7
Integrating Approaches to Reducing Risk from Distribution Systems

The few regulations that govern water quality in distribution systems are the result of years of research leading to the demonstration of a risk to the water-consuming public from specific contaminants. The development of regulations is a complex process that includes cost analysis (EPA, 2003) and, more recently, stakeholder input as described in the Federal Advisory Committee Act. Many state regulatory agencies are either reluctant to or prohibited by statute to require measures to protect drinking water beyond those mandated by federal statute. However, drinking water utilities may independently choose to conform to industry standards to design and operate their systems beyond regulatory requirements.

Standards are useful to water suppliers that have adopted such a precautionary stance. Recommended Standards for Water Works: Ten State Standards (The Great Lakes-Upper Mississippi River Board of State Public Health and Environmental Managers, 2003), NSF International, and the American National Standards Institute (ANSI) are third party producers of standards that are widely used in the drinking water industry. Voluntary adoption of standards by a utility requires reallocation of resources. Nevertheless adoption of certain standards is almost universal for community water systems, such as ANSI/NSF 60 governing components that come in contact with drinking water, ANSI/NSF 61 governing additives to water, and many American Water Works Association (AWWA) standards related to design of infrastructure such as D100-96—Welded Steel Tanks for Water Storage. Other widely used AWWA standards related to distribution system integrity include the C651—Disinfecting Water Mains, C652—Disinfection of Water-Storage Facilities, and D101-53 (R86)—Inspecting and Repairing Water Tanks, Standpipes, Reservoirs, and Elevated Tanks for Water Storage. In addition to industry standards, AWWA “Manuals of Water Supply Practices,” such as M6 Water Audits and Leak Detection, are commonly used by drinking water utilities to enhance their operations and service to the public.

In 1999 a technical workgroup was organized to develop a Drinking Water Distribution System Assessment Workbook, which began the process that culminated in the G200 Standard. The purpose of the G200 standard is to “define the critical requirements for the operation and management of water distribution systems, including maintenance of facilities” (AWWA/ANSI, 2004). Several components of the G200 standard relate directly to issues highlighted in the U.S. Environmental Protection Agency (EPA) Distribution System White Papers (see Chapter 1) and characterized as high priority by this committee (see Appendix A).



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Drinking Water Distribution Systems: Assessing and Reducing Risks 7 Integrating Approaches to Reducing Risk from Distribution Systems The few regulations that govern water quality in distribution systems are the result of years of research leading to the demonstration of a risk to the water-consuming public from specific contaminants. The development of regulations is a complex process that includes cost analysis (EPA, 2003) and, more recently, stakeholder input as described in the Federal Advisory Committee Act. Many state regulatory agencies are either reluctant to or prohibited by statute to require measures to protect drinking water beyond those mandated by federal statute. However, drinking water utilities may independently choose to conform to industry standards to design and operate their systems beyond regulatory requirements. Standards are useful to water suppliers that have adopted such a precautionary stance. Recommended Standards for Water Works: Ten State Standards (The Great Lakes-Upper Mississippi River Board of State Public Health and Environmental Managers, 2003), NSF International, and the American National Standards Institute (ANSI) are third party producers of standards that are widely used in the drinking water industry. Voluntary adoption of standards by a utility requires reallocation of resources. Nevertheless adoption of certain standards is almost universal for community water systems, such as ANSI/NSF 60 governing components that come in contact with drinking water, ANSI/NSF 61 governing additives to water, and many American Water Works Association (AWWA) standards related to design of infrastructure such as D100-96—Welded Steel Tanks for Water Storage. Other widely used AWWA standards related to distribution system integrity include the C651—Disinfecting Water Mains, C652—Disinfection of Water-Storage Facilities, and D101-53 (R86)—Inspecting and Repairing Water Tanks, Standpipes, Reservoirs, and Elevated Tanks for Water Storage. In addition to industry standards, AWWA “Manuals of Water Supply Practices,” such as M6 Water Audits and Leak Detection, are commonly used by drinking water utilities to enhance their operations and service to the public. In 1999 a technical workgroup was organized to develop a Drinking Water Distribution System Assessment Workbook, which began the process that culminated in the G200 Standard. The purpose of the G200 standard is to “define the critical requirements for the operation and management of water distribution systems, including maintenance of facilities” (AWWA/ANSI, 2004). Several components of the G200 standard relate directly to issues highlighted in the U.S. Environmental Protection Agency (EPA) Distribution System White Papers (see Chapter 1) and characterized as high priority by this committee (see Appendix A).

