The Essential Handbook of Ground Water Sampling - Chapter 2 doc

Implementation of a comprehensive and well thought out SAP should ensure that ground-water sample collection procedures are consistent from one sampling event to the next, thus reducing

The Ground-Water Sampling and Analysis Plan

(SAP): A Road Map to Field Sampling Procedures Gillian L Nielsen

CONTENTS

Objectives of the SAP 35

Preparation of the SAP 36

Selection of Field Protocols to Be Incorporated into the SAP 36

Well Headspace Screening 37

Water-Level and Product-Thickness Measurement 37

Field Quality Assurance and Quality Control 40

Purposes of Field Quality Control Samples 42

Purging and Sampling Device Selection and Operation 44

Sampling Point Purging Methods 44

Field Measurement of Water-Quality Indicator Parameters and Turbidity 45

Sample Pretreatment Options 45

Filtration 45

Physical and Chemical Preservation of Ground-Water Samples 46

Field Equipment Cleaning Procedures 46

Documenting a Sampling Event 47

Written Records 48

Electronic Records 52

Audio-Visual Records 53

References 53

Objectives of the SAP

As discussed inChapter 1,there is a great deal of complex science behind ground-water sampling Much of this science drives the selection of sampling methods and equipment for each site To ensure that sampling teams are aware of requirements for sample collection, a site-specific SAP must be written by an experienced practitioner and followed by the sampling team The objectives of a typical SAP are summarized inTable 2.1 Implementation of a comprehensive and well thought out SAP should ensure that ground-water sample collection procedures are consistent from one sampling event to the next, thus reducing the potential for sampling team related error and bias This, in turn, should ensure that the data generated, both in the field and as a result of laboratory analysis of samples, are comparable and without peaks and valleys referred to as ‘‘data bounce.’’

35

Preparation of the SAP

The SAP should be written by an experienced practitioner who has relevant field experience and who can identify potential sources of error and bias in each component of the ground-water sample collection process In addition, working experience in a laboratory or working closely with laboratory personnel is an advantage

Prior to submitting the SAP to regulatory agency personnel for their approval, it is recommended that field sampling team personnel have the opportunity to review and provide honest input on procedures contained within the SAP Communication between all levels of personnel involved in the sampling program will ensure that the final SAP is not only technically correct for the site-specific program, but that field protocols are practical and realistic and based on good science All SAP writers are encouraged to remember this saying: ‘‘nothing is impossible for the person who does not have to do it.’’

A procedure may sound good on paper, but if the sampling team finds the procedure to be too cumbersome or too confusing, shortcuts will be made in the field, which can introduce substantial sampling error, imprecision, and bias Project personnel need to remember that for most ground-water SAPs, once the document has received regulatory approval for implementation, procedural changes cannot be made randomly in the field Deviation from the documented protocol will call into question all results from field measurements and subsequent data generated by laboratory analysis of collected samples

Selection of Field Protocols to Be Incorporated into the SAP

As illustrated in Table 2.1, the SAP details specific standard operating procedures for a number of work tasks to be implemented during the sampling event While preparing the SAP, a great deal of thought needs to go into the selection of protocols for each of the work tasks most appropriate for any individual site This includes methods and equipment for wellhead screening, water-level and product-thickness measurement, field quality

TABLE 2.1

Objectives of a Sampling and Analysis Plan

Provide a written statement of objectives of the sampling program

Provide a schedule for sample collection (number of wells, when and how frequently they should be sampled) Provide detailed procedures for all aspects of the ground-water sample collection process to be implemented by the sampling team to ensure sampling accuracy and precision including:

/ Well integrity inspection

/ Wellhead screening for volatile or combustible vapors

/ Water-level and product-thickness measurement

/ Field QAuQC measures

/ Purging and sampling device selection and operation

/ Well purging procedures and management of purge water

/ Parameters required for ground-water sample analysis

/ Field equipment calibration procedures

/ Field parameter measurement procedures

/ Field equipment decontamination procedures

/ Sample collection procedures, including sample container selection, sample pretreatment requirements, order of sample collection, and sample container filling

/ Sample handling and preparation for shipment

/ Documentation of sampling event activities

Provide written documentation of field procedures for outside evaluation

Provide a vehicle for project management and budgeting

assurance (QA) and quality control (QC), sampling point purging and sample collection, field parameter measurement, and field equipment decontamination

