DRAFT TECHNICAL SUMMARY

Transcription

1 DRAFT TECHNICAL SUMMARY To: Anne Tonella-Howe, Glenn Boettcher, Terry Smith City of Mercer Island Date: 4-November-2014 From: Andrew Hill, Melinda Friedman Confluence Project: City of Mercer Island Microbial Occurrence Response and Distribution System Best Practices Roadmap Phase 1 1. Overview In September 2014, the City of Mercer Island (City) experienced multiple E. coli detections in various locations of its distribution system (DS). The first positive result and following positive results two days later triggered a precautionary boil water notice implemented by the City with support from the Washington State Department of Health (DOH). DOH and the City jointly agreed to lift the boil water order after repeat samples were absent, only to re-impose the order when additional positive results were obtained a few days later. With guidance and oversight from DOH, the City implemented a response action plan that included increased monitoring, inspection activities, booster chlorination, and flushing activities, with the goals being to try to identify potential causes, document existing conditions, and improve DS water quality to fully eradicate the problem. The City has contracted with Confluence Engineering Group LLC (Confluence) to conduct an After Action evaluation to pursue the following objectives: Phase 1: 1) Review system data and information to assess potential causative factors and identify data gaps; 2) Evaluate the City s current routine and response O&M activities relative to industry standards and DS best management practices (BMPs); Phase 2: 1) Conduct additional investigations as needed to fill key data gaps; and 2) Develop recommendations for new and/or modified system practices to minimize the risk of future events. This report summarizes activities associated with Phase 1 and presents key preliminary findings and recommendations based on an evaluation of available data/records and staff interviews. Key findings have been categorized as follow: o o o Contamination Risks Water Quality Management Additional Considerations Resource Availability Written Documentation Data Management Recommendations fall into three areas: (1) additional investigations to fill key data gaps; (2) Action Plan items for immediate implementation related to the DOH-coordinated Incident Action Plan; and (2) preliminary long-term Action Plan recommendations, which will be refined based on the findings from addi- Phase 1: DRAFT Preliminary Findings and Recommendations 1

2 tional investigations. The recommendations are intended to reduce risk of future microbial contamination, improve public health protection, better prepare the City to identify and respond to water quality events, and ensure that the City s practices are consistent with industry-accepted BMPs. 2. Contamination Risks Microbial contamination of drinking water systems and positive coliform results can occur in four primary ways: Source water/treatment breakthrough Direct contamination of the distribution system through various pathways (e.g., crossconnections, physical breaches in infrastructure, intentional contamination/sabotage, etc.) Biofilm proliferation and release from pipe walls Sample stand contamination/sample collection issues Each of these mechanisms was evaluated as summarized below Source Water/Treatment Breakthrough Although emphasis has primarily been on the City s DS, there remains the potential for the contamination to have originated from the water supply, as supported by the following: a) DOH reported that there were no issues with SPU treatment processes and that its bacteriological tests were satisfactory. b) There was unusually heavy rainfall on 9/23/2014. Heavy rainfall increases runoff and has been shown to increase bacteria and particles levels in watersheds. An increase in source bacteria can increase occurrence in treated water, particularly considering the Cedar water supply is unfiltered and bacterial clumps may be shielded from UV and chlorine disinfection processes. c) For the two-day period 9/24 to 9/25, SPU reported a total of 7 positive total coliform (TC+) samples from 3 separate systems served. Of these 7 detections, 5 different bacteria were identified in speciation (E. coli was only observed for Mercer Island). For context, of the 10,000 samples collected and analyzed by SPU each year from direct and wholesale systems, there were only 2 TC+ total in 2014 prior to 9/24, 1 TC+ in all of 2011, and 4 TC+ in all of d) The City does not have control over source/poe water quality conditions. However, the City could choose to monitor more frequently at the SPU connection (prior to boosting) to confirm source water quality Direct Contamination of the Distribution System For direct contamination of the DS to occur, all three of the following conditions must occur simultaneously at one or more locations: There must be a physical pathway, e.g., a hole in a storage tank screen, leaking pipe joints, submerged air-vacuum valve vents, unprotected cross-connections, main repairs, main installations, etc.; Within pressurized portions of the distribution system, there has to be a driving force that serves as the mechanism to allow contamination to enter through the pathway (i.e., loss of pressure or sufficient back-pressure); and A contaminant source must be present (bird or animal droppings, sewage or other source of fecal contamination). Phase 1: Preliminary Findings and Recommendations 2

