6 Conducting a Ground-Water Sampling Event David M. Nielsen and Gillian L. Nielsen CONTENTS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Field Preparation for a Ground-Water Sampling Event . . . . . . . . . . . . . . . . . . . . . . . 155 Site Orientation and Sampling Event Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 155 Conducting the Sampling Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Sampling Point Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Well Headspace Screening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Water-Level Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Well Purging and Field Parameter Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 157 Sample Collection Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Order of Container Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Sample Collection Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Protocols for Collecting Field QC Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Trip Blanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Temperature Blanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Field Blanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Equipment Blanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Blind Duplicate Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 Field Spiked Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 Field Split Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 Ground-Water Sample Pretreatment Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 165 Sample Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 In-Line Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Positive-Pressure Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Negative-Pressure Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Sample Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Preparation of Sample Containers for Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Cleanup of the Work Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Delivery or Shipment of Samples to the Laboratory . . . . . . . . . . . . . . . . . . . . . . . 170 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 153 © 2007 by Taylor & Francis Group, LLC Introduction After the SAP has been prepared, and has received regulatory and client approval for implementation, the sampling team will travel to the field site to collect ground-water samples using the protocols and procedures contained in the SAP. Each sampling team member should have a personally assigned copy of the SAP on hand in the field to refer to if there is ever a need for clarification of a field procedure. Table 6.1 summarizes the field activities that will be implemented by a sampling team during a typical ground- water sampling event for a long-term ground-water monitoring program. A similar schedule of activities will be followed for most other ground-water sampling events. These activities are presented in the chronological order in which they would occur in the field. To be effective, sampling team members need to work together and develop a system to ensure efficient use of time and resources. This will come with time and experience as sampling team members work together at each field site. Sampling teams should create a system of checks and balances to ensure that errors are not made as a result of omission, use of improper protocols, unfamiliarity with equipment, or failure to read and understand the SAP. ASTM International has published a guide (ASTM Standard D 5903 [ASTM, 2006a]) on planning and preparing for a ground-water sampling event that provides an excellent ‘‘to do’’ list for sampling team members to follow to TABLE 6.1 Typical Field Components of a Ground-Water Sampling Event for a Long-Term Monitoring Program Review of site map for facility orientation Prepare field notebook for daily entries Check all sample containers supplied by the laboratory for breakage and to be sure all required containers (and a few extra containers) are available for each well to be sampled Check all QC sample containers supplied by the laboratory Calibrate all field equipment (e.g., PID and water-quality instrumentation) Initial trip to inspect each well for structural integrity, measure headspace levels of volatile or combustible gases or vapors, take water-level or product-thickness measurements, and prepare the wellhead for sample collection by anchoring plastic sheeting on the ground surface (in the order from upgradient to downgradient locations) Ensure that containment systems are in place to manage any purge water generated (e.g., 55 gal drums at each well) if required Prepare purging and sampling equipment Travel to first hydraulically upgradient well to be sampled with all equipment, sample containers, preservatives, filtration equipment, decontamination supplies, field notebook, sample labels, sample security tags and seals, chain-of-custody forms, shipping manifests, PPE, and garbage bags for solid waste Take a second water-level measurement to provide information necessary for purging method (depth to static water level, height of the water column, and volume of the well) Purge