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<br />7A - ATTACHMENT NO.3 <br />Saltworks Proposal- Water Group Summary Report (22 January 2010) Page 43 <br /> <br />The graywater systems described in the OMS Supply Report are in the category <br />recognized by the State of California as "simple systems," meaning they gather not more <br />than 250 gallons per day of graywater from multiple outlets in a single residence for use <br />on site. All graywater systems in California must have bypass valves installed that allow <br />the "operator," most often the resident, to discharge the graywater to the sanitary sewer. <br />This bypass requirement allows the operator an option for disposal during system <br />maintenance or during operational problems; it also makes the graywater supply quantity <br />variable and uncertain because it is managed by individual operator choice. <br /> <br />The OMS Supply Report describes that graywater could supply up to 130 AFY from <br />graywater systems that could be installed within the residential land use component of <br />the project, with each home's graywater supplying water for toilet flushing and backyard <br />irrigation for that home. Of the 130 AFY of anticipated supply, 66 percent could meet <br />toilet flushing demand for the house year round, and the remaining 34 percent could <br />supply backyard irrigation during all but the rainy winter months. <br /> <br />3.6.2 Description of Rainwater as a Source of Supply <br /> <br />Rainwater as a water supply source involves capturing or "harvesting" rainwater from <br />rooftops, storing it in aboveground or underground tanks, and using it for non-potable <br />uses at the same property. Rainwater harvesting can reduce the need for potable water <br />supply if it replaces indoor uses like toilet flushing, and it can also reduce the volume of <br />stormwater runoff generated from development. Rainwater harvesting is often a <br />component of "low impact development." Rainwater is most commonly used for <br />landscape irrigation. In California, the Department of Public Health (COPH) considers <br />harvested rainwater an auxiliary water supply source much like an irrigation well if it is <br />captured for use at a home for irrigation. CD PH requires any site with an auxiliary water <br />supply to install appropriate backflow prevention to protect the public water system. <br /> <br />According to the OMS Supply Report, no use of rainwater is currently planned for the <br />project because of the availability of recycled water and graywater, and due to the <br />unpredictability of rainfall and the annual long period without rainfall relative to expected <br />storage capacity and need. The OMS Supply Report indicates that up to 230 AFY could <br />be harvested from roofs in the residential/mixed use land classifications, if the need <br />arose for an alternate non-potable source of supply. <br /> <br />3.6.3 Unresolved Issues Regarding Graywater and Rainwater <br />California allows graywater use under prescribed conditions for outdoor irrigation. The <br />OMS Supply Report plans for implementing graywater for irrigation are aligned well with <br />State law. <br /> <br />Since the publication of the OMS Supply Report, the State of California has adopted very <br />limiting regulations regarding indoor use of graywater for uses such as toilet flushing. <br />These regulations, in Chapter 16A of the California Plumbing Code, state that if <br />graywater is treated on site to meet the recycled water criteria of California Code of <br />Regulations Title 22 for unrestricted reuse (i.e. equivalent of tertiary treatment), it can be <br />used indoors for the uses approved in Title 22, including toilet flushing. This condition is <br />exceedingly complex, costly, and would be difficult to meet for the project. Essentially, <br />each site using graywater for toilet flushing would be required to have an onsite <br />treatment system that achieves the water quality standard of tertiary-treated recycled <br /> <br />36 <br />