3 After comprehensive inspection efforts by the City, no specific sites were identified that presented the requisite combination of all three conditions for direct contamination of or intrusion into the pressurized distribution system. However, individual factors that can increase risk of contamination were identified in some cases, as discussed below. The City also considered and evaluated the possibility of sabotage or intentional contamination; however, there were no events, alarm conditions, and no claims or reports of credible threats that would suggest this. Despite any evidence of purposeful contamination, the City continues to look into ways to enhance its infrastructure security Physical Contamination Pathways 1) Reservoirs: a. The City cleans its two reservoirs every three years. Only small quantities of silt are observed. This exceeds common industry practices of cleaning reservoirs approximately every 3-5 years. b. A comprehensive inspection of the reservoirs (by the City, DOH, and divers) following the contamination event did not find any contamination sources or breaches in reservoir infrastructure that could have allowed contamination to enter the reservoirs. c. The reservoirs do not appear to be a source of increased contamination risk. 2) Main Leaks, Repairs, and Installations: a. The most recent main break/repair was on 9/14/2014 in the 492 zone (remote from MI- 3, which was the location of the original E. coli positive sample). The area was isolated and the main was repaired under positive pressure using standard practices. Field crews noted no unusual conditions or contamination risk. b. The most recent main replacement activity was completed in June 2014, three months prior to the event. This activity was in the 492 zone towards the south end of the island. c. During main installation, new pipes/fittings and exposed connections present a potential contamination pathway; however, a detailed review of existing practices and specifications reveal that the City places heavy emphasis on and enforcement of inspection and cleaning measures to prevent contamination during all aspects of the process. The City s release-to-service specifications for flushing, disinfection, and testing all reference AWWA standards. d. Contamination risk during main installation projects could be further reduced by including specifications that the pipe supplier provide pipe end caps or wraps or that the contractor install these for pipes during the storage phase. e. The City averages about 8 main breaks per year, system wide. This translates to approximately 6 breaks per year per 100 miles of pipe, which is considerably less than industry optimization goal of 15 breaks/leaks per year per 100 miles of utility-owned pipes. f. The City conducts a leak detection survey each year. The average system leakage was 9%, below the 10% criterion in the Water Use Efficiency Rule. The 2014 survey did not uncover any major issues. Most leaks are reported on the customer side of the meter. g. The contamination event was not likely associated with main leak, break, repair, or installation practices. 3) Bypass Valve Vault Phase 1: Preliminary Findings and Recommendations 3

4 a. The high-zone bypass valve could serve as a contamination pathway if the valve is leaking or if associated pressure gauge/pilot tubing is leaking and/or if the tubing connections are not properly closed off. b. Upstream and downstream pressure measurements taken shortly after the contamination event indicated that the valve was pressurized, and no water was observed leaking out of the pipe or valve. c. A section of pilot tubing was disconnected from the valve, however the petcock valve between the tubing and the valve was closed. Again, there was no evidence of leaking. 4) Air-Vacuum Valve Vaults: a. Most of the air-vacuum valves are co-located with PRVs in vaults. b. All 86 PRV vaults and air-vacuum valve assemblies were inspected following the contamination event. c. Although the City s current design standards require above-ground venting, there are several older air-vacuum relief vents that are housed below-grade in vaults and manholes that are susceptible to flooding see Figure 1. Some of the valves/vaults appear to have deferred cleaning and maintenance needs. Some of these vents may be unscreened and/or exposed to dirt. d. The City has rated each of its vaults according to flooding vulnerability and developed a prioritized list for follow-up inspections after heavy or sustained rainfall events. Since the initial inspection phase, the City has conducted three additional rounds of inspection for those vaults considered highest risk. In none of these inspections has the accumulated water level been found to have reached the vent level. e. Vaults with air-vacuum valves that are not vented above-grade pose a contamination risk to the DS if dirt is allowed to enter the vent and/or the vault floods to the level of the vent. However, per above, these conditions have not been identified to occur for any of the vaults or valves. Figure 1. Air-Vacuum valve in manhole (photo taken 10/4/2014) Phase 1: Preliminary Findings and Recommendations 4

