The reason for uranium exploration and uranium mining in northern Arizona, during a period of low yellowcake price, was the high grade and compact nature of the uranium mineralization contained in some of the collapse breccia pipes in the region. In 1982, total production cost for breccia pipe uranium was about $10/lb U308 concentrate that then sold for approximately $40/lb. Later inflation-corrected cost data published by EFN in the Canyon Mine Environmental Impact Statement confirms the 1982 total cost quotation. In 2007 US dollar terms, the total cost to produce a pound of U308 from the average pipe was about $24. Average ore reserves for an individual mineralized pipe at that time were determined to be about 3.5 million pounds U308, with an average grade of about 0.6 percent U308, then giving the average economically mineralized pipe an approximate before-tax, undiscounted in-ground value of about $105 million (more than $225 million in 2007 US dollars).[http://pubs.usgs.gov/bul/b2004/html/bull2004model_for_solutioncollapse_brecc.htm] The breccia pipe mineral deposits range from 1000 to 1800 feet deep and have a vertical extent of up to 600 feet. The pipes typically have a diameter. A shaft is usually required to access the deposits. In some cases where a mineralized pipe occurs near a deep canyon, a decline can be used instead of a shaft to access the ore during mining.