United States 	Environmental Protection 	Agency

Technologies and Costs for Corrosion Control to Reduce Lead in Drinking Water

Office of Water (4607M) EPA 816-R-20-007 July 2020 www.epa.gov/safewater Disclaimer Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Table of Contents

1	Introduction	1 1.1	Background	1 1.2	Document Organization and Overview	3 2	Caustic Addition for pH Adjustment	4 2.1	Operating Principle	4 2.2	Effectiveness of Caustic Addition for pH Adjustment	5 2.3	Raw Water Quality Considerations	7 2.4	Critical Design Parameters	8 3	Corrosion Inhibitor Addition	9 3.1	Operating Principle	9 3.2	Effectiveness for Reducing Lead Concentrations	10 3.3	Raw Water Quality Considerations	13 3.4	Pre- and Post-Treatment Needs	13 3.5	Residuals Management Needs	14 3.6	Critical Design Parameters	14 3.6.1	Chemical Type and Dose	14 3.6.2	Post-Treatment pH Requirements	15 4	Pilot Testing	16 4.1	Design Inputs and Assumptions	17 4.1.1	Number of Pipe Segments or Jars	17 4.1.2	Study Duration and Operation	18 4.1.3	Labor Assumptions	19 4.1.4	Sampling Location and Frequency	19 5	POU Treatment	21 5.1	Operating Principle	21 5.2	Effectiveness for Lead Removal	22 5.3	Raw Water Quality Considerations	22 5.4	Waste Generation and Residuals Management Needs	22 5.5	Critical Design Parameters	22 6	Costs for Treatment Technologies and Pilot Testing	24 6.1	Introduction	24 6.1.1	Overview and Cost Modeling Approach	24 6.1.2	WBS Models	24 6.1.3	WBS Model Accuracy	27 6.2	Costs for Chemical Addition for pH Adjustment	27 6.2.1	Model Components and Assumptions	27 6.2.2	Cost Equations	30 6.3	Costs for Corrosion-Inhibitor Addition	31 6.3.1	Model Components and Assumptions	31 6.3.2	Cost Equations	35 6.4	Costs for POU Technologies	36 6.4.1	Model Components and Assumptions	36 6.4.2	Cost Estimates	39 6.5	Costs for Pilot Testing	39 6.5.1	Design Inputs and Assumptions	39 6.5.2	Cost Estimates	41 7	References	42 Appendix A: Cost Equations	46

List of Exhibits

Exhibit 2-1. Chemical Addition Options for pH Adjustment	4 Exhibit 2-2. Typical Schematic Layout for Caustic Feed	5 Exhibit 2-3. Effectiveness of pH Adjustment	6 Exhibit 2-4. Studies of Lead Concentration Variations across Systems or Treatment Plants	7 Exhibit 3-1. Typical Schematic Layout for Phosphate Feed	10 Exhibit 3-2. Corrosion Inhibitor Effectiveness	11 Exhibit 4-1. General Schematic Layout for Pipe Rack Pilot Testing Apparatus	17 Exhibit 4-2. On-Off Schedule Recommended in AWWARF (1994)	18 Exhibit 6-1. Model Size Categories Based on the EPA's Flow Characterization Paradigm	25 Exhibit 6-2. Cost Elements Included in All WBS Models	26 Exhibit 6-3. Estimates of Post-Treatment pH Values by Starting pH and Phosphoric Acid Dose	29 Exhibit 6-4. Solution Strength and Density for Default Chemicals	33 Exhibit 6-5. WBS Model Changes to Estimate Retrofit Capital Costs	35 Exhibit 6-6. POU Model Assumptions for Pour-Through Devices for Short-Term Use 	36 Exhibit 6-7. POU Model Assumptions for Plumbed-In Devices for Long-Term Use	37 Exhibit 6-8. Design Inputs that Determine Number of Pipe Segments or Coupons	39 Exhibit 6-9. Design Inputs for Study Duration and Operation	40 Exhibit 6-10. Design Inputs for Pilot Study Labor	40 Exhibit 6-11. Design Inputs for Pilot Study Sampling and Analysis	41

List of Abbreviations and Acronyms AL	action level ALE	action level exceedance Alk	alkalinity ANSI	American National Standards Institute C	carbon °C	degree Celsius Ca	calcium CCT	corrosion control technology CaCO3	calcium carbonate CO2 	carbon dioxide  CO3[-2] 	carbonate DIC	dissolved inorganic carbon ECI	Employment Cost Index EPA or Agency	U.S. Environmental Protection Agency °F 	degree Fahrenheit ft	feet gpm	gallons per minute GW	groundwater H	hydrogen ion H2CO[3] 	carbonic acid HCO3[-] 	bicarbonate H3PO4 or PA 	phosphoric acid HVAC	heating, ventilating, and air conditioning K2CO3 	potassium carbonate  KOH 	potassium hydroxide lbs/gal	pounds per gallon LCR	Lead and Copper Rule LSL	lead service line LSLR	lead service line removal ug/L	micrograms per liter m[2] 	square meter MGD	million gallons per day mg/L	milligrams per liter mol/m[2]/min	mole per square meter per minute na	not applicable Na2CO3 	sodium carbonate NaHCO3 	sodium bicarbonate  NaOH 	sodium hydroxide NPDES	National Pollution Discharge Elimination System NSF	NSF International  OH[-]	hydroxide ion O&M	operation and maintenance P	phosphorus Pb	lead Pb90	90[th] percentile lead concentration  Pb3(CO3)2(OH)2	hydrocerussite  Pb3O4 	minium Pb5(PO4)3Cl	chloropyromorphite  Pb5(PO4)3OH	hydroxylpyromorphite PbCO3	cerussite  PbO2	lead dioxide PLC	programmable logic controller PO4	orthophosphate POU	point-of-use RO	reverse osmosis SW	surface water TBA	to be added TDP	Technology Design Panel TDS	total dissolved solids TL	trigger level WBS	work breakdown structure WTP	water treatment plant WWTP	wastewater treatment plant Zn	zinc ZO	zinc orthophosphate

Introduction Background Exposure to lead can have acute and chronic health effects. The 2013 Integrated Science Assessment for Lead (USEPA, 2013) and the U.S. Department of Health and Human Services' National Toxicology Program Monograph on Health Effects of Low-Level Lead (NTP, 2012) have both documented the association between lead and adverse cardiovascular, renal, reproductive, immunological, and neurological effects; and cancer. Furthermore, the NTP (2012) concludes that there is sufficient evidence of health effects associated with low-level lead exposure. The most robustly studied and most susceptible subpopulations are developing fetuses, infants, and young children. Exposure to lead is known to present serious health risks to the brain and nervous system of children. Even low-level lead exposure is of particular concern to children because their growing bodies absorb more lead than adults do, and their brains and nervous systems are more sensitive to the damaging effects of lead.  Sources of lead include lead-based paint, drinking water, and contaminated soil. Lead enters drinking water mainly from corrosion of lead-containing plumbing materials such as lead service lines (LSLs), solder, and brass fittings and fixtures. Lead was widely used in plumbing materials until Congress banned its use in 1986. There are an estimated 6.3 to 9.3 million homes served by LSLs, and unknown millions of older homes with solder and brass plumbing materials that do not meet the current no-lead standards (USEPA, 2020a).  To reduce the health risks of lead exposure, the U.S. Environmental Protection Agency (the EPA or Agency) established a drinking water regulation for lead in 1991 as part of the Lead and Copper Rule (LCR) (USEPA, 1991). The Agency promulgated an action level (AL) of 0.015 milligrams per liter (mg/L) [15 micrograms per liter (ug/L)] and defined an action level exceedance (ALE) as more than 10 percent of household monitoring samples exceeding the AL during a monitoring period. An ALE prompts a drinking water system to reduce lead exposure through various actions such as corrosion control technology (CCT) adoption or modification, lead service line removal (LSLR), source water monitoring, and public education program implementation.  The EPA has revised the rule since 1991. Interim rules in 2000 and 2007 improved monitoring, reporting, and public outreach requirements. The final long-term LCR revisions add a trigger level (TL) of 0.01 mg/L (10 ug/L) that prompts actions. Following a TL exceedance, systems with a CCT must re-optimize it and those without one must conduct a CCT study, unless they are small systems serving 3,300 or fewer people that elect a non-CCT option. The final revisions also require the re-optimization or installation of a CCT in the event of an ALE, except among small systems serving 3,300 or fewer people that choose an alternative lead-reduction strategy. The EPA estimated the national costs of the LCR revisions using system-level estimates of CCT changes and costs, or alternative lead-reduction strategies such as LSL removal or installing and maintaining point-of-use (POU) devices. This document addresses the two CCT treatment technologies used to estimate costs: pH adjustment by caustic addition and corrosion inhibition by phosphate addition. It provides treatment effectiveness information and describes the modeling approach used to estimate costs. The EPA combined these technologies into three CCT options for the cost analysis, described in further detail in Section 5: Modify pH: adding caustic to increase pH Add phosphate (P) or orthophosphate (PO4) with pH post-treatment: adding a phosphate inhibitor followed by adding a caustic, as needed, to offset a reduction in pH if the phosphate chemical would lower pH by 0.1 standard units or more Add phosphate or orthophosphate and modify pH: adding a phosphate inhibitor and caustic to increase pH to an optimal level for passivation. Drinking water systems adopt or modify CCTs to mitigate conditions that promote lead corrosion from plumbing materials. Corrosion is the result of complex chemical, physical, and biological interactions that occur when water comes into contact with metal plumbing materials. There are three different lead corrosion mechanisms (USEPA, 2016):  Uniform corrosion, where the electrochemical interaction occurs along the pipe wall, resulting in a relatively uniform loss of metal across the entire surface; Non-uniform corrosion, where metal is lost from a localized point, causing pitting and mounding in some cases; and Galvanic corrosion, which results from a coupling of dissimilar metals or internally in metallic alloys.  Lead corrosion processes begin with oxidants in water (e.g., oxygen or chlorine) that oxidize insoluble lead (Pb[0]) present in plumbing materials into soluble divalent lead(II), which then enters water and can interact with other water constituents to form scale products that reattach to plumbing materials, forming a passivating layer scale that inhibits corrosion of metal beneath the scale. For example, if chlorine levels are sufficient for lead(IV) compounds to form, then lead oxides such as plattnerite or lead dioxide (PbO2) and minium (Pb3O4) can form scales that have low solubility (Burlingam et al., 2006; Mohammadzadeh et al., 2015; USEPA, 2016). Water containing carbonates can form lead carbonates such as hydrocerussite (Pb3(CO3)2(OH)2) and cerussite (PbCO3), which are common scale products when pH and dissolved inorganic carbon (DIC) are sufficiently high (Noel et al., 2014).  Corrosion inhibitors further reduce lead solubility. When a system adds orthophosphate for corrosion control, scale can comprise low-solubility lead(II) phosphate solids; both hydroxylpyromorphite (Pb5(PO4)3OH) and chloropyromorphite (Pb5(PO4)3Cl) have been found in distribution systems (Davidson et al., 2004; Schock et al., 2005). Scale dissolution and saturation rates depend on water characteristics such as pH and DIC content, as well as contact time (e.g., stagnation). Hydraulic changes can dislodge scale, increasing the presence of particulate lead in drinking water. The objective of CCTs is to passivate corrodible distribution system materials by creating conditions for stable scales to form on these materials. Caustic addition  -  adding sodium hydroxide  -  increases pH, which reduces corrosion and can encourage scale formation. Phosphate addition encourages low-solubility scale formation. This document also addresses the effectiveness and cost estimates for POU filtration devices, which differ from CCTs. These devices can reduce exposure to lead at a single faucet, especially following premise plumbing disruptions such as LSLRs. Document Organization and Overview This report is organized as follows: Evaluation of CCT options and POU devices for complying with potential perchlorate standards   Caustic addition for pH adjustment (Chapter 2)  Phosphate addition to inhibit corrosion (Chapter 3)  POU treatment (Chapter 5) Pilot testing for CCT selection Chapter 4) Costs for CCT, POU, and pilot testing (Chapter 6). For each technology, the corresponding chapter provides an overview of how the treatment operates and summarizes its effectiveness for reducing lead corrosion in premise plumbing. Each technology summary also incorporates available findings with respect to variability under different source water conditions. Each summary concludes with a compilation of the engineering design specifications available from the documents reviewed. Chapter 6 (along with Appendix) presents estimated costs for installing and operating each of the technologies or options discussed in Chapters 2 through 5. Appendix A provides complete cost equations for the technology options. Caustic Addition for pH Adjustment Operating Principle The pH of water indicates how acidic (or basic) the water is based on the concentration of hydrogen ions (H[+]). The value of pH is a logarithmic scale that ranges from 0 to 14, with a pH value of 7 representing neutral or neither acidic nor basic; values less than 7 indicate increasing acidity as they remove farther away from the neutral value of 7 (i.e., higher concentrations of the hydrogen ion, H[+]). Conversely, values greater than 7 indicate basic solutions (i.e., higher concentrations of hydroxide ion, OH[-]). Acidic waters tend to be more corrosive for metals. Therefore, increasing the pH of water distributed to customers will tend to reduce corrosion. Higher pH levels can also facilitate scale formation as saturated compounds attach to plumbing materials and/or better protect existing passivating scale by reducing dissolution rates. Chemicals can be added to raise the pH of water. Exhibit 2-1 provides a summary of the pH adjustment chemicals noted in the EPA Guidance (USEPA, 2016). Some chemicals directly increase hydroxide ions (e.g., sodium hydroxide), while others indirectly increase hydroxide ions through reactions (e.g., sodium carbonate).  The chemical dosage required to affect pH levels depends on several factors, including water alkalinity. Alkalinity refers to the buffering capacity of a water body or the ability of the water to resist change in pH levels by neutralizing acids and bases. All of the chemicals listed in Exhibit 2-1 also increase alkalinity and may increase DIC, which is the sum of inorganic carbon species: carbon dioxide (CO2), carbonic acid (H2CO3), bicarbonate (HCO3[-]), and carbonate (CO3[-2]).  Exhibit 2-1. Chemical Addition Options for pH Adjustment Chemical Water Quality Effects Sodium hydroxide (NaOH; caustic soda) Increases pH Increases alkalinity [1.25 mg/L as calcium carbonate (CaCO3) per 1 mg/L NaOH] No DIC impact Sodium carbonate  (Na2CO3) Increases pH Increases alkalinity (0.94 mg/L as CaCO3 per 1 mg/L Na2CO3) Increases DIC (0.11 mg/L as carbon, C, per 1 mg/L Na2CO3) Sodium bicarbonate (NaHCO3; baking soda) Increases pH Increases alkalinity (0.60 mg/L as CaCO3 per 1 mg/L NaHCO3) Increases DIC (0.14 mg/L as C per 1 mg/L NaHCO3) Potassium hydroxide  (KOH; caustic potash) Increases pH Increases alkalinity (0.89 mg/L as CaCO3 per 1 mg/L KOH) No DIC impact Potassium carbonate (K2CO3; potash) Increases pH Increases alkalinity (0.72 mg/L as CaCO3 per 1 mg/L K2CO3) Increases DIC (0.09 mg/L as C per 1 mg/L K2CO3) Source: USEPA (2016, Exhibit 3.1).

