Location # 8   This sampling location is in an area that receives water from the Softwood Plant. Samples are collected at a hose bib near the first house on the cul de sac ( which has 12 homes total). For this example, the location of these sample locations is illustrated in Figure B. 1 Significant Excursion Guidance Manual Proposal Draft July 2003 B 6 Significant Excursion Evaluation Report Page 2 Report date: October 16th, 2004 3) Attach ( or provide in the Supplemental Data Form) all available water quality data for the round of sampling in which the significant excursion occurred. At a minimum, include all TTHM and HAA5 results from the sampling period. You should also consider including pH, temperature, alkalinity, TOC, disinfectant residual, and any other data that you think would be useful.

a) Were there any unusual circumstances associated with this round of sampling?

Yes No X If yes, please explain.

b) Were all analytical QA/ QC measures met?

Sample preservation Yes X No____

Sample holding time Yes X No____

Other If no, please explain.

4) Attach ( or provide in the Supplemental Data Form) historical TTHM and HAA5 data for the location( s) at which the significant excursion( s) occurred. Provide at least three years of data, if available. Significant Excursion Guidance Manual Proposal Draft July 2003 B 7 Significant Excursion Evaluation Report Page 3 Report date: October 16th, 2004 5) What caused your excursion( s) to occur?

Sections A through F starting on page 4 can help you determine the possible cause( s) of your excursion. Please note there may be more than one factor which resulted in your excursion.

Section A: Source water quality change Section B: Process upset at treatment plant Section C: Planned change or maintenance activities at plant Section D: Planned distribution system operations or maintenance activities Section E: Unplanned events in distribution system If you already suspect a cause, go directly to that section. If you read Sections A through E and are unable to determine a cause of your excursion, then complete Section F.

Consecutive systems should also contact their wholesaler to identify the cause( s) of the significant excursion( s).

6) List steps taken or planned to reduce DBP peak levels.

We are considering adjustments of the coagulation processes to improve TOC removal including: increasing the coagulant dose, evaluation of alternative coagulants, evaluation of coagulant aids, lowering the pH of coagulation, use of a pre oxidant ( permanganate or chlorine dioxide), and use of PAC. Significant Excursion Guidance Manual Proposal Draft July 2003 B 8 Significant Excursion Evaluation Report Page 4 Report date: October 16th, 2004 A. Source Water Quality Changes ° Did any of the events listed below take place before the DBP excursion to cause TOC levels to increase?   Heavy rain fall   Flooding   Spring snow melt/ runoff   Significant decrease in rainfall or source flow   Algae bloom ° Did any of the events listed below take place before the DBP excursion to cause bromide levels to increase?   Significant decrease in rainfall or source flow   Brackish or seawater intrusion ° Did pH and/ or alkalinity significantly change?

° If two or more supplies are used, was a greater portion of water drawn from the one with higher TOC?

° Was raw water stored for an unusually long period of time resulting in a significant increase in water temperature?

Conclusions:

Did source water quality changes cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

The most probable cause of the DBP excursion noted during the September 2004 sampling even was a rapid increase of the organic matter concentration in the Softwood River. Following two days of heavy rainfall the TOC measured in the plant influent increased from 2.7 mg/ L to 8.4 mg/ L. At the same time, turbidity of the source water also increased from 5 ntu to a maximum of 98 ntu. The coagulant ( ferric chloride) dose was increased from 20 mg/ L to 75 mg/ L to match water quality changes. For the duration of this high turbidity/ high NOM event, the pH of coagulation was maintained between 61. and 6.3. The higher coagulant dose prevented any significant increases of turbidity in the settled water, but the concentration of TOC in the plant effluent increased from 1.8 mg/ L to 3.8 mg/ L. Jar testing conducted at the time of the event indicated that a further increase of the coagulant dose ( dosages up to 120 mg/ L were tested) would have not significantly improved TOC removal under the pH conditions presently used to conduct the coagulation process.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 9 Significant Excursion Evaluation Report Page 5 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ° Was raw water stored for an unusually long time, providing additional contact time for DBP formation after prechlorination?

° Were there changes in coagulation practices? S Were there any changes or malfunctions of the coagulation process in the days leading to the excursion? S Were the coagulant dose and pH properly adjusted for incoming source water conditions?

° Were there changes in chlorination practices?   Were there any changes in chlorine dose at any location in the plant?   Were there changes in plant flow that may have resulted in longer than normal residence time at any location in the plant? S Did the pH change at the point of chlorine addition?

° Were there changes in settling practices? S Was there excess sludge build up in the settling basin that may have carried over to the point of disinfectant addition? S Was there any disruption in the sludge blanket that may have resulted in carryover to the point of disinfection?

° Were there changes in filtration practices? S Have filter run times been changed to meet raw water quality changes? S Were there any spikes in individual filter effluent turbidity ( which may indicate particulate or colloidal TOC breakthrough) in the days leading to the excursion? S Did chlorinated water sit in the filter for an extended period of time? S Were all filters run in a filter to waste mode during initial filter ripening? S Were any filters operated beyond their normal filter run time? S If GAC filters are used: Is it possible the adsorptive capacity of the GAC bed was reached before reactivation occurred? S If biological filtration is used: Were there any process upsets that may have resulted in breakthrough of TOC ( particularly biodegradable TOC)?

° Were there changes in plant flow that may have resulted in an unusually high residence time in the clearwell on the days prior to the excursion? S For example, a temporary plant shutdown.

Continued on next page Significant Excursion Guidance Manual Proposal Draft July 2003 B 10 Significant Excursion Evaluation Report Page 6 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ( Continued)

Conclusions:

Did a process upset in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 11 Significant Excursion Evaluation Report Page 7 Report date: October 16th, 2004 C. Planned Change or Maintenance Activities for the Treatment Plant ° Was there a recent change ( or addition) of pre oxidant?

° Was there any maintenance in the basin that may have stirred sludge from the bottom of the basin and caused it to carry over to the point of disinfectant addition?

° Did you change the type or manufacturer of the coagulant?

° Were there any changes in disinfection practices in the days prior to the excursion? S For example, a switch from chloramines to free chlorine for burnout period. S Discontinuation of ozone which forms very little TTHM.

° Was a filter( s) taken off line for an extended period of time that caused the other filters to operate near maximum design capacity and creating the conditions for possible breakthrough?

° Were any pumps shut down for maintenance, leading to changes in flow patterns or hydraulic surges?

Conclusions:

Did a planned maintenance or operational activity in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 12 Significant Excursion Evaluation Report Page 8 Report date: October 16th, 2004 D. Planned Distribution System Operations or Maintenance Activities ° Was a tank drained for cleaning or other maintenance? S Was the tank drained to waste or to the distribution system? S Was a larger volume than normal drained to the distribution system?

° If booster disinfection is used, was the booster disinfectant dose higher than the normal booster disinfectant dose for that season?

° Were there any system maintenance activities in the days prior to DBP excursion? Including:   Repairing mains or installing new mains   Closure of valves to isolate sections of pipes ° Were the pipes flushed properly or were the appropriate valves re opened after work was completed?

° Did any pump or pipeline maintenance occur that would have changed the flow pattern in the area the sample was drawn from? S Change in flow can cause water in stagnant areas to be drawn into another area.

° Did any pipeline replacement occur? S Disinfecting piping in contact with drinking water could result in a high concentration of chlorine entering the distribution system and thus increase DBPs.

Conclusions:

Did a planned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 13 Significant Excursion Evaluation Report Page 9 Report date: October 16th, 2004 E. Unplanned Distribution System Events ° Were there increases in demand that caused older water in storage tanks to be drawn into the system? S Were there any major fire events? S Did one or more storage tank have greater than average drawdown preceding the time of DBP peak excursion?

° Were there decreases in demand that resulted in longer than normal system residence times? S Were there any large customers off line?

° Did any main breaks occur causing changes in flow patterns in the influence area of the sample location?

° If you collect water temperature inside storage tanks, was the temperature inside the tank higher than normal for the season?

° Were any storage tanks hydraulically locked out of the system for an extended period and then used preceding the time of DBP peak excursion?

° Did changes in overall water demand cause a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

° Were there large variations in localized system pressures that were different from the normal pressure range that could have caused a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

Conclusions:

Did an unplanned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 14 Significant Excursion Evaluation Report Page 10 Report date: October 16th, 2004 F. If you were unable to identify the cause of your significant excursion( s) after reviewing Sections A through E, are you able to identify another potential cause of your increase in DBP concentrations? Explain.

Note: If you are unable to determine the cause of your excursion you may wish to consider:

° More frequent raw water temperature monitoring. ° More frequent raw water TOC monitoring. ° Increased disinfectant residual monitoring in the distribution system. ° Tracer studies to characterize distribution system water age. ° Development of a hydraulic model to characterize the distribution system.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 B 15 Supplemental Data Form for the Significant Excursion Evaluation Report Report date: October 16th, 2004 Report prepared by: Robert Doe, P. E.

System name: Elm City 1) Water quality data from significant excursion sampling period.

Location No. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 Location Name TTHM ( ug/ L) 63 72 81 78 55 121 77 146 HAA5 ( ug/ L) 52 39 51 66 58 72 59 98 Free Chlorine ( mg/ L) 1.8 1.3 NA NA NA 1.1 NA 0.8 Total Chlorine ( mg/ L) 2.1 1.8 NA NA NA 1.8 NA 1.2 pH 7.9 8.0 8.3 8.1 7.8 8.3 7.5 8.2 2) Supplemental data from each treatment facility:

Plant # 1: Hardwood Plant Plant # 2: Softwood Plant Raw Water Temperature: NA Raw Water Temperature: NA Plant Effluent Water Temperature: 20 ° C Plant Effluent Water Temperature: 20 ° C Raw Water TOC: 2.2 mg/ L ( Avg. < 2.0mg/ L) Raw Water TOC: 3.8 mg/ L ( Avg.< 2.0mg/ L)

Other Data: Other Data: Inf. turb. 98 ntu ( Avg. < 20 ntu)

3) Historical TTHM and HAA5 data at significant excursion sampling locations.

TTHM Data ( ug/ L) HAA5 Data ( ug/ L)

Monitoring # __ 5__ #__ 6__ #__ 7__ #__ 8__ Monitoring # __ 8__ #____ # ___ # ___ Location Location Date  1999 43 58 45 49 Date  1999 56 Date  2000 51 49 56 64 Date  2000 47 Date  2001 46 69 41 69 Date  2001 33 Date  2002 48 61 73 66 Date  2002 34 Date  2003 34 44 53 79 Date  2003 43 Avg. 99 03 44 56 54 65 Avg. 99 03 43 Attach additional sheets if necessary Appendix C Changes in Treatment Plant Operation Significant Excursions Identified Using the " Maximum Concentration Approach" This page intentionally left blank. Significant Excursion Guidance Manual Proposal Draft July 2003 C 1 The first part of this appendix includes general system information and a summary of TTHM and HAA5 data that resulted in Elm City having to perform a significant excursion evaluation. This information as part of the documentation of a significant excursion. Only the Significant Excursion Report is required to be completed by systems that experience a significant excursion.

