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Item 3.7 Adopt Drinking Water Master Plan Supplements Request for City Council Action DEPARTMENT INFORMATION ORIGINATING DEPARTMENT REQUESTOR: MEETING DATE: Utilities Utility Manager Neidermeier May 13, 2024 PRESENTER(s) REVIEWED BY: ITEM #: Consent AE2S Engineer Schaefer City Administrator/Finance Director Flaherty 3.7 – Drinking Water Master Plan Supplements STRATEGIC VISION MEETS : THE CITY OF OTSEGO: Is a strong organization that is committed to leading the community through innovative communication. X Has proactively expanded infrastructure to responsibly provide core services. Is committed to delivery of quality emergency service responsive to community needs and expectations in a cost-effective manner. Is a social community with diverse housing, service options, and employment opportunities. Is a distinctive, connected co mmunity known for its beauty and natural surroundings. AGENDA ITEM DETAILS RECOMMENDATION: City Staff is recommending City Council adopt three Technical Memorandums as supplements to Drinking Water Master Plan. ARE YOU SEEKING APPROVAL OF A CONTRACT? IS A PUBLIC HEARING REQUIRED? No No BACKGROUND/JUSTIFICATION: The Otsego Drinking Water Master Plan was completed in February 2020 and adopted by the City Council. Several changes occurred after the adoption of the Master Plan including restrictions on new Mount Simon wells, rapid residential growth, and additional investigation into the flexibility of blended water sources in the drinking water distribution system. The Central Wellfield Implementation Planning intended to update the phasing of drinking water infrastructure while also examining water sources other than the Mount Simon aquifer. Initial results and recommendations of the additional planning were presented to the City Council in a study session format in January 2024. The attached technical memoranda represent the written documentation of those results for adoption as a supplement to the 2020 Drinking Water Master Plan. SUPPORTING DOCUMENTS ATTACHED: Due to the size of the technical memorandums attached to this Request for City Council Action, they were made available in electronic format only. • Tech Memo 1 - Basis of Planning – Water Demand (May 1, 2024) • Tech Memo 2 - Central Wellfield Planning (May 1, 2024) • Tech Memo 3 - Treatment and Distribution Alternative Development (May 1, 2024) POSSIBLE MOTION PLEASE WORD MOTION AS YOU WOULD LIKE IT TO APPEAR IN THE MINUTES: Motion to adopt Technical Memorandums 1, 2, and 3, dated May 1, 2024, as supplements to the Otsego Drinking Water Master Plan dated February 2020. BUDGET INFORMATION FUNDING: BUDGETED: Fund 601 - Water Utility Yes Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 1 of 10 ~ 1 Technical Memorandum: Basis of Planning – Water Demand Otsego Central Wellfield Implementation Planning To: Kurt Neidermeier Utility Manager City of Otsego From: Ryan Hanson, PE Scott Schaefer, PE AE2S Date: May 1, 2024 Project No: P05409-2022-007 1 SUMMARY The basis of planning technical memorandum (TM) is used to update current and projected water demand for the City of Otsego to determine water supply needs into the future. Historical water usage and land use data were provided by the City to make demand projections out to 2090. Where data was not available or in need of update, industry standard equations and typical values were used in conjunction with City input to provide a reasonable determination of existing and projected water demand. 2 EXISTING SYSTEM Otsego’s water system consists of nine (9) wells (with another well currently under construction), four (4) wellhouses, four (4) elevated water towers, one (1) booster station, and distribution components including reducing valve stations, pipes, valves, and hydrants. The water system consists of a west side and an east side that is currently being joined by the East-West Watermain Connection Project that will be completed in 2024. For this reason, the rest of the analysis will be based on one combined system. A map of the water system is shown in Figure 2.1 Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 2 of 10 ~ Figure 2.1 – Existing Water System Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 3 of 10 ~ 2.1 SUPPLY The City’s nine (9) wells, ranging from 172 to 494 feet deep, draw drinking water from the Tunnel City-Wonewoc and Mt. Simon groundwater aquifers (see Table 2.1). The wells are conveyed to one of four (4) wellhouses where chorine is added for disinfection, fluoride is added for dental health, and polyphosphate is added for holding iron and manganese in solution. The City’s newest well, Well 10, was constructed in 2022 and supplies Wellhouse 4, which is currently in the design phase of being converted to a filtration water treatment plant. Table 2.1 - Water Supply Wells Well No. Unique Well No. Year Installed Capacity (gpm) Well Depth (Feet) Geologic Unit Status Supplied Wellhouse 2 622715 1998 400 172 Tunnel City-Wonewoc Emergency[1] Wellhouse 1 3 657343 2001 600 370 Tunnel City-Wonewoc Active Wellhouse 2 4 696888 2003 1,000 494 Mt. Simon Active Wellhouse 3 5 696889 2004 1,000 490 Mt. Simon Active Wellhouse 3 6 709269 2004 1,000 343 Mt. Simon Active Wellhouse 1 7 721663 2005 1,000 429 Mt. Simon Active Wellhouse 4[2] 8 752116 2007 1,200 437 Mt. Simon Active Wellhouse 2 9 848409 2020 1,200 323 Tunnel City-Wonewoc Active Wellhouse 1 10 867646 2022 700 270 Tunnel City-Wonewoc Active Wellhouse 4[2] 11[3] 880246 2024 500 320 Tunnel City-Wonewoc In Construction Wellhouse 3 [1] Well 2 is used as an emergency well due to high levels of radium. [2] Wellhouse 4 is in the design phase of being converted to a filtration water treatment facility. [3] Well 11 is currently under construction with initial pumping tests producing 500 gallons per minute (gpm) of capacity. 2.2 WATER STORAGE Otsego currently has four (4) elevated tanks that provide storage for their distribution system (See Table 2.2). As the system grows in demand, more facilities will be required to provide the necessary equalization and emergency storage. Table 2.2 – Existing Storage Facilities Storage Facility Capacity of Storage Facility (Million Gallons) Overflow Elevation (ft) Water Tower #1 0.40 1055 Water Tower #2 1.00 1120 Water Tower #3 1.00 1120 Water Tower #4 1.50 1120 Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 4 of 10 ~ 3 WATER USE This section updates water use history with current information and provides new water use projections based on new utility data. 3.1 HISTORICAL WATER USE Historical water use was obtained from the City’s last 5 years of Water Conservations Reports to Minnesota Department of Natural Resources (DNR) and is presented in Table 3.1. Some key water demand factors to note: Average Daily Demand: The average daily demand (total annual demand divided by 365) has almost doubled since 2019, with a 5-year average of 2.0 MGD. Maximum Daily Demand: Maximum day demand generally occurs during a summer month when precipitation is at its lowest amount and irrigation is at its highest amount. Maximum daily demand has increased by over three million gallons since 2019, with a 5-year average of 5.6 MGD. This increase is in part due to the recent droughts that the state has experienced. Peaking Factor: The water demand peaking factor is the ratio of the average maximum day to the average day. The DNR has set a goal of reducing the peaking factor to less than 2.6. Otsego had an average peaking factor of 2.8 for 2019-2023. Residential Per Capita Water Demand: The DNR has set a goal of reducing the residential per capita water demand to less than 75 gallons per capita per day (gpcd). The City’s 2019-2023 average was 102 gpcd. Unaccounted (Non-revenue) Loss: Unaccounted for water use is the volume of water withdrawn from all source water minus the volume of water delivered. The value represents water “lost” by miscalculated water use due to inaccurate meters, water lost through leaks or water that is used but unmetered or otherwise undocumented. The DNR has set a goal of reducing unaccounted for water to less than 10%. Otsego achieves this goal by having less than 2% unaccounted water. Table 3.1 – Historical Water Use (2019 – 2023) Year Population Served Residential Water Usage (MG) Per Capita Demand (GPCD) Non- Residential Water Usage (MG) Total Annual Pumped (MG) Avg. Daily Demand (MGD) Max. Daily Demand (MGD) Peaking Factor 2019 13,861 409.8 81.0 74.7 491.1 1.4 3.6 2.6 2020 15,122 563.0 102.0 89.5 655.8 1.8 5.2 2.9 2021 16,888 702.7 114.0 92.5 797.2 2.2 6.2 2.8 2022 18,402 685.1 102.0 91.9 780.6 2.1 6.3 2.9 2023 19,467 788.7 111.0 110.6 904.6 2.5 6.7 2.7 Average 629.9 102.0 91.8 725.8 2.0 5.6 2.8 Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 5 of 10 ~ 3.2 LAND USE AND SERVICE CONNECTION PROJECTIONS Water demand projections are dependent on the future land use and resulting future residential and non-residential (i.e. commercial, industrial, office, public) utility connections. The 2022 Comprehensive Plan future land use map (Figure 3.1), completed by the City Planner, was used as the basis for future land use acreages. Projected service connections were estimated based on updated densities and acreage for future land use types and is presented in Table 3.2 and Table 3.3. Using projected residential household densities multiplied by the land area, a total number of households within each land use type can be calculated. Using this method, it is anticipated that the City will have a total of 26,300 residential households on City water by buildout (see Table 3.2). For this study, we are assuming buildout will be reached by 2090. There is a portion of the City’s population that has private wells and are not served by the City’s water supply. It was assumed that “Rural Residential” land use type would remain on private wells while approximately 70% of “LD Residential – Large Lot” would connect to City water. It is also anticipated that most of the “Rural” land use type would eventually transition to low to medium density residential area and be served by the City utilities. Using the same method, it is anticipated that there will be 2,140 non-residential utility connections by 2090 (see Table 3.3). Non-residential includes commercial, office, industrial, and public land use sectors, as well as specified irrigation connections. Table 3.2 – Projected Residential Service Connections Land Use Type Projected Acres Density (connections/acre) Projected Connections[1] LD Residential 5,842 2.5 11,700 LD Residential (Large Lot) 2,349 0.7 900[2] LD/MD Res 1,551 4 5,000 MD/HD Res 543 8 3,500 Rural 1,866 2.5[3] 3,700 Rural Residential 1,424 0 0 Mixed Use (40% Residential) 228 21 1,500 Total Residential Utility Connections 26,300 [1] Projected residential connections were reduced by 20% to account for filler space (i.e., ROW, parks, ponds, etc.). [2] Anticipated that approximately 70% of LD Residential – Large Lot connect to utility. [3] Expected to transition from Rural to Low to Medium Density residential housing by 2085. Table 3.3 – Projected Non-Residential Service Connections Land Use Type Projected Acres Density (connections/acre) Projected Connections Mixed Use (60% Non-Residential) 228 2 300 Commercial 490 2 100 Industrial 1,575 0.25 200 Light Industrial 693 0.1 40 Office 554 0.05 1,100 Public/Quasi Public 896 2 400 Total Commercial/Industrial/Public Utility Connections 2,140 Basis of Planning – Water Demand City of Otsego, MN P05409-2022-007 ~ 6 of 7 ~ Figure 3.1 – Future Land Use Map (Source: 2022 Comprehensive Plan) Basis of Design – Water Demand City of Otsego, MN P05409-2022-007 ~ 7 of 10 ~ With buildout expected to be accomplished by 2090, residential and non-residential utility connections between 2023 and 2090 can be interpolated into the future (see Table 3.4). The new residential utility connections have seen a big boom over the last 5 years, with a 5-year average of 375 new residential connections per year. It is assumed that the current increased growth rate will continue with 375 new households connected to the utility per year through 2030 followed by a consistent growth rate of 300 households connected per year through 2090 to the projected residential buildout of 26,300 households on City water. Using the City’s population conversion factor of 2.9 people per household, the population served for the City of Otsego is estimated to be 76,300 people by 2090. For simplicity, commercial utility connections between 2023 and 2090 were interpolated assuming a steady rate of growth. Table 3.4 – Projected Service Connections Year Households Served Residential Connections Added Per Year People per Household[1] Population Served Non- Residential Connections Non-Residential Connections Added Per Year 2019 4,818 282 2.88 13,861 178 8 2020 5,266 448 2.87 15,122 183 5 2021 5,815 549 2.90 16,888 188 5 2022 6,177 362 2.98 18,402 191 3 2023 6,410 233 3.04 19,467 203 12 2025 7,200 375 2.90 20,900 260 23 2030 8,700 300 2.90 25,300 410 29 2040 11,700 300 2.90 34,000 690 29 2050 14,700 300 2.90 42,700 980 29 2060 17,700 300 2.90 51,400 1,270 29 2070 20,700 300 2.90 60,100 1,560 29 2080 23,700 300 2.90 68,800 1,850 29 2090 26,300 260 2.90 76,300 2,140 29 [1] Average household size in Otsego is 2.9 people household, which is expected to continue. 