TM_NW.pdf

TUCSON WATER DEPARTMENT

Impacts of Targeted Emerging Contaminants on Water Supplies and Capital Assets

Technical Memorandum

UPDATES TO NORTHWEST AREA

WELLS ALTERNATIVES EVALUATION

FINAL | August 2022

TUCSON WATER DEPARTMENT

Impacts of Targeted Emerging Contaminants on Water Supplies and Capital Assets

Technical Memorandum

UPDATES TO NORTHWEST AREA WELLS

ALTERNATIVES EVALUATION

FINAL | August ͮͬͮͮ

NORTHWEST AREA WELLS ALTERNATIVES EVALUATION | IMPACTS OF TARGETED EMERGING CONTAMINANTS | TUCSON WATER

FINAL | AUGUST 2022 | i pw://Carollo/Documents/AZ/Tucson Water/201340-000000/03 Reports and Studies/02 Deliverables/TM NW/TM NW.docx

Contents Technical Memorandum – Updates to Northwest Area Wells Alternatives Evaluation

1.0 Introduction 1

1.1 Report Organization 2

2.0 Water Quality and Infrastructure 2

2.1 EPA Guidance Background and Tucson Potable Water Quality Operational Guidelines 2

2.2 Groundwater Quality Data 4

2.3 Existing Potable Water Infrastructure 6

2.3.1 Age and Condition of Wells 7

3.0 Blending Alternatives 7

4.0 Treatment Technologies 10

4.1 Pretreatment for Solids Removal 10

4.2 GAC Adsorption for PFAS Removal 10

4.3 IX for PFAS Removal 11

4.4 UV AOP for 1,4-dioxane Removal 12

4.5 Treatment Technology Benefits and Challenges 13

4.6 Treatment Alternatives 14

5.0 Evaluation of Alternatives 14

5.1 Conceptual Design Criteria 14

5.2 Simplified Process Schematics 17

5.3 Conceptual Site Layouts 17

5.4 Conceptual Replacement Well and Treatment Cost Opinions 17

5.4.1 Economic Analysis of Cost Opinions 17

6.0 Summary and Conceptual Implementation Plan 20

6.1 Summary 20

6.2 Conceptual Implementation Plan 21

7.0 References 21

Appendices Appendix A Simplified Process Schematics

Appendix B Conceptual SIte Layouts

Appendix C Conceptual Capital and Annual Operations and Maintenance Cost Opinions

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Tables Table 1 Federal Regulatory Status for PFAS, 1,4-dioxane, and TCE 3

Table 2 Tucson Water PFAS Operational Guidelines for the Potable System(1) 3

Table 3 Ground Water Quality Data 5

Table 4 Existing Potable Water Infrastructure 6

Table 5 Age and Condition of Wells 7

Table 6 Average Concentration of Individual Wells and the Cluster Blends 9

Table 7 Southern Cluster Wells 1,4-dioxane Blending Plan 9

Table 8 Benefits and Challenges of Feasible Treatment Technologies 13

Table 9 Treatment Alternatives Matrix 14

Table 10 Design Capacities 14

Table 11 GAC Adsorption Conceptual Design Criteria 15

Table 12 IX Conceptual Design Criteria 16

Table 13 UV AOP System Conceptual Design Criteria 16

Table 14 Conceptual Centralized Wellhead 1,4-dioxane and PFAS Treatment Cost Opinions 18

Table 15 Conceptual Implementation Plan for Central Well Cluster 22

Table 16 Conceptual Implementation Plan for Southern Well Cluster 22

Figures Figure 1 PFAS Speciation for NW Area Wells Removed from Service 4

Figure 2 1,4-dioxane Concentrations for NW Area Wells Removed from Service 6

Figure 3 NW Area Wells and Cluster 8

Figure 4 Example Pressure GAC Adsorption Pressure Vessels 11

Figure 5 Example IX Pressure Vessels 12

Figure 6 Example LPHO UV Reactors 12

Figure 7 Centralized Wellhead 1,4-dioxane and PFAS Treatment Conceptual Cost Opinion 19

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Abbreviations AACE Association for the Advancement of Cost Engineering ADWR Arizona Department of Water Resources AFFF aqueous film-forming foams Carollo Carollo Engineers, Inc.

cf cubic feet CMAR Construction Manager at Risk EBCT empty bed contact time

EPA U.S. Environmental Protection Agency GAC granular activated carbon gpm gallons per minute gpm/sq ft gallons per minute per square foot

HA Health Advisory HFPO hexafluoropropylene oxide hp horsepower

IX ion exchange LPHO low pressure high output MCL maximum contaminant level MRL Method Reporting Limit ng/L nanograms per liter NW Northwest O&M operations and maintenance

PFAS perfluoroalkyl PFBS perfluorobutanesulfonic acid PFHpA perfluoroheptanoic acid PFHxA perfluorohexanoic acid

PFHxS perfluorohexanesulfonic acid PFOA perfluorooctanoic acid PFOS perfluorooctane sulfonic acid ppb parts per billion ppm parts per million ppt parts per trillion

SCADA supervisory control and data acquisition SDWA Safe Drinking Water Act TCA trichloroethane TCE Trichloroethene

TM technical memorandum Tucson Water City of Tucson Water Department UV AOP ultraviolet light advanced oxidation process

VOC volatile organic compounds

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Technical Memorandum

UPDATES TO NORTHWEST AREA WELLS

ALTERNATIVES EVALUATION

1.0 Introduction

The City of Tucson Water Department (Tucson Water) supplies water to about 731,000 people over a service area of nearly 400 square miles in the Tucson, Arizona metropolitan area. The utility maintains approximately 200 active production or standby wells and hundreds of monitoring wells used to measure groundwater levels and test groundwater quality.

Groundwater quality monitoring results indicated the presence of 1,4-dioxane and perfluoroalkyl substances (PFAS), particularly perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), in wells in the Northwest (NW) area exceeding Safe Drinking Water Act (SDWA) Lifetime Drinking Water Health Advisory (HA) levels published by the U.S. Environmental Protection Agency (EPA). Trichloroethene (TCE), a regulated compound with a maximum contaminant level (MCL), was detected in one of the production wells in NW area.

1,4-dioxane is a synthetic chemical used as a stabilizer for chlorinated solvents (particularly 1,1,1-trichloroethane [TCA]) and is used in products such as paint strippers, greases, and waxes. PFAS are fluorinated organic chemicals, which among consumer product applications, are also part of aqueous film-forming foams (AFFF), that are or were commonly used for suppressing aircraft fires and for training to fight such fires. TCE is used as a solvent for degreasing metals in manufacturing processes, in addition to a variety of consumer applications. EPA's Drinking Water Health Advisory levels are not enforceable standards but are included among the factors EPA considers when setting new or revised SDWA MCLs, which are enforceable standards.

