corrosion control study pipe loop study report …

CORROSION CONTROL STUDY

PIPE LOOP STUDY

REPORT SUPPLEMENT FOR THE

EXPANDED EXECUTIVE SUMMARY

PREPARED FOR:

CITY OF FLINT

By

Cornwell Engineering Group, Inc

as a subcontractor to

Arcadis

Cornwell Engineering Group

712 Gum Rock Court

Newport News, VA 23606

(757) 873-1534

January 18, 2021

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TABLE OF CONTENTS

Table of Figures ............................................................................................................................. iii

List of Tables ................................................................................................................................. iv

Introduction ..........................................................................................................................1

Current Conditions ...............................................................................................................1

WTP and Distribution System Water Quality .........................................................1

Lead in the Distribution System: LCR and Residential Sampling Data ................12

Pipe Loop Study Methods and Materials ...........................................................................17

Set Up and Equipment ...........................................................................................17

Daily Operations ....................................................................................................21

Sampling procedures and Analytical methods .......................................................24

Coupon Study Methods and Materials ...................................................................26

Study Operational Adjustments and Events ..........................................................26

Pipe Loop Water Quality ...................................................................................................30

Lead Service Line Rigs Water Quality ..................................................................30

Galvanized Pipe and Brass Fixture Loops .............................................................36

References ..........................................................................................................................40

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TABLE OF FIGURES

Figure 1 Weekly median pH at CSII and Tap (1/1/2016 – 6/30/2020) ................................. 4

Figure 2 WTP Tap pH Control Chart (1/1/2016 – 6/30/2020) .............................................. 4

Figure 3 pH percentile of all distribution system sites, excluding CSII (1/1/2016 –

5/22/2020) ............................................................................................................... 5

Figure 4 pH in the distribution system by WQP monitoring site (12/13/2017 -

5/22/2020) ............................................................................................................... 6

Figure 5 Orthophosphate residual at CSII and Tap (1/1/2016 – 6/30/2019) ......................... 7

Figure 6 Orthophosphate residual at CSII and Tap Control Chart (1/1/2016 –

6/30/2019) ............................................................................................................... 7

Figure 7 Orthophosphate residual in the distribution system by WQP monitoring

site (12/13/2017 - 5/22/2020).................................................................................. 8

Figure 8 Tap Alkalinity and DIC (1/1/2016 - 6/30/2020) ..................................................... 9

Figure 9 DIC in the distribution system (12/13/2017 - 5/22/2020) ..................................... 10

Figure 10 Free chlorine residual at CSII and Tap (1/1/2016 - 6/30/2020) ............................ 11

Figure 11 Free chlorine residual in the distribution system (12/13/2017 - 6/30/2020) ......... 12

Figure 12 Percent of lead measurements by compliance period ........................................... 14

Figure 13 Percentile distribution of 1st and 5th L samples in both 2019 compliance

periods ................................................................................................................... 15

Figure 14 Percent of lead measurements of 1st and 5th L samples for both 2019

compliance periods ............................................................................................... 16

Figure 15 Percentile distribution of lead by sample period and volume ............................... 17

Figure 16 Example LSL Rig (left) and Galvanized/Fixture Rig (right) ................................ 19

Figure 17 Early Operational Changes and Total Lead, using D1 and D2 as an

Example. ............................................................................................................... 29

Figure 18 Flowrate and Key Operational Adjustments on Total Lead using D1 and

D2 as an Example. ................................................................................................ 29

Figure 19 Measured temperature for flowing samples from the LSL rigs (5/9/2019 –

8/21/20) ................................................................................................................. 31

Figure 20 Measured free chlorine for flowing samples from the LSL rigs (5/9/2018 –

8/21/2020) ............................................................................................................. 32

Figure 21 pH box-plot for LSL rig flowing samples during 1.2gpm-Dose1 ........................ 33

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Figure 24 Orthophosphate box-plot for LSL rig flowing samples during 1.2gpm-

Dose1 .................................................................................................................... 35


Dose1 .................................................................................................................... 35


Dose2 .................................................................................................................... 36

Figure 27 Measured temperature for flowing samples from the galvanized and

fixture rigs ............................................................................................................. 37

Figure 28 Measured free chlorine for flowing samples from the galvanized and

fixture rigs ............................................................................................................. 37

Figure 29 Flowing sample pH from the galvanized and fixture rigs ..................................... 38

Figure 30 Flowing sample orthophosphate from the galvanized and fixture rigs ................. 39

LIST OF TABLES

Table 1 Changes to target WQPs on December 13, 2017 .................................................... 1

Table 2 Treatment chemicals used at Flint WTP ................................................................. 2

Table 3 Median CSII, Tap, and Distribution System WQPs ............................................... 2

Table 4 Historical 90th percentile lead and copper for LCR compliance .......................... 14

Table 5 Pipe Rig Study Test Material Information ............................................................ 20

Table 6 Timer-Operated Flow Schedule ............................................................................ 21

Table 7 Weekly Operator Schedule ................................................................................... 22

Table 8 Flow-Dose Analysis Periods for LSL Rigs by Operational Characteristics ......... 31

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INTRODUCTION

This document serves as a supplement to the Pipe Loop Study Expanded Executive Summary. The

Expanded Executive Summary included a brief discussion of pipe loop study operations and

included loop study lead data, statistical analyses, and final optimal corrosion control treatment

(OCCT) recommendations for the City of Flint, MI.

This supplement provides further information regarding the loop study methods and materials,

current conditions in the distribution system, and discussion relating loop study data to current

distribution system conditions.

CURRENT CONDITIONS

The recommendations from the pipe loop study include maintaining the current target

orthophosphate residual at 3.5 mg/L PO4 until it is determined that all lead service lines (LSLs)

have been removed from the distribution system. This recommendation was based on the pipe loop

results, as well as LCR sampling data that showed that lead levels have decreased over time and

are currently relatively low: the second-half of 2019 compliance period had a 90th percentile of 4

µg/L. Flint is also rapidly replacing their lead service lines.

This section therefore provides a detailed analysis of current distribution system water quality

parameter (WQP) conditions, which are important to assess in relation to lead sampling data to

ensure Flint is maintaining stable distribution system conditions conducive to effective CCT

moving forward.

WTP and Distribution System Water Quality

Data from Flint WTP monthly operating reports were available from 2016 through June 2020 and

WQP monitoring data were available from late 2015 through mid-May 2020. For most analyses,

data were used after the official interim changes in target treatment on December 13, 2017 for

monitoring at the entry point and the Enhanced Water Quality Monitoring (EDWM) sites in place

in the distribution system (MDEQ 2017). Changes to target WQPs are shown in Table 1. No new

interim targets were set in the distribution system. This time period was determined to be the most

representative of current operating conditions at the Flint WTP and throughout the distribution

system, which is important when drawing conclusions from pilot data in the context of full-scale

impacts.

Table 1 Changes to target WQPs on December 13, 2017

Parameter Unit EP Target EP Range EDWM

Target

EDWM

Range

pH s.u. 7.5 7.2 – 7.9 7.5 7.2 – 7.9

Orthophosphate Residual mg/L as PO4 3.6 3.3 – 4.0 3.3 3.1 – 4.5

Free Chlorine Residual mg/L 1.5 – 1.8 1.4 – 1.9 -- --

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Daily data from monthly operating reports (MORs) and weekly Enhanced Water Quality

Parameter Monitoring (EWDM) reports were utilized to assess Great Lakes Water Authority

(GLWA) influent water as measured at Control Station 2 (CSII), adjusted water quality as

measured at the plant tap, and distribution system water quality. The MORs also contained the

distribution system TCR free chlorine data used in this analysis. All location-specific WQP data,

excluding free chlorine measurements, were obtained from the available weekly EWDM reports.

