DATA COLLECTION
QUALITY ASSURANCE j
FOR THE
NATIONWIDE URBAN RUNOFF PROGRAM
Water Planning Division
U.S. Environmental Protection Agency
Washington, D.C. 20460
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FOREWORD
Environmental monitoring and data collection activities are an essential
part of the Nationwide Urban Runoff Program (NURP). The need for com-
parability, transferability, and nationwide assessment mandates the in-
corporation of acceptable Q'uality Assurance (QA) programs in all NURP
designated prototype projects. The purpose of this report is to provide
guidance to project personnel who are responsible for developing QA
programs for inclusion in their NURP projects and to assist them in
their task.
Dennis N. Athayde, Manager
Nationwide Urban Runoff Program
Nonpoint Sources Branch
Washington, D.C. 20460
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DATA COLLECTION QUALITY ASSURANCE
FOR THE
NATIONWIDE URBAN RUNOFF PROGRAM
WATER PLANNING DIVISION
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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PREFACE
The material contained in this report primarily represents an edited as-
semblage of excerpts from other USEPA publications pulled together within
the context of the Nationwide Urban Runoff Program. Consequently, any
credit belongs to the many unnamed USEPA personnel who served on the
various committees responsible for writing the original source documents.
The undersigned accepts responsibility for selection of what is included
and for any of his own experientially derived notions that have crept in
as well as for the modest amount of new material presented.
Philip E. Shelley, Ph.D.
EG&G Washington Analytical
Services Center, Inc.
Rockville, MD 20850
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VII
CONTENTS
Page
FOREWORD ii
PREFACE iii
I. INTRODUCTION 1
II. GENERAL 2
III. QUALITY ASSURANCE CONTROL COORDINATOR 4
Qualifications 4
General Duties and Responsibilities 5
IV. LABORATORY QUALITY ASSURANCE PROGRAM 7
V. QUALITY ASSURANCE IN THE FIELD 9
General 9
Quality Assurance in Sample Collection 9
Equipment Calibration 11
Sample Preservation and Handling 13
Parameters Requiring Special Precautions 24
VI. CHAIN OF CUSTODY PROCEDURES 26
Introduction 26
Survey Planning and Preparation 27
Sampling Collection, Handling and Identification. . . 27
Transfer of Custody and Shipment 30
Laboratory Custody Procedures 31
Evidentiary Considerations 34
VII. SAMPLING EQUIPMENT CLEANING 35
VIII QUALITY ASSURANCE COSTS 40
References 41
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viii
LIST OF ILLUSTRATIONS
Figure Page
1 Sample Identification Tag Example 29
2 Chain of Custody Record 32
LIST OF TABLES
Table Page
I Quality Assurance Procedures for Field Analysis
and Equipment 14
II Recommendation for Sampling and Preservation of
Samples According to Measurement 20
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QUALITY ASSURANCE
for the
NATIONWIDE URBAN RUNOFF PROGRAM
I. INTRODUCTION
Data collection and analysis will form one of the most important informa-
tion sources for the Nationwide Urban Runoff Program (NURP). Therefore,
it is essential that the monitoring programs that produce these data be
soundly based and that they incorporate Quality Assurance (QA) as an in-
tegral part of their structure. This is as necessary for problem assess-
ment monitoring as it is for Best Management Practice (BMP) effectiveness
monitoring. A rather thorough discussion of 208 monitoring requirements,
methods, and costs is contained in Appendix D of the Areawide Assessment
Procedures Manual (AAPM), and the user is encouraged to become familiar
with that material before embarking on any data collection activity under
NURP. The following material is intended to augment the AAPM in the area
of QA, and it should be incorporated in such NURP efforts.
The need for comparability, transferabi1ity, and nationwide assessment
mandate the incorporation of QA by all NURP designated prototype projects,
However, local exigencies dictate that a procrustean bed approach to
standardization of QA programs is not at all desirable. Therefore, what
follows should be viewed as illustrative rather than prescriptive and
should be used as a guide in developing sound, sensible QA programs that
will be workable at the local level for inclusion in NURP prototype proj-
ects. As these QA programs are developed, they should be forwarded to
USEPA Regional and Headquarters Offices for review and comment prior to
implementation. In this way, the necessary degree of standardization can
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be obtained without placing undue restrictions on any particular proto-
type project.
II. GENERAL
No monitoring program can be any better than its quality control program
allows it to be. In order to be effectively transformed into informa-
tion, we need more than simple values as monitoring data products. We
need to know something about the data quality, i.e., about the "goodness"
or truthfulness of the data. Two terms that relate to the data-gathering
process are conventionally used to describe data quality: accuracy and
precision. Accuracy refers to the agreement between the measurement and
the true value of the measurand, with the discrepancy normally referred
to as error; precision refers to the reproducibility (repeatability) of
a measurement when repeated on a homogenous time-stationary measurand,
regardless of the displacement of the observed values from the true value,
and thus indicates the number of significant digits in the result. We
are, therefore, interested in establishing the best estimate of a meas-
ured quantity and the degree of precision of this estimate from a series
of repeated measurements. Calibration, whether it be of a piece of flow
measurement equipment, a chemical method for wastewater analysis, a
stormwater management model, or whatever, is simply the process of de-
termining estimates of accuracy and precision.
Discrepancies between the results of repeated observations, or errors,
are inherent in any measurement process, since it is recognized that the
true value of an object of measurement can never be exactly established.
These errors are customarily classified into two main groups: systematic
and random (or accidental) errors. Systematic errors usually enter into
records with the same sign and frequently with either the same magnitude
(e.g., a zero offset) or with an establishable relationship between the
magntitude of the measurement and the error. The methods of symmetry and
substitution are frequently used to detect and quantify systematic errors.
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In the method of symmetry, the test is repeated in a symmetrical or re-
versed manner with respect to the particular condition that is suspect.
In the method of substitution, the object of measurement is replaced by
one of known magnitude (a calibration standard), an instrument with a
known calibration curve is substituted for the measuring instrument in
question, and so on. Thus, systematic errors bear heavily on the accu-
racy of the measurement.
Random errors, on the other hand, are due to irregular causes, too many
in number and too complex in nature to allow their origin to be deter-
mined. One of their chief characteristics is that they are normally as
likely to be positive as negative and, therefore, are not likely to have
a great effect on the mean of a set of measurements. The chief aim of a
data quality assurance effort is to account for systematic errors and
thereby reduce errors to the random class, which can be treated by simple
probability theory in order to determine the most probable value of the
object of observation and a measure of the confidence placed in this
determination.
