11-Attachment A - Preliminary Design Report.pdf

South County Drinking Water Facility

Preliminary Design Report May 2026 – Final

South County Drinking Water Facility Preliminary Design Report

Client Name: Hillsborough County

Project Name: South County Drinking Water Facility

Document No: 260325115047_36e63908 Project No: D4068900

Revision No: 2 Project Manager: Erik Jorgensen

Date: May 28, 2026 Prepared By: Jacobs

Doc status: Final

Document History and Status

Revision Date Description Author Checked Reviewed Approved

0 4/16/2026 Basis of Design Report, Draft

Jacobs

1 5/15/2026 Retitled Preliminary Design Report, Draft

Jacobs

2 5/28/2026 Preliminary Design Report, Final

Jacobs

Jacobs Engineering Group Inc.

5401 West Kennedy Boulevard Suite 300 Tampa, FL 33609 United States

T +1 813 676 2300 www.jacobs.com

© Copyright 2026 Jacobs Engineering Group Inc.. All rights reserved. The content and information contained in this document are the property of the Jacobs group of companies (“Jacobs Group”). Publication, distribution, or reproduction of this document in whole or in part without the written permission of Jacobs Group constitutes an infringement of copyright.

Jacobs, the Jacobs logo, and all other Jacobs Group trademarks are the property of Jacobs Group.

NOTICE: This document has been prepared exclusively for the use and benefit of Jacobs Group client. Jacobs Group accepts no liability or responsibility for any use or reliance upon this document by any third party.

260325115047_36e63908 i

Contents Acronyms and Abbreviations ........................................................................................................................................ vii

1. Introduction ........................................................................................................................................................ 1-1

1.1 Project Background .............................................................................................................................................. 1-1

1.1.1 Location ....................................................................................................................................................... 1-1

1.1.2 Facility Goals and Objectives ............................................................................................................... 1-2

1.2 Report Organization ............................................................................................................................................. 1-3

2. Hydraulic and System Integration Evaluations .......................................................................................... 2-1

2.1 Incoming Water Supply Sources and Water Quality ................................................................................ 2-1

2.1.1 Incoming Water Supplies ...................................................................................................................... 2-1

2.1.2 Incoming Flows and Pressures............................................................................................................ 2-2

2.1.3 Incoming Water Quality ......................................................................................................................... 2-6

2.2 System Hydraulics and SCDWF Pump Station Considerations ........................................................ 2-16

2.2.1 Hydraulic Considerations ................................................................................................................... 2-16

3. Process Design Considerations ...................................................................................................................... 3-1

3.1 Treatment Process Overview ............................................................................................................................ 3-1

3.1.1 Disinfection and Disinfectant Residuals .......................................................................................... 3-1

3.1.2 Tampa Bay Regional Water and Treated Ground Water Blending ....................................... 3-9

3.1.3 Finished Water Chemical Addition ................................................................................................. 3-11

4. Major Unit Operations ...................................................................................................................................... 4-1

4.1 Chemical Storage and Feed .............................................................................................................................. 4-1

4.1.1 Storage and Feed System Design Methodology ......................................................................... 4-1

4.1.2 Disinfection Chemicals........................................................................................................................... 4-2

4.1.3 Alternative Ammonia Chemical Comparison ............................................................................. 4-11

4.1.4 Finished Water Chemicals .................................................................................................................. 4-12

4.1.5 Chemical Facility Layout .................................................................................................................... 4-17

4.1.6 Process Control ...................................................................................................................................... 4-17

4.2 Water Storage ...................................................................................................................................................... 4-20

4.2.1 System Storage Requirements Overview ..................................................................................... 4-20

4.2.2 Storage Tank Options and Recommendation ........................................................................... 4-21

4.2.3 Water Storage Tank Design Criteria ............................................................................................... 4-23

4.2.4 Process Control Considerations ...................................................................................................... 4-24

4.2.5 Tank Design Considerations ............................................................................................................. 4-24

4.3 Pump Station ....................................................................................................................................................... 4-24

4.3.1 Hydraulic Model .................................................................................................................................... 4-25

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4.3.2 Modeled Pump Station Configuration Overview ...................................................................... 4-30

4.3.3 Alternative Comparison and Recommendation ....................................................................... 4-42

4.3.4 Description of Proposed Piping Systems ..................................................................................... 4-44

4.3.5 Pump Design Criteria Summary ...................................................................................................... 4-46

4.3.6 Pump Station Control Strategy ....................................................................................................... 4-47

5. Site Plan ............................................................................................................................................................... 5-1

5.1 Conceptual Site Plan ............................................................................................................................................ 5-1

