RFQ_24_25-10_Attachment__1-_SMWTP_PDR_Signed_and_Sealed_01.14.2025.pdf

CITY OF SANFORD

Main WTP Advanced Treatment Upgrades

Preliminary Design Report FINAL / January 2025

Main WTP Advanced Treatment Upgrades

Preliminary Design Report FINAL / January 2025

This item has been digitally signed and sealed by Jeremy O’Neal on the date adjacent to the seal.

Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies.

Carollo Engineers, Inc.

200 E Robinson Street, Suite 1400 Orlando, Florida 32801 407.478.4642 407.377.4343

PRELIMINARY DESIGN REPORT

JANUARY 2025 / FINAL / CAROLLO

CITY OF SANFORD

MAIN WTP ADVANCED TREATMENT UPGRADES i

Contents

SECTION 1 INTRODUCTION 1

1.1 Background and Purpose 1

1.2 Description of Project 2

1.2.1 Description of Existing Water Supply System 2

1.2.2 Summary of Impacts to Existing Treatment Facilities 7

SECTION 2 REGULATORY REQUIREMENTS 8

2.1 Florida Department of Environmental Protection 8

2.1.1 Permit to Construct Public Water System Components 8

2.1.2 Air Quality Permit 8

2.1.3 Wastewater Collection Transmission System Permit 9

2.1.4 Environmental Resource Program Permit 9

2.2 City of Sanford 9

2.2.1 Industrial User Discharge Permit 9

2.2.2 Site Development Permit 10

2.2.3 Building Department Permitting 10

SECTION 3 BASIS OF DESIGN 11

3.1 Capacity and Description 11

3.2 Water Quality Data 12

3.2.1 Raw Water Quality 13

3.2.2 Finished Water Quality 27

3.2.3 Distribution System Disinfection Byproducts 33

3.3 Summary of Bench-Scale Testing 34

3.3.1 RSSCTs and Hydrogen Peroxide Quench Testing 34

3.3.2 Collimated Beam Testing 35

3.4 Treatment Goals 37

3.5 Water Quality for Process Design 38

SECTION 4 DESIGN CRITERIA 42

4.1 General 42

4.1.1 Design Capacity 42

4.1.2 Overall Treatment Process 42

4.2 Civil 44

4.2.1 Site Layout 44

4.2.2 Yard Piping 48

4.2.3 Drainage 50

4.2.4 Stormwater Management System 50

4.2.5 Stormwater Requirements 55

4.2.6 Access Road 56

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4.3 Hydraulic Profile 56

4.4 Process Mechanical 56

4.4.1 Raw Water Well Pumps 56

4.4.2 Hydrogen Peroxide Storage and Feed System 57

4.4.3 UV AOP System 61

4.4.4 GAC System 62

4.4.5 Ground Storage Tanks 65

4.5 Materials 66

4.6 Structural 66

4.6.1 Structural Basis of Design 66

4.6.2 Foundation Design 68

4.6.3 Applicable Code References 68

4.6.4 Standards 69

4.6.5 Architectural Materials and Massing 69

4.7 Electrical 70

4.7.1 Existing Utility Feeds 70

4.7.2 Determining Available Power from Existing Utility Transformers 70

4.7.3 Existing Equipment 70

4.7.4 New Equipment 72

4.8 Instrumentation and Controls 72

4.8.1 General Scope of Work 72

4.8.2 General Design Elements 73

4.8.3 Instrumentation and Standards 77

4.8.4 Control System 77

4.8.5 SCADA System Modifications 79

4.8.6 Site Security 79

4.8.7 Control System Integration 79

4.8.8 PDR Drawings 80

4.9 HVAC 80

4.9.1 HVAC Basis of Design 80

4.9.2 Reference Codes and Standards 81

4.10 Plumbing 81

4.10.1 Plumbing Basis of Design 81

4.10.2 Reference Codes, Standards, and Documents 81

4.10.3 Water Systems 82

4.10.4 Drainage Systems 82

4.11 Construction Considerations 82

4.11.1 Pipe and Treatment Facility Disinfection 82

4.11.2 Construction Phasing 82

SECTION 5 LIST OF TECHNICAL SPECIFICATIONS 84

SECTION 6 COST ESTIMATE AND ESTIMATED SCHEDULE 90

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MAIN WTP ADVANCED TREATMENT UPGRADES iii

Appendices

APPENDIX A SOURCE WATER CHARACTERIZATION AND BENCH-SCALE TESTING TM

APPENDIX B ELECTRICAL BILLING STATEMENTS

APPENDIX C CITY OF SANFORD WATER PROJECTIONS (NOVEMBER 2023 CIP MEETING)

APPENDIX D DETAILED COST TABLE

APPENDIX E LEGAL DESCRIPTION AND SURVEY

Tables Table 1 Potable Supply Production Wells for the City of Sanford 3 Table 2 Existing SMWTP High Service Pumps 7 Table 3 Source Water Characterization Sampling Results (Non-PFAS Parameters) 14 Table 4 Available Raw Water Quality Data for Wells Serving SMWTP (excluding

1,4-Dioxane, PFAS, and 2023 MOR data), Provided by the City 15 Table 5 Water ARC Bench Scale Testing Raw Water 1,4-Dioxane Measurements 18 Table 6 Source Water Characterization Sampling Results (PFAS Parameters) 20 Table 7 Finished Water Quality, 2018 through 2023 27 Table 8 Summarized RSSCT Results 35 Table 9 National Drinking Water Regulations for PFAS 37 Table 10 Assumed Raw Water Quality for UV AOP, per Well 40 Table 11 UV AOP Design Water Quality 41 Table 12 Aboveground Piping Color Code 48 Table 13 Raw Water Well Pump Design Criteria 57 Table 14 Hydrogen Peroxide Chemical Characteristics and Dosage Information Design

Criteria 58 Table 15 Hydrogen Peroxide Chemical Storage and Containment Design Criteria 59 Table 16 Hydrogen Peroxide Chemical Pumps and Piping Design Criteria 60 Table 17 Hydrogen Peroxide Dilution, Feed Piping, and Mixing Design Criteria 60 Table 18 UV AOP System Design Criteria 61 Table 19 GAC System Design Criteria 62 Table 20 GAC Media Replacement 63 Table 21 GAC Backwash System Design Criteria 64 Table 22 GAC Backwash Waste Pump Station Design Criteria 65 Table 23 GST Design Criteria 66 Table 24 Wind Design Parameter Summary 67 Table 25 Seismic Design Parameter Summary 67 Table 26 Typical Live Loads 68 Table 27 Instrumentation List 77 Table 28 Typical Control Panel Components 78 Table 29 Climate Assumptions for HVAC 80 Table 30 Proposed HVAC Indoor Design Criteria 81