The statistical measures of location or central tendency (e.g., the var-
ious averages, mean, median, mode, etc.) are related to accuracy. The
statistical measures of dispersion or variability (e.g., variance and
standard deviation, coefficient of variation, and other measures derived
from central moments of the probability density function) are related to
precision.
Even lacking enough data for statistical treatment, there are some anno-
tations that the data gatherer can make to increase the usefulness of the
data. For example, inspection of equipment and records may indicate pe-
riods of instrument malfunction or failure (e.g., power interruptions).
These facts are important and should form a part of the total record.
There may be circumstances discovered during site visits that would have
an effect on preceding data that cannot be readily determined, e.g.j a
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partially blocked sampler intake, a rag caught in the notch of a weir,.
etc. These facts should also be noted and, where at all feasible, some
qualitative notation as to expected data quality (e.g., poor, very good,
etc.) should be made.
III. QUALITY ASSURANCE CONTROL COORDINATOR
Assignment of responsibility is essential in establishing a viable qual-
ity assurance (QA) program. Therefore, a QA control coordinator should
be designated and given responsibility for the entire monitoring QA pro-
gram. Although the level of effort expended by this person will be a
direct function of the size of the overall monitoring program, where at
all possible it should be considered a full-time position. In its mini-
mal requirements for a water quality assurance program, the USEPA pro-
vides the following guidance for this position.
A. Qualifications
1. The coordinator should have, as a minimum, a bachelor's
degree in chemistry, biology, or microbiology, with at least
5 years of experience in his respective discipline. In addi-
tion, the coordinator must have actively worked in a water
quality laboratory for at least 2 years. Experience in sta-
tistical quality control techniques and/or academic courses
in mathematics and statistics is also highly desirable.
2. The coordinator maintains close liaison with the appropriate
USEPA Regional Analytical Quality Control Coordinator and is
responsible for the overall quality assurance program in his
laboratory. The coordinator should report to the appropriate
level: In no case should his function be subordinate to an
individual responsible for direct conduct of sampling or
analyses.
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B. General Duties and Responsibilities
The coordinator is responsible for developing and implementing an inter
and intralaboratory quality control program. Specific duties include,
but are not necessarily limited to:
1. Participating in the overall quality control plan. This
includes all elements of the sampling and analytical pro-
grams. The coordinator carries out this activity within
USEPA quality control and methodology guidelines. Other
recommended and accepted procedures can be used to supple-
ment these guidelines.
2. Administering the interlaboratory quality control program
as a continuing in-house activity to ensure the integrity
and validity of analytical data.
3. Measuring the precision and/or accuracy of analytical re-
sults. Provides online quality control of samples, i.e.,
reference samples, duplicates, control charts, and spiked
and audit samples.
4. Providing a permanent record of instrument and analyst
performance as a basis for evaluating data.
5. Identifying training needs and technical methodology gaps.
6. Upgrading the overall quality of laboratory performance
by recommending procedural and personnel changes, as re-
quired, to ensure the validity and integrity of the data.
7. Coordinating the inter and intralaboratory quality control
program with the Environmental Monitoring and Support
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Laboratory, Cincinnati (ESMl.-CIN), and other governmental
and commercial laboratories. This involves participating
in round-robin methodology studies and providing quality
control check samples to requesting laboratories.
8. Evaluating and discussing the results of activities out-
lined in items 1 through 7 above with the appropriate
individuals involved. When an analysis is out of control
or a discrepancy is noted, the coordinator should be noti-
fied and appropriate corrective action should be taken.
The coordinator should develop a training program to ensure a minimal
level of proficiency. He must recognize variations in ability and pro-
vide training to ensure that professional skills are appropriate to the
task. Training programs should be administered in order to develop that
level of competence which is necessary to carry out assigned functions.
Moreover, these programs should be carried out in full cooperation with
USEPA regional analytical quality control coordinators.
The coordinator should establish basic requirements (equipment, proper
facilities, etc.) for operating a water quality laboratory. These re-
quirements should not be included as part of the quality assurance budget.
Laboratory facilities should provide an environment free from atmospheric
contaminant levels, which can affect the desired analyses. The labora-
tory should be cjean, air-conditioned and/or heated, and have a well-
lighted work area. Safety features and other facilities consistent with
operational requirements should be provided.
The coordinator will implement his planned quality assurance program with
an initial onsite laboratory evaluation. Subsequent performance of anal-
ysis on audit samples and participation in split sample programs with the
USEPA regional office should also be required.
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IV. LABORATORY QUALITY ASSURANCE PROGRAM
The Environmental Monitoring and Support Laboratory (EMSL) has prepared
a handbook for analytical quality control that provides sufficient in-
formation to allow inauguration or reinforcement of a program that will
emphasize early recognition, prevention, and correction of factors lead-
ing to breakdowns in the validity of data products from water and waste-
water laboratories.
A very important step that must be established before proceeding to the
tests and studies discussed in the following paragraphs is the establish-
ment of the precision and accuracy of methods used in the particular an-
alytical laboratory involved. However, as one parameter is tested and
its testing methods are checked for precision and accuracy, the test
procedures that follow, can be started for that parameter. After a 6- to
12-month period, all methods used in the laboratory should have been
tested for precision and accuracy, and the following tests and studies
begun.
According to the handbook cited above, actual samples, not standards,
should be used to determine the precision and accuracy of the methods.
The resulting data should be compared with published interlaboratory
precision/accuracy data to determine that the analyses are in control.
Once these data are documented, the procedural steps that follow should
be practiced on a routine basis. Check the handbook for specific details.
Quality control check samples (reference samples) are provided as a tech-
nical service free of charge to the requestor, and can be obtained through
the appropriate USEPA regional analytical quality control coordinator.
Do not use them on a daily basis; rather, use them as an independent check
on the entire system approximately every 3 to 6 months. The samples were
prepared as sterile concentrate and are in sealed vials. Constituents
available include mineral series, mercury, LAS, chlorophyll, and others
to be announced.
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The following studies are for laboratory performance and methods valida-
tion. They should be included in the overall quality assurance effort,
and the results documented to ensure that data are valid.
1. Methods Validation Studies. The laboratory should partici-
pate in round-robin studies conducted according to official
programs to determine the interlaboratory precision and
accuracy of mthods.
