2017-05-11_PERMIT FILE - C1981012 (18)

Home Browse Search

In TRIM COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Control Division Fact Sheet- Page 23, Permit No. C00000906 Sodium Absorption Ratio (SAR), Adiusted SAR (Outfall 001) Outfall 001: The capped limit for SAR is set out in the WQA, and is established as a 30 -day average limit. Note that the SAR limit may change based on the actual EC of the effluent, as based on the SAR/EC equation (SAR = (7.1 * EC) - 2.48), which is the limitation expressed in the permit. Note that the maximum SAR is capped at the value of the SAR/EC equation using the EC limit calculated in the WQA or 9, whichever is less. High bicarbonate concentrations also adversely affect plant growth because bicarbonate combines with calcium and magnesium and will precipitate out of solution, lowering the amount of available calcium. For this reason, the effluent SAR will be calculated as the adjusted SAR, which takes into account the amount of bicarbonate in the effluent. The SAR limit is expressed as a Pass/Fail limit, and the permittee will be required to determine the SAR limit based on the above equation. The permittee will report the adjusted SAR of the effluent, and determine whether this value meets the allowable SAR as determined by the equation (or the capped value). Reporting of the effluent Ca, Mg, Na, and HCO3 will be required for confirmation of calculations. See the Definitions of Terms Section of the permit for detailed instructions on how to calculate the adjusted SAR using the HCO3 and Ca concentrations. Monitoring data indicate that the facility may not be able to consistently meet the limitation. Therefore, a compliance schedule is included in the permit for outfall 001. Organics - The effluent is not expected or known to contain organic chemicals, and therefore, limitations for organic chemicals are not needed in this permit. Whole Effluent Toxicity (WET) Testing For outfall 001 chronic WET testing has been determined to be applicable based on the instream waste concentrations calculated in the WQA. This facility has reasonable potential to discharge metals and TDS at concentrations that may be toxic to aquatic organisms that are not adequately controlled by chemical specific effluent limits. Although the previous effluent data show no violations of the permit limit, chronic WET testing will be included in the permit for outfall 001. Chemical additives in waste streams of ponds 007 and 008 have reasonable potential to cause aquatic toxicity; therefore, acute WET testing at outfalls 007 and 008 are included in the permit. Acute WET testing is applied based on the intermittent nature of the discharge, and a delayed effective date is applied to allow the facility time to evaluate results. WET testing is not required at outfall 010 at this time (stormwater subject to the federal ELG at Subpart D, but without mine water contribution). This determination was based on effluent data from outfall 001 (Subpart B and Subpart D), which show no violations of the WET permit limit during the previous permit term. Further, the permittee did not identify that any chemicals are added to discharges from this outfall, which if added, could have reasonable potential to cause aquatic toxicity. The permittee should read the WET testing section of the permit carefully, as this information has been updated in accordance with the Division's updated policy, Implementation of the Narrative Standard for Toxicity in Discharge Permits Using Whole Effluent Toxicity (Sept 30, 2010). The permit outlines the test requirements and the required follow-up actions the permittee must take to resolve a toxicity incident. The permittee should also read the above mentioned policy which is available on the Permit Section website. The permittee should be aware that some of the conditions outlined above may be subject to change if the facility experiences a change in discharge, as outlined in the permit. Such changes shall be reported to the Division immediately. C. Parameter Speciation Total / Total Recoverable Metals For standards based upon the total and total recoverable methods of analysis, the limitations are based upon the same method as the standard.