SAMPLE COLLECTION

Laboratory-Data Files

QUALITY ASSURANCE

-electronic files

-original documents

-forms

-duplicate copies

Data review

-manual checks

-verification

DATA MANAGEMENT

SAMPLE ANALYSIS

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006–1242

Quality-Assurance Plan for the Analysis of Suspended 

Sediment by the U.S. Geological Survey in Montana
COVER PHOTOGRAPHS: Top: Collecting suspended-sediment sample at Clark Fork at Turah Bridge, near Bonner, Mont.

Photograph by Kent A. Dodge, U.S. Geological Survey, taken June 2, 2004.

Bottom right: Processing suspended-sediment sample through a sieve to determine the

percentage of sediment mass finer than 0.062-millimeter diameter (silt size and smaller).

Photograph by Kent A. Dodge, U.S. Geological Survey, taken January 17, 2002.
Quality-Assurance Plan for the Analysis of 

Suspended Sediment by the U.S. Geological 

Survey in Montana

By Kent A. Dodge and John H. Lambing

Open-File Report 2006–1242

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Dodge, K.A., and Lambing, J.H., 2006, Quality-assurance plan for the analysis of suspended sediment by the 

U.S. Geological Survey in Montana: U.S. Geological Survey Open-File Report 2006-1242, 25 p.
iii

Contents

Abstract...........................................................................................................................................................1

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

Quality-Assurance Policies..........................................................................................................................1

Sediment-Laboratory Certification ....................................................................................................2

Personnel Responsibilities and Training...........................................................................................2

Documentation Requirements............................................................................................................2

Laboratory Safety..................................................................................................................................2

Quality-Assurance Procedures...................................................................................................................3

Laboratory Equipment..........................................................................................................................3

Electronic Balances ....................................................................................................................3

Ovens ...........................................................................................................................................4

Conductivity Meters ....................................................................................................................5

Decanting Equipment..................................................................................................................6

Filtering Equipment......................................................................................................................6

Laboratory Supplies..............................................................................................................................6

Sample Bottles .............................................................................................................................6

Crucibles and Filters....................................................................................................................7

Evaporation Dishes......................................................................................................................8

Sieves ...........................................................................................................................................8

Desiccators...................................................................................................................................9

Distilled Water..............................................................................................................................9

Sample Management...........................................................................................................................9

Field Documentation .................................................................................................................10

Shipment and Storage ..............................................................................................................10

Sample Inventory.......................................................................................................................10

Sample Analysis..................................................................................................................................10

Laboratory Procedures.............................................................................................................10

Sample-Weight Determination.......................................................................................10

Sample Preparation..........................................................................................................14

Filtration Method........................................................................................................................14

Evaporation Method..................................................................................................................15

Composited Samples.................................................................................................................15

Particle-Size Analysis ...............................................................................................................16

Sediment-Weight Determination.............................................................................................17

Calculation of Results ...............................................................................................................17

Analytical Quality Control..................................................................................................................17

Internal Testing...........................................................................................................................17

Evaporation Blanks...........................................................................................................20

Sample Blanks...................................................................................................................20

Filter Blanks .......................................................................................................................20

Field Replicates.................................................................................................................20

Method-Comparison Replicates ....................................................................................21
iv

Extracted Sample Water..................................................................................................21

External Testing..........................................................................................................................21

Sediment Laboratory Quality-Assurance Program.....................................................21

Laboratory Reviews..........................................................................................................22

Data Management..............................................................................................................................22

Laboratory-Data Files................................................................................................................22

Data Review................................................................................................................................22

Publication ...........................................................................................................................................24

Summary........................................................................................................................................................24

References Cited..........................................................................................................................................24

Figures

1–6. Photographs showing:

1. Analytical balance electronically connected to laboratory computer terminal.......4

2. Mechanical-convection oven for drying sediment in evaporation dishes ................5

3. Convection oven for drying sediment in crucibles ........................................................6

4. Vacuum-hose system and workbench for decanting water from

suspended-sediment samples...........................................................................................7

5. Manifold for vacuum filtration of suspended-sediment samples through 

crucibles................................................................................................................................8

6. Suspended-sediment sample poured through a 0.062-millimeter sieve to 

separate sand from fine sediment....................................................................................9

7. Example of a water-quality field form used to document information about

water-quality samples collected by U.S. Geological Survey personnel ...........................11

8. Example of a sediment-sample field form used to document information about

suspended-sediment samples collected by observers........................................................12

9. Flow chart showing operational sequence for the analysis of suspended-sediment 

samples in the Montana Sediment Laboratory......................................................................13

10. Example of an analytical request form used to document information about

sediment samples shipped to the U.S. Geological Survey Iowa Sediment 

Laboratory....................................................................................................................................18

11. Example of a form used to document information about sediment-data distribution

in the USGS Montana Water Science Center........................................................................23

Table

1. Factors for converting suspended-sediment concentration from parts per million to

milligrams per liter......................................................................................................................19

Contents—Continued
Conversion Factors, Abbreviated Water-quality Units, and 

Acronyms

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

gram (g) 0.03527 ounce (oz)

gram per cubic centimeter (g/cm3) 0.03613 pound per cubic inch (lb/in.3)

kilogram per square centimeter (kg/cm2) 28.96 inch of mercury at 60°F (in Hg)

liter (L) 0.2642 gallon (gal)

liter per minute (L/min) 0.2642 gallon per minute (gal/min)

milliliter (mL) 0.06102 cubic inch (in.3)

millimeter (mm) 0.03937 inch (in.)

Watt (W) 0.001340 horsepower (hp)

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8x°C)+32

Abbreviated water-quality units used in this report:

μS/cm microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C)

mg/L milligrams per liter

ppm parts per million

Acronyms used in this report:

CVO Cascades Volcano Observatory, Vancouver, Wash.

EDI Equal Discharge Increment

NWIS National Water Information System

SLEDS Sediment Laboratory Environmental Data System

SLQA Sediment Laboratory Quality-Assurance Program

USGS U.S. Geological Survey

WRD Water Resources Discipline of the U.S. Geological Survey

Quality-Assurance Plan for the Analysis of Suspended 

Sediment by the U.S. Geological Survey in Montana

By Kent A. Dodge and John H. Lambing

Abstract

A quality-assurance plan has been developed for use 

by the sediment laboratory of the U.S. Geological Survey 

Montana Water Science Center in conducting activities related 

to the analysis of suspended sediment. The plan documents 

quality-assurance policies for sediment-laboratory certification, personnel responsibilities and training, documentation 

requirements, and laboratory safety. The plan also documents 

quality-assurance procedures related to laboratory equipment 

and supplies, sample management, sample analysis, analytical 

quality control, and data management.

Introduction

Suspended-sediment samples are routinely collected 

from streams and analyzed for concentration and particlesize distribution by the U.S. Geological Survey (USGS) in 

response to various data-collection objectives. The procedures 

used to collect these samples are described in reports by Guy 

and Norman (1970), Edwards and Glysson (1999), and U.S. 

Geological Survey (variously dated). Laboratory theory and 

methods of sediment analysis are described by Guy (1969). 

Although the latter report is used as a primary guide for the 

standard analytical procedures used by the USGS Montana 

Water Science Center Sediment Laboratory (herein referred to 

as the Montana Sediment Laboratory), the report does not 

specifically address quality assurance. Quality-assurance 

practices used by sediment laboratories of the USGS depend 

on the size of the sediment program, the objectives of the datacollection program, and the methods used by individual 

laboratories. Many of the quality-assurance practices 

commonly used by USGS sediment laboratories are described 

in reports by Knott and others (1992) and Lambing and Dodge 

(1993).

This report describes the policies and procedures used 

to assure the quality of results from the analysis of about 

3,000 suspended-sediment samples processed annually by 

the Montana Sediment Laboratory in Helena, Mont. The plan 

documents quality-assurance policies for sediment-laboratory 

certification, personnel responsibilities and training, 

documentation requirements, and laboratory safety. The 

plan also documents quality-assurance procedures related 

to laboratory equipment and supplies, sample management, 

sample analysis, analytical-quality control, and data management. The procedures might be applicable to other laboratories 

having production capabilities similar to those of the Montana 

Sediment Laboratory.

Quality-Assurance Policies

Quality-assurance policies are a comprehensive set of 

requirements and guidelines that specify the measures used 

to produce data of known quality. These measures include 

quality-control procedures that test the performance of 

individual components of the laboratory operational system 

and are systematically applied to identify, quantify, and control 

errors in order to evaluate the accuracy and precision of the 

analytical data.

The assurance of data quality on a continuing basis is 

achieved by a management program that includes developing an operational design, acquiring necessary equipment and 

expertise to perform laboratory operations, and implementing quality-control procedures to systematically review and 

evaluate the analytical results. This management program 

is implemented by assigning responsibilities for the various 

components of laboratory operations to qualified personnel 

who have received adequate training. Data quality is verified 

by documenting and evaluating the results of numerous 

quality-control checks integrated throughout all phases of 

sample processing.

The USGS Montana Water Science Center (herein 

referred to as Center) supports quality-assurance objectives 

by designating discipline specialists who provide technical 

oversight to operations within their respective areas of expertise (Moreland, 1995). This staffing organization includes 

a Sediment Specialist, who is responsible for developing 

sediment programs and maintaining the technical adequacy 

of laboratory operations. Operational guidelines adapted 

from formal publications and internal USGS memoranda 

are applied in accordance with USGS policies on analysis of 

sediment samples.
Within the Montana Sediment Laboratory, the qualitycontrol system contains operational checks and documentation 

that enable determination of the accuracy and precision of the 

analytical data. Quality-control procedures are implemented 

systematically throughout the operational sequence required to 

process suspended-sediment samples and report data. Quality 

control for equipment and procedures include actions ranging 

from equipment checks and simple observations to systematic, 

documented test results. Unacceptable errors that are identified through systematic checks are promptly evaluated for 

corrective action. If the corrective action requires a change in 

procedure, the operational guidelines are changed accordingly. 

Procedural changes that implement non-standard methods 

require approval from the USGS Office of Surface Water. 

Quality control, therefore, incorporates both standard guidelines and appropriate modifications to meet the objectives of 

maintenance and improvement of data quality.

Sediment-Laboratory Certification

In accordance with Office of Surface Water Technical 

Memorandum No. 91.11, “Certification Training for Sediment 

Laboratories,” personnel responsible for the quality of laboratory results in each USGS sediment laboratory or contract 

laboratory must complete Water Resources Discipline (WRD) 

certification requirements. The policy specifies that in order 

for a laboratory chief to meet the first step of certification, the 

chief must attend WRD training to operate a sediment laboratory. This training includes an initial 1-week training period 

under a certified laboratory chief and attendance at periodic 

meetings of sediment-laboratory chiefs. Upon successful 

completion of this training, these employees become certified sediment-laboratory chiefs and are authorized to provide 

certification training in their Centers.