Well Headspace Screening

The first task implemented by the sampling team at each sampling point is opening the well and screening the headspace above the water column in the well for the presence of volatile or combustible gases and vapors The SAP must detail which instrumentation is required for screening the well headspace (e.g., photoionization detectors [PIDs] [Figure 2.1], flame ionization detectors [FIDs], or combustible gas indicators) and how the data are to be used (e.g., health and safety personal protective equipment [PPE] selection) It must also indicate how the equipment is to be calibrated, operated, and maintained throughout the sampling event Equipment for headspace screening is selected based on the types of contaminants known to be present at the site Table 2.2 lists the types of equipment that may be used for well headspace screening and their applications Nielsen

et al (2006) describes the use of PIDs and FIDs in more detail for headspace screening, and Maslansky and Maslansky (2006) describes how to use data from PIDs and FIDs to select the most appropriate PPE

Factors that must be considered in the selection of headspace screening equipment include: type of data generated (qualitative versus quantitative), ability to detect the parameters of concern, ease of calibration; sources of interference, and ease of use Readers are directed to Maslansky and Maslansky (1993, 1997, 2006) for detailed discussions on the applications and limitations of each of the types of instrumentation presented in Table 2.2 and for guidance on how to incorporate and interpret data from wellhead screening in a health and safety plan

Water-Level and Product-Thickness Measurement

Following well headspace screening, the next task is to take water-level or product-thickness measurements (Figure 2.2).In this portion of the SAP, specific procedures for

FIGURE 2.1

Well headspace screening must be done with the appropriate instrument This PID is used to detect volatile organic compounds (VOCs) associated with petroleum hydrocarbons and organic solvents.

where, when, and how to take water-level and, if applicable, separate-phase product-measurements (LNAPL or DNAPL) must be described in detail These product-measurements must be taken in all sampling points prior to any purging and sampling activities, to ensure that the data are collected under as close to the same environmental and atmospheric conditions as possible This is of particular concern when taking water-level measurements, which are potentially affected by a number of environmental variables including changes in ambient air pressure (especially problematic for shallow, unconfined formations), tides, changes in levels of nearby rivers, precipitation events, and operation

of nearby pumping wells

A number of different methods are available for water-level measurement, including ploppers (or poppers), chalked tapes, electronic water-level gauges, pressure transducers, bubblers, sonic devices, floats, and acoustic probes The method appropriate for any given site depends on the measurement accuracy required, the depth to static water level

TABLE 2.2

Examples of Instrumentation Appropriate for Well Headspace Screening

Instrumentation Class of Contaminant of Concern Example Application

PID Volatile organic vapors and gases

and some inorganics

Dry cleaning facility for PCE and TCE

FID Volatile to semi-volatile organic

vapors

Underground storage tanks with jet fuel

Combustible gas indicator

(may be combined with

an oxygen meter)

Flammable vapors Landfills where methane may

accumulate in wells Toxic gas sensors Vapors containing known toxics Industrial facility where H 2 S is

generated

FIGURE 2.2

Water-level measurements should be taken in all wells in a sampling program prior to purging and sampling of the wells (to collect data for piezometric surface mapping) and again just before purging (to determine the well volume for well-volume purging or the initial static water level for low-flow purging and sampling) This water-level gauge will be used to track drawdown in a well during low-flow purging and sampling.

in the wells included in the sampling program, well diameter, whether single measurements or continuous data are required, and the possible sources of interference present in the well ASTM Standard D 4750 (ASTM, 2006a) discusses some of the practices available for measurement of water levels in monitoring wells including ploppers, carpenter’s chalk on a steel tape, and a variety of electronic water-level gauges.Chapter 7 discusses these and other water-level measurement methods in detail

Water-level data are used for a variety of applications including determining the volume of water in the sampling point, determining the direction of ground-water flow and the hydraulic gradient (horizontal and vertical), and calculating the rate of ground-water flow Readers are directed to Chapter 7 for a detailed discussion on ground-water-level data interpretation and presentation ASTM Standard D 6000 (ASTM, 2006b) also provides a discussion on methods for presentation of water-level information obtained from ground-water investigations

At sites with petroleum hydrocarbon contamination, some monitoring wells and direct-push tools may contain a separate-phase layer of product (LNAPL), which must be measured in addition to the water level The thickness of this layer is referred to as the

‘‘apparent product thickness,’’ which reflects the amount of hydrocarbon that has accumulated in the well — not the actual thickness of product in the formation