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Table 31 List of Technical Specifications 84 Table 32 Cost to Construct Facilities 91 Table 33 Estimated Implementation Schedule 91

Figures Figure 1 City of Sanford WTPs and Potable Supply Wells 4 Figure 2 City of Sanford Potable Water Service Area and Storage Tanks 6 Figure 3 Historical SMWTP Flow 11 Figure 4 Historical SAWTP Flow 12 Figure 5 Historical Golf Course Wellfield (GC-) 1,4-Dioxane 16 Figure 6 Historical Oregon Avenue Wellfield (OA-) 1,4-Dioxane 17 Figure 7 Historical Twin Lakes Wellfield (TL-) 1,4-Dioxane 18 Figure 8 Potable Supply Well PFOS 19 Figure 9 Potable Supply Well PFOA 22 Figure 10 Potable Supply Well PFHxS 23 Figure 11 Potable Supply Well PFNA 24 Figure 12 Potable Supply Well HFPO-DA 24 Figure 13 Potable Supply Well PFBS 25 Figure 14 Potable Supply Well Hazard Index (Calculated) 26 Figure 15 Historical POE 1,4-Dioxane 29 Figure 16 Historical SMWTP POE PFOS 30 Figure 17 Historical SMWTP POE PFOA 31 Figure 18 Historical SMWTP POE PFHxS 32 Figure 19 Historical SMWTP POE Hazard Index 32 Figure 20 Distribution System Total TTHM Highest LRAA 33 Figure 21 Distribution System HAA5 Highest LRAA 34 Figure 22 UV Dose Oxidant Product Defined using the Initial Oxidant Concentration as a Function of TOC 36 Figure 23 Existing Site Map 45 Figure 24 Overall Site Plan 47 Figure 25 FEMA Flood Map 52 Figure 26 Overall Site Existing Elevation Map 53 Figure 27 Water Treatment Plant Existing Elevation Map 54 Figure 28 Single-Line Drawing of Utility Feed to Main WTP Control Building MCC-1 and

MCC-2 71

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MAIN WTP ADVANCED TREATMENT UPGRADES 1

SECTION 1 INTRODUCTION

1.1 Background and Purpose

The City of Sanford (City) owns and operates the Sanford Main Water Treatment Plant (SMWTP) and Sanford Auxiliary Water Treatment Plant (SAWTP) which provide drinking water to its customers. Water produced by these facilities must comply with the drinking water quality standards set by the Florida Department of Environmental Protection (FDEP) and the United States Environmental Protection Agency

(USEPA).

The purpose of this project is to reduce per- and polyfluoroalkyl substances (PFAS), 1,4-dioxane, and total trihalomethanes (TTHM) precursors in the SMWTP finished water. This project does not include upgrades to the SAWTP.

On April 10, 2024, the USEPA finalized the national primary drinking water regulation (NPDWR) for PFAS.

Starting in April 2029, both the SMWTP and SAWTP will be required to meet the maximum contaminant levels (MCL) for PFAS based on the running annual average (RAA) of quarterly samples collected at the point of entry (POE). The City has monitored PFAS at the SMWTP POE quarterly since 2021.

Additionally, the groundwater supply wells for the SMWTP have been historically shown to contain variable concentrations of 1,4-dioxane. Several wells have exhibited concentrations above the USEPA one-in-one-million (10-6) lifetime excess cancer risk level of 0.35 µg/L for drinking water, which is equivalent to the Health Advisory Level (HAL) set by the Florida Department of Health (FDOH).

Two samples collected from the SMWTP POE, one in 2013 and another in 2016, contained 1,4-dioxane concentrations above the HAL. The City has since implemented a well management strategy to minimize the use of the two wells with the highest and second highest historical 1,4-dioxane concentrations (Twin Lakes Well No. 2 [TL-2] and Oregon Avenue Well No. 5 [OA-5], respectively) to keep POE 1,4-dioxane concentrations below the HAL. Managing 1,4-dioxane POE concentrations through a blending strategy will become more challenging as regulated PFAS are present at concentrations exceeding their respective MCLs in the wells that have lower 1,4-dioxane levels.

The SMWTP has also exhibited TTHM locational running annual average (LRAA) concentrations in the distribution system above the MCL of 80 micrograms per liter (µg/L) in 2017 and 2020. The City has implemented flushing programs to mitigate this issue. However, flushing will become more challenging to implement as water conservation is critical for meeting future demands due to groundwater withdrawal limits.

To address these concerns, Carollo Engineers, Inc. (Carollo) developed a facility plan that included an evaluation of treatment alternatives and the development of conceptual designs. The facility plan evaluated three treatment alternatives for the SMWTP to address PFAS, 1,4-dioxane, and TTHM. The selected treatment approach consists of an ultraviolet light advanced oxidation process (UV AOP) followed by granular activated carbon (GAC). GAC treatment will quench residual hydrogen peroxide and remove PFAS and TTHM-precursors.

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MAIN WTP ADVANCED TREATMENT UPGRADES 2

1.2 Description of Project

1.2.1 Description of Existing Water Supply System

This subsection provides general information about the City’s existing public water systems (PWS).

Information in this subsection was primarily obtained from the May 2022 sanitary survey conducted by FDEP, from information provided by the City, or from the March 2024 Construction Completion and Request for Clearance for recent SMWTP upgrades (by others).

1.2.1.1 Water Treatment Plants

The City owns and operates two WTPs: the SMWTP (PWS ID: 3590205-01) and the SAWTP (PWS ID: 3590205-02). These two facilities have rated capacities of 10.08 million gallons per day (mgd) (7,000 gallons per minute [gpm]) and 4.608 mgd (3,200 gpm) maximum daily flow (MDF), respectively.

This project is focused on the SMWTP, located at 3701 Country Club Road, Lake Mary, Florida 32746.

SMWTP and SAWTP share a distribution system to meet customer demand in the service area.

1.2.1.2 Source Water Wells

Figure 1 shows the locations of the City’s two drinking water treatment plants (WTPs), raw water supply wells, and City limits. Table 1 lists the 13 production wells serving the SMWTP and four wells that serve the SAWTP along with the treatment processes at each WTP. The City is permitted to withdraw groundwater from the Floridan Aquifer by consumptive use permit (CUP) 162 issued by the St Johns River Water Management District (SJRWMD). The City’s current 10-year CUP, issued in December 2016 and expiring in February 2026, permits the City to withdraw a combined 9.58 mgd (average day) from its four wellfields.