For example, adding sodium hydroxide is a common method to adjust pH for corrosion control in a distribution system. The dissolved sodium hydroxide adds hydroxide ions, while the sodium cations can indirectly increase alkalinity through reactions with carbon dioxide in the water that result in additional calcium carbonate formation; however, there are no carbon atoms to affect DIC.  Integrating a chemical addition process with an existing water system requires chemical storage equipment as well as equipment to mix the needed chemical dose into the water. Exhibit 2-2 provides a schematic drawing for a caustic feed process. The drawing includes chemical storage (the storage tank shown is optional because storage options can include drums or totes), a metering pump to feed the chemical into an existing water pipeline, valves for flow control, and pH-monitoring instruments to control the dose. Optional features include an inline mixer; transfer pumps for a day tank; and heat (i.e., heat tracer), if needed, to prevent freezing in colder climates. Feed system equipment requirements will vary by chemical type, strength, dosage, and system size. Exhibit 2-2. Typical Schematic Layout for Caustic Feed

Source: USEPA (2020b).

Effectiveness of Caustic Addition for pH Adjustment Exhibit 2-3 summarizes recent studies of pH adjustment effectiveness for reducing lead concentrations in drinking water, which include bench-scale studies of scale formation and dissolution rates; pipe loop studies of alternative CCT options, including chemical addition to increase pH; and intertemporal studies of changes in lead concentrations over time as the CCT changes.  Exhibit 2-3. Effectiveness of pH Adjustment Study Type and Source pH Adjustment Initial Lead Concentration Post-Treatment Lead Concentration Pipe loop study  Kim et al. (2011) NaOH  -  pH increased from 7.1 to 8.7  > 400 ug/L total Pb  < 200 ug/L total Pb (post-stagnation samples)[a] Pipe loop study  Kim et al. (2011) NaOH  -  pH increased from 7.8 to 9.6  > 25 ug/L total Pb  < 10 ug/L total Pb (flow samples)[b] London, Ontario, 8 homes with LSLs  Kim et al. (2011)[c]  NaOH  -  pH increased from 7.1 to 7.6  NaOH  -  pH increased from 7.6 to 8.1 > 10 ug/L total Pb in 6 homes  Approximately 50% total Pb reduction   No additional Pb reduction  System well treatment Schock et al. (2005) NaOH  -  pH increased from 6.3 to 7.5 77 ug/L Pb90 2 ug/L Pb90 (97% decrease) Coupon test Hosseinibalajadeh (2018) NaOH  -  pH increased from 7.6 - 7.7 range to 8.5 - 9.2 range Pb concentration in control samples: 100 to 140 ug/L Pb concentration 80%+ lower than control samples Pipe loop study Gagnon and Doubrough (2011) NaOH  -  to maintain pH of 7.5 (with orthophosphate) Pb concentration in pH 7.9 samples: 2 to 16 ug/L Pb concentration in pH 7.5 samples: 1.9 to 9.5 ug/L Bench test of hydrocerussite dissolution rates[d] Noel et al. (2014)  Increased pH from 7.5 to 8.5  Increased pH from 7.5 to 10   Added DIC of 10 mg/L Not applicable  -  study of dissolution rates of synthesized hydrocerrusite   Dissolution rate decreased by 75%  Dissolution rate decreased by 80%  Dissolution rate decreased by 40 to 90% across pH changes Pipe Loop Study Xie and Giammer (2011) DIC 10 mg/L / pH 10  DIC 50 mg/L / pH 8.5 No control loop data Pb < 15 ug/L  Pb > 20 ug/L  Pipe Loop Study Doré et al. (2019) NaOH  -  pH increased from 7.9 to 8.3 16-hour stagnation: 79.5 ug/L median; 180 ug/L Pb90 Flowing: 1.7 ug/L median; 7.8 ug/L Pb90 16-hour stagnation: 84.1 ug/L median Pb; 162 ug/L Pb90 Flowing: 1.5 ug/L median Pb; 2.9 ug/L Pb90 Pb = lead; Pb90 = 90th percentile lead concentration.  a. Particulate lead fraction rose from 10% at a pH value of 7.1 to more than 50% at pH values greater than 8.5. b. Lead concentrations for the zero L/minimum flow rate oscillated between 15 and 50 ug/L from 7.1 and 8.4 pH values, but remained below 20 ug/L at higher pH values. The particulate lead fraction generally exceeded 80% of total lead across pH values. c. None of the 6 homes where Pb > 10 ug/L. Following a CCT adoption, none of the homes consistently had Pb < 10 ug/L. Particulate lead accounted for > 70% of total lead in most samples. d. Hydrocerussite was synthesized from a supersaturated lead carbonate solution at a pH value of 9.0 +- 0.5 (NaOH addition).

In general, higher pH levels tend to be associated with reduced lead corrosion, in particular uniform corrosion. Possible causes of this reduction include lower scale dissolution rates at higher pH levels. Schock et al. (2005) found that adding caustic to raise the pH value from 6.3 to 7.5 led to a 97 percent reduction in lead, achieving a post-treatment lead concentration well below 10 ug/L. Kim et al. (2011) reported an approximate 50 percent lead concentration reduction in homes with LSLs after caustic addition raised the pH values from 7.1 to 7.6, although further increases to 8.1 had no incremental effect. Pipe loop studies reported in Kim et al. (2011) showed pH value increases to 9.6 resulted in 60 percent reductions in lead and concentrations below 10 ug/L in flow samples. At pH values greater than 9.0, low DIC levels may result in a low dissolution of hydrocerrusite (Xie and Giammer, 2011; Noel et al., 2014). Cross-sectional studies have also reported variations in lead concentrations across systems or treatment plants that have different pH and alkalinity levels (Exhibit 2-4). Although these studies do not demonstrate the effect of raising pH on lead concentrations, they show correlations between pH or alkalinity levels and lead monitoring results. Knox et al. (2005) did not find a significant relationship between pH or alkalinity levels and lead concentrations; all four service areas had low lead concentrations. For systems that did not add a corrosion inhibitor, Dodrill and Edwards (1995) found that the 90th percentile values among systems with low alkalinity (< 30 mg/L) and low pH levels (< 7.4) tended to exceed 10 ug/L.  Exhibit 2-4. Studies of Lead Concentration Variations across Systems or Treatment Plants Study Type and Source CCT or pH and Alkalinity Levels Lead Concentration System tap samples to compare different CCTs across four service areas  Knox et al. (2005) CCT descriptions:  Capilano: no CCT  -  pH 6.1, alkalinity 1.1 mg/L   Seymour: Na2CO3  -  pH 6.8, alkalinity 7.4 mg/L   Coquitlam: Na2CO3  -  pH 6.8, alkalinity 6.8 mg/L   Newton: Na2CO3  -  pH 8.1, alkalinity 14.3 mg/L  Mean Pb (first liter):  Capilano: 4 - 8 ug/L Pb  Seymour: 4 - 8 ug/L Pb  Coquitlam: 4 - 5 ug/L Pb  Newton: 5 - 6 ug/L Pb Multi-system study of tap sample results Dodrill and Edwards (1995)[a]  pH <= 7.8 and alkalinity > 74 mg/L   pH 7.4 - 7.8 and alkalinity >= 30 mg/L  pH > 8.4 and any alkalinity value  For pH values <= 8.4, systems in 30 - 74 mg/L alkalinity range  Mean Pb90 < 10 ug/L  Mean Pb90 < 10 ug/L  Mean Pb90 < 10 ug/L  Statistically significantly lower Pb90 values compared to systems in the < 30 mg/L alkalinity range a. System tap sample results were categorized into 16 strata based on 4 pH categories (< 7.4, 7.4 - 7.8, 7.81 - 8.4, and > 8.4) and 4 alkalinity categories (< 30 mg/L, 30 - 74 mg/L, 75 - 175 mg/L, and > 174 mg/L as CaCO3). The results reported here are for systems that did not report using corrosion inhibitors. Raw Water Quality Considerations The sodium hydroxide dose (in mg/L) depends on several raw water quality characteristics. The dose varies with the influent pH and target pH values. Other water parameters include alkalinity in mg/L as CaCO3, total dissolved solids (TDS) in mg/L, and temperature in degrees Celsius (°C). To estimate costs for the LCR revision, the EPA assumed the following scenarios: Raw water pH of 6.5 and 20 mg/L alkalinity (as CaCO3) and target pH of 7.5; Raw water pH of 6.5 and 50 mg/L alkalinity (as CaCO3) and target pH of 7.5; Raw water pH of 7 and 50 mg/L alkalinity (as CaCO3) and target pH of 7.5; and Raw water pH of 7 and 100 mg/L alkalinity (as CaCO3) and target pH of 7.5. For all four scenarios, the default TDS was 200 mg/L and the influent water temperature was 10°C. Section 5.2.1 provides the equations that the EPA used to derive sodium hydroxide demand given water quality inputs. These equations reflect carbonate chemistry only and do not account for other constituents that can affect the alkalinity of water (e.g., ammonia, chlorine, phosphate, silicates). In most drinking water treatment scenarios, the concentrations of these other constituents will be much lower than those of the carbonate species (Najm, 2001). Critical Design Parameters  The following critical design parameters are specific to sodium hydroxide addition and affect dosage as well as chemical storage and delivery equipment: Chemical type and strength Chemical storage Distance between chemical supply and water pipeline feed point. The EPA assumed that smaller systems [i.e., having design flows of less than 1 million gallons per day (MGD)] would use sodium hydroxide from 55-gallon drums that contain the chemical at 25 percent strength by weight. Larger systems (i.e., having design flows equal to or greater than 1 MGD) would store more concentrated sodium hydroxide  -  50 percent by weight  -  in a storage tank large enough to hold a 30-day supply, and dilute the chemical in a day tank before injecting it into the water pipeline. The higher-strength chemical may require heat tracing and insulation given a freeing point of about 14°C (58° Fahrenheit, F). In either case, the caustic nature of sodium hydroxide requires secondary containment in the form of concrete curbing and a chemical-resistant coating to contain the maximum volume of a spill. The distance between the chemical storage area and the metering pump and feed point for the water pipeline affects overall piping costs. The EPA assumed that smaller systems would have an average of 100 feet (ft) between the storage and the feed point, while larger systems would have an average of 200 ft between these two locations. Section 5.2 provides additional descriptions of these and other process design assumptions made by the EPA to develop cost estimates for the rule.  Corrosion Inhibitor Addition Operating Principle Drinking water systems commonly add phosphate, usually in the form of orthophosphate, to control corrosion in their distribution systems, including as part of their strategies for compliance with the federal LCR. This rule identifies the addition of phosphate-based corrosion inhibitors among the treatment options to be considered in optimizing corrosion control (40 CFR 141.82(c)(1)(iii)). As a corrosion control treatment chemical, orthophosphate is believed to combine with lead and copper in plumbing materials to form insoluble compounds, thereby reducing lead and copper levels at the tap. The effectiveness of this process depends on the orthophosphate dosage and water characteristics such as pH. For LCR revisions, the EPA is recommending that systems needing to add or modify their CCT follow an ALE dose orthophosphate at 1 mg/L phosphorus (P), at a pH value of 7.5. A variety of different chemical solutions are available to provide orthophosphate for corrosion control. These include zinc orthophosphate, sodium orthophosphate, potassium orthophosphate, phosphoric acid (H3PO4), and blended solutions of polyphosphate and orthophosphate. The specific solution chosen for corrosion control will depend on factors, including the characteristics of the water treated, treatment goals other than corrosion control, economics, and downstream impacts of the treatment chemical. Each chemical solution has advantages and disadvantages. For example, under certain conditions, zinc orthophosphate can have the secondary benefit of helping protect cement and cement mortar-lined pipes, but excessive levels of zinc can affect zinc levels in discharges from downstream wastewater treatment facilities. Blends with polyphosphates can aid in iron and manganese control, but excess polyphosphate can actually increase lead solubility. Polyphosphate can also hinder calcium carbonate precipitation, which otherwise helps to reduce metal releases. Phosphoric acid is potentially cheaper than zinc orthophosphate, but it is a strong acid that can require safety precautions. Use of high-concentration phosphoric acid (e.g., 75 percent) is, therefore, not recommended for small systems (USEPA, 2003, 2016; Schneider et al., 2007; Williams, 2010; Tramfloc, 2012). Of the various orthophosphate solutions, zinc orthophosphate is among the more commonly used. For example, one drinking water provider reports that, of its 78 facilities with phosphate-based corrosion control programs, 88 percent use zinc orthophosphate (Schneider et al., 2007). Zinc orthophosphate solutions themselves are available in a variety of blends and formulations, with ratios of phosphate to zinc ranging from 1:1 up to 10:1 or 15:1 (Schneider et al., 2007; Mid South Chemical, 2016; USEPA, 2016). The work breakdown structure (WBS) model for phosphate feed includes standard designs that use common formulations of either zinc orthophosphate or phosphoric acid (see Section 6.3). Blended polyphosphate  -  orthophosphate mixtures may not provide the same type of passivation protection as orthophosphate. These blends include proprietary mixtures of polyphosphate to sequester iron, manganese, and calcium in water to prevent scale formation and staining; and orthophosphate to passivate lead and/or copper plumbing materials. Blends, however, may not form scales containing crystalline lead - orthophosphate solids. Instead, they may form a porous layer comprising aluminum, calcium, phosphorus, and lead that may slough off if the water quality changes or if physical disturbances dislodge loosely adhered scale (Wasserstrom et al., 2017). Exhibit 3-1 provides a schematic drawing for phosphorus feed. The phosphate feed model includes components for chemical storage, pump transfer, mixers, feed pumps and piping, and process controls. The cost model provides cost estimates for a process that is an addition to an existing treatment plant. Exhibit 3-1. Typical Schematic Layout for Phosphate Feed

