Installation of leakage barriers to enhance yield of mineral deposits in unlined solar pond systems

Abstract

Slurry walls and methods of using those slurry walls to seal unlined solar ponds are provided. The slurry walls are formed from a mixture comprising clay and cement in water. A trench is keyed into the dike surrounding the solar pond, down to a geotechnically predetermined level. The slurry is deposited into the trench and allowed to harden, after which it is covered with a membrane or other covering. The inventive slurry walls reduce, and preferably prevent, leakage of water from the solar pond.

We claim: 
     
         1 . A slurry wall formed from a hardened mixture, the mixture before hardening comprising:
 from about 3% to about 25% by weight cement, based upon the total weight of the mixture taken as 100% by weight;   from about 1% to about 15% by weight clay, based upon the total weight of the mixture taken as 100% by weight; and   water.   
     
     
         2 . The wall of  claim 1 , wherein said cement is selected from the group consisting of Types II-V Portland cements, blast furnace slag cement, and mixtures thereof. 
     
     
         3 . The wall of  claim 1 , wherein said clay is selected from the group consisting of bentonite clay, modified bentonite clay, sepiolite clay, attapulgite clay, and mixtures thereof. 
     
     
         4 . The wall of  claim 1 , wherein said water comprises the following properties:
 a pH of from about 6.0 to about 9.5;   a hardness of less than about 400 ppm;   an alkalinity of less than about 400 ppm;   a total dissolved solids of less than about 4,000 ppm;   a density of from about 1.0 gm/cc to about 1.04 gm/cc; and   an apparent viscosity of from about 0.8 cP to about 2 cP.   
     
     
         5 . The wall of  claim 4 , wherein said mixture comprises Portland Cement and bentonite. 
     
     
         6 . The wall of  claim 5 , wherein said mixture comprises about 17% by weight Portland Cement and about 6% by weight benonite, based upon the total weight of the mixture taken as 100% by weight. 
     
     
         7 . The wall of  claim 1 , wherein said water comprises the following properties:
 a pH of from about 7.0 to about 9.0;   a hardness of less than about 600 ppm;   an alkalinity of less than about 400 ppm;   a total dissolved solids of less than about 200,000 ppm;   a density of from about 1.05 gm/cc to about 1.21 gm/cc; and   an apparent viscosity of from about 0.8 cP to about 2 cP.   
     
     
         8 . The wall of  claim 7 , wherein said mixture comprises Portland Cement, blast furnace slag cement, and sepiolite. 
     
     
         9 . The wall of  claim 8 , wherein said mixture comprises about 1% by weight Portland Cement, about 12.5% by weight blast furnace slag cement, and about 5.5% by weight sepiolite, based upon the total weight of the mixture taken as 100% by weight. 
     
     
         10 . The wall of  claim 1 , wherein said slurry wall has a permeability of less than about 1×10 −4  cm/sec. 
     
     
         11 . The wall of  claim 1 , wherein said slurry wall has an unconfined compressive strength of at least about 2.5 psig about 7 days after said slurry wall is formed. 
     
     
         12 . The wall of  claim 1 , wherein said slurry wall has a slake decay of less than about 20% by volume at about 30 days after said slurry wall is formed. 
     
     
         13 . The wall of  claim 1 , wherein said mixture is capable of hardening within about 7 days after said slurry wall is formed, as measured by a penetrometer. 
     
     
         14 . The wall of  claim 1 , wherein said mixture has a Marsh Funnel viscosity of from about 20 seconds to about 70 seconds.