Elevated Lead in D.C. Drinking Water – A 

Study of Potential Causative Events, Final 

Summary Report 

Office of Water (4607M) EPA 815-R-07-021 www.epa.gov/safewater August 2007 

 

 Printed on Recycled Paper 
Authorship: 

This report was developed under the direction of EPA’s Office of Ground Water and 

Drinking Water and was prepared by HDR/EES through EPA's contract with

Environomics, Inc. Questions concerning this document should be addressed to: 

Kira Smith 

Office of Ground Water & Drinking Water 

U.S. Environmental Protection Agency 

Mail Code 4607M 

1200 Pennsylvania Avenue NW 

Washington, DC 20460-0001 

Email: Smith.Kira@epamail.epa.gov
Elevated Lead in D.C. Drinking Water – A Study of Potential Causative Events 

Final Summary Report 

Table of Contents 

EXECUTIVE SUMMARY ..............................................................................................................1

1. INTRODUCTION AND SUMMARY ..........................................................................................2

1.1 Background ..............................................................................................................................2

1.2 Purpose of Study .....................................................................................................................3

1.3 Study Findings .........................................................................................................................3

1.3.1 Combination of Factors that Contributed to Lead Release........................................3

1.3.2 Causative Events .......................................................................................................6

1.3.3 Potential Sources of Lead Release ...........................................................................8

1.4 Organization of Report ..........................................................................................................11

2. HISTORY AND EVALUATION OF LEAD MONITORING PROGRAM..................................12

2.1 Sampling Protocols ...............................................................................................................12

2.2 First-Draw Lead Results........................................................................................................13

2.2.1 Historical Data..........................................................................................................13

2.2.2 LCR 90th Percentile Reassessment........................................................................16

2.3 Second-Draw Lead Results...................................................................................................16

2.4 Designation of Optimal Corrosion Control Treatment.......................................................17

2.5 Lead Service Line Replacement Program...........................................................................20

3. WATER TREATMENT FACILITIES .......................................................................................22

3.1 Water Quality at Distribution System Entry Points ............................................................22

3.2 Findings from Sanitary Surveys of Water Treatment Facilities ........................................24

4. DISCUSSION OF DISTRIBUTION SYSTEM CONDITIONS..................................................26

4.1 Water Quality Trends.............................................................................................................26

4.1.1 pH.............................................................................................................................26

4.1.2 Alkalinity...................................................................................................................27

4.1.3 Temperature.............................................................................................................28

4.1.4 Total Chlorine...........................................................................................................30

4.1.5 Conductivity.............................................................................................................30

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4.2 Lead Sources..........................................................................................................................31

4.2.1 Lead Source Evaluation Using Lead Profiling .........................................................32

4.2.2 Source Water Lead Levels.......................................................................................36

4.2.3 Distribution Mains ....................................................................................................36

4.3 Findings from Sanitary Surveys in the Distribution System.............................................37

5. CAUSATIVE FACTORS OF ELEVATED LEAD LEVELS.....................................................38

5.1 Combination of Factors Contributed to Lead Release.......................................................39

5.1.1 Sources of Lead.......................................................................................................41

5.1.2 Historical Use of Elevated Free Chlorine.................................................................41

5.1.3 Low pH Operating Levels and pH Variations...........................................................41

5.1.4 Conversion from Elevated Free Chlorine to Chloramines .......................................41

5.2 Lead Scales and Solubility....................................................................................................41

5.2.1 Oxidation Reduction Potential (ORP) ......................................................................42

5.2.2 Lead Scales .............................................................................................................44

5.2.3 Theory and Ongoing Research Pertaining to Pb (IV) ..............................................46

5.3 Lead Release from Piping Systems and Other Lead-Bearing Materials ..........................47

5.3.1 Soluble Lead from Piping.........................................................................................47

5.3.2 Particulate Lead from Piping....................................................................................48

5.3.3 Faucets, Solder, and Other Home Plumbing...........................................................51

5.3.4 Distribution Mains ....................................................................................................52

5.4 Impacts of Historical Use of Elevated Free Chlorine Concentrations..............................53

5.5 Distribution System pH Levels and pH Variations .............................................................55

5.5.1 pH Variations............................................................................................................56

5.5.2 Spatial pH Variations ...............................................................................................58

5.5.3 Seasonal pH Variations ...........................................................................................58

5.5.4 Lower pH and Modified OCCT.................................................................................59

5.5.5 Optimal Corrosion Control Treatment (OCCT) ........................................................59

5.6 Conversion from Elevated Free Chlorine to Chloramines for Final Disinfection............61

5.6.1 LCR Monitoring Results...........................................................................................61

5.6.2 Historical Data on Wastewater Metals.....................................................................64

5.6.3 Lead Levels during Temporary Disinfectant Change...............................................64

5.6.4 Lead Profiling during Temporary Disinfectant Change............................................66

5.7 Distribution System Water Quality Characteristics............................................................74

5.7.1 Alkalinity...................................................................................................................74

5.7.2 Temperature and Specific Conductance .................................................................74

5.7.3 Natural Organic Matter.............................................................................................75

5.7.4 Nitrification ...............................................................................................................76

5.8 Galvanic Corrosion of Lead Service Lines..........................................................................76

5.9 Effect of Grounding Currents on Lead-Bearing Components...........................................78

5.10 City-Wide Meter Replacement Program ............................................................................80

5.11 Drought Conditions and Effects on Corrosivity of DCWASA Water ..............................81

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6. CURRENT STATUS OF DCWASA SYSTEM AND POSSIBLE FOLLOW-ON WORK.........85

6.1 Current LCR Compliance Status of DCWASA System.......................................................85

6.2 Possible Follow-on Evaluation.............................................................................................85

6.2.1 DCWASA-Related Follow-on Evaluations ...............................................................85

6.2.2 Research to Enhance Understanding of Lead Release ..........................................86

7. ABBREVIATIONS ..................................................................................................................89

8. REFERENCES .......................................................................................................................90

List of Tables 

Table 1. Summary of possible causative events affecting lead release .......................................6

Table 2. Summary of possible sources of lead release ................................................................9

Table 3. Monitoring program for first-draw lead samples – comparisons of DCWASA and 

HDR/EES calculations............................................................................................................15

Table 4. Monitoring program for second-draw lead samples – comparisons of DCWASA and 

HDR/EES calculations............................................................................................................17

Table 5. Minimum required pH for distribution system entry points ...........................................18

Table 6. Sources of data and information for water quality parameters .....................................26

Table 7. Disinfection regime corresponding to when profile data was collected at sites 

within the DCWASA system...................................................................................................33

Table 8. Average lead concentration and mass for profiles during the temporary disinfectant 

change (12 profiles) and chloramination (15 profiles) ............................................................35

Table 9. Summary of Optimal Corrosion Control Treatment (OCCT) Decisions and Actions.....40

Table 10. Summary evaluation of data and information – lead release from piping systems.....51

Table 11. Summary evaluation of data and information – faucets, solder, and other home 

plumbing.................................................................................................................................52

Table 12. Summary evaluation of data and information – water in distribution mains..............52

Table 13. Summary evaluation of data and information – distribution system pH variations.....61

Table 14. LCR lead results for January through June 2003 .......................................................65

Table 15. LCR lead results for March through June 2004 ..........................................................66

Table 16. Maximum lead levels measured from profiles during chloramination and periods of 

temporary disinfectant change to free chlorine ......................................................................73

Table 17. Summary evaluation of data and information – conversion from free chlorine to 

chloramines for final disinfection ............................................................................................73

Table 18. Summary evaluation of data and information – galvanic corrosion of lead service 

lines........................................................................................................................................78

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Table 19. Summary evaluation of data and information – grounding currents that affect 

corrosion of lead-bearing components...................................................................................79

Table 20. Lead release from bronze water meters in laboratory study.......................................80

Table 21. Summary evaluation of data and information – city-wide meter replacement 

program..................................................................................................................................80

Table 22. Source water quality data (1998 through 2000)..........................................................81

Table 23. Summary evaluation of data and information – drought conditions and their 

effect on corrosivity of DCWASA water..................................................................................84

List of Figures 

Figure 1. Timeline of operational events and key regulatory determinations for the DCWASA 

system......................................................................................................................................5

Figure 2. Finished water pH compared to minimum required pH at distribution system entry 

points (July 1, 2000 – June 30, 2004) ....................................................................................19

Figure 3. Average distribution system pH measured at different OWQP monitoring sites over 

different time periods. The 3-month running average pH value is shown for comparison 

(July 1, 2000 – October 26, 2004)..........................................................................................20

Figure 4. Finished water pH measured at the distribution system entry points (1998 – 2004). 

Drought periods are designated using solid and dashed lines...............................................22

Figure 5. Finished water alkalinity measured at the distribution system entry points (1998 – 

2004; no alkalinity data was available for 2000 – 2001).........................................................23

Figure 6. Finished water temperature at distribution system entry points (1998 – 2004) ...........23

Figure 7. Finished water chlorine residual concentration at distribution system entry points 

(1998 – 2004).........................................................................................................................25

Figure 8. Specific conductance of untreated water (1999 – 2002) ............................................25

Figure 9. Average daily pH of water samples collected at various sampling sites within the 

distribution system (1998 – 2004). The 3-month running average pH in the distribution 

system is shown for comparison. ...........................................................................................27

Figure 10. Average daily alkalinity of water samples collected from various sampling sites 

within the distribution system (1998 – 2004). The 3-month running average alkalinity 

value in the distribution system is shown for comparison. .....................................................28

Figure 11. Average daily pH and alkalinity of water samples collected at various sampling 

sites within the distribution system (1996 – 2004)..................................................................29

Figure 12. Average daily temperature of water collected from sampling sites within the 

distribution system (2001 – 2004) ..........................................................................................29

Figure 13. Average daily total chlorine concentration for water samples collected from various 

sampling sites throughout the distribution system (2001 – 2004). .........................................30

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Figure 14. Average daily specific conductance for water samples collected from various 

sampling sites throughout the distribution system (1998 – 2004). The 3-month running 

average specific conductance for water in the distribution system is 

shown for comparison. ...........................................................................................................31

Figure 15. Lead profile for tap water samples from House #8 

(sample collected March 9, 2004) ..........................................................................................33

Figure 16. Average mass of lead contributed from various sources for profiles experiencing a 

temporary switch to free chlorine and those exposed to chloramination disinfection 

(unadjusted for actual volume of exposure). ..........................................................................35

Figure 17. ORP (mV) vs. date for the 4th High Pressure Zone during the temporary 

disinfectant change (April 2, 2004 through May 7, 2004) and after the temporary 

disinfectant change ................................................................................................................43

Figure 18. Potential-pH diagram for the lead system corresponding to DC WASA water 

(Schock and Giani, 2004).......................................................................................................45

Figure 19. Average contribution of dissolved and particulate lead as a percentage of the total 

lead concentration in distribution system water samples (December 2003 through March 

2004) ......................................................................................................................................48

Figure 20. Lead profile data for House #22 (sample collected April 30, 2004) under conditions 

of water hammer that cause high levels of particulate lead release (Particulate Lead = Total 

Lead – Soluble Lead) .............................................................................................................49

Figure 21. Free and total chlorine residual as a function of time illustrating periods of lower 

chlorine residuals at the distribution system entry points in the early 1990s (January 1992 

through December 2004) .......................................................................................................54

Figure 22. Average free and total chlorine concentrations for water samples collected from 

different sampling sites within the distribution system (1998 -2004)......................................54

Figure 23. Average Free Chlorine Concentration (over the LCR compliance period) and 90th 

Percentile Lead vs. Time........................................................................................................55

Figure 24. Average daily pH at the distribution system entry points (Dalecarlia and McMillan) 

and in the distribution system (1998 through 2004) ...............................................................57

Figure 25. Difference between the average water pH at the distribution system entry points and 

the average pH of water collected at different sampling sites throughout the distribution 

system (1998 through 2004) ..................................................................................................58

Figure 26. Average daily pH and lead concentrations in first draw water samples before and 

after the conversion from free chlorine to chloramines as the residual disinfectant...............60

Figure 27. Lead concentrations in first draw water samples collected during different time 

intervals (July 1997 through December 2004) .......................................................................63

Figure 28. Average and 90th percentile lead concentrations in first draw water samples during 

different compliance periods (January 1992 through December 2004) .................................63

Figure 29. Average lead concentrations in first draw water samples collected during different 

months (July 1997 through October 2004).............................................................................64

Figure 30. Lead profiles for House #1 when a) chloramines were being used as the disinfectant 

(sample collected January 13, 2004) and b) during a temporary switch to free chlorine as the 

disinfectant (sample collected April 29, 2004)........................................................................68

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Figure 31. Lead profiles for House #2 when a) chloramines were being used as the disinfectant 

(sample collected February 24, 2004) and b) during a temporary switch to free chlorine as 

the disinfectant (sample collected April 26, 2004)..................................................................69

Figure 32. Lead profiles for House #3 when a) chloramines were being used as the disinfectant 

(sample collected March 30, 2004) and b) during a temporary switch to free chlorine as the 

disinfectant (sample collected April 30, 2004)........................................................................70

Figure 33. Lead profiles for House #4 when a) chloramines were being used as the disinfectant 

(sample collected March 31, 2004) and b) during a temporary switch to free chlorine as the 

disinfectant (sample collected May 7, 2004). .........................................................................71

Figure 34. Lead profiles for House #5 when a) chloramines were being used as the disinfectant 

(sample collected February 9, 2004) and b) during a temporary switch to free chlorine as the 

disinfectant (sample collected May 18, 2004). .......................................................................72

Figure 35. Average daily alkalinity and lead concentration in first draw water samples before 

and after the conversion from free chlorine to chloramines as the residual disinfectant........75

Figure 36. Surface potential along the length of directly coupled lead and copper 

service lines ...........................................................................................................................77

Figure 37. Impressed current impacts for separate DC (upper) and AC (lower) tests on surface 

potential of a lead service line coupled to copper tubing........................................................79

Figure 38. Average daily specific conductance of water at the distribution system entry points 

during drought periods ...........................................................................................................82

Figure 39. Average daily alkalinity of water at the distribution system entry points during 

drought periods ......................................................................................................................83

Figure 40. Average daily temperature of water at the distribution system entry points during 

drought periods ......................................................................................................................83

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Appendix A 

Timeline 

Summary of Administrative Orders 

Summary of Sanitary Surveys 

Supplement to History and Evaluation of Lead Monitoring Program 

Summary of Corrosion Control Studies 

Summary of Lead Service Line Replacement Program 

Summary of Correspondence on Designation of Optimal Corrosion Control Treatment 

Lead Profiles 

Appendix B 

Study Approach 

Appendix C 

Peer Review Information 
EXECUTIVE SUMMARY 

The District of Columbia Water and Sewer Authority (DCWASA) owns and operates a 

system that delivers water produced by the U.S. Army Corps of Engineers Washington 

Aqueduct (WA) to customers in Washington, D.C. During compliance monitoring for the 

Lead and Copper Rule (LCR) in July 2000 through June 2001, DCWASA exceeded the 

15-μg/L action level (AL) for lead at the 90th percentile in home tap sampling. DCWASA 

repeatedly exceeded the AL during subsequent monitoring through the period ending in 

December 2004. 

A combination of factors – not a single source or a single causative event – contributed 

to the problematic release of lead in water at consumers’ taps in the DCWASA system. 

The primary source of lead release was attributed to the presence of lead service lines 

(LSLs) in the DCWASA service area. Since the mid-1990s, three notable occurrences in 

the DCWASA system likely contributed to elevated lead releases during 2000 through 

2004. These are highlighted below. 

• During the mid-1990s, the concentration of residual free chlorine was increased to the 

range of 2.2 to 3.2 mg/L for the purpose of controlling coliform occurrence in the water 

distribution system. These relatively high free chlorine concentrations likely facilitated 

the formation of Pb (IV) scales in the form of lead dioxide (PbO2) in lead service pipes. 

These Pb (IV) scales exhibit relatively low lead solubility under normal ranges of pH 

and alkalinity in public water systems when compared to Pb (II) compounds. Lead 

scales on the interior of lead service lines are likely comprised of various forms of 

lead, including both Pb (II) and Pb (IV), and the chemical composition of the scales 

likely changes with varying water quality conditions. 

• The pH of the distributed water in Washington, D.C. exhibited seasonal variations that 

fluctuated from approximately 7.0 to 8.9 during the period from 1992 to 2004. pH 

levels at the lower end of this range would not be considered optimal for lead 

corrosion control according to the conventional understanding that forms the basis for 

the LCR and assumes the presence of Pb (II) as the dominant scale. In D.C., 

however, and as stated above, relatively high free chlorine concentrations likely 

facilitated the formation of Pb (IV) as the dominant scale, which exhibits relatively low 

lead solubility at the lower pH levels experienced in the DCWASA system. 

• On November 1, 2000, WA converted the residual disinfectant from free chlorine to 

chloramines for the purpose of lowering disinfection byproducts to meet new 

regulatory requirements. This conversion facilitated a reduction in oxidation reduction 

potential (ORP) to a range that favors the predominance of Pb (II) scales, which are 

highly influenced by low and fluctuating pH levels. This conversion from free chlorine 

to chloramines likely changed the nature of the predominant scale from Pb (IV) to 

Pb (II) and thus facilitated an increase in the release of lead from the lead service lines 

into the water at consumers’ taps. 

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1. INTRODUCTION AND SUMMARY 

This section provides the following: 

• Background information regarding operating conditions and events prior to and during 

the monitoring periods when the District of Columbia Water and Sewer Authority 

(DCWASA) exceeded the lead action level (AL) of the Lead and Copper Rule (LCR) 

during compliance monitoring in 2000 through 2004. 

• A description of the study’s purpose and an in-depth analysis of potential causative 

events. 

• A summary of the findings of the study. Possible causes of high lead levels in 

DCWASA tap samples are identified and discussed. 

• An overview and road map for the reader regarding the contents of subsequent 

sections in this report. 

1.1 Background 

DCWASA owns and operates a system that delivers water to Washington, D.C. Water is 

diverted from the Potomac River and treated at two water treatment plants, Dalecarlia 

and McMillan, operated by the U.S. Army Corps of Engineers’ Washington Aqueduct 

(WA). Both water treatment plants provide finished drinking water to the DCWASA 

service area. 

Historically, full conventional treatment has been provided using aluminum sulfate (alum) 

for coagulation, gravity filtration, free chlorine for disinfection, fluoride addition for dental 

health, and lime addition for reducing corrosion (USACE, 2006). The pH of the 

distributed water exhibited seasonal variations that fluctuated from approximately 7.0 to 

8.9 from 1992 to 2004. During the mid-1990s, WA increased the concentration of free 

chlorine to the range of 2.2 to 3.2 milligrams per liter (mg/L) for the purpose of controlling 

coliform occurrence in the DCWASA distribution system. On November 1, 2000, WA 

converted from using free chlorine to chloramines at both plants to provide a residual 

disinfectant in the distribution system less likely to form regulated disinfection 

byproducts. In August 2004, orthophosphate was added at both plants for corrosion 

control and pH levels were adjusted to accommodate this new chemical treatment. 

DCWASA met the lead AL of 15 micrograms per liter (μg/L) per the LCR during 

compliance monitoring from July 1994 through September 1999. In February 2000, 

USEPA Region 3 reduced the requirement for LCR tap monitoring to once per year at 

50 sites as allowed by the LCR. At the request of WA and DCWASA, the minimum pH 

requirement at entry points and distribution system sites was lowered and the letter of 

OCCT designation was implemented with the approval of United States Environmental 

Protection Agency (USEPA) effective July 1, 2000. 

Subsequently, average pH levels were observed to be as low as approximately 7.0 in 

the distribution system during 2001 and 2002. Reduced monitoring continued through 

the LCR compliance monitoring period of July 2001 – June 2002 because DCWASA had 

reported LCR 90th percentile monitoring results below the regulatory AL during July 

2000 – June 2001. In 2004, USEPA Region 3 reassessed 90th percentile results for the 

LCR monitoring period of July 2000 – June 2001. USEPA determined that the originally 

 2 
reported LCR 90th percentile values had not included all samples, and that the AL had 

been exceeded during the July 2000 – June 2001 LCR compliance monitoring period 

(Rizzo, 2005b). DCWASA also exceeded the AL in five LCR monitoring periods 

subsequent to the July 2000 – June 2001 monitoring period. DCWASA was required by 

USEPA to implement, among other LCR requirements that follow exceedance of the AL, 

a lead service line replacement program per the LCR. A lead service line replacement 

program was commenced in June 2003. 

1.2 Purpose of Study 

The presence of lead is pervasive in piping systems and plumbing components including 

lead service lines (LSLs), brass faucets, lead-tin solder, meters, valves, and other 

components. Lead can enter the water supply from lead-bearing materials in either the 

soluble or particulate form. 

USEPA decided to perform an in-depth analysis that would document and determine, to 

the extent possible, the source(s) and cause(s) of elevated lead levels at DCWASA 

consumers’ taps. USEPA anticipates that this evaluation, which is summarized in this 

document, can be used by USEPA, states, and public water systems to assist in their 

efforts to reduce lead in drinking water and avoid the conditions that resulted in elevated 

lead levels in Washington, D.C. in 2000 – 2004. 

1.3 Study Findings 

This section provides the following: 

• A summary of findings, including an evaluation of the combination of factors that 

contributed to lead release at consumers’ taps. 

• A description of the causative events and possible sources of lead that contributed to 

lead releases in the DCWASA service area. 

1.3.1 Combination of Factors that Contributed to Lead Release 

Figure 1 illustrates the timeline of events from 1992 to 2004 highlighting operations and 

regulatory compliance decisions, 90th percentile lead levels, shifts in disinfectants and 

pH, coliform events, and other key dates and related activities associated with lead 

released at consumers’ taps in the DCWASA service area. 

Based on a review of existing conditions and service line profiling, the primary source of 

lead release was attributed to the presence of lead service lines in the DCWASA service 

area. Since the mid-1990s, three notable occurrences in the DCWASA system likely 

contributed to elevated lead releases during 2000 through 2004. These notable 

occurrences pertained to water quality changes and conditions as described below. 

• The first notable water quality change occurred in the mid-1990s when the 

concentration of residual free chlorine was increased to 4.0 mg/L and subsequently 

maintained in the range of 2.2 to 3.2 mg/L; this change was implemented for the 

purpose of controlling coliform occurrence in the water distribution system. 

These relatively high free chlorine concentrations likely facilitated the formation of 

Pb (IV) scales in the form of lead dioxide (PbO2) in lead service lines. The 

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 4 

 

conventional understanding that forms the basis for the LCR assumes the presence 

of Pb (II) as the dominant scales. Lead scales on the interior of lead service lines are 

likely comprised of various forms of lead, including both Pb (II) and Pb (IV), and the 

chemical composition of the scales likely changes with varying water quality 

conditions. Lead dioxide scales generally exhibit relatively low lead solubility under 

normal ranges of pH and alkalinity in public water systems when compared with 

Pb (II) compounds. 

• The second notable water quality condition pertains to the fluctuating and low pH of 

the water in the DCWASA system. pH of the water is an important factor in the 

control of lead solubility. The pH of the distributed water in Washington, D.C. 

exhibited seasonal variations that fluctuated from approximately 7.0 to 8.9 during 

1992 to 2004. pH levels at the lower end of this range are not considered optimal for 

lead corrosion control based on the conventional understanding of lead solubility per 

the LCR, assuming that Pb (II) is the dominant form of scales. 

In Washington D.C., as stated above, relatively high free chlorine concentrations 

applied to the service area during the mid-1990s likely facilitated the formation of 

Pb (IV) as the dominant scale. Pb (IV) exhibits relatively low lead solubility at the 

lower pH levels experienced in the DCWASA system. Consequently, lead levels 

were low during LCR compliance monitoring during the mid-1990s. 

• The third notable water quality change occurred when WA converted the residual 

disinfectant from free chlorine to chloramines beginning November 1, 2000. The 

residual disinfectant conversion was implemented for the purpose of lowering 

disinfection byproducts to meet new regulatory requirements. This conversion 

facilitated a reduction in oxidation reduction potential (ORP) to a range that favors 

the predominance of Pb (II) scales. Pb (II) species generally are highly influenced by 

low and fluctuating pH levels. This conversion from free chlorine to chloramines 

likely facilitated the release of lead in water while operating at low, fluctuating pH 

conditions. Lead release likely increased after pH was allowed to drop further when 

the minimum pH requirements at entry points and distribution sites were lowered at 

the request of WA and DCWASA and implemented with the approval of USEPA 

effective July 1, 2000. 

In summary, the combination of the three water quality conditions described above – 

historical use of elevated free chlorine concentrations, low pH operating levels and pH 

variations, and conversion from free chlorine to chloramines – in addition to the 

presence of lead service lines in the DCWASA service area, likely caused and 

contributed to elevated lead levels during LCR compliance monitoring periods from July 

2000 through December 2004.*

 

*

 It should be noted that not all systems containing lead-bearing materials are expected to exceed 

the LCR 90th percentile for lead when implementing a switch from free chlorine to chloramines. 
Figure 1. Timeline of operational events and key regulatory determinations for the DCWASA syste

[Note: DCWASA either met the Action Level or was not required to perform monitoring from 1994 to 2000. Available LCR compliance data for DCand discussed in Section 2 of this report.] 
1.3.2 Causative Events 

This section identifies possible causative events and provides an evaluation of the 

relative contribution of each event to elevated lead levels in DCWASA consumers’ taps. 

For the purpose of this report, a causative event is defined as a notable occurrence, 

such as change in treatment or operations, or an external event or condition that 

potentially affected water quality and lead release in the DCWASA system. 

The primary source of lead release was attributed to the presence of lead service lines in 

the DCWASA service area (see Section 1.3.3). Findings pertaining to causative events 

are summarized in Table 1 and discussed below. 

Table 1. Summary of possible causative events affecting lead release

Causative Event Evidence and Likelihood of Causative Event Affecting 

Lead Release in Water at Consumers’ Taps 

Historical use of 

elevated free chlorine 

concentrations 

The increase in free chlorine concentration in the mid-1990s 

likely modified ORP conditions in the DCWASA service area 

that would facilitate a change in predominant lead scales 

from Pb (II) to Pb (IV) species. Theoretical considerations 

support the likelihood that lead solubility would be lower for 

Pb (IV) species in DCWASA water. Although the system was 

operated at low and varying pH levels, DCWASA met the AL 

during LCR compliance monitoring from 1994 to 2000. 

Distribution system pH 

levels and pH variations 

pH levels and pH variations appear to be important 

contributing factors to high lead release from scales. Low and 

varying pH levels in the system were not optimum for lead 

control, especially Pb (II) control. 

Conversion from 

elevated free chlorine to 

chloramines for final 

disinfection 

The change in disinfectant from elevated free chlorine levels 

to chloramines likely modified redox conditions that would 

facilitate a change in predominant lead scale from Pb (IV) to 

Pb (II) species. Based on available evidence, it is highly likely 

that the different oxidation-reduction potential of the water 

and responses of scales were involved in significant lead 

release, especially at low pH levels. 

Drought conditions Statistical analyses of specific conductance, alkalinity, and 

temperature were performed during drought conditions. Data 

yield no definitive trends. 

1.3.2.1 Historical Use of Elevated Free Chlorine Concentrations 

Lead scales on the interior of lead service lines are likely comprised of various forms of 

lead, and the chemical composition likely changes with changing operating conditions 

including changes in water quality. As mentioned previously, the concentration of 

residual free chlorine was increased during the mid-1990s to the range of 2.2 to 3.2 

mg/L for the purpose of controlling coliform occurrence in the water distribution system. 

 6 
These relatively high free chlorine concentrations likely facilitated the formation of Pb (IV) 

scales in the form of PbO2 in lead service lines. 

Analysis of lead service line specimens by Schock and Giani (2004) confirmed that 

tetravalent lead (Pb (IV)) scale was present on interior lead pipe surfaces in the 

DCWASA system. The Pb (IV) solid, PbO2, is thought to be much less soluble over the 

normal range of pH and alkalinity in public water systems than common Pb (II) solids 

including cerussite, PbCO3, and hydrocerussite, Pb3(OH)2(CO3)3, as described by 

Schock et al. (2001). Accordingly, the relatively high redox potential of the DCWASA 

water due to the high free chlorine concentration likely reduced the amount of lead 

release from lead pipe, and therefore, DCWASA met the AL during LCR compliance 

monitoring from 1994 to 2000. 

1.3.2.2 Distribution System pH Levels and pH Variations 

Conventional understanding of lead control in drinking water per the LCR is based on 

the presumption that Pb (II) solids control lead solubility and that manipulation of basic 

water chemistry (pH, alkalinity) can produce stable mineral forms, including cerussite 

and hydrocerussite, that passivate a corroding lead surface. Typically, lower pH levels 

contribute to higher lead solubility, and higher pH levels are associated with lower lead 

solubility. 

The Potomac River source water quality fluctuates seasonally and some of these 

fluctuations are observed in the finished water. To avoid significant calcium carbonate 

(CaCO3) precipitation, minimum pH levels in the finished water were varied seasonally 

as established by the USEPA on May 17, 2002 (retroactive to the monitoring period 

beginning July 1, 2000) as Optimal Corrosion Control Treatment (OCCT). As such, the 

pH of water entering the distribution system was purposefully varied by WA. The pH 

varied even more within the distribution system due to other factors such as seasonal 

fluctuations and site-specific conditions in the distribution system. 

Historical water quality data collected at the Dalecarlia and McMillan water treatment 

plants indicate seasonal pH fluctuations that varied from approximately 7.5 to 8.8 during 

1992 to 2004. Distributed water pH was allowed to drop further below pH 7.5 when the 

pH requirements at entry points and distribution sites were lowered at the request of WA 

and DCWASA and implemented with the approval of USEPA effective July 1, 2000. The 

lowering of average pH values during monitoring periods from July 2000 to December 

2004 is an important factor that potentially contributed to lead release in DCWASA tap 

water, especially when chloramination conditions favored the formation and dominance 

of Pb (II) scales. 

Elevated lead levels were reported during the July 2000 – June 2001 LCR monitoring 

period. pH fluctuations occurred before, during, and after the July 2000 – June 2001 

LCR monitoring period. Thus, pH fluctuations alone were not likely the cause of 

elevated lead levels. Before the disinfectant conversion to chloramines, DCWASA met 

the requirements of the LCR while using elevated free chlorine concentrations. 

DCWASA exceeded the AL for lead during the monitoring period that coincided with the 

change in disinfectant and the lowering of the operating pH level. The change in pH 

operating levels, and pH variations in the distribution system, were therefore likely 

contributing factors to elevated lead levels at consumers’ taps. 

 7 
1.3.2.3 Conversion from Elevated Free Chlorine to Chloramines for Final 

Disinfection 

On November 1, 2000, DCWASA converted from free chlorine to chloramines as the 

residual disinfectant to reduce the potential formation of regulated disinfection 

byproducts. As stated earlier, the relatively high concentration of free chlorine that was 

used for residual disinfection prior to the conversion to chloramines likely facilitated the 

formation and predominance of Pb (IV) species in lead service lines and other leadbearing components. The different oxidation potentials of elevated free chlorine and 

chloramines, and the responses of lead scales (found on lead service lines, and possibly 

other lead-bearing components) to this change in disinfectant were likely significant 

factors in the release of lead into tap water. 

Theoretical and empirical evidence documenting this potential cause of lead release 

includes the following: lead scale analysis, scale formation and solubility analysis, and 

tap sampling from lead service lines. Common Pb (IV) solids in an elevated redox 

condition, such as in the presence of elevated free chlorine, include PbO2. In 

comparison, common Pb (II) solids at lower redox conditions are generally considered to 

be predominated by lead species such as cerussite and hydrocerussite (Schock et al., 

2001). Hence, changing the oxidation-reduction state of the water through a disinfectant 

change likely increased the amount of lead release from lead pipe. The change from 

elevated levels of free chlorine to chloramines lowered the ORP of the distributed water, 

likely causing a shift in predominance from Pb (IV) to Pb (II) species, and thus facilitating 

the release of lead at consumers’ taps. 

Further, tap sampling in the form of lead profiling conducted at specific home locations 

before and after the temporary disinfectant change in 2004 provides additional 

information regarding the likelihood that this conversion was a factor in lead release by 

the service line and uptake by water passing through the pipe. 

1.3.2.4 Drought Conditions and Effects on Corrosivity of DCWASA Water 

Drought conditions may have resulted in different water quality conditions in the source 

waters that could have influenced finished water quality and corrosion potential. There 

is a substantial amount of information and data on the source water quality during these 

time periods, but it is difficult to relate it to the corrosion potential of the distributed water. 

The statistical analysis of specific conductance, alkalinity, and temperature during 

drought conditions, which was conducted as part of this investigation, does not implicate 

drought as a major factor in lead release. Drought conditions may have played a 

contributing role in increased lead corrosion; however, the impact of drought conditions 

on water quality parameters that affect corrosion was not investigated further. 

1.3.3 Potential Sources of Lead Release 

This section identifies possible sources of lead in the DCWASA system. For the 

purpose of this report, a source of lead release is defined as a piping material or 

plumbing component that contains lead, including brass faucets, lead service lines, 

solder, meters, etc. Galvanic corrosion and electrical grounding are also included in this 

discussion because these conditions can induce the release of lead from a piping 

material or plumbing component. This section also provides an evaluation of the relative 

likelihood of lead release from each of the possible sources. Findings are summarized 

in Table 2 and discussed below. 

 8 
Table 2. Summary of possible sources of lead release 

Source of Lead Evidence and Likelihood of Source Affecting Lead Release 

in Water at Consumers’ Taps 

Lead service lines Lead profiling indicates that the majority of lead released is from 

lead service lines and is predominantly in the soluble form. 

Intermittent spikes of particulate lead were noted. 

Faucets, solder, and 

other home 

plumbing 

Lead profiling indicates some contribution, but these sources are 

likely not the major contributor. Findings related to this causative 

factor are also based on reported lead release from premise 

piping components in similar plumbing systems. 

Galvanic corrosion 

of lead service lines 

Data are limited but indicate low likelihood of contribution to lead 

release. 

Grounding currents Data are limited but indicate low likelihood of contribution to lead 

release. 

City-wide meter 

replacement 

Data are limited and indicate some soluble lead release. Major 

impact on lead levels at consumers’ taps is unlikely. 

Distribution mains Published reports indicate that this source is not a meaningful 

source of lead. Some flushed samples are very low in lead levels 

and others are elevated, which is likely due to release of lead 

from service lines and premise piping rather than from 

distribution mains. 

1.3.3.1 Lead Service Lines 

Given that many service lines connected to the DCWASA distribution system are made 

of lead, and profiling indicates that the majority of lead release was from lead service 

lines, lead service lines are therefore considered the major source of lead release in the 

DCWASA system. Further, lead scales on the interior of lead service lines likely are 

comprised of a variety of compounds that co-exist in the lead scales. The conversion to 

chloramines, along with varying pH levels, likely affected the stability of scales and thus 

resulted in release of lead from the lead service lines and uptake by water at consumers’ 

taps in the DCWASA system. 

The potential exists for lead-bearing scales to be detached from the service line or home 

plumbing during plumbing disturbances and to enter the water column as particles. One 

example of this scenario is the disturbance associated with partial replacement of lead 

service lines, which results in release of lead scales from the portion of the line 

remaining in service. Particulate lead spikes do occur in tap samples, but they are 

relatively infrequent, of short duration, and thus are not likely the major factor in causing 

the sustained high lead levels at the consumers’ taps. 

1.3.3.2 Faucets, Solder, and Other Home Plumbing 

Faucets, solder, and other home plumbing can potentially contribute to total lead 

measured in water collected at the tap. Brass faucets and 50 : 50 tin : lead solder, 

 9 
historically used to join copper piping in home plumbing systems, contain lead. Lead 

profiling indicates that home plumbing components are a likely contributing source, but 

not the major source of lead in tap samples. Analogous lead profiling data also indicate 

that common end-use plumbing components contribute lead to standing water. In 

addition to site-specific lead profiling, industry data demonstrate that home plumbing 

potentially contributes to total lead. However, available data do not provide compelling 

evidence that faucets, solder, and other home plumbing were predominant lead 

contributors in the DCWASA service area. 

1.3.3.3 Galvanic Corrosion of Lead Service Lines 

In the service lines and premise piping systems, there are sites where lead and other 

metals are directly connected, resulting in galvanic couplings. The coupling of these 

dissimilar metals could result in the release of lead to the water. There is very little 

information on this potential cause and no site-specific data are available for review. A 

laboratory investigation of this issue conducted by Reiber and Dufresne (2005) regarding 

DCWASA conditions indicates that galvanic couplings likely contribute very little to lead 

release. 

1.3.3.4 Grounding Currents that Affect Corrosion of Lead-Bearing Components 

It is possible that lead may be released to the water column at sites where the electrical 

systems have been grounded to water piping systems. There is very little information on 

the potential effect of grounding currents on corrosion of lead-bearing materials, and no 

site-specific data are available. An investigation of this cause conducted by Reiber and 

Dufresne (2005) regarding DCWASA conditions indicates that grounding likely 

contributes very little to lead release. 

1.3.3.5 City-Wide Meter Replacement Program 

There are two potential sources of lead release and uptake by the water associated with 

meter replacement: (1) disturbance of adjacent piping, causing release of scales 

containing lead (particles); and (2) release of soluble lead directly from the meter itself 

due to water chemistry. There are data available on water quality conditions and the 

effect on lead release from meters in a site-specific study (Keefer and Giani, 2005). 

However, little or no data are available on the potential release of particulate lead 

associated with meter replacement. Testing of meters for lead release indicated that 

some release occurred, but the contribution is small and likely not a major contributor to 

elevated lead at the tap. 

1.3.3.6 Distribution Mains 

Water in the utility’s distribution mains was assessed during this study by reviewing 

pertinent reports and by evaluating lead profiling data collected after a thorough flushing 

of the tap for a period considered sufficient to bring fresh water in from the main. The 

reports (Keefer and Giani, 2005; Giani et al., 2005a) indicate that lead from the 

distribution system is very low. However, lead profiling yielded conflicting data regarding 

the presence and contribution of lead in the distribution mains. Many flushed samples 

were reported at detection limits for lead, but others were reported at elevated lead 

levels. The higher than expected lead levels could have been caused by either release 

of lead from components in the utility system, or by release of lead from the lead service 

 10 
lines or premise piping and plumbing. Based on available data and information, it is the 

study team’s best professional judgment that the distribution system components were 

not a major contributing factor in lead levels at consumers’ taps. 

1.4 Organization of Report 

This section (Section 1) summarizes the findings of a study conducted by HDR/EES to 

document and evaluate the potential causative events and parameters contributing to 

the elevated lead levels in the Washington, D.C. drinking water system. The remaining 

sections of this report provide supporting data, information, and discussion. The 

contents of the remaining sections of this report are highlighted below. 

• Section 2 describes the history of DCWASA’s lead monitoring program and 

HDR/EES’s independent evaluation of reported compliance data. 

• Section 3 provides documentation of reported water quality data at distribution 

system entry points (i.e., the Dalecarlia and McMillan Water Treatment Plants) and 

findings from sanitary surveys of water treatment facilities. 

• Section 4 provides documentation of water quality data collected in the distribution 

system, identification of the occurrence and evaluation of lead sources, and findings 

from sanitary surveys in the distribution system. 

• Section 5 provides an evaluation of the combination of factors that contributed to the 

problematic release of lead. This section also provides an in-depth discussion of 

causative factors that potentially contributed to elevated lead levels including each of 

the possible causative events (i.e., historical use of elevated free chlorine 

concentrations; distribution system pH levels and pH variations; conversion from free 

chlorine to chloramines for final disinfection; and drought conditions) and each of the 

identified possible sources of lead release (i.e., lead service lines; faucets, solder, 

and other home plumbing; galvanic corrosion of lead service lines; grounding 

currents; city-wide meter replacement; and distribution mains). 

• Section 6 provides a brief summary of the current LCR compliance status of the 

DCWASA system and it identifies possible follow-on work based on available 

findings and conclusions drawn from this study. 

Documents prepared as part of this evaluation include: (1) this Summary Report, 

(2) supporting hard copy materials in three-ring binders, and (3) a data evaluation report 

per the requirements of the Quality Assurance Project Plan (QAPP). 

 11 
2. HISTORY AND EVALUATION OF LEAD MONITORING 

PROGRAM 

This section includes the following: 

• The sampling protocols used for first- and second-draw sampling. 

• DCWASA’s 90th percentile calculations for first- and second-draw lead results and 

HDR/EES’s reassessment of those results. 

• USEPA Region 3 designation of OCCT. 

• Description of DCWASA’s lead service line replacement program. 

USEPA Region 3 provided HDR/EES with laboratory sample reports; 90th percentile 

calculations; and correspondence related to LCR monitoring, including first-draw and 

second-draw samples. To facilitate data evaluation, hard copies of LCR compliance 

data were entered into Excel® spreadsheets. In addition, HDR/EES received electronic 

data files containing compliance monitoring data for the compliance periods of January 

through June and July through December of 2004. 

2.1 Sampling Protocols 

First- and second-draw samples were analyzed for lead, copper, and iron using EPA 

Method 200.8 at WA’s certified laboratory. In addition, USEPA Region 3 provided 

correspondence on designation of OCCT. 

It appears that first-draw samples were collected by homeowners per LCR protocol. 

Although not required by regulations, homeowners have routinely collected a seconddraw sample from their taps as well as requested by DCWASA. The protocol for 

collecting this second-draw sample has changed through the years as described below. 

DCWASA’s 2004 sampling instructions directed homeowners to collect first-draw 

samples after a 6- to 8-hour period of no water use. The second-draw sample was 

collected at the same tap after allowing the water run at a slow pace until the water 

turned cold. Prior to 2004, second-draw samples were collected immediately after the 

first-draw sample without allowing the water to run until there was a temperature change 

(Rizzo, 2005b). G. Rizzo of USEPA Region 3 estimated that DCWASA had been using 

this sampling procedure for second-draw samples for several years prior to the LSL 

replacement program, which commenced in 2003 (Rizzo, 2005b). 

Prior to June 2002, information was not readily available regarding the recommended 

protocol, nor were specific instructions on whether to remove the faucet aerator device 

when collecting tap samples for LCR monitoring. In June 2002, which corresponds to 

the last month of the July 1, 2001 through June 30, 2002 monitoring period, customers 

were instructed to remove aerators. Following this, for the January 1 to June 30, 2003 

full monitoring period, customers were again instructed to remove the devices before 

sampling. This changed from the July 1 to December 31, 2003 monitoring period 

onward, when customers were instructed to leave the aerators in place. Currently, these 

instructions requiring customers to leave the aerators in place are still provided as the 

appropriate sampling protocol (Smith, 2006). Similarly, instructions or a protocol for 

 12 
removal of point-of-use (POU) treatment devices during LCR sampling were not defined 

until 2004 (Rizzo, 2004). 

The relevance of both the aerator removal protocol and POU devices to lead levels and 

LCR monitoring are discussed in Section 5 of this report. 

2.2 First-Draw Lead Results 

This section provides documentation of historical LCR first-draw lead sampling results as 

reported by DCWASA and an evaluation of these data by HDR/EES. This section also 

provides a summary of the 90th percentile reassessment by USEPA. 

2.2.1 Historical Data 

For LCR first-draw lead results, 90th percentile calculations prepared by DCWASA were 

reviewed and re-calculated using either tabular data, laboratory data sheets, or Excel 

spreadsheet data received from USEPA (tabular data and laboratory data sheets from 

Data Binder 1 of 3 for Elevated Lead in D.C. Drinking Water – A Study of Potential 

Causative Events, prepared by HDR/EES October 13, 2006; Excel spreadsheet data for 

LCR compliance period of July – December 2004 received from USEPA). The results of 

this analysis are summarized in Table 3, where values in bold indicate differences 

between DCWASA results and results obtained by HDR/EES. These differences involve 

total sample count, numerical ordering of sample results in the 90th percentile 

calculations, and/or removal of duplicate compliance sites. 

For comparison with the DCWASA results, HDR/EES calculated different values for 90th 

percentile lead levels and/or the percentage of samples exceeding the AL for the 

following monitoring periods: 

• July – December 1992 

• July – December 1993 

• January – June 1994 

• January – June 1999 

• July – December 2003 

• January – June 2004 

• July – December 2004 

For the monitoring period from July to December 1992, DCWASA’s 90th percentile lead 

level does not exceed the AL, whereas the 90th percentile lead level calculated by 

HDR/EES does exceed the AL. For the monitoring periods July – December 1993 and 

January – June 1994, the 90th percentile lead levels calculated by HDR/EES are lower 

than the 90th percentile lead level calculated by DCWASA. Both DCWASA and 

HDR/EES calculations show that the 90th percentile lead level was greater than the 15-

μg/L AL during every monitoring period in years 2001 through 2004. 

 13 
A review of the July – December 1992 laboratory sampling information found that 30 of 

the 125 samples exceeded the 15-μg/L action level for lead, but 15 of these 30 samples 

were not listed in numerical order in DCWASA’s 90th percentile calculations. When the 

sample results were listed in numerical order, and duplicates were removed, the 

resulting 90th percentile value calculated by HDR/EES was 39 μg/L compared with 15 

μg/L reported by DCWASA. 

For the January – June 1993 period, the total sample count appeared to be 115 

compared with 114 in DCWASA’s calculations; however, the 90th percentile result was 

not affected. For the July – December 1993 period, four sites were originally listed as 

duplicate samples; however, an additional six sites were found to also have been 

sampled twice during this period, and one site was sampled three times. DCWASA 

included all results from these sites in its calculations, and included all duplicate sites in 

its sample count, for a total sample count of 131. HDR/EES’s calculations used only one 

value from these six additional duplicate addresses and one triplicate (the highest 

value), for a total sample count of 119, and calculated a lower 90th percentile value than 

DCWASA. By way of background, USEPA regulations, as clarified in a memorandum 

dated November 23, 2004 (Grumbles, 2004), now require that all sample results from a 

system’s sampling pool be used in compliance calculations during the LCR monitoring 

period. If confirmation samples are taken, both the original and confirmation must be 

used in the 90th percentile calculation. 

For the July – December 1997 and July – December 1998 compliance periods, 

HDR/EES identified a different number of valid compliance samples; however, the 

calculated 90th percentile result did not differ. For the January – June 1999 period, 

laboratory sampling reports indicate that 17 first-draw samples had a lead concentration 

of “<10 ppb”; however, DCWASA’s 90th percentile calculations, which converted the 

data to mg/L, show no samples with a lead concentration of <0.010 mg/L, which is 

equivalent to <10 ppb. Two samples listed in DCWASA’s 90th percentile calculations 

(0.031 mg/L and 0.055 mg/L) could not be confirmed by the laboratory sample reports. 

Also, DCWASA’s 90th percentile calculations show a total of 106 first-draw samples, but 

the laboratory summary report indicates only 81 first-draw-samples. Thus, HDR/EES’s 

calculation resulted in a different 90th percentile lead level. 

For the remainder of the compliance periods, where differences in either 90th percentile 

calculations and/or percentage of samples greater than the AL were calculated (July – 

December 2003; January – June 2004; July – December 2004), the differences were 

relatively minor and could be attributed to the number of valid samples, 90th percentile 

calculations, or differences in hard copy tabular data versus Excel spreadsheet data. In 

all of these compliance periods, both DCWASA and HDR/EES calculated 90th percentile 

values above the AL. 

 14 
Table 3. Monitoring program for first-draw lead samples – comparisons of 

DCWASA and HDR/EES calculations 

DCWASA Results HDR/EES Results Reason for Different Results

Monitoring 

Period 

N 

90th 

Percentile 

Lead 

(μg/L) 

% 

Samples 

Lead 

Conc. 

> 15 μg/L 

N 

90th 

Percentile 

Lead 

(μg/L) 

% 

Samples 

Lead 

Conc. 

> 15 μg/L 

Jan – Jun 

1992 129 18 12 128 18 12 One duplicate value removed. 90th percentile result not affected. 

Jul – Dec 

1992 125 15 10 122 39 22 

Three duplicate values removed, 

plus difference in other valid 

samples used. 90th percentile result 

affected. 

Jan – Jun 

1993 114 11 4 115 11 4 One additional sample. 90th 

percentile result not affected. 

Jul – Dec 

1993 131 37 21 119 29 19 

One triplicate and 11 duplicate 

samples removed, plus difference in 

total number of valid samples. 90th 

percentile result affected. 

Jan – Jun 

1994 114 22 14 114 14 8 

Five data points not confirmed by 

laboratory reports. 90th percentile 

results affected. 

Jul – Dec 

1994 115 12 7 115 12 7 NA 

Jan – Jun 

1997 112 6 4 112 6 4 NA 

Jul – Dec 

1997 115 8 4 114 8 4 One duplicate value removed. 90th 

percentile result not affected. 

Jul – Dec 

1998 108 7 4 100 7 4 

Five duplicates and three raw water 

samples removed. 90th percentile 

result not affected. 

Jan – Jun 

1999 106 5 6 81 <10 4 

Difference in total number of valid 

samples and conversion from ppb to 

mg/L. 90th percentile result affected.

Jul–Sep 

1999 55 12 5 55 12 5 NA 

Jul 2000 – 

Jun 2001 50 8 8 50 8 8 NA 

Jul 2000–

Jun 2001 

(revised 

calculations

- see 2.2.2) 

52 36 17 53 36 17 One additional sample included. 

90th percentile result not affected. 

Jul 2001 – 

Jun 2002 53 75 49 53 75 49 NA 

Jan – Jun 

2003 104 40 26 104 40 26 NA 

July – Dec 

2003 108 63 32 108 61 32 

Difference in 90th percentile 

calculation method. 90th percentile 

result affected. 

Jan – Jun 

2004 108 59 68 108 58 68 

Difference in 90th percentile 

calculation method. 90th percentile 

result affected. 

