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<br />The types are defined as fol lows: <br /> <br />(a) Desirable - Those characteristics and concentrations <br />of substances in the raw surface water which represent <br />high-qual ity water In al I respects for use as publ ic <br />water supplies. The treatment cost of water meeting <br />these criteria is less than is possible with waters <br />meeting usable criteria. <br /> <br />(b) Usable - Those characteristics and concentrations of <br />substances in raw surface waters which wi II al low the <br />production of a safe, clear, potable, aesthetically <br />pleasing, and acceptable public water supply which <br />meets the limits of Public Health Service Drinkin~ <br />Water Standards~ after removal of sediments and <br />conventional treatment including chlorination. <br /> <br />(c) Undesirable - Water not meeting the usable criteria <br />but, with additional treatment, can be made acceptable <br />for public supplies by application of existing treat- <br />ment processes. <br /> <br />The Nebraska Department of Health conducts a continuous program of <br />analyzin~ the quality of raw water suppl ies. Tests of nearly a thousand <br />wel Is in 400 communities show that samples in slightly over 200 commu- <br />nities had one or mere chemical components in concentrations greater <br />than allowed under usable quality criteria. This does not necessarily <br />mean that al I the supplies for the municipal ity have undesirable charac- <br />teristics since a number of wel Is may be supplying water to the systems. <br />It does indicate that there are local problem areas or specific water- <br />bearing strata with water having undesirable characteristics. <br /> <br />Deep well waters in the State contain relatively few bacteria and <br />usually no harmful types. Chlorination of public suppl ies is recommended <br />because of the chances for contamination within the distribution system. <br /> <br />Excess iron and manganese combined are the most prevalent chemical <br />components that degrade the state's ground water below "usable." This <br />condition was found in 189 locations, mostly In the eastern third of <br />the State (Figure 2). Although these chemicals usually produce no <br />adverse physiological effects, they do give water an objectionable taste <br />and stain water fixtures. <br /> <br />Excess sodium, sulfates, chlorides, and nitrates are found in some <br />wel I samples from widely scattered locations. These may cause physiological <br />distress in humans. Excess sodium was found in 30 communities (Figure 3), <br />excess sulfates in nine communities, excess chlorides in two communities, <br />and excess nitrates in one community. Locating another source of supply <br />is usually less costly than' tryin~ to remove these substances. <br /> <br />6/ Public Health Service Drinkin~ Water Standards, U. S. Department <br />of Health, Education & Welfare, PHS Pub. 956, Washington, D. C., 1962. <br /> <br />11 <br />