Sites with parameter concentrations that have equaled or exceeded drinking water standard(s) (DWS), including location and parameter(s) are shown in Table 3.8-7A.  Impaired lakes and streams with site type, name, length of impaired stream reach, area of impaired lake, designated use standard and parameter(s) exceeded is shown in Table 3.8-7B.  Figure 3.8-10 shows the location of exceedences and impairment keyed to Table 3.8-7.  All community water systems are regulated under the Safe Drinking Water Act and treat water supplies to meet drinking water standards.  Not all parameters were measured at all sites; selective sampling for particular constituents is common.  A description of water quality data sources and methods is found in Volume 1, Appendix A.  Information on contamination sites in the basin is in Section 3.0.6 Water Supply - Contamination Sites.

Well, Mine or Spring sites that have equaled or exceeded drinking water standards (DWS)

• Refer to Table 3.8-7A.
• Fifty-six sites have parameter concentrations that have equaled or exceeded DWS. 
• The parameter most frequently equaled or exceeded was fluoride.
• Other parameters commonly equaled or exceeded in the sites measured in this basin were cadmium, arsenic, nitrates, total dissolved solids, lead, antimony, beryllium and radionuclides.

Lakes and Streams with impaired waters

• Refer to Table 3.8-7B.
• Water quality standards were exceeded in one reach of Mineral Creek and in one reach of the San Pedro River.
• The parameters exceeded in Mineral Creek included copper and selenium.
• The parameters exceeded in the San Pedro River were E. coli and selenium.
• Both reaches are part of the ADEQ water quality improvement effort called the Total Maximum Daily Load  (TMDL) program.  The TMDL report for Mineral Creek is not yet complete, however, cleanup by the mining company ASARCO is ongoing.  Investigation is underway for the impaired portion of the San Pedro River in this basin.

Effluent Dependent Reaches

• See Figure 3.8-10
• There is one small portion of an unnamed tributary to Alder Creek that is effluent dependent.  The source of the effluent is from the Summerhaven wastewater treatment facility located in the Tucson AMA.

Click to view Table 3.8-7 Water Quality Exceedences in the Lower San Pedro Basin

Click to view Figure 3.8-10 Lower San Pedro Basin

Water Quality Conditions

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