Personnel Responsibilities and Training

All personnel involved in sediment operations are responsible for quality assurance within the scope of their duties. The 

Sediment Specialist is responsible for the overall evaluation 

and approval of the quality of sediment data within the Center. 

Implementation of any procedural change requires approval by 

the Sediment Specialist. The Sediment Specialist is assisted 

by the laboratory supervisor who oversees daily laboratory operations, establishes analytical priorities, and reviews 

all analytical results and quality-control data generated by 

the laboratory. The laboratory supervisor consults with the 

Sediment Specialist to resolve problems identified by qualitycontrol checks. Sample management, analysis, and data entry 

are performed by two laboratory assistants, who also check 

equipment condition and document all calibration checks to 

verify acceptable performance.

Implementation of quality assurance begins with 

adequate training of laboratory personnel to develop the 

necessary expertise to accurately and efficiently analyze water 

samples for sediment. This training is provided by qualified 

staff with formal USGS training and experience. Laboratory 

manuals detailing procedures, equipment operation, and datadocumentation requirements are provided to assist laboratory 

analysts. New analysts are trained for each phase of sample 

processing and data entry until the analyst has demonstrated 

the ability to independently and correctly perform all procedures. The USGS Office of Surface Water also requires that 

each USGS sediment laboratory have at least one analyst 

certified through proficiency training to perform analyses 

to agency standards. Proficiency training is provided by the 

Office of Surface Water.

Documentation Requirements

All analytical quality-control measurements are documented in laboratory quality-control logbooks for each 

major component of sediment analysis. In addition, data 

that document the performance of analytical equipment are 

routinely entered into the logbooks. Records of equipment 

calibration, cleaning, and adjustments are entered in the 

logbooks at the time of servicing.

All quality-control records are periodically reviewed 

by the laboratory supervisor. These records are reviewed to 

identify subtle but systematic errors that might not be detected 

by casual observation. Persistent deviations of quality-control 

data from original characteristics are investigated to identify 

the possible source of variation. The deviations of the qualitycontrol data are brought to the attention of the Sediment 

Specialist and tests are designed to isolate the source of error. 

Evaluations of test data are used to assess the need for adjustment or servicing of equipment, or modification of analytical 

procedures.

The information used in the analytical processing of 

suspended-sediment samples is recorded on several forms. 

Some forms are designed to allow systematic entry of all pertinent data necessary to analyze, track, and report sample data. 

All final forms are stored in station files as a permanent record 

of data processing.

Laboratory Safety

Instructions and safety precautions for a wide range of 

activities that occur in the Center water-quality laboratory, of 

which the Montana Sediment Laboratory is a part, are generally described by Skinner and others (1983) and specifically in 

the USGS Montana Water Science Center Chemical Hygiene 

Plan (a document available in the Center). These manuals 

describe various laboratory procedures, hazards, safety precautions, and chemical storage requirements. All personnel who 

routinely or periodically work in the laboratory are required 

to read and sign the Chemical Hygiene Plan, which is prominently displayed in the laboratory.

Laboratory restrictions and emergency procedures are 

identified on signs placed on laboratory walls. An emergency 

 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
safety shower, eyewash fountain, and acid-spill cleanup kit are 

located in the laboratory. Operation of the shower, eyewash 

fountain, and hood exhaust fans are checked periodically 

and inspections are documented in logbooks. Personal-safety 

supplies and equipment such as rubber gloves, goggles, 

aprons, and a chemical fume hood are provided. Two fire 

extinguishers, mounted on the walls (one in the center of the 

laboratory and the other by the safety shower), are checked 

annually by a certified specialist. All chemicals are stored in 

metal cabinets appropriate for the specific types of chemicals, 

clearly marked with identifying labels, and dated. A list of 

chemicals that are stored in the laboratory is displayed on 

the door of the red fireproof cabinet and is updated annually. 

Material Safety Data Sheets are located at the entrance to the 

laboratory and are readily accessible to all laboratory personnel.

Quality-Assurance Procedures

The following sections describe the specific procedures 

used for assuring the quality of the equipment and supplies 

used in the analysis of suspended sediment in the Montana 

Sediment Laboratory. The process and manner used to 

record relevant information necessary for accurate sample 

management, sample analysis, and data management also are 

described.

Laboratory Equipment

The weighing, processing, and analysis of sediment 

samples require a wide variety of equipment. Electronic 

balances, ovens, conductivity meters, vacuum pumps, and 

laboratory-grade thermometers are obtained from commercial 

sources. Specialized types of equipment, such as decanting 

or filtering devices, generally are assembled or fabricated to 

conform with processing requirements of individual laboratories. Storage shelves and processing benches also might 

require custom fabrication. A computer system is used for 

routine data entry and storage to enable efficient data management and retrieval, which is especially important for large 

numbers of analyses and maintenance of historical data files.

Equipment that operates properly and within specified 

limits of calibration is essential for producing reliable analytical results. Equipment is systematically checked to verify 

acceptable performance. Equipment that fails to meet accuracy 

standards is either calibrated or promptly serviced to achieve 

conformance with standards. Calibration of equipment is 

performed according to guidelines of the manufacturer and the 

USGS. Maintenance of equipment to assure proper operation 

is systematically performed in accordance with maintenance 

schedules recommended by manufacturers.

The ability of commercially available equipment to 

meet technical requirements of sample processing is evaluated prior to purchase. This equipment is tested and calibrated 

before its initial use to ensure proper performance. Manuals 

describing equipment operation are available for each piece of 

commercial equipment and serve as the operational instructions for laboratory personnel. Manufacturer representatives 

are consulted if problems with commercial equipment occur. 

Specially fabricated equipment is designed and tested for 

technical adequacy prior to use in sample processing.

All equipment checks, calibration, cleaning, and maintenance are documented in appropriate logbooks as part of 

routine quality control. Information about performance checks 

and calibration measurements for each electronic balance, 

oven, oven thermometer, and conductivity meter is recorded in 

a logbook. The date and analyst’s initials are recorded for each 

log entry, followed by the performance data and comments for 

each item checked. The logbooks are periodically reviewed to 

evaluate equipment performance and to implement corrective 

actions, if necessary. In addition, manufacturer’s operation 

manuals, maintenance schedules, and service forms provided 

by professional service representatives are stored in equipment 

files for each instrument. These documents are stored near 

each instrument for immediate access.

Electronic Balances

Two types of balances, macro and analytical, are used 

to determine the mass of sediment samples and containers1. 

The balances are electronic, provide digital readout, and have 

weighing capabilities that encompass the expected range of 

sample weights with an acceptable level of accuracy and precision. Weight is displayed in grams (g).

The macro balance is used for items that weigh 100 g or 

more. Such items typically include empty sample bottles (tare 

weight) and the sample (water-sediment mixture). The macro 

balance used in the Montana Sediment Laboratory is capable 

of determining weight ranging from 0.1 to 4,000 g, with a 

precision of ±0.05 g.

The analytical balance is used for items that weigh 

100 g or less. These items typically include sediment containers (crucibles and evaporation dishes) used in laboratory 

analysis of sediment weight. The analytical balance used in 

the Montana Sediment Laboratory is capable of determining weight ranging from 0.0001 to 162 g, with a precision of 

±0.0001 g. This balance is equipped with an internal 

counterweight balance for automatic calibration. The analytical balance is electronically connected to the laboratory 

computer terminal, which enables electronic transfer and 

storage of balance readings. Thus, transcription errors are 

eliminated (fig. 1).

Both balances are located in an area of minimal vibration 

(restricted foot traffic) and where humidity and temperature 

are not subject to excessive change. The macro balance is 

mounted on a marble table to minimize vibrations that could 

affect the weight readings. The analytical balance is mounted 

1

 To conform to traditional use, the word “weight” is subsequently used in 

place of the technically correct term “mass.”

Quality-Assurance Procedures 
Figure 1. Analytical balance electronically connected to laboratory computer terminal.

on a sand-filled, marble-top table. This balance also has a 

protective hood with sliding Plexiglas panels surrounding the 

balance pan to provide a dust-free environment and to eliminate air currents during the weighing process (fig. 1).

The macro and analytical balances are calibrated by automatic balance controls prior to use each day. The calibration 

procedure is verified by weighing a series of analytical reference weights recommended by the balance manufacturer. This 

check provides an independent test of the internal counterweight balance used for automatic calibration. For each daily 

calibration check, the operator uses at least three reference 

weights that encompass the extremes and midpoint of the 

expected range of sample weights. All weight measurements 

for the daily calibration check are recorded in a logbook for 

each balance. If the results from the reference weights exceed 

prescribed error limits, sensitivity of the balance is adjusted 

as described in the manufacturer’s manual. If these adjustments fail to correct the error, the balance is internally cleaned 

and calibrated by the manufacturer’s service representative. 

Regardless of balance performance, both balances are cleaned 

annually and then calibrated with American Society for 

Testing and Materials Class 1 traceable weights by a service 

representative. The date and type of service are documented in 

the logbook of each balance.

During sample processing, analytical balance readings 

can drift slightly as a result of sensitivity to humidity and 

temperature changes, vibrations, or static electricity. The 

analyst is responsible for closely monitoring any tendency for 

the balance to drift from a zero (0.0000 g) reading when the 

balance pan is empty. To ensure that particulate material is not 

causing drift, the pan is cleaned periodically with a fine-hair 

brush. To minimize the effect of persistent drift, the balance 

is re-zeroed by a reset button on the balance-control panel 

after every 10 weighings, or more frequently if drift exceeds 

0.0002 g. If the balance drifts more than 0.0004 g, a buildup of 

static electricity or moisture absorption from the air might be 

indicated. Static electricity in the typically dry environment of 

Montana is controlled by placement of the sediment container 

on a wooden platform prior to placement in the balance. A 

plastic platform on the balance pan also aids in minimizing 

static drift. Moisture absorption is minimized by weighing 

containers promptly after removal from desiccators. If the drift 

becomes excessive (greater than about 0.0005 g), the balance 

is internally recalibrated. If the drift cannot be corrected, the 

balance is serviced by the manufacturer’s representative.

Ovens

Two electric ovens are used to dry the sediment, the 

sediment containers, and various types of laboratory equipment. Both ovens are equipped with internal temperature 

sensors for monitoring oven performance.

The mechanical-convection oven (Oven 1) is controlled 

with a timer, an alarm system, and air-circulation blowers. 

This oven, which is used to dry water-sediment mixtures in 

evaporation dishes, is operated at about 93°C. Because evaporation dishes might contain 100-250 mL of sample, temperatures must be maintained at less than the boiling point of water 

 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 2. Mechanical-convection oven for drying sediment in evaporation dishes.

(96°C at about 4,000 ft above sea level) to prevent splattering 

of samples and loss of sediment or cross-contamination of 

samples. The oven alarm system sounds when the temperature 

reaches 94°C, thereby indicating the oven temperature is near 

the boiling point. The capacity of this oven is about 100 dishes 

(fig. 2).

