U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12,1999--Volume 1 of 3--Contamination From Hard-Rock Mining, Water-Resources Investigation Report 99-4018A

Transport Modeling of Reactive and Non-Reactive Constituents from Summitville, Colorado: Preliminary Results from the Application of the OTIS/OTEQ Model to the Wightman Fork/Alamosa River System

By James W. Ball, Robert L. Runkel, and D. Kirk Nordstrom

This report is available in pdf format: Ball.pdf 518KB

ABSTRACT

Reactive-transport processes in the Wightman Fork/Alamosa River system downstream of the Summitville Mine, south-central Colorado, were simulated under low-flow conditions using the OTIS and OTEQ solute transport modeling programs. Simulation results revealed that Ca, Cu, Mg, Mn, Na, Zn, Cl, F, and SO₄ are conservative in the stream reach, whereas pH, Fe, and Al are non-conservative. Simulations that allow precipitation of Fe(OH)₃ and Al(OH)₃ match observed water quality more closely than conservative simulations. The pH could not be adequately simulated without assuming that tributary inflows had pH values of about 8 or higher and alkalinities of 50-110 milligrams per liter (mg/L). Subsequent sampling confirmed these predictions.