The Oregon Avenue, Hidden Lakes, Twin Lakes, and Golf Course wellfields are individually limited to maximum annual groundwater withdrawals of 5.4 mgd, 4.6 mgd, 2.4 mgd, and 2.4 mgd, respectively, when averaged over the year. The City is also within the Central Florida Water Initiative (CFWI) area, which may impact Floridan Aquifer withdrawal limits on future CUP renewals.

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MAIN WTP ADVANCED TREATMENT UPGRADES 3

Table 1 Potable Supply Production Wells for the City of Sanford

WTP Treatment Process(1)

Well Field Well Name(2) Well No. Well Capacity (gpm)(3)

Casing Diameter (in)(3)

Well Depth (ft)(3)

SMWTP Aeration Fluoridation Chlorination Phosphate Blend

Twin Lakes

Twin Lakes Wellfield – U TL-2 1,347 20 500 Twin Lakes Wellfield – V TL-3 813 20 500

Golf Course

Golf Course – M GC-1 658 12 545 Golf Course – N GC-2 719 12 540 Golf Course – O GC-3 712 12 525 Golf Course – P GC-4 354 8(4) 536 Golf Course – Q GC-5 809 12 550 Golf Course – R GC-6 655 8(4) 565

Oregon Avenue

Oregon Ave Wellfield-W OA-1 1,427 12 700 Oregon Ave Wellfield-X OA-2 979 12 607 Oregon Ave Wellfield-Y OA-3 1,093 12 650 Oregon Ave Wellfield-Z OA-4 970 12 650 Oregon Ave Wellfield-AA OA-5 784 12 575

SAWTP Ozonation

GAC

Fluoridation Chlorination Phosphate Blend

Hidden Lakes

Hidden Lakes-7R-G HL-7R 2,095 24 410

Hidden Lakes-8R-H HL-8R 1,796 18 500

Hidden Lakes-9I HL-9 717 8(4) 303

Hidden Lakes-12L HL-12 711 8(4) 300

Notes:

(1) According to the most recent sanitary survey conducted by FDEP (May 2022). Corrosion inhibitor type is based on recent

Distribution and Entry Point Water Quality Parameters submitted to FDEP.

(2) OA-4 and GC-6 were out of service at the time of report. Per the May 2022 sanitary survey, HL-10 and HL-11 have not been used in recent years because they are abandoned. SAWTP aquifer storage and repump (ASR) well is not shown.

(3) The May 2022 sanitary survey occasionally has different information than shown in this table. This information was provided by the City and assumed to be accurate for calculating blended water quality. Flows per well will be confirmed during subsequent design phase.

(4) According to the City, GC-4, GC-6, HL-9, and HL-12 were each re-cased in 2005 from 12 ft to 8 ft (inner case diameter).

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CITY OF SANFORD

MAIN WTP ADVANCED TREATMENT UPGRADES

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Data Sources: World Navigation Map:

Seminole County GIS, FDEP, Esri, Tom Torn, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, EPA, NPS, US Census Bureau, USDA, USFWS Modified from FDEP Geospatial Open Data ['Public Water Supply (PWS) Plants (Non· Federal)'], Seminole County GIS data ['citylimits.gdb', 'Parcels.gdb'], Disclaimer: Features shown in this figure are for planning purposes and represent approximate locations.

Engineering and/or suJVey accuracy is not implied.

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CITY OF SANFORD

MAIN WTP ADVANCED TREATMENT UPGRADES 5

1.2.1.3 Treatment Facilities

The existing treatment facilities at the SMWTP include GST tray aerators and chemical feed systems of sodium hypochlorite for disinfection, fluorosilicic acid for fluoride addition, and a phosphate blend for corrosion control. The GST cascade tray aerators are used for hydrogen sulfide removal, and the capacities of the aerators are listed in the next subsection. No changes will be made to the SMWTP’s existing maximum day permitted capacity or to the existing sodium hypochlorite, fluorosilicic acid, or phosphate blend storage and feed systems.

1.2.1.4 Storage Tanks

Figure 2 shows the City’s drinking water service area and storage reservoirs. SMWTP has two existing GSTs to store aerated water from the raw water supply wells. The northern GST was installed in the 1960s and the southern GST was installed in the 1980s. The original drawings for the two tanks indicate that these tanks each have a storage capacity of 700,000 gallons, or 0.70 million gallons (MG). These GSTs both have cascade tray aerators. The May 2022 sanitary survey and record drawings indicate the northern tray aerator has a capacity of 2,800 gpm and the southern tray aerator has a capacity of 3,500 gpm.

The City’s drinking water distribution system also includes two elevated steel storage tanks (Silver Lake Elevated Tank and Mellonville Elevated Tank) and one concrete GST (French Avenue GST). The Silver Lake and Mellonville elevated tanks have storage capacities of 0.25 MG each. The French Avenue GST has a capacity of 1.0 MG.

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CITY OF SANF ORD

MAIN WTP ADVANCED TREATMENT UPGRADES

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PRELIMINARY DESIGN REPORT

JANUARY 2025 /FINAL/ CAROLLO

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Data Sources: World Navigation Map:

Seminole County GIS, FDEP, Esri, Tom Torn, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, EPA, NPS, USDA, USFWS

Modified from: FDEP Geospatial Open Data ['Public Water Supply (PWS) Tanks (Non Federal)'], SJRWMD Geospatial Open Data ['Public Water Supply Area SJRWMD'], Seminole County GIS data ('citylimits.gdb', 'Parcels.gdb']

Disclaimer: Features shown in this figure are for planning purposes and represent approximate locations.

Engineering and/or sUJvey accuracy is not implied.

n :::r ii, CITY OF SANFORD

MAIN WTP ADVANCED TREATMENT UPGRADES 7

1.2.1.5 High Service Pumps

Table 2 shows the capacities of the existing high service pumps (HSPs) at the SMWTP.

Table 2 Existing SMWTP High Service Pumps

Pump No. Type Capacity (gpm) Head (ft) HSP 1 Horizontal Split-Case 3,000 196 HSP 2 Horizontal Split-Case 3,000 196 HSP 3 Horizontal Split-Case 3,000 196 HSP 4 Horizontal Split-Case 3,000 196

1.2.2 Summary of Impacts to Existing Treatment Facilities

This project will add the following components to the SMWTP:

New well pumps and motors for the 12 raw water wells supplying water to the SMWTP.

A hydrogen peroxide storage and feed system, including chemical injection and a static mixer.

Two UV AOP reactors (one duty/ one standby).

Ten GAC pressure vessels (nine duty/ one standby).