This appendix is provided as an example of a system in which changes in treatment plant operations led to a DBP Significant Excursion. Possible strategies to reduce excursions are presented in Chapter 4, but they are not to be included in the identification and documentation process. Appendices B, D, and E provide similar examples for systems in which changes in source water quality, changes in distribution system, and multiple causes resulted in a significant excursion.

This example assumes the state has chosen to use 100 µ g/ L TTHM and 75 µ g/ L HAA5 as the trigger levels for determining that a significant excursion has occurred and that a significant excursion evaluation is required.

Background Information for this Example System Description:

General system characteristics: Service area: Elm City plus surrounding suburban areas Production: Annual average daily demand 15 MGD Source Water Information: Hardwood Lake ( surface water) pH: from 6.9 to 7.5 Alkalinity: from 82 to 98 mg/ L as CaCO3 TOC: from 2.1 to 4.0 mg/ L as C Bromide: from 0.04 to 0.1 mg/ L Turbidity: 1 to 100 ntu Softwood River ( surface water) pH: from 6.8 to 7.9 Alkalinity: from 77 to 94 mg/ L as CaCO3 TOC: from 1.6 to 9.4 mg/ L as C Bromide: from 0.03 to 0.1 mg/ L Turbidity: 2 to 115 ntu Significant Excursion Guidance Manual Proposal Draft July 2003 C 2 Treatment Provided: Hardwood, conventional ( 15 MGD design, 7.5 MGD average) Softwood River, conventional with GAC ( 20 MGD design, 7.5 MGD average) Primary and residual disinfection: Chlorine/ chlorine at both plants Summary of Stage 2 DBPR Monitoring Locations: Table C. 1 summarizes the Stage 2 DBPR monitoring locations used by Elm City. Sample locations are marked in the distribution system schematic presented in Figure C. 1.

Table C. 1 Stage 2 DBPR Monitoring Locations Location Description Location # 1 Hardwood Plant  average residence time Location # 2 Hardwood Plant  high TTHM Location # 3 Hardwood Plant  high HAA5 Location # 4 Hardwood/ Softwood Mix Zone  high TTHM Location # 5 Hardwood/ Softwood Mix Zone  high TTHM Location # 6 Hardwood/ Softwood Mix Zone  high TTHM Location # 7 Softwood Plant  average residence time Location # 8 Softwood Plant  high HAA5 Significant Excursion Guidance Manual Proposal Draft July 2003 C 3 Pineville MIXING ZONE Softwood River WTP Hardwood WTP Elevated Storage Tank Ground storage tank Pump station 2 Oakville 1 3 Elmville 5 Downtown Appleville Weeping Willow Poplarville Cedarville Cypressville 6 7 4 8 Peak DBP location Figure C. 1 Schematic of Elm City Distribution System and Stage 2 DBPR Monitoring Locations Significant Excursion Guidance Manual Proposal Draft July 2003 C 4 DBP Excursion Investigation:

During the last sampling period which took place in September 2004, Elm City experienced unusually high TTHM values ( relative to the LRAA) at five monitoring locations (# 4, # 5, # 6, # 7, # 8). Similarly, unusually high HAA5 values were detected at two monitoring locations (# 7 and # 8). DBP data from the previous year and most recent sampling period ( five quarters total) are presented in Table C. 2.

Table C. 2. TTHM and HAA5 Monitoring Data Loc atio n TTHM ( ug/ L) HAA5 ( ug/ L)

Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg. Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg.

# 1 54, 67, 58, 75 65 118 74 52, 37, 30, 41 40 84 48 # 2 68, 68, 55, 69 63 145 77 38, 45, 28, 19 33 75 42 # 3 66, 52, 71, 72 64 122 74 41, 46, 45, 39 43 58 47 # 4 50, 55, 51, 61 55 82 60 42, 43, 38, 34 39 54 42 # 5 34, 48, 55, 50 44 68 48 32, 43, 55, 38 42 37 43 # 6 44, 62, 58, 60 49 70 53 45, 33, 41, 40 40 53 42 # 7 40, 41, 37, 46 41 58 46 21, 38, 28, 19 27 29 29 # 8 49, 39, 50, 76 52 78 56 43, 39, 41, 45 42 49 44 1Data for sampling conducted on September 2003, December 2003, March 2004 and June 2004. Data relevant to peak excursions are bold and underlined.

Unusually high TTHM samples were collected at locations # 1, # 2, and # 3, and unusually high HAA5 samples were collected at locations # 1 and # 2. The results are significantly higher than both the LRAA at those locations for the previous 12 month period and the historic TTHM and HAA5 values at those locations for the years 1999 2003 ( see Significant Excursions Evaluation Report). Significant excursion were identified when DBP levels exceeded 100 µ g/ L TTHM or 75 µ g/ L HAA5. All of the monitoring locations affected by high DBP are located in the area served by the Hardwood plant. The city staff has reason to believe that a process change occurred during treatment operations at the Hardwood plant caused this increase in DBP levels. Significant Excursion Guidance Manual Proposal Draft July 2003 C 5 Significant Excursion Report date: October 16th, 2004 Evaluation Report Report prepared by: Ronald Doe, P. E.

Page 1 System name: Elm City 1) When was the significant excursion sample( s) collected? What were the TTHM and HAA5 concentrations?

Location No. # 1 # 2 # 3 # ______

Location description Hardwood Plant  average residence time Hardwood Plant  high TTHM Hardwood Plant  high HAA5 Sample collection date Sept. 4th, 2004 Sept. 4th, 2004 Sept. 4th, 2004 Sample collection time 1 p. m. 3 p. m. 11 a. m.

TTHM LRAA Concentration ( ug/ L) 74 77 74 TTHM Concentration ( ug/ L) 118 145 122 HAA5 LRAA Concentration ( ug/ L) 48 42 HAA5 Concentration ( ug/ L) 84 75 Note: Attach additional sheets if you observed more than four significant excursions during this round of sampling.

2) Where did the excursion( s) occur? Attach a schematic of your system, sketch your system in the space below, or have a schematic of your system available to review with your state at the time of your next sanitary survey. Indicate the location( s) of the significant excursion( s) on your schematic.

Location # 1   Represents average residence time of water leaving the Hardwood Plant. It is located in the Oakville neighborhood. There are no storage facilities between the treatment plant and this location.

Location # 2   Sample tap is a hose bib at a building located in Pineville in a zone of the distribution system with water age greater than average. Water in this area is from the Hardwood Plant.

Location # 3   This location is located in the Downtown area. Water is primarily from the Hardwood Plant. A ground storage tank is near this location.

The location of these sample locations is illustrated in Figure C. 1. Significant Excursion Guidance Manual Proposal Draft July 2003 C 6 Significant Excursion Evaluation Report Page 2 Report date: October 16th, 2004 3) Attach ( or provide in the Supplemental Data Form) all available water quality data for the round of sampling in which the significant excursion occurred. At a minimum, include all TTHM and HAA5 results from the sampling period. You should also consider including pH, temperature, alkalinity, TOC, disinfectant residual, and any other data that you think would be useful.

a) Were there any unusual circumstances associated with this round of sampling?

Yes No X If yes, please explain.

b) Were all analytical QA/ QC measures met?

Sample preservation Yes X No Sample holding time Yes X No Other If no, please explain.

4) Attach ( or provide in the Supplemental Data Form) historical TTHM and HAA5 data for the location( s) at which the significant excursion( s) occurred. Provide at least three years of data, if available. Significant Excursion Guidance Manual Proposal Draft July 2003 C 7 Significant Excursion Evaluation Report Page 3 Report date: October 16th, 2004 5) What caused your excursion( s) to occur?

Sections A through F starting on page 4 can help you determine the possible cause( s) of your excursion. Please note there may be more than one factor which resulted in your excursion.

Section A: Source water quality change Section B: Process upset at treatment plant Section C: Planned change or maintenance activities at plant Section D: Planned distribution system operations or maintenance activities Section E: Unplanned events in distribution system 6) List steps taken or planned to reduce DBP peak levels.

Plan to calibrate standby pumps for future maintenance of coagulant process feed pumps. Considering improvements to coagulant process monitoring ( daily verification with pump catch, streaming current monitoring). Significant Excursion Guidance Manual Proposal Draft July 2003 C 8 Significant Excursion Evaluation Report Page 4 Report date: October 16th, 2004 A. Source Water Quality Changes ° Did any of the events listed below take place before the DBP excursion to cause TOC levels to increase?   Heavy rain fall   Flooding   Spring snow melt/ runoff   Significant decrease in rainfall or source flow   Algae bloom ° Did any of the events listed below take place before the DBP excursion to cause bromide levels to increase?   Significant decrease in rainfall or source flow   Brackish or seawater intrusion ° Did pH and/ or alkalinity significantly change?

° If two or more supplies are used, was a greater portion of water drawn from the one with higher TOC?

° Was raw water stored for an unusually long period of time resulting in a significant increase in water temperature?

Conclusions:

Did source water quality changes cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 C 9 Significant Excursion Evaluation Report Page 5 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ° Was raw water stored for an unusually long time, providing additional contact time for DBP formation after prechlorination?

° Were there changes in coagulation practices? S Were there any changes or malfunctions of the coagulation process in the days leading to the excursion? S Were the coagulant dose and pH properly adjusted for incoming source water conditions?

° Were there changes in chlorination practices?   Were there any changes in chlorine dose at any location in the plant?   Were there changes in plant flow that may have resulted in longer than normal residence time at any location in the plant? S Did the pH change at the point of chlorine addition?

° Were there changes in settling practices? S Was there excess sludge build up in the settling basin that may have carried over to the point of disinfectant addition? S Was there any disruption in the sludge blanket that may have resulted in carryover to the point of disinfection?

° Were there changes in filtration practices? S Have filter run times been changed to meet raw water quality changes? S Were there any spikes in individual filter effluent turbidity ( which may indicate particulate or colloidal TOC breakthrough) in the days leading to the excursion? S Did chlorinated water sit in the filter for an extended period of time? S Were all filters run in a filter to waste mode during initial filter ripening? S Were any filters operated beyond their normal filter run time? S If GAC filters are used: Is it possible the adsorptive capacity of the GAC bed was reached before reactivation occurred? S If biological filtration is used: Were there any process upsets that may have resulted in breakthrough of TOC ( particularly biodegradable TOC)?