3.3 FUTURE WATER DEMAND Future water demands are based on historical water demands, population, utility connections, and land use projections. A detailed list of water demand projections to 2090 is shown in Table 3.5 and a discussion of key parameters are provided in the sections that follow. Basis of Design – Water Demand City of Otsego, MN P05409-2022-007 ~ 8 of 10 ~ Table 3.5 - Future Water Demand Year Residential Non-Residential Water Demands Population Served Number of Households Served Per Capita Usage (GPCD) No. of Connections Projected Daily Use (gal/con.) Avg. Daily Demand (MGD) Peaking Factor Max. Day Demand (MGD) 2019 13,861 4,818 81 178 1,150 1.3 2.7 3.5 2020 15,122 5,266 102 183 1,340 1.8 2.9 5.2 2021 16,888 5,815 114 188 1,348 2.2 2.8 6.2 2022 18,402 6,177 102 191 1,318 2.1 3.0 6.3 2023 19,467 6,410 111 203 1,330 2.5 2.7 6.7 2025 20,900 7,200 110 260 1,400 2.7 3.0 8.0 2030 25,300 8,700 95 405 1,400 3.0 3.0 8.9 2040 34,000 11,700 75 690 1,400 3.5 2.6 9.1 2050 42,700 14,700 75 980 1,400 4.6 2.6 11.9 2060 51,400 17,700 75 1,270 1,400 5.6 2.6 14.7 2070 60,100 20,700 75 1,560 1,400 6.7 2.6 17.4 2080 68,800 23,700 75 1,850 1,400 7.8 2.6 20.2 2090 76,300 26,300 75 2,140 1,400 8.7 2.6 22.6 Residential Per Capita Water Demand: The projected average day residential demand is equal to the residential gallons per capita per day (GPCD) multiplied by the projected population. The current 5-year average per capita demand is approximately 102 GPCD. The DNR has set a goal of reducing the residential per capita water demand to less than 75 GPCD by 2040. A summary of the projected growth versus water demand is provided in Figure 3.2 to better understand the relationship between future population growth and water demand. The residential connections are presented as residential equivalents (REC’s), which is how the City tracks customers. To allow for flexibility of meeting the DNR’s per capita demand goal of 75 GPCD, the average and maximum day demands are presented as a range from 75 GPCD to 100 GPCD. The City has set a goal of attaining the recommended 75 GPCD. Therefore, the per capita demand used for calculating future water demand is reduced to 75 GPCD by 2040 and for planning purposes remains at 75 GPCD beyond 2040. If the reduction in per capita demand is not met by 2040, the resulting future average day demand will be higher than projected. It should be noted that reducing water demand is inherently challenging as it requires people to change their habits. This tech memo will not directly address approaches to reducing water demands, and a separate effort to begin water demand reduction efforts is recommended. It is also assumed based upon much of the demand being driven by turf irrigation that reducing overall demand will lower the demand peaking factor. Basis of Design – Water Demand City of Otsego, MN P05409-2022-007 ~ 9 of 10 ~ Figure 3.2 – Projected Population Growth vs. Water Demand Future Non-residential Water Demand: Non-residential water demand consists of commercial, office, industrial, and public land use sectors, as well as specified irrigation connections. Based on 2019-2023 data, the non-residential demand was 1,300 gallons per connection per day. It is expected that Otsego’s future non-residential users will be in similar industries using similar amounts of water. To determine future non-residential water demand, projected non-residential connections were multiplied by 1,400 gallons per connection per day to leave some room for unaccounted for irrigation connections. Average Daily Demand: The average daily demand is determined by summing the residential and non-residential demands. This results in a future average day demand of 8.7 MGD at buildout. This is 3.5 times higher than 2023 average day demands. Max Daily Demand: Peak, or maximum day, demand is determined by multiplying the average demand by a peaking factor. The DNR has set a goal of reducing the peaking factor to less than 2.6. The current peaking factor of 3.0 was used through 2040 and then the DNR goal of 2.6 was used for 2040 and beyond. This results in a future maximum day demand of 22.6 MGD at buildout. 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000 55,000 60,000 65,000 70,000 75,000 80,000 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000 55,000 60,000 65,000 70,000 75,000 80,000 Residential RECsPopulation ServedPopulation Served Residential RECs AVG. 375 RES. RECs/YR PROJECTED 375 RES. RECs/YR (to 2030) PROJECTED 300 RES. RECs/YR (to 2090) 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070 2075 2080 2085 2090Demand (MGD)Year 100 GPCD 90 GPCD 75 GPCD 100 GPCD 90 GPCD 75 GPCD Basis of Design – Water Demand City of Otsego, MN P05409-2022-007 ~ 10 of 10 ~ Unaccounted (Non-revenue) Loss: Unaccounted for water use is the volume is not accounted for in these projections because the City has less than 2% in unaccounted for water. If water loss and unaccounted for water starts to noticeably increase, demand projections should be increased by that percentage for more accurate planning. 4 FUTURE WATER SUPPLY The adequacy of a city’s well supply is evaluated based on its firm capacity, which assumes the largest well is out of service. To meet the needs of the system, firm capacity should equal or exceed the maximum day demand in accordance with AWWA (American Water Works Association) recommendations. The firm capacity analysis of Otsego’s wells is summarized below in Table 4.1. Due to the age of some of their wells, it is unrealistic to plan a system based upon their theoretical pumping capacity. Recent analysis of the system provided actual capacities of wells when they are pumping together, which is supplied below. The resulting total actual capacity of the City’s wells is equal to 96% of the theoretical capacity. The actual capacity value should be used for further analysis. Table 4.1 – Firm Capacity for Combined System Wellhouse Well No. Theoretical Capacity Actual Capacity GPM MGD GPM MGD Wellhouse 1 Well 6 1,200 1.7 2,100 3.0 Well 9 1,200 1.7 Wellhouse 2 Well 3 600 0.9 1,400 2.0 Well 8 1,200 1.7 Wellhouse 3 Well 4 1,000 1.4 2,200 3.2 Well 5 1,000 1.4 Well 11[1] 500 0.7 Wellhouse 4 Well 7 1,000 1.4 1,700 2.4 Well 10 700 1.0 Total Capacity 8,400 12.1 7,400 10.7 Total Firm Capacity 7,200 10.4 6,200 8.9 NOTES: Combined System capacity includes expected wells that will be supplying the system at the time of connecting the East and West systems. [1] Well 11 is under development and is currently anticipated to add a theoretical capacity of 500 gpm to Wellhouse 3. The total actual capacity of Otsego’s active wells is 8,400 gpm (12.1 MGD) with the anticipated Well 11 capacity included. As a result, the firm capacity of the system, which assumes the largest well out of service, would be 6,200 (8.9 MGD). With a future maximum day demand of 15,700 gpm (22.6 MGD), the City of Otsego will need to add a minimum of 9,500 gpm (13.7 MGD) in water supply capacity to reliably deliver an adequate firm capacity to meet peak demand. Future memorandums will lay out implementation planning to achieve this additional capacity. Central Wellfield Planning City of Otsego, MN P05409-2022-007 ~ 1 of 3 ~ Technical Memorandum: Central Wellfield Planning Otsego Central Wellfield Implementation Planning To: Kurt Neidermeier Utility Manager City of Otsego From: Ryan Hanson, PE Nancy Zeigler, PE Scott Schaefer, PE AE2S Date: May 1, 2024 Project No: P05409-2022-007 1 SUMMARY This central wellfield planning technical memorandum (TM) is used to establish projected well capacity for the City of Otsego, focused on water availability in the Central Wellfield area. As part of this analysis, LRE Water (LRE) was contracted to complete a desktop evaluation of available groundwater resources for future planning and expansion of the City’s well fields. A summary of LRE’s findings can be found in Appendix of this memorandum. 2 WATER SUPPLY NEEDS As stated in the previous memorandum, the City of Otsego’s existing water supply system consists of nine (9) wells (with an additional well currently under construction), four (4) wellhouses (Wellhouse 4 is finishing up design to be converted to a water treatment facility), and one (1) booster station. With a future maximum day demand of 22.6 MGD (15,700 gpm) established in the Technical Memorandum – Basis of Planning, the City of Otsego will need to add a minimum of 9,500 gpm (13.7 MGD) in water supply capacity to reliably deliver an adequate firm capacity to meet peak demand. Central Wellfield Planning City of Otsego, MN P05409-2022-007 ~ 2 of 3 ~ 3 CENTRAL WELLFIELD ANALYSIS The previous 2020 Drinking Water Master Plan evaluated several systemwide treatment scenarios to establish a path for future water supply and treatment for the City. The recommended plan included a larger collector water treatment plant (WTP) in a centralized area of the system. To supply this WTP, it was planned that a Central Wellfield (CWF) would need to be established with an expected capacity of 8,000 gpm. It should be noted that the CWF’s capacity was based off previous water master planning and did not include updated projected water demands in the Technical Memorandum – Basis of Planning and pump tests completed on Well 10 and Well 11. Previous studies had anticipated that the water supply for the Central WTP would be accomplished by drilling additional Mt. Simon aquifer wells, however new legislation has restricted the City of Otsego from applying for additional water appropriations for use from the Mt. Simon-Hinkley aquifer unless no other water sources (groundwater or surface water) are available. As a result, the City of Otsego is looking into adding other aquifers to provide their needed future water supply capacity. To evaluate the available groundwater resources for future planning and expansion of the City’s CWF, LRE Water (LRE) was contracted to complete a desktop evaluation. Since municipal wells have not yet been drilled in the CWF, LRE focused on available geotechnical information to assess groundwater availability. Their study expanded on previous studies completed for the City and used the Metro model 3 model (MM3) to provide an overview of the groundwater resources in the CWF and Northwest Wellfield (NWWF) area. A summary of their findings can be found in Appendix of this technical memorandum. In summary, their findings concluded that long-term yields of 8,000 gpm could not be achieved from the NWWF and CWF alone. It was found that significant well interference occurs when developing large numbers of wells in the CWF. As the number of wells increases, the yield per well decreases but the total well-field yield increases at a slower rate. Predicted well yields were contingent on the location, geology and number of nearby wells, but the modeling suggests that well yields are expected to be around 250 - 325 gpm per well for constant 24-hour pumping. This would suggest that roughly 32 wells would be required to meet the 8,000 gpm demand of the CWF. In reality, wells are not pumped on a constant 24-hour pumping schedule. Typical operations would alternate well pumps to meet demands. LRE predicts that higher rates would likely apply to these wells if shorter duration of pumping was used. However, on peak demand days, which usually occur during mid-day of the warm summer months with high irrigation demands, when all the wells would be required, interference between wells could result in diminished capacities. For these reasons, pursuing a CWF capable of supplying 8,000 gpm is not recommended, especially since updated information from the Technical Memorandum – Basis of Planning would actually required the CWF to produce a minimum of 9,500 gpm (13.7 MGD). It is recommended that the City space out future TCW wells as much as possible and potentially split up the CWF into a north and south area to minimize interference. Central Wellfield Planning City of Otsego, MN P05409-2022-007 ~ 3 of 3 ~ 4 FUTURE WELLS As discussed above, the City of Otsego will need to add a minimum of 9,500 gpm (13.7 MGD) in water supply capacity to reliably deliver a firm capacity to meet peak demand. Without the ability to add additional Mount Simon wells and lack of available capacity from the CWF, the City will be required to create multiple TCW wellfields that are spaced out to minimize interference between the wells. With proper spacing, future wells could be able to produce 500 gpm per well under normal conditions. This strategy and estimated pumping capacity will be used in future memorandums for treatment scenarios. Future geological studies and test wells will be required in these areas to better define the capacity of TCW wells. ROCKY MOUNTAIN | MIDWEST | SOUTHWEST | TEXAS Minneapolis – St. Paul | Office: 612-805-0919 | LREWATER.COM December 6, 2023 Nancy Zeigler, PE Advanced Engineering and Environmental Services, Inc. (AE2S) 6901 East Fish Lake Road, Suite 184 Water Tower Place Business Center Maple Grove, MN 55369-5457 Kurt Neidermeier Utility Manager City of Otsego 13400 90th Street NE Otsego, MN 55330 RE: Supplemental Desktop Hydrogeologic Assessment – Potential Central Wellfield (CWF) Area City of Otsego, MN Dear Ms. Zeigler and Mr. Neidermeier, This correspondence provides Advanced Engineering and Environmental Services, Inc. (AE2S) and the City of Otsego (City) with the results of LRE Water’s desktop assessment of the City’s Potential Central Wellfield (CWF) Area (CWF Assessment). INTRODUCTION OBJECTIVES The purpose of the CWF Assessment, as outlined in LRE proposal dated January 19, 2023, is to expand upon the results of LRE’s April 8, 2022, Desktop Hydrogeologic Assessment – Future Expansion of the Northwest Wellfield and Development of a Central Wellfield report. The primary objective of the CWF Assessment is to provide an estimate of additional TCW aquifer wells and wellfield yields based on the City’s 2050 projected water demands. Nancy Zeigler December 6, 2023 Page 2 of 9 In addition, LRE completed a high-level evaluation of sand and gravel aquifers for potential future wellfield development based on the Minnesota Geological Survey (MGS) and Minnesota Department of Natural Resources’ (DNR) Wright County Geologic Atlas, (Atlas) Part A (Tipping, 2013) and Part B (Barry, 2018). A summary of groundwater quality, and recommendations where the sand and gravel aquifers may have the potential to be developed are also provided. PREVIOUS WORK AND CWF ASSESSMENT TASKS LRE’s April 8, 2022, report provided an overview of the groundwater resources in the City’s Northwest Wellfield (NWWF) Area and the CWF Area shown on Figure 1. The study was completed to identify the groundwater resources other than the Mt. Simon Aquifer. The study determined that the Tunnel City-Wonewoc (TCW) bedrock aquifer is the most reliable source. The Quaternary-age buried artesian sand and gravel aquifers (QBBA) were also identified as possible sources. Following this assessment, the City constructed a new TCW aquifer well (Well No. 10) in the NWWF adjacent to Well No. 7, which pumps from