the well using the prescribed protocol, containing any purge water as necessary Collect field water-quality data (i.e., indicator parameters) Collect ground-water samples in the prescribed order of container filling, using required sample collection protocols Filter and physically and chemically preserve any parameter specified in the SAP Collect required field QC samples Complete required labels, seals, and tags, affix to the appropriate sample bottles, and place the sample bottles in shipping containers for storage or transport during the rest of the day’s field activities Complete the chain-of-custody form Dispose of any solid wastes generated during the sampling event (e.g., disposable gloves, plastic sheeting, disposable filters, disposable tubing, or suspension cord) Clean any portable equipment prior to transporting it to the next sampling location At the end of the day, complete the shipping manifest and ship samples to the laboratory 154 The Essential Handbook of Ground-Water Sampling © 2007 by Taylor & Francis Group, LLC ensure that the sampling event is well organized and that delays associated with poor preparation are avoided. The guide also provides good check lists of typical sampling equipment and supplies needed in the field. Field Preparation for a Ground-Water Sampling Event Site Orientation and Sampling Event Preparation Upon arrival at a field site, sampling team members should meet with facility personnel to learn of any changes related to facility operations, such as safety procedures, personnel changes, traffic pattern changes, locations of support systems such as fresh water or electricity for the sampling team to use, on-site construction, or other changes that have occurred at the site since the last sampling event. This is also a good time to be updated on field site conditions such as weather or any reports related to structural damage of any of the wells (e.g., if a well has been buried by waste or construction activities and if the protective casing of a well has been damaged by heavy equipment). It is helpful to have a current facility map available during this site orientation meeting to identify areas of concern on the map, especially if new sampling team members or facility personnel are present. This information can be of tremendous value to sampling teams as they plan their day and before they conduct an inspection of all wells scheduled for sampling during the event. Following site orientation, the sampling team should relocate to either an established field office or to a predetermined area located upgradient and away from high traffic areas to prepare equipment and materials for the day’s sampling event. This includes preparation of the field notebook; organization of sample containers, labels, and security tags and seals; organization of QC sample containers; and calibration of field instrumentation that will be used for headspace measurement in sampling points and for water-quality indicator parameter measurement. All instrumentation calibration should be done according to manufacturers’ instructions under field conditions. The timing and frequency of calibration should be in accordance with the SAP, which will commonly require, at a minimum, daily calibration and periodic calibration checks of all equipment. After all equipment is checked and calibrated, the sampling team should visit each well to conduct the next phase of the sampling event. Conducting the Sampling Event Sampling Point Inspection Prior to purging and sampling, the sampling team needs to physically inspect each well to ensure that it is structurally sound for sampling. As discussed earlier, reports on possible well damage from facility personnel are very helpful, especially if damage is severe enough to make location of the well difficult. Table 6.2 summarizes features that should be inspected by the sampling team prior to opening the protective casing and the well. If the well inspection indicates that there is obvious or suspected damage, detailed field notes should be made and photographs taken (if permitted) to describe the damage, including mention of any report made by facility personnel. The SAP should be consulted to determine the most appropriate course of action. In general, if there is any possibility Conducting a Ground-Water Sampling Event 155 © 2007 by Taylor & Francis Group, LLC that the observed well damage could result in a detrimental impact on sample chemistry, the location should not be sampled because samples may not be representative of true formation water chemistry. An evaluation should be made as to whether the well can be repaired or whether damage is significant enough to warrant decommissioning of the existing well and replacing it with another. This determination may be made by project managers rather than sampling team personnel, but it should be made in a timely fashion to avoid the possibility of the damaged well acting as a conduit for downward movement of surface contaminants into the formation. Well Headspace Screening If the well appears to be structurally sound, instrumentation for well headspace screening should be used to take ambient or