° Were there changes in plant flow that may have resulted in an unusually high residence time in the clearwell on the days prior to the excursion? S For example, a temporary plant shutdown.

Continued on next page Significant Excursion Guidance Manual Proposal Draft July 2003 C 10 Significant Excursion Evaluation Report Page 6 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ( Continued)

Conclusions:

Did a process upset in the treatment plant cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

The combination of two process changes at the Hardwood Plant is the most probable cause of the DBP excursion noted during the September 2004 sampling event. Specifically the two events were:

° Pre oxidation of raw water with chlorine for taste and odor control following an algae bloom in Hardwood Lake. Chlorine addition to the raw water is not a routine practice.

° Ferric chloride was underfed for two days around the September 2004 sampling resulting in a decrease in TOC removal at the Hardwood Plant. The increased TOC concentration passing through the treatment process has probably lead to increased formation of TTHM and HAA5. The low ferric dose was the result of poor calibration of the standby pumps that were placed in service during the maintenance of the feed pumps that are normally used. It was noticed that pH of coagulation increased from the usual 5.5 to 6.2 range to 7.1 to 7.3.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 C 11 Significant Excursion Evaluation Report Page 7 Report date: October 16th, 2004 C. Planned Change or Maintenance Activities for the Treatment Plant ° Was there a recent change ( or addition) of pre oxidant?

° Was there any maintenance in the basin that may have stirred sludge from the bottom of the basin and caused it to carry over to the point of disinfectant addition?

° Did you change the type or manufacturer of the coagulant?

° Were there any changes in disinfection practices in the days prior to the excursion? S For example, a switch from chloramines to free chlorine for burnout period. S Discontinuation of ozone which forms very little TTHM.

° Was a filter( s) taken off line for an extended period of time that caused the other filters to operate near maximum design capacity and creating the conditions for possible breakthrough?

° Were any pumps shut down for maintenance, leading to changes in flow patterns or hydraulic surges?

Conclusions:

Did a planned maintenance or operational activity in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey.

Significant Excursion Evaluation Report Page 8 Report date: October 16th, 2004 Significant Excursion Guidance Manual Proposal Draft July 2003 C 12 D. Planned Distribution System Operations or Maintenance Activities ° Was a tank drained for cleaning or other maintenance? S Was the tank drained to waste or to the distribution system? S Was a larger volume than normal drained to the distribution system?

° If booster disinfection is used, was the booster disinfectant dose higher than the normal booster disinfectant dose for that season?

° Were there any system maintenance activities in the days prior to DBP excursion? Including:   Repairing mains or installing new mains   Closure of valves to isolate sections of pipes ° Were the pipes flushed properly or were the appropriate valves re opened after work was completed?

° Did any pump or pipeline maintenance occur that would have changed the flow pattern in the area the sample was drawn from? S Change in flow can cause water in stagnant areas to be drawn into another area.

° Did any pipeline replacement occur? S Disinfecting piping in contact with drinking water could result in a high concentration of chlorine entering the distribution system and thus increase DBPs.

Conclusions:

Did a planned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey.

Significant Excursion Evaluation Report Page 9 Report date: October 16th, 2004 Significant Excursion Guidance Manual Proposal Draft July 2003 C 13 E. Unplanned Distribution System Events ° Were there increases in demand that caused older water in storage tanks to be drawn into the system? S Were there any major fire events? S Did one or more storage tank have greater than average drawdown preceding the time of DBP peak excursion?

° Were there decreases in demand that resulted in longer than normal system residence times? S Were there any large customers off line?

° Did any main breaks occur causing changes in flow patterns in the influence area of the sample location?

° If you collect water temperature inside storage tanks, was the temperature inside the tank higher than normal for the season?

° Were any storage tanks hydraulically locked out of the system for an extended period and then used preceding the time of DBP peak excursion?

° Did changes in overall water demand cause a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

° Were there large variations in localized system pressures that were different from the normal pressure range that could have caused a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

Conclusions:

Did an unplanned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 C 14 Significant Excursion Evaluation Report Page 10 Report date: October 16th, 2004 F. If you were unable to identify the cause of your significant excursion( s) after reviewing Sections A through E, are you able to identify another potential cause of your increase in DBP concentrations? Explain.

Note: If you are unable to determine the cause of your excursion you may wish to consider:

° More frequent raw water temperature monitoring. ° More frequent raw water TOC monitoring. ° Increased disinfectant residual monitoring in the distribution system. ° Tracer studies to characterize distribution system water age. ° Development of a hydraulic model to characterize the distribution system.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 C 15 Supplemental Data Form for the Significant Excursion Evaluation Report Report date: October 16th, 2004 Report prepared by: Ronald Doe, P. E.

System name: Elm City 1) Water quality data from significant excursion sampling period.

Location No. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 Location Name TTHM ( ug/ L) 118 145 122 82 68 70 58 78 HAA5 ( ug/ L) 84 75 65 58 47 53 30 50 Free Chlorine ( mg/ L) 0.6 0.8 0.2 NA NA 1.1 NA 0.8 Total Chlorine ( mg/ L) 0.8 1.2 0.4 NA NA 1.8 NA 1.2 pH 8.2 8.5 7.9 8.1 7.8 8.3 7.5 8.2 2) Supplemental data from each treatment facility:

Plant # 1: Hardwood Plant Plant # 2: Softwood Plant Raw Water Temperature: NA Raw Water Temperature: NA Plant Effluent Water Temperature: 20 ° C Plant Effluent Water Temperature: 20 ° C Raw Water TOC: 2.2 mg/ L ( Avg.

2.0mg/ L) Raw Water TOC: 1.8 mg/ L ( Avg.

2.0mg/ L) Other Data: Other Data: Inf. turb. 25 ntu ( Avg.

20 ntu)

3) Historical TTHM and HAA5 data at significant excursion sampling locations.

TTHM Data ( ug/ L) HAA5 Data ( ug/ L)

Monitoring # 1 # 2 # 3 # Monitoring # 1 # 2 # # Location Location Date  1999 61 78 45 Date  1999 32 56 Date  2000 55 59 56 Date  2000 29 47 Date  2001 70 69 41 Date  2001 48 23 Date  2002 64 81 73 Date  2002 36 34 Date  2003 66 54 53 Date  2003 41 45 Avg. 99 03 63 68 54 Avg. 99 03 37 45 Attach additional sheets if necessary Appendix D Changes in Distribution System Operation Significant Excursions Identified Using the " Maximum Concentration Approach" This page intentionally left blank. Significant Excursion Guidance Manual Proposal Draft July 2003 D 1 The first part of this appendix includes general system information and a summary of TTHM and HAA5 data that resulted in Elm City having to perform a significant excursion evaluation. This information is not required e as part of the documenntation of a significant excursion. Only the Significant Excursion Report is required to be completed by systems that experience a significant excursion.

This appendix is provided as an example of a system in which changes in distribution system operations led to a DBP Significant Excursion. Possible strategies to reduce excursions are presented in Chapter 4, but they are not to be included in the identification and documentation process. Appendices B, C, and E provide similar examples for systems in which changes in source water quality, changes in treatment plant operations, and multiple causes resulted in a significant excursion.

This example assumes the state has chosen to use 100 µ g/ L TTHM and 75 µ g/ L HAA5 as the trigger levels for determining that a significant excursion has occurred and that a significant excursion evaluation is required.

Background Information for this Example System Description:

General system characteristics: Service area: Elm City plus surrounding suburban areas Production: Annual average daily demand 15 MGD Source Water Information: Hardwood Lake ( surface water) pH: from 6.9 to 7.5 Alkalinity: from 82 to 98 mg/ L as CaCO3 TOC: from 2.1 to 4.0 mg/ L as C Bromide: from 0.04 to 0.1 mg/ L Turbidity: 1 to 100 ntu Softwood River ( surface water) pH: from 6.8 to 7.9 Alkalinity: from 77 to 94 mg/ L as CaCO3 TOC: from 1.6 to 9.4 mg/ L as C Bromide: from 0.03 to 0.1 mg/ L Turbidity: 2 to 115 ntu Significant Excursion Guidance Manual Proposal Draft July 2003 D 2 Treatment Provided: Hardwood, conventional ( 15 MGD design, 7.5 MGD average) Softwood River, conventional with GAC ( 20 MGD design, 7.5 MGD average) Primary and residual disinfection: Chlorine/ chlorine at both plants Summary of Stage 2 DBPR Monitoring Locations: Table D. 1 summarizes the Stage 2 DBPR monitoring locations used by Elm City. Sample locations are marked in the distribution system schematic presented in Figure D. 1.

Table D. 1 Stage 2 DBPR Monitoring Locations Location Description Location # 1 Hardwood Plant  average residence time Location # 2 Hardwood Plant  high TTHM Location # 3 Hardwood Plant  high HAA5 Location # 4 Hardwood/ Softwood Mix Zone  high TTHM Location # 5 Hardwood/ Softwood Mix Zone  high TTHM Location # 6 Hardwood/ Softwood Mix Zone  high TTHM Location # 7 Softwood Plant  average residence time Location # 8 Softwood Plant  high HAA5 Significant Excursion Guidance Manual Proposal Draft July 2003 D 3 Pineville MIXING ZONE Softwood River WTP Hardwood WTP Elevated Storage Tank Ground storage tank Booster disinfection 2 Oakville 1 3 Elmville 5 Downtown Appleville Weeping Willow Poplarville Cedarville Cypressville 6 7 4 8 Peak DBP site Figure D. 1 Schematic of Elm City Distribution System and Stage 2 DBPR Monitoring Locations Significant Excursion Guidance Manual Proposal Draft July 2003 D 4 DBP Excursion Investigation:

During the last sampling period which took place in September 2004, Elm City experienced unusually high TTHM values ( relative to the LRAA) at monitoring location # 2. DBP data from the previous year and most recent sampling period ( five quarters total) are presented in Table D. 2.

