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I I I I I I I I I I I I I I I I I I I Section 2 - Study Area Descriptions well was 10.7 mg/l as N and the minimum concentration from the wells was 5.7 mg/las N. 3. Uranium The Department of Public Health and Environment currently has no standard for uranium. There is, however, a proposed level of 30 pci/l by the EP A that is expected by the end of 1995 4. Manganese: Manganese levels were about 0.18 mg/l, or approximately 3.5 times higher than the secondary SDW A standard of 0.05 mg/I. 5. Sulfate: Sulfate concentrations averaged about 944 mg/l, which is almost 700 mg/l higher than the 250 mg/l MCL. 6. IDS: Total dissolved solids averaged 1,855 mg/I. The MCL for IDS is 500 mg/I. 7. Sodium: Though no enforceable standards for sodium currently exist, sodium levels in 1993 were about 154 mg/I, which is much greater than the recommended limit for drinking water of 20 mg/I. Water Quality Trends While most water quality variables in Tables 2.5 and 2.6 were not part of the City's water quality testing program until recently, some variables including total dissolved solids, hardness and sulfates were analyzed as early as 1950. A comparison of the 1950 concentrations of TDS, hardness and sulfates with 1993 concentrations is shown in Table 2.7. TDS levels have more than doubled since 1950, from a concentration of 875 mg/l to more than 1850 mg/I. Similar increases have also been observed for both sulfate and hardness. Data showing an increase in nitrate concentrations since 1950 are not available, however, since 1970 the nitrate concentration has increased from approximately 5.5 mg/l to the current concentration of around 8.3 mg/I. mSlI as ton except as no e Variable 1950 1993 Percent Concentration Concentration Increase Total Dissolved Solids 875 1855 53% Hardness, as CaC03 725 1025 29% Sulfate 525 945 44% TABLE 2.7 WATER QUALITY TRENDS ( Il t t d) MONTGOMERY WATSON Page 2-'0