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A-1 Review Feasibility Study for West Water Treatment Plant0 A—I, CITY OF Development was approved in 2005 for a treatment plant and a small park. The Fax: 952.227.1110 MEMORANDUM CHANHASSEN Harrison Road and Galpin Boulevard. 2310 Coulter Boulevard TO: Todd Gerhardt, City Manager 7700 Market Boulevard On July 28, 2014, the City Council reviewed options to treat the water from the PO Box 147 FROM: Paul Oehme, Dir. of Public Works /City Engineer G Chanhassen, MN 55317 refine options for treatment of the west well field. Planning & DATE: July 27, 2015 0 Administration Phone: 952.227.1100 SUBJ: Review Draft Feasibility Study for West Water Treatment Plant Fax: 952.227.1110 report for treatment of the western well field. The City contracted with SEH Building Inspections Consultants to complete a feasibility study. Phone: 952.227.1180 BACKGROUND Fax: 952.227.1190 DISCUSSION Phone: 952.227.1300 The 2003, a water treatment plant study recommended treating the east well field Engineering wells first since these were the wells that have the highest iron and manganese Phone: 952.227.1160 content. Water treatment for the west well field was planned to be phased in as Fax: 952.227.1170 needed. Finance mandatory chlorine and fluoride as required from the State of Minnesota. About Phone: 952.227.1140 The East Water Treatment Plant was constructed in 2005 and treats the iron and Fax: 952.227.1110 manganese in the low zone area. Park & Recreation The City purchased a piece of property at the time the Lake Harrison Phone: 952.227.1120 Development was approved in 2005 for a treatment plant and a small park. The Fax: 952.227.1110 location is at the south end of Manchester Road at the intersection of Lake Recreation Center Harrison Road and Galpin Boulevard. 2310 Coulter Boulevard Phone: 952.227.1400 On July 28, 2014, the City Council reviewed options to treat the water from the Fax: 952.227.1404 western wells for iron and manganese. At that meeting staff was directed to refine options for treatment of the west well field. Planning & Natural Resources Phone: 952.227.1130 In March 2014, staff received proposals from consultants for drafting a feasibility Fax: 952.227.1110 report for treatment of the western well field. The City contracted with SEH Consultants to complete a feasibility study. Public Works 7901 Park Place DISCUSSION Phone: 952.227.1300 Fax: 952.227.1310 The City's East Water Treatment Plant removes iron and manganese from the east Senior Center field by a gravity filtration process. The wells in the west side of the city are not Phone: 952.227.1125 filtered for iron and manganese. All of the City's water is treated with the Fax: 952.227.1110 mandatory chlorine and fluoride as required from the State of Minnesota. About 33% of the City's water supply remains unfiltered prior to delivery to the water Website distribution system. This percentage is expected to grow as the City develops. www.ci.chanhassen.mn.us The City has drafted a feasibility study to look at removing iron and manganese from the western wells. Also included was a pilot plant study to look at what Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow Todd Gerhardt July 27, 2015 Review Draft Feasibility Study for West Water Treatment Plans Page 2 filtration process is the most cost effective approach to removal of iron and manganese. The pilot study findings were also used for cost estimating of a filtration plant. Primary Drinking Water Standards Primary Standards are legally enforceable standards that public water suppliers are required to meet. Primary standards protect public health by regulating the levels of certain contaminants in public water supplies. Primary drinking water standards include regulations for levels of- microorganisms, disinfectants, disinfectant byproducts, inorganic chemicals, organic chemicals and radionuclides. The City of Chanhassen's drinking water does not exceed any primary drinking water standards. Secondary Drinking Water Standards Secondary Standards are non - enforceable guidelines which regulate contaminants such as iron, manganese, and hardness that cause aesthetic or cosmetic effects, such as taste, odor and color, and can cause problems with piping. Manganese The secondary standard for manganese is 0.05 milligrams per liter (mg/L; equivalent to parts per million [ppm]). Water with concentrations of manganese above the secondary standard can cause black or brown staining on fixtures and taste complaints. The drinking water from Chanhassen's unfiltered wells consistently exceeds the Secondary Standard for manganese with concentrations ranging from 0.33 mg/L to 0.46 mg/L. Iron The secondary standard for iron is 0.3 mg/L. Water with concentrations of iron above the secondary standard causes reddish -brown staining on fixtures. The drinking water from the west Well Nos. 3 and 9 exceed the secondary standard for iron with concentrations of 0.5 mg/L and 0.93 mg/L, respectively. Hardness Although not included as a secondary standard, water above 120 mg/L hardness is considered hard water. Hard water causes scaling on fixtures and can eventually cause piping to become plugged. The drinking water from Chanhassen's wells is considered hard with a hardness ranging from 260 mg/L to 320 mg/L. The City has chosen not to treat for hardness because well water does not require the water to be softened and softening water is much more expensive capital cost and operational and maintenance then filtering for iron and manganese. The level to which water is softened is also a personal preference and everyone has a different point where they think water should be softened. In communities that have softening plants, many residents choose to still soften their water. For these reasons, the City has chosen not to soften the water at a City level. Water Quality Concerns Associated with Iron and Manganese Chanhassen has some unique water quality issues caused by the high zone's untreated water and the way it directly influences portions of the city's treated low zone areas. The area, referred to as the "Minnewashta Loop ", comprises