The convection oven (Oven 2) is used to dry crucibles 

containing filters that retain the sample sediment. Because 

temperatures in excess of about 110°C can break down molecular hydration bonds of some clay minerals in the sediment, 

the convection oven is operated at a maximum temperature 

of 103°C. The operating temperature can exceed the boiling 

point of water because there is no water-sediment mixture in 

crucibles. This oven is equipped with a simple on/off switch 

and is monitored by a digital thermometer mounted on the 

oven exterior. The capacity of this oven is about 150 crucibles 

(fig. 3).

Oven temperature is read twice during each day of operation and recorded in the logbook for each oven. Oven thermometers are checked twice annually at their normal operating 

temperature (90-103°C), with results recorded in the logbook 

for each oven. The digital thermometer of Oven 1 is checked 

with a calibration thermometer of known accuracy (plus 

or minus 0.1°C). The readings are compared and recorded. 

The digital thermometer on Oven 2 is checked by placing a 

full-immersion calibration thermometer on the center shelf. 

The results of these tests are recorded in the oven logbooks. 

The digital thermometer on Oven 1 and the internal sensor of 

Oven 2 are replaced if temperature comparisons vary or cannot 

be adjusted by plus or minus 2.0°C.

Conductivity Meters

A laboratory-grade conductivity meter is used to measure 

specific conductance of suspended-sediment samples that are 

processed by the evaporation (rather than filtration) method. 

This measurement is used to estimate the concentration of 

dissolved solids within the water-sediment mixture to determine the need for a dissolved-solids correction. After evaporation, the solid-phase residue contains precipitated salts. 

Correction for the additional weight of dissolved solids that 

is not part of the particulate material originally suspended in 

the stream is necessary for some samples. The meter also is 

used to verify the purity of the deionized water that is used 

for various water-quality activities. The conductivity meter 

in the Montana Sediment Laboratory is capable of measuring 

specific conductance ranging from 1 to 100,000 μS/cm.

Calibration of the conductivity meter is checked each 

day before use with standard solutions of known specific 

conductance obtained from the USGS National Water Quality 

Laboratory. Two standards are used that bracket the expected 

range of specific conductance for the sample. The meter is 

recalibrated if more than a 3-percent difference exists between 

the known value of the standard solution and the displayed 

value of the meter. If specific conductance of the standard 

solution is not within an acceptable range after calibration, 

the sensor is cleaned and the meter is checked with another 

Quality-Assurance Procedures 
Figure 3. Convection oven for drying sediment in crucibles.

standard solution of equal or similar specific conductance to 

verify the exceedance of calibration limits. If the meter is in 

error, the sensor is replaced and the meter is retested. All the 

standard solutions used for calibration checks have a clearly 

marked expiration date that indicates freshness of the solution. 

Standard solutions are discarded when the prescribed expiration date is reached.

Decanting Equipment

After initial sample weights have been obtained, sample 

bottles have been allowed to stand undisturbed for several 

days and the sediment has settled to the bottom of the bottle, 

decanting equipment is used to remove most of the overlying sediment-free portion (supernatant) of the water-sediment 

mixture. The decanting equipment consists of a J-shaped 

nozzle made of a firm material (such as copper) inserted 

into flexible tubing and connected to a vacuum system. The 

hose system is suspended above a workbench on which the 

sediment samples are placed for processing (fig. 4). The 

decanted water moves through outflow tubing into a collection 

jug having a capacity of 38 L (10 gal). The vacuum pump used 

in this system is operated by a 124 W (1/6 hp) motor.

Filtering Equipment

Filtering equipment is used to separate the sediment from 

a water-sediment mixture by drawing the mixture through 

crucibles that have perforated bottoms and glass-fiber filters. 

A glass-fiber filter is placed on the bottom of the crucible to 

allow the passage of water while retaining the sediment. The 

crucibles are seated in rubber holders mounted in a fabricated 

crucible manifold (fig. 5). The bottom of each rubber holder is 

connected by a portal tube and each portal has a separate valve 

to control the in-line vacuum to individual crucibles. Sample 

water vacuumed through crucibles moves through outflow 

tubing into the same collection jug used for the decanted 

supernatant from the water-sediment mixture in sample 

bottles. A separate manifold is used for each of the two sizes 

of crucibles used in the Montana Sediment Laboratory.

Laboratory Supplies

A variety of laboratory supplies are needed to process and 

analyze suspended-sediment samples. Laboratory supplies that 

are selected must meet technical and durability performance 

requirements. Some of the items are disposable and purchased 

on a regular basis. Other items are reusable and can be cleaned 

and reused many times.

Sample Bottles

Standard suspended-sediment samplers used by the 

USGS accommodate different sizes and types of sample 

bottles (Edwards and Glysson, 1999). The most common types 

of sample bottles used in the Center are the pint glass “milk” 

bottle and the quart glass “mayonnaise” bottle; however, newer 

samplers designed for ultra-clean water-quality sampling (U.S. 

Geological Survey, variously dated) typically use 1-L and 3-L 

plastic bottles.

The sample bottles are reusable and are cleaned prior 

to collection of a water sample. The cleaning removes any 

residue that can remain after the analytical process. Sample 

bottles are cleaned by soaking in a water bath with a laboratory detergent, followed by a hot, tap-water rinse in an 

automatic dishwasher. Washed bottles are turned upside down 

in a wire carrying case to air dry. After drying, the bottles are 

turned upright and capped, and are then ready for field use. 

Before capping, the bottles are inspected for chips, cracks, 

or excessive residue. Bottles with large chips or cracks are 

discarded to prevent breakage in the field. Bottles with visible 

residue or staining that requires additional cleaning are rinsed 

with a 10-percent hydrochloric acid solution, using appropriate safety apparatus such as goggles and protective gloves. 

After acid rinsing, the bottles are rewashed and rinsed with tap 

water. Cleaning procedures for all types of sediment containers used in the Montana Sediment Laboratory are documented 

in the Chemical Hygiene Plan and are posted at the primary 

cleaning station.

 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 4. Vacuum-hose system and workbench for decanting water from suspended-sediment 

samples.

Glass sample bottles may be used for many years; 

therefore, bottle weights to the nearest 1 g (without labels, 

tags, or caps) are permanently etched into the surface as a 

record of tare weight. Plastic bottles are not as durable as glass 

bottles; the tare weights are recorded on the surface using a 

felt tip marker with permanent ink. Plastic bottles are regularly 

checked to verify the accuracy of the tare weight. Five percent 

of each batch of processed sample bottles (both glass and 

plastic) are randomly selected and reweighed on the macro 

balance after cleaning and drying. If the measured weight 

of any bottle differs by more than 2 g from the tare weight 

recorded on the bottle, the new tare weight is recorded on the 

bottle. All bottles that require extra cleaning by acid rinsing 

are weighed to verify the tare weight, with corrections made as 

necessary. If a chip is discovered on a glass bottle, the bottle is 

reweighed and the new tare weight is etched onto the bottle.

Crucibles and Filters

Crucibles are small porcelain or glass vessels that are 

resistant to heat and have a perforated base that allows the 

passage of water. Two sizes and types of crucibles are used 

by the Montana Sediment Laboratory. One type is made of 

porcelain with a base diameter of 2.4 cm and a capacity of 

about 25 mL. Porcelain crucibles have an array of uniform 

perforations in the base. The other type is made of glass with 

a base diameter of 4.25 cm and a capacity of about 50 mL. 

Glass crucibles have a base composed of an integrated frittedglass disk. All crucibles are individually numbered with hightemperature paint or indelible marker for identification.

Both types of crucibles are cleaned after completion of 

analysis by first removing the filter. The porcelain crucibles 

are soaked in a laboratory-grade detergent and then rinsed 

with hot tap water in the dishwasher. The glass crucibles with 

the fritted-glass disk in the base are soaked in warm tap water 

and then rinsed with hot tap water in the dishwasher. The glass 

crucibles are periodically cleaned using an ultrasound water 

bath to remove particles that can become lodged in the fritted 

glass. If residues are not successfully removed by ultrasound, 

the crucibles are soaked in a 10-percent solution of hydrochloric acid and then rewashed.

Filters are seated on the bottom of the crucible to retain 

sediment during sample filtration. The only filter type authorized by the USGS for suspended-sediment analysis is the 

Whatman glass-microfiber filter No. 934-AH or equivalent 

(C.W. Boning, U.S. Geological Survey, written commun., 

1992). Filters are always placed in crucibles with the rough 

side facing the sample to prevent fiber loss during filtration.

After the crucibles have been cleaned, new filters of 

the correct diameter are placed in the crucibles with forceps. 

The filters are rinsed with about 25 mL of distilled water by 

filling the crucible with distilled water and applying vacuum 

Quality-Assurance Procedures 
Figure 5. Manifold for vacuum filtration of suspended-sediment samples through crucibles.

pressure. The vacuum serves to seat the filters and helps 

remove loose fibers. The crucibles and filters are oven-dried 

for about 2 hours at 105°C to remove any moisture and 

allowed to cool for about 15 minutes.

After cooling, crucibles are transferred to a desiccator 

and remain moisture- and dust-free until needed. Because the 

weight of the individual filters placed in the crucibles can vary, 

a new tare weight for each crucible plus filter is determined for 

each analysis. Crucible plus filter tare weights are recorded to 

the nearest 0.0001 g.

Evaporation Dishes

Evaporation dishes are small bowls made of heat-resistant 

glass that have a funneled lip for pouring. Evaporation dishes 

used in the Montana Sediment Laboratory have capacities of 

either 140 or 290 mL. The dishes are individually numbered 

with high-temperature paint or indelible marker for identification.

Evaporation dishes are cleaned by soaking in warm tap 

water or soap solution, lightly brushed to remove sediment 

without scratching the glass, and rinsed with hot tap water in 

the dishwasher. The dishes are then oven-dried for 2 hours 

at 105°C. After cooling for about 15 minutes, the dishes are 

transferred to desiccators for storage.

Sieves

Sieves are shallow metal pans with a standard-sized mesh 

opening that are used to separate sediment based on the size of 

the sediment in the sediment sample. Sediment particles with a 

median axis larger than the mesh openings are retained on the 

screen, whereas smaller sediment particles will pass through 

the screen. The operational definition used by the USGS to 

differentiate between sand and fine sediment (silt and clay) is 

a diameter of 0.062 mm (Guy, 1969). A 3-in. diameter sieve 

with a 0.062-mm mesh is used by the Montana Sediment 

Laboratory (fig. 6) to separate sand from fine sediment.

Distilled water is used to rinse the retained sediment from 

the screen to a crucible or evaporation dish to ensure that all 

sediment from a sample has been transferred. This rinse generally constitutes adequate cleaning of the sieve before processing the next sample. The sieve is inspected for particles that 

can clog the screen after each sample is processed. Occasionally a few particles can become lodged in the mesh openings 

of the screen and cannot be removed by rinsing. When particles become lodged in the mesh openings, the sieve is gently 

cleaned with a nylon brush or immersed in an ultrasound bath. 

