City of Lacey 2018 Corrosion Control Evaluation. (blank page)

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2 City of Lacey 2018 Corrosion Control Evaluation (blank page) 2

3 City of Lacey 2018 Corrosion Control Evaluation Contents EXECUTIVE SUMMARY PROJECT BACKGROUND SYSTEM INFORMATION Water Sources Source and Distribution System Treatment ph Adjustment at Source S Iron and Manganese Treatment Facilities Contact Time at S System-wide Chlorination Waterline Flushing Program Pipeline and Plumbing Materials Distribution Lines and Facilities Home Plumbing WATER QUALITY DATA Entry Point Source Water Quality Distribution Tap Water Quality Residential Tap Sampling for Lead and Copper Customer Complaints EVALUATION OF CURRENT CORROSION CONTROL IN THE LACEY SYSTEM Passivating Scales Solubility Modeling RECOMMENDED TREATMENT FOR OPTIMIZING CORROSION CONTROL Optimal Level for ph Treatment Strategy Blending Analyses and Hydraulic Modeling Blending Zone for Source S Sources S24/S25 Hot Spot Analysis for 188 Pressure Zone Blending Zone for Source S Blending Zone for Source S Available ph Treatment Methods Source S Sources S17, S01/S18, and S23/S ACTION PLAN

4 City of Lacey 2018 Corrosion Control Evaluation 6.1 Schedule for Treatment Installation Monitoring Distribution Monitoring Customer Tap Sampling Entry Point Monitoring Evaluation Process for Optimization Considerations for Revisions to the LCR Approach and Recommendations for Revisions Relating to New Copper Surfaces References List of Tables Table 1. Wells Supplying the Lacey Water Department... 7 Table 2. Average Source Water Quality Results, 2011 and Table 3. Percent annual source production during distribution sampling May 2017 April Table 4. Lead and Copper at Entry To Distribution Table 5. Distribution Taps: Ranges of Results from Samples Collected Table th percentiles for Tap Samples Collected Table 7. Summary of LCR samples collected within the 188 pressure zone Table 8. Water quality in 188 PZ when 2011 LCR samples collected Table 9. Schedule for Installing OCCT List of Figures Figure 1. Lacey Water System Schematic... 8 Figure 2. Monthly source production during distribution sampling May 2017 April Figure 3. ph Ranges at Distribution Tap Sites Sampled Figure 4. Customer Tap Sample Sites, Figure 5. Gallons pumped from sources in during Standard LCR tap sampling Figure 6. Theoretical Lead (cerussite) and Copper (malachite and cupric hydroxide) Solubility at Each Entry Point Figure 7a, 7b and 7c. Modeled Solubilities for Lead, Aged Copper and New Copper for source group Figure 8. Expected ph at different blending levels near Source 6 (Judd Hill) Figures 9a and 9b. Maps of Hydraulic Modeling Under Summer Operation (9a left: Blending under Current Conditions; 9b right: Predicted areas above, and below ph 7 after Treatment Installation) Figure 10. Expected ph at different blending levels for McAllister (S20) and treated Madrona (S23/28) 32 Figure 11. Predicted ph with source treatment at S17, S01/S18, S23/S Figure 12. Flowchart for Evaluating Tap Monitoring Results Appendices A Letter from DOH outlining CCT steps for Lacey B. Technical Memorandum from Confluence Engineering Group, LLC (2018): ph Treatment Recommendations C. Source Entry Point Water Quality Data D. Distribution Tap Water Quality Data 4

5 City of Lacey 2018 Corrosion Control Evaluation EXECUTIVE SUMMARY In 2018, the City of Lacey Water System, PWSID # 43500Y, completed a desktop corrosion control evaluation of the water system that meets requirements for a large system that supplies a population >50,000. The study was triggered following sampling at residential taps, and while the lead results were very low, they were not low enough to exempt the system from completing a corrosion control study. Consequently, the Washington State Department of Health required that the system conduct a corrosion control study and recommend treatment for optimizing the water system for corrosion control. In recent years the Lacey water system has experienced a number of changes affecting water sources, water conveyance and water treatment. This corrosion control study therefore represents water quality of current sources supplying the system, as indicated by distribution tap samples collected for this study in Solubility modeling was used to evaluate source and distribution tap data, and indicated that the water system is nearly optimized for lead control. The system will be optimized for lead control by ensuring ph 7.0 within the distribution system. While action levels for copper are met which would suggest that the system is optimized for copper control, copper release can be lowered further by increasing ph within the system. Although raising ph is especially beneficial to control copper release from new copper surfaces, cross-linked polyethylene has been the material of choice by builders for the last years. Therefore, corrosion control treatment will be optimized when ph in the water system is raised to ph 7.0. To achieve this water treatment goal, Lacey is proposing to install three new ph adjustment treatment facilities, at sources S17, S01/S18, and S23/S28 to increase entry point ph at these sources to ph 7.4. All three are wellfield locations. Treatment will be installed in a stepwise manner, to coincide with planned replacement wells to be constructed at sources S17 and S01. In addition, dosing of caustic soda at the existing ph adjustment facility at source S04 was increased, to increase ph at the entry from ph 7.4 to 7.6. Sources that were not selected for treatment are small sources that blend in the distribution system with non-corrosive or treated sources, or, in the case of Sources S24 and S25, are isolated within a pressure zone that has met Action Levels since tap sampling began in Pre-design, design and construction of the three new facilities will occur from Baseline monitoring in the distribution system will track ph in the distribution as the new treatment facilities come on-online, with particular focus on monitoring within zones that blend with untreated sources. In 2025, after the third treatment facility is constructed and is meeting stable entry point ph levels, customer tap samples will be collected and distribution monitoring frequency will be increased. Because the Lacey water system is complex and has multiple blending zones, a flow chart was developed to help evaluate tap sampling results and to identify appropriate next steps based on the monitoring results. The Action Plan for implementing optimal corrosion control treatment is based on meeting the requirements of the current Lead and Copper Rule, but the City recognizes that the Federal Lead and Copper Rule is under revision and the extent of revisions is unknown at this time. Portions of the Action Plan may need to be revisited when the Lead and Copper Rule is revised. 5

6 City of Lacey 2018 Corrosion Control Evaluation 1.0 PROJECT BACKGROUND The Lacey Water System was regulated as a medium-sized system under the Federal Lead and Copper Rule until 2010, when notified by the Washington State Department of Health (DOH) that the system must complete the corrosion control requirements for a system serving >50,000 people. In December 2010, Lacey notified DOH of its intent to conduct a corrosion control study and complete subsequent corrosion control treatment steps. At the time, Lacey was planning to construct a ph adjustment facility for source S04 in 2011, and was anticipating that water purchased from the City of Olympia was going to change from surface water to a groundwater source. The final study report 1 was completed and submitted to DOH in March The report included distribution data collected after the source S04 ph adjustment facility became operational, and concluded that the Lacey water system would be fully optimized when water from source S30 (intertie with the City of Olympia) was treated to increase its ph, and when source S01 (an infrequently-used source) was replaced. DOH approved the conclusions in the report in April However, by 2015 Lacey started planning for inactivating the Olympia intertie as a permanent source, and met with DOH in early 2016 to discuss remaining corrosion control steps. The parties agreed that Lacey could collect lead and copper tap samples after the intertie was inactivated, to evaluate whether the Lacey system would now qualify for the (b)(3) exemption 2. Meeting the exemption would eliminate the need for completing the corrosion control study. Tap samples were collected in , and whereas the results for lead were very low, they did not meet the criteria for a (b)(3) exemption. In February 2017 DOH provided notice to Lacey to complete a corrosion control study by August The letter from DOH is attached as Appendix A. The expectation is for Lacey to collect additional distribution and source samples to represent the current sources of supply to the system, to update the analyses and recommend additional treatment to optimize the system for corrosion control. Lacey contracted Confluence Engineering Group ( Confluence ) to analyze the updated data, make treatment recommendations, and identify treatment goals for Lacey sources. These analyses and recommendations are summarized in this updated report, and are based on a Technical Memorandum from Confluence that is attached to this report (Appendix B). 1 City of Lacey Corrosion Control Evaluation Final Report March CFR (b)(3) states a water system is deemed to be optimized for corrosion control if results from two consecutive 6-month monitoring periods demonstrate that the difference between the 90 th percentile tap water lead level and the highest source water lead concentration is < mg/l. 6

7 City of Lacey 2018 Corrosion Control Evaluation 2.0 SYSTEM INFORMATION The Lacey water system includes three treatment facilities (see Section 2.2), seven storage reservoirs, and seven primary pressure zones and three sub-zones that serve clients at varying elevations. A schematic showing the distribution system, major facilities and pressure zones is shown in Figure Water Sources The Lacey water system is completely self-supplied with 20 groundwater wells that are owned and operated by the city (Table 1). Source S01, though, has been offline since 2016 and is planned to be replaced in As shown on the Water Facilities Inventory (WFI), the system has 16 regulated sources that include 12 individual wells and 4 wellfields (with two wells per wellfield). Sources that are regulated as wellfields are noted in Table 1. All sources are approved for year-round supply. Table 1. Wells Supplying the Lacey Water Department DOH ID Source Name(s) Year Online Completed Depth (ft) Aquifer S01 Well Qga S02 1 Well Qpg S03 1 Well Qpg S04 Well Qga S06 Well 6C; Judd Hill Qpg/TQu S07 Well TQu S09 Well TQu S10 Well Qpg S15 2 Beachcrest well Qga S16 2 Beachcrest well Qga S19 3 Hawks Prairie Well TQu S20 McAllister Qpg S21 4 Madrona well Qpg S22 4 Madrona well Qpg S24 Nisqually Well 19A Qpg S25 Nisqually Well 19C Qpg S27 Evergreen Estates Qpg S28 Madrona well Qpg S29 Betti well Qpg S31 3 Hawks Prairie Well TQu 1 Regulated as wellfield S18 by DOH 2 Regulated as wellfield S17 by DOH 3 Regulated as wellfield S32 by DOH 4 Regulated as wellfield S23 by DOH 7

8 City of Lacey 2018 Corrosion Control Evaluation Figure 1. Lacey Water System Schematic 8

9 City of Lacey 2018 Corrosion Control Evaluation (blank page) 9

10 City of Lacey 2018 Corrosion Control Evaluation 2.2 Source and Distribution System Treatment Source treatment in the Lacey water system consists of three treatment facilities: a ph adjustment facility, and two iron and manganese treatment facilities. In addition, a contact time chamber was constructed at source S10. Water quality in the distribution system is maintained with system-wide chlorination and a routine waterline flushing program. Treatment facilities and water quality programs are described below ph Adjustment at Source S04 Although treatment was not triggered by source or tap sample results, Lacey s comprehensive water system plans recommended corrosion control at source S04 to address a history of corrosion of new copper pipe in the vicinity of the well. The facility was constructed in The facility was designed to treat source water with 25% caustic soda (sodium hydroxide solution) to achieve a target ph of 7.6 and alkalinity within mg/l. Evaluations of water quality and treatment alternatives for source S04 concluded that low ph was the primary factor affecting the corrosivity of the water, and results from a relatively high concentration of dissolved carbon dioxide compared to nearby sources S09 and S10 (HDR 2007). ph adjustment was determined to be more suitable for corrosion control than calcium carbonate precipitation and corrosion inhibitor chemicals because well 4 supplies a pressure zone that is fed by multiple wells, and will blend with other sources in the system that do not need corrosion control treatment (HDR 2007). ph adjustment using caustic soda was the recommended treatment for source S04 based on its ability to meet treatment goals along with its process flexibility, lower capital cost and footprint, and simplicity of operation (HDR, 2007) Iron and Manganese Treatment Facilities The city operates two iron and manganese treatment facilities. The first was a design-build ATEC facility constructed at source S07 in The well 7 ATEC facility oxidizes iron and manganese with potassium permanganate and 0.8% sodium hypochlorite prior to filtering through pyrolusite media. The second facility, referred to as the Hawks Prairie Water Treatment Facility (HPWTF), was constructed at source S19 in 2008 with capacity to also treat future source S31. The HPWTF oxidizes constituents in raw S19/S31 water with air injection followed by 0.8% sodium hypochlorite injection. Then the water containing the oxidants is filtered through manganese greensand before passing through a contact time chamber to achieve breakpoint chlorination. Both iron and manganese treatment facilities were designed to meet target finished water goals of <0.15 mg/l for iron, and <0.025 mg/l for manganese (<50% of the MCLs for iron and manganese) Contact Time at S10 A contact time chamber at well 10 (S10) was installed in 2007, after numerous coliform-positive samples occurred following a well rehabilitation project. The same 0.8% sodium hypochlorite solution used for system disinfection is injected into raw water, which then passes through an underground contact time chamber. Raw source water is sampled quarterly for bacteria, but coliforms have not been detected since the contact time chamber was constructed. Since primary source disinfection is not required at this time, contact time is provided but Lacey does not list this as a disinfected source System-wide Chlorination The Lacey water system has been chlorinated on a permanent basis since System-wide chlorination was initiated after several non-acute total coliform violations occurred in The violations 10

