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! <br /> <br /> 2. Water Use Drivers <br /> <br /> Data drivers for each water usc sector arc defined in Exhibit <br /> <br /> Exhibit 3. Water Use Drivers by Sector <br /> <br /> Water Use Sector Water Use Driver Source <br /> Single Family Number of single family RWC Housing Element, <br /> dwelling units 1999-2006 <br /> Multiple Family Number of multiple family RWC Housing Element, <br /> dwellin~ units 19c'~-2006; RWC plannin~ <br /> Commercial Number of employees ABAG '~ <br /> Commemial Irrigation Number of employees ABAG <br /> Government Population ABAG <br /> Other Population ABAG <br /> Residential Irrigation Number of multiple family RWC Housing Element, <br /> dwelling units 1999-2006; RWC planning <br /> <br /> The values of these data drivers are shown in Appendix A in 5-year increments over the <br /> forecast period. These dwelling unit, employee, and population estimates are the best <br /> current information available. They can and should be updated as expectations of future <br /> circumstances change. <br /> For the single-family residential class, dwelling units are segmented into six categories <br /> based on the year the dwelling unit was constructed. Water use patterns are known to <br /> vary with vintage based on factors such as water fixture efficiency and size of landscape. <br /> We obtained year built by obtaining tax assessor information f~om San Marco County <br /> and linking this information with thc water use billing data via parcel number. We <br /> defined the categories, partly, to match the years associated with key plumbing codc <br /> changes. <br /> For the multiple-family residential class, dwelling units are segmented into three <br /> categories based on the number of dwelling units at a site. The categories include homes <br /> with 2 to 4, 5 to 25, and over 25 dwelling units. Water use patterns are known to vary <br /> with the number of units at a site based on factors relating to demogmphics and <br /> landscaping. We were not able to obtain year built information for each account in this <br /> sector. <br /> 3. Water Use Coefficients <br /> The water usc coefficients are based on analysis of historical water use billing records. <br /> The coefficients mirror the water usc driver framework. We investigated adjusting the <br /> coefficients for weather, water prices, and water conservation technologies. The sections <br /> below describe how the coefficients are adjusted for each. <br /> <br /> Page 4 <br /> <br /> <br />