5 5) Temporary Construction Connections a. In response to the event, the City re-investigated all 45 active construction sites. No major issues or risks were identified. b. Most connections involve a garden hose attached to a hose bib downstream of an existing meter, for temporary use washing tools and watering concrete. Thus, risks, where they exist, are generally associated with back-siphonage as opposed to back-pressure and thus require a low pressure event in the system as a driving force. c. All active construction sites are routinely visited by Development Services. As part of each visit, connections to the water system are evaluated. Although the City doesn t have code requiring use of backflow devices for temporary construction connections, the inspector attempts to enforce the use of backflow devices (including use of a simple brass check valve for garden hoses). d. Typical construction-related connections and water use appear to present a low risk of contamination; however, risk could be lowered further with strict code or policy requiring use of approved backflow devices. 6) Cross Connections: a. In follow-up to the event, the City conducted comprehensive inspection and backflow assembly testing activities to investigate cross-connection risks. The City originally identified 24 high-hazard sites (medical, dental, veterinary, etc.) that did not have up-to-date test reports. This number was later reduced to 18 to exclude restaurants. All sites were subsequently tested and one along waterfront failed and was repaired. This location was deemed unlikely to have contributed to the event since it was in a low pressure zone for which there was no means of the water travelling up to higher zones. b. Due to current staffing levels, the Cross-Connection Control Program (CCCP) is not as robust as it should be with regard to site surveys, obtaining annual testing results, and enforcement. c. The City s Cross Connection Control Ordinance has not been updated since the 1980 s. d. Clearer authority to implement and enforce the CCCP is needed. e. Premises with an unapproved auxiliary water supply (such as irrigation water from the lake) that are interconnected with the potable water supply are a high health risk hazard and must have the appropriate backflow prevention device. f. The CCCP could benefit from better coordination between permit, building department, and water department to stay on top of what is out there and changes in site/hazard conditions. The City believes they are aware of about 80% of what is currently out there. g. Unprotected cross connections pose a significant contamination risk to the DS since contamination can be caused by back-siphonage (low pressure on the utility side) or back pressure (high pressure on the customer side). 7) Fire Hydrants: a. Leaking fire hydrant seats force water through the drain ports into the ground immediately surrounding the hydrant. This water can either drain naturally into well-draining soil or accumulate around the base of the hydrant in the case of poor-draining soil conditions. In the case of a back-siphonage or back-pressure event this could result in contamination to the DS. These types of leaks are very common and many were found during the recent leak sur- Phase 1: Preliminary Findings and Recommendations 5