Currently the Flint WTP adds chemicals for additional treatment to boost pH (when necessary),

free chlorine residual, and orthophosphate residual of purchased GLWA water. The chemicals

used and the dose median and ranges are shown in Table 2. Typical WQPs, as measured at CSII,

tap, and throughout the distribution system are shown in Table 3.

Table 2 Treatment chemicals used at Flint WTP

Chemical Purpose Unit Dose Median Dose Range

Orthophosphate*

(Phosphoric Acid) Corrosion Inhibitor mg/L as PO4 2.4 0.7 – 2.8

Sodium Hypochlorite Disinfection mg/L as Cl2 1.1 0.7 – 1.7

25% Caustic Soda pH adjustment mg/L 4.0 0.8 – 7.4

*Note: This is dose not orthophosphate residual. GLWA water entering the plant already has

orthophosphate residual around 1.2 mg/L as PO4

Table 3 Median CSII, Tap, and Distribution System WQPs

Measured Parameters Unit

CSII

(pre-

Adjust)

Tap Distribution

System

pH s.u. 7.3 7.6 7.6

Alkalinity mg/L as CaCO3 80 84 84

Total Hardness mg/L as CaCO3 102 102 102

Non-Carbonate Hardness mg/L as CaCO3 32 34 --

Calcium mg/L 28 28 28

Magnesium mg/L 7.8 8.0 --

Chloride mg/L 15 15 15

Sulfate mg/L 16 -- 17

Orthophosphate mg/L as PO4 1.3 3.6 3.5

Free Chlorine Residual mg/L 1.0 1.7 1.5

Calculated Parameters

Dissolved Inorganic Carbon (DIC) mg/L as C 21.2 21.1 21.1

CSMR mg/mg 0.93 -- 0.88

Parameters in Table 3 were analyzed due to their importance in CCT. Trending and analysis of

individual parameters will be discussed throughout this section.

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For some parameters, control charts were developed as a way to characterize the consistency or

variability of the measurements and concentrations over a certain time period. Control charts

presented are Shewhart median control charts as described in Cornwell et al. (2015) and Grant

(1964). Control charts calculations involve grouping data and then identifying the median and

range of each group to characterize the data over a specific time period. The overall median of

these group medians plotted as a constant value over the given time period. Upper and lower

control limits (UCL and LCL, respectively) are based on this median and the overall median of

group ranges (i.e., median variability within the groups). The group medians are plotted as

individual data points. If group medians typically fall within the UCL and LCL, that indicates less

variability in the data. MOR data in these control charts were grouped weekly.

pH

Figure 1 presents weekly median pH measurements for CSII and the plant tap. Influent CSII

GLWA weekly median pH from 2016 to mid-2020 typically varied from about 7.2 to 7.5 with few

exceptions. CSII weekly median pH exhibited noticeable variability over the time period analyzed,

but the overall distribution of measurements did not appear to change dramatically over time. In

early 2017, the target pH leaving the tap was raised to 7.5. MORs showed the addition of 25%

caustic soda beginning in February 2017. Figure 1 shows the median pH coming from the tap

increased closer to a target pH of 7.5 mid-2017. Figure 2 is a control chart of the pH data at the

Flint WTP tap after pH adjustment, analyzed in two different time periods, before and after the

increase in pH set in December 2017 (Table 1). Figure 2 shows periods of time where median tap

pH falls outside of the UCL and LCL, which indicates room for improvement in pH consistency

leaving the plant.

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Figure 1 Weekly median pH at CSII and Tap (1/1/2016 – 6/30/2020)

Figure 2 WTP Tap pH Control Chart (1/1/2016 – 6/30/2020)

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The pH in the distribution system increased as well once the Flint WTP began dosing caustic.

Figure 3 shows a percentile distribution by year for all of the distribution system WQP monitoring

sites in the EWDM reports, excluding CSII. This figure shows a general increase in pH distribution

after 2017. It also shows that 2018-2020 distributions of pH measurements were similar and

relatively consistent. The 10th percentile to 90th percentile range was 7.39 to 7.72 in 2019 and 7.42

to 7.64 for 2020 (through 5/22/2020).

Figure 4 is a modified box plot of pH values at each distribution system site from 12/13/2017

through 5/22/2020 (after the target WQP changes outlined in Table 1). The median pH of all of

these sites during this time period at each site ranges from 7.53-7.65. Figure 4 shows little

variability in the middle fifty percent of distribution system pH data, with the difference between

the seventy-fifth and twenty-fifth percentiles of each site being less than 0.2. Figure 4 also shows

that the pH in the distribution system is overall well maintained within the target range of 7.2 –

7.9. The minimum pH at sites #14 (1) and #4 were both <7.2. These were singular values for both

sites and the next lowest value for sites #14 (1) and #4 during this time period was 7.27 and 7.20,

respectively.

Figure 3 pH percentile of all distribution system sites, excluding CSII (1/1/2016 – 5/22/2020)

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Figure 4 pH in the distribution system by WQP monitoring site (12/13/2017 - 5/22/2020)

Orthophosphate

Orthophosphate residual, already present in the water purchased from GLWA, is boosted at the

Flint WTP and acts as a corrosion inhibitor in the distribution system. The orthophosphate residual

in finished GLWA water entering the WTP is about 1.2 mg/L as PO4. When the water reaches the

Flint WTP, phosphoric acid is added in order to increase orthophosphate residual to a target

residual of 3.6 mg/L PO4 (Table 1). The current target range requires the orthophosphate at the

entry point to be maintained within 3.2 mg/L PO4 to 4.5 mg/L PO4. Figure 5 and Figure 7 show

that orthophosphate residual leaving the WTP and in the distribution system has been well

maintained.

Figure 5 displays measured phosphate residual data from CSII and at the tap over time, which

visually appears to be relatively stable for both locations. Similar to orthophosphate at the tap, the

distribution system does not have much variation in the measured values at each WQP monitoring

site. Figure 6 is a control chart of the same data and shows that the orthophosphate residual at the

tap is well controlled. The bounds of the UCL and the LCL are relatively close to the median of

group medians, signifying low variability in weekly measurements. Additionally, the low number

of values outside these limits show that measurements are consistent and well controlled near the

overall median of group medians. Keeping the orthophosphate controlled as shown is essential to

maintaining the water chemistry entering the distribution system.

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Figure 5 Orthophosphate residual at CSII and Tap (1/1/2016 – 6/30/2019)

Figure 6 Orthophosphate residual at CSII and Tap Control Chart (1/1/2016 – 6/30/2019)

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Figure 7 is a modified box plot of orthophosphate measurements in the distribution system. This

figure shows that orthophosphate residual was well maintained in the distribution system, with no

values below 3.0 mg/L PO4 at any of the WQP sites. The median orthophosphate concentration

was typically close to 3.5 mg/L PO4, and each site has relatively consistent measurements: the

middle fifty percent of data, also known as the interquartile range (IQR), is contained within a

small range for each site.