Two new 0.70 MG GSTs to replace the two existing GSTs due to the age of the tanks and space constraints.

Relocated chemical injection locations for sodium hypochlorite, fluorosilicic acid, and phosphate blend.

Yard piping, including bypass piping around the UV reactors and GAC vessels and bypass piping around the GSTs.

Relocated POE sampling tap and chemical analyzers.

Relocated finished water flowmeter and a new bypass flowmeter.

This project is anticipated to lower the concentrations of regulated PFAS, 1,4-dioxane, and disinfection byproduct (DBP) precursors in the finished water from the SMWTP. The design treatment capacity for these upgrades is 10.08 mgd, which is equal to the existing maximum day permitted capacity of the

SMWTP.

The construction cost of this project is estimated to be $48.5 million, as detailed in Section 6.0.

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MAIN WTP ADVANCED TREATMENT UPGRADES 8

SECTION 2 REGULATORY REQUIREMENTS

This section outlines the permitting requirements identified for this project. Permit applications will be submitted for the necessary permits to construct the facilities detailed in this document, including the following:

FDEP permit to construct potable water components (Form 62-555.900(1), F.A.C., Application for a Specific Permit to Construct PWS Components).

FDEP wastewater collection transmission system permit (Notification/ Application for Constructing a Domestic Wastewater Collection/ Transmissions System).

Environmental Resource Program (ERP) Permit.

City of Sanford Industrial User Discharge Permit.

City of Sanford Site Development Permit.

City of Sanford Building Permit.

2.1 Florida Department of Environmental Protection

The FDEP has jurisdiction over drinking water facilities, air quality, waste disposal, and stormwater management for this project.

2.1.1 Permit to Construct Public Water System Components

Construction of the new treatment processes detailed in this document will require FDEP to issue a Specific Permit to Construct Public Water System (PWS) Components. The permit application will need to include the following attachments:

A check for the application processing fee.

A signed and sealed engineering report.

Signed and sealed engineering plans.

A signed and sealed application form, including signatures from the City.

2.1.2 Air Quality Permit

No generator modifications or additions are proposed under this project. Since only power generator emissions are currently regulated, no modification to the air quality permit is required.

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MAIN WTP ADVANCED TREATMENT UPGRADES 9

2.1.3 Wastewater Collection Transmission System Permit

A permit will be required for the proposed connection of the backwash waste tank to an existing 6-inch forcemain, located parallel to the SMWTP on the opposite side of Country Club Road. The application, Notification/ Application for Constructing a Domestic Wastewater Collection/ Transmissions System, will need to be submitted to FDEP with the following attachments:

A check for the application processing fee.

Signed and sealed engineering plans and specifications, including lift station design calculations.

A signed application form.

2.1.4 Environmental Resource Program Permit

An ERP permit is required under Ch. 62-330, F.A.C., for development or construction activities with the objective of flooding prevention, protection of surface waters from stormwater runoff pollution, and preservation of wetlands. FDEP will review the stormwater calculations for this project. There is an existing ERP permit for this site held by the SJRWMD. During the detailed design phase, there will be a preapplication meeting held with FDEP and SJRWMD. It is assumed that a General Permit will satisfy the requirement for an ERP under Ch. 62-330, F.A.C. Based on subsection 403.814(12), F.S., a General Permit is available for qualifying activities having less than 10 acres of total project area and less than 2 acres of impervious surface. This permit requires “an electronic self-certification” which certifies that the system was designed by a professional engineer registered in Florida and complies with the requirements listed in subsection 403.814(12), F.S.

2.2 City of Sanford

2.2.1 Industrial User Discharge Permit

The SMWTP will require an industrial wastewater discharge permit from the City prior to discharging process water to the sewer. This permit may establish flow or pollutant limits on the discharge stream from the SMWTP. Depending on the backwash and rinse to waste flow rate from the GAC pressure vessels, the SMWTP may be classified as a significant industrial user (SIU).

During startup, the GAC backwash will include fines (GAC particulate) and arsenic. During regular operation, GAC backwash will include total suspended solids (TSS). The backwash waste stream will not contain desorbed PFAS or total organic carbon (TOC) from the GAC. The waste stream from the GAC backwash waste tanks will be routed to an existing forcemain adjacent to the SMWTP that feeds the Sanford North Water Reclamation Facility.

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2.2.2 Site Development Permit

A permit will be required from the City of Sanford Development Services Department prior to applying for a building permit from the City of Sanford Building Division. Building Division permitting is described in the following subsection. The Site Development Permit application process will require the following:

A preapplication conference.

An approved Development Plan.

A Site Development Permit application.

An engineer’s or contractor’s certified cost estimate of the proposed site development.

The development plan includes all requirements for both the Site Plan and Engineering Plan submittal checklists as detailed by the Development Services Department. All submittals for the Site Development Permit application process will require:

A completed application through the City’s Citizen Serve Portal.

The applicant’s Affidavit of Ownership and Designation of Agent Form.

The required plans uploaded into the Citizen Serve Portal.

The payment of an application fee.

2.2.3 Building Department Permitting

A building permit will be required from the City of Sanford Building Division. The permit application and project drawings will be sent to the Building Division for review.

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MAIN WTP ADVANCED TREATMENT UPGRADES 11

SECTION 3 BASIS OF DESIGN

3.1 Capacity and Description

The permitted maximum day rated capacity of the SMWTP is 10.08 mgd. Figure 3 shows the average and maximum monthly finished water flow for the SMWTP since 2004.

The SAWTP and SMWTP have an interconnected distribution system. Figure 4 shows the historical average and maximum monthly flows for the SAWTP since 2004.

Flow data for both WTPs were compiled from available FDEP database records and monthly operating reports (MORs). Data from 2014 onward were compiled from daily MOR flows. From August 2023 through July 2024, the average and maximum day flow for the SMWTP were about 5.51 and 6.77 mgd, respectively.

Figure 3 Historical SMWTP Flow

1/1/2004 1/1/2008 1/1/2012 1/1/2016 1/1/2020 1/1/2024 1/1/2028

Fl ow

(m gd

SMWTP Maximum Day Rated Capacity SMWTP Maximum Daily Flow (Per Year) SMWTP Maximum Daily Flow (Per Month) SMWTP Average Daily Flow (Per Month)

MAIN WTP ADVANCED TREATMENT UPGRADES 12

Figure 4 Historical SAWTP Flow

This preliminary design provides treatment upgrades for the SMWTP within the confines of the existing treatment plant’s permitted capacity. Treatment processes were sized to hydraulically treat the SMWTP’s maximum day rated capacity of 10.08 mgd. The sizing of the individual treatment processes was based on the anticipated raw water quality and the respective treatment goals at the SMWTP.