Source: USEPA (2020c). Effectiveness for Reducing Lead Concentrations Exhibit 3-2 summarizes the studies that demonstrate the effectiveness of corrosion inhibitors for passivating lead to reduce lead concentrations in distribution systems. The studies include a wide range of types such as pipe loop studies of multiple CCT strategies, and time-series studies of system monitoring during CCT changes and cross-sectional data reviews. The study results generally indicate that orthophosphate addition can reduce lead solubility for waters with pH values greater than 7.0. Exhibit 3-2. Corrosion Inhibitor Effectiveness Study Type and Source pH Alkalinity (CaCO3) Corrosion Inhibitor Treated Water Impact Theoretical solubility models (literature survey) McNeill and Edwards (2002) < 7.6

Orthophosphate addition Predicted reduction in Pb

8.0 40 milligram Ca/L 1 mg/L polyphosphate Predicted increase in Pb solubility Pipe rack (literature survey) McNeill and Edwards (2002) 6.0 7 2 mg/L polyphosphate Reduced Pb

7.5 Low 1 mg/L orthophosphate Reduced Pb

7 - 8 150 - 300 Polyphosphate Increased Pb

7.2 Various 1 mg/L ZO Reduced Pb

7.4 - 7.8 6 - 12 9.3 mg/L ZO (as zinc, Zn) Reduced Pb Tap water sampling (literature survey) McNeill and Edwards (2002) 6.7 8 - 12 3 - 5 mg/L ZO No reduction in Pb

8 - 9 Low 2 mg/L orthophosphate (pH adjusted from 6.3) Reduced Pb

7.2 Soft 2 mg/L polyphosphate Reduced Pb

Various

ZO addition Lower Pb compared to utilities with pH > 8.0

Various

ZO addition Generally lower Pb compared to utilities without ZO

Various

ZO addition Reduced Pb at 50% of utilities

< 7.5 Soft 3 - 5 mg/L orthophosphate Reduced Pb90 Surface water system Bradley and Horscroft. (2018) 1992: 8.0 - 8.2 7.0 - 7.1

no ZO (WTP 1) ZO dose 0.05 - 0.07 mg/L (as P) (WTP 2 and 3) 21.9 ug/L (Pb90, across all WTPs)

1997: 7.4

ZO dose 0.2 mg/L (as P) 1998: 10.2 ug/L Pb90 1999: 9.2 ug/L Pb90

2001: 7.2

ZO dose 0.4 mg/L (as P) 2002: 13.4 ug/L Pb90

2005: 7.2

ZO dose 0.5 mg/L (as P) 2005: 9.4 ug/L Pb90 2008: 6.0 ug/L Pb90 2011: 5.9 ug/L Pb90 2014 : <= 5.0 ug/L Pb90 Surface water treatment plant[a] (mixed system) Docherty and Kariuki (2019) 7.89 - 7.96

No inhibitor 2008 - 2009: 10 - 35% exceeded 10 ug/L Pb

7.83 - 7.86

PA dose 2 mg/L (PO4) 2018 - 2019: 10% exceeded 10 ug/L Pb Pipe loop study (within surface water distribution system) Docherty and Kariuki (2019) 7.89 - 7.96

No inhibitor  Loop 1: 9.5 - 105 ug/L Pb  Loop 2: 11.6 - 208 ug/L Pb  Loop 3: 6.9 - 84.8 ug/L Pb

7.83 - 7.86

PA dose 2 mg/L (PO4)  Loop 1: 3.0 - 7.1 ug/L Pb  Loop 2: 2.8 - 9.8 ug/L Pb  Loop 3: 2.6 - 8.8 ug/L Pb Bench-scale study of orthophosphate Tam and Elefsiniotis (2009) >= 7.5 Soft Orthophosphate addition ~ 70% reduction in Pb concentrations Pipe loop study Churchill et al. (2000) 6.0 - 6.3 1.5 - 3.7 No inhibitor (control loop) 0.5 to 2.0 mg/L Pb (8- and 16-hour stagnation samples)

7 20 ZO dose of 0.37 mg/L as Zn[b] Pb lower than control loop levels after 210 days, except for 1 spike of ~ 2.0 mg/L

7.5 20 ZO dose of 1.0 mg/L as Zn[b] < 0.05 to 0.5 mg/L Pb after 68 days

8 - 9 20 - 30 No inhibitor Pb levels exceeded control loop Pipe loop study Doré et al. (2019) 7.9 90 No inhibitor Pb, 16-hour stagnation: 79.5 ug/L median; 180 ug/L Pb90 Pb, flowing:  1.7 ug/L median; 7.8 ug/L Pb90

7.9 90 Orthophosphate 1 mg/L (P) Pb, 16-hour stagnation: 20.8 ug/L median; 62.8 ug/L Pb90 Pb flowing: 0.43 ug/L median; 1.0 ug/L Pb90 Pipe loop study Gagnon and Doubrough (2011) 7.5 7.0 4.6 +-3.4 Orthophosphate and polyphosphate blend added 1 mg/L product dose Pb at 7.5 pH: 7.4 ug/L mean (0.2 ug/L standard deviation) Pb at 7.0 pH: 23 ug/L mean (14.5 ug/L standard deviation) Pipe loop study Woszczynski et al. (2015) 6.7 - 7.4

Orthophosphate addition (0.8 mg/L) Total Pb median less than 15 ug/L Median dissolved Pb less than 10 ug/L Tap water sampling (1992 American Water Works Association survey) Dodrill and Edwards (1995) < 7.4 7.4 - 7.8 7.81 - 8.4 > 8.4 > 74 > 74 >= 30 Any level No inhibitor  -  261 utilities Average Pb90 across systems is < 10 ug/L for these pH-alkalinity combinations

< 7.4 Any level > 8.4 < 30 > 74 Any level Phosphate inhibitor added[c] Average Pb > 15 ug/L[d] Average Pb < 10 ug/L Average Pb < 10 ug/L[e] Continuously stirred reactors Noel et al. (2014) 7.5

No inhibitor: DIC 0 mg/L DIC 10 mg/L DIC 50 mg/L Dissolution rate: > 19 mol/m[2]/min 1.4 - 1.8 mol/m[2]/min 1.4 - 1.7 mol/m[2]/min

7.5

Orthophosphate 4 mg/L (P) DIC = 0 mg/L 0.04 mol/m[2]/min Pipe Loop Study Xie and Giammer (2011) 7.5

Orthophosphate 1 mg/L (P) DIC = 10 mg/L Pb < 15 ug/L Ca/L = calcium per liter, mol/m[2]/min = mole per square meter per minute, PA = phosphoric acid, ZO = zinc orthophosphate Alkalinity reported mg/L as CaCO3 unless noted otherwise; left blank if value not reported. Notes: a. Docherty and Kariuki (2019) also reported that the addition of PA did not have an impact on downstream wastewater treatment plant influent or effluent; values for pH, total phosphorus, and soluble phosphorus were consistent before and after the treatment change. b. Zinc content was 8.3% with a zinc-to-phosphate ratio of 1:3. c. Aggregate results reported for all systems adding a phosphate inhibitor included 51 using orthophosphate, 53 using polyphosphate, 5 using an ortho-poly blend, and 7 using an unknown type. Thus, the results do not clearly distinguish the effects of orthophosphate use versus polyphosphate use to sequester iron. d. The average 90th percentile Pb level for the subset of systems adding orthophosphate was half of the average 90th percentile for the subset adding polyphosphate, which exceeded the average for systems not adding inhibitors. e. Polyphosphate inhibitors raised the average Pb release for systems in the pH > 8.4 and alkalinity in the 30 - 74 mg/L range categories by 91% compared to systems without inhibitor addition.