2. Audit Sampling Programs. The laboratory should partici-
pate in the use of split, blind, performance check samples
and other audit-type samples that are prepared either on
an intra or interlaboratory basis. The resulting compara-
tive data should compare favorably with the established
precision and accuracy data of the respective measurements.
In terms of day-to-day activities, the normal working routine should
require:
1. That duplicate samples be run approximately 10 to 20 per-
cent of the time to verify the reproducibility of the re-
spective methods. Data should compare favorably with
initially established precision data.
2. That known amounts of standard material be added to samples
on a 1-to-l concentration basis to verify the ability of
the method to measure the particular constituent under con-
sideration. Again, approximately 10 to 20 percent of the
time should be spent on this activity. The resulting data
should compare favorably with the initially established
accuracy data.
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3. That some systematic, documented method for recording
quality assurance data be in routine use. The method
should be prepared so that it is available for future
reference and can be readily understood and interpreted
by all concerned.
V. QUALITY ASSURANCE IN THE FIELD
A. General
Quality assurance in the field is probably one of the most slighted as-
pects of any monitoring QA program. This is especially important since
it is here that most errors and inconsistencies are found. All NURP QA
programs should adequately address QA in the field. It is especially
important that standardized routines be developed and reduced to writing
to impart clear understanding to all involved and avoid miscommunication.
Such trite phrases as "manual samples shall be obtained using best ac-
ceptable procedures" should be avoided, and explicit descriptions used
instead. The following discussion only serves to highlight some of the
aspects that must be considered. For a discussion of field procedures
for flow measurement, sampling, etc., refer to the AAPM.
B. Quality Assurance in Sample Collection
Control checks should be performed during the actual sample collection.
These checks are used to determine the performance of the sample collec-
tion system. In general, the most common errors produced in monitoring
are usually caused by improper sampling, poor preservation, or lack of
adequate mixing during compositing and testing. The following checks
will help the QA Coordinator to determine when the sample collection
system is out-of-control:
1. Duplicate Samples. At selection stations on a random time
frame, collect duplicate samples using the field equipment
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installed at the site. If automatic sampling equipment is
not installed at the site, collect duplicate grab samples.
This will provide a proficiency check for precision.
2. Split Samples. Aliquots of the collected sample may be
given to other laboratories as a check on the main labora-
tory procedures. Differences between results can then be
evaluated and the cause of the difference usually identified.
3. Spiked Samples. Known amounts of a particular constituent
should be added to an actual sample or blanks of deionized
water at concentrations where the accuracy of the test
method is satisfactory. The amount added should be coor-
dinated with the laboratory. This method will provide a
proficiency check for accuracy of the field sampling
procedures.
4. Sample Preservative Blanks. Acid and other chemical pre-
servatives can become contaminated after a period of use
in the field. The sampler should add the same quantity of
preservative to a sample of distilled water as normally
would be added to the wastewater sample. This preservative
blank is sent to the laboratory for analysis and the blank
is subtracted from the sample value. Liquid chemical pre-
servatives should be changed every two weeks or sooner if
contamination occurs.
5. Precision, Accuracy, and Control Charts. A minimum of
seven sets each of comparative data for duplicates, spikes,
split samples and blanks should be collected to define ac-
ceptable estimates of precision and accuracy criteria for
data validation. See EPA's "Handbook for Analytical
Quality Control in Water and Wastewater," or W. J. Youden's
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"Statistical Techniques for Collaborative Tests," for dis-
cussions of precision, accuracy, and quality control charts
and their calculations.
C. Equipment Calibration
When equipment is used in a monitoring program, it must be well main-
tained and calibrated if readings are to have validity and, therefore,
such efforts form an important part of a quality control program. Un-
fortunately, in view of the wide number of equipment types and designs
that might be employed, the only real guidance that can be offered is
to follow the manufacturer's directions and specifications. The impor-
tant thing is that calibration be performed in a systematic fashion and
that the results of all calibrations and checks be recorded permanently.
The use of equipment tags that indicate when the last calibration was
performed and where details of the calibration can be found in the per-
manent record is usually warranted. With the implication that manufac-
turer's specifications should always be followed, a few general
guidelines for field equipment are given below.
1. Automatic samplers should have all operating aspects
checked out in the laboratory before being taken to the
field. Equipment used in long-term installations should
be checked out at least monthly and often weekly, depend-
ing upon design. Superficial checkout and maintenance
should be performed whenever samples are collected. For
constant aliquot volume type composites, aliquot volume
should be verified in the field after installation. Sam-
pling equipment should be recalibrated immediately after
use in the field.
2. Flow-measuring devices should be calibrated immediately
before and after use in the field. The frequency of de-
veloping full range calibration curves will depend upon
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the type of device involved. At least three spot checks
(one in the lower quarter of range, one near midrange,
and one in the upper quarter of range) are usually re-
quired to verify a calibration curve established earlier
and for large, fixed flow measurement stations.
3. Direct-reading field instruments should be calibrated im-
mediately before and after use in the field. In addition,
spot checks'should be made at reasonable intervals through-
out the sampling schedule.
4. Fixed continuous monitoring devices should be calibrated
in the laboratory prior to installation. Wherever possi-
ble, results should be verified by approved manual method-
ology. The calibration of sensors should be checked' at
least weekly, and preferably on a daily basis.
A calibration plan should be developed and implemented for all field an-
alysis test equipment and calibration standards to include: calibration
and maintenance intervals; listing of required calibration standards;
environmental conditions requiring calibration; and a documentation
record system.
Written calibration procedures should be provided for all measuring and
test equipment. A procedure should:
1. Specify where the procedure is applicable, e.g., free re-
sidual chlorine by amperometric titration at power plant
cooling water effluents.
2. Provide a brief description of the calibration procedure.
A copy of the manufacturer's instructions is usually
adequate.
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3. List calibration standards, reagents, and accessory equip-
ment required.
4. Specify the documentation, including an example of the
format used in the field quality assurance log book.
Field equipment should be labeled to indicate the calibration date, when
calibration expires and when maintenance is due.
Table I summarizes quality assurance procedures for field analyses gen-
erally conducted during sampling inspections.
D. Sample Preservation and Handling
Having collected a representative sample in question, .there remains the
problem of sample preservation and analysis. It is a practical impossi-
bility either to perform instant analyses of the sample on the spot or
to completely and unequivocally preserve it for subsequent examination.
