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snow and thunderstorms. The flow in the North Fork of Cement Creek just above Gladstone <br /> presently ranges between 15.7 million gallons per day (mgd) at the end of May to 0.23 mgd at <br /> the end of January. The flow in Cement Creek above Gladstone may have been greater prior <br /> to mining due to increased discharge from springs (see section 3.1.7). The flow in Eureka <br /> Creek just below the Terry Tunnel typically ranges from 7.2 mgd in early June to 0.17 mgd in <br /> late October. The flow in Eureka Creek was calculated by adding the measured flow above the <br /> Terry Tunnel to the measured flow from the Terry Tunnel and does not include the flow from <br /> McCarty Basin (which is not measured). The rate of flow in Eureka Creek (below the present <br /> portal of the Terry Tunnel) probably has not been significantly affected by mining. <br /> 3.2.2 Surface-Water Chemistry <br /> There are no recorded measurements of the water chemistry of Eureka Creek or Cement Creek <br /> prior to mining. Early accounts, at the very onset of mining in the 1870's, relate that locally <br /> the natural quality of water was so poor that certain streams were "undrinkable" (Rhoda, 1984). <br /> This is not surprising considering the tremendous volume of sulfides dispersed throughout the <br /> bedrock (see section 3.1.1). These sulfides react with meteoric water to release acid and <br /> mobilize metals. <br /> Eureka Creek above the Terry Tunnel is presently neutral (average pH from 1987-1991 was <br /> 7.1). Eureka Creek above the 'terry Tunnel may have had a lower pH prior to mining because <br /> surface drainages flowing over outcrops within the highly mineralized Sunnyside Basin would <br /> be expected to have reacted with sulfides. For example, a drainage above the Washington Vein <br /> aanjumi\sumty\110361\oct9l.Rpt 29 <br />