To measure the thickness of LNAPL, one of three methods can be used: (1) hydrocarbon-sensitive and water-sensitive pastes applied to a measuring tape; (2) an electronic oil
/water interface probe; and (3) a clear, acrylic hydrocarbon bailer (API, 1989) The first method requires the application of a hydrocarbon-sensitive paste to one side of a tape and a water-sensitive paste to the other side The tape is lowered into the well and as the LNAPL and water contact the pastes, color changes occur The depths of each color change are measured, with the difference between the changes indicating LNAPL thickness The depth to ground water, which must be adjusted because of the presence of LNAPL, is indicated by the color change on the side of the tape coated with the water-sensitive paste Compensation factors and the significance of the LNAPL in the well are discussed in API (1989) and Testa and Winegardner (1991)

Electronic oil
/water interface probes are capable of determining the depth to ground water using a conductive probe similar to that used in an electronic water-level gauge In addition, they are equipped with one of three hydrocarbon-detecting sensors: (1) infrared; (2) optical; or (3) a float The meter emits different audible tones or different indications via lights (i.e., continuous versus flashing) when the probe contacts the LNAPL and then the LNAPL
/water interface This method is quicker than using pastes but is much more expensive It is also less accurate than the measuring tape with pastes when measuring thin layers of hydrocarbon Quoted accuracies and detection capabilities of most oil
/

water interface probes are usually between 0.12 and 0.06 in

Clear hydrocarbon bailers are useful for collecting a grab sample of the LNAPL layer, which can be visually examined and measured within the bailer To measure LNAPL thickness, the bailer is lowered to the point at which the first fluid in the well is encountered, then lowered an amount slightly less than the length of the bailer To ensure

a measurement of the full LNAPL thickness, the bailer must be long enough to ensure that its top will be above the air
/LNAPL interface, when the bottom check valve is below the LNAPL
/water interface Of the three methods, this is the least accurate method for LNAPL measurement because the thickness of product in the bailer is never an exact indication of what is in the well It is always less than the product thickness in the well by

a factor that depends on the diameter of the bailer (compared with the diameter of the well) and the design of the check valve

Field Quality Assurance and Quality Control

A ground-water sampling event generates information and measurements used for making important site-specific decisions such as determining whether a facility design is effective at preventing impacts to the environment, determining whether ground-water contamination is present at a site, determining whether contamination poses an exposure risk to off-site receptors, determining whether natural attenuation is an appropriate remedial alternative for a site, or determining the most effective remedial design for a site Given the significance of these decisions and their potential associated costs, it is critical that all analytical and field measurement data are not only technically sound but also scientifically and legally defensible An important component of the SAP is a detailed field QAuQC program which, when implemented, provides sampling teams with the confidence that the results of the sampling event will be technically correct and defensible

A QA program may be defined as those operations and procedures that are undertaken

in the field to provide measurement data of a stated quality with a stated probability of being correct (Taylor, 1985) The QA program documents administrative and field procedures that are designed to monitor management of the project as well as field sample collection and measurement activities Table 2.3 summarizes the key adminis-trative and field elements of a field QA program for ground-water sampling

When followed, a field QAuQC program will ensure that all data generated through field measurement and analysis are accurate and precise with a minimum amount of error and bias The QAuQC program ensures that the data produced are defensible if the project is subject to litigation, because it provides clear documentation of field procedures and outlines the system of checks and balances that were used to verify sampling and field measurement accuracy and precision ASTM Standard D 7069 provides a standard guide for field QA in a ground-water sampling event (ASTM, 2006c)

Samples referred to as field QC samples should be collected during every sampling event (Table 2.4) The purpose of field QC samples varies with the type of sample collected, but these samples provide a formal means of verifying the precision and accuracy of various components of field sample collection procedures Field QC samples are commonly collected at one or more designated sampling points after all laboratory samples have been collected at that (those) point(s) This ensures that sufficient sample volume is available for collection of samples for laboratory analysis

TABLE 2.3

Key Elements of a Field QA Program

Administrative elements

Project description and definition of project objectives

Project fiscal information (travel, support services, expendable supplies, equipment needs)

Schedule of tasks and products (field activities, analysis, data review, reporting)

Project organization and responsibility

Selection of appropriately trained and experienced personnel for field and management roles

Field elements

Implementation of technically sound SOPs

Documentation of protocols for operation, calibration, and maintenance of all field instrumentation Collection of field QC samples (which, when, how, and how many)

Adherence to required sample pretreatment methods and holding times

Use of chain-of-custody procedures

Record keeping procedures that incorporate good laboratory practices (GLPs)

Methods for checking accuracy of field parameter measurements

Description of corrective actions to be implemented if an error is detected at any point in the field