the deeper Mt. Simon aquifer. The following activities were completed to meet the objectives of this CWF Assessment: • Met with the City and AE2S to discuss the objectives and refine the scope of work; • Obtained and reviewed relevant information including the Atlas Part A and Part B; • Provided thickness and distribution maps of sand and gravel aquifers within City’s limits shown on Figure 1, and identified areas in the City where the QBBA and the Mississippi River (River) alluvial aquifer has the potential to be developed; • Summarized the water quality of the QBAA and TCW aquifers based on data provided by the City, Minnesota Department of Health (MDH), the Part B of the Atlas; and, • Used the Metro Model 3 model (MM3) to estimate the maximum yield from the TCW aquifer in the CWF area without exceeding the DNR’ 50 % safe-yield threshold limits. Nancy Zeigler December 6, 2023 Page 3 of 9 PROJECTED WATER DEMAND The City is interested in developing the TCW aquifer in CWF Area to meet a future demand of 8,000 gallons per minute (gpm) or approximately 11.5 million gallons per year. The 8,000 gpm is in addition to what is currently provided by the City’s existing wells (Wells No. 2 through 10). The target rate for each TCW aquifer well is assumed to pump 500 gpm based on the current capacities of the City’s existing wells. In addition to the CWF Area, additional TCW aquifer wells in the NWWF may be required, or future development of the QBAAs and/or River alluvial aquifer. RESULTS HYDROGEOLOGY This section provides an overview of the hydrogeology. For more details refer to LRE’s April 8, 2022 report, Tipping (2013), and Barry (2018). The primary geologic units within the City limits consist of Quaternary-age unconsolidated sands, gravels and till, underlain by Cambrian-age and Proterozoic-age bedrock. Surficial Aquifer and QBAAs The surficial geology from Plate 3 in Tipping (2013) is shown on Figure 2 and the bedrock geology from Plate 2 is on Figure 3. The surficial deposits consist of River alluvium, lacustrine, and glacial till and outwash deposits. The glacial till units separate the buried sand and gravel deposits that makeup the QBAAs. Geologic cross section transects B-B’ and C-C’ from Plate 8 in Barry (2018), and B-B’ from Plate 4 in Tipping (2013) are shown on Figures 2 and 3. These illustrate the hydrogeology of the unconsolidated sediments and major aquifers from west to east across the northern and southern portions of the City. The cross sections are shown on Figures 4, 5 and 6. The uppermost sands and gravels are found along River and makeup the surficial alluvial and shallow aquifers. These are designated on the cross sections as units ha, wmt, and nts. The most significant QBBAs within the City limits include units designated as cg, cgi, ms, prs and psu. The approximate thickness and extent of the QBBAs from DNR’s sand distribution models are shown on Figures 7 through 11. Nancy Zeigler December 6, 2023 Page 4 of 9 Bedrock Aquifers The bedrock formations from youngest to oldest include the Cambrian-age TCW , Eau Claire Formation, Mt. Simon Sandstone, and the Proterozoic-age Hinckley Sandstone, Fond du Lac, and Solar Church Formations. There are several bedrock faults that cross through the City that may have localized effects on the TCW aquifer and TCW well yields. The bedrock aquifers that supply water to the City are the TCW and Mt. Simon, which are separated by the Eau Claire Formation, which is classified as an aquitard. City Wells No. 2 and 3 pump from the TCW, and Wells No. 4 through 8 from the Mt. Simon. No further development of the Mt. Simon is permitted by the DNR per Minnesota Statute 103G.271, Subdivision 4a. As a result, the City is currently required to evaluate other sources, which include the TCW, QBBA, and River alluvial aquifers. GROUNDWATER QUALITY Standards The Environmental Protection Agency (EPA) has established the National Primary Drinking Water Regulations (NPDWR) that provide maximum contaminant level (MCL) and are legally enforceable primary standards that apply to public water systems. The EPA has also established National Secondary Drinking Water Regulations (NSDWRs) that set non-mandatory water quality standards. These standards establish guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. The EPA does not enforce these secondary maximum contaminant levels (SMCLs), which include iron, manganese and total dissolved solids (TDS). The Minnesota Department of Health (MDH), however, has established a health- based value (HBV) of 100 micrograms per liter (ug/L) (or 0.1 milligrams per liter (mg/L) for manganese. The following table summarizes the current MCLs for iron, manganese, combined radium (Radium 226 and 228), gross alpha, arsenic and TDS. Parameter MCL (SMCL) HBV Iron (0.3 mg/L) - Manganese (0.05 mg/L) 0.1 mg/L Combined Radium 5.00 pCi/L - Gross Alpha 15.00 pCi/L - Arsenic 0.01 mg/L - TDS (500 mg/L) - mg/L = milligrams per liter; pCi/L = picocuries per liter; - Not applicable, HBV not applied. Nancy Zeigler December 6, 2023 Page 5 of 9 Raw Water Data and Sources Raw water quality data was obtained from the City for the City’s wells, and from the MDH for the City, City of Rogers and Joint Powers Water Board’s (JPWB) (i.e., cities of Albertville, St. Michael and Hanover) public supply wells. Manganese and arsenic concentrations were obtained from the Atlas Part B (Barry, 2018) and are shown on Figure 12. The results are provided in Attachment 1 and summarized below for the QBAA and TCW aquifers. QBBA Quality Water quality representative of the QBBA aquifer from the JPWB’s wells is as follows: d Joint Powers Board Well No. (depth in ft). 1 2 3 5 (365) (281) (221) (370) Alkalinity (mg/L) - - 370 370 Hardness (Ca as CaCo3) (mg/L) - - - - Combined Radium (pCi/L) 2.4 2.4 2.3 2.4 - Not available Manganese and arsenic concentrations from select wells in the QBBAs are shown on Figure 12 and are as follows: Manganese (mg/L) Min 0.18 Max 0.81 Avg 0.53 Arsenic (mg/L) Min 0.003 Max 0.022 Avg 0.008 Values on bold exceed the MCL, SMCL or HBV. TCW Aquifer Quality Water quality data representative of the TCW aquifer from the City and City of Rogers’ public wells are summarized below. Nancy Zeigler December 6, 2023 Page 6 of 9 Otsego Well No. (depth in ft). Rogers Well No. (depth in ft) 1 2 3 3 4 6 7 (201) (172) (370) (370) (367) (374) (362) Alkalinity (mg/L) - - 230* 340 350 400 410 Hardness (Ca as CaCo3) (mg/L) - - 225* 240 220 280 220 Iron (mg/L) - - 0.72* - - - - Manganese (mg/L) - - 0.15* - - - - Arsenic (mg/l) - - - - - - - Combined Radium (pCi/L) Min 4.2 6 2 - - - - Max 7.8 7.9 3 - - - - Avg 6.3 7 2.1 - - - - Not available; * = provided by City; Values in bold exceed the MCL, SMCL or HBV. Water Quality Summary Based on the limited data, wells in the QBBAs generally have lower combined radium concentrations, but are higher in manganese. In general, the QBAA is also expected to have higher iron and arsenic concentrations relative to the TCW (Barry, 2018). Alkalinity and hardness appear to be similar in the aquifers. Data for TDSs is not avaibale, but concentrations are anticipated to be higher in the QBAAs compared to the TCW (Albin and Bruemmer, 1983). FUTURE TCW WELLFIELD YIELD EVALUATION To meet the water demands of the projected 2050 population growth, the City needs to increase their peak water production by approximately 8,000 gpm. The City’s focus to meet this demand is development of the CWF, along with adding several additional wells to the existing NWWF. The 8,000 gpm is in addition to what the City is currently pumping from its existing wells shown on Figure 1. To aid the City in their groundwater resource planning for future population-based water demands, LRE utilized the Metropolitan Council’s Metro Model 3 (“MM3”) numerical groundwater flow model (MODFLOW code) to simulate the maximum possible yields for a number scenarios and considering the DNR’s regulatory safe-yield thresholds. Pumping from a maximum of 20 additional TCW wells was simulated in the initial stead-state and transient model runs (Figure 13). A summary of the results are provided in this section and details are provided in LRE’s technical memorandum in Attachment 2. LRE’s evaluation includes: Nancy Zeigler December 6, 2023 Page 7 of 9 • a limited review of the MM3 including a preliminary parameter analysis, and MM3 model parameter updates based on this review and pumping test results; • development of aquifer drawdown triggers; • MODFLOW -based steady-state and transient well yield projections; • a basic sensitivity analysis; and, • wellfield interference evaluation. LRE analysis involved estimating future wellfield yields using both a steady-state and a transient modeling approach. The following points summarize LRE’s findings. 1. Steady-state modeling indicated the long-term yields of 8,000 gpm could not be achieved from the NWWF and CWF alone. 2. Significant well interference occurs when developing large numbers of wells in the CWF. As the number of wells increases, the yield per well decreases but the total well-field yield increases at a slower rate. The estimated maximum yields for the steady-state scenario are as follows: Scenario Total Yield (gpm) Yield Per Well (gpm) 8 Total Wells 5 CWF Wells 2,605 326 12 Total Wells 9 CWF Wells 3,596 300 20 Total Wells 17 CWF Wells 4,840 242 3. Well yields are contingent on the location, geology and number of nearby wells, but well yields are expected to be around 250 to 300 gpm per well. This is assuming a constant 24-hour pumping schedule. Higher rates would likely apply if shorter pumping durations are used. 4. Transient model results indicated that a peak yield of 8,000 gpm could not be achieved. This indicates that the aquifer properties, in combination with the effects of well interference, limit the ability of the wells to extract the desired 8,000 gpm within the extent of the two wellfields. The estimated maximum yields for the transient scenario are as follows: Nancy Zeigler December 6, 2023 Page 8 of 9 Scenario Minimum Total Yield (gpm) Maximum Total Yield (gpm) 12 Wells with 9 in CWF 2,759 4,197 20 Wells with 17 in CWF 3,923 5,738 5. These results were generated using the MM3, which is a reasonable representation of the groundwater system. As wells are installed, and more aquifer and pumping test data is available for the aquifer, these estimates could be revisited to improve the reliability of our predictions. RECOMMENDATIONS LRE recommends the following based on the results of this CWF Assessment. • Discuss projected demand and future wellfield development plans with the DNR; • Construct a large diameter test well or a MDH approved public supply well and an observation well(s), and complete an aquifer pumping test if the City decides to develop a CWF. The test should be run for a minimum of 72-hours to observe any aquifer boundary conditions. • Analyze the aquifer pumping test data from the CWF to determine site-specific aquifer parameters, refine the groundwater model and rerun the CWF scenarios; • Complete a more detailed desktop assessment of the potential sand and gravel target areas shown on Figure 14, and develop an investigation workplan if the City decides to pursuit these aquifers. The priority target areas appear to be adjacent to the River along the north and northeast corner of the City. Other locations are the sands and gravels in the NWWF and areas near the CWF. Sample a select number of private wells in these area to characterize the water quality before proceeding with any field investigation tasks; and, • Evaluate other areas of the City for other TCW wellfield locations. Nancy Zeigler December 6, 2023 Page 9 of 9 We look forward to discussing the results with you and if you have any questions, please contact me at dave.hume@lrewater.com or (612) 805-0919. Sincerely, LRE W ATER Dave Hume, PG VP Midwest Operations Date: 12/5/23 DSH REFERENCES Albin, D.R. and Bruemmer, L.B., 1983. Minnesota Ground-Water Quality. U/S. Geological Survey Open-File Report 87-0733. Barry, J.D., 2018, Geologic Atlas of Wright County, Minnesota (Part B): Minnesota Department of Natural Resources, County Atlas Series C-30, Report and Plates 7–9, (http://www.dnr.state.mn.us/waters/programs/gw_section/mapping/platesum/wrigcga.ht ml). Tipping, Robert G. 2013. C-30 Geologic Atlas of Wright County, Minnesota [Part A]. Retrieved from the University of Minnesota Digital Conservancy, http://hdl.handle.net/11299/159422. !? !?!? !? !? !?!? !? !? !? Northwest Wellfield Expansion Area Potential Central Wellfield Area OTSEGO 7 721663 OTSEGO 5 696889 OTSEGO 4 696888 OTSEGO 1 554501 OTSEGO 3 657343 OTSEGO 2 622715 OTSEGO 6 709269 OTSEGO 8 752116 OTSEGO 10 867646 Wells 7 and 10 are approximatly 65 feet apart OTSEGO 9 848409 GG18 GG39 GG119 GG42 GG37 GG12 GG13 GG36 GG19 GG1 GG39 GG13 GG42 GG42 GG12 GG36GG19 ¨§¦94 £¤10£¤10 £¤169 ST101 ST201 ST101 70th St NE 65th St NE 70th St N E Mississippi R.C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02e.mxd, 6/30/2023, 3:09:19 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community 5013AEN06_02e.MXD 6/30/2023 1 CITY WELL LOCATIONS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: 0 6,000 Feet ± Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City of Otsego Boundary 1-Mile Buffer !? !?!? !? !? !?!? !? !? !?Otsego OTSEGO 8 OTSEGO 3 OTSEGO 1 OTSEGO 6 OTSEGO 9 OTSEGO 2 OTSEGO 5OTSEGO 4 OTSEGO 7 OTSEGO 10 GG18 GG39 GG119 GG42 GG37 GG36 GG19 GG22 GG42 GG42 GG39 GG13 GG12 GG36 ¨§¦94 £¤169£¤10 ST101 County Road 37 NE 70th St NE Labeaux Ave 70th St NE B - B' C - C' ht wmt vt ng vt tct tct cg nls ht cg cg ct cg htw htw cg 28 0 260300 280300 280300280280 280280280300 2803 0 0 260300260280300 2 8 0300280300 28030028030030 0 300 300 300280 300 300 300 2803002802803 0 0 300 280 300300280300 2803 0 0300 2802 8 0260300 300280300 C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02c.mxd, 6/23/2023, 9:06:42 AM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas Part B. Minnesota Geological Survey (MGS) Wright Co. Geologic Atlas Part A. 5013AEN06_02c.MXD 6/23/2023 2 SURFICIAL GEOLOGY AND CROSS SECTION LOCATIONS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: Alluvial scarp Middle Terrace scarp Flow direction, former streams Buried channel SURFICIAL GEOLOGY Holocene alluvium Holocene peat deposits wmt nls ng nlc htw ht vt vtw tco tct cg ct Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 Part A Plate 4 Cross Section Part B Plate 8 Cross Section 0 6,000 Feet ±!?Otsego Well City of Otsego Boundary B - B' !