Jul – Dec 

2004 130 59 31 142 51 28 

Difference in number of valid 

samples due to difference in hard 

copy versus Excel spreadsheet 

data. 90th percentile result affected.

N = Number of samples used in 90th percentile calculation; NA = Not Applicable 

Note: Bold: Values in bold font indicate differences between HDR/EES and DCWASA calculations. 

 15 
2.2.2 LCR 90th Percentile Reassessment 

DCWASA met the lead AL of 15 μg/L per the LCR during compliance monitoring from 

July 1994 through September 1999. As allowed by the LCR, in February 2000 USEPA 

Region 3 reduced the requirement for LCR tap monitoring to once per year at 50 sites. 

The DCWASA system continued the reduced monitoring through the July 2001 – June 

2002 monitoring period, because DCWASA had reported an LCR 90th percentile value 

below the AL during the July 2000 – June 2001 LCR monitoring period. In 2004, USEPA 

Region 3 determined that DCWASA had not included all sample results in its original 

90th percentile calculations for the July 2000 to June 2001 period. As listed in Table 3, 

USEPA Region 3 recalculated the 90th percentile lead level for this monitoring period 

using all sample results (Rizzo, 2005b). This reassessment showed that the 90th 

percentile lead level during the July 2000 – June 2001 monitoring period was not 8 μg/L, 

as originally reported by DCWASA, but it was actually higher at 36 μg/L, which exceeded 

the AL. 

2.3 Second-Draw Lead Results 

DCWASA requested that homeowners collect second-draw samples from 1997 through 

2004. For the 1997 monitoring periods, second-draw samples were collected and 

analyzed, but 90th percentile values were not calculated or reported by DCWASA. 

Second-draw sample results are not used for LCR compliance purposes; however, 90th 

percentile lead values were calculated for comparison to the AL. HDR/EES reviewed 

lead concentrations in second-draw samples, checked results against laboratory sample 

reports, converted hard copy data to digital form, and calculated 90th percentile values. 

The results of this analysis are summarized in Table 4. In summary, 90th percentile 

calculations for second-draw samples were greater than 15 μg/L in the July – September 

1999 monitoring period, and in every monitoring period from 2001 to 2004. 

Differences in results were found for the following monitoring periods: July – December 

1998; January – June 1999; January – June 2004; and July – December 2004. These 

differences, highlighted in bold in Table 4, involve differences in total sample count 

and/or numerical ordering of sample results in the 90th percentile calculations. 

For example, in the July – December 1998 monitoring period, 99 second-draw samples 

were collected. Therefore, the 90th percentile lead concentration should be equal to the 

lead concentration of the 89th sample with samples listed in ascending order of lead 

concentration. This 89th sample is equal to 7.0 μg/L; therefore, the 90th percentile lead 

concentration is determined to be 7.0 μg/L compared with 6.6 μg/L calculated by 

DCWASA. DCWASA did not provide details or documentation of the procedure used for 

calculating the 90th percentile. 

For the January – June 1999 period, laboratory sampling reports indicate that 15 

second-draw samples had a lead concentration of “<10 ppb”; however, DCWASA’s 90th 

percentile calculations, which converted the data to mg/L, show no samples with a lead 

concentration of <0.010 mg/L, which is equivalent to <10 ppb. One sample listed in 

DCWASA’s 90th percentile calculations (0.022 mg/L) could not be confirmed by the 

laboratory sample reports. Also, DCWASA’s 90th percentile calculations show a total of 

105 second-draw samples, but the laboratory summary report indicates only 79 seconddraw samples. Thus, HDR/EES’s calculation resulted in a different 90th percentile lead 

level. 

 16 
Table 4. Monitoring program for second-draw lead samples – comparisons of 

DCWASA and HDR/EES calculations 

DCWASA Results HDR/EES Results 

Reason for 

Different Results 

Monitoring 

Period N

90th 

Percentile 

Lead 

Conc. 

(μg/L) 

% 

Samples 

Lead 

Conc. 

> 15 μg/L 

N

90th 

Percentile 

Lead Conc. 

(μg/L) 

% Samples 

Lead Conc. 

> 15 μg/L 

Jan – Jun 1997 - - - 93 7 5 NA 

Jul–Dec 1997 - - - 109 7 4 NA 

Jul–Dec 1998 108 6.6 3 105 7 3 90th percentile 

calculation 

Jan – Jun 1999 106 4 4 78 <10 4 

Number of valid 

samples; data 

conversion from 

ppb to mg/L; one 

data point not 

confirmed by 

laboratory report 

Jul–Sep 1999 55 15 9 55 15 9 NA 

Jul 2000–Jun 

2001 50 11 6 50 11 6 NA 

Jul 2000–Jun 

2001 (revised 

calculations by 

USEPA Region 

3) 

- 34 15 58 34 15 NA 

Jul 2001–Jun 

2002 53 80 46 52 80 46 NA 

Jan – Jun 2003 104 21 17 104 21 16 NA 

Jul–Dec 2003 108 43 27 108 43 27 NA 

Jan – Jun 2004 108 75 60 109 73 60 Number of valid 

samples 

Jul–Dec 2004 130 45 28 134 42 28 Unknown* 

N = Number of samples used in 90th percentile calculation; NA = Not Applicable 

Note: DCWASA did not calculate or report second-draw lead concentrations for the two monitoring periods in 1997. 

*DCWASA’s reported 90th percentiles were presented in a cover letter, but calculation details were not available. 

Bold: Values in bold font indicate differences between HDR/EES and DCWASA calculations. 

2.4 Designation of Optimal Corrosion Control Treatment 

In July 1997, USEPA Region 3 conditionally designated OCCT as maintenance of a 

slightly positive Langelier Saturation Index (LSI) through pH adjustment. As a condition 

of this designation, USEPA Region 3 issued an Administrative Order requiring WA and 

DCWASA to jointly assess the feasibility of alternative corrosion control treatment 

including use of sodium hydroxide for pH control, and use of a non-zinc orthophosphate 

corrosion inhibitor. 

Modeling results from the caustic soda study (Malcolm Pirnie Inc., 1998a) indicated that 

excessive calcium carbonate precipitation would occur if a pH of 8.5 was maintained 

throughout the year using either lime or caustic soda. The study also concluded that 

caustic soda would provide some benefits in terms of process control and maintenance 

requirements. The corrosion inhibitor study (Malcolm Pirnie Inc., 1998b) concluded that 

zinc orthophosphate would not provide any long-term benefits over orthophosphate in 

 17 
controlling lead levels in the water, and the chemical costs for zinc orthophosphate are 

approximately twice the chemical costs for phosphoric acid. The corrosion inhibitor 

study recommended that phosphoric acid be used at a dosage rate of 1.0 mg/L as 

phosphate (PO4) if WA decided to use corrosion inhibitors as a lead control strategy. 

On February 29, 2000, USEPA Region 3 designated the use of pH adjustment as the 

OCCT for the systems served by WA. This designation required WA to maintain the 

highest pH level attainable at the entry points to the distribution system without causing 

excessive CaCO3 precipitation in the distribution system (USEPA, 2000). 

USEPA Region 3 also designated Optimal Water Quality Parameters (OWQP), 

including an enforceable minimum pH of 7.7±0.3 to be maintained at the entry points to 

the distribution system and at all tap sample locations. In response to this designation, 

DCWASA and WA proposed modifications to the OWQP that would allow the minimum 

finished water pH requirement to change monthly to account for seasonal water quality 

changes in the Potomac River, as summarized in Table 5. DCWASA and WA also 

proposed a change to the minimum pH requirement at distribution system sites from 7.7 

to 7.0 (source: correspondence from DCWASA and WA, respectively, to USEPA Region 3

 on May 1 and May 3, 2000). Two years later, on May 17, 2002, the USEPA revised 

its designation of OWQP by approving WA’s and DCWASA’s proposal, and indicated the 

effective date was retroactive to the monitoring period that began on July 1, 2000. 

Table 5. Minimum required pH for distribution system entry points 

Month Minimum 

pH Month Minimum pH Month Minimum pH 

January 7.7 May 7.5 September 7.4 

February 7.8 June 7.4 October 7.5 

March 7.7 July 7.4 November 7.5 

April 7.6 August 7.4 December 7.6 

Figure 2 shows finished water pH at both distribution system entry points (Dalecarlia and 

McMillan Water Treatment Plants) and the required minimum pH. The pH at the 

Dalecarlia entry point has been below the established minimum pH only five times (<1% 

of data collected) since the OWQP designation became effective July 1, 2000. The pH 

at the McMillan entry point to the distribution system has been below the established 

minimum pH only one time (<1% of data collected) since July 1, 2000. Finished water 

pH levels routinely ranged from about 7.7 up to 8.5 and greater. 

 18 
Figure 2. Finished water pH compared to minimum required pH 

at distribution system entry points (July 1, 2000 – June 30, 2004) 

9.0

8.5

8.0

7.5

7.0

6.5

Jul-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Dec-03 Jun-04 Dec-04

Dalecarlia Plant McMillan Plant Minimum pH required

pH

On April 30, 2004, USEPA Region 3 designated use of zinc orthophosphate for partial 

system application in the 4th High Pressure Zone. This is a designated zone in 

northwest Washington, D.C. that is hydraulically isolated from the rest of the distribution 

system (USEPA, 2004b, 2006). On May 28, 2004, USEPA Region 3 modified the April 

30, 2004 designation of OCCT to use orthophosphate instead of zinc orthophosphate for 

the 4th High Pressure Zone. 

On August 3, 2004, USEPA Region 3 modified the interim designation of OCCT for WA 

and DCWASA to consist of application of orthophosphate system-wide, subject to stated 

conditions and water quality parameters. The interim OCCT designation was slightly 

modified and clarified on August 20, 2004 and September 8, 2004. USEPA Region 3

stipulated that, during the distribution system passivation period, WA was required to 

meet a pH range of 7.7 ± 0.3 for finished water leaving both water treatment plants. A 

goal of 7.7 ± 0.1 was set, though this was not enforceable. For distribution system 

samples, the same enforceable pH range (7.7 ± 0.3) and non-enforceable pH goal 

(7.7 ± 0.1) was applied to DCWASA. 

 19 
Figure 3 shows the average distribution system pH at the 12 OWQP Monitoring Sites in 

the DCWASA distribution system from July 1, 2000 through October 26, 2004. The 12 

OWQP Monitoring Sites were identified by DCWASA in correspondence to USEPA 

Region 3 dated May 1, 2000. For OWQP monitoring through the date of the USEPA’s 

designation of orthophosphate treatment (July 1, 2000 through August 3, 2004), results 

show the minimum pH was 7.0, thus demonstrating compliance with the OWQP 

minimum pH of 7.0. After designation of orthophosphate treatment, OWQP monitoring 

results were reported through October 26, 2004. Where sufficient data are available, the 

3-month running average is shown as a solid line in Figure 3. 

Figure 3. Average distribution system pH measured at different OWQP monitoring sites 

over different time periods. (July 1, 2000 – October 26, 2004) 

Solid line = 3-month 

running average

9.0

8.5

8.0

pH

7.5

7.0

6.5

Jul-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Dec-03 Jun-04 Dec-04

 

2.5 Lead Service Line Replacement Program 

Since 2002, DCWASA has been required to replace 7% of the lead service lines on an 

annual basis due to AL exceedance. 

• In September 2003, DCWASA updated its inventory of lead service lines and 

estimated that of the system’s 120,000 service connections, 23,071 were lead 

service lines. On October 24, 2003, DCWASA reported that during the period 

October 1, 2002 to September 20, 2003, it had replaced 385 lead service lines 

through physical replacement including 79 “full” replacements and 306 “partial” 

replacements (DCWASA Lead Service Replacement Program Annual Report for 

2003; USEPA Region 3, June 17, 2004). 

 20 
A partial lead service line replacement (PLSLR) means that something other than the 

entire length of the service line is replaced (Code of Federal Regulations, Title 40, § 

141.84(d)). Title 40 CFR §141.84 requires that a public water system replace the 

portion of the lead service line owned by the system, but does not require that the 

system bear the cost of replacing portions of the line that the system does not own. 

• On October 8, 2004, DCWASA reported that it had replaced 1,793 lead service lines 

for the period October 1, 2003 to September 30, 2004 (DCWASA Lead Service 

Replacement Program Annual Report for 2004). No details were provided in the 

2004 report on full versus partial replacements. 

Full and partial lead service line replacements can disturb protective scales on pipes or 

connected components and thus cause the release of lead. The full and partial lead 

service line replacements that have been undertaken by DCWASA are not considered 

major factors in elevated lead release during LCR compliance monitoring beginning July 

2000 because the LSL replacement program did not commence until lead levels were 

already elevated. DCWASA failed to meet the 90th percentile AL during July 2001 

through December 2004, and the LSL replacement program was triggered by failure of 

DCWASA to meet the 90th percentile AL. Accordingly, LSLs were replaced during the 

timeframes of October 1, 2002 through September 30, 2003 and October 1, 2003 

through September 30, 2004. Further evaluation of DCWASA’s LSL replacement 

program could help determine the extent to which lead service line replacement may 

have contributed to elevated lead levels at overall or at individual consumers’ taps during 

later periods of exceedance. 

Follow-up monitoring required by the LCR at monitoring locations during 2002 through 

2004 may have recorded spikes or temporary elevated lead levels due to scale 

disturbance, possibly exacerbated by cutting and replacement techniques (Wujek, 2005; 

Boyd et al., 2004). Although not clear, the LCR definitions of Tier 1 sampling sites do not 

appear to exclude partial LSL replacement sites from continuing as Tier 1 sampling sites 

(40 §141.86 (3), (i), (ii)). As such, the impact of the PLSLR program could have 

contributed to elevated lead levels in compliance monitoring data during 2002 through 

2004 if the PLSLR sites were used for subsequent compliance monitoring. Without 

additional information, it is difficult to assess or disregard the effects of PLSLR 

techniques on elevated lead levels overall or at individual homes where replacements 

were made. Additional analyses of LSLR sites compared to compliance monitoring sites 

during 2002 through 2004 would therefore be needed to determine if the LSLR program 

affected compliance monitoring results at LCR monitoring locations. 

 21 
3. WATER TREATMENT FACILITIES 

This section describes the following: 

• Water quality data collected at the two entry points to the distribution system. 

• Findings from 1999 and 2003 sanitary surveys of WA-owned facilities. 

Data for analysis of water treatment facilities were compiled from daily water quality 

monitoring results from the Dalecarlia and McMillan plants and from sanitary surveys of 

WA and DCWASA facilities. 

3.1 Water Quality at Distribution System Entry Points 

WA collects daily samples for chlorine residual, temperature, pH, and alkalinity at the 

two entry points to the distribution system located at the Dalecarlia and McMillan Water 

Treatment Plants. HDR/EES reviewed water quality data from 1998 through mid-2004 

with the exception of alkalinity data, which were not available for years 2000 – 2001. 

The review of water quality data showed that the two water treatment plants produce 

water with similar variations in temperature, pH, and alkalinity. As shown in Figure 4, the 

pH of samples collected at the distribution system entry points generally varied 

seasonally from 7.7 to 8.5. Figure 5 shows that alkalinity varies widely, typically ranging 

from about 40 to 100 mg/L as CaCO3 in recent years. Water temperature, shown in 

Figure 6, varies seasonally from about 35 to 85°F. 

Figure 4. Finished water pH measured at the distribution system entry points (1998 – 

2004). Drought periods are designated using solid and dashed lines 

First 

Drought 

Period

Second 

Drought 

Period

9.0

8.5

8.0

pH 

7.5

7.0

6.5

Jan-98 Jun-98 Dec-98 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Dec-03 May-04 Nov-04

Dalecarlia McMillan

 22 
Figure 5. Finished water alkalinity measured at the distribution system entry points (1998 – 

2004; no alkalinity data was available for 2000 – 2001) 

160

140

120

) 3 OCa100 as C L/g

80

my (itnkali

60

lA

40

20

0

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

Dalecarlia McMillan

Figure 6. Finished water temperature at distribution system entry points (1998 – 2004) 

100

90

80

F)

70 o e (rut

60

erampeT

50

40

30

20

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

Dalecarlia McMillan

 23 
Figure 7 illustrates chlorine residuals for samples collected at the Dalecarlia and 

McMillan plants for years 1998 – 2004. These data were provided electronically as 

Excel spreadsheets. Results were reported as free chlorine prior to November 1, 2000 

(disinfectant conversion) and as total chlorine afterward. Prior to the conversion, free 

chlorine results indicate fluctuations ranging from approximately 2.2 to 3.2 mg/L. After 

the conversion, chlorine residual increased and total chlorine measurements typically 

ranged from 3.3 to 3.9 mg/L. Since fall 2003, total chlorine appears to have stabilized in 

the typical range of 3.5 to 4.0 mg/L. 

WA has analyzed the conductivity of untreated water on a monthly basis since 1999. 

HDR/EES reviewed the available untreated water conductivity data from 1999 through 

2002, as presented in Figure 8. Conductivity appears to vary seasonally, increasing in 

the second half of each year and occurring at lower levels during the spring and early 

summer. The average conductivity of the source water was 318 micromhos per 

centimeter (1 micromhos per centimeter = 1 microsiemen per centimeter), and 3-month 

average values ranged from 238 to 437 micromhos per centimeter. 

3.2 Findings from Sanitary Surveys of Water Treatment Facilities 

HDR/EES reviewed sanitary surveys of facilities owned by WA. The contents of the 

sanitary surveys are described below. 

• The 1999 sanitary survey documented 73 potential sanitary risks, such as the need 

for a comprehensive watershed protection program for the Dalecarlia Reservoir, and 

for updating standard operating procedures for water treatment process operations. 

At the time of the 2003 survey, 21 of these 73 potential sanitary risks had been fully 

addressed; 11 had been partially addressed; 7 were no longer applicable to the WA 

system; and 34 were not addressed. 

• The 2003 sanitary survey team identified 37 sanitary deficiencies, including 32 of the 

45 sanitary risks identified in the 1999 survey that had not been addressed or only 

partially addressed. These 37 sanitary deficiencies included development of a 

comprehensive cross connection control program; development of a comprehensive 

watershed protection program for the Dalecarlia Reservoir; updating of standard 

operating procedures for water treatment process operations; an optimization 

program for each water treatment plant (WTP) including detailed filter evaluations; 

development of procedures to minimize hydraulic changes in filter operations during 

backwash; and clearwell modifications to minimize vandalism and pathogen intrusion. 

It is difficult to determine whether findings from these sanitary surveys had any influence 

on tap lead levels. Further examination of pre-1999 sanitary survey data for water 

treatment facilities may provide more information about events that preceded elevated 

lead release. Sanitary survey results specific to the distribution system are also 

discussed in Section 4 and include data prior to 1999. 

 24 
Figure 7. Finished water chlorine residual concentration at distribution system entry 

points (1998 – 2004) 

5.0

4.0

(mg/L) tion 

3.0

ranteoncne C2.0 Chlori

1.0

0.0

Jan-98 Jun-98 Dec-98 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Dec-03 May-04

Dalecarlia McMillan

Disinfection using Free Chlorine Disinfection using Chloramines

Figure 8. Specific conductance of untreated water (1998 – 2002) 

500

450

400

cm)

350

S/ μ (ce

300

ctanu

250

ndc Co

200

ecifi

150

Sp

100

50

0

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

Untreated Water 3-month Average - Untreated Water

 25 
4. DISCUSSION OF DISTRIBUTION SYSTEM 

CONDITIONS 

This section discusses: 

• Conditions in the DCWASA distribution system from 1998 – 2004 including water 

quality trends, lead sources, and other relevant findings from sanitary surveys. 

• Available data and information used to identify the major lead sources in or 

connected to the distribution system. 

4.1 Water Quality Trends 

Water quality data collected in the distribution system are reported here as daily average 

parameters for years 1998 through 2004. Data were provided either in digital format or 

as hard copy laboratory reports or a combination of both. Data were provided in digital 

format for pH, temperature, free and total chlorine, conductivity, and sampling location 

for 2001 through 2004. Distribution system pH and alkalinity data were also provided in 

hard copy reports for years 1998 to 2004. Data and sampling locations included in hard 

copy reports were transcribed into Excel spreadsheets. Available data and information 

were then combined into a single spreadsheet. Daily averages were calculated for each 

parameter based on all available data by sampling location for the years 1998 through 

2004. The total number of sampling locations varied by period and parameter; that is, 

the average value for a given day could have been based on one sampling location or 

15 locations, depending on available data. For sampling periods with both hard copy 

and digital formats available, the digital format was used in this report. 

Table 6 summarizes the sources of data and information that are discussed in Sections 

4 and 5 of this report. Updated water quality data, sampling dates, and sampling 

locations are included in the three-ring binders as supplemental information for this final 

report. 

Table 6. Sources of data and information for water quality parameters 

Parameter Hard Copy Reports a Digital For mat

pH 8/3/98 – 12/18/00 3/2/01 – 12/30/04 

Alkalinity 8/3/98 – 6/30/04 – 

Temperature 8/3/98 – 12/18/00 3/2/01 – 12/30/04 

Total chlorine – 3/2/01 – 12/30/04 

Conductivity 8/3/98 – 6/30/04 – 

ORP 4/5/04 – 7/6/04 4/05/04 – 7/6/04 

a. Hard copy reports were transcribed into Excel spreadsheets and merged with data provided in digital 

format. 

4.1.1 pH 

Average daily pH and 3-month running average pH values are shown in Figure 9. The 

line in Figure 9 represents 3-month average pH based on the average of all samples 

collected during the previous month, the current month, and next month (i.e., the 3-

month average for June is the average pH for samples collected in May, June, and July). 

 26 
Breaks in the 3-month average plot line indicate periods when sufficient data was not 

available to compute the 3-month average. The average daily pH appears to vary 

seasonally, peaking in March or April annually except for 2002 and 2003. In late 2001 

and early 2002, the distribution system pH was significantly lower than in other years, 

with 3-month average pH values less than 7.5. In 2003, the peak pH value occurred in 

early February. The average distribution system pH value for the 1998 through 2004 

period was 7.8 with a range of 7.0 to 8.7. It is noteworthy that average pH levels in the 

distribution system vary widely on a seasonal basis from as low as 7.0 - 7.2 to greater 

than 8.5. 

Figure 9. Average daily pH of water samples collected at various sampling sites within the 

distribution system (1998 – 2004). The 3-month running average pH 

in the distribution system is shown for comparison.

Solid line = 3-month 

average

9.0

8.5

8.0 pH

7.5

7.0

6.5

Jan-98 Aug-98 Mar-99 Oct-99 May-00 Jan-01 Aug-01 Mar-02 Oct-02 Jun-03 Jan-04 Aug-04

4.1.2 Alkalinity 

As shown in Figure 10, the average daily alkalinity appeared to vary seasonally, peaking 

during the winter months, until 2003. In 2003, the peak alkalinity level occurred in 

August. During 2003 and 2004, the distribution system alkalinity decreased overall and 

yielded an average of 68 mg/L as CaCO3 (note: alkalinity data do not indicate whether 

measurements were reported as CaCO3 – this has been assumed.) The average 

distribution system alkalinity for samples collected from 1998 to mid-2004 is 78 mg/L as 

CaCO3. 

 27 
Figure 10. Average daily alkalinity of water samples collected from various sampling sites 

within the distribution system (1998 – 2004). The 3-month running average alkalinity value 

in the distribution system is shown for comparison. 

`

160

140

120

) CaCO3 100 s (mg/L a

80

inityla

60

Alk

40

20

0

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

Distribution System Alkalinity 3-month Sample Average 

Average daily alkalinity and pH values are plotted as a function of time in Figure 11. 

From the data reported in Figure 11 it is evident that periods of lower alkalinity in the 

distribution system did not necessarily correspond to lower pH (more acidic) values. For 

example, in March of 1999 through 2001 and March 2004 there were seasonally 

associated spikes in pH (to approximately pH 8.5) which corresponded to drops in 

alkalinity. From April to September 2002, during which the pH remained at a relatively 

constant value of 7.3, the distribution system alkalinity had decreased from roughly 100 

to 60 mg/L as CaCO3. However, the onset of changes in pH and alkalinity did not 

correspond with one another, suggesting that alkalinity alone was not the principal 

determinant in the lower pH values that were observed in the distribution system over 

time. 

4.1.3 Temperature 

The average daily temperature for water in the distribution system is shown in Figure 12. 

The temperature varied seasonally, fluctuating from a low of about 40 to 45° F to a high 

of about 80 to 85° F and peaking in July to August every year. 

 28 
Figure 11. Average daily pH and alkalinity of water samples collected at various sampling 

sites within the distribution system (1996 – 2004) 

pH

Alkalinity

9.0 160

140

8.5

120

)3

100

8.0

CaCO as L

pH

80

/ity (mg

7.5

60

kalinlA

40

7.0

20

6.5 0

Dec-96 Sep-97 Jul-98 May-99 Mar-00 Jan-01 Nov-01 Sep-02 Jun-03 Apr-04 Feb-05 Dec-05

Figure 12. Average daily temperature of water collected from sampling sites within the 

distribution system (2001 – 2004)

90

80

70

F)

o e (ruatr60 epmeT

50

40

30

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

 29 
4.1.4 Total Chlorine 

WA converted from free chlorine to chloramines as a secondary disinfectant in 

November 2000. Since implementing the disinfectant conversion, WA has switched 

periodically from chloramines to free chlorine to address nitrification during the following 

dates (Rizzo, 2006): 

• March 13 to May 13, 2002 

• March 10 to April 10, 2003 

• April 2 to May 7, 2004 

These periods are referred to as temporary disinfectant changes for the purposes of this 

report. Figure 13 shows average daily total chlorine data for water samples collected in 

the distribution system in 2001 through 2004. Data collected during the temporary 

disinfectant changes are highlighted in Figure 13. In general, data indicate that the total 

chlorine residual in the distribution system during the temporary disinfectant changes 

was dosed at the same levels as during chloramination. 

Figure 13. Average daily total chlorine concentration for water samples collected from 

various sampling sites throughout the distribution system (2001 – 2004). 

Chloramination

Temporary switch to free

chlorine 

5

4

L) (mg/ Chlorine

3

Total

2

1

0

Mar-01 Aug-01 Feb-02 Aug-02 Feb-03 Aug-03 Feb-04 Aug-04

4.1.5 Conductivity 

DCWASA reported values for specific conductance of water in the distribution system at 

varying intervals and intermittently since 1997. HDR/EES included distribution system 

data from 1998 through 2004. Available data are shown in Figure 14. Similar to data for 

 30 
untreated water (Figure 8), conductivity in the distribution system appears to vary 

seasonally, increasing in the second half of each year and occurring at lower levels 

during the spring and early summer. The average conductivity in the distribution system 

is 355 micromhos per centimeter, and 3-month average values range from 218 to 495 

micromhos per centimeter. The magnitude of these conductivity measurements is 

comparable to the untreated source water. 

Figure 14. Average daily specific conductance for water samples collected from various 

sampling sites throughout the distribution system (1998 – 2004). The 3-month running 

average specific conductance for water in the distribution system is shown for 

comparison. 

Solid line = moving

average

550

500

)

450

cmS/ μ(e nc400 at Conduc 350 ificpecS300

250

200

Jan-98 Jul-98 Feb-99 Aug-99 Mar-00 Sep-00 Apr-01 Nov-01 May-02 Dec-02 Jun-03 Jan-04 Jul-04

4.2 Lead Sources 

This section discusses available data and information that were used to identify possible 

sources of lead in the DCWASA drinking water supply. Data and information collected 

from the Potomac River were used to assess background lead levels in the natural water 

source. Additional reports and limited data from samples collected directly from 

distribution mains were used to assess lead levels in the distribution system. Lead 

profiling data collected at homes were used to assess the contribution of lead service 

lines and premise plumbing. 

In 2003, DCWASA, with the assistance of Dr. Marc Edwards, developed and 

implemented a data collection protocol to identify the lead profiles at individual homes. 

This protocol was utilized at several homes throughout the city to determine the source 

of lead, the form of the lead (dissolved or particulate), and lead concentrations within the 

home, the service line, and the water main. Data from 28 lead profiles collected from 

December 8, 2003 through July 6, 2004 were available for review and are displayed 

 31 
graphically in Appendix A (Moser, 2006). Additional profiles were provided later (Odom, 

2006) covering the timeframe since orthophosphate inhibitor was implemented. These 

additional profiles are included in Appendix A, but have not been analyzed in detail. 

4.2.1 Lead Source Evaluation Using Lead Profiling 

4.2.1.1 Lead Profiling – Methods and Approach 

Twenty-eight lead profiles were developed for 19 homes. The sampling protocol called 

for an initial sample to be collected in the morning after high water use (samples listed 

as ‘0’ or ‘00’ on the profiles in Appendix A), followed by a 6 to 8 hour stagnation period 

after which sequential 1 liter samples were collected at the tap (samples 1 – 20 for 

example) (Giani et al., 2005a). In addition, some samples were collected after the final 

sequential sample followed by a period of allowing the water to flow. For example, 

samples listed as 25+3, etc. on the profiles indicate results from samples collected after 

the water was allowed to run for 3 minutes after collecting the 25th liter. An additional 

sample was collected after turning the faucet on and off several times over a 1-minute 

period, then allowing the water to run 30 seconds prior to collection. Results from these 

samples are indicated as “X” on the graphs in Appendix A and represent a water 

hammer condition to evaluate detachment of particulate lead. DCWASA staff removed 

aerators on taps prior to conducting these lead profiles (Rizzo, 2006c). 

Depending on the length and diameter of in-house plumbing and the lead service line at 

each site, lead results analyzed from selected 1-liter samples drawn from the kitchen tap 

were correlated to one of the three types of piping based on the corresponding volumes. 

For example, at one home, the first 4 liters of water withdrawn from the kitchen tap 

represented the in-house plumbing; the 5th through 9th liters represented the lead 

service line, and the 10th and additional liters represented the water main. Lead levels 

were analyzed on liters 1, 2, and 4 (home piping); 5, 7, and 9 (lead service line); and on 

liters 13, 17, 21, 25, and 45 (the main). 

Of the 28 profiles, some were completed at the same houses during one or both 

disinfectant regimes, and before and after events such as partial lead service line 

replacement (PLSLR). Additional information is provided in Table 7. 

 32 
Table 7. Disinfection regime corresponding to when profile data was collected 

at sites within the DCWASA system 

Disinfection

Regime 

Dates Additional Information Number of 

profiles 

Dec 2003 - 

Apr 1, 2004 

Chloramines 

before 

temporary 

disinfectant 

change 

No PLSLR 12 

Repeat after PLSLR 2 

Apr 2, 2004 - 

May 7, 2004 

During 

temporary 

disinfectant 

change 

During temporary disinfectant 

change 

4 

Repeat of house profiled 

during chloramines and prior 

temporary disinfectant change 

7 

May 18, Jun 28 

and Jul 6, 2004 

Chloramines 

after temporary 

disinfectant 

change 

Chloramines only 1 

Repeat of house profiled 

during chloramines before 

temporary disinfectant change 

2 

TOTAL 28

Figure 15 shows a typical profile that has been observed in the DCWASA system. The 

time period corresponds to chloramine disinfection and is prior to addition of 

orthophosphate inhibitor. The lead service line shows significantly higher lead levels 

than both in-home plumbing and the distribution main. Results from profiling are 

described in Section 5, and additional profiles are supplied both in Section 5 and 

Appendix A. 

Figure 15. Lead profile for tap water samples from House #8 

(sample collected March 9, 2004)

In-house Lead Service Line Main

Plumbing

180

160

140

120

pb)

100

d (pa

80

Le

60

40

20

0

1 2 3 5 7 9 11 14 17 20 24 29 29+3 29+10 00 X

Liter

Total Lead Dissolved Lead

 33 
4.2.1.2 Discussion of Results 

Profiles from five homes connected to the DCWASA distribution system were discussed 

by Giani et al. (2005a). The five homes had lead service lines and exceeded the 15-

μg/L AL of the LCR within the past 2 years. All of the profiles discussed by Giani et al.

(2005a) were collected during a period when chloramines were used for disinfection. 

One of the homes discussed by Giani et al. (2005a) had lead profiles developed before 

and after partial replacement of the lead service line. Overall findings from this study 

indicate that the highest lead concentrations were observed in the water samples that 

stagnated in the lead service line, compared with water samples representing in-house 

plumbing and the water main. 

Additional lead profiles were collected by DCWASA during chloramination and during the 

temporary disinfectant change in 2004. Results are shown and discussed in later 

sections of this report. Similar to the profiles discussed above, these additional profiles 

collected before and after the temporary disinfectant change indicate that the lead 

service line contributed the highest lead concentrations at the tap. Over 80% of the 

profiles collected during these periods (chloramination and temporary disinfectant 

change) displayed elevated lead levels from the service line portion of the sampling 

profile. 

Using 27 of the 28 profiles shown in Appendix A, an average concentration of lead 

measured from each lead source (first liter [faucet and associated piping]; premise 

[remainder of home plumbing]; lead service line; and main) was calculated. Information 

on which sequential samples represented the first liter, remainder of premise piping, and 

lead service line was contained in spreadsheets received from the USEPA (Moser, 

2006). One set of profile data could not be used because it did not contain information 

about which samples represented the premise piping, lead service line, and water main. 

Table 8 presents the average lead concentration of the first liter (faucet and associated 

piping), premise (remainder of home plumbing), LSL, and main, and the average mass 

of lead attributed to these sources. The lead mass data is also represented graphically in 

Figure 16. The data is presented separately for profiles during the temporary disinfectant 

change and chloramination. The average mass of lead from the lead service line during 

the temporary disinfectant change and chloramination were 157 and 470 μg, 

respectively. In contrast, during the temporary disinfectant change and chloramination 

the mass of lead in the first-liter sample (faucet and associated piping) was calculated to 

be 21 and 26 μg, and the remaining home piping was 23 and 72 μg, respectively. The 

mass of lead was not calculated for main samples since background lead levels in the 

distribution system were assumed to be < 2 μg/L (Keefer and Giani 2005) and any lead 

measured from these samples was likely due to pickup of lead from the lead service line. 

Results shown in Table 8 and Figure 16 are not exact measurements of the lead 

contribution of the lead service line, faucet, home piping, and main to lead levels 

measured at the tap, but merely represent an average of lead released from each of 

these sources. These results implicate lead service lines as the primary source of lead 

measured at the tap, compared with lead release from premise plumbing and 

components (e.g., solder and faucets). 

 34 
Table 8. Average lead concentration and mass for profiles during the temporary 

disinfectant change (12 profiles) and chloramination (15 profiles) 

Profiles Under the Influence of a Temporary Switch to Free Chlorine

Concentration, μg/L Mass of Lead, μg 

1st Liter Premise LSL Main 1st Liter Premise LSL 

Average 21 13 22 6 21 23 157 

STD 31 18 18 4 31 22 141 

Profiles Under the Influence of Chloramine Disinfection Only 

Concentration, μg/L Mass of Lead, μg 

Average 26 31 73 23 26 72 470

STD 15 18 50 27 15 44 271

21 23

157

26

72

Free Chlorine

Chloramines

500 470

450

400

g)

350

ected (

μ

300

 Coll

250

 Lead

200

ass of

150 M

100

50

0

First Liter Premise LSL

Figure 16. Average mass of lead contributed from various sources for profiles 

experiencing a temporary switch to free chlorine and those exposed to chloramination 

disinfection (unadjusted for actual volume of exposure). 

 35 
4.2.2 Source Water Lead Levels 

Lead levels from Potomac River source water are frequently at the ”no-detect” level, and 

reported as less than 2 μg/L (Keefer and Giani, 2005). For the purposes of this report, 

”source water” is defined as raw water from the Potomac River and ”finished water” is 

defined as treated water leaving the Dalecarlia or McMillan plants. Finished water lead 

levels are presumably also at the non-detect level. This is difficult to confirm because 

samples collected at the tap represent water that passed through the mains and was 

possibly affected by additional lead uptake due to lead solubilization and release from 

lead service lines and plumbing components. 

4.2.3 Distribution Mains 

Total lead level samples that are normally considered representative of water entering 

the lead service line, were collected at the 28 profiles during the temporary disinfectant 

change and chloramination. Samples included water drawn from the service connection 

and plumbing and the distribution main in the DCWASA distribution system (labeled as 

‘0’ or ‘00’ on the profiles in Appendix A). The lead levels in these samples ranged from 1 

to 115 μg/L, with an average total lead value of 16 μg/L. These samples were collected 

in the morning after flushing the water, according to the procedure described in Giani et 

al. (2005a), so presumably they represent water from the main. These values were 

higher than expected based on negligible source and finished water lead levels. It can 

be difficult to clearly identify lead contributions solely from the distribution main through 

profiling, even with the appropriate flushing regime that yields samples representative of 

the distribution main. It is the consultant’s best professional judgment that lead profiling 

data indicate the likelihood of continued dissolution and pick-up of lead from the service 

connection including the lead service line and/or other lead sources between the main 

and the tap and dispersion characteristics of premise piping systems, rather than a 

notable lead source in the DCWASA water distribution system. 

Studies on lead pipes with a range of exposure areas show that the initial rapid rate of 

lead release is very important to overall lead levels. According to Fick’s Law of Diffusion 

and assuming an initial negligible lead concentration in water from the main, a large 

concentration gradient can occur between the LSL and bulk water, thereby leading to 

exponential rapid lead release, up to equilibrium solubility (Kirmeyer et al., 2000; Van 

den Hoven et al., 1987). Stagnation time studies of lead pipes and lead-bearing brass 

components (Lytle and Schock, 2000) also demonstrate rapid initial lead release. 

Water samples collected directly from the distribution system provide a more reliable 

indication of lead levels in the system. Average lead levels in water samples collected in 

the distribution system are reportedly less than 2 μg/L (Keefer and Giani, 2005). In 

water quality laboratory reports originating from the WA laboratory, supplied to 

HDR/EES and characterized as distribution system data, lead data were not generally 

reported. HDR/EES identified some isolated reports in which lead data were reported. It 

is not clearly identified in all cases where samples were measured – some are cited as 

taps and water meters and marked as type ’Sp’, and one is identified as type ‘Dist’ and 

lists lead level of 0.519 μg/L (June 13, 2001). This limited information, along with the 

Keefer and Giani report (2005), suggests that water passing through the distribution 

mains of the DCWASA system contributes minimally to lead levels at the tap. 

 36 
4.3 Findings from Sanitary Surveys in the Distribution System 

HDR/EES reviewed recent sanitary surveys of the DCWASA system. A sanitary survey 

was completed in 1995 to identify problems and develop recommended mitigation 

measures associated with bacteriological activity in the distribution system. Survey 

findings contained 185 recommendations, including a number of sanitary deficiencies at 

distribution system reservoirs. Follow-up sanitary surveys were conducted in 1996, 

1998, and 2002 to document progress on the 185 original recommendations from the 

1995 survey, and to identify any additional needs. During this time, the distribution 

system underwent major rehabilitation including inspection, cleaning, and rehabilitation 

of storage facilities; cleaning of several large mains; development of a unidirectional 

flushing program; new operation and maintenance (O&M) manuals; an improved Total 

Coliform Rule (TCR) sampling plan and sampling sites; clearwell improvements; and 

staff training. While it is possible that implementation of the unidirectional flushing 

program and/or main cleaning may have impacted release of dissolved and particulate 

lead from lead service lines connected to the distribution system, the extent of this 

impact would be difficult to determine. 

 37 
5. CAUSATIVE FACTORS OF ELEVATED LEAD LEVELS 

The purpose of this section is to identify and describe the evaluation of potential 

causative factors that contributed to elevated lead levels in the Washington, D.C. 

drinking water system. As used in this report, the term “causative factors” includes both 

sources of lead and causative events. The term “causative events” includes historical 

use of elevated free chlorine concentrations, changes in pH and pH variations, and 

conversion from elevated free chlorine to chloramines. 

HDR/EES reviewed, summarized, and evaluated the following data and information: 

water quality data; LCR compliance data; sanitary survey reports; corrosion control study 

reports; correspondence on OCCT; recently completed laboratory studies; lead profile 

information; and information on DCWASA’s lead service line replacement program. 

These data, reports, and studies were used to identify and prioritize causes of elevated 

lead levels in drinking water at consumers’ taps in the DCWASA service area. The 

following causative factors were considered for this evaluation: 

• Lead release from piping systems and other lead-bearing materials 

• Historical use of elevated free chlorine concentrations 

• Distribution system pH levels and pH variations 

• Conversion from elevated free chlorine to chloramines for final disinfection 

• Water quality characteristics in the distribution system 

• Galvanic corrosion of lead service lines 

• Effect of grounding currents on lead-bearing components 

• City-wide meter replacement program 

• Drought conditions and effects of corrosivity on DCWASA water 

Section 5.1 discusses the integration of the potential causative factors listed above and 

draws conclusions about the combination of factors that contributed to lead release at 

consumers’ taps in Washington, D.C. prior to the 2000 to 2004 LCR compliance 

monitoring. Section 5.2 provides background information regarding oxidation reduction 

potential, lead scales, theory, and ongoing research pertaining to the combination of 

factors that can contribute to lead release in drinking water systems. Sections 5.3 

through 5.11 provide separate evaluations of the causative factors listed above. 

 38 
5.1 Combination of Factors Contributed to Lead Release 

A combination of factors – not a single source or a single causative event – contributed 

to the problematic release of lead in water at consumers’ taps in the DCWASA system. 

Figure 1 in Section 1 illustrates the timeline of events beginning in 1992 that highlights 

operations and regulatory compliance decisions, 90th percentile lead levels, shifts in 

disinfectants and pH, coliform events, and other key dates and related activities. Table 9 

provides a summary of decisions by USEPA pertaining to OCCT and actions by 

DCWASA. The primary source of lead release was attributed to the presence of lead 

service lines in the DCWASA service area. Since the mid-1990s, three notable 

occurrences took place in the DCWASA system that likely contributed to elevated lead 

releases during 2000 through 2004: (1) historical use of elevated free chlorine 

concentrations; (2) low pH operating levels and pH variations; and (3) conversion from 

elevated free chlorine to chloramines. These three notable occurrences pertained to 

water quality changes and water quality conditions. Sources of lead and water quality 

occurrences are summarized below. 

 39 
Table 9. Summary of Optimal Corrosion Control Treatment (OCCT) Decisions and 

Actions 

Date OCCT Decisions and Actions 

July 16, 1997 USEPA Region 3 designates OCCT as maintenance of a slightly 

positive Langelier Saturation Index (LSI) through pH adjustment. 

USEPA Region 3 issues an Administrative Order (AO) that the 

above designation is subject to the condition that WA and 

DCWASA jointly assess feasibility of alternate corrosion control 

treatment including pH adjustment with sodium hydroxide and 

addition of a non-zinc orthophosphate corrosion inhibitor. 

February 29, 2000 As a result of the corrosion control feasibility studies, USEPA 

Region 3 designated pH adjustment as the OCCT for the WA 

distribution systems. This designation required that: 

• WA maintain highest pH attainable (without causing calcium 

carbonate precipitation) at entry points to the distribution 

system. 

• A minimum pH of 7.7 maintained at entry points to the 

distribution system and at all tap samples within the 

distribution system. 

May 1, 2000 DCWASA proposed modifications to the OCCT designation set by 

USEPA Region 3. The modifications included the following: 

• Allow minimum pH requirement to change monthly to 

account for seasonal changes (maximum of 7.8 in February 

and minimum of 7.4 in June –September) 

• Reduce minimum pH in the distribution system from 7.7 to 

7.0 

May 17, 2002 USEPA revised its designation of OCCT to accept the 

modifications proposed by DCWASA and WA on May 1, 2000 

noting that the decision had been verbally agreed to in 2000. The 

designation was made effective from the LCR monitoring period 

which began on July 1, 2000. 

April 30, 2004 USEPA Region 3 designated use of zinc orthophosphate for 

partial system application in the 4th High Pressure Zone (a 

hydraulically isolated zone of the DCWASA distribution system). 

May 28, 2004 USEPA Region 3 modified the April 30, 2004 designation to use 

orthophosphate, instead of zinc orthophosphate. 

August 3, 2004 

(modified Aug. 7, 

Sept. 20, 2004) 

USEPA Region 3 modified the interim designation of OCCT to 

consist of the following: 

• Application of orthophosphate system-wide 

• Interim WQP 

o WA pH 7.7 +/- 0.3 (entry points) 

o DCWASA pH 7.7 +/- 0.3 (distribution system) 

• WQP Goal 

o WA pH 7.7 +/- 0.1 (entry points) 

o DCWASA pH 7.7 +/- 0.1 (distribution system)

 

 40 
5.1.1 Sources of Lead 

The primary source of lead release was attributed to the presence of LSLs in the 

DCWASA service area. Faucets, lead-tin solder, and other home plumbing components 

likely contributed, but were not the major sources of lead release in samples collected at 

consumers’ taps. 

5.1.2 Historical Use of Elevated Free Chlorine 

The first notable water quality change occurred in the mid-1990s when the concentration 

of residual free chlorine was increased to the range of 2.2 to 3.2 mg/L, which was 

implemented for the purpose of controlling coliform occurrence in the water distribution 

system. These relatively high free chlorine concentrations likely facilitated the formation 

of Pb (IV) scales in the form of lead dioxide (PbO2) in lead service pipes. Lead dioxide 

scales generally exhibit relatively low lead solubility under normal ranges of pH and 

alkalinity in public water systems when compared to Pb (II) compounds. Lead scales on 

the interior of lead service lines are likely comprised of various forms of lead, including 

both Pb (II) and Pb (IV), and the chemical composition of the scales likely changes with 

varying water quality conditions. 

5.1.3 Low pH Operating Levels and pH Variations 

The second notable occurrence pertains to the fluctuating and low pH of the water 

supply in the DCWASA system. pH of the water is an important factor in the control of 

lead solubility. The pH of the distributed water in Washington, D.C. exhibited seasonal 

variations that fluctuated from approximately 7.0 to 8.9 during 1992 to 2004. pH levels 

at the lower end of this range would not be considered optimal for lead corrosion control 

based on the conventional understanding of lead solubility per the LCR, which assumes 

that the dominant form of scales is Pb (II). In Washington, D.C., however, and as stated 

above, relatively high free chlorine concentrations during the mid-1990s likely facilitated 

the formation of Pb (IV) as the dominant scale, which exhibits relatively low lead solubility 

at the lower pH levels experienced in the DCWASA system. 

5.1.4 Conversion from Elevated Free Chlorine to Chloramines 

The third notable water quality change occurred when WA converted the residual 

disinfectant from free chlorine to chloramines beginning November 1, 2000. The 

residual disinfectant conversion was implemented for the purpose of lowering 

disinfection byproducts to meet new regulatory requirements. This conversion facilitated 

a reduction in ORP to a range that favors the predominance of Pb (II) scales. Pb (II) 

species generally are highly influenced by low and fluctuating pH levels. This 

conversion from free chlorine to chloramines likely facilitated the release of lead in water 

while operating at low, fluctuating pH conditions. Lead release may also have been 

impacted when the minimum pH requirements at entry points and distribution sites were 

lowered at the request of WA and DCWASA and the request was approved by USEPA 

Region 3 effective July 1, 2000. 

5.2 Lead Scales and Solubility 

As previously mentioned, it is likely that the lead scales on the interior of lead service 

lines are comprised of various forms of lead, including both Pb (II) and Pb (IV). It is also 

 41 
likely that the chemical composition of these scales changes with varying water quality 

conditions. Pb (II) scales, the dominant form of scales expected in public water systems 

based on conventional understanding per the LCR, are highly influenced by low and 

fluctuating pH levels. Pb (IV) scales, which can be formed in unique situations such as 

elevated free chlorine concentrations, exhibit relatively low lead solubility under normal 

ranges of pH and alkalinity in public water systems when compared with Pb (II) scales. 

5.2.1 Oxidation Reduction Potential (ORP) 

Oxidation reduction potential (ORP) is defined as the potential required to transfer 

electrons from an oxidant to a reductant (Symons et al., 2000). Recent research on lead 

corrosion shows that the bulk ORP value of water can increase in the presence of free 

chlorine compared to chloramines. Lytle and Schock (2005b) noted that where leadbearing materials are present, Pb (IV) in the form of PbO2 is “associated with waters of 

persistently high ORP”. The authors note that the high ORP is a result of maintaining a 

sufficiently high level of free chlorine residual whether due to low oxidant demand or 

where high free chlorine concentrations are necessary to address microbiological 

concerns in the distribution system. In lead precipitation experiments, Lytle and Schock 

(2005b) found that at a maximum free chlorine residual dose of 3 mg/L, the ORP was 

approximately 0.942 V corrected to the Standard Hydrogen Electrode (SHE), and when 

the study concluded and free chlorine was 0 mg/L, ORP was approximately 0.440V 

(SHE). Vasquez et al. (2006) evaluated several different source waters under different 

treatment regimes and found ORP was higher in waters with free chlorine (0.9 V) than in 

waters with chloramines (0.68 V). Switzer et al. (2006) measured equilibrium potentials 

for free chlorine and monochloramine resulting in ORP of 1.02 V and 0.65 V, 

respectively. Research also demonstrates that ORP can influence the dominant lead 

species, (Lytle and Schock, 2005b; Switzer et al., 2006). Further, ORP is influenced by 

several factors including the following: pH (Lytle and Schock, 2005b), temperature 

(Vasquez et al., 2006), chlorine residual and concentration (Vasquez et al., 2006), and 

dissolved oxygen concentration (Khanal et al., 2003). 

Some ORP data were available for the DCWASA distribution system. Hydrant sampling 

was conducted by DCWASA in 2004 at sites within the 4th High Pressure Zone, a 

designated zone in northwest Washington, D.C. that is hydraulically isolated from the 

rest of the distribution system (USEPA, 2004b, 2006). Hydrant sampling was conducted 

during a period of temporary disinfectant change to free chlorine (April 1, 2004 through 

May 7, 2004) and after converting back to chloramines (Odom, 2006b). Only two 

hydrant sites were sampled during both periods. However, all data from the 4th High 

Pressure Zone hydrant sampling, even where only one value was available, are plotted 

in Figure 17. 

