Water Systems Study - Mount Pleasant, Michigan€¦ · Water Systems Study . Prepared For: Charter Township of Union, Michigan City of Mount Pleasant, Michigan . July 26, 2019 Project

Project No. 180984 July 26, 2019

Water Systems Study

Prepared for: Charter Township of Union

City of Mount Pleasant, Michigan

Fishbeck, Thompson, Carr & Huber, Inc. engineers | scientists | architects | constructors

Water Systems Study

Prepared For: Charter Township of Union, Michigan

City of Mount Pleasant, Michigan

July 26, 2019 Project No. 180984

Table of Contents

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1.0 Executive Summary .......................................................................................................................................1

2.0 Introduction ...................................................................................................................................................5

3.0 Overview of Existing Systems ........................................................................................................................6 3.1 Charter Township of Union Overview ..............................................................................................6

3.1.1 Township System Description .............................................................................................6 3.1.2 Township Well System and Capacity ...................................................................................6 3.1.3 Township Treatment Facilities ............................................................................................6 3.1.4 Township Distribution System ............................................................................................7 3.1.5 Existing System Demands ....................................................................................................7 3.1.6 Projected System Demands ................................................................................................8 3.1.7 Water Storage Assessment .................................................................................................8

3.2 City of Mount Pleasant Overview .....................................................................................................9 3.2.1 City System Description .......................................................................................................9 3.2.2 City Well System and Capacity ............................................................................................9 3.2.3 City Treatment Facility ........................................................................................................9 3.2.4 City Reservoir and High Service Pumping Station ............................................................ 10 3.2.5 City Distribution System ................................................................................................... 10 3.2.6 Existing System Demands ................................................................................................. 10 3.2.7 Projected System Demands ............................................................................................. 11 3.2.8 Water Storage Assessment .............................................................................................. 11

4.0 Water Quality and Regulatory Review ....................................................................................................... 12 4.1 Water Quality Standards ............................................................................................................... 12 4.2 NPDES Discharge Standards .......................................................................................................... 12 4.3 Capacity Requirements ................................................................................................................. 13

5.0 Township Water Treatment ....................................................................................................................... 14 5.1 Current Process Stream ................................................................................................................. 14 5.2 Conceptual Basis of Design............................................................................................................ 14 5.3 Siting Considerations and Criteria ................................................................................................. 15 5.4 Raw Water Supply Expansion ........................................................................................................ 15

5.4.1 Raw Water Supply Expansion Costs ................................................................................. 15 5.5 Water Treatment Objectives ......................................................................................................... 16 5.6 Water Softening Technologies ...................................................................................................... 16

5.6.1 Ion Exchange Softening .................................................................................................... 16 5.6.2 Lime Softening .................................................................................................................. 17 5.6.3 Membrane Softening ....................................................................................................... 18

5.7 Water Treatment Alternatives Development ............................................................................... 20 5.7.1 Ion Exchange Softening with Pretreatment ..................................................................... 20 5.7.2 Lime Softening – Single Stage Treatment ........................................................................ 21 5.7.3 Membrane Softening with Pretreatment ........................................................................ 23

5.8 Waste Stream Disposal Discussion ................................................................................................ 25 5.8.1 Backwash Disposal ........................................................................................................... 25

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5.8.2 Ion Exchange Brine Discharge Stream Alternatives ......................................................... 25 5.8.3 Lime Residuals Disposal Alternatives ............................................................................... 26 5.8.4 Membrane Concentrate Disposal Alternatives ................................................................ 26 5.8.5 Township Wastewater Treatment Plant .......................................................................... 27

5.9 Treatment Alternatives Comparison ............................................................................................. 31 5.9.1 Water Quality Comparison ............................................................................................... 31 5.9.2 Economic Comparison ...................................................................................................... 31

5.10 Township Distribution System Reconfiguration ............................................................................ 32 5.10.1 Existing Township System ................................................................................................ 32

5.10.1.1 System Description ....................................................................................... 32 5.10.1.2 Hydraulic Modeling ....................................................................................... 32

5.10.2 Improved Township System ............................................................................................. 33 5.10.2.1 System Description ....................................................................................... 33 5.10.2.2 Hydraulic Modeling ....................................................................................... 33

5.10.3 Water Storage Assessment .............................................................................................. 34 5.11 Additional Operations and Maintenance Costs ............................................................................ 35 5.12 Project Phasing Considerations ..................................................................................................... 35

5.12.1 Project Phasing Overview ................................................................................................. 35 5.12.2 Phase One 36

5.12.2.1 Phase One Projects Description .................................................................... 36 5.12.2.2 Phase One Projects Costs ............................................................................. 36

5.12.3 Phase Two 37 5.12.3.1 Phase Two Projects Description ................................................................... 37 5.12.3.2 Phase Two Projects Costs ............................................................................. 37

6.0 Township Receives Softened Water from City ........................................................................................... 38 6.1 Current Process Stream ................................................................................................................. 38 6.2 Conceptual Basis of Design............................................................................................................ 38 6.3 Raw Water Supply Expansion ........................................................................................................ 39

6.3.1 Addition of Township Wells Evaluation ........................................................................... 39 6.3.2 Additional Well Development .......................................................................................... 41 6.3.3 Raw Water Supply Expansion Costs ................................................................................. 41

6.4 Siting Considerations and Criteria ................................................................................................. 41 6.5 City Water Treatment Facility Expansion ...................................................................................... 41

6.5.1 Aeration System ............................................................................................................... 42 6.5.2 Clarification System .......................................................................................................... 42 6.5.3 Recarbonation System ..................................................................................................... 42 6.5.4 Filtration System .............................................................................................................. 42 6.5.5 Backwash Disposal ........................................................................................................... 42 6.5.6 Lime Sludge Disposal ........................................................................................................ 42 6.5.7 Chemical Feed Modifications ........................................................................................... 43 6.5.8 Instrumentation and Control ........................................................................................... 43 6.5.9 Advantages and Disadvantages for Township and City ................................................... 43 6.5.10 City Plant Expansion Costs................................................................................................ 44

6.6 Finished Water Pumping and Storage ........................................................................................... 44

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6.6.1 Existing Reservoir and High Service Pumping Station ...................................................... 44 6.6.2 Additional Storage and New High Service Pumping Station ............................................ 45 6.6.3 Finished Water Pumping and Storage Costs .................................................................... 45

6.7 Distribution System Evaluation ..................................................................................................... 46 6.7.1 Booster Pumping Stations ................................................................................................ 47 6.7.2 Water Storage Assessment .............................................................................................. 47

6.7.2.1 Combined System Storage Assessment ........................................................ 47 6.7.2.2 City System Storage Assessment .................................................................. 48 6.7.2.3 Township System Storage Assessment ......................................................... 48

6.7.3 Hydraulic Modeling Analysis ............................................................................................ 49 6.7.3.1 City System Modeling Analysis ..................................................................... 49 6.7.3.2 Combined System Modeling Analysis ........................................................... 50

6.7.4 Distribution System Costs ................................................................................................ 50 6.8 Additional Operations and Maintenance Costs ............................................................................ 51 6.9 Project Phasing Considerations ..................................................................................................... 52

6.9.1 Project Phasing Overview ................................................................................................. 52 6.9.2 Phase One ......................................................................................................................... 53

6.9.2.1 Phase One Projects Description .................................................................... 53 6.9.2.2 Phase One Projects Costs ............................................................................. 53

6.9.3 Phase Two ........................................................................................................................ 54 6.9.3.1 Phase Two Projects Description ................................................................... 54 6.9.3.2 Phase Two Projects Costs ............................................................................. 55

7.0 City Low Pressure Area ............................................................................................................................... 56 7.1 Water Main Improvements ........................................................................................................... 56 7.2 Boosting Pressure from City .......................................................................................................... 56

7.2.1 City Booster Station Sizing ................................................................................................ 56 7.2.2 City Booster Station Costs ................................................................................................ 57

