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-28- Boron (B) also has exceeded Colorado acceptable levels for agricultural use in Grassy Creek surface water during mining activity. A sample from March 29, 1982 at SW4 had .80 mg/1 of B verses .75 mg/1 for acceptable agriculture use. Sampling at the downstream site (SW1) showed decreased B levels which never exceeded the Colorado standard for irrigation. Elevated levels of Fe, and Mn have also been noted in the alluvial monitoring wells along Grassy Creek. The following data was received for samples taken on March 29, 1982. MWl is located immediately downstream of mining activity. MW3 is located further downstream at the permit boundary. Upstream MW1 Fe 3.21* Mn 1.47 Downstream MW3 0.17 0.12 *All data in mg/1 The elevated level of Fe may have been partially due to concentration resulting from a dry water year where little recharge of fresh water from streamflow was available to the alluvium. Elevated levels of Fe and Mn are also expected to result from ground water flow through reclaimed mine sites. The interburden/overburden samples show elevated levels of Fe and Mn. The underburden samples show elevated levels of Mn and B with Fe levels above the suspect level as suggested by Montana guidelines for overburden analyses. Further discussion of the effects of ground water percolation through reclaimed mine sites can be found in the Ground Water Section of this document. The conductivity levels in the alluvial wells are fairly stable and range from a low of 500 to a high of 700 umhos/cm. The quality of surface water and alluvial water of Grassy Creek does not appear to have been degraded to a significant degree by mining. Due to the lack of pre-mining quality data it is not possible to quantitatively determine what impacts have occurred. However, based on analysis of the disturbed strata it seems likely that iron, manganese, and total dissolved solids are slightly increased due to leaching through spoil piles. It is likely that the water in the regraded spoils has not yet reached equilibrium in respect to quantity and quality. The initial waters discharging as springs and seeps from the spoil piles will probably contain worst case leaching of metals and dissolved solids. The spoil waters should reach an equilibrium at such time that the readily leachable elements are removed. It is not expected that the short-term, worst case leachate quality will preclude downstream use of Grassy Creek water for irrigation. In the long-term sense, once equilibrium is reached in the spoil waters, the degrading effect on the surface water should be minimal and insignificant in terms of usability.