<IP_ADDRESS> Disinfectant Residual Data Because chlorine and chloramines decay over time, low disinfectant residuals relative to those leaving the treatment facility ( or entering through a consecutive system entry point) can generally be The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 22 Sources of disinfectant residual data:  TCR data  Stage 1 DBPR data ( for some systems)  Operational sample sites  Sampling in response to customer complaints considered an indicator of increased water age. A review of disinfectant residual data from existing distribution system monitoring sites can help identify the areas of your system with the highest residence time and those with average residence time. Sources of disinfectant residual data may include regular compliance monitoring sites ( e. g., Total Coliform Rule ( TCR) or Stage 1 DBPR monitoring sites), operational sample sites, or special sites sampled in response to customer complaints. Combining the data from these various sample sites may help you better understand the change in disinfectant residual as water flows through your distribution system and, consequently, help you choose the required SMP sample sites.

There are cases, however, where lower disinfectant residuals do not necessarily indicate greater water age. Common factors that can influence disinfectant residual decay and affect the relationship between residual levels and water age are:

° Pipe material and internal lining ° Corrosion condition in the pipe ° Biofilm growth in the pipe ° Accumulation of sediment in the pipe ° Booster disinfection In particular, use of disinfectant residual data becomes difficult when booster disinfection is applied. Booster disinfection is the practice of adding a disinfectant in the distribution system to raise the disinfectant residual concentration and is commonly used in peripheral zones of the distribution system or near storage tanks where water age may be high and disinfectant residuals are low. TTHM and HAA5 levels are likely to increase after a booster disinfectant is applied. Additional TTHM and HAA5 may be formed due to the greater concentration of disinfectant available for reaction with DBPs precursors. Furthermore, the additional disinfectant prevents the biological degradation of HAA5, thus favoring their accumulation in the areas of the distribution system affected by booster chlorination.

If your system does not have much disinfectant residual data, or if you are not able to identify sites with average or high residence times based on your existing data, you may want to collect additional disinfectant residual data from your system to better characterize your system and provide a better basis for selecting SMP sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 23 1) High TTHM and High HAA5 Sites Booster Disinfection If your system uses booster disinfection continuously or intermittently, the high TTHM and HAA5 sites should not be located before a booster disinfection station.

Low Disinfectant Residual Relative to System Average Low disinfectant residuals relative to the system average generally indicate longer residence times, and may correlate with higher TTHM and HAA5 concentrations. Very low or no disinfectant residual, however, could also indicate biological decay of HAA5, and should generally not be chosen as your high HAA5 site.

° When selecting preliminary high HAA5 sites, locations with free chlorine residuals less than 0.2 mg/ L or chloramine residuals less than 0.5 mg/ L should not be selected because of the potential for biodegradation of HAA5.

° High HAA5 sites should have no significant increase in recorded HPCs to ensure a low potential for HAA5 biodegradation. If you have HPC data, a comparison of disinfectant residual and HPC data can help you more precisely determine the threshold disinfectant residual below which HPC levels begin to increase. However, HPC testing is not required as a part of the IDSE.

Review Disinfectant Residual Data from the Warmer Months Because disinfectant residuals typically decay faster during the summer, a review of data from the summer months may be more useful in identifying areas with consistently low residuals. During the winter, disinfectants are usually more persistent, and residuals can often be maintained in relatively old water within a distribution system. The correlation between residence time and residual decay is less pronounced in the colder months.

2) Average Residence Time Sites One of the best ways to calculate average residence time is by using a hydraulic model ( see Chapter 3 for information on hydraulic modeling). However, if this tool is not available, calculating the average disinfectant residual in your distribution system can help you identify locations with average water residence time ( this method is not valid for areas in the influence of booster disinfection). When calculating average disinfectant residual, it is important that you use data from sites that are representative of your entire distribution system. One way to do this is to limit data to those collected at your TCR monitoring sites ( the TCR requires that all monitoring sites combined represent the The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 24 distribution system). Use of historical data or other data ( e. g., data from customer complaints) could skew the results if a large portion of the data are from a single area.

Assuming your disinfectant residual data are representative of your distribution system, the following analysis of TCR monitoring data can be used to help identify sites with average residence time:

1) Calculate an average disinfectant residual at each of your TCR sites using data from your warmest months ( chlorine decay is more pronounced in warmer temperatures so you are more likely to see larger changes in chlorine residual from one point to the next).

2) Using averages from the individual sites, calculate an overall distribution system average residual concentration.

3) Those sites with an average residual close to the distribution system average can be considered representative of average residence time in the distribution system.

Note, if your system has booster disinfection, then residual data collected after those locations will skew this analysis. You should either omit that data or estimate what the residual would be without the added disinfectant. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 25 Monthly Average ( mg/ L) Jun Jul Aug # 1 1.4 1.3 1.6 1.4 # 2 0.7 0.9 0.7 0.8 # 3 1.0 0.9 1.2 1.0 # 4 0.6 0.6 0.7 0.6 # 5 0.9 1.2 1.4 1.2 # 6 0.4 0.5 0.4 0.4 # 7 0.2 0.3 0.6 0.4 # 8 1.5 1.7 1.7 1.6 # 9 0.9 0.7 0.8 0.8 # 10 0.5 0.3 0.8 0.5 Distribution System Ave 0.8 0.8 1.0 0.9 Site Average ( mg/ L) Site ID Example 8.12 System Average Disinfectant Residual Calculation A system with June, July, and August as their warmest months has the residual data below. The averages for the system and each site are calculated as shown. Note that sites # 2, # 3, and # 9 have average chlorine residual concentrations close to the system average. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 26 <IP_ADDRESS> DBP Data Non compliance DBP ( TTHM and HAA5) data, collected in addition to your Stage 1 DBPR compliance monitoring data, can be useful in selecting high TTHM and high HAA5 SMP sites. Remember, however, that Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites ( 141.602( b)). For surface water systems, historical DBP data should be evaluated with respect to raw water quality conditions before and during the sampling period ( e. g., changes in TOC concentration from year to year can significantly affect DBP levels). DBP data should not be used for the purpose of estimating average residence time because DBP formation is complex and dependent on many factors. ( See Appendix B for a discussion of DBP formation.)

If your system has extensive non compliance TTHM and HAA5 data at a variety of sites throughout your distribution system, you may wish to consider completing an SSS based on your historical data, possibly with a limited amount of new monitoring. See Chapter 3 if you think you may be able to use historical data alone or in combination with other data for an SSS.

High TTHM and High HAA5 Sites Regulatory compliance data ( including all data collected under the Stage 1 DBPR) are not a definitive source for identifying the representative high TTHM and HAA5 concentrations. There may now be other areas with higher TTHM and HAA5 concentrations that have not been sampled or do not have high historical results due to differences in flow or water quality at the time of sampling. Therefore, historical data should always be used in conjunction with other data sources and tools. Results from a Simulated Distribution System ( SDS) test can also be helpful in evaluating TTHM and HAA5 data. ( Section 8.4.3 describes the SDS test and how it can be used in conjunction with DBP data to select SMP sites and Appendix D describes the recommended procedure for conducting the SDS test.)

Good candidates for high TTHM and HAA5 sites include:

° Historic sample sites with high TTHM concentrations in areas with long residence times.

° Historic sample sites with high HAA5 concentrations in areas that consistently maintain a disinfectant residual.

° Historic sample sites with TTHM/ HAA5 concentrations that are close to the TTHM/ HAA5 concentration from an SDS test for maximum residence time. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 27 8.4.3 Simulated Distribution System Laboratory Test An SDS laboratory test is another tool that can be used in conjunction with Stage 1 DBPR compliance monitoring or other DBP data to select SMP sites. In the SDS test, finished water samples are collected ( generally at system entry points) and stored for selected periods of time at chemical and environmental conditions simulating those occurring in the distribution system ( e. g., temperature and pH). These samples are analyzed for TTHM and HAA5 concentrations at the end of the selected holding time. Appendix D describes the recommended procedures for conducting an SDS test. Note that this procedure would have to be modified if a system has a booster disinfection station.

One use of an SDS test is to confirm that existing Stage 1 DBPR or other DBP monitoring sites represent the maximum water residence time. For this purpose, SDS samples should be collected in conjunction with ( preferably on the same day or 1 to 3 days before) the DBP samples collected from the distribution system. At least one SDS sample should be stored for a period of time approximately equal to the maximum residence time, then analyzed for TTHM and HAA5 concentrations. ( Note: an SDS sample must have a detectable disinfectant residual at the end of the holding time.) It would also be useful in evaluating results to hold an SDS sample for a period of time equal to your average system residence time. If your maximum residence time is more than 5 days, a third SDS test, at a residence time between the average and maximum residence time, is recommended. All SDS samples should be stored at the same temperature as the distribution system water ( see Appendix D for suggested procedures).

If distribution system TTHM of HAA5 results are equivalent to or higher than the SDS maximum residence time TTHM or HAA5 results, you can infer that the site is likely representative of high TTHM or HAA5 levels. Remember that you cannot use Stage 1 DBPR sites for the SMP; however, you may wish to investigate other locations with similar hydraulic and disinfectant residual characteristics for your high TTHM SMP sites ( and high HAA5 sites if they meet other criteria). Examples 8.13 and 8.14 demonstrate how SDS test results and data from Stage 1 DBPR and operational monitoring sites can be used to select SMP sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 28 Example 8.13 Using the SDS Test to Evaluate Operational Monitoring Locations ( Big City Water)

Big City Water has collected the following distribution system data and SDS test results.

Sample Location/ Type TTHM ( µ g/ L) HAA5 ( µ g/ L)

SDS at Maximum Residence Time1 78 46 Stage 1DBPR Max Residence Time # 1 75 45 Stage 1DBPR Max Residence Time # 2 71 35 Operational Location # 1 79 43 Operational Location # 2 40 50 Operational Location # 3 80 45 Operational Location # 4 61 50 Note: In this example, the SDS sample was collected on a Monday; distribution system samples were collected during that week. 1 Maximum residence time determined using the results of a previously conducted tracer study.

Based upon the SDS results for Big City presented above, the following conclusions can be drawn:

° Stage 1 DBPR max residence time # 1 most likely represents high TTHM and HAA5 concentrations.

° Stage 1 DBPR max residence time # 2 may represent high TTHM, but not HAA5 ( possible biodegradation).

° Operational locations # 1 and # 3 most likely represent high TTHM and HAA5 concentrations.

° Operational locations # 2 and # 4 represent only high HAA5 concentrations.

For this example, high TTHM SMP sites should be located in areas with similar characteristics to Stage 1 DBPR max residence time # 1 and # 2, or operational locations # 1 and # 3. High HAA5 sites should be located in areas with similar characteristics to operational locations # 2 and # 4 ( as long as there is a disinfectant residual concentration). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 29 Example 8.14 Using the SDS Test to Evaluate Operational Monitoring Locations ( Blue Ridge Water)

Blue Ridge Water has the following SDS and distribution system data.

Sample Location/ Type TTHM ( µ g/ L) HAA5 ( µ g/ L)

SDS at Maximum Residence Time1 100 67 Stage 1DBPR Max Residence Time # 1 98 55 Stage 1DBPR Max Residence Time # 2 72 58 Operational Location # 1 65 45 Operational Location # 2 95 62 Operational Location # 3 91 72 Operational Location # 4 80 62 Note: In this example, the SDS sample was collected on a Monday; distribution system samples were collected during that week. 1 Maximum residence time calculated using an hydraulic model.

Based upon the SDS results for Blue Ridge presented above, the following conclusions can be drawn:

° Stage 1 DBPR max residence time # 2 may not be representative of high TTHM concentrations.

° Operational locations # 2 and # 3 most likely represent high TTHM and HAA5 concentrations.

° Operational location # 4 represents only high HAA5 concentrations.

For this example, high TTHM SMP sites should be located in areas with similar characteristics to Stage 1 DBPR max residence time # 1 or operational locations # 2 and # 3. High HAA5 sites should be located in areas with characteristics similar to operational location # 4 ( as long as there is a disinfectant residual concentration and no evidence of bacteriological activity). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 30 SDS results must viewed with caution. Distribution system conditions are complex and cannot be perfectly replicated in the laboratory, so some error is expected. Also, if you do not have a good idea as to your true maximum distribution system residence time, your SDS results may indicate your Stage 1 DBPR sites are inadequate when, in fact, they are representative of maximum residence time. Similarly, if the SDS test conditions are not representative to the treatment ( i. e., source and finished water quality) and distribution system conditions, the test results can be misinterpreted. If your system uses booster chlorination, the SDS test should be run for a finished water sample and a sample taken after the addition of the booster disinfectant dose.

Another use of an SDS test is to help describe DBP formation in the distribution system and, in conjunction with Stage 1 DBPR compliance monitoring and other data, determine average and maximum residence time. Appendix D describes how SDS tests can be used to estimate average and maximum residence time using DBP and chlorine residual data.