7.3 Township Supply ........................................................................................................................... 57 7.3.1 Township Supply Description ........................................................................................... 57 7.3.2 Township Supply Cost Estimate ....................................................................................... 58

8.0 Financial Impacts ........................................................................................................................................ 59 8.1 Project Capital Costs ...................................................................................................................... 59 8.2 Operation and Maintenance Costs................................................................................................ 60 8.3 Revenue Requirements ................................................................................................................. 61

8.3.1 Development of Recommended Rate Track .................................................................... 61 8.3.2 Explanation of Information in Rate Tracks ....................................................................... 62

8.4 Recommended Rate Tracks ........................................................................................................... 63 8.4.1 Township Softening Rate Tracks ...................................................................................... 63

8.4.1.1 Township Ion Exchange Softening Rate Track .............................................. 63 8.4.1.2 Township Lime Softening Rate Track ............................................................ 64 8.4.1.3 Township Membrane Softening Rate Track ................................................. 65

8.4.2 City Providing Softened Water Rate Tracks ..................................................................... 66 8.4.2.1 City Providing Softened Water City Rate Track ............................................ 67 8.4.2.2 City Providing Softened Water Township Rate Track ................................... 68

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8.4.2.3 Wholesale Rate Study Discussion ................................................................. 69 8.4.3 Boosting Pressure to City’s Southern Area Water Rate Tracks ........................................ 69

8.4.3.1 City Booster Station Rate Track .................................................................... 69 8.4.3.2 Township Supply Southern Area of City System Rate Track ......................... 70

9.0 Rate Implications ........................................................................................................................................ 72

10.0 Conclusions and Recommendations .......................................................................................................... 73

List of Abbreviations/Acronyms

FTCH Fishbeck, Thompson, Carr & Huber, Inc. gpm Gallons Per Minute gr/gal grains per gallon RO Reverse Osmosis NF Nanofiltration MG million gallons mgd million gallons per day mg/L milligrams per liter MCL maximum contaminate level NPDES National Pollutant Discharge Elimination System ppm parts per million USEPA United States Environmental Protection Agency List of Tables

Table 1 - Softening Options Capital Costs Comparison ..............................................................................................1 Table 2 – Projected Rate Change Comparison ...........................................................................................................2 Table 3 – Township Wells and Permitted Capacities .................................................................................................6 Table 4 - Township Average Hydraulic Grade and Pressure Ranges ..........................................................................7 Table 5 – Current Township Water Demands ............................................................................................................7 Table 6 – Projected 2038 Township Water Demands ................................................................................................8 Table 7 – City Active Wells and Permitted Capacities ................................................................................................9 Table 8 - City Average Hydraulic Grade and Pressure Range .................................................................................. 10 Table 9 – City Existing Water Demands ................................................................................................................... 10 Table 10 – City 2038 Projected Water Demands .................................................................................................... 11 Table 11 - Township Raw Water Supply Expansion Costs ....................................................................................... 16 Table 12 – Township Ion Exchange Softening Flows ............................................................................................... 17 Table 13 – Township Membrane Softening Flows .................................................................................................. 20 Table 14 – Ion Exchange Advantages and Disadvantages ....................................................................................... 21 Table 15 – Ion Exchange Softening Key Components ............................................................................................. 21 Table 16 – Lime Softening Advantages and Disadvantages .................................................................................... 23 Table 17 – Lime Softening Key Components ........................................................................................................... 23 Table 18 – Membrane Advantages and Disadvantages .......................................................................................... 24 Table 19 – Membrane Softening Key Components ................................................................................................. 25 Table 20 – Township WWTP Projected Average Wastewater Flows ...................................................................... 28 Table 21 – Existing and Projected Peak Hour Flows for Collection System ............................................................ 29 Table 22 - WTP Downstream Pipe Capacities .......................................................................................................... 29

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Table 23 – Wastewater Collection System Peak Flows ........................................................................................... 30 Table 24 - Softening Options Costs Comparison ..................................................................................................... 31 Table 25 - Township Softening Options Additional O&M Costs .............................................................................. 35 Table 26 - Phase One Projects Estimated Costs ...................................................................................................... 37 Table 27 - Phase Two Projects Estimated Costs ...................................................................................................... 37 Table 28 – City and Township Water Demands ...................................................................................................... 39 Table 29 – Existing Deerfield Wells Hydraulics ........................................................................................................ 40 Table 30 – Addition of Mission Well Field Hydraulics ............................................................................................. 40 Table 31 - Raw Water Supply Expansion Costs ....................................................................................................... 41 Table 32 – City Supplied Softened Water Advantages and Disadvantages ............................................................. 43 Table 33 - Plant Expansion Costs ............................................................................................................................. 44 Table 34 - Finished Water Pumping and Storage Costs .......................................................................................... 46 Table 35 - Distribution System Costs ....................................................................................................................... 51 Table 36 - Additional O&M Costs for City ................................................................................................................ 52 Table 37 - Additional O&M Costs for Township ...................................................................................................... 52 Table 38 – Phase One Projects Estimated Costs ..................................................................................................... 54 Table 39 – Phase One Township Only Estimated Costs .......................................................................................... 54 Table 40 – Phase Two Projects Estimated Costs ..................................................................................................... 55 Table 41 - City Booster Station Costs ...................................................................................................................... 57 Table 42 – Township Supply Costs .......................................................................................................................... 58 Table 43 - Softened Water Alternatives Estimated Costs ....................................................................................... 59 Table 44 - Comparison of O&M Costs ..................................................................................................................... 60 Table 45 – Township Ion Exchange Softening Alternative Rate Track .................................................................... 64 Table 46 – Township Lime Softening Alternative Rate Track .................................................................................. 65 Table 47 – Township Membrane Softening Alternative Rate Track ........................................................................ 66 Table 48 – City Wholesale Rate Estimate ................................................................................................................ 67 Table 49 – City Provide Softened Water City Rate Track ........................................................................................ 67 Table 50 – City Provide Softened Water Township Rate Track ............................................................................... 68 Table 51 – City Booster Station for Southern Area Rate Track ............................................................................... 70 Table 52 – Township Supply Southern Area of City System Rate Track for City ..................................................... 70

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List of Figures

Figure 1 – Union Township Existing System Figure 2 – Flow Schematic Figure 3 – Mount Pleasant Existing System Figure 4 – Iron Removal Process Diagram Figure 5 – Possible Future Well Locations Figure 6 – Ion Exchange System Figure 7 – Lime Softening Schematic Figure 8 – Membrane Softening Schematic Figure 9 – Ion Exchange Conceptual Site Plan Figure 10 – Lime Softening Conceptual Site Plan Figure 11 – Membrane Softening Conceptual Site Plan Figure 12 – Union Township Sanitary System Figure 13 – Union Alone Existing Peak Hour 2017 Figure 14 – Union Alone Existing Peak Hour 2038 Figure 15 – Union Existing MDD 2017 Figure 16 – Union Alone Existing MDD 2038 Figure 17 – Union Township Updated Figure 18 – Union Alone Improvements Peak Hour 2038 Figure 19 – Union Alone Improved Peak Hour 2038 Figure 20 – Union Alone Improved MDD 2038 Figure 21 –Union Alone Improved MDD 2038 Figure 22 – City Raw Water System Figure 23 –MTP Plant Expansion Schematic Figure 24 – MTP Plant Lower Level Plan Figure 25 – MTP Plant Upper Level Plan Figure 26 – New Chemical Building Figure 27 –New Reservoir and HSPS Figure 28 – Combined Distribution System Figure 29 – Mount Pleasant Existing Peak Hour 2015 Figure 30 – Mount Pleasant Existing Peak Hour 2038 Figure 31 – Mount Pleasant Existing MDD 2015 Figure 32 – Mount Pleasant Existing MDD 2038 Figure 33 – MTP Combined System Crawford MDD 2038 Figure 34 – Union Combined System Crawford MDD 2038 Figure 35 – MTP Combined System Broomfield MDD 2038 Figure 36 – Union Combined System Broomfield MDD 2038 Figure 37 – MTP Combined System Crawford Peak Hour 2038 Figure 38 – Union Combined System Crawford Peak Hour 2038 Figure 39 – MTP Combined System Broomfield Peak Hour 2038 Figure 40 – Union Combined System Broomfield Peak Hour 2038 Figure 41 – Low Pressure Area Booster Station