6 vey. Due to current staffing levels, the City does not have a fire hydrant repair or maintenance program Driving Force for Intrusion There were no unusual pressure events known to City staff or recorded by SCADA immediately before or during the contamination event that would have caused a high magnitude hydraulic disturbance or low pressure event. However, it is noteworthy that there are no pressure transducers or records located within the DS; thus, the occurrence of pressure transients capable of causing a backflow or backsiphonage cannot be ruled out. Common causes of pressure events include main breaks, main installations and repairs, pump station operations, flushing, fire-fighting, and rapid imposition of demand through valve operations. 1) The high-zone bypass operation could present risk of a system pressure transient due to pump and valve start/stop cycles. During this operation, the pressure-regulating bypass valve slowly opens and modulates to meet demand in the Pumped Zone, while the high-service pump station ramps down. During reservoir fill periods (when the incoming supply pressure is lower), the pump station ramps up to meet zone pressure as the bypass valve closes. 2) The bypass valve was activated for the first time in 2014 on 9/24/2014 at 10:50 am, approximately two hours after the first positive E. coli sample was collected from site MI-3. The bypass valve operated continuously until 2:30 am on 9/26/2014, at which point the reservoir fill cycle started, the bypass valve closed, and the pump station was re-activated. At noon on 9/26/2014, the pump station was ramped down and the bypass valve re-opened. Its operation continued until 10:50 am on 9/27/ ) The possibility of a low-pressure transient occurring due to valve/pump station operations cannot be ruled out. A pressure transient could have served as the mechanism to draw contamination from an unprotected cross connection or leakage point into the distribution system. It is noteworthy that 3 of the 4 positive samples on 9/26/2014 were located in the Pumped Zone served by the pump station. 4) There were no fire flow tests or known fire-fighting activities prior to the event. 5) During its on-going flushing activities, the City reportedly performs slow valve and hydrant operation so as to minimize the likelihood of sudden changes in velocity and pressure. 6) The most recent main break/repair was on 9/14/2014 in the Pumped Zone (remote from MI-3). The area was isolated and the main repaired under positive pressure using standard practices Contaminant Source 1) The vault housing the pressure-regulating bypass valve was found to be partially flooded due to heavy rainfall and a failed sump pump see Figure 2. On 10/7/2014, SPU staff collected a sample of standing water from within the vault. The sample was found to be positive for E. coli. Although this presents a possible source, a clear pathway for contaminant introduction was not identified. As noted previously, the valve was under positive pressure and there was no evidence of leaking. Also, the water level was 3-4 feet below the pilot tubing at the time of inspection. 2) No other samples were collected from other system vaults to determine if E. coli or other fecal indicators were present. 3) Unprotected cross-connections could serve as a potential contaminant source to the DS. Phase 1: Preliminary Findings and Recommendations 6

7 Figure 2. Bypass valve vault with standing water (photo taken 10/9/2014) 2.3. Biofilm and Pipe Deposits Biofilm proliferation is often associated with TC+ samples since there are many species of total coliforms that can survive and grow within the biofilm/sediment/pipe wall environment. Conversely, while it is possible for E. coli to have been associated with pipe wall biofilm, it is unlikely that the E. coli originated from within the DS environment (i.e., biofilm or scale). Research indicates that E. coli generally do not colonize biofilm in cold, low nutrient water supplies such as those in the Pacific Northwest. Biofilm are often most prevalent in areas with high water age, low chlorine residuals, and unlined cast iron pipe, and while likely not directly involved with the contamination event, the presence of robust biofilms are indicative of needed improvements in main cleaning, water age management, and disinfectant residual management Pipe Conditions 1) The City s DS pipe inventory is primarily 50+ year old unlined cast iron (UCI), with lesser amounts of asbestos cement and newer cement-lined ductile iron. 2) Recent pipe samples suggest that the UCI pipe may be heavily tuberculated in certain areas see Figure 3. Extensive corrosion scale can negatively impact water quality by exerting a large disinfectant demand and impairing secondary disinfection efficacy. Tubercles can also harbor bacteria and support biofilm growth. 3) AC pipe reportedly shows a red-colored slime. This is indicative of biofilm enriched with iron (possibly from mobilized corrosion products). 4) Although these pipe/deposit conditions are similar to other systems in the region, they are indicative of the need for additional maintenance. Challenges with biofilm control may be related to the City s inability to apply high-velocity unidirectional flushing for main cleaning due to island-wide constraints on discharge disposal. The presence of extensive scale/tubercles on UCI pipe is indicative of the need for additional maintenance involving main cleaning, rehabilitation, or replacement. The Phase 1: Preliminary Findings and Recommendations 7