In many cases, regulatory programs dictate which QC samples are required to be included in the sampling protocol Unfortunately, in many instances, only minimum attention is paid to incorporating these samples into a sampling program When an SAP is prepared for any site, it is important to incorporate not only those QC elements required

to satisfy regulatory requirements, but also those system checks that will facilitate data validation When determining the level of field QAuQC independently of regulatory guidelines, the political sensitivity of the site being monitored needs to be evaluated A higher level of QAuQC is generally warranted if the site is operating under a consent order, if there is a strong public opinion about detrimental site impacts, or if the site is about to be sold QAuQC levels should also be higher than normal at sites where the concentration of contaminants in samples is very close to action levels or analytical method detection limits Under these circumstances, because critical decisions are made based on comparison of sampling results to action levels, it is important to have the utmost confidence in the accuracy and precision of the samples and the field data collected In long-term monitoring programs or in programs where there are sufficient numbers of sampling points to warrant multiple sampling teams, field QAuQC efforts should be elevated to ensure consistency between sampling teams Without good field QAuQC, it can be difficult to directly compare results generated by two different sampling teams at a single site, even if they are implementing the same sampling protocol Table 2.4 presents a list of the various QC samples that may be included in a field QC program, with the typical frequency of collection for each type of sample If a ground-water sampling program is subject to scrutiny by outside groups, such as attorneys or regulatory agency personnel, the ratio of QC samples to sampling locations will decrease (i.e., instead of a 1:10 ratio, some QC samples may be required at a 1:5 ratio) There is a tendency to try to increase the ratio of sampling locations to QC samples in an effort to save costs As an example, the authors recently reviewed an SAP that incorporated equipment blanks to verify the effectiveness of field equipment decontamination procedures The plan indicated that an equipment blank would be collected after every

30 sampling locations (rather than every ten locations) to save money When laboratory results were reported, a contaminant was detected not only in each of the 30 samples collected but also in the equipment blank As a consequence, all 30 of the sampling points had to be resampled (rather than ten) to determine whether the contaminant concentra-tions were real or whether the data indicated that there was a problem with field equipment cleaning procedures

TABLE 2.4

Common Field QC Samples

Type of QC Sample Recommended Frequency of Collection

Trip blank One per shipment a per day per laboratory

Temperature blank One per shipping container

Field blank One per waste management unit

Equipment blank One for every ten sampling points

Blind duplicate sample One for every ten sampling points

Spiked sample One for every ten samples submitted for analysis

Field split sample Variable, but at least one upgradient location and two

downgradient locations should be sampled

a The term ‘‘shipment’’ must be defined for each project For example, if ten coolers are

being sent to a laboratory, under one definition, all ten coolers might be defined as a

single shipment In another regulatory program, each cooler could be considered to be

an individual shipment.

In addition to selecting which and how many QC samples will be incorporated into the sampling program, it is important to select which parameters should be analyzed on each

of the QC samples so that the information derived from their analysis will be meaningful Ideally, each QC sample will be analyzed for the same parameters as the ground-water samples This will provide the most meaningful information and will permit identifica-tion of any potential problems for any of the analytes of interest This, however, is also the most expensive strategy and, consequently, the least likely to be implemented More likely, regulatory guidance will be referenced to put together a short ‘‘required’’ list of analytes In many cases, regulatory guidance requires that field QC samples be analyzed for volatile constituents because that group of analytes is most sensitive to handling However, not all sites are concerned with volatiles, so important resources may be expended on potentially inconsequential analyses

Purposes of Field Quality Control Samples

It is important that sampling team members understand the purpose of each type of QC sample to understand the importance of collecting the samples correctly The purpose of each of the QC samples presented inTable 2.4will be described herein Details on how to collect each QC sample are found inChapter 6

A trip blank is a blank designed to determine whether anything associated with the preparation of the sample containers by the laboratory, shipment of the empty containers

to the field, traveling in the field with the sampling team during the sampling event, and return shipment to the laboratory could have any impact on sample integrity This blank

is prepared by the laboratory and requires no preparation or handling by the field sampling team

The purpose of a temperature blank is to provide a formal mechanism for the laboratory to confirm actual sample temperatures upon arrival at the laboratory When samples arrive at the laboratory, temperatures should be checked in sample containers of differing volume and placement within the shipper This can be done using: (1) a certified thermometer inserted into one or more sample containers; (2) a calibrated infrared gun to determine the surface temperature of individual containers; or (3) a specially prepared

40 ml sentry vial (Figure 2.3) that contains a permanently affixed certified thermometer,

