HomeMy WebLinkAbout2024-02-20 Council meeting -Water Supply Strategies
WATER SUPPLY STRATEGIES
Approve Water System Study
Findings, Recommendations and Next Steps
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WATER SUPPLY STUDIES
Well 2 Treatment for PFAS (Authorized on September 5, 2023).
Water Distribution System Modeling for New Water Supply Source Locations (Authorized on September 5, 2023).
South Area Water Treatment Plant (WTP) for Future Wells (Authorized on October 17, 2023).
Revised Capital Improvement Plan for Neighborhood Connections to City Water.
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FINDINGS
WELL 2 TREATMENT FOR PFAS
Well 2 production capacities are needed to meet peak summer demands until Well 6 is operational.
Temporary IX treatment for PFAS at Well 2 is feasible.
Permanent IX treatment for PFAS at Well 2 is dependent upon further evaluation and MDH approval for long-term use of a pressure cartridge filter for iron and manganese (Fe/Mn) pretreatment.
Treatment for PFAS at Well 2 using granular activated carbon (GAC) filter media is not feasible. Limited by building footprint and lack of sanitary sewer.
Prefabricated trailer mounted systems are available for use in 2024.
Evoqua: 450 gpm IX filters, six vessels per trailer, only one trailer available for 2024 (min. 6-mo. rental). Costs: $260k initial fill and startup, $15k/mo rental, freight and demobilization
at cost+30%
WaterSurplus: 650 gpm IX filters, eight vessels per trailer, multiple trailers available for 2024. Costs: $141k initial fill and startup, $27k/mo (two year rental rate), $3k demobilization.
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RECOMMENDATIONS
WELL 2 TREATMENT FOR PFAS
Proceed with design phase engineering for an Anion Exchange (IX) Treatment at Well 2 using paired 8-ft diameter steel pressure vessels within the existing building footprint and raised
roof. The roof needs to be raised to accommodate the 15-ft. tall steel pressure vessels.
Pretreatment for IX filtration is required. A pressure cartridge filter for iron and manganese (Fe/Mn) pretreatment is recommended.
Secure a Grant Agreement Amendment to fund design phase engineering services.
Obtain sampling and detailed testing of Well 2 for design purposes.
Proceed with direct procurement of the treatment vessels/equipment for accelerated delivery.
Operate Well 2 on emergency basis only through peak 2024 summer demands. We are not recommending the trail er mounted rental filters for use in 2024.
Initiate building modifications as early as Summer 2024 in preparation of treatment equipment.
Initiate Well 2 rehabilitation and pump replacement in Fall 2024.
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PROJECT DETAILS
WELL 2 TREATMENT FOR PFAS
Treatment capacity is 800 gpm. Limited by building and site footprint.
Schedule. Treatment system to be online by Spring 2025, prior to peak water demands.
Cost. $2.40 million. All equipment is by purchased (no rentals).
Expected life of IX media between replacement is estimated at 2-4 years.
Estimated IX media replacement costs, including wastewater and media disposal is $225,000 per change-out ($150k media, $55k disposal, $20k labor).
Expected service life of treatment system equipment is 50+ years (repaint interior and exterior of vessels every 20 years). The equipment has a salvage or resale value within the design
life.
Temporary IX treatment for PFAS at Well 2 is feasible. Permanent IX treatment for PFAS at Well 2 is dependent upon further evaluation and MDH approval for long-term use of a pressure
cartridge filter for iron and manganese (Fe/Mn) pretreatment.
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PROJECT DETAILS
WELL 2 TREATMENT FOR PFAS
Building modifications include process piping, fittings, valving and meters; removal of hydropneumatic tank, air compressor and associated small piping systems; replacement of west side
exterior “knock-out” block wall; sealing the generator room grated window openings, installation of exterior wall insultation and unit heaters, and revision of access doors.
Building modifications also include removal of the interior wall, raising the roof by increasing the exterior wall heights, and pouring concrete pads for the steel vessels. A new double
wide 16-ft. tall garage door would be installed.
Chemical feed equipment modifications will be required .
Electrical and control modifications will be required.
Replacement back-up generator is recommended.
Well rehabilitation and new well pump with a variable frequency drive (VFD) is recommended.
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QUESTIONS?
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WATER DISTRIBUTION MAP
Northern Water Supply Plan
Well 6 & 7
Northern Water
Supply Plan
Well 2
Well 4
Well 5
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Well 6 & 7
Southern Water
Supply Plan
with Treatment
Well 2
Well 4
Well 5
WATER DISTRIBUTION MAP
Southern Water Supply Plan
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Option A1: Systemwide Delivery with North Wells (Wells 4 and 5) and South WTP (for Wells 6 and 7).
Option A1 Works really Good
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Option A2: Option A1 with North WTP for Wells 4 and 5 (combining delivery point).
Option A2 Works really Good
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Option C2: SPRWS Systemwide Delivery
with Southern Connection Point (HPZ).
Option C2: Recommended for SPRWS system wide delivery. Requires Booster Station PRV and operational adjustments. It is recommended to construct a dedicated transmission line to the Intermediate
Pressure Zone (Water Tower 2).