5.2 Entrance Road, Site Access, Loading Zones, and Parking ..................................................................... 5-1

5.3 Site Survey ............................................................................................................................................................... 5-2

5.4 Stormwater, Floodplain, and Erosion Control ............................................................................................ 5-2

5.5 Fencing ...................................................................................................................................................................... 5-3

5.6 Utilities ...................................................................................................................................................................... 5-3

5.7 Applicable Codes, Standards, and Design Criteria ................................................................................... 5-3

6. Environmental Assessments ........................................................................................................................... 6-1

6.1 Wetland Delineation and Unified Mitigation Assessment Methodology ........................................ 6-1

6.2 Species Field Survey ............................................................................................................................................. 6-1

6.3 Phase 1 Environmental Site Assessment ..................................................................................................... 6-1

7. Geotechnical Investigations ............................................................................................................................ 7-1

7.1 Existing Information ............................................................................................................................................. 7-1

7.1.1 Regional Geology ..................................................................................................................................... 7-1

7.1.2 Sinkhole Formation Favorability ........................................................................................................ 7-1

7.1.3 Historical Geotechnical Explorations ............................................................................................... 7-2

7.2 Subsurface Conditions ........................................................................................................................................ 7-3

7.3 Preliminary Foundation Considerations ....................................................................................................... 7-3

7.4 Additional Geotechnical Investigations ........................................................................................................ 7-4

8. Permitting ............................................................................................................................................................ 8-1

8.1 Permitting Overview ............................................................................................................................................. 8-1

8.2 Environmental Resource Permit...................................................................................................................... 8-2

8.3 National Pollutant Discharge Elimination System ................................................................................... 8-2

8.4 Fuel Tank Permit ................................................................................................................................................... 8-2

8.5 Department of Health – Public Water System Permit ............................................................................ 8-3

8.6 Site Development Permit ................................................................................................................................... 8-3

8.7 Special Use Permit ................................................................................................................................................ 8-3

8.8 Right of Way and Traffic Control Permits .................................................................................................... 8-3

8.9 Building Permit ...................................................................................................................................................... 8-3

8.10 Hillsborough County Environmental Protection Commission ............................................................ 8-4

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8.11 Florida Fish and Wildlife Conservation Commission - Gopher Tortoise ......................................... 8-4

9. Architecture ......................................................................................................................................................... 9-1

9.1 Applicable Codes and Standards .................................................................................................................... 9-1

9.2 Energy Code Criteria ............................................................................................................................................ 9-1

9.3 Facility Descriptions and Code Evaluations ................................................................................................ 9-2

9.3.1 Operations and High Service Pump Station Building ................................................................ 9-2

9.3.2 Maintenance Building ............................................................................................................................ 9-7

10. Project Delivery Approach ............................................................................................................................ 10-1

11. References ........................................................................................................................................................ 11-1

Appendices A Utility Master Plan

B Test Well Data

C Water Quality Blend Data

D Pump Selections

E Geotechnical Report

Tables 2-1 Projected Point of Connection Flows to Meet SCDWF Demands .................................................................... 2-2

2-2 Maximum Flow Conditions ............................................................................................................................................. 2-3

2-3 South Hillsborough Wellfield (Test Well Data) Water Quality (2021, 2023) ............................................. 2-7

2-4 Tampa Bay Regional Surface Water Treatment Plant Water Quality (August 2024 to December 2024) ................................................................................................................................................................ 2-8

2-5 Tampa Bay Water Desalination Plant Water Quality (January to December 2025) ............................. 2-10

2-6 Anticipated Range of Influent Water Quality ....................................................................................................... 2-11

2-7 SHP (SWTP/Desalination Blend) and SHWF Water Quality Blend ............................................................... 2-12

2-8 SHP Point of Connection (SWTP Only) and SHWF Water Quality Blend ................................................... 2-13

2-9 SHP Point of Connection (Desalination) and SHWF Water Quality Blend ................................................ 2-15

2-10 Demand Projections Used for Modeling ................................................................................................................ 2-20

2-11 Distribution System Improvements Included in Model Scenarios ............................................................... 2-21

3-1 Mass Balance for Average Water Quality and Flow Conditions (Water Quality Data from between January-October of 2025) .............................................................................................................................................. 3-3

3-2 Mass Balance for Minimum pH Conditions .............................................................................................................. 3-5

3-3 Mass Balance for Maximum pH Conditions ............................................................................................................. 3-7

3-4 Blending Location Comparison ................................................................................................................................. 3-11

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4-1 Chemical Systems and Uses ........................................................................................................................................... 4-1