11 City of Lacey 2018 Corrosion Control Evaluation were not attributed to source wells so 0.8% sodium hypochlorite is injected at all well sites for the purpose of maintaining a disinfectant residual in the distribution system. Chlorination is intended to achieve a target concentration of approximately 0.5 mg/l free chlorine in the distribution system, although typically concentrations range from mg/l Waterline Flushing Program The city started a routine unidirectional flushing (UDF) program in UDF systematically progresses from source(s) to the periphery of the distribution system, and uses water valves to isolate and control flow direction and velocities that scour the waterlines. The progression from source to periphery ensures that clean water is used for flushing each section of pipe and that material cleaned from pipe walls is discharged from the system to an appropriate discharge location. Lacey s UDF program was initiated to address frequent and extreme brown water events that could not be controlled by spot flushing, and to prepare the distribution system for system-wide chlorination. The initial two years of the program focused on removing legacy iron and manganese deposits, as well as reducing biofilms containing iron and sulfur bacteria. The UDF program is now focused on preventing brown water episodes by removing residual iron and manganese deposits, to raise chlorine residuals in dead ends, and to manage iron and sulfur bacteria that are still present but are greatly inhibited by chlorine and water treatment that reduces available food sources. Generally, the entire system is flushed over a 3-5 year cycle although some areas of the system are flushed every 1-2 years. Lacey may expand the program in the future to include service line flushing and targeted waterline swabbing. 2.3 Pipeline and Plumbing Materials Pipeline and plumbing materials provide the source of metals that can be leached into drinking water. Materials can include copper, iron and galvanized metal used in piping; brass fixtures and fittings containing lead, arsenic and/or zinc; and fluxes and solder used in both manufacture and installation of piping Distribution Lines and Facilities Distribution lines At the beginning of 2018, the distribution system consisted of approximately 2.1 million linear feet of water main. The majority of pipe is six to twelve inches in diameter. The approximate percentages of materials in the distribution system are as follows: PVC or Polyethylene: 59.5 % Lined Ductile Iron: 21.8% Asbestos Cement: 16.8% Other (includes concrete, galvanized metal, and unknown ): 2% Although asbestos cement can be vulnerable to corrosion, city staffs have observed that tree roots cause the most damage to asbestos cement waterlines. Waterlines with a history of leaks and breaks are identified for replacement through the city s semi-annual waterline replacement program, and often includes replacing some asbestos cement pipe. Operations and maintenance staffs have observed evidence of corrosion in the water system such as tuberculated parts and fittings. However, many breaks 11

12 City of Lacey 2018 Corrosion Control Evaluation and leaks are attributed to poor materials, such as bad gaskets or older non-standard valves and fittings, or poor installation. Waterline corrosion has not been cited as a reason for waterline repairs or replacement. Lead service lines have not been used in the Lacey Water system, and lead goosenecks have not been found in older parts of the system that were constructed with non-standard materials. The Lacey water system itself was created in 1968, well after lead goosenecks were commonly used, and the city s waterline replacement program has replaced waterlines and service connections from many of the acquired water systems. Water System Components All new and replaced water system components meet NSF materials requirements and AWWA standards. However, non-standard components such as fittings and valves were used in some water systems acquired by the City of Lacey, particularly in the Huntamer s Water System that became the Lacey Water System in Lacey replaces non-standard materials when they are found during repairs or as part of waterline replacement projects. The Reduction of Lead in Drinking Water Act took effect in January 2014 and requires all materials used in water systems, brasses in particular, to be certified lead-free. This Act amended the Safe Drinking Water Act to reduce the allowable lead content in all products in contact with drinking water from 8% to a weighted average of 0.25% (using a wetted surface based averaging formula). The new lead-free components are certified under NSF/ANSI Standard 372. The only allowable exceptions are for devices associated with non-potable uses, such as toilets, tub fillers, shower valves, and service saddles. In addition, fire hydrants and water main gate valves 2 or greater in diameter are exempt from meeting the no-lead requirements. The intent of the Reduction of Lead in Drinking Water Act is to directly address lead release into drinking water. Studies have shown that lead-free brass alloy components release minimal amounts of lead and other metals compared to lead-containing components (Sandvig 2009). Before January 2014, Lacey started transitioning to the new lead-free components as they became available. Dezincification of brass fittings has been associated with lead release into drinking water and has caused large failures in some water systems. Zhang and Edwards (2011) reported that use of dezincificationresistant and low zinc brasses created a higher risk for lead release compared to brasses with higher zinc content, especially if the low-zinc product was not also low-lead or lead-free. There are no indications that dezincification has been a problem in the Lacey water system Home Plumbing In the Lacey water service area, materials used in home plumbing are predominately copper and cross linked polyethylene (PEX), although galvanized pipe and PVC have also been used. Copper pipe was used extensively in new construction in the 1980s and 1990s, but over the past fifteen years the use of PEX for water plumbing has increased steadily and is now used in the construction of most commercial buildings and subdivisions. At the time of the 2014 Corrosion Study, Lacey s Building Official estimated that PEX was used in at least 80% of new construction served by the Lacey water system. By 2018, PEX is reported as the material of choice by contractors that construct the vast majority of new housing served by the Lacey water system, and consequently is being used in almost all new residential construction (Wade Duffy, Lacey Building Official, pers. comm.). The city s materials surveys have mainly focused on identifying single-family residences that qualify as Tier One sites for residential lead and copper tap sampling under the current Lead and Copper Rule, i.e., residences constructed between and with all (or mostly all) original plumbing. The original 12

13 City of Lacey 2018 Corrosion Control Evaluation pool of Tier One homes used for tap sampling declined as older homes were renovated, or replaced, so in 2016 county parcel information was used to identify homes served by the water system that were constructed between During this construction period approximately 1,340 homes were built, which represents <6% of the single family connections to the water system. This list was used to contact residences for participating in tap sampling in ; sampling results are summarized in Section WATER QUALITY DATA This Section describes source (entry point) water quality and distribution system water quality from samples collected for the 2014 Corrosion Control Study and this 2018 Corrosion Control Study Update. Residential tap sample results for lead and copper results are also presented here. 3.1 Entry Point Source Water Quality For this updated corrosion control study, source samples were collected quarterly in to characterize water quality of sources currently supplying the Lacey water system. Changes in sources since the 2014 study are the following: Source S04 has been treated with caustic soda since 2013 to raise ph. Source S30 (intertie with Olympia) was inactivated in Source S01, identified in the 2014 study as a corrosive source, was offline during due to pumping issues and is anticipated to remain offline until it is replaced (planned for 2020). As a result, this source was only sampled once for this study. Source S31 was approved as a new source and was used in , but was offline from late 2016 through May 2018 due to sanding and mechanical issues. As a result, this source was not sampled for this study but its construction report indicates water quality very similar to source S19. Both sources are treated for iron and manganese at the Hawks Prairie Treatment Facility. For this study, sources were sampled quarterly from July 2017 to April Data collection for this study focused on parameters identified by DOH (Appendix A). Water samples were analyzed for alkalinity, calcium, and sulfate; in addition, temperature, ph, specific conductance, and free and total chlorine were measured in the field. Sources were also sampled quarterly in 2011 for the 2014 study. All water quality results from 2011 and are compiled in Appendix C. Average results are summarized in Table 2. Monthly water production from sources is summarized in Figure 2 for the period when water quality samples were collected. Table 3 summarizes these data as percent annual production. 13

14 City of Lacey 2018 Corrosion Control Evaluation Table 2. Average Source Water Quality Results, 2011 and Site Temp C ph Specific Conductance (µs/cm) TDS Free Chlorine Total Chlorine Alkalinity (mg/l CaCO3) Hardness (mg/l CaCO3) Calcium Iron Manganese Silica Chloride Sulfate S < S <0.1 < S04* <0.1 < S <0.1 < S <0.1 < S S <0.1 < S S < S <0.1 < S <0.1 < S <0.1 < S <0.1 < S <0.1 < S <0.1 < S <0.1 < *Results for ph and alkalinity from S04 are entry point samples collected from (after installation of ph adjustment) 14

15 gallons produced 450,000, ,000, ,000, ,000, ,000, ,000, ,000, ,000,000 50,000,000 0 Figure 2. Monthly source production during distribution sampling May 2017 April 2018 Table 3. Percent annual source production during distribution sampling May 2017 April 2018 Well S01 S18 S04 S06 S07 S09 S10 S17 S20 S23 S24 S25 S27 S28 S29 S32 % Page 15

16 Table 4 provides lead and copper from corrosion study samples and compliance inorganic contaminant (IOC) samples collected within the study periods. Lead and copper concentrations are below detection limits at most entry points, although there have been intermittent detections of both lead and copper. Table 4. Lead and Copper at Entry To Distribution Source Compliance IOC Data, Lead Copper 2011 Study Lead Dec 2016 source samples Lead mg/l) Compliance IOC Data, 2017 Lead Copper Study Lead S01 <0.002 < 0.02 <0.001 < < 0.02 NS S04 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S06 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S07 < <0.001 <0.001 < <0.001 S09 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S10 <0.002 < 0.02 < <0.001 < 0.02 <0.001 S17 <0.001 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S18 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S19 <0.002 < 0.02 <0.001 <0.001 NS NS <0.001 S20 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S24 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S25 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S27 <0.002 < 0.02 <0.001 <0.001 <0.001 < 0.02 <0.001 S < 0.02 <0.001 <0.001 < <0.001 S29 < <0.001 <0.001 NS NS <0.001 NS = not sampled 3.2 Distribution Tap Water Quality Twelve distribution taps (sample stations) were sampled at least quarterly from July 2017 to April 2018 to represent water quality in the distribution when supplied by sources currently used by the City of Lacey. Locations of the taps in relation to the system s pressures zones are shown in Figure 3. Eight of the sites were also sampled quarterly in 2011 for the 2014 Corrosion Control Study; sites were originally selected from Lacey s Stage 1 and Stage 2 disinfection byproducts sampling programs but changes were made to improve the geographic distribution and to sample near Tier One sites where customer lead and copper tap samples were collected in The ranges of water quality parameters sampled in are provided in Table 2, and the ranges of ph at the tap sites are shown in Figure 3. The ph results, in particular, illustrate how ph in the distribution system increased from not using S01 or the intertie with Olympia; in 2011, the minimum ph measured in the distribution system was 6.5, but was 6.8 in These results also support the selection of sources for corrosion control, discussed further in Section 5. 16

17 S29 SS30 SS90 SS12 S25 S24 SS55 SS14 SS41 S07 S23 S28 SS11 S06 S01 S18 9 SS02 SS17 SS91 S20 S27 SS07 S09 S10 SS659 9 S04 9 Source well, ID# Distribution Sample Site Figure 3. ph Ranges at Distribution Tap Sites Sampled Orange and red dots show blending zones for sources S06, S17, S18, S20, S27, S23/S28, S24 and S25 17

18 Results for key parameters are summarized below in Table 5, and all results are provided in Appendix D. The ranges of results in Table 5 reflect the variations in water quality between the aquifers that supply the Lacey system. Distribution tap sites in the south part of the 337 zone showed the most variability between sampling rounds, reflecting the differences in water quality between sources S04, S09 and S10 that supply this area, and the high variability in the usage of these sources. Sites with high values for conductivity, alkalinity and hardness also indicate the migration of water from source S29, which pumps into the 400 zone but can supply the 337 zone via the Britton Parkway PRV. Table 5. Distribution Taps: Ranges of Results from Samples Collected Sample Station (pressure zone) SS zone SS zone SS zone SS zone SS zone SS zone SS zone SS zone SS zone SS zone SS zone SS zone ph (s.u.) Temperature ( C) Specific Conductance (µs/cm) Alkalinity (mg/l CaCO3) Calcium Sulfate Residential Tap Sampling for Lead and Copper Residential tap samples were collected in September 2016 and March 2017 to evaluate whether the inactivation of the Olympia intertie was sufficient for optimizing corrosion control in the Lacey water system. Source samples for lead were also collected in December Locations that were sampled are shown in Figure 4, which also shows locations where lead concentrations were above the maximum quantifiable level of mg/l. As shown in Table 6, the 90 th percentiles for both lead and copper were below Action Levels. However, the September 2016 results did not meet the requirements for a (b)(3) exemption because the difference between the 90 th percentile and the highest source lead concentration (0.001 mg/l) was not < mg/l. Sources supplying the system during customer tap sampling are shown in Figure 5. 18

19 Zone 275!!!!!!! PUGET SOUND Zone 375 Zone 224!!!! Lacey! Zone UV 510!!!!!!!!!!!!! Lead and copper tap sites sampled for first time in Zone 188 Zone 211 Zone 422!!! Zone 337! Zone 460!!! = Lead results mg/l = Lead results < mg/l Figure 4. Customer Tap Sample Sites,