8 City s current main replacement program uses pipe size (fire flow capacity), age, and main break frequency as criteria for prioritization. Water quality is not considered in the prioritization process. 5) The City s current main replacement frequency (2,500 ft/year, on average) amounts to approximately 0.4% of the City s DS inventory. This is below the industry recommended benchmark of > 1% replacement per year (AwwaRF, 2005). Figure 3. Internal scale buildup on 4-inch unlined cast iron main (left) and 2-inch service (right) Main Cleaning Practices 1) The City has a routine preventative water main flushing program which involves system-wide unidirectional flushing (UDF) on a fixed schedule (50% of the mainline DS each year, alternating between north and south areas), as well as annual flushing of dead-ends. The City also conducts local conventional flushing in response to low chlorine residuals. 2) The program objective is bulk water turnover to improve chlorine residual, i.e., it is not for main cleaning. The City cannot typically achieve scouring velocities because of severe limitations on water disposal to both the storm and sanitary sewer systems. Typically, velocities above 6 fps are needed to effectively scour biofilm and clean in pits/recesses of tuberculated pipe. Table 1 illustrates that, at the maximum flushing flow rate used by the City because of disposal limitations (500 gpm), the flushing velocity is insufficient to promote cleaning, particularly for pipes that are 8 inch diameter. Table 1. Flushing velocities (in fps) achieved as a function of flow rate and pipe diameter Flow Rate Main Size (inches) (gpm) ) System-wide UDF strictly for bulk water turnover is not a typical industry practice for long-term chlorine residual maintenance since it achieves only a temporary reduction in water age. This is supported by: Phase 1: Preliminary Findings and Recommendations 8

9 a. The frequent need to repeat flush in certain high water age areas, e.g., near MI-3. b. Reported flushing duration of 20 to 120 minutes per hydrant, depending on location, with limited ability to restore residual in some cases. Effective UDF (when used on a large scale for main cleaning) typically only requires 2 to 10 minutes per loop to achieve background chlorine and turbidity levels Sample Collection Conditions It is unlikely that the positive coliform results were caused by issues with sample stand cleanliness or sample collection procedures, for the following reasons: 1) Positive samples were collected separately by both SPU and City staff 2) DOH and SPU arrived on-site and confirmed use of proper techniques by City staff 3) Dedicated, continuous-flowing sample stands are used which should be representative of flowing water conditions (best case) versus stagnant water quality conditions. 4) Field crews sanitize sample stands quarterly 3. Water Quality Management An evaluation of water quality management was conducted to understand certain conditions leading up to and at the time of the event, as well as to assess the degree to which the City documents baseline conditions and is able to track and respond to potential water quality upset indicators. Although the City purchases 100% of its water from SPU and, as a wholesale customer, does not have control over the quality of water received, it does have the ability to monitor and control water quality within its DS. 1) The chlorine residual is typically about 1.2 mg/l entering the storage tanks and mg/l entering the DS. The City practices reservoir turnover strategies that include rapid fill-drain cycles and seasonal level setpoints. 2) With the exception of online chlorine residual analyzers at the reservoir and First Hill pump station sites, the City does not routinely monitor, track, or trend chlorine residual or other parameters within its DS. Current routine DS water quality monitoring activities are based on regulatory requirements, for which grab samples are collected and analyzed by SPU staff. The results are reported in hardcopy format to the City 1-2 weeks later. Only if a result is below 0.2 mg/l does SPU notify the City right away. The City does not electronically track or trend these reported water quality data, but does review and assess the results to determine if/where response measures such as flushing are warranted. The City is in on-going discussion with SPU about options to improve data reporting timeliness and format. 3) Prior to the event, the City had a goal to maintain chlorine residual 0.5 mg/l throughout the DS. Since the event, the goal has been raised to 1 mg/l to enhance microbial protection. a) Routine UDF and reactive conventional flushing are currently performed (as existing resources allow) to attempt to meet this goal. b) There are portions of the DS that occasionally/seasonally fall below this goal and receive more regular response flushing (e.g., the northwest portion near sample stand MI-3. See Figure 4). It is difficult to determine the extent to which residuals fall below this goal system-wide since chlorine residual monitoring is limited and data are not tracked. Phase 1: Preliminary Findings and Recommendations 9