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1.0 Executive Summary The Charter Township of Union (Township) and the City of Mount Pleasant (City) retained Fishbeck, Thompson, Carr & Huber, Inc. (FTCH) to evaluate options to provide the Township’s residents with softened water and to provide the southern portion of the City water system with higher pressures. The goal used for the softening portion of the study was to soften water to between 50 to 150 milligrams per liter (mg/L) or 3 to 9 grains per gallon (gr/gal) of hardness. A target hardness of 120 mg/L, or 7 gr/gal, was used to size the equipment for each process considered. An existing hydraulic model of the City water system was used to evaluate different alternatives to provide higher pressures to the southern portion of the City system, including supplying that portion of the City system from the Township water system.

Two options were evaluated to provide softened water to the Township’s residents. The first option was to add additional treatment steps to the Township’s existing treatment system. Three alternatives were evaluated: Ion Exchange (IX), Lime Softening, and Reverse Osmosis Membrane Softening (RO). The second option was to have the City provide softened water to the Township. Both the Township and City water systems were evaluated based on water demand projections through the year 2038 to ensure the facilities were sized to handle future growth in the respective systems.

The alternatives for the Township-owned softening option require upgrades to the Township raw water supply system, the Isabella Treatment Facility, the sanitary system (where needed), and the water distribution system. The feasibility and cost of each softening alternative was evaluated.

The second option evaluated providing the Township’s residents with softened water from the City. As the Township operates at a higher hydraulic grade than the City, two booster pump stations are needed to pump water from the City to the Township. The City’s existing treatment plant and high service pumping facilities have enough available treatment capacity to meet both the Township’s and City’s current water demands. However, the demand projections developed for the combined system estimate that in 2026 the facilities would require expansion to accommodate demand growth in the Township.

Cost estimates were developed for each water softening alternative which included both capital costs and the additional operation and maintenance costs. The improvements for each were broken into phases which would be implemented over time, as required by the projected increases in water demand.

The estimated total project capital costs of each of these softening alternatives is shown in Table 1. Note, no Operation and Maintenance (O&M) costs are included in the table.

Table 1 - Softening Options Capital Costs Comparison

Softening Alternatives

Township Softening Expansion Option City Supply Option Ion Exchange

Softening Alternative

Lime Softening Alternative

Reverse Osmosis Softening

Alternative

City Supply Softened Water

Alternative Project Capital Costs $25,417,000 $30,178,000 $36,348,000 $46,929,000

The impact of these capital projects on rates was evaluated. Projected rate tracks were developed for the Township and City that would ensure financial stability of each utility if the Township were to proceed with one


of the alternatives. These rate tracks took several financial metrics into account including: Debt Coverage Ratio, Minimum Cash Reserves, and Optimal Operating Income. For the Township rate tracks, larger rate increases were shown over a period from 2019 – 2023. After 2023, rate increases were at a level similar to the inflation rate. The larger rate increases varied from 17.5% - 21.5% per year over the initial five-year period. The City rate track, in the case of supplying the Township, remained at steady rate increases intended to keep up with inflation until the City Water Treatment Plant and high service pumping facilities required expansion. At this point, rates were increased to maintain the target debt coverage ratio. Table 2 provides a summary of the projected rate adjustment for each of the alternatives.

Table 2 – Projected Rate Change Comparison

Fiscal Year

Township Ion Exchange Softening

Township Lime Softening

Township Reverse Osmosis Softening

City Supplies Softened Water

City Supplies Softened Water

Projected Township Rate Changes




Projected City Rate Changes

2019 17.50% 21.50% 20.50% 18.50% 2.70% 2020 17.50% 21.50% 20.50% 18.50% 2.70% 2021 17.50% 21.50% 20.50% 18.50% 2.70% 2022 17.50% 21.50% 20.50% 18.50% 2.70% 2023 17.50% 21.50% 20.50% 18.50% 2.70% 2024 2.70% 2.70% 2.70% 2.70% 2.70% 2025 2.70% 2.70% 2.70% 2.70% 2.70% 2026 2.70% 2.70% 2.70% 2.70% 2.70% 2027 2.70% 2.70% 2.70% 2.70% 6.50% 2028 2.70% 2.70% 2.70% 2.70% 6.50% 2029 2.70% 2.70% 2.70% 2.70% 6.50% 2030 2.70% 2.70% 2.70% 2.70% 6.50% 2031 2.70% 2.70% 2.70% 2.70% 6.50%

The rate increases are not appreciably different between the options, suggesting that the Township can choose the option that is preferred based on factors other than the costs alone. It is recommended that the Township choose whichever option it considers to be the best for the Township moving forward. If the Township were to choose the option of receiving softened water from the City, it is recommended that the Township maintain their treatment facilities in working condition. If maintained, the Township’s treatment facilities could be used to provide water to the Township customers in the case of an emergency or for re-commissioning in the future.

There are benefits to the City to provide water to the Township as it will increase the City’s revenue in the short-term. The City water plant currently operates well below its design capacity. As demands increase with the Township connected, the plant capacity is projected to be exceeded in about 7 years, due to increases in water usage in the Township. The City plant would then need to be expanded. The intent is that the costs of the plant expansion would be paid for primarily by the Township. This study has assumed that the City would issue bonds to pay for the expansion, and that these costs would be recouped from the Township by water usage fees.

There are also rate increases to the City that occur in conjunction with the plant expansion. When the plant is expanded, it is also recommended that a new high service pumping station and reservoir be built at the plant. The need for this is two-fold. It is needed from a capacity standpoint, due to increased demands from the Township. It is also needed to replace the existing Island facility which is aging and in marginal condition, which


benefits the City. For this reason, it is assumed that some of the cost of the high service pumping station and reservoir would be paid by the City, through bonding and rate increases. These improvements are expected to be needed at some point, regardless of whether the Township connects. However, if the Township does not connect, the City would have more control over the timing of this project and could potentially choose to delay it further into the future.

One important factor to consider in comparing softened water treatment options is that the need to expand the City water plant depends on the timing of increases in demand. If demands in the Township increase more gradually than projected, the Phase Two projects, and their costs could be delayed. If the Phase Two project were delayed, the option of connecting to the City may become more attractive, compared to other options.

The study also developed recommendations for addressing a low-pressure issue in the southern portion of the City’s water system. The southern portion of the City water system is at a higher elevation and subsequently has low pressure problems. Three alternatives were evaluated to alleviate these problems. The first alternative was to replace any undersized pipes that were constricting flow to the southern portion of the system. The second alterative was a booster station designed to provide a higher pressure to the southern portion of the system, which would be isolated from the rest of the system, forming a new pressure district. The third alternative was to supply the southern portion of the City system from the Township, which runs at a higher pressure. In this case, the City would act as a wholesale customer of the Township.

For the first alternative, it was determined through hydraulic modeling that no “bottlenecks”, or undersized pipes, existed in the connection to the southern area of the system. The second alternative, a booster station at the boundary of the southern area of the system, was found to be viable with the addition of two Check Valve vaults installed at the northern end of the new pressure district that would open to allow flow into the district in the event of an emergency. For the third alternative, a 12-inch transmission main would be run across Deerfield Road to connect the Township system to the City system. A meter vault would be installed to measure the flow from the Township to the City. The southern portion of the City system would be isolated from the main part of the City system to create a new pressure district. In addition, two Check Valve vaults would be installed at the northern end of the new pressure district that would open to allow flow into the district in the event of an emergency.

