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Page 2 of 3 <br />• For the UWFGSC site, these parameters include sulfate (339 mg /1) and <br />magnesium (101 mg /1). The period of record for water quality data <br />collection at this site is 2007 — present. <br />• For the LGSC site, a maximum value for sodium (215 mg /1) was recorded <br />in August 2012. Other high values of sodium were recorded in May 2012 <br />and October 2012 at this site, indicating a possible trend that should be <br />monitored closely in the future. The period of record for this site extends <br />back to 1983. <br />4. The Division has the following observations regarding groundwater data (no direct <br />response is required from Colowyo although these comments are related to comment <br />number 2 above): <br />• Per the R2 values for groundwater, there is one significant trend in the data. In <br />Gossard well, TDS has been increasing over the entire period of record, although it <br />has been decreasing since 2006. Recent values have been approximately 1,700 mg /1. <br />• For the reporting year of the 2012 AHR, in one of the wells concentrations of two <br />parameters reached the maximum values of the entire recording period. In the MT- <br />95-02 well, sulfate (1,090 mg /1) and sodium (181 mg /1) were at all-time highs (the <br />period of record for this well is 1984 to 2012), but there is not a significant long -term <br />trend for either parameter in this well. <br />• The high sulfate value mentioned above is higher than the domestic drinking water <br />standard. As there are domestic wells in the area, this may become a concern if <br />levels of this parameter continue at this level or rise in the future. <br />5. Data from DMRs was not provided in the AHR, but a review of this data is an important <br />aspect of water quality at the Colowyo Mine. I reviewed this data (in DMR reports <br />submitted by Colowyo) and found the following exceedances of regulatory limitations <br />(CDPHE was informed of the exceedances). <br />• First quarter: At Outfalls 001A, 004A, 007A, 01OA, and 011A exceedances of <br />limitations for TSS and Total Recoverable Iron were detected. (High TSS values <br />were not detected at Outfall 010A). A request for waiver of primary standards was <br />made to CDPHE, and evidence was provided that the exceedances were due to <br />snowmelt. The alternate limitation for settleable solids was met at all outfalls. <br />• Second quarter: <br />o At Outfall 01OA (discharge from East Taylor Pond) the discharge limitation <br />was exceeded for Total Suspended Solids in June. Alternate limitations were <br />not applicable to these exceedances. It is believed that algae in the pond are <br />the problem, and Colowyo has committed to cleaning the pond to prevent <br />future exceedances. <br />o At Outfall 011A (discharge from West Taylor Pond) the discharge limitations <br />were exceeded for Total Suspended Solids and Total Recoverable Iron in <br />March 2012. Colowyo indicated that alternate limitations were applicable due <br />to snowmelt runoff (precipitation data support this assertion), and the <br />Settleable Solids limitation was not exceeded. <br />