Tucson Water commissioned an evaluation of the potential impacts of targeted emerging contaminants on water supplies and capital assets including developing blending approaches and alternative treatment process technologies to reduce concentrations of PFAS, 1,4-dioxane, and TCE at specific potable production wells. The evaluation includes preliminary engineering information necessary for comparison of the blending and treatment alternatives and for advancing the implementation of groundwater quality improvements as a pro-active public health measure.

Media change-out projections and cost opinions presented in this study were completed prior to the July 7, 2022 update to Tucson Water’s PFAS operational guidelines. For this study, a potable water system operational guideline of < 2 ppt for PFOA+PFOS+PFHxS+PFHpA was considered for cost opinions.

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1.1 Report Organization

This technical memorandum (TM) is organized into the following sections and appendices.

• Section 1.0 - Introduction

• Section 2.0 - Water Quality and Infrastructure

• Section 3.0 - Blending Alternatives

• Section 4.0 - Treatment Technologies

• Section 5.0 - Evaluation of Alternatives

• Section 6.0 - Summary and Conceptual Implementation Plan

• Appendix A - Simplified Process Schematics

• Appendix B - Conceptual Site Layouts

• Appendix C - Conceptual Capital and Annual Operations and Maintenance Cost Opinions

2.0 Water Quality and Infrastructure

The following sections present a review of the regulatory background, Tucson's water quality operational guidelines, current water quality, and the existing infrastructure in place for the water systems considered in this study. Due to the age of the wells in the project area, Tucson Water asked Carollo Engineers, Inc.

(Carollo) to investigate which of the project wells are approaching the end of their service lives and may need to be replaced.

2.1 EPA Guidance Background and Tucson Potable Water Quality Operational Guidelines

PFAS are not currently regulated by EPA, but the agency recently updated non-enforceable Lifetime Drinking Water HAs for the following compounds:

• Interim Updated HA of 0.004 parts per trillion (ppt) for PFOA and 0.02 ppt for PFOS.

• Final HA of 2,000 ppt for PFBS and 10 ppt for GenX chemicals.

EPA announced the updates on June 15, 2022, with a notice subsequently published in the Federal Register on June 21, 2022 (87 FR 36848). The updates supersede the earlier 2016 HAs of 70 ppt for PFOA and PFOS.

Although 1,4-dioxane is also not currently regulated by EPA under the SDWA, EPA published Drinking Water HA in 2011 for the chemical (2011 Edition of the Drinking Water Standards and Health Advisories). The corresponding drinking water concentration representing a 1 x 10-6 excess cancer risk level (one in one million) for 1,4-dioxane is 0.35 parts per billion (ppb).

EPA established an MCL of 5 ppb for TCE as part of the Phase I volatile organic compounds (VOC) Rule, promulgated July 7, 1987 (52 FR 25690). The MCL became effective in 1989. Table 1 summarizes the SDWA HAs for PFAS and 1,4-dioxane and the SDWA MCL for TCE.

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Table 1 Federal Regulatory Status for PFAS, 1,4-dioxane, and TCE

Parameter SDWA Guidance (HA) or

Regulation (MCL) Units Value

PFOA(1) HA ppt 0.004

PFOS(1) HA ppt 0.02

PFBS(2) HA ppt 2,000

GenX Chemicals(2) HA ppt 10

1,4-dioxane(3) HA ppb 0.35

TCE(4) MCL ppb 5.0 Notes:

(1) EPA's interim updated HAs for PFOA and PFOS (June 15, 2022).

(2) EPA's final HAs for PFBS and GenX chemicals (June 15, 2022).

(3) Based on a 1 x 10-6 excess lifetime cancer risk (2011 Edition of the Drinking Water Standards and Health Advisories).

(4) National Primary Drinking Water Standard.

Abbreviations:

PFOA = perfluorooctanoic acid; PFOS = perfluorooctanesulfonic acid; PFBS = perfluorobutanesulfonic acid GenX = hexafluoropropylene oxide (HFPO) dimer acid and its ammonium salt; TCE = Trichloroethene

MCLs are legally enforceable drinking water standards, while HAs serve as informal technical guidance to assist Federal, state, and local officials, as well as managers of public or community water systems, in protecting health. HAs are not legally enforceable Federal standards and may change if new toxicological assessments from EPA become available. In the absence of enforceable Federal drinking water standards, Tucson Water recently updated its operational guidelines for the potable water system with respect to PFAS, as shown in Table 2. Tucson Water's treatment goals for 1,4-dioxane and TCE are <0.1 and <0.5 ppb, respectively.

Table 2 Tucson Water PFAS Operational Guidelines for the Potable System(1)

Parameter Units Potable Water Quality Operational Guidelines(1)

PFOS ppt <2

PFOA ppt <2

PFHxS ppt 7

PFHpA ppt 7

PFBS ppt 420

PFHxA ppt 200,000

GenX ppt 10 Notes:

(1) Effective July 7, 2022. Tucson Water's previous operational guideline for combined concentrations of PFOS, PFOA, PFHxS, and PFHpA was 18 ppt.

Abbreviations:

PFOA = perfluorooctanoic acid; PFOS = perfluorooctanesulfonic acid; PFHxS = perfluorohexanesulfonic acid;

PFHpA = perfluoroheptanoic acid; PFHxA = perfluorohexanoic acid; PFBS = perfluorobutanesulfonic acid;

GenX = hexafluoropropylene oxide (HFPO) dimer acid and its ammonium salt

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2.2 Groundwater Quality Data

Tucson Water owns several potable production wells in the NW area. During 2018-2019, nine of the wells in this area were taken out of service due to detections of PFAS, 1,4-dioxane, and/or TCE. Table 3 shows the water quality results from the most recent sampling done at these nine production wells.

Figure 1 and Figure 2 show the PFAS speciation and 1,4-dioxane concentrations, respectively, from the most recent sampling event. Wells Y-001B, Y-004A, Z-013A, Z-015A, and A-057B have PFAS concentrations greater than Tucson Water operational guideline of <2 ppt. Wells Y-001B, Y-004A, Z-013A, Z-015A, and Z-005A have 1,4-dioxane concentrations greater than the Tucson Water treatment goal of 0.1 ppb. TCE was found only in Z-002A at a concentration of 2.5 ppb. A detailed summary of all historical PFAS and 1,4-dioxane data is shown in the Northwest Area Wells Alternatives Evaluation Technical Memorandum (Carollo, 2020).

The wells were taken out of service on the following dates:

• Wells Z-002A on March 9, 2016.

• Wells Z-014B and Y-001B on September 22, 2016.

• Wells Z-005A, Z-015A and Z-013A on September 19, 2016.

