One way to show high residence time sites 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 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 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 the system moves away 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 3 15 ° 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 preliminary site selections.

In some cases, there can 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 " mixing zone" and may act as a hydraulic dead end. Mixing zones can occur anywhere in the distribution system, but occur more often in the central portion of a distribution system. If the water demand in the mixing zone is low, then the water age and TTHM concentrations could be high. Water distribution system models can be useful in locating mixing zones and identifying high TTHM sites within the mixing zone.

High HAA5 Sites The criteria and procedure for selecting high HAA5 sites using a hydraulic model is generally the same as that described above for selecting high TTHM sites with one important difference: the sites chosen to represent high HAA5 should 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. It is generally recommended that high HAA5 sites be selected in areas with a minimum chlorine residual of 0.2 mg/ L or a minimum chlorine residual or 0.5 mg/ L.

Average Residence Time Sites Average residence time sites can be selected from sites with residence times close to the flowweighted 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. Preliminary 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 preliminary sites do not have to be chosen at the exact location of a model node, The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 16 just in the general area identified by the model results. Selected sites should represent the entire distribution system and should not be clustered.

3.4.3 Performing At Least One Round of Sampling Although hydraulic models can be used to reasonably predict residence times, the behavior of HAA5 cannot be directly predicted based on residence time in a distribution system. Therefore, to meet the rule requirement of demonstrating model accurately characterized expected TTHM and HAA5 levels ( 40 CFR 141.604( a)), this approach recommends systems perform at least one round of sampling at preliminary sites ( i. e., collecting dual sample sets at each site). Generally, the TTHM concentrations from this sampling should confirm the model predictions of residence time and verify the selection of preliminary sites.

If only one round of sampling is performed, it should occur in the month of peak TTHM levels or water temperature in the distribution system. Additional rounds of sampling are allowed and encouraged. All results should be considered in the selection of Stage 2B compliance monitoring sites and included in the IDSE report. Stage 1 DBPR compliance monitoring and other historical TTHM and HAA5 data should be considered, if available, and included in the IDSE report.

If the results from Stage 1 DBPR compliance monitoring and the single round of sampling are not reasonably consistent with modeled residence times, the potential reason for the discrepancy should be explained in the IDSE report. If factors such as demand variations, distribution system operations, tank operations, tank cleaning, or new construction are thought to have impacted the sampling results, then the specifics of these factors should be included in the IDSE report. One or more additional rounds of sampling may also be performed and are encouraged. Modeling revisions might be needed if actual conditions during the sampling were found to be different than modeled conditions. In this case, select new preliminary sites and repeat the monitoring.

It is recognized that distribution system modeling results usually do not completely reflect the true range and variability of hydraulic and water quality conditions that exist in distribution systems. This limitation of modeling allows for some amount of variability between sampling and modeling results. However, if significant inconsistencies exist between modeling results and the required one round of sampling, then additional explanation would need to be provided in the IDSE report.

3.5 Alternative SSSs EPA recognizes that there are many combinations of data and analyses that can be used for an SSS. Potential combinations include, but are not limited to:

° Historical data supplemented with new data The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 17 ° Historical data and tracer study results ° New TTHM and HAA5 data, distribution system modeling, and tracer study results In general, any alternative SSS should be representative of the majority of the distribution system, including the extremities, and provide equivalent or superior data for the selection of Stage 2B monitoring sites compared to an IDSE SMP.

Section 3.5.1 lists questions that States should consider when evaluating an alternative SSS. Sections 3.5.2 and 3.5.3 provide guidelines for two alternative SSSs: historical DBP data supplemented with new DBP data, and historical or new DBP data combined with a tracer study. The guidelines listed in this section are NOT definitive   SSSs will always be evaluated on a case by case basis by the State.

3.5.1 Evaluation of Alternative SSSs The following is a list of questions that States should consider when evaluating an SSS:

1) Does the study adequately evaluate the extremities? Does the study target other potential areas with long water residence times?

2) Do the historical data meet the specified criteria for analytical quality and represent existing distribution system conditions ( see section 3.3)?

3) Does the study cover at least 1 continuous year?

4) Are there data representing the month of peak TTHM or highest temperature?

3.5.2 Historical Data Combined with New Data The total number of samples analyzed should be equal to or greater than the total number of samples required for the IDSE SMP ( see Tables 1.4 and 1.5). The type of monitoring site should also satisfy the SMP requirements. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 18 Historical data should meet the requirements and general guidelines in section 3.3. New sampling should be performed to fill in " gaps" in historical data as needed to meet the minimum number of samples and coverage of the distribution system. Treatment, source water, and distribution system conditions should be similar during the historical and new sampling periods, in accordance with the requirements and guidelines in sections 3.3.4 and 3.3.5. In cases where all historical data are used for some locations and all new data for other locations, there should be no permanent changes to treatment, source water, and distribution system conditions that affect the overall magnitude of TTHM and HAA5 concentrations between the historical and new data sampling periods. The selected sites should adequately represent the entire distribution system.

3.5.3 Historical or New DBP Data Combined with a Distribution System Tracer Study Time of travel 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. When pipe diameters in a model are inaccurate, model predictions can be very different than the actual hydraulic conditions in a 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 SSS may not be cost effective. However, if your system is considering a tracer study for some other purpose ( e. g., calibrating a hydraulic model), Example 3.1 Monitoring Requirements for a Surface Water System Serving More Than 10,000 People If your system is a producing surface water system serving more than 10,000 people using free chlorine for residual disinfection, your combined historical and new TTHM and HAA5 data should represent, at minimum:

1) At least eight sample sites per treatment plant, with at least one representing a near entry point, two representing average residence time areas, three representing high TTHM areas, and two representing high HAA5 areas.

1) At least six TTHM and HAA5 sample results from each site ( equivalent to requirements for SMP monitoring), with at least one group of samples collected during the month of historical peak TTHM levels or high water temperature. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 19 consideration should be given to using the tracer study as a tool for the IDSE SSS. Also, results from previously conducted tracer studies may be very useful in identifying areas in the distribution system with high and average residence times.

Tracer studies can be performed 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 which reduces 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 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 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 ° Sites prior to the last fire hydrant in remote areas with few customers The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 20 To adequately characterize distribution system residence time, tracer concentrations must 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 site will only be accurate to within 8 hours. Furthermore, the proximity of sample sites 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 more closely together.

The following are general guidelines for using a tracer study as part of a SSS:

° In general, the tracer study should reflect the existing distribution system configuration and should have been conducted within the last 10 years. If permanent and significant changes to demand, piping, pumping, or storage have occurred since the tracer study was completed, the study may not be suitable for an SSS.

° The tracer study should generally represent conditions of high DBP formation potential and high water age ( typically summer months and low demand periods for most systems).

° The tracer study should be detailed enough to provide good characterization of water residence time for the entire distribution system. Not all extremities must be covered by the study, but the data should be complete enough to allow for a reasonable extrapolation of the results to cover the entire distribution system.

° If the tracer study does not provide residence time information for the extremities of the distribution system, then historical TTHM and HAA5 data should be reviewed if available, or new data should be collected at expected representative high TTHM and HAA5 sites.

° Regardless of the level of detail of the tracer study, systems should have historical data for at least one complete round of sampling at the preliminary sites or should perform at least one new round of sampling at the preliminary sites ( see section 3.4.3 for guidance on conducting one round of sampling). At a minimum, one round of sampling should occur during the month of historical peak TTHM levels or highest water temperature, if the historical peak TTHM month is unknown. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 21 3.6 Selecting Stage 2B Compliance Monitoring Sites Using SSS Results This section describes procedures for using results of an SSS to select Stage 2B compliance monitoring sites. Tables 3.1 and 3.2 summarize the Stage 2B monitoring requirements for producing and 100 percent purchasing systems, respectively ( Chapter 1 also provides this information).

Section 3.6.1 addresses selection of high TTHM and high HAA5 sites, while Section 3.6.2 addresses selection of average residence time Stage 2B sites using SSS results ( note that only a subset of systems need to select average residence time sites, as addressed in Section 3.6.2). Section 3.6.3 provides examples of site selection. Appendix K contains an example IDSE report where a hydraulic model was used to select Stage 2B compliance sites, and Appendix J contains an example IDSE report where historical data were used to select Stage 2B compliance sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 22 Table 3.1 Stage 2B Plant based Compliance Monitoring Requirements for Producing Systems1,2 System Size ( Population Served3) Number of Distribution System Sites ( by type of site) per Plant4 Total Number of Sites per Plant Monitoring Frequency5 Stage 1 Average Residence Time 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 typically a system's retail population. It should not include populations served by consecutive systems that purchase water from that system. 4 For the purposes of the Stage 2 DBPR compliance monitoring, a consecutive system entry point that operates for at least 60 consecutive days per year must be considered a plant ( 40 CFR 141.601( d)). 5 Monitoring frequency is the approximate number of days between monitoring events. A dual sample set must be collected at each site, unless otherwise noted. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and site. 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 site, then only one sample is collected at each site. If they occur at the same site, then a dual sample set is collected at that site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 23 Table 3.2 Stage 2B Population based Compliance Monitoring Requirements for 100 Percent Purchasing Systems1,2 System Size ( Population Served3) Number of Distribution System Sites ( by type of site) per System Total Number of Sites per System Monitoring Frequency4 Stage 1 Average Residence Time Highest TTHM Highest HAA5 Surface Water Systems5 < 500  1 1 26 Every 365 days 500  4,999  1 1 26 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 typically 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 site, unless otherwise noted. A dual sample set is one TTHM and one HAA5 sample that is taken at the same time and site. 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 site, then only one sample is collected at each site. If they occur at the same site, then a dual sample set is collected at that site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 24 3.6.1 Selecting High TTHM and HAA5 Sites Selection Using a Historical Data SSS The following steps detail how Stage 2B sites should generally be selected based on historical TTHM and HAA5 data. These steps also apply to systems using a combination of historical and new data.

1) Calculate the Locational Running Annual Average ( LRAA) for TTHM and HAA5 concentrations at each historical data site. Historical data should cover at least 1 full year. If your data covers a longer period, calculate separate annual averages for each full year. Select the data for the year with highest average for each site ( see the example in Appendix L for sample calculations).

2) Calculate the LRAA for TTHM and HAA5 concentrations at the Stage 1 DBPR maximum residence time site( s). If your data covers more than 1 year, calculate separate averages for each full year. Select the data for the year with highest average for each site.

3) Select high TTHM and high HAA5 sites starting with the highest TTHM and HAA5 LRAAs from both the Stage 1 DBPR compliance monitoring sites and historical data sites.