8.4.4 Models A water distribution system model is a computer program that simulates the hydraulic behavior of water in a distribution system. Water distribution system models are widely used in the water industry for planning and operations. Several public domain and commercial software modeling packages are available. For instance, EPA developed a water quality modeling software package, EPANET, that is available without charge via the internet. Your water distribution system model should be adequately calibrated when selecting SMP sample sites ( see Chapter 3 for a discussion of model calibration).

A water distribution system hydraulic model can predict water age in a distribution system when it is run under extended period simulation conditions ( i. e., water production, demand, etc., are allowed to change over time). In addition, most models can track the movement of water from each plant or supply point through the distribution system. Model results can provide a picture of the influence zone of each entry point and identify blending zones.

The size of your system and the degree of skeletonization of your hydraulic model will determine how useful the model can be for selecting SMP sites. Skeletonization refers to the degree of detail relating to distribution system piping in your model. Highly skeletonized models may only show large distribution mains and omit much of the smaller piping in individual subdivisions or other areas of the distribution system. In such cases, highly skeletonized models may be of limited use in large systems To obtain a free copy of EPANET go to:

http:// www. epa. gov/ ordntrnt/ ORD/ NRMRL/ wswrd/ epanet. html The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 31 where small pipes account for significant localized increases in system residence time. Because hydraulic models usually are somewhat skeletonized and have varying degrees of calibration and accuracy of demand allocation, best professional judgement should always be used when analyzing the results and using model outputs to assist in the selection of preliminary sites.

It is highly recommended that existing, calibrated water distribution and water quality models be used to estimate water age, identify influence zones, and identify mixing zones to help select SMP sample sites. If a model does not already exist, the time and expense to create a new model and train staff solely for use in selecting IDSE SMP sample sites may not be justified. Model development or enhancement may be justified if you intend to employ the model for other uses in addition to the selection of SMP sample sites.

If you have an existing, detailed, well calibrated distribution system model, as well as appropriately trained staff to operate the model and evaluate results, you may wish to consider completing an SSS based on the use of your model and a limited amount of new testing. Chapter 3 describes the requirements for an SSS using a water distribution system model.

<IP_ADDRESS> High TTHM Sites Water distribution system modeling software can be used to identify high residence time locations ( most often your high TTHM sites) when used in the Extended Period Simulation ( EPS) mode. When the run time of an EPS model is long enough to produce a consistent pattern of water age values at all nodes, sometimes with repeating fluctuations due to diurnal variations in water demands, then the water age values at the model nodes can be used for the purpose of identifying high residence time locations.

One way to show high residence time locations is by color coding each model node according to its residence time. High TTHM sites should be chosen from the area or areas of the distribution system where the high residence time model nodes are located. The sample sites do not have to be chosen at the exact location of a model node, just in the general area identified by the model results.

Precautions in using model data to select high TTHM/ HAA5 sites include:

° If no water demand is applied to dead end nodes in a model or if the water demand in a dead end is highly uncertain, the water age results for those nodes can be unrealistic and meaningless.

° The accuracy of water age estimates from a model generally decreases as the model moves from large diameter mains to small diameter mains to subdivision piping and dead ends. This is due to the increasing uncertainty in water usage rates as one moves from large, aggregate demands to smaller demands exerted by a few customers or a single customer. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 32 ° If the model is skeletonized, the model results for high residence time areas should be compared to maps of the actual distribution system piping and to actual customer locations in those areas before sample sites are finalized in order to assure that the sample site is representative of the actual distribution system and not just the skeletonized model in the high residence time areas.

° Residence time is just one factor for identifying high TTHM sites and should be compared with other distribution system data ( e. g., disinfectant residual data) before making your preliminary SMP site selections.

Because water distribution system models usually are somewhat skeletonized and have varying degrees of calibration and accuracy of demand allocation, best professional judgement should always be used when analyzing the results and using model outputs to assist in the selection of preliminary SMP sample sites.

Blending Zones In some cases, there may be zones in the distribution system where water flowing from opposite directions meet. This can occur in:

° Long, looping mains ° The interface of the influence zones of two or more different supply points ° Areas where different pressure zones meet within one system This type of area is sometimes called a " blending zone" and may act as a hydraulic dead end. Blending zones can occur anywhere in the distribution system, but they more often occur in the central portion of a distribution system. If the water demand around the blending zone is low, then the water age and TTHM and HAA5 concentrations could be high. Hydraulic models can be useful in locating blending zones and identifying high TTHM or HAA5 locations within the blending zone.

<IP_ADDRESS> High HAA5 Sites The criteria and procedure for selecting preliminary high HAA5 SMP sites using a water distribution system model is generally the same as that described for selecting high TTHM sites with one important difference: the locations chosen to represent high HAA5 must have a detectable disinfectant residual. HAA5 concentrations typically increase in distribution systems as water age increases but can also decrease if disinfectant residuals are not present and biological activity is high. High HAA5 sites should be chosen from locations with a high residence time and a detectable disinfectant residual. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 33 <IP_ADDRESS> Average Residence Time Sites Average residence time SMP sites can be selected from locations with residence times close to the flow weighted mean of all nodal residence times ( or system average). As with selecting high TTHM/ HAA5 sites, color coding nodes by nodal residence time can be helpful. SMP sample sites should be chosen from the area or areas of the distribution system where the nodal residence time is close to the system average. The SMP sample sites do not have to be chosen at the exact location of a model node, just in the general area identified by the model results.

8.4.5 Tracer Studies Tracer studies can be used to determine actual water residence times in a distribution system under specific conditions and are sometimes used to calibrate water distribution system models. They are particularly useful for predicting water residence time in areas of a system where there is uncertainty about true pipe diameters due to poor records or the buildup of corrosion deposits affecting system hydraulics. When pipe diameters in a model are inaccurate, model predictions can be very different from the actual hydraulic conditions in a distribution system.

You can perform a tracer study by monitoring the concentration of a conservative constituent ( i. e., a chemical that does not degrade over time) through the distribution system. Chemicals used for tracers must not be harmful to people or the environment. Tracer chemicals can be substances that are:

° Specially injected or normally injected in the water for treatment purposes ( e. g., hydrofluorosilic acid or sodium fluoride)

° Characteristic of the finished water ( e. g., hardness, conductivity)

Before injecting any tracer, a baseline concentration of the tracer in the distribution system water should be determined ( fluoride, the most common tracer, may be normally present in trace amounts). If your system adds fluoride, you can turn off the fluoride feed for a period of time, and monitor the resulting decrease of its concentration throughout the distribution system.

If you do not routinely add fluoride to the finished water, you can conduct tracer tests by injecting a small dose of fluoride ( about 1 mg/ L) into the water entering the distribution system. However, flouride can interact with the material deposited inside pipes and storage facilities, reducing the accuracy of the calculated residence times. As a result, you must inject sufficient fluoride to meet the " fluoride demand" of your distribution system while assuring that fluoride concentrations in the distribution system do not exceed allowable concentrations of 4 mg/ L ( the primary maximum contaminant limit ( MCL) for fluoride is 4 mg/ L and the secondary MCL which is non enforceable is 2 mg/ L). If other tracers are used such as calcium chloride or sodium chloride, State environmental agencies may require that food grade chemicals are used or that other assurances are made concerning The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 34 the safety of the tracer. With some tracer chemicals, systems may want to consider notifying sensitive users.

When selecting tracer monitoring locations, you should consider the following:

° Major intersections or branches in large transmission mains ° Branches in minor mains where flow is split between two or more groups of customers ° Storage tanks ° Entry points to large commercial or industrial users ° Prior to the last fire hydrant in remote areas with few customers To adequately characterize distribution system residence time, tracer concentrations should be measured frequently and in relatively close proximity to one another. The frequency of sampling will determine the accuracy of the study results. For example, if sampling is conducted every 8 hours the water age at a given location will only be accurate to within 8 hours. Furthermore, the proximity of sample locations to one another will also affect the accuracy of the study results. It may be appropriate to space samples far apart on large transmission mains, but within the distribution system ( which contains many piping and hydraulic interactions) samples should be located closer together.

Optimally, tracer studies should be conducted under conditions that represent high DBP formation ( typically summer months). Also, the study should be detailed enough to provide good characterization of the entire distribution system. Not all extremities must be covered by the study, but the data must be complete enough to allow for a reasonable extrapolation of the results to cover the entire distribution system.

Although tracer studies often provide very good information, they can be time consuming and costly. Conducting a tracer study solely for the IDSE SMP may not be cost effective. However, if you are considering a tracer study for some other purpose ( e. g. calibration of a water distribution system model), consideration should be given to using the tracer study as a tool for the IDSE SMP.

Results from previously conducted tracer studies may be very useful in identifying areas in the distribution system with high and average residence times. Typically, the study should have been conducted within the past 10 years and represent the existing distribution system configuration. However, if your system has implemented operational changes that permanently and significantly changed the flow of water through your distribution system ( i. e., new transmission mains, addition of large industrial users, significant development in formerly unpopulated or remote areas, etc.) since your tracer study, the study will be of limited use in selecting SMP sample locations. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 35 If you have recently conducted or are planning to conduct a detailed tracer study of your system, you may want to consider completing an alternative SSS ( see Chapter 3).

1) High TTHM and High HAA5 Sites High residence time locations should be identified on a map of the system based on the tracer study field results. SMP sample sites should be chosen from the area or areas of the distribution system where these high residence time tracer study sites are located. The SMP sample sites do not have to be chosen at the exact location of the tracer study monitoring sites, just in the general area identified by the study.

When selecting high TTHM and high HAA5 sites based on tracer study results it is important to remember that residence time is just one factor in identifying high TTHM and high HAA5 sites. Residence time estimates should be compared with other distribution system data ( e. g., disinfectant residual data) before making your final sample site selections. Areas with high residence time but low or no disinfectant residual may have microbiological activity which can degrade HAA5. Consequently, high HAA5 sites may not necessarily be located at areas with high residence times.

2) Average Residence Time The residence time at all sites sampled during the tracer test field effort should be plotted on a map of the system. The overall system average age should be calculated by determining the median residence time results obtained during the field test. Sites with residence times approximately equal to the median of tracer study results should be identified on the map and the required SMP sample sites chosen from within these areas.

8.4.6 System Operating Data System operating data, such as pump run times, pumping rates, tank level data or flow rates, metered flows between pressure zones, and demand data for large users may be helpful in understanding overall water flow patterns in your distribution system. For example, storage tank configuration and operation can have a significant impact on maximum and average residence times in the areas of a system " downstream" of the storage tank. Pumping rates and flow metering between pressure zones can provide a direct indication of the movement of water through your system. A review of billing records can identify your largest customers. Areas of your system " upstream" of your largest customers are likely to have fresher water than areas downstream of these customers. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 36 Distribution System Map Residence Time ( Days)

Residual Data ( mg/ L)

DBP Data ( : g/ L) 0.5 2.1 1.4 1.5 0.8 1.9 2.5 3.0 1.1 1.9 1.3 1.0 0.9 0.7 0.5 0.3 15 44 24 18 31 63 85 77 1.7 1.0 0.4 0.5 0.1 1.1 1.4 1.5 8.4.7 Geographic Information System ( GIS)

Geographic information system ( GIS) software is capable of assembling, storing, manipulating, and displaying geographically referenced data. ArcView and Intergraph are examples of two packages currently available. GIS allows large amounts of distribution system data to be compiled and users to query those data to identify areas in a distribution system meeting specified criteria. It is equivalent to plotting various data on individual see through maps and laying those maps on top of each other so all data can be viewed together ( Figure 8.2 depicts this concept).

Figure 8.2 Conceptual Diagram of GIS The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 37 Table 8.4 summarizes the data storage capabilities of a typical GIS application.

Table 8.4 Summary of GIS Data Storage Capabilities General System Data Structural Data Operational Data Water Quality Data Land uses and zoning Population density Pipe diameter and length Valves and fittings Pumps Pipe age Pipe material Pipe maintenance history Pipe velocities System pressure Pressure zones Residence time Temperature Residual disinfectant Total coliforms HPC DBPs While GIS applications can be a valuable tool for evaluating many types of distribution system data geographically, they are not hydraulic models and cannot predict system conditions. GIS applications are a framework for displaying information related to your distribution system. This means residence times, system pressures, pipe velocities, and other operational data should be collected by some other method ( e. g., hydraulic model or field measurements) and entered into the GIS database.

After hydraulic and water quality data are integrated into a GIS application, users can query the data to locate areas which meet several criteria for SMP sites. For example, a user may request locations where the residence time exceeds 4 days, the free chlorine residual is between 0.2 and 0.5 mg/ L, and the HPC count is less than 500 cfu/ mL. Most GIS applications can highlight those locations on a map of the distribution system. The user can then select geographically diverse locations from these areas for the purposes of IDSE SMP monitoring.

