LAKE
CHARTER TOWNSHIP
SPECIAL
BOARD MEETING
7:00 p.m.
ROLL
CALL/PLEDGE OF ALLEGIANCE/MEMBERS PRESENT
Clerk Payne called the roll. Board members present were John Gast, Supervisor, Betty Korcek, Treasurer; Gloria Payne, Clerk; Tom Carson, Trustee; Fritz Wolf, Trustee and Terry Eichler, Trustee. Mike Jasper, Trustee was absent. Twenty-three visitors were present.
GUESTS PRESENT
Scott Dienes, Lake Charter Townships legal counsel.
Wayne Langeland, Fishbeck, Thompson, Carr & Huber, Inc.
Larry Merritt, Merritt Engineering, Inc.
SET AGENDA
One addition was made to the agenda. It was moved by Korcek seconded by Eichler to add the bill of Fred M. Ott to the agenda for approval. All ayes, motion carried.
WATER INTAKE PROJECT PRESENTATION
Supervisor Gast turned the floor over to Wayne Langeland of Fishbeck, Thompson, Carr and Huber who presented the board with the proposed lake water intake system for Lake Charter Township and South Shore Power. The board was presented with the following:
1.0 EXECUTIVE SUMMARY
The proposed South Shore Power Plant in Lake Charter Township, Berrien County, Michigan, will use water from Lake Michigan for process cooling. South Shore Power will construct a new raw water intake, pump station, and water main to convey lake water to both the Lake Charter Township Water Treatment Plant and to South Shore Power. By the terms of a development agreement between South Shore Power and Lake Charter Township, South Shore Power is proceeding with design development of the lake water intake system. South Shore Power will fund and construct the lake water intake system, but ownership and operations responsibility of the raw water supply infrastructure will revert to Lake Charter Township after construction.
The raw water intake and water main will be built to a capacity of 8 million gallons per day (MGD); a maximum of 5 MGD will be reserved for South Shore Power and 3 MGD will be available to Lake Charter Township. At the option of Lake Charter Township, the system infrastructure can be upgraded initially to facilitate future expansion to an ultimate capacity of 16 MGD. The decision to exercise this option must be approved by Lake Charter Township soon to allow design to proceed.
Two types of water intake systems were considered: a submerged intake with screened inlets and an infiltration bed intake. A submerged screen intake was selected for this application because of the good water quality provided by this type of intake as well as the long-term reliability and maintainability demonstrated at numerous installations on the Great Lakes. The proposed intake is similar to the existing intake that services the Lake Charter Township water treatment system, but uses a fine screen installed in the lake to avoid the need for a mechanically cleaned screen at the pump station.
The proposed intake would be constructed adjacent to the existing Lake Charter Township raw water pump station. The intake system would consist of a static screen intake, reinforced concrete intake piping buried at the lake bottom, shore pump station, and raw water transmission piping to the Lake Charter Township Water Treatment Plant and extending to South Shore Power. The system would include a chemical feed system for control of zebra mussel intrusion and a standby generator for redundant electric power.
Design and construction of the 8 MGD system is estimated to cost $10.4 million and will be fully funded by South Shore Power. At the option of the Township, the intake system infrastructure can be upgraded at the time of original design and construction to accommodate future raw water flow rates up to 16 MGD. This upgrade includes an additional intake screen, larger intake pipe, larger shore pump station structure, and larger raw water transmission main to the Lake Charter Township Water Treatment Plant. The cost to Lake Charter Township to exercise this option is $1,880,000. In order to realize the 16 MGD capacity in the future, the Township would need to install two additional vertical turbine pumps with associated variable frequency drives, modify system controls, and upgrade the electrical service distribution and standby power capacity.
South Shore Power is proposing the construction of a nominal 500-megawatt power plant in Lake Charter Township, Berrien County, Michigan. Water for cooling system makeup and other non-potable water uses for this combined cycle plant will be supplied via a new intake from Lake Michigan. The proposed lake water intake will have a minimum capacity of 8 MGD of which 5 MGD is allocated to South Shore Power and 3 MGD is available for Lake Charter Township.
According to the terms of a development agreement between South Shore Power and Lake Charter Township, South Shore Power is proceeding with design development of the lake water intake system. South Shore Power is responsible for funding and constructing the approved lake water intake system. Ownership and operations responsibility of the raw water supply infrastructure will revert to Lake Charter Township after construction.