TTHM and HAA5 LRAAs are the most important factors to consider when selecting Stage 2B monitoring sites. However, the Stage 2 DBPR 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 site) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 2 The 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 3 25 If you do not use your highest TTHM and HAA5 LRAAs to select your Stage 2B sites, you must provide justification for your selection in your IDSE report ( 40 CFR 141.605). 2 Selection Using a Water Distribution System Model SSS The first step in selecting Stage 2B sites is to compare the model predicted residence times for your preliminary sites with the TTHM and HAA5 concentrations from the one round of sampling, Stage 1 compliance monitoring results, and any other historical TTHM and HAA5 data. Are the results consistent? In other words, do those sites with the highest residence time also represent those sites with the highest TTHM concentrations?

Ideally, the preliminary or Stage 1 DBPR sites with the highest TTHM and HAA5 sampling results should be selected as the Stage 2B high TTHM and high HAA5 sites. However, TTHM and HAA5 data collected during the one round of sampling at preliminary sites may not represent typical levels. Distribution conditions at the time of sampling should be taken into account. EPA recognizes that one round of samples reflects only a snapshot of the distribution system. Modeled data represent a more comprehensive picture of the distribution system, and therefore, may not agree with the sampling results. If your modeled data and sampling results do not agree and you select a site based on modeled results, you should explain your rationale for selecting that site in your IDSE report.

For example, say that a model predicts that " Site A" normally receives water from the West Tank during the daytime hours. The TTHM and HAA5 results from Site A were much lower than expected, compared to other sites. Upon reviewing the tank operating data from the day of sampling, it is likely that the site was not receiving water from the West Tank during the time of sampling due to low system demand that day. In this situation, the system may want to select Site A as a Stage 2B compliance monitoring site based on the modeled data and noting in the IDSE report the discrepancy between modeled data and sample results.

You should also consider other factors such as geographic coverage when selecting sites. It is acceptable to pick a site with a slightly lower TTHM or HAA5 result over another if the selected site provides better geographic coverage; however, you must provide your rationale for selection in the IDSE report. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 3 100 percent purchasing ground water systems serving at least 10,000 people were not required to have average residence time sites for Stage 1 DBPR. 100 percent purchasing surface water systems may have an average residence time Stage 1 DBPR site, depending on the monitoring plan for their combined distribution system.

July 2003  Proposal Draft All Systems 3 26 3.6.2 Selecting Average Residence Time Sites The following systems are required to select average residence time site( s) for the Stage 2B ( 40 CFR 141.605):

° 100 percent purchasing surface water or ground water systems serving at least 10,000 people ° Producing surface water systems serving at least 10,000 people.

One of the purposes of the Stage 2B average residence time site is to ensure that a historical data record of system DBP levels is maintained ( i. e., systems keep one site the same from Stage 1 to Stage 2 DBPR). Producing systems can meet this goal by selecting their Stage 2B average residence time site from their three Stage 1 DBPR average residence time sites ( guidelines for selecting from Stage 1 DBPR compliance monitoring sites are provided below). 100 percent purchasing systems may not have average residence time sites under the Stage 1 DBPR requirements. 3 In these situations, they must alternate between high HAA5 and high TTHM sites to fill the required number of Stage 1 average residence time sites.

Producing Systems Systems must select their Stage 2B average residence time site ( one per plant) from the three existing Stage 1 DBPR average residence time sites. Stage 2B average residence time sites should have the highest TTHM or highest HAA5 LRAA among the Stage 1 DBPR average residence time sites, considering the most recent year of data. If the high TTHM and high HAA5 LRAAs do not occur at the same site, consider other factors such as geographical coverage and how close LRAAs are to the MCLs, in order to decide between the two sites. Considering the second situation, if the high TTHM LRAA is 70 µ g/ L and high HAA5 LRAA is 35 µ g/ L, then the site with the high TTHM LRAA is the better choice. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 27 3.6.3 Examples of Stage 2B Site Selection This section provides examples of Stage 2B site selection:

Example 3.2 Selecting Stage 2B Sites from Historical Data Example 3.3 Maintaining an Historical Record Example 3.4 Providing Geographical Coverage When Choosing Stage 2B Sites The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 28 Example 3.2 Selecting Stage 2B Sites from Historical Data A producing water system serves 90,000 people and has one surface water treatment plant. This system must select 4 Stage 2B compliance sites: 2 high TTHM sites; 1 high HAA5 site; and 1 from the 3 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 historical sites ( these data represent the seven highest TTHM and HAA5 LRAAs).

Site TTHM LRAAs HAA5 LRAAs A ( Stage 1 max. residence time) 70 ( 1st year) , 69 ( 2nd year) 51 ( 1st year), 49 ( 2nd year)

B ( historical high TTHM site) 66 ( 1st year), 64( 2nd year) 40 ( 1st year), 38 ( 2nd year)

C ( historical high HAA5 site) 72 ( 1st year), 71 ( 2nd year) 53 ( 1st year), 50 ( 2nd year)

D ( historical high TTHM site) 76 ( 1st year), 72 ( 2nd year) 50 ( 1st year), 49 ( 2nd year)

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. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 29 Example 3.2 Selecting Stage 2B Sites from Historical Data ( cont.)

Selecting the High TTHM Sites Site D has the highest TTHM LRAA. Therefore, this site is chosen as the first of the high TTHM sites. Site C has the next highest TTHM LRAA, and Site A has a slightly lower TTHM LRAA than Site C. The difference in the TTHM values between Site A and Site C is minimal, and Site A is a Stage 1 DBPR " maximum compliance" site. Because the difference between the TTHM LRAAs of Site A and C are minimal, and Site A would maintain a historic record of sampling, Site A is chosen as the second high TTHM site.

Selecting the High HAA5 Site Site C has the highest HAA5 LRAA. Sites A and D have almost as high HAA5 LRAAs. However, because Sites A and D have already been chosen as the high TTHM sites, Site C is chosen as the high HAA5 site.

A Water Treatment Plant B C Example 3.4 Providing Geographic Coverage when Choosing Stage 2B Sites In general, the two representative highest TTHM sites ( per plant) should not be from the same area of the distribution system. Consider the following example   The two highest TTHM LRAAs in the distribution system are from adjacent historical 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 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 3 30 3.7 Reporting Results to the State You are required to include your proposed Stage 2B compliance monitoring sites in your IDSE report. At a minimum, your IDSE report must include:

° A schematic of the distribution system ° All studies, reports, data, analytical results, and modeling to support your SSS ° All TTHM and HAA5 analytical results from Stage 1 DBPR compliance samples collected during the period of the IDSE ° 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 Example 3.3 Maintaining an Historical Record A 100% purchasing system serves 4,000 people and purchases all of its water. This system must select two Stage 2B compliance sites: one high TTHM and one high HAA5 site. The table below lists historical and Stage 1 DBPR compliance monitoring results for this system.

Sample Sites LRAA TTHM ( µ g/ L) HAA5 ( µ g/ L)

Historical # 1 ( High TTHM) 71 51 Historical # 2 ( High TTHM) 65 45 Historical # 3 ( High HAA5) 60 53 Stage 1 DBPR max residence time site 69 51 Because the TTHM LRAA for the Stage 1 DBPR site is only slightly lower than the maximum TTHM LRAA ( Historical # 1), the system chooses the Stage 1 DBPR site over Historical # 1 for the Stage 2B high TTHM site to maintain the historic DBP record at that site. Historical # 3 is selected as the high HAA5 site because this site has the highest HAA5 LRAA. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 3 31 Example reports for SSSs are in appendices to this manual, as listed in Table 3.3.

Table 3.3 Example IDSE Reports Appendix System Characteristics Appendix K SSS for a System Using a Hydraulic Model Appendix L SSS for a System Using Historical Data The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 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 The Stage 2 DBPR defines a combined distribution system as the totality of the distribution systems of wholesale systems and of the consecutive systems that receive finished water from those wholesale systems ( 40 CFR 141.2).

July 2003  Proposal Draft 100 Percent Purchasing Systems 4 1 4.0 Standard Monitoring Program Requirements for 100 Percent Purchasing Systems 4.1 Introduction This chapter describes the Initial Distribution System Evaluation ( IDSE) Standard Monitoring Program ( SMP) requirements for 100 percent purchasing systems. 1 IDSE and Stage 2B Disinfectants and Disinfection Byproducts Rule ( DBPR) monitoring requirements for 100 percent purchasing systems are based on population served and source water type, not on the number of plants as under the Stage 1 DBPR. Since these systems do not have treatment plants, a population based monitoring program is more practical than the alternative method of determining the number of plants by the number of entry points.

The SMP requirements presented in this chapter include monitoring frequency, sample sites, and schedules. Chapter 8 builds on this chapter by describing how to select SMP monitoring sites. Chapter 8 also describes how SMP results are used to select Stage 2B DBPR compliance monitoring sites and lists the minimum requirements for the IDSE SMP report. The remainder of this chapter is organized as follows:

4.2 Schedule for Conducting the SMP 4.3 SMP Monitoring Requirements 4.4 Timing of Sample Collection 4.5 Sampling Protocol Although some guidance in this chapter is appropriate for other system types, this chapter solely addresses 100 percent purchasing systems . Refer to Chapters 5 through 7 for guidance directed towards systems that produce some or all of their finished water.

4.2 Schedule for Conducting the SMP All systems conducting the SMP must prepare an IDSE report. Systems must either submit their report [ 2 years after rule promulgation] if they are on the early schedule, or [ 4 years after rule promulgation] if they are on the late schedule. The schedule is based on population of the largest system in the combined distribution system. 2 Section 1.1 describes how systems determine when their IDSE report is due ( i. e., if they are on the large or small system schedule). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 2 It is recommended that systems begin SMP planning no later than 18 months before their IDSE report is due to the State. The 18 months allows for 3 months of planning, 12 months of SMP sampling, and 3 months for analyzing the final round of samples, reviewing the results, choosing the new compliance sites, and completing the IDSE report. Table 4.1 shows IDSE report due dates and the latest recommended SMP sampling start dates for systems on the early and late schedules.

Table 4.1 Consecutive System IDSE Report Schedule Schedule Type1 IDSE Report Due Date2 Recommended SMP Sampling Start Date Figure of Schedule ( on next page)

Early Schedule [ 2 years after rule promulgation] No later than [ 9 months after rule promulgation] Figure 4.1 Early System Late Schedule [ 4 years after rule promulgation] No later than [ 2 years and 9 months after rule promulgation] Figure 4.2 Late System 1 See section 1.1 to determine your schedule type. 2 40 CFR 141.600( c).