Figure 7 Orthophosphate residual in the distribution system by WQP monitoring site

(12/13/2017 - 5/22/2020)

Alkalinity and Dissolved Inorganic Carbon

Dissolved inorganic carbon (DIC) was calculated for paired pH and alkalinity data from 2016 to

mid-2020 for CSII, tap, and distribution system WQP sites. Alkalinity and DIC from the tap are

shown in Figure 8. DIC and alkalinity data show similar trends over the time period analyzed. DIC

ranged from 18 to 19 mg/L as C, until around July 2017 when alkalinity and DIC both increased

and became more variable. Both parameters appear to have become more stable mid-2018, as

shown in Figure 8. After December 13, 2017, when target WQPs were changed, the alkalinity

ranged from 66 – 100 mg/L as CaCO3 and DIC ranged from 17 – 26 mg/L as C. DIC is a function

of both pH and alkalinity, so changes in pH have some effect on the calculated value.

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Figure 8 Tap Alkalinity and DIC (1/1/2016 - 6/30/2020)

DIC in the distribution system appears stable with a median at all WQP sites around 21 mg/L as

C, as shown in Figure 9. Data included in Figure 9 spans the same time period of about two and a

half years as shown previously in Figure 7.

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Figure 9 DIC in the distribution system (12/13/2017 - 5/22/2020)

Free Chlorine and Scale Analysis

Maintaining proper free chlorine residual is important for controlling bacteria and other

microbiological organisms that may be present in drinking water. GLWA water entering the water

treatment plant, measured at CSII, typically has a free chlorine residual within the range of 0.8 to

1.0 mg/L, shown in Figure 10. Beginning in June 2016, sodium hypochlorite has been added at the

Flint water plant to boost the free chlorine residual leaving the plant. Currently, the chlorine

residual is boosted to a target concentration of about 1.5 to 1.8 mg/L (Table 1). Maintenance of

free chlorine residual in the distribution system, in addition to disinfection, is important for

ensuring pipe scales are stable if crystalline oxidized lead compounds are found in pipe scales

(lead (IV)).

Free chlorine affects the oxidation and reduction potential (ORP) of the water, which has the

potential to impact pipe scales in the distribution system (Schock & Lytle 2011). A decrease in

ORP could lead to solids that are stable with higher ORP to transition into more soluble lead (II)

compounds (Lytle & Schock 2005). Pipe scale analyses on harvested Flint pipes completed by

Williams et al. (2018) showed crystalline layers near the pipe wall contained some oxidized lead

(IV), plattnerite (PbO2). Williams et al. (2018) mentions that this layer closest to the pipe wall was

mostly lead (II) compounds “cerussite (PbCO3) and lead phosphate” and contained “hydrocerussite

(Pb3(CO3)2(OH)2)” as well as the more soluble lead (II) oxide “litharge (PbO)”. Additionally,

Cornwell conducted scale analysis for two LSLs in late-2017 (Cornwell Engineering Group 2018).

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Pipes were cleaned, sent to the University of Florida (UF), and scale layers were extracted by

visual and textural differences with assistance from Cornwell staff. One of the pipes, indicated in

Cornwell Engineering Group (2018) as F-Pb-2300, was the same pipe used in the study indicated

as A1 as shown in Table 5. Amorphous aluminum and magnesium were found, as well as

crystalline lead (IV) (plattnerite) in both pipes and lead (II) (hydrocerussite) in only F-Pb-2300

(A1). The presence of plattnerite in both analyses suggests maintaining free chlorine residual, and

therefore ORP, could be influential on the stability of some LSL scales when lead pipes persist in

the Flint distribution system.

Figure 10 shows that the free chlorine concentration leaving the WTP is typically within 1.6 to 1.8

mg/L.

Figure 10 Free chlorine residual at CSII and Tap (1/1/2016 - 6/30/2020)

Figure 11 displays a modified box plot of free chlorine residual measurements in the distribution

system at the Total Coliform Rule (TCR) monitoring sites from December 2017 through June

2020, sorted by descending median free chlorine residual which ranges from 1.1 to 1.8 mg/L. All

of the sites during this time period had a median free chlorine residual above 1.0 mg/L, though site

19 had minimum values below 0.2 mg/L.

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Figure 11 Free chlorine residual in the distribution system (12/13/2017 - 6/30/2020)

Lead in the Distribution System: LCR and Residential Sampling Data

Flint is currently monitoring for lead and copper rule (LCR) compliance on a semi-annual basis.

In addition to sampling for compliance, the City collects supplemental lead data from residential

homes in order to further monitor the concentration of lead in the distribution system. The

compliance samples are the only ones that are used for determining potential action level

exceedance, but additional sampling and sampling methods are also helpful to provide more

insight to the distribution system. One of the additional sets of data collected is in the Flint’s

Residential sampling database. This data includes 250 mL, 750, and 1 L samples from different

residences in the City.

To supplement data obtained from the pipe loop studies, lead data from the distribution system

were used to compare to data from the pilot study. This analysis is shown in the accompanying

Expanded Executive Summary document. The 5th L compliance samples were used to make

comparisons with current system data to values obtained from the harvested lead service line pipe

loop study. Residential data (250- and 750-mL samples from the tap in the Flint distribution

system) were used to make comparisons to pipe loop data from the galvanized and brass fixture

loops.

For both the samples analyzed for loop studies by Cornwell, compliance, and the residential lead

data analyzed by Flint, the reporting limit for lead was 1 µg/L. Cornwell used the reporting limit

of 1 µg/L for measured values below the reporting limit, while EGLE uses 0 µg/L for analysis on

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values below the reporting limit. In order to stay consistent with values used by EGLE, data listed

as 0 µg/L was kept at 0 and not changed to match Cornwell’s procedures for data analysis.

LCR Data

In 2018, revisions were made to Michigan’s lead and copper rule. These new revisions require a

second sample to be taken at homes with a lead service line in addition to the first liter draw (EGLE

2018). The second sample, at liter five from the tap, is intended to capture water that is more

representative of the service line. The highest lead and copper results from the two samples are

then used for compliance calculations of the 90th percentile. The 2018 Michigan LCR sampling

revisions were implemented beginning in the first compliance period of 2019. Additional

revisions, including lowering of the lead action level from 15 to 12 µg/L, will go into effect in

January 1, 2025 (EGLE 2018).

Flint has received two follow up or routine lead and copper tap monitoring and reporting violations

(SDWIS Violation Code 52). These violations occurred in the compliance periods beginning on

July 1, 2019 and January 1, 2020. These violations were issued when Flint failed to provide the

minimum number of samples required for compliance (60 samples). According to EGLE,

compliance is determined using only Tier 1 samples. Because the service line material is unknown

at the time samples are being collected, the City confirmed the service line materials after all of

the samples were collected. Revisions in the 2018 Michigan LCR also included changes in the

“tiering” for sampling sites. These revisions removed “copper with lead solder” from Tier 1 sites

and changed the designation to Tier 3 sites beginning in the 2019 compliance period. Therefore, if

only Tier 1 sites are used in compliance calculations, homes without lead pipes as service line

material or household plumbing are currently excluded from compliance sampling and results

(even if lead solder is present). Because Flint has been replacing Tier 1 sites at such a rapid rate,

EGLE has allowed Tier 2 sites to be used for compliance as well. Once all of the lead service lines

have been replaced, the Flint will move to the Tier 3 or “Other” category for compliance.

Flint switched back to GLWA water in mid-October 2015 and began adding orthophosphate in

early December 2015. Table 4 shows that for the compliance period immediately following the

switch back to GLWA and the addition of corrosion inhibitor (2016 January-June), Flint still had

a 90th percentile above the action level at 20 µg/L. After this compliance period, the 90th percentile

for lead has been below the current action level of 15 µg/L. Copper has been historically well

below the action level of 1300 µg/L in each compliance period, as shown in Table 4.

