Mineral exploration of a claim within Tombstone Territorial Park should not be allowed to proceed, a board has recommended to the Yukon government.

The Yukon Environmental Socio-economic Assessment Board (YESAB) issued its recommendation Tuesday.

"The project will have significant adverse environmental and socio-economic effects in and outside the Yukon that cannot be mitigated,” the board says.

The government has 30 days from the issuance of the recommendation to either accept, reject or modify the recommendation.

Canadian United Minerals Inc. staked the 18 Horn claims in 1997, before the area was protected.

The claim is located within the Cloudy mountain range, part of the Ogilvie Mountains and within the headwaters of the Blackstone River.

According to the YESAB report, exploration work began on the claims in 1998 and 1999; little to no exploration occurred after 2001.

In 2010 and 2011, "(the company) was ordered by Yukon Government to clean up the site after many years of inactivity, which left scattered debris and contaminated soil,” the report says.

In April of 2010, Canadian United Minerals submitted a project proposal that was rejected after the YESAB recommendation was supported by the government.

The report says the government decision body indicated that that decision would not stop the company from submitting a revised project proposal, which it did in May 2011.

Lewis Rifkind, the Yukon Conservation Society's (YCS's) mining co-ordinator, said this morning the society is pleased with the outcome of the assessment and hopes the government will accept it.

"All mining operations should respect the environment. This particular one, because it's within Tombstone park, it's not necessarily how it's operated or the standards, it's because of the geographic location,” said Rifkind, explaining why the YCS believes the YESAB recommendation should be accepted.

YESAB received and considered 896 comments about the Horn claims.

Rifkind said the YCS did mobilize its local supporters on the issue, while the Yukon chapter of the Canadian Parks and Wilderness Society (CPAWS) reached out to its national membership to make submissions, although a form letter was not used.

The YESAB report says the majority of the comments were received from outside the territory. Ultimately, many were deemed "not relevant,” as they were "based on an obvious misunderstanding of the project location, project details and objective of the assessment.”

The executive director of CPAWS Yukon could not be reached for comment before press time this afternoon.

The Horn claims have been controversial since they were staked, as the area was set to be protected and was covered under the Tr'ondek Hwech'in Land Claims Agreement.

It was the subject of a legal challenge before the Supreme Court of the Yukon.

Calls to the Tr'ondek Hwech'in regarding the decision were not returned.

In a 2010 letter to YESAB, Tr'ondek Hwech'in Chief Eddie Taylor, Nacho Nyak Dun Chief Simon Mervyn and Gwich'in Tribal Council president Richard Nerysoo expressed their concerns about the project proposal submitted that year by Canadian United Minerals.

"The area in which the activities are proposed to take place has unparalleled cultural and spiritual value to our peoples,” the letter says.

"This was one of our most important historic places of refuge and remains so as a place to gather plants, harvest caribou and find solace. It would be impossible to overstate the importance of the Blackstone Uplands.”

The letter also mentions the ongoing land use planning for the Peel watershed which would protect all of the Blackstone River except what is in the park.

"Clearly, any damage to the upper Blackstone will have serious effects further downstream. Our efforts to protect the lower portion of the drainage will be meaningless if the upper portion is compromised.”

The letter concludes by asking YESAB to recommend the proposal be rejected, which it did later that year.

Dan Macdonald, a spokesman for the Department of Energy, Mines and Resources, said this morning the department will take some time to review the recommendation and the project application and would prefer not to comment further.

"But the YESAB recommendations will be given full consideration when preparing the decision document,” Macdonald said.

The Yukon Chamber of Mines has also refrained from commenting until the final decision has been given.

Attempts to reach Joel White, the president of Canadian United Minerals, before deadline were unsuccessful.