Agenda - 08-30-2011 - 1a - Laserfiche WebLink

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7 DRAFT-03/11/2011 Triangle Regional ~'Vater Supply PIan Population Estimates Orange County prepared population estimates for its service areas by performing a land use analysis to determine the total potential population at build-out based on available acreage. In general; the available land area slated for development was broken down into three economic development service areas: Efland-Mebane, Eno and Hillsborough. Each of these areas were divided into smaller nodes, which are blocks of land with a relatively homogeneous-land use. These nodes included several non-residential land use types, and residential land use of low and high density. All of the service areas contain some designated areas of residential land. Population estimates were-based on capacity assumptions, which ~Nere made forthe available area in the residential land use nodes. In total, 10,248 acres were contained in a-total of six low-density residential nodes and one high-density node. Within each node, a percentage of the total area was deemed "not developable" to accommodate the space needed for transportation infrastructure, utilities, open space, etc. The percentages of remaining developable land varied by node but ranged from 50% to 75%. After the developable land was calculated, the number of households was then determined in each node. The amount of developable land area was multiplied by an assumed household densityof two households per acre for low-density residential areas and four households per acre for high-density residential areas. -Once the number of households was estimated, the.population was then determined: Population was calculated by multiplying the number of households by an assumed rate of 235 persons per household, regardless of whether the housing unit-was high- or low-density. This population was determined to be the total population at build-out. Orange County determined the population at ten-year increments by assuming the percentage of build-out achieved at each interval. In 2010, the population was estimated at 0.5% of the built-out population. By 2020, it was assumed the population would reach i5% ofbuild-out. Each subsequent forecast year (10 year increments) increased the percentage of build-out by 20%, starting with 35% in 2030 and culminating~in 96% of the total built-out population being present in 2060. Water Demand Projections The Orange County- Planning Department used a land use analysis to also estimate future water use. Like the population estimate methodology described above, water demand was first calculated at build-out, and then the forecast year demand projections were calculated based on the percentages of build-out reached. Future water demand was determined at ten-year increments by assuming the percentage of the built-out water demand achieved at each of these intervals. In 2010, water demand was estimated at 0.5% of the built-out water demand. By 2020, it was assumed the water demand would reach 15% of the built-out water demand. Each subsequent forecast year (10 year increments) increased the percentage of the built- out water demand by 20%, starting with 35% in 2030 and culminating in 95% of the built-out water demand occurring in 2060. Residential sector demands were based on the projected population and a per capita usage rate. Population projections are described in the population estimate section above. The assumed'per capita water use rate utilized for this analysis is 70 gallons per person day. Non-residential demand was calculated on a per area basis. Each of the three economic development service areas contain defined non-residential nodes. These node types include areas designated as Economic Development District (EDD), Commercial Node (CN), Commercial Industrial Node (CII~, Urban Growth Area (UGA), and others. Even though the node descriptions provided some information concerning the division of non- residential demand into sectors such as commercial, industrial, etc., it was decided to list all of the nodes as simply non-residential. As with the residential nodes, Orange County again assumed that only 75 % of Page 2