20 gallons pumped Table th percentiles for Tap Samples Collected Number of mg/l Lead mg/l Copper Year tap samples 90 th percentile Max result 90 th percentile Max result < Source of table: Confluence (2018) The history of tap sampling for the main Lacey system is provided in Table 6; note that prior to 1998, the Lacey system included the main system, and two satellite systems. The systems were consolidated in Over the history of tap sampling, lead concentrations have generally been low, and 90 th percentiles were below Action Levels during each sampling period. For copper, 90 th percentiles have also been below Action Levels but maximum results were higher during earlier sampling rounds. Overall, tap sample results illustrate that the Lacey system has been in compliance with Action Levels, and while lead concentrations are generally low, copper release is more of an issue. 450,000, ,000, ,000, ,000, ,000, ,000, ,000, ,000,000 50,000,000 0 S30 S32 S29 S28 S27 S25 S24 S23 S20 S17 S10 S09 S07 Figure 5. Gallons pumped from sources in during Standard LCR tap sampling 20

21 3.4 Customer Complaints The city started maintaining a database of water quality and pressure complaints in As shown in Table 6, in recent years most documented water quality complaints are regarding brown water and brown staining, followed by taste and odor, and chlorine. The 2014 study report describes in more detail the history of copper-related customer complaints that were received by the city from Most of the complaints were from new construction in that time period, especially in the vicinity of untreated Lacey source S04. Since the ph adjustment facility for S04 came online in 2013, the city has received only one complaint related to copper staining. However, as discussed in Section 2.3.2, in the last 15 years or so, the use of copper plumbing in residences has declined considerably and is now relatively rare. Complaints relating to hard water increased after source S29 came online in Complaints have transitioned to questions, typically regarding what is scale and how to prevent scale buildup, and to request data to support the selection of on-premise water softening treatment; questions and data requests are not included in the complaint database. Table 6. Customer Water Quality Complaints, Year Brown water/ brown staining Blue water/ blue staining Taste and Odor Chlorine taste/odor Scale/ hard water Pressure high/low unknown the complaint database started in 1998; complaints related to copper in 1994 are from files 2 none recorded in the database 21

22 4.0 EVALUATION OF CURRENT CORROSION CONTROL IN THE LACEY SYSTEM Lacey s 2014 Corrosion Control Study concluded that ph adjustment at sources S04, S30 and S01 would optimize the system by addressing the most corrosive sources and by increasing the ph profile within the distribution system. At the time, corrosion control treatment at S04 was provided using caustic soda, and the City of Olympia was planning to install aeration to treat their McAllister wellfield (Lacey source S30). However, to date S04 is Lacey s only source with corrosion control treatment, since neither S01 nor S30 are supplying the system. For this 2018 Study update, water quality data from Section 3 were used to evaluate sources that are currently supplying the Lacey system. Because corrosion scales play an important role in metals release, this section includes a discussion on corrosion scales, followed by an evaluation of the solubility of lead and copper scales as a function of ph and dissolved inorganic carbon (DIC) found at each of Lacey s sources. This solubility analysis forms the basis of the treatment recommendations discussed in Section 5. The analysis in this section, and treatment recommendations in Section 5, are from solubility modeling and a water quality evaluation conducted by Confluence Engineering Group, LLC for the City. Confluence provided their findings and recommendations in a Technical Memorandum that is summarized below and cited within this report as Confluence (2018). The full Technical Memorandum is provided in Appendix B. 4.1 Passivating Scales Passivating scales are corrosion products that form and accumulate on the pipe surface, leaving protective layers (scale) that suppress further metal release. Confluence (2018) described that, scales can be complex, layered, and impacted by the water quality the pipe has been exposed to in the past. Scales can form naturally over time, but can also be induced by ph/alkalinity adjustment or the addition of corrosion inhibitors. Whereas corrosion is the electrochemical interaction that mobilizes lead and copper from source materials, interactions between corrosion products (scales) and the physical, chemical and biological characteristics of water will affect the release of metals into drinking water. However, source water quality is often the main driver for metals release. Copper On copper pipe, the initial scales that form depend on water quality and physical properties. Generally in new pipe the initial scales that form on elemental copper are cupric hydroxide (Cu(OH) 2) and cuprite (Cu 2O), which are relatively soluble scales. Total copper release is initially controlled by oxidationreduction reactions, and as the layers form and age, precipitation and dissolution can become the primary mechanisms controlling copper release (Xiao et al., 2007). The chemistry of the pipe surface will change as the scales form, dehydrate, grow thicker, and age. Generally the most corrosion protection is provided when outer scales consist of relatively insoluble forms such as tenorite (CuO) or malachite (Cu 2 (OH) 2 CO 3). Formation of these scales will depend on conditions present in the system that can either hasten or inhibit the transition to these more insoluble forms. Another complicating factor is that one or more forms of scale can be present, and can control the release of soluble as well as particulate copper (Xiao et al., 2007). Lead Scales that form on lead-containing pipes and fixtures are typically dominated by hydrocerussite (Pb(II) 3(CO 3) 2(OH)2) or cerussite (Pb(II)CO3). Lead oxide (PbO 2) can dominate under highly oxidizing conditions, such as maintaining a high free chlorine residual. Other lead scales can dominate but co-occur with these lead carbonate scales in the presence of high alkalinity or ph >10. When corrosion inhibitors 22

23 are used, lead scales formed will depend on whether orthophosphate or blended phosphates are used (EPA 2016). 4.2 Solubility Modeling The Lacey water system is complex; it has multiple pressure zones and multiple source entry points. The twenty sources supplying the system draw from three aquifers with varying water quality characteristics. Passivating scales that form in residential plumbing will vary depending on which sources supply the homes, whether scale is in equilibrium with water, and whether there are other physical, chemical or biological factors affecting corrosion. Although models cannot address all of these factors to predict absolute values for solubility of lead and copper scales, models can provide conservative estimates of likely trends in solubility (Confluence 2018). Solubility modeling for this study was conducted by Confluence Engineering Group LLC using WaterPro The solubilities of lead and copper were modeled for each source, using median water quality values at source entry points and the dominant scales expected to be present. Lead solubility was modeled for cerussite as the dominant lead scale present, and modeling predicted little variability between sources for lead solubility. Because aging of copper scale is a significant factor for copper control, Confluence modeled copper solubility for both insoluble cupric hydroxide scale and soluble malachite scales. The predicted solubilities of lead and copper are shown in Figure 6. As shown in the figure, sources S04, S07, S09, S10 and S19/S32 are the least corrosive to copper scale typically formed in new copper pipe (cupric hydroxide), and sources S06, S17 and S18 are the most corrosive to new copper pipe. However, once scales age and malachite scale is formed, copper solubility at all sources is predicted to be reduced considerably. Figure 6. Theoretical Lead (cerussite) and Copper (malachite and cupric hydroxide) Solubility at Each Entry Point (source: Confluence(2018)) 23

24 Confluence then grouped the sources based on ph and DIC (Table 7) and used solubility modeling to evaluate the impact of ph adjustment on lead and copper solubilities. Figure 7 shows the modeled solubilities of lead, aged copper and new copper for these groups. Table 7. Source Grouping under Current Treatment Conditions Group Sources DIC ph TDS Ca ALK mg/l as C s.u. mg/l mg/l mg/l as CaCO3 G1 9, G2 20,23,24,25,27, G3 4,7, G4 6,17, G Source: Confluence (2018) Based on the solubility modeling results for individual sources and the grouped sources, Confluence (2018) reached the following conclusions: Lead solubility is in good control as long as ph is 7.0. Given that the system is in compliance with the copper action level, the sources are optimized for copper under the existing lead and copper rule but there can be some marginal benefit by raising ph to 7.0 if tenorite is present on aged pipe surfaces. The Group 1 wells (S09 and S32) and Group 3 wells (treated source S04, and sources S07 and S10) have water quality that is not corrosive to lead or copper. The sources with combined higher DIC and lower ph are the most corrosive to new copper surfaces. These include the Group 4 wells (sources S06, S17 and S18) which have ph from and DIC of approximately 30 mg/l, and the Group 2 wells (sources S20, S23, S27, S28, S24 and S25) which have ph from and DIC of approximately 20 mg/l. Source S29 (Group 5) has low ph and high DIC, which not corrosive to lead but is corrosive to new copper due to its high DIC. Source S01 is highly corrosive based on data collected for the 2014 study, but was not included in this analysis because it has been offline and the City plans to replace the well. These observations and conclusions were then used to recommend a treatment strategy. 24

25 Figure 7a, 7b and 7c. Modeled Solubilities for Lead, Aged Copper and New Copper for source groups 25

26 5.0 RECOMMENDED TREATMENT FOR OPTIMIZING CORROSION CONTROL Confluence used results from solubility modeling along with source and distribution water quality to develop optimal water quality parameters and a prioritized, step-wise treatment strategy for adjusting ph at selected source wells. Treatment is focused on meeting requirements of the existing Lead and Copper Rule. Considerations for meeting anticipated changes to the Lead and Copper Rule, including revised treatment goals, are discussed in Section 6.4. Confluence recommended treatment at selected sources with the objective of raising the ph profile within the distribution system. This approach was selected mainly for lead control, but will also fully optimize the system for copper control under the current LCR. The treatment strategy discussed in this section is supported by a blending analysis and hydraulic modeling to assure that optimal water quality parameters can be met. 5.1 Optimal Level for ph Based on the solubility analysis, Confluence recommended the following water quality treatment goal: Optimal corrosion control treatment for lead is achieved at ph 7.0 in the distribution system. Optimal corrosion control treatment will be reached when each wellsite selected for ph adjustment treatment achieves a minimum ph of 7.4 at the entry point. Confluence did not recommend specific targets for alkalinity, noting that source wells have adequate alkalinity and do not need alkalinity adjustment. 5.2 Treatment Strategy Lacey s strategy for optimizing corrosion control treatment is to use a prioritized, step-wise approach that targets Lacey s most corrosive sources first for installation of treatment, followed by large sources that can increase ph throughout large areas of the system. Treatment is proposed at the following sources, in the following order: 1. Increase the caustic feed at source S04, to raise ph to 7.6. The treatment facility has sufficient capacity to increase the dose, and the City started implementing this recommendation in September Install ph adjustment treatment to increase entry point ph to at the following sources: a. Beachcrest wells (wellfield source S17). This will include sources S15, S16 and the new Beachcrest replacement well that is currently in construction. Adding treatment to these wells will address the most corrosive sources that supply the system at this time. b. College street wells 1, 2 and 3 (sources S01 and S18). Lacey is planning to drill a replacement well for Source S01 in 2020, so adding treatment at this site will coincide with construction of the new well. c. Madrona wells 1, 2 and 3 (sources S23 and S28). These wells have the largest capacity to supply the water system. These are large capacity wells that supply both the 400 and 337 pressure zones, and blend within a significant portion of the system. 26

27 This treatment strategy considers the complexity of the Lacey water system, the likely level of improvement in water quality with additional treatment, spatial distribution of the wells, and plans for additional supply and investments. Due to the significant amount of blending that occurs in the Lacey system, Confluence did not recommend treatment at all sources, particularly lower capacity sources S06 and S20, and did not recommend treatment at source S29, which is not corrosive to lead. Another consideration for treatment is that Lacey is still a growing system and is planning system improvements (e.g., new reservoirs, and piping connections) that will increase the use of treated sources in the future, and should increase blending in the system. Consequently, monitoring at customer taps and in the distribution will be an important element of the Action Plan for determining whether additional source treatment will be needed in the future. Monitoring will also support any needed changes that may need to be made when the Long-Term Lead and Copper Rule revisions are adopted. The Action Plan and monitoring are discussed in Section Blending Analyses and Hydraulic Modeling As noted in Section 4.2, source S04 is already treated, and sources S07, S09, S10 and S32 do not require treatment. Because the treatment strategy does not propose treatment at sources S06, S20, S24, S25, or S27, Confluence completed a blending analysis to evaluate expected ph in the distribution system when untreated sources blend with noncorrosive and/or treated sources. The ph targets include ph 7.0, to meet the requirements of the current LCR, and ph 7.2, which is anticipated to be a target for future revisions in the LT-LCR. The focus of the analysis was on sources S06 (Judd Hill), S24/S25 (Nisqually wells), S20 (McAllister) and S27 (Evergreen Estates), which all have ph < 7.0. The complete blending analysis is within Appendix A of Confluence (2018). To illustrate how treatment and blending can be used to meet the water goal throughout the system, and particularly at Tier One sites, Confluence graphed optimal blending ratios needed to meet ph 7.0 under a treatment scenario whereby sources S01/S18, S23/S28, and S27 are treated to a ph endpoint of 7.4. Lacey s hydraulic model was then used to assess where blending occurs in the system (Fig 9a), and to what extent the optimal blending ratios can be met by adding treatment to sources (Fig 9b). After the proposed treatments are installed, ph is predicted to be 7.0 throughout most of the distribution system, with two exceptions: the 188 pressure zone (supplied by wells S24 and S25), and a small area in the 400 zone that is supplied primarily by source S20. The blending analyses for sources S06, S24/ S25, S20 and S27 are discussed below Blending Zone for Source S06 The blending analysis completed for S06 is shown below in Figure 8. The analysis shows that ph 7.0 can be maintained by blending untreated S06 water with uncorrosive or treated sources, as long as the blends contain 75% S06 water. 27