background readings and the readings recorded. After background has been established, the well cap should be removed and the probe quickly inserted into the well headspace. After the headspace reading has stabilized or peaked, the probe should be removed from the sampling point and allowed to cycle fresh ambient air through the instrument to purge any vapors that may be present in the instrumenta- tion. The highest reading recorded and the type of instrument response (e.g., a rapid rise and drop or a gradual increase to stabilization) should be documented in the field notes. If readings indicate that volatile or combustible vapors or gases are present, the sampling team must refer to the SAP and the site health and safety plan to determine whether personnel should upgrade their PPE. In some wells, samplers may hear the sound of air rushing out of the well or a whistling sound when the well cap is removed. This is usually indicative of a well not being properly vented and an air-pressure buildup occurring as a result of a hydraulic pressure increase in the formation since the last sampling event. The sound is the pressurized air being released from the well as it attempts to equilibrate with atmospheric pressure. Equilibration of air pressure should occur within the time taken to screen the wellhead, but the water level in the well may continue to recover for anywhere from several seconds or minutes (in high hydraulic conductivity formations) to several hours or even days (in low hydraulic conductivity formations). TABLE 6.2 Well Inspection Checklist Check identification markings on the well Check the surface seal to ensure that it is intact with no cracks Check the above-grade protective casing and the well cap to be sure neither has been damaged (or the cap removed) Check to be sure that the locking mechanisms are in place and undamaged Check to be sure that the protective bumper guards are in place and undamaged Check to be sure that the protective painted surfaces are not weathered or altered or require repainting or etching Check to be sure that the valve-box covers or vault lids are present and in good condition for flush-to-grade installations Check to be sure that the vault lid security mechanisms are intact and rust-free for flush-to-grade completions Check to be sure that the gasket seals in flush-to-grade completions are present and water tight Check to be sure that there is no standing water inside the flush-to-grade vault; if water is present, note the depth, color, and appearance of any visible contamination of standing water (note especially if the water level is level with the top of the inner well casing cap) Note if there is any flow of water into the vault from either ground surface or below ground surface (around the vault seal) 156 The Essential Handbook of Ground-Water Sampling © 2007 by Taylor & Francis Group, LLC Water-Level Measurement After the water level in the well has stabilized, water-level measurements should be taken following the protocol documented in the SAP. To take a water-level measurement, samplers need to know the location of the surveyed reference measuring point on each well — this is the point to which all water-level measurements should be made. The reference measuring point should be physically marked on the well casing or outer protective casing but, in some cases, it may not be, so its description should be documented in the SAP. To ensure precision, the sampler should note the units of measure on the gauge tape and test the water-level gauge prior to lowering it into the well. After testing, the sampler should measure the depth to static water level and should take a minimum of three independent water-level readings (for precision) at least 5 to 10 sec apart. This is especially critical in unvented wells in which the water level may still be recovering; multiple measurements with different results indicate that the water level is not stable enough to record representative measurements. Results of water-level measurements should be recorded to an accuracy of 90.01 ft in the field notebook. Water levels should be measured in all wells at the site in as short a time interval as possible, before purging and sampling of any of the wells is attempted. These water-level data will be used for determining the direction, gradient, and rate of ground-water flow across the site. On large sites with many wells, a full day or more could be spent implementing this first phase of the ground-water sampling event. Between wells, the water-level gauge must be cleaned following protocols documented in the SAP to prevent potential cross- contamination of sampling locations. Well Purging and Field Parameter Measurement After well inspections are complete and the first set of water-level data is collected, the sampling team should return to the first upgradient sampling location to begin well purging and sampling. Prior to purging, a purge-water containment system must be in place. Commonly, this involves placing a 55 gal drum at each well or towing a 500 gal tank on a trailer behind the field truck to contain purge water. The device selected for purging the well