Data that was analyzed for compliance in the 2019 July-December period was only comprised of

49 samples. 123 total samples were taken during the sampling period, but only 49 of these were

Tier 1 sites.

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Table 4 Historical 90th percentile lead and copper for LCR compliance

Compliance Period 90th Percentile Lead (µg/L) 90th Percentile Copper (µg/L)

2016 January-June 20 170

2016 July-December 12 120







Figure 12 shows that the percentage of lead samples in each compliance period that are below

detect has also increased since 2016. This visually shows lower lead values are more frequent than

they were in earlier sampling periods.

Figure 12 Percent of lead measurements by compliance period

The changes to the LCR implemented in the 2019 compliance period also updated the sampling

procedure to require the collection of a 1st and 5th L sample instead of just 1st L at each location.

The maximum lead value between these two samples at each LCR sample location is used for

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compliance (EGLE 2018). Comparison of the percentile distribution of lead concentration between

the 1st and 5th L samples shown in Figure 13 show that the values between the two are similar, but

the 1st L is slightly higher. The 1st L sample is more representative of sources from household

plumbing while the 5th L is more representative of concentrations in the service lines. The

distributions look similar in both compliance periods. Figure 14 shows the same data but is

presented as the percentage of lead concentration in six different bins.

Figure 13 Percentile distribution of 1st and 5th L samples in both 2019 compliance periods

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Figure 14 Percent of lead measurements of 1st and 5th L samples for both 2019 compliance

periods

Residential Sampling Data

Sequential sampling can be used to help identify the location of the lead source in the household

plumbing. Residential sampling involved sampling the first 250 mL and then immediately

sampling the next 750 mL as a separate sample. These two samples can indicate where the lead is

present within the first 1 L that comes from the customer’s tap. Residential data sampling was

initiated as supplemental to compliance data to help monitor lead and copper in customer homes.

Data analyzed in this section were from June 5, 2017 through August 20, 2020. The time periods

analyzed were separated into two 6-month periods per year, January through June and July through

December. These sample periods are similar to the compliance LCR periods but residential

samples in this data set were not used for compliance. Data were used up to the 2020 January

through June sampling period.

Figure 15 shows the percentile distribution of the 250- and 750-mL samples for the earliest set of

data available (2016 January-June) to the first half of 2020 (2020 January-June). Figure 15

supports observation of an overall reduction in lead observed from 2016 to 2020 in the previous

two figures. These percentile distributions show the 250 mL sample distributions in both years

may have slightly higher lead values overall. However, this difference in lead concentration

between the two sample volumes within the same sampling does not appear to be substantial.

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Figure 15 Percentile distribution of lead by sample period and volume

PIPE LOOP STUDY METHODS AND MATERIALS

Set Up and Equipment

Water Sources

Water utilized during the equilibration of test materials was Flint WTP finished water, accessed

via hose bibs near the rigs. During the study period, test materials flowed with GLWA water routed

from Control Station #2 (CSII), with varying orthophosphate doses as test conditions dictated. This

water needed to be routed outside for a portion of the distance from CSII to the pipe rig study

location inside the plant. Water pressure was reduced to a target flowing pressure of under 20 psi

prior to entering the rigs via a pressure reducing valve (PRV). The main header line from CSII

connected to header manifolds which connected to the individual hoses for each rig. A bypass

valve was installed to serve as a bleed line in an effort to prevent the hose from freezing during

colder weather.

Pipe Rig Design

An example LSL rig and an example galvanized/faucet rig are shown in Figure 16.

Four LSL rigs located in the Flint WTP flowed with finished Flint water prior to the start of this

study as part of previous research by others, described in Williams et al. (2018). These four rigs

contained four harvested LSLs each, for a total of sixteen LSL pipes that were available for testing.

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Each LSL was approximately 48” in length, though this length varied, with an internal diameter

(ID) of ¾” (Williams et al. 2018). Water entered the rigs from a hose connection near the bottom

of the rack. Flow control and measurement was possible at the rig- and pipe-level via diaphragm

valves and rotameters. Each pipe was able to get a different orthophosphate dose on the LSL racks

due to each pipe having a chemical feed check valve and static mixer, allowing for greater

flexibility in the test conditions. There were sample taps per-pipe after the static mixers which

were originally used for flowing sample collection but it was apparent that flowing samples

collected at this location increased the flowrate of the pipe, thus diluting the sample. Once noticed,

flowing sample collection was adjusted to the same sample valve used for stagnation metals

sampling, located after the test material. An electrically actuated ball valve, controlled by a timer

on the rig, was located on the effluent line of each rig. For this study, the timers were also

connected to an outlet which allowed for power-cycling the orthophosphate pumps to feed

chemical only when the valve was open.

Four additional rigs were set up in early March 2019 to supplement the data generated from the

LSL rigs with data from harvested galvanized pipe (instructions to outside personnel providing

these pipes for testing were to only provide galvanized lines previously preceded by lead) and new

brass fixtures. These newer racks contained one chemical feed port on the rig header, allowing

each rig to only test one orthophosphate dose condition. Flow measurement was possible for the

rig itself and for individual pipes and flow control was achieved by diaphragm valves located on

each pipe prior to the test materials. The three galvanized lines were located on the top shelf of the

rack. Five brass faucet-bodies were daisy-chained and connected to Schedule 40 PVC on the shelf

below the galvanized lines. Similar to the LSL racks, a timer controlled an electrically actuated

ball valve on the effluent line and an electrical outlet located on the rig for the orthophosphate feed

pumps.

The harvested LSLs and galvanized pipes were connected to the PVC piping by plastic tubing

fitted over the test material attached to the PVC and test material by hose clamps. Threaded

connections on the new brass fixtures allowed for direct connection to the PVC piping by using

fittings.

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Figure 16 Example LSL Rig (left) and Galvanized/Fixture Rig (right)

Lead Service Lines and Materials Description

The harvested LSLs and galvanized pipe were removed from the distribution system by others as

part of ongoing replacement efforts in Flint. The harvested LSLs were mostly already connected

to the rigs, apart from “Pipe 1” on each rig (e.g. A1, B1, etc.) which were harvested and placed in

the rigs in late 2017. Table 5 shows the known information regarding the harvested materials from

the distribution system. The five brass fixtures daisy-chained together per rig were the faucet body

portions of the Proplus Model KF1885.

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Table 5 Pipe Rig Study Test Material Information

LSL Rigs (Rigs A – D) Galvanized/Fixture Rigs (Rigs E – H)

Study

ID Material Location ID†

Stud

y ID Material Location ID

A1 Harv. LSL 2300 Vernon Ave.‡ E1 New Brass N/A

A2 Harv. LSL 2614-02 E2 Harv. Galvanized 1921 Chippewa St

A3 Harv. LSL 2614-03 E3 Harv. Galvanized 2302 Basset Place

A4 Harv. LSL 2614-01 E4 Harv. Galvanized 1715 Tacoma

B1 Harv. LSL 2317 Vernon Ave.‡ F1 New Brass N/A

B2 Harv. LSL 742-2 F2 Harv. Galvanized 1219 Mann

B3 Harv. LSL 742-4 F3 Harv. Galvanized 518 E 12th St

B4 Harv. LSL 742-3 F4 Harv. Galvanized 2465 Gibson St

C1 Harv. LSL 2417 Vernon Ave.‡ G1 New Brass N/A

C2 Harv. LSL 2301-3 G2 Harv. Galvanized 1232 Roosevelt

C3 Harv. LSL 2301-2 G3 Harv. Galvanized 3310 Clairmont

C4 Harv. LSL 2301-4 G4 Harv. Galvanized 1115 W 2nd

D1 Harv. LSL 2402 Vernon Ave.‡ H1 New Brass N/A

D2 Harv. LSL 749-1 H2 Harv. Galvanized 708 Stockton St

D3 Harv. LSL 749-3 H3 Harv. Galvanized 714 Oak

D4 Harv. LSL 749-4 H4 Harv. Galvanized 601 Asylum

Notes: † LSL location IDs are the written identifier codes on the existing tags, present before

the start of the present study

‡ These pipes have “Vernon St.” written on the tags, but this street does not exist in Flint,

and therefore was assumed to be Vernon Ave.

