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<br />. <br /> <br />. <br /> <br />Laboratory evaluations--In addition to the laboratory identification work <br />mentioned above, the clay samples are also being tested to determine <br />their sealing potential (See Tables I and II). ,lhile general agreement <br />has been noted between the laboratory test results and the field trial <br />results (See Table III), some descrepancies have been found. Excellent <br />materials from a lab test angle have produced poor sealing results in <br />field trials. Conversely, clay materials rated poor in the laboratory <br />have produced excellent field trial results. Undoubtedly, part of the <br />problem is related to the need for better test procedures; thus, new <br />and modified procedures are being developed, The general objective <br />of the work is to develop simple economical lab test procedures that <br />can be used for clay specification purposes. However, it is also <br />obvious that the correlation problem between lab and field also ref- <br />lects a need for improved field trial procedures. <br /> <br />Procedure development trials--As may be seen in Table III and Map II, <br />the field trial phase of the procedure development work is well advanced <br />for a relatively few clays in several restricted areas of the State. <br />For example, consider the canal (multiple-dam) and reservoir (blanketing) <br />work with the S49 clay in the area surrounding Salida. As time and funds <br />become available, work in new areas of the State will be initiated. <br />However, since the trial work is funded and organized at local level, <br />it is important to realize that the presence or absence of trials in <br />any particular area of the State depends largely on the local interest <br />in initiating such work--from the standpoint of either or both (a) the <br />owners of canals, and (b) the producers of clays. Past project expe- <br />rience indicates that finding contractors or irrigation districts will- <br />ing to invest their ingenuity and funds in field trials is not normally <br />a problem; nevertheless, the local interest is necessary before the <br />trial work will materialize. For a general idea of the installation <br />procedures utilized in development work to date, see Photos I through <br />B. Detailed procedure write-ups are planned and will be prepared <br />when the results and evaluations for any particular method warrant such <br />publications. Several publications, subject to change as additional <br />evaluations are completed, are available now upon request. <br /> <br />. <br /> <br />Quality of clay--Another important part of the development work is con- <br />cerned with the clay itself, Producing a suitably uniform clay product <br />of acceptable quality for sealing purposes is a tougher problem than <br />connnonly appreciated. While it is true that the sealing quality and <br />consequently also the reputation of good local clays have been damaged <br />by careless mining and production methods, in fairness to the clay pro- <br />ducers, it should be pointed out that they are faced with several impor- <br />tant unresolved problems. For example, many clay deposits are extremely <br />variable--in quality, in thickness, and in lateral extent. Perhaps the <br />most pressing problem, however, is the absence, at present, of suitable <br />specifications for canal and reservoir sealing clays. Of the various <br />problems, the specification problem is probably the most important: <br />removing that problem would remove the major uncertainty of the present <br /> <br />-11- <br /> <br />1021 <br />