should be lowered into the well (if portable) or, in the case where dedicated pumps are installed, the accessory equipment required for pump operation should be brought to the well and set up on the plastic sheeting placed around it. For portable pumps, an effort should be made to closely match the length of the tubing used for the pump with the depth at which the pump will be set in the well. Excess tubing can affect the temperature of the water sampled and reduce the flow rate. Increases in temperature can affect dissolved gases and trace metals in samples (Parker, 1994; Stumm and Morgan, 1996). Prior to purging the well, instrumentation to be used for water-quality analysis should be calibrated (Figure 6.1). If a flow-through cell is to be used, it should be assembled with the water-quality instrumentation, typically a multiparameter sonde, installed. The unit should be placed out of direct sunlight to avoid overheating of the cell and sensors. An effort should be made to keep tubing lengths that connect the flow-through cell to the pump discharge as short as possible. As mentioned earlier, excessive lengths of tubing may result in increases in temperature, which can have a detrimental effect on sample chemistry. All sampling supplies, such as disposable gloves and paper towels, as well as sample containers, QC sample containers and supplies, preservatives, filtration equipment, labels, security tags and seals, the field notebook, and chain-of-custody forms, should be Conducting a Ground-Water Sampling Event 157 © 2007 by Taylor & Francis Group, LLC organized and ready for use at the well following purging. After all equipment is in place, purging should be conducted in accordance with the SAP. Sample Collection Procedures After a well has been purged and is deemed ready for sampling, the sampling team must disconnect any flow-through cell equipment from the pump discharge tube and prepare to collect samples for laboratory analysis, and field QC samples. Sampling team members must be consistent in the manner in which they collect and pretreat samples on a parameter-specific basis to ensure both accuracy and precision between sampling events. Table 6.3 provides a checklist of sample collection elements that sampling team members should verify at each well during a sampling event. Each of these items must be addressed in the site-specific SAP. Order of Container Filling The sampling team should assemble sample containers provided by the laboratory for each parameter or suite of parameters to be analyzed at that particular well and containers required for any field QC samples that will be collected at that location. The sampling team should verify against the SAP that containers provided are correct for the analytes of interest, and they should inspect each container to ensure that it is in good physical condition (clean, not damaged, good fitting caps and seals, etc.) and ensure that there are sufficient numbers of containers to meet the needs of the sampling program. The containers should then be arranged in the correct order for filling, particularly in situations where there may be an insufficient volume of water in the wells to fill all sample containers. U.S. EPA guidance recommends that ground-water samples be collected in a particular order, with those parameters that are most sensitive to handling being collected first, followed by those less sensitive to handling (U.S. EPA, 1991). Figure 6.2 illustrates the recommended order for sample container filling. In addition to the sensitivity of a parameter to handling, it is critical that the relative importance or significance of each parameter be evaluated on a site-by-site basis when establishing the order of sample collection. For example, at a mining facility, there may be FIGURE 6.1 Calibration of a multiparameter sonde to be used with a flow-through cell to measure indicator parameters during low-flow purging and sampling. 158 The Essential Handbook of Ground-Water Sampling © 2007 by Taylor & Francis Group, LLC no interest in VOCs at all, and total metals may be the major concern. In this situation, it is wise to collect this parameter first to ensure that a representative sample for the most important constituents can be submitted for analysis rather than leave it toward the end as is suggested by Figure 6.2. This is particularly critical when sampling low-yield wells, which may not have a sufficient volume of water available to fill all sample containers. TABLE 6.3 Checklist of Critical QAuQC Sample Collection Elements All required water-quality measurements have been made, recorded, and checked for accuracy prior to disconnecting the flow-through cell Laboratory analyses to be performed on samples from each well are confirmed The correct sample containers and required sample volumes are checked and confirmed The order of and methods for sample collection (bottle filling) are clearly documented Field quality control samples to be collected (which kind, when, where, and how) are documented for each sampling location The correct types of filtration equipment, including filters of the correct filter pore size, are present at the well