To ensure smooth execution of an SMP, systems should begin planning several months ( at least three months is recommended) before the first sample date. A written SMP sample plan must be prepared before systems begin sampling. An SMP plan must be submitted with the IDSE report and include, at a minimum:

° The number of required sample sites ° The specific site of all selected SMP sample sites ° The rationale for selection of SMP sample sites ( not required, but recommended)

° A sampling schedule Figures 4.1 and 4.2 show the latest dates by which systems should begin planning, sampling, and preparing the report for an IDSE SMP. Figure 4.1 presents the early schedule and Figure 4.2 presents the late schedule. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 3 23 22 21 20 19 1 18 17 16 15 14 13 12 11 10 9 8 7 6 24 5 4 3 2 Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report [ Year 2] [ Year 1]

[ Year 4] [ Year 3] [ Year 1 and 2] Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report 47 46 45 44 43 42 41 40 39 38 37 48 35 34 33 32 31 30 29 28 27 26 25 36 Figure 4.1 Early Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates)

Figure 4.2 Late Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 3 For the purposes of this guidance manual, surface water systems are the same as subpart H systems   they use surface water or ground water under the direct influence of surface water ( GWUDI) as a source. Surface water systems include all mixed systems ( i. e., those that use surface and ground water). Ground water systems are those that use only ground water as a source.

July 2003  Proposal Draft 100 Percent Purchasing Systems 4 4 Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites. 4.3 SMP Monitoring Requirements Table 4.2 summarizes the number of sites, sampling frequency, and total number of samples that must be collected for 100 percent purchasing surface and ground water systems3 ( 40 CFR 141.602( a) and ( b)). The number of sites and samples is based on the population of the system. All of a system's IDSE SMP samples must be dual samples sets, meaning one total trihalomethane ( TTHM) and one five haloacetic acids ( HAA5) sample that is taken at the same time and location. Chapter 8 provides guidance for selecting SMP sites to meet the requirements of the IDSE. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 5 Table 4.2 SMP Sampling Requirements for 100 Percent Purchasing Systems1 System Size ( Population Served3) Number of Distribution System Sites ( by location type) per System Total Number of Sites per System Monitoring Frequency for the 1 year IDSE Period5 Near Entry Point4 Average Residence Time High TTHM High HAA5 Surface Water Systems6 < 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 ( 40 CFR 141.602 ( b)) 2 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. 3 Population served is typically a system's retail population. It should not include populations served by consecutive systems that purchase water from that system.

4 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. 5 Monitoring frequency is the approximate number of days between monitoring events. 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. 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). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 6 0 10 20 30 40 50 60 70 80 90 Jan 01 Feb 01 Mar 01 Apr 01 May 01 Jun 01 Jul 01 Aug 01 Sep 01 Oct 01 Nov 01 Dec 01 Jan 02 Feb 02 Mar 02 Apr 02 May 02 Jun 02 Jul 02 Month Highest Distribution System DBP Concentration ( ug/ L)

0 10 20 30 40 50 60 70 80 TTHM HAA5 Temperature ( F) Average Distribution System Temperature ( degrees Fahrenheit) Highest DBP value occurred in June 4.4 Timing of Sample Collection A system's monitoring schedule must be determined using historical disinfection byproduct ( DBP) data or temperature data ( 40 CFR 141.602( a)). DBP data should be used as the primary indicator, and then temperature data if DBP data are not sufficient. The month with the highest TTHM or HAA5 concentration ( whichever of the two is highest) or maximum temperature is referred to as the controlling month.

Systems may select any date in the controlling month to sample and should consider dates when staff are available to collect samples. The other rounds of sampling must be scheduled around the controlling month at the required sampling frequency listed in Table 4.2. The sampling dates for the entire year must be scheduled and documented in the system's sampling plan before collecting the first sample. Systems can select a start date prior to the controlling month provided the controlling month is included in their schedule. Figure 4.3 and Table 4.3 provides an example of how to select the controlling month using hypothetical distribution system data.

Figure 4.3 Example Historic DBP and Temperature Data The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 7 Table 4.3 Example of Historic DBP and Temperature Data Month TTHM ( µ g/ L) HAA5 ( µ g/ L) Average Distribution System Temp. ( F)

Mar. 2001 41 15 48 Apr. 2001 52 May 2001 55 June 2001 82 31 65 July 2001 73 Aug. 2001 71 Sept. 2001 64 36 70 Oct. 2001 60 Nov. 2001 53 Dec. 2001 40 32 50 Jan. 2002 48 Feb. 2002 46 Mar. 2002 45 50 50 Apr. 2002 52 May 2002 56 June 2002 67 23 60 In this example, the highest DBP level was the TTHM value from June 2001. Therefore the controlling month is June and the IDSE SMP sampling must be scheduled to include that month. If no DBP data were available, July would have been selected as the controlling month because it has the highest average distribution system temperature.

In the example, if the system must monitor quarterly, using the data in Figure 4.3 and Table 4.3 the four sampling dates should be scheduled approximately every 90 days considering June as the controlling month as follows:

° First Tuesday in March 2003 ° First Tuesday in June 2003 ( controlling month) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 8 ° First Tuesday in September 2003 ° First Tuesday in December 2003 Chloramine systems that routinely convert to free chlorine for a " burnout period" must still set their schedules according to the highest DBP ( or temperature) month ( 40 CFR 141.602( a)), regardless of whether chloramine or free chlorine is used during the controlling month.

SMP samples should be collected as scheduled. EPA recognizes extenuating circumstances can occur that may delay sampling ( e. g., an ice storm). Any deviations from the scheduled sampling days must be noted in the IDSE report ( 40 CFR 141.604( a)).

4.5 Sampling Protocol Generally, it is best to collect samples in the morning to allow the samples to be packed and shipped the same day if systems are sending them to a contract laboratory. Samples should be collected in a manner that ensures they are representative of the water in the distribution system at that sampling point. If sampling from indoor plumbing, samples should be collected from the cold water line. The line between the sample tap or faucet and the distribution system should be flushed. This can usually be accomplished by opening the faucet where the sample is collected and allowing the water to run for a few minutes. When the water temperature stabilizes, this indicates fresh water from the distribution system is being obtained.

The sample bottles should contain appropriate dechlorinating agents/ preservatives prior to filling. Sampling and storage protocols outlined in the approved analytical methods must be followed. Contact the laboratory analyzing the samples for their recommended sampling and preservation protocols. Appendix C provides more detailed information on sampling procedures and approved sampling methods. Samples must be analyzed by laboratories that have received certification by EPA or the State.

If a sample is lost or broken, take a replacement sample as soon as possible. Systems only need to resample for the lost sample bottle; they do not need to resample the entire set. For example, if a TTHM sample is broken during shipping, the system would resample only for TTHM as soon as possible at the given site. Make sure to note the deviation in sampling schedule for this sample in the IDSE report.

Sampling near Fire Hydrants Fire hydrants or blow offs in locations that could impact the water reaching a sampling point should not be flushed prior to the collection of the DBP samples, because that could significantly change the " age" of the water being sampled. The intent of the DBP sampling effort is to obtain water that is representative of what the customers normally receive. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft 100 Percent Purchasing Systems 4 10 Continue to Chapter 8   SMP Site Selection The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 1 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). See Chapter 1 for additional guidance on classifying systems.

2 For the purposes of this guidance manual, surface water systems are the same as " subpart H" systems   they use surface water or ground water under the direct influence of surface water ( GWUDI) as a source. Surface water systems include all mixed systems ( i. e., those that use surface and ground water). Ground water systems are those that use only ground water as a source.

July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 1 5.0 Standard Monitoring Program Requirements for:

Producing Surface Water Systems Serving at Least 10,000 People 5.1 Introduction This chapter describes the Initial Distribution System Evaluation ( IDSE) Standard Monitoring Program ( SMP) requirements for producing surface water systems1, 2 serving at least 10,000 people. These requirements include monitoring frequency, sample sites, and scheduling. Chapter 8 builds on this chapter by describing how final SMP monitoring sites should be selected using various sources and tools. Chapter 8 also describes how SMP results are used to select Stage 2B Disinfectants and Disinfection Byproducts Rule ( DBPR) compliance monitoring sites and lists the minimum requirements for the IDSE SMP report. The remainder of this section is organized as follows:

5.2 Schedule for Conducting the SMP 5.3 Number of Samples Required 5.4 Sample Site Requirements 5.5 Timing of SMP Sample Collection 5.6 Sampling Protocol Although some guidance in this chapter is appropriate for other system types and sizes, this chapter specifically addresses producing surface water systems serving at least 10,000 people. Refer to Chapters 6 and 7 for guidance directed towards other producing system types. Refer to Chapter 4 for guidance directed towards 100 percent purchasing systems.

5.2 Schedule for Conducting the SMP All surface water systems serving at least 10,000 people are on the large system schedule and must submit their IDSE report [ 2 years after rule promulgation]. It is recommended that systems begin planning their SMP no later than [ 6 months after rule promulgation]. The 18 months includes 3 months for planning, 12 months of SMP sampling, and 3 months to analyze the final round of samples, review the results, choose the new compliance sites, and complete the IDSE report. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 2 23 22 21 20 19 1 18 17 16 15 14 13 12 11 10 9 8 7 6 24 5 4 3 2 Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report [ Year 2] [ Year 1] To ensure smooth execution of an SMP, systems should begin planning several months ( at least three months is recommended) before the first sample date. A written SMP sample plan must be prepared before beginning sampling. The plan must be submitted with the IDSE report and include, at a minimum:

° The number of required sample sites ° The specific site of all selected SMP sample sites ° The rationale for selection of SMP sample sites ( not required but recommended)

° A sampling schedule Figure 5.1 shows the latest recommended dates by which systems should begin planning, sampling, and preparing the report for an SMP to meet regulatory requirements.

Figure 5.1 Large System Schedule for Conducting the SMP ( Showing Latest Recommended Start Dates) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 3 Approximately Every 60 Days for 1 Year HAA5 TTHM 5.2.1 Consecutive Water Systems and Wholesalers The IDSE SMP report is due at the same time as that of the largest system in the combined distribution system. Therefore, if a small system serving less than 10,000 people buys water from a system serving at least 10,000 people, they must submit their report on the large system schedule, or [ 2 years after rule promulgation]. EPA recommends that systems share information about their IDSE report schedule with all wholesale purchasers of their water. Coordination with systems that purchase water from systems serving at least 10,000 people is not required, but is strongly recommended.

5.3 Number of Samples Required Producing surface water systems serving at least 10,000 people must collect samples every 2 months over a 1 year period. Samples must be collected at eight sites per plant and analyzed for total trihalomethanes ( TTHM) and five haloacetic acids ( HAA5). These sites must be different than the Stage 1 DBPR compliance monitoring sites. All systems' IDSE SMP samples must be dual samples sets, meaning one TTHM and one HAA5 sample that is taken at the same time and location. For a system with one plant, a total of 48 dual sample sets are required during the 1 year monitoring period ( see the illustration below).