Information was not available for this study regarding whether the ORP data in Figure 17 

were reported as field data or if the ORP values were corrected to the standard 

hydrogen electrode (SHE). Furthermore, the limited available data were evaluated for 

the purpose of characterizing a relative difference in ORP during chlorination compared 

to chloramination in the DCWASA system. The limited data appear to show higher ORP 

values during a temporary change in disinfectant to free chlorine compared to the 

subsequent return to use of chloramines in the DCWASA system. 

As demonstrated in Figure 17, ORP levels were at least 150 mV higher during the 

temporary change to free chlorine compared to periods when chloramines were in use. 

During the temporary disinfectant change to free chlorine, the measured ORP values 

 42 
were ≥ 650 mV. After the temporary disinfectant change, and a return to chloramines, 

most sites showed an ORP in the 450 to 500 mV range. 

Theoretical calculations of ORP based on other available parameters may also be 

helpful in understanding historical redox conditions in the DCWASA service area 

Figure 17. ORP (mV) vs. date for the 4th High Pressure Zone during the temporary 

disinfectant change (April 2, 2004 through May 7, 2004) and after the temporary 

disinfectant change

4th high pressure zone 

orthophosphate 

application

Temprary switch to 

free chlorine

Temporary switch to 

free chlorine 

900

850

800

750

700

V)mP (

650

RO

600

550

500

450

400

4

r-04

04

4

rr-04

4

May-04

04

0yAp

a

Jun-04Jun-04

0

Ap

Ap

Ju

Jul-0

nl-04

y-Ma

Ju

M

32nd & Rittenhouse St. Reno & Upton St Tenley Circle&Yuma St. 33rd & Upland Terrace 38th&Fulton St 38th&Rodman

39th&Yuma St 45th &Cathedral Ave

49th &Glenbrook St 4H-1 dn7-11 4313 Wisconsin Ave

Nebraska & Mass Ave

For the data shown in Figure 17, there are no applicable lead data from the same 

hydrant samples to correlate before, during, and after the temporary disinfectant change. 

However, system-wide data collected before, during, and after the temporary disinfectant 

change exists in the form of both LCR data (Table 3) and lead profiles from houses 

(Section 5 and Appendix A). The LCR data in Table 3, although somewhat limited, 

indicates that lead levels measured during the temporary disinfectant change using free 

chlorine were lower than lead levels measured afterward during routine chloramination in 

the DCWASA system. 

The lead profile data in Section 5.6 for periods before and during the temporary 

disinfectant change generally show a reduction in lead release during the temporary 

disinfectant change. As shown in Figure 17, ORP data plotted after June 1, 2004 were 

collected in the 4th High Pressure Zone during the partial system orthophosphate 

application (Appendix A). Lead levels from samples collected after orthophosphate 

application were not evaluated as part of this report. However, current LCR compliance 

results suggest that lead levels have been effectively reduced by the addition of 

orthophosphate inhibitor to the water supply (DCWASA, 2005, 2006). 

 43 
5.2.2 Lead Scales 

Control of lead in drinking water generally has been presumed to be controlled by Pb (II) 

solids that form on lead-containing materials. However, more recent evaluations of 

scale materials on lead service lines have indicated the presence of Pb (IV) in the form of 

PbO2 solids under certain distributed water quality conditions (Schock et al., 2001; 

Schock and Giani, 2004; Schock, 2005; Schock et al., 2005). In theory, Pb (IV) solids 

have a lower solubility than Pb (II) carbonate solids and will be stable in waters that have 

a high ORP. Evidence has been gathered that Pb (IV) is formed under high ORP 

conditions but it becomes unstable once ORP is lowered, and that the absence of a high 

free chlorine residual (such as during chloramination) allows the occurrence of lower 

ORPs (Schock and Giani, 2004; Lytle and Schock, 2005b). Therefore, by switching to 

chloramines, the ORP of the water may be lowered, allowing Pb (IV) solids to 

decompose via several possible reaction pathways. During the transformation, lead 

levels in the water may increase and the more soluble Pb (II) carbonate species may be 

formed as described by Schock and Giani (2004). 

Figure 18 illustrates the electrochemical (EC) potential-pH diagram that is helpful in 

understanding lead release events (Schock and Giani, 2004; Lytle and Schock, 2005b). 

The numbered boxes show how the sequence of treatment changes formed the PbO2

passivating film associated with Pb (IV) during elevated free chlorine concentrations, and 

then destabilized the Pb (IV) species when the pipe scales reverted to the predominance 

of Pb (II) species during subsequent chloramination in the DCWASA system. 

Point 1 (Figure 18) corresponds to a period in the early 1990s of low free chlorine 

residual, Pb (II) scale dominance, and lead release problems. Initiation of high free 

chlorine residuals and flushing in 1994 moved the system chemistry to the 

predominance of Pb (IV) scales (PbO2 ) as shown by Point 2. The change to 

chloramines for secondary disinfection on November 1, 2000 moved the ORP back into 

approximately the area of Point 3, thus causing further lead species transformation back 

to Pb (II) and an increase in lead levels at the tap. The DCWASA LCR lead level results 

described previously and the reported analyses of scales on excavated lead service 

lines support this mechanism. Lead service lines that were excavated prior to the 

conversion to chloramination (i.e., lead pipes exposed to water when elevated levels of 

free chlorine were used) primarily contained Pb (IV) compounds (plattnerite and 

scrutinyite) with only traces of Pb (II) compounds (cerussite and hydrocerussite) (Schock 

and Giani, 2004; Schock, 2005). 

As demonstrated by theory and recent research, free chlorine residual levels can impact 

lead release depending on the dominant form of lead, i.e., Pb (IV) or Pb (II), in scales on 

lead service pipes. Additional data and discussion regarding free chlorine residual levels 

in the DCWASA distribution system are presented in Section 5.4. 

 44 
Figure 18. Potential-pH diagram for the lead system corresponding to DC WASA water 

(Schock and Giani, 2004) 

Conditions of low free chlorine residuals during the early 1990s and chloramines since 

2000 suggest the possibility of similar ORP values in the DCWASA system and similarly 

the predominance of Pb (II) scales as proposed by Schock and Giani (2004). The 

solubility of Pb (II) is reasonably well established and believed much higher than Pb (IV) 

over the normal range of pH in public water systems. However, current understanding of 

Pb (IV) solubility is largely based on solubility models, and additional data gaps exist with 

respect to alkalinity/DIC and other water quality parameters. 

The effectiveness of orthophosphate in conditions whereby Pb (IV) scales are the 

predominant species is not well understood. If an orthophosphate inhibitor had been 

added to the DCWASA water supply for corrosion control in the early 1990s when Pb (II) 

was presumably dominant, it may have been more effective as OCCT (than pH 

adjustment) before, during, and following the switch from free chlorine to chloramines for 

final disinfection. If orthophosphate treatment was used as OCCT in the early 1990s, 

DCWASA may have avoided elevated lead levels in customers’ taps. However, if an 

orthophosphate inhibitor had been added to the DCWASA water supply during the mid 

to late 1990s when elevated free chlorine was added to the water supply, then it is not 

known how effective the orthophosphate inhibitor would have been compared to pH 

adjustment. Currently, little information is available regarding the effectiveness of 

orthophosphate treatment under Pb (IV) scale conditions, which are presumed to have 

been dominant due to elevated free chlorine concentrations before the disinfectant 

switch. Accordingly, this topic could benefit from further research to better understand 

the impact of orthophosphate inhibitor under different disinfectant, ORP, and scale 

conditions. 

 45 
It is important to point out that changing from free chlorine to chloramine disinfection 

does not always correspond to elevated lead release. Pb (IV) formation is associated 

with systems that have high ORP, which can be caused by a variety of mechanisms 

including high free chlorine dosages (Schock and Giani, 2004). Free chlorine residual 

levels are discussed further in Section 5.4. 

Systems that do not have a history of such high ORP conditions may have maintained a 

Pb (II) scale and never have been in a Pb (IV) regime. The accepted corrosion control 

mechanism, based on Pb (II) and optimal corrosion control including pH adjustments, 

would have been effective in those systems, and possibly not altered by chloramines, 

since Pb (II) scale was already dominant as the passivating layer. Follow-on work with 

other systems that have had disinfectant changes in the presence of Pb (IV) scales could 

provide additional insight with regard to understanding the complex interrelationship of 

lead scales and water quality. 

5.2.3 Theory and Ongoing Research Pertaining to Pb (IV) 

Theory and developing research on tetravalent lead can potentially improve 

understanding of the treatment changes and conditions that influence lead scales and 

lead release. As more information becomes available, it may further explain the 

causative factors for the increased lead release in the DCWASA system. 

According to recent studies (Lytle and Schock, 2005a; Switzer et al., 2006), 

transformation of elemental lead, Pb(0), to divalent lead, Pb (II), occurs in both 

chloraminated and chlorinated water systems. The transformation of existing Pb (II) to 

Pb (IV) is not well understood beyond the presence and absence of free chlorine and the 

corresponding measured ORP values. Similarly, details of the dissolution and 

precipitation behavior of Pb (IV) are still not well understood (Lytle and Schock, 2005b; 

Switzer et al., 2006). 

Solubility differences between Pb (II) and Pb (IV) may also be important. The solubility 

constants (Ksp) of PbO2, Pb3(OH)2(CO3)2 (hydrocerrussite) and PbCO3 (cerussite) at 

10-66 , 10-18.8, and 10-13, respectively (Switzer et al., 2006; Marani et al., 1995) allow 

calculations that show PbO2 is much less soluble than Pb (II) solids. This comparison of 

solubility constants indicates that PbO2 potentially dissolves less readily than the two 

Pb (II) mineral forms. Although speciation and solubility data for all of the various Pb (II) 

and Pb (IV) compounds that may be involved is scarce, models suggest that Pb (IV) 

solubility is generally lower than Pb (II) solubility (Schock et al., 2001). 

In the Schock et al. (2001) study, lead scales from pipes in the Cincinnati distribution 

system were examined using several mineral characterization techniques. The study 

identified a passivating film consisting of polymorphs of Pb (IV) in the form of PbO2 on all 

of the pipe samples. In the study, solubility vs. pH relationships were developed for 

PbO2 using three values of the Gibb’s free energy of formation obtained from the 

literature. The solubility-pH relationships all predict that PbO2 has a much lower 

solubility than Pb (II) in the form of PbCO3 and that the solubility of Pb (IV) in the form of 

PbO2 decreases with decreasing pH. The authors note that the solubility–pH 

minimization trend for Pb (IV) is the opposite of that for Pb (II); i.e., Pb (IV) solubility tends 

to decrease with decreasing pH, approaching a minimum solubility at approximately pH 

4. Based on these models, a change to a much more soluble form of lead (i.e., Pb (II) 

mineral forms) offers a potential explanation for the sustained increase in lead release in 

the DCWASA system. The earlier predominance of the relatively low solubility Pb (IV) 

 46 
could explain why the lower pH range did not adversely affect lead levels in that time 

period, as might have been expected based on Pb (II) solubility. Under these 

assumptions, the switch to chloramines in November 2000 and the reduction in minimum 

allowable distribution system pH are conditions that would likely not have been optimal 

for the Pb (II) scales. 

5.3 Lead Release from Piping Systems and Other Lead-Bearing 

Materials 

Lead from piping can potentially be released in either the soluble or particulate form. 

While particulate lead is important and can contribute to elevated lead in some 

instances, soluble lead appears to be the primary form of lead measured in DCWASA 

tap samples. The predominant source of soluble lead in the DCWASA tap samples is 

attributed to lead service lines. Other components, fittings and piping materials made of 

lead-bearing materials such as brass, bronze and solder potentially can contribute to 

elevated lead levels at consumers’ taps. These sources of lead are discussed below. 

5.3.1 Soluble Lead from Piping 

Figure 19 was developed by evaluating a specific sample from the lead profile data 

(Section 5.2 and Appendix A) for every available profile and calculating the average 

particulate and dissolved lead concentrations as a percentage of total lead. This 

process was repeated for the 5th through 9th liters, which correspond to the lead service 

line. Profiles were restricted to those collected during disinfection with chloramines from 

December 8, 2003 through March 31, 2004. Profiles at sites with partial lead service line 

replacements were omitted due to erratic results from particulate lead spikes. The 

results listed below clearly show the predominance of soluble lead over particulate lead. 

 47 
Figure 19. Average contribution of dissolved and particulate lead 

as a percentage of the total lead concentration in distribution system water 

samples (December 2003 through March 2004) 

n = number of 

samples used to 

calculate the 

average 

Particulate 

Soluble 

6th liter (n = 7)

11%

89%

5th liter (n = 10)

14%

86%

7th liter (n = 8)

13%

87%

8th liter (n = 4)

10%

90%

9th liter (n = 7)

14%

86%

Figure 19 shows soluble lead in the approximate range of 86 to 90 percent based on 

HDR/EES’s review of available lead profiles. This observation is consistent with findings 

reported by Giani et al. (2005a) regarding lead levels in unfiltered and filtered samples 

collected for lead profiling at five homes in the DCWASA system. In the study, the 

filtered sample represents the amount of dissolved lead in the water, while the unfiltered 

sample represents the total lead in the water. The conclusions of the Giani et al. 

(2005a) study were that the majority of elevated lead concentrations were due to 

dissolved lead, and the lead profiles presented, similar to HDR/EES’s review, show that 

approximately 85 to 90 percent of the total lead was in dissolved form. Based on these 

findings, the detachment of lead particles from piping systems does not appear to be a 

significant cause of elevated lead levels in the DCWASA system. Both the profiles 

evaluated by HDR/EES and in the Giani study suggest that soluble lead is much more 

important in terms of relative contribution to lead levels at consumers’ taps. 

5.3.2 Particulate Lead from Piping 

Based on the results from the lead profiles, it appears that particulate lead release from 

piping systems is not a significant system-wide problem with respect to samples 

collected for LCR compliance, but may occur intermittently due to site-specific conditions 

and hydraulics. 

 48 
The potential exists for lead particles (scale) to be disturbed and to detach from pipe 

surfaces including in-house plumbing and lead service lines. Release of particulate lead 

could be caused by a variety of factors, including hydraulic scour, physical disturbance 

such as vibration (which could occur during service line replacement), chemical changes 

in the water that might exacerbate release of particulate lead, and/or site-specific flow, 

piping, and environmental conditions. 

There are limited situations where high-particulate lead was measured in the DCWASA 

service area. For example, the first sample from Profile #22, as illustrated in Figure 20 

shows a relatively high concentration of total lead. Typically, the majority of total lead is 

in dissolved form. However, high-particulate lead may be observed occasionally as 

related to site-specific piping, water use patterns, or high flow rate during sample 

collection that can cause shearing of particulate lead from the piping system. 

Figure 20. Lead profile data for House #22 (sample collected April 30, 2004) under 

conditions of water hammer that cause high levels of particulate lead release 

(Particulate Lead = Total Lead – Soluble Lead) 

In-house Lead Main

Plumbing Serivce Line

180

160

140

120

) Lead (ppb100

80

60

40

20

0

1 2 3 5 7 9 10 11 13 15 18 21 24 27 27+3 27+10 0 X

Liter

Total Lead Dissolved Lead

The majority of the samples collected to evaluate water hammer effects (Sample ‘X’ in 

Appendix A) exhibited high dissolved lead levels, i.e., little particulate lead. However, at 

Profiles #16, #17, #22, #23 (Appendix A) the water hammer condition likely dislodged 

particulate lead, indicating that occurrence of particulate lead may be related to hydraulic 

conditions. 

In a report to USEPA Region 3, Dr. Marc Edwards (Edwards, 2003) noted that LCR 

sampling results may not take into consideration use of filtration devices on kitchen taps 

and that sampling procedures at these sites should be checked and documented. Since 

 49 
2004, DCWASA’s LCR sampling instructions have directed homeowners to remove 

water filters from the sampling tap before taking the sample or to collect the sample from 

a tap which does not have a filter (Rizzo, 2004). 

A common configuration for faucets includes an aerator attached to the end of the 

faucet. This aerator may serve as a trap for particulate lead that has been released from 

piping systems. During June 2002 (the last month of the July 1, 2001 through June 30, 

2002 compliance monitoring period), customers were instructed to remove the aerators 

prior to collecting samples. The instructions for removing the devices prior to sampling 

continued through the January 1 to June 30, 2003 monitoring period. From July 1 to 

December 31, 2003, customers were instructed to leave the aerators in for lead 

monitoring samples, and this procedure is still in effect (Smith, 2006). The impact of 

leaving the aerator in place during sampling is that lead particles may be trapped in the 

aerator rather than included in the sample. If these particles build up, they could provide 

an additional lead source to the water. A sample drawn for compliance purposes from a 

tap where the aerator is still in place would more likely represent human exposure 

conditions. 

With respect to particulate lead release from lead service lines, it is possible that partial 

replacement of lead service lines could result in release of lead scale and cause a 

corresponding increase in particulate lead measured at the tap. Since 2002, DCWASA 

has been required to replace 7% of the lead service lines on an annual basis due to lead 

action level exceedances. Wujek (2005) reported that particles in the remaining partial 

lead service line piping were disturbed and released to the water column for a temporary 

period of time after the replacement. While partial lead service line replacements may 

have negatively impacted lead levels in the DCWASA system (i.e., due to the possible 

release of lead particles to the water column) the extent of the impact cannot be 

determined based on current information. 

 50 
Table 10 summarizes the evaluation of data and information regarding lead release from 

piping systems. 

Table 10. Summary evaluation of data and information – 

lead release from piping systems 

Data and Information 

Considered 

Evaluation of Data and Information as 

Pertaining to this Possible Cause 

HDR/EES analysis of DCWASA 

Lead Profiles in Excel spreadsheet 

obtained from USEPA Region 3. 

Lead service line piping is the predominant source of lead 

measured at the tap. 

Approximately 86-90% of total lead is in the soluble form. 

Approximately 85-90% (calculated by HDR/EES from 

graphs in paper) of the total lead is in the soluble form. 

Particulate lead occurs in limited instances, likely related to 

site-specific piping and water use, and/or flow rate during 

sample collection. 

Giani et al., 2005a. 

5.3.3 Faucets, Solder, and Other Home Plumbing 

Typical plumbing and premise piping in residences and buildings can consist of leadbearing materials such as brass or bronze fittings and components and tin-lead solder 

used to join copper piping. End-use devices such as faucets and plumbing fixtures also 

can contain lead-bearing materials that can contribute to lead uptake in the water. Prior 

to the promulgation of the Lead and Copper Rule in 1991, lead solder and flux used to 

join copper premise piping and faucets and fixtures comprised of brass were shown to 

be major sources of lead in tap water (Samuels and Meranger, 1984; Schock and Neff, 

1988; Gardels and Sorg, 1989; AwwaRF, 1990; USEPA, 1991). 

Giani et al. (2005a) evaluated the primary source of lead in the DCWASA system using 

lead profile data collected at five homes. This study indicated that the highest lead 

concentrations were observed in the water samples which stagnated in the lead service 

line compared with water samples representing in-house plumbing and the water main. 

Results from additional lead profiles also indicate that the lead service line contributes 

the highest lead concentrations at the tap. Over 80% of the profiles available for review 

in this study displayed elevated lead levels from the service line portion of the sampling. 

An estimate of the relative mass of lead from faucets, solder, and other home plumbing 

indicates that approximately 24 μg of lead may be associated with the first liter sample 

(faucet and associated piping) and 50 μg of lead may be associated with the remaining 

home piping and components prior to the lead service line. In the DCWASA system, as 

in other analogous systems, whether lead service lines are present or not, other 

plumbing components can still potentially result in exceedance of the LCR 90th percentile 

AL at the consumers tap (Boyd et al., 2006b). 

 51 
As discussed previously in Section 4.2, the average mass of lead release attributed to 

the LSL was 157 μg during the temporary disinfectant change to free chlorine and 470 

μg during routine chloramination (Table 8). It is important to reiterate that these values 

are based on average mass loadings of each source in the system. Based on results 

from Giani et al. (2005a) and estimates of the mass loading of lead from various portions 

of home and service piping, it appears that while faucets, solder, and other home 

plumbing contribute to lead levels measured at the tap, they are not the predominant 

source of lead in the DCWASA system. Table 11 contains a summary of the data and 

information related to faucets, solder, and other home plumbing. 

Table 11. Summary evaluation of data and information – faucets, solder, and other 

home plumbing 

Data and Information Considered Evaluation of Data and Information 

Pertaining to this Possible Cause 

Giani et al., 2005a. 

HDR/EES analysis of DCWASA Lead Profiles in 

Excel spreadsheet obtained from USEPA Region 

3. 

Faucets, solder, and home piping contribute to lead 

at the tap, but they are not the predominant source. 

5.3.4 Distribution Mains 

As discussed in Section 4.2, the distribution mains and other system components 

connected to the DCWASA distribution system are not likely a major contributing source 

of lead at the tap. While review of the lead profile data contained numerous instances 

where thoroughly flushed samples from the water main still contain measurable lead, it is 

likely, as explained in Section 4.2, that rapid release of lead from the lead service line 

and/or home systems or dispersion and mixing characteristics of the premise plumbing 

caused the higher than expected results in the flushed samples. Even without 

acknowledging the rapid release from LSLs or other components, the results from water 

in the main are still notably lower in the lead profiles than in the lead service lines. Table 

12 summarizes the evaluation of data and information regarding water in distribution 

mains. 

Table 12. Summary evaluation of data and information – 

water in distribution mains 

Lead in flushed samples and in samples 

targeting the main is often detectable and 

many samples are greater than 10 μg/L, likely 

due to rapid release of lead from service and 

premise piping. 

Data and Information Considered Evaluation of Data and Information 

Pertaining to this Possible Cause 

Keefer and Giani, 2005 

Lead Profiles 

Lead levels in the distribution system are low, 

typically <2 μg/L. 

 52 
5.4 Impacts of Historical Use of Elevated Free Chlorine 

Concentrations 

Chlorine residual data from the DCWASA entry points and distribution system locations 

were provided for review. Data from the points of entry to the distribution system include 

free chlorine measurements from January 1992 to October 2000, and total chlorine 

residual measurements from November 2000 (after the switch to chloramines) through 

December 2004. These data are shown in Figure 21. 

To address Total Coliform Rule (TCR) problems in the distribution system in the early to 

mid-1990s the free chlorine residual was increased from approximately 1 – 2 mg/L to 3 – 

4 mg/L at entry points to the distribution system. As discussed previously in Section 5.2, 

this lower chlorine residual period was thought to correspond to low ORP and 

predominance of Pb (II) scales (Schock and Giani, 2004). Figure 21 shows the periods 

of lower free chlorine residual at the distribution system entry points in the early 1990s 

when lead release problems were first observed. Corresponding free chlorine levels 

within the distribution system prior to 1998 were not available for review, but it can be 

assumed that residual levels within the distribution system would have been lower than 

those measured at the point of entry. The 1994 –1995 period of elevated free chlorine 

residuals, and up until chloramination in November of 2000, were periods of low lead 

release – thought to correspond to higher ORP and Pb (IV) scale dominance (Schock 

and Giani, 2004). 

Figure 22 shows free chlorine residual levels measured within the distribution system 

from 1998 through 2004, which captures the period before and after the switch to 

chloramines. Prior to the switch to chloramines and during the period of low lead 

release (i.e., 1994 to October of 2000), free chlorine levels were approximately 2 mg/L 

within the distribution system. As expected, after the switch to chloramines, the free 

chlorine residual decreased to very low levels (i.e., typically less than 0.5 mg/L), aside 

from seasonal switches back to free chlorine for nitrification control/prevention purposes. 

The decrease in free chlorine levels associated with the switch to chloramination may 

have created ORP conditions that were similar to the early 1990s when free chlorine 

residuals were also relatively low and Pb (II) scales were thought to be dominant. As 

described previously in Section 5.2, the operating pH was also reduced in July of 2000, 

which may have contributed further to Pb (II) release under chloraminating conditions. 

 53 
Figure 21. Free and total chlorine residual as a function of time illustrating periods 

of lower chlorine residuals at the distribution system entry points in the early 

1990s (January 1992 through December 2004) 

TCR violations

Exceed LCR 90th 

percentile AL

Administrative Orders issued by 

USEPA Region 3 requiring 

flushing and improved 

disinfection

Higher minimum free chlorine residual Exceed LCR 90th 

percentile AL

pH OCCT minimum 

dist. sys 7.0; entry 

points 7.4-7.8

Disinfection using Free Chlorine Disinfection using Chloramines 5

4

Chlorine Concentration (mg/L)

3

2

1

0

2

2

3

4

5

6

7

8

9

0

1

2

3

4

9

n-9

c-9

9

9

9

ccccv-9

-0

v-9

0

v-9

v

-

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t-0

t-0

a

e

e

e

e

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o

o

o

o

o

o

c

c

J

D

D

D

D

D

N

N

N

N

N

N

O

O

Dalecarlia McMillan

Figure 22. Average free and total chlorine concentrations for water samples collected 

from different sampling sites within the distribution system (1998 -2004) 

Free Chlorine

Total Chlorine

5

lorine Concentration (mg/L) 

4

3

h stribution System C

2

i

1

Average D

0

16-Nov-97 31-Mar-99 12-Aug-00 25-Dec-01 9-May-03 20-Sep-04 2-Feb-06

 54 
Figure 23 shows a plot of average free chlorine residual levels during LCR compliance 

monitoring periods along with the 90th percentile lead data for the period January 1992 – 

December 2004. The 90th percentile lead levels were low (less than the LCR AL) during 

periods of high free chlorine residuals (July – Dec 1994 through July – Sept 1999) and 

high (greater than the LCR AL) during periods of low free chlorine residuals 

corresponding to disinfection with chloramines (July 2001 – June 2002 through July – 

Dec 2004). Statistical analyses were not performed due to limited data. However, the 

graph presents interesting information about a potential relationship between free 

chlorine residuals and lead release that could be explored as follow-on work. 

Figure 23. Average Free Chlorine Concentration (over the LCR compliance period) and 

90th Percentile Lead vs. Time 

Average Free Chlorine

90th Percentile Lead

4 80

L)

70

g/

ation 

m

r

(ation 

nt

3 60

rnt

Conce

e

50

ad 

onc

 Le

C

aw

ne 

2 40 r

g/L)

 Chlori

D

m(

trs

30

 Fie

e Fre

entil

age

1 20

rce

erAv

th P

10

09

0 0

 92

2

3

ec 93

 94

4

7

8

9

2

3

9 c 

 9

 9

9

 01

4

 9

e

 97

c

ec 9

e 99

 0

03

04

e

e

e

0

e

Dec

e

t p

e

c 

c 

Jun

De

Jun

e

D

Jun

n

De

D

Jun

e

n

Jun

Jun

u

S

 D

nly-

-

ynyn-J

lyynly-

 - Ju

-

y -

- June 0

 - De

Ja

Ju

Jan

Jul

Ja

Jul

Ja

Ju

Jul

Ja

Ju

0

n -

y 0

 01

ly

Ja

Jul

Jan

Ju

Jul

ly Ju

Compliance Period

5.5 Distribution System pH Levels and pH Variations 

This section provides information about the following: 

• pH variations and their effect on lead corrosion and solubility 

• Spatial and seasonal pH variations 

• The possible effect of lower operating pH per OCCT designation 

• OCCT changes and their quantifiable impact on lead release 

 55 
5.5.1 pH Variations 

An evaluation of pH data collected at the entry points and within the DCWASA 

distribution system indicated that pH variations were observed seasonally as well as 

spatially from the entry points to sampling locations within the distribution system. pH 

has a significant influence on lead corrosion and solubility, especially for the typically 

observed Pb (II) species such as cerussite and hydrocerussite. Varying pH levels can 

significantly affect the formation of protective scales on the interior of the pipes and the 

capability of the system to maintain these scales in a stable form. In a recent study, Lytle 

and Schock (2005a) found that changes in pH could destabilize passivating films on pipe 

interiors, possibly resulting in increased lead solvency and release of scale particles. 

Several corrosion control studies prepared for DCWASA or WA recommended that 

distribution system pH should be maintained at a consistent level. For example, a study 

by ECG, Inc. (1994) concluded that WA water treatment plants should optimize current 

practices by rigorously maintaining a consistent pH level that would optimize the 

Langelier Saturation Index in the positive range, as close to zero as possible. An expert 

review of the ECG study (1994) by Jonathan Clement in 1996 recommended that 

maintenance of a consistent distribution system pH, regardless of treatment selection, 

should be addressed. Clement (1996) also recommended that pH variations of more 

than 0.5 pH units should be avoided. A study by CH2MHill (2004) evaluated two 

corrosion control options, both of which required a constant pH: (1) maintaining a 

constant, high pH at the two water treatment plants using either quicklime (current 

practice) and/or sodium hydroxide; and (2) feeding a corrosion inhibitor such as 

orthophosphate while maintaining a constant pH of about 7.7 throughout the year. A 

summary of these corrosion control study reports is provided in Appendix A. 

Daily average pH at the entry points to the distribution system (Dalecarlia and McMillan 

Water Treatment Plants) and daily average pH in the distribution system are plotted as a 

function of time in Figure 24. 

 56 
Figure 24. Average daily pH at the distribution system entry points (Dalecarlia and 

McMillan) and in the distribution system (1998 through 2004) 

Conversion to 

Chloramines

July 00 - OCCT min 

pH req'd in dist. 

system lowered 7.7 

to 7.0

Temporary 

switch to free 

chlorine

9.0

8.5

8.0

pH

7.5

7.0

6.5

89

-99

-00

9

0

ul-9

-0

-01

1

2

3

3

4

4

0

-02

-0

-0

-0

-0

0

-04

gJan

J

Jan

Jul

Jan

JulJan

Jul

ulAu

c

Jan

Jul

Jan

J

De

Dist. Sys pH pH Dalecarlia pH McMillan

The differences in daily average pH for samples collected at the entry points compared 

to samples collected in the distribution system are plotted as a function of time in Figure 

25. A positive difference as shown in Figure 25 is an indication that the daily average pH 

was lower in the distribution system compared to the entry point. A negative difference 

indicates that the pH in the distribution system was higher than the pH at one of the 

entry points. In some cases this observation was attributed to the difference in pH at 

both entry points, and thus the pH in the distribution system could have been 

intermediate between pH at Dalecarlia and McMillan entry points. 

 57 
Figure 25. Difference between the average water pH at the distribution system entry points 

and the average pH of water collected at different sampling sites throughout the 

distribution system (1998 through 2004) 

Reduced pH OCCT

Conversion 

to 

to free chlorine

)

1.0

emtsyst. Ss Diu

0.5

nimt inoP rytn

0.0

 (EHp e incnre

-0.5

ffeiD

-1.0

8

9

-99

9

0

00

01

1

1

2

3

9

9

9

-0

0

02

0

03

0

04

04

4

gr-0

Jann

vSepebl

-

-

nu

p

v-0

A

Ju

No

u

y

A

F

J

ec

ct-

-

-

D

Ma

O

Mar

AugJan

Ju

No

Dalecarlia Entry Point - Dist. Sys McMillan Entry Point - Dist. Sys

Temporary switch 

5.5.2 Spatial pH Variations 

Data in Figure 24 and Figure 25 indicate that pH levels in the distribution system were 

frequently 0.5 pH units less than, and in some instances as much as 1 pH unit less than, 

the pH of finished water discharged from the water treatment plants. In Figure 25 the 

difference in pH is calculated by subtracting the average pH value in the distribution 

system from that at the respective distribution system entry points (Dalecarlia and 

McMillan). These data indicate pH differences greater than the recommended allowable 

pH difference based on studies by Clement (1996) and CH2MHILL (2004). As such, 

these spatial pH variations could have caused adverse impacts on the stability of lead 

scales and thus contributed to lead release. 

5.5.3 Seasonal pH Variations 

Figure 24 shows seasonal variation in pH, which was allowed to occur in the DCWASA 

distribution system as part of the modified OCCT. During 1998 and 1999, the seasonal 

trend in the average daily pH in the distribution system generally followed the seasonal 

trend exhibited by the finished water discharged at the water treatment plants. 

 58 
5.5.4 Lower pH and Modified OCCT 

Beginning with the reduced pH OCCT in 2000, the average daily pH in the distribution 

system appeared to be noticeably lower than the finished water at the treatment plants 

during 2000, 2001 and 2002. The cause of this change in pH between the point of entry 

and distribution system is unknown. During 2000 and previously, pipe scales 

presumably were acclimated to conditions of free chlorine and likely were dominated by 

Pb (IV) species. After the switch to chloramines in November 2000, the average daily pH 

in the distribution system generally remained low during 2001 and 2002. Under these 

new conditions, the pipe scales likely were disrupted by the change in ORP and 

chemical interactions likely were dominated by Pb (II) species. Further, low pH conditions 

presumably were not favorable for the formation of stable lead scales. As a 

consequence, low pH conditions, coupled with a reduction in ORP, likely contributed to 

elevated lead levels after the switch in disinfectant to chloramines. 

While Pb (IV) compounds are thought to have lower solubility than Pb (II) species, 

solubility models also suggest that Pb (IV) solubility decreases with decreasing pH. As 

discussed in a Section 5.2, in Pb (II) and Pb (IV) solubility models, Schock et al. (2001) 

found that the PbO2 solubility minimum could occur at around pH 4. This phenomena is 

opposite of the trend observed with Pb (II) where solubility was reduced with increasing 

pH (Schock and Giani, 2004). Based on this understanding, the lower pH range in the 

DCWASA system may have previously been adequate for maintaining Pb (IV) scales 

under high free chlorine conditions, but too low of a pH for maintaining Pb (II) scales 

under chloramine conditions. 

5.5.5 Optimal Corrosion Control Treatment (OCCT) 

The OCCT changes affecting pH control are discussed in detail in Section 2.4. This 

section provides more in-depth analyses of the OCCT changes in an effort to quantify 

their impact on lead release. 

Distribution system pH varied from 7.0 to 8.9 over the years 1998 to 2004, and it 

appears to vary seasonally, peaking in March or April every year except for the year 

2002 (Figure 3, Figure 9, and Figure 24). In late 2001 and early 2002, distribution 

system pH was significantly lower than in other years, with 3-month average pH values 

less than 7.5. 

System-wide pH data were analyzed to determine if statistical differences in pH occurred 

before and after the observed increase in the 90th percentile lead levels for the 

DCWASA system. Figure 26 shows a plot of the average, range, and standard deviation 

of daily average pH data collected before and after the compliance period of July 2000 

through June 2001. For each “box and whisker” diagram shown in the graph, the 

horizontal line in the center of the box represents the average, the symmetrical box 

represents the standard deviation, and the vertical bar represents the minimum and 

maximum average of daily pH data collected during the designated compliance period (x 

axis). The solid circles depict the 90th percentile lead levels (secondary y axis) for the 

designated compliance periods. The disinfectant conversion, which occurred on 

November 1, 2000, and the change in allowable minimum pH for OCCT, which occurred 

in February, 2000, are shown by the vertical lines annotated in Figure 26. Results 

indicate that the average pH before the disinfectant conversion ranged from 7.6 to 8.1 

and it ranged from 7.4 to 7.9 after disinfectant conversion. Results also indicate that the 

standard deviation and ranges of pH data appear to be similar, with the exception of the 

 59 
narrow range of values measured during the July through December 1999 compliance 

period. While the pH range before and after the conversion is similar, the lowest pH 

values occurred after the conversion during the July 2001 – June 2002 LCR monitoring 

period. This period corresponds with the highest 90th percentile lead level as shown in 

Figure 26. 

Figure 26. Average daily pH and lead concentrations in first draw water samples before 

and after the conversion from free chlorine to chloramines as the residual disinfectant 

Conversion to 

Chloramines

pH 7.7 pH 7.0

Avg. pH I Min/Max Avg. pH

Std. 90th-Percentile

Deviation Lead Conc.

9.0 80

70

8.5

60

)

50

g/L

8.0 μ pH

40

7.5

30

First Draw Lead (

20

7.0

10

6.5 0

July - Dec Jan - June July - Dec Jan - June July 2000 - July 2001- July - Dec Jan - June July - Dec Jan - June July - Dec

1998 1999 1999 2000 June 2001 June 2002 2002 2003 2003 2004 2004

Lead data were evaluated as a function of pH before and after the pH changes in July 

2000 as defined in the OCCT, and prior to orthophosphate addition. No correlation could 

be found between total first draw lead concentrations and the average daily distribution 

system pH values. The lack of a correlation between these two parameters was likely 

due to: (1) the variability of both lead levels and pH levels measured, and using an 

aggregate of pH and lead data collected at different locations throughout or connected to 

the distribution system; and (2) variations between lead sources and lead levels in 

individual LCR monitoring sites. The results did show that system-wide lead levels were 

greater after OCCT pH changes (most of the data also corresponds to the postchloramines conversion period). 

Table 13 summarizes the evaluation of data and information regarding distribution 

system pH variations. 

 60 
Table 13. Summary evaluation of data and information – 

distribution system pH variations 

Data and Information Considered Evaluation of Data and Information 

Pertaining to this Possible Cause 

Distribution system pH and alkalinity, 1998–2004 

Distribution system entry points, pH and alkalinity, 

1998–2004 (except for alkalinity data missing for 

2000–2001) 

HDR/EES analysis of WA pH data for entry points to 

the distribution system 1992-2004 in conjunction with

other historical events (OCCT and disinfection 

changes) 

HDR/EES analysis of DCWASA lead data for LCR 

compliance, 1998–2004 

Correspondences pertaining to LCR compliance 

(USEPA and DCWASA, 1997–2004) 

Corrosion control studies (ECG, 1994; CH2MHill, 

2004) 

Expert review (Clement, 1996) 

Schock and Giani (2004) 

Data is plentiful, but confounding factors 

make interpretation difficult. The cause of 

lower distribution system pH levels 

compared to entry point pH levels following 

the disinfectant change is unclear. 

pH variations and lower pH likely play an 

important contributing role to scale 

disturbance and lead release, along with a 

disinfectant change. 

5.6 Conversion from Elevated Free Chlorine to Chloramines for 

Final Disinfection 

On November 1, 2000, WA converted from free chlorine to chloramines for final 

disinfection to reduce disinfection byproduct formation and to improve residual 

disinfection in the distribution system. This change from free chlorine to chloramines has 

been implicated as a potential causative factor in lead release, especially from lead 

service lines. This section provides discussion on lead compliance monitoring data and 

historical wastewater metals information collected before and after the conversion to 

chloramines. In addition, this section provides discussion on special sampling data 

collected during periods when WA switched to free chlorine for biofilm control (referred 

to as a temporary disinfectant change) and lead profiling data collected during the 

temporary disinfectant change. Further discussion is provided in this section with regard 

to recent advances in theoretical understanding of oxidation reduction potential and its 

impact on lead scales and the solubility of various forms of lead. 

5.6.1 LCR Monitoring Results 

To evaluate how lead levels changed before and after the conversion to chloramines, 

lead compliance monitoring data were evaluated both on a compliance period basis and 

on a monthly basis for the time period from July 1997 through October 2004. Figure 27 

shows the LCR compliance data for this period, indicating when the minimum allowable 

pH at distribution system sites was lowered from 7.7 to 7.0, and when the conversion 

 61 
from free chlorine to chloramines occurred. The minimum allowable pH in the distribution 

system was lowered immediately prior to collection of compliance samples for the July 

2000 to June 2001 compliance period. The conversion to chloramines occurred in 

November 2000 in the middle of this compliance monitoring period. A total of 53 valid 

compliance samples were collected during the July 2000 through June 2001 compliance 

period, with 40 samples collected from July through October 2000 when DCWASA was 

using free chlorine and 13 samples collected in June 2001 after the switch to 

chloramines. Although there are several high lead levels measured prior to the 

conversion (levels of 119 μg/L, 113 μg/L, and 128 μg/L), the percentage of samples with 

lead levels >15 μg/L was greater after the conversion to chloramines (46%) than before 

the conversion (8%). 

Three elevated lead results occurred just prior the switch to chloramines. It is difficult to 

determine, but unlikely that these few results have any significance with respect to pH. 

A lead result occasionally reached this magnitude earlier under higher pH and high free 

chlorine residuals. Similarly an occasional elevated result occurs under current 

conditions with orthophosphate (Smith, 2007). It is possible that lead release and low 

lead levels had been maintained by the high oxidation-reduction potential of the water 

and not controlled by pH. 

Figure 28 displays the average and 90th percentile lead levels by compliance period. 

The average and 90th percentile lead levels were higher after chloramination began, 

when compared to the seven previous compliance periods. Figure 29 again shows the 

LCR compliance data for the period from 1997 through 2004, with the overall average 

lead level before conversion to chloramines (when free chlorine was used from July 

1997 through October 2000) of 5 μg/L, approximately one-fourth the average lead level 

measured after conversion to chloramines (November 2000 through July 2004), which 

was 22 μg/L. This difference is significant, with a p-level of 0.0000 (t-test statistics as 

reported using StatSoft® STATISTICA software, Release 5.1). The p-level represents 

the probability of error involved in accepting the hypothesis that there is a difference in 

the two means. 

 62 
Figure 27. Lead concentrations in first draw water samples collected during different time 

intervals (July 1997 through December 2004) 

Free Chlorine Chloramines

July 00 - OCCT 

minimum pH 

requirement in dist. 

system lowered from 

7.7 to 7.0

Orthophosphate 

added systemwide

300

250

200

L)g/ μ (ade150 l LatoT

100

50

0

Mar-97 Dec-97 Oct-98 Aug-99 Jun-00 Apr-01 Feb-02 Nov-02 Sep-03 Jul-04

July - Dec 1997 July - Dec 1998 Jan - June 1999 July - Sept 1999

July 2000 - June 2001 July 2001 - June 2002 Jan - June 2003 July - Dec 2003

Jan - June 2004 July - Dec 2004

Figure 28. Average and 90th percentile lead concentrations in first draw water 

samples during different compliance periods (January 1992 through December 

2004) 

Average

90th percentile

Free Chlorine Chloramines

OCCT Minimum pH 

Requirement in 

Dist. Sys. lowered 

from 7.7 to 7.0

Orthophosphate 

Added

80

70

L)g/ μ

60

on (atitr

50

nenc Co

40

dae L

30

awt Dr

20

rsFi

10

0

2

3

4

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Ju

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JaJul

e

n - 

 -

 - 

Ja

n

Jul

aJ

 0

July

- Ju

July

Ja

Jan

 00 ly Ju

Compliance Period

 63 
Figure 29. Average lead concentrations in first draw water samples collected during 

different months (July 1997 through October 2004) 

Average after 

chloramines = 22 μg/L

11/2000 to 07/2004

Average before 

chloramines = 5 μg/L

07-1997 to 07/2000

Free Chlorine Chloramines

OCCT Minimum pH 

Requirement in 

Dist. Sys. lowered 

from 7.7 to 7.0

Orthophosphate 

Added

70

60

g/L)

50

μ (adeaw L

40

r Dstri

30

e FgaverA

20

10

0

7

7

8-9

8

r-99

9

2

3

-9

01

1

2

2

3

4

ul-9

Dec-9

00

00

0

9

04

y

Oct

Ma

g-Au

anJun-

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0

ov

p-0

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r-Ap

Se

eb

ulDecy-0

gJ

M

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Oct-0

r-0

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5.6.2 Historical Data on Wastewater Metals 

DCWASA examined historical data on lead, copper, and zinc loading to the Blue Plains 

Wastewater Treatment Facility before and after the November 1, 2000 conversion to 

chloramines to determine if the change increased metals loading. DCWASA found no 

significant increase in lead, copper, or zinc levels after November 2000 (Rizzo, 2004). 

5.6.3 Lead Levels during Temporary Disinfectant Change 

Chloraminated systems may periodically switch to free chlorine for the purpose of 

controlling microbial regrowth in the distribution system. This section discusses the 

temporary switch to an alternate disinfectant (free chlorine) for both 2003 and 2004. 

USEPA Region 3 compared LCR lead results during 2003 during a temporary switch to 

free chlorine to periods when chloramine was used for disinfection. Table 14 presents 

the LCR sampling results for the first half of 2003 when free chlorine was used from 

March 10 to April 10, 2003. Sampling results show that after chloramine addition was 

resumed in April, the number of samples with elevated lead levels increased. Another 

potential contributing factor to the higher number of samples with elevated lead levels in 

late spring may have been higher water temperature; however, it is difficult to evaluate 

the relative impact of water temperature versus the change in disinfectant practices on 

changes in lead levels measured at the tap. 

 64 
Table 14. LCR lead results for January through June 2003 

LCR Sampling Results 

Before March 10, 

2003 (chloramines)* 

March 10–April 

10, 2003 

(free chlorine)** 

From April 11 

(chloramines)*** 

Number of samples 22 29 53 

Range of First Draw Lead (μg/L) ND to 62 ND to 21 ND to 118 

Average First Draw Lead (μg/L) 7 5 13

Number of Samples >15 μg/L 3 2 12

% of Samples > 15 μg/L 14 7 23

ND = Not Detected. Source: USEPA Region 3

*LCR samples January 1 through January 31, 2003 

**LCR samples March 13 through March 28, 2003 

***LCR samples April 17 through June 30, 2003 

USEPA Region 3 also presented lead results in samples collected at 12 specific 

sampling sites during the March through April 2003 free chlorine period and samples 

collected at these same sites during the July 1, 2001 to June 30, 2002 monitoring period 

when chloramine was being used. Of these 12 sites, 8 had lead levels greater than 15 

μg/L during the 2001 through 2002 monitoring period (chloramine period), whereas only 

5 sites had elevated lead levels during the March 2003 monitoring period (free chlorine 

period). While not a rigorous statistical evaluation, these results suggest that elevated 

lead levels occurred during use of chloramines. 

HDR/EES summarized LCR lead results for the period in 2004 when free chlorine or 

chloramines were used. These results are presented in Table 15. These data indicate 

that higher lead levels were apparently measured during chloramination compared with 

lead levels measured during the period of free chlorine use. It is worth noting that some 

of the data in Table 15, after the temporary disinfectant change to free chlorine, includes 

the period after June 1, 2004 when orthophosphate had been introduced into the 4th 

High Pressure Zone, which was almost 3 months earlier than orthophosphate addition to 

the entire DCWASA system (Appendix A – Timeline). Based on available location data 

from LCR monitoring and maps of the 4th High Pressure Zone, some sampling sites 

included in the analysis shown in Table 15 may be in the 4th High Pressure Zone. This 

scenario could cause additional variability because some results may be affected by 

orthophosphate. Further spatial analyses may be beneficial to more clearly define 

conditions under which samples were taken, and potential impact on lead results. 

 65 
Table 15. LCR lead results for March through June 2004 

Before April 2, 

2004 

(chloramines)* 

April 2, 2004 to May 

7, 2004 

(temporary 

disinfectant change 

to free chlorine)** 

From May 8, 2004 

(chloramines)** 

Number of samples 28 12 30 

Range of First Draw Lead (μg/L) 2 – 190 3 – 38 1 – 97 

37

23 

77%

4 

17

33%

Average First Draw Lead (μg/L) 28 

# Samples >15 μg /L 19 

% of Samples >15 μg /L 68% 

*LCR samples March1, 2004 through April 1, 2004 

**LCR samples April 7, 2004 through April 29, 2004 

***LCR samples June 2, 2004-June 17, 2004. 

5.6.4 Lead Profiling during Temporary Disinfectant Change 

Limited LCR data for lead were available during the temporary disinfectant change. 

Consequently, HDR/EES also reviewed an additional source of data – lead profiles – 

taken during chloramine disinfection and during a temporary change to free chlorine 

disinfection. 

Lead profile data collected during periods of chloramination was compared to periods of 

free chlorine use during the 2004 temporary switch to free chlorine. Fourteen profiles 

were completed during the period when chloramines were used (December 2003 

through March 2004); 12 profiles were completed during the temporary switch to free 

chlorine that occurred from April 1, 2004 through May 7, 2004; 2 sites were completed 

after the temporary switch to free chlorine when chloramines were re-introduced to the 

system (May 8, 2004 through July 16, 2004); and 17 profiles were completed after 

orthophosphate addition (December 2004 through January 2006). Appendix A contains 

graphical summaries of these 45 lead profiles grouped by the period in which they were 

collected (i.e., during chloramination, during the temporary switch to free chlorine, after 

the temporary switch to free chlorine when chloramination was resumed, and during 

post-orthophosphate addition). Review of these data indicates that higher lead levels 

were experienced during the period when chloramination was implemented when 

compared with periods when free chlorine was used temporarily. 

Lead profile data were collected at five specific sites during periods of chloramination 

and periods of the temporary switch to free chlorine, providing data with which to 

compare the impact of disinfection change on lead levels at specific sites. These data 

are displayed in Figure 30 through Figure 34. Each profile is annotated to indicate which 

samples were representative of standing water in the premise plumbing, the lead service 

line, or the water main. This information regarding the segment of the piping system 

was based on notes included with the sampling results. Results from four of the five sites 

indicate that lead levels were lower during periods of free chlorine compared with lead 

levels measured when chloramines were used for disinfection. At House #1 (Figure 30), 

total lead levels representative of the lead service line reached 80 μg/L when 

chloramines were used, but were less than 10 μg/L during the temporary switch to free 

chlorine. House #2 (Figure 31) shows profiles after a partial lead service line 

replacement, during both chloramination and during the temporary switch to free 

chlorine. There appears to be a small increase in lead levels in the LSL segment during 

 66 
the temporary switch to free chlorine, possibly due to scale disturbance. However, the 

lead levels measured during both periods were relatively low, making it difficult to 

distinguish differences that may have been due to the disinfectant conversion. In 

addition, the date for the background sample (sample “0”) and the first liter sample 

indicate anomalous results with dissolved lead higher than total lead. The reason for this 

anomaly is unknown but could also be attributed to analytical inconsistencies at these 

low lead levels. 

