2017-01-20_REVISION - C2009087 - Laserfiche WebLink

Home Browse Search

the PSCM) exhibited an excursion of the iron standard from 2011 through 2015, except one occurrence during January 2014 at NPDES4 with a concentration of 1.55 mg/l. Sixty samples were collected and analyzed for iron (TREC) at NPDES4 between January 2011 and December 2015, and 59 out of 60 were below the iron standard. Therefore, these excursions on Fish Creek are not caused by either mining operation. The nitrite standard, 0.05 mg/1, was exceeded once at Site SSF13 with a value of 0.06 mg/1. Site SSF13 exists on Fish Creek downstream of the confluences of Cow Camp and Bond Creeks. The nitrite value at Site SSM 1 (Fish Creek upstream of the confluences of Cow Camp and Bond Creeks) from a sample collected on the same day (6/14/11) was 0.04 mg/l. No excursions of this standard occurred at SSC10, SSB12, NPDES4 or NPDES8 discharges. Therefore, thisexcursion on Fish Creek was not caused by either mining operation. Also, nitrites are unstable in aerated water (Hem, 1989), and will oxidize to nitrates. As a result of the 2014 Upper Colorado River Basin Rulemaking Hearings, the CWQCC assigned a temporary modification for the chronic aquatic life selenium standard of 4.6 ug/1 in Segment 13g, which removed the numeric limit and set it to a narrative standard of "current conditions". The temporary modification was established due in part to significant uncertainty regarding the numeric standard necessary to protect uses, and because there is substantial uncertainty about the extent to which existing quality is the result of natural or irreversible human -induced conditions. The temporary modification is set to expire on December 31, 2018. Because the current chronic aquatic life standard is set at "current conditions", only the acute aquatic life selenium standard of 18.6 ug/1 was compared to data collected from 2011 and 2015. No exceedances of the acute aquatic life selenium standard (18.4 ug/1) occurred from 2011 through 2015 at NPDES4 or any surface water sites downstream, including lower Fish Creek Site SSF13, so attainment of the acute standard is being met at all sites including those located downstream.. PSCM discharges surface runoff and spoil leachate into Segment 13i (Grassy Creek and tributaries from the source to immediately above the confluence with Scotchmans Gulch) of the Yampa River based on Colorado Water Quality Control Commission (CWQCC) Regulation 33. As mentioned previously, Regulation 33 was recently revised in August 2014 as part of the Upper Colorado River Basin Rulemaking Hearings. PSCM is required to monitor 17 parameters in that 28