McNeill and Edwards (2002) showed through various study types that orthophosphate addition tends to reduce lead corrosion in pH ranges from 7 to 8, even in "soft" water with low-alkalinity levels. Their cross-sectional research also generally illustrates that polyphosphate addition can exacerbate lead corrosion unless pH and alkalinity values are both low.  Bradley and Horscroft (2018) provided time-series data that show lead concentrations declining from a 90th percentile value of 21.9 ug/L in 1992 when zinc orthophosphate was not used at one water treatment plant (WTP) or added in small doses of less than 0.1 mg/L (as P) to 90th percentile values below 5.0 ug/L in 2014 at a dose of 0.5 mg/L (as P).  Docherty and Kariuki (2019) reported that a phosphoric acid dose of 2 mg/L (as PO4) reduced lead monitoring concentrations from as many as 35 percent samples exceeding 10 ug/L to only 10 percent exceeding 10 ug/L. Their concurrent pipe loop study results similarly showed substantial reductions in lead concentrations, especially in the upper-bound estimates, which declined from values greater than 80 ug/L to values less than 10 ug/L.  Churchill et al. (2000), Gagnon and Doubrough (2011), Woszczynski et al. (2015), and Doré et al. (2019) used pipe loops to evaluate the effects of orthophosphate addition on lead while also varying water parameters such as pH, alkalinity, or stagnation times. Churchill et al. (2000) reported that only the pipe loops with inhibitor addition had lower lead concentrations than the control loop. Doré et al. (2019) reported that orthophosphate addition reduced lead levels by about 60 percent for stagnation samples and by 80 percent or more in non-stagnation samples. Gagnon and Doubrough (2011) reported that adjusting pH to 7.5 while adding an orthophosphate-polyphosphate blend resulted in a mean lead concentration of 7.4 ug/L compared to a mean lead concentration of 23.4 ug/L at a pH of 7.0. Woszczynski et al. (2015) reported median total lead concentrations below 15 ug/L and dissolved lead less than 10 ug/L following orthophosphate addition. All four studies demonstrate the effectiveness of orthophosphate for lead reduction.  Noel et al. (2014) conducted a study of lead scale formation and dissolution as a function of pH, DIC, and orthophosphate. They found that the hydrocerussite dissolution rate decreased as pH increased in a solution without DIC or orthophosphate, and adding DIC reduced the dissolution rate. Adding orthophosphate (without DIC) also decreased the dissolution rate and led to scale containing a lead(II) phosphate solid hydroxylpyromorphite. The addition of DIC as well as orthophosphate resulted in no formation of lead(II) phosphate. The authors ascribe the low dissolution rate to orthophosphate blocking reactive sites on the hydrocerussite surface.  Raw Water Quality Considerations The treatability literature indicates that three raw water quality factors affect the effectiveness of corrosion inhibitors that contain orthophosphate. First, pH levels for many of the studies for which orthophosphate reduced lead concentrations tended to be between 7.0 and 8.0; 7.5 was a common target pH value. The studies summarized in Exhibit 3-2 report alkalinity, which includes a component of DIC (i.e., the sum of carbon in carbon dioxide, carbonic acid, carbonate, and bicarbonate). Low levels of alkalinity in neutral to basic waters suggest low DIC concentrations; high DIC concentrations can enhance scale dissolution. Pre- and Post-Treatment Needs  As noted above, orthophosphate corrosion inhibitors are more effective when feed water pH is in the 7.0 to 8.0 range. Therefore, feed waters with lower pH values will require caustic addition or another type of adjustment (e.g., aeration to remove carbon dioxide or lime addition) to raise pH values.  Because orthophosphate inhibitors are acidic, if their addition reduces treated water pH, then post-treatment pH adjustment may be needed. For example, Dodrill and Edwards (1995) report that zinc orthophosphate liquids have pH values of 1 - 2. Chemical manufacturers report that phosphoric acid (sold as 36 or 75 percent phosphoric acid) has pH values of 1.0 - 2.5. The ability of feed water to buffer the addition of these acidic chemicals will depend on the dose and feed water alkalinity. Bench or pilot tests such as pipe loop tests will indicate whether pH adjustment is necessary. Residuals Management Needs  Adding orthophosphate to drinking water does not generate residuals for the drinking water system, but will increase the phosphorus load for downstream wastewater treatment plants (WWTPs). These WWTPs may have narrative or numerical phosphorus discharge limits in their National Pollution Discharge Elimination System (NPDES) permits. The effect on WWTPs with narrative NPDES permit limits is difficult to assess because changes in receiving water quality is uncertain. The WWTPs that are operating just within their numeric limits may have to adopt or modify treatment to remove the additional phosphorus loadings. Critical Design Parameters  Key design parameters for orthophosphate corrosion inhibitors are: Chemical type and dose Post-treatment pH adjustment. The sections below discuss each of these parameters in more detail. As noted in Section 3.1, Chapter 5 identifies the specific values for each parameter used in the EPA's cost estimates. Chemical Type and Dose Although there are different orthophosphate-based inhibitors available, the two options included in the EPA's cost analysis reflect common corrosion control chemical formulations used for CCTs: Zinc orthophosphate with a 3:1 phosphate-to-zinc ratio and a solution strength of 36 percent as PO4 Phosphoric acid (36 or 75 percent as H3PO4). The dose can be specified either in mg/L as phosphorus or as orthophosphate. For the purpose of cost analysis, the EPA assumed that systems needing to add or modify an orthophosphate feed process would need a dose of 3.2 mg/L (orthophosphate). As shown in Exhibit 3-2, lower doses effectively achieved lead concentrations below either the AL of 15 ug/L or the TL of 10 ug/L. Therefore, the assumed target dose of 3.2 mg/L (orthophosphate) may exceed the dose necessary for some systems to lower 90th percentile lead concentrations. Post-Treatment pH Requirements If corrosion inhibitor addition results in a pH reduction in poorly buffered waters, post-treatment pH adjustment may be needed to maintain corrosion control efficacy. Caustic addition can increase pH without affecting alkalinity and/or DIC.  Pilot Testing The EPA also estimated costs for pilot testing CCT technologies. Pilot tests enable systems to test the effectiveness of their CCT before installing a new process or modifying an existing CCT process. There are two types of pilot tests for CCTs. Many of the effectiveness studies in Chapters 2 and 3 were pipe loop studies, which use conditioned pipes to test the effects of CCT alternatives on lead release. A less resource-intensive pilot study option is a coupon test, which uses small pieces or "coupons" of metal to test dissolution in different water qualities. The EPA developed two tools to estimate LCR pilot testing. The first tool estimates the cost of constructing and installing a pipe rack pilot test apparatus, operating the pilot unit, and performing a laboratory analysis of samples. The pipe rack cost tool uses design and operating assumptions that are based on the protocol described in AWWARF (1994), along with information provided by the EPA's Office of Research and Development on pipe rack testing in Flint, Michigan. Specifically, it assumes the use of one or more pipe racks. As shown in Exhibit 4-1, each rack segment has the requisite chemical feed equipment, mixers, and water flow control valves; as well as meters and sampling ports before and after the harvested pipe segment. The tool assumes the test pipe segments are service line laterals removed from the distribution system and that the focus of the pilot test is on controlling lead releases from these laterals. The apparatus for coupon tests is less complex. Instead of a rig with a water feed system, instrumentation, and harvested lead pipes, a coupon test uses bottles or jars and lead coupon strips and instruments needed for water quality measurements. The following sections provide descriptions of the more complex pipe rack pilot testing and notes indicate which components also apply to coupon tests.  Exhibit 4-1. General Schematic Layout for Pipe Rack Pilot Testing Apparatus

Design Inputs and Assumptions  Key design inputs and assumptions for the pilot tests are: Number of pipe segments or jars Study duration and operation Labor assumptions Sampling frequency and location. The following sections provide descriptions of each input and parameter. Number of Pipe Segments or Jars Pilot testing conditions will vary because feed water and CCT objectives vary across systems. These variations affect the number of CCT options a system may want to evaluate. The number of pipe segments needed includes a control pipe segment and an additional one for each CCT option being tested. To provide for replicate tests, the cost tool includes an identical pipe rack for each replicate with the same set of test conditions. For measuring lead levels, AWWARF (1994) recommends three replicates for each test condition. Exhibit 4-1 shows three pipe racks, corresponding to a test with three replicates.  The number of pipe racks affects most of the costs estimated in the tool. The number of racks affects equipment requirements, chemical demand, electricity demand, and monitoring costs. For coupon tests, the number of bottles or jars with lids depends on the number of conditions to test, the number of replicates, and the interval between jar swaps. The three factors in conjunction with study duration (addressed below) determine the number of jars or bottles. For each jar swap, Cornwell and Wagner (2019) recommended preparing the replacement jar for water changes and moving the coupon from the old water to the new water. Tight lid seals mitigate pH changes (Cornwell and Wagner, 2019). Study Duration and Operation The length of a pipe rack study depends on the lengths of three study phases: The startup period, during which the pilot process operates without chemicals to verify consistent results for metal releases The stabilization period, which is the time required for metal levels to stabilize under ongoing CCT conditions The operating period, which is the period of stable operation under ongoing treatment conditions during which data collection occurs for treatment comparisons. For pipe segments that are harvested from a distribution system, AWWARF (1994) provided information for typical durations such as a one-month startup period, a six-month stabilization period, and a four-month operating period. Non-harvested pipes may require longer startup or conditioning periods.  The study duration affects pilot test operating and monitoring costs. One factor to consider is whether the operating period is long enough to achieve a recommended number of measurements for data analysis. Peer reviewers of the tool recommended at least 30 measurements.  Coupon tests last long enough to reach a steady state in the concentration of lead in the water. Four to six weeks is a sufficient study length to achieve this steady state (Cornwell and Wagner, 2019). During earlier water changes, measured lead concentrations in the old jars will be higher as the coupon is conditioned. Lead concentrations will decline, reaching a steady state that indicates the effectiveness of the CCT in reducing lead releases. Rack operation includes the amount of time per day the pilot rack operates and the water flow rate. The daily operating time is the total time in hours per day during which water flows through the test pipe segments. During the remaining hours, water is standing in the pipe segments. AWWARF (1994) recommends the on-off schedule shown in Exhibit 4-2. This schedule results in water flow for a total of 3.5 hours per day.  Exhibit 4-2. On-Off Schedule Recommended in AWWARF (1994) Time of Day Cycle 7:30 a.m. On 8:30 a.m. Off 4:30 p.m. On 5:00 p.m. Off 7:30 p.m. On 8:00 p.m. Off 10:30 p.m. On 11:00 p.m. Off 1:30 a.m. On 2:00 a.m. Off 4:30 a.m. On 5:00 a.m. Off