• Wells A-053A and A-057B on July 18, 2018.

Figure 1 PFAS Speciation for NW Area Wells Removed from Service

Y-001B Y-004A Z-013A Z-014B Z-015A A-053A A-057B Z-002A Z-005A

Co nc en tr at io n (n g/ L)

Well

PFBS

PFHxA

PFHxS

PFHpA

PFOA

PFOS

MRL

Method Reporting Limit (MRL) = 2 ppt

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Table 3 Ground Water Quality Data

Parameter Units Well

Y-001B(1) Well

Y-004A(1) Well

Z-013A(2) Well

Z-014B(3) Well

Z-015A(4) Well

A-053A(5) Well

A-057B(6) Well

Z-002A(7) Well

Z-005A(8)

PFOS(9) ppt 88.1 59 120 <2 80 <2 18 <2 <2

PFOA(9) ppt 18.1 19.6 27 <2 17 <2 <2 <2 <2

PFHxS(9) ppt 59.2 30.9 53 <2 72 <2 11.9 <2 <2

PFHpA(9) ppt 5.7 5.3 6.8 <2 6.2 <2 <2 <2 <2

PFOS + PFOA +

PFHxS + PFHpA(9) ppt 171.1 114.8 206.8 <2 175.2 <2 33.9 <2 <2

PFHxA(9) ppt 10.6 13.8 13 <2 16 <2 <2 <2 <2

PFBS(9) ppt 7 10.8 10 <2 7.8 <2 3.7 <2 <2

1,4-dioxane(10) ppb 0.66 0.98 1.39 <0.1 0.42 <0.1 <0.1 <0.1 0.18

TCE(11) ppb <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 2.5 <0.5 Notes:

(1) Data from sampling conducted on 12/16/2021.

(2) PFAS data from sampling conducted on 07/01/2020 and 1,4-dioxane data from sampling conducted on 12/28/2020.

(3) PFAS data from sampling conducted on 09/23/2020 and 1,4-dioxane data from sampling conducted on 12/28/2020.

(4) PFAS data from sampling conducted on 06/16/2020 and 1,4-dioxane data from sampling conducted on 12/29/2020.

(5) PFAS data from sampling conducted on 10/26/2021 and 1,4-dioxane data from sampling conducted on 12/17/2021.

(6) PFAS data from sampling conducted on 12/16/2021 and 1,4-dioxane data from sampling conducted on 03/12/2020.

(7) Data from sampling conducted on 10/30/2018.

(8) Data from sampling conducted on 01/04/2022.

(9) MRL for PFAS is 2 ppt.

(10) MRL for 1,4-dioxane is 0.1 ppb.

(11) MRL for TCE is 0.5 ppb.

Abbreviations:

PFOA = perfluorooctanoic acid; PFOS = perfluorooctanesulfonic acid; PFHxS = perfluorohexanesulfonic acid; PFHpA = perfluoroheptanaonic aid; PFHxA = perfluorohexanoic acid;

PFBS = perfluorobutanesulfonic acid; TCE = trichloroethene; MRL = Method Reporting Limit; ppt = parts per trillion; ppb = parts per billion

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Figure 2 1,4-dioxane Concentrations for NW Area Wells Removed from Service

2.3 Existing Potable Water Infrastructure

Table 4 summarizes key information for the NW area wells affected by 1,4-dioxane, PFAS, and TCE. Duty cycles are assumed to be 100 percent for the purpose of this study.

Table 4 Existing Potable Water Infrastructure

Well Name Actual Pumping Capacity

(gpm) ADWR Permitted Pumping

Capacity Motor Horsepower

(hp)

Y-001B 740 720 50

Y-004A 935 2000 125

Z-013A 800 800 125

Z-014B 900 900 150

Z-015A 900 900 125

A-053A 243 244 100

A-057B 558 575 100

Z-002A 558 558 50

Z-005A 315 400 75 Abbreviations:

gpm = gallons per minute; ADWR = Arizona Department of Water Resources; hp = horsepower

0.00

0.50

1.00

1.50

Y-001B Y-004A Z-013A Z-014B Z-015A A-053A A-057B Z-002A Z-005A

Co nc en tr at io n (p pb

1,4-Dioxane

MRL

Method Reporting Limit (MRL) = 0.1 ppb

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2.3.1 Age and Condition of Wells

Due to the age of the wells in the project area, Tucson Water asked Carollo to investigate which of the project wells are approaching the end of their service life and may need to be replaced. Table 5 shows the age and condition of the project wells classified as "good", "fair", or "poor" by Tucson Water based upon operations and maintenance experience.

Table 5 Age and Condition of Wells

Well Date Drilled Deepening Date Condition

Y-004A 1982 Fair

Y-001B 2007 Good

Z-013A 1972 1983 Poor

Z-014B 1983 Poor

Z-015A 1974(1) Poor

A-053A 1959 1976 Poor

A-057B 1998 Fair

Z-002A 1952 1975 Poor

Z-005A 1942 1947, 1978 Poor Notes:

(1) Sliplined in 2019.

3.0 Blending Alternatives

These nine wells were grouped into three clusters: Northern (Y-004A and Y-001B), Central (Z-013A, Z-014B and Z-015A), and Southern (A-053A, A-057B, Z-002A and Z-005A) clusters. Figure 3 shows the clustering based upon geographic location of these wells and feasibility of centralized treatment at proposed well sites.

One strategy for meeting water quality operational guidelines is to blend water from alternative groundwater sources with water from the study area's affected wells. Due to the differences in contaminant concentration among different wells of the area and relatively low concentration in the southern cluster wells, blending wells of the same cluster was evaluated. Table 6 shows the concentration of the contaminants (PFAS, 1,4-dioxane, and TCE) in the individual well and the blend of each cluster. The Northern and Central cluster wells don't meet the operational guidelines for PFAS and 1,4-dioxane after blending. The southern cluster wells blended water meets Tucson Water treatment goal for 1,4-dioxane only but not for PFAS, while the TCE concentration is less than EPA's MCL of 5 ppb.

Due to the difference in 1,4-dioxane concentrations among the Southern cluster wells, they must be blended in a specific order to meet the treatment goal for 1,4-dioxane. Table 7 shows the 1,4-dioxane blending plan for the Southern cluster wells. Z-005A must operate with Z-002A, A-057B, Z-002A+A-053A, Z-002A+A-057B, or A-053A+A-057B. Z-005A cannot be operated alone or solely with A-053A.

