Document ID: EPA-HQ-OW-2002-0043-0146
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2003-07-22T04:00Z

iii
STAGE
2
DISINFECTANTS
AND
DISINFECTION
BYPRODUCTS
RULE
United
States
Environmental
Protection
Agency
Office
of
Water
(
4601)
EPA
[
No.
TBD]
July
2003
Draft
This
text
is
a
draft
provided
for
public
comment.
It
has
not
had
a
final
review
for
technical
accuracy
or
adherence
to
EPA
policy;
do
not
quote
or
cite
except
as
a
public
comment.
SIGNIFICANT
EXCURSION
GUIDANCE
MANUAL
i
Note
on
the
Stage
2
Disinfectants
and
Disinfection
Byproducts
Significant
Excursion
Guidance
Manual,
July
2003
Draft
Purpose:

The
purpose
of
this
guidance
manual,
when
finalized,
is
solely
to
provide
technical
information
for
water
systems
and
States
to
use
for
identifying
and
reducing
significant
excursions
of
DBP
levels.
The
Stage
2
Disinfectants
and
Disinfection
Byproducts
Rule
(
Stage
2
DBPR)
contains
a
provision
for
significant
excursions.
EPA
is
developing
the
Stage
2
DBPR
to
reduce
DBP
occurrence
peaks
in
the
distribution
system
based
on
changes
to
compliance
monitoring
provisions.

This
guidance
is
not
a
substitute
for
applicable
legal
requirements,
nor
is
it
a
regulation
itself.
Thus,
it
does
not
impose
legally­
binding
requirements
on
any
party,
including
EPA,
states,
or
the
regulated
community.
Interested
parties
are
free
to
raise
questions
and
objections
to
the
guidance
and
the
appropriateness
of
using
it
in
a
particular
situation.
Although
this
manual
describes
many
methods
for
complying
with
significant
excursion
requirements,
the
guidance
presented
here
may
not
be
appropriate
for
all
situations,
and
alternative
approaches
may
provide
satisfactory
performance.
The
mention
of
trade
names
or
commercial
products
does
not
constitute
endorsement
or
recommendation
for
use.

Authorship:

This
manual
was
developed
under
the
direction
of
EPA's
Office
of
Water,
and
was
prepared
by
The
Cadmus
Group,
Inc.
and
Malcolm
Pirnie,
Inc.
Questions
concerning
this
document
should
be
addressed
to:

Thomas
Grubbs
and
Mike
Finn
U.
S.
Environmental
Protection
Agency
Mail
Code
4607M
1200
Pennsylvania
Avenue
NW
Washington,
DC
20460­
0001
Tel:
(
202)
564­
5262
(
Thomas
Grubbs)
(
202)
564­
5261
(
Mike
Finn)
Fax:
(
202)
564­
3767
Email:
Grubbs.
Thomas@
epamail.
epa.
gov
and
Finn.
Michael@
epamail.
epa.
gov
Request
for
comments:

EPA
is
releasing
this
manual
in
draft
form
in
order
to
solicit
public
review
and
comment.
The
Agency
would
appreciate
comments
on
the
content
and
organization
of
technical
information
presented
in
this
manual.
Please
submit
any
comments
no
later
than
90
days
after
publication
of
the
Stage
2
Disinfectants
and
Disinfection
Byproducts
Rule
proposal
in
the
Federal
Register.
Detailed
procedures
for
submitting
comments
are
stated
below.
ii
Procedures
for
submitting
comments:

Comments
on
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guidance
manual
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EPA's
Water
Docket.
You
may
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mail,
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courier.

·
 
To
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Once
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OW­
2002­
0043.
If
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·
 
To
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2002­
0043.

·
 
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0043.

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For
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commenting,
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note
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is
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viewing
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by
statute.
Significant
Excursion
Guidance
Manual
July
2003
Proposal
Draft
iii
Contents
Tables
and
Figures
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iv
Acronym
List
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v
1.0
Introduction
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1­
1
1.1
What
is
a
Significant
DBP
Excursion?
.
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1­
1
1.2
What
Should
Systems
do
to
Address
Significant
Excursions?
.
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.
1­
3
1.3
Organization
of
this
Guidance
Manual
.
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1­
3
2.0
Causes
of
Significant
DBP
Excursions
.
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2­
1
2.1
Fundamentals
of
DBP
Formation
.
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2­
1
2.2
Impacts
of
Changes
in
Source
Water
Quality
on
DBP
Concentrations
.
.
.
.
.
.
.
2­
2
2.3
Impacts
of
Changes
in
Treatment
Plant
Operations
on
DBP
Concentrations
.
.
2­
8
2.4
Impacts
of
Distribution
System
Characteristics
on
DBP
Concentration
.
.
.
.
.
2­
15
3.0
Identifying
the
Cause
Of
and
Documenting
Your
DBP
Significant
Peak
Excursion
.
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3­
1
4.0
Best
Management
Practices
and
Distribution
System
Improvements
to
Reduce
DBP
Concentrations
.
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4­
1
4.1
Modifications
to
Improve
Water
Quality
in
Storage
Tanks
.
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4­
1
4.1.1
Minimizing
Hydraulic
Residence
Time
of
Storage
Tanks
.
.
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.
4­
2
4.1.2
Improving
Mixing
Characteristics
of
Storage
Tanks
.
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4­
2
4.2
Decommissioning
Storage
Tanks
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4­
5
4.3
Modifications
to
Improve
Water
Quality
in
Pipes
.
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4­
5
4.3.1
Minimizing
Hydraulic
Residence
Time
in
Pipes
.
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4­
6
4.3.2
Reducing
Disinfectant
Demand
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4­
7
4.4
Booster
Disinfection
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4­
8
4.5
Overall
Strategy
to
Manage
Water
Age
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4­
9
Significant
Excursion
Guidance
Manual
July
2003
Proposal
Draft
iv
Tables
and
Figures
Tables
1.
Example
1­
1
TTHM
and
HAA5
Monitoring
Data
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1­
2
2.1
Free
Chlorine,
TTHM,
and
HAA5
Data
for
Five
Storage
Tanks
.
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2­
15
Figures
2.1
Effect
of
NOM
Concentration
on
TTHM
and
HAA5
Concentration
.
.
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.
2­
3
2.2
Impact
of
Water
Temperature
on
DBP
Speciation
.
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2­
4
2.3
Impact
of
Bromide
on
TTHM
Speciation
.
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2­
5
2.4
Effect
of
pH
on
TTHM
Formation
.
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2­
6
2.5
Impact
of
Pre­
chlorination
Dose
on
In­
Plant
DBP
Formation
.
.
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2­
7
2.6
Effect
of
Disinfectant
Residual
and
Residence
Time
on
TTHM
.
.
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.
2­
9
2.7
Effect
of
Point
of
Chlorination
on
TTHM
and
HAA5
Concentrations
.
.
.
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.
.
.
.
2­
10
2.8
Effect
of
Disinfectant
Residual
and
Residence
Time
on
TTHM
.
.
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.
2­
15
2.9
Effect
of
Point
of
Chlorination
on
TTHM
and
HAA5
Concentrations
.
.
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.
2­
16
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
v
Acronyms
CFD
Computational
Fluid
Dynamic
CFR
Code
of
Federal
Regulations
CT
Disinfectant
residual
×
contact
time
DBP
Disinfection
Byproduct
DOC
Dissolved
Organic
Carbon
EPA
Environmental
Protection
Agency
FACA
Federal
Advisory
Committees
Act
GAC
Granular
Activated
Carbon
HAA5
Haloacetic
Acids
[
total
of
five]
HPC
Heterotrophic
Plate
Count
IDSE
Initial
Distribution
System
Evaluation
IESWTR
Interim
Enhanced
Surface
Water
Treatment
Rule
LRAA
Locational
Running
Annual
Average
LT1ESWTR
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
MCL
Maximum
Contaminant
Level
M­
DBP
Microbial­
Disinfectants/
Disinfection
Byproduct
MG
Milligrams
MGD
Million
Gallons
per
Day
NOM
Natural
Organic
Matter
QA/
QC
Quality
Assurance/
Quality
Control
SCADA
Supervisory
Control
and
Data
Acquisition
Stage
2
DBPR
Stage
2
Disinfectants
and
Disinfection
Byproducts
Rule
SWTR
Surface
Water
Treatment
Rule
THM
Trihalomethane
TOC
Total
Organic
Carbon
TTHM
Total
Trihalomethanes
Significant
Excursion
Guidance
Manual
ProposalDraft
July
2003
1­
1
1.0
Introduction
The
Stage
2
Microbial­
Disinfection
Byproducts
(
M/
DBP)
Agreement
in
Principle
acknowledges
that
significant
excursions
of
DBP
levels
will
sometimes
occur,
even
when
systems
are
in
full
compliance
with
the
enforceable
Maximum
Contaminant
Level
(
MCL).
EPA
has
developed
this
manual
to
give
guidance
to
States
and
public
water
systems
on
identifying
significant
excursions
and
how
to
conduct
peak
excursion
evaluations
and
reduce
such
peaks.
The
specific
objectives
of
this
manual
are
to:

°
Define
significant
DBP
excursions
°
Summarize
requirements
for
addressing
significant
excursions
°
Provide
a
methodology
for
identifying
the
cause
of
significant
excursions
°
Provide
guidance
for
documenting
significant
excursions
°
Present
the
options
available
to
reduce
DBP
concentrations
in
the
distribution
system
°
List
additional
references
1.1
What
is
a
Significant
DBP
Excursion?

The
Stage
2
Disinfectants
and
Disinfection
Byproducts
Rule
(
DBPR),
under
Stage
2B,
requires
systems
to
meet
a
running
annual
average
of
80
µ
g/
L
for
total
trihalomethanes
(
TTHM),
and
60
µ
g/
L
for
haloacetic
acids
(
HAA5)
at
each
monitoring
location
in
the
distribution
system
(
40
CFR
141,
Subpart
Q,
Appendix
A).
Because
the
individual
samples
are
averaged
over
one
year
to
determine
compliance
with
the
Stage
2
DBPR,
the
DBP
levels
at
a
given
location
can
fluctuate
throughout
the
year.
This
is
normal
and
generally
the
result
of
seasonal
changes
in
water
temperature
and/
or
organic
content.

States
must
define
the
criteria
for
determining
that
a
significant
DBP
excursion
has
occurred
as
a
special
primacy
condition
of
the
Stage
2
DBPR
(
40
CFR
142.16).
One
approach
a
State
might
use
in
identifying
a
significant
excursion
is
to
define
a
maximum
concentration
that,
if
exceeded,
would
require
an
evaluation.
For
example,
a
State
may
define
a
significant
DBP
excursion
as
any
compliance
sample
that
exceeds
the
following:

°
TTHM
concentration
of
100
µ
g/
L
°
HAA5
concentration
of
75
µ
g/
L
Another
approach
a
State
may
take
to
defining
a
significant
DBP
excursion
is
to
compare
results
from
individual
quarterly
measurement
from
compliance
monitoring
with
the
LRAAs
Significant
Excursion
Guidance
Manual
ProposalDraft
July
2003
1­
2
computed
for
that
period.
Using
40
µ
g/
L
for
TTHM
and
30
µ
g/
L
for
HAA5
as
a
benchmark,
a
significant
excursion
occurrs
under
the
following
conditions:

°
For
TTHM,
the
difference
between
a
quarterly
location
measurement
and
the
quarterly
LRAA
is
>
30
µ
g/
L
and
the
LRAA
is
$
40
µ
g/
L
for
TTHM
a
significant
excursion
has
occurred.

°
For
HAA5,
the
difference
between
a
quarterly
location
measurement
and
the
quarterly
LRAA
is
>
25
µ
g/
L
and
the
LRAA
is
$
40
µ
g/
L
for
TTHM
EPA
developed
this
approach
based
on
analyses
of
data
collected
under
the
Information
Collection
Rule
(
ICR).
The
following
example
illustrates
how
a
significant
excursion
is
identified
with
the
"
difference
approach."

Example
­
Significant
Excursion
Occurrence
Identified
by
the
Difference
Approach
Your
system
is
required
to
monitor
at
4
SMP
locations.
During
the
last
sampling
period
which
took
place
in
June
2004,
your
city
experienced
higher
HAA5
values
relative
to
the
LRAA
at
one
monitoring
location
(#
4).
DBP
data
from
the
previous
year
and
most
recent
sampling
period
(
five
quarters
total)
are
presented
in
the
table
below.

Example
TTHM
and
HAA5
Monitoring
Data
Locations
TTHM
(
ug/
L)
HAA5
(
ug/
L)

LRAA
Pre­
June
2004
Avg.
June
2004
Data
LRAA
June
2004
Avg.
LRAA
Pre­
June
2004
Avg.
June
2004
Data
LRAA
June
2004
Avg.

#
1
65
63
67
40
52
40
#
2
63
72
64
33
59
38
#
3
64
81
68
43
51
46
#
4
49
79
66
40
84
50
1Data
for
sampling
conducted
on
June
2004,
September
2004,
March
2004,
and
December
2003.
Data
relevant
to
peak
excursions
are
bold
and
underlined.

Data
for
June
2004
at
location
#
2
meet
the
criteria
of
significant
excursion.
Specifically,
the
significant
excursion
was
identified
using
the
following
two­
step
procedure:

Monitoring
location
#
2
(
HAA5
Significant
Excursion):

Step
1:
Is
the
quarterly
pre­
June
2004
LRAA
(
HAA5)
>
30
µ
g/
L?
If
yes
a
significant
excursion
is
possible.
Significant
Excursion
Guidance
Manual
ProposalDraft
July
2003
1­
3
The
quarterly
Pre­
June
2004
LRAA
(
HAA5)
is
33
µ
g/
L
(
see
Table
1­
1)
and
is
greater
then
25
µ
g/
L,
thus
a
significant
excursion
is
possible
(
see
definition
of
significant
excursion
in
section
1.1).

Step
2:
Is
the
difference
between
the
quarterly
location
measurement
for
HAA5
and
quarterly
pre­
June
2004
LRAA
(
HAA5)
>
25
µ
g/
L?
If
yes
a
significant
excursion
has
occurred.

Quarterly
location
measurement
is
59
µ
g/
L
and
the
quarterly
Pre­
June
2004
LRAA
(
HAA5)
is
33
µ
g/
L
(
see
data
in
table).

59
­
33
µ
g/
L
=
26
µ
g/
L.

The
difference
between
quarterly
location
measurement
and
quarterly
Pre­
June
2004
LRAA
is
greater
than
25
µ
g/
L,
thus
a
significant
excursion
has
occurred
(
see
definition
of
significant
excursion
in
section
1.1).

1.2
What
Should
Systems
do
to
Address
Significant
Excursions?

A
significant
excursion,
as
defined
above,
is
not
a
violation
of
the
Stage
2
DBPR
and
does
not
require
any
public
notification
or
reporting
as
significant
excursions
or
violations
in
your
Consumer
Confidence
Reports.
Reducing
DBP
concentrations
is
a
primary
objective
of
the
Stage
2
DBPR
and
is
an
important
goal
in
providing
quality
drinking
water.
Chapter
4
of
this
guidance
manual
suggests
operational
improvements,
alternative
disinfection
strategies,
and
DBP
precursor
removal
technologies
that
can
be
used
to
reduce
DBP
concentrations.

The
Stage
2
DBPR
does
require
you
to:

1)
Evaluate
distribution
system
operational
practices
to
identify
opportunities
to
reduce
DBP
levels
(
such
as
tank
management
and
to
reduce
residence
time
and
flushing
programs
to
reduce
disinfectant
demand).

2)
Review
the
evaluation
with
your
State
no
later
than
the
next
sanitary
survey.

Because
it
may
be
a
few
years
between
the
significant
excursion
and
your
next
sanitary
survey,
EPA
strongly
encourages
systems
to
take
immediate
steps
to
identify
and
document
the
cause
of
the
excursion.

1.3
Organization
of
this
Guidance
Manual
This
guidance
manual
is
organized
as
follows:

°
Chapter
1
­
Introduction:
Presents
the
Stage
2
DBPR
requirements
for
addressing
significant
DBP
excursions.
Significant
Excursion
Guidance
Manual
ProposalDraft
July
2003
1­
4
°
Chapter
2
­
Causes
of
Significant
DBP
Excursions:
Identifies
the
most
common
causes
of
significant
DBP
excursions.