The procedure by which GIS identifies preliminary SMP sample locations is similar to the process an individual might use if they were doing the analysis by hand. However, GIS is capable of looking at a larger amount of data in an integrated manner, without the excess time of plotting the data manually. Purchasing a GIS application solely for the purpose of conducting the IDSE may not be efficient because there will be a considerable effort involved in getting the system up and running. However, if your system currently utilizes or is planning to purchase a GIS application, consideration should be given to using the application as a tool for identifying SMP sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 38 8.5 Methodology for Selecting Final SMP Sites As described in the previous section, various data sources and tools can be used to identify SMP sites, but some may provide more accurate estimates of high TTHM and HAA5 locations or average residence time locations than others. How do you prioritize the data and combine data sources and tools to select final SMP sites? This section addresses this question by providing general guidelines for ( 1) identifying all possible preliminary SMP sites and ( 2) narrowing down the preliminary sites to final SMP sites. Detailed guidance for identifying preliminary sites using each data source or tool was provided in section 8.4   this section focuses on combining tools to select preliminary and final sites.

A key to selecting final SMP sites is the ability to plot preliminary sites on a detailed map of your distribution system. You should always visually confirm that SMP sites provide geographic coverage of the distribution system and are in expected areas of high and average residence time ( as predicted by a hydraulic model or other data source) and that you are not missing key areas that may not have been sampled in the past. If you have GIS capabilities, queries can be extremely useful in automating the site selection process. In particular, GIS queries can be used to evaluate multiple data sources for you rather than having you perform the time consuming process of evaluating multiple parameters by hand or in a spreadsheet.

The information and considerations presented in this section are not intended to be limiting or prescriptive. EPA recognizes DBP formation is system specific and the guidance provided in this manual will not apply to every system. The operational experience and knowledge of system personnel and all available information should be considered in selecting SMP sample sites. Best professional judgement should be exercised in the specific application of guidelines in this manual.

8.5.1 Identifying Preliminary Sites Using Combinations of Tools and Data Sources This section contains a multi step process that allows you to use any combination of the following data sources with maps to select preliminary sites:

° Water distribution system model outputs ° Tracer study results ° Disinfectant residual data ° DBP data All steps involve plotting preliminary sites on a map of your distribution system. Figure 8.3 is flow chart that indicates at which step you should start, depending on your available data sources. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 39 Do you have a water model or tracer study? Start at Step 1 Do you DBP Data? Start at Step 2 Yes No Do you Disinfection Residual Data? Start at Step 3 Yes No Start at Step 4 No Yes Figure 8.3 Starting Point for Preliminary Site Selection The steps in this section focus on identifying preliminary high TTHM and high HAA5 sites at locations of high residence time. Guidance for selecting average residence time sites ( for 100 percent The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 40 purchasing systems serving at least 10,000 people and for producing surface water serving at least 10,000) is presented separately at the end of each step.

Step 1  Using Modeling and Tracer Study Results Identifying Preliminary High TTHM and High HAA5 Sites Residence Time Sites Use output from your water distribution system model or tracer study results to identify areas with the highest residence times. You should identify at least twice as many preliminary SMP sites as required. For example, from Table 8.1 producing ground water systems serving 500 to 9,999 people must have one high TTHM and one high HAA5 site per plant for the SMP; therefore, they should select at least two preliminary high TTHM sites and two preliminary high HAA5 sites per plant using model or tracer study data. Plot all preliminary sites on a map of your distribution system.

Identifying Preliminary Average Residence Time Sites Use output from your water distribution system model or tracer study results to identify areas with average residence times. You should identify at least twice as many preliminary SMP sites as required.

C For 100 percent purchasing systems serving at least 10,000 people, see Table 8.1 for the number of average residence time sites that are required for the SMP. ( 100 percent purchasing systems serving less than 10,000 people do not have to select average residence time sites).

C For producing systems providing surface water in whole or in part, at least four preliminary sites per plant should be identified ( two SMP sites per plant are required). Plot all preliminary average residence time sites on a map of your distribution system.

Step 2  Using TTHM and HAA5 Data Note: DBP data are generally not useful in identifying average residence time sites. Only preliminary high TTHM and high HAA5 sites are covered in this step.

If you completed Step 1:

Determine if the high TTHM and HAA5 locations correspond to areas with high water residence time. It is possible that the water distribution system model or tracer study did not capture mixing effects or other factors leading to higher residence times than predicted. If the high TTHM and The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 41 HAA5 data occur outside predicted areas of high residence time, you should select additional preliminary sites to cover these areas.

If you did not complete Step 1:

Review TTHM and HAA5 data and identify areas with the highest TTHM and HAA5 concentrations ( and/ or areas with similar characteristics to sites with high TTHM and HAA5 concentrations). Plot these areas on your distribution system map.

Step 3  Using Disinfectant Residual Data If you completed Step 1:

Identifying preliminary high TTHM and high HAA5 sites residence time sites:

On a map of your system, identify areas with low disinfectant residual concentration compared to finished water. ( It may be helpful to record the average concentration for the summer months or the minimum monthly concentration on a map of you system). Determine if the areas with high residence times identified in Step 1 correspond to areas with low disinfectant residuals. ( Note, the use of booster disinfection will affect this correlation.) It is not unusual for disinfectant residual data to show different trends compared to hydraulic model outputs. It is possible that a hydraulic model or tracer study did not capture mixing effects or other factors leading to higher residence times than predicted. Disinfectant residual can be influenced by other factors, such as internal corrosion, biological activity, etc. ( refer to section <IP_ADDRESS> for a more complete description of other factors affecting disinfectant residual decay). Thus, low disinfectant residual is not a definitive indication of long residence time.

If areas with low disinfectant residuals are identified outside predicted areas of high residence time, you may wish to select additional preliminary SMP sites to cover these areas. For preliminary high HAA5 sites, a minimum residual of 0.2 mg/ L chlorine or 0.5 mg/ L chloramine should be present.

Identifying preliminary average residence time sites:

On a map of your system, identify areas of average residence time based on disinfectant residual data. ( See section <IP_ADDRESS> for guidance on identifying areas of average residence time using disinfectant residual data.) Do average residence time sites identified by your water distribution system model or tracer study in Step 1 correspond with average residence time sites identified by evaluating disinfectant residual data? Identify additional preliminary SMP sites for average residence times if your residual data show different locations than results from your model or tracer study. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 42 If you did not complete Step 1:

Identifying preliminary high TTHM and high HAA5 sites residence time sites Evaluate your disinfectant residual data from warmer months and identify areas with the lowest or no residual concentrations. These locations are likely those with the highest residence time, and represent potential locations for high TTHM and HAA5 SMP sites. ( High HAA5 sites should be limited to those sites with a free chlorine residual of at least 0.2 mg/ L or a chloramine residual of at least 0.5 mg/ L.) Identify at least twice as many SMP sites as required. Plot these areas on your distribution system map.

Identifying preliminary average residence time sites Using disinfectant residual data from your TCR monitoring locations ( and flow data, if available), calculate the average system and locational average disinfectant residuals. Section <IP_ADDRESS> discusses these methodologies. Identify those locations with average disinfectant residuals approximately equal to the system average. Identify at least twice as many preliminary SMP sites as required. Plot these areas on your distribution system map.

Step 4  Map Review Review your water distribution system map to identify additional preliminary SMP locations representative of high TTHMs and high HAA5 not identified in Steps 1 through 3 where:

° There is light development or low residential population far away from a treatment plant ° An area is served by one or more distribution system storage facilities, especially if the storage facility( s) have high water residence times ° An area is served by booster disinfection stations You should not select preliminary sites at the very end of a water main past the last customer. A better location would be at the last group of customers.

8.5.2 Selecting Final SMP Sites from Preliminary Sites The following are general guidelines for choosing final SMP sites from your list of The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 43 preliminary sites identified in accordance with section 8.5.1. Specific guidelines for very small systems serving less than 500 people are at the end of section <IP_ADDRESS>. EPA recognizes there are systemspecific factors that may lead you to select final sites that do not specifically meet these guidelines. If you deviate from the guidelines, provide justification to your State in your IDSE Report.

<IP_ADDRESS> Selecting High TTHM and HAA5 SMP Sites ( All Systems)

1) Select SMP sites in hydraulically different areas ( i. e., do not select two sites close to one another).

2) Select SMP sites in geographically different areas and separated from existing Stage 1 DBPR sites.

3) Prioritize sites that meet the most siting criteria and those identified based on more than one data source. For example, a preliminary high TTHM site that has low disinfectant residual, is near the edge of the distribution system and is downstream of a tank would be a likely SMP site.

4) Select high TTHM sites located after storage facilities and booster disinfection stations.

5) Select high TTHM sites in areas with the lowest or no residual disinfectant ( unless your system uses booster disinfection).

6) Generally, select high HAA5 sites with a minimum of 0.2 mg/ L chlorine residual or 0.5 mg/ L chloramine residual for all observations.

7) Locate at least one of your high TTHM sites in a remote area of your distribution system. If you are only required to select one high TTHM site, it is strongly recommended that you locate this site away from the treatment plant, near the last group of customers ( but prior to the last fire hydrant).

8) DBP data are important as long as they represent your current system configuration. If you have a historical TTHM or HAA5 data in an area, these data can be used to prioritize sites ( or select one over another) when other data shows no difference between the sties. For example, if disinfectant residual data are the same for three sites over the same periods, then the DBP data can be used to select a high TTHM/ HAA5 site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 44 Special Considerations for Storage Tanks 9) Understanding the impact of storage tanks on water movement and water age in a distribution system is complicated by a variety of specific physical and operational characteristics. The mixing characteristics of storage tanks are impacted by the inlet/ outlet piping configuration, inlet momentum, temperature, and duration of drain/ fill cycles. For example, horizontal inlets at the base of storage tanks, oversized inlet piping which results in low inlet momentum, and short drain/ fill cycles are all potential causes of poor mixing in storage tanks. A methodology for evaluating storage tank mixing characteristics is presented in Water Quality Modeling of Distribution System Storage Facilities ( Grayman et al. 2000).

Tanks with poor mixing characteristics and common inlet/ outlet piping may operate in a " last in   first out" mode, meaning that the freshest water in the tank is the first to be discharged during a drain cycle. During periods of higher than normal demand, when drain periods may be extended, these tanks may discharge water from the upper regions of the tank where water age is substantially ( e. g., several days or weeks) higher than water in the lower regions of the tank. If you suspect poor mixing in one or more of your storage tanks, areas receiving the stored water from those tanks may occasionally have high DBP concentrations.

Tank level data can be used to assess the theoretical average residence time of water in a tank; however, the mixing characteristics of the tank must be thoroughly understood to adequately estimate the true average water age in a storage tank ( Uber et al. 2002). It is important to understand that distribution system storage facilities can have significant but variable impacts on water age. As a result, high TTHM and HAA5 sites should typically be located downstream of distribution system storage facilities.

Specific Guidance for Systems Serving Less Than 500 People 10) Select a high TTHM site in a high residence time area that is not near your Stage 1 DBPR site. ( Your Stage 1 DBPR site should be located in an area of your distribution system that represents your maximum residence time.)

11) Locate your high HAA5 site in a location other than near your high TTHM and Stage 1 DBPR sites. If those two sites cover the high residence time areas of your distribution system, then select a site in an area with average residence time ( see section <IP_ADDRESS> for determining average residence time based on disinfectant residual data) for your high HAA5. The highest HAA5 concentrations may not occur at the highest residence time locations. There may be system specific factors that cause HAA5 to biodegrade and, therefore, areas with average residence time may have the highest HAA5 concentrations. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 45 <IP_ADDRESS> Selecting Average Residence Time Sites SMP sites representing average residence time are required for:

C 100 percent purchasing systems serving at least 10,000 people C Producing surface water systems serving at least 10,000 people From the preliminary average residence time sites, select final average residence time sites that are geographically diverse from the other SMP sites and existing Stage 1 DBPR average residence time compliance sampling sites.

8.6 Stage 2B DBPR Site Selection and IDSE Reporting Requirements ( 40 CFR 141.605)

Once the SMP monitoring period has ended, the Stage 2B compliance monitoring sites can be selected from the SMP and Stage 1 DBPR results ( or Stage 2A DBPR for systems on the late IDSE schedule). Selection must be based on the average TTHM and HAA5 concentrations measured over the SMP monitoring period at each site, or locational running annual averages ( LRAAs). Tables 8.5 and 8.6 summarize the Stage 2B site requirements for 100 percent purchasing and producing systems, respectively.

