WSP05260 - Laserfiche WebLink

Home Browse Search

. o CD IV 1\::> . . OTHER WATER QUALITY ASPECTS (Continued) powerplants in the basin with a return of the cooling water to the streams or reservoirs could present a potential for temperature increase. For this and other water quality reasons most of the cooling water discharges from future fossil fuel powerplants will not be allowed to return to the rivers. 3. El! The pH of the waters in the Colorado River Basin usually range from about 7 to 8. Formerly there were a number of streams receiving acid mine drainage. In these cases the pH was lowered to levels which pre- cluded the est.ablishment of aquatic life and the use of the river for fishery and other purposes. Much of these condi tions, however, have been corrected by controlling the mine discharges. 4. Heavy Metals Various heavy metals such as copper, lead, zinc, iron, manganese, arsenic, selenium, and cyanide are found in the waters of the basin. These have varied from trace amounts to potentially hazardous levels. The presence of these heavy metals is generally contributed by drainage from active and inactive mining operations. Iron, arsenic, cadmium, selenium, and manganese concentrations occasionally exceed the Public Health Drinking Water Standards in some basin streams. This is particularly evident in the upper reaches of the Colorado, Uncompahgre, and San Juan Rivers and their tributaries. It has been determined that heavy metal concentrations have a marked effect on the aquatic life. Certain reaches of stream have been completely devoid of bottom organisms and fish because of these toxic effects. Approval of the Section 404 permit for the Ridgway Dam, Dallas Creek Project, required a monitoring program to determine the effects of the reservoir on the heavy metals found in the Uncompahgre River. Heavy metals monitoring has also been done on the Dolores Project as well as other projects in the basin. 5. Toxic Materials In addition to the toxic effects of heavy metal concentration, toxic materials are also contributed to the stream through industrial and agricultural operations. Limited long-term monitoring at four surveillance stations located on the Colorado River has in the past detected the pesticides ODD, DOE, DOT, dieldrin, and endrin. A compre- hensive evaluation of the effects of pesticides upon water quality cannot be made at this time because of the lack of sufficient water quality' data and incomplete knowledge of the physiological and other effects of pesticides in human, wildlife, fish, and other biological forms. The mere presence of a pesticide in water does not necessarily 103