1、Designation: D 6634 01 (Reapproved 2006)Standard Guide forthe Selection of Purging and Sampling Devices for Ground-Water Monitoring Wells1This standard is issued under the fixed designation D 6634; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the characteristics and operatingprinciples of purging and sampling d
3、evices available for use inground-water monitoring wells and provides criteria for select-ing appropriate devices for specific applications. The selecteddevice(s) should be capable of purging the well and providingvalid representative samples of ground water and any includeddissolved constituents. T
4、he scope does not include proceduresfor purging or collecting samples from monitoring wells,sampling devices for non-aqueous phase liquids, diffusion-typesampling devices or sampling from devices other than moni-toring wells.1.2 This guide reviews many of the most commonly useddevices for purging an
5、d sampling ground-water monitoringwells. The practitioner must make every effort to ensure thatthe purging and sampling methods used, whether or not theyare addressed in this guide, are adequate to satisfy themonitoring objectives at each site.1.3 This guide offers an organized collection of informa
6、tionor a series of options and does not recommend a specific courseof action. This document cannot replace education or experi-ence and should be used in conjunction with professionaljudgement. Not all aspects of this guide may be applicable inall circumstances. This ASTM standard is not intended to
7、represent or replace the standard of care by which the adequacyof a given professional service must be judged, nor should thisdocument be applied without consideration of the many uniqueaspects of a project. The word “Standard” in the title of thisdocument means only that the document has been appro
8、vedthrough the ASTM consensus process.1.4 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory li
9、mitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 5088 Practices for Decontamination of Field EquipmentUsed at Waste SitesD 6452 Guide for Purging Methods for Wells Used forGround-Water Quality Investigations3. Summary of Guide3.1 The primary objective of ground-water sampling pro-
10、grams is to collect representative samples of ground water.Depending on the purging and sampling protocol, this mayrequire that the well is purged of all stagnant water, or untilpre-determined purging criteria are met. Therefore, device(s)selected for use in ground-water sampling programs must becap
11、able of purging the well as needed and/or delivering to thesurface, a sample representative of in-situ ground-water con-ditions. A number of factors can influence whether or not aparticular sample or set of samples is representative, and one ofthe significant elements of sample collection protocols
12、is thesampling mechanism (1, 2, 3).33.2 In selecting a purging and/or sampling device for use ina ground-water monitoring well, a number of factors must beconsidered. Among these are 1) outside diameter of the device;2) materials from which the device and associated equipmentare made; 3) overall imp
13、act of the device on ground-watersample integrity with respect to the analytes of interest; 4)ability to control the discharge rate of the device; 5) depth towater; 6) ease of operation and servicing; 7) reliability anddurability of the device; 8) portability of the device and1This guide is under th
14、e jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Monitoring.Current edition approved July 1, 2006. Published July 2006. Originally approvedin 2001. Last previous edition approved in 2001 as D 6634 01.2For refer
15、enced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to a list of references at t
16、he end ofthis standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.required accessory equipment, if applicable; 9) other opera-tional limitations of the device; and 10) initial and operatingcost of the device and accessory equipm
17、ent. Based on theseconsiderations, each of the devices available for purging and/orsampling ground water from monitoring wells has its ownunique set of advantages and limitations.4. Significance and Use4.1 Appropriate purging and sampling equipment must beused to ensure that samples collected from m
18、onitoring wellsrepresent the ground-water chemistry of the desired waterbearing zone.4.2 This guide is intended to be a common reference forpurging and sampling devices. It can be applied to ground-water quality sampling from monitoring wells used for ground-water contamination evaluation, water sup
19、ply characterization,and research.4.3 This guide includes a number of general guidancestatements that are not directly related to the operating prin-ciples or characteristics of the equipment. These statements aregiven to assist the user in understanding the application of theequipment, which could