TTHM and HAA5 LRAAs are the most important factors to consider when selecting Stage 2B DBPR monitoring locations. However, the rule allows for some flexibility in selecting Stage 2B compliance sites. Other factors should be considered and may lead to selecting a site with a slightly lower LRAA over another site. The following conditions are possible reasons why you may select a site with a lower LRAA over another site:

° The site provides for more complete geographic coverage of the entire distribution system ° The site allows you to maintain an historical record ° Sampling at that site provides the opportunity to collect other water quality or operational data ( e. g., chloramine systems may want to collect nitrate data at that location) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 1The Stage 2 DBPR does not specify a difference between two LRAAs that allows selection of a site with the lower LRAA for Stage 2B. EPA recognizes there is uncertainty and variability associated with the TTHM and HAA5 data quality. While the LRAA calculation reduces the impact of these to some extent, they can cause a small difference between two LRAAs to be statistically insignificant and thus, making the selection of the Stage 2B site dependent on other factors. The intent of the Stage 2 DBPR is to reduce peak DBP concentrations in the distribution system. You should use best professional judgment to select Stage 2B sites with consideration to the intent of the rule and demonstrate to the State the reason for the selection.

July 2003  Proposal Draft All Systems 8 46 If you do not use your highest TTHM and HAA5 LRAAs to select your Stage 2B DBPR sites, you must provide justification for your selection in your IDSE report. 1 The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 47 Table 8.5 Stage 2B Compliance Monitoring Requirements for 100 Percent Purchasing Systems1,2 System Size ( Population Served3) Number of Distribution System Sites ( by location type) per System Total Number of Sites per System Monitoring Frequency4 Stage 1 Average Residence Time Site Highest TTHM Highest HAA5 Surface Water Systems5 < 500  1 1 25 Every 365 days 500  4,999  1 1 25 Every 90 days 5,000  9,999  1 1 2 Every 90 days 10,000  24,999 1 2 1 4 Every 90 days 25,000  49,999 1 3 2 6 Every 90 days 50,000  99,999 2 4 2 8 Every 90 days 100,000  499,999 3 6 3 12 Every 90 days 500,000  1,499,999 4 8 4 16 Every 90 days 1.5 million  < 5 million 5 10 5 20 Every 90 days > 5 million 6 12 6 24 Every 90 days Ground Water Systems < 500  1 1 26 Every 365 days 500  9,999  1 1 2 Every 365 days 10,000  99,999 1 2 1 4 Every 90 days 100,000  499,999 1 3 2 6 Every 90 days > 500,000 2 4 2 8 Every 90 days 1 ( 40 CFR 141.605 ( e))

2 For the purpose of this guidance manual, 100 percent purchasing systems are those systems that buy or otherwise receive all of their finished water from one or more wholesale systems year round. 3 Population served is usually a system's retail population. It should not include populations served by consecutive systems that purchase water from that system. 4 Monitoring frequency is the approximate number of days between monitoring events. A dual sample set must be collected at each location, unless otherwise noted. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and location. 5 For the purpose of this guidance manual, " surface water systems" are equivalent to subpart H systems ( i. e., any system that uses surface water or GWUDI as a source, including all mixed systems that use some surface water or GWUDI and some ground water). 6 Dual sample sets are not required at both the high TTHM and the high HAA5 site   if the highest TTHM and HAA5 levels occur at a different locations, then only one sample is collected at each location. If they occur at the same location, then a dual sample set is collected at that location. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 48 Table 8.6 Summary of Stage 2B Compliance Monitoring Requirements for Producing Systems1,2 System Size ( Population Served3) Number of Distribution System Sites ( by location type) per Plant4 Total Number of Sites per Plant Monitoring Frequency5 Stage 1 Average Residence Time Site Highest TTHM Highest HAA5 Surface Water Systems6 < 500  1 1 27 Every 365 days 500  9,999  1 1 2 Every 90 days > 10,000 1 2 1 4 Every 90 days Ground Water Systems < 500  1 1 27 Every 365 days 500  9,999  1 1 2 Every 365 days > 10,000  1 1 2 Every 90 days 1 ( 40 CFR 141.605 ( a))

2 For the purpose of this guidance manual, producing systems are those that do not buy 100 percent of their water year round ( i. e., they produce some or all of their own finished water). 3 Population served is usually a system's retail population. It should not include populations served by consecutive systems that purchase water from that system. 4 For the purpose of the Stage 2 DBPR compliance monitoring, a plant can be either a treatment plant ( that provides, at a minimum, disinfection using a disinfectant other than UV) or a consecutive system entry point that operates for at least 60 consecutive days per year. 5 Monitoring frequency is the approximate number of days between monitoring events. A dual sample set must be collected at each location, unless otherwise noted. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and location. 6 For the purpose of this guidance manual, " surface water systems" are equivalent to subpart H systems ( i. e., any system that uses surface water or GWUDI as a source, including all mixed systems that use some surface water or GWUDI and some ground water). 7 Dual sample sets are not required at both the high TTHM and the high HAA5 site   if the highest TTHM and HAA5 levels occur at a different locations, then only one sample is collected at each location. If they occur at the same location, then a dual sample set is collected at that location.

8.6.1 100 Percent Purchasing Systems The rule requires 100 percent purchasing systems to use the following protocol for selecting Stage 2B sites from IDSE and Stage 1 compliance monitoring data.

1) Site with the highest TTHM LRAA The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 49 2) Site with the highest HAA5 LRAA ( not previously selected)

3) Existing Stage 1 DBPR compliance monitoring site 4) Site with the highest TTHM LRAA ( not previously selected)

Repeat the protocol, selecting from the remaining sites, until the required number has been selected. For # 3, alternate between highest HAA5 and highest TTHM of Stage 1 DBPR average residence time sites, not previously selected.

8.6.2 Producing Systems The rule requires producing systems to select the required amount of sites for each plant using the following protocols:

Large surface water systems For each plant, select sites with following:

1) Highest TTHM LRAA 2) Highest TTHM LRAA 3) Highest HAA5 LRAA 4) Existing Stage 1 DBPR Average Residence Time site with the highest TTHM or HAA5 LRAA. If you do not have a Stage 1 Average Residence Time site, then you must choose the next highest HAA5 site.

Small surface water systems and all ground water systems Select sites with the highest TTHM LRAA and HAA5 LRAA for each plant.

° Systems serving 500 to less than 10,000 people   if the highest TTHM and HAA5 occur at the same site for a given plant, then your system may monitor at only that site for that plant.

° Systems serving less than 500   you are required to take one TTHM and one HAA5 sample per year per plant. If the high TTHM and HAA5 for a given plant occurred at different sites, then you only need to collect a TTHM sample at the high TTHM site and a HAA5 sample at the high HAA5 site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 50 8.6.3 Examples of Stage 2B DBPR Site Selection This section provides examples of Stage 2B DBPR site selection:

Example 8.15 Selecting Stage 2B DBPR Sites from SMP Data Example 8.16 Maintaining an Historical Record Example 8.17 Providing Geographical Coverage When Choosing Stage 2B DBPR Sites The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 51 Example 8.15 Selecting Stage 2B DBPR Sites from SMP Data A producing system serves 90,000 people and has one surface water treatment plant. This system must select four Stage 2B DBPR compliance sites ( from Table 8.9): two high TTHM sites; one high HAA5 site; and one from the three existing Stage 1 DBPR average residence time compliance sites. The table below lists the TTHM and HAA5 LRAAs for all Stage 1 DBPR compliance monitoring sites and three of the eight SMP sites ( these data represent the seven highest TTHM and HAA5 LRAAs).

Site TTHM LRAAs HAA5 LRAAs A ( Stage 1 max. residence time) 64 39 B ( SMP high TTHM site) 66 40 C ( SMP high HAA5 site) 72 52 D ( SMP high TTHM site) 76 50 E ( Stage 1 avg. residence time) 57 48 F ( Stage 1 avg. residence time) 42 30 G ( Stage 1 avg. residence time) 55 50 Selecting the Average Residence Time Site The average residence time site should have either the highest TTHM or highest HAA5 LRAA of the Stage 1 DBPR average residence time sites. The water system may choose either Site E ( highest TTHM LRAA) or Site G ( highest HAA5 LRAA). With two valid options, the site providing the best geographic coverage is preferred. Site G is located downstream of an elevated tank and is the only site that receives water from that tank; therefore, the water system selects Site G.

Selecting High TTHM and High HAA5 Sites Sites C and D have both the highest TTHM and HAA5 LRAAs ( they can represent the two high TTHM sites or one high TTHM site and one high HAA5). One more high TTHM or high HAA5 site must be chosen between Sites A and B. The differences in LRAAs between Site A and Site B are minimal. Site A was first selected as a THM Rule " maximum" compliance site and is now a Stage 1 site DBPR. To maintain the historic record of sampling, Site A is chosen. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 52 Example 8.16 Maintaining an Historical Record A producing system serves 4,000 people and has one ground water treatment plant. This system must select two Stage 2B compliance sites ( from Table 8.9): one high TTHM and one high HAA5 site. A comparison of SMP and Stage 1 DBPR compliance monitoring results are presented in the table below.

Sample Locations with Highest LRAAs LRAA TTHM ( µ g/ L) HAA5 ( µ g/ L)

SMP # 1 High TTHM 72 51 SMP # 2 High TTHM 65 56 SMP # 3 High HAA5 60 51 Stage 1 DBPR max residence time site 70 51 Because the TTHM LRAA for the Stage 1 DBPR site is only slightly lower than the maximum TTHM LRAA ( SMP # 1), the system chooses the Stage 1 DBPR site over SMP # 1 for the Stage 2B DBPR high TTHM site to maintain the historic DBP record at that site. SMP # 2 is selected as the high HAA5 site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 53 8.7 Reporting Results to the State The rule requires the following data and information be included in your IDSE report to the State ( 40 CFR 141.604):

° The original SMP plan and an explanation of any deviations from that plan ° All TTHM and HAA5 analytical results from the SMP ° All TTHM and HAA5 analytical results from Stage 1 DBPR compliance samples collected during the period of the IDSE ° A schematic of your distribution system with the results, location, and date of all IDSE SMP and compliance samples noted ° Data used to justify IDSE SMP site selections ° Proposed Stage 2B compliance monitoring sites with justification for selection of each proposed site ° Proposed month( s) during which Stage 2B monitoring is to be conducted Water Treatment Plant A B C Example 8.17 Providing Geographic Coverage When Choosing Stage 2B DBPR Sites In general, the two representative high TTHM sites ( per plant) should not be from the same area of the distribution system.

The two highest TTHM LRAAs in the distribution system are from adjacent SMP sample sites ( Sites A and B). The site with the third highest TTHM LRAA is on the far side of the distribution system ( site C). In this case, consider selecting sites A and C or B and C as Stage 2B DBPR sites for a broader geographical coverage of the distribution system. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 54 Refer to Appendices E through J for example IDSE reports based on source water and system size ( see Table 8.10).

Remember that TTHM and HAA5 data collected for the SMP are not to be included in compliance calculations for the Stage 1 or Stage 2A DBPR. Also, results from the SMP should not be reported in your Consumer Confidence Report.

If you do not receive notification that your Stage 2B site selection was acceptable by [ 3 years after rule promulgation] for systems on the early schedule or [ 6 years after rule promulgation] for systems on the late schedule, you should contact your State to verify your Stage 2B sites meet compliance requirements.

Table 8.7 Example IDSE Reports Appendix System Characteristics Appendix E SMP for Producing Surface Water System (> 10,000)

Appendix F SMP for Producing Ground Water System (> 10,000)

Appendix G SMP for Producing Surface Water System ( 500  9,999)

Appendix H SMP for Producing Ground Water System (< 10,000)

Appendix I SMP for Producing Surface Water System (< 500)

Appendix J SMP for 100 Percent Purchasing Surface Water System Appendix A Impacts of an Alternative Population Based Monitoring Approach This page intentionally left blank. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 1 A. 1 Introduction The Stage 2 DBPR includes monitoring requirements that were recommended by the Stage 2 M DBP Federal Advisory Committee ( Stage 2 FACA) in the Agreement in Principle ( USEPA 2000). Many of these monitoring requirements were based on those in the 1979 TTHM Rule and Stage 1 DBPR. For example, the frequency of monitoring under the Stage 1 DBPR is a function of source water type ( ground or surface water), size of system, and the number of plants per system. For the Stage 2 DBPR, as under the Stage 1 DBPR, the Stage 2 FACA recommended that compliance sampling be required on a per plant basis. This recommendation is based on the assumption that as systems increase in size, they will tend to have more plants and increased complexity of water treatment and distribution, thereby warranting increased monitoring to represent DBP occurrence in the distribution system. The Stage 2 FACA also recommended higher frequency monitoring for systems using surface water than those using ground water because ground water tends to have lower and more stable concentrations of organic DBP precursors than surface water. Furthermore, since many ground water systems have multiple wells/ entry points drawing water from the same aquifer, the Stage 2 FACA recommended that these wells be considered as a single plant with the same monitoring requirements prescribed for one plant, if approved by the State.

