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Response 1985 AHR <br />Page 2 <br />Response• <br />The data indicates that discharge in Fish Creek shows historical variation. <br />Station 1002 recently was measured and the discharge measurements reveal the <br />station is functioning properly. <br />MLRD Comment: <br />Analytical laboratory data can be checked using three methods: mass balance <br />analyses, a comparison of calculated and gravimetrically determined total <br />dissolved solids (TDS) values or a comparison of electrical conductivity and <br />total dissolved solids (TDS). A random survey of mass balance showed cations <br />consistently being reported at levels ten percent higher than anions. <br />Consequently, calculated TDS should have been ten percent higher than the <br />gravimetric determination. However, calculated TDS and the gravimetric TDS <br />had no consistent relationship with each other. We strongly recommend that <br />you request the lab to achieve greater compatibility between these values. <br />The comparison of EC and TDS is the least rigorous quality check, because the <br />relationship is site specific. Natural waters low in sulfates generally <br />should show the relationship: <br />TDS = 0.6EC <br />As sulfate concentrations rise (as in waters surrounding coal mines) this may <br />become a 1:1 relationship. However, there is no documentation that we are <br />aware of which ever shows EC lower than TDS and a random check showed low EC's <br />40 percent of the time. We recommend that standards be used frequently out in <br />the field to calibrate the conductivity meter, and that laboratory analyses of <br />EC be run on a random basis to verify field procedures. <br />Response• <br />In reference to the comment about the laboratory, TCC will discuss the matter <br />with its lab and request they ensure their reports are accurate. In reference <br />to field measurements of EC the contractor has purchased a new meter and it <br />will be checked against a standard prior to use and recalibrated as needed. <br />MLRD Comment: <br />Detection limits for four elements were not low enough to ascertain whether <br />the water was meeting stream standards. <br />