Table D. 2 TTHM and HAA5 Monitoring Data Loc atio n TTHM ( ug/ L) HAA5 ( ug/ L)

Quarterly Pre Sept 2004 Data1 LRAA Pre Sept 2004 Sept 2004 Data LRAA incl. Sept 2004 Quarterly Pre Sept 2004 Data1 LRAA Pre Sept 2004 Sept 2004 Data LRAA incl. Sept 2004 # 1 54, 67, 58, 75 65 72 68 52, 37, 30, 41 40 53 40 # 2 49, 39, 50, 76 52 122 72 43, 39, 41, 45 42 49 44 # 2 68, 68, 55, 69 63 69 65 38, 45, 28, 19 33 40 33 # 3 66, 52, 71, 72 64 76 68 41, 46, 45, 39 43 58 47 # 4 50, 55, 51, 61 55 82 60 42, 43, 38, 34 39 54 42 # 5 34, 48, 55, 50 44 68 48 32, 43, 55, 38 42 37 43 # 6 44, 62, 58, 60 49 70 63 45, 33, 41, 40 40 53 42 # 7 40, 41, 37, 46 41 58 46 21, 38, 28, 19 27 29 29 # 8 68, 68, 55, 69 63 69 65 38, 45, 28, 19 33 40 33 1Data for sampling conducted on September 2003, December 2003, March 2004 and June 2004. Data relevant to peak excursions are bold and underlined.

Unusually high TTHM concentrations were observed at location # 2. The results are significantly higher than both the LRAA at those locations for the previous 12 month period and the historic TTHM and HAA5 values at those locations for the years 1999 2003 ( see Significant Excursions Evaluation Report). Data for September 2004 meets the criteria of peak excursion. The city staff does not believe that treatment plant or source water quality changes caused the increase in the DBP level because such changes would likely impact all locations supplied by the treatment plant or source water, but only one location was affected by high DBP level. The city Significant Excursion Guidance Manual Proposal Draft July 2003 D 5 staff believes that distribution system operations in the vicinity of the location caused the increase in the DBP level.

Significant Excursion Report date: October 16th, 2004 Evaluation Report Report prepared by: Ronald Doe, P. E.

Page 1 System name: Elm City 1) When was the significant excursion sample( s) collected? What were the TTHM and HAA5 concentrations?

Location No. # 2 # ______ # ______ # ______

Location description Hardwood Plant  high TTHM Sample collection date Sept. 4, 2004 Sample collection time 2 p. m.

TTHM LRAA Concentration ( ug/ L) 72 TTHM Concentration ( ug/ L) 122 HAA5 LRAA Concentration ( ug/ L)

HAA5 Concentration ( ug/ L)

Note: Attach additional sheets if you observed more than four significant excursions during this round of sampling.

2) Where did the excursion( s) occur? Attach a schematic of your system, sketch your system in the space below, or have a schematic of your system available to review with your state at the time of your next sanitary survey. Indicate the location( s) of the significant excursion( s) on your schematic.

Location # 2   Represents high residence time of water leaving the Hardwood Plant. It is located in the Pineville neighborhood. An elevated storage tank also supplies water to this subdivision.

The location of these sample locations is illustrated in Figure D. 1. Significant Excursion Guidance Manual Proposal Draft July 2003 D 6 Significant Excursion Evaluation Report Page 2 Report date: October 16th, 2004 3) Attach ( or provide in the Supplemental Data Form) all available water quality data for the round of sampling in which the significant excursion occurred. At a minimum, include all TTHM and HAA5 results from the sampling period. You should also consider including pH, temperature, alkalinity, TOC, disinfectant residual, and any other data that you think would be useful.

a) Were there any unusual circumstances associated with this round of sampling?

Yes No X If yes, please explain.

b) Were all analytical QA/ QC measures met?

Sample preservation Yes X No Sample holding time Yes X No Other If no, please explain.

4) Attach ( or provide in the Supplemental Data Form) historical TTHM and HAA5 data for the location( s) at which the significant excursion( s) occurred. Provide at least three years of data, if available. Significant Excursion Guidance Manual Proposal Draft July 2003 D 7 Significant Excursion Evaluation Report Page 3 Report date: October 16th, 2004 5) What caused your excursion( s) to occur?

Sections A through F starting on page 4 can help you determine the possible cause( s) of your excursion. Please note there may be more than one factor which resulted in your excursion.

Section A: Source water quality change Section B: Process upset at treatment plant Section C: Planned change or maintenance activities at plant Section D: Planned distribution system operations or maintenance activities Section E: Unplanned events in distribution system If you already suspect a cause, go directly to that section. If you read Sections A through E and are unable to determine a cause of your excursion, then complete Section F.

Consecutive systems should also contact their wholesaler to identify the cause( s) of the significant excursion( s).

6) List steps taken or planned to reduce DBP peak levels.

Considering modifications to configuration of inflow piping at the Pineville tank to improve mixing. Significant Excursion Guidance Manual Proposal Draft July 2003 D 8 Significant Excursion Evaluation Report Page 4 Report date: October 16th, 2004 A. Source Water Quality Changes ° Did any of the events listed below take place before the DBP excursion to cause TOC levels to increase?   Heavy rain fall   Flooding   Spring snow melt/ runoff   Significant decrease in rainfall or source flow   Algae bloom ° Did any of the events listed below take place before the DBP excursion to cause bromide levels to increase?   Significant decrease in rainfall or source flow   Brackish or seawater intrusion ° Did pH and/ or alkalinity significantly change?

° If two or more supplies are used, was a greater portion of water drawn from the one with higher TOC?

° Was raw water stored for an unusually long period of time resulting in a significant increase in water temperature?

Conclusions:

Did source water quality changes cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 9 Significant Excursion Evaluation Report Page 5 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ° Was raw water stored for an unusually long time, providing additional contact time for DBP formation after prechlorination?

° Were there changes in coagulation practices? S Were there any changes or malfunctions of the coagulation process in the days leading to the excursion? S Were the coagulant dose and pH properly adjusted for incoming source water conditions?

° Were there changes in chlorination practices?   Were there any changes in chlorine dose at any location in the plant?   Were there changes in plant flow that may have resulted in longer than normal residence time at any location in the plant? S Did the pH change at the point of chlorine addition?

° Were there changes in settling practices? S Was there excess sludge build up in the settling basin that may have carried over to the point of disinfectant addition? S Was there any disruption in the sludge blanket that may have resulted in carryover to the point of disinfection?

° Were there changes in filtration practices? S Have filter run times been changed to meet raw water quality changes? S Were there any spikes in individual filter effluent turbidity ( which may indicate particulate or colloidal TOC breakthrough) in the days leading to the excursion? S Did chlorinated water sit in the filter for an extended period of time? S Were all filters run in a filter to waste mode during initial filter ripening? S Were any filters operated beyond their normal filter run time? S If GAC filters are used: Is it possible the adsorptive capacity of the GAC bed was reached before reactivation occurred? S If biological filtration is used: Were there any process upsets that may have resulted in breakthrough of TOC ( particularly biodegradable TOC)?

° Were there changes in plant flow that may have resulted in an unusually high residence time in the clearwell on the days prior to the excursion? S For example, a temporary plant shutdown.

Continued on next page Significant Excursion Guidance Manual Proposal Draft July 2003 D 10 Significant Excursion Evaluation Report Page 6 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ( Continued)

Conclusions:

Did a process upset in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 11 Significant Excursion Evaluation Report Page 7 Report date: October 16th, 2004 C. Planned Change or Maintenance Activities for the Treatment Plant ° Was there a recent change ( or addition) of pre oxidant?

° Was there any maintenance in the basin that may have stirred sludge from the bottom of the basin and caused it to carry over to the point of disinfectant addition?

° Did you change the type or manufacturer of the coagulant?

° Were there any changes in disinfection practices in the days prior to the excursion? S For example, a switch from chloramines to free chlorine for burnout period. S Discontinuation of ozone which forms very little TTHM.

° Was a filter( s) taken off line for an extended period of time that caused the other filters to operate near maximum design capacity and creating the conditions for possible breakthrough?

° Were any pumps shut down for maintenance, leading to changes in flow patterns or hydraulic surges?

Conclusions:

Did a planned maintenance or operational activity in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 12 Significant Excursion Evaluation Report Page 8 Report date: October 16th, 2004 D. Planned Distribution System Operations or Maintenance Activities ° Was a tank drained for cleaning or other maintenance? S Was the tank drained to waste or to the distribution system? S Was a larger volume than normal drained to the distribution system?

° If booster disinfection is used, was the booster disinfectant dose higher than the normal booster disinfectant dose for that season?

° Were there any system maintenance activities in the days prior to DBP excursion? Including:   Repairing mains or installing new mains   Closure of valves to isolate sections of pipes ° Were the pipes flushed properly or were the appropriate valves re opened after work was completed?

° Did any pump or pipeline maintenance occur that would have changed the flow pattern in the area the sample was drawn from? S Change in flow can cause water in stagnant areas to be drawn into another area.

° Did any pipeline replacement occur? S Disinfecting piping in contact with drinking water could result in a high concentration of chlorine entering the distribution system and thus increase DBPs.

Conclusions:

Did a planned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

Refer to the explanation following Section E.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 13 Significant Excursion Evaluation Report Page 9 Report date: October 16th, 2004 E. Unplanned Distribution System Events ° Were there increases in demand that caused older water in storage tanks to be drawn into the system? S Were there any major fire events? S Did one or more storage tank have greater than average drawdown preceding the time of DBP peak excursion?

° Were there decreases in demand that resulted in longer than normal system residence times? S Were there any large customers off line?

° Did any main breaks occur causing changes in flow patterns in the influence area of the sample location?

° If you collect water temperature inside storage tanks, was the temperature inside the tank higher than normal for the season?

° Were any storage tanks hydraulically locked out of the system for an extended period and then used preceding the time of DBP peak excursion?

° Did changes in overall water demand cause a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

° Were there large variations in localized system pressures that were different from the normal pressure range that could have caused a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

Conclusions:

Did an unplanned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

The city staff believes distribution system operations caused the peak THM excursion. Therefore, the likelihood that distribution issues contributed to the peak THM excursion has been explored first. To determine the cause of the THM peak excursion, the city staff reviewed the following information for a period of two weeks prior to the occurrence of peak THM excursion:

° System maintenance activities ° Main breaks ° System pressure fluctuations ° Overall system demand ° Water level in storage tanks ° Boost disinfection operation Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 14 System maintenance activities: Installation of a new 12 inch main for a new development in Elmville subdivision was completed. The city staff reviewed the main disinfection logbook which indicated that the new main was flushed properly, and chlorine residual in the pipe was 1 mg/ L before it was connected to the rest of the water system. Three valves were closed to isolate sections of pipes from the rest of the water system. during installation of the new main. These valves were checked to make sure that they were all opened after installation of the new main was completed. One valve was found to be inadvertently left in the closed position. However, the closure of this valve did not affect the water quality in Pineville subdivision where the peak THM concentration occurred. The city's hydraulic model indicated that water does not flow from Elmville to Pineville and closing the valve in the pipe in Elmville does not alter the water flow patters in Pineville.