Upon further analysis of the Stage 2 FACA recommendations, EPA has identified the following issues related to the monitoring requirements of the Stage 2 DBPR:

° Basing increased monitoring on numbers of water treatment plants per system, as opposed to population alone, may result in either excessive or insufficient samples to represent DBP occurrence in the distribution system.

° The proposed sampling requirements for mixed systems ( i. e., those receiving surface water and disinfecting ground water in their distribution system) may be excessive, depending upon the system's characteristics.

° The proposed monitoring requirements, based on additional samples per water treatment plant, pose unique implementation issues for systems with temporary supplies during the year.

To address these issues, the Stage 2 DBPR uses two approaches to monitoring for two different groups of systems:

1) The plant based approach is dependent on population served, source water, AND the number of plants in a system ( as with Stage 1 DBPR compliance monitoring) and applies to systems that produce some or all of their own finished water ( called producing systems in Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 2 this manual). For the purpose of the Stage 2 DBPR, a plant can be either a treatment plant ( that provides, at a minimum, disinfection using a disinfectant other than UV) or a consecutive system entry point that operates for at least 60 consecutive days per year.

° The population based approach that is dependent on population served and source water and applies to only those systems that purchase 100 percent of their finished water from other systems ( called 100 percent purchasing systems in this manual).

Section V( F)( 2) of the Stage 2 DBPR preamble describes the monitoring issues in detail and requests comment on them, particularly the significance of a plant based ( the proposed monitoring scheme) versus a population based monitoring approach ( monitoring requirements based on population and source type only).

The purpose of this Appendix is to describe how this guidance manual would be revised if the Stage 2 monitoring scheme were changed to a population based approach. First, section A. 2 presents EPA's proposed framework for an alternative population based monitoring scheme. Section A. 3 then discusses a revised organization and consolidation of chapters for this guidance manual to reflect a population based approach monitoring scheme for all systems.

A. 2 Summary of Alternative Population Based Approach The Stage 2 DBPR requires monitoring for ( 1) the IDSE and ( 2) Stage 2A and Stage 2B compliance. Currently, monitoring requirements are based on population and source water only for 100 percent purchasing systems, and based on population, source water, and number of plants for producing systems. Under the alternative population based approach, the proposed monitoring requirements for 100 percent purchasing systems would be applied to all systems. The following exhibits summarize the IDSE and Stage 2B monitoring requirements for the population based approach. ( These requirements are identical to those presented in Chapters 1, 4, and 8 for 100 percent purchasing.)

° Table A. 1   IDSE SMP monitoring requirements for Population based Approach ° Table A. 2   Stage 2B routine samples required for Population based Approach Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 3 Table A. 1 IDSE SMP Sampling Requirements for Population based Approach System Size ( Population Served) Number of Distribution System Sites2 ( by location type) per System Total Number of Sites per System Monitoring Frequency for the 1 year IDSE period4 Near Entry Point3 Average Residence Time High TTHM High HAA5 Surface Water Systems5 < 500   1 1 2 Every 180 days 500  4,999   1 1 2 Every 90 days 5,000  9,999  1 2 1 4 Every 90 days 10,000  24,999 1 2 3 2 8 Every 60 days 25,000  49,999 2 3 4 3 12 Every 60 days 50,000  99,999 3 4 5 4 16 Every 60 days 100,000  499,999 4 6 8 6 24 Every 60 days 500,000  < 1.5 million 6 8 10 8 32 Every 60 days 1.5 million  < 5 million 8 10 12 10 40 Every 60 days > 5 million 10 12 14 12 48 Every 60 days Ground Water Systems < 500   1 1 2 Every 180 days 500  9,999   1 1 2 Every 90 days 10,000  99,999 1 1 2 2 6 Every 90 days 100,000  499,999 1 1 3 3 8 Every 90 days > 500,000 2 2 4 4 12 Every 90 days 1 For the purposes of this manual, 100 percent purchasing systems are those systems that buy or otherwise receive all of their finished water from one or more wholesale systems year round.

2 A dual sample set must be collected at each location. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and location.

3 See section 8.2 for requirements when the number of entry points in a system is different from the number of required near entry point sites in this table.

4 Monitoring frequency is the approximate number of days between monitoring events.

5 For the purposes of this guidance manual, " surface water" systems are equivalent to " subpart H" systems and include systems that provide GWUDI. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 4 Table A. 2 Stage 2B Compliance Monitoring Requirements for Population based Approach System Size ( Population Served) Number of Distribution System Sites2 ( by location type) per System Total Number of Sites per System Monitoring Frequency3 Existing Stage 1 Compliance Sites Highest TTHM Highest HAA5 Surface Water Systems4 < 500  1 1 25 Every 365 days 500  4,999  1 1 25 Every 90 days 5,000  9,999  1 1 2 Every 90 days 10,000  24,999 1 2 1 4 Every 90 days 25,000  49,999 1 3 2 6 Every 90 days 50,000  99,999 2 4 2 8 Every 90 days 100,000  499,999 3 6 3 12 Every 90 days 500,000  1,499,999 4 8 4 16 Every 90 days 1.5 million  < 5 million 5 10 5 20 Every 90 days > 5 million 6 12 6 24 Every 90 days Ground Water Systems < 500  1 1 25 Every 365 days 500  9,999  1 1 2 Every 365 days 10,000  99,999 1 2 1 4 Every 90 days 100,000  499,999 1 3 2 6 Every 90 days > 500,000 2 4 2 8 Every 90 days 1 For the purposes of this manual, 100 percent purchasing systems are those systems that buy or otherwise receive all of their finished water from one or more wholesale systems year round.

2 A dual sample set must be collected at each location, unless otherwise noted. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and location.

3 Monitoring frequency is the approximate number of days between monitoring events.

4 For the purposes of this guidance manual, " surface water" systems are equivalent to " subpart H" systems and include systems that provide GWUDI.

5 Dual sample sets are not required at both the high TTHM and the high HAA5 site   if the highest TTHM and HAA5 levels occur at a different locations, then only one sample is collected at each location. If they occur at the same location, then a dual sample set is collected at that location. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 5 A. 3 Revised Guidance Manual Organization The IDSE and Stage 2B requirements are less complex with a monitoring scheme that is based only on population served and source water type ( the population based approach) compared to plantbased requirements. Table A. 3 hypothesizes how this manual might be revised if the monitoring requirements were to change. Note two chapters will be deleted and no additional chapters will be necessary.

Table A. 3 Revised Chapter Organization and Content Reflecting a Population Based Monitoring Approach for All Systems Current Chapter Chapter Revisions 1  Introduction Revised. ( Remove distinctions between producing and 100 percent purchasing system).

2  Criteria for IDSE Waiver and Reporting Requirements Same 3  System Specific Study Same 4  SMP Requirements for 100 Percent Purchasing Systems Revised to present SMP requirements for all systems, SW and GW.

5  SMP Requirements for Producing Systems, SW serving > 10,000 people Deleted. Revised Chapter 4 will cover all systems.

6  SMP Requirements for Producing Systems, SW serving 500  9,999 people and GW serving > 10,000 people Deleted. Revised Chapter 4 will cover all systems.

7  SMP Requirements for Producing Systems, SW serving < 500 people and GW serving < 10,000 people Revised to address only systems serving less than 500 people. Becomes Chapter 5.

8  SMP Site Selection and Reporting Same, becomes Chapter 6. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft A 6 References EPA, 2000. Stage 2 M DBP Agreement in Principle. Microbial/ Disinfection Byproducts ( M DBP) Federal Advisory Committee. September 12, 2000. Appendix B Factors Affecting Disinfection Byproduct Formation This page intentionally left blank. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 1 B. 1 Introduction The purpose of this appendix is to identify and discuss the factors that affect formation of disinfection byproducts ( DBPs) in water treatment processes and distribution systems. This appendix is intended to serve as a tool for systems for the purpose of identifying IDSE sample locations and Stage 2B monitoring locations. It is divided into the following sections:

B. 2 Factors Affecting DBP Formation B. 3 Disinfectant Type B. 4 Disinfectant Dose B. 5 Time Dependency of DBP Formation B. 6 Concentration and Characteristics of DBP Precursors B. 7 Water Temperature B. 8 Water pH B. 2 Factors Affecting DBP Formation Organic DBPs ( and oxidation byproducts) are formed by the reaction between organic substances and oxidizing agents ( e. g., chlorine and ozone) that are added to water during treatment. In most water sources, natural organic matter ( NOM) is the most significant constituent of organic substances and DBP precursors. NOM is often measured as total organic carbon ( TOC) and as such the two terms are used interchangeably in much of the discussion presented in this appendix. Major factors affecting the type and amount of DBPs formed include:

° Type of disinfectant, dose, and residual concentration ° Contact time and mixing conditions between disinfectant ( oxidant) and precursors ° Concentration and characteristics of precursors ° Water temperature ° Water chemistry ( including pH, bromide ion concentration, organic nitrogen concentration, and presence of other reducing agents such as iron and manganese)

B. 3 Disinfectant Type Organic DBPs can be subdivided into halogenated and non halogenated byproducts. Halogenated organic disinfection byproducts are formed when organic compounds found in water react with free chlorine, free bromine, or free iodine. The formation reactions take place in both the treatment plant and the distribution system. Free chlorine can be introduced to water directly as a Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 2 primary or secondary disinfectant, as a byproduct of the manufacturing of chlorine dioxide, or as a component in the formation of chloramines for secondary disinfection. Reactions between NOM and chlorine lead to the formation of a variety of halogenated DBPs including THMs and HAAs.

Free chlorine and ozone oxidize bromide ion to hypobromite ion/ hypobromous acid, which in turn can react with NOM to form brominated DBPs ( e. g., bromoform). The presence of bromide affects both the rate and yield of DBPs. As the ratio of bromide to NOM ( measured as total organic carbon) increases, the percentage of brominated DBPs increases. For example, Krasner ( 1999) reported the rate of THM formation is higher in waters with increased concentrations of bromide. Oxidation of organic nitrogen can lead to the formation of DBPs containing nitrogen, such as haloacetonitriles, halopicrins, and cyanogen halide ( Reckhow et al. 1990; Hoigné and Bader 1988). Brominated DBPs can also form by bromine substitution in the chlorinated byproducts. Hypobromous acid is a more effective substituting agent, while hypochlorous acid is a better oxidant ( Krasner 1999).

Non halogenated DBPs may form when precursors react with strong oxidants. For example, the reaction of organics with ozone and hydrogen peroxide results in the formation of aldehydes, aldoand keto acids, and organic acids ( Singer 1999). Chlorine can also trigger the formation of some nonhalogenated DBPs ( Singer and Harrington 1993). Many of the non halogenated DBPs are biodegradable.

Studies have documented that chloramines produce significantly lower DBP levels than free chlorine, and there is no clear evidence that the reaction of NOM and chloramine leads to the formation of THMs ( Singer and Reckhow 1999; EPA 1999). Predictions of an empirical DBP formation model calibrated using ICR data indicated that THMs and HAAs are formed in full scale plants and distribution systems under chloraminated conditions at a fraction of the amount that would be expected based on observations of DBP formation under free chlorine conditions. The amount of formation with chloramines varied from 5 percent to 35 percent of that calculated for free chlorine, depending on the individual DBP species ( Swanson et al. 2001).

It is possible that DBPs might form during the mixing of chlorine and ammonia, when free chlorine might react with NOM before the complete formation of chloramines. In addition, monochloramine slowly hydrolyzes to release free chlorine in water. This free chlorine may contribute to the formation of small amounts of additional DBPs in the distribution system. The benefits of low DBP formation with chloramines are especially important at the extremities of the distribution system where high DBP levels can found.

The application of chlorine dioxide does not produce significant amounts of organic halogenated DBPs. Only small amounts of total organic halides ( TOXs, the class of halogenated organic byproducts that includes THMs and HAAs) are formed. However, THMs and HAAs will form if excess chlorine is added to water to ensure complete reaction with sodium chlorite during the production of chlorine dioxide.

To date, there is no evidence to suggest that ultraviolet irradiation ( UV) results in the formation Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 3 of any disinfection byproducts; however, little research has been performed in this area. Most of the research regarding application of UV and DBP formation has focused on chlorinated DBP formation as a result of UV application prior to the addition of chlorine or chloramines. The evidence suggests UV does not affect chlorinated DBP formation.

Ozone does not produce chlorinated DBPs; however, ozone can alter the reactions between chlorine and NOM and affect the speciation of chlorinated DBPs when chlorine is added downstream. In waters with sufficient bromide concentrations, ozonation can lead to the formation of bromate and other brominated DBPs. Bromate, like THMs and HAAs, is a regulated DBP. Ozonation of natural waters also produces aldehydes, haloketones, ketoacids, carboxylic acids, and other types of biodegradable organic material. The biodegradable fraction of organic material can serve as a nutrient source for microorganisms, and should be removed to prevent microbial regrowth in the distribution system.