Ten years of finished water flows (2014 through 2023) were compiled from MORs to evaluate the maximum to average day demand peaking factor. The 10-year maximum to average day peaking factors for the combined PWS flow and for the SMWTP alone were calculated at approximately 1.25 and 1.40, respectively. These values were calculated to estimate the average daily flow when the SMWTP reaches its maximum day rated capacity of 10.08 mgd. Assuming a maximum day peaking factor of 1.40, the calculated average day design flow for the SMWTP at design capacity is about 7.22 mgd.

3.2 Water Quality Data

This section presents raw and finished water quality data for the SMWTP and distribution system DBPs for the shared SMWTP-SAWTP distribution system. Because this project is focused on the SMWTP, this section does not include data for the SAWTP other than the general finished water quality summary shown in Table 7.

1/1/2004 1/1/2008 1/1/2012 1/1/2016 1/1/2020 1/1/2024 1/1/2028

Fl ow

(m gd

SAWTP Maximum Day Rated Capacity SAWTP Maximum Daily Flow (Per Year) SAWTP Maximum Daily Flow (Per Month) SAWTP Average Daily Flow (Per Month)

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3.2.1 Raw Water Quality

3.2.1.1 Data Sources

Carollo sampled 11 of the 13 wells that supply water to the SMWTP to characterize its source water quality. Carollo did not sample two of the wells, GC-6 and OA-4, because they were out of service at the time of sampling. Table 3 shows the water quality sampling results for the source water characterization, excluding PFAS sampling results which are presented in Section 3.2.1.3. Table 3 also shows whether water quality results were measured in the field or by the laboratory.

Source water characterization sampling results generated by Carollo were compiled with data from City sampling events and Carollo’s bench testing efforts (summarized in Section 3.3) to define raw water quality for the design of the UV AOP and GAC treatment systems. Historical 1,4-dioxane data were provided by the City and included results from a variety of sampling entities. 1,4-Dioxane data and trends are presented in Section 3.2.1.2. Wells were also sampled by the City for PFAS, and these data are shown in Section 3.2.1.3.

Table 4 shows supplemental raw water quality data provided by the City for alkalinity, bromide, nitrite, and TOC. The SMWTP MORs in 2023 also included raw and finished water quality results for alkalinity, total hardness, calcium hardness, magnesium hardness, chloride, fluoride, iron, and pH. These MOR data are not shown in Table 4 but were compiled to further characterize raw water quality. Alkalinity data from this source were not used to supplement other data sources because of the difference between the results and those from other sampling efforts. The water quality used for the design is defined in Section 3.5.

CITY OF SANFORD

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Table 3 Source Water Characterization Sampling Results (Non-PFAS Parameters)

Field/ Lab Parameter Units GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-5 TL-2 TL-3 Sample Date(1) 2/28/2024 2/28/2024 2/28/2024 2/28/2024 2/28/2024 3/20/2024 3/20/2024 3/20/2024 2/28/2024 5/22/2024 3/20/2024 Field pH s.u. 7.32 7.16 7.45 7.6 7.13 7.58 7.62 7.54 7.73 7.81 7.47 Field Dissolved Oxygen mg/L 2.62 0.86 2.23 2.87 2.01 3.37 3.57 3.03 3.65 3.36 2.5 Field UV254(5) 1/cm 0.011 0.056 0.05 0.055 0.058 0.019 0.08 0.017 0.045 NA 0.025 Field Conductivity uS/cm 400 395 313 329 324 350 538 350 559 391 338 Field Temperature °C 23.9 24.1 24 23.9 23.3 24.2 23.7 24 23.9 24.3 23.8 Field Turbidity NTU 0.19 1.89 0.08 0.36 0.37 0.63 0.12 0.98 0.15 0.1 0.22 Field Total Sulfide - Rep 1 mg/L S2- 0.00 0.00 1.03 0.50 0.22 0.09 0.24 0.00 0.43 0.24 0.10 Field Total Sulfide - Rep 2 mg/L S2- 0.00 0.00 1.03 0.53 0.25 0.09 0.24 0.00 0.43 0.25 0.10 Field Total Sulfide - Rep 3 mg/L S2- 0.00 0.01 1.00 0.52 0.23 0.08 0.23 0.00 0.40 0.22 0.10 Lab Bromide(2) ug/L 100 U 100 U 100 U 100 U 100 U 100 U 250 100 U 370 110 I J3 100 U Lab Total Organic Carbon mg/L 1.1 2.5 1.3 2 1.8 1.3 3 1.3 1.4 0.84 I 1.6 Lab UV254(3) 1/cm NA NA NA NA NA 0.02 0.076 0.019 NA 0.018 0.029 Lab Total Alkalinity mg/L as CaCO₃ 170 180 150 160 160 150 150 150 140 130 150 Lab Total hardness as CaCO3 mg/L 230 210 180 180 190 180 220 190 220 170 180 Lab Iron mg/L 0.014 U 0.16 0.022 I 0.016 I 0.087 0.13 V 0.087 V 0.063 V 0.027 I 0.045 0.42 Lab Manganese mg/L 0.0033 0.013 0.0014 0.0023 0.0074 0.0095 0.0024 0.0093 0.0014 0.0019 0.011 Lab 1,4-Dioxane ug/L 0.16 0.081 0.098 0.075 0.081 0.25 0.15 0.41 0.28 0.97 0.17 Lab Ammonia (as N) mg/L 0.066 0.43 0.32 0.36 0.33 0.22 0.046 0.091 0.19 0.014 U 0.11 Lab Chloride mg/L 35 42 26 30 24 47 100 45 100 45 35 Lab Fluoride(4) mg/L 0.2 I Q 0.2 U Q 0.24 I Q 0.24 I Q 0.2 U Q 0.47 0.22 I 0.56 0.24 I Q 0.2 I 0.47 Lab Sulfate mg/L 38 18 18 11 13 20 40 19 42 18 21 Lab Turbidity NTU 0.3 I 2 0.2 I 0.4 1.2 2.7 0.4 0.85 0.2 I 0.2 I 2.5 Lab Total Dissolved Solids mg/L 320 390 240 250 260 270 430 310 400 200 250 Lab Nitrate as N(4) mg/L 1.8 Q 0.38 I Q 0.2 U Q 0.2 U Q 0.23 I Q 0.2 U 0.2 U Q 0.35 I 0.2 U Q 0.2 U 0.2 U Lab Nitrite as N(4) mg/L 0.2 U Q 0.36 I Q 0.2 U Q 0.2 U Q 0.28 I Q 0.2 U 0.2 U Q 0.2 U 0.2 U Q 0.2 U 0.2 U Lab Nitrate Nitrite as N(4) mg/L 1.8 Q 0.74 I Q 0.4 U Q 0.4 U Q 0.51 I Q 0.4 U 0.4 U Q 0.4 U 0.4 U Q 0.4 U 0.4 U

Abbreviations: NA – Result not available.

