|
<br />Academy of Sciences-National Academy of Engineering,
<br />1973). This wale, must be of reasonably good quality to
<br />encourage plant growth (preferably less than 2,000 mg/l
<br />dissolved-solids concentration). Even now. water
<br />demands for revegetation pose serious problems, particu-
<br />larly in the Four Corners area of Arizona, New Mexico,
<br />Utah, and Colorado.
<br />Oil and gas extraction generally involves only nominal
<br />water demands for drilling, somc 37,000 acre-ft
<br />(45.6 million m') of freshwater annually nationwide.
<br />However, where water Hooding is employed as a second-
<br />ary recovery technique, somewhat larger quantities of
<br />water are needed to drive oil toward recovery wells.
<br />Where saltwater is available for this use (that is, forma-
<br />tion waters produced with oil), it is generally preferable
<br />to freshwater, but in some fields freshwater is used for
<br />water nooding. Magnitude of use is highly variable and
<br />depends upon formation characteristics, but generally is
<br />modest compared to other energy-industry demands.
<br />Buttermore (1966, p.6-8) calculated that the total
<br />demand for secondary recovery nationwide in 1962 was
<br />about 560,000 acre-ft (690 million m') of which
<br />157,000 acre.ft (194 million m') was frcshwater. The
<br />remainder was saline water, most of which was produced
<br />with oil.
<br />Uranium mining involves water demands for dust con-
<br />trol, ore beneficiation, and revegetation similar to coal
<br />mining, but tonnage handled is much less than for coaL
<br />thus, the total water requirements are lower. As in coal
<br />mining, quality of the water generally is not critical for
<br />these uses. Where surface mining is practiced, water
<br />requirements for revegetation are comparable to those of
<br />coal mining.
<br />The U.S_ Atomic Energy Commission (1972, table
<br />S-3A) estimates that the area disturbed in surface mining
<br />of uranium, normalized for annual requirements of a
<br />typicai 1,000 mw (megawatts, electric output) light.
<br />water reactOr generating station, would be 17 acres
<br />(6.9 hectares). The water requirement for revegetation at
<br />that rate would be trivial even for great increases in
<br />nuclear generation. For a rough comparison, it is esti-
<br />mated that mining for comparable energy production by
<br />a typical coal-fired electric plant would result in about
<br />10 times more land disturbance.
<br />Oil-shale mining is expected to become a major indus-
<br />try in several parts of Colorado, Utah, and Wyoming
<br />underlain by the Green River Formation. Shale will be
<br />extracted by surface mining, underground mining, and
<br />perhaps as an adjunct to in situ underground retorting.
<br />Retorting of shale mined by surface or underground con-
<br />ventional methods will be done on Or near the mining
<br />site, and large volumes of loosely compacted waste will
<br />be produced in the retorting process. Water demands for
<br />
<br />mining, processing, waste disposal, and land reclamation
<br />are intimately related, One of the largest demands is for
<br />compaction and revegetation of retort-plant waste which
<br />comprises some 40 percent of the total water use. The
<br />Department of the Interior's Final Environmental
<br />Impact Statement for the Prototype Oil Shale Leasing
<br />Program (U.s. Department of the Interior, i973) esti.
<br />mates consumptive water demand of from 121,000 to
<br />189,000 acre.ft (149 million to 233 million m') per year
<br />at a production rate of I million barrels (158,899 m')
<br />per day of shale oil, or from 2.5 to 4 volumes of water
<br />consumed per volume of oil produced.
<br />
<br />TRANSPORT
<br />
<br />The only significant use of water in energy transport,
<br />aside from in-stream navigation use, is for slurry lines.
<br />Slurry lines have been used for many years in the eastern
<br />coal districts, but one of the more recent installations is
<br />the slurry line extending from the Black Mesa coal mine
<br />in northeastern Arizona to the Mojave Power Plant on
<br />the Colorado River at the southern tip of Nevada
<br />273 miles (440 km) away. A slurry line was adopted
<br />because the terrain made ir economically attracth'e vis-
<br />a-vis rail transportation, the only other reasonable mode
<br />of conveyance. Another plant, the Navajo Power Plant
<br />(under construction) near Lake Powell is to be supplied
<br />from the sante mine by a railroad built for that purpose.
<br />Water for the Mojave slurry lines is supplied by wells
<br />pumping some 3,200 acre.n (3.9 million m') per year
<br />from a thick extensive sandstone aquifer that underlies
<br />Black Mesa. In this area, recharge from precipitation is
<br />negligibly small, and the pumped water is mainly with-
<br />drawn from storage, The power plant, rated at 1,500
<br />mw, consumes about 23,000 acre-ft (28 million m') per
<br />year for cooling and other plant uses; thus, the water use
<br />for transport is only about one-sixth that of the plant
<br />consumption. At the plant the slurry water is separated
<br />from the coal and treated, and part is used in the plant
<br />water supply.
<br />
<br />REFINING
<br />
<br />Most energy fuels require some degree of refining
<br />before ultimate use. Some or parts of these processes are
<br />carried out at or near the site of extraction, that is, gas
<br />scrubbing, coal washing, oil-shale retorting, and uranium-
<br />ore concentration. In other instances, the raw material
<br />may be transported to industrial centers for all or part of
<br />the refming process as is the case with crude oil, solvent
<br />refining of coal. and uranium enrichment and reactor-
<br />fuel fabrication.
<br />
<br />2
<br />
|