B. 4 Disinfectant Dose The concentration of disinfectant can affect the formation of DBPs. In general, changes in the disinfectant dose have a great impact on DBP formation during primary disinfection. This is because the amount of disinfectant added during primary disinfection is usually less than the long term demand and the disinfectant is the limiting reactant in DBP formation reactions. Although disinfectant dose can affect DBP formation during secondary disinfection, the effect is less significant than in primary disinfection. During secondary disinfection DBP formation reactions may be precursor limited since an excess of disinfectant is added to the water. In the distribution system, DBP formation reactions become disinfectant limited when the free chlorine residual drops to low levels. Singer and Reckhow ( 1999) suggested a chlorine concentration of 0.3 mg/ L as a rule of thumb.

In many systems booster disinfection is applied to raise disinfectant residual concentration, especially in remote areas of the distribution system or near storage tanks where water age may be high and disinfectant residuals can be low. The additional chlorine dose applied to the water at these booster facilities can increase THM and HAA levels when sufficient precursors remain in the water. Booster chlorination can also maintain high HAA concentrations because the increased free chlorine residual can prevent the biodegradation of HAAs.

B. 5 Time Dependency of DBP Formation In general, DBPs continue to form in drinking water as long as disinfectant residuals and reactive DBP precursors are present. Therefore, the longer the contact time between the disinfectant/ oxidant and NOM, the greater the amount of DBPs that can be formed. This accumulation is a consequence of the formation of THMs and HAAs and their associated chemical stabilities, which are generally quite high in the disinfected drinking water as long as a significant disinfectant residual is still present ( Singer and Reckhow 1999). Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 4 High TTHM values usually occur where the water age is the oldest. Unlike THMs, HAAs cannot be consistently related to water age because HAAs are known to biodegrade over time when the disinfectant residual is low. This might result in relatively low HAA concentrations in areas of the distribution system where disinfectant residuals are depleted.

In contrast to chlorination byproducts, ozonation byproducts form more rapidly, but their period of formation is much lower than that of chlorination byproducts( Singer and Reckhow 1999). This is the result of the quick dissipation of ozone residuals in drinking water treatment plants.

B. 6 Concentration and Characteristics of DBP Precursors The formation of halogenated DBPs is related to the concentration of NOM at the point of chlorination. Greater DBP levels are formed in waters with high concentrations of precursors. Studies conducted with different fractions of NOM have indicated the reaction between chlorine and NOM with high aromatic content tends to form higher DBP levels than NOM with low aromatic content. For this reason, UV absorbance ( typically indicated by UV absorbance at 254 nm [ UV 254]), which is generally attributed to the aromatic and unsaturated components of NOM, is considered a good predictor of the tendency of a source water to form THMs and HAAs ( Owen et al. 1998; Singer and Reckhow 1999). It should be noted, however, that the more highly aromatic precursors, characterized by high UV 254, in source waters are more easily removed by coagulation. Thus, it is the UV 254 measurement immediately upstream of the point( s) of chlorination within a treatment plant that is more directly related to THM and HAA formation potential.

B. 7 Water Temperature The rate of formation of THMs increases with increasing temperature. HAA formation rates may also increase with temperature, though the effects are less pronounced. Consequentially, the highest THM and HAA levels may occur in the warm summer months. However, water demands are often higher in warmer months, resulting in lower water age within the distribution system and helping to control DBP formation. Furthermore, high temperature conditions in the distribution system promote the accelerated depletion of residual chlorine, which can mitigate DBP formation and promote biodegradation of HAAs ( unless chlorine dosages are increased to maintain high residuals). ( Singer and Reckhow 1999). For these reasons, depending on the specific system, the highest THM and HAA levels may be observed during months which are warm, but not necessarily the warmest.

Seasonal trends affect differently where high THM and HAA concentrations might be found. For example, when water is colder, microbial activity is typically lower and DBP formation kinetics are slower. Under these conditions, the highest THM and HAA concentrations might appear coincident with the oldest water in the system. In warmer water, the highest HAA concentrations might appear in Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 5 fresher water, which is likely to contain higher disinfectant residuals that can prevent the biodegradation of HAAs.

B. 8 Water pH In the presence of NOM and chlorine, THM formation increases with increasing pH, whereas the formation of HAAs and other DBPs increase with decreasing pH. The increase of THMs at higher pH values is likely due to base catalyzed reactions that lead to THM formation. HAA formation pathway can be altered at high pH since their precursors can hydrolyze ( Singer and Reckhow 1999).

The major byproducts of ozonation are not affected by base hydrolysis. However, the rate of decomposition of ozone to hydroxyl radical is accelerated as pH increases. This occurrence is thought to be responsible for the decrease of some byproducts ( e. g., aldeydes) and the increase of others ( e. g., carbonyl byproduct and total organic halides; Singer and Reckhow 1999). The application of ozone to bromide containing waters leads to the formation of hypobromite and hypobromous acid. At low pH, the equilibrium shifts to hypobromous acid which can react with NOM to form halogenated byproducts such as bromoform and dibromoacetic acid ( Singer and Reckhow 1999). Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft B 6 References EPA, 1999. Alternative Disinfectants and Oxidants Guidance Manual. EPA 815 R 99 014.

Hoigne J., and H. Bader. 1988. " The formation of Trichloronitromethane ( chloropicrin) and Chloroform in a Combined Ozonation/ Chlorination Treatment of Drinking Water." Water Resources. 22 ( 3): 313.

Krasner S. W., 1999. " Chemistry of Disinfection By Product Formation", in Formation and Control of Disinfection By Products in Drinking Water, Singer P. C. editor, American Water Works Association, Denver CO.

Reckhow, D. A., P. C. Singer, and R. L. Malcom. 1990. " Chlorination of Humic Mateials: Byproduct Formation and Chemical Interpretations." Environ. Sci. Technol. 24( 11): 1655.

Singer, P. C. and D. A. Reckhow. 1999. " Chemical Oxidation." Water Quality and Treatment, 5th edition. Letterman R. D. technical editor, American Water Works Association, McGraw Hill, New York, NY.

Singer, P. C. ( editor) 1999. Formation and Control of Disinfection Byproducts in Drinking Water. American Water Works Association, Denver, CO.

Singer, P. C., and G. W. Harrington. 1993. " Coagulation of DBP Precursors: Theoretical and Practical Considerations." Conference proceedings, AWWA Water Quality Technology Conference, Miami, FL.

Swanson, W. J., Z. Chowdhury, R. Summers, and G. Solarik. 2001. " Predicting DBPs at Full Scale: Calibration and Validation of the Water Treatment Plant Model Using ICR Data" Conference proceedings, 2001 AWWA Annual Conference and Exhibition, Washington, DC. Appendix C TTHM and HAA5 Sampling Protocol This page intentionally left blank. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 1 C. 1 Introduction TTHM and HAA5 samples must be properly collected and analyzed to ensure accurate analytical results. For example, THMs are volatile chemicals, meaning they can move from the liquid phase to the gas phase under ambient conditions. Therefore, care must be taken to make sure that no air bubbles are present in the filled sample vial. This appendix summarizes information on proper sample collection, handling, and laboratory analytical techniques.

C. 2 Analytical Methods Table C. 1 lists the analytes that are included in TTHM and HAA analyses.

Table C. 1 TTHM and HAA Analytes Analyte Group Code Analytes in Group ( Abbreviation for Analyte)

HAA5 Haloacetic acids: Dibromoacetic acid ( DBAA) Dichloroacetic acid ( DCAA) Monobromoacetic acid ( MBAA) Monochloroacetic acid ( MCAA) Trichloroacetic acid ( TCAA)

HAA9 HAA5 plus four additional analytes Bromochloroacetic acid ( BCAA) Bromodichloroacetic acid ( BDCAA) Chlorodibromoacetic acid ( CDBAA) Tribromoacetic acid ( TBAA)

TTHM Trihalomethanes: Bromodichloromethane ( BDCM) Bromoform ( CHBr3) Chloroform ( CHCl3) Dibromochloromethane ( DBCM)

Table C. 2 lists the approved laboratory analytical methods for TTHM and HAA5 along with guidelines for sample collection and storage. These guidelines include type of sample container, preservative and dechlorinating agents, pH, and sample collection. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 2 Table C. 2 Sampling Requirements of TTHM and HAA5 Analyses Analyte Group Analytical Method Sample Container Material2 Preservative/ Dechlorinating Agent ( Recommended amount) Storage Guidelines Sample Collection Guidelines TTHM EPA 502.2 40 ml  120 ml screw cap glass vials with PTFE faced silicone septum Options: ( 1) 3 mg Na2S2O3/ 40 mL sample or ( 2) 3 mg Na2S2O3/ 40 mL sample and immediate acidification using HCl to pH < 2 or ( 3) 25 mg ascorbic acid/ 40 mL sample and immediate acidification using HCl to pH < 2. Option 1 may be used if THMs are the only compounds being determined in the sample. Options 2 & 3 require the sample to be dechlorinated prior to the addition of acid. Keep at 4 ° C.

14 days maximum hold time3. Fill bottle to just overflowing but do not flush out preservatives.

No air bubbles.

Do not overfill.

Seal sample vials with no head space.

If ascorbic acid is used to dechlorinate TTHM samples, then the samples MUST be acidified. Acidification of TTHM samples containing Na2S2O3 is required if the samples will also be analyzed for VOCs. In both cases, the pH must be adjusted at the time of sample collection, not later at the laboratory. EPA 524.2 40 ml  120 ml screw cap glass vials with Teflon faced silicone septum EPA 551.1 60 ml screw cap glass vials with PTFE faced silicone septum 1 g phosphate buffer & NH4Cl or Na2SO3 mixture per 60 mL sample ( mixture consists of 1 part Na2HPO4, 99 parts KH2PO4 , and 0.6 parts NH4Cl or Na2SO3. 1g per 60 mL results in a pH of 4.5 5.5 and 0.1 mg NH4Cl or Na2SO3 per mL of sample.)

HAA5 EPA 552.1 250 ml ( approx.) amber glass bottles fitted with Teflonlined screw caps 0.1 mg NH4Cl per mL of sample EPA 552.2 50 ml ( approx.) amber glass bottles fitted with Teflonlined screw caps EPA 552.34 50 ml ( approx.) amber glass bottles fitted with Teflonlined screw caps SM 6251 B 40 ml or 60 ml screw cap glass 65 mg NH4Cl 1 ( 40 CFR 141.131 ( b))

2 Selection of container should be coordinated with the laboratory. 3 The holding time has been changed to 14 days for all HAA5 samples as a part of the Stage 2 DBPR. 4 EPA Method 552.3 has been added as an approved HAA5 method as part of the Stage 2 DBPR. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 3 C. 2.1 Sampling Procedure It is important to follow sampling procedures provided by your certified laboratory. Sampling procedures may vary slightly among individual laboratories; you should contact your laboratory to learn their procedures. The following is common procedure for collecting samples for TTHM and HAA5 analyses.

You will need:

1) Sample vials provided by laboratory ( most laboratories will provide sample vials with proper preservative and dechlorinating agents)

2) Small bottle of 1: 1 hydrochloric acid and eye dropper or pasteur pippettes ( pH adjustment is necessary for some TTHM methods)

3) Water proof labels and permanent ( indelible ink) marker 4) Ice/ coolant and cooler Procedure:

1) Label each sample vial. Use waterproof labels and indelible ink. Each label should include:

° Unique sample ID ° System name ° Sample location ° Sample date and time ° Analysis required, if not already on label 2) Remove the aerator from the tap, if there is one present.

3) Open the water tap and allow the system to flush until the water temperature has stabilized ( usually about 3 5 minutes). The purpose of this step is to ensure the sample does not represent stagnant water that has sat for a long time in the water line between the street and the faucet. The sample should be representative of the water flowing through the distribution system at the chosen sampling point.

4) Adjust the flow so that no air bubbles are visually detected in the flowing stream. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 4 5) Slowly fill the sample vial almost to the top without overflowing. Use the bottle cap to add a small amount of additional sample water while simultaneously capping the vial to achieve a headspace free sample. Be careful not to rinse out any of the preservative/ dechlorinating agent during this process. After the bottle is filled, invert three or four times.

6) If collecting TTHM samples that require acidification, let the sample set for about 1 minute, allowing the dechlorinating chemical to take effect. Carefully open the vial and adjust the pH of TTHM sample to < 2 by adding approximately 4 drops of hydrochloric acid for every 40 mL of sample ( amount of acid needed will depend on buffering capacity of sample). Recap the vial, and invert three or four times.

7) Invert the vial and tap it to check for air bubbles. If bubbles are detected, carefully open the vial and add more sample water using the cap to achieve a headspace free sample.

8) Immediately cool the samples to 4oC by placing them in a cooler with frozen refrigerant packs or ice, or in a refrigerator. Samples should be maintained at this temperature during shipping to the laboratory.

9) Complete the Sample Chain of Custody provided by the laboratory and include it with the sample shipment.