4-2 SHP Free Chlorine Dose Calculations ......................................................................................................................... 4-3

4-3 SHWF Free Chlorine Dose Calculations ..................................................................................................................... 4-4

4-4 SHWF Ammonia Dose Calculations ............................................................................................................................ 4-4

4-5 SHWF Free Chlorine Dose Calculations (No Ozone) ............................................................................................. 4-4

4-6 SHWF Ammonia Dose Calculations (No Ozone) .................................................................................................... 4-4

4-7 Sodium Hypochlorite Dosing Pump Design Criteria for the Regional Water Stream .............................. 4-5

4-8 Sodium Hypochlorite Dosing Pump Design Criteria for the SHWF Water Stream ................................... 4-6

4-9 Sodium Hypochlorite Dosing Pump Design Criteria for the HSPS Trim ....................................................... 4-6

4-10 Sodium Hypochlorite Storage Tanks Design Criteria ........................................................................................... 4-7

4-11 Ammonium Sulfate Dosing Pump Design Criteria for the SHP Water .......................................................... 4-7

4-12 Ammonium Sulfate Design Criteria for the SHWF Water ................................................................................... 4-8

4-13 Ammonium Sulfate Design Criteria for the HSPS Trim ....................................................................................... 4-8

4-14 Ammonium Sulfate Storage Tanks Design Criteria .............................................................................................. 4-9

4-15 Ammonium Hydroxide Dosing Pump Design Criteria for the Regional Water Stream ........................... 4-9

4-16 Ammonium Hydroxide Dosing Pump Design Criteria for the SHWF Water Stream ............................. 4-10

4-17 Ammonium Hydroxide Dosing Pump Design Criteria for the HSPS Trim ................................................. 4-10

4-18 Ammonium Hydroxide Storage Tanks Design Criteria ..................................................................................... 4-11

4-19 Alternative Ammonia Chemical Comparison ....................................................................................................... 4-11

4-20 Sodium Hydroxide Dosing Pump Design Criteria for the Combined Water Stream ............................. 4-14

4-21 Sodium Hydroxide Storage Tank Design Criteria ............................................................................................... 4-15

4-22 Corrosion Inhibitor Dosing Pump Design Criteria for the Combined Water Stream ............................. 4-16

4-23 Corrosion Inhibitor Storage Tank Design Criteria ............................................................................................... 4-17

4-24 2028 Normal Operations Storage ............................................................................................................................ 4-21

4-25 2028 With One Tank Offline ....................................................................................................................................... 4-21

4-26 Drinking Water Storage - Design Criteria and Tank Sizes ............................................................................... 4-23

4-27 Storage Tank Key Features .......................................................................................................................................... 4-24

4-28 Pump Suction Piping Summary ................................................................................................................................. 4-26

4-29 Upper and Lower Flow and Total Dynamic Head that Pumps Must Meet ................................................ 4-28

4-30 Vertical Turbine Pump and Horizontal Split Case Pump Station Alternatives Summary ................... 4-43

4-31 Selected Alternative Design Criteria ........................................................................................................................ 4-46

4-32 Recommended Alternative Size and Materials of Construction ................................................................... 4-46

8-1 Permit Requirements Summary ................................................................................................................................... 8-1

9-1 Energy Code Criteria.......................................................................................................................................................... 9-1

9-2 Operations and High Service Pump Station Building Code Information ...................................................... 9-2

9-3 Operations and High Service Pump Station Building Structure and Materials .......................................... 9-3

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9-4 Maintenance Building Code Information .................................................................................................................. 9-7

9-5 Maintenance Building Structure and Materials ...................................................................................................... 9-8

Figures 1-1 Facility Location Plan ........................................................................................................................................................ 1-2

2-1 Anticipated General Configuration of SHP Balm Point of Connection at SCDWF .................................... 2-4

2-2 Potential SHP Point of Connection Delivery Pressures ....................................................................................... 2-6

2-3 Projected Chloramine Decay Curve.......................................................................................................................... 2-16

2-4 Extent of the Hillsborough County Urban Service Area, Including the RP2 and WVR2 Regions ..... 2-19

2-5 Demand Projections for the South Central Service Area ................................................................................. 2-20

2-6 Diurnal Demand Patterns Based on Mass Balance Analysis of 2025 Supervisory Control and Data Acquisition Data .................................................................................................................................................... 2-22

2-7 Map of Proposed South County Distribution System Improvements (Red) Included in Modeling ........................................................................................................................................................................ 2-23

2-8 System Curve for the 2050 Maximum Day Demand Peak Hour Demand with the SCBPS in Service ............................................................................................................................................................................. 2-25