Operating flow per segment is the water flow rate in gallons per minute (gpm) through each test pipe segment during the daily operating time. AWWARF (1994) recommends an operating flow per segment of 1 gpm. Combined with the recommended daily operating time discussed above, this flow results in total throughput of 180 to 210 gallons per day per segment, similar to a typical household (AWWARF, 1994).  These rack operation inputs affect the total quantity of chemicals used during the pilot test. They also affect the ability to test the effects of stagnation time on lead release. For coupon tests, labor requirements primarily include preparing the water and treatment conditions in new jars and measuring lead concentrations in old jars (Cornwell and Wagner, 2019). Water must be adjusted to replicate finished water to distribution system conditions, including disinfectant residual before modifying for CCT conditions. Labor requirements also include switching coupons to fresh jars, recording pH values in old jars, and preparing old jars for analysis.  Labor Assumptions The tool requires multiple assumptions to quantify the operator hours required for installation and operation of the pipe racks. Installation labor covers building and installing the pipe racks. The value used for this assumption is the average of installation labor estimates for Flint, Michigan, and for example designs in AWWARF (1994), measured in hours of labor per pipe segment. Operating labor includes separate assumptions covering labor during the startup, stabilization, and operating periods. The values used for these assumptions, measured in hours per week, are based on estimates presented in AWWARF (1994). As noted above, the labor demand for coupon tests primarily depends on the number of jars needed for the study.  Sampling Location and Frequency Sampling location and frequency affects the monitoring instrument costs as well as laboratory analysis costs for constituents that cannot be quantitated immediately using benchtop analysis such as pH and temperature. For each parameter of interest, the assumptions include the number of samples per month during each of the study periods (i.e., startup, stabilization, and operation). Specific samples include: Running influent samples, which are taken during periods of flow to measure water quality of the initial influent to the whole apparatus (at sample tap S1 in Exhibit 4-1) Running treated water samples, which are taken during periods of flow to measure operational consistency following chemical addition and before each test pipe segment (at sample taps S2 in Exhibit 4-1) Standing water samples, which are taken after periods of stagnation to measure corrosion-related parameters following each pipe segment (at sample taps S3 in Exhibit 4-1). Coupon tests require laboratory analysis of lead concentrations in each jar. Cornwell and Wagner (2019) recommended checking the pH in the jars. In the coupon tool, a benchtop instrument accomplishes this analysis.  POU Treatment Operating Principle A POU device uses a miniaturized version of a centralized treatment process to meet water quality standards for consumption at individual taps (e.g., a kitchen sink). When a system installs, controls (i.e., owns), and maintains POU devices at all customer locations where water is consumed (e.g., residences), it can forego centralized treatment (USEPA, 2006). Because POU devices treat a small fraction of the water delivered by a system, a compliance program that relies on POU devices may be more cost-effective for smaller systems that tend to incur higher average costs than larger systems because investments in centralized treatment equipment tend to have high fixed costs and, therefore, exhibit returns to scale. POU devices use different operating principles to remove lead  -  primarily adsorption and steric exclusion. Because lead can occur in dissolved and particulate forms, devices capable of removing either form provide better protection. POU filters that contain dense blocks of activated carbon can remove lead through adsorption. Carbon filters have very high surface areas [e.g., a gram of carbon can have a surface area of 1,000 square meters (WQA, 2016)], providing substantial contact area. The carbon surface area also has pores ranging in size from less than 100 to more than 1,000 angstroms (WQA, 2016) or 0.01 to 0.001 micrometers (or microns), providing adsorption sites for lead compounds of varying sizes. Adsorption occurs when a solid substance such as activated carbon attracts and removes molecules from a bulk solution; for lead compounds, the attraction occurs via various physical and/or chemical interactions that vary with water and carbon surface chemistry and contact time (Salih et al., 2014). As adsorption sites become filled with lead and competing compounds (e.g., organics or chlorine), the filter becomes less effective and must be removed and replaced with a new carbon filter. When POU devices are in residences, exhausted filters can be disposed of with household solid waste.  The POU devices, themselves, come in a variety of types: Pour-through pitcher: gravity-fed water drips through a filter in a water pitcher; the filter removes the target contaminant through adsorption and/or entrainment. Faucet mount filter: a diverter mounted on the outlet of a faucet that can divert water through a filter that removes the target contaminant, often through adsorption and/or entrainment. Counter-top filter: a diverter attached to a faucet routes water through a nearby filter that removes the target contaminant, often through adsorption or entrainment. Plumbed-in filter: a device that attaches to the cold-water service line under a sink and delivers filtered water to the faucet or separate tap. Water that flows through the device passes through one or more filters  -  typically sand, carbon, and/or reverse osmosis (RO) filters  -  to remove one or more target contaminants through multiple methods including adsorption, entrainment, and steric exclusion. Refrigerator filter: a filter similar to a faucet-mount filter that treats water delivered to refrigerator ice makers and/or water dispensers. POU devices may be used as long- or short-term options to reduce lead exposure. For long-term use, one of the attached filters may be more convenient because they provide treatment at the water tap. For short-term use such as temporary treatment following LSL removal, a pour-through pitcher may suffice, although it is slower because the pressure forcing water through the filter is substantially reduced (i.e., gravity-based instead of water-line pressure). For long-term POU treatment, a water system would need to purchase, install, and maintain POU devices for all customers potentially exposed to lead. Usually, a system would install a single POU device at the kitchen tap for each residential customer. Nonresidential customers might require multiple devices (e.g., for drinking fountains). Installation requires retrofitting the device into existing plumbing fixtures. Maintenance primarily consists of filter replacement, often on a fixed schedule that varies by filter type. Monitoring water quality at individual treated water taps may also be necessary. For short-term POU treatment, a system would need to deliver the pour-through pitcher and enough filters to last throughout the period when elevated lead levels may persist.  Effectiveness for Lead Removal For POU programs to comply with the proposed LCR revisions, POU devices must be certified for lead removal. POU devices can be certified for lead removal under two standards: NSF International (NSF)/American National Standards Institute (ANSI) Standard 53 for Drinking Water Treatment Units, which is the nationally recognized standard for evaluating and certifying drinking water treatment systems for the reduction of contaminants from drinking water. NSF/ANSI Standard 58 for RO Drinking Water Treatment Systems, which is the corresponding standard specific for RO devices that treat potable water.  Both standards require that POU devices effectively remove lead from an initial concentration of 150 ug/L to less than 15 ug/L (NSF, 2020). Several organizations such as NSF, Underwriters Laboratories, and the Water Quality Association provide third-party testing and certification to ensure that POU devices meet drinking water treatment standards. Raw Water Quality Considerations Because POU devices will be installed at service taps that are downstream of a system's entry point to the distribution system, the EPA assumed that the raw water entering a POU device will be water that is suitable for consumption except for a potential exceedance of the lead AL. Waste Generation and Residuals Management Needs  The POU treatment process waste comprises used filter cartridges. As waste disposal methods must comply with state and local regulations, the used cartridge filters may be included in household solid waste (USEPA, 2006). Critical Design Parameters  In addition to the POU devices themselves, several components of the design of a POU program are primary cost drivers, which include: POU device installation  POU device maintenance. Chapter 6 discusses each of these parameters in more detail and identifies the specific values for each used in the EPA's cost estimates.

Costs for Treatment Technologies and Pilot Testing  Introduction Overview and Cost Modeling Approach This chapter presents estimated costs for installing and operating the technologies discussed in Chapters 2 through 5. Based on the information in those chapters, particularly the data on engineering design specifications, the EPA developed WBS cost estimating models for each corrosion control or lead removal technology. The WBS models are spreadsheet-based engineering models for individual treatment technologies, linked to a central database of component unit costs. The EPA developed the WBS model approach as part of an effort to address recommendations made by the Technology Design Panel (TDP), which convened in 1997 to review the Agency's methods for estimating drinking water compliance costs (USEPA, 1997).  In general, the WBS approach involves breaking a process down into discrete components for the purpose of estimating unit costs. The WBS models represent improvements over past EPA cost estimating methods by increasing comprehensiveness, flexibility, and transparency. By adopting a WBS-based approach to identify the components that should be included in a cost analysis, the models produce a more comprehensive assessment of the capital and operating requirements for a treatment system. Documentation for individual WBS models (USEPA, 2020b, 2020c) provides complete details on the structure, content, and use of the models. The EPA used the WBS models to develop the costs presented in this chapter. The models and their documentation can be accessed via the LCR docket. The remainder of this section provides a brief overview of the common elements of all WBS models and information on the anticipated accuracy of the resulting cost estimates. Subsequent sections describe how the EPA used each individual technology-specific WBS model to estimate costs for perchlorate treatment and present the resulting cost estimates. WBS Models Each WBS model contains the work breakdown for a particular treatment process, and preprogrammed engineering criteria and equations that estimate equipment requirements for user-specified design requirements (e.g., system size, influent water quality). Each model also provides unit and total cost information by component (e.g., individual items of capital equipment) and sums the individual component costs to obtain a direct capital cost. Additionally, the models estimate add-on costs (e.g., permits, pilot study, and land acquisition costs for each technology), indirect capital costs, and annual operation and maintenance (O&M) costs, thereby producing a complete compliance cost estimate. Primary inputs common to all WBS models include design flow and average flow in MGD. Each WBS model has default designs (i.e., input sets) that correspond to the eight standard flow sizes in the EPA's flow characterization paradigm for public water systems (see Exhibit 6-1), but the models can also generate designs for many other combinations of flows. To estimate costs for perchlorate compliance, the EPA fit cost curves to the WBS estimates for up to 49 different flow rates. Thus, the cost estimates in Sections 6.2 and 6.3, and Appendix A are in the form of equations. Exhibit 6-1. Model Size Categories Based on the EPA's Flow Characterization Paradigm Size Category Population Served Design Flow (MGD) Average Flow (MGD) 1 25 - 100 0.030 0.007 2 101 - 500 0.124 0.035 3 501 - 1,000 0.305 0.094 4 1,001 - 3,300 0.740 0.251 5 3,301 - 10,000 2.152 0.819 6 10,001 - 50,000 7.365 3.200 7 50,001 - 100,000 22.614 11.087 8 Greater than 100,000 75.072 37.536

Another input common to all of the WBS models is "component level" or "cost level." This input drives the selection of materials for equipment items that can be constructed with different materials. For example, a low-cost system might include fiberglass pressure vessels and polyvinyl chloride piping. A high-cost system might include stainless steel pressure vessels and stainless steel piping. The component-level input also drives other model assumptions that can affect the total cost of the system, such as building quality and heating and cooling. The component-level input has three possible values: low, mid, and high cost. To estimate costs for perchlorate compliance, the EPA generated separate cost curves for each of the three component levels, thus creating a range of cost estimates for use in national compliance cost estimates. The third input common to all WBS models is system automation, which allows the design of treatment systems that are operated manually or with varying degrees of automation (i.e., with control systems that reduce the need for operator intervention). The cost estimates in the technology-specific sections below are for systems that are fully automated, minimizing the need for operator intervention and reducing operator labor costs. WBS models generate cost estimates that include a consistent set of capital, add-on, indirect, and O&M costs. Exhibit 6-2 identifies these cost elements, which are common to all WBS models and included in the cost estimates below. This exhibit also provides references for further information on the methods and assumptions used in the WBS models to estimate the costs for each of these cost elements. Exhibit 6-2. Cost Elements Included in All WBS Models Cost Category and Components Included For Further Information Direct Capital Costs Technology-specific equipment (e.g., vessels, basins, pumps, blowers, treatment media, piping, valves) Technology-specific sections below Instrumentation and system controls USEPA (2020b, 2020c), Appendix A Buildings USEPA (2020b, 2020c), Appendix B Residuals management equipment USEPA (2020b, 2020c), Appendix C Add-On Costs Land Permits Pilot testing USEPA (2020b, 2020c), Chapter 2 Indirect Capital Costs Mobilization and demobilization Architectural fees for treatment building Equipment delivery, equipment installation, and contractor's overhead and profit Sitework  Yard piping Geotechnical Standby power Electrical infrastructure Process engineering Contingency Miscellaneous allowance Legal, fiscal, and administrative  Sales tax Financing during construction Construction management USEPA (2020b, 2020c) Appendix D O&M Costs Operator labor for technology-specific tasks (e.g., managing regeneration, backwash, media replacement) Materials for maintenance and operation of technology-specific equipment Replacement of technology-specific equipment that occurs annually (e.g., treatment media) Energy for operation of technology-specific items of equipment (e.g., blowers, mixers) Technology-specific sections below Operator labor for O&M of process equipment Operator labor for building maintenance Managerial and clerical labor Materials for maintenance of booster or influent pumps Materials for building maintenance Energy for operation of booster or influent pumps Energy for lighting, ventilation, cooling, and heating USEPA (2020b, 2020c), Appendix E Residuals management operator labor, materials, and energy Residuals disposal and discharge costs USEPA (2020b, 2020c), Appendix C