Preservative techniques can only retard the chemical and biological
changes that inevitably continue following extraction of the sample from
its parent source. In the former case, changes occur that are a func-
tion of the physical conditions - metal cations may precipitate as hy-
droxides or form complexes with other .constituents; cations or anions
may change valence states under certain reducing or oxidizing conditions;
constituents may dissolve or volatize with time, and so on. In the lat-
ter case, biological changes taking place may change the valence state
of an element or radical; soluble constituents may be converted to or-
ganically bound materials in cell structures; cell lysis may result in
release of cellular material into solution, etc.
Preservation methods are relatively limited and are generally intended
to retard biological action, retard hydrolysis of chemical compounds and
complexes, and reduce volatility of constituents. They are generally
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TABLE I. QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT
Parameter
General
Quarterly
1. Dissolved Oxygen
(a)
Membrane
Electrode
(b)
Winkler-Azide
method
PH - Electrode
Method
Enter the make,
model, serial and/or
ID number for each
meter in a log book.
Report data to
nearest 0.1 mg/1.
Record data to
nearest 0.1 mg/1
Enter the make,
model, serial and/or
ID number for each
meter in a log book.
(i) Calibrate meter us-
ing manufacturer's
instructions or
Winkler-Azide method.
(ii) Check membrane for
air bubbles and holes.
Change membrane and
KC1 if necessary.
(iii) Check leads, switch
contracts, etc. for
corrosion and shorts
if meter pointer re-
mains offscale.
Duplicate analysis
should be run as a
precision check.
Duplicate values
should agree within
±0.2 mg/1.
(i) Calibrate the system
against standard buffer
solutions of known pH
value, e.g. ,4,7, and
9 at the start of a
sampling run.
Check instrument cali-
bration and linerarity
using a series of at
least three dissolved
oxygen standards.
Take all meters to the
laboratory for mainte-
nance, calibration, and
quality control checks.
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TABLE I. QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT (Cont'd)
Parameter
General
Quarterly
2. PH (Cont'd)
(ii) Periodically check the
buffers during the
sample run and record
the data in the log
sheet or book.
(iii) Be on the alert for er-
ratic meter response
arising from weak batter-
ies, cracked electrode,
fouling, etc.
(iv) Check response and lin-
earity following highly
acidic or alkaline sam-
ples. Allow additional
time for equilibration.
(v) Check against the clos-
est reference solution
each time a violation is
found.
(vi) Rinse electrodes thor-
oughly between samples
and after calibration.
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TABLE I. QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT (Cont'd)
Parameter
General
Quarterly
3. Conductivity
Residual Chlorine
Amperometric
Titration
Enter the make,
model, serial and/or
ID number for each
meter in a log book.
Enter the make,
model, ID and/or
serial number of
each titration ap-
paratus in a log
book. Report re-
sults to nearest
0.01 mg/1.
(i) Standardize with KC1
standards having similar
specific conductance
values to those antici-
pated in the samples.
Calculate the cell con-
stant using two differ-
ent standards.
Cell Constant = Stand-
ard Value/Actual Value
Specific Conductance =
Reading x Cell Constant
(ii) Rinse cell after sample
to prevent carryover.
(i) Refer to instrument
manufacturer's in-
structions for proper
operation and calibra-
tion procedures.
Take all meters to lab
for maintenance, cal-
ibration and quality
control checks.
Check temperature
compensation.
Check date of last
platinizing and re-
platinizing if
necessary.
Analyze NBS or EPA
reference standard and
record actual vs ob-
served readings in the
log.
Biweekly: Return in-
strument to lab for
maintenance and addi-
tion of fresh, stand-
ardized reagents.
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TABLE I. QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT (Cont'd)
Parameter
General
Quarterly
5. Temperature
(a) Manual
Enter the make,
model, serial
number and/or ID
number and temper-
ature range for
each thermometer.
All standardization
shall be against a
NBS or NBS calibrated
thermometer. Readings
shall agree within
±1°C. If enforcement
action is anticipated
calibrate the ther-
mometer before and
after analysis. All
data shall be read to
the nearest 1°C. Re-
port data between 10° -
99°C to two significant
figures .
(i) Check for air spaces
or bubbles in the col
umn, cracks, etc.
Compare with a known
source if available.
Biweekly: Check at two
temperatures against a
NBS or equivalent
thermometer. Enter
data in a log book.
Temperature readings
shall agree within
±1°C or the thermometer
shall be replaced or
recalibrated.
Initially and Biannually;
Accuracy shall be de-
termined throughout the
expected working range
0° to 50°C. A minimum
of three temperatures
within the range should
be used to verify ac-
curacy. Preferable
ranges are: 5° - 10°,
15° - 25°, 35° - 45°C.
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TABLE I. QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT (Cont'd)
Parameter
General
Quarterly
(b) Thermistors;
Thermographs,
etc.
Flow Measurement
Automatic
Samplers
Enter the make, model ,
serial and/or ID num-
ber of the instrument
in a log book. All
standardization shall
be against a NBS or
NBS calibrated ther-
mometer. Readings
should agree within
±1°C. If enforcement
action is anticipated
refer to the procedure
listed in 5(a) above.
Enter the make, model,
serial and/or ID num-
ber of each flow mea-
surement instrument
in a log book.
Enter the make, model,
serial and/or ID num-
ber of each sampler in
a log book.
Check thermistor or sens-
ing device for response
and operation according
to the manufacturer's
instructions. Record ac-
tual vs standard temper-
ature in log book.
Install the device in
accordance with the
manufacturer's instruc-
tions and with the pro-
cedures given in
Section VI of this manual.
Inspect equipment for proper
functioning, inspect intake
and sample transport tubing
and clean as required.
Initially and
Biannually:
Accuracy shall be de-
termined throughout the
expected working range
0° to 50°C. A minimum
of three temperatures
within the range should
be used to verify ac-
curacy. Preferable
5° - 10°,
45°C
ranges are:
1 K°
- 25°, 35° -
Annually:
Affix record of cali-
bration NBS, manufac-
turer or other, to the
instrument log.
Check intake velocity
vs head (minimum of
three samples), and
clock time setting vs
actual time interval.
00
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limited to pH control, chemical addition, refrigeration, and freezing.