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !(!( !(!( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( 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!( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!( !( !( !( !(!( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !(!( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !(!( !( !( !( !(!( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !(!(!(!(!(!(!( !( !( !( !(!( !( !( !(!(!(!(!(!(!( !(!(!(!(!(!(!(!(!( !(!(!( !(!(!( !( !(!(!( !(!( !( !(!(!(!( !(!(!(!( !( !( !(!(!( !(!(!(!( !(!( !( !( !( !(!(!(!(!(!(!(!(!(!( !(!(!( !( !(!(!(!(!(!( !(!(!(!(!( !( !(!(!( !(!(!(!(!(!(!( !( !(!(!(!( !(!(!( !(!(!( !(!( !(!( !( !(!(!(!( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !(!(!(!(!(!(!(!(!(!(!(!(!( !(!(!(!(!(!(!(!(!(!( !(!(!(!(!(!(!( !(!(!( !(!( !(!(!(!( !( !(!( !(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( !(!(!(!(!(!(!(!(!(!(!( !( !(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( !( !(!(!(!(!( !(!(!(!(!( !(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!( !(!(!(!( !(!( !( !(!(!(!( !(!( !(!(!( !( !(!( !( !( !( !(!( !( !(!( !(!(!(!( !( !(!(!(!(!( !(!(!( !( !(!( !(!( !(!( !( !(!( !(!( !( !( !( !( !(!( !(!( !( !( !(!(!(!(!(!(!(!(!(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !( !( !(!( !( !(!(!( !(!( !( !( !(!( !(!( !(!( !(!( !( !( !( !( !( !( !( !( !(!( !(!( !(!( !( !( !(!( !( !( !( !(!( !( !( !(!( !( !(!( !(!( !( !( !( !( !( !( !(!(!(!(!(!( !(!( !(!( !(!(!(!(!(!(!(!(!( !( !(!(!(!(!(!( !(!(!(!( !( !( !( !(!( !(!( !(!(!( !( !(!(!( !( !( !( !(!( !( !(!(!( !(!( !( !( !(!( !( !( !(!( !(!( !( !(!( !(!(!( !( !(!( !(!( !(!( !(!( !( !( !(!( !( !( !( !( !( !( !( !( !(!(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !( !(!(!( !( !(!( !( !(!( !( !(!( !( !( !(!( !( !( !( !( !(!( !(!( !( !( !( !( !( !( !( !( !(!(!(!( !( !( !( !( !( !(!( !( !( !( !(!( !(!(!(!(!( !(!( !(!(!( !( !( !(!( !( !(!(!( !( !( !( !( !( !( !(!( !( !( !( !( !( !(!( !(!(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!( !(!(!( !(!(!(!(!(!(!(!( !( !( !( !(!( !( !( !( !( !( !(!( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !( !(!(!( !(!( !( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !? !?!? !? !? !?!? !? !? !? OTSEGO 5 696889 OTSEGO 4 696888 OTSEGO 1 554501 OTSEGO 3 657343 OTSEGO 2 622715 OTSEGO 6 709269 OTSEGO 8 752116 OTSEGO 10 867646 OTSEGO 7 721663 OTSEGO 9 848409 GG18 GG39 GG119 GG42 GG37 GG12 GG13 GG36 GG19 GG1 GG39 GG13 GG42 GG42 GG12 GG36GG19 ¨§¦94 £¤10£¤10 £¤169 ST101 ST201 ST101 70th St NE 65th St NE 70th St N E Mississippi R. B - B' C - C' Ctc Ctc Ce Cs Cw Cw Cw Cm CeCm Ce Cm Cw Ce Ctc Cw Ce Mss Cm Ctc Ce Ctc Cj Ctc Cw Cw Cw Cw Ctc Cj Ctc Cm Cj Cw Ce Cm Cw Ctc Mss Cj Cw Cs Ce Cm Ce Cj Ce Cw Cs Ctc Cw Cs Ctc Cw Cw Cs Cj Cs Ctc Ctc Cm Cw Ctc Cw Cj Cs Cj Cw Cw Ctc Ctc Ctc Cs Ctc Cw Cw Ctc Cs Cj Cs Cw Cs Cw Cs Ctc Cw Ctc Cs Cs Ctc Cs Ctc Cs Cs Cw Cs Ctc Cw Cw Cs Cw Ctc C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02f.mxd, 6/23/2023, 9:06:11 AM, NAD 1983 UTM Zone 15NFeet Sources: Service Layer Credits: Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community Bedrock geology is taken from the Metro Model 3. Minnesota Geological Survey (MGS) Wright Co. Hydrogeologic Atlas Part A. 5013AEN06_02f.MXD 6/23/2023 3 FIRST ENCOUNTERED BEDROCK, FAULTS, AND MINNESOTA GEOLOGICAL SURVEY AND LRE CROSS SECTION LOCATIONS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: PALEOZOIC BEDROCK MESOPROTEROZOIC BEDROCK Jordan Sandstone St. Lawrence Formation Tunnel City Group Wonewoc Sandstone Eau Claire Formation Mt. Simon Sandstone Mt. Simon SandstoneCj Cs Ctc Cw Ce Cm Mss Approximate Fault Location Wright County Geologic Atlas Part B Plate 8 Cross Section 0 6,000±!?Otsego Well City of Otsego Boundary 1-Mile Buffer Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 B - B' Part A Plate 4 Cross Section C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02g.mxd, 6/23/2023, 9:09:35 AM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Minnesota Geological Survey (MGS) Wright Co. Hydrogeologic Atlas Part B. 5013AEN06_02g.MXD 6/23/2023 4 WRIGHT COUNTY GEOLOGIC ATLAS PART B PLATE 8 CROSS SECTION B-B' THROUGH CITY OF OTSEGO BOUNDARY CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: Approximate City of Otsego Boundary Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02h.mxd, 6/23/2023, 9:10:00 AM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Minnesota Geological Survey (MGS) Wright Co. Hydrogeologic Atlas Part B. 5013AEN06_02h.MXD 6/23/2023 5 WRIGHT COUNTY GEOLOGIC ATLAS PART B PLATE 8 CROSS SECTION C-C' THROUGH CITY OF OTSEGO BOUNDARY CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: Approximate City of Otsego Boundary Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02g.mxd, 6/23/2023, 9:09:35 AM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Minnesota Geological Survey (MGS) Wright Co. Hydrogeologic Atlas Part A. 5013AEN06_02g.MXD 6/23/2023 6 OTSEGO, MNWRIGHT COUNTY GEOLOGIC ATLAS PART A PLATE 4 CROSS SECTION B-B' THROUGH CITY OF OTSEGO BOUNDARY CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENTAE2S FILE:DATE:FIGURE: Approximate City of Otsego Boundary Prepared By:LRE WaterMinnesota OfficeMinneapolis / St. Paul(651) 341-8199 B' !? !?!? !? !? !?!? !? !? !?Otsego OTSEGO 8OTSEGO 3 OTSEGO 1 OTSEGO 6 OTSEGO 9 OTSEGO 2 OTSEGO 5OTSEGO 4 OTSEGO 7 OTSEGO 10 GG18 GG12 GG39 GG119 GG42 GG13 GG22 GG37 GG36 GG19 GG83 GG35 GG116 GG22 GG42 GG42 GG39 GG22 GG13 GG12 GG36 GG19 ¨§¦94 £¤169£¤10 ST101 ST241 ST201 ST101 141st Ave N County Road 37 NE BurnsPkwy 70th St NE N Diamond Lake Rd 70th St NE 141st Ave N C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_01y.mxd, 6/22/2023, 5:26:48 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas. 5013AEN06_01y.MXD 6/22/2023 7 MS AQUIFER SAND AND GRAVEL THICKNESS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: 0 1.5 Miles ± Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City Boundary 1-Mile Buffer Notes:Sand rasters are taken from MN DNR'sWright County Geologic Atlas Part A. Sand Thickness (feet)72 0 Sand Thickness (20-foot interval) !? !?!? !? !? !?!? !? !? Otsego OTSEGO 8OTSEGO 3 OTSEGO 1 OTSEGO 6 OTSEGO 9 OTSEGO 2 OTSEGO 5OTSEGO 4 OTSEGO 7 OTSEGO 10 GG18 GG12 GG39 GG119 GG42 GG13 GG22 GG37 GG36 GG83 GG35 GG116GG19 GG22 GG42 GG42 GG39 GG22 GG13 GG12 GG36 GG19 ¨§¦94 £¤169£¤10 ST101 ST241 ST201 ST101 141st Ave N County Road 37 NE BurnsPkwy 70th St NE N Diamond Lake Rd 70th St NE 141st Ave N C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_01w.mxd, 6/22/2023, 5:27:34 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas. 5013AEN06_01w.MXD 6/22/2023 8 CG AQUIFER SAND AND GRAVEL THICKNESS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: 0 1.5 Miles ± Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City Boundary 1-Mile Buffer Notes:Sand rasters are taken from MN DNR'sWright County Geologic Atlas Part A. Sand Thickness (feet)94 0 Sand Thickness (20-foot interval) !? !?!? !? !? !?!? !? !? !?Otsego OTSEGO 8OTSEGO 3 OTSEGO 1 OTSEGO 6 OTSEGO 9 OTSEGO 2 OTSEGO 5OTSEGO 4 OTSEGO 7 OTSEGO 10 GG18 GG12 GG39 GG119 GG42 GG13 GG22 GG37 GG36 GG19 GG83 GG35 GG116 GG22 GG42 GG42 GG39 GG22 GG13 GG12 GG36 GG19 ¨§¦94 £¤169£¤10 ST101 ST241 ST201 ST101 141st Ave N County Road 37 NE BurnsPkwy 70th St NE N Diamond Lake Rd 70th St NE 141st Ave N C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_01x.mxd, 6/22/2023, 5:28:18 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas. 5013AEN06_01x.MXD 6/22/2023 9 CG1 AQUIFER SAND AND GRAVEL THICKNESS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: 0 1.5 Miles ± Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City Boundary 1-Mile Buffer Notes:Sand rasters are taken from MN DNR'sWright County Geologic Atlas Part A. Sand Thickness (feet)94 0 Sand Thickness (20-foot interval) !? !?!? !? !? !?!? !? !? !?Otsego OTSEGO 8OTSEGO 3 OTSEGO 1 OTSEGO 6 OTSEGO 9 OTSEGO 2 OTSEGO 5OTSEGO 4 OTSEGO 7 OTSEGO 10 GG18 GG12 GG39 GG119 GG42 GG13 GG22 GG37 GG36 GG19 GG83 GG35 GG116 GG22 GG42 GG42 GG39 GG22 GG13 GG12 GG36 GG19 ¨§¦94 £¤169£¤10 ST101 ST241 ST201 ST101 ST241 141st Ave N County Road 37 NE BurnsPkwy 70th St NE N Diamond Lake Rd 70th St NE 141st Ave N C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_01z.mxd, 6/22/2023, 5:27:11 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas. 5013AEN06_01z.MXD 6/22/2023 10 PRS AQUIFER SAND AND GRAVEL THICKNESS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: 0 1.5 Miles ± Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City Boundary 1-Mile Buffer Notes:Sand rasters are taken from MN DNR'sWright County Geologic Atlas Part A. Sand Thickness (feet)59 0 Sand Thickness (20-foot interval) !? !?!? !? !? !?!? !? !? !?Otsego OTSEGO 9 OTSEGO 7 OTSEGO 5OTSEGO 4 OTSEGO 1 OTSEGO 3 OTSEGO 2 OTSEGO 6 OTSEGO 8 OTSEGO 10 GG18 GG12 GG39 GG119 GG42 GG13 GG22 GG37 GG19 GG83 GG35 GG116 GG22 GG42 GG36 GG42 GG39 GG22 GG13 GG12 GG36 GG19 ¨§¦94 £¤169£¤10 ST101 ST241 ST201 ST101 141st Ave N County Road 37 NE BurnsPkwy 70th St NE N Diamond Lake Rd 70th St NE 141st Ave N C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02a.mxd, 6/22/2023, 5:26:02 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community Minnesota Well Index Database. Minnesota Geological Survey (MGS) Wright County Hydrogeologic Atlas. 5013AEN06_02a.MXD 6/22/2023 11 PSU AQUIFER SAND AND GRAVEL THICKNESS CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 !?Otsego Well City Boundary 1-Mile Buffer 0 1.5 Miles ±Notes:Sand rasters are taken from MN DNR'sWright County Geologic Atlas Part A. Sand Thickness (feet)134 0 Sand Thickness (20-foot interval) C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02i.mxd, 6/29/2023, 3:37:33 PM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Minnesota Geological Survey (MGS) Wright Co. Hydrogeologic Atlas Part B Plate 7. 5013AEN06_02i.MXD 6/29/2023 CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENT AE2S OTSEGO, MN FILE:DATE:FIGURE: Prepared By: LRE Water Minnesota Office Minneapolis / St. Paul (651) 341-8199 WRIGHT COUNTY GEOLOGIC ATLAS PART B PLATE 7 WATER CHEMISTRY THROUGH CITY OF OTSEGO BOUNDARY 12 LRE_Central_1 LRE_Central_2 LRE_Central_3 LRE_Central_4 LRE_Central_5 LRE_Central_6 LRE_Central_7 LRE_Central_8 LRE_Central_9 LRE_Central_10 LRE_Central_11 LRE_Central_12 LRE_Central_13 LRE_Central_14 LRE_Central_15 LRE_Central_16 LRE_Central_17 LRE_NWWF_1 LRE_NWWF_2 LRE_NWWF_3 Service Layer Credits: Source: Esri, Maxar, Earthstar Geographics, and the GIS User CommunityThis product is for reference purposes only and is not tobe construed as a legal document or survey instrument. ^_ CN 5013AEN07 | APRIL 2023 FIGURE 13SIMULATED HYPOTHETICAL WELLS 750 0 750 1,500 2,250 3,000 3,750 Feet 1:35,6931 in = 2,974.4 feet Models Wells Potential Wells Model Grid Northwest Wellfield Potential Central Wellfield !? !?!? !? !? !?!? !? !? !?OTSEGO 7721663 OTSEGO 5696889 OTSEGO 4696888 OTSEGO 1554501 OTSEGO 3657343 OTSEGO 2622715 OTSEGO 6709269 OTSEGO 8752116 OTSEGO 10867646 Wells 7 and 10 are approximatly 65 feet apart OTSEGO 9848409 GG18 GG39 GG119 GG42 GG37 GG12 GG13 GG36 GG19 GG1 GG39 GG13 GG42 GG42 GG12 GG36GG19 ¨§¦94 £¤10£¤10 £¤169 ST101 ST201 ST101 70th St NE 65th St NE 70 th St N E Mississippi R.C:\GIS\GIS\AE2S_Otsego_MN\maps\5013AEN06_02j.mxd, 7/3/2023, 10:07:10 AM, NAD 1983 UTM Zone 15NSources: Service Layer Credits: Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community 5013AEN06_02j.MXD 7/3/2023 14 LOCATIONS OF POTENTIAL SAND AND GRAVEL AQUIFERS FOR FURTHER EVALUATION CITY OF OTSEGO HYDROGEOLOGIC ASSESSMENTAE2S OTSEGO, MN FILE:DATE:FIGURE: 0 6,000 Feet ± Prepared By:LRE WaterMinnesota OfficeMinneapolis / St. Paul(651) 341-8199 !?Otsego Well City of Otsego Boundary Potential Sand and Gravel Aquifers for Further Evaluation ATTACHEMENT 1 GROUNDWATER QUALITY Well Name Otsego 1Otsego 2Otsego 3Otsego 4Otsego 5Well Depth201 172 370 494 490AquiferWonewoc WonewocTunnel City‐WonewocMt. SimonMt.Simon‐HinckleyMin‐‐220 2/5/2013 310 12/22/2004 290 6/10/2013Max‐‐230 6/10/2013 310 12/22/2004 290 6/10/2013Average‐‐225 310 12/22/2004 290Min‐‐150 6/10/2013‐190 6/10/2013Max‐‐150 6/10/2013‐190 6/10/2013Average‐‐150‐190Min2.28/5/20091.48/5/2009< 1 3/16/2012* 2.1 1/22/2004 1.4 1/22/2009Max2.75/12/20152.9 8/14/2018 1.7 8/29/2022 2.1 1/22/2009 1.4 1/22/2009Average2.4 2.2 1.1 2.1 1.4Min1.95/12/20154.3 1/21/2015 < 1 1/21/2015* 1.4 1/22/2004 3.2 1/22/2009Max5.15/12/20155.0 8/14/2018 1.5 6/16/2015 2.5 1/22/2009 3.2 1/22/2009Average3.9 4.6 1.1 2 3.2Min4.25/12/20156 8/5/2009 2 * 3.5 1/22/2004 4.6 1/22/2009Max7.85/12/20157.9 8/14/2018 3 * 4.6 1/22/2009 4.6 1/22/2009Average6.3 7 2.1 4.1 4.6*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L)Alkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L) Well NameWell DepthAquiferMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageAlkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L)Otsego 6Otsego 7Otsego 8Otsego 9343 429 437 323Mt. Simon Mt. Simon Mt. Simon Mt. Simon‐260 2/5/2013 170 6/10/2013‐270 6/10/2013 180 2/5/2013‐265 175‐170 6/10/2013 130‐170 6/10/2013 130‐170 130< 1 10/17/2016‐2.7 8/5/2009 1.9 8/29/20221.9 6/10/2020*‐10 8/29/2022 2.3 12/16/20201.6‐7.19 2.1< 1 1/21/2015*‐3.8 8/5/2009 1.5 12/16/20201.9 10/17/2016*‐7.6 6/5/2017 2.7 8/29/20221.36‐5.6 2.02.2 1/21/2015‐6.5 8/5/2009 3.8 12/16/20203.3 8/5/2009‐15.5 6/27/2018 4.6 8/29/20222.92‐12.9 4.1*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L) Well NameWell DepthAquiferMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageAlkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L)Joint Powers Board 1Joint Powers Board 2Joint Powers Board 3Joint Powers Board 4365 281 221 401Eau Claire‐Mt.SimonQuaternary buried artesian aquiferQBAA Mt. Simon‐‐370 12/7/2011 350 12/7/2011‐‐370 12/7/2011 350 12/7/2011‐‐370 350‐‐‐‐‐‐‐‐‐‐‐‐< 14/18/2006< 1 11/3/2006 < 1 4/25/2006 14.4 4/25/2006< 14/18/2006< 1 11/3/2006 < 1 