Regional Water System
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Wylie Water Treatment Plant Conversion to Biologically Active Filtration;
Project No. 101-0390-15; Additional Engineering Services
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SUBJECT
recommendation
Authorize additional engineering services to Carollo Engineers, Inc. in the amount of $1,021,900 to an existing Engineering Services Agreement (ESA) to address additional scope needed for plant conversion to Biologically Active Filtration (BAF).
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PURPOSE
Additional funding is needed to complete the final design phase of converting the Wylie Water Treatment Plants to BAF. The additional services are needed due to changes to the original concept with a goal to preserve clearwell storage volume and rerouting of piping to preserve space on the plant for future process needs. The addition of new scope to add chlorine dioxide to the Plant I and II reclaim stream to mitigate future high levels of manganese also added to the need for more engineering services.
RECOMMENDATION
The Executive Director and NTMWD staff recommend the Board of Directors authorize additional engineering services to an existing ESA as follows:
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Consultant: |
Carollo Engineers, Inc. |
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Scope: |
Additional services for Final Engineering Design |
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Project: |
No. 101-0390-15, Wylie Water Treatment Plant (WTP) Conversion to Biologically Active Filtration |
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Amount: |
$1,021,900 |
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Committee: |
This will be an item on the January 22, 2025, Water Committee meeting agenda |
DRIVER(S) FOR THIS PROJECT
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Strategic Objective: |
1.1 High Quality Services |
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☒ Regulatory Compliance |
☐ Asset Condition |
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☐ Capacity |
☒ Redundancy/Resiliency |
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☐ Relocation or External Requests |
☐ Operational Efficiency |
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☐ Safety |
☐ Administrative |
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☐ Policy |
☐ Other _____________ |
BACKGROUND
The complex interconnectivity of the four Wylie Water Treatment Plants (WTPs) presents many possible process flow paths for the implementation of the Biologically Active Filtration (BAF) treatment process. Phase I of Preliminary Engineering was undertaken to develop the most viable of those path options and performed a high-level comparative evaluation based on the relative effects on water quality, operability, constructability, and planning level construction cost.
A subsequent Phase II of Preliminary Design concentrated on the recommended configuration alternative for developing the basis of design for the remainder of the project and the advancement of that alternative to 30% design documents. The current design phase split construction into three phases - the first of which was awarded in October 2024 with Administrative Memorandum No. 24-6069. The second phase is to be awarded in February 2025, and the third and final phase in May 2025.
PROJECT PURPOSE
• Enhance the removal of organics to improve finished water quality and thereby produce water less prone to residual disinfection depletion.
• Moderate the flow rate variability through the filters to maintain particulate capture and protect against flow-related turbidity volatility.
• Accomplish miscellaneous upgrades to support chemical addition, contact time, polishing capabilities, and in-plant water quality monitoring and control that is critical to effective initial BAF operations.
PROJECT COMPONENTS
• Addition of chlorine contact volume at Wylie WTP’s I, III and IV via new basins, piping, or clearwell conversion.
• Major piping relocations and interconnects to accommodate revised flow paths. Major piping includes large flow meters and isolation valves enclosed in vaults
• Installation of chemical injection points and associated piping and trenches
• Programmable logic controller-based filter automation and valve controller improvements.
• The forecasted overall construction cost for all elements is currently $83,902,000.
ADDITIONAL ENGINEERING SERVICES
• Services related to Wylie WTP I and IV design elements, including:
o Revise post filter flow strategy to preserve clearwell volume and add a dedicated chlorine contact facility. Reduces the need for an additional clearwell which requires more space the chlorine contactor on an already congested facility
o Rerouting of Plant IV filter effluent piping to preserve open areas on Plant IV for future process needs
o New mixing structure on Plant IV to combine effluents from Plant IV North and South to achieve more stable water entering clearwell.
• Design services for manganese mitigation via chlorine dioxide addition at WTP’s I and II as recommended by Wylie WTP Filter Pilot Study.
ENGINEERING SERVICES FEE
Description Amount
Original ESA $5,803,659
Proposed Additional Services $1,021,900
Revised ESA Amount $6,825,559
FUNDING
Funding to Carollo Engineers Inc. in the amount of $1,021,900 is to be made available from the Regional Water System Capital Improvement Fund.