The screen also is inspected prior to each use to ensure that it 

is taut and has no tears. A sieve is replaced if the screen cannot 

be completely cleaned, is no longer taut, or has become torn.

 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 6. Suspended-sediment sample poured through a 0.062-millimeter sieve to separate 

sand from fine sediment.

Desiccators

To maintain a constant sample weight, crucibles and 

evaporation dishes are stored in desiccators after they are 

removed from the drying oven. Storage in desiccators prevents 

the absorption of moisture by filters, sediment, or container 

surfaces, and also prevents the deposition of airborne particles.

Moisture reduction is achieved by a desiccant placed at 

the bottom of the desiccator. The desiccant is granular calcium 

sulfate, which has a large moisture-absorption capacity. The 

desiccant contains a moisture indicator that changes color as 

moisture is absorbed; thus, desiccant color is checked before 

the desiccator is used. If the desiccant color has changed, the 

desiccant is either replaced or recycled according to manufacturer’s instructions. The desiccant is recycled by baking it to 

restore the original color and absorption capacity.

Desiccators are inspected before use to ensure that the 

seal between the jar and lid is airtight. All desiccators are 

cleaned and regreased as needed. With the desiccant removed, 

a laboratory-grade detergent is used to clean the entire desiccator. New grease is applied to the jar rim and lid to maintain 

an airtight seal. Inspections and maintenance of all desiccators are documented in a logbook that is kept in the sediment 

laboratory.

Distilled Water

Distilled water is used in sediment-laboratory operations for rinsing sediment from sample bottles into crucibles 

and evaporation dishes, seating filters in crucibles, cleaning 

conductivity-meter sensors, rinsing sieves, and preparing test 

samples. An electric still is used in the Montana Sediment 

Laboratory that produces about 4 L of distilled water per hour 

from tap water. The criterion for acceptable quality of distilled 

water in the Center is a specific conductance of 5 μS/cm or 

less. If this criterion is exceeded, the still is disassembled and 

cleaned according to the manufacturer’s instructions.

As part of the overall Center quality-assurance program 

for water-quality activities (Knapton and Nimick, 1991), 

distilled water is tested for specific conductance whenever the 

laboratory conductivity meter is calibrated. Results of these 

quality-assurance tests are recorded in the logbook for the 

conductivity meter.

Sample Management

Sample management includes the handling, treatment, 

and documentation required to manage sediment samples 

after collection and prepare them for laboratory analysis. The 

quality of sediment data is largely dependent on thorough 

Quality-Assurance Procedures 
documentation of sample identity, which is achieved by 

tracking the sample from the time of collection through 

analysis and data entry. Sample integrity is maintained by 

strictly adhering to established procedures for sample processing. All pertinent sample information is documented on a 

laboratory-number worksheet and a dish-report worksheet 

during sample processing to enable crosschecking of sample 

identity, dish assignment, and field information.

Field Documentation

The documentation for individual samples begins in the 

field with clear and complete recording of pertinent information on the sample-bottle tag promptly after sample collection. 

This information includes the station name, station number, 

date and time of collection, gage height, water temperature, 

sampling method, sampling points of a multiple-bottle set, 

and collector’s initials. The same information is entered on a 

standard water-quality field form (fig. 7). Observers who are 

contracted to collect samples for the Center also document 

sample-collection information onsite using a standard 

sediment-sample field form (fig. 8). Supporting information 

regarding the sample collection and remarks on hydrologic or 

water-quality conditions also are reported on the field form.

Shipment and Storage

After sample collection, the tightly capped bottles are 

placed in secure carrying cases for shipment from the field 

to either a USGS office or the observer’s residence. Samples 

typically are transported in the field vehicle used for sampling 

trips. During winter, samples that are transported in field 

vehicles are protected from freezing by vehicle heaters. For 

overnight storage in the field, bottles are either protected from 

freezing using vehicle heaters or by transferring the bottles to a 

heated inside location. After transport from the field, samples 

are stored indoors—in a cool, dark location—to prevent evaporation, freezing, or algae growth that could degrade sample 

integrity. Samples stored at an observer’s residence are picked 

up by USGS personnel about every 6 weeks during routine site 

visits and taken to the field office for storage until samples are 

transported to the Montana Sediment Laboratory in Helena. 

Personnel of the Center office in Helena return sediment 

samples directly to the Montana Sediment Laboratory upon 

completion of a field trip; personnel from outlying field offices 

transport samples to the Montana Sediment Laboratory 

periodically on visits to the Center office.

Sample Inventory

When samples arrive at the Montana Sediment Laboratory, samples are immediately taken to a storage area for 

initial inventory, and receipt of all samples is documented. 

Sample tags are cross-checked with documentation on copies 

of field forms to assure that no bottles are missing and that 

information from both sources agree. Bottles are inspected for 

breakage, loose caps, spillage, or missing labels. Samples that 

cannot be positively identified or whose integrity is known to 

be degraded are removed from the processing sequence, and 

the conditions are noted on the field and laboratory forms. 

To facilitate processing, the samples are sorted according to 

station number and sample type and arranged in chronological 

order.

Sample Analysis

Sample analysis includes all the laboratory procedures 

used to document, prepare, and treat the samples during 

analytical processing. Also included are various qualitycontrol tests that indicate the accuracy and precision of the 

analytical results.

Two types of sample analysis are performed by the 

Montana Sediment Laboratory—suspended-sediment concentration and sand-fine size separation (fig. 9). Samples collected 

by observers from a single vertical in a stream on a daily or 

frequent basis typically are analyzed only for suspendedsediment concentration. Samples collected periodically by 

USGS personnel from multiple verticals in a stream cross 

section are analyzed for both suspended-sediment concentration and sand-fine size separation.

Laboratory Procedures

A variety of laboratory procedures are used to analyze 

suspended-sediment samples depending on the study objective, type of sample, and condition of the sample. Sediment 

analysis consists largely of weight determinations made at 

various stages in a sequence of steps that separate the sediment 

from the original water-sediment mixture of the sample. The 

primary reference of standard methodology for sedimentlaboratory operations is Guy (1969).

Sample-Weight Determination

The initial step in the analytical sequence is weighing 

the sample before any physical laboratory treatment. All 

samples are weighed within 2 weeks of receipt at the Montana 

Sediment Laboratory to minimize potential evaporation that 

would decrease the weight of the water in the water-sediment 

mixture.

Before samples are weighed on the macro balance, dirt 

or foreign material is wiped from the outside of the sample 

bottle. Then the sample gross weight, which includes the 

weight of the water-sediment mixture plus the weight of the 

sample bottle, is recorded. To obtain this value, the combined 

weight of the bottle cap and bottle tag is subtracted from the 

sample gross weight. An average of the combined weight of a 

bottle cap and tag is used as a tare correction. This step eliminates the need to remove caps and tags from each bottle before 

weighing. This correction is entered into the macro balance 

10 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 7. Example of a water-quality field form used to document information about water-quality samples collected by 

U.S. Geological Survey personnel.

Quality-Assurance Procedures 11
Figure 8. Example of a sediment-sample field form used to document information about suspended-sediment samples collected by 

observers.

UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY, MONTANA WATER SCIENCE CENTER

OBSERVER SEDIMENT SAMPLE FIELD FORM

STATION ________________________________________ MONTH _______________ YEAR _______

DAY TIME GAGE

HEIGHT TEMP

DEG C

NUMBER

OF

BOTTLES

GAGE

HEIGHT

WATER

TEMP

DEG C

NUMBER

OF

BOTTLES

SAMP

LOC. REMARKS

W B

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Use the first four columns after the day, unless you are requested to sample more than once daily.

OBSERVER’S SIGNATURE _________________________________________________________________________________

TIME

WATER

12  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 9. Operational sequence for the analysis of suspended-sediment samples in the Montana Sediment Laboratory.

SINGLE VERTICAL SAMPLES BY OBSERVER

Specific conductance measured (if evaporation method is used)

Field data and sample weights entered into computer

CONCENTRATION ANALYSIS

Samples decanted

Dishes tare-weighed and assigned to samples

Sediment transferred from sample bottle to dish

Sediment dried in oven

Sediment dishes cooled, then transferred to desiccator

Dried sediment weighed and concentration calculated by

Sediment Laboratory Environmental Data System computer program

Analyses printed on paper copy

Data reviewed, copies made

Original data filed in computation folder

for daily sediment stations

Copies of original data stored in laboratory folders

CROSS-SECTION SAMPLES BY U.S. GEOLOGICAL SURVEY

Specific conductance measured (if evaporation method is used)

Field data and sample weights entered into computer

CONCENTRATION AND SAND-FINE SIZE ANALYSIS

Samples decanted

Dishes tare-weighed and assigned to samples

Sample poured from bottle to dish through a 0.062-millimeter

sieve to separate the sand and fine sediment fractions

Sand retained on sieve is rinsed into dish

Sand and fine sediment dried in oven

Sand and fine sediment cooled, then transferred to desiccator

Dried sand and fine sediment weighed. Concentration and

percent finer than 0.062 millimeter calculated by Sediment 

Laboratory Environmental Data System computer program

Analysis printed on paper copy

Data reviewed, copies made

Electronic data files retrieved and sent to Data Management

Unit for entry into National Water Information System database.

Original paper copies stored in station water-quality folders

Copies of original data stored in laboratory folders

Samples transported to laboratory log-in area

Samples weighed

Samples organized by station number and sample type

Samples transported to laboratory

SAMPLES COLLECTED

Quality-Assurance Procedures 13
and is subsequently subtracted from the sample gross weight. 

The sample gross weight is recorded in bold notation on the 

bottle tag.

Sample Preparation

After the sample gross weight is determined for each 

bottle, the samples are brought from the storage area to the 

laboratory for processing preparation. At this step, the samples 

are inspected for sediment quantity to determine whether 

filtration or evaporation is required. The determination is 

based on the depth of sediment in the bottom of the sample 

bottle and the likelihood of clogging a filter. If the analyst 

decides that the sample is to be processed by evaporation, 

specific conductance is measured and a known volume of 

water is decanted from the surface of the sample to determine 

a dissolved-solids correction.

Sample data are entered in stages that correspond to the 

physical processing of the samples. Sediment Laboratory 

Environmental Data System (SLEDS), a computer program 

developed by the Cascades Volcano Observatory (CVO) of 

the USGS (U.S. Geological Survey, SLEDS training manual, 

no date), is used to enter, compute, and store sample information and analytical results for samples collected by observers 

and USGS personnel. Documentation of the SLEDS training 

manual is available in the Montana Sediment Laboratory, or 

from CVO in Vancouver, Wash.

The SLEDS program is formatted into three menus: 

(1) LOGIN menu, which includes entry of field data, requested 

analyses, and bottle weights (gross and tare); (2) ANALYSES 

menu, which includes assignment of dishes to samples, entry 

of dish tare weights, and entry of dish gross weight after 

sediment is dried; and (3) REPORTS menu, which generates 

output summary reports and electronic data files for computer 

data entry.