28 Figure 8. Expected ph at different blending levels near Source 6 (Judd Hill) Source: Confluence (2018) Hydraulic modeling showed that these blends can be easily accommodated under current summer operating scenarios (Figure 9b). The amount of supply provided by S06 is shown in Figure 2 and Table 3; both show that S06 does not provide a lot of supply to the water system, particularly during winter months. The limited source of influence of S06 is evident in water quality parameter samples collected at sample stand SS02, located just east of source S06 (Figure 3). The average ph at SS02 during was 7.3, which indicates blending with noncorrosive source S07. Based on the blending analysis and hydraulic modeling, and very low production, S06 is not recommended for treatment. However, the Action Plan (discussed in Section 6) recommends adding a water quality parameter monitoring location in the blending zone of S06 to verify that the treatment goal is being met after treatments are installed. 28

29 Figures 9a and 9b. Maps of Hydraulic Modeling Under Summer Operation (9a left: Blending under Current Conditions; 9b right: Predicted areas above, and below ph 7 after Treatment Installation) Page 29

30 Sources S24/S25 Hot Spot Analysis for 188 Pressure Zone A hot spot analysis approach was used to evaluate the long-term impact of providing untreated S24 and S25 water at customer s taps, and to support a decision to not add corrosion control treatment on sources S24 and S25. The 188 pressure zone is a good candidate for this analysis, since there has been little change in the source of supply, and residences served, for over 20 years. Also, there is a period of record of LCR tap samples that have been collected in the 188 pressure zone since Sources S24 and S25 have always been the main source of supply to this part of the water system. Both wells are pumped every month, but S25 is the main source, supplying 70-80% of the demand. The area is a non-expanding part of the Lacey water system, due to Thurston County regulations that limit development within the flood plain of the Nisqually River. As a result, Lacey s 2013 Water System Comprehensive Plan projected 0% growth for single family, multi-family, and commercial connections from According to the Water Comprehensive Plan, in 2011 there were 241 water connections in the 188 pressure zone, which at the time represented 1% of the total number of connections supplied by the Lacey Water system and 1.4% of the ERUs. These percentages were used to justify the sample size evaluated for the Hot Spot Analysis. As shown in Table 7, there have been six rounds of LCR sampling with 5 samples collected. This is an adequate sample size to evaluate the 188 zone, since during these years the entire Lacey water system was required to collect at least 30 samples under its reduced monitoring schedule. Meaning, samples collected from the 188 zone in 2002, 2005, 2008 and 2011 comprised over 15% of the total system sample pool, but represented approximately 1% of the total population served. The 90 th percentiles for both lead and copper were below Action Levels. When compared to 90 th percentiles for the entire system, the 188 pressure zone had comparable 90 th percentiles for lead, and lower 90 th percentiles for copper. Of 63 samples collected since 1993, the only samples > mg/l (three total) were collected during the 1993 and 1995 sample rounds. Table 7. Summary of LCR samples collected within the 188 pressure zone 188 zone System LCR yr n max Pb 90 %ile Pb max Cu 90 %ile Cu 90 %ile Pb 90 th %ile Cu NA 0.46 NA < not sampled 30

31 In 2011, LCR tap samples were collected on September 20, Water quality samples were collected from sources S24 and S25, and at sample station #55 in the 188 zone, on October 5, These samples were collected to support Lacey s 2014 Corrosion Control Study, and illustrate water quality at the time the LCR tap samples were collected (Table 8). Table 8. Water quality in 188 PZ when 2011 LCR samples collected Site Date ph Alkalinity (mg/l CaCO3) Hardness (mg/l CaCO3) Temp C Calcium Chloride Sulfate Avg ph, 2011, S24 10/4/ S25 10/4/ SS55 10/5/ from quarterly samples results in Appendices C and D. The ph results from each of the sites are no different from average results from quarterly samples collected in 2011, and (Appendices C and D). Overall, the history of LCR tap sample results show that there is little risk of exceeding Action Levels in the 188 zone when not adding treatment to sources S24 and S25. Consequently, treatment is not recommended at this time to meet the current Lead and Copper Rule Blending Zone for Source S20 Blending ratios for S20 were evaluated for blending with treated sources S23/S28 (the Madrona wells), and considered blending occurring within Lacey s Steilacoom and Union Mills reservoirs. Blends of S20 with the Madrona wells represent current operations in summer/higher demand periods, when the Madrona wells are used more. Blending S20 with the Madrona wells treated to ph 7.4 is shown in Figure 10. The blending analysis shows that ph 7.0 can be maintained as long as the blends contain 90% S20 water, or at least 10% treated water from the Madrona wells. Figure 11 shows where these blends occur, based on hydraulic modeling of areas receiving >90% S20 water (shown in red). Figure 9b also shows that the area where blending will not achieve ph 7.0 can be reduced by piping improvements proposed by the City. The reduced area (shown in orange) does not include any Tier One homes; most homes were constructed after Another consideration for source S20 is that it has a relatively small water right that is being fully exercised, so blends containing S20 water are not expected to increase, and actually should decrease over time. The conclusion from the analysis is that untreated S20 water presents very low risk to Tier One homes, so treatment is not recommended for source S20. However, this conclusion will be verified through the monitoring proposed in Section 6. 31

32 Figure 10. Expected ph at different blending levels for McAllister (S20) and treated Madrona (S23/28) Blending Zone for Source S27 Ratios for blending untreated S27 water with treated sources S23/S28 (the Madrona wells) is expected to be the same as for S20, since water quality at both sources is very similar. Consequently, ph 7.0 can be maintained as long as the blends contain <90% S27 water (or S27 combined with S20), i.e., blends contain at least 10% treated water from the Madrona wells. Figure 11 shows where hydraulic modeling predicts that ph will be < 7.0 if both S27 and S20 are untreated. This area does not include any Tier One homes. The hydraulic modeling analysis was based on current operations, but operating conditions are expected to change due to growth in water demand and planned system improvements. Primarily, blends with treated water from the Madrona wells are expected to consist of larger percentages of Madrona well water as demand and system improvements allow greater use of the Madrona wells during winter months. Consequently, as conditions change in the system it may not be necessary to add treatment onto S27, but the need will be determined by tap sampling conducted after treatment is installed at the Madrona wells. With this in mind, the Action Plan (Section 6) includes water quality parameter monitoring within the impact zone(s) of S20 and S27, and pre-designing treatment for S27 if needed in the future. 32

33 Figure 11. Predicted ph with source treatment at S17, S01/S18, S23/S Available ph Treatment Methods Lacey s 2014 Corrosion Control Study evaluated all required corrosion control methods and eliminated all from consideration except ph adjustment using caustic soda or aeration. Please see the 2014 study for detailed discussions on treatment evaluation. For this study, Confluence (2018) evaluated available treatment methods primarily passivation through ph/alkalinity adjustment and passivation through use of inhibitors based on updated information in the EPA Revised Corrosion Control Treatment Guidance Manual (USEPA 2016) and current industry practices. Confluence did not recommend using orthophosphate inhibitors because ph adjustment of sources to ph would be required anyway for orthophosphate inhibitors to be effective. But, based on the ranges of ph and DIC of Lacey sources, treatment options for reducing copper corrosion for source with ph less than 7.2. and DIC of 5-35 mg/l as C is to raise ph using potash, caustic soda, silicates, or aeration (USEPA 2016; Confluence 2018). 33

34 Lacey has caustic soda treatment at S04 and is familiar with its use. Advantages associated with caustic are, 1) the relatively low capital costs compared with aeration, 2) caustic dosing is relatively easy to adjust to different treatment end points, and 3) caustic would not significantly increase the alkalinity of the already fairly high alkalinity sources. However, the major downside to caustic soda is that it is a hazardous chemical requiring safety measures in the treatment plant to prevent exposure to the operators and accidental overfeed. Additional downsides include costs associated with operation and maintenance and rising costs of caustic product. Whereas soda ash or potash are not needed because Lacey source wells do not need alkalinity adjustment, Confluence noted that these could be used in lieu of caustic soda. Aeration is used successfully by the Cities of Olympia and Tumwater, and consequently is being considered for Lacey s sources. Aeration is in an attractive option because it does not add chemicals to the water and is safer to operate and maintain, and potentially will have lower lifecycle operations and maintenance costs. Confluence noted that aeration would be the most appropriate treatment strategy for higher DIC wells such as the Beachcrest wells. But, Confluence noted that a downside of aeration systems is that there is less flexibility to adjust ph endpoints, and there will be a limitation on the upper ph endpoints that can be achieved. Confluence estimated the percent carbon dioxide removals that would be needed to achieve ph 7.4 at the entry point for all the corrosive supplies, and found that aeration would need to strip 60-70% of the carbon dioxide. A higher ph endpoint than 7.4 may not be feasible for all sources Source S04 Source S04 is currently treated with 25% caustic soda and at the time OWQP and LCR tap samples were collected in , S04 was treated to ph 7.4 at the entry point. The well is operated at a maximum pumping capacity of 750 gpm, and since caustic treatment was installed, the well has produced an average of MG per year. The proposed adjustment to treatment is to increase the current dose to achieve a ph of 7.6 at the entry point. This change was implemented in September Increasing the dose to increase ph at S04 was easily accommodated using existing equipment with minor operational modifications. The treatment facility was originally sized for a larger capacity than currently available at the site, and there is additional metering pump capacity to increase the dose further if needed. There are three 1000-gallon tanks on site for storing caustic soda. The city currently gets monthly deliveries and uses an average of 1,500 gallons/month. Increasing the ph endpoint to 7.6 was estimated to increase chemical usage by about 135 gallons per month Sources S17, S01/S18, and S23/S28 Confluence recommends ph adjustment at these sources, and modeled planning level treatment estimates for the Group 2, 3, and 5 wells (i.e., all corrosive sources) using caustic soda, soda ash, and aeration. For each method, Confluence modeled chemical dosages or aeration needed to achieve ph 7.4, and to achieve the upper limit of ph that can be achieved without causing calcium carbonate precipitation. All three of these treatment methods are viable for treating sources S17, S01/S18 and S23/S28, and will be considered in more depth during the pre-design phase of the facilities. 34

35 6.0 ACTION PLAN This Action Plan addresses the schedule for implementation, and processes to be followed for using monitoring data to confirm when treatment is optimized. Possible next steps for actions or additional are also included here. In summary, this Action Plan includes the following: A schedule for the sequential approach to installing corrosion control treatment in the Lacey water system, starting with the most corrosive sources. A monitoring approach for collecting distribution tap samples and customer tap samples. A process for evaluating monitoring results to assess when treatment is optimized, and possible next steps, if warranted by the monitoring results, to meet current LCR requirements. Considerations for revisions to the LCR relating to new copper surfaces. 6.1 Schedule for Treatment Installation The schedule and approach to treatment is based on sequential addition of treatment facilities to achieve ph 7.0 in the distribution system. The schedule, shown in Table 9, addresses the more corrosive sources first, i.e., S01 and S17, but considers that the City has been planning to drill new replacement wells at both the S17 and S01 well sites, and the new wells need to be constructed and tested for yield and water quality characteristics in order to design appropriate treatment facilities. Note that the schedule for installing treatment at S23/S28 includes two additional years for land acquisition to be able to accommodate a new facility at the well site. Table 9. Schedule for Installing OCCT Year S04 S17 S18/S01 S23/S Increase caustic dose to Pre-design 1 Pre-design Pre-design 2020 Design Drill S01 replacement well 2 Design/Land Acquisition 2021 Construction Design Design/Land Acquisition 2022 Startup Construction Design/Land Acquisition 2023 Startup Construction 2024 Startup 2025 Collect tap samples & Identify OWQPs for sources 1 Replacement well for S15 drilled late 2018, currently in construction 2 Replacement well for S01 is anticipated to be approved as part of wellfield S18 35

36 6.2 Monitoring The Department of Health has requested that when Lacey submits its Project Report for treatment installation at sources S23/S28, the report should include a Sampling Plan that addresses distribution OWQP tap sampling, customer tap sampling for lead and copper, and entry point OWQP sampling. The Department will then request that the City recommend Optimal Water Quality Parameters for all entry points, and after that the Department will assign OWQPs and Lacey s monitoring requirements for determining compliance with optimal corrosion control treatment. The following monitoring steps include baseline monitoring to help evaluate blending assumptions and treatment effectiveness as the three facilities come online, as well as considerations for entry point, distribution and customer tap monitoring that will be required after treatment is installed Distribution Monitoring Before OCCT Installed Baseline monitoring for water quality parameters (WQPs) will start in 2019, and will determine baseline conditions throughout the system, especially in blending areas of sources that will remain untreated under this Action Plan. In addition to the twelve (12) distribution sites sampled for this study (see Table 5 and Figure 3), distribution sample locations will be added in the following areas: S06 (Judd Hill) in blending zone with S18 S20 - in blending zone with Madrona wells S27 in blending zone with Madrona and Union Mills reservoir (337 zone blended water). Nisqually Confluence (2018) recommended collecting distribution samples quarterly, for the following parameters: ph, temperature, alkalinity, and conductivity. After OCCT Installed After the third treatment facility is installed (at sources S23/S28), the frequency of distribution monitoring will be increased to monthly to determine the effectiveness of achieving the goal of at least ph 7.0 in the distribution system blending zones. Samples will be collected for ph, alkalinity, and conductivity. This robust data set will be used by Lacey to recommend optimal water quality parameters (OWQPs) for each source, i.e., the minimum ph at the entry point of each source once treatment is optimized for the system Customer Tap Sampling Customer tap samples will be collected in 2025, after the third treatment system is installed (at source S23/S28) and treatment systems at S17, S01/S18 and S23/S28 have been operational and meeting entry point targets for at least 4-6 months. Based on the current LCR requirements, sampling will consist of two consecutive 6-month rounds of LCR tap monitoring that prioritize Tier 1 homes. Sampling may need 36