4/25/2006 14.4 4/25/2006< 1< 1< 1 14.41.44/18/20061.3 11/3/2006 1.3 4/25/2006 7.5 4/25/20061.44/18/20061.3 11/3/2006 1.3 4/25/2006 7.5 4/25/20061.4 1.3 1.3 7.52.4 2.3 11/3/2006 2.3 4/25/2006 21.9 4/25/20062.4 2.3 11/3/2006 2.3 4/25/2006 21.9 4/25/20062.4 2.3 2.3 21.9*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L) Well NameWell DepthAquiferMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageAlkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L)Joint Powers Board 5Joint Powers Board 6Joint Powers Board 7Riverbend MHP 1370 480 386Quaternary buried artesian aquiferHinckley Mt. Simon370 12/5/2011 370.0 12/5/2011‐‐370 12/5/2011 370.0 12/5/2011‐‐370‐‐‐‐‐‐‐‐‐‐‐‐‐‐< 1 11/14/2006 < 1 4/13/2006 < 1 7/31/2006 1.6 10/4/2007< 1 11/14/2006 < 1 4/13/2006 < 1 7/31/2006 4.4 10/3/2006< 1< 1< 12.41.4 11/14/2006 1.3 4/13/2006 2.1 7/31/2006 1.6 10/4/20071.4 11/14/2006 1.3 4/13/2006 2.1 7/31/2006 2.8 10/3/20061.4 1.30 2.1 2.12.4 11/14/2006 2.3 4/13/2006 3.1 7/31/2006 3.6 10/4/20072.4 11/14/2006 2.3 4/13/2006 3.1 7/31/2006 7.2 10/3/20062.4 2.3 3.1 4.9*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L) Well NameWell DepthAquiferMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageAlkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L)Riverbend MHP 2Rogers 3Rogers 4Rogers 6309 370 367 374Mt. Simon WonewocTunnel City‐WonewocWonewoc‐Eau Claire‐340 6/25/2013 350 6/25/2013 400 6/25/2013‐340 6/25/2013 350 6/25/2013 400 6/25/2013‐340 350 400‐240 6/25/2013 220 6/25/2013 280 6/25/2013‐240 6/25/2013 220 6/25/2013 280 6/25/2013‐240 220 2801.2 5/22/2007‐‐‐2.6 10/3/2006‐‐‐1.675‐‐‐1.5 5/22/2007‐‐‐3.1 10/4/2007‐‐‐2.1‐‐‐2.7 5/22/2007‐‐‐5.3 10/3/2006‐‐‐3.875‐‐‐*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L) Well NameWell DepthAquiferMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageMinMaxAverageAlkalinity (mg/L)Hardness Ca as CaCO3 (mg/L)Radium‐226 (pCi/L)Radium‐228 (pCi/L)Radium‐Combined (pCi/L)Rogers 7362Tunnel City‐Wonewoc410 6/25/2013410 6/25/2013410220 6/25/2013220 6/25/2013220‐‐‐‐‐‐‐‐‐*Multiple dates exhibit this data value‐No DataCombined radium maximum contaminant levels are 5.00 (pCi/L) ATTACHMENT 2 Desktop Hydrogeologic Assessment - Central Wellfield Area Expansion City of Otsego Moldel Results and Simulated Well Yield Estimates ROCKY MOUNTAIN | MIDWEST | SOUTHWEST | TEXAS 1221 Auraria Parkway Denver, CO 80204 | Office: 303-455-9589 | LREWATER.COM Memorandum To: Nancy Zeigler, PE, AE2S From: Scott Stokes and Jacob Bauer, P.G., LRE Water Copy to: Reviewed by: Jacob Bauer and Dave Hume, P.G., LRE Water Date: June 9, 2023 Project: 5013AEN07 – Desktop Hydrogeologic Assessment - Central Wellfield Area Expansion, City of Otsego Subject: Model Results and Simulated Otsego Well Yield Estimates Introduction This memorandum provides the results of LRE Water’s (“LRE”) estimation of potential Tunnel City-Wonewoc (TCW) bedrock aquifer well yields for the City of Otsego (“City”). These results are part of a more comprehensive desktop assessment completed by LRE that includes mapping the sand and gravel aquifers based on the Minnesota Department of Natural Resources (DNR) Wright County Geologic Atlas (Barry, 2018), a high-level summary of water quality. To meet the water demands of the projected 2050 population growth, the City needs to increase their peak water production by approximately 8,000 gpm. The City’s focus to meet this demand is development of a future wellfield in an area referred to as the Central Wellfield (CWF), along with adding several additional wells to the existing Northwest Wellfield (NWWF). The City’s existing wells, and CWF and NWWF are shown on Figure 1. The TCW analysis provided below is to aid the City in their groundwater resource planning for future population-based water demands. This evaluation is based on results derived using the Metropolitan Council’s Metro Model 3 (“MM3”) groundwater model. LRE’s evaluation includes: (1) a limited review of the MM3 including a preliminary parameter analysis, and MM3 model parameter updates based on this review and pumping test results; (2) development of aquifer drawdown triggers; (3) MODFLOW -based steady-state and transient well yield projections; (4) a basic sensitivity analysis; and, (5) wellfield interference evaluation. Nancy Zeigler, PE Page 2 of 7 MM3 Model Description and Updates The MM3 groundwater model is a MODFLOW model developed by Barr Engineering in 2014 (Metropolitan Council, 2014). The model is steady state and consists of 9 layers that represent from oldest to youngest, the alluvial and outwash sand and gravel aquifers, undifferentiated Cretaceous-age geologic units, the St. Peter Sandstone, the Prairie du Chein Group, the Jordan Sandstone, the St. Lawrence Formation, the Tunnel City group, the Wonewoc Sandstone, the Eau Claire Formation and the Mt. Simon Sandstone. The model utilizes MODFLOW -NWT (Niswonger and others, 2011) and covers much of the eleven counties within the Twin Cities metropolitan area, with the City being situated near the north-central portion of the model domain (Figure 1). A significant component of the model is groundwater pumping . The MM3 model was developed in 2014, and updates to pumping were therefore needed. These updates included (1) updating the pumping rates of the City’s wells using the maximum annual pumpage from the previous 5 years, and (2) incorporating additional high-capacity wells within 10 miles of the City that were constructed after 2014 and thus not incorporated in the original model. The aquifer of interest is the TWC. Near the City, model layers 6 and 7 represent the TCW. Hydraulic conductivity and transmissivity from these layers were evaluated and compared to local aquifer test data to determine if the model’s current parameters are suitable for simulating local well yields. We utilized pumping test data from City W ells No. 1, 3 and 10 along with a test conducted on an irrigation well in Prairie Park. We found that the current model’s parameters reasonably match those derived from the pumping test. Additionally, LRE conducted a sensitivity analysis was conducted that simulated a 25 % increase and decrease in the TWC’s transmissivity to account for parameter uncertainty (discussed more below). Aquifer Safe-Yield Trigger Level Another component to consider when estimating well yields is considering the DNR’s regulatory safe-yield threshold for confined aquifers. The DNR has established a two-tiered aquifer protection threshold to ensure the long-term viability of a confined aquifer being pumped and to prevent the exceedance of the aquifer safe yield (as defined by MN Rule 6115.0630 Definitions Subp.16). These thresholds allow for appropriation from the aquifer, but also establish minimum water level elevations to be maintained as a safeguard to protect the aquifer. The two constraints LRE needed to consider were:  Constraint 1: the water level in the pumping well cannot drop to level below the top the TCW aquifer (i.e., transitioning from a confined aquifer to an unconfined aquifer). Nancy Zeigler, PE Page 3 of 7  Constraint 2: pumping from new wells cannot cause the confined aquifer water level in a monitoring well (water level above the confining unit) to drop below the 50-percent threshold. Figure 2 illustrates these constraints in a conceptual cross section. To address Constraint 1, LRE used the multi-node well package to simulate future pumping wells and set the pumping level to be just above the top of layer 6 (top of TCW aquifer). Doing this allows the model to calculate the maximum pumping rate that still results in a water level above the top of the aquifer. To address Constraint 2, LRE used simulated water levels (prior to adding future City wells) to estimate the water levels within adjacent monitoring wells. Future City wells were then simulated, and the resulting water levels were compared to the previously calculated baseline water levels. Recent Well No. 10 Aquifer Pumping Test The City recently conducted a step-rate aquifer pumping test and a 24-hour constant rate pumping test at maximum rate of approximately1,200 gpm on Well No. 10, which is completed in the Wonewoc Formation of the TCW aquifer. The results of the pumping test analysis are presented in LRE’s March 19, 2023 City of Otsego, Well No. 10 memorandum, and this test predicts aquifer transmissivity values of between 783 to 1,115 feet squared per days (ft2/d). We compared this transmissivity to the values present in the MM3 and found that transmissivity within the MM3 at the location of the pumping test is approximately 830 ft2/d, falling in the range of transmissivities derived from the aquifer test. This means the base case parameters used in the original MM3 model appear to be a good approximation of the local hydrogeology of the TCW, although, a sensitivity analysis was conducted to account for potential uncertainty in the models parameters. Well Yield Projections and Sensitivity Analysis To meet the water demands of the projected 2050 population growth, the City needs to increase their peak water production by approximately 8,000 gpm. LRE utilized MM3 to estimate bedrock yields for future City wells constructed in the NWWF and CWF, which are both shown on Figure 3. Two modeling approaches were used to estimate yields, (1) steady-state modeling that estimates long-term sustainable yields and (2) transient modeling that incorporates the City’s demand curve. In both approaches, LRE simulated wells constructed in the TCW aquifer with well screens that extended through both layers with the exception that if the Tunnel City was not present (eroded away), than only the Wonewoc would be screened. We used the multi-node well package to simulate these wells, which allows the model to determine the maximum pumping rate that satisfied drawdown Constraint 1 above. Nancy Zeigler, PE Page 4 of 7 Steady-State Modeling The MM3 is a steady-state model that does not consider temporal variability in any of the model’s components. This form of modeling is particularly useful when projecting long -term sustainable yields because it assumes that the groundwater system is in equilibrium with all the stresses of the model and thus provides a conservative estimate of well yields. For the steady-state analysis, future City wells were placed in model cells that (1) did not have an already existing well and (2) more than half the cell fell within the extent of the wellfield (Figure 3). This resulted in 3 wells being placed in the NWWF and 17 wells being placed in the CWF. The 17 wells in the CWF were assigned on a grid of 1640 ft by 1640 ft (500 m by 500m). Other well configurations were also simulated with fewer wells, which are discussed more in the Well Interference Section. Additionally, Well 10 was simulated in the model but was not included in the well yield totals. This configuration of wells was simulated with three model scenarios, (1) a base case scenario (Base Case) which uses the original transmissivity from the MM3 model, (2) a low transmissivity scenario (Low T) which reduced the transmissivity of the TCW aquifer in the vicinity of the City by 25 percent and (3) a high transmissivity scenario (High T) which increased the transmissivity of the TCW aquifer in the vicinity of the city by 25 percent. The resulting steady state total wellfield yields (for all 20 future City wells) ranged between 3,900 and 5,700 gpm (Table 1, Figures 4 - 7). For the Base Case 20-well run, the yield per well is approximately 242 gpm. Current well yields for W ells No. 1, 2 and 3 were reported to range between approximately 400 to 600 gpm. These yields are higher than the modeled yields, although, MM3 assumes steady-state continuous pumping and simulates 20 wells in closer proximity to each other that causes well interference, which is also a cause of the lower modeled well yields. It is important to note that these results are steady state which means these figures should approximate the long-term sustainable yield from these wells while satisfying the DNR ‘s Constraints 1 and 2 under these conditions. Regarding drawdown water level triggers/limits, most modeled wells satisfy the triggers (Constraint 2). Some wells did exceed the triggers by small amounts, but it was not by a substantial amount and LRE did not iterate over various pumping rates to achieve an exact trigger water level solution. A python script was developed to efficiently graph each well’s yield and water level, these graphs can be seen in Attachment A. Based on the steady-state results, the TCW in the NWWF and CWF is unlikely to sustain 8,000 gpm even when simulating 20 potential new TCW wells. This is in part due to the aquifer’s transmissivity, but also the relatively small land area in which the 20 wells were simulated, particularly in the CWF. Having 17 wells constructed within the same aquifer in an area the size of the CWF causes significant well interference. This means that each well is lowering the water level of the other nearby wells resulting in lower yields of the neighboring wells. Additionally, this analysis does not consider well efficiency, which is affected by well construction, and could result in lower yields than predicted by the model. It is important to note that these results simulate long- Nancy Zeigler, PE Page 5 of 7 term constant sustainable yield and do not consider pumping fluctuations that consider the City’s demand curve. The Transient Modeling section below will discuss the incorporation of the City’s demand curve. Table 1. Total Wellfield Yield for 20 wells Scenario Total Yield (gpm) Low T 3,900 Base Case 4,840 High T 5,700 Well Interference As discussed above, pumping wells completed in the same aquifer near one another cause well interference and reduce yields. The CWF has 17 wells that are located in a relatively small area resulting in substantial well interference. To evaluate the degree of well interference caused by the 20 well configuration (three NWWF wells and 17 CWF wells), LRE simulated two additional well configurations. One configuration reduced the wells in the CWF from 17 to 9 (total wells between both wellfields is 12) and the other reduced the CWF to 5 wells (total wells between both