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Option C3: Separate North (IPZ) and South Water Delivery System (HPZ & LPZ).
North WTP for Wells 4 and 5 (combining delivery point).
SPRWS Southern Connection Point.
Option C3: Separate North and South water delivery system works well. Allows for opportunity to purchase SPRWS for South Water Delivery System and maintain Wells 2, 4 and 4 for North
water delivery system.
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WATER DISTIRBUTION SYSTEM MODELING FOR
NEW WATER SUPPLY SOURCE LOCAITONS
Adopt a revised Water System Plan to construct and operate a systemwide water supply delivery system with North Wells (Wells 2, 4 and 5) and South WTP (for Wells 6 and 7) – Option A1.
Work closely with MDH to test and monitor PFAS at Wells 4 and 5. If PFAS exceedance is determined, initiate the design and construction of a centralized Water Treatment Plant to be constructed
at Tana Ridge Park to treat both Well 4 and Well 5. Initiate raw watermain and distribution system infrastructure improvements recommended for Alternative A2.
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QUESTIONS?
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Well 6 & 7
Southern Water
Supply Plan
with Treatment
Well 2
Well 4
Well 5
WATER DISTRIBUTION MAP
Southern Water Supply Plan
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WATER DISTRIBUTION MAP
Other possible Well/Treatment Locations
Well 2
Well 4
Well 5
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A permanent water treatment plant (WTP) and construction of Well 6 at Stonegate Park is feasible. The full use of the park for recreational purposes will be lost with the exception of
the playground equipment. The property is city owned.
A permanent water treatment plant (WTP) and construction of Well 6 just north of 10th Street and the Inwood subdivision is feasible. Property will need to be acquired. A Comprehensive
Plan Amendment will be required to extend sanitary sewer to the WTP and to revise the zoning from RAD to Public Facilities.
The Public Works Facility site resides within the White Bear Lake Court Order 5-mile radius and is therefore not feasible.
A permanent water treatment plant (WTP) should be constructed with an initial 3,000 to 4,000 GPM capacity to serve at least two water supply wells (Well 6 and Well 3 or 7). The treatment
plant should be designed to allow for expansion for 1 additional water supply well and should be designed to meet the projected 2024 Water Supply Demands.
It is recommended that the water treatment plant (WTP) be designed to include pretreatment for iron and manganese (Fe/Mn).
FINDINGS
SOUTH AREA WATER TREATMENT PLANT (WTP)
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A pilot study is recommended to inform the water treatment plant design parameters and to optimize the treatment design. The total estimated cost for a pilot study is in the $250,000
to $350,000 range and can take approximately six to nine months to complete.
When pretreatment for Fe/Mn is provided, IX media has demonstrated greater treatment capacity compared to GAC during pilot studies performed on similar water quality. IX media tends
to have greater efficacy for removing certain PFAS compounds that are present in Lake Elmo’s water supply.
Assuming an April 16, 2024 design authorization for Well 6 and the South Water Treatment Plant, the plant will be operational for peak 2027 summer water supply demands. This assumes
a 36-month design and construction schedule. Depending on the commencement date of the pilot study, and the initial findings, the completion date for the WTP could be extended by six
to nine months.
The opinion of probable cost for the treatment facility is $45M including a 20% contingency and soft costs.
FINDINGS
SOUTH AREA WATER TREATMENT PLANT (WTP)
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Secure a MPCA Grant Agreement Amendment to fund design phase engineering services and the construction of a Test Well and Stonegate Park.
Initiate Project design and construction phase services.
Proceed with design phase engineering for Well 6 and a PFAS Water Treatment Plant to be located in the south part of the city in the high-pressure zone.
Consider Stonegate Park
Consider sites north of 10th Street.
Proceed with detailed site layout and investigations including the construction of a Test Well.
Consider initiation of a pilot plant study to optimize the WTP design.
It is recommended that the water treatment plant (WTP) be designed to include pretreatment for iron and manganese (Fe/Mn).
RECOMMENDATIONS
SOUTH AREA WATER TREATMENT PLANT (WTP)
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QUESTIONS?
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2024 – Homestead (18)
2025
2025 -- Packard Park/Eden Park/20th St Cir (68)
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2026 -- Tartan Meadows/Klondike (39)
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2027 -- Downs Lake/Sunfish Ponds/Forest (54)
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NEIGHBORHOOD CONNECTIONS
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RECOMMENDATIONS /
REQUESTED COUNCIL ACTION
Staff is recommending that the City Council approve the preliminary findings and recommendations as presented at the Council meeting, or as amended by the Council, and direct staff to
initiate preliminary and final designs for improvements as recommended, and to apply for the applicable 3M Settlement Grant Funding through the MPCA.
“Move to approve the preliminary findings and recommendations as presented at the Council meeting, or as amended by the Council, and direct staff to initiate preliminary and final designs
for the improvements as recommended, and to apply for the applicable 3M Settlement Grant Funding through the MPCA.”
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WATER SUPPLY CAPACITY
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WATER SUPPLY CAPACITY
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WATER SUPPLY CAPACITY
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