C. 2.2 Regarding Loss of Samples Samples may be " lost" due to a number of reasons:

° Bottle broken during shipment from the water system to the laboratory ° Sample improperly collected ( e. g., sample bottle not completely filled)

° Sample improperly shipped ( e. g., not kept cold during shipment)

° Sample improperly preserved ( e. g., not dechlorinated)

° Bottle is broken or lost at the laboratory ° Quality control doesn't meet method specifications when sample is analyzed Resampling for the lost sample should be conducted as soon as possible after the loss is determined. Only the lost sample needs to be recollected, not the entire sample set that was collected together. Make sure to note the loss of sample and resample date as a deviation in your IDSE report. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 5 C. 3 Analytical Method Descriptions The following are brief summaries of the approved TTHM and HAA5 methods.

C. 3.1 EPA Method 502.2 Highly volatile organic compounds with low water solubility are extracted ( purged) from the sample matrix by bubbling an inert gas through a 5 mL aqueous sample. Purged sample components are trapped in a tube containing suitable sorbent materials. When purging is complete, the sorbent tube is heated and back flushed with helium to thermally desorb trapped sample components onto a capillary gas chromatography ( GC) column. The column is temperature programmed to separate the method analytes which are then detected with a photoionization detector ( PID) and an electrolytic conductivity detector ( ELCD) placed in series. Analytes are quantitated by procedural standard calibration. The PID is not required, if only TTHMs are being determined.

Identifications are made by comparison of the retention times of unknown peaks to the retention times of standards analyzed under the same conditions used for samples. Additional confirmatory information can be gained by comparing the relative response from the two detectors. For absolute confirmation, a gas chromatography/ mass spectrometry ( GC/ MS) determination according to USEPA Method 524.2.

Highly volatile compounds with low water solubility, including TTHMs, are extracted from the water sample by bubbling an inert gas through 5 mL of the sample. The chemical compounds that are extracted from the water sample are then trapped in a tube that contains material to which the chemicals attach, or sorb. Once the extraction process has been completed, the tube containing the extracted chemicals is treated with helium, and the mixture of helium and chemicals enters a capillary gas chromatography ( GC) column. The column is temperature programmed to separate the chemicals extracted from the water, which are then detected with a photoionization detector ( PID) and an electrolytic conductivity detector ( ELCD) placed in series. The amount of each chemical is determined using procedural standard calibration. The PID is not required if only TTHMs are being measured.

Chemical compounds are identified by comparing the retention times of unknown GC peaks with retention times for chemical standards analyzed under the same conditions. Confirmation can be made by comparing the relative response from the two detectors. For absolute confirmation of results, a gas chromatography/ mass spectrometry ( GC/ MS) determination can be made using U. S. EPA Method 524.2.

For a complete description of this method see EPA publication: EPA/ 600/ R 95/ 131 Methods for the Determination of Organic Compounds in Drinking Water: Supplement III. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 6 C. 3.2 EPA Method 524.2 Volatile organic compounds, including TTHMs, are extracted from the water sample by bubbling an inert gas through the sample. Extracted compounds are trapped in a tube that contains material to which the chemicals attach, or sorb. When the extraction process is complete, the tube is heated and flushed with helium to de sorb the trapped chemicals into a capillary gas chromatography ( GC) column interfaced with a mass spectrometer ( MS). The GC column is temperature programmed to allow for the separation of different chemicals, which are then detected with the MS. Compounds detected by the GC are identified by comparing their measured mass spectra and retention times with reference mass spectra and retention times in a database. Reference mass spectra and retention times for different compounds are obtained by measuring calibration standards under the same conditions that are used for the water samples. The concentration of each compound is measured by comparing the MS response of the compound with the MS response of another compound used as an internal standard. Surrogate chemicals, whose concentrations are known in every sample, are measured using the same internal standard calibration procedure.

For a complete description of this method see EPA publication: EPA/ 600/ R 95/ 131 Methods for the Determination of Organic Compounds in Drinking Water: Supplement III.

C. 3.3 EPA Method 551.1 A 50 mL volume of the sample is extracted using either 3 mL of methyl tert butyl ether ( MTBE) or 5 mL of pentane. A small sub sample of the extract ( 2 µ L) is then injected into a GC equipped with a fused silica column for separation, and a linearized electron capture detector for analysis. Concentrations of different chemical compounds are determined by comparing their measured amounts to standard calibration curves.

A typical sample can be extracted and analyzed using this method in 50 minutes for chlorinated byproducts ( e. g., HAA5) and chlorinated solvents, and in two hours for all of the compounds analyzed by this method. Results can be confirmed by using a second, different GC column, by using primary confirmation columns installed in a single injection port, or by a separate confirmation analysis.

For a complete description of this method see EPA publication: EPA/ 600/ R 95/ 131 Methods for the Determination of Organic Compounds in Drinking Water: Supplement III.

C. 3.4 EPA Method 552.1 A 100 mL volume of the sample is adjusted to pH 5.0 and extracted using a pre conditioned miniature anion exchange column. The chemical compounds to be analyzed are first eluted using small amounts of acidic methanol, and are then esterified directly in this medium after adding a small volume The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft C 7 of methyl tert butyl ether ( MTBE) as a co solvent. The methyl esters are partitioned into the MTBE phase, and are identified and measured using capillary column gas chromatography with an electron capture detector ( GC/ ECD).

For a complete description of this method see EPA publication: EPA/ 600/ R 92/ 129 Methods for the Determination of Organic Compounds in Drinking Water: Supplement II.

C. 3.5 EPA Method 552.2 The pH of a 40 mL volume of sample is adjusted to less than 0.5, and the sample is extracted using 4 mL of methyl tert butyl ether ( MTBE). The haloacetic acids that have been partitioned are then converted to their methyl esters by adding acidic methanol and heating them slightly. The acidic extract is then returned to neutral pH using a saturated solution of sodium bicarbonate. The chemical compounds of interest are identified and measured using capillary column gas chromatography with an electron capture detector ( GC/ ECD). Chemical concentrations are determined using standard calibration procedures.

For a complete description of this method see EPA publication: EPA/ 600/ R 95/ 131 Methods for the Determination of Organic Compounds in Drinking Water: Supplement III.

C. 3.6 EPA Method 552.3 [ to be developed]

C. 3.7 Standard Method 6251 B The sample is extracted using methyl tert butyl ether ( MTBE) at an acidic pH. A salting agent is added during the extraction process to increase the extraction's efficiency. Once extracted, compounds are methylated using diazomethane solution to produce methyl ester or other ether derivatives that can be separated in a gas chromatograph. A gas chromatograph equipped with a fused silica capillary column and an electron capture detector ( GC/ ECD) is used for analysis. Alternative detectors can be used if quality control criteria are met. Calibration standards are extracted, methylated, and analyzed in the same manner as the water samples to compensate for less than 100% recoveries during sample preparation.

For a complete description of this method see Standard Methods for the Examination of Water and Wastewater: 21st Edition published jointly by the APHA, AWWA, and WEF. Appendix D Simulated Distribution System Test This page intentionally left blank. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft D 1 D. 1 Introduction An SDS test involves storing a sample of disinfected finished water in a manner that reflects the conditions ( pH, temperature, and residence time) of the distribution system. The purpose of an SDS test is to evaluate the potential of the finished water to form TTHM and HAA5 in the distribution system conditions at different residence times. An SDS test is site specific and therefore, there is no universal set of conditions that applies to all systems.

Section D. 2 provides the recommended procedure for conducting an SDS laboratory test. Section D. 3 describes how SDS tests can be used in conjunction with Stage 1 DBPR and other DBP monitoring data to estimate average and maximum residence times.

D. 2 Recommended SDS Test Procedure A separate SDS sample should be collected for each distribution system residence time to be evaluated. The following protocol is recommended for collecting, storing, and analyzing an SDS sample:

Test Conditions ° The pH of the sample should be that of the distribution system water ( ± 0.2). No pH adjustments should be made after collecting the finished water samples for any of the SDS tests.

° The sample should be held at a temperature comparable to the distribution system temperature between the treatment plant and the TTHM sampling points in the distribution system for the corresponding time period. The goal should be a temperature within ± 2 ° C of either the water entering the distribution system or the water at the DBP sampling point being evaluated. If major temperature fluctuations occur in the distribution system during the SDS tests, these should be taken into account when analyzing the data.

° The holding time of an SDS test begins when an SDS sample is collected, and ends when the sample is transferred into sample bottles ( with appropriate preserving and dechlorinating agents) for TTHM and HAA5 analysis. The total reaction time actually begins with the addition of chlorine based oxidants at the treatment plant.

° A disinfectant residual should be present at the end of the holding time. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft D 2 Sample Collection ° SDS samples should be collected at the entry point to the distribution system, after the final addition of chlorine and/ or ammonia or any chemicals added for corrosion control or pH adjustment are completely mixed in treated water. ( In cases where systems use chloramines for secondary disinfection, SDS sample collection will typically be at the location where the system measures free ammonia to control the dosing of ammonia). If systems employ booster disinfection, then a second SDS sample collected after booster disinfectant addition and a separate SDS analysis are recommended.

° SDS samples should be collected in 250 mL amber glass bottles ( or larger) with TFE lined screw caps, and should be collected head space free, with no addition of any preservatives or dechlorinating agents. ( The sample should be of sufficient volume for all the analyses needed for SDS sample analyses, i. e., DBPs, disinfectant residual, pH, etc.) Prior to collecting the samples, the bottles should be pre treated with concentrated chlorine solution and copiously rinsed with deionized water, then oven dried at 180 / C for an hour, to ensure that the glassware is chlorine demand free.

Holding Time The holding time represents a residence time pre determined by the system. The system could conduct several SDS tests at a range of residence times to develop a kinetic curve ( see section D. 3). The system could also use estimated residence times of DBP sampling sites in the distribution system and compare the SDS results to its DBP results.

Sample Storage The bottle containing an SDS sample is best stored in the treatment plant where it is collected.

° It can be suspended in the plant clearwell to maintain it at the finished water temperature, or in a container in a sink with a constant flow of finished or distributed water running through the container.

° The collected sample may be transported to an off site laboratory, provided it is maintained at the desired storage temperature during transport and for the duration of the test. During the holding time at the laboratory, an SDS sample can be placed in an incubator ( set at the selected distribution system temperature ± 2 / C) or in a container in a sink with a constant flow of finished or distributed water running through the container ( if the laboratory receives water from the same distribution system being tested). Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft D 3 Sample Analysis At the end of a specified residence time, an SDS sample is analyzed for several parameters ( disinfectant residual, TTHM, and HAA5, pH, temperature).

° The SDS sample should be divided by pouring it into sample bottles containing the appropriate dechlorinating agents/ preservatives for each analysis. The TTHM sample bottle should be filled first, followed by the HAA5 sample bottle. Care must be taken to not aerate the sample during this splitting process, in order to prevent the loss of volatile THMs.

° Immediately after the TTHM and HAA5 sample bottles are filled, the pH, temperature, and disinfectant residual concentration should be determined in the remaining aliquot of the SDS sample. If no disinfectant residual is detected, then the result of this SDS test should be thrown out.

° The TTHM and HAA5 samples should be analyzed within the holding time specified by the method.

° The TTHM and HAA5 analyses should be conducted by a laboratory certified under the drinking water certification program to perform those analyses. Appendix C describes TTHM and HAA5 laboratory analyses.

D. 3 Using SDS Tests to Determine Average and Maximum Residence Time For systems that do not have good information about their residence time, a number of SDS tests can be conducted and compared to Stage 1 compliance monitoring data to help estimate average and maximum residence time. It should be noted that the SDS tests should be conducted in conjunction ( preferably done on the same day or a couple of days before) with the Stage 1 DBP compliance monitoring sampling.

Because DBP formation is not linear, it is recommended that a kinetic curve be developed to describe the system specific DBP formation. To create a useful curve, a minimum of four SDS samples should be collected at the finished water sampling location. Analysis should begin immediately for the first sample ( aliquots should be transferred to sample vials with appropriate preservation and dechlorinating agents for TTHM and HAA5 anlaysis, and chlorine residual, pH, and temperature should be analyzed immediately thereafter). This represents time zero. A second sample should be stored at the finished or distribution system temperature ( see section D. 2 for details) for an estimated maximum distribution system residence time ( this selected time interval will be a best guess estimate). The other two SDS samples are stored for two intermediate time intervals that equally subdivide the maximum Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft D 4 0 10 20 30 40 50 60 70 80 0 1 2 3 4 5 6 7 8 9 10 Residence Time ( days) DBP Concentration ( ug/ L)

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Free Chlorine Residual (

mg/

L)

TTHM HAA5 Chlorine residence time ( e. g., if you estimate that your maximum residence time is 6 days, store your other two SDS samples for 2 days and 4 days). At the end of the selected storage times, transfer the sample aliquots to appropriate TTHM and HAA5 sample bottles ( with preservation and dechlorinating agents) for analysis. Plot the the resultant TTHM and HAA5 data ( : g/ L) on the y axis and corresponding holding times ( days) on the x axis. An example kinetic curve with disinfectant residual data is presented in Figure D. 1.

