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<br />nl':,""J"J? <br />{)~..u (J I.) " ,.,.j <br /> <br />. <br /> <br />Hydrology <br /> <br />the valley alluvium of St. Vrain Creek and its plains area tributaries. <br />This aquifer is believed to be already substantially developed as far <br />as present economic conditions and agriculture are concerned. There <br />may be additional water supply in this aquifer that could be developed' <br />for M&I purposes. <br /> <br />Quali ty of Water <br /> <br />. <br /> <br />Municipal and Industrial <br /> <br />The chemical quality of the surface water produced in the <br />mountainous area of the St. Vrain Creek basin is excellent for M&I <br />needs--low in alkalinity, hardness, and dissolved solids. During <br />high-runoff periods, most of the water available for M&I purposes <br />is turbid. A few communities use water that is transported in <br />unlined canals, primarily agricultural, and this water is always <br />turbid. The color of the water prior to treatment exceeds the <br />upper limits of the U. S. Public Health Service and Colorado Public <br />Health Service standards for treated water. Although color has <br />little sanitary significance, it is indicative of organic matter in <br />colloidal suspension or mineral matter in solution and is undesirable <br />aesthetically. <br /> <br />Biologically, there is an opportunity for contamination of the <br />water supplies in nearly all parts of the basin because of public <br />access to and habitation of the stream and storage areas. Biological <br />quality ,of St. Vrain Creek belQw Longmont is poor, as discussed under <br />"Problems and Needs of the Area." <br /> <br />Agricultural <br /> <br />The chemical quality of the water in the upper reaches of the <br />basin is also well suited for irrigation. In 1957, 1958, and 1960 <br />samples of surface water were obtained from the St. Vrain Creek at <br />Lyons and Mead, Boulder Creek near Orodell, Middle Boulder dreekat <br />Nederland, South Boulder Creek near Eldorado Springs, Coal Creek near <br />Plainview, and Lefthand Creek near Boulder under a cooperative water- <br />sampling and analysis program performed by the U. S. Geological Survey. <br /> <br />. <br /> <br />These analyses show the surface waters to be relatively low in <br />soluble salts and sodium. The specific conductance ranged from <br />21.5 to 322 micromhos (EC x 106), with the general range running <br />below 100 micromhos. The sodium content ranged from 12 to 37 percent, <br />with the general range running below 25 percent. <br /> <br />14 <br /> <br />A::l.. <br /> <br />~', , _ _, ,- _ i ' " <br />~_~__~_L~"-, ^' '__",""''';i"",,-.ffik\.';j..>.;_~:~'-;j.;~--4::<;~'.P,(,,~ ' <br /> <br />\' <br /> <br />