At the option of Lake Charter Township, the infrastructure capacity can be increased at the time of original construction to allow ready expansion of the raw water intake system to 16 MGD. The incremental cost for this upgrade would be the responsibility of Lake Charter Township. When demand for water in the future is projected to exceed the available capacity, Lake Charter Township can complete the upgrade of the intake system to achieve a total intake capacity of 16 MGD with all the additional capacity being available to Lake Charter Township. In order for the system design to move forward, Lake Charter Township must decide if they wish to pay to upgrade the system infrastructure to accommodate the increased future capacity.
Traditionally, Great Lakes municipal water intakes and some smaller industrial water intakes have utilized open cribs installed at the lake bottom. Crib intakes incorporate large grating or wooden slats to prevent large fish and debris from entering the intake pipe. Smaller fish and debris are removed using mechanical screens at a shore pump station. The existing Township water system intake is similar to this style and uses grating at the intake for coarse screening and a mechanically cleaned screen at the pump station for removal of smaller solids. Intake cribs can also be fitted with fine static screens to further limit the entrainment of marine organisms and debris in the intake water. This submerged screen intake has been used in many power plant applications and eliminates the need for additional screening at the shore pump station. Zebra mussel infestations on the Great Lakes have caused concern with some intakes; however, chlorination of the intake piping and the use of new materials have been effective in zebra mussel control. A chlorine feed system for the control of zebra mussels has recently been installed at the Township intake. Generally, crib-style intakes with the static screen offer the following advantages:
· Highly reliable.
· Readily accessible for inspection and maintenance.
· Proven methods for control of zebra mussels.
· Good control of underwater construction quality.
· Produces good quality water.
· Additional screening at the pump station is not required.
An alternative type of intake that is often used on fast-moving fresh water streams, and has been applied to some Lake Michigan supplies, is an infiltration bed or gallery. The infiltration bed consists of a header and lateral system placed below the lake bottom and overlaid with an engineered gravel bed and native sands. The infiltration bed functions similar to a sand filter to pre-filter the water and prevent even small solids from entering the intake system, usually producing high-quality source water.
Water intakes installed on the Great Lakes are predominantly submerged-style intakes, many of which have been in service for a number of years. A recent survey indicates that there are approximately 159 water intakes installed on the Great Lakes in the states of Michigan, Wisconsin, Illinois, and Indiana. Only 7 of these intakes utilize the infiltration bed type design. Most of those intakes are either not currently in operation or have experienced operation problems. Typical operation problems involve reduced intake capacity, but water quality is an issue with one recently constructed system.
Reliability is a major consideration for both the municipal water supply and the power plant cooling water. Based on the operational history of the two primary types of intakes and following the recommendation of the project-engineering consultant, South Shore Power is recommending a submerged screen for the lake water intake.
3.0 INTAKE SYSTEM AND TRANSMISSION MAIN
CONCEPTUAL DESIGN
Submerged intakes typically consist of an inlet structure, pipeline conduit, and shore well structure. The shore well provides a housing and suction reservoir for the raw water pumps, and usually a wide spot in the line allowing for hydraulic surge dissipation in the event of pump or power failure. Submerged intake capacity is primarily a function of pipe diameter, pipe length, and depth of the shore well structure. Variable lake water levels also affect intake capacity, so design must consider the lowest levels anticipated.
For submerged intakes on the Great Lakes, depth of the inlet below the water surface is a major consideration due to the potential for sand intrusion or ice formation at the intake if too shallow a depth is provided. Variable and unpredictable movements of sand and sand bar formations are common along the shallower shore areas. Ice can also form on intake structures, depending on velocity of flow through the intake and on weather/atmospheric heat loss conditions. With deeper intake inlet structures, the probability of ice formation is significantly reduced. Along the eastern Lake Michigan shore, intake depths are typically in the 20- to 46-foot range. In order to obtain these depths, submerged eastern shore Lake Michigan intake pipe lengths range from 1,500 to 6,100 feet. At least 30 feet of submergence is recommended over intake screens to help prevent icing problems.
