The firm said it had now settled an agreement, which will result in the dismissal of the appeal.
In June, the company told investors it had received the long-awaited operating permit, the final one needed to get the mine up and running.
But an appeal was subsequently filed by a coalition of non-governmental organizations (the petitioners).
All appeals are reviewed by the Environmental Appeals Board (EAB), noted Excelsior in Friday's statement.
"As per the terms of the agreement, Excelsior, the EPA, and the petitioners have submitted to the EAB a joint stipulated motion to dismiss the appeal.
"It is anticipated that the EAB will accept the joint motion to dismiss the appeal which, subject to notice by the EAB, will prompt the EPA to lift the stay, thereby resulting in the UIC permit becoming effective with permanence."
The mining company added: "With all key permits in place and effective, Excelsior will be in a position to commence construction upon the completion of its project financing plan.
"Excelsior's Gunnison Copper project remains poised to be the next new copper producer in the United States."
The project is an advanced, low cost, environmentally friendly in-situ recovery copper project.
A feasibility study projected an after-tax NPV (net present value) of US$807 million and an IRR (internal rate of return) of 40% using a US$2.75 per pound copper price and a 7.5% discount rate.
Shares added over 10% to stand at $1.05.