Sites with parameter concentrations that have equaled or exceeded drinking water standard(s) (DWS), including location and parameter(s) are shown in Table 3.13-6A.  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 3.13-6B.  Figure 3.13-10 shows the location of exceedences and impairment keyed to Table 3.13-6.  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 3.13-6A.

• Sixty-seven sites have parameter concentrations that have equaled or exceeded DWS. 

• Frequently equaled or exceeded parameters include arsenic and fluoride. 

• Other parameters commonly equaled or exceeded in the sites measured in this basin were cadmium, lead, nitrates, beryllium, mercury and total dissolved solids.

Lakes and Streams with impaired waters

• Refer to Table 3.13-6B.
• Water quality standards were exceeded in three reaches of the San Pedro River.
• The parameter exceeded was different for each reach; E. coli, nitrates and copper.
• Two of the three impaired stream reaches, San Pedro River from the Mexican border to Charleston and from Babocomari to Dragoon Wash, are part of the ADEQ water quality improvement effort called the Total Maximum Daily Load  (TMDL) program.  Sampling to create a TMDL report is ongoing.

Effluent Dependent Reaches

• See Figure 3.13-10
• There is one effluent dependent reach, Walnut Gulch, in the vicinity of Tombstone.

Click to view Table 3.13-6 Water Quality Exceedences in the Upper San Pedro Basin

Click to view Figure 3.13-10 Upper San Pedro Basin

Water Quality Conditions

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