Cost estimates and projected rate tracks were developed for these alternatives. For either option, only inflationary rate increases were recommended for the City. Either the second or third alternative is a viable option for the City water system in terms of both feasibility and financial soundness.

Future steps to implement treatment will require consideration and decisions by the Township. Next steps may include:

• The Township should decide whether to further pursue providing softened water to its customers.

• The Township should decide if expanding their plant to include softening or if connecting to the City is preferred.

• If connecting to the City is preferred, discussions on how to structure an agreement between the City and Township should begin. This step may include:


o Decide whether the Township would be wholesale customer, or whether an Authority would be formed.

o Discuss and negotiate rates.

o Complete a wholesale cost of service study.

• If the Township prefers to implement softening at its plant, the Township would decide which treatment option is preferred and develop that option in more detail. This could include pilot testing.


2.0 Introduction The Charter Township of Union (Township) and the City of Mount Pleasant (City) have retained Fishbeck, Thompson, Carr & Huber, Inc. (FTCH) to evaluate alternatives to provide the Township’s residents with softened water (water with between 50 to 150 milligrams per liter (mg/L) or 2.9 to 8.8 grains per gallon (gr/gal) of hardness). Currently, the Township provides its residents with unsoftened water. Two options to supply the Township with softened water were evaluated.

The first option investigated was to utilize the Township’s existing water system and add an additional treatment step at one or more of the Township treatment plants to soften the water. There were three treatment process alternatives to soften the water that were evaluated as part of the study including Reverse Osmosis (RO), Ion Exchange (IX), and Lime Softening. Each alternative was evaluated to determine the advantages and disadvantages of the treatment process, the feasibility of the treatment process, and the estimated costs of installing the treatment process.

The second option investigated was to have the Township obtain softened water from the City water system. The City system provides its customers with softened water through a single-stage lime softening WTP. The existing City treatment plant has excess treatment capacity that is not projected to be utilized in the future by the City customers. This approach included the installation of booster stations to provide water to the Township at a higher pressure, water main improvements to tie the Township and City system together initially, and an expansion of the City treatment plant and associated facilities occurring as water demand increases dictate. The advantages and disadvantage, the feasibility and cost of these improvements were evaluated.

An issue in the City water system was also addressed as part of this study. There is a portion of the City water system to the south that is at a higher elevation and subsequently has low pressure problems. Three alternatives were evaluated to provide higher pressures to this area including: replacing any water main “bottlenecks” preventing flow to the area, adding a booster station to boost pressures from the main portion of the City system, and connecting this area of the system to the Township which operates at a higher hydraulic grade line.


3.0 Overview of Existing Systems 3.1 Charter Township of Union Overview 3.1.1 Township System Description The Township’s water system includes seven wells in three well fields, three iron removal plants, three elevated water storage tanks, one ground storage tank, three control valve stations, and approximately 73 miles of water main. The Township’s system is relatively young, with construction beginning in the late 1980s.

3.1.2 Township Well System and Capacity The well system is comprised of seven wells, which are broken into three well fields. Well Nos. 3 and 4 supply the Meridian Treatment Facility and primarily serve the West Side Lower Pressure Zone. Well Nos. 1, 7, and 10 supply the Isabella Treatment Facility and Well Nos. 8 and 9 supply the Mission Treatment Facility. Both the Isabella and Mission Treatment Facilities primarily serve the Upper Pressure and Broadway Lower Pressure Zones. The Meridian Treatment Facility primarily serves the West Side Lower Pressure Zone. Water can be transferred between the pressure districts via control valve stations. The active wells and their capacities are as indicated in Table 3. It should be noted that the pumping rate allowed from some of the well fields is limited by aquifer restrictions.

Table 3 – Township Wells and Permitted Capacities

Well Field Name Well Name Individual Well Capacity (gpm) Total Well Field Capacity (gpm)

Meridian Well No. 3 380

*400 Well No. 4 380

Isabella Well No. 1 400

*1,100 Well No. 7 700 Well No. 10 400

Mission Well No. 8 400

800 Well No. 9 400 Total Capacity 3,060 Firm Capacity 2,000

The total capacity of all the wells is approximately 3,060 gpm or 4.41 million gallons per day (mgd) and the firm capacity, or capacity with the largest well out of service, is approximately 2,000 gpm or 2.88 mgd.

3.1.3 Township Treatment Facilities The Township currently operates three iron removal treatment facilities located as shown in Figure 1. Each facility utilizes sodium hypochlorite for oxidation of iron and disinfection, and phosphate for corrosion control. Each facility has dedicated Type 1 wells that pump through pressure filters. The Isabella Treatment Facility has an air scour system to aid in the backwash process for the pressure filters at the facility. The Isabella and Mission Treatment Facilities primarily serve the East Side Upper Pressure Zone and Broadway Lower Pressure Zone; the


Meridian Treatment Facility primarily serves the West Side Lower Pressure Zone. There are control valve stations that allow water to flow from the Upper Pressure Zone to the Lower Pressure Zones.

3.1.4 Township Distribution System The existing Township water distribution system consists of three pressure zones, three elevated tanks, one ground storage tank, and three control valve stations. There are control valves between all connected pressure districts that allow controlled flow between the districts.

The Upper Pressure Zone is supplied by the Isabella Treatment Facility, which is supplied by three wells and provides flow to the zone through three high service pumps, and the Mission Treatment Facility, which is supplied by two wells. For water storage, the Upper Pressure Zone utilizes the Deerfield Elevated Storage Tank and a ground storage tank at the Isabella Treatment Facility. This zone has the highest pressures in relation to the other pressure zones.

The West Side Lower Pressure Zone is supplied by the Meridian Treatment Facility, which is supplied by two wells. The Lincoln Elevated Storage Tank provides elevated storage for the west side lower pressure zone. This zone has higher pressures than the Broadway Lower Pressure Zone, but lower pressures than the Upper Pressure Zone.

The Broadway Lower Pressure Zone is supplied from the east pressure district through a control valve. The Broadway Elevated Storage Tank provides elevated storage for the zone.

A map of the existing Township water distribution system is shown in Figure 1.

Each pressure zone has an elevated tank that sets the available pressure throughout its zone. The elevated tank operating ranges and typical pressure ranges for each zone are helpful for understanding how the pressure zones within the Township compare to each other and to the City system. The typical operating pressures and elevated tank operating ranges for each of the Townships pressure zones are shown in Table 4.

Table 4 - Township Average Hydraulic Grade and Pressure Ranges

Pressure Zone Name Elevated Tank Name Elevated Tank Operating

Ranges Average Pressure

Ranges Upper Pressure Zone Deerfield 959.7 - 968.7 55 - 80 Lower Pressure Zone #1 (Broadway) Broadway 893.0 - 899.0 51 - 63 Lower Pressure Zone #2 (West Side) Lincoln 942.0 - 949.5 48 - 86

3.1.5 Existing System Demands The current Township average daily and maximum daily water demands were obtained from the 2017 Reliability Study. Table 5 shows the Township demands and the peaking factors between the average, maximum, and peak hour demands.

Table 5 – Current Township Water Demands

Water Demands Average Day

(mgd) Max Day

(mgd) Peak Hour

(mgd) ADD/MDD

Peaking Factor MDD/PHD

Peaking Factor Current Township Water Demands 0.94 2.36 5.64 2.51 2.33


3.1.6 Projected System Demands The Township 2036 projected average daily water demands were also obtained from the 2017 Reliability Study. The projected average daily water demands for 2038 were assumed to be equivalent to the 2036 demands. The 2038 projected maximum day demands were provided to FTCH by the Township for this study. It should be noted that the calculated 2038 average day to maximum day demand peaking factor was much higher than the peaking factor found in the 2017 Reliability Study. The peak hour demands were adjusted down to account for this higher peaking factor and in response to what FTCH perceived as a high initial estimate of the maximum day demand to peak hour demand peaking factor. The projected peak hour demands were obtained using a peaking factor of 1.5. Table 6 shows the projected Township demands.

