Laserfiche WebLink
3. TEXT CHANGES <br />Water quality of the perched aquifer is classified as a <br />calcium-magnesium bicarbonate type with TDS ranging <br />from 200 to 400 mg/1 al the higher ele:vatioas of the basin. <br />At lower elevations in the basin, water quality shifts to <br />a sodium-sulfate bicarbonate with TDS ranging from 400 <br />to 900 mg/I. <br />Groundwater in the upper aquifer system is classified as <br />a sodium bicarbonate type with sulfate decreasing as a major <br />anion in deeper water zones. Generally, concentrations of <br />dissolved solids increase with aquifer depth and in a northerly <br />direction. TDS concentrations range from 400 to 2,000 mg/ <br />I. This increase may be related to the natural dissolution <br />of minerals and to groundwater movement from the lower <br />to the upper aquifer (Weeks et al. 1974). Calcium, <br />magnesium, and sulfate concentrations are generally greater <br />in the upper aquifer than in the lower aquifer. Sodium, <br />bicarbonate, and Ouoride are higher in the lower aquifer. <br />The lower aquifer water is generally classified as a sodium <br />bicarbonate type. Total dissolved solid concentrations of the <br />lower aquifer vary Erom about 500 m,g/1 to nearly 40,000 <br />mg/1 and are dependent on depth and location. Dissolved <br />solid concentrations of 63,000 mg/I have been reported <br />(Weeks et al. 1974); however, this is not characteristic of <br />lower aquifer water quality and is believed to have been <br />caused by drilling operations near the: dissolution surface. <br />Limited data indicate that the quality of lower aquifer water <br />deteriorates as it approaches the dissolution surface (Welder <br />and Saulnier 1978). <br />3431 Sire Specific <br />Limited data o[ groundwater sampled on and near the <br />sodium lease tracts indicates that the upper aquifer water <br />tends to be asodium-sulfate-bicarbonate type and typically <br />contains 500-600 mg/1 TDS, although some samples <br />indicated IeveLs as high as 1,000 mg/I. This data is a <br />composite of aB water bearing zones io the upper aquifer, <br />and doesn't distinguish between the perched aquifer and <br />remaining upper aquifer. Compared to the lower aquifer, <br />it contains lower concentrations of TDS, fluoride, and <br />chloride, and higher concentrations of calcium, magnesium, <br />and sulfate. Water quality in the upper aquifer fluctuates <br />from meeting the Colorado groundwater quality standards <br />for drinking water as contained in "The Basic Standards <br />for Groundwater" (Colorado Water Quality Control <br />Commission 1987) to exceeding those standards in fluoride <br />and pH, and marginally mceting the standards in iron. These <br />variances occur by location on lease and by water bearing <br />zones of the upper aquifer. Agricultural standards are also <br />extxxded because of high levels of fluoride and pH. <br />Dissolved solid concentrations in the lower aquifer range <br />from 650 to 9,610 mg/1(USGS, MMC 1981; WRC 1983- <br />1984) with mast samples falling in the 1,000 to 2,000 mg/ <br />1 range. The lower aquifer does cot meet the state standards <br />for drinking water because of high concenvations of fluoride <br />and marginal pH. The lower aquifer does not meet the <br />state standards for agriculture because of excessive fluoride <br />and marginal pH. <br />Table 3-2 shows some selected water quality parameters <br />for the lease area and the state standards. This table is based <br />TABLE 3-2 <br />WATER QUALITY PARAMETERS <br />FOR THE SODIUM LEASE AREA AND STATE STANDARDS <br /> <br />Parameter Upper <br />Aquifer a Lower <br />Aquifer • Colorado Htmrm <br />Health Standards Colorado Agricul- <br />filial Sfaitdards <br />pH (units) 8.6 to 8.7 8.50 6.5-8.5 6.5-8.5 <br />Fluoride (mg/1) 1.4 to 20.5 23.50 4.0 2.0 <br />Iron (mg/q 0.26 0.12 0.3 5.0 <br /> All Waters <br /> nand Limit <br />TDS (mg/I) 855 2,210 0-500 400 mg/i or 1.25 times the background level, <br /> whichever is least restrictive. <br /> 501-10,000 1.25 times the background value. <br /> 10,001 or No limit <br /> greater <br />a Samples collected in August 1984 (ram web IRI-PW-2 (Industrial Resources, Inc. 1984). Upper aquifer was also <br />sampled in 1981 at the site of the MMC/USGS pump test about 1 mile from the proposed well field (Weston <br />1984). <br />3-9 <br />