80. 



The second priority was storage in especially prepared excava- 

 tions in shale at depth. The experience record comes from cavities 

 that have been prepared at a number of places for storage of hydro- 

 carbons in very recent years. Some of the advantages are that rela- 

 tively thick shale beds are scattered widely over the United States; 

 there are sites that probably could be obtained for this use near sev- 

 eral of the existing installations as well as potential future sites. 

 Furthermore, the cost is low. When we use as a basis of cost evalua- 

 tion the operations now under way for the storage of hydrocarbons, 

 figures ranging from $3 to $7 per barrel were cited as representative 

 of the cost for the preparation of this type of underground cavity. The 

 research needed here is study of the stability of shale in the presence 

 of these particular aqueous solutions. 



The third order of preference -- and on this particular item 

 there was considerable diversity of opinion -- was infiltration into 

 particular low-permeable beds with a suitable high clay content for the 

 fixing of these materials in place. This infiltration above the water 

 table bears some similarity to the Hanford operation as it was des- 

 cribed, but with certain modifications. The needed research indicated 

 here was (a) study of the hydrodynamic profile of the system; (b) devel- 

 opment of proper tracer for water; (c) study of behavior of a suitably 

 simulated solution to determine exchange characteristics; and, of 

 course, (d) highly detailed investigations of water-table fluctuations in 

 any area that might be considered for this type of disposal. It should 

 be pointed out that only those areas with low water table, which would 

 largely limit this matter to some of the western areas, would be usable. 



The fourth order of preference was deep, abandoned dry mines. 

 It was the consensus of opinion that if a proper dry mine could be lo- 

 cated it might be a very feasible method of disposal, but that such mines 

 would be extremely difficult to come by and might very well not be in 

 the vicinity of any site where they would be needed. If such a structure 

 could be located, it was indicated that some research would be needed 

 on he at -dissipation problems under the particular conditions obtaining 

 in that mine . 



The fifth and last category that was judged to be worthy of consid- 

 eration was disposal in properly covered shale and clay pits on the sur- 

 face. The consensus was that at the present state of knowledge, it is 

 not a desirable means of disposing of high level wastes, but that it 

 would be desirable to have continued research on base exchange and 

 self- sealing characters in the hope that this method might become fea- 

 sible for high-level waste in the future. Research on self-sealing 