EMSL in its Methods for Chemical Analysis of Water and Waste has com-
piled a list of recommendations for preservation of samples according
to the measurement analysis to be performed. In order to provide an
overview for some common parameters, this list has been reproduced here
as Table II. For other parameters and program design, reference should
be made to the Parameter Handbook of the AAPM.
Proper sample handling is also essential to successful results from any
monitoring program. Great pains taken in all other areas may be for
nought if samples are accidentally exchanged or otherwise misidentified.
The same sample identification system obviously would not be suitable
for all types of monitoring programs all across the country, but every
program must have one, and it should be thoroughly understood by all in-
volved. A few general guidelines are given below.
1. Each sample container must have a designation, normally a
number, that uniquely distinguishes it from all other
samples in the program.
2. When frequent sampling over a long time period is involved,
consideration should be given to incorporating a temporal
indication as a part of the sample identification number;
e.g., the number of the week in a year, the last two dig-
its of the year, etc. The temptation to code too much in-
formation about the sample into its identification number
must be resisted, however, or else the risk of mixups due
to unauthorized abbreviations becomes too great.
3. Consideration should be given to the use of preprinted,
stickyback labels in many instances. Be certain, however,
that they are waterproof.
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20
TABLE II. RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT1
Measurement
Aci di ty
Alkalinity
Arsenic
BOD
Bromide
COD
Chloride
Chlorine Req
Color
Cyanides
Dissolved Oxygen
Probe
Winkler
Fluoride
Hardness
Iodide
MBAS
Metals
Dissolved
Suspended
Total
Vol
Req
(ml)
100
100
100
1000
100
50
50
50
50
500
300
300
300
100
100
250
200
100
Container
P,G2
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,6
P,G
G only
G only
P,G
P,G
P,G
P.G
P,G
Preservative
Cool, 4°C
Cool, 4°C
HN03 to pH<2
Cool, 4°C
Cool, 4°C
H2S04 to pH<2
None Req
Det on Site
Cool, 4°C
Cool, 4°C
NaOH to pH 12
Det on site
Fix on site
Cool, 4°C
Cool, 4°C
HN03 to pH<2
Cool, 4°C
Cool, 4°C
Filter on site
HN03 to pH<2
Filter on site
HNOQ to pH<2
Holding
Time6
24 Hr
24 Hr
6 Mo
6 Hr3
24 Hr
7 Days
7 Days
No Holding
24 Hr
24 Hr-
No Holding
4-8 Hr
7 Days
7 Days
24 Hr
24 Hr
6 Mo
6 Mo
5 Mo
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21
TABLE II. RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT1 (Cont'd)
Measurement
Mercury
Dissolved
Total
Nitrogen
Ammonia
Kjeldahl
Nitrate
Nitrite
NTA
Oil and Greese
Organic Carbon
PH
Phenol ics
Vol
Req
(ml)
100
100
400
500
100
50
50
1000
25
25
500
Container Preservative
P,G Filter
HN03 to pH<2
P,G HN03 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
P,G Cool, 4°C
G only Cool , 4°C
H2S04 or
HC1 to pH<2
P,G , Cool, 4°C
H2S04 to pH<2
P,G Cool, 4°C
Det on site
G only Cool 4°C
Holding
Time6
38 Days
(Glass)
13 Days
(Hard
Plastic)
38 Days
(Glass)
13 Days
(Hard
Plastic)
24 Hrk
7 Days
24 Hr4
24 Hr4
24 Hr
24 Hr
24 Hr
6 Hr3
24 Hr
H3P04 to pH<4
l.Og CuS04/l
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22
TABLE II. RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT1 (Cont'd)
Measurement
Phosphorus
Ortho-
phosphate,
Dissolved
Hydrolyzable
Total
Total ,
Dissolved
Residue
Filterable
Non- Filterable
Total
Volatile
Settleable Matter
Selenium
Silica
Specific
Conductance
Sulfate
Sulfide
Sulfite
Temperature
Vol
Req
(ml)
50
50
50
50
100
100
100
100
1000
50
50
100
50
500
50
1000
Container
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P,G
P only
P,G
P,G
P,G
P,G
P,G
Preservative
Filter on site
Cool, 4°C
Cool,4°C
HpSO. to pH<2
Cool , 4°C
Filter on site
Cool, 4°C
Cool, 4°C
Cool, 4°C
Cool, 4°C
Cool, 4°C
None Req
HN03 to pH<2
Cool, 4°C
Cool, 4°C
Cool, 4°C
2 ml zinc
acetate
Det on site
Det on site
Holding
Time6
24 Hr4
24 Hr4
7 Days
24 Hr1*
7 Days
7 Days
7 Days
7 Days
24 Hr
6 Mo
7 Days
24 Hr5
7 Days
24 Hr
No Holding
No Holding
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23
TABLE II. RECOMMENDATION FOR SAMPLING AND PRESERVATION
OF SAMPLES ACCORDING TO MEASUREMENT1 (Cont'd)
Measurement
Threshold Odor
Turbidity
Vol
Req
(ml)
200
100
Container
G only
P,G
Preservative
Cool,
Cool ,
4°C
4°C
Holding
Time6
24 Hr
7 Days
1 More specific instructions for preservation and sampling are
found with each procedure as detailed in this manual. A general
discussion on sampling water and industrial wastewater may be
found in ASTM, Part 23, p. 72-91 (1973).
2 Plastic or Glass
3 If samples cannot be returned to the laboratory in less than
6 hours and holding time exceeds this limit, the final reported
data should indicate the actual holding time.
"* Mercuric chloride may be used as an alternate preservative at a
concentration of 40 mg/1, especially if a longer holding time is
required. However, the use of mercuric chloride is discouraged
whenever possible.
5 If the sample is stabilized by cooling, it should be warmed to
25°C for reading, or temperature correction made and results
reported at 25°C.
6 It has been shown that samples properly preserved may be held
for extended periods beyond the recommended holding time.
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24
4. The use of color-coded labels has been successful where sample
splitting or different preservation techniques are employed.
In the latter case, for example, a green label could indicate
that nitric acid had been added and that, therefore, an analyst
could obtain aliquots from this sample for metal analyses, etc.
5. The type of sample, date, and any preservatives added should
be written on the sample label in the field. Additional in-
formation should be noted in the field notebook and on supple-
mental forms where used.
6. The foregoing should be observed in addition to any chain-
of-custody procedures that are involved.
