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

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water quality goal for hexavalent chromium could range from $11,000,000 to $46,200,000 per year, or between $247 and $1,030 per household per year. Coliform Bacteria, Total — The BAT for removal of coliform bacteria in drinking water has been determined by USEPA to be disinfection. The City already disinfects all water served to the public. Chlorine or chloramines is used to disinfect the water because it is an effective disinfectant and residual concentrations can be maintained to guard against biological contamination in the water distribution system. Coliform bacteria are indicator organisms that are ubiquitous in nature. They are a useful tool because of the ease in monitoring and analysis. The City collects weekly samples for total coliforms at various locations in the distribution system and monthly at each well. If coliform bacteria are detected in the drinking water sample, it indicates a potential problem that needs to be investigated and followed up with additional sampling. It is not unusual for a system to have an occasional positive sample. Although USEPA set the MCLG for total coliforms at 0 percent positive, there is no commercially available technology that will guarantee 0 percent positive every single month; therefore, the cost of achieving the PHG cannot be estimated. The City will continue several programs that are in place to prevent contamination of the water supply with microorganisms. These include: • Disinfection using chlorine or chloramines and maintenance of a chlorine residual at every point in the distribution system • Monitoring throughout the distribution system to verify the absence of total coliforms and the presence of a protective chlorine residual • Flushing program in which water pipelines known to have little use are flushed to remove stagnant water and bring in fresh water with residual disinfectant • Cross - connection control program that prevents the accidental entry of non - disinfected water into the drinking water system. Gross Alpha, Gross Beta, and Uranium — The only BAT for the removal of gross alpha in water for large water systems is reverse osmosis, which can also remove gross beta, and uranium, if detected. Gross alpha and gross beta were detected above the MCLG in the surface water supplied by MWDSC. Uranium was detected above the PHG in the local groundwater (Wells 16, 18, 20, 21, 24, 27, 28, 29, 30, 33, 34, 35, 36, 37, 38, 39, and 41) and in the surface water supplied by MWDSC. The cost of providing treatment using reverse osmosis to reduce gross alpha levels in local groundwater and in MWDSC surface water to the MCLG of 0 picoCurie per liter (pCi /I) (and consequently gross beta in MWDSC surface water below the MCLG; and uranium in local groundwater and in MWDSC surface water below the PHG) was calculated. Because the DLR for gross alpha is 3 pCi /l, treating gross alpha to 0 pCi /I means treating it to below the DLR of 3 pCi /I. Achieving the water quality goal for gross alpha could range from $8,630,000 to $73,600,000 per year, or between $193 and $1,640 per household per year. of Santa Ana Exhibit 1 75C -8 2016 PHG Report