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GA-1 • EXHIBIT GA GA.1 INTRODUCTION The information used in development of this report included publications of the U.S. Geological Survey, data from groundwater investigations conducted by Rio Blanco Oil Shale Company and Multi Mineral Corporation, and investigations conducted by Industrial Resources, Inc. in support of this mine permit application. GA.2 SURFACE WATER GA.2.1 Regional Setting The NaTec Minerals,, Inc. (NaTec) nahcolite solution mine project area is located in the Piceance Basin, in northwestern Colorado (see Figure GA-1). The climate of the area is semi-arid, with annual precipitation ranging from about 12 inches at 6,000 feet to • about 15 inches at 6,800 feet (Ege et al, 1978). Precipitation generally occurs as snow from November to March and as rain during the remainder of the year. Annual potential evapotranspiration for horizontal surfaces ranges from 46 inches at 6,000 feet to 43 inches at 6,800 feet. The sodium lease tracts are located between Yellow Creek and Ryan Gulch which are part of the Piceance hydrologic basin. The primary source of streamflow to Ryan Gulch and Yellow Creek is groundwater discharge. The primary flow periods include runoff from snowmelt beginning in March and continuing through June or July. Streamflow for the remainder of the year is maintained almost totally by groundwater discharge with approximately 80 percent of streamflow in the basin being supplied by groundwater (WeeY.s et al, 1974). GA.2.2 Site Drainages The four sodium lease tracts are primarily located in the Yellow . Creek drainage. One lease tract, C-0118327, partially extends into Horse Draw drainage, a tributary to Piceance Creek. Site drainages are shown on Figure GA-2.