After the appropriate method of analysis is selected 

(filtration or evaporation), information for individual sample 

bottles is initially entered in the LOGIN menu. The initial 

data entry includes station number, project number, medium 

code, sample type, hydrologic condition, collector’s initials, 

sample collection date, collection time, gage height, sampling 

station (cross-section location), water temperature, specific 

conductance (if required), sample gross weight, and bottle tare 

weight.

The next step in sample preparation is to enter data in the 

ANALYSES menu. This menu allows the user to enter data 

into four subroutines: Tare weights, Dish report, Dish assignment, and Gross weights. In the Tare weights subroutine, a 

file is created that assigns crucibles and evaporation dishes to 

sediment samples. Dishes are identified by dish type (crucibles 

or evaporation dishes), a unique dish number, and the tare 

weight (the tare weight for crucibles is determined with clean 

filters in place). After the tare weights have been determined, 

the containers are either used immediately or stored in desiccators until needed. All containers are handled with tongs to 

prevent moisture or finger oils from adhering to the container 

surface.

The next step in sample preparation is arranging the 

sample bottles on the processing bench by station number and 

in chronological order. As the bottles are arranged, dishes are 

assigned to each sample in the Dish assignment subroutine of 

SLEDS. This subroutine allows the user to choose the number 

of dishes and the type of material (composite, sands, or fines) 

that will be added to each dish. The Dish report subroutine 

is normally used to create a report that documents which 

dishes are assigned to which samples. This subroutine also is 

used when bottle tare weights need to be determined after the 

sediment sample is removed. This report allows the analyst to 

accurately match the sample bottle with the assigned dishes.

The samples are allowed to sit for a minimum of 

24 hours, which allows all sediment to settle to the bottom of 

the bottle. After complete settling, most of the overlying water 

is decanted. The overlying water can be removed because 

all the sediment is retained at the bottom of the bottle and 

the original weight of the sample (sample gross weight) has 

previously been determined and recorded. A J-shaped tube 

connected to a vacuum hose is inserted into each bottle and 

held carefully at the water surface. As the water is suctioned 

off (fig. 4) and the water level begins to drop, the J-tube is 

slowly lowered while decanting the overlying water. The 

water is decanted at a withdrawal rate of about 1.0 L/min 

(0.3 gal/min) under a vacuum pressure of 0.5 kg/cm2 (15 in. 

mercury). The decanted water is drained into a collection jug 

for subsequent disposal. Vacuum withdrawal proceeds until 

the water is decanted to about 25 mm (1 in.) above the bottom 

of the bottle. Because the entry port of the J-tube is above the 

bottom of the tube and slow withdrawal of the overlying water 

prevents turbulence, all of the original sediment and about 

30 mL of sample is retained in the bottle after decanting. Final 

separation of sediment from the remaining water-sediment 

mixture is achieved by filtration or evaporation.

Filtration Method

The filtration method is used to analyze samples having 

a suspended-sediment concentration of less than about 

300 mg/L. The advantage of this method is that water passes 

through the Whatman glass-microfiber filter but sediment is 

retained; thus, any dissolved solids present in the water also 

are removed. As a result, drying and weighing of the sediment 

can proceed directly without any correction for the weight of 

dissolved solids. The disadvantage of the filtration method is 

that a large quantity of sediment, especially fine sediment, can 

quickly clog the filter and prevent the passage of water. The 

size of the crucible to be used is determined on the basis of 

the amount of sediment in the bottle. Prior to filtration, a Dish 

report containing the crucible assignment for the sample is 

retrieved and a final crosscheck between the crucible and the 

sample bottle is made to verify a correct match.

14  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
The crucibles are firmly seated in rubber holders on 

the manifold (fig. 5) and the vacuum pump is started. Each 

crucible is rinsed with distilled water to wet the filter to 

ensure a good seating and facilitate uniform sample dispersal. The vacuum line to the first crucible of the sequence is 

then opened by an in-line valve. A glass funnel attached to a 

movable ring-stand (figs. 5 and 6) is positioned over the first 

crucible. The sample is vigorously stirred with a rubber-tipped 

stirring rod and the stirring rod is rinsed with distilled water 

while in the bottle to remove any sediment; the rod is then 

placed in the next bottle in the sequence. The contents of the 

bottle are slowly poured into the glass funnel to drain into the 

first crucible that is under a vacuum. To prevent overfilling 

of the crucible, the sample is poured at a rate that does not 

exceed the filtration rate. As the sample is filtered through 

the crucible, the bottle and glass funnel are rinsed thoroughly 

with distilled water to flush all the remaining sediment into the 

crucible. When rinsing is complete, the vacuum line to the first 

crucible is closed and the line to the second crucible is opened. 

The same procedure is repeated for each bottle and crucible in 

the manifold.

After the entire manifold of crucibles has been processed, 

the crucibles are placed in chronological sequence in a drying 

tray. Rubber tips on fingers are used for secure and clean 

handling during the transfer. The next set of crucibles is 

inserted into the manifold, verified for cross-match, and the 

above procedures repeated. When the drying tray is full, the 

tray of crucibles is placed in the convection oven for 3-4 hours 

at 100-103°C.

After oven drying, the crucibles are allowed to cool for 

about 15 minutes. Hot crucibles are not placed into desiccators 

because air expansion caused by heating could force the lid 

off the desiccator. The warm crucibles are placed in desiccators for a minimum of 4 hours before final weighing to allow 

final cooling and prevent moisture accumulation from ambient 

humidity. The crucibles are stacked in reverse chronological 

order from the bottom of the desiccator to allow subsequent 

removal from the top in chronological order to facilitate data 

entry. Warm crucibles must not be placed in the analytical 

balance because the heat will cause erratic readings.

Evaporation Method

The evaporation method is used to analyze samples 

having a large quantity of fine sediment that cannot be easily 

filtered (generally more than 300 mg/L). The evaporation 

method requires that the initial concentration be adjusted for 

the weight of dissolved solids that precipitate as a solid residue 

as the water evaporates. The dissolved-solids concentration 

and the volume of the sample after decanting (30 mL) is 

needed to calculate the weight of the dissolved solids present 

in the decanted sample.

The method used by the Montana Sediment Laboratory 

is to measure the dissolved-solids concentration in an aliquot 

of supernatant (the clear, overlying water in the sample bottle) 

withdrawn from each sample. Aliquots of known volume are 

evaporated in the oven in dishes and subsequently weighed to 

determine the net weight of the dissolved-solids residue. The 

dissolved-solids correction for evaporated sediment samples is 

determined using the equation:

DSC = [AB/C]D

where

DSC is the dissolved-solids correction, in grams;

A is the volume of water-sediment mixture in 

each bottle after decanting, in milliliters;

B is the net weight of dissolved-solids residue in 

evaporation dish, in grams;

C is the volume of supernatant aliquot, in 

milliliters; and

D is the number of sample bottles in sample set.

The DSC is then subtracted from the total-sediment 

weight for the sample set to determine a final concentration. If 

a sand-fine size separation is determined for samples analyzed 

by the evaporation method, the DSC is subtracted from the 

net weight of the fine fraction because the fine fraction is the 

portion of the sample that passed through the sieve and retains 

the stream water from the original water-sediment mixture in 

the sample bottle (the sand fraction only retains distilled water 

from the sieve rinse).

Similar to the filtration method, the sample bottles and 

corresponding evaporation dishes are arranged in sequence 

on a processing bench. A Dish report is retrieved and used to 

crosscheck and verify the correct match of bottle to dish.

The evaporation dishes are placed in the mechanical oven 

at 92-94°C until standing water has evaporated (up to 24 hours 

for samples with large quantities of fine sediment). After 

the standing water has been evaporated from the dish, the 

samples are dried for an additional hour at 103°C (to remove 

any residual moisture adhering to sediment particles) and 

then allowed to cool for about 15 minutes in the oven. When 

no longer hot, the dishes are transferred to desiccators for a 

minimum storage time of 4 hours for additional cooling and 

drying before they are weighed.

Composited Samples

The average concentration of suspended sediment in the 

cross section of a stream is determined by collecting a depthintegrated sample at multiple verticals across the stream using 

procedures described by Edwards and Glysson (1999). The 

procedures provide a volume of sample from each vertical 

that is proportional to the flow (discharge-weighted), thereby 

allowing individual bottles from multiple verticals to be 

composited and analyzed collectively.

(1)

Quality-Assurance Procedures 15
Each bottle of a multi-bottle cross-sectional sample 

may be analyzed individually for concentration if the equaldischarge increment (EDI) sampling method was used 

(Edwards and Glysson, 1999, p. 51). Concentration analysis of 

each bottle indicates the cross-sectional variation in concentration across the stream. Bottles of a cross-sectional sample set 

obtained by other sampling methods are not analyzed 

individually, but rather are physically composited to determine 

total sample and total-sediment weights for all the bottles 

combined. If the samples are collected by the EDI method, the 

volume of sample in each bottle needs to be equal or nearly 

equal to be composited (Edwards and Glysson, 1999, p. 49.) 

The average cross-sectional concentration for composited 

samples is calculated from the ratio of total-sediment weight 

to total-sample weight.

Visual inspection of sediment quantity is used as a guide 

to determine the number of crucibles or evaporation dishes 

needed to composite multi-bottle sample sets. For samples 

having very small sediment quantities, the contents from 

several or all bottles of a cross-sectional sample set can be 

filtered through one or two crucibles without substantial 

clogging of the filter. Samples having a larger quantity of 

sediment or predominance of fine material might require a 

separate crucible or evaporation dish for each bottle. Samples 

having very large sediment quantities that are processed only 

by the evaporation method might require splitting the contents 

of a single bottle into two or more dishes to accommodate 

the extra rinse water needed to extract the sediment. Regardless of the number of containers used to composite bottles of 

a cross-sectional sample, the dish-identification numbers and 

tare weights are clearly recorded along with the corresponding sample-identification information for each sample bottle 

processed. Thorough documentation of the compositing 

process enables tracking of the sample treatment, accurate 

calculation of concentration, and the assignment of analytical 

results to the correct sample.

Particle-Size Analysis

The distribution of particle size is determined by the 

proportion of sediment weight in each of two sediment-size 

classes relative to the total-sediment weight. The particle-size 

analysis conducted by the Montana Sediment Laboratory 

is the sand-fine separation, which determines the weight of 

suspended sediment in two size classes—the coarse fraction 

having particle diameters equal to or greater than 0.062 mm 

(sand size and larger), and the fine fraction having particle 

diameters less than 0.062 mm (silt size and smaller). The 

particle diameter of 0.062 mm represents the transition 

between the two fractions (Guy, 1969) and is, by convention, 

termed “sand-fine break” (also referred to as sand-silt break, 

as 0.062 mm represents the break in the size scale between 

very fine sand and coarse silt). A particle-size analysis typically is performed only on cross-sectional samples, although 

the analysis also is performed on some single-vertical samples 

with unusually large concentrations.