2-9 Map of System Pressures for 2050 Maximum Day Demand Peak Hour Demand with SCDWF High Service Pump Station at 100 mgd ................................................................................................................ 2-26

2-10 System Head Curves (Pump Station Discharge Hydraulic Grade Line Versus Flow) for Various Demand and Operating Conditions ......................................................................................................................... 2-27

2-11 System Head Curves (Pump Station Discharge Hydraulic Grade Line Versus Flow) with Emergency Scenarios ..................................................................................................................................................... 2-28

2-12 Pressure Results for 2028 Minimum Day, Minimum Hour Demand Condition Showing Higher System Pressures North of SCDWF .......................................................................................................................... 2-29

2-13 Pressure Results for 2028 Maximum Day Demand Peak Hour Demand Condition Showing Higher System Pressures South of SCDWF ........................................................................................................... 2-30

2-14 Traditional Bypass Around the SCDWF Ground Storage Tanks and SCDWF High Service Pump Station – Conceptual ...................................................................................................................................................... 2-31

2-15 SCDWF High Service Pump Station Internal Bypass – Conceptual .............................................................. 2-32

2-16 Combined Bypass Concepts ........................................................................................................................................ 2-32

3-1 Process Flow Diagram ...................................................................................................................................................... 3-2

3-2 Yard Piping and Ground Storage Tank Layout with In Tank Blending .......................................................... 3-9

3-3 Yard Piping and Ground Storage Tank Layout with In Pipe Blending Layout ......................................... 3-10

3-4 Example of In Pipe Blending Piping Layout .......................................................................................................... 3-10

4-1 Chemical Facility Layout ............................................................................................................................................... 4-19

4-2 Storage Tank Volume .................................................................................................................................................... 4-20

4-3 Storage Tank Volume - Excludes Little Manatee River Area Demand ....................................................... 4-22

4-4 Storage Tank Volume - Includes Little Manatee River Area Demand ........................................................ 4-23

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4-5 Vertical Turbine Pump Hydraulic Model Overview ............................................................................................ 4-27

4-6 Horizontal Split Case Pump Hydraulic Model Overview .................................................................................. 4-27

4-7 Upper and Lower Pump Operating Range ............................................................................................................. 4-28

4-8 Example Pump Curve and Operating Regions ..................................................................................................... 4-29

4-9 Flowserve Model 39 ELL Pump Curve ..................................................................................................................... 4-31

4-10 Vertical Turbine Pump Four Duty Pump System and Pump Curves ........................................................... 4-32

4-11 Flowserve Model 400-LNN-725 Pump Curve ..................................................................................................... 4-33

4-12 Vertical Turbine Pump Four Duty Pump System and Pump Curves ........................................................... 4-34

4-13 Flowserve Model 34 ELK Pump Curve .................................................................................................................... 4-35

4-14 Vertical Turbine Pump Five Duty Pump System and Pump Curves ............................................................ 4-36

4-15 Flowserve Model 400-LNE-900 Pump Curve ...................................................................................................... 4-37

4-16 Horizontal Split Case Pump Five Duty Pump System and Pump Curves .................................................. 4-38

4-17 Flowserve Model 32 SNM Pump Curve .................................................................................................................. 4-39

4-18 Vertical Turbine Pump Six Duty Pump System and Pump Curves ............................................................... 4-40

4-19 Flowserve Model 350-LNN-575 Pump Curve ..................................................................................................... 4-41

4-20 Horizontal Split Case Pump Six Duty Pump System and Pump Curves..................................................... 4-42

5-1 Conceptual Site Plan ......................................................................................................................................................... 5-4

7-1 U.S. Geological Survey Map (St. Petersburg 30 × 60-Minute Quadrangle) ................................................ 7-1

7-2 Florida Geological Survey Sinkhole Formation Favorability Map ................................................................... 7-2

9-1 Overall Operations and High Service Pump Station Building Layout. ........................................................... 9-5

9-2 Operations Area Layout ................................................................................................................................................... 9-6

9-3 Maintenance Building Layout ..................................................................................................................................... 9-10

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Acronyms and Abbreviations µmhos/cm micromho(s) per centimeter µg/L microgram(s) per liter

°C degrees Celsius

ADD average day demand

AOR allowable operating range

ASTM ASTM International

BODR Basis of Design Report

CARV combination air release valve

CCPP calcium carbonate precipitation potential

CFD computational fluid dynamics

CHWTF Central Hillsborough Water Treatment Facility

Cl2 chlorine

CLDIP cement-lined ductile iron pipe

CMAR construction manager at-risk

CMU concrete masonry unit

CT concentration time

C.U. color unit(s)