wellfields is 8). As seen in Figure 8 and Table 2, the 20 well configuration produced the highest total yield but the lowest yield per well. In contrast, the 8 well configuration produced the lowest total yield but the highest yield per well. This shows that there are diminishing returns as the number of wells increase in the CWF and the cost of well construction may out way the increase in well yield after a certain number of wells are constructed in the CWF. Table 2. Total Wellfield Yield vs Number Simulated Wells Scenario Total Yield (gpm) Yield Per Well (gpm) 8 Total Wells 5 CWF Wells 2605 326 12 Total Wells 9 CWF Wells 3596 300 20 Total Wells 17 CWF Wells 4840 242 Nancy Zeigler, PE Page 6 of 7 Transient Modeling As discussed previously, the MM3 is a steady-state model. To incorporate the City’s demand curve, LRE converted the MM3 model into a transient model. To do this LRE added 12 transient stress periods to the end of the model, each stress period being one month long (a total model time of 12 months). Two future well configurations were simulated in the transient model, one with 3 wells in the NWWF and 9 wells in the CWF and another with 3 wells in the NWWF and 17 wells in the CWF. Pumping was evening distributed to the wells. The timing and quantity of pumping was generated using the demand curve provided by the City and assuming a peak demand of 8,000 gpm. The model was simulated using the same low and high transmissivities as the steady-state model but when using a transient model aquifer storage needs to be considered. Like transmissivity, we used a low and high specific storage to take into consideration a range in aquifer storage. The low storage (1x10-6 m-1) was derived from the lowest TCW specific storage found in the MM3 aquifer storage dataset, the higher storage (7x10-6 m-1) was derived from a two well pumping test conducted on an irrigation well within the City. These specific storage values are fairly low but are consistent with bedrock aquifers. The transient model runs resulted in a peak demand yield (yield during July) ranging between 2,759 – 4,197 gpm for the 12 well configuration and 3,923 – 5,738 gpm for the 20 well configuration (Table 3, Figure 9). These results are similar to the sustainable yields from the steady-state analysis due to the small specific storage of the TCW aquifer. Similar to the steady- state results, the wellfields cannot extract the desired peak demand of 8,000 gpm due to aquifer properties and, to a smaller degree, well interference. Table 3. Transient Model Peak Demand Wellfield Yields Scenario Minimum Total Yield (gpm) Maximum Total Yield (gpm) 12 Wells with 9 in CWF 2,759 4,197 20 Wells with 17 in CWF 3,923 5,738 Conclusion LRE conducted an analysis that involved estimating future wellfield yields using both a steady- state and a transient modeling approach. The following points summarize LRE’s findings. 1. Steady-state modeling indicated the long-term yields of 8,000 gpm could not be achieved from the NWWF and CWF alone. Nancy Zeigler, PE Page 7 of 7 2. Significant well interference occurs when developing large numbers of wells in the CWF. As the number of wells increases, the yield per well decreases but the total well- field yield increases at a slower rate. 3. Well yields are contingent on the location, geology and number of nearby wells, but well yields are expected to be around 250 - 300 gpm per well. This is assuming a constant 24-hour pumping schedule, higher rates would likely apply if shorter duration of pumping are used. 4. Transient model results indicated that a peak yield of 8,000 gpm could not be achieved. This indicates that the aquifer properties, in combination with the effects of well interference, limit the ability of the wells to extract the desired 8,000 gpm within the extent of the two wellfields. 5. These results were generated using the MM3, which is a reasonable representation of the groundwater system. As wells are installed, and more aquifer and pumping test data is available for the aquifer, these estimates could be revisited to improve the reliability of our predictions. Included with this memo are two attachments. Attachment A presents additional steady-state model results and Attachment B contains the PowerPoint presentation. References Barry, J.D., 2018, Geologic Atlas of Wright County, Minnesota (Part B): Minnesota Department of Natural Resources, County Atlas Series C-30, Report and Plates 7–9, (http://www.dnr.state.mn.us/waters/programs/gw_section/mapping/platesum/wrigcga.html). Metropolitan Council. 2014. Twin Cities Metropolitan Area Regional Groundwater Flow Model, Version 3.0. Prepared by Barr Engineering. Metropolitan Council: Saint Paul, MN. Niswonger, R.G., Panday, S., Ibaraki, M., 2011. MODFLOW -NWT, A Newton formulation for MODFLOW -2005: U.S. Geological Survery Techniques and Methods 6-A37, 44 p. Figures !. !. !. !.!. !. !. !. !. !. Well1Aquifer:Wonewoc Well2Aquifer:TCW Well3Aquifer:TCW Well4Aquifer:Mt. Simon Well5Aquifer:Mt. Simon Well6Aquifer:Mt. Simon Well7Aquifer:Mt Simon Well8Aquifer:Mt.Simon Well9Aquifer:Mt. Simon Well10Aquifer:Wonewoc Service Layer Credits: Source: Esri, Maxar, Earthstar Geographics, and the GIS User CommunityThis product is for reference purposes only and is not tobe con stru ed as a legal document or survey instrument. ^_ CN 5060COS01 | JANUARY 2023 FIG U R E 1SITE M A P A NDMODEL G R I D 1,750 0 1,750 3,500 5,250 7,000 8,750 Feet 1:87,8061 in = 7 ,3 17.2 fe et Cities Wells !.TCW !.Mt. Simon !.Wonewoc Model Grid Northwest Wellfield Central Wellfield Figure 2 Administrative Pumping Constraints DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Pumping Well Monitoring Well Aquifer Confining Unit Confining Unit Drawdown Water Level (50% decrease from Original Confining Water Level) Original Confining water level Water level limit in well LRE_Central_1 LRE_Central_2 LRE_Central_3 LRE_Central_4 LRE_Central_5 LRE_Central_6 LRE_Central_7 LRE_Central_8 LRE_Central_9 LRE_Central_10 LRE_Central_11 LRE_Central_12 LRE_Central_13 LRE_Central_14 LRE_Central_15 LRE_Central_16 LRE_Central_17 LRE_NWWF_1 LRE_NWWF_2 LRE_NWWF_3 Service Layer Credits: Source: Esri, Maxar, Earthstar Geographics, and the GIS User CommunityThis product is for reference purposes only and is not tobe construed as a legal document or survey instrument. ^_ CN 5013AEN07 | APRIL 2023 FIGURE 3SIMULATED HYPOTHETICAL WELLS 750 0 750 1,500 2,250 3,000 3,750 Feet 1:35,6931 in = 2,974.4 feet Models Wells Potential Wells Model Grid Northwest Wellfield Potential Central Wellfield Figure 4 Total Yields DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Figure 5 Low Transmissivity Well by Well Yields DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Figure 6 Base Case Transmissivity Well by Well Yields DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Figure 7 High Transmissivity Well by Well Yields DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Figure 8 Total Yield and Yield per Well as a Function of Total Number of Wells DATE: 4/6/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 0 1000 2000 3000 4000 5000 6000 7000 Total Yield (gpm)LowT_LowS_12 Well LowT_LowS_20 Well HighT_HighS_12 Well HighT_HighSs_20 Wells Figure 9 Transient Model Results: Total Monthly Wellfield Yields DATE: 5/16/2023 AUTHOR: SS CHECKED BY: JB 1221 Auraria Parkway, Denver, CO 80204 Attachment A: Individual Well Yield Results Low Transmissivity Well by Well Results LRE_CENTRAL_1LRE_CENTRAL_10LRE_CENTRAL_11LRE_CENTRAL_12LRE_CENTRAL_13LRE_CENTRAL_14LRE_CENTRAL_15LRE_CENTRAL_16LRE_CENTRAL_17LRE_CENTRAL_2LRE_CENTRAL_3LRE_CENTRAL_4LRE_CENTRAL_5LRE_CENTRAL_6LRE_CENTRAL_7LRE_CENTRAL_8LRE_CENTRAL_9LRE_NWWF_1LRE_NWWF_2LRE_NWWF_3Total Yield0 1000 2000 3000 4000 5000 6000 Yield (gpm)Low Transmissivity Yields LRE_CENTRAL_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_1 Well Yield LRE_CENTRAL_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_1 Drawdown Target Water Level LRE_CENTRAL_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_2 Well Yield LRE_CENTRAL_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_2 Drawdown Target Water Level LRE_CENTRAL_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_3 Well Yield LRE_CENTRAL_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_3 Drawdown Target Water Level LRE_CENTRAL_4 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_4 Well Yield LRE_CENTRAL_4 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_4 Drawdown Target Water Level LRE_CENTRAL_5 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_5 Well Yield LRE_CENTRAL_5 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_5 Drawdown Target Water Level LRE_CENTRAL_6 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_6 Well Yield LRE_CENTRAL_6 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_6 Drawdown Target Water Level LRE_CENTRAL_7 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_7 Well Yield LRE_CENTRAL_7 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_7 Drawdown Target Water Level LRE_CENTRAL_8 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_8 Well Yield LRE_CENTRAL_8 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_8 Drawdown Target Water Level LRE_CENTRAL_9 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_9 Well Yield LRE_CENTRAL_9 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_9 Drawdown Target Water Level LRE_CENTRAL_10 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_10 Well Yield LRE_CENTRAL_10 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_10 Drawdown Target Water Level LRE_CENTRAL_11 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_11 Well Yield LRE_CENTRAL_11 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_11 Drawdown Target Water Level LRE_CENTRAL_12 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_12 Well Yield LRE_CENTRAL_12 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_12 Drawdown Target Water Level LRE_CENTRAL_13 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_13 Well Yield LRE_CENTRAL_13 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_13 Drawdown Target Water Level LRE_CENTRAL_14 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_14 Well Yield LRE_CENTRAL_14 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_14 Drawdown Target Water Level LRE_CENTRAL_15 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_15 Well Yield LRE_CENTRAL_15 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_15 Drawdown Target Water Level LRE_CENTRAL_16 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_16 Well Yield LRE_CENTRAL_16 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_16 Drawdown Target Water Level LRE_CENTRAL_17 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_17 Well Yield LRE_CENTRAL_17 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_17 Drawdown Target Water Level LRE_NWWF_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_1 Well Yield LRE_NWWF_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_1 Drawdown Target Water Level LRE_NWWF_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_2 Well Yield LRE_NWWF_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_2 Drawdown Target Water Level LRE_NWWF_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_3 Well Yield LRE_NWWF_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_3 Drawdown Target Water Level Base Case Well by Well Results LRE_CENTRAL_1LRE_CENTRAL_10LRE_CENTRAL_11LRE_CENTRAL_12LRE_CENTRAL_13LRE_CENTRAL_14LRE_CENTRAL_15LRE_CENTRAL_16LRE_CENTRAL_17LRE_CENTRAL_2LRE_CENTRAL_3LRE_CENTRAL_4LRE_CENTRAL_5LRE_CENTRAL_6LRE_CENTRAL_7LRE_CENTRAL_8LRE_CENTRAL_9LRE_NWWF_1LRE_NWWF_2LRE_NWWF_3Total Yield0 1000 2000 3000 4000 5000 6000 Yield (gpm)Base Case Transmissivity Yields LRE_CENTRAL_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_1 Well Yield LRE_CENTRAL_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_1 Drawdown Target Water Level LRE_CENTRAL_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_2 Well Yield LRE_CENTRAL_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_2 Drawdown Target Water Level LRE_CENTRAL_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_3 Well Yield LRE_CENTRAL_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_3 Drawdown Target Water Level LRE_CENTRAL_4 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_4 Well Yield LRE_CENTRAL_4 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_4 Drawdown Target Water Level LRE_CENTRAL_5 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_5 Well Yield LRE_CENTRAL_5 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_5 Drawdown Target Water Level LRE_CENTRAL_6 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_6 Well Yield LRE_CENTRAL_6 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_6 Drawdown Target Water Level LRE_CENTRAL_7 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_7 Well Yield LRE_CENTRAL_7 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_7 Drawdown Target Water Level LRE_CENTRAL_8 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_8 Well Yield LRE_CENTRAL_8 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_8 Drawdown Target Water Level LRE_CENTRAL_9 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_9 Well Yield LRE_CENTRAL_9 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_9 Drawdown Target Water Level LRE_CENTRAL_10 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_10 Well Yield LRE_CENTRAL_10 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_10 Drawdown Target Water Level LRE_CENTRAL_11 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_11 Well Yield LRE_CENTRAL_11 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_11 Drawdown Target Water Level LRE_CENTRAL_12 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_12 Well Yield LRE_CENTRAL_12 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_12 Drawdown Target Water Level LRE_CENTRAL_13 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_13 Well Yield LRE_CENTRAL_13 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_13 Drawdown Target Water Level LRE_CENTRAL_14 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_14 Well Yield LRE_CENTRAL_14 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_14 