Main breaks: A road repair worker in Pineville subdivision damaged a 12 inch water main that runs along that road. The broken section of the water main was isolated and shut off within two hours. However, it is anticipated that there was significant loss of water during those two hours. Hydraulic analyses using the city's hydraulic model have indicated that the piping network in Pineville does not have any stagnant zones with high residence time. Also, using the city's hydraulic model to simulate the main break by creating artificial demand at the location of the main break indicated that the influence of the main break did not draw water from any stagnant zones towards the sample location where peak THM excursion occurred.

System pressure fluctuations: The distribution system pressure in the Pineville subdivision was generally within the normal range expected for the month of September, approximately 52 65 psi. However, the pressure was about 10 psi lower at the location of the main break for about two hours. As soon as the damaged section of the main was isolated, the pressure at that location returned to the normal pressure range generally expected for the month of September. The piping network in Pineville does not have any stagnant zones. There may be stagnant zones outside the Pineville subdivision, but the lower pressure in the vicinity of the peak THM occurrence did not impact water flow patterns outside the Pineville subdivision, as verified by the city's hydraulic model.

Overall system demand: The total hourly distribution system demand was checked using treatment plant production figures and tank level data. The hourly total system demand during September 2004 ranged between 14 17 mgd, which was also the general range for the system demand during the month of September for 1999 2003. An unusual increase or decrease in the total system demand was not observed two weeks prior to the peak THM occurrence. The loss of water due to the main break did not cause a significant change in the overall system demand. Therefore, there was not any unusual shift in the water demand patterns and water flow patterns in the vicinity of stagnant zones and thus did not contribute to the peak THM occurrence.

Water level in storage tanks: The hourly water level for all the tank in Elm City was plotted using the SCADA system data. The water levels fluctuated within the normal range for all the tanks except for the elevated tank located in Pineville. The water level in the Pineville tank generally fluctuates approximately 20 feet to 35 feet above the bottom of the tank. The water level in this tank dropped to about 12 feet above the bottom of the tank at the time of the main break and then rose to normal levels once the broken section of the main was isolated. The increased water demand and pressure drop at the location of the main break was responsible for the unusual drop in the water level of the Pineville tank. The proximity of Sample Location 2 to the main break also decreased the pressure at the sampling location, this allowing the water from the top portion of the tank to reach that location during the main break. The SCADA data indicated that the average inflow rate into the tank is 1000 gpm and the inlet diameter is 36 inches. This inflow rate and inlet diameter may not provide adequate momentum to mix the water near the top portion of the tank where the water came from during the main break. Therefore, the water age in the top portion of the tank was higher and may have caused the peak DBP level at Sample Site 2. Significant Excursion Guidance Manual Proposal Draft July 2003 D 15 Booster disinfection operation:

There is a booster disinfection station located in the Polarville subdivision. The disinfectant residual leaving this booster station was within the normal range of 1 2 mg/ L. Pineville subdivision receives all the water either from the treatment plant directly or from the Pineville tank. It does not receive any portion of its water from the booster station. Thus, the disinfectant residuals at the booster station did not contribute to peak THM occurrence at Location 2. Significant Excursion Guidance Manual Proposal Draft July 2003 D 16 Significant Excursion Evaluation Report Page 10 Report date: October 16th, 2004 F. If you were unable to identify the cause of your significant excursion( s) after reviewing Sections A through E, are you able to identify another potential cause of your increase in DBP concentrations? Explain.

Note: If you are unable to determine the cause of your excursion you may wish to consider:

° More frequent raw water temperature monitoring. ° More frequent raw water TOC monitoring. ° Increased disinfectant residual monitoring in the distribution system. ° Tracer studies to characterize distribution system water age. ° Development of a hydraulic model to characterize the distribution system.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 D 17 Supplemental Data Form for the Significant Excursion Evaluation Report Report date: October 16th, 2004 Report prepared by: Ronald Doe, P. E.

System name: Elm City 1) Water quality data from significant excursion sampling period.

Location No. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 Location Name TTHM ( ug/ L) 72 122 82 68 68 70 58 69 HAA5 ( ug/ L) 53 38 58 54 37 53 29 40 Free Chlorine ( mg/ L) 1.5 0.1 NA 0.5 0.8 1.1 NA 0.9 Total Chlorine ( mg/ L) 1.7 0.2 NA 0.7 1.1 1.5 NA 1.2 pH 7.9 8.0 8.3 8.1 7.8 8.3 7.5 8.2 2) Supplemental data from each treatment facility:

Plant # 1: Hardwood Plant Plant # 2: Softwood Plant Raw Water Temperature: NA Raw Water Temperature: NA Plant Effluent Water Temperature: 20 ° C Plant Effluent Water Temperature: 20 ° C Raw Water TOC: 2.2 mg/ L ( Avg.

2.0mg/ L) Raw Water TOC: 1.8 mg/ L ( Avg.

2.0mg/ L)

Other Data: Other Data: Inf. turb.: 25 ntu ( Avg

20 ntu)

3) Historical TTHM and HAA5 data at significant excursion sampling locations.

TTHM Data ( ug/ L) HAA5 Data ( ug/ L)

Monitoring Location # 2 #_____ #_____ #_____ Monitoring Location # 2 #_____ #_____ #_____

Date  1998 61 Date  1998 32 Date  1999 55 Date  1999 29 Date  2000 70 Date  2000 48 Date  2001 64 Date  2001 36 Date  2002 49 Date  2002 43 Avg. 98 02 60 Avg. 98 02 49 Attach additional sheets if necessary Appendix E Changes in Treatment Plant and Distribution System Operation Significant Excursions Identified Using the " Maximum Concentration Approach" This page intentionally left blank. Significant Excursion Guidance Manual Proposal Draft July 2003 E 1 The first part of this appendix includes general system information and a summary of TTHM and HAA5 data that resulted in Elm City having to perform a significant excursion evaluation. This information is not required when documenting a significant excursion. Only the Significant Excursion Report is required to be completed by systems that experience a significant excursion.

This appendix is provided as an example of a system in which changes in both treatment plant and distribution system operations led to a DBP Significant Excursion. Possible strategies to reduce excursions are presented in Chapter 4, but they are not to be included in the identification and documentation process. Appendices B through D provide similar examples for systems in which one primary change either in source water quality, treatment plant operations, or distribution system operations resulted in a significant excursion.

This example assumes the state has chosen to use 100 µ g/ L TTHM and 75 µ g/ L HAA5 as the trigger levels for determining that a significant excursion has occurred and that a significant excursion evaluation is required.

Background Information for this Example System Description:

General system characteristics: Service area: Elm City plus surrounding suburban areas Production: Annual average daily demand 15 MGD Source Water Information: Hardwood Lake ( surface water) pH: from 6.9 to 7.5 Alkalinity: from 82 to 98 mg/ L as CaCO3 TOC: from 2.1 to 4.0 mg/ L as C Bromide: from 0.04 to 0.1 mg/ L Turbidity: 1 to 100 ntu Softwood River ( surface water) pH: from 6.8 to 7.9 Alkalinity: from 77 to 94 mg/ L as CaCO3 TOC: from 1.6 to 9.4 mg/ L as C Bromide: from 0.03 to 0.1 mg/ L Turbidity: 2 to 115 ntu Significant Excursion Guidance Manual Proposal Draft July 2003 E 2 Treatment Provided: Hardwood, conventional ( 15 MGD design, 7.5 MGD average) Softwood River, conventional with GAC ( 20 MGD design, 7.5 MGD average) Primary and residual disinfection: Chlorine/ chlorine at both plants Summary of Stage 2 DBPR Monitoring Locations: Table E. 1 summarizes the Stage 2 DBPR monitoring locations used by Elm City. Sample locations are marked in the distribution system schematic presented in Figure E. 1.

Table E. 1 Stage 2 DBPR Monitoring Locations Location Description Location # 1 Hardwood Plant  average residence time Location # 2 Hardwood Plant  high TTHM Location # 3 Hardwood Plant  high HAA5 Location # 4 Hardwood/ Softwood Mix Zone  high TTHM Location # 5 Hardwood/ Softwood Mix Zone  high TTHM Location # 6 Hardwood/ Softwood Mix Zone  high TTHM Location # 7 Softwood Plant  average residence time Location # 8 Softwood Plant  high HAA5 Significant Excursion Guidance Manual Proposal Draft July 2003 E 3 Pineville MIXING ZONE Softwood River WTP Hardwood WTP Elevated Storage Tank Ground storage tank Pump station 2 Oakville 1 3 Elmville 5 Downtown Appleville Weeping Willow Poplarville Cedarville Cypressville 6 7 4 8 Peak DBP location Figure E. 1 Schematic of Elm City Distribution System and Stage 2 DBPR Monitoring Locations Significant Excursion Guidance Manual Proposal Draft July 2003 E 4 DBP Excursion Investigation:

During the last sampling period which took place in September 2004, Elm City experienced unusually high TTHM values ( relative to the LRAA) at three monitoring locations (# 1, # 2, # 3). Similarly, unusually high HAA5 values were detected at two monitoring locations (# 1 and # 2). DBP data from the previous year and most recent sampling period ( five quarters total) are presented in Table E. 2.

Table E. 2 TTHM and HAA5 Monitoring Data Loc atio n TTHM ( ug/ L) HAA5 ( ug/ L)

Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg. Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg.

# 1 54, 67, 58, 75 65 118 74 52, 37, 30, 41 40 84 48 # 2 68, 68, 55, 69 63 145 77 38, 45, 28, 19 33 75 42 # 3 66, 52, 71, 72 64 122 74 41, 46, 45, 39 43 58 47 # 4 50, 55, 51, 61 55 82 60 42, 43, 38, 34 39 54 42 # 5 34, 48, 55, 50 44 68 48 32, 43, 55, 38 42 37 43 # 6 44, 62, 58, 60 49 70 53 45, 33, 41, 40 40 53 42 # 7 40, 41, 37, 46 41 58 46 21, 38, 28, 19 27 29 29 # 8 49, 39, 50, 76 52 78 56 43, 39, 41, 45 42 49 44 1Data for sampling conducted on September 2003, December 2003, March 2004 and June 2004. Data relevant to peak excursions are bold and underlined.

