What evidence is there in the archaeological record for the very-long-term performance of mine waste disposal facilities? A paper from twenty-five years ago gives some interesting answers. I refer to Evidence for the Long-term Stability of Uranium Mill Tailings: Survivability of Ancient Man-Made Earthen Structures by Lindsey, Mishma, and King, published in the Fifth Symposium on Uranium Mill Tailings Management held in Fort Collins, Colorado, December 1982.

They describe earthen mounds worldwide. Archaeologists identify these factors as important to mound stability:

  • Faunalturbation: Disturbance by animals including burrowing, digging, and soil turn-over by earthworms.
  • Floralturbation: Disturbance by roots growth and decay, particularly by trees.
  • Cryoturbation: Soil disturbance by freezing and thawing actions including frost heave.
  • Graviturbation: Mass wasting including mixing and movement of soil and rock debris downslopes, principally under the influence of gravity without the aid of flowing media such as wind or water. This includes solifluction, gelifluction, frost creep, and soil creep.)
  • Argilliturbation: Disturbance from the expansion and contractions of clay; this is particularly important in humid climates and in structures that experience alternate wetting and drying of clay.
  • Aeroturbation: This is disturbance of the surface mantle by soil gases and wind that results primarily in the loss of the finer fraction of the soil.
  • Aquaturbation: Disturbance of the soil by the action of artesian water. And surely this includes common soil erosion?
  • Crystalturbation: Soil disturbance by the growth and wasting of crystals including salts.
  • Seismiturbation; Soil disturbance from seismic activity, including earthquakes and ground tremors.

And of course there is water erosion and the action of man—digging up the mound to get at treasure or building materials.

They tell us that the oldest major mound site in the United States is Poverty Point in Louisiana. This mound was started around 1,500 B.C. and consists of concentric ring mounds and several large conical mounds. The site is over one-kilometer wide and the diameter of the rings (which are only 2-meters high) is over 1,200 meters. The large conical mound is over 23-meters high and has a diameter of 198 meters.

The largest mound in the United States is Monk’s Mound at Cahokia in East St. Louis, Illinois. The mound is 316-meters long, 241-meters wide and over 31-meters high. It contains about 600,000 cubic meters of soil. It was occupied between 900 and 1,700 A.D.

These two mounds demonstrate that in the absence of human intrusion, reclaimed mine waste disposal facilities can stand more or less intact for many centuries.

Throughout the American Southwest are ancient rock structures including the most spectacular, Chaco Canyon and Mesa Verde. The durability of the rock used to construct the structures at these sites tells us of the long-term integrity of rip-rap properly selected.

I await eagerly the appearance of the first EIS to use the procedures of forward-looking archaeology, including all the X-turbations listed above to evaluate the post-closure performance of a mine waste disposal facility.

Finally a note on another form of turbation. David Maxwell of Statistical Research Inc. told me that a few years back, he coined a new term for a type of "turbation": "Zalophoturbation" (from Zalophus californicus, the California sea lion). He was working on San Nicolas Island, west of Santa Catalina, and the sites were in sand dunes, and were being actively destroyed by the activities of the sea lions, who would sun themselves on the dunes. Sea lions are nimble in the water, but pretty clumsy on sand, and destroyed huge portions of the sites being investigated!