Drawdown Target Water Level LRE_CENTRAL_15 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_15 Well Yield LRE_CENTRAL_15 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_15 Drawdown Target Water Level LRE_CENTRAL_16 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_16 Well Yield LRE_CENTRAL_16 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_16 Drawdown Target Water Level LRE_CENTRAL_17 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_17 Well Yield LRE_CENTRAL_17 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_CENTRAL_17 Drawdown Target Water Level LRE_NWWF_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_1 Well Yield LRE_NWWF_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_NWWF_1 Drawdown Target Water Level LRE_NWWF_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_2 Well Yield LRE_NWWF_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_NWWF_2 Drawdown Target Water Level LRE_NWWF_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_3 Well Yield LRE_NWWF_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)Well: LRE_NWWF_3 Drawdown Target Water Level High Transmissivity Well by Well Results LRE_CENTRAL_1LRE_CENTRAL_10LRE_CENTRAL_11LRE_CENTRAL_12LRE_CENTRAL_13LRE_CENTRAL_14LRE_CENTRAL_15LRE_CENTRAL_16LRE_CENTRAL_17LRE_CENTRAL_2LRE_CENTRAL_3LRE_CENTRAL_4LRE_CENTRAL_5LRE_CENTRAL_6LRE_CENTRAL_7LRE_CENTRAL_8LRE_CENTRAL_9LRE_NWWF_1LRE_NWWF_2LRE_NWWF_3Total Yield0 1000 2000 3000 4000 5000 6000 Yield (gpm)High Transmissivity Yields LRE_CENTRAL_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_1 Well Yield LRE_CENTRAL_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_1 Drawdown Target Water Level LRE_CENTRAL_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_2 Well Yield LRE_CENTRAL_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_2 Drawdown Target Water Level LRE_CENTRAL_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_3 Well Yield LRE_CENTRAL_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_3 Drawdown Target Water Level LRE_CENTRAL_4 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_4 Well Yield LRE_CENTRAL_4 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_4 Drawdown Target Water Level LRE_CENTRAL_5 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_5 Well Yield LRE_CENTRAL_5 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_5 Drawdown Target Water Level LRE_CENTRAL_6 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_6 Well Yield LRE_CENTRAL_6 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_6 Drawdown Target Water Level LRE_CENTRAL_7 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_7 Well Yield LRE_CENTRAL_7 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_7 Drawdown Target Water Level LRE_CENTRAL_8 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_8 Well Yield LRE_CENTRAL_8 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_8 Drawdown Target Water Level LRE_CENTRAL_9 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_9 Well Yield LRE_CENTRAL_9 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_9 Drawdown Target Water Level LRE_CENTRAL_10 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_10 Well Yield LRE_CENTRAL_10 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_10 Drawdown Target Water Level LRE_CENTRAL_11 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_11 Well Yield LRE_CENTRAL_11 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_11 Drawdown Target Water Level LRE_CENTRAL_12 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_12 Well Yield LRE_CENTRAL_12 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_12 Drawdown Target Water Level LRE_CENTRAL_13 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_13 Well Yield LRE_CENTRAL_13 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_13 Drawdown Target Water Level LRE_CENTRAL_14 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_14 Well Yield LRE_CENTRAL_14 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_14 Drawdown Target Water Level LRE_CENTRAL_15 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_15 Well Yield LRE_CENTRAL_15 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_15 Drawdown Target Water Level LRE_CENTRAL_16 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_16 Well Yield LRE_CENTRAL_16 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_16 Drawdown Target Water Level LRE_CENTRAL_17 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_CENTRAL_17 Well Yield LRE_CENTRAL_17 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_CENTRAL_17 Drawdown Target Water Level LRE_NWWF_1 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_1 Well Yield LRE_NWWF_1 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_1 Drawdown Target Water Level LRE_NWWF_2 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_2 Well Yield LRE_NWWF_2 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_2 Drawdown Target Water Level LRE_NWWF_3 WELLID 0 200 400 600 800 1000 Yield (gpm)LRE_NWWF_3 Well Yield LRE_NWWF_3 WELLID 600 650 700 750 800 850 900 950 1000 Water Level (ft amsl)LRE_NWWF_3 Drawdown Target Water Level Attachment B: PowerPoint Presentation OTSEGO BEDROCK WELLFIELD YIELD EVALUATION City of Otsego SIMULATED WELLFIELDS Simulated pumping in two wellfields •Northwest Wellfield (NWWF) •3 Wells •Central Wellfield (CWF) •17 Wells Drawdown Constraints •Water level in well cannot go unconfined •Water level above confining unit cannot but reduced by more than 50% at a distance from the well SIMULATED TOTAL WELLFIELD YIELDS •Wellfield yields from simulated 3 NWWF wells and 17 CWF wells (total wells 20) •Simulated the 20 wells using low, base case and high transmissivity scenarios (based on field data) Table 1. Total Wellfield Yield for 20 wells Scenario Total Yield (gpm)Low T 3,900Base Case 4,840High T 5,700 WELLFIELD YIELDS WITH DIFFERENT NUMBERS OF WELLS Varied the number of wells simulated in the CWF •20 total wells with 17 CWF wells •12 total wells with 9 CWF wells •8 total wells with 5 CWF wells More wells = more total yield but lower yield per well Table 2. Total Wellfield Yield vs Number Simulated Wells Scenario Total Yield (gpm)Yield Per Well (gpm) 8 Total Wells 5 CWF Wells 2605 326 12 Total Wells 9 CWF Wells 3596 300 20 Total Wells 17 CWF Wells 4840 242 CONCLUSIONS •Total model-estimated wellfield yield •3,900 –5,700 gpm •Well yield per well goes up with less wells in the CWF •Wellfield yields are limited by (1) quality of the aquifer and (2) area available for wellfield development TRANSIENT MODELING •Converted the model into a transient model. •Incorporated the cities demand curve into the potential wells (based on an 8000 gpm peak demand). •Simulated using a low transmissivity combined with a low specific storage and a high transmissivity combined with a higher specific storage. •Low storage: was derived from the Metro Model 3 dataset (1x10-6 m-1) •Higher storage: was derived from a two well pumping test conducted in Otsego (7x10-6 m-1) Table. Total Wellfield Yields Scenario Minimum Total Yield (gpm)Maximum Total Yield (gpm) 12 Wells with 9 in CWF 2759 4197 20 Wells with 17 in CWF 3923 5738 0 1000 2000 3000 4000 5000 6000 7000 Total Yield (gpm)LowT_LowS_12 Well LowT_LowS_20 Well HighT_HighS_12 Well HighT_HighSs_20 Wells Figure Modeled Pumping Rate From Chicot Aquifer 1221 Auraria Parkway, Denver, CO 80204 TRANSIENT WELL YIELDS WITH DEMAND CURVE INCLUDED Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 1 of 13 ~ Technical Memorandum: Treatment and Distribution Alternative Development Otsego Central Wellfield Implementation Planning To: Kurt Neidermeier Utility Manager City of Otsego From: Ryan Hanson, PE Scott Schaefer, PE AE2S Date: May 1, 2024 Project No: P05409-2022-007 1 ALTERNATIVES EVALUATION – WATER TREATMENT ALTERNATIVE DEVELOPMENT AND OBJECTIVES With the Central Wellfield (CWF) unable to produce the required supply for a larger collector water treatment plant (WTP) as previously planned, treatment alternatives need to be reevaluated to determine the best suited approach for the City. After analyzing Otsego’s distribution system layout, water source locations, and distribution modeling results, three (3) systemwide treatment alternatives were developed. The primary objectives of the treatment alternatives are to provide a treatment system to accommodate current/projected design service populations. As discussed in the Technical Memorandum – Basis of Planning, land use plans and historic demands were used to establish current and projected demands. Population and demand projections are summarized in Table 1.1. To meet future maximum day demands, the treatment alternatives were established to reliably deliver treated water capacity is capable supplying at least 22.6 MGD (15,700 gpm). Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 2 of 13 ~ Table 1.1 – Firm Capacity for Combined System Current Population Served (2023) 19,467 Current Peak Day Demand, MGD (2023) 6.7 Projected 2090 Population Served ~76,300 Projected 2090 Peak Day Demand, MGD ~22.6 The following factors were used for evaluating and sizing treatment facilities: · Capacity was based on projected water demands. · Proximity to existing wellhouses, wells, or future wellfields. · A computer model of the distribution system was used for evaluating each alternative and required transmission main location and size to meet desirable distribution pressures and available fire flows. An emphasis on a phased approach was used for evaluating treatment alternatives. A phased approach to systemwide treatment improvements has the following benefits: · Lowers initial investment; · Delays operation, maintenance and repair/replacement costs; · Reduces construction duration; · Provides flexibility for unforeseen growth patterns, either slower or faster than anticipated; and, · Provides flexibility to accommodate future regulatory requirements. All alternatives will require land acquisition and additional utility services costs (power, sanitary, natural gas, internet), which is not included in this analysis. 2 ALTERNATIVES EVALUATED The City-AE2S team considered many alternatives and variations in the initial alternatives development process and narrowed those considerations to three (3) alternatives for further consideration. Alternatives that were screened and deemed reasonable are further evaluated in this report. Each of the alternatives were hydraulically modeled based on an anticipated future distribution system grid to determine pipe size requirements. Thes alternatives evaluated include: · Alternative 1: Dispersed WTP System · Alternative 2: Two Larger WTPs · Alternative 3: Surface Water WTP 3 ALTERNATIVE 1: DISPERSED WTPS This treatment alternative proposes individual treatment facilities to be constructed within the vicinity of each existing pumping facility. Where possible, existing pumping facilities could be upgraded or expanded to include pressure filtration. In addition, the proposed CWF would be split into a North Wellfield (NWF) and a South Wellfield (SWF) that would each supply a WTP. A Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 3 of 13 ~ summary of the proposed treatment facilities and their resulting capacity for this alternative are summarized in Table 3.1. To reliably deliver enough water during peak days, the treatment is sized for a treated firm capacity (largest well out of service) that exceeds the projected maximum day demand. Table 3.1 - Alternative 1: Dispersed WTPs - Treatment Plant Sizing Water Treatment Plant Water Source[1] Treated Capacity[2] Wellhouse 1 WTP Wellhouse 1 & New TCW Well 2,600 gpm (3.7 MGD) Wellhouse 2 WTP Wellhouse 2 & New TCW Well 1,900 gpm (2.7 MGD) Wellhouse 3 WTP Wellhouse 3[3] 2,200 gpm (3.2 MGD) Wellhouse 4 WTP Wellhouse 4 1,700 gpm (2.4 MGD) North Wellfield WTP Nine (9) New TCW Wells 4,500 gpm (6.5 MGD) South Wellfield WTP Eight (8) New TCW Wells 4,000 gpm (5.8 MGD) Total Treated Water Supply 16,900 gpm (24.3 MGD) Firm Treated Water Supply 15,700 gpm (22.6 MGD) [1] New Tunnel City-Wonewoc (TCW) wells are assumed to average 500 gpm each in capacity. [2] Treated capacities are calculated using actual pumping capacities of wellhouses. [3] Depending on location of WTP, an additional TCW well may be possible to supply treatment plant. Figure 3.1 depicts conceptual locations of the WTPs and the resultant hydraulic modeling results for the distribution system. In total, Alternative 1 proposes that six (6) treatment facilities be constructed to provide systemwide treatment. This alternative allows each treatment facility to be tailored to the specific water quality at the site-specific wells to treat accordingly, as well as provide a better option for phased implementation based on need for treatment. Some other considerations for this alternative include the following: · Positives: o Best option for utilization of existing wellhouses and associated infrastructure. o Dispersed treatment spread across the City allows more operational flexibility to manage water demands. o Decrease transmission main diameters. o Closer proximity to wells will result in decreased raw watermain costs. o Smaller WTPs at the wellhouses could allow for pressure filtration which typically reduces the overall capital cost and operational costs for those WTPs. · Negatives: o Higher overall operational costs to maintain more WTPs. o Limited space available for WTPs near existing wellhouses that could result in the need to procure land. o More WTPs makes retrofitting treatment to adapt to changing regulations more challenging. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 4 of 13 ~ Figure 3.1 – Treatment Alternative 1: Dispersed Treatment Note: All WTP locations are conceptual and will require further analysis for siting. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 5 of 13 ~ 4 ALTERNATIVE 2: TWO LARGER WTPS This treatment alternative proposes two larger WTPs. Existing and future wells would pump to two larger centrally located WTPs. The most economical approach would be to have Wellhouse 1 convey to a larger East WTP, while Wellhouse 3 would convey to a West WTP for treatment. Due to the location and difficulty connecting Wellhouse 2 to the East WTP, it was assumed that this wellhouse and associated wells would be decommissioned. As for Wellhouse 4, it will remain independent as this project is already in the design phase. A summary of the proposed treatment facilities and their resulting capacity for this alternative are summarized in Table 4.1. To reliably deliver enough water during peak days, the treatment is sized for a treated firm capacity (largest well out of service) that exceeds the projected maximum day demand. Table 4.1 - Alternative 2: Two Large WTPs - Treatment Plant Sizing Water Treatment Plant Water Source[1] Treated Capacity[3] Wellhouse 4 WTP Well 7 & 10 1,700 gpm (2.4 MGD) West WTP Wells 4, 5, 11, Eight (8) New TCW Wells, One (1) New Mt. Simon Well[2] 7,200 gpm (10.4 MGD) East WTP Wells 3, 8, 6, 9 & Nine (9) New TCW Wells 8,000 gpm (11.5 MGD) Total Treated Water Supply 16,900 gpm (24.3 MGD) Firm Treated Water Supply 15,700 gpm (22.6 MGD) [1] New Tunnel City-Wonewoc (TCW) wells are assumed to average 500 gpm each in capacity. [2] New Mt. Simon well to replace Well 8. New well assumed to average 1,000 gpm each in capacity. [3] Treated capacities are calculated using actual pumping capacities of wellhouses. Figure 4.1 depicts conceptual locations of the WTPs and the resultant hydraulic modeling results for the distribution system. In total, Alternative 2 proposes that three (3) treatment facilities be constructed to provide systemwide treatment. This alternative greatly reduces the number of facilities needed while still allowing for phased implementation based on need for treatment. Some other considerations for this alternative include the following: · Positives: o Less WTPs makes retrofitting treatment to adapt to changing regulations easier. o WTP siting for the East and West WTP is flexible. o Less WTPs consolidates operations and results in reduced operational costs. o Dispersed treatment spread across the City allows more operational flexibility to manage water demands. · Negatives: o Larger flows near WTPs require increased transmission main diameters. o Longer distance from existing wellhouses and potential future wells results in increased raw watermain costs. o Larger WTPs would likely be best suited for gravity filtration versus pressure filtration, which increases the overall capital costs as operational costs for those WTPs. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 6 of 13 ~ Figure 4.1 – Treatment Alternative 2: Two Larger WTPs Note: All WTP locations are conceptual and will require further analysis for siting. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 7 of 13 ~ 5 ALTERNTIVE 3: SURFACE WATER WTP This treatment alternative proposes a centralized treatment facility to treat surface water. Preliminary siting proposes that the surface water facility is most feasible to be located in the north central or northeast part of the City. Surface water could then be pulled from the Mississippi and/or a series of collector wells along the river. To supplement the surface water facility, this alternative also proposes that Wellhouse 3 and Wellhouse 4 would be treated, while Wellhouse 1 and Wellhouse 2 would be decommissioned. A summary of the proposed treatment facilities and their resulting capacity for this alternative are summarized in Table 5.1. To reliably deliver enough water during peak days, the treatment is sized for a treated firm capacity (largest well out of service) that exceeds the projected maximum day demand. Table 5.1 - Alternative 4: Surface Water Treatment - Treatment Plant Sizing Water Treatment Plant Water Source Treated Capacity Wellhouse 4 WTP Well 7 & 10 1,700 gpm (2.4 MGD)[2] Wellhouse 3 WTP Wells 4, 5, & 11 2,200 gpm (3.2 MGD)[2] Central WTP Mississippi River/Collector Wells[1] 12,800gpm (18.5 MGD) Total Treated Water Supply 16,700 gpm (24.2 MGD) Firm Treated Water Supply 15,700 gpm (22.6 MGD) [1] Collector wells are considered under the influence of surface water and are treated as a surface water source. [2] Treated capacities are calculated using actual pumping capacities of wellhouses. Figure 5.1 depicts conceptual locations of the WTPs and the resultant hydraulic modeling results for the distribution system. In total, Alternative 3 proposes that three (3) treatment facilities be constructed to provide systemwide treatment. The addition of treatment at Wellhouse 3 and Wellhouse 4 allows for the City to meet average day demands until the City is ready for the surface water facility. Some other considerations for this alternative include the following: · Positives: o Less wells results in reduced raw watermain costs. o Surface water is considered a more sustainable water supply. o Less WTPs consolidates operations and results in reduced operational costs. o Provides softened water at the centralized facility, which results in decreased in home softeners sending chlorides to the waste water treatment facility. o Less WTPs makes retrofitting treatment to adapt to changing regulations easier. o Siting for the surface water WTP is flexible. · Negatives: o Surface water is more susceptible to changing water quality conditions. o Significantly higher operations and maintenance costs to operate a lime softening WTP. o Increased staff and staff training to operate a surface water WTP. o Larger flows near WTPs require increased transmission main diameters. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 8 of 13 ~ Figure 5.1 – Treatment Alternative 3: Surface Water Treatment Note: All WTP locations are conceptual and will require further analysis for siting Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 9 of 13 ~ 6 OPINIONS OF PROBABLE COSTS – WATER TREATMENT ALTERNATIVES The construction cost estimates presented are based on 2024 dollars. Detailed financial analysis should provide an inflation factor, which is checked and adjusted annually through the life of the facilities. The conceptual opinion of probable cost was developed based on previous project data. This cost opinion represents a Class 4 Estimate based on the definitions of the Association for Advancement of Cost Engineering (AACE) International. This level of cost opinion is appropriate for planning level evaluations made with incomplete information. The cost opinion at this level of engineering is considered to have an accuracy range of +50/-30 percent. More accurate costs cannot be determined until a design process has been completed. The alternatives presented may require the procurement of additional land. Engineering (design, bidding, and construction) and legal/administrative were assumed to be approximately 15 percent of construction costs. Construction contingency was assumed to be 20 percent. A summary of probable construction and capital costs for water treatment alternatives are presented in Table 6.1. Additional storage and booster station long-term planning are included in all three scenarios. Table 6.1 - Opinion of Probable Construction and Capital Costs – (2024 $) Item Total Probable Cost (w/ Contingency & Engineering) Alternative 1: Dispersed System Alternative 2: Two Large WTPs Alternative 3: Surface Water WTP Wells $28,980,000 $28,980,000 - Decommission Wells/Wellhouses - $552,000 $1,208,000 Raw Watermain $19,174,000 $31,504,000 $16,920,000 Surface Water Intake / Collector Wells - - $17,250,000 Water Supply Subtotal $48,154,000 $61,036,000 $35,378,000 Finished Watermain $45,683,000 $72,398,000 $76,443,000 Storage $33,120,000 $33,120,000 $33,120,000 Booster Station $5,520,000 $5,520,000 $5,520,000 PRV $1,725,000 $2,070,000 $1,725,000 Distribution System Subtotal $86,048,000 $113,108,000 $116,808,000 Treatment $115,575,000 $89,355,000 $166,290,000 Treatment Subtotal $115,575,000 $89,355,000 $166,290,000 Total Probable Cost $249,777,000 $263,499,000 $318,476,000 7 RECOMMENDATION The above information for the multiple alternatives including layouts, costs, advantages, and disadvantages was presented to the City of Otsego’s Public Works Subcommittee. After reviewing the three alternatives and associated capital costs with the City, it was determined that a Kepner-Tregoe analysis is not necessary and Alternative 1: Dispersed Treatment should be pursued. This alternative allows each treatment facility to be tailored to the specific water quality Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 10 of 13 ~ at the site-specific wells to treat accordingly, as well as provide a better option for phased implementation based on need for treatment. 8 PHASING PLAN Development of a phasing plan is a critical component of a water system plan document and the planning process. The water infrastructure phasing plan will follow the Alternative 1: Dispersed Treatment system plan and include major capital improvement projects and their anticipated initiation/operational year. The following factors are the primary considerations in determining when specific equipment and phase initiations are required for facilities: · Capacity: Any time a critical facility approaches capacity, a new phase is required (unless it is determined with certainty that no additional growth will occur). Capacity is not the only phasing factor; however, it is the primary driver for many phase initiations. · Regulatory: While it is possible that regulatory phasing factors may coincide with capacity requirements, regulatory requirements on their own are a factor. They can dictate the decision to move to a new technology or add a unit process in an earlier phase rather than expand using existing technology. Additionally, regulatory expectations can allow for specific items to be planned for, but not provided/built until later phases. · Miscellaneous: Additional drivers, such as current deficiencies or deficiencies that develop between phases, may exist and require smaller scale, interim projects to address outside of the major phases. Discussion of these items is limited in this memorandum to existing issues. · Age/Condition: The age and condition of existing facilities can be a driver for capital projects. Age/condition will be a trigger for equipment maintenance or replacement. Age and condition is a more common project driver for systems that are not experiencing growth and the associated capacity expansions, but age and condition items are often addressed during projects with Capacity or Regulatory drivers. It should be noted that it is common for two or more of these project drivers to be present when a project is initiated. 8.1 Wells, Storage, WTP & Distribution System The addition of wells, towers, WTPs and resulting trunk watermains will be dependent on population growth and resulting water demands. Following Alternative 1, a long-range phasing plan of the key projects that are anticipated through 2090 is provided in Figure 8.1. Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 11 of 13 ~ Figure 8.2 – Long-Range Phasing Plan Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 12 of 13 ~ 8.1.1 Wells & Treatment Figure 8.1 shows the projected average and maximum day demands with a range of residential usages between 75 and 100 gallons per capita per day (GPCD), to allow for flexibility of meeting the DNR’s per capita demand goal. The City is striving to provide WTP capacity (i.e. delivered water that has receive filtration treatment) to meet maximum day demands as quickly as possible, which are phased to meet average day demands by 2027 with the addition of the Wellhouse 3 WTP and maximum day demands by 2035 with Phase 2 of the South Central WTP. After the addition of Well 11, the timing of future water supply wells is determined by the timing of specific water treatment plants. It is important to provide enough well total capacity to ensure that well firm capacity remains about maximum day demands. Future well locations and associated capacities will need to be analyzed further in future studies. For this analysis, it was assumed that all future wells will have a capacity of 500 gpm. 8.1.2 Storage The proposed timing of storage facilities is determined by increasing demands and are typically sized to provide: 1) Equalization Storage – to meet hourly system water demands exceeding supply pumping capacity, 2) Fire Protection Storage – to meet the demands of firefighting, and 3) Emergency Storage – to provide water reserves for contingencies such as system failures, power outages, and other emergencies. Figure 8.2 shows the projected water storage requirements through 2090 and the associated expected timing of additional storage. The actual timing of storage improvements will be dependent on actual population growth rates and demands, as well as phasing of treatment plants. Figure 8.1 – Water Storage Timing (2025-2090) 0 2 4 6 8 10 12 2025 2030 2035 2040 2045 2050 2055 2060 2065 2070 2075 2080 2085 2090System Storage Volume (MG)Year Total Storage Needed Existing Tower #3 Existing Tower #4 New South Central WTP - Phase 1 Clearwell New Tower #5 New North Central WTP Clearwell New Tower #6 Existing Tower #2 Existing Tower #1 Water Treatment Alternative Development City of Otsego, MN P05409-2022-007 ~ 13 of 13 ~ 8.2 Phasing 20-Year Phasing Plan Table 8.1 presents the project planning timelines projected to occur within the next 20 years. Updated costs can be found in the City’s Capital Improvements Plan. Table 8.1 – City of Otsego’s Water Infrastructure 20-Year Phasing Plan Phase Capital Improvements Project Projected Project Initiation Year Projected Project On-Line Year Treatment for Wellhouse No. 3 Well 11 & Raw Water Main 2024 2025 Wellhouse No. 3 Water Treatment Plant 2024 2026 Trunk Watermain Improvements for WTP (Minimum) 2024 2026 South Central Water Treatment Plant - Phase 1 New South Central WTP 2024 2028 Clearwell (1.5 MG) 2024 2028 Trunk Watermain Improvements for WTP (Minimum) 2026 2028 Four (4) New Wells & Raw Water Main 2026 2028 South Central Water Treatment Plant - Phase 2 Four (4) New Wells & Raw Water Main 2033 2035 Treatment for Wellhouse No. 1 Wellhouse No. 1 Water Treatment Plant 2037 2040 New Well & Raw Water Main 2038 2040 Trunk Watermain Improvements (Minimum) for WTP 2038 2040 Distribution System Needs Additional Trunk Watermain Improvements (Development Driven) 2024 2040 Tower 5 (1.5 MG) 2040 2042