20、ultimately affect the selection process.5. Objectives of Well Purging and Sampling5.1 The primary objective of ground-water sampling pro-grams is to obtain samples that are representative of existingground-water conditions retaining the physical and chemicalproperties of the ground water in a specif
21、ic water-bearingzone.46. Criteria for Selection of Purging and SamplingDevices6.1 When selecting purging and/or sampling device(s), anumber of criteria must be evaluated as discussed below. Basedon these criteria, each device has a unique set of advantagesand limitations that define suitability to s
22、ite-specific applica-tions.6.2 Outside Diameter of the Device If the well(s) to bepurged and sampled is (are) already in place, the initialconsideration in selecting a device is whether or not the well(s)will accommodate the device. It is important to consider thatthe wells may not be plumb, may hav
23、e constrictions in thecasing (i.e. at joints), or may contain other obstructions thatmake the effective inside diameter of the well smaller than theinside diameter of the casing. Alternately, if the monitoringwells are not in place, it may be more prudent to first select adevice that meets the requi
24、rements of the sampling programand then select the size of the casing to be used in the wells.The smaller the inside diameter of the well, the more limitedthe selection of devices becomes. The majority of ground-water monitoring wells installed at various types of sites aresmall-diameter wells, or w
25、ells with inside diameters of 4 in.(100 mm) or less. All of the devices described herein will fitinto a 4 in. (100 mm) inside diameter well, most can beinstalled in a 2 in. (50 mm) inside diameter well, and severalcan be used in wells of 0.75 in. (19 mm) inside diameter orless.6.3 Materials and Manu
26、factureThe choice of materialsused in the construction of purging and sampling devicesshould be based upon knowledge of the geochemical environ-ment and how the materials may interact with the sample viaphysical, chemical, or biological processes. Materials used inthe manufacture of purging and samp
27、ling devices and associ-ated tubing, hoses, pipes and support lines (e.g., rope, cable orchain) may be a source of bias or error. Materials used shouldnot sorb analytes from samples, desorb previously-sorbedanalytes into samples, leach matrix components of the materialthat could affect analyte conce
28、ntrations or cause artifacts, or bephysically or chemically degraded due to water chemistry.Materials commonly used in the manufacture of samplingdevices include rigid polyvinyl chloride (Type I PVC), stain-less steel, polytetrafluorethylene (PTFE)5, polyethylene (PE),polypropylene (PP), flexible po
29、lyvinyl chloride (Type II PVC),fluoroelastomers5polyvinylidene fluoride (PVDF), andBuna-N, ethylene-propylene diene monomer (EPDM) andsilicone rubbers. Studies are available which indicate therelative sorption/desorption rates of these materials, theirpotential for alteration of the sample chemistry
30、, and theirranking of desirability for use in sampling devices (1, 4, 7, 8,9, 10). Extrusions and molded parts made of polymericmaterials may contain surface traces of organic extrusion aidsor mold release compounds. Also, some formulations ofpolymeric materials may contain fillers or processing add
31、itivesthat can leach from the material and alter sample quality.Traces of cutting oils, solvents or surface coatings may bepresent on metallic materials. These should be removed and,once removed, should not affect sample chemistry. It isgenerally preferable to use materials produced without the useo
32、f these processing or surface coatings. Metallic materials aresubject to corrosion; electropolishing or other surface passiva-tion processes can improve corrosion resistance. Corrosion andresidues from unfinished metallic materials could affect samplequality.6.4 Impact on Sample IntegrityWhile it is
33、 not particularlyimportant to preserve the chemical integrity of water purgedfrom a monitoring well, the device(s) chosen for purging andsampling should be evaluated to ensure that they minimizephysical or chemical alteration of the water in the well and thesubsequent sample by their methods of deli
34、vering water to thesurface. Because the subsurface environment is under differenttemperature, pressure, gas content, and redox potential condi-tions than those at the surface, precautions must be taken toensure that these conditions are preserved as much as possible4For example, the plasticizers in