37 to be modified to comply with sampling and schedule revisions in the LT-LCR. Results of tap samples will be evaluated using the process shown in Figure 12. Figure 12 provides a process for determining whether treatment is optimized under the current Lead and Copper Rule, and next steps to take if Action Levels, or the water quality target, are not met Entry Point Monitoring Monitoring at all entry points (including untreated sources) is required after treatments are installed. Biweekly monitoring, at a minimum, will be required at entry points for ph and chemical dosing (if applicable). However, more frequent monitoring, even in-line monitoring, is recommended to more closely track treatment and to minimize the potential for incurring treatment technique violations. Violations are determined as a function of the frequency of monitoring, so more frequent monitoring allows for more timely correction of drifting or outlier results. Rather than monitoring all entry points, Lacey anticipates reducing the number of sites that will be monitored by identifying representative entry points for untreated sources that have similar water quality. In-line monitoring analyzers will be installed at all treated sources. Ideally, in-line analyzers will be installed at the representative untreated sources at least one year before OWQP monitoring requirements take effect. 6.3 Evaluation Process for Optimization Figure 12 provides a process for determining whether treatment is optimized under the current Lead and Copper Rule, and next steps to take if Action Levels, or the water quality target, are not met. This process is applicable to the current LCR, but will likely need to be re-evaluated according to requirements of the revised LCR after the LT-LCR is adopted. Ultimately, customer tap samples will indicate whether additional treatment needs to be added to the system. The City is proactively planning to predesign treatment for source S27, in case customer tap samples exceed Action Limits and treatment must be installed within a Federally mandated timeframe. However, this is not anticipated to be necessary since the system has been in compliance with Action Levels since the Lead and Copper Rule was enacted. Distribution monitoring results will indicate whether blending meets the water quality target within blending zones for untreated sources S06, S20 and S27. If ph in the distribution is < 7.0 in any of these blending zones, Figure 12 identifies next steps, including operational changes to improve CCT. Operational changes may include the following: increasing ph at entry points changing call orders to increase amount of treated water entering the distribution system changing settings on pressure reducing valves to promote As shown in Figure 12, if Action Levels continue to be met but ph targets are not met within the distribution system, the City may choose to conduct a Hot Spot analysis within the impact zone(s) that are not meeting ph 7.0. The city will coordinate with the Department on the design of a hot spot analysis, particularly in blending zones that have few, if any, Tier One homes. 37

38 Figure 12. Flowchart for Evaluating Tap Monitoring Results 90 th percentile of LCR Tap Samples Pb mg/l Cu 1.30 mg/l Pb mg/l Cu 1.30 mg/l AL exceeded b(3) Criteria Met, System Optimized WQPs within optimal range? Identify what changed Yes No Identify Risk Areas System Optimized Increase Treatment Levels if Possible Evaluate Alternative Operational Strategies to Increase the Proportion of Non-Corrosive or Treated Sources to the Area Complete Investigative Tap Sampling Following DOH s Hot Spot Approach. If the issue is Copper, then prioritize on new construction System Optimized Pb mg/l Cu 1.30 mg/l 38 Pb/Cu AL Install Treatment to the source(s) supplying the area

39 6.4 Considerations for Revisions to the LCR For several years, EPA has been developing revisions to the LCR that include regulatory options for improving the existing rule to strengthen public health protection and to clarify implementation. Revisions are still in the process of being considered, and the schedule for updating the rule has been delayed several times. The current timeframe projects that a public review draft will be released sometime in While issues with the existing rule have been identified, there is still uncertainty regarding which issues will be addressed in the revisions and, more to the point, the specific requirements that will be associated with them. Dates for implementation will also be identified in the revisions Approach and Recommendations for Revisions Relating to New Copper Surfaces Anticipated revisions to the Rule include isolating and separating lead and copper tap monitoring, and may include monitoring sites with new copper installations. Revisions that address new copper surfaces could require increasing the water quality target for optimizing treatment in the Lacey water system, since solubility analysis (Section 4.2) identified several sources that are corrosive to new copper surfaces. Confluence recommended a water quality goal of ph 7.2 in the distribution system for protecting new copper surfaces. However, as noted earlier, at this time copper is not the material of choice for new development in Lacey, so it may be necessary to conduct a materials analyses within impact areas that do not meet ph 7.2 to evaluate whether copper plumbing is present. This will be particularly important within the 400 zone, where most new development is occurring and where blending analyses showed that ph 7.2 may not be met in the vicinity of untreated sources S20 and S27. If additional treatment appears to be warranted to increase ph in the 400 pressure zone, source S27 (Evergreen Estates) was identified as a potential for treatment because it has a larger pumping capacity, and a larger water right, than source S20. Lacey plans to pre-design treatment for S27 while the other sources are in pre-design, but will hold on to the plans while monitoring is occurring following treatment at sources S23/S28. 39

40 References City of Lacey, City of Lacey Corrosion Control Evaluation Final Report. March Confluence Engineering Group, LLC ph Treatment Recommendations, Water Quality Consultant Project Task 1, December 28, HDR, City of Lacey Well 4 Final Treatment Process Selection Report. January RH2 Engineering, Wells Nos. 1, 2, and 3, Well No. 4, and Madrona Wells ph Adjustment Facilities. Technical Memorandum July 13, Sandvig, A.M., Non-leaded brass A summary of performance and costs. Journal AWWA, 101:7:83. USEPA Optimal Corrosion Control Treatment Evaluation Technical Recommendations for Primary Agencies and Public Water Systems. EPA 816-B March Washington State Department of Health, Water System Design Manual. DOH (Rev. 12/09). Xiao, W., S. Hong, Z. Tang, S., Seal, and J.S. Taylor, Effects of blending on surface characteristics of copper corrosion products in drinking water distribution systems. Corrosion Science 49(2007) Zhang Y., and M. Edwards, Zinc content in brass and its influence on lead leaching. Journal AWWA, 103:7:76. 40

41 Appendix A from DOH Outlining OCCT Steps for Lacey 41

42 42

43 43

44 Appendix B. Technical Memorandum from Confluence Engineering Group, LLC (2018): ph Treatment Recommendations 44

45 To: Puna Lovell, City of Lacey Subject: FINAL - ph Treatment Recommendations From: Virpi Salo-Zieman, PE Melinda Friedman, PE Stephen Booth, Ph.D, PE Danbi Won, EIT Project: Water Quality Consultant Project, Task 1 Amendment 1 CC: Julie Rector, City of Lacey Date: December 28 th, 2018 CONTENTS 1. Introduction Background Literature Review The Role of Scales Optimal Corrosion Control Treatment (OCCT) Strategies Potential Long Term LCR Revisions (LT-LCR) City of Lacey Water Quality Evaluation Lead and Copper Tap Samples Solubility Modeling Distribution System Water Quality Treatment Evaluation Point of Entry Optimal Water Quality Parameters (OWQPs) Existing LCR Point of Entry OWQPs Future LT-LCR Distribution System OWQPs Existing LCR Distribution System OWQPs Future LT-LCR Chemical Selection and Dosing Additional Water Quality Considerations Summary of Findings and Recommendations References Appendix A Blending Analysis Appendix B Action Plan Appendix C - Planning Level Cost Estimates for Caustic Soda ph Adjustment Facilities (RH2 Engineering) Page 1

46 1. Introduction The City of Lacey (City) contracted with Confluence Engineering Group, LLC to develop an optimal corrosion control plan for the City. The objective of this Task is to evaluate Lacey s current water quality against the drinking water industry s current understanding of optimal corrosion control and determine if adjustments are needed. The evaluation considered the following: Current water quality and treatment conditions Existing Lead and Copper Rule (LCR) requirements, which drive the basis for optimization recommendations in this report Impacts of possible long-term revisions to the LCR (LT-LCR) and future optimization considerations Key recent literature and generally accepted industry practices Lead and copper solubility theory 2. Background According to City s Water Resources staff: Lacey s service population increased above 50,000 people and therefore, the water system is now considered a large system under the LCR. As a large system, the City must complete a corrosion control study and provide optimal corrosion control Since the previous study (completed in 2014), the City has stopped purchasing water from the City of Olympia, which used to provide close to 30% of the total supply. Other changes include inactivation of Source 1 (Well 1) and addition of a new source (S31) in the Hawks Prairie wellfield. Well 1 is scheduled for replacement in the future. The City has also made upgrades that allow for expanded use of the Madrona wells (S21, S22, S28). During 2016 and 2017, Lacey collected two standard monitoring sets of lead and copper tap samples with a goal to qualify for the b(3) exemption (40 CFR (b)(3)) that would have deemed the system optimized for corrosion control without further steps. The results from these two sets showed that the City continues to meet both action levels, but only met the b(3) 90 th percentile Practical Quantitation Level criteria of mg/l for lead in one of the two sample rounds (the 90 th percentile lead levels for 2016 and 2017 were mg/l and mg/l, respectively). Therefore, this corrosion control evaluation was required and the City needs to have optimal water quality parameters assigned. 3. Literature Review When the LCR was first promulgated in 1991, EPA established maximum contaminant level goals (MCLGs) of zero for lead and 1.3 mg/l for copper. While the rule has been revised several times and corrosion theory has evolved, these goals have not changed indicating them being adequately protective of public health. Significant changes in the corrosion theory relate to lead corrosion and optimal corrosion control treatment (OCCT). Advances have also been made in understanding factors impacting copper corrosion. Current industry knowledge of corrosion as it relates to the City s water system is summarized below. Page 1

47 3.1. The Role of Scales The scales that have formed on the pipe surfaces over time control the effectiveness of (and ability to optimize) corrosion control treatment. The scales can be complex, layered, and impacted by the water quality the pipe has been exposed to in the past. The scales are considered to be either passivating films that are formed when the pipe material and water react directly with each other, or deposits of precipitated or otherwise sorbed compounds (EPA 2016). The characteristics of the scale and its structure determines how much metal could be released into the water. The most desirable conditions support the formation of insoluble and adherent scales such as lead and copper oxides. Soluble and less adherent scales tend to release more metals. Releases can also be expected with changing water quality conditions when the scales are trying to reach a new equilibrium. Lead pipe scales are typically dominated by hydrocerussite (Pb(II) 3(CO 3) 2(OH) 2) or cerussite (Pb(II)CO 3), which are both Pb(II) -carbonate compounds. Under highly oxidizing conditions, lead oxide, a Pb(IV)- compound, can form and become the dominant mineral. Copper-based scales are typically cuprite (Cu(I) 2O), cupric hydroxide (Cu(II)(OH) 2, tenorite (Cu(II)O), and malachite (Cu(II) 2(OH) 2CO 3). When orthophosphate is used, these metals tend to form various phosphate scales (EPA 2016). The presence of other metals such as aluminum, iron or manganese, calcium, or organic matter will also influence the type and properties of the scales that form. Solubility models predict the metal solubility from the scale in equilibrium with the water. It is important to note that theoretical models generally tend to over-predict soluble concentrations, and therefore, can be considered conservative. Because they do not predict absolute values, they should be used to evaluate likely trends in solubility, rather than actual metals concentrations presented on the y-axis. Additional limitations with use of theoretical models include: Models assume conditions at equilibrium o o The time component to reach equilibrium under varying distribution system water quality conditions is not known. Frequent changes between significantly different source water qualities, such as low DIC surface waters and high DIC groundwaters, likely prevent equilibrium from being reached. Models represent specific chemistry conditions o o Real world distribution system conditions vary considerably seasonally, spatially, etc. Models do not consider impacts of competing ions, or other chemical, physical, and microbial conditions that affect scale formation and stability in distribution systems. Pb(II) and Cu(I/II) Solubility Figure 1 shows the classical ph/alkalinity diagrams for lead and copper solubilities developed by Schock and Lytle (2011). These diagrams show lead and copper solubility as a function of ph and DIC, for a wide range of DIC conditions. These indicate that at ph of less than 8, increasing DIC generally lowers lead solubility, while around ph 8, lead solubility flattens out for some DIC conditions, and then there is a flipflop, where increasing DIC causes increased lead solubility. Copper solubility tends to decrease with decreasing DIC at any ph level and generally with increasing ph. Copper solubility and release due to uniform corrosion in the system is not only related to the water quality characteristics and conditions (ph, DIC, ORP), but also to the aging process of the pipe materials and scales. According to Schock and Lytle (2011), in the most ideal case, uniform corrosion of copper is Page 2