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Drinking Water Distribution Systems: Assessing and Reducing Risks These include Section 4.1.1: Compliance with regulations, 4.1.3: Disinfectant residual maintenance, 4.2.1 System pressure monitoring and requirements, 4.2.2 Backflow prevention, and 4.3.1 Storage facilities. As listed in Table 7-1, G200 includes requirements related to water quality, distribution system management, and facility operation and maintenance. The standard references several existing standards such as those cited above. TABLE 7-1 G200 Requirements Section Title Requirement 4.1 Water Quality 4.1.1 Compliance with regulatory requirements Meet or exceed regulatory requirements. 4.1.2 Monitoring and control   4.1.2.1 Sampling plan Establish plan, review annually, analyze/trend data, have action plan to respond to changes. 4.1.2.2 Sample sites Include all types of locations including dead ends and storage. Past problem areas require more sampling. 4.1.2.3 Sample collection Use Standard Methods, standardized labels and chain of custody forms. 4.1.2.4 Sample taps Protect from contamination. Inspect annually. 4.1.3 Disinfectant residual maintenance   4.1.3.1 Disinfectant residual Maintain detectable or HPC ≤ 500 CFU/mL. 4.1.3.2 Nitrification control Monitor free ammonia, control chlorine-to-ammonia ratio. 4.1.3.2.2 Nitrification monitoring Monitor nitrification indicator parameters. 4.1.3.3 Booster disinfection   4.1.3.3.1   Document residual goals. Monitor compliance with goals. 4.1.3.3.2   Maintain operating procedures that take into account seasonal variation, quality, flow, and system operations. 4.1.3.3.3   Written Plan showing response to variation between goals and observed values. 4.1.3.4 Disinfection byproduct monitoring and control   4.1.3.4.1   Monitor and control DBPs. Set goals for DBPs at critical points. 4.1.3.4.2   Have action plan to respond to levels that exceed goals. 4.1.4 Requirements for utilities not utilizing a disinfectant residual Monitor and record HPC. 4.1.4.1 Response program Have action plan to respond when HPC levels are above goals.

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Drinking Water Distribution Systems: Assessing and Reducing Risks Section Title Requirement 4.1.5 Internal corrosion monitoring and control   4.1.5.1 Prevention and response program Have action plan to respond to internal corrosion and deposition. 4.1.6 Aesthetic water quality parameters   4.1.6.1 Color and staining Have action plan to address color and staining. 4.1.6.2 Taste and odor Have action plan to address taste and odor. 4.1.7 Customer relations   4.1.7.1 Customer inquiries Have system to document customer inquires. 4.1.7.2 Service interruptions Have system to document planned and unplanned service interruptions. 4.1.8 System flushing Develop and implement a systematic flushing program. 4.2 Distribution System Management Programs 4.2.1 System pressure   4.2.1.1 Minimum residual pressure Minimum pressure > 20 psi. 4.2.1.2 Pressure monitoring Monitor pressure. Pressure alarms may be used. 4.2.2 Backflow prevention Have program at least as stringent as AWWA M14. 4.2.3 Permeation prevention Address in utility operation plan. 4.2.4 Water losses   4.2.4.1 Water loss Have goal for the amount of water loss. Document calculation. 4.2.4.2 Response program Have action plan to respond if goal is not met. 4.2.4.3 Leakage Quantify leakage on annual basis. 4.2.5 Valve exercising and replacement   4.2.5.1 Valve exercising program Have valve exercising program. 4.2.6 Fire hydrant maintenance and testing   4.2.6.1 Maintenance and testing Comply with AWWA M17. 4.2.7 Materials in contact with potable water   4.2.7.1 Approved coatings or linings Specify in accordance to AWWA standards, NSF 61, or other. 4.2.8 Metering   4.2.8.1 Metering requirements Determine daily peak flows and maximum day peak flows. 4.1.8.2 Metering devices Meters shall meet AWWA requirements or other applicable standard. 4.2.8.3 Testing Test as recommended in AWWA M6. 4.2.8.4 Repair and replacement programs Have program that includes records to verify conformance with AWWA M6.

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Drinking Water Distribution Systems: Assessing and Reducing Risks Section Title Requirement 4.2.9 Flow   4.2.9.1 Flow requirements Be capable of delivering maximum day demand and fire flow. 4.2.10 External corrosion   4.2.10.1 Leaks/breaks Have a standardized system for recording and reporting leaks and breaks. 4.2.10.2 Monitoring program Have external corrosion monitoring plan. 4.2.11 Design review for water quality   4.2.11.1 Policies and procedures Have standardized design procedures that review construction projects to reduce potential for water quality degradation. 4.2.11.2 Records Prepare as-built drawings. 4.2.12 Energy management   4.2.12.1 Energy management program Review and optimize electrical energy usage. 4.3 Facility Operation and Maintenance 4.3.1 Treated water storage facilities   4.3.1.1 Storage capacity Establish minimum operating levels in storage facilities. 4.3.1.2 Operating procedures Write Standard Operating Procedures for turning over facilities and minimizing water age. 4.3.1.3 Inspections Write Standard Operating Procedures for facility inspection. 4.3.1.4 Maintenance Have a maintenance program for facilities. 4.3.1.5 Disinfection Facilities shall be disinfected according to ANSI/AWWA C652. 4.3.1.6 Additional requirements All facilities shall be covered. 4.3.2 Pump station operation and maintenance   4.3.2.1 Operating procedures Write Standard Operating Procedures describing the operation of each pump station. 4.3.2.2 Maintenance program Write Standard Operating Procedures describing the maintenance of the equipment in each pump station. 4.3.3 Pipeline rehabilitation and replacement   4.3.3.1 Rehabilitation and replacement program Have a program for evaluating and upgrading the distribution system. 4.3.4 Disinfection of new or repaired pipes   4.3.4.1 Disinfection of new or repaired pipes Disinfect according to ANSI/AWWA C651 requirements. 4.3.4.2 Bacteriological testing Testing shall be performed according to ANSI/AWWA C651. 4.3.4.3 Disposal of chlorinated water Disposal shall follow local, state, and federal regulations.