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Figure 3 NW Area Wells and Cluster

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Table 6 Average Concentration of Individual Wells and the Cluster Blends

Cluster Well/Blend Flow

(gpm)

PFOS + PFOA +

PFHxS + PFHpA

(ppt)(1)

1,4-dioxane (ppb)(2)

TCE

(ppb)(3)

Northern

Y-004A 935 114.8 0.98 <0.5

Y-001B 740 171.1 0.66 <0.5

Blend 1,675 139.7 0.84 <0.5

Central

Z-013A 800 206.8 1.39 <0.5

Z-014B 900 <2 <0.1 <0.5

Z-015A 900 175.2 0.42 <0.5

Blend 2,600 124.3 0.48 <0.5

Southern

A-053A 243 <2 <0.1 <0.5

A-057B 558 29.9 <0.1 <0.5

Z-002A 558 <2 <0.1 2.5

Z-005A 400 <2 0.18 <0.5

Blend 1,759 9.5 0.04 0.65 Notes:

(1) MRL for PFAS is 2 ppt.

(2) MRL for 1,4-dioxane is 0.1 ppb.

(3) MRL for TCE is 0.5 ppb.

Abbreviations:

PFOA = perfluorooctanoic acid; PFOS = perfluorooctanesulfonic acid; PFHxS = perfluorohexanesulfonic acid;

PFHpA = perfluoroheptanaonic aid; MRL= Method Reporting Limit; ppt = parts per trillion; ppb = parts per billion

Table 7 Southern Cluster Wells 1,4-dioxane Blending Plan

Operational Scenario

Z-005A(1) gpm (mgd)

Z-002A gpm (mgd)

A-053A gpm (mgd)

A-057B gpm (mgd)

Total Flow gpm (mgd)

Blended 1,4-dioxane

Concentration (ppb)

1 400 -- -- -- 400 0.18

2 400 558 -- -- 958 0.08

3 400 -- 243 -- 643 0.11

4 400 -- -- 558 958 0.08

5 400 558 243 -- 1,201 0.06

6 400 558 -- 558 1,516 0.05

7 400 -- 243 558 1,201 0.06

8 400 558 243 558 1,759 0.04 Notes:

(1) Assumes 1,4-dioxane concentration of 0.18 ppb from most recent 2022 data.

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4.0 Treatment Technologies

PFAS and 1,4-dioxane can be treated by several different treatment technologies. The following sections provide an overview and review the benefits and challenges of each treatment technology considered in the study.

4.1 Pretreatment for Solids Removal

Pretreatment removal of solids typically produced by wells is prudent for all groundwater treatment systems to protect downstream process equipment. In the event of a well casing failure, or if sand, gravel, or other sediment are present in the well discharge flow, pretreatment will mitigate potentially damaging effects of sediment. For example, if sediment is deposited in ultraviolet (UV) light advanced oxidation process (AOP) reactor vessels, UV lamp sleeves can begin to foul or potentially break. If sediment gathers on top of granular activated carbon (GAC) media or ion exchange (IX) resin beds, differential pressure across the media will increase, leading to additional backwash requirements. On the other hand, backwashing of IX resin is not recommended, and thus a more robust pretreatment system must be designed.

For the purposes of this evaluation, duplex bag filter units are assumed to be included for the influent stream of all GAC groundwater treatment systems. Automatic backwash strainers and bag filters are assumed for IX treatment systems.

4.2 GAC Adsorption for PFAS Removal

GAC is a porous material with a high volumetric surface area that effectively adsorbs many contaminants, including varieties of PFAS. Carbon life for PFAS removal can vary widely depending on the carbon type, target contaminant concentrations, background water quality, and PFAS carbon chain length. In general, GAC adsorbs longer-chain PFAS (e.g., PFOS and PFOA) better than shorter-chain PFAS (e.g., PFHxA and PFBS).

When UV AOP is used, GAC can also be employed for hydrogen peroxide quenching (i.e., neutralization).

Regardless of use, the GAC media must be replaced with new carbon and sent for off-site disposal or regeneration once active adsorption sites become loaded. The bed life for GAC used just for hydrogen peroxide quenching exceeds that of GAC used to remove PFAS.

GAC adsorption systems require a backwash supply and equalization and settling provisions. That is, carbon particle degradation can occur during this technology's initial loading as well as normal operations, resulting in carbon fines that require periodic backwashing to reduce pressure loss through the contactors.

Backwashing is also required to reverse carbon bed compression, which can occur during normal operations and also as a result of built-up sediment commonly produced by wells, particularly as they age; however, the rate of backwashing required to prevent compression becomes lower after the initial media installation.

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This evaluation examined two types of GAC contactors: pressure and gravity. GAC processes either use pressure contactors or gravity contactors to allow water to pass through. Pressure contactors are generally more cost effective for smaller treatment systems, whereas gravity contactors are more cost effective for larger installations.

Figure 4 shows a typical example of a full-scale GAC pressure adsorption lead/lag pressure vessel system installed in southern Arizona.

Figure 4 Example Pressure GAC Adsorption Pressure Vessels

4.3 IX for PFAS Removal

Synthetic IX resins can also be used for PFAS removal. An IX treatment system uses pressure vessels, like GAC pressure contactors but with an IX resin bed installed instead of GAC media. This type of resin provides dual-removal mechanisms of IX and adsorption technology to remove PFAS from groundwater.

The resin's removal capacity diminishes over time with the volume of water treated, after which it must be replaced and sent off-site for disposal. Unlike with GAC, IX regeneration technology for resins used in PFAS treatment is not yet commercially available. Backwashing IX resin beds is not recommended, as disturbing the mass transfer zones can reduce the PFAS removal efficiency. This condition highlights the need for robust pretreatment that removes sediment, a topic that is discussed in Section 4.1.

Figure 5 shows a typical example of full-scale IX vessels in southern Arizona. These vessels are similar to those used in GAC applications, with minor differences in the internals to accommodate and retain different media particle sizes.

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Figure 5 Example IX Pressure Vessels

4.4 UV AOP for 1,4-dioxane Removal

UV AOP can be used to destruct specific trace level contaminants in water. Under this form of treatment, UV light and hydrogen peroxide form hydroxyl radicals that oxidize contaminants, including 1,4-dioxane.

All excess hydrogen peroxide that leaves the UV reactors must be quenched to maintain a free chlorine residual in the distribution system, which can be completed using GAC.

This evaluation specifically studied a low-pressure, high-output (LPHO) UV lamp system in series with GAC pressure contactors. LPHO lamps have low UV intensities and are more energy-efficient compared to medium-pressure lamps, resulting in lower power costs. Figure 6 shows an example of LPHO UV AOP reactors.

Figure 6 Example LPHO UV Reactors

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4.5 Treatment Technology Benefits and Challenges

Table 8 summarizes benefits and challenges for each of the PFAS and 1,4-dioxane treatment technologies considered in this study.

Table 8 Benefits and Challenges of Feasible Treatment Technologies

Treatment Technology

Benefits Challenges

GAC Adsorption

• Effective in removing PFAS.

