Chapter 4 – Future Supply & Demand and Projected Needs, Lecture notes of Construction

Download Chapter 4 – Future Supply & Demand and Projected Needs and more Lecture notes Construction in PDF only on Docsity! Park City and Snyderville Basin Water Supply Study Special Report 4-1 Chapter 4 – Future Supply & Demand and Projected Needs 4.1 Introduction This chapter presents the process used to determine future water demands and projected needs within the study area. It includes a discussion of population projections, determination of future demands, and calculation of future supplies which are assumed to be available without implementing any of the supply components described in Chapter 5. From this data, conclusions were drawn about projected water needs for 2030 and 2050. 4.2 Population Projections Two different methodologies for projecting future population were considered: The Governor’s Office of Planning and Budget (GOPB), in conjunction with local Area of Governments (AOG), is the agency responsible for preparing population and other demographic projections for the State of Utah. In May 2005, the Mountainland AOG broke down the latest Governor's Office of Planning and Budget population projections for Summit County by incorporated cities and towns with the remainder as the balance of county. The city projections include Park City’s estimated population for each decade from 2010 through 2050. Using this data and the 2000 Census tract data as a guide to future population distribution, the population of the study area in 2030 was estimated to be 64,300. For 2050, the projected population was estimated to be 86,300. Table 4- 1 contains the GOPB population estimates for the study area. The other approach taken to forecast population for the study area was to consider the maximum potential development within the Basin. Summit County has adopted a land use plan (Snyderville Basin General Plan) that identifies where development will be permitted and how densely it will be allowed to develop. Park City also has a similar land use plan that establishes the projected densities within the city limits. Using the densities associated with each land use, populations at build out were estimated for the various land use categories. Comparatively, the two methods produced somewhat different results. While the GOPB projections estimate a study area population of approximately 86,300 by 2050, the build out method estimated the ultimate population within the study area to be only 75,600. Although the build-out method is often useful for planning purposes, this method assumes that current zoning laws and associated population densities will remain unchanged for the next 45 years. As experience in other communities demonstrates, zoning laws can and do change when property values increase and pressures mount to accommodate growth. Therefore, the higher GOPB population estimates were not considered unreasonable and are used for the purposes of this study. Park City and Snyderville Basin Water Supply Study Special Report 4-2 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 2001 2010 2020 2030 2040 2050 Year A cr e- Fe et w/o Conservation With Conservation 4.3 Projected Future Demands 4.3.1 Demand Modeling UDWR has developed the Utah Water Demand/Supply model to project the future water demands. UDWR’s base water use data for the year 2001 and the GOPB population projections were used to estimate water demands within the study area for each 10-year period from 2010 to 2050. These demands were projected both with and without water conservation. Figure 4-1 shows the projected demands with and without conservation. FIGURE 4-1 Projected Future Water Demands TABLE 4-1 Snyderville Basin Population Projections Population City/Area 2001 2010 2020 2030 2040* 2050* Park City 7,647 10,987 15,339 19,776 19,325 20,904 Balance of Snyderville Basin** 16,212 23,002 34,320 44,541 55,303 65,423 TOTAL 23,859 33,989 49,659 64,317 75,603 86,327 Source: Governor’s Office of Planning and Budget, “2005 Baseline City Projections,” June 2005. * The Governor's Office of Planning and Budget (GOPB) models projections to 2030, all projections beyond this date are estimated using other methods and are provided by GOPB for scenario analysis. ** Estimated based on 2000 Census population distribution. Park City and Snyderville Basin Water Supply Study Special Report 4-5 Recognizing the importance of water conservation to Utah’s future, the Utah Legislature passed the Water Conservation Plan Act in 1999. This act requires each water retailer with more than 500 connections, and all water conservancy districts, to prepare water conservation plans and submit them to UDWR. Water conservation plans are to be updated and resubmitted every 5 years from the original submittal date. In addition to this legislative requirement, the state’s water funding boards require any entity requesting funds for water projects to have a water conservation plan in place, regardless of its size. Only five of the eight systems in the study area are required by law to prepare a water conservation plan. Of the three that are not required to do so, only High Valley Water has submitted a plan. Although the Water Conservation Plan Act has helped elevate the importance of water conservation planning in the Snyderville Basin area, water providers in the area must set strong water conservation goals and ensure they are met by implementing appropriate measures. If a significant effort to achieve water conservation goals is not made, it may be difficult to justify large investments in new water development projects by state and Federal Governments. Many western mountain resort communities have implemented stricter watering ordinances, such as no outside watering or using only native plants requiring no additional water on all new construction. If Government entities in the study area were to implement similar ordinances for all new construction, the conservation goals discussed above could be more easily met. The current per capita use for indoor residential, commercial, and institutional categories amounts to about 150 gpcd. With a current total water use of 317 gpcd, there is a significant potential for reduction of outdoor water use in the study area. Water conservation efforts within the Snyderville Basin have yielded significant results in recent years. All three of the major water suppliers within the Study area (Park City, Mountain Regional Water Special Service District, and Summit Water Distribution Company) have realized declines in total demand in the neighborhood of 25 percent in just a few years. While drought-related responses certainly played a significant role in these reductions, it is likely that residents within the Basin will maintain at least a portion of these gains into the future. In order to help this to happen, the conservation message will need to continue to be emphasized during years of normal and above normal precipitation. 