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stream sites in the Grassy Creek basin. Standards that were exceeded <br />(excluding ammonia and sulfide) are: <br /> <br />Parameter # of S <br />Iron 5/5 <br />of Excursions <br />All iron excursions occurred in April, and were the result of high <br />suspended solids caused by snowmelt runoff. The two sites upstream of <br />mining (SSG1 and SSLGS) were among the sites experiencing exceedences. <br />Ammonia values require extra calculations to determine exceedences. The <br />standard is 0.06 mg/1 un-ionized NH3, while the method detects both un- <br />ionized NH3 and ionized NH4. The following table calculates the actual <br />un-ionized NH3 concentration of the exceedences reported on Table 14. <br />Site Date NH3+NH4,mg/1 pH Temp,C $NH3 NH3 conc., mg/1 <br />NPDES3 9/3/03 0.03 8.34 17.8 6.8 0.021 <br />This sample did not exceed the ammonia standard. <br />Sulfide values also require extra calculations. The standard is 0.002 <br />mg/1 un-ionized H2 S, while the method detects for un-ionized x2S and <br />ionized HS. The following table calculates the actual un-ionized H2S <br />concentration of the exceedences reported on Table 14. <br />Site Date H2S+HS,mg/1 pH $H25 H2S concentration, mg/1 <br />NPDES3 4/8/03 0.04 8.24 5.9 0.002 <br />NPDES3 9/3/03 0.04 8.34 4.9 0.002 <br />SSG1 4/8/03 0.09 8.23 5.9 0.005 A <br />SSLGS 4/10/03 0.80 8.11 7.5 0.060 A <br />A = exceedence <br />Only two samples experienced exceedences of the sulfide standard. Both <br />sites are upstream of mining. However, any sulfides present in surface <br />water should eventually oxidize to sulfates. <br />23 <br />