FIGURE 2.3

Temperature blanks (in this case, the vial with the dark dot on the top) are used to provide the laboratory with a convenient means of checking sample temperatures upon arrival of a shipment of samples at the lab.

usually provided by the laboratory The latter method, called a temperature blank, is preferred by some laboratories because it does not require that a foreign object (a thermometer) be inserted into the sample container (which could result in sample contamination) The infrared method is preferred by other laboratories because it is fast, does not require that a thermometer be inserted into the sample container, and permits evaluation of a number of sample containers of differing volumes throughout the sample shipper Regardless of which method is used by the laboratory, when sample temperatures are checked, the laboratory will look for an arrival temperature of

4 928C If the arrival temperature is outside of this range, the sampling team will be contacted to discuss an appropriate course of action: resample the well or analyze the received sample, with a disclaimer stating that the analyzed sample was not appro-priately preserved with respect to temperature

At some field sites, there is a concern that ambient air contamination levels may be sufficiently high to influence concentrations of contaminants detected in ground-water samples In some instances, trace quantities of VOCs may be gained by a ground-water sample through contact with atmospheric air, causing a positive bias in their determina-tion (Gillham et al., 1983) A good example of a site where this is a common problem is the corner service station At these sites, ground-water monitoring wells are commonly installed in the vicinity of pump islands When samplers purge and sample these wells, the station typically remains open for business, meaning that as wells on one side of the pump island are sampled, station customers may dispense fuel into their vehicle on the other side

of the island Under these circumstances, ambient air is contaminated by fumes from the dispenser and exhaust fumes from adjacent vehicles, which contain the same volatile constituents for which ground-water samples will be analyzed To quantify the extent to which ambient conditions may influence sample chemistry, a field blank is collected

A fourth important field QC sample is the equipment blank Whenever a piece of equipment is used in more than one sampling location, it should be cleaned between locations (Figure 2.4) It will be necessary to collect an equipment blank to verify the effectiveness of field equipment cleaning procedures (see Chapter 8 for more detailed discussions on field equipment cleaning procedures) Two forms of equipment blank can

be collected The first, sometimes referred to as a rinseate blank, is designed to determine whether, following equipment cleaning, soluble contaminants remain on the surfaces of the equipment In some cases, contaminants may not readily solubilize in control water, but may remain on the surface of cleaned equipment as a residue To determine whether a residue remains on a surface following cleaning, a wipe or swipe sample may be collected

To test the precision of sampling teams, a blind duplicate sample is collected as part of the field QC program The objective of the blind duplicate is to collect two samples of ground water that are as close to chemically identical as possible There are two procedures for collecting blind duplicates — one procedure for nonvolatile parameters and a second procedure for parameters requiring the use of 40 ml VOC vials Detailed procedures on how to collect each type of duplicate sample are provided inChapter 6

In many regulatory agency guidance documents, a field QC sample called a spiked sample is presented as a means to determine whether there is any matrix activity (most often in the form of microbial activity) that might alter sample chemistry from the time a sample is collected to the time it is extracted or analyzed by the laboratory Samplers must remember that once filled, sample containers continue to be living, breathing environ-ments that may undergo chemical and physical changes, especially where no chemical preservatives are used Spiked samples can be an effective means of determining whether field chemical and physical preservation methods are appropriate Field spiked samples should not be confused with spiked samples used by the laboratory as part of its internal

QC program

The final QC sample that is commonly incorporated into a ground-water sampling program is a field split sample Field split samples are collected for the purpose of verifying the performance of one laboratory against a laboratory of known performance levels Typically, field split samples are collected when a regulatory agency wishes to evaluate the performance of a new or unknown laboratory against the regulatory agency’s approved laboratory to ensure the accuracy of sample analysis

Purging and Sampling Device Selection and Operation

Many devices are available for purging and sampling ground water These devices and their operational characteristics are described in detail in Chapter 3 The SAP must include a description of the devices selected for use on a task-specific basis It should also include information on how to operate the selected devices and how to maintain the equipment to ensure proper operation in the field While not always required by regulatory agencies when reviewing SAPs, it is highly recommended that the SAP includes, as an appendix, the operations manuals for each device specified for purging and sampling This provides sampling team members with critical equipment-specific information such as operating procedures, calibration procedures, troubleshooting tips, spare parts lists, and contact information for equipment repair

Sampling Point Purging Methods

Most traditional approaches to ground-water sampling are based upon the assumption that all water that resides in sampling points between sampling events is stagnant

FIGURE 2.4

An equipment blank is collected by passing a rinse of final control water over the surface of a piece of equipment after it has been used and then cleaned.