Chanhassen's western border and runs from Highway 5 g: \eng \public \_2015 projects \15 -3 west water treatment plant feasiblity study \072715 bkgd ws west wtp review feasiblity report2.doc Todd Gerhardt July 27, 2015 Review Draft Feasibility Study for West Water Treatment Plans Page 3 north up Minnewashta Parkway to Highway 7 then east to Highway 41. This area is a large hydraulic loop linked to the low zone's treated water on the southern end and the high zone's untreated water on the northern side at Highway 7 and Highway 41. During periods of normal to low use, this area is served with treated water, however, in periods of high use the demand is heavily supplemented from the unfiltered western wells. This condition causes troublesome rusty water complaints throughout the Minnewashta Loop area. The only remedy for these complaints is to perform localized hydrant flushing to remove the discoloration. Unfortunately, this activity only introduces more untreated high zone influence on the low zone and also has a dramatic effect on chlorine residuals. Chlorine is added to the water to guard against disease causing pathogens. The City's untreated water has a high chlorine demand because it is rich with iron and manganese. These elements chemically oxidize together with chlorine in distribution piping, bringing them out of solution and creating discolored material. This condition makes for an uneven chlorine residual throughout the city; higher in the east and lower to the west. Well Nos. 3 and 9 located on Galpin Boulevard north of Highway 5 are low zone wells directly connected to the distribution system and are not treated by the East Water Treatment Plant. These supportive wells offer water production in periods of high city demand; however, they also bear negative water quality issues upon the low zone. The areas most affected with discolored water from these wells are along W. 78th Street and include Arboretum Village Townhomes, the Vasserman Trail area, and the Walnut Grove HOA. Treated areas of the city not under any direct or indirect influence from the high zone experience very little or no discolored water throughout the year. M1� -r }Icy {' :� y.tiv.la` r � w.lis 5R , �; + � - � -� ^•�( •� � � C" L `f"a a ''r IAbll 12 I _ _ vkw ] ► I I �... S7� Y1YII 10- �YIMII�13`I High F,,, Low a ® Treated/Untreated Zone `A July 23, 20 14 g: \eng \public \_2015 projects \15 -3 west water treatment plant feasiblity study \072715 bkgd ws west wtp review feasiblity report2.doc Todd Gerhardt July 27, 2015 Review Draft Feasibility Study for West Water Treatment Plans Page 4 Treatment Filter Plant Considerations The Comprehensive Plan and the Capital Improvement Plan both have a treatment plant proposed for the City -owned property at the northwest corner of Galpin Boulevard and Lake Harrison Drive. This property is zoned Residential - Single Family. City Code Section 20- 612(7) states that utility services are a permitted use so no zoning change is necessary if a treatment plant is to be constructed on this property. The feasibility study completed, soil borings, a site evaluation, treatment plant layout and a rendering of a concept plant. Soil borings were taken to identify any poor soils that would need to be removed and for structural consideration of the building. The water table was also measured to set the underground storage tanks. Since this is a residential area, the concept should blend into the area. For this reason the project should have an extensive landscape plan. Also a neighborhood park is planned to be constructed on the north side of the plant site after the facility is constructed. The site plan for the water plant should discourage the area around the plant for pedestrians. The plant is very similar to the form and function at the East Water Treatment Plant. The size of the plant is also the same the East Plant. g: \eng \public \_2015 projects\15 -3 west water treatment plant feasiblity study \072715 bkgd ws west wtp review feasiblity report2.doc Todd Gerhardt July 27, 2015 Review Draft Feasibility Study for West Water Treatment Plans Page 5 CAPITAL COST OPINION Based on current construction costs and plant size, below is the Capital Cost Estimate for the plant. Construction Cost $15,630,000 Contingency (10 %) $ 1,563,000 Construction Total $17,193,000 Engineering/and other indirect costs (13 %) $ 2,235,000 Total Cost $19,428,000 The cost also including extending raw water main from the existing wells to the treatment plant and modifications to the existing wells. Staff discussed a phased -in approach with the City Council where several smaller plants would be constructed over time to avoid a one -time large capital expenditure. This approach was dismissed because the City would still have iron and manganese problems until the last plant is constructed and the cost to construct up to three plants versus one large plant would be more. Furthermore, the life cycle cost and labor to run several plants would be more than one large plant. If a water treatment plant were to be built, a full -time plant operator will also need to be hired. Staff is planning to give a detailed review of the findings of the feasibly report at the Council Work Session. Attached: Rendering Layout Raw Water Main Figure g: \eng \public \_2015 projects \15 -3 west water treatment plant feasiblity study \072715 bkgd ws west wtp review feasiblity report2.doc �� 3D CONCEPTUAL CUT - DO NOT MOVE �q �L F N I It 1 PUM e. .lo 1 MRM 1 K&ivmm D 1 WETLAND -D 1 left w low we 10 � on WE %LANL — — — _ _ _ /// oN TUAL SITE LAYOUT E E cS 0 w U U g a 0 I L-I-Z LNend 750,000 Gal Proposed Raw Water Main MM W Tower — " Alternate Raw Water Main Well 15 3.5 MG Lake Lucy Existing Raw Water Main Reservoir Existing Well ^• 8 Existing Elevated Storage Existing WTP Alternate Raw Watermain Existing Waterlines Alignment - 10" Raw Parks ® Watermain Lakes Well 7 mN r Proposed Well B WTP Site Lake Lake Lucy Harrison 16" Raw Watermain a Existing Raw Watermain Well 3 Existing Raw Watermain� L a k e A no 0 500 1.000 2,000 Feet Well 9 «...� «.., �.a... 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