The 810,000 tons/yr of TDS disposed in ponds is about one-fourth of the estimated 3.1 

 million tons/yr of salt accumulation in the San Joaquin Valley's west side. CH2M HILL's 

 estimate is 743,800 tons/yr. 



Assuming the density of evaporites as 2.66 g/cm' (thenardite) the annual volume of salts 

 accumulating in the ponds is about 164,500 cubic yds or an average deposition thickness 

 of0.17in/yr. 



Assuming the density of evaporites as 1.28 g/cm^ (not well-developed crystalline forms), 

 about 342,000 cubic yds of salt are accumulating in the ponds annually or an average 

 deposition thickness of 0.36 in/yr. 



The above range of estimates on annual salt deposition in ponds indicate huge amounts 

 available for possible salt harvesting or for disposal. However, the presence of toxic 

 elements in the salt deposits may constrain how these salts are ultimately disposed. 



▲ Best Design and Management Practices 



• The factors and conditions sustaining evaporation and salt deposition rates were 

 evaluated. Many of these factors are not readily manageable (changeable) while a few 

 may be manageable such as regulating salinity levels or increasing absorbed net solar 

 radiation using a dye, 2-Naphthol Green. 



• Evaporation rate of water is strongly affected by salinity of the pond water. Typically, 

 salinity in ponds are lowest in the winter and spring, and highest in the summer and fall. 



• In addition to pond water salinity, formation of salt crusts on the surface of water bodies 

 severely restricts evaporation rates. 



• Use of cells in pond facilities with gates to serially transfer water of varying salinities 

 may sustain evaporation rates. 



• Pond water depth appears not to be a major factor influencing evaporation rates. 



• To minimize seepage of pond water into underlying ground water basins and adjacent 

 lands, perimeter interceptor drains are recommended. If seepage needs to be further 

 controlled, collector drains could be installed beneath the ponds. 



• Other methods of reducing seepage losses are the deposition of algal mats or burial of 

 straw layers in pond bottoms. 



• The ORMAT process is being advanced to enhance evaporation rates. Due to proprietary 

 constraints, the initial capital costs and effectiveness are not readily available or known. 



• The best management options and design features to sustain evaporation and salt 

 precipitation rates may be overridden by considerations to make ponds safer to wildlife 

 by making the ponds less attractive and reducing contaminant hazards. 



page 1.14 