WBS Model Accuracy Costs for a given system can vary depending on site-specific conditions (e.g., raw water quality, climate, local labor rates, and location relative to equipment suppliers). The costs presented in this section are based on national average assumptions and include a range (represented by low-, mid-, and high-cost curves), which is intended to encompass the variation in costs that systems would incur to implement CCTs. To validate the engineering design methods used by WBS models and increase the accuracy of the resulting cost estimates, the EPA has subjected the individual models to a process of external peer review by nationally recognized technology experts.  The EPA received peer-review comments on the caustic feed model in April 2018. One reviewer who evaluated the model responded that the resulting estimates would be in the range of budget estimates (+30 to -15 percent). A second reviewer agreed that the estimates would be in the same range of budget estimates and be conservative (i.e., high) for larger systems. A third reviewer responded that the estimates would be between the order of magnitude (+50 to -30 percent) and the budget estimates (+30 to -15 percent), but closer to the budget estimates if a specific revision were made. The EPA made the specific revision suggested, along with many others, in response to these peer-review comments. The EPA received peer-review comments on the phosphate feed model in April 2018. One reviewer who evaluated the model responded that the resulting estimates would be in the range of budget estimates (+30 to -15 percent). A second reviewer agreed that the estimates would be in the same range of budget estimates, but overall would be low for larger systems. A third reviewer responded that the estimates would be between the order of magnitude (+50 to -30 percent) and the budget estimates (+30 to -15 percent), but closer to the budget estimates if a specific revision were made. The EPA made the specific revision suggested, along with many others, in response to these peer-review comments.  The WBS version of the POU model underwent peer review in 2006. Reviewers felt that the default assumptions may tend to overstate "out-of-pocket" costs to systems because very small systems could use volunteers to perform some tasks. While this may be true, the EPA's model is designed to estimate opportunity costs for a successful POU program that is consistent with the EPA's POU Guidance, which does not include volunteers. Because several POU model line items such as tap sampling and public education costs would double-count other LCR costs, the EPA only used the portion of the WBS version that estimates device installation and filter replacement costs. Unlike the base POU model, the version used for the LCR included an option to use a mixture of POU devices. Costs for Chemical Addition for pH Adjustment Model Components and Assumptions USEPA (2020b) provides a description of the engineering design process used by the WBS model for caustic feed to estimate costs for pH adjustment using sodium hydroxide. In addition to the common WBS direct capital cost items listed in Exhibit 6-2, the caustic feed model includes the following components: Storage for sodium hydroxide (tanks for larger design flows and 55-gallon drums for smaller design flows) and secondary containment Transfer/recirculation pumps to move sodium hydroxide from bulk storage to the day tanks Metering pumps to add sodium hydroxide to the existing water pipeline Static mixers to mix sodium hydroxide into the existing water flow Associated piping, valves, and instrumentation Incremental system control components that are required to integrate with the existing treatment process' control system. Because the model estimates costs for a process that is an addition to an existing treatment plant, it excludes certain costs that would be required in constructing a full new treatment plant. Specifically, the caustic feed model does not include: Pilot study costs (see Section 6.5 for a description of coupon and pipe loop study costs, which the EPA estimates independently) Yard piping, because installing the add-on process should not require additional exterior water pipelines  Geotechnical costs, because the pre-existing geotechnical survey for the treatment plant should be sufficient to cover the construction associated with the add-on process Standby power costs, because the additional electrical demand from the add-on process should not require significant additional standby capacity Financing during construction based on the assumption that construction of the add-on process will take less than one year. The cost estimates include incremental costs for building space and land to reflect the opportunity cost of the space occupied for chemical storage, piping, and the chemical feed system. The costs do not include incremental space conditioning costs, however, based on the assumption that an existing treatment facility will be sufficiently heated or cooled, as needed. The O&M calculations include annual labor, maintenance materials, and energy usage based on the engineering design, O&M critical design assumptions, and input values. The caustic addition model includes technology-specific O&M elements for chemical usage.  The input sheet accepts the design parameters that determine fundamental process requirements. In addition to system size (i.e., design and average flows), parameter values establish key water quality characteristics, identify treatment requirements, and affect basic equipment requirements. Key design inputs include the following, which are described below: Scenario  Solution strength  Chemical storage configuration Include heat tracing and insulation Include inline static mixer. Scenario The WBS model for caustic feed includes several scenarios for pH adjustment for the LCR cost analysis. Daily hydroxide demand is based on average flow, temperature, TDS, initial alkalinity, and initial and target pH values. The following scenarios identify raw water quality characteristics that affect the sodium hydroxide dose, which the model uses to calculate the dose required using equations from Najm (2001) and Trussell (1998): 11.7 mg/L for raw water pH of 6.5 and 20 mg/L alkalinity (as calcium carbonate) and target pH of 7.5 29.2 mg/L for raw water pH of 6.5 and 50 mg/L alkalinity (as calcium carbonate) and target pH of 7.5 7.0 mg/L for raw water pH of 7 and 50 mg/L alkalinity (as calcium carbonate) and target pH of 7.5 14.1 mg/L for raw water pH of 7 and 100 mg/L alkalinity (as calcium carbonate) and target pH of 7.5. For all four scenarios, the EPA assumed the following default values: a temperature of 10°C and TDS of 200 mg/L. Based on these assumptions, the hydroxide demand is as follows. In addition to these adjustment scenarios, the EPA estimated costs for pH adjustment for medium and large systems that add phosphoric acid as a corrosion inhibitor. As noted in Section 3.4, phosphoric acid addition may reduce treated water pH, thereby requiring post-treatment adjustment to return pH to its initial level. The effect varies by initial pH and phosphoric acid dose (see Exhibit 6-3). The EPA estimated incremental caustic addition costs for all pH changes greater than 0.1 (standard units). Exhibit 6-3. Estimates of Post-Treatment pH Values by Starting pH and Phosphoric Acid Dose Initial pH 0.525 mg/L (PO4) 1.5 mg/L (PO4) 2.65 mg/L (PO4) 3.2 mg/L (PO4) 7.7 7.6 7.4 7.2 7.2 7.8 7.6 7.4 7.2 7.2 7.9 7.7 7.4 7.3 7.2 8 7.7 7.5 7.3 7.2 8.3 7.9 7.6 7.3 7.3 8.4 8 7.6 7.4 7.3 8.6 8.1 7.6 7.4 7.3

All estimates assume alkalinity is 20 mg/L (as calcium carbonate), water temperature is 10°C, and TDS are 200 mg/L. Post-treatment pH values become raw water pH values for the caustic addition model. The WBS model for caustic addition provides documentation for the calculations that translate water quality conditions and pH targets into caustic dose. Solution Strength  Solution strength affects chemical storage requirements, chemical demand computations, and chemical costs. For systems with smaller design flows (less than 1 MGD), chemical costs are for 55-gallon drums that contain 25 percent solution by weight. For systems with larger design flows (1 MGD or higher), chemical costs are for deliveries of 50 percent solution to storage tanks with 30-day capacities.  Chemical Storage Configuration Most jurisdictions require secondary containment for sodium hydroxide. Therefore, the model includes the cost of secondary containment in the form of concrete curbing around the storage area, and chemical-resistant coating for the curbing and the underlying concrete pad. The secondary containment design assumes sufficient capacity to contain 110 percent of the volume of the largest container (i.e., a 55-gallon drum or storage tank) or 10 percent of the total volume in all containers, whichever is larger. It also provides six inches of additional freeboard above this capacity despite the indoor storage assumption to ensure a minimum reasonable curb height. The estimate of total storage required is based on the standard 30 days of chemical storage.  To estimate process piping costs, the EPA assumed that the chemical supply is located 100 ft from the feed point for small systems (less than 1 MGD design flow) and 200 ft from the feed point for large systems (greater than or equal to 1 MGD design flow). The model includes chemical feed piping to cover these lengths. The model standard designs use direct feed from 55-gallon drums for small systems (less than 1 MGD design flow) and storage tanks with separate day tanks for larger systems (greater than or equal to 1 MGD design flow). Include Heat Tracing and Insulation For larger systems (greater than or equal to 1 MGD design flow) that store sodium hydroxide in storage tanks and use day tanks  -  both suitable for caustic materials  -  the EPA assumed the use of heat trace and insulation for the chemical storage tanks to prevent freezing. The freezing point for a sodium hydroxide 50 percent solution is 58 degrees Fahrenheit (Chempace, no date). Therefore, tank designs include costs for heat trace and insulation. Include Inline Static Mixer? For all system sizes, the EPA included a static mixer at the point of sodium hydroxide injection. Some systems, particularly larger systems, might already have a mixer at or near the point of injection (usually just prior to distribution) for use in mixing other chemicals (e.g., fluoride, residual disinfectant) and, therefore, not require another mixer. Therefore, this assumption may slightly overstate costs for some systems. Cost Equations There are more than 300 cost curve equations for pH adjustments. The curves, which translate a design flow value (QD in mgd) or an average flow (QA in mgd) into a cost estimate, vary by pH adjustment scenario, source water, system size, component level (low-, mid-, or high-cost), and type of cost (capital or O&M). Appendix A provides all of the equations. Below is an example of a set of capital cost equations and corresponding O&M for systems that adjust pH value from a starting value of 7.7 to 9.2. The curves are for the mid-cost component level for ground water systems. Capital Cost Equations: Small flows (QD < 1): 2907.7673 x QD[3]  -  1,146.17 x QD[2] + 99.9714 x QD + 15,053.422 Medium flows (1 <= QD < 10): 12.5076 x QD[3]  -  228.0535 x QD[2] + 2,108.849 x QD + 47,509.166 Large flows (QD >= 10): 0.0085 x QD[3]  -  3.2445 x QD[2] + 673.5505 x QD + 49,256.623. O&M Cost Equations: Small flows (QA < 1): 17,800.775 x QA[3]  -  6,629.4289 x QA[2] + 5,929.4753 x QA + 2,911.1473 Medium flows (1 <= QA < 10): 119.3809 x QA[3]  -  953.6126 x QA[2] + 6,580.5879 x QA + 2,235.9504  Large flows (QA >= 10): 0.2757 x QA[3]  -  30.8739 x QA[2] + 2,310.4039 x QA + 18,660.352. Costs for Corrosion-Inhibitor Addition Model Components and Assumptions USEPA (2020c) provides a description of the engineering design process used by the WBS model for phosphate feed. The model provides estimates of capital and O&M costs for corrosion control to reduce lead concentrations. In addition to the common WBS direct capital cost items listed in Exhibit 6-2, the phosphate feed model includes the following technology-specific equipment: Storage for phosphate solution (tanks, drums, or totes) Transfer/recirculation pumps to move phosphate solution from bulk storage to the day tanks Metering pumps to add phosphate solution to the existing water pipeline Static mixers to mix phosphate solution in the existing water flow (optional) Associated piping, valves, and instrumentation Incremental system control components required to integrate with the existing treatment process' control system. Because the model estimates costs for a process that is an addition to an existing treatment plant, it excludes certain costs that would be required in constructing a full new treatment plant. Specifically, the phosphate feed model does not include: Pilot study costs (see Section 6.5 for a description of coupon and pipe loop study costs, which the EPA estimates independently) Yard piping, because installing the add-on process should not require additional exterior water pipelines  Geotechnical costs, because the pre-existing geotechnical survey for the treatment plant should be sufficient to cover the construction costs associated with the add-on process Standby power costs, because the additional electrical demand from the add-on process should not require significant additional standby capacity. In addition, the model assumes construction of the add-on process will take less than one year, and excludes financing during construction for all system sizes. The O&M calculations include annual labor, maintenance materials, and energy usage based on the engineering design, O&M critical design assumptions, and input values. The technology-specific O&M elements for chemical usage include daily chemical demand based on average flow and dosage (e.g., 3.2 mg/L as orthophosphate).  For systems with smaller design flows (less than 1 MGD), chemical costs are for 55-gallon drums that contain 25 percent solution by weight. For systems with larger design flows (1 MGD or higher), chemical costs are for deliveries of 50 percent solution to storage tanks with 30-day capacities, and heat trace and insulation to prevent freezing. As noted in Section 2.4, the EPA estimated costs for four pH-adjustment scenarios, which result in varying sodium hydroxide doses. The model includes design parameters that determine fundamental process requirements. These parameters include system size (i.e., design flow and average flow) and: Scenario Specific chemical(s) added Dose required Solution strength, density, and price (if a user-defined chemical is chosen) Chemical storage configuration Heat tracing and insulation Inline static mixer Retrofit capital cost assumptions. Scenario The WBS model for phosphate feed for the LCR has several treatment scenarios to reflect different dosage rates. The highest rate of 3.2 mg/L (as orthophosphate) generates costs for systems needing to add or adjust orthophosphate feed following an ALE. The EPA also generates cost curves for three lower dosages to estimate baseline costs for systems that already use orthophosphate as a corrosion inhibitor: 0.525 mg/L, 1.5 mg/L, and 2.65 mg/L, all as orthophosphate.  Specific Chemical(s) Added The EPA used the following common corrosion control chemical formulations to estimate chemical demand and costs for the LCR revisions: Zinc orthophosphate with a 3:1 phosphate-to-zinc ratio and a solution strength of 36 percent as orthophosphate  Phosphoric acid at 75 percent as phosphoric acid. The WBS model's standard designs use phosphoric acid at 75 percent as H3PO4 for large systems with design flows greater than or equal to 1 MGD. The standard designs use the default zinc orthophosphate solution for smaller systems, consistent with the EPA guidance that phosphoric acid is not recommended for small systems (USEPA, 2003). Dose Required As noted above, the dose is an input to the WBS model. The input can be expressed in either mg/L as phosphorus or in mg/L as orthophosphate. Based on the dose required, the chemical chosen, and the design flow, the model calculates the design solution feed rate in gallons per hour. If this feed rate is less than the minimum chemical meter pump size specified on the critical design assumptions sheet, the model will generate a metering pump cost based on the minimum size, even if it is larger than necessary. In this case, the model will also recommend using a more dilute solution, because this would result in a higher, more practical feed rate and could be more cost-effective. Solution Strength, Density, and Price The WBS model uses a default price that corresponds to the chemical formulation, along with the default values for solution strength and density shown in Exhibit 6-4.  Exhibit 6-4. Solution Strength and Density for Default Chemicals Chemical Bulk Density (lbs/gal) Solution Strength as P[a] ZO (36% as PO4) 13.1 11.7% PA (36% as H3PO4) 10.14 11.4% PA (75% as H3PO4) 13.17 23.7% lbs/gal = pounds per gallon. a. Converted using the equations shown below.