Timer Flow Schedule

Each pipe rig had a digital timer which controlled power to an outlet and the rig’s electrically

actuated ball valve based on the set schedule. The LSL rig timer schedule during the equilibrated

lead period used for data analysis is shown in Table 6. Table 6 also shows the galvanized and

fixture rig schedule, which was adjusted in late 2019 to increase stagnation time to eleven hours

from the previous eight hours.

21

Table 6 Timer-Operated Flow Schedule

LSL Rigs (Rigs A – D) Galvanized/Fixture Rigs (Rigs E – H)

Time Valve Position Time Valve Position

12:00 am Closed 10:00 am Open

2:30 am Open 10:30 am Closed

3:00 am Closed 12:30 pm Open

11:00 am Open 1:30 pm Closed

11:30 am Closed 3:30 pm Open

2:00 pm Open 4:00 pm Closed

3:00 pm Closed 6:30 pm Open


5:00 pm Closed 10:30 pm Open


8:00 pm Closed

11:30 pm Open

Study Equipment

There were two general categories of equipment utilized for this study apart from the pipe rigs

themselves: chemical feed equipment and sampling and analytical equipment. The chemical feed

equipment consisted of the peristaltic pumps, pump heads, and other items necessary to dose

orthophosphate to rigs during periods of flow. Peristaltic pump drives were outfitted with multiple

stacked pump heads in order to feed the same dose to multiple pipes. Pump-specific tubing was

utilized for carrying the orthophosphate dilution from the storage tanks to the chemical feed ports

on the rigs. The feed tubing was inserted into the existing chemical feed ports on each pipe using

a tubing adapter. As mentioned previously, the peristaltic pumps were plugged into a timer-

controlled outlet to ensure orthophosphate was only dosed during periods of flow. The

orthophosphate product utilized for this study was a sodium-neutralized orthophosphate product,

trade name Shannon Chemical Corp. SLI-5179. This product is specified as 36% by weight

orthophosphate as PO4 (Shannon Chemical Corporation).

Daily Operations

Cornwell had a dedicated engineering staff member on site as rig operator to complete daily tasks

required to produce data for this study. Tasks included sample collection for stagnating and

flowing samples, flowing sample WQP analysis, chemical feed dilution preparation, collecting

flow and pressure readings, performing rig maintenance as necessary, and ensuring data was

logged and entered into the data sheets.

The schedule shown in Table 7 summarizes the operational tasks regularly performed by Cornwell

throughout the week and these individual tasks are described in more detail below. The discussion

in this section applies primarily to the period of the study which was determined to have

equilibrated lead which was used for analysis and to make recommendations, as described in the

loop study Expanded Executive Summary document. This time period will occasionally be

22

referred to in this section as the study analysis period. Major operational changes will be discussed

in a separate portion of this section.

Table 7 Weekly Operator Schedule

TASK † MON TUE WED THU FRI

Collect Stagnation Samples

(Lead)

Collect Stagnation Samples

(PO4) ‡

Collect Flowing Samples and Test

(pH, Temperature, PO4) (Cl2 - weekly)

Record Rig Pressure and Flow x3 x3 x3 x3 x3

Record Individual Pipe Flow x3 x3 x3 x3 x3

Record Chemical Pump Flow x3 x3 x3 x3 x3

Record Daily Cumulative Flow

Record Daily Chemical Dilution Usage

Upload Data using Data Sheet and Excel File

Create Chemical Feed Dilution As

Needed

As

Needed

As

Needed

As

Needed

As

Needed

Adjust Pump Tubing/ Troubleshoot Pumps As

Needed

As

Needed

As

Needed

As

Needed

As

Needed

Note: † Sample collection frequency was adjusted based on holidays and operator availability on

a case-by-case basis

‡ Stagnation water quality parameters collected from June 2019, typically on a regular

basis

Stagnant Sample Collection

Prior to the first flow period on a stagnation sampling day, labels were first filled out and applied

to sample bottles. Stagnant samples were collected from all pipes near the end of the longest

stagnation period of the flow schedule shown in Table 6. Prior to collecting the samples for each

pipe, it was important to first close the manual ball valves located after the test materials and waste

a set amount of water which was not in contact with the test material. After samples were collected,

half of the samples were prepared for filtered lead analysis each sampling period such that each

pipe had one filtered lead sample per week. Clean syringes and new syringe filters were used to

filter 50 mL of sample into clean, labelled bottles. Chain of custody (COC) forms for the collected

samples were filled out and a tracking file was updated when samples were packed for shipment.

Typically, once per week beginning in June 2019, stagnant samples were collected and analyzed

for orthophosphate at the end of the stagnation period similar to stagnation lead samples.

Flowing Sample Collection

During the equilibrated period used for lead data analysis, flowing water quality was typically

analyzed twice per week as shown in Table 7. Free chlorine per-rig was typically measured weekly.

23

This schedule allowed time to perform the “bathtub-fill” events on Fridays, which will be

discussed in the General Operations and Maintenance portion of this section. Samples were

collected, as feasible, over the course of the workday flow periods depending on the rigs sampled

on a given day. Sample pH, temperature, orthophosphate, and free chlorine were measured for

flowing samples according to the procedures described in the Sampling Procedures and Analytical

Methods section of this document.

Prior to the first flow period, a sample from the sample tap was collected from one of the rigs for

conditioning the pH probe before flowing samples were collected. When both sets of rigs were

operating with GLWA water and varying orthophosphate doses, timer schedules were staggered

to ensure each set of rigs had enough flow available. This staggered schedule enabled the operator

to pull samples from as many pipes as possible from the LSL rigs (Rigs A-D), test WQPs on these

samples, then collect as many samples as possible from the galvanized and fixture rigs (Rigs E-H)

once the first flow period for these rigs began. Between sampling events, the pH probe was

reconditioned in water from the GLWA bleed line. After all flowing samples are analyzed, the pH

probe was stored in storage solution and the lab area was cleaned and organized. During the time

period used for lead data analysis, the pH probe was cleaned and calibrated weekly, typically on

Monday.

General Operations and Maintenance

When on-site, the rig operator visually assessed the rigs to detect potential leaks. When a leak was

detected at the connection to the test material, it was fixed by tightening the hose clamps in place.

Leaks found at any other connection on the rig were resolved by undoing the connection, removing

damaged thread tape, applying new thread tape, and securing the connection. Flint WTP staff

provided additional maintenance assistance as necessary.