Laboratory Qualifiers:

U – Indicates that the compounds were analyzed for but not detected.

I – The reported value is between the laboratory method detection limit and the laboratory practical quantitation limit.

Q – Sample held beyond the accepted holding time.

V – Indicates that the analyte was detected at or above the method detection limit in both the sample and the associated method blank and the value of 10 times the blank value was equal to or greater than the associated sample value.

J3 – Estimated value; value may not be accurate. Spike recovery or RPD outside of criteria.

Notes:

(1) Wells GC-6 and OA-4 were out of service at the time of sampling.

(2) The laboratory indicated some bromide samples required dilution due to peak interference.

(3) UV254 results were not reported for 2/28/24 samples because laboratory was directed to not report or charge for those analyses due to samples being out of hold. If necessary for analyses, field results for these wells were used.

(4) Samples were re-run for nitrate, nitrite, and fluoride at a lower dilution despite some samples being out of hold. The result with the lower dilution factor is presented in this table.

(5) Field UV254 was not measured for TL-2 due to a broken meter.

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Table 4 Available Raw Water Quality Data for Wells Serving SMWTP (excluding 1,4-Dioxane, PFAS, and 2023 MOR data), Provided by the City

Sample Date(1) Parameter Units GC-1 GC-2 GC-3 GC-4 GC-5 GC-6 OA-1 OA-2 OA-3 OA-4 OA-5 TL-2 TL-3 6/24/2024 Alkalinity mg/L as CaCO₃ 171 179 149 162 166 6/25/2024 Alkalinity mg/L as CaCO₃ 165 169 141 165 7/31/2024 Alkalinity mg/L as CaCO₃ 161 8/12/2024 Alkalinity mg/L as CaCO₃ 149 10/11/2016 Bromide µg/L 83 I 120 100 69 U 87 I 120 10/12/2016 Bromide µg/L 110 270 84 I 240 340 73 I 10/19/2016 Bromide µg/L 11/9/2016 Bromide µg/L 110 100 83 I 77 I 85 I 110 130 280 75 I 250 320 82 I 2/27/2017 Bromide µg/L 2/28/2017 Bromide µg/L 96 I 89 I 74 I 86 I 120 73 I 3/1/2017 Bromide µg/L 250 96 I 210 310 10/17/2023 Bromide µg/L 120 I 280 I 110 I 340 I 120 I 100 U 10/18/2023 Bromide µg/L 120 I 100 I 100 U 100 U 100 U 6/24/2024 Bromide µg/L 200 400 260 230 180 6/25/2024 Bromide µg/L 280 390 88 200 7/31/2024 Bromide µg/L 120 8/12/2024 Bromide µg/L 360 6/24/2024 Nitrite mg/L as N 0.025 U 0.025 U 0.025 U 0.025 U 0.025 U 6/25/2024 Nitrite mg/L as N 0.025 U 0.025 U 0.025 U 0.025 U 7/31/2024 Nitrite mg/L as N 0.025 U 8/12/2024 Nitrite mg/L as N 0.0504 6/24/2024 TOC mg/L 1 2.2 1.2 1.6 1.6 6/25/2024 TOC mg/L 0.87 I 2.5 0.65 I 1.2 7/31/2024 TOC mg/L 1 8/12/2024 TOC mg/L 0.94 I

Laboratory Qualifiers:

U – Compound was analyzed for but not detected. The reported value is the method detection limit for the sample analyzed.

I – The reported value is between the laboratory method detection limit and the laboratory practical quantitation limit.

Notes:

(1) Not all wells were sampled on each of the sampling dates.

CITY OF SANFORD

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3.2.1.2 1,4-Dioxane

1,4-Dioxane concentrations in the composite raw water feeding the SMWTP treatment process will depend on which wells are in operation. Samples have been collected to measure 1,4-dioxane concentrations in raw water supply wells serving the SMWTP since 2016. This dataset was used to develop the UV AOP design criteria. When compared to the other two wellfields supplying water to the SMWTP, the Golf Course wells have had historically lower 1,4-dioxane concentrations. Figure 5 shows that historical 1,4-dioxane concentrations measured from Golf Course wellfield samples prior to 2023 were below

0.12 µg/L. Four of the last five Well GC-1 sample results have ranged from 0.15 to 0.16 µg/L, which is higher than historical levels but less than half of the HAL. The Golf Course wellfield samples collected in late 2023, except for Well GC-1, had 1,4-dioxane concentrations lower than detection limits. However, the detection limits were higher than usual for these samples, which is shown as an increase in concentrations in Figure 5. Similarly, the Golf Course wellfield samples collected in June 2024 also had higher than usual detection limits.

Figure 6 shows historical 1,4-dioxane concentrations measured from the Oregon Avenue wellfield were generally higher than those from the Golf Course wellfield. The maximum 1,4-dioxane concentration for Well OA-5 was above the HAL at 0.42 µg/L. Similar to Well GC-1, the 1,4-dioxane concentrations measured from Wells OA-1 and OA-3 have been higher in recent samples when compared to historical concentrations. Unlike GC-1, the measured 1,4-dioxane concentrations in recent Well OA-3 samples have been higher than the HAL, overtaking OA-5 as the Oregon Avenue well with the highest 1,4-dioxane.

Historical Well OA-3 1,4-dioxane concentrations were approximately half of recent concentrations.

Figure 5 Historical Golf Course Wellfield (GC-) 1,4-Dioxane

0.00

0.05

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0.45

0.50

1/1/16 1/1/18 1/1/20 1/1/22 1/1/24

1, 4-

Di ox an e

(µ g/

L)

GC-1 GC-1 DUP GC-2 GC-3

GC-4 GC-5 GC-6

FDOH HAL = 0.35 µg/L

Blank/White-filled points = Not Detected

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Figure 6 Historical Oregon Avenue Wellfield (OA-) 1,4-Dioxane

Figure 7 shows that samples from Well TL-2 have historically had the highest 1,4-dioxane concentrations, with a maximum of 0.97 µg/L from the Carollo sampling event in May 2024. Since samples have been collected from Well TL-2, only two samples have had 1,4-dioxane below the HAL. These two samples were collected by others (i.e., not collected by Carollo or the City). Well TL-3 1,4-dioxane concentrations have been consistently below the HAL, with the previous four samples having 1,4-dioxane concentrations of

0.17 to 0.19 µg/L.