8 Sites per plant × 6 Sample Periods = 48 Dual Samples Sets Section 1.1 provides guidelines for estimating the number or plants in a system. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 4 *** Examples for Determining Number of Plants, Sites, and Samples***

Example 5.1 A system serving 100,000 people operates one surface water treatment plant and receives water from two disinfecting ground water systems, at separate entry points, for more than60 consecutive days per year.

Total plants: 3 ( one surface water and two ground water) Total SMP sites: 8 sites per plant × 3 plants = 24 sites Total Samples: 24 sties × 6 sample periods = 144 dual samples Example 5.2 A system serving 35,000 people purchases treated surface water through one entry point and has three wells. Chlorine is added at each well site. The State determined that two of the wells draw from the same aquifer and that the third well draws from a different aquifer.

Total plants: 3 ( one for the purchased water entry point, the second for the two wells drawing from the same aquifer, and the third for the well drawing from another aquifer) Total sites: 8 sites per plant × 3 plants = 24 sites Total Samples: 24 sites × 6 sample periods = 144 dual samples Example 5.3 A system serves 90,000 people, purchases treated water from one wholesaler, through five entry points, and has two wells which they use on a daily basis. The wholesaler has three surface water treatment plants. Three of the entry points receive water from plant A and two of the entry points receive water from plant B. The State approved multiple consecutive entry points to be considered as one plant   the three entry points receiving water from plant A are one plant and the two entry points receiving water from plant B are a second plant. The two wells feed into one pumphouse where chlorine is added; this is considered one treatment plant.

Total plants: 3 ( two plants for the consecutive entry points and one ground water) Total SMP sites: 8 sites per plant × 3 plants = 24 sites Total Samples: 24 sites × 6 sample periods = 144 dual samples The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 5 Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites.

P u r c h a s e d W a t e r E n t r y P o i n t # 1 P u r c h a s e d W a t e r E n t r y P o i n t # 2 S u r f a c e W a t e r T r e a t m e n t P l a n t 5.4 Sample Site Requirements Sample site requirements depend on a system's residual disinfectant type. Table 5.1 summarizes the SMP site requirements for producing surface water systems serving at least 10,000 people. The required SMP sample sites listed in Table 5.1 are in addition to Stage 1 DBPR compliance monitoring sites. Chapter 8 describes how real entry point sites are selected for chlorine and chloramine systems and provides guidance for selecting all other SMP sites to meet the requirements of the IDSE.

Table 5.1 SMP Sample Sites for Producing Surface Water Systems Serving at Least 10,000 People Residual Disinfectant Type Number of SMP Sample Sites Required per Plant Near Entry Point Average Residence Time High TTHM High HAA5 Total Dual Samples per Plant Chlorine 1 2 3 2 8 Chloramines 2 2 2 2 8 5.4.1 Changing Disinfectants During the SMP Period If systems anticipate a change in residual disinfectant during the 1 year SMP sampling period, selection of SMP sites should be based on the disinfectant expected to be in use at the end of the sampling period. Figure 5.2 shows an example timeline where a system uses free chlorine at the start of the SMP, but changes to chloramines before the end of the SMP sampling period. In this case, sample site selection should be performed as required for chloraminated systems. Thus, two sample sites ( instead of one) near the entry point and four sites ( instead of five) representative of highest TTHM and HAA5 should be selected. In both cases, two average residence time sites are required.

If systems are unsure as to whether their disinfectant conversion will take place during the SMP sampling period, they should select sites based on SMP requirements for a chlorine system. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 6 SMP Sampling Period Months Planned Conversion to Chloramines SMP must be based on chloramine requirements. 23 22 21 20 19 1 18 17 16 15 14 13 12 11 10 9 8 7 6 24 5 4 3 2 Rule Promulgation Figure 5.2 Planned Conversion to Chloramines 5.5 Timing of SMP Sample Collection A system's monitoring schedule must be determined using historical disinfection byproduct ( DBP) data or temperature data ( 40 CFR 141.602( a)). DBP data should be used as the primary indicator, and then temperature data if DBP data are not sufficient. The month with the highest TTHM or HAA5 concentration ( whichever of the two is highest) or maximum temperature is referred to as the controlling month.

Systems may select any date in the controlling month to sample and should consider dates when staff are available to collect samples. The other rounds of sampling must be scheduled around the controlling month at two month intervals. The sampling dates for the entire year must be scheduled and documented in the system's sampling plan before collecting the first sample. Systems can select a start date prior to the controlling month provided the controlling month is included in their schedule. Figure 5.3 and Table 5.2 provides an example of how to select the controlling month using hypothetical distribution system data. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 7 0 10 20 30 40 50 60 70 80 90 Sep 00 Oct 00 Nov 00 Dec 00 Jan 01 Feb 01 Mar 01 Apr 01 May 01 Jun 01 Jul 01 Aug 01 Sep 01 Oct 01 Nov 01 Dec 01 Jan 02 Feb 02 Mar 02 Apr 02 May 02 Jun 02 Month Highest Distribution System DBP Concentration ( ug/ L)

0 10 20 30 40 50 60 70 80 90 Average Distribution System Temperature ( degrees F)

TTHM HAA5 Temperature ( F) Highest DBP value occurred in July Figure 5.3 Example Historic DBP and Temperature Data The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 8 Table 5.2 Example of Historic DBP and Temperature Data Month TTHM ( µ g/ L) HAA5 ( µ g/ L) Average Distribution System Temp. ( F)

Nov. 2000 50 Dec. 2000 43 Jan 2001 43 29 40 Feb 2001 43 Mar. 2001 45 Apr. 2001 62 45 50 May 2001 60 June 2001 70 July 2001 85 42 74 Aug. 2001 78 Sept. 2001 70 Oct. 2001 55 38 60 Nov. 2001 49 Dec. 2001 42 Jan. 2002 48 32 40 Feb. 2002 41 Mar. 2002 44 Apr. 2002 50 53 48 May 2002 62 In this example, the highest DBP level was the TTHM value from July 2001. Therefore, the controlling month is July and the SMP sampling must be scheduled considering that month. If no DBP data were available, August would have been selected as the controlling month because it has the highest average distribution system temperature. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 9 For the example in Figure 5.3 and Table 5.2, the six sampling dates should be scheduled approximately every 60 days with July as the controlling month as follows:

° First Thursday in March 2003 ° First Thursday in May 2003 ° First Thursday in July 2003 ( controlling month)

° First Thursday in September 2003 ° First Thursday in November 2003 ° First Thursday in January 2004 Chloramine systems that routinely convert to free chlorine for a " burnout period" must still set their schedules according to the highest DBP ( or temperature) month ( 40 CFR 141.602( a)), regardless of whether chloramine or free chlorine is used during the controlling month.

SMP samples should be collected as scheduled. EPA recognizes extenuating circumstances can occur that may delay sampling ( e. g., an ice storm). Any deviations from the scheduled sampling days must be noted in the IDSE report ( 40 CFR 141.604( a)).

5.6 Sampling Protocol Generally, it is best to collect samples in the morning to allow the samples to be packed and shipped the same day if systems are sending them to a contract laboratory. Samples should be collected in a manner that ensures they are representative of the water in the distribution system at that sampling point. If sampling from indoor plumbing, samples should be collected from the cold water line. The line between the sample tap or faucet and the distribution system should be flushed. This can usually be accomplished by opening the faucet where the sample is collected and allowing the water to run for a few minutes. When the water temperature stabilizes, this indicates fresh water from the distribution system is being obtained.

The sample bottles should contain appropriate dechlorinating agents/ preservatives prior to filling. Sampling and storage protocols outlined in the approved analytical methods must be followed. Contact the laboratory analyzing the samples for their recommended sampling and preservation protocols. Appendix C provides more detailed information on sampling procedures and approved sampling methods. Samples must be analyzed by laboratories that have received certification by EPA or the State. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Surface Water Systems (> 10,000) 5 10 Continue to Chapter 8   SMP Site Selection If a sample is lost or broken, take a replacement sample as soon as possible. Systems need to resample only for the lost sample bottle; they do not need to resample the entire set. For example, if a TTHM sample is broken during shipping, systems would resample only for TTHM as soon as possible at the given site. Make sure to note the deviation in sampling schedule for this sample in the IDSE report.

Sampling near Fire Hydrants Fire hydrants or blow offs in locations that could impact the water reaching a sampling point should not be flushed prior to the collection of the DBP samples, because that could significantly change the " age" of the water being sampled. The intent of the DBP sampling effort is to obtain water that is representative of what the customers normally receive. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 1 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). See Chapter 1 for additional guidance on classifying systems.

2 For the purposes of this guidance manual, surface water systems are the same as " subpart H" systems   they use surface water or ground water under the direct influence of surface water ( GWUDI) as a source. Surface water systems include all mixed systems ( i. e., those that use surface and ground water). Ground water systems are those that use only ground water as a source.

July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 1 6.0 Standard Monitoring Program Requirements for:

Producing Surface Water Systems Serving 500 to 9,999 People or Producing Ground Water Systems Serving at Least 10,000 People 6.1 Introduction This chapter describes the Initial Distribution System Evaluation ( IDSE) Standard Monitoring Program ( SMP) requirements for producing surface water systems 1, 2 serving 500 to 9,999 people and producing ground water systems serving at least 10,000. These requirements include monitoring frequency, sample sites, and schedules. Chapter 8 builds on this chapter by describing how to select SMP monitoring sites. Chapter 8 also describes how SMP results are used to select Stage 2B Disinfectants and Disinfection Byproducts Rule ( DBPR) compliance monitoring sites and lists the minimum requirements for the IDSE SMP report. The remainder of this chapter is organized as follows:

6.2 Schedule for Conducting the SMP 6.3 SMP Monitoring Requirements 6.4 Timing of Sample Collection 6.5 Sampling Protocol Although some guidance in this chapter is appropriate for other system types and sizes, this chapter specifically addresses producing surface water systems serving 500 to 9,999 people and producing ground water systems serving at least 10,000 people. 100 percent purchasing systems should refer to Chapter 4, and producing systems of other source water types and system sizes should refer to Chapters 5 and 7. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 3 The Environmental Protection Agency ( EPA) defines a combined distribution system as the totality of the distribution systems of wholesale systems and of the consecutive systems that receive finished water from those wholesale systems.

July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 2 23 22 21 20 19 1 18 17 16 15 14 13 12 11 10 9 8 7 6 24 5 4 3 2 Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report [ Year 2] [ Year 1] 6.2 Schedule for Conducting the SMP All systems conducting the SMP must prepare an IDSE report. Systems must either submit their report [ 2 years after rule promulgation] if they are on the large system schedule, or [ 4 years after rule promulgation] if they are on the small system schedule. The schedule is based on population of the largest system in the combined distribution system. 3 Section 1.4 describes how systems determine when their IDSE report is due ( i. e., if they are on the large or small system schedule).