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Drinking Water Distribution Systems: Assessing and Reducing Risks Section Title Requirement 5.1 Documentation Required 5.1.1 General Include statements of policy and quality objectives, standard operating procedures etc. 5.1.2 Examples of documentation Document to include requirements of Section 4. 5.1.3 Control of documents Establish procedures to review and approve and maintain documents. 5.1.4 Control of records Maintain evidence of conformity to requirements of this standard. 5.2 Human Resources 5.2.1 General Personnel performing work on the DS will be competent on the basis of appropriate education, training, skills, test requirements, and experience. 5.2.2 Competence, awareness, and training The utility shall provide training and determine competence. SOURCE: Excerpted, with permission, from AWWA/ANSI G200 (2004). © 2004 by American Water Works Association. As discussed in Chapter 2, the use of the standards such as ANSI/NSF 60, ANSI/NSF 61, and AWWA G200 and Manuals of Practice have advantages over programs such as Hazard Analysis and Critical Control Points (HACCP) in that they are more easily adapted to the dynamic nature of drinking water distribution systems. Use of a standard such as G200 that is intended to assess whether the system can be managed under all conditions is appropriate for utilities that desire to operate beyond regulatory requirements. To minimize the public health risks of distribution systems, it is recommended that drinking water utilities adopt G200 or an equivalent program in order to develop distribution system management plans that combine their regulatory requirements and available voluntary standards. The purpose of this chapter is to discuss certain elements of G200 that deserve more thoughtful consideration because emerging science and technology are altering whether and how these elements are implemented by a typical water utility. Much of the current scientific thrust is in the development of new monitoring methods, models, and methods to integrate data, all to better inform decision making. MONITORING Drinking water of “acceptable quality” is defined by the Safe Drinking Water Act (SDWA) and its amendments and is framed in terms of the Maximum Contaminant Levels (MCLs), treatment techniques, rules, and regulations promulgated under the Act. The regulations contain significant monitoring require-

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Drinking Water Distribution Systems: Assessing and Reducing Risks ments that prescribe the sampling frequency (minimum monitoring frequencies), sampling locations, testing procedures, record keeping, and the water quality parameters to be monitored, and are classified according to system size and vulnerability. The regulations also cover specific reporting procedures to be followed if a contaminant exceeds an MCL. Failure to have the proper water quality analyses performed or to report the results to the state primacy agency can result in the water system having to provide public notification. Under the SDWA, monitoring or treatment techniques are required for all contaminants regulated under the Act, both at the entry point to a water distribution system and, in some cases, at various locations within the system. Rules and regulations that explicitly require monitoring in the distribution system include the Total Coliform Rule (TCR), the Surface Water Treatment Rule (SWTR) and Long-Term Enhanced Surface Water Treatment Rule (LTESWTR), Lead and Copper Rule (LCR), and the Stage 2 Disinfectants/Disinfection By-Products Rule (Stage 2 D/DBPR). These requirements are summarized in Table 7-2. Routine compliance monitoring is a useful tool for detecting and assessing some common water quality problems throughout a system if the event is large enough and long enough in duration to be detected (Byer and Carlson, 2005). Note that pressure monitoring is not required by any of the existing rules, which is unfortunate. The compliance monitoring required by the SDWA is limited in its ability to protect public health because the end-point or customer tap monitoring required under the regulations is typically (1) not sufficient to provide early warning of contamination, (2) not indicative of what could have gone wrong between the treatment plant and the consumer’s tap so as to effectively guide remediation, and (3) too limited across space (too few sampling locations) and time (discrete small volume samples are collected too infrequently) to provide information that applies to every potential user. The realities of financial and personnel resources in most cases preclude expanding monitoring programs to cover vastly larger areas and periods of time. Rather, it is more useful for utilities to consider how to control the processes taking place within the distribution system, as well as activities to maintain the processes, such that the risk of the customer being exposed to contaminated drinking water is minimized. This concept hinges on viewing a water distribution system as a linkage of processes working together to maintain flow, pressure, and water quality. These processes include pumping, valving, metering, transmission, distribution, service, storage, and corrosion control, to name a few. Though each individual distribution system is a unique linkage of processes, the processes have common characteristics that allow generalizations to be made about their control. For example, the number of storage tanks from one system to another may be different, but there are common problems with hydraulic retention time and chlorine loss in all storage tanks. The variety of pipes used (materials and sizes) will differ from one system to another, but cast iron displays a common corrosion problem in all systems.