The intake screens proposed for this project are cylindrical assemblies of wedge-wire screens with 1/8-inch slot size installed at the end of the intake piping in the lake. The wedge-wire screens are fabricated of stainless steel or copper alloy, which are resistant to zebra mussel attachment. Screens are sized to limit the inlet water velocity to less than 0.3 foot per second to minimize the potential for fouling from frazil ice and to limit impingement and entrainment of marine organisms at the screen surface.
Submerged intakes require protection from excessive zebra mussel infestation. Chemical treatment of the intake pipe is usually practiced using a chlorine or polymer solution, which is fed only when the intake is drawing water. The chemical feed pipe is typically installed inside the intake pipe from the shore well to the inlet structure.
In addition to the intake system, South Shore Power will be constructing a cooling water discharge pipe and lake outfall. The cooling water discharge piping and outfall design will be reviewed and approved by the Michigan Department of Environmental Quality. Cooling water discharge piping will be installed in a private easement adjacent to the right-of-way in conjunction with the new raw water main. Ownership responsibility of this system will be retained by South Shore Power.
Two raw water capacity systems are described in this report. The base system is rated for 8 MGD where all intake system components are designed for this capacity. The expandable alternative is also rated for 8 MGD; however, all infrastructure components, such as intake screens, intake pipe, pump station structure, and raw water transmission main, are sized for 16 MGD. This expandable system will allow for an economical expansion of the intake system by Lake Charter Township in the future.
Design criteria for the major elements of the intake system are summarized in Table 1.
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Table 1 Basis of Design for Submerged Screen Intake System Alternatives |
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System Description |
Base System 8 MGD |
Expandable Alternative 8 MGD Expandable to 16 MGD |
|
|
System
Capacity |
|
|
|
|
Current Rated Capacity, MGD |
8 |
8 |
|
|
Future Rated Capacity, MGD |
8 |
16 |
|
|
Intake |
|
|
|
|
Number of Intake Pipes |
1 |
1 |
|
|
Intake Pipe Diameter, Inches |
24 |
30 |
|
|
Intake Pipe Length, Feet |
4,800 |
4,800 |
|
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Intake Submergence, Feet (Note 1) |
30 |
30 |
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|
Number of Intake Screens |
2 |
3 |
|
|
Screen Size (Each) |
28" dia. x 102" |
28" dia. x 102" |
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|
Pump Station |
|
|
|
|
Caisson Diameter, Feet |
20 |
25 |
|
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Caisson Depth, Feet Below Grade |
63 |
67 |
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Number of Pumps |
3 |
3 initial/5 future |
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Pump Capacity (Each), MGD |
4 |
4 |
|
|
Pump Discharge Head, Feet |
148 |
170 |
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|
Pump Motor Horsepower (Each), Hp |
150 |
150 |
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Notes: |
1.
Submergence
is based on observed low water level of Elev. 576.1 (IGLD datum). |
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The proposed intake design includes intake screens installed in the lake at a submergence of approximately 30 feet. Based on lake bottom profiles developed during a 1992 lake bottom survey at the original Lake Charter Township water intake, the intake pipe would be approximately 4,800 feet in length. At a design capacity of 8 MGD, the intake pipe would be 24 inches in diameter. Expanding the capacity to 16 MGD would require a 30‑inch-diameter intake pipe. Two static wedge-wire screens would be installed initially to provide a rated capacity of 8 MGD. For the expandable alternative, the installation of a third intake screen at the time of initial construction is recommended so that no additional marine construction work would be required at the time of a future upgrade. The intake pipe would likely be installed using trenchless technologies, such as horizontal directional drilling or microtunneling, from the pump station caisson to the shoreline. The construction method would be selected based on soil conditions, cost, and permitting requirements. Open-cut methods would likely be used to install the remainder of the intake pipe in the lake.
The intake pipe would discharge into a raw water pump station wet well. The pump station would be located adjacent to the existing Lake Charter Township pump station. The specific location of the proposed pump station will be evaluated further during preliminary design. A deep caisson structure would function as the pump station wet well. The diameter and depth of the caisson would be dependent on the intake capacity. At 8 MGD capacity, the caisson would have a 20-foot inside-diameter and a total depth of 63 feet below grade. An expandable intake system would require a caisson with a 25-foot inside-diameter and a total depth of 67 feet below grade. Vertical turbine pumps would be installed to transmit water to the Lake Charter Township Water Treatment Plant and to South Shore Power. Three 4 MGD capacity pumps (two duty, one standby) would be installed for the 8 MGD capacity. To allow for operational flexibility, each pump would be equipped with a variable frequency drive. A pump house would be built at grade above the wet well caisson to house equipment and controls. Although electric utility power will be the primary power source for the pump station, a standby diesel generator will be provided to supply power to the station on a utility outage.