10 c) In certain portions of the DS, there may be more cost-effective and sustainable approaches to maintain chlorine residual that can reduce the on-going flushing burden. However, some degree of on-going system flushing is a positive practice for which the City is well-poised to continue. Figure 4. Free chlorine trend over time at TCR site MI-3 4) The City s current reservoir turnover and flushing practices are based upon DS water quality maintenance goals; however, water quality preservation has not been a key factor in other system O&M and CIP decisions such as main cleaning and replacement. 5) The City has a DOH-approved TCR monitoring plan. However, the sample locations approved in this plan did not provide adequate spatial or geographic coverage of the DS to allow for increased understanding of the possible origin or sequence of the contamination event(s). 6) The City does not have a water quality surveillance or control plan. Surveillance water quality monitoring would provide better and timelier insight into baseline conditions and excursions that may be an early indicator of increasing risk and/or a potential contamination event. 7) The City plans to procure a potable booster chlorination system (using hypochlorite solution) for use at the reservoir site to provide more flexible operations and improve DS residual conditions. 8) Historically, online chlorine analyzers were not calibrated or cross-checked on a fixed schedule. 4. Additional Potential Contributing Factors 4.1. Resource Availability 1) Due to staff and resource limitations relative to current workload needs, several industryrecommended preventative maintenance activities are not performed or are only done when time allows. In some instances, other trained and certified maintenance staff are used to join water crews to catch up on water system maintenance functions. 2) A large amount of crew time is spent on flushing and repairs. 3) There is a growing backlog of deferred system maintenance needs that have the potential to negatively impact the system now or the future. These impacts include reliability, integrity, hydraulic and water quality performance, and life-cycle costs. These include: Phase 1: Preliminary Findings and Recommendations 10

11 a) Large inventory of aging and heavily-corroded mains. Current main replacement funding is not keeping up with needs when the water quality risks of sub-standard mains are considered. b) Lack of a main cleaning program. c) Numerous outdated air-vacuum relief valves that do not meet current design standards and present cross-connection/intrusion risks. d) Lack of a fixed schedule for inspection and maintenance of hydrants. Industry recommendations include annual inspection/testing of fire hydrants and critical valves. 4) Additional staff and budget are needed to effectively perform these industry-recommended practices, as well as the additional practices and recommendations provided in this report. A more detailed analysis of system conditions and alternative strategies for water quality control is needed to determine recommended long-term staffing needs and additional funding for capital and operations programs Written Documentation The City does not have documented SOPs for preventative and response O&M activities. To retain institutional knowledge and ensure consistent application of best practices, the City should develop and document SOPs for existing and recommended new/modified practices including: 1) Inspection of vaults and valves 2) Maintenance of vaults and valves 3) Bypass valve operation 4) Storage facility inspection 5) Booster disinfection 6) Chlorine residual analyzer calibration 7) Surveillance water quality monitoring a) Sample collection and analysis b) Data analysis and trending c) Response activities to alert/action levels 8) Unidirectional Flushing loop development and implementation 9) Field analytical equipment up-keep, replacement, and calibration 4.3. Data Management Improvements are needed to allow for more effective asset management, data management, and data visualization. 1) Current field data collection/retention is mostly paper-based, associated with point-in-time data collection (inspections, maintenance reports, map markups, etc.). It is very time-consuming for IT to format and enter into electronic database. This slowed the City s ability to rapidly create system maps needed to respond to recent event. a) Paper-based retention makes it more difficult to track asset inspection and maintenance histories. Phase 1: Preliminary Findings and Recommendations 11