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Drinking Water Distribution Systems: Assessing and Reducing Risks TABLE 7-2 Federal Distribution System Water Quality Monitoring Requirements Regulation Monitoring Requirement Total Coliform Rule Samples must be collected at sites that are representative of the water throughout the distribution system based on a sample siting plan that is subject to review by the primacy regulatory agency. The minimum number of samples that must be collected per month depends on the population served by the system. For each positive total coliform sample, there are various repeat sampling requirements. Surface Water Treatment Rule (SWTR) and multiple Long-Term Enhanced Surface Water Treatment Rules (LTESWTRs) Disinfectant residuals must be measured at TCR monitoring sites. Disinfectant residual must be monitored at the entry to the distribution system. Larger systems (> 3,300 population) must provide continuous monitoring. Systems serving less than 3,300 population can take grab samples. Lead and Copper Rule (LCR) All systems serving a population > 50,000 people must do water quality parameter (WQP) monitoring. Samples must be collected for Pb/Cu at Tier I sites. The number of sample sites for Pb/Cu and water quality monitoring is based on system size. Stage 2 Disinfectants/ Disinfection By-Products Rule (DBPR) Standard Monitoring Program requires one year of data on THMs and HAAs. Number of sampling locations based on utility size and source characteristics. Modeling can reduce sampling requirement. SOURCE: Owens (2001) and Lansey and Boulos (2005). In addition to being a linkage of processes, the distribution system is also a reactor, in that treated drinking water begins to change physically (e.g., iron and manganese particles settle out), chemically (e.g., chlorine begins to decompose) and biologically (e.g., bacterial cells begin to adhere to pipe surfaces and form biofilms) as soon as water leaves the treatment plant. Each of the processes display common tendencies to promote these changes irrespective of how they are linked within a distribution system. Real-time feedback on whether a utility’s distribution system processes are in or out of control goes beyond the regulatory requirements for water quality monitoring mentioned above. The following sections discuss monitoring for process control; they are intended to build upon discussions of detection methods and tools, such as such Geographic Information System (GIS) and hydraulic modeling, found earlier in the report. A systematic strategy for distribution system monitoring to detect water quality alterations is comprised of the following actions: (1) develop a list of parameters to be monitored, (2) assess appropriate temporal and spatial scales for monitoring, (3) develop a response plan for monitored parameters, and (4) implement. Each of these activities is discussed

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Drinking Water Distribution Systems: Assessing and Reducing Risks below, focusing on recent scientific developments that should lead to improvement in how the activities are conducted. Parameters to be Monitored The parameters that are useful for monitoring distribution system processes may include those that are required from a regulatory point of view (e.g., turbidity, chlorine residual), but likely would include others. The key requirements are that the monitoring parameters can be measured relatively quickly, inexpensively, and (ideally) continuously at multiple locations in the system. The parameters should be selected with consideration for the potential mechanisms that may induce adverse changes in water quality. For example, in corrosive waters passing through ductile iron pipe, conductivity, pH, and oxidation reduction potential (ORP) may be useful. In waters passing through polymeric pipe or vulnerable to intrusion in contaminated overlying soils, UV254 or TOC may be useful. Table 7-3 lists sentinel parameters that could be used to indicate changes in distribution system integrity. These parameters include indicators of physical deterioration (pressure changes, main breaks, water loss, or corrosion), hydraulic failure (turbidity, complaints of low flow or pressure) or a water quality failure TABLE 7-3 Sentinel Parameters for Distribution System Integrity Parameter Physical Hydraulic Water Quality Routine (Primary) Pressure X X   Turbidity X X (flow reversals) X Disinfectant residual   X (water age) X Main breaks X     Water loss X     Color X (corrosion)   X Coliforms X (sanitary, main break)   X (biofilms) Flow velocity and direction   X (pipes, tanks)   pH, Temperature     X Chemical parameters X X X Secondary TOC     X UV Adsorption     X T&O X (permeation) X (water age) X (biofilms) Metals X (corrosion)   X Nitrite     X (nitrification) HPC     X (biofilms??) Tank level/volume   X   Note: Bold entries indicate those parameters for which on-line real-time sensors are available.

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Drinking Water Distribution Systems: Assessing and Reducing Risks (particulates, tastes, odors, or color). For some of the parameters (listed in bold), on-line monitoring equipment is available to provide real-time control of distribution system operations. Most methods for monitoring physical characteristics of water (e.g., flow, velocity, water level in a storage tank) tend to be relatively inexpensive, quite durable, and able to generate continuous, real-time, on-line data (Grayman et al., 2004; Panguluri et al., 2005a). Less available in on-line, real-time versions are methods for detecting inorganic chemicals, synthetic organic chemicals, volatile organic chemicals, and radionuclides. The direct real time detection of biological changes within distribution systems remains beyond current technology (Bernosky, 2005). Pressure. One of the most important parameters for utilities to consider monitoring for is transient pressure change using high-speed, electronic pressure data loggers. Recent research has documented the frequency and magnitude of pressure transient events (Friedman et al., 2004; Gullick et al., 2005). High-speed data loggers are required for monitoring distribution system pressure transients because such transients may last for only seconds and may not be observed by conventional pressure monitoring. High-speed pressure data loggers can measure pressures at a rate of up to 20 samples per second, allowing measurement of sudden changes in pressure. The units can be programmed with preset alarm levels to notify operators when specific thresholds have been exceeded. Additionally, some units can be programmed to capture and store specific data surrounding a pressure transient event, permitting the episode to be analyzed and corrective actions to be determined. Turbidity. Turbidity in distribution systems, which can be can be caused by suspended sediments, oxidized iron or manganese, or other corrosion products, is another critical parameter for which on-line, real-time methods are available. Various models exist but in the finished water distribution system, turbidity probes need to be sensitive at low ranges (i.e., < 1 NTU). Measurement accuracy may be improved further by employing wiper or shutter mechanisms that are activated immediately prior to measurements to avoid interferences from particulates or air bubbles. In general, turbidity units from different manufacturers behave similarly, and calibration frequencies vary from weekly up to three monthly intervals, but require a good level of operator skill. On-line turbidimeters are being used successfully under the Partnership for Safe Water Program to monitor low level (< 0.3 NTU) turbidity, and therefore should prove valuable for low level turbidity in distribution system monitoring. Disinfectant Residual. Disinfectant residual monitors can measure free chlorine, chloramines, or ORP. The principle of detection for residual on-line sensors relies on either polarographic, voltametric, or colorimetric methods which can influence their sensitivity, calibration, and interferences from other water quality parameters. Operation of an ORP sensor is similar to that of the pH sensor where a two-electrode system is used to make potentiometric meas-

