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<br />. ,"':.-.__-4 <br /> <br />been very high. While various new types of relatively low-cost techniques <br />have been proposed for inactive mines, few have actually been shown to be <br />cost-effective under field conditions. <br /> <br />..... <br />'"'-1 The Colorado Department of Natural Resource' s \f.i TIed La.nd Reclamation <br />en Division, under a grant from the U.S. Office or Surface Mining, is <br />0) evaluating the feasibility of controlling inac~ive mine discharge and <br />restoring water quality. The study has focused on two priority areas--the <br />Arkansas River near Leadville and Clear Creek in the vicinity of Idaho <br />Springs. <br /> <br />4) Urban Runoff - The principal pollutants associated with urban runoff <br />are oxygen demanding substances, metals and fecal coliform bacteria. The <br />principal areas experiencing urban runoff problems include the major <br />metropolitan areas of the State, including Denver, Colorado Springs, and <br />some mountain communities subject to high growth pressures and <br />corresponding land disturbance. Urban runoff in Summit County has <br />contributed to water quality problems in Dillon Reservoir. Other <br />reservoirs which are beginning to experience problems as a result of <br />urbanization in their watersheds include Cherry Creek and Chatfield in the <br />Denver Area. <br /> <br />C. Drinking Water Problems <br /> <br />Generally, the quality of drinking water supplies in Colorado is good. <br />However, due to its location at the source of surface drinking water <br />supplies, Colorado does not have to contend with many pollutants which are <br />frequently encountered in downstream sources. However, the low turbidity, <br />temperature and alkalinity of this "pristine" runoff makes removal of <br />microbiological contaminants quite difficult since conventional treatment <br />relies heavily upon chemical reactions which are inhibited by these <br />factors (low turbidity, temperature and alkalinity). <br /> <br />Of high concern is the protozoan, Giardia lamblia. Giardia, is somewhat <br />resistant to disinfection and therefore must be removed by complete <br />conventional treatment in order to assure a,safe water supply. Of the 165 <br />community surface water supplies in Colorado approximately 10% lack <br />adequate capability to remove Giardia and similarly sized particulates. <br />Assuring the provision of pathogen free water is the highest priority for <br />the Colorado Drinking Water program. Therefore, assurance of proper <br />treatment of surface supplies is heavily emphasized. Colorado requires <br />disinfection of all public water supplies. Therefore, the 560 community <br />groundwater supplies generally do not have microbiological problems. <br /> <br />With respect to chemical contaminants in water Colorado, is similarly <br />fortunate. Of 725 community supplies, only about 5% cannot meet drinking <br />water standards for inorganic chemicals. Nitrates in excess of standards <br />occur in the South Platte alluvium. Selenium has been found in excess of <br />current standards in the Arkansas Valley and San Juan Basin. Excess <br />fluoride has been encountered in several locations. Standards for both <br />selenium and fluoride will probably be revised upward due to recent health <br />findings, this change will most likely bring Colorado systems into <br />compliance with standards. <br /> <br />-9- <br /> <br />l., <br /> <br />,. -~- , <br /> <br />o ,,'>li <br />" 1li~''':'..d;:''~,' "'''' ~,,~ <br />