• Well-established technology with multiple sources of media and equipment.

• Mechanically simple and low operations and maintenance (O&M) requirements.

• Lower media unit costs compared to ion exchange resins.

• Relatively low power requirements to overcome additional headloss through contactors.

• Effective in quenching hydrogen peroxide.

• Uncertainty in media replacement frequency can be estimated through testing and may vary over time.

• May be less effective in removing short-chain PFAS according to literature and full-scale operations.

• Backwashing is typically required for removal of carbon fines and to reverse increased pressure losses due to GAC bed compression during normal operation.

Requires backwash supply and spent wash water management.

IX

• Well-established technology with multiple sources of media and equipment.

• Potentially longer media bed life and, consequently, less frequent resin replacement requirements compared to GAC media, depending on site-specific water quality.

• May be more effective for removing selected (i.e., shorter-chain) PFAS compounds.

• Does not require backwash system.

• Uncertainty in media replacement frequency can be estimated through testing and may vary over time.

• Potentially higher headloss through contactors compared to GAC, depending on liquid loading rate and bed depth.

• Robust pre-treatment for sediment removal necessary to protect physical integrity of media and avoid backwash.

• More susceptible to biological fouling of bed compared to GAC, especially for non-continuous operation.

• Higher unit media costs for IX versus GAC might not be offset by longer IX bed life, depending on water quality conditions.

• For PFAS, media generally requires landfill disposal or incineration at appropriately permitted facilities.

• Hydrogen peroxide exposure is detrimental to the resin.

UV AOP

• Well-established technology currently utilized for full-scale 1,4-dioxane treatment.

• Local full-scale facility in operation.

• Primarily automated process operation.

• Peroxide chemical storage/feed system necessary.

• Peroxide does not readily absorb UV light, so the peroxide residual must be quenched for a free chlorine residual to be maintained in the distribution system.

• Hydrogen peroxide scavenges hydroxyl radicals, which impacts the efficacy of the AOP.

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4.6 Treatment Alternatives

Carollo identified three well sites as potential locations for PFAS and 1,4-dioxane treatment facilities.

Table 9 summarizes the treatment techniques evaluated at each well site.

Table 9 Treatment Alternatives Matrix

Cluster Combined Treatment Site PFAS Treatment 1,4-dioxane Treatment

Northern Y-001B GAC Pressure Contactors UV-H2O2 AOP

Central Z-013A GAC Pressure Contactors UV-H2O2 AOP

Southern A-057B GAC or IX Pressure Contactors Space Reserved

5.0 Evaluation of Alternatives

The following sections present a review of the recommended treatment alternatives for the NW area production well sites. The following sections include conceptual design criteria, simplified process schematics, conceptual site layouts, and conceptual cost opinions at each cluster.

5.1 Conceptual Design Criteria

All the wells under consideration were grouped to form a cluster based upon geographic location, and each cluster was evaluated for centralized well treatment for removal of the targeted contaminants. Due to the poor condition of some of the project wells shown in Table 5, the cost of adding onsite replacement wells (to match existing flow capacity) at the sites with wells in "poor" condition and treatment facilities were included. Table 10 shows the assumed design capacities which form the fundamental basis of process equipment sizing for alternative treatment systems.

Table 10 Design Capacities

Cluster Units Combined Design Capacity

Northern Cluster at Y-001B gpm (mgd) 1,675 (2.4)

Central Cluster at Z-013A gpm (mgd) 2,600 (3.7)

Southern Cluster at A-057B gpm (mgd) 1,759 (2.5)

Table 11 shows conceptual design criteria assumed for GAC adsorption systems at all three well clusters.

GAC treatment systems would be configured as lead/lag contactors in series to extend the empty bed contact time and overall carbon bed life.

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Table 11 GAC Adsorption Conceptual Design Criteria

Parameter Units Northern Cluster at New Site Central Cluster at Well Z-013A

Southern Cluster at Well Z-013A

Configuration - Lead-lag series operation Lead-lag series operation Lead-lag series operation

Number of Treatment Trains No. 2 3 2

Number of Contactors per Train No. 2 2 2

No. of Contactors No. 4 6 4

Vessel Diameter ft 12 12 12

Design Flow gpm (mgd) 1,675 (2.4) 2,600 (3.7) 1,759 (2.5)

Design Flow/Train gpm 838 867 880

Design Liquid Loading Rate gpm/sq ft 7.8 7.7 7.4

Media Size mesh 12 x 40 12 x 40 12 x 40

Carbon Type Re-agglomerated bituminous coal-derived

Re-agglomerated bituminous coal-derived

Re-agglomerated bituminous coal-derived

Dry Weight of Carbon/ Contactor lb 20,000 20,000 20,000

Carbon Bed Depth ft 5.9 5.9 5.9

Empty Bed Contact Time (EBCT) min 5.7 5.8 6.0

Backwash Flow Rate per Contactor @ approx. 30% Bed Expansion gpm 1,244 1,244 1,244

Backwash Equalization Tank Active Volume (minimum for 15 minute backwash) gallons 18,661 18,661 18,661

Backwash Equalization Tank Diameter ft 15.5 15.5 15.5

Abbreviations:

gpm/sq ft = gallons per minute per square foot

Table 12 shows conceptual design criteria assumed for IX treatment as an alternative at the Southern cluster only. Similar to GAC systems, IX treatment systems would also be configured as lead/lag contactors in series to extend the empty bed contact time and overall resin bed life.

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Table 12 IX Conceptual Design Criteria

Parameter Units Southern Cluster at Well Z-013A

Configuration - Lead-lag series operation

Number of Treatment Trains No. 2

Number of Contactors per Train No. 2

No. of Contactors No. 4

Vessel Diameter ft 10

Design Flow gpm (mgd) 1,759 (2.5)

Design Flow/Train gpm 880

IX Bed Surface Area/Vessel sq ft 78.5

Design Liquid Loading Rate gpm/sq ft 11.2

Media Type PFAS selective IX resin

Volume of Resin/Vessel cf 336

IX Resin Bed Depth ft 4.3

EBCT min 2.9 Abbreviation:

cf = cubic feet

Table 13 shows the conceptual design criteria for the UV AOP system for 1,4-dioxane removal considered in this study.