48 inhibited by the formation of a duplex film consisting of a layer of cuprite, Cu 2O, underneath a layer of either tenorite or malachite. While these layers will theoretically form under equilibrium conditions, the process can take years, even decades, and includes intermediary steps with more or less stable and soluble compounds (such as cupric hydroxide solids (Schock and Lytle 2011)). More research is needed to understand the complex chemistry of aqueous copper and potential public health implications. As discussed below, revisions to the LCR may require additional sampling at newer copper installations. Although plumbing materials present in the City s water system are at different stages of aging and experience different dominant scale types, a conservative approach for considering compliance with the LT-LCR would be to assume fresh copper surfaces and the presence of cupric hydroxide, the more soluble intermediate copper scale. Figure 1. Lead and Copper Solubility as a Function of ph for Varying DIC (Schock and Lytle, 2011, and 2018 webinar) A similar solubility evaluation approach was used to evaluate the corrosive tendencies of the City s source waters. The theoretical lead and copper solubilities were modelled under current water quality conditions using WaterPro_6.30 and are discussed in Section Optimal Corrosion Control Treatment (OCCT) Strategies The current industry understanding of OCCT for lead and copper control has advanced into the following: 1) Passivation through ph/alkalinity adjustment 2) Passivation through use of phosphate- or silicate-based inhibitors 3) Formation of a Pb(IV) scale through maintenance of a high free chlorine residual/high oxidationreduction potential (ORP) These OCCT strategies are all based on controlling soluble lead and copper. However, optimal corrosion control treatment can also reduce particulate lead to some degree when stable scales are formed and maintained. Calcium carbonate precipitation is no longer a recommended treatment technology for lead and copper control since it has been found to be non-uniform across plumbing surfaces. Additional information on these treatment strategies is provided in Table 1. Page 3

49 Higher ORP, which is largely controlled by secondary disinfectant type and residual, impacts the formation of lead (IV) scales, iron release, manganese release, and co-occurring lead present in iron and manganeserich scales. The role of microbial influenced corrosion can also be an important factor contributing to metals release in distribution systems and premise plumbing (AWWA M58, 2017). The lead and copper rule working group (LCRWG) has defined a range of water quality conditions that are considered corrosive to homes with new copper (Figure 2), since these conditions prevent passivation of new copper surfaces. Further or additional actions may be required when water quality falls within the shaded, corrosive area, as discussed in Section 5. Figure 2. Conditions that are Corrosive to New Copper Surfaces as Defined by the Lead and Copper Rule Working Group (Roth et al., 2016) 3.3. Potential Long Term LCR Revisions (LT-LCR) The LCR is undergoing revisions. In addition to potential changes to OCCT described above, other issues with the current LCR may be addressed through the revision process. A series of stakeholder meetings have been held over the past several years, and the following issues have been raised for consideration. Some of these considerations are based directly on lessons learned from the developments in Flint, Michigan: EPA recognizes that the LCR is too complicated to comply with and enforce. A more prescriptive regulation, with less discretion/judgment allotted to utilities and states is needed. A more integrated approach to minimizing lead exposure is needed, considering contributions from water, paint, soil, dust and other potential sources. Proactive lead service line (including gooseneck) replacement programs may be required. Clarifications of sampling requirements are needed, such as the recent directive prohibiting flushing before stagnation period and use of narrow-mouthed bottles. Need for increased optimal water quality parameter monitoring to verify process control. Need to establish health-based, household action levels for lead. Need for a health-based benchmark for lead (rather than action level) to communicate health risk. Isolate and separate lead and copper issues. Strengthen transparency and public education programs, particularly for at-risk populations. Page 4

50 Specific requirements and the degree to which the items listed above will be included the LT-LCR are currently uncertain. The release date for the draft LT-LCR has been delayed several times. The current projection is that a draft will be released for public comment in Page 5

51 Table 1 Overview of Corrosion Control Treatment Options (Source: Confluence Engineering Group Project Files) Technique and Chemicals Used Benefits Challenges and Problems Calcium Carbonate Precipitation Potential (CCPP) Raise ph and adjust Calcium Increase CCPP to 4-10 mg/l Maintain positive Langelier Saturation Index. Limited Poor/ineffective lead and copper corrosion control Does not form uniform, non-porous passivated layer Can have excessive precipitation and reduction in pipe capacities. Carbonate Passivation Raise ph and/or alkalinity Various combinations of caustic soda, carbon dioxide, soda ash, sodium bicarbonate, and/or lime Carbon dioxide stripping Inhibitor Addition Phosphate addition (using zinc orthophosphate, phosphoric acid, or tripotassium phosphate) Silicate addition (various percent concentrations and ratios) Formation of Pb(IV) Scale Use elevated free chlorine residual to favor formation of Pb(IV) scales Binds lead and copper by forming carbonate complexes Suitable in lower-alkalinity water if adequate buffering capacity maintained Creates beneficial ph conditions for stabilizing chloramine residual (where used) Does not add nutrients to water Possibly requires only single chemical addition Binds lead and copper by forming phosphate complexes Possibly provides longer-lasting protection against intermittent fluctuations in treatment (e.g., blending with other waters, treatment interruption) Effective over a range of water quality conditions Pb (IV) scale is less soluble and more stable compared to Pb (II) scale formed under routine oxidation-reduction conditions Can cause CCPP in hard waters (white precipitate) Significant fluctuations in ph and DIC (e.g. surface water vs groundwater) can cause lead-carbonate to dissolve, porous scales, particulate lead May require multiple chemical additions to hit specific ph/alkalinity/dic targets in low alkalinity waters Some alkalinity-adjustment chemical feed systems (solids/powders) can be difficult to operate Polyphosphate is not effective for lead control Silicate is very expensive and not used in larger applications Silicates can raise ph of finished water Orthophosphate effective over ph range Increases downstream wastewater nutrient (and zinc, if used) loading Nutrient loading may promote biofilm growth if disinfectant residual decreases, and will promote algae growth in exposed reservoirs Insufficient dose can accelerate corrosion, and overdose can cause milky water Nutrients may exacerbate microbially-influenced corrosion Can form increased disinfection by-products Can result in increased customer taste and odor complaints Page 6

52 4. City of Lacey Water Quality Evaluation 4.1. Lead and Copper Tap Samples The history of lead and copper tap sample results were characterized in the City s 2014 Corrosion Study and updated through In general, copper levels have decreased and lead levels have remained low. Table 2 presents the 90 th percentiles for the compliance sample sets for the Lacey main system (excluding historical results of any satellite system like Beachcrest that have since been consolidated into the main system). Table 2. Lead and Copper Tap Sample Results Number of mg/l Lead mg/l Copper Year tap samples 90 th percentile Max result 90 th percentile Max result < Based on historical monitoring results, the system meets both action levels and therefore, by definition the City can be considered optimized for copper corrosion under the current rule and qualified for reduced monitoring. Yet the results show that copper levels are somewhat elevated, and if the LT-LCR were to separate copper sites from lead sites and require sampling from newer copper construction, further action to reduce copper corrosion may be required. Lead results are low indicating good lead control. In fact, the City failed to meet the b(3) definition of optimization by mg/l in one of two full monitoring rounds (2016). Had the City met the b(3) criteria, no further treatment would be required for either lead or copper under the current LCR. However, if the future rule includes an individual household action level, further measures may be needed to address specific locations. The modeling scenarios in Section 4.2 help identify which wells would benefit most from additional treatment Solubility Modeling The City has monitored water quality characteristics at entry points and at twelve sites in the distribution system on a quarterly basis in 2011 and approximately every two months starting July The medians of the available data at each entry point were used to evaluate the theoretical lead and copper solubility in thermodynamic equilibrium with the minerals predicted by the model (WaterPro_6.30) to be most prevalent in the scale. Table 3 summarizes the water quality for the currently active sources. Figure 3 shows the corresponding modeled lead and copper solubilities. Because of the aging process of the copper scales, the modeling was completed for both cupric hydroxide (new surfaces) and malachite (aged surfaces). As shown in the figures, once malachite is formed, the copper solubility is significantly lower, and on the same scale as copper results measured by the City during LCR sampling. According to the City, the vast majority of copper within the City s system is aged, since most new construction is using PEX plumbing, rather than copper plumbing materials. The dominant lead scale is predicted to be cerussite (Pb II) based on the water quality at the entry points. In areas where Page 7

53 chlorine residuals are typically greater than mg/l, it is possible that plattnerite (Pb (IV)) could form, further lowering soluble lead levels. Table 3. Summary of Water Quality Characteristics used for Solubility Modeling at Each Entry Point 1 TDS ph Alkalinity Calcium Temp Chloride Sulfate DIC S# Source Name mg/l s.u. mg/l as CaCO3 mg/l o C mg/l mg/l mg/l as C S24 Nisqually 19a S25 Nisqually 19c S04 Well S06 Well 6C; Judd Hill S07 Well S09 Well S10 Well S18 Well 2 & S17 Beachcrest S32 Hawks Prairie S20 McAllister S23 Madrona 1& S27 Evergreen S28 Madrona S29 Betti Median values were calculated from the available data (quarterly samples in 2011 and July December 2017) for all other parameters except the highest calcium concentration was selected as a more conservative measure. Figure 3. Theoretical Lead (cerussite) and Copper (malachite and cupric hydroxide) Solubility at Each Entry Point Based on solubility modeling (Figure 3), the most corrosive sources to fresh copper surfaces are S6, S17, and S18. To evaluate the impact of ph adjustment with caustic soda on lead and copper (new and aged) Page 8

54 solubilities, the wells were grouped into categories based on ph and DIC. ph and DIC are the controlling variables for corrosion control when using carbonate passivation. The ranges of water quality for these groups are presented in Table 4. The ranges of chemistry in the City s sources, specifically ph and DIC, behave differently for lead versus copper as described in Section 3.1 and shown in Figure 4 (a-c). Lead solubility tends to decrease with increasing DIC and ph until about ph 8, while copper solubility tends to decrease with decreasing DIC and increasing ph. Table 4. Source Grouping under Current Treatment Conditions Group Sources DIC ph TDS Ca ALK mg/l as C s.u. mg/l mg/l mg/l as CaCO3 G1 9, G2 20,23,24,25,27, G3 4,7, G4 6,17, G Figure 4(a). Modeled lead solubilities. Stars indicate the water quality groups; S1 represents water quality from the currently inactive Well 1. Page 9

55 Figure 4 (b). Modeled copper solubilities in equilibrium with malachite (solid lines) and tenorite (dashed lines) representing aged surfaces and existing LCR. Blue line shows the copper action level. Stars indicate the water quality groups; S1 represents water quality from the currently inactive Well 1. Figure 4 (c). Modeled copper solubilities in equilibrium with cupric hydroxide representing new surfaces for potential LT-LCR. Blue line shows the copper action level. Stars indicate the water quality groups; S1 represents water quality from the currently inactive Well 1. Page 10

56 The results from the solubility modeling with regard to the existing LCR and potential future LT-LCR are summarized below. Existing LCR 1. Lead solubility (Figure 4a) is in good control for higher DIC wells as long as the ph is 7.0. Some additional benefit is obtained with increasing ph to 7.2, with only marginal benefit associated with raising the ph above 7.2. The exception is under low DIC conditions ( 10 mg/l C). The City s sources with DIC of 10 mg/l C already have a median ph above 7.5 and are therefore optimized. 2. Aged copper surfaces (Figure 4b) show very low copper solubility with formation of malachite or tenorite. The City s sources are optimized with regard to copper solubility under the existing LCR given compliance with the copper action level. However, marginal additional benefit could be realized by raising the ph 7.0, assuming some tenorite is present (dashed lines). If malachite (solid lines) is the dominant copper form in the scales, very little additional benefit is anticipated by raising the ph 7.0. Future LT-LCR 1. As shown in Figure 4c, solubility of new copper surfaces (cupric hydroxide equilibrium) is predicted to significantly decrease until approximately ph 7.2, after which the degree of benefit begins to taper off, up to a ph of approximately The sources with combined higher DIC and low ph are the most corrosive to new copper surfaces. o Betti well (G5), with a DIC 40 mg/l as C and ph of 7.2, is corrosive to new copper surfaces due to its high DIC. Given the elevated hardness, it would be difficult to raise the ph further without causing significant calcium carbonate precipitation issues. Blending Betti water with either Hawks Prairie or Madrona will reduce the DIC and the corrosivity. o The Group 4 wells (Sources 6, 17, and 18), with DIC of about 30 mg/l as C and ph of are also corrosive to new copper surfaces. o There are two Groups (#2 and #3) with DIC of approximately 20 mg/l C. Sources 4, 7, and 10 (Group 3) already have entry point ph s around 7.4 and therefore, would not be considered significantly corrosive to new copper. The Group 2 wells have ph from and are considerably more corrosive to new copper surfaces. o Source 4 already has caustic soda addition in place and in the interim, increasing the level of treatment at this source to ph 7.6 would likely off-set the lower ph of several of the sources in the area (Sources 1, 18, and 6). The water quality from the other sources that also serve this area (Sources 9, 7, and 10) are considered non-corrosive. o Source 1 was not included in the above analysis because it was offline during the timeline. The City has now indicated that this well may be rehabilitated or replaced and brought back to service. According to the 2011 data and the one sample that was completed in 2017, this source has a finished water ph of 6.7 and DIC of 26 mg/l as C, which indicates highly corrosive characteristics to new copper surfaces. Page 11

