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C. Water Storage in High Zone.0 CITY OF MEMORANDUM CU N SEN TO: Todd Gerhardt, City Manager 7700 Market Boulevard PO Box 147 FROM: Paul Oehme, Director of Public Works /City Engineer Chanhassen, MN 55317 corrosion. The condensation that forms on the tank also generates complaints DATE: May 23, 2011 Administration SUBJ: Discuss Need for Additional Water Storage in the High Zone Phone: 952.227.1100 and motors needed to supply the tower and is a very inefficient way to supply Fax: 952.227.1110 water. Also, the undersized storage facility leaves little time for utility staff to Building Inspections BACKGROUND Phone: 952.227.1180 tank at this time is undersized for fire flow design. Fax: 952.227.1190 Needs Analysis Fax: 952.227.1110 In November 2008, the city completed an update to the Comprehensive Water Engineering Plan. As part of the plan, a storage analysis was performed that recommended Phone: 952.227.1160 additional storage be constructed in the existing high service zone. The high Fax: 952.227.1170 zone water area has seen significant growth in recent years, which has driven the need for additional storage capacity. Finance Phone: 952.227.1140 The city has two main pressure zones. The low zone area services about 88% of Fax: 952.227.1110 the current city demand. Two water towers service this area along with the east Park & Recreation water treatment plant. The high zone area is serviced by two wells and a Phone: 952.227.1120 200,000 water tower located next to Minnetonka West Middle School. The Fax: 952.2271110 tower was constructed in 1970 when the population of Chanhassen was about 4,875. The high zone is mainly in a residential service area which has seen Recreation Center significant growth in the past 10 years. Currently, the demand in the high zone 2310 Coulter Boulevard area can be as little as 100,000 gallons a day during the winter months and as Phone: 952.227.1400 much as 1,800,000 during peak summer time usage (2007). Fax: 952.227.1404 'r Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow Since the high zone does not have much storage capacity, during high demand Planning & Natural Resources periods the tank cycles continuous) which causes man problems. The p Y Y Y P high Phone: 952.227.1130 cycling causes condensation to form on the tank which accelerates tank Fax: 952.227.1110 corrosion. The condensation that forms on the tank also generates complaints from adjacent properties because the condensation can fall off the tank and land Public Works on their property. The continuous cycling also puts additional stress on pumps 7901 Park Place and motors needed to supply the tower and is a very inefficient way to supply Phone: 952.227.1300 water. Also, the undersized storage facility leaves little time for utility staff to Fax: 952.227.1310 respond to power outages and start auxiliary power generation. In addition, the Senior Center tank at this time is undersized for fire flow design. Phone: 952.227.1125 Needs Analysis Fax: 952.227.1110 One of the most critical roles that a water distribution system provides, Web Site especially in urban areas, is fire protection. The Insurance Services Office (ISO) www.ci.chanhassen.mn.us provides a score for municipalities based on their ability to meet industry standards for required fire flow based on building size, occupancy class, 'r Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 2 construction type, etc. Lower scores indicate better ability of systems to suppress fires and typically result in lower insurance rates for commercial and industrial property. The standard required available fire flow that ISO has is 3,500 gpm for 3 hours. Since this is mostly a residential area and all the commercial buildings are sprinkled, the fire marshal recommends using a 2,750 gpm for two hour fire flow. Another industry guideline for required available fire flow is the American Water Works Association (AWWA). According to AWWA, the minimum fire flow available at any given point in a system should not be less than 500 gpm at a residual pressure of 20 psi. This minimum criterion represents the amount of water required to provide for two standard hose streams on a fire in a typical residential area with spacing greater than 100 feet. The distance between buildings and the corresponding recommended fire flow for residential areas is summarized in Table 1. Table 1: Recommended Residential Fire Flow Rates Distance Between Buildings (ft) Needed Fire Flow (gpm) More than 100 500 31 -100 750 11 -30 1000 Less than 11 1500 These two standards are typically used as guidelines when planning and designing for available fire flow. While the majority of the high service zone includes residential -type construction, there are several large commercial buildings, such as the Minnetonka Middle School that could require substantial available fire flow needs. In addition, past discussions with the Fire Chief and Utility Department have indicated that on more than one occasion, the existing available storage was nearly depleted during fire suppression operations at some of the large residential properties located in this zone. To provide a longer period of available fire flow, additional storage is required. Calculations have been performed based on this recommended available fire flow and are shown in Table 2. g: \eng \public \_2011 projects \1 1 