head Filter preconditioning procedures have been followed The correct type and volumes of chemical preservatives (if required) are present Procedures have been established to verify arrival temperature and end pH of samples requiring chemical preservation Sample container labels and security tags and seals (if required) are ready to be completed The appropriate chain-of-custody forms are available for completion immediately following sampling Sample shipping containers, compliant with applicable DOT and IATA shipping regulations, are ready for delivering samples to the lab by hand, laboratory courier, or commercial carrier Most Sensitive To Handling Least Sensitive To Handling Based on U.S. EPA, 1991 1. Volatile Organic Compounds (VOCs) 2. Total Organic Carbon (TOC) 3. Total Organic Halogen (TOX) 4. Samples Requiring Field Filtration 5. Samples for Additional Field Parameter Measurement (Independent of Purging Data) 6. Large-Volume Samples for Extractable Organic Compounds 7. Samples for Total Metals 8. Samples for Nutrient Anion Determinations FIGURE 6.2 U.S. EPA guidelines on the order of sample container filling. Conducting a Ground-Water Sampling Event 159 © 2007 by Taylor & Francis Group, LLC Sample Collection Protocols In addition to establishing the order of sample container filling, sampling teams must follow correct procedures for collecting the ground-water samples. Without exception, ground-water samples should always be collected directly from the discharge tubing from the sampling device and at no time during container filling should anything but sample (e.g., discharge tubing, sampler’s gloves, or filtration equipment) be allowed to enter the sample container or contact the mouth of the sample container. Use of funnels and transfer vessels should be avoided during sample collection because, as secondary forms of sample handling, they introduce potential sources of error and bias. Turbulent flow, aeration, and sample cross-contamination can result from the use of funnels and transfer vessels during sample decanting. Caps should be kept on sample containers until the moment they are ready to be filled, and containers should be resealed immediately upon filling. At no time should the inside of the caps be allowed to come in contact with the ground surface, sampling equipment, or sampler’s fingers. This can result in the transfer of contaminants to the inner cap surface and can introduce contaminants into the sample. If a cap is accidentally dropped onto the ground surface, it should be replaced with a new, clean cap. Once delivered to ground surface, ground-water samples come into contact with atmospheric conditions. Sampling team members should make every attempt to minimize the time during which samples are exposed to atmospheric conditions, as a number of significant changes to the sample, affecting a wide range of analytes, may otherwise occur. Exposure of a sample to atmospheric conditions results in changes in the pressure and temperature of the sample. Additional changes include increases in the levels of DO and other gases and resultant changes in the redox state of ground-water samples. Most ground water is depleted in oxygen content due to chemical and biological reactions that occur during the infiltration process. When a ground-water sample is exposed to atmospheric conditions, the following processes may take place: oxidation of organics; oxidation of sulfide to sulfate; oxidation of ammonium to nitrate; and oxidation of dissolved metals to insoluble precipitates (Stumm and Morgan, 1996). The latter process is very important in terms of sample stability. Multivalent aqueous-phase species, such as Fe, Mn, and As, may be oxidized from a reduced state (Fe 2' to Fe 3' ;Mn 3' to Mn 4' ; and As 3' to As 5' ), causing colloid-sized metal oxides and hydroxides to precipitate (Gillham et al., 1983; Puls et al., 1990; Ryan and Gschwend, 1990; Backhus et al., 1993). Because the kinetics of Mn oxidation are considerably slower than those for Fe, it is possible to collect a sample that is representative for one constituent (Mn) and not for another (Fe), depending on how rapidly the sample is preserved after collection (Gibb et al., 1981). Because the oxidation of iron is particularly critical to maintaining sample integrity, it is worth discussing further. Under anoxic to suboxic conditions, ground water often contains high concentrations of dissolved iron (Fe 2' ). Upon exposure to atmospheric conditions, Fe 2' oxidizes to Fe 3' , which precipitates as iron oxide or iron hydroxide, causes an increase in solution pH, and produces a rust-colored residue of colloid-sized particles in sample bottles. Iron hydroxide is known to adsorb or co-precipitate a number of other metals, including Cu, Zn, Co, Cd, As, Hg, Ag, Pb, V and even some organic species (Gibb et al., 1981; Gillham et al., 1983; Barcelona et al., 1984; Stoltzenburg and Nichols, 1986; Stumm and Morgan, 1996). The kinetics of oxidation-induced precipitation and subsequent sorption processes is such that they can occur within seconds or minutes (Reynolds, 1985; Puls et al., 1992). The end result is that a number of previously