Laserfiche WebLink
segment per its CDPS and CDRMS permits, which is provided in Table 8. Table 9 provides a <br />statistical summary of the water quality over years 2011 to 2015 for PSCM's Outfall NPDES2 <br />and Stream Sites SSG1, SSG2 and YSG5. Table 10 provides a comparison of those data with the <br />Segment 13i standards. <br />Table 10 indicates the pH standard was exceeded once at Site SSG2 with a value of 6.44 on <br />6/3/13. The pH values upstream at Sites NPDES2, NPDES3 and SSG1 on the same day were <br />7.56, 8.31 and 7.57, respectively. The pH value downstream at Site YSG5 on the same day was <br />8.35 so the exceeded value appears to be in error. <br />Table 10 also indicates the total recoverable (TR) iron standard of 1.0 mg/l was exceeded a total <br />of twenty times (out of 46 samples) at Grassy Creek Sites SSG1 (Grassy Creek upstream of <br />PSCM outfalls), SSG2 and YSG5 (both are Grassy Creek sites downstream of PSCM outfall <br />NPDES2). High TR iron values are normally associated with high total suspended solids. No <br />excursions of this standard occurred at PSCM NPDES2. Only one excursion of the iron TR <br />standard occurred out of 62 samples collected at PSCM Outfall NPDES3 during 2011 through <br />2015. Due to the absence of high iron TREC found in samples from both outfalls, it is clear that <br />these excursions on Grassy Creek are not caused by the mining operation. <br />As a result of the 2014 Upper Colorado River Basin Rulemaking Hearings, the CWQCC assigned <br />a temporary modification for the chronic aquatic live selenium standard of 4.6 ug/l in Segment <br />13i, which removed the numeric limit and set it to a narrative standard of "current conditions". <br />The temporary modification was established due in part to significant uncertainty regarding the <br />numeric standard necessary to protect uses, and because there is substantial uncertainty about the <br />extent to which existing quality is the result of natural or irreversible human -induced conditions. <br />The temporary modification is set to expire on December 31, 2018. Because the current chronic <br />aquatic life standard is set at "current conditions", only the acute aquatic life selenium standard of <br />18.6 ug/l was compared to data collected from 2011 and 2015. <br />Site YSG5 is located on segment 13j of Grassy Creek downstream of its confluence with <br />Scotchman's Gulch. The chronic aquatic life selenium standard for this lower segment of Grassy <br />Creek remains at 4.6 ug/l. Table 9 indicates several samples analyzed for all three forms of <br />29 <br />