E. Parameters Requiring Special Precautions
1. Organics. Preservatives, holding times, sampling procedures,
and sample aliquots or volume for specific organic analysis
should be determined prior to each survey after consultation
with appropriate lab personnel. The survey leader should
provide, if possible, the following information: raw prod-
ucts; chemical processes; and types of wastewater treatment.
This will assist the laboratory in making their recommenda-
tions regarding sampling and handling procedures. Normally,
a one to four liter grab sample, collected in a glass jar
with a teflon or cleaned aluminum foil lined screw cap, will
provide a sufficient sample volume. Normally, if biological
activity cannot be stopped by addition of a preservative,
samples should be iced until analysis and received in the
laboratory within 24 hours.
2. Acidity - Alkalinity. Compositing of grab samples for acidity,
alkalinity, and suspended solids analysis should not be done
if a waste discharge varies outside the pH range specified
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25
in NPDES permits. Mixing acid grab samples with neutral or
basic grab samples changes the acidity-alkalinity relation-
ship and results in a composite sample which may not be rep-
resentative of the discharge during the compositing period.
The acid-base reaction may also dissolve a portion of the
inorganic solids. Thus, a discharge which varies outside
the pH range specified in the NPDES permit should be ana-
lyzed for acidity, alkalinity and suspended solids on an
individual "grab" sample basis.
3. Miscellaneous Parameters. Based on present knowledge, the
following parameters should not be collected using automatic
samples but should be preserved at the time of sample col-
lection whether the sample is a grab sample or a composite
of grab samples.
(a) Dissolved Parameters
Samples should be membrane filtered at the time of collec-
tion, if at all possible, and composited if necessary under
acidified conditions. In any case, preservation should not
be performed until after filtration.
(b) Mercury, Total
Samples for mercury analysis must be acidified at the time
of collection. The addition of potassium dichromate will
help stabilize dissolved mercury, see El-Awady, et. al.
(c) Phenolics and Cyanides
Simple phenolic compounds and free cyanide may signifi-
cantly degrade if not preserved at the time of sample col-
lection. If the sample contains residual chlorine, it is
also necessary to dechlorinate the sample prior to
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26
preservation. Standard Methods recommends the use of
ferrous sulfate as a dechlorination agent for phenolics
and ascorbic acid for cyanide.
(d) Sulfide and Sulfite
Table II lists cooling to 4 degrees Centigrade as the pre-
servative for sulfide, while there is no acceptable preser-
vative listed for sulfite and the sample must be analyzed
at the time of collection.
VI. CHAIN OF CUSTODY PROCEDURES
Although strict Chain of Custody procedures will in all likelyhood not
be warranted for most NURP designated prototype projects, the procedures
developed by the USEPA of Enforcement should be thoroughly reviewed and
used as a framework for developing sample handling procedures for each
project. Recommended Chain of Custody procedures as presented in the
USEPA NPDES Compliance Sampling Inspection Manual are presented below.
A. Introduction
As in any other activity that may be used to support litigation, regula-
tory agencies must be able to provide the chain of possession and cus-
tody of any samples which are offered for evidence or which form the
basis of analytical test results introduced into evidence in any water
pollution case. It is imperative that written procedures be available
and followed whenever evidence samples are collected, transferred,
stored, analyzed, or destroyed. The primary objective of these proce-
dures is to create an accurate written record which can be used to
trace the possession and handling of the sample from the moment of its
collection through analysis and its introduction as evidence.
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27
A sample is in someone's "custody" if:
1. It is in one's actual physical possession; or
2. It is in one's view, after being in one's physical
possession, or
3. It is in one's physical possession and then locked up so
that no one can tamper with it; or
4. It is kept in a secured, area restricted to authorized
personnel only.
B. Survey Planning and Preparation
The evidence gathering portion of a survey should be characterized by
the conditions stipulated in the permit or the minimum number of samples
required to give a fair representation of the wastewater quality. The
number of samples and sampling locations, determined prior to the sur-
vey, must satisfy the requirements for NPDES monitoring or for estab-
lishing a civil or criminal violation.
A copy of the study plan should be distributed to all survey partici-
pants in advance of the survey date. A pre-survey briefing is helpful
to reappraise survey participants of the objectives, sampling locations
and chain of custody procedures that will be used.
C. Sampling Collection, Handling and Identification
1. It is important that a minimum number of persons be involved
in sample collection and handling. Guidelines established
in this manual for sample collection, preservation and hand-
ling should be used. Field records should be completed at
the time the sample is collected and should be signed or
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28
initialed, including the date and time, by the sample col-
lector(s). Field records should contain the following
information:
(a) unique sample or log number;
(b) date and time;
(c) source of sample (including name, location and sample
type);
(d) preservative used;
(e) analyses required;
(f) name of collector(s);
(g) pertinent field data (pH, DO, Cl residual, etc.);
(h) serial numbers on seals and transportation cases.
2. Each sample is identified by affixing a pressure sensitive
gummed label or standardized tag on the container(s). This
label should contain the sample identification number, date
and time of sample collection, source of sample, preserva-
tion used and the collector(s)' initial(s). Analysis re-
quired should be identified. Where a label is not available,
the same information should be affixed to the sample con-
tainer with an indelible, water proof, marking pen. Examples
of sample identification tags are illustrated in Figure I.
3. The sample container should then be placed in a transporta-
tion case along with the chain of custody record form, per-
tinent field records and analysis request form as needed.
All records should be filled out legibly in pen.
The use of the locked and sealed chests will eliminate the
need for close control of individual sample containers.
However, there will undoubtedly be occasions when the use
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29
EPA,
Z Station No. Date Time Sequence No.
f
2 Station Location
n,a».
Csmp,
BOD M,»»U Remarb /Preservative:
Solidi _,, . u . Gil «n«J Gr*«*«
COD D 0
Nutrient* Bflct,
Samplers
GENERAL CHEMISTRY
1
2 Official Sample No. <
O ui
0 g 1
rf «J 1
.
^ /)u
6 a
UI 3
* 0
Da
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30
of a chest is inconvenient. On those occasions, the sampler
should place a seal around the cap of the individual sample
container which would indicate tampering if removed.
4. When samples are composited over a time period, unsealed
samples can be transferred from one crew to the next crew.
A list of samples will be made by the transferring crew
and signed for by a member of the receiving crew. They will
either transfer the samples to another crew or deliver them
to laboratory personnel who will then acknowledge receipt
in a similar manner.