Table 13 UV AOP System Conceptual Design Criteria

Parameter Units Northern Cluster at New Site Central Cluster at Well Z-013A

Design Capacity gpm (mgd) 1,675 (2.4) 2,600 (3.7)

Target Contaminant -- 1,4-dioxane 1,4-dioxane

Log Reduction -- 1.25 1.25

Lamp Fouling Factor -- 0.9 0.9

UVT % 97 97

Reactor Model -- TrojanUVFlex™48SL TrojanUVFlex™48SL

Number of Duty Trains -- 1 1

Flow per Train gpm 1,675 2,600

Reactors per Train -- 1 1

Number of Lamps per Train -- 96 96

Lamp Technology -- LPHO LPHO

Flange Connection Size in 24 24

Peroxide Dose ppm 10.7 21.5

Peroxide Concentration % 35% 35%

Peroxide 30-day Storage gallons 1,916 5,957 Abbreviation:

ppm = parts per million

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5.2 Simplified Process Schematics

Simplified process schematics in Appendix A show the treatment strategies considered for the three NW area well site clusters evaluated. The simplified process schematics shows IX contactors as lead/lag vessel systems, GAC contactors as lead/lag vessel systems, and UV AOP in series with GAC contactors as lead/lag vessel systems.

5.3 Conceptual Site Layouts

Appendix B shows example conceptual centralized wellhead treatment layouts for each cluster at different sites: Northern at Y-001B, Central at Z-013A, and Southern at A-057B. The illustrated treatment systems include solids pretreatment using desanders or automatic backwash strainers, bag filters, UV AOP, and GAC or IX contactors based on site-specific requirements. The site layouts also show a backwash waste equalization tank used for settling carbon fines and solids from periodic GAC contactor backwashing. The Southern cluster site layouts have illustrations for both GAC and IX treatment for PFAS removal, and space reserved for a UV AOP building.

The proposed central cluster treatment site (wellsite Z-013A) has limited space for the process equipment;

therefore, Tucson Water may consider the feasibility of acquiring the parcel (owned by Circle K) west of the wellsite.

5.4 Conceptual Replacement Well and Treatment Cost Opinions

Carollo developed conceptual-level capital and annual operations and maintenance cost opinions for the blending and treatment alternatives. The cost opinion tables appear in Appendix C. Tucson Water provided costs for well drilling and equipping in the 2018 Tucson Water technical memorandum Cost Estimate to Replace Potable Production Lost due to PFAS Detections.

The capital cost opinions are expressed in February 2022 dollars (corresponding 20-Cities Average Engineering News Record Construction Cost Index = 12,684). Cost opinions are consistent with Class 4 Estimates as defined by the Association for the Advancement of Cost Engineering (AACE) International. This level of engineering cost estimating is generally made with limited information, including process block diagrams, preliminary equipment lists, and conceptual layouts. Typical accuracy for Class 4 Estimates is expected to be in the range of -30 to +50 percent.

The cost opinions do not include any costs for adding additional Supervisory Control and Data Acquisition (SCADA)/communications equipment. Tucson Water would coordinate alignment of SCADA/communications hardware and software at sites as part of any treatment facility implementation.

5.4.1 Economic Analysis of Cost Opinions

Carollo prepared economic analyses for all treatment alternatives evaluated. These values represent the sum of capital cost opinions and the present worth of annual operations and maintenance cost projections, assuming a discount rate of 4 percent and term of 20 years. The total capital cost is split into its component cost of pipeline-only and treatment-only costs. Table 14 shows the economic analysis for all conceptual-level costs. Figure 7 shows a comparison of capital costs, annual operations and maintenance costs, total present worth, and equivalent annual and unit treatment costs for all treatment alternatives.

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Table 14 Conceptual Centralized Wellhead 1,4-dioxane and PFAS Treatment Cost Opinions

Cost Opinions Northern Cluster at

Well Y-001B Site

GAC+UVAOP

Central Cluster at Well Z-013A Site

GAC+UVAOP

Southern Cluster at Well A-057B Site GAC Adsorption

Southern Cluster at Well A-057B Site

Ion-Exchange

Capital - Treatment System

$16,190,000 $28,540,000 $19,740,000 $21,110,000

Capital - Pipeline $3,550,000 $5,220,000 $5,620,000 $5,620,000

Total Capital Cost $19,600,000 $33,520,000 $25,080,000 $26,480,000

Annual O&M Cost(1) $740,000 $1,090,000 $120,000 $130,000

Present Worth of Capital Cost

Present Worth of Annual O&M(1,2)

$10,057,000 $14,813,000 $1,631,000 $1,767,000

Total Present Worth(1,2) $29,660,000 $48,330,000 $26,710,000 $28,250,000

Equivalent Annual and Unit Treatment Cost

Annualized Capital Cost(1,2)

$1,442,000 $2,467,000 $1,846,000 $1,949,000

Total Equivalent Annual Cost(1,2)

$2,182,000 $3,557,000 $1,966,000 $2,079,000

Cost per 1,000 Gallons Treated(1,2)

$2.48 $2.60 $2.13 $2.25

Notes:

(1) Media changeout frequencies and the corresponding costs represent 2 ppt for PFOA+PFOS+PFHxS+PFHpA.

(2) Assuming a discount rate of 4 percent annually and a term of 20 years.

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Figure 7 Centralized Wellhead 1,4-dioxane and PFAS Treatment Conceptual Cost Opinion

$20

$34

$25 $26

$0.7 $1.1 $0.1 $0.1

$30

$48

$27 $28

$0

$10

$20

$30

$40

$50

$60

Northern Cluster

UV AOP + GAC

Central Cluster

UV AOP + GAC

Southern Cluster

GAC

Southern Cluster

IX

Co st

M ill io ns

Capital Cost Annual O&M Present Worth

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6.0 Summary and Conceptual Implementation Plan

6.1 Summary

This section summarizes the finding of this TM and a conceptual implementation plan.

1. EPA published an Updated Lifetime Drinking Water HAs for the following PFAS compounds on June 15, 2022:

a. Interim Updated HA of 0.004 ppt for PFOA and 0.02 ppt for PFOS.

b. Final HA of 2,000 ppt for PFBS and 10 ppt for GenX chemicals.

The SDWA HA for 1,4-dioxane is 0.35 ppb based on a 1x10-6 excess lifetime cancer risk. The SDWA enforceable MCL for TCE is 5 µg/L. While Drinking Water Health Advisories are not enforceable standards, they represent EPA's recommendations for public water systems and will be taken under consideration in any forthcoming EPA rulemaking that may result in enforceable MCLs.

2. Tucson Water removed nine wells in the NW area from service due to detections of PFAS, 1,4-dioxane, and/or TCE. All the wells with PFAS detections have been taken out of service:

a. Wells Z-002A on March 9, 2016,

b. Wells Z-014B and Y-001B on September 22, 2016,

c. Wells Z-005A, Z-015A and Z-013A on September 19, 2016,

d. Wells A-053A and A-057B on July 18, 2018.

3. Wells Y-004A, Y-001B, Z-013A, Z-014B, Z-015A, A-053A, A-057B, and Z-005A would require water quality improvements to meet Tucson Water's potable water system operational guidelines for PFAS and/or 1-4 dioxane and to address detectable levels of TCE produced by Well Z-002A.

