APPCOR11909 - Laserfiche WebLink

Home Browse Search

1, Coldwater segment with table value standards. There are no site specific standazds so that any instream increases in metals concentrations must meet table values. If [he mine proponents predict ins[ream metal concentrations will increase, an adequate monitoring program is needed along with contingency plans to limit metal increases to those allowed by the existing stream standazds. Table 2.05.6-8 of the Lorencito application predict that [he worst case iron concentrations at the PRS-3 (The Purgatoire River downstream of the mine) would increase from 0.44 to 2.14 mg/l. Past DOW experience indicates that at an 2.4 mg/I iron concentration other metals (specifically cadmium, copper and zinc) are typically present in levels either acutely or chronically toxic to aquatic life. The application needs to address the issue of reduced trout numbers due to increased metal concentrations. Stream standards are set to protect trout populations. If the mine meets the existing stream standards for this Purgatory River segment there should not be adverse impacts to the brown trout population. 3. Detection limits for water quality analvses The application indicates that certain water quality parameters were present at levels less than detection limits. These metals include silver, copper and mercury. The surface water quality detection limits listed in various sections of the application indicated that all water analyses were performed by ICP analysis. ICP detection limits are often higher than ecologically pertinent concentrations. For example, the copper ICP detection limit is 10 parts per billion. A copper level of ] 0 parts per billion can be lethal to trout. Consequently, it is imperative to determine the copper concentrations in surface water a[ levels lower than those produced by ICP analysis. Other mines and municipalities throughout Colorado employ laboratory procedures that produce accurate, replicable data at concentrations far less than ICP results. The DOW requests that the applicant use the following laboratory protocols and detection limits: Parameter method detection limit cadmium graphite furnace 0.1 parts per billion copper 1.0 parts per billion zinc flame as 10 parts per billion selenium graphite furnace 2 parts per billion silver 0.05 parts per billion nitrite calorimetric 3 parts per billion 7'he applicant needs to begin collecting water quality data using these, or other, appropriate techniques that produce the same, or lower, detection limits. The DOW requests the inclusion of selenium into the suite of parameters monitored by the applicant. Selenium is an issue on the entire Arkansas River Basin. The dazk shales referred to in the application are an indication that selenium levels may be an issue in Lorencito Canyon. 4. Decreased water quali[v in Lorencito Canvon and the Purgatory River The application indicates that the water quality in Lorencito Canyon will be "decreased." This degradation will also result in deceased water quality in the Purgatoire River. The application also indicates that