Table 6 – Projected 2038 Township Water Demands

Water Demands Average

Day (mgd) Max Day

(mgd) ADD/MDD

Peaking Factor Peak Hour

(mgd) MDD/PHD

Peaking Factor Township Projected Water Demands 1.40 4.46 3.19 6.69 1.5

3.1.7 Water Storage Assessment Storage capacity for the Township system was evaluated to determine if the existing system provides adequate storage for when the projected demands are met. The calculations used were as follows:

(Equalization Storage) + (Higher of Fire Storage or Emergency Storage) = Required Storage -or-

Fire Storage + Emergency Storage = Required Storage

The greater of the two calculations was used for required storage. For equalization storage, which is intended to provide for operational flexibility to meet varying demands, a value of 25% of the MDD is generally accepted. The maximum fire flow requirement in the system is 3,500 gpm for 3 hours. The Township uses a fire flow value of 2,500 gpm for 2 hours as a requirement. Emergency storage, which considers major power outages or main breaks, or similar, considers the need for ADD storage for an extended duration. A 24-hour emergency was considered in this evaluation.

The projected ADD and MDD for the Township system are 1.40 mgd and 4.46 mgd, respectively. The equalization storage required is 1.12 MG. For fire flow, 2,500 gpm for 2 hours equals 0.30 MG. For emergency storage, a 24-hour emergency with ADD equals 1.40 MG. The needed storage for the Township will be equal to the emergency storage plus the equalization storage needed.

Entering the appropriate values in the above equation: 1.12 MG + 1.40 MG = 2.52 MG of storage is required. The Township system has three elevated tanks and a ground storage tank. The elevated tanks have volumes of 0.5, 0.2 & 0.2 MG, respectively. The ground storage tank has a volume of 0.50 MG. The tanks’ volumes together equal 1.4 MG of existing usable storage, which is less than the calculated required volume of storage for the Township system. From this evaluation, it appears that the Township would need to add 1.12 MG of additional storage to meet the projected demand 2038 requirements. This could be achieved with additional ground storage at the Isabella Facility, additional elevated storage, or some combination of the two.


3.2 City of Mount Pleasant Overview 3.2.1 City System Description The City’s water system includes six vertical wells in three well fields, a horizontal groundwater collector well, a lime softening WTP, two elevated water storage tanks, two ground storage tanks, a high service pump station, and approximately 89 miles of water main. The City system is older, with the average age of water main over 60 years old.

3.2.2 City Well System and Capacity The well system is comprised of six vertical wells and a horizontal collector well, which are broken into three well fields. The active wells and their capacities are as indicated in Table 7.

Table 7 – City Active Wells and Permitted Capacities

Well Field Name Well Name Well Capacity (gpm) Well Capacity

(mgd)

Broomfield Well No. 6 670 0.97

Well No. 20 500 0.72

Deerfield Well No. 16 620 0.89 Well No. 17 340 0.49

West Well No. 18 1,000 1.44 Well No. 19 1,000 1.44 Ranney Collector 2,050 2.95

Total Capacity 6,180 8.90 Firm Capacity 4,130 5.95

gpm – gallons per minute mgd – million gallons per day

The West Well Field is located at the Island Facility (Island). The West Well Field includes the Ranney Horizontal Collector Well, Well No. 18, and Well No. 19. It should be noted that Wells 18 and 19 cannot be operated at the same time due to issues with water quality and capacity; however, this does not affect the firm capacity of the raw water supply because the Ranney Collector is the largest well. The Broomfield Well Field is located south of Broomfield Street just east of the Intramural fields of Central Michigan University (CMU). The Broomfield Well Field contains Well Nos. 6 and 10. The Deerfield Well Field is located near the intersection of Deerfield and Mission Roads. The Deerfield Well Field contains Well Nos. 16 and 17.

3.2.3 City Treatment Facility The City Treatment Facility (WTP) is a single-stage lime softening treatment plant. The WTP has a treatment capacity of 8.25 mgd. Water is then conveyed to two ground storage reservoirs one with a volume of 1.0 MG and one with a volume of 2.0 MG, on the Island.

Raw water is supplied and conveyed to the WTP via the City well system. At the WTP, water is first passed through an aeration step to strip off carbon dioxide and reduce the quantity of softening chemical needed,


thereby reducing the volume of residuals produced. Softening chemicals including lime, soda ash, and ferric chloride are added to raise the pH and to precipitate Calcium and Magnesium Hardness. The water then flows by gravity to a set of two solids contact clarifiers, where flocculation, sedimentation, and clarification occur in each basin. The clarified water flows by gravity to a recarbonation tank where carbon dioxide is added to lower the pH of the water. The carbonated water is then filtered via two banks of dual media gravity filters with four filter cells each. The filters are periodically backwashed, the solids are removed, and the backwash water is routed to an onsite backwash seepage lagoon. Polyphosphate for corrosion control and Sodium Hypochlorite for disinfection are added to the filtered water. Fluoride is also added to the water before it flows by gravity out of the Plant to the Island. Fluoride is dosed to current standards, 0.6 – 0.7 parts per million (ppm). The City’s raw water has a naturally occurring fluoride concentration of 0.3 ppm. Note that the Township’s raw water shows a similar naturally occurring fluoride concentration.

A schematic of the existing City Plant is shown in Figure 2.

3.2.4 City Reservoir and High Service Pumping Station Finished water from the Plant runs through a gravity transmission main to two finished water reservoirs at the Island. A high service pump station on the Island pumps water from the finished water reservoirs to the City water distribution system using four high service vertical turbine pumps.

3.2.5 City Distribution System The existing distribution system has a single pressure district with two elevated storage tanks: the Isabella Road Elevated Tank with a volume of 1.0 MG, and the Kinney Avenue Elevated Tank with a volume of 0.5 MG. The existing City system is shown in Figure 3.

The elevated tank operating ranges and typical pressure ranges for the City are helpful for understanding how the City system operates. The typical operating pressures and elevated tank operating ranges for the City system are shown in Table 8.

Table 8 - City Average Hydraulic Grade and Pressure Range Pressure Zone Name Elevated Tank Name Average Hydraulic Grade Range Average Pressure Range

City Main Pressure District Kinney Street 885 - 899 41 - 65 Isabella Road 885 - 899

3.2.6 Existing System Demands The City’s existing average daily and maximum daily water demands were pulled from the 2015 Sanitary Survey. Peak hour demands were calculated by multiplying the maximum day demands by a peaking factor of 1.5. Table 9 shows the existing City demands.

Table 9 – City Existing Water Demands Water Demands Average Day (mgd) Max Day (mgd) Peak Hour (mgd)

City Existing Water Demands 1.79 3.29 4.94


3.2.7 Projected System Demands The City’s projected 2038 average daily and maximum daily water demands were also pulled from the 2015 Sanitary Survey. Projected peak hour demands were calculated by multiplying the maximum day demands by a peaking factor of 1.5. Table 10 shows the projected City demands.

Table 10 – City 2038 Projected Water Demands Water Demands Average Day (mgd) Max Day (mgd) Peak Hour (mgd)

City Projected Water Demands 2.00 3.69 5.54

Note that the City’s raw water and treatment plant’s firm capacities will be sufficient to meet the projected 2038 maximum day demands for the City’s customers alone.

3.2.8 Water Storage Assessment Storage capacity for the City system was evaluated to determine if the existing system provides adequate storage for when the projected demands are met. The calculations used were as follows:

(Equalization Storage) + (Higher of Fire Storage or Emergency Storage) = Required Storage -or-

Fire Storage + Emergency Storage = Required Storage

The greater of the two calculations was used for required storage. For equalization storage, which is intended to provide for operational flexibility to meet varying demands, a value of 25% of the MDD is generally accepted. The maximum fire flow requirement in the system is 3,500 gpm for 3 hours. Emergency storage, which considers major power outages or main breaks, or similar, considers the need for ADD storage for an extended duration. A 24-hour emergency was considered in this evaluation.