At House #3 (Figure 32), total lead levels reach 24 μg/L in the LSL segment during 

chloramination. During the temporary switch to free chlorine, the first 1-liter sample 

exhibited high total lead (110 μg/L) primarily due to particulate lead. The remaining 

samples were less than 10 μg/L during the temporary switch to free chlorine. The high 

particulate lead for House #3 at sample ‘X’ could be attributed to scale disturbance and 

detachment of particulate lead, since ‘X’ represents water hammer conditions, as 

discussed previously. At House #4 (Figure 33), the highest total lead levels measured 

were 110 μg/L during chloramination and only reached 9.7 μg/L during the temporary 

switch to free chlorine. Total lead levels at House #5 (Figure 34) reached 82 μg/L during 

chloramination and 45.6 μg/L during the temporary switch to free chlorine. These 

results, as summarized in Table 16, therefore indicate lower lead levels during the 

temporary switch to free chlorine than during chloramination. Additional details 

regarding special conditions (such as partial LSL replacements) under which the profiles 

were conducted are listed in Appendix A. Table 17 summarizes the evaluation of data 

and information regarding conversion from free chlorine to chloramines for final 

disinfection. 

 

 67 
Figure 30. Lead profiles for House #1 when a) chloramines were being used as the 

disinfectant (sample collected January 13, 2004) and b) during a temporary switch to free 

chlorine as the disinfectant (sample collected April 29, 2004). 

180

160

140

120

Lead (ppb) 100

80

60

40

20

0

1 2 4 5 7 9 13 17 21 25 45 X 0

Liter

In-house 

LSL Main Plumbing a

Total Lead Dissolved Lead

180

In-house Lead Service Main Plumbing 160 Line

140

b

120

)pb100 pead (

80

L

60

40

20

0

1 2 4 5 7 9 13 17 21 25 25+3 25+10 0 X

Liter

Total Lead Dissolved Lead

 68 
Figure 31. Lead profiles for House #2 when a) chloramines were being used as the 

isinfectant (sample collected February 24, 2004) and b) during a temporary switch to free 

chlorine as the disinfectant (sample collected April 26, 2004). 

180

160

140

120

 (ppb) 100 dLea

80

60

40

20

0

1 2 4 5 6 8 10 12 14 16 18 21 24 27 27+3 27+10 X 0

Liter

In -house Lead 

Plumbing Service 

Line

Main

a

Total Lead Dissolved Lead

180

160

140

120

)bp100 pad (

80

Le

60

40

20

0

1 2 4 5 6 8 10 12 14 16 16+3 16+5 16+7 16+9 16+11 X 0

Liter

In-house Lead Main

Plumbing Service 

Line

b

Total Lead Dissolved Lead

d

 69 
Figure 32. Lead profiles for House #3 when a) chloramines were being used as the 

disinfectant (sample collected March 30, 2004) and b) during a temporary switch to free 

chlorine as the disinfectant (sample collected April 30, 2004). 

a

180

160

140

120

)pb100 pead (

80

L

60

40

20

0

1 2 3 5 7 9 10 11 13 15 18 21 24 27 0 27+3 27+10 X

Liter

In-house Lead Service Main

Plumbing Line

Total Lead Dissolved Lead

b

180

160

140

120

b) (pp

100

Lead

80

60

40

20

0

1 2 3 5 7 9 10 11 13 15 18 21 24 27 27+3 27+10 0 X

Liter

In-house Lead Main

Plumbing Serivce Line

Total Lead Dissolved Lead

 70 
180

160

140

120

Lead (ppb) 100

80

60

40

20

0

0 1 2 3 4 5 7 9 11 13 15 18 21 24 27 27+3 27+10 X

Liter

1 2 3 4 5 7 9 11 13 15 18 21 24 27 00 27+3 27+10 X

Liter

Total Lead Dissolved Lead

180

160

140

120

Lead (ppb) 100

80

60

40

20

0

In-house Lead Main Plumbing Serivce Line b 

In-house Lead Main Plumbing Service Line a 

Information was not available for 

Dissolved Lead at Liter 9

Total Lead Dissolved Lead

Figure 33. Lead profiles for House #4 when a) chloramines were being used as the 

disinfectant (sample collected March 31, 2004) and b) during a temporary switch to free 

chlorine as the disinfectant (sample collected May 7, 2004). 

 71 
Figure 34. Lead profiles for House #5 when a) chloramines were being used as the 

disinfectant (sample collected February 9, 2004) and b) during a temporary switch to free 

chlorine as the disinfectant (sample collected May 18, 2004). 

Total Lead Dissolved Lead

b 

180

160

140

120

Lead (ppb) 100

80

60

40

20

0

1 2 4 5 6 7 8 9 11 13 16 19 19+3 19+10 0 X

Liter

In-house Lead Main Plumbing Serivce Line

a 

180

160

140

120

Lead (ppb) 100

80

60

40

20

0

1 2 4 5 6 7 8 9 11 13 16 19 19+3 0 X

Liter

In-house Lead Main

Plumbing Service Line

Total Lead Dissolved Lead

 72 
Table 16. Maximum lead levels measured from profiles during 

chloramination and periods of temporary disinfectant change to free chlorine 

Maximum Lead Level Measured During Profile 

House Temporary disinfectant 

change to free chlorine Chloramination 

1 81 5.4

2 7 7

3 24 5.7*

4 110 9.7

5 82 45.6

*First draw contained high particulate lead; next highest sample was 5.7 μg/L lead. 

Table 17. Summary evaluation of data and information – conversion from free 

chlorine to chloramines for final disinfection 

Data and Information Considered Evaluation of Data and Information 

Pertaining to this Possible Cause 

DCWASA lead monitoring data, 1994–

2004. 

USEPA Region 3 analysis of LCR lead 

results for free chlorine periods vs. 

chloramines periods, 2002–2003. 

HDR/EES analysis of LCR lead results for 

free chlorine periods vs. chloramines 

periods, 2004. 

HDR/EES analysis of DCWASA Lead 

Profiles in Excel spreadsheet obtained 

from USEPA Region 3. 

Higher lead levels were measured and the number of 

samples with elevated lead levels increased when 

chloramines were used, when compared to periods 

when free chlorine was used as a disinfectant. 

HDR/EES analysis of DCWASA 4th High 

Pressure Zone hydrant WQP monitoring 

data (specifically ORP) in the timeframe 

leading up to, during and after the 2004 

free temporary disinfectant change 

Higher lead levels in LCR monitoring and lead profiles 

correspond to the periods of lower ORP typically 

observed during disinfection with chloramines. Lead 

levels in LCR monitoring and lead profiles appear to 

be lower during a period of higher ORP corresponding 

to the 2004 free temporary disinfectant change. 

Laboratory and field studies as reported by 

Schock, Lytle, and Giani (see references) 

on mechanism and presence of Pb (IV) 

versus Pb (II) compounds on the interior of 

lead service pipes.

Occurrence of Pb (IV) compounds on DCWASA lead 

service line specimens supports the theory of 

formation of Pb (IV) compounds under higher ORP 

conditions. 

USEPA Region 3 report on loadings to 

Wastewater Treatment Plant (WWTP) 

2004 (report by G. Rizzo, USEPA Region 

3, Spring 2004). 

No significant difference in lead, copper, and zinc 

loading to the Blue Plains Wastewater Treatment 

Facility after the conversion to chloramines. 

 73 
5.7 Distribution System Water Quality Characteristics 

Water quality characteristics such as alkalinity, specific conductance, temperature, and 

organic levels and speciation can impact pipe scale formation and lead release in water 

distribution systems. Furthermore, the occurrence of biological events like nitrification 

also can potentially affect lead release in lead service line and premise piping. This 

section provides an evaluation of available water quality data regarding these 

characteristics in relation to lead levels in DCWASA tap water samples. 

5.7.1 Alkalinity 

System-wide alkalinity data were analyzed to determine if any statistical differences 

occurred before and after the pH adjustment for OCCT or following the disinfectant 

conversion. As shown in Figure 35, the average alkalinity in tap water samples ranged 

from 64 to 112 mg/L as CaCO3 before the pH adjustment for OCCT and the disinfectant 

conversion. The average alkalinity ranged from 57 to 89 mg/L as CaCO3 after the OCCT 

pH adjustment and disinfectant conversion. The range and standard deviation values 

also appear to be similar, except for the period when conversion occurred (2000-2001) 

and in the following compliance period (2001-2002). Both of these periods cover an 

entire year rather than 6 months, which could explain the higher variability in these 

results. These results generally indicate that the variation in alkalinity did not appear to 

be a primary contributor to the observed increase in lead following the conversion to 

chloramination. This is based on the fact that elevated lead levels persisted during both 

higher and lower alkalinity concentrations. A linear regression analysis between total 

lead concentrations and alkalinity in the distribution system before and after the OCCT 

pH change (not shown here) further indicated that there was no correlation between the 

two parameters. 

5.7.2 Temperature and Specific Conductance 

Temperature and specific conductance were also evaluated with regards to their 

variability before, during, and after the July 2000 – June 2001 LCR monitoring period 

(data not shown). For both parameters, there was no observed difference in their 

variability, and no correlation with lead levels, over these time periods. Nevertheless, 

previous findings indicate that either of these parameters, acting in concert with other 

parameters or by themselves, may influence corrosion rates. 

Water temperature can affect lead corrosion rates (Schock et al., 1996); however, the 

impact of fluctuations in water temperature on corrosion rates is not straightforward. 

This is because temperature affects many other processes and parameters such as 

buffering capacity, lead solubility, dissolved inorganic carbon solubility, and processes 

like dissolution, diffusion, and precipitation. Schock et al., (1996) indicated that the 

response of passivated pipes to temperature variation will depend on the solubility 

trends of the non-lead solids which comprise the scale. 

Specific conductance or conductivity is a function of the concentration and composition 

of dissolved solids in a water sample. Ions of particular interest in drinking water systems 

include sodium, calcium, magnesium, chloride, carbonate, and sulfate (AWWA, 2005). 

Increased conductivity values are indicative of higher concentrations of these and other 

ions. Greater conductivity means that the water is better able to complete the 

electrochemical circuit and conduct a corrosive current (AWWA, 2005). If sulfate and 

 74 
chloride are present at sufficient concentrations the water is likely to exhibit increased 

corrosiveness towards iron-based materials, depending on the mass ratio of chloride to 

sulfate. If the conductivity is composed primarily of bicarbonate and hardness ions, the 

water may be highly corrosive towards copper (Schock, 1999). Waters with low 

conductivity may also be corrosive to lead and increase lead solubility, since these 

waters tend to dissolve (corrode) materials with which they are in contact in an attempt 

to reach equilibrium (AWWA, 2005). 

160 80

70 140

60

)

120

 CaCO3

L)g/

50 μ( 

s

100

on

a

i

g/L 

t

40

m

entra

nity (

80

lia

30

d Conc

Alk

Lea

60

20

40 10

20 0

July - Dec Jan - June July - Dec July 2000 - July 2001- Jan - June July - Dec Jan - June July - Dec

1998 1999 1999 June 2001 June 2002 2003 2003 2004 2004

Alkalinity

90th Percentile First

Draw Lead

Conversion to 

Chloramines

pH 7.7 pH 7.0

Figure 35. Average daily alkalinity and lead concentration in first draw water samples 

before and after the conversion from free chlorine to chloramines as the residual 

disinfectant 

5.7.3 Natural Organic Matter 

Previous research has suggested that natural organic matter (NOM) can influence 

corrosion processes (Colling et al., 1987, Marani et al., 1995, Schock et al., 1996; 

Hopwood et al., 2002; Korshin et al., 2005). The impact of NOM on corrosion processes 

depends on its concentration and physicochemical characteristics (Korshin et al., 2005). 

The characteristics of NOM may become altered by drinking water treatment processes, 

subsequently changing its impact on corrosion rates in distribution systems (Korshin et 

al., 2005). Korshin et al., (2005) found that NOM increased the soluble levels of lead 

and tin significantly. Here, the presence of NOM in suspension caused larger colloidal 

lead and solder particles to break down into smaller formations or contribute to soluble 

metal. Additionally, amorphous films were observed to form on corroding lead surfaces 

in the presence of NOM, though it was not noted whether this film acted as a passivating 

layer. Nevertheless, it was concluded that the concentration and characteristics of NOM 

present, in addition to pH and alkalinity, may be one of the important factors in 

 75 
establishing the predominance of and transitions between alternative lead solids during 

corrosion. 

5.7.4 Nitrification 

The occurrence of nitrification events in the DCWASA distribution system was 

investigated for potential impacts on water quality. While nitrification does not directly 

influence corrosion, it could potentially affect distribution system pH and alkalinity. The 

Washington Aqueduct has been sampling for nitrification indicator parameters (e.g., 

nitrite, nitrate, ammonia, pH, and bacteria), but no evidence suggesting that widespread 

nitrification was occurring in the distribution system was found (Rizzo, 2004). 

Furthermore, the occurrence of nitrification in the distribution system has not been 

documented by either DCWASA or USEPA Region 3 (Rizzo, 2005b). Although a more 

rigorous analysis of water quality data may reveal more information on the occurrence 

and subsequent impacts of nitrification in the DCWASA distribution system, based on 

the findings to date, it does not appear to be a significant factor. 

5.8 Galvanic Corrosion of Lead Service Lines 

One issue of concern associated with partial replacement of lead service lines with 

copper piping is the potential for galvanic corrosion. Galvanic couplings can create loss 

of metal at the anode and subsequent release into the water column. Theoretically, this 

mechanism could have a significant impact on lead corrosion rates when copper and 

lead are coupled. However, there is some uncertainty regarding the duration of 

accelerated corrosion rates caused by the coupling and whether an accelerated 

corrosion rate would be observed when the surface of the lead piping has been 

passivated. Partial LSLR was conducted during a timeframe when DCWASA continued 

to fail to meet the LCR 90th percentile AL. Therefore, the potential impact of this 

process on lead levels in service lines was evaluated further. 

Reiber and Dufresne (2005) conducted a laboratory study to characterize the electrical 

impacts associated with galvanically-coupled lead and copper service lines to determine 

if replacing a portion of a lead pipe with copper piping might cause accelerated lead 

release in drinking water. This study was conducted using lead service lines which had 

been recently removed from DCWASA residences and water which had a baseline 

chemistry comparable to DCWASA’s, including similar pH, alkalinity, hardness, and 

conductivity. The study was conducted under controlled laboratory conditions designed 

to accelerate lead release. 

Reiber and Dufresne (2005) used two experimental set-ups for this evaluation: indirectly 

coupled cells and directly coupled pipe segments. Polarization cells connected in a 

hydraulic series with electrical connections between individual cells were used for 

evaluating indirectly connected lead and copper pipe segments. This approach allowed 

the researchers to manipulate cathode and anode ratios, the current flow between cells, 

and evaluate metal release. In the second experimental approach, 3⁄4-inch diameter 

copper tubing was directly connected to each lead service line section. To ensure 

electrical coupling, the lead service line was grooved to match the end of the copper 

segment. In both experimental approaches, electrodes were used to measure changes 

in the pipe surface potential. The electrodes could measure potential shifts of a millivolt 

or less, while the theoretical impact of galvanic corrosion was expected to be on the 

order of hundreds of millivolts. 

 76 
For the indirectly coupled experimental approach, the researchers found that the 

galvanic impact could be measured immediately for passivated lead service lines; 

however, the change in the pipe surface potential was on the order of only a few 

millivolts. A much greater shift in surface potential was measured when unpassivated 

lead service lines were indirectly coupled to copper piping. 

When the pipes were directly connected, there was no significant impact on the pipe 

surface corrosion potential for the passivated lead service lines. However, the 

unpassivated lead piping did experience an electrochemical impact when directly 

coupled to the copper piping. Figure 36 presents a profile illustrating the surface 

potential along the length of directly coupled lead (passivated and unpassivated 

conditions) and copper service lines. Sample locations are represented by the electrode 

sites. The surface potential of the passivated lead service line deviates only slightly from 

the freely corroding lead surface potential, and only for the section of pipe that is within 

approximately 4 centimeters of the direct coupling. 

Figure 36. Surface potential along the length of directly coupled 

lead and copper service lines 

Water flow 

direction 

This study also showed that the chlorine residual (free or combined) elevated the 

galvanic effect on the lead-copper couple by accelerating the galvanic influence on the 

copper service line, but the overall impact was nearly imperceptible on the lead service 

line. According to the investigators, conductivity had a greater effect on the galvanic 

process than chlorine residual. 

It was also determined that for well-aged, passivated DCWASA lead service line 

specimens, the area of galvanic influence was limited when coupled to a new length of 

copper tubing, as in a partial lead service line replacement. Therefore, galvanic 

corrosion was likely not a major contributing factor to elevated lead levels initially or 

 77 
during continued failure to meet the LCR 90th percentile AL. A summary of the galvanic 

corrosion data from Reiber and Dufresne (2005) is given in Table 18. 

Data and Information 

Considered 

Evaluation of Data and Information Pertaining to this 

Possible Cause 

Reiber and Dufresne (2005) Laboratory testing results indicate that galvanic coupling of lead 

and copper service lines (e.g., partial lead pipe replacements) 

likely contributed minimally to lead release in drinking water in 

connections to the DCWASA distribution system. 

Table 18. Summary evaluation of data and information – 

galvanic corrosion of lead service lines 

5.9 Effect of Grounding Currents on Lead-Bearing Components 

The impact of grounding currents on metal release from piping systems has been 

studied with the primary focus on copper tubing (Reiber and Dufresne, 2005). With 

respect to lead service lines, studies have produced conflicting results (Bell, 1998 and 

AwwaRF, 1996) regarding whether grounding currents present at the external pipe 

surface impact metal release from the internal pipe surface to drinking water. 

Reiber and Dufresne (2005) conducted a laboratory study to investigate whether 

grounding currents could have a significant and prolonged impact on metals release 

from lead service lines and leaded-brass appurtenances. This study utilized a flowthrough recirculation loop consisting of DCWASA lead service line segments, new 

copper tubing, water reservoir, and flow control and pumping hardware. High 

impedance reference electrodes were sited along the lead service line segments to 

monitor surface potential on the interior of the pipe while different current forms, 

amperages, voltages and grounding scenarios were applied to the test rig. Testing did 

not intend to replicate distribution system conditions, but instead to evaluate various 

scenarios by generating the highest possible metal release and the greatest lead service 

line surface effects. 

Results showed that impressed currents (AC or DC) on lead service lines and copper 

service lines, including grounding type currents, had no impact on the internal corrosion

of the household service lines or any other plumbing appurtenances that were tested. 

Figure 37 presents profiles of the surface potential response to AC and DC currents. 

The investigators concluded that there is likely no acceleration of corrosion associated 

with the conventional practice of electrical system grounding to household water 

systems. Reiber and Dufresne (2005) indicate that this may be the case because 

imposing an external current on the pipeline changes the potential of all surfaces, both 

external and internal, and everything in contact with the piping. The internal surface 

potential relative to the water contained in the pipe may not change since the potential of 

the water has been shifted to an amount equal to the shift of the potential of the interior

pipe surface. Corrosion would occur when the internal surface potential changes 

relative to the water in the pipe. Table 19 shows the summary evaluation of data and 

information related to grounding currents. 

 78 
Figure 37. Impressed current impacts for separate DC (upper) and AC (lower) tests on 

surface potential of a lead service line coupled to copper tubing 

Table 19. Summary evaluation of data and information – grounding currents that 

affect corrosion of lead-bearing components 

Data and Information 

Considered 

Evaluation of Data and Information Pertaining to this 

Possible Cause 

Reiber and Dufresne (2005) Laboratory testing results indicate that grounding currents 

on lead service lines and copper service lines had no 

discernable impacts on the internal corrosion of the 

household service lines or any other plumbing 

appurtenance that were tested. 

 79 
5.10 City-Wide Meter Replacement Program 

From March 2002 through May 2005, more than 116,000 meters were replaced in the 

DCWASA system by contractors (data from Raymond Hanesworth, DCWASA). This 

meter replacement program could be a potential cause of lead release into the drinking 

water in two ways: (1) soluble lead release from the meters themselves; and/or (2) 

disturbance of connective piping that could release and expose lead-bearing scales. 

Keefer and Giani (2005) conducted a laboratory study from April to June 2004 to 

evaluate lead release from two new bronze water meters and subsequent uptake by 

water. Three different water treatment strategies were tested: free chlorine disinfection, 

chloramine disinfection, and chloramine disinfection with orthophosphate addition. The 

tap water used in the study contained lead levels that were less than 2 μg/L. Lead levels 

were measured after water was held in the meters for various stagnation periods ranging 

from 15 minutes to 23 hours. All three water treatment strategies resulted in some lead 

release by the meter and uptake by the water as summarized in Table 20. 

Table 20. Lead release from bronze water meters in laboratory study 

Water Treatment Strategy 

Lead Levels after 

Stagnation Period 

(μg/L) 

Stagnation Periods 

Used (hrs) 

Free chlorine disinfection 14-165 0.25-21 

Chloramine disinfection 20-145 0.5-23 

Chloramine + orthophosphate 2-22 0.5-18 

Source: Keefer and Giani (2005) 

The results of this study suggest that bronze meters may contribute to elevated lead 

levels in drinking water (Keefer and Giani, 2005). However, lead profiles were used by 

Keefer and Giani (2005) to illustrate why lead release from bronze meters may in fact 

not substantially increase lead levels in samples collected at residential taps. This 

conclusion was based on the following: dilution effects from the meter to the tap; dilution 

effects during sample collection; and the age of the bronze meter. There is little other 

data available on the potential release of lead and the contribution to lead levels at the 

tap associated with meter replacement. Based on currently available data and 

information, the contribution of lead by the city-wide meter replacement programs is 

small and likely not a major contributor to lead levels at the tap. Table 21 is a summary 

evaluation of data and information related to the city-wide meter replacement program. 

Table 21. Summary evaluation of data and information – city-wide meter 

replacement program 

Data and Information 

Considered 

Evaluation of Data and Information Pertaining to this 

Possible Cause 

Keefer and Giani (2005) Laboratory testing results indicate that bronze meters could 

contribute lead levels to drinking water. However, the 

contribution of lead is likely not substantial due to dilution 

effects (in plumbing and in the sampling container) and the 

age of the bronze meter. 

 80 
5.11 Drought Conditions and Effects on Corrosivity of DCWASA 

Water 

Two periods of drought conditions have occurred in recent years in the Washington, 

D.C. area. From the fall of 1998 through the early summer of 1999, lower than normal 

rainfall contributed to drought conditions in the Potomac River basin (Steiner and Hagen, 

2000). From the fall of 2001 through the summer of 2002, below normal rainfall and 

record low groundwater levels and stream flows were observed (Kiang and Hagen, 

2004). 

Available source water quality data were reviewed for the period of January 1998 

through September 2004 to compare water quality conditions during the aforementioned 

drought periods (fall 1998 to summer 1999 and fall 2001 to summer 2002) and the 

interim period (fall 2000 to summer 2001). A limited review of source water-specific 

conductance and alkalinity data, collected on a monthly basis and summarized in Table 

22, shows no obvious differences between the drought periods and the period with 

assumed normal precipitation. 

Table 22. Source water quality data (1998 through 2000) 

Period 

Specific 

Conductance 

(μS/cm)a

Alkalinity 

(mg/L as CaCO3)

b

Temperature 

(°F)b

Average Range Average Range Average Range 

Jan 1998 – Aug 1998 ND ND 97 83-106 61 38-85 

Sep 1998 – Aug 1999 

(Drought) 315 233-371 109 69-132 60 31-88 

Sep 1999 – Aug 2001 300 195-405 81 64-108 60 33-85 

Sep 2001 – Aug 2002 

(Drought) 340 204-454 73 30-117 63 35-87 

Sep 2002 – Dec 2004 339 273-392 62 40-95 53 33-78 

ND – No data available. 

a Untreated source water data. 

b Entry point data collected at McMillan Water Treatment Plant. Similar alkalinity and water 

temperature values were observed for the Dalecarlia plant. 

Figure 38 shows the average daily conductivity of water at the distribution system entry 

points during the two drought periods reported from January 1998 through December 

2004. It was assumed that a drought could cause an increase in conductivity during low 

rainfall periods as a result of reduced dilution effects. The data shown in Figure 38 do 

not show a clear indication that the conductivity of water entering the distribution system 

increased or decreased substantially during the drought periods relative to non-drought 

periods. 

 81 
Figure 38. Average daily specific conductance of water at the distribution system entry 

points during drought periods 

500

450

)mc

400

hos/mμ ce (

350

natcudn

300

oic Cifec

250

Sp

200

150

Jan 1998 - Aug 1998 Sept 1998 - Aug 1999 Sept 1999 - Aug 2001 Sept 2001 - Aug 2002 Sept 2002 - June 2004

Drought Periods

The average daily alkalinity for water at the distribution system entry points is shown in 

Figure 39. During the first drought period, alkalinity increased relative to that measured 

in the preceding period; however, alkalinity was lower during the second drought period. 

In fact, the average alkalinity values showed a decreasing trend following the drought 

which occurred during 1998-1999. Thus, these data do not indicate a clear relationship 

between finished water alkalinity and drought conditions. 

The average daily finished water temperature at the distribution system entry points is 

shown in Figure 40. From the data shown here the average finished water temperature 

did not differ substantially during the two drought periods relative to the non-drought 

ones. Indeed, periods of drought do not have to necessarily correspond to periods of 

elevated air temperatures. Instead drought is a measure of precipitation. Similar to other 

parameters, these data do not show a clear indication of a meaningful change in 

temperature which could impact the corrosion potential of water entering the distribution 

system. 

 82 
Figure 39. Average daily alkalinity of water at the distribution system entry points during 

drought periods 

160

140

)

120

 CaCO3 as

100

L/ity (mg

80

kalinlA

60

40

20

Jan 1998 - Aug 1998 Sept 1998 - Aug 1999 Sept 1999 - Aug 2001 Sept 2001 - Aug 2002 Sept 2002 - June 2004

Drought Periods

Figure 40. Average daily temperature of water at the distribution system entry points 

during drought periods 

100

90

80

F)

o e (

70

eraturpTem

60

50

40

30

Jan 1998 - Aug 1998 Sept 1998 - Aug 1999 Sept 1999 - Aug 2001 Sept 2001 - Aug 2002 Sept 2002 - June 2004

Drought Periods

 83 
Drought conditions may also quantitatively and qualitatively affect the concentrations 

and characteristics of NOM entering raw water systems (Volk et al., 2002; Maurice et al., 

2001). These changes result from changes in the amount and origin of the water that 

enters a surface water system. For instance, during drought periods there is less surface 

water runoff, and in turn a greater portion of the river’s base flow is groundwater 

seepage. The organic loading rate to a river may be lower during drought periods and 

may thus exert a lower chlorine demand compared to non-drought periods. The limited 

amount of water quality data (entry point and average distribution system free chlorine 

concentrations) that was available for the DCWASA system did not indicate that this was 

the case during the two drought periods and did not show any difference relative to the 

non-drought periods. This cannot be directly linked to the amount of NOM entering the 

DCWASA distribution system, as no data was available on the concentration or 

character of these organics. However, it is likely that any changes in NOM 

concentrations that occurred during the drought periods were not significant enough to 

dramatically alter the chlorine demand or in turn the ORP of the finished water. 

Based on available source water quality data and the data evaluation discussed above, 

results do not implicate drought as a major factor in causing lead release. This 

conclusion is based on the observations that the noted water quality parameters, which 

may affect corrosion rates, did not change appreciably during the two drought periods 

relative to non-drought ones. These observations are summarized in Table 23. 

Table 23. Summary evaluation of data and information – drought conditions and 

their effect on corrosivity of DCWASA water 

Data and Information Considered Evaluation of Data and Information 

Pertaining to this Possible Cause 

Steiner and Hagen (2000) 

Kiang and Hagen (2004) 

HDR/EES analysis of DCWASA lead data for 

LCR compliance, 1998 – 2004. 

HDR/EES analysis of available data for 

specific conductance, alkalinity, and 

temperature, 1998 – 2004. 

Data yields no definitive trend. 

Drought conditions likely were not a major 

contributor to elevated lead levels. 

 84 
6. CURRENT STATUS OF DCWASA SYSTEM AND 

POSSIBLE FOLLOW-ON WORK 

This section provides a brief summary of the current LCR compliance status of the 

DCWASA system. In addition, this section identifies possible follow-on work based on 

available findings and conclusions drawn from this study. 

6.1 Current LCR Compliance Status of DCWASA System 

DCWASA, in conjunction with the USEPA and WA, has been conducting a series of 

studies aimed at: (1) determining the possible cause(s) of high lead levels since LCR 

compliance monitoring in July 2000 - June 2001; and (2) identifying solutions to reduce 

and control lead levels at consumers’ taps. As part of these studies, DCWASA 

conducted a partial system application of orthophosphate in a portion of the distribution 

system known as the 4th High Pressure Zone beginning June 1, 2004. Based on results 

of this demonstration test, orthophosphate was subsequently added as treatment at the 

WA water treatment facilities to cover the entire DCWASA system beginning August 23, 

2004 for the purpose of lowering lead levels at the tap. 

The OCCT designation was modified and clarified on August 3, 2004 and September 8, 

2004 to consist of application of orthophosphate subject to stated conditions and water 

quality parameters (source: correspondence from USEPA Region 3 to WA and 

DCWASA dated August 3, 2004). USEPA Region 3 stipulated that WA meet a pH 

range of 7.7±0.3 for finished water leaving both water treatment plants during the 

distribution system passivation period. A goal of 7.7±0.1 was set, although this pH 

range was not enforceable. For distribution system samples, the same enforceable pH 

range (7.7±0.3) and non-enforceable pH goal (7.7±0.1) applied to DCWASA. 

Based on recent compliance monitoring information (DCWASA 2005; 2006), DCWASA 

was below the LCR lead action level for two consecutive 6-month monitoring periods in 

2005 since commencing system-wide addition of orthophosphate in August 2004. 

6.2 Possible Follow-on Evaluation 

Follow-on evaluations could be conducted for the purpose of understanding further 

factors that contributed to the occurrence of elevated lead levels at consumers’ taps in 

the DCWASA system. In addition, follow-on evaluations could be conducted for the 

purpose of enhancing current understanding of the interrelationships of water chemistry 

and scales on metals release in drinking water systems. Additional work activities that 

could address these issues are described below. 

6.2.1 DCWASA-Related Follow-on Evaluations 

This section outlines suggested follow-on evaluations aimed at providing further 

clarification with regard to specific conditions and events that contributed to elevated 

lead levels in the DCWASA system. Suggested topics include the following: 

• Reduced pH and alkalinity in distributed water during 2001 – 2002 

• Consequences of partial and full LSL replacement 

 85 
6.2.1.1 Reduced pH and Alkalinity in Distributed Water during 2001 – 2002 

The pH and alkalinity of finished water at the Dalecarlia and McMillan plants exhibited 

seasonal variations and fluctuations during the study period from 1992 to 2004. The pH 

and alkalinity of the distributed water generally followed the seasonal variations of the 

finished water, except during 2001 – 2002 when the pH and alkalinity of the distributed 

water were notably lower than the finished water discharged at the plants. The 

occurrence of nitrification in the distribution system has not been documented by 

DCWASA or USEPA Region 3 (Rizzo, 2005b). More research is therefore needed to 

understand the cause of reduced pH and alkalinity in the distributed water during 2001 – 

2002 and its possible impacts on lead release and corrosion control in the DCWASA 

system. 

6.2.1.2 Consequences of Partial and Full LSL Replacement 

DCWASA has replaced a large number of lead service lines in the service area. Data 

gaps exist regarding the effectiveness of partial lead service line replacement programs 

on reducing lead levels at consumers’ taps, and whether there are any short- or longterm negative impacts such as elevated lead spikes or disturbance of existing scales. 

This suggested follow-on work could improve understanding of the impact and 

consequences of performing partial or full lead service replacements on lead release 

and compliance with the LCR. 

6.2.2 Research to Enhance Understanding of Lead Release 

This section identifies follow-on evaluations that could enhance understanding of lead 

release associated with a change in treatment and potentially could be applicable to 

other utility situations. These suggested topics include the following: 

• Lead release in analogous systems following disinfectant change 

• Effectiveness of orthophosphate on lead scales 

• Effects of chloride and sulfate levels on lead release under chlorination, 

chloramination, and a disinfectant change 

• Characterization of ORP as a function of disinfection regime and ORP impact on 

lead scales 

• Improved understanding of the mechanisms and factors influencing the formation of 

Pb (IV) scales 

• Impact of changes in treatment processes on lead scale formation and lead release 

6.2.2.1 Lead Release in Analogous Systems following Disinfectant Change 

This report considered the importance of the complex interrelationships of ORP and pH 

on the predominance of Pb (II) or Pb (IV) in scales, and ultimately the release of lead from 

LSL during a change in disinfectant in the DCWASA system. Aspects of these 

interrelationships have been considered as contributing factors in metals release at other 

systems such as Greater Cincinnati Water Works and City of Madison Water Utility 

 86 
(Schock et al., 2001; Lytle and Schock, 2005b). Further analysis of analogous drinking 

water systems could be conducted by developing case studies to understand the 

complex interrelationships of these water quality parameters and system conditions on 

metals release associated with a change in disinfectant. 

6.2.2.2 Effectiveness of Orthophosphate on Lead Scales 

This report addresses the timeframe prior to system-wide application of orthophosphate 

inhibitor for corrosion control (i.e., prior to August 2004). Current information about 

orthophosphate effectiveness is based primarily on the presence and behavior of Pb (II) 

species. Little information is currently available regarding interactions of orthophosphate 

with Pb (IV) species. Consequently, it is difficult to predict the impact of using 

orthophosphate for corrosion control during a transition between Pb (II) and Pb (IV) 

regimes or under conditions in which Pb (IV) is the dominant species. More research is 

needed to understand the interaction of orthophosphate with different lead species and 

corrosion scales. 

6.2.2.3 Effects of Chloride and Sulfate Levels on Lead Release under Chlorination, 

Chloramination, and a Disinfectant Change 

The impact of the chloride and sulfate ratio on lead release is a topic that has not been 

investigated for the DCWASA system, primarily because data were not available. This 

topic is an area that warrants additional study to understand further the multiple and 

competing factors, in conjunction with a disinfectant change, that impact lead release. 

Chloride increases lead corrosion while sulfate appears to mitigate the corrosive effects 

of chloride. Consequently, the chloride/sulfate ratio is recognized as an important 

parameter in lead corrosion studies (Reiber et. al, 1997). Recent research, including 

studies pertaining to both free chlorine and chloramines disinfection, also demonstrates 

a correlation between chlorides, sulfates and lead release (Taylor et al., 2005; Tang et 

al., 2006). 

Proposed further work could include reviewing relevant data, if available, from other 

systems that use water from Washington Aqueduct such as Fairfax and Arlington. 

6.2.2.4 Characterization of ORP as a Function of Disinfection Regime and ORP 

Impact on Lead Scales 

There are data gaps in understanding the importance of ORP under different disinfection 

regimes as discussed in Section 5. More information is needed about ORP conditions in 

actual systems before, during, and after disinfectant changes. More information is also 

needed on how changes in ORP increase or decrease metals release. Improved 

understanding of the role of ORP on lead scale formation, passivation and water 

chemistry conditions could provide utilities with needed operational information for 

improved control of metals release. 

6.2.2.5 Improved Understanding of the Mechanisms and Factors Influencing the 

Formation of Pb (IV) Scales 

The mechanisms of Pb (IV) formation are not well understood, as described previously in 

this report. For example, Switzer et al. (2006) highlighted data gaps in the mechanisms 

of PbO2 formation. Lytle and Schock (2005b) identified the need for more research to 

 87 
 88 

determine the ORP threshold for PbO2 stability, its solubility in relation to pH, and the 

relationship to disinfectant type, residual, and oxidant demand in the pipe scale. . 

Korshin et al. (2005) discussed the influence of natural organic matter on corroding lead 

materials. Further fundamental research in these areas could enable a better 

understanding of the conditions that most likely facilitate and maintain Pb (IV) formation 

in drinking water systems. 

6.2.2.6 Impact of Changes in Treatment Processes on Lead Scale Formation and 

Lead Release 

More research on the formation and stability of Pb (IV) scales under a variety of different 

conditions is needed. Lytle and Schock (2005b) identified the need for elucidating the 

decomposition pathway of PbO2 scales because serious problems potentially could 

occur with treatment changes that result in lowering of the redox potential. Additional 

research is therefore needed to understand how temporary and long-term changes in 

disinfectant affect the formation of lead scale and short- and long-term lead release at 

consumers’ taps. Other possible treatment changes such as pH adjustment and 

coagulant changes could potentially affect scales formation and stability. This 

information could form the basis for developing decision-tools that utilities could use to 

predict how treatment changes and chemical conditions will impact lead scales and lead 

release. 
7. ABBREVIATIONS 

μg/L micrograms per liter 

AC alternating current 

AL action level 

AO Administrative Order 

DC District of Columbia (or direct current) 

DCWASA District of Columbia Water and Sewer Authority 

DS distribution system 

EC electrochemical 

GIS Geographic Information Systems 

LCR Lead and Copper Rule 

LSI Langelier Saturation Index 

LSL lead service line 

LSLR lead service line replacement 

MCL maximum contaminant level 

mg/L milligrams per liter 

NE northeast 

NOM natural organic matter 

NSF National Sanitation Foundation 

NW northwest 

O&M operations and maintenance 

OCCT Optimal Corrosion Control Treatment 

ORP Oxidation Reduction Potential 

OWQP Optimal Water Quality Parameters 

PbO2 lead dioxide 

PLSLR partial lead service line replacement 

PO4 phosphate 

POU point-of-use 

ppb parts per billion 

ppm parts per million 

PQAPP Programmatic Quality Assurance Project Plan 

SE southeast 

SHE standard hydrogen electrode 

SOP standard operating procedures 

SW southwest 

SWTR Surface Water Treatment Rule 

TCR Total Coliform Rule 

THM trihalomethane 

TTHM total trihalomethane 

USACE United States Army Corps of Engineers 

USEPA United States Environmental Protection Agency 

WA Washington Aqueduct 

WASUA Water and Sewer Utility Administration 

WTP water treatment plant 

WWTP wastewater treatment plant 

 89 
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Appendix A 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

Final Report
 

Timeline 

July 1992 

District of Columbia Water and Sewer Authority (DCWASA) exceeded the lead action 

level for the Jan. to June 1992 monitoring period, the first required round of Lead and 

Copper Rule (LCR) compliance monitoring (source: July 16, 1997 correspondence from 

USEPA Region 3 to DCWASA). 

January 1993 

District of Columbia Water and Sewer Authority (DCWASA) exceeded the lead action 

level for the July to December 1992 monitoring period, the second required round of 

LCR compliance monitoring (source: July 16, 1997 correspondence from USEPA Region 3

 to DCWASA). 

September 29, 1993 

Administrative Order (AO) issued to Water and Sewer Utility Administration (WASUA) for 

acute and routine violations of the Total Coliform Rule (TCR) in September 1993. 

WASUA was required to submit a plan for improving the flushing program. 

October 15, 1993 

AO issued to the Washington Aqueduct (WA) for "virtual" violation of the TCR, i.e., 

numerous coliform positive samples at the entry points to the distribution system. 

December 7, 1993 

Turbidity MCL violation at Dalecarlia water treatment plant (source: 1995 Sanitary 

Survey of the Drinking Water Distribution System of the District of Columbia). 

January 1994 

DCWASA reported that the lead action level was exceeded for the July to Dec. 1993 

monitoring period (source: CDM memo12/12/03). 

March 2, 1994 

AO issued to the WA due to a violation of the turbidity requirements of the Surface Water 

Treatment Rule (SWTR). The AO required the WA to perform a Comprehensive 

Performance Evaluation at the Dalecarlia and McMillan water treatment plants, and to 

comply with the filtration, disinfection, reporting and public notification requirements of 

the Safe Drinking Water Act. It also required the WA to develop a source water 

monitoring program, to analyze capital improvement needs at both water treatment 

plants, and to evaluate procedures for emergency notification of plant personnel. 

June 1994 

WA submitted a corrosion control report to USEPA Region 3 that recommended 

optimum corrosion control treatment as pH control to maintain a positive Langelier 

Saturation Index. 

Final Report, May 31, 2007 A-1 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

July 1994 

WASUA reported that the lead action level was exceeded for the Jan. to June 1994 

90th monitoring period (source: CDM memo12/12/03, and DCWASA percentile 

calculations). 

June 1995 

WASUA recorded an acute Total Coliform Rule violation for E. coli (source: 1996 FollowUp Sanitary Survey of the Drinking Water Distribution System of the District of 

Columbia). 

October 1995 

WASUA violated the TCR MCL (more than 5% of samples were total coliform positive) 

(source: 1996 Follow-Up Sanitary Survey of the Drinking Water Distribution System of 

the District of Columbia). 

November 1995 

WASUA recorded two acute violations of the TCR and USEPA Region 3 issued a 

limited boil water notice for the areas involved (source: 1996 Follow-Up Sanitary Survey 

of the Drinking Water Distribution System of the District of Columbia). Because of these 

events, USEPA Region 3 issued an AO that requires a rational plan of action to improve 

TCR compliance based on recommendations in the 1995 sanitary survey. 

June 1996 

WASUA violated the TCR MCL (more than 5% of samples were total coliform positive) 

(source: 1996 Follow-Up Sanitary Survey of the Drinking Water Distribution System of 

the District of Columbia). 

July 1996 

WASUA violated the TCR MCL (more than 5% of samples were total coliform positive) 

(source: 1996 Follow-Up Sanitary Survey of the Drinking Water Distribution System of 

the District of Columbia). 

July 12, 1996 

AO issued to WASUA which incorporated the November 1995AO and the routine 

monthly TCR violation in June 1996. 

August 1996 

WASUA violated the TCR MCL (more than 5% of samples were total coliform positive) 

(source: 1996 Follow-Up Sanitary Survey of the Drinking Water Distribution System of 

the District of Columbia). 

July 16, 1997 

USEPA Region 3 conditionally designated Optimized Corrosion Control Treatment 

(OCCT) as maintenance of a slightly positive Langelier Saturation Index through pH 

adjustment (source: correspondence from USEPA Region 3 to WA and DCWASA 

7/16/97). As a condition of this designation, USEPA Region 3 issued an AO for WA and 

DCWASA to jointly assess the feasibility of alternate corrosion control treatment 

including use of sodium hydroxide for pH control, and use of a non-zinc orthophosphate 

corrosion inhibitor. 

Final Report, May 31, 2007 A-2 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

October 1, 1996 

DCWASA was created (note no longer named WASUA). 

February 2000 

USEPA Region 3 designated the use of pH adjustment as the OCCT for the 

Washington Aqueduct and DCWASA. This designation required WA to maintain the 

highest pH level attainable at the entry points to the distribution system without causing 

excessive calcium carbonate precipitation in the distribution system. USEPA Region 3

designated that a minimum pH of 7.7 be maintained at the entry points to the distribution 

system and at all tap samples within the distribution system (source: correspondence 

from USEPA Region 3 to WA and DCWASA 2/29/00). USEPA Region 3 also reduced 

the requirement for LCR tap monitoring to once per year at 50 sites during the period 

June-September. 

DCWASA established a supplemental monitoring plan to supplement the TCR 

monitoring program focusing on worst-case areas (Source: 2002 Sanitary Survey). 

November 1, 2000 

WA initiated addition of chloramines for final disinfection in the distribution system, 

replacing free chlorine addition (source: CDM memo12/12/03). 

November 1, 2000 

WA converted from a dry alum feed system to a liquid alum feed system (source: CDM 

memo 12/12/03). 

2000 

Drought conditions may have affected source and finished water quality sufficiently to 

affect lead solubility (source: CDM memo12/12/03). 

May 17, 2002 

Retroactive to the monitoring period which began on July 1, 2000, USEPA Region 3

revised its designation of OWQP for minimum monthly pH at entry points to the 

distribution system as follows: January (7.7), February (7.8), March (7.7), April (7.6), 

May (7.5), June (7.4), July (7.4), August (7.4), September (7.4), October (7.5), 

November (7.5), and December (7.6). Also, the minimum pH at distribution system tap 

sample locations would change from 7.7 to 7.0 (source: correspondence from USEPA 

Region 3 to WA and DCWASA 5/17/02). 

Aug. 26, 2002 

DCWASA reported that more than 10% of samples exceeded the lead action level of 15 

ppb for the July 1, 2001 to June 30, 2002 monitoring period (samples collected July-Aug. 

2001 and June 2002) (source: correspondence from DCWASA to USEPA Region 3). 

May 20, 2003 

DCWASA outlined its 2003 Lead Replacement Program in a letter to USEPA Region 3. 

The program was accepted by USEPA Region 3 in a letter dated June 27, 2003. 

DCWASA was required to replace 7% of its lead services per year as long as the system 

continues to exceed the lead action level. In lieu of physical replacement, the 

regulations allow service lines to be sampled to demonstrate that the water is below the 

lead action level. 

Final Report, May 31, 2007 A-3 
 

 

 

 

 

 

 

 

July 29, 2003 

DCWASA reported that more than 10% of samples exceeded the lead action level for 

the Jan. to June 2003 monitoring period (source: correspondence from DCWASA to 

USEPA Region 3). 

September 2003 

DCWASA completed an initial inventory of lead service lines (Source: Report on the 

Material Evaluation and Initial Inventory Sept. 2003). As of Sept. 30, 2002, there were 

23,071 known lead service lines in the DC water distribution system. 

October 2003 

USEPA Region 3’s independent corrosion expert found no reasons for DCWASA to not

implement phosphate addition for corrosion control but recommended additional studies 

be conducted to further diagnose the DCWASA lead problem and proposed corrective 

actions. 

October 24, 2003 

DCWASA reported that 385 lead services were physically replaced between 10/01/02 

and 09/30/03, and 1,241 lead service lines were sampled in lieu of physical replacement 

(source: DCWASA’s Lead Service Replacement Program Annual Report for 2003). 

January 2004 

DCWASA developed a research strategy and presented it to WA, Arlington County, The 

City of Falls Church, and USEPA Region 3. 

January 26, 2004 

DCWASA reported that more than 10% of samples exceeded the lead action level for 

the July to Dec. 2003 monitoring period (source: correspondence from DCWASA to 

USEPA Region 3). 

February 2004 

USEPA formed the Technical Expert Working Group to address the problem of elevated 

lead levels. 

April 30, 2004 

USEPA Region 3 designated use of zinc orthophosphate for partial system application 

in the 4th High Pressure Zone (source: correspondence from USEPA Region 3 to WA 

and DCWASA 8/3/04). 

May 28, 2004 

USEPA Region 3 modified its April 30, 2004 designation of OCCT for the DC 

distribution system to use orthophosphate instead of zinc orthophosphate for the 4th High 

Pressure Zone (correspondence from USEPA Region 3 to WA and DCWASA 8/3/04). 

June 1, 2004 

4th The partial system application of orthophosphate to the High Pressure Zone 

commenced (source: correspondence from USEPA Region 3 to WA and DCWASA 

8/3/04). 

Final Report, May 31, 2007 A-4 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

June 17, 2004 

USEPA Region 3 issued an AO requiring DCWASA to develop a plan for updating its 

materials evaluation used for sampling and its inventory of lead service lines, and a plan 

for conducting follow-up sampling after partial replacement of a lead service line (Docket 

No. SDWA-03-2004-0259DS). 

July 6, 2004 

DCWASA exceeded the lead action level for the Jan. to June 2004 monitoring period 

(source: correspondence from DCWASA to USEPA Region 3). 

August 3, 2004 

USEPA modified the interim designation of OCCT for the DC distribution system to 

consist of application of orthophosphate subject to stated conditions and water quality 

parameters (source: correspondence from USEPA Region 3 to WA and DCWASA 

8/3/04). This designation was slightly modified and clarified on September 8, 2004. 

USEPA stipulated that the WA meet a pH goal of 7.7 ±0.1 for finished water leaving both 

WTPs, and 7.7 ±0.1 for water samples from the distribution system during the 

passivation period. 

August 23, 2004 

The Washington Aqueduct began feeding an orthophosphate corrosion inhibitor 

(sources: DCWASA memo undated, CH2MHill pH study report 11/30/04). 

September 8, 2004 

The interim designation of OCCT of August 3rd 2004 was slightly modified and clarified 

(source: correspondence from USEPA Region 3 to WA and DCWASA 09/08/2004) 

October 2004 

DCWASA reported that 1,793 lead services were physically replaced between 10/1/03 

and 9/30/04 (source: correspondence from DCWASA to USEPA Region 3 10/8/04). 

November 30, 2004 

A consultant completed a pH study report evaluating how WA can tighten pH control at 

the two WTPs to meet the pH goal of 7.7 +/- 0.1 pH units. The report also includes 

recommendations for reducing finished water turbidity at the Dalecarlia WTP (source: 

CH2MHill Report, 11/30/04). 

January 2005 

DCWASA exceeded the lead action level for the July to Dec. 2004 monitoring period 

(source: DCWASA Lead and Copper Compliance Report). 

January 14, 2005 

USEPA Region 3 issued a supplemental AO to DCWASA related to lead service line 

inventories, replacement program, sampling methodology and public notification. 

(Docket No. SDWA-03-2005-0025DS). 

June 2005 

DCWASA met the LCR 90th percentile AL for the monitoring period Jan-Jun 2005. 

December 2005 

DCWASA met the LCR 90th percentile AL for the monitoring period Jul-Dec 2005. 

Final Report, May 31, 2007 A-5 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

Final Report 

Administrative Orders 

The Administrative Orders (AOs) issued to the Washington Aqueduct (WA), the Water 

and Sewer Utility Administration (WASUA) and District of Columbia Water and Sewer 

Authority (DCWASA) are listed below in chronological order. WASUA was part of the 

District of Columbia Department of Public Works until it was replaced by DCWASA on 

October 1, 1996. 