DO dissolved oxygen

DOH Department of Health

DSD Development Services Division

EA each

EPA U.S. Environmental Protection Agency

EPC Environmental Protection Commission

ERP Environmental Resource Permit

ESA Environmental Site Assessment

FAC Florida Administrative Code

FBC Florida Building Code

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FBCEC Florida Building Code, Energy Conservation

FDEP Florida Department of Environmental Protection

FEMA Federal Emergency Management Agency

FGS Florida Geological Survey fps foot/feet per second

FRP fiberglass reinforced plastic

FWC Fish and Wildlife Conservation Commission

FWPS finished water pump station gal gallon(s) gpd gallon(s) per day gph gallon(s) per hour gpm gallon(s) per minute gpm/m gallon(s) per minute per meter

GST ground storage tank

HGL hydraulic grade line

I&C instrumentation and control

HAA5 haloacetic acids five hp horsepower

HRT hydraulic residence time

HSC horizontal split case

HSPS high service pump station kWhr kilowatt-hour(s)

LCR Lead and Copper Rule

LS lump sum

LSI Langelier Saturation Index

MCSF minimum continuous stable flow

MDD maximum day demand mg milligram(s)

MG million gallon(s)

260325115047_36e63908 ix mg/L milligram(s) per liter mgd million gallon(s) per day

MOU memorandum of understanding

N/A not available

NAVD88 North American Vertical Datum of 1988 ng/L nanogram(s) per liter

NH3-N ammonia as nitrogen

NPDES National Pollutant Discharge Elimination System

NPSHa net positive suction head available

NPSHr net positive suction head required

NTU nephelometric turbidity unit(s)

O3 ozone

O&M operations and maintenance

PDR Preliminary Design Report

PFOA perfluorooctanoic acid

PFOS perfluorooctane sulfonate

POC point of connection

POR preferred operating range psi pound(s) per square inch

RFS Regional Facility Site

ROW right of way

RP2 Residential Planned-2 rpm revolution(s) per minute

Rule Wetlands Application Rule

SCADA supervisory control and data acquisition

SCBPS South County Booster Pump Station

SCDWF South County Drinking Water Facility

SF square foot (feet)

SHARP South Hillsborough Aquifer Recharge Program

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SHP South Hillsborough Pipeline

SHWF South Hillsborough Wellfield

SST stainless steel s.u. standard unit(s)

SWFWMD Southwest Florida Water Management District

SWTP surface water treatment plant

TBW Tampa Bay Water

TDH total dynamic head

TDS total dissolved solids

TOC total organic carbon

TTHM total trihalomethanes

USGS U.S. Geological Survey

VFD variable-frequency drive

VTP vertical turbine pump

WRD Water Resources Department

WTP water treatment plant

WVR2 Wimauma Village Residential

Section 1

Introduction

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1. Introduction The purpose of this Preliminary Design Report (PDR) is to document the conceptual‑level design for the proposed South County Drinking Water Facility (SCDWF). This report compiles the information needed to define facility requirements, hydraulics and system integration, and equipment and process preferences, as well as building programming for the Operations and High Service Pump Station and Maintenance buildings. The selected unit‑process alternatives and supporting information presented herein will form the foundation for subsequent detailed design. Design criteria for all disciplines will be included in the Basis of Design Report (BODR) included in the detailed design.

1.1 Project Background

The Hillsborough County Water Resources Department (WRD) has launched an important infrastructure program, the One Water Program, to address short-term and long-term water and wastewater needs in the County’s South-Central Service Area. The One Water Program complements the existing surrounding areas, is sensitive to current environment, and provides a sustainable and resilient approach. The One Water Program’s wastewater improvements are underway. The WRD is ready to proceed with the long-term water improvements and intends to design and build the new SCDWF project using the construction manager at risk (CMAR) delivery model. The project includes design and construction of a new water treatment facility that will receive water from Tampa Bay Water’s (TBW’s) new South Hillsborough Pipeline (SHP) and future South Hillsborough Wellfield (SHWF), further treat the water, and then deliver it into the County’s water distribution system. The existing water distribution system is currently supplied by two water treatment facilities, Central Hillsborough and Lithia. The new SCDWF is needed to meet growing demands in the southern reaches of the South-Central Service Area.