The projected ADD and MDD for the City system are 2.00 mgd and 3.69 mgd, respectively. The equalization storage required is 0.92 MG. The volume of storage needed to meet the fire flow requirement is 0.63 MG. For emergency storage, a 24-hour emergency with ADD equals 2.00 MG. The needed storage for the City will be equal to the emergency storage plus the equalization storage needed.

Entering the appropriate values in the above equation: 0.92 MG + 2.00 MG = 2.92 MG of storage is required. The City system has two elevated tanks and two ground storage tanks. The elevated tanks have volumes of 0.5 and 1.0 MG, respectively. The ground storage tanks have volumes of 1.0 & 2.0 MG. The storage tanks’ volumes together equal 4.5 MG of existing usable storage, which is more than the calculated required volume of storage for the City system. From this evaluation, it appears the City will not need to add additional storage to meet the requirements of their existing system at projected demands.


4.0 Water Quality and Regulatory Review 4.1 Water Quality Standards Public water supply requirements have been established by the Michigan Safe Drinking Water Act; Act 399, Public Acts of 1976 as amended; and associated Administrative Rules. The Michigan Maximum Contaminant Levels, Action Levels, Monitoring Requirements, etc. have been adopted from regulations developed by the U.S. Environmental Protection Agency (USEPA) under the authority of the federal Safe Drinking Water Act (SDWA) of 1974 and subsequent amendments in 1979, 1986 and 1996.

The federal maximum contaminant levels (MCLs) include Primary and Secondary MCLs. The Primary MCLs are related to health protection and include bacteriological, chemical, and physical contaminants. The Primary MCLs are enforceable by the Michigan Department of Environmental Quality (MDEQ) under authority of the Michigan and federal SDWAs.

The Secondary MCLs cover constituents that adversely affect the aesthetic quality of water, such as taste, odor, and appearance. Iron, manganese, and hardness are aesthetic concerns for which there are no enforceable drinking water standards, but only secondary guidelines. The Secondary MCLs for iron and manganese are 0.3 and 0.05 mg/L respectively.

MDEQ’s classification of different levels of hardness is as follows: Hardness (mg/L as CaCO3) Hardness (gr/gal as CaCO3) Classification 50 - 125 2.92 – 7.31 Excellent 125 - 250 7.31 – 14.62 Satisfactory Greater than 250 Greater than 14.62 Objectionable Most of the water systems FTCH has worked with elect to soften water to the 120 – 140 mg/L hardness level. For the purposes of this study, we have assumed a 120 mg/L (or 7.01 gr/gal) hardness level would be provided. The Township and City comply with USEPA and MDEQ regulations for public water suppliers. Contaminants of concern are outlined in the Federal Safe Drinking Water Act and the State of Michigan’s Act 399 and include Microbial, Inorganic, Pesticide and Herbicides, and Radioactive contaminants.

4.2 NPDES Discharge Standards Wastewater discharges associated with the production of potable water, such as from a chemical softening or iron and manganese removal process, require a National Pollutant Discharge Elimination System (NPDES) discharge permit. Discharge permits associated with the disposal of filter backwash water would need to be maintained for the respective treatment options.

This report also considers the discharge of membrane softening reject water, or concentrate, to either the Township Wastewater Treatment Plant via the sanitary sewer system or the Chippewa River. State regulations typically require that Total Dissolved Solids (TDS) concentrations discharged to a receiving stream be limited to 500 ppm on the average and no greater than 750 ppm as a maximum. Receiving stream National Pollutant Discharge Elimination System (NPDES) discharge permits typically require that the above criteria be met within the mixing zone of the stream at low flow conditions. Most membrane softening concentrate streams are


greater than 1,500 ppm TDS prior to dilution. The township would be required to show through modeling that they are not degrading the quality of the stream. A detailed study would need to be conducted to establish allowable effluent quantities and concentrations. If a discharge permit were to be obtained, the Township would be required to conduct routine monitoring of the effluent quantity and quality. Publicly Owned Treatment Works (POTWs) are not a “controllable” source and are typically exempt from the TDS limit.

4.3 Capacity Requirements The capacity requirements of a water system’s source and treatment are set based on the Michigan Safe Drinking Water Act; Act 399, Public Acts of 1976 as amended; and associated Administrative Rules. Those requirements include:

• Maintaining a total developed groundwater source capacity of a system, unless otherwise specified by the reviewing authority, that shall equal or exceed the design maximum day demand with the largest producing well out of service.

• The firm capacity of the system, including the water source and treatment facilities, shall be designed for maximum day demand at the design year.

The MDEQ also has an unofficial guideline for existing systems of planning for expansion of source and treatment capacity when the maximum day demands of the system exceed 80% of the source and treatment firm capacity. This unofficial guidance is used as a benchmark in this study, with all source and treatment facilities designed to meet this guideline.

As part of the development of a new water system (note, this would include the addition of a major wholesale customer or formation of an Authority), a Capacity Development Plan is required by the MDEQ. A Capacity Development Plan is intended to ensure that the new system has the technical, financial, and managerial capacity to supply clean water to its customers.


5.0 Township Water Treatment This section of the report provides a summary of the existing water treatment processes used in the Township, and a summary of changes needed to provide water softening using Township-owned facilities.

5.1 Current Process Stream Iron and manganese are present in many Michigan groundwater supplies and can provide aesthetic concerns for end users. Iron typically exists in its reduced or dissolved state and can be easily oxidized by physical or chemical means to convert it to an insoluble form that can be filtered out. The facilities required for pressure filtration are shown schematically in Figure 4.

Iron treatment involves oxidizing the iron in solution utilizing either an aeration process or chemical oxidants such as chlorine, potassium permanganate, or ozone. In the past, the Township used aeration for oxidation of the iron. In recent years, the Township has transitioned to chemical oxidation using chlorine.

Once the iron is oxidized, filtration is accomplished utilizing either vertical or horizontal pressure filters. Each of the Township’s three treatment facilities utilizes a media profile consisting of 18 inches of sand and 12 inches of anthracite.

Pressure filtration requires backwashing to remove accumulated solids from the filter media. Filter backwash water containing iron solids is currently discharged to a red water lagoon onsite. An alternative method of backwash disposal would involve a concrete tank for equalization with the backwash pumped to the sanitary sewer.

At the Meridian and Mission Treatment Facilities, water is pumped from the wells, through the filters, and to the distribution system using only the well pumps. At the Isabella Treatment Facility, filtered water is first pumped to an onsite 500,000-gallon ground storage tank. From there, the water is pumped to the distribution system via high service pumps. Polyphosphate for corrosion control and Sodium hypochlorite for disinfection are added to the water prior to entering the distribution system.

5.2 Conceptual Basis of Design The following design information and assumptions were used to evaluate equipment and treatment, storage, and supply alternatives considered in this report.

After review and consideration of the options for locating the proposed softening process, we have assumed that softening would be centralized at the Isabella Treatment Plant site. The two existing wells that serve the Mission Treatment Plant (Well No. 8 and 9) would be routed to the Isabella Treatment Plant via a new 16-inch raw water transmission main. It has also been assumed that four additional wells, each with an assumed capacity of 500 gpm, would be constructed. Both the Mission and Meridian Treatment Plants were assumed to remain on standby with annual operation and maintenance (O&M) performed on them to ensure they can operate if need be. This annual cost is included in the O&M costs for each of the softening options of the Township.


5.3 Siting Considerations and Criteria There are many factors to consider when selecting a treatment plant location including existing master planning, future land use projections, visibility, and area requirements. Hydraulic implications include proximity to existing raw water and potable water main of appropriate capacity. The proximity to existing sanitary sewer connections of adequate size is another important hydraulic consideration.