September 29, 1993 

An Emergency AO was issued to WASUA for acute and routine violations of the TCR in 

September 1993. A copy is not available. 

October 15, 1993 

An Emergency AO was issued to the Washington Aqueduct for "virtual" violation of the 

TCR, i.e., numerous coliform positive samples were found at the entry points to the 

distribution system. The AO required application of a filter aid chemical at the McMillan 

water treatment plant, speciation of all fecal coliform positive samples, additional 

monitoring at both water treatment plants’ individual filters, Giardia and Cryptosporidium 

monitoring at water treatment plant reservoirs, and development of a written protocol for 

data review. This AO was superseded by the March 1, 1994 AO. 

March 1, 1994 

An Emergency AO was issued to the Washington Aqueduct due to a violation of the 

turbidity requirements of the Surface Water Treatment Rule (SWTR). It superseded the 

AO dated October 15, 1993. The AO required the WA to perform a comprehensive 

performance evaluation at the Dalecarlia and McMillan water treatment plants, and to 

comply with the filtration, disinfection, reporting and public notification requirements of 

the Safe Drinking Water Act. It also required WA to develop a source water monitoring 

program, to analyze capital improvement needs at both water treatment plants, and to 

evaluate procedures for emergency notification of plant personnel. 

November 1995 

Proposed AO issued to WASUA for previous violations of the TCR and to correct 

deficiencies found in the 1995 sanitary survey. A copy of the final AO is not available 

but its content is equal to the draft AO (per G. Rizzo of USEPA Region 3 in email to K. 

Martel, 4/11/05). 

July 12, 1996 

AO issued to WASUA which incorporated the November 1995 AO. The AO required 

WASUA to notify the public of its November 1995 acute MCL violation and monthly MCL 

violations of October 1995 and June 1996. WASUA was also required to develop the 

following programs: public notification, financial management, flushing and disinfection, 

storage tank maintenance and cross connection control. 

A-6 
 A-7 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

July 16, 1997 

USEPA Region 3 issued an AO for WA and DCWASA to jointly assess the feasibility of 

alternate corrosion control treatment including use of sodium hydroxide for pH control, 

and use of a non-zinc orthophosphate corrosion inhibitor. 

June 17, 2004 

USEPA Region 3 issued an administrative order requiring DCWASA to develop a plan 

for updating its materials evaluation used for sampling and its inventory of lead service 

lines, and a plan for conducting follow-up sampling after partial replacement of a lead 

service line (Docket No. SDWA-03-2004-0259DS). 

Jan. 14, 2005 

USEPA Region 3 issued a supplemental administrative order to the June 17, 2004 order 

discussed above. This order indicated that DCWASA had used an unapproved and 

inappropriate method of five-minute flushing in determining whether some of the lead 

service lines needed to be replaced. This order required that DCWASA determine how 

many lead service lines had “passed” (meaning contributed less than 15 parts per billion 

of lead), as presented in the September 2003 Annual Report for Lead Service Line 

Replacement Program, using this incorrect methodology. Additionally, DCWASA was 

required to determine how many of these lines had been replaced without being reported 

to USEPA in 2003 and 2004. USEPA required DCWASA to physically replace lead 

service lines equal in number to the number of LSLs passed in the 2003 report, less the 

number that were physically replaced in 2003-2004. DCWASA was required to provide 

notification to customers whose lead service lines had incorrectly passed due to using 

the incorrect methodology. DCWASA shall (Docket No. SDWA-03-2005-0025DS). 
Final Report, May 31, 2007 A-8 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

Final Report
 

Summary of Sanitary Surveys 

1995 Sanitary Survey of the Drinking Water Distribution System of the District of 

Columbia 

The 1995 survey was conducted from April to June. The survey objectives were to identify the 

problems associated with bacteriological activity in the District of Columbia (DC) system and 

provide recommendations to alleviate those problems. The survey included both the storage 

facilities and the distribution system operated and maintained by WASUA and the WA Division 

of the U.S. Army Corp. of Engineers. Laboratory data for 1993 through 1995 indicated elevated 

bacteriological activity in service reservoirs and the DCWASA distribution system. The 

distribution system reservoirs had not been drained and inspected in approximately 20 years, 

and on-site inspections of the reservoirs revealed numerous sanitary deficiencies. Survey 

findings included 185 recommendations that addressed treatment practices, cross connections, 

distribution system O&M practices, consecutive systems, and operating procedures. Ninety one 

recommendations were developed for reservoir facilities and operating conditions. 

1996 Follow-Up Sanitary Survey of the Drinking Water Distribution System of the District 

of Columbia 

The 1996 survey was conducted during the month of September. Since the 1995 Sanitary 

Survey Report was completed, the DC formed a new Regional Water and Sewer Authority 

(WASA) to oversee operations of its water and sewer systems. Of the 185 recommendations in 

the 1995 survey, 23 were fully completed, and 129 were under contract or part of a future plan. 

Seven storage tanks were drained, cleaned, and inspected. An improved flushing program was 

initiated. SOPs consistent with AWWA standards for water main disinfection practices were 

developed. Numerous other engineering projects were underway, such as a reservoir 

inspection program, design of reservoir improvements, clearwell improvements, development of 

O&M manuals, creation of a hydraulic model to evaluate system pressures, and plant process 

control improvements. 

1998 Follow-Up Sanitary Survey of the Drinking Water Distribution System of the District 

of Columbia 

A follow-up survey was conducted from July through September of 1998. Of the 185 

recommendations identified during the 1995 Sanitary Survey, 77 were completed, and 31 had 

not been addressed. For 15 of the 31 recommendations that were not addressed, some form of 

corrective action had been taken, but this had failed to eliminate the sanitary risk. The 

remaining 77 recommendations were under contract, planned for a future contract, under 

consideration, or part of a long term plan. Findings from the 1998 Sanitary Survey related to 

water quality monitoring included: 

•	 No coliform violations were observed between the summer of 1996 and the 1998 

follow-up survey 

•	 The TCR sampling plan and sampling sites were approved as more representative of 

distribution system water quality. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Final Report, May 31, 2007 A-9 

In terms of operations and maintenance, the 1998 survey found that WA and DCWASA 

continued to make significant progress in distribution system rehabilitation work, which included 

clearwell improvements; corrosion control evaluations; finished water reservoir cleaning, 

inspection, improvements and operating procedures; development of flushing program, and 

reduction in cross connection hazards. Training was provided to utility staff on flushing, pipe 

and valve repair, water main disinfection, backflow prevention and cross-connection control. 

Additional training recommended in the 1998 survey included: 

•	 Use of new O&M manuals and SOPs during training sessions, 

•	 Development of a written training program for coliform sampling, 

•	 Training for storage tank O&M, and 

•	 Training of new staff (e.g. flushing crews, inspectors). 

1999 Sanitary Survey and Review of Turbidity Risk of the Washington Aqueduct 

The 1999 sanitary survey of facilities owned by Washington Aqueduct (WA), conducted during 

February and March, documented 73 potential sanitary risks. The major water quality 

improvements that were identified as necessary to address the sanitary deficiencies are 

summarized below. (Note: the responses in parentheses indicate whether the deficiency had 

been addressed at the time of the 2003 survey.) 

•	 Need comprehensive watershed protection program for Dalecarlia Reservoir (no). 

•	 Develop and implement a comprehensive cross connection control program (no). 

•	 Update SOPs for WTP process operations and train operators on current procedures 

(no). 

•	 Include coagulant aid and filter aid polymers in jar testing (yes). 

•	 Remove dead eels from open well at gatehouse at McMillan Reservoir (yes). 

•	 Initiate treatment plant valve exercising program (partially meets, all valves not 

included in program). 

•	 Reduce amount of backlogged maintenance tasks with more focus on prioritizing 

(partially meets, current process does not include prioritization). 

•	 Clean out WTP sedimentation basins on regular schedule (yes). 

2002 Follow-Up Sanitary Survey of the Drinking Water Distribution System of the District 

of Columbia 

The 2002 survey was conducted from June through August. Of a total of 193 recommendations 

identified during the 2002 survey, 8 were new recommendations, and 92 had been completed. 

Twelve recommendations had been re-opened, primarily because facility O&M manuals had not 

been used to train operations staff. At the time of the survey, the following observations were 

made: 

•	 Since the original sanitary survey in 1995, all water storage facilities have been 

cleaned and inspected and most have been completely rehabilitated. The two 

remaining storage facilities that require major maintenance are under contract. 

•	 In May of 1999, the Water Quality Division established a 16-person flushing team to 

conduct unidirectional flushing of the entire distribution system every 2 years. 

Recommendations related to the flushing program included modifications to address 

problem areas, hydrant operating procedures, pressure monitoring, establishment of 

programs to address dead-ends and blow-offs. 

•	 WA made no progress on a cross-connection control program. DCWASA 

established a cross-connection control program, but staff shortages limited program 

implementation. 
 

 

 

 

 

 

 

 

•	 Since chloramination began in November 2000, an increase in total coliform 

positives was observed each year. 

•	 Staff training is needed on storage tank O&M, facility O&M manuals, on-site 

inspections, and distribution system operator certification. 

•	 Total coliform sampling sites should be reevaluated to assure they represent 

distribution system conditions and are not influenced by biofilms present in building 

plumbing. 

•	 There is a need for an integrated database that could store all data and process 

information related to water quality and system operations. 

October 17, 2003 Sanitary Survey of the Washington Aqueduct Draft Report

A sanitary survey of the facilities owned by WA (including intake works on the Potomac River, 

 transmission mains, two WTPs, and pumping stations) was conducted for USEPA Region 3 by the Cadmus Group. Finished water storage and the distribution system were not included in the scope of this survey. The sanitary survey team also conducted an optimization evaluation of the two WTPs based on turbidity data from July 2002 to June 2003. Of 37 sanitary deficiencies identified, the 9 highest priorities included: 

 

 

 

 

 

 

 

 

 

 

 

Final Report, May 31, 2007 A-10 

•	 Develop and implement a comprehensive cross connection control program, 

including procedures for tagging and inspecting devices. 

•	 Establish an optimization program for each WTP, including detailed filter evaluations. 

•	 Update SOPs for WTP process operations and train staff on current procedures. 

•	 Install an automatic switchover system for the chlorine feed system at the Dalecarlia 

WTP. 

•	 Formalize new solids handling plan for Dalecarlia WTP and incorporate it into SOPs. 

•	 Always add PAC1 as a primary coagulant at McMillan WTP due to the presence of 

two open reservoirs between the alum addition point and the treatment plant. 

•	 Move sampling ports for turbidimeters on individual filters so they monitor total filter 

effluent. 

•	 Develop procedures to minimize hydraulic changes in filter operations during 

backwash. 

•	 Properly seal clearwell openings to reduce the chance of material entry. Improve 

clearwell vent termination points to minimize vandalism and animal entry (screening). 
Final Report, May 31, 2007 A-11
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

Final Report 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Supplement to History and Evaluation of Lead Monitoring Program 

USEPA Region 3 provided HDR/EES with laboratory sample reports, 90th percentile 

calculations and correspondence related to Lead and Copper Rule (LCR) monitoring, 

including first draw and second draw samples. HDR/EES reviewed 90th percentile 

calculations prepared by DCWASA and checked them against original laboratory 

reports. The results of this analysis are discussed in the main body of the report. This 

appendix lists numbers of LCR monitoring sites that exceeded the action level in each 

monitoring period. Separate tables are provided for first draw samples (Table 1) and 

second draw samples (Table 2). 

First Draw Lead Results 

Table 1 shows the number of DCWASA sample sites where lead concentrations were 

measured at levels higher than 15 μg/L and how many of those sites exceeded the 

Action Level in two or more LCR monitoring periods. 

­ Table 1 First Draw Lead Samples Listing of Sample Sites Where Lead Levels Were > 15 μg/L
 

Monitoring Period 

Number of Sample Sites 

Exceeding Action Level of 

15 μg/L 

Number of Sample Sites 

Exceeding Action Level in Two or 

More LCR Monitoring Periods January – June 1992 16 10 

July – December 1992 28 15 

January – June 1993 5 4 

July – December 1993 23 15 

January – June 1994 9 7 

July – December 1994 8 7 

January – June 1997 5 3 

July – December 1997 5 3 

July – December 1998 4 3 

January – June 1999 3 1 

July-Sept. 1999 3 2 

July 2000 – June 2001 4 4 

Revised July 2000-June 

2001 

by USEPA Region 3

9 9 

July 2001 – June 2002 26 22 

January – June 2003 30 20 

July – December 2003 35 28 

January – June 2004 73 30 

July – December 2004 40 24 
Final Report, May 31, 2007 A-12
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Second Draw Lead Results 

Table 2 lists the addresses for sample sites where lead concentrations of second draw 

samples were measured at levels higher than 15 μg/L and how many of those sites 

exceeded the Action Level in two or more LCR monitoring periods. 

Table 2 Second Draw Lead Samples ­

Listing of Sample Sites Where Lead Levels Were > 15 μg/L
 

Monitoring Period Number of Sample Sites 

Exceeding Action Level 

of 15 μg/L 

Number of Sample Sites 

Exceeding Action Level in 

Two or More LCR 

Monitoring Periods 

January – June 1997 4 2 

July-Dec. 1997 4 4 

July-Dec. 1998 3 2 

January – June 1999 3 1 

July-Sept. 1999 5 4 

July 2000 – June 2001 3 3 

July 2000 – June 2001 

(revised by USEPA Region 3) 

9 9 

July 2001-June 2002 24 24 

January – June 2003 17 15 

July-Dec. 2003 29 26 

January – June 2004 63 25 

July-Dec. 2004 35 21 
 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Final Report
 

Summary of Corrosion Control Studies 

June 1994 Corrosion Control Study (ECG, Inc.) 

The purpose of this corrosion control study was to determine the most effective treatment 

approach to control lead and copper corrosion in drinking water supply lines. The study 

included a desktop study, a screening evaluation of corrosion inhibitors using jar testing, and 

full-scale pipe loop experiments. Technical and cost constraints were identified for specific 

corrosion control treatment alternatives. The desktop study found that optimizing the pH and 

alkalinity was intrinsically related to the calcium hardness adjustment and calcium carbonate 

precipitation potential. The results of the screening evaluation showed that zinc orthophosphate 

demonstrated lower dissolved lead concentrations in the static system than the silicates, 

polyphosphates or straight orthophosphate. Both the silicates and the polyphosphates actually 

showed elevated dissolved lead concentrations when compared with the control conditions. 

Three pipe loop models were constructed to test finished water at the Dalecarlia water treatment 

plant. One model was used to test a zinc orthophosphate (1:5 ratio); a second model was used 

to test a pH/alkalinity/calcium hardness adjustment, and a third model served as a control (no 

corrosion control inhibitor or water quality adjustment implemented). These pipe loops were 

monitored for lead and copper concentrations in standing and flowing water samples, as well as 

for direct metal corrosion from coupons and inserts over a 10-month study period. The second 

pipe loop (pH/alkalinity/calcium hardness adjustment alternative) had severe calcium carbonate 

deposition problems. Zinc orthophosphate showed lower corrosion rates and reduced lead 

concentrations in the water in 84% of days studied; however, the use of zinc orthophosphate 

system-wide must be questioned due to discrete samples with elevated lead concentrations, 

overall costs, and downstream treatment of phosphorous and zinc. 

The study concluded that WA water treatment plants should optimize current practices by 

maintaining a consistent pH level, which would optimize the Langelier Saturation Index in the 

positive range, as close to zero as possible. Further, it was recommended that WA calculate 

Calcium Carbonate Precipitation Potential (CCPP) in the distribution system on a daily basis 

after treatment with the goal of keeping the CCPP at or near 0; (the study determined that it was 

not feasible to obtain CCPP levels between 4 and 10). The study noted that further research 

was needed to study the optimal balance of corrosion control, scaling and trihalomethane 

formation potential. 

Dec. 1996 Expert Review (Jonathon Clement) 

An expert review, commissioned by USEPA, was conducted to review the June 1994 corrosion 

control study and supplemental system information, including a sanitary survey, pipe material 

information and water quality data for the period of September 1995 to August 1996 (pH, 

alkalinity, chlorine, and calcium). The selection of corrosion control strategy was driven by the 

high percentage of unlined cast iron pipe in the DCWASA system (approximately 73% of total 

miles of main). Comments were based primarily on the supplementary information. Two viable 

treatment strategies for lead control included: (1) stabilize and increase the pH to 9.0, and (2) 

maintain the pH between 7.4 and 7.8 and add orthophosphate. The use of orthophosphate was 

not recommended unless site-specific testing was conducted with unlined cast-iron pipe loops, 

Final Report, May 31, 2007 A-13 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

constructed with DCWASA distribution system mains, to determine the effects of 

orthophosphate on iron release and red water. The alternative of pH adjustment to 9.0 

appeared to be more appropriate; however, potential issues with calcium precipitation, THM 

formation potential and water disposal issues (higher pH) required further evaluation. 

Additionally, the recommendations indicated that, regardless of treatment selection, maintaining 

a consistent distribution system pH should be addressed. The study recommended avoiding pH 

variations of more than 0.5 pH units. 

Jan. 1998 Caustic Soda Feasibility Study (Malcolm Pirnie) 

This feasibility study, conducted for the Washington Aqueduct, addressed Conditions 1a and 1b 

of the conditional designation of Optimum Corrosion Control Treatment, dated July 16, 1996. 

This condition required WA and DCWASA to determine the feasibility of switching from lime to 

sodium hydroxide to control pH. The feasibility assessment included: (part 1a) a determination 

of the highest pH that could be maintained using sodium hydroxide without causing exceedance 

of the total trihalomethane MCLs and excessive precipitation of calcium carbonate in the 

distribution system, and (part 1b) estimation of construction costs and annual O&M costs for the 

sodium hydroxide feed system. A spreadsheet model was used to estimate the maximum pH 

that could be maintained using lime or caustic soda while preventing excessive precipitation of 

calcium carbonate. The modeling results indicated that excessive calcium carbonate 

precipitation using caustic soda would begin at pH 0.2 units higher than when using lime. 

Additionally, modeling results indicated that excessive precipitation would occur if a pH of 8.5 

was maintained throughout the year for either lime or caustic soda. Caustic soda would provide 

some benefits in terms of process control and maintenance requirements. Disinfection byproduct levels were estimated to be the same whether caustic soda or lime was used. The 

chemical cost of caustic soda was approximately 6.5 times higher than lime for a desired target 

finished water pH of 7.4, and was approximately 5.0 times higher than lime for a desired target 

finished water pH of 8.5. The capital cost of the caustic soda feed system was estimated at 

$720,000 (1997 dollars). 

May 1998 Corrosion Inhibitor Study for Dalecarlia and McMillan Water Treatment Plants 

(Malcolm Pirnie) 

The corrosion inhibitor study, conducted for the Washington Aqueduct, included three primary 

tasks: (1) determine the approximate corrosion inhibitor dosage rate; (2) estimate phosphate 

levels in wastewater; and (3) estimate capital and O&M costs for the corrosion inhibitor feed 

system. The consultant also reviewed the current literature and immersion tests conducted by 

ECG Inc. to compare the relative benefits of zinc orthophosphate and orthophosphate 

(phosphoric acid). The study concluded: 

1.	 Zinc orthophosphate does not provide any long-term benefits over orthophosphate in 

controlling lead levels in the water. 

2.	 The chemical costs for zinc orthophosphate are approximately twice the chemical costs 

for orthophosphate. 

3.	 If WA decides to use corrosion inhibitors as a lead control strategy, orthophosphate 

should be used at a dosage rate of 1.0 mg/L as PO4. 

4.	 Assuming a phosphate dose of 1.0 mg/L as PO4, the maximum phosphate concentration 

to reach the wastewater treatment plant would be approximately 1.0 mg/L as PO4, which 

would result in a 10% increase in phosphorous levels at the wastewater treatment plant 

under the worst case scenario. 

5.	 The total estimated capital costs for an orthophosphate feed system are $350,000 and 

$220,000 for the Dalecarlia and McMillan plants, respectively. 

Final Report, May 31, 2007 A-14 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6.	 The annual O&M costs of orthophosphate are $166,000 and $148,000 for the Dalecarlia 

and McMillan plants, respectively. The annual cost savings due to reduction in lime 

usage is approximately $30,000 for each plant. 

Oct. 2003 Expert Review – Draft Report (Marc Edwards) 

This expert review, conducted for USEPA Region 3, was based on an extensive literature 

review and a few experiments. The report found no reasons for DCWASA to not implement 

phosphate addition for corrosion control but recommended that additional studies and corrective 

actions should be conducted to further diagnose the DCWASA lead problem. The report also 

indicated that it could not be determined whether phosphate addition would address the lead 

problem. The following prioritized action items were recommended for mitigating the lead 

problem: 

a.	 Compare LCR sampling protocols for the seven utilities treating Potomac River water, 

and compare samples for the old and new sampling protocols. Determine if the new 

sampling protocol mobilizes more particulate lead. Check use of filtration devices on 

kitchen taps at LCR sampling sites, and document sampling procedures used at these 

sites. 

b.	 Initiate a corrosion study of brass, pure lead and lead-solder coupled to copper to 

evaluate galvanic corrosion, chloramine corrosion and the combined effect of nitrate and 

chloramine on each lead-bearing material. 

c.	 Conduct a filtration analysis of solids present in the DCWASA system and try to 

determine their source. 

d.	 Conduct a study or review existing data, if available, on nitrification events in the 

DCWASA system and sister systems served by the Dalecarlia water treatment plant. 

e.	 Examine historical data on lead, copper and zinc loading to the sewage treatment plant 

from the DCWASA system, before and after chloramine disinfection was initiated 

(November 2000). 

f.	 Examine whether DCWASA’s practice of switching disinfectants each Spring (from 

chloramine to free chlorine) adversely affects corrosion control. 

Spring 2004 USEPA Region 3 /DCWASA Response to Edwards’ Recommendations 

This paper was developed to provide background information for DC city council and 

congressional hearings during 2004. This response included the following information with 

respect to the Expert Review from 2003: 

•	 DCWASA has initiated a plan to study corrosion rates of brass, pure lead and lead 

solder before and after corrosion control treatment. 

•	 DCWASA has collected filtrate samples and will have them analyzed per 

recommendation. 

•	 DCWASA has conducted monitoring for parameters that would indicate the occurrence 

of nitrification. The sampling effort has not found evidence of nitrification in the system. 

•	 A review of wastewater treatment plant data has indicated that no significant increase in 

lead, copper, or zinc levels occurred after conversion to chloramine. 

April 2004 Desktop Corrosion Control Study (CH2MHill) 

This study reviewed water quality changes in WA customers’ distribution systems and 

engineering reports on corrosion control and LCR compliance strategies. Corrosion control 

options that are evaluated included: (1) maintaining a constant, high pH at the two water 

treatment plants using either quicklime (current practice) and/or sodium hydroxide, and (2) 

feeding a corrosion inhibitor such as orthophosphate while maintaining a constant pH of about 

7.7 throughout the year. 

Final Report, May 31, 2007 A-15 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mathematical modeling conducted for this study found that adjustment of finished water pH to 

8.5 resulted in severely elevated levels of calcium carbonate precipitation potential, indicating 

that excessive calcium precipitation would occur. The report concluded that pH adjustment to 

pH 8.8 year-round is not advisable for the Washington Aqueduct. 

The report concluded that orthophosphate appears to be the “reoptimized” best treatment for 

Washington Aqueduct. However, further testing was recommended using partial system 

application of phosphoric acid. The report also recommended that the Washington Aqueduct 

conduct pilot-scale testing using pipe loops of DCWASA lead service lines to help determine 

optimal corrosion inhibitor feed rates. The Optimum Corrosion Control Treatment document 

was prepared and submitted to USEPA for approval. 

July 2004 Evaluation of Orthophosphate Addition Effects on Microbial Water Quality 

(Anne Camper) 

The purpose of this technical memo was to address four specific questions posed by Cadmus. 

The four questions and answers are summarized below. 

1.	 Considering DCWASA’s distribution system infrastructure and water quality, do 

you believe that orthophosphate addition will help control biofilm growth? More 

specifically, how will the addition of orthophosphate affect TCR compliance? It is 

probable that phosphate addition will have a beneficial effect on regrowth in the 

DCWASA system in the long term. In the short term, there may be some elevated 

bacterial counts. In areas of the distribution system that were not flushed prior to 

phosphate addition, increased bacterial counts are probable. 

2.	 What detrimental effects could there be in a distribution system such as 

DCWASA’s from maintaining an orthophosphate residual of 3 mg/L? The only 

potential effect on microbial growth/biofilms would be the rate at which surfaces are 

impacted by the corrosion inhibitor and the time required to reach equilibrium. 

3.	 Can the Aqueduct reduce the disinfectant residual concentration in the DCWASA 

distribution system without adversely impacting TCR compliance? If corrosion 

control has a positive impact on microbial counts, it is possible that the chloramines 

dose can be reduced, as long as dead ends and low flow areas continue to have a 

measurable residual. 

4.	 DCWASA practices unidirectional flushing in their distribution system and 

routinely flushes the entire system approximately every two years. How important 

is unidirectional flushing for the DC distribution system? In your opinion, how 

often should WASA flush their entire system? Flushing should be considered as 

part of DC’s program to improve microbial water quality. Because of the predominance 

of unlined cast iron pipes in the DC system, flushing is critical for maintaining water 

quality, particularly in low flow areas where loose deposits accumulate. It is difficult to 

determine flushing frequency as it depends on many factors including water quality, cost, 

historical flushing practices, personnel resources, water availability during drought 

conditions, and disposal of flushing water. 

Nov. 2004 pH Study Report for Washington Aqueduct (CH2M Hill) 

The purpose of this report was to evaluate alternatives and recommend process changes for 

achieving optimized pH control at the Dalecarlia and McMillan water treatment plants. Four 

Final Report, May 31, 2007 A-16 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

alternatives were evaluated: (1) optimize existing pH control equipment; (2) replace existing lime 

slakers with batch-type slaker systems; (3) trim final pH with caustic while continuing to use lime 

for base load pH adjustment; and (4) replace lime feed with caustic feed. Recommendations 

were based on the third alternative: trim final pH with caustic and use lime for base pH 

adjustment. The report recommended that the existing lime feeders be replaced with properly 

sized feeders to improve control of lime feed. 

Effects of External Currents and Dissimilar Metal Contact on Corrosion and Metals 

Release From Lead Service Lines (HDR and Cadmus) 

The purpose of this project was to use laboratory-scale testing rigs to identify whether grounding 

and/or galvanic currents can have a significant and prolonged impact on metals release from 

lead service lines and leaded-brass appurtenances. Different forms of grounding currents (AC 

vs. rectified) were impressed on both scaled and un-scaled lead service lines used in the testing 

rigs. Galvanic currents were generated using the coupling of different lengths of copper tubing 

to the lead service lines while the surface potential was measured. The testing was not 

intended to replicate distribution system conditions but to evaluate various scenarios that 

generate the highest possible metal release and the greatest lead service line surface effects. 

The draft final report on this project was issued in November 2005. 

Technical Support on Nitrification Inhibition From Zinc (Virginia Military Institute and 

Cadmus) 

This project was a preliminary step towards assessing the potential impacts of zinc-phosphate, 

a proposed corrosion control chemical for drinking water, on the operation of the Arlington 

County (VA) wastewater treatment plant. More specifically, this project evaluated the 

concentration of zinc that could be tolerated by the biological nitrogen removal processes at the 

wastewater treatment plant. The findings of this project will help determine whether or not zinc 

at the proposed zinc orthophosphate dose would have an adverse impact on biological nutrient 

removal processes at the Arlington plant. The project consists of bench scale studies as well as 

a brief literature review. The estimated final report on this project was issued in September 

2005. 

Characterization of Natural Organic Matter in DC Drinking Water (Univ. Washington and 

Cadmus) 

The purpose of this project was to characterize the properties and reactivity of NOM, including 

seasonal variations, in the raw and treated water to improve understanding of DBP formation, 

the effectiveness of existing treatment on NOM removal, and the role of NOM in metal solubility. 

Project activities include sample collection and laboratory-scale studies. The final report on this 

project was issued in May 2006. 

(On-going) Proposed Flow-Through, Lead Pipe Loop Test Plan (CH2MHill) 

The primary purpose of the pipe loop testing at the Washington Aqueduct is to evaluate the 

effectiveness of alternate corrosion control strategies on reducing lead concentrations in DC 

drinking water. A comparison of the effectiveness of two alternate corrosion inhibitors 

(phosphoric acid and zinc orthophosphate) will be conducted. Finished water produced at the 

WA’s Dalecarlia WTP will be used as the source water for the testing. Samples of lead service 

lines excavated from the DCWASA system will be used to construct the proposed pipe loops. 

Final Report, May 31, 2007 A-17 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(On-going) Evaluation of Potential Mechanisms of Lead Release Related to Conversion 

from Free Chlorine to Chloramines and Evaluation of Scale from Lead Service Line 

Specimens Excavated from the DCWASA System. 

The USEPA has evaluated the potential mechanism of lead release in the DCWASA system by 

conducting theoretical evaluations and laboratory studies related to the solubility of potential 

lead solids that may be present in the system based on water quality conditions and by 

evaluating the scale components from several lead service line specimens excavated from 

DCWASA’s distribution system. Results of these evaluations have been presented at the 

AWWA Water Quality Technology Conferences in 2001 and 2004 (Schock, 2001; Schock and 

Giani, 2004) and in a presentation to the Virginia Section of AWWA in April 2005 (Schock, 2005) 

and are summarized here. These presentations indicate that a mechanism potentially 

responsible for the change in lead levels with the conversion from free chlorine to chloramines 

relates to the solubility of Pb (II) vs. Pb (IV) pipe scales. Control of lead in drinking water has 

generally been presumed to be controlled by Pb (II) solids that form on lead containing materials. 

Pb (IV) has a lower theoretical solubility than Pb (II) carbonate solids, and its presence may result 

in relatively low lead levels. USEPA has evaluated the theoretical formation of Pb (IV) 

compounds, which can form under relatively high oxidation-reduction (ORP) potentials, and the 

lower ORP of chloraminated water when compared to water with free chlorine (Schock, 2001; 

Schock and Giani, 2004; Schock, 2005). 

By switching to chloramines, the ORP of the DCWASA water may have been lowered, causing 

Pb (IV) solids to convert to more soluble Pb (II) solids and resulting in release of lead and higher 

lead levels measured at the tap. This mechanism, along with supporting theoretical, laboratory, 

and field water quality and scale analysis data are summarized in these papers and 

presentations, including evidence of the presence of Pb (IV) solids in lead service line pipes 

excavated from the DCWASA system prior to the switch to chloramines. These LSL specimens 

primarily contained Pb (IV) compounds (plattnerite and scrutinyite) with only traces of Pb (II) 

compounds (cerrusite and hydrocerrusite). In addition, lead levels, measured in residential 

homes in the DCWASA system, decreased during a one-month switch to free chlorine in April of 

2004 when compared to lead levels from the same sites during chloramination. The USEPA is 

continuing with these investigations. 

Final Report, May 31, 2007 A-18 
Final Report, May 31, 2007 A-19 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

Final Report
 

Summary of Lead Service Line Replacement Program 

From 2002 - 2005, DCWASA was required to replace 7% of the lead service lines in the system 

each year due to exceedances of the lead action level. 

Sept. 2003 Report on the Materials Evaluation and Initial Inventory 

In September 2003, DCWASA updated its inventory of lead service lines and estimated that of 

the system’s 120,000 service connections, 23,071 were lead service lines (count as of 

September 30, 2003). 

Inventory of Lead Service Lines (2004 map) 

DCWASA developed a map at a scale of 1:16,000 that shows the approximate locations of lead 

service lines in the distribution system, based on the initial inventory conducted in 2003. Of the 

estimated 23,071 lead service lines in the system, the map presents those that could be 

geocoded. In Task 6, this map will be reviewed as part of an evaluation of lead levels in the 

system. 

2003 Sampling Results of Lead Service Lines (2004 map) 

DCWASA developed a map in 2004 at a scale of 1:16,000 that shows lead sampling results for 

lead service lines. The map delineates sample results less than or equal to 15 ppb, sample 

results between 15 ppb and 300 ppb, and sample results greater than or equal to 300 ppb. In 

Task 6, this map will be used, along with distribution system water quality data, to determine if 

there is a statistically significant correlation between elevated lead levels and other water quality 

parameters, such as pH, for different geographical areas. 

Oct. 24, 2003 Annual Report of DCWASA’s Lead Service Line Replacement Program 

On October 24, 2003, DCWASA reported that during the period October 1, 2002 to September 

30, 2003 it had replaced 385 lead service lines through physical replacement including 79 “full” 

replacements and 306 “partial” replacements. A “partial” replacement means that something 

other than the entire length of the service line is replaced (Code of Federal Regulations, Title 

40, § 141.84(d)). Title 40 CFR §141.84 requires that a public water system replace the portion 

of the lead service line owned by the system, but does not require that the system bear the cost 

of replacing portions of the line that the system does not own. 

2003-2004 Replacement of Lead Service Lines (2004 map) 

DCWASA developed a map at a scale of 1:16,000 that shows both completed lead service line 

replacements and those planned to be replaced in 2004. This map shows that 524 

replacements had been completed and 817 were scheduled for 2004. 

Oct. 8, 2004 Annual Report DCWASA’s Lead Service Replacement Program 

DCWASA reported that it had replaced 1,793 lead service lines between October 1, 2003 and 

September 30, 2004. 
Summary of Correspondence on Designation of Optimal Corrosion Control
 

Treatment
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Final Report, May 31, 2007 A-20 

Final Report
 

 

 

Environomics Contract 68-C-02-042
 

Work Assignment WA 4-13
 

July 16, 1997 

USEPA Region 3 conditionally designated Optimized Corrosion Control Treatment (OCCT) as 

maintenance of a slightly positive Langelier Saturation Index through pH adjustment. As a 

condition of this designation, USEPA Region 3 issued an Administrative Order (AO) for WA and 

DCWASA to jointly assess the feasibility of alternate corrosion control treatment including use of 

sodium hydroxide for pH control, and use of a non-zinc orthophosphate corrosion inhibitor. 

USEPA Region 3 set a deadline of September 15, 1997 for completing the assessment. 

August 15, 1997 

DCWASA responded to USEPA Region 3’s July 16, 1997 letter outlining plans for WA to 

conduct studies on corrosion control treatment and DCWASA to conduct studies on the effects 

of these treatments on wastewater plants. WA will conduct studies on sodium hydroxide 

including estimation of construction costs and O&M costs for a sodium hydroxide and 

phosphate feed systems. The letter acknowledges the Sept. 15, 1997 deadline for these 

studies. 

September 4, 1997 

WA responded to USEPA Region 3’s July 16, 1997 letter outlining the same proposed and ongoing studies outlined by DCWASA in their Aug. 15, 1997 letter. WA revised the estimated 

schedule for completing these studies to be November 1, 1997 for the caustic soda studies and 

March 1998 for the phosphate studies. 

February 29, 2000 

USEPA Region 3 designated the use of pH adjustment as the OCCT for the WA distribution 

systems which required the WA to maintain the highest pH level attainable at the entry points to 

the distribution system without causing excessive calcium carbonate precipitation in the 

distribution system. USEPA also designated that a minimum pH of 7.7 be maintained at the 

entry points to the distribution system and at all tap samples within the distribution system. 

USEPA Region 3 also reduced the requirement for LCR tap monitoring to once per year at 50 

sites. 

May 1, 2000 

In response to USEPA Region 3’s Feb. 29th letter, DCWASA proposed modifications to the 

Optimal Water Quality Parameters. The proposed modifications were developed jointly by WA, 

DCWASA and USEPA Region 3. Specifically, the proposed modifications would allow the 

minimum finished water pH requirement to change monthly to account for seasonal changes in 

untreated water quality as follows: January (7.7), February (7.8), March (7.7), April (7.6), May 

(7.5), June (7.4), July (7.4), August (7.4), September (7.4), October (7.5), November (7.5), and 

December (7.6). Also, the minimum pH at distribution system sites would change from 7.7 to 

7.0, and would be measured at 12 sites vs. 10 sites proposed by USEPA Region 3. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Final Report, May 31, 2007 A-21 

May 3, 2000 

In response to USEPA Region 3’s Feb. 29th letter, WA proposed modifications as outlined in 

DCWASA’s May 1st letter. One additional suggestion was that the proposed Optimal Water 

Quality Parameters be made effective for the 6 month monitoring period beginning July 1, 2000. 

May 17, 2002 

USEPA Region 3 revised its designation of OWQP with respect to the minimum monthly entry 

point pH requirements per proposed levels requested by DCWASA and WA in May 2000, noting 

that the decision had been verbally agreed between WA and USEPA Region 3 in 2000. The 

decision was made effective from the LCR monitoring period which began on July 1, 2000, The 

OWQP for the distribution system tap samples was changed to a minimum pH of 7.0. 

April 30, 2004 

USEPA Region 3 designated use of zinc orthophosphate for partial system application in the 4th 

High Pressure Zone. 

May 28, 2004 

USEPA Region 3 modified its April 30, 2004 designation of OCCT for the DC distribution 

system to use orthophosphate instead of zinc orthophosphate for the 4th High Pressure Zone. 

Aug. 3, 2004 

USEPA Region 3 modified the interim designation of OCCT for the DCWASA distribution 

system to consist of application of orthophosphate subject to stated conditions and water quality 

parameters (source: correspondence from USEPA Region 3 to WA and DCWASA 8/3/04). 

Specifically, USEPA Region 3 has stipulated that the WA will meet a pH goal of 7.8 +/-0.1 

(7.7+/-0.1 per later revisions August 20, 2004 and September 7, 2004) for finished water leaving 

both water treatment plants, and 7.7 +/-0.1 for water samples from the distribution system 

during the passivation period. 
Final Report, May 31, 2007 

LEAD PROFILES
 

A-22 
Final Report, May 31, 2007 A-23
 

Profile 

No. 

Date of 

profile 

Profile 

Quadrant Special Profile Conditions 

Profiles Collected during Chloramination 

1 12/8/2003 NW 2 12/15/2003 NW 

3 1/5/2004 NW 

4 1/13/2004 NW Repeat of Profile 1 following par

5 2/9/2004 NE 

6 2/24/2004 NW Repeat of Profile 3 following par

7 3/2/2004 NW 

8 3/9/2004 NW 

9 3/16/2004 NW 

10 3/24/2004 NW 11 3/24/2004 SE

12 3/30/2004 NW 13 3/31/2004 NW 14 4/1/2004 NW 

Profiles Collected during Temporary Switch to Alternative Disinfectant (free chlorine

15 4/5/2004 NW 

16 4/6/2004 NW 

17 4/6/2004 NW 

18 4/13/2004 NW 
Final Report, May 31, 2007 A-24
 

Profile 

No. 

Date of 

profile 

Profile 

Quadrant Special Profile Conditions 

19 4/26/2004 NW Second repeat of Profile 3 following partial LSL replacemen

20 4/27/2004 SE Repeat of Profile 1

21 

4/29/2004 NW 

Second repeat of Profile 1 following partial LSL replacemen

22 4/30/2004 NW Repeat of Profile 1

23 5/3/2004 NW Repeat of Profile 1

24 5/3/2004 NW Repeat of Profile 1

25 5/7/2004 NW Repeat of Profile 1

Profiles Collected during Chloramination, after Temporary Switch to Alternate Disinfectant (fre

26 5/18/2004 NE Repeat of Profile 

27 6/28/2004 NW Second 28 7/6/2004 NW 

Profiles Collected after Orthophosphate Addition 

29 7/16/2004 NW Second 

30 11/30/2004 NW 

31 12/6/2004 NW 32 1/6/2005 NW Second 

33 1/25/2005 NW 34 2/22/2005 NW 
Final Report, May 31, 2007 A-25
 

Profile 

No. 

Date of 

profile 

Profile 

Quadrant Special Profile Conditions 

35 3/30/2005 NW 36 4/29/2005 NW 37 5/16/2005 NW 38 6/1/2005 NW 

39 6/7/2005 NW 

40 7/25/2005 NW 41 9/28/2005 NW 42 10/5/2005 NE 

43 11/29/2005 NW 

44 12/12/2005 N 45 1/27/2006 NE 

(Notes on Profile Graphs to follow: 1. Flowing samples designated ‘0’ or ‘00’ and samples collected that were representative of the water measurable lead due to rapid release of lead from the lead service line to the water as it flowed througand/or back siphonage of water from branches of premise piping. 2. Samples designated “X” reflect water hammer conditions 3. Samples designated “25+3” for example; indicate samples collected after allowing the water to flow 

the 25th liter stagnation sample was collected. 
Final Report, May 31, 2007. 

I.	 Profiles Collected during Chloramination 

180 

In-house Plumbing LSL Main 

160 

140 

120 

100 

80 

60 

40 

20 

0 

0 1 2 4 5	 7 9 13 17 21 25 25+3 X 

Liter 

Total Lead Dissolved 

12-08-03 (Profile No. 1) 

) bp(pd aeL

12-15-03 (Profile No. 2)
 

250 

180 

In-house Plumbing Lead Main Service
 160 

Line
 

140 

120 

100 

80 

60 

40 

20 

0 

d aeLl taoT

0 1 2 3 4 5 6 7 9 11 13 13+3 X 

Liter 

Total Lead Dissolved Lead 

A-26 
Final Report, May 31, 2007. 

 

 

 

 

1-5-04 (Profile No. 3) 

180
 

In-house Plumbing Lead Service Line Main 

160
 

140
 

120
 

) bp100
 (pd ae

80
 L

60
 

40
 

20
 

0
 

1 2 4 5 6 8 10 12 14 16 16+3 X 0
 

Liter 

Total Lead Dissolved Lead 

* Footnote to Profiles: Flowing samples designated ‘0’ or ‘00’ and samples collected that 

were representative of the water main may have measurable lead due to rapid release of 

lead from the lead service line to the water as it flowed through the service piping, and/or 

back siphonage of water from branches of premise piping. 

A-27 
Final Report, May 31, 2007. 

1-13-04 (Profile No. 4)
 

100
 

In-house Plumbing LSL Main 

90
 

80
 

70
 

) 

60
 

bp(p

50
 

d aeL

40
 

30
 

20
 

10
 

0
 

1 2 4 5 7 9 13 17 21 25 45 X 0
 

Liter 

Total Lead Dissolved Lead 

2-9-04 (Profile No. 5)
 

100
 

In-house Plumbing Lead Service Line Main 

90
 

80
 

70
 

) 

60
 

bp(p

50
 

d aeL

40
 

30
 

20
 

10
 

0
 

1 2 4 5 6 7 8 9 11 13 16 19 19+3 0 X
 

Liter 

Total Lead Dissolved Lead 

A-28 
Final Report, May 31, 2007. 

2/24/04 (Profile No. 6)
 

Lead (ppb) 

20
 

15
 

10
 

5
 

0 

Total Lead Dissolved Lead 

In-house Plumbing Lead 

Service 

Line 

Main 

1 2 4 5 6 8 10 12 14 16 16+3 16+5 16+7 16+9 16+11 X 0
 

Liter 

 

 

Lead (ppb) 

3-2-04 (Profile No. 7) 

180
 

In-house Plumbing Lead Service Line 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

Main 

1 2 4 5 7 9 11 13 15 18 21 21+3 21+10 X
 0 

Liter 

Total Lead Dissolved Lead 

A-29 
Final Report, May 31, 2007. 

 

 

3-9-04 (Profile No. 8)
 

Lead (ppb) 

180
 

In-house Plumbing Lead Service Line Main
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

1 2 3 5 7 9 11 14 17 20 24 29 29+3 29+10 00 X
 

Liter 

Total Lead Dissolved Lead 

 

 

 

 

Lead (ppb) 

3-16-04 (Profile No. 9) 

180
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0 

Detailed information was not available to 

differentiate among in-house plumbing, 

lead service lines, and the water main Total Lead Dissolved Lead 

1 2 4 6 9 12 15 18 21 24 27 31 35 39 39+3 39+10 X
 0 

Liter 

A-30 
Final Report, May 31, 2007. 

3-24-04 (Profile No. 10)
 

180
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

In-house 

Plumbing 

LSL Main 

1 2 3 4 6 8 10 12 14 17 20 23 26 30 0 30+3 30+10 X
 

Liter 

Lead (ppb) 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

3-24-04 (Profile No. 11) 

180
 

In-house Lead Service 

Plumbing Line 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

Main 

1 2 4 6 8 10 12 14 17 20 23 26 29 33 33+3 33+10 0 X
 

Liter 

Total Lead Dissolved Lead 

A-31 
Final Report, May 31, 2007. 

 

 

3/30/04 (Profile No. 12)
 

120
 

110
 

100
 

90
 

80
 

70
 

60
 

50
 

40
 

30
 

20
 

10
 

0
 

In-house Lead Service Line 

Plumbing 

Main 

1 2 3 5 7 9 10 11 13 15 18 21 24 27 0 27+3 27+10 X
 

Liter 

Lead (ppb) 

Total Lead Dissolved Lead 

 

 

 

 

Lead (ppb) 

3/31/04 (Profile No. 13) 

180
 

In-house Plumbing
 Lead Service Line Main
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

00 1 2 3 4 5 7 9 11 13 15 18 21 24 27 27+3 27+10 X
 

Liter Information was not available for
 

Dissolved Lead at Liter 9
 

Total Lead Dissolved Lead 

A-32 
Final Report, May 31, 2007. 

 

 

4-1-04 (Profile No. 14)
 

Lead (ppb) 

180
 In-house Lead Service Line Main 

Plumbing 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

1 2 3 4 6 8 10 12 14 17 20 23 26 30 30+3 30+10 00 X
 

Liter 

Total Lead Dissolved Lead 

II. Profiles Collected during Chlorine Burn
 

A-33 
Final Report, May 31, 2007. 

 

 

4-5-04 (Profile No. 15)
 

Lead (ppb) 

180
 

In-house Plumbing Lead Service Line Main
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

0 1 2 3 4 5 7 9 11 13 15 18 21 24 27 27+3 27+10 X
 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

4-6-04 (Profile No. 16) 

180
 In -house Lead Service Line 

Plumbing 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

Main 

1 2 3 4 5 7 9 11 13 15 18 21 24 27 0 27+3 27+10 X
 

Liter 

Total Lead Dissolved Lead 

A-34 
Final Report, May 31, 2007. 

 

 

4-6-04 (Profile No. 17)
 

Lead (ppb) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

Total Lead Dissolved Lead 

In -house Lead Service Line 

Plumbing 

Main 

1 2 3 4 6 8 10 12 14 16 19 22 25 28 28+3 28+10 X 

Liter 

 

 

 

4-13-04 (Profile No. 18)
 

0 

20 

40 

60 

80 

100 

120 

140 

160 

180 

Lead (ppb) 

In -house Lead Service Line 

Plumbing 

Main 

1 2 3 4 6 8 10 12 14 16 19 22 25 28 00 28 + 3 28 + X 

10 

Liter 

Total Lead Dissolved Lead 

A-35 
Final Report, May 31, 2007. 

 

 

4/26/04 (Profile No. 19)
 

Lead (ppb) 

20
 

15
 

10
 

5
 

0 

Total Lead Dissolved Lead 

Lead Service Main 

Line 

In -house Plumbing 

1 2 4 5 6 8 10 12 14 16 18 21 24 27 27+3 27+10 X 0
 

Liter 

 

 

Lead (ppb) 

4-27-04 (Profile No. 20) 

180
 In -house Lead Service 

Plumbing Line 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

Main 

1 2 4 6 8 10 12 14 17 20 23 26 29 33 33+3 33+10 0 X
 

Liter 

Total Lead Dissolved Lead 

A-36 
Final Report, May 31, 2007. 

 

 

4/29/04 (Profile No. 21)
 

Lead (ppb) 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

In-house Plumbing Lead Service Line Main 

1 2 4 5 7 9 13 17 21 25 25+3 25+10 0 X 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

4-30-04 (Profile No. 22)
 

160 

180 

In-house 

Plumbing 

Lead Service Line Main 

140 

120 

100 

80 

60 

40 

20 

0 

1 2 3 5 7 9 10 11 13 15 18 21 24 27 27+3 27+10 0 X 

Liter 

Total Lead Dissolved Lead 

A-37 
Final Report, May 31, 2007. 

 

 

5-3-04 (Profile No. 23)
 

Lead (ppb) 

160 

180 

In-house 

Plumbing 

Lead Service Line Main 

140 

120 

100 

80 

60 

40 

20 

0 

1 2 3 4 6 8 10 12 14 17 

Liter 

20 23 26 30 30+3 30+10 0 X 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

5-3-04 (Profile No. 24) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house 

Plumbing 

Lead Service Line Main 

1 2 3 4 6 8 10 12 14 17 20 23 26 30 30+3 30+10 0 X 

Liter 

Total Lead Dissolved Lead 

A-38 
Final Report, May 31, 2007. 

 

 

5-7-04 (Profile No. 25)
 

Lead (ppb) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house 

Plumbing 

Lead Service Line Main 

1 2 3 4 5 7 9 11 13 15 18 21 24 27 00 27+3 27+10 X 

Liter 

Total Lead Dissolved Lead 

A-39 
Final Report, May 31, 2007. 

III. Profiles Collected during Chloramination, after Chlorine Burn
 

 

 

5-18-04 (Profile No. 26)
 

Lead (ppb) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house Plumbing Lead Service Line Main 

1 2 4 5 6 7 8 9 11 13 16 19 19+3 19+10 0 X 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

6-28-04 (Profile No. 27)
 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house 

Plumbing 

Lead Service Line Main 

0 2 4 8 12 17 23 30 30+10 01(15) 

Liter 

Total Lead Dissolved Lead 

A-40 
Final Report, May 31, 2007. 