The new SCDWF average‑day supply and treatment capacity is constrained by available water sources, 60 million gallons per day (mgd) from SHP and 7 to 12 mgd from the SHWF. The peak capacity to the South County Potable Water Distribution System is 100 mgd, which is limited by the design capacity of the new high‑service pump station (HSPS). While these values define the normal operating envelope, it may be feasible—on a temporary and emergency basis—to increase influent supply through coordination with Tampa Bay Water. Such measures would require operational agreement and verification to ensure system reliability and compliance with established performance criteria.

The major facilities anticipated for the SCDWF are as follows:

Ground storage tanks High service pump station Backup generators with fuel tanks Chemical storage and feed Maintenance building Operations and High Service Pump Station building Associated electrical infrastructure

1.1.1 Location

The SCDWF will be located on a County‑owned parcel near the intersection of Balm Road and Balm Riverview Road in Balm, Florida, as shown on Figure 1-1. The site is situated within the County’s South‑Central Service Area and provides convenient access to major transportation corridors. The surrounding area consists primarily of agricultural and low‑density residential land uses, with adequate buffer space to accommodate facility infrastructure and minimize potential impacts to nearby properties.

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1.1.2 Facility Goals and Objectives

The goals and objectives of the SCDWF are centered on delivering a reliable, resilient, and sustainable source of treated drinking water to support the long‑term needs of Hillsborough County’s South‑Central Service Area. The primary goals of the facility include the following:

Provide safe, reliable, sustainable, and resilient drinking water service to current and future residents of South Hillsborough County through the 2050 planning period.

Complete facilities on time to receive and treat water from TBW when the SHP is operational.

Provide infrastructure and facilities that meet regulatory requirements and are designed with flexibility to meet future regulatory requirements and increased water demand through the 2050 planning period.

Integrate the new facility with existing infrastructure and facilities to optimize operation of the entire water distribution system.

These goals provide the framework for evaluating design alternatives, establishing performance criteria, and ensuring that the facility meets regulatory requirements, operational expectations, and the County’s vision for future growth and system reliability.

Figure 1-1. Facility Location Plan

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1.2 Report Organization

This PDR is organized into the following sections:

1. Introduction

2. Hydraulic and System Integration Evaluations

3. Process Design Considerations

4. Major Unit Operations

5. Site Plan

6. Environmental Assessments

7. Geotechnical Investigations

8. Permitting

9. Architecture

10. Project Delivery Approach

11. References

12. Appendices

Section 2

Hydraulic and System Integration Evaluations

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2. Hydraulic and System Integration Evaluations As part of the preliminary design phase of the SCDWF project, the design team undertook hydraulic and system integration evaluations to support early decision-making and establish preliminary design criteria for the facility.

Preliminary results and recommendations associated with the hydraulic and system integration evaluations, including data tables, graphs, schematics, maps, and figures, were compiled into PowerPoint presentation files and presented to the Hillsborough County project team during technical meetings to support decision-making. Follow-up evaluations were performed in response to stakeholder questions and requests.

This section summarizes the evaluations performed, along with results, recommendations, and County decisions to inform the design of the SCDWF in the next phase of the project. Results and recommendations from the hydraulic and system integration evaluations are organized into the following two main sections:

Incoming Water Supply Sources and Water Quality (Section 2.1) System Hydraulics and SCDWF Pump Station Considerations (Section 2.2)

2.1 Incoming Water Supply Sources and Water Quality

2.1.1 Incoming Water Supplies

The incoming water supply sources to Hillsborough County’s new SCDWF will be supplied by TBW. At this time, the supply sources are anticipated to include finished surface water and desalinated water conveyed from TBW’s Regional Facility Site (RFS) and finished groundwater supplied by a proposed TBW groundwater treatment plant adjacent to Hillsborough County’s SCDWF site. Within the future planning horizon, no additional supply sources have been identified for the SCDWF site.

The finished water from the RFS will be conveyed to SCDWF via a new 60-inch pipeline (the SHP) to a new point of connection (POC) at the SCDWF site. Hillsborough County and TBW agreed to a memorandum of understanding (MOU) for the new SHP POC on August 20, 2020. The MOU provides for supply of up to 60 mgd to the SHP POC at SCDWF with a delivery pressure of 30 pounds per square inch (psi). The same MOU also provides for an additional POC at Hillsborough County’s Lithia Water Treatment Plant (WTP) for supply of up to 45 mgd at a delivery pressure of 30 psi. However, in accordance with the MOU, the simultaneous supply to both POCs shall not exceed a combined 65 mgd. The SHP is currently under construction with a scheduled completion date of November 2028. Hillsborough County’s intention is to complete construction and to also be online by November 2028.

