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Attachment B -4- <br /> Comments <br /> 4-Comments on Tidal Dilution of the Stockton Regional Wastewater <br /> Control Facility Discharge Into the San Joaquin River <br /> April 2001 <br /> 11. The Report does not discuss the governing equations of the model. There is also no <br /> discussion of any simplifications to the governing equations that may be pertinent to <br /> the application of the model. <br /> 12. The Report does not discuss the attributes and limitations of the model. This is very <br /> important due to the impaired condition of the receiving water. Does the model have <br /> limitations that would cause concern or uncertainty in the results? <br /> 13. The Report documents the process of calibrating the lateral dispersion. However, <br /> there is no discussion of any calibration of the main purpose of the model, river <br /> concentration. It does not appear that the model was calibrated or tested to make sure <br /> the results seemed reasonable. <br /> 14. The Report does not discuss the level of confidence in the model results. There must <br /> be some uncertainty considering the complex tidal conditions. <br /> The Report poorly documents the water quality model, omitting important information <br /> needed to determine the validity of the results. Models can be useful to estimate <br /> environmental conditions when based on sound principles with conservative input <br /> parameters and boundary conditions. However, actual data provides absolute <br /> measurements that override the usefulness of any model estimate. The Regional Board's <br /> estimation of allowable dilution is based on actual flow data. The submitted Report does <br /> not provide justification to make any changes to this evaluation. <br />