The WBS model requires input of the chemical's solution strength as percent of phosphorus, bulk density in lbs/gal, and price in dollars per gallon. Chemical solution strengths can be specified in various units depending on the specific chemical used, such as percent of orthophosphate or percent of phosphoric acid. These values need to be converted to the units used in the WBS model (percent of phosphorus) using one of the following equations:               %P= MPMPO4x%PO4 =30.973894.9714x%PO4=%PO43.0662, or:           %P= MPMH3PO4x%H3PO4 =30.973897.9952x%H3PO4=%H3PO43.1638, where: %P=solution strength in percent as P, %PO4=solution strength in percent as PO4, %H3PO4=solution strength in percent as H3PO4, MP=molar mass of P in grams per mole, MPO4=molar mass of PO4 in grams per mole, and MH3PO4=molar mass of H3PO4 in grams per mole Chemical Storage Configuration The WBS model standard designs that the EPA used to estimate costs for the LCR revisions include direct feed from 55-gallon drums for small systems (less than 1 MGD design flow) and storage tanks with separate day tanks for larger systems (greater than or equal to 1 MGD design flow). Heat Tracing and Insulation The EPA did not include costs for heat tracing or insulation for the orthophosphate feed costs. The freezing point for a zinc orthophosphate formulation similar to the model's default is negative 20°F (Mid South Chemical, 2016). Phosphoric acid's freezing point is below 0°F at 36 percent phosphoric acid and 0°F at 75 percent phosphoric acid. Therefore, storage tanks for the default solutions should not require heat tracing and insulation, particularly if they are located inside a building (which is a default model assumption).  Inline Static Mixer For all system sizes, the EPA included a static mixer at the point of sodium hydroxide injection. Some systems, particularly the larger systems, might already have a mixer at or near the point of injection (usually just before distribution) for use in mixing other chemicals (e.g., fluoride, residual disinfectant) and, therefore, do not require another mixer. Therefore, this assumption may slightly overstate costs for some systems. Retrofit Capital Cost Assumptions Some systems that currently have caustic feed for pH adjustment in place may need to increase the dose of sodium hydroxide to achieve a greater pH level. System operators faced with a need to increase dosage could take a range of "retrofit" actions that include the following:     Continue to operate their existing chemical feed process without any change to equipment (because they have sufficient capacity or could switch to more concentrated chemicals or more frequent storage refills)     Continue to operate their existing chemical feed process, but add supplemental equipment to increase their capacity (e.g., a second tank and/or pump)     Continue to operate some parts of their process (e.g., piping and valves), but replace other parts (e.g., pumps, storage tanks) with larger-capacity equipment     Completely replace the entire process with equipment that is sized to the new dosage. The specific actions a given system might take from within this range is likely to depend on both the incremental increase in dosage and onsite-specific factors. Site-specific factors could include the layout of the treatment plant, the age of the existing equipment, the specific chemicals used, and whether or not the existing equipment has unused capacity because of safety factors or planned population growth. The different retrofit actions would entail very different capital costs. For example, continuing to operate without change (#1 above) would result in no additional capital expenditures. Complete replacement (#4 above) could have capital costs that are the same as installing a new chemical feed system.  To be conservative (i.e., err on the side of higher costs), the EPA assumed that all systems in the "Adjust CCT" and "Find & Fix" categories, regardless of incremental dose, would retrofit their chemical feed processes using an approach that comes close to complete replacement (#4 above). Accordingly, the EPA estimated retrofit capital costs for systems in these categories using the same method as for systems in the "Install CCT" category, excluding only the following specific capital items: Static mixers (which are sized to the treated water flow, not the chemical dosage) Instrumentation (specifically pH meters) located on the treated water line System controls Land Buildings Building permits Architectural fees Sitework. Exhibit 6-5 provides specific details on how the EPA excluded these items from the WBS model results. Exhibit 6-5. WBS Model Changes to Estimate Retrofit Capital Costs Excluded Item Model Change Static mixers Set the "Include static mixer?" input to "no" Instrumentation on the treated water line Set the "pH meters" critical design assumption to zero System controls Set the output sheet priority-selection values to zero for all line items in the "PLC Units" WBS category for all sizes and component levels Land Set the "Include land?" input to "no" Buildings and building permits Set the "Include buildings?" input to "no" Architectural fees Set the "Include architectural fee?" indirect assumption to 0 Sitework Set the "Include sitework costs?" indirect assumption to 0 PLC = programmable logic controller.

Cost Equations There are more than 1,500 cost curve equations related to orthophosphate addition. Many of the equations include costs for pH adjustment as well. The curves, which translate a design flow value (QD in mgd) or an average flow (QA in mgd) into a cost estimate vary by scenario, technology (e.g., pH adjustment or post-treatment), pH values, orthophosphate dose, source water, system size, component level (low-, mid-, or high-cost), and type of cost (capital or O&M). Appendix A provides all of the equations. Below is an example of a set of capital cost equations for systems that need to add CCT  -  either zinc orthophosphate or phosphoric acid at a dose of 3.2 mg/L (as orthophosphate) and adjust pH value from a starting value of 7 to 7.2. The curves are for the mid-cost component level for ground water systems. Capital Cost Equations: Small flows (QD < 1): 11,581.3258 x QD[3]  -  24,197.3466 x QD[2] + 25,964.7623 x QD + 56,110.735 Medium flows (1 <= QD < 10): 54.0.129 x QD[3]  -  1,141.6115 x QD[2] + 14,006.3734 x QD + 122827.07 Large flows (QD >= 10): 0.0557 x QD[3]  -  22.3691 x QD[2] + 499.0668 x QD + 151,785.56. O&M Cost Equations: Small flows (QA < 1): 13,164.5768 x QA[3]  -  2,737.7578 x QA[2] + 21,492.7169 x QA + 5,657.501  Medium flows (1 <= QA < 10): 133.6227 x QA[3]  -  1,204.1535 x QA[2] + 19,273.1514 x QA + 4,762.7111 Large flows (QA >= 10): 0 x QA[3] + 9.0972 x QA[2] + 10,192.5611 x QA + 38,266.344. Costs for POU Technologies Model Components and Assumptions The Cost Evaluation of Point-of-Use and Point-of-Entry Treatment Units for Small Systems: Cost Estimating Tool and User Guide (USEPA, 2007) document provides a complete description of the WBS model for POU technologies. The full POU model contains several types of costs such as monitoring and public education that double-count costs included elsewhere in the LCR cost analysis. Therefore, the EPA developed a streamlined version of the POU cost model that includes only device costs, installation costs, and filter replacement costs. For the LCR, there are two types of POU treatment. The first is short-term use of a POU device for filtration following LSLR. For this use, the EPA assumed that systems would provide households POU pour-through devices with carbon block filters certified to remove lead for a period of at least six months. Exhibit 6-6 provides assumptions the EPA used to estimate one-time, per-household costs of $44, including device costs and shipping.  Exhibit 6-6. POU Model Assumptions for Pour-Through Devices for Short-Term Use  Parameter Category Value POU device 100% pour-through pitchers sold with filters that are certified to remove lead. Filter capacity ranged from 120 to 320 gallons. Average pitcher (with one filter) cost across vendor products is $32.65.  Installation labor time No installation required. POU device shopping cost is $6. Filter replacement Shorter-lived filters require replacement during the 6-month usage period. The EPA used the following assumptions to estimate filter capacity for six months:  2.58 people  -  average household size (Census Bureau, 2012)  x 1.426 liters/day  -  average direct and indirect water consumption (USEPA, 2019)  x 365 days/year  x 1/3.7854 gallons/liter = 355 gallons/year (rounded).  Six months of use would require 178 gallons, which exceeds the filter capacity range for some filters The average replacement cost is $5.66.

The second type of POU treatment is a plumbed-in device that provides long-term lead removal through a certified carbon block filter. To derive costs for this type of POU treatment, the EPA assumed a mix of two different types of plumbed-in devices:  Faucet-mounted units  -  the filter housing attaches to the end of a faucet Counter-top units  -  the filter housing that sits on the counter has a water line attached to the faucet. Exhibit 6-7 provides the assumptions the EPA used to estimate annual, per-household costs of $116, including device, installation, filter replacement costs. The following sections provide more discussion of these assumptions. Exhibit 6-7. POU Model Assumptions for Plumbed-In Devices for Long-Term Use Parameter Category Value POU device 75% faucet-mounted devices sold with filters that are certified to remove lead. Filter capacity ranged from 100 to 200 gallons. Average cost across vendor products is $29.25. 25% counter-top devices sold with filters that are certified for remove lead. Filter capacity ranged from 450 to 1,000 gallons. Average cost across vendor products is $123.87.  Installation labor time 0.6 hours to schedule POU device installation ($30.48/hour clerical wage rate[a]). 0.5 hours to install faucet-mounted device ($39.17/hour plumber wage rate[b]). 1.5 hours to install counter-top device ($39.17/hour plumber wage rate). Filter replacement Based on the annual household consumption rate estimate shown in Exhibit 6-6, filter replacement frequencies, labor time, and filter costs are: Faucet-mounted: 3 replacements/year, 0.6 hours for scheduling and filter replacement ($31.20/hour[c]), and $29.54/year average cost for replacement filters Counter-top: 0.5 replacements/year, 0.6 hours for scheduling and filter replacement ($31.20/hour), and $34.81/year average cost for replacement filters. a. The clerical wage rate is from the WBS models. It reflects a $22.69 base wage rate and a multiplier of 1.5 to incorporate benefits. This wage rate from 2007 was then escalated to 2017 dollars using the Employment Cost Index (ECI) ratio of 140.4/104.525 (BLS, 2019a). b. The plumber wage rate is based on the May 2019 wage rate of $26.86 (BLS, 2019b) and a multiplier of 1.5 to incorporate benefits. The product is deescalated from 2019 dollars to 2017 dollars using the ECI ratio of 140.4/144.4. c. The wage rate of $31.20 is an average of the clerical rate of $30.48 and the WBS technical wage rate of $31.91. The latter is based on a 2007 base wage rate of $23.76, a multiplier of 1.5 to include benefits, and the same ECI ratio as the clerical wage rate to escalate the estimate from 2007 to 2017 dollars. The rate applies to the combined estimate of administrative scheduling time and filter replacement time.