It is recommended that systems begin planning the SMP no later than 18 months before the IDSE report is due to the State. The 18 months includes 3 months of planning, 12 months of SMP sampling, and 3 months for analyzing the final round of samples, reviewing the results, choosing the new compliance sites, and completing the IDSE report. Figures 6.1 and 6.2 show the latest recommended dates by which systems should begin planning, sampling, and preparing the report for an SMP to meet regulatory requirements. Figure 6.1 represents the large system schedule and Figure 6.2 represents the small system schedule.

Figure 6.1 Large System Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 3 [ Year 4] [ Year 3] [ Year 1 and 2] Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report 47 46 45 44 43 42 41 40 39 38 37 48 35 34 33 32 31 30 29 28 27 26 25 36 Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites. Figure 6.2 Small System Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates)

A written SMP sample plan must be prepared before systems begin sampling. The plan must be submitted with the IDSE report and include, at a minimum:

° The number of required sample sites ° The specific site of each selected SMP sample site ° The rationale for selection of SMP sample sites ( not required, but recommended)

° A sampling schedule 6.3 SMP Monitoring Requirements Table 6.1 summarizes the number of sites, sampling frequency, and total number of samples that must be collected per plant in a system ( this sampling requirement is in addition to the Stage 1 DBPR compliance monitoring). All of a system's IDSE SMP samples must be dual sample sets, meaning one total trihalomethane ( TTHM) and one five haloacetic acids ( HAA5) sample that is taken at the same time and location. The SMP sample sites are in addition to The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 4 TTHM Approximately Every 90 Days HAA5 Stage 1 DBPR compliance monitoring sites ( 40 CFR 141.602( a)). Chapter 8 provides guidance for selecting SMP sites to meet the requirements of the IDSE.

Table 6.1 Summary of SMP Sampling Requirements1 Source Type and Population Served Number of Sites Sampling Frequency Total Dual Samples per Plant Surface Water ( 500  9,999) and Ground Water (> 10,000) 2 per plant   1 high TTHM and 1 high HAA5 every 3 months for 1 year 8 1 40 CFR 141.602( a))

For producing surface water systems serving 500 to 9,999 people and ground water systems serving at least 10,000 people and having one plant, a total of 8 dual sample sets is required, and each must be analyzed for TTHM and HAA5 ( see the illustration below).

2 Sites per Plant × 4 Sample Periods = 8 Dual Samples Sets Section 1.1 provides guidelines for estimating the number or plants in a system. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 5 *** Examples for Determining Number of Plants, Sites, and Samples***

Example 6.1 A system serving 6,000 people operates one surface water treatment plant and receives water from two other surface water systems, at separate entry points, for more than 60 consecutive days per year.

Total plants: 3 ( one surface water and two consecutive entry points) Total SMP sites: 2 sites per plant × 3 plants = 6 sites Total samples: 6 sites × 4 monitoring periods = 24 dual sample sets Example 6.2 A system serves 5,000 people, purchases treated surface water through one entry point, and has three wells. Chlorine is added at each well site. The State determined that two of the wells draw from the same aquifer and that the third well draws from a different aquifer.

Total plants: 3 ( one for the purchased water entry point, the second for the two wells drawing from the same aquifer, and the third for the well drawing from another aquifer) Total sites: 2 sites per plant × 3 plants = 6 sites Total samples: 6 sites × 4 monitoring periods = 24 dual sample sets Example 6.3 A system serves 25,000 people, purchases treated ground water from one wholesaler, through five entry points, and has two wells. The State approved multiple consecutive entry points to be considered as one plant   the three entry points receiving water from plant A are one plant and the two entry points receiving water from plant B are a second plant. The two wells feed into one pumphouse where chlorine is added; this is considered one treatment plant.

Total plants: 3 ( two plants for the consecutive entry points and one ground water) Total SMP sites: 2 sites per plant × 3 plants = 6 sites Total samples: 6 sites × 4 monitoring periods = 24 dual sample sets The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 6 6.4 Timing of Sample Collection A system's monitoring schedule must be determined using historical disinfection byproduct ( DBP) data or temperature data ( 40 CFR 141.602( a)). DBP data should be used as the primary indicator, and then temperature data if DBP data are not sufficient. The month with the highest TTHM or HAA5 concentration ( whichever of the two is highest) or maximum temperature is referred to as the controlling month.

Systems may select any date in the controlling month to sample and should consider dates when staff are available to collect samples. The other rounds of sampling must be scheduled around the controlling month at three month intervals. The sampling dates for the entire year must be scheduled and documented in a system's sampling plan before collecting the first sample. Systems can select a start date prior to the controlling month provided the controlling month is included in their schedule. Figure 6.3 and Table 6.2 provide an example of how to select the controlling month using hypothetical distribution system data. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 7 0 10 20 30 40 50 60 70 80 90 Jan 01 Feb 01 Mar 01 Apr 01 May 01 Jun 01 Jul 01 Aug 01 Sep 01 Oct 01 Nov 01 Dec 01 Jan 02 Feb 02 Mar 02 Apr 02 May 02 Jun 02 Jul 02 Month Highest Distribution System DBP Concentration ( ug/ L)

0 10 20 30 40 50 60 70 80 TTHM HAA5 Temperature ( F) Average Distribution System Temperature ( degrees Fahrenheit) Highest DBP value occurred in June Figure 6.3 Example Historic DBP and Temperature Data The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 8 Table 6.2 Example of Historic TTHM and Temperature Data Month TTHM ( µ g/ L) HAA5 ( µ g/ L) Average Distribution System Temp. ( F)

Mar. 2001 41 15 48 Apr. 2001 52 May 2001 55 June 2001 82 31 65 July 2001 73 Aug. 2001 71 Sept. 2001 64 36 70 Oct. 2001 60 Nov. 2001 53 Dec. 2001 40 32 50 Jan. 2002 48 Feb. 2002 46 Mar. 2002 45 50 50 Apr. 2002 52 May 2002 56 June 2002 67 23 60 In this example, the highest DBP level was the TTHM value from June 2001. Therefore, the controlling month is June and the SMP sampling must be scheduled to include that month. If no DBP data were available, July would have been selected as the controlling month because it has the highest average distribution system temperature.

In the example, if the system must monitor quarterly, using the data in Figure 6.3 and Table 6.2, the four sampling dates should be scheduled approximately every 90 days considering June as the controlling month as follows:

° First Monday in March 2003 ° First Monday in June 2003 ( controlling month) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 9 ° First Monday in September 2003 ° First Monday in December 2003 Chloramine systems that routinely convert to free chlorine for a " burnout period" must still set their schedules according to the highest DBP ( or temperature) month ( 40 CFR 141.602( a)), regardless of whether chloramine or free chlorine is used during the controlling month.

SMP samples should be collected as scheduled. EPA recognizes extenuating circumstances can occur that may delay sampling ( e. g., an ice storm). Any deviations from the scheduled sampling days must be noted in the IDSE report ( 40 CFR 141.604( a)).

6.5 Sampling Protocol Generally, it is best to collect samples in the morning to allow the samples to be packed and shipped the same day if systems are sending them to a contract laboratory. Samples should be collected in a manner that ensures they are representative of the water in the distribution system at that sampling point. If sampling from indoor plumbing, samples should be collected from the cold water line. The line between the sample tap or faucet and the distribution system should be flushed. This can usually be accomplished by opening the faucet where the sample is collected and allowing the water to run for a few minutes. When the water temperature stabilizes, this indicates fresh water from the distribution system is being obtained.

The sample bottles should contain appropriate dechlorinating agents/ preservatives prior to filling. Sampling and storage protocols outlined in the approved analytical methods must be followed. Contact the laboratory analyzing the samples for their recommended sampling and preservation protocols. Appendix C provides more detailed information on sampling procedures and approved sampling methods. Samples must be analyzed by laboratories that have received certification by EPA or the State.

If a sample is lost or broken, take a replacement sample as soon as possible. Systems need to resample only for the lost sample bottle; they do not need to resample the entire set. For example, if a TTHM sample is broken during shipping, the system would resample only for TTHM as soon as possible at the given site. Make sure to note the deviation in sampling schedule for this sample in the IDSE report.

Sampling near Fire Hydrants Fire hydrants or blow offs in sites that could impact the water reaching a sampling point should not be flushed prior to the collection of the DBP samples, because that could significantly change the The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft Producing Systems SW ( 500 9,999) and GW (> 10,000) 6 10 Continue to Chapter 8   SMP Site Selection " age" of the water being sampled. The intent of the DBP sampling effort is to obtain water that is representative of what the customers normally receive. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 1 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). See Chapter 1 for additional guidance on classifying systems.

2 For the purposes of this guidance manual, surface water systems are the same as " subpart H" systems   they use surface water or ground water under the direct influence of surface water ( GWUDI) as a source. Surface water systems include all mixed systems ( i. e., those that use surface and ground water). Ground water systems are those that use only ground water as a source.

July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 1 7.0 Standard Monitoring Program Requirements for:

Producing Surface Water Systems Serving Less Than 500 People or Producing Ground Water Systems Serving Less Than 10,000 People 7.1 Introduction This chapter describes the Initial Distribution System Evaluation ( IDSE) Standard Monitoring Program ( SMP) requirements for producing surface water systems1, 2 serving less than 500 people and producing ground water systems serving less than 10,000 people. These requirements include monitoring frequency, sample sites, and schedules. Chapter 8 builds on this chapter by describing how to select SMP monitoring sites. Chapter 8 also describes how SMP results are used to select Stage 2B Disinfectants and Disinfection Byproducts Rule ( DBPR) compliance monitoring sites and lists the minimum requirements for the IDSE SMP report. The remainder of this chapter is organized as follows:

7.2 Schedule for Conducting the SMP 7.3 Number of Samples Required 7.4 Sample Site Requirements 7.5 Timing of Sample Collection 7.6 Sampling Protocol Although some guidance in this chapter is appropriate for other system types and sizes, this chapter specifically addresses producing surface water systems serving less than 500 people and producing ground water systems serving less than 10,000 people. 100 percent purchasing systems should refer to Chapter 4, and producing systems of other source water types and system sizes should refer to Chapters 5 and 6. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual 3 The Environmental Protection Agency ( EPA) defines a combined distribution system as the totality of the distribution systems of wholesale systems and of the consecutive systems that receive finished water from those wholesale systems.

July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 2 7.2 Schedule for Conducting the SMP All systems conducting the SMP must prepare an IDSE report. Systems must either submit their report [ 2 years after rule promulgation] if they are on the large system schedule, or [ 4 years after rule promulgation] if they are on the small system schedule. The schedule is based on population of the largest system in the combined distribution system. 3 Section 1.4 describes how systems determine when their IDSE report is due ( i. e., if they are on the large or small system schedule).