35、flexible PVC can contaminate samples withphthalate esters. The use of silicone rubber tubing, which contains no plasticizers,can obviate this problem; however, the potential for sample bias due to sorption/desorption exists with both materials (9). These pumps can be used with theintermediate vessel
36、 system described above, so that the sample contacts only theintake tubing and vessel, avoiding contact with the pump mechanism tubing.Alternatively, using silicone rubber tubing at the pump head only can minimize thisproblem (20, 23).5PTFE is also commonly known by the trade name Teflont, which inc
37、ludesother fluoropolymer formulations. Teflon is a registered trademark of E. I. DuPontDe Nemours 2) the operator is not familiar enough with the device tooperate it properly; or 3) the operating manual supplied withthe device does not clearly outline the procedures for properuse. Thus, it is not on
38、ly important to select a device that issimple to operate, but also to provide proper training for theoperator(s) of the device. Since mechanical devices are subjectto malfunction or failure, it may be desirable to service thedevice in the field or have a replacement device available.Some of the devi
39、ces described herein may be too complex forfield repairs, requiring servicing by the manufacturer or aqualified service facility.6.8 Reliability and DurabilityReliability and durabilityare two additional factors related to maintenance that warrantattention. Devices used in some monitoring programs m
40、ust becapable of operating for extended periods of time in subsurfaceenvironments containing a variety of chemical constituents thatmay cause corrosion of metallic parts or degradation of plasticmaterials (8). This is especially true where devices are dedi-cated to wells and thus are continually exp
41、osed to potentiallyaggressive chemical environments.6.9 Portability vs. DedicationIn practice, purging andsampling devices are employed in one of two modes: portable(used in multiple wells) or dedicated (installed for use in asingle well). Dedicating sampling equipment eliminates theneed to decontam
42、inate this equipment after each use, and caneliminate the potential for cross-contamination of wells andsamples and possible contamination from handling or improperstorage of portable equipment. Dedicated equipment can alsobe more cost effective to use in routine monitoring programsdue to reduced fi
43、eld labor and the elimination of the cost ofdecontamination and analytical blanks. Portable equipmentmust be cleaned between use in each monitoring well ordiscarded after use to avoid cross-contamination of wells andsamples. In addition, the components must withstand thenecessary cleaning processes.
44、 Some devices, by virtue of theirdesign, may be difficult to disassemble to clean. It may be morepractical to clean these devices by circulating cleaning solu-tions and rinses through the device and any associated tubing,hose or pipe in accordance with Practices D 5088, or to replacethe associated t
45、ubing, hose or pipe. Field decontaminationoperations can be difficult due to the need for sufficientdecontamination supplies, exposure of the equipment to poten-tial contaminants, and the handling and disposal of the decon-tamination waste water and supplies. Where field decontami-nation is not prac
46、tical or possible, it may be simpler to usededicated devices or take a number of portable samplingdevices into the field and decontaminate them later at a moreappropriate location. Following any cleaning procedure, equip-ment blanks should be collected to assess the effectiveness ofthe cleaning proc
47、edure.6.9.1 The remote location of some monitoring wells orrough terrain may require that the sampling device andaccessory equipment selected (i.e. tubing or tubing bundles,hose reels, battery packs, generators, compressed air source,controlling devices, decontamination equipment and supplies,purge
48、water containers, etc.) be highly portable. While somedevices can be hand-carried to remote sites, some manufactur-ers have mounted their equipment on backpack frames, smallwheeled carts and specialized vehicles in an effort to improveportability. Other equipment is too bulky and heavy to betranspor
49、ted in the field without being vehicle-mounted.6.10 Other Operational Characteristics Operationalcharacteristics such as solids handling capability, ability to rundry, cooling requirements, and intermittent discharge must beconsidered in the application of some purging and samplingD 6634 01 (2006)3devices. Some devices may experience increased wear ordamage as solids pass through the device causing reducedoutput or failure. Solids may also clog check valves and/orpassages, which can reduce discharge rate or, in the case ofgrab samplers, cause the retained sample to leak out.6.1