°
Chapter
3
­
Identifying
the
Cause
Of
and
Documenting
Your
DBP
Significant
Peak
Excursion:
Provides
a
template
for
documenting
a
significant
excursion
in
addition
to
guidance
for
identifying
the
cause.

°
Chapter
4
­
Best
Management
Practices
and
Distribution
System
Improvements
to
Reduce
DBP
Concentrations:
Summarizes
the
options
available
to
reduce
DBP
significant
concentrations,
including
operational
changes
and
distribution
system
modifications.

°
Chapter
5
­
References
Appendix
A
discusses
the
fundamentals
of
DBP
formation.
Appendices
B
through
E
are
examples
of
completed
evaluation
reports
compiled
when
the
significant
excursion
is
identified
using
the
"
maximum
concentration
approach"
(>
100
µ
g/
L
for
TTHMs
and
>
75
µ
g/
L
for
HAA5).
Appendice
F
is
an
examples
of
completed
evaluation
reports
compiled
when
the
significant
excursion
is
identified
using
the
"
difference
approach."
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
1
2.0
Causes
of
Significant
DBP
Excursions
Significant
excursions
typically
occur
as
a
result
of
changes
in
source
water
quality,
changes
in
treatment
plant
operations
or
as
a
result
of
distribution
system
characteristics
or
changes
that
impact
DPB
levels.
This
chapter
discusses
each
of
these
causes,
and
is
organized
as
follows:

2.1
Fundamentals
of
DBP
Formation
2.2
Impacts
of
Changes
in
Source
Water
Quality
on
DBP
Concentrations
2.3
Impacts
of
Changes
in
Treatment
Plant
Operations
on
DBP
Concentrations
2.4
Impacts
of
Distribution
System
Characteristics
on
DBP
Concentrations
Chapter
3
follows
with
a
guide
to
identifying
causes
of
specific
DBP
excursion
events.

2.1
Fundamentals
of
DBP
Formation
TTHM
and
HAA5
are
primarily
formed
by
the
reaction
of
chlorine
or
chloramines
with
natural
organic
matter
(
NOM).
The
amount
of
TTHM
and
HAA5
formed
is
impacted
by
a
number
of
occurrences
including
the
following
factors:

°
NOM
concentration
°
NOM
characteristics
°
Chlorine
or
chloramine
concentration
°
Concentration
of
other
DBP
precursors
(
e.
g.,
bromide)

°
pH
°
Temperature
°
Reaction
time
(
contact
time)

The
following
sections
discuss
how
each
of
these
factors
affects
the
formation
of
TTHM
and
HAA5
and
how
changes
in
these
parameters
may
result
in
increases
in
TTHM
and
HAA5
concentrations.
Greater
detail
regarding
the
formation
of
TTHM
and
HAA5
is
provided
in
Appendix
A.

2.2
Impacts
of
Changes
in
Source
Water
Quality
on
DBP
Concentrations
Changes
in
source
water
quality
that
affect
the
reaction
between
NOM
and
chlorine
or
chloramines
can
increase
TTHM
and
HAA5
concentrations.
Typically,
changes
that
increase
TTHM
and
HAA5
concentrations
include
the
following
occurrences:
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
2
°
Increase
in
source
water
NOM
°
Increase
in
source
water
temperature
°
Increase
in
source
water
bromide
concentration
°
Changes
in
NOM
characteristics
°
Changes
in
other
source
water
characteristics
(
e.
g.,
pH
or
alkalinity)

°
Change
in
source
of
water
supply
2.2.1
Increase
in
Source
Water
NOM
NOM
is
a
precursor
to
the
formation
of
TTHM
and
HAA5.
Therefore,
increases
in
the
source
water
NOM
concentration
not
addressed
by
adjustments
in
the
treatment
process
can
lead
to
increased
formation
of
TTHM
and
HAA5
both
in
the
plant
and
in
the
distribution
system.

Surface
water
sources
may
have
increases
in
organic
matter
following
periods
of
heavy
rainfall
which
causes
greater
surface
water
runoff.
These
events
do
not
need
to
occur
locally
to
result
in
an
increase
in
NOM.
A
rainfall
event
miles
upstream
from
a
raw
water
intake
can
result
in
increased
NOM
concentrations.
Other
causes
of
increased
NOM
concentrations
include
lake
or
reservoir
turnover,
river
scour,
and
point
source
pollution
(
e.
g.,
wastewater
treatment
plant
discharges,
filter
backwash
or
other
discharges
from
upstream
water
treatment
plants,
and
industrial
discharges).
Some
plant
operation
changes
can
cause
increases
in
source
water
NOM
(
e.
g.,
inadequate
sludge
removal
in
pre­
sedimentation
or
sedimentation
basins).

Figure
2.1
shows
the
effect
of
NOM
concentration
(
measured
as
total
organic
carbon
[
TOC])
and
time
on
TTHM
and
HAA5
concentrations.
As
NOM
concentration
increases,
both
TTHM
and
HAA5
concentrations
also
increase.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
3
Effect
of
Organic
Content
on
TTHM
and
HAA5
Concentration
0
20
40
60
80
100
0.5
1
1.5
2
TOC
(
mg/
L)
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
Figure
2.1
Effect
of
NOM
Concentration
on
TTHM
and
HAA5
Concentration
(
chlorine
dose
4.3
mg/
L)

Source:
A.
Franchi
and
C.
Hill
(
2002).

2.2.1
Increase
in
Source
Water
Temperature
The
rate
of
reaction
between
chlorine
(
and
chloramines)
and
NOM
increases
as
the
water
temperature
increases.
As
a
result,
TTHM
and
HAA5
concentrations
can
be
higher
during
periods
of
warmer
source
water
temperatures.
Most
water
supplies
experience
seasonal
temperature
changes
with
higher
temperatures
in
the
summer
and
early
fall
and
lower
temperatures
in
the
winter
and
early
spring.
The
magnitude
of
the
increase
is
dependent
on
a
number
of
­
specific
factors,
including
source
water
type
(
ground
or
surface
water),
climate,
and
hydrology.

Surface
water
temperatures
are
normally
impacted
by
ambient
temperatures
and
other
environmental
factors,
such
as
rainfall
and
snow
melt,
while
ground
water
temperatures
generally
exhibit
less
seasonal
variability.
Raw
water
storage
can
also
effect
the
source
water
temperature.
Specifically,
long
holding
times
in
raw
water
storage
basins
in
summer
months
can
significantly
increase
temperatures.

Water
temperature
can
also
affect
the
relative
concentrations
of
TTHM
and
HAA5
resulting
in
the
formation
of
proportionally
more
TTHM
or
HAA5.
Figure
2.2
illustrates
this
effect.
In
the
example,
TTHM
is
the
predominant
species
formed
at
a
water
temperature
of
24
°
C.
However,
the
situation
is
reversed
with
greater
HAA5
than
TTHM
concentrations
when
the
water
temperature
reaches
3
°
C.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
4
TTHM
and
HAA5
Concentrations
(
T
=
24
C)

0
20
40
60
80
0
5
10
15
20
25
Water
Age
(
days)
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
TTHM
and
HAA5
Concentrations
(
T
=
3
C)

0
20
40
60
80
0
5
10
15
20
25
Water
Age
(
days)
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
Figure
2.2
Impact
of
Water
Temperature
on
DBP
Speciation
Source:
A.
Franchi
and
C.
Hill
(
2002).

2.2.3
Increase
in
Source
Water
Bromide
Concentration
Some
source
waters
may
experience
periodic
changes
in
bromide
concentration.
For
example,
as
an
aquifer's
water
level
decreases,
the
bromide
concentration
of
ground
water
from
that
aquifer
may
increase,
resulting
in
higher
than
normal
bromide
levels
during
drought
conditions.
As
the
aquifer
is
recharged,
bromide
concentrations
are
diluted
to
normal
levels.
Brackish
water
or
seawater
intrusion
into
ground
water
and
surface
water
sources
due
to
withdrawals
or
drought
conditions
are
other
potential
causes
of
increased
bromide
concentrations.

An
increase
in
the
source
water
bromide
concentration
can
increase
the
formation
of
brominated
THM
and
HAA
species.
This
may
be
accompanied
by
corresponding
decreases
in
chlorinated
THM
and
HAA
species.
However,
it
can
result
in
an
overall
increase
in
TTHM
and
HAA5
concentrations.

Figure
2.3
demonstrates
the
impact
of
bromide
concentration
on
THM
speciation.
The
figure
shows
individual
THM
species
as
a
percent
of
TTHM.
For
this
particular
source
water,
at
low
bromide
concentrations
the
TTHM
concentration
consists
almost
entirely
of
chloroform.
As
the
bromide
concentration
increases,
the
concentration
of
the
brominated
THM
species
increases,
and
is
accompanied
by
a
decrease
in
the
chlorinated
THM
species
(
both
as
a
percent
and
as
a
measured
concentration).
Although
not
shown,
similar
trends
can
occur
for
HAA
species.
Significant
Excursion
Guidance
Manual
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Draft
July
2003
2­
5
Variation
in
TTHM
Speciation
with
Increasing
Influent
Bromide
Concentration
0%
20%
40%
60%
80%
100%

0.035
0.077
0.09
0.17
0.22
Influent
Bromide
(
mg/
L)
Percent
of
TTHM
CHCl3
BDCM
DBCM
CHBr3
Figure
2.3
Impact
of
Bromide
Concentration
on
TTHM
Speciation
Source:
C.
Hill
(
2002).
[
To
be
published.]

2.2.4
Change
in
NOM
Characteristics
The
characteristics
of
NOM
in
a
system
can
have
significant
impacts
on
the
formation
of
DBPs.
NOM
can
be
derived
from
many
sources
in
a
watershed,
such
as
decomposition
of
vegetation
and
dead
organisms.
Water
and
wastewater
treatment
plant
discharges,
agricultural
and
urban
area
runoff,
and
septic
system
leachate
discharge
are
other
potential
sources
of
NOM.

NOM
is
typically
classified
as
either
hydrophilic
(
more
soluble)
or
hydrophobic
(
less
soluble
and
containing
a
greater
aromatic
fraction).
Hydrophilic
NOM
is
more
difficult
to
remove
than
hydrophobic
NOM,
but
also
forms
fewer
DBPs
than
hydrophobic
NOM
(
Liang
and
Singer,
2001).
Therefore,
an
increase
in
the
concentration
of
hydrophobic
NOM
may
be
accompanied
by
an
increase
in
DBP
concentrations.
Potential
causes
which
may
change
the
balance
between
hydrophilic
and
hydrophobic
fractions
of
NOM
include
the
following
events:

°
Rain
events
that
can
wash
organic
matter
of
terrestrial
origin
(
normally
more
hydrophilic)
into
a
receiving
water
body.

°
Algal
blooms
that
result
in
the
production
of
aquagenic
organic
matter
(
more
hydrophobic).

°
Surface
water
intrusion
into
ground
water
supplies
which
can
affect
the
composition
of
NOM
in
the
blended
water.
Significant
Excursion
Guidance
Manual
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July
2003
2­
6
Effect
of
pH
on
TTHM
Formation
0
10
20
30
40
50
60
0
50
100
150
Time
(
hours)
TTHM
(
ug/
L)
pH
=
7.5
pH
=
9
2.2.5
Changes
in
Other
Source
Water
Characteristics
Changes
in
other
source
water
characteristics,
such
as
pH
or
alkalinity,
can
impact
TTHM
and
HAA5
formation.
Increases
in
pH
can
affect
DBP
formation
in
several
ways.
Most
coagulation
processes
using
metal
salts,
such
as
alum
and
ferric
chloride,
are
optimized
at
pH
less
than
7.
Therefore,
increases
in
source
water
pH
may
be
detrimental
to
the
coagulation
process
(
assuming
no
pH
control
is
available
at
the
treatment
plant),
resulting
in
less
NOM
removal
and
leaving
more
NOM
available
for
reaction
with
chlorine
or
other
disinfectants
downstream
in
the
treatment
process.

Increasing
pH
conditions
typically
lead
to
increasing
TTHM
and
decreasing
HAA5
concentrations.
Figures
2.4
(
for
TTHM
only)
and
2.5
(
for
TTHM
and
HAA5)
illustrates
this
effect.
It
is
worth
mentioning
that
many
plants
adjust
pH
to
above
7
for
corrosion
control
and,
thus
affect
the
balance
between
TTHM
and
HAA5
concentrations.

Figure
2.4
Effect
of
pH
on
TTHM
Formation
Source:
Plot
obtained
using
the
mathematical
model
developed
by
Amy
et
al.
(
1987).
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
7
7.6
8.8
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
pH
Effect
of
pH
on
TTHMs
and
HAA5
Concentrations
HAA5
TTHMs
Figure
2.5
Effect
of
pH
on
TTHM
and
HAA5
Formation
(
results
obtained
through
SDS
tests,
DBPs
measured
after
a
time
correspondent
to
plant
effluent,
the
chlorine
residual
after
application
was
2.3
mg/
L)

Source:
Data
from
Franchi
et
al.,
2002
Increases
in
source
water
alkalinity
can
also
result
in
an
increase
in
TTHM
and
HAA5
concentrations.
Alkalinity
serves
as
a
buffer
and
minimizes
the
reduction
in
pH
which
typically
results
from
the
addition
of
a
coagulant
during
the
treatment
process.
High
alkalinity
can
reduce
NOM
removal
during
treatment
as
a
result
of
the
higher
process
pH.

2.2.6
Change
in
Raw
Water
Supply
Seasonal
changes
in
source
water
supplies
or
the
use
of
a
temporary
water
supply
may
also
result
in
an
increase
in
TTHM
and
HAA5
concentrations.
For
example,
a
system
that
supplements
a
low­
NOM
ground
water
source
with
surface
water
supply
during
the
summer
may
experience
increases
in
DBPs
as
a
result
of
increased
source
water
NOM,
or
increases
in
source
water
temperature
(
surface
water
supplies
are
typically
warmer
than
ground
water
supplies
during
summer
months).
On
the
other
hand,
a
system
that
supplements
its
surface
water
supply
with
high­
bromide
ground
water
may
also
experience
an
increase
in
DBP
concentrations.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
8
2.3
Impacts
of
Changes
in
Treatment
Plant
Operations
on
DBP
Concentrations
Changes
or
deficiencies
in
treatment
practices
can
increase
TTHM
and
HAA5
concentrations.
This
section
describes
the
potential
impact
of
common
changes
in
treatment
processes,
including
the
following
common
treatment
units:

°
Pretreatment
°
Coagulation/
flocculation
°
Settling
°
Filtration
°
Disinfection
Lastly,
this
section
discusses
the
impact
of
treatment
plant
shutdowns
on
DBP
formation.

2.3.1
Pretreatment
The
primary
causes
of
increased
TTHM
and
HAA5
formation
resulting
from
the
pretreatment
process
include:

°
Increases
in
raw
water
storage
holding
time
°
Poorly
controlled
or
excessive
pre­
chlorine
dose
°
Change
in
oxidant
As
previously
discussed,
the
rate
of
TTHM
and
HAA5
formation
increases
as
temperature
increases.
Long
detention
times
in
raw
water
storage
basins
may
cause
source
water
temperature
to
increase
and
consequently,
increase
the
amount
of
TTHM
and
HAA5
formed.

Pre­
oxidation
of
raw
water
with
chlorine
is
a
common
practice
used
for
several
reasons,
including
color
removal,
taste
and
odor
control,
iron
and
manganese
removal,
hydrogen
sulfide
control
and
removal,
and
coagulation
enhancement.
However,
because
of
the
large
concentration
of
NOM
and
the
long
residence
time
available
for
the
reaction
with
chlorine
adding
chlorine
to
the
raw
water
can
result
in
high
DBP
concentrations.
Figure
2.6
illustrates
that
greater
DBP
concentrations
are
produced
when
chlorine
is
added
to
the
raw
water
than
when
added
to
the
settling
basin
effluent.

Figure
2.6
Effect
of
Pre­
Chlorination
on
In­
Plant
DBP
Formation
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
9
Effect
of
Pre­
Chlorination
on
In­
Plant
DBP
Formation
0
5
10
15
20
25
30
Pre­
chlorination
Post­
sedimentation
point
of
chlorine
addition
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
(
results
obtained
through
SDS
tests,
DBPs
measured
after
a
time
correspondent
to
plant
effluent,
the
chlorine
residual
after
application
was
1.5
mg/
L)

Source:
A.
Franchi
and
C.
Hill
(
2002).