 

 

7-6-04 (Profile No. 28)
 

Lead (ppb) 

180
 

In-house Plumbing Lead Service Line Main
 

160
 

140
 

120
 

100
 

80
 

60
 

40
 

20
 

0
 

00 1 2 3 5 7 9 11 13 15 18 21 24 27 27+3 27+10 X
 

Liter 

Total Lead Dissolved Lead 

IV. Profiles Collected after Orthophosphate Addition
 

A-41 
Final Report, May 31, 2007. 

 

 

7-16-04 (Profile No. 29)
 

Lead (ppb) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house Plumbing Lead Service Line Main 

00 1 2 3 4 5 7 9 11 13 15 18 21 24 27 27+3 27+10 X 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

11-30-04 (Profile No. 30)
 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house Plumbing Lead Service Line Main 

1 2 3 4 5 6 8 10 12 14 17 20 23 26 0 26+3 26+10 X 

Liter 

Total Lead Dissolved Lead 

A-42 
Final Report, May 31, 2007. 

 

 

12-6-04 (Profile No. 31)
 

Lead (ppb) 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 

In-house 

Plumbing 

Lead Service Line Main 

1 2 3 4 5 7 9 11 12 13 15 17 20 23 26 00 26+3 26+10 X 

Liter 

Total Lead Dissolved Lead 

 

Lead (ppb) 

1-6-05 (Profile No. 32)
 

20 

In-house LSL Main Plumbing 18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

1 2 3 4 6 8 10 12 14 17 20 23 26 30 0 30+3 30+10 X 

Liter 

Total Lead Dissolved Lead 

A-43 
Final Report, May 31, 2007. 

 

 

1-25-05 (Profile No. 33)
 

Lead (ppb) 

20
 

In-house Plumbing Lead Service Line Main
 

18
 

16
 

14
 

12
 

10
 

8
 

6
 

4
 

2
 

0
 

1 2 3 4 6 8 10 12 14 16 18 21 24 27 27+3 27+10 0 X
 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

2-22-05 (Profile No. 34)
 

90
 

20
 

18
 

16
 

14
 

12
 

10
 

8
 

6
 

4
 

2
 

0
 

Total Lead Dissolved Lead 

In-house Plumbing Lead Service Line Main 

0 1 2 3 5 7 9 11 12 13 15 17 20 23 26 26+3 26+10 X
 

Liter 

A-44 
Final Report, May 31, 2007. 

 

 

3-30-05 (Profile No. 35)
 

Lead (ppb) 

20 

In-house Plumbing Lead Service Line Main 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

00 1 2 3 5 7 9 11 12 13 15 18 21 24 27 27+3 27+10 X 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

4-29-05 (Profile No. 36)
 

20 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

In-house 

Plumbing 

Lead Service Line Main 

0 1 2 4 6 8 9 10 12 14 15 17 20 23 26 26+3 26+10 X 

Liter 

Total Lead Dissolved Lead 

A-45 
Final Report, May 31, 2007. 

 

 

5-16-05 (Profile No. 37)
 

Lead (ppb) 

18 

20 

In-house Plumbing Lead Service Line Main 

16 

14 

12 

10 

8 

6 

4 

2 

0 

0 1 2 4 5 6 7 9 10 11 

Liter 

13 15 17 20 23 23+3 23+10 X 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

6-1-05 (Profile No. 38)
 

20 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

Total Lead Dissolved Lead 

In-house 

Plumbing 

Lead Service Line Main 

00 1 2 3 5 6 7 9 11 12 13 15 17 20 23 23+3 23+10 X 

Liter 

A-46 
Final Report, May 31, 2007. 

 

 

6-7-05 (Profile No. 39)
 

Lead (ppb) 

20 

In-house Plumbing Lead Service Line Main 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

0 1 2 3 4 6 8 9 10 11 13 15 18 21 24 24+3 24+10 X 

Liter 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

7-25-05 (Profile No. 40)
 

18 

20 

In-house 

Plumbing 

Lead Service Line Main 

16 

14 

12 

10 

8 

6 

4 

2 

0 

0 1 2 3 4 5 7 8 9 11 

Liter 

13 15 17 20 23 23+3 23+10 X 

Total Lead Dissolved Lead 

A-47 
Final Report, May 31, 2007. 

 

 

9-28-05 (Profile No. 41)
 

Lead (ppb) 

18 

20 

In-house 

Plumbing 

Lead Serivce Line Main 

16 

14 

12 

10 

8 

6 

4 

2 

0 

00 1 2 4 5 6 7 9 10 11 

Liter 

13 15 17 20 23 23+3 23+10 X 

Total Lead Dissolved Lead 

 

 

Lead (ppb) 

10-5-05 (Profile No. 42)
 

100 

120 

In-house 

Plumbing 

Lead Service Line Main 

80 

60 

40 

20 

0 

0 1 2 3 4 5 6 7 9 11 13 15 17 20 23 23+3 23+10 X 

Liter 

Total Lead Dissolved Lead 

A-48 
Final Report, May 31, 2007. 

 

 

11-29-05 (Profile No. 43)
 

Lead (ppb) 

20 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

In-house 

Plumbing 

Lead Service Line Main 

0 1 2 3 4 5 6 7 9 11 13 15 17 20 23 23+3 23+10 X 

Liter 

Total Lead Dissolved Lead 

 

Lead (ppb) 

20 

In-house Lead Service Line Main 

Plumbing 18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

0 1 2 3 4 5 6 7 9 11 13 15 17 20 23 23+3 23+10 X 

Liter 

Total Lead Dissolved Lead 

12-12-05 (Profile No. 44) 

A-49 
Final Report, May 31, 2007. 

 

 

1-27-06 (Profile No. 45)
 

Lead (ppb) 

20
 

18
 

16
 

14
 

12
 

10
 

8
 

6
 

4
 

2
 

0
 

Total Lead Dissolved Lead 

In-house Plumbing Lead Service Line Main 

0 1 2 3 4 5 6 7 9 11 13 15 17 20 20+3 20+10 X
 

Liter 

 

 

Lead (ppb) 

1-27-06 (Profile No. 45) 

20
 

In-house Plumbing Lead Service Line 

18
 

16
 

14
 

12
 

10
 

8
 

6
 

4
 

2
 

0
 

Main 

0 1 2 3 4 5 6 7 9 11 13 15 17 20 20+3 20+10
 X
 

Liter 

Total Lead Dissolved Lead 

A-50 
Appendix B 
Study Approach 

The study was conducted in two steps: 1) gathering, organizing and summarizing the 

available information, and listing potential causes of elevated lead levels; and 2) 

evaluating and determining the most probable causes. 

Step 1: Gathering, Organizing, and Summarizing Available Information 

Based on data and other information provided by EPA, the contractor produced the 

following: 

- Technical memorandum with preliminary findings and identifying additional 

data needs 

- 3-ring binder containing all reports and data gathered and reviewed 

- Data evaluation report 

Data and information initially provided by EPA to the contractor included the following: 

Studies and Reports

• Caustic soda feasibility study, 1998 

• Electrochemical pipe loop study on lead leaching rates from lead service line (LSL) 

coupons under various treatment scenarios 

• Sanitary survey reports for WTPs and distribution system since 1990 

• Microbial Comprehensive Performance Evaluation (CPE) Report for the treatment 

plants 

• Optimum Corrosion Control Treatment (OCCT) studies and approvals (original 1993-

2000, revised 2004) 

• Available data from a flow-through pipe loop study looking at corrosion rates under 

various treatment scenarios (study not yet started- expected completion June 2005 at 

earliest) 

• Lead in Water Survey – 1990 materials survey estimating LSLs and other sources of 

lead in the distribution system 

• LSL partial replacement method study – study conducted that looked at three methods 

of cutting pipe and thorough flushing: homes were “profile sampled” before and for 

two weeks after the partial LSL replacement work, May 2004 

Treatment Related Data and Information

• WTP treatment schematics and chemical dosing information 

• Raw and Finished Water Parameters from both WTPs 

o Monthly average and maximum flow rates 

o Monthly average pH 

o Free and total ammonia 

o Free and total chlorine 

o Monthly average alkalinity as CaCO3

o Calcium 

o Conductivity 

o Magnesium 
o Temperature 

o Calcium hardness, both total and dissolved 

o Total coliform bacteria 

o Fluoride 

o Dissolved, suspended and total solids 

o Bromide 

o Chloride 

o Sulfate 

o Total Organic Carbon – raw, settled and filtered 

o Metals (EPA method 200.8) 

• Entry Points to the Distribution System: 

o Haloacetic Acid (HAA5), total and individual concentrations 

o Total Trihalomethanes (TTHMs) and four individual trihalomethanes (THMs) 

Distribution System Data and Information

• Distribution system atlas or atlases 

• Total coliform (presence/absence) 

• LCR water quality parameter data: pH, alkalinity, calcium 

• HPC bacteria – limited data in terms of locations and monitoring duration 

• TTHM and HAA5 

• Nitrate and nitrite, both measured as Nitrogen 

• Metals 

• Lead first draw (LCR compliance) 

• Lead second draw (earlier years, this was the second liter of water; changed in 2003 

to represent water sitting in the service lines) 

• Lead profiling data (conducted from late 2003 through August 2004) performed at 

customer homes to collect every liter of water from the tap out through the water 

main 

• Lead first and second draw customer service samples, February 2003-present. 

• LSL replacement samples from LSLs that were not replaced 2003-2004 

Step 2: Evaluating and Determining Probable Causes 

Completed Data Review

Based on additional data identified in Step 1 and then provided by EPA to the contractor, 

the data review was completed. 

Additional data requested by the contractor as part of step 1, and provided by EPA to the 

extent it was available, included: 

- Data free chlorine and chloramines at entry points to the distribution system and 

within the distribution system, 1994-2004 (or most current) DC WASA dates of 

periodic free chlorine use, 2001-2004 (or most current) 

- Additional lead profiles in DC WASA system 

- Inventory of partial LSL replacement, 1999-2004 (or most current) 
- Meter specifications 

- Alkalinity data for distribution system entry points, 2000-2001 

- Source water quality data 1996-1998; 2003-2004 (or most current) 

Statistical Analyses

The contractor performed various statistical analyses on water quality data to determine 

correlations that could be made regarding the causes for elevated lead levels. 

Evaluation of Causes

The contractor evaluated potential causes in two ways: 

1. The likelihood of being a significant factor in lead release and uptake by the water 

2. The magnitude of the release in relation to the lead level at the tap 

For example, the uptake of lead by the water exposed to a water meter might be 

significant and well documented. However, the contribution of that small segment of 

water to the elevated lead at the tap might be small. Thus, in this instance, the conclusion 

would be that water meters are not a significant cause of elevated lead at the tap. 

Report

The contractor provided a draft report that included information and findings of both 

steps 1 and 2 for EPA and peer review comments. 
Appendix C 
Peer Review of Elevated Lead in D.C. Drinking 

Water – A Study of Potential Causative Events 

July 5, 2007 

Horsley Witten Group, Inc. 

90 Route 6A 

Sandwich, MA 02563 

Prepared for: 

United States Environmental Protection Agency 

Office of Ground Water and Drinking Water 
Peer Review Report:	 Page 2 

Elevated Lead in D.C. Drinking Water 

Peer Review Report of the Draft Study of Potential Causative Events from 

Elevated Lead in D.C. Drinking Water 

Contents of document: 

1.	 Summary of peer review process and associated documentation 

2.	 Summary table of expertise criteria and selected peer reviewers’ names and 

affiliations 

3. Peer review charge
 

Appendix I: Peer Reviewer Credentials
 

Appendix II: Peer Reviewer Comments
 
 

Peer Review Report: Page 3 

Elevated Lead in D.C. Drinking Water 

1. Summary of peer review process and associated documentation 

The EPA study: “Elevated Lead in D.C. Drinking Water – A Study of Potential 

Causative Events”, documents a detection of lead in the District of Columbia Water and 

Sewer Authority’s (DCWASA) water delivery system. DCWASA exceeded the 15-μg/L 

action level (AL) for the Lead and Copper Rule during July 2000 to June 2001 at the 90th 

percentile in home tap sampling, and repeatedly exceeded the AL during subsequent 

monitoring through the period ending December 2004. This study evaluates the potential 

causative events and parameters contributing to the elevated lead levels in the D.C. 

drinking water system. 

EPA hired a contractor, Horsley Witten Group, Inc. (H&W), to facilitate a peer review of 

the study in accordance with the "Peer Review Handbook", 3rd Edition, EPA 100-B-98-

001, hereinafter, "Handbook”). The peer review is intended to provide a focused, 

objective evaluation of the study and causative events leading up to the contamination 

incident. EPA addresses the criticisms, suggestions, and new ideas provided by the 

technical reviewers prior to redrafting the reviewed work. Comprehensive, objective 

technical reviews contribute to good science and regulatory acceptance of precedentsetting methodologies and controversial issues within the scientific and regulated 

communities. 

H&W began the review process by reviewing the recommended list of potential 

reviewers provided by EPA and selecting 3 peer reviewers to review the document. Two 

of the three reviewers were selected based on their scientific or technical expertise in 

issues associated with lead corrosion in distribution and plumbing systems. The third 

reviewer is a representative of a drinking water utility with relevant experience. 

Reviewers were screened for potential conflicts of interest, as specified in the Peer 

Review Handbook. H&W queried reviewers to determine their availability to participate 

in the review, and found two of the three chosen reviewers had scheduling conflicts and 

could not participate. H&W found two reviewers of equal expertise, with no conflicts, to 

replace the initially chosen reviewers. A revised reviewer list was developed and 

forwarded to the WAM for approval on April 6, 2007. 

After receiving approval of the list of reviewers, H&W emailed the reviewers one 

electronic copy of the pre-decision draft document entitled “Elevated Lead in D.C. 

Drinking Water – A Study of Potential Causative Events” dated February 23, 2007, along 

with one electronic copy of the Peer Review Charge, instructions, and appendices. H&W 

contacted reviewers periodically throughout the review period to answer any questions 

reviewers had, and to determine whether reviewers would indeed be able to provide 

comments by the set deadline of April 20, 2007. H&W received reviewers’ comments, 

compiled comments into an EPA-approved format, and submitted each comment 

document to EPA. 

H&W compiled and maintained a record of all potential peer reviewers, including names, 

affiliations, addresses, phone numbers, qualifications, and potential conflicts of interest. 
 

Peer Review Report: Page 4 

Elevated Lead in D.C. Drinking Water 

H&W has obtained agreements to honor confidentiality from reviewers, since the review 

document is a pre-decisional draft not for general public distribution. An explanation of 

such was included in both H&W’s subcontract to reviewers as well as a letter of 

instruction. 

H&W assembled the peer review record, which consisted of: the draft work products 

reviewed; the Charge; all materials provided to the reviewers; and reviewer comments. 

H&W submitted the peer review record to EPA on May 3, 2007. 

Information on the areas of expertise, the names, affiliations, and resumes of the selected 

peer reviewers are included in this document in Appendix I. 

The peer reviewers’ comments are provided in Appendix II. 
Peer Review Report: Page 5 

Elevated Lead in D.C. Drinking Water 

2. Summary Table of Expertise Criteria and Selected Peer Reviewers’ 

Names and Affiliations 

Peer Reviewers of “Elevated Lead in D.C. Drinking Water – A Study of Potential 

Causative Events” 

Criteria for Selecting Peer Reviewers Peer Reviewer 

Scientific/technical expertise regarding lead corrosion in 

distribution and plumbing systems. 

Carol Rego, 

CDM 

Chief Operating Officer of a major drinking water utility. John S. Young, Jr. 

American Water 

Scientific/technical expertise regarding lead corrosion in 

distribution and plumbing systems. 

John F. Ferguson, 

Ph.D. 

University of 

Washington 
 

 

 

 

 

Peer Review Report: Page 6 

Elevated Lead in D.C. Drinking Water 

 3. Peer Review Charge 

Elevated Lead in D.C. Drinking Water – A Study of Potential Causative Events 

 

Background 

In 2004, EPA convened a series of expert workshops in light of concerns raised about the 

effectiveness of the Lead and Copper Rule (LCR). The recommendations from these 

workshops led EPA to consider several actions, which included short-term and long-term 

revisions to the LCR, additional expert workshops, new and expanded guidance, and 

additional research. In terms of additional research, EPA identified a need to perform an 

in-depth analysis to document and determine to the extent possible the cause or causes of 

elevated lead levels in the District of Columbia (D.C.) drinking water. 

Immediately prior to 2000, D.C. drinking water did not typically show lead levels that 

exceeded the LCR action level of 0.015 mg/L. On November 1, 2000, the Washington 

Aqueduct, which operates the Dalecarlia and McMillan Water Treatment Plants, switched 

from free chlorine to chloramine disinfection. Since early 2001, the D.C. Water and 

Sewer Authority (DCWASA) reported some elevated lead levels in drinking water 

samples from D.C. residents' taps. 

This study documents and evaluates the potential causative events and parameters 

contributing to the high levels of lead in D.C. drinking water. Section 1 provides a 

summary of the document, including background information. Sections 2, 3, and 4 

provide background information on the lead monitoring program, water treatment 

facilities, and distribution system conditions. Section 5 discusses the following causative 

factors along with the likelihood of each contributing to the situation: 

1. Lead release from piping systems 

2. Conversion from free chlorine to chloramines for final disinfection 

3. Water quality parameters in the distribution system 

4. Other lead-bearing materials 

5. Galvanic corrosion of lead service lines 

6. Effect of grounding currents on lead-bearing components 

7. City-wide meter replacement program 

8. Drought conditions and effects on corrosivity of DCWASA water 
 

 

 

 

Peer Review Report:	 Page 7 

Elevated Lead in D.C. Drinking Water 

The study concludes that (1) the primary source of lead release was attributed to the 

presence of lead service lines (LSLs) in the DCWASA distribution system, and (2) the 

major causative factor of high lead levels at the consumers’ taps was likely the change in 

oxidation state (as indicated by ORP) resulting from the conversion from free chlorine to 

chloramines. The relatively high concentration of free chlorine that was used for residual 

disinfection prior to the conversion to chloramines likely facilitated the formation of 

Pb (IV) species in the DCWASA distribution system. Additional contributing factors were 

likely related to low operating pH levels and pH variations in the distribution system 

which, based on conventional understanding of Pb (II) solubility per the LCR, would lead 

to greater Pb (II) release. Faucets, solder, and other home plumbing components likely 

contributed, but were not the major source of lead release to DCWASA tap samples. 

Please find attached a copy of the draft study and appendices for your review. This 

version of the report reflects Agency comments received on an earlier draft. We expect 

that this version of the report, with some additional minor modifications, will be the final 

version. Your comments will be useful in preparing the final version of the report and 

discussing the findings of the study with the public. 

To assist in your review of the study, we ask that you pay particular attention to the 

following questions: 

a.	 Does the study consider potential causative events that are appropriate? Are the 

causative events and factors considered all relevant to the purpose of the study? 

What additional causative events or factors, if any, should be considered? 

b.	 Does the study consider each causative event adequately? Is the data presented 

all relevant to the purpose of the study? 

c.	 Do the data and analyses support the conclusions? Are there additional analyses 

that could better support the conclusions? What additional conclusions, if any, 

can be reached based on the data and analyses? 

d.	 Section 6 of the study identifies possible follow-on work based on available 

findings and conclusions drawn from the study. Which, if any, of the 

recommended follow-on work should EPA undertake? What additional follow-on 

work and/or research should EPA undertake as a result of this study? 
Appendix I: Peer Reviewer Credentials 
General Biographical Information 

JOHN F. FERGUSON 

Professor of Civil Engineering 

University of Washington 

304 More Hall, Box 352700 

Seattle, WA 98195-2700 

(206) 543-5176 

(206) 543-1543 Fax 

jferg@u.washington.edu 

Academic Background 

Ph.D. Stanford University 1970 

M.S.C.E. Stanford University 1964 

B.S.C.E (with honors) Stanford University 1963 

Professional History 

 

 

5/2005 

Professor, Department of Civil Engineering, University of Washington, Seattle, WA, 1979­

present; Chair 1992-1997; Associate Chair 1987-1992; Acting Chair 1986-1987; Environmental 

Engineering and Science Program Director 1983-1987. 

Visiting Scientist, Norwegian Water Research Institute, Oslo, 1979-80. 

Associate Professor, Department of Civil Engineering, University of Washington, Seattle, WA, 

1974-1979. 

Assistant Professor, Department of Geography and Environmental Engineering, The Johns 

Hopkins University, Baltimore, MD, 1970-1974. 

Research Fellow, Division of Engineering and Applied Physics, Harvard University, Cambridge, 

MA, 1969-1970. 

Research Engineer, Los Angeles County Sanitation Districts, Lancaster, CA, 1964-1966 

Refereed Journal Publications 

Ferguson, J.F. and P.L. McCarty (1971) Effects of carbonate and magnesium on calcium

phosphate precipitation, Environ. Sci. Technol., Vol. 5, 434-540. 

Jenkins, D., J.F. Ferguson, and A.B. Menar (1971) Chemical processes for phosphate removal, 

Water Res., Vol. 5, 369-389. 

1
 
Ferguson, J.F. and J. Gavis (1972) A review of the arsenic cycle in natural waters, Water Res., 

Vol. 6, 1259-1274. 

Gavis, J. and J.F. Ferguson (1972) The cycling of mercury through the environment, Water Res., 

Vol. 6, 989-1008. 

Ferguson, J.F., D.J. Jenkins, and J. Eastman (1973) Calcium phosphate precipitation at slightly 

alkaline pH values, Jour. Water Pollution Control Fed., Vol. 45, 620-631. 

Gavis, J. and J.F. Ferguson (1975) Kinetics of carbon dioxide uptake by phytoplankton at high pH, 

Limnol. Ocean. Vol. 20, 211-221. 

Anderson, M.A., J.F. Ferguson, and J. Gavis (1976) Arsenate adsorption on amorphous aluminum

hydroxide, J. Colloid Interface Science, Vol. 54, 391-399. 

Ferguson, J.F. and T.A. King (1977) A model for phosphate removal with aluminum addition, 

Jour. Water Pollution Control Fed., Vol. 49, 646-658. 

Ferguson, J.F., G.F.P. Keay, M.S. Merrill, and A. Benedict (1979) Powdered activated carbon 

contact stabilization in activated sludge, JWPCF, Vol. 51, 2314-2323. 

Eastman, J.A. and J.F. Ferguson (1981) Solubilization of particulate organic carbon during the 

acid phase of anaerobic digestion, JWPCF, Vol. 53, 352-366. 

Benjamin, M.M., J.F. Ferguson, and M.E. Buggins (1981) Treatment of sulfite evaporator 

condensate with an anaerobic reactor, TAPPI, Vol. 65, 96-101. 

Asplund, R., B.W. Mar, and J.F. Ferguson (1982) Total suspended solids in highway runoff in 

Washington State, ASCE, JEED, Vol. 108, 391-404. 

Herrera, C.F., J.F. Ferguson, and M.M. Benjamin (1982) Evaluation of the potential for 

contamination of drinking water from the corrosion of tin/antimony solder, JAWWA, Vol. 74, 368­

376. 

Ferguson, J.F., B.J. Eis, and M.M. Benjamin (1983). The fate and effect of bisulfite in anaerobic 

treatment, JWPCF, Vol. 55, 1355-1365. 

Benjamin, M.M., S.L. Woods, and J.F. Ferguson (1984) Toxicity and biodegradability of pulp mill 

waste constituents exposed to anaerobic bacteria, Wat. Res., Vol. 18, 601-607. 

Ferguson, J.F., B.J. Eis, and M.M. Benjamin (1984) Neutralization in anaerobic treatment of an 

acidic waste, Wat. Res., Vol. 18, 573. 

Hendrickson, K.J., M.M. Benjamin, and J.F. Ferguson (1984) Removal of silver and mercury from

spent COD test solutions, JWPCF, Vol. 56, 468-473. 

Ferguson, J.F. and L. Vrale (1984) Chemical aspects of the lime seawater process, JWPCF, Vol. 

56, 355-363. 

Nitchals, D.R., M.M. Benjamin, and J.F. Ferguson (1985) Anaerobic treatment of caustic 

extraction waste with sulfite evaporator condensate, JWPCF, Vol. 57. 253-262. 

Reiber, S.H., J.F. Ferguson, and M.M. Benjamin (1987) Corrosion monitoring and control in the 

Pacific Northwest, Jour. Am. Wat. Works Assoc., Vol. 79, No. 2, 71-74. 

2
 
Stone, A., D. Spyridakis, M.Benjamin, J. Ferguson, J. Richey, and S. Osterhus (1987) The effects 

of short-term changes in water quality on copper and zinc corrosion rates, Jour. Am. Wat. Works 

Assoc., Vol. 79, No. 2, 75-82. 

Schultz, M., M.M. Benjamin, and J.F. Ferguson (1987) Adsorption and desorption of metals on 

ferrihydrite, Environ. Sci. Technol., Vol. 21, 863-869. 

Woods, S.L., J.F. Ferguson, and M.M. Benjamin (1988) Characterization of chlorophenol and 

chloromethoxybenzene biodegradation during anaerobic treatment, Environ. Sci. Technol., Vol. 

23, 62-68. 

Reiber, S., J.F. Ferguson, and M.M. Benjamin (1988) An improved method for corrosion rate 

measurement by weight loss, J. Am. Water Works Assoc., Vol. 80, No. 11, 41-46. 

Nordqvist, K.R., M.M. Benjamin, and J.F. Ferguson (1988) Effects of cyanide and polyphosphates 

on adsorption of metals from simulated and real metal plating wastes, Water Research, Vol. 22, 

837-846. 

Puhakka, J.A., J.F. Ferguson, M.M. Benjamin, M. Salkinoja-Salonen (1989) Sulfur reduction and 

inhibition in anaerobic treatment of simulated pulp mill wastewater, Systematic and Applied

Microbiology, Vol 11, 202-206. 

Puhakka, J.A., M.M. Benjamin, J.F. Ferguson, and M. Salkinoja-Salonen (1990) Effect of 

molybdate ions on methanation of simulated and natural wastewater, Appl. Microbiol. Biotechnol.,

Vol. 32, 494-498. 

Puhakka, J.A., M. Salkinoja-Salonen, J.F. Ferguson, and M.M. Benjamin (1990) Carbon flow in 

acetoclastic enrichment cultures from pulp mill effluent treatment, Water Research, Vol 24, 505­

519. 

Paulson, A.J., M.M. Benjamin, and J.F. Ferguson (1990) Zn solubility in low carbonate solution, 

Water Research, Vol. 23, 1563-1569. 

Banerjee, S., J.J. Horng, J.F. Ferguson (1991) Field Experience with Electrokinetics at a 

Superfund Site, Transporation Research Record, 1312, 167-174 

Labib, F., J.F. Ferguson, M.M. Benjamin, M. Merigh, and N.L. Ricker (1992) Anaerobic butyrate 

degradation in a fluidized bed reactor: The effects of increased concentrations of H2 and acetate, 

Environ. Sci. Technol., Vol. 26, 369-376. 

Wang, S-H., J.F. Ferguson, and J.L. McCarthy (1992) The decolorization and dechlorination of 

kraft bleach plant effluent solutes by use of three fungi: Ganaderma lacidum, Coriolus versicolor 

and Hericium erinaceum, Holzforschung, Vol. 46, 219-223. 

Labib, F., J.F. Ferguson, M.M. Benjamin, M. Merigh, N.L., and N.L. Ricker (1993) Mathematical 

modeling of an anaerobic butyrate degrading consortia: Predicting their response to organic

overloads, Environ. Sci. Technol., Vol. 27, No. 13, 1673-2884. 

Edwards, M. and J.F. Ferguson (1993) Accelerated testing of copper corrosion, J. Amer. Water 

Works Assoc., Vol. 85, No. 10, 105-113. 

Long, J.L., H.D. Stensel, J.F. Ferguson, S.E. Strand, J.E. Ongerth (1993) Anaerobic and aerobic 

treatment of chlorinated aliphatic compounds, Jour. Environ. Engineering, Vol 119, 303-320. 

3
 
Makinen, P.M., T.J. Theno, J.F. Ferguson, J.E. Ongerth, and J.A. Puhakka (1993) Chlorophenol 

toxicity removal and monitoring in aerobic treatment recovery from process upsets, Environ. Sci. 

Technol., Vol 27, 1434-1439. 

Wang, S.-H., J.L. McCarthy, and J.F. Ferguson (1993) Utilization of glucososaccharinic acid and 

components of kraft black liquor as energy sources for growth of anaerobic bacteria, 

Holzforschung, Vol. 47, 141-148. 

Perkins, P.S., S.J. Komisar, J.A. Puhakka, and J.F. Ferguson (1994) Effects of electron donors and 

metabolic inhibitors on reductive dechlorination of 2,4,6-trichlorophenol, Water Research, Vol. 

28, No. 10, 2101-2107. 

Ryding, J.M., J.A. Puhakka, J.F. Ferguson, and S.E. Strand (1994) Degradation of chlorinated 

phenols by a toluene enriched microbiol culture, Water Research, Vol 28, No. 9, 1897-1906. 

Ofjord, G.D., J.A. Puhakka, and J.F. Ferguson (1994) Reductive dechlorination of Aroclor 1254 

by marine sediment cultures, Environ. Sci. Technol., Vol 25, No. 13, 2286-2294. 

Edwards, M., J.F. Ferguson, and S.H. Reiber (1994) The pitting corrosion of copper, JAWWA, Vol. 86, No. 7, 74-90. 

Puhakka, J.A., R.P. Herwig, P.M. Koro, G.V. Wolfe, and J.F. Ferguson (1995) Biodegradation of 

chlorophenols by mixed and pure cultures from a fluidized-bed reactor, Appl. Microbiol.

Biotechnol.,Vol. 42, 951-957. 

Sletten, R.S., M.M. Benjamin, J.J. Horng, and J.F. Ferguson (1995) Physical-chemical treatment 

of landfill leachate for metals removal, Water Research, Vol. 29, No. 10, 2376-2386. 

Porter, R.L. and J.F. Ferguson (1995) Improved monitoring of corrosion processes, JAWWA, Vol. 

87, No. 11, 85-95. 

Männistö, M.K., E.S. Melin, J.A. Puhakka, and J.F. Ferguson (1996) Biodegradation of PAH 

mixtures by a marine sediment enrichment, Jour. Polycyclic Aromatic Hydrocarbons, Vol. 11, 27­

34. 

Chen, C., J.A. Puhakka, and J.F. Ferguson (1996) Transformation of 1,1,2,2-tetrachloroethane 

under methanogenic conditions, Environ. Sci. Technol., Vol. 30, No. 2, 542-547. 

Korshin, G.V., S.A.L. Perry, M.A. Edwards, and J.F. Ferguson (1996) The influence of natural 

organic matter on corrosion of copper in potable water, JAWWA, Vol. 88, No. 7, 36-47. 

Melin, E.S., J.A. Puhakka, S.E. Strand, K.J. Rockne, and J.F. Ferguson (1996) Fluidized-bed 

enrichment of marine ammonia-to-nitrite oxidizer and their ability to cometabolically oxidize 

chloroaliphatics, Int. Biodet. Biodegrad..,Vol 38, No. 1, 9-18. 

Melin, E.S., J.F. Ferguson, J.A. Puhakka, (1997) Pentachlorophenol biodegradation kinetics of an 

oligotrophic fluidized-bed enrichment culture, Appl. Microbiol. Biotechnol. 47, 675. 

Ballapragada, B.S., H.D. Stensel, J.A. Puhakka, J.F. Ferguson (1997) Effect of hydrogen on 

reductive dechlorination of chlorinated ethenes, Environ. Sci. Technol. 31, 1728-1734. 

4
 
Melin, E.S., J.A. Puhakka, J.F. Ferguson, (1998) Enrichment and operation strategies for 

polychlorophenol degrading microbial cultures in an aerobic fluidized-bed reactor, Wat. Environ. 

Res., 70(2), 171-180. 

Ward, A., H.D. Stensel, J.F. Ferguson, G. Ma, S. Hummel (1998) Effect of autothermal treatment 

on anaerobic digestion in the dual digestion process. Wat. Sci. Tech. 38, 435-442 

Mohn, H., J.A. Puhakka, J.F. Ferguson (1999) Effects of electron donors on degradation of 

pentachlorophenol in a methanogenic fluidized bed reactor. Environmental Technology, 20:909­

920. 

Zou, S., K.M. Anders,

reactors under methan

Korshin, G.V., J.F. Fe

corrosion of leaded br

Magar, V.S., H.D.

dechlorination of pe

Environ. Sci. Technol.

Chen, C., B.S. Ballapr

transformation of 1,1,

305. 

Zou, S., K.M. Anders,

 J.F. Ferguson (1999) Pentachlorophenol dechlorination in fluidized bed 

ogenic conditions. Bioremediation Journal, 3(2): 93-104 

rguson, A.N. Lancaster (1999) Influence of natural organic matter on the 

ass in potable water. Corrosion Science, 42(1), 53-62. 

 Stensel, J.A. Puhakka, J.F. Ferguson (1999) Sequential anaerobic 

ntachlorophenol: Competitive inhibition effects and a kinetic model. 

33, 1604-1611. 

agada, J.A. Puhakka, S.E. Strand, and J.F. Ferguson (1999) Anaerobic 

1-trichloroethane by municipal digester sludge. Biodegradation, 10, 297­

 J.F. Ferguson (2000) Biostimulation and bioaugmentation of anaerobic 

pentachlorophenol degradation in contaminated soils. Bioremediation Journal, 4(1), 19-25. 

Ferguson, J.F. and J.M.H. Pietari, (2000) Anaerobic transformations and bioremediation of 

chlorinated solvents, Environmental Pollution, 107, 209-215 . 

Zou, S., H.D. Stensel, J.F. Ferguson (2000) Carbon tetrachloride degradation: Effect of microbial 

growth substrate and vitamin B12 content. Environ. Sci. Technol. 34(9), 1751-1757. 

Magar, V.S., H.D. Stensel, J. Puhakka, J.F. Ferguson (2000) Characterization studies of an 

anaerobic, pentachlorophenol-dechlorinating enrichment culture. Bioremediation Journal, 4(4),

285-293. 

Moen, G., H.D. Stensel, R. Lepistö, J.F. Ferguson (2003) Effects of solids retention time on the 

performance of thermophilic and mesophilic digestion of combined municipal wastewater sludges, 

Water Environment Research, 75(6), 539-548. 

Korshin, G.V., J.F. Ferguson, A.N. Lancaster (2005) Influence of natural organic matter on the 

morphology of corroding surfaces of lead surfaces and behavior of lead-containing particles, 

Water Research, 39, 811-818. 

Pietari, J.M.H., Herwig, R.P. and J.F. Ferguson, Characterization of a psychrotrophic, anaerobic 

tetrachloroethene and trichloroethene dechlorinating enrichment, submitted to Environ. Sci. 

Technol. 

Pietari, J.M.H., Herwig, R.P. and J.F. Ferguson, Isolation and characterization of a PCE to cDCE 

dechlorinating strain JPD-1, manuscript in preparation (pending replication of DNA sequencing). 

5
 
 

Conklin, A.S., Bucher, R.H., Stensel, H.D. and J.F. Ferguson, Oxygen inhibition and toxicity in 

anaerobic sludge digestion, submitted Water Environ. Research. 

Conklin, A, Stensel, HD, and JF Ferguson (2005) The growth kinetics and competition between 

Methanosarcina and Methanosaeta in mesophilic anaerobic digestion, submitted Water Environ. 

Research. 

Fully-Refereed Conference Proceedings 

Ferguson, J.F and R..L. Horres (1979) Two-step precipitation of calcium phosphates, Progress 

Water Technology, Suppl. 1, 157-170. 

Damhaug, T., J.F. Ferguson, H. Buset, and R. Brusletto (1981) Control of alum addition in 

wastewater treatment, Wat. Sci. Tech., Munich, 531-537. 

Brown, C.A., K.E. Kiernan, J.F. Ferguson, and M.M. Benjamin (1984) Treatability of recreational 

vehicle wastewater in septic systems at highway rest areas, Transportation Research Record, Vol 

995, 1-11. 

Hakulinen, R., S. Woods, J.F. Ferguson, and M.M. Benjamin (1985) The role of facultative 

anaerobic microorganisms in anaerobic biodegradation of chlorophenols, Wat. Sci. Tech., Vol. 17, 

289-301. 

Ferguson, J.F. and M.M. Benjamin (1985) Studies of anaerobic treatment of sulfite process 

wastes, Wat. Sci. Tech., Vol. 17, 113-121. 

Qiu, R., J.F. Ferguson, and M.M. Benjamin (1987) Sequential anaerobic and aerobic treatment of 

Kraft pulping wastes, Wat. Sci. Tech. 19, 

Ferguson, J.F. and E. (Jonsson) Dalentoft (1991) Investigation of anaerobic removal and 

degradation of organic chlorine from Kraft bleaching wastewaters, Wat. Sci. Tech., Vol 24, 241­

250 

Rasmussen, G., S.J. Komisar, J.F. Ferguson, (1992) Transformation of Tetrachloroethane to 

Ethene in Mixed Methanogenic Cultures: Effect of Electron Donor, Biomass Levels, and 

Inhibition, in Bioremediation of Chlorinated and Polycyclic Aromatic Hydrocarbon 

Compounds, R.E. Hinchee, et al., eds. Lewis Publishers, p. 309-313. 

Puhakka, J.A., P.M. Makinen, M. Lundin, and J.F. Ferguson (1993) Aerobic and anaerobic 

biotransformation and treatment of chlorinated pulp bleach waste constituents, Wat. Sci. Tech., 

Vol. 29, No. 5-6, 73-80. 

Ferguson, J.F. (1994) Anaerobic and aerobic treatment for AOX removal, Wat. Sci, Tech., Vol. 29, 

No. 5-6, f149-162. 

6
 
Melin, E.S., J.A. Puhakka, M. Mannisto, and J.F. Ferguson (1995) Degradation of polycyclic 

aromatic hydrocarbons by a marine fluidized-bed enrichment, in Biological Unit Processes for 

Hazardous Waste Treatment, Vol. 9 of Proceedings of 3rd International Symposium on In Situ 

and On-Site Bioreclamation, Hinchee, Skeen and Sayles, eds., Battelle Press, Columbus, OH, 325­

330. 

Magar, V.S., H. Mohn, J.A. Puhakka, H.D. Stensel, and J.F. Ferguson (1995) Reductive 

dechlorination of pentachlorophenol by enrichments from municipal digester sludge, in 

Bioremediation of Chlorinated Solvents, Vol. 4 of Proceedings of 3rd International Symposium 

on In Situ and On-Site Bioreclamation, Hinchee, Leeson and Semprini, eds., Battelle Press, 

Columbus, OH, 77-83. 

Ballapragada, B.S., J.A. Puhakka, H.D. Stensel, and J.F. Ferguson (1995) Development of 

tetrachloroethene transforming anaerobic cultures from municipal digester sludge, in 

Bioremediation of Chlorinated Solvents, Vol. 4 of Proceedings of 3rd International symposium 

on In Situ and On-Site Bioreclamation, Hinchee, Leeson and Semprine, eds, Battelle Press, 

Columbus, OH. 

Puhakka, J.A., E.S. Melin, K.T. Jarvinen, P.M. Koro, J.A. Rintala, P. Makinen, W.K. Shieh, and 

J.F. Ferguson (1995) Fluidized-bed biofilms for chlorophenol mineralization, Wat. Sci. Tech.., 

Vol. 31, No. 1, 227-235. 

Korshin, G.V., J.F. Ferguson, A. Lancaster, H. Wu (1997) Influence of Humic Substances on the 

Corrosion of Copper- and Lead-Containing Materials in Potable Water, in The Role of Humic 

Substances in the Ecosystems and in Environmental Protection, Drozd, Gonet, Senesi, Weber, 

eds., International Humic Substances Society, Wroclaw, Poland. 

A. S. Conklin, J. D. Zahller, R. H. Bucher, H. D. Stensel and J. F. Ferguson (2004) 

Acetoclastic and Hydrolytic Activity in Anaerobic Digestion – Keys to Process Stability, 

Anaerobic Digestion 2004, 10th World Congress, Montreal, August. 

A. J. Straub, A. C. Conklin, J. F. Ferguson, H. D. Stensel (2005) Use of the ADM1 to investigate 

the effects on mesophilic digester stability of acetoclastic methanogens population dynamics. 

The First International Workshop on the IWA Anaerobic Digestion Model No. 1, 4-6 September 

2005, Lyngby, Denmark 

Abstract and Non-Refereed Conference Proceedings and Other Non-Journal Articles 

(incomplete listing) 

Ferguson, J.F., D. Jenkins, and W. Stumm (1971) Calcium phosphate precipitation in wastewater 

treatment, in Water 1970 Chem. Engr. Prog. Symposium Series, Vol. 67, 107. 

7
 
Ferguson, J.F. and D. Simmons (1975) The fate of nitrogen and phosphorus in Back River subestuary, in Waste Treatment Studies, Chesapeake Research Consortium, Baltimore. 

Gavis, J.W. Pasciak, and J.F. Ferguson (1975) Diffusion transport and kinetics of nutrient uptake 

by phytoplankton, (abstract), ACS National Meeting. 

Ferguson, J.F. and D.N. Given (1976) Chemical precipitation in water softening and iron and 

manganese removal, Proceedings, 18th Annual Public Water Supply Engineers’ Conference,

University of Illinois, 5-24. 

Ferguson, J.F., G.F.P. Keay, M.S. Merrill, and A.H. Benedict (1976) Powdered activated carbonbiological treatment: Low detention time process, Proceedings 31st Purdue Industrial Waste 

Conference, 468-478. 

Spencer, R., A. J. Shuckrow, and J.F. Ferguson (1976) The addition of powdered activated carbon 

to anaerobic digestors effects on methane production, Extended Abstracts for ASCE-EED National 

Meeting, Seattle. 

Woods, S.L., J.F. Ferguson, and M.M. Benjamin (1981) Assessing the toxicity of sulfite 

evaporator condensate to methanogens, Proceedings ASCE Water Forum-81, San Francisco. 

Ferguson, J.F. (1985) Anaerobic treatment of pulping and bleaching waste streams, Proc. AICHE 

1985 National Meeting, presented August, 1985, Seattle, WA. 

Jurgensen, S.L., M.M. Benjamin, and J.F. Ferguson (1985) Treatability of thermomechanical 

pulping process effluent with anaerobic biological reactors, Proc. 1985 TAPPI Environmental 

Conference, presented April, 1985, Mobile, AL. 

Ferguson, J.F. (1986) Plumbing materials and water quality deterioration in Water Quality

Concerns in the Distribution System, AWWA Proceedings, Denver, CO. 

Labib, F., J.F. Ferguson, and M.M. Benjamin (1988) The response of a butyrate fed anaerobic 

fluidized bed reactor to transient loading, Proc. 43rd Purdue Industrial Waste Conference, Lewis 

Publishers, 363-371. 

Ferguson, J.F., Luonsi, A., and D. Ritter (1990) Sequential anaerobic/aerobic biological treatment 

of bleaching wastewaters, Proc. TAPPI Environmental Conference, Seattle, April, 1990, 333-338. 

Rumpf, M. I. and J.F. Ferguson (1990) Anaerobic pretreatment of a landfill leachate for metals 

and organics removal, Proc. 1990 ASCE Envir. Engr. Specialty Conference, Washington, D.C., 

552-559. 

Leif, W., J.F. Ferguson, and M.M. Benjamin (1990) Assessing the corrosion of lead tin solder 

(abstract), AWWA Water Quality Technology Conference, San Diego, November. 

Hodges, L.M., S.J. Komisar, H.D. Stensel, J.F. Ferguson (1990) Volatile organic degradation in 

fermentation reactors. Proc. 63rd Annual Conference of the Water Pollution Control Federation, 

Wash. D.C. 

Ferguson, J.F., E. Tuomi, and H.D. Stensel (1991) Advanced biological treatment for groundwater 

contaminants: Development of specialized aerobic consortia, Proceedings Paper, Air and Waste

Management Association, Vancouver. 

8
 
LaFond, R.A. and J.F. Ferguson (1991) Anaerobic and aerobic biological processes for removal of 

chlorinated organics from Kraft bleaching wastes, Proc. TAPPI Environmental Conference, San 

Antonio, 797-805. 

Ferguson, J.F. (1993) Anaerobic and aerobic treatment for AOX removal, Proc. TAPPI-1993 

Environmental Conference, 857-864. 

Ferguson, J.F., G.V. Korshin, S.A.L. Perry, and B. Faris, (1993) Evaluation of water quality 

effects on corrosion of copper and lead-tin solder in Portland water, Proc. 1993 Water Quality

Technology Conference,AWWA, Miami, FL, 1481-1499. 

Ofjord, G.D., J. Lee, JA. Puhakka, R.P. Herwig, and J.F. Ferguson (1993) Dechlorination of 

Pentachlorophenol and polychlorinated biphenyls by marine sediment enrichments, Proc. IAWAQ 

Specialized Conference on Aquatic Sediments, Milwaukee, WI. 

Ballapragada, B.S., V.S. Magar, J.A. Puhakka, H.D. Stensel, and J.F. Ferguson (1994) Fate and 

biotransformation of tetrachloroethene and pentachlorophenol in anaerobic digesters, Proc. 1994 

Wat. Environ. Fed. Annual Conference, Chicago. 

Korshin, G.V. and J. F. Ferguson (1996) Effects of natural organic matter on corrosion of copper 

and lead-containing brass in potable waters, Proc. Intl. Workshop on Internal Corrosion in Water

Distribution Systems, Gothenburg, Sweden. 

Hinck, M.L., J.A. Puhakka, J.F. Ferguson (1996) Resistance of EDTA and DTPA to Aerobic and 

Anaerobic Biodegradation, Proc. 5th IAWQ Symposium on Forest Industry Wastewaters,

Vancouver, B.C. 

Ferguson, J.F., S.H. Reiber, G.V. Korshin, R.L. Porter, and M.A. Edwards (1996) Development in 

pipe coupon monitoring techniques for corrosion control studies, Proc. Intl. Workshop on Internal

Corrosion in Water Distribution Systems, Gothenburg, Sweden. 

Boyle, M.F., B.S. Ballapragada, H.D. Stensel, J.F. Ferguson (1997) Chloroethene dechlorination 

kinetics of enrichments developed under different loading conditions, Proc. Fourth Int’l In Situ 

and On-Site Bioremediation Symposium, New Orleans. 

Zou, S, K.M. Anders, J.F. Ferguson (1997) Biostimulation and bioaugmentation of anaerobic 

pentachlorophenol degradation, Proc. Fourth Int’l In Situ and On-Site Bioremediation 

Symposium, New Orleans. 

Korshin, G.V., J.F. Ferguson (1997) Effects of Ozonation and Chlorination of NOM on Corrosion 

of Lead and Copper. AWWA Annual Conference, Atlanta. 

Ward, A, H.D. Stensel, J.F. Ferguson, G. Ma, S. Hummel (1997) Preventing growth of pathogens 

in post-pasteurized biosolids, Proc.WEF Annual Conf., Chicago. 

Maco, R. S., H.D. Stensel, J.F. Ferguson (1998) Impacts of solids recycling strategies on 

anaerobic digester performance, Proc. WEF Annual Conf., Orlando FL, [Vol. 2, pp. 213-230] 

Zou, S., H.D. Stensel, J.F. Ferguson (1998) Biological treatment of carbon tetrachloride in soil 

vapor extraction contaminated gases, Vol. 2 of Proceedings of the International Conference on 

Decommissioning and Decontamination and on Nuclear and Hazardous Waste Management, 

American Nuclear Society, Denver, CO. pp 1045-1050. 

9
 
Pietari, J.M.H., J.F. Ferguson (1999) Characterization of a psychrophilic TCE-dechlorinating 

culture and comparison with a mesophilic dechlorinating culture. In Situ and On-Site 

Bioremediation Symposium, San Diego, April. 

Pietari, J.M.H., R.P. Herwig, J.L. McLarnan, J.F. Ferguson (1999) Characterization of an 

anaerobic PCE or TCE to cis-1,2-DCE dechlorinating psychrotrophic enrichment. American Soc. 

Microbiol. Annual Meeting, Chicago, May. 

Ferguson, J.F., G.V. Korshin (1999) Effects of humic substances on drinking water quality. Proc. 

4th Finnish Conference of Environ. Sciences, Tampere, Finland. May 

Elardo, P., Danowski, P., J. Ferguson (1999) Options for treating stormwater runoff from woodpreserving facilities, Industrial Wastewater, Nov/Dec 1999, pp 34-39. 

Bucher, B., G. Newman, R. Moore, R. Lepisto, H.D. Stensel, J.F. Ferguson (2001) Pilot Plant 

Investigation of Thermophilic-Mesophilic Digestion for a Full-Scale Retrofit, Biosolids 2001, 

Proceedings Joint WEF/AWWA Biosolids and Plant Residuals Conference, San Diego, February 

(13) 

Moen, G., Stensel, H.D., Lepisto, R., J.F. Ferguson (2001) Effect of Solids Retention Time on the 

Performance of Thermophilic and Mesophilic Digestion, WEFTEC, October. 

J.M.H. Pietari, R.P. Herwig, J.F. Ferguson (2001) Characterization of tetrachloroethene and cis1,2-dichloroethene dechlorinating cultures with terminal restriction fragment length 

polymorphism (T-RFLP) analysis, In situ and On-site Biormediation, 6th International 

Symposium, San Diego.June. 

J.M.H. Pietari, R.P. Herwig, J.F. Ferguson (2002) Characterization of a microaerophilic and 

psychrotrophic, tetrachloroethene to cis-1,2-dichloroethene dechlorinating bacterium, Strain JPD1, American Society of Microbiology National Meeting, Salt Lake City, UT, May. 