Similar to the concentration analysis, containers are 

assigned to the sample set and their identification numbers 

and tare weights are recorded. The containers are further 

identified on the Dish report as to whether they will receive 

the sand (equal to or greater than 0.062 mm) or fine (less 

than 0.062 mm) fraction. Judgment by experienced laboratory personnel is required to ensure that enough containers 

are assigned for each fraction. The Dish report also is used 

to crosscheck and verify the correct match of the bottle to 

container.

To determine the proportion of sediment in each of the 

two size classes, the sediment is physically separated by 

pouring the decanted sample through a 3-in. diameter sieve 

having mesh openings of 0.062 mm (fig. 6). The first sample 

bottle of the sample set is slowly poured through the sieve 

and drained through the glass funnel into the first container 

assigned to the fine fraction. The sample bottle is thoroughly 

rinsed, with all rinse water also drained through the sieve into 

the same container. The sieve retains all sediment particles 

greater than 0.062-mm diameter. The glass funnel with the 

sieve is subsequently moved to the next container assigned 

to the fine fraction and the next bottle of the sample set is 

poured. The process is repeated until all sample bottles of the 

set have been poured and rinsed through the sieve and into the 

fine-fraction containers. The sediment on the screen accumulated from all the bottles is gently rinsed with distilled water 

over the last fine-fraction container to ensure that all material 

finer than 0.062 mm is flushed off of the sand and through the 

screen. At this point, all coarse sediment (sand fraction) from 

the entire sample set resides on top of the sieve screen. The 

sieve is lifted out of the funnel and the interior surface of the 

funnel is thoroughly rinsed with distilled water into the last 

fine-fraction container to remove any residual fine sediment.

The final step in the separation is to transfer the coarse 

sediment from the sieve to the container assigned to the sand 

fraction. This transfer is accomplished by moving the glass 

funnel over the coarse-fraction container. The sieve is inverted 

into the glass funnel so that the coarse sediment is now on the 

underside of the screen. The coarse sediment is backflushed 

into the coarse-fraction container by thoroughly rinsing the 

sieve and funnel with distilled water. All containers for the 

sample set are then transferred to the oven for drying.

In addition to the two size fractions, other size classes can 

be determined. Complete particle-size distribution typically is 

analyzed only for samples having large suspended-sediment 

concentrations or for special studies because the analytical 

procedures generally require a substantial quantity of sediment 

(1 g or more). Complete particle-size distribution is not 

determined in the Montana Sediment Laboratory, but rather 

the samples are sent to the USGS Iowa Sediment Laboratory 

in Iowa City, Iowa, which routinely analyses sediment for 

more than two size classes. Quality assurance for complete 

particle-size analysis is implemented according to policies and 

procedures of the Iowa Sediment Laboratory, as described by 

Matthes and others (1992).

16  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Samples determined to have a quantity of sediment that 

is sufficient for a complete size analysis are weighed and 

then decanted and transferred to small shipping bottles. The 

original bottle tag containing the field information is attached 

to the shipping bottle. The sample net weight (sample gross 

weight minus bottle tare weight) is recorded on the tag and 

labeled “sample net weight.” All field information and sample 

weights for samples shipped to the Iowa Sediment Laboratory 

are manually recorded on a laboratory-analysis form, which is 

kept in files at the Montana Sediment Laboratory. The samples 

are then shipped in a special padded carton, and a form from 

the Iowa Sediment Laboratory that contains sample-collection 

and analytical request information (fig. 10) is included. The 

original form is filed at the Montana Sediment Laboratory and 

a copy is shipped with the samples.

Sediment-Weight Determination

After the sediment has been oven-dried, the containers 

are removed from the ovens, cooled, and transferred to 

desiccators for storage until final weighing. Weighing can 

begin when the containers have been desiccated for at least 

4 hours.

The containers are sequentially placed on the balance pan 

to maintain chronological order for daily samples2. Balance 

doors are always closed before recording a weight. After a 

container is placed on the pan and the container and balance 

are stable, the weight is recorded. The weight of the container 

plus dry sediment (and dissolved-solids residue for evaporated samples) is recorded as the sediment gross weight. After 

this weight is recorded, the dish is removed and placed in a 

holding tray. Dishes are not washed for reuse until the analytical results have been reviewed and accepted as satisfactory by 

the laboratory supervisor. Reweighing may be needed to verify 

questionable results.

The sediment tare weight (dish weight) and weight of 

the dissolved-solids residue, if applicable, are subtracted from 

the sediment gross weight to obtain the sediment net weight, 

which is the weight of the dry sediment. Gross weights is 

the last subroutine of SLEDS in the ANALYSES menu and 

is used for entering the weight of the dry sediment. These 

subtractions are done automatically by the SLEDS program.

Calculation of Results

After the weight of dry sediment has been determined, 

the suspended-sediment concentration can be calculated. The 

analytical procedures for determining suspended-sediment 

concentration use the measurement of weight rather than 

volume, so the reported concentrations actually represent a 

ratio of sediment weight to sample weight ratio or parts per 

million (ppm.) This unit of measure is essentially equivalent to 

2

 Even though the Montana Sediment Laboratory organizes dishes sequentially, final weights can be entered in any order because a specific dish is 

assigned to a specific sample in the Dish assignment subroutine of SLEDS. 

the ratio of weight to volume or milligrams per liter (mg/L) at 

concentrations less than about 8,000 ppm. At concentrations 

of 8,000 ppm or greater, a correction for change in specific 

weight is applied in accordance with conversion factors listed 

in table 1. This correction converts concentration values in 

parts per million to milligrams per liter. Suspended-sediment 

concentration is calculated according to the equation:

C = (A/B)(1,000,000)

where

C is the suspended-sediment concentration, in 

parts per million;

A is the net weight of dry sediment, in grams; 

and

B is the net weight of sample, in grams.

The concentration is automatically calculated by the 

SLEDS program. Significant figures reported for concentration are 1 for 1-9 mg/L, 2 for 10-99 mg/L, and 3 for concentrations equal to or greater than 100 mg/L.

The results of particle-size analyses are reported as 

percent of total-sediment weight finer than an indicated 

particle diameter. The sand-fine separation analysis by the 

Montana Sediment Laboratory is reported as percent of 

suspended sediment finer than 0.062 mm. Other size classes 

analyzed by the Iowa Sediment Laboratory are reported in the 

same manner for each particle-size analysis.

The percent of sediment finer than 0.062 mm is calculated by adding the sediment net weight from all bottles 

of a sample set to determine a total-sediment net weight. 

The weight of the fine fraction is determined by adding the 

individual sediment net weights for each of the fine-fraction 

containers. The combined-sediment net weight of the fine 

fraction (minus the dissolved-solids correction, if applicable) 

is then divided by the total-sediment net weight of the sample 

set and multiplied by 100 to obtain the percent of sediment 

finer than 0.062 mm.

Analytical Quality Control

Analytical quality control is used to maintain and verify 

the adequate performance of analytical procedures in order 

to produce data of known quality. Implementation of analytical quality control includes internal testing of quality-control 

samples and external testing by the Sediment Laboratory 

Quality Assurance (SLQA) Program and formal USGS laboratory reviews. Records of analytical quality control are systematically reviewed to identify sources of error.

Internal Testing

Internal testing of the analytical process includes recording all analytical results for the following quality-control 

samples: evaporation blanks, sample blanks, filter blanks, 

(2)

Quality-Assurance Procedures 17
Figure 10. Example of an analytical request form used to document information about sediment samples shipped to the U.S. Geological Survey Iowa Sediment Laboratory.

This is____ of ____ sites [forms] in this case. ____total bottles in this case.

INDIVIDUAL BOTTLE INFORMATION -- 1 line for each bottle (arrow /ditto down to duplicate ) Grey columns required

Return analyses and empty containers to:

U.S. Geological Survey

Montana Water Science Center Sediment Lab

3162 Bozeman Ave.

Helena, MT 59601

(for Lab use only)

Pos.

No.

in

Case

Sample Start

Date

(mm-dd-yy )

Start or 

Mean

Time

(24hr)

Sample End

Date

(mm-dd-yy)

OPTIONAL

End

Time

(24hr)

OPT.

Set

ID

Bottle

No. in

Set

Gage

Height

Water

Temperature

 (° C)

Sampling

Method

(see

codes

above)

Lab

Analysis

Code(s)

Requested

(above)

Collector

Initials

Remarks

Bottle

Condition

codes

Lab Sample ID

1233456

Station No.:

______________

Station Name:

_____________________________________

Time Datum: MST [ie., PDT] District Code: __

Shipped by: _____________ Phone No.: _____________ Billing Account No.: ______________ Project Chief: ______________________Parameter Family:

Suspended

Bed-Material

 Bedload

 Total Medium:

___ (see codes on back) Sample Type: ___ Hydrologic Condition: ___ Hydrologic Event: ___

Enter in table below: Sampling Method: Bedload: Single Equal Width Increment (1000) Multiple Equal Width Increment (1010) Unequal Width Increment (1020)

Suspended: EWI (10) EDI (20) Single-Vertical (30) Fixed Single Vertical-BOX (920) Pumping (900) Single-stage (910) Partial-Depth (930) Partial-Width (940) Point (50) Grab (70)

Lab Analysis Codes Requested: (C) Concentration (SF) Sand-Fine (SA) Sand (Z) Full-Size (BD) Bulk-Density (LOI) Loss-on-Ignition (DS) Dissolved-Solids (T) Turbidity

(CC) Composite-Concentration (CSF) Composite Sand-Fine (CSA) Composite Sand-Analysis (CZ) Composite Full-Size (SC) Specific Conductance

Lab

________ Date Shipped: ___________ Date Rec’d ____________by_____

Possibly Hazardous? Explain_______________________________________________________________

U. S. GEOLOGICAL SURVEY SEDIMENT LAB ANALYSIS REQUEST

SW / SEDIMENT SAMPLE INFORMATION AT A SITE (SLAR v. 1.03)

18  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Quality-Assurance Procedures 19

Table 1. Factors for converting suspended-sediment concentration from parts per million to 

milligrams per liter1.