An
increase
in
the
chlorine
dosage
can
increase
TTHM
and
HAA5
concentrations.
High
chlorine
dosages
may
be
intentionally
applied
during
periods
of
algal
bloom
for
the
control
of
color,
taste,
and
odor.
There
can
also
be
unintentional
results
of
poor
chemical
feed
regulation
amplified
by
a
decrease
in
water
volume
processed
by
the
plant
or
equipment
failure.
Changes
in
the
plant
process
which
involve
the
use
of
pre­
oxidation
with
chlorine
(
i.
e.,
for
arsenic
treatment)
may
also
increase
DBP
formation.
Figure
2.7
demonstrates
the
impact
of
the
chlorine
dose
on
in­
plant
DBP
formation.

A
change
in
the
pre­
oxidant
type
may
result
in
an
increase
in
DBP
concentrations.
Systems
that
change
from
using
potassium
permanganate
as
a
pre­
oxidant
(
which
does
not
form
TTHM
and
HAA5)
to
using
chlorine
for
disinfection
credit
may
experience
increases
in
TTHM
and
HAA5
as
a
result.
Similarly,
systems
that
switch
from
chlorine
to
ozone
will
likely
experience
a
decrease
in
plant
TTHM
and
HAA5
concentrations.
However,
ozonation
can
result
in
increases
in
bromate
concentrations
(
also
a
regulated
DBP)
in
systems
with
sufficient
bromide
present
in
the
source
water.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
10
Effect
of
Chlorine
Dose
on
In­
Plant
DBP
Formation
20
25
30
35
40
45
50
2
2.5
3
3.5
Chlorine
Dose
(
mg/
L)
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
Figure
2.7
Impact
of
Increasing
Chlorine
Dose
on
In­
Plant
DBP
Formation
(
results
obtained
through
SDS
simulations,
DBPs
measured
after
a
time
correspondent
to
plant
effluent,
the
chlorine
added
after
flash­
mixing,
residual
after
application
was
1.5
mg/
L)

Source:
A.
Franchi
and
C.
Hill
(
2002).

2.3.2
Coagulation/
Flocculation
The
primary
causes
of
increased
TTHM
and
HAA5
formation
during
the
coagulation/
flocculation
process
include
the
following
events:

°
Changes
in
the
raw
water
matrix
that
are
not
adequately
addressed
with
process
control.

°
Spikes
in
the
influent
NOM
concentration
(
e.
g.,
when
backwash
water
is
returned
to
the
plant
influent)
that
are
not
addressed
by
treatment
process
adjustments
(
e.
g.,
coagulant
dose).

°
Poor
regulation
of
coagulant
feed
rate
or
coagulant
equipment
failure.

°
Poor
regulation
of
chemicals
(
including
lime,
caustic,
or
acid)
used
to
control
pH
and/
or
chemical
feed
equipment
failure.

The
coagulant
type
(
e.
g.,
alum
or
ferric
chloride)
and
dose
are
critical
to
the
effective
removal
of
NOM.
An
inadequate
coagulant
dose
or
poorly
selected
coagulant
may
result
in
a
larger
fraction
of
NOM
passing
through
the
coagulation/
flocculation
and
settling
processes.
This
increased
NOM
concentration
can
lead
to
increased
formation
of
TTHM
and
HAA5.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
11
Filter
backwash
may
contain
elevated
concentrations
of
NOM.
If
no
additional
treatment
(
e.
g.,
coagulation/
settling)
of
recycled
backwash
water
is
provided,
it
is
important
to
adjust
the
coagulant
dose
to
account
for
the
resulting
increase
in
NOM.
Similarly,
if
an
increase
in
source
water
NOM
is
not
accompanied
by
a
corresponding
increase
in
the
coagulant
dose,
additional
NOM
will
likely
be
present
at
the
point
of
chlorination
and
will
likely
increase
TTHM
and
HAA5
formation.

During
coagulation,
pH
variations
can
affect
NOM
removal
and
DBP
formation.
Generally,
NOM
removal
decreases
as
pH
increases.
If
less
NOM
is
removed
during
the
coagulation
process,
then
more
NOM
is
available
for
TTHM
and
HAA5
formation
in
the
downstream
treatment
process
(
see
Figure
2.1).
Since
higher
pHs
favor
THM
formation
reactions,
increasing
pH
tends
to
increase
TTHM
levels
in
relation
to
HAA5
(
see
Figures
2.4
and
2.5).

2.3.3
Settling
If
a
chlorine
residual
is
carried
through
the
settling
basin,
TTHM
and
HAA5
levels
can
increase
as
a
result
of:

°
Poor
regulation
of
chlorine
dose
due
to
improper
feed
rate
control
or
equipment
failure
°
Increased
holding
time
for
settling
due
to
reductions
in
plant
flow
Both
of
these
circumstances,
independently
or
in
combination,
can
cause
increases
in
TTHM
and
HAA5
concentrations.
The
effects
of
increasing
chlorine
dose
on
TTHM
and
HAA5
levels
have
been
previously
illustrated
in
Figure
2.7.

Process
changes
can
still
result
in
the
occurrence
of
peak
TTHM
or
HAA5
even
if
the
chlorine
residual
is
not
carried
through
the
settling
basin(
s).
For
example,
poor
or
inadequate
removal
of
sludge
from
the
settling
basin,
as
well
as
maintenance
in
the
basin
that
stirs
or
moves
the
sludge,
can
release
soluble
or
particulate
NOM.
This
"
additional"
NOM
load
is
available
for
reaction
with
chlorine
in
the
basin,
or
may
be
carried
through
the
settling
process
to
the
point
of
disinfection
addition.

2.3.4
Filtration
Increases
in
organic
loading
during
a
filter
cycle,
or
the
breakthrough
of
particles
at
the
end
of
the
filter
cycle
run,
result
in
an
increase
of
DBPs
entering
the
distribution
system.
When
biologically
active
filters
and
granular
activated
carbon
(
GAC)
filters
are
used
for
organic
precursors
removal,
breakthroughs
may
be
a
concern
because
soluble
organic
compounds
can
be
released.
Likewise,
when
GAC
columns
are
used
for
DBP
removal
after
chlorination,
exhaustion
of
adsorptive
capacity
may
result
in
sudden
TTHM
and
HAA5
peak
concentrations
in
the
finished
water.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
12
2.3.5
Disinfection
The
following
disinfection
related
events
can
increase
the
formation
of
TTHM
and
HAA5:

°
Increased
chlorine
dose
and/
or
residual
(
intentional
or
unintentional)

°
Increased
holding
time
of
water
in
the
clearwell
°
Changing
point
of
chlorine
addition
°
Changes
in
primary
disinfectant
type
°
Free
chlorine
"
burnout"
periods
in
chloraminated
systems
Systems
are
required
by
the
Surface
Water
Treatment
Rule
(
SWTR),
Interim
Enhanced
Surface
Water
Treatment
Rule
(
IESWTR)
and
Long
Term
1
Enhanced
Surface
Water
Treatment
Rule
(
LT1ESWTR)
to
maintain
a
certain
level
of
CT
(
disinfectant
residual
×
contact
time)
for
disinfection.
As
the
disinfectant
dose
decreases,
the
required
contact
time
increases
to
maintain
a
required
level
of
CT,
and
vice
versa.
An
increase
in
the
disinfectant
dose
(
particularly
chlorine)
can
increase
TTHM
and
HAA5
concentrations.
The
change
in
disinfectant
dose
may
be
intentional
or
unintentional.
For
example,
systems
that
control
the
disinfectant
dose
manually
and
not
based
on
plant
flow
may
experience
increases
in
TTHM
and
HAA5
if
the
plant
flow
rate
suddenly
decreases
or
the
dose
is
not
adjusted
frequently
to
account
for
reductions
in
plant
flow.
In
such
instances,
those
systems
would
likely
be
overdosing
chlorine.
On
the
other
hand,
a
system
may
intentionally
increase
the
dose
to
account
for
a
decrease
in
water
temperature
and
maintain
the
required
CT
(
CT
requirements
increase
as
water
temperature
decreases).
Figure
2.8
shows
the
impact
of
residence
time
on
TTHM
concentrations
at
two
disinfectant
residual
concentrations.
The
effect
of
residence
time
on
HAA5
concentrations
is
similar,
but
less
pronounced.
In
other
words,
HAA5
formation
occurs
more
rapidly
and
may
not
increase
as
significantly
as
TTHM
over
long
periods
of
time
(
particularly
in
chloraminated
systems).
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
13
Effect
of
Disinfectant
Residual
on
TTHM
Concentration
0
5
10
15
20
25
30
35
40
45
0
25
50
Distribution
System
Residence
Time
(
hours)
TTHM
(
ug/
L)
Chlorine
=
1
mg/
L
Chlorine
=
3
mg/
L
Figure
2.8
Effect
of
Disinfectant
Residual
and
Residence
Time
on
TTHM
Source:
Plot
obtained
using
the
mathematical
model
developed
by
Amy
et
al.
(
1987).

Poor
mixing
in
the
clearwell
can
result
in
dead
zones
where
the
hydraulic
residence
time
is
significantly
higher
than
the
residence
time
of
the
bulk
of
the
water
passing
through
the
clearwell.
As
a
result
of
the
increased
contact
(
i.
e.,
reaction)
time,
TTHM
and
HAA5
concentrations
may
be
significantly
higher
in
the
dead
zones.
Section
2.4
discusses
this
issue
in
greater
detail.
A
reduction
in
system
demand
(
particularly
in
a
system
with
little
or
no
storage
beyond
the
clearwell)
may
also
result
in
longer
hydraulic
residence
times
in
the
clearwell
and
increased
TTHM
and/
or
HAA5
concentrations.

In
addition
to
changes
in
detention
time
and
dose
in
the
clearwell,
changing
the
point
of
chlorine
(
or
other
disinfectant)
addition
can
have
a
significant
impact
on
TTHM
and
HAA5
formation.
Systems
that
practice
pre­
chlorination
(
i.
e.,
addition
of
chlorine
to
raw
water)
will
likely
form
more
TTHM
and
HAA5
as
a
result
of
the
higher
NOM
content
of
the
water
prior
to
coagulation
and
clarification,
as
well
as
the
increased
contact
time
through
the
treatment
plant.
Similar
effects
are
likely
for
systems
that
add
chlorine
to
the
rapid
mix
basin,
as
NOM
typically
has
not
yet
been
removed
from
the
raw
water
at
this
point
in
the
treatment
plant.
Systems
that
add
chlorine
following
clarification,
or
post­
filtration,
will
likely
experience
lower
TTHM
and
HAA5
concentrations
because
of
the
removal
of
NOM
prior
to
chlorine
addition.

Figure
2.9
shows
the
effect
of
the
point
of
chlorination
on
treatment
plant
TTHM
and
HAA5
concentrations.
As
shown
in
the
figure,
there
is
little
difference
in
TTHM
and
HAA5
between
pre­
chlorination
and
rapid
mix.
This
is
primarily
due
to
the
fact
that
no
NOM
has
been
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
14
Effect
of
Alternative
Locations
for
Chlorine
Addition
Point
on
In­
Plant
DBP
Formation
0
5
10
15
20
25
30
Prechlorination
Rapid
Mix
Postflocculation
Postsedimentation
point
of
chlorine
addition
TTHM
or
HAA5
(
ug/
L)

TTHM
HAA5
removed
from
the
water
at
this
point
in
the
treatment
process.
However,
when
the
point
of
chlorine
addition
is
moved
to
post­
sedimentation,
in­
plant
TTHM
and
HAA5
concentrations
are
reduced
by
greater
than
70%
and
50%,
respectively.

Figure
2.9
Effect
of
Point
of
Chlorination
on
TTHM
and
HAA5
Concentrations
Source:
A.
Franchi
and
C.
Hill
(
2002).

Systems
that
change
the
point
of
chlorine
addition
seasonally
to
adjust
for
changes
in
raw
water
quality
may
experience
fluctuations
in
DBPs
as
a
result
of
those
changes.
For
example
systems
where
pre­
chlorination
is
used
seasonally
to
control
taste
and
odor
may
see
increases
in
TTHM
and
HAA5
concentrations
during
those
periods.

Many
systems
have
converted
to
chloramines
for
secondary
disinfection
to
reduce
TTHM
and
HAA5
formation.
Use
of
chloramines
can
lead
to
nitrification
in
the
distribution
system,
causing
microbiological
and
taste
and
odor
problems.
Some
chloraminated
systems
periodically
switch
to
free
chlorine
for
a
"
burnout"
period
to
inactivate
the
nitrifying
bacteria.
During
these
burnout
periods,
systems
may
experience
temporary
increases
in
TTHM
and
HAA5
concentrations.

2.3.6
Plant
Shutdowns
Plant
shutdowns
and
routine
start/
stop
operations
can
lead
to
peak
TTHM
and
HAA5
concentrations.
During
shutdowns,
the
holding
time
of
chlorinated
water
within
the
plant
can
be
long
and
result
in
the
formation
of
higher
than
normal
TTHM
and
HAA5
concentrations.
When
the
plant
is
placed
back
in
service,
water
containing
high
TTHM
and
HAA5
levels
may
enter
the
distribution
system.
Similar
increases
in
TTHM
and
HAA5
concentrations
may
be
observed
at
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
15
the
beginning
of
each
working
cycle
at
plants
that
operate
less
than
24
hours
per
day.
Effect
of
filter
spikes
coagulation
not
optimized
in
start/
stop
operations.
Even
small
start
spikes
can
increase
NOM.
In
these
plants,
the
residence
time
can
be
extremely
long.
If
a
plant
practices
pre­
chlorination,
significant
concentrations
of
TTHM
and
HAA5
may
form
in
the
treatment
plant.

2.4
Impacts
of
Distribution
System
Characteristics
on
DBP
Concentration
This
section
discusses
distribution
system
conditions
which
may
result
in
higher
than
normal
formation
of
TTHM
and
HAA5.
Specifically,
this
section
discusses:

°
Poor
mixing
and
inadequate
volume
turnover
in
storage
tanks
°
Dead
ends
and
stagnant
zones
in
the
distribution
system
°
Use
of
booster
disinfection
°
System
maintenance
activities
2.4.1
Poor
Mixing
and
Inadequate
Volume
Turnover
in
Storage
Tanks
To
illustrate
water
quality
problems
associated
with
storage
tanks,
Table
2.1
presents
free
chlorine,
TTHM,
and
HAA5
concentrations
at
the
top
and
bottom
of
three
tanks.
Each
tank
has
a
common
inlet/
outlet
located
at
the
bottom
of
the
tank.
Each
tank
is
also
poorly
mixed,
as
evidenced
by
the
difference
in
free
chlorine
concentrations
at
the
top
and
bottom
of
the
tank,
but
each
has
a
different
associated
water
quality
problem.

Table
2.1
Free
Chlorine,
TTHM,
and
HAA5
Data
for
Five
Storage
Tanks
Tank
No.
Free
Cl2
@
Top
of
Tank
Free
Cl2
@
Bottom
of
Tank
TTHM
@
Top
of
Tank
TTHM
@
Bottom
of
Tank
HAA5
@
Top
of
Tank
HAA5
@
Bottom
of
Tank
1
0.3
1.3
110
72
57
61
2
0.2
1.0
130
59
12
44
3
0.0
1.0
98
99
31
61
Source:
Mahmood
(
2002).
[
To
be
published.]

Tank
1
Free
chlorine
concentration
is
relatively
low
at
the
top
of
the
tank.
TTHM
concentration
is
higher
in
the
top
of
the
tank.
HAA5
concentration
is
fairly
consistent
indicating
HAA5
formation
has
stopped,
or
more
likely
the
early
stages
of
biodegradation
of
HAA5.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
16
Tank
2
Like
Tank
1,
TTHM
concentration
has
increased
in
the
top
of
the
tank,
but
biodegradation
of
HAA5
has
clearly
begun.

Tank
3
Based
on
TTHM
data,
it
would
appear
the
tank
is
well
mixed.
However,
the
difference
in
free
chlorine
and
HAA5
concentrations
indicate
otherwise.
This
demonstrates
the
importance
of
looking
at
multiple
parameters
when
evaluating
mixing
in
storage
tanks.