Satterberg, J.M., Herwig, R.P., and J.F. Ferguson (2003) Dehalogenation of tetrachlorethylene in 

estuarine sediment enrichments: characterization of the dechlorinating microbial community and 

effect of sulfate reduction inhibition. NIEHS Superfund Basic Research Program Annual 

Meeting, Dartmouth, NH, November 

Conklin, A.S., Bucher, R.H., Stensel, H.D. and J.F. Ferguson (2004) Oxygen inhibition and 

toxicity in anaerobic sludge digestion, Water Environment Federation Biosolids Specialty 

Conference, Salt Lake City, UT, February. 

Conklin, A.S., Zahller, J.D., Bucher, R.H., Stensel, H.D., and J.F. Ferguson (2004) Acetoclastic 

and hydrolytic activity in anaerobic digestion—keys to process stability, Anaerobic Digestion 

2004, International Water Association Specialty Conference, Montreal, Quebec, August. (Vol. 2, 

pp 833-838). 

10
 
Bouwman, R., Langwaldt, J.H., J.F. Ferguson, R. Lepistö (2004) Toxicity and biodegradation of 

long chain fatty acids in thermophilic anaerobic sludge, Anaerobic Digestion 2004, International 

Water Association Specialty Conference, Montreal, Quebec, August. 

Bucher, RH, Zahller, JD, Conklin, AS, Ferguson, JF and HD Stensel (2004) Evaluation and 

Modeling of Staged Anaerobic Digestion, Anaerobic Digestion 2004, International Water 

Association Specialty Conference, Montreal, Quebec, August 

Conklin, A., Stensel, HD, and JF Ferguson, The growth kinetics and competition between 

Methanosarcina and Methanosaeta in mesophilic anaerobic digestion, accepted for presentation at 

WEFTEC, October 2005, Washington DC 

Conklin, A, Zahller, J, Stensel, HD, and JF Ferguson, Development of a tool to monitor anaerobic 

digester stability and capacity and its application to full-scale digesters, accepted for presentation

at WEFTEC, October 2005, Washington DC 

Books, Chapters 

Jenkins, D., V. Snoeyink, J.F. Ferguson, and J. Leckie (1971) Water Chemistry Laboratory 

Manual, Assoc. of Environmental Engineering Professors, 1971 (revised 1973, 1980), publisher in 

1980 John Wiley and Sons. 

Jenkins, D., A.B. Menar, and J.F. Ferguson (1973) Recent studies of calcium phosphateprecipitation in wastewaters, in Applications of New Concepts of Physical-Chemical 

Wastewater Treatment, Progress in Water Technology, Vol. 1, Pergamon Press. 

Ferguson, J.F. and M.A. Anderson (1974) Chemical forms of arsenic in water supplies and their 

removal, in Chemistry of Water Supply, Treatment and Distribution, Vol. 1, A. Rubin, ed. 

Ann Arbor Science Publishers, Ann Arbor. 

Ferguson, J.F. (1975) Chemical precipitation modeling in sanitary engineering, in Mathematical 

Modeling for Water Pollution Control Processes, T.M. Keinath and M.P. Wanielista, eds., Ann 

Arbor Science Publishers, Ann Arbor. 

Ferguson, J.F. (1985) Corrosion arising from low alkalinity, low hardness or high neutral salt 

content water, Chapter 8 in EBI/AWWARF Project Book, June, 1985. 

Ferguson, J.F., O. Von Franque, and M.R. Schock (1996) Corrosion in copper in potable water 

systems, Chapter 5 in Internal Corrosion in Water Distribution Systems, 2nd ed., AWWARF, 

Denver, CO. 

Ferguson, J.F., R. Ryder, E.A. Vik, and I. Wagner (1996) Mitigation of corrosion impacts, Chapter 

8 in Internal Corrosion in Water Distribution Systems, 2nd ed., AWWARF, Denver, CO. 

Reports, Discussions, and Other Scholarly Papers 

Ferguson, J.F. and D. Jenkins (1973) Discussion of “Pilot Plant Tests of a Phosphate Removal 

Process,” by Levin, Topal, Tarnay and Samworth, appearing in JWPCF, Vol 45, 552-555. 

11
 
Ferguson, J.F., G.F.P. Keay, and E.N.D. Amoo (1975) Combined PAC biological contact 

stabilization treatment of municipal wastewater, Report to Metro. 

Ferguson, J.F. and Brown and Caldwell Engineers (1976) Comparison of powdered activated 

carbons for municipal wastewater treatment, Report to Amoco Corporation. 

Ferguson, J.F., K.B. Parrish, D.W. Browne, S. Lellelid, and R.O. Sylvester (1977) A study of 

wastewater handling, holding, and disposal from Washington State ferries, Washington State

Highway Department Research Program Report, Vol 27, 1. 

Ferguson, J.F. (1979) Discussion of “Alkalinity—A Neglected Parameter” by Neilson and 

Bundgaard, Prog. Water Technology. 

Horner, R.R., S.J. Burges, J.F. Ferguson, B.W. Mar, and E.B. Welch (1979) Highway runoff 

monitoring: The initial year, May 1977-August 1978, Highway Runoff Water quality Research

Project Report 2, Department of Civil Engineering, University of Washington. 

Vause, K.H., J.F. Ferguson, and B.W. Mar (1980) Water quality impacts associated with leachates 

from highway woodwaste embankments, Highway Runoff Water Quality Research Project 4,

Department of Civil Engineering, University of Washington. 

Asplund, R., J.F. Ferguson, and B.W. Mar (1980) Characterization of highway runoff in 

Washington State, Highway Runoff Water Quality Research Project 6, Department of Civil 

Engineering, University of Washington. 

Banerjee, S., J.J. Horng, J.F. Ferguson, and P.O. Nelson (1988) Field scale feasibility study of 

electro-kinetic remediation, Final Report, EPA CR811762-01, August. 

Reiber, S.R., M.M. Benjamin, and J.F. Ferguson (1988) Internal corrosion within the Everett 

distribution system, Technical Report, prepared for Department of Public Works, City of Everett, 

March. 

Benjamin, M.M., S.H. Reiber, J.F. Ferguson, E.A. Vanderwerff, and M.W. Miller (1990) 

Chemistry of corrosion inhibitors in potable water, AWWARF report. 

Ferguson, J.F. (1993) Anaerobic and Aerobic Biological Treatment of Bleaching Effluents to

Remove Chlorinated Organics, The Chlorine Institute, Washington, D.C. 

Edwards, M., T.E. Meyer, J. Rehring, J. Ferguson, G. Korshin, and S. Perry (1996) Role of 

inorganic anions, NOM, and water treatment processes in copper corrosion, American Water 

Works Research Foundation, Denver, CO, 152 pp. 

Ferguson, J.F. (1996) Have we bitten off more than we can chew, or is environmental engineering 

more than we thought it was? Water Environment Research, 68:3, 259. 

Ferguson, J.F. (1997) The system is the thing, Water Environment Research 69:6, 1065. 

Korshin, G.V., J.F. Ferguson, A.N. Lancaster and H. Wu (1999) Corrosion and Metal Release for 

Lead Containing Materials: Influence of Natural Organic Matter and Corrosion Mitigation, 

AWWARF report, Denver, CO. 176 pp. 

Ballapragada, B.S., Stensel, H.D., J.F. Ferguson, V.S. Magar, J.A. Puhakka (1998) Toxic 

Chlorinated Compounds: Fate and Biodegradation in Anaerobic Digestion, Water Environ. Res. 

Foundation, Project 91-TFT-3 

12
 
Newton, C.D., H.D. Stensel, J.F. Ferguson, (1999) Discussion of “A systematic artifact that 

significantly influences anaerobic digestion efficiency measurement, by S.S. Beall, D. Jenkins, 

S.A. Vidanage, Wat. Environ. Res. 71, 1257-58. 

Borton, D., Ferguson, J., Fisher, R., Hall, E., Hall T., Joutijarvi, T., Luonsi, A. Munkittrick, K.,

and M. Priha (2004) 2003 IWA Symposium and Fate and Effects Conference, Paperi ja Puu, 86:5,

346-348. 

Ferguson, JF (2004) Engineering Controls for Ballast Water Discharge: Developing Research

Needs, Report of an NSF-sponsored workshop. 

Sponsored Research since 1985 

Funded (current funding in bold) 

8/85-6/88 Treatment of Waste Contaminated Ground by Electro-Kinetics (Co-PI, Banerjee), EPA, 

$255,000. 

9/85-3/88 Chemistry and Application of Corrosion Inhibitors in Potable Water (Co-PI, Benjamin), 

AWWA Research Foundation, $120,000. 

6/85-11/88 Transient Response Studies and On-Line Control in Anaerobic Wastewater Treatment 

Reactors (Co-PI, Benjamin and Ricker), NSF, $330,000. 

1984-1990 Monitoring Water Quality (Co-PIs, Benjamin, Spyridakis), EPA, $350,000. 

11/86-12/87 TFSC Model Development and Technical Assistance (Co-PI, Stensel, Benjamin), Metro, 

$89,000. 

5/87-10/87 Corrosion Evaluation in the Everett Water Supply System (Co-PI, Benjamin), City of 

Everett, $34,000. 

6/87-11/87 Evaluation of Dellchem Treatment at Tacoma North End (Co-PI, Stensel), WA Dept. of 

Ecology, $35,000. 

5/88-9/89 Evaluation of Pretreatment for Discharge of Cedar Hills Leachate to the Metro Sewer 

System (Co-PI, Benjamin), King County (as subcontract to QGNF Co), $207,000. 

8/88-7-90 Toxics Biodegradation in Municipal Wastewater Treating Using Fermentation, Anoxic 

and Anaerobic Process Modifications (Co-PI, Stensel), EPA, $239,000. 

10/89-10/93 Advanced Biological Treatment Technology to Reduce Health Risk of Halogenated 

Organic Contaminants (Co-PIs, Stensel, Strand, Herwig), NIEHS, $1,020,000; 

4/92-4/95 $900,000; 

4/95-4/00 $1,000,000 

4/00-4/06 currently $183,000 per year 

6/90-7/92 Advanced Biological Treatment of Bleaching Wastes, The Chlorine Institute, $208,000. 

13
 
6/91-6/94 Biodegradation of Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons in 

Contaminated Marine Sediments (Co-PIs, Staley, Herwig), Office of Naval Research, 

$375,000. 

9/92-9/94 The Role of Inorganic Anions and Natural Organic Matter in the Corrosion of Copper 

Pipe (Co-PI, Marc Edwards, U. CO), AWWARF, $200,000. 

3/92-3/95 Dehalogenation of Organic Pollutants in Anaerobic Digestion (Co-PI, Stensel), METRO, 

$125,000, WERF, $362,000. 

4/92-4/96 Bioremediation of Marine Sediments (Co-PI, Stensel), Office of Naval Research, 

$210,000. 

9/94-9/96 Corrosion and Metal Release for Lead-Containing Materials: Influence of Natural 

Organic Matter and Corrosion Mitigation, AWWARF, $200,000. 

10/94-9/04 Graduate Fellowships and Advanced Wastewater Research, (Co-PI, Stensel) King Co. 

Department of Natural Resources, currently $101,000 per year 

3/95-7/01 Tools for Evaluating the Effects of Subsurface Restoration Technologies on Uncertainty 

and Risk Reduction, subproject of Consortium for Risk Evaluation with Stakeholder 

Participation, (Co-PI, Stensel, Massmann) U.S. Dept. of Energy, $150,000 per year. 

6/96-6/97 Pentachlorophenol Treatment Alternatives, Western Wood Preservers Institute, $25,000. 

12/00-12/03 Post Optimization Lead and Copper Control Monitoring Strategies, AWWARF #2679, 

(Co-Investigator, with Korshin [G. Kirmeyer of Economic & Engineering Services, Inc. is 

PI]) $400,000 total project. 

10/01-9/02 RM-03 Control of Contaminant Migration, CRESP, Department of Energy, $71,422, PI. 

6/02-9/05 Tank Waste Initiative, CRESP, Department of Energy, $89,000, UW budget supporting 

my activities (with Korshin) 

3/03-2/04 Engineering Controls for Ballast Water Discharges: A Workshop to Develop Research 

Needs, NSF, $84,000. 

10/03-9/06 Acetoclastic and Hydrolytic Activity in Anaerobic Digestion—Keys to Process Stability 

and Process Control, NSF, $505,000. (PI with Stensel and Stahl). 

5/05-4/08 Fundamental Mechanisms of Lead Oxidation: Effects of Chlorine, Chloramine and 

Natural Organic Matter on Lead Release in Drinking Water, NSF, $477,011. (Co-PI with 

Korshin) 

14
 
 

Project Reports (reports to sponsors) 

Some, not all, are listed in “Reports, Discussions, Other Scholarly Publications” above 

Invited Lectures and Seminars, last 10 years 

Lecture at Duke University, 1988. 

Seminar on Bleaching and the Environment, Pacific Northwest TAPPI, Seattle, WA, 1988. 

Paper presented at American Society of Microbiology Northwest Meeting, Seattle, WA, 1989. 

Berg Lecture, Department of Civil Engineering, University of Washington, 1990. 

Lecture at Workshop on Corrosion Monitoring and Control, Oslo, Norway, 1990. 

Lecture at University of Aalborg, Denmark, 1990. 

Lecture at Purdue University, 1990. 

Paper presented at TAPPI Environmental meeting, Seattle, WA, 1990 

Lecture to Department of Ecology engineers, Redmond, WA, 1990. 

Position paper presented at National Conference on Environmental Engineering Education, Corvallis, 

1991 

Lecture at Wastewater Technology Centre, Hamilton, Ontario, 1992 

Speaker at EPA Workshop on Lead and Copper Rule, Chicago, IL, 1992 

Lectures on Anaerobic Treatment of Forest Industry Wastewaters at Nanjing Forestry University, 

Nanjing, China April, 1992 

AWWA Conference on Lead and Copper Rule, Seattle, WA, 1993. 

Speaker at Oregon Graduate Institute seminar, 1994 

Lectures on Anaerobic Treatment of Industrial Wastewaters at Chengdu University of Science and

Technology, Chengdu, China April, 1994 

Speaker at WERF Symposium, Miami Beach, FL, 1995. 

Biological Dehalogenation in Marine Sediments, ONR Workshop, Bethesda, MD, 1996 

15
 
Applied Microbiology: Anaerobic Processes, CRESP Symposium, Seattle, WA, 1996 

Invited speaker, Nessling Symposium on Bioremediation, Helsinki, Finland, 1998 

Invited speaker, 4th Finnish Conference of Environmental Sciences, Tampere, Finland, 1999 

Presented Doctoral Course on Advances in Biological Wastewater Treatment at Tampere University 

of Technology, Tampere, Finland, May, 1999 

Speaker at Civil Engineering Departmental Seminar, University of Minnesota, April, 2001 

3rd IAWPRC Symposium on Forest Industry Wastewaters, Tampere, Finland, 1990. 

AWWA Water Quality Technology Conference, San Diego, 1990. 

TAPPI Environmental Conference, San Antonio, TX, 1991. 

Air and Waste Management Association Conference, Vancouver, B.C., 1991. 

TAPPI Environmental Conference, Boston, MA, 1993. 

4th IAWQ Conference on Forest Industry Wastewater, Tampere, Finland, 1993. 

AWWA Annual Conference, Atlanta, 1997 

12th Annual WEF Residuals and Biosolids Management Conference, Bellevue, 1998 

WEF Annual Conference, Orlando, 1998 

Presentations Given at Conferences, last 10 years 

Professional Society Membership 

American Association for the Advancement of Science, since 1966 

American Chemical Society, 1970-1980 

Association of Environmental and Science Engineering Professors, since 1971 

American Society of Civil Engineers, since 1963 

American Society of Limnology and Oceanography, 1969-1980 

American Water Works Association, since 1975 

International Water Association, since 1990 

TAPPI (Technical Association of the Pulp and Paper Industry), since 1980 

Water Environment Federation, since 1966 

16
 
Professional Society and Other Service 

AWWA Student Activities Committee, 1974-1977, Member Control Group, 1980-82 

AEEP Distinguished Lecturer Committee, 1974-78, Chair 1978 

WPCF Water Reuse Committee, 1974 

Program Committee, ASCE-EED National Conference, Chairman, 1975-76 

ASCE-EED Sessions Committee, 1976-77 

AEEP Board of Directors, 1978-81 

ASCE-EED Publications Committee, Acting Editor, Jour. Environ. Engr. Div., 1978-82 

WPCF Awards Committee - H.P. Eddy Award, 1978-82, ‘84-87, Chair, 1987 

WPCF Program Committee - Research Symposium Subcommittee, 1978-82 

AWWA Corrosion and Stability Research Committee, Chairman, 1980-84, Member 1985-1992 

AWWA/Engler Bunte Joint Committee on Corrosion in Water Systems, 1983-86, ‘92-95 

Scientific Programme Committee, IAWPRC Symposium on Forest Industry Wastewater, 

1989-90, 91-92, 95-96, 99. 

Chair, Remediation of Solvents in Subsurface Environments Research Symposium, NIEHS, 1996 

Management Group, IWA Specialty Group on Forest Industry Wastewaters, 1990-present 

6th National Conference on Environ. Engr. Education, Steering Committee1990-93 

TAPPI Water Quality Committee, 1991-1995 

AWWA Research Division Board of Trustees, 1992-present, Vice-Chair, 1995-97, Chair, 1998 

-2001, Technical and Educational Council, member 1998-2001. 

Editorial Board of Review for Water Environment Research, 1995-1999 

Chair, Organizing and Program Committees, 7th IWA Symposium on Forest Industry Wastewaters, 

June 2003, Seattle,WA 

Member, ScientificCommittee, 8th IWA Symposium on Forest Industry Wastewaters, April 2006, 

Vitoria, Brazil 

Review panel, NIEHS Superfund Basic Research Program program projects, September, 2004 

Participant, Technical Workshop on Ballast Water Management for Vessels Declaring No Ballast 

Onboard, U.S. Coast Guard, Cleveland, May, 2005 

Participant, Evaluating Ballast Water Treatment Systems Onboard Ships, Pacific Marine Fisheries 

Commission, Portland, June, 2005 

Review panel, NSF IGERT preproposal (BES program), April 2004, Washington DC 

Reviews Made--typical for last 10 years 

Journal Number 

Water Research 

Environmental Health Perspectives 

Environmental Science and Technology 

Journal of Environmental Engineering, ASCE 

Journal of American Water Works Association 

Water Environment Research 

(on Editorial Board of Review through 9/99, handling ~30 papers per year)

other journals (e.g. Biotech. Bioengr., Can. J. Microbiol., Biodegradation) 

5/yr

1/yr

3/yr

3/yr

2/yr

3/yr

~3/yr 

Proposals: 

17
 
 

Awards and Honors 

 

 

Proposal Review Panels, Environmental Engineering, EPA, 1995, 1997, NSF 2001, 2002, 2005 

others (NSF, Canadian NSERC, Hong Kong, Korea and Singapore research agencies,

regional agencies and foundations) ~4/yr 

National Merit Scholar, 1959-1963 

Tau Beta Pi, 1962 

AEC Fellowship in Nuclear Science and Engineering, 1963-1964 

EPA Predoctoral Fellowship, 1966-1969 

EPA Postdoctoral Fellowship, 1969-1970 

H.P. Eddy Award for Outstanding Research (Water Pollution Control Federation), 1974 

H.P. Eddy Award for Outstanding Research (Water Pollution Control Federation), 1978 

H.P. Eddy Award for Outstanding Research (Water Pollution Control Federation), 1984 

Award for Best Research Paper, American Water Works Association, 1984 

Academic Advisor to winner of 1984 AWWA Academic Achievement Award for best 

doctoral dissertation, 1984 

Award for Outstanding Publication, American Water Works Association, 1988. 

Award for Best Distribution System Paper, American Water Works, Association, 1990. 

Berg Lecturer, Department of Civil Engineering, University of Washington, 1990. 

Society of Scholars, Johns Hopkins University, 2002 

Teaching, last 10 years 

No. of Course Title Instructor's 

Course Quarter Students Avg of Items 1-4 

 CEWA 456 

 CIVE 350 

CEWA 556 

CEWA 550 

A1988 

W1989 

Sp 1989

A1989 

 Aquatic Chemistry 

 Envir. Engineering-Water & Air 

Industrial Waste Treatment 

 Biological Waste Treatment 

3.70 

CIVE 350 W1990 80 Envir. Engineering-Water & Air 3.01 

 CEWA 470 W1990 Solid Waste Disposal 

 CEWA 550 A1990 36 Microbiological Process Fund. 3.44 

 CEWA 456 A1990 Aquatic Chemistry 2.64 

 CEWA 470 W1991 Solid Waste Disposal 

CEWA 556 Sp1991 25 Industrial Waste Treatment 3.92 

 CIVE 350 A1991 Envir. Engin.-Water & Air 3.60 

CIVE 485 A1992 29 Aquatic Chemistry 3.71 

CIVE 350 W1993 82 Envir. Engineering-Water & Air 3.30 

 CEWA 550 A1993 26 Micro. Process Fundamentals Form X 

 CEWA 551 W1994 18 Biological Treatment Systems Form X 

 CEWA 550 A1994 27 Micro. Process Fundamentals 3.42 

18
 
 

CIVE 350 W1995 86 Envir. Engineering-Water & Air 3.34 

 CEWA 550 A1995 25 Micro. Process Fundamentals 3.4 

CIVE 350 W1996 63 Envir. Engineering-Water & Air 3.5 

 CEWA 550 A1996 13 Micro. Process Fundamentals 1.9 

CIVE 350 W1997 62 Envir. Engineering-Water & Air 3.5 

CIVE 350 A1997 40 Envir. Engineering-Water & Air 3.06 

 CEWA 550 A1997 10 Micro. Process Fundamentals 2.88 

 CIVE 485 W1998 14 Aquatic Chemistry 3.56 

CEWA 558 S1998 9 Industrial Waste Treatment 

 CEWA 550 A1999 18 Micro. Process Fundamentals 3.43 

 CEWA 551 W2000 11 Physical-Chemical Treatment Proc. 3.29 

CIVE 350 S2000 58 Envir. Engineering-Water & Air 3.22 

 CEE 540 A2000 10 Micro. Process Fundamentals 

 CEE 541 W2001 5 Biological Treatment Systems 

CEE 549 S2001 5 Advanced Environ. Engr. Topics 3.25 

CEE 500 C/D S2001 20 EES/HWR Seminar 

 CEE 482 A 2001 14 Wastewater treatment 3.12 

CEE 544 W 2002 7 Physical-Chemical treatment 4.32 

CEE 350 S 2002 65 Intro Environmental Engr. Science 2.6 

Short Courses, Workshops, and Other Educational Programs 

Teaching workshop, March 30, 2001 

Chaired Doctoral Degrees 

G. Lee Christensen (JHU) 1972 

Mark A. Anderson (JHU) 1974 

John Eastman 1977 

David N. Given 1978 

Ronald D. Hilburn 1983 

Sandra L. Woods 1985 

 Foroozan Labib 1989 

 Jao-Jia Horng 1993 

 Simeon J. Komisar 1993 

 Bhaskar Ballapragada 1996 

 Krista M. Anders 2000 

Siwei Zou (continuing)

 Jaana Pietari 2002 

 Anne Conklin 2004 

Hyun-shik Chang (co-advise with Korshin) (continuing) 

Chaired Master Degrees 

David Refling (JHU) 1974 

Elaine Friebele (JHU) 1975 

David N. Given (JHU) 1975 

Thomas A. King (JHU) 1975 

George F.P. Keay 1975 

Sylvia Burges 1976 

19
 
Richard R. Spencer 1976 

John P. Wilson-vanOsdel 1976 

Cornelius J. Marx 1976 

Karl B. Parrish, Jr. 1976 

Steven M. Lellelid 1977 

David W. Browne 1977 

Ronald L. Horres 1977 

Allan D.Kissam 1977 

Ronald D.Hilburn 1977 

Stephen M. Hart 1978 

Mary S. Anderson 1978 

Anne Crawford 1978 

Kimberly A. Cox 1978 

Sonthi Vannasaeng 1978 

Wang-Cheng Tseng 1978 

Mario Kato 1979 

Paul Snyder 1979 

Michael J. Brown 1980 

Kurt H. Vause 1980 

Sandra L. Woods 1980 

Carlos Herrera 1980 

Mark B. Buggins 1980 

Paul S. Snyder 1980 

Brian J. Eis 1982 

David R. Nitchals 1983 

Michael S. Kuenzi 1984 

Karl R. Nordqvist 1985 

James C. Ebbert 1986 

Ronald S. Sletten 1987 

Chung Feng Chung 1987 

Byung K. Maeng 1987 

Sheila J. Baran 

Gregory L. Pierson

Christopher A. Arts

Yun-Peng Shih

John Galasso 

Mary I. Rumpf 

Eva Jonsson 

Dennis Ritter 

Laura Hodges

Ronald A. LaFond 

Karl S. Bosworth 

William T. Leif 

Per H. Ollestad 

Patricia S. Perkins 

Ron L. Porter 

Grete Rasmussen 

John Ryding

Sophia Gudmundsdottir 

Andy Haub

Jean H. Lee 

Margareta Lundin

Paivi Makinen 

Gro D. Ofjord 

1989 

1989 

1989 

1989 

1989 

1989 

1990 

1990 

1991 

1991 

1992 

1992 

1992 

1992 

1992 

1992 

1992 

1993 

1993 

1993 

1993 

1993 

1993 

20
 
Krista M. Anders 1994 

Samuel A. L. Perry 1994 

Stacy A. Koch 1995 

Henning Mohn 1995 

Matthew L. Hinck 1995 

Kara Nelson 1996 

Patricia A. Danowski 1997 

Pamela A. Elardo 1997 

Rebecca S. Maco 1997 

Hao Wu 1997 

Alice Lancaster 1997 

Michael Boyle 1997 

Siwei Zou 1997 

Jaana M.H. Pietari 1999 

Lisette L. Nenninger 1999 

Cheryl Stadlman 1999 

Janel Duffy 2001 

Se-Yeun Lee 2002 

Veronica Henzi (with J. Cooper) 2003 

Pragya Singh (co-advise with G. Korshin) 2002 

Jessica Satterberg 2004 

Benni Jonsson (continuing)

Tom Chapman (continuing) 

Dan Wang (continuing) 

Virpi Salo (continuing) 

Other Student Supervision (service on graduate degree committees): 

 not listed 

Departmental Service, since 1988 

1988 Civil Engineering Undergraduate Curriculum Review Committee 

1988-1992 Chairman, Civil Engineering Undergraduate Education Committee 

1988 Organizer, Evans Lectureship 

1989-1991 Graduate Program Advisor, Environmental Engineering & Science 

1997-1998 Chair, Centennial Reunion Planning Committee 

1999-2000 Graduate Application Coordinator for Environmental Engineering & Science 

2002-present Undergraduate Admissions and Scholarship Committee 

2002-2003 Coordinator for Environmental Engineering and Science Area 

2004-2005 Coordinator graduate admissions for Environ. Engin. Science 

21
 
 

College Service since 1988 

1987-88 College Undergraduate Engineering Curriculum Review Committee 

1991-present Valle Scholarship and Exchange Program, Associate Director 

University Service since 1988 

1990 Graduate School Review Committee for Environmental Health Ph.D. 

Program 

1997 Chair, Graduate School Review Committee for Department of Environmental Health 

2003 Member, Graduate School Review Committee for School of Aquatic and Fishery Sciences 

Community Service 

Internal Corrosion Study Advisory Committee, Seattle Water Dept., 1975-76 

Cedar-Tolt Watershed Management Advisory Committee, Seattle Water Dept., 1976-79 

Toxicant Study, Scientific Advisory Panel, Municipality of Metropolitan Seattle, 1978-81 

National Service, partial listing 

Peer Review Panel for EPA Research Center at Illinois Institute of Technology, 1985 

Western Regions Hazardous Substances Research Center, Scientific Advisory Board, 1985-92 

 EPA National Risk Management Laboratory Review Panel, 1997 

American Water Works Association Research Foundation, member Materials Issues Group, 1998 

NSF Review Panel, 2001, 2002, 2005 

Other Service, since 1996 

Department of Civil Engineering Review, University of British Columbia, 1996 

Department of Civil Engineering, University of Portland, Advisory Committee to Envir. Engr. Program, 

1998 

Consulting Experience, since 1990 

Corrosion impacts for San Francisco, Santa Cruz, and Los Angeles water systems, Camp, Dresser, 

and McKee, Inc., 1990 

Corrosion and blue water in East Bay MUD system; James M. Montgomery Engineers, 1990. 

Corrosion evaluation for Santa Clara Valley Water District; Kennedy, Jenks, Chilton, 1991. 

Corrosion evaluation for Portland Water Bureau; Economic and Environmental Services, Inc., 

1992-94 

22
 
Evaluate anaerobic bioremediation for Western Processing site, Landau Associates, 1993. 

Consult on treatment of deicing wastewaters, Port Authority of Seattle, 1995. 

Corrosion and red water evaluation for Tucson, AZ, CDM, 1996 

Pollution of City Waterway, Tacoma, WA; Aitken, St. Louis, Siljeg, 1996-1997 

Copper corrosion evaluation for Prescott, AZ, HDR Engineering, 1997 

Evaluation of Anoxic Gas Flotation alternatives for King Co. DNR, Brown & Caldwell, 1999 

Corrosion evaluation of treatment changes for Santa Clara Valley W.D., CDM, 1999 

Corrosion study for corrosion inhibitors for City of Santa Cruz, CDM, 2000 

Corrosion study for corrosion inhibitors and coagulant change for Santa Clara Valley Water 

District, 2001 

Court-appointed expert on corrosion field testing, Judge Peter Lichtman, L.A. Co. Superior Court, 

February-July, 2001. 

Evaluation of data from San Francisco PUC regarding turbidity in their transmission lines, CDM, 

2002 

Corrosion inhibition evaluation for CCWD/ City of Brentwood, CDM, 2004 

23
 
A
 

Carol A. Rego, P.E. 

Vice President 

Education 

B.S. – Civil Engineering, 

University of Massachusetts/ 

Dartmouth (1982) 

Registration 

Professional Engineer: 

Massachusetts (1988), Maine, 

Connecticut, Rhode Island, 

and New Hampshire 

Ms. Rego has 25 years of experience in water and water supply. Her expertise 

includes treatability studies; process selection and drinking water research; 

Safe Drinking Water Act (SDWA) compliance; water supply planning; and 

water treatment plant evaluation, operations, and design. 

Project Director/Technical Advisor. Ms. Rego serves as a senior project 

director and technical advisor for several drinking water projects in the New 

England Area including the Portland, Maine UV Disinfection Feasibility 

study; Reading, Massachusetts NDMA evaluation; Springfield Water and 

Sewer Commission optimization study; Lewiston and Auburn, Maine Safe 

Drinking Water Act compliance evaluation; water treatment plant upgrade 

for the City of Woonsocket, Rhode Island; and water quality consulting for 

the Providence (Rhode Island) Water Supply Board, including a 2-year lead 

and copper corrosion control optimization program. 

Officer-in-Charge, City of Cambridge, MA Water Quality and Treatment 

Consulting. Ms. Rego is overseeing various projects for the City including 

optimization of mixing and water quality in the Payson Park finished water 

storage reservoir; disinfection tracer studies for enhanced treatment; and 

developing a long-term water supply strategy. 

Officer-in-Charge, City of Newport, RI, Compliance Evaluation and Water 

Treatment Plant Improvements Projects. In response to new and upcoming 

drinking water regulations, the City of Newport undertook a comprehensive 

treatment evaluation, culminating in a plan of coordinated improvements to 

meet future regulations, as well as future water demands. The complexity of 

the Newport supply, treatment and distribution system further added to this 

challenge. This includes a complicated system of nine reservoirs having a 

wide range in quality that can change quickly. It also includes two treatment 

plants with different processes, one of which has equipment that is much 

beyond its useful life. Finally, the distribution system includes several 

pressure zones, several consecutive systems, and extended water age 

concerns. Ms. Rego is directing the city’s systematic approach to achieving 

integrated treatment including: 

	 Detailed evaluation of distribution system water quality interrelationships 

between proposed disinfection modifications (chloramines) and corrosion 

control treatment. This includes a year-long pipe loop study evaluating the 

effects of various NOM-pH-Pb-ORP relationships. 

	 Audit inspection of treatment plants to identify physical and reliability 

deficiencies. 
 

Carol A. Rego, P.E 

 Testing program including enhanced coagulation, organics removal 

optimization (MIEX), DBP formation kinetics, alternate coagulants, and 

alternate secondary disinfectant (chloramines). 

 Short-term improvements including the addition of chloramines for 

secondary disinfection at both WTPs to reduce formation of disinfection 

byproducts, optimization of existing processes for TOC removal and CT 

compliance. 

 Multi-pronged testing program including pipe scale analyses; bench-scale 

testing (chloramine decay, chlorine-to-ammonia ratio, DBP formation, 

coupon testing for metal (lead) release, corrosion rates, and scale 

formation); and limited pipe-loop testing. 

Project Manager/Technical Manager, Lead and Copper Rule Corrosion 

Optimization/Control Studies. Ms. Rego has helped several New England 

utilities develop approaches for corrosion optimization under the Lead and 

Copper Rule. These communities include Salem/Beverly, Needham, New 

Bedford, Worcester, Wakefield, and Woburn, Massachusetts; Brewer, 

Lewiston and Auburn, Maine; and Newport, Providence, Westerly, 

Pawtucket and Woonsocket, Rhode Island. For the Rhode Island Department 

of Health (RIDOH), she conducted a corrosion control study for the state's 43 

small surface and groundwater systems. She also assisted many of these 

communities with their public notification efforts. 

Technical Manager, Lead and Copper Rule Corrosion Optimization/Control 

Studies. Ms. Rego assisted the Salem Beverly Water Supply Board (SBWSB) 

(Massachusetts) with optimization of their corrosion control treatment and 

development of a regulatory compliance strategy. After many years of being 

in compliance, the SBWSB exceeded the Action Level for lead. The program 

included review of historical data, establishing sampling plans for 

lead/copper (Pb/Cu) at the tap and water quality parameters (WQPs), benchscale testing of alternative corrosion treatment strategies, implementation of 

the recommended treatment strategy, public notification/education program, 

and routine sampling for WQPs and Pb/Cu following changes in treatment. 

Technical Specialist, Lead and Copper Rule Compliance, Various Industrial 

Clients. Ms. Rego conducted an engineering study to address lead and 

copper concerns in the IBM East Fishkill (NY) West Complex distribution 

system. This included development of a sampling and analysis plan to 

evaluate water quality parameters in the West Complex system followed by a 

detailed implementation plan for the recommended treatment modifications. 

Ms. Rego also provided lead and copper rule drinking water regulatory and 

technical expertise for a food processing facility located in Killingly, 

Connecticut and the Pratt & Whitney manufacturing facility in Middletown, 

Connecticut. 

Honors/Awards 

Massachusetts Society of 

Professional Engineers, Young 

Engineer of the Year (1992) 

Dexter Brackett Award, Most 

Meritorious Paper: Journal of the 

New England Water Works 

Association (1997) 

A
 
A
 

Carol A. Rego, P.E 

Project Manager, US Coast Guard Shipboard Technology Evaluation 

Program (STEP). The STEP is designed to encourage the voluntary 

installation and testing of onboard ballast water treatment systems on 

merchant vessels by offering “equivalency” to the new ballast water 

management regulation. The project includes: (1) A desktop assessment of 

currently available and advanced prototype ballast water treatment systems 

intended for use onboard vessels; (2) marine biology and civil engineering 

Review Panel; and (3) assistance in the review and upgrade of STEP standard 

documents. 

Project Manager, Water Supply/Treatment Plan. For Manchester Water 

Works (MWW) in New Hampshire, Ms. Rego directed a yearlong study to 

develop a long-range view of MWW’s water supply and treatment options 

along with a plan for how to implement this vision. Ms. Rego reviewed 

MWW’s water supply situation from multiple perspectives ranging from 

supply source adequacy to the deterioration of aging facilities. Her work also 

included review of existing source and finished water quality data, the 

existing treatment process, current and proposed regulations, evaluation of 

the future Merrimack River supply quality, and establishment of treated 

water quality goals. She developed a series of supply and treatment 

alternatives that were evaluated on the basis of cost (capital, operational and 

life cycle), overall effectiveness in meeting the established water quality goals, 

and non-cost factors such as reliability, ease of operations, public acceptance, 

and environmental compatibility. Ms. Rego continued as the project manager 

for the design of the 50-mgd plant upgrade, which features ozone, new filters, 

additional clearwell capacity, provisions for UV disinfection, and 

improvements to the facility’s electrical, structural and architectural systems. 

Officer-in Charge, Water Distribution System and Water Treatment 

Upgrade Projects. Ms. Rego oversaw a chloramine conversion project for the 

City of New Bedford, Massachusetts, and the upgrade of a filtration plant for 

the Town of Wakefield, Massachusetts. She helped both communities secure 

State Revolving Loan Funding (SRF). Also for New Bedford, Ms. Rego is 

overseeing a water main rehabilitation project involving 29,000 feet of main 

replacement and relining. She is also responsible for completion of a 

transmission main reinforcement program for New Bedford involving line 

valve replacement on 42,380 feet of 48-inch cast iron and concrete main; 

20,000 feet on twin 36-inch cast iron mains; and 22,750 feet of 42-inch concrete 

main. 

Task Manager, Ultraviolet Disinfection Fouling Study. For New York City, 

Ms. Rego is the task manager for an ultraviolet disinfection fouling study for 

the unfiltered Catskill and Delaware surface water supply systems. The 12-

month-long study will evaluate low pressure high output and medium 

pressure UV reactors in side-by-side testing. The study objectives are to 

investigate fouling potential on the exterior surfaces of lamp quartz sleeves 

(with and without chlorine addition upstream of the UV reactors); evaluate 

algae growth potential on surfaces distant from the UV lamps; independently 

evaluate the performance of each reactor’s sleeve cleaning system (i.e., the 
 

Carol A. Rego, P.E 

cleaning systems for each reactor will not be compared to each other); and 

compile O&M information (e.g., cleaning regime, personnel requirements, 

etc.). 

Task Manager, Water Quality and Treatability Studies. For New York City, 

Ms. Rego was the task manager for the water quality and treatability studies 

for the 1,900-mgd Catskill and Delaware surface water supply systems. She 

developed testing protocols and associated water quality sampling plans, and 

oversaw the direction and execution of a multi-year pilot study for the 

presently unfiltered New York City supply. Her work included 

accompanying source water quality studies to anticipate treatment challenges 

and future regulatory compliance issues. 

Project Manager, Enhanced Disinfection Study. Ms. Rego’s work for New 

York City also included a two-year disinfection study to investigate the use of 

alternative disinfectants (ozone, chlorine dioxide, chlorine, and UV) for 

primary disinfection under a continued filtration avoidance scenario. The 

study determined the appropriate disinfectant dose and system configuration 

to provide various levels of pathogen inactivation without subsequent 

filtration. Other objectives included evaluating multiple, sequential 

disinfectants for enhanced inactivation, determining the levels of 

biodegradable organic matter and disinfection byproducts produced, and 

assessing the impacts of an ozone disinfection alternative on the distribution 

system. 

Officer-in-Charge and Technical Director, Flint’s Pond Microfiltration 

Plant. Ms. Rego was the officer-in-charge for studies and design of a 1.6-mgd 

microfiltration plant for the Town of Lincoln, Massachusetts. As part of this 

work, she directed a 4-month pilot testing study for the town’s presently 

unfiltered surface water supply—Flint’s Pond. Her work also included source 

water quality and SDWA compliance assessments, and State Revolving Loan 

Funding (SRF). CDM provided construction management and inspection 

services for the project, which recently went into operation in the summer of 

2003. 

Task Manager, Pilot Testing. For the Philadelphia Water Department (PWD), 

Ms. Rego developed the protocols for a three-year pilot-testing program at its 

Baxter and Belmont plants. The focus of the first year was on short-term, lowor no-capital cost modifications to optimize the existing plants in light of 

regulatory compliance and cost issues. The second phase of the testing 

program evaluated alternative oxidant and advanced clarification methods. 

PWD will evaluate alternative disinfectants (focusing on ozone) in the third 

phase. 

Project Manager, Information Collection Rule Program. Ms. Rego was the 

project manager for Information Collection Rule (ICR) sampling programs for 

the City of Brockton, Massachusetts, and for the Massachusetts Water 

Resources Authority (MWRA), Boston. She also directed ICR pilot studies for 

the City of New Bedford, Massachusetts, and rapid small-scale column testing 

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Carol A. Rego, P.E 

(RSSCT) studies for Brockton, Massachusetts, both evaluating granular 

activated carbon (GAC) for precursor removal. 

Technical Advisor, Water Quality Assessment. Ms. Rego was a technical 

advisor for the Drinking Water Quality Assessment and Improvement 

Program for the District of Columbia Water and Sewer Authority (WASA). 

Her work included reviewing and evaluating water treatment and 

distribution system water quality and operating practices to develop 

recommendations and an implementation plan to improve the District’s 

compliance with the Total Coliform Rule (TCR). 

Task Manager, Distribution System Water Quality Improvement Program. 

Also for MWRA, Ms. Rego was the special task manager for the distribution 

system water quality improvement program. She developed a program to 

revise the primary and secondary disinfection practice to improve 

distribution system residuals and improve compliance with the Total 

Coliform Rule. System features included open reservoirs, rechlorination 

following initial chloramination, and simultaneous implementation of new 

corrosion control treatment. She participated in a water quality workshop for 

MWRA staff and community representatives on integrating corrosion control 

and disinfection improvements. 

Project Manager, Water System Improvements. For water system 

improvements conducted for the City of Worcester, Massachusetts, Ms. 

Rego’s duties included project coordination and preparation of plans and 

specifications for a $65 million capital improvement project being constructed 

under eight construction contracts. These contracts include a 50-mgd water 

filtration plant, pump station modifications, water storage tanks, raw and 

finished water transmission mains, and distribution system improvements. 

Also included are design, construction, and operation of the pilot testing 

facility; preliminary design; detailed site selection studies; plant design 

criteria; plant layout; analysis of distribution systems; storage and pumping 

facilities; and cost-effective analyses. Ms. Rego was responsible for all 

permitting and public education requirements associated with the project. 

Project Manager, Operator Training and Startup. Ms. Rego developed and 

conducted operator training and oversaw the start-up of the Worcester water 

filtration plant, featuring on-line particle counters for each of the eight filters, 

and the source and finished water. The plant achieves greater than 3-log 

particle removal in the Giardia and Cryptosporidium size range and exceeds all 

production and water quality goals. 

Technical Director, Water Treatment Plant Studies. Ms. Rego was also the 

technical director for the Pilot Plant Studies, Quittacas WTP (45 mgd) in New 

Bedford, Massachusetts. The project evaluated the technical, water quality, 

and cost issues to convert from full conventional treatment to direct filtration 

and to convert from free chlorine to chloramine residual disinfection. 

A
 
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Carol A. Rego, P.E 

Project Engineer, Water System Improvement Project. Ms. Rego was project 

engineer for the final design of Worcester’s major water system 

improvements project. This project received an ACEC award for engineering 

excellence. She prepared plans and specifications and provided 

multidisciplinary coordination for eight construction contracts that included a 

50-mgd water filtration plant, five water storage tanks, pump station 

modifications, raw and finished water transmission mains, and distribution 

system improvements. 

Project Engineer, Facilities Plan. Ms. Rego also served as project engineer for 

a facilities plan and preliminary design for ozone primary disinfection 

facilities for the Portland Water District in Maine. In this role, she was 

responsible for the technical completion of the project, including site selection 

studies and facilities layout. She was also project engineer for an SDWA 

Impact Study for the Bridgeport Hydraulic Company in Connecticut. 

Process Consultant, Water Treatment Plant. Ms. Rego conducted a water 

treatment plant process study for the Town of Weymouth, Massachusetts. She 

was also a project engineer for a 10-mgd water treatment facility at Ludlow 

Reservoir in Springfield and for water treatment studies for the Champlain 

Water District in South Burlington, Vermont. 

Process Consultant, International Water Treatment Plant Projects. Her 

international work includes serving as process consultant for the Treatment 

Process Upgrade Program, Public Utilities Board, Republic of Singapore. 

Other international work includes serving as a Process Consultant for Siu Ho 

Wan (40 mgd), Ma On Shan (60 mgd), and Ngau Tam Mei (120 mgd) 

Treatment Works, Hong Kong Water Supplies Department. 

Professional Activities 

Organizing Committee, National Academy of Engineering, 2007 US Frontiers 

of Engineering Symposium, Redmond, WA. 

AWWA Research Foundation, Research Advisory Council, 1998-2004 

AWWA Research Foundation, Research Chair, Customer Workgroup of the 

Research Advisory Council, 1999 and 2000 

AWWA Research Foundation, Research Chair, Environmental Leadership 

Workgroup of the Research Advisory Council, 2001–2003 

U.S. Environmental Protection Agency (USEPA) National Drinking Water 

Advisory Council (NDWAC) Working Group on Research, 2000-2002 

AWWA Research Foundation, Project Advisory Committee for Improvement 

of the Ozonation Process Through the Use of Static Mixers, 1998-2000 
 

 

Carol A. Rego, P.E 

Invited Participant – Drinking Water Research Needs Expert Workshop, 

sponsored by USEPA and AWWA Research Foundation, Leesburg, Virginia, 

September 1999 

AWWA Research Foundation, Project Advisory Committee for Optimizing 

Filtration in Biological Filters, 1995-1999 

Publications/Presentations 

Case Studies in the Integrated Use of Scale Analyses to Solve Lead Problems, with 

M.R. Schock, National Risk Management Research Laboratory, USEPA, 

Cincinnati, Ohio, 2007 AWWA Distribution Research Symposium, Reno, NV, 

March 3, 2007. 

Understanding the Relationship Between Organic Precursor Fractions and 

Formation of NDMA and CNX in a Groundwater Supply, with D.A. Reckhow, 

University of Massachusetts, proceedings of the AWWA Water Quality 

Technology Conference, Denver, Colorado, November 6, 2006. 

Two Approaches to Address Calcium Carbonate Scaling Resulting from Optimal 

Corrosion Control Treatment, AWWA Inorganic Contaminants Workshop, 

Austin, Texas, January 31, 2006. 

Simultaneous Compliance Issues with Corrosion Control BAT: More than Just 

Primary Standards, with W.T. Wanberg, Town of Needham and M.R. Schock, 

U.S. EPA, AWWA Water Quality Technology Conference, Quebec City, 

Quebec, November 2005. 

Case Studies – LCR and DBPR Simultaneous Compliance, Virginia AWWA 

Section Drinking Water Quality Committee Seminar, Richmond, VA, April 13, 

2005. 

Case Study: One City’s Long-Term Strategy to Balance Multiple Water Quality 

Objectives, with James Ricci, Water Superintendent and Charles Kennedy, 

Assistant Superintendent, City of New Bedford, presented at the New 

England Water Works Association Water Quality Symposium, Boxborough, 

MA, May 19, 2005. 

Lead and Copper Corrosion Control Theory Update, with M.R. Schock, U.S. EPA, 

Cincinnati, OH, NEWWA Spring Joint Regional Conference and Exhibition, 

Worcester, Massachusetts, April 6, 2005. 

Evaluating and Improving Water Quality in Distribution Storage Reservoirs, with 

T.W. D. MacDonald, Manager of Water Operations, Cambridge Water 

Department, presented at the NEWWA Spring Joint Regional Conference and 

Exhibition, Worcester, Massachusetts, April 6, 2005. 

Controlling Both Calcium and Lead: A Unique Situation in New England, with 

William T. Wanberg, New England Water Works Association Annual 

Conference, Newport, Rhode Island, September 21, 2004. 

A
 
Selection, Construction and Operation of Membranes for a Small System, New York 

Section of the American Water Works Association Spring Meeting, Saratoga 

Springs, New York, April 29, 2004. 

Chloramine Conversion: What Distribution System Changes Should You Expect? 

with James Ricci and Charles Kennedy, NEWWA Spring Joint Regional 

Conference and Exhibition, Worcester, Massachusetts, March 31, 2004. 

Prepare Now for Public Notification, NEWWA Spring Joint Regional Conference 

and Exhibition, Worcester, Massachusetts, April 2002. 

Implementing the First Surface Water Microfiltration System in Massachusetts, 

with L. Sorgini, proceedings of the American Water Works Association 

Membrane Technology Conference, San Antonio, Texas, March 2001. 

Manchester’s Water Supply and Treatment Plan, with David B. Paris, NEWWA ~ 

NHWWA ~ GMWEA Meeting, West Lebanon, New Hampshire, January 

2001. 

The Feasibility of Constructing a Medium-Pressure UV Facility for New York City’s 

Catskill and Delaware Supplies, with O. Schneider, J. Herzner, D. Nickols, and 

D. Malanchuk, proceedings of the American Water Works Association Water 

Quality Technology Conference, Salt Lake City, Utah, November 2000. 

Microfiltration: Meeting Water Quality Challenges for Small Systems, with L. 

Sorgini, proceedings of the American Water Works Association Annual 

Conference, Denver, Colorado, June 2000. 

Impacts of Corrosion Control on Heavy Metals Concentrations: Three Years of 

Operating Experience, New England Water Environment Association Spring 

Conference, Bretton Woods, New Hampshire, June 5, 2000. 

Treating Waste Filter Backwash with Low Pressure Membranes, New England 

A
 

Carol A. Rego, P.E 

Water Works Association Water Quality Symposium, Boxborough, 

Massachusetts, May 2, 2000. 

Ultraviolet Light (UV) Disinfection for Drinking Water, with D. Nickols, Edwin 

C. Tifft Jr. Water Supply Symposium, New York Section of the American 

Water Works Association, Liverpool, New York, October 20, 1999. 

Microfiltration: Meeting Water Quality Challenges for Small Systems, with L. 

