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<br />Studies[12,13,14] conducted on post-mining spoils in northwestern <br />Colorado indicate that the resulting TDS concentt-ation of spoil- derived <br />waters ranges from approximately 3,000 mg/L to 3,900 mg/L. The variability in <br />concentration is dependent upon water residence time and the chemical and <br />physical properties of the spoil. <br /> <br />~~ Saline water is a byproduct of the production of oil and gas in the <br />i..O Basin. It is not uncommon to produce several times the amount of saline <br />-1 waters as oil. Approximately 25,000,000 barrels of saline waters were <br />~..ii produced during December 1985 in Colorado from oil and gas operators. The <br />salinity of production waters varies greatly from location to location and is <br />dependent upon the producing formation. Common disposal techniques include <br />evaporation, injection, and discharge to local drainages. <br /> <br />The future development of the oil shale resources in Colorado, Utah, <br />and Wyoming has the potential to increase salt loading to the Colorado River. <br />Salt increases can be attributed to the consumptive use of good quality water, <br />mine dewatering, and, if surface retorting is used, the leaching of spoil <br />materials similar to that of surface coal mining. <br /> <br />Some states have enacted drilling and ground water laws to protect <br />water quality. In the Colorado River Basin, ground water laws and strict <br />enforcement are essential to prevent further saline aquifer movement and salt <br />loading. Many small saline ground water springs and/or flowing wells that are <br />probably linked to drilling activities have been identified in the Basin and <br />listed in previous progress reports. Seismograph drilling activities may be <br />particularly disruptive to shallow ground water systems, and stricter <br />regulation and enforcement should be considered. <br /> <br />The Meeker Dome salinity unit i~ one area where Reclamation has <br />plugged abandoned oil exploration drilling holes anticipating that the <br />aquifers are static and the saline water would not find another path back to <br />the surface. <br /> <br />6. Salinity Control Projects <br /> <br />The implementation of salinity control units'pre\rented about 156,400 <br />tons per year of salts from reaching the river in 1988. By 2010, salinity <br />control uni ts will need to prevent slightly more than a million iulIS per year <br />of salt from entering the Colorado River. To achieve this goal, a mix of <br />salinity control methods are being investigated and constructed. Saline <br />springs and seeps may be collected for disposal by evaporation, industrial <br />use, or deep well injection. See Part VII, the Paradox Unit, for an example <br />of a deep well injection alternative. Other methods include both on- and <br />off-farm delivery system and irrigation improvements which reduce the loss of <br />,water and reduce salt pickup by i~proving irrigation practices and by lining <br />canals, laterals, and ditches. See the Grand Valley Unit as an example of <br />these kinds of improvements. <br /> <br />7. Erosion <br /> <br />Several researchers[lS,16,17,18] have shown that erosion of saline <br />shales and dissolution of efflorescence (surface salts) increase salinity <br />during runoff events. These and previous studies have primarily focused on <br />conditions caused by summer and fall thundershowers. Lower elevation snowmelt <br />on marine (saline) geologic formations may contribute more significantly to <br /> <br />V-6 <br />