The Isabella Treatment Facility was expanded in 2010 and currently serves as the home base for the Township’s Water Department. The facility houses administration, meeting, and storage spaces in addition to the water treatment facilities. The site also has a ground storage tank and adequate land to accommodate treatment expansion. These reasons support the use of the Isabella site for future treatment processes. The biggest drawback to the site is the lack of a connection to the Township’s sanitary sewer system.

5.4 Raw Water Supply Expansion The existing raw water supply of the Township system, which is described in more detail in Section 3.1.2, consists of seven groundwater supply wells in three separate well fields. There are currently aquifer restrictions on each of the wellfields, limiting the amount of water that can be pumped from each separate wellfield as indicated in Table 3. The firm capacity of the raw water supply for the Township needs to meet or exceed a design production capacity of 4.80 mgd, a value based on projected demand increases for the next 20 years. The current firm capacity of the Township’s raw water supply is 2.88 mgd. In addition, the raw water supply from the Meridian Well Field could not supply the expanded Isabella Treatment Facility due to the distance from it. These wells and the Meridian Treatment Facility would be left on standby as a backup in case of emergency. The raw water supply will need to be expanded in conjunction with the new Isabella Treatment Facility to have adequate capacity for the Township’s projected demands.

An additional four wells will need to be drilled and developed to meet the capacity requirements. Without completing a hydrogeological study of the area, some base assumptions were used. For the purposes of this study, it has been assumed that the new wells would be constructed in the locations shown on Figure 5. A new 16-inch raw water transmission main would be installed to convey raw water from the new well sites to the treatment facility. It was assumed that each well would yield 500 gpm, or 0.72 mgd, of capacity. This would bring the Township firm raw water supply capacity to 3,600 gpm or 5.18 mgd, above the design production capacity.

5.4.1 Raw Water Supply Expansion Costs To estimate the cost of well development and well house construction, some assumptions were made. Each well site was assumed to require 4 acres of property acquisition, a wellhouse and pump, standby power, a new power service, and telemetry. The cost of the 16-inch raw water transmission main was developed based on bid tabs from similar projects. Costs are separated into the IX and Lime softening options and the RO softening option because the RO option requires additional raw water supply capacity. The costs for the Raw Water Supply Expansion are shown in Table 11.


Table 11 - Township Raw Water Supply Expansion Costs

Component IX and Lime Estimated Cost RO Estimated Cost

Well Development New Supply Wells $2,040,000 $2,720,000

Raw Water Transmission Main $1,950,000 $1,950,000

Subtotal $3,990,000 $4,670,000

General Conditions, OHP (12%) $479,000 $560,000

Project Subtotal $4,469,000 $5,230,000

Conceptual Design Contingency (20%) $894,000 $1,046,000

Construction Cost Opinion $5,363,000 $6,276,000

Engineering and Inspection (15%) $805,000 $941,000

Total Project Cost $6,168,000 $7,217,000

5.5 Water Treatment Objectives The primary goal of the Township is to determine the most effective method of providing softened water to its residents. Each treatment technology considered in this analysis maintains the Townships ability to reduce iron and manganese concentrations below the secondary MCLs of 0.3 and 0.05 ppm. The Township’s stated goal for softened water ranged between a minimum of 50 mg/L and a maximum of 150 mg/L of total hardness. A target hardness of 120 ppm was used to evaluate and compare softening alternatives. Although Arsenic removal is not the primary consideration for treatment for the Township, both the iron removal and softening alternatives to be considered can remove arsenic below the primary MCL of 10 ppb.

5.6 Water Softening Technologies Softening alternatives to be evaluated in this report are sodium-based ion exchange, single-stage lime softening, and membrane softening alternatives including Reverse Osmosis (RO) and Nanofiltration (NF). The following is a general discussion of the treatment technologies to be evaluated in this study.

5.6.1 Ion Exchange Softening Ion Exchange Softening is a process that removes hardness by adsorption onto an ion exchange resin. During this process, sodium (and alternatively potassium) ions are exchanged for the calcium and magnesium hardness ions. A typical process flow schematic for an ion exchange system is provided as Figure 6.

This process results in the removal of nearly all the calcium and magnesium, reducing the hardness to almost 0 mg/L. Some hardness in the water is desirable to provide a stable and non-corrosive water. To achieve that, the process normally includes bypassing a stream of filtered water that is blended with the ion exchange treated water to achieve the target hardness level. Based on the total hardness of the raw water, it was assumed that approximately 25 to 35% of the filtered water would bypass the ion exchange process. The ion exchange resin must be regenerated periodically using a regenerate solution (typically sodium chloride brine solution) to replenish the exchange sites.


The sodium-based ion-exchange process will result in an increase in the treated water sodium concentration. For every 40 mg/L of calcium removed, 46 mg/L of sodium are released to the water; for every 24 mg/L of magnesium removed, 46 mg/L of sodium are released.

There is no MCL for sodium; therefore, elevated sodium concentrations do not pose a compliance issue. However, in 2003 the USEPA issued a Drinking Water Advisory that recommended that sodium concentrations in drinking water not exceed 30 to 60 mg/L. Furthermore, a maximum sodium concentration of 20 mg/L was recommended for at risk people, such as those with high blood pressure and heart disease. A detailed water analysis was not available at the time of this study; therefore, we were not able to predict the resultant sodium concentration in the softened water if ion exchange softening was employed. However, based on the total hardness concentration of the raw water we would expect the sodium concentration of the ion exchanged treated water to be in the range of 80 to 120 mg/L, assuming the process removes all the calcium and magnesium from the treated water.

The ion exchange regeneration process requires a significant amount of salt. At the current average flow of 0.94 mgd of softened water, the Township would consume approximately 7,600 pounds of salt per day to meet the target finished water hardness. Salt would be delivered to the WTP on a regular basis to maintain the brine tanks.

The ion exchange waste stream would have a Total Dissolved Solids (TDS) concentration of approximately 10,000 – 40,000 mg/L. The high TDS concentrations could make disposal of this waste stream challenging.

Ion exchange softening would require approximately 6% excess filtered water flow to compensate for the new waste stream. Based on the total hardness of the raw water, estimated daily waste stream volumes were calculated based on both current and projected 2038 demands and provided in Table 12 below.

Table 12 – Township Ion Exchange Softening Flows

Process Stream

Current Demand (mgd) Projected 2038 Demand (mgd) Average Day Max Day Average Day Max Day

Plant Finished Water Demand 0.94 2.36 1.40 4.46

Ion Exchange Required Influent 1.00 2.50 1.48 4.72

Ion Exchange Waste Stream 0.06 0.14 0.08 0.26

5.6.2 Lime Softening Lime softening is a proven technology that many Michigan water supplies use to soften groundwater in Michigan. Lime softening removes calcium and magnesium hardness, along with iron and manganese, by a process of chemical precipitation. In addition, lime softening is also effective in removing arsenic and radionuclides, when present in the groundwater.

In conventional lime softening, the pH of the water must typically be increased a pH of about 9 to precipitate calcium carbonate and, if needed, raised further to a pH of 11 or greater to precipitate magnesium. If there is insufficient alkalinity present in the water, the alkalinity must be increased with the addition of soda ash.

The need to go to the higher pH level will depend on the actual raw and desired magnesium hardness. Data for the raw water magnesium hardness was unavailable. Magnesium hardness more than 40 mg/L can contribute to


scaling in boilers and hot water heaters. Thus, the desired treated water magnesium concentration is typically 40 mg/L or less. However, a slightly higher concentration might be tolerable.

Lime softening can be either single-stage or two-stage split treatment. Two-stage treatment could be considered to reduce operating costs by reducing both the chemicals required and the sludge production. However, for the purposes of this evaluation, we have assumed single-stage treatment, which would result in lower capital costs.