0.00

0.05

0.10

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0.25

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D io xa ne

(µ g/

L)

OA-1 OA-1 DUP OA-2 OA-3

OA-3 DUP OA-4 OA-5 OA-5 DUP

Blank/White-filled points = Not Detected

FDOH HAL = 0.35 µg/L

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Figure 7 Historical Twin Lakes Wellfield (TL-) 1,4-Dioxane

Samples were also collected by Carollo’s Water ARC® applied research center during bench studies for this project. The 1,4-dioxane concentrations from these samples were included when characterizing the water quality per well used in the UV AOP design, described in Section 3.5, but are not shown in Figure 5 through Figure 7. Table 5 shows these 1,4-dioxane concentrations.

Table 5 Water ARC Bench Scale Testing Raw Water 1,4-Dioxane Measurements

Sample Date Analysis Parameter Units Well Result 5/21/2024 1,4-Dioxane µg/L OA-3 0.40 5/21/2024 1,4-Dioxane µg/L OA-3 0.41 5/21/2024 1,4-Dioxane µg/L OA-3 0.41 8/1/2024 1,4-Dioxane µg/L OA-2 0.17 8/1/2024 1,4-Dioxane µg/L OA-3 0.46 8/1/2024 1,4-Dioxane µg/L TL-2 0.57 8/1/2024 1,4-Dioxane µg/L GC-2 0.076

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1/1/16 1/1/18 1/1/20 1/1/22 1/1/24

1, 4-

D io xa ne

(µ g/

L)

TL-2 TL-2 DUP

TL-3 TL-3 DUP

Blank/White-filled points = Not Detected

CITY OF SANFORD

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3.2.1.3 PFAS

In 2023 and 2024, the City collected samples to quantify PFAS in the wells that supply the SMWTP. Well GC-6 was not sampled because it was out of service and has effectively been abandoned, pending formal notice to FDEP. As part of the source water characterization sampling previously discussed, Carollo also collected samples between February and May 2024 for 11 of the wells that supply the SMWTP. Wells GC-6 and OA-4 were out of service at the time of sampling. Table 6 shows the PFAS results from the source water characterization sampling.

This section compares the City-collected sample results to the results from the samples collected by Carollo. Excluding Well OA-4, the City has collected more than one PFAS sample at each of the wells that supply water to the SMWTP. The charts in this section show the results for the multiple samples collected by the City as “City Sampling”, “City Sampling (2)”, and “City Sampling (3)”. All charts show values below the detection limit (i.e., “U” laboratory qualifier) as the associated detection limit rather than zero. The PFAS MCLs and rule trigger levels (RTL) are only shown on charts for reference since compliance for these parameters is at the POE, not at the wells. The RTLs are equal to one-half of the respective MCLs and are described further in Section 3.2.2.3.

Figure 8 shows that Well GC-1 and Well GC-2 have the highest PFOS of all wells sampled. GC-4, GC-5, OA-1, and OA-3 also have PFOS concentrations above the MCL of 4 ng/L. GC-3, OA-2, and TL-3 showed higher PFOS for the Carollo sampling events versus the City sampling events (i.e., the minimum difference between results for the Carollo sample and City samples was greater than 1 ng/L). Results in this section are from individual samples, and additional monitoring will help refine conclusions as design progresses.

Figure 8 Potable Supply Well PFOS

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4 OA-5 TL-2 TL-3

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

Ra w

W el l W at er P

FO

S

(n g/

L)

Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

* Indicates well not sampled by Carollo.

Values below detection plotted as detection limit.

Point of Entry Limits (for Reference):

Running Annual Average (RAA) Maximum Contaminant Level (MCL)

Single Sample Rule Trigger Level (RTL)

CITY OF SANFORD

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Table 6 Source Water Characterization Sampling Results (PFAS Parameters)

Parameter Units MCL(4) GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-5 TL-2 TL-3 Sample Date(1,2) 2/28/2024 2/28/2024 2/28/2024 2/28/2024 2/28/2024 3/20/2024 3/20/2024 3/20/2024 2/28/2024 5/22/2024 3/20/2024 Regulated PFAS PFOS ng/L 4.0 15 13 3 5.2 5.7 4.8 4 5.4 1.9 1.7 3.4 PFOA ng/L 4.0 8.1 6.6 2.6 3.3 3.5 3.9 4 4.4 1.7 2 3.8 PFHxS(3) ng/L 10 6.3 5.8 2.8 3.5 3.6 2.6 4 3.8 2.4 2.2 2.9 HFPO-DA(3) ng/L 10 0.33 U 0.34 U 0.33 U 0.35 U 0.35 U 0.33 U 0.34 U 0.34 U 0.32 U 0.33 U 0.34 U PFNA(3) ng/L 10 0.48 I 0.34 I 0.16 U 0.19 I 0.26 I 0.36 I 0.22 I 0.33 I 0.16 U 0.16 U 0.4 I PFBS(3) ng/L - 11 5.9 2.9 2.8 3.5 4.1 5 5.6 3.1 2.2 6 Unregulated PFAS, at least one detected result PFHxA ng/L - 4.2 3.7 1.2 I 1.9 1.8 2 1.7 2.3 0.81 U 1.6 2.1 PFHpA ng/L - 2.3 2.1 0.66 I 1.2 I 1 I 1.1 I 1.1 I 1.6 I 0.44 I 0.8 I 1.5 I PFBA ng/L - 6.5 3.3 1.9 1.6 I 2.4 2.9 3.2 3.3 1.5 I 1.4 I 3.3 PFPeA ng/L - 5.2 3.7 1.4 I 2.1 2.1 2.3 2.1 3 0.91 I 1.7 2.7 PFPeS ng/L - 1 I 1.1 I 0.54 I 0.71 I 0.62 I 0.72 I 0.9 I 0.92 I 0.52 I 0.53 I 0.73 I PFHpS ng/L - 0.99 I 0.59 I 0.26 I 0.27 I 0.27 U 0.25 U 0.3 I 0.36 I 0.24 U 0.25 U 0.26 U Unregulated PFAS, no detected results PFEESA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U NFDHA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U PFUnA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U NMeFOSAA ng/L - 0.33 U 0.34 U 0.33 U 0.35 U 0.35 U 0.33 U 0.34 U 0.34 U 0.32 U 0.33 U 0.34 U 6:2 FTS ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U NEtFOSAA ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U PFDoA ng/L - 0.33 U 0.34 U 0.33 U 0.35 U 0.35 U 0.33 U 0.34 U 0.34 U 0.32 U 0.33 U 0.34 U PFDA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U PFTeDA ng/L - 0.33 U 0.34 U 0.33 U 0.35 U 0.35 U 0.33 U 0.34 U 0.34 U 0.32 U 0.33 U 0.34 U PFMPA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U

