75D - PH WATER QUALITY - Laserfiche WebLink

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was all summarized in our 2004, 2005, and 2006 Annual Water Quality Reports, which were mailed to all of our customers. (Reference No. 3) Guidelines Followed: The Association of California Water Agencies (ACWA) formed a work group, which prepazed guidelines for water utilities to use in preparing these required reports. The ACWA guidelines were used in the prepazation of this report. Best Available Technology and Cost Estimates: Both the USEPA and CDHS adopt what are known as BATs or Best Available Technology, which are the best known methods of reducing contaminant levels to the MCL. Costs can be estimated for such technologies. However, since many PHGs and all MCLGs aze set lower than the MCL, it is not always possible nor feasible to determine what treatment is needed to further reduce a constituent downwazd to or neaz the PHG or MCLG, many of which are set at zero. Estimating the costs to reduce a constituent to zero is difficult, if not impossible because it is not possible to verify by analytical means that the level has been lowered to zero. In some cases, installing treatment to try and further reduce very low levels of one constituent may have adverse effects on other aspects of water quality. Constituents Detected That Exceed a PHG or a MCLG: The following is a discussion of constituents that were detected in one or more of our drinking water sources at levels above PHG. Naturally Occurring Urauium The PHG for Natural Uranium is 0.43 pCi/L. The MCL or drinking water standard for Natural Uranium is 20 pCi/L. We have detected Natural Uranium in 3 of our 20 wells at levels 4.45 to 10.4 pCi/L. The levels detected were below the MCL. The category of health risk associated with Natural Uranium, and the reason that a drinking water standard was adopted for it, is that people who drink water containing Natural Uranium above the MCL throughout their lifetime could experience an increased risk of cancer. The 20 pCi/L MCL established by the CDHS if complied with should have no adverse health effect. The numerical risk for cancer for water containing Uranium at the PHG level of 0.43 pCi/L is one case in 1,000,000. The large water system BAT for Natural Uranium to lower the levels below the PHG is Ion Exchange. Total water production for all affected wells is 32,446 gallons per minute. Based on the USEPA studies, the initial cost to treat one thousand gallons of water at 80 percent removal efficiency for lazge water systems ranges from $0.50 to $0.65. The on going cost for the treatment ranges from $0.50 to $0.65 per thousand gallons of water treated. For the City of Santa Ana, the estimated cost to install such treatment systems (Ion Exchange) ranges between $6.45 and $20.0 Million. The cost to operate the treatment facilities will range from $6.45 to $7.9 million per yeaz. The cost to build the treatment facilities would result in an assumed increased cost for each customer of $18.53 to $57.45 in the first year and from $18.50 to $22.70 per customer annually. 2 75D-4