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timothy, both moderately sensitive species, are found in the area. Various species of clover were also found. Moderately sensitive species comprise 11.7% of the Trout Creek Area cover on a weighted average basis. The vegetative cover of the Fish Creek area is reported on Table 4, Fish Creek Alluvial Valley Floor. In addition to the 1986 field season sampling, data from the TCC Life of Mine Permit submittal was used to characterize the region, which is described under Rule 2.04.10. The location of those transects is shown on Map 18, Premining Vegetation, in the permit. Data was collected from both native sagebrush/meadow vegetation areas, formerly irrigated pastures, and irrigated pasture 13. The total vegetative cover is 87.5%. Of that amount, grasses cover 46.7%, grasslike plants cover 10.0%, fortis comprise 19.7%, and woody plants cover 11.1%. The moderately tolerant species, crested wheatgrass, slender wheatgrass, smooth brome, mountain brome, and wheat are found in this region. Similar moderately tolerant species, intermediate wheatgrass, western wheatgrass, bluebunch wheatgrass, wheatgrass, tall fescue, foxtail barley, Idaho fescue, and sheep fescue were also found in the Fish Creek area. The total cover of moderately tolerant species is 8.9%. The moderately sensitive species in this area include timothy, and various clovers. The coverage of these plants is 2.8%. In summary, the area of the Foidel Creek alluvial valley floor which was studied supports 13.4% of moderately tolerant species and 4.6% of moderately sensitive species in an area of 10.1 acres. The area which was sampled is undeveloped rangeland. The sampled portion of Middle Creek has 26.8% of moderately tolerant species and 14.5% of moderately sensitive species. The area covers about 212.4 acres of irrigated land and 9.3 acres of undeveloped rangeland. The Trout Creek alluvial valley floor region supports 16.1°~ of moderately tolerant species and 11.7% of moderately sensitive species. This region has about 221.8 acres of irrigated land which is cut for hay, and 95.2 acres of irrigated land which is more typical of a sagebrush/meadow type community. The sampled region of the Fish Creek alluvial floor covers 1309.1 acres. Moderately tolerant species cover 8.9% and moderately sensitive species cover 2.8% of the area. About 56.6 acres are irrigated land and about 1252.5 acres are undeveloped rangeland or formerly irrigated land. As stated in the article of Maas and Hoffman, a moderately tolerant species may experience some decrease in yield at a soil extract EC of 3.0 mmhos/cm (3,000 umhos/cm). A moderately sensitive species may experience decrease at 1.5 mmhos/cm (1500 umhos ECe). Using a conversion factor of 1.5 to describe the salinity of the irrigation water, moderately tolerant species may be affected by water with an excess of 2000 umhos/cm, and moderately sensitive species may experience decreases in yield with water having an excess of 1000 umhos/cm. The CMLRD has chosen to establish the material damage standard at 1000 umhos/cm for irrigated water; this corresponds to a soil extract EC of 1500 umhos/cm. Apparently, the standard is based on the premise that moderately sensitive species dominate the areas of concern. The data collected by TCC do not support this assumption. The percentage of cover of moderately sensitive plants in the Foidel Creek and Fish Creek alluvial valley floor regions does not exceed five percent (4.6% and 2.8% respectively). The Middle Creek region supports 14.5% of moderately 3