Laserfiche WebLink
<br />All iron excursions were the result of high suspended solids. None of <br />the iron excursions were at a NPDES site. The two stream sites that <br />experienced excursions are upstream of Seneca's discharges. SCC is <br />proposing that this iron standard be changed to an ambient-based <br />standard in the same June 2008 CDPHE hearing mentioned above. <br />One stream site, SSG3, experienced an exceedance to the mercury <br />standard, 0.01 ug/1, with a value of 0.2 ug/1. This value is equal to <br />the detection limit for analyses done on stream samples. No other <br />historic mercury value was greater than the detection limit. This site <br />monitors discharges from a pre-SMCRA mining area. <br />One stream site, SSLG5, exceeded the nitrite standard. This site is <br />upstream of the mining area. Nitrites are unstable in aerated water and <br />will oxidize into nitrates (Hem, 1989). <br />Two samples from NPDES3 experienced exceedances of the sulfide standard <br />(0.002 mg/1 un-ionized). The analytical method available to SCC detects <br />both dissolved sulfides and acid-soluble metallic sulfides present in <br />suspended matter. It is suspected that a large portion of the sulfides <br />detected is of the latter type, which would bias the un-ionized results <br />high. Any dissolved sulfides present in surface water should eventually <br />oxidize to sulfates. <br />NPDES Effluent Criteria (Permit No. CO-0000221). No excursions of NPDES <br />effluent criteria occurred this year. <br />Surface Water Summary. water discharged from the Seneca II Mine is not <br />used directly for irrigation. Indirectly, although, water discharged <br />from the mine is significantly diluted by water from either Fish Creek <br />or the Yampa River before it is diverted and used for irrigation. No <br />irrigation exists on Grassy Creek below Seneca II. Due to the relative <br />amount of dilution by additional water from both sources, the ambient <br />water qualities of Fish Creek and the Yampa River are the dominant <br />factors in determining their suitability for irrigation. Water <br />21 <br />~. <br />