[Conversion factors are based on the assumption that the density of water is 1.000 g/cm3 plus or minus 

0.005 g/cm3, the range of temperature is 0-29 degrees Celsius, the specific gravity of sediment is 2.65, and 

the dissolved-solids concentration is less than 10,000 ppm. Abbreviations: g/cm3, grams per cubic centimeter; 

ppm, parts per million]

Suspended-sediment 

concentration range 

(ppm)

Conversion factor

Suspended-sediment 

concentration range 

(ppm)

Conversion factor

0 – 7,990 1.00 327,000 – 336,000 1.26

8,000 – 23,700 1.01 337,000 – 346,000 1.27

23,800 – 39,200 1.02 347,000 – 356,000 1.28

39,300 – 54,300 1.03 357,000 – 366,000 1.29

54,400 – 69,200 1.04 367,000 – 375,000 1.30

69,300 – 83,700 1.05 376,000 – 385,000 1.31

83,800 – 98,000 1.06 386,000 – 394,000 1.32

98,100 – 112,000 1.07 395,000 – 403,000 1.33

113,000 – 126,000 1.08 404,000 – 412,000 1.34

127,000 – 139,000 1.09 413,000 – 421,000 1.35

140,000 – 153,000 1.10 422,000 – 429,000 1.36

154,000 – 166,000 1.11 430,000 – 438,000 1.37

167,000 – 178,000 1.12 439,000 – 446,000 1.38

179,000 – 191,000 1.13 447,000 – 455,000 1.39

192,000 – 203,000 1.14 456,000 – 463,000 1.40

204,000 – 215,000 1.15 464,000 – 471,000 1.41

216,000 – 227,000 1.16 472,000 – 479,000 1.42

228,000 – 251,000 1.17 480,000 – 487,000 1.43

240,000 – 251,000 1.18 488,000 – 495,000 1.44

252,000 – 262,000 1.19 496,000 – 502,000 1.45

263,000 – 273,000 1.20 503,000 – 510,000 1.46

274,000 – 284,000 1.21 511,000 – 517,000 1.47

285,000 – 295,000 1.22 518,000 – 525,000 1.48

296,000 – 306,000 1.23 526,000 – 532,000 1.49

307,000 – 316,000 1.24 533,000 – 539,000 1.50

317,000 – 326,000 1.25

1

W.H. Durum, U.S. Geological Survey, written commun., 1972.
field replicates, method-comparison replicates, and extracted 

sample water. These internal tests are used to verify that 

procedures were properly implemented during sample analysis 

and provide evidence of the presence and magnitude of 

consistent bias resulting from systematic procedural errors. 

The type and magnitude of error provide guidance in modifying procedures to correct the error. Inconsistent variability 

resulting from random procedural error is less easily identified 

and controlled. These errors are controlled in a general manner 

by adequate training and supervision of laboratory analysts 

and by a prompt review of analytical results by the laboratory 

supervisor. Results of all analyses of quality-control samples 

are recorded in a quality-control logbook and periodically 

reviewed by the laboratory supervisor.

Two distilled-water sample blanks are analyzed for every 

bench of samples (120 bottles). One blank (300 mL of distilled 

water) is placed at the beginning of the analytical sequence 

as an initial reference and one is placed at the end to optimize 

detection of possible cross contamination. The sample gross 

weight is measured, and the blank sample is processed as an 

actual sample. Both filtration and evaporation methods are 

used in this quality-control test, depending on the method that 

is used at the time of processing.

After drying, the weight of the container (and filter, if 

applicable) is determined for the distilled-water sample blanks 

and compared to the original tare weight. The criterion for 

an acceptable deviation from a zero change in net weight is 

±0.0003 g (equivalent to 1 mg/L for a 300-mL sample). If 

the change in the net weight of the sample blank exceeds the 

equivalent of 1 mg/L, which represents the minimum reporting level for suspended-sediment concentration, the balance 

calibration is checked. If the balance is correctly reading a 

value ±0.0003 g, analytical procedures and previous results 

are reviewed to evaluate the need for additional testing or 

corrective actions. Adjustments to analytical results for the 

sediment samples are applied if the net sediment weight of the 

sample blanks equals or exceeds 0.0006 g, which represents 

an equivalent concentration of 2 mg/L (twice the minimum 

reporting level.)

Filter Blanks

Filter blanks are used to identify systematic errors 

resulting specifically from loss of filter fiber during filtration 

of samples. Whereas sample blanks attempt to collectively 

identify errors for a series of processing steps, filter blanks 

define the probable magnitude of error associated with a 

single step in the analytical process. Potential loss of filter 

fiber is minimized by rinsing and seating filters in crucibles 

with distilled water under a vacuum. This seating procedure 

is performed after the cleaning process and is designed to 

remove loose fibers before drying and obtaining a crucible tare 

weight.

Two filter blanks are processed for every bench of 

samples when the filtration method is used. All data are 

recorded in a quality-control logbook. A container tare weight 

(with filter) is determined for each filter blank. A volume of 

50 mL of distilled water (similar to the volume of a decanted 

sample) is poured into the crucible and vacuumed through 

the filter. The crucible is then dried in the same manner as 

routine samples. After drying and cooling, the crucibles are 

placed in desiccators. Final weights are obtained and recorded, 

then compared to the original tare weights. Consistent weight 

losses of 0.0003 g or greater indicate a potential problem that 

requires additional testing and evaluation for corrective action.

Field Replicates

Field replicates can be obtained in different ways to 

provide an assessment of precision (reproducibility) of 

analytical results. Replicate samples are two or more samples 

20 Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana

Evaporation Blanks

Evaporation blanks are used to document the volume of 

sample potentially lost to evaporation during extended field 

storage. Analytical results can be affected if an excessive 

quantity of water evaporates during storage, decreasing the 

original sample volume. Evaporation of water from the sample 

decreases the sample net weight, which could result in an 

increase in concentration. Sample evaporation is most likely 

to occur in observer-collected daily samples that are stored at 

an observer’s residence for an extended period. Evaporation is 

minimized by using tight-fitting bottle caps, keeping bottles in 

a dark, cool location during storage, and promptly weighing 

samples within 2 weeks after arrival at the Montana Sediment 

Laboratory.

Evaporation blanks consist of a tightly capped sample 

bottle containing 300 mL of distilled water. The sample gross 

weight is determined, and one blank per 120 bottles is placed 

in the cases of empty sample bottles supplied to the observer 

during site visits. Therefore, the evaporation blank is exposed 

to the same ambient temperature, sunlight, and humidity as the 

suspended-sediment samples collected and stored by observers. After the samples are retrieved from the observer’s residence and brought to the laboratory, the evaporation blanks are 

reweighed to determine the magnitude of any weight loss. The 

weight of water evaporated can then be used to evaluate the 

effect on concentrations and determine if adjustments need to 

be made to the sample net weights measured in the laboratory. 

All evaporation data are recorded in a quality-control logbook 

and reviewed by the laboratory supervisor.

Sample Blanks

Samples of distilled water are analyzed with routine 

suspended-sediment samples to document the probable magnitude of systematic processing and weighing errors. Weight 

might be gained from the transfer of sediment between bottles 

owing to incomplete rinsing of the decanting J-tube, stirring 

rod, or funnel. Weight gains also might result from incomplete 

oven drying or subsequent moisture absorption after containers 

are removed from the oven. Weight loss might result if filter 

fibers are detached during filtration.
considered to be essentially identical in composition. Replicate 

samples can be obtained in the field by either repeating the 

collection process to obtain two or more independent composite samples or by splitting a single composite sample into two 

or more subsamples. The individual replicate samples are then 

analyzed separately.

Precision of analytical results for field replicates are 

affected by numerous sources of variability within the field 

and laboratory environments which include variations in 

environmental conditions, sample collection, sample processing, and sample analysis. Because of the numerous sources 

of variability, if the concentrations determined for the replicate samples are within 10 percent of each other, the overall 

process of sample collection and analysis is considered to be 

acceptable.

Method-Comparison Replicates

To assess the comparability of results obtained by the 

filtration and evaporation methods, replicate samples with 

a known and identical sediment concentration are analyzed 

independently using each method (filtration and evaporation). Because several aspects of processing differ between 

the two methods, the resulting concentrations are compared 

to detect and quantify significant differences. The results 

also are compared to a theoretical concentration, based on 

the sample volume and sediment weight used to make the 

method-comparison replicate sample. Method comparisons are 

conducted twice annually.

For the methods-comparison test, three sets of four clean, 

glass-sample bottles are weighed to verify that the etched tare 

weights are correct. A volume of 300 mL of distilled water 

is added to each bottle. Identical weights of sediment are 

measured on dry, tared containers for each of three ranges of 

sediment weight. Sediment weights of 0.0010, 0.0300, and 

0.1000 g are used to provide small, medium, and large concentrations of filterable sediment that represent a typical environmental range. The measured sediment is carefully transferred 

to the bottles. Sample gross weights are then measured and the 

three sets of quality-control samples are processed as routine 

samples by the two methods. For the three ranges of sediment 

weight, two bottles are processed by each method to provide 

duplicate results within and between the methods. Because 

distilled water is used, quality-control samples processed 

by the evaporation method do not require a dissolved-solids 

correction.

After drying and determining the sediment net weight, 

concentrations are calculated for each quality-control 

sample. The method comparison is considered acceptable 

if the concentrations determined by each method are within 

5 percent of each other and the theoretical concentration. 

Concentrations of duplicate samples for each method are 

considered to have acceptable precision if the values are within 

5 percent. If concentrations between or within methods differ 

by more than 5 percent, another set of method-comparison 

replicates is processed. If the second round of testing results in 

unacceptable method comparison or precision, procedures are 

reviewed to evaluate possible sources of the differences and 

corrective actions are implemented.

Extracted Sample Water

The overlying water that is decanted from the sample 

bottles (after the sediment has settled to the bottom) is 

collected in a large glass jug and disposed of when the bottle 

is full. If settling is complete within the sample bottles and 

decanting is done carefully, this decanted water will contain 

at most a negligible amount of sediment. Sample water that is 

vacuumed through crucible filters during the filtration process 

also is drained to the same collection jug. Improperly seated 

filters at the base of crucibles could allow sediment to pass by 

the sides of the filter. To verify that sediment is not lost during 

the decanting or filtration process, quality-control samples 

of the extracted sample water removed by the vacuum are 

periodically analyzed, typically twice yearly or when the water 

in the collection jug visually appears to be cloudy. The turbidity of the water is noted before each disposal to determine if 

additional testing is needed.

Duplicate samples of about 300 mL are poured from the 

collection jug after thorough agitation into tared glass sample 

bottles. The sample gross weights are measured and the entire 

300-mL sample volume is processed by the filtration method. 

The crucibles are dried and the sediment net weight is determined. Concentrations determined for samples of extracted 

water are considered to be acceptable if they do not exceed the 

minimum reporting level of 1 mg/L (0.0003 g per 300 mL of 

sample). If results are unacceptable, the process is evaluated 

and retested until acceptable results are achieved.

External Testing

Participation in external testing and laboratory reviews 

provides evidence that the Montana Sediment Laboratory 

procedures comply with standardized methods and that 

analytical results meet acceptance criteria. Results from testing 

are compared with other USGS sediment laboratories, and 

outside reviews provide guidance on established and emerging 

laboratory protocols.

Sediment Laboratory Quality-Assurance Program

The Sediment Laboratory Quality-Assurance (SLQA) 

program is implemented by the USGS Office of Water 

Quality and is designed to determine the bias and precision of 

sediment-concentration analyses determined by sediment laboratories of the USGS. Quality-assurance samples of known 

sediment concentration are distributed by the USGS Branch of 

Quality Systems to all USGS sediment laboratories (Gordon 

and Newland, 2000). The quality-assurance samples contain 

particle sizes ranging from sand to clay. The qualityassurance samples are analyzed by each laboratory using 

standard methods and the results are reported to the USGS 

Quality-Assurance Procedures  21
Branch of Quality Systems. An inter-laboratory comparison 

of results is used to determine the bias and precision of results 

from the individual sediment laboratories. Results are 

distributed to each laboratory to indicate performance over 

the range of sediment concentrations tested. Laboratories with 

unacceptable performance results are required to conduct 

additional testing and might be required to submit to an onsite 

audit of laboratory equipment and procedures by the USGS 

Branch of Quality Systems.