57 4.3. Distribution System Water Quality The City collects distribution system water quality parameter (WQP) samples from 12 sites covering all pressure zones. WQP sampling locations are shown as yellow triangles in Figure 5. City sources are shown as blue stars. LCR tap monitoring locations are shown as green and purple dots, with purple indicating a location with lead > mg/l. Page 12

58 Figure 5. Water System Map. Location of sources (blue stars); WQP sampling sites (yellow triangles); LCR tap sample locations (green and purple dots). Page 13

59 DIC mg/l as C ph Results from 2011, 2017, and 2018 sampling rounds are shown in Figure 6. The large ph increase between 2011 and 2017 is primarily due to discontinuation of the Olympia supply Pressure Zone 400 Pressure Zone 188 Zone 224 Zone Sample Site 2011 Median ph 2017 Median ph 2018 Median ph Figure 6. Median Distribution System ph (2011, 2017, and 2018) The DIC in the distribution system (Figure 7) is mostly between mg/l as C, consistent with the majority of City s well supplies. The influence of low DIC Hawk s Prairie Well can be seen on site 36 in the 400 zone, while the influence of the high DIC Betti Well is not noticeable in the medians of the data set Pressure Zone 400 Pressure Zone 188 Zone Sample Site Figure 7. Median Distribution System DIC (2011, 2017, and 2018) 224 Zone 2011 Median 2017 Median 2018 Median 5. Treatment Evaluation The City s water system is complex with multiple pressure zones and sources that draw from different aquifers and have variable water quality characteristics. The City s LCR tap sample results indicate optimal conditions for copper under the existing LCR, and nearly optimal conditions for lead. Based on the 2017 supply records, about 34% of the total supply is already noncorrosive or does not require additional corrosion control treatment. Treatment recommendations summarized in this section consider this supply complexity, the likely level of improvement in water quality with additional treatment, spatial distribution Page 14

60 of the wells, blending of wells, and future plans for additional supply and investments. It is not feasible or likely necessary to treat all active sources that might be corrosive to new copper surfaces when some sources serve built-out areas that are not zoned for new construction. Furthermore, according to the City s Building Official, PEX started being used in the later 1990 s, and has been used in the majority of homes starting in It is now used almost exclusively in large developments. Therefore, the recommended approach includes prioritized and step-wise improvements that focus on optimizing corrosion control treatment to maximize public health protection associated with potential lead release, while also considering the need for enhanced copper control under a future, more stringent LT-LCR Point of Entry Optimal Water Quality Parameters (OWQPs) Existing LCR For the water quality characteristics of the City s supply portfolio, optimal corrosion control treatment for the existing LCR is achieved at ph 7.0. Given the complexity of the City s system and significant blending between sources, within reservoirs, and across pressure zones, not all sources will need treatment to reach ph 7.0 within the distribution system. ph 7.4 should be targeted for sources with existing treatment, those selected for future treatment, and any new wells that are brought on line in the future. Specific treatment recommendations are summarized below. Once treatment is installed as summarized below, the City s portfolio of non-corrosive sources will increase from approximately 34% to approximately 84% of pumped capacity. 1. Increase the caustic feed to raise ph at Well 4 to 7.6. The treatment facility was sized for a larger supply capacity than currently available at the site. The City should also add supply capacity at this site to fully utilize the existing treatment. 2. Install ph adjustment treatment to increase the entry point ph to at the following sources: a. G2 Wells: i. Madrona Wells 1, 2, and 3 (S23 and S28). As large capacity wells, this would benefit the 400 and 337 zones, and under some operating schemes, the 188 zone. ii. Evergreen Estates (S27) to address the areas of new growth that may include newer copper plumbing and typical winter operating conditions. b. G4 Wells: i. S18 in conjunction with replacing Well 1 (S1) which would result in ph increase in 337 zone. ii. S17 in conjunction with replacement of one of the Beachcrest wells Point of Entry OWQPs Future LT-LCR The future LT-LCR may require sampling from homes with newer copper plumbing. As shown in Figure 8, raising the ph of Groups 2 and 4, as proposed above, would also shift these sources into the noncorrosive zone for new copper surfaces. Page 15

61 Figure 8. Impact of Increasing ph of G2 and G4 Wells on Copper Corrosion 5.3. Distribution System OWQPs Existing LCR Some degree of blending will occur within the distribution system, raising the ph of a significant portion of the remaining 16% of untreated sources. A detailed blending analysis was conducted and results are shown in Appendix A, and used to support the recommendations below. Key WQP recommendations for distribution system sites under the existing LCR include: 1. The ph within portions of the distribution system that serve Tier 1 homes (potentially containing leaded materials) should be maintained A few small areas will likely continue to receive untreated water. The City will attempt to minimize these areas over time through: a. Operational modifications to enhance blending, b. Preferential source use, c. Increasing entry point ph for large producers (such as Madrona Wells), or d. Confirming through special monitoring and plumbing investigations that lead and copper levels are below action levels (i.e., Hot Spot analysis). Given the complexity of the system, a set of WQP Bins have been developed to visualize and track the anticipated impacts of treatment and blending, as shown in Figure 9. The overarching objective is to meet Bins 1 and 2, since they were developed to ensure optimal lead corrosion control, and should be beneficial under the existing and future LT-LCR. An Action Plan (Appendix B) has been developed to describe water quality monitoring (including routine and investigative monitoring) that will help to understand the impact from each source and installed treatment over time. This information will be used by the City to determine if: Optimization has been reached Treatment at additional sources or modifications to existing treatment is needed, or If other operational strategies should be implemented to ensure optimization under the current and future LT-LCR. The Action Plan may need to be modified once the LT-LCR is published and in effect. Page 16

62 Figure 9. Anticipated WQP Bins after Treatment Installation at S23&28, S18, S1, S17, and S27. (Note: if S27 is not treated, Bin 3 will also include areas that receive 50% S27) Distribution System OWQPs Future LT-LCR 1. The ph within portions of the distribution system that serve Tier 1 homes (potentially containing leaded materials) should be maintained The ph within the portions of the distribution system that are expanding and may have homes with newer copper plumbing should be maintained at 7.2. These areas should be identified through review of construction records combined with WQP monitoring after recommended treatments discussed in Section 5.1 are operational, in accordance with the City s LCR Action Plan Chemical Selection and Dosing Based on the EPA Revised Corrosion Control Treatment Guidance Manual (USEPA, 2016), the recommended treatment for reducing copper corrosion for source with ph less than 7.2 and DIC of 5-35 mg/l as C is to raise ph using potash, caustic soda, silicates, or aeration. Table 5 provides a summary of potential treatment strategies for all untreated sources (including increased caustic soda dosage at Well 4). Planning level cost estimates for treatment using caustic soda have been developed and are summarized in Appendix C. Cost estimates for soda ash and aeration are under development. The City has caustic soda treatment in place at S04 and is familiar with its use. Caustic soda would not significantly increase the alkalinity of the already fairly high alkalinity sources and would be relatively easy to adjust to different treatment end points. However, caustic is a hazardous chemical requiring safety measures in the treatment plant to prevent exposure (operators) and accidental overfeed. The estimated Page 17

63 dose to reach ph 7.4 and the maximum dose to avoid undesirable carbonate precipitation in the distribution system are presented in Table 5. Aeration is typically the most appropriate strategy for higher DIC wells such as in the City s Group 4 wells. The level of aeration needed to achieve the desired entry point ph was estimated for all the corrosive supplies using chemical equilibrium modeling (Table 5). Aeration would need to strip 60-70% of the carbon dioxide to reach ph of 7.4. Efficient aeration processes such as packed towers often require breaking head and repumping making aeration less cost-effective compared caustic soda based on capitol costs. However, the major advantage of aeration is the lack of chemicals and potentially lower lifecycle O&M costs. There is also less flexibility to meet different ph endpoints with an aeration system as it cannot be easily adjusted. Furthermore, it may not be possible to actually reach the upper limits using an aeration approach. This would need to be confirmed through piloting and/or additional modeling, communication with vendors, etc. Adding orthophosphate would not be an option unless implemented system-wide which would mean also treating the sources that are not considered corrosive to lead or copper. Furthermore, orthophosphates are most effective in the ph range , so ph adjustment would be required anyway. Therefore, orthophosphate treatment was not considered cost effective or advisable for the City. Because the wells have adequate alkalinity, use of soda ash or potash are not needed, but could be used in lieu of caustic soda. Soda ash dose and performance were evaluated and the estimated doses for cost planning purposes are also included in the Table 5. Soda ash doses are higher than the caustic doses due to the increases in alkalinity. Soda ash would likely be brought to site in powder format. Page 18

64 Table 5. Summary of Modeled Treatment Options for the City s Sources Sources Pumping Rate Dose to reach ph As 100% NaOH or Soda Ash 2 Expected capacity after replacement 3 Upper ph limit to avoid calcium carbonate precipitation Dose to reach upper ph limit Upper ph limit 3 Dose to reach ph 7.4 Dose to reach upper ph limit Upper ph limit 3 CO2 removed to reach ph 7.4 CO 2 removed to reach ph 7.4 CO2 remaining at 7.4 CO 2 removed to reach Upper limit CO2 remaining at Upper limit # Name gpm mg/l 1 s.u. mg/l 1 s.u. mg/l % mg/l % mg/l s.u. S04 Well (additional) Caustic Soda Soda Ash Aeration Madrona Well S Madrona Well S28 Madrona Well S01 Well 1 300/ n/a n/a n/a Well S Well S17 Beachcrest Well Beachcrest Well S27 Evergreen Estates S20 McAllister S06 Well 6C; Judd Hill S29 Betti Well Upper ph limit Page 19

65 5.6. Additional Water Quality Considerations Increasing the system ph may increase the formation of trihalomethanes (THMs), although the groundwater is typically low in organic carbon and results from the City s 2017 Water Quality Report indicate that the maximum result obtained was 10 ppb. Therefore, the proposed increase in ph is not anticipated to result in a regulatory concern due to increased THM formation. Increasing the ph in range of improves chemical stability of legacy iron and manganese in the distribution and provides an environment of lower metal solubility in general. In addition, pipe scales are more stable with smaller swings in the ph and more stable water quality conditions in the distribution. The City receives occasional inquiries regarding very hard to remove scales on fixtures, shower stalls, etc. Since these deposits cannot be removed with acidic products, it is very likely that they are silica-based deposits. Several of the City s wells have silica levels that could be considered problematic in terms of causing evaporative spotting and accumulation. Raising the ph will not impact the behavior of silica in the City s distribution system, unless the ph is raised to > 9.5, the point at which silica precipitation can begin to occur. Should the City increase chlorine levels to reduce iron release from pipes or for other reasons, a resultant increase in ORP will occur, which can be beneficial especially for lead control. Under highly oxidizing conditions, Pb(IV) scales may form which are very stable and less soluble than the Pb(II) carbonate-based scales, which are presumed to dominate under current ph, ORP, and DIC conditions. 6. Summary of Findings and Recommendations 1) Lead solubility is in good control in the City s system, and is nearly optimized, as demonstrated by compliance monitoring results. However, some minor additional benefit could be realized by raising the ph to 7.0 in areas with Tier 1 homes, likely allowing the City to meet the b(3) criteria definition of optimization, and assisting with compliance with a future, more stringent LT-LCR. 2) The City meets the copper action level and is optimized for copper under the existing LCR. Copper solubility is in good control for aged surfaces dominated by malachite or tenorite. 3) Several of the City s sources have water quality that is considered corrosive to new copper surfaces. The sources with combined higher DIC and low ph are the most corrosive to new copper surfaces, and could require treatment under the LT-LCR. 4) Given the complexity of the City s system and significant blending between sources, ph 7.4 should be targeted for sources with existing treatment, those selected for future treatment, and any new wells that are brought on line in the future. 5) For the water quality characteristics of the City s supply portfolio: a) Optimal corrosion control treatment for the existing LCR is achieved at ph 7.0. b) Optimal corrosion control treatment for the potential LT-LCR is achieved at ph 7.2 for new copper surfaces. This should be revisited based on the final, published LT-LCR. c) Treatment of selected sources to ph 7.4 will help maintain these water quality goals throughout the vast majority of the distribution system, under the existing and future LT-LCR. 6) It is not feasible or necessary to treat all the sources in the City s system considering that not all of them are of significant capacity or supplying homes that are at risk of copper or lead corrosion. Page 20

