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2015 URBAN WATER MANAGEMENT PLAN <br />3.6.2.3 Water Quality <br />3.6.2.3.1 Imported Water <br />Metropolitan is responsible for providing high quality potable water throughout its service area. Over <br />300,000 water quality tests are performed per year on Metropolitan's water to test for regulated <br />contaminants and additional contaminants of concern to ensure the safety of its waters. Metropolitan's <br />supplies originate primarily from the CRA and from the SWP. A blend of these two sources, proportional <br />to each year's availability of the source, is then delivered throughout Metropolitan's service area. <br />Metropolitan's primary water sources face individual water quality issues of concern. The CRA water <br />source contains higher total dissolved solids (TDS) and the SWP contains higher levels of organic matter, <br />lending to the formation of disinfection byproducts. To remediate the CRA's high level of salinity and the <br />SWP's high level of organic matter, Metropolitan blends CRA and SWP supplies and has upgraded all of <br />its treatment facilities to include ozone treatment processes. In addition, Metropolitan has been engaged <br />in efforts to protect its Colorado River supplies from threats of uranium, perchlorate, and chromium VI <br />while also investigating the potential water quality impact of emerging contaminants, N- <br />nitrosodimethylamine (NDMA), and pharmaceuticals and personal care products (PPCP). While <br />unforeseeable water quality issues could alter reliability, Metropolitan's current strategies ensure the <br />deliverability of high quality water. <br />The presence of Quagga Mussels in water sources is a water quality concern. Quagga Mussels are an <br />invasive species that was first discovered in 2007 at Lake Mead, on the Colorado River. This species of <br />mussels form massive colonies in short periods of time, disrupting ecosystems and blocking water <br />intakes. They are capable of causing significant disruption and damage to water distribution systems. <br />Controlling the spread and impacts of this invasive species within the CRA requires extensive <br />maintenance and results in reduced operational flexibility. It also resulted in Metropolitan eliminating <br />deliveries of CRA water into Diamond Valley Lake to keep the reservoir free from Quagga Mussels. <br />3.6.2.3.2 Groundwater <br />OCWD is responsible for managing the OC Basin. To maintain groundwater quality, OCWD conducts an <br />extensive monitoring program that serves to manage the OC Basin's groundwater production, control <br />groundwater contamination, and comply with all required laws and regulations. A network of nearly 700 <br />wells provides OCWD a source for samples, which are tested for a variety of purposes. OCWD collects <br />600 to 1,700 samples each month to monitor OC Basin water quality. These samples are collected and <br />tested according to approved federal and state procedures as well as industry- recognized quality <br />assurance and control protocols. <br />Salinity is a significant water quality problem in many parts of southern California, including Orange <br />County. Salinity is a measure of the dissolved minerals in water including both TDS and nitrates. <br />OCWD continuously monitors the levels of TDS in wells throughout the OC Basin. TDS currently has a <br />California Secondary Maximum Contaminant Level (MCL) of 500 mg /L. The portions of the OC Basin with <br />the highest levels are generally located in the Cites of Irvine, Tustin, Yorba Linda, Anaheim, and <br />Fullerton. There is also a broad area in the central portion of the OC Basin where TDS ranges from 500 to <br />700 mg /L. Sources of TDS include the water supplies used to recharge the OC Basin and from onsite <br />arcadis.wm <br />M� y 1 3 -17 <br />