Wells, springs and mine sites with parameter concentrations that have equaled or exceeded drinking water standard(s), including location and parameter(s) are shown in Table 7.4-7A.  Impaired lakes and streams with site type, name, length of impaired reach, area of impaired lake, designated use standard and parameter(s) exceeded is shown in Table  7.4-7B.  Figure 7.4-9 shows the location of water quality occurrences keyed to Table 7.4-7.  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. 

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

• Refer to Table 7.4-7A.
• Two hundred and forty-six wells have parameter concentrations that have equaled or exceeded drinking water standards.
• The most common parameter equaled or exceeded was fluoride. 
• Other parameters equaled or exceeded include arsenic, cadmium, lead, nitrate, selenium and total dissolved solids.

Lakes and Streams with impaired waters

• Refer to Table 7.4-7B.
• The water quality standard for boron and selenium was equaled or exceeded in one 28 mile reach of the Gila River, a portion of this reach is also in the Yuma Basin.  The standard for organics and dissolved oxygen was equaled or exceeded at Painted Rock Borrow Pit Lake.
• Neither the reach of the Gila River nor the lake are part of the ADEQ water quality improvement effort, the Total Maximum Daily Load (TMDL) Program, at this time. 

Table 7.4-7 Water Quality Exceedences in the Lower Gila Basin

Figure 7.4-9 Lower Gila Basin Water Quality Exceedences

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