Daily cumulative flows for rigs A-D were recorded between flow periods 2 and 3. Remaining

dilution volume was recorded after flow period 3. Flowing pressure and flow rates were recorded

for each pipe during each flow period during which an operator was on site. During the side-by-

side coupon study, water would be taken from the appropriate pre-LSL tap during flow period 2

to prepare coupon samples.

Rig flowing pressure, rig flow rate, and individual pipe flow rate were typically recorded three

times each day an operator was on site. Instantaneous flow meters (rotameters) allowed for the

flow rate to be visibly observed and recorded by the operator and pressure was recorded from the

pressure gauge situated on the common line near the beginning of each rig, shown in Figure 16.

Cumulative flow was recorded daily from flow totalizers on each pipe (LSL rigs) and each rig

(galvanized and fixture rigs). The volume of orthophosphate dilution remaining was also recorded

daily in order to track usage. Stagnant samples were taken for lead analysis approximately twice

per week. Chemical feed rates were reviewed after each water quality parameter test. Pump rates

were initially set based on concentration calculations and were adjusted using the ratio method as

needed throughout the study. Rig pressures and flows, individual pipe flows, and chemical pump

24

flows were recorded daily. Operating procedures included documenting readings from either flow

meters, flow totalizers, or the digital pump displays. Chemical use per day was recorded daily by

reading the graduation on the storage tanks. The chemical use and flow totals were used as a double

check on the flow rates and timer operation. Pump tubing was adjusted for the peristaltic pumps

at least weekly or more frequently if conditions dictated. Tubing was adjusted by opening the pump

head and drawing an unused section of tubing into the pump head before closing it again. Sections

of tubing were replaced after the entire section had been used in the pump head.

Typically, every Friday beginning in February 2019, LSLs were put through a “bathtub fill” event.

These pipes would be allowed to flow at 3 gpm of unadjusted GLWA water for 30 minutes. This

process was completed once every three weeks per pipe. During this time, chemical feed lines

were inspected and adjusted as necessary.

Chemical Dilution

Chemical dilutions of orthophosphate product Shannon Chemical Corp SLI-5179 were prepared

as needed according to ratios set by feed calculations and expected usage rates. For example,

beginning in May 2019, storage tank “OS-1” was prepared with a 1:400 dilution. Unadjusted

GLWA water was utilized as dilution water which negligibly impacted the amount of phosphate

in the feed stock. Dilutions were prepared during periods of stagnation by first adding the measured

SLI-5179 to the storage tank, filling to the 100 L line with GLWA water, and stirring.

Sampling procedures and Analytical methods

Sampling Procedures

Flowing samples were originally analyzed 3 times per week for pH, temperature, and

orthophosphate. Once the “bathtub fill” events began, these analyses were performed twice per

week to accommodate the new workload. Flowing samples were taken by manual sample grabs

from the sample taps downstream of the test materials after allowing pipes at least five minutes to

flow before sampling. After the sample tap valve was opened, the ball valve downstream of the

tap needed to be actuated in order for water to flow from the tap. The first 500-750 mL of water

was wasted from each line on a rig. The manual ball valves were then reopened and the sample

taps closed to allow the rig to return to its typical flowing state. This process was repeated for

every line on one rig. After allowing all lines to return to their standard flowing state,

approximately 400 mL was collected from each line by manually actuating the sample taps and

closing the post-tap ball valve. These samples were used to immediately analyze pH and

temperature and to measure orthophosphate residual. This process was repeated for each rig. The

same flowing sample process was used to measure free chlorine for one pipe on each rig.

Lead stagnation samples were collected typically twice weekly, one sample from each pipe.

Sample bottles were prepared by affixing a label that indicated the line to be sampled, the date and

time of the sample grab, sampler name, sample number and analysis to be completed. After

preparing the sample bottles, samples were collected after water had stagnated in the test materials

25

for approximately eight hours (LSL rigs) or eleven hours (galvanized and fixture rigs). These

samples were collected by manually closing all ball valves immediately downstream of the sample

taps. Taps were individually manually actuated and the appropriate volume of water was wasted

from each line on a rig into a graduated cylinder. The amount to be wasted was determined using

volume calculations as well as a profile analysis and was 80 mL for each of the brass lines, varied

from 95 to 130 mL for LSLs, and varied from 95 to 250 mL for the galvanized pipes. Stagnation

sequential samples were also collected during the study to help assess wastage calculations. After

wasting, a sample of approximately 250 mL was collected in an appropriately labeled sample

bottle. This process was repeated for each rig until all lines had been sampled. Once per week, an

aliquot of the stagnation sample from each test material was passed through a 0.45 µm pore

diameter MCE filter to assess filtered lead. These samples were filtered by drawing approximately

25 mL of the sample into a clean syringe, attaching a new 0.45 µm pore diameter MCE filter, and

expelling the sample through the filter into an appropriately labeled, new or cleaned sample bottle.

This process was done twice for each sample to have a total filtered sample volume of

approximately 50 mL. There were instances in which the filtered lead exceeded the total lead for

the same sample. This will be discussed further in the Study Operation Adjustments and Events

section of this document.

Analytical Procedures

Temperature and pH were measured using a Hanna Edge pH meter and accompanying probe as

soon as possible after collecting the flowing grab sample. Meter calibration and probe cleaning

occurred typically weekly during the study analysis period. Before collecting the flowing samples,

the probe was first removed from the storage solution and immersed in a stagnation sample to

allow the probe to equilibrate. Flowing and stagnation samples were collected on different days of

the week, allowing this sample to not affect other sampling efforts. As soon as feasible after

collecting samples, the probe was immersed in the test samples and the operator collected readings

for temperature and pH. Samples were all measured in cleaned glass beakers and stirred with a

magnetic stirrer rod and associated stirring plate during sample analysis. This process was

completed for other samples, and if necessary, the probe was temporarily stored in the stagnation

sample used for probe equilibration between flow periods. After sampling was finished for a given

day, the probe was reinserted into storage solution and the station was cleaned.

Sample orthophosphate was measured using a Hach DR900 and Orthophosphate sample kits (trade

name Hach Test N’ Tubes) according to Hach Method 8048. Due to this method having a stated

range maximum of 5.0 mg/L as PO4, a 1:2 dilution was performed for all samples coming from

lines with target orthophosphate concentrations of 5.0 mg/L as PO4 using a 100 mL volumetric

flask and TenSette pipet. The measurements for these lines were recorded as presented by the

instrument, but calculations in the analysis files corrected for this dilution.

Free chlorine was measured using the Hach DR900 according to Hach Method 8021. Samples

were measured typically weekly due to this parameter not being deliberately adjusted for the study.

26

Stagnation samples tested for total or filtered lead were sent to Cornwell Laboratories in Newport

News, VA for analysis via EPA Method 200.9. After receipt in Newport News, samples were

acidified in the sample bottle to a pH of less than 2.0 using 1:1 HNO3.

Coupon Study Methods and Materials

A limited coupon study was conducted alongside the pipe loop study in order to provide further

information regarding the lead solubility of the water entering the harvested LSLs. At first, sixteen

total lead coupon assemblies were set up onsite for testing. These assemblies consisted of a lead

coupon hanging from a plastic hook superglued to a plexiglass piece. The original conditions tested

consisted of duplicates collected twice per week from pipes of each target orthophosphate dose.

Four additional coupons were tested using water from the 3.5 mg/L as PO4 target orthophosphate

dose but with different immersion periods: two coupons were immersed in fresh water every day

an operator was on-site and two different coupons were immersed in new water every week. In

October 2018, many of these conditions were discontinued and only select coupons were

continued. Single replicates of the GLWA water, 2.0, 3.0, 4.0 and 5.0 mg/L as PO4 twice per week

conditions were continued. Both duplicates of the 3.5 mg/L as PO4 twice per week conditions

continued. The side-by-side coupon study was discontinued in January 2020.