It is recommended that systems begin planning the SMP no later than 18 months before the IDSE report is due to the State. The 18 months includes 3 months of planning, 12 months of SMP sampling, and 3 months for analyzing the final round of samples, reviewing the results, choosing the new compliance sites, and completing the IDSE report. Table 7.1 shows IDSE report due dates and the latest recommended SMP sampling start dates for systems on the small and large system schedules.

Table 7.1 IDSE Report Schedule Schedule Type IDSE Report Due Date Recommended SMP Sampling Start Date Figure of Schedule ( on next page)

Large System Schedules [ 2 years after rule promulgation] No later than [ 9 months after rule promulgation] Figure 7.1 Large System Small System Schedule [ 4 years after rule promulgation] No later than [ 2 years and 9 months after rule promulgation] Figure 7.2 Small System Note: See section 1.4 to determine the schedule type. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 3 23 22 21 20 19 1 18 17 16 15 14 13 12 11 10 9 8 7 6 24 5 4 3 2 Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report [ Year 2] [ Year 1] To ensure smooth execution of an SMP, systems should begin planning several months ( at least three months is recommended) before the first sample date. A written SMP sample plan must be prepared before systems begin sampling. The plan must be submitted with the IDSE report and include, at a minimum:

° The number of required sample sites ° The specific site of all selected SMP sample sites ° The rationale for selection of SMP sample sites ( not required, but recommended)

° A sampling schedule Figures 7.1 and 7.2 show the latest dates by which systems should begin planning, sampling, and preparing the report for an SMP to meet regulatory requirements. Figure 7.1 represents the schedule for consecutive systems with a large system in the combined distribution system and Figure 7.2 represents the small system schedule.

Figure 7.1 Large System Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 4 [ Year 4] [ Year 3] [ Year 1 and 2] Submit IDSE Report to State/ Primacy Agency Rule Promulgation [ Actual Timeline to be provided] Start SMP Monitoring 1 Year of Monitoring Begin Planning for IDSE SMP Start Preparing Report 47 46 45 44 43 42 41 40 39 38 37 48 35 34 33 32 31 30 29 28 27 26 25 36 TTHM Once every 6 months for 1 year HAA5 Figure 7.2 Small System Schedule for Conducting the IDSE SMP ( Showing Latest Recommended Start Dates)

7.3 Number of Samples Required Producing surface water systems serving fewer than 500 people and ground water systems serving fewer than 10,000 people must collect samples every 6 months over a 1 year period ( this sampling requirement is in addition to Stage 1 DBPR monitoring). Samples must be collected at two sites per plant and analyzed for total trihalomethane ( TTHM) and five haloacetic acids ( HAA5). All of a system's IDSE SMP samples must be dual sample sets, meaning one TTHM and one HAA5 sample that is taken at the same time and location. For systems with one plant, a total of 4 dual sample sets are required, and each should be analyzed for TTHM and HAA5 ( see the illustration below).

2 Sites per Plant × 2 Sample Periods = 4 Dual Sample Sets The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 5 *** Examples for Determining Number of Plants, Sites, and Samples***

Example 7.1 A system serves 450 people, purchases treated surface water through one entry point, and has two wells. Chlorine is added at each well site. The State determined that the two wells draw from the same aquifer.

Total plants: 2 ( one for the purchased water entry point and one for the two wells drawing from the same aquifer) Total sites: 2 sites per plant × 2 plants = 4 sites Total samples: 8 samples Example 7.2 A system serves 300 people, purchases treated surface water from one wholesaler through two entry points. The State allowed the multiple consecutive entry points to be considered as one plant.

Total plants: 1 ( one plant for both consecutive entry points) Total SMP sites: 2 sites per plant × 1 plant = 2 sites Section 1.1.4 provides guidelines for estimating the number or plants in a system.

7.4 Sample Site Requirements Systems must select two SMP sample sites per plant, meeting the following criteria:

° One site representative of the highest TTHM concentration in the system ° One site representative of the highest HAA5 concentration in the system ° Sites must be different than the Stage 1 DBPR monitoring sites The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 6 Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites. In many small systems, the highest HAA5 concentration would be expected to occur at the same site as the highest TTHM concentration. However, in some systems ( often those with low disinfectant residual levels and high maximum water age) the HAA5 concentration can decrease in some parts of the distribution system, because HAA5 can biodegrade when no residual disinfectant is present. The highest HAA5 site will not be the same as the highest TTHM site. As a result, this situation is described and help is provided. Chapter 8 provides guidance for selecting SMP sites to meet the requirements of the IDSE.

7.5 Timing of Sample Collection One of the system's sampling dates must occur in the month with the highest water temperature in their distribution system ( systems should already be taking the Stage 1 DBPR compliance samples during this month). The system's other sampling date must be 6 months before or after the high distribution system water temperature month. The 6 month interval should be maintained as closely as possible ( 40 CFR 141.602( a)).

SMP samples should be collected as scheduled. EPA recognizes extenuating circumstances can occur that may delay sampling ( e. g., an ice storm). Any deviations from the scheduled sampling days must be noted in the IDSE report ( 40 CFR 141.604( a)).

This regimen is expected to typically result in one sample date occurring in the summer ( July through September), and the second in the winter ( January March).

7.6 Sampling Protocol Generally, it is best to collect samples in the morning to allow the samples to be packed and shipped the same day if systems are sending them to a contract laboratory. Samples should be collected in a manner that ensures they are representative of the water in the distribution system at that sampling point. If sampling from indoor plumbing, samples should be collected from the cold water line. The line between the sample tap or faucet and the distribution system should be flushed. This can usually be accomplished by opening the faucet where the sample is collected and allowing the water to run for a few minutes. When the water temperature stabilizes, this indicates fresh water from the distribution system is being obtained.

The sample bottles should contain appropriate dechlorinating agents/ preservatives prior to filling. Sampling and storage protocols outlined in the approved analytical methods must be followed. Contact the laboratory analyzing the samples for their recommended sampling and preservation The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003 Proposal Draft Producing Systems SW (< 500) and GW (< 10,000) 7 7 Continue to Chapter 8   SMP Site Selection protocols. Appendix C provides more detailed information on sampling procedures and approved sampling methods. Samples must be analyzed by laboratories that have received certification by EPA or the State.

If a sample is lost or broken, take a replacement sample as soon as possible. Systems only need to resample for the lost sample bottle; they do not need to resample the entire set. For example, if a TTHM sample is broken during shipping, the system would resample only for TTHM as soon as possible at the given site. Make sure to note the deviation in sampling schedule for this sample in the IDSE report.

Sampling near Fire Hydrants Fire hydrants or blow offs in locations that could impact the water reaching a sampling point should not be flushed prior to the collection of the disinfection byproduct ( DBP) samples, because that could significantly change the " age" of the water being sampled. The intent of the DBP sampling effort is to obtain water that is representative of what the customers normally receive. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 1 Data Sources and Tools Disinfectant residual, maps, models, etc.

Select Preliminary Sites Narrow Down Selection Select Final Sites General Approach to SMP Site Selection 8.0 Standard Monitoring Program Site Selection and Reporting 8.1 Introduction Chapters 4 through 7 of this manual provided detailed requirements for conducting an Initial Distribution System Evaluation ( IDSE) Standard Monitoring Program ( SMP). This chapter, which applies to all system types, system sizes, and source water types, expands on those chapters by providing technical guidance for selecting SMP monitoring sites using various tools.

The general approach for selecting SMP sites is to use available data sources and analysis tools to select a large number of potential sites ( referred to as preliminary sites). From that group of sites, systems should consider geographic coverage and other distribution system factors to narrow down preliminary sites to final SMP sites.

This chapter is organized as follows:

Background Information 8.2 Description of SMP Site Types 8.3 Considerations for Systems with More than One Plant or Entry Point 8.4 Data Sources and Tools for Identifying Preliminary SMP Sites The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 2 SMP Site Selection 8.5 Methodology for Selecting Final SMP Sites Stage 2B Site Selection Based on SMP Results and Reporting 8.6 Stage 2B DBPR Site Selection and IDSE Reporting Requirements 8.7 Reporting Results to the State 8.2 Description of SMP Sample Site Types Tables 8.1 and 8.2 summarize the SMP sample site requirements according to system type, system size, and source water type ( Chapter 1 also provides this information). As shown in the tables, there are four types of sampling locations defined for the SMP: near entry point, average residence time, high total trihalomethane ( TTHM), and high five haloacetic acids ( HAA5). Sections 8.2.1 through 8.2.3 provide descriptions of each type of sample site. Note that all sample site types are not required for all systems and, as stated in Chapters 4 through 7, the Stage 1 DBPR compliance monitoring sites cannot be used as SMP sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 3 Table 8.1 SMP Sampling 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 Frequency for the 1 year IDSE Period5 Near Entry Point4 Average Residence Time High TTHM High HAA5 Surface Water Systems6 < 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 ( 40 CFR 141.602 ( b)) 2 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. 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 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. 5 Monitoring frequency is the approximate number of days between monitoring events. A dual sample set must be collected at each 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). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 4 Table 8.2 SMP Sampling Requirements for Producing Systems1,2 System Size ( Population Served3) Residual Disinfectant Number of Distribution System Sites ( by location type) for each Plant Total Number of Sites per Plant Monitoring Frequency4 Near Entry Point Average Residence Time High TTHM High HAA5 Surface Water Systems5 < 500 Chlorine or Chloramines   1 1 2 Every 180 days 500  9,999 Chlorine or Chloramines   1 1 2 Every 90 days > 10,000 Chlorine 1 2 3 2 8 Every 60 days Chloramines 2 2 2 2 8 Ground Water Systems < 10,000 Chlorine or Chloramines   1 1 2 Every 180 days > 10,000 Chlorine or Chloramines   1 1 2 Every 90 days 1 ( 40 CFR 141.602( 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 Monitoring frequency is the approximate number of days between monitoring events. 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. 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).

As described in previous chapters, the monitoring requirements for producing systems are based on the number of plants. The Stage 2 DBPR does not define a plant, but does specify the following:

° Consecutive system entry points receiving disinfected water for at least 60 consecutive days must be considered a plant ( 40 CFR 141.602( a))

° Multiple entry points or multiple wells drawing from the same aquifer may be considered as one plant ( 40 CFR 141.601( d)) The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 5 Example 8.1 Less Required than Entry Points in the Systems A 100 percent purchasing system receives ground water from two wholesalers and serves 300,000 people. Approximately 70 percent of the system's water is purchased from Wholesaler A, the remaining 30 percent from Wholesaler B. The IDSE SMP requirements for this system include one near entry point site ( see Table 8.1). This system should locate its near entry point site near the Wholesaler A consecutive system entry point. For guidance purposes, any location where disinfected water enters the distribution system should be considered a " plant". See Chapter 1, section 1.1 for guidance on determining number of plants in a system.