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 3 Table 2: Storage Capacity Needs for the High Pressure Zone Water storage capacity should be adequate to sustain normal system demands as well as fire protection operations. The storage volume capacity analysis for the high pressure zone is shown in Table 2. This table shows that the existing Melody Hill Tank is not capable of providing 2,750 gpm as recommended. In addition, the amount of storage required to provide 2 hours of 2,750 gpm of available fire flow for full build -out is shown to be approximately 725,000 gallons. This volume gives the city capacity to supply a 2,750 gpm fire flow rate for two hours while concurrently meeting projected maximum day demands on the system. The standard tank size for this demand is 750,000 gallons. The goal of this study is to provide the following: • A needs analysis for a new elevated water storage tank. • An analysis of six sites for construction of a proposed elevated water storage tank. gAeng \pub1ic \_2011 projects \11 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Existing Ultimate Projected Demand 2 Hour Fire 2,750 gpm 2 Hour Fire 2,750 gpm A Average Daily Water Use in gpd 411,750 484,830 B Maximum/Average Day Ratio 3.1 3.1 C Maximum Day Water Use in gpd 1,800,000 1,900,000 D Maximum Day Water Use in gpm 1,250 1,319 E Firm Pumping Supply Capacity in gpm 2,000 2000 F ISO Design Fire Fighting Rate in gpm 2,750 2,750 G Fire Fighting Duration in Hours 2 2 H Design Fire Fighting Volume in gal. (F x G x 60min/hour) 330,000 330,000 I Total Coincident Demand in gpm (D + F) 4,000 4,069 J Required Draft from Storage in gpm (I - E) 2,000 2,069 K Adjusted Fire Fighting Storage in gal ( G x 60 min/hr x J) 240,000 248,333 L Equalization Storage in gal/day ( C x 25 %) 450,000 475,000 M Total Storage Need in gal ( K + L ) 690,000 723,333 N Existing Elevated Storage in gallons 200,000 200,000 Water storage capacity should be adequate to sustain normal system demands as well as fire protection operations. The storage volume capacity analysis for the high pressure zone is shown in Table 2. This table shows that the existing Melody Hill Tank is not capable of providing 2,750 gpm as recommended. In addition, the amount of storage required to provide 2 hours of 2,750 gpm of available fire flow for full build -out is shown to be approximately 725,000 gallons. This volume gives the city capacity to supply a 2,750 gpm fire flow rate for two hours while concurrently meeting projected maximum day demands on the system. The standard tank size for this demand is 750,000 gallons. The goal of this study is to provide the following: • A needs analysis for a new elevated water storage tank. • An analysis of six sites for construction of a proposed elevated water storage tank. gAeng \pub1ic \_2011 projects \11 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 4 • Provide a site recommendation for the construction of an elevated water storage tank. • Identify site improvements needed to build a water storage tank. • Provide preliminary geotechnical analysis of the existing site soils to determine a general foundation design for cost estimation. • Provide a cost estimate for the design and construction of a new elevated water storage tank. • Provide a schedule to complete the design and construction of a new elevated water storage tank along with the demolition of the existing 200,000 gallon Melody Hill elevated water storage tank. Alternative Sites Over the past 2 years, staff has evaluated many sites for future water storage. Included in this report are six alternative sites that were reviewed in greater detail. Staff discussed the idea of constructing a water tower on the Minnewashta Park property, but Carver County could not allow this type of structure on their property because of the land purchase agreement requirements established at the time of acquisition. Staff also evaluated Herman Field Park for a tower, but the elevations of the park are too low to cost effectively build a tower. Site #1 — West of Hazeltine Boulevard near Well No. 8 A residential lot on the west side of Hazeltine Boulevard near Minnewashta Regional Park was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: • Pressure changes to the system were very minimal and would likely not result in any noticeable impact to the current service that residents are provided. • Available fire flow changes are slightly improved in the southern and western portions of the service area. Modeling indicates that available fire flows will be reduced approximately 200 gpm north of Lake Lucy Road and increase approximately 200 gpm south of Longacres Drive. • Approximately 1,300 feet of 12 -inch watermain should be constructed to connect existing trunk mains along the west side of Hazeltine Boulevard. In addition, a road crossing of TH 41 will be required to complete the connection. • The site has one of the lowest elevations of all the sites analyzed and would result in a water tower nearing 170 feet in total height. This height requires additional foundation and structural design due to the additional wind loads and over - tipping. g:\eng\publjc\ projects \11 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 5 • A 170 -foot water tower at this location may meet with some resistance by residents on the east side of TH 41 since some of their views of Lake Minnewashta would be obstructed. Site #2 — Adiacent