dissolved species are removed from solution and may be removed from the sample if it is filtered, resulting in significant negative bias for a number of analytes. Sample preservation methods (e.g., acidification) are meant to prevent such sample alteration, but are only 160 The Essential Handbook of Ground-Water Sampling © 2007 by Taylor & Francis Group, LLC effective if the sample is preserved prior to the occurrence of these reactions. The only commonly analyzed parameters that generally remain unaffected by exposure to atmospheric conditions are major ions. A special sampling procedure must be used for samples collected for VOC analysis to prevent the loss of volatile constituents from the sample. VOC samples must be collected in specially designed 40 ml vials using a technique that is referred to as zero-headspace sampling, in which sample vials are filled at a relatively slow rate (Figure 6.3). Some U.S. EPA documents (i.e., U.S. EPA, 1986) recommend sampling at a rate of 100 mlumin, which is too slow for many sites, especially those where atmospheric contributions of contaminants are of concern. A sample collection rate of 200 to 250 mlumin is more reasonable for volatile constituents. This rate is fast enough to minimize contact with ambient air, but is not so fast that sample aeration, agitation, or turbulence occur during sample collection. To collect a zero-headspace sample, ground water is collected directly from the pump discharge tubing or the grab sampling device in a controlled manner. To fill the vial, the container is held on an angle and water is allowed to gently flow down the inside wall of the container. As the container fills, it is slowly straightened to vertical. Once vertical, the vial is filled until a positive meniscus forms on top of the water, taking care not to overfill the vial and wash out any chemical preservatives that may be in the vial (Figure 6.4). The cap is then carefully placed on top of the vial without disturbing the meniscus and tightened to the manufacturer-recommended degree of tightness. The samplers should then invert the vial and carefully tap it against the heel of their hand to check for the presence of any bubbles that may have been trapped in the vial during filling. If bubbles are detected, the sampler must refer to the SAP for procedures on how to handle the vials. If the bubbles are the size of a pinhead or smaller, one trick to implement in the field is to hold the vial vertically, carefully turn the cap one fourth to half turn back (as if taking the cap off) to release the pressure in the vial and then retighten the cap. Using this technique, most small bubbles will be lost and the sample will be zero headspace without having to open the vial and expose the sample to atmospheric conditions again. If, however, the bubbles are larger than pinhead size, it may be necessary to discard the vial and resample. Samplers should refrain from opening FIGURE 6.3 Collecting samples for VOC analysis requires use of a slow, controlled discharge rate. A rate of about 200 to 250 mlumin is a good compromise which allows collection of samples without agitation and turbulence, while minimizing the time with which the sample is in contact with atmospheric conditions. Conducting a Ground-Water Sampling Event 161 © 2007 by Taylor & Francis Group, LLC a vial with headspace and ‘‘topping off’’ the sample until a zero-headspace sample is collected. This may result in either loss of constituents through volatilization into ambient air or contamination of the sample in some cases where atmospheric levels of volatile constituents are high. In addition, there is a risk that chemical preservatives will be washed out of the vial during this topping-off process, resulting in an improperly preserved sample. For most parameters other than VOCs, sample collection rates of less than 500 mlumin are appropriate (Puls and Barcelona, 1996). Protocols for Collecting Field QC Samples Trip Blanks A trip blank is prepared and provided by the laboratory as a standard QC sample. The laboratory ships a set of containers prepared for the required list of analytes that are filled with laboratory-prepared water (usually deionized water) of known and documented quality. The containers are labeled by the laboratory as being trip blanks and are shipped to the field along with the empty sample containers. Trip blanks should be documented by the laboratory on the accompanying chain-of-custody forms. After receipt in the field by the sampling team, the trip blanks should be inspected to ensure that all are present, that all containers are in good physical condition, and that there is no headspace in the VOC vials used for trip blanks. Any problems with trip blanks should be documented on the chain-of-custody forms and the laboratory should be notified immediately. The trip blanks should always be kept with the sample containers throughout the sample collection event and should be treated just like samples with regard to temperature control and packaging for shipment to the laboratory. At no time should any of the trip blank containers be opened and exposed to atmospheric conditions. If samples are sent to more than one laboratory, separate trip blanks should be submitted to each laboratory involved in sample analysis. FIGURE 6.4 To fill a VOC vial with zero-headspace, it is necessary to form a positive meniscus on the water surface prior to affixing the cap on the vial. For vials containing a chemical preservative, it is important not to overfill the vial to ensure that the preservative is not washed out. 162 The Essential Handbook of Ground-Water Sampling © 2007 by Taylor & Francis Group, LLC [...]