Unusually high TTHM samples were collected at locations # 1, # 2, and # 3, and unusually high HAA5 samples were collected at locations # 1 and # 2. The results are significantly higher than both the LRAA at those locations for the previous 12 month period and the historic TTHM and HAA5 values at those locations for the years 1998 2002 ( see Significant Excursions Evaluation Report). Significant excursions were identified when DBP levels exceeded 100 µ g/ L TTHM or 75 µ g/ L HAA5. All of the monitoring locations affected by high DBP are located in the area served by the Hardwood plant. The city staff has reason to believe that a process change that occurred during treatment operations at the Hardwood plant caused this increase in DBP levels. Significant Excursion Guidance Manual Proposal Draft July 2003 E 5 Significant Excursion Report date: October 16, 2004 Evaluation Report Report prepared by: Ronald Doe, P. E.

Page 1 System name: Elm City 1) When was the significant excursion sample( s) collected? What were the TTHM and HAA5 concentrations?

Location No. # 1 # 2 # 3 # ______

Location description Hardwood Plant  average residence time Hardwood Plant  high TTHM Hardwood Plant  high HAA5 Sample collection date Sept. 4, 2004 Sept. 4, 2004 Sept. 4, 2004 Sample collection time 3 p. m. 2 p. m. 12 noon TTHM LRAA Concentration ( ug/ L) 74 77 74 TTHM Concentration ( ug/ L) 118 145 122 HAA5 LRAA Concentration ( ug/ L) 48 42 HAA5 Concentration ( ug/ L) 84 75 Note: Attach additional sheets if you observed more than four significant excursions during this round of sampling.

2) Where did the excursion( s) occur? Attach a schematic of your system, sketch your system in the space below, or have a schematic of your system available to review with your state at the time of your next sanitary survey. Indicate the location( s) of the significant excursion( s) on your schematic.

Location # 1   Represents the average residence time of water leaving the Hardwood Plant. It is located in the Oakville neighborhood. There are no storage facilities between the treatment plant and this location Location # 2   Sample tap is a hose bib at a building located in Pineville in a zone of the distribution system with water age greater than average. Water in this area is from the Hardwood Plant.

Location # 3   This location is located in the downtown area. Water is primarily from Hardwood Plant. A ground storage tank is near this location. Significant Excursion Guidance Manual Proposal Draft July 2003 E 6 Significant Excursion Evaluation Report Page 2 Report date: October 16, 2004 3) Attach ( or provide in the Supplemental Data Form) all available water quality data for the round of sampling in which the significant excursion occurred. At a minimum, include all TTHM and HAA5 results from the sampling period. You should also consider including pH, temperature, alkalinity, TOC, disinfectant residual, and any other data that you think would be useful.

a) Were there any unusual circumstances associated with this round of sampling?

Yes No X If yes, please explain.

b) Were all analytical QA/ QC measures met?

Sample preservation Yes X No Sample holding time Yes X No Other If no, please explain.

4) Attach ( or provide in the Supplemental Data Form) historical TTHM and HAA5 data for the location( s) at which the significant excursion( s) occurred. Provide at least three years of data, if available. Significant Excursion Guidance Manual Proposal Draft July 2003 E 7 Significant Excursion Evaluation Report Page 3 Report date: October 16, 2004 5) What caused your excursion( s) to occur?

Sections A through F starting on page 4 can help you determine the possible cause( s) of your excursion. Please note there may be more than one factor which resulted in your excursion.

Section A: Source water quality change Section B: Process upset at treatment plant Section C: Planned change or maintenance activities at plant Section D: Planned distribution system operations or maintenance activities Section E: Unplanned events in distribution system If you already suspect a cause, go directly to that section. If you read Sections A through E and are unable to determine a cause of your excursion, then complete Section F.

Consecutive systems should also contact their wholesaler to identify the cause( s) of the significant excursion( s).

6) List steps taken or planned to reduce DBP peak levels.

Considering modifications to configuration of inflow piping at the Pineville tank to improve mixing.

Considering improvements to coagulant process monitoring ( daily verification of coagulant dose delivered with pump catch, streaming current monitoring) to minimize possible process upsets. Significant Excursion Guidance Manual Proposal Draft July 2003 E 8 Significant Excursion Evaluation Report Page 4 Report date: October 16, 2004 A. Source Water Quality Changes ° Did any of the events listed below take place before the DBP excursion to cause TOC levels to increase?   Heavy rain fall   Flooding   Spring snow melt/ runoff   Significant decrease in rainfall or source flow   Algae bloom ° Did any of the events listed below take place before the DBP excursion to cause bromide levels to increase?   Significant decrease in rainfall or source flow   Brackish or seawater intrusion ° Did pH and/ or alkalinity significantly change?

° If two or more supplies are used, was a greater portion of water drawn from the one with higher TOC?

° Was raw water stored for an unusually long period of time resulting in a significant increase in water temperature?

Conclusions:

Did source water quality changes cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 9 Significant Excursion Evaluation Report Page 5 Report date: October 16, 2004 B. Process Upset at Treatment Plant ° Was raw water stored for an unusually long time, providing additional contact time for DBP formation after prechlorination?

° Were there changes in coagulation practices? S Were there any changes or malfunctions of the coagulation process in the days leading to the excursion? S Were the coagulant dose and pH properly adjusted for incoming source water conditions?

° Were there changes in chlorination practices?   Were there any changes in chlorine dose at any location in the plant?   Were there changes in plant flow that may have resulted in longer than normal residence time at any location in the plant? S Did the pH change at the point of chlorine addition?

° Were there changes in settling practices? S Was there excess sludge build up in the settling basin that may have carried over to the point of disinfectant addition? S Was there any disruption in the sludge blanket that may have resulted in carryover to the point of disinfection?

° Were there changes in filtration practices? S Have filter run times been changed to meet raw water quality changes? S Were there any spikes in individual filter effluent turbidity ( which may indicate particulate or colloidal TOC breakthrough) in the days leading to the excursion? S Did chlorinated water sit in the filter for an extended period of time? S Were all filters run in a filter to waste mode during initial filter ripening? S Were any filters operated beyond their normal filter run time? S If GAC filters are used: Is it possible the adsorptive capacity of the GAC bed was reached before reactivation occurred? S If biological filtration is used: Were there any process upsets that may have resulted in breakthrough of TOC ( particularly biodegradable TOC)?

° Were there changes in plant flow that may have resulted in an unusually high residence time in the clearwell on the days prior to the excursion? S For example, a temporary plant shutdown.

Continued on next page Significant Excursion Guidance Manual Proposal Draft July 2003 E 10 Significant Excursion Evaluation Report Page 6 Report date: October 16, 2004 B. Process Upset at Treatment Plant ( Continued)

Conclusions:

Did a process upset in the treatment plant cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

Ferric chloride was underfed for two days prior to the September 2004 sampling event resulting in lower TOC removal at the Hardwood plant. The increased TOC concentration passing through the treatment process contributed to increased formation of TTHM and HAA5 at Locations 1, 2, and 3 as these locations are supplied by the Hardwood treatment plant. The low ferric dose was the result of poor calibration of the standby feed pumps that were placed in service during the maintenance of the duty feed pumps. The pH of coagulation increased from the usual 5.5 to 6.2 range to 7.1 to 7.3 during the low coagulant dose.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 11 Significant Excursion Evaluation Report Page 7 Report date: October 16, 2004 C. Planned Change or Maintenance Activities for the Treatment Plant ° Was there a recent change ( or addition) of pre oxidant?

° Was there any maintenance in the basin that may have stirred sludge from the bottom of the basin and caused it to carry over to the point of disinfectant addition?

° Did you change the type or manufacturer of the coagulant?

° Were there any changes in disinfection practices in the days prior to the excursion? S For example, a switch from chloramines to free chlorine for burnout period. S Discontinuation of ozone which forms very little TTHM.

° Was a filter( s) taken off line for an extended period of time that caused the other filters to operate near maximum design capacity and creating the conditions for possible breakthrough?

° Were any pumps shut down for maintenance, leading to changes in flow patterns or hydraulic surges?

Conclusions:

Did a planned maintenance or operational activity in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 12 Significant Excursion Evaluation Report Page 8 Report date: October 16, 2004 D. Planned Distribution System Operations or Maintenance Activities ° Was a tank drained for cleaning or other maintenance? S Was the tank drained to waste or to the distribution system? S Was a larger volume than normal drained to the distribution system?

° If booster disinfection is used, was the booster disinfectant dose higher than the normal booster disinfectant dose for that season?

° Were there any system maintenance activities in the days prior to DBP excursion? Including:   Repairing mains or installing new mains   Closure of valves to isolate sections of pipes ° Were the pipes flushed properly or were the appropriate valves re opened after work was completed?

° Did any pump or pipeline maintenance occur that would have changed the flow pattern in the area the sample was drawn from? S Change in flow can cause water in stagnant areas to be drawn into another area.

° Did any pipeline replacement occur? S Disinfecting piping in contact with drinking water could result in a high concentration of chlorine entering the distribution system and thus increase DBPs.

Conclusions:

Did a planned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

One area of the Pineville subdivision was flushed in response to customer complaints about water quality. The flushing activity created additional water demand in that area and reduced the pressure in the vicinity of the fire hydrants that were flushed. The low pressure altered water flow patterns and caused more than normal drawdown from one of the storage tanks. Simulation of the flushing activities using the city's hydraulic model indicated that a change in water flow pattern caused water from one of the stagnant zones in Oakwood subdivison to flow to the flushed areas. As the water flowed towards the flushed areas, it flowed through the vicinity of Location 3 bringing old water to this location.

An overview of the tank level data from SCADA indicated that the water level in Pineville tank generally drops to about 10 feet below the maximum tank water level of 35 feet. However, at the time of the flushing activities, the water level in this tank dropped 25 feet below the maximum tank water level. This unusual drop in water level caused the relatively unmixed water with high age to be drawn into the distribution system and reach Location 2 which is located close to the tank.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 13 Significant Excursion Evaluation Report Page 9 Report date: October 16, 2004 E. Unplanned Distribution System Events ° Were there increases in demand that caused older water in storage tanks to be drawn into the system? S Were there any major fire events? S Did one or more storage tank have greater than average drawdown preceding the time of DBP peak excursion?

° Were there decreases in demand that resulted in longer than normal system residence times? S Were there any large customers off line?

° Did any main breaks occur causing changes in flow patterns in the influence area of the sample location?

° If you collect water temperature inside storage tanks, was the temperature inside the tank higher than normal for the season?

° Were any storage tanks hydraulically locked out of the system for an extended period and then used preceding the time of DBP peak excursion?

° Did changes in overall water demand cause a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

° Were there large variations in localized system pressures that were different from the normal pressure range that could have caused a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

Conclusions:

Did an unplanned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 14 Significant Excursion Evaluation Report Page 10 Report date: October 16, 2004 F. If you were unable to identify the cause of your significant excursion( s) after reviewing Sections A through E, are you able to identify another potential cause of your increase in DBP concentrations? Explain.