5. Color slides or photographs taken of the sample outfall loca-
tion and of any visible pollution are recommended to facili-
tate identification and later recollection by the inspector.
A photograph log should be made at the time the photo is
taken so that this information can be written later on the
back of the photo or the margin of the slide. This should
include the signature of the photographer, time, date, site
location and brief description of the subject of the photo.
Photographs and written records, which may be used as evi-
dence, should be handled in such a way that chain of custody
can be established.
D. Transfer of Custody and Shipment
1. When transferring the possession of the samples, the trans-
feree must sign and record the date and time on the chain of
custody record. Custody transfer, if made to a sample
custodian in the field, should account for each individual
sample, although samples may be transferred as a group.
Every person who takes custody must fill in the appropriate
section of the Chain of Custody Record. To prevent undue
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31
proliferation of custody records, the number of custodians
in the chain of possession should be as few as possible.
2. The field custodian or field inspector, if a custodian has
not been assigned, is responsible for properly packaging
and dispatching samples to the appropriate laboratory for
analysis.
This responsibility includes filling out, dating and signing,
the appropriate portion of the Chain of Custody Record. A
Chain of Custody Record format containing the necessary pro-
cedural elements is illustrated in Figure 2.
3. All packages sent to the laboratory should be accompanied by
the Chain of Custody Record and other pertinent forms. A
copy of these forms should be retained by the origination
office (either carbon or photo copy).
4. Mailed packages can be registered with return receipt re-
quested. If packages are sent by common carrier, receipts
should be retained as part of the permanent chain of custody
documentation.
5. Samples to be shipped must be so packed as not to break and
the package so sealed or locked that any evidence or tamper-
ing may be readily detected.
E. Laboratory Custody Procedures
1. A specific person shall be designated custodian and an al-
ternate designated to act as custodian in the custodian's
absence. All incoming samples shall be received by the
custodian, who shall indicate receipt by signing the
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32
CHAIN OF CUSTODY RECORD
SURVEY
STATION
NUMBER
STATION LOCATION
DATE
Relinquished by: (Signomn)
Relinquished by: /s,g/wiu/-»i
Relinquished by: (s;9noiu.-«;
Relinquished by: (Signatun)
Dispatched by: isignotun)
Method of Shipment:
Date;
TIME
SAMPLERS: is**,**)
SAMPIE TYPE
Water
Comp.
Crab.
Air
SEO.
NO.
NO. OF
CONTAINERS
ANALYSIS
REQUIRED
Received by: (s.flnoru«j
Received by: (i;ono
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33
accompanying custody forms and who shall retain the signed
forms as permanent records.
2. The sample custodian shall maintain a permanent log book to
record, for each sample, the person delivering the sample,
the person receiving the sample, date and time received,
source of sample, sample identification or log number, how
transmitted to the laboratory and condition received
(sealed, unsealed broken container, or other pertinent
remarks). A standardized format should be established for
log book entries.
3. A clean, dry, isolated room, building, and/or refrigerated
space that can be securely locked from the outside shall be
designated as a "sample storage security area".
4. The custodian shall ensure that heat-sensitive, light-
sensitive samples, radioactive, or other sample materials
having unusual physical characteristics, or requiring
special handling, are properly stored and maintained prior
to analysis.
5. Distribution of samples to the section chiefs who are re-
sponsible for the laboratory performing the analyses shall
be made only by the custodian.
6. The laboratory area shall be maintained as a secured area,
restricted to authorized personnel only.
7. Laboratory personnel are responsible for the care and cus-
tody of the sample once it is received by them and shall be
prepared to testify that the sample was in their possession
and view or secured in the laboratory at all times from the
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34
moment it was received from the custodian until the time
that the analyses are completed.
8. Once the sample analyses are completed, the unused portion
of the sample, together with all identifying labels, must
be returned to the custodian. The returned tagged samples
should be retained in the custody room until permission to
destroy the sample is received by the custodian.
9. Samples shall be destroyed only upon the order of the
Laboratory Director, in consultation with previously des-
ignated Enforcement Officials, or when it is certain that
the information is no longer required or the samples have
deteriorated. The same procedure is true for tags and
laboratory records.
F. Evidentiary Considerations
Reducing chain of custody procedures as well as the various promulgated
laboratory analytical procedures to writing will facilitate the admis-
sion of evidence under rule 803(6) of the Federal Rules of Evidence
(PL. 93-575). Under this statute, written records of regularly con-
ducted business activities may be introduced into evidence as an ex-
ception to the "Hearsay Rules" without the testimony of the person(s)
who made the record. Although preferable, it is not always possible to
have the individuals who collected, kept, and analyzed samples testify
in court. In addition, if the opposing party does not intend to con-
test the integrity of the sample or testing evidence, admission under
the Rule 803(6) can save a great deal of trial time. For these reasons,
it is important that the procedures followed in the collection and ana-
lysis of evidentiary samples be standardized and described in an in-
struction manual which, if need be, can be offered as evidence of the
"regularly conducted business activity" followed by the lab or office
in generating any given record.
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35
In criminal cases however, records and reports of matters observed by
police officers and other law enforcement personnel are not included
under the business record exceptions to the "Hearsay Rule" previously
cited (see Rule 803(8), P.L. 93-595). It is arguable that those por-
tions of the compliance inspection report dealing with matters other
than sampling and analysis results come within this exception. For this
reason, in criminal actions records and reports of matter observed by
field investigators may not be admissible and the evidence may still
have to be presented in the form of oral testimony by the person(s) who
made the record or reports, even though the materials come within the
definition of business records. In a criminal proceeding, the opposing
counsel may be able to obtain copies of reports prepared by witnesses,
even if the witness does not refer to the records while testifying, and
if obtained, the records may be used for cross-examination purposes.
Admission of records is not automatic under either of these sections.
The business records section authorized admission "unless the source of
information or the method or circumstances of preparation indicate lack
of trustworthiness," and the caveat under the public records exception
reads "unless the sources of information or other circumstances indicate
lack of trustworthiness."
Thus, whether or not the inspector anticipates that his or her compliance
inspection report will be introduced as evidence, he or she should make
certain that the report is as accurate and objective as possible.
VII. SAMPLING EQUIPMENT CLEANING
The proper cleaning of all equipment used in the sampling of water and
wastewater is essential to ensuring valid results from laboratory ana-
lyses. Cleaning protocols should be developed for all sampling equip-
ment early in the design of the monitoring program. Here, also, the
laboratory analyst should be consulted, both to ensure that the
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36
procedures and techniques are adequate as well as to avoid including
practices that are not warranted in view of the analyses to be
performed.