4. The nine wells were grouped into three clusters for centralized well treatment:

a. Northern: Wells Y-004A and Y-001B.

b. Central: Wells Z-013A, Z-014B and Z-015A.

c. Southern: Wells A-053A, A-057B, Z-002A and Z-005A.

The clustering was based upon geographic location of these wells and feasibility of centralized well treatment.

5. The southern cluster wells can meet Tucson Water operation guidelines for 1,4-dioxane by blending but not for PFAS, while the Northern and Central cluster wells do not meet operational guidelines for both PFAS and 1,4-dioxane after blending.

6. Effective treatment technologies are available to reduce PFAS and 1,4-dioxane concentrations to reliably meet Tucson Water's operational guidelines and to reduce TCE concentrations to less than reportable levels. UV AOP and GAC or IX are well-established and demonstrated for municipal water treatment.

7. Centralized well treatment for each cluster was evaluated at different sites:

a. Northern at Y-001B.

b. Central at Z-013A.

c. Southern at A-057B.

All three well sites studied can accommodate the full range of treatment facility alternatives evaluated in this study.

8. Wells Z-013A, Z-014B, Z-015A, A-053A, Z-002A and Z-005A are on the order of 20-80 years old and in poor condition, indicating the need for replacement wells to re-activate sustained pumping activities at the sites. Replacement wells would have the same design capacity as the current wells.

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6.2 Conceptual Implementation Plan

Conceptual implementation plans were developed for advancing groundwater treatment capital projects for the Central and Southern well clusters, as shown in Table 15 and Table 16, respectively. An implementation plan for the northern cluster was not developed since Tucson Water can pump water into that zone from lower zones. Capital cost opinions for the Central and Southern well clusters were projected over four year periods covering design, construction, and commissioning phases:

• Engineering design during Year 1.

• Construction between Year 2 and Year 4.

- Construction Manager at Risk (CMAR) project delivery method.

• Resident engineering and construction administration during construction years.

7.0 References

Carollo Engineers, Inc. Impacts of Targeted Emerging Contaminants on Water Supplies and Capital Assets:

Technical Memorandum: Northwest Area Wells Alternatives Evaluation. December 2020.

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Table 15 Conceptual Implementation Plan for Central Well Cluster

Table 16 Conceptual Implementation Plan for Southern Well Cluster

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Appendix A

SIMPLIFIED PROCESS SCHEMATICS

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Figure A.1 GAC Adsorption Process Flow Diagram

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FINAL | AUGUST 2022 | A-2

Figure A.2 Ion Exchange Process Flow Diagram

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Figure A.3 UV AOP and GAC Process Flow Diagram

NORTHWEST AREA WELLS ALTERNATIVES EVALUATION | IMPACTS OF TARGETED EMERGING CONTAMINANTS | TUCSON WATER

Appendix B

CONCEPTUAL SITE LAYOUTS

Legend

50.00

PimaMaps Print

Notes:

100.0

Feet

This map is static output from an internet mapping site and no warranty is expressed or implied as to the accuracy, reliability, currency or completeness of the data, and is for reference only 2/4/2022

Parcels

UVAOP

TREATMENT

BUILDING

RELOCATE

BAG FILT

ER

22,000 GAL

BACKWASH TANK

(Dia = 16 ft)

(H = 15 ft)

BACKWASH W

ASTE TO SANITARY SEWER

EXISTING GATE

TREATED W

ATER

HYDRO

TANK

DRAFT

NORTHERN CLUSTER - CENTRALIZED TREATMENT AT Y-001B (UV AOP + GAC LEAD/LAG)

NEW GATE

SANITARY SEWER

BACKWASH SUPPLY

PURGE TANK

PROPERTY BOUNDARY

a Parcels

GAC Pressure Contactor Footprint

UVAOP Building

Bag Filter Footprint

Desanders

GAC Backwash Tank

Purge Tank

New Raw Water Pipeline

GAC Contacted Water

GAC Backwash Supply

GAC Backwash Waste

Backwash Recycle

New Gate

New Pavement

12-FT DIAMETER GAC

CONTACTOR (6

TO DISTRIBUTIO

N SYSTEM

POTABLE W

ATER LINE

FROM W

ELL

SITE

Y-00 4A

DESANDER

VIRTUAL PUMP LAYDOWN AREA

(30ft x 8ft)

03/30/2022August 2022

This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map are subject to Pima County's ITD GIS disclaimer and use restrictions.

Notes:

Legend

2550 0

Feet 12/2019

PURGE TANK

EXISTING WELL PUMP

TREATED WATER

PROPERTY BOUNDARY and PROPOSED NEW

FENCE

TO DISTRIBUTION SYSTEM

UVAOP TREATMENT BUILDING

BAG FILTERSDESANDERS

12-FT DIAMETER GAC CONTACTOR (6)

EXISTING FENCE

FROM WELL SITES Z-014B &Z-015A

22,000 GAL BACKWASH TANK

(Dia = 16 ft) (H = 15 ft)

BACKWASH RECYCLE PUMPS

BACKWASH RECYCLE

EXISTING GATE

EXISTING GATE NEW GATE

CENTRAL CLUSTER - CENTRALIZED TREATMENT AT Z-013A (UV AOP + GAC LEAD/LAG) Parcels

GAC Pressure Contactor Footprint

UVAOP

Building

Bag Filter Footprint

Desanders

GAC Backwash Tank

Purge Tank

New Raw Water Pipeline

GAC Contacted Water

GAC Backwash Supply

GAC Backwash Waste

Backwash Recycle

Existing Distribution System

New Gate

INA RD

POTENTIAL WELL REDRILL LOCATION

DRAFT

NEW DRIVEWAYW Camino de las Capas H

YD

R

O P

N

EU

M

AT

IC

TA

N K

CIRCLE K PARCEL

TUCSON WATER PARCEL 2

BACKWASH WASTE TO SANITARY SEWER

BACKWASH SUPPLY

POTABLE WATER LINE

TUCSON WATER PARCEL 1

VIRTUAL PUMP LAYDOWN AREA

(30ft x 8ft)

10' X 73' TR

AILER

+ TR

U

C K

County's ITD GIS disclaimer and use restrictions.