Under
normal
daily
operation,
older
water
or
unmixed
portions
of
the
stored
water
at
the
top
of
these
tanks
may
not
be
utilized.
However,
events
such
as
a
main
break
or
fire
flow
can
draw
water
from
the
portions
of
the
tank
with
high
water
age
(
and
high
TTHM
and/
or
HAA5
concentrations)
into
the
distribution
system.

2.4.2
Dead
Ends
and
Stagnant
Zones
in
the
Distribution
System
Dead
ends
in
a
distribution
system
can
lead
to
excessive
water
age.
A
dead
end
may
be
the
result
of
distribution
piping
configuration
(
e.
g.,
the
actual
end
of
a
long
pipe
with
few
connections)
or
valving
configuration
(
e.
g.,
a
closed
valve
that
prevents
flow
from
one
area
to
another).

The
water
age
in
a
stagnant
zone
can
also
be
very
high.
Stagnant
zones
are
created
when
water
flow
from
opposing
directions
meets
at
a
location
where
there
is
little
or
no
water
demand.
There
is
no
net
water
movement
in
any
direction
in
that
particular
location
and,
therefore,
fresh
water
cannot
flow
to
a
stagnant
zone
from
other
areas.
When
there
is
an
unusual
shift
in
water
demand
pattern
in
the
vicinity
of
a
stagnant
zone,
high
age
water
from
the
stagnant
areas
can
flow
to
other
parts
of
the
distribution
system
and
become
available
for
consumption.
The
shift
in
water
demand
pattern
can
be
due
to
several
factors
including:
unusually
high
water
demand
(
e.
g.
large
customers
on/
off
line);
increased
seasonal
demand;
changes
in
the
water
pressure,
or
flow
patterns
and
flow
rates
(
e.
g.,
when
a
seasonal
groundwater
source
is
directly
fed
into
the
distribution
system).

Figure
2.10
shows
the
effect
of
distribution
system
residence
time
on
TTHM
concentrations
for
both
free
chlorine
and
chloraminated
systems.
Note
that
the
effect
of
water
age
is
more
dramatic
for
chlorine
systems
than
for
chloramine
systems
(
see
Appendix
A
for
a
discussion
of
formation
kinetics).
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
17
Relationship
Between
TTHM
Concentrations
and
Distribution
System
Residence
Time
40
80
120
160
200
0
10
20
30
40
50
60
Residence
Time
(
hours)
TTHM
(
ug/
L)
Free
Chlorine
Chloramines
Figure
2.10
Relationship
Between
TTHM
and
Distribution
System
Residence
Time
Source:
A.
Franchi
and
C.
Hill
(
2002).

2.4.3
Booster
Disinfection
Booster
disinfection
is
often
used
to
maintain
a
disinfectant
residual
in
sections
of
a
distribution
system
that
might
not
otherwise
maintain
a
residual.
In
some
cases,
booster
disinfection
is
used
on
an
intermittent
basis
based
on
water
quality
conditions.
For
example,
the
loss
of
chlorine
residual
in
certain
sections
of
a
distribution
system
may
be
due
to
a
seasonal
change
in
the
source
water,
changes
in
the
water
demand,
or
may
occur
during
the
summer
when
higher
temperatures
promote
microbial
growth
and
increase
chlorine
demand,
warranting
use
of
booster
chlorination.

When
properly
controlled
and
coordinated
with
the
treatment
plant
disinfection
process,
booster
disinfection
can
be
used
to
reduce
average
distribution
system
DBP
concentrations.
To
accomplish
this,
the
disinfectant
dose
applied
at
the
plant
must
be
minimized
to
reduce
DBP
formation
while
maintaing
the
necessary
residual
in
the
distribution
system
prior
to
the
boosting
station.
The
booster
disinfectant
dose
is
then
added
to
maintain
a
residual
to
the
end
of
the
system.

While
booster
disinfection
can
reduce
system
average
DBP
concentrations,
DBPs
are
likely
to
increase
after
booster
disinfection
is
applied.
Table
2.2
illustrates
this
point,
showing
DBP
concentrations
for
locations
before
and
after
booster
disinfection.
Prior
to
booster
disinfection
(
water
age
=
24
to
40
hours),
the
TTHM
concentration
remained
fairly
constant
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
2­
18
because
the
disinfectant
residual
was
nearly
depleted.
On
the
other
hand,
as
the
disinfectant
residual
depleted
(
suggesting
microbiological
activity),
the
HAA5
concentration
decreased
substantially.
After
booster
chlorination,
both
TTHM
and
HAA5
concentrations
increased
(
HAA5
increased
beyond
the
concentrations
present
before
biodegradation).

Table
2.2
Effect
of
Booster
Chlorination
on
TTHM
and
HAA5
Concentrations
(
Concentrations
measured
at
various
locations
in
the
distribution
system)

Before
Booster
Chlorine
Addition
After
Booster
Chlorine
Addition
Water
Age
(
Hours)
2
24
40
41
50
70
TTHMs
(
ppb)
66
130
150
160
170
170
HAA5
(
ppb)
41
47
7
77
95
71
Free
Chlorine
Residual
(
mg/
L)
2.6
0.3
0.0
1.0
2.2
0.5
Source:
A.
Franchi
and
C.
Hill
(
2002)

The
location
of
the
booster
station
can
also
impact
the
effectiveness
of
booster
disinfection
at
reducing
system
average
DBP
levels.
The
use
of
several
smaller
booster
stations
closer
to
the
end
of
the
system
may
be
more
effective
in
reducing
system
average
DBP
levels
compared
to
a
single
large
station
that
treats
a
much
larger
percentage
of
the
system
water,
some
of
which
may
not
need
additional
disinfection.
Several
smaller
booster
stations
can
also
allow
the
total
amount
of
added
disinfectant
to
be
reduced
compared
to
a
single
large
booster
station.

2.4.4
System
Maintenance
Activities
Disinfection
of
new
or
repaired
distribution
system
piping
is
typically
accomplished
using
a
highly
concentrated
(>
25
ppm)
chlorine
solution.
Failure
to
properly
flush
a
section
of
new
or
repaired
pipe
before
placing
it
into
service
can
introduce
excessive
amounts
of
chlorine
to
the
distribution
system
and
result
in
short­
term
spikes
in
TTHM
and
HAA5
concentrations.
AWWA
Standard
C651­
99,
Disinfecting
Water
Mains,
provides
more
detailed
information
regarding
the
disinfection
of
new
and
repaired
distribution
system
piping.

Frequently,
pipe
repair
work
is
accompanied
by
the
closure
of
valves
to
isolate
sections
of
pipes.
This
changes
the
flow
patterns
in
surrounding
areas
of
the
distribution
system,
which
can
potentially
cause
stagnant
water
with
high
DBP
levels
to
flow
into
areas
of
the
distribution
system
serving
customers.
Also,
after
repair
work
is
completed,
the
repair
crew
may
fail
to
open
all
the
valves
that
were
closed
due
to
construction
work
which
can
create
artificial
dead
ends.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
1
3.0
Identifying
the
Cause
Of
and
Documenting
a
DBP
Significant
Peak
Excursion
Under
the
Stage
2
DBPR,
if
a
significant
excursion
occurs,
systems
are
required
to
evaluate
distribution
system
operations
to
identify
opportunities
to
reduce
DBP
levels
and
discuss
the
evaluation
with
the
State
no
later
than
the
next
sanitary
survey
(
40
CFR
141.626).
This
chapter
provides
guidelines
to
help
identify
the
cause
of
an
excursion
event
and
presents
a
template
for
documenting
the
evaluation
of
it
(
referred
to
as
a
"
Significant
Excursion
Evaluation
Report").
Distribution
system
best
management
practices
that
can
be
implemented
to
reduce
peak
DBP
concentrations
are
discussed
in
Chapter
4.

The
Significant
Excursion
Evaluation
Report
form
begins
on
page
3­
3.
A
supplemental
form
for
recording
water
quality
data
is
presented
on
page
3­
13.
While
the
use
of
these
forms
is
not
required,
a
significant
excursion
evaluation
report
should
be
detailed
enough
to
provide
information
regarding
the
location
and
cause
of
the
excursion,
as
well
as
any
proposed
changes
or
actions
intended
to
prevent
the
reoccurrence.
At
a
minimum,
the
documentation
should
include:

1.
Location,
date,
and
time
that
the
excursion
sample(
s)
was
collected.
(
Were
multiple
excursions
recorded
during
this
sampling
period?
If
so,
and
it
is
believed
the
excursions
are
related,
only
one
report
is
needed.)

2.
Schematic
or
map
showing
the
location
of
each
excursion
relative
to
the
distribution
system
and
treatment
plant(
s).

3.
Summary
of
monitoring
results
from
this
sampling
period.

4.
Historical
summary
of
DBP
concentrations
at
the
excursion
sample
location(
s).
(
Has
this
sample
location
had
a
significant
excursion
before?
If
yes,
when
did
the
previous
excursion(
s)
occur?)

5.
Perceived
cause
of
the
significant
excursion.
The
template
in
this
chapter
includes
a
checklist
to
help
identify
the
cause(
s)
of
the
peak.

6.
Steps
taken
or
planned
to
reduce
future
peaks.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
2
Examples
of
peak
excursion
evaluation
reports
and
completed
checklists
are
provided
in
the
appendices:

Appendix
Cause
of
Significant
Peak
Excursion
B
Changes
in
source
water
quality
C
Changes
in
treatment
plant
operation
D
Changes
in
distribution
system
operation
E
Changes
in
treatment
plant
and
distribution
system
operation
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
3
Significant
Excursion
Report
date:

Evaluation
Report
Report
prepared
by:

Page
1
System
name:

1)
When
was
the
significant
excursion
sample(
s)
collected?
What
were
the
TTHM
and
HAA5
concentrations?

Location
No.
#
#
#
#

Location
description
Sample
collection
date
Sample
collection
time
TTHM
LRAA
Concentration
(
ug/
L)

TTHM
Concentration
(
ug/
L)

HAA5
LRAA
Concentration
(
ug/
L)

HAA5
Concentration
(
ug/
L)

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

2)
Where
did
the
excursion(
s)
occur?
Attach
a
schematic
of
your
system,
sketch
your
system
in
the
space
below,
or
have
a
schematic
of
your
system
available
to
review
with
your
state
at
the
time
of
your
next
sanitary
survey.
Indicate
the
location(
s)
of
the
significant
excursion(
s)
on
your
schematic.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
4
Significant
Excursion
Evaluation
Report
Page
2
Report
date:

3)
Attach
(
or
provide
in
the
Supplemental
Data
Form)
all
available
water
quality
data
for
the
round
of
sampling
in
which
the
significant
excursion
occurred.
At
a
minimum,
include
all
TTHM
and
HAA5
results
from
the
sampling
period.
You
should
also
consider
including
pH,
temperature,
alkalinity,
TOC,
disinfectant
residual,
and
any
other
data
that
you
think
would
be
useful.

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

Yes
No
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

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

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

5)
What
caused
your
excursion(
s)
to
occur?

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

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

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

6)
List
steps
taken
or
planned
to
reduce
DBP
peak
levels.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
6
Significant
Excursion
Evaluation
Report
Page
4
Report
date:

A.
Source
Water
Quality
Changes
°
Did
any
of
the
events
listed
below
take
place
before
the
DBP
excursion
to
cause
TOC
levels
to
increase?
 
Heavy
rain
fall
 
Flooding
 
Spring
snow­
melt/
runoff
 
Significant
decrease
in
rainfall
or
source
flow
 
Algae
bloom
 
Reservoir
turnover
°
Did
any
of
the
events
listed
below
take
place
before
the
DBP
excursion
to
cause
bromide
levels
to
increase?
 
Significant
decrease
in
rainfall
or
source
flow
 
Brackish
or
seawater
intrusion
°
Did
pH
and/
or
alkalinity
significantly
change?

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

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

Conclusions:

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

Yes
No
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
7
Significant
Excursion
Evaluation
Report
Page
5
Report
date:

B.
Process
Upset
at
Treatment
Plant
°
Was
raw
water
stored
for
an
unusually
long
time,
providing
additional
contact
time
for
DBP
formation
after
prechlorination?

°
Were
there
changes
in
coagulation
practices?
S
Were
there
any
changes
or
malfunctions
of
the
coagulation
process
in
the
days
leading
to
the
excursion?
S
Were
the
coagulant
dose
and
pH
properly
adjusted
for
incoming
source
water
conditions?
S
Were
there
any
feed
pump
failures,
or
were
feed
pumps
operating
at
improper
feed
rate?

°
Were
there
changes
in
chlorination
practices?
 
Were
there
any
changes
in
chlorine
dose
at
any
location
in
the
plant?
 
Were
there
changes
in
plant
flow
that
may
have
resulted
in
longer
than
normal
residence
time
at
any
location
in
the
plant?
S
Did
the
pH
change
at
the
point
of
chlorine
addition?
S
Were
there
any
feed
pump
failures,
or
were
feed
pumps
operating
at
improper
feed
rate?

°
Were
there
changes
in
settling
practices?
S
Was
there
excess
sludge
build­
up
in
the
settling
basin
that
may
have
carried
over
to
the
point
of
disinfectant
addition?
S
Was
there
any
disruption
in
the
sludge
blanket
that
may
have
resulted
in
carryover
to
the
point
of
disinfection?
S
Were
there
large
changes
in
plant
flow
rate
that
may
have
resulted
in
a
decrease
in
settling
time
or
carry
over
of
process
solids?

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

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

°
Were
there
any
other
equipment
failures
or
process
upsets?

Continued
on
next
page
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
8
Significant
Excursion
Evaluation
Report
Page
6
Report
date:

B.
Process
Upset
at
Treatment
Plant
(
Continued)

Conclusions:

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

Yes
No
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
9
Significant
Excursion
Evaluation
Report
Page
7
Report
date:

C.
Planned
Change
or
Maintenance
Activities
for
the
Treatment
Plant
°
Was
there
a
recent
change
(
or
addition)
of
pre­
oxidant?

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

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

°
Were
there
any
changes
in
disinfection
practices
in
the
days
prior
to
the
excursion?
S
For
example,
a
switch
from
chloramines
to
free
chlorine
for
burnout
period.
S
Discontinuation
of
ozone.
S
Prechlorination
affecting
biological
filtration
°
Was
a
filter(
s)
taken
off­
line
for
an
extended
period
of
time
that
caused
the
other
filters
to
operate
near
maximum
design
capacity
and
creating
the
conditions
for
possible
breakthrough?

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

Conclusions:

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

Yes
No
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
10
Significant
Excursion
Evaluation
Report
Page
8
Report
date:

D.
Planned
Distribution
System
Operations
or
Maintenance
Activities
°
Was
a
tank
drained
for
cleaning
or
other
maintenance?
S
Was
the
tank
drained
to
waste
or
to
the
distribution
system?
S
Was
the
tank
returned
to
service
directly
to
the
system
after
disinfection
with
a
high
residual
remaining
S
Was
a
larger
volume
than
normal
drained
to
the
distribution
system?

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

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

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

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

Conclusions:

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

Yes
No
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
11
Significant
Excursion
Evaluation
Report
Page
9
Report
date:

E.
Unplanned
Distribution
System
Events
°
Were
there
increases
in
demand
that
caused
older
water
in
storage
tanks
to
be
drawn
into
the
system?
S
Were
there
any
major
fire
events?
S
Did
one
or
more
storage
tank
have
greater
than
average
drawdown
preceding
the
time
of
DBP
peak
excursion?

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

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

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

°
Were
any
storage
tanks
hydraulically
or
mechanically
isolated
from
the
system
for
an
extended
period
and
then
used
preceding
the
time
of
DBP
peak
excursion?

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

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

Conclusions:

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

Yes
No
If
yes,
please
explain:

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
12
Significant
Excursion
Evaluation
Report
Page
10
Report
date:

F.
If
you
were
unable
to
identify
the
cause
of
your
significant
excursion(
s)
after
reviewing
Sections
A
through
E,
are
you
able
to
identify
another
potential
cause
of
your
increase
in
DBP
concentrations?
Explain.

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

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

Attach
all
supporting
operational
or
other
data
which
led
you
to
conclude
this
was
the
cause
of
your
excursion(
s)
or
make
sure
this
data
is
available
during
your
sanitary
survey.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
3­
13
Supplemental
Data
Form
for
the
Significant
Excursion
Evaluation
Report
Report
date:

Report
prepared
by:

System
name:

1)
Water
quality
data
from
significant
excursion
sampling
period.