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Parameter Units MCL(4) GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-5 TL-2 TL-3 Sample Date(1,2) 2/28/2024 2/28/2024 2/28/2024 2/28/2024 2/28/2024 3/20/2024 3/20/2024 3/20/2024 2/28/2024 5/22/2024 3/20/2024 8:2 FTS ng/L - 0.49 U 0.51 U 0.49 U 0.53 U 0.53 U 0.5 U 0.51 U 0.51 U 0.49 U 0.49 U 0.52 U PFTrDA ng/L - 0.33 U 0.34 U 0.33 U 0.35 U 0.35 U 0.33 U 0.34 U 0.34 U 0.32 U 0.33 U 0.34 U 9Cl-PF3ONS ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U 4:2 FTS ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U 11Cl-PF3OUdS ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U PFMBA ng/L - 0.25 U 0.25 U 0.25 U 0.26 U 0.27 U 0.25 U 0.25 U 0.26 U 0.24 U 0.25 U 0.26 U ADONA ng/L - 0.41 U 0.42 U 0.41 U 0.44 U 0.44 U 0.42 U 0.42 U 0.43 U 0.41 U 0.41 U 0.43 U

Laboratory Qualifiers:

U – Indicates that the compounds were analyzed for but not detected.

I – The reported value is between the laboratory method detection limit and the laboratory practical quantitation limit.

V – Indicates that the analyte was detected at or above the method detection limit in both the sample and the associated method blank and the value of 10 times the blank value was equal to or greater than the associated sample value.

Notes:

(1) Wells GC-6 and OA-4 were out of service at the time of sampling.

(2) PFAS was not typically detected in associated field blanks. 5/22/24 TL-2 Field blank had HFPO-DA concentration above detection (0.35 I V).

(3) PFHxS, PFNA, HFPO-DA, and PFBS are also regulated by the USEPA through a calculated Hazard Index (HI) equal to HI = [HFPO-DA (ng/L)]/10 + [PFBS (ng/L)]/2000 +

[PFNA (ng/L)]/10 + [PFHxS (ng/L)]/10. The MCL for the HI is 1 (unitless).

(4) Compliance with the MCL is based on the RAA of results at the POE.

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Similar to PFOS occurrence, Figure 9 shows that GC-1 and GC-2 have the highest PFOA of the tested wells, with concentrations ranging from about 6 to 8 ng/L. Carollo sampling had higher PFOA for wells GC-3, GC-4, GC-5, OA-1, and OA-2 when compared to the samples collected by the City.

Figure 9 Potable Supply Well PFOA

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

Ra w

W el l W at er P

FO

A

(n g/

L)

Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

Point of Entry Limits (for Reference):

Running Annual Average (RAA) Maximum Contaminant Level (MCL)

Single Sample Rule Trigger Level (RTL)

* Indicates well not sampled by Carollo.

Values below detection plotted as detection limit.

CITY OF SANFORD

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PFHxS has an individual contaminant MCL of 10 ng/L, with compliance determination based on the RAA at the POE. PFHxS is also included in the calculated hazard index (HI). Figure 10 shows that GC-1 and GC-2, like PFOA and PFOS, have the highest PFHxS of the wells sampled. However, the PFHxS concentrations from these wells are about half of the MCL. Wells GC-3, OA-1, OA-3, and TL-3 had higher PFHxS for the Carollo sampling events when compared to the City sampling events.

Figure 10 Potable Supply Well PFHxS

Figure 11 and Figure 12 show raw water PFNA and HFPO-DA results. Generally, sample results were below 1 ng/L for these two compounds. One TL-2 sample had a measured concentration of 1.84 ng/L for both PFNA and HFPO-DA. These results agree with the POE results discussed in the next subsection, which showed PFNA and HFPO-DA have consistently been measured below detection limits at the SMWTP POE.

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4 OA-5 TL-2 TL-3

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

Ra w

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FH

xS

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L)

Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

Point of Entry Limits (for Reference):

Running Annual Average (RAA) Maximum Contaminant Level (MCL)

Single Sample Rule Trigger Level (RTL)

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Figure 11 Potable Supply Well PFNA

Figure 12 Potable Supply Well HFPO-DA

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

Ra w

W el l W at er P

FN

A

(n g/

L) Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

* Indicates well not sampled by Carollo.

Values below detection plotted as detection limit.

Point of Entry Limits (for Reference):

Running Annual Average (RAA) Maximum Contaminant Level (MCL)

Single Sample Rule Trigger Level (RTL)

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4 OA-5 TL-2 TL-3

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

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FP

O

-D A

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Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

Point of Entry Limits (for Reference):

Running Annual Average (RAA) Maximum Contaminant Level (MCL)

Single Sample Rule Trigger Level (RTL)

CITY OF SANFORD

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PFBS does not have an individual MCL. However, PFBS is included in the HI calculation. Given the high health-based water concentration (HBWC) for PFBS as the numerator in the HI calculation (2,000 ng/L versus 10 ng/L for all other PFAS), PFBS concentrations would need to be much higher than the values shown in Figure 13 to meaningfully contribute to the HI.

Figure 13 Potable Supply Well PFBS

Figure 14 shows the calculated HI for the individual samples collected by the City and Carollo. Wells GC-1, GC-2, and TL-2 have the highest calculated HI of the wells sampled. The trends in HI are similar to PFHxS because two of the other main elements of the HI, PFNA and HFPO-DA, were typically below 1 ng/L in the well samples.

GC-1 GC-2 GC-3 GC-4 GC-5 OA-1 OA-2 OA-3 OA-4* OA-5 TL-2 TL-3

Sanford Main WTP

Ra w

W el l W at er P

FB

S

(n g/

L)

Carollo Sampling City Sampling City Sampling (2) City Sampling (3)

* Indicates well not sampled by Carollo.

PFBS does not have a Point of Entry Maximum Contaminant Level.

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Figure 14 Potable Supply Well Hazard Index (Calculated)

PFAS samples were also collected by Carollo’s Water ARC® applied research center as part of the bench-scale rapid small-scale column tests (RSSCT) for this project. The PFAS concentrations from these samples are not shown in this section.

As previously stated, this section shows results from single sampling events, and some wells had concentrations, particularly for PFOS and PFOA, that were higher for Carollo samples when compared to the City’s samples.