Sorgini, New England Water Works Association Annual Conference, 

Burlington, Vermont, September 22, 1999. 

A New Look at an Old Technology: Slow Sand Filtration, with S. Tarallo, 

proceedings of the American Water Works Association Annual Conference, 

Chicago, Illinois, June 1999. 
 

Carol A. Rego, P.E 

Worcester Corrosion Control Retrofit—An Example of a Project Partnership 

Approach, with R. Hoyt and P. Guerin, Joint Regional Operations Conference, 

New England Water Works Association, Worcester, Massachusetts, April 7, 

1999. 

Alternatives to Achieve Enhanced Disinfection for New York City, with J. Herzner 

et al., Proceedings, International Ozone Association, Pan American Group 

Annual Conference, Vancouver, British Columbia, October 1998. 

Newsletters Are Consumer Friendly, Joint Regional Operations Conference, New 

England Water Works Association, Marlborough, Massachusetts, April 1, 

1998. 

Implementing Corrosion Control Treatment: Balancing Water Supply and 

Wastewater Needs Through a Partnership Approach with R. Moylan and T. Walsh, 

Proceedings, WEFTEC ‘97, Chicago, Illinois, October 1997. 

Do Interim Improvements Prior to Permanent Facility Construction for SWTR 

Compliance Provide Worthwhile Public Benefit? with S. Seckinger et al., 

proceedings of the American Water Works Association Annual Conference, 

Atlanta, Georgia, June 1997. 

Round Robin HAA Testing Prompts Uncertainty in USEPA Method 552.1, with S. 

Seckinger and J. Occhialini, proceedings of the American Water Works 

Association Water Quality Technology Conference, Boston, Massachusetts, 

November 1996. 

Balancing Corrosion Control, Disinfection and Distribution System Water Quality 

for Boston, with B. Johnson, et al., proceedings of the American Water Works 

Association Water Quality Technology Conference, Boston, Massachusetts, 

November 1996. 

Pushing the Envelope: Integrating Ultra-High Clarification and Filtration Loading 

Rates, American Water Works Association, Engineering and Construction 

Conference, Denver, Colorado, March 1996. 

Ozone Applications for Filtration and Non-Filtration Alternatives, International 

Ozone Association Pan American Group Conference on Ozone for Drinking 

Water Treatment, Cambridge, Massachusetts, November 1995. 

Evaluating Contract Operations for a New Water Filtration Plant, with R. Moylan 

and J. Ridge, presented at the American Water Works Association Annual 

Conference, Toronto, Canada, June 1996. 

Washwater Recycle Optimization, presented at the American Water Works 

Association Annual Conference, Anaheim, California, June 1995. 

Dissolved Air Flotation Optimization: A Case Study, with D. Nickols, et al., poster 

presentation at the American Water Works Association Annual Conference, 

Anaheim, California, June 1995. 

A
 
 

 

A
 

Carol A. Rego, P.E 

Pilot Scale Evaluation of Residuals Management Options, with S. Seckinger, et al., 

poster presentation at the American Water Works Association Annual 

Conference, Anaheim, California, June 1995. 

Treatment Process Strategies to Meet Varying Water Quality Goals: Evaluating the 

Costs and Benefits, poster presentation at the American Water Works 

Association Water Quality Technology Conference, San Francisco, California, 

November 1994. 

The Crypto Challenge: Optimizing Treatment For Cryptosporidium Control, New 

England Water Works Association Annual Conference, Montreal, Quebec, 

September 1994. 

Small System Compliance: CT Versus DBPs, Proceedings of the American Water 

Works Association Annual Conference, New York City, June 1994. 

Small System Compliance: CT Versus DBPs, Proceedings of the American Water 

Works Association Engineering Design Conference, Cincinnati, Ohio, March 

1994. 

Water Treatment Plant Siting: Balancing Public, Environmental and Engineering 

Needs, with R. Moylan et al., Proceedings of the American Water Works 

Association Annual Conference, San Antonio, Texas, June 1993. 

Optimization and SDWA Compliance at a New England Water Treatment Plant, 

with J. Buckley et al., New England Water Works Association, Randolph, 

Massachusetts, December 1992. 

Review of the New Lead and Copper Regulations, Maine Water Utilities 

Association, Old Town, Maine, October 1991. 

Removal of Total Oxidant Species of Chlorine Dioxide Disinfection by Granular 

Activated Carbon, with J. Thompson, Proceedings of the American Water 

Works Association Annual Conference, Cincinnati, Ohio, June 1990. 

Evaluation of Alternative Water Supplies for Worcester, Massachusetts, New 

England Water Works Association, Milford, Massachusetts, May 1988. 

Ozone-Direct Filtration for the Worcester Water Supply, with P. Prendiville et al., 

Proceedings of the American Water Works Association Annual Conference, 

Kansas City, Missouri, June 1987. 
 

 

JOHN S. YOUNG, JR.
 

Home: 109 Kingsdale Avenue 

Cherry Hill, New Jersey 08003 

 856-424-0718 

Business: American Water 

1025 Laurel Oak Road 

Voorhees, New Jersey 08043 

 856-346-8250 

Education: B. S. Civil Engineering, Duke University, 1975; 

M.S. Environmental Engineering, University of North Carolina at Chapel Hill, 

August 1977 (two year program) 

Professional Summary 

John Young joined the American Water System in 1977 as the Director of Water Quality for the Eastern 

Division. He held increasingly responsible positions in engineering and water quality and in 1991 was 

named Vice President – Engineering. In this position, he was responsible for planning, capital program 

delivery, operational enhancements and employee development. Mr. Young has been active in and held 

leadership positions in a number of professional and civic organizations. Mr. Young has more than 25 

years of experience in the planning, design, construction management and operation of water and 

wastewater systems. He has also provided expert testimony and lectures in those areas. During 2000 and 

2001, Mr. Young was the integration lead for the major acquisition of Citizens Water Resources. 

John Young is Chief Operating Officer (COO) of American Water and holds a seat on the company’s 

Board of Directors. He was responsible for a wide range of corporate functions, including identifying and 

implementing operational improvements; managing the Americas Region capital program; and directing 

risk management in the areas of health and safety, security and event management. He was also 

responsible for environmental compliance, management, and stewardship; engineering; research and 

technology; and assessment of commercial and growth initiatives. 

Young is an active member of several professional organizations, including a Board Member of the 

Design/Build Institute of America and past New Jersey AWWA Section Chair and Fuller Awardee. He 

also serves on the USEPA National Drinking Water Advisory Council (NDWAC). 

Employment Record: 

Chief Operating Officer American Water 

10/05 – Present	 Responsible for developing and integrating the Company’s 

strategic plan including establishing balance between the 

company’s immediate business goals and long-term vision, 

developing and implementing policies, procedures and 

standards, as well as maintaining and enhancing the 
Vice President – Operations and American Water 

Investment Performance Responsible for the following functions/activities: 

11/03 – 10/05 

1) Identifying and implementing operational 

improvements, and efficiencies and best practices 

across the business; 

2) Managing the Americas Region $600M capital 

program; 

3) Risk Management – Health & Safety, Security and 

Event Management; 

4) Environmental compliance, management and 

stewardship; 

5) Engineering; 

6) Research & Technology. 

7) Assessment of commercial and growth initiatives. 

Vice President – Technical Services American Water 

1/03 – 11/03 Responsible for managing the American Water technical 

services including the engineering, environmental 

management and research functions. Additionally, 

responsible for improving business performance through 

identifying and implementing operational efficiencies, 

material procurement and energy management initiatives. 

Provide technical leadership for commercial opportunities 

to maximize value and performance. 

Vice President – Engineering American Water Works Service Co., Inc. 

4/91 – 1/03 Responsible for managing the engineering function of the 

American Water System. This includes the preparation of 

comprehensive planning studies for system operations in 

twenty-two (22) states and the design, design overview and 

construction management or projects involving water 

supply, treatment, pumping, distribution and transmission 

facilities. Responsibilities also include development of 

engineering standards, project management procedures, 

employee development and business development. 

Director – Engineering Design American Water Works Service Co., Inc. 

1/86 – 4/91 Responsible for managing engineering design for American 

System Engineering Office. Responsibilities include: 

1) Review and approval of in-house design of water 

treatment, pumping and storage facilities. 

2) Development of detailed design concepts and 

coordination of water works design and construction. 

3) Pilot plant testing and start-up of new or expanded 

facilities. 

4) Instruction at training seminars. 

5) Technical presentations. 

6) Expert testimony. 

company’s image and quality service. 
Director – Engineering Planning American Water Works Service Co., Inc. 

9/84 – 12/85 Responsible for managing engineering planning for 

American System Engineering Office. This group 

developed Comprehensive Planning Studies for water 

systems which included water demand projections and 

regional water supply plans, analysis of sources of supply 

and production facilities and modeling of distribution 

systems. 

Supervising Engineer American Water Works Service Co., Inc. 

10/82 – 9/84 Served as project engineer for the major design projects 

within System Engineering Office and supervised 

personnel on other design and planning projects. 

System Environmental Engineer American Water Works Service Co., Inc. 

12/79 – 10/82 Project engineer with primary responsibility for process, 

hydraulic, chemical feed and instrumentation and control 

design and coordination of structural, electrical and HVAC 

for new and renovated water works facilities. These 

facilities included turbidity removal, greensand filtration, 

lime softening, GAC adsorption, air stripping and residual 

solids processing. 

System Water Quality Engineer American Water Works Service Co., Inc. 

10/78 – 12/79 Evaluated the performance and efficiency of treatment 

facilities for American System Water Quality Office. 

Director of Water Quality – American Water Works Service Co., Inc. 

Eastern Division Responsible for the review and implementation of 

9/77 – 10/78 recommendations to improve finished and raw water 

quality, treatment efficiency and laboratory. 

Teaching Assistant University of North Carolina 

9/76 – 6/77 Involved the preparation and instruction of laboratory 

exercises for three graduate level courses in water and 

wastewater unit processes. 

Student Research Assistant Bogue Sound Water Quality Study 

9/75 – 9/76 University of North Carolina 

Duties included field sampling and collection of 

background data to develop recommendations for pollution 

abatement. 

Assistant Engineer Wiggins-Rimer & Associates 

1975, 1976 (part-time) Collection and analysis of watershed and stream flow data 

for 208 regional water quality/quantity planning studies. 

Professional Certifications Registered Professional Engineer in multiple states. 

Professional Organizations: National Drinking Water Advisory Council (2001-___) 

NDWAC Affordability Workgroup 

NDWAC Water Security Workgroup 
American Water Works Association 

Standards Council Member 

Chair – AWWA/ASDWA Additives 

1992-1994 New Jersey Section Program 

1994-1999 New Jersey Section Board of Trustees 

1997 New Jersey Section Chair 

1994 Fuller Award Recipient 

American Society of Civil Engineers 

Design/Build Institute of America – Board Member 

Civic:	 Trinity Presbyterian Church 

1989 – 1992 Board of Deacons 

1992 Moderator – Board of Deacons 

1994 – 1996 Elder – Session 

1996 President – Board of Trustees 

1998 Chair - $1.5 Million Capital Campaign 

Presentations and Publications: 

6	 “Emerging Water Utility Trends” presented at the New Jersey Section – American Water 

Works Association, March 2007. 

6	 “Effective Water Utility Management – Goals, Performance, Planning & Leadership” 

presented at the New Jersey American Water Works Association Seminar, February 

2007. 

6	 “Challenges and Benefits of Total Water Management” Published in Underground 

Infrastructure Management; November/December 2006. 

6	 “Challenges and Benefits of Total Water Management”, Published in Journal of the 

American Water Works Association; June 2006. 

6	 “A Paradigm Shift for Owners”, Design-Build and the Water/Wastewater Sector: Risks 

and Opportunities, Published in Design-Build DATELINE; January 2006. 

6	 “Emerging Water Utility Trends” presented at the Association of Metropolitan Water 

Agencies, 2005 Annual Meeting; October 2005. 

6	 “American Waters Business Process Transformation: Enhancing Asset Management” 

presented at the American Water Works Association, National Convention; June 2005. 

6	 “High Performance Supply Chain” presented at the International Utilities and Energy 

Conference – Barcelona, Spain; April 2005. 

6	 “Affordability: An Industry Perspective” presented at the National Association of Water 

Company Conference; October 2004. 
6	 “Small Systems Affordability” presented at the National Association of Regulatory 

Utility Commissioners (NARUC) Conference; February 2003. 

6	 “Automation and Instrumentation, Making the Most of Technology in Our Operations” 

presented for American Water Works Association teleconference; November 2000. 

6	 “The Future of Drinking Water Treatment” presented to the American Water Works 

Association – Water Quality Technology Conference; November 1999. 

6 “Waste Stream Recycle” presented to U.S. EPA Stakeholders Meeting for Filter 

Backwash Recycle Rule; July 1998. 

6 “Innovative Project Delivery Techniques” presented to the American Water System – 

Annual Business Forum; April 1997. 

6	 “Facility Reliability and Reserve Capacity” presented to the American Water System – 

Annual Business Forum; May 1996. 

6	 “Facility Automation” presented to the American Water System – Annual Business 

Forum”; May 1995. 

6	 “Source Remediation” presented to the American Water System – Annual Business 

Forum”; May 1995. 

6	 “Industry Leadership through Participation in Water Industry Activities” presented to the 

American Water System – Annual Business Forum; May 1994. 

6	 “Preparing a Request for Proposal” presented to the American Commonwealth 

Management Service meeting; March 1990. 

6	 “Using Technology as a Management Tool – Management through Facility Design” 

presented at American Water System Management Seminar; May 1988. 

6	 “Process Selection for Arsenic Removal” presented to the Indiana Section – American 

Water Works Association; November 1987. 

6	 “Pilot Treatment Studies for the Kentucky River” presented to the Kentucky-Tennessee 

Section – American Water Works Association; September 1987. 

6	 “On-Line Instrumentation – Practical Consideration” presented to the New Jersey Section 

– American Water Works Association; March 1986. 

6	 “Pilot-Scale Investigation of Air Stripping for Removal of Volatile Organics” presented 

to New Jersey Section – American Water Works Association; September 1981. 

6	 “Utilization of Belt Filter Press for Dewatering Water Treatment Plant Sludge” presented 

to the New Jersey Section – American Water Works Association; September 1981. 
6	 “Operating Experience with Granular Activated Carbon” presented to the New Jersey 

Section – American Water Works Association; September 1979. 

6	 “Chloroform Formation in Public Water Supplies: A Case Study” presented to the 97th 

Annual Convention of the American Water Works Association; May 1977. Published in 

Journal of the American Water Works Association; February 1979. 

6	 “Adsorption of Alkyl Phenols by Activated Carbon”; Singer, Yen, Young; presented at 

American Chemical Society – Division of Environmental Chemistry; September 1978. 

6	 “Adsorption of Phenolic Constituents of Coal Conversion Wastewaters”; Singer, Yen, 

Young; presented at the Purdue Industrial Waste Conference; 1977. 

Guest Lecturer: Johns Hopkins University: “Pilot Studies for Process Selection”. 

 Rowan University: “Challenges in the Water Industry”. 

 Lehigh University: “Water Treatment Process Selection Criteria” 

Instructor: American Water System – Water Treatment Plant Design Course. 
 

Appendix II: Peer Reviewer Comments 
 

 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

General Comments 

The organization of the chapters isn’t clear to a reader. The report needs a roadmap, just a paragraph at 

the end of chapter 1 that says LMP data will be presented and analyzed in Chapter 2, .... And the 

evidence about all the causative factors will be evaluated and presented in Chapter 5...etc. 

Chapter 1 

The readability of the figures, when printed in black and white, is problematic in several cases, which I 

will note below. The text should certainly omit references to the color of data symbols and lines. Even 

in this era, it is too much to assume that all readers will view the report on their computers or have a 

color copy available. Please review the figures in black and white and make the necessary adjustments. 

Some are just fine, but others could be improved. 

Much of the literature on the D.C. lead issue is in the gray literature and may not be available to many 

readers. I include WQTC Proceedings, AwwaRF reports, reports to DCWASA and EPA and all the 

internal DCWASA information. When these sources are used, it is important to include more 

information about what the study entailed and what the results are. I will note instances where I think 

more explanation is needed. 

At several fairly key points in the presentation extensive lists of citations are given. In one case (p.48), 

when I went to the papers that I could access (3 in journals. The other 7 in are in gray literature.) I 

found that two of them had no data that supported the statement in the text. Please be sure that a 

citation has specific information that supports a specific statement in the report. 

Paragraph 2, line 2. The term “consecutive” system (also used in the Executive Summary) doesn’t have 

a common meaning to many readers. Either explain or just omit the word. 

Page 1 

1st Paragraph 3 line 6 should change as to because Page 1 

Last Paragraph line 2 add lead-tin before solder Page 1 

Paragraph 2, Two issues with the causative mechanism Page 4 

Paragraph 2, line 6 delete “major” before Pb (IV) solids. There weren’t any others identified, or even 

considered. 

Page 4 

Last Paragraph, line 1 change became to were Page 4 

Paragraph 1 The presence of brass and bronze fittings in the service connection and consumer 

plumbing should be acknowledged. 

Page 5 

Need to provide an overview of what is to come in the report. Page 6 

Paragraph 2, line 1 should read “lead, copper and iron, using EPA Page 7 

The reanalysis of the LCR reports is somewhat interesting, but not very important, since only the JulDec 1992 values change significantly. I would like to know if all sites were selected with lead service 

lines, or if some had copper with lead-tin solder plumbing. A little more information about the 

sampling protocol would be appreciated. 

Page 8 & 9 

Same point as above. The detailed explanation of the small differences between the reported and the 

reanalyzed results doesn’t add much to the reader’s understanding of the problem. Given the lack of 

information about how DCWASA did their analysis, we can’t even get insight into why the differences 

occurred. 

Page 12 

The pH story for the plants and the distribution system is complicated and important, regarding Pb (II) 

solubilities. At this point, we can see that the pH at the entry points seems basically ok, considerably 

above the allowable minimums in warm weather. The distribution system picture is less clear. It looks 

like there are a few values below about 7.3, which really doesn’t tell us much. However, when a much 

larger data base is presented in Figure 28, it is clear that there was a much more prominent period of 

low pH values that may have had a lot to do with Pb (II) solubility and high lead levels. It is too bad 

that the initial data set misleads the reader. Perhaps words could be added that would make the reader 

aware that the story is going to be more complicated and clearer about low pH values in the distribution 

system. 

Page 13 

Page 1 of 6 
 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

General Comments (continued) 

Figure 1. I suggest that the authors try using small symbols (x) with different shapes. The gray squares 

form a band with little information discernable about the black diamonds (Dalecarlia plant) data. 

Page 14 

Paragraph 1 last line. Please don’t refer to the red line. Page 15 

Figure 2. The figure seems to have several different data symbols, but there is no explanation about 

what distinguishes them. 

Page 15 

I know that the purpose of the report isn’t to place blame for the crisis that the high lead levels created. 

But the partial LSL replacement activities by DCWASA certainly has to rank high on a list of 

ineffectual actions. I think the details on the number of partial and the number of complete 

replacements should be incorporated into the report. Were lead profiles done at any houses where a 

complete replacement was done? 

Page 16 

Figure 7 solid line segments would be easier to see. ( as used in Figure 9) Page 20 

Figure 11 The chlorine burn data are almost impossible to distinguish from the chloramine data. Page 25 

It isn’t clear to me why some of the profile results are discussed here and others in Chapter 5. In that 

connection I don’t see the relevance of the sentence about one home being sampled before and after 

partial LSL replacement. 

Page 29 

The point that LSLs are a primary source of lead is clear. However, I don’t think the method of 

subtracting the “background” sample values is justifiable. The lead in those samples surely comes from 

the LSLs, too. If there are actual measures of lead in distribution main pipes (Keefer and Giani, 2005), 

then those values could be used to indicate the contribution due to the mains. Please tell us what Keefer 

and Giani measured. 

The calculation of a percentage contribution to the lead concentration is hard to interpret, especially 

since the overall average concentration isn’t defined or presented. Figure 14 could be replaced by a 

table with average concentrations for the 1st liter, for the rest of the premise plumbing, for the LSL and 

for the main (based on samples from the mains). These values should be presented along with the 

average volume of water in the first three categories, and the concentration and volume should be 

multiplied to give the average contribution of lead from the three source areas for the lead profiles. 

Standard deviations for concentrations, volumes and mass loadings should also be presented. 

In calculating these concentrations and mass contributions, I think it would be justified to separate 

samples collected during chloramination, from those affected by the chlorine burns and the 

orthophosphate addition. It might be informative to present the average results for each of these 

periods. 

It should be pointed out that lead levels in quite a few samples of flowing water, originating upstream of 

the LSLs, had lead concentrations consistently exceeding the action level. This indicates that for these 

homes nearly all the water likely had high lead concentrations. 

Section 4.2.3. It would be better just to present the concentrations in the source water and from 

distribution main samples. The argument about diffusion and dissolution from LSLs should be in the 

previous section, as an explanation for the anomalous values seen in the lead profiles and as a 

justification for not subtracting the 0 or 00 lead levels. 

Page 30 

Table 7. The statement about Giani, et al should be modified. “Large fractions of” particulate lead 

occur in... 

Page 36 

Figure 17. Several minor points. Could add dates of chlorine burn periods. If it is possible, it certainly 

would be easier to read these figures with the x-axis labeled with simple dates, like 1/97, 7/97, 1/98, 

7/98 etc. Trying to read the exact dates, see the very small (sometimes obscured) mark on the axis, and 

figure out when something happened, is pretty difficult. The orthophosphate addition should be marked 

with a horizontal arrow, like the other treatment changes. 

Page 37 

Figure 21. It is stated that this house had a partial LSL replacement, but the volumes associated with 

the LSL seem to change in the two profiles. What was going on? 

Page 43 

Page 2 of 6 
 

 

 

 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

General Comments (continued) 

First paragraph. This discussion of ORP has the same problems that I discussed above. The measured 

ORP is not a thermodynamic oxidation reduction potential in nearly every case because it responds to 

all oxidation/reduction couples in a highly non-linear fashion, depending on how active each couple is 

on the electrode surface. 

Page 47 

Measured ORP levels need to be described more. Are these simply the recorded values? If so, tell us 

what the reference electrode was. If they are corrected to the standard hydrogen electrode scale (EH), 

then this needs to be stated. 

Oxygen should be added to the list of water quality variables that affect measured ORP values. 

Last paragraph. Schock, 2001 isn’t in references. Do you mean Schock, et al. 2001? I read the three 

papers that are in journals in this series of ten citations. Two of the three do not present evidence in 

support of the statement that Pb (IV) is in scale on LSLs. Please review use of citations, so that cited 

work has specific information that supports the specific statement in the text. 

Page 48 

1st Paragraph, line 5. The statement that “Pb (IV) solids convert” is not clear. They must be reduced to 

Pb (II) to become more soluble, and if they are reduced, then some other substance must be oxidized. 

They hypothesis about causation has a significant gap. 

Page 49 

2nd Paragraph. Line 6. Very little has been said previously about the role of high free chlorine residuals. 

This probably is a good point, at least in that the higher chlorine dosages probably maintained chlorine 

residuals into the service lines and consumer plumbing and provided enough oxidizing capacity to form 

significant amounts of PbO2 

Page 49 

Last Paragraph. Line 1. The relation between free chlorine and measured ORP should be shown, 

perhaps as a plot of free chlorine concentration vs. ORP. The logarithmic relation that is alluded to 

actually would predict a very weak dependence of ORP on chlorine concentration over the range used 

in D.C. 

Page 49 

2nd Paragraph. 1st sentence. The sentence isn’t clear. It can be improved some by saying “If an 

orthophosphate inhibitor had been added”, but the point about Pb (II) phosphate scales being protective 

is a) either very obvious based on experience of many utilities or b) completely unknown if the authors 

are thinking that free chlorine would still have oxidized Pb to form Pb (IV). 

Page 50 

This paragraph is a very important summary of the hypothesized causation of high Pb levels. The roles 

of free chlorine and low pH are very reasonable. There is a need for a mechanism of Pb (IV) reduction 

and a statement that the lead levels found in the lead profiles are reasonably consistent with Pb (II) 

solubility at pH between 7 and 7.5. The effort to make comparative statements about other systems are 

less convincing. There is no data presented that relates to other systems’ free chlorine or measured 

ORP levels and the occurrence of Pb (IV). The purpose of the last two sentences isn’t clear to me. The 

last sentence makes it clear that DCWASA has a fairly low alkalinity, which has been stated before. 

The preceding sentence may be intended to imply that maybe Pb (IV) is present in these field studies. 

However, if it just a statement that many high alkalinity systems have lower lead levels that Pb (II) 

solubility would indicate, that point probably isn’t necessary. 

Page 51 

2nd paragraph, line 6. The sentence seems to be an overstatement of what ORP measurements indicate. 

I’d suggest saying. The transformation of existing Pb (II) to Pb (IV) is not well understood beyond the 

presence and absence of free chlorine and the corresponding measured ORP values. 

Page 52 

3rd paragraph. The second sentence could be restated: The solubility constants of PbO2, Pb3 (OH) 

2(CO3)2 (hydrocerussite) and PbCO3 (10-66, 10-18.8 and 10-13, respectively) allow calculations that show 

PbO2 is much less soluble than the Pb (II) solids. 

Page 52 

4th paragraph. The observation by Schock and Giani that Pb (IV) solubility tends to decrease with 

decreasing pH needs to be explained, since it certainly isn’t the usual pattern for metal oxides. This is a 

case of a significant observation from a non-accessible source needs some explanation so the reader can 

understand why the authors are drawing their conclusion. 

Page 52 

Page 3 of 6 
 

 

 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

General Comments (continued) 

Last line. An explanation of what Schock and Giani did is needed, e.g. what minerals in the films, how 

much of a pH change, etc. 

Page 53 

3rd paragraph. The point about travel times in the distribution system hardly needs to be noted given the 

scale of the Figure. You really couldn’t see a delay of 2 or 3 days in the data in even if it were 

uniformly present. 

Page 54 

Regarding pH in distribution system. It appears that the much larger pH decreases in 2001 and 2002 

correlate with lower alkalinities (I’m not real clear whether this is source water or finished water 

alkalinity), but some discussion is needed of why the many low pH values were found. 

Page 55 

2nd para. 3rd sentence. The sentence isn’t clear. Does the last phrase mean that the solubility minimum 

may be a pH values that are slightly acidic? If the details of the predicted solubility of Pb (IV) are 

given, it may be very clear. 

Page 56 

4th sentence. Schock 2004 isn’t in references. Page 56 

Line 6 change “appeared to be” to “was”. Page 56 

Omit references to blue and yellow lies in Figure 30. Page 56 

Figure 30. I suggest including pH data even for the non-LCR monitoring periods, especially for JulyDec. 2002. The correlation of pH and alkalinity (Figure 32) is important to see. Also, I think it would 

be better it the lead values weren’t connected with a line—just use a nice, big symbol on the data point. 

Page 57 

Figure 31 and Figure 33. These figures show almost nothing. We know that lead was higher postOCCT, but probably because chloramines were used and the pH was too low. We also know that lead 

was lower pre-OCCT, but this is because the change to chloramines hadn’t occurred. The correlations 

show only that there is no correlation. It is misleading even to plot the lines. 

Page 58 

1st paragraph. It is stated that isolated instances of nitrification were found, then it is said that 

nitrification hasn’t been documented. These contradict each other. 

Page 59 

Figure 32. There is a floating piece of text (no data) that needs to be moved. Page 60 

The issue of lead levels in the lead profile results from the mains are as discussed regarding p. 29. Lead 

levels in samples nominally from the main that are consistently above 10 ug/L are pretty important. 

Page 61-62 

Last Paragraph. The comparisons can and should be based on the amounts of lead contributed by the 

three source areas, rather than on this computed concentration 

Page 62 

Galvanic corrosion. The work done by Reiber and Dufresne needs more description of what they did 

experimentally and what they measured. For example the flow direction in the pipes in Figure 34 

should be indicated. 

Page 63 

I recall that Marc Edwards talked about a different galvanic corrosion process, namely the deposition of 

copper and the oxidation of lead, when part of a LSL was replaced with copper tubing. Should this 

mechanism be discussed? 

Grounding currents. Again, explanation of what Reiber and Dufresne did is needed to accept that there 

was no impact on internal corrosion. Some explanation of why this conclusion is opposite the statement 

in the first sentence, namely that currents have been implicated in metal release. 

Page 65 

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Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

Potential Causative Events 

a) 1. Does the study consider potential 

causative events that are appropriate? 

a) 2. Are the causative events and 

factors considered all relevant to the 

purpose of the study? 

a) 3. What additional causative events 

or factors, if any, should be 

considered? 

This is the first occasion where ORP changes are invoked as 

a causative factor. I’d like to raise several points that the 

authors should consider. First, the thermodynamic oxidation 

reduction potential is probably hardly changed at all when 

free chlorine is replaced with chloramines. The EH values 

computed for the pH, ammonia, chloride, and chlorine 

concentrations are almost the same. The “oxidation state” of 

the water really isn’t different. Second, the measured ORP 

reflects the contribution of all redox couples in the water, 

with each having a thermodynamic potential and highly 

variable reaction kinetics at the measuring electrode surface. 

The differences in measured ORP values when chloramines 

are used instead of chlorine reflect the kinetics of reaction of 

chloramine at the surface, more so than a change in the 

oxidation reduction potential. Thus, it seems likely that 

chloramine isn’t reactive enough to influence lead oxidation 

very much. It is just good luck that chloramine also isn’t 

reactive enough to influence the measured ORP very much, 

either. The argument should be restated to avoid the 

implication that the oxidation potential is lower with 

chloramine. 

The evidence seems to clearly indicate that the LSLs 

contained higher lead concentrations after the pH drop and 

switch to chloramination. This leads us to think that PbO2 

reduction must be a source of the lead. We can agree that 

free chlorine can cause PbO2 to form and to keep it stable, but 

what is reducing the PbO2 in the presence of chloramine? 

This is a big hole in the argument about causation. There 

doesn’t seem to be any evidence that pertains to the 

substance that is being oxidized when PbO2 is being 

reduced. 

Data Relevance 

b) 1. Does the study consider each 

causative event adequately? 

No specific comments. See general comments. 

b) 2. Is the data presented all relevant 

to the purpose of the study? 

No specific comments. See general comments. 

Data Analyses and Conclusions 

c) 1. Do the data and analyses support 

the conclusions? 

c) 2. Are there additional analyses that 

could better support the conclusions? 

c) 3. What additional conclusions, if 

any, can be reached based on the data 

and analyses? 

The principal conclusions, that formation of PbO2 was 

formed during use of free chlorine, that the change to 

chloramine and reduction of allowable pH in the distribution 

system, and that lead service lines are the predominant source 

of the lead, are reasonable and plausible. The report also 

does a good job of looking at a range of factors that do not 

seem to have a major role. 

Page 5 of 6 
 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #1 

EPA Question Reviewer Comments Reference 

(Page in 

Document) 

Follow-on Work 

d) 1. Section 6 of the study identifies 

possible follow-on work based on 

available findings and conclusions 

drawn from the study. Which, if any, 

of the recommended follow-on work 

should EPA undertake? 

d) 2. What additional follow-on work 

and/or research should EPA undertake 

as a result of this study? 

I like the idea of using a GIS system to look for correlations 

in the data. However, it may well turn out that there really 

isn’t enough data to see strong relations and, further, that the 

distribution of the LSLs in the system may obscure some 

water quality or treatment correlations that may be important. 

I also agree that more needs to be known about the impact of 

orthophosphate in this complex system and that more 

research is needed to really understand the mechanism of Pb 

(IV) formation and reduction. 

Page 6 of 6 
 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #2 

EPA Question Reviewer Response Reference 

(Page in 

document) 

General Comments 

In terms of “simultaneous compliance” issues, additional discussion should 

be included on the significant emphasis by DCWASA on “solving” TCR 

related problems in the distribution system being a major factor in 

subsequent decisions and events. 

Figure 18. Check the Y-axis title (should it also state 90th percentile in 

addition to average?). 

Figure 18 

Figure 19. The note stating “average (Pb) level before chloramines = 5 

ug/L” is misleading since this only considers data from July 1997 to the 

time of the conversion. The true “average” Pb level “before chloramines” 

(i.e., considering all of the data) I suspect might be greater than 5 ppb. 

Figure 19 

Potential Causative Events 

a) 1. Does the study consider 

potential causative events that 

are appropriate?

 Yes. 

a) 2. Are the causative events 

and factors considered all 

relevant to the purpose of the 

study? 

I would not consider “Lead Released from Piping Systems/Lead Service 

Lines” (Sections 1.3.1 and 5.1) to be a causative factor in and of itself. For 

example, if CCT had been optimized (before or after conversion to 

chloramine), then lead release would not have happened on its own. I 

would consider this a resultant outcome of the other causative 

events/factors but not a contributing factor per se. 

Sections 1.31 

& 5.1 

a) 3. What additional 

causative events or factors, if 

any, should be considered? 

My understanding is that WA made other treatment changes at or around 

the time of chloramine conversion. One such change included the type of 

alum used (from dry alum to liquid alum) and also attempts (over the years) 

to gain better “control” of the aluminum coagulation process. Snoeyink 

(2003) has noted possible protective or detrimental effects of aluminumcontaining scales on Pb release. Another treatment change was WA’s 

implementation of enhanced coagulation practices, which might be 

associated with increased residual aluminum concentrations. 

Page 1 of 3 
 

 

 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #2 

EPA Question Reviewer Response Reference 

(Page in 

document) 

Data Relevance 

b) 1. Does the study consider 

each causative event 

adequately? 

For “Lead Released from Lead Service Lines” (Section 1.3.1) the report 

states “Given that many service lines in the DCWASA distribution system 

are made of lead, this source is a major cause of high lead levels.” Along 

similar lines to the comment in (a) 2. above, the presence of (many or 

some) lead service lines does not cause high lead levels. 

Section 1.3.1 

Table 1 (Summary of Causative Factors for High Lead Levels) – I would 

disagree with the “medium” contribution assigned to this item. Based on 

the data presented in the remainder of the report as well as “conventional” 

Pb (II) theory, the improper corrosion control treatment in place prior to or 

simultaneous with the conversion to chloramine is as “equal” a contributor 

to the high lead levels seen after chloramine conversion. Had CCT been 

optimized (e.g., using an orthophosphate inhibitor), it is unlikely that the 

lead release would have been of the same magnitude. In fact, Section 5.3.2 

states that the OCCT pH may have been “too low of a pH for maintaining 

Pb (II) scales under chloramine conditions.” The OCCT designated in 

February 2000 and subsequent designation of OWQPs, and the OCCT 

designated in May 2002 (retroactive to July 2000) were inappropriate. 

Section 5.3.2 

Distribution System pH Levels and pH Variations (Section 1.3.3 and 

elsewhere) – At a pH of 7.0, 90th percentile Pb levels should not have been 

<15 ppb, in turn, raising a flag that the CCT mechanism wasn’t what it 

appeared to be. Such explanation as to how 90th Percentile Pb levels were 

being maintained below the 15 ppb Action Level despite lower-thanoptimal pH for Pb (II) passivation might have led to awareness that other 

factors needed to be considered related to the chloramine conversion. This 

type of discussion should be included in this section as well as in related 

paragraphs in Section 4 and highlighted as a “reality check” on theoretical 

Section 1.3.3 

models. There is some discussion toward this end in Section 5.2.7 (4th 

paragraph) but this linkage should also be carried into the sections 

discussing (inadequate) pH levels. 

Section 5.2.7 

b) 2. Is the data presented all 

relevant to the purpose of the 

study? 

Chlorine burn data (e.g., Table 8 in Section 5.2.3) – discussion should be 

added as to the likelihood (in theory) that Pb levels are/can be impacted in 

the relatively brief time period of a Cl2 burn. What is the theory to explain 

the kinetics/reaction rates for this? Perhaps this is an item to consider under 

future research needs? Can, in theory, such a change affect Pb levels that 

quickly? (one month) 

Table 8, 

Section 5.2.3 

Data Analyses and Conclusions 

c) 1. Do the data and analyses 

support the conclusions? 

Yes, with the exception of comments noted in (c) 3 below relative to the 

“significance” of the inadequate (too low) pH. 

Figure 19 

Page 2 of 3 
 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #2 

EPA Question Reviewer Response Reference 

(Page in 

document) 

c) 2. Are there additional 

analyses that could better 

support the conclusions? 

Section 4.2.2 – Data for Pb at the “Point-of Entry” (POE) should be 

presented and discussed rather than reliance on sampling from the 

distribution system mains to infer POE levels. In addition, the report 

defines “source water” as raw water from the Potomac River. This is 

confusing with respect to conventional terminology used in the LCR and 

various guidance documents in which a “source water sample” is defined as 

“A sample collected at entry point(s) to the distribution system 

representative of each source of supply after treatment.” 

Section 4.2.2 

Section 5.8 Drought Conditions and Effects on Corrosivity of DCWASA 

Water – One consideration is whether drought conditions may have 

affected the nature of the natural organic matter (NOM) in a manner than 

affected the chlorine demand of the finished water, in turn affecting ORP, 

etc. 

Section 5.8 

c) 3. What additional 

conclusions, if any, can be 

reached based on the data and 

analyses? 

As noted in Comment (b) 1, I disagree with the “medium” contribution 

assigned to the “distribution system pH levels and pH variations” factor as 

presented in the Table 1 (Summary of Causative Factors for High Lead 

Levels). Based on the data presented in the remainder of the report as well 

as “conventional” Pb (II) theory, the improper corrosion control treatment in 

place prior to or simultaneous with the conversion to chloramine is as 

“equal” a contributor to the high lead levels seen after chloramine 

conversion. 

Table 1 

Follow-on Work 

d) 1. Section 6 of the study 

identifies possible follow-on 

work based on available 

findings and conclusions 

drawn from the study. 

Which, if any, of the 

recommended follow-on 

work should EPA undertake? 

Pb (IV) as a corrosion control treatment mechanism needs much greater 

understanding and research, including under what conditions/factors does 

Pb (IV) form, remain stable, etc. The effects of orthophosphate addition 

under various ORP conditions are also important to understand (e.g., for 

various system changes, can orthophosphate bind soluble lead to keep up 

with the rate of Pb release from existing scales that may break down). 

d) 2. What additional followon work and/or research 

should EPA undertake as a 

result of this study? 

Fundamental research in Pb (IV) is needed. Some examples include: 

defining threshold ORP levels to maintain protective scales; determining 

the feasibility of converting Pb (IV) scales to some possible new Pb 

orthophosphate compounds; etc. 

As noted above, the impact of chlorine burn on Pb solubility (and reaction 

kinetics thereof in short periods of time in which such switches generally 

take place) would also be of significant interest to utilities. 

Page 3 of 3 
 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #3 

EPA Question Reviewer Comment/Response Reference 

(Page in 

document) 

General Comments 

Given the prevalence and importance of chloramination for many water 

utilities, it is important that the casual reader does not directly link 

chloramination with lead problems. While the Washington, DC lead 

problems are an important “lesson learned”, the Executive Summary and 

Report should emphasis that the problem resulted from a “perfect storm” 

(historical high chlorine dosage, presence of lead scales and lead service 

lines, poor pH control, and chloramination). One or two of these 

occurrences, in isolation, may not have resulted in the problem. The data 

and conclusions presented in Section 5.2.6 should be emphasized and be 

presented in the format that can be easily understood by the typically water 

utility professional. 

Section 5.2.6 

I also have a concern with how the sources of lead were characterized 

between the faucet, in-house plumbing, lead service line and distribution 

system (example p.29 and 30). While the text states that the lead service 

lines were the primary source of lead and no or limited lead should be 

present in the distribution system (water mains prior to meter and service 

line), several of the figures do not support this conclusion. The engaged 

reader should understand that the “distribution samples” are pulled through 

the lead service lines and in-house plumbing, and are not indicative of 

distribution system water quality. However, the casual reader might draw 

the wrong conclusion. Therefore, I would consider either removing the 

data from the graphs or footnoting why there was a presence of lead in the 

distribution system samples. Question - Was any direct sampling/lead 

analysis done from the distribution system during the study period? Also, 

was only lead sampling done at locations without lead service lines? 

Page 29 & 30 

Additionally, the author frequently reference that the lead service lines are 

part of the distribution system (p.72 and other references). Most utilities do 

not consider service lines part of the distribution system. 

Page 72 

Potential Causative Events 

a) 1. Does the study consider 

potential causative events that 

are appropriate?

 Yes. The study considers all of the classic causative events for lead 

corrosion (pH, redox, temperature, etc) and adequately explains how these 

events interact to cause the lead problems. However, given the variability 

in pH, conductivity, temperature, total chlorine, etc., the reader is not 

convinced that the original Optimal Corrosion Control Treatment (OCCT) 

guidelines were correct. This issue is important because the study does not 

establish that lead control was effective prior to the chloramine conversion. 

In addition to the change in pH levels, the variability in other OCCT 

parameters and lead sampling results suggest that lead control was 

questionable even prior to the chloramine conversion. As shown in Figure 

17, the set of the three data points (red triangles) with lead levels ranging 

between 100 and 150 μg/L, on or before the conversion to chloramines, 

indicate that lead control was already questionable prior to chloramine 

conversion. 

Page 1 of 5 
 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #3 

EPA Question Reviewer Comment/Response Reference 

(Page in 

document) 

a) 1. continued Also, the process for setting the current OCCT has not been described 

(page 71) and it is not clear that the new parameters (when orthophosphate 

is applied) are appropriate. Given the large variability seen in the water 

quality parameters (page 13) it is not clear how the pH 7.7±0.3 is 

appropriate or will be consistently achieved. 

Page 71 

Page 13 

a) 2. Are the causative events 

and factors considered all 

relevant to the purpose of the 

study? 

In general, yes. However, the potential causative effects parameters such 

as conductivity and temperature need to have their role better described in 

the report. For example, are these parameters important because they are 

used in the calculation of corrosion indexes or impact lead solubility? 

a) 3. What additional 

causative events or factors, if 

any, should be considered? 

The study needs to de-emphasize individual causative factors and focus 

more on the chain of events. A chart with a timeline dating back to 1990 

would be useful to help understand the entire situation. Included in the 

chart/timeline should be a description of key decisions, 90th percentile 

lead levels, shifts in pH and chlorine, coliform events, and DBP values. 

There is a need to place more emphasis on the fact that corrosion control 

was an issue prior to the chloramine conversion and question whether the 

OCCT/OWQP was appropriate. In the Appendix (pA-20) is a timeline of 

the OCCT decisions. A better summary of the reasoning behind the 

decisions would be helpful. 

Page A-20 

The decision to drop the allowable distribution system pH from 7.7 to 7.0 

is not emphasized strongly enough as a causative factor. Running a 

system at pH 7.0 with no phosphate and lead service lines is a poor 

operating decision. Change in pH occurred in July 1, 2000. Conversion to 

chloramines occurred November 2000. Average 1st draw lead samples 

increased between December 1999 and November 2000. Second- draw 

samples were greater than 15ppb in the July – September monitoring 

period. It is unlikely that the change to chloramines could have 

solubilized the lead (IV) so quickly. It may not be possible to ascertain 

whether the change in pH directly resulted in lead release or if it affected 

existing scales to allow the chloramine to solubilize the lead (IV). 

Additionally, it is possible that drought conditions increased the levels of 

sulfate and/or chlorine in the water. The lack of these data does not 

exclude the role of the drought on lead corrosion. Potentially, chloride 

and sulfate information from other nearby utilities (Fairfax) could be used 

in this assessment. 

Page 2 of 5 
 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #3 

EPA Question Reviewer Comment/Response Reference 

(Page in 

document) 

Data Relevance 

b) 1. Does the study consider 

each causative event 

adequately? 

In general, yes. However, as previously stated, more focus needs to be on 

the pre-existing conditions prior to chloramination. Specifically more 

emphasis needs to be placed on pH. For example, I believe that the 

“Distribution system pH levels and pH variations” listed in Table 1 should 

have a “High” rating for its “Relative Contribution to High Lead Levels’ 

especially since p.53 states, “varying ph levels can significantly affect the 

formation of protective scales on the interior of the pipes and the capability 

of the system to maintain those scales in a stable form”. 

Table 1 & 

Page 53 

Washington, DC had a unique combination of factors contributing to their 

lead problems. USEPA allowed Washington, DC more flexibility in their 

treatment during the 1990s than would be allowed by most States. 

Appendix A summarizes the feasibility studies performed in 1998 to 

analyze various post treatments schemes. While I believe it would be 

difficult to include a statement in the Report, it would be interesting to 

know whether it was an economic decision that led to the poor pH control 

and lead corrosion prior to chloramination. 

Appendix A 

In the section on the sanitary surveys (p20) the last line states “it is unlikely 

that findings from these sanitary surveys had any influence on tap lead 

levels”. However, only results from sanitary surveys from 1999 onward are 

presented. A big question is – did earlier deficiencies lead to the coliform 

issues which in turn led to the decision to go to higher chlorine levels? I 

agree that it is unlikely that it was the prime causative event, but it may 

have resulted in a cascade of events. 

Page 20 

b) 2. Is the data presented all 

relevant to the purpose of the 

study? 

Yes. However, I would spend less time focusing on the “chlorine burn” 

issue. See response to question c) 1. 

See Q. c) 1. 

Data Analyses and Conclusions 

c) 1. Do the data and analyses In general, yes. However, I have issues with the entire analyses associated Figure 19 

support the conclusions? with the “chlorine burn”. For example, the data in Figure 19 shows 

considerable variability in monthly lead levels. Although the two dates 

when the “chlorine burn” occurs show dips in average lead levels, there are 

other examples of low average lead levels when chloramines were used 

(Feb 03, Jan 04, Jul 04). This variability in lead levels makes it impossible 

to conclude that the conversion back to chlorine had any statistically 

significant reduction in lead. The dips in lead levels during the chlorine 

burn are not distinguishable from the normal variability in lead levels. 

Page 3 of 5 
 

 

 

 

 

 

 

 

 

 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #3 

EPA Question Reviewer Comment/Response Reference 

(Page in 

document) 

c) 1. continued On page 39, paragraph 4, there is no statistical analysis to suggest that 8 of 

12 sites with elevated lead levels were different from 5 of 12 sites. On 

page 40, the report suggests that a monthly average of 28 μg/L is different 

from 17 μg/L which is different from 37 μg/L. However, the statistical 

analysis provided does not support this statement. Application of a t-test 

for these data is inaccurate since these are not paired data. A 

nonparametric test (Wilcoxon) would be more appropriate. Given the 

highly variable results for lead, it is not clear that these differences are 

meaningful. If the data from the 4th High Pressure Zone was removed 

(orthophosphate treatment) would the data have been more conclusive? 

Page 39 & 40 

As shown in Figure 21, if analytical inconsistencies could account for a 

difference between 1 and 6 μg/L of lead, then how can the report conclude 

that small variations between the “chlorine burn” and “chloramine” lead 

data be significant. Again, interpretation of the data has been performed 

using only “eyeball” statistics. 

Figure 21 

Finally, the term “chlorine burn” is poor and misleading. 

c) 2. Are there additional 

analyses that could better 

support the conclusions? 

The author might consider calculating various corrosion indexes under 

variable water quality conditions in assessing the corrosion potential before 

and after chloramine conversion. 

c) 3. What additional 

conclusions, if any, can be 

reached based on the data and 

analyses? 

I believe the author reached many proper conclusions during his analysis of 

the data. However, the Washington, DC lead occurrences must be put in 

the proper prospective. The conclusions need to emphasize the pre-existing 

conditions in the Washington, DC system prior to chloramination and the 

other numerous factors that contributed to the lead problems post 

chloramination. The author needs to continually emphasize that other 

water utilities need to fully understand the combination of factors in the 

Washington, DC system before relating this experience to the operation of 

their system. 

Follow-on Work 

d) 1. Section 6 of the study I believe the proposed DCWASA-related follow on evaluation would have 

identifies possible follow-on limited value. It is general knowledge that lead service lines are a (the) 

work based on available primary source of lead in drinking water. I am not convinced that the 

findings and conclusions proposed geographic information system work (GIS) to plot the sampling 

drawn from the study. data and other water quality characteristics in the distribution system 

Which, if any, of the between before and after the LCR monitoring period will provide valuable 

recommended follow-on information. Given the variability in the water quality throughout the 

work should EPA undertake? distribution system and the variability of lead levels at individual sampling 

locations, I am not convinced that any additional good correlation will be 

derived. Also, if this study is performed, I am not also convinced that a 

sophisticated GIS system is needed to complete the study. 

Page 4 of 5 
 

 

Peer Review of “Elevated Lead in D.C. Drinking Water – A Study of Potential Causative 

Events” 

REVIEWER COMMENTS 

Reviewer #3 

EPA Question Reviewer Comment/Response Reference 

(Page in 

document) 

d) 2. What additional followon work and/or research 

should EPA undertake as a 

result of this study? 

There are several areas of follow-up work/research that might be valuable: 

• Additional research can be performed to define ORP conditions 

under different chlorine and chloramination conditions/residuals. 

For example, would lower free chlorine residuals in the 

Washington, DC system reduce the Pb (IV) formation and the 

problems with chloramine conversion? 

• Additional knowledge is needed on the impact the treatment 

changes on scale formation and solubility of trivalent lead? 

• Utilities should develop a better understanding of the impact of lead 

service lines replacement (especially partially replacement) on 

compliance and lead levels. Specifically, is there any value in doing 

partial lead service line replacement or would this action have a 

tendency to negatively impact on compliance? 

• Research could be performed to determine the impact of meter life 

on lead concentrations in drinking water. 

• Given the presence of particulate lead in the Washington, DC 

samples and the relatively small health effects associated with 

particular lead, the overall importance of particular lead in the 

regulatory compliance strategy should be investigated and possibly 

reconsidered. 

Page 5 of 5