Figure D. 1 SDS Test Kinetic Curve To estimate the residence time of monitoring sites in the distribution system, use the DBP results from the monitoring sites and the kinetic curve developed from the SDS tests. For example, the TTHM result from a Stage 1 compliance monitoring sample was 40 µ g/ L. Using Figure D. 1, 40 µ g/ L of TTHM corresponds to a residence time of 2 days. Combining these data with disinfectant residual data from each of the four SDS samples may also be useful.

When designing SDS studies, systems using booster disinfection must consider the application Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft D 5 of disinfectants in the distribution system. For systems that employ booster chlorination in the distribution system, another SDS sample should be taken after the re chlorination station and the residence time should simulate the distribution system conditions downstream of the re chlorination station. Appendix E IDSE SMP Report for Producing Surface Water Systems Serving $ 10,000 People This appendix is provided as an example IDSE report for producing surface water systems serving at least 10,000 people and opting to complete the Standard Monitoring Program ( SMP).

Chapter 5 presents the detailed SMP requirements for these systems, and Chapter 8 provides guidance on selecting SMP sites and Stage 2B compliance monitoring sites based on SMP results. Chapter 8 also presents the IDSE reporting requirements. The application of the basic guidance on SMP site selection and Stage 2B compliance monitoring site selection is shown in this example, along with several instances of the use of best professional judgement being applied.

The italicized text within the appendix consists of comments and explanations and is not intended to represent the recommended content of an actual IDSE Report. This page intentionally left blank. Initial Distribution System Evaluation Report for Elm City PWSID Number: US1111111 Address: 1234 Main Street Elm City, US 99999 Contact Person: Mr. Ronald Doe, P. E.

Phone Number: 123 555 0000 Fax Number: 123 555 0001 Email Address: Rdoe@ ci. elmcity. us System Type: Community, surface water Population Served: 160,000 This page intentionally left blank. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 1 I. SMP PLAN 1. System Description:

This section of the report should include a summary of typical system operating characteristics ( and how they change on a seasonal basis if appropriate) explaining how sources are used to meet system demands, where high water age is expected to occur, and any special aspects of operation that could affect DBP concentrations in the distribution system. Information about water treatment processes and source water quality data should also be in this section, including a brief description of the water treatment process train.

General system characteristics: Service area: Elm City plus surrounding suburban areas Production: Annual average daily production = 15 MGD Source Water Information: Hardwood Lake ( surface water) pH: from 6.9 to 7.5 Alkalinity: from 82 to 98 mg/ L as CaCO3 TOC: from 2.1 to 4.0 mg/ L as C Softwood River ( surface water) pH: from 6.8 to 7.9 Alkalinity: from 77 to 94 mg/ L as CaCO3 TOC: from 1.6 to 4.4 mg/ L as C Entry points and service areas under the influence of each entry point: ( Entry points should be tied to source( s) and typical flows noted)

Entry points: Hardwood Plant: Design Capacity = 20 mgd Average Daily Production = 7.5 mgd Softwood River Plant: Design Capacity = 20 mgd Average Daily Production = 7.5 mgd Customers located in the Industrial Park area, Oakville, Pineville, and south downtown areas generally receive water from the Hardwood Plant Customers located in the Cypressville, Cedarville, Poplarville, and north downtown areas generally receive water from the Softwood Plant Customers located in the Weeping Willow Community, Appleville, and central downtown areas generally receive a mixture of water from both plants Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 2 Treatment Provided: Hardwood   ferric chloride coagulation, flocculation, sedimentation, dual media filtration Softwood River   ferric chloride coagulation, flocculation, sedimentation, dual media filtration, followed by GAC Primary and residual disinfection: Chlorine/ chlorine at both plants Description of distribution system: Distribution system ( estimated length of lines and range of diameter): About 400 miles, 4"  56" ( approximately 6 MG total pipe volume)

5 storage tanks of 10 MG total capacity 1 ground tank 4 MG capacity 4 elevated tanks 6 MG capacity Following recent customer complaints in areas downstream of the Cherry Hill tank, the city evaluated mixing conditions in each distribution system tank. As a result, the city made some inlet/ outlet modifications at both the Cherry Hill and Apple Drive tanks to improve tank mixing.

The average residence time of water in the distribution system is six to eight days.

Pump stations: Station # 1 is located at the ground storage tank ( in Pineville). This pump is primarily used during peak demands and low pressure situations. The pump is timed to turn on in the morning and evening during peak demand and when the pressure drops below 40 psi at a point downstream of the pump station.

Stations # 2 and # 3. These pumps are used to boost system pressure when the pressure in the areas downstream of these pumps ( Weeping Willow and Poplarville) drops below 40 psi.

Booster chlorination facilities: Facility # 1 is located on Cherry Hill Ave. ( downstream of the Cherry Hill storage tank at pump station # 3). This facility is occasionally used during the summer when remote locations downstream of the booster chlorination facility lose residual.

Facility # 2 is located at the intersection of Second Ave. and 11th St. ( in a mixing zone) in an area of the distribution system where chlorine residuals are frequently low. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 3 Poplarville Softwood River WTP Hardwood WTP Elevated Storage Tank Ground storage tank Pump station Chlorine Booster Station Appleville Weeping Willow Oakville Pineville Cedarville Cypressville Downtown Industrial Park PS2 CB2 PS3 CB1 PS1 Elm City Water Distribution System Apple Drive EST Jackson EST Cherry Hill EST Pineville GST East EST 2. Schematic of the distribution system: Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 4 3. SMP monitoring requirements:

The Elm City system serves approximately 160,000 people and has two surface water plants. Therefore, a total of 16 SMP sample sites ( 8 per plant) are required to be sampled approximately every 60 days for one year ( 6 dual sample sets per site) for TTHM and HAA5. Because it uses chlorine as a disinfectant in the distribution system, three sites representative of high TTHM are required, but only one site near the entry point is required.

Required SMP Sample Sites SMP Site Type Number of Sites in the Hardwood Plant Influence Zone Number of Sites in the Softwood River Plant Influence Zone Near entry to the distribution system 1 1 Average residence time 2 2 Representative of high TTHM 3 3 Representative of high HAA5 2 2 Available Data:

Report all data that helped in sample site selection. If you have bromide, TOC, or HPC data, these may be helpful for justifying Stage 2B site selection. For this example, only tables with limited data are presented for Stage 1 DBPR sample sites and the sites chosen as SMP sample sites. Your report should include data for all sites that were considered for SMP sites.

Chlorine residual and HPC data were available for Total Coliform Rule sample sites and the 8 Stage 1 DBPR sample sites. The chlorine data for the summer months of June, July, August, and September were reviewed, and monthly averages and an overall average were calculated. Table E. 1 presents these data and shows which sites were chosen as SMP sites.

Quarterly HPC data was also available for the same year and at the same sites as the free chlorine data. The four results for each site were averaged. The quarterly results and yearly average values are presented in Table E. 2. The results are ordered based on the Stage 1 DBPR and SMP site numbers. Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 5 Table E. 1 Elm City Distribution System   Free Chlorine Residual ( Cl2) Data Sample Site ID # Source/ Plant Stg. 1 Site Type SMP Site # SMP Site Type Free Chlorine Residual ( mg/ L)

June July Aug. Sept. Avg.

Stg. 1 # 1 SRP Avg. 0.6 0.9 1.1 0.8 0.9 Stg. 1 # 2 SRP Avg. 0.6 0.7 0.8 1.2 0.8 Stg. 1 # 3 SRP Avg. 0.3 0.6 0.3 0.2 0.4 Stg. 1 # 4 SRP Max. 0.2 0.3 0.5 0.3 0.6 Stg. 1 # 5 HP Avg. 0.9 0.7 1.0 1.2 1.0 Stg. 1 # 6 HP Avg. 0.2 0.8 0.8 0.5 0.6 Stg. 1 # 7 HP Avg. 0.8 0.9 0.3 0.8 0.7 Stg. 1 # 8 HP Max. 0.2 1.0 0.7 0.1 0.6 TCR # 5 HP 1 E 1.6 1.4 1.6 1.5 1.5 TCR # 4 HP 2 A 0.8 0.6 0.9 0.8 0.8 TCR # 15 HP 3 A 0.6 0.4 0.4 0.4 0.5 TCR # 16 HP 4 H 0.6 0.2 0.5 0.4 0.4 TCR # 8 HP 5 H 0.4 0.3 0.3 0.5 0.4 TCR # 2 HP 6 T 0.3 0.4 0.2 0.2 0.3 TCR # 9 HP 7 T 0.3 0.2 0.2 0.4 0.3 TCR # 12 HP 8 T ND 0.1 0.1 0.3 0.1 TCR # 10 SRP 9 E 1.4 1.2 0.9 1.7 1.3 TCR # 11 SRP 10 A 0.6 0.6 0.5 0.9 0.7 TCR # 13 SRP 11 A 0.5 0.3 0.4 0.5 0.6 TCR # 6 Mix/ SRP 12 H 0.7 0.4 0.8 1.0 0.7 TCR # 1 SRP 13 H 0.5 0.8 0.9 0.4 0.7 TCR # 7 Mix/ SRP 14 T 0.3 0.4 0.7 0.6 0.5 TCR # 3 SRP 15 T 0.2 0.6 0.3 0.2 0.3 TCR # 14 Mix/ SRP 16 T 0.6 0.7 0.6 0.6 0.6 Distribution System Warm Months Average 0.6 Mix  Mixing Zone TCR  Total Coliform Rule E  Near Entry Point HP  Hardwood Plant Stg. 1  Stage 1 DBPR A  Average Residence Time SRP  Softwood River Plant ND  Non Detection T  Representative High TTHM H  Representative High HAA5 Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 6 Table E. 2 Elm City Distribution System   Heterotrophic Plate Counts ( HPC) Data Sample Site ID # Source/ Plant Stg. 1 Site Type SMP Site # SMP Site Type HPC ( cfu/ mL)

4th Qtr. 1st Qtr. 2nd Qtr. 3rd Qtr. Avg.

Stg. 1 # 1 SRP Avg. 56 42 276 345 180 Stg. 1 # 2 SRP Avg. 82 136 246 146 152 Stg. 1 # 3 SRP Avg 140 215 615 557 382 Stg. 1 # 4 SRP Max 280 163 263 446 288 Stg. 1 # 5 HP Avg. 140 66 236 364 201 Stg. 1 # 6 HP Avg. 50 42 222 223 134 Stg. 1 # 7 HP Avg 53 42 72 84 63 Stg. 1 # 8 HP Max 196 45 425 653 330 TCR # 5 HP 1 E 12 8 12 34 17 TCR # 4 HP 2 A 78 86 364 384 228 TCR # 15 HP 3 A 35 62 92 147 84 TCR # 16 HP 4 H 34 76 89 97 74 TCR # 8 HP 5 H 68 43 57 79 62 TCR # 2 HP 6 T 35 43 45 64 47 TCR # 9 HP 7 T 156 278 359 169 240 TCR # 12 HP 8 T 233 214 546 456 362 TCR # 10 SRP 9 E 67 14 42 35 40 TCR # 11 SRP 10 A 43 34 224 156 114 TCR # 13 SRP 11 A 54 65 65 573 189 TCR # 6 Mix/ SRP 12 H 53 64 123 94 83 TCR # 1 SRP 13 H 50 34 63 113 65 TCR # 7 Mix/ SRP 14 T 69 43 43 37 48 TCR # 3 SRP 15 T 70 212 332 356 242 TCR # 14 Mix/ SRP 16 T 66 53 53 153 81 Mix  Mixing Zone TCR  Total Coliform Rule E  Near Entry Point HP  Hardwood Plant Stg. 1  Stage 1 DBPR A  Average Residence Time SRP  Softwood River Plant T  Representative High TTHM H  Representative High HAA5 Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft E 7 4. Summary of selected SMP sample sites:

Present the rationale for the selection of the SMP sample sites in your system, as well as a schematic showing their location within the distribution system.

Sample sites were chosen to represent diverse geographical areas of the distribution system. Each site is shown on the map of the distribution system in section I. 6. Water quality data obtained from residual chlorine ( Table E. 1) and HPC ( Table E. 2) monitoring were considered in the selection of the SMP monitoring sites.

SMP Site # 1   Entry point to the distribution system for Hardwood Water Treatment Plant. This site is where the first group of customers receives water.

SMP Site # 2   Represents average residence time of water leaving the Hardwood Plant. Based on chlorine monitoring results at TCR sample sites, we identified the areas within the system where chlorine levels equaled approximately 50 percent of the initial residual concentration at the high service pumps and chose this site from within those areas. There are no storage facilities between the treatment plant and this site.