Location
No.
#
1
#
2
#
3
#
4
#
5
#
6
#
7
#
8
Location
Name
TTHM
(
ug/
L)

HAA5
(
ug/
L)

Free
Chlorine
(
mg/
L)

Total
Chlorine
(
mg/
L)

pH
2)
Supplemental
data
from
each
treatment
facility:

Plant
#
1:
Plant
#
2:
Raw
Water
Temperature:
Raw
Water
Temperature:

Plant
Effluent
Water
Temperature:
Plant
Effluent
Water
Temperature:

Raw
Water
TOC:
Raw
Water
TOC:

Other
Data:
Other
Data:

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

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

Monitoring
#
_____
#_____
#_____
#_____
Monitoring
#
_____
#_____
#_____
#_____
Location
Location
Date
1
Date
1
Date
2
Date
2
Date
3
Date
3
Date
4
Date
4
Date
5
Date
5
Avg.
Avg.

Attach
additional
sheets
if
necessary
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
4­
1
4.0
Best
Management
Practices
and
Distribution
System
Improvements
to
Reduce
DBP
Concentrations
It
is
common
to
find
higher
TTHM
and
HAA5
concentrations
in
the
distribution
system
compared
to
concentrations
leaving
the
treatment
plant.
In
systems
using
free
chlorine
for
secondary
disinfection,
significant
increases
in
TTHM
and
HAA5
may
occur
in
the
distribution
system.
Water
age,
type
and
concentration
of
NOM,
the
disinfectant
type,
and
residual
concentration
in
the
finished
water
are
all
factors
that
can
affect
TTHM
and
HAA5
concentrations.
The
previous
chapter
provided
guidelines
for
identifying
and
documenting
the
cause
of
significant
excursions.
This
chapter
describes
several
options
that
can
be
used
to
reduce
peak
DBP
concentrations
in
the
distribution
system,
and
is
divided
into
the
following
sections:

4.1
Modifications
to
Improve
Water
Quality
in
Storage
Tanks
4.1.1
Minimizing
Hydraulic
Residence
Time
of
Storage
Tanks
4.1.2
Improving
Mixing
Characteristics
of
Storage
Tanks
4.2
Decommissioning
Storage
Tanks
4.3
Modifications
to
Improve
Water
Quality
in
Pipes
4.3.1
Minimizing
Hydraulic
Residence
Time
in
Pipes
4.3.2
Reducing
Disinfectant
Demand
4.4
Booster
Disinfection
4.5
Overall
Strategy
to
Manage
Water
Age
4.1
Modifications
to
Improve
Water
Quality
in
Storage
Tanks
As
discussed
in
Section
2.4,
storage
tanks
that
are
underutilized
and
have
poor
mixing
characteristics
can
have
water
with
a
high
residence
time
in
certain
portions
of
the
tank,
causing
high
DBP
formation.
Further,
high
temperatures
in
tanks
during
the
summer
season
can
increase
DBP
formation.
Storage
tanks
should
be
designed
and
operated
so
the
overall
hydraulic
residence
time
is
minimized
and
the
water
is
well
mixed.
Generally,
water
mixing
in
the
finished
water
storage
tanks
is
not
achieved
through
mechanical
mixers,
but
through
the
kinetic
energy
of
the
tank
inflow.
Low
average
hydraulic
residence
time
and
adequate
mixing
are
critical
factors
for
minimizing
DBP
formation
in
storage
tanks.

Quiescent
conditions
in
storage
tanks
may
lead
to
sediment
accumulation.
This
accumulation
may
result
in
loss
of
disinfectant
residual
and
increased
DBP
formation.
Operating
procedures
(
control
of
empty/
fill
periods),
inspections
and
maintenance
activities
can
minimize
this
problem.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
4­
2
4.1.1
Minimizing
Hydraulic
Residence
Time
of
Storage
Tanks
Excessive
hydraulic
residence
time
in
a
storage
tank
can
result
in
older
water
with
high
DBP
levels.
The
average
hydraulic
residence
time
can
be
estimated
by
the
following
equation:

Average
hydraulic
residence
time
=
[
Vmax/(
Vmax
­
Vmin)]/
N
where,
Vmin
=
average
minimum
daily
volume
Vmax
=
maximum
daily
volume
N
=
number
of
drain/
fill
cycles
per
day
Example
4.1
shows
how
this
formula
can
be
used
to
calculate
residence
time
in
a
real
tank.
The
formula
assumes
that
a
tank
is
ideally
mixed.
In
tanks
with
poor
mixing
characteristics,
the
residence
time
of
portions
of
the
water
can
be
much
higher
than
the
average.
The
average
hydraulic
residence
time
in
a
storage
tank
can
be
reduced
when
the
volume
turnover
is
increased
by
extending
drain
cycles
and/
or
increasing
the
number
of
drain/
fill
cycles
per
day.
Pumps
may
need
to
be
added
to
a
storage
tank
to
pump
out
water
from
the
tank
into
the
distribution
system
and
thus
increase
the
volume
turnover
of
the
tank.
Changes
in
pumping
cycles
may
be
needed
to
increase
volume
turnover.

4.1.2
Improving
Mixing
Characteristics
of
Storage
Tanks
The
following
factors
effect
the
mixing
characteristics
of
storage
tanks:

°
Fill
time
°
Inlet
momentum
°
Inlet/
outlet
pipe
location,
orientation,
and
tank
dimensions
Desktop
theoretical
evaluations
of
hydraulic
residence
time,
fill
time,
and
inlet
momentum
can
be
used
to
predict
water
mixing
characteristics
of
a
storage
tank.
In
addition,
Example
4.1
Calculating
the
Average
Hydraulic
Residence
Time
Assume
Your
City
has
a
3­
MG
storage
tank
located
in
the
distribution
system.
The
maximum
volume
(
Vmax)
in
the
tank
is
2
MG
at
any
given
time
during
a
day.
The
minimum
volume
(
Vmin)
in
the
tank
is
1
MG
at
any
given
time
during
the
day.
There
are
four
drain/
fill
cycles
(
N)
per
day.
Calculate
the
average
hydraulic
residence
time
of
the
tank.

Average
hydraulic
residence
time
=
[
2/(
2
­
1)]/
4
=
0.5
days
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temperature
measurements
inside
a
storage
tank
can
be
an
effective
tool
in
predicting
the
water
mixing
characteristics
of
the
tank.
A
temperature
profile
can
be
developed
by
continually
measuring
the
water
temperature
at
various
depths
in
the
tank
over
the
course
of
several
days.
The
temperature
profile
can
then
be
compared
against
tank
water
level
data
to
determine
the
effectiveness
of
mixing
and
the
existence
of
thermal
stratification
in
the
tank.

While
the
desktop
theoretical
evaluations
and
temperature
measurements
can
describe
mixing
characteristics
quantitatively,
computational
fluid
dynamic
(
CFD)
modeling
can
describe
mixing
characteristics
qualitatively
by
providing
visual
images
of
water
mixing
inside
a
tank.
The
impact
of
design
changes
on
mixing
characteristics
can
be
effectively
visualized
using
CFD
modeling,
making
this
modeling
a
very
useful
tool
to
supplement
desktop
theoretical
evaluations
and
temperature
measurements.

The
mixing
predictions
can
be
used
to
identify
a
storage
tank
with
inadequate
mixing
characteristics
and,
therefore,
a
potential
for
high
DBP
formation.
Based
on
the
evaluations
of
mixing
characteristics,
physical
and
operational
modifications
can
then
be
recommended
to
improve
storage
tank
mixing.

4.1.2.1
Increasing
Fill
Time
For
a
tank
operating
in
a
fill
and
drain
mode,
mixing
occurs
primarily
during
the
fill
cycle.
As
a
result,
if
a
tank
is
relatively
well­
mixed
at
the
end
of
each
fill
cycle,
then
significant
variations
in
water
age
and
DBP
levels
within
the
tank
are
unlikely.
Experimentation
has
shown
that
the
time
required
for
good
mixing
is
dependent
upon
the
volume
of
water
in
the
tank,
the
inlet
diameter,
and
the
filling
flow
rate.
For
some
types
of
tanks,
researchers
have
developed
empirical
relationships
for
the
mixing
time
theoretically
required
to
completely
mix
the
water
in
the
tank
(
Grayman
et
al.,
2000).
It
is
generally
desirable
for
the
actual
filling
time
to
exceed
this
theoretical
mixing
time.
Therefore,
one
way
of
increasing
fill
time
is
to
allow
the
tank
to
drain
to
a
lower
level
before
refilling.

4.1.2.2
Increasing
Inlet
Momentum
Inlet
momentum
(
defined
as
velocity
×
flow
rate)
is
a
key
factor
for
mixing
of
water
in
storage
tanks.
The
higher
the
inlet
momentum,
the
better
the
mixing
characteristics
in
the
storage
tanks.
Increasing
the
flow
rate
could
be
a
simple
way
to
increase
momentum,
but
may
not
be
practical
due
to
limitations
of
system
hydraulics.
For
example,
a
pump
may
not
be
available
at
the
tank
location
and
the
distribution
system
pressure
may
not
be
high
enough
to
get
desirable
increases
in
flow
rates.
In
some
cases,
even
if
a
pump
were
available,
it
may
not
be
possible
to
increase
the
pumping
rate
into
the
tanks.
In
such
cases,
it
may
be
more
feasible
to
increase
the
inlet
momentum
by
increasing
the
velocity
with
a
reduced
inlet
diameter.

4.1.2.3
Optimizing
Inlet
Location
and
Orientation
Mixing
a
fluid
requires
a
source
of
energy
input.
In
distribution
system
storage
tanks,
this
energy
is
normally
introduced
during
tank
filling.
As
water
enters
a
tank,
a
jet
is
formed
and
the
water
present
in
the
tank
is
drawn
into
the
jet.
Circulation
patterns
are
formed
that
result
in
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4
mixing.
The
path
of
the
jet
must
be
long
enough
to
allow
the
mixing
process
to
develop
for
efficient
mixing
to
occur.
Therefore,
the
inlet
jet
should
not
be
pointed
directly
towards
nearby
impediments
such
as
a
wall,
the
bottom
of
the
tank,
or
deflectors.
The
degree
and
speed
of
mixing
depends
primarily
upon
the
size
of
the
tank
and
the
momentum
of
the
incoming
jet.

The
location
and
orientation
of
the
inlet
pipe
relative
to
the
tank
walls
can
have
a
significant
impact
on
mixing
characteristics.
For
example,
when
the
height
of
a
tank
is
much
larger
than
the
diameter
or
width,
the
location
of
the
inlet
pipe
at
the
bottom
of
the
tank
in
the
horizontal
direction
is
likely
to
cause
the
water
jet
to
hit
the
vertical
wall
of
the
tank
resulting
in
loss
of
inlet
momentum
and
incomplete
water
mixing.
Besides
geometrical
characteristics
of
tanks,
the
mixing
of
water
is
also
depend
on
the
initial
water
depth
in
the
tank.
When
water
level
is
high
and
the
inlet
pipe
is
oriented
horizontally,
the
inlet
momentum
may
not
be
sufficient
to
completely
mix
water
during
the
fill
cycle.
Under
both
situations,
high
concentrations
of
DBPs
may
form
in
the
older
water
stagnating
at
the
top
of
the
tank.

4.1.2.4
Avoiding
Baffles
Water
can
be
forced
to
flow
through
a
storage
tank
either
in
a
completely
mixed
state
or
a
plug
flow
manner.
In
treatment
plant
contact
chambers
where
there
is
generally
simultaneous
inflow
and
outflow,
internal
baffles
are
sometimes
placed
in
tanks
to
encourage
plug
flow
and
avoid
short­
circuiting
and
dead
zones.
However,
in
distribution
system
tanks
and
reservoirs
that
are
generally
"
fill
and
draw"
operations,
and
where
a
mixed
condition
is
preferable
to
plug
flow,
baffles
can
inhibit
mixing
and
produce
zones
of
poor
mixing.
These
zones
have
higher
water
age
and
therefore
higher
DBP
formation
potential.
Therefore,
baffles
should
not
be
used
in
distribution
system
storage
facilities
under
most
circumstances.

4.1.2.5
Avoiding
Tank
Stratification
The
temperature
difference
through
the
depth
of
a
storage
tank
is
referred
to
as
thermal
stratification.
Thermal
stratification
can
be
either
the
result
or
the
cause
of
poor
mixing.
Depending
on
the
location
of
the
inlet
pipe
and
tank
geometry,
the
water
entering
the
tank
from
buried
pipes
may
be
cooler
than
the
bulk
water
in
the
tank
during
the
summer
or
warmer
than
the
bulk
water
in
the
tank
during
the
winter.
In
tanks
with
poor
mixing
characteristics
(
i.
e.,
insufficient
volume
turnover
or
inlet
momentum),
colder,
denser
water
may
hover
in
the
lower
depths
of
the
tank,
whereas
the
warmer,
less
dense
water
will
have
a
tendency
to
rise
to
the
top
of
the
tank.
Temperature
differences
of
less
than
1
°
C
can
affect
mixing
characteristics.

Generally,
tall
tanks
and
tanks
with
large
diameter
inlets
located
near
the
bottom
of
the
tank
have
a
greater
potential
for
thermal
stratification.
If
significant
temperature
differences
are
experienced,
then
the
orientation
and
diameter
of
the
inlet
pipes
may
need
to
be
modified
to
reduce
the
potential
for
stratification.
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5
4.2
Decommissioning
Storage
Tanks
A
tank
may
be
oversized
for
the
water
system
needs
and,
thus,
it
may
not
be
possible
to
get
adequate
flow
and
water
turnover
in
the
tank.
A
storage
tank
may
also
be
hydraulically
locked
out
of
the
distribution
system
due
to
high
system
pressures
and
low
system
demand,
resulting
in
excessive
water
age
and
high
DBP
formation
potential.
When
events
such
as
main
breaks
or
fire
flow
cause
the
water
from
these
tanks
to
be
drawn
into
the
distribution
system,
the
areas
receiving
water
from
the
tank
may
have
higher
than
normal
DBP
levels.
For
a
tank
that
is
hydraulically
locked
out
under
normal
system
operating
conditions,
physical
modifications
are
ineffective
to
significantly
improve
mixing
characteristics.
In
such
cases,
operational
changes
(
such
as
reducing
normal
operating
tank
water
level
or
increasing
draw
cycle
time
duration)
or
permanent
decommissioning
can
be
considered
to
prevent
water
with
high
DBP
levels
from
entering
the
distribution
system.

Before
a
tank
is
decommissioned,
the
effects
of
taking
the
tank
out
of
service
should
be
determined.
A
distribution
system
analysis
should
be
performed
to
make
sure
that
the
tank
is
not
needed
for
equalization
storage,
fire
flow,
or
emergency
conditions
such
as
main
breaks
or
treatment
plant
shutdowns.

4.3
Modifications
to
Improve
Water
Quality
in
Pipes
System
piping
improvements
to
reduce
DBP
levels
include
reducing
the
hydraulic
residence
time
of
water
in
the
pipes
and
reducing
the
overall
disinfectant
demand
so
that
the
average
chlorine
dose
for
the
finished
water
is
lowered.

The
hydraulic
residence
time
of
the
water
in
the
pipes
can
be
lowered
by:

°
Looping
of
dead­
ends
and
re­
routing
of
valves
°
Using
blow­
offs
°
Replacing
oversized
pipes
with
smaller
diameter
pipes
The
overall
disinfectant
demand
can
be
lowered
by:

°
Replacing
or
cleaning
and
lining
of
unlined
cast
iron
pipes
°
Flushing
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4­
6
4.3.1
Minimizing
Hydraulic
Residence
Time
in
Pipes
4.3.1.1
Looping
of
Dead­
Ends
and
Re­
routing
of
Valves
The
highest
DBP
concentrations
in
a
system
are
often
observed
in
dead
ends
with
stagnant
water.
Water
in
dead
ends
experience
long
contact
times
for
DBP
formation.
Construction
of
new
pipes
to
loop
dead
ends,
thereby
eliminating
them,
can
eliminate
the
stagnation
of
water
and
reduce
residence
time,
decreasing
the
opportunity
for
the
formation
of
high
DBP
levels.
However,
looping
can
also
result
in
the
creation
of
an
even
larger
section
of
very
slow
moving
water.
The
specific
hydraulic
response
of
a
system
to
looping
must
be
assessed
to
determine
if
looping
will
improve
water
flow
and
reduce
hydraulic
residence
time.