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Drinking Water Distribution Systems: Assessing and Reducing Risks urements. The calibration frequency for these monitors is usually on a monthly basis. Typical data from continuous monitoring of total chlorine residual is shown in Figure 7-1. Flow. In-line meters are available to measure flow in the distribution system but are typically used only to monitor flows into distribution system sub-districts. Monitoring flows by sub-district can be compared to customer meter data to indicate the amount of leakage in specific areas of the distribution system. Flows can be influenced by pumping regimes, storage tank operations, and manipulations of hydrants or blow-off valves. Use of a well-calibrated distribution system hydraulic model along with pump, tank, and flow data is required to generate detailed descriptions of distribution system water velocities and flow reversals. pH. Measurements of pH are made with a pH meter using a glass indicator electrode. These measurements are reliable, but the meter requires regular calibration to avoid drift. Temperature. Temperature thermistors typically work over a relatively small temperature range and can be very accurate within that range. The measurements are very reliable and typically do not require routine calibrations. FIGURE 7-1 Data from a continuous, on-line chlorine analyzer, showing how a total chlorine residual can vary through a day and the need to relate this to system operations. SOURCE: Data from Philadelphia Water Department, Bureau of Laboratory Services.

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Drinking Water Distribution Systems: Assessing and Reducing Risks Chemical Parameters. For chemical parameters, EPA has been examining the reliability of on-line sensors under the Environmental Technology Verification (ETV) Program (EPA, 2004a,b). Currently this program has examined 40 monitoring and treatment technologies and plans to conduct additional testing under the newly formed Technology Testing and Evaluation Program (TTEP)—an off shoot of the ETV program, which is not dependant upon voluntary vendor involvement. This independent testing is providing a valuable database on the reliability of on-line monitors (http://www.epa.gov/etv/). The sensors being developed are not specific for the chemical contaminants themselves. Rather, the premise of the research is that a chemical contaminant in a distribution system would elicit a pattern of changes in other, primary parameters that can be easily measured in real time, such that changes in their detection would indicate the presence of the contaminant. Table 7-4 shows the responsiveness of various water quality parameters to a range of contaminants in controlled experimental tests. It should be noted that the actual ability of the on-line sensors shown in Table 7-4 to detect a target contaminant in field situations has not been ascertained. Hence, whether a particular pattern of shifts in a battery of on-line analysis results can be reliably associated with a particular type of contaminant (e.g., malathion) is uncertain. Another National Research Council committee is in the process of examining research needs in the area of drinking water homeland security, and further discussion of this issue may be found in its report. TABLE 7-4 Responsiveness of parameters that can be easily measured on-line to various contaminants Contaminant Compound Water Quality Parameter Free/total chlorine ORP TOC SC Turbidity NH3 N2 NO3- Cl- Ferricyanide NC (F+ w/DPD test) + ++a + + F-   F- F- Malathion (pesticide) + + + NC +       + Glyophosphate (herbicide) + + + NC NC       + Nicotine (organic) ++   ++ NC           Arsenic trioxide ++ ++ NC   + ++ ++     Aldicarb ++   ++             Groundwater + + NC + NC       + Wastewater + + + + +       + Key: ++ = very responsive, + = responsive, F+ = false positive, F- = false negative, NC = no change Abbreviations: ORP, oxidation/reduction potential; TOC, total organic carbon; SC, specific conductance. aMay be due to bound carbon in the cyanide complex, from Hall et al. (2005). Note: For the pesticides and herbicides, commercial products were used that had different concentrations of organic compounds. SOURCE: Adapted from Hall et al. (2005).