to the Existing Melody Hill Tank Minnetonka School District property directly adjacent to the west of the existing water tower was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: • The new tower would connect to the distribution system at the same location as the existing Melody Hill Tower. No change to system hydraulics will occur. • Available fire flow changes will not occur as the tower location and existing water main would remain in place. • No additional water main, other than the connection from the tank to existing water main is required. • The site is the highest in elevation of the three sites analyzed and would result in a tower of approximately 130 feet in height. • The existing water tower is located on a relatively small lot with no room to build a new elevated water tower. Therefore, property owned by the Minnetonka School District would need to be acquired directly to the west of the existing tower. Unfortunately, this property is currently used as athletic fields which are at a premium. The school district is not inclined to allow this property for city use. • Shadow and visual impacts would be great for the property just north of the existing tank. Site #3 — North of Minnetonka Middle School Minnetonka School District property directly north of the parking lot was identified as an alternate site to the athletic fields. This site was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: • The new tower would connect to the same distribution system as the existing water tower. Pressure changes to the system are very minimal and would likely not result in any noticeable impact to the current service that residents are provided. • Available fire flow changes will be very localized in comparison to the existing water tower. Specifically, available fire flow will increase dramatically at the Minnetonka Middle School due to the tower being located very near the school. g: \eng \public\ 2011 projects \11 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 6 • The tower location should be looped into the distribution system with one 12 -inch water main connecting to Hazeltine Boulevard (TH 41) to the west and also Melody Hill Road on the north. • The proposed site is slightly lower in elevation as compared to the Melody Hill Tower, but falls within the normal height of water towers. The height to overflow is estimated at 148 feet. • The site is currently used as a storm water retention pond. The pond will require fill material be brought in to make the site level for construction. • This site would require a lot of site improvements to construct a tower. Site #4 — West Side of TH 41 West of Minnetonka Middle School A lot on the west side of TH 41 that is informally for sale has been analyzed for siting the proposed water tower. This site was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: • Pressure changes to the system are very minimal and would likely not result in any noticeable impact to the current service that residents are provided. • Available fire flow changes will be very localized in comparison to the existing water tower. Specifically, available fire flow will increase dramatically at the Minnetonka Middle School due to the tower being located very near the school. • The site currently has the necessary trunk 12 -inch watermain adjacent to the property. No significant trunk water main extension would be necessary. • The site is the lowest elevation of the sites analyzed and would result in a water tower nearing 185 feet in total height. This height requires additional foundation and structural design due to the additional wind loads and overtipping. • This parcel is a little over 6.5 acres. Currently, the property is informally for sale; however, the owner is not willing to sell off a portion of the property. The current asking price is $3,000,000. Site #5 — SW Corner of Minnetonka Middle School Minnetonka School District property in the southwest corner of the site was identified as an alternate site. This site was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: g: \eng \public\ 2011 projects \l 1 -03 - high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 7 • Pressure changes to the system are very minimal and would likely not result in any noticeable impact to the current service that residents are provided. • Available fire flow changes will be very localized in comparison to the existing water tower. • The site currently has the necessary trunk 12 -inch water main (TH 41) approximately 200 feet from the site. No significant trunk water main extension would be necessary. • The proposed site is slightly lower in elevation as compared to the Melody Hill Tower, but falls within the normal height of water towers in Minnesota. The height to overflow is estimated at 160 feet. The height of the tower may be able to be lower depending on final design grades. • The site is currently used as a storm water retention pond. The pond will need to be relocated on the site. • Some utilities will need to be relocated including storm water piping as well as some overhead power lines. • This parcel is available and is the preferred site by the Minnetonka School District. Site #6 — South Central Location of Minnetonka Middle School (Near Track) Minnetonka School District property located on the south side adjacent to the track was identified as another alternate site. This site was evaluated for