Closed
valves
can
create
artificial
dead­
ends
and
lead
to
the
development
of
high
DBP
levels.
The
closed
valves
may
remain
undetected
until
serious
water
quality
or
fire
emergency
problems
develop.
Attention
should
be
paid
to
identify
valves
set
in
the
wrong
position
and
correct
their
setting
to
lower
detention
time
in
the
system.
A
complete
database
of
all
valves
in
the
system
is
essential
for
identifying
broken
or
lost
valves
that
may
affect
water
flow.
Distribution
system
models
and/
or
system
maps
can
be
useful
tools
to
identify
the
occurrence
of
dead
ends
and
determine
what
type
of
piping
or
valve
modifications
may
be
needed.

4.3.1.2
Using
Blow­
Offs
Blow­
offs
can
be
used
in
areas
of
high
water
age
and
as
an
alternative
to
looping.
A
continuous
or
automatic
intermittent
blow­
off
can
remove
old
water
from
a
distribution
system
and
pull
fresh
water
into
areas
that
otherwise
would
become
stagnant.
Fresh
water
entering
an
area
affected
by
a
blow­
off
will
have
had
a
shorter
contact
time
between
precursors
and
chlorine
and,
generally,
lower
DBP
levels.

Continuous
or
automatic
intermittent
blow­
offs
can
be
used
on
a
seasonal
basis
when
DBP
peaks
are
more
likely
to
occur
(
e.
g.,
during
high
water
temperature
periods)
and
can
vary
based
on
geographical
regions.
The
need
for
and
appropriate
locations
of
blow­
offs
can
be
determined
by
analyzing
distribution
system
historical
records
for
low
disinfectant
residuals,
presence
of
total
coliforms
or
nusiance
bacteria
(
fecal
coliforms
are
not
a
result
of
water
age
or
regrowth,
they
are
an
indicator
of
contamination),
high
heterotrophic
plate
counts
(
HPCs),
and
high
TTHM
and
HAA5
concentrations.
A
distribution
system
model
can
be
used
to
develop
time­
of­
travel
estimates
that
can
help
in
choosing
optimal
blow­
off
locations.

4.3.1.3
Replacing
Oversized
Pipes
Pipe
size
affects
water
velocity
and,
in
turn,
detention
time.
In
portions
of
the
distribution
system
where
pipes
are
oversized,
the
hydraulic
residence
times
are
longer
than
needed
and
can
lead
to
formation
of
high
DBP
concentrations.
The
pipes
in
abandoned
areas
may
still
be
part
of
the
overall
distribution
system,
but
may
not
be
required
or
may
be
too
large,
causing
excessive
hydraulic
residence
time.
When
planning
replacement
projects,
the
pipe
sizes
should
be
reassessed
based
on
current
needs,
redevelopment
plans,
and
fire
protection.
Where
appropriate,
the
pipe
sizes
can
be
reduced
or
sections
of
pipes
valved
off
if
they
are
no
longer
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7
needed
to
reduce
the
residence
time
of
water
and
the
potential
for
the
formation
of
DBP
peak
concentrations.
Distribution
system
models
can
be
used
as
a
tool
to
determine
the
appropriate
pipe
diameters.

4.3.2
Reducing
Disinfectant
Demand
4.3.2.1
Replacing,
Cleaning,
and
Lining
of
Cast
Iron
Pipes
Corrosion
and
biofilms
in
unlined
cast
iron
pipes
or
sediment
deposits
can
exert
a
disinfectant
demand
that
lowers
chlorine
residual.
Utilities
are
often
forced
to
increase
chlorine
dosages
at
the
treatment
plant
or
use
booster
chlorination
to
supply
enough
chlorine
to
maintain
sufficient
residual
in
the
portions
of
their
distribution
system
with
unlined
cast­
iron
pipe.
This
results
in
an
excess
of
chlorine
in
other
areas
of
the
distribution
system
which
can
lead
to
DBP
peaks.

Systems
can
reduce
localized
chlorine
decay
(
and
thus,
reduce
the
overall
concentration
needed
to
maintain
a
residual
in
all
parts
of
the
system)
through
pipeline
replacement
programs.
Alternatively,
pipeline
cleaning­
and­
lining
can
be
used
to
reduce
chlorine
residual.
Pipeline
cleaning
methods
include
high
pressure
sand
blasting,
various
rodding
methods,
and
chemical
cleaning.
Among
the
more
common
lining
materials
are
cement­
mortar,
asphalt
(
bituminous),
epoxy
resins,
rubber,
and
calcite.
Cement
is
most
commonly
used,
although
several
types
of
degradation
of
cement
material
can
occur
in
the
presence
of
acidic
waters
or
waters
that
are
aggressive
to
calcium
carbonate
(
e.
g.
soft
waters).
For
example,
soft
waters
can
progressively
hydrolize
calcium
silicates
constituents
of
concrete
into
silica
gels
producing
soft
surfaces,
and
leach
calcium
hydroxide
from
the
cement
lining
(
AWWA,
2002).
Both
of
these
occurrences
can,
in
the
long
run,
compromise
the
integrity
of
the
lining.

4.3.2.2
Flushing
Frequent
flushing
can
be
an
effective
tool
to
control
DBP
peaks
by
cleaning
pipes
that
exert
chlorine
demand
and
by
lowering
water
age.
When
the
chlorine
demand
is
lowered,
the
chlorine
dose
at
the
treatment
plant
or
booster
disinfection
facilities
may
be
lowered,
leading
to
lower
DBP
formation.
There
are
alternative
flushing
methods:
emergency
flushing,
conventional
flushing
of
dead­
ends
and
problem
areas,
and
directional
(
also
known
as
unidirectional)
flushing.

Conventional
flushing
is
conducted
by
opening
hydrants
(
it
does
not
include
directing
the
flow
with
valves)
and
is
considered
routine
distribution
system
maintenance.
Similar
to
blowoffs
conventional
flushing
of
high
detention
areas
is
an
effective
tool
for
controlling
the
occurrence
of
DBP
peaks
and
can
reduce
the
need
for
looping
dead­
ends.
When
conducted
on
a
regular
basis,
conventional
flushing
can
achieve
temporary
reduction
of
DBPs
primarily
by
discarding
old
water
and
allowing
fresher
water
to
enter
the
affected
area.
However,
with
this
method
it
is
difficult
to
control
the
quality
of
water
entering
the
main
being
flushed
and
it
is
possible
that
the
quality
of
this
water
may
not
be
superior
to
that
leaving
the
system.
In
addition,
conventional
flushing
is
less
than
optimal
in
controlling
other
factors
that
can
contribute
to
high
DBP
levels,
since,
in
most
pipes,
the
velocity
of
5
to
6
ft/
s
required
to
remove
sand,
sediments,
corrosion
byproducts,
and
other
debris
is
not
achieved
(
Joseph
and
Pimblett,
2000).
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Guidance
Manual
Proposal
Draft
July
2003
4­
8
Directional
(
or
unidirectional)
flushing
is
a
more
effective
method
for
DBP
reduction.
It
is
conducted
in
a
systematic
manner
directing
the
flow
to
enhance
the
flushing
of
the
desired
main.
A
properly
designed
and
implemented
directional
flushing
program
can
achieve
water
velocities
to
more
than
5
ft/
s
that
can
scour
the
pipe
(
Joseph
and
Pimblett,
2000).
In
addition
to
increasing
water
flow
in
the
selected
main,
directional
flushing
can
reduce
the
impact
of
other
factors
contributing
to
the
formation
of
high
DBP
concentrations
including
biofilms,
the
accumulation
of
sediments,
and
the
build­
up
of
corrosion
For
a
successful
directional
flushing
program,
the
order
in
which
pipes
are
flushed,
the
hydrants
that
must
be
opened,
and
the
valves
that
must
be
closed
or
opened
must
be
carefully
planned.
Directional
flushing
should
be
configured
to
maximize
water
velocity
when
an
hydrant
is
opened
while
minimizing
the
chance
of
dirty
water
reaching
customers.
Water
that
enters
the
main
being
flushed
flows
from
other
sections
that
have
already
been
cleaned.
Usually,
this
requires
that
flushing
start
at
a
source
of
supply
and
worked
outward
in
the
distribution
system.
Accurate
maps
of
the
system,
hydraulic
models,
and
a
complete
database
of
valves
and
hydrants
facilitate
planning
and
execution
of
directional
flushing
programs.

Emergency
flushing
(
or
spot
flushing)
is
performed
in
response
to
customer
complaints
for
color,
taste,
or
odor
problems,
and
in
response
to
other
water
quality
problems,
such
as
insufficient
disinfectant
residual,
evidence
of
nitrification,
or
positive
coliform
results.
This
type
of
flushing,
is
not
effective
for
DBP
control
because
of
the
small
volumes
of
water
moved
and
low
velocities
acheived.

Regardless
of
the
flushing
method
implemented,
systems
should
identify
problem
periods
and
areas
using
historical
records.
The
appropriate
timing
of
flushing
can
be
a
key
factor
for
reducing
DBP.

4.4
Booster
Disinfection
Practical
considerations
may
not
allow
appropriate
piping
or
operational
modifications
for
reducing
hydraulic
residence
time
or
disinfectant
demand
in
remote
parts
of
the
distribution
system.
In
such
cases,
the
use
of
booster
disinfection
can
be
considered
to
maintain
a
more
consistent
disinfectant
residual
throughout
large
distribution
systems.
Booster
disinfection
provides
the
opportunity
to
increase
chlorine
residual
in
only
the
areas
that
require
it,
allowing
the
average
chlorine
residual
and
resulting
average
DBP
formation
to
be
kept
as
low
as
possible.

If
the
majority
of
a
distribution
system
is
confined
to
an
area
near
the
plant
but
a
small
part
of
the
system
is
far
away
from
the
plant,
a
large
dose
of
disinfectant
needs
to
be
added
at
the
plant
to
maintain
the
minimum
required
disinfectant
residual
in
the
remote
part
of
the
system.
In
such
cases,
the
residual
concentration
in
the
majority
of
a
system
near
the
plant
would
be
higher
than
what
is
required.
The
use
of
a
booster
disinfection
in
the
remote
part
of
the
system
to
maintain
the
minimum
required
disinfectant
residual
can
reduce
the
disinfectant
dose
at
the
plant
and
limit
DBP
formation
throughout
the
majority
the
system.

It
is
important
that
the
disinfectant
dose
added
at
booster
stations
is
carefully
calibrated
to
changes
in
water
quality
conditions
and
disinfection
needs.
Booster
disinfection
doses
should
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
4­
9
be
flow
or
dose
paced
to
avoid
overfeeding
disinfectant.
Where
chlorine
is
overfeed,
high
DBPs
levels
can
be
found
in
water
downstream
of
the
boosting
station.

4.5
Overall
Strategy
to
Manage
Water
Age
Water
age
can
contribute
to
the
formation
of
high
DBP
concentrations
within
the
distribution
system.
Generally,
as
long
as
chlorine
residuals
and
reactive
DBP
precursors
are
present
in
drinking
water,
DBPs
continue
to
form.
Thus,
the
longer
the
contact­
time
between
chlorine
and
NOM,
the
greater
the
concentration
of
DBPs
that
can
be
found
in
water
as
a
result
of
the
continuous
formation
and
accumulation.
This
accumulation
is
a
consequence
of
the
formation
of
THMs
and
HAAs,
and
their
associated
chemical
stabilities,
which
are
generally
quite
high
in
disinfected
drinking
water
as
long
as
a
significant
disinfectant
residual
is
still
present
(
Singer
and
Reckhow,
1999).

In
the
distribution
system,
when
the
contact
time
between
NOM
and
chlorine
may
be
long,
DBP
levels
greater
than
those
in
the
finished
water
leaving
the
plant
are
often
found.
High
TTHM
values
usually
occur
where
the
water
age
is
the
oldest.
Unlike
THMs,
HAAs
cannot
be
consistently
related
to
water
age
because
HAAs
are
known
to
biodegrade
over
time
when
the
disinfectant
residual
is
low.
This
might
result
in
relatively
low
HAA
concentrations
in
areas
of
the
distribution
system
where
disinfectant
residuals
are
depleted.

In
addition
to
high
DBP
concentrations,
high
water
age
may
also
result
in
other
water
quality
problems
including
increased
microbial
activity,
and
taste
and
odor
problems.
Water
age
is
controlled
through
system
design
and
operational
strategies
including
tank
management
(
sections
4.1.1
and
4.1.2),
flushing
(
section
4.3.2),
looping
of
dead­
ends
(
section
4.3.1)
and
re­
routing
of
valves
(
section
4.3.1),
and
using
blow­
offs
(
section
4.3.1).
All
of
these
strategies
have
been
presented
in
detail
in
relevant
sections
of
this
report.
Figure
4.1
schematically
illustrates
a
overall
strategy
for
water
age
management
and
achievement
of
water
quality
goals.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
4­
10
Significant
Excursion
Guidance
Manual
Proposal
Draft
5­
1
July
2003
5.0
References
Amy
G.
L.,
Chadick
P.
A.,
Chowdhury
Z.
K.,
"
Developing
Models
for
Predicting
Trihalomethane
Formation
Potential
and
Kinetics,"
Journal,
American
Water
Works
Association,
Vol.
79,
No.
7,
July
1987.

Franchi
A.,
Singer
P.
C.,
Chowdhury
Z.,
Carter
J.,
Grace
N.
O.,
2002,
Evaluation
of
"
low­
cost"
strategies
for
the
control
of
trihalomethanes
and
haloacetic
acids,
paper
presented
at
the
AWWA
Water
Quality
Technology
annual
conference,
Seattle,
WA.

Franchi
A.
and
Hill
C.,
2002,
Factors
Affecting
DBP
Formation
in
the
Distribution
System,
Paper
Presented
at
the
Water
Quality
from
Source
to
Tap,
AWWA
Chesapeake
Section
Seminar.

Grayman
W.,
Rossman
L.,
Arnold
C.,
Deininger
R.,
Smith
C.,
Smith
J.,
Schnipke
R.
,
2000,
Water
Quality
Modeling
of
Distribution
System
Storage
Facilities,
AWWARF.

Hill
C.
,
2003.
Managing
Distribution
System
Water
Quality.
Ohio
Section
AWWA
Southeast/
Southwest
Joint
Meeting,
April
15,
2003.

Liang
L.,
and
Singer
P.
C.
,
Factors
Influencing
the
Formation
and
Relative
Distribution
of
Haloacetic
Acids
and
Trihalomethanes
under
Controlled
Chlorination
Conditions,
2001
AWWA
Water
Quality
and
Technology
Conference.

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

Stephane
J.
and
Pimblett
J.,
2000,
Unidirectional
Flushing
Program
Is
Clean
Sweep,
Opflow,
v.
26,
No.
1.
Appendix
A
Formation
and
Control
of
Disinfection
Byproducts
This
page
intentionally
left
blank.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
1
A.
1
Introduction
The
purpose
of
this
appendix
is
to
identify
the
factors
that
affect
formation
of
disinfection
byproducts
(
DBPs)
in
water
treatment
processes
and
distribution
systems.
It
is
intended
to
serve
as
a
tool
for
systems
in
identifying
potential
strategies
for
reducing
DBP
concentrations.
This
appendix
is
divided
into
two
main
sections.
Section
A.
2
discusses
the
factors
that
affect
DBP
formation.
Section
A.
3
discusses
options
for
controlling
DBP
formation
in
general
terms;
it
is
not
intended
to
provide
guidance
on
implementation
of
DBP
control
strategies.

A.
2
Formation
of
DBPs
Organic
DBPs
(
and
oxidation
byproducts)
are
formed
by
the
reaction
between
organic
substances,
inorganic
compounds
such
as
bromide,
and
oxidizing
agents
that
are
added
to
water
during
treatment.
In
most
water
sources,
natural
organic
matter
(
NOM)
is
the
major
constituent
of
organic
substances
and
DBP
precursors.
Total
organic
carbon
(
TOC)
is
typically
used
as
a
surrogate
measure
for
NOM
levels.
The
two
terms
are
used
interchangeably
in
much
of
the
discussion
presented
here.
The
following
major
factor
affecting
the
type
and
amount
of
DBPs
formed.