Laboratory Reviews

All USGS sediment laboratories undergo a formal 

review of facilities and operations every 3 years. The review 

is conducted by a team of sediment specialists designated by 

the USGS Office of Surface Water. The review is designed to 

evaluate laboratory operations, identify deficiencies in procedures, and provide recommendations for correcting problems 

or improving quality. Quality-control logbooks are reviewed 

to evaluate documentation procedures and the performance of 

laboratory equipment.

Data Management

Determination of suspended-sediment concentration and 

particle-size distribution requires numerous tabulations of data 

and mathematical calculations. The accuracy of the data from 

the Montana Sediment Laboratory is systematically checked 

and the values are technically reviewed to assure that the data 

are reasonable for the prevailing hydrologic conditions and 

site characteristics. Analytical results in electronic databases 

and report manuscripts are verified prior to public release of 

sediment data.

Laboratory-Data Files

All data generated during the sequence of steps from 

sample collection through analysis are stored in various files 

that permit the tracking, retrieval, storage, and transmittal of 

data. The files consist of electronic data and original documents and forms. Electronic data are retrieved as paper copy 

and filed.

Data entered in the computer during laboratory analysis 

are stored in electronic files generated by the SLEDS program. 

These data are retrievable by a laboratory-identification 

number assigned to each sample. Paper copies of the analytical 

results are stored in the Center in both the water-quality station 

files and the Montana Sediment Laboratory files.

The analytical progress of samples collected by USGS 

personnel and observers at daily sediment stations is tracked 

using a sediment-data distribution form (fig. 11). This form 

is used to record sample-collection dates, sample type, and 

completion status of laboratory analysis, including the dates 

of shipment and receipt of analytical results for samples sent 

to the Iowa Sediment Laboratory. Subsequent distribution of 

laboratory data to the computation folders maintained by field 

offices, water-quality files in the Center’s Data Management 

Unit, and cooperating agencies also is documented on this 

form.

The potential loss of sediment data from either electronic 

or paper files requires that a duplicate copy of both be kept in 

paper files. Paper copies of all electronic and laboratory-data 

forms are stored at separate locations in at least two independent files. Copies, rather than original documents, are mailed 

from the laboratory in response to data requests.

Data entered into the computer are subject to damage or 

loss during power failure or equipment malfunction. Losses 

are minimized by nightly backup of the SLEDS database. The 

tapes are on a monthly rotation with the first day-of-the-month 

tape saved for 2 years. Tapes that are saved in January and July 

are archived.

Data Review

The quality of suspended-sediment data generated by 

the Montana Sediment Laboratory is maintained by following 

the procedures described in this report and by performing a 

systematic review of analytical results before data release. The 

systematic review includes checks of all manual calculations 

and periodic checks of the SLEDS computer-program algorithms. In addition, data for individual steps of the analytical 

sequence are checked when analytical results appear erroneous. Although quality-control measures integrated into the 

analytical sequence are designed to minimize systematic 

errors, all random errors cannot be prevented. Therefore, additional review of the data in a hydrologic context can identify 

questionable values that need to be further evaluated. For 

any unusual values, the sediment container is inspected and, 

in some instances, reweighed to verify the original results. 

Remarks on field forms that note the sampler’s observations 

of stream conditions also are inspected for further verification. If adequate verification of unusual values is not possible, 

the analytical result is not approved and is not entered in the 

Center’s water-quality database.

Manual calculations of concentration and particle-size 

distribution made by the laboratory analyst are verified by an 

independent checker. The verification applies to all sample 

data that are recorded. The manual calculations used to 

determine the final results are noted directly on the laboratory 

analysis form. If corrections are not necessary, the checker 

initials the analysis form and routes it to the laboratory supervisor. If corrections are necessary, the original value is crossed 

out and the correct value is written above the original entry; 

the correction is initialed and the analysis form is then routed 

to the laboratory supervisor for final review.

Calculations by the SLEDS program are periodically 

checked to ensure that automatic computations are correct. On 

a quarterly basis, data for selected samples are manually calculated to determine sediment concentration, corrections for 

dissolved-solids concentration, and conversion from parts per 

million to milligrams per liter. Results of these calculations are 

22  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Figure 11. Example of a form used to document information about sediment-data distribution in the USGS Montana Water Science Center.

SAMPLE

DATE(S)

SAMPLE TYPE HELENA

S-S

COPIES TO

COMPUTATION

FOLDER

COPIES TO

DATA

MANAGEMENT

DISTRIBUTION DATE

SENT RECEIVED

SAMPLE

TRACKING

FOLDER

COOPERATOR

OBSERVER FIELD SHEETS SENT

MONTH

SAMPLE 

TRACKING 

FOLDER

COMP.

FOLDER

OCT

NOV

DEC

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

DISTRIBUTION RECORD OF SEDIMENT DATA

(Obs, X-sect, BM)

IOWA CITY LAB

Quality-Assurance Procedures  23
compared to values calculated by SLEDS to verify accuracy. 

Discrepancies between SLEDS and manual results are brought 

to the attention of the Center’s Information Technology 

Specialist, who evaluates the extent of the discrepancy.

The final step before approval of laboratory data for 

transmittal to the Center’s water-quality database or daily 

sediment computation folders is a technical review by the 

laboratory supervisor. Concentration and particle-size data 

for all samples are reviewed to verify completeness, proper 

computational procedure, adequate documentation when 

routine procedures are changed, consistency of results for all 

quality-control samples, and hydrologically reasonable values. 

The data are retrieved after transmittal of the SLEDS data 

files into the Center’s water-quality database and verified by 

comparison to original documents.

Final approval of the sediment data in the water-quality 

database is completed by the Center Water-Quality Specialist, typically at the end of a water year when all water-quality, 

sediment, and hydrologic data are reviewed. After final 

approval, the Data Management Unit transfers the Center 

water-quality data files to the National Water Information 

System (NWIS) of the USGS where the sediment data can 

be accessed along with corresponding water-quality data 

collected concurrently with the suspended-sediment sample. 

These data can be accessed at http://waterdata.usgs.gov/mt/

nwis/.

Publication

Sediment data that have been approved for release are 

compiled and published annually by the Center in the report 

series “Water Resources Data, Montana” (U.S. Geological Survey, issued annually). Montana Sediment Laboratory data published in these reports include instantaneous 

suspended-sediment concentration and particle-size distribution (suspended-sediment percent finer than 0.062 mm) for 

periodic cross-sectional samples collected by USGS personnel. Sediment data for single-vertical samples collected by 

observers are not published, but are used to compute daily 

mean suspended-sediment concentrations at daily sediment 

stations using procedures described by Porterfield (1972). 

Values approved for publication are verified before printing 

the annual report.

Summary

The quality-assurance plan for the analysis of suspendedsediment samples by the USGS Montana Water Science 

Center Sediment Laboratory describes the quality-assurance 

policies and procedures to assure the quality of analytical 

results. Policies include requirements and guidelines for 

sediment-laboratory certification, personnel responsibilities 

and training, documentation requirements, and laboratory 

safety. All individuals involved in the processing and management of sediment data are required to adhere to designated 

practices and policies.

Quality-assurance procedures for processing suspendedsediment samples include the acquisition and maintenance of 

laboratory equipment and supplies. Sample management and 

analysis relies on strict adherence to procedures that follow 

established guidelines for analytical procedures and qualitycontrol testing. Data management requires accurate documentation of samples from the time of collection through final 

review and approval of analytical results.

References Cited

Edwards, T.K., and Glysson, G.D., 1999, Fields methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p. [Available online at http://water.usgs.gov/

pubs/twri/]

Gordon, J.D., and Newland, C.A., 2000, U.S. Geological 

Survey quality-assurance project for sediment analysis: 

U.S. Geological Survey Fact Sheet 031-00, 4 p.

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p. [Available 

online at http://water.usgs.gov/pubs/twri/]

Guy, H.P., and Norman, V.W., 1970, Field methods for measurement of fluvial sediment: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3, chap. C2, 

59 p. [Available online at http://water.usgs.gov/pubs/twri/]

24  Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana
Knapton, J.R., and Nimick, D.A., 1991, Quality assurance for 

water-quality activities of the U.S. Geological Survey in 

Montana: U.S. Geological Survey Open-File Report 91-216, 

41 p.

Knott, J.M., Sholar, C.J., and Matthes, W.J., 1992, Quality 

assurance guidelines for the analysis of sediment concentration by U.S. Geological Survey sediment laboratories: U.S. 

Geological Survey Open-File Report 92-33, 22 p.

Lambing, J.H., and Dodge, K.A., 1993, Quality assurance 

for laboratory analysis of suspended-sediment samples by 

the U.S. Geological Survey in Montana: U.S. Geological 

Survey Open-File Report 93-131, 34 p.

Matthes, W.J., Jr., Sholar, C.J., and George, J.R., 1992, Quality assurance plan for the analysis of fluvial sediment by 

laboratories of the U.S. Geological Survey: U.S. Geological 

Survey Open-File Report 91-467, 31 p.

Moreland, J.A., 1995, Quality-assurance plan for waterresources activities in Montana—1995: U.S. Geological 

Survey Open-File Report 91-194 rev., 23 p.

Porterfield, George, 1972, Computation of fluvial-sediment 

discharge: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. C3, 66 p. [Available 

online at http://water.usgs.gov/pubs/twri/]

Skinner, E.L., Watterson, C.A., and Chemerys, J.C., 1983, 

Laboratory safety handbook: U.S. Geological Survey OpenFile Report 83-131, 52 p.

U.S. Geological Survey, issued annually, Water resources 

data, Montana: U.S. Geological Survey Water-Data Report. 

[Selected reports available online at http://pubs.usgs.gov/

wdr/#MT/]

U.S. Geological Survey [variously dated], National field manual for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chaps. A1-A9. [Available online at http://pubs.water.usgs.

gov/twri9A/]

U.S. Geological Survey [no date], Sediment Laboratory Environmental Data System training manual: 45 p.

U.S. Geological Survey Memorandum (public access) Office 

of Surface Water Technical Memorandum 91.11, August 

14, 1991, Certification training for sediment laboratories. 

[Available from the U.S. Geological Survey at http://water.

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References Cited  25
For additional information contact:

Director, Montana Water Science Center

U.S. Geological Survey

3162 Bozeman Avenue

Helena, Montana 59601

Telephone: 1-406-457-5900

World Wide Web: http://mt.water.usgs.gov/
Dodge and Lambing—Quality-Assurance Plan for the Analysis of Suspended Sediment by the U.S. Geological Survey in Montana—Open-File Report 2006–1242