8.2.1 Near Entry Point SMP Sites The rule does not have specific location requirements for near entry point sites. EPA recommends locating these sites between the treatment facility or consecutive system entry point and before or near the first customer. Data from this site represent the minimum residence time and can be used as a baseline for interpreting changes in water quality as water travels through the distribution system. DBP data from near entry point sites can also be used to identify opportunities for improvements at the treatment plant.

The next two sections provide additional guidance for selecting near entry point SMP sites.

<IP_ADDRESS> Near Entry Point SMP Sites for 100 Percent Purchasing Systems As indicated in Table 8.1, the number of near entry point sites required for 100 percent purchasing systems depends only on the source water type and population served. As a result, a situation may exist where a system has more or less actual consecutive system entry points than the number of near entry points sites required by Table 8.1 or Table 8.2. If this occurs, the rule requires the following adjustments ( 40 CFR 141.6022( b)):

° If the required number of near entry point SMP sites is less than the actual number of consecutive system entry points, first select sites at the entry points delivering surface water in order from the highest to lowest flow, then select sites at the entry points delivering ground water, in order from the highest to lowest flow, until the required number of SMP sites have been identified. ( See Example 8.1.)

° If the required number of near entry point SMP sites is more than the actual number of consecutive system entry points, the " excess" near entry point sites must be distributed The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 6 A B C D Your City Distribution System From Big City WTP Example 8.3 Multiple Entry Points on One Transmission Line Your City receives water from Big City through a single transmission main with multiple consecutive system entry points ( A, B, C, and D) and little difference in average flows. The State has determined these entry points are a single source and the estimated water age at each entry point is similar. In this case, A, B, C, or D would be acceptable and should be among high TTHM and high HAA5 sites so that the total number of SMP sites is met. These excess sites must be distributed in the order of high TTHM, high HAA5 . ( see Example 8.2.)

Multiple Entry Points Considered as One Plant Multiple consecutive entry points may be considered a single plant with approval from the State ( 40 CFR 141.601( d)). There is no provision in the rule designating which entry point must be used to locate the near entry point site. A location near any entry point or prior to the first group of customers for any one entry point should be acceptable. However, if the average flow differs significantly between the entry points, you should consider using the entry point with the greatest flow to locate your nearentry point SMP site. ( See Examples 8.3 and 8.4.) Example 8.2 Excess Near entry Point Site Requirements A 100 percent purchasing system receives surface water from three wholesalers and serves 550,000 people. The IDSE SMP requirements for this system include six near entry point sites ( see Table 8.1), but the system has only 3 consecutive system entry points. This system must select 3 near entry point sites. According to the rule stated above, the remaining 3 near entry point sites would be distributed as follows: 2 high TTHM sites and 1 high HAA5 site. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 7 A B C Your City Distribution System From Big City WTP Example 8.4 Multiple Entry Points with Different Flows Your City receives water from Big City at three consecutive system entry points ( A, B and C). Entry points A and B are branches of a common main; entry point C is off a separate main. The State has determined these entry points are a single source and the estimated water age at each entry point is similar. 50 percent of Your City's water enters through A, 20 percent through B, and 30 percent through C. Your city selects a near entry point SMP site near A because the majority of water enters through this entry point.

<IP_ADDRESS> Near Entry Point SMP Sites for Producing Systems The rule requires producing surface water systems that serve at least 10,000 people to select near entry point sites depending on the total number of plants in the system and the residual disinfectant type ( 40 CFR 141.602 ( a)) ( see Table 8.2).

° Chlorinated systems must select one near entry point SMP site per plant ° Chloraminated systems must select two near entry point SMP sites per plant The requirements differ between chlorinated systems and chloraminated systems because DBP formation differs under chloraminated and chlorinated conditions. Chloramine residuals are more stable than chlorine residuals and, therefore, do not react as readily with organic compounds in the water. Based on evaluation of Information Collection Rule ( ICR) data, DBP concentrations in chloraminated systems vary less throughout the distribution system than in chlorinated systems. HAA5, in particular, can peak at or near the entry point to the distribution system in a chloraminated system. ( Appendix B describes DBP formation in more detail.) As recommended in the beginning of section 8.2.1, any sites between the treatment facility ( or entry point) and a first group of customers should be acceptable for chloraminated systems. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 8 Well # 1 A B First group of customers for Well # 1 Well # 2 First group of customers for Well # 2 Example 8.5 Multiple Entry Points The system has two wells which the State determined were drawing from the same aquifer and could be considered as one plant. Site A or Site B would be acceptable for their near entry point site. Ground Water Wells or Multiple Entry Points Considered as One Plant Multiple ground water wells drawing from one aquifer and delivering disinfected water directly to the distribution system may be considered a single plant with approval from the State. Locations prior to the first group of customers of any well are an acceptable near entry point SMP site. Similarly, for multiple consecutive entry points considered as a single plant, any entry point would be acceptable for a near entry point SMP site. ( See Example 8.5.)

8.2.2 Average Residence Time SMP Sites Sites with average residence time should represent the average water age that is delivered to the majority of customers in the distribution system. In most distribution systems, average residence time is not simply one half the maximum residence time. Ideally, it should be a flow weighted or population weighted average residence time. EPA recognizes that determining this value is very complex and, at best, most systems can only make a rough estimate. Section 8.4 provides methodologies for estimating average residence time with various types of data and tools.

8.2.3 High TTHM and High HAA5 Sites It is not the intent of the SMP to identify peak daily or hourly DBP concentrations. Instead, high TTHM and high HAA5 sites should be chosen to represent areas in the distribution system with the highest annual average DBP concentrations. Higher temperatures and increased residence time typically lead to higher TTHM and HAA5 concentrations. However, HAA5 can biodegrade when disinfectant residual levels are low or non existent and, therefore, a high HAA5 site may not be the site with the longest residence time. These principles are the basis of the guidance provided for selecting high TTHM and high HAA5 SMP sites. Table 8.3 summarizes the typical characteristics of distribution The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 9 system areas with high TTHM and high HAA5 levels. Section 8.4 further describes how data sources and analysis tools can be used to identify these areas in the distribution system.

Table 8.3 Summary of Characteristics of High TTHM and High HAA5 Areas Area Characteristics High TTHM S Long residence time ( e. g. remote areas with few customers or low water demand) S Low or no disinfectant residual, also high heterotrophic plant count ( HPC) or history of positive coliform S Downstream of storage facilities S Areas with historical data showing high TTHM High HAA5 S Residence time can vary S Low but existing disinfectant residual ( to prevent biodegradation) S May be downstream of storage facilities S Areas with historical data showing high HAA5 Note: These are only general characteristics; DBP formation in distribution systems is system specific.

8.3 Considerations for Systems with More than One Plant or Entry Point This section describes how systems with multiple plants or entry points should distribute the sites with respect to the influence zone of each plant or entry point.

8.3.1 100 Percent Purchasing Systems with More Than One Consecutive System Entry Point The 100 percent purchasing systems are not required to assign SMP sample sites to the influence zone of a particular entry point. When selecting average residence time and high TTHM/ high HAA5 SMP sites, 100 percent purchasing systems should consider the quantity and quality of water received at each consecutive system entry point. For example, if one entry point supplies 75 percent of the water then more SMP sites should be located in the influence zone of that supply. Geographic distribution of SMP locations should also be considered. Examples 8.6 and 8.7 illustrate how sites could be distributed with respect to multiple entry points. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 10 LEGEND SMP Sample Site Storage Tank Oakville WTP Entry Point ( 25%) Mapleton WTP Influence Zone Oakville WTP Influence Zone Mapleton WTP Entry Point ( 75%)

E   Entry Point A   Average T   High TTHMs H   High HAA5 E E A A A H H H T T T T Example 8.6 Large and Small Surface Water Entry Points Your City is a 100 percent purchasing system serving 30,000 people and purchases chlorinated water from two surface water wholesalers ( Mapleton and Oakville). Your City is required to identify 12 SMP sites ( from Table 8.1   2 near entry points, 3 average, 4 high TTHM, and 3 high HAA5 sites). On average, Mapleton supplies Your City with 75 percent of its water; while Oakville provides only 25 percent. The water quality from each is similar.

Site selection rationale:

Based on the average flow split and similar water quality, approximately 75 percent ( 9) of the sites should be in the influence zone of the Mapleton supply and the remaining 25 percent ( 3) should be in the influence zone of the Oakville source. As shown in the schematic, in order to achieve a good geographic coverage of the distribution system, 2 of the Mapleton sites are located in The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 11 Deep Rock Well Entry Point ( 60%) Lory RiverWTP Influence Zone Deep Rock Well Influence Zone Lory River WTP Entry Point ( 40%)

LEGEND SMP Sample Site Storage Tank E   Entry Point A   Average T   High TTHMs H   High HAA5 E E A A A H H H T T T T Example 8.7 Surface Water and Ground Water Entry Points Your City is a 100 percent purchasing system serving 48,000 people with purchased water from two water wholesalers. The Lory River WTP supplies 40 percent of the demand with surface water. The Deep Rock well supplies 60 percent of the demand with ground water. Your City is required to identify 12 SMP sites as follows: 2 near entry point, 3 average residence time, 4 high TTHM, and 3 high HAA5.

SMP selection rational:

More sites are placed within the influence area of the Lory River WTP because it is a surface water source and thus, more likely to have higher DBP levels. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 12 8.3.2 Producing Systems with More than One Plant As indicated in Table 8.2, the rule specifies the number of SMP sites for each plant. For most systems, the distribution areas of the plants are not distinctly separate. However, systems can usually identify the primary influence zones of each plant and should use these zones to assign SMP sites. Recognizing that the boundaries of influence zones can overlap and change on a daily, hourly, and seasonal basis, SMP sites should be chosen within the typical ( during normal operating mode) influence zone boundaries, as best can be determined.

Once sample sites have been selected based on the typical influence zone boundaries, the samples must be collected as scheduled, regardless of the actual source of water serving the site at the time of sampling ( 40 CFR 141.602( c)). If it is suspected or known that the source of water supplying a particular SMP site is different during sample collection, then this should be noted and taken into consideration when evaluating the results of the SMP. However, identification of the source of supply to each sample site during each sampling event is not required.

Where overlap exists between two or more influence zones, the water quality, quantity, and operating characteristics should be considered when locating SMP sites. There are numerous scenarios that could exist when a distribution system is supplied with water from more than one plant. The following sections provide general guidance and examples for four specific scenarios:

° One plant produces the majority of the water ( Example 8.8)

° One plant supplies water with much higher TTHM/ HAA5 concentrations than the other plant( s) ( Example 8.9)

° The system purchases water for less than 60 consecutive days per year ( Example 8.10)

° The system has a seasonal source of water ( used at least 60 consecutive days per year, but less than 100 percent of the time) ( Example 8.11)

The guidelines for these four scenarios are general and will not apply to all systems and all situations; you should always use best professional judgement when selecting SMP sites.