Type
of
disinfectant,
dose,
and
residual
concentration

Contact
time
and
mixing
conditions
between
disinfectant
(
oxidant)
and
precursors

Concentration
and
characteristics
of
precursors

Water
temperature

Water
chemistry
(
including
pH,
bromide
ion
concentration,
organic
nitrogen
concentration,
and
presence
of
other
reducing
agents
such
as
iron
and
manganese)

A
summary
of
these
factors
follows.

A.
2.1
Impact
of
Disinfection
Method
on
Organic
DBP
Formation
Organic
DBPs
can
be
subdivided
into
halogenated
and
non­
halogenated
byproducts.
Halogenated
organic
disinfection
byproducts
are
formed
when
organic
and
inorganic
compounds
found
in
water
react
with
free
chlorine,
free
bromine,
or
free
iodine.
The
formation
reactions
may
take
place
in
the
treatment
plant
and
the
distribution
system.
Free
chlorine
can
be
introduced
to
water
directly
as
a
primary
or
secondary
disinfectant,
or
as
a
byproduct
of
the
manufacturing
of
chlorine
dioxide
and
chloramines.
Reactions
between
NOM,
bromide
and
iodide
ions
and
chlorine
lead
to
the
formation
of
a
variety
of
halogenated
DBPs
including
THMs
and
HAAs.
Further,
the
oxidation
of
organic
nitrogen
can
lead
to
the
formation
of
DBPs
Significant
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Guidance
Manual
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July
2003
A­
2
containing
nitrogen,
such
as
haloacetonitriles,
halopicrins,
and
cyanogens
halides
(
Reckhow
et
al.,
1990;
Hoigné
and
Bader,
1988).

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

Trussell
and
Umphres
(
1978)
reported
that
the
presence
of
bromide
can
affect
both
the
rate
and
the
yield
of
DBPs,
as
well
as
that
as
the
ratio
of
bromide
to
NOM
(
measured
as
total
organic
carbon)
increases,
the
percentage
of
brominated
DBPs
also
increases.
Free
chlorine
and
ozone
oxidize
bromide
ion
to
hypobromite
ion/
hypobromous
acid.
Hypobromous
acid
is
a
more
effective
substituting
agent
than
hypochlorous
acid
(
a
better
oxidant)
and
can
in
turn
react
with
NOM,
forming
brominated
DBPs
such
as
bromoform,
and
mixed
bromo­
chloro
species
(
Krasner,
1999).
Similarly,
the
presence
of
iodide
may
result
in
the
formation
of
mixed
chlorobromoiodomethanes
byproducts
(
Bichsel
and
Von
Gunten,
2000).

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

When
chloramination
is
used,
it
is
possible
that
DBPs
might
form
if
chlorine
is
added
before
ammonia.
If
the
mixing
process
is
inefficient,
it
is
also
possible
that
DBPs
might
form
during
the
mixing
of
chlorine
and
ammonia.
In
this
case,
free
chlorine
might
react
with
NOM
before
the
complete
formation
of
chloramines.
In
addition,
monochloramine
slowly
hydrolyzes
to
release
free
chlorine
in
water.
This
free
chlorine
may
contribute
to
the
formation
of
small
amounts
of
additional
DBPs
in
the
distribution
system.

The
application
of
chlorine
dioxide
does
not
produce
significant
amounts
of
organic
halogenated
DBPs
unless
chlorine
is
formed
as
an
impurity
in
the
generation
process.
Only
small
amounts
of
total
organic
halides
(
TOXs,
a
surrogate
measure
for
halogenated
organic
compounds
including
THMs
and
HAAs)
are
formed.
However,
THMs
and
HAAs
will
form
if
excess
chlorine
is
added
to
water
to
ensure
complete
reaction
with
sodium
chlorite
during
the
production
of
chlorine
dioxide.
Significant
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2003
A­
3
To
date,
there
is
no
evidence
to
suggest
that
ultraviolet
irradiation
(
UV)
results
in
the
formation
of
any
disinfection
byproducts;
however,
little
research
has
been
performed
in
this
area.
Most
of
the
research
regarding
application
of
UV
and
DBP
formation
has
focused
on
chlorinated
DBP
formation
as
a
result
of
UV
application
prior
to
the
addition
of
chlorine
or
chloramines
(
Malley
et
al.,
1995).
Malley,
et
al.
conducted
studies
comparing
the
effects
of
UV
light
followed
by
chlorination
versus
chloramination.
Evidence
suggests
UV
does
not
affect
DBP
formation
in
either
of
these
two
cases.

Ozone
does
not
directly
produce
chlorinated
DBPs.
However,
if
chlorine
is
added
before
or
after
ozonation
mixed
bromo­
chloro
DBPs
as
well
as
chlorinated
DBPs
can
form.
Ozone
can
alter
the
reactions
characteristics
of
NOM
and
affect
the
concentration
and
speciation
of
halogenated
DBPs
when
chlorine
is
subsequently
added
downstream.
In
waters
with
sufficient
bromide
concentrations,
ozonation
can
lead
to
the
formation
of
bromate
and
other
brominated
DBPs.
Bromate,
like
TTHMs
and
HAA5,
is
a
regulated
DBP.
Ozonation
of
natural
waters
also
produces
aldehydes,
haloketones,
ketoacids,
carboxylic
acids,
and
other
types
of
biodegradable
organic
material.
The
biodegradable
fraction
of
organic
material
can
serve
as
a
nutrient
source
for
microorganisms,
and
should
be
removed
to
prevent
microbial
regrowth
in
the
distribution
system.

To
date,
many
of
the
byproducts
that
result
from
chlorination
or
from
alternative
disinfectants
are
still
unknown
and
unregulated.
One
explanation
for
this
shortcoming
is
that
these
compounds
are
too
polar
or
too
high
in
molecular
weight
to
be
detected
using
conventional
gas
chromotography
techniques
(
James,
1999).
As
more
refined
analytical
techniques
become
available
additional
classes
of
disinfection
byproducts
may
be
scrutinized.

A.
2.2
Disinfectant
Dose
The
concentration
of
disinfectant
can
affect
the
formation
of
DBPs.
As
the
concentration
of
disinfectant
increases
the
production
of
DBPs
also
increases
and
formation
reactions
continue
as
long
as
precursors
(
NOM)
and
disinfectant
are
present.
In
general,
the
impact
of
disinfectant
concentration
is
greater
during
primary
disinfection
than
during
secondary
disinfection.
The
amount
of
disinfectant
added
during
primary
disinfection
is
usually
less
than
the
long­
term
demand,
therefore,
the
concentration
of
disinfectant
is
often
the
limiting
factor
while
unreacted
precursors
are
available.
On
the
contrary,
during
secondary
disinfection
DBP
formation
reactions
are
often
precursor
limited
since
an
excess
of
disinfectant
is
added
to
the
water
to
maintain
a
residual
concentration
(
Singer
and
Reckhow,
1999).
In
distribution
systems,
DBP
formation
reactions
can
become
disinfectant­
limited
when
the
free
chlorine
residual
drops
to
low
levels.
As
a
rule
of
thumb,
Singer
and
Reckhow
(
1999)
suggested
this
event
takes
place
when
the
chlorine
concentration
drops
below
approximately
0.3
mg/
L.

In
many
systems
booster
disinfection
is
applied
to
raise
disinfectant
residual
concentration,
especially
in
remote
areas
of
the
distribution
system
or
near
storage
tanks
where
water
age
may
be
high
and
disinfectant
residuals
can
be
low.
The
additional
chlorine
dose
applied
to
the
water
at
these
booster
facilities
may
increase
THM
and
HAA
levels.
Further,
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
4
booster
chlorination
can
maintain
high
HAA
concentrations
because
the
increased
disinfection
residuals
can
prevent
the
biodegradation
of
HAAs.
However,
as
discussed
further
in
Section
A.
3.4
booster
chlorination
can
also
be
useful
in
decreasing
DBP
levels
by
reducing
levels
of
secondary
disinfectant
needed
in
the
finished
water
leaving
the
plant.

A.
2.3
Time
Dependency
of
DBP
Formation
In
general,
DBPs
continue
to
form
in
drinking
water
as
long
as
disinfectant
residuals
and
reactive
DBP
precursors
are
present,
and
the
longer
is
the
contact
time
between
disinfectant/
oxidant
and
NOM
present,
the
greater
is
the
amount
of
DBPs
that
can
be
formed.
High
concentrations
of
DBPs
can
accumulate
in
water.
This
is
a
consequence
of
the
chemical
stabilities
of
THMs
and
HAAs,
which
are
generally
quite
high
in
the
disinfected
drinking
water
as
long
as
a
significant
disinfectant
residual
is
still
present
(
Singer
and
Reckhow,
1999).

High
THM
levels
usually
occur
where
the
water
age
is
the
oldest.
Unlike
THMs,
HAAs
cannot
be
consistently
related
to
water
age
because
HAAs
are
known
to
biodegrade
over
time
when
the
disinfectant
residual
is
low.
This
might
result
in
relatively
low
HAAs
concentrations
in
areas
of
the
distribution
system
where
disinfectant
residuals
are
depleted.

In
contrast
to
chlorination
byproducts,
ozonation
byproducts
form
more
rapidly,
but
their
period
of
formation
is
much
shorter
than
that
of
chlorination
byproducts.
This
is
due
to
the
quicker
dissipation
of
the
ozone
residual
compared
to
chlorine
(
Singer
and
Reckhow,
1999).

A.
2.4
Concentration
and
Characteristics
of
Precursors
The
formation
of
halogenated
DBPs
is
related
to
the
concentration
of
NOM
at
the
point
of
chlorination.
In
general
greater
DBP
levels
are
formed
in
waters
with
higher
concentrations
of
precursors.
Studies
conducted
with
different
fractions
of
NOM
have
indicated
the
reaction
between
chlorine
and
NOM
with
high
aromatic
content
tends
to
form
higher
DBP
levels
than
NOM
with
low
aromatic
content.
For
this
reason,
UV
absorption
at
254
nm
[
UV254],
which
is
generally
linked
to
the
aromatic
and
unsaturated
components
of
NOM,
is
considered
a
good
predictor
of
the
tendency
of
a
source
water
to
form
THMs
and
HAAs
(
Owen
et
al.,
1998;
Singer
and
Reckhow,
1999).
Specific
ultraviolet
light
absorbance
(
SUVA)
is
also
often
used
to
characterize
aromaticity
and
molecular
weight
distribution
of
NOM.
This
parameter
is
defined
as
the
ration
between
UV254
and
the
dissolved
organic
carbon
(
DOC)
concentration
of
water
(
Letterman
et
al.,
1999).
It
should
be
noted,
that
the
more
highly
aromatic
precursors,
characterized
by
high
UV254,
in
source
waters
are
more
easily
removed
by
coagulation.
Thus,
it
is
the
UV254
measurement
immediately
upstream
of
the
point(
s)
of
chlorination
within
a
treatment
plant
that
is
more
directly
related
to
THM
and
HAA
formation
potential.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
5
A.
2.5
Water
Temperature
Significant
Excursion
Guidance
Manual
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July
2003
A­
6
The
rate
of
formation
of
THMs
and
HAAs
increases
with
increasing
temperature.
Consequently,
the
highest
THM
and
HAA
levels
may
occur
in
the
warm
summer
months.
However,
water
demands
are
often
higher
during
these
months,
resulting
in
lower
water
age
within
the
distribution
system
which
helps
to
control
DBP
formation.
Furthermore,
high
temperature
conditions
in
the
distribution
system
promote
the
accelerated
depletion
of
residual
chlorine,
which
can
mitigate
DBP
formation
and
promote
biodegradation
of
HAAs
unless
chlorine
dosages
are
increased
to
maintain
high
residuals
(
Singer
and
Reckhow,
1999).
For
these
reasons,
depending
on
the
specific
system,
the
highest
THM
and
HAA
levels
may
be
observed
during
months
which
are
warm,
but
not
necessarily
the
warmest.

Seasonal
trends
affect
differently
where
high
THM
and
HAA
concentrations
might
be
found.
For
example,
when
water
is
colder,
microbial
activity
is
typically
lower
and
DBP
formation
kinetics
are
slower.
Under
these
conditions,
the
highest
THM
and
HAA
concentrations
might
appear
coincident
with
the
oldest
water
in
the
system.
In
warmer
water,
the
highest
HAA
concentrations
might
appear
in
fresher
water,
which
is
likely
to
contain
higher
disinfectant
residuals
that
can
prevent
the
biodegradation
of
HAAs.

A.
2.6
Water
pH
In
the
presence
of
NOM
and
chlorine,
THM
formation
increases
with
increasing
pH,
whereas
the
formation
of
HAAs
and
other
DBPs
decrease
with
increasing
pH.
The
increased
THM
production
at
high
pH
is
likely
promoted
by
base
hydrolysis
(
favored
at
high
pH).
HAAs
are
not
sensitive
to
base
hydrolysis
but
their
precursors
are.
Consequently,
pH
can
alter
their
formation
pathways
leading
to
decreased
production
with
increasing
pH
(
Singer
and
Reckhow,
1999).

The
major
byproducts
of
ozonation
are
not
affected
by
base
hydrolysis.
However,
pH
can
play
a
role
by
affecting
the
rate
of
decomposition
of
ozone
to
hydroxyl
radical.
The
decomposition
of
ozone
accelerates
as
pH
increases.
This
occurrence
is
thought
to
be
responsible
for
the
decrease
of
some
byproducts
(
e.
g.,
aldeydes)
and
the
increase
of
others
(
e.
g.,
carbonyl
byproduct
and
total
organic
halides;
Singer
and
Reckhow,
1999).
Water
pH
affects
the
balance
of
hypobromite
and
hypobromous
acid
formation
during
the
ozonation
of
waters
containing
significant
concentrations
of
bromides.
At
low
pH,
the
equilibrium
shifts
to
the
less
reactive
hypobromous
acid.
Consequently,
the
overall
formation
of
bromate
decrease
as
pH
decrease
(
Singer
and
Reckhow,
1999).
On
the
other
hand,
Song
et
al.
(
1997)
suggested
that
lower
pHs
favor
the
formation
of
TOX
(
most
likely
TOBr)
during
ozonation.
Singer
and
Reckhow
(
1999)
attributed
this
occurrence
to
the
concurrent
suppressed
decomposition
of
ozone,
changes
in
the
speciation
of
the
oxidized
bromine
and
the
hydrolysis
of
brominated
byproducts.

A.
3
Control
of
DBPs
Alternatives
to
minimize
the
formation
of
DBPs
focus
on
the
removal
of
precursors
during
treatment,
modifications
of
the
oxidation
and
disinfection
processes,
control
of
oxidants
dose
and
residual,
reduction
of
the
residence
time
in
the
distribution
system,
and
removal
of
Significant
Excursion
Guidance
Manual
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Draft
July
2003
A­
7
DBPs
after
formation.
Because
DBPs
are
difficult
to
remove
after
they
have
formed,
control
strategies
typically
focus
on
the
first
four
methods.

A.
3.1
Improving
Precursors
Removal
The
removal
of
organic
precursors
can
be
improved
by
optimizing
coagulation
practices
or
by
employing
advanced
precursor
removal
processes
such
as
granular
activated
carbon
(
GAC)
adsorption,
membrane
filtration,
or
biofiltration.

The
process
of
improving
the
removal
of
NOM
during
the
coagulation
process
is
defined
as
enhanced
coagulation.
Greater
NOM
removal
can
be
obtained
with
adjustments
in
treatment
practice,
specifically
pH
reduction
and
increased
coagulant
dosage.
The
coagulation
of
NOM
appears
to
be
most
efficient
in
the
5
to
6
pH
range.