Fresh water for coupon samples was collected from LSL rigs after orthophosphate dosage but

before water contacted the test materials. At least five minutes after the beginning of a flow period,

water was drawn from the pre-LSL sample tap into a clean, labeled coupon sample bottle from a

pipe with the appropriate orthophosphate test condition. Coupon assemblies were then carefully

transferred from the previously stagnating water to the freshly collected water. The bottles were

filled as much as possible and the coupon assemblies did not have holes in order to allow for

samples to be headspace free when stagnating.

As mentioned in the Expanded Executive Summary document for this study, the LSL rig sample

taps utilized for this coupon study were noted to increase flow for the line being sampled

potentially due to no upstream flow control. For this reason, flowing samples were collected from

the sample taps immediately following the test materials starting in July 2018. However, for the

purposes of this coupon study, samples continued to be collected from before the LSLs. Therefore,

fresh coupon water during this coupon study likely contained slightly less orthophosphate than the

target orthophosphate typically flowing through the pipes being sampled.

Study Operational Adjustments and Events

This section aims to provide a summary of major operational changes or events during the entire

study period, beginning when Cornwell was first onsite and extending into the study analysis

period. A significant amount of information in this section has also been presented in the study

Expanded Executive Summary document.

27

Lead Service Line Rigs

In March 2018, Cornwell staff arrived on site and began collecting samples. Rigs A, B, and D were

switched to GLWA water plus sodium orthophosphate dilution, if applicable, on April 5, 2018.

Rig C was switched to GLWA water plus caustic soda dilution and appropriate orthophosphate

doses on April 9, 2018. In early May 2018, the caustic feed was turned off for Rig C, effectively

creating triplicate pipes for the 1.2, 2.5, 3.0, and 4.0 mg/L as PO4 conditions. From May 22, 2018

ball valves post-LSLs were closed prior to stagnation sampling to isolate the individual test

materials and from July 23, 2018 flowing samples were collected post-LSL in order to prevent

orthophosphate dilution in samples collected. In July 2018 and early August 2018, initial wastage

was included in the flowing sample collection procedures. Figure 17 shows the impact of the above

operational changes on total lead, using pipes D1 and D2 as an example. There are several data

points in these figures higher than the maximum y-axis values, but the scales were zoomed in to

show trends. Note the increase in apparent particulate lead during the 1 gpm operational period

beginning around the same time post-LSL ball valves were closed prior to stagnation sampling.

Pressures were increased for the LSL rigs in early October 2018 due sample taps not flowing post-

LSL when opened during a rig flow period. Pipe C3 disconnected shortly after in mid-October

2018, pressures were then decreased, and pipe C3 was reconnected with new vinyl tubing a few

days later. This tubing connects to the outer diameter of the LSLs and the PVC piping. However,

this new tubing failed several days after reinstallation and was replaced again with thicker tubing.

In December 2018, tubing sections began to be replaced with braided vinyl tubing post-LSLs. It

was also observed approximately at this time that pipes did not appear to be flowing full or there

was trapped air in the tubing connecting the LSLs to the PVC piping. Attempting to resolve this

issue without major rig modifications failed. Also, in December 2018 a stagnation sampling

flowrate of about 0.5 gpm was enacted and pH meter calibration and cleaning increased to weekly.

Another LSL disconnected in late December 2018, and by the end of January 2019 all of the post-

LSL tubing was replaced with braided tubing.

Several further operational adjustments were made in an attempt to understand erratic lead levels

noted in the rigs. Filtered lead samples were regularly collected beginning on February 12, 2019.

Between February 18 and 19, 2019, pipes D1 and D2 operated at 1.5 gpm, several pipes were

operated for 30 minutes at 3 gpm, and investigative sampling efforts occurred. Despite a low-flow

bleed line, a header freeze occurred before the morning of February 28, 2019. Once thawed, all

pipes were adjusted from 1.0 to 1.2 gpm on February 28, 2019. Once header freezing was no longer

a concern, all pipes were again adjusted up to 1.5 gpm on May 20, 2019.

The regular schedule of “bathtub-fill” events, which consisted of adjusting LSLs to 3 gpm for

thirty minutes every three weeks, began in May 2019 and flowing water quality parameters were

adjusted to twice per week to accommodate. Stagnant orthophosphate began to be collected once

per week on Fridays in June 2019. To illustrate the impact of increasing the pipe flowrates and

beginning a regular schedule of exposing pipes to 3 gpm for 30 minutes, Figure 18 shows D1 and

D2 lead data from early September 2018 onward delimited by target flowrate. For analysis

28

purposes, data collected during the short 1.5 gpm period for pipes D1 and D2 between February

18 and 19, 2019 were not included in the 1.5 gpm data used for the comparisons described in Table

8 and the Expanded Executive Summary report. Pipes D1 and D2 were maintained at the same

orthophosphate target dose for the entire duration of the test. All other pipes were switched to a

different target dose than the original test conditions on February 24, 2020, but D1 and D2

maintained a target orthophosphate concentration of 3.5 mg/L as PO4 throughout the study.

The bathtub fill event procedure was adjusted in August 2019 in order to prevent potential

orthophosphate feed interruptions after an operations error caused the 4.0 mg/L as PO4 conditions

to not have phosphate for a few days in July 2019. Orthophosphate doses were refined in

September 2019 to get more consistent readings closer to targets. The bleed line flow rate needed

to be increased after another line freeze on December 11, 2019 which depressurized the rigs and

potentially drained the rigs for a period of time before rigs were flowing again in the second flow

period of the day. The pre-LSL vinyl tubing ruptured for pipes A1 and A2 in January 2020 and for

pipe C3 in February 2020 and these tubing connections were reattached by plant maintenance staff

before the Cornwell operator could replace the connections with braided tubing.

In early 2020, it was noticed that the number of samples where the filtered lead exceeded the total

lead appeared to increase and the difference between the two readings also increased albeit at the

low lead levels being measured. Suspected samples were re-run by the laboratory and data files

were updated. However, this issue again came up in May 2020. The exact cause of the difference

was never determined but out of precaution washed laboratory bottles for filtered lead analysis

were no longer used and bottles were switched to entirely new bottles for all lead samples in June

2020. Also, all Flint samples were run by themselves on the instrumentation following extensive

machine clean out.

29

Figure 17 Early Operational Changes and Total Lead, using D1 and D2 as an Example.

Figure 18 Flowrate and Key Operational Adjustments on Total Lead using D1 and D2 as an

Example.

30

Galvanized and Fixture Rigs

The galvanized and fixture rigs were assembled in March 2019 in order to assess orthophosphate

dose performance on materials other than LSLs due to the rapid replacement of LSLs in the Flint

distribution system. These rigs flowed in a limited operations capacity during the equilibration

phase when the pipes flowed on finished Flint water. Stagnation samples were collected twice per

week for these lines. Four galvanized pipes were available shortly after the rigs were built, but the

remaining eight galvanized pipes were not delivered until fall 2019.

