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<br />estimate of formation permeability requirements and availability. An <br />assessment of potential subsurface environmental impacts will also be <br />performed. <br />If these activities indicate potential success, it is anticipated <br />that a test well would be drilled to more fully define subsurface <br />characteristics and potential environmental impacts of injecting. <br />Actual injection testing would be conducted during advance planning <br />and feasibility of the project would be subject to favorable results of <br />the testing. A cursory estimate of the construction costs of the <br />project injection well and appurtenant facilities is $8 million. <br />B. High Recovery Desalting Alternatives <br />For desalting options considered, higher recovery results in less <br />reject brine, and consequently lower costs for brine disposal. It also <br />reduces the loss of water from the river and the amount of water <br />rights to be acquired. Compared to 70-percent recovery, 80-percent <br />recovery reduces brine by 1/3 and 90-percent recovery by 2/3. <br />The electrodialysis desalting (ED) process is more costly to <br />construct than reverse osmosis (RO), but has lower operating cost at <br />recovery rates of 90 percent or more with La Verkin Springs' water. <br />Lime-ion exchange pretreatment uses less chemicals than the <br />lime-soda ash process, particularly with high recovery desalting. <br />The reject brine can be used to regenerate the ion-exchange modules, <br />and less sludge is produced than by the lime-soda ash process. At <br />the present time, a degree of confidence with which to recommend <br />feasibility is shared only by the RO process with the proven lime- <br />soda ash pretreatment, The opportunity for greater recovery with <br />less chemical use through ion exchange pretreatment holds promise for <br />increased effiCiency and these concepts are being pursued before a <br />firm decision is made on which method is more feasible. A contracted <br />field study to investigate the compatibility of various pretreatment <br />technologies with high recovery desalting options is underway on site. <br />The results of this study are anticipated to have important applica- <br />tions to the La Verkin Springs Unit as well as other salinity control <br /> <br />002530 <br /> <br />21 <br />