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The City of Santa Ana (City) water system has approximately 45,256 service <br />connections. The following constituents were detected at one or more locations within <br />the drinking water system at levels that exceeded the applicable PHGs or MCLGs: <br />• Arsenic — naturally -occurring in local groundwater. <br />• Bromate — formed when naturally -occurring bromide reacts with ozone during the <br />disinfection process in surface water purchased from Metropolitan Water District <br />of Southern California (MWDSC). <br />• Perchlorate — industrial contamination in local groundwater. <br />• Gross alpha particle activity (gross alpha) — naturally -occurring in local <br />groundwater and surface water purchased from MWDSC. <br />• Gross beta particle activity (gross beta) — naturally -occurring in surface water <br />purchased from MWDSC. <br />• Radium, Combined (sum of Radium-226 and Radium-228) — naturally -occurring <br />in surface water purchased from MWDSC. <br />• Uranium — naturally -occurring in local groundwater and in surface water <br />purchased from MWDSC. <br />The accompanying chart shows the applicable PHG or MCLG and MCL for each <br />contaminant identified above. The chart includes the maximum, minimum, and average <br />concentrations of each contaminant in drinking water supplied by the City in calendar <br />years 2019 through 2021. <br />4.0 Numerical Public Health Risks <br />Section 116470(b)(2) of the Health and Safety Code requires disclosure of the <br />numerical public health risk, determined by OEHHA, associated with the MCLs, PHGs <br />and MCLGs. Available numerical health risks developed by OEHHA for the <br />contaminants identified above are shown on the accompany chart. Only numerical risks <br />associated with cancer -causing chemicals have been quantified by OEHHA. <br />City ity ouncil Ij 23 — 6 port <br />