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(DDW) for use in revising or developing a Maximum Contaminant Level (MCL) in drinking water. The MCL is the highest level of a contaminant that is allowed in drinking water. California MCLs cannot be less stringent than federal MCLs and must be as close as is technically and economically feasible to the PHGs. DDW is required to take treatment technologies and cost of compliance into account when setting an MCL. Each MCL is reviewed at least once every five years. Total chromium and two radiological contaminants (gross alpha particle and gross beta particle) have MCLs but do not yet have designated PHGs. For these contaminants, the Maximum Contaminant Level Goal (MCLG), the federal U.S. Environmental Protection Agency (USEPA) equivalent of PHGs, is used in the PHG Report. N- nitrosodimethylamine (NDMA) has a PHG of 3 nanograms per liter and 1,2,3 - trichloropropane (1,2,3 -TCP) has a PHG of 0.7 nanogram per liter but both are not regulated in drinking water with a primary drinking water standard. Bromodichloromethane, bromoform, and dichloroacetic acid are three disinfection byproducts that have federal MCLGs of 0 but are not individually regulated with primary drinking water standards. According to the ACWA guidance and instructions from DDW, these five chemicals do not have to be included in the PHG Report because they do not have an existing MCL. 3.0 Identification of Contaminants Section 116470(b)(1) of the Health and Safety Code requires public water systems serving more than 10,000 service connections to identify each contaminant detected in drinking water that exceeded the applicable PHG. Section 116470(f) requires the MCLG to be used for comparison if there is no applicable PHG. The City of Santa Ana (City) water system has approximately 44,739 service connections. The following constituents were detected at one or more locations within the drinking water system at levels that exceeded the applicable PHGs or MCLGs: • Arsenic — naturally- occurring in local groundwater and in surface water purchased from the Metropolitan Water District of Southern California (MWDSC) • Coliform Bacteria, Total — naturally- occurring in the environment but can also be an indicator of the presence of other pathogenic organisms originating from sewage, livestock or other wildlife. • Chromium, Hexavalent — naturally- occurring in local groundwater; industrial contamination in groundwater • Perchlorate — industrial contamination in groundwater • Gross alpha particle activity (gross alpha) — naturally- occurring in surface water purchased from MWDSC • Gross beta particle activity (gross beta) — naturally- occurring in surface water purchased from MWDSC • Uranium — naturally- occurring in local groundwater and in surface water purchased from MWDSC. City of Santa Ana Exhibit 1 75C -5 2016 PHG