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Drinking Water Distribution Systems: Assessing and Reducing Risks tribution network, operation and maintenance, and overall management to continually provide safe drinking water and to identify any deficiencies that may adversely impact a public water system’s ability to provide a safe, reliable water supply.” The TCR has a requirement for periodic sanitary surveys for all small systems that collect less than five samples per month. The SWTR requires an annual on-site inspection for surface water systems that do not filter. The IESWTR now requires a survey for all surface water and groundwater-under-the-direct-influence systems and requires that each of eight elements be addressed (source; treatment; distribution system; finished water storage; pumps, pump facilities, and controls; monitoring and reporting and data verification; system management and operation; and operator compliance with state requirements) as well as the correction of significant deficiencies. These surveys are required every three to five years. A sanitary survey might reveal an absence of training, use of standards, routine inspections, or certifications that could be predictive of a loss of distribution system integrity. The distribution system components of the sanitary survey include: Distribution system maps and records, field sampling and measurements, system design and maintenance Finished water storage location, capacity, design, painting, cleaning and maintenance, security Pumps and pump facilities and controls capacity, condition, pumping station Water system management and operation administrative records, water quality goals, water system management, staffing, operations and maintenance manuals and procedures, funding Operator compliance with state requirements such as certification and competency. The Drinking Water Academy developed software for use by state sanitary inspectors in accomplishing all aspects of a sanitary survey with some level of uniformity. This software can be used during field inspections with a PDA or Tablet PC (http://www.epa.gov/safewater/dwa/e-sansurvey.html). A benefit to using this mechanism for promoting G200 is that the sanitary surveys encompass a wide variety of activities and would likely capture those felt to be of highest priority for reducing risk (e.g., cross-connection control and water storage facility inspections). Indeed, the EPA’s Sanitary Survey program could be reviewed and compared to G200 to see whether the former might be expanded. However, this approach is likely to succeed only if sufficient funds are provided to support more comprehensive sanitary surveys. In addition, current regulations for the sanitary survey exempt or avoid a large number of water supply systems, effectively limiting the reach of this mechanism.

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Drinking Water Distribution Systems: Assessing and Reducing Risks GASB Accounting Requirements. Another approach for encompassing some of the elements of G200 and the committee’s high priority activities under existing federal regulations is through the Government Accounting Standards Board (GASB) Statement 34 on Basic Financial Statements and Management’s Discussion and Analysis for State and Local Governments (GASB, 1999). This regulation requires that all capital assets be documented and reported in financial statements by looking at the long-term health of government institutions throughout the United States, including municipally owned water utilities (Romer et al., 2004). The reporting includes the valuation of infrastructure and related disclosure of deferred maintenance costs on treatment plants, pump stations, storage facilities, and distribution systems (Donahue, 2002), and thus is well positioned to provide the asset management functions called for in G200 and in Chapter 4. Indeed, GASB 34 has encouraged the application of asset management in order to meet requirements (Cagle, 2005). With respect to the specific problems that cause water quality deterioration in distribution system, GASB 34 may “inadvertently become the regulatory mandate for corrosion control since uncontrolled asset deterioration can negatively impact financial statements and, therefore, limit or degrade the ability of a utility to raise money for capital improvement using bonds. Utilities that have good corrosion control programs will have better financial statements and bond ratings” (Romer et al., 2004). State Regulatory Approach In lieu of federal regulations, state regulations could require adherence to G200 or the committee’s list of preferred activities for reducing risk in distribution systems. This approach is limited primarily by the fact that some states would legally be unable to make such modifications, while others could. State and Local Building and Plumbing Codes. A logical avenue would be to consider enhancing state building and plumbing codes to cover more issues or simply to make enforcement of current codes more uniform. Tables 2-3 through 2-5 show that states vary in their enforcement of state and local codes for plumbing, health, building, real estate, etc. Clearly, more stringent details within these codes could be applied. These codes are, however, unlikely to be able to cover all activities considered to be of high priority for reducing distribution system risk. Similarly, design and construction requirements at the state level could be modified to capture important elements of G200. Tables 2-3 through 2-5 show that the SDWA and states already have in place design and construction standards, enforced largely through the permitting process. Permits are required when a new system is built or when a significant change to an existing system is made. State building codes could be expanded, for example, to require inspections for cross connections prior to granting building permits on existing proper-

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Drinking Water Distribution Systems: Assessing and Reducing Risks ties or prior to closing of a sale (as is the case for radon inspections in some jurisdictions). The permit process could also address the design of service lines and premise plumbing for water quality maintenance (e.g., existence of dead ends, oversized lines, compatible materials), the extent of lead and copper corrosion, hot water system maintenance, the level of disinfectant residual at taps, and the presence of scale and sediment. State Revolving Fund. Another possibility is that to qualify for a loan from the State Revolving Fund a utility would have to demonstrate that it is adhering to G200 or an equivalent list of activities. The 1996 Amendments (Public Law 104-182) to the SDWA established the Drinking Water State Revolving Fund (DWSRF), intended to facilitate compliance with applicable national drinking water regulations or significantly further the health protection objectives of SDWA. States operate their respective DWSRF programs using annual capitalization grants from EPA and a 20 percent matching contribution from the state. Up to 30 percent of the federal grant can be used to assist public water systems serving disadvantaged communities through subsidized loans or loan forgiveness. However, under SDWA section 1452(a)(3) states are prohibited from providing DWSRF assistance to a public water supply that does not have the technical, managerial, and financial capability to ensure compliance with the requirements of the SDWA. EPA could clarify that any public water system that does not have a program for managing the distribution system such as G200 should be viewed as lacking such capability. The SDWA does allow a public water system to receive DWSRF funding if the owner or operator of the system that lacks capacity agrees to undertake feasible and appropriate changes in operations (including ownership, management, accounting, rules, maintenance, consolidation, alternative water supply, or other procedures) that the state determines would ensure the system’s technical, managerial, and financial capacity. This provision could be used to promote the use of G200 by requiring that a public water system, as a condition of receiving DWSRF funding, agree to develop a plan for the implementation of those elements of G200 that are feasible given the size, complexity and resources of the system. It should be noted that the State Revolving Fund is generally used for capital investment, but it might be used to comply with G200 if it had to do with construction practices in some way. This might, however, dilute the objective of the Fund, which is to bring water supplies into compliance. Bond Ratings. In addition to facilitating the acquisition of DWSRF funding by small, disadvantaged communities, implementation of G200 could also improve a drinking water utility’s access to capital in other ways, particularly for municipally owned water systems. Drinking water utilities in the United States have historically depended on the municipal bond market to finance both the development of public water supplies and their expansion into surrounding