Stagnation time was increased for these newer rigs on December 16, 2019 from eight hours to

eleven hours. Stagnation sampling waste volume was adjusted December 19, 2019. All pipes

remained on finished Flint water until rigs were switched to GLWA water with varying target

orthophosphate doses, using SLI-5179 dilution, on April 20, 2020. Regular data collection

occurred for these rigs beginning on April 23, 2020. On June 17, 2020, the target flowrates for the

galvanized lines and brass fixture lines were adjusted to 1.5 gpm and 1.0 gpm, respectively.

In September 2019, the automatic effluent ball valve for Rig F was noted to have a slight leak

during stagnation and this issue was believed to be solved at the time. However, in late July 2020

and early August 2020, the automatic ball valves were noted to be apparently leaking during

stagnation and were adjusted accordingly. In mid-September 2020 these valves were checked and

adjusted, if necessary, and regularly checked to ensure no leakage during stagnation. Similar to the

LSL rigs, filtered lead samples showed much higher lead numbers than the total lead figures for

certain periods of time, especially in early 2020 and May 2020. Certain suspect samples were rerun

and washed bottles were no longer used for sample collection beginning in early June 2020.

PIPE LOOP WATER QUALITY

The rig water quality and operational data presented in this section is shown for the time periods

coinciding with the study analysis periods used to make recommendations. For the LSL rigs,

therefore, data presented in this section is shown for samples or measurements collected within

the flow-dose analysis periods shown in Table 8, or between May 9, 2019 and August 21, 2020.

Table 8 is reproduced from the Expanded Executive Summary document for reference. For the

galvanized and fixture rigs, these data were collected between when the rigs were switched to

GLWA water in late April 2020 through August 20, 2020.

Lead Service Line Rigs Water Quality

This section presents the WQPs for the LSLs for each of the four different lead service line loop

flow-dose periods as outlined in Table 8. As mentioned previously, the Cornwell rig operator

regularly collected data for pH, temperature, orthophosphate, and free chlorine. Additionally, the

rig operator checked individual pipe and rig flows, rig pressures, daily totalized flow, chemical

feed flowrates, and orthophosphate dilution remaining.

31

Table 8 Flow-Dose Analysis Periods for LSL Rigs by Operational Characteristics

Operational Time

Period ID

Phosphate Dose

Regime

Target Flowrate per

Pipe (gpm) Date Range

1.2 gpm-Dose1 Original (Dose 1) 1.2

5/09/19 to 5/19/19

and

11/1/19 to 2/23/20

1.5 gpm-Dose1 Original (Dose 1) 1.5 5/20/19 to 10/31/19

1.2 gpm-Dose2 Switched (Dose 2) 1.2 2/24/20 to 6/15/20

1.4 gpm-Dose2 Switched (Dose 2) 1.4 6/16/20‡ to 8/21/20†

Notes:

† Statistical analyses completed for data through 8/13/20

‡ Stagnation lead samples collected 6/16/20 prior to the flowrate change

Figure 19 shows temperature measured during flowing sample collection for all samples collected

from the LSL rigs, with each flow-dose period indicated on the figure. Flowing temperature varied

seasonally and peak temperatures typically occurred in August or early September. Note these

readings were collected on flowing water samples and it is possible that the ambient temperature

could have impacted stagnant water temperature in the pipes, though this parameter was not

measured.

Figure 19 Measured temperature for flowing samples from the LSL rigs (5/9/2019 – 8/21/20)

32

Figure 20 shows free chlorine measurements during the study which were collected per-rig,

typically once per week. Disinfectant residual was not supplemented during the test period and

varied seasonally. However, measured free chlorine was typically above 0.75 mg/L as Cl2. The

lowest free chlorine residuals were measured in the late summer of 2019, with the minimum of

0.20 mg/L measured from the Rig A flowing sample in early August 2019.

Figure 20 Measured free chlorine for flowing samples from the LSL rigs (5/9/2018 –

8/21/2020)

Flowing water pH was measured regularly from samples collected from the LSL rigs, typically

twice per week during the study analysis period. Measured pH was generally between 7.4 and 7.6

s.u. excluding occasional variability and lower than typical measurements in early-June 2019.

Figure 21, Figure 22, and Figure 23 show the distribution of pH measurements for the 1.2gpm-

Dose1, 1.5gpm-Dose1, and 1.4gpm-Dose2 data collection time periods, respectively.

Measurements in these figures were grouped by the target orthophosphate for the pipes during the

flow-dose time period analyzed. Summary data for the 1.2gpm-Dose2 time period is not shown

due to these data not being utilized for statistical analyses as described in the Expanded Executive

Summary document. Figure 22, Figure 23, and Figure 24 show that pH measured in the rigs were

typically similar between orthophosphate doses and flow-dose data analysis periods.

33

Figure 21 pH box-plot for LSL rig flowing samples during 1.2gpm-Dose1


34


Figure 24, Figure 25, and Figure 26 show the distribution of flowing sample orthophosphate

measurements during 1.2gpm-Dose1, 1.5gpm-Dose1, and 1.4gpm-Dose2, respectively. Figure 26

shows that orthophosphate measurements during 1.5gpm-Dose1 were more variable than the other

analysis periods and slightly lower than targets.

35

Figure 24 Orthophosphate box-plot for LSL rig flowing samples during 1.2gpm-Dose1


36


Galvanized Pipe and Brass Fixture Loops

WQPs were also measured for the galvanized pipe and brass fixture rigs. However, due to each rig

having identical water quality, samples were only analyzed per-rig for pH, temperature,

orthophosphate, and free chlorine. These parameters were typically measured twice per week

except for free chlorine which was typically measured once per week.

The galvanized and fixture rigs were kept at constant orthophosphate dose during the study period,

so there are no distinct dose periods as there were in the LSL rigs. The flow rate was changed

during the study analysis period for these rigs but the measured lead concentrations did not indicate

that this change in flow rate had an impact on lead levels and therefore the flow periods were not

analyzed separately. The study period for these rigs was much shorter than the LSL rigs. Figure

27 shows temperature measurements for flowing samples from the galvanized and fixture rigs

varied seasonally from 7.6 to 21.9°C.

Similar to the LSL rigs, the free chlorine residual measured from flowing samples was relatively

high throughout the test period with a median of about 0.90 mg/L. Figure 28 shows free chlorine

measurements from flowing samples were highest in the colder months at around 1.0 mg/L and

decreased to about 0.8 mg/L once water temperatures were over 20°C.

37

Figure 27 Measured temperature for flowing samples from the galvanized and fixture rigs

Figure 28 Measured free chlorine for flowing samples from the galvanized and fixture rigs

38

Figure 29 shows measured pH for the galvanized and fixture rig flowing samples through 8/20/20

was generally between 7.4 and 7.6, with some variations.

Figure 29 Flowing sample pH from the galvanized and fixture rigs

Figure 30 shows the measured orthophosphate from flowing samples collected from the galvanized

and fixture rigs through 8/20/20. Figure 29 and Figure 30 together show that as orthophosphate

dose target increased between rigs, measured pH decreased slightly. Although the orthophosphate

product utilized for this study was a pH neutralized sodium orthophosphate, measured pH appeared

to be slightly affected by orthophosphate dose. Figure 29 shows the magnitude of difference was

not large, but it was noticeable and consistent.

39

Figure 30 Flowing sample orthophosphate from the galvanized and fixture rigs

40

REFERENCES

Cornwell, D., R. Brown, & N. McTigue. 2015. “Controlling Lead and Copper Rule Water Quality

Parameters.” Journ. AWWA, 107 (2): E86-E96.

Cornwell Engineering Group. 2018. Pipe Scale Analysis. Corrosion Control Treatment Study

Engineering Memorandum.

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