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~. _~ ~") <br />z <br />Should you wish to discuss the items below, I encourage you to <br />contact me or Susan Morrison. Following are the adequacy concerns <br />which need to be addressed in order for the Division to make the <br />findings required by Rule 2.07.6(2)(c). <br />1. Section 2.5.3.5 of the Edna permit (Hydrologic Balance) and <br />the Division's January 14, 1987 Findings of Compliance for the Edna <br />Mine contains several predictions of hydrologic impacts from mining <br />operations based upon baseline data, projections and water quality <br />standards. These include, <br />a. a prediction that maximum total dissolved solids <br />(TDS) concentrations in Trout Creek surface water in the <br />permit area will not exceed 607 mg/1 (page 21 of <br />Findings), <br />b. a prediction that the mean annual TDS concentration <br />of Trout Creek surface water in the permit area during <br />' dry years will equal 330 mg/1 (page 2.5-104) and will <br />equal 196 mg/1 during "normal" years (page 2.5-103) and, <br />c. a prediction that impacts to irrigated crops in the <br />Trout Creek alluvial valley floor adjacent to the permit <br />area may occur if Trout Creek surface water specific <br />conductivity exceeds 1.0 mmhos/cm (page 21 of Findings). <br />Data in the February, 1992 Annual Hydrology Monitoring Report (AHR) <br />for the Edna Mine indicates that surface water TDS at sampling <br />sites TR-C and D has exceeded predicted levels on several <br />occasions. It also indicates that the mean annual TDS <br />concentration in Trout Creek from 1986-91 was 434 mg/1 (compared to <br />the 330 mg/1 prediction). Specific conductivity measurements <br />during the past two years have frequently exceeded 1.0 mmhos/cm at <br />Trout Creek sampling sites. Many of these readings are attributed <br />to faulty equipment in the 1992 AHR. <br />P & M needs to update section 2.5.3 of the Edna permit to <br />incorporate results of hydrologic monitoring since 1981 into the <br />analysis and predictions in the permit. The discrepancies <br />mentioned above should be explained. A discussion of these topics <br />might include reference to lower flows than predicted, influences <br />other than mining (such as increased farming activities alluded to <br />in the AHR), sampling and lab problems and any other factors which <br />may have contributed to the water quality results that have been <br />observed to date. <br />2. Page 2.5-95 contains an equation which was apparently used to <br />derive TDS numbers from electrical conductivity measurements. Page <br />