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Appendices SEIR No. 339 City of Anaheim Response to Comments Appendix D. Water Supply Memo ---PAGE BREAK--- Appendices The Planning Center October 2010 This page intentionally left blank. ---PAGE BREAK--- MEMORANDUM To: Bill Halligan, The Planning Center From: Michael D. Swan, PE Date: October 14, 2010 Subject: Errata Sheet, The Platinum Triangle Water Supply Assessment, City of Anaheim As part of its demand assumptions, the Water Supply Assessment (WSA) stated it assumed that an individual resident would use 70 gallons per day (gpd). Water policy experts from Psomas and the City’s Public Utilities Department staff have further analyzed this figure based on more recent data. Based on this further review, both Psomas and the City’s Public Utilities Department believe that the previously-stated assumption that an individual residing in the type of residential product envisioned in The Platinum Triangle would use 70 gpd significantly overstates per capita demand. This is so, because the 70 gpd figure was based on residential housing product type more typical of larger, detached single family homes that are fundamentally different than the residential product type envisioned in The Platinum Triangle, and (ii) the 70 gpd figure assumes the use of older (and in many cases now, unavailable) and much more inefficient water fixtures (toilets, dishwashers, and clothes washers), than will be available and developers will actually be compelled to install in housing products within The Platinum Triangle. Detached, single family residential dwelling units by their nature attract a different demographic that generally uses more water per capita. Typically these occupants are family orientated, often with children and one parent who stays at home throughout the day. The water demands of a stay-at-home parent with children at home at least part of the day are much higher increased cooking use; increased dishwasher use; increased laundry use; increased toilet and bathroom use; children’s baths; multiple showers, etc.) than a prototypical urban professional who may not be home at all throughout most of the day (minimal cooking; limited laundry; showers at gym some days of week, more travel, etc.). Moreover, the older, less efficient water fixtures that were assumed with the 70 gpd figure are up to fifty percent less efficient than those available and in most instances required to be installed in modern residential housing. For these reasons, both Psomas and the City’s Public Utilities Department staff believe a more realistic per capita demand for residential dwelling units within The Platinum Triangle is 45 gpd. This is consistent with the water use rates of similar, newer housing product types in Irvine, as determined by the Irvine Ranch Water District and by a study conducted by the American Water Works Association (included in Appendix A to the WSA showing that typical household water demand can be cut from 69.3 gpd to 45.2 gpd by installing more water efficient water fixtures). The 105 gpd per dwelling unit (du) used in the WSA (assuming the overstated and highly conservative 70 gpd times 1.5 people/du) is effectively an amount sufficient for daily water supply for approximately 2.33 people per dwelling unit at the more realistic 45 gpd (105/45). ---PAGE BREAK--- Bill Halligan Page 2 of 2 October 14, 2010 2ANA012900 2 Thus, the WSA effectively assumes the total water demand generated could support approximately 2.33 persons per unit in the residential product envisioned in The Platinum Triangle. If the actual resident per unit figure were in line with the figures occurring in downtown San Diego, the Irvine Business Complex, and those projects already completed in The Platinum Triangle (1.5; 1.3; and 1.4 persons per unit, respectively), then the Water Supply Assessment obviously conservatively overestimated water demand.