4.3.3 Wastewater Dilution Requirements For the Snyderville Basin Water Reclamation District (SBWRD) to meet its State Discharge Permit requirements for discharging its treated M&I wastewater to East Canyon Creek, it has to rely on a minimum stream flow for dilution of the effluent to meet the designated beneficial uses for East Canyon Creek. The SBWRD is considering an upgrade to its treatment facility from the existing “Type 1” effluent treatment to reverse osmosis in order to comply with phosphorus limits. The current limit for phosphorus is 100 ppb, but the state is looking at reducing the limit to 50 ppb. SBWRD recently completed a very costly upgrade of its treatment system to meet the 100 ppb limit, and if this additional upgrade is necessary, it may be cheaper to purchase water for instream dilution flows, or to reduce its discharge volume by reuse. Park City and Snyderville Basin Water Supply Study Special Report 4-6 Under a contract with SBWRD, Kleinfelder, Inc., recently completed a flow augmentation study on East Canyon Creek to determine the quantity of water that would be required to maintain minimum instream flows to allow achievement of beneficial uses designated for East Canyon Creek (“East Canyon Creek Flow Augmentation Feasibility Study: Summit and Morgan Counties, Utah, February 2005”). That study concluded that the maximum amount of augmentation to meet the instream flow goals is calculated to be approximately 1,095 acre-feet, which would provide a minimum 6 cfs for instream flow from July through September. This requirement is shown in the study for the year 2030, since 2030 is the planning time frame of the SBWRD. As the population increases, however, an additional 500 acre-feet would be needed by the year 2050 for a total need of about 1,600 acre-feet in 2050. SBWRD is interested in planning this future demand as part of the overall long-term demand addressed by this current study. Including this industrial water requirement of 1,100 acre-feet for 2030 and 1,600 acre-feet for 2050 as a part of the projected demand leaves water reuse as a potential development option that may be used to meet future needs. 4.3.4 Susceptible Mine Tunnel Flows A large portion (approximately 50 percent) of the water used by Park City comes from old mine tunnels. The mining operations have ceased and the tunnels used for water supply are being maintained by Park City for water supply purposes. Because the tunnels are old and the maintenance being performed is only sufficient to keep the water flowing, if a tunnel collapse were to occur, the city's ability to meet peak demands would be at least temporarily reduced until repairs could be made or replacement sources developed. The city is also concerned that maintenance of the tunnels will become increasingly more difficult and expensive as the tunnels age and as the availability of qualified miners continues to decline. The tunnels also have unique water quality issues associated with their use for drinking water purposes. The mines are former lead and silver mines and they contain heavy metals, arsenic, antimony, and other potential contaminants. The city has to carefully operate the tunnel systems so as to limit the amount of contaminants in the water supply. It also has to treat some of the water from the tunnels to remove contaminants. Concern over the long-term effects of potential contaminants on the water supply raises issues with the reliability of these sources. For these reasons, the city is interested in developing 2,000 acre-feet of additional supply to provide backup in case of emergencies even though they are expected to continue using the mine tunnel water as long as it is available and of acceptable quality. 4.3.5 Adjusted M&I Demand Adding the effluent dilution requirement (1,100 to 1,600 acre-feet per year) and susceptible mine tunnel volume (2,000 acre-feet per year) to the total demand projected with conservation as shown previously in Table 4-3 yields an adjusted total M&I demand for the study area as shown in Table 4-4. For purposes of this study, the 2030 demand of 23,000 acre-feet per year (with conservation) and 2050 demand of 27,000 acre-feet per year (with conservation) are the demands that will need to be met by a combination of the projected reliable supplies discussed below and the water supply development options presented in Chapter 5. Park City and Snyderville Basin Water Supply Study Special Report 4-7 4.4 Projected Reliable Supplies There are a number of water supply resources in the study area which were not included in the existing supplies discussed in Chapter 2 but which, for purposes of this report, are assumed to be available supplies for 2030 and 2050. These include the Lost Creek Canyon Pipeline Project, the Jordanelle Special Service District import, additional groundwater supplies, and agricultural water conversions. Also, the need for continued system surplus/reserve will continue into the future. Following is a discussion of each, including the amount by which they are expected to affect future available supplies. It is important to note that this study assumes that these water supply resources are developed concurrently with the growing population and are utilized to become part of the projected reliable supplies. 4.4.1 Lost Creek Canyon Pipeline The Lost Creek Canyon Pipeline Project was completed and dedicated in October 2004. The current capacity of this project is 1,600 acre-feet per year. The source water comes from shallow wells near the Weber River above Rockport Reservoir. The existing infrastructure included in this importation project consists of the following: a shallow groundwater well system on the Weber River; a booster pump station; approximately 27,000 linear feet of 24-inch water transmission line to convey water from the well system to the Signal Hill Water Treatment Plant; a 3 MGD (2,080 gpm), expandable to 6 MGD (4,200 gpm), membrane water treatment plant located on the ridgeline above Three Mile Canyon; and two open reservoirs totaling approximately 15 acre-feet of raw water storage (Aqua Engineering, 2003). Current agreements contemplate that the pipeline may potentially convey up to 6,600 acre-feet per year to the Snyderville Basin. Although an expansion of the water importation capability of this system is presented as a potential water supply system component in Chapter 5, for purposes of TABLE 4-4 Adjusted M&I Demands Population or Volume (acre-feet) 2030* 2050* Population 64,300 86,300 Calculated M&I Demand 25,300 32,000 Water Conservation (2,300) (5,000) Net M&I Demand 23,000 27,000 Minimum Instream Flow / Effluent Dilution Requirement 1,100 1,600 Susceptible Mine Tunnel Flows 2,000 2,000 Adjusted M&I Demand 26,100 30,600 * Rounded to nearest 100 acre-feet.