The EPA assumed that 75 percent of devices would be the more cost-effective, faucet-mounted units; but that 25 percent of households may need the more expensive, counter-top device. The EPA assumed an average useful life of three years for both types of devices to annualize the capital costs (i.e., device costs and installation expenses). The EPA did not include RO POU devices in the cost estimate for the LCR. Although these devices are certified for lead removal, they are not cost-effective. They tend to be more expensive because they require multiple filter housings and a treated water storage tank. They have to be plumbed under the sink because of space requirements and have a waste line for the membrane reject stream, thereby incurring higher installation costs. There are multiple filters and a membrane to replace, which increases maintenance costs. POU Device Installation Installation of POU devices will be the responsibility of the water system. The utility can, however, hire a licensed plumber or representative of the product manufacturer to install these devices. Based on the variety of plumbing issues encountered among older housing units in a rural community and the risk of water damage, systems may prefer to use a licensed plumber to perform the installations (USEPA, 2006).  The POU model contains an assumption of a 0.5-hour installation for the simpler, faucet-mounted device; but a longer 1.5-hour installation time for the counter-top device. A variety of factors such as existing plumbing conditions and travel distance will affect installation times across sites. These estimates are consistent with case study data. In a Grimes, California, arsenic demonstration program (NSF, 2005), POU adsorptive filter installation times ranged from 15 minutes to 3 hours, depending on the accessibility of piping and the need for additional lines (e.g., to provide treated water to ice-makers). The mean device installation time was one hour. Total plumber billing records indicated that twice as much time was spent on all installation-related activities (e.g., additional time to obtain special plumbing fittings and return visits to homes when residents missed their appointments). The EPA assumed that including clerical time to facilitate installation would minimize such issues. The EPA also assumed a total of 0.6 hour of clerical time per household to initially schedule the installation and collect faucet manufacturer information (approximately 30 minutes), and provide follow-up appointment reminders (approximately 5 minutes). Scheduling efforts are likely to vary across customers, with some being relatively easy to schedule, while others may require multiple calls to identify and contact the correct homeowners or to handle situations such as homeowner reluctance to participate or language barriers (USEPA, 2006). POU Device Maintenance Maintenance for either of the POU devices primarily includes replacing the carbon block filters. As noted above, replacement schedules are based on the treatment capacities, which vary by type of device and across vendors. The EPA estimated average annual replacement frequencies based on vendor information about treatment capacity (reported in gallons), the estimated annual usage based on average household size (Census Bureau, 2012), and direct and indirect water consumption rates (USEPA, 2019).  Faucet-mounted filters require more frequent replacement, ranging from 1.7 to 3.55 replacements per year. The EPA assumed an average of three replacements per year. Given the frequency range and the replacement filter cost range of $6.73 to $16.20 per filter, the EPA estimated an average annual filter replacement cost of $29.54 across seven different products. Counter-top filters require less frequent replacement, ranging from 0.36 to 0.79 replacements per year. The EPA assumed an average of 0.5 replacements per year. Given the frequency range and the replacement filter cost range of $31.16 to $69.95 per filter, the EPA estimated an average annual filter replacement cost of $34.81 across five different products. In addition to replacement filter costs, maintenance costs include scheduling time and the time required to change filters. The Grimes case study cost analysis (NSF, 2005) used an estimate of 15 minutes per filter change out. The EPA added 15 minutes to include time to schedule the replacement appointment and 5 minutes for a follow-up appointment reminder. Thus, the total time for replacement is 0.6 hours. Cost Estimates  The POU cost estimate for the pour-through pitcher is the sum of the original pitcher purchase price ($33.98) and the shipping cost ($6.00), rounded to $40 per household. The POU cost estimate for the long-term, plumbed-in POU devices includes capital costs and O&M costs. The annual cost per household is $114 if capital costs are annualized using a 7 percent discount rate and $111 if capital costs are annualized using a 3 percent discount rate. Costs for Pilot Testing  For the purpose of estimating costs of the final LCR revisions, the EPA assumed that certain systems would need to conduct pipe rack studies with harvested service lines to select or optimize CCTs and others would use coupon studies. This section documents the design inputs and assumptions that the EPA used to estimate pilot testing costs and the final cost estimates. Design Inputs and Assumptions Number of Pipe Segments or Jars Exhibit 6-8 provides a summary of design assumptions the EPA used in tools to estimate pilot study costs. The design inputs for the pipe rack study result in an apparatus with 9 pipe segments for systems serving up to 50,000 people (i.e., 3 replicates of 2 CCT options and a control segment) and 12 pipe segments for systems serving greater than 50,000 people (i.e., 3 replicates of 3 CCT options and a control segment). For the coupon test, the design inputs result in eight coupons. Exhibit 6-8. Design Inputs that Determine Number of Pipe Segments or Coupons Assumption Coupon Test All System Sizes Pipe Rack System Sizes up to 50,000 Pipe Rack System Sizes > 50,000 Control condition No Yes Yes Number of CCT options 4 2 3 Replicates 1 3 3

The number of conditions tested is a significant factor in total pilot testing costs. Specific details of each condition (i.e., specific chemicals and dosages) will have a small effect on the overall total costs because the chemical use is small compared to other cost components such as equipment, labor, and laboratory analysis. The specific conditions tested for the coupon test included phosphoric acid addition dosed at 2.5 mg/L, 3 mg/L, 3.5 mg/L, and 4 mg/L, all as phosphate. The conditions tested for the pipe rack studies were:  Control condition (i.e., no CCT chemical added) Phosphoric acid addition at 2.5 mg/L as phosphate Phosphoric acid addition at 3 mg/L as phosphate Phosphoric acid addition at 3.5 mg/L as phosphate (for systems serving greater than 50,000 people). Study Duration and Operation The EPA made the study duration assumptions shown in Exhibit 6-9. The coupon study assumption was based on Cornwell and Wagner (2019) and the pipe loop study durations were based on AWWARF (1994). Exhibit 6-9. Design Inputs for Study Duration and Operation Assumption Coupon Test All System Sizes Pipe Rack System Sizes up to 50,000 Pipe Rack Systems Sizes > 50,000 Startup period na 1 month 1 month Stabilization period na 6 months 6 months Operating period na 4 months 4 months Total duration 6 weeks 11 months 11 months Interval between jar swaps 3.5 days na na

Labor Assumptions Labor assumptions for the pilot studies affect labor costs; Exhibit 6-10 shows a summary of labor hour inputs by activity or study period. To build and install the apparatus, the EPA assumed a time-per-line segment of 18.4 hours based on the averages of 21.3 hours (AWWARF, 1994) and 15.5 hours (Williams, et al. 2018). The EPA assumed a third party would install the apparatus. Exhibit 6-10. Design Inputs for Pilot Study Labor Assumption Coupon Test All System Sizes Pipe Rack System Sizes up to 50,000 Pipe Rack System Sizes > 50,000 Installation na Installation: 18.4 hours per segment Installation: 18.4 hours per segment Startup period Preparation/testing: 3 hours/swap Swap: 10 minutes/jar/swap Operator: 40 hours/week Operator: 40 hours/week Stabilization period

Operator: 20 hours/week Operator: 20 hours/week Operating period

Operator: 20 hours/week Operator: 20 hours/week Supervisor hours 10% of operator hours 10% of operator hours 10% of operator hours

The EPA assumed operator time of 40 hours per week during the startup phase and 20 hours per week for subsequent phases based on AWWARF (1994) recommendations. The EPA assumed supervisor time equal to 10 percent of operator time. For the coupon test, the EPA assumed 3 hours per swap to collect the finished water and adjust it to distribution system conditions. The EPA added 10 minutes per swap per jar for preparing fresh jars to individual treatment conditions, switching coupons to fresh jars, recording pH in old jars, and preparing old jars for lead analysis. The EPA assumed supervisor time was equal to 10 percent of operator time. Sampling Location and Frequency For the pipe rack, sampling location options include influent and treated water. Samples can also be taken while water is running or during a stagnation period. Sampling frequency will vary across the study periods and by constituent. Exhibit 6-11 provides a summary of the sampling frequencies and locations that the EPA assumed to estimate pilot study costs. The higher sampling frequencies coincide with the operation period; the lower frequencies occur during the startup and stabilization period. For the coupon study, the EPA assumed one pH test and one lead test per jar per swap (i.e., every 3.5 days). Exhibit 6-11. Design Inputs for Pilot Study Sampling and Analysis Constituent Coupon Test All System Sizes Pipe Rack System Sizes up to 50,000 Pipe Rack System Sizes > 50,000 Alkalinity 0 4 - 8  4 - 8  Ammonia 0 4 - 8 (influent) 4 - 8 (influent) Calcium 0 4 - 8 (influent and treated) 4 - 8 (influent and treated) Chloride 0 0 0 Color 0 4 - 8 (influent) 4 - 8 (influent) Copper 0 0 0 Dissolved oxygen 0 Benchtop analysis Benchtop analysis Heterotrophic plate count 0 4 - 8 (influent) 4 - 8 (influent) Iron 0 4 - 8 (influent) 4 - 8 (influent) Lead 1 per jar 4 - 8 4 - 8 Orthophosphate 0 4 - 8 (influent and treated) 4 - 8 (influent and treated) pH Benchtop analysis Benchtop analysis Benchtop analysis Sulfate 0 0 0 Temperature 0 Benchtop analysis Benchtop analysis Total and free chlorine 0 4 4 Total coliform 0 4 - 8 (influent) 4 - 8 (influent) TDS 0 Benchtop analysis Benchtop analysis

Cost Estimates The EPA derived the following cost estimates from the pilot study cost tools using the assumptions noted above: $7,205 average coupon study cost  $276,249 for pipe rack testing for systems serving up to 50,000 people  $342,476 for pipe rack testing for systems serving greater than 50,000 people.  The estimates for pipe rack testing are highly dependent on the parameters included in the sampling scheme. Exhibit 6-12 shows the potential impact of different sampling assumptions on the cost of pipe rack testing. Exhibit 6-12. Incremental Change in Pipe Rack Testing Cost for Different Sampling Assumptions Parameters Sampled Pipe Rack System Sizes up to 50,000 Pipe Rack System Sizes > 50,000 Default parameters (a) $276,249 $342,476 Add: copper +$31,561 +$41,528 Add: chloride and sulfate  +$19,359 +$25,167 Subtract: ammonia, calcium, color, dissolved oxygen, heterotrophic plate count, iron, temperature, total and free chlorine, total coliform, TDS -$31,290 -$37,859 a. Default parameters are those shown in Exhibit 6-11: alkalinity, ammonia, calcium, color, dissolved oxygen, heterotrophic plate count, iron, lead, orthophosphate, pH, temperature, total and free chlorine, total coliform, and TDS.

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Appendix A: Cost Equations This appendix presents the cost equations included in the national cost analysis. The equations take one of the following forms, identified by which coefficients (C1 through C10) are nonzero: Cost 	= C1 Q[C2],  or	= C3 Ln(Q) + C4,  or	= C5 e[(][C6] Q),  or	= C7 Q[3] + C8 Q[2] + C9 Q + C10, where Q is the design flow in MGD for total capital costs, or average flow in MGD for annual O&M costs. Equations are designated as whether they are for small, medium, or large systems. These equations apply as follows: Small system equations apply where the design flow (Q) is less than 1 MGD  Medium system equations apply where the design flow (Q) is 1 MGD or greater, but less than 10 MGD Large system equations apply where the design flow (Q) is 10 MGD or greater The EPA developed each equation using the method described in Section 6.1.2. Separate equations are presented for surface water (SW) and groundwater (GW). The equations are further categorized by component level (low, mid, or high cost) and whether the equation pertains to capital or O&M costs. The equations are also categorized according to "technology." The technology categories are defined as follows: Modify pH: Equations in this category reflect the cost of using caustic addition to increase pH from a given starting pH to an optimal ending pH. Add orthophosphate (PO4) with pH post-treatment: Equations in this category reflect the cost of adding a specified dosage of phosphate. These equations also include the cost of caustic addition to maintain the initial starting pH, if the orthophosphate chemical added would lower the pH value by 0.1 standard units or more. More specifically, as discussed in Section 6.3.1, the EPA assumed that large and medium systems would add phosphate in the form of phosphoric acid, which can lower pH by an amount that depends on the phosphoric acid dose, initial pH, and alkalinity. Therefore, the EPA included caustic addition costs in some of the equations for large and medium systems (see Section 6.2.1 for more details). On the other hand, as discussed in Section 6.3.1, the EPA assumed small systems (less than 1 MGD design flow) would add phosphate in the form of zinc orthophosphate, which is less corrosive than phosphoric acid. The EPA assumed zinc orthophosphate addition would not significantly lower pH and, therefore, did not include caustic addition costs in the equations for small systems (less than 1 MGD design flow). Add phosphate (PO4) and modify pH: Equations in this category reflect the cost of adding a specified dosage of phosphate and the cost of using caustic addition to increase pH to an optimal ending pH. For large and medium systems, the caustic addition costs included in these equations account for the potentially lower pH caused by phosphoric acid addition, as discussed above. As indicated in the definitions above, the technology categories determine which WBS model, or combination of WBS models, the EPA used to develop the individual equations. Exhibit A-1 shows the combinations for each technology category. Exhibit A.1. WBS Models Used for Each CCT Technology Category Technology Category WBS Models Used for Small Flow Systems  (< 1 MGD design flow) WBS Models Used for Medium and Large Flow Systems  (>= 1 MGD design flow) Modify pH Caustic feed Caustic feed Add PO4 with pH post-treatment Phosphate feed Phosphate feed or phosphate feed + caustic feed[a] Add PO4 and modify pH Phosphate feed + caustic feed Phosphate feed + caustic feed a. The caustic feed cost was added to the phosphate feed cost if the latter lowered pH by 0.1 or more. See Section 6.3 for assumptions about these impacts by PO4 dose and initial pH.

Finally, the equations are categorized according to "scenario" categories, which are defined as follows: Existing CCT: Equations in this category are for estimating the baseline costs for systems that already have a CCT in place under the current regulation prior to revisions. This category includes equations for O&M costs only because capital costs for an existing CCT are already "sunk" and are not needed to calculate incremental costs of increasing the caustic and/or orthophosphate dose. Install a CCT: Equations in this category are for estimating the cost of installing and operating a new CCT for systems that do not currently have a CCT in place. Accordingly, this category includes equations for both total capital and O&M costs. Adjust a CCT and Find & Fix: Equations in these categories are for systems that currently have a CCT in place, but that will need to change their CCT practices (e.g., increase orthophosphate dose). This category includes equations for both total capital and O&M costs, but the capital costs are less than those incurred by systems installing a new CCT, reflecting a retrofit of existing capital equipment.