12 b) Paper-based retention renders field data less actionable, particularly with regard to water quality. For example, the City does not currently trend DS chlorine residual conditions since the data are not electronically managed. 2) Data collection practices are not always consistent; thus data quality is impaired. 3) Electronic recordkeeping and real-time asset management have become very common within the industry over the past 10 years as the technology has matured. 4) More effective data management would produce on-going benefits including improved system understanding (e.g., asset condition, maintenance history), timely and actionable information (e.g., water quality upsets), and avoided time with paper-to-electronic transition. It is also consistent with other recommendations herein to develop and fund an asset management program, scheduled preventative maintenance, and a surveillance water quality monitoring program. 5. Conclusions and Recommendations Despite comprehensive testing and inspection efforts by the City, no specific sites were identified that presented the requisite combination of conditions for intrusion within the distribution system, i.e., a contamination source, pathway, and mechanism. Locations or events that present risk factors in one or possibly two conditions were identified, but not all three. Furthermore, the possibility that contamination was present in the water entering the Mercer Island system cannot be completely ruled out. It is probable that the event(s) were associated with a transitory condition as opposed to on-going contamination, based on comprehensive DS monitoring that has produced all non-detects each day since 10/1/2014. It cannot be concluded if detections on different days in late September were due to separate contamination events or a one-time event, given that bacteria can be particle-associated (shielded from disinfection) and may not travel uniformly within the DS. Since the contamination source has not yet been identified, there is potential for future contamination events should similar conditions recur. Given the potential array of causes and the fact that it occurred in spite of the City s best efforts to protect and maintain its system, this incident should be viewed as an opportunity for all parties involved (the City, SPU, DOH, and other SPU purveyors) to work together and re-examine their existing practices related to water quality surveillance and communications. Specific to the City, the lack of a clear cause has served as the driver to further examine its own system and take steps to mitigate cross-connection and intrusion risks, enhance secondary disinfection, address pipe deposits, and increase DS water quality surveillance. The City has diligently performed additional measures and best practices to enhance water quality, including booster chlorination at the reservoirs and extensive flushing to turn over the water. The City has also used this experience to conduct a detailed examination of its O&M practices to identify opportunities to improve practices and reduce risk. City staff and crew demonstrate a high degree of integrity, proficiency, and diligence in their efforts to preserve water quality and maintain the City s water system. Existing practices and procedures reflect the utility s strong commitment to public health protection; there are no signs of taking shortcuts. Unlike most utilities in the region that purchase 100% of their water, the City had/has an established robust numerical goal for chlorine residual and undertakes specific O&M measures to meet this goal throughout its system. Where they exist, the City s short-comings relative to industry BMPs and benchmarks for asset management are primarily due to a lack of resources and funding relative to the high demands of an aging distribution system. Additional investigations, staffing, and funding are needed to allow the City to ad- Phase 1: Preliminary Findings and Recommendations 12

13 dress deferred system maintenance items, identify more cost-effective strategies to address residual maintenance challenges, and operate in a more preventative fashion overall. Table 2 summarizes preliminary recommendations for the City based on the data and findings from Phase 1. These recommendations reflect industry practices geared towards assessment and mitigation of microbial contamination risks and measures to better understand and more cost-effectively control distribution system water quality. Recommendations noted as long-term will be refined as additional investigations and near-term action plan items are pursued. Phase 1: Preliminary Findings and Recommendations 13

14 Classification Resource Impacts Table 2. Preliminary Recommendations Matrix Additional Investigation to Fill Key Data Gaps Immediate Implementation/ Incident Response Long-Term Recommendation Short-term/Temporary Labor Resource Need Long-Term/On-Going Labor Resource Need Probable Capital/Contractor Cost Impact Status (Date) Reduce Contamination Risks Assessment M-A-1 Verify that the bypass operation does not produce pressure transients. Install high-frequency pressure recorders at strategic locations within the DS and collect data before and during periods of valve use, including startup/shutdown of both valve and pump station. M-A-2 Rate system vaults/valves for cross-connection risk; inspect high-risk vaults periodically and after sustained rainfall and prioritize for retrofit. M-A-3 Conduct comprehensive field survey to develop an up-to-date database of device locations and cross-connection risks. Emphasis on premise isolation and high hazard sites including commercial customers and waterfront properties. M-A-4 Increase hazard survey of commercial customers. Mitigation and Control M-M-1 Replace or upgrade air-vacuum valves with below-grade relief vents to be consistent with current design standards, i.e., provide an above-grade air gap with screen. M-M-2 Develop, implement, and document a regular inspection and preventative maintenance schedule for vaults, PRVs, and air-vacuum relief valves/vents. M-M-4 Develop an updated cross-connection control program ordinance that includes clear policy on device installation, testing requirements (including temporary/construction connections), and enforcement. M-M-5 Enhance enforcement of annual testing of premise isolation devices. M-M-6 Conduct routine inspection of active construction sites to ensure appropriate backflow devices are used, with appropriate enforcement procedures. M-M-7 Develop and implement a plan to prioritize and accelerate installation of premise isolation devices on existing services. M-M-8 M-M-9 Educate public/customers about importance of backflow prevention and testing. Encourage customers to report local conditions regarding potential crossconnections. Update specifications for contractor main installation projects that the pipe supplier provide pipe end caps or wraps or that the contractor install these for pipes during the storage phase.

