Laserfiche WebLink
<br /> <br />element not mentioned could grow into concentrations that would be considered toxic <br />by water quality standards. <br />The Division does not determine a material's toxicity. Rather, we rely on water <br />quality standards developed by the Water Quality Control Commission to be <br />protective of designate or potential future uses of water. In that regard, review of <br />surface water quality data for the Dolores shows no regular exceedances of water <br />quality standards for the stream reach adjacent to the proposed operation. <br />B. Proposed safeguards are insuj~ciettt to asst+re containment of the_following <br />constituents: <br />• mineral salts of As, Ba, Be, Cd, Cr, Hg, <br />• other chromates, <br />• other compounds which are ntt+ch [Wore toxic than metallic mercury, <br />• iron in solttion, <br />• particulate iron potentially fatal for persons with heart problems, and <br />• arty and all other dissolved salts <br />• radon, U~js, and plutonium. <br />RESPONSE: The suite of rocks noted in the Geology section above does not <br />contain minerals that would tend to incorporate or concentrate toxic concentrations <br />of the elements specified in the various objection letters. Moreover, the suite of <br />elements mentioned in the several objection letters is not characteristic of deposits <br />found in Colorado. There is nothing about the native rock suite - andesite, <br />quartzite or shale -that would produce water having the composition noted by the <br />elements listed in the objections. <br />Chromium. Chromium is generally not found in elevated concentrations in <br />rocks of Colorado or its streams. Cr does occur in trace quantities in many types <br />of rocks found herein, but concentrating mechanisms by gravel mining are not <br />evident. <br />chromates. chromates are characteristic of pollution related to industrial <br />applications like chrome plating shops, but not rock weathering. <br />Cadmium, arsenic and iron. Cadmium, arsenic, and iron do occur in several <br />mining areas in Colorado, although not in adjacent to gravel deposits. These <br />elements tend to derive from weathering of sulfide minerals, such as are common <br />at base and precious metal mines where acid drainage occurs or has developed due <br />to mining. Dissolved iron tends to precipitate rather quickly once neutral pH <br />waters dilute metal-bearing acidic waters. Cadmium and arsenic tend also to be <br />removed quickly from solution due to sorption by iron hydroxides. Given that the <br />nearest known source for high concentrations of these elements is the Dolores <br />9 <br />