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-4- Total ion concentrations require the destruction of particle {eg.: sand grain) structure and/or the dissolving of all tightly bound ions prior to analysis. Therefore, the total ion concentration tests for ion concentrations which do not readily interact with the chemistry of the water. If one is interested in the ion concentrations which could cause toxicity to plants, animals, or man; one is interested in those ion concentrations which are readily absorbed or extracted. Thus, total ion concentrations yield erroneously high values, where as total recoverable ion concentrations are more representative of the ion concentrations which can be adsorbed from the water directly or readily extracted from the surfaces of suspended sediment particles. It was very unfortunate that CF&I ran total ion concentrations on water quality analyses and that their data Baas thrown out in preparing the receiving stream standards. However, the Water Quality Control Commission and the Colorado Health Department were justified in throwing out erroneously high values, especially when threshold toxic ion concentrations are being raised to reflect the natural or ambient conditions. The use of erroneously high values would have biased the standards towards the high end and allow a higher pollution level in the Purgatoire River and its tributaries. I do not agree with CF&I's contention that there is no trace metal toxicity problem with discharges from the mining operations. I agree with CF&I's contention that dissolved trace elerents in discharges from the mining operations are not at toxic levels due to the buffering capacity of the waters. Recoverable or easily extracted ions on suspended sediments may pose a significant toxicity problem. The water discharging from the Allen and Maxwell Mine sites have a neutral pH and sufficient buffering capacity to convert dissolved toxic metals to insoluble adsorbed complexes on suspended sediment particles, or to insoluble suspended colloidal particles. These insoluble adsorbed complexes and colloidal particles are unstable and can be made soluble with slight changes in pH, ionic balance and/or oxidation/reduction potential. These adsorbed complexes and colloidal particles do represent toxic constituents within surface waters. If infested by man or other animals, the digestive enzymes and acids can cause these complexes and colloids to break down and thus release the toxic ions. The toxic ions can also enter the bodies of aquatic animals through their respiratory systems, or may foul the respiratory system of aquatic animals causing suffocation. Plants in contact with adsorbed complexes and colloidal particles can break down these materials and adsorb the toxic elements. The toxic elements adsorbed by plants can: 1) cause death of the plant, 2) reduce productivity of the plant, and/or 3) be concentrated by the plant. If the toxic ion is concentrated by the plants, the plants could become toxic to animals dependent upon them for a food supply, or toxic to animals through the release of toxic ions and organic complexes upon the death of the plant.