One Plant Supplies the Majority of the Water In systems where one plant delivers substantially more water than another, an equal distribution of sites within influence zones may result in disproportionate coverage of the distribution system. That is, the sites representing a large treatment plant must cover a wider geographic area than the sites representing a smaller plant. Example 8.8 illustrates this situation and provides an SMP selection approach that maximizes coverage of the distribution system while still locating SMP sites for each plant in the appropriate zone of influence. In the example, SMP sites required for the smaller plant are used The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 13 Red SW treatment plant Well # 1 Well # 2 Red Plant Influence Zone Legend Red plant SMP Site Green plant SMP site ¬ Well Green Plant Influence Zone ¬ ¬ E Entry Point A   Average T   High TTHMs H   High HAA5 H H H H E E A A A A T T T T T T Example 8.8 Producing System with One Large and One Small Plant A system supplying 12,000 people has 2 chlorinated plants, Red and Green. The Red plant is a surface water treatment plant that provides 8 MGD. The Green plant is supplied by 2 wells drawing from the same aquifer, produces 1 MGD, and has been approved by the State as drawing from a common aquifer. Generally, the Green plant supplies the east area of the distribution system and the Red plant supplies all other areas. From Table 8.2, a total of 8 SMP sites for each plant are required for mixed surface and ground water systems.

Site selection rationale:

For both plants, the 8 required SMP sites are located in the influence zone of the respective plant. Because the Green plant has a much smaller influence area, Green's sites are selected to cover the overlapping mixing zone, thus allowing the 8 Red sites to cover the larger Red influence zone. This arrangement of sites respects the requirement to locate sites within individual plant influence to cover the entire area of the overlapping influence zones; SMP sites for the large plant are located exclusively in the influence zone of the large plant. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 14 One Plant Supplies Water with Much Higher DBP Concentrations Than the Others Systems should also consider quality of water when locating SMP sites. The overall objective of the IDSE SMP is to identify sites in the distribution system where water with representative high TTHM and HAA5 concentrations is delivered to customers. If you suspect that the high TTHM and/ or high HAA5 sites will be in the influence zone of a particular plant on more than a seasonal basis, you should locate SMP sites to maximize coverage in that influence zone. Example 8.10 shows how SMP sites can be located when one source is suspected of having high TTHM/ HAA5 concentrations. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 15 Riverdale WTP Influence Zone LEGEND Riverdale SMP Sample Sites Spring Hills Sample Site Riverdale WTP ( 60%) Spring Hills WTP Influence Zone Spring Hills WTP ( 40%)

E   Entry Point A   Average T   High TTHMs H   High HAA5 E E T T T T T T H H H H A A A A Example 8.9 Producing System with One High and One Low DBP Plant Your City is a producing system serving 85,000 people. Your City operates 2 plants   Riverdale ( a surface water plant with moderate to high source water TOC levels) and Spring Hills ( a low TOC ground water plant). Riverdale provides approximately 60 percent of your daily demand and Spring Hills the remaining 40 percent. Both plants use free chlorine for primary and secondary disinfection.

From Table 8.2, Your City is required to select 8 SMP sample locations for each treatment plant ( a total of 16 sites). Since the Spring Hills supply is likely to have lower DBP concentrations than the Riverdale supply, locate the Riverdale SMP sites exclusively in the Riverdale influence zone and use the Spring Hills SMP sites to cover the mixing zone. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 16 Emergency Connections ( Used Less Than 60 Consecutive Days per Year)

Consecutive entry points used on a temporary basis that provide water for less than 60 consecutive days per year are not considered to be " plants" under the IDSE SMP requirements ( 141.602 ( d)( 2)). In other words, systems do not have to identify near entry point, average residence time, or high TTHM/ HAA5 SMP sites for these entry points. However, typical water demand patterns in the area of the distribution system supplied by the temporary source ( influence zone) should be considered when locating SMP sites ( see Example 8.10).

Example 8.10 Producing Systems with Temporary Sources ° A large surface water system buys water during the highest temperature month( s) from a system with a low TOC ground water source. In this case, SMP sites should not be located in the influence zone of the temporary source; focus should be on other areas of the distribution system. The reason for this is the influence zone of the temporary source is likely to have lower DBP concentrations than areas served by the surface water supply.

° A large surface water system buys water that is low TOC ground water source, but not during the highest temperature month( s). In this case, you should consider locating SMP sites in the influence zone of your temporary source because the zone will be more representative of your surface water source during the highest temperature month. This is particularly applicable if you believe the area has high TTHM or high HAA5 levels when it is supplied by your normal surface water supply. You should be cognizant, however, of which source is providing the water that you are collecting during your SMP. If you collect a sample that is not representative of your surface water source, you should note this information in your IDSE report and consider that when selecting final Stage 2B DBPR compliance monitoring sites ( see sections 8.6 and 8.7 for guidelines for selecting Stage 2B DBPR compliance monitoring sites and completing your IDSE report). The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 17 Purchasing Water on a Part time Basis ( Used at Least 60 Consecutive Days per Year)

If a system buys water from a wholesale system on a part time or seasonal basis, for more than 60 consecutive days of the year, the source is considered to be a " plant" under the IDSE SMP requirements ( 141.602 ( d)( 2)). As with plants operating year round, the SMP sites for a seasonal plant should be located in the influence zone of that plant. Although the seasonal plant would not be providing water to the SMP sites all the time, the SMP sampling sites should not be modified once sampling has begun ( SMP sites should remain fixed for the 1 year monitoring period).

Even if water from a seasonal plant is known to have low DBP concentrations relative to water provided by other plants ( e. g., a seasonal ground water supply in a surface water system), the eight sites for the seasonal plant should still be selected within the influence zone of that plant. DBP data of all plants are important in evaluating the entire distribution system.

Example 8.11 illustrates the SMP site selection for a large producing system that operates two surface water plants and purchases water during the summer to meet increased seasonal demands. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 18 Purchased Water Influence Zone Elm Plant Influence Zone Maple Plant Influence Zone Legend Maple plant SMP Site Purchased water entry point SMP site Elm plant SMP site Maple SW treatment plant Elm SW treatment plant Entry point for purchased water E   Entry Point A   Average T   High TTHMs H   High HAA5 E E E H H H H H T T T T T T T T T H A A A A A A Example 8.11 Producing System with Seasonal Plants A system serving chlorinated water to 55,000 people has three plants: Maple plant ( 6 MGD surface water), Elm plant ( 3 MGD surface water), and purchased water from a neighboring city ( 2 MGD in summer only   for more than 60 consecutive days).

Site selection rationale:

The Maple plant and Elm plant influence zones mostly overlap; together, their sites cover the entire area except the influence zone of the purchased water. Although the system only purchases during the summer, those sites will be sampled during the entire 1 year SMP sampling period and will represent the surface water plants' water quality for a majority of the year. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 19 Tracer Studies System Operating Data Hydraulic Model Maps Geographic Information System ( GIS) SDS Tests Water Quality Data 8.4 Data Sources and Tools for Identifying Preliminary SMP Sites Several sources of information can be used to help select SMP sites that represent average residence time, high TTHM, and high HAA5 concentrations ( see Figure 8.1 below).

Figure 8.1 Data Sources and Tools for Selecting SMP Sites These data sources and tools are best applied in combination with each other. For example, a map is critical in assessing geographic and population coverage; however, it is of limited use when used alone to identify average residence time or high HAA5 sites.

Generally, data used to identify SMP sites should be less than 10 years old and represent the current distribution system and treatment plant( s) configuration. Chapter 3 discusses the quality of data recommended for use in a historical data based SSS.

This section describes how each data source can be used to identify preliminary SMP sites representing high TTHM, high HAA5, and average residence time. Section 8.5 presents step by step methodologies for using combinations of these data sources to select final SMP sites. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 20 8.4.1 Maps Map features that may be helpful in selecting SMP sites include:

° Length and diameter of pipes ° Age of pipes ° Pressure zone delineations with valving identified ° Location of distribution system pumping stations ° Location and configuration of storage facilities ° Location of fire hydrants and flush valves ° Existing land use ° Population density ° Location of booster disinfection stations ° Entry points with source type noted ° System boundary lines <IP_ADDRESS> High TTHM and High HAA5 Sites Generally, areas with light development, with low residential population density, or between pressure zones that are furthest away from the treatment plant( s) are likely to have the longest residence times. Therefore, these areas have potentially high TTHM concentrations and, provided there is a detectable disinfectant residual, high HAA5 concentrations.

In general, sites at the very end of a distribution system main with no customers should not be selected:

° In many distribution systems, there may be no customers at the actual physical end of some dead end sections of a water main. Water quality at this type of location is not truly " representative" of water in the distribution system that is delivered to customers.

High TTHM ( and in some cases HAA5) SMP sites should be generally located near the ends of the distribution system at or before the last group of customers or in mixing zones.

Sample sites should be located prior to the last fire hydrant.

Sample sites should not be located at a dead end where there are no customers. The Stage 2 DBPR Initial Distribution System Evaluation Guidance Manual July 2003  Proposal Draft All Systems 8 21 ° High TTHM and, in some cases, high HAA5 SMP sites should generally be chosen near the end of the distribution system at the last group of customers or in mixing zones where " hydraulic dead ends" might occur. Samples should always be collected at locations prior to ( upstream of) the last fire hydrant.

Storage facilities in a distribution system increase water age. During tank drain cycles, water age immediately downstream of a storage facility may be significantly ( e. g., several days or more) older than " fresh" water upstream of the storage facility. As a result, areas of a distribution system receiving water that has been stored may have higher TTHM and HAA5 concentrations than areas that do not receive any stored water. Therefore, you should generally locate your high TTHM sites and, in some cases, high HAA5 sites downstream of storage facilities.

<IP_ADDRESS> Average Residence Time Sites Average residence time is the average age of water delivered to the majority of customers in a distribution system. Estimating average distribution system residence time based solely on maps can be difficult and requires a thorough understanding of your distribution system. Under ideal circumstances, maps are just one tool that can be combined with other data and tools ( e. g., disinfectant residual data, hydraulic modeling) to identify areas that are representative of average water age. These other data and tools are discussed further in sections 8.4.2 through 8.4.7.

Approximate average residence time areas can be identified by looking for service areas with the most development. If a few large customers exist in a system, then their location should be identified and the effect of water flowing to them taken into consideration. In many systems that do not have large individual customers, highly developed areas in the approximate geographic center of the distribution system are potential average residence time sites.

8.4.2 Distribution System Water Quality Data Systems routinely sample for various water quality parameters as required by regulations or for operational purposes. A review of recent historical DBP and/ or disinfectant residual data ( free chlorine or chloramine) can be very useful in the selection of SMP sample sites.