Alamosa River

Where acid drainage is well developed and extensive, the costs of remediation can be high. In the Summitville, Colorado district (USA), for example, efforts to limit the contamination of fertile irrigated farmlands in the nearby San Luis Valley and protect aquatic life in the Alamosa River will cost an estimated 100 million or more (Plumlee, 1994a). 

Green, C.H., The Solubility of Manganese and Coincident Release of Metals Based on the Reduction of Alamosa River Basin Soils, Colorado, Master s thesis, Colorado State University, 1992. 

Figure 9 Downstream profiles in the Wightman Fork/Alamosa River system of (a) pH measured and simulated (b) dissolved aluminum concentrations measured and simulated (c) dissolved iron concentrations measured and simulated and (d) copper concentrations measured and simulated. Simulations were obtained with the OTEQ code after calibration on tracer-injection data and Fe(II/III) determinations.

Ball J. W., Runkel R. L., and Nordstrom D. K. (2003) Evaluating remedial alternatives for the Alamosa River and Wightman Fork, Summitville, Colorado application of a reactive-transport model to low- and high-flow synoptic studies. In Environ. Sci. Environ. Comput. (ed. P. Zanetti). EnviroComp Institute, Fremont, CA, vol. 2 (in press). 

Application to Copper and Zinc Problems in the Alamosa River, Colorado... 

Figure 2. Stu

The Use Attainability Assessment (UAA) as well as recent USEPA monitoring indicated that water quality standards in the basin were not being met due to a combination of the natural geologic conditions and metals contamination due to mining. The UAA also discussed historic aquatic life uses in the basin (6). Anecdotal evidence fiom local persons and a variety of other Forest Service, Division of Wildlife, and USEPA data are reported to indicate that the Alamosa River supported at least a limited fishery until 1990. While there is evidence of mining activity in the upper Alamosa River, it was determined to be a minimal influence of stream water quality. 

Table 1. Pre-Mining concentrations in the Alamosa River below the mouth of Wightman Fork (AR 45.4)...

Concentrations of dissolved and total zinc were nearly identical and indicated the limited partitioning of zinc to the iron oxides at pH conditions in the Alamosa River (<7.0) for the pre-Galactic scenario. While the concentration of total copper is reduced by 82% firom Wightman Fork to Terrace Reservoir through combined adsorption (to bed sediments) and dilution, the zinc concentration is reduced 1 47%. Zinc and copper are both removed to the bed sediments, although zinc is removed less efficiently. If pH were in the range of 7.S-8.0 in the system, both zinc and copper adsorption would be enhanced and the associated dissolved metal in the water column would be decreased further. 

The pre-mining water quality for copper and zinc during 11 time is shown in Figures 8-9 and, as for copper, would represent the highest seasonal concentrations for both dissolved and total metals in the Alamosa River downstream of Wightman Fork. Total copper concentrations decrease 1 66%... 

Medine, A. J. Technical Assessment of Pre-Mining and Pre-Galactic Water Quality for Wightman Fork and the Alamosa River. USEPA, National Risk Management Research Laboratory, Cincinnati, OH, 1997. 

CDPHE. Use Attainability Assessment Alamosa River Watershed through 1996. Posey, H. H. Woodling, J. Campbell, A. and Pendletoit J. A. USEPS and Colorado WQCC, July 12,1996. 

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