The groundwater supply to TBW’s proposed groundwater treatment plant adjacent to the SCDWF will come from TBW’s SHWF, which is in the development stage. An MOU for the POC associated with the SHWF supply and treatment is not in place and is currently in discussion between Hillsborough County and TBW. At this time, the SHWF POC supply flow rate and delivery pressure are unknown, with the potential capacity being, in part, dependent on the volume of water supply credits that can be supported by the South Hillsborough Aquifer Recharge Program (SHARP). For purposes of planning for the SCDWF, it was assumed that the future water supply through the SHWF POC could vary between an annual average flow of 7 mgd and 12 mgd at buildout of the SHWF.

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2.1.2 Incoming Flows and Pressures

2.1.2.1 SHP and SHWF Point of Connection Flows

TBW will deliver to the SCDWF finished surface water and desalinated water through the SHP POC and groundwater via the SHWF POC. The quantity of flow and proportion of flow from each POC will vary in response to a number of factors, including details of MOUs, variable SCDWF demands, the size and implementation schedule of the SHWF, and TBW operating protocols. Table 2-1 provides a projected breakdown of water supply flows from each of the two POCs as required to meet the projected SCDWF demands based on the minimum and maximum likely wellfield supply. Understanding the breakdown of flow contributions between the two sources provides a basis for analyzing overall influent water quality and informs the design of piping and chemical feed systems at the SCDWF.

The quantity of water supply ultimately available from the SHWF POC is currently unconfirmed and depends on the to-be-determined wellfield capacity, as well as the available water supply credits provided through SHARP. In addition, it is anticipated that the SHWF POC will not be available until after the SCDWF is operational, and the capacity of the SHWF is anticipated to increase over time as production well construction is completed and placed into service. Table 2-1 reflects two potential SHWF flow rate scenarios (increasing from 0 to 7 mgd over time for the low-flow scenario and increasing from 0 to 12 mgd over time for the high-flow scenario). Projected flows from the SHP POC were established as the difference between the SCDWF demand (based on 2026 Comprehensive Utility Master Plan [Exhibit K] projections, included in Appendix A) and the anticipated SHWF flows. Projections are provided for minimum, average, and maximum flow conditions in planning years 2029, 2030, and 2050.

Table 2-1. Projected Point of Connection Flows to Meet SCDWF Demands

Year Flow Criteria SCDWF Demand Flow, mgd

SHWF Low Flow, mgd

SHP High Flow, mgd

SHWF High Flow, mgd

SHP Low Flow, mgd

Minimum Flow 8 0 8 0 8

Average 10 0 10 0 10

Maximum Day 20 0 20 0 20

Minimum Flow 12 2 10 2 10

Average 15 3 12 4 11

Maximum Day 30 5 25 6 24

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Year Flow Criteria SCDWF Demand Flow, mgd

SHWF Low Flow, mgd

SHP High Flow, mgd

SHWF High Flow, mgd

SHP Low Flow, mgd

Minimum Flow 28 2 26 2 26

Average 35 5 30 6 29

Maximum Day 50 7 43 12 38

Notes:

TBW RFS Pump Station minimum flow = ~10 mgd.

2029 minimum SHP flow of 8 mgd assumes at least 2 mgd of flow to Lithia WTP.

SHWF flows to be negotiated in future MOU and based on credit assumptions for permitted annual average flow.

SHP flow is based on total SCDWF demand minus SHWF flow.

2050 is used as the long-term planning condition in lieu of buildout, in accordance with County direction.

SCDWF demands are based on Hillsborough County 2026 Comprehensive Utility Master Plan (Exhibit K) projections included in Appendix A.

Three maximum day flow conditions were also evaluated and included in Table 2-2. These scenarios represent flow conditions when the SCDWF is using more flow than the projected demand within the planning horizon, up to the flow limitation of the SHP POC and the anticipated flow limitation of the SHWF

POC.

Table 2-2. Maximum Flow Conditions

Flow Criteria SCDWF Demand Flow, mgd

SHP Flow, mgd

SHWF Low Flow, mgd

SHP Flow, mgd

SHWF High Flow, mgd

Maximum Flow Condition 1

60 53 7 48 12

Maximum Flow Condition 2

67 60 7 55 12

Maximum Flow Condition 3

72 N/A N/A 60 12

Notes:

Maximum Flow Condition 1 sets the maximum total flow rate for this scenario to 60 mgd. The SHWF low flow represents the highest of the low flows out of the wellfield (0–7 mgd) along with the SHWF high flow that represents the highest of the high flows out of the wellfield (0–12 mgd). The SHP flows are adjusted to meet the SCDWF demand of 60 mgd.