A
number
of
sources
have
documented
that
granular
activated
carbon
(
GAC)
and
nanofiltration
(
NF)
can
be
more
effective
DBP
precursor
removal
processes
than
conventional
coagulation
treatment
(
McGuire
et
al.,
1989;
Owen
et
al.,
1998;
Snoeyink
et
al.,
1999;
Jacangelo,
1999;
Taylor
and
Wiesner,
1999;
and
references
therein).
Reverse
osmosis
(
RO)
can
also
be
very
effective
for
removing
precursors.
However,
when
precursor
removal
(
as
opposed
to
demineralization)
is
the
primary
treatment
objective,
NF
is
usually
preferred
to
RO
because
of
its
lower
operating
pressure
and
associated
costs.
Both
NF
and
RO
can
remove
bromide
(
Jacangelo,
1999)
while
GAC
does
not
appear
to
remove
bromide
to
any
significant
extent
(
Snoeyink
et
al.,
1999)

Biofiltration
can
be
used
to
remove
a
portion
of
the
NOM
from
water
by
converting
it
into
inorganic
carbon
(
CO2)
and
it
is
considered
a
viable
treatment
alternative
for
precursors
removal
(
Hozalski
and
Bouwer,
1999).
In
general,
the
ideal
location
for
a
biofilter
is
in
a
rapid
media
filter
and
its
performance
can
vary
from
one
plant
to
another
depending
on
factors
such
as
NOM
source
and
characteristics,
use
of
ozone
for
preoxidation,
residence
time
in
the
biofilter,
media
type,
and
water
temperature
(
Hozalski
and
Bouwer,
1999).

Watershed
management
practices
as
well
as
timing
and
location
of
withdrawals
can
also
achieve
reductions
of
DBP
precursors
in
the
raw
water.
The
extent
of
the
benefit
of
implementing
this
strategy
is
site
specific.

A.
3.2
Disinfection
and
Oxidation
Methods
and
Disinfectant
Dose
Chlorination
generally
produces
the
highest
THM
and
HAA
levels.
Other
oxidation
alternatives
to
chlorine
(
e.
g.,
use
of
ozone,
chloramines,
chlorine
dioxide,
potassium
permanganate,
and
UV
radiation)
can
be
used
to
minimize
the
formation
of
TTHM
and
HAAs.
Generally,
decreasing
the
disinfectant
dose
and
residual
reduces
DBP
levels
(
see
Section
A.
2).
However,
when
considering
disinfectant
changes
it
is
important
to
consider
disinfection
needs
and
maintain
the
appropriate
CT
for
disinfection.
Some
alternative
disinfectants
cannot
be
used
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
8
for
secondary
disinfection.
A
detailed
discussion
of
alternative
disinfectants
can
be
found
in
the
Alternative
Disinfectants
and
Oxidants
Guidance
Manual
(
USEPA,
1999,
815­
R­
99­
014).

A.
3.3
Shifting
the
Point
of
Disinfectant
Application
Shifting
the
point
of
disinfectant
application
from
upstream
to
downstream
of
the
coagulation/
settling
process
can
significantly
reduce
the
formation
of
DBPs
for
two
main
reasons:
the
amount
of
precursors
is
reduced
prior
to
disinfectant
addition,
and
(
particularly
for
chlorination)
the
contact
time
between
disinfectant
and
NOM
is
reduced.
The
implementation
of
this
strategy
must,
however,
take
into
account
disinfection
needs.
Adequate
contact
time
must
be
always
provided
after
the
application
of
disinfectant
to
achieve
the
desired
inactivation
of
microorganisms.

A.
3.4
Control
of
DBP
Formation
in
the
Distribution
System
For
systems
maintaining
free
chlorine
residual,
significant
DBP
formation
can
occur
in
the
distribution
system.
A
long
detention
time
in
the
distribution
system,
the
presence
of
NOM
in
the
finished
water
and
the
presence
of
free
chlorine
residual
can
promote
this
occurrence.
It
is
not
uncommon
that
water
leaving
a
treatment
plant
with
low
THM
and
HAA
concentrations
is
found
to
have
high
levels
of
these
compounds
in
the
distribution
system.
Generally,
application
of
secondary
disinfectant
(
particularly
chlorine)
to
form
and
maintain
a
residual
in
the
distribution
system
results
in
DBP
formation.
Implementation
of
distribution
system
water
quality
monitoring,
minimization
of
"
dead
ends,"
optimization
of
storage
tank
utilization,
execution
of
effective
planned
system
flushing
and
management
of
water
age
can
minimize
DBP
formation.

In
some
cases,
booster
chlorination
has
also
been
used
to
control
disinfectant
application
and
minimize
DBP
formation.
For
example,
where
the
majority
of
the
distribution
system
is
in
a
confined
area
near
the
plant,
but
a
small
part
is
far
away
from
the
plant
a
large
dose
of
disinfectant
would
be
required
to
maintain
a
residual
in
the
extreme
part
of
the
system.
A
much
higher
residual
concentration
than
is
needed
would
be
present
in
the
majority
of
the
system.
Thus,
booster
disinfection
in
the
extreme
part
of
the
system
could
dramatically
reduce
the
disinfectant
dose
at
the
plant
and
reduce
DBP
formation
through
the
system.
However,
it
must
also
be
noted
that
in
areas
following
booster
disinfection
facilities,
the
residence
time
is
often
long.
If
conditions
favor
formation
(
i.
e.
water
age,
temperature,
NOM
concentration)
the
additional
disinfectant
added
might
lead
to
the
formation
of
high
TTHM
and
HAA
levels.
Increased
disinfectant
residual
can
also
prevent
biodegradation
of
HAA,
further
increasing
distribution
system
levels.
The
use
or
addition
of
booster
disinfection
requires
careful
consideration
in
any
DBP
control
strategy.

A.
3.5
Assessing
DBP
Formation
and
Control
with
the
WTP
Model
If
a
utility
determines,
based
upon
distribution
system
monitoring,
that
the
DBP
levels
in
their
system
need
to
be
reduced,
they
may
consider
implementing
treatment
changes
in
their
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
9
water
treatment
plant.
To
evaluate
the
potential
impact
of
treatment
changes
on
distribution
system
DBP
levels
prior
to
the
implementation
of
these
changes,
a
system
may
consider
using
the
Water
Treatment
Plant
Simulation
Model
(
WTP
Model)
as
a
preliminary
tool.
This
model
was
initially
developed
to
support
the
DBP
rule
making
process
and
was
later
revised
to
improve
the
predictive
accuracy
using
data
collected
under
the
Information
Collection
Rule
(
ICR).
The
WTP
Model
consists
of
empirical
models
developed
from
bench­,
pilot­,
and
full­
scale
treatability
data.
The
majority
of
the
predictive
algorithms
have
been
verified
with
independent
data
sets
(
Solarik
et
al.,
1999),
and
many
key
algorithms
have
been
calibrated
using
ICR
data
from
full­
scale
surface
water
treatment
plants
(
Swanson
et
al.,
2001).
A
description
of
the
original
model
was
presented
by
Harrington,
et
al.
(
1992)
and
is
available
from
the
USEPA's
Technical
Support
Center
in
Cincinnati.
The
WTP
Model
was
developed
as
a
central
tendency
model,
and
was
not
specifically
designed
to
yield
site
specific
predictions.
However,
a
significantly
improved
form
of
the
WTP
Model
(
Version
2.0)
currently
under
review
by
the
agency
will
facilitate
site
specific
calibration
of
the
model.
Extensive
experiments
to
determine
water
quality
characteristics
are
required
to
validate
site
specific
model
use.

In
addition
to
simulating
the
effects
of
traditional
surface
water
treatment
processes,
such
as
coagulation
(
or
lime
softening),
flocculation,
sedimentation,
and
filtration,
the
WTP
Model
supports
many
advanced
disinfection
and
DBP
control
processes,
such
as:

Enhanced
coagulation

GAC
adsorption

Microfiltration/
ultrafiltration

Nanofiltration/
reverse
osmosis

Ozonation

Biological
filtration

Chlorine
dioxide
addition
The
WTP
Model
generates
predictions
of
bromate
formation
during
ozonation,
chlorite
formation
during
chlorine
dioxide
addition,
and
THM,
HAA,
and
TOX
formation
due
to
free
chlorine
and
chloramine
addition.
These
predictions
are
generated
at
the
effluent
of
each
unit
treatment
process
and
within
the
distribution
system
(
detention
times
are
required
as
inputs).
The
WTP
Model
also
calculates
CT
values
achieved
for
the
various
disinfectants
used
during
treatment
and
log
inactivation
values
for
virus,
Giardia,
and
Cryptosporidium.
Thus,
the
program
can
be
used
to
evaluate
the
relative
effects
of
treatment
modifications
on
disinfection
and
DBP
formation.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
10
References
Bichsel,
Y.,
and
Von
Gunten
U.,
2000.
Environmental
Science
and
Technology,
34
(
13):
2784
Harrington,
G.
W.,
Z.
K.
Chowdhury,
and
D.
M.
Owen.
1992.
Journal
of
the
American
Water
Works
Association,
84(
11):
78.

Hozalski,
R.
M.,
and
E.
J.
Bouwer,
1999.
Biofiltration
for
removal
of
natural
organic
matter.
In
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
Singer,
P.
C.
(
editor)
American
Water
Works
Association,
Denver,
CO.

Hoigne
J.,
and
H.
Bader.
1988.
The
formation
of
trichloronitromethane
(
chloropicrin)
and
chloroform
in
a
combined
ozonation/
chlorination
treatment
of
drinking
water.
Water
Resources.
22
(
3):
313.

Jacangelo,
J.
G..
1999.
Control
of
disinfection
by­
products
by
pressure­
driven
membrane
processes.
In
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
Singer,
P.
C.
(
editor)
American
Water
Works
Association,
Denver,
CO.

James,
M.
S.
1999.
"
Disinfection
by­
products:
an
historical
perspective."
In
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
Singer,
P.
C.
(
editor)
American
Water
Works
Association,
Denver,
CO.

Letterman,
R.
D.,
A.
Amirtharajah,
and
C.
R.
O'Melia.
1999.
Coagulation
and
flocculation.
In
Water
quality
and
treatment.
5th
edition.
Letterman
R.
D.
technical
editor,
American
Water
Works
Association,
McGraw­
Hill,
New
York,
NY.

Malley,
J.
P.,
J.
P.
Shaw,
and
J.
D.
Ropp.
1995.
Evaluation
of
by­
products
produced
by
treatment
of
groundwaters
with
ultraviolet
irradiation.
AWWA
Research
Foundation
Report
and
AWWA,
Denver
CO.

Owen
et
al.,
1998.
Removal
of
DBP
precursors
by
GAC
adsorption.
AWWA
Research
Foundation
Report
No.
90744,
Denver
CO.

Krasner
S.
W.,
1999.
Chemistry
of
disinfection
by­
product
formation,
In
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
Singer,
P.
C.
(
editor)
American
Water
Works
Association,
Denver,
CO.

Reckhow,
D.
A.,
P.
C.
Singer,
and
R.
L.
Malcom.
1990.
Chlorination
of
humic
materials:
byproduct
formation
and
chemical
interpretations.
Environmental
Science
and
Technology.
24(
11):
1655.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
A­
11
Singer,
P.
C.
and
D.
A.
Reckhow.
1999.
Chemical
oxidation.
In
Water
quality
and
treatment.
5th
edition.
Letterman
R.
D.
technical
editor,
American
Water
Works
Association,
McGraw­
Hill,
New
York,
NY.

Singer,
P.
C.
(
editor)
1999.
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
American
Water
Works
Association,
Denver,
CO.

Singer,
P.
C.,
and
G.
W.
Harrington.
1993.
Coagulation
of
DBP
precursors:
theoretical
and
practical
considerations.
Conference
proceedings,
AWWA
Water
Quality
Technology
Conference,
Miami,
FL.

Snoeyink,
V.
L.,
Kirisits,
M.
J.,
C.
Pelekani,
1999.
"
Adsorption
of
disinfection
by­
product
precursors."
In
Formation
and
control
of
disinfection
by­
products
in
drinking
water.
Singer,
P.
C.
(
editor)
American
Water
Works
Association,
Denver,
CO.

Solarik,
G.,
R.
S.
Summers,
J.
Sohn,
W.
J.
Swanson,
Z.
K.
Chowdhury,
and
G.
Amy.
1999.
Extensions
and
verification
of
the
Water
Treatment
Plant
Model
for
DBP
formation.
Conference
proceedings,
1999
American
Chemical
Society
Conference,
Anaheim,
CA.

Song,
R.
P.,
P.
Westerhoff,
R.
Minear,
and
G.
L.
Amy.
1997.
Journal
of
the
American
Water
Works
Association,
89(
6):
69.

Swanson,
W.
J.,
Z.
Chowdhury,
R.
Summers,
and
G.
Solarik.
2001.
Predicting
DBPs
at
full­
scale:
calibration
and
validation
of
the
Water
Treatment
Plant
Model
using
ICR
data.
Conference
proceedings,
2001
AWWA
Annual
Conference,
Washington,
DC.

Taylor
J.
S.,
Wiesner
M.,
1999.
Membranes.
In
Water
quality
and
treatment.
5th
edition.
Letterman
R.
D.
technical
editor,
American
Water
Works
Association,
McGraw­
Hill,
New
York,
NY.

USEPA,
1999.
Alternative
disinfectants
and
oxidants
guidance
manual.
EPA
815­
R­
99­
014.
Appendix
B
Changes
in
Source
Water
Quality
Significant
Excursions
Identified
Using
the
"
Maximum
Concentration
Approach"
This
page
intentionally
left
blank.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
B­
1
The
first
part
of
this
appendix
includes
general
system
information
and
a
summary
of
TTHM
and
HAA5
data
that
resulted
in
Elm
City
having
to
perform
a
significant
excursion
evaluation.
This
information
is
not
required
as
part
of
the
documentation
of
a
significant
excursion.
Only
the
Significant
Excursion
Report
is
required
to
be
completed
by
systems
that
experience
a
significant
excursion.

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

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

Background
Information
for
this
Example
System
Description:

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

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

During
the
last
sampling
period
which
took
place
in
September
2004,
Elm
City
experienced
unusually
high
TTHM
values
(
relative
to
the
LRAA)
at
two
monitoring
locations
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
B­
4
(#
6,
#
8).
Similarly,
unusually
high
HAA5
values
were
detected
at
one
monitoring
location
(#
8).
DBP
data
from
the
previous
year
and
most
recent
sampling
period
(
five
quarters
total)
are
presented
in
Table
B.
2.

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

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

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

Unusually
high
TTHM
samples
were
collected
at
locations
#
6
and
#
8,
and
unusually
high
HAA5
samples
were
collected
at
location
#
8.
The
results
are
significantly
higher
than
both
the
LRAA
at
those
locations
for
the
previous
12­
month
period
and
the
historic
TTHM
and
HAA5
values
at
those
locations
for
the
years
1999­
2003
(
see
Significant
Excursions
Evaluation
Report).
Significant
excursion
were
identified
when
DBP
levels
exceeded
100
µ
g/
L
TTHM
or
75
µ
g/
L
HAA5.
All
of
the
monitoring
locations
affected
by
high
DBP
are
located
in
the
area
served
by
the
Softwood
plant
or
in
the
mixing
zone.
The
city
staff
has
reason
to
believe
that
a
water
quality
change
that
has
occurred
in
Softwood
River
caused
the
increase
in
DBPs.
Significant
Excursion
Guidance
Manual
Proposal
Draft
July
2003
B­
5
Significant
Excursion
Report
date:
October
16th,
2004
Evaluation
Report
Report
prepared
by:
Robert
Doe,
P.
E.

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

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

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

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

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

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

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

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

Sample
preservation
Yes
X
No____

Sample
holding
time
Yes
X
No____

Other
If
no,
please
explain.

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

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

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

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

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

Background
Information
for
this
Example
System
Description:

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

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

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

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

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

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

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

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

Location
No.
#
1
#
2
#
3
#
______

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

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

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

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

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

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

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

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

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

20
ntu)

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

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

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

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

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

Background
Information
for
this
Example
System
Description:

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

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

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

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

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

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

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

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

Location
No.
#
2
#
______
#
______
#
______

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

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

HAA5
Concentration
(
ug/
L)

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

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

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

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

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

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

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

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

Refer
to
the
explanation
following
Section
E.

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

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

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2.0mg/
L)

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

20
ntu)

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

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

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

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

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

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

Background
Information
for
this
Example
System
Description:

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

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

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

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

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

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

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

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

Location
No.
#
1
#
2
#
3
#
______

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

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

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

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

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

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

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

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

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

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

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

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

Background
Information
for
this
Example
System
Description:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Yes
No
X
If
yes,
please
explain.

b)
Were
all
analytical
QA/
QC
measures
met?

Sample
preservation
Yes
X
No____

Sample
holding
time
Yes
X
No____

Other
If
no,
please
explain.

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
X
No
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

Conclusions:

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

Yes
No
X
If
yes,
please
explain:

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

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

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

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

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

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

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

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

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

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

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