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Red Creek Quarry Baseline Water Investigation Section 6 <br /> <br /> <br />6-11 <br />DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this docu ment. <br />6.2.2 Elevated Constituent Concentrations in Surface Water <br />Surface water data were compared to the water quality standards for COARU14A segment based on <br />the watershed designation for Red Creek (Figure 6-9) from the Colorado Department of Public Health <br />and Environment Clean Water GIS website (https://cdphe.colorado.gov/clean-water-gis-maps). <br />Surface water data were elevated with respect to the standards for several total and dissolved <br />metals/metalloids, nitrite, total phosphorus, total chlorine and dissolved sulfide (Appendix H). The <br />elevated metal/metalloid results are mainly from the Stilling Well sample collected during the first <br />quarterly sampling event (August 2022). Results from the Stilling Well are likely reflective of shallow <br />alluvial water in contact with the creek bed sediments and not the water flowing within Red Creek. <br />High turbidity from the Stilling Well also likely affected the total and dissolved metal/metalloid <br />concentrations of the sample. <br />Concentrations of dissolved selenium, dissolved sulfide, total chlorine, and Escherichia coli (E. coli) <br />had more than one elevated surface water quality result (Appendix H). E. coli are bacteria found in <br />the lower intestines of humans and animals. The presence of E. coli in the surface water samples is <br />likely the result of fecal matter from cows or other animals close to and within Red Creek. Evidence <br />of animals (cows and other wildlife) was observed over multiple sampling events in the area of all <br />three surface water sites. <br />Time trend plots were generated of dissolved selenium to evaluate changes in concentration <br />(Figure 6-10). Data from SW RC1 had lower concentrations of dissolved selenium during May and <br />July of 2023 than the previous two quarters. Location SW RC1 is a shallow pool of water without <br />much flow (mostly stagnant) with a silty bottom that can become suspended during the sample <br />collection (Photo 6-2). The lower concentrations of dissolved selenium may be the result of increased <br />direct precipitation during the days to weeks prior to the sampling events or the result of <br />heterogeneity of the sample source due to suspended solids from the pool bottom becoming <br />entrained in the sample during collection. <br /> <br />Photo 6-2. Surface water location SW RC1