Any forward-looking information and the assumptions made with

respect thereto speaks only as of the date of this news release. Denison does not undertake any obligation to publicly update or revise

any forward-looking information after the date of t his news release to conform such information to act ual results or to changes in

Denison's expectations except as otherwise required by applicable legislation.

Cautionary Note to United States Investors Concerni ng Estimates of Measured, Indicated and Inferred Mi neral Resources

and Probable Mineral Reserves: This news release may use the terms 'measured', 'i ndicated' and 'inferred' mineral resources.

United States investors are advised that while such terms have been prepared in accordance with the definition standards on mineral

reserves of the Canadian Institute of Mining, Metal lurgy and Petroleum referred to in Canadian Nationa l Instrument 43-101 Mineral

Disclosure Standards ("NI 43-101") and are recogniz ed and required by Canadian regulations, the United States Securities and

Exchange Commission ("SEC") does not recognize them. 'Inferred mineral resources' have a great amount of uncertainty as to their

existence, and as to their economic and legal feasibility. It cannot be assumed that all or any part of an inferred mineral resource will

ever be upgraded to a higher category. Under Canadi an rules, estimates of inferred mineral resources m ay not form the basis of

feasibility or other economic studies. United States investors are cautioned not to assume that all or any part of measured or

indicated mineral resources will ever be converted into mineral reserves. United States investors are also cautioned not to

assume that all or any part of an inferred mineral resource exists, or is economically or legally mine able. The estimates of

mineral reserves in this news release have been prepared in accordance with NI 43-101. The definition of probable mineral reserves

used in NI 43-101 differs from the definition used by the SEC in the SEC's Industry Guide 7. Under th e requirements of the SEC,

mineralization may not be classified as a "reserve" unless the determination has been made, pursuant to a "final" feasibility study that

the mineralization could be economically and legall y produced or extracted at the time the reserve det ermination is made. Denison

has not prepared a feasibility study for the purpos es of NI 43-101 or the requirements of the SEC. Ac cordingly, Denison's probable

mineral reserves disclosure may not be comparable t o information from U.S. companies subject to the re porting and disclosure

requirements of the SEC.