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Dr. Kent Butler October 21, 1985 Page 2 At the time these demands were projected, the City used a value of 3.5 persons per living unit. It is recognized that this figure has been dropping due to the decrease in average family size, and the City has recently adopted a value of 3.0 persons per living unit for their planning purposes. Since it is not yet clear what effect this change will have upon water use, it is prudent to assume that the projected demands for each living unit will be unchanged. As more water demand data becomes available, it may be possible to justi fy lower demand values in the future. The resulting demands used for this study are as follows: 1. Average Day: 711 gallons per living unit equivalent (LUE)/day or 0.5 gallons per minute (gpm)/LUE 2. Peak Day: 1,421 gallons/LUE/day or 1.0 gpm/LUE 3. Maximum Hour: 2,560 gallons/LUE/day or 1.78 gpm/LUE The study area contains a wide range of elevations, making the establishment of multiple pressure planes necessary. Although initially this area can be served most economically by a separate system, additional growth in this area will make desirable the connection of the proposed system and the City's existing system. For this reason, the pressure planes should be designed to be compatible with those of the City where practical. It is recommended that the study area be divided approximately along the 650-foot contour line. For most of the area, Post Road provides a convenient division between pressure planes. These areas will be referred to as the Upper Pressure Plane, with an overflow elevation of about 905 feet, and the Lower Pressure Plane, with an overflow elevation of approximately 767 feet. However, there is an isolated area east of Interstate Highway 35 which is too high to be served by the Lower Pressure Plane proposed to serve the adjacent areas. Since it is not practical to connect this area to the Upper Pressure Plane, even in the future, it is recommended that an intermediate pressure plane be established for this area. This will be referred to as the Northeast Pressure Plane in this report and will have an overflow elevation of approximately 815 feet. It is recommended that this plane extend west to 1. H. 35 and south to the 620 foot contour line. The approximate boundaries of the proposed pressure planes and MUDs are shown in Figure 1. WATER SUPPLY The Edwards Aquifer extends below a portion of the study area, and is known to contain an abundant supply of high-quality water. The City of San Marcos and Maxwell Water Supply Company, as well as many others, currently operate wells for domestic water supply, and this aquifer is the 1 09i cal water supply source for the study area as well. Whil e the yi el d to be expected from an individual well is not known precisely, it appears from prel imi nary tests performed by others that 1,000-1,500 gpm or more can be obtained without excessive drawdown of the water table. For the