As an example, Lair has set down the standard operating procedures for
the cleaning of sample bottles and field equipment used by USEPA
Region IV Surveillance and Analysis field personnel engaged in NPDES
compliance monitoring. They are reproduced below for a typical auto-
matic sampler (manufactured by ISCO) and related sampling equipment.
2-1/2 Gallon Pyrex Glass Composite Bottles
1. Rinse twice with spectro grade acetone.
2. Rinse throughly with hot tap water using a bottle brush to
remove particulate matter and surface film.
3. Rinse thoroughly three times with tap water.
4. Acid wash with at least 20-percent hydrochloric acid.
5. Rinse thoroughly three times with tap water.
6. Rinse thoroughly three times with distilled water.
7. Rinse thoroughly with petroleum ether and dry by pulling
room air through bottle.
8. Dry in drying oven overnight.
9. Cap with aluminum foil.
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37
ISCO Glass Sampler Bottles
1. One spectro grade acetone rinse.
2. Dishwasher cycle (wash and tap water rinse, no detergent).
3. Acid rinse with at least 20-percent hydrochloric acid.
4. Dishwasher cycle, tap and distilled water rinse cycle,
no detergent.
5. Replace in covered ISCO bases.
Sample Tubing (1/4. 3/8, or 1/8 pexcon or tygon)
1. Do not reuse sample tubing. No cleaning required. New
sample tubing is to be used for each new sampling setup.
2. Use Teflon tubing where samples for organics are to be
collected.
ISCO Pump Tubing
1. Rinse by pumping hot tap water through tubing for at least
2 minutes.
2. Acid wash tubing by pumping at least a 20-percent solution
of hydrochloric acid through tubing for at least 2 minutes,
3. Rinse by pumping hot tap water through tubing for at least
2 minutes.
4. Rinse by pumping distilled water through tubing for at
least 2 minutes.
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38
Teflon Sample Tubing
1. Teflon sample tubing should be cleaned in the same manner
as the 2-1/2-gallon Pyrex sample containers.
ISCO Rotary Funnel and Distributor
1. Clean with hexane to remove any grease deposits.
2. Rinse thoroughly with hot water and a bottle brush to
remove particulate matter and surface films.
3. Use a squeeze bottle of 20-percent hydrochloric acid and
rinse thoroughly, rinse funnel as well as funnel and
distributor depressions.
4. Rinse thoroughly with tap water.
5. Rinse thoroughly with distilled water.
6. Replace in sampler.
ISCO Sample Headers
1. Rinse entire header with hexane or petroleum ether.
2. Disassemble header and rinse thoroughly with hot tap water,
using a bottle brush to remove particulate matter and
surface films.
3. Rinse the plastic portion of the header with at least a
20-percent solution of hydrocholoric acid. Do not use
acid on the metal parts.
-------
39
4. Rinse thoroughly with tap water.
5. Reassemble header.
6. Rinse all header parts thoroughly with distilled water.
One-Gallon Plastic Sample Containers
1. Use only new bottles when sampling wastewater sources.
One-Quart Wide-Mouth Bottles for Organics, Pesticides, Oil, and Grease
Samples
1. Use only new bottles with Teflon liners.
2. Rinse twice with petroleum ether and allow to dry.
One-Pint Narrow-Mouth Bottles for Phenol Samples
1. Use new bottles only.
One-Pint Narrow-Mouth Mercury Sample Bottles
1. Use only new bottles.
2. Rinse with at least 20-percent nitric acid.
3. Rinse at least three times with distilled water.
One-Liter Plastic Storemore Cyanide Sample Bottles
1. Use only new bottles.
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40
VIII. QUALITY ASSURANCE COSTS
It is impossible to provide absolute cost estimates in dollars for a
quality assurance program. Cost/manpower ratios can be used, however,
to help in estimating or determining if resource allocations are in
balance to ensure that the necessary emphasis is being placed on quality
control.
In terms of management budgets, a cost ratio of approximately 10 percent
monies/manpower to total monitoring budget indicates that there is a
sufficient response to develop a minimal water quality assurance pro-
gram. This is an average figure since resources will vary according to
the stage of the program and to the program work schedule. In addition,
it should be recognized that individual elements of the overall quality
assurance effort will vary with time and with phases of the program,
i.e., management, field sampling laboratory analysis, data handling,
etc. For programs where there is considerable emphasis on litigation
data, quality control cost ratios of one-third or more might be appro-
priate. Average ratios for a rather complete quality assurance program
will usually fall in the 15- to 20-percent range.
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41
REFERENCES
Model State Water Monitoring Program, U.S. Environmental Protection
Agency, Office of Water and Hazardous Materials, Monitoring and Data
Support Division, Washington, D.C. EPA-440/9-74-002, (1975).
Handbook For Analytical Quality Control In Water And Wastewater
Laboratories, U.S. Environmental Protection Agency, Technology
Transfer, Washington, D.C. (1972).
Quality Assurance Handbook For Air Pollution Measurement Systems.
Volume I. Principles. U.S. Environmental Protection Agency, Office of
Research and Development, Environmental Monitoring & Support Lab,
Research Triangle Park, N.C., EPA-600/9-76-005, (1976).
Youden, W. J., "Statistical Techniques For Collaborative Tests",
Association of Official Analytical Chemists, Washington, D.C. (1973).
El-Awady, A. A., R. B. Miller and M. J. Carter, "Automated Method for
the Determination of Total and Inorganic Mercury in Water and Wastewater
Samples", Anal. Chem.. Volume 48, No. 1, 110-116, Jan. 1976
Standard Methods For The Examination Of Water And Wastewater^, 14th Ed.,
APHA, Washington, D.C.(1976).
Methods For Chemical Analysis Of Water And Waste, 1974, U.S.
Environmental Protection Agency, Office of Technology Transfer,
Washington, D.C. (1974).
Areawide Assessment Procedures Manual, U.S. Environmental Protection
Agency, Municipal Environmental Research Laboratory, Cincinnati, OH.
EPA-600/9-76-014 (1976).
NPDES Compliance Sampling Inspection Manual, U.S. Environmental
Protection Agency, Office of Enforcement, Water Enforcement Compliance
Branch, Washington, D.C. (1977).
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