The facilities required for single-stage lime softening are indicated in Figure 7. The water would first pass through an aeration step to strip off carbon dioxide. This reduces the quantity of chemicals required and the quantity of residuals produced. The water would next flow to solids contact clarifiers where precipitation and clarification would occur with the addition of lime and possibly soda ash. This process can utilize either mechanical reactor clarifiers or non-mechanical upflow clarifiers such as those used by the City of Mount Pleasant.

The next major process is gravity filtration, but just prior to filtration, the pH of the water must be adjusted to end the chemical precipitation process. This can be accomplished with the addition of carbon dioxide. Some plants also add a small dose of polyphosphate to sequester the calcium and magnesium ions. The water would then be sent to dual media gravity filters to remove any remaining precipitated solids.

Filtered water would be sent to a clear well and ultimately be pumped to the distribution system. An additional process step might include the addition of an orthophosphate for corrosion control. Sodium hypochlorite would also be added for disinfection.

Residuals to be dealt with include the sludge which would be removed from the bottom of the clarifiers during the treatment process operations and the filter backwash wastewater. The sludge is typically routed to either onsite sludge storage ponds or to a thickening/storage tank/dewatering system.

The filter backwash wastewater is generated when the filters are backwashed to remove accumulated solids. It can typically be routed to one of three potential processes: (a) backwash seepage basins; (b) backwash holding ponds or tanks and ultimately recycled back through the plant; or (c) sent to the sanitary sewer.

The decant from sludge ponds or the filtrate from the dewatering system and the backwash can potentially be discharged to a seepage basin, sent to the sanitary sewer, or recycled to the intake of the treatment plant. The best option would be chosen as part of preliminary design if the Township were to move forward . For the purposes of the report, it was assumed that a second lagoon would be built and the NPDES permit would be maintained.

It is important to note that if any water to be recycled from either the backwash or the sludge processes came from open ponds or basins, the treatment plant would be classified as a surface WTP, which has much more stringent regulations to adhere to.

The solids generated from these processes must be removed and properly disposed of. These residuals are typically suitable for use as soil conditioners on crop lands because of their pH and buffering capabilities.

5.6.3 Membrane Softening Membranes have been used to treat water for many years. Their predominant use originated with the desalinization of brackish and sea waters. However, that same technology has been also applied to soften water.


Membrane softening can be accomplished in two different ways. Reverse osmosis (RO) membranes, which remove virtually all dissolved solids including hardness components, can be used. This necessitates that some flow be bypassed around the RO membranes, to provide an optimal hardness in the blended water. Nanofiltration (NF), another membrane process, could be considered a “loose RO” system. Typically, with NF membranes, all the flow goes through the membranes and they reject most, but not all, the dissolved solids and hardness components. The primary difference between NF and RO is the molecular size of dissolved contaminants that can be removed. Both NF and RO are primarily available as spiral wound membrane elements with a very similar appearance.

In addition to hardness removal, membranes offer treatment benefits which other softening technologies may not. RO membranes can remove currently regulated contaminants such as metals, organics, pesticides, and pathogens (including viruses), and have been shown to be effective in removing many of the emerging contaminants of concern, as well as unregulated emerging contaminants regulated by the Environmental Protection Agency (EPA) and the MDEQ. RO membranes are also flexible in the contaminants they can treat, not requiring changes to the process to treat specific contaminants. Membrane processes sometimes require a degasification step for the removal of dissolved gasses such as hydrogen sulfide and carbon dioxide. The need for these removal facilities can be determined as part of the pilot testing.

The presence of iron presents a treatment challenge for membranes. Unlike many other components of hardness and dissolved solids, iron can readily change to an insoluble state by oxidation or through the metabolic action of naturally occurring bacteria. As a result, plants typically pretreat for the removal of iron prior to membrane treatment. For many groundwater supplies, iron filtration would typically be needed anyway on that portion of the flow that bypasses the membrane treatment process. We have assumed that the existing iron removal process at the Isabella Plant would be maintained and expanded, to remove iron prior to the RO process.

The process includes three basic flow streams: the feed, the permeate (or purified water), and the concentrate (or waste stream). The membrane elements are housed within pressure vessels which are secured to factory assembled skids. The pressure vessels are arranged in stages, where the concentrate from the first stage becomes the feed for the subsequent stage. The permeate from each stage is blended together to create the resultant product stream. The concentrate from each of the stages forms the waste stream.

High pressure is required to force the water through the semi-permeable membranes. Membranes are susceptible to fouling from particulate or suspended solids in the water stream. Iron must typically be removed by iron oxidation as discussed previously. The feed water is also passed through microfilters prior to the membranes. Additionally, an acid or antiscalant is typically fed prior to the membranes to ensure the minerals in the feed stream remain in the dissolved ionic form.

Permeate exiting the membrane equipment will have essentially zero hardness, have low alkalinity, and can be very corrosive. Membrane softening would also remove dissolved bicarbonate alkalinity, resulting in permeate with a depressed pH. As a result, pH adjustment will be needed. pH adjustment is typically accomplished by using either degasifiers (air stripping to remove dissolved carbon dioxide) or by adding sodium hydroxide or soda ash. For the purposes of this study, it is assumed that sodium hydroxide (caustic) would be the pH adjustment method. Treated water would be blended with bypassed water to provide a blended water free of iron at the target hardness of 120 mg/L.


The concentrate would be high in Total Dissolved Solids (TDS) and sometimes presents disposal challenges. Based on the total hardness of the raw water, the expected concentrate waste stream TDS concentration would range from 2,000 to 2,600 mg/L. Alternatives for concentrate disposal include surface water discharge, sanitary sewer, and deep well injection. The concentrate stream would be a sizable volume, typically ranging from 20 to 30% of the inlet flow.

The membrane elements would require chemical cleaning on a routine basis, typically every six months. A clean in place (CIP) system consisting of a large tank and a CIP pump delivers cleaning solution to each membrane unit by permanent piping that terminates near each unit. CIP flows can range as high as 1,500 gpm at 60 psi and may require neutralization prior to disposal. A variety of acid and alkaline cleaners must be stored onsite for use in the CIP process.

Membrane softening would require additional filtered water flow to compensate for the new waste streams, similar to ion exchange softening. Based on the total hardness of the raw water, estimated daily waste stream volumes were calculated based on both current and projected demands and provided in Table 13. The percentage of water that is rejected as concentrate in the RO system is approximately 25%, much higher than in ion exchange softening.

Table 13 – Township Membrane Softening Flows

Process Stream Current Demand (mgd) Projected Demand (mgd)

Average Day Max Day Average Day Max Day

Plant Finished Water Demand 0.94 2.36 1.40 4.46

Membrane Required Influent 1.25 3.15 1.87 5.95

Concentrate Waste Stream 0.31 0.79 0.47 1.49

The anticipated membrane softening process is indicated schematically in Figure 8. Water pumped from the wells would pass through pretreatment for iron removal prior to delivery to the existing 500,000-gallon ground storage tank. High pressure membrane feed pumps would draw from this tank and transfer the filtered water through the membrane skids. As membranes are intolerant of chlorine or other oxidants, sodium bisulfite would be added to the feed water to remove any potential chlorine remaining after the iron pretreatment step. An antiscalant would also be added to the feed water to ensure that minerals in the water remain in solution. A portion of the filtered water would bypass the membrane system to be blended with the permeate water in a new 1.5 MG clear well. New high service pumps would draw the softened water from the new clear well and pump to the distribution system. Phosphate would be added for corrosion control and sodium hypochlorite would be added for maintaining a disinfectant residual prior to entering the distribution system.

5.7 Water Treatment Alternatives Development This section of the report develops and compares the alternatives for providing softened water.

5.7.1 Ion Exchange

Documents

Water Systems Study - Mount Pleasant, Michigan€¦ · Water Systems Study . Prepared For: Charter Township of Union, Michigan City of Mount Pleasant, Michigan . July 26, 2019 Project