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RPR 22 2003 08:36 FR WRIGHT WRTER 3034801020 TO 19709295595 <br />ti <br />~. <br />1~1=C~IVED ~ <br />MEMOR.~INDlJM <br />MAY 0.2 2 <br />Division of Minerals a~~ealogy Henry Bazbe <br />Mountain Coal Company <br />From: Wright Wazer Engineers, Inc. <br />David B. Mehan <br />Dr. Robert Weiner <br />Date: Apri121, 2003 <br />Re: Recommended Level of Alkalinity Adjustment for WET Tests <br />P.02i05 <br />At our recommendation, Mountain Coal Company (MCC) requested, in an April 2003 letter to the <br />Water Quality Control Division, that the whole effluent toxicity (WET test) procedure for Outfall <br />017 be modified to adjust the alkalinity of the test water to a maximum of 1,000 mg/L. This <br />memorandum provides the basis for this recommended maximum concentration of alkalinity. <br />EVALUATION <br />The recommended maximum concentration was evaluated three ways, as follows. <br />l) Relationship Between Alkalinity and TVlostalitp from Past Test: The relationship <br />between alkalinity and percent mortality of Daphnie magna from past WET tests for Outfall <br />017 was investigated. A plot of this relationship using 100°/a effluent concentration data <br />from WET tests, the November, 2002 PTI, and the January 2003 TIES is shown on the <br />attached Figure 1. <br />Figure 1 shows that the lowest concentration of alkalinity that caused a WET test failure <br />with Daphnia at the 100 percent effluent concentration was 1,860 mg/L. The equation on <br />this figure, which is statistically significant ai the 95°/a level of confidence, predicts a "no <br />effects" concentration of 1,368 mg/L alkalinity. <br />2) STR Model: The "STR model" that was developed by the Gas Research Institute was run <br />with the ionic composition of the water from Outfall 017 from a December 2003 analysis <br />(during the period that a "pattern of toxicity" existed with the WET tests) with three <br />scenarios: <br />a) Constant alkalinity with series of dilutions of other ions. <br />b) Series of dilutions of all anions and cations. <br />c) Constant ions with series of dilutions of alkalinity. <br />Wright Water Engineers, tap„ 2480 W, 26°1 Awnve, Ste. t00A, Donver, CO 90211 <br />Tel, 3031490.1700; Fax. 303/480.7020, e-mall:krvMght~wrighlwetor.wm <br />