... of the adhesives on the back of the seal during analysis Security seals and tags are used © 2007 by Taylor & Francis Group, LLC Conducting a Ground- Water Sampling Event 169 FIGURE 6. 6 Sample seals on VOC vials must be affixed around the lid as shown here FIGURE 6. 7 If the sample seal on a VOC vial covers the septum, the constituents of the adhesive from the seal may be detected in the analysis as the. .. M.J Barcelona, Ground- Water Sampling for Metals Analysis, EPAu540u 4-8 9u001, Superfund Ground Water Issue, U.S Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC, 6 pp., 1989 Puls, R.W and M.J Barcelona, Low-Flow (Minimal-Drawdown) Ground- Water Sampling Procedures, EPAu540u 5-9 5u504, Ground Water Issue, U.S Environmental Protection Agency, Office of Solid Waste... filled If a grab -sampling device such as a bailer is used, samplers must first determine whether a bottom-emptying device is to be used to decant the sample from the device If so, then samplers must alternate between containers frequently to avoid filling one container with the bottom portion of the water column in the bailer and the other with water from the top of the water column in the bailer Alternating... earlier, but these containers are labeled as field blanks The deionized water- filled containers are accompanied by an identical but empty set of sample containers To collect a field blank for parameters other than VOC analysis, the water- filled and empty containers are taken to the point of ground- water sample collection and the volume of water is transferred from the filled containers to the equivalent... ASTM Standard D 69 11, ASTM International, West Conshohocken, PA, 6 pp., 2006b Backhus, D.A., J.N Ryan, D.M Groher, J.K MacFarlane, and P.M Gschwend, Sampling colloids and colloid-associated contaminants in ground water, Ground Water, 31(3), pp 466 Á 479, 1993 Barcelona, M.J., J.A Helfrich, E.E Garske, and J.P Gibb, A laboratory evaluation of ground- water sampling mechanisms, Ground- Water Monitoring... Preserve the filtered ground- water sample as required on a parameter-specific basis 6 Release the pressure from the filtration equipment and disconnect it from the sampling device discharge tubing © 2007 by Taylor & Francis Group, LLC Conducting a Ground- Water Sampling Event 167 7 Discard any disposable materials (e.g., filter media) in accordance with the sitespecific waste-management provisions of the. .. preferred for groundwater sample filtration (U.S EPA, 1991) There are two general categories of positive-pressure filtration equipment: (1) in-line filtration equipment used with pumping devices; and (2) remote pressurized filtration equipment that is not in line with a pumping device © 2007 by Taylor & Francis Group, LLC The Essential Handbook of Ground- Water Sampling 166 FIGURE 6. 5 Positive-pressure... managed in accordance with the SAP If required by the SAP, all purge water should be containerized and records made of the volume of purge water generated The well should then be locked or otherwise secured Delivery or Shipment of Samples to the Laboratory At the end of the day, samples are either hand delivered (preferred to avoid loss or damage of samples) or shipped to the laboratory for analysis... and the duplicate set of samples They must then alternately fill one vial from the primary set of containers, then the other vial from the duplicate set of containers This process continues until all of the vials are filled in succession All samples should be collected using the zero-headspace sampling technique described earlier Duplicate samples are referred to as ‘‘blind’’ samples because the sampling. .. Handbook of Ground- Water Sampling 168 6 Collect the filtrate into a flask or other transfer vessel 7 Release the negative pressure at the vacuum pump connected to the filtration equipment 8 Transfer the filtrate into a prepared sample container, taking care not to agitate the sample, increase turbulence, or introduce airborne contaminants into the sample 9 Preserve the filtered ground- water sample . (around the vault seal) 1 56 The Essential Handbook of Ground- Water Sampling © 2007 by Taylor & Francis Group, LLC Water- Level Measurement After the water level in the well has stabilized, water- level. transporting it to the next sampling location At the end of the day, complete the shipping manifest and ship samples to the laboratory 154 The Essential Handbook of Ground- Water Sampling © 2007. integrity through inclusion of the adhesives on the back of the seal during analysis. Security seals and tags are used 168 The Essential Handbook of Ground- Water Sampling © 2007 by Taylor &