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Projected Water DemandsTable 4. Projected Water Demands �5 I Z- 3:5 q "Pa, Per Average Maximum Capita Day Day Year Ending Served Demand Demand Demand Population (gpcd) (MGD) (MGD) 2005 36,000 102 3.7 13.4 2010 42,200 103 4.3 15.4 2015 48,400 103 5.0 17.4 2020 54,600 104 5.7 19.6 (East Ravine Build -Out) 2030 67,800 109 7.4 23.9 Build -Out of 124,500 123 15.3 45.1 Ultimate Study Area �5 I Z- 3:5 q "Pa, Treatment Alternatives Alternate 1 - Two Water Treatment Plants 81 st Street WTP 33 MGD $ 38,000,000 South WTP 14 MGD $ 18,200,000 Treatment Costs $ 56,200,000 Raw Water Main Costs $ 11, 900, 000 Total Costs $ 68,100,000 Alternate 2 - Three Water Treatment Plants Idsen WTP 18 MGD $ 23,400,000 81 st Street WTP 15 MGD $ 19,500,000 South WTP 14 MGD $ 18,200,000 Treatment Costs $ 61,100,000 Raw Water Main Costs $ 9,700,000 Total Costs $ 70,800,000 Executive Introduction This report presents a Comprehensive Water Supply and Distribution Plan of a water system that will meet both the near -term and ultimate needs of the City of Cottage Grove. The most recent Comprehensive Water Plan was completed in 1995. Growth and Water Demand Cottage Grove has experienced steady growth over the last 10 years. From 1990 to 2000, its population increased by 33 %, going from a population of 22,935 to 30,582. The 2004 estimated population was 34,800. Water needs will continue to increase as the City builds to an estimated 20:30 served population of approximately 68,400. The ultimate saturation population is estimated to be about 125,000. Water use has increased steadily as population has grown. The City of Cottage Grove currently pumps approximately 130 million gallons of water into the system each year. Maximum day water use was on July 10, 2001 with 13.1 million gallons being pumped in one day (MGD). The projected water demand for 2030 is a daily average of 7.3 MGD with an estimated daily maximum of 24.1 MGD. The projected ultimate average day demand is 15.4 MGD and the ultimate maximum day demand is 45.1 MGD. Projected water demands were based on the City's land use designations for the 2030 Future Land Use Plan. Existing Facilities The existing water supply and distribution system has served Cottage Grove's needs quite well. The existing distribution system operates under three pressure zones, due to the variation in the City's topography. The high water level for each pressure zone is as follows: High Zone 1093 Intermediate Zone 990 Low Zone 935 The City presently obtains its raw water supply from 3 wells in the Low Zone, 7 wells in the Intermediate Zone, and 1 well in the High Zone, A booster station pumps water from the Intermediate Zone to the High Zone. Cottage Grove Water Supply and Distribution Plan Six storage facilities stabilize pressures in all zones during peak water demands, and also serve as a source of water during fires or power outages. There is a total existing useful storage volume of 4.65 million gallons. Water from the supply wells is chlorinated, fluoridated, and pumped into the system. Raw water from the Jordan aquifer is considered to be hard and has occasional high concentrations of iron and manganese, but does not require treatment at this time. The need for treatment in the future will be evaluated in light of customer desires and mandates of the Safe Drinking Water Act, 2030 Capital Improvements The recommended improvements necessary to meet Cottage Grove's estimated 2030 trunk water supply and distribution needs will cost about $29,900,000. Improvements include: 1 new well to replace 2 existing smaller capacity wells that are nearing the end of their expected life. • 7 new wells. 2 new storage towers. • trunk distribution system improvements. Ultimate Water System The improvement program for Cottage Grove's ultimate trunk water supply and distribution system is estimated to cost $114,400,000. The cost is broken down as follows: Supply Facilities $10,400,000 Storage Facilities 14,400,000 Distribution System 21 600,000 Total $46,400,000 The ultimate system shown on the map in the back of this report consists of the near -term improvements plus the following: • 12 new wells to serve the growth of the City. 1 new standby well for redundancy. This will bring the total number of supply wells up to 21. an additional 4 water storage towers, for a total of 12 storage reservoirs. . over 70 miles of additional trunk water distribution mains. • 2 proposed sites for water treatment plants, in case of future raw water quality problems. Cottage Gi °ove Water Supply and Distribution Plan 11 Economic Analysis This report recommends that the City maintain the current system of using area charges and connection charges to finance the proposed Capital Improvement Plan. Area charges of $ per acre developed are proposed to pay for 100% of distribution system costs and 25% of supply and storage costs.. Connection charges of $ per residential equivalent connection are proposed to pay for 75% of supply and storage costs. The City should review the Capital Improvement Program annually and modify the program to better serve community development needs. The entire water supply and distribution plan should be revised every 5 to 10 years. Recommendations Based upon the results and analysis of this study, it is recommended that Cottage Grove City Council: 1. Adopt this study and the Capital Improvement Program as a guide to the orderly expansion of the City's water system. 2. Adopt the proposed emergency preparedness and conservation plans included in this study and submit them to the Metropolitan Council and Department of Natural Resources for their approval. 3. Annually review the Capital Improvements Program and water system service charges to better serve community development needs. 4. Expedite acquisition of sites for wells, storage facilities, potential water treatment sites, and any easements required to connect these sites to the water system. 5. Monitor water quality and consumer complaints to screen out problems with high iron and manganese concentrations and insure compliance with drinking water quality standards. The need for water treatment should be evaluated if raw water quality problems arise in the future. Cottage Grove Water Supply and Distf °ibution Plan rrr