Maximum Flow Condition 2 represents a SHP maximum flow of 60 mgd plus 7 mgd from the SHWF low flow rate for a capacity of 67 mgd or the SHWF high flow rate which reduces the SHP flow to 55 mgd but remains at 67 mgd.

Maximum Flow Condition 3 represents a maximum flow of 60 mgd from SHP and a projected SHWF maximum of 12 mgd for a capacity of 72 mgd. Note: this option is not available for the SHWF low flow rate and identified as “N/A.”

N/A = not available

Some key observations from the flow analysis are as follows:

The minimum flow that can be delivered through the SHP from TBW’s regional HSPS is about 10 mgd due to pump turndown limitations. Assuming 2 mgd of flow is being sent to the SHP Lithia POC, the minimum flow to be received at the SCDWF would be 8 mgd.

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The SHWF is not anticipated to be in operation when the SCDWF comes online. Therefore, all source water flow to the SCDWF in early operation will come through the SHP POC only. Typical average water quality for the SHP supply water alone is provided in Table 2-3.

Flow contributions through the SHWF will increase over time in the early years as additional wells are completed or permitted quantities (i.e., SHARP credits or Water Use Permit purchases) are acquired.

The ultimate quantity of flows from the SHWF are not known at this time but are estimated to be between 7 and 12 mgd on an annual average basis.

The SHP MOU provides for sufficient water supply (60 mgd at 30 psi) to meet projected maximum day SCDWF demands through the 2050 planning horizon for the facility (50 mgd per 2026 Comprehensive Utility Master Plan [Exhibit K], included in Appendix A).

The two planned POCs provide a potential maximum of 72 mgd of water supply (assuming 12 mgd from the SHWF). This exceeds the 2050 maximum day demand (MDD) for the SCDWF and provides an opportunity to distribute additional flows from the SCDWF to mitigate an emergency outage elsewhere in the County’s system.

Influent piping and chemical feed systems were sized to handle an SHP flow of 60 mgd and an SHWF flow of 12 mgd per County direction received at the progress meeting on February 16, 2026.

2.1.2.2 Typical SHP and SHWF Point of Connection Pressures

As defined in the SHP MOU, the committed delivery pressure by TBW to the SHP POC is 30 psi. As shown on Figure 2-1, delivery pressure will be measured just upstream of the flow control valve in the POC piping. The actual delivery pressure upstream of the flow control valve depends on the operating conditions within TBW’s transmission system and may be higher than 30 psi at any given time. However, since the SHP POC at the SCDWF is currently the hydraulically farthest POC from TBW’s regional HSPS, it is likely that TBW will target a relatively narrow pressure band at this location, estimated to be 30 to 35 psi.

Since an MOU for the SHWF is not yet executed, the committed delivery pressure by TBW to the SHWF POC is not known at the time of development of this PDR. It is anticipated that the delivery pressure for the SHWF POC will be in the 20 to 30 psi range, based on the delivery pressure at other TBW groundwater POCs.

It is important to note that the incoming pipeline pressures downstream of the flow control valve at both POCs will be largely influenced by SCDWF storage tank levels and will be less than 30 psi during typical flow scenarios.

Figure 2-1. Anticipated General Configuration of SHP Balm Point of Connection at SCDWF

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2.1.2.3 Potential SHP Point of Connection Pressure in Emergency Scenario

While it is expected that TBW will typically operate its transmission system to target the minimum required POC pressure, its system is capable of delivering significantly higher pressure to the SHP POC under lower flow rates. This capability to deliver higher than the committed delivery pressure could potentially be leveraged to mitigate an emergency scenario if requested by Hillsborough County and supported by TBW.

Considering this opportunity, the design team evaluated potential emergency scenarios under which higher delivery pressure from TBW could be leveraged to convey a reduced volume of water supply directly into Hillsborough County’s distribution system (thereby bypassing the proposed pump station and storage tanks). This could potentially provide mitigation for the following situations:

Early supply of additional water to the County distribution system to meet demands should the SHP be completed and commissioned prior to completion of the SCDWF pump station.

Long-term capability for direct conveyance to the distribution system, bypassing the SCDWF tanks and pumps, to partially mitigate an SCDWF pump station outage scenario.

Options related to the configuration of bypass piping to support these mitigation concepts are discussed in more detail in Subsection 2.2.1.5. In this subsection, the focus is on the feasibility of such emergency mitigation from a flow and pressure perspective.

Figure 2-2 illustrates the potential delivery pressure to the SHP POC based on the capability of TBW’s pumping and transmission system, compared to the expected typical delivery pressure range (30 to 35 psi) and the committed delivery pressure in accordance with the MOU (30 psi).