the following: hydraulic impact to the high service zone, modifications to the existing system, constructability, and lot availability. The analysis resulted in the following: • Pressure changes to the system are very minimal and would likely not result in any noticeable impact to the current service that residents are provided. • Available fire flow changes will be very localized in comparison to the existing water tower. • The site is approximately 1,200 feet away from the nearest trunk water main along TH 41. • The site is very close in elevation to the existing Melody Hill Tank site and will result in a tank with an overflow height of approximately 142 feet. • This parcel is located directly north of several residential properties and would significantly impact visual sight lines to the north of these properties. • The school district indicated this would be an acceptable site for a tower. gAeng \public \_2011 projects \11 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 8 A summary of the sites is included in Table 3 and ranks each of the sites on a scale of 1 to 6 with 1 being the best site. Table 3: Summary of Proposed Tower Sites RECOMMENDATIONS Elevated water storage facilities can be very difficult to site, especially within developed residential areas. Site availability, along with visual impacts to aesthetics can provide challenges beyond the normal sighting requirements such as system hydraulics. Working with a public partner such as the Minnetonka School District to locate potential sites can be a very successful strategy. Therefore, based on the analysis of the six sites, it is recommended the city pursue an agreement with the Minnetonka School District to site the new 750,000 gallon water tower on Site No. 5. The reasons for this recommendation are for the following: • The site is available per preliminary discussions with the Minnetonka School District. • The site rates overall the best. • Of the sites considered, it appears to have some of the least impacts to visual aesthetics due to proximity to residential properties. The shadow of the tank will impact the school building. • While it has some additional site improvement costs, they are relatively small in comparison to the overall cost of the project. gAeng \pub1ic \_2011 projects \I 1 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Site Additional Site No. Acquisition/ Site Elevation Visual Site Site Sum Total Impacts Hydraulics Construction Ownership Required Site No. 1 3 5 4 6 4 22 Site No. 2 6 1 6 1 1 15 Site No. 3 4 3 3 5 6 21 Site No. 4 5 6 2 2 2 17 Site No. 5 1 4 1 3 5 14 Site No. 6 2 2 5 4 3 16 RECOMMENDATIONS Elevated water storage facilities can be very difficult to site, especially within developed residential areas. Site availability, along with visual impacts to aesthetics can provide challenges beyond the normal sighting requirements such as system hydraulics. Working with a public partner such as the Minnetonka School District to locate potential sites can be a very successful strategy. Therefore, based on the analysis of the six sites, it is recommended the city pursue an agreement with the Minnetonka School District to site the new 750,000 gallon water tower on Site No. 5. The reasons for this recommendation are for the following: • The site is available per preliminary discussions with the Minnetonka School District. • The site rates overall the best. • Of the sites considered, it appears to have some of the least impacts to visual aesthetics due to proximity to residential properties. The shadow of the tank will impact the school building. • While it has some additional site improvement costs, they are relatively small in comparison to the overall cost of the project. gAeng \pub1ic \_2011 projects \I 1 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 9 Required Site Improvements for Recommended Site The site will require some improvements to make it usable for a new elevated water storage tank. Improvements required for the site include the following: • Relocation of the storm water retention pond. • Grading of the site to raise the location of the proposed tower to reduce the height of the tower. • Relocation of storm water piping/outlet structure. • Relocation of water service to the school building. • Relocation of approximately 500 feet of overhead power lines. • Install 200 feet of 16 -inch water main to TH 41. • Site improvements including bituminous driveway and fencing around tank. Geotechnical Analysis A soil boring was obtained on the school property to assess the condition of the soils for the support of a 750,000 gallon water tower. This was an exploratory boring for informational purposes only and should not be used for the design of the tower. Additional borings will need to be drilled underneath the actual proposed foundation of the tank during design to determine requirements for the tank foundation. The boring obtained was only used to help estimate the cost of the footing design. Based upon this information, it is likely the tower will have to be built on piles. Visual Impacts Once the final site is selected, virtual reality images (VRIs) will be prepared. The VRIs will depict what the elevated tank will look like from multiple locations. The VRIs are scaled based on the actual proposed dimensions of the tank, along with the distance from locations where digital pictures are taken. These will provide a good