Notes:

Legend

25.0050.0 0

Feet 12/3/2019

Parcelse

EXISTING WALL

BAG FILTER

DESANDER

EXISTING

WELL PUMP

EXISTING GATE

22,000 GAL BACKWASH TANK

(Dia = 16 ft) (H = 15 ft)

TO DISTRIBUTION SYSTEM

BACKWASH SUPPLY

BACKWASH WASTE

TO SANITARY SEWER

12' GAC CONTACTOR

(TYP OF 4)

West River Road

HYDRO PNEUMATIC

TANK

TREATED WATER

FROM WELL SITES Z-005A

& Z-002A

FROM WELL SITE

A-053A

NEW WALK-IN GATE

DRAFT

PROPERTY BOUNDARY

TUCSON WATER PARCEL

PIMA COUNTY PARCEL

SA

N

IT

AR

Y

SE

W

ER

GALERIA DEL RIO PARCEL

PURGE TANK

Parcels

GAC Pressure Contactor Footprint

Bag Filter Footprint

Desanders

GAC Backwash Tank

Purge Tank

New Raw Water Pipeline

GAC Contacted Water

GAC Backwash Supply

GAC Backwash Waste

Backwash Recycle

New Gate

New Pavement

NEW SLIDING GATE

ASPHALT

PAVEMENT

BACKWASH RECYCLE PUMPS

PO

TA

BL

E

W

AT

ER

L

IN

E

SOUTHERN CLUSTER - CENTRALIZED TREATMENT AT A-057 (GAC LEAD/LAG )

RELOCATED WALL

SPACE RESERVED FOR

UVAOP BUILDING

BACKWASH RECYCLE

VIRTUAL PUMP

LAYDOWN AREA

(30ft x 8ft)

County's ITD GIS disclaimer and use restrictions.

Notes:

Legend

25.0050.0 0

Feet 12/3/2019

Parcels

EXISTING WALL

EXISTING

WELL PUMP

EXISTING GATE

TO DISTRIBUTION SYSTEM

10' IX CONTACTOR

(TYP OF 4)

West River Road

HYDRO PNEUMATIC

TANK

TREATED WATER

FROM WELL SITES Z-005A

& Z-002A

FROM WELL SITE

A-053A

DRAFT

PROPERTY BOUNDARY

TUCSON WATER PARCEL

PIMA COUNTY PARCEL

GALERIA DEL RIO PARCEL

BAG FILTER

BACKWASH RECYCLE PUMPS

NEW SLIDING GATE

ASPHALT

PAVEMENT

SA

N

IT

AR

Y

SE

W

ER

e Parcels

IX Pressure Contactor Footprint

Bag Filter Footprint

Automatic Backwash Filter

Backwash Tank

Purge Tank

New Raw Water Pipeline

IX Contacted Water

Backwash Supply

Backwash Recycle

New Gate

New Pavement

SOUTHERN CLUSTER - CENTRALIZED TREATMENT AT A-057 (IX LEAD/LAG)

NEW WALK-IN GATE

PO

TA

BL

E

W

AT

ER

L

IN

E

RELOCATED WALL

BACKWASH RECYCLE

SPACE RESERVED FOR

UVAOP BUILDING

AUTOMATIC BACKWASH

FILTRATION SYSTEM

12,000 GAL BACKWASH TANK

(Length = 50 ft) (Width = 8 ft)

VIRTUAL PUMP

LAYDOWN AREA

(30ft x 8ft)

NORTHWEST AREA WELLS ALTERNATIVES EVALUATION | IMPACTS OF TARGETED EMERGING CONTAMINANTS | TUCSON WATER

Appendix C

CONCEPTUAL CAPITAL AND ANNUAL OPERATIONS

AND MAINTENANCE COST OPINIONS

Northwest Area Wells Alternatives Evaluation Update PFAS and 1,4-dioxane Treatment Only

Conceptual Cost Opinions

03/30/2022

Northern Cluster Central Cluster Well Y-001B

UV AOP + GAC

Well Z-013A

UV AOP + GAC

Well A-057B

GAC

Well A-057B

IX

Wells: Y-001B, Y-004A Wells: Z-013A, Z-014B, Z-015A

Wells: Z-005A, Z-002A, A-057B, A-053A

Wells: Z-005A, Z-002A, A-057B, A-053A

CAPITAL COST1

DIRECT COST2

Site Work3 25% $602,000 $747,000 $387,000 $448,000 Yard Piping and Valves4 45% $1,407,000 $1,745,000 $904,000 $1,045,000 Foundation $131,000 $108,000 $131,000 $108,000 UV AOP Building $659,000 $659,000 Pump Replacement $132,000 $132,000 $132,000 $132,000 Onsite Well Drilling5,6 $2,680,000 $3,160,000 $3,160,000 Onsite Well Equipping5 $1,337,000 $1,337,000 $1,337,000 New Source Sampling5 $5,000 $5,000 $5,000

Process Equipment

UVAOP $915,000 $915,000

GAC

Contactors $929,000 $1,394,000 $929,000 Media $114,000 $172,000 $114,000

Anion Exchange Contactors $869,000 Media $390,000

Backwash Tank $90,000 $90,000 $90,000 $61,000 Backwash Return Pump $14,000 $14,000 $14,000 $14,000 Desanders $87,000 $142,000 $142,000 Automatic Backwash Filtration System $197,000 Bag Filters $259,000 $259,000 $259,000 $259,000

Installation3 30% $718,000 $892,000 $460,200 $533,000 Electrical4 25% $782,000 $970,000 $502,000 $581,000 I&C4 10% $313,000 $388,000 $201,000 $232,000

SUBTOTAL DIRECT COST $7,150,000 $12,650,000 $8,770,000 $9,370,000

Contingency7 30% $2,145,000 $3,795,000 $2,631,000 $2,811,000

TOTAL DIRECT COST $9,295,000 $16,445,000 $11,401,000 $12,180,000

INDIRECT COST

General Conditions, Overhead, Profit & Risk8 22% $2,045,000 $3,618,000 $2,508,000 $2,680,000 Bonds and Insurance8 3% $279,000 $493,000 $342,000 $365,000 Tax (65% of 8.7% Tucson Rate)8 6% $136,000 $169,000 $88,000 $101,000

TOTAL INDIRECT COST $2,460,000 $4,280,000 $2,940,000 $3,150,000

TOTAL CONSTRUCTION COST $11,760,000 $20,730,000 $14,340,000 $15,330,000

Engineering, Administration, and Legal9 25% $2,940,000 $5,183,000 $3,585,000 $3,833,000 Escalation9 13% $1,489,000 $2,626,000 $1,816,000 $1,942,000

TOTAL CAPITAL COST $16,190,000 $28,540,000 $19,740,000 $21,110,000

Hydrogen Peroxide (35%) $80,000 $250,000 Media Changeout Frequency for 18 ppt PFAS breakthrough (years)10,13 0.3 0.4 Media Changeout Frequency for 70 ppt PFAS breakthrough (years)11,14 0.6 0.6 Media Changeout Frequency for 2 ppt PFAS breakthrough (years)12 0.3 0.3 4.2 9.6 Media Changeout (including spent media management)10,13 $334,000 $461,000 $24,000 $12,000 Media Changeout Lower Bound (including spent…