15 Classification Resource Impacts Table 2. Preliminary Recommendations Matrix (Cont'd) Additional Investigation to Fill Key Data Gaps Immediate Implementation/ Incident Response Long-Term Recommendation Short-term/Temporary Labor Resource Need Long-Term/On-Going Labor Resource Need Probable Capital/Contractor Cost Impact Status (Date) Enhance Water Quality Management Assessment W-A-1 Develop and field test metrics for identification of mains to be included in CIP based on water quality impacts. W-A-2 W-A-3 Collect pipe specimens (dedicated extractions, samples/taps of opportunity) to assess condition and nature of deposit. Secondary benefit is to differentiate lined vs unlined iron for maps. Investigate the cause of low chlorine residuals, to include: identification of chronic problem areas through baseline monitoring, analysis of temporal water quality trends after flushing, hydraulic modeling to assess water age, and chlorine-demand decay tests. W-A-4 Conduct bench-testing to assess the increase in disinfection byproduct (DBP) formation associated with various booster chlorination targets. W-A-5 Conduct a desktop evaluation of main cleaning options to identify the most promising options relative to the types of pipes and deposits in the City's DS. W-A-6 Plan and conduct controlled field demonstrations of candidate main cleaning options. Evaluate feasibility, performance, costs, other impacts, etc. to identify preferred full-scale cleaning approach. Identify data collection/monitoring practices before, during, and after cleaning. W-A-7 Assess mixing/short-circuiting within the reservoirs. Evaluate passive and active mixing options and implement selected option. W-A-8 Identify additional routine TCR sample locations to improve system coverage. Update TCR plan and obtain DOH approval. Install sample stands. W-A-9 W-A-10 W-A-11 Develop and implement short- and long-term DS surveillance water quality monitoring plan, to include locations, parameters, methods, frequencies, proper sample collection protocols, etc. Develop DS baseline water quality conditions (once booster chlorination operation is in place). Identify seasonal trends. Develop various alert/action levels. Develop and implement a plan for electronic data magement and analysis of water quality data collected under surveillance monitoring program, to enable system tracking and timely response activities. W-A-12 Update/calibrate the hydraulic model to operate in extended period simulation to support water age modeling analysis. Mitigation and Control W-C-1 Develop an asset management program that emphasizes preventative cleaning, rehabilitation and main replacement. Metrics to classify mains and select/prioritize maintenance activities should incorporate water quality factors in addition to existing criteria. W-C-2 Acquire an asset management geodatabase and field tablets for crew that allow for direct access/entry of field data, maps, SCADA, etc. W-C-3 Develop and document SOPs for preventative and response O&M activities. W-C-4 Conduct main cleaning, rehabilitation, and replacement consistent with a long-term asset management program. W-C-5 Investigate and implement chlorine residual maintenance strategies for chronic problem areas to identify potential site-specific alternatives to continued frequent flushing. W-C-7 Develop and implement a water quality response plan to respond to excursions identified from surveillance monitoring. W-C-8 Automate the booster chlorination operation with a control panel. Automation should include flow-pacing and use of a dedicated continuous residual analyzer to confirm the dosed residual is within a target range, with appropriate alarm conditions for off-spec operation. W-C-9 Follow manufacturer-recommended calibration schedule for online chlorine analyzers. Calibration should be cross-checked using field instruments.