Note: If you are unable to determine the cause of your excursion you may wish to consider:

° More frequent raw water temperature monitoring. ° More frequent raw water TOC monitoring. ° Increased disinfectant residual monitoring in the distribution system. ° Tracer studies to characterize distribution system water age. ° Development of a hydraulic model to characterize the distribution system.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 E 15 Supplemental Data Form for the Significant Excursion Evaluation Report Report date: October 16, 2004 Report prepared by: Ronald Doe, P. E.

System name: Elm City 1) Water quality data from significant excursion sampling period.

Location No. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 Location Name TTHM ( ug/ L) 118 145 122 82 68 70 58 78 HAA5 ( ug/ L) 84 75 58 54 37 53 29 49 Free Chlorine ( mg/ L) 1.5 0.1 NA 0.5 0.8 1.1 NA 0.9 Total Chlorine ( mg/ L) 1.7 0.2 NA 0.7 1.1 1.5 NA 1.2 pH 7.9 8.0 8.3 8.1 7.8 8.3 7.5 8.2 2) Supplemental data from each treatment facility:

Plant # 1: Hardwood plant Plant # 2: Softwood plant Raw Water Temperature: NA Raw Water Temperature: NA Plant Effluent Water Temperature: 20 ° C Plant Effluent Water Temperature: 20 ° C Raw Water TOC: 3.2 mg/ L ( ave = 2.0) Raw Water TOC: 1.8 mg/ L ( ave = 2.0)

Other Data: Other Data: Plant influent turbidity = 25 ntu Average = 20 ntu 3) Historical TTHM and HAA5 data at significant excursion sampling locations.

TTHM Data ( ug/ L) HAA5 Data ( ug/ L)

Monitoring # _ 1__ #_ 2__ #__ 3_ #___ Monitoring # _ 1_ _ #_ 2__ #____ #___ Location Location Date 1998 61 78 45 Date 1998 32 56 Date 1999 55 59 56 Date 1999 29 47 Date 2000 70 69 41 Date 2000 48 23 Date 2001 64 81 73 Date 2001 36 34 Date 2002 66 54 53 Date 2002 43 45 Avg. 63 68 54 Avg. 38 45 Attach additional sheets if necessary Appendix F Changes in Source Water Quality Significant Excursions Identified Using the " Difference Approach" This page intentionally left blank. Significant Excursion Guidance Manual Proposal Draft July 2003 F 1 The first part of this appendix includes general system information and a summary of TTHM and HAA5 data that resulted in Elm City having to perform a significant excursion evaluation. This information is not required as part of the documentation of a significant excursion. Only the Significant Excursion Report is required to be completed by systems that experience a significant excursion.

This appendix is provided as an example of a system in which changes in source water quality led to a DBP Significant Excursion. Possible strategies to reduce excursions are presented in Chapter 4, but they are not to be included in the identification and documentation process. Appendices C through E provide similar examples for systems in which changes in treatment plant operations, changes in distribution system, and multiple causes resulted in a significant excursion.

This example assumes the state has chosen to use the " difference approach" ( see Chapter 1.1) for determining that a significant excursion has occurred and that a significant excursion evaluation is required.

Background Information for this Example System Description:

General system characteristics: Service area: Elm City plus surrounding suburban areas Production: Annual average daily demand 15 MGD Source Water Information: Hardwood Lake ( surface water) pH: from 6.9 to 7.5 Alkalinity: from 82 to 98 mg/ L as CaCO3 TOC: from 2.1 to 4.0 mg/ L as C Bromide: from 0.04 to 0.1 mg/ L Turbidity: 1 to 100 ntu Softwood River ( surface water) pH: from 6.8 to 7.9 Alkalinity: from 77 to 94 mg/ L as CaCO3 TOC: from 1.6 to 9.4 mg/ L as C Bromide: from 0.03 to 0.1 mg/ L Turbidity: 2 to 115 ntu Significant Excursion Guidance Manual Proposal Draft July 2003 F 2 Treatment Provided: Hardwood, conventional ( 15 MGD design, 7.5 MGD average) Softwood River, conventional with GAC ( 20 MGD design, 7.5 MGD average) Primary and residual disinfection: Chlorine/ chlorine at both plants Summary of Stage 2 DBPR Monitoring Locations: Table F. 1 summarizes the Stage 2 DBPR monitoring locations used by Elm City. Sample locations are marked in the distribution system schematic presented in Figure F. 1.

Table F. 1 Stage 2 DBPR Monitoring Locations Location Description Location # 1 Hardwood Plant  average residence time Location # 2 Hardwood Plant  high TTHM Location # 3 Hardwood Plant  high HAA5 Location # 4 Hardwood/ Softwood Mix Zone  high TTHM Location # 5 Hardwood/ Softwood Mix Zone  high TTHM Location # 6 Hardwood/ Softwood Mix Zone  high TTHM Location # 7 Softwood Plant  average residence time Location # 8 Softwood Plant  high HAA5 Significant Excursion Guidance Manual Proposal Draft July 2003 F 3 Pineville MIXING ZONE Softwood River WTP Hardwood WTP Elevated Storage Tank Ground storage tank Pump station 2 Oakville 1 3 Elmville 5 Downtown Appleville Weeping Willow Poplarville Cedarville Cypressville 6 7 4 8 Peak DBP location Figure F. 1 Schematic of Elm City Distribution System and Stage 2 DBPR Monitoring Locations Significant Excursion Guidance Manual Proposal Draft July 2003 F 4 DBP Excursion Investigation:

During the last sampling period which took place in September 2004, Elm City experienced unusually high TTHM and HAA5 levels ( relative to the LRAA). DBP data from the previous year and most recent sampling period ( five quarters total) are presented in Table F. 2.

Table F. 2 TTHM and HAA5 Monitoring Data Loc atio n TTHM ( ug/ L) HAA5 ( ug/ L)

Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg. Quarterly Pre Sept. 2004 Data1 LRAA Pre Sept. 2004 Avg. Sept. 2004 Data LRAA Sept. 2004 Avg.

# 1 54, 67, 58, 75 65 63 67 52, 37, 30, 41 40 52 40 # 2 68, 68, 55, 69 63 72 64 38, 45, 28, 19 33 39 33 # 3 66, 52, 71, 72 64 81 68 41, 46, 45, 39 43 51 46 # 4 50, 55, 51, 61 55 78 62 42, 43, 38, 34 39 66 45 # 5 34, 48, 55, 50 44 79 55 32, 43, 55, 38 42 58 49 # 6 44, 62, 58, 60 49 121 66 45, 33, 41, 40 40 72 47 # 7 40, 41, 37, 46 41 77 50 31, 38, 28, 19 27 59 37 # 8 49, 39, 50, 76 52 146 76 43, 39, 41, 45 42 98 56 1Data for sampling conducted on September 2003, December 2003, March 2004 and June 2004. Data relevant to peak excursions are bold and underlined.

Unusually high TTHM samples were collected at locations # 5, # 6, # 7 and # 8, and unusually high HAA5 samples were collected at locations # 6, # 7 and # 8. The results are significantly higher than both the LRAA at those locations for the previous 12 month period and the historic TTHM and HAA5 values at those locations for the years 1999 2003 ( see Significant Excursions Evaluation Report). Significant excursions ( see Chapter 1.1) were identified if:

° the difference between quarterly location measurement and quarterly LRAA is > 30 µ g/ L and the LRAA is $ 40 µ g/ L for TTHM. and/ or ° the difference between quarterly location measurement and quarterly LRAA is > 25 µ g/ L and LRAA is $ 30 µ g/ L for HAA5. Significant Excursion Guidance Manual Proposal Draft July 2003 F 5 All of the monitoring locations affected by high DBP are located in the area served by the Softwood plant or in the mixing zone. The city staff has reason to believe that a water quality change that has occurred in Softwood River caused the increase in DBPs. Significant Excursion Guidance Manual Proposal Draft July 2003 F 6 Significant Excursion Report date: October 16th, 2004 Evaluation Report Report prepared by: Robert Doe, P. E.

Page 1 System name: Elm City 1) When was the significant excursion sample( s) collected? What were the TTHM and HAA5 concentrations?

Location No. # 5 # 6 # 7 # 8 Location description Hardwood/ Softwood Mix Zone   High TTHM Hardwood/ Softwood Mix Zone   High TTHM Softwood plant   average residence time Softwood plant   High HAA5 Sample collection date Sept. 4th, 2004 Sept. 4th, 2004 Sept. 4th, 2004 Sept. 4th, 2004 Sample collection time 10 a. m. 2 p. m. 11 a. m. 3 p. m.

TTHM LRAA Concentration ( ug/ L) 55 66 50 76 TTHM Concentration ( ug/ L) 79 121 77 146 HAA5 LRAA Concentration ( ug/ L) 47 27 56 HAA5 Concentration ( ug/ L) 72 59 98 Note: Attach additional sheets if you observed more than four significant excursions during this round of sampling.

2) Where did the excursion( s) occur? Attach a schematic of your system, sketch your system in the space below, or have a schematic of your system available to review with your state at the time of your next sanitary survey. Indicate the location( s) of the significant excursion( s) on your schematic.

Location # 5   This site is in the downtown area and is located in the Hardwood/ Softwood plants mixing zone.

Location # 6   This sample location is a faucet at a connection located in Weeping Willow  a zone of the distribution system that has been recently developed. This connection is located downstream from a chlorine booster station. Water in this area is generally a mix of water from the Hardwood and Softwood River Plants.

Location # 7   Represents average residence time of water leaving the Softwood Plant.

Location # 8   This sampling location is in an area that receives water from the Softwood Plant. Samples are collected at a hose bib near the first house on the cul de sac ( which has 12 homes total).

For this example, these sample locations are illustrated in Figure F. 1 Significant Excursion Guidance Manual Proposal Draft July 2003 F 7 Significant Excursion Evaluation Report Page 2 Report date: October 16th, 2004 3) Attach ( or provide in the Supplemental Data Form) all available water quality data for the round of sampling in which the significant excursion occurred. At a minimum, include all TTHM and HAA5 results from the sampling period. You should also consider including pH, temperature, alkalinity, TOC, disinfectant residual, and any other data that you think would be useful.

a) Were there any unusual circumstances associated with this round of sampling?

Yes No X If yes, please explain.

b) Were all analytical QA/ QC measures met?

Sample preservation Yes X No____

Sample holding time Yes X No____

Other If no, please explain.

