Rio Alto Mining Limited
TSX VENTURE : RIO
FRANKFURT : MS2

Rio Alto Mining Limited

September 21, 2009 09:30 ET

Rio Alto Mining Limited: Files Environmental Impact Assessment and Engages European Investment Relations Firm

VANCOUVER, BRITISH COLUMBIA--(Marketwire - Sept. 21, 2009) - Rio Alto Mining Limited ("Rio Alto") (TSX VENTURE:RIO)(FRANKFURT:MS2) is pleased to announce that as manager of La Arena S.A. it has filed an Environmental Impact Assessment ("EIA") with Peruvian authorities to develop a 24,000 tonne per day open pit gold oxide mine at La Arena.

Prior to filing the EIA with the Ministry of Energy and Mines, consultations were held with various government agencies including the National Water Authority, the Ministry of Agriculture, the Energy and Mines Authority for the Province of La Libertad and the Municipality of Huamachuco. Lodging the EIA with the Ministry of Energy and Mines is a major milestone in the permitting and development process for La Arena and follows more than two years of study and preparation by the staff of La Arena S.A., Rio Alto and external consultants directed by Tecnologia XXI S.A.

The review and approval of the EIA is expected to be completed in six to nine months, which allows Rio Alto to target the start of production at La Arena during the fourth quarter of 2010.

Throughout the EIA approval process Rio Alto will continue with detailed engineering, metallurgical testing, geotechnical assessments and community relations efforts to prepare for construction and development upon receipt of environmental approvals for an open pit gold oxide mine. Work recently completed and ongoing at La Arena includes:

- In early September, 100 tonnes of representative run-of-mine ore was collected for definitive metallurgical test work leading to detailed process plant design;

- Sterilization (condemnation) drilling of approximately 5500 meters to confirm that planned infrastructure locations are barren of economic mineralization started in August and will be finished in late October;

- Topographical and aerial survey work was completed, in August, to an accuracy of one meter to allow for detailed engineering of site infrastructure;

- Vector Peru S.A. conducted a geophysical survey of the underground aquifer at La Arena to target water wells and for hydrogeological studies;

- A power demand report was prepared for discussions with a large distributor for the supply of power to the gold oxide project. An estimate of power and associated capital costs should be received some time in October;

- Several exploration targets were revisited and prioritized for future work.

"I am very pleased with the progress we are making at the La Arena Project" commented Alex Black, Director & COO. "Our management team is working tirelessly to ensure we meet our target for first production in Q4 2010."

The Company is also pleased to announce that, on September 18, 2009, it engaged the services of Axino AG ("Axino") of Stuttgart, Germany as an investor relations firm at an annual fee of EUR 22,500 to be paid in advance from working capital and 200,000 options to purchase common shares in the capital of the Company. The initial term of the engagement is for one year. Options granted under this engagement are subject to approval by the TSX-V and would, if approved, have a five-year term, be exercisable at $0.35 per share, which was 17 per cent more than the closing price of the Company's shares on the day immediately preceding the grant, and would vest as to 25% on each of the 3, 6, 9 and 12 month anniversaries from the date of grant.

A German and Swiss based investor relations and corporate communications firm Axino also provides services as a Deutsche Borse listing partner, prepares independent research and conducts investment banking services for and on behalf of natural resource companies. Axino will translate, into German, and disseminate Company announcements and assist with interaction between European investors and the Company. Prior to this engagement Axino had no interest in Rio Alto or its securities or any right to acquire any such interests.

"Rio Alto Mining combined with Mexican Silver Mines in late July and since then our team has done an outstanding job." stated Feisal Somji, President and CEO. "The Company has an 18-month development timeline and we are on track to reach production before the end of 2010. Investor relations efforts in Europe along with upcoming marketing efforts in Peru and in North America should bring recognition of recent accomplishments and help reflect the value of La Arena in our share price."

Rio Alto Mining Limited (TSX VENTURE:RIO)(FRANKFURT:MS2) is focused on developing the La Arena Gold Oxide Project in Peru with production targeted for Q4 2010 and exploring for silver on three former silver producing properties in north eastern Mexico. The Company's principal objective is to become the next company in Peru to bring a gold project into production and to use cash flow from production to further develop its assets in Peru and Mexico. To learn more about Rio Alto Mining Limited, please visit: www.mexicansilvermines.com. Financial information and other information can also be found at www.sedar.com.

Forward Looking Statements

Certain of the statements made and information contained within this press release are "forward-looking information" within the meaning of the Ontario Securities Act or "forward-looking statements" within the meaning of Section 21E of the Securities Exchange Act of 1934 of the United States. Forward-looking statements are subject to a variety of risks and uncertainties which could cause actual events or results to differ from those reflected in the forward-looking statements, including, without limitation, risks and uncertainties relating to foreign currency fluctuations; risks inherent in mining including environmental hazards, industrial accidents, unusual or unexpected geological formations, ground control problems and flooding; risks associated with the estimation of mineral resources and reserves and the geology, grade and continuity of mineral deposits; the possibility that future exploration, development or mining results will not be consistent with the Company's expectations; the potential for and effects of labour disputes or other unanticipated difficulties with or shortages of labour or interruptions in production; actual ore mined varying from estimates of grade, tonnage, dilution and metallurgical and other characteristics; the inherent uncertainty of production and cost estimates and the potential for unexpected costs and expenses, commodity price fluctuations; uncertain political and economic environments; changes in laws or policies, foreign taxation, delays or the inability to obtain necessary governmental permits; and other risks and uncertainties. More particularly, and without limitation, this press release contains forward-looking information with respect to the timing of environmental approvals for a 24,000 tonne per day gold oxide mine at La Arena and the timing of expected production from La Arena. Forward-looking information is based on various assumptions including, without limitation, the expectations and beliefs of management, the assumed long-term prices of mineral commodities; that the Company can access financing, appropriate equipment and sufficient labour and that the political environment where the Company operates will continue to support the development and operation of mining projects. Should one or more of these risks and uncertainties materialize, or should underlying assumptions prove incorrect actual results may vary materially from those described in forward-looking statements. The Company assumes no obligation to update or revise, except as may be required under law, forward-looking statements to reflect new events or circumstances. Accordingly, readers are advised not to place undue reliance on forward-looking statements.

ON BEHALF OF THE BOARD OF RIO ALTO MINING LIMITED

Feisal Somji, B.Sc., MBA, President and Chief Executive Officer

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts the responsibility for the adequacy or accuracy of this release.

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