visual image to show concerned residents, especially at neighborhood meetings. In addition to VRIs, a shadow study will be conducted to show the impact of the shadows cast by the proposed water tower. The shadow drawing calculates the angle of the sun throughout various days of the year, as well as various times of the day to determine the extent of the shadow cast by the tower. Again, this drawing will serve to show concerned residents the potential impacts of the tower on adjoining properties. Project Cost Estimate The preliminary cost estimate is based upon 2011 construction. In addition to the construction estimate, a contingency of 5 percent (5 %), land acquisition cost estimate, engineering, legal, soils reports investigations and administrative indirect costs are included. g: \eng \public\ 2011 projects \] 1 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 10 Table 4: Opinion of Probable Project Cost Item Cost Site Work $150,000 Foundation Construction $150,000 Tank Construction $1,450,000 Subtotal Construction $1,750,000 Land Purchase $150,000 Contingency (5 %) $87,000 Engineering, Legal, Admin. $125,000 Total Project Cost $2,112,000 Schedule A preliminary schedule for the tank project is shown below. Preliminary soils analysis should be verified by a geotechnical analysis during the design phase of the new tower. In addition, the schedule is based on the soil surcharge taking place over the winter months which should allow for ample time for settlement to occur. • City Council Review • Neighborhood Meetings • School Board approves tank agreement • Authorization for Design • Bidding • Soils Surcharging • Foundation and Tank Construction • Tank Construction Substantial Completion • Remove Melody Hill Tower separately Summary May 23, 2011 June 2011 June 2011 July 2011 September 2011 October 2011 June - September 2012 June 2013 June 2013 — contracted out As identified in the last Comprehensive Water Study and based on this current analysis, additional water storage is needed in the high pressure zone. Based on the high cost of tower maintenance, it is economically feasible to construct one larger water tower to provide additional storage in addition to replacing the capacity of the existing Melody Hill Tower. The school district appears to be an accommodating partner and is working with the city to develop a site that is feasible for a new elevated water storage tank. Staff discussed the project g: \eng \public \_2011 projects \l 1 -03 - high zone tower project \bkgd ww 052311 discuss project need.doc Mr. Todd Gerhardt Discuss Water Storage in High Zone May 23, 2011 Page 11 with the Minnetonka School Board on May 19, 2001. Therefore, it is recommended that the site ( #5) in the southwest corner of the school property be selected. ATTACHMENTS 1. Pressure Zones Map 2. High Pressure Zone Parcel Elevation Evaluation 3. Virtual Image of Proposed Water Storage Facility 4. Minnetonka Middle School West Water Storage Evaluation Locations 5. Capital Improvement Plan — Project # W -042 gAeng \public \_2011 projects \1 1 -03 -high zone tower project \bkgd ww 052311 discuss project need.doc a f C 3 C - Pap Pldp City of it1 Ch Pressure Zones C3 High Pressure Zone ( 12% ) C3 Low Pressure Zone ( 88% ) May 14, 2010 G/ G/S/ Prolects9 /CJ38IWaterPressuraZoneMep High Zone Water Storage Parcel Elevation Evaluation 1� h -- ' Zoning Rural Residential District Single Family Residential District Legend Mixed Low Density Residential District ;.} Planned Unite Devel. /Residential District 8 Water Storage Sites Agriculture Estate District M Areas with elevation = 1040 Adequate Neighborhood Business District Areas with elevation >= 1050 Good Office Institutional District 0 City owned property is Natural EnviromentLake if Recreational Lake G: IENG IJoleenlEngProjectsl Paull HighPressure �� \ .3' �� i � � . :�/ \� z �> *y / \2J ,��� � �2y y \� � x. » «, � !�: � ..� � � .� \ \ \ < -.� §�� . � ,: <} `� � \ -` » $ w { � ` \� / � ` �{ � . . � \� � � .2�% ��y� �� . .� � /) y/ � � t A, ©: � ?. High Zone Water Storage Minnetonka Middle School West Location -4 � f� Site 2 3 -- Site 3 A.y , ., /r' yj Site 5 �r • 7z Site 6 i L or ,wb 1 f. '.L� •� 0 60 120 240 360 480 Feet G: IENGUoleenlEngProjectslPaul HghPressure Capital Improvement Program 2011 thru 2015 Department Water System Improvements City of Chanhassen, MN Contact Paul Oehme Project # W -042 Project Name H igh Zone Elevated Storage Tank . Account #1 700 - 7025 -4751 Account #3 Account #2 Account #4 Type Improvement Useful Life Category Utilities Priority n/a Description I total rroject Lost Dit,7VU'uVU Based on current and projected system demands, the high zone should have additional storage capacity. The 2008 water comprehensive plan recommends a total of- 750,000 gallons for storage. Currently, the high zone only has 200,000 gallons of storage. The-location of the tank has not yet been determined, but a few locations were identified in the 2008 comprehensive plan. A tank siting study should be completed to identify the best location. Justification To meet current and future water demands for the high zone area and to meet recommended fire flow storage'requirements. I Expenditures 2011 2012 2013 2014 2015 Total Construction 1,900,000 1,900,000 Total 1,900,000 1,900,000 Funding Sources 2011 2012 2013 2014 2015 Total Water Utility Fund 1,900,000 1,900,000 Total 1,900,000 1,900,000 Budget Impact/Other 135