4) Attach ( or provide in the Supplemental Data Form) historical TTHM and HAA5 data for the location( s) at which the significant excursion( s) occurred. Provide at least three years of data, if available. Significant Excursion Guidance Manual Proposal Draft July 2003 F 8 Significant Excursion Evaluation Report Page 3 Report date: October 16th, 2004 5) What caused your excursion( s) to occur?

Sections A through F starting on page 4 can help you determine the possible cause( s) of your excursion. Please note there may be more than one factor which resulted in your excursion.

Section A: Source water quality change Section B: Process upset at treatment plant Section C: Planned change or maintenance activities at plant Section D: Planned distribution system operations or maintenance activities Section E: Unplanned events in distribution system If you already suspect a cause, go directly to that section. If you read Sections A through E and are unable to determine a cause of your excursion, then complete Section F.

Consecutive systems should also contact their wholesaler to identify the cause( s) of the significant excursion( s).

6) List steps taken or planned to reduce DBP peak levels.

We are considering adjustments of the coagulation processes to improve TOC removal including: increasing the coagulant dose, evaluation of alternative coagulants, evaluation of coagulant aids, lowering the pH of coagulation, use of a pre oxidant ( permanganate or chlorine dioxide), and use of PAC. Significant Excursion Guidance Manual Proposal Draft July 2003 F 9 Significant Excursion Evaluation Report Page 4 Report date: October 16th, 2004 A. Source Water Quality Changes ° Did any of the events listed below take place before the DBP excursion to cause TOC levels to increase?   Heavy rain fall   Flooding   Spring snow melt/ runoff   Significant decrease in rainfall or source flow   Algae bloom ° Did any of the events listed below take place before the DBP excursion to cause bromide levels to increase?   Significant decrease in rainfall or source flow   Brackish or seawater intrusion ° Did pH and/ or alkalinity significantly change?

° If two or more supplies are used, was a greater portion of water drawn from the one with higher TOC?

° Was raw water stored for an unusually long period of time resulting in a significant increase in water temperature?

Conclusions:

Did source water quality changes cause or contribute to your significant excursion( s)?

Yes X No If yes, please explain:

The most probable cause of the DBP excursion noted during the September 2004 sampling even was a rapid increase of the organic matter concentration in the Softwood River. Following two days of heavy rainfall the TOC measured in the plant influent increased from 2.7 mg/ L to 8.4 mg/ L. At the same time, turbidity of the source water also increased from 5 ntu to a maximum of 98 ntu. The coagulant ( ferric chloride) dose was increased from 20 mg/ L to 75 mg/ L to match water quality changes. For the duration of this high turbidity/ high NOM event, the pH of coagulation was maintained between 61. and 6.3. The higher coagulant dose prevented any significant increases of turbidity in the settled water, but the concentration of TOC in the plant effluent increased from 1.8 mg/ L to 3.8 mg/ L. Jar testing conducted at the time of the event indicated that a further increase of the coagulant dose ( dosages up to 120 mg/ L were tested) would have not significantly improved TOC removal under the pH conditions presently used to conduct the coagulation process.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey.

Significant Excursion Evaluation Report Page 5 Report date: October 16th, 2004 Significant Excursion Guidance Manual Proposal Draft July 2003 F 10 B. Process Upset at Treatment Plant ° Was raw water stored for an unusually long time, providing additional contact time for DBP formation after prechlorination?

° Were there changes in coagulation practices? S Were there any changes or malfunctions of the coagulation process in the days leading to the excursion? S Were the coagulant dose and pH properly adjusted for incoming source water conditions?

° Were there changes in chlorination practices?   Were there any changes in chlorine dose at any location in the plant?   Were there changes in plant flow that may have resulted in longer than normal residence time at any location in the plant? S Did the pH change at the point of chlorine addition?

° Were there changes in settling practices? S Was there excess sludge build up in the settling basin that may have carried over to the point of disinfectant addition? S Was there any disruption in the sludge blanket that may have resulted in carryover to the point of disinfection?

° Were there changes in filtration practices? S Have filter run times been changed to meet raw water quality changes? S Were there any spikes in individual filter effluent turbidity ( which may indicate particulate or colloidal TOC breakthrough) in the days leading to the excursion? S Did chlorinated water sit in the filter for an extended period of time? S Were all filters run in a filter to waste mode during initial filter ripening? S Were any filters operated beyond their normal filter run time? S If GAC filters are used: Is it possible the adsorptive capacity of the GAC bed was reached before reactivation occurred? S If biological filtration is used: Were there any process upsets that may have resulted in breakthrough of TOC ( particularly biodegradable TOC)?

° Were there changes in plant flow that may have resulted in an unusually high residence time in the clearwell on the days prior to the excursion? S For example, a temporary plant shutdown.

Continued on next page Significant Excursion Guidance Manual Proposal Draft July 2003 F 11 Significant Excursion Evaluation Report Page 6 Report date: October 16th, 2004 B. Process Upset at Treatment Plant ( Continued)

Conclusions:

Did a process upset in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 F 12 Significant Excursion Evaluation Report Page 7 Report date: October 16th, 2004 C. Planned Change or Maintenance Activities for the Treatment Plant ° Was there a recent change ( or addition) of pre oxidant?

° Was there any maintenance in the basin that may have stirred sludge from the bottom of the basin and caused it to carry over to the point of disinfectant addition?

° Did you change the type or manufacturer of the coagulant?

° Were there any changes in disinfection practices in the days prior to the excursion? S For example, a switch from chloramines to free chlorine for burnout period. S Discontinuation of ozone which forms very little TTHM.

° Was a filter( s) taken off line for an extended period of time that caused the other filters to operate near maximum design capacity and creating the conditions for possible breakthrough?

° Were any pumps shut down for maintenance, leading to changes in flow patterns or hydraulic surges?

Conclusions:

Did a planned maintenance or operational activity in the treatment plant cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 F 13 Significant Excursion Evaluation Report Page 8 Report date: October 16th, 2004 D. Planned Distribution System Operations or Maintenance Activities ° Was a tank drained for cleaning or other maintenance? S Was the tank drained to waste or to the distribution system? S Was a larger volume than normal drained to the distribution system?

° If booster disinfection is used, was the booster disinfectant dose higher than the normal booster disinfectant dose for that season?

° Were there any system maintenance activities in the days prior to DBP excursion? Including:   Repairing mains or installing new mains   Closure of valves to isolate sections of pipes ° Were the pipes flushed properly or were the appropriate valves re opened after work was completed?

° Did any pump or pipeline maintenance occur that would have changed the flow pattern in the area the sample was drawn from? S Change in flow can cause water in stagnant areas to be drawn into another area.

° Did any pipeline replacement occur? S Disinfecting piping in contact with drinking water could result in a high concentration of chlorine entering the distribution system and thus increase DBPs.

Conclusions:

Did a planned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 F 14 Significant Excursion Evaluation Report Page 9 Report date: October 16th, 2004 E. Unplanned Distribution System Events ° Were there increases in demand that caused older water in storage tanks to be drawn into the system? S Were there any major fire events? S Did one or more storage tank have greater than average drawdown preceding the time of DBP peak excursion?

° Were there decreases in demand that resulted in longer than normal system residence times? S Were there any large customers off line?

° Did any main breaks occur causing changes in flow patterns in the influence area of the sample location?

° If you collect water temperature inside storage tanks, was the temperature inside the tank higher than normal for the season?

° Were any storage tanks hydraulically locked out of the system for an extended period and then used preceding the time of DBP peak excursion?

° Did changes in overall water demand cause a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

° Were there large variations in localized system pressures that were different from the normal pressure range that could have caused a change in water demand patterns in the vicinity of dead ends and/ or stagnant zones in the system?

Conclusions:

Did an unplanned distribution system maintenance or operational activity cause or contribute to your significant excursion( s)?

Yes No X If yes, please explain:

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 F 15 Significant Excursion Evaluation Report Page 10 Report date: October 16th, 2004 F. If you were unable to identify the cause of your significant excursion( s) after reviewing Sections A through E, are you able to identify another potential cause of your increase in DBP concentrations? Explain.

Note: If you are unable to determine the cause of your excursion you may wish to consider:

° More frequent raw water temperature monitoring. ° More frequent raw water TOC monitoring. ° Increased disinfectant residual monitoring in the distribution system. ° Tracer studies to characterize distribution system water age. ° Development of a hydraulic model to characterize the distribution system.

Attach all supporting operational or other data which led you to conclude this was the cause of your excursion( s) or make sure this data is available during your sanitary survey. Significant Excursion Guidance Manual Proposal Draft July 2003 F 16 Supplemental Data Form for the Significant Excursion Evaluation Report Report date: October 16th, 2004 Report prepared by: Robert Doe, P. E.

System name: Elm City 1) Water quality data from significant excursion sampling period.

Location No. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 Location Name TTHM ( ug/ L) 63 72 81 78 79 121 77 146 HAA5 ( ug/ L) 52 39 51 66 58 72 59 98 Free Chlorine ( mg/ L) 1.8 1.3 NA NA NA 1.1 NA 0.8 Total Chlorine ( mg/ L) 2.1 1.8 NA NA NA 1.8 NA 1.2 pH 7.9 8.0 8.3 8.1 7.8 8.3 7.5 8.2 Data relevant to peak excursions are bold and underlined.

2) Supplemental data from each treatment facility: Plant # 1: Hardwood Plant Plant # 2: Softwood Plant Raw Water Temperature: NA Raw Water Temperature: NA Plant Effluent Water Temperature: 20 ° C Plant Effluent Water Temperature: 20 ° C Raw Water TOC: 2.2 mg/ L ( Avg. < 2.0mg/ L) Raw Water TOC: 3.8 mg/ L ( Avg.< 2.0mg/ L)

Other Data: Other Data: Inf. turb. 98 ntu ( Avg. < 20 ntu)

3) Historical TTHM and HAA5 data at significant excursion sampling locations.

TTHM Data ( ug/ L) HAA5 Data ( ug/ L)

Monitoring # __ 5__ #_ 6__ #__ 7__ #__ 8__ Monitoring # __ 6__ #___ 7_ #__ 8__ #_____ Location Location Date  1999 43 58 45 49 Date  1999 57 52 56 Date  2000 51 49 56 64 Date  2000 48 39 47 Date  2001 46 69 41 69 Date  2001 45 48 33 Date  2002 48 61 73 66 Date  2002 51 56 34 Date  2003 34 44 53 79 Date  2003 45 31 43 Avg. 99 03 44 56 54 65 Avg. 99 03 49 45 43 Attach additional sheets if necessary