66 7) The risk assessment, source capacity, blending analysis, and potential impacts to overall distribution system water quality led to the following recommendations which will increase the ph to 7.4 in more than 84% of the City s pumped capacity entering the distribution system. a) Increase the caustic feed to raise the ph at Well 4 to 7.6. b) Install ph adjustment treatment to increase the entry point ph to at the following sources: i. S23 and S28 ii. S17 in conjunction with replacement of one of the Beachcrest wells that will also increase the source s capacity. iii. S18 in conjunction with replacing Well 1 (S1). iv. S27 as the major winter supply source. 8) After treatment is installed, evaluate remaining areas of higher risk for lead and copper corrosion separately as summarized in Appendix B Action Plan. The Action Plan should be used to help the City determine when the system has reached optimal corrosion control. The Action Plan is based primarily on the existing LCR, but should nonetheless be beneficial towards compliance with a future, more stringent LT-LCR. However, action triggers may need to be modified depending on final LT-LCR revisions. Page 21

67 References AWWA, 2017, Internal Corrosion Control in Water Distribution Systems, Manual of Water Supply Practices M58, 2 nd edition. AWWA Webinar: Lead and Copper Corrosion 101: Principles and Guidance, January 17, 2018, Darren Lytle and Michael Schock, USEPA Roth. D.R, Cornwell, D.A., Brown, R.A. and Via, S.H,. 2016, Copper Corrosion Under the Lead and Copper Tule Long-Term Revisions. Journal AWWA, 108:4 April. Schock, M.R and Lytle, D.A Internal Corrosion and Deposition Control. Water Quality and Treatment: A Handbook of Drinking Water, 6th ed., New York: McGraw-Hill USEPA, Optimal Corrosion Control Treatment Evaluation Technical Recommendations for Primacy Agencies and Public Water Systems. EPA 816-B March Page 22

68 Appendix A Blending Analysis Appendix B Action Plan Appendix C - Planning Level Cost Estimates for Caustic Soda ph Adjustment Facilities (RH2 Engineering) Page 23

69 APPENDIX A - BLENDING ANALYSIS Blending analyses were completed for the areas that will receive water from sources that were not prioritized for treatment. This includes S06 Judd Hill, S20 - McAllister, and S24/25 - Nisqually. The goal of the analyses was to evaluate the expected water ph in the distribution system within the zone of influence of these sources after blending with treated sources. S06 Judd Hill Area S06, Judd Hill, is a relatively small source. Its total contribution to the City s supply portfolio was 3-4% in and increased use is not planned. S06 will blend to some degree with water from S07 (Well 7) and S18 (wellfield for Wells 2 and 3) in the distribution system. Results of the analysis are shown in Figure 1. Assuming treated sources are treated to ph 7.4, ph 7.0 (Bin 2) can be reached once the blend fraction decreases below 75% Judd Hill water (e.g., at least 25% Well 7/S18 water). ph 7.2 (Bin 3) can be reached only when 25% of the blend is Judd Hill water and at least 75% of the water in the distribution system is from Well 7 or treated S18. Increasing the S18 entry point ph to 7.6 will reduce the amount of S18 water needed to reach ph 7.2 (Bin 3) down to 50%. Figure 1. Expected ph at different blending levels near Source 6 (Judd Hill). Nisqually (S24/24), 188 Zone The 188 zone is supplied by Sources 24 and 25 and can receive some water from the 400 zone through the Nisqually PRV. According to the City, Madrona and Betti wells would be the main sources supplying this PRV and consequently, the 188 zone, when the PRV is operational. The blending analysis was completed with the larger of the Nisqually sources, S25 (the Nisqually wells have very similar water quality). Figure 2 shows the modeled ph in the distribution system when blending S25 with Betti or treated Madrona water. To provide a minimum ph of 7.2, no more than 40% Nisqually water can be in the blend (need at least 60% treated Madrona water at ph 7.4). However, Nisqually is a non-expanding portion of the system, and new copper plumbing is not anticipated in this region. There are a few homes that meet Tier 1 construction dates, so lead solder may be present. Thus, the target of the blending analysis is to meet a minimum ph of 7.0. This can be met if the water in the distribution system has at least 25% of the other supplies, that is, no more than 75% Nisqually water. 1

70 Increasing the treatment at Madrona to a higher entry point ph would lower the needed blending level to meet the various ph targets. The average ph of Betti well is 7.15 and therefore, blended water ph would not go above ph 7.2 to meet Bin 3, but will meet Bin 2 (ph 7). Figure 2. Expected ph at different blending levels in the 188 Zone around Source 25 (Nisqually 19C). McAllister (S20) and Evergreen Estates (S27), 337 Zone Both McAllister (S20) and Evergreen Estates (S27) have been significant supplies for the City representing 10% and 16% of the total volume pumped in 2016 and 2017, respectively. S27 is also a priority well to meet winter demand. These sources typically serve the south 400-pressure zone where there are no Tier 1 homes and the southwest portion of the 337 zone (through PRVs). Both of these areas have experienced growth and are still growing making them at higher risk for copper corrosion. All new development is using PEX-piping, but there is a large development with copper piping (no lead) near S27. To address this, the City is planning to install treatment at S27, after the other priority treatments have been completed. S27 was prioritized for treatment over S20 because of its larger water right and the plan is to blend S20 with treated S27 when the S20 is in use. As shown in Figure 3, the blending analyses indicates that if Evergreen is treated to ph 7.6, 50% blending level would be needed to maintain a minimum ph of 7.2 (Bin 3). To meet the Bin 2 criteria (maintain ph 7.0), the proportion of S20 in the overall supply can increase to greater than 90%. 2

71 Figure 3. Expected ph at different blending levels for McAllister (S20) with treated Evergreen Estates (S27) Figure 4 shows the modeled distribution water ph when McAllister (S20) mixes with treated Madrona water. Having more than 40% of S20 supply will drop the distribution water ph below 7.2 (Bin 3), unless Madrona is treated to a minimum ph of 7.6. In this case, up to 50% S20 water can be in the blend while meeting Bin 3 criteria (maintain ph 7.2). To meet the Bin 2 criteria (maintain ph 7.0), the proportion of S20 in the overall supply can increase to greater than 90%. Figure 4. Expected ph at different blending levels for McAllister (S20) and treated Madrona (S23/28) The SW 337 zone has several Tier 1 homes. In the distribution system, the water from S20 and S27 may blend with each other, Madrona, or, if the PRV(s) are open to the 337 Zone, the sources supplying the Steilacoom and Union Mill reservoirs. The sources that feed these major reservoirs in the 337 zone include Sources 4, 7, 18, 9, and 10. Source 6 is not large enough in capacity to reach the reservoirs. 3

72 To estimate the water quality in the Steilacoom and Union Mill reservoirs, a hypothetical blend of the sources supplying that reservoirs was created. The blended portions of the sources were based on average volume pumped from each source in 2016 and This was considered to be more representative of the stored water than using the individual pumping capacities of the wells. Table 1 presents the blended water quality and the proportion of each source used to create the blend. Adding treatment to S18 has a significant overall impact on the ph of the reservoir water in the 400 zone. The increased treatment at S04 slightly increased the blended water ph in the reservoir, but did not change the overall blended water characteristics. Increasing the ph of S27 to a minimum of 7.4 will be compatible with the anticipated chemistry in the blending zones. Table 1. Estimated water quality in Steilacoom and Union Mill Reservoirs based on supply blending Source # S04 S07 S09 S10 S18 Proportion of the blend % 32.1% 3.0% 27.2% 26.4% Pump capacity (gpm) 750 1, , Water Quality / Treatment Condition TDS mg/l ph s.u. Alkalinity mg/l as CaCO3 Ca mg/l DIC mg/l as C Current Reservoir Water Reservoir Water after S18 Treated to ph 7.4 Reservoir Water after S04 Treated to ph 7.6 and S18 Treated to ph based on total gallons of water pumped from these sources in 2016 and However, since treatment installation at S27 could take several years, Figure 5 was created to show impacts of untreated Evergreen Estates (S27) water blending with treated Madrona water and also with Steilacoom Reservoir water within the 337 zone. Greater than 90% untreated S27 water can be accommodated in the blend while still maintaining ph 7.0 (Bin 2). Figure 5. Expected ph at different blending levels of S27 and Other 337 Zone Blended Supplies. 4

73 APPENDIX B - ACTION PLAN STEPS TO REACH OCCT Due to the complexity of the City s water system with multiple sources, treatments, water quality characteristics of supplies, and vintage of the homes, there is no simple solution for system-wide optimal corrosion control. The approach laid out in the corrosion control optimization report prioritized treatment installations to the largest, most corrosive sources that will have the most significant impact in the overall system. Additionally, the treatment locations were prioritized to target location of Tier 1 homes receiving water from untreated sources with corrosive water quality. To confirm and evaluate the level of optimization in the City s water system, the following steps are proposed: 1) Conduct WQP monitoring to determine baseline conditions throughout the system, especially in areas of highest concern including: a) Quarterly monitoring for ph, temperature, alkalinity, and conductivity (for source tracing) b) Add locations in the blending zones receiving water from untreated, potentially corrosive, sources i) Nisqually due to potential Tier 1 homes, but non-expanding so no new copper ii) Judd Hill Adequate blending during summer when metals release is highest, but potential hot spot during winter conditions, some Tier 1 era homes iii) S20 service area Blending zone with Madrona iv) S27 service area Blending zone with Madrona and Union Mills reservoir (337 zone blended water). S27 to be treated but new WQP site needed to establish baseline conditions. 2) Treatment installation for the sources to increase entry point ph to a minimum of 7.4 a) 400 Zone i) Install CCT at S23/28 (will also impact 337 zone) ii) Install CCT at S17 iii) Install CCT at S27 (will also impact 337 zone) b) 337 Zone i) Increase caustic dose at S04 ii) Install CCT at S18 and S01-replacement With these installations, at least 84% of the available source pumping capacity will be either noncorrosive or treated for corrosion control. Additional capacity will likely be available with the redevelopment of S17 and S01. 3) After treatment installation at S17, S23/28, and S18, WQP monitoring to determine the need for increasing EP targets or modified well operational strategies for achieving the goal of at least ph 7.0 in the DS blending zones, and confirm the need for construction/installation of treatment at S27. a) ph, alkalinity, and conductivity b) Biweekly monitoring at entry points c) Monthly monitoring at the current 12 WQP sites and the additional sites selected for targeting the areas summarized in item 1b) above. 1

74 4) After the treatment systems at S17, S23/28, and S18 have been operational and meeting EP targets for at least 4-6 months, conduct 2 consecutive 6-month rounds of LCR tap monitoring in accordance with the LCR requirements (prioritizing Tier 1 homes). 5) Evaluate Results using Flow Chart below (to be re-evaluated according to requirements of the revised LT-LCR). 6) If results indicate optimized corrosion control, provide results and recommendations for optimal water quality parameter set points for each entry point and within the distribution system (by pressure zone if appropriate) to the Department of Health. 2

75 90 th percentile of LCR Tap Samples Pb mg/l Cu 1.30 mg/l Pb mg/l Cu 1.30 mg/l AL exceeded b(3) Criteria Met, System Optimized WQPs within optimal range? Identify what changed Yes No Identify Risk Areas System Optimized Increase Treatment Levels if Possible Evaluate Alternative Operational Strategies to Increase the Proportion of Non-Corrosive or Treated Sources to the Area Complete Investigative Tap Sampling Following DOH s Hot Spot Approach. If the issue is Copper, then prioritize on new construction System Optimized Pb mg/l Cu 1.30 mg/l Pb/Cu AL Install Treatment to the source(s) supplying the area 3

76 TECHNICAL MEMORANDUM Client: Confluence Engineering Group/City of Lacey Project: Water Quality Consultant Project File: CEG Project Manager: Dan Mahlum, PE Composed by: Barney Santiago, PE Reviewed by: Dan Mahlum, PE and Rick Ballard, PE Subject: Well Nos. 1, 2, and 3, Well No. 4, and Madrona Wells ph Adjustment Facilities Date: July 13, 2018 Signed: 07/13/2018 Signed: 07/13/2018 BACKGROUND Washington State Department of Health (DOH) has required the City of Lacey (City) to update its 2014 corrosion control study and identify additional treatment to optimize corrosion control. The City retained Confluence Engineering Group (Confluence) to evaluate current source and distribution water quality and recommend treatment that focuses on ph adjustment at the City s sources. The City will use this information to update its 2014 corrosion control study for DOH approval. Confluence determined that the preferred locations for implementing additional ph adjustment would be the Well Nos. 1, 2, and 3 site (DOH Source # S01 and S18), Well No. 4 (S04), and the Madrona Well Nos. 1, 2, and 3 site (S23 and S28). Confluence recommended caustic soda doses for these sources and retained RH2 Engineering, Inc., (RH2) to assist with estimating costs of the new ph adjustment facilities. This technical memorandum summarizes the expected chemical usage, sizes chemical feed and storage equipment, and presents conceptual construction and project cost estimates for the proposed facilities. Well No. 4 currently has a ph adjustment system; this evaluation will include operational changes to accommodate higher caustic soda doses at this site. 7/13/ :07 AM J:\DATA\CEG\ \TECH MEMO\RH2 TECH MEMO RE COST FOR PH ADJUSTMENT FACILITIES.DOCX