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Drinking Water Distribution Systems: Assessing and Reducing Risks areas (Cutler and Miller, 2005). The same practices that are encouraged by the implementation of G200 may also help improve a municipality’s bond rating. The two main categories of long-term bonds available to municipalities are general obligation bonds, secured by a pledge of the government’s taxing power, and revenue bonds, secured by the exclusive (in most cases) pledge of a project’s revenues. The following five factors are generally used by bond rating authorities for general obligation bonds: (1) general economy, (2) debt structure, (3) financial condition, (4) demographic factors, and (5) management practices of the governing body and administration. Because of this last factor (management and administrative practice), a utility that follows the elements of G200 as outlined in Table 7-1 along with a sound pricing policy should be in a position to receive a better bond rating, as well as to obtain funding under the DWSRF, than a utility that does not adhere to G200. Federal Guidance In lieu of a regulatory incentive for adopting G200, EPA could advocate a list of preferred activities as a way of meeting federal regulations for distribution systems. This might appear in updated versions of guidance manuals. The EPA already provides extensive guidance to help water utilities achieve and maintain compliance, including a capacity development program to assist water systems in achieving SDWA compliance (Stubbart, 2005). The program addresses managerial, technical, and financial capacities involving all aspects of the system from source water through treatment to distribution. Technical aspects include how to provide certified operators and reliable infrastructure. Especially with small systems, the program can help identify weaknesses and in turn identify avenues for support to eliminate those weaknesses. It also discusses the various support that is needed to fund and maintain an adequate distribution system maintenance and replacement program. CONCLUSIONS AND RECOMMENDATIONS This chapter has discussed the limitations of compliance monitoring to detect, respond to, and protect against an internal or external contamination event in the distribution system that might jeopardize public health. To affect real risk reduction from contaminated distribution systems, efforts beyond compliance monitoring are required. The AWWA G200 standard outlines voluntary activities that if implemented would provide substantial risk reduction from distribution systems. Many elements of G200 are critical to maintaining distribution system integrity, although they do not necessarily suffer from scientific or technological limitations. The reader is referred to previous chapters for conclusions and recommendations on these activities, which include cross-connection control, maintenance of storage facilities, asset management, and training and certi-

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Drinking Water Distribution Systems: Assessing and Reducing Risks fication of system operators, inspectors, foremen, and managers. The following conclusions and recommendations pertain to those elements of G-200 for which emerging science and technology are altering whether and how these elements are implemented by a typical water utility. The committee recognizes that because of cost and personnel limitations these recommendations are probably not feasible for many medium- and small-sized utilities at the present time. Nonetheless, the monitoring and modeling activities discussed represent an endpoint toward which utilities should be striving. It is hoped that the gap between what is needed to affect water quality improvement and what utilities are capable of will shrink in the near future. Distribution system integrity is best evaluated using on-line, real-time methods to provide warning against any potential breaches in sufficient time to effectively respond and minimize public exposure. This will require the development of new, remotely operated sensors and data collection systems for continuous public health surveillance monitoring. These types of systems should be capable of accurately (with sufficient precision) determining the nature, type, and location/origin of all potential threats to distribution system integrity. The availability, reliability, and performance of on-line monitors are improving, with tools now available for detecting pressure, turbidity, disinfectant residual, flow, pH, temperature, and certain chemical parameters. These devices have reached the point for greater full-scale implementation. Additional research is needed to optimize the placement and number of monitors. Research is needed to better understand how to analyze data from on-line, real-time monitors in a distribution system. This should focus on algorithms that can integrate real-time hydrological conditions, water quality inputs, and operational data to evaluate and interpret on-line monitor signals, establish alarm triggers, and suggest remedial actions. A number of companies are selling (and utilities are deploying) multi-parameter analyzers. These companies, as well as EPA, are assessing numerical approaches to convert such data into a specific signal (or alarm) of a contamination event—efforts which warrant further investigation. Some of the data analysis approaches are proprietary, and there has been limited testing reported in “real world” situations. Furthermore, when multiple analyzers are installed in a given distribution system, the pattern of response of these analyzers in space provides additional information on system performance, but such spatially distributed information has not been fully utilized. To the greatest degree possible, this research should be conducted openly (and not in confidential or proprietary environments). A rigorous standardized set of network model development and calibration protocols should be developed. While there is a general agreement in the modeling profession that the extent of development and calibration required for a water distribution network model depends largely upon its intended use, there are no universally accepted standards and there is currently no apparent