The screened intake would require a chemical feed system using chlorine or polymer to inhibit the growth of zebra mussels within the intake pipe and wet well. Chemical storage and feed equipment would be installed at the pump house, and a chemical feed pipe would be installed inside the intake pipe to transfer chemicals to the intake screen area.
For the expandable alternative, infrastructure, marine, and structural components of the intake system would be sized for the future capacity to allow ready upgrade of the system to 16 MGD. Future additional work required by Lake Charter Township to increase the system capacity to 16 MGD includes the following:
· Installation of two vertical turbine pumps with associated piping and valves.
· Installation of variable frequency drives and electrical feeds to new pumps.
· Modification of pump controls to accommodate additional pumps.
· Upgrade of electrical service and emergency standby generator capacity.
Figure 1 included at the end of this report shows the proposed location of the lake water intake and shore pump station. Figure 2 provides a conceptual layout of the shore pump station and caisson.
3.3 Raw Water Transmission Main
A raw water transmission main must be installed from the shore pump station to the water treatment plant and continue on to South Shore Power. Pipeline size from the shore pump station to the water treatment plant is dependent on the ultimate system design capacity. The pipeline size that supplies water to the power plant from the water treatment plant is fixed at 16-inches and no future flow capacity is required. Design criteria for the raw water transmission main is summarized in Table 2.
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Table 2 Basis of Design for Submerged Screen Intake System Alternatives |
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|
System Description |
Base System 8 MGD |
Expandable Alternative 8 MGD Expandable to 16 MGD |
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System
Capacity |
|
|
|
Current Rated Capacity, MGD |
8 |
8 |
|
Future Rated Capacity, MGD |
8 |
16 |
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Raw Water
Transmission Main |
|
|
|
Transmission Main Diameter to Water Plant, Inches |
20 |
30 |
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Transmission Main Length to Water Plant, Feet |
6,320 |
6,320 |
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Transmission Main Diameter to Power Plant, Inches |
16 |
16 |
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Transmission Main Length to Power Plant, Feet |
1,325 |
1,325 |
The construction methods selected for the installation of the raw water transmission piping are dependent on constructability, regulatory requirements, easement restrictions, placement of existing utilities, and cost. The pipelines will be installed through critical dunes areas and the construction method must avoid disturbance of dune slopes. Pipelines will also cross an interstate highway, a county road, and a railroad right-of-way. Each of these crossings will require special consideration and approval of the construction methods.
The proposed route, as shown in Figure 1, for the raw water transmission main incorporates three main segments. Segment 1 from the shore pump station to the I-94 highway crossing presents the greatest challenge. Due to the location of existing utilities, the best alternative will be to install the raw water transmission main in a new easement located immediately south of the right-of-way. Piping can be installed using open-cut techniques for most of the segment, but some sand fill may be required along the existing road embankment. Pipe installation at two large dunes situated on the south side of the road will likely be done via bore and jack. Segment 2 from the I-94 highway crossing to the water treatment plant includes highway crossings at I-94 and Red Arrow Highway. Bore and jack methods will likely be used for the highway crossings. The balance of the pipeline can be installed using open-cut methods because all other surface features can be properly restored. The raw water transmission main can be located in the road right-of-way, provided sufficient space is available, or it could be located in an adjacent private easement. Segment 3 from the water treatment plant to the power plant includes a CSX railroad crossing, which will need to be done via bore and jack. All other portions of the piping could be done using open-cut methods with suitable restoration.
To provide redundancy for raw water piping for the benefit of both Lake Charter Township and South Shore Power, consideration will be given to interconnecting raw water piping immediately downstream of the existing and proposed shore pump stations. Similarly, piping connections at the water treatment plant should allow raw water to be directed to South Shore Power regardless of which raw water main is being utilized. The major benefit to this piping arrangement is that on a service interruption of either raw water main, water could be supplied to both Lake Charter Township and South Shore Power through the second main.