Answer to Question #343 Submitted to "Ask the Experts"

Q

With reference to question #268: I seem to recall from a ranger talk I heard about 12 years ago that there is an old uranium mine just below the south rim of the Grand Canyon and that the tailings are still there. The ranger indicated that they had measured increased levels at that location. Does anyone know if I am remembering correctly? Are uranium deposits more abundant in that area of the country? Thanks!

A

ORPHAN MINE Park: Grand Canyon National Park (GRCA) State: Arizona County: Coconino USGS Quadrangle: Bright Angel, Arizona (15') Location: T31n,R2W,Sec.14 Visitor Access: Orphan Mine is located on the south rim of the Grand Canyon between Maracopa Point and Powell Memorial. The immediate vicinity is visited by at least 1.5 million people each year. Visitors walking along the canyon rim must detour around the site. The large headframe and other structures on the site attract curious visitors. The chain-link fence around the mine workings is often in a state of disrepair, and is only partly effective where it joins the rim. Hazards: The main shaft is 1,500 feet deep and is accessible via a ladderway exposed just below the canyon rim. The remaining structures, foundations, and trash also present physical hazards. Radiation levels are elevated throughout the compound and in a visitor-use area to the west, with combined beta and gamma sometimes exceeding 3.0 mR/hour. Magnitude: The mine occupies 20 acres of land on and below the rim of Grand Canyon. Openings consist of three adits and a subsidence pit (30 feet diameter by 250 feet deep) approximately 1,000 feet below the rim, and a 2½ compartment shaft (13 feet x 5 feet) with a ladderway opening just below the rim. The main shaft is 1,600 feet deep and reaches the ore body via a drift 1,200 feet long. Five structures remain on the rim. Resource Impacts: Approximately ten acres of land on the rim are radiologically contaminated (in excess of 0.057 mR/hour) with ore and waste rock. Mine History and Current Ownership: Orphan Mine was first worked for copper in 1906. Uranium was discovered in the ore and mined from 1953 to 1972. Uranium content in ore shipments was as much as 4.9 percent and approached 80 percent in individual samples. The patented land was acquired by National Park Systems in 1963, but extraction rights were retained by the operator until August 1988.

Gary S. Freeland, Program Manager
Arizona Radiation Regulatory Agency Radiation Measurements Laboratory

Editor's Note: Freeland has indicated that the mine recently has undergone a clean up. He expects to receive a copy of the report in November 2000. Let us know if you would like a copy of the report.