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Drinking Water Distribution Systems: Assessing and Reducing Risks movement toward establishing such standards. Poorly defined and calibrated models can lead to management decisions being made based on false or erroneous data, and recommendations that may not even work. Continued research is needed to improve network model development and calibration methodologies (including optimization techniques) and in standardization of calibration. In addition, improved monitoring technology, such as more affordable meters that can be inserted into distribution pipes and automated monitoring for use in conjunction with tracer studies, will greatly improve calibration of distribution system models. Additional research, development, and experimental applications in data integration are needed so that distribution system models can be used in real-time operation. Real-time monitoring and modeling of water distribution systems to assist water utilities in making informed operational decisions under routine and emergency conditions requires the integration of network models with SCADA systems, which has yet to be accomplished at most utilities. The SCADA system can be used to update the boundary conditions in the network model such as tank water levels, pump on/off status, isolation valve status, control valve settings, and system demands, and the model can in turn be used to identify the “best” operational strategy for the selected facilities and pass their control logic back to the SCADA system for implementation. The ability to integrate network models with SCADA systems offers a number of benefits to the water industry including at a minimum: confirmation of normal system performance; real-time calibration; system trouble shooting; projection of operating scenarios; evaluating “what-if” scenarios; training for and responding to emergencies; and improvement of overall operations. These benefits can only be realized if both systems can communicate quickly and properly with one another. Continued work is needed to develop data integration standards that will allow seamless data exchange for monitoring and controlling system operations and make them available to the water industry. Further development is also needed to expand the ability of GIS to enable time-series data (e.g., historical or obtained from real-time measurements) to be associated with geospatial attributes. REFERENCES American Water Works Association/American National Standards Institute (AWWA/ANSI). 2004. G-200: Distribution Systems Operation and Management. Denver, CO: AWWA. AWWA Engineering Computer Applications Committee. 1999. Calibration guidelines for water distribution system modeling. In: Proceedings of the 1999 AWWA Information Management and Technology Conference, New Orleans, Louisiana, April 1999.

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Drinking Water Distribution Systems: Assessing and Reducing Risks Berry, J., W. Hart, C. Phillips, and J. Uber. 2004. A General Integer-Programming-Based Framework for Sensor Placement in Municipal Water Networks. World Water & Environmental Resources Congress, EWRI-ASCE. Bernosky, J. J. 2005. Distribution system security. Pp. 155–181 In: Distribution System Water Quality Challenges in the 21st Century: A Strategic Guide. M. J. MacPhee (ed.). Denver, CO: AWWA. Booth, D. E., P. Alam, S. N. Ahkam, and B. Osyk. 1989. A robust multivariate procedure for the identification of problem savings and loan institutions. Decision Sciences Journal 20(2):320–333. Boulos, P. F., B. W. Karney, D. J. Wood, and S. Lingireddy. 2005. Hydraulic transient guidelines for protecting water distribution systems. J. Amer Water Works Assoc. 97(5):111–124. Boulos, P. F., K. E. Lansey, and B. W. Karney. 2006. Comprehensive Water Distribution Systems Analysis for Engineers and Planners. Pasadena, CA: MWH Soft Publisher. Buchberger, S. G., J. T. Carter, Y. H. Lee, and T. G. Schade. 2003. Random demands, travel times and water quality in deadends. Denver, CO: AWWA. Bukhari, Z., and M. W. LeChevallier. 2006. Early warning systems to protect distribution system water quality. A report submitted to American Water, Voorhees, NJ. Burlingame, G. A. 1999a. Solving customers’ taste and odor complaints—Part 1: the importance of the first response. Opflow 25(10):10–11. Burlingame, G. A. 1999b. Solving customers’ taste and odor complaints—Part 2: tracking odors to their source. Opflow 25(11):6–7. Byer, D., and K. H. Carlson. 2005. Real-time detection of intentional chemical contamination in the distribution system. J. Amer Water Works Assoc. 97(7):130–133. Cagle, R. F. 2005. Daddy, are we there yet? Underground Infrastructure Management Jan/Feb:43–46. Cesario, L. 1995. Modeling, analysis, and design of water distribution systems. Denver, CO: AWWA. Clark, R. M., and J. A. Coyle. 1990. Measuring and modeling variations in distribution system water quality. J. Amer. Water Works Assoc. 82(8):46–53. Clark, R. M., and R. M. Males. 1986. Developing and applying the water supply simulation model. J. Amer. Water Works Assoc. 78(8):6l–65. Clark, R. 1998. Chlorine demand and TTHM formation kinetics: a second-order model. J. Environmental Engineering 124(1):16–24. Clark, R. M., and W. M. Grayman. 1998. Modeling water quality in drinking water distribution systems. Denver, CO: AWWA. Clark, R. M., W. M. Grayman, and R. M. Males. 1988. Contaminant propagation in distribution systems. Journal of Environmental Engineering, ASCE 114(4):929– 943. Clark, R. M., and M. Sivaganesan. 1998. Predicting chlorine residuals and the formation of TTHMS in drinking water. Journal of Environmental Engineering 124(12):1203– 1210. Clark, R. M., and M. Sivaganesan. 2002. Predicting chlorine residuals in drinking water: a second order model. Journal of Water Resources Planning and Management 128(2):1–10. Clark, R. M., R. Thurnau, M. Sivaganesan, and P. Ringhand. 2001. Predicting the formation of chlorinated and brominated by-products. Journal of Environmental Engineering 127(6):493–501.

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