75C - PH - RPT ON WATER QUALITY - Laserfiche WebLink

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5.0 Identification of Risk Categories Section 116470(b)(3) of the Health and Safety Code requires identification of the category of risk to public health associated with exposure to the contaminant in drinking water, including a brief, plainly worded description of those terms. The risk categories and definitions for the contaminants identified above are shown on the accompanying chart. 6.0 Description of Best Available Technology Section 116470(b)(4) of the Health and Safety Code requires a description of the BAT, if any is available on a commercial basis, to remove or reduce the concentrations of the contaminants identified above. The SATs are shown on the accompanying chart. 7.0 Costs of Using Best Available Technologies and Intended Actions Section 116470(b)(5) of the Health and Safety Code requires an estimate of the aggregate cost and cost per customer of utilizing the BATS identified to reduce the concentration of a contaminant to a level at or below the PHG or MCLG. In addition, Section 116470(b)(6) requires a brief description of any actions the water purveyor intends to take to reduce the concentration of the contaminant and the basis for that decision. Arsenic — The BATS for removal of arsenic in water for large water systems are: activated alumina, coagulation /filtration, electrodialysis, ion exchange, lime softening, oxidation /filtration, and reverse osmosis. Arsenic was detected above the PHG in the local groundwater (Wells 37 and 38) and in surface water supplied by MWDSC. The City is in compliance with the MCL for arsenic. The estimated cost to reduce arsenic levels in local groundwater and in MWDSC surface water to below the PHG of 0.004 microgram per liter (Ng /1) using ion exchange was calculated. Because the DDW detection limit for purposes of reporting (DLR) for arsenic is 2 pg /l, treating arsenic to below the PHG level means treating arsenic to below the DLR of 2 pg /I. There are numerous factors that may influence the actual cost of reducing arsenic levels to the PHG. Achieving the water quality goal for arsenic could be approximately $7,440,000 per year, or $166 per household per year. Chromium, Hexavalent — The BATs for removal of hexavalent chromium in water are: reduction to chromium III (trivalent chromium) prior to coagulation /filtration, ion exchange, and reverse osmosis. Hexavalent chromium was detected above the PHG in the local groundwater (Wells 20, 21, 24, 29, 30, 33, 34, 35, 36, 37, 39, and 41). The City is in compliance with the MCL. for hexavalent chromium. The estimated cost to reduce hexavalent chromium levels in local groundwater to below the PHG of 0.02 lag /I using ion exchange was calculated. Because the DLR for hexavalent chromium is 1 lag /l, treating hexavalent chromium to below the PHG level means treating hexavalent chromium to below the DLR of 1 pg /l. There are numerous factors that may influence the actual cost of reducing hexavalent chromium levels to the PHG. Achieving the City of Santa Ana 4 2016 PHG Report Exhibit 1 75C -7