2012-01-26_PERMIT FILE - C1981018A

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• Surface water in the lease and adjacent areas is predominantly of the calcium-sulfate type. Ionic concentrations of sodium and magnesium approach and occasionally exceed those of calcium. The normally high calcium and magnesium concentrations in the area relative to sodium result in low sodium adsorption ratios (rarely exceeding 2.0) and, thus, low sodium hazards (Richards, 1954). Total dissolved solids concentrations in the area are quite variable, both spatially and temporally. No significant difference exists between dissolved solids contents of the White River above and below lease area tributaries. With the exception of two questionable measurements, salt concentrations varied from 255 to 788 milligrams per liter at the upper station (SW12-1, averaging 486 milligrams per liter) and from 250 to 705 milligrams per liter at the lower station (SW11-2, averaging 470 milligrams per liter). As expected, dissolved solids contents of the White River vary inversely with flow (see Figure II.C-20), with the lowest concentrations coming during periods of high flow, primarily in the months of May and June when most of the flow is derived from snowmelt. As flows decrease later in the year and the majority of the flow in the river is derived from groundwater discharge, the high-flow dilution effect becomes less pronounced and concentrations tend to increase. A duration curve of dissolved solids load of the White River above Rangely, Colorado (Figure II.C-21) was prepared using the station's long-term flow duration curve and a dissolved solids discharge rating curve developed from available U.S. Geological Survey data. Through arithmetic integration (see Table II.C-6), • the average dissolved solids discharge at the station was determined to be 645 tons per day (235,550 tons per year). This converts to an average total dissolved solids concentration at the station of 381 milligrams per liter. This represents an increase in the dissolved solids load of 225 tons per day and an increase in the concentration of 137 milligrams per liter relative to the White River near Meeker, Colorado (lorns et al., 1965b). According to the U.S. Department of Agriculture (1966), much of the increased salt load and concentration of the White River at Rangely relative to Meeker probably originates in the Piceance Creek Basin, the mouth of which is located approximately 32.4 miles upstream from the lease area and 37.1 miles upstream from the gaging station on the White River above Rangely. Dissolved solids concentrations of Red Wash at SW1-1 varied between 230 and 1504 milligrams per liter. Data collected during the snowmelt period in April 1979 indicate that a majority of the dissolved solids content of Red Wash originates in the headwaters. Inflowing water in April 1979 in two Red Wash tributaries at Highway 40, located at the base of the headwater mountains, had an average dissolved solids concentration of 1343 milligrams per liter, accounting for 94 percent of the salt load and 89 percent of the concentration measured at SW1-1. This high salt concentration from the upper elevations is likely due to the outcropping of the saline Mancos Shale in portions of headwaters of the Red Wash Basin (Stose, 1935). Because of this condition, it is postulated that flow events with relatively high dissolved solids contents result from snowmelt or thunderstorm events which flow across the Mancos Shale outcrops in the foothills. On the other hand, low dissolved solids concentrations (such as that measured in August, 1979) probably result when thunderstorm events centered in the lower portions of the Red Wash Basin, with runoff source areas confined to those parts of i Permit Renewal #3 (Rev. 8/99) II.C-37