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t.:",C~-';:;/3 l.. (.... '1 Population and Water use Projections Based on recent Census figures the population in Yuma County increased from about 76,000 people in 1980 to about 105,000 people in 1990. As shown in Figure ____, the Carollo Report estimated population in the service area of the Main street Plant to increase from 63,600 in 1990, to 126,600 in 2025. Based on historical data, the maximum July use rate averages about 400 gallons per day per capita. Using the above population forecasts, and including estimates for the East Mesa Treatment Plant service area the maximum day use for the city of Yuma could increase from about 26.5 Mgaljd in 1990 to up to 65 Mgaljd in 2025. Recommended Modifications Following a review of the data and consideration of alternatives the Carollo Report recommended modifications to the city's treatment system be implemented in three phases; Short Term Improvements, Initial Expansion, and Ultimate Expansions. Short Term Improvements were those recommended as absolutely necessary to temporarily meet demands. These are currently being implemented. The Short-Term improvements would allow the Main Street Plant to produce 30 Mgaljd through the year 1994, when the Initial Expansion of the Main Street Plant is scheduled to be completed. These short term improvements include improving the chemical feed systems, the process units, and some of the backwash systems, as well as upgrading filters, replacing valves, and improving canal water delivery .capacity. Under the Initial Expansion the capacity of the Main Street Plant would be increased to 40 Mgaljd. with the Initial Expansion demands could be met through the year 2000. The Initial Expansion focused on the Main Street Plant as this site had adequate land for the expansion, and,the expansion could be implemented prior to 1995 to meet the Yuma Crossing National Historic Landmark time schedule. A listing of the improvements and their estimated cost was taken from the Carollo Report and is shown in Figure . The Initial Expansion was estimated to cost about $19 million based on 1994 dollars. J -- Ultimate Expansion provides for an additional 30 Mgaljd treatment capacity to be implemented in three 10 Mgaljd Sub-Phases. This additional capacity that would meet the additional water demand from population growth between the years 2000 and 2025. Recognizing that there was no additional land at